Abstract:
A method for repairing a liquid crystal display. The method includes preparing a liquid crystal panel including a signal pad part and a repair pad part connected to signal lines; testing a driving circuit connected to the signal pad part on the liquid crystal panel; opening signal links connecting the signal lines and the signal pad part, connected to the driving circuit, if the driving circuit is detected in a defect as a result of the test; and mounting a repair driving circuit to be connected to the repair signal pad part on the liquid crystal panel.

Description:
[0001]    This application claims the benefit of Korean Patent Application No. 2008-049657, filed May 28, 2008, which is hereby incorporated by reference as if fully set forth herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a liquid crystal display, and more particularly, to a liquid crystal display and method for repairing the same, in which a defective gate driving integrated circuit is easily repaired without damage to a liquid crystal panel. 
         [0004]    2. Discussion of the Related Art 
         [0005]    As an information-oriented society has been developed, display devices have various shapes. In order to satisfy the above requirement, various flat panel display devices, including a liquid crystal display (LCD), a plasma display panel (PDP), an electro luminescent display (ELD), a vacuum fluorescent display (VFD), etc., have been researched, and some flat panel display devices have been used already as display devices in several apparatuses. 
         [0006]    Among the above flat panel display devices, the LCD, which has advantages, such as an excellent image quality, a light weight, a thin profile, and a low power consumption, is being most widely used as a mobile image display device in place of a cathode ray tube (CRT). Further, in addition to the purpose of the mobile image display device, such as a monitor of a notebook computer, the LCD is variously developed and used as a television receiving a broadcast signal and displaying an image or a monitor of a computer. 
         [0007]      FIG. 1  is a cross-sectional view of a liquid crystal display of the related art. 
         [0008]    With reference to  FIG. 1 , the liquid crystal display (LCD) includes a liquid crystal panel, in which liquid crystal cells are arranged in a matrix, and driving integrated circuits  50  to drive the liquid crystal cells. The liquid crystal panel is produced by bonding a first substrate  10 , on which a thin film transistor array is formed, and a second substrate, on which a color filter array is formed, through a cell process such that a liquid crystal layer is interposed between the first substrate  10  and the second substrate. 
         [0009]    The first substrate  10  is a thin film transistor substrate, and includes a plurality of gate lines, a plurality of data lines intersecting with the plurality of gate lines such that a gate insulating film is formed between the plurality of gate lines and the plurality of data lines to define pixel regions, thin film transistors respectively formed at the intersections between the gate lines and the data lines, and pixel electrodes respectively formed at the pixel regions and connected to the thin film transistors. 
         [0010]    The second substrate is a color filter substrate, and includes a black matrix layer to shield other regions except for the pixel regions from light, R, G, and B color filter layers to express colors, and common electrodes on the color filter layers. 
         [0011]    The thin film transistor substrate and the color filter substrate are bonded to each other such that the liquid crystal layer is interposed between the two substrates. 
         [0012]    The driving integrated circuits include a plurality of data driving integrated circuits to provide an pixel voltage signal to the data lines of the liquid crystal-panel, and a plurality of gate driving integrated circuits to provide a gate pulse to the gate lines of the liquid crystal panel. 
         [0013]    Gate pads connected to the gate lines and data pads connected to the data lines are respectively connected to the gate driving integrated circuits and the data driving integrated circuit through an anisotropic conductive film (hereinafter, referred to as an ACF)  24 . That is, the ACF  24  includes a thermosetting resin  24 b and conductive balls  24   a,  and the ACF  24  electrically connects the gate pads and the data pads to the gate driving integrated circuits and the data driving integrated circuits respectively by thermocompression. 
