JP2000276104A - Display element and liquid crystal element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal element which has a practical brightness and which is capable of a high speed response and also a gradation control and in which moving picture quality is enhanced without using complex circuits. SOLUTION: This display element holds chiral smetic liquid crystal which indicates a phase transition series of an isotropic phase-to-a cholesteric phase-to- a chiral smetic phase at the time of a lowered temp. between one pair of substrates in which an uniaxial orientation is applied to at least the substrate of one side and orients molecules of the liquid crystal so as to indicate monostable states by the impressing of a voltage and to indicate a first transmissivity by being tilted by the impressing of a voltage having a first polarity and to indicate a second transmissivity smaller than the first transmissivity by being tilted to an opposite side by the impressing of a voltage having a second polarity, Then, the display element performs assigning intensity levels in the interval of the transmissivity which is indicated at the monostable states and the maximum value of the first transmissivity by dividing one frame into a period when the voltage having the first polarity is impressed and a period when the voltage having the second polarity is impressed which is shorter than the period when the voltage having the first polarity is impressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device, and more particularly to a liquid crystal device used for a light valve used in a flat panel display, a projection display, a printer, and the like.

[0002]

2. Description of the Related Art Conventionally, in a nematic liquid crystal element, an active matrix type liquid crystal element in which an active element such as a transistor (for example, a thin film transistor (TFT)) is arranged for each pixel has been developed. At present, as a mode of a nematic liquid crystal used in the active matrix type liquid crystal element, for example, M.P. M. Schadt and W.S. Applied Phys by W. Helfrich
sics Letters, Vol. 18, No. 4 (197
Twisted Nermatic (Twisted N) shown on pages 127 to 128
e) mode is widely used. Also, recently, an in-plane switching mode using a lateral voltage has been announced, and the viewing angle characteristics which have been a drawback of the twisted nematic mode liquid crystal display have been improved.

In addition, as a typical example of a nematic liquid crystal element which does not use an active element such as a TFT described above, a super twisted nematic (Super Twist) is used.
ted Nematic) mode. in this way,
A liquid crystal element using a nematic liquid crystal has various modes, but in any of the modes, there is a problem that a response speed of the liquid crystal takes several tens of milliseconds or more.

As an improvement over the above-mentioned drawbacks of the conventional nematic liquid crystal element, an element in which the liquid crystal exhibits bistability (SSFLC / Surface Stabilize) is used.
dFLC) has been proposed by Clark and Lagerwell (JP-A-56-107216, U.S. Pat. No. 4,367,924).
Specification). As the liquid crystal exhibiting the bistability, a ferroelectric liquid crystal exhibiting a chiral smectic C phase is generally used. In this ferroelectric liquid crystal, when a voltage is applied, a voltage acts on the spontaneous polarization of the liquid crystal molecules, and the molecules undergo inversion switching, so that a very fast response speed is obtained and a bistable state with memory properties is obtained. Can be expressed.
Further, since the viewing angle characteristics are excellent, it is considered that the display element is suitable as a high-speed, high-definition, large-area display element or a light valve.

On the other hand, recently, antiferroelectric liquid crystals exhibiting a tristable state of liquid crystal have been receiving attention. In the antiferroelectric liquid crystal, as in the case of the ferroelectric liquid crystal, reversal switching of molecules is performed by the action of spontaneous polarization of liquid crystal molecules, so that a very fast response speed can be obtained. This liquid crystal material is characterized in that there is substantially no spontaneous polarization when no voltage is applied since the liquid crystal molecules have a molecular arrangement structure in which the spontaneous polarization cancels each other when no voltage is applied.

A ferroelectric liquid crystal and an antiferroelectric liquid crystal that perform inversion switching by such spontaneous polarization are liquid crystals exhibiting a smectic liquid crystal phase. That is, the realization of a liquid crystal element using a smectic liquid crystal is expected in the sense that the problem relating to the response speed of the conventional nematic liquid crystal can be solved.

[0007]

As described above, a smectic liquid crystal having spontaneous polarization is expected for a next-generation display or the like having a high-speed response performance. In particular, a mode using the above-mentioned bistable state or tristable state is expected. In such a case, it was theoretically difficult to realize gradation display within one pixel.

In recent years, as a mode for controlling gradation using a liquid crystal exhibiting a chiral smectic phase (chiral smectic liquid crystal), a “short-pitch type ferroelectric liquid crystal” and a “polymer stable ferroelectric liquid crystal” have been proposed. And "thresholdless antiferroelectric liquid crystal" have been proposed, but none of them has reached a level sufficient for practical use.

On the other hand, recent studies have shown that simply increasing the response speed of a liquid crystal portion of a conventional type device (mode using a nematic phase) in a liquid crystal device does not provide a high-speed response characteristic to a moving image as perceived by a human ( Religious Technique EID96-4
p. 19). According to these research results, as a method for human beings to perceive high-speed moving image display, using a method of reducing the time aperture ratio to 50% or less by using a shutter or a 2 × speed display method is effective in improving moving image quality. It is concluded that there is.

However, in the conventional mode using the nematic phase, the response speed of the liquid crystal is insufficient, so that the above-described moving image display method cannot be used, and also the chiral smectic of the high speed response that has been proposed so far. Liquid crystal element, furthermore, the above-mentioned "short pitch type ferroelectric liquid crystal", "polymer stable ferroelectric liquid crystal",
In order to achieve the high-speed and good moving image display described above using “thresholdless antiferroelectric liquid crystal”, the disadvantage that the driving method and peripheral circuits become complicated no matter which smectic mode is used. It had a cost increase. In addition, when the time aperture ratio is completely set to 50% or less, it is clear that the brightness of the entire display element becomes 50% or less, which causes a reduction in display luminance.

The present invention has been made in view of such a problem, and an object thereof is to provide a display element, particularly a liquid crystal element, which has a high response speed and a high level while ensuring practical brightness. It is an object of the present invention to provide an inexpensive liquid crystal element capable of adjusting the tone and improving moving image quality without using a complicated circuit. Another object of the present invention is to reduce power consumption in a display element and a liquid crystal element.

[0012]

The object of the present invention described above is achieved by the following constitution.

That is, the display element of the present invention is a display element for displaying an image by individually controlling a plurality of pixels. One frame is divided into at least two fields, and the display information is displayed for each pixel in the first field. , And display in the first field substantially at the second luminance that is smaller than the first luminance at a fixed rate for each pixel in the remaining fields of one frame. The period in which the same image as the displayed image is displayed at the first luminance is set longer than the period in which the image is displayed at the second luminance.

Further, the liquid crystal element of the present invention is a liquid crystal element for displaying an image by individually controlling a plurality of pixels. A liquid crystal element including a pair of substrates subjected to an alignment process, electrodes for driving liquid crystal for each pixel, and a polarizing plate disposed outside at least one of the substrates, wherein one frame covers at least two fields. In the first field, an image is displayed at a first luminance corresponding to the display information for each pixel in the first field, and the second luminance which is smaller than the first luminance at a constant rate for each pixel in the remaining fields of one frame. The same image as the image displayed in the first field is displayed at the luminance of the first luminance, and the period of displaying at the first luminance is set to be longer than the period of displaying at the second luminance. That And butterflies.

In particular, in the liquid crystal device of the present invention, the liquid crystal is a chiral smectic liquid crystal, and when no voltage is applied, the liquid crystal exhibits a first state in which the average molecular axis of the liquid crystal is monostable. When a polarity voltage is applied, the average molecular axis of the liquid crystal tilts from the first state to one side at an angle corresponding to the applied voltage value, and a second polarity voltage having a polarity opposite to the first polarity. At the time of application, the average molecular axis of the liquid crystal tilts at an angle corresponding to the applied voltage value from the first state to the side opposite to the side tilted when the voltage of the first polarity is applied, and has the first polarity. It is preferable that the tilt angle from the first state in the maximum tilt state of the average molecular axis of each liquid crystal when a voltage is applied and when the voltage of the second polarity is applied is different from each other.

Further, in the first field, the liquid crystal of each pixel is tilted from the first state at an angle corresponding to the voltage value by applying a first polarity voltage having a value corresponding to display information. In the remaining fields of the first frame, the liquid crystal of each pixel is turned at the angle corresponding to the voltage value by applying a second polarity voltage having a value corresponding to the display information. From one state, the liquid crystal of each pixel exhibits a third transmittance in the first state by tilting to a side opposite to the side tilted when the voltage of the first polarity is applied, to exhibit a second transmittance. An element that performs gradation display by continuously changing the transmittance between the maximum value of the first transmittance and the third transmittance is preferable.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a display device according to the present invention, an image is formed by a field displayed at high luminance (first luminance) and a field displayed at low luminance (second luminance).
By displaying an image having substantially the same content but different in luminance in each of these fields, a moving image that can be perceived at high speed by a human can be obtained. It is possible to realize moving image display without significantly reducing brightness. In particular, by setting the second luminance to 1/5 or less of the first luminance, a high-speed moving image quality effect can be better obtained.

The display element is used in the form of an element for displaying an image by optically modulating external light, an EL element, or a self-luminous element such as a plasma display.

Particularly, it is preferably applied to a liquid crystal element.
In the case of a liquid crystal element, for example, a liquid crystal device in which an external light source is provided in a liquid crystal element configured as a transmission type, and each pixel of the liquid crystal element is optically modulated to have a transmittance according to display information, and in a first field, By turning on the light source at the first illuminance and turning on the second illuminance lower than the first illuminance in the remaining fields, the above-described high-speed moving image quality and bright display can be realized. Even in such a device,
It is preferable that the second illuminance is set to be 1/5 or less of the first illuminance.

