Abstract:
A method of repairing a defect in a liquid crystal display panel is provided. The method comprises: providing an array substrate, a plurality of pixel regions over the array substrate, and at least one of the pixel regions comprising a transistor, a pixel electrode, a storage capacitor having an upper electrode and a bottom electrode, a defect positioned in the storage capacitor; performing a cutting process to divide the pixel electrode into a first portion and a second portion not connecting to each other, wherein said first portion of said pixel electrode is corresponding to the storage capacitor having said defect; and electrically connecting the second portion of the pixel electrode to one of the scan lines.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a liquid crystal display panel and repairing method thereof, and more particularly, to a method able to repair bright dot defect or other pixel defect problem in an array substrate of a liquid crystal display panel. 
         [0003]    2. Description of the Prior Art 
         [0004]    A conventional liquid crystal display (LCD) panel normally includes a thin film transistor array substrate (array substrate), a color filter substrate (CF substrate) having a common electrode thereon disposed over the array substrate, and a liquid crystal layer interposed there between. Please refer to  FIGS. 1-2 .  FIGS. 1-2  are schematic diagrams illustrating an array substrate of a conventional LCD panel, where  FIG. 1  is a top view of a portion of the array substrate, and  FIG. 2  is a cross-sectional view of the array substrate shown in  FIG. 1  along the line PP′. As shown in  FIG. 1-2 , the conventional array substrate  10  includes a plurality of scan lines  12 , a plurality of data lines  14 , a plurality of pixel regions  16  defined by the scan lines  12  and the data lines  14 , and a plurality of common lines  20  arranged in alternately with the scan lines  12 . Each pixel region  16  has at least a thin film transistor  18  and a pixel electrode  22  corresponding to the thin film transistor  18 . The pixel electrode  22  is disposed facing the common electrode of the CF substrate (not shown), in which the liquid crystal is interposed between the pixel electrode  22  and the common electrode. In addition, the overlapping region of the pixel electrode  22  and the common line  20  form a storage capacitor on common line (Cst on common). Each thin film transistor  18  serves as a switch in each pixel region  16 . In the displaying operation, the common electrode of the CF substrate is usually receiving a common voltage. Following, a particular pixel region is selected through a corresponding scan line  12  receiving a scan signal and then the pixel electrode  22  of the pixel region  16  is written into a pixel voltage via a corresponding data line  14  receiving a data signal. Sequentially, the voltage difference between the pixel electrode  16  and common electrode makes the liquid crystal rotate to a predetermined direction to control the illumination out from the CF substrate and then a display is achieved. 
         [0005]    The storage capacitor assists the pixel region  16  to operate normally, however, any processing defects or particles occurring in the storage capacitor may lead to malfunction of the storage capacitor. For instance, if a particle  24  unexpectedly falls into the storage capacitor region, the particle  24  may lead to a short-circuitry between the pixel electrode  22  and the common line  20 . In such a case, the voltage of the pixel electrode  22  will be identical to the voltage of the common line  20 . Since the common line  20  and the common electrode of the CF substrate usually have the same voltage, the voltage of the pixel electrode  22  and the voltage of the common electrode of the CF substrate will be identical. This fails the pixel region  16 . Furthermore, if the LCD is a normally white (NW) type LCD, back light will pass through the liquid crystal layer and cause a bright dot defect because no voltage difference exists between the pixel electrode  22  and the common electrode. In addition to the particles, other defects such as a dielectric layer loss or a common line loss that makes the pixel electrode  22  and the common line  20  short-circuited will also cause the bright dot defect in an NW type LCD. 
         [0006]    Accordingly, there is a need to provide a simply and effective repairing method of the pixel to solve the display problems due to particles or other defects. 
       SUMMARY OF THE INVENTION 
       [0007]    It is an objective of the present invention to provide a liquid crystal display and repairing method thereof to solve the bright dot defect and other pixel defect problem. 
         [0008]    It is another objective of the present invention to provide a liquid crystal display and repairing method which is easy to be implemented in the manufacture process. 
         [0009]    According to an embodiment of the present invention, a method of repairing a defect in a liquid crystal display panel is provided. The method comprises: providing an array substrate comprising a plurality of scan lines and data lines disposed over the array substrate and together defining a plurality of pixel regions, and at least one of the pixel regions comprising a transistor, a pixel electrode electrically connected to a source/drain electrode of the transistor, a storage capacitor having an upper electrode and a bottom electrode, wherein the pixel electrode is electrically coupled to the storage capacitor, and there is a defect positioned in the storage capacitor; subsequently, performing a cutting process to divide the pixel electrode into a first portion and a second portion not connecting to each other, wherein the first portion of the pixel electrode is corresponding to the storage capacitor having the defect; and then electrically connecting the second portion of the pixel electrode to one of the scan lines. 
