JP2001281631A - Liquid crystal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the inhomogeneous state of aligned state of a liquid crystal. SOLUTION: A chiral smectic liquid crystal 2 is used and alignment control films 6a, 6b are disposed in the liquid crystal panel P1. An arithmetic average roughness Ra of the alignment control films 6a, 6b is controlled to satisfy Ra<0.5 nm. Thereby, the aligned state of the chiral smectic liquid crystal 2 is made homogeneous with an oblique bookshelf structure and the display quality is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal device used for a flat panel display, a projection display, a printer, and the like.

[0002]

2. Description of the Related Art (1) Conventionally, a nematic liquid crystal or a chiral smectic liquid crystal is used for a liquid crystal panel (liquid crystal element) for displaying various information using a liquid crystal. Smectic liquid crystals are preferred. Hereinafter, this point will be described.

There are the following liquid crystal panels using a nematic liquid crystal. * An active matrix type liquid crystal panel in which a switching element such as a transistor is arranged in each pixel, and is a twisted nematic (Twisted N).
(e.g., M. Schadt and W. Helfrich, Applied Phys)
sics Letters, Vol. 18, No. 4 (197
(Issued Feb. 15, 2001), pp. 127-128) * Also an active matrix type liquid crystal panel, in which the viewing angle is improved by using an in-plane switching mode using a horizontal electric field. * A liquid crystal panel that does not use the switching element as described above, and is a super twisted nematic (su
(Per Twisted Nematic) Mode However, in any liquid crystal panel, there is a problem that the response speed of the liquid crystal takes several tens of milliseconds or more.

As a solution to such a problem, a liquid crystal panel using a liquid crystal exhibiting bistability has been proposed by Clark (cl.).
ark) and Lagerwell (JP-A-56-107216,
U.S. Pat. No. 4,367,924). As the liquid crystal exhibiting this bistability, a ferroelectric liquid crystal exhibiting a chiral smectic C phase is generally used. Since the ferroelectric liquid crystal performs inversion switching by spontaneous polarization, a very fast response speed can be obtained and a bistable state having a memory property can be developed. Further, since the viewing angle characteristics are also excellent, it is considered that they are suitable as a high-speed, high-definition, large-area display element or a light valve.

On the other hand, recently, antiferroelectric liquid crystals exhibiting three stability have attracted attention. This antiferroelectric liquid crystal also performs reversal switching by spontaneous polarization similarly to the ferroelectric liquid crystal, so that a very fast response speed can be obtained. This liquid crystal material is characterized in that no spontaneous polarization exists when no electric field is applied, because the liquid crystal molecules have a molecular arrangement structure in which the liquid crystal molecules cancel each other when no electric field 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 panel using a smectic liquid crystal is expected in the sense that the problem of the response speed that the nematic liquid crystal has conventionally can be solved.

(2) Although it is a chiral smectic liquid crystal having the above-mentioned advantages, since it generally shows a bistable state or a tristable state, it is difficult to realize gradation display.

In order to enable a gradation display, various thresholds such as "thresholdless antiferroelectric liquid crystal", "short pitch type ferroelectric liquid crystal", and "polymer stable ferroelectric liquid crystal" are used. Liquid crystals have been proposed, but none are in the research and development stage and have yet to be commercialized.

(3) A problem when displaying a moving image using a liquid crystal panel will be described.

When displaying a moving image using a liquid crystal panel, it has been relied on an increase in the response speed of the liquid crystal. However, it has recently been impossible to obtain a high-speed response characteristic of a moving image that can be sensed by humans only by such an increase in the speed. It has been clarified by research (IEICE Technical Report EID96-4p.19). That is, in order to make humans feel that moving image display is performed at a high speed, a method of using a shutter to reduce the time aperture ratio to 50% or less (that is, a method of intermittently displaying a still image at a time ratio of 50% or less) or , * It is clear that it is better to use the double speed display method.

The nematic liquid crystal is not suitable for displaying moving images because of its low response speed as described above. However, the chiral smectic liquid crystal requires a liquid crystal panel driving method and peripheral circuits to display moving images. Becomes complicated,
There was a problem that the cost of the liquid crystal panel also increased.

(4) An example of a conventional liquid crystal panel that can solve the above-described problem will be described.

Therefore, as a result of intensive studies, from the high temperature side, an isotropic liquid phase (ISO.)-Cholesteric phase (Ch) -chiral smectic C phase (SmC ^* ) or an isotropic liquid phase (ISO) .)-Chiral smectic C phase (SmC ^* ) using a chiral smectic liquid crystal exhibiting a phase transition series, particularly when the liquid crystal is not applied with a driving voltage, the average molecular axis of the liquid crystal molecule is monostable. * When a driving voltage of one polarity is applied, the average molecular axis of the liquid crystal molecules is shifted from the mono-stabilized position by an angle corresponding to the magnitude of the driving voltage. * When a driving voltage of another polarity is applied, the average molecular axis of the liquid crystal molecules is shifted from the monostable position to the other side at an angle corresponding to the magnitude of the driving voltage. Tilt, * A liquid crystal in which a tilt angle in a case where a maximum tilt state is obtained by applying a drive voltage of the first polarity is different from a tilt angle in a case where a maximum tilt state is obtained by applying a drive voltage of the other polarity. The panel was proposed (Japanese Patent Application No. 10-17714).
No. 5).

According to such a liquid crystal panel, high-speed response and gradation control can be performed, and the moving image quality can be improved without using a complicated circuit.

[0015]

In the above-mentioned liquid crystal panel, the chiral smectic liquid crystal arbitrarily forms a symmetric chevron structure, an oblique bookshelf structure, or an asymmetric chevron structure (for example, an oblique bookshelf alignment region and a chevron alignment region). In some cases, the orientation region may be mixed), and there has been a demand for further improvement in the technique for uniformizing the orientation.

Therefore, an object of the present invention is to provide a liquid crystal element which prevents non-uniform alignment.

[0017]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and comprises a pair of substrates disposed with a predetermined gap therebetween, and a chiral substrate disposed between the pair of substrates. A smectic liquid crystal, first and second electrodes arranged so as to sandwich the chiral smectic liquid crystal, and an alignment control film arranged so as to be in contact with the chiral smectic liquid crystal and aligning the liquid crystal, and
In a liquid crystal device which displays an image in a plurality of frame periods per second based on applying a voltage to the chiral smectic liquid crystal through the first and second electrodes, one frame period includes at least two fields. A desired image is displayed at the first luminance in at least one field period of one frame period, and the image is displayed in one frame period.
In the remaining field period during the program period, an image substantially the same as the image displayed at the first luminance is displayed at a second luminance smaller than the first luminance and larger than 0, and The arithmetic average roughness Ra is characterized by Ra <0.5 nm.

