KR0123056B1 - Driving method of liquid crystal display elements with switching transistor - Google Patents

Abstract

A method of driving a liquid crystal display having a switching transistor is provided. In a liquid crystal display having a plurality of switching transistors each of which includes m row electrodes, n column electrodes, a gate, a source and a drain, one of the row electrodes being connected to the gate, one of the column electrodes being connected to the source, the liquid crystal display consisting of pixel electrodes connected to the drain to receive scanning pulse through the m row electrodes, scanning pulses having an identical timing are applied to the liquid crystal display by two lines in the odd field of each frame, and scanning pulse is applied to only even line in the even field.

Description

Method of driving a liquid crystal display device having a switching transistor

1 is a view showing a TFT equivalent circuit of a general liquid crystal display panel.

2 is a waveform diagram showing a driving signal of a liquid crystal display panel according to the related art.

3 is a waveform diagram illustrating a scanning signal in an odd field according to an exemplary embodiment of the present invention.

4 is a waveform diagram showing a scanning signal at an even field time according to an embodiment of the present invention.

5 is a view showing a polarity change in the column electrode according to the first embodiment of the present invention.

6 is a view showing a polarity change in the column electrode according to the second embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix liquid crystal display (hereinafter referred to as AM LCD), and more particularly, to a method of driving a liquid crystal display device in which each pixel is controlled by a switching transistor.

Recently, as the personalization of OA devices, the trend toward the portability of small TVs, and in particular in the information age, the demand for light and small components of the display device has been maximized. As a display device, TFT LCD (thin film transistor liquid crystal display) has high image quality and light and small size advantages comparable to CRT (cathod ray tube), and the demand is gradually increasing. have.

In the TFT LCD, pixels are arranged in a matrix form on a glass substrate, and each pixel is connected with a gate wiring, which is an X-axis wiring, and a data wiring, which is a Y-axis wiring, and each pixel is provided with a TFT, which is a switching element. .

In addition, the active matrix driving method using the switching transistor has an advantage of achieving excellent image quality in contrast with the conventional STN multiplex method.

An equivalent circuit of the liquid crystal display panel having the above advantages is shown in FIG. 1. In the drawing, reference numeral 11 denotes a switching transistor (which serves as a device) and is made of amorphous-silicon (a-Si). The reference numeral 14 denotes a capacitor of the liquid crystal layer, the reference numeral 12 denotes a row electrode, and the reference numeral 13 denotes a column electrode. In this case, the row electrode and the column electrode are connected to the gate and the source of the switching transistor, respectively.

Where i, i + 1,... … Indicates a scanning line.

The liquid crystal display panel is composed of a lower substrate on which a switching transistor and a pixel electrode are formed, and an upper substrate on which a color filter and an opposite electrode are formed, and a predetermined driving signal is applied to the liquid crystal injected therebetween to display an image. . At this time, on both substrates, an alignment material such as polyimide, which has been oriented by a rubbing method, is applied to align the liquid crystal.

2 (a) to 2 (d) show driving signals of a liquid crystal display panel according to the prior art, and FIGS. 2 (a) and 2 (b) show primary and secondary row electrodes. A scanning pulse applied to (12) is shown. At this time, the scan pulse has a period of T and a pulse width of H. … It is applied sequentially in the form of the back. The pulse width H is obtained by dividing the period T by the number of effective scanning lines (row electrodes). When the scan pulse is applied, the switching transistor 11 is turned on so that the signal {second (c)} applied from the column electrode 13 is transferred to the pixel electrode 15. On the other hand, during the period in which the scan pulse is not applied, the switching transistor is turned off and no signal is applied to the pixel electrode. FIG. 2 (d) shows the voltage waveform applied to the pixel electrode when the scanning pulse is applied.

However, the following problem occurs when driving a high-resolution screen in which the number of row electrodes and column electrodes is increased by the above method. That is, since the scan pulse period is constant as T, the number of scan lines is increased, so that the H pulse width is decreased and the number of column lines is increased, thereby increasing the main clock. This means that drive ICs and other components must be driven at higher frequencies. However, such a high frequency display device not only acts as a deterrent to low power consumption (battery driving), which is an advantage of LCD, but also causes various noise and waveform distortion.

Next, let's take a look at the problems caused by using NTSC signal and HDTV signal for TV. The signals are divided into an odd line and an even line signal as interlaced signals, and only an odd line is applied to an even field and an even line is applied to an even field. Are combined to form a screen (1 frame). However, when such interlaced scanning is performed on the LCD screen, a problem occurs that flicker occurs.

