KR101461021B1 - Driving circuit for liquid crystal display device and method for driving the same - Google Patents

Abstract

The present invention includes R, G, and B sub-pixels divided into an image display area and a viewing angle control area to improve the brightness efficiency of the image when the wide viewing angle is realized and to display the interference image in the narrow viewing angle And more particularly, to a driving apparatus for a liquid crystal display device and a driving method thereof.

To this end, the liquid crystal display device of the present invention includes a liquid crystal panel having a plurality of unit pixels, a driving control unit for driving gate lines and data lines of the liquid crystal panel, and a viewing angle control voltage Wherein the plurality of unit pixels comprise R, G, and B sub-pixels divided into an image display area and a viewing angle control area, A first NMOS TFT for supplying a video signal to the pixel electrode in response to a scan pulse input from the current one gate line among the gate lines; A second NMOS TFT for supplying an external common voltage to the lower common electrode in accordance with a viewing angle control voltage from the viewing angle control line; And a third NMOS TFT electrically connecting the lower common electrode and the pixel electrode in response to a scan pulse from the previous gate line so that the potentials of the lower common electrode and the pixel electrode become equal to each other.

A video display area, a viewing angle control area, a light / narrow viewing angle, a viewing angle selection signal,

Description

TECHNICAL FIELD [0001] The present invention relates to a driving apparatus for a liquid crystal display device and a driving method thereof. BACKGROUND OF THE INVENTION [0002]

The present invention relates to a liquid crystal display, and more particularly, to a liquid crystal display having sub-pixels R, G, and B divided into a video display area and a viewing angle control area, The present invention relates to a driving apparatus for a liquid crystal display device and a driving method thereof, which can display an interference image in color in an implementation.

In general, a liquid crystal display displays an image by injecting liquid crystal between two substrates and adjusting an optical transmittance of the liquid crystal by applying an electric field to liquid crystal through opposing electrodes through the liquid crystal.

Such a liquid crystal display device can be classified into a vertical electric field application type or a horizontal electric field application type liquid crystal display device depending on the direction of the electric field driving the liquid crystal.

The vertical field-applied liquid crystal display device is a TN (Twist Namatic) mode in which liquid crystal is driven by a vertical electric field between a pixel electrode and a common electrode arranged opposite to upper and lower substrates, respectively. In the TN mode, since the common electrode of the upper substrate and the pixel electrode of the lower substrate, both of which form a vertical electric field, are formed as transparent electrodes, a large aperture ratio can be secured. However, since the liquid crystal is driven in the vertical direction by the vertical electric field, the movement of the liquid crystal in the light traveling in the lateral direction affects the viewing angle to be about 90 degrees.

The horizontal electric field applied type liquid crystal display device is an IPS (In Plane Switching) mode in which liquid crystal is driven by a horizontal electric field between a pixel electrode and a common electrode which are arranged side by side on a lower substrate. In the IPS mode, since the liquid crystal is driven in the horizontal direction, there is almost no movement in the vertical direction, and thus the viewing angle is widened to about 160 degrees by giving less influence to the light traveling in the lateral direction.

2. Description of the Related Art [0002] In recent years, a liquid crystal display device having a liquid crystal panel having a quad type cell structure including one ECB (Electrical Controlled Birefringence) sub-pixel and three RGB sub-pixels in order to arbitrarily switch between a wide viewing angle and a narrow viewing angle A display device was developed.

1, a quad-type liquid crystal cell has R sub-pixel, G sub-pixel, B sub-pixel and ECB sub-pixel, in which R and G sub-pixels are horizontally configured and ECB and B sub- And is configured horizontally with the pixel.

The R and ECB sub-pixels vertically positioned to each other are commonly connected to the first data line DL1, and the G and B sub-pixels are commonly connected to the second data line DL2. In addition, the R and G sub-pixels horizontally positioned to each other are commonly connected to the first gate line GL1, and the ECB sub-pixel and the B sub-pixel are commonly connected to the second gate line GL2.

Here, the ECB sub-pixel is used to adjust the wide viewing angle mode and the narrow viewing angle mode. In other words, each sub-pixel of R, G, and B is used to display the original image, and the ECB sub-pixel is used to display the interference image so that the original image can not be seen exactly in the lateral direction of the liquid crystal panel (for example, about 45 degrees from the front) Can be used.

Specifically, in the narrow viewing angle mode, while the original image is displayed on the RGB sub-pixels, the interference image is also displayed on each ECB sub-pixel so that the original image and the interference image are simultaneously displayed in the lateral direction. In other words, only the original image is seen on the front face of the liquid crystal panel, and the interference image is not seen. However, when viewed from the side of the liquid crystal panel, the original image and the interference image overlap.

However, in a conventional liquid crystal panel having a quad-type cell structure, since the ECB sub-pixel does not transmit light in the wide viewing angle mode, there is a problem that the luminance is reduced by the area occupied by the ECB sub-pixels. Specifically, since the area occupied by the ECB sub-pixels in the liquid crystal panel of the quad-type cell structure is 25%, the brightness is reduced by about 25% as compared with the liquid crystal panel of the general RGB stripe structure, thereby lowering the brightness efficiency.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to selectively implement a wide viewing angle and a narrow viewing angle, to improve luminance efficiency of a wide viewing angle, And a method of driving the liquid crystal display device.

According to another aspect of the present invention, there is provided an apparatus for driving a liquid crystal display, including: a liquid crystal panel having a plurality of unit pixels; a driving controller for driving gate lines and data lines of the liquid crystal panel; And a viewing angle control unit for supplying a viewing angle control voltage to the viewing angle control lines of the liquid crystal panel, wherein the plurality of unit pixels include R, G, and B Wherein the viewing angle control region includes a first NMOS TFT for supplying a video signal to the pixel electrode in response to a scan pulse input from a current one gate line among the gate lines; A second NMOS TFT for supplying an external common voltage to the lower common electrode in accordance with a viewing angle control voltage from the viewing angle control line; And a third NMOS TFT electrically connecting the lower common electrode and the pixel electrode in response to a scan pulse from the previous gate line so that the potentials of the lower common electrode and the pixel electrode become equal to each other.

Wherein the viewing angle control region includes a first capacitor for maintaining a difference voltage between a video signal applied to the pixel electrode and an external common voltage applied to the upper common electrode until the next voltage is charged according to the viewing angle control voltage, A second capacitor for holding a difference voltage between an applied video signal and a lower common electrode voltage applied to the lower common electrode until a next voltage is charged, and a second capacitor for holding a voltage of the pixel electrode and the lower common electrode And a third capacitor for maintaining the difference voltage of the external common voltage applied to the upper common electrode until the next voltage is charged.

