Abstract:
A liquid crystal display penel includes a substrate, a hole disposed in the substrate, and an opaque substance filling in the hole. The hole is configured to be located in an area corresponding to a bright point. The liquid crystal display penel may minimize a defect ratio and improve a yield by darkening the bright point.

Description:
[0001]     This application claims the benefit of Korean Patent Applications Nos. P2005-50615 filed in Korea on Jun. 13, 2005, and P2005-71948 filed in Korea on Aug. 5, 2005, each of which is hereby incorporated by reference by its entirety.  
       BACKGROUND  
       [0002]     1. Technical Field  
         [0003]     The invention relates to a liquid crystal display panel and repairing method thereof, and more particularly, to a repairing system of a liquid crystal display panel capable of minimizing a defect ratio and improving a yield.  
         [0004]     2. Related Art  
         [0005]     A liquid crystal display (LCD) device controls the light transmittance of a liquid crystal material in accordance with a video signal to display a picture. The liquid crystal display device includes a liquid crystal display panel in which liquid crystal cells are arranged in a matrix shape, and a drive circuit that drives the liquid crystal display panel.  
         [0006]     The liquid crystal display device is divided into two types in accordance with the electric field direction driving a liquid crystal material. For a twisted nematic (“TN”) mode, a vertical direction electric field is used and for an in-plan switch ISP mode, a horizontal direction electric field is used.  
         [0007]     For the TN mode, the liquid crystal material is driven by a vertical electric field between a pixel electrode and a common electrode which are arranged to be opposite in an upper substrate. The TN mode has a large aperture ratio and a small viewing angle. For the IPS mode, the liquid crystal material is driven by a horizontal electric field between the pixel electrode and the common electrode which are arranged in parallel on a lower substrate. The IPS mode has a large viewing angle and a small aperture ratio.  
         [0008]      FIG. 1  is a sectional view illustrating a liquid crystal display panel  1  of TN mode of the related art. Referring to  FIG. 1 , the related art TN mode liquid crystal display panel  1  includes an upper array substrate  2 , a lower array substrate  32 , and a liquid crystal material  52  injected into an inner space between the upper array substrate  2  and the lower array substrate  32 . The upper array substrate  2  (or a color filter array substrate) includes a black matrix  4 , a color filter  6 , a common electrode  18 , and an upper alignment film  8  which are sequentially formed on an upper substrate  2 . The lower array substrate  32  includes a thin film transistor (hereinafter, referred to as “TFT”), a pixel electrode  16  and a lower alignment film  38  which are formed on the lower substrate  32 .  
         [0009]     If the liquid crystal display panel  1  is driven in an IPS mode, it may have the common electrode  18  formed on the lower substrate  32 . An overcoat layer is formed on the color filter  6  of the upper substrate  2 . The overcoat layer compensates a step difference of the color filter  6 .  
         [0010]     In the upper array substrate  2 , the black matrix  4  is formed on the upper substrate  2  and corresponds to an area of gate lines and data lines (not shown) and a TFT area of the lower array substrate  32 . The black matrix  4  prevents light leakage and absorbs an external light, thereby acting to increase contrast. A cell area is provided where a color filter  6  is to be formed. The color filter  6  is formed to extend to the black matrix  4  and the cell area is divided by the black matrix  4 . The color filter  6  is formed with R, G and B filters to realize R, G and B colors. A common voltage is supplied to the common electrode  18  to control the movement of the liquid crystal material  52 . A pattern spacer  13  acts to keep a cell gap between the upper array substrate  2  and the lower array substrate  32 .  