In this case, when the projected area of a predetermined region in the orientation control film is S and the surface area of the orientation control film in the region is Sr, (Sr / S) <1.020. May be.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. (1) First, the configuration of the liquid crystal element according to the present embodiment will be described with reference to FIGS.

The liquid crystal device according to this embodiment, as indicated at P ₁ and P ₂ in FIGS. 1 and 2, a pair of substrates 1a arranged with a predetermined spacing, and 1b, the pair A chiral smectic liquid crystal 2 disposed in a gap between the substrates 1a and 1b, first and second electrodes 3a and 3b disposed so as to sandwich the chiral smectic liquid crystal, and disposed so as to be in contact with the chiral smectic liquid crystal 2. And alignment control films 6a and 6b for orienting the liquid crystal, and are driven by applying a voltage to the chiral smectic liquid crystal 2 via the first and second electrodes 3a and 3b (for example, , Gradation display).

[0021] Incidentally, as this liquid crystal element P ₁ and P _2, the first and second electrodes 3a, a plurality per second based on applying a voltage to said chiral smectic liquid crystal 2 via the 3b frame - arm period Preferably, one frame period is divided into at least two field periods and displayed, and a desired image is displayed at a first luminance in at least one field period during one frame period. In the remaining field period of one frame period, an image which displays substantially the same image as the image displayed at the first luminance at a second luminance smaller than the first luminance and larger than 0 is used. preferable.

(2) Next, the alignment control films 6a and 6b used in the present embodiment will be described.

In the present embodiment, the arithmetic average roughness of the alignment control films 6a and 6b after rubbing (ie, the arithmetic average roughness)
The absolute value (Ra) of the deviation from the center plane to the surface in the quantitative plane) should preferably be set to Ra <0.5 nm.

The projected area of a predetermined area on the orientation control films 6a and 6b (the projected area of the area where the roughness is measured in the vertical direction) is S, and the orientation control films 6a and 6b in the area are defined as S.
Assuming that the surface area of 6b (the actual area of the surface including the unevenness existing in the alignment control film after rubbing) is Sr, it is preferable to set (Sr / S) <1.020.

Further, by appropriately selecting the materials of the alignment control films 6a and 6b and the processing conditions of the uniaxial alignment processing,
It is preferable to adjust the magnitude α of the pretilt angle of the liquid crystal molecules (that is, the angle formed by the liquid crystal molecules with respect to the alignment control films 6a and 6b near the interface between the alignment control films 6a and 6b).

As the alignment control films 6a and 6b, * a film made of an organic material such as polyimide, polyimide amide, polyamide or polyvinyl alcohol is applied to form a film, and a uniaxial alignment such as rubbing treatment is performed on the surface of the film. Examples include a treated film and an obliquely deposited film formed by depositing an inorganic material made of an oxide or nitride such as * SiO on the substrates 1a and 1b at a predetermined angle from an oblique direction.

The orientation control films 6a and 6b described above are
What is necessary is just to arrange on both sides of the chiral smectic liquid crystal 2,
In this case, considering the liquid crystal material used, the relationship between the uniaxial alignment processing directions (particularly the rubbing direction) is * parallel (both uniaxial alignment processing directions are parallel and the same direction), and antiparallel (both uniaxial alignment processing directions are parallel And in the opposite direction), * a relationship of crossing within a range of 45 ° or less. In addition, in order for the liquid crystal 2 to have an oblique bookshelf structure as described later, it is generally preferable that the uniaxial alignment processing direction is anti-parallel, but in the present invention, it has been confirmed that the same alignment is obtained even in parallel rubbing. The oblique bookshelf can be stably and uniformly aligned in both parallel rubbing and anti-parallel rubbing.

In the case where the alignment control films 6a and 6b are formed of polyimide and the liquid crystal 2 is in a monostable mode (monostable FLC mode), unlike other SSFLCs, the uniaxial film formed by the alignment control films is used. It has been found that the orientation does not cause any problem as compared with the conventional art.

However, the C1 orientation of the chevron structure and the C2 orientation
In some cases, an orientation or an oblique bookshelf appears in a small area, and further uniformity of the orientation is required.

The present inventor has studied diligently by changing the structure of the orientation control film, the firing temperature, the rubbing conditions, and the like. As a result, it was found that the structure of the alignment control film of the present invention, which is easily oriented, may be made of a structurally solid type material (for example, a material having a short alkylene chain in the long chain direction in a polyimide structure). Was. In addition, it was found that the rubbing strength could be increased or the firing temperature could be adjusted even for a structurally insecure type material (a material having a long alkylene chain in the long chain direction in the polyimide structure). .
Then, it was found that the correlation with the surface state of the alignment control film after the rubbing treatment was larger than the correlation with the structure of the alignment control film.

That is, in order to stably and uniformly align in the oblique bookshelf structure, it is sufficient that the surfaces of the alignment control films 6a and 6b are smooth, and no irregularities are formed even by the rubbing treatment. It was found that the value of (Sr / S) should be within the above range.

(3) Next, the chiral smectic liquid crystal 2 used in the present embodiment will be described.

In the present embodiment, the isotropic liquid phase (ISO.)-Cholesteric phase (Ch)-
Chiral smectic C phase (SmC ^* ) or isotropic liquid phase (ISO.)-Chiral smectic C phase (Sm
It is preferable to use a chiral smectic liquid crystal showing a phase transition series of C ^* ).

Preferred compounds constituting such a chiral smectic liquid crystal will be specifically described below.

[0035]

Embedded image

[0036]

Embedded image

In order to perform gradation display with the above-described liquid crystal element, the memory property (bistability) shown in FIGS. 3 and 4 is lost, and the positions of the liquid crystal molecules are continuously changed according to the applied voltage. It is preferable to use a liquid crystal that changes gradually. Hereinafter, this point will be described.