Further, in the present invention, a liquid crystal element using a chiral smectic liquid crystal in which the liquid crystal exhibits a monostable state when no voltage is applied as described above is a mode for obtaining the effects of the present invention most preferably.

Hereinafter, preferred embodiments of the present invention will be described.
The alignment state and switching process of a chiral smectic phase in a liquid crystal element using a chiral smectic liquid crystal will be described with reference to the drawings in comparison with a conventional SSFLC type.

In the model described below, the description is made based on the relationship between the liquid crystal molecules and the virtual cone, the smectic layer normal line, and the average uniaxial alignment processing axis which can be in the range of the positions of the liquid crystal molecules. A plurality of liquid crystal molecules exist in the liquid crystal element, and are twisted to some extent in the normal direction of the substrate, for example, and are optically observed as a behavior of an average molecular axis (for example, by observation with a polarizing microscope). That is, the average molecular axis defined in the present invention substantially corresponds to the behavior of a single liquid crystal molecule.

In the SSFLC, bistability, that is, memory properties is exhibited by stabilizing liquid crystal molecules in two states in an SmC ^* phase (chiral smectic C phase). This memory state will be described with reference to the models shown in FIGS.

FIG. 1 is a diagram schematically showing a liquid crystal molecule and a layer structure of a liquid crystal (a structure of a smectic layer) in an SSFLC type device. In the device, as shown in FIGS. 1A and 1B, the liquid crystal molecules 14 are sandwiched between the substrates 11 and 12 by the liquid crystal molecules 14.
Rises at a predetermined pretilt angle α from the substrates along the uniaxial orientation direction R of each substrate near the interface between the substrates 11 and 12 (in this example, the uniaxial orientation directions R of both substrates are parallel and the same direction, That is, a setting is made such that the liquid crystal molecules rise in the same direction with respect to the substrate), and a smectic layer 16 having a chevron structure forming an inclination angle δ with respect to the substrate normal between the substrates 11 and 12 is formed.

On the other hand, the liquid crystal molecules 14
Switching between two positions on the wall surface of the virtual cone 15 having an apex angle of Θ (Θ: cone angle which is a physical property inherent to the liquid crystal material), and stably exists near the two positions in a state where no voltage is applied when no voltage is applied. I do. In addition, the alignment state in which the smectic layer 16 forms a chevron structure shown in FIGS. 6A and 6B depends on the relationship between the direction of the pretilt of the liquid crystal molecules 14 between the substrates and the bending direction of the chevron structure of the smectic layer 16. The orientation state of (a) is called C1 orientation, and the orientation state of (b) is called C2 orientation.

Here, in the SSFLC orientation state shown in FIG. 1, both the C1 orientation state and the C2 orientation state are generally
By satisfying the relationship of δ, the liquid crystal molecules 14 are formed in the virtual cone 15 in substantially the entire thickness direction including the kink position of the smectic layer 16 having the chevron structure (the bent portion at the center between the substrates) between the substrates 11 and 12 when no voltage is applied. Stable within 2
Position and a bistable state develops.

FIGS. 2A and 2B respectively show FIGS.
9A and 9B show projections of liquid crystal molecules onto the bottom surface 17 of the virtual cone 15 in the C1 alignment state and the C2 alignment state shown in FIGS.
4b shows a bistable state (projections 18a, 18b).

In an element in which the liquid crystal exhibits a bistable alignment state as described above, one of the pair of polarizing plates under crossed Nicols has one average molecular axis in the bistable state (position of liquid crystal molecules).
, The switching between the bistable states is performed, and the display in black (dark state) and white (bright state) is performed. This switching is performed, for example, by generating a domain from one state to the other state, that is, accompanied by generation and disappearance of a domain wall. However, when display is performed using such a switching mechanism, basically, only binary display of black and white can be performed, and it is difficult to display a gray scale (halftone) between black and white.

On the other hand, in the liquid crystal device of the present invention, in order to realize gradation display in the device using the chiral smectic liquid crystal, the memory property (bistability) as shown in FIGS. 1 and 2 is lost. The position of the liquid crystal molecules is made continuously variable by an applied voltage. Due to this setting, in the present invention, the isotropic phase (I
A liquid crystal material exhibiting a phase transition series of (so) -cholesteric phase (Ch) -SmC ^* or Iso-SmC ^* is used.

FIG. 3A shows a process of forming a layer (smectic layer) structure of a liquid crystal material exhibiting a Ch-SmA-SmC ^* phase transition sequence at least at a reduced temperature in a liquid crystal device. 4 shows a process of forming a layer structure of a liquid crystal material exhibiting a Ch-SmC ^* phase transition series at a lower temperature. In the figure, the arrow R indicates the direction of the average uniaxial orientation processing axis in the device. The liquid crystal molecules 14 can be switched along the wall surface of the virtual cone 15 when a voltage is applied.

Here, the “average uniaxial alignment processing axis” means that the uniaxial alignment processing is performed on the surfaces of both substrates constituting the element which are in contact with the liquid crystal, and the directions (for example, rubbing directions) are parallel and the same direction. When the directions are opposite to each other (anti-parallel) and when only one of the substrates has been subjected to the uniaxial orientation processing, it corresponds to the axis itself of the uniaxial orientation processing, and the direction in which the uniaxial orientation processing has been applied to both substrates. When the rubbing directions (for example, rubbing directions) cross each other, they correspond to the axes in the center direction of both the uniaxial orientation processing axes, that is, half the cross angle. Further, the “direction” of the average uniaxial alignment processing axis is, for example, a direction in which liquid crystal molecules stand up with respect to the substrate in the vicinity of the substrate on which the alignment processing has been performed, that is, a direction to a side where pretilt occurs, and When only uniaxial orientation processing is performed and when uniaxial orientation processing is performed on both substrates and the direction (for example, the rubbing direction) is parallel and the same direction, the processing direction itself is used, and the two substrates are parallel to each other. In the case where the processing in the opposite direction is performed (anti-parallel), the processing direction is on one of the substrates, and the direction (for example, the rubbing direction) on which the uniaxial alignment processing is performed on both substrates crosses each other. In that case, it is the direction of its central axis.

As shown in FIG. 3A, in the case of a liquid crystal material having an SmA phase in the phase transition series, the direction of the normal direction of the smectic layer (horizontal arrow LN) and the direction of the uniaxial alignment process in the SmA phase coincide. Thus, the liquid crystal molecules 14 are arranged to form a smectic layer structure. And in the SmC ^* phase,
The liquid crystal molecules 14 tilt from the smectic layer normal direction LN and stabilize near the edge of the virtual cone 15 or at a position slightly inside the edge.

On the other hand, FIG. 3 preferably used in the present invention
As shown in (b), in the phase transition series that does not include the SmA phase, for example, during the phase transition from the Ch phase to the SmC ^* phase,
The liquid crystal molecules 14 are arranged so as to be inclined with respect to the normal direction LN of the smectic layer and slightly inclined from the average uniaxial alignment processing direction R to form a smectic layer structure.

In the present invention, the liquid crystal molecules 14 are SmC
^* Adjusted to stabilize at a position inside the edge of virtual cone 15 within the operating temperature range within the phase. Here, as a case of “stabilizing at a position inside the edge of the virtual cone 15”, a structure in which the smectic layer has an inclination angle such as a chevron structure or an oblique bookshelf structure is considered, but a complete bookshelf structure is used. Even in the case where the pretilt angle is high, the polar interaction at the substrate interface is strong, and the bulk molecules are twisted, the stabilization may occur inside the cone edge. In the case of a material with a remarkable electroclinic effect, the electric field causes molecules to tilt further outside the virtual cone edge,
In the liquid crystal device of the present invention, the deviation angle between the molecular alignment direction and the layer normal direction when an electric field is applied is larger than the deviation angle between the molecular alignment direction and the layer normal direction when no electric field is applied, that is, for example, when no electric field is applied. When the direction of the liquid crystal molecules at the time coincides with one of the polarization axes of crossed Nicols and the state is the darkest, the optical axis of the liquid crystal is shifted even when a voltage of either positive or negative polarity is applied, and birefringence is developed. Because of this feature, the present invention is also applicable to a material in which liquid crystal molecules are tilted to the outside of the edge of the virtual cone by the application of such a voltage.

Here, as one embodiment of the present invention, a case having a layer inclination angle such as a chevron structure or an oblique bookshelf will be described in detail with reference to FIG. 4 using a model. FIG. 4A shows a change in the arrangement of liquid crystal molecules in a phase transition series not including the SmA phase, as in FIG. 3B. For example, during the phase transition from the Ch phase to the SmC ^* phase (particularly, SmC phase). ^* Just below the phase transition temperature), liquid crystal molecules 14
Are arranged so as to be inclined with respect to the normal direction LN of the smectic layer to form a smectic layer structure.

However, in FIG. 4A, the difference in cone angle コ ー ン (１ ／ of the vertex angle of the virtual cone 15) in the SmC ^* phase, for example, between the high temperature side (TEMP ₁ ) and the low temperature side (TEMP ₂ ). Exists.

Here, the high temperature side TEMP₁Cone in
角₁, Low temperature side TEMP_TwoThe cone angle at_TwoWhen
Θ₁<Θ_TwoWhen using a material that satisfies the relationship
Normally, the smectic layer at each of these temperatures
Interval d₁And d_TwoD in between₁> D_Two Is established. Obedience
Tentatively, temperature TEMP₁Bookshelf structure in
Temperature TEMP_TwoThen
At least the relational expression δ = cos^-1(D_Two/ D₁) Fill layer
Will have a tilt angle δ.

