Patent Abstract:
A liquid crystal display device and a driving method thereof for preventing a brightness difference between horizontal line blocks are disclosed. In the liquid crystal display device, a liquid crystal display panel has a liquid crystal cell matrix. A power supply generates a common voltage. Common lines directly on a substrate of the liquid crystal display panel are connected to a common electrode of the liquid crystal cell. A common voltage compensator compensates for the common voltage into a large resistance value with a resistance value greater than a combination of resistances of the common lines and the large resistance directly between the power supply and the common lines.

Full Description:
This application claims the benefit of Korean Patent Application No. P2003-100655 filed in Korea on Dec. 30, 2003, which is hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a liquid crystal display, and more particularly to a liquid crystal display device and a driving method thereof that prevents gravity degradation to thereby improve picture quality. 
     2. Description of the Related Art 
     Generally, a liquid crystal display (LCD) controls the light transmittance of a liquid crystal using an electric field to display a picture. The LCD includes a liquid crystal display panel having liquid crystal cells arranged in a matrix, and a driving circuit for driving the liquid crystal display panel. 
     In the liquid crystal display panel, gate lines and data lines are arranged such that the gate lines and the data lines cross each other. The liquid crystal cell is positioned at each area where the gate lines cross the data lines. The liquid crystal display panel is provided with a pixel electrode and a common electrode for applying an electric field to each of the liquid crystal cells. Each pixel electrode is connected, via source and drain electrodes of a thin film transistor as a switching device, to any one of the data lines. The gate electrode of the thin film transistor is connected to any one of the gate lines thereby allowing the application of a pixel voltage signal to the pixel electrodes for each line. 
     The driving circuit includes a gate driver for driving the gate lines, a data driver for driving the data lines, a timing controller for controlling the gate driver and the data driver, and a power supply for supplying various driving voltages used in the LCD. The timing controller controls a driving timing of the gate driver and the data driver and applies a pixel data signal to the data driver. The power supply generates driving voltages such as a common voltage VCOM, a gate high voltage VGH and a gate low voltage VGL, etc. The gate driver sequentially applies a scanning signal to the gate lines to sequentially drive the liquid crystal cells on the liquid crystal display panel line by line. The data driver applies a data voltage signal to each of the data lines when the scanning signal is applied to one of the gate lines. Accordingly, the LCD controls the light transmittance by an electric field applied between the pixel electrode and the common electrode in response to the pixel voltage signal for each liquid crystal cell, thereby displaying a picture. 
     The data driver and the gate driver directly connected to the liquid crystal display panel integrate into a plurality of integrated circuits (IC&#39;s). Each of the integrated data drive IC&#39;s and gate drive IC&#39;s mount in a tape carrier package (TCP) and connect to the liquid crystal display panel by a tape automated bonding (TAB) system. In addition, the integrated data drive IC&#39;s and gate drive IC&#39;s may mount onto the liquid crystal display panel using a chip on glass (COG) system. 
     Herein, the drive IC&#39;s connected, via the TCP, to the liquid crystal display panel by the TAB system receives control signals and driving voltages input from the exterior over signal lines provided on a printed circuit board (PCB) connected to the TCP. In addition, the data drive IC&#39;s are connected, in series via signal lines provided on the data PCB, to each other, and commonly receive control signals and a pixel data signal from the timing control signal and driving voltages from the power supply. The gate drive IC&#39;s are connected, in series via signal lines provided on the gate PCB, and commonly receive control signals from the timing controller and driving voltages from the power supply. 
     The drive IC&#39;s mounted onto the liquid crystal display panel by the COG system are connected to each other by a line on glass (LOG) system in which signal lines are mounted on the liquid crystal display panel (i.e., a lower glass substrate) and receive control signals and driving voltages from the timing controller and the power supply. 
     Commonly, when the drive IC&#39;s are connected to the liquid crystal display panel by the TAB system, a LOG system is adopted to eliminate the PCB, thereby permitting the manufacturing of thin liquid crystal displays. Particularly, the gate drive IC&#39;s require relatively small signal lines. The small signal lines are provided on the liquid crystal display panel by the LOG system and thereby eliminate the gate PCB. Thus, the gate drive IC&#39;s of a TAB system are connected, in series, to each other over signal lines mounted on the lower glass substrate of the liquid crystal display panel. The gate drive IC&#39;s commonly receive control signals and driving voltage signals, which are hereinafter referred to as “gate driving signals”. 
