KR101036687B1 - Liquid crystal display device and method for driving the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and a driving method thereof, wherein a scan signal and a test signal are applied to pixels of a dummy pixel unit provided in a liquid crystal display panel, and a kickback voltage is applied by applying a pixel voltage from a pixel of the dummy pixel unit through a dummy line. Since it is possible to set the optimum common voltage level considering the effect of the kickback voltage, it is possible to easily and accurately set the optimum common voltage level of individual liquid crystal display panels even when the liquid crystal display panels have different kickback voltages. do.

Description

Liquid crystal display and its driving method {LIQUID CRYSTAL DISPLAY DEVICE AND METHOD FOR DRIVING THE SAME}

1 is an exemplary view showing a general liquid crystal display device.

FIG. 2 is an exemplary diagram showing an equivalent circuit for each pixel arranged in a matrix form on a liquid crystal display panel in FIG.

3 is a drive waveform diagram of a pixel in FIG. 2;

4 is an exemplary view showing a block configuration of a liquid crystal display according to the present invention.

FIG. 5 is an exemplary view showing a planar configuration of a pixel provided in the dummy pixel portion in FIG. 4; FIG.

FIG. 6 is an exemplary view showing an equivalent circuit of a pixel provided in the dummy pixel portion in FIG. 5; FIG.

7 is an exemplary view showing a liquid crystal display device of a small model.

8A and 8B are driving waveform diagrams of pixels according to the line inversion driving of the small liquid crystal display in Fig. 7;

*** Explanation of symbols for main parts of drawing ***

210: liquid crystal display panel 211: pixel portion

212: dummy pixel 220: driving unit                 

221: common voltage compensation unit DL1: dummy line

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display and a driving method thereof, and more particularly, to compensate for an influence of a kick-back voltage (ΔVp) that causes poor image quality such as flicker or afterimage. The present invention relates to a liquid crystal display device and a driving method thereof, which are suitable for improvement.

In general, cathode ray tube (CRT), which is one of the widely used display devices, is mainly used for monitors such as TV, measuring instruments, information terminal devices, etc. And it could not respond actively to the request of weight reduction.

Accordingly, in order to replace the cathode ray tube, a liquid crystal display (LCD), a plasma display panel (PDP), and a field emission display (LCD) have advantages of small size, light weight, and low power consumption. Various flat panel display devices such as FED) and electroluminescence display (ELD) have been actively researched and developed.

In the flat panel display device, the liquid crystal display device may artificially adjust the alignment direction of liquid crystal molecules having directionality using polarization to transmit and block light by optical anisotropy according to the alignment direction of the liquid crystal. Application as a flat panel display. Recently, an active matrix form in which a plurality of pixels are arranged in a matrix form and selectively supplies image information to each pixel through a switching element such as a thin film transistor (TFT) provided in each pixel. type) is widely used because it provides excellent image quality.

The liquid crystal display as described above will be described in more detail with reference to the accompanying drawings.

1 is an exemplary view showing a general liquid crystal display.

Referring to FIG. 1, a liquid crystal display includes a liquid crystal display panel 10 in which pixels are arranged in a matrix form; A gate driver 20 coupled to one short side of the liquid crystal display panel 10 to apply a scan signal to gate lines of the liquid crystal display panel; The data driver 30 is coupled to one long side of the liquid crystal display panel 10 to apply an image signal to data lines of the liquid crystal display panel.

The liquid crystal display panel 10 includes first and second substrates bonded to each other to maintain a constant cell gap, and a liquid crystal layer formed on the cell gaps of the first and second substrates. A thin film transistor array is formed on the first substrate, and a color filter array is formed on the second substrate.

A common electrode and a pixel electrode are formed in the liquid crystal display panel 10 where the first substrate and the second substrate are opposed to each other to apply an electric field to the liquid crystal layer. That is, by controlling the voltage applied to the pixel electrode while the voltage is applied to the common electrode, the light transmittance of the pixels can be adjusted individually.

On the first substrate, data lines for transmitting an image signal supplied from the data driver 30 and gate lines for transmitting a scan signal supplied from the gate driver 20 intersect each other. Pixels are individually formed in regions where the lines cross each other.