         [0010]    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 
         [0011]      FIGS. 1-2  are schematic diagrams illustrating a conventional array substrate. 
           [0012]      FIGS. 3-8  are schematic diagrams illustrating a method of repairing a defect in an array substrate of an LCD panel in accordance with the first embodiment of the present invention. 
           [0013]      FIG. 9  is a schematic diagram illustrating a method of repairing a defect in an array substrate of an LCD panel in accordance with the second embodiment of the present invention. 
           [0014]      FIG. 10  is a schematic diagram illustrating a method of repairing a defect in an array substrate of an LCD panel in accordance with the third embodiment of the present invention. 
           [0015]      FIG. 11  is a schematic diagram illustrating a method of repairing a defect in an array substrate of an LCD panel in accordance with the fourth embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Please refer to  FIGS. 3-8 .  FIGS. 3-8  are schematic diagrams illustrating a method of repairing a defect in an array substrate of an LCD panel in accordance with the first embodiment of the present invention.  FIGS. 3 ,  5  and  7  are top views of the array substrate,  FIG. 4  including  FIG. 4   a  and  FIG. 4   b  are cross-sectional views of the array substrate shown in  FIG. 3  along a line AA′,  FIG. 6  is a cross-sectional view of the array substrate shown in  FIG. 5  along a line BB′, and  FIG. 8  is a cross-sectional view of the array substrate shown in  FIG. 7  along a line CC′. As shown in  FIG. 3  and  FIG. 4 , an array substrate  30  is provided. The array substrate  30  includes a plurality of scan lines  32  arranged in parallel, a plurality of data lines  34  arranged perpendicular to the scan lines  32  disposed over the array substrate  30 , a plurality of pixel regions  36  defined by the scan lines  32  and the data lines  34 , a plurality of thin film transistors  38  disposed in each pixel region  36 , and a plurality of common lines  40  arranged in alternately with the scan lines  32 . The common lines  40  and the scan lines  32  are formed by the same lithography process, and the common lines  40  and the scan lines  32  are normally referred to as metal 1 (M1). The data lines  34  are formed subsequent to the scan lines  32 , and the data lines  34  are therefore usually referred to as metal 2 (M2). The array substrate  30  further includes a plurality of pixel electrodes  42  disposed in each pixel region  36 , and electrically connected to the source/drain of each thin film transistor  38  via a through hole D. As  FIG. 4  shows, the array substrate  30  also has an intermediary layer including a dielectric layer  44  and a passivation layer  46  disposed between the common lines  40  and the pixel electrodes  42 . It is noted that the array substrate  30  further includes a connecting bridge  34   a  (as shown in  FIG. 3  and  FIG. 4 ) in each pixel region  36  in case of repairing requirement. The connecting bridge  34   a  is formed in the M2 layer, and the function of the connecting bridge  34   a  will be detailed in following description. 
         [0017]    This embodiment illustrates a Cst on common type LCD, and thus a portion of each pixel electrode  42  overlaps each of the common line  40  in each pixel region  36  to form a storage capacitor region. In the storage capacitor region, the common line  40  and the pixel electrode  42  respectively serve as a bottom electrode and an upper electrode of the storage capacitor, and the dielectric layer  44  and the passivation layer  46  serve as a capacitor dielectric layer so as to from a storage capacitor in each pixel region  36 . 
         [0018]    However, in the manufacture process of the array substrate, due to unexpected reasons, defects may occur in the storage capacitor region. As shown in  FIG. 3 ,  FIG. 4  and  FIG. 5 , if a defect  48 , such as a particle defect (as shown in  FIG. 4   a ) or a loss of portion of the dielectric layer  44  and a loss of portion of the passivation layer  46  (as shown in  FIG. 4   b ), unexpectedly occurs to the storage capacitor region in one of the pixel region  36 , the pixel region  36  will fail. In this embodiment, whether the defect  48  is the particle defect (shown in  FIG. 4   a ) or the loss defect (shown in  FIG. 4   b ), the pixel electrode  42  and the common line  40  are electrically connected, thereby forming a short-circuitry. But it is noted that, the method of the present invention which will be described as following can be not only applied to the situation that the defect  48  must make pixel electrode  42  and common line  40  be short-circuited but also the situation that the defect  48  just makes the storage capacitor malfunction or work non-normally. 
