JP2000292773A - Liquid crystal device and driving method for liquid crystal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the picture quality from becoming worse as the temperature varies by setting the ratio of the transmissivity of liquid crystal below a specific value when a voltage is applied and removed. SOLUTION: This element is equipped with smectic liquid crystal 2 arranged between a couple of substrates 1a and 1b, a 1st electrode 3 and a 2nd electrode 4 which are arranged sandwiching the liquid crystal 2, multiple switching elements 5 which are connected to the 2nd electrode 4 and arranged for each pixel, 3rd electrodes G1, G2... which are connected to their gates, and 4th electrodes S1, S2... which are connected to the sources. While the 4th electrodes S1, S2... and 1st electrode 3 are held at a specific potential, the switching elements 5 are turned on by the application of a gate voltage to the 3rd electrodes G1, G2..., so that the 4th electrodes S1, S2... and the 2nd electrode 4 are driven at the same potential. Here, the ratio of the transmissivity T% of the liquid crystal when the voltage is applied to the transmissivity Td of the liquid crystal when the voltage is removed is so set that Td/T<0.1.

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 using liquid crystal and a method for driving the liquid crystal device.

[0002]

2. Description of the Related Art Conventionally, a CRT has been known as a display for displaying various information.
It is widely used in TVs and VTRs that output moving images, or in monitors of personal computers.

[0003] However, this CRT has various problems, that is, * due to its characteristics, a still image suffers from deterioration of visibility due to flicker and scanning stripes due to insufficient resolution, and deterioration of a fluorescent lamp due to burn-in. Or the electromagnetic waves generated by the CRT have a bad effect on the human body,
There is a problem that the health of DT workers may be harmed, and a problem that the structure requires a space behind the screen, which hinders space saving in offices and homes. Various types of liquid crystal devices have been developed to solve the problem of the CRT. * For example, twisted nematic (twiste
d nematic (TN) liquid crystal is known, which is disclosed by M. Schadt.
And W. Helfrich
"Applied Physics Letters (Appl
ied PhysicsLetters), Volume 18,
No. 4 (issued February 15, 1971), pages 127-1
Page 28 ".

In recent years, as a liquid crystal element using such a liquid crystal, an active matrix type liquid crystal element has been developed, and a display of 10 to 12 inches has been manufactured with a high yield due to rapid progress in production technology. Such a liquid crystal element includes a transistor (TF) in each pixel.
T), which solves the problem of crosstalk and the like, but has the problem that the response speed of the liquid crystal is slow, the image quality of moving images is inferior, and the viewing angle is narrow. * On the other hand, a display element of a type that controls transmitted light in combination with a polarizing element using the refractive index anisotropy of ferroelectric liquid crystal molecules (liquid crystal molecules exhibiting ferroelectricity) is known as Clark. ) And Lagerw
all) (JP-A-56-1072).
No. 16, US Pat. No. 4,367,924).
This ferroelectric liquid crystal generally has a chiral smectic C phase (SmC *) or H phase (SmC *) in a specific temperature range.
H *), and in this state, takes one of the first optical stable state and the second optical stable state in response to the applied electric field, and changes the state when no electric field is applied. It has the property of maintaining (i.e., bistable memory property), and also exhibits a very fast response speed because it performs inversion switching by spontaneous polarization. Furthermore, since the visual characteristics are also excellent, it is considered that they are particularly suitable as high-speed, high-definition, large-screen display elements or light valves. * Recently, Chandan, Takezoe et al. Have proposed a liquid crystal element using a liquid crystal exhibiting antiferroelectricity (hereinafter referred to as “antiferroelectric liquid crystal”) (Japan).
ese Journal of Applied Ph
ysics 27, 1988, L729). This antiferroelectric liquid crystal forms a display element by utilizing the refractive index anisotropy and spontaneous polarization of liquid crystal molecules, like the ferroelectric liquid crystal. In addition, this antiferroelectric liquid crystal generally has a chiral smectic CA phase (Sm
CA *), and in this state, when no electric field is applied, the average optical stable state is in the normal direction of the smectic layer, but the average optical stable state is tilted away from the normal direction of the layer by the application of an electric field. It has a state. Since the liquid crystal element using the antiferroelectric liquid crystal performs switching using spontaneous polarization as described above, it exhibits a very fast response speed and a high-speed display element or light valve. It is expected as. * As for this antiferroelectric liquid crystal material, a material having a small hysteresis and a V-shaped response characteristic having characteristics advantageous for gradation display has recently been discovered (for example, Japanese Journal of Applied Physics).
ied Physics) Vol. 36, 1997, 35
86). Also, it has been proposed to use this type of liquid crystal for an active matrix type liquid crystal element to realize a high-speed display (Japanese Patent Laid-Open No. 9-50049).
No.). However, driving these types of liquid crystals requires very large charges at present, which is a major barrier to realizing them.