The gate driver 20 sequentially applies a scan signal to the gate lines so that pixels arranged in a matrix form are selected one by one, and the data driver 30 is one line selected through the data lines. The image signal is supplied to the pixels of.

As described above, a thin film transistor, which is used as a switching element, is formed in each pixel in order to selectively supply the image signal applied through the data lines, one line to the pixels.

In the thin film transistor formed in each pixel, a gate electrode is connected to the gate line, a source electrode is connected to the data line, and a drain electrode is connected to the pixel electrode of the pixel to form a data line according to a scan signal of the gate line. The image signal applied through this is selectively applied or blocked to the pixel electrode of the pixel.

FIG. 2 is an exemplary diagram showing an equivalent circuit for each pixel arranged in a matrix form on the liquid crystal display panel 10 in FIG.

Referring to FIG. 2, a pixel includes a thin film transistor 100 having a gate electrode connected to a gate line 101, a source electrode connected to a data line 103, a drain electrode of the thin film transistor 100, and a drain electrode. The driving of the liquid crystal display panel having the liquid crystal capacitor 102 and the storage capacitor 104 connected in parallel between the common electrode voltage Vcom and having such an equivalent circuit of pixels is described in detail with reference to the waveform diagram of FIG. 3. The explanation is as follows.

2 and 3, the common voltage Vcom is applied to the common electrode, and the voltage Vdata of the image signal is applied to the source electrode of the thin film transistor 100 through the data line 103. The signal Vg is applied to the gate electrode of the thin film transistor 100 through the gate line 101.

Therefore, first, in the turn-on period of the thin film transistor 100 to which the scan signal Vg of the nth frame is applied at high potential, the positive image signal voltage Vdata is transferred from the source electrode to the pixel electrode through the drain electrode. Supplied to and drives the liquid crystal, and charged to the storage capacity 104. In this case, the positive image signal voltage Vdata applied to the pixel electrode is gradually charged due to the influence of the liquid crystal capacitor 102 and the storage capacitor 104 in the turn-on period of the thin film transistor 100. As shown in FIG. 3, the waveform is represented by a pixel voltage Vp.

When the scan signal Vg transitions from a high potential to a low potential and the thin film transistor 100 is turned off, the gate electrode is formed due to parasitic capacitance caused by the overlap between the gate electrode and the drain electrode of the thin film transistor 100. Since the voltage variation of s affects the pixel electrode connected to the drain electrode, a voltage drop occurs from the charged pixel voltage Vp, which is referred to as kickback voltage ΔVp.

In the turn-off period of the thin film transistor 100 to which the scan signal Vg is applied at low potential, the pixel voltage Vp charged in the storage capacitor 104 is supplied to the pixel electrode to maintain driving of the liquid crystal. do.

On the other hand, in the n + 1 frame, since the above-described inversion driving method is applied, the negative image signal voltage Vdata is supplied from the source electrode to the pixel electrode through the drain electrode to drive the liquid crystal, and the storage capacitor 104 is charged.

Ideally, the pixel voltage Vp of the n + 1th frame is equal to the pixel voltage Vp of the nth frame in the turn-on, transition, and turn-off periods of the thin film transistor 100 based on the common voltage Vcom. Although the voltage waveform should be symmetrical, the pixel voltage Vp of the nth frame and the pixel voltage Vp of the nth + 1th frame are not symmetrical with each other due to the kickback voltage ΔVp. Flickering and afterimages occur in an image displayed on the display panel, which causes a problem of deterioration in image quality.

In order to prevent the deterioration of the image quality, the level of the common voltage Vcom should be adjusted such that the pixel voltage Vp of the nth frame and the pixel voltage Vp of the n + 1th frame are symmetrical with respect to the common voltage Vcom. .

However, as described above, in order to adjust the level of the common voltage Vcom so that the pixel voltage Vp of the nth frame and the pixel voltage Vp of the n + 1th frame are symmetric with respect to the common voltage Vcom. First, the kickback voltage ΔVp should be measured accurately, but the conventional liquid crystal display has a problem in that the kickback voltage ΔVp cannot be accurately measured.