Therefore, at the temperature TEMP ₂ , a chevron structure or an oblique bookshelf structure is formed. 4 (b) and 4 (c) show the layer structure, c-director state, and projection on the bottom surface of the virtual cone when the chevron structure is used. As shown in the figure, a normal bistable SSFL
Similarly to C, from the relationship between the rubbing direction and the layer inclination angle, C1,
C2 can be defined. According to the principle described above,
The liquid crystal molecules 14 are adjusted so as to be stabilized at a position inside the edge of the virtual cone 15.

3 (a) and 3 (b) and FIG. 4 (a)
In such a case, for example, liquid crystal molecules as shown in FIGS.
14 is a bistable orientation state of a chevron structure, that is,
It should be stable in two qualitatively parallel states.
(B), the binding force of the uniaxial orientation treatment in the case shown in FIG.
Becomes stronger, and only one of these two states becomes stable.
As a result, the memory property is lost. FIG.
(B), Ch-SmC shown in FIG.^*During phase transition
(SmC^*Just below the phase transition temperature), as shown in FIG.
Different layer normal directions (LN ₁And LN _Two)
It is conceivable that a mectic layer structure is formed. this
The top and bottom of the cell holding the chiral smectic liquid crystal
The state of uniaxial orientation processing of a pair of substrates (conditions such as
If the material is completely symmetric, as shown in FIG.
Two smectic layer structures are formed at an equal ratio.

In the liquid crystal device of the present invention, only one of the two layer structures shown in FIG. 5 is aligned, that is, the direction of deviation between the average uniaxial alignment processing axis and the normal direction of the smectic layer is constant. As shown in FIG. 4 (b) or (c), the liquid crystal molecules 14 are stabilized inside one edge of the virtual cone 15 in the state where no voltage is applied, and the memory property of the SmC ^* phase is lost. The orientation state has been obtained.

Next, in a cell having an alignment state of the liquid crystal element of the present invention, that is, an alignment state in which one of the layer structures in the SmC ^* phase is preferentially formed as shown in FIG. 5, the inversion of the liquid crystal molecules 21 with respect to the voltage. A behavior model (projection on the top surface, side surface, and bottom surface of the cone) of the element will be described with reference to FIG. In FIG. 6, the inversion behavior with respect to the electric field is described using the C2 orientation state in a parallel rubbing cell (a cell in which rubbing treatment is performed in the same direction parallel to both substrates). The cell orientation and the like can be discussed in the same way.

In FIG. 6, the behavior (I) when viewed from above the cell, the behavior in the cell sectional direction (II), and the projection of the SmC ^* phase onto the virtual cone bottom (I
II). In the case of I, it indicates the average molecular axis of the liquid crystal molecules in the cell cross-sectional direction.

First, as shown in FIG. 6B, when no voltage is applied, the liquid crystal molecules 14 (the projections 18 on the bottom surface 17 of the virtual cone are oriented slightly deviated from the average uniaxial orientation direction (arrow R)). The spontaneous polarization 19 of the liquid crystal is oriented substantially in the same direction between the substrates. Here, one of the polarization axes (P) coincides with the position of the liquid crystal molecule when no voltage is applied. d) A cell is arranged below, and a dark state (black state) is displayed by setting the amount of light transmitted through the liquid crystal to a minimum state (minimum transmittance).

When a voltage is applied to this alignment state, as shown in FIGS. 6A and 6C, the liquid crystal molecules 14 move in accordance with the polarity of the voltage E with respect to the position where no voltage is applied. Tilt (switching) with spontaneous polarization 19 aligned in different directions
I do. The tilt angle (see II) based on the liquid crystal molecule position when no voltage is applied depends on the magnitude of the applied voltage (absolute value of the voltage). As shown, the tilt angle when a voltage of one polarity is applied (in the case of applying a positive voltage) and the tilt angle when a voltage of the other polarity is applied (in the case of applying a negative voltage) are as follows. ,
If the polarities of the voltages are opposite, even if they have the same absolute voltage value, they are greatly different.

Here, the transmittance exhibited by the liquid crystal when a voltage of the first polarity is applied to the liquid crystal is the first transmittance, and the transmittance exhibited by the liquid crystal when the voltage of the second polarity is applied to the liquid crystal. The second transmittance and the transmittance when no voltage is applied are defined as a third transmittance. In the present invention, “transmittance” indicates “light transmittance”.

In the case of FIG. 6, when no voltage is applied, the molecules are already monostable in a direction inclined from the normal direction of the smectic layer, and when a sufficiently large electric field is applied to each of the positive and negative sides. In FIG. 6A or FIG. 6C, the molecules are arranged so that the direction of the spontaneous polarization of the molecules near the substrate interface is also directed to the electric field direction similarly to the bulk portion. Since it exists on the edge, the maximum tilt state can be obtained based on the position when no voltage is applied. As a result, a uniform orientation state with almost no twist at the molecular position with the layer normal axis as the symmetry axis is formed. The maximum tilt state of the liquid crystal molecules is defined as a tilt angle in a maximum tilt state based on a position when no voltage is applied by applying a voltage of one polarity and a tilt angle in a maximum tilt state by applying a voltage of the other polarity. In FIG. 6, the angle in the maximum tilt state when the positive voltage is applied is adjusted to be larger than the angle in the maximum tilt state when the negative voltage is applied.

Here, for example, when the refractive index anisotropy Δn of the liquid crystal and the cell thickness are d and Δnd is set near half the wavelength of visible light, the positive polarity as shown in FIG. At the applied voltage of, as the voltage (absolute value) increases,
The amount of light emitted from the liquid crystal element, that is, the amount of light passing through the element continuously changes and increases, and the alignment state as shown in the figure is obtained, and a predetermined tilt state is obtained. Then, in the tilt state (the maximum value of the first transmittance), it is possible to obtain the maximum amount of transmitted light and the amount of light that is the most different from the amount of light transmitted when no voltage is applied (most different in the range of positive voltage application).

On the other hand, as shown in FIG. 6 (a), when a negative voltage is applied, the amount of light transmitted through the liquid crystal element increases, but the optical response amount is very small and a predetermined voltage (positive polarity) is applied. When the liquid crystal molecules are in a predetermined tilt state at the same absolute value as the voltage side (the second maximum transmittance state), the amount of transmitted light is the most different from the amount of transmitted light when no voltage is applied (negative voltage applied). ), That is, the maximum transmitted light amount. However, the maximum transmitted light amount when the negative voltage was applied and FIG.
The difference from the transmitted light amount when no voltage is applied shown in FIG.
In the case (c), the difference between the maximum transmitted light amount when the positive voltage is applied and the transmitted light amount when no pressure is applied, that is, the maximum transmitted light amount in the liquid crystal element is obtained when the positive voltage is applied. be able to.

Here, for example, when a pair of polarizing plates as shown in FIG. 6D is used, the position of the liquid crystal molecules 14 when no voltage is applied in the state of maximum tilt of the liquid crystal molecules 14 when a positive voltage is applied. The tilt angle is 45
° or less, the liquid crystal molecules 14
, That is, in the state of maximum tilt (the state of the maximum value of the first transmittance), the maximum amount of transmitted light when the positive voltage is applied is obtained. On the other hand, the tilt angle is 45 °
If it is larger, the maximum amount of transmitted light when a positive voltage is applied is obtained when the liquid crystal molecules 14 are inside the edge of the virtual cone 15. When a negative voltage is applied, the maximum transmitted light amount when the negative voltage is applied is obtained in the maximum tilt state (the second transmittance maximum value state) in any of the above cases.

Examples of the voltage (V) -light transmittance (T) characteristics of an element exhibiting the switching behavior of liquid crystal molecules as described above,
In particular, FIG. 7 shows an example of an element in which a maximum transmittance is obtained when liquid crystal molecules are in a maximum tilt state when a positive voltage is applied.
Shown in When a positive voltage is applied, the transmittance increases due to the tilt of the liquid crystal molecules along the voltage value, and shows a maximum transmittance T ₁ at a voltage V ₁ or higher. On the other hand, when a negative voltage is applied, the liquid crystal molecules tilt along the voltage value, and the transmittance slightly increases. However, when the voltage is −V ₁ or less, the maximum transmittance T _2, which is much smaller than T ₁ , is saturated. I do.

The switching operation of the liquid crystal device of the present invention as shown in FIG. 6 and the characteristics as shown in FIG.
The present invention is applied to an active matrix type liquid crystal element having an FT, applying an AC drive waveform, causing the liquid crystal portion to function as an optical shutter, and applying a unipolar voltage (for example, a positive voltage application shown in FIG. The time aperture ratio is reduced to 50% or less by combining the voltage application period of the opposite polarity (for example, the period of using the optical response characteristic by applying the voltage on the negative polarity side shown in FIG. 7). In this case, the same effect as that of the method can be obtained. Thus, a liquid crystal element with improved moving image quality can be realized without using complicated peripheral circuits and the like.

