JPH10301149A - Liquid crystal display element and driving method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display element using antiferroelectric liquid crystal capable of displaying stable gradation. SOLUTION: Between substrates 11, 12, a liquid crystal layer 21 is enclosed, which shown an antiferroelectric phase in a bulk state according to applied voaltages and which shows a mixing phase in which liquid crystal molecules having a tilt to main surfaces of the substrates 11, 12 and those of other phase are mixed in a state of being sandwiched between the substrates 11, 12 and being applied with a voltage across the substrates 11, 12. Since proportions of molecules of each phase forming the mixing phase and orientation state of the mesophase liquid crystal vary according to the impressed voltages, an optical axis of the liquid crystal layer 21 is continuously varied according to the impressed voltages. Therefore, gradation display becomes possible by arranging polarizing plates 23, 24 to sandwich the substrates 11, 12.

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 an antiferroelectric liquid crystal (AFLC), and more particularly to an antiferroelectric liquid crystal display device capable of gradation display and a driving method thereof. .

[0002]

2. Description of the Related Art A ferroelectric liquid crystal display device using a ferroelectric liquid crystal has attracted attention in that a high-speed response and a wide viewing angle can be obtained as compared with a TN mode liquid crystal display device using a nematic liquid crystal. I have. 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. The antiferroelectric liquid crystal display element displays an image by utilizing the stability of the alignment state of the antiferroelectric liquid crystal.

More specifically, an antiferroelectric liquid crystal has three stable states in the alignment of liquid crystal molecules.
Is applied to the liquid crystal, the liquid crystal molecules are arranged in the first direction according to the polarity of the applied voltage.
(2) When a voltage equal to or lower than a second threshold lower than the first threshold is applied to the first ferroelectric phase or the second ferroelectric phase arranged in the second direction, And the second ferroelectric phase is oriented to an antiferroelectric phase that is in a different arrangement state. By setting the direction of the transmission axis of a pair of polarizing plates disposed on both sides of the liquid crystal display element with reference to the optical axis in the antiferroelectric phase, the light transmittance is controlled by the applied voltage to display an image. be able to.

[0004] The antiferroelectric liquid crystal has a first or second ferroelectric phase or an antiferroelectric phase as long as the applied voltage changes within a range between the first and second threshold values. Is maintained. That is, it has a memory property. The conventional antiferroelectric liquid crystal display device is driven by a simple matrix utilizing this memory property.

[0005] The memory properties of antiferroelectric liquid crystals are as follows.
Alternatively, it is determined by a voltage difference between a voltage at which a phase transition from the second ferroelectric phase to the antiferroelectric phase and a voltage at which the phase transition from the antiferroelectric phase to the first or second ferroelectric phase. The larger the voltage difference, the higher the memory property of the alignment state. That is, the larger the hysteresis of the optical characteristic, the higher the memory property.

For this reason, in the conventional anti-ferroelectric liquid crystal display element driven by simple matrix, the liquid crystal having a large voltage difference is used as the anti-ferroelectric liquid crystal.

[0007]

However, a conventional antiferroelectric liquid crystal display device using an antiferroelectric liquid crystal having a high memory property cannot arbitrarily control the light transmittance. That is, the control of the display gradation is almost impossible, and the gradation display cannot be realized.

The present invention has been made in view of the above circumstances, and has as its object to provide an antiferroelectric liquid crystal display device capable of realizing a clear gradation display.

[0009]

In order to achieve the above object, a liquid crystal display device according to a first aspect of the present invention is a liquid crystal display device in which a plurality of pixel electrodes and active elements connected to the pixel electrodes are arranged in a matrix. And the other substrate on which a common electrode opposed to the pixel electrode is formed, and sealed between the substrates to form a chiral smectic CA phase in a bulk state, and the one substrate and the other substrate And a liquid crystal layer having liquid crystal molecules aligned with a tilt with respect to the main surface of the substrate.

The liquid crystal used in this liquid crystal display element is a so-called antiferroelectric liquid crystal which forms a chiral smectic CA phase in a bulk state. However, by enclosing between the substrates, liquid crystal molecules that are aligned with a tilt with respect to the main surface of the substrate appear, and the alignment of the tilted liquid crystal molecules and other liquid crystal molecules depends on the applied electric field. Change. For this reason, the director of the liquid crystal continuously changes according to the applied voltage, and a gray scale display is possible.

The tilt of the liquid crystal molecules with respect to the main surface of the substrate is given, for example, by the interaction at the interface between the liquid crystal and the alignment treatment performed on the substrate surface, that is, the interface effect.

The tilt of the liquid crystal molecules with respect to the main surface of the substrate is given by, for example, an applied electric field.

The alignment state of the liquid crystal when no electric field is applied is affected by the interface effect between the substrate and the liquid crystal.
For this reason, when the alignment control force due to the interface effect is smaller than the intermolecular force for maintaining the antiferroelectric phase of the liquid crystal molecules, the liquid crystal maintains the antiferroelectric phase as in the case of the bulk. . When the alignment regulating force is sufficiently larger than the intermolecular force, the liquid crystal molecules form a ferri phase. When the orientation regulating force is larger than the intermolecular force and smaller than the orientation regulating force for forming the ferri phase, a mixed phase is formed.

For example, the liquid crystal is formed by applying an electric field.
The liquid crystal molecules are composed of a liquid crystal material in which an alignment state of an intermediate phase is formed by moving along a cone drawn by the molecules of the chiral smectic CA phase.

The tilt means a tilt with respect to the main surface of the substrate on a plane substantially perpendicular to the substrate.

In order to achieve the above object, a second aspect of the present invention is provided.
The liquid crystal display element according to the aspect of the present invention, one substrate on which an electrode is formed, the other substrate on which an electrode opposed to the electrode is formed, and a liquid crystal molecule that is sealed between the substrates and forms a smectic phase. Forming an antiferroelectric phase that has a spontaneous polarization and draws and arranges a double helical structure in a bulk state, and between the one substrate and the other substrate, the main surfaces of the one and the other substrates And a liquid crystal layer including liquid crystal molecules having a tilt, connected to the electrode of the one substrate and the electrode of the other substrate, and applying a voltage between the electrodes, thereby causing the liquid crystal molecules in the liquid crystal layer to change. And driving means for controlling the director of the liquid crystal layer to perform gradation display by moving along the cone drawn by the molecules of the chiral smectic CA phase.

According to this structure, the director of the liquid crystal layer is controlled by applying an electric field to move the liquid crystal molecules in the liquid crystal layer along the cone drawn by the molecules of the chiral smectic CA phase. . Therefore,
The director can be continuously changed, and an arbitrary gradation can be displayed.

