JPH07333580A - Ferroelectric liquid crystal display device and method for driving ferroelectric liquid crystal display element - Google Patents

Abstract

PURPOSE:To provide a ferroelectric liquid crystal display device which is capable of displaying gradation with simple constitution and does not generate sticking of display. CONSTITUTION:The DHF liquid crystals 11 of the TFT liquid crystal display element formed by using the DHF liquid crystals 11 are oriented to a first orientation state in which the liquid crystal molecules are oriented in nearly a first direction, a second orientation state in which the liquid crystal molecules are oriented in nearly a second state and an arbitrary orientation state which is intermediate of the first and second orientation states according to the voltage impressed between pixel electrodes 3 and a counter electrode 7. The optical axis of one polarizing plate of a pair of the polarizing plates 13, 14 is set in the direction which is substantially intermediate of the first direction and the second direction and the optical axis of the other polarizing plate is set to intersect orthogonally with the optical axis of the one polarizing plate. One pulse of which the absolute value of the voltage corresponds to a display gradation and the polarity changes with every frame is impressed to the DHF liquid crystals 11 of the respective pixels over plural frames for one piece of image data in the selection period of the respective pixels.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device using a ferroelectric liquid crystal (including an antiferroelectric liquid crystal) and a driving method thereof, and more particularly to a ferroelectric liquid crystal display device capable of gradation display and The present invention relates to a driving method of a ferroelectric liquid crystal display element.

[0002]

2. Description of the Related Art Ferroelectric liquid crystal display elements have been attracting attention because of their high-speed response and wide viewing angle as compared with TN mode liquid crystal display elements using nematic liquid crystals. As a ferroelectric liquid crystal display element, a ferroelectric liquid crystal display element using a ferroelectric liquid crystal and an antiferroelectric liquid crystal display element using an antiferroelectric liquid crystal are known.

Studies on the practical use of a ferroelectric liquid crystal display device have hitherto been made on a ferroelectric liquid crystal called SS-F liquid crystal. However, the ferroelectric liquid crystal display element using the SS-F liquid crystal cannot change the transmittance stepwise and cannot perform gradation display.

Therefore, a ferroelectric liquid crystal display device capable of displaying gray scales has been studied, and it has been proposed to use a ferroelectric liquid crystal in which the spiral pitch of the chiral smectic phase is smaller than the substrate interval of the display device. Of this type of ferroelectric liquid crystal, one having a memory property is called an SBF liquid crystal, and one having a non-memory property is called a DHF liquid crystal (“LIQUID
CRYSTALS '', 1989, Vol.5, NO.4, pages 1171 to
See page 1177).

Further, in the ferroelectric liquid crystal display element using the DHF liquid crystal, the DHF liquid crystal is enclosed between the substrates in a state having a spiral structure. In the DHF liquid crystal, when a voltage having a sufficiently large absolute value is applied between the electrodes facing each other with the liquid crystal layer interposed therebetween, the director of the liquid crystal molecule is substantially aligned in the first direction according to the polarity of the applied voltage. And the second alignment state in which the director of the liquid crystal molecules is substantially aligned in the second direction, and the absolute value of the applied voltage becomes the first alignment state or the second alignment state. If less than
Due to the distortion of the spiral of the molecular alignment, the average orientation of the directors of the liquid crystal molecules is in the intermediate orientation state between the first and second directions.

In the ferroelectric liquid crystal display element using the SBF liquid crystal, the SBF liquid crystal is enclosed between the substrates in a spiral structure. The SBF liquid crystal has a long axis direction (director) of liquid crystal molecules depending on the polarity of the applied voltage when a voltage whose absolute value is equal to or greater than a predetermined value is applied between electrodes facing each other with a liquid crystal layer interposed therebetween.
Is in a first alignment state in which the liquid crystal molecules are substantially aligned in the first direction or in a second alignment state in which the director of the liquid crystal molecules is substantially aligned in the second direction, and the absolute value of the applied voltage is the first When the voltage is smaller than the voltage that causes the alignment state or the second alignment state, the director is in an intermediate alignment state in which liquid crystal molecules aligned in the first direction and liquid crystal molecules aligned in the second direction are mixed.

Conventionally, in a liquid crystal display device using DHF liquid crystal or SBF liquid crystal, the optical axis of one polarizing plate is set parallel to the first or second direction, and the optical axis of the other polarizing plate is one. It is arranged so as to be orthogonal to the optical axis of the polarizing plate.

However, in the ferroelectric liquid crystal display device having such a structure, even if a voltage corresponding to the gradation to be displayed is applied to the liquid crystal, the applied voltage and the pixel transmittance do not correspond, and the level is practical. Gradation display cannot be realized. this is,
The optical characteristics (relationship between applied voltage and transmittance) of these liquid crystal display elements have large hysteresis, and even if a voltage corresponding to the display gradation is applied to the liquid crystal, the display gradation is affected by the voltage applied before that. Is not uniquely determined.

In order to control the display gradation by reducing the influence of this hysteresis, a voltage for temporarily aligning the liquid crystal molecules in the first or second direction is applied during the selection period of each pixel, and then the display gradation is changed. A method of driving a liquid crystal display element by applying a corresponding voltage has also been proposed. However, such a driving method has a problem that the driving circuit becomes complicated and the selection period of each pixel becomes long.

On the other hand, the antiferroelectric liquid crystal display element displays an image by utilizing the stability of the alignment state of the antiferroelectric liquid crystal. That is, the antiferroelectric liquid crystal has three stable states in the orientation of the liquid crystal molecules, and when a voltage equal to or higher than the first threshold value is applied to the liquid crystal, the liquid crystal molecules become first in accordance with the polarity of the applied voltage. A voltage having an absolute value lower than the first threshold value and the second threshold value and oriented in a first ferroelectric phase arranged in one direction or a second ferroelectric phase arranged in a second direction. When is applied, the average alignment direction of the liquid crystal molecules is oriented in the antiferroelectric phase in a direction substantially parallel to the normal of the smectic phase layer. By setting the directions of the transmission axes of the pair of polarizing plates arranged on both sides of the liquid crystal display element with reference to the optical axis of the antiferroelectric phase, it is possible to control the light transmittance and display an image.

