JP2000275617A - Liquid crystal element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a liquid crystal element which is provided with practical brightness, fast response, besides a controllable gray scale and improved dynamic image quality without using a complicated circuit. SOLUTION: A chiral smectic liquid crystal, which exhibits a phase transition sequence of an isotropic phase - a cholesteric phase - a chiral smectic phase corresponding to lowering of the temperature, is held between a pair of substrates at least one of which is subjected to uniaxial alignment treatment and is aligned so as to exhibit a monostabilized state under application of a voltage and under application of another voltage with the second polarity and to exhibit the first transmissivity caused by tilting of the liquid crystal molecules under application of another voltage with the first polarity. An element is attained which has specified hysteresis characteristics or a specified ion quantity and which displays a gray scale between the transmissivity exhibited in the monostabilized state and the maximum value of the first transmissivity by dividing a frame period into one voltage application period with the first polarity and the other voltage application period with the second polarity which is shorter than the former one.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates 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. Furthermore, an element in which an active element is combined with a liquid crystal exhibiting a chiral smectic C phase has been proposed (Japanese Patent Laid-Open No. 4-212126).

On the other hand, recently, an antiferroelectric liquid crystal (thresholdless antiferroelectric liquid crystal) and an active element are combined,
Devices that exhibit a V-shaped voltage-transmittance characteristic have attracted 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. Recent research has shown that no response characteristics can be obtained (Religion Technique EID96-4p.
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 a 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 above-described chiral smectic liquid crystal device having a high response speed. In order to realize good moving image display at a high speed by using the method described above, there is a problem that a driving method and peripheral circuits are complicated, which has caused a cost increase.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a liquid crystal device using a liquid crystal exhibiting a chiral smectic phase (chiral smectic liquid crystal), which has a high speed response and It is an object of the present invention to provide an inexpensive liquid crystal element capable of gradation control and having improved moving image quality without using a complicated circuit. Also, the present invention
An object is to reduce power consumption of a liquid crystal element.

[0010]

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

The first liquid crystal element of the present invention is a liquid crystal element for displaying an image by individually controlling a plurality of pixels, and comprises a chiral smectic liquid crystal, a liquid crystal element sandwiching the liquid crystal, and at least one liquid crystal. A liquid crystal element comprising a pair of substrates having a uniaxial orientation treatment applied to an interface thereof, an electrode for driving liquid crystal for each pixel, and a polarizing plate disposed outside at least one of the substrates, and when no voltage is applied. Shows the first state in which the average molecular axis of the liquid crystal is monostable, and when a voltage of the first polarity is applied, the average molecular axis of the liquid crystal is shifted from the first state at an angle corresponding to the applied voltage value. Tilt to one side,
When a voltage having a second polarity opposite to the first polarity is applied, the average molecular axis of the liquid crystal maintains the monostable first state, and the minimum transmittance of the element is 0% and the maximum transmittance is 0%. Assuming that the transmittance is 100%, in the voltage-transmittance curve when the triangular wave is applied, the following γ when the voltage of the first polarity is applied:
If the value is 3 or more, the following hysteresis parameter value T
_diff [%] is 50% or less, and γ = _V95% / V5 _% V5 _% : A voltage applied to a liquid crystal having a transmittance of 0% to reach a transmittance of 5% _V95% : A transmittance is increased 95% transmittance when applied to 0% liquid crystal
Voltage _{T diff = T d -T u T} u [%] to reach: below V _u and V transmittance when the transmittance is applied to the liquid crystal of 0% the average voltage of _d T _d [%]: below V _u the average voltage of V _d is the transmittance of 100
% Transmission V _u when applied to the liquid crystal of: voltage-transmittance transmittance is applied to the liquid crystal of 0% reaches 50% V _d: transmittance transmittance is applied to 100% liquid of 50
% One frame is divided into at least two fields,
In the first field, an image is displayed by applying a voltage of the first polarity of a value corresponding to the display information for each pixel, and in the remaining field of one frame, a voltage of the second polarity is applied to each pixel. The period in which the voltage of the first polarity is applied is set longer than the period in which the voltage of the second polarity is applied.

A second liquid crystal element according to the present invention is a liquid crystal element for displaying an image by individually controlling a plurality of pixels, and comprises a chiral smectic liquid crystal and at least one liquid crystal which sandwiches and opposes the liquid crystal. A pair of substrates that have been subjected to a uniaxial orientation treatment at the interface with the electrodes, an electrode that drives liquid crystal for each pixel,
An active element for controlling a voltage applied to each pixel,
A polarizer disposed outside at least one of the substrates, the liquid crystal element performing analog gray scale display by active matrix driving, and when no voltage is applied, a first molecule in which the average molecular axis of the liquid crystal is monostable. When a voltage of the first polarity 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 is opposite to the first polarity. When a voltage of the second polarity is applied, the average molecular axis of the liquid crystal maintains the monostable first state, and the volume resistance of the liquid crystal is 5 × 1.
0 ¹¹ Ωcm or more, and spontaneous polarization Ps [nC / cm ² ]
And the internal ion rearrangement Q _t during the selection period of one pixel
[NC / cm ² ] has a relationship of 2Ps + Q _t ≦ 30 [nC / cm ² ], one frame is divided into at least two fields, and the first value of the value corresponding to the display information for each pixel in the first field An image is displayed by applying a voltage of the second polarity, and in the remaining field of one frame, a voltage of the second polarity is applied to each pixel, and the period of applying the voltage of the first polarity is the second period. Is set longer than the period of applying the voltage having the polarity of.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The alignment state and switching process of a chiral smectic liquid crystal in a liquid crystal device of the present invention will be described below 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, 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 property 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 C1 and C2 orientation states 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 a device using a 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 (the horizontal arrow LN in the drawing) coincides with the direction of the uniaxial alignment treatment in the SmA phase. 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 along the average uniaxial alignment processing direction R to form a smectic layer structure. That is, the layer normal direction L
N is formed in a direction shifted from the average uniaxial orientation processing direction R. In particular, the present invention is adjusted so that the liquid crystal molecules 14 are stabilized at the position of the edge of the virtual cone 15 in the temperature range within the SmC ^* phase.

In each of FIGS. 3A and 3B,
For example, the liquid crystal molecules 14 as shown in FIGS. 1 and 2 should be stable in a bistable alignment state of a chevron structure, that is, in two states substantially parallel to the substrate. In the case shown in FIG. The binding force of the uniaxial orientation treatment becomes stronger, and only one of the two states becomes stable (monostable), and the memory property is lost.

Hereinafter, this mono-stabilization phenomenon will be specifically described. In the liquid crystal material exhibiting the Ch-SmC ^* phase transition series, the layer normal direction and the uniaxial alignment processing direction are misaligned as described above. Accordingly, when two molecular positions where the liquid crystal molecules are on the cone and parallel to the substrate surface in the SmC ^* phase are respectively U1 and U2, the angle formed by one of the molecular positions with the uniaxial alignment processing direction is Smaller is more stable, and the bistability is broken.

