Abstract:
An apparatus and method for inspecting a liquid crystal display device is provided. The apparatus includes: a camera photographing a front surface of a liquid crystal panel; a back light irradiating light to the liquid crystal panel; a diffuser sheet diffusing the light generated from the back light; a prism sheet converting the diffused light so as to be perpendicularly incident to a rear surface of the liquid crystal panel; a probe unit applying an inspection signal to the liquid crystal panel; and a frequency converter converting a frequency of the light generated from the back light. The apparatus for inspecting the liquid crystal display device according to the invention detects bad sub-pixels, impossible to detect with the naked-eye, improving the quality of the liquid crystal display device.

Description:
This application claims the benefit of Korean Patent Application No. P2004-26735, filed on Apr. 19, 2004, which is hereby incorporated by reference for all purposes as if fully set forth herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus and method for inspecting a liquid crystal display panel, and more particularly to an apparatus and method that improves the reliability of the inspection process. 
     2. Description of the Related Art 
     A liquid crystal display (LCD) device displays a picture in response to image signals by controlling the amount of light transmitted through the device. Because of the characteristics of the LCD device, such as light weight, thin body, and low power consumption, the application of LCD devices continues to increase. LCD devices are commonly used in office automation equipment, notebook computers, and the like. 
     Continued advances in LCD technology in the areas of screen size, high definition and low power consumption have lead to the rapid replacement of cathode ray tubes with LCD panels. As a result of research and development and mass production technology, active matrix LCD devices that provide excellent picture quality and low power consumption are being developed with larger display size and higher resolution. 
     Manufacturing methods for active matrix liquid crystal display devices include a substrate cleaning process, a substrate patterning process, an alignment forming/rubbing process, a substrate bonding/liquid crystal injection process, an inspection process, a repair process, and a mounting process. 
     The substrate cleaning process removes impurities which may contaminate the substrate surface of the liquid crystal display device. The substrate patterning process generally includes an upper substrate patterning process and a lower substrate patterning process. For example, during the upper substrate patterning process a common electrode and a black matrix are formed. During the lower substrate patterning process, for example, signal lines such as data and gate lines and the like are formed. Furthermore, a thin film transistor(TFT) is formed at a intersection of the data line and the gate line, and a pixel electrode is formed at a pixel region defined between the data line and the gate line, wherein the data line is connected to a source electrode of the TFT. 
     During the alignment film forming/rubbing process an alignment film is coated onto the upper and lower substrate and the alignment direction of the alignment film is formed, for example, by rubbing the alignment film with a rubbing cloth. 
     During the substrate bonding/liquid crystal injection process the upper substrate and the lower substrate are sealed together and a liquid crystal material and spacers are injected between the substrates through an injection hole forming a liquid crystal panel. 
     The inspection process includes an electrical inspection that is conducted after the signal lines and pixel electrode are formed on the substrate, and an electrical and naked-eye inspection that is conducted after the substrate bonding/liquid crystal injection process is completed. 
     During the repair process a determination is made as to whether the substrates that failed the inspection process are repairable. 
     During the mounting process a tape carrier package TCP comprising integrated circuits such as a gate drive IC and a data drive IC mounted thereon is connected to the liquid crystal panel. The integrated circuits may also be directly mounted on the substrate using a chip-on-glass(COG) technique or a tape automated bonding(TAB) technique using the TCP. 
       FIG. 1  illustrates an auto probe inspecting device  60  used during the inspection process. As illustrated in  FIG. 1 , the auto probe inspecting device  60  comprises a probe unit  10  and a back light unit BU. 
     The probe unit  10  provides signals from a generator and a controller (not shown) for driving the liquid crystal panel during the inspection process. The probe unit  10  includes: a probe base  14  having a hole in which the liquid crystal panel to be inspected is inserted; a printed circuit board(PCB) base  18  installed at adjacent edges of the probe base  14 ; a plurality of TCP blocks  16  connected to the PCB base  18 ; and a plurality of probe blocks  12  connected to the TCP blocks  16 . In addition, each probe block  12  has a manipulator  24  that reduces the collision and friction forces generated upon installing the liquid crystal panel  2  in the probe unit  10 . 