Further, according to a third aspect of the present invention, there is provided a method of driving a liquid crystal display element, wherein a liquid crystal of an antiferroelectric phase in which liquid crystal molecules are arranged in a bulk state in a double helical structure between a pair of substrates. And by applying an electric field to the liquid crystal, the molecules of the liquid crystal are aligned with a tilt with respect to the main surface of the substrate, and the liquid crystal molecules are drawn by molecules of a chiral smectic CA phase. By moving along the cone, the liquid crystal director is controlled to perform gradation display.

According to this driving method, liquid crystal exhibiting an antiferroelectric phase in a bulk state is sealed between substrates in a state where the liquid crystal has a helical structure, and the liquid crystal molecules move along the cone by applying an electric field. Thus, it is possible to orient the substrate so as to have a tilt with respect to the main surface of the substrate, and to control the tilt to continuously change the director of the liquid crystal layer. Therefore, an arbitrary gradation can be displayed.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An antiferroelectric liquid crystal display device capable of displaying a halftone according to an embodiment of the present invention will be described below with reference to the drawings.

This antiferroelectric liquid crystal display device is of an active matrix type and includes a pair of transparent substrates (for example, glass substrates) 11 and 12. In FIG. 1, a lower substrate (hereinafter, referred to as a lower substrate) 11 includes a transparent pixel electrode 13.
And active elements 14 connected to the pixel electrodes 13 are arranged in a matrix.

The active element 14 is composed of, for example, a thin film transistor (hereinafter, TFT) 14. TFT
Reference numeral 14 denotes a gate electrode formed on the substrate 11, a gate insulating film covering the gate electrode, a semiconductor layer formed on the gate insulating film, a source electrode and a drain electrode formed on the semiconductor layer. , Consisting of

Further, as shown in FIG. 2, a gate line (scan line) is provided between the rows of the pixel electrodes 13 on the lower substrate 11.
15 are wired. Further, a data line (gradation signal line) 16 is wired between columns of the pixel electrodes 13.
The gate electrode of each TFT 14 corresponds to the corresponding gate line 15
And the drain electrode is connected to the corresponding data line 16.
It is connected to the.

The gate line 15 is connected to a row driver (row drive circuit) 31 via an end 15a. The data line 16 is connected to a column driver (column driving circuit) 32 via an end 16a. The row driver 31 scans the gate line 15 by applying a gate signal described later. On the other hand, the column driver 32 receives the display data (gradation data) and applies a data signal corresponding to the display data to the data line 16.

The gate line 15 has a length T except for the end 15a.
It is covered with a gate insulating film (transparent film) of FT14. The data line 16 is formed on the gate insulating film.
The pixel electrode 13 is made of ITO or the like, is formed on a gate insulating film, and is connected at one end to a source electrode of the TFT 14.

In FIG. 1, a transparent common electrode 17 facing each pixel electrode 13 of a lower substrate 11 is formed on an upper substrate (hereinafter, upper substrate) 12. Common electrode 17
Is made of ITO or the like, is made up of one electrode having an area covering the entire display area, and is applied with a reference voltage V0. The pixel electrode 13 and the common electrode 17 control the alignment direction of the liquid crystal molecules by applying a voltage to the liquid crystal layer 21 therebetween, and continuously change the director (average direction of the long axis of the liquid crystal molecules). Thereby, the optical axis of the liquid crystal layer is continuously controlled, thereby controlling the display gradation.

Alignment films 18 and 19 are provided on the electrode forming surfaces of the lower substrate 11 and the upper substrate 12, respectively. The alignment films 18 and 19 are horizontal alignment films, which have been subjected to an alignment process by rubbing in the same direction (a third direction 21C in FIG. 3 described later), so that liquid crystal molecules in the vicinity are aligned in the alignment direction 21C.
It has an alignment regulating force to be arranged in a matrix. Alignment film 1
8 and 19 are made of, for example, an organic polymer compound such as polyimide having a thickness of about 25 to 35 nm, are subjected to an alignment treatment such as rubbing, and have a dispersion force esd of 30 to 50 and a polar force esp of relatively high. A weak one of about 3 to 20 can be used.

The lower substrate 11 and the upper substrate 12 are adhered to each other at the outer peripheral edge thereof via a frame-shaped sealing material 20.
A liquid crystal layer 21 is sealed in a region surrounded by the sealant 20 between the substrates 11 and 12, forming a liquid crystal cell 25. The thickness of the liquid crystal layer 21 is regulated by a transparent spacer 22. The spacers 22 are scattered in the liquid crystal sealing area.

The liquid crystal layer 21 has (1) a chiral smectic CA ^* (SmCA ^* ) phase in a bulk state, and (2) a liquid crystal molecule depending on the polarity of the applied voltage when a sufficiently large voltage is applied. 3, a ferroelectric phase substantially oriented in the first direction 21A or the second direction 21B, and (3) liquid crystal aligned with a tilt with respect to the main surfaces of the substrates 11, 12 when an intermediate voltage is applied. It is composed of a liquid crystal material that forms a mixed phase in which liquid crystal molecules of an intermediate phase containing molecules are mixed. The details of the liquid crystal layer 21 will be described later.

A pair of polarizing plates 2 are provided above and below the liquid crystal display element.
3, 24 are arranged. As shown in FIG. 3, the optical axis (hereinafter referred to as the transmission axis) 23A of the lower polarizing plate 23 is set substantially parallel to the normal direction of the smectic layer, which substantially coincides with the third direction 21C. An optical axis (hereinafter referred to as a transmission axis) 24A of the upper polarizing plate 24 is set substantially perpendicular to a transmission axis 23A of the lower polarizing plate 23.

In the antiferroelectric liquid crystal display device in which the transmission axes of the polarizing plates 23 and 24 are set as shown in FIG. 3, the director of the liquid crystal layer 21 is substantially oriented in the first or second orientation direction 21A or 21B. Occasionally, the transmittance becomes almost maximum (the display is the brightest). Further, when the director of the liquid crystal layer 21 is substantially oriented so as to face the third direction 21C, the transmittance becomes substantially minimum (display is darkest).

That is, the liquid crystal molecules move in the first or second direction 2
1A and 21B, the light in the linearly polarized state that has passed through the transmission axis 23A of the polarizing plate 23 on the incident side is the liquid crystal layer 21.
The polarization state changes due to the birefringent action of
4, the light having a component parallel to the transmission axis 24A of the output side polarizing plate 24 is transmitted, and the display becomes bright. In a state where the director faces the third direction 21C, the polarizing plate 23 on the incident side is used.
Of the liquid crystal layer 21 hardly receives the birefringent action of the liquid crystal layer 21. For this reason, the polarizing plate 2 on the incident side
The linearly polarized light passing through 3 passes through the liquid crystal layer 21 as linearly polarized light, is almost absorbed by the polarizing plate 14 on the emission side, and the display becomes dark. When the liquid crystal layer 21 is in the optically intermediate state,
A gradation corresponding to the direction of the director is obtained.