In other words, in order to measure the kickback voltage ΔVp, the liquid crystal display panel needs to be decapped to measure the voltage of the pixel electrode. In this case, the liquid crystal capacitor 102 is not formed when the liquid crystal display panel is decapsulated. Accurate kickback voltage DELTA Vp cannot be measured.

Accordingly, in order to improve the deterioration of the image quality, a common voltage Vcom is applied to the liquid crystal display panel to apply the same signals as the actual driving environment, and the operator observes the image displayed on the liquid crystal display panel to minimize flicker or afterimage. The level of was adjusted manually.

However, in the conventional method as described above, there may be a variation in observation of flicker or an afterimage for each operator, which may cause a case where the set level of the common voltage Vcom does not provide an optimal image.

In addition, an error may occur as the operator adjusts the level of the common voltage Vcom by manual operation, and there is a problem in that productivity is reduced due to a separate work time required for flicker adjustment.

Accordingly, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to compensate for the effect of the kickback voltage that causes poor image quality, such as flicker or afterimage, to improve image quality. A display device and a driving method thereof are provided.

A liquid crystal display device for achieving the object of the present invention includes a pixel portion provided in the liquid crystal display panel for displaying an image; A further pixel portion disposed outside the pixel portion of the liquid crystal display panel; A driver for driving the pixel portion and the dummy pixel portion; A dummy line for applying a pixel voltage of the dummy pixel unit driven by the driver to the driver; And a common voltage compensator for detecting a kickback voltage from the pixel voltage of the dummy pixel and adjusting the level of the common voltage.

The driving method of the liquid crystal display device for achieving the object of the present invention comprises the steps of driving a dummy pixel unit provided in the liquid crystal display panel; Detecting a kickback voltage by receiving a pixel voltage from the driven dummy pixel unit; Compensating for the level of the common voltage through the kickback voltage.

The liquid crystal display and the driving method thereof according to the present invention as described above will be described in detail with reference to the accompanying drawings.

4 is an exemplary view showing a block configuration of a liquid crystal display according to the present invention.

Referring to FIG. 4, the liquid crystal display according to the present invention includes a pixel portion 211 provided in the liquid crystal display panel 210 to display an image; A dummy pixel unit 212 disposed outside the pixel unit 211 of the liquid crystal display panel 210; A driving unit 220 driving the pixel unit 211 and the dummy pixel unit 212 by applying a scan signal, a common voltage, and an image signal to the pixel unit 211 and the dummy pixel unit 212; A dummy line DL1 for applying the pixel voltage of the dummy pixel unit 212 driven by the scan signal, the common voltage and the image signal to the driver 220; A common voltage compensator 221 is configured to detect a kickback voltage by receiving the pixel voltage of the dummy pixel unit 212 from the driver 220, and adjust the level of the common voltage through the driver 220.                     

The liquid crystal display panel 210 includes first and second substrates bonded to each other to maintain a constant cell gap, and a liquid crystal layer formed on the cell gaps of the first and second substrates. The thin film is formed on the first substrate. The transistor array is formed, and the color filter array is formed on the second substrate.

The common electrode and the pixel electrode are formed on the liquid crystal display panel 210 where the first substrate and the second substrate are opposed to each other to apply an electric field to the liquid crystal layer. That is, by controlling the voltage applied to the pixel electrode while the voltage is applied to the common electrode, the light transmittance of the pixels can be adjusted individually.

On the first substrate, data lines for transmitting an image signal supplied from the driver 220 and gate lines for transmitting a scan signal supplied from the driver 220 cross each other, and the data lines and the gate lines are intersected with each other. Pixels are individually formed in regions that intersect with each other.

In the pixel portion 211 of the liquid crystal display panel 210, pixels are arranged in a matrix in an area where the data lines and the gate lines intersect each other.

At least one pixel may receive a scan signal from the driver 220 through a dummy gate line and a test signal through a data line in the dummy pixel unit 212 of the liquid crystal display panel 210. In some cases, one row of pixels may be formed. That is, one row of pixels may be formed in the dummy pixel portion 212 of the liquid crystal display panel 210 by the process conditions of simultaneously forming the pixels. In addition, in order to make the signal characteristic due to the influence of the adjacent pixels the same as those of the pixels formed in the pixel portion 211, one row of pixels is arranged on the dummy pixel portion 212 of the liquid crystal display panel 210. Can be formed. In addition, one row of pixels may be formed in the dummy pixel unit 212 of the liquid crystal display panel 210 to detect the kickback voltage in the plurality of pixels. For example, one row of pixels may be formed in the dummy pixel unit 212 of the liquid crystal display panel 210 to detect the kickback voltage for each of the red, green, and blue pixels.