The reason why such flicker occurs is as follows. The electric field applied between the upper and lower plates is generally driven in alternating directions. When the voltage applied to the upper plate is referred to as Vcom, the signal voltage applied through the TFT of the lower plate is alternately applied based on the Vcom voltage. That is, when the data voltage is inverted around the common voltage, if the voltage between the top and the bottom is not applied symmetrically, the brightness difference occurs when the data voltage is higher than Vcom and lower than Vcom, and the brightness difference is visually detected. And appear as flicker. As a result, image quality may be blurred or flickered on the display screen.

Accordingly, the present invention is to solve the above problems, 1) switching to be able to stably drive a high-resolution screen with an increased number of row electrodes and column electrodes, and 2) to remove flicker generated in the LCD screen during interlaced scanning It is an object of the present invention to provide a method for driving a liquid crystal display device having a transistor.

The active matrix liquid crystal display device driving method according to the present invention for achieving the above object has m multiple row electrodes and n multiple column electrodes, one of the row electrodes having a gate, a source, and a drain. A liquid crystal display device comprising a plurality of switching transistors configured to be connected and one of the column electrodes connected to a source, and a pixel electrode connected to a drain of the switching transistor to supply scan pulses through m row electrodes. In the odd field of each frame (to a plurality of row electrodes), scan pulses having the same timing are applied for two lines, and only even lines are scanned pulses in the even field.

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

3 is a diagram illustrating a scan signal during an odd field according to the first embodiment of the present invention, and FIG. 4 is a diagram showing a scan signal during an even field according to an embodiment of the present invention. to be.

As shown in the figure, the input data signal is an interlaced scanning signal, but the timing of the scan pulse is adjusted so that 2H (frequency is 1/2) at the same timing every two lines during the odd field (FIG. 3). Scan with the pulse width, and during the even field (figure 4) only the even lines (scan 2, scan i + 3 ……, where i = 1,3,5 ……) To be authorized. That is, the pulse width H can be represented by H = 2T / M when the period of the scanning pulse is T and the effective number of scanning lines is M.

In this case, the data voltage is applied to the odd field as the non-inverting voltage, the even field to the inverting voltage in the first frame, the odd field to the inverting voltage in the second frame, and the even field to the non-inverting voltage. Is applied. From the subsequent third frame, the above process is repeated.

5 shows a change in polarity of the liquid crystal voltage appearing in one column when the scan pulse and the voltage are applied as in the first embodiment. In the figure, the + signal represents the non-inverting voltage and the-signal represents the inverting voltage. In the even field of each frame, the line inversion effect can be seen. That is, the effect of line inversion can be obtained by field inversion.

Subsequently, a third embodiment will be described. The difference between the above embodiment and the first embodiment is as follows. That is, the data signal is scanned to have a pulse width of 2H at the same timing for the odd field during the odd field and only the even line for the even field, and the signal of the data voltage is inverted in line units (low electrode units). It is. The change in polarity of the liquid crystal appearing in one column at this time is shown in FIG. In this case, the process is repeated from the third frame. In the figure, the + signal represents the non-inverting voltage and the-signal represents the inverting voltage. In the even field of each frame, the line inversion effect can be seen. That is, the effect of line inversion can be obtained by field inversion. In this case, it can be seen that the scan pulses of the odd line and the even line are both applied to the odd fields of the first and second embodiments, and only the scan pulses of the even line are applied to the even field.

As described above, according to the present invention, by reducing the frequency to 1/2, the scan pulse is applied at the same timing with two lines of 2H pulse width during the odd field, and the even pulse is applied only during the even field during the even field. Field inversion enables the effect of line inversion, which not only reduces flicker, but also prevents noise distortion caused by high frequencies when driving a high resolution screen with an increased number of row electrodes and column electrodes. You can do it.

Claims (5)

a plurality of switching transistors having m plurality of row electrodes and n plurality of column electrodes, one of the row electrodes having a gate, a source, and a drain, the one of the column electrodes being configured to be connected to a source; A liquid crystal display device comprising a pixel electrode connected to a drain of the switching transistor and supplied with a scan pulse through m row electrodes, wherein the scan pulse has the same timing two lines in the odd field of each frame (for a plurality of row electrodes). Is applied, and only an even line is scanned by an even line in the even field. The method of driving an active matrix liquid crystal display device according to claim 1, wherein the width H of the scan pulse is 2T / M when T is a scan pulse period and M is the number of effective scan lines. The method of claim 1, wherein the switching transistor is made of amorphous silicon or a polycrystalline silicon thin film transistor. The method of claim 1, wherein the odd field and the even line scan pulses are applied to the odd field, and the even field scan pulses are applied to the even field. 2. The method of claim 1, wherein the pulse applied to the row electrode is interlaced scanning.