JPS63195625A - Method for driving liquid crystal display element - Google Patents

Abstract

PURPOSE:To prevent a crosstalk from being generated by utilizing signal voltage-pulse width dependency and applying a positive and a negative voltage alternately so as to cancel the adverse influence of charge accumulation. CONSTITUTION:Ferroelectric liquid crystal is charged and scanning electrode arrays Xn and signal electrode arrays Yn intersecting orthogonally with them are arranged in matrix on both surfaces of the liquid crystal through orienting films. Pulses which are not high enough for state variation are applied to scanning lines which are not scanned currently in the former half of a scanning period, pulses which are high enough for state variation are applied to signal lines corresponding to dark display picture elements, and pulses which do not have enough pulse with for state variation are applied to signal lines corresponding to light display picture elements. In the latter half of the scanning period, on the other hand, pulses which are high enough for state variation are applied to scanning lines which are scanned currently, pulses which are not high enough for state variation are applied to signal lines which are not scanned currently, and pulses which are not high enough for state variation are applied to signal lines corresponding to light display picture elements. Consequently, the possibility of the generation of crosstalk is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] This is a driving method for driving a liquid crystal display element using ferroelectric liquid crystal without fear of crosstalk occurring.

During the first half of the scan period, scan lines that are not currently being scanned are pulsed with insufficient pulses to change state;

A pulse sufficient to change the state is applied to the signal line corresponding to the dark display pixel (opaque state S), and a pulse sufficient to change the state is applied to the signal line corresponding to the dark display pixel (opaque state S).
A pulse with a pulse width insufficient for changing the state is applied to the signal line corresponding to the transparent state, and in the second half of the scanning period,
A pulse sufficient to cause a state change is applied to the scan line that is currently being scanned.

A pulse insufficient to change the state is applied to the scan line that is not currently scanned, while a bright display pixel (transparent S) is applied to the signal line.
) is a method of driving a liquid crystal display element by applying a pulse insufficient for a state change to a signal line corresponding to a state change.

[Industrial application field]

The present invention relates to a method for driving a liquid crystal display element using ferroelectric liquid crystal. In particular, the present invention relates to a driving method capable of driving a liquid crystal display element using ferroelectric liquid crystal without fear of generating crosstalk.

[Conventional technology]

LCD display? T! Conventionally, the twisted nematic type has been mainly used for closing.

This twisted nematic liquid crystal display device is
It consists of a cell filled with twisted nematic liquid crystal, sandwiched between crossed nicols (two polarizing plates whose polarization directions are perpendicular to each other), and when no electric field is applied, the cell is twisted. - Since the long axis of nematic liquid crystal molecules is twisted by 90t' at the interface between the upper and lower substrates, the polarization direction of the incident polarized light changes in the liquid crystal, making this liquid crystal display transparent, but when an electric field is applied, The operating principle is that since the liquid crystal molecules are aligned perpendicularly to the substrate, the polarization direction of the incident polarized light does not change in the liquid crystal, making the liquid crystal display device opaque.

On the other hand, a liquid crystal display device using a ferroelectric liquid crystal with spontaneous polarization has a structure in which both sides of a cell filled with ferroelectric liquid crystal are sandwiched by crossed nicols, and the configuration diagram is shown in Figure IB2. In figure 0, 1 is an analyzer, and 1]
is a polarizer, 2.21 is a transparent electrode, and 3.31
is an alignment film, 4 is a power source, S is a ferroelectric liquid crystal, and 7 is a light source. This is because when the cell gap is narrow1, the helical structure of the chiral smectic C phase disappears due to the strong influence of the alignment control force at the substrate interface.If rubbing is performed, the liquid crystal molecules are uniformly aligned parallel to the substrate. At this time, the direction of spontaneous polarization is based on the principle that two stable states are achieved: one upward and one downward with respect to the substrate.
Corresponding to this bistable state, a transparent state and an opaque state are realized.

When a twisted-nematic type liquid crystal display device uses multiplex driving, as the display capacity increases, sufficient voltage to drive the liquid crystal is applied not only to one selected pixel but also to non-selected pixels and half-selected pixels. This has the disadvantage of causing crosstalk.