In particular, the first polarity (in the case of FIG. 6, positive polarity)
Angle of maximum tilt state of liquid crystal molecules (average molecular axis) when voltage is applied and second polarity (negative polarity in FIG. 6)
The ratio of the liquid crystal molecules (average molecular axis) to the angle of the maximum tilt state when the voltage is applied is preferably 5 or more, and the liquid crystal molecules (average molecular axis) when the first polarity (positive) voltage is applied. maximum and transmitted light quantity (quantity of transmitted light for example in T ₁ of the at characteristic of FIG. 7), the liquid crystal molecules (average molecular axis when a voltage is applied to the second polarity (negative polarity) from the liquid crystal element at a predetermined tilt state of) ) In the maximum tilt state (for example, T in the characteristic of FIG. 7).
₂ ) is preferably adjusted to 5 or more (ie, the difference between the maximum value of the second transmittance and the third transmittance is the maximum value of the first transmittance and the third transmittance). １ ／ or less of the difference), the most remarkable effect of improving the moving image quality can be obtained.

Next, the mechanism of inversion of liquid crystal molecules in the alignment state of the liquid crystal device of the present invention will be described.

In the state of alignment of liquid crystal molecules in the SSFLC shown in FIGS. 1 and 2, in order for the liquid crystal molecules 14 to switch between bistable states, it is necessary to exceed an energy barrier having a predetermined height. The existence of this energy barrier is the origin of bistability. On the other hand, in the liquid crystal element of the present invention, in the alignment state as shown in FIG. 5, for example, the liquid crystal molecules 14 are extremely stabilized at a position close to one side of the bistable potential in SSFLC. . As a result, only one stable state exists, and a stable state corresponding to the magnitude of the applied voltage exists in an analog manner.
In addition, since the applied voltage and the stable molecular position correspond one-to-one, inversion can be realized continuously and without domain generation.

FIGS. 8 and 9 show models of the state of the energy barrier (potential).

FIGS. 8A and 8B show potential states in the bistable orientation state in the SSFLC for the C1 orientation state and the C2 orientation state, respectively. A1 and A2 indicate the potential of each state of the bistable state. As is clear from these figures, C1
The state of the potential slightly differs depending on the orientation and the C2 orientation. In the case of CSF orientation in SSFLC, the opening angle of liquid crystal molecules at the liquid crystal-substrate interface is larger than that in the case of C2 orientation (FIGS. 2A and 2B).
), The height of the energy barrier is also increased.

On the other hand, FIGS. 9A and 9B show the potential states in the alignment state in the liquid crystal element of the present invention for the C1 alignment state and the C2 alignment state, respectively. B1 is the potential of the liquid crystal molecules when no voltage is applied (in the case of FIG. 6B), and B2 is the potential of the liquid crystal molecules at the maximum tilt by applying a voltage of one polarity (in the case of FIG. 6C). , B3 are the potentials of the liquid crystal molecules at the maximum tilt due to the application of the voltage of the other polarity (FIG. 6).
(Case (a)).

As shown in the case of SSFLC described above, C
When one of the bistable states is stabilized for each of the alignment states having different energy barrier heights between the bistable states of 1 orientation and C2 orientation, the respective driving characteristics are different. . In particular, in the C1 orientation state having a high energy barrier, as shown in FIG. 9A, two bistable states remain even when one of the bistable potentials (B1) is extremely stabilized. There remains a state in which one or both of them are in a metastable state (B2 also has a higher potential level but is more stable than the surroundings). Thus, when responding by applying a voltage, a stable state corresponding to the magnitude of the applied voltage exists in an analog manner until a certain potential is reached, and since the applied voltage and the stable molecular position correspond one-to-one, Although continuous inversion without generation of domains can be realized, a discontinuous orientation state is formed when a certain potential is exceeded, that is, a discontinuous inversion behavior accompanied by generation of domain walls may occur. is there.

On the other hand, in the C2 orientation state, since the energy barrier in the case of bistable SSFLC is low, as shown in FIG. 9B, one of (B1) is in an extremely stabilized state. In this case, inversion can be realized continuously up to the state of B2 without generation of a domain. Furthermore, it can be understood from these figures that the driving voltage is more likely to be higher in the C1 orientation.

From the above-mentioned points, regarding the alignment state in the liquid crystal element of the present invention, from the viewpoint of analog gradation performance and low driving voltage, C
It is desirable to use two orientations. Alternatively, in the case of an orientation state in which the C1 orientation and the C2 orientation are mixed, it is desirable that the pretilt angle be low in order to minimize variations in these characteristics. Alternatively, antiparallel rubbing is desirable.

FIGS. 6A to 6C and FIG.
As shown in (1), the liquid crystal molecules 14 are stabilized inside one edge of the virtual cone 15 in a state where no voltage is applied, and the alignment state in the SmC ^* phase and the switching behavior at the time of voltage application where the memory property is lost are shown. A liquid crystal element having an optical response characteristic as shown in FIG.
The cell design was adjusted and the liquid crystal material Ch-SmC ^*
This is realized by performing a process for giving a bias to the internal potential in the cell during the phase transition.

The chiral smectic liquid crystal material includes, for example, a hydrocarbon-based liquid crystal material having a phenylpyrimidine skeleton, a biphenyl skeleton, and a phenylcyclohexane ester skeleton, in which the interlayer spacing of the smectic layer is within the temperature range of the chiral smectic phase. d changes (the layer interval d _tc at the maximum temperature of the chiral smectic phase is the maximum value (d <d _tc , d: the layer interval within the temperature range of the chiral smectic phase)), and the chevron in the cell In the case of a material having a structure, 3 ° <δ <Θ (δ: the inclination angle of the smectic layer with respect to the substrate normal in the cell of the liquid crystal material, Δ: the cone angle inherent to the liquid crystal material described above, ie, the top of the virtual cone It is also possible to use a liquid crystal composition in which components are appropriately selected and blended so that the angle is １ ／).

Further, like a hydrocarbon-based liquid crystal material having a naphthalene skeleton or a polyfluorine-based liquid crystal material, the layer interval d is substantially constant within the temperature range of the chiral smectic phase, and δ ≦ 3 ° in the cell. A liquid crystal that has a component blend such that Θ just below the phase transition temperature from the high temperature side to the chiral smectic phase increases with the temperature drop in the temperature range of the chiral smectic phase Use the composition.

Θ in the chiral smectic phase of the liquid crystal material
Ideally, the contrast between the maximum light amount state and the minimum light amount state by switching, for example, 22.5 ° or more in order to further increase the maximum transmittance T ₁ under the characteristics as shown in FIG. It is. When Θ is very large, the tilt from the monostable state due to the application of the electric field to the opposite polarity, that is, the tilt toward the side of FIG. 6A also becomes a large angle. Transmittance T _{2 at} the time of
And the actual time aperture ratio may become 100%. Therefore, Θ is preferably less than 30 °. Further, if the change in temperature due to the temperature Δ is large, the darkest state set between the polarizing plates under the crossed Nicols may not be kept constant. For this reason, in the driving temperature range of the liquid crystal element,
Is preferably set to 3 ° or less.

As in the case of a general SmC ^* phase material, the liquid crystal molecules are tilted from the normal of the smectic layer to reduce the layer interval. However, when the liquid crystal material has a bookshelf layer structure spontaneously as in the case of a polyfluorinated liquid crystal material, for example, the bulk is measured at lower temperatures. It is considered that the change in the layer spacing d is extremely small due to the characteristic of the material that the layer spacing becomes longer, which is a reason why it is difficult to obtain a chevron structure. in this case,
The interfacial molecules may be oriented in the rubbing direction by the uniaxial orientation regulating force, and the bulk molecules may be oriented in a direction deviated from the rubbing direction depending on the temperature characteristics of the tilt angle. At this time, molecules near the interface are also oriented in a direction deviated from the rubbing direction by the application of an electric field.

On the other hand, as shown in FIG. 5, only one of the two layer structures developed is aligned, that is, the deviation direction between the average uniaxially oriented axis and the normal direction of the smectic layer is made constant. For imparting a bias of the internal potential in the device for: 1) Ch-SmC ^* phase transition or Iso-SmC ^*
During the phase transition, a positive or negative DC voltage is applied between the pair of substrates. 2) An alignment film (alignment control film) made of different materials is used for a pair of upper and lower substrates. 3) A method for treating an alignment film on a pair of upper and lower substrates (film formation conditions,
(Treatment conditions such as rubbing intensity and UV irradiation) are changed. 4) The type or thickness of a layer provided under the alignment film of the pair of upper and lower substrates is changed. There are various methods such as
Either means may be used.

In particular, as the DC application condition according to 1), D
In order to avoid a change (electretization) in which the alignment film itself has a permanent dipole by applying C for a long time,
In the vicinity of the Ch-SmC ^* phase transition, it is preferable that the DC be applied for a minimum time necessary for aligning the layers in one direction. Specifically, 100mV or more and 10V
It is preferable to apply a DC voltage in the following range.

The liquid crystal material as described above and the above 2) to
The ions in the alignment film and the liquid crystal material set in 4) are TF
It is desirable to reduce as much as possible so as not to adversely affect the T drive.

In the liquid crystal device of the present invention, a large uniaxial alignment regulating force is required for monostable liquid crystal molecules (average molecular axis) when no voltage is applied. Regarding this alignment regulating force, a method of evaluating the alignment regulating force using a cholesteric liquid crystal is disclosed in Uchida et al. (Liquid Crystals,
5, p. 1127 (1989)). That is, the orientation regulating force can be evaluated by evaluating the “effective twist angle” determined by the torque balance between the helical pitch in the cholesteric phase and the orientation regulating force.
In the present invention, this uniaxial orientation regulating force is defined as follows using this idea.

