KR20160004134A - Liquid crystal display device - Google Patents

Abstract

Provided is a liquid crystal display device. The liquid crystal display device determines whether or not a certain pattern is included in an image signal inputted from the outside and reverses a polarity of a data signal generated in a data driving unit to prevent a common voltage ripple phenomenon, thereby improving image quality. The liquid crystal display device includes: a liquid crystal panel in which multiple gate lines and multiple data lines are arranged to display an image; the data driving unit outputting the data signal to each of the data lines of the liquid crystal panel; and a timing control unit determining whether or not the certain pattern is present in the image signal inputted from the outside, outputting at least one from a first polarity signal and a second polarity signal reverse to the first polarity signal to the data driving unit, and controlling the polarity of the data signal outputted from the data driving unit.

Description

[0001] Liquid crystal display device [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly, to a liquid crystal display capable of improving image quality defects generated when a specific pattern is displayed on a liquid crystal display.

The demand for flat panel display devices is gradually increasing. As a flat panel display device, a liquid crystal display (LCD), a plasma display panel (PDP), a field emission display (FED) and an organic light emitting diode (OLED) have been actively studied. However, , The liquid crystal display device is now in the spotlight because of the realization of a large-area screen.

The liquid crystal display implements an image by adjusting the light transmittance of the liquid crystal cell according to the gray level value of the data signal. However, when a DC voltage is applied to the liquid crystal cell for a long time, the liquid crystal cell deteriorates to cause sticking phenomenon, which causes a residual image on the image displayed on the liquid crystal panel.

In order to prevent this, an inversion type liquid crystal display device has been proposed in which a data signal is inverted based on a common voltage. The inversion method is classified into a frame inversion, a line inversion, a column inversion, and a dot inversion. Among them, the dot inversion method implements an image of good image quality compared to the frame inversion method and the line inversion method.

In a liquid crystal display device driven by a dot-inversion method, the image quality may be degraded according to the correlation between the polarity of the data voltage charged in the liquid crystal cell and the displayed image pattern.

FIG. 1 is a diagram showing the polarity of each pixel when a liquid crystal display driven by a conventional vertical two-dot inversion method displays a specific pattern.

Referring to FIG. 1, a conventional vertical two-dot inversion type liquid crystal display device has RGB pixels arranged in a stripe form. Each pixel has a polarity inverted in the horizontal direction and is driven to have a polarity inverted by two pixels in the vertical direction.

The liquid crystal display device includes a plurality of data drivers DIC1 to DIC3. Each of the plurality of data drivers DIC1 to DIC3 may output a data signal generated by a version method with a vertical two-dot on the plurality of data lines of the liquid crystal panel. Here, one data driver is connected to six pixels adjacent in the horizontal direction of the liquid crystal panel. Other data drivers adjacent thereto have different polarity patterns.

Therefore, the Nth and (N + 2) th horizontal lines of the liquid crystal panel are arranged in the order of the polarity pattern of +, -, +, -, -, +, -, +, - +, -, +, -, +, +, -, +, -, +, and - from the first pixel to the twelfth pixel are repeated in the N + Quot; in a polar pattern.

In this case, the sixth pixel connected to the first data driver DIC1 and the seventh pixel connected to the second data driver DIC2 in adjacent pixels, i.e., the Nth horizontal line, which are connected to different data drivers in the horizontal direction, And have the same polarity.

Thus, the polarity of the data signal is not canceled between the data drivers, and ripples are generated in the common voltage Vcom. This ripple of the common voltage Vcom becomes more severe when a specific pattern is displayed on the liquid crystal display device, for example, a smear pattern as shown in Fig.

The ripple generated in the common voltage Vcom varies the level of the common voltage Vcom and the level of the data signal applied to each pixel of the liquid crystal panel changes in accordance with the level variation of the common voltage Vcom. This causes a luminance difference between the data lines, which causes image quality defects such as vertical dim in the image displayed on the liquid crystal display device.

An object of the present invention is to provide a liquid crystal display device capable of suppressing occurrence of ripples of a common voltage when a specific pattern is displayed on a liquid crystal display device, thereby improving image quality defects.