     For instance, as shown in  FIG. 1 , a liquid crystal display omitting a gate PCB by utilizing LOG-type signal lines includes a liquid crystal display panel  1  and a plurality of data TCP&#39;s  8  connected between the liquid crystal display panel  1  and a data PCB  12 . The liquid crystal display also includes a plurality of gate TCP&#39;s connected to other side of the liquid crystal display panel  1 , data drive IC&#39;s  10  mounted in the data TCP&#39;s  8 , and gate drive IC&#39;s  16  mounted in the gate TCP&#39;s  14 . 
     The liquid crystal display panel  1  includes a lower substrate  2  provided with various signal lines and a thin film transistor array, an upper substrate  4  provided with a color filter array, and a liquid crystal injected between the lower substrate  2  and the upper substrate  4 . The liquid crystal display panel  1  has a picture display area  21  consisting of liquid crystal cells provided at intersections between gate lines  20  and data lines  18  in order to display a picture. At the outer area of the lower substrate  2  located at the outer side of the picture display area  21 , data pads extending from the data lines  18  and gate pads extending from the gate lines  20  are positioned. Further, a LOG-type signal line group  26  for transferring gate driving signals applied to the gate drive IC  16  is positioned at the outer area of the lower substrate  2 . 
     The data TCP  8  is mounted with the data drive IC  10 , and is provided with input pads  24  and output pads  25  electrically connected to the data drive IC  10 . The input pads  24  of the data TCP  8  are electrically connected to the output pads of the data PCB  12  while the output pads  25  are electrically connected to the data pads on the lower substrate  2 . Particularly, the first data TCP  8  is further provided with a gate driving signal transmission line group  22  electrically connected to the LOG-type signal line group  26  on the lower substrate  2 . The gate driving signal transmission line group  22  applies gate driving signals from the timing controller and the power supply, via the data PCB  12 , to the LOG-type signal line group  26 . 
     The data drive IC&#39;s  10  convert digital pixel data signals into analog pixel voltage signals and applies the analog voltage signals to the data lines  18  on the liquid crystal display panel. 
     Similarly, a gate drive IC  16  is mounted on the gate TCP  14 , and is provided with a gate driving signal transmission line group  28  electrically connected to the gate drive IC  16  and output pads  30 . The gate driving signal transmission line group  28  is electrically connected to the LOG-type signal line group  26  on the lower substrate  2  while the output pads  30  are electrically connected to the gate pads on the lower substrate  2 . 
     Each gate drive IC  16  sequentially applies a scanning signal such as a gate high voltage signal VGH during an interval to a gate line  20  in response to input control signals. Further, the gate drive IC  16  applies a gate low voltage signal Vgl to the gate line  20  in an interval other than the interval supplied where the gate high voltage signal VGH is supplied. 
     The LOG-type signal line group  26  usually includes signal lines that supply driving voltage signals from the power supply, such as a gate high voltage signal VGH and a gate low voltage signal VGL. The LOG-type signal line group  26  also includes a common voltage signal VCOM, a ground voltage signal GND and a supply voltage signal VCC. Furthermore, the LOG-type signal line group  26  has gate control signals from the timing controller, such as a gate start pulse GSP, a gate shift clock signal GSC and a gate enable signal GOE. The LOG-type signal line group  26  further includes a common line LVCOM for supplying a common voltage VCOM. 
     A LOG-type common line LVCOM is arranged, in parallel, in a fine pattern in a very confined narrow space like a pad portion positioned at an outer area of a picture display part  21 . The LOG-type common line LVCOM is formed from a gate metal layer similar to the gate lines  20 . A metal such as AlNd having a relatively large resistivity of 0.046 is usually used as the gate metal. As the LOG-type signal common line LVCOM is formed in a fine pattern within a confined area and is made from a gate metal having a relatively large resistivity value, the LOG-type signal common line LVCOM has a greater resistance than the signal lines formed from a copper film at an existent gate PCB. Because a resistance value of the LOG-type common line LVCOM is in proportion to a line length, a line resistance value increases as the LOG-type common line LVCOM extends away from the data PCB  12 , thereby attenuating a gate driving signal. As a result, the common voltage VCOM transferred over the LOG-type common line LVCOM is distorted due to its line voltage value, thereby causing picture quality deterioration of a picture displayed on the picture display part  21 . 