In the liquid crystal device of the present invention, when the Ch phase exists, the cholesteric pitch in the Ch phase is p, and the cell thickness is d _{g. In the} absence of the alignment control force, the twist angle in the cell is φ. Then, d _g / p = φ /
The relationship is 2π. Further, when the uniaxial orientation is regulated in parallel on the upper and lower substrates, and the orientation regulating force is infinite, φ becomes zero. The value of φ can be easily evaluated by measuring the optical rotation under a polarizing microscope as in the report by Uchida et al. That is, in the cell, the virtual pitch p ^* (= larger than the original pitch p) due to the alignment regulating force.
2π · d _g / φ) has a, p ^* = alignment regulating force when p can be in other words zero, p ^* = alignment regulating force at the time of infinity also is infinite.

In the present invention, it is preferable that at least p ^* ≧ 2 × p for monostabilization. It is more preferable that p ^* ≧ 10 × p. It is preferable to appropriately adjust the uniaxial alignment processing conditions (rubbing conditions, etc.), the alignment film thickness, the alignment film type, the firing conditions, etc. under the above conditions 2) to 4) in consideration of these values. .

In the liquid crystal device of the present invention, when a voltage-transmittance curve at the time of applying a triangular wave is obtained, hysteresis may exist. However, when driven by an AC waveform as in the case of an element having an actual TFT, optical modulation is not continuously performed from a white state to a halftone state as in the case of applying a triangular wave. There is no particular problem. That is, since the optical modulation is always performed while inverting the black and white in accordance with the applied polarity, for example, when the optical modulation is performed from white to a halftone, the white state passes through the black alignment state and then the intermediate state. Because of the modulation to the key alignment state, when AC is applied, one polarity is always reset to the black side and writing is performed, so the influence of the history of the previous state is considerably affected. Can be suppressed.

Hereinafter, the structure of the liquid crystal device of the present invention will be described with reference to embodiments. FIG. 10 is a cross-sectional view schematically showing a configuration of one pixel of one embodiment of the liquid crystal element of the present invention.
The liquid crystal element 80 shown in the figure has a liquid crystal layer 85, preferably a chiral smectic liquid crystal, sandwiched between a pair of substrates 81a and 81b made of a highly transparent material such as glass and plastic.

The substrates 81a and 81b are provided with electrodes 82a and 82b made of a material such as In ₂ O ₃ or ITO for applying a voltage to the liquid crystal layer 85, respectively. In the case of a simple matrix type, the electrodes are formed, for example, in a stripe shape, and cross each other to form a matrix electrode structure. In the case of the active matrix type, which is preferable for the present invention, pixel electrodes are arranged in a dot pattern for each pixel on one substrate, and a TFT or MIM
An active element (switching element) such as a metal-insulator-metal is connected, and a common electrode is provided on the other substrate on one surface or in a predetermined pattern to form an active matrix electrode structure.

On the electrodes 82a and 82b, an insulating film 83a made of a material such as SiO ₂ , TiO ₂ , Ta ₂ O ₅ having a function of preventing a short circuit between the electrodes if necessary. , 83b are provided.

Further, on the insulating films 83a and 83b, alignment films 84a and 84b which are in contact with the liquid crystal layer 85 and function to control the alignment state are provided. At least one of the alignment films 84a and 84b is subjected to a uniaxial alignment process. As such a film, for example, polyimide,
A rubbing treatment is applied to the surface of a film obtained by applying a solution of an organic material such as polyimide amide, polyamide, or polyvinyl alcohol, or an inorganic material obtained by depositing an oxide or nitride such as SiO at a predetermined angle from a diagonal direction with respect to a substrate. An oblique deposition film of a material can be used.

The orientation films 84a and 84b may have different pre-tilt angles of the liquid crystal molecules of the liquid crystal layer 85 (the film surfaces near the liquid crystal molecule orientation film) depending on the selection of the material and the conditions of the processing (uniaxial alignment processing and the like). (The angle made with respect to).

When each of the alignment films 84a and 84b is a film that has been subjected to a uniaxial alignment treatment, the uniaxial alignment treatment direction (particularly, the rubbing direction) of each film is determined to be parallel, antiparallel, or the like depending on the liquid crystal material used. Alternatively, it can be set to cross in a range of 45 ° or less.

Further, in the liquid crystal device of the present invention, it is sufficient that the uniaxial alignment treatment is performed on the interface between at least one of the pair of substrates and the liquid crystal, and the invention is not limited to the above-mentioned alignment film.

The substrates 81a and 81b are opposed via a spacer 86. The spacer 86 is provided on the substrate 8.
The distance (cell gap) between 1a and 81b is determined, and silica beads or the like are used. For the cell gap determined here, the optimum range and the upper limit are different depending on the difference in the liquid crystal material, but the uniform molecular orientation is uniform, or the average molecular axis of the liquid crystal molecules is substantially in the average direction of the alignment processing axis when no voltage is applied. In order to develop an alignment state that is substantially the same as the axis, it is preferable to set the range to 0.3 to 10 μm.

In addition to the spacers 86, adhesive particles made of a resin material such as an epoxy resin may be dispersed in order to improve the adhesiveness between the substrates 11a and 11b and improve the impact resistance of the chiral smectic liquid crystal. Yes (not shown).

In the liquid crystal element 80 having the above structure, the liquid crystal layer 85
In the case where a chiral smectic liquid crystal is used, the composition of the material is adjusted, and furthermore, the processing of the liquid crystal material and the element configuration, for example, the materials of the alignment films 84a and 84b, the processing conditions, and the like are appropriately set to obtain the above-described FIG. As shown in the figure, when no voltage is applied, the liquid crystal shows an alignment state in which the average molecular axis (liquid crystal molecules) of the liquid crystal is monostable, and when driving, a voltage of one polarity (first polarity) is applied. The tilt angle based on the position where the average molecular axis is monostable is continuously changed according to the magnitude of the voltage, and when a voltage of the other polarity (second polarity) is applied, the average molecular axis of the liquid crystal becomes The tilt is made at an angle corresponding to the magnitude of the applied voltage, and the characteristic is such that the maximum tilt angle by applying the first polarity voltage is larger than the maximum tilt angle by applying the second polarity voltage. Preferably, as the chiral smectic liquid crystal material, a material exhibiting a phase transition series of Iso-Ch-SmC ^* or a phase transition series of Iso-SmC ^* at a reduced temperature is used.
The state where the memory property is lost by SmC ^* is formed by the above-described processes 1) to 4).

The chiral smectic liquid crystal includes a biphenyl skeleton exhibiting the above-described characteristics (characteristics relating to a cone angle あ る, a property value inherent to the liquid crystal material, a layer interval d of the smectic layer, and a tilt angle δ). A composition in which a hydrocarbon liquid crystal material having a phenylcyclohexane ester skeleton, a phenylpyrimidine skeleton, or the like, a naphthalene liquid crystal material, or a polyfluorinated liquid crystal material is appropriately selected and adjusted is used.

Under such characteristics, a polarizing plate is provided outside at least one of the substrates 81a and 81b, and the cell is arranged so that the cell is in the darkest state when no voltage is applied. By the transmittance change accompanying the continuous change of the tilt angle, for example, the transmitted light amount of the element can be controlled in an analog manner with the characteristics shown in FIG.

The liquid crystal element includes substrates 81a and 81b.
At least one of these may be provided with at least R (red), G (green), and B (blue) color filters to form a color liquid crystal element.

The liquid crystal device of the present invention is a transmissive device in which polarizing plates (not shown) are provided on both sides of substrates 81a and 81b, ie, both substrates 81a and 81b are translucent substrates. A device that modulates incident light (for example, light from an external light source) from the substrate side and emits the light to the other side, or a reflective liquid crystal element in which a polarizing plate is provided on at least one substrate side, that is, the substrate 81a and A type that modulates incident light and reflected light and emits light to the incident side by providing a reflective plate on at least one side of 81b or using a reflective material as one substrate itself or a member separately provided on the substrate. And any of the above elements can be applied.

A drive circuit for supplying a gradation signal is connected to the liquid crystal element of the present invention, and by applying the above-described voltage, a continuous change in tilt angle from the monostable position of the average molecular axis of the liquid crystal can be achieved. By utilizing the characteristic that the amount of light transmitted from the element changes continuously, gradation display can be performed. For example, an analog gray scale display can be performed by using one substrate of a liquid crystal element as an active matrix substrate provided with the above-described TFT and the like, and performing active matrix driving by amplitude modulation with a driving circuit.

Hereinafter, a case where the liquid crystal element of the present invention is configured using the above-described active matrix substrate will be described with reference to FIGS.

FIG. 11 is a plan view schematically showing the structure of one substrate (active matrix substrate), in which driving means is connected to one embodiment of the liquid crystal element of the present invention of the active matrix type. It is.

In the configuration shown in FIG. 11, in the panel section 90 corresponding to the liquid crystal element, gate lines G ₁ and G _{2 in the} horizontal direction on the drawing corresponding to the scanning signal lines connected to the scanning signal driver 91 as the driving means. ,..., And the source lines S ₁ , S ₂ ,... In the vertical direction in the drawing corresponding to the information signal lines connected to the information signal driver 92 as driving means are provided so as to be orthogonal to each other while being insulated from each other. In addition, a thin film transistor (TFT) 94 as an active element (switching element) and a pixel electrode 95 are provided corresponding to the pixel at each intersection. Note that FIG. 11 shows only a 5 × 5 pixel area for convenience. As the switching element, an MIM element can be used in addition to the TFT.

The gate lines G ₁ , G ₂ ,... Are connected to the gate electrodes (not shown) of the TFT 94, and the source lines S ₁ , S ₂ ,.
Is connected to a source electrode (not shown) of the TFT 94, and the pixel electrode 95 is connected to a drain electrode (not shown) of the TFT 94.