Next, the alignment films 18 and 19 and the liquid crystal layer 21 will be described in more detail. The liquid crystal layer 21 is, for example, a liquid crystal containing a liquid crystal composition having a skeletal structure represented by Chemical Formula 1 as a main component, and has physical properties as shown in Table 1.

[0034]

Embedded image

[0035]

Table 1 Phase Series Crystal -30 ° C-SmCA ^* -69 ° C-SmA-80 ° C-I
SO Spontaneous polarization 229 nC / cm ² Cone angle θ 32 ゜ Spiral pitch 1.5 microns

Here, the cone angle is the angle between the cone axis drawn by the liquid crystal and the cone, and the intersection angle between the first direction 21A and the second direction 21B is 2θ which is twice the cone angle θ. Equivalent to.

In a bulk state, the liquid crystal material of the liquid crystal layer 21 has a layer structure and a helical structure of a molecular arrangement as shown in FIG. 4, and adjacent liquid crystal molecules are placed on a virtual cone for each layer. Has a double helical structure in which a helix is shifted by approximately 180 °, and the spontaneous polarization is canceled between liquid crystal molecules of adjacent smectic layers.

On the other hand, a liquid crystal having such a structure and physical properties has a barrier against potential energy of an antiferroelectric phase and a ferroelectric phase smaller than that of a normal antiferroelectric liquid crystal. In comparison with the above, the order of the antiferroelectric phase is easily disordered, and the phase transition precursor phenomenon is large.
The phase transition precursor phenomenon is shown in FIG. 3 before the phase transition from the antiferroelectric phase to the ferroelectric phase occurs when the electric field applied to the liquid crystal molecules forming the antiferroelectric phase is gradually increased. It refers to the phenomenon that the transmittance of the liquid crystal element in the optical arrangement increases,
An increase in transmittance means that the liquid crystal molecules behave before phase transition. The behavior of the liquid crystal molecules before the phase transition means that the barrier of the potential energy between the antiferroelectric phase and the ferroelectric phase is small.

The liquid crystal layer 21 has the alignment films 18, 1
9 at the interface (interface effect), that is, the orientation control force due to the orientation treatment. Therefore, due to the relationship between the alignment regulating force and the intermolecular force for maintaining the liquid crystal material in the antiferroelectric phase, the liquid crystal layer 21 has (1) an antiferroelectric phase and (2)
Either ferri phase or (3) mixed phase.

(1) When the intermolecular force of the molecules constituting the liquid crystal layer 21 is strong, and the intermolecular force for maintaining the antiferroelectric molecular alignment is sufficiently stronger than the alignment regulating force. In other words, the liquid crystal layer 21 becomes an antiferroelectric phase as in the bulk state. Specifically, the layer thickness (cell gap) of the liquid crystal layer 21 is substantially equal to one pitch (natural pitch) of the spiral structure of the liquid crystal material (1.5 microns). Further, the liquid crystal molecules receive an alignment regulating force due to the alignment treatment of the alignment films 18 and 19, and the intermolecular force for maintaining the antiferroelectric phase of the liquid crystal molecules of the liquid crystal material is larger than the alignment regulating force due to the alignment treatment. Therefore, the liquid crystal molecules between the substrates 11 and 12
As schematically shown in FIGS. 5 and 6A, an antiferroelectric phase in which the double helical structure has disappeared is formed.

When no voltage is applied to the liquid crystal layer 21, the liquid crystal molecules of the adjacent smectic layer are changed to the first liquid crystal molecules shown in FIG.
Direction 21A and the second direction 21B are alternately oriented, and the director (the average direction of the major axis of the liquid crystal molecules) is normal to the layer (smectic layer) formed by the SmCA ^* phase (or the third direction). 21C). At this time,
Spontaneous polarization Ps of liquid crystal molecules in adjacent smectic layer
Point in opposite directions as shown in FIG. 5, and the spontaneous polarizations of adjacent smectic layers cancel each other. The optical axis of the liquid crystal layer 21 spatially averaged is
Normal direction of smectic layer (or third direction 21C)
Almost matches.

On the other hand, by applying a sufficiently positive voltage (voltage equal to or higher than the saturation voltage) to the liquid crystal layer 21 as shown in FIG.
As shown in (B), the liquid crystal molecules are aligned so as to be substantially aligned in the first direction 21A. In this state, the spontaneous polarization of the liquid crystal molecules is oriented substantially in the same direction, and the liquid crystal exhibits a first ferroelectric phase. On the other hand, by applying a sufficiently negative voltage (voltage equal to or lower than the saturation voltage) to the liquid crystal layer 21,
As shown in (C), the liquid crystal molecules are aligned so as to be substantially aligned in the second direction 21B. In this state, the spontaneous polarization of the liquid crystal molecules is oriented in substantially the same direction, and the liquid crystal exhibits a second ferroelectric phase. In these states, the optical axis of the liquid crystal layer 21 is the first axis.
21A or the second direction 21B.

As described above, the liquid crystal molecules of the liquid crystal layer 21 are:
The alignment control force of the alignment films 18 and 19 weakens the order of the molecular arrangement at the interface with the liquid crystal layer 21, so that the liquid crystal molecules easily move along a virtual cone as shown in FIG.
Also, the barrier between the potential energy of the antiferroelectric phase and the ferroelectric phase of the liquid crystal layer 21 is small, and the order of the molecular arrangement of the antiferroelectric phase is relatively easily disturbed by the action of the interface with the alignment films 18 and 19. Therefore, when an intermediate voltage is applied to the liquid crystal layer 21, a part of the liquid crystal molecules behaves (moves) along a virtual cone of the chiral smectic CA ^* phase as shown in FIG. As shown in (2), the substrate 11 and 12 are tilted (with a tilt) with respect to the main surfaces thereof.

Therefore, when a low voltage is applied,
The liquid crystal molecules of the antiferroelectric phase (the liquid crystal maintaining the antiferroelectric phase order shown in FIG. 5) and the tilt with respect to the substrate surface as shown in FIGS. 8 and 6 (D) and (E). It becomes a state where the held liquid crystal is mixed.