On the other hand, when the above-mentioned ferroelectric liquid crystal is driven by an active matrix type liquid crystal element, there is no such problem, and high-speed driving is possible.

[0006]

In the above-mentioned active matrix type liquid crystal device, the characteristics of the applied voltage (writing voltage) and the light transmittance are as shown in FIG. 5, for example. Since the temperature dependency is large, there is a problem that a gradation shift occurs locally or entirely depending on the temperature of the liquid crystal element to be driven, thereby deteriorating the image quality.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a liquid crystal element which prevents deterioration of image quality due to a temperature change, and a method of driving the liquid crystal element.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and includes a pair of substrates disposed with a predetermined gap therebetween, and a smectic disposed between the pair of substrates. A liquid crystal, a first electrode and a second electrode that constitute a plurality of pixels and are arranged to sandwich the smectic liquid crystal, and a plurality of switching elements connected to the second electrode and arranged for each pixel; A state in which a third electrode connected to the gate of the switching element and a fourth electrode connected to the source of the switching element are provided, and the fourth electrode and the first electrode are held at a predetermined potential. In the liquid crystal element driven by turning on the switching element based on the application of the gate voltage to the third electrode so that the fourth electrode and the second electrode have the same potential, the voltage is applied. Transmittance of the liquid crystal in the case and the (%) is T, the transmittance of the liquid crystal in the case where removal of the voltage (%) in the case of the T _d, their permeability,

[0009]

(Equation 5) Is set so that

Further, according to the present invention, a pair of substrates arranged with a predetermined gap therebetween, a smectic liquid crystal arranged between the pair of substrates, a plurality of pixels are formed, and the smectic liquid crystal is sandwiched therebetween. Arranged as the first
An electrode, a second electrode, a plurality of switching elements connected to the second electrode and arranged for each pixel, a third electrode connected to the gate of the switching element, and a source connected to the source of the switching element. And a fourth electrode, wherein the switching element is turned on based on application of a gate voltage to the third electrode while the fourth electrode and the first electrode are maintained at a predetermined potential. In the method of driving a liquid crystal element in which the fourth electrode and the second electrode are set to the same potential and a writing voltage is applied to the liquid crystal, the transmittance (%) of the liquid crystal when a voltage is applied is T, When the transmittance (%) of the liquid crystal when the voltage is removed is _Td , the transmittance of the liquid crystal is:

[0011]

(Equation 6) Is set so that

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS.
An embodiment of the present invention will be described.

The liquid crystal element P driven in this embodiment
As shown in FIGS. 1 and 2, a pair of substrates 1a and 1b arranged with a predetermined gap therebetween, a smectic liquid crystal 2 arranged between the pair of substrates 1a and 1b,
A first electrode 3 and a second electrode 4 that constitute a plurality of pixels and are arranged to sandwich the smectic liquid crystal 2;
A plurality of switching elements 5 connected to the second electrode 4 and arranged for each pixel; third electrodes G ₁ , G ₂ ,... Connected to the gates of the switching elements 5; The fourth electrodes S ₁ , S ₂ ,... Connected to the sources
And an active matrix type including:

Next, a method of driving the liquid crystal element P according to the present embodiment will be described with reference to FIG. Here, FIG. 3 is a timing chart showing an example of a driving method of the liquid crystal element according to the present invention, and (a) shows the third electrodes G ₁ , G
₂ is a diagram showing the timing of the gate voltage V _g applied to the gate of the switching element 5 through a ..., (b)
Is a diagram showing the timing of the voltage applied to the source of the switching element 5 via the fourth electrodes S ₁ , S ₂ ,... (C) is a diagram showing the voltage applied to the smectic liquid crystal 2 FIG. 2D is a diagram showing the optical response of the smectic liquid crystal 2.