In such a configuration, the scanning signal driver 9
The gate lines G ₁ , G ₂ ,... Are, for example, line-sequentially scanned and selected by 1 to supply a gate voltage, and the information signal driver 92 synchronizes with the gate line scanning selection to write each pixel according to the write information. When the information signal voltage is applied to the source lines S ₁ , S ₂ ,.
And is applied to each pixel electrode via the TFT 94.

FIG. 12 is a schematic diagram showing an example of a cross-sectional structure of each pixel portion (for one bit) in the panel configuration as shown in FIG. In the structure shown in FIG.
Matrix substrate 2 provided with pixel electrodes 95
The liquid crystal layer 49 having spontaneous polarization is sandwiched between the counter substrate 40 having the common electrode 42 and the common electrode 42, and the liquid crystal capacitance (C _lc ) 31
Is configured.

The active matrix substrate 20 shown in FIG. 11 shows an example in which an amorphous Si TFT is used as the TFT 94. The TFT 94 is formed on a substrate made of glass or the like, and has the gate lines G ₁ , G ₂ ,.
Nitride (SiN) on the gate electrode 22 connected to
_x ), a semiconductor layer 24 made of a-Si is provided via an insulating film (gate insulating film) 23 made of a material such as
The source electrode 2 is formed on the semiconductor layer 24 via ohmic contact layers 25 and 26 made of n ⁺ a-Si, respectively.
7, the drain electrode 28 is provided apart from each other. The source electrode 27 is connected to the source lines S ₁ , S ₂ ,
, And the drain electrode 28 is connected to a pixel electrode 95 made of a transparent conductive film such as ITO. Also, TF
The channel protective film 29 covers the semiconductor layer 24 at T94. The TFT 94 is turned on by applying a gate pulse to the gate electrode 22 during a period in which the corresponding gate line is selected for scanning.

Further, in the active matrix substrate 20, the insulating film 23 (continuously provided with the insulating film on the gate electrode 22) is formed by the pixel electrode 95 and the storage capacitor electrode 30 provided on the substrate 21 side of the electrode. A storage capacitor (C _s ) 32 is provided in parallel with the liquid crystal capacitor 31 due to the structure of holding the film. When the storage capacitor electrode 30 has a large area, the storage capacitor electrode 30 is formed of a transparent conductive film such as an ITO film in order to reduce the aperture ratio.

The T of the active matrix substrate 20
On the FT 94 and the pixel electrode 95, an alignment film 43a that has been subjected to a uniaxial alignment process such as a rubbing process for controlling the alignment state of the liquid crystal is provided. On the other hand, the opposite substrate 4
In the case of 0, a common electrode 42 and an alignment film 43b for controlling the alignment state of liquid crystal are laminated on a substrate 41 made of glass or the like with the same thickness as the entire surface. In the present invention, it is only necessary that the interface between at least one of the pair of substrates and the liquid crystal is subjected to a uniaxial alignment treatment, and the present invention is not limited to the above-mentioned alignment film.

The above cell structure is used by being sandwiched between a pair of polarizing plates (not shown) whose polarization axes are orthogonal to each other.

In the pixel portion of the cell having the above structure, a chiral smectic liquid crystal having spontaneous polarization is used as the liquid crystal layer 49 as described with reference to FIG. 10, and the switching operation shown in FIG. 6 and the switching operation shown in FIG. It is set to show optical characteristics.

As the TFT 94 shown in FIGS. 11 and 12, a polycrystalline Si (p-Si) TFT can be used.

FIG. 13 shows an equivalent circuit of a pixel portion of the panel of FIG. 12, and FIG. 14 shows an example of a driving waveform. Active matrix driving in the liquid crystal element of the present invention will be described.

In the active matrix driving of the liquid crystal element of the present invention, for example, a period (one frame) for displaying certain information in one pixel is divided into a plurality of fields (for example, 1F and 2F shown in FIG. 14). In the field, a transmitted light amount corresponding to predetermined information is obtained on average. Hereinafter, an example in which one frame is divided into two fields when the liquid crystal layer 49 has the optical characteristics shown in FIG. 7 will be described.

FIG. 14A shows a voltage applied to one gate line serving as a scanning signal line connected to an arbitrary pixel when focusing on an arbitrary pixel. In the liquid crystal device having the structure shown in FIGS. 11 and 12, the gate lines G ₁ ,
G _2, ... it is selected, for example, line-sequentially, the first gate lines is a predetermined gate voltage V _g is applied in the selection period T _on,
Applied voltage V _g to the gate electrode 22, TFT 94 is turned on. In a non-selection period T _off corresponding to a period in which another gate line is selected, no voltage is applied to the gate electrode 22, and the TFT 94 is in a high resistance state (off state).

[0103] FIG. 14 (b) shows the voltage V _s applied to the pixel of the information signal lines (source lines). FIG.
As shown in (a), when a gate voltage is applied to the gate electrode 22 during the selection period T _on in each field, the source electrodes S ₁ , S ₂ ,. 27, a predetermined source voltage (information signal voltage) V _s
(To a potential V _c of the common electrode 42 the reference potential) is applied.

Here, in the first field (1F) constituting one frame, the information is written in the pixel, for example, the voltage-transmittance characteristic as shown in FIG. 7 corresponding to the liquid crystal used. the potential V of the common electrode 42 of positive polarity source voltage (data signal voltage) (reference potential level V _x corresponding to the optical state or display information (transmittance) to be obtained
_c ) is applied. At this time, since the TFT 94 is in the ON state, the voltage V applied to the source electrode 27 is
_x is applied to the pixel electrode 95 via the drain electrode 28, and the liquid crystal capacitance (C _ls ) 31 and the storage capacitance (C _s ) 32 are charged, and the potential of the pixel electrode 95 becomes the information signal voltage V _x
become. Since TFT94 is a high resistance (off-state) in the non-selection period T _off of the gate line which the pixel belongs is followed, this non-selection period, the liquid crystal capacitance (C _lc) 31 and a storage capacitor (C _s) 32 maintaining the state in which the charge accumulated in the selection period T _on stored, the voltage V _x is maintained.
Then, the voltage V _x throughout the duration of the first field 1F to the liquid crystal layer 49 is applied in the pixel, the liquid crystal part of the pixel optical state corresponding to the voltage value (transmitted light quantity) is obtained.

Next, during the selection period T _{on of} the second field (2F), the source voltage (−V _x ) having the voltage value V _x having the opposite polarity and the same absolute value as the first field 1F is applied. The voltage is applied to the electrode 27. At this time, TFT 94 is on state, the voltage -V _x is applied to the pixel electrode 95, the liquid crystal capacitance (C _lc) 31 and a storage capacitor (C _s) 32 is charged, the potential of the pixel electrode 95 is the information signal It becomes the voltage -V _x.
Subsequently, during the non-selection period T _off , the TFT 94 has a high resistance (off state), so that the liquid crystal capacitance (C _lc ) 31 and the storage capacitance (C _s ) 32 have the selection period T during this non-selection period.
_The state where the charge charged in _on is accumulated is maintained, and the voltage-
V _x is maintained. Then, the liquid crystal layer 4 in the pixel
9 voltage -V _x through the second field 2F period is applied to, in the pixel optical state corresponding to the voltage value (transmitted light quantity) is obtained.

FIG. 14C shows the voltage value V _pix actually held in the liquid crystal capacitance and the storage capacitance of the pixel as described above and applied to the liquid crystal layer 49, and FIG. The actual optical response (optical response in the case of a transmissive liquid crystal element) is schematically shown. (C), the same level (absolute value) of only the applied voltage polarity is reversed each other through two fields 1F and 2F is a V _x. on the other hand,
(D), the the first field 1F, for example, gradation display state corresponding to V _x on the basis of the characteristics shown in FIG. 7 (amount of transmitted light) is obtained, the second field 2F, -V
Although the gradation display state corresponding to _x is obtained, in fact obtained only a slight change in amount of transmitted light according to the characteristics shown in FIG. 7, for example, less than the amount of transmitted light T _x, close to the zero level T becomes _y .

In the active matrix driving as described above, when a chiral smectic liquid crystal is used, gradation display based on good high-speed response is possible, and at the same time,
A case where the time aperture ratio is set to 50% or less by dividing a certain level of gradation display in one pixel into a first field for obtaining a high transmitted light amount and a second field for obtaining a low transmitted light amount and continuously performing the division. Similarly, the moving image high-speed response characteristics perceived by human eyes are improved. Further, in the second field, the transmitted light amount does not become completely zero due to a slight switching operation of the liquid crystal molecules, so that the luminance perceived by human eyes during the entire frame period is secured. In the present invention, since the first field is set to be longer than the second field, the time integration value of the amount of transmitted light is improved as compared with the case where the time aperture ratio is set to 50% or less. Bright display is realized. In addition, transmission type liquid crystal elements, etc.
When a light source is used, the illuminance of the light source can be reduced and power consumption can be reduced because the time integration value of the transmitted light amount is improved.

Furthermore, since the voltage of the same level is inverted and applied to the liquid crystal layer 49 in the first and second fields, the voltage actually applied to the liquid crystal layer 49 is converted into an alternating current,
Deterioration of the liquid crystal is prevented.

