JPH0713520A - Driving method for ferroelectric liquid crystal device - Google Patents

Abstract

PURPOSE:To shorten scanning time in order to enable high-speed writing and to suppress flickering of display without deviation in electric charges over the entire part of the waveforms of one frame so as to assure stable operation by impressing at least one pulse to compensate the deviation of the electric charges generated in a selection period, in the non-selection period just before the selection period. CONSTITUTION:While -V1 is impressed in the first period t1 of the selection period which is the timing existing at the top in one frame Tf and V2 in the second period t2 to each of common electrodes C1, C2..., a voltage value Vr is impressed by disposing a reset period tr in the position just before the selection pulse of the next frame. This impression is executed by disposing the reset period tr at the final of the non-selection period just before the selection period ts and impressing the pulse voltage Vr of the polarity reverse from the polarity of the deviation in the electric charges generated in the selection period. The generation of the deviation in the electric charges within one time of the writing time is thus obviated.

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 writing method in which one stable state is selected in the first field and the other stable state is selected in the second field, after applying a pulse for resetting the display state to one state within the selected time, One-frame reset writing method in which a pulse of a threshold voltage or less is applied to hold the state or a pulse of a threshold voltage or more is applied to enter the other state, and four or more pulses are applied during the selection period There was a 4-pulse method for resetting and writing, and so on.

[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.

Further, the one-frame reset writing method described above has a drawback that it is not preferable because the driving waveform causes a bias in charge. Furthermore, in the above-mentioned four-pulse method, four or more pulses are applied within the selection period in order to eliminate this electric bias, and the problems of display flicker and asymmetry of threshold characteristics can be alleviated. However, since four or more pulses are still required, the time required for writing becomes long, which is not suitable for high speed writing.

The present invention has been made in view of the above circumstances, and an object of the present invention is to shorten the scanning time to enable high-speed writing, and to check the charge distribution in the entire waveform of one frame. Another object of the present invention is to provide a driving method of a ferroelectric liquid crystal device which suppresses display flicker and operates stably.

[0006]

That is, according to the present invention, a signal for resetting the ferroelectric liquid crystal to one stable state and a write signal subsequent to this signal are applied during the selection period of the scanning signal voltage. The compensation pulse is applied during the non-selection period immediately before the selection waveform is applied in order to compensate for the bias of the electric charge generated in the. Thus, there is no bias of electric charge, flicker of display is suppressed, and stable display driving can be performed.

[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, with respect to each of the common electrodes C1, C2, ..., −V1 in the first period t1 of the selection period ts which is the timing located at the beginning in one frame Tf, and V2 (V1> V2 in the second period t2). > 0) while applying the reset period tr at the final timing in one frame Tf, that is, immediately before the selection pulse of the next frame,
A voltage value Vr (V2>Vr> 0) is applied.

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

FIG. 3 shows each pixel section a2 when a common signal and a segment signal having the waveforms shown in FIG. 2 are given.
It shows a composite waveform at b2 and c2. In the first period t1 of the selection period ts, the absolute values of the voltages for resetting the ferroelectric liquid crystal to one state | V1 + Vb1 | and |
V1-Vb2 | is set so as to be larger than the absolute value | Vth1 | of the threshold voltage required to attain this state.

The voltage waveform applied during the subsequent second period t2 is larger than the absolute value Vth2 of the threshold voltage required to switch one stable state of the ferroelectric liquid crystal to the other state. Voltage V2 + Vb2 as described above, or a voltage V2 -Vb2 equal to or lower than a threshold voltage Vth2 for maintaining the one reset state as it is.
It is made possible to select ON or OFF of the pixel by either applying.

At this time, in the selection period ts, the electric charge is either negative or positive. Therefore, in order to compensate for this, resetting is performed at the final timing of the non-selection period immediately before the selection period ts. Allocate period tr,
A pulse voltage Vr having the opposite polarity to the charge bias generated during the selection period is applied. By doing so, it is possible to prevent the bias of charges from being generated within one writing time. Here, it is desirable that the application time of the compensation pulse is as short as possible. Specifically, for example, when the minimum pulse widths of the scanning signal and the data signal are equidistant, it is effective to use the minimum pulse width as the compensation pulse.

As described above, the pulse for compensating the bias of the electric charge is applied immediately before the selection pulse is applied, so that a bias voltage is applied to the entire non-selection period to compensate for the bias of the electric charge. For example, flicker is less likely to occur and is stable, and high-speed write operation can be performed.

[0014]

As described in detail above, according to the present invention, a signal for resetting the ferroelectric liquid crystal to one stable state and a write signal subsequent to this signal are applied during the selection period of the scanning signal voltage. In order to compensate the bias of the electric charge generated in the above, the compensation pulse is applied in the non-selection period immediately before the application of the selected waveform, so that the scanning time can be shortened to enable high-speed writing and the entire waveform of one frame. It is possible to provide a driving method of a ferroelectric liquid crystal device that has no bias of electric charges, suppresses display flicker, and can perform 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 signal for resetting one stable state of a ferroelectric liquid crystal within a scanning signal voltage selection period and a signal for selecting the other stable state or holding the reset state following this signal. A ferroelectric liquid crystal device, characterized in that at least two pulses for selection are applied, and at least one pulse for compensating for the bias of charges generated in the selection period in the non-selection period immediately before the selection period is applied. Driving method.