Driving of the liquid crystal element P in the present embodiment is carried out by: * maintaining the fourth electrodes S ₁ , S ₂ ,... And the first electrode 3 at a predetermined potential (see FIG. 2B). , * A gate voltage V _g2 is applied to the third electrodes G ₁ , G ₂ ,... (See FIG. 3A), * thereby turning on the switching element 5 and turning on the fourth electrodes S ₁ , S _2, ... and to the second electrode 4 at the same potential, * thereby applying a write voltage V _D to the smectic liquid crystal 2 may be performed by.

[0016] In this case, application of the write voltage V _D to such smectic liquid crystal 2, * the fourth electrode S _1, S _2, 0V potential of the first electrode 3 to apply a write voltage V _D ... to (See FIG. 3B). * A state in which the potential of the fourth electrodes S ₁ , S ₂ ,... Is set to 0 V, and the write voltage V _D is applied to the first electrode 3. , And * a predetermined voltage may be applied to the fourth electrodes S ₁ , S ₂ ,... And the first electrode 3 (in such a case, a combination of the predetermined voltages may be used). Write voltage V
_D ).

In this case, it is _preferable to apply the reset voltage V _R before applying the write voltage V _D to the smectic liquid crystal 2 (see FIG. 3C). The method includes: * applying a reset voltage V _R to the fourth electrodes S ₁ , S ₂ ,... And setting the potential of the first electrode 3 to 0 V (see FIG. 2B). The potential of the four electrodes S ₁ , S ₂ ,... Is set to 0 V and the reset voltage V _R is applied to the first electrode 3, or * the fourth electrodes S ₁ , S ₂ ,. being applied respectively (if such is obtained by synthesizing a predetermined voltage is the reset voltage V _R) a predetermined voltage to the electrode 3, in any of the states of, * the third electrode G _1, G _2, ... , A gate voltage V _g1 is applied to the second electrode 4 (see FIG. 2A), and the switching element 5 is turned on to apply the same potential to the fourth electrodes S ₁ , S ₂ ,. * The method of applying the reset voltage V _R to the smectic liquid crystal 2 by the method is as follows. it can.

[0018] Note that the size of the write voltage V _D may be variably controlled in accordance with the display gradation, magnitude of the reset voltage V _R is, for example or to be constant at -10 V, or the write voltage V _D It is preferable to perform variable control according to the size.

The write voltage V _D and the reset voltage V
It is preferable that _R and _R have opposite polarities and that a DC component hardly occurs.

In this specification, the writing voltage V _D is a voltage applied to the smectic liquid crystal 2 for displaying an image (that is, a voltage applied between the first electrode 3 and the second electrode 4). ) means, and the reset voltage V _R, means a voltage applied to the smectic liquid crystal 2 for resetting the image (i.e., a voltage applied between the first electrode 3 and the second electrode 4) It shall be.

In the present embodiment, the transmittance (%) of the liquid crystal 2 when a voltage is applied is expressed by T
When the transmittance (%) of the liquid crystal 2 when the voltage is removed is _Td , their transmittances are as follows:

[0022]

Equation 7 It is set to be.

This can be achieved by controlling the time Δt during which the writing voltage V _D is applied to the smectic liquid crystal 2 (hereinafter referred to as “writing voltage application time”) and the spontaneous polarization of the liquid crystal 2. . Specifically, the writing voltage application time Δt and the spontaneous polarization of the liquid crystal 2 may be set to the “appropriate range” shown in FIG.

It is ideal that the liquid crystal element P is in the above-mentioned appropriate range at any temperature.
It is sufficient that the temperature is within the above-mentioned appropriate range at a temperature of not more than 40 ° C., and it is sufficient that the temperature is within the above-mentioned appropriate range at a temperature of not more than 40 ° C. or 30 ° C. or less.

The upper limit of the write voltage application time Δt is defined based on the driving frequency (for example, when driving at a driving frequency of 60 Hz, one frame period F ₀ is about 16.7 msec, and the reset period F ₁ Is not considered, the one-frame period F ₀ is the upper limit), so that the spontaneous polarization of the smectic liquid crystal 2 is 10 n
C / cm ² or less.

