JPH01298319A - Method of driving liquid crystal - Google Patents

Abstract

PURPOSE:To improve the writing speed of one screen by constituting the selection period of a piece of line electrode of 3 pulses having equal pulse widths. CONSTITUTION:A piece of the line electrode is constituted of the three pulses having the equal pulse widths. The 1st pulse P1 is set at the voltage value to make compensation so as to prevent the impression of a DC component to a liquid crystal; the 2nd pulse P2 is set at the voltage value to make control in such a manner that the liquid crystal is unifired in a stable arranging state, and the 3rd pulse P3 is set at the voltage value at which the attainment of the inversion threshold is controlled by the combination with the signals of row electrodes. Since the selection period of the line signal is constituted of the min. pulses required for operation of the surface stabilized ferroelectric liquid crystal in such a manner, the rewriting speed of one screen is extremely improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for driving a liquid crystal device by matrix driving a surface-stabilized ferroelectric liquid crystal.

[1 Summary of the Invention] The present invention relates to a method for driving a liquid crystal device, and relates to a method for driving a liquid crystal device, in which the selection period of one row electrode is constituted by three pulses having equal pulse widths, thereby improving the J change speed for one screen. This is what I did.

[Conventional technology]

Surface-stabilized ferroelectric liquid crystals (5SFLCs) respond rapidly to pulsed voltages of 1, positive or negative polarity.

2. Assumes two stable array states.

3. Has a threshold value determined by the pulse width (Pw) and voltage value (Vp) of the externally applied voltage, and P that exceeds the threshold value
Under wXVp conditions, of the two stable alignment states,
The arrangement of liquid crystal molecules changes from one arrangement state to the other arrangement state (reversal).

4. Pw does not exceed the threshold after inversion.

Under the Vp condition, the array state of the inverted light is maintained (memory property).

It has the following characteristics. FIG. 3 shows an example of a method of extracting two array states of 5SFLC as optical brightness and darkness using two orthogonal polarizing plates. Further, FIG. 4 shows the state of optical modulation by voltage.

On the other hand, the matrix drive method is a method in which a large number of picture elements arranged in a matrix are driven by a combination of signal voltages applied to row and column electrodes, as shown in FIG. Apply the row electrode selection signal while keeping it common. 2. By matching with the column signal, the arrangement state of liquid crystal molecules at the intersection of the row and column electrodes corresponds to the on/off information contained in the column signal. 3. Continuing, the written information is not changed during the non-selection period.

That is what it is. FIG. 6 shows an example of signal voltages applied to row and column electrodes in the matrix drive method.

[Problem to be solved by the invention] By the way, 5SF is used as a liquid crystal placed at the intersection of row and column electrodes.
When using LC, considering the characteristics of 5SFLC, a. It is difficult to write on and off states at the same time, so a method must be used to write on and off states at different timings.

Furthermore, in order to prevent deterioration of the liquid crystal material, it is necessary to ensure that no DC component is applied to the bj& product (the average value of the applied voltage is Ov).

It is necessary to develop a matrix driving method that satisfies these constraints.

In response to this, various matrix driving methods have been proposed in the past.

(1) Television Society Technical Report (ITEJ Te
chnicalReport, Vol. 10
, Na47, pp13-18.

10'87-15, Feb, 1987) f21
National Technical Report
rt (Vol, 33, N.

1, pp 44-47, Feb, 1987
) However, all of these driving methods are characterized in that the net selection period consists of at least four or more pulses with a pulse width that directly contributes to inversion.

On the other hand, the rewriting time for one screen is (selection time for one row electrode) x (number of row electrodes), so in order to shorten the rewriting time for one screen, the row electrode selection time must be shortened. This is very important.

[Means to solve the problem]

The present invention provides a driving method for a liquid crystal device that drives a surface-stabilized ferroelectric liquid crystal in a matrix manner, in which the selection period of one row electrode is constituted by three pulses having equal pulse widths, and the first pulse P1 is a driving method for driving a surface-stabilized ferroelectric liquid crystal. The second pulse P2 is set to a voltage value that controls the liquid crystals to be aligned in a stable alignment state, and the third pulse P3 is set to a voltage value that compensates so that no DC component is applied to the column electrodes. This is a method of driving a liquid crystal device, characterized in that voltage values are set such that reaching a reversal threshold is controlled by combination.