The antiferroelectric liquid crystal has a first or second ferroelectric phase or an antiferroelectric phase in each range with the first and second threshold values as boundaries even if the applied voltage changes. It has a memory property of maintaining the oriented state. The conventional antiferroelectric liquid crystal display device is driven by a simple matrix by utilizing this memory property. The memory property of the alignment state of the antiferroelectric liquid crystal is determined by the voltage at which the liquid crystal undergoes a phase transition from the first or second ferroelectric phase to the antiferroelectric phase and the antiferroelectric phase to the first or second ferroelectric phase. It is determined by the voltage difference between the phase transition voltage and the voltage. The larger this voltage difference, the higher the memory property of the alignment state. Therefore, in the conventional antiferroelectric liquid crystal display element,
As the antiferroelectric liquid crystal, the liquid crystal having a large voltage difference is used. However, in the conventional anti-ferroelectric liquid crystal display device using the anti-ferroelectric liquid crystal having a high memory property, it is almost impossible to control the display gradation, and the gradation display cannot be realized.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a ferroelectric liquid crystal display device having a simple structure and capable of gradation display, and a driving method thereof. And

[0013]

In order to achieve the above object, in a ferroelectric liquid crystal display device according to a first aspect of the present invention, one substrate on which a pixel electrode is formed is opposed to the pixel electrode. The liquid crystal display device having the other substrate on which the counter electrode is formed, the ferroelectric liquid crystal disposed between the two substrates, and the pair of polarizing plates disposed at a position sandwiching the two substrates, A ferroelectric liquid crystal display element that exhibits substantially the same optical change corresponding to a change in absolute value of voltages having different polarities applied between the pixel electrode and the counter electrode, and a signal corresponding to a display image are displayed. And driving means for alternately applying a voltage having an absolute value corresponding to this signal and having a different polarity between the pixel electrode and the counter electrode over a plurality of frames.

According to a second aspect of the present invention, there is provided a method for driving a ferroelectric liquid crystal display device, wherein a pixel electrode and one substrate on which a plurality of thin film transistors connected to the pixel electrode are arranged in a matrix form and the pixel electrode. It is arranged between the other substrate on which the opposing electrode is formed and between these substrates, has a layered structure, and has liquid crystal molecules in a first direction according to a voltage applied between the pixel electrode and the opposing electrode. A substantially aligned first alignment state and a second alignment state in which liquid crystal molecules are aligned in a second direction.
And the average alignment direction of liquid crystal molecules is the first
Of the ferroelectric liquid crystal that is oriented in an intermediate alignment state that is an arbitrary direction between the first direction and the second direction, and is disposed on the one substrate side, and is substantially the same as the normal line of the ferroelectric liquid crystal layer. One polarizing plate having an optical axis set in a direction parallel to, and the other polarizing plate arranged on the other substrate side and having an optical axis orthogonal or parallel to the optical axis of the one polarizing plate, In the method for driving a ferroelectric liquid crystal display element, the voltage is applied to the pixel electrode via the active element for each frame, the voltage having an absolute value corresponding to a display gradation and different polarities. To do.

[0015]

According to the above structure, a ferroelectric liquid crystal display element exhibiting substantially equal optical changes corresponding to changes in absolute values of voltages having different polarities applied between the pixel electrode and the counter electrode, That is, the optical axis of one of the polarizing plates is set to an intermediate direction between the first and second directions, and the optical axis of the other polarizing plate is arranged so as to be orthogonal or parallel to the optical axis of the one polarizing plate. A ferroelectric liquid crystal display element is used. Therefore, substantially the same gradation is displayed for voltages having the same absolute value but different polarities. Since voltages having different polarities and substantially equal absolute values are alternately applied to the liquid crystal over a plurality of frames, one gradation can be displayed by the average brightness of the plurality of frames, and the polarities can be displayed. Even if the optical characteristics for different applied voltages are different, good gradation display can be performed. Further, by applying one pulse of the voltage corresponding to the display gradation in each selection period, it is possible to perform arbitrary gradation display. Further, it is possible to eliminate the bias of the electric charges applied to the liquid crystal and prevent the image sticking phenomenon of the display. Therefore, according to the present invention, gradation display is possible with a simple configuration.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) First, the structure of a ferroelectric liquid crystal display device according to this embodiment will be described. FIG. 1 is a sectional view of a ferroelectric liquid crystal display element, and FIG. 2 is a plan view of a transparent substrate on which pixel electrodes and active elements of the ferroelectric liquid crystal display element are formed. This ferroelectric liquid crystal display element is of an active matrix type and has a pair of transparent substrates (for example, glass substrates).
Have one and two. In FIG. 1, the lower transparent substrate (hereinafter,
On a lower substrate 1, pixel electrodes 3 made of a transparent conductive material such as ITO and thin film transistors (hereinafter, referred to as TFTs) 4 having sources connected to the pixel electrodes 3 are formed in a matrix.

As shown in FIG. 2, gate lines (scanning lines) 5 are arranged between the rows of the pixel electrodes 3, and data lines (gradation signal lines) 6 are arranged between the columns of the pixel electrodes 3. The gate electrode of each FTF 4 is connected to the corresponding gate line 5, and the drain electrode is corresponding to the data line 6
It is connected to the. The gate line 5 is connected to the row (scan driver) driver 21 via the end 5a, and the data line 6 is connected to the column driver (signal driver) 22 via the end 6a. The row driver 21 scans the gate line 5 by applying a gate voltage described later.
On the other hand, the column driver 22 receives the display signal (gradation signal) and applies the data signal corresponding to the display signal to the data line 6.

In FIG. 1, an upper transparent substrate (hereinafter, upper substrate) 2 is provided with a counter electrode 7 facing each pixel electrode 3 of the lower substrate 1 and to which a reference voltage V0 is applied. Alignment films 8 and 9 are provided on the electrode formation surfaces of the lower substrate 1 and the upper substrate 2, respectively. The alignment films 8 and 9 are horizontal alignment films made of an organic polymer compound such as polyimide, and their facing surfaces are subjected to an alignment treatment by rubbing.

The lower substrate 1 and the upper substrate 2 are adhered to each other at their outer peripheral edges via a frame-shaped sealing material 10. A liquid crystal 11 is enclosed in a region surrounded by the substrates 1 and 2 and the sealing material 10. The liquid crystal 11 is a chiral smectic C
It is a ferroelectric liquid crystal in which the spiral pitch of the phase is smaller than the distance between the substrates 1 and 2 and does not have the memory property of the alignment state. The liquid crystal 11 has a spiral pitch of 700 nm to 400 nm or less, which is a wavelength in the visible light band (for example, 400 nm to 300 nm).
nm), the spontaneous polarization is large, and the cone angle is about 2
7 degrees to 45 degrees (desirably 27 degrees to 30 degrees)
Of the ferroelectric liquid crystal composition. In addition, in FIG.
Reference numeral 12 indicates a transparent gap material that regulates the distance between the substrates 1 and 2, and the gap material 12 is arranged in a scattered state in the liquid crystal enclosing region.

