Abstract:
A method and apparatus for testing a liquid crystal display device are provided to detect a defect location precisely and rapidly without requiring a jig. The method includes providing an inspection apparatus as a removable portion of the liquid crystal display device; inspecting the display part of the liquid crystal display device using the inspection apparatus; removing the inspection apparatus from the liquid crystal display device after the inspection is completed; and attaching driving circuits to the liquid crystal display device having the inspection apparatus removed therefrom.

Description:
This application is a Divisional of application Ser. No. 10/669,460, filed on Sep. 25, 2003, now U.S. Pat. No. 7,046,030 the entire contents of which are hereby incorporated by reference and for which priority is claimed under 35 U.S.C. §120. The present application claims, under 35 U.S.C. § 119, the priority benefit of Korean Patent Application No. P2003-28644, filed May 6, 2003, the entire contents of which are herein fully incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to a liquid crystal display (LCD) device and, more particularly, to a method and apparatus for testing an LCD device to detect a defective location on the LCD device precisely and rapidly without requiring a jig. 
     2. Description of the Related Art 
     Display apparatuses have become important as visual information transferring media. Among the display apparatuses, a cathode ray tube is widely used at present, but is disadvantageous in that its weight and volume are large. Therefore, various types of flat display apparatuses have been developed that are capable of overcoming the defects of the cathode ray tube. An LCD, a field emission display (FED), a plasma display panel (PDP), and an electroluminescence (EL) display are different examples of flat display apparatus. Most of these apparatuses are available in the market. 
     The LCD device is easily adaptive due its smallness which improves productivity. Thus, it is quickly replacing the cathode ray tubes in many applications. In particular, the LCD device of an active matrix type for driving a liquid crystal cell by using a thin film transistor (hereinafter referred to as “TFT”) has an advantage in that the picture quality it provides is excellent, and its power consumption is low. Such LCDs have been rapidly developed into a large size and high definition due to the recent productivity technology and research. 
     As shown in  FIG. 1 , in the LCD of the active matrix type, a color filter substrate  22  and a TFT array substrate  23  are assembled with a liquid crystal layer  15  therebetween. The LCD shown in  FIG. 1  represents a portion of a total effective display. 
     The color filter substrate  22  includes an upper glass substrate  12 , and a color filter  13  and a common electrode  14  formed thereon. Attached on a front surface of the upper glass substrate  12  is a polarization plate  11 . In the color filter  13 , the color filter layers of red, green and blue colors are disposed and transmit a light of special wavelength bandwidth to display a color. A black matrix (not shown) is formed between the color filters  13  of the adjacent color. 
     Data lines  19  and gate lines  18  cross each other on the entire surface of a lower glass substrate  16  in the TFT array substrate  23 . TFTs  20  are formed at the intersections of the gate and data lines  18  and  19 . A pixel electrode  21  is formed at a cell region between each of the data lines  19  and gate lines  18  on the entire surface of the lower glass substrate  16 . Each TFT  20  switches a data transfer path between the corresponding data line  19  and the corresponding pixel electrode  21  in response to a scanning signal from the corresponding gate line  18  and thus drives the corresponding pixel electrode  21 . A polarization plate  17  is installed on a rear surface of the TFT array substrate  23 . 
     The liquid crystal layer  15  adjusts a transmitting quantity of an incident light via the TFT array substrate  23  in response to an electric field applied thereto. The polarization plates  11  and  17  installed on the color filter substrate  22  and the TFT array substrate  23  transmit the light polarized to one direction. When the liquid crystal layer  15  is at 90°TN mode, the polarization directions of the polarization plates  11  and  17  vertically cross each other. An alignment film (not shown) is formed on the facing surfaces of the color filter substrate  22  and the TFT array substrate  23 . 
     A process for fabricating the LCD device of the active matrix type is divided into a substrate cleaning, a substrate patterning, an alignment forming/rubbing, a substrate assembling/a liquid crystal material injecting, a mounting, an inspecting and a repairing. 
