JPS648831B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for driving a matrix display panel.

A matrix display panel has drive electrodes arranged in a matrix in both the X and Y directions and is used to display characters, graphs, or images. For example, in the case of a liquid crystal display, display is performed using (N×M) pixels formed by N data lines and M timing lines. At this time, multiplex driving is normally used in which one timing line is selected and data is written and driven from the data line to the pixels in that column, and the period during which data corresponding to one pixel is applied is 1/1/2 of the total. M, which is usually called duty.
Generally, for image or graphic display, 100 timing lines are required.

FIG. 1 shows the drive electrode arrangement of a liquid crystal matrix panel. Data line S1 forming a drive electrode
~Sn, and the timing lines C1 to Cm constitute (n×m) pixels.

FIG. 2 is an example of the driving waveform of the pulse in FIG. 1,
Since the timing lines C1, C2, . . . Cm are scanned, the duty becomes 1/m due to the m timing lines. In the case of image display, gradation is required, and gradation can be achieved by modulating the width of the driving pulse applied to the data line, as shown in FIG. One problem when displaying television images using the raster scan method using such a drive system and panel is that in the case of a normal television signal, the number of scanning lines corresponding to the timing line is 525 in one frame.
books, and odd and even fields respectively.
Since it is constructed by interlacing 262.5 lines at a time, if the image is displayed as it is, a drive with a duty of 1/262.5 will be required. Also, if the resolution is reduced to half, it will be necessary to drive at a duty of 1/131.25. However, with this driving duty, it is currently difficult to obtain sufficient contrast with liquid crystals. Therefore, it is necessary to equivalently lower the driving duty of the liquid crystal by some means and improve the contrast of the display to make the display body easier to view.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method for driving a liquid crystal matrix panel in which the contrast can be improved.

The present invention increases the effective value ratio of ON/OFF applied to the liquid crystal by making the period in which no information is included before and after the vertical erase period in the video signal a state in which no voltage is applied to the liquid crystal. In addition to improving the contrast, one out of every r scanning lines is omitted to the extent that it does not interfere with image display, so that it does not contribute to the display. The contrast is further improved in a state in which no is applied.

To explain the present invention in more detail, we will proceed based on a commonly used NTSC video signal as an example. Figure 3 shows the signal system, where signal A is the vertical synchronization signal VS, and B is the horizontal synchronization signal H.
-S and C are enlarged views, and D represents video signals V and S. Also, Figure 4 shows the horizontal synchronization signal in Figure 3 in an easy-to-understand manner, and the time of one field is 1/60 second, or 16.667 milliseconds, and this includes 262.5 scanning lines. ing.
In the case of a liquid crystal matrix panel, it is possible to recognize images even with half this number of scanning lines, that is, 131, so if, for example, one out of every two scanning lines is thinned out and displayed, the drive is equivalent to 1/131 duty. However,
Actually, the image information is 200-220 out of 262.5
It is sufficient to display a book; rather, the period of 40 to 60 scanning lines, including the remaining vertical blanking period, often does not contain any information signals.
Therefore, for example, if only the 20th to 240th scanning sections in Fig. 4 are displayed, and the period from 1 to 19241 to 262.5 is a rest period, the number of timing lines on the panel will be:
There will be 220 pieces. However, the timing line line selection period remains 1/131.25, but during the rest period, the timing line and data line potentials are kept the same so that the effective value is not applied to the liquid crystal display, so that the same selection period is maintained. However, the effective value ratio of the liquid crystal can be improved, and therefore the contrast can be improved.

Furthermore, even if the scanning lines in this effective image range are appropriately thinned out, the image does not appear to be significantly distorted and appears to be similar to normal images. For example, in Fig. 4, if one out of every r lines is omitted and displayed in the usable scanning range (one out of every three lines in the drawing), the actual usable scanning lines will be multiplied by (r-1)/r and will be equal to this amount. Driving duty can be lowered. Moreover, if the data line and timing line are kept at the same potential during this period, the effective value ratio of ON/OFF is improved and the contrast is improved. That is, according to the present invention, contrast can be greatly improved without lowering the apparent image resolution.

Generally speaking, taking the V-NV voltage averaging method as an example, if the duty is 1/D, the effective value ratio when the liquid crystal is lit and when it is not lit, which is a measure of contrast, is Therefore, in the conventional method, D is 262.5.

On the other hand, the number of scanning lines allocated during the pause period is M
By driving so that the effective value becomes 0 during the pause period and the omission period in which the number of omitted scanning lines is one for every r lines, the effective value ratio is Therefore, the ratio of equation (2) is clearly larger than that of (1). For example, N=10, D=262.5, M=60, r=3
Assuming this, the ratio is 1.111 in the conventional case, but it increases to 1.182 in the driving method of the present invention, and it can be seen that the contrast is improved by 2 to 3 times.