According to an aspect of the present invention, there is provided a liquid crystal display device including: a liquid crystal panel for displaying an image by arranging a plurality of gate lines and a plurality of data lines; A data driver for outputting a data signal to each of the plurality of data lines of the liquid crystal panel; And a second polarity signal that is inverted from the first polarity signal and outputs the first polarity signal and the second polarity signal to the data driver according to a determination result, And a timing controller for controlling the polarity of the output data signal.

The liquid crystal display according to the present invention determines whether the input image includes a smear pattern to determine the inversion / non-inversion of the polarity signal, thereby canceling the polarity of the data signal between the adjacent data driving units to prevent ripple phenomenon of the common voltage can do. As a result, it is possible to improve image quality defects such as a vertical dim to be generated in the liquid crystal display device.

FIG. 1 is a diagram showing the polarity of each pixel when a liquid crystal display driven by a conventional vertical two-dot inversion method displays a specific pattern.
2 is a view illustrating a liquid crystal display device according to an embodiment of the present invention.
3 is a diagram illustrating a connection between the data driver and the inversion controller shown in FIG.
4 is a diagram showing a configuration of the inversion control unit shown in Fig.
5 is a diagram illustrating an operation of the inversion control unit.
6A and 6B are diagrams illustrating a vertical 2-dot inversion driving method of a liquid crystal display device according to an embodiment of the present invention.

Hereinafter, a liquid crystal display device according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a diagram illustrating a liquid crystal display according to an embodiment of the present invention, and FIG. 3 is a diagram illustrating a connection between the data driver and the inversion controller shown in FIG.

Referring to FIG. 2, a liquid crystal display 100 according to an embodiment of the present invention may include a liquid crystal panel 110, a gate driver 120, a data driver 130, and a timing controller 140.

The liquid crystal panel 110 includes pixels formed in regions where the plurality of gate lines GL1 to GLn and the plurality of data lines DL1 to DLm are intersected and partitioned. Each of these pixels includes a thin film transistor TFT formed at the intersection between the corresponding gate line GL1 through GLn and the data line DL1 through DLm and a liquid crystal capacitor Clc connected between the thin film transistor TFT and the common electrode And a storage capacitor Cst. The thin film transistor TFT supplies a data signal supplied through the data lines DL1 to DLm to the liquid crystal capacitor Clc in response to a gate signal provided through the gate lines GL1 to GLn.

Various inversion methods such as a frame inversion, a line column inversion, and a dot inversion method can be used to drive the liquid crystal panel 110 described above. The frame inversion method inverts the polarity of the data signal supplied to the liquid crystal panel 110 every time the frame is changed. The line column inversion method inverts the polarity of a data signal supplied to the liquid crystal panel 110 according to a line (column) of the liquid crystal panel 110. The dot inversion method inverts the polarity of a data signal supplied to a pixel adjacent to a vertical line or a horizontal line direction of the liquid crystal panel 110. In addition, the polarity of the data signal supplied to the liquid crystal panel 110 is inverted for each frame.

Of these inversion methods, a dot inversion method which provides excellent image quality is used, and a version method with a vertical two dot is used. In the version with vertical two dot, the polarity of the data signal supplied to the liquid crystal panel 110 is inverted in the horizontal direction by one pixel unit and inverted in the vertical direction by two pixels. In this embodiment, an example in which the liquid crystal display device 100 is driven by a version method with vertical two-dot will be described as an example.

The gate driver 120 outputs a gate signal to each of the plurality of gate lines GL1 to GLn of the liquid crystal panel 110 according to a gate control signal GCS provided from the timing controller 140. [ The gate signal is sequentially output to the plurality of gate lines GL1 to GLn for one horizontal period 1H to turn on the thin film transistors TFT connected to the gate lines GL1 to GLn.

The data driver 130 outputs data signals to the plurality of data lines DL1 to DLm of the liquid crystal panel 110 according to the data control signal DCS provided from the timing controller 140. [ The data signal may be output in synchronization with a timing at which the gate signal is output from the gate driver 120. The data driver 130 receives one line of pixel data RGB 'from the timing controller 140 and converts the pixel data RGB' into an analog data signal using the gamma voltage.

Referring to FIG. 3, the data driver 130 may include a plurality of data ICs 130_1 to 130_N. Each of the data ICs 130_1 to 130_N includes six channels and each channel may be connected to each of the plurality of data lines DL1 to DLm of the liquid crystal panel 110 in a one-to-one correspondence.