To control the value of T _d / T not by the spontaneous polarization of the smectic liquid crystal 2 but by the writing voltage application time Δt, as shown in FIGS. 3 (a) to 3 (c), .. And the _first electrodes S ₁ , S ₂ ,.
It is necessary to apply a gate voltage V _g3 at a predetermined timing to turn on the switching element 5 and remove the voltage applied to the second electrode 4 in a state where the potentials of the electrodes 3 are both 0 V.

Next, the meaning of the above equation will be described with reference to FIG. Here, FIGS. 4A and 4B are schematic diagrams for explaining how the liquid crystal is inverted. FIG. 4A is a diagram showing the state of the liquid crystal molecules in an electric field-free state, and FIG. 4B is a schematic diagram of the liquid crystal when a small voltage is applied. FIG. 3C is a diagram showing a state of the molecule, and FIG. 4C is a diagram showing a state of the liquid crystal molecule when a large small voltage is applied.

Now, when a voltage is applied between the first electrode 3 and the second electrode 4, the smectic liquid crystal 2 is inverted. The inversion mode includes an inversion mode called * Swing. (See Figure (b))
And * Latch inversion mode (refer to Fig. (C))
And Although the amount of liquid crystal molecules inverted in the swing mode and the amount of liquid crystal molecules inverted in the latch mode differ depending on the magnitude and time of the applied voltage (writing voltage), generally, the liquid crystal molecules inverted in the swing mode are: The liquid crystal molecules that are away from the substrates 1a and 1b and that are inverted in the Latch mode are liquid crystal molecules that are close to the substrates 1a and 1b.

When the applied voltage is removed while the liquid crystal molecules are inverted, the liquid crystal molecules inverted in the * Swing mode return to the state before voltage application (black stable state), but are inverted in the * Latch mode. The liquid crystal molecules maintain the state when the voltage is applied.

Therefore, the ratio of the transmittance T when the voltage is applied to the transmittance T _d when the voltage is removed is T _d /
T indicates the ratio of the liquid crystal molecules inverted in the Latch mode. That is, by measuring the transmittance when the voltage is applied and when the voltage is removed, the amount of the liquid crystal molecules that are inverted in the Latch mode can be quantitatively obtained.

On the other hand, the present inventor has found that the temperature dependence of transmittance-voltage (writing voltage) is much smaller for liquid crystal molecules inverted in the swing mode than for liquid crystal molecules inverted in the latch mode. Was found.

Therefore, in order to reduce the temperature dependency as a whole of the liquid crystal element, it is sufficient to reduce the number of liquid crystal molecules that are inverted in the Latch mode.

[0033]

(Equation 8) In this case, the temperature dependence of the transmittance-write voltage can be reduced to a level that does not hinder practical use.

Hereinafter, the materials and the like of the components of the liquid crystal element P will be described in detail.

In the present embodiment, the above-described substrate 1
Glass and plastic may be used for a and 1b.

The first electrode 3 and the second electrode 4 have I
n ₂ O ₃ or ITO (Indium Tin Oxide)
The electrodes 3 and 4 may be formed on the respective substrates 1a and 1b. The electrodes 4 to which the switching elements 5 are connected are arranged in a matrix in the form of dots, and the other electrode 3 is connected to the other substrate 1a.
It is preferable to form the entire pattern or a predetermined pattern.

Further, on the surface of each of the electrodes 3 and 4, a green-green film (not shown) for preventing a short circuit between these electrodes.
It is preferable that such a green film is made of SiO ₂ , TiO _2
2 , Ta ₂ O ₅ or the like.

Further, an alignment control film (not shown) for controlling the alignment state is preferably disposed at a position in contact with the smectic liquid crystal 2, and the alignment control film may include an inorganic substance (silicon monoxide, silicon dioxide, oxidized silicon oxide). Aluminum, zirconia, magnesium fluoride, cesium oxide, silicon nitride, silicon carbide, boron nitride, etc.) and organic substances (polyvinyl alcohol, polyimide, polyamide,
Polyester, polyimide amide, polyester imide, polyparaxylene, polycarbonate, polyvinyl acetal, polyvinyl chloride, polystyrene, polysiloxane, cellulose resin, melanin resin, urea resin, and acrylic resin may be used. Among them, polyimide is preferable in order to obtain better uniaxial orientation. In such a case, a polyamic acid that is soluble in a solvent may be applied and baked to form the resist. In order to perform patterning, resist application, etching and cleaning may be performed. The surface of the orientation control film may be rubbed with a fibrous material such as velvet, cloth or paper.