Wherein the viewing angle control voltage is supplied to each of the viewing angle control lines at a level for turning on the second NMOS TFT in the wide viewing angle mode and is set to a level for turning off the second NMOS TFT in the narrow viewing angle mode, Line.

According to another aspect of the present invention, there is provided a driving apparatus for a liquid crystal display including a liquid crystal panel having a plurality of unit pixels, a driving control unit driving gate lines and data lines of the liquid crystal panel, And a viewing angle control unit for supplying a viewing angle control voltage to the viewing angle control lines of the liquid crystal panel, wherein the plurality of unit pixels are divided into R, G And a B sub-pixel, wherein the viewing angle control region includes a first NMOS TFT for supplying a video signal to a pixel electrode in response to a scan pulse from a current one gate line among the gate lines; A second PMOS TFT for supplying an external common voltage to the lower common electrode in accordance with the viewing angle control voltage from the viewing angle control line; And a third NMOS TFT electrically connecting the lower common electrode and the pixel electrode in accordance with the viewing angle control voltage so that the potentials of the lower common electrode and the pixel electrode become equal to each other.

Wherein the viewing angle control region includes a first capacitor for maintaining a difference voltage between a video signal applied to the pixel electrode and an external common voltage applied to the upper common electrode until the next voltage is charged according to the viewing angle control voltage, A second capacitor for holding a difference voltage between an applied video signal and a lower common electrode voltage applied to the lower common electrode until the next voltage is charged; And a third capacitor that holds the difference voltage of the external common voltage applied to the common electrode until the next voltage is charged.

Wherein the viewing angle control voltage is supplied to each of the viewing angle control lines at a level that turns on the second PMOS TFT and turns off the third NMOS TFT in the wide viewing angle mode, And turning off the third NMOS TFT and turning on the third NMOS TFT. The image display region and the viewing angle control region are each provided with R, G, and B color filters, and the upper common electrode is independently supplied with the external common voltage.

According to another aspect of the present invention, there is provided a method of driving a liquid crystal display device including a liquid crystal panel having a plurality of unit pixels, a driving control unit driving gate lines and data lines of the liquid crystal panel, And a viewing angle control unit for supplying a viewing angle control voltage to the viewing angle control lines of the liquid crystal panel, wherein the plurality of unit pixels are divided into an image display area and a viewing angle control area, In the driving method of the apparatus, the driving of the viewing angle control region includes supplying a video signal to the pixel electrode in accordance with a scan pulse input from the current gate line using the first NMOS TFT; Supplying an external common voltage to a lower common electrode in accordance with a viewing angle control voltage from the viewing angle control line using a second NMOS TFT; And electrically connecting the lower common electrode and the pixel electrode in such a manner that the potentials of the lower common electrode and the pixel electrode become equal to each other in response to a scan pulse from the previous gate line using the third NMOS TFT.

Wherein the driving of the viewing angle control region uses a first capacitor to maintain a difference voltage between an image signal applied to the pixel electrode and an external common voltage applied to the upper common electrode according to the viewing angle control voltage until the next voltage is charged Maintaining the differential voltage between the video signal applied to the pixel electrode and the lower common electrode voltage applied to the lower common electrode until the next voltage is charged using the second capacitor, And maintaining the difference voltage between the voltage of the pixel electrode and the lower common electrode and the external common voltage applied to the upper common electrode until the next voltage is charged.

Wherein the viewing angle control voltage is supplied to each of the viewing angle control lines at a level for turning on the second NMOS TFT in the wide viewing angle mode and is set to a level for turning off the second NMOS TFT in the narrow viewing angle mode, Line. ≪ / RTI >

According to another aspect of the present invention, there is provided a method of driving a liquid crystal display including a liquid crystal panel having a plurality of unit pixels, a driving control unit driving gate lines and data lines of the liquid crystal panel, And a viewing angle control unit for supplying a viewing angle control voltage to the viewing angle control lines of the liquid crystal panel, wherein the plurality of unit pixels are divided into an image display area and a viewing angle control area, In the driving method of the apparatus, the driving step of the viewing angle control region includes supplying a video signal to the pixel electrode in response to a scan pulse from the current one gate line among the gate lines using a first NMOS TFT; Supplying an external common voltage to a lower common electrode according to the viewing angle control voltage from the viewing angle control line using a second PMOS TFT; And electrically connecting the lower common electrode and the pixel electrode using the third NMOS TFT so that the potentials of the lower common electrode and the pixel electrode become equal to each other according to the viewing angle control voltage.

 Wherein the driving of the viewing angle control region uses a first capacitor to maintain a difference voltage between an image signal applied to the pixel electrode and an external common voltage applied to the upper common electrode according to the viewing angle control voltage until the next voltage is charged Maintaining the differential voltage between the video signal applied to the pixel electrode and the lower common electrode voltage applied to the lower common electrode until the next voltage is charged using the second capacitor, And maintaining the difference voltage between the voltage of the lower common electrode and the external common voltage applied to the upper common electrode according to the viewing angle control voltage until the next voltage is charged.

Wherein the viewing angle control voltage is supplied to each of the viewing angle control lines at a level that turns on the second PMOS TFT and turns off the third NMOS TFT in the wide viewing angle mode, And turning off the third NMOS TFT and turning on the third NMOS TFT.

The driving apparatus of the liquid crystal display apparatus and the driving method thereof according to the embodiment of the present invention having the above-described features have the following effects.

A driving apparatus and a driving method of a liquid crystal display according to the present invention include a plurality of sub-pixels including an image display region and a viewing angle control region, and a liquid crystal of a viewing angle control region in the same manner as the image display regions in a wide viewing angle mode. The brightness of the image can be improved and the brightness efficiency of the image can be improved. In the narrow viewing angle mode, unlike the driving method of the image display region, the viewing angle can be reduced by driving the liquid crystal in the viewing angle control region to form a vertical electric field. At this time, color filters are provided in the viewing angle control region to increase the display efficiency of the image and display the interference image in color.

Hereinafter, a driving apparatus and a driving method of a liquid crystal display according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram showing a driving apparatus of a liquid crystal display according to a first embodiment of the present invention.