The liquid crystal 11 forms a uniform layer structure by directing the normal of the layer structure of the chiral smectic C phase toward the alignment treatment direction of the alignment films 8 and 9. Further, since the spiral pitch is smaller than the substrate interval, the spiral pitch is enclosed between the substrates 1 and 2. When a voltage having a sufficiently large absolute value is applied between the pixel electrode 3 and the counter electrode 7,
The liquid crystal 11 has a first alignment state in which an average director of liquid crystal molecules is aligned in a first direction and a second alignment state in which an average director of liquid crystal molecules is aligned in a second direction, depending on the polarity of an applied voltage. It is set to one of the orientation states. Also,
When a voltage whose absolute value is lower than the voltage for aligning the liquid crystal molecules in the first or second alignment state is applied between the pixel electrode 3 and the counter electrode 7, the spiral of the molecular alignment of the liquid crystal 11 is distorted and the liquid crystal 11
The average director of is in an intermediate alignment state in which it is oriented in a direction between the first direction and the second direction.

A pair of polarizing plates 1 is provided above and below the liquid crystal display element.
3, 14 are arranged. The relationship between the transmission axes of the polarizing plates 13 and 14 and the alignment direction of the liquid crystal molecules of the liquid crystal 11 will be described with reference to FIG. In FIG. 3, reference numerals 11A and 11B indicate
Reference numeral 13 indicates the alignment direction of liquid crystal molecules (average director direction) in the first and second alignment states of the liquid crystal 11.
A and 14A indicate the directions of the transmission axes of the lower polarizing plate 13 and the upper polarizing plate 14 in FIG.

When a voltage having one polarity and a sufficiently large absolute value is applied to the liquid crystal 11, the liquid crystal 11 is in the first alignment state, and the average director of the liquid crystal molecules is the first alignment direction indicated by the chain line. Oriented to 11A. When a voltage having the other polarity and a sufficiently large absolute value is applied to the liquid crystal 11, the liquid crystal 11 is in the second alignment state, and the average director of the liquid crystal molecules is aligned in the second alignment direction 11B indicated by the chain double-dashed line. To do. On the other hand, when the applied voltage is 0, the average director of the liquid crystal molecules is the normal direction of the smectic phase layer of the liquid crystal,
That is, the direction 11C is intermediate between the first and second alignment directions 11A and 11B.

First orientation direction 11A and second orientation direction 1
The deviation angle θ from 1B varies depending on the type of the liquid crystal 11, but is selected to be 25 ° to 45 °, preferably 27 ° to 4 °.
It is 5 °. One of the polarizing plates 13 and 14,
For example, the transmission axis 14A of the upper polarizing plate 14 is set substantially parallel to the normal direction of the smectic phase layer of the liquid crystal 11. The transmission axis 13A of the lower polarizing plate 13 is substantially orthogonal to the transmission axis 14A of the upper polarizing plate 14.

In the ferroelectric liquid crystal display device in which the transmission axes of the polarizing plates 13 and 14 are set as shown in FIG.
Alternatively, the transmittance is highest (display is brightest) in the first or second alignment state in which the liquid crystal molecules are aligned in the second alignment directions 11A and 11B, and the liquid crystal molecules are almost in the normal direction of the smectic phase layer. When oriented in the parallel intermediate direction 11C, the transmittance is the lowest (display is darkest). More specifically, when the director of the liquid crystal molecules is oriented in the first or second alignment direction 11A, 11B, the linearly polarized light that has passed through the incident side polarization plate (polarizer) is non-linearly polarized light by the polarization action of the liquid crystal 11. Becomes Then, of the light that has passed through the liquid crystal layer, a component parallel to the transmission axis of the emission side polarization plate (analyzer) is transmitted through the analyzer and emitted, and the display becomes bright. On the other hand, when the director of the liquid crystal molecules is oriented in the intermediate direction 11C, the linearly polarized light passing through the incident side polarization plate is the liquid crystal 1
It receives almost no polarization effect of 1 and passes through the liquid crystal layer as it is as linearly polarized light. Therefore, most of the light that has passed through the liquid crystal layer is absorbed by the emission side polarization plate, and the display becomes dark.

The average direction of the director of the liquid crystal 11 is
It continuously changes between the alignment directions 11A and 11B according to the polarity of the applied voltage and the voltage value (absolute value). Therefore, the transmittance of this ferroelectric liquid crystal display element can be continuously changed.

Next, the characteristics of the liquid crystal 11 will be described.
When the polarizing plates 13 and 14 are arranged as shown in FIG. 3, the transmittance becomes the lowest when no voltage is applied to the liquid crystal 11 (between the electrodes 3 and 7), and the absolute value of the applied voltage increases as the applied voltage increases. , The transmittance increases. In this embodiment, as shown in FIG. 4A, the cycle is relatively long (0.
When a triangular wave voltage of about 1 Hz) is applied, an optical response characteristic of which continuously and smoothly changes as shown in FIG. 4 (A) is used. Further, it is desirable that the hysteresis of the optical response characteristic is small.

Further, as shown in FIG. 4B, a ferroelectric liquid crystal having a clear threshold value in the optical response characteristic, that is, a characteristic in which the transmittance changes abruptly with a slight change in voltage is not desirable.

Next, a method of driving the ferroelectric liquid crystal display device having the above structure will be described with reference to FIGS. 5 (A) and 5 (B). FIG. 5A shows a waveform of a gate pulse applied to the gate line 5 connected to the TFT 4 of the first row by the row driver 21, and FIG.
3 shows a waveform of a data signal applied to. Note that, for ease of understanding, only the data signals for the pixels in the first row are shown, and the data signals for the other rows are not shown.