     This will be described in detail with reference to  FIG. 2  below. 
     Referring to  FIG. 2 , a LOG-type common line LVCOM of a related art LCD is included in the LOG-type signal line group  26 . The LOG-type common line LVCOM comprises a first LOG-type common line  50  provided at one edge of the liquid crystal display panel, and a second LOG-type common line  51  provided which intervenes with the first LOG-type common line  50  at the picture display area  21 . The first LOG-type common line  50  consists of third to sixth LOG-type common lines  50   a  to  50   d  connected between a first data TCP  8  and the respective first to fourth gate TCP&#39;s  14 A to  14 D. When a liquid crystal in an in-plane switch (IPS) mode is driven with a horizontal electric field, the LOG-type common line LVCOM further includes a dummy common line  53  connected to the third to sixth LOG-type common lines  50   a  to  50   d  and to a common electrode (not shown) provided at the pixel area. On the other hand, when a liquid crystal in a twisted nematic (TN) mode is driven with a vertical electric field, the LOG-type common line LVCOM is connected to the common electrode provided at the upper substrate by a silver dot (not shown). 
     The third to sixth LOG-type common lines  50   a  to  50   d  have line voltage values a, b, c and d proportional to their line lengths. In addition, the third to sixth LOG-type common lines  50   a  to  50   d  are connected, via the first to fourth gate TCP&#39;s  14 A to  14 D, to each other in series. 
     In other words, the gate drive IC  16  mounted in the first gate TCP  14 A is supplied with a first common voltage VCOM 1  voltage-dropped in proportion to the first line resistance value a of the third LOG-type common line  50   a . The first common voltage VCOM 1  is applied, via the first gate drive IC  16 , to common electrodes at a first horizontal line block A. 
     The gate drive IC  16  mounted in the second gate TCP  14 B is supplied with a second common voltage VCOM 2  voltage-dropped in proportion to the second line resistance value a+b of the third LOG-type common line  50   a  and the fourth LOG-type common line  50   b  connected to each other in series. The second common voltage VCOM 2  is applied, via the second gate drive IC  16 , to common electrodes at a second horizontal line block B. 
     The gate drive IC  16  mounted in the third gate TCP  14 C is supplied with a third common voltage VCOM 3  voltage-dropped in proportion to the third line resistance value a+b+c of the third to fifth LOG-type common line  50   a  to  50   c  connected to each other in series; The third common voltage VCOM 3  is applied, via the third gate drive IC  16 , to common electrodes at a third horizontal line block C. 
     The gate drive IC  16  mounted in the fourth gate TCP  14 D is supplied with a fourth common voltage VCOM 4  voltage-dropped in proportion to the fourth line resistance value a+b+c+d of the third to sixth LOG-type common line  50   a  to  50   d  connected to each other in series. The fourth common voltage VCOM 4  is applied, via the fourth gate drive IC  16 , to common electrodes at a fourth horizontal line block D. Particularly, as it goes from the first gate driving IC  16  toward the fourth gate driving IC  16 , line resistance values a, b, c and d of the first and second LOG-type common lines  51  and  52  are added to each other, thereby resulting in the first to fourth common voltages VCOM 1  to VCOM 4  applied to the horizontal line blocks A to D having a relationship of VCOM 1 &gt;VCOM 2 &gt;VCOM 3 &gt;VCOM 4 . 
     As the common voltages VCOM 1  to VCOM 4  supplied to the common electrodes are differentiated for each gate drive IC  16  in that manner, a brightness difference is generated among the horizontal line blocks A to D connected to different gate drive IC&#39;s  16 . The brightness difference among the horizontal line blocks A to D results in horizontal brightness bands that cause a deterioration of picture quality. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a liquid crystal display device and a driving method thereof that is adaptive for preventing a brightness difference between horizontal line blocks. 