The liquid crystal display device shown in FIG. 2 includes a liquid crystal panel 2 having R, G, and B sub-pixels divided into an image display region and a viewing angle control region; A driving control unit for driving the gate lines GL1 to GLn and the data lines DL1 to DLm of the liquid crystal panel 2; And a viewing angle control unit 10 for driving the viewing angle control lines CL of the liquid crystal panel 2 according to a viewing angle selection signal SES input from the outside.

The drive control unit includes a data driver 4 for driving the data lines DL1 to DLm of the liquid crystal panel 2, a gate driver 6 for driving the gate lines GL1 to GLn of the liquid crystal panel 2, And ECB data together with the image data RGB so that the unit pixels form a wide viewing angle or a narrow viewing angle according to the viewing angle selection signal SES and the externally inputted image data RGB, And a timing controller 8 for supplying the data to the data driver 4 or a common voltage supply unit (not shown).

The liquid crystal panel 2 includes a liquid crystal panel 2 and a liquid crystal panel 2 each having an image display region defined by a plurality of gate lines GL1 through GLn and data lines DL1 through DLm and a plurality of viewing angle control lines CL1 through CLn, Sub-pixels. Each of these sub-pixels includes at least one thin film transistor (TFT) (T1 to T3) and a plurality of liquid crystal capacitors Clc connected to any one of the TFTs T1 to T3 Respectively.

The liquid crystal capacitor Clc provided in the image display region of each sub pixel is composed of a pixel electrode connected to the first TFT T1 and a common electrode which vertically or horizontally faces the pixel electrode with the liquid crystal therebetween. The first TFTs T1 provided in the image display region supply image signals from the data lines DL1 to DLm to the pixel electrodes in response to the scan pulses from the gate lines GL1 to GLn. The liquid crystal capacitor Clc charges the difference voltage between the video signal supplied to the pixel electrode and the lower common electrode voltage supplied to the common electrode, and adjusts the light transmittance by varying the arrangement of the liquid crystal molecules according to the difference voltage. do. The storage capacitor Cst is connected in parallel to the liquid crystal capacitor Clc so that the video signal charged in the liquid crystal capacitor Clc is maintained until the next video signal is supplied. The storage capacitor Cst may be formed by overlapping the pixel electrode with the previous gate line with the insulating film interposed therebetween, or the pixel electrode may be formed by overlapping the storage line with the insulating film interposed therebetween.

The liquid crystal capacitor Clc provided in the viewing angle control region of each sub pixel is formed to overlap with a lower common electrode provided in the form of a plate or a plurality of slits on the lower substrate with an insulating film interposed therebetween, So that the upper common electrode and the liquid crystal are opposed to each other. Accordingly, in the viewing angle control region, the viewing angle is controlled by driving the liquid crystal horizontally or vertically according to the viewing angle control voltage input through the viewing angle control lines CL1 to DLn. The liquid crystal panel 2 of the present invention will be described in more detail below with reference to the accompanying drawings.

The data driver 4 receives the video data RGBE aligned from the timing controller 8 using the source start pulse SSP and the source shift clock SSC among the data control signal DCS from the timing controller 8, Into an analog voltage, that is, a video signal. Specifically, the data driver 4 latches the image data RGBE input according to the source shift clock SSC of the data control signal DCS, and then, in response to the source output enable (SOE) signal, And supplies a video signal for one horizontal line to each of the data lines DL1 to DLm for every one horizontal period in which scan pulses are supplied to the data lines GL1 to GLn. At this time, the data driver 4 selects a positive or negative gamma voltage having a predetermined level according to the grayscale value of the input image data RGBE, and outputs the selected gamma voltage to each of the data lines DL1 to DLm as a video signal. .

The gate driver 6 sequentially generates scan pulses in response to a gate control signal GCS from the timing controller 8, for example, a gate start pulse GSP and a gate shift clock GSC, The pulse width of the scan pulses is controlled according to the GOE signal. Then, the scan pulses whose pulse widths are controlled are again supplied with the gate-on voltages sequentially to the gate lines GL1 to GLn. Specifically, the gate driver 6 sequentially shifts the gate start pulse GSP from the timing controller 8 in accordance with the gate shift clock GSC to generate a scan pulse sequentially. On the basis of the gate output enable (GOE) signal, the pulse width of the scan pulses is controlled to sequentially supply the gate-on voltages whose pulse widths are controlled to the gate lines GL1 to GLn. On the other hand, the gate-off voltage is supplied during the period when no gate-on voltage is supplied to the gate lines GL1 to GLn.

The timing controller 8 generates ECB data E using image data RGB input from the outside in accordance with a viewing angle control signal SES input from a user. Specifically, when the viewing angle control signal SES is inputted so that the liquid crystal panel 2 is operated in the wide viewing angle mode, the timing controller 8 controls the ECB data E (E) so that the luminance of the image data RGB ) And supplies them to the viewing angle control regions. Here, the ECB data E may be generated so as to correspond to the average, maximum, or minimum gradation value of the image data RGB. If the viewing angle control signal SES is input so that the liquid crystal panel 2 operates in the narrow viewing angle mode, the timing controller 8 outputs ECB data E previously set to display an interference image or the like in each viewing angle control area, .

As described above, the timing controller 8 includes at least one memory and outputs the ECB data E to display the interference image in each of the viewing angle control areas according to the viewing angle control signal SES, And outputs the ECB data E so that the luminance of the image is increased. Here, when the liquid crystal panel 2 outputs the ECB data E so as to display the interference image, the ECB data E can be supplied to a power supply part, not shown, particularly a common voltage supply part. Then, the common voltage supply unit generates a common voltage (hereinafter referred to as an external common voltage) corresponding to the ECB data E and supplies the generated common voltage to the common electrode provided on the upper substrate of the liquid crystal panel 2.

The ECB data E is preset and stored in at least one memory so as to correspond to the maximum, minimum, or average gradation value of the image data (RGB) or a predetermined interference image, respectively. Specifically, the ECB data E can be the display gray scale value of the viewing angle control area corresponding to the maximum, minimum, or average gray scale value of R, G, B image data.

As described above, the timing controller 8 generates the ECB data E and supplies the ECB data E to the data driver 4 together with the input image data RGB, as well as the viewing angle control signal SES) to the viewing angle control unit 10 again. Then, the timing controller 8 controls the data and gate drivers 4 and 6 by generating gate and data control signals GCS and DCS.