5A and 5B, TF represents one frame period, TS represents a selection period of pixels in the first row, and TO represents a non-selection period. Each selection period TS is, for example, about 45 μ
Seconds. In this embodiment, as shown in FIG. 5B, voltage values VD and −V having opposite polarities and the same absolute value are selected according to the display gradation during the selection period of two consecutive frames.
A drive pulse (writing pulse) having D is applied to the data line 6. That is, one display data (display signal)
With respect to, the two drive pulses having the voltage values of + VD and -VD are applied one each in each selection period of the two frames. The polarity and voltage value of the drive pulse are the polarity and voltage of the data signal with respect to the reference voltage V0. The reference voltage V0 is the same as the voltage applied to the counter electrode 7.

In this driving method, the minimum value of the write voltage VD is set to V0, and the maximum value Vmax is set to a value slightly lower than the voltage at which saturation of the transmittance occurs (Vsat in FIG. 4A), and V0 to Vmax are set. The write voltage VD is controlled within the range.

When the ferroelectric liquid crystal display element is driven by using the gate signal and the data signal having the above waveforms,
In the selection period TS of each row, the drive pulse voltage (writing voltage) VD is applied to the pixel electrode 3 via the TFT 4 which is turned on by the gate pulse. When the gate pulse is turned off and the non-selection period TO is entered, the TFT 4 is turned off and a voltage (pixel capacity) corresponding to the write voltage VD is formed by the pixel electrode 3, the counter electrode 7 and the liquid crystal 11 between them. Held in. Therefore, during the non-selection period TO, the transmittance of the pixel has a value corresponding to the holding voltage of the pixel capacitance,
That is, the value is maintained at the value corresponding to the write voltage VD.

In this embodiment, the liquid crystal 11 whose transmittance changes continuously with respect to the change of the applied voltage is used, and furthermore, the optical arrangement shown in FIG. 3 is adopted.
The transmittance with respect to the absolute value of the writing voltage VD is uniquely determined, and the transmittance is controlled by the absolute value of the writing voltage VD, so that clear gradation display can be realized. Further, since voltages of positive and negative opposite polarities for one pixel data are applied by two consecutive frames, even if the optical characteristics for positive and negative voltages are different, it is observed as an average value of these optical changes. It is possible to perform clear gradation display even if there is a difference in optical characteristics with respect to positive / negative and reverse polarity voltages.

Further, in two consecutive frames, voltages having opposite polarities and equal absolute values are applied to each pixel (pixel electrode), so that the DC voltage component is not biasedly applied to the liquid crystal 11. Therefore, the display burn-in phenomenon and the deterioration of the liquid crystal do not occur.

Concrete Example 1 FIG. 6 shows a liquid crystal having an I-SA transition temperature of 62.5 ° C. and an SA-
Using DHF liquid crystal with SC ^* transition temperature of 61.2 ° C and helical pitch of 0.15 μm, the alignment treatment direction and the transmission axis direction of the polarizing plate are set as shown in FIG. The period is set to 60 μS, the drive pulses having the same absolute value as shown in FIG. 5B have different polarities in the two frames, and the write voltage is increased from 0 V to 10 V in 0.5 V units, and then, , Shows the relationship between the applied voltage and the transmittance when it is lowered. As is clear from this graph, according to this driving method, by changing the writing voltage, the transmittance changes continuously, and further, the display gradation is almost uniquely determined according to the writing voltage, and Key display becomes possible.

When liquid crystal 11 (between electrodes 3 and 7) is applied with a voltage of opposite polarity and the same absolute value, the transmissivities thereof are slightly different and are not completely the same. Therefore, in order to prevent flicker of the display image, the frame period T
It is desirable to set F to 1/30 seconds or less.

(Second Embodiment) In the first embodiment, the DHF liquid crystal is used as the ferroelectric liquid crystal 11, but the SBF liquid crystal may be used as the liquid crystal 11. The SBF liquid crystal is a ferroelectric liquid crystal in which the spiral pitch of the chiral smectic phase is smaller than the distance between the substrates 1 and 2 and which has bistability. The SBF liquid crystal has a helical pitch of 700 nm to 400 nm or less, which is a wavelength in the visible light band (for example, 400 nm to 30 nm).
0 nm), the spontaneous polarization is large, and the cone angle is large (for example, about 27 degrees to 45 degrees (desirably 2 degrees).
7 ° to 30 °)) ferroelectric liquid crystal composition.

Since the SBF liquid crystal 11 has a spiral pitch smaller than the distance between the substrates, the SBF liquid crystal 11 has a spiral structure.
It is enclosed between two. When the SBF liquid crystal is used, the relationship between the transmission axes of the polarizing plates 13 and 14 and the alignment direction of the liquid crystal molecules of the SBF liquid crystal 11 is the same as that of the first embodiment. That is, when a voltage having one polarity and a sufficiently large absolute value is applied, the SBF liquid crystal 11 is in the first stable state,
The director of the liquid crystal molecules is aligned in the first alignment direction 11A shown by the solid line in FIG. When a voltage of the other polarity and a value whose absolute value is sufficiently large is applied, the SBF liquid crystal 11 enters the second stable state, and the liquid crystal molecules are aligned in the second alignment direction shown by the broken line in FIG. 3B. First orientation direction 11A
The deviation angle θ between the second alignment direction 11B and the second alignment direction 11B is
Although it varies depending on the type, it is selected from 25 ° to 45 °, preferably from 27 ° to 45 °.

The transmission axis 14A of one of the polarizing plates, for example, the upper polarizing plate 14, has alignment directions 11A and 11A as shown in FIG.
It is substantially parallel to the intermediate direction 11C of B. The transmission axis 13 A of the lower polarizing plate 13 is the transmission axis 1 of the upper polarizing plate 14.
It is almost orthogonal to 4A. Polarizing plate 1 as shown in FIG.
The liquid crystal display element in which the transmission axes 13A and 14A of 3 and 14 are set has the highest transmittance when the liquid crystal molecules are aligned in the first alignment direction 11A or the second alignment direction 11B, as in the first embodiment. When the liquid crystal molecules are oriented in the intermediate direction 11C, the transmittance becomes the lowest.

The other structure of the ferroelectric liquid crystal display device of this embodiment is the same as that of the first embodiment.

Also in the configuration of the second embodiment, in response to a video signal, a write voltage having different polarities and the same absolute value is applied to two consecutive frames to drive the liquid crystal display element. It is possible to display a gradation image corresponding to the absolute value of the drive pulse.