     In order to achieve these and other objects of the invention, a liquid crystal display device according to one embodiment of the present invention includes: a liquid crystal display panel having a liquid crystal cell matrix; a power supply generating a common voltage; common lines directly on a substrate of the liquid crystal display panel and connected to a common electrode of the liquid crystal cell; and a common voltage compensator for compensating for the common voltage using a large resistance with a value greater than a combination of resistances of the common lines and the large resistance directly between the power supply and the common lines. 
     A liquid crystal display device according to another embodiment of the present invention includes: a liquid crystal display panel having a plurality of data lines and a plurality of gate lines crossing each other and having liquid crystal cells arranged in a matrix; a data driving circuit group at a first side of the liquid crystal display panel and having a plurality of data integrated circuits; a first gate driving circuit group at a second side of the liquid crystal display panel and having a plurality of gate integrated circuits; a second gate driving circuit group at a third side of the liquid crystal display panel and having a plurality of gate integrated circuit; a power supply generating a common voltage; common lines directly on a substrate of the liquid crystal display panel; and a common voltage compensator compensating for the common voltage using a large resistance with a resistance value greater than a combination of resistances of the common lines and the large resistance directly between the power supply and the common lines. 
    
    
     
       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 schematic plan view illustrating a configuration of a conventional line on glass (LOG) type liquid crystal display device; 
         FIG. 2  is a view for explaining a division phenomenon between horizontal line blocks caused by a line resistance of the LOG-type common line shown in  FIG. 1 ; and 
         FIG. 3  is a schematic plan view illustrating a partial configuration of a LOG-type liquid crystal display device according to a first embodiment of the present invention; 
         FIG. 4  depicts a silver dot for making a connection between a common line of a TN-mode liquid crystal display device and a common electrode of the upper substrate thereof; 
         FIG. 5  is a schematic plan view illustrating a partial configuration of a LOG-type liquid crystal display device according to a second embodiment of the present invention; and 
         FIG. 6  is a schematic plan view illustrating a partial configuration of a LOG-type liquid crystal display device according to a third embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawing. 
     Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to  FIGS. 3 to 6 . 
       FIG. 3  illustrates a liquid crystal display device according to a first embodiment of the present invention. 
     The liquid crystal display device according to the first embodiment of the present invention includes a liquid crystal display panel  34 , a plurality of data TCP&#39;s  40  connected between the liquid crystal display panel  34  and a data PCB  44 , a plurality of gate TCP&#39;s  46 A to  46 D connected to an adjacent side of the liquid crystal display panel  34 , data drive IC&#39;s  42  mounted on the data TCP&#39;s  40 , gate drive IC&#39;s  48 A to  48 D mounted in the gate TCP&#39;s  46 A to  46 D, a power supply  50  for generating driving voltages supplied to the gate drive IC&#39;s  48  and the data drive IC&#39;s  42 , and a timing controller (not shown) controlling the gate drive IC&#39;s  48  and the data drive IC&#39;s  42 . 
     The liquid crystal display panel  34  includes a lower substrate  36  provided with various signal lines and a thin film transistor array, an upper substrate  38  provided with a color filter array, and a liquid crystal injected between the lower substrate  36  and the upper substrate  38 . Such a liquid crystal display panel  34  displays a picture on a picture display area  121  using liquid crystal cells provided at intersections between gate lines (not shown) and data lines (not shown). At the outer area of the lower substrate  36  located at the outer side of the picture display area  121 , data pads extending from the data lines and gate pads extending from the gate lines  56  are positioned. Further, a LOG-type signal line group (not shown) for transferring gate driving signals applied to gate drive IC&#39;s  48 A to  48 D is positioned at the outer area of the lower substrate  36 . 
     The data TCP  40  is mounted with the data drive IC  42 , and is connected, via input and output pads connected to the data drive IC  42 , to output pads of the data PCB  44  and data pads of the lower substrate  36 . Particularly, the first data TCP  40  further includes a gate driving signal transmission line group (not shown) connected to the LOG-type signal line group on the lower substrate  36 . The gate driving signal transmission line group applies gate driving signals from the power supply  50  and the timing controller, via the data PCB  44 , to the LOG-type signal line group. 
     The power supply  50  generates driving voltages, such as a common voltage VCOM, a gate high voltage VGH and a gate low voltage VGL, required for the liquid crystal display device using an input power source. 