In the above-described active matrix driving, 2
In total one frame consisting of fields, the amount of transmitted light obtained by averaging the T _x and T _y is obtained. Therefore, the information signal voltage V
Regarding _s , image information (gradation information) to be obtained by the pixel in the actual frame in accordance with the characteristics shown in FIG.
In the first field 1F, the gradation state with a higher transmission light level than the desired gradation state is selected and applied by selecting and applying a voltage value capable of obtaining a transmission light amount larger by a predetermined level in accordance with. It is also preferable to display.

In the display element of the present invention, the period for displaying at the first luminance is set longer than the period for displaying at the second luminance. For example, in the above-described active matrix driving of the liquid crystal element, the first field 1F is set to be longer than the second field 2F. At this time, the first field period is F ₁ , the second field period is F ₂ , the voltage value of the first polarity applied to the liquid crystal layer in the first field is V ₁ , and the voltage value is applied to the liquid crystal layer in the second field. When the voltage value of the second polarity is V ₂ , in the present invention, F ₁ > F ₂ , and preferably, F ₁ × V ₁ = F ₂ × V ₂
And In this way, by setting the length of each period and the voltage value, the integrated value of the voltage applied in each field becomes the same, and the DC component applied to the liquid crystal layer becomes substantially zero, and Deterioration is minimized.

[0111]

EXAMPLES (Example 1) [Preparation of liquid crystal cell] An IT having a thickness of 700 mm was used as a transparent electrode.
A pair of glass substrates having an O film and having a thickness of 1.1 mm were prepared. On the transparent electrode of the substrate, the following repeating unit P
A polyimide precursor having Ia was applied by spin coating, and then pre-dried at 80 ° C. for 5 minutes, and then baked at 200 ° C. for 1 hour to obtain a polyimide film having a thickness of 200 °. .

[0112]

Embedded image

Subsequently, the polyimide film on the substrate was subjected to a rubbing treatment with a nylon cloth as a uniaxial orientation treatment. The conditions of the rubbing treatment were as follows: a rubbing roll in which nylon ("NF-77" manufactured by Teijin Limited) was bonded to a roll having a diameter of 10 cm, a pushing amount of 0.3 mm, a feed speed of 10 cm / s, a rotation speed of 1,000 rpm, and a feed frequency of 4 Times.

Next, as a spacer on one of the substrates,
Silica beads having an average particle size of 2.0 μm were scattered and opposed to each other so that the rubbing directions of the substrates were antiparallel to each other (anti-parallel) to obtain cells having a uniform cell gap (empty cells of a single pixel). .

[Preparation of Active Matrix Cell] An a-type cell using a transparent electrode and a polyimide alignment film of the same materials and conditions as in the above-described method of manufacturing a single pixel cell, and having a silicon nitride film as a gate insulating film on one substrate. An active matrix substrate having a SiTFT is used.
G and B color filters were provided to produce an active matrix cell (panel) having the pixel structure shown in FIG.
The screen size is 10.4 inches and the number of pixels is 800 x 600
X: RGB.

[Adjustment of Liquid Crystal Composition] A liquid crystal composition LC-1 was prepared by mixing the following liquid crystal compounds. The numerical values described in the structural formula are weight ratios at the time of mixing.

[0117]

Embedded image

The physical properties of the liquid crystal composition LC-1 are shown below.

[0119]

Embedded image

The liquid crystal composition LC-1 was injected at a temperature of an isotropic phase into the single pixel cell and the active matrix cell manufactured by the above process, and cooled to a temperature showing a chiral smectic liquid crystal phase. Before and after -SmC ^* phase transition, a cooling process was performed by applying an offset (direct current) voltage of -5 V to produce liquid crystal element samples A (single pixel) and B (active matrix type).
The following items were evaluated for the sample.

(1) Alignment state The alignment state of the liquid crystal of the device sample A was observed with a polarizing microscope. As a result, at room temperature (30 ° C.), the darkest axis was slightly deviated from the rubbing direction when no voltage was applied, and an almost uniform alignment state in which the layer normal direction was only one direction in the entire cell was observed. .

(2) Optical Response In order to measure the electro-optical response of the liquid crystal device, the cell of the device sample A was placed under a cross microscope with a polarizing microscope equipped with a photomultiplier. It was arranged so that it might become.

± 30 V at 30 ° C., 0.2 Hz
Observing the optical response when the triangular wave was applied, the amount of transmitted light (transmittance) gradually increased in accordance with the magnitude of the applied voltage when the voltage of the positive polarity was applied. On the other hand, the state of the optical response at the time of application of the voltage of the negative polarity is that although the amount of transmitted light changes with respect to the voltage level, the maximum transmittance is
When compared with the maximum transmittance when a positive voltage is applied, 1/1
It was about 0.

(3) Rectangular Wave Response With respect to the device sample A, the optical level was measured while applying a rectangular wave voltage of 60 Hz (± 5 V) and changing the voltage, using the same device as the triangular wave response.

As a result, it was confirmed that the optical response sufficiently responded to the voltage of the positive polarity, and the optical response did not depend on the previous state, and a stable halftone state was obtained. An optical response of about 1/10 of the case of applying a positive voltage having the same voltage absolute value to a negative voltage was confirmed, and the average value of the optical response to positive and negative voltages did not depend on the previous state. It was confirmed that a stable halftone was obtained.

The rise time (time when 90% of the transmittance when a voltage for obtaining a predetermined transmittance is applied to the liquid crystal in the darkest state) due to the application of the rectangular wave voltage having the positive polarity is obtained. The response speed in the fall time (time from the saturated transmittance state by applying a voltage for obtaining a predetermined halftone state to 10% of the saturated transmittance) is as follows when a high voltage (about 5 V) is applied. Are 0.7 ms and 0.3 respectively
ms, and 2.0 ms and 0.2 ms, respectively, when a low voltage (approximately 1 V) was applied, and high-speed response was confirmed as compared with switching using a general nematic liquid crystal.

(4-1) Actual driving / moving image quality evaluation A Moving image quality was evaluated using element sample B which is an active matrix panel using TFTs. This video quality evaluation was a subjective evaluation by about 10 non-experts, and was evaluated using the following five-point scale (category). As the images used for evaluation, three types (skin color chart, tourist information board, yacht harbor) were selected from BTA high-definition standard images (still images), and 432 × 168 pixels at the center of the three types were cut out and used.

Further, these images were moved at a constant speed of 6.8 (deg / s), which is about the general moving speed of a television program, to produce moving images, and the blurring of the images was evaluated.

Scale 5: Good moving image quality with no sharpness at the periphery of the screen and no sharpness Scale 4: Little blurring at the periphery of the screen Scale 3: The blur at the periphery of the screen is observed, and fine characters are discriminated. Difficult Scale 2: The peripheral blur of the screen is remarkable, and large characters are difficult to distinguish. Scale 1: Remarkable blur on the entire screen, and the original image is almost indistinguishable.

The output of the image source from the computer at this time was a picture rate such that 60 screens were sequentially scanned (progressive) per second.

First, as for the display on the TFT panel side (sample), 60 frames were displayed per second, and frame inversion driving was performed without dividing one frame into a plurality of fields. As a result, a slight blurring of the moving image quality was observed. Subjectively evaluating the degree of this peripheral blur, the above 5
It was about 3 to 4 on a graded scale.

Further, one frame is divided into two fields, a positive voltage is applied in the first field, and a negative voltage (the voltage level in both fields is the same) in the subsequent field, and the apparatus is operated substantially at a frequency of 120 Hz. If
Flicker was not observed at all, and moving image quality with almost no perceived blur was observed.

When this evaluation is carried out using a general CRT, all of the evaluations are 5 in a 5-level evaluation, and when a commercially available TFT type liquid crystal element which takes several tens of milliseconds is used, the evaluation is 2 to 5 in a 5-level evaluation.
The evaluation result was about 3.

At this time, the screen (maximum)
To keep the luminance 200 cd / m ^2, it was necessary to set the backlight brightness to 5130cd / m ² or more. This is because the aperture ratio of the panel of the element sample B is 7
This is because the effective transmittance of the liquid crystal element including the polarizing plate and the color filter was 5.5%, and the total transmittance was 3.9%. Here, the numerical value of “transmittance” means that the amount of incident light from the backlight incident on each member is 100%.
Means the ratio of the output light amount to the incident light amount.

The effective transmittance of the liquid crystal element portion is 5.5%: the transmittance of the polarizing plate alone is 39% in a paranicol state, the transmittance of the color filter portion is 29%, and the transmittance of the liquid crystal cell is 49%. (Based on a paranicol polarizer)
39 x 0.29 x 0.49 = 0.055.

Details of transmittance of liquid crystal cell portion: 90% of 1 in the first field (positive voltage application period) with high luminance
/ 2 (because the time is half of one frame), which is 1/2 of 8% in the subsequent second field (negative voltage application period), and is (90 × 1/2) + (8 × 1/2) ) = 49
(%).

(4-2) Actual driving / moving image quality evaluation B Next, one frame is divided into two fields with a time ratio of 2: 1 and driven at substantially 120 Hz (pulse width is 11.1). 1 ms and 5.6 ms), positive voltage of 0 to 6 V in the first field, 0 to 1 in the subsequent field
2V negative polarity voltage (voltage level in both fields is 1: 2
), A flicker was not observed at all, and a moving image in which no peripheral blur was felt was observed, and an ideal moving image was obtained. In the above five-grade evaluation, the rating was 4.

At this time, the screen (maximum)
The backlight brightness to maintain the luminance 200 cd / m ² can be reduced to 4000 cd / m ^2, was power consumption can be reduced by 22%. This is because the aperture ratio of the panel of the device sample B is 70%, the effective transmittance of the liquid crystal device portion including the polarizing plate and the color filter is 7.1%,
This is because the total transmittance was 5.0%.