         [0014]    In case that the driving integrated circuits are bonded to the pads of the liquid crystal panel by the ACF  24 , when the driving integrated circuit have a defect, the whole liquid crystal panel must be thrown away, thus causing the reduction of a yield and the increase of a manufacturing cost. Further, when the ACF  24  is cured once through heat, the ACF  24  becomes hard and is not easily detached from the pads and the driving integrated circuits, and may cause damage to the gate pads even if the ACF  24  is detached from the pads and the driving integrated circuits using heat and physical force. Moreover, the residual ACF  24  must be removed using chemical products even if a process for repairing the defective driving integrated circuit is carried out, and thus the process is complicated. 
       SUMMARY OF THE INVENTION 
       [0015]    Accordingly, the present invention is directed to a liquid crystal display and method for repairing the same. 
         [0016]    One object of the present invention is to provide a method for repairing a liquid crystal display, in which a defective gate driving integrated circuit is easily repaired without damage to a liquid crystal panel. To achieve this object and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a method for repairing a liquid crystal display includes preparing a liquid crystal panel including a signal pad part and a repair pad part connected to signal lines; testing a driving circuit connected to the signal pad part on the liquid crystal panel; opening signal links connecting the signal lines and the signal pad part, connected to the driving circuit, if the driving circuit is detected in a defect as a result of the test; and mounting a repair driving circuit to be connected to the repair signal pad part on the liquid crystal panel. 
         [0017]    A liquid crystal display includes a liquid crystal panel including a signal pad part and a repair pad part connected to signal lines; a driving circuit connected to the signal pad part on the liquid crystal panel; and a repair driving circuit connected to the repair signal pad part on the liquid crystal panel, if the driving circuit is detected in a defect, wherein signal links connecting the signal lines and the signal pad part, connected to the defective driving circuit, is opened. 
         [0018]    It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
           [0020]      FIG. 1  is a cross-sectional view of a liquid crystal display of the related art; 
           [0021]      FIG. 2  is a plan view of a liquid crystal display in accordance with a first embodiment of the present invention; 
           [0022]      FIG. 3  is a cross-sectional view of the liquid crystal display, taken along the line I-I′ of  FIG. 2 ; 
           [0023]      FIGS. 4A to 4C  and  FIGS. 5A to 5C  are enlarged cross-sectional views of the region A of  FIG. 2 , illustrating a process for repairing a gate driving circuit; 
           [0024]      FIG. 6  is a plan view of a liquid crystal display in accordance with a second embodiment of the present invention; 
           [0025]      FIG. 7  is a cross-sectional view of the liquid crystal display, taken along the line II-II′ of  FIG. 6 ; and 
           [0026]      FIGS. 8A to 8C  and  FIGS. 9A to 9C  are enlarged cross-sectional views of the region B and the region B′ of  FIG. 6 , illustrating a process for repairing a gate driving circuit. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
         [0028]      FIG. 2  is a plan view of a liquid crystal display in accordance with a first embodiment of the present invention, and  FIG. 3  is a cross-sectional view of the liquid crystal display, taken along the line I-I′ of  FIG. 2 . 
         [0029]    With reference to  FIGS. 2 and 3 , the liquid crystal display in accordance with the first embodiment of the present invention includes a liquid crystal panel  115 , on which liquid crystal cells LCs are arranged in a matrix, and driving circuits to drive the liquid crystal cells LCs. The liquid crystal panel  115  is produced by bonding a first substrate  110 , on which a thin film transistor array is formed, and a second substrate  112 , on which a color filter array is formed, through a cell process such that a liquid crystal layer is interposed between the first and second substrates  110  and  112 . 
         [0030]    The first substrate  110  is a thin film transistor substrate, and includes a plurality of gate lines GL 1 ˜GLn, a plurality of data lines DL 1 ˜DLm intersecting with the plurality of gate lines GL 1 ˜GLn such that a gate insulating film is formed between the gate lines GL 1 ˜GLn and the data lines DL 1 ˜DLm to define pixel regions, thin film transistors (hereinafter, referred to TFTs) respectively formed at the intersections between the gate lines GL 1 ˜GLn and the data lines DL 1 ˜DLm, and pixel electrodes respectively formed at the pixel regions and connected to the TFTs. 
