KR20090060062A - Driving method of liquid crystal display device - Google Patents

Abstract

A driving method of a liquid crystal display device are provided to reduce the distortion of a common voltage by turning on a second image alternately when displaying the first image and a second image surrounding the first mage. A first and a second data driving circuit(142,144) receive a polarity reverse signal and outputs a data signal. A liquid crystal panel is connected with one of a first and a second data diving circuit while having a pixel of quad type composed of sub-pixels. In adjacent two pixels, one is driven when a first sub-pixel is on and a second sub-pixel is off while the other is driven when the first sub-pixel is off and a second sub-pixel is on.

Description

Driving method of liquid crystal display device

The present invention relates to a liquid crystal display device, and more particularly, to a driving method of a liquid crystal display device capable of selectively implementing a wide viewing angle and a narrow viewing angle.

LCD displays have advantages such as thin, light weight, low power consumption, and are widely used in monitors for personal computers, monitors for notebook computers, personal portable terminals, and wall-mounted televisions.

Referring to the drawings, such a liquid crystal display device will be described in more detail. 1 is a view schematically showing a configuration of a general liquid crystal display device.

As illustrated in FIG. 1, the liquid crystal display device includes a liquid crystal panel 10 for displaying an image, a gate driving circuit 20 for generating and supplying a signal for operating elements of the liquid crystal panel 10, and a data driving circuit ( 30).

The liquid crystal panel 10 includes a plurality of gate lines 12 and data lines 14 that cross each other to define a pixel area. In each pixel area, a thin film transistor T connected to the gate line 12 and the data line 14, a liquid crystal capacitor C _LC and a storage capacitor C _ST connected to the thin film transistor T are positioned.

Although not shown, the gate driving circuit 20 and the data driving circuit 30 are connected to a timing controller on a printed circuit board. The timing controller receives the image signal RGB data and the control signal from an external system (not shown) and rearranges the image signal RGB data. In addition, the timing controller generates gate control signals GSP, GOE, and GSC and data control signals SOE, SSC, POL, and SSP necessary for driving the gate driving circuit 20 and the data driving circuit 30, thereby generating a gate. Supply gate control signals GSP, GOE, and GSC to the driving circuit 20, and supply data control signals SOE, SSC, POL, and SSP and rearranged image signals RGB data to the data driving circuit 30. do. Here, the gate control signal includes a gate start pulse (GSP), a gate output enable (GOE) and a gate shift clock (GSC), and the data control signal includes a source output. Includes source enable enable (SOE), source sampling clock (SSC), polarity reverse signal (POL) and source start pulse (SSP).

The gate driving circuit 20 supplies the gate signal V _G to the gate wiring 12 of the liquid crystal panel 10 according to the gate control signals GSP, GOE, and GSC from the timing controller, and the data driving circuit. 30, the data signal Vdata is supplied to the data line 14 of the liquid crystal panel 10 in accordance with the data control signals SOE, SSC, POL, and SSP and the image signal RGB data from the timing controller. .

Therefore, the liquid crystal panel 10 displays an image by the gate signal V _G and the data signal Vdata.

The minimum unit for displaying an image of a liquid crystal display device is a pixel, and in general, a pixel includes red, green, and blue sub pixels.

2 is a diagram schematically illustrating a pixel structure of such a liquid crystal display device. As shown in FIG. 2, in the conventional liquid crystal display, subpixels R, G, and B, which implement red, green, and blue colors, are sequentially and repeatedly arranged. The red, green, and blue subpixels R, G, and B constitute one pixel PXL, which is the minimum unit for displaying an image.

As mentioned above, the liquid crystal display is widely used in various fields as an image display medium, and the narrow viewing angle problem, which has been raised at the beginning of development, has been solved by the development of various wide viewing angle modes.

However, in recent years, the necessity of narrow viewing angle for the liquid crystal display device has been raised in terms of security and privacy protection, and in particular, this problem becomes more apparent when using a portable device.

In order to induce a narrow viewing angle according to necessity, a method of selecting a wide viewing angle mode and a narrow viewing angle mode by adding a liquid crystal panel for viewing angle adjustment to an upper portion or a lower portion of a liquid crystal panel displaying an image and having a wide viewing angle has been proposed. However, in this case, since a separate liquid crystal panel has to be added, there is a disadvantage in that the manufacturing process and the cost increase and the power consumption increases.

Accordingly, as another method of adjusting the viewing angle, a pixel structure in which a white subpixel for adjusting the viewing angle is added to the red, green, and blue subpixels has been proposed.