When the applied voltage is further increased, the number of liquid crystal molecules in the antiferroelectric phase (the liquid crystal molecules maintaining the antiferroelectric phase arrangement shown in FIG. 6A) decreases, and the The number of tilted liquid crystal molecules increases, and further, some of the molecules are turned into a ferroelectric phase (liquid crystal molecules having a ferroelectric phase order) by reversing the alignment direction. For this reason, the liquid crystal of the antiferroelectric phase, the liquid crystal of the ferroelectric phase, and the liquid crystal of the intermediate phase oriented with a tilt are mixed.

In this state, as shown in FIG. 9, the liquid crystal of the antiferroelectric phase, the liquid crystal of the ferroelectric phase, and the liquid crystal of the intermediate phase are mixed in the region of the wavelength size of the visible light. Optically, characteristics in which the optical characteristics of these minute regions are averaged are obtained.

In this specification, the state in which the liquid crystal molecules in the intermediate state oriented with the tilt with respect to the main surface of the substrate is present means that the liquid crystal in the other phase and the liquid crystal in the intermediate state with the tilt are mixed. And is called a mixed phase.

In this mixed phase, the ratio of liquid crystal molecules in the antiferroelectric phase, liquid crystal molecules in the ferroelectric phase, and liquid crystal molecules in the intermediate state,
In addition, the average alignment direction of the liquid crystal molecules in the intermediate alignment state (the alignment direction projected on the main surface of the substrate) changes continuously according to the polarity and value of the applied voltage. Therefore, the director of the liquid crystal (the average orientation direction of the liquid crystal molecules) is as shown in FIG.
As shown in (A) to (E), it changes continuously between the first direction 21A and the second direction 21B according to the applied voltage.

(2) The intermolecular force of the liquid crystal molecules of the liquid crystal material constituting the liquid crystal layer 21 is relatively weak, and the alignment regulating force is relatively strong as compared with the intermolecular force for maintaining the antiferroelectric phase. In this case, the liquid crystal molecules of the liquid crystal layer 21 are disturbed from the antiferroelectric state under the influence of the alignment regulating force. Here, if the difference between the energy of the antiferroelectric molecular arrangement of the liquid crystal and the energy of the ferroelectric molecular arrangement is relatively small and the threshold value is clear, the antiferroelectric alignment order is broken. A part of the liquid crystal molecules is sealed between the substrates 11 and 12 by forming a ferri phase in which the liquid crystal molecules in a state where the double helical structure has disappeared in units of minute regions are aligned in the same direction.

In the ferri phase, FIG. 10 is a perspective view, and FIG.
As shown in the projection on the substrate plane, the liquid crystal molecules
And the liquid crystal molecules in an intermediate state do not exist in the direction 21A or the second direction 21B. However, unlike the antiferroelectric phase, the first direction 21A
The liquid crystal molecules arranged in the second direction 21B and the liquid crystal molecules arranged in the second direction 21B are not alternately arranged, and the liquid crystal molecules are arranged in the same direction in units of minute regions (regions smaller than the wavelength size of visible light). For this reason, the liquid crystal layer 21
As shown in (1), a state in which the minute regions in which the liquid crystal molecules are oriented in the first direction and in the first alignment state and the minute regions in which the liquid crystal molecules are oriented in the second direction and in the second alignment state are mixed. Becomes At this time, the spontaneous polarization Ps of the liquid crystal molecules is canceled between adjacent regions as shown in FIG. The spatially averaged optical axis of the liquid crystal layer 21 substantially coincides with the normal direction of the smectic layer (or the third direction 21C).

By applying a sufficiently high positive voltage (voltage equal to or higher than the saturation voltage) to the ferri-phase liquid crystal layer 21 having the molecular arrangement shown in FIG. 13 (A), as shown in FIG. 13 (B). Then, the liquid crystal molecules are aligned in a state of being substantially aligned in the first direction 21A. In this state, the spontaneous polarization of the liquid crystal molecules is oriented substantially in the same direction, and the liquid crystal exhibits a first ferroelectric phase. On the other hand, by applying a sufficiently negative voltage (voltage equal to or lower than the saturation voltage) to the liquid crystal layer 21, the liquid crystal molecules are substantially aligned in the second direction 21B as shown in FIG. Orient. In this state, the spontaneous polarization of the liquid crystal molecules is oriented in substantially the same direction, and the liquid crystal exhibits a second ferroelectric phase. In these states, the optical axis of the liquid crystal layer 21 is in the first direction 21A.
Alternatively, they substantially coincide with the second direction 21B.

As described above, the liquid crystal molecules of the liquid crystal layer 21 are:
The order of the molecular arrangement at the interface with the liquid crystal layer 21 is weakened by the alignment regulating force of the alignment films 18 and 19, and the alignment is easy to move along a virtual cone. Further, the order of the molecular arrangement of the ferri phase is relatively easily disturbed by the action of the interface with the alignment films 18 and 19. Therefore, when an intermediate voltage is applied to the liquid crystal layer 21, a part of the liquid crystal molecules behaves (moves) along a virtual cone of the chiral smectic CA ^* phase as shown in FIG. Molecules of the substrate 1 as shown in FIG.
It becomes a state inclined with respect to the main surfaces 1 and 12 (a state having a tilt).

Therefore, in the state where the voltage is applied, as shown in FIGS. 13D and 13E, adjacent liquid crystal molecules are commonly directed in the first direction 21A or the second direction 21B. The state is a mixed phase in which a minute region showing a ferroelectric phase (or a ferri phase) and liquid crystal molecules having a tilt with respect to the substrate surface are mixed. Further, when the applied voltage is increased, the number of liquid crystal molecules arranged in the first or second direction decreases and the number of liquid crystal molecules arranged in the second or first direction increases according to the polarity. Further, the number of liquid crystal molecules tilted with respect to the substrate surface also increases.

In this mixed phase, a state in which liquid crystal molecules oriented in the first direction 21A, liquid crystal molecules oriented in the second direction 21B, and liquid crystal molecules tilted relative to the substrate surface are mixed. FIG. 14 schematically shows this.