         [0031]    Each of the TFTs includes a gate electrode branched off from the gate line GL, the gate insulating film formed on the front surface of the substrate provided with the gate electrode, a semiconductor layer formed on the gate insulating film so as to be overlapped with the gate electrode, a source electrode branched off from the data line DL and formed on the semiconductor layer, and a drain electrode formed on the semiconductor layer so as to be opposite to the source electrode. 
         [0032]    The thin film transistor substrate  110  and the second substrate  112 , i.e., a color filter substrate, are bonded to each other such that the liquid crystal layer is interposed between the two substrates  110  and  112 . The second substrate  112  includes a black matrix layer to shield other regions except for the pixel regions from light, R, G, and B color filter layers to express colors, and common electrodes on the color filter layers. 
         [0033]    The driving circuits include a plurality of data driving integrated circuits  140  located at a region of the first substrate  110  exposed by the second substrate  112 , i.e., at a non-display region, to provide an pixel voltage signal to the data lines DL 1 ˜DLm of the liquid crystal panel  115 , and a gate driving circuits  150  located at the non-display region to provide a scan pulse to the gate lines. GL 1 ˜GLn of the liquid crystal panel  115 . 
         [0034]    The gate driving circuit  150  is mounted on the first substrate  110 , in which driving integrated circuits are mounted on a circuit substrate using a thin film transistor of a poly silicon type by a low temperature poly silicon (LTPS) process. Further, the gate driving circuit  150  sequentially supplies a scan pulse to the gate lines GL 1 ˜GLn through a plurality of gate links  127 , and sequentially drive the liquid crystal cells LCs on the liquid crystal panel  115  line by line. 
         [0035]    The data driving integrated circuits  140  supply a pixel voltage signal to the respective data lines DL 1 ˜DLm whenever the scan pulse is supplied to any one of the gate lines GL 1 ˜GLn. 
         [0036]    Gate pads connected to the gate lines GL 1 ˜GLn are connected to the gate driving circuit  150  through an ACF  124 . That is, the ACF  124  includes conductive balls  124   a  and a thermosetting resin  124   b,  and electrically connects the gate pads and the gate driving circuit  150  by thermocompression. 
         [0037]    Here, the gate driving circuit  150  is separated from a display region, and when the gate driving circuit  150  has a defect, a process for repairing the defective gate driving circuit  150  is required. Thus, after the defective gate driving circuit  150 , a gate pad part connected to the defective gate driving circuit  150 , and a region of the substrate  110  provided with the defective gate driving circuit  150  and the gate pad part connected to the defective gate driving circuit  150  are cut off by scribing using a wheel or the gate links  127  are opened using a laser, a repair gate driving circuit  160  is mounted on the substrate  110  between the defective gate driving circuit  160  and the display region, i.e., at the non-display region. The repair gate driving circuit  160  is connected to a repair gate pad part by the ACF  124 , and the repair gate pad part are previously formed with the gate pads. 
         [0038]    By the repair gate driving circuit  160  being mounted on the repair gate pad part and, as described above, the liquid crystal panel  115  has an increased width compared with the liquid crystal panel of the related art. However, since the repair gate pad part and the repair gate driving circuit  160  are mounted in a margin range of a backlight unit, the substantial size of a bezel is not increased. The width WA of the non-display region of the thin film transistor substrate  110  exposed by the color filter substrate  112  of the liquid crystal panel  115  is larger than the total sum of the width WI of the gate driving circuits  150  and the width WJ of the repair gate driving circuit  160 . 
         [0039]    The data driving integrated circuits  140  are respectively mounted on a plurality of tape carrier packages (hereinafter, referred to as TCPs)  130 , and are connected between a printed circuit board  120  and the liquid crystal panel  115 . The data driving integrated circuits  140  convert digital data signals into analog pixel voltage signals according to a data control signal, and supply the analog pixel voltage signals to the data lines DL 1 ˜DLm through a plurality of data links  147 . 