The viewing angle control unit 10 sequentially supplies the viewing angle control voltage CCS to the viewing angle control line CL of the liquid crystal panel 2 in accordance with the viewing angle control signal SES input from the timing controller 8. [ Here, the viewing angle control voltage CCS is a voltage of a level for turning on or off the second TFT T2 provided in the viewing angle control regions of each sub-pixel, thereby turning on the second TFT T2 Off voltage for turning off the second TFT T2 or a turn-off voltage for turning off the second TFT T2.

FIG. 3 is a plan view schematically showing a unit pixel of the liquid crystal panel shown in FIG. 2. FIG. 4 is an equivalent circuit diagram showing the R viewing angle control region and the G viewing angle control region in FIG. 3 in more detail. 5 is a structural cross-sectional view showing the R viewing angle control area and the R image display area in FIG.

The stripe type unit pixels shown in Figs. 3 to 5 represent unit pixels in the case where the liquid crystal panel 2 is made of an amorphous-Si (a-Si) panel. Specifically, the unit pixels of the a-Si panel are composed of R, G, and B sub-pixels R, G, and B adjacent to each other. In each unit pixel, the R subpixel R, the G subpixel G, and the B subpixel B are formed in the horizontal direction. Each of the R, G and B sub-pixels R, G and B has an image display area and a viewing angle control area ECB_R, G and B, respectively, and each of the image display area and the viewing angle control areas ECB_R, And B are formed in a direction perpendicular to each other.

Referring to FIG. 4, each of the viewing angle control regions ECB_R, G, and B includes a first TFT T1 for supplying a video signal to a pixel electrode in response to a scan pulse from one of the gate lines GLn, A second TFT T2 for supplying an external common voltage Vcom1 to the lower common electrode in accordance with the viewing angle control voltage CCS from the control line CL and a second TFT T2 for supplying a scan pulse from the previous gate line GLn- And a third TFT (T3) for making the potentials of the lower common electrode and the pixel electrode equal to each other. Accordingly, a first capacitor (C1) is formed between the pixel electrode and the upper common electrode, a second capacitor (C2) is formed between the pixel electrode and the lower common electrode, and a third capacitor C3 are formed.

In general, only the NMOS transistor may be formed in each sub-pixel due to the characteristics of the a-Si panel. Accordingly, the first to third TFTs T1 to T3 provided in the respective viewing angle control regions ECB_R, G, and B can be NMOS transistors, and the viewing angle control voltage CLK inputted through the viewing angle control line CL (CCS), or in a narrow viewing angle mode.

4 and 5, the liquid crystal panel 2 includes a lower substrate 10 for controlling the orientation of the liquid crystal layer 30 to adjust the amount of light transmitted to the upper substrate 20. [

Each unit pixel of the lower substrate 10 forms a horizontal electric field to form image display regions R, G, and B for controlling the orientation of the liquid crystal layer 30 and a horizontal or vertical electric field depending on the driving mode of the viewing angle Angle control areas ECB_R, G, and B for controlling the orientation of the liquid crystal layer 30 in the horizontal or vertical direction. Each of the viewing angle control regions is formed by an IPS structure forming a fringe field, and each of the viewing angle control regions ECB_R, G, and B is formed by mixing an ECB structure and an IPS structure according to a driving mode. Here, each of the viewing angle control regions ECB_R, G, and B forms a vertical electric field in accordance with a difference voltage between the lower common electrode voltage Vcom and the external common voltage Vcom1, and the image signal and the lower common electrode voltage Vcom Are applied, a horizontal electric field is formed, respectively.

The first TFT T1 is located at the intersection of the nth gate line GLn and the second data line DL2 in the image display region and the pixel line connected to the first TFT T1 is connected to the nth gate line GLn. The pixel electrodes 17 are formed in a shape having a plurality of slits in parallel with the data lines DL1 to DLn, which are connected to the pixel lines. The lower common electrode 16 is formed in a plate shape with the pixel electrodes 17 and the insulating film 18 interposed therebetween. The lower common electrodes 16 may be connected to each other through a common line (not shown) parallel to the gate lines GL1 to GLn and may be formed on the entire surface of the lower substrate 10 to form respective viewing angle control regions ECB_R , G, and B may be electrically connected to the lower common electrodes 16 of the image display region. That is, the fringe field is formed by the lower common electrode 16 and the pixel electrode 17 in the image display region.

In the present invention, only the structure in which the lower common electrode 16 is formed on the lower substrate 10 and the pixel electrode 17 is formed on the lower common electrode 16 with the insulating film 18 therebetween is described. However, The positions and structures of the electrode 16 and the pixel electrode 17 are changed so that the fringe field can be formed. Therefore, only the structure in which the pixel electrode 17 is formed on the lower common electrode 16 with the insulating film 18 therebetween will be described.

As described above, the image display area can be implemented in various forms within the scope of the structure for forming the fringe field. For example, the pixel electrodes 17 formed in a shape having a plurality of slits may be formed in a straight line shape parallel to each other, or may be formed such that multi domains having different directions of liquid crystal orientation are formed between the pixel electrodes 17 You may. Particularly, when each of the sub-pixels has a bent structure, the response speed and the color shift are improved and the image quality is improved.

In addition, red, green, and blue color filters are formed on the upper substrate 20 in the image display area and the viewing angle control areas ECB_R, G, and B of the sub-pixels, respectively.

The first TFT T1 is disposed at an intersection of one of the gate lines GLn + 2 and the first data line DL1 in the viewing angle control regions ECB_R, G and B, The pixel electrode 17 is connected. The pixel electrodes 17 may be formed in a shape having a plurality of slits in parallel with the data lines DL1 to DLm connected to the pixel lines. The lower common electrode 16 may be formed in a plate shape with the pixel electrodes 17 and the insulating film 18 interposed therebetween. The lower common electrodes 16 are connected to each other through a common line (not shown) parallel to the gate lines GL1 to GLn. As described above, the pixel electrodes 17 and the lower common electrode 16 of the viewing angle control regions ECB_R, G, and B can be configured to form fringe fields in the same manner as the image display region.

An upper common electrode 22 is provided on the upper substrate 20 facing the pixel electrode 17 so as to face the lower common electrode 16 in the viewing angle control regions ECB_R, G, An external common voltage Vcom1 is applied to the upper common electrode 22 in accordance with the viewing angle driving mode to form a vertical electric field with the pixel electrode 17 and the lower common electrode 16 to control the viewing angle. The upper common electrode 22 and the external common voltage Vcom1 supply terminal may be separated from each other and electrically connected to each other by any one of the TFTs T1 to T3 according to the driving mode.

