KR20040017708A - A liquid crystal display - Google Patents

Abstract

PURPOSE: A liquid crystal display is provided to offset a difference in a charging rate by reversing the polarity of a gray voltage by the unit pixel of one pixel in a vertical direction and two pixels in a horizontal direction. CONSTITUTION: A data driver(30) arranges picture data provided from a timing controller(50) by data lines on a liquid crystal panel(10), and selects a gray voltage(Vgray) appropriate for the picture data. The data driver reverses the polarity of the selected voltage by the one horizontal scanning period by using a reverse signal. At the same time, the data driver reverses the polarity of the selected gray voltage by the consecutive two pixels of the data line. Each gray voltage of which the polarity is reversed is output to each data line of the liquid crystal panel.

Description

Liquid crystal display device {A LIQUID CRYSTAL DISPLAY}

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 employing an inversion driving method in which polarity is inverted in pixel units of one vertical pixel and two horizontal pixels in a liquid crystal panel.

In recent years, display devices such as personal computers and televisions have been required to be lighter and thinner, and in order to satisfy such demands, liquid crystal displays (LCDs) instead of cathode-ray tubes (CRTs) are required. Flat panel displays such as displays have been developed and put into practical use in various fields.

The liquid crystal panel of the liquid crystal display device includes a substrate on which a pixel pattern is formed in a matrix form and a substrate opposite thereto. A liquid crystal material having an anisotropic dielectric constant is injected between the two substrates. An electric field is applied between the two substrates, and by controlling the intensity of the electric field, the amount of light transmitted through the substrate is controlled to display a desired image.

In such a liquid crystal display, n-bit RGB data of red, green, and blue is input from an external graphic source. The RGB data is converted in a data format by a timing controller of a liquid crystal display, an analog gray voltage suitable for RGB data is selected in a data driving IC, and the selected gray voltage is displayed on the liquid crystal panel. The display operation is performed by being applied to the pixel. Here, the gray voltage is a direct current component. When the DC gray voltage of the same polarity is applied to the pixels on the liquid crystal panel continuously, there is a problem in that the liquid crystal material deteriorates in each liquid crystal pixel. In order to prevent such liquid crystal deterioration, a driving method for inverting the polarity of the gray scale voltage in units of pixels, lines, or frames of a liquid crystal panel has been proposed. The present invention relates to a liquid crystal display device to which an inversion driving method is applied, in which the polarity of the applied voltage is inverted and driven in a pixel unit of a predetermined region.

1 is a form of a dot inversion method, and a liquid crystal panel for explaining an inversion driving method for inverting and driving the polarities of pixels in units of two pixels in a vertical direction (Y direction) and one pixel in a horizontal direction (X direction) of the liquid crystal panel. The polar pattern of is shown. As illustrated in FIG. 1, polarities are inverted in one pixel in the X direction and two pixels in the Y direction, that is, in a 2 × 1 pixel unit of the liquid crystal panel, and polarities of adjacent unit pixels are opposite to each other. The inversion driving method in units of 2 × 1 pixels is widely used because it consumes less current and reduces flicker in the screen than the inversion driving method of inverting one pixel, that is, a dot unit. However, in the case of applying the above-described inversion driving method, there is a problem in that faint horizontal stripes occur across the entire screen due to the difference in charge rate between pixels having opposite polarities among the Y-direction pixels of the liquid crystal panel, which causes display quality. This causes a decrease.

2 is a view for explaining the cause of such a difference in filling rate.