         [0040]    When the driving circuits bonded to the liquid crystal panel  115  using the ACF  124  has a defect, a process for the defective integrated circuit is required. 
         [0041]      FIGS. 4A to 4C  and  FIGS. 5A to 5C  are enlarged cross-sectional views of the region A of  FIG. 2 , illustrating a process for repairing the gate driving circuit  150 . 
         [0042]    As shown in  FIG. 4A , the gate driving circuit  150  to sequentially supply a scan pulse to the gate lines through the plurality of gate links  127  is mounted on the non-display region of the first substrate  110  exposed by the second substrate  112 . 
         [0043]    When the gate driving circuit  150  of the finished liquid crystal display has a defect, as described above, the whole liquid crystal panel  115  must be thrown away, thus causing the reduction of a yield and the increase of a manufacturing cost. The gate driving circuit  150  is bonded to the gate pads  125  through thermocompression using the ACF including the conductive balls  124   a  and the thermosetting resin  124   b.  The ACF  124  becomes hard and is not easily detached from the gate pads  125  and the gate driving circuit when the ACF  124  is cured once through heat, and may cause damage to the gate pads  125  even if the ACF  124  is detached from the gate pads  125  and the gate driving circuit using heat and physical force. Further, the residual ACF must be removed using chemical products even if a process for repairing the defective gate driving circuit  150  is carried out and thus the process is complicated. Thus, an effective repairing process is required. 
         [0044]    As shown in  FIG. 4B , the gate links  127  between the gate pads  125  and the repair gate pads  122  are opened using a laser. Thereafter, as shown in  FIG. 4C , the repair gate driving circuit  160  is connected to the repair gate pads  122  between the defective gate driving integrated circuit  150  and the display region through thermocompression using the ACF  124 . The repair gate pads  122  are previously formed on gate links  127  with the gate pads  125  between the gate pads  125  and the gate lines. 
         [0045]    By the repair gate driving integrated circuit  160  being mounted on the repair gate pads  122 , as described above, the liquid crystal panel  115  has an increased width. However, since the repair gate driving circuit  160  are mounted in a margin range of a backlight unit, the substantial size of a bezel is not increased. 
         [0046]      FIGS. 5A to 5C  are enlarged cross-sectional views of the region A of  FIG. 2 , illustrating a process for repairing a gate driving circuit in accordance with another embodiment of the present invention. 
         [0047]    As shown in  FIGS. 5A to 5C , when the gate driving integrated circuit  150  of the finished liquid crystal display has a defect, a region of the substrate  110  provided with the defective gate integrated circuit  150  and the gate pads  125  connected to the defective gate driving circuit  150  is cut off by scribing, etc. Thereafter, a new repair gate driving circuit  160  is connected to repair gate pads  122  by thermocompression using the ACF  124 . 
         [0048]    The repair gate pads  122  are previously formed on gate links  127  with the gate pads  125  between the gate pads  125  and the gate lines. 
         [0049]    By disconnecting or removing the defective gate driving circuit  150  and forming the new repair gate driving circuit  160 , as described above, it is not necessary to apply heat or physical force to the liquid crystal panel  115  to detach the defective gate driving circuit  150  from the liquid crystal panel  115 , and thus it is possible to prevent damage to the gate pads  125 , thereby enhancing the yield of the liquid crystal display. Further, it is not necessary to remove the residual ACF  124  using chemical products, thus solving the complication of the process. 
         [0050]      FIG. 6  is a plan view of a liquid crystal display in accordance with a second embodiment of the present invention, and  FIG. 7  is a cross-sectional view of the liquid crystal display, taken along the line II-II′ of  FIG. 6 . 
         [0051]    With reference to  FIGS. 6 and 7 , the liquid crystal display in accordance with the second embodiment of the present invention includes a liquid crystal panel  115 , on which liquid crystal cells LCs are arranged in a matrix, and driving circuits to drive the liquid crystal cells LCs. The liquid crystal panel  115  is produced by bonding a first substrate  110 , on which a thin film transistor array is formed, and a second substrate  112 , on which a color filter array is formed, through a cell process such that a liquid crystal layer is interposed between the first and second substrates  110  and  112 . 