In this mixed phase, the ratio of the liquid crystal molecules in the first and second ferroelectric phases to the liquid crystal molecules in the intermediate state, and the average orientation direction of the liquid crystal molecules in the intermediate state (the orientation projected on the main surface of the substrate) Direction) changes continuously according to the polarity and value of the applied voltage. For this reason, as shown in FIGS. 13A to 13E, the director of the liquid crystal (the average orientation direction of the liquid crystal molecules) changes between the first direction 21A and the second direction 21B according to the applied voltage. Varies continuously between

(3) The intermolecular force of the liquid crystal molecules of the liquid crystal material constituting the liquid crystal layer 21 is relatively weak, and the alignment regulating force is relatively strong as compared with the intermolecular force for maintaining the antiferroelectric phase. In addition, when the difference between the energy of the antiferroelectric molecular arrangement of the liquid crystal molecules and the energy of the ferroelectric molecular arrangement is weak and not clear, the alignment regulation is weaker than the alignment regulating force for generating the ferri phase. A part of the liquid crystal molecules is inverted by the force, and a part of the liquid crystal molecules is in an intermediate state in which the liquid crystal molecules are tilted and aligned with the main surface of the substrate according to the cone drawn by the molecules of the smectic CA phase. Therefore, the liquid crystal molecules are sealed between the substrates in a mixed phase state in which the double helical structure has disappeared.

That is, as shown in FIG. 15, the adjacent liquid crystal molecules are in a small region showing a ferroelectric phase in which the first direction 21A or the second direction 21B is commonly oriented, and the adjacent liquid crystal molecules are in the first direction 21A or the second direction 21B. A mixed phase in which a minute region showing an antiferroelectric phase alternately oriented in the first direction 21A and the second direction 21B and a minute region showing an intermediate phase composed of liquid crystal molecules tilted with respect to the substrate surface are mixed. Becomes The size of these minute regions is smaller than the wavelength of light, and the characteristics of a plurality of regions are optically averaged.

When a voltage is applied, the number of liquid crystal molecules arranged in the first or second direction decreases, and the number of liquid crystal molecules arranged in the second direction 21B or 21A increases, depending on the polarity. I do. Also, the liquid crystal molecules originally having a tilt with respect to the substrate surface are in the second direction 21B or the first direction 21B.
A, and the number of tilted liquid crystal molecules also increases.

In this mixed phase, the ratio of the liquid crystal molecules in the antiferroelectric phase, the liquid crystal molecules in the ferroelectric phase and the liquid crystal molecules in the intermediate state,
The average alignment direction of the liquid crystal molecules in the intermediate state (the alignment direction projected on the main surface of the substrate) continuously changes according to the polarity and value of the applied voltage. Therefore, the director of the liquid crystal (the average orientation direction of the liquid crystal molecules) is shown in FIGS.
(C), the first direction 21 according to the applied voltage.
A continuously changes between A and the second direction 21B.

By applying a sufficiently high voltage (voltage equal to or higher than the saturation voltage) with a positive polarity to the liquid crystal layer 21 of the mixed phase having the molecular arrangement shown in FIG. 16A, as shown in FIG. Then, the liquid crystal molecules are aligned in a state of being substantially aligned in the first direction 21A. In this state, the spontaneous polarization of the liquid crystal molecules is oriented substantially in the same direction, and the liquid crystal exhibits a first ferroelectric phase. On the other hand, by applying a negative voltage and a sufficiently high voltage (voltage equal to or lower than the saturation voltage) to the liquid crystal layer 21, the liquid crystal molecules are substantially aligned in the second direction 21B as shown in FIG. Orient. In this state, the spontaneous polarization of the liquid crystal molecules is oriented in substantially the same direction, and the liquid crystal exhibits a second ferroelectric phase. In these states, the optical axis of the liquid crystal layer 21 is in the first direction 21A.
Alternatively, they substantially coincide with the second direction 21B. Therefore, the director of this liquid crystal (the average orientation direction of liquid crystal molecules) is
As shown in FIGS. 16A to 16E, the voltage continuously changes between the first direction 21A and the second direction 21B according to the applied voltage.

In any of the alignment characteristics (1) to (3), when no voltage is applied between the electrodes, the director of the liquid crystal layer 21 substantially coincides with the third direction 21C. The first direction 21A and the second direction 2 according to
1B. Therefore, the optical characteristics have no flat portion near the applied voltage of 0 V, and the optical characteristics continuously and smoothly change as the absolute value of the applied voltage increases. Further, the transmittance curve is also symmetric with respect to the polarity of the applied voltage. When a voltage whose absolute value is equal to or higher than the saturation voltage is applied, the transmittance is saturated. Furthermore, the hysteresis is very small.

As an example, the relationship between the transmittance and the applied voltage of the liquid crystal display device of this embodiment (Example 1) is shown in FIG.
7 (A). This liquid crystal display element is mainly composed of a liquid crystal having a skeletal structure represented by Chemical Formula 1, and has a liquid crystal composition having physical properties as shown in Table 1. The liquid crystal composition is used as a liquid crystal layer 21 to reduce a cell gap. The liquid crystal layer 21 is sealed at 1.5 μm in a state where the spiral structure drawn by the molecules of the liquid crystal layer 21 is broken. The alignment films 18 and 19 are made of an organic polymer compound such as polyimide having a thickness of about 25 to 35 nm, rubbed, and have a dispersing force esd of 38 to 35 nm.
41, the polar force esp was about 4-10.

As a comparative example, the liquid crystal was sealed while maintaining the spiral structure drawn by the liquid crystal molecules with a cell gap of 5 μm, and the transmittance with respect to the applied voltage of the liquid crystal display element (Comparative Example 1) under the same other conditions was used. Is shown in FIG. 17 (B).

The characteristics shown in FIGS. 17A and 17B are obtained by applying a triangular wave between the electrodes 13 and 17 facing each other. As shown in FIG. 17 (A), the applied voltage-transmittance characteristic of the liquid crystal display element of Example 1 does not have a definite threshold value, the transmittance changes continuously, and the polarity of the applied voltage varies. Symmetrical with very low hysteresis and high contrast. Therefore, it can be understood that the transmittance with respect to the applied voltage is almost uniquely determined, the intermediate gradation can be stably displayed, and the image with high contrast can be stably displayed.

On the other hand, as shown in FIG. 17B, in Comparative Example 1, the interaction between the alignment films 18 and 19 and liquid crystal molecules in the middle of the liquid crystal layer 21 in the thickness direction was weak, and the total thickness of the liquid crystal layer was small. , The applied voltage-transmittance characteristic has a threshold value, has a large hysteresis, and a smooth applied voltage-transmittance characteristic cannot be obtained. Also, the contrast is small.

The fact that the liquid crystal molecules behave as described above according to the applied voltage in the liquid crystal display element of Example 1 is, for example, shown in FIG. 18 and FIG.
The determination can be made from the enlarged views of the display surface shown in (A) to (C).

FIG. 18 shows a conoscopic image of a liquid crystal material in a bulk state. In this figure, melanops (bright spots)
Two are generated in a direction substantially perpendicular to the electric field E.
It is almost symmetrical. This indicates that the liquid crystal molecules are an antiferroelectric phase having a double helical structure.

