Abstract:
The invention relates to an in-plane-switching liquid crystal display for large pixel type scarcely producing defects and easily repairing defects. The in-plane-switching liquid crystal display  10  of the invention comprises a plurality of pads  34 , and each pad connects to a pixel electrode  42 . Besides, each pixel electrode  42  is surrounded by the common electrode  48 . When the pixels enlarge, the defects scarcely occur. Even if the defect occurs, the defect can be easily repaired.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an in-plane-switching liquid crystal display for large pixel type scarcely producing defects and easily repairing defects. 
     2. Description of the Related Art 
     Recently, because liquid crystal display has been utilized in thin type large screen television, liquid crystal displays are becoming large. For the purpose utilizing the liquid crystal display in the television, because many peoples may watch the same television simultaneously, the liquid crystal display must have wide viewing angle compared with the liquid crystal display of personal computer. The in-plane-switching liquid crystal display is one of wide viewing angle liquid crystal display. 
     The in-plane-switching liquid crystal display comprises an array substrate and a color filter substrate corresponding to the array substrate. There is a distance between the array substrate and the color filter substrate. Besides, liquid crystal molecules fill between the array substrate and the color filter substrate.  FIG. 6  shows a conventional array substrate  60  of in-plane-switching liquid crystal display. The array substrate  60  is manufactured according to the following steps (1) to (8). (1) A transparent insulated substrate (glass substrate, etc., is provided. (2) Gate lines  62  and Cs (storage capacity) lines  64  are formed on the glass substrate. (3) A first insulated layer is formed by CVD (chemical vapor deposition) method. (4) TFTs (Thin film transistors)  66 , signal lines  68 , pads  70  and pixel lines  72  are formed on the same layer. The gate electrodes of TFT  66  are a portion of the gate line. The drain electrodes of TFT  66  are connected to the signal lines  68 . The pads  70  are corresponding to the Cs lines  64 , and the insulated layer is between the pads  70  and the Cs lines  64 . The pixel lines  72  are used to connect the pads  70  and the source electrodes. (5) A second insulated layer is formed on the TFT  66 , signal lines  68 , pads  70  and pixel lines  72 . (6) Through holes  74  are formed on the second insulated layer and disposed above the corresponding position of the pads  70 . (7) Pixel electrodes  76  and common electrodes  78  are formed. (8) An alignment layer is formed on the pixel electrodes  76  and the common electrodes  78 . 
     The pixel electrodes  76  connect to the pads  70  via the through hole  74 , and are of stripe shape in the pixel. The number of the pixel electrodes is arbitrary. The common electrodes  78  are of a strip shape, and are formed on the same layer of the pixel electrodes  76 . The pixel electrodes  76  are parallel to the common electrodes  78 . The pixel electrodes  76  and the common electrodes  78  induce electric field parallel to the glass substrate, and the intensity of the electric field affect the alignment of the liquid crystal molecules. 
     Furthermore, the common electrodes  78  are also formed on the peripheral area of the pixel, and a portion of the common electrodes  78  overlap the signal lines  68  so that the common electrodes  78  can shield the electric field inducing by the signal lines  68  to prevent the malfunction of liquid crystal molecules. On the inside area of the pixel, the common electrodes  78  that are corresponding to the pixel electrodes  76  do not overlap the signal lines  68  and disconnected in the middle of the pixel. 
     The resolution of the television is fixed. Therefore, when the liquid crystal display is utilized in the television, the liquid crystal display must match the television. That is, when televisions are becoming large and liquid crystal displays are also becoming large, each pixel is becoming large at the fixed number of pixels. 
     The distance between the pixel electrodes  76  and the common electrodes  78  can be determined by the characteristic of the liquid crystal molecules. When the size of the pixel enlarges, the number of the pixel electrodes  76  and the number of common electrodes  78  in the pixel must increase. Therefore, the number of the disconnected common electrodes  78  increases, and the resistance of the common electrodes  78  will increase so that the interference will lower the quality of the screen in showing the picture. 
     All of the pixel electrodes  76  connect to the pads  70  via the through holes  74  on the second insulated layer. Sometimes, because one through hole  74  is formed defectively, the connection between the pixel electrode  76  and the pad  70  will be bad. Besides, when the first insulated layer has a broken hole during forming the Cs line  64 , the voltage potential of the pixel electrode  76  will be the same as that of the Cs line  64 . It cannot apply the predetermined voltage to all the pixel electrodes  76  of the pixel, and the whole pixel becomes defective. 
