JPH0713521A - Driving method for ferroelectric liquid crystal device - Google Patents

Abstract

PURPOSE:To enable high-speed writing, to lessen flickering of display and to make stable operation without generating deviation in electric charges by impressing reset pulses to scanning electrodes in the non-selection period just before a selection period, setting the one orientation state of pixels and correcting the deviation in the electric charges by the reset pulse and selection pulses. CONSTITUTION:While selection pulses changing from -Vo to Vo are impressed to each of common electrodes C1, C2..., at a selection period ts with a top timing of one frame Tf the reset pulses changing from Vo to -Vo are impressed thereto by disposing a reset period trs at the final timing in one frame Tf, i.e., by disposing a reset time trs in the position just before the selection pulses of the next frame. Further, An on or off state is arbitrarily selectrable if bipolar pulses of the phases reverse from each other are impressed to segment electrodes in synchronization with the selection period. The deviation in the electric charges is corrected by matching the reset pulse and the selection pulses.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of driving a ferroelectric liquid crystal device.

[0002]

2. Description of the Related Art For example, chiral smectic C (SmC
^* ) Phase-divided liquid crystal element using ferroelectric liquid crystal
As a time-division driving method for driving value display, conventionally, one writing operation (one frame) is divided into two fields,
A two-field write method in which one stable state is selected in the first field and the other stable state is selected in the second field, resetting and writing one state by applying four or more pulses during the selection period. 4-pulse method, which applies a pulse that resets the display state to one state within the selected time, and then a pulse below the threshold voltage to maintain this state, or a pulse above the threshold voltage to maintain the other state There was a one-frame reset writing method for applying the voltage.

[0003]

However, in the above-mentioned two-field method, since the writing operation is not performed in one of the unselected fields, flicker is conspicuous in the display with many changes, and the two stable states are not noticeable. There was a problem that the threshold voltages of the two must be equal. Further, in the two-field method, the selection time for one scanning line needs to be four times or more the response time of the liquid crystal, which is disadvantageous for high-speed writing.

The four-pulse method can alleviate the problems of display flicker and asymmetry of threshold characteristics, but it also requires a long time for writing and is not suitable for high-speed writing.

Further, the one-frame reset writing method has a drawback that it is not preferable because the drive waveform causes a bias in charge. The present invention has been made in view of the above circumstances, and an object thereof is to provide a ferroelectric liquid crystal capable of high-speed writing, small display flicker, and stable operation without causing a bias of charges. It is to provide a driving method of the device.

[0006]

That is, according to the present invention, a reset pulse is applied to the scan electrode in the non-selection period immediately before the selection period of the scan signal voltage to set one alignment state of the pixel. The correction bias is corrected by the reset pulse and the selection pulse, and the scanning time is shortened to enable high-speed writing, and
It is possible to make the display flickering sufficiently small and to eliminate the bias of the electric charge to perform stable display driving.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 illustrates an electrode configuration of a ferroelectric liquid crystal device having a matrix structure, 11 is a common electrode group, 12 is a segment electrode group, C1, C2, ...
1, S2, ... are individual segment electrodes, a1, a2,
..., b1, b2, ..., c1, c2, ..., d1, d2,
, E1, e2, ... Represent pixel portions.

In the electrode configuration as described above, the drive signal waveforms applied to the common electrodes C1, C2, ... And the segment electrodes S1, S2 ,. That is, to each of the common electrodes C1, C2, ..., A selection pulse changing from −V0 to V0 is applied at the selection timing ts at the leading timing in one frame Tf, while the final timing in one frame Tf, That is, the reset time trs is arranged immediately before the selection pulse of the next frame, and the reset pulse changing from V0 to -V0 is applied.

On the other hand, for example, the segment electrode S1
Is applied to the segment electrode S2, a signal to be repeatedly turned on and off alternately, and a signal to be repeatedly turned off to the segment electrode S3. I shall.

FIG. 3 shows a composite waveform at each electrode when a common signal and a segment signal having the waveforms shown in FIG. 2 are given. As shown in (1) to (3) of the same drawing, in any of the pixel portions a2, b2, c2,
At the reset time trs immediately before the selection time ts, the voltage "-
A reset pulse of (V0 + Vb) "is applied. Here, the voltage V0 + Vb is set to be higher than the threshold voltage Vth1 for selecting the first stable state, and the voltage V0-Vb is set to be lower than this threshold voltage Vth1. In addition, the absolute value of the threshold voltage for obtaining the second stable state | V
If the voltage value of the reset pulse is set to be larger than th2 |, the reset pulse will always reset to this second state. Therefore, if bipolar pulses having mutually opposite phases are applied to the segment electrodes in synchronization with the selection time, it is possible to arbitrarily select the on or off state, and by combining the reset pulse and the selection pulse as shown in the figure. It is possible to correct the charge bias.

[0011]

As described above in detail, according to the present invention, a reset pulse is applied to the scan electrode in the non-selection period immediately before the selection period of the scan signal voltage to set one orientation state of the pixel. Since the charge bias is corrected by the reset pulse and the selection pulse, the scanning time can be shortened to enable high-speed writing, and the display flicker can be sufficiently reduced and the charge bias can be eliminated. It is possible to provide a driving method of a ferroelectric liquid crystal device capable of performing stable display driving.

[Brief description of drawings]

FIG. 1 is a diagram showing an electrode configuration of a ferroelectric liquid crystal device having a matrix structure according to an embodiment of the present invention.

2 is a timing chart showing signal waveforms applied to the common electrode and the segment electrode of FIG.

FIG. 3 is a timing chart showing a composite signal waveform in each pixel portion according to the signal waveform of FIG.

[Explanation of symbols]

11 ... Common electrode group, 12 ... Segment electrode group, C1, C2
... common electrodes, S1, S2 ... are segment electrodes, a1,
a2, b1, b2, c1, c2, d1, d2, e1, e
2 ... Pixel part.

Claims (1)

[Claims] 1. A reset pulse is applied to the scan electrode in a non-selection period immediately before a selection period of a scan signal voltage to set one alignment state of the pixel, and the reset pulse and the selection pulse are electrically charged. A method for driving a ferroelectric liquid crystal device, which comprises correcting the bias.