KR100612360B1 - Liquid crystal display - Google Patents

Abstract

The present invention relates to a liquid crystal display device. According to the present invention, the noise included in the system reset signal is removed and then applied to the scan driver. In this way, the phenomenon in which the color displayed on the panel is fixed to any one of the R, G, and B colors due to the noise can be prevented.

LCD, Field Sequential Driving, Scan Driver

Description

Liquid crystal display

1 is a view showing a pixel of a conventional TFT-LCD.

2 is a waveform diagram illustrating a driving method of a conventional analog liquid crystal display device.

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

4 is a diagram illustrating a reset signal controller according to a first embodiment of the present invention.

5 is a diagram illustrating a reset signal controller according to a second exemplary embodiment of the present invention.

The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device of the field sequential driving method.

Recently, display devices are also required to be lighter and thinner in accordance with the light weight and thickness of personal computers and televisions, and according to such demands, flat displays such as liquid crystal displays (LCDs) instead of cathode ray tubes (CRTs) are required. Panel type displays are being developed.

An LCD applies an electric field to a liquid crystal material having an anisotropic dielectric constant injected between two substrates, and adjusts the intensity of the electric field to control the amount of light transmitted to the substrate from an external light source (backlight). A display device for obtaining an image signal.

Such LCDs are typical of portable flat panel displays, and among them, TFT-LCD using a thin film transistor (TFT) as a switching element is mainly used.

In the TFT-LCD, each pixel may be modeled as a capacitor having a liquid crystal as a dielectric, that is, a liquid crystal capacitor. The equivalent circuit of each pixel in the LCD is shown in FIG.

As illustrated in FIG. 1, each pixel of the liquid crystal display includes a TFT 10 having a source electrode and a gate electrode connected to the data line Dm and the scan line Sn, respectively, and a drain electrode and a common voltage Vcom of the TFT. It includes a liquid crystal capacitor (Cl) connected between and a storage capacitor (Cst) connected to the drain electrode of the TFT.

In Fig. 1, when the scan signal is applied to the scan line Sn and the TFT 10 is turned on, the data voltage Vd supplied to the data line is applied to each pixel electrode (not shown) through the TFT. Then, an electric field corresponding to the difference between the pixel voltage Vp and the common voltage Vcom applied to the pixel electrode is applied to the liquid crystal (equivalently represented by the liquid crystal capacitor in FIG. 1), and thus transmittance corresponding to the intensity of the electric field. To allow light to pass through. In this case, the pixel voltage Vp should be maintained for one frame or one field. In FIG. 1, the storage capacitor Cst is used to maintain the pixel voltage Vp applied to the pixel electrode.

In general, the liquid crystal display may be divided into two methods, a color filter method and a field sequential driving method, according to a method of displaying a color image.

A color filter type liquid crystal display device forms a color filter layer composed of three primary colors of red (R), green (G), and blue (B) on one of two substrates, and transmits the amount transmitted through the color filter layer. Display the desired color by adjusting. The color filter type LCD synthesizes R, G, and B colors by adjusting the amount of light transmitted through the R, G, and B color filter layers to transmit light emitted from a single light source to the R, G, and B color filter layers. To display the desired color.

As described above, in a liquid crystal display device that displays color using a single light source and a three-color color filter layer, since each unit pixel is required for each of the R, G, and B regions, three times as many pixels are used as for a black and white display. It is necessary. Therefore, in order to obtain a high resolution image, sophisticated manufacturing technology of a liquid crystal display panel is required.

In addition, there is a manufacturing problem that a separate color filter layer must be formed on the liquid crystal display substrate, and there is a problem that the light transmittance of the color filter itself must be improved.

The liquid crystal display of the field sequential driving method periodically turns on independent light sources of R, G, and B colors, and applies a color signal corresponding to each pixel in synchronism with the lighting cycle to display a full color image. Get it. That is, according to the liquid crystal display of the field sequential driving method, R, G, and B primary colors output from R, G, and B backlights to one pixel without dividing one pixel into R, G, and B unit pixels. By time-divisionally displaying the light of the image, the color image is displayed using the afterimage effect of the eye.

An example of such a field sequential driving method is an analog driving method.