At least one pixel formed in the dummy pixel unit 212 may be covered by a black matrix formed on the second substrate of the liquid crystal display panel 210 so as not to affect the image quality.

The driver 220 sequentially applies a scan signal to the gate lines of the pixel unit 211 and the dummy pixel unit 212 so that pixels arranged in a matrix form are selected one by one, and the data lines The image signal is supplied to the pixels of one line selected through the above. In this case, the driver 220 may include a gate driver for applying a scan signal to the gate lines, and a data driver for applying an image signal to the data lines.

As described above, a thin film transistor is used as a switching element in each pixel to selectively supply an image signal applied through data lines to pixels of the pixel portion 211 and the dummy pixel portion 212 one by one. Is formed.

In the thin film transistor formed in each pixel, a gate electrode is connected to the gate line, a source electrode is connected to the data line, and a drain electrode is connected to the pixel electrode of the pixel to form a data line according to a scan signal of the gate line. The image signal applied through this is selectively applied or blocked to the pixel electrode of the pixel.

The liquid crystal display according to the present invention is driven by an inversion method. That is, when an electric field in a constant direction is continuously applied to the liquid crystal layer, the liquid crystal is deteriorated, and an afterimage occurs in an image displayed from the liquid crystal display panel by the DC voltage component. Therefore, in order to prevent deterioration of the liquid crystal and to remove the DC voltage component, the voltage value of the image signal applied to each pixel is set to the voltage of positive (+) and negative (-) with respect to the common voltage applied to the common electrode. This driving method is called an inversion method.

The inversion driving method is a frame inversion method in which a voltage value of an image signal is supplied with an opposite polarity whenever a frame of an image is changed, and a voltage value of the image signal is supplied with an opposite polarity whenever a gate line is changed. A line inversion scheme and a dot inversion scheme in which the voltage values of the image signal are supplied to the neighboring pixels with opposite polarities and are supplied with the opposite polarities whenever one frame of the image is changed.

Among the inversion driving methods described above, the dot inversion method suppresses screen distortions such as flicker and crosstalk compared to the frame inversion method or the line inversion method to provide an image having excellent image quality, but to neighboring pixels. As the positive (+) and the negative (-) image signals are supplied differently, the power consumption is very high. Therefore, the line inversion method is applied to a small liquid crystal display device applied to wireless communication.                     

The liquid crystal display device according to the present invention configured as described above is driven as follows.

First, the driver 220 selects a pixel of the dummy pixel unit 212 by applying a scan signal through a gate line, and applies a test signal through a data line to the pixel voltage of the pixel of the dummy pixel unit 212. Charge it.

The dummy line DL1 applies the pixel voltage charged in the pixel of the dummy pixel unit 212 to the driver 220. In this case, when the dummy pixel unit 212 is formed in an area adjacent to the driving unit 220, the length of the dummy line DL1 is shortly patterned to minimize the resistance value and simplify the design to form the dummy line DL1. The process can be carried out easily.

The common voltage compensator 221 detects a kickback voltage by receiving a pixel voltage from the driver 220 and adjusts the level of the common voltage through the common voltage compensator. In this case, the common voltage compensator 221 may be designed in the driver 220. The common voltage compensator 221 may designate a difference between the test signal applied to the pixel of the dummy pixel unit 212 and the pixel voltage supplied through the dummy line DL1. Detect kickback voltage through

5 is an exemplary view showing a planar configuration of a pixel included in the dummy pixel unit 212.

Referring to FIG. 5, the pixel provided in the dummy pixel unit 212 is defined in a rectangular region in which the dummy gate line DGL11 arranged in the horizontal direction and the data line DL11 arranged in the vertical direction cross each other. The pixel includes a thin film transistor TFT11 and a pixel electrode PE11. In this case, the pixel provided in the dummy pixel unit 212 may include a storage capacitor (not shown) electrically connected to the pixel electrode PE11.