     The back light unit BU includes: back lights  20  that irradiate light on a rear surface of the liquid crystal panel  2 ; and a back light housing  22  on which the back lights  20  are secured. 
     A method of inspecting the liquid crystal panel  2  using the auto probe inspection device  60  according to the related art is as follows. First, the liquid crystal panel  2  is inserted into the hole of probe unit  10  such that the manipulators  24  engage the edge and corner of the liquid crystal panel  2  and contact is made between the pads  26  of the liquid crystal panel  2  and probe blocks  12 . The back lights  20  receive power from a power source (not shown) and generate light that is transmitted to the liquid crystal panel  2 . Thereafter, inspection signals generated from a signal driver and controller (not shown) are switched to each TCP block  16  through the PCB base  18 . The inspection signals are transmitted through the TCP block  16  to pads  26  of the liquid crystal panel  2  via the probe block  12  and are then supplied to the signal lines connected to the pads  26 . A worker checks for bad pixels generated on the liquid crystal panel, as well as, inspects the pixel driving of the liquid crystal panel in accordance with a signal control of the signal driver using the naked-eye. 
     Accordingly, in the related art inspection method determination of a bad pixel is based on the vision of the work. This results in errors during the inspection process depending upon the health and eye condition of the worker performing the inspection. Furthermore, the eyes are susceptible to fatigue when exposed to light rays. Thus the light generated from the back light  20  increases visual fatigue in the worker. Accordingly, there is a problem in that the reliability of the inspection result is decreases because result is not uniform. 
     Further, since the back light  20  employs a line light emission not a surface light emission, the light generated from the back light  20  is not uniformly incident to the entire surface of the liquid crystal panel  2 . Accordingly, illumination at the center of the liquid crystal panel is different from the illumination at the edge of the liquid crystal panel. As a result, the liquid crystal panel is not uniformly illuminated. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to an apparatus and method for inspecting a liquid crystal display panel that substantially obviates one or more of the problems due to limitations and disadvantages of the related art. 
     An advantage of the present invention is that it increases the reliability of the inspection process. 
     Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, an apparatus for inspecting a liquid crystal display panel comprises a probe unit applying an inspection signal to the liquid crystal panel, a light source irradiating light to the liquid crystal panel, an optical sheet, stacked between the light source and the liquid crystal panel, and an optical system receiving the inspection signal and data from the liquid crystal panel. 
     In another aspect of the present invention, a method is provided for inspecting liquid crystal comprising uniformly irradiating the liquid crystal panel, supplying the liquid crystal panel with driving signals, scanning the liquid crystal panel with an optical device, processing the scanning data to determine defects in the liquid crystal panel, and displaying the detected defects. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. 
       In the drawings: 
         FIG. 1  is a perspective view illustrating a related art apparatus for inspecting a liquid crystal display panel; 
         FIG. 2  is a schematic view illustrating an apparatus for inspecting a liquid crystal display panel according to a first embodiment of the present invention; 
         FIG. 3  is a detailed view illustrating a camera shown in  FIG. 2 ; 
         FIG. 4  is a detailed view illustrating an inspecting apparatus shown in  FIG. 2 ; 
         FIG. 5  is a schematic view illustrating an apparatus for inspecting a liquid crystal display panel according to a second embodiment of the present invention; 
         FIG. 6  is a detailed view illustrating an inspecting apparatus shown in  FIG. 5 ; 
         FIG. 7  is a detailed view illustrating a liquid crystal panel shown in  FIGS. 2 and 5 ; 
         FIG. 8  is a flowchart illustrating a method of inspecting a liquid crystal display panel according to a first embodiment of the invention; and 
         FIG. 9  is a flowchart illustrating a method of inspecting a liquid crystal display panel according to a second embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Reference will now be made in detail to an embodiment of the present invention, example of which is illustrated in the accompanying drawings. 