     Generally, impurities on the substrate surface of the LCD device are removed by a detergent in the substrate cleaning process. The substrate patterning process is divided into a patterning process of the color filer substrate and a patterning process of the TFT array substrate. The alignment film forming/rubbing process involves applying an alignment film to each of the color filter substrate and the TFT array substrate and rubbing the alignment film. The substrate assembling/liquid crystal injecting process is to assemble the color filter substrate and the TFT array substrate by using a sealant, to inject the liquid crystal and a spacer through a liquid crystal injection hole and then to seal the liquid crystal injection hole. 
     In the mounting process of the liquid crystal panel, a tape carrier package (hereinafter referred to as “TCP”) is connected to a pad part on the substrate, wherein the TCP has integrated circuits mounted thereon such as a gate drive integrated circuit and a data drive integrated circuit. Such drive integrated circuits may be directly mounted on the substrate by using a chip on glass (hereinafter referred to as “COG”) method besides a TAB (Tape Automated Bonding) using the TCP described above. 
     The inspecting process includes a first electrical inspection performed after forming a variety of signal wirings such as the data line and the gate line on the TFT array substrate and the pixel electrode, and a second electrical inspection and a visual inspection performed after the substrate assembly/liquid crystal injection process. Specifically, the electrical inspection of the signal wirings of the TFT array substrate and the pixel electrode of the lower substrate performed before the substrate assembling process may reduce an undesirable ratio and a waste matter and may find a defective substrate capable of repairing at an early stage. 
     The repairing process performs a restoration for a repairable substrate determined by the inspecting process. However, in the inspecting process, defective substrates beyond repair are discarded. 
     The device as shown in  FIG. 2  may be used in an inspection process carried out before the substrate assembling. The inspection device shown in  FIG. 2  is fully described in U.S. Pat. No. 5,377,030. 
     Referring to  FIG. 2 , the inspection device of the related art includes an inspection switch device  34  for selectively supplying a voltage from an inspection power supply  36  to a video signal input wiring, and a voltage from a current-voltage amplifier  38  under the control of a driving signal generation unit  35 , a scanning switch device  30  for supplying the inspection voltage from the video signal input wiring  32  to the data lines  28  of a TFT array  46  of an active matrix LCD under control of an H scanning circuit  24 , a V scanning circuit  42  for driving the gate lines  26  of the TFT array  46  under control of the driving signal generation unit  35 , and a determining unit  40  for determining an electrical defect in the TFT array  46 . The data lines  28  and gate lines  26  cross each other in the TFT array  46 , and TFTs are formed at their intersections. Further, common wirings  33  and a storage capacitor Cst between the common wirings  33  and a drain electrode of the TFT are formed in the TFT array  46 . 
     The inspection of the TFT array  46  includes a sequence of loading a substrate having the TFT array  46  formed thereon to the inspection device, writing the inspection voltage to the TFT array  46  and reading a signal from the TFT array  46 . 
     After loading the substrate having the TFT array  46  to the inspection device, the writing process of the inspection voltage is performed. In the writing process of the inspection voltage, the inspection switch device  34  is connected to the first terminal  34   a  and the scanning switch device  30  is turned on under control of the H scanning circuit  24 . Accordingly, the inspection voltage generated from the inspection power supply  36  is supplied to the data lines  28  of the TFT array  46  via the inspection switch device  34 , the video signal input wiring  32  and the scanning switch device  30 . At the same time, the V scanning circuit  42  supplies a test scan voltage to the gate lines  26  under control of the driving signal generation unit  35 . Then the TFTs are turned on in the selected lines of the TFT array  46 , and the inspection voltage on the data lines  28  is charged to the storage capacitors Cst via the TFTs. 
     In the reading process of the inspection voltage, the inspection switch device  34  is connected to the second terminal  34   b  and the scanning switch device  30  is turned on under control of the H scanning circuit  24 . At the same time, the V scanning circuit  42  supplies the test scan voltage to the gate lines  26  under control of the driving signal generation unit  35 . Then, the TFTs are turned on in the selected lines of the TFT array and the voltage of the corresponding storage capacitor Cst is supplied to the current-voltage amplifier  38  via the TFTs, the data line  28 , the scanning switch device  30 , the video signal input wiring  32  and the inspection switch device  34 . The voltage read from the storage capacitor Cst is supplied to the determining unit  40  after being amplified by the current-voltage amplifier  38 , and the determining unit  40  determines if there is a defect in the TFT array  46  based on the voltage supplied by the current-voltage amplifier  38 . 