The thin film transistor TFT11 extends at a predetermined position of the dummy gate line DGL11 and extends at a predetermined position of the data line DL11 to correspond to the gate electrode GE11. A source electrode SE11 having an overlapping region and a drain electrode DE11 corresponding to the source electrode SE11 based on the gate electrode GE11 and overlapping the gate electrode GE11 with a predetermined region. Equipped.

The source electrode SE11 and the drain electrode DE11 are uniformly spaced apart on the gate electrode GE11, and the drain electrode DE11 is in electrical contact with the pixel electrode PE11 through the drain contact hole DC11. . In this case, the pixel electrode PE11 may be formed of a conductive material having a high light transmittance. For example, indium tin oxide (ITO) or indium zinc oxide (IZO) may be applied.

When the thin film transistor TFT11 is provided with a semiconductor layer (not shown) and a scan signal is supplied at high potential to the gate electrode GE11 through the dummy gate line DGL11, the source electrode SE11 and the drain electrode DE11. A conductive channel is formed therebetween.

That is, when the scan signal is supplied to the gate electrode GE11 of the thin film transistor TFT11 through the dummy gate line DGL11 from the above-described driving unit 220 at high potential, the source electrode SE11 of the thin film transistor TFT11 A conductive channel is formed between the drain electrode DE11, and a test signal supplied from the driver 220 to the source electrode SE11 through the data line DL11 is transmitted to the drain electrode DE11 through the conductive channel. Since the drain electrode DE11 is connected to the pixel electrode PE11 through the drain contact hole DC11, a test signal supplied to the drain electrode DE11 is applied to the pixel electrode PE11.

In the section in which the scan signal is applied at high potential, the test signal is applied to the pixel electrode PE11 to drive the liquid crystal and is charged in a storage capacity (not shown). At this time, the voltage of the test signal applied to the pixel electrode PE11 is gradually charged under the influence of the liquid crystal capacity and the storage capacity.

When the scan signal transitions from the high potential to the low potential, the voltage variation of the gate electrode GE11 is changed due to the parasitic capacitance caused by the overlap of the gate electrode GE11 and the drain electrode DE11 of the thin film transistor TFT11. The voltage drop of the kickback voltage is generated from the voltage of the test signal charged in the storage capacitor by affecting the pixel electrode PE11 connected to the drain electrode DE11. The storage capacitor has a voltage difference of the kickback voltage from the voltage of the test signal. The pixel voltage is maintained.

In addition, the pixel voltage charged in the storage capacitor is supplied to the pixel electrode PE11 to maintain the driving of the liquid crystal in the section in which the scan signal is applied at the low potential.

The pixel voltage supplied to the pixel electrode PE11 is applied to the driver 220 through the dummy line DL1 electrically connected to the pixel electrode PE11. In this case, the dummy line DL1 may be formed of the same material as that of the pixel electrode PE11 and may be patterned and formed at the same time as the pixel electrode PE11.

The driver 220 applies the test voltage applied to the pixels of the dummy pixel unit 212 and the pixel voltage applied through the dummy line DL1 to the common voltage compensator 221, and applies the common voltage compensator ( 221 detects a kickback voltage by using the difference between the test voltage and the pixel voltage, and then applies a control signal to the driver 220 to adjust the level of the common voltage to be applied to the pixels of the pixel unit 211.

6 is an exemplary diagram showing an equivalent circuit for the pixels of the dummy pixel portion 212 configured as described above.

Referring to FIG. 6, the equivalent circuit for the pixel of the dummy pixel unit 212 includes a thin film transistor TFT21 having a gate electrode connected to the dummy gate line DGL21 and a source electrode connected to the data line DL21. The liquid crystal capacitor 202 and the storage capacitor 204 connected in parallel between the drain electrode of the thin film transistor TFT21 and the common electrode voltage Vcom are connected to the drain electrode of the thin film transistor TFT21. The dummy line DL2 applies the pixel voltage charged in the 204 to the driver.

The liquid crystal display according to the present invention as described above may be applied to the liquid crystal display of the small model, which will be described in detail as follows.

7 is an exemplary view showing a liquid crystal display of a small model.