     As shown in  FIG. 7 , there are a plurality of through holes  74  on the second insulated layer and above the pads  70 , and a plurality of pixel electrodes  76  connect to the pad  70  via the through holes  75  respectively to form the array substrate  61  of the in-plane-switching liquid crystal display. Even if one of the through holes  75  has defect, only the pixel electrode  76  connected to the defected through hole  74  becomes bad and the other pixel electrodes  76  can still work normally. However, when one of the pixel electrodes  76  change into high resistance characteristic, the angle of the AC current with square waveform flown to the pixel electrode  76  may become a circular shape and induce DC current component. After some time, the DC current may flow to the adjacent pixel electrode  76  by the alignment layer. After the liquid crystal display is used for a few hours, the voltage potentials of the two pixel electrodes  76  are the same so that the whole pixel cannot be switched. 
     Given the above, because the size of the pixel increases, various problems can easily occur. When a problem occurs, it will lower the quality of the liquid crystal display. Furthermore, the problem causes bad manufacturing yield of the liquid crystal display. 
     Prior art 1 discloses a liquid crystal display having large open ratio by decreasing a leakage electric field form the data line. A portion of the common electrode overlaps on the data line to prevent the leakage electric field. However, prior art 1 only discloses that the leakage electric field is shielded to enlarge the open ratio, and does not disclose that the defect caused by the large type pixel can be repaired. Prior art 1 is Japan Patent Publication No. 10-186407 (as shown in  FIG. 1 ). 
     SUMMARY OF THE INVENTION 
     The purpose of the present invention is to provide an in-plane-switching liquid crystal display for large pixel type scarcely producing defects and easily repairing defects. 
     The in-plane-switching liquid crystal display of the invention comprises: a transparent insulated substrate; a plurality of gate lines formed on the transparent insulated substrate and being parallel to each other; a plurality of Cs lines formed between the gate lines; an insulated layer formed on the transparent insulated substrate and covering the gate lines and the Cs lines; a transistor formed on the insulated layer and having a drain electrode, a source electrode, and a gate electrode being part of the gate line; a signal line being perpendicular to the gate lines with said insulated layer therebetween, and connected to the drain electrode; a pixel line formed on the insulated layer in a direction the same as the gate lines and connected to the source electrode; a plurality of pads corresponding to the Cs line with said insulated layer therebetween; a resin layer formed on the insulated layer and covering the transistor, the signal line, the pixel line and the pads; a plurality of first through holes formed in the resin layer that is formed on the pads; a plurality of second through holes formed in the resin layer that is formed on the pixel line, wherein the number of the second through holes is equal to that of the first through holes; and a plurality of pixel electrodes extending the second through holes, the resin layer and the first through holes to connected the signal lines and the pads. The in-plane-switching liquid crystal display of the invention has a plurality of pads respectively connected to the pixel electrodes. 
     The in-plane-switching liquid crystal display of the invention further comprises: a first common electrode and a second common electrode, the first common electrode formed on the resin layer and overlapped the corresponding position of the gate lines and the signal line; the second common electrode formed on the resin layer, connected to the first common electrode, and the first common electrode and the second common electrode surrounding the pixel electrode. Because the first common electrode and the second common electrode surround the pixel electrode, the second common electrode is not disconnected. 
     The pixel electrodes are formed on the surface of the resin layer, and extend in a reverse direction extending from the first through hole to the second through hole. 
     The in-plane-switching liquid crystal display of the invention has a plurality of pads respectively connected to the pixel electrodes. When one gate line or pad is bad, the gate line is cut or the pad and the Cs line are welded. Therefore, the invention does not repair the whole pixel, but can repair per a unit of each sub-pixel. 
     The first common electrode and the second common electrode surround the pixel electrode, and the second common electrode is not disconnected in the middle section. Accordingly, the invention can prevent the interference caused by high resistance of the common electrode. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a front view of the array substrate of the in-plane-switching liquid crystal display, according to the invention. 
         FIGS. 2   a – 2   b  illustrate section views of the array substrate of the in-plane-switching liquid crystal display, wherein  FIG. 2   a  is a section view from X–X′ section in  FIG. 1 ,  FIG. 2   b  is a section view from Y–Y′ section in  FIG. 1 . 