As the switching element 5, TF
A thin film transistor such as T can be used, and specifically, a semiconductor such as an amorphous silicon-based one, a polysilicon type one, a microcrystal-based one, or single crystal silicon may be used.

Further, a spacer (not shown) may be arranged in the gap between the substrates 1a and 1b, and the dimension of the gap may be defined by the spacer. For this spacer, silica beads or the like may be used. The gap size may be adjusted according to the liquid crystal material.However, a uniform uniaxial orientation can be achieved, or the average molecular axis of the liquid crystal molecules in the state where no voltage is applied is set in the average direction of the alignment processing axis. In order to make the axis substantially coincide with the axis, it is preferable to set the range of 0.3 to 10 μm. For example, the gap size between the substrates 1a and 1b on which the chiral smectic liquid crystal 2 is disposed is preferably set to be equal to or less than half the helical pitch of the chiral smectic liquid crystal 2 in a bulk state.

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 to improve the adhesion between the substrates 1a and 1b and the shock resistance of the liquid crystal element P. And good.

Further, for example, a color filter (not shown) may be arranged on at least one of the substrates 1a and 1b so that color display can be performed.

The liquid crystal element P may be of a transmission type or a reflection type. In the case of a transmissive type, it is preferable to make both substrates 1a and 1b transparent and to arrange a backlight device for illumination. In the case of a reflective type, a function of reflecting light to one of the substrates 1a and 1b is provided. Should be given. Here, as a method of imparting the function of reflecting light, a method of providing a reflection plate separately from the substrate, a method of forming the substrate itself with a reflection member, and a method of forming a reflection film on the substrate Method, and the like. The liquid crystal element P may be applied to a direct-view type or a transmissive type.

On the other hand, as the smectic liquid crystal 2, a chiral smectic liquid crystal such as a ferroelectric liquid crystal can be cited. It is better to do the following.

The chiral smectic liquid crystal composition used in the present invention preferably has a structure in which a terminal portion of a fluorocarbon and a hydrocarbon portion are bound by a central nucleus, and has a smectic intermediate phase or a potential smectic intermediate phase. A fluorine-containing liquid crystal compound is desirable because it has a small bookshelf and a stable bookshelf structure.

In the fluorine-containing liquid crystal compound, the terminal portion of the fluorocarbon is a group represented by -D ¹ -C _xa F _2xa -X (where xa is 1 to 20;
Represents -H or -F, D ¹ is, -CO-O- (CH
_{2) ra -, - O- (} CH 2) ra -, - (CH 2) ra -,
_{-O-SO 2 -, - SO} 2 -, - SO 2 - (CH 2) ra
_{-, - O- (CH 2)} ra -O- (CH 2) rb -, - (C
H ₂ ) _ra -N (C _pa H _{2pa + 1} ) -SO _{2- or-} (C
_{H 2) ra -N (C pa} H 2pa + 1) represents the -CO-. ra
And rb are 20 independently, pa is 0-4), _{^{or, -D 2 - (C xb F}} 2xb -O) za -C ya F
A group represented by _{2ya + 1} (provided that xb is independently 1 to 10 for each (C _xb F _2xb -O);
Is 1 to 10, za is 1 to 10, and D ² is
_{-CO-O-C rc H 2rc} , -O-C rc H 2rc -, - C rc
H _2rc- , -O- (C _sa H _2sa -O) _ta -C _rd H _{2rd
-, - O-SO 2 -} , - SO 2 -, - SO 2 -C rc H
_{2rc -, - C rc H 2rc} -N (C pb H 2pb +1) -SO 2
—, —C _rc H _2rc —N (C _pb H _{2pb + 1} ) —CO—, a single bond, and rc and rd are each independently 1 to 20
_Wherein sa is independently 1 to 10 for each (C _sa H _2sa -O), ta is 1 to 6, and pb is 0 to 4). .

Particularly preferably, a fluorine-containing liquid crystal compound represented by the following general formula (I) or (II) can be used.

[0048]

Embedded image Represents

Ga, ha, and ia each independently represent an integer of 0 to 3 (provided that ga + ha + ia is at least 2).