For example, the first data IC 130_1 of the data driver 130 may include six channels, and each channel may be connected to the first to sixth data lines DL1 to DL6 of the liquid crystal panel 110 have. The second data IC 130_2 adjacent to the first data IC 130_1 may include six channels and each channel may include seventh to twelfth data lines DL7 to DL12 of the liquid crystal panel 110, Respectively.

The plurality of data ICs 130_1 to 130_N may be connected to the odd data IC and the even data IC. For example, the first data IC 130_1 to the (N-1) data IC 130_ (N-1) among the plurality of data ICs 130_1 to 130_N are connected to each other, and the second data IC 130_2 N data IC 130_N may be connected to each other.

The data driver 130 may control the timing controller 140 according to one of the polarity signals provided from the inversion controller 150 of the timing controller 140, for example, the first polarity signal POLC and the second polarity signal POLC ' To the data signal having the polarity pattern of the version system of vertical 2 dots, and outputs the data signal. Here, the odd-numbered data IC and the even-numbered data IC of the plurality of data ICs 130_1 to 130_N can output data signals having different polarity patterns.

Referring again to FIG. 2, the timing controller 140 may generate a gate control signal GCS and a data control signal DCS from a control signal CS provided from an external system. The control signal CS may be vertical / horizontal synchronizing signals (VSync / HSync), a data enable (DE) signal, a clock signal (CLK), and the like. The gate control signal GCS may be output to the gate driver 120 and the data control signal DCS may be output to the data driver together with the pixel data RGB '

The timing controller 140 may process the image signal RGB supplied from the external system to generate pixel data RGB 'and output the pixel data RGB' to the data driver 130.

The timing control unit 140 may include an inversion control unit 150. The inversion control unit 150 determines whether there is a specific pattern, for example, a smear pattern, from the video signal RGB input to the timing control unit 140, and outputs one of the first polarity signal POLC and the second polarity signal POLC ' Can be generated. One of the generated first polarity signal POLC and second polarity signal POLC 'may be output to the data driver 130 to control the polarity pattern of the data signal generated by the data driver 130. The first polarity signal POLC and the second polarity signal POLC 'may have an inverted phase.

The common voltage generator (not shown) can generate the common voltage Vcom from the high-potential voltage supplied from the outside and supply the generated common voltage Vcom to the liquid crystal panel 110. [

Fig. 4 is a diagram showing the configuration of the inversion control unit shown in Fig. 2, and Fig. 5 is a diagram showing an operation example of the inversion control unit.

Referring to FIGS. 2, 4 and 5, the inversion control unit 150 may include a pattern recognition unit 151 and a polarity (POL) signal generation unit 153.

The pattern recognition unit 151 can determine whether a specific pattern exists in the video signal RGB input to the timing control unit 140. [ The pattern recognition unit 151 can output the determination signal PR according to the determination result to the polarity signal generation unit 153. [

The pattern recognition unit 151 can generate a judgment signal PR composed of 2-bit data and output one of them. Here, the determination signal PR may be one of 00, 01, 10, and 11.

The determination signal PR 00 may indicate that no specific pattern exists in the video signal RGB. The determination signal PR 01 may indicate that a smear pattern exists in the video signal RGB. The determination signal PR 10 indicates that a shut-down pattern exists in the video signal RGB and the determination signal PR 11 indicates that a flicker pattern exists in the video signal RGB. .

In the present embodiment, it is assumed that the pattern recognition unit 151 generates a 2-bit decision signal PR. However, the decision signal PR may include a plurality of bits Data may be generated.

The polarity signal generating unit 153 may output one of the first polarity signal POLC and the second polarity signal POLC 'according to the determination signal PR output from the pattern recognition unit 151. [ The second polarity signal POLC 'may be an inverted signal of the first polarity signal POLC.

On the other hand, the phenomenon that the image quality defect occurs due to the lack of polarity cancellation between the adjacent data ICs becomes worse when the smear pattern is displayed on the liquid crystal panel 110. Accordingly, the polarity signal generating unit 153 can output the second polarity signal POLC 'according to the determination signal PR to be output when the pattern recognition unit 151 has a smear pattern in the video signal RGB .