         FIG. 3  shows Gate line and Cs line on the glass substrate. 
         FIG. 4  shows signal line, TFT, pixel line and pad on the insulated layer. 
         FIG. 5  illustrates a section view of the in-plane-switching liquid crystal display. 
         FIG. 6  illustrates a front view of the array substrate of the conventional in-plane-switching liquid crystal display. 
         FIG. 7  illustrates a front view of the array substrate having a plurality of pads, according to the conventional in-plane-switching liquid crystal display. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The figures illustrate the embodiment of the in-plane-switching liquid crystal display according to this invention. Referring to  FIG. 5 , an in-plane-switching liquid crystal display  10  comprises an array substrate  12  and a color filter substrate  14  corresponding to the array substrate  12 . There is a distance between the array substrate  12  and the color filter substrate  14 . The sealant  18  is used to seal liquid crystal molecules  16  between the array substrate  12  and the color filter substrate  14 . The liquid crystal molecules  16  are driven to show picture. The array substrate  12  having pixel electrodes to drive the liquid crystal molecules  16  is described as follows. 
     (The First Embodiment) 
     As shown in  FIGS. 1 ,  2   a  and  2   b , the array substrate  12  has a plurality of layers on the glass substrate  20 , and has the patterned lines in the longitudinal direction and the horizontal direction. The glass substrate  20  can be any other transparent insulated substrate. Besides, the circuit pattern that comprises gate lines  22 , shown in  FIG. 1 , continues in a longitudinal direction or a horizontal direction. 
     As shown in  FIGS. 2   a ,  2   b  and  3 , there is a plurality of gate lines  22  formed on the glass substrate  20 . The gate lines  22  are parallel to each other. For example, if the glass substrate  20  is a rectangle with a long width, the gate lines  22  are formed in a transverse direction. Furthermore, the Cs lines are formed between the gate lines  22 , and are parallel to the gate lines  22 . 
     An insulated layer  26  is formed on the glass substrate  20 , and covers the gate lines  22  and the Cs lines  24 . The insulated layer  26  is formed by utilizing the CVD technique. The material of the insulated layer may be SiO x  or SiN x . 
     As shown in  FIGS. 2   a ,  2   b  and  4 , a plurality of signal lines  30  are formed on the insulated layer, and are parallel to each other. The signal lines  30  cross the gate lines  22  in space, and the signal lines  30  are above the gate lines  22 . The insulated layer  26  is between the signal lines  30  and the gate lines  22 . The signal lines  30  are perpendicular to the gate lines  22 . The signal lines  30  and the gate lines  22  are on different layers, and are formed as a matrix. In a front view, an area surrounded by the signal lines  30  and the gate lines  22  is a pixel. Therefore, the in-plane-switching liquid crystal display  10  has a plurality of pixels. The signal lines are made of aluminum, etc. Besides, although the signal lines  30  are shown to be of a mountain shape (“&lt;” shape) in the figure, the signal lines  30  are taken as straight line for convenience. 
     TFT  28  is disposed at the intersection between the gate lines  22  and the signal lines  30 . TFT  28  is the same as the conventional TFT, and has a drain electrode, a source electrode and a gate electrode to be a switch element. The TFT  28  is set above the gate lines  22 , and a portion of the gate lines  22  is taken as the gate electrode. The signal lines  30  connect to the drain electrode. The gate line  22  is applied with voltage to turn on the TFT  28 . As the TFT  28  is turned on, the signal line  30  is applied a predetermined voltage, and the predetermined voltage is applied to the pixel electrode so as to drive the liquid crystal molecules  16 . 
     In the pixel, a pixel line  32  is formed on the insulated layer  26 . The pixel line  32  has a terminal connected to the source electrode. The pixel line  32  is formed in the same direction as the gate lines  22 , but the pixel line  32  does not overlap the gate lines  22 . When the pixel line  32  overlaps the gate lines  22 , the common electrode will connect to the pixel electrode on the same layer. The pixel line  32  is a path for providing the predetermined voltage from the source electrode of the TFT  28  to the pixel electrode. 
     In the pixel, a plurality of pads  34  are formed on the insulated layer  26  that is above the Cs line  24 . The Cs line  24  corresponds to the pads  34 , and the insulated layer  26  is between the Cs line  24  and the pads  26  to form a storage capacity. The storage capacity is used to be the capacitor of holding the voltage of the pixel. The number of the pads  34  is the same as the number of the pixel electrodes. The conventional in-plane-switching liquid crystal display utilizes one pad connected to all pixel electrodes. However, the in-plane-switching liquid crystal display of the invention utilizes one pad connected to one pixel electrode. 