         [0019]    Taking the loss defect (shown in  FIG. 4   b ) for example, when the defect  48  is detected, the pixel region  36  having the defect  48  needs to be repaired. As shown in  FIGS. 5 and 6 , a cutting process is performed along and near the both two sides of the common line (as the cutting lines  47  shown in  FIG. 5  and  FIG. 6 ) to divide the pixel electrode  42  having the defect  48  into a first portion  421  substantially corresponding to the common line  40 , a second portion  422 , and a third portion  423 , not connecting to each other. In this embodiment, the cutting process is a laser cutting process, but not limited. In addition, the cutting depth is not limited to the pixel electrode  42 , and can be deeper, even can reach the upper surface of the array substrate  30  (as shown in the  FIG. 6 ). To ensure the electrical disconnection of the pixel electrode  42  and the common line  40 , the passivation layer  46  or the dielectric layer  44  can be cut along with the pixel electrode  42  in the cutting process. It is appreciated that the cutting line is along both sides of the common line  40 , but the cutting line should not be too close to the sides of the common line  40  for preventing the electrical connection between the pixel electrode  42  and the common line  40  through the cutting line. After the cutting process, the pixel electrode  42  is divided into three portions, and the first portion  421  having the defect  48  is isolated from the second portion  422  and the third portion  423 . 
         [0020]    Sequentially, as shown in  FIGS. 7 and 8 , the second portion  422  of the pixel electrode  42  is electrically connected to the gate electrode  35  of the scan lines  32  through welding the source/drain electrode  37  and the gate electrode  35  together at the point E, and the third portion  423  of the pixel electrode  42  is electrically connected to another scan lines  32  through respectively welding the connecting bridge  34   a  and the pixel electrode  42  together at the point F as well as welding the connecting bridge  34   a  and the another gate line  32  together at the point G. In this embodiment, the electrical connection between the second portion  422  and the gate electrode  35 , and between the third portion  423  and another scan line  32  is achieved by laser welding, but not limited. As shown in  FIGS. 7 and 8 , the source/drain  37  which electrically contacts with the pixel electrode  42  via the through hole D overlaps the gate electrode  35  of the thin film transistor  38 , and thus the source/drain  37  and the gate electrode  35  can be directly welded as shown in  FIG. 8 . On the other hand, the third portion  423  and another scan line  32  are not overlapping. In such a case, the connecting bridge  34   a , which is part of the M2 layer, and interposed between the third portion  423  and the scan line  32 , serves as a connecting media between the third portion  423  and the scan line  32  as shown in  FIG. 8 . Therefore, the third portion  423  can be connected to the scan line  32  by welding through the connecting bridge  34   a . Since the second portion  422  and the third portion  423  are respectively connected to the scan lines  32  and are respectively provided a voltage of the scan line  32 , voltage differences will respectively exist between the second portion  422  and the common electrode of the CF substrate (not shown) as well as between the third portion  423  and the common electrode. Consequently, the bright dot defect is eliminated while displaying in case the LCD is NW type. It is appreciated that although there is no voltage difference between the first portion  421  and the common electrode, back light will be shaded by the common line  40 . Thus, bright dot defect in the first portion  421  will also be eliminated. 
         [0021]    Please refer to  FIG. 9 .  FIG. 9  is a schematic diagram illustrating a method of repairing a defect in an array substrate of an LCD panel in accordance with the second embodiment of the present invention. This embodiment also illustrates a Cst on common type LCD similar to the first embodiment, thus like elements are denoted by like numerals, and are not detailed redundantly. As shown in  FIG. 9 , an array substrate  30  is provided, and a defect  48  unexpectedly appears. Different from the first embodiment is that the defect  48  in the second embodiment is a common line loss or breakage. Usually, a common line loss, as shown in  FIG. 9 , makes the common line break and have two broken side portions, the first broken side portion  401  and the second broken side portion  402 . The common line loss or breakage not only leads to failure of the storage capacitor of the pixel region  36  having the defect  48 , but also failure of all the pixel regions  36  using the same common line  40 . 
         [0022]    Then, a cutting process is then performed to divide the pixel electrode  42  having the defect  48  into a first portion  421  substantially corresponding to the common line  40  and including the defect  48 , a second portion  422 , and a third portion  423  not connecting to each other. The first portion  421  also has two portions corresponding to and overlapping the two broken side portions  401  and  402  of the common line  40 . Subsequently, the second portion  422  is electrically connected to the scan line  32 , and the third portion  423  is electrically connected to another scan line  32  through the connecting bridge  34   a  by laser welding, for instance. In addition, the first portion  421  of the pixel electrode  42  is electrically connected to the broken common line  40  through respectively welding the broken common line  40  and the first portion  421  together at the point H of the first broken side portion  401  and at the point I of the second broken side portion  402 . 