As described above, in the viewing angle control regions ECB_R, G, and B, the video signal applied to the pixel electrode 17 and the video signal applied to the upper common electrode 22 in accordance with the viewing angle control voltage CCS from the viewing angle control portion 10 A first capacitor C1 for holding the differential voltage of the common voltage Vcom1 until the next voltage is charged is formed. The difference voltage between the video signal applied to the pixel electrode 17 and the lower common electrode voltage Vcom applied to the lower common electrode 16 is applied to the viewing angle control regions ECB_R, The second capacitor C2 is held. Here, the second capacitor C2 is a capacitor for improving brightness of an image by transmitting light in a wide viewing angle mode.

The voltage of the pixel electrode 17 and the lower common electrode 16 and the voltage of the external common voltage Vcom1 applied to the upper common electrode 22 are controlled in accordance with the viewing angle control voltage CCS in the viewing angle control regions ECB_R, ) Is maintained until the next voltage is charged. In other words, when the external common voltage Vcom1 is applied to the upper common electrode 22 of the upper substrate at the time when the voltage of the pixel electrode 17 and the voltage of the lower common electrode 16 are coupled, the viewing angle control region ECB_R , G, and B), they are driven in a narrow viewing angle mode by forming a vertical electric field.

More specifically, the potential of the pixel electrode 17 and the potential of the lower common electrode 16 are coupled when the third TFT T3 is turned on, so that their potentials become similar or equal. Thus, when the external common voltage Vcom1 is applied to the upper common electrode 22 at the time when the potential of the pixel electrode 17 becomes equal to or equal to the potential of the lower common electrode 16, the viewing angle control regions ECB_R, B) forms a vertical electric field.

In particular, the method of driving the viewing angle control regions ECB_R, G, and B will be described below.

First, when the user intends to drive the liquid crystal panel 2 in the wide viewing angle mode, the third TFT T3 first applies the scan pulse from the previous-stage gate line GLn-1 to the pixel electrode 17 and the lower common The potential of the electrode 16 is made equal.

Thereafter, when the scan pulse is supplied to the current gate line Gn, the third TFT T3 is turned off, and the pixel electrode 17 and the lower common electrode 16 are electrically separated from each other. At this time, the first TFT T1 may be turned on to supply a video signal to the pixel electrode 17, and the viewing angle control line CL may be supplied with a high-level viewing angle for turning on the second TFT T2, The control voltage CCS is supplied. As described above, when the second TFT T2 is turned on by a high-level viewing-angle control voltage CCS of, for example, 10 V, the lower common electrode 16 and the upper common electrode 22 are turned off by an external common voltage Vcom1 or the lower common electrode voltage Vcom to form a fringe field with the pixel electrode 17. [ That is, the viewing angle control regions ECB_R, G, and B drive the liquid crystal horizontally by forming a horizontal electric field.

Next, when a scan pulse is supplied to the next-stage gate line Gn + 1, at least one of the first to third TFTs T1 to T3 is turned off. Accordingly, the lower common electrode voltage and the difference voltage between the pixel electrodes 17 are floated while maintaining the voltage level of the video signal. As described above, in each of the viewing angle control regions ECB_R, G, and B of the wide viewing angle mode, the liquid crystal is driven horizontally by the viewing angle control voltage CCS for turning on the second TFT T2 to display on the liquid crystal panel 2 It is possible to increase the luminance of the image. That is, in the viewing angle control areas ECB_R, G, and B, images corresponding to the image signal generated by the ECB data E generated from the timing controller 8 may be displayed and the same image as the image display area may be displayed It is possible.

On the other hand, in the narrow viewing angle mode, the viewing angle control voltage CCS is kept at a low level, for example, 0V so that the second TFT T2 is not turned on.

More specifically, when a scan pulse is applied to the gate line Gn-1, the third TFT T3 is turned on, so that the potentials of the pixel electrode 17 and the lower common electrode 16 become equal to each other. When the scan pulse is supplied to the current gate line Gn, the third TFT T3 is turned off and the pixel electrode 17 and the lower common electrode 16 are electrically separated from each other. At this time, the pixel electrode 17 is charged by the video signal inputted through the first TFT T1 and the lower common electrode 16 is charged by the coupling voltage according to the video signal from the pixel electrode 17 to the second capacitor C2. That is, in the narrow viewing angle mode, the viewing angle control regions ECB_R, G, and B charge the voltage of the lower common electrode 16 and the difference voltage between the upper common electrode 22 of the upper substrate to form a vertical electric field, . At this time, the interference image preset by the timing controller 8 can be displayed on the viewing angle control areas ECB_R, G, and B.

As described above, in the narrow viewing angle mode, the liquid crystals of the viewing angle control regions ECB_R, G, and B are tilted by the vertical electric field formed between the lower common electrode 16 and the upper common electrode 22, However, light leakage occurs in the left and right viewing angles. Since the liquid crystals in the viewing angle control regions ECB_R, G, and B are not twisted but tilted only at the front of the viewing angle control regions ECB_R, G, and B, Will not be observed. However, in the left and right viewing angles, it is observed that light leaks. When the user observes the liquid crystal panel 2 in the left and right viewing angles from the viewpoint that each sub pixel constitutes one unit pixel, And the contrast ratio CR is lowered. Therefore, the viewing angles in the left and right viewing angles can be reduced. The video signals supplied to the viewing angle control regions ECB_R, G, and B may have the same voltage as the lower common electrode voltage applied to the lower common electrode 16 or a voltage lower than the threshold voltage, . A lower common electrode voltage Vcom equal to the voltage in the wide viewing angle mode is applied to the lower common electrode 16 and 1 to 4 V or (-4) is applied to the upper common electrode 22, An external common voltage Vcom1 is applied so that an electric field difference of - (-1) V is induced. At this time, the external common voltage Vcom1 applied to the upper common electrode 22 can be either DC or AC.

6 is a block diagram showing a driving apparatus for a liquid crystal display according to a second embodiment of the present invention.

