KR100853215B1 - Liquid crystal display - Google Patents

Abstract

The present invention relates to a liquid crystal display device. The liquid crystal display includes a liquid crystal panel assembly including a plurality of pixels arranged in a matrix, a data driver for applying a data signal voltage corresponding to a gray level signal to the pixel, and receiving the gray level signal and a control input signal. And a signal controller for controlling the data signal driver. The data signal voltage includes a normal data signal voltage and a black data signal voltage. The data driver applies the normal data signal voltage to odd pixels of odd pixel rows, applies the black data signal voltage to even pixels, and applies the black data signal voltage to odd pixels of even pixel rows. Data applied to an even-numbered pixel, and applied to (4n + 1) -th (n = 0, 1, ...) and (4n + 2) -th pixels of an odd-numbered pixel row. The polarity of the signal voltage is positive, and the polarity of the data signal voltage applied to the (4n + 3) -th and (4n + 4) -th pixels is negative. The type of data signal voltage of one frame and the polarity of the data signal voltage are opposite to the previous frame. Therefore, when the normal data signal and the black data signal are alternately applied in time and space, the image quality is improved since the liquid crystal charging time is not reduced.

LCD, LCD, Invert drive, Dot invert, Line invert impulsive, impulsive

Description

Liquid crystal display {LIQUID CRYSTAL DISPLAY}

1 is a block diagram of a liquid crystal display according to an exemplary embodiment of the present invention.

2 is an equivalent circuit diagram for one pixel.

3A and 3B are diagrams schematically illustrating types of signals applied to a pixel and polarities of the liquid crystal display according to the exemplary embodiment of the present invention.

4 is a diagram illustrating a data signal applied to a pixel and a luminance change according to the application of the data signal according to an exemplary embodiment of the present invention.

The present invention relates to a liquid crystal display device.

A general liquid crystal display device includes two display panels and a liquid crystal layer having dielectric anisotropy interposed therebetween. The desired image is obtained by applying an electric field to the liquid crystal layer and adjusting the intensity of the electric field to adjust the transmittance of light passing through the liquid crystal layer. Such liquid crystal displays are typical of portable flat panel displays (FPDs), and among them, TFT-LCDs using thin film transistors (TFTs) as switching elements are mainly used.

In such a liquid crystal display, since the response speed of the liquid crystal molecules itself is slow, the screen is not clear and blurring occurs, so to solve the problem, an impulsive driving method for inserting a black screen for a short time is required. Developed.

Such an impulsive driving method includes a method of making the entire screen black by flashing the backlight at a predetermined period (impulsive emission type) and applying a black data signal to the pixel at a predetermined period (cyclic resetting type).

However, since these methods have a slow response speed of the backlight or the liquid crystal, there is a problem in that image quality is degraded due to afterimages of the screen or flicker. In particular, in the latter case, the application time of the data signal is reduced.

Therefore, the technical problem of the present invention is to solve such a conventional problem, and to improve the image quality without increasing the data signal application frequency.

A liquid crystal display device according to one feature for achieving the object of the present invention,

A liquid crystal panel assembly comprising a plurality of pixels arranged in a matrix form,

A data driver which selects a gray voltage corresponding to the gray level signal and applies it to the pixel as a data signal voltage; and

A signal controller configured to control the data signal driver by receiving a control input signal for controlling the gray level signal and the display of the gray level signal

It includes.

Preferably, the data signal voltage includes a normal data signal voltage and a black data signal voltage, and the data driver alternately applies the normal data signal voltage and the black data signal voltage to the pixel in time and space under the control of the signal controller.

The data driver inverts the polarity of the data signal voltage every two pixels in the row direction, and inverts the polarity of the data signal voltage every column.

In addition, the data driver applies a normal data signal voltage to odd pixels of an odd pixel row, applies a black data signal voltage to even pixels, a black data signal voltage to odd pixels of an even pixel row, The normal data signal voltage is applied to even-numbered pixels.