For example, when the determination signal PR output from the pattern recognition unit 151 is 00, 10, and 11, the polarity signal generation unit 153 outputs the first polarity signal POLC to each data IC (130_1 to 130_N). When the determination signal PR output from the pattern recognition unit 151 is 01, the second polarity signal POLC 'may be output to each of the data ICs 130_1 to 130_N of the data driver 130.

6A and 6B are diagrams illustrating a vertical 2-dot inversion driving method of a liquid crystal display device according to an embodiment of the present invention.

6A, if the smear pattern does not exist in the image signal RGB input from the outside, the inversion control unit 150 may output the first polarity signal POLC to the data driver 130. FIG. For example, the pattern recognition unit 151 of the inversion control unit 150 may output the determination signal PR 00, and the polarity signal generation unit 153 may generate the first polarity signal POLC according to the determination signal PR, Can be output.

The data driver 130 may generate a data signal having a polarity pattern of a version system with vertical two dots according to the first polarity signal POLC. The data signal may be generated by alternating the polarity with reference to the common voltage Vcom. The data driver 130 may output the data signals to the plurality of data lines DL1 to DLm of the liquid crystal panel 110. [ Accordingly, the polarity of each pixel of the liquid crystal panel 110 can be inverted in units of one pixel in the same horizontal line, and inverted in units of two pixels in the same vertical line.

Since six pixels are connected to one data IC of the data driver 130, the polarity of each pixel of the liquid crystal panel 110 can be repeated with the same polarity in units of 12 pixels in the same horizontal line.

Therefore, the Nth and (N + 1) th horizontal lines of the liquid crystal panel 110 are arranged in the order of +, -, +, -, +, -, +, - Polarity. +, -, +, -, +, +, -, +, -, +, and - from the first pixel to the twelfth pixel, the N + 2 and N + 3 horizontal lines of the liquid crystal panel 110, Quot; polarity "

Here, the first to sixth pixels of the horizontal line are connected to the first data IC 130_1 of the data driver 130 and the seventh to twelfth pixels are connected to the second data IC 130_2 of the data driver 130 . Accordingly, the sixth pixel and the seventh pixel connected to the first data IC 130_1 and the second data IC 130_2 and adjacent to each other, that is, the horizontal line have the same polarity to each other, , There is little difference between the data signals applied to the two pixels, so that the magnitude of the ripple generated in the common voltage Vcom may be insignificant. Therefore, the level of the common voltage Vcom is hardly changed.

6B, if the smear pattern exists in the image signal RGB input from the outside, the inversion control unit 150 can output the second polarity signal POLC 'to the data driver 130. In this case, For example, the pattern recognition unit 151 of the inversion control unit 150 can output the determination signal PR 01, and the polarity signal generation unit 153 generates the second polarity signal POLC 'according to the determination signal PR, Can be output.

The second polarity signal POLC 'is a signal which is inverted with the first polarity signal POLC as described above. Accordingly, the data driver 130 inverts the polarity of the data signal according to the second polarity signal POLC '. At this time, the data driver 130 may invert the polarity of the data signal according to the second polarity signal POLC 'in the region where the smear pattern is generated.

For example, as shown in FIG. 6B, an image having a smear pattern in a specific pixel region of the liquid crystal panel 110 may be input to the inversion control unit 150 of the timing control unit 140. The smear pattern may exist in the vertical direction in the fourth to sixth pixels and the tenth to twelfth pixels among the pixels of the horizontal line of the liquid crystal panel 110. [

The inversion control unit 150 may output the second polarity signal POLC 'instead of the first polarity signal POLC to the data driver 130 according to the presence of the smear pattern. For example, the pattern recognition unit 151 of the inversion control unit 150 can output the determination signal PR 01, and the polarity signal generation unit 153 generates the second polarity signal POLC 'according to the determination signal PR, Can be output.

The data driver 130 may generate a data signal having a polarity opposite to that of the data signal generated by the first polarity signal POLC according to the second polarity signal POLC '. The data driver 130 may output the data signals to the plurality of data lines DL1 to DLm of the liquid crystal panel 110. [

Accordingly, the first to third pixels in the N and N + 1 horizontal lines of the liquid crystal panel 110 become "+, -, +", and the fourth to sixth pixels become "+, + "Polarity. In other words, the first data IC 130_1 of the data driver 130 supplies the first, second and third pixels of the N, N + 1 horizontal lines according to the first polarity signal POLC with "+, -, + And a data signal having a polarity of "+, -, +" is output to the fourth to sixth pixels of the N, N + 1 horizontal lines according to the second polarity signal POLC ' can do.