As described above, a liquid crystal containing no SmA phase
(That is, the isotropic liquid phase (ISO.)
Cholesteric phase (Ch) -Chiral smectic C phase
(SmC^*) Or isotropic liquid phase (ISO.)
Larsmectic C phase (SmC ^*) Indicates the phase transition series
In the case of a chiral smectic liquid crystal), for example, FIG.
As shown in FIG.^*Process of phase transition to phase
Thus, the liquid crystal molecules 30 move with respect to the smectic layer normal direction LN.
And slightly inclined from the average uniaxial orientation processing direction R.
To form a smectic layer structure 32.
You. In the present invention, the liquid crystal molecules 30 are made of SmC^*Aiuchi
Within the operating temperature range of the inside of the edge of the virtual cone 31
It is adjusted to be stabilized by the position.

Here, as one embodiment of the present invention, a case having a layer inclination angle such as a chevron structure or an oblique bookshelf will be described in detail with reference to FIG. 6A using a model. FIG. 6A shows a change in the arrangement of liquid crystal molecules in a phase series not including the SmA phase, as in FIG. 5B. For example, a process of phase transition from the Ch layer to the SmC ^* phase (particularly, the SmC ^* phase) The liquid crystal molecules 30 are arranged so as to be inclined with respect to the normal direction LN of the smectic phase, and a smectic layer structure 32 is formed.

However, in FIG. 6A, there is a difference in the cone angle Θ (１ ／ of the apex angle of the virtual cone 31) in, for example, the high temperature side (T1) and the low temperature side (T2) in the SmC ^* phase. .

Here, the cone angle on the high temperature side (T1) is Θ1, the cone angle on the low temperature side (T2) is Θ2,
When using a material that satisfies the relationship of Θ1 <Θ2,
In a normal case, a relationship of d1> d2 is established between the spacings d1 and d2 of the smectic layer at these temperatures. Accordingly, if it is assumed that the layer structure has a bookshelf structure at the temperature T1, the layer tilt angle δ that satisfies at least the relational expression δ = cos ⁻¹ (d2 / d1) at the temperature T2.

Therefore, at the temperature T2, a chevron structure or an oblique bookshelf structure is formed. 6 (b) and 6 (c) show the layer structure, c-director state, and projection onto the bottom surface of the virtual cone in the case of a chevron structure. As shown in the figure, C1 and C2 can be defined based on the relationship between the rubbing direction and the layer inclination angle, similarly to the normal bistable SSFLC. According to the principle described above, the liquid crystal molecules 30 are adjusted so as to be stabilized at a position inside the edge of the virtual cone 31.

In each of FIGS. 5A, 5B and 6A, for example, the liquid crystal molecules 30 as shown in FIGS. Should be stable in two substantially parallel states,
In the case shown in FIG. 5B and FIG. 6A, the binding force of the uniaxial orientation processing becomes strong, and only one of these two states becomes stable, and the memory property is lost. FIG.
(B), at the time of the Ch-SmC ^* phase transition shown in FIG. 6A (immediately below the transition temperature to the SmC ^* phase), as shown in FIG.
It is conceivable that a smectic layer structure showing different layer normal directions (LN1 and LN2) is formed. At this time, if the state of uniaxial alignment processing (conditions such as processing direction, alignment material, etc.) of a pair of upper and lower substrates of the cell sandwiching the chiral smectic liquid crystal is completely symmetric, the two smectic layers as shown in FIG. The structures are formed in even proportions.

On the other hand, as shown in FIG. 7, only one of the two layer structures developed is aligned, that is, the deviation direction between the average uniaxially oriented axis and the normal direction of the smectic layer is constant. For the bias of the internal potential in the element for liquid crystal 2 between a pair of substrates during Ch-SmC ^* phase transition
To apply a positive or negative DC voltage to the liquid crystal 2 or to apply the alignment control films 6 a and 6 b made of different materials to the liquid crystal 2.
And a method of changing the processing method (film forming conditions and processing conditions such as rubbing intensity and UV light irradiation) for a pair of alignment control films 6a and 6b disposed so as to sandwich the liquid crystal 2. And a pair of alignment control films 6 a and 6 so as to sandwich the liquid crystal 2.
In addition, a method of arranging b and arranging an underlayer on the back side (substrate side) of each orientation control film and varying the film type and thickness of the underlayer can be used.

When the above method is used, in order to avoid a phenomenon (electret formation) in which the alignment control film itself has a permanent dipole, the application time of the DC voltage is
It is preferable to keep the time necessary and sufficient (minimum) for aligning the layers in one direction during the Ch-SmC ^* phase transition. Further, the magnitude of the DC voltage is preferably in the range of 100 mV to 10 V (preferably, 1 V to 8 V).

When the liquid crystal element is of an active matrix type, ions in the alignment control film and the liquid crystal material are TF
It is preferable to reduce as much as possible so as not to adversely affect the T drive.

In the liquid crystal device having the above structure, the composition of the chiral smectic liquid crystal 2 is adjusted, and the processing of the liquid crystal material and the device configuration, for example, the materials of the alignment control films 6a and 6b, the processing conditions, and the like are appropriately set. As shown in FIG. 8, when no driving voltage is applied, the average molecular axis of the liquid crystal molecules is in a monostable alignment state (FIG. 8B).
*) * When a driving voltage of one polarity is applied, the average molecular axis of the liquid crystal molecules is tilted to one side from the monostable position at an angle corresponding to the magnitude of the driving voltage. (The same figure
(See (c)), * When a driving voltage of another polarity (the opposite polarity to the above-mentioned one polarity; the same applies hereinafter) is applied, the average molecular axis of the liquid crystal molecules is reduced by the magnitude of the driving voltage. Tilt from the mono-stabilized position to the other side (ie, the side opposite to the side that tilts when the voltage of one polarity is applied) at a corresponding angle (see FIG. 3A), * The tilt angle in the case of the maximum tilt state by applying the drive voltage of one polarity is larger than the tilt angle in the case of the maximum tilt state by applying the drive voltage of the other polarity. It is good to show it. In other words, the liquid crystal 2 used in the present embodiment has lost the inherent memory property (bistability) of the chiral smectic liquid crystal, and the magnitude of the tilt angle can be continuously controlled by the applied voltage. Accordingly, the light amount of the liquid crystal element can be continuously changed, thereby enabling gradation display.