     However, since the substrate (having the TFT array  46 ) to be inspected is not equipped with the driving circuit and the inspection device, a separate jig is needed to accommodate the driving signal generation unit  35 , the H scan circuit  24 , the V scan circuit  42 , the scanning switch device  30 , the video signal input wiring  32 , the inspection switch device  34 , the inspection power supply  36 , the current-voltage amplifier  38  and the determining unit  40 . As a result, there is a problem that the inspection device of the related art shown in  FIG. 2  needs a high price jig. Further, if the resolution of the LCD or a model is changed, the jig needs to be changed correspondingly. On the other hand, if the TFT array  46  is inspected by a block dividing method concurrently driving a plurality of gate lines  26  and a plurality of data lines  28 , the number of input/output terminals of the jig and the circuit price of the jig may be reduced. However, there is another problem that a defect location within the block cannot be detected with precision. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a method and apparatus for testing an LCD display device which can detect a defective location precisely and rapidly without requiring a jig. 
     It is another object of the present invention to provide a method and apparatus for testing an LCD which overcomes the limitations and problems of the related art. 
     In accordance with an aspect of the invention, a method of inspecting a liquid crystal display device using an inspection apparatus, the inspection apparatus including a light source, at least one inspection line and at least one inspection switch device connected to the inspection line, the method includes: providing a substrate, wherein the substrate includes a plurality of signal wirings, a plurality of drive switches, and a plurality of capacitors formed in an effective display area of the substrate; radiating a light generated from the light source of the inspection apparatus onto the at least one inspection switch device and thereby supplying an inspection voltage from the at least one inspection line to a corresponding one of the drive switches through the signal wirings, so as to charge a corresponding one of the capacitors; and determining if there is a defect in the effective display area of the substrate by reading the charged voltage of the corresponding one of the capacitors. 
     In accordance with an aspect of the invention, a method of inspecting a substrate device, the substrate device including signal wirings, drive switches and capacitors formed in a main area of the substrate device, and an inspection line and an inspection switch formed at an exterior of the main area, the drive switches being coupled to the capacitors, the inspection switch being coupled to the inspection line, the method includes: supplying an inspection voltage to the inspection line of the substrate device; charging one of the capacitors with the inspection voltage through the signal wirings; and determining if there is a defect in the substrate device by reading the charged voltage of the capacitor. 
     In accordance with an aspect of the invention, a method of inspecting a display part of a liquid crystal display device, the method includes: providing an inspection apparatus as a removable portion of the liquid crystal display device; inspecting the display part of the liquid crystal display device using the inspection apparatus; removing the inspection apparatus from the liquid crystal display device after the inspection is completed; and attaching driving circuits to the liquid crystal display device having the inspection apparatus removed therefrom. 
     In accordance with an aspect of the invention, a method of inspecting a display part of a liquid crystal display device, the method includes: providing an inspection apparatus as an integral part of the liquid crystal display device; inspecting the display part of the liquid crystal display device using the inspection apparatus; covering the inspection apparatus with a light cut-off layer after the inspection is completed; and attaching driving circuits to the liquid crystal display device after the inspection is completed. 
     In accordance with an aspect of the invention, an inspection apparatus for a liquid crystal display device, the liquid crystal device including a plurality of signal wirings, a plurality of driving switch devices and a plurality of capacitors formed on a substrate and formed in an effective display area of the liquid crystal display device, the apparatus includes: at least one inspection line formed at an exterior of the effective display area of the liquid crystal display device; at least one inspection switch device connected to the at least one inspection line and formed at an exterior of the effective display area; a light source to radiate light onto the at least one inspection switch device, so as to turn on the at least one inspection switch device and to charge an inspection voltage from the at least one inspection line onto one of the capacitors; and a control part to read the charged voltage of the one of the capacitors and thereby determine if there is a defect in the effective display area of the liquid crystal display device. 