Here, the red, green, and blue subpixels have a driving mode capable of realizing a wide viewing angle, and the white subpixels have different driving modes for adjusting the viewing angle. When a wide viewing angle is required, the white subpixel is turned off, and when a narrow viewing angle is required, the white subpixel is turned on, so that the viewing angle can be selectively adjusted.

On the other hand, in order to prevent deterioration of the liquid crystal due to the application of a DC voltage, the liquid crystal display device inverts a pair of complementary gradation voltages based on a common voltage for the same data signal alternately to change the polarity of the gradation voltage. To perform. In this inversion driving method, the desired image is displayed correctly only when the voltage difference between the pair of complementary gray voltages and the common voltage is the same.

However, when a specific image pattern is displayed, the potential of the common voltage may be changed by coupling between the data signal and the common voltage. Due to the distortion of the common voltage, the voltage difference between the pair of gray voltages and the common voltage is unbalanced, and thus crosstalk is generated in which the luminance difference occurs between the same data signals. Such cross talk is a cause of deterioration of image quality.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of driving a liquid crystal display device capable of controlling a viewing angle that can prevent cross talk from occurring when a specific image pattern is displayed.

In order to achieve the above object, the liquid crystal display device driving method of the present invention includes a first and second data driving circuit for receiving a polarity inversion signal and outputting a data signal, and one of the first and second data driving circuits; 12. A liquid crystal display device comprising a liquid crystal panel having a quad type pixel connected to the first to fourth sub pixels, wherein the first sub pixel of one of the two adjacent pixels is driven to an on state, and the second sub pixel is driven. Driving the pixel in an off state; Driving the first subpixel of the other two adjacent pixels in an off state and driving the second subpixel in an on state, wherein the subpixels of the on state connected to the first data driving circuit are positively polarized. (positive polarity), and the sub-pixels in the off state connected to the second data driving circuit have negative polarity.

The first subpixel is positioned between the two adjacent second subpixels, and the first subpixel has the same polarity as one of the two adjacent second subpixels and has a different polarity from the other one.

Each of the first and second data driving circuits is connected to (4i + 2) data lines, where i is a natural number, and each of the data lines is connected to one of the first and second sub pixels.

First and second polarity inversion control signals for controlling the polarity of the polarity inversion signal are supplied to the first and second data driving circuits, respectively, and the first and second polarity inversion signals have the same value.

The second sub-pixel receiving the data signal from the (4i + 2) th data line connected to the first data driving circuit is the first sub-pixel receiving the data signal from the first data line connected to the second data driving circuit. Has a different polarity.

The third sub-pixel has the same on / off state as the first sub-pixel, and the fourth sub-pixel is off.

The first to third subpixels have a liquid crystal driving mode in a horizontal electric field, and the fourth subpixel has a liquid crystal driving mode in a vertical electric field.

According to the present invention, a liquid crystal display having a quad-type pixel structure consisting of red, green, blue, and white subpixels and having a viewing angle control, includes a first image in the center of the screen and a second image around the first image. When displaying, the second image is displayed by turning red, green, and blue subpixels on and off alternately for each pixel, and a signal having the same polarity is applied to the data lines connected to the first stage of the plurality of data driving circuits. Be sure to Therefore, positive and negative polarities alternately appear along the horizontal direction, so that polarization is not generated, and distortion of the common voltage can be reduced. For this reason, horizontal crosstalk can be reduced.

Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment of the present invention.

3 is a view schematically illustrating a pixel structure of a liquid crystal display according to the present invention. As shown in FIG. 3, in the liquid crystal display according to the present invention, the sub pixels R, G, B, and W, which implement red, green, blue, and white, respectively, constitute one pixel PXL. These pixels PXL are repeatedly arranged. In this case, the pixel PXL has a quad type structure in which red, green, blue, and white subpixels R, G, B, and W are disposed adjacent to each other. Here, the red subpixel R contacts the green subpixel G along the horizontal direction, the white subpixel W along the vertical direction, and the blue subpixel B along the diagonal direction.

The red, green, and blue subpixels R, G, and B have a driving mode capable of realizing a wide viewing angle, and the white subpixel W has a different driving mode for adjusting the viewing angle. For example, the red, green, and blue subpixels R, G, and B may be driven in a horizontal electric field mode, and the white subpixel W may be driven in a vertical electric field mode.

Therefore, when a wide viewing angle is required, the white subpixel W is in an off state, and when a narrow viewing angle is required, the white subpixel W is in an on state, so that the viewing angle can be selectively adjusted. have.