The liquid crystal display device shown in FIG. 6 has the same configuration as that of the first embodiment except for the sub-pixel configurations of the liquid crystal panel 102. That is, the configurations of the gate and data drivers 104 and 106 excluding the liquid crystal panel 102, the timing controller 108, and the viewing angle control unit 110 are the same as those of the liquid crystal display device according to the first embodiment. Accordingly, the description of the remaining components except for the sub-pixel configuration of the liquid crystal panel 102 and the operation method of the viewing angle control unit 110 will be replaced with the above detailed description with reference to FIG.

7 is an equivalent circuit diagram showing the R view angle control area and the G view angle control area in Fig. 6 in more detail.

The sub-pixels of the stripe structure shown in Figs. 6 and 7 represent sub-pixels in the case where the liquid crystal panel 2 is made of a poly-Si (poly-Si) panel. Specifically, the unit pixels of the p-Si panel are composed of R, G, and B sub-pixels each having red, green, and blue, that is, the image display area and the viewing angle control areas ECB_R, G, and B, respectively. In each unit pixel, R sub-pixel R, G sub-pixel G and B sub-pixel B are formed in the horizontal direction. The viewing angle control areas ECB_R, G, and B are formed in a vertical direction in the image display area.

6, the viewing angle control regions ECB_R, G, and B include a first TFT T1 for supplying a video signal to a pixel electrode in response to a scan pulse from one of the gate lines GLn, A second TFT T2 for supplying an external common voltage Vcom1 to the lower common electrode in accordance with the viewing angle control voltage CCS from the display panel CL, And a third TFT T3 for performing the same operation. Accordingly, a first capacitor (C1) is formed between the pixel electrode and the upper common electrode, a second capacitor (C2) is formed between the pixel electrode and the lower common electrode, and a third capacitor C3 are formed.

Generally, in the case of a p-Si panel, an NMOS transistor and a PMOS transistor may be formed in each sub-pixel. Accordingly, the first and third TFTs T1 and T3 provided in the viewing angle control regions ECB_R, G and B may be NMOS transistors and the second transistor T2 may be PMOS transistors. The viewing angle control regions ECB_R, G and B of the p-Si panel can be driven in the wide viewing angle mode or the narrow viewing angle mode according to the viewing angle control voltage CCS inputted through the viewing angle control line CL.

4 and 5, the liquid crystal panel 102 according to the second embodiment also controls the orientation of the liquid crystal layer 30 to control the amount of light transmitted to the upper substrate 20 And a substrate 10.

The sub-pixel of the lower substrate 10 forms a fringe field to form an image display area for controlling the orientation of the liquid crystal layer 30 in the horizontal direction and a liquid crystal layer 30 for forming a horizontal or vertical electric field according to the viewing angle drive mode, Angle control areas ECB_R, G, and B for controlling the orientation horizontally or vertically. 5, the fringe fields are formed, and the viewing angle control areas ECB_R, G, and B are formed by mixing the ECB structure and the IPS structure according to the viewing angle mode. The viewing angle control regions ECB_R, G, and B form a vertical electric field according to the difference between the voltage of the lower common electrode voltage Vcom and the voltage of the pixel electrode and the external common voltage Vcom1 of the upper common electrode, And the lower common electrode voltage is applied, a horizontal electric field is formed.

5 and 7, the lower common electrode 16 provided in the R, G, and B sub-pixels R, G, and B includes a common line (not shown) parallel to the gate lines GL1 to GLn, And the lower common electrodes 16 of the image display region except for the viewing angle control regions ECB_R, G, and B may be electrically connected to each other. That is, the image display regions of the respective sub-pixels form a fringe field by the lower common electrode 16 and the pixel electrode 17 to drive the liquid crystal.

In the present invention, only the structure in which the lower common electrode 16 is formed on the lower substrate 10 and the pixel electrode 17 is formed on the lower common electrode 16 with the insulating film 18 therebetween is described. However, The electrode 16 and the pixel electrode 17 can be formed because the fringe field is formed even if the positions and structures of the electrode 16 and the pixel electrode 17 are changed. Therefore, in the present invention, only the structure in which the pixel electrode 17 is formed on the lower common electrode 16 with the insulating film 18 therebetween will be described.

The first TFT T1 is disposed at an intersection of one of the gate lines GLn + 2 and the first data line DL1 in the viewing angle control regions ECB_R, G and B, The pixel electrode 17 is connected. The pixel electrodes 17 are formed in a shape having a plurality of slits in parallel with the data lines DL1 to DLm connected to the pixel lines. The lower common electrode 16 is formed in a plate shape with the pixel electrodes 17 and the insulating film 18 interposed therebetween. The lower common electrode 16 is connected to each other through a common line (not shown) parallel to the second gate line GL2. As described above, the pixel electrodes 17 and the lower common electrode 16 of the viewing angle control regions ECB_R, G, and B may have the same fringe field configuration as the respective image display regions.

An upper common electrode 22 is provided on the upper substrate 20 facing the pixel electrode 17 so as to face the lower common electrode 16 in the viewing angle control regions ECB_R, G, An external common voltage Vcom1 is applied to the upper common electrode 22 to control a viewing angle while forming a vertical electric field with the pixel electrode 17 and the lower common electrode 16. [

As described above, in the viewing angle control regions ECB_R, G, and B, the video signal applied to the pixel electrode 17 and the video signal applied to the upper common electrode 22 in accordance with the viewing angle control voltage CCS from the viewing angle control portion 10 A first capacitor C1 for holding the differential voltage of the common voltage Vcom1 until the next voltage is charged is formed. The difference voltage between the video signal applied to the pixel electrode 17 and the lower common electrode voltage Vcom applied to the lower common electrode 16 is applied to the viewing angle control regions ECB_R, A second capacitor C2 for holding the capacitor C2 is formed. Here, the second capacitor C2 is a capacitor for improving brightness of an image by transmitting light in a wide viewing angle mode.

The difference voltage between the voltage of the lower common electrode 16 and the external common voltage Vcom1 applied to the upper common electrode 22 according to the viewing angle control voltage CCS is applied to the viewing angle control regions ECB_R, And a third capacitor C3 for holding the voltage until it is charged is constituted. In other words, when the external common voltage Vcom1 is applied to the upper common electrode 22 of the upper substrate at the time when the voltages of the pixel electrode 17 and the lower common electrode 16 become the same, the viewing angle control regions ECB_R, B) is driven in a narrow viewing angle mode by forming a vertical electric field. More specifically, the potential of the pixel electrode 17 and the potential of the lower common electrode 16 become the same when the third TFT T3 is turned on. Thus, when the external common voltage Vcom1 is applied to the upper common electrode 22 at the time when the potential of the pixel electrode 17 becomes equal to the potential of the lower common electrode 16, the viewing angle control regions ECB_R, A vertical electric field is formed.