The analog driving method sets a plurality of gray voltages corresponding to the number of gray scales to be displayed, selects one gray voltage corresponding to gray data among the gray voltages, and drives the liquid crystal panel with the selected gray voltage, thereby applying the applied gray voltage. Gradation display is performed with the amount of transmitted light corresponding to.

2 is a diagram illustrating a driving voltage and a transmitted light amount according to a conventional LCD driving apparatus.

Referring to FIG. 2, in the R field section T1 for displaying the R color, a driving voltage of the V11 level is applied to the liquid crystal so that light corresponding to the driving voltage of the V11 level passes through the liquid crystal. In the G field section T2 for displaying the G color, a driving voltage of the V12 level is applied so that light corresponding to the driving voltage of the V12 level passes through the liquid crystal. Then, in the B field section T3 for displaying the B color, a driving voltage of the V13 level is applied to obtain a light transmittance corresponding to the driving voltage of the V13 level. The desired color image is displayed by the sum of the R, G, and B lights transmitted in the T1, T2, and T3 sections, respectively.

Referring to FIG. 2, the period in which the R color is actually displayed is a period Tr from the time t2 to t3 when the R backlight is emitted, and the G color is displayed in the period from the time t5 to t6 when the G backlight is emitted ( Tg), and the color B is displayed in the period Tb from the time t8 to t9 when the B backlight emits light.

On the other hand, in the conventional field sequential driving method, the data driver applying the data signal to the LCD panel is more sensitive to the signal applied when the system is reset than the scan driver. Therefore, when noise is included in the reset signal, there is a problem in that the color displayed on the panel is fixed to one of R, G, and B and turned off.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a field-sequential driving liquid crystal display device that displays a stable screen by removing noise included in a system reset signal applied to a scan driver.

According to an aspect of the present invention, a liquid crystal display device includes a plurality of scan lines for transmitting a scan signal, a plurality of data lines insulated from and intersect the scan lines, and an area surrounded by the scan lines and the data lines. A liquid crystal display panel including a plurality of pixels formed in a matrix form having switching elements connected to the scan line and the data line, respectively; A gate driver for sequentially supplying scan signals to the scan lines; A gray voltage generator which generates a gray voltage corresponding to gray data; A data driver for supplying a gray voltage and a reset voltage output from the gray voltage generator and the reset voltage generator to a corresponding data line; A reset signal controller which removes noise of a reset signal input from the outside and outputs the noise to the data driver; A light source sequentially outputting red, green, and blue light to one pixel; And a light source controller controlling a lighting time point of the light source.

The reset signal controller may include a resistor and a capacitor connected in series between the reset signal input terminal and a ground, and a signal output from a contact point of the resistor and the capacitor is input to the data driver.

In addition, the reset signal controller may include a counter circuit for counting the number of pulses of the input signal,

Outputting the input signal to the data driver when the pulse signal is input for a predetermined predetermined clock pulse,

A signal input for a period shorter than the predetermined clock pulse is determined as a noise signal and is not output to the data driver.

DETAILED DESCRIPTION Hereinafter, exemplary 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. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention. Like parts are designated by like reference numerals throughout the specification.

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

As shown in FIG. 3, the liquid crystal display according to the exemplary embodiment of the present invention includes a liquid crystal display panel 100, a scan driver 200, a data driver 300, a gray voltage generator 400, a timing controller ( 500, a reset signal controller 600, light emitting diodes 700a, 700b, and 700c that output R, G, and B light sources, respectively, and a light source controller 800.

A plurality of scan lines (not shown) are formed in the liquid crystal display panel 100 to transmit a gate-on signal, and are insulated from and intersect with the plurality of scan lines to transmit gray data voltages and reset voltages corresponding to gray data. A data line (not shown) is formed for this purpose. A plurality of pixels arranged in a matrix form is surrounded by a scan line and a data line, and each pixel includes a thin film transistor (not shown) and a drain electrode of the thin film transistor, in which a gate electrode and a source electrode are connected to the scan line and the data line, respectively. A pixel capacitor (not shown) and a storage capacitor (not shown) are connected to each other.