     In accordance with an aspect of the invention, an apparatus for inspecting a substrate of a liquid crystal display device, the substrate including a plurality of signal wirings, a plurality of drive switches and a plurality of capacitors formed in an effective display area of the substrate, the apparatus includes: a light source to radiate light; at least one inspection line formed at an exterior of the effective display area of the substrate; at least one inspection switch device connected to the at least one inspection line and formed at an exterior of the effective display area of the substrate, wherein the at least one inspection switch device is radiated with the light from the light source so as to be turned on to supply an inspection voltage of the at least one inspection line to a corresponding one of the drive switches, whereby a corresponding one of the capacitors is charged through the signal wirings; and a determining part to determine if there is a defect in the effective display area of the substrate by reading the charged voltage of the corresponding one of the capacitors. 
     In accordance with an aspect of the invention, a display part of a liquid crystal display device, includes: a substrate; a display circuit on the substrate for performing a display function of the liquid crystal display device; and an inspection apparatus formed at an exterior of the display circuit and being a removable portion of the liquid crystal display device, wherein after the display circuit is inspected for any defect using the inspection apparatus, the inspection apparatus is removed from the liquid crystal display device. 
     In accordance with an aspect of the invention, a display part of a liquid crystal display device, includes: a substrate; a display circuit on the substrate for performing a display function of the liquid crystal display device; an inspection apparatus formed as an integral part of the liquid crystal display device at an exterior of the display circuit; and a light cut-off layer covering the inspection apparatus after the display circuit is inspected using the inspection apparatus; and driving circuits attached to the liquid crystal display device after the display circuit is inspected using the inspection apparatus. 
     These and other objects of the present application will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects of the invention will be apparent from the following detailed description of the embodiments of the present invention with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view illustrating a liquid crystal display device of an active matrix type of the related art; 
         FIG. 2  is a circuit diagram illustrating an inspection device of the related art for inspecting a liquid crystal display device; 
         FIG. 3  is a block diagram illustrating an inspection device of a liquid crystal display device according to an embodiment of the present invention; 
         FIG. 4  illustrates a substrate of a liquid crystal display device according to an embodiment of the present invention; 
         FIG. 5  is a diagram for explaining a writing process of an inspection voltage with respect to an inspection method of a liquid crystal display device according to an embodiment of the present invention; 
         FIG. 6  is a diagram for explaining a reading process of a storage capacitor voltage with respect to an inspection method of a liquid crystal display device according to an embodiment of the present invention; 
         FIG. 7  illustrates a state that a data driving circuit and a gate/scan driving circuit are installed on a substrate of a liquid crystal display device after an edge of the substrate is removed along a cutting line  400  shown in  FIG. 4  according to an embodiment of the present invention; and 
         FIG. 8  illustrates a state that an inspection circuit shown in  FIG. 4  is shielded with a light cutting-off layer, and a data driving circuit and a gate driving circuit are installed on a substrate of a liquid crystal display device according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
     Hereinafter, as referring to  FIGS. 3 to 8 , the preferred embodiments of the present invention will be explained in full detail. 
     Referring to  FIG. 3 , an inspection device for a liquid crystal display according to a preferred embodiment of the present invention includes a light source  1  for radiating a light  1   a  on a substrate  8  to be inspected, a writing and reading circuit  6 , a voltage source  7  for supplying an inspection voltage to the writing and reading circuit  6 , a light source driving circuit  2  for driving the light source  1 , a display device  4 , and a controlling and determining circuit  3  for controlling a user interface device  5 . All the components of the inspection device are operatively coupled. The substrate  8  includes a TFT array formed thereon and is part of a liquid crystal display device. 
     The light source  1  is driven by a power from the light source driving circuit  2  to generate the light  1   a  which will then be focused on the substrate  8  to be inspected. 
     The writing and reading circuit  6  supplies the inspection voltage from the voltage source  7  (or some other source) to an inspection terminal of the substrate  8  under control of the controlling and determining circuit  3 , and reads the voltage generated in the substrate  8  in response to the inspection voltage. The writing and reading circuit  6  supplies the read voltage to the controlling and determining circuit  3 . 
