Abstract:
A method for repairing light spots in an LCD. An LCD is provided, comprising an array plate, a bottom polarized plate thereunder, a color filter plate over the array plate and a top polarized plate over the color filter plate. The LCD is inspected to locate light spots, and shields are formed on the top polarized plate to cover the light spots, thereby repairing the light spots.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a method for fabricating a liquid crystal display, and more particularly, to a method for repairing light spots therein.  
         [0003]     2. Description of the Related Art  
         [0004]     Liquid crystal displays have become widely used, with a working principle based on alignment condition of liquid crystal molecules changing by application of an electrical field to change the path of light passing therethrough. One LCD type is passive matrix and the other active matrix. Color of each pixel is determined by current of an end transistor in the row and the start transistor in the column. Advantages of passive matrix LCD are low cost and small size, however, slow scanning speed and small viewing angle are drawbacks. In active matrix LCD, each pixel is controlled by a transistor, and scanning is fast.  
         [0005]     The active matrix LCD includes more than million transistors and display units, each display unit consisting of three sub display units(R, G, B).  
         [0006]     Dot defects are formed during process of the active matrix LCD, creating light or dark defects. LCD units having fewer than five dot defects are considered as A class, however, because light defects, light defects are more noticeable to users, they are repaired into dark defects.  
         [0007]     There are three major causes of light spot defects. As shown in the point C of  FIG. 1 , the first cause is the broken circuit between the TFT  12  and the pixel electrode  10 . The second cause is the broken channel D of the TFT  12 , such that the TFT cannot be operated. The third cause is the short circuit E between the pixel electrode  10  and the signal line SL, as shown in the point E of  FIG. 1   
         [0008]     Light spots resulting from the three situations described can be repaired by cutting the line between pixel electrode  10  and the signal line SL. The light spot in the first and second cases can be repaired by connecting the line between pixel electrode  10  and the gate line GL, however, both present low repair yield.  
         [0009]     As well, laser repair presents limitations, such as reduced voltage of the gate line. Light spot defects from scratching of the polarized plate, scratches of film on glass or defects on the Black Matrix BM of the color filter substrate cannot be repaired by laser repair, wherein defects on BM of the color filter substrate may be generated during process of the color filter, ESD punching through the film or scratching the color filter substrate surface. As well, defects in BM may also be generated during LCD process.  
         [0010]     Japanese publication numbers 5-2160 and 4-301615, and U.S. Pat. Nos. 5,546,206 and 6,097,462 disclose methods of repairing light spot defects by laser, however, the low repair yield problem remains unsolved.  
       SUMMARY OF THE INVENTION  
       [0011]     An object of the present invention is to provide a method of repairing light spot defect not repairable by laser, such that repair yield is increased.  
         [0012]     To achieve the above objects, the present invention provides a method for repairing light spots in an LCD. A display, comprising a light source, a bottom polarized plate over the light source, an array substrate over the bottom polarized plate, a color filter substrate over the array substrate and a top polarized plate over the color filter substrate is provided. The LCD is inspected to locate light spots. A plurality of shields are formed to block light paths from the light source through the light spots.  
         [0013]     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The present invention can be more fully understood by reading the subsequent detailed description in conjunction with the examples and references made to the accompanying drawings, wherein:  
         [0015]      FIG. 1  is a plane view of an array showing a pixel containing light spot defects.  
         [0016]      FIG. 2  is a cross section of the LCD.  
         [0017]      FIG. 3  is a circuit diagram of the LCD.  
         [0018]      FIG. 4  is a plane view of the array.  
         [0019]      FIG. 5  is a flowchart of the light spot repair of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]     The present invention will be described in detail with reference to the accompany drawings.  
       FIRST EMBODIMENT  
       [0021]     In  FIG. 2 , a liquid crystal display  40  includes an array substrate  20 , an opposite color filter substrate  34 , a liquid crystal layer  28  therein, a top polarized plate  38  on the color filter substrate  34  and the bottom polarized plate  36  below the array substrate  20 . As shown in  FIG. 3 , signal lines (SL 1 , SL 2  . . . SLn) and gate lines (GL 1 , GL 2  . . . GLm) are formed on the substrate arranged in a matrix. A pixel is defined by neighboring gate lines and signal lines. A TFT device is disposed on each pixel, each (T 11 , T 12 , T 21 , . . . , Tnm) connected respectively to a pixel electrode  402 . The pixel electrode comprises a patterned transparent conductive film, such as an ITO film (Indium tin oxide film).  
         [0022]     As shown in  FIG. 2 , an alignment film  26  is formed on the substrate in one direction. The array substrate  20  is covered with a common electrode  32 , a patterned transparent and conductive film, such as ITO. As well, an alignment film  30  is formed on the common electrode  32 , in a direction perpendicular to that of the alignment film  26 . Liquid crystal  28  is injected into the gap between the alignment film  30  on the color filter substrate  34  and the alignment film  26  on the array substrate  20 . A top polarized plate  38  and a bottom polarized plate  36  are respectively disposed outside the color filter substrate  34  and array substrate  20 . Light absorption axes of top polarized plate  38  and bottom polarized plate  36  are perpendicular.  