On the other hand, in the liquid crystal layer 21 in a state in which the liquid crystal material is sealed between the substrates, substantially no black is displayed as shown in FIG. Next, when the voltage is increased, as shown in FIG. 19C, almost the whole becomes white, and it can be seen that the liquid crystal molecules are aligned in the first or second direction. On the other hand, in the intermediate state, as shown in FIG. 19B, the whole becomes darker or brighter depending on the applied voltage. Therefore, it is understood that a mixed phase is generated at an intermediate voltage.

As described above, the liquid crystal layer 21 of this embodiment is
Liquid crystal molecules behave along the cone from the first or second alignment state to the second or first alignment state according to the applied voltage. Therefore, the average alignment direction of the liquid crystal layer 21 changes continuously according to the applied voltage, and the transmittance changes continuously. Therefore, an arbitrary gradation can be displayed.

In FIG. 3, the transmission axis 23A of the lower polarizing plate 23 is arranged substantially parallel to the normal direction of the smectic layer of the liquid crystal layer 21, and the transmission axis 24A of the upper polarizing plate 24 is arranged at right angles to the transmission axis 23A. The transmission axis 23A of the lower polarizing plate 23 and the transmission axis 24A of the upper polarizing plate 24 are determined in various arrangements according to the required electro-optical characteristics of the liquid crystal display device.

For example, when a liquid crystal material having a cone angle θ of about 22.5 ° is used, as shown in FIG. 20A, the transmission axis 23A of the lower polarizing plate 23 is made parallel to the second direction 21B. The transmission axis 24A of the upper polarizing plate 24 may be arranged to be orthogonal to the transmission axis 23A of the lower polarizing plate 23. In this configuration, when a sufficiently large negative voltage (above the threshold value) is applied to the liquid crystal layer 21, the director moves in the second direction 21.
The display is darkest because it faces B. On the other hand, when a sufficiently large voltage (more than the threshold value) of the positive polarity is applied, the display is brightest because the director faces the first direction 21A.

When a liquid crystal material having a cone angle larger than 22.5 ° is used, one of the transmission axis 23A of the lower polarizing plate 23 and the transmission axis 24A of the upper polarizing plate 24 is adjusted by the method of forming the smectic layer of the liquid crystal layer 21. It may be arranged within a range of an angle smaller than the cone angle θ with respect to the line, and the other optical axis may be arranged substantially orthogonal to one optical axis. By using such an optical arrangement, it is possible to drive the liquid crystal without setting the liquid crystal to a ferroelectric phase, to prevent display burn-in and the like, and to suppress flicker.

For example, when using a liquid crystal material having a cone angle of 32 ° as shown in Chemical Formula 1, as shown in FIG. 20B, the transmission axis 23 A of the lower polarizing plate 23 is
1 Normal direction of smectic layer (almost 21C direction)
, For example, in a direction intersecting at 22.5 °.
Further, the transmission axis 24A of the upper polarizing plate 24 is disposed substantially orthogonal to the transmission axis 23A.

The director of the liquid crystal layer formed of the liquid crystal material has an angle range of 22.5 ° with respect to the normal direction of the smectic layer (approximately 21C direction) (range between 23A and 21D). ), The amount of transmitted light is controlled by applying a voltage between the opposing electrodes in a voltage range lower than that in which the liquid crystal layer forms a ferroelectric phase. With this configuration, the display becomes darkest when the director coincides with the direction 23A of the transmission axis, and the direction 21D in which the director is inclined by 45 ° with respect to the direction 23A.
Brightest when facing. Therefore, it is not necessary to set the director in the first direction 21A and the second direction 21B to obtain the maximum gradation from the minimum gradation. That is, the liquid crystal can be driven without setting the ferroelectric phase.

Even when this optical arrangement is adopted, the behavior of molecules and the phase change in the liquid crystal layer 21 with respect to the applied voltage are as described above, and the director of the liquid crystal layer 21 is in the first direction 21A and the second direction. It changes continuously between the direction 21B. Therefore, an arbitrary gradation can be displayed. Further, as compared with the optical arrangement shown in FIG. 3, flicker is reduced and a ferroelectric phase is not formed in the liquid crystal layer 21.
Screen burn-in is suppressed, and the contrast of the display screen and the display quality can be increased.

FIG. 20 (B) shows the above-mentioned liquid crystal cell (a cell in which a liquid crystal composition having a skeletal structure represented by Chemical Formula 1 as a main component and having the physical properties shown in Table 1 enclosed in a cell gap of 1.5 μm). FIG. 21A shows the relationship between the applied voltage and the transmittance of the liquid crystal display element (Example 2) to which the optical arrangement shown in FIG. As a comparative example, FIG. 2 shows the relationship between the transmittance and the applied voltage of a liquid crystal display device (Comparative Example 2) having the same configuration as that of Example 2 except that the cell gap was 5 μm.
This is shown in FIG.

The characteristics shown in FIGS. 21A and 21B are obtained by applying a triangular wave between the electrodes 13 and 17 facing each other. As shown in FIG. 21A, the applied voltage-transmittance characteristic of the liquid crystal display element of Example 2 does not have a definite threshold value, the transmittance changes continuously, and the Symmetrical, with low hysteresis and high contrast. On the other hand, as shown in FIG. 21B, in Comparative Example 2, the applied voltage-transmittance characteristic has a threshold value, the hysteresis is large, and a smooth applied voltage-transmittance characteristic cannot be obtained. Also, the contrast is small.

FIG. 21 also confirms that the liquid crystal display device of this embodiment has excellent gradation display capability.

Next, a method of driving the display element having the above configuration will be described with reference to FIG. FIG. 22A shows the row driver 3
1 shows a gate signal applied to the gate line 15 of an arbitrary row, and FIG. 22B shows a data signal applied to each data line 16 by the column driver 32 in synchronization with a gate pulse. The voltage of the data signal is set to a voltage that does not align the liquid crystal layer 21 in the ferroelectric phase, that is, a voltage corresponding to the transmittance to be displayed between VTmax and VTmin. FIG.
(C) shows a change in transmittance when the data pulse shown in FIG. 22 (B) is applied.

Each gate signal is turned on as a gate pulse during the selection period of the corresponding row. The TFT 14 in the selected row is turned on by the gate pulse. During the period when the TFT 14 is on, that is, during the writing period, the TFT 1
The data signal corresponding to the display gray scale via the pixel electrode 1
3 and the counter electrode 17. When the gate pulse is turned off, the TFT 14 is turned off, and the pixel electrode 13
The voltage applied between the pixel electrode 13 and the counter electrode 17 is held in the pixel capacitance formed by the pixel electrode 13, the counter electrode 17, and the liquid crystal layer 21 therebetween. For this reason, FIG.
As shown in (1), the display gradation corresponding to the hold voltage is held until the next selection period of this row. Therefore, according to this driving method, an arbitrary gradation image can be displayed by controlling the voltage of the data pulse.