In this case, the tilt angle when the maximum tilt state is obtained by applying the driving voltage of one polarity is equal to the tilt angle when the maximum tilt state is obtained by applying the voltage of the other polarity. Preferably, the tilt angle in the case of the maximum tilt state by applying the driving voltage of one polarity is 5 times the tilt angle in the case of the maximum tilt state by applying the voltage of the other polarity. It is better to make it twice as large.

Further, the tilt angle in the case of the maximum tilt state by applying the voltage having the other polarity may be substantially 0 ° (see FIG. 9).

As the chiral smectic liquid crystal 2 used in the present embodiment, a hydrocarbon liquid crystal material having a biphenyl skeleton, a phenylcyclohexane ester skeleton, a phenylpyrimidine skeleton, or the like, a naphthalene liquid crystal material, or a polyfluorine liquid crystal material is appropriately selected. Adjust it.

The helical pitch of the chiral smectic liquid crystal 2 in the bulk state is determined by the cell thickness (the substrates 1a and 1b).
The gap is preferably longer than twice.

(4) Next, components of the liquid crystal elements P ₁ and P ₂ will be described.

The substrates 1a and 1b may be made of a highly transparent material such as glass or plastic.

The electrodes 3a and 3b may be made of a material such as In ₂ O ₃ or ITO (indium tin oxide), and these electrodes 3a and 3b may be formed on the respective substrates 1a and 1b. .

Further, on the surface of each of the electrodes 3a, 3b, a green-green film 5a, 5b for preventing a short circuit between these electrodes.
5b is preferably formed (FIG. 1 shows both green and green films 5a and 5a).
b, only the insulating film 5b is shown in FIG. 2), and the green films 5a and 5b may be made of SiO ₂ , TiO ₂ , Ta ₂ O ₅ or the like.

Further, a spacer (see reference numeral 8 in FIG. 1) made of silica beads or the like may be arranged in the gap between the substrates 1a and 1b, and the size of the gap may be defined by the spacer 8. Note that the gap size may be adjusted according to the liquid crystal material. However, uniform uniaxial alignment can be achieved, or the average molecular axis of liquid crystal molecules in a state where no voltage is applied is changed to the average direction of the alignment processing axis R. Is preferably set in the range of 0.3 to 10 μm in order to substantially coincide with the axis of (1).

Further, adhesive particles (not shown) made of epoxy resin or the like are dispersed and arranged in the gap between the substrates 1a and 1b, and the adhesiveness between the two substrates 1a and 1b and the liquid crystal elements P ₁ and P _2.
It is good to improve the impact resistance of the dies.

Further, the liquid crystal elements P ₁ and P ₂ may be of a transmission type or a reflection type. In the case of the transmission type, both substrates 1a and 1b need to be transparent, and in the case of the reflection type, one of the substrates 1a and 1b needs to have a function of reflecting light. Here, as a method of imparting the function of reflecting light, * a method of providing a reflecting plate or a reflecting film separately from the substrate, * a method of forming the substrate itself with a reflecting member, and the like. Can be.

Further, in the case of a transmission type liquid crystal element, a polarizing plate may be disposed on both substrates (so that their polarization axes are orthogonal to each other). In the case of a reflection type liquid crystal element, at least one of them is provided. What is necessary is just to provide a polarizing plate in a board | substrate. In such a case, the cells are arranged so as to be in the darkest state when no voltage is applied, and when a voltage is applied, the transmission of the element with the characteristic as shown in FIG. The amount of light (the amount of light emitted from the element) can be controlled in an analog manner with a change in voltage.

Further, the liquid crystal elements P ₁ , P _{2 according} to the present invention
May be a simple matrix type or an active matrix type.
a and 3b may be formed in a stripe shape and arranged so as to intersect each other. In the case of an active matrix type, the first electrodes 3b are arranged for each pixel, and the switching elements 4 are provided on each first electrode 3b. And when the switching element 4 is turned on, the first and second
It is preferable to apply a voltage between the electrodes 3a and 3b. The switching element 4 may be a TFT or M
IM (Metal-Insulator-Metal)
Etc. may be used.

In such a case, a driving circuit 21 is connected to the switching element 4, and a voltage is supplied from the driving circuit 21 to the first electrode 3 b via the switching element 4 to constitute a liquid crystal device. Is also good.

In such a case, in order to perform the above-described gradation display by the liquid crystal element, it is preferable that the driving circuit 2 supplies a gradation signal.

Further, the above-mentioned liquid crystal elements P ₁ , P ₂
May be used for color display. As a method of performing such a color display, there are a method of arranging a color filter in each pixel, a method of sequentially irradiating a liquid crystal element with light of a different color without using such a color filter, and A method of changing an image in synchronization with irradiation (a so-called field sequential method).

[0064] (5) Next, an example of an active matrix type liquid crystal device _{P 1} configuration using TFT, FIG. 2 and FIG. 10
This will be described with reference to FIG.

[0065] The liquid crystal element P ₁ shown in the figures, a pair of glass substrates 1a arranged with a predetermined spacing, 1b, comprises a, the entire surface of one glass substrate 1a, the common electrode having a uniform thickness (Second electrode) 3a is formed, and the common electrode 3a
Is formed with an orientation control film 6a.

[0066] Further, on the side of the other glass substrate 1b, as shown in FIG. 10, gate lines _G 1, _{G 2,} ... are arranged in large numbers in the X-direction, the gate lines _G 1, _{G 2,} ... and In the figure, a large number of insulated source lines S ₁ , S ₂ ,... Then, these gate lines G ₁ ,
A pixel electrode (first electrode) made of a thin film transistor (amorphous SiTFT) 4 as a switching element or a transparent conductive film such as an ITO film is provided at a pixel at each intersection of G ₂ ,... And source lines S ₁ , S ₂ ,. 3b, the storage capacitor electrode 7 and the like are arranged.

Of these, the amorphous Si TFT 4 is
As shown in FIG. 2, a gate electrode 10, an insulating film (gate insulating film) 5b made of silicon nitride (SiNx),
A-Si layer 11 or n ⁺ a-Si layer 12 which is a semiconductor layer;
13, a source electrode 14, a drain electrode 15, and a channel protection film 16 for protecting a channel. That is, the gate electrode 10 is formed for each pixel on the glass substrate 1b, the surface of the gate electrode 10 is covered with the insulating film 5b, and the surface of the insulating film 5b is located at the position where the gate electrode 10 is formed. An a-Si layer 11 is formed. On the surface of the a-Si layer 11, n ⁺ a-Si layers 12 and 13 are formed so as to be separated from each other, and the source electrode 14 is provided on each of the n ⁺ a-Si layers 12 and 13.
And the drain electrode 15 are formed to be separated from each other. Further, the a-Si layer 11 and the electrodes 14, 1
Channel protection film 16 is formed so as to cover 5.