The scan driver 200 sequentially applies a scan signal to the scan line, thereby turning on the TFT to which the gate electrode is connected to the scan line to which the scan signal is applied.

The timing controller 500 receives the gray level data signals R, G, and B data, the horizontal synchronization signal Hsync, and the vertical synchronization signal Vsync from an external or graphic controller (not shown), and controls necessary signals Sg, Sd and Sb are supplied to the scan driver 200, the data driver 300, and the light source controller 800, respectively, and the gray scale data R, G, and B DATA are supplied to the gray voltage generator 400.

The gray voltage generator 400 generates a gray voltage having a magnitude corresponding to gray data and supplies it to the data driver 300. The data driver 300 applies the gray voltage output by the gray voltage generator 400 to the corresponding data line. The reset signal controller 600 removes noise included in the input reset signal and inputs the noise to the data driver 300.

The light emitting diodes 700a, 700b, and 700c respectively output light corresponding to R, G, and B to the LCD panel, and the light source controller 800 controls the lighting timing of the light emitting diodes 700a, 700b, and 700c. In this case, according to an exemplary embodiment of the present invention, the timing controller 500 may be configured to supply the grayscale data from the data driver 300 to the data line and to turn on the R, G, and B light emitting diodes by the light source controller 800. It can be synchronized by the control signal provided by.

On the other hand, the reset signal controller 600 according to an embodiment of the present invention may be configured as an analog or digital circuit.

FIG. 4 shows a reset signal controller constructed of an analog circuit as the reset signal controller according to the first embodiment of the present invention.

As shown in FIG. 4, the reset signal controller 600 according to the first embodiment of the present invention includes a resistor R and a capacitor C connected in series. An input reset signal is input to one end of the resistor R, and a signal output from the contact point of the resistor R and the capacitor C is input to the data driver 300. At this time, since the resistor R and the capacitor C operate as low pass filters, the high frequency signal included in the reset signal is removed and then input to the data driver 300.

FIG. 5 illustrates a reset signal controller configured of a digital circuit as a reset signal controller according to a second embodiment of the present invention.

As shown in FIG. 5, the reset signal controller 600 according to the second embodiment of the present invention is configured with a digital counter circuit. The digital counter circuit is set to count the input pulse signal and regard the input signal as a reset signal only when the pulse signal is continuously input for a predetermined clock pulse. Therefore, a signal input for a period shorter than a predetermined clock pulse is regarded as a noise signal, not a reset signal, and is not output to the data driver 300, and a signal continuously input for a predetermined clock pulse period is determined as a reset signal. To the data driver 300. Therefore, no noise signal is input to the data driver 300, only a reset signal is input.

Although the above has been described with reference to embodiments of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

As described above, according to the present invention, by effectively removing the noise included in the reset signal input to the data driver, the color displayed on the panel is fixed to one of the R, G, and B colors due to the noise. You can prevent it.

Claims (4)

A matrix form having a plurality of scan lines for transmitting a scan signal, a plurality of data lines insulated from and intersecting the scan lines, a switching element formed in an area surrounded by the scan lines and data lines, and connected to the scan lines and data lines, respectively. A liquid crystal display panel including a plurality of pixels arranged in a line; A gate driver for sequentially supplying scan signals to the scan lines; A gray voltage generator which generates a gray voltage corresponding to gray data; A data driver for supplying a gray voltage and a reset voltage output from the gray voltage generator and the reset voltage generator to a corresponding data line; A reset signal controller which removes noise of a reset signal input from the outside and outputs the noise to the data driver; A light source sequentially outputting red, green, and blue light to one pixel; And It includes a light source controller for controlling the lighting time of the light source, The reset signal controller, And a counter circuit for counting the number of pulses of an input signal, and outputting the input signal to the data driver when the pulse signal is input for a predetermined clock pulse. The method of claim 1, The reset signal controller, And a signal input for a period shorter than the predetermined clock pulse is determined as a noise signal and is not output to the data driver. delete The method of claim 1, The reset signal controller, A resistor connected between the reset signal input terminal and the data driver, and a capacitor connected between the resistor and the contact of the data driver and ground; And a signal output from the contact point of the resistor and the capacitor are input to the data driver.

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