     The data drive IC&#39;s  42  convert digital pixel data signals into analog pixel voltage signals to apply them to the data lines on the liquid crystal display panel  34 . 
     Similarly, gate drive IC&#39;s  48 A to  48 D are mounted on the gate TCP&#39;s  46 A to  46 D and are connected, via output pads connected to the gate drive IC&#39;s  48 A to  48 D, to the gate pads of the lower substrate  36 . 
     Each gate drive IC  48 A to  48 D sequentially applies a scanning signal, that is, a gate high voltage signal VGH to a gate line  56  in response to input control signals. Further, each gate drive IC  48 A to  48 D applies a gate low voltage signal Vgl to the gate line  56  in the interval other than when the gate high voltage signal VGH is applied. 
     The LOG-type signal line group usually consists of LOG-type signal lines for supplying driving voltage signals from the power supply  50 , such as a gate high voltage signal VGH, a gate low voltage signal VGL, a common voltage signal VCOM, a ground voltage signal GND and a supply voltage signal VCC, and LOG-type control lines for supplying gate control signals from the timing controller, such as a gate start pulse GSP, a gate shift clock signal GSC and a gate enable signal GOE. Such a LOG-type signal line group ia formed from a gate metal similar to the gate lines. 
     The LOG-type signal line group further includes a common line for supplying a common voltage VCOM. 
     The LOG-type common line consists of a first LOG-type common line  150  included in the LOG-type signal line group, and a second LOG-type common line  151  arranged in parallel to the first LOG-type common line  150  having the picture display area  121  therebetween. 
     Herein, when a liquid crystal in an in plane switch (IPS) mode is driven with a horizontal electric field, the LOG-type common line further includes a dummy common line  153  connected to the third to sixth LOG-type common lines  150   a  to  150   d  and to a common electrode (not shown) provided at the pixel area. On the other hand, when a liquid crystal in a twisted nematic (TN) mode is driven with a vertical electric field, the LOG-type common line LVCOM is connected to the common electrode provided at the upper substrate by silver dots  28   a  to  28   d  as shown in  FIG. 4 . 
     Input terminals of the first and second LOG-type common lines  150  and  151  are provided with attenuating resistors Rb and Rc having a relatively large resistance value. The attenuating resistors Rb and Rc are identical to line resistance a, b, c and d of the first and second common lines  150  and  151 , so that it becomes possible to prevent a voltage difference of the common electrode for each gate drive IC  48  caused by the line resistances. 
     The first and second attenuating resistors Rb and Rc are connected in series to the gate driving signal output terminal of the power supply  50 . Further, a dummy resistor Ra for controlling a difference of common voltages applied to the first and second common lines  150  and  151  may be provided between the first attenuating resistor Rb and the power supply. 
     The attenuating resistors Rb and Rc are connected in series to the line resistances a, b, c and d of the third to sixth LOG-type common lines  150   a  to  150   d  provided between the gate TCP&#39;s  46 A,  46 B,  46 C and  46 D, and has the same resistance as the total sum a+b+c+d of the line resistances a, b, c and d of the LOG-type common lines as indicated in the following equation:
 
 Ra, Rc=a+b+c+d   (1)
 
     Such attenuating resistors Ra and Rb limit the current of a common voltage signal to thereby limit the current applied to the third to sixth LOG-type common lines  150   a  to  150   d  connected in series to the attenuating resistors Rb and Rc and reduce a resistance deviation between the lines. 
     Reducing the current reduces the affect of the line resistances a, b, c and d of the LOG-type common lines on the voltage supplied to each gate drive IC. Thus, the gate drive IC&#39;s  48 A,  48 B,  48 C and  48 D are supplied with voltage signals having substantially the same level. 
     As mentioned above, in the LCD according to the first embodiment of the present invention, line resistances of the first and second common lines  150  and  151  are reduced by the attenuating resistors Rb and Rc provided at each input terminal of the first and second common lines  150  and  151 , so that resistances loaded onto the input terminals of the gate drive IC&#39;s  48 A,  48 B,  48 C and  48 D become substantially equal to each other. Thus, as the substantially same common voltage signal is applied to the common electrodes to thereby prevent a brightness difference between horizontal line blocks A, B, C and D. 
       FIG. 5  shows a liquid crystal display device according to a second embodiment of the present invention. 