However, assuming that the intensity of the uniaxial orientation treatment is infinitely close to zero, irrespective of the angle between the uniaxial orientation treatment direction and the layer normal direction, U1 and U1
No difference in the stability (potential) of No. 2 should be seen (FIG. 4 (a)). Therefore, even if a material exhibiting the Ch-SmC ^* phase transition series is used, a device having bistability can be realized.

Next, when the uniaxial orientation treatment is performed but the strength is not sufficient (FIG. 4B), U1 and U2
, A difference occurs in the potential, and the bistability is lost. However, in the state of FIG. 4B, one of the bistable states is stable, but the other state also exists as a metastable alignment state. In such an orientation state, for example, the hysteresis is very large at the time of triangular wave response, a steep threshold characteristic is observed, and bistability is re-expressed by applying a certain DC bias electrically. A phenomenon is observed. In other words, in such an element that does not realize sufficient monostability, it is considered that continuous tone control using an active matrix may be difficult. On the other hand, as shown in FIG. , There is no metastable state,
This makes it possible to achieve complete monostable, and the continuous tone control characteristics are greatly improved.

The height of the bistable energy barrier in FIG. 4A is considered to change depending on the liquid crystal material characteristics and the cell configuration. That is, qualitatively, it is assumed that the height of the energy barrier changes depending on the amount of anti-electric field generated by the liquid crystal element itself. Therefore, in order to design a liquid crystal element such that a metastable state does not exist, it is desirable to previously set the height of the energy barrier low by designing a cell so as to increase the amount of internal counter electric field. For example, it is desirable to provide a polyimide alignment film having sufficiently high insulation properties on both the upper and lower substrates as the alignment film.

At the time of the Ch-SmC ^* phase transition shown in FIG. 3B, as shown in FIG. 5, two different layer normal directions (L
It is considered that a smectic layer structure showing N ₁ and LN ₂ ) is formed. At this time, if the uniaxial alignment state (conditions such as processing direction, alignment material, etc.) of the pair of upper and lower substrates of the cell holding the chiral smectic liquid crystal is completely symmetric, the two smectic layers as shown in FIG. The structures are formed in even proportions.

In the liquid crystal device of the present invention, first, an appropriate liquid crystal material is used, a cell design is prepared, and further, the inside of the cell is changed during the Ch-SmC ^* phase transition or the Iso-SmC ^* phase transition of the liquid crystal material. By performing a process for giving a bias to the potential, only one of the two layer structures shown in FIG. 5 is aligned, that is, the deviation direction between the average uniaxially oriented axis and the normal direction of the smectic layer is constant. As a result, the liquid crystal molecules 14 are mono-stabilized to one edge of the virtual cone 15 to obtain an SmC ^* phase alignment state in which the memory property is lost. The method of imparting the bias of the internal potential is as follows ^: 1) At the time of 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. Although various methods are conceivable, any of them may be used.

In particular, as a 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.

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. The behavior will be described with reference to FIGS. FIG. 6 shows a model of the behavior of liquid crystal molecules in the virtual cone 15 of the liquid crystal due to voltage application, and FIG. 7 shows the orientation state of the liquid crystal in the cell when viewed from the top of the cell and when viewed from the side. In this case, the model when viewed from the projection on the bottom surface of the virtual cone is shown.

When no voltage is applied as shown in FIG. 6B, the liquid crystal molecules 14 are substantially along the average uniaxial alignment processing direction (arrow R), and the virtual cones 15 in which the liquid crystal molecules switch by applying a voltage. Stably arranged at one end (edge) side. In the case where the liquid crystal molecules 14 are in a state of being monostable at the edge of the virtual cone 15, the smectic layer structure is substantially a bookshelf structure (layer tilt angle δ is 3 ° or less) and the pretilt angle of the liquid crystal molecules 14 is Is extremely small (the orientation state shown in FIG. 7A) or when the smectic layer structure is an oblique bookshelf structure and the layer inclination angle δ substantially matches the pretilt angle (FIG. 7A).
(The orientation state shown in (b)).

Here, the cells are arranged under crossed Nicols (FIG. 6 (d)) in which one of the polarization axes (P) coincides with the uniaxial alignment processing direction R, and the amount of light passing through the liquid crystal is kept in the minimum state (minimum transmission). Ratio) to display a dark state (black state). In the present invention, when a voltage of the second polarity is applied to the liquid crystal, the transmittance in the state where no voltage is applied is the first transmittance, and when the voltage of the first polarity is applied to the liquid crystal, Is the second transmittance. In the present invention, “transmittance” indicates “light transmittance”.

When, for example, the refractive index anisotropy Δn of the liquid crystal and the cell thickness are d and Δnd is set in the vicinity of half the wavelength of visible light, the alignment state as shown in FIG. On the other hand, when a voltage of the first polarity (positive in the case of FIG. 6) is applied, as shown in FIG. 6C, the liquid crystal molecules 14 move according to the polarity of the voltage with respect to the position where no voltage is applied. Tilt (switch). The tilt angle depends on the magnitude of the applied voltage. On the other hand, a second polarity opposite to the first polarity (in the case of FIG. 6, negative polarity)
Is applied, the liquid crystal molecules 14 remain at the same position as when no voltage is applied. Thus, when a voltage of the first polarity (positive polarity) is applied, as the absolute value of the voltage increases, the transmittance of the liquid crystal in the cell increases, and the amount of light transmitted through the liquid crystal changes to increase. When the liquid crystal molecules 14 are tilted to a predetermined position in the virtual cone 15 (the maximum value of the second transmittance), a maximum transmitted light amount most different from the transmitted light amount when no voltage is applied is obtained. Can be When a negative voltage is applied, the transmittance of the liquid crystal does not change (the first transmittance remains), and the amount of light transmitted through the liquid crystal is maintained at the minimum.

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 maximum tilt state of the liquid crystal molecules 14 when a positive voltage is applied The tilt angle is 45
When the angle is smaller than °, the liquid crystal molecules 14
, That is, in the maximum tilt state, the maximum transmitted light amount when the positive voltage is applied can be obtained. On the other hand, when the tilt angle is 45 ° or more, when the liquid crystal molecules 14 are inside the edge of the imaginary cone 15, the maximum amount of transmitted light when a positive voltage is applied is obtained.

An example of the voltage (V) -transmittance (T) characteristic of an element exhibiting the switching behavior of liquid crystal molecules as described above, particularly, the maximum transmission when the liquid crystal molecules are in a maximum tilt state when a positive voltage is applied. FIG. 8 shows the characteristics of the element when the ratio can be obtained.
Shown in When a positive polarity voltage is applied, the transmittance (second 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 do not tilt regardless of the voltage value (absolute value), and the transmittance is 0 (first transmittance) as in the case where no voltage is applied even at −V _1. It is.