On the other hand, ferroelectric liquid crystals have memory properties (the property of retaining the current state even if the voltage application is stopped), voltage application direction (polarity) dependence (the direction of spontaneous polarization is the direction of the applied voltage (positive or negative))
characteristics that change in response to), signal voltage pulse width dependence (
As shown in Figure 3, when the pulse voltage of the applied voltage pulse is fixed, there is a minimum pulse width (threshold pulse width) at which spontaneous polarization reversal occurs, and the pulse width is at this threshold value. properties determined according to the voltage value of the applied voltage pulse)
It has properties such as charge accumulation property (property of charge accumulation at the interface between the liquid crystal and the alignment film).

In addition, because it has steep pickle properties, in principle,
It has the advantage that multiplex drive for large capacity display is possible.

[Problem to be Solved by the Invention 3] Liquid crystal display devices using ferroelectric liquid crystals have the above-mentioned advantages in principle, but since they are still under development, a method for driving them has not been established.

For example, when the density of one pixel becomes high, problems such as crosstalk are inevitable.

An object of the present invention is to provide a method for driving a liquid crystal display element that effectively operates in a liquid crystal display device using ferroelectric liquid crystal without causing crosstalk or the like.

[Means for solving problems]

The means adopted by the present invention to achieve the above object is that a ferroelectric liquid crystal is sealed, and a scanning electrode array (Xi) is arranged on both sides of the scanning electrode array (Xi) with an alignment film interposed therebetween, and a signal electrode is disposed orthogonally thereto. In the method for driving a liquid crystal display element in which columns (Yn) are arranged in a matrix, each electrode constituting the scanning electrode column (X1) is provided with the ferroelectric liquid crystal in a first stable state. A scanning signal having a voltage and a pulse width sufficient to orient the ferroelectric liquid crystal is sequentially applied in a scanning manner, and at a time when the ferroelectric liquid crystal is not scanned, a voltage and a pulse width sufficient to orient the ferroelectric liquid crystal to a first stable state are applied. The ferroelectric liquid crystal is applied to the signal line in which a state change is required in the pixel corresponding to the scanning line that is currently being scanned, among the electrodes constituting the signal electrode array (Yll). A pulse voltage having a voltage and pulse width sufficient to align the liquid crystal to a stable state of 1 is applied, and a state change is sought for the pixel corresponding to the scanning line that is currently being scanned. A method of driving a liquid crystal display element by applying a voltage that does not have a sufficient voltage and pulse width to align the liquid crystal display element to a first stable state,
More specifically, a ferroelectric liquid crystal is sealed, and a scanning electrode array (Xn) and a signal electrode array (Yn) disposed orthogonally thereto are arranged in a matrix on both sides of the liquid crystal via an alignment film. In the method for driving a liquid crystal display element, in the first half of the scanning period, a pulse having a pulse width insufficient for changing the state is applied to the scanning line (Xn) which is not currently scanned, while a pulse having a pulse width insufficient for changing the state is applied to the signal line. , a pulse sufficient for the state change is applied to the signal &1 (Yn) corresponding to the dark display pixel (opaque state), and a pulse sufficient for the state change is applied to the signal line (Yn) corresponding to the bright display pixel (transparent state 8). A pulse with a sufficient pulse width is applied, and in the second half of the scanning period, the scanning line (Xn) that is currently being scanned is
for.

A pulse sufficient for a state change is applied, a pulse having an insufficient pulse width for a state change is applied to the scanning line (Xn) which is not currently scanned, and a bright display pixel (transparent state) is applied to the signal line. This is a method of driving a liquid crystal display element by applying a pulse having a pulse width insufficient for changing the state to the signal line (Y3) corresponding to the signal line (Y3).

[Function] The present invention is characterized by the above-mentioned signal voltage pulse width dependence (as shown in FIG. 3, when the pulse voltage of the applied voltage pulse is fixed, the minimum pulse width (threshold This method skillfully utilizes the property that the threshold pulse width is determined according to the voltage value of the applied voltage pulse. This skillfully utilizes the combination of the above-mentioned dependence on the signal voltage pulse width and the need to apply positive and negative voltages alternately as much as possible in order to cancel out the negative effects of the charge accumulation at the interface. Even under conditions, for non-written iIi elements.