Referring to FIG. 7, the liquid crystal display of the small model includes a liquid crystal display panel 310 in which pixels are arranged in a matrix form; A driver 320 mounted on one side of the liquid crystal display panel 310 in a chip-on-glass (COG) manner to drive pixels of the liquid crystal display panel 310; The driver 320 includes a flexible printed circuit (FPC) 330 for applying an image signal, a control signal, a driving voltage, and the like to the driver 320.

As described above, the liquid crystal display according to the present invention includes a pixel portion for displaying an image on the liquid crystal display panel 310, a dummy pixel portion provided outside the pixel portion of the liquid crystal display panel 310, and the dummy pixel. A dummy line for applying a negative pixel voltage to the driver 320 is provided, and a kickback voltage is detected by applying the pixel voltage of the dummy pixel part to the driver 310, thereby adjusting a common voltage level. Compensation unit is provided.

The dummy line is electrically connected to one side of the liquid crystal display panel 310 through a driver and a bonding pad mounted in a chip-on-glass manner.

The driving unit may further include a control register for driving the dummy pixel unit at a specific gray level according to a set resist value, and a register for selecting whether to drive the dummy pixel unit.

The above-described line inversion driving of the small liquid crystal display as described above will be described in detail with reference to the waveform diagrams of FIGS. 8A and 8B.

First, referring to the waveform diagram shown in FIG. 8A, the common voltage Vcom is applied to the common electrode in the form of a pulse in which the high potential and the low potential are alternated on a gate line basis, and the image signal voltage Vdata is applied to the common voltage ( Are sequentially applied through the data lines in the form of pulses with potentials opposite to Vcom).

As described above, when the common voltage Vcom is applied to the common electrode in the form of pulses in which the high potential and the low potential are alternated on a gate line basis, the liquid crystal is driven as compared with the case where the common voltage Vcom is applied at a constant voltage. It is possible to minimize the level of the image signal voltage (Vdata) to be made, thereby reducing the power consumption of the liquid crystal display panel.

8B shows a case where the common voltage Vcom and the image signal voltage Vdata shown in FIG. 8A are applied to one pixel.

Referring to the waveform diagram of FIG. 8B, first, in the nth frame, the scan signal Vg is applied to the gate electrode of the thin film transistor, the common voltage Vcom is applied to the common electrode at high potential, and the image signal voltage Vdata. It is applied at a potential opposite to the common voltage Vcom.

Therefore, in the period in which the scan signal Vg is applied at high potential, a negative voltage (−) corresponding to the difference between the image signal voltage Vdata and the common voltage Vcom is supplied to the pixel electrode to drive the liquid crystal, and the storage capacitor Is charged. At this time, the negative voltage (-) supplied to the pixel electrode is gradually charged due to the influence of the liquid crystal capacitor and the storage capacitor in the section where the scan signal Vg is applied at a high potential, and as shown in FIG. Vp) appears as a waveform.

In the case where the scan signal Vg transitions from a high potential to a low potential, the voltage variation of the gate electrode influences the pixel electrode connected to the drain electrode due to parasitic capacitance caused by the overlap between the gate electrode and the drain electrode of the thin film transistor. Gives a voltage drop of the kickback voltage from the pixel voltage Vp.

In the period where the scan signal Vg is applied at a low potential, the pixel voltage Vp charged in the storage capacitor is supplied to the pixel electrode PE11 to maintain driving of the liquid crystal.

On the other hand, in the n + 1th frame, since the aforementioned inversion driving method is applied, the scan signal Vg is applied to the gate electrode of the thin film transistor, the common voltage Vcom is applied to the common electrode at low potential, and the image signal. As the voltage Vdata is applied to a potential opposite to the common voltage Vcom, a positive voltage (+) according to the difference between the image signal voltage Vdata and the common voltage Vcom is applied to the pixel electrode to drive the liquid crystal. And the storage capacity is charged. At this time, the positive voltage (+) supplied to the pixel electrode is gradually charged due to the influence of the liquid crystal capacitor and the storage capacitor in the section where the scan signal Vg is applied at a high potential, and as shown in FIG. Vp) appears as a waveform.