(Third Embodiment) In the first and second embodiments, the DHF liquid crystal and the SBF liquid crystal which are the ferroelectric liquid crystal are used as the liquid crystal 11, but the anti-ferroelectric liquid crystal (hereinafter, AFLC) is used. May be. Since the spiral pitch of AFLC is larger than the distance between the substrates, the substrate 1 in the state where the spiral structure disappears,
It is enclosed between two. When a voltage having one polarity and a certain threshold voltage (ON threshold voltage) or more is applied, the average director of the liquid crystal molecules is in the first direction 11A.
When a voltage having a polarity opposite to that of the ON threshold voltage is applied, the average director is oriented in the second direction 11B indicated by the chain double-dashed line, and the ON threshold is When a voltage equal to or lower than another threshold voltage (OFF threshold voltage) lower than the value voltage is applied, the average director is oriented so as to face the third direction 11C. Also ON
When a voltage between the threshold voltage and the OFF threshold voltage is applied, the average director is between the first direction 11A and the third direction 11C or the second direction 11B and the third direction. It is oriented so as to be between 11C, and is in an optical intermediate state.

The transmission axes of the pair of polarizing plates 13 and 14 are the first
Similar to the embodiment, they are arranged as shown in FIG.

In this embodiment, for example, the following three types of antiferroelectric liquid crystals can be used. (1) The antiferroelectric phase is exhibited only in a very narrow range where the applied voltage is near 0 V, and the characteristic curve of the optical response is steep,
A liquid crystal with almost no flat region in the region showing the antiferroelectric phase. FIG. 7 shows an example of optical response characteristics of this type of antiferroelectric liquid crystal. This optical response characteristic is shown in FIG.
It is obtained by applying the triangular wave voltage of sufficiently low frequency of about 0.1 Hz as shown in FIG. This antiferroelectric liquid crystal has a characteristic that it exhibits an antiferroelectric phase only in a very narrow applied voltage region of about ± 0.5 V, has a steep characteristic curve, and is flat in a region that exhibits an antiferroelectric phase. There is almost no real area. Since this type of antiferroelectric liquid crystal has a wide range of applied voltage exhibiting the antiferroelectric-ferroelectric phase transition precursor phenomenon, it has innumerable intermediate optical states depending on the applied voltage, and its optical response characteristics Since there is no clear threshold value, it is suitable for the driving method of the present invention.

(2) When the applied voltage is 0V, the average long axis of the molecules are not aligned with the normal direction of the layer, and when the applied voltage is 0V, 2
An antiferroelectric liquid crystal in which the average long axis direction of molecules is aligned with the normal direction of the layer at two voltage values, and the transmittance is minimized. FIG. 8 shows an example of the optical response characteristics of this type of antiferroelectric liquid crystal. This optical response characteristic also has a pair of polarizing plates arranged as shown in FIG.
It was obtained by applying a triangular wave voltage having a sufficiently low frequency of about 0.1 Hz. In the edge ferroelectric liquid crystal having this characteristic, the average molecular long axis direction is not aligned with the layer normal direction at the applied voltage of 0 V, and the average molecular long axis direction is at the two layers of the voltage value other than the applied voltage of 0 V. It is aligned in the normal direction and has the minimum transmittance. That is, the voltage region in the dark state is separated into two, and there is no flat portion near the applied voltage of 0V. Since this type of antiferroelectric liquid crystal has a wide range of applied voltage exhibiting the antiferroelectric-ferroelectric phase transition precursor phenomenon, it has innumerable intermediate optical states depending on the applied voltage, and its optical response characteristics Since there is no clear threshold value, it is suitable for the driving method of the present invention.

The first and second antiferroelectric liquid crystals have a large cone angle of 30 ° to 45 ° (preferably 35 ° or more), a spontaneous polarization of about 200 or more, and a phase sequence I. , SmA (Smectic A
Phase), ASmC ^* (anti (anti) smectic C ^* phase)
It is a liquid crystal that undergoes a phase transition with.

(3) Antiferroelectric liquid crystal having a very small hysteresis width of optical response characteristics FIG. 9 shows an example of the optical response characteristics of this type of antiferroelectric liquid crystal. This optical response characteristic is also obtained by arranging a pair of polarizing plates as shown in FIG. 3 and applying a triangular wave voltage having a sufficiently low frequency of about 0.1 Hz to the antiferroelectric liquid crystal.
The antiferroelectric liquid crystal having this characteristic has a very narrow hysteresis width of the optical response characteristic of 0.5 V or less. This type of antiferroelectric liquid crystal is also suitable for the driving method of the present invention.

The other construction of the liquid crystal display element in the third embodiment is the same as that in the first and second embodiments.

Also in the anti-ferroelectric liquid crystal display element having such a structure, by applying a write voltage having different polarities and an absolute value according to a display gradation to two consecutive frames, the first embodiment is applied. Similar to the example, any gradation image can be displayed.

Concrete Example 2 FIG. 10 shows the alignment treatment direction and the transmission axis direction of the polarizing plate.
5B, each selection period is set to 60 μS, the two frames are set to have different polarities as shown in FIG. 5B, the write voltage is increased in units of 0.5 V from 0 V to 10 V, and then, The relationship between the applied voltage and the transmittance when the voltage is lowered is shown. As is clear from this graph, according to this driving method, by changing the write voltage,
The transmittance changes continuously, and the display gradation is uniquely determined according to the writing voltage, which enables gradation display.

(Fourth Embodiment) Next, a drive circuit of a liquid crystal display element for displaying a moving image such as a television image by using the drive method according to the first embodiment will be described. FIG. 11 shows the structure of the liquid crystal display device of this embodiment.

A normal NTSC composite signal supplied from the outside is converted into a digital signal by the A / D converter 51 and supplied to the separation circuit 53. The separation circuit 53 separates the sync signal, the luminance signal, and the hue signal from the supplied digital signal. The separated sync signal is supplied to the clock circuit 65 and the write control circuit 67. Further, the luminance signal and the hue signal are supplied to the demodulation / conversion circuit 55.

The demodulation / conversion circuit 55 generates RGB luminance signals from the luminance signal and the hue signal, and supplies them to the first port of the frame memory 57. Frame memory 5
Reference numeral 7 is composed of a dual port memory having a storage capacity for one screen (one frame), and sequentially stores the RGB luminance signals supplied to the first port. D / A converter 59
Is the R output from the second port of the frame memory 57.
Analog luminance signals corresponding to GB luminance signals + R, + G,
Convert to + B. At this time, the inverted luminance signals -R, -G,-
B is also output. The selector 61 alternately selects the RGB analog luminance signals + R, + G, + B and the inverted luminance signals -R, -G, -B supplied from the D / A converter 59 and supplies them to the liquid crystal display module 63.