         [0052]    The first substrate  110  is a thin film transistor substrate, and includes a plurality of gate lines GL 1 ˜GLn, a plurality of data lines DL 1 ˜DLm intersecting with the plurality of gate lines GL 1 ˜GLn such that a gate insulating film is formed between the gate lines GL 1 ˜GLn and the data lines DL 1 ˜DLm to define pixel regions, thin film transistors (hereinafter, referred to TFTs) respectively formed at the intersections between the gate lines GL 1 ˜GLn and the data lines DL 1 ˜DLm, and pixel electrodes respectively formed at the pixel regions and connected to the TFTs. 
         [0053]    Each of the TFTs includes a gate electrode branched off from the gate line GL, the gate insulating film formed on the front surface of the substrate provided with the gate electrode, a semiconductor layer formed on the gate insulating film so as to be overlapped with the gate electrode, a source electrode branched off from the data line DL and formed on the semiconductor layer, and a drain electrode formed on the semiconductor layer so as to be opposite to the source electrode. 
         [0054]    The thin film transistor substrate  110  and the second substrate  112 , i.e., a color filter substrate, are bonded to each other such that the liquid crystal layer is interposed between the two substrates  110  and  112 . The second substrate  112  includes a black matrix layer to shield other regions except for the pixel regions from light, R, G, and B color filter layers to express colors, and common electrodes on the color filter layers. 
         [0055]    The driving circuits include a plurality of data driving integrated circuits  140  located at the region of the first substrate  110  exposed by the second substrate  112 , i.e., at a non-display region, to provide an pixel voltage signal to the data lines DL 1 ˜DLm of the liquid crystal panel  115 , and a gate driving circuit  150  located at the non-display region to provide a gate pulse to the gate lines GL 1 ˜GLn of the liquid crystal panel  115 . The gate driving circuit  150  is formed by a low temperature poly silicon (LTPS) process, in which the gate driving circuit  150  is formed on a circuit substrate using a thin film transistor of a poly silicon type. 
         [0056]    The gate driving circuit  150  is mounted on the first substrate  110 , sequentially supply a scan pulse to the gate lines GL 1 ˜GLn through a plurality of gate links  127 , and thus sequentially drive the liquid crystal cells LCs on the liquid crystal panel  115  line by line. The data driving integrated circuits  140  supply a pixel voltage signal to the respective data lines DL 1 ˜DLm whenever the scan pulse is supplied to any one of the gate lines GL 1 ˜GLn. 
         [0057]    Gate pads connected to the gate lines GL 1 ˜GLn are connected to the gate driving circuits  150  through an ACF  124 . That is, the ACF  124  includes conductive balls  124   a  and a thermosetting resin  124   b,  and electrically connects the gate pads and the gate driving circuits  150  by thermocompression. 
         [0058]    Here, the gate driving circuit  150  is formed at a first non-display region  170 , and when the gate driving circuit  150  has a defect, a process for repairing the defective gate driving circuit  150  is required. Thus, the defective gate driving circuit  150 , the gate pads connected to the defective gate driving circuit  150 , and a region of the substrate  110  provided with the defective gate driving circuit  150  and the gate pads connected to the defective gate driving circuit  150  are cut off by scribing using a wheel or the gate links  127  are opened using a laser. Thereafter, a new repair gate driving circuit  160  is formed at a second non-display region  175  opposite to the defective gate driving circuit  150 , and is connected to repair gate pads. The repair gate pads are previously formed on the second non-display region  175  with the gate pads on the first non-display region  170 . 