In order to prevent deterioration of the liquid crystal, the liquid crystal display according to the present invention uses a two-dot inversion driving method.

FIG. 4 is a diagram schematically illustrating a polarity form of a subpixel in a liquid crystal display device to which a two-dot inversion driving method according to the present invention is applied.

As shown in FIG. 4, the polarity is inverted in units of two adjacent sub-pixels to drive "++-++-" in the horizontal direction. At this time, the polarity is reversed in units of four sub-pixels in the vertical direction to drive "++++ ----".

By the way, when displaying a specific image pattern in the liquid crystal display of the present invention crosstalk occurs, in particular, such crosstalk occurs mainly when the system is terminated.

5 shows a screen state when crosstalk occurs in the liquid crystal display of the present invention. As illustrated in FIG. 5, the first image is displayed on the first area 110 positioned at the center of the screen, and the second area 120 and the first area (up and down) located on the first area 110 ( When the second image is to be displayed on the third region 130 positioned at left and right sides of the 110, an image different from the third region 130 is displayed on the second region 120.

For example, when a white image is displayed in the first region 110 and a gray image is displayed in the second and third regions 120 and 130, the second image is displayed by a horizontal cross-talk. The image of the region 120 is displayed darker than the image of the third region 130.

In this case, the images of the second region 120 and the third region 130 are displayed by alternately turning on / off the red, green, and blue subpixels for each pixel. In addition, the red and blue subpixels of the second and third regions 120 and 130 are driven in the same on / off state, and the green subpixel is driven in the opposite state to the red and blue subpixels.

When driving a specific image pattern in this way, horizontal crosstalk is generated because the polarity of each region is largely biased.

This will be described in more detail with reference to FIG. 6. FIG. 6 is a diagram illustrating polar shapes and on / off states of subpixels when crosstalk occurs in the liquid crystal display of the present invention. Here, the pixels illustrated in FIG. 6 correspond to the second region 120 of FIG. 5.

As shown in FIG. 6, the first to k-th data lines D1,..., And Dk: k is a natural number are connected to the first data driver circuit 142, and to the second data driver circuit 144. The (k + 1) th data line to the lth data line (D (k + 1), ..., Dl: where l is a natural number greater than k) are connected, and the (l + 1) th data line is connected to the third data driving circuit 146. +1) Data line to m-th data line (D (l + 1), ..., Dm: m is a natural number larger than l) is connected, and the fourth data driving circuit 148 is made of (m + 1) The data wirings to the nth data wirings D (m + 1), ..., Dn: n is a natural number larger than m are connected. At this time, each of the data driving circuits 142, 144, 146, and 148 is connected with (4i + 2) data wires, and k data wires may be connected with each other. Where i is a natural number. For example, 642 data wires may be connected to each data driving circuit 142, 144, 146, and 148.

Each data wiring (D1, ..., Dk, D (k + 1), ..., Dl, D (l + 1), ..., Dm, D (m + 1), ..., Dn ) In the vertical direction, i.e., the data lines D1, ..., Dk, D (k + 1), ..., Dl, D (l + 1), ..., Dm, D (m + 1) , ..., Dn) are connected to a plurality of sub pixels arranged along a direction parallel to each other.

In order to adjust the polarity of the pixel voltage applied to each sub-pixel, the polarity inversion signal POL is applied to the first to fourth data driving circuits 142, 144, 146, and 148 from a timing controller (not shown). . In addition, the first or second polarity inversion control signals POLC_odd and POLC_even are applied to the first to fourth data driving circuits 142, 144, 146, and 148 to provide an inversion of the polarity inversion signal POL. To control. The first and second polarity inversion control signals POLC_odd and POLC_even have a high or low value. When the first and second polarity inversion control signals POLC_odd and POLC_even have high values, the polarity inversion signal POL is in a normal polarity state having the polarity of the input signal. When the two polarity inversion control signals POLC_odd and POLC_even have a low value, the polarity inversion signal POL is in an inversion polarity state having a polarity opposite to the input signal.

As mentioned above, the liquid crystal display according to the present invention includes a quad type pixel (PXL of FIG. 3) composed of red, green, blue, and white subpixels (R, G, B, and W of FIG. 3). It is powered by a two-dot inversion method.