The alignment state as shown in FIGS. 6 and 7 and the characteristic 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. 8). 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. 8). The same effect can be obtained as in the method of performing the above. Thus, a liquid crystal element with improved moving image quality can be realized without using complicated peripheral circuits and the like.

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 alignment state of the liquid crystal molecules in the SSFLC shown in FIGS. 1 and 2, in order for the liquid crystal molecules 14 to switch between the 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. 6, for example, the liquid crystal molecules 14 are extremely stabilized at a position near 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. 9 and 10 show models of the state of the energy barrier (potential).

FIGS. 9A and 9B 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. 10A and 10B 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). Show.

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. I will. In particular, in the C1 orientation state having a high energy barrier, as shown in FIG. 10A, 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). As a result, when responding by applying a voltage,
Until a certain potential is reached, a stable state corresponding to the magnitude of the applied voltage exists in an analog manner, and the applied voltage and the stable molecular position correspond one-to-one, so it is continuous and does not involve domain generation. Although inversion can be achieved,
When a certain potential is exceeded, a discontinuous orientation state may be formed, that is, a discontinuous inversion behavior accompanied by generation of a domain wall may occur.

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. 10B, one (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.

As described above, the alignment state in the liquid crystal element of the present invention is determined in the parallel rubbed cell from the viewpoint of analog gray scale performance and low driving voltage.
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.

In the liquid crystal device of the present invention, when a voltage-transmittance curve at the time of applying a triangular wave is obtained, there may be a slight hysteresis. However, in the case of driving with an AC waveform as in the case of an element having an actual TFT, the optical modulation is not continuously performed from the white state to the halftone state as in the case of applying a triangular wave. No problem. That is, according to the characteristics shown in FIG. 8, 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 halftone, the white state is changed. After passing through the black alignment state, the light is modulated into the halftone alignment state, so that when alternating current is applied, the drive is always reset to the black side with one polarity and then writing is performed. In principle, it is hardly affected by the state history.

In the first liquid crystal device of the present invention, the hysteresis parameter value T _diff and the γ value in the triangular wave response are set to specific levels. These hysteresis parameter values and γ values are defined below.

When no voltage is applied, a triangular wave is applied to a transmission type element in which the amount of transmitted light is 0, that is, the first transmittance is the minimum transmittance of the element, and the minimum transmittance is 0% and the maximum transmittance is 10%.
When a graph is drawn with the applied voltage on the horizontal axis and the transmittance on the vertical axis assuming 0%, as shown in FIG. 16, there is no optical response to the electric field of one polarity, and the other polarity. Optical response only to the electric field of At this time, two curves are drawn: a curve drawn when changing from low voltage to high voltage (rising curve) and a curve drawn when changing from high voltage to low voltage (falling curve). General. Depending on the conditions, the two may completely overlap and become one.

In the present invention, the γ value is the transmittance at the time when the amount of light is maximum in the rising curve (the maximum value of the second transmittance).
Is set to 100%, a voltage at which the transmittance reaches 5% when applied to a liquid crystal having a transmittance of 0% is V _5% , and a voltage at which the transmittance is 95% is applied to a liquid crystal having a transmittance of 0%. The voltage is defined as V _95%, and γ = V _95% / V _5% is defined. The γ value is 1 or more. However, as the γ value approaches 1, the threshold characteristics become steeper and the gradation control becomes more difficult. Conversely, if this value is sufficiently larger than 1, element characteristics excellent in gradation controllability can be obtained. In the first liquid crystal element of the present invention, the value of γ is set to 3 or more to enable stable gradation control.

When the liquid crystal having a transmittance of 0% is applied to the rising edge of the triangular wave response polarity, the transmittance becomes 50%.
% At V _u , and a transmittance of 1 at the time of falling.
The voltage at which the transmittance becomes 50% when applied to 00% liquid crystal is V
_d, and two transmittances _Tu [%], T that can be obtained when a voltage of the average value (V _u + V _d ) / 2 is applied.
The difference T _diff [%] of _d [%] is defined as a hysteresis parameter in the present invention.

With respect to the hysteresis, as described above, the influence at the time of actual driving does not need to be considered in principle, but T _diff [%] becomes a large value exceeding about 50%. In this case, the history of the previous state may affect actual driving. It is presumed that this is because when T _diff [%] is large, potential bistable element characteristics appear and the previous state history remains even after black reset. Therefore, also in the first liquid crystal element of the present invention, the hysteresis parameter T _diff [%] is evaluated as an index of monostability, and is set to 50% or less.

Next, the second liquid crystal device of the present invention will be described. The second liquid crystal element of the present invention is an active matrix liquid crystal element, in which the spontaneous polarization value and the allowable value of internal ions are set to specific levels. This point will be described below. In this description, the response of the liquid crystal and internal ions is sufficiently slow as compared with the gate-on period.
That is, since the reversal of spontaneous polarization and the movement of internal ions during the gate-on period are slight, the problem is described as a problem within the retention time after the gate-on period (the most severe condition setting).

[0057] Since the capacitance C _s is the active matrix cell, commonly referred to as storage capacitor (storage capacitance) is given to be in parallel to the liquid crystal capacitance C _lc, upon applying a driving voltage V _op is the liquid crystal element The charge of Q = V _op × (C _lc + C _s ) is injected as the charge Q into the. Next, after charge injection, the inversion of spontaneous polarization and the rearrangement of internal ions, that is, ions move in the cell by the voltage applied to the liquid crystal layer, and are reconstructed into a new ion distribution in the cell thickness direction. The phenomenon occurs.

[0058] Since the movement of the charge is reversed component of spontaneous polarization 2 × Ps, relocation of the internal ion is Q _t,
The charge of “2 × Ps + Q _t ” moves.

Note that the value of Ps here is a value of spontaneous polarization that has contributed to the change in the liquid crystal alignment, and may be different from the Ps value in the physical property values of the liquid crystal material. That is, if a liquid crystal molecule is 5% in the cell in order to obtain a 50% transmittance.
Assuming that it is inverted by 0%, the spontaneous polarization value that contributed to the transfer of the internal charge is 50% of the Ps value (Ps ₀ ) in the physical property value of the liquid crystal material. However, when a voltage equal to or higher than the saturation voltage is applied and all the liquid crystal molecules are switched, the Ps value becomes equal to Ps _0, and thus the Ps value may be considered as the Ps value of the liquid material properties.

[0060] On the other hand, the relocation component Q _t of the internal ion exactly is the partial involved in the actual driving condition (voltage and frequency).