Each of L ¹ and L ² is independently a single bond, -C
O-O-, -O-CO-, -COS-, -S-CO-,
-CO-Se-, -Se-CO-, -CO-Te-,-
_{Te-CO -, - CH 2} CH 2 -, - CH = CH -, -
C≡C -, - CH = N - , - N = CH -, - CH 2 -O
_{-, - O-CH 2 -} , - CO- or represent -O-.

Each of X ¹ , Y ¹ and Z ¹ is A ¹ , A ² , A
³ , independently of -H, -Cl, -F, -B
r, -I, represent _{-OH, -OCH 3, -CH 3,} -CN, or -NO _2, each of ja, ma, na are independently an integer of 0-4.

J ¹ is -CO-O- (CH ₂ ) _ra -,-
_{O- (CH 2) ra -,} - (CH 2) ra -, - O-SO 2
_{-, - SO 2 -, -} SO 2 - (CH 2) ra -, - O-
(CH ₂ ) _ra -O- (CH ₂ ) _rb -,-(CH ₂ ) _{ra-
N (C pa H 2pa + 1} ) -SO 2 -, or - (CH _{2) ra} -
_{N (C pa H 2pa + 1} ) represents the -CO-. ra and rb
Is independently 1 to 20, and pa is 0 to 4.

R ¹ is _{-OC qa} H _{2qa -OC qb} H
_{2qb + 1, -C qa H 2qa} -O-C qb H 2qb + 1, -C qa H
_{^{2qa -R 3, -O-C qa}} H 2qa -R 3, -CO-O-C
_qa H _2qa -R ^3, or represents _{-O-CO-C qa H 2qa} -R 3, linear, may be either branched (wherein, R ³ is, -O-CO-C _qb H _{2qb + 1} , -CO-O-
_{C qb H 2qb + 1, -H} , -Cl, -F, -CF 3, -NO
₂ , -CN, and qa and qb are independently 1-20).

R ² represents C _xa F _2xa -X (X is -H
Or -F, and xa is an integer of 1 to 20).

[0055]

Embedded image Represents

Gb, hb and ib are each independently 0 to 3
(Where gb + hb + ib is at least 2).

Each of L ³ and L ⁴ is independently a single bond, -C
O-O-, -O-CO-, -CO-S-, -S-CO
-, -CO-Se-, -Se-CO-, -CO-Te
-, - Te-CO -, - (CH 2 CH 2) ka - (ka is 1~4), - CH = CH - , - C≡C -, - CH = N
-, - N = CH -, - CH 2 -O -, - O-CH 2 -,
Represents -CO- or -O-.

X ² , Y ² and Z ² are A ⁴ , A ⁵ and A
⁶ is independently -H, -Cl, -F, -B
_{r, -I, -OH, -OCH 3} , -CH 3, -CF 3,
Represents —O—CF ₃ , —CN, or —NO ₂ , and each of jb, mb, and nb represents an integer of 0 to 4.

J ² is —CO—O—C _rc H _2rc —, _{—O
-C rc H 2rc -, - C} rc H 2rc -, - O- (C sa H 2sa
-O) _ta -C _rd H _2rd- , -O-SO _2- , -SO _{2
-, - SO 2 -C rc H} 2rc -, - C rc H 2rc -N (C pb
_{H 2pb + 1) -SO 2 -} , - C rc H 2rc -N (C pb H
_{2pb + 1} ) -CO-, wherein rc and rd are independently 1-2.
0, sa is independently 1 to 10 for each (C _sa H _2sa -O), ta is 1 to 6, pb is 0 to 4
It is.

R ⁴ is —O— (C _qc H _2qc —O) _wa —C
_{qd H 2qd + 1, - (} C qc H 2qc -O) wa -C qd H 2qd + 1,
^{_{-C qc H 2qc -R 6, -O}} -C qc H 2qc -R 6, -CO
^{_{-O-C qc H 2qc -R 6}} , or _{-O-CO-C qc} H 2qc
Represents —R ^{6 and} may be linear or branched (provided that R ⁶ is —O—CO—C _qd H _{2qd + 1} , —CO—
_{O-C qd H 2qd + 1} , -Cl, -F, -CF 3, -NO
₂ , -CN, or -H, qc and qd are