In order to apply the two-dot inversion method, the data lines D1 and D (l + 1) and the second and fourth data driving circuits connected to the first ends of the first and third data driving circuits 142 and 146. Signals of different polarities should be applied to the data lines D (k + 1) and D (m + 1) connected to the first ends of the 144 and 148. Accordingly, the first polarity inversion control signal POLC_odd is connected to the first and third data driving circuits 142 and 146, and the second polarity inversion control signal POLC_even is connected to the second and fourth data driving circuits 144. 148 and the first polarity inversion control signal POLC_odd and the second polarity inversion control signal POLC_even have different values. For example, the first polarity inversion control signal POLC_odd has a high value and the second polarity inversion control signal POLC_even has a low value.

When the image pattern shown in FIG. 5 is displayed in the liquid crystal display device driven as described above, the red subpixel R and the blue subpixel B are turned on in the first pixel PXL with reference to FIG. 3. The green subpixel G is turned off, and the red subpixel R and the blue subpixel B are turned off in the second pixel PXL, and the green subpixel G is turned on. do. This on / off state is repeated along the horizontal and vertical directions. Here, the white sub-pixel W of each pixel PXL is used for viewing angle control and is in an off state in all the pixels PXL.

At this time, when looking at the polarity and the on / off state of the sub-pixels for each position, all of the sub-pixels of the on state located in the first portion 122, that is, the first to third columns are all positive (positive) state (positive polarity) The sub-pixels in the on state positioned in the second portion 124, that is, the fourth to seventh columns, all have negative polarity in the negative state.

Accordingly, polarity skew occurs along the horizontal direction, and the distortion of the common voltage appears severely because the degree of change in the data signal level is large in the panel as a whole.

FIG. 7 is a graph illustrating a data signal Vdata and a common voltage signal Vcom measured when the image pattern is driven in FIG. 5. The first point A1 and the third area of the second area 120 of FIG. The value measured at the second point A2 of 130 is shown.

As shown in FIG. 7, the coupling occurs between the data signal Vdata and the common voltage signal Vcom due to the change of the data signal Vdata output from the data driving circuit, and the first point A1. The value of the common voltage signal Vcom at the second point A2 and A2 are changed, and a large ripple difference between the common voltage signal Vcom is shown. At this time, the change in the common voltage signal Vcom is more severe in the second region 120 of FIG. 5 due to polarity bias, and thus the difference between the common voltage signal Vcom at the first point A1 and the second point A2 is different. (V _A12 ) occurs. This is the result of displaying different images in the second area (120 in FIG. 5) and the third area (130 in FIG. 5).

Accordingly, a preferred embodiment of the present invention provides a driving method in which a horizontal crosstalk does not occur when displaying a specific image pattern in a liquid crystal display device having a viewing angle control including quad type pixels.

FIG. 8 is a diagram illustrating a method of driving a specific image pattern of a liquid crystal display according to an exemplary embodiment of the present invention, and shows polar shapes and on / off states of subpixels. Here, since the structure of the liquid crystal display shown in FIG. 8 is the same as that of FIG. 6, the same reference numerals are given to the same parts, and description thereof will be briefly or omitted.

As shown in FIG. 8, in a liquid crystal display capable of controlling a viewing angle including quad type pixels, when the first image is displayed at the center of the screen and the second image is displayed around the first image, red and green colors are displayed. The second image is displayed by alternately turning on / off each of the blue subpixels for each pixel, and data lines D1 and D (connected to the first stage of each data driving circuit 142, 144, 146, and 148. k + 1), D (l + 1), and D (m + 1) are applied with signals of the same polarity. Accordingly, the first polarity inversion control signal POLC_odd connected to the first and third data driving circuits 142 and 146 and the second polarity inversion control signal POLC_even connected to the second and fourth data driving circuits 144 and 148. ) All have the same value. For example, the first polarity inversion control signal POLC_odd and the second polarity inversion control signal POLC_even have a high value. In this case, the polarity inversion signal applied to each data driving circuit 142, 144, 146, and 148 ( POL) becomes a normal polarity state in which the polarity of the input signal remains as it is.

In this case, looking at the polarity and the on / off state of the sub-pixels for each position, the first and third data driving circuits of the sub-pixels of the on state located in the first portion 122, that is, the first to third columns Subpixels corresponding to (142, 146) have positive polarity in the positive state, and subpixels corresponding to the second and fourth data driving circuits (144, 148) are negative in the negative state. It has a negative polarity. Further, of the subpixels in the on state positioned in the second portion 124, that is, the fourth to seventh columns, the subpixels corresponding to the first and third data driving circuits 142 and 146 are in a negative state. Negative polarity is negative, and subpixels corresponding to the second and fourth data driving circuits 144 and 148 have positive polarity in a positive state.