There is no voltage application that would cause a state change, and this works as an effective method for driving a liquid crystal display element.

〔Example〕

Hereinafter, a method for driving a liquid crystal display element according to an embodiment of the present invention will be further explained with reference to the drawings.

1a is a plan view of a liquid crystal display device having 3×3 pixels.
In the figure, x1, x2, x3 are scanning electrodes, and Y
1, Y2, and Y3 are signal electrodes. The intersection of the scanning electrode and the signal electrode is a pixel, the pixel shown with diagonal lines is a dark display pixel (opaque state!fA), and the pixel without diagonal line is a bright display pixel (transparent state). , the voltage of the pulse voltage applied to each electrode is assumed to be constant, and only the pulse width is controlled. Although the reverse control method is also possible, this method is practical and advantageous.

See FIGS. 1b and 1C. FIG. 1b shows each scanning electrode X1. X2, x3 and each signal electrode Y1. A time chart of pulse voltages applied to Y2 and Y3 is shown, and FIG. 1C shows each pixel XI-Yl, Xl-
A time chart of pulse voltages applied to Y2, . . . is shown.

B. Initialization step Apply a pulse voltage having a pulse width sufficient for transparency to all scanning electrodes Xn to make all pixels opaque (1-1
).

A pulse voltage having a pulse width sufficient to bring about a state change is applied to all signal electrodes Yn to make all pixels transparent (1-2).

Scanning process of first scanning line X1 In the first half of the scanning period, scanning lines (X2,
A pulse having a pulse width insufficient for a state change (a pulse with a width of 2 or 3 that is sufficient for a state change) is applied to X3). On the other hand, the signal line has dark display pixels (opaque state).
A pulse sufficient for a state change is applied to the signal line (Yl, Y2) corresponding to (a pulse with a circumferential width sufficient for the state change)
is applied (2-1).

In the second half of the scanning period, a pulse sufficient for a state change is applied to the scan line (xl) that is currently being scanned, and a pulse width that is insufficient for a state change is applied to the scan lines (X2, X3) that are not currently scanned. (a pulse of lunar radiation with a pulse width sufficient for the state change) is applied. On the other hand, a pulse with a pulse width insufficient for a state change (273-width pulse that is sufficient for a state change) is applied to the signal line (Y3) corresponding to the bright display pixel (transparent state). (2-2).

C. Scanning process of second scanning line X2 In the first half of the scanning period, scanning lines (Xl,
A pulse having a pulse width insufficient for a state change (a 273-width pulse that is sufficient for a state change) is applied to X3). On the other hand, a dark display pixel (opaque S
), a pulse sufficient to change the state is applied to the signal line (Y) corresponding to the signal line (Y) corresponding to the bright display pixel (transparent state).
A pulse having a pulse width insufficient for a state change (a pulse with a tail width sufficient for a state change) is applied to Y2, Y3) (3-1).

In the second half of the scanning period, the scanning M (X2) that is currently being scanned
A pulse sufficient for a state change is applied to the scan line (Xi, Apply.

On the other hand, in the signal lines (Y2, Y3) corresponding to the bright display pixels (transparent state), a pulse having a pulse width insufficient for a state change (sufficient for a state change) is 2/3 of the pulse width. (3-2).

2. Scanning process of third scanning line x3 In the first half of the scanning period, scanning lines (XI,
A pulse having a pulse width insufficient for a state change (a 273-width pulse that is sufficient for a state change) is applied to X2). On the other hand, the signal line has a dark display pixel (opaque S)
A pulse sufficient to change the state is applied to the signal line (Y3) corresponding to the bright display pixel (transparent state), and the signal line (Y3) corresponding to the bright display pixel (transparent state) is
Yl, Y2) have a pulse width insufficient for a state change (a pulse with a circumference width sufficient for a state change)
is applied (4-1).

In the second half of the scanning period, pulses sufficient for state change are applied to the scanning lines (x3) that are currently being scanned.