In particular, the method of driving the viewing angle control regions ECB_R, G, and B will be described below.

When the user desires to drive the liquid crystal panel 2 in the wide viewing angle mode, the third TFT T3 is turned off and the second TFT T2 is turned on. The viewing angle control voltage CCS is set to a low level example For this, keep it at 0V.

When the scan pulse is supplied to the current gate line Gn, the first TFT T1 is turned on to supply the image signal to the pixel electrode 17, and the lower common electrode 16 and the upper common electrode 22 Is charged by the external common voltage Vcom1 or the lower common electrode voltage Vcom to form a fringe field. That is, in the viewing angle control regions ECB_R, G, and B, the liquid crystal is horizontally driven by forming a horizontal electric field.

Next, when a scan pulse is supplied to the next-stage gate line Gn + 1, at least one of the first to third TFTs T1 to T3 is turned off. Accordingly, the lower common electrode 16 maintains the potential of the external common voltage Vcom1, and the pixel electrode maintains the voltage level of the video signal and is floated. As described above, the viewing angle control regions ECB_R, G, and B in the wide viewing angle mode cause the liquid crystal to be horizontally driven by the viewing angle control voltage CCS that turns on the second TFT T2 to raise the brightness of the displayed image .

On the other hand, in the narrow viewing angle mode, the third TFT T3 is turned on, and the viewing angle control voltage CCS is kept at a high level, for example, 10V or more so that the second TFT T2 is turned off.

In this case, since the third TFT T3 is turned on, the pixel electrode 17 and the lower common electrode 16 are electrically connected to each other, so that the potentials become the same. At this time, when the scan pulse is supplied to the current gate line Gn, the pixel electrode 17 and the lower common electrode 16 are charged by the video signal input through the first TFT T1. That is, in the narrow viewing angle mode, the viewing angle control regions ECB_R, G, and B are formed by filling the voltage that equally applies to the lower common electrode 16 and the pixel electrode 17 and the difference voltage between the upper common electrode 22 of the upper substrate The liquid crystal is vertically driven by forming a vertical electric field. At this time, the interference image preset by the timing controller 108 can be displayed in the viewing angle control areas ECB_R, G, and B.

As described above, in the narrow viewing angle mode, the liquid crystals of the viewing angle control regions ECB_R, G, and B are tilted by the vertical electric field formed between the lower common electrode 16 and the upper common electrode 22, However, light leakage occurs in the left and right viewing angles. Since the liquid crystals in the viewing angle control regions ECB_R, G, and B are not twisted but tilted only at the front of the viewing angle control regions ECB_R, G, and B, Will not be observed. However, in the left and right viewing angles, it is observed that light leaks. When the user observes the liquid crystal panel 102 at the left and right viewing angles from the viewpoint that each sub pixel constitutes one unit pixel, And the contrast ratio CR is decreased. Therefore, the viewing angles in the left and right viewing angles can be reduced. The video signals supplied to the viewing angle control regions ECB_R, G, and B may have the same voltage as the lower common electrode voltage applied to the lower common electrode 16 or a voltage lower than the threshold voltage, . A lower common electrode voltage Vcom equal to the voltage in the wide viewing angle mode is applied to the lower common electrode 16 and 1 to 4 V or (-4) is applied to the upper common electrode 22, An external common voltage Vcom1 is applied so that an electric field difference of - (-1) V is induced. At this time, the external common voltage Vcom1 applied to the upper common electrode 22 can be either DC or AC.

As described above, the driving apparatus of the liquid crystal display and the driving method thereof according to the embodiment of the present invention include a plurality of sub pixels composed of the video display area and the viewing angle control area. In the wide viewing angle mode, The brightness of the image can be improved by driving the liquid crystals of the viewing angle control areas ECB_R, G, and B in the same manner as the first embodiment. In the narrow viewing angle mode, the viewing angle can be reduced by driving the liquid crystals of the viewing angle control regions ECB_R, G, and B to form a vertical electric field, unlike the driving method of the image display region. At this time, color filters are provided in the viewing angle control region to increase the display efficiency of the image and display the interference image in color.

The liquid crystal display of the present invention is advantageous in that the additional common electrode 22 is additionally formed only on the upper substrate 20 of the viewing angle control regions ECB_R, G, and B so that the manufacturing cost is relatively small and the manufacturing process is relatively simple. The upper common electrode 22 added to the upper substrate 20 is floated in the wide viewing angle mode or the same voltage as that of the lower common electrode 16 is allowed to flow. In the narrow viewing angle mode, It is very easy to drive the vehicle.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Will be apparent to those of ordinary skill in the art.

1 is a view showing a conventional quad type liquid crystal cell.

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a liquid crystal display (LCD).

3 is a plan view schematically showing a unit pixel of the liquid crystal panel shown in Fig.

4 is an equivalent circuit diagram more specifically showing the R viewing angle control area and the G viewing angle control area in Fig.

FIG. 5 is a structural cross-sectional view illustrating an R viewing angle control area and an R image display area in FIG. 3;

6 is a configuration diagram showing a driving device of a liquid crystal display device according to a second embodiment of the present invention.

7 is an equivalent circuit diagram more specifically showing the R viewing angle control area and the G viewing angle control area in Fig.

Claims (14)