The waveform of the pixel voltage Vp of the nth + 1th frame should ideally be a waveform symmetrical with the pixel voltage Vp of the nth frame, but due to the kickback voltage, the pixel voltage Vp of the nth + 1th frame The pixel voltages Vp of the n + 1th frame do not become symmetrical with each other, and thus, flicker or afterimage occurs in an image displayed on the liquid crystal display panel, thereby deteriorating image quality.

Therefore, in the present invention, as described above, the dummy pixel unit is provided in the liquid crystal display panel, and the scan signal and the test signal are applied to the pixel of the dummy pixel unit, and the pixel voltage of the pixel of the dummy pixel unit is shared through the dummy line. After applying to the voltage compensator and detecting the kickback voltage according to the difference between the test signal and the pixel voltage through the common voltage compensator to adjust the level of the common voltage to be applied to the pixels of the liquid crystal display panel, such as flicker or afterimage The deterioration of image quality can be prevented.

As described above, the liquid crystal display and the driving method thereof according to the present invention apply a scan signal and a test signal to the pixels of the dummy pixel unit provided in the liquid crystal display panel, and apply the pixel voltage from the pixels of the dummy pixel unit through the dummy line. After detecting the kickback voltage, it is possible to set an optimal common voltage level considering the kickback voltage.

Therefore, even when the liquid crystal display panels have different kickback voltages, it is possible to easily and accurately set the optimum common voltage level of the individual liquid crystal display panels. It is possible to prevent the effect of improving the image quality of the liquid crystal display device.

Claims (12)

A pixel portion provided in the liquid crystal display panel to display an image; A dummy pixel unit disposed outside the pixel unit of the liquid crystal display panel; A driver for driving the pixel portion and the dummy pixel portion; A dummy line for applying a pixel voltage of the dummy pixel unit driven by the driver to the driver; A common voltage compensator for detecting a kickback voltage from the pixel voltage of the dummy pixel part and adjusting a level of the common voltage through the dummy voltage part; And the dummy pixel unit includes at least one pixel receiving a scan signal from the driver through a dummy gate line and a test signal through a data line. delete The liquid crystal display of claim 1, wherein the dummy pixel unit includes a row of pixels receiving a scan signal from the driver through a dummy gate line and a test signal through a data line. The liquid crystal display device according to claim 1, wherein the dummy pixel portion is covered by a black matrix. The liquid crystal display of claim 1, wherein the common voltage compensator is formed in the driver. 2. The semiconductor device of claim 1, wherein the pixel of the dummy pixel portion comprises: a dummy gate line arranged in a horizontal direction; A data line arranged in a vertical direction and crossing the dummy gate line; A thin film transistor having a dummy gate line and a gate electrode connected thereto, and a data line and a source electrode connected thereto; A pixel electrode electrically connected to the drain electrode of the thin film transistor; And a storage capacitor electrically connected to the pixel electrode, wherein the dummy line is connected to the pixel electrode to apply a pixel voltage of the pixel electrode to the driver. The pixel device of claim 1, wherein the pixel of the dummy pixel unit comprises: a thin film transistor having a gate electrode connected to a dummy gate line and a source electrode connected to a data line; And a liquid crystal capacitor and a storage capacitor connected in parallel between the drain electrode and the common voltage of the thin film transistor, wherein the dummy line is connected to the drain electrode of the thin film transistor to charge the pixel voltage charged in the storage capacitor to the driving unit. Liquid crystal display device characterized in that the application. The liquid crystal display of claim 1, wherein the dummy line is formed of the same material as the pixel electrodes of the pixels provided in the pixel portion and the dummy pixel portion. The liquid crystal display of claim 1, wherein the driving unit is mounted on the liquid crystal display panel in a chip-on-glass (COG) manner. Driving a dummy pixel unit provided in the liquid crystal display panel; Detecting a kickback voltage by receiving a pixel voltage from the driven dummy pixel unit; Compensating for the level of the common voltage through the kickback voltage; And the at least one pixel receives a scan signal from a driver through a dummy gate line and a test signal from a data line. The driving method of claim 10, further comprising compensating for the level of the common voltage and then driving the pixel unit provided in the liquid crystal display panel in an inversion manner. The driving method of claim 10, further comprising compensating the level of the common voltage and then driving the pixel unit provided in the liquid crystal display panel in a line inversion manner.

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