As illustrated in FIG. 2, in the pixels arranged in the Y direction of the liquid crystal panel, polarities are inverted in units of two pixels, among which pixels having opposite polarities (n + 1 pixel and n + 2 pixel in FIG. 2). Are different from each other by the pixel voltage Vp including the image information. That is, when two pixels are charged with a positive polarity and then changed to a negative polarity, the charging rates of the second pixel to which positive polarity is applied and the first pixel to be charged with negative polarity are mutually different. different. More specifically, when the polarity of the voltage applied to the pixel is inverted by 2 pixel units in the Y direction of the liquid crystal panel, that is, when a change in the applied voltage occurs, between the two pixels to which the polarity is applied in reverse AC coupling occurs due to the parasitic capacitance C _parasitic present, thereby reducing the charge rate of the pixel immediately before the polarity is reversed. In addition, as the voltage change rate of the data driver applying the pixel voltage Vp to the liquid crystal panel, that is, the slew rate increases, the AC coupling increases, and the charge rate difference between pixels having opposite polarities in the Y direction is increased. Increases. This filling rate difference occurs over the entire surface of the liquid crystal panel and is recognized by the user's eye, which appears in the form of a horizontal stripe pattern.

The present invention is to solve the conventional problems under the technical background as described above, driving by inverting the polarity in the unit of a predetermined pixel (1 × 2 pixels) consisting of 1 pixel in the vertical direction and 2 pixels in the horizontal direction of the liquid crystal panel In particular, an object of the present invention is to provide a liquid crystal display device employing a polarity inversion scheme in which the polarization of the Y-direction pixels of the liquid crystal panel is driven by inverting the polarity in units of one pixel.

1 is a view for explaining a polarity inversion scheme applied to a conventional liquid crystal display device.

2 is a view for explaining a difference in charge rate between adjacent pixels when a conventional polarity inversion scheme is applied.

3 is a diagram showing the overall configuration of a liquid crystal display according to a first embodiment of the present invention.

4 is a view illustrating in more detail the data driver shown in FIG. 3;

FIG. 5 is a view showing waveforms of signals used in the data driver shown in FIG. 4; FIG.

6 illustrates a polarity inversion scheme applied to a liquid crystal display according to a first embodiment of the present invention.

7A and 7B illustrate panel structures and polarity inversion schemes applied to a liquid crystal display according to a second exemplary embodiment of the present invention.

FIG. 8 is a diagram showing a format of RGB data applied to the panel structure shown in FIG. 7A. FIG.

(Explanation of symbols for the main parts of the drawing)

10 liquid crystal panel 20 gate driver

30: data driver 40: voltage generator

50: timing control section 31: shift register section

32: D / A conversion section 33: latch section

The liquid crystal display device of the present invention for achieving the above object,

A liquid crystal panel comprising a plurality of gate lines, a plurality of data lines crossing the gate lines, and pixels formed at intersections of the gate lines and the data lines;

A timing controller configured to receive image data and a synchronization signal provided from an external graphic source, generate a control signal for driving the liquid crystal panel, and perform format conversion of the image data;

A voltage generator configured to generate a gray voltage and a gate voltage for driving the liquid crystal panel;

A gate driver sequentially scanning each gate line of the liquid crystal panel by one horizontal scanning period using the gate voltage; And,

Arranging image data provided by the timing controller for each data line on the liquid crystal panel, selecting a gray voltage corresponding to the image data, and inverting the polarity of the selected voltage by one horizontal scanning period using an inversion signal; At the same time, it includes a data driver for inverting the polarity of the selected gray voltage in two consecutive pixel units of the data line, and outputting each of the polarity inverted gray voltages to each data line of the liquid crystal panel.

In the above-described liquid crystal display device, the data driver drives the polarity by inverting the polarity for each unit pixel (1 × 2 pixel) in the horizontal direction 2 pixels and the vertical direction 1 pixel of the liquid crystal panel using the inversion signal REV. Therefore, since the polarity is inverted for each pixel between the pixels positioned in the vertical direction of the liquid crystal panel, the influence of AC coupling may appear for each pixel in the vertical direction, thereby canceling the charge rate difference. In addition, since the polarity is inverted in units of 1 × 2 pixels, the advantages of the polarity inversion scheme of the existing 2 × 1 pixels can be maintained.

The objects, technical configurations, and effects thereof of the present invention described above will become more apparent from the following description of the embodiments.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

A liquid crystal display and a driving method thereof according to an embodiment of the present invention will now be described in detail with reference to the drawings.