     As shown in  FIGS. 2   a – 2   b , a resin layer (polymer)  36  is formed on the insulated layer  26  and covers the signal line  30 , the TFT  28 , the pixel line  32  and the pads  34 . By disposing the resin layer  36 , the common electrode overlaps the signal line  30  so as to raise the open ratio of the liquid crystal display. 
     A plurality of first through holes  38  are formed in a portion of the resin layer  36  that is formed on the pads  34  respectively. Furthermore, a plurality of second through holes  40  are formed in the resin layer  36  that is formed on the pixel line  32 . The number of the second through holes  40  is equal to the number of the first through holes  38 . 
     As shown in  FIG. 1 , the pixel electrodes  42  are used to connect the pixel line  32  and pads  34 . According to the arrangement of the second through holes  40 , the surface of the resin layer  36  and the first through holes  38 , the pixel line  32  connects to the pads  34  by the pixel electrodes  42 . The pixel electrodes  42  are formed on the surface of the resin layer  36 , and extend in a reverse direction extending from the first through holes  38  to the second through holes  40 . The pixel electrodes  42  are made of ITO (indium tin oxide). 
     On the surface of the resin layer  36 , a first common electrode  44  is formed and overlaps the corresponding position of the gate lines  22  and the signal line  30 . A second common electrode  46 , which is connected to the first common electrode  44 , is formed, and the first common electrode  44  and the second common electrode  46  surround the pixel electrode  42 . The first common electrode  44  and the second common electrode  46  are formed as a common electrode  48 . The pixel electrodes  42  are parallel to the common electrode  48  on the resin layer  36 . In the conventional in-plane-switching liquid crystal display, the common electrodes are disconnected inside the pixel area. However, according to the in-plane-switching liquid crystal display of the invention, the common electrode  48  is not separated but is integrated to one line inside the pixel area. 
     As shown in  FIG. 1 , the common electrode  48  surrounds the pixel electrodes  42 . An area surrounded by the common electrode  48  is a sub-pixel having a pixel electrode  42 . The pixel has a plurality of sub-pixels, for example, there are three sub-pixels in the pixel of  FIG. 1 . 
     An alignment layer  50  is formed on the resin layer  36  having pixel electrode  42  and the common electrode  48 . The above structures are used to form the array substrate  12  of the in-plane-switching liquid crystal display of the invention. The in-plane-switching liquid crystal display  10  of the invention utilizes the deposition method, for example CVD method, to deposit the material and the conventional sputter technique. 
     As given above, according to the invention, each pixel electrode  42  connects to a pad  34 . When one pad  34  and the Cs line  24  are short-circuited, the whole pixel becomes a bright point. Therefore, laser can cut the pixel electrode  42  connecting short-circuited pad  34 . The cut position is near the second through hole  40 . Only the sub-pixel having the cut pixel electrode  42  will become a dark point, and the other sub-pixels have no influence. That is, the in-plane-switching liquid crystal display of the invention can be repaired per a unit of each sub-pixel. 
     On the contrary, when the pixel electrode  42  is cut in manufacturing the in-plane-switching liquid crystal display, it uses laser to weld the pad  34  of the pixel electrode  42  and the Cs line  24 . The situation will be the same as the above case, and the sub-pixel can be repaired. 
     Furthermore, by cutting the defective portion of the pixel electrode  42 , the potential of the normal portion of the pixel electrode  42  will decrease the storage capacity to produce DC current. The sub-pixel having DC current can raise the predetermined voltage to compensate the brightness due to the dark point of the repaired sub-pixel. 
     Inside the pixel area, the common electrode  48  surrounds a pixel electrode  42 . That is, the pads  34  and the first through holes  38  do not obstruct the common electrode  48 , and the common electrode  48  does not interrupt in the middle section. Even if the pixel enlarges, the resistance of the common electrode  48  does not become high, and the crosstalk described in the prior art scarcely occurs. 
     Although the invention has been described with respect to the embodiment thereof, it should be realized that the invention is not limited by the embodiment. Additionally, the improvements, various changes and modifications may be made therein by the one skilled in the art without departing from the spirit and scope of the invention.