The effective transmittance of the liquid crystal element portion is 7.1%: the transmittance of the polarizing plate alone is 39% in a paranicol state, the transmittance of the color filter portion alone is 29%, and the transmittance of the liquid crystal cell is 63%. (Based on a paranicol polarizer)
39 x 0.29 x 0.63 = 0.071.

Details of transmittance of liquid crystal cell portion: 90% of the first field (positive voltage application period) with high luminance
/ 3 (because the time ratio in one frame is 2: 1),
In the subsequent second field (negative voltage application period), it is 1/3 of 8%, and (90 × 2/3) + (8 × １ ／) = 6
3 (%).

[0141]

As described in detail above, according to the present invention,
A bright and high-quality display device for displaying moving images can be obtained, and furthermore, a liquid crystal device capable of displaying practical brightness, high-speed response, and gradation can be obtained.Especially, in a chiral smectic liquid crystal device, a complicated circuit is required. There is provided a highly durable liquid crystal element capable of improving moving image quality without using the same and at the same time preventing deterioration of liquid crystal and displaying good moving image quality for a long period of time. In a transmissive liquid crystal element, power consumption can be reduced by reducing the illuminance of a backlight light source.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing liquid crystal molecules and a liquid crystal layer structure in a liquid crystal alignment state in an SSFLC type liquid crystal element.

FIG. 2 is a schematic diagram showing projection of liquid crystal molecules onto a virtual cone bottom surface in the liquid crystal alignment state of FIG.

FIG. 3 is a schematic diagram showing an alignment state in each liquid crystal phase of an embodiment of an SSFLC type liquid crystal element and a liquid crystal element of the present invention.

FIG. 4 is a schematic view showing an alignment state in a chiral smectic liquid crystal phase in one embodiment of the liquid crystal element of the present invention.

FIG. 5 is a schematic diagram showing an orientation state in a chiral smectic C phase.

FIG. 6 is a schematic diagram showing the inversion behavior of liquid crystal molecules by applying a voltage in a chiral smectic liquid crystal phase in one embodiment of the liquid crystal device of the present invention.

FIG. 7 is a diagram showing an example of a voltage-transmittance characteristic in the liquid crystal element of the present invention.

FIG. 8 is a schematic diagram showing a potential state in a bistable orientation state in SSFLC.

FIG. 9 is a schematic diagram showing a potential state in an alignment state in the liquid crystal element of the present invention.

FIG. 10 is a cross-sectional view schematically showing the structure of one pixel of one embodiment of the liquid crystal element of the present invention.

FIG. 11 is a schematic plan view showing a configuration example when the liquid crystal element of the present invention is applied to an active matrix type.

FIG. 12 is a schematic cross-sectional view showing a configuration example of one pixel when the liquid crystal element of the present invention is applied to an active matrix type.

FIG. 13 is a diagram showing an equivalent circuit of the element structure shown in FIG.

FIG. 14 is a diagram showing an example of a driving waveform and an optical response when the liquid crystal element of the present invention is driven in an active matrix.

[Explanation of symbols]

11, 12 Substrate 13 Liquid crystal 14, 14a, 14b Liquid crystal molecule 15 Cone 16 Smectic layer 17 Cone bottom 18, 18a, 18b Projection of liquid crystal molecule to virtual cone bottom 19 Spontaneous polarization 20 Active matrix substrate 21 Substrate 22 Gate electrode 23 Gate insulation Film 24 semiconductor layer 25, 26 ohmic contact layer 27 source electrode 28 drain electrode 29 channel protective film 30 storage capacitor electrode 31 liquid crystal capacitor 32 storage capacitor 40 counter substrate 41 substrate 42 common electrode 43a, 43b alignment film 49 liquid crystal layer 50 spontaneous polarization 80 Liquid crystal element 81a, 81b Substrate 82a, 82b Electrode 83a, 83b Insulating film 84a, 84b Alignment film 85 Liquid crystal layer 86 Spacer 90 Panel 91 Scanning signal driver 92 Information signal driver 94 TFT 95 Pixel electrode

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Kadoba 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Makoto Mori 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Canon Inc. (72) Inventor Takashi Moriyama 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term within Canon Inc. (reference) 2H093 NA16 NA53 NA55 NC34 ND06 NF17 NH11 5C080 AA10 BB05 DD02 DD03 DD08 EE19 EE29 FF11 GG12 JJ02 JJ03 JJ05 JJ06

Claims (17)

[Claims] 1. A display element for displaying an image by individually controlling a plurality of pixels, wherein one frame is divided into at least two fields, and a first field corresponding to display information for each pixel in a first field. An image is displayed at the luminance, and the same image as the image displayed in the first field at the second luminance which is smaller than the first luminance at a fixed rate for each pixel in the remaining fields of one frame. Wherein the period for displaying at the first luminance is set longer than the period for displaying at the second luminance. 2. The display device according to claim 1, wherein the second luminance is equal to or less than 1/5 of the first luminance. 3. A liquid crystal element for displaying an image by controlling a plurality of pixels individually, wherein a uniaxial alignment treatment is applied to an interface between a liquid crystal and at least one of the liquid crystals to face the liquid crystal. A liquid crystal element including a pair of substrates, an electrode for driving liquid crystal for each pixel, and a polarizing plate disposed outside at least one substrate, wherein one frame is divided into at least two fields, In the field, an image is displayed at the first luminance according to the display information for each pixel, and 1
In the remaining fields of the frame, the same image as the image displayed in the first field is displayed at a second luminance smaller than the first luminance at a fixed rate for each pixel, and the first image is displayed. A liquid crystal element, wherein a period for displaying at the luminance is set longer than a period for displaying at the second luminance. 4. The liquid crystal device according to claim 3, wherein the second luminance is equal to or less than 1/5 of the first luminance. 5. The liquid crystal of each pixel is optically modulated so as to have a first transmittance in the first field, and the liquid crystal of each pixel has a first transmittance in a field displaying at a second luminance. 4. The liquid crystal device according to claim 3, wherein optical modulation is performed such that the second transmittance is lower at a fixed rate than the second transmittance. 6. The second transmittance is 1/1 of the first transmittance.
The liquid crystal element according to claim 5, wherein the number is 5 or less. 7. The liquid crystal is a chiral smectic liquid crystal, shows a first state in which the average molecular axis of the liquid crystal is monostable when no voltage is applied, and when the voltage of the first polarity is applied, the liquid crystal is a chiral smectic liquid crystal. The average molecular axis tilts from the first state to one side at an angle corresponding to the applied voltage value, and when a voltage having a second polarity opposite to the first polarity is applied, the average molecular axis of the liquid crystal is Is tilted from the first state at an angle corresponding to the applied voltage value to the side opposite to the side tilted when the voltage of the first polarity is applied, and when the voltage of the first polarity is applied and when the second polarity is applied. 7. The liquid crystal device according to claim 5, wherein tilt angles from the first state in the maximum tilt state of the average molecular axis of each liquid crystal when a voltage is applied are different from each other. 8. In the first field, the liquid crystal of each pixel is tilted from the first state at an angle corresponding to the voltage value by applying a first polarity voltage having a value corresponding to display information. Exhibiting a first transmittance, and in the remaining fields of the first frame, the liquid crystal of each pixel is driven by applying a second polarity voltage having a value corresponding to display information at an angle corresponding to the voltage value. From the state, tilted to the side opposite to the side that was tilted when the voltage of the first polarity was applied, and exhibited a second transmittance,
The liquid crystal of each pixel exhibits a third transmittance in the first state,
8. The liquid crystal device according to claim 7, wherein gradation display is performed by continuously changing the transmittance between the maximum value of the first transmittance and the third transmittance. 9. The liquid crystal device according to claim 8, wherein the third transmittance is a minimum transmittance that can be displayed by the liquid crystal device, and a maximum value of the first transmittance is a maximum transmittance. 10. The difference between the maximum value of the second transmittance and the third transmittance is １ ／ or less of the difference between the maximum value of the first transmittance and the third transmittance. Item 10. A liquid crystal device according to item 9. 11. The voltage value of the first polarity is higher than a voltage value according to display information, and a liquid crystal of a pixel to which the voltage value is applied has a transmittance higher than a transmittance according to display information. The liquid crystal device according to any one of claims 8 to 10, which is provided. 12. The phase transition series of the chiral smectic liquid crystal is an isotropic phase-cholesteric phase-chiral smectic C phase or an isotropic phase-chiral smectic C phase from a high temperature side, and the smectic phase of the liquid crystal in the device. The liquid crystal element according to claim 7, wherein a normal direction of the layer is one direction. 13. The liquid crystal device according to claim 7, wherein a helical pitch of the chiral smectic liquid crystal in a bulk state is longer than twice a cell thickness. 14. A period F ₁ for displaying at the first transmittance.
And a voltage value V ₁ of the first polarity applied to the liquid crystal during the period,
And, the relationship between the period F ₂ and said period a second voltage value -V ₂ of polarity applied to the liquid crystal between the display at a second transmission rate, F ₁
> Is F _2, and a liquid crystal device according to any one of claims 8 to 13 is _{F 1 × V 1 = F 2} × V 2. 15. The liquid crystal element includes a pixel electrode and an active element for each pixel, and performs analog gray scale display.
15. The liquid crystal element according to any one of items 14 to 14. 16. A liquid crystal device of a transmission type.
A liquid crystal element according to any one of the above. 17. A reflection type liquid crystal element.
A liquid crystal element according to any one of the above.