         [0023]    In this embodiment, the first portion  421  of the pixel electrode  42  is isolated from the second portion  422  and the third portion  423  in the cutting process, and electrically connected to the common line  40  through the laser welding process. The electrical connection of the first portion  421  and the common line  40  enables the first portion  421  to serve as a substitute circuit. Accordingly, the bright dot defect is eliminated by electrically connecting the second portion  422  and the third portion  423  to the corresponding scan lines  32 , and the common line loss is repaired by electrically connecting the broken common line  40  with the first portion  421 . 
         [0024]    Please refer to  FIG. 10 .  FIG. 10  is a schematic diagram illustrating a method of repairing a defect in an array substrate of an LCD panel in accordance with the third embodiment of the present invention. As shown in  FIG. 10 , the array substrate  50  includes a plurality of scan lines  52  arranged in parallel, a plurality of data lines  54  arranged perpendicular to the scan lines  52  disposed over the array substrate  50 , a plurality of pixel regions  56  defined by the scan lines  52  and the data lines  54 , a plurality of thin film transistors  58  disposed in each pixel region  56 , and a plurality of pixel electrodes  62  disposed in each pixel region  56  and electrically connected to the source/drain of each thin film transistor  58 . Different from the above embodiments, this embodiment illustrates a Cst on gate type LCD, and thus an auxiliary electrode  64  which is made of M2 and electrically contacts the pixel electrode  62  via a through hole J and overlaps the scan line  52 . 
         [0025]    The auxiliary electrode  64  disposed between the pixel electrode  62  and the scan line  52  in each pixel region  56  and is electrically connected to the corresponding pixel electrode  62 . Therefore, the pixel electrode  62  and the auxiliary electrode  64  serve as an upper electrode of the storage capacitor, and a portion of the scan line  52  serves as a bottom electrode. 
         [0026]    In a normal case, the auxiliary electrode  64  is not electrically connected to the data line  54 . However, due to some unexpected factors in the manufacture process of array substrate, the auxiliary electrode  64  and the data line  54  may be short-circuited, thereby forming a defect  66  known as M2 residue as shown in  FIG. 10 . Since the auxiliary electrode  64  is electrically connected to the pixel electrode  62 , the short-circuitry between the auxiliary electrode  64  and the data line  54  will cause failure of the pixel region  56 . 
         [0027]    In this embodiment, a cutting process e.g. a laser cutting process is performed to divide the pixel electrode  62  into a first portion  621  having the defect  66 , and a second portion  622  not connecting to each other. Subsequently, the second portion  622  is electrically connected to the scan line  52  by laser welding at point K, for instance. Since the first portion  621  having the defect  66  is isolated from the second portion  622 , and the second portion  622  is electrically connected to the scan line  52 , a voltage difference will exist between the second portion  622  of the pixel electrode  62  and the common electrode of the CF substrate (not shown) and the effect of the defect  66  can be eliminated. 
         [0028]    Please refer to  FIG. 11 .  FIG. 11  is a schematic diagram illustrating a method of repairing a defect in an array substrate of an LCD panel in accordance with the fourth embodiment of the present invention. This embodiment also illustrates a Cst on common type LCD similar to the first embodiment, thus like elements are denoted by like numerals, and are not detailed redundantly. As shown in  FIG. 11 , an array substrate  30  is provided. The array substrate  30  includes a defect  48  in the storage capacitor region. For instance, as the previous mentioned, the defect  48  may be a dielectric layer loss or a particle that causes a short-circuitry between the pixel electrode  42  and the common line  40 . It is appreciated that the array substrate  30  of this embodiment does not include a connecting bridge disposed in each pixel region  36 . 
         [0029]    Subsequently, a cutting process is performed to divide the pixel electrode  42  having the defect  48  into a first portion  421  including the defect  48 , and a second portion  422  which is substantially like a U-shaped structure, not connecting to each other. In the cutting process, please note that the common line  40  is also cut so that one section of the common line  40  having the defect  48  is isolated from other sections of the common line  40 . 
         [0030]    Following that, the first portion  421  of the pixel electrode  42  is electrically connected to one of the scan lines  32  through welding at a point L, and the second portion  422  of the pixel electrode  42  is electrically connected to the common line  40  corresponding to the second portion  422  through respectively welding at both two sides of the second portion  422  corresponding to the two terminals of the U-shaped structure, such as at the points M and N. In this embodiment, the first portion  421  of the pixel electrode  42 , which is isolated from the second portion  422 , is electrically connected to the scan line  32  to eliminate the bright dot defect. On the other hand, the second portion  422  is electrically connected to the common line  40  and serves as a substitute circuit of the section of the common line  40  having the defect  48 . Consequently, the pixel regions  36  using the same common line  40  can operate normally. 
         [0031]    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.