In the liquid crystal display according to the first exemplary embodiment of the present invention, a method of inverting polarity in pixels of a predetermined region of the liquid crystal panel, that is, 1 × 2 pixels, is applied. By doing so, since the polarities of the Y-direction pixels of the liquid crystal panel are inverted in units of one pixel, the effect of AC coupling due to the parasitic capacitor appears to be the same in all the pixels, and therefore, in each pixel disposed in the Y direction of the liquid crystal panel The difference in filling rate may be offset. Embodiments of the present invention show an example for implementing the polarity inversion scheme in units of 1 × 2 pixels. In the first embodiment, the polarity inversion scheme is implemented through the data driver, and in the second embodiment, the pixel of the liquid crystal panel is implemented. The polarity inversion scheme is implemented through structure and input order of RGB data.

First, a liquid crystal display according to a first embodiment of the present invention will be described with reference to the drawings.

3 illustrates the overall structure of the liquid crystal display according to the first exemplary embodiment of the present invention, FIG. 4 illustrates the data driver of FIG. 3 in more detail, and FIG. 5 illustrates the data driver of FIG. The waveform of the signal used is shown, and FIG. 6 shows a polar pattern by the polarity inversion method applied to the liquid crystal display according to the first embodiment of the present invention.

As shown in FIG. 3, the liquid crystal display according to the first exemplary embodiment of the present invention includes a liquid crystal panel 10, a gate driver 20, a data driver 30, a voltage generator 40, and a timing controller 50. ).

Although not shown in detail through the drawings, the liquid crystal panel 10 includes a plurality of gate lines, a plurality of data lines perpendicular to the gate lines, and pixels formed at intersections of the gate lines and the data lines. Each pixel is disposed in a matrix structure. Each pixel includes a thin film transistor having a gate electrode and a source electrode connected to a gate line and a data line, and a pixel capacitor and a storage capacitor connected to a drain electrode of the thin film transistor. .

In such a pixel structure, when a gate signal for selecting a corresponding gate line is applied by the gate driver 20, the thin film transistor of the pixel connected to the gate line is turned on, and then each data line is driven by the data driver 30. An image data voltage representing image information is applied as a data signal. This voltage is applied to the pixel capacitor and the sustain capacitor through the thin film transistor of the pixel to drive these capacitors, thereby performing a predetermined display operation.

The timing controller 50 receives RGB data, a synchronization signal SYNC, a data enable signal DE, and a clock signal CLK from an external graphic source (not shown). The timing controller 50 converts a format of the input RGB data RGB data according to a data standard required by the data driver 30, and synchronizes the synchronization signal SYNC, the data enable signal DE, and the like. The control signals CONT1 and CONT2 to be used in the gate driver 20 and the data driver 30 are generated and output using the clock signal CLK. In addition, the timing controller 50 may include a load signal TP used to control a timing at which the data driver 30 applies a data signal to each pixel of the liquid crystal panel 10, and data applied to each pixel. An inverted signal REV, which is used as a reference signal for determining the polarity of the signal, is generated and output to the data driver 30.

The voltage generator 40 generates and outputs a gray voltage Vgray and a gate voltage Vgate, which are voltages that are actually applied to the data line and the gate line of the liquid crystal panel 10. Here, the gray voltage Vgray has a plurality of voltage levels and is transmitted to the data driver 30. The gate voltage Vgate includes a gate on voltage and a gate off voltage, and is transmitted to the gate driver 20.

The gate driver 20 includes a plurality of gate driver ICs each responsible for a predetermined number of gate lines on the liquid crystal panel 10, and the control signal CONT1 and the voltage generator provided by the timing controller 50. Each gate line on the liquid crystal panel 10 is sequentially scanned in units of one horizontal scanning period using the gate voltage Vgate provided at 40. For example, the gate driver 20 applies a gate-on voltage to a gate line to which a pixel line to which image information is to be written, applies a gate-off voltage to the remaining gate lines, and the application time of the gate-on voltage is 1 horizontal. Injection period. As described above, the process of applying the gate-on voltage for each gate line is sequentially performed for all the gate lines.