The gate electrode 10 of the TFT 4 is connected to the scanning signal driver 20 via the above-described gate lines G ₁ , G ₂ ,..., And the source electrode 14 of the TFT 4 is connected via the source lines S ₁ , S ₂ ,. And the drain electrode 15 of the TFT 4 is connected to the pixel electrode 3b.

Incidentally, the above-mentioned storage capacitor electrode 7 is formed on the surface of the glass substrate 1b, and the above-mentioned insulating film 5 is formed.
b is formed to a position that covers the storage capacitor electrode 7 and the glass substrate 1b, and the source electrode 14 and the pixel electrode 3 described above are formed.
b is formed on the surface of the insulating film 5b. As a result, the storage capacitor electrode 7 and the pixel electrode 3b are arranged with the insulating film 5b interposed therebetween.
So that the storage capacitor C _s provided in the form of a parallel with the liquid crystal 2 is configured (see FIG. 11). Note that this storage capacitor electrode 7 is preferably formed of transparent ITO in order to prevent a decrease in aperture ratio when the area is increased.

Further, as shown in FIG.
An alignment control film 6b is formed on the surface of the pixel electrode 3 or the pixel electrode 3b, and a uniaxial alignment process (rubbing process) is performed on the surface.

Further, a chiral smectic liquid crystal 2 having spontaneous polarization is disposed in the gap between the glass substrates 1a and 1b and between the pixel electrode 3b and the common electrode 3a, and the liquid crystal capacitance C _lc is increased. (See FIG. 11).

[0072] On both sides of the liquid crystal element P _1, are a pair of polarizing plates (not shown) is disposed in a relationship that polarization axes are orthogonal to each other.

Although the amorphous Si TFT 4 is used in the liquid crystal element P ₁ shown in FIG. 2, the present invention is not limited to this, and a polycrystalline Si (p-Si) TFT may be used.

[0074] (6) Next, an example of a method of driving the liquid crystal device P ₁ described above.

When driving the liquid crystal element according to the present invention, a voltage may be applied to the chiral smectic liquid crystal 2 via the first and second electrodes 3a and 3b.

In this case, the first and second electrodes 3a, 3a
b to change the voltage applied to the chiral smectic liquid crystal 2 (see FIG. 9 as the chiral smectic liquid crystal 2).
In the case of using a liquid crystal having the characteristics shown in FIG. 12, the absolute value of the voltage is the same and only the polarity is changed.
As shown in (d), one still image may be displayed continuously at high luminance (first luminance) Tx and low luminance (second luminance) Ty. Here, it is preferable that the ratio of the luminance between the case where the image is displayed at high luminance and the case where the image is displayed at low luminance (that is, the ratio between the first luminance and the second luminance) is larger than 5. Then, a moving image may be displayed by changing the still image displayed at the high luminance and the low luminance. Hereinafter, a specific description will be given.

As shown in FIG. 12, one frame period F ₀ is divided into a plurality of field periods F ₁ , F ₂ ,.
One displays a still image of high luminance at a field period F _1, in the next field period F ₂ consecutive may display the low luminance of the still image (approximately the same tone image with high brightness of the image). Hereinafter, the driving method will be described.

Here, FIG. 12 is a diagram showing an example in which each frame period F ₀ is divided into _two field periods F ₁ and F ₂ , and FIG. 12A shows one gate line G _i. FIG. 2B shows a state in which a gate voltage Vg is applied to FIG.
Shows how the source voltage Vs is applied to the source line S _j of a certain one, FIG. (C), the pixel at the intersection of the gate lines G _i and the source line S _j (i.e., the liquid crystal 2) FIG. 4D is a diagram illustrating a state in which the voltage V _pix is applied, and FIG. 4D is a diagram illustrating a change in the amount of transmitted light in the pixel. In addition,
The liquid crystal 2 has a characteristic shown in FIG.

[0079] Now, a period of time the gate line _{G i} of a certain one (selection period T _on) only the gate voltage Vg is applied (see FIG. (A)), the source line _{S j} of a certain one, the gate in the selection period T _on in synchronization with the application of the voltage Vg, the common electrode 3a
Source voltage Vs (= + V
x) is applied (see FIG. 3B). Then, the TFT 4 of the pixel is turned on by the application of the gate voltage Vg, the source voltage Vx is applied via the TFT 4 and the pixel electrode 3b, and the liquid crystal capacitance _Clc and the storage capacitance Cs are charged.

By the way, in the non-selection period T _off other than the selection period T _on , the gate voltage Vg is changed to the other gate lines G ₁ ,
G ₂ ,... And the gate line G shown in FIG.
_No voltage is applied to _i , and the TFT 4 of the pixel is turned off.
Accordingly, the liquid crystal capacitor C _lc and the storage capacitor Cs hold the charged electric charges during this period (FIG. 9C).
reference). Thus, 1 is the liquid crystal 2 through the field period F ₁ becomes the voltage V _pix (= + Vx) is continuously applied, so that the substantially the same amount of transmitted light Tx is maintained (see FIG. (D)).

[0081] In the next field period F _2, is applied again the gate voltage Vg to the gate line G _i as described above (see FIG. (A)), the synchronization with the source line S _j to this, previous A source voltage −Vx having a polarity opposite to that of the source voltage is applied (see FIG. 3B). As a result, the source voltage −V
x is charged in the liquid crystal capacitor _Clc and the storage capacitor Cs, and the charge is held in the non-selection period _Toff (see FIG. 3C). Thereby, one field period F
₂ , the voltage V _pix (= −Vx) is continuously applied to the liquid crystal 2, and the substantially same transmitted light amount Ty is maintained (see FIG. 3D).

[0082] Incidentally, according to the driving method shown in FIG. 12, the liquid crystal 2 is switched in accordance with the size of each field period F _1, F ₂ units at an applied voltage, different for each field period F _1, F ₂ units Gradation display state (transmitted light amount T
x, Ty) is obtained, frame - total amount of transmitted light obtained by averaging them Tx, the Ty-free period _{F 0} is obtained.