FIG. 5 explains the drive waveform of the present invention, and represents the timing using the horizontal synchronizing signal H-S as a standard. One screen consists of one frame of odd and even fields, and one field is 1/60 second. For simplicity, odd and even fields are considered to be the same signal. Of the 262.5 scanning lines within one field period, m lines are used as the display period, and p lines and q lines near the vertical blanking period are set as rest periods. Furthermore, for m books, one for every r books is omitted from display. Timing line C1~
Cm' is scanned sequentially from C1 within the display period,
End with Cm′. m' is r-1/r times m and r
Each book has a pause period in which nothing is selected.
At this time, amplitude-modulated display data is input to the data lines S1 to Sn. The amplitude of this data line is
In the odd averaging method of Vo-NVo, it becomes 2Vo. What is characteristic about this waveform is that during the idle periods p and q, the data line is V _NSD in odd frames,
In even frames, V _NSE is set to the same potential as the non-selection level of the timing line, and no voltage is applied to the liquid crystal during the rest period, that is, to prevent the effective value from increasing during this period. At the same time, one out of every r data lines is set to the non-selection level of the timing line. Further, the frame signal f _L is a basic signal for AC inversion drive every odd number frame and even number frame.

FIG. 6 is a block diagram of a data line drive circuit for realizing the method shown in FIG. 5, and is composed of voltage selection circuits 10 to 16. Voltage selection circuit 10
-12 are circuits for inverting the polarity according to the frame signal _fL , and voltage selection circuits 13-14 select r- out of p, q, and m out of the entire scanning period.
The idle period is a circuit for making the data line equal to the non-selection level of the timing line by the idle period signal f _D corresponding to the period 1/r times. Further, the voltage selection circuits 15 to 16 follow the display data input Di.
This circuit inputs the drive output to the data line Si, and n blocks 17 are prepared.

FIG. 7 is an example of a scanning circuit for timing lines when m scanning lines are thinned out to r scanning lines. Shift register 70 receives clock pulse _YCL and start pulse
It is constituted by a gate 71 which is started by Ysp and changes the selected state to a non-line selection state by the thinning period signal INH, and a driver 72 which selects the drive potential.
B is the operating waveform of B. This waveform is an example in which one out of three waveforms is omitted, and it can be seen that one selection period between selection inputs W2 and W3 is omitted. Naturally, during this omitted period, the data line is at the same potential as the non-selected voltage level of timing selection, as shown in FIG. 5, so that no effective value is applied to each pixel.

As described above, in the present invention, a liquid crystal is sealed within a pair of substrates, a plurality of electrodes are arranged in a matrix in the row direction and column direction on the substrates, and sampled video image signals are applied to the column electrodes. In a liquid crystal display device in which a scanning signal is supplied to the row electrodes, the voltage level of the video image signal and the voltage level of the scanning signal are substantially equal to each other near the vertical blanking period of the video image signal. Since the display device has a video image signal converting means that is identical in terms of image quality, the duty can be significantly lowered and the contrast can be increased compared to conventional liquid crystal display devices. Furthermore, since a part of the scanning signal within the effective period of the video image signal is omitted, and the voltage level of the scanning signal and the video image signal are made substantially equal during the omitted period, Furthermore, a display device with a lower duty ratio and significantly improved contrast can be realized.

[Brief explanation of the drawing]

Figure 1 shows an example of the configuration of a liquid crystal matrix panel.
FIG. 2 shows the driving waveform, and FIGS. 3 and 4 show examples of signals of the raster scan system, where VS is a vertical synchronizing signal and H-S is a horizontal synchronizing signal. FIG. 5 shows an example of driving waveforms according to the present invention, where p and q are idle periods, m is a display period, C1 to Cm' are timing line signal waveforms, and Si is a data line signal waveform. Also the 6th
This figure is a block diagram for forming the drive waveform of the data line in FIG. 5, and is composed of voltage selection circuits 10 to 16. FIG. 7 shows a timing line scan circuit used in the present invention and its operating waveforms.

Claims (1)

[Claims] 1. A liquid crystal is sealed within a pair of substrates, and a plurality of electrodes are arranged in a matrix in the row and column directions on the substrates, and sampled video image signals are applied to the column electrodes. In a liquid crystal display device in which a scanning signal is supplied to the row electrodes, the voltage level of the video image signal and the voltage level of the scanning signal are substantially equal to each other near the vertical blanking period of the video image signal. 1. A liquid crystal display device comprising video image signal converting means that are identical to each other. 2. A liquid crystal is sealed within a pair of substrates, and a plurality of electrodes are arranged in a matrix in the row and column directions on the substrates, sampled video image signals are supplied to the column electrodes, and the row electrodes are In a liquid crystal display device to which a scanning signal is supplied, the voltage level of the video image signal and the voltage level of the scanning signal are made substantially the same near the vertical blanking period of the video image signal, and A video image signal in which a part of the scanning signal within an effective display period of the video image signal is omitted, and the voltage level of the scanning signal and the voltage level of the video image signal are substantially equal to each other during the omitted period. A liquid crystal display device characterized by being provided with a conversion means.