     The controlling and determining circuit  3  controls the light source driving circuit  2  to turn on or off the light source  1  and controls the writing and reading circuit  6 . Further, the controlling and determining circuit  3  compares the read voltage from the writing and reading circuit  6  with a predetermined reference voltage and determines a badness/defectiveness of the substrate  8  being inspected in accordance with the comparison result. Then the controlling and determining circuit  3  generates determination result data and supplies the determination result data to the display device  4  so that the determination result can be displayed to a user or an inspection operator. This allows the user or inspection operator to recognize the defectiveness of the substrate  8  in real time. The user or inspection operator can issue a command or instruction to process the defective substrate via the user interface  5  such as a keyboard, a mouse, etc. 
     The controlling and determining circuit  3  can include a ROM (or other memory) having the predetermined reference data voltages stored therein in a lookup table or some other format, so that the reference voltages can be accessed and used to compare with the read voltage. The controlling and determining circuit  3  can include an operation device for performing the detect determination test for the substrate. The operation device may be implemented with one or more computer programs embodied on a computer-readable medium such as ROM, optical disc, etc. 
     Further, the inspection device according to the embodiment of the present invention includes a stage for moving the substrate  8  to be inspected and/or a unit for moving the light source  1  such as an actuator. 
       FIG. 4  illustrates an example of a TFT array substrate of a liquid crystal device according to the embodiment of the present invention. For instance, the substrate  8  in  FIG. 3  can be the substrate having the structure shown in  FIG. 4 . 
     Referring to  FIG. 4 , the TFT array substrate according to the present invention includes data lines DL 1  to DLm and gate lines DGL and GL 1  to GLn crossing mutually, TFTs formed at the intersections of the data lines DL 1  to DLm and the gate lines DGL and Gl 1  to GLn, a storage capacitor Cst connected to each of the TFTs, an electrostatic damage protection line  404  crossing with the data lines DL 1  to DLm and the gate lines DGL and GL 1  to GLn, electrostatic damage protection devices  403   a  and  403   c  connected between the electrostatic damage protection line  404  and the data lines DL 1  to DLm, and electrostatic damage protection devices  403   b  and  403   d  connected between the electrostatic damage protection line  404  and the gate lines DGL and GL 1  to GLn. These components are all operatively coupled. 
     An inspecting voltage is applied selectively or simultaneously to the data lines DL 1  to DLm during the inspecting process, whereas the video data is supplied to the data lines DL 1  to DLm upon a normal driving. 
     The gate lines DGL and GL 1  to GLn include an uppermost dummy gate line DGL not connected to the TFTs and the gate lines GL 1  to GLn connected to the TFTs. The gate lines DGL and GL 1  to GLn supply the inspection voltage to the TFTs during the inspection process to select a line having the inspection voltage supplied thereto, and supply the driving scan voltage to the TFTs to select the line having the video data voltage supplied thereto upon a normal driving. 
     The gate electrodes of the TFTs are connected to the gate lines GL 1  to GLn and the source electrodes of the TFTs are connected to the data lines DL 1  to DLm. The drain electrodes of the TFTs are connected to the storage capacitors Cst. Each TFT is turned on when the scan voltage higher than the threshold voltage of the corresponding TFT is supplied to the corresponding one of the gate lines GL 1  to GLn, which in turn supplies the voltage on the corresponding one of the data lines Dl 1  to DLm to the corresponding storage capacitor Cst. 
     For each TFT, the storage capacitor Cst is formed between the drain electrode of the TFT and the prestage gate line or is formed between the drain electrode of the TFT and a separate common electrode line (not shown). The storage capacitor Cst charges the inspection voltage during the inspection process and then discharges the charged voltage. The controlling and determining circuit  3  shown in  FIG. 3  compares the voltage discharged from the storage capacitor Cst with a predetermined reference voltage in the inspection process, and thus determines a point of defect such as the short of the TFT and the storage capacitor, or the short and the open circuit problem of the corresponding gate line and the corresponding data line based on the comparison results. 