[0083] Incidentally, the amount of transmitted light Ty in the second field period F _2, is substantially 0 level significantly less than Tx, frame - transmitted light quantity of the whole beam period, first by the averaging of the transmitted light amount as described above Field period F ₁
Of the transmitted light amount. Therefore,
In actual driving, frame - based on the amount of transmitted light to be obtained in the whole arm period (the gray level of the display image), (to be higher than the display gradation) transmitted light quantity Tx of the first field period F ₁ determines, What is necessary is just to apply the voltage Vx which obtains this transmitted light quantity Tx.

In the case of driving as described above, the voltage of the positive polarity (+ V) during the odd field period (for example, F ₁ ).
x) is applied to the liquid crystal 2, and a negative voltage (−Vx) is applied to the liquid crystal 2 in an even field period (for example, F ₂ ). And the deterioration of the liquid crystal 2 is prevented.

[0085] Further, in the first field period F ₁ performs high-brightness display, in order to perform the next field period F ₂ at low luminance display, the time the aperture ratio is much less than 50%. Therefore, when a moving image is displayed on such a liquid crystal element, the image quality is good.

(7) Next, a method for manufacturing the liquid crystal element according to the present embodiment will be described. In manufacturing the above-described liquid crystal element, * a step of arranging a pair of substrates 1a and 1b with a predetermined gap therebetween; * a step of arranging a chiral smectic liquid crystal 2 between the pair of substrates 1a and 1b. * A step of arranging a pair of electrodes 3a and 3b so as to sandwich the chiral smectic liquid crystal 2; and * an alignment control film 6a and 6b for aligning the chiral smectic liquid crystal 2 so as to be in contact with the liquid crystal 2. Steps and are performed in an appropriate order.

The chiral smectic liquid crystal 2 disposed between the electrodes 3a and 3b is cooled down from the high temperature side, and the chiral smectic liquid crystal 2 at the time of phase transition to the chiral smectic C phase (SmC ^* ) is included in the pair. A DC voltage is applied through the electrodes 3a and 3b.

The magnitude of the DC voltage is 100 mV
The range is not less than 10 V and not more than 10 V (preferably, not less than 1 V and not more than 8 V).

(8) Next, effects of the present embodiment will be described.

According to the present embodiment, the orientation control films 6a,
By setting the surface roughness and the like of 6b in the above range, the entire liquid crystal becomes an alignment having an oblique bookshelf structure, and a liquid crystal element having a uniform liquid crystal layer structure can be manufactured. The occurrence of inner unevenness can be prevented.

Further, by using a chiral smectic liquid crystal 2 having no bistability, gradation display is possible, and moving picture quality can be improved by continuous display with low luminance and high luminance.

Further, according to the present embodiment, a liquid crystal element having a high response speed can be obtained.

[0093]

The present invention will be described below in more detail with reference to examples. (Example 1) <Preparation of liquid crystal composition> First, the following liquid crystal compounds were mixed at the weight ratios shown on the right side of each, to prepare a liquid crystal composition LC used in this example.

[0094]

Embedded image

The physical parameters of the liquid crystal composition LC are as follows.
Shown below. 83.6 61.2 -10.2 Phase transition temperature (° C.): ISO. → Ch → SmC^* → Cry spontaneous polarization (30 ° C.): Ps = 2.9 nC / cm²  Cone angle (30 ° C.): Θ = 23.3 ° SmC^*Spiral pitch in phase (30 ° C): 20 μm or more

<Preparation of Liquid Crystal Cell> First, a thickness of 1.1 mm
A 700 ° ITO film (indium tin oxide film) 3a, 3b was formed as a transparent electrode on each of the pair of glass substrates 1a, 1b. Note that the transparent electrodes 3a and 3b were not patterned, and the liquid crystal cell was a single pixel.

Then, polyamic acid (LP-64, manufactured by Toray Industries, Inc.) was spin-coated on the transparent electrodes 3a and 3b of the substrate, and this was pre-dried at 80 ° C. for 5 minutes and at 200 ° C. for 60 minutes. After baking for minutes, the orientation control films (polyimide films) 6a and 6b having a thickness of 300 ° were formed. Thereafter, a rubbing treatment (uniaxial orientation treatment) with a nylon cloth was performed on the alignment control films 6a and 6b. For this rubbing treatment, a rubbing roll having a diameter of 10 cm and nylon (NF-77 / manufactured by Teijin Limited) bonded to the outer peripheral surface was used, the pushing amount was 0.3 mm, and the feeding speed was 50 cm.
/ Sec, the number of rotations is 1000 rpm, and the number of feeds is 2
Times. When the surface roughness Ra of the alignment control films 6a and 6b was measured using an AFM (scanning probe microscope), Ra = 0.39 and Sr / S = 1.0009. The measurement conditions were as follows: a Si cantilever (tetrahedral type) was used as the probe, the tapping mode was used as the scanning mode, and the scanning range was 3.0 μm × 3.0 μm.

Subsequently, on one of the substrates, the average particle size was 1.
A 5 μm silica bead (spacer) 8 is scattered, and a pair of substrates 1a and 1b are bonded together so that their rubbing directions are anti-parallel to each other. Obtained. The pretilt angle of the cell measured by a crystal rotation method was 0.7 °.

The liquid crystal composition LC is injected into the cell produced by such a process at an isotropic phase temperature, cooled to a temperature at which the liquid crystal exhibits a chiral smectic liquid crystal phase, and the liquid crystal undergoes a phase transition from the Ch phase to the SmC ^* phase. In this case, an offset voltage (DC voltage) of -5 V was applied to produce a liquid crystal panel.

The alignment state, optical response, rectangular wave response, and layer tilt angle of the manufactured liquid crystal panel were examined. The results were as follows.

1. Orientation State When the orientation state of the liquid crystal was observed by a polarizing microscope, it was found that the entire liquid crystal had an oblique bookshelf structure.

At room temperature (30 ° C.), the darkest axis was slightly deviated from the rubbing direction when no voltage was applied, and a uniform alignment state in which the layer normal direction was only one direction in the entire cell was observed. .

2. Optical Response In order to measure the electro-optical response exhibited by the liquid crystal panel, the liquid crystal panel was placed under a crossed Nicol on a polarizing microscope equipped with a photomultiplier so that the polarization axis was in a dark field with no voltage applied.