The liquid crystal display module 63 has the structure shown in FIGS. However, in this embodiment, the liquid crystal display element displays a color image, and an R, G, or B color filter is arranged on each pixel electrode 3 in FIGS.

The clock circuit 65 includes the A / D converter 51,
A clock signal for controlling the operations of the separation circuit 53 and the demodulation / conversion circuit 55 is generated and supplied to these. The write control circuit 67 supplies a write control signal to the frame memory 57 in response to the synchronization signal from the separation circuit 53. The read control circuit 69 supplies a read control signal to the frame memory 57 to read the data stored in the frame memory 57 to the second port, and supplies a conversion timing signal to the D / A converter 59 to read from the frame memory 57. The converted RGB digital video signal is converted into an RGB analog video signal, a selection control signal is supplied to the selector 61, and a timing control signal is supplied to the row driver and the column driver 22 of the liquid crystal display module 63.

Next, the operation of the display device having the above configuration will be described with reference to FIG.
The timing chart will be described. The NTSC composite signal shown in FIG. 12A is sequentially supplied to the A / D converter 51. The A / D converter 51 follows the conversion timing signal supplied from the clock circuit 65.
The NTSC composite signal is sequentially converted into a digital signal and supplied to the separation circuit 53. The separation circuit 53 follows the timing signal supplied from the clock circuit 65.
The sync signal, the luminance signal, and the hue signal are separated from the digital signal supplied from the A / D converter 51.

The demodulation / conversion circuit 55 generates an R luminance signal, a G luminance signal, and a B luminance signal from the luminance signal and the hue signal,
It is supplied to the frame memory 57. Write control circuit 67
12B, the write enable signal is turned on (active) in the first frame of two consecutive frames according to the synchronization signal supplied from the separation circuit 53, and the writing is performed in the second frame. The enable signal is turned off (inactive).

Therefore, the frame memory 57 sequentially stores the supplied R, G, B luminance signals for each frame in accordance with the write control signal from the write control circuit 67. Therefore, the frame memory 57 is, for example, as shown in FIG.
, The RG of the Nth frame, the N + 2th frame ...
The B luminance signal is sequentially stored.

The frame memory 57 reads the stored RGB luminance signal in accordance with a control signal including the read enable signal shown in FIG. 12C from the read control circuit 69 and supplies it to the D / A converter 59. The D / A converter 59 converts the digital RGB luminance signals read from the frame memory 57 into the corresponding RGB analog luminance signals + R, + G, + B and their inverted luminance signals -R, -G,-.
Convert to B. The selector 61 sequentially selects the RGB analog luminance signals + R, + G, + B and the inverted luminance signals -R, -G, -B supplied from the D / A converter 59 in accordance with the selection switching signal shown in FIG. And supplies it to the liquid crystal display module 63. Therefore, for example, in the Nth frame, the (N + 2) th frame, ...
B analog luminance signals + R, + G, + B are selected and output, and negative RGB inversion luminance signals -R, -G, -B are output in the (N + 1) th frame, the (N + 3) th frame, ....

The column driver 22 sequentially samples the RGB analog luminance signal and its inverted signal supplied from the selector 61, and outputs a corresponding driving pulse to each data line 6.
Apply to. On the other hand, the row driver 21 uses the gate line 5
A gate pulse is sequentially applied to scan the gate line 5. Therefore, the TFT 4 connected to the gate line 5 to which the gate pulse is applied is turned on, and the corresponding pixel electrode 3
A drive pulse is applied to. When the selection period TS of the row is completed and the non-selection period TO is reached, the gate pulse is turned off, the TFT 4 is also turned off, the voltage of the drive pulse is held in the pixel capacitance, and each of the gradations corresponds to the held voltage. Pixels are displayed.

With such a configuration, the RGB luminance signals stored in the frame memory 57 are read twice, converted into analog luminance signals of different polarities, and supplied to the liquid crystal display module 63. Therefore, the first to third
As described in the embodiment, in two consecutive frames, drive pulses having absolute values according to the display gradation and having different polarities are sequentially applied to each pixel (pixel electrode 3), and an arbitrary gradation is obtained. The image is displayed. Although the configuration for displaying the television image of the NTSC system has been illustrated, other configurations may be used and other images may be displayed.

Further, in the fourth embodiment, the frame frequency of the NTSC composite signal and the frame frequency of the liquid crystal display module 63 are the same. However, for example, the frame frequency of the NTSC composite signal is 60 Hz and the frame frequency of the liquid crystal display module 63. May be 30 Hz (1 image is formed in 2 frames, so 15 fields / sec), and the frame frequencies of the two may be different. In this case, for example, the write control circuit 67 writes the RGB brightness data in the frame memory 57 in the unique write cycle, the read control circuit 69 reads the RGB brightness data from the frame memory 57 in the unique read cycle, and supplies the RGB brightness data to the subsequent circuit. You can do it.

In the configuration of FIG. 11, the selector 61 is arranged at the subsequent stage of the D / A converter 59 to select one of the positive and negative polarities of the analog luminance signal output from the D / A converter 59. Under the control of the circuit 69, the D / A converter 59 may be caused to output only the analog luminance signal having the necessary polarity at that time, and the signal may be supplied to the column driver 22.

In FIG. 3, the transmission axis 14A of one polarizing plate 14 is aligned with the intermediate direction 11C between the first direction 11A and the second direction 11B, and the transmission axis 13A of the other polarizing plate 13 is changed to the transmission axis 14A. However, the transmission axis 13A of the other polarizing plate 13 may be parallel to the transmission axis 14A. Further, the absorption axis of one polarizing plate 14 is made to coincide with the intermediate direction 11C between the first direction 11A and the second direction 11B,
The absorption axis of the other polarizing plate 13 may be made orthogonal to the absorption axis of the one polarizing plate 14. In this case, the transmittance of the liquid crystal display element becomes maximum when the applied voltage is 0 (or almost 0), and the transmittance decreases as the absolute value of the applied voltage increases. But again, if the absolute values are equal,
The transmittance becomes equal regardless of the polarity, and the driving method of the present invention can be applied.