     The device for protecting an electrostatic discharge damage (hereinafter referred to as “ESD protection device”) bypasses the static electricity caused during the fabricating process or the normal driving to the electrostatic damage protection line (hereinafter referred to as “ESD protection line”) and thus protects the TFT array of an effective display from the static electricity. A ground voltage GND or a common voltage Vcom is supplied to the ESD protection line  404 . 
     Further, the TFT array substrate according to the present invention includes first to third inspection lines  401 ,  402  and  405  formed at an outer edge portion of the TFT array of the effective display, first and third inspection TFTs T 1  and T 3  having their gate terminals connected to the first inspection line  401 , second TFTs T 2  connected between the second inspection line  402  and the gate lines GL 1  to GLn of the TFT array, capacitors C 1  each connected between the first and the second TFTs T 1  and T 2 , fourth TFTs T 4  connected between the third inspection line  405  and the data lines DL 1  to DLm of the TFT array, and capacitors C 2  each connected between the third and fourth TFTs T 3  and T 4 . 
     The first inspection line  401  receives from, e.g., the voltage source  7  a gate-off voltage (Vg-off) lower than the threshold voltage of the first and the third TFTs T 1  and T 3  and supplies it to the TFTs T 1  and T 3  in the inspection process, while upon the normal driving, it is provided with no voltage. 
     The second inspection line  402  receives from, e.g., the voltage source  7  a gate-on voltage (Vg-on) higher than the threshold voltage of the second and the fourth TFTs T 2  and T 4  and supplies it to the TFTs T 1 , T 2 , and T 3  in the inspection process, while upon the normal driving, it is provided with no voltage. 
     The third inspection line  405  receives from, e.g., the voltage source  7  the inspection voltage Vds and supplies it to the sources of the fourth TFTs T 4  in the inspection process. It also receives the read voltage Vcst from the data lines DL 1  to DLm. The third inspection line  405  is provided with no voltage upon the normal driving. 
     For each first TFT T 1 , the gate electrode of the first TFT T 1  is connected to the first inspection line  401  and the source electrode of the first TFT T 1  is connected to the second inspection line  402 . The drain electrode of the first TFT T 1  is connected to the capacitor C 1 . The first TFT T 1  is turned on by a photo current generated due to the exposure to the light  1   a  from the light source  1  in the inspection process and thereby supplies a gate-on voltage (Vg-on) on the second inspection line  402  to the capacitor C 1 . 
     For each second TFT T 2 , the gate electrode of the second TFT T 2  is connected to the capacitor C 1  and the source electrode of the second TFT T 2  is connected to the second inspection line  402 . The drain electrode of the second TFT T 2  is connected to the corresponding one of the gate lines GL 1  to GLn. The second TFT T 2  is turned on in response to the voltage of the capacitor C 1  in the inspection process, and the turned-on T 2  supplies the gate-on voltage (Vg-on) on the second inspection line  402  to the corresponding one of gate lines GL 1  to GLn and thus to the TFTs of the array connected to that gate line. 
     For each third TFT T 3 , the gate electrode of the third TFT T 3  is connected to the first inspection line  401  and the source electrode of the third TFT T 3  is connected to the second inspection line  402 . The drain electrode of the third TFT T 3  is connected to the capacitor C 2 . The third TFT T 3  is turned on by the photo current generated due to the exposure to the light from the light source  1  in the inspection process, which supplies a gate-on voltage (Vg-on) on the second inspection line  402  to the capacitor C 2 . 
     For each fourth TFT T 4 , the gate electrode of the fourth TFT T 4  is connected to the capacitor C 2  and the source electrode of the fourth TFT T 4  is connected to the third inspection line  405 . The drain electrode of the fourth TFT T 4  is connected to the corresponding one of the data lines DL 1  to DLm. The fourth TFT T 4  is turned on in response to the voltage of the capacitor C 2  in the inspection process, which in turn supplies the inspection voltage Vds on the third inspection line  403  to the corresponding one of the data lines DL 1  to DLm. Also, it supplies the read voltage Vcst from the corresponding one of the data lines DL 1  to DLm to the third inspection line  405  for reading by the writing and reading circuit  6 . 
     When the first and third TFTs T 1  and T 3  are turned on, the capacitors C 1  and C 2  charge the voltage and constantly supply the charged voltage to the gate terminal of the second and fourth TFTs T 2  and T 4 , to thereby stably maintain the gate voltage of the second and fourth TFTs T 2  and T 4 . 