[For production]

According to this, since the selection period of the row signal is constituted by the minimum pulse required for the operation of the 5SFLC, the rewriting speed of one screen can be greatly improved.

〔Example〕

The present invention is characterized in that the row electrode selection period is composed of three pulses having the same pulse width in matrix driving of the 5SFLC.

This is intended to improve the speed of rewriting one screen.

That is, FIG. 1 collectively shows the combinations of row and column signals according to the present invention.

In this figure, in matrix drive of 5SFLC,
To address the constraint that ON and OFF states must be written at different timings, this invention uses two pulses with the same pulse width and opposite polarity, an initialization pulse (Pg), and a switching pulse during the selection period of the row signal.・Pulse (P3)
is used.

Here, the initialization pulse P2 is necessary to align the liquid crystal into one of two stable alignment states. Therefore, the voltage (VI)z) of the initialization pulse must be set so that, when combined with the column (No. 3), it exceeds the threshold even at the minimum applied voltage. Equivalent to writing OFF).

On the other hand, the switching pulse P, in combination with the column signal, changes the arrangement state of the liquid crystal in each pixel area on the common row electrode from the arrangement state previously written by the initialization pulse to the other state. Necessary to decide whether to change to array state. An inversion occurs when the combination of switch song pulses and column signals causes the voltage applied to the picture element to exceed a threshold, writing off (or on). If the threshold value is not exceeded, the initialization pulse will turn on (or turn off)
The array state will be maintained.

Therefore, the switch song pulse voltage (Vpz) is controlled in combination with the column signal so that it exceeds the threshold when it reaches the maximum voltage, and so that it does not exceed the threshold when it reaches the minimum voltage. Must be set.

Furthermore, in order to prevent a DC component from being applied to the liquid crystal, one pulse (Pl; DC compensation pulse) having the same pulse width as the initialization and switch song pulses was added. Therefore, the selection period of the row signal consists of three pulses with the same pulse width.
It was decided to consist of several pulses.

On the other hand, since the voltage waveform applied to the column electrodes can write any information, it does not depend on the on/off 1n information.
Must be symmetrical. Therefore, when the column signal is inverted, the voltage waveform (A) or (+3>) is used as a combination, and when it is not inverted, the voltage waveform (C) is used as a combination.

The voltage waveform of (D) is not preferable because Vpz must be set high.

Furthermore, during the non-selection period of the row signal, there is a degree of freedom in the voltage waveform as long as care is taken not to apply a DC component to the liquid crystal. (E) for the column signals of (A) and (C). (B
), (C) for column signals (E) or (F)
is possible as a row signal during the non-selection period.

Note that FIG. 2 illustrates the operation in the case of a combination of (F) as the non-selection period of the row signal and (A) and (B) as the column signals.

Therefore, according to the present invention, since the selection period of the row signal is constituted by the minimum pulse necessary for the operation of the 5SFLC, the rewriting speed of one screen can be greatly improved.

In addition, in the present invention, as proposed in the above-mentioned documents, it is also possible to superimpose an alternating current on the row signal during the non-selection period.

Note that the combination shown in Figure 1 can be used as a matrix drive method even when the polarity of each voltage pulse is reversed, since the 5SFLC responds to pulses of either positive or negative polarity. Of course.

〔Effect of the invention〕

According to this invention, since the selection period of the row signal is constituted by the minimum pulse necessary for the operation of the 5SFLC,
It is now possible to increase and improve the rewriting speed of one screen.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams for explaining the present invention, Figures 3 and 4 are diagrams for explaining 5SFLC, and Figures 5 and 6 are diagrams for explaining the conventional technology. It is. Pl, P2. P3 is a pulse.

Claims (1)

[Claims] In a method for driving a liquid crystal device in which a surface-stabilized ferroelectric liquid crystal is driven in a matrix, the selection period of one row electrode is constituted by three pulses having equal pulse widths, and the first pulse is as described above. The voltage value is set to compensate so that no DC component is applied to the liquid crystal, the second pulse is set to a voltage value that controls the liquid crystal to be aligned in a stable alignment state, and the third pulse is a combination with the column electrode signal. 1. A method for driving a liquid crystal device, characterized in that the voltage value is set to a voltage value at which reaching a reversal threshold is controlled by.