Preferably, the polarity of the data signal voltage applied to the (4n + 1) th (n = 0, 1, ...) and (4n + 2) th pixels of the odd pixel row is positive, and (4n + 3 The polarity of the data signal voltage applied to the () th and (4n + 4) th pixels is negative.

Preferably, the type of data signal voltage of one frame and the polarity of the data signal voltage are opposite to the previous frame.

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.                     

Next, a liquid crystal display device according to an embodiment of the present invention will be described. 1 is a diagram illustrating a liquid crystal display according to an exemplary embodiment of the present invention.

1 is a block diagram of a liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram of one pixel.

As shown in FIG. 1, a liquid crystal display according to the present invention includes a liquid crystal panel assembly (hereinafter, referred to as a liquid crystal display panel) 300 and a gate driver 420 connected thereto. A data driver 430, a driving voltage generator 560 connected to the gate driver 420, a gray voltage generator 570 connected to the data driver 430, And a signal controller 550 for controlling them.

The liquid crystal panel 300 includes a plurality of signal lines G ₁ -G _n , D ₁ -D _m and a plurality of pixels connected thereto in an equivalent circuit, and each pixel includes the signal lines G ₁ -G _n. And a switching element Q connected to D ₁ -D _m , a liquid crystal capacitor C _lc , and a storage capacitor C _st connected thereto. The signal lines G ₁ -G _n , D ₁ -D _m transmit a scanning signal or a gate signal, and the plurality of scanning signal lines or gate lines G ₁ -G _n extending in the row direction. And a data signal line or data line D ₁ -D _m which transmits an image signal or a data signal and extends in the column direction. The switching element Q is a three-terminal element, the control terminal of which is connected to the gate line G ₁ -G _n , the input terminal of which is connected to the data line D ₁ -D _m , and the output terminal of the liquid crystal capacitor ( C _lc ) and one terminal of the holding capacitor C _st .

The liquid crystal capacitor C _lc is connected to the output terminal of the switching element Q and a common voltage V _com or a reference voltage. The other terminal of the holding capacitor C _st is connected to another voltage, for example a reference voltage. However, the other terminal of the holding capacitor C _st may be connected to the gate line directly above (hereinafter referred to as a "previous gate line"). The former is called a separate wire type and the latter is called a prior gate type.

Meanwhile, the liquid crystal panel assembly 300 may be schematically illustrated as shown in FIG. 2. For convenience, only one pixel is shown in FIG. 2.

As shown in FIG. 2, the assembly 300 includes a lower panel 100 and an upper panel 200 facing each other and a liquid crystal layer 3 therebetween. The lower panel 100 includes gate lines G _i-1 , G _i , a data line D _j , a switching element Q, and a storage capacitor C _st . The liquid crystal capacitor C _lc has two terminals as the pixel electrode 190 of the lower panel 100 and the reference electrode 270 of the upper panel 200, and the liquid crystal layer 3 between the two electrodes 190 and 270 is It functions as a hereditary body. The liquid crystal layer 3 of the present exemplary embodiment may take the OCB mode, for example, in which case the liquid crystal molecules are bent in a symmetrical direction with respect to a surface positioned in the middle of the lower panel 100 and the upper panel 200. Is oriented.

The pixel electrode 190 is connected to the switching element Q, and the reference electrode 270 is formed on the entire surface of the upper panel 200 and is connected to the common voltage V _com .

Herein, the liquid crystal molecules change their arrangement according to the change of the electric field generated by the pixel electrode 190 and the reference electrode 270, and thus the polarization of light passing through the liquid crystal layer 3 changes. The change in polarization is represented by a change in transmittance of light by a polarizer (not shown) attached to the display panels 100 and 200.

In the pixel electrode 190, a separate wiring to which the reference voltage is applied is provided on the lower panel 100 to overlap the pixel electrode 190 to form the storage capacitor C _st . For the previous gate way form the two terminals of the pixel electrode 190 is maintained with a previous gate line (G _i-1) by being overlapped with the previous gate line (G _i-1), an insulator as a medium capacitor (C _st).