     The inspection process on the TFT array substrate according to an embodiment of the present invention includes a sequence of loading the TFT array substrate shown in  FIG. 4  or other substrate to the inspection device, writing the inspection voltage Vds to the TFT array and reading the return signal from the TFT array in response to the inspection voltage. Here, the loading step may be optional if the inspection device is part of the TFT array substrate (which will be discussed later in more detail). More specifically, the TFT array substrate shown in  FIG. 4  is loaded in the inspection device and then the writing process of the inspection voltage as shown in  FIG. 5  is performed. 
     Referring to  FIG. 5 , in the writing process of the inspection voltage, the inspection voltage Vds (e.g., from the voltage source  7 ) via the reading and writing circuit  6  shown in  FIG. 3  is supplied to the third inspection line  405 , and the light is radiated by the light source  1  onto a semiconductor layer of the first TFT T 1  and in turn onto a semiconductor layer of the third TFT T 3 . In this writing process, the first TFT T 1  is turned on by the photo current generated in its semiconductor layer and the second TFT T 2  is turned on by the voltage of the capacitor C 1 . The second TF 1  T 2 , as turned on, supplies the gate-on voltage (Vg-on) on the second inspection line  402  to the corresponding one of the gate lines GL 1  to GLn. Similarly, the third TFT T 3  is turned on by the photo current generated in its semiconductor layer and the fourth TFT T 4  is turned on by the voltage of the capacitor C 2 , so as to supply the inspection voltage Vds on the third inspection line  405  to the corresponding one of the data lines DL 1  to DLm. Then the TFTs of the effective display area connected to the corresponding gate line are turned on to pass the inspection voltage Vds through the TFT(s) and to charge the inspection voltage Vds to the corresponding storage capacitor Cst. That is, the storage capacitor Cst charges electric charges supplied through a current path i via the third inspection line  405 , the corresponding one of the data lines DL 1  to DLm and the TFT in the TFT array in the writing process of the inspection voltage. 
     In one embodiment, the light source  1  sequentially radiates the light  1   a  to the first and third TFTs T 1  and T 3  by moving with a constant speed or moving of the stage for supporting the TFT array substrate, or simultaneously radiates the light  1   a  to all the first and third TFTs T 1  and T 3 . During the sequential radiating, all the first TFTs T 1  can be sequentially radiated and, at the same time or before or after, all the third TFTs T 3  can be sequentially radiated. In the alternative, the first and second TFTs T 1  and T 3  can be selectively radiated if a particular area (e.g., a particular TFT or Cst) on the TFT array needs to be inspected. Other variations are possible. 
     After the writing process of the inspection voltage, the reading process of the read voltage is performed, as shown in  FIG. 6 . Referring to  FIG. 6 , in the reading process of the read voltage, no voltage is applied from an external to the third inspection line  405  and the light source  1  radiates the light  1   a  to the semiconductor layer of the first TFT T 1  and to the semiconductor layer of the third TFT T 3 . In the reading process, the first TFT T 1  is turned on by the photo current generated in its semiconductor layer and the connected second TFT T 2  is turned on by the voltage of the capacitor C 1  to supply the gate-on voltage (Vg-on) on the second inspection line  402  to the corresponding one of the gate lines DGL and GL 1  to GLn. Similarly, the third TFT T 3  is turned on by the photo current generated in its semiconductor layer and the connected fourth TFT T 4  is turned on by the voltage of the capacitor C 2  to form the current path between the corresponding one of the data lines DL 1  to DLm and the third inspection line  405 . Consequently, the TFTs of the effective display connected to the corresponding gate line are turned on to form the current path between the storage capacitor Cst and the corresponding data lines. Then the voltage Vcst of the storage capacitor Cst (charged with the inspection voltage) is discharged along the current path including the corresponding TFT, the corresponding data line and the third inspection line  405 , which will then be supplied to the writing and reading circuit  6  shown in  FIG. 3 . 