[0064]

As described above, according to the present invention, in a liquid crystal display element using a ferroelectric liquid crystal, one pulse of a voltage corresponding to a display gradation is applied during each selection period of a plurality of frames. It is possible to perform arbitrary gradation display only. Further, since the pulses having different polarities are applied to one gray scale in a plurality of frames, the display gray scales are averaged even when the relationship between the applied voltage and the transmissivity is distorted, and an appropriate gray scale is obtained. Is displayed. Further, it is possible to eliminate the deviation of the electric charges applied to the liquid crystal and prevent the image sticking phenomenon of the display. Further, even when the display characteristics are slightly different for voltages having different polarities, an appropriate image can be displayed.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a liquid crystal display element according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a configuration of a lower substrate of the liquid crystal display element shown in FIG.

FIG. 3 is a plan view showing directions of transmission axes of upper and lower polarizing plates and orientation directions of liquid crystal molecules.

FIG. 4 is a graph showing the relationship between applied voltage and transmittance,
(A) shows an example when the DHF liquid crystal used in the first embodiment is used, and (B) shows an example when the DHF liquid crystal which is not desirable to be used in the first embodiment is used.

FIG. 5 is a waveform diagram for explaining a driving method of the ferroelectric liquid crystal display element according to the first embodiment of the present invention,
FIG. 3A is a diagram showing a waveform of a gate signal supplied to a gate line by the method for driving a ferroelectric liquid crystal display element according to the first embodiment of the present invention. FIG. 6B is a diagram showing a waveform of a data signal supplied to a data line by the driving method of the ferroelectric liquid crystal display element according to the first example.

FIG. 6 is a graph showing the relationship between the applied voltage and the transmittance in a specific example of the DHF liquid crystal display device according to the first embodiment of the present invention.

FIG. 7 is a graph showing optical response characteristics for explaining an antiferroelectric liquid crystal usable in the third embodiment of the present invention.

FIG. 8 is a graph showing an optical response characteristic for explaining an antiferroelectric liquid crystal usable in a third embodiment of the present invention.

FIG. 9 is a graph showing optical response characteristics for explaining an antiferroelectric liquid crystal usable in the third embodiment of the present invention.

FIG. 10 is a graph showing the relationship between the applied voltage and the transmittance in a specific example of the antiferroelectric liquid crystal display element according to the third embodiment of the present invention.

FIG. 11 is a block diagram of a drive circuit for a ferroelectric liquid crystal display element according to a fourth embodiment of the present invention.

FIG. 12 is a timing chart for explaining the operation of the circuit shown in FIG.

[Explanation of symbols]

1 ... Transparent substrate, 2 ... Transparent substrate, 3 ... Pixel electrode, 4 ...
TFT, 5 ... Gate line, 6 ... Data line, 7 ...
-Counter electrode, 8 ... Alignment film, 9 ... Alignment film, 10 ... Sealing material, 11 ... Liquid crystal, 12 ... Sealing material, 13 ... Polarizing plate,
14 ... Polarizing plate, 21 ... Row driver, 22 ... Column driver, 41 ... First sample-hold circuit, 42 ... Second sample-hold circuit, 43 ... Inversion Circuit, 44
..Adders, 45 ... Selectors, 46 ... Timing circuits,
47 ... Voltage generating circuit, 51 ... A / D converter, 53 ...
Separation circuit, 55 ... Demodulation / conversion circuit, 57 ... Frame memory, 59 ... D / A converter, 61 ... Selector, 63 ...
・ Liquid crystal display module, 65 ... Clock circuit, 67 ...
Write control circuit, 69 ... Read control circuit

[Procedure amendment]

[Submission date] November 28, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

As shown in FIG. 2, gate lines (scanning lines) 5 are arranged between the rows of the pixel electrodes 3, and data lines (gradation signal lines) 6 are arranged between the columns of the pixel electrodes 3. The gate electrode of each TFT 4 is connected to the corresponding gate line 5, and the drain electrode is corresponding to the data line 6
It is connected to the. The gate line 5 is connected to the row (scan driver) driver 21 via the end 5a, and the data line 6 is connected to the column driver (signal driver) 22 via the end 6a. The row driver 21 scans the gate line 5 by applying a gate voltage described later.
On the other hand, the column driver 22 receives the display signal (gradation signal) and applies the data signal corresponding to the display signal to the data line 6.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

The lower substrate 1 and the upper substrate 2 are adhered to each other at their outer peripheral edges via a frame-shaped sealing material 10. A liquid crystal 11 is enclosed in a region surrounded by the substrates 1 and 2 and the sealing material 10. The liquid crystal 11 is a chiral smectic C
It is a ferroelectric liquid crystal in which the spiral pitch of the phase is smaller than the distance between the substrates 1 and 2 and does not have the memory property of the alignment state. The liquid crystal 11 has a helical pitch of 700 nm to 400 nm or less, which is a wavelength in the visible light band (for example, 400 nm to
300 nm), large spontaneous polarization and a cone angle of about 27 ° to 45 ° (desirably 27 ° to 30 °). 1, reference numeral 12 denotes the conservation catcher <br/>-up material to regulate the spacing between the substrates 1 and 2, a gap material 12 are arranged in a dotted state liquid crystal sealing area.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0044

[Correction method] Change

[Correction content]

(2) When the applied voltage is 0V, the average long axis of the molecules are not aligned with the normal direction of the layer, and when the applied voltage is 0V, 2
An antiferroelectric liquid crystal in which the average long axis direction of molecules is aligned with the normal direction of the layer at two voltage values, and the transmittance is minimized. FIG. 8 shows an example of the optical response characteristics of this type of antiferroelectric liquid crystal. This optical response characteristic also has a pair of polarizing plates arranged as shown in FIG.
It was obtained by applying a triangular wave voltage having a sufficiently low frequency of about 0.1 Hz. An antiferroelectric liquid crystal having this characteristic has an average molecular major axis direction which is not aligned with the layer normal direction at an applied voltage of 0 V, and the average molecular major axis direction is at a voltage of two layers other than the applied voltage of 0 V. It is aligned in the normal direction and has the minimum transmittance. That is, the voltage region in the dark state is separated into two, and there is no flat portion near the applied voltage of 0V. Since this type of antiferroelectric liquid crystal has a wide range of applied voltage exhibiting the antiferroelectric-ferroelectric phase transition precursor phenomenon, it has innumerable intermediate optical states depending on the applied voltage, and its optical response characteristics Since there is no clear threshold value, it is suitable for the driving method of the present invention.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0045

[Correction method] Change

[Correction content]

The first and second antiferroelectric liquid crystals have a large cone angle of 30 ° to 45 ° (preferably 35 ° or more), a large spontaneous polarization of about 200 or more, and a phase sequence of I. , SmA (Smectic A
Phase) and SmCA ^* (chiral smectic CA ^* ) .