The seventh to ninth pixels in the N and N + 1 horizontal lines of the liquid crystal panel 110 have polarities of "-, +, -", and the tenth to twelfth pixels are "-, +, Quot; polarity ". In other words, the second data IC 130_2 of the data driver 130 applies a voltage of "-, +, -" to the seventh to ninth pixels of the N, N + 1 horizontal lines according to the first polarity signal POLC And a data signal having a polarity of "-, +, -" is output to the tenth to twelfth pixels of the N, N + 1 horizontal lines according to the second polarity signal POLC ' can do.

Accordingly, since the sixth pixel and the seventh pixel of the adjacent pixels connected to the first data IC 130_1 and the second data IC 130_2 have polarities different from each other and polarity is canceled, It is possible to prevent the ripple from being generated in the voltage Vcom.

In the Nth and (N + 1) th horizontal lines of the liquid crystal panel 110, the thirteenth to fifteenth pixels may have the same polarity as the first, second, and third pixels. Accordingly, the twelfth pixel and the thirteenth pixel which are connected to the second data IC 130_2 and the third data IC 130_3, respectively, have mutually different polarities to perform polarity cancellation, so that the common voltage Vcom It is possible to prevent ripples from being generated.

On the other hand, the pixels of the N + 2 and N + 3 horizontal lines of the liquid crystal panel 110 have polarities opposite to each other in the smear pattern except that they have the opposite polarity to the pixels of the N and N + 1 horizontal lines The configuration is the same. Therefore, even in the N + 2 and N + 3 horizontal lines of the liquid crystal panel 110, polarity can be canceled between adjacent pixels by being connected to different data ICs.

As described above, the timing controller 140 of the liquid crystal display device 100 may control the polarity of the data signal output from the data driver 130 to be inverted when the smear pattern is included in the video signal RGB input from the outside Can be controlled. Accordingly, the liquid crystal display device 100 according to the present embodiment can prevent ripples from being generated in the common voltage Vcom by canceling the polarity between a plurality of data ICs of the data driver 130, It is possible to improve image quality defects such as vertical dim in the image displayed on the display screen.

While a number of embodiments have been described in detail above, it should be construed as being illustrative of preferred embodiments rather than limiting the scope of the invention. Therefore, the invention should not be construed as limited to the embodiments described, but should be determined by equivalents to the appended claims and the claims.

100: liquid crystal display device 110: liquid crystal panel
120: Gate driver 130: Data driver
140: a timing control unit 150:

Claims (8)

A liquid crystal panel in which a plurality of gate lines and a plurality of data lines are arranged to display an image;
A data driver for outputting a data signal to each of the plurality of data lines of the liquid crystal panel; And
The method comprising: determining whether a specific pattern exists in an image signal input from the outside; outputting one of the first polarity signal and the second polarity signal inverted to the first polarity signal to the data driver according to a determination result, And a timing controller for controlling the polarity of the data signal. The method according to claim 1,
Wherein the timing control unit comprises:
A pattern recognition unit for determining whether patterns exist in the video signal and outputting a determination signal; And
And a polarity signal generator for outputting one of the first polarity signal and the second polarity signal according to the determination signal. 3. The method of claim 2,
Wherein the polarity signal generator outputs the second polarity signal according to a determination signal output from the pattern recognition unit when the specific pattern exists in the video signal. 3. The method of claim 2,
Wherein the determination signal is a signal composed of 2-bit data. 3. The method of claim 2,
Wherein the data driver inverts a polarity of a data signal output to the plurality of data lines according to the second polarity signal in an area where the specific pattern exists. The method according to claim 1,
Wherein the specific pattern is a smear pattern. The method according to claim 1,
Wherein the first polarity signal and the second polarity signal are polarity signals having a polarity pattern of a version system in which vertical 2 dots are provided. The method according to claim 1,
Wherein the data driver includes a plurality of data ICs each having a channel corresponding to one of the plurality of data lines,
Wherein the odd-numbered data IC and the even-numbered data IC among the plurality of data ICs have a polarity that is inverted with respect to each other.

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