     In one embodiment, the order or manner in which the first and third TFT(s) T 1  and T 3  are radiated during the reading process of the inspection procedure can be the same as or reverse of the order or manner in which the first and third TFT(s) T 1  and T 3  are radiated in the writing process of the inspection voltage. In another embodiment, the first and third TFT(s) T 1  and T 3  can be radiated selectively according to an order in which particular areas of the TFT array are desired to be inspected. 
     The writing and reading circuit  6  amplifies the read voltage Vcst supplied from the TFT array, removes a noise therein and supplies the processed read voltage Vcst to the controlling and determining circuit  3 . The controlling and determining circuit  3  compares the read voltage Vcst with a predetermined reference data voltage to determine the presence of a defect in the storage capacitor of the TFT array and in the TFT and the presence of short and/or open circuit defectiveness in the data lines DL 1  to DLm and gate lines GL 1  to GLn in accordance with the comparison results. The precise location of the defect can be quickly identified by examining which one of the first TFTs T 1  and which one of the third TFTs T 3  have been radiated to read the charge inspection voltage. This is because each of the first TFTs T 1  is assigned to one of the gate lines, and each of the third TFTs T 3  is assigned to one of the data lines. 
     The controlling and determining circuit  3  supplies the data of the read voltage Vcst and/or the comparison result to the display device  4  or other indication device to allow an inspection operator or user recognize the defect in real time. 
     In one embodiment, the inspection device is a removable part of the TFT array substrate. In this case, the edge of the TFT array substrate is cut off along a cutting line  400  of  FIG. 4  upon the scribing process. Accordingly, the first to the fourth TFTs T 1  to T 4 , the capacitors C 1  and C 2  and the first to the third inspection lines  401 ,  402  and  405  are removed from the TFT array substrate after the inspection is completed. Then, after forming the liquid crystals Clc by the alignment film forming/rubbing process and the substrate assembling/liquid crystal injecting process, integrated circuits of a data driving circuit  702  and a scan driving circuit  701  are mounted on the TFT array substrate as shown in  FIG. 7 . 
     The data driving circuit  702  supplies video data to the data lines DL 1  to DLm under control of the timing controller (not shown). The scan driving circuit  701  sequentially supplies a scan pulse to the gate lines GL 1  to GLn in response to the gate start pulse from the timing controller to select the lines to which the video data voltage is supplied. This process is known. 
     In other variations, upon the scribing process, the first to the fourth TFTs T 1  to T 4 , the capacitors C 1  and C 2  and the first and the third inspection lines  401 ,  402  and  405  may be remained on the TFT array substrate without being removed from the TFT array substrate. In this case, as shown in  FIG. 8 , it is preferred to form a light cut-off layer  803  covering or overlapping the inspection device including the TFTs T 1  to T 4  and the inspection lines, so that the TFTs T 1  to T 4  on the edge of the TFT array substrate do not cause a false operation. Then, after forming the liquid crystal cells Clc by the alignment film forming/rubbing process and substrate assembling/liquid crystal injecting process, the integrated circuits of a data driving circuit  802  and a scan driving circuit  801  are mounted on the TFT array substrate. 
     The processing steps and computer programs of the present invention are implementable using existing computer programming language. Such computer program(s) may be stored in memories such as RAM, ROM, PROM, etc. associated with computers. Alternatively, such computer program(s) may be stored in a different storage medium such as a magnetic disc, optical disc, magnet-optical disc, etc. Such computer program(s) may also take the form of a signal propagating across the Internet, extranet, intranet or other network and arriving at the destination device for storage and implementation. The computer programs are readable using a known computer or computer-based device. 
     As described above, the method and apparatus for inspecting the liquid crystal display device provide the inspection lines and the TFTs at an edge area of the TFT array substrate, radiate the light to the TFTs in order to charge the inspection voltage to the storage capacitor of the TFT array substrate, and read the voltage of the storage capacitor of the TFT array substrate to find the defect in the TFT and the storage capacitor formed on the TFT array substrate and the short and the open circuit problems of the signal wirings. As a result, the method and apparatus for inspecting the liquid crystal display device according to the present invention do not need a separate jig and can detect the defect location precisely and rapidly. 
     Although the present 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.