FIG. 2 shows a MOS transistor as an example of the switching element Q, which is implemented as a thin film transistor having amorphous silicon or polysilicon as a channel layer in an actual process.

Unlike in FIG. 2, the reference electrode 270 may be provided in the lower panel 100. In this case, both electrodes 190 and 270 are linearly formed.                     

On the other hand, in order to implement color display, each pixel should be able to display color, which is provided by a color filter 230 of red, green, or blue in a region corresponding to the pixel electrode 190. It is possible. The color filter 230 is mainly formed in the corresponding region of the upper panel 200 as shown in FIG. 2, but may be formed above or below the pixel electrode 190 of the lower panel 100.

Referring back to FIG. 1, the gate driver 420 and the data driver 430 may also be referred to as scan drivers and source drivers, respectively, and may include a plurality of gate driver ICs and data driver ICs. Is common. Each IC may exist separately from the liquid crystal panel assembly 300 or be mounted on the assembly 300, and may be assembled in the same process as the signal lines G ₁ -G _n , D ₁ -D _m and the thin film transistor Q. It may be formed over the (300).

The gate driver 420 is connected to the gate lines G ₁ -G _n of the liquid crystal panel assembly 300 to determine the gate on voltage V _on and the gate off voltage V _off from the driving voltage generator 560. The combined gate signal is applied to the gate lines G ₁ -G _n .

The data driver 430 is connected to the data lines D ₁ -D _m of the assembly 300, and selects a gray voltage from the gray voltage generator 570 as the data signal D _1. -D _m ).

The operation of the gate driver 420, the data driver 430, and the driving voltage generator 560 is controlled by the signal controller 550 that is external to the liquid crystal panel assembly 300 and connected thereto. Explain.

The signal controller 550 controls an RGB data signal R, G, B and its display from an external graphic controller (not shown), for example, vertical synchronization. A vertical synchronizing signal (V _sync ), a horizontal synchronizing signal (H _sync ), a main clock (CLK), and a data enable signal (DE) are provided. The signal controller 550 generates a gate control signal and a data control signal based on the control input signal, and appropriately processes the gray level signals R, G, and B according to the operating conditions of the liquid crystal panel 300, and then controls the gate control signal. Is sent to the gate driver 420 and the driving voltage generator 560, and the data control signal and the processed grayscale signals R ', G', and B 'are sent to the data driver 430.

The gate control signal includes a vertical synchronization start signal (STV) for indicating the start of output of the gate on pulse (high period of the gate signal), and a gate clock signal for controlling the output timing of the gate on pulse. CPV) and a gate on enable signal (OE) for limiting the width of the gate on pulse. Among them, the gate-on enable signal OE and the gate clock signal CPV are supplied to the driving voltage generator 560. The data control signal includes a horizontal synchronization start signal (STH) indicating the start of input of the gray scale signal, a load signal (load signal, LOAD or TP) for applying a corresponding data voltage to the data line, and a polarity of the data voltage. An inversion control signal RVS and a data clock signal HCLK to invert.

The gate driver 420 sequentially applies gate-on pulses to the gate lines G ₁ -G _n in accordance with the gate control signal from the signal controller 550, thereby providing a single row connected to the gate lines G ₁ -G _n . The switching element Q is turned on. At the same time, the data driver 430 generates grayscale voltages corresponding to the grayscale signals R ', G', and B 'in the pixel row in which the switching element Q turned on in response to the data control signal from the signal controller 550. The analog voltage from the unit 570 is supplied as a data signal to the corresponding data lines D ₁ -D _m . The data signal supplied to the data lines D ₁ -D _m is applied to the corresponding pixel through the turned-on switching element Q. In this manner, gate-on pulses are sequentially applied to all of the gate lines G ₁ -G _n during one frame to apply data signals to all pixel rows. At this time, if the inversion control signal RVS is supplied after the data signal is applied to one pixel, the polarity of the data signal of the next row is changed. According to the exemplary embodiment of the present invention, the normal data signal and the black data signal are alternately applied to each pixel.