     Because the liquid crystal display device shown in  FIG. 5  has the same elements as the liquid crystal display device shown in  FIG. 3  except that a gate drive circuit group including a plurality of gate TCP&#39;s mounted with gate drive IC&#39;s is provided at both the left and right sides of a liquid crystal display panel (hereinafter referred to as “double gate liquid crystal display device), a detailed explanation as to the elements identical to the first embodiment will be omitted. 
     In the double gate liquid crystal display device shown in  FIG. 5 , gate lines of the liquid crystal display panel are divided into the left and right sides, and a data driving circuit converts the digital data into analog gamma voltages and applies them to all the data lines and pixels in synchronization with a scanning pulse. 
     A first gate drive circuit group  172  at the left side sequentially applies a scanning pulse to the gate lines included in the left-half area of the liquid crystal display panel, whereas a second gate drive circuit group  174  at the right side sequentially applies a scanning pulse to the gate lines included in the right-half area of the liquid crystal display panel in synchronization with the first gate drive circuit group  172 . 
     A LOG-type signal line group of the double gate liquid crystal display device includes a common line LVCOM for supplying a common voltage VCOM. 
     The LOG-type common line consists of a first LOG-type common line  150  included in the left LOG-type signal line group of the liquid crystal display panel, and a second LOG-type common line  151  arranged in parallel to the first LOG-type common line  150  with a picture display area  121  therebetween and included in the right LOG-type signal line group of the liquid crystal display panel. 
     Input terminals of the first and second LOG-type common lines  150  and  151  have attenuating resistors Rb and Rc with a relatively large resistance value. The attenuating resistors Rb and Rc reduce the affect of the line resistances a, b, c and d of the first and second LOG-type common lines  150  and  151  to prevent a voltage difference along the common electrode for each gate drive IC  48  caused by the line resistances. 
     The first and second attenuating resistors Rb and Rc are connected, in series, to the common voltage signal output terminal of the power supply and are built therein. Further, a dummy resistor Ra for controlling a difference of common voltages applied to the first and second common lines  150  and  151  may be provided between the first attenuating resistor Rb and the power supply. 
     The attenuating resistors Rb and Rc are connected, in series, to the line resistances a, b, c and d of the third to sixth LOG-type common lines  150   a  to  150   d  provided between the gate TCP&#39;s  46 A,  46 B,  46 C and  46 D, and has the same resistance as the total sum a+b+c+d of the line resistances a, b, c and d of the LOG-type common lines. 
     Such attenuating resistors Rb and Rc reduce the affect of the line resistances a, b, c and d of the LOG-type common lines on the voltage supplied to each gate drive IC. Thus, the gate drive IC&#39;s  48 A,  48 B,  48 C and  48 D are supplied with voltage signals having substantially the same level. 
     As mentioned above, in the LCD according to the second embodiment of the present invention, the first and second gate drive circuit groups  172  and  174  are provided at the left and right sides of the liquid crystal display panel, and line resistances of the first and second common lines  150  and  151  are reduced by the attenuating resistors Rb and Rc provided at each input terminal of the first and second common lines  150  and  151 , so that resistances loaded onto the input terminals of the gate drive IC&#39;s  48 A,  48 B,  48 C and  48 D become substantially equal to each other. Thus, as the substantially same common voltage signal is applied to the common electrodes to thereby prevent a brightness difference between horizontal line blocks A, B, C and D. 
       FIG. 6  shows a liquid crystal display device according to a third embodiment of the present invention. 
     Because the liquid crystal display device shown in  FIG. 6  has the same elements as the liquid crystal display device shown in  FIG. 3  except that a gate drive circuit group including a plurality of gate TCP&#39;s mounted with gate drive IC&#39;s is provided at both the left and right sides of a liquid crystal display panel and the data PCB is positioned at both the upper and lower portion of a liquid crystal pattern (hereinafter referred to as “double-gate and double-source liquid crystal display device), a detailed explanation as to the elements identical to the first embodiment will be omitted. 
     In the double-gate and double-source liquid crystal display device shown in  FIG. 6 , gate lines of the liquid crystal display panel are divided into the left and right sides while data lines of the liquid crystal display panel are separated into the upper and lower portions thereof. 