Scan 1 not actually scanned! A pulse having a pulse width insufficient for a state change (a pulse having a pulse width sufficient for a state change) is applied to (Xi, X2).

On the other hand, the signal line (Yl, Y2) corresponding to the bright display pixel (transparent state) receives a pulse with a pulse width insufficient for a state change (a 273-width pulse that is sufficient for a state change). is applied (4-2).

Each scanning electrode X1. X2, x3 and each signal electrode Y1, Y2
．． When a pulse voltage is applied to Y3 in this way, a voltage as shown in FIG. 1C is applied to each image 1iX1-Yl, XI-Y2, etc., and the above 3
A liquid crystal display device having ×3 pixels is driven.

〔Effect of the invention〕

As explained above, in the method for driving a liquid crystal display element according to the present invention, there is no risk of applying a voltage that would cause a state change to a non-written pixel under any conditions, and there is no possibility of crosstalk occurring under any conditions. There is no fear of this occurring, and it can function as an effective method for driving a liquid crystal display device using ferroelectric liquid crystal.

[Brief explanation of the drawing]

FIG. 1a is a plan view of a two-step liquid crystal display device driven in a method for driving a liquid crystal display device according to an embodiment of the present invention. FIG. 1b is a time chart of pulse voltages applied to each scanning line and signal line in the method for driving a liquid crystal display element according to an embodiment of the present invention. FIG. 1C is a time chart of pulse voltages applied to each pixel in a method for driving a liquid crystal display device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a liquid crystal display device using ferroelectric liquid crystal. FIG. 3 is a graph explaining the signal voltage pulse width dependence of ferroelectric liquid crystal. Xn...scanning electrode, Yn...signal electrode, 1.-fist analyzer, 1]...[Co., Ltd.] polarizer, 2.21...fist transparent electrode, 3.31 fist 1] @ alignment film, 41. Power supply. 5...Ferroelectric liquid crystal. 7. Conflict/Light source. Book Q rIll-1#-53IE! Fig. 1a The present invention wA'h, = ice-24 to Nate F Fig. 1b The present invention 轡 winter hts 2 a 4 now, -t Fig. 10

Claims (1)

[Claims] [1] A ferroelectric liquid crystal is sealed, and a scanning electrode array (Xn) and a signal electrode array (Yn) disposed orthogonally thereto are arranged in a matrix on both sides of the ferroelectric liquid crystal via an alignment film. In the method for driving a liquid crystal display element arranged in a shape, each electrode constituting the scanning electrode array (Xn) is supplied with a voltage and a pulse sufficient to orient the ferroelectric liquid crystal in a first stable state. A scanning signal having a width of
Applying a voltage that does not have enough voltage and pulse width to align the signal electrodes to a stable state causes a state change to the pixel corresponding to the currently scanned scanning line among the electrodes constituting the signal electrode array (Yn). A pulse voltage having a voltage and pulse width sufficient to orient the ferroelectric liquid crystal in the first stable state is applied to the signal line where the ferroelectric liquid crystal is required to undergo a state change in the pixel corresponding to the currently scanned scanning line. A method for driving a liquid crystal display element, characterized in that a voltage that does not have enough voltage and pulse width to orient the ferroelectric liquid crystal in a first stable state is applied to a signal line for which the ferroelectric liquid crystal is not required to be in a first stable state. [2] In the first half of the scanning period, there are scanning lines (
A pulse having a pulse width insufficient for a state change is applied to the signal line (Xn), while a pulse sufficient for a state change is applied to the signal line (Yn) corresponding to the dark display pixel (opaque state). A pulse with an insufficient pulse width for the state change is applied to the signal line (Yn) corresponding to the bright display pixel (transparent state), and in the latter half of the scanning period, the signal line (Xn) corresponding to the bright display pixel (transparent state) is ), a pulse sufficient for a state change is applied, a pulse with an insufficient pulse width for a state change is applied to the scanning line (Xn) that is not currently scanned, and a signal line is applied to a bright display pixel. 2. The method of driving a liquid crystal display element according to claim 1, wherein a pulse having a pulse width insufficient for changing the state is applied to the signal line (Y3) corresponding to the transparent state.