         [0023]     The LCD is illuminated with a light  42  to locate light spots therein, such as at the broken circuits between TFT  12  and pixel electrode  10 , broken circuits of the tunnel in TFT  12 , particles on color filter substrate  34  or array substrate  20 , scratches on polarized plates  36  and  38 , or on the BM (Black Matrix).  
         [0024]     Referring to  FIG. 2 , a shield  44  is formed on the top polarized plate  38  according to the positions detected, repairing the light spots. The shield  44  may be formed by opaque organic or inorganic coating, such as ink or dye. In  FIG. 4 , the shield must be larger than the square with the short side  404  of the pixel  402 , but a maximum of half the area of the neighboring pixel  406 , and preferably one third of the area of the neighboring pixel  406  remains uncovered.  
         [0025]     The shield  44  is removable by solvent, such as IPA, to be reworkable. Referring to  FIG. 5 , the LCD is inspected by the light inspecting system (S 500 ), and considered acceptable, if no light spots are found (S 510 ), or unacceptable (S 502 ). The LCD is repaired by forming shields to cover light spots (S 504 ) and is then rechecked (S 506 ). Repair is complete (S 508 ) if no light spots are found after repair, however, if light spots still exist, repeat repair is required (S 502 ).  
         [0026]     As shown in  FIG. 2 , light  42  can pass the polarized plate  36 , being polarized in one direction if the common electrode  32  and the pixel electrode  22  are powered off. Light  42  passes TFT substrate  20 , the pixel electrode  22 , and the liquid crystal layer  28 , with the direction of light  42  being polarized 90° by the effect of the liquid crystal molecule. Because light  42 , after polarization, is the same direction as plate  38 , light can pass the LCD, resulting in display.  
       SECOND EMBODIMENT  
       [0027]     In  FIG. 2 , LCD  40  includes an array substrate  20 , a color filter substrate  34 , a liquid crystal layer  28  therein, a top polarized plate  38  on the color filter substrate and a bottom polarized plate  36  below the array substrate  20 .  
         [0028]     The LCD is illuminated with light  42  to locate light spots therein, such as at broken circuits between TFT  12  and pixel electrode  10 , broken circuits in the tunnel in TFT  12 , particles on the color filter substrate  34  or the array substrate  20 , or scratches in polarized plate  36  or  38  in the BM (Black Matrix).  
         [0029]     Referring to  FIG. 2 , a shield  44   a  is formed on the bottom of the bottom polarized plate  36  according to the positions detected, thereby repairing the light spots. The shield  44  may be formed by opaque organic or inorganic coating, such as ink or dye. As shown in  FIG. 4 , the shield must be larger than the square with the short side  404  of the pixel  402 , however, a maximum of half the area of the neighboring pixel  406 , and preferably one third of the area of the neighboring pixel  406 , remains uncovered.  
       THIRD EMBODIMENT  
       [0030]     In  FIG. 2 , the liquid crystal display  40  includes an array substrate  20 , a color filter substrate  34 , a liquid crystal layer  28  therein, a top polarized plate  38  on the color filter substrate  34 , and a bottom polarized plate  36  below the array substrate  20 .  
         [0031]     The LCD is illuminated with a light  42  to locate light spots therein, such as at broken circuits between TFT  12  and pixel electrode  10 , at broken circuits in the tunnel in TFT  12 , particles on the color filter substrate  34  or the array substrate  20 , or scratches in polarized plate  36  or  38 , or in the BM (Black Matrix).  
         [0032]     Referring to  FIG. 2 , a shield  44   b  is formed on the color filter substrate  34  according to the positions detected, thereby repairing the light spots. The shield  44  may be formed by opaque organic or inorganic coating, such as ink or dye. As shown in  FIG. 4 , the shield must be larger than the square with the short side  404  of the pixel  402 , however, a maximum of half the area of the neighboring pixel  406 , and preferably one third of the area of the neighboring pixel  406 , remains uncovered.  
       FOURTH EMBODIMENT  
       [0033]     In  FIG. 2 , the liquid crystal display  40  includes an array substrate  20 , a color filter substrate  34 , a liquid crystal layer  28  therein, a top polarized plate  38  on the color filter substrate  34 , and a bottom polarized plate  36  below the array substrate  20 .  
         [0034]     The LCD is illuminated with a light  42  to locate positions of light spots therein, such as at broken circuits between TFT  12  and pixel electrode  10 , broken circuits in the tunnel in TFT  12 , particles on the color filter substrate  34  or the array substrate  20 , or scratches in polarized plate  36  or  38  in the BM (Black Matrix).  
         [0035]     Referring to  FIG. 2 , a shield  44   c  is formed on the bottom of the array substrate  20  in located positions, covering the light spot, thereby repairing the light spots. The shield  44  may be formed by opaque organic or inorganic coating, such as ink or dye. As shown in  FIG. 4 , the shield must be larger than the square with the short side  404  of the pixel  402 , however, a maximum of half the area of the neighboring pixel  406 , and preferably one third of the area of the neighboring pixel  406  remains uncovered.  
         [0036]     The advantage of the present invention is that particles or scratches irreparable by laser can be repaired by forming shields on the top polarized plate, the bottom polarized plate, the color filter substrate, or the array substrate.  
         [0037]     While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of thee appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.