         [0059]    By the repair gate driving circuit  160  being mounted on the repair pads on the first substrate  110 , as described above, the liquid crystal panel  115  has an increased width compared with the conventional liquid crystal panel. However, since the repair gate pads and the repair gate driving circuit  160  are mounted within a margin range of a backlight unit, the substantial size of a bezel is not increased. Further, the total sum of the widths WA′ and WA″ of the first and second non-display regions  170  and  175  of the thin film transistor substrate  110  exposed by the color filter substrate  112  of the liquid crystal panel  115  is larger than the total sum of the width WI of the gate driving circuit  150  and the width WJ of the repair gate driving circuit  160 . 
         [0060]    The data driving integrated circuits  140  are respectively mounted on a plurality of tape carrier packages (hereinafter, referred to as TCPs)  130 , and are connected between a printed circuit board  120  and the liquid crystal panel  115 . The data driving integrated circuits  140  convert digital data signal into analog pixel voltage signals according to a data control signal, and supply the analog pixel voltage signal to the data lines DL 1 ˜DLm through a plurality of data links  147 . 
         [0061]      FIGS. 8A to 8C  and  FIGS. 9A to 9C  are enlarged cross-sectional views of the region B and the region B′ of  FIG. 7 , illustrating a process for repairing a gate driving circuit. 
         [0062]    As shown in  FIG. 8A , the gate driving circuit  150  to sequentially supply a scan pulse to the gate lines through the plurality of gate links  127  is mounted on the region of the first substrate  110  exposed by the second substrate  112 , i.e., the first non-display region  170 . Here, when the gate driving circuit  150  has a defect, the gate links  127  are opened using a laser, as shown in  FIG. 8B . Thereafter, as shown in  FIG. 8C , a new repair gate driving circuit  160  is mounted on a second non-display region  175  opposite to the defective gate driving circuit  150 , and is connected to repair gate pads  122 , formed in advance, by thermocompression using the ACF  124 . 
         [0063]    Here, the gate pads  125  are connected to one end of each of the gate lines, and the repair gate pads  122  are connected to the other end of each of the gate lines. 
         [0064]      FIGS. 9A to 9C  are enlarged cross-sectional views of the region B and the region B′ of  FIG. 6 , illustrating a process for repairing a gate driving circuit in accordance with another embodiment of the present invention. 
         [0065]    When the gate driving circuit  150  of the finished liquid crystal display has a defect, as shown in  FIG. 9A , the first non-display region  170  of the first substrate  110  provided with the defective gate driving circuit  150  and the gate pads connected to the defective gate driving circuit  150  is cut off by scribing, as shown in  FIG. 9B . Thereafter, a new repair gate driving circuit  160  is mounted on the second non-display region  175  opposite to the defective gate driving circuit  150 , and is connected to the repair gate pads  122 , formed in advance, by thermocompression using the ACF  124 . Here, the gate pads  125  are connected to one end of each of the gate lines, and the repair gate pads  122  are connected to the other end of each of the gate lines. 
         [0066]    By disconnecting or removing the defective gate driving circuit  150  and forming the new repair gate driving circuit  160 , as described above, it is not necessary to apply heat or physical force to the liquid crystal panel  115  to detach the defective gate driving circuit  150  from the liquid crystal panel  115 , and thus it is possible to prevent damage to the gate pads  125 , thereby enhancing the yield of the liquid crystal display. Further, it is not necessary to remove the residual ACF  124  using chemical products, thus solving the complication of the process. 
         [0067]    Although the embodiments of the present invention describe the repairing method of repairing a gate driving circuit, the present invention may be applied to a repairing method of a data driving integrated circuit. 
         [0068]    The liquid crystal display and method repairing the same of the present invention has several effects, as follows. 
         [0069]    Since a defective gate driving circuit is disconnected or removed and a new repair gate driving circuit is formed, it is not necessary to apply heat or physical force to a liquid crystal panel to detach the defective gate driving circuit from the liquid crystal panel, and thus it is possible to prevent damage to gate pads, thereby enhancing the yield of the liquid crystal display. Further, it is not necessary to remove a residual ACF using chemical products, thus solving the complication of the process. 
         [0070]    It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.