When the resistance value of the liquid crystal is low, the charge amount Q _reset remaining in the cell is reduced even by the charge flowing through the ohmic resistance component. In assuming that the TFT is actually driven at 60 Hz, one frame period is one time.
In order to reduce the voltage decrease due to the ohmic resistance component to 10% or less during this period, the volume resistance of the liquid crystal should be 5 × 10 ¹¹ Ωcm or more (the actual liquid crystal resistance in a 2 μm thick cell). Is 1.0 × 10 ⁸ Ω (the dielectric constant ε of the liquid crystal is 3.5 to 7, the cell thickness is 1 to 2 μm, and the capacitance of the liquid crystal layer is 1.5 to 6.2 [nF / cm ² ]
From the CR time constant).

On the other hand, if the above conditions are satisfied, the voltage drop is dominated by other factors described below. Hereinafter, a voltage drop due to factors other than the ohmic resistance component will be described.

After the completion of switching and the rearrangement of internal ions, the charge amount Q _reset remaining in the cell is represented by Q
_{reset = V op × (C lc} + C s) - a _{(2 × Ps + Q t)} . Then, the value V _{reset of the} internal voltage is determined from the residual charge amount represented by the above equation, and the voltage holding ratio HVR is determined by the ratio of this value to the applied voltage V _op . _{That, HVR = V reset / V op} = [{V op × (C lc + C s) - (2 × Ps + Q t)} / (C lc + C s)] / V op = 1- (2 × Ps + Q t) / {V _op × (C _lc + C _s )}.

As a general liquid crystal display, 60H
Matrix drive of z drive (16.7 m for one frame period)
s), the dielectric constant ε of the liquid crystal is 3 to 6, and the cell thickness is 1 to
When the thickness is 2 μm, the capacitance of the liquid crystal layer is 1.3 to 5.3 [nF /
cm ² ], and the maximum drive voltage is 5 V. At this time, the maximum value of “Q _t ” in the above equation is Q _t measured in a pulse of 5 V and 16.7 ms. Here, assuming XGA~SXGA panels 10-20 inch, in order to secure the aperture ratio above a certain level, the storage capacitor C _s is required to be within 5 times the capacity C _lc of the liquid crystal layer.

If the preferable value of the voltage holding ratio is 50% or more, “2 × Ps + Q _t ” in the above equation is 30 [nC / c
m ² ]. If the voltage holding ratio is more preferably 80% or more, “2 × Ps + Q
_t ”needs to be 12 [nC / cm ² ] or less. In addition, V _op within the gate-on period (when the XGA to SXGA panel is assumed, the gate-on period is a minimum of 16.3 μs).
× (C _lc + C _s ) to complete the charge injection.
It is necessary to set the mobility value of T.

As described above, the condition of the ion amount, particularly the value of “2 × Ps + Q _t ” is set to 30 [nC / cm ² ].
In the following, it is necessary to appropriately select a liquid crystal material and an alignment film material in order to reduce the concentration to preferably 12 [nC / cm ² ] or less, and to perform purification and the like as necessary.

The present inventors have paid special attention to the content ratio of the compound having an ester skeleton in the liquid crystal composition.
If but less 50%, 5V, can be an effective Q _t measured in the pulse of 16.7ms to 30 [nC / cm ^2] or less, the content ratio of more ester skeleton Compound 2
If less 0%, were obtained 5V, the result of the effective Q _t measured in the pulse of 16.7ms can be 12 [nC / cm ^2] or less.

Here, since the magnitude of Ps can be set almost freely (in the range of 0 to several tens) by changing the ratio of the chiral component, it is assumed that Ps is close to the minimum value 0. did.

Incidentally, Japanese Patent Publication No. 6-105332 discloses that
Using a liquid crystal material having a Ch-SmC ^* phase transition series,
It is disclosed that AC driving is performed for a liquid crystal element that can be in a monostable state when no voltage is applied. However, in the liquid crystal element described in the publication, when looking at the applied voltage-transmitted light intensity, there is a voltage range having a memory state,
The hysteresis is large, and the manner in which the transmittance rises with an increase in the applied voltage substantially has a threshold value. Because of the steepness, stable gradation control cannot be performed even by using active matrix driving. Further, in the device described in this publication, an ester-based compound is used as a liquid crystal material as a main component, it is difficult to remove impurities in the liquid crystal material, and the liquid crystal purity cannot be sufficiently increased. Is not suitable for the drive from the viewpoint that the voltage holding ratio cannot be secured.

The combination of the first liquid crystal element and the second liquid crystal element of the present invention is also preferably applied.

Hereinafter, an embodiment of the liquid crystal device of the present invention will be described with reference to FIG. FIG. 11 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 includes a pair of substrates 81a and 81 made of a highly transparent material such as glass and plastic.
A chiral smectic liquid crystal layer 85 is sandwiched between 1b.

Each of the substrates 81a and 81b has an In for applying a voltage to the chiral smectic liquid crystal layer 85.
Electrodes 82a and 82b made of a material such as ₂ O ₃ and ITO are provided. In the case of a simple matrix type (in the case of the first liquid crystal element of the present invention), 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 (the preferred embodiment of the first liquid crystal element of the present invention and the second liquid crystal element of the present invention), pixel electrodes are arranged in a dot pattern on one substrate for each pixel, and each pixel electrode TFT and 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, alignment films 84a and 84b which are in contact with the liquid crystal layer 85 and function to control the alignment state are provided on the insulating films 83a and 83b. 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 a pretilt angle of the liquid crystal molecules of the liquid crystal layer 85 (a film surface near the orientation film of the liquid crystal molecules) depending on the selection of the material and the conditions of the treatment (uniaxial orientation treatment or the like). (The angle made with respect to).

When the orientation films 84a and 84b are both uniaxially oriented films, the uniaxial orientation direction (especially the rubbing direction) of each film may be parallel, anti-parallel, or parallel depending on the liquid crystal material used. Alternatively, it can be set to cross in a range of 45 ° or less.

As an alignment film, an organic film is used on at least one of the substrates, and the retardation value is
Since it is considered that the organic alignment film is sufficiently stretched as the origin of the uniaxial alignment control, the size is preferably 0.05 nm or more.

In the liquid crystal device of the present invention, it is necessary that the uniaxial alignment regulating force be sufficiently large in order to stabilize the 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 Crystal).
s, 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 case where the Ch phase exists in the liquid crystal element of the present invention, the cholesteric pitch in the Ch phase is p and the cell thickness is d _{g. In the} absence of the alignment regulating 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 and the like), the alignment film thickness, the alignment film type, the firing conditions, and the like in consideration of these values.

Further, in the liquid crystal device of the present invention, it is sufficient that the uniaxial alignment treatment is applied to the interface between at least one of the pair of substrates and the liquid crystal, and the present 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 spacer 86, in order to improve the adhesiveness between the substrates 11a and 11b and to improve the impact resistance of the chiral smectic liquid crystal, adhesive particles made of a resin material such as an epoxy resin may be dispersed. Yes (not shown).