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0063

[Correction method] Change

[Correction content]

In FIG. 3, the transmission axis 14A of one polarizing plate 14 is aligned with the intermediate direction 11C between the first direction 11A and the second direction 11B, and the transmission axis 13A of the other polarizing plate 13 is changed to the transmission axis 14A. However, the transmission axis 13A of the other polarizing plate 13 may be parallel to the transmission axis 14A. In this case, when the applied voltage is 0 (or almost 0), the liquid crystal
The transmittance of the display element is maximum, and the absolute value of the applied voltage is large.
The transmittance decreases as the intensity increases. But in this case
However, if the absolute values are the same, the transmittance is the same regardless of the polarity.
The driving method of the present invention can be applied. Also, a direction 11C intermediate between the first direction 11A and the second direction 11B.
The absorption axis of one of the polarizing plates 14 may be aligned with each other, and the absorption axis of the other polarizing plate 13 may be orthogonal to the absorption axis of the one polarizing plate 14.

Claims (10)

[Claims] 1. A substrate on which a pixel electrode is formed, another substrate on which a counter electrode facing the pixel electrode is formed, and a liquid crystal having ferroelectricity disposed between the two substrates, A pair of polarizing plates arranged at positions sandwiching the two substrates, and substantially corresponding to a change in absolute value of voltages having different polarities applied between the pixel electrode and the counter electrode. And a ferroelectric liquid crystal display element exhibiting an optical change equal to, and receiving a signal corresponding to a display image and applying a voltage having an absolute value corresponding to the signal and having a different polarity between the pixel electrode and the counter electrode. A ferroelectric liquid crystal display device, comprising: a driving unit that alternately applies the voltage over a frame. 2. A substrate between one substrate on which a pixel electrode and active elements connected to the pixel electrode are arranged in a matrix, another substrate on which a counter electrode facing the pixel electrode is formed, and between the substrates. A first alignment state in which liquid crystal molecules are arranged in a layered structure and liquid crystal molecules are substantially aligned in a first direction according to a voltage applied between the pixel electrode and the counter electrode; and liquid crystal molecules are in a second direction. Ferroelectricity in which the liquid crystal molecules are aligned in a second alignment state in which they are roughly aligned, and an intermediate alignment state in which liquid crystal molecules are arranged so that their average alignment direction is an arbitrary direction between the first and second alignment states. Liquid crystal, one polarizing plate disposed on the one substrate side and having an optical axis set in a direction substantially parallel to the normal direction of the layer of the ferroelectric liquid crystal, and one polarizing plate on the other substrate side. And the optical axis of the one polarizing plate is orthogonal or parallel to the optical axis of the one polarizing plate. A ferroelectric liquid crystal display device including the other polarizing plate that is set, and a signal that is connected to the active device and that defines a display image, and receives a signal that defines a display image, and an absolute value becomes a display gradation. A ferroelectric liquid crystal display device, comprising: a driving unit that applies a plurality of voltage pulses corresponding to each other and common to a plurality of frames, the polarity of which is inverted every frame to the pixel electrode via the active element. . 3. The driving means applies a voltage corresponding to one signal representing a display gradation of each pixel, the absolute value of which is substantially the same and the polarity of which is different, to the pixel electrode for each frame. The ferroelectric liquid crystal display device according to claim 1 or 2, wherein 4. The driving means corresponds to one signal representing a display gradation of each pixel, and applies a voltage having substantially the same absolute value and different polarities to the pixel electrode over an even number of frames. The ferroelectric liquid crystal display device according to claim 1 or 2, wherein the voltages are applied alternately and sequentially. 5. The active element comprises a thin film transistor whose one end of a current path is connected to a corresponding pixel electrode, and the driving means includes a gate line connected to the gates of the plurality of thin film transistors in a corresponding row, A data line connected to the other end of the current path of the plurality of thin film transistors in the corresponding column; and row driving means for supplying a gate voltage for turning on the thin film transistor to the gate line of the corresponding row in each selection period, The column driving means for applying a voltage having an absolute value corresponding to the display gradation and different polarities to the data line for each frame in each selection period, the ferroelectric device according to claim 2. Liquid crystal display device. 6. The liquid crystal is composed of a liquid crystal material that exhibits optical response characteristics without a clear threshold value when a low frequency triangular voltage is applied between the pixel electrode and the counter electrode. The ferroelectric liquid crystal display device according to any one of claims 1 to 5. 7. The ferroelectric substance according to claim 1, wherein the liquid crystal is composed of any one of DHF liquid crystal, SBF liquid crystal and antiferroelectric liquid crystal. Liquid crystal display device. 8. A substrate on which a plurality of pixel electrodes and thin film transistors connected to the pixel electrodes are arranged in a matrix, another substrate on which a counter electrode facing the pixel electrode is formed, and between these substrates. And has a layered structure and has a first alignment state in which liquid crystal molecules are substantially aligned in a first direction in accordance with a voltage applied between the pixel electrode and a counter electrode, and liquid crystal molecules in a second direction. A second alignment state that is roughly aligned, and a ferroelectric liquid crystal that is aligned in an intermediate alignment state in which the average alignment direction of liquid crystal molecules is an arbitrary direction between the first direction and the second direction. , One of the polarizing plates disposed on the one substrate side and having an optical axis set in a direction substantially parallel to the normal line of the ferroelectric liquid crystal layer, and the one polarizing plate disposed on the other substrate side. The optical axis is set to be orthogonal or parallel to the optical axis of the polarizing plate of In the method for driving a ferroelectric liquid crystal display device including the other polarizing plate, a voltage pulse whose absolute value corresponds to a display gradation and whose polarity is different for each frame for one display gradation is activated. A method for driving a ferroelectric liquid crystal display element, characterized in that the voltage is applied to the pixel electrode via an element. 9. The liquid crystal is composed of a liquid crystal material that exhibits optical response characteristics without a clear threshold value when a low frequency triangular wave voltage is applied between the pixel electrode and the counter electrode. The method for driving a ferroelectric liquid crystal display element according to claim 8. 10. The liquid crystal is a DHF liquid crystal, an SBF liquid crystal,
10. The method for driving a ferroelectric liquid crystal display element according to claim 8 or 9, wherein the method is constituted by any one of antiferroelectric liquid crystals.