As illustrated in FIG. 4, the data driver 30 includes a shift register 31, a D / A converter 32, and a latch 33. The shift register unit 31 receives the image data RGB DATA and sequentially shifts the data so that the serially input data corresponds to each data line of the liquid crystal panel 10. Next, the D / A converter 32 receives the output of the shift register 31, the gray voltage Vgray, and the inverted signal REV, and outputs the image data output from the shift register 31. The gray level corresponding to the data is selected from the gray voltage Vgray according to the arrangement. At this time, the D / A converter 32 inverts the polarity of the gray voltage selected for each data line by one horizontal scan period by using the inverted signal REV having the waveform shown in FIG. 5. By doing so, as illustrated in FIG. 6, the polarity of pixels positioned in the vertical direction (Y direction) of the liquid crystal panel may be inverted by one pixel unit. At the same time, the D / A converter 32 equalizes polarities of gray voltages corresponding to two consecutive data lines, and inverts polarities of gray voltages corresponding to the next two data lines. By doing so, as illustrated in FIG. 6, the polarity of the pixels positioned in the horizontal direction (X direction) of the liquid crystal panel may be inverted in units of two pixels. Next, the latch unit 33 outputs the gray voltage for each data line selected by the D / A converter 32 to the liquid crystal panel 10 according to the load signal TP. In FIG. 5, voltage signals Y _4n to Y _4n-3 show waveforms of the gray voltages output from the latch unit 33 to the liquid crystal panel 10 for four data lines. Here, VGMA6 to VGMA10 are gray voltages of negative polarity, and VGMA1 to VGMA5 are gray voltages of positive polarity.

As described above, in the first exemplary embodiment of the present invention, the data driver 30 uses the inverted signal REV to generate two horizontal pixels and one vertical pixel unit pixel (1 × 2) of the liquid crystal panel 10. Each pixel is driven by inverting its polarity. Therefore, since the polarity is inverted for each pixel between the pixels positioned in the vertical direction of the liquid crystal panel, the influence of AC coupling may appear for each pixel in the vertical direction, thereby canceling the charge rate difference. In addition, since the polarity is inverted in units of 1 × 2 pixels, the advantages of the polarity inversion scheme of the existing 2 × 1 pixels can be maintained.

Next, a liquid crystal display according to a second exemplary embodiment of the present invention will be described with reference to FIGS. 7 to 8.

In the second embodiment of the present invention, in the structure of the liquid crystal panel, the nth R, G, B pixels and the n-1th R, G, B pixels on the nth (relative to the vertical direction of the liquid crystal panel) gate lines It is characterized by the configuration that is connected alternately. As shown in FIG. 7A, an RGB pixel of the current line and an RGB pixel of the previous line are connected to the gate line in an up-and-down alternating manner in an arbitrary gate line by three pixel units of RGB. Therefore, when any n-th gate line is selected, the n-th pixel and the n-th pixel in the vertical direction are alternately selected in units of three RGB pixels. The data driver inverts the polarity of the voltage applied to each data line in units of one horizontal scanning period, and at the same time, inverts the polarity of the selected gray voltage in successive one pixel units of the data line. In this case, as shown in FIG. 7B, the polarity inversion of the modified 1 × 2 pixel unit may be implemented. That is, as illustrated in FIG. 7B, one pixel in the middle of a 1 × 2 pixel having the same polarity has a different polarity from surrounding unit pixels. Also in the case of the second embodiment, since the polarity is inverted in units of one pixel between pixels located in the vertical direction of the liquid crystal panel, the same effect as in the first embodiment can be obtained. In the second embodiment, image signals must be alternately written to the n-th RGB pixel and the n-1th RGB pixel of the liquid crystal panel, so that as shown in FIG. 8, the RGB data of the nth line and the n-1th line The format of the RGB data must be adjusted in the timing controller or an external graphic source so that the RGB data appear alternately.