± 30 V at 30 ° C., 0.2 Hz
When the optical response when the triangular wave voltage was applied was observed, the amount of transmitted light gradually increased in accordance with the magnitude of the applied voltage when the voltage of the positive polarity was applied. On the other hand, the optical response at the time of application of the voltage of the negative polarity shows that the transmitted light amount changes with respect to the voltage level, but the maximum light amount is about 1/8 of the maximum transmittance at the time of the application of the positive polarity voltage. Met.

In this liquid crystal panel, domain switching was performed until the saturation voltage was reached.

3. Rectangular Wave Response A rectangular wave voltage of 60 Hz (± 5 V) was applied to the liquid crystal panel, and the optical response was observed as described above while changing the voltage.

As a result, when a positive voltage is applied,
The optical response was sufficient, and it was confirmed that the optical response did not depend on the previous state and a stable halftone state was obtained. On the other hand, when a negative polarity voltage is applied, an optical response of about ８ of the maximum transmittance when a positive polarity voltage of the same magnitude (absolute value) is applied is observed. It was confirmed that the average value did not depend on the previous state and a stable halftone was obtained.

The rise time due to the application of the positive-polarity square wave voltage (the time when the transmittance becomes 90% of the transmittance to be obtained by applying a predetermined voltage from the darkest state).
And the fall time (time when the transmittance becomes 10% of the transmittance from the saturated transmittance state at a predetermined voltage) when the high voltage (approximately 5 V) is applied. 8
mV, 0.3 mV, and 2.1 ms and 0.2 ms, respectively, when a low voltage (approximately 1 V) was applied, and high-speed response was confirmed as compared with switching with a general nematic liquid crystal. Was.

4. Measurement of Layer Inclination Angle In this measurement, a liquid crystal panel dedicated to X-ray measurement was used. In this liquid crystal panel, glass substrates 1a and 1b each having a thickness of 80 μm were used to minimize absorption of X-rays. Other structures were the same as those of the liquid crystal panel manufactured in this example.

When the tilt angle of the liquid crystal layer in the liquid crystal panel was measured, one θ was observed, and it was apparent that the liquid crystal layer had an oblique bookshelf structure.

(Comparative Example 1) In this comparative example, a liquid crystal panel having the same structure as in Example 1 was manufactured in the same manner as in Example 1 except that the rubbing roll feed speed was set to 5 cm / sec and the number of feeds was set to 6. Produced. When the surface roughness Ra of the alignment control films 6a and 6b was measured by the same method as in Example 1, it was Ra = 0.67 nm and Sr / S = 1.0031.

The pretilt angle measured by the crystal rotation method was 2.5 °.

The liquid crystal panel manufactured in this comparative example was also subjected to the same alignment state, optical response,
When the rectangular wave response and the inclination angle of the layer were examined, the results were as follows.

1. At room temperature (30 ° C.), a uniform alignment state was observed in which the darkest axis was slightly deviated from the rubbing direction and the layer normal direction was only one direction in the entire cell. The alignment had a chevron structure over the entire surface of the substrate.

[0115] 2. Optical response The same observation result as in Example 1 was obtained. In the liquid crystal panel of this comparative example, domainless switching was performed until the saturation voltage was reached.

3. Rectangular Wave Response When the same rectangular wave voltage as in Example 1 was applied and the optical response was observed, similar results were obtained. Therefore, according to the present liquid crystal panel, it was found that analog gradation display by amplitude modulation by TFT active matrix driving was possible.

4. Measurement of the inclination angle of the layer Two θs were observed, and it was apparent that the layer had a chevron structure.

(Examples 2 to 13) Orientation control films 6a and 6b
(Structural formula), surface roughness Ra, and surface area were different from each other as shown in the following table. Other configurations and manufacturing methods were the same as in Example 1.

The alignment state, optical response, rectangular wave response, and layer tilt angle of the manufactured liquid crystal panel were examined. The results were as follows.

[0120] 1. At room temperature (30 ° C.), a uniform alignment state was observed in which the darkest axis was slightly deviated from the rubbing direction and the layer normal direction was only one direction in the entire cell. In all liquid crystal panels, the liquid crystal panel had an oblique bookshelf structure over the entire surface of the substrate.

2. Optical Response In order to measure the electro-optical response exhibited by the liquid crystal panel, the liquid crystal panel was placed under a crossed Nicol on a polarizing microscope equipped with a photomultiplier so that the polarization axis was in a dark field with no voltage applied.

± 30 V at 30 ° C., 0.2 Hz
When the optical response when the triangular wave voltage was applied was observed, the amount of transmitted light gradually increased in accordance with the magnitude of the applied voltage when the voltage of the positive polarity was applied. On the other hand, the optical response at the time of application of the voltage of the negative polarity shows that the transmitted light amount changes with respect to the voltage level, but the maximum light amount is about 1/8 of the maximum transmittance at the time of the application of the positive polarity voltage. Met.

3. Rectangular Wave Response A rectangular wave voltage of 60 Hz (± 5 V) was applied to the liquid crystal panel, and the optical response was observed as described above while changing the voltage.

As a result, when a positive voltage is applied,
The optical response was sufficient, and it was confirmed that the optical response did not depend on the previous state and a stable halftone state was obtained. On the other hand, when a negative polarity voltage is applied, an optical response of about ８ of the maximum transmittance when a positive polarity voltage of the same magnitude (absolute value) is applied is observed. It was confirmed that the average value did not depend on the previous state and a stable halftone was obtained.

[0125] 4. Measurement of Layer Inclination Angle In this measurement, a liquid crystal panel dedicated to X-ray measurement was used. In this liquid crystal panel, glass substrates 1a and 1b each having a thickness of 80 μm were used to minimize absorption of X-rays. Other structures were the same as those of the liquid crystal panel used for measuring the alignment state and the like.

When the tilt angle of the liquid crystal layer in the liquid crystal panel was measured, one θ was observed, and it was apparent that the liquid crystal panel had an oblique bookshelf structure.

[0127]

[Table 1]

(Comparative Examples 2 to 11) Orientation control films 6a and 6b
(Structural formula), surface roughness Ra, and surface area were different from each other as shown in the following table. Other configurations and manufacturing methods were the same as in Example 1.

The alignment state, optical response, rectangular wave response, and layer tilt angle of the manufactured liquid crystal panel were examined. The results were as follows.