3A, 3B, and 4, a data signal applying method according to an exemplary embodiment of the present invention will be described in more detail.

3A and 3B schematically illustrate types of signals (ie, normal data signals or black data signals) applied to each pixel of a liquid crystal display according to an exemplary embodiment of the present invention, and their polarities. Showing a frame.

Here, the displays "+" and "-" indicate the polarity of the data signal applied to the pixel electrode 190 of FIG. 2 with respect to the common voltage V _com of the common electrode 270 of FIG. 2.

As shown in Figs. 3A and 3B, one embodiment of the present invention employs a two-dot inversion scheme for changing the polarity of the data signal every two pixels in the row direction and a line inversion scheme for changing the polarity every column. In addition, the normal data signal and the black data signal are alternately applied in both the row and column directions.

That is, in the case of the first frame illustrated in FIG. 3A, a normal data signal is applied to an odd pixel of an odd pixel row, and a black data signal is applied to an even pixel. On the contrary, the black data signal is applied to the odd pixels of the even pixel rows and the normal data signal is applied to the even pixels. On the other hand, the data signals applied to the (4n + 1) th (n = 0, 1, ..) and (4n + 2) th pixels of the odd pixel row are positive, and the (4n + 3) th and (4n + The data signal applied to the 4th pixel is negative. On the contrary, the data signals applied to the (4n + 1) th and (4n + 2) th pixels of the even-numbered pixel row are negative, and the data signals applied to the (4n + 3) th and (4n + 4) th pixels are It is positive.

As shown in FIG. 3B, the second frame is opposite to the first frame. That is, the data signal of the opposite type to the first frame is applied to each pixel with the opposite polarity.                     

The waveform of the data signal supplied to one pixel and the resulting luminance change are shown in FIG. 4, respectively.

As shown in Fig. 4, in the embodiment of the present invention, the normal data signal of "+" polarity is applied in the first frame, and the black data signal of "-" polarity is supplied in the next frame. Since an embodiment of the present invention relates to a liquid crystal display device of OCB mode that is normally white, the gray scale voltage of the largest gray scale voltage corresponds to black gray scale. In the third frame, a normal data signal of "+" polarity is applied, and in a fourth frame, a black data signal of "-" polarity is applied.

As such, when the normal data signal and the black data signal are alternately applied in time and space, the image quality is improved because the liquid crystal charging time is not reduced.

Although the preferred embodiments of the present invention have been described in detail above, 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 rights.

Claims (5)

In the liquid crystal display of OCB mode, A liquid crystal panel assembly comprising a plurality of pixels arranged in a matrix form, A data driver which selects a gray voltage corresponding to the gray level signal and applies it to the pixel as a data signal voltage; and A signal controller which receives the gray level signal and a control input signal for controlling the display of the gray level signal to control the data signal driver; Including, The data signal voltage includes a normal data signal voltage and a black data signal voltage. The data driver alternately applies the normal data signal voltage and the black data signal voltage to the pixel in time and space under the control of the signal controller. Liquid crystal display. In claim 1, And the data driver inverts the polarity of the data signal voltage every two pixels in a row direction and inverts the polarity of the data signal voltage every column. The method of claim 1 or 2, The data driver applies the normal data signal voltage to odd pixels in an odd pixel row, and applies the black data signal voltage to even pixels. The black data signal voltage is applied to odd pixels of an even pixel row, and the normal data signal voltage is applied to even pixels. Liquid crystal display. In claim 3, The polarity of the data signal voltage applied to the (4n + 1) th (n = 0,1, ...) and (4n + 2) th pixels of the odd pixel row is positive, and the (4n + 3) th and The polarity of the data signal voltage applied to the (4n + 4) th pixel is negative. In claim 4, A liquid crystal display device in which the type of data signal voltage of one frame and the polarity of the data signal voltage are opposite to the previous frame.

Images