       FIG. 2  is a schematic view illustrating an apparatus for inspecting a liquid crystal display panel according to a first embodiment of the invention. As illustrated in  FIG. 2 , the apparatus includes: an optical data processor  40  that obtains and processes data from a liquid crystal panel to be inspected; and an auto probe inspector  80  that holds the panel to be inspected and supplies driving signals to the panel during the inspection process. 
     As illustrated in  FIG. 3 , the optical data processor  40  includes: a camera  42 , for example, a charge coupled device(CCD) camera; control means  44  for moving the camera  42  in a horizontal and/or a vertical direction; and data processing means  50  for processing data captured from the camera  42 . 
     The camera  42  may operate in a line camera mode, wherein the camera scans the liquid crystal panel line by line, and/or in an area camera mode, wherein the camera scans predefined areas of the liquid crystal panel. The rate at which the camera  42  captures data is about  1000  frames per second. 
     Control means  44  moves camera  42  in a vertical direction in order to control the focal point from the panel and moves the camera  42  in a vertical direction in order to scan the panel. 
     Data processing means  50  includes vision hardware  56  that processes data transmitted from the camera  42 , picture display  54  that displays the picture processed through vision hardware  56 , and defect map  52  that identifies defects in the inspected liquid crystal panel  102 . 
     As illustrated in  FIG. 4 , the auto probe inspector  80  includes a back light  90  that receives power from an exterior power source (not shown) to generate light; a back light housing  92  on which the back light  90  is secured, a diffuser sheet  94  stacked on the back light  90 ; a prism sheet  96  stacked on the diffuser sheet  94 ; a probe unit  70 , and a driver (not shown) that generates the power and driving signals supplied to the probe unit  70 . 
     The back light  90  irradiates a rear surface of the liquid crystal panel  102 . The light generated from the back light  90  has, for example, a frequency in a range of about 30 Hz to about 60 Hz. The back light housing  92  to which back light  90  is secured, prevents leakage of the light generated from the back light  90 , and improves the efficiency of the light. 
     Diffuser sheet  94  diffuses the light generated from the back light  90 . Accordingly, the light passing through the diffuser sheet is uniformly incident to the entire surface of the prism sheet  96 . The light incident to the prism sheet  96  passes through the prism sheet  96  and is converted such that it exits vertically from an upper surface of the prism sheet  96 . As a result, the light exiting from the prism sheet  96  has uniform illumination. 
     The probe unit  80  includes: a probe base  74 , having a hole in which the liquid crystal panel  102  may be inserted; a printed circuit board(PCB) base  78  installed on adjacent edges of the probe base  74 ; a plurality of TCP blocks  76  connected to the PCB base  78 ; and a plurality of probe blocks  72  connected to the TCP blocks  76 . In addition, each probe block  72  has a manipulator  84  that reduces collision and friction forces generated upon inserting the liquid crystal panel  102  into the probe unit  70 . 
     A driver (not shown) includes: a power driver supplying a power to the probe unit  70 , which applies a signal to the liquid crystal panel  102 ; and a signal driver generating a signal for driving a pixel of the liquid crystal panel. 
     A method of inspecting a liquid crystal display panel according to a first embodiment of the invention is illustrated in  FIG. 8 . As illustrated in  FIG. 8 , the liquid crystal panel  102  is engaged with the probe unit  70  at step  800 . Upon insertion, pads  86  formed at the edge of the liquid crystal panel  102  are engaged with the probe block  72 . At step  802 , the back light  90  uniformly irradiates a rear surface of the liquid crystal panel  102 . More particularly, the light generated from the back light  90  passes through a diffuser sheet  94  and the diffused light then passes through a prism sheet  96  such that the light that exits the prism sheet is perpendicularly incident to a rear surface of the liquid crystal panel  102 . Driving signals are then supplied, at step  804 , to the panel through probe blocks  72 . The camera  42  scans the liquid crystal panel  102  line by line and/or area by area, and transmits the scanning data to the data processor  50  via a cable  58  at step  806 . The data processor  50  processes the scanning data received from the camera to detect defects in the panel. The defect map  52  then displays the detected defects on a display for worker confirmation. 