As described above, in the liquid crystal display according to the first exemplary embodiment of the present invention, the data driver 30 uses the inversion signal REV so that the two pixels in the horizontal direction and one pixel in the vertical direction of the liquid crystal panel 10 are adjusted. By driving by inverting polarity for each unit pixel (1 × 2 pixel), the polarity is inverted for every pixel between the pixels positioned in the vertical direction of the liquid crystal panel, and the influence of AC coupling appears for every pixel in the vertical direction, thereby causing a difference in charge rate. May be offset. In addition, since the polarity is inverted in units of 1 × 2 pixels, the advantages of the polarity inversion scheme of the existing 2 × 1 pixels can be maintained. In the liquid crystal display according to the second exemplary embodiment of the present invention, the n th R, G, B pixels and the n-1 th R, G, B pixels are arranged on the n th (relative to the vertical direction of the liquid crystal panel) gate line. By configuring the liquid crystal panel to be alternately connected and inverting the polarity of the voltage applied to each data line by one pixel unit, the polarity is inverted by one pixel unit between pixels located in the vertical direction of the liquid crystal panel. The same effect as in the first embodiment can be obtained.

As described above, preferred embodiments of the present invention have been described in detail, but the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of the invention.

Claims (5)

A liquid crystal panel comprising a plurality of gate lines, a plurality of data lines crossing the gate lines, and pixels formed at intersections of the gate lines and the data lines; A timing controller configured to receive image data and a synchronization signal provided from an external graphic source, generate a control signal for driving the liquid crystal panel, and perform format conversion of the image data; A voltage generator configured to generate a gray voltage and a gate voltage for driving the liquid crystal panel; A gate driver sequentially scanning each gate line of the liquid crystal panel by one horizontal scanning period using the gate voltage; And, Arranging image data provided by the timing controller for each data line on the liquid crystal panel, selecting a gray voltage corresponding to the image data, and inverting the polarity of the selected voltage by one horizontal scanning period using an inversion signal; At the same time, a data driver for inverting the polarity of the selected grayscale voltage in units of two consecutive pixels of the data line, and outputting the polarized grayscale voltages to the respective data lines of the liquid crystal panel. Liquid crystal display. The method of claim 1, The data driver A shift register unit which receives the image data from the timing controller and sequentially shifts the image data so as to correspond to each data line of the liquid crystal panel; Receiving the output of the shift register, the gray voltage output from the voltage generator and the inverted signal output from the timing controller, select the gray level corresponding to the data from the gray voltage according to the image data output from the shift register. By using the inversion signal, the polarity of the gray voltage selected for each data line is inverted by one horizontal scanning period, and at the same time, the polarity of the gray level voltage corresponding thereto is output in two consecutive data lines. D / A conversion unit; And, And a latch unit configured to output a gray voltage for each data line whose polarity is inverted by the D / A converter according to a load signal output from the timing controller. Liquid crystal display. The method according to claim 1 or 2, The pixels in the vertical direction of the liquid crystal panel are inverted in polarity in units of one pixel, and the pixels in the horizontal direction are driven in inverted polarities in units of two pixels. Liquid crystal display. And a plurality of gate lines, a plurality of data lines crossing the gate lines, and pixels formed at intersections of the gate lines and the data lines, wherein the nth gate line includes an nth RGB pixel and an n-1th RGB pixel. A liquid crystal panel configured to connect pixels alternately up and down; A timing controller configured to receive image data and a synchronization signal provided from an external graphic source, generate a control signal for driving the liquid crystal panel, and perform format conversion of the image data; A voltage generator configured to generate a gray voltage and a gate voltage for driving the liquid crystal panel; A gate driver sequentially scanning each gate line of the liquid crystal panel by one horizontal scanning period using the gate voltage; And, Arranging image data provided by the timing controller for each data line on the liquid crystal panel, selecting a gray voltage corresponding to the image data, and inverting the polarity of the selected voltage by one horizontal scanning period using an inversion signal; At the same time, the data driver includes a data driver configured to invert the polarity of the selected gray voltage in the unit of one pixel of the data line, and to output each of the polarity inverted gray voltages to each data line of the liquid crystal panel. Liquid crystal display. The method of claim 4, wherein In the timing controller or an external graphic source, the format of the RGB data is adjusted so that the RGB data of the n-th line and the RGB data of the n-th line appear alternately. Liquid crystal display.