In the liquid crystal element 80 having the above-mentioned structure, the composition of the chiral smectic liquid crystal layer 85 is adjusted. By appropriately setting the material processing and element configuration, for example, the materials of the alignment films 84a and 84b, processing conditions, and the like, as shown in FIGS. 3B, 6, and 7, when no voltage is applied, It shows an alignment state in which the average molecular axis (liquid crystal molecules) of the liquid crystal is monostable. During driving, when a voltage of one polarity (first polarity) is applied, the average molecular axis is changed according to the magnitude of the applied voltage. The tilt angle with respect to the monostabilized position changes continuously, and when a voltage of the other polarity (second polarity) is applied, the average molecular axis of the liquid crystal is subjected to an average uniaxial alignment treatment in the same manner as when no voltage is applied. Substantially coincides with the axis and applied To exhibit such properties as not to tilt by the size of the pressure. Preferably, as a chiral smectic liquid crystal material, Iso-Ch-S
Using a phase transition series of mC ^* or a phase transition series of Iso-SmC ^* , a state where the memory property is lost by SmC ^* is formed by the above-described processes 1) to 4).

Further, the above-mentioned γ, hysteresis characteristics and ion amount are set by preparing a liquid crystal material or the like according to the desired constitutional requirements of the liquid crystal element.

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, the transmitted light amount of the element can be controlled in an analog manner, for example, with characteristics as 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 a continuous change of the tilt angle from a monostable position of the average molecular axis of the liquid crystal by application of the voltage as described above. 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. 12 is a plan view schematically showing the structure of one of the substrates (active matrix substrates) in which a driving means is connected to one embodiment of the liquid crystal element of the present invention.

In the configuration shown in FIG. 12, in the panel section 90 corresponding to the liquid crystal element, horizontal gate lines G ₁ , G ₂ corresponding to the scanning signal lines connected to the scanning signal driver 91 as the driving means in the drawing. ,..., And the source lines S ₁ , S ₂ ,. 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. FIG. 12 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. 13 is a schematic diagram showing an example of a 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.

In the active matrix substrate 20, an example in which an amorphous Si TFT is used as the TFT 94 is shown. The TFT 94 is formed on a substrate made of glass or the like, and an insulating film (gate insulating material) made of a material such as silicon nitride (SiN _x ) is formed on the gate electrode 22 connected to the gate lines G ₁ , G ₂ ,. A) through the membrane 23
A semiconductor layer 24 made of -Si is provided, and a source electrode 27 and a drain electrode 28 are provided on the semiconductor layer 24 via ohmic contact layers 25 and 26 made of n ⁺ a-Si respectively. Have been. The source electrode 27 is connected to the source lines S ₁ , S ₂ ,... Shown in FIG. 12, and the drain electrode 28 is connected to a pixel electrode 95 made of a transparent conductive film such as ITO. In addition, the channel protective film 29 covers the semiconductor layer 24 in the TFT 94. 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. 11, and the alignment as shown in FIG. 3, FIG. 6 to FIG. It is set to indicate the state and the optical characteristics.

Incidentally, as the TFT 94 shown in FIGS. 12 and 13, a polycrystalline Si (p-Si) TFT can be used.

FIG. 14 shows an equivalent circuit of a pixel portion of the panel shown in FIG. 13, and FIG. 15 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. 15). 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. 8 will be described.

FIG. 15A shows a voltage applied to one gate line serving as a scanning signal line connected to a pixel when focusing on an arbitrary pixel. In the liquid crystal device having the structure shown in FIGS. 12 and 13, 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).

[0105] FIG. 15 (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) that constitutes one frame, the information is written to the pixel, for example, the voltage-transmittance characteristic as shown in FIG. 8 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, in 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 that of 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.

FIG. 15C 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 (transmitted light quantity) corresponding to V _x on the basis of the characteristics shown in FIG. 8 is obtained, in the second field 2F, -V
_The transmitted light amount becomes 0 level by _x . Accordingly, in the entire frame, the transmitted light amount obtained by averaging _Tx and 0 is obtained.

In the active matrix driving as described above, when a chiral smectic liquid crystal is used, gradation display based on good high-speed response can be performed.
By performing a gradation display of a certain level in one pixel into a first field for obtaining a high transmitted light amount and a second field for which the transmitted light amount is 0, and performing them continuously, the time aperture ratio becomes 50%.
%, The high-speed moving image response characteristic perceived by human eyes is also good. 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. Further, in the case of a transmissive liquid crystal element, the illuminance of the backlight light source can be reduced and power consumption can be reduced because the time integration value of the amount of transmitted light is improved.

Further, 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 voltage,
Deterioration of the liquid crystal is prevented.

In the above-described active matrix driving, 2
In one entire frame composed of fields, a transmitted light amount obtained by averaging _Tx and 0 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. Preferably, it is displayed.

In the liquid crystal element of the present invention, the period for applying the first polarity voltage is set longer than the period for applying the second polarity voltage. 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 , preferably F ₁
× V ₁ = F ₂ × V ₂ . 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.

[0113]

EXAMPLES (Example 1) [Preparation of liquid crystal cell] A pair of glass substrates having a thickness of 1.1 mm and having an ITO film having a thickness of 700 ° formed as transparent electrodes (electrode area: 1 cm ² ) were prepared. On the transparent electrode of the substrate,
A commercially available “SE-7992” (manufactured by Nissan Chemical Industries, Ltd.) is applied as an alignment film by a spin coating method, followed by pre-drying at 80 ° C. for 5 minutes, followed by heating and baking at 200 ° C. for 1 hour to form a film. A polyimide film having a thickness of 200 mm was obtained. Incidentally, when a commercially available "KN5015LA" (manufactured by Chisso Corporation) as a high-purity liquid crystal material for a TFT type liquid crystal element was injected into a cell using this alignment film and the ion amount was measured, the ion amount was below the measurement limit. Therefore, since it is considered that no impurity ions are generated from the alignment film, the amount of impurities in the following examples can be regarded as the amount of impurity ions in the liquid crystal material itself.

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, silica beads having an average particle size of 1.6 μm were sprayed as spacers on one of the substrates, and the substrates were opposed to each other so that the rubbing directions of the substrates were antiparallel to each other. Gap (1.
55 μm) (single pixel empty cell).

The birefringence phase difference (retardation) of this cell was measured by the following method to find that it was 0.08 nm.
Met.

The measuring method of the refraction phase difference (retardation) is as follows.

As an apparatus, an automatic birefringence measuring apparatus “ADR-300LC-A” manufactured by Oak Manufacturing Co., Ltd. was used. This apparatus comprises a main body having an XY automatic positioning stage and a dedicated optical system, a power supply box, a control personal computer, and the like. The optical system uses a He-Ne laser.

In the measurement, a laser was incident at an incident angle of 0 ° (perpendicular incidence), the stage on which the measurement substrate was set was rotated by 360 °, and a refractive index ellipsoid was calculated from the value of the detected birefringence phase difference. Ask.

The actual measurement was performed as follows.