[0130] 1. At room temperature (30 ° C.), a uniform alignment state was observed in which the darkest axis was slightly deviated from the rubbing direction and the layer normal direction was only one direction in the entire cell. Further, there were an alignment state in which the oblique bookshelf alignment region and the chevron alignment region were mixed in a half ratio, and an alignment state in which the entire surface had a chevron structure.

[0131] 2. Optical response The same observation result as in Example 1 was obtained. In the liquid crystal panel of this comparative example, domainless switching was performed until the saturation voltage was reached.

3. Rectangular Wave Response When the same rectangular wave voltage as in Example 1 was applied and the optical response was observed, similar results were obtained. Therefore, according to the present liquid crystal panel, it was found that analog gradation display by amplitude modulation by TFT active matrix driving was possible.

4. Measurement of layer inclination angle The measurement results are as shown in the table below.

[0134]

[Table 2]

[0135]

As described above, according to the present invention,
By setting the surface roughness or the like of the alignment control film in the above range, a liquid crystal element having a uniform liquid crystal layer structure can be manufactured, and generation of alignment defects and in-plane unevenness can be prevented.

Further, by using a chiral smectic liquid crystal having no bistability, gradation display is possible, and moving image quality can be improved by continuous display with low luminance and high luminance.

Further, according to the present invention, a liquid crystal element having a high response speed can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of the structure of a liquid crystal element according to the present invention.

FIG. 2 is a sectional view showing another example of the structure of the liquid crystal element according to the present invention.

FIG. 3 is a schematic diagram showing a layer structure of liquid crystal molecules and liquid crystal in a liquid crystal alignment state in an SSFLC type element.

FIG. 4 is a schematic view showing a director in a liquid crystal alignment state shown in FIGS. 3 (a) and 3 (b).

5A is a schematic diagram showing an alignment state in each liquid crystal phase in SSFLC, and FIG. 5B is a schematic diagram showing an alignment state in each liquid crystal phase in one embodiment of the liquid crystal element according to the present invention. FIG.

FIG. 6 is a schematic view showing an alignment state of a chiral smectic liquid crystal.

FIG. 7 is a schematic view illustrating an alignment state in a chiral smectic liquid crystal phase in one embodiment of the liquid crystal element of the present invention.

FIG. 8 is a diagram for explaining inversion behavior of liquid crystal molecules when a voltage is applied.

FIG. 9 is a diagram showing an example of a voltage-transmittance characteristic of a liquid crystal.

FIG. 10 is a circuit diagram illustrating a structure of a liquid crystal element according to the present invention.

FIG. 11 is a diagram showing an equivalent circuit of an element structure.

FIG. 12 illustrates an example of a method for driving a liquid crystal element according to the present invention.

[Explanation of symbols]

1a, 1b Glass substrate (substrate) 2 Chiral smectic liquid crystal 3a Common electrode (second electrode) 3b Pixel electrode (first electrode) 4 TFT (switching element) 6a, 6b Alignment control film P ₁ Liquid crystal panel (liquid crystal element) P ₂ Liquid crystal panel (liquid crystal element)

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Takashi Moriyama, Inventor 3- 30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Takeshi Kadoba 3- 30-2 Shimomaruko, Ota-ku, Tokyo Inside Non-corporation (72) Inventor Ryuichiro Isobe 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Masahiro Terada 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. F-term (reference) 2H090 HA11 HB03Y HB07Y HB08Y HC05 HC15 HD14 KA14 KA15 LA04 MA04 MA11 MB01 MB06 2H093 NA16 NA33 NA55 NC34 NC35 ND06 ND32 ND35 NE04 NF17 NF20 NG02 5C006 AA14 AC15 BA11 BB16 FA04 AE05 JJ05 JJ06

Claims (9)

[Claims] 1. A pair of substrates disposed with a predetermined gap therebetween, a chiral smectic liquid crystal disposed between the pair of substrates, and a first and a second liquid crystal arranged to sandwich the chiral smectic liquid crystal. Comprising two electrodes and an alignment control film arranged to be in contact with the chiral smectic liquid crystal and aligning the liquid crystal, and applying a voltage to the chiral smectic liquid crystal via the first and second electrodes. In a liquid crystal element displaying an image in a plurality of frame periods per second based on the following, one frame period is divided into at least two field periods and displayed, and the first frame period is divided into at least one field period in one frame period. A desired image is displayed at a luminance of 1
In the remaining field period during the frame period, the first
At a second luminance that is smaller than the luminance of
A liquid crystal element which displays substantially the same image as the image displayed at the luminance of: wherein the arithmetic average roughness Ra of the alignment control film is Ra <0.5 nm. 2. When the projected area of a predetermined region in the orientation control film is S and the surface area of the orientation control film in the region is Sr, (Sr / S) <1.020. The liquid crystal device according to claim 1, wherein 3. The liquid crystal device according to claim 1, wherein a ratio between the first luminance and the second luminance is larger than 5. 4. The method according to claim 1, wherein the chiral smectic liquid crystal has a high temperature.
Liquid phase (ISO.)-Cholesteric phase
(Ch) -chiral smectic C phase (SmC^*),or
Is an isotropic liquid phase (ISO.)-Chiral smectic
Phase C (SmC ^*A) a liquid crystal exhibiting a phase transition series of
The normal direction of the smectic layer of the liquid crystal is substantially one
4. The method according to claim 1, wherein:
Liquid crystal element. 5. The first electrode is disposed for each pixel, a switching element is connected to each first electrode, and a voltage is applied between the first and second electrodes when the switching element is turned on. The liquid crystal element according to any one of claims 1 to 4, wherein gray scale display is performed by applying a voltage. 6. The method according to claim 1, wherein the temperature of the chiral smectic liquid crystal is lowered from a high temperature side, and a DC voltage is applied to the liquid crystal when the liquid crystal undergoes a phase transition to a chiral smectic C phase (SmC ^* ). The liquid crystal device according to claim 1. 7. The liquid crystal device according to claim 6, wherein the magnitude of the DC voltage ranges from 100 mV to 10 V. 8. The liquid crystal device according to claim 7, wherein the magnitude of the DC voltage ranges from 1 V to 8 V. 9. The liquid crystal device according to claim 1, wherein a helical pitch of the chiral smectic liquid crystal in a bulk state is longer than twice a cell thickness.