         [0011]     In the lower array substrate  32 , the TFT includes a gate electrode  9  formed on the lower substrate  32  along with a gate line; semiconductor layers  14 ,  47  overlapping the gate electrode  9  with a gate insulating film  44  disposed therebetween; and source/drain electrodes  40 ,  42  formed together with a data line (not shown) with the semiconductor layers  14 ,  47  disposed therebetween. The TFT supplies a pixel signal to a pixel electrode  16  from the data line in response to a scan signal from the gate line. The pixel electrode  16  is in contact with the drain electrode  42  of the TFT via a contact hole. A passivation film  50  is formed between the pixel electrode  16  and the drain electrode  42  and made from a transparent conductive material with high light transmittance. Upper and lower alignment films  8  and  38  are used to align the liquid crystal material  52  and formed by applying an alignment material such as polyimide and performing a rubbing process.  
         [0012]     If a defect is generated at each thin film of the upper array substrate  2  and the lower array substrate  32  of the related art liquid crystal display panel  1 , a repair is performed by using a rework or laser. However, if a particle is soundly settled between the thin films of both the upper array substrate  2  and the lower array substrate  32 , the repair may be difficult with the rework or laser.  
         [0013]      FIG. 2  is a sectional view for explaining an alignment defect caused by particle in the air, and  FIG. 3  is a photo illustrating a bright point caused by the particle upon realizing a picture.  
         [0014]      FIG. 2  illustrates particle  55  that occurs during manufacturing process of a liquid crystal display panel  1 . In the chamber within which a designated thin film is formed or in case that it is moved to a separate chamber or a third location to form another thin film, the particle  55  may be soundly settled between the thin films, e.g., the common electrode  18  and the upper alignment film  8  as shown in  FIG. 2 . The alignment film  8  adjacent to the particle  55  may not be uniformly rubbed in a rubbing process, thereby generating a non-uniform alignment area A. Further, a portion of the color filter is separated by a defect on the process upon forming the color filter. Accordingly, a problem that the particle is intermixed is frequently generated.  
         [0015]     The non-uniform alignment area A generates the light leakage in the liquid crystal display panel  1 , and such a light leakage intercepts a light transmittance of the liquid crystal material. As a result, a bright point appears in the liquid crystal display panel as shown in  FIG. 3 . A dark point is an area that appears dark in case of realizing a high gray, and a bright point is an area that appears bright by the light leakage in case of realizing a low gray. Human eyes are relatively more sensitive to the bright point than the dark point. Thus, a stricter standard applies to the bright point defect than the dark point defect in determining the quality of the panel. A liquid crystal display panel having a bright point defect may be wasted or subject to a substantially reduced marketability. Accordingly, there is a need of a repair method that substantially minimizes a defect rate of a panel caused by a bright point.  
       SUMMARY  
       [0016]     By way of example only, in one embodiment, a liquid crystal display panel includes a substrate, a hole disposed in the substrate and an opaque substance filling in the hole. The hole is configured to be located in an area corresponding to a bright point.  
         [0017]     In other embodiment, a method for repairing a liquid crystal display panel having a substrate is provided. An area corresponding to a bright point is sensed and a hole is formed on the substrate. The hole is configured to be located in the area corresponding to the bright point. The hole is filled in with an opaque substance. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]     These and other objects of the invention will be apparent from the following detailed description of the embodiments with reference to the accompanying drawings, in which:  
         [0019]      FIG. 1  is a sectional view illustrating a liquid crystal display panel of TN mode of the related art.  
         [0020]      FIG. 2  is a sectional view for explaining an alignment defect caused by particle in the air;  
         [0021]      FIG. 3  is a photo illustrating a bright point defect of  FIG. 2 .  
         [0022]      FIGS. 4A and 4B  are sectional views illustrating a liquid crystal display panel according to an embodiment;  
         [0023]      FIGS. 5A and 5B  are sectional views illustrating light irradiated to a micro hole from a backlight unit;  
         [0024]      FIG. 6A  to  6 e are sectional views illustrating a method of repairing the liquid crystal display panel of  FIG. 4A  according to a first embodiment;  
         [0025]      FIG. 7A  to  7 D are sectional views illustrating a method of repairing the liquid crystal display panel of  FIG. 4A  according to a second embodiment; and  
         [0026]      FIG. 8A  to  8 D are sectional views illustrating a method of repairing the liquid crystal display panel of  FIG. 4A  according to a third embodiment. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0027]     Reference will now be made in detail to the preferred embodiments, examples of which are illustrated in the accompanying drawings.  