An alignment film having a predetermined thickness was applied to a 75 mm × 75 mm ITO substrate, baked, and set in the present apparatus.
This is performed to eliminate the influence of birefringence between the glass substrate and the alignment film base (background measurement).

Here, the incident azimuth angle was set to 0 ° and the inclination angle was set to 0 °, the refractive index and the film thickness of a predetermined alignment film were input, and the measurement was started. The measurement points at this time were 81 points, and the average was obtained.

Next, the substrate was taken out, rubbed under predetermined conditions, and the same operation was performed. After the measurement, a predetermined birefringence phase difference (retardation) is obtained by subtracting the background birefringence phase difference data from the rubbed birefringence phase difference data.

[Production of Active Matrix Cell] An active matrix having an a-Si TFT using a transparent electrode and a polyimide alignment film of the same materials and under the same conditions as described above, and further having one substrate provided with a silicon nitride film as a gate insulating film. An R, G, and B color filter was formed on the other substrate to form an active matrix cell (panel) having a pixel structure shown in FIG. The storage capacity (C _s ) of the TFT was set to be five times the capacity (C _lc ) of each liquid crystal. The screen size was 10.4 inches, and the number of pixels was 800 × 600 × RGB.

[Preparation of Liquid Crystal Compositions] The following liquid crystal compounds were mixed at the following weight ratios to prepare liquid crystal compositions A to G.

[0126]

[Table 1]

As physical properties parameters of the liquid crystal compositions A to G, the phase transition temperature at the time of cooling from the isotropic phase (Iso) is shown in Table 2.
Table 3 shows spontaneous polarization, tilt angle, and helical pitch in the SmC ^* phase at T _c −T = 10 ° C. (T _c is a Ch → SmC ^* phase transition temperature).

[0128]

[Table 2]

[0129]

[Table 3]

The liquid crystal compositions A to G are injected into each of the single pixel cell (1) and the active matrix cell (2) manufactured at the above process at the temperature of the Iso phase, and the liquid crystal is cooled to a temperature showing a chiral smectic phase. And liquid crystal element samples A (1) to G (1), A (2) to G
(2) was produced. During this cooling, a cooling process was performed by applying an offset (direct current) voltage of +3 V before and after the Ch-SmC ^* phase transition. The following evaluation was performed on such a sample.

1. Alignment state The alignment states of the liquid crystals of the device samples A (1) to G (1) were observed with a polarizing microscope.

As a result, an alignment state was observed in which the darkest axis was substantially parallel to the rubbing direction, and a substantially uniform alignment state was obtained in which the layer normal direction was only one direction in the whole cell.

2. Triangular Wave Response In order to measure the electro-optical response exhibited by the liquid crystal element, the cells of the element samples A (1) to G (1) were placed under a crossed Nicol under a polarizing microscope equipped with a photomultiplier, and the polarization axis was adjusted in the rubbing direction. It was arranged so as to be in the field of view.

In addition, ± 5 V at T _c -T = 10 ° C.
Observing the optical response when a 0.2 Hz triangular wave is applied, the amount of transmitted light (transmittance) gradually increases according to the magnitude of the applied voltage when the voltage of the positive polarity is applied. It was also found that, when a negative voltage was applied, the transmitted light amount did not substantially change from the black state when no voltage was applied.

When the voltage is cut off from the state where a positive voltage is applied (white display), the state is relaxed to a black state (switching).
It was confirmed that.

Further, as can be seen from the optical response, in each of the element samples, the γ characteristic was gradual and the threshold value of the rise did not clearly exist. That is, in the rising curve, the transmittance is 95, which is the maximum transmittance.
% And comprising voltage V _95%, 5% and becomes the voltage of the maximum transmittance when the _5% V, shows the value of 5 or greater even in _{γ = V 95% / V 5} % is one of the device sample Was. From this result, it was found that each of the element samples was excellent in continuous gradation.

Next, the amount of hysteresis was evaluated.
That is, the voltage at which the transmittance at the rise in the triangular wave response curve reaches 50% is V _u , and the transmittance at the fall is 5%.
The voltage reaches 0% and V _d, and their average value of the voltage _{(V u + V d) /} 2 can be taken when applying the two transmission T _u, the difference T _diff of T _d evaluated for each sample . Table 4 shows the results.

[0138]

[Table 4]

From the above results, regarding the element samples A (1) and B (1), the hysteresis parameter T _diff
Is more than 50%, which causes a problem in gradation display in active matrix driving. However, as for the element samples C (1) to G (1), the value of the hysteresis parameter is also small. Good gradation display performance can be expected.

3. Rectangular Wave Response With respect to the device samples A (1) to G (1), the optical level was changed while applying a 60 Hz rectangular wave and changing the voltage (in the range of +5 V to -5 V) using the same device as the triangular wave response. It was measured.

As a result, all the elements responded only to the voltage of the positive polarity, and it was possible to change the luminance level by changing the voltage level. However, for the element samples A (1) and B (1), since the value of the above-mentioned hysteresis parameter T _diff is large, the optical response depends on the previous state, and a stable halftone could not be obtained.

On the other hand, element samples C (1) to G
Regarding (1), since the above-mentioned hysteresis parameter is small, it has been confirmed that the optical response does not depend on the previous state and a stable halftone can be obtained. Therefore, with respect to the element samples C (1) to G (1), analog gradation display can be performed by amplitude modulation by active matrix driving.

The rise time (90% of the transmittance to be obtained by applying a predetermined voltage from the darkest state) by applying the positive rectangular wave voltage (all of the saturation voltages are about 5 V) is applied.
%, And a fall time (a time at which the transmittance becomes 10% of the transmittance from a saturated transmittance state at a predetermined voltage) in response to a high voltage (about 5 V). At the time of 0.6 to 0.9 ms and 0.2 to 0. 0 ms, respectively.
3 ms, and when a low voltage (approximately 1 V) is applied, they are 1.6 to 2.1 ms and 0.3 to 0.5 ms, respectively.
High-speed response was confirmed even when compared with switching using a general nematic liquid crystal.

4. Measurement of ion amount and voltage holding ratio For element samples A (1) to G (1), T _c −T =
The internal ion rearrangement (Q _t ) at 10 ° C., the voltage holding ratio, and the actual liquid crystal resistance value in the cell were measured. The results are shown in Tables 5 to 7. Here, the resistance of the liquid crystal in Table 7 is a value measured in an Al electrode cell having a cell gap of 2 μm, and is calculated from the actual liquid crystal resistance of element samples A (1) to G (1). It is almost completely consistent with the value. The calculated voltage holding ratio in Table 7 is obtained by calculating the time constant from the actual liquid crystal resistance value and the liquid crystal capacitance (2 nF) in the cell.

For the measurement, a liquid crystal voltage holding ratio measurement system “VHR-1A / S type” manufactured by Toyo Technica Co., Ltd. and a liquid crystal cell ion density measurement system were used, the applied voltage was ± 5 V, and 16.7 ms after the gate signal was turned off. The value of the subsequent internal voltage was measured, and the ratio to the applied voltage of 5 V was calculated to obtain the voltage holding ratio of each sample.