A liquid crystal display device comprising: a liquid crystal panel having a plurality of unit pixels; a driving control unit for driving gate lines and data lines of the liquid crystal panel; and a viewing angle control unit for supplying a viewing angle control voltage to viewing angle control lines of the liquid crystal panel The driving device comprising: The plurality of unit pixels include R, G, and B sub-pixels, Wherein each of the R, G, and B sub-pixels is divided into an image display area and a viewing angle control area that displays an image having the same color as the image display area, The viewing angle control region of each of the R, G, and B sub- A first NMOS TFT for supplying a video signal to a pixel electrode in response to a scan pulse input from a current gate line of the gate lines; A second NMOS TFT for supplying an external common voltage to the lower common electrode in accordance with a viewing angle control voltage from the viewing angle control line; And And a third NMOS TFT electrically connecting the lower common electrode and the pixel electrode in response to a scan pulse from the previous gate line so that the potentials of the lower common electrode and the pixel electrode become equal to each other. The method according to claim 1, The viewing angle control area A first capacitor for maintaining a difference voltage between a video signal applied to the pixel electrode and an external common voltage applied to the upper common electrode until the next voltage is charged according to the viewing angle control voltage, A second capacitor for holding a difference voltage between a video signal applied to the pixel electrode and a lower common electrode voltage applied to the lower common electrode until the next voltage is charged; And a third capacitor for maintaining the difference voltage between the voltage of the lower common electrode and the external common voltage applied to the upper common electrode according to the viewing angle control voltage until the next voltage is charged. Driving device. 3. The method of claim 2, The viewing angle control voltage And the second NMOS TFTs are supplied to the respective viewing angle control lines at a level for turning on the second NMOS TFTs in the wide viewing angle mode, And the second viewing angle control signal is supplied to each of the viewing angle control lines at a level that turns off the second NMOS TFT in the narrow viewing angle mode. A liquid crystal display device comprising: a liquid crystal panel having a plurality of unit pixels; a driving control unit for driving gate lines and data lines of the liquid crystal panel; and a viewing angle control unit for supplying a viewing angle control voltage to viewing angle control lines of the liquid crystal panel The driving device comprising: The plurality of unit pixels include R, G, and B sub-pixels, Wherein each of the R, G, and B sub-pixels is divided into an image display area and a viewing angle control area that displays an image having the same color as the image display area, The viewing angle control area A first NMOS TFT for supplying a video signal to the pixel electrode in response to a scan pulse from the current one gate line among the gate lines; A second PMOS TFT for supplying an external common voltage to the lower common electrode in accordance with the viewing angle control voltage from the viewing angle control line; And And a third NMOS TFT electrically connecting the lower common electrode and the pixel electrode so that the potentials of the lower common electrode and the pixel electrode become equal to each other according to the viewing angle control voltage. 5. The method of claim 4, The viewing angle control area A first capacitor for maintaining a difference voltage between an image signal applied to the pixel electrode and an external common voltage applied to the upper common electrode until the next voltage is charged according to the viewing angle control voltage, A second capacitor for holding a difference voltage between a video signal applied to the pixel electrode and a lower common electrode voltage applied to the lower common electrode until the next voltage is charged; And a third capacitor for maintaining the difference voltage between the voltage of the lower common electrode and the external common voltage applied to the upper common electrode according to the viewing angle control voltage until the next voltage is charged. A driving device for a display device. 6. The method of claim 5, The viewing angle control voltage In the wide viewing angle mode, the second PMOS TFT is turned on and the third NMOS TFT is turned off, And in the narrow viewing angle mode, the second PMOS TFT is turned off and the third NMOS TFT is turned on. delete 6. The method according to claim 2 or 5, The upper common electrode And the external common voltage is supplied independently. And a viewing angle control unit for supplying a viewing angle control voltage to the viewing angle control lines of the liquid crystal panel, wherein the liquid crystal panel includes a plurality of unit pixels, a driving control unit for driving the gate lines and the data lines of the liquid crystal panel, A method of driving a liquid crystal display comprising R, G, and B sub-pixels in which a plurality of unit pixels are divided into an image display area and a viewing angle control area, The R, G, and B sub-pixels are configured to display an image having the same color as the image display region, and the R, G, and B sub-pixels have respective R, G, And, The step of driving the viewing angle control region Supplying a video signal to the pixel electrode in accordance with a scan pulse input from the current gate line using the first NMOS TFT; Supplying an external common voltage to a lower common electrode in accordance with a viewing angle control voltage from the viewing angle control line using a second NMOS TFT; And And electrically connecting the lower common electrode and the pixel electrode in response to a scan pulse from the previous gate line using the third NMOS TFT so that the potentials of the lower common electrode and the pixel electrode become the same. 10. The method of claim 9, The step of driving the viewing angle control region Maintaining a difference voltage between a video signal applied to the pixel electrode and an external common voltage applied to the upper common electrode by using a first capacitor until the next voltage is charged according to the viewing angle control voltage, Maintaining a difference voltage between a video signal applied to the pixel electrode and a lower common electrode voltage applied to the lower common electrode using a second capacitor until the next voltage is charged, And maintaining the difference voltage between the voltage of the lower common electrode and the external common voltage applied to the upper common electrode until the next voltage is charged by using the third capacitor. 11. The method of claim 10, The viewing angle control voltage And the second NMOS TFTs are supplied to the respective viewing angle control lines at a level for turning on the second NMOS TFTs in the wide viewing angle mode, And in the narrow viewing angle mode, the second NMOS TFT is supplied to each of the viewing angle control lines at a level that turns off the second NMOS TFT. And a viewing angle control unit for supplying a viewing angle control voltage to the viewing angle control lines of the liquid crystal panel, wherein the liquid crystal panel includes a plurality of unit pixels, a driving control unit for driving the gate lines and the data lines of the liquid crystal panel, A method of driving a liquid crystal display comprising R, G, and B sub-pixels in which a plurality of unit pixels are divided into an image display area and a viewing angle control area, The R, G, and B sub-pixels are configured to display an image having the same color as the image display region, and the R, G, and B sub-pixels have respective R, G, And, The step of driving the viewing angle control region Supplying a video signal to a pixel electrode in response to a scan pulse from a current one gate line among the gate lines using a first NMOS TFT; Supplying an external common voltage to a lower common electrode according to the viewing angle control voltage from the viewing angle control line using a second PMOS TFT; And And electrically connecting the lower common electrode and the pixel electrode so that the potentials of the lower common electrode and the pixel electrode become equal to each other using the third NMOS TFT according to the viewing angle control voltage. 13. The method of claim 12, The step of driving the viewing angle control region Maintaining a difference voltage between a video signal applied to the pixel electrode and an external common voltage applied to the upper common electrode by using a first capacitor until the next voltage is charged according to the viewing angle control voltage, Maintaining a difference voltage between a video signal applied to the pixel electrode and a lower common electrode voltage applied to the lower common electrode using a second capacitor until the next voltage is charged, And maintaining the difference voltage between the voltage of the lower common electrode and the external common voltage applied to the upper common electrode according to the viewing angle control voltage until the next voltage is charged by using the third capacitor And a driving method of the liquid crystal display device. 14. The method of claim 13, The viewing angle control voltage In the wide viewing angle mode, the second PMOS TFT is turned on and the third NMOS TFT is turned off, And in the narrow viewing angle mode, the second PMOS TFT is turned off and the third NMOS TFT is turned on.

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