FIG. 22A shows a liquid crystal display device of Example 2.
Driving by the driving method shown in FIG.
It increases sequentially from 5 V to +5 V, and further, from +5 V to −5
FIG. 23 shows a change in transmittance when sequentially decreasing to V. From FIG. 23, it can be understood that any gray scale can be stably displayed by using the driving method in FIG.

Next, an example of the configuration of the column driver 32 that enables such driving will be described with reference to FIG. As shown in FIG. 24, the column driver 32 includes a first sample / hold circuit 41 and a second sample / hold circuit 42.
, An A / D (analog / digital) converter 43, a timing circuit 44, and a voltage conversion circuit 45.

The first sample-and-hold circuit 41 samples and outputs a signal component (one image data) VD ′ for a corresponding pixel from an externally supplied analog display signal.
Hold. The second sample-and-hold circuit 42 receives the hold signal VD 'from the first sample-and-hold circuit 41.
Sample hold. The A / D converter 43 is connected to the second
A / D-converts the hold signal of the sample-and-hold circuit 42 to digital gradation data. The timing circuit 44 supplies a timing control signal for instructing the first and second sample and hold circuits 41 and 42 to perform sampling and holding during each selection period TS.

The voltage conversion circuit 45 outputs a voltage corresponding to the digital gradation data output from the A / D converter 43 (a voltage of a driving system necessary for displaying a gradation indicated by the digital gradation data) VD And outputs it to the corresponding data line 16. The voltage conversion circuit 45 separates the power supply system of the signal processing system from the power supply system of the drive system. The output voltage VD of the voltage conversion circuit 45 is applied to the liquid crystal layer 21 during the writing period when the TFT 14 in the corresponding row is on, and is held between the opposing electrodes 13 and 17 while the TFT 14 is off.

The first sample / hold circuit 41, the second sample / hold circuit 42, and the A / D converter 43
And the voltage conversion circuit 45 are arranged for each column of pixels, and the timing circuit 44 is commonly arranged for a plurality of columns.

The configuration of the column driver 32 is not limited to the configuration shown in FIG. For example, a sample and hold circuit included in the A / D converter 43 may be used as the second sample and hold circuit 42. Furthermore, A /
After performing a certain process on the output data of the D converter 43, the processed data may be supplied to the voltage conversion circuit 45 and converted into the voltage of the driving system. Further, after the processed data is once converted into a gradation signal having a voltage of a signal processing system, the voltage conversion circuit 45 may convert the data into a voltage of a driving system. Various timing signals may be supplied from outside the column driver 32.
Further, the image data itself may be constituted by digital data.

The present invention is not limited to the above embodiment,
Various modifications and applications are possible. For example, the antiferroelectric liquid crystal of the present invention is not limited to a liquid crystal having a skeleton structure shown in Chemical Formula 1 as a main component, and any liquid crystal that forms another mixed phase can be used. The same applies to its physical properties. Further, the material, thickness, and the like of the alignment film can be appropriately changed. The combination of the liquid crystal material and the alignment film is arbitrary as long as a mixed phase including liquid crystal molecules aligned with a tilt can be formed in a state where a voltage is applied. The thickness of the liquid crystal layer 21 is also arbitrary as long as the mixed phase can be formed over the entire thickness. Furthermore, even if a region where the mixed phase is not formed partially occurs, it is acceptable as long as it does not substantially affect the display.

In the embodiment, the transmission axis 23A of the polarizing plate 23 and the transmission axis 24A of the polarizing plate 24 are arranged at right angles. However, the polarizing plates 23 and 24 may be arranged so that they are parallel to each other. . The optical axis of the polarizing plate may be an absorption axis.

The present invention can be applied not only to an antiferroelectric liquid crystal display device using a TFT as an active element but also to an antiferroelectric liquid crystal display device using an MIM as an active element. Further, as shown in FIG. 25, the present invention provides a simple matrix type (passive matrix type) display in which a scanning electrode 71 and a signal electrode 72 orthogonal to the scanning electrode 71 are arranged on the opposing surfaces of the opposing substrates 11 and 12. It is also applicable to devices.

[0090]

As described above, according to the present invention, although the liquid crystal display device uses a liquid crystal exhibiting antiferroelectricity, the display gradation is continuously changed to provide an arbitrary gradation. Images can be displayed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure of a liquid crystal display device according to an 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 diagram illustrating a relationship between a transmission axis of a polarizing plate and an alignment direction of liquid crystal molecules.

FIG. 4 is a diagram for explaining a double helical structure drawn by liquid crystal molecules of a liquid crystal in a bulk state.

FIG. 5 is a diagram for explaining an orientation state of liquid crystal molecules in an antiferroelectric phase sealed between substrates.

FIGS. 6A to 6E are diagrams showing a relationship between an applied voltage of a liquid crystal forming an antiferroelectric phase in a state where no voltage is applied and a molecular orientation.

FIG. 7 is a diagram for explaining the behavior of liquid crystal molecules when an intermediate voltage is applied.

FIG. 8 is a diagram for explaining an alignment state of liquid crystal molecules when an intermediate voltage is applied to a liquid crystal forming an antiferroelectric phase in a state where no voltage is applied.

FIG. 9 is a diagram for explaining an alignment state of a liquid crystal when an intermediate voltage is applied to a liquid crystal forming an antiferroelectric phase in a state where no voltage is applied.

FIG. 10 is a diagram showing an arrangement of liquid crystal molecules in a ferri phase.

FIG. 11 is a diagram showing an arrangement of liquid crystal molecules in a ferri phase.

FIG. 12 is a diagram showing an arrangement of liquid crystal molecules in a ferri phase.

FIG. 13 is a diagram for explaining an alignment state of liquid crystal molecules when a voltage is applied to a liquid crystal that forms a ferri phase when no voltage is applied.

FIG. 14 is a diagram for explaining an alignment state of liquid crystal molecules when a voltage is applied to a liquid crystal that forms a ferri phase when no voltage is applied.

FIG. 15 is a diagram for explaining an alignment state of a liquid crystal forming a mixed phase in a state where no voltage is applied.

FIG. 16 is a diagram for explaining a change in alignment state with respect to an applied voltage of a liquid crystal forming a mixed phase in a state where no voltage is applied.