         [0028]      FIGS. 4A and 4B  are sectional views illustrating a liquid crystal display panel according to one embodiment.  FIG. 4A  illustrates that a micro hole is formed in a lower substrate and  FIG. 4B  illustrates that a micro hole is formed in an upper substrate.  
         [0029]     Referring to  FIGS. 4A and 4B , a liquid crystal display panel  170  according to the embodiment includes an upper array substrate  102 , a lower array substrate  132  and a liquid crystal material  152 . The upper array substrate (or a color filter array substrate)  102  has a black matrix  104 , a color filter  106 , a common electrode  118 , a pattern spacer  113 , and an upper alignment film  108  which are sequentially formed on an upper substrate  102 . The lower array substrate (or a thin film transistor substrate)  132  has a thin film transistor (hereinafter, referred to as “TFT”), a pixel electrode  116  and a lower alignment film  138  which are formed on a lower substrate  132 . The liquid crystal material  152  is injected into an inner space between the upper array substrate  102  and the lower array substrate  103 .  
         [0030]     In the upper array substrate  102 , the black matrix  104  is formed in an area of gate lines and data lines (not shown) and a TFT area of the lower array substrate  132 . It provides a cell area where a color filter  106  is to be formed. The black matrix  104  is formed of polyimide, in which a pigment of carbon system is mixed, to prevent light leakage and absorbs an external light, thereby acting to increase contrast. The color filter  106  is formed to extend to the black matrix  104  and the cell area divided by the black matrix  104 . The color filter  106  is formed with R, G and B filters to realize R, G and B colors. A common voltage is supplied to the common electrode  118  to control the movement of the liquid crystal material  152 . The pattern spacer  113  operates to keep a cell gap between the upper array substrate and the lower array substrate.  
         [0031]     In the lower array substrate  132 , the TFT includes a gate electrode  109  formed along with a gate line; semiconductor layers  114 ,  147  overlapping the gate electrode  109  with an interposed gate insulating film  144 ; and source/drain electrodes  140 ,  142  formed together with a data line (not shown) with the semiconductor layers  114 ,  147  disposed therebetween. The TFT supplies a pixel signal to a pixel electrode  116  from the data line in response to a scan signal from the gate line.  
         [0032]     The pixel electrode  116  is in contact with a drain electrode  142  of the TFT via a passivation film  150  disposed between the pixel electrode  116  and the drain electrode  142 . The pixel electrode  116  is formed of a transparent conductive material with high light transmittance. The upper and the lower alignment films  108  and  138  have the liquid crystal material  152  aligned and are formed by applying an alignment material such as polyimide and performing a rubbing process. If the liquid crystal display panel  170  is driven in an IPS mode, it may have the common electrode  118  formed on the lower substrate  132 . An overcoat layer (not shown) is formed on the color filter  106  of the upper substrate  102 . The overcoat layer compensates for a step difference of the color filter  106 .  
         [0033]     A bright point may be generated at an area where an alignment defect of the liquid crystal display panel  170  is generated by a particle  155  intermixed in the liquid crystal display panel  170 . The liquid crystal display panel  170  provides a micro hole  165  formed in one of the upper substrate  102  and the lower substrate  132  corresponding to the area where the bright point is generated. An opaque substance  260  may fill in some part of the micro hole  165 . A transparent substance  270  may fill in other part of the micro hole  165  after the opaque substance fills in the micro hole  165 . In  FIG. 4B , the micro hole  165  is formed in the upper substrate  102  and filled in with the opaque substance  260  and the transparent substance  270 .  
         [0034]      FIG. 5A  illustrates that the opaque substance  260  filled in the micro hole  165  intercepts light irradiated to the liquid crystal display panel  170  of  FIG. 4A  from a backlight unit  120 . The backlight unit  120  is arranged on a rear surface of the lower array substrate  132  in  FIG. 5A . Due to the interception of light, it is possible to darken the area where the alignment defect of the liquid crystal display panel  170  is generated, i.e., the area where the bright point is generated.  
         [0035]     In  FIG. 5A , the opaque substance  260  fills in only some part of the micro hole  165 . Referring to  FIG. 5B , the opaque substance  260  fully fills in the micro hole  165 . Light irradiated to the area where the bright point is generated from the backlight unit  120  is intercepted. Further, the light from the backlight unit  120 , which is irradiated to cells adjacent to the micro hole  165 , may be intercepted by the opaque substance  260 . Accordingly, the aperture ratio of the cells adjacent to the micro hole  165  may become reduced. It is desirable that the opaque substance  260  fills in only some part of the micro hole  165  rather than the entire micro hole  165 .  
         [0036]     In  FIGS. 6A-6E , a method of repairing the liquid crystal display panel of  FIG. 4A  according to the first embodiment is described. In  FIGS. 6A-6E , the micro hole  165  is formed in the lower substrate  132 . Accordingly, the lower substrate  132  is disposed in an upper position with respect to the upper substrate  102  for convenience of explanation in  FIGS. 6A-6E . In other embodiment, the micro hole  165  may be formed in the upper substrate  102  or both the upper and lower substrates  102  and  132  upon needs.  
         [0037]     In  FIG. 6A , a bright point is generated in the liquid crystal display panel  170  by the particle  155  intermixed between the common electrode  118  and the upper alignment film  108 . Accordingly, the micro hole  165  is formed in the lower substrate  132  corresponding to the area where the bright point is generated.  
         [0038]     In this embodiment, the micro hole  165  is formed by using a micro drill. The micro hole  165  may be formed in a range of 20 μm to 500 μm in accordance with a size of the liquid crystal display panel  170  and a degree of a light leakage caused by the intermixed particle  155 . An end drill capable of forming a circle type micro hole and a straight type micro hole in accordance with a shape of the intermixed particle  155  may be used with the micro drill. Alternatively, or additionally, a micro milling may be used as a device for forming the micro hole  165 . The micro milling may form an accurate and various shapes of micro hole  165 .  
         [0039]     In other embodiment, a laser may be used to form the micro hole  165 . In  FIG. 6B , a laser  161  is used to form the micro hole  165 . The laser  161  may include a ND YAG (Neodymium: Yttrium Aluminum Garnet) laser having a wavelength of 266 nm. Various other lasers having a wavelength of 50˜300 nm are possible.  
         [0040]     In  FIG. 6C , a colored pigment  410  such as a black or gray pigment is dropped by using an ink jet in the micro hole  165  formed in the lower substrate  132 . The micro hole  165  is filled in with the colored pigment  410 . The colored pigment  410  may include materials used for the color filter  106  or materials realizing color identical to the color filter  106 . The colored pigment  410  is dropped to the extent that it fills in some part of the micro hole  165 , as shown in  FIG. 6C .  
         [0041]     In  FIG. 6D , a transparent pigment  420  is dropped in the micro hole  165  after the colored pigment  410  is dropped. The transparent pigment  420  fills in the remaining part of the micro hole as shown in  FIG. 6E .  
         [0042]     As described above, when the bright point is generated in the liquid crystal display panel  170 , the micro hole  165  is formed by the micro drill  160 , the micro milling or the laser in the lower substrate  132 . The micro hole  165  is generated in the area corresponding to the bright point of the liquid crystal display panel  170 . The colored pigment  410  fills in the formed micro hole  165  to darken the bright point such that light from the backlight unit  120  ( FIGS. 5A and 5B ) may not pass through the liquid crystal display panel  170 . As a result, a generation of a bright point may be reduced and a defect ratio may be minimized. Accordingly, a yield of the liquid crystal display panel  170  may improve.  
         [0043]      FIGS. 7A  to  7 D illustrate a method of repairing the liquid crystal display panel  170  of  FIG. 4A  according to a second embodiment. In  FIGS. 7A  to  7 D, the lower substrate  132  is shown at the upper position with respect to the upper substrate  102  for convenience of description only. In  FIG. 7A , the colored pigment  410  such as a black or a gray pigment is dropped in the micro hole  165 .  
         [0044]     In  FIG. 7B , the colored pigment  410  fully fills in the micro hole  165  to the extent that it slightly covers a surface of the lower array substrate  132 . In  FIG. 7C , an etchant is applied to remove the colored pigment  410  from an upper part of the micro hole  165 . As a result, the colored pigment  410  remains only in some part of the micro hole  165 , which is shown as a lower part of the micro hole  165  in  FIG. 7D . After the colored pigment  410  is partially removed from the micro hole  165 , the transparent pigment  420  may fill in the remaining part of the micro hole  165 , as previously shown in  FIGS. 6C and 6D .  
         [0045]      FIGS. 8A  to  8 D illustrate a method of repairing the liquid crystal display panel  170  of  FIG. 4A  according to a third embodiment. In  FIGS. 8A  to  8 D, the lower substrate  132  is illustrated at the upper position for convenience of description. In  FIG. 8A , a colored electrode material  510  is deposited in the micro hole  165  on the lower substrate  132 . The colored electrode material  510  is also deposited on the surface of the lower substrate  132 , as shown in  FIG. 8A . The colored electrode material  510  may include a black-colored electrode material such as chrome (Cr) or molybdenum (Mo) by using a deposition method.  
         [0046]     In  FIG. 8B , an etchant may be used to remove some of the colored electrode material  510  applied to the lower substrate  132 . The colored electrode material  510  remains in some part of the micro hole  165  as a result of etching as shown in  FIG. 8C . Because the micro hole  165  formed on the lower substrate  132  does not perfectly penetrate the lower substrate  132 , the etchant may not reach the colored electrode material  510  filled in the micro hole  165  and it may not remove the colored electrode material  510  shown in  FIG. 8C  with ease as. On the other hand, the colored electrode material  510  deposited on the surface of the lower substrate  132  is easily removed by the etchant. After the etching, a transparent pigment  520  may fill in the remaining part of the micro hole  165 , as shown in  FIG. 8D .  
         [0047]     In this embodiment, the colored electrode material  510  is applied by using the deposition method such as a vacuum deposition. The vacuum deposition may be used with the colored pigment as previously described.  
         [0048]     The method, as described above in connection with the first, second and third embodiments, may be in use with various types of a liquid crystal display panel such as a liquid crystal display panel of electrical controlled birefringence (ECB), vertical alignment (VA) mode, IPS mode and TN mode.  
         [0049]     As described above, when the bright point is generated in the liquid crystal display panel, the micro hole is formed by the micro drill, the micro milling or the laser in the lower substrate, the upper substrate or both substrates. The micro hole is generated in the area corresponding to the bright point of the liquid crystal display panel. The colored pigment or the colored electrode material fills in the formed micro hole to darken the bright point such that light from the backlight unit may not pass through the liquid crystal display panel. As a result, a generation of the bright point may be substantially reduced and a defect ratio may be minimized. Accordingly, the liquid crystal display panel may be repaired and the marketability of the liquid crystal display panel may be preserved. Accordingly, a yield of the liquid crystal display panel may improve.  
         [0050]     Although the invention has been explained by the embodiments shown in the drawings described above, it should be understood to the ordinary skilled person in the art that the invention is not limited to the embodiments, but rather that various changes or modifications thereof are possible without departing from the spirit of the invention. Accordingly, the scope of the invention shall be determined only by the appended claims and their equivalents.