Accordingly, since the positive and negative polarities alternate in the horizontal direction, the degree of change in the data signal level cancels each other, thereby reducing the distortion of the common voltage.

FIG. 9 is a diagram illustrating a screen state according to the driving method of FIG. 8, and FIG. 9 illustrates the same image pattern as FIG. 5.

As illustrated in FIG. 9, images of the second region 120 positioned above and below the first region 110 and the third region 130 positioned at the left and right sides of the first region 110 have similar luminance. It can be seen that it appears.

10 is a graph illustrating a data signal Vdata and a common voltage signal Vcom measured when the image pattern is driven in FIG. 9. The data signal Vdata and the common voltage signal Vcom of FIG. 10 are measured at the first point A1 of the second region 120 and the second point A2 of the third region 130 in FIG. 9. This is measured at the same point as the values of FIG.

As shown in FIG. 10, the ripple difference of the common voltage signal Vcom is reduced. This is because (+) and (-) polarities alternately appear along the horizontal direction, so that the bias is eliminated, the degree of change in the data signal level cancels each other, and the distortion of the common voltage is reduced. In addition, the difference in the common voltage signal between the first point A1 and the second point A2 also hardly appears, so that an image of similar luminance is displayed.

The present invention is not limited to the above embodiments, and various changes and modifications can be made without departing from the spirit of the present invention.

1 is a view schematically showing a configuration of a general liquid crystal display device.

2 is a diagram schematically illustrating a pixel structure of a liquid crystal display including red, green, and blue subpixels.

3 is a view schematically illustrating a pixel structure of a liquid crystal display according to the present invention.

FIG. 4 is a diagram schematically illustrating the polarity of the subpixels in the liquid crystal display device to which the two-dot inversion driving method according to the present invention is applied.

5 is a diagram illustrating a screen state when crosstalk occurs in the liquid crystal display of the present invention.

FIG. 6 is a diagram illustrating polar shapes and on / off states of subpixels when crosstalk occurs in the liquid crystal display of the present invention.

FIG. 7 is a graph illustrating a data driving circuit output signal and a common voltage signal measured at two points of FIG. 5.

FIG. 8 is a diagram illustrating polar shapes and on / off states of subpixels when a specific image pattern is displayed on a liquid crystal display by a driving method according to an exemplary embodiment of the present invention.

9 is a diagram illustrating a screen state according to the driving method of FIG. 8.

FIG. 10 is a graph illustrating a data signal and a common voltage signal measured when driving the image pattern of FIG. 9.

Claims (8)

A quad type pixel connected to the first and second data driving circuits receiving the polarity inversion signal and outputting a data signal, and one of the first and second data driving circuits, the first to fourth sub-pixels A liquid crystal display device comprising a liquid crystal panel having: Driving a first subpixel of one of the two adjacent pixels in an on state and a second subpixel in an off state; Driving the first subpixel of the other two adjacent pixels in an off state and the second subpixel in an on state Including, The subpixels in the on state connected to the first data driving circuit have positive polarity, and the subpixels in the off state connected to the second data driving circuit have negative polarity. How to drive the display device. The method according to claim 1, Wherein the first subpixel is positioned between the two adjacent second subpixels, and the first subpixel has the same polarity as one of the two adjacent second subpixels and has a different polarity from the other one. A driving method of a liquid crystal display device. The method according to claim 1, Each of the first and second data driving circuits is connected to (4i + 2) data lines, where i is a natural number, and each of the data lines is connected to one of the first and second sub pixels. A driving method of a liquid crystal display device characterized by the above-mentioned. The method according to claim 3, First and second polarity inversion control signals for controlling the polarity of the polarity inversion signal are supplied to the first and second data driving circuits, respectively, and the first and second polarity inversion signals have the same value. A driving method of a liquid crystal display device. The method according to claim 4, The second sub-pixel receiving the data signal from the (4i + 2) th data line connected to the first data driving circuit is the first sub-pixel receiving the data signal from the first data line connected to the second data driving circuit. And a polarity different from that of the liquid crystal display device. The method according to claim 1, And the third sub pixel has the same on / off state as the first sub pixel. The method according to claim 1, And the fourth sub-pixel is in an off state. The method according to claim 7, And the first to third subpixels have a liquid crystal driving mode of a horizontal electric field method, and the fourth subpixel has a liquid crystal driving mode of a vertical electric field method.

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