     A first source driving circuit group  182  at the upper portion of the liquid crystal display panel converts the digital data into analog gamma voltages and applies them to all the data lines and pixels in the upper-half area in synchronization with an upper-half scanning pulse. 
     On the other hand, a second source driving circuit group  184  at the lower portion of the liquid crystal display panel converts the digital data into analog gamma voltages and applies them to all the data lines and pixels in the lower-half area in synchronization with an lower-half scanning pulse. 
     A first gate drive circuit group  172  at the left side sequentially applies a scanning pulse to the gate lines included in the left-half area of the liquid crystal display panel, whereas a second gate drive circuit group  174  at the right side sequentially applies a scanning pulse to the gate lines included in the right-half area of the liquid crystal display panel in synchronization with the first gate drive circuit group  172 . 
     A LOG-type signal line group of the double-gate and double-source liquid crystal display device includes a common line LVCOM for supplying a common voltage VCOM. 
     The LOG-type common line consists of a first LOG-type common line  150  included in the left LOG-type signal line group of the liquid crystal display panel and a second LOG-type common line  151  arranged in parallel to the first LOG-type common line  150  with a picture display area  121  therebetween and included in the right LOG-type signal line group of the liquid crystal display panel. 
     The first and second LOG-type common lines  150  and  151  receive a common voltage from the power supply  50  positioned within the data PCB  44  provided at the upper and lower portions of the liquid crystal display panel, respectively. 
     Upper and lower input terminals of the first and second LOG-type common lines  150  and  151  are provided with attenuating resistors Rb and Rc having a relatively large resistance value. The attenuating resistors Rb and Rc reduce the line resistances a, b, c and d of the first and second LOG-type common lines  150  and  151 , so that it becomes possible to prevent a voltage difference of the common electrode for each gate drive IC  48  caused by the line resistances. 
     The first and second attenuating resistors Rb and Rc are connected in series to the common voltage signal output terminal of the power supply and are built therein. Further, a dummy resistor Ra for controlling a difference of common voltages applied to the first and second common lines  150  and  151  may be provided between the first attenuating resistor Rb and the power supply. 
     The attenuating resistors Rb and Rc are connected in series to the line resistances a, b, c and d of the third to sixth LOG-type common lines  150   a  to  150   d  provided between the gate TCP&#39;s  46 A,  46 B,  46 C and  46 D, and has the same resistance as the total sum a+b+c+d of the line resistances a, b, c and d of the LOG-type common lines. 
     Such attenuating resistors Rb and Rc reduce the affect of the line resistances a, b, c and d of the LOG-type common lines on the voltage supplied to each gate drive IC. Thus, the gate drive IC&#39;s  48 A,  48 B,  48 C and  48 D are supplied with voltage signals having substantially the same level. 
     As mentioned above, in the LCD according to the third embodiment of the present invention, the first and second gate drive circuit groups  172  and  174  including a plurality of gate integrated circuits are provided at the left and right sides of the liquid crystal display panel and the first and second data integrated circuit groups  182  and  184  are provided at the upper and lower portions of the liquid crystal display panel, and line resistances of the first and second common lines  150  and  151  are reduced by the attenuating resistors Rb and Rc provided at each input terminal of the first and second common lines  150  and  151 , so that resistances loaded onto the input terminals of the gate drive IC&#39;s  48 A,  48 B,  48 C and  48 D become substantially equal to each other. Thus, as the substantially same common voltage signal is applied to the common electrodes to thereby prevent a brightness difference between horizontal line blocks A, B, C and D. 
     Meanwhile, the double-gate and double-source structures in the second and third embodiments can effectively drive a liquid crystal display panel as the liquid crystal display panel increases in size, thereby permitting more effective driving of the large-dimension liquid crystal display panel. 
     As described above, according to the present invention, the input terminals of the LOG-type common lines are provided with resistors having a larger value than the total sum of line resistances of the LOG-type common lines. Accordingly, the line resistances of the LOG-type common lines become relatively smaller in comparison with attenuating resistors to reduce the voltage difference between gate driving signals for each gate drive integrated circuit, so that it become possible to prevent a brightness difference between the horizontal line blocks caused by the line resistance difference. 
     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.

Technology Classification (CPC): 6