17A is a graph showing an applied voltage-transmittance characteristic when a low frequency triangular wave voltage is applied to the antiferroelectric liquid crystal display element of Example 1 employing the optical arrangement of FIG. And (B) shows Comparative Example 1 in which the gap length was 5 microns.
5 is a graph showing an applied voltage-transmittance characteristic of FIG.

FIG. 18 is a conoscopic image of a liquid crystal in a bulk state.

FIGS. 19A to 19C are diagrams showing micrographs of a liquid crystal display element.

FIGS. 20A and 20B are diagrams showing another example of the relationship between the transmission axis of a polarizing plate and the orientation direction of liquid crystal molecules.

FIG. 21A is a graph showing applied voltage-transmittance characteristics when a low-frequency triangular wave voltage is applied to the antiferroelectric liquid crystal display element of Example 2 employing the optical arrangement of FIG. (B) shows Comparative Example 2 in which the gap length was 5 microns.
5 is a graph showing an applied voltage-transmittance characteristic of FIG.

FIGS. 22A to 22C are timing charts for explaining a method of driving the antiferroelectric liquid crystal display device of the present invention.

FIG. 23 is a diagram showing an applied voltage-transmittance characteristic when the liquid crystal display element of Example 2 is driven using the driving methods shown in FIGS. 22 (A) to (C).

FIG. 24 is a block diagram showing a configuration example of a driver circuit for realizing the driving methods shown in FIGS.

FIG. 25 is a diagram illustrating a configuration of a simple matrix type liquid crystal display element.

[Explanation of symbols]

11: transparent substrate (lower substrate), 12: transparent substrate (upper substrate), 13: pixel electrode, 14: active element (TF
T), 15: gate line (scan line), 16: data line (gradation signal line), 17: common electrode, 1
8 ... alignment film, 19 ... alignment film, 20 ... sealing material, 21.
..Liquid crystal layer, 22 spacer, 23 polarizing plate (lower polarizing plate), 24 polarizing plate (upper polarizing plate), 25 liquid crystal cell,
31 ... row driver, 32 ... column driver, 71 ... scanning electrode, 72 ... signal electrode

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI G09G 3/36 G09G 3/36 (72) Inventor Jun Ogura 5 Casio Computer Co., Ltd. Hachioji Research, 2951 Ishikawacho, Hachioji-shi, Tokyo Inside

Claims (11)

[Claims] A first substrate on which a plurality of pixel electrodes and active elements connected to the pixel electrodes are arranged in a matrix; a second substrate on which a common electrode facing the pixel electrodes is formed; And a liquid crystal layer having liquid crystal molecules arranged with a tilt with respect to the main surface of the substrate between the one substrate and the other substrate to form a chiral smectic CA phase in a bulk state. A liquid crystal display element comprising: 2. An alignment film, which has been subjected to an alignment process for tilting the liquid crystal molecules with respect to a main surface of the substrate due to an interface effect with the liquid crystal layer, is formed on a facing surface of the one and other substrates. The liquid crystal display device according to claim 1, wherein: 3. The liquid crystal display device according to claim 1, wherein the liquid crystal layer has liquid crystal molecules tilted with respect to the main surface of the substrate by an applied electric field. 4. The liquid crystal layer includes a ferroelectric phase liquid crystal, an antiferroelectric phase liquid crystal, and an intermediate phase in which liquid crystal molecules are arranged with a tilt with respect to the main surfaces of the one and the other substrates. 2. The liquid crystal display device according to claim 1, wherein a mixed phase is formed by mixing liquid crystal. 5. The liquid crystal layer forms a chiral smectic CA phase in a bulk state, and no voltage is applied between the pixel electrode and the common electrode between the one substrate and the other substrate. In an electric field state, an antiferroelectric phase is formed, and in an electric field applied state in which a voltage is applied between the pixel electrode and the common electrode, the antiferroelectric phase, the ferroelectric phase, and the intermediate phase oriented in other states are formed. 2. The liquid crystal display element according to claim 1, wherein the liquid crystal display element is made of a liquid crystal material forming a mixed phase to be mixed. 6. The liquid crystal layer forms a chiral smectic CA phase in a bulk state, and no voltage is applied between the pixel electrode and the common electrode between the one substrate and the other substrate. A ferri phase is formed in an electric field state, and a mixed phase is formed in which a ferroelectric phase and an intermediate phase oriented in other states are mixed in an electric field applied state in which a voltage is applied between the pixel electrode and the common electrode. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is made of a liquid crystal material. 7. The liquid crystal layer forms a chiral smectic CA phase in a bulk state, and an intermediate between the one substrate and the other substrate is oriented to an antiferroelectric phase, a ferroelectric phase, and another state. 2. A liquid crystal material comprising a liquid crystal material forming a mixed phase which is mixed with a phase.
3. The liquid crystal display device according to item 1. 8. The liquid crystal layer is made of a liquid crystal material in which liquid crystal molecules move along a cone drawn by molecules of a chiral smectic CA phase by application of an electric field, whereby an alignment state of an intermediate phase is formed. 2. The method according to claim 1, wherein
8. The liquid crystal display device according to any one of items 1 to 7. 9. The liquid crystal layer according to claim 1, wherein the liquid crystal layer has liquid crystal molecules arranged on a plane substantially perpendicular to the substrate with a tilt relative to the substrate. 2. The liquid crystal display device according to claim 1. 10. A substrate on which an electrode is formed, another substrate on which an electrode facing the electrode is formed, and liquid crystal molecules sealed between the substrate and forming a smectic phase have spontaneous polarization. Then, an antiferroelectric phase is formed in a bulk state to draw and arrange a double helical structure, and a tilt is formed between the one substrate and the other substrate with respect to the main surfaces of the one and the other substrates. A liquid crystal layer containing the liquid crystal molecules, and an electrode of the one substrate and an electrode of the other substrate, and by applying a voltage between the electrodes, the liquid crystal molecules in the liquid crystal layer are converted into chiral smectic CA. A liquid crystal display element comprising: a driving unit that controls a director of the liquid crystal layer to perform gradation display by moving along a cone drawn by liquid crystal molecules of a phase. 11. A liquid crystal of an antiferroelectric phase in which liquid crystal molecules are arranged in a bulk state in a double helical structure in a bulk state between a pair of substrates, and an electric field is applied to the liquid crystal to form a liquid crystal. By orienting the molecules with a tilt with respect to the main surface of the substrate, and by moving the liquid crystal molecules along a cone drawn by the molecules of the chiral smectic CA phase, the director of the liquid crystal is controlled. A method for driving a liquid crystal display element, which performs gradation display.