[0146]

[Table 5]

[0147]

[Table 6]

[0148]

[Table 7]

5-1. Actual driving / moving image quality evaluation A Moving image quality evaluation was performed using element samples A (2) to G (2) which are active matrix panels 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). Three kinds of images (skin color chart, tourist information board, yacht harbor) were selected from BTA high-definition standard images (still images), and 43
2 × 168 pixels 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 create 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: Small blur 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.

At this time, the output of the image source from the computer was set to 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 at a frequency of substantially 120 Hz. If
Flicker was not observed at all, and moving image quality with almost no perceived blurring was observed. The above five-level evaluation showed a level of 5 (Table 8).

In addition, when this evaluation is performed 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 that takes a response of several tens of ms is used, the evaluation is 2 to 5 in a 5-level evaluation.
The evaluation result was about 3. Table 8 shows the results.

[0156]

[Table 8]

As can be seen from the above results, C (2) and D (2) are slightly dark, but there is no problem of color reproducibility or afterimage.
A high-quality liquid crystal display that can display moving images with a high-speed response performance and has almost good performance has been realized. Furthermore, E
(2), F (2) and G (2) are bright, have no afterimage,
A high-quality liquid crystal display with almost satisfactory color reproducibility and moving image display has been realized.

At this time, in order to keep the screen (maximum) luminance at 200 cd / m ² with the panel of G (2) in a white display state, the backlight luminance is set to 5500 cd / m ^2.
It was necessary to set above. This is because the aperture ratio of the panel of this device sample G (2) is 70%, the effective transmittance of the liquid crystal device portion including the polarizing plate and the color filter is 5.2%, and the total transmittance is 3.6%. Because it was. still,
Here, the numerical value of “transmittance” means the ratio of the amount of emitted light to the amount of incident light with the amount of incident light from the backlight incident on each member being 100%.

Breakdown of the effective transmittance of the liquid crystal element portion of 5.2%: 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 46%. (Based on a paranicol polarizing plate)
39 x 0.29 x 0.46 = 0.052.

Details of transmittance of liquid crystal cell portion: 92% 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 0% in the subsequent second field (negative voltage application period), and therefore, 92 x 1/2 = 46 (%).

5-2 Actual driving / moving image quality evaluation B Next, with respect to the element sample G (2), one frame was divided into two fields at a time ratio of 2: 1 and driven at substantially 120 Hz (pulse). The width is 11.1m
s and 5.6 ms), when a positive voltage of 0 to 5 V is applied in the first field, and a negative voltage of 0 to 10 V is applied in the subsequent field (the voltage level of both fields is 1: 2), and the operation is performed. A moving image in which no flicker was observed and no peripheral blur was observed was observed, and an ideal moving image was obtained. In the above five-level evaluation, it was a level of 4 to 5.

At this time, the screen (maximum)
Backlight brightness to maintain the luminance 200 cd / m ² is reduced to 4120cd / m ^2, the power consumption was able to reduce by 25%. This is the device sample G
This is because the aperture ratio of the panel (2) was 70%, the effective transmittance of the liquid crystal element including the polarizing plate and the color filter was 6.9%, and the total transmittance was 4.9%.

The effective transmittance of the liquid crystal element portion is 6.9%: 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 61%. (Based on a paranicol polarizing plate)
39 x 0.29 x 0.61 = 0.069.

Details of transmittance of liquid crystal cell: 92% of 2% in the first field (high voltage application period) with high brightness
/ 3 (because the time ratio in one frame is 2: 1),
Subsequent second field (negative voltage application period) 0% 1
/ 3, therefore 92 × 2/3 = 61 (%).

[0165]

As described in detail above, according to the present invention,
A chiral smectic liquid crystal element capable of high-speed response and gray scale display can be obtained. In particular, the moving image quality can be improved without using a complicated circuit, and at the same time, the deterioration of the liquid crystal can be prevented, and a good moving image quality can be displayed for a long time. A liquid crystal element with high durability is provided. 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 diagram illustrating a potential state in a chiral smectic liquid crystal element.

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 schematic view illustrating an example of an alignment state in the liquid crystal element of the present invention.

FIG. 8 is a diagram illustrating an example of a voltage-transmittance characteristic in the liquid crystal element of the present invention.

FIG. 9 is a schematic diagram showing a potential state in a bistable orientation state in SSFLC.

FIG. 10 is a schematic diagram showing a potential state in an alignment state in the liquid crystal element of the present invention.

FIG. 11 is a cross-sectional view schematically illustrating a structure of one pixel of an embodiment of the liquid crystal element of the present invention.

FIG. 12 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. 13 is a schematic cross-sectional view illustrating a configuration example of one pixel when the liquid crystal element of the present invention is applied to an active matrix type.

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

FIG. 15 is a diagram illustrating an example of a driving waveform and an optical response when an active matrix drive is performed on the liquid crystal element of the present invention.

FIG. 16 is a diagram showing another example of the voltage-transmittance characteristic in the liquid crystal element of the present invention.

[Explanation of symbols]

11, 12 Substrate 13 Liquid Crystal 14, 14a, 14b Liquid Crystal Molecule 15 Cone 16 Smectic Layer 17 Cone Bottom 18, 18, a, 18b Projection of Liquid Crystal Molecule onto Virtual Cone Bottom 20 Active Matrix Substrate 21 Substrate 22 Gate Electrode 23 Gate Insulating Film 24 Semiconductor Layers 25 and 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 Opposite 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 section 91 Scan 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 Inside Canon Inc. (72) Takashi Moriyama, Inventor 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Shinichi Nakamura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. F-term (for reference) 2H090 HB08Y KA09 KA14 LA04 MA02 MB01 2H093 NA16 NA33 NA43 NA53 NC34 ND06 ND39 NE02 NE04 NE06 NF14 NF19 NH02 NH05 NH15 NH18 5C006 AA01 AA14 AA16 AA22 AF44 BA13 BB12 FA01FA04 GA03 FA04 BB05 DD03 DD08 DD26 EE19 EE29 FF11 FF12 JJ02 JJ03 JJ04 JJ05 JJ06

Claims (21)