       FIG. 5  is a schematic view illustrating an apparatus for inspecting a liquid crystal display panel according to a second embodiment of the present invention. As illustrated in  FIG. 5 , the inspecting apparatus of the liquid crystal display device according to the second embodiment of the present invention has configuration elements identical to those of the inspecting apparatus shown in  FIG. 2  except the addition of a frequency converter  198 . Accordingly, a detailed description of the identical configuration elements is omitted. 
     Frequency converter  198  adjusts the frequency of the light generated from the back light  190 . For example, the frequency the light generated from the back light  190  (which may be in the range of 30 Hz to 60 Hz) is adjusted to be substantially equal to the photographic frequency of the camera  42 , for example, 1,000 Hz. Accordingly, it is possible to prevent flicker generated by the difference between the frequencies. 
     As compared to the inspecting apparatus according to the second embodiment, the inspecting apparatus according to the first embodiment of the invention, a flicker can be generated since there may be a difference between the frequency of the light generated by the back light and the rate at which the CCD obtains the scanning data. 
     A method of inspecting a liquid crystal display panel according to a second embodiment of the invention is illustrated in  FIG. 9 . As illustrated in  FIG. 9 , the liquid crystal panel  102  is engaged with a probe unit  170  at step  901 . Upon insertion of the liquid crystal panel, pads  186  formed at the edge of the liquid crystal panel  102  are engaged with probe blocks  172 . Then, the liquid display panel is uniformly irradiated. More specifically, the frequency of the light generated from the back light  190  is adjusted to be substantially equal to the photographic frequency of the camera  42 . Then at step  905 , the adjust frequency light is passes through diffuser sheet  194 , and the diffused light passes through prism sheet  196  such that the light that exits prism sheet is perpendicularly incident to a rear surface of the liquid crystal panel  102 . At step  907 , driving signals are supplied to the liquid crystal panel  102  through probe block  172 . The camera  42  scans the liquid crystal panel  102  for line by line and/or area by area, and transmits the scanning data to data processor  50  via a cable  58  at step  909 . The data processor processes the transmitted data to detect defects in the panel and the defect map displays the detected defects on a display for confirmation by a worker, at step  911 . 
     An exemplary structure of the liquid crystal panel is illustrated in  FIG. 7 . As illustrated in  FIG. 7 , the liquid crystal panel comprises an upper substrate  210 , a lower substrate  220 , a liquid crystal material injected between the upper and the lower substrates  210  and  220 , a first polarizing plate  228  stacked on a rear surface of the lower substrate  220 , and a second polarizing plate  224  stacked on a front of the upper substrate  210 . 
     On the upper substrate  210 , a color filter  204 , a common electrode  206 , and a black matrix are formed. On the lower substrate  220 , signal lines such as a data line  218 , a gate line  212  and the like are formed. Further, a thin film transistor(TFT)  216  is formed at a cross of the data line  218  and the gate line  212 , and a pixel electrode  214  is formed at a pixel region defined between the data line  218  and the gate line  212 . A liquid crystal material  208  is injected between the upper substrate  210  and the lower substrate  220  formed as set forth above. 
     The first polarizing plate  228  is stacked on the rear surface of the lower substrate  220  to polarize the light generated from the back light unit so as to be passed through the lower substrate  220 . 
     The second polarizing plate  224  re-polarizes the polarized light passing through the liquid crystal material  208  so as to make a user can recognize the polarized light as a picture. 
     As described above, the inspecting apparatus of the liquid crystal display device according to the present invention uses an optical sheet, for example, a diffuser sheet and a prism sheet, to solve the problem of irregular illumination thus it is possible to uniformly irradiate the light from the back light to the entire surface of the liquid crystal panel. Furthermore, the inspecting apparatus of the liquid crystal display device according to the second embodiment of the present invention is capable of removing the flicker generated by a difference between the frequency of the light generated from the back light and the frequency of the camera, by adjusting the frequency of the light generated to be substantially equal to the photographic frequency of the camera. 
     It will be apparent to those skilled in the art that various modifications and variation can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.