[Claims] 1. A liquid crystal element for displaying an image by individually controlling a plurality of pixels, wherein a uniaxial alignment process is applied to an interface between a chiral smectic liquid crystal and at least one of the liquid crystals to face the liquid crystal. A liquid crystal device comprising a pair of substrates, an electrode for driving liquid crystal for each pixel, and a polarizing plate disposed outside at least one of the substrates, and when no voltage is applied, the average molecular axis of the liquid crystal is Shows a mono-stabilized first state, when a voltage of the first polarity 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, When a voltage of a second polarity opposite to the first polarity is applied, the average molecular axis of the liquid crystal maintains the monostable first state, the minimum transmittance of the device is 0%, and the maximum transmittance is 0%. When the ratio is 100%, the voltage when triangular wave is applied In the transmittance curve, the following γ value at the time of applying the first polarity voltage is 3 or more, the following hysteresis parameter value T _diff [%] is 50% or less, and γ = V _95% / V _5% V _{5 %} : A voltage applied to a liquid crystal having a transmittance of 0% to reach a transmittance of 5% V _95% : A voltage applied to a liquid crystal having a transmittance of 0% has a transmittance of 95%
Voltage _{T diff = T d -T u T} u [%] to reach: below V _u and V transmittance when the transmittance is applied to the liquid crystal of 0% the average voltage of _d T _d [%]: below V _u the average voltage of V _d is the transmittance of 100
% Transmission V _u when applied to the liquid crystal of: voltage-transmittance transmittance is applied to the liquid crystal of 0% reaches 50% V _d: transmittance transmittance is applied to 100% liquid of 50
% One frame is divided into at least two fields,
In the first field, an image is displayed by applying a first polarity voltage of a value corresponding to the display information for each pixel, and in the remaining field of one frame, a second polarity voltage is applied to each pixel. A liquid crystal element characterized in that a period for applying the first polarity voltage is set longer than a period for applying the second polarity voltage. 2. The liquid crystal of each pixel exhibits a first transmittance when no voltage is applied and a voltage having a second polarity is applied, and the liquid crystal of each pixel exhibits a second transmittance when a voltage having the first polarity is applied. By changing the tilt angle of the average molecular axis of the liquid crystal from the monostabilized position according to the magnitude of the applied first polarity voltage, the maximum value of the second transmittance and the second 2. The liquid crystal device according to claim 1, wherein the transmittance is continuously changed between one transmittance. 3. The liquid crystal device according to claim 2, wherein the first transmittance is a minimum transmittance of the device, and a maximum value of the second transmittance is a maximum transmittance of the device. 4. The phase transition series of the chiral smectic liquid crystal is an isotropic phase-cholesteric phase-chiral smectic C phase or isotropic phase-chiral smectic C phase from a high temperature side. A liquid crystal device according to any one of the above. 5. The helical pitch of the chiral smectic liquid crystal in a bulk state is longer than twice the cell thickness.
5. The liquid crystal device according to any one of items 1 to 4. 6. The liquid crystal device according to claim 1, wherein the liquid crystal device includes a pixel electrode and an active element for each pixel, and performs analog gradation display.
6. The liquid crystal element according to any one of 5. 7. A 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 claim 6, which is provided. 8. The liquid crystal device according to claim 1, which is a transmission type liquid crystal device. 9. The liquid crystal device according to claim 1, which is a reflective liquid crystal device. 10. A period F ₁ during which the voltage of the first polarity is applied, a voltage value V ₁ of the first polarity applied to the liquid crystal during the period, and a period F ₁ during which the voltage of the second polarity is applied. relationship between the voltage value -V ₂ of the second polarity applied to the liquid crystal between _two and said period is a F _1> F _2, and claim a _{F 1 × V 1 = F 2} × V 2 10. The liquid crystal device according to any one of 6 to 9. 11. A liquid crystal element for displaying an image by individually controlling a plurality of pixels, wherein a uniaxial alignment treatment is applied to an interface between a chiral smectic liquid crystal and at least one of the liquid crystals to face the liquid crystal. A pair of substrates, an electrode for driving liquid crystal for each pixel, an active element for controlling a voltage applied to each pixel, and a polarizing plate disposed outside at least one of the substrates. A liquid crystal element that performs analog gray scale display, wherein, when no voltage is applied, the average molecular axis of the liquid crystal shows a first state in which the average molecular axis is monostable. The axis tilts from the first state to one side at an angle corresponding to the applied voltage value, and when a voltage of a second polarity having a polarity opposite to the first polarity is applied, the average molecular axis of the liquid crystal is Monostabilization Maintaining a first state of being, and a volume resistance value of the liquid crystal is 5 × 10 ¹¹ Ωcm or more, the spontaneous polarization Ps [nC / cm ^2] rearrangement of the internal ions in the selection period of a pixel and Q _t [NC / cm ² ] has a relationship of 2Ps + Q _t ≦ 30 [nC / cm ² ], one frame is divided into at least two fields, and the first value of the value corresponding to the display information for each pixel in the first field An image is displayed by applying a voltage of the second polarity, and in the remaining field of one frame, a voltage of the second polarity is applied to each pixel. The liquid crystal element is set to be longer than a period for applying a voltage having a polarity of 12. The (2Ps + Q _t ) is 12 [nC /
cm ² ] or less. 13. A liquid crystal of each pixel exhibits a first transmittance by no voltage application and a voltage application of a second polarity, and a liquid crystal of each pixel exhibits a second transmittance by application of a first polarity voltage. By changing the tilt angle of the average molecular axis of the liquid crystal from the monostabilized position according to the magnitude of the applied first polarity voltage, the maximum value of the second transmittance and the second 13. The liquid crystal device according to claim 11, wherein the transmittance is continuously changed between one transmittance and one transmittance. 14. The liquid crystal device according to claim 13, wherein the first transmittance is a minimum transmittance of the device, and a maximum value of the second transmittance is a maximum transmittance of the device. 15. 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. A liquid crystal device according to any one of the above. 16. The liquid crystal device according to claim 11, wherein a helical pitch of the chiral smectic liquid crystal in a bulk state is longer than twice a cell thickness. 17. The liquid crystal of a pixel to which 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 element according to claim 11, wherein the liquid crystal element is provided. 18. A transmission type liquid crystal element.
8. The liquid crystal device according to any one of items 7. 19. A reflection type liquid crystal element.
8. The liquid crystal device according to any one of items 7. 20. Assuming that the minimum transmittance of the device is 0% and the maximum transmittance is 100%, in a voltage-transmittance curve when a triangular wave is applied, the following γ value when a voltage of the first polarity is applied is 3 or more. And the following hysteresis parameter value T _diff
20. The liquid crystal device according to claim 11, wherein [%] is 50% or less. γ = _V95% / V5 _% V5 _% : voltage applied to a liquid crystal having a transmittance of 0% to reach a transmittance of 5% _V95% : transmittance applied to a liquid crystal having a transmittance of 0% 95%
Voltage _{T diff = T d -T u T} u [%] to reach: below V _u and V transmittance when the transmittance is applied to the liquid crystal of 0% the average voltage of _d T _d [%]: below V _u the average voltage of V _d is the transmittance of 100
% Transmission V _u when applied to the liquid crystal of: voltage-transmittance transmittance is applied to the liquid crystal of 0% reaches 50% V _d: transmittance transmittance is applied to 100% liquid of 50
Voltage reaching% 21. 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 11 to 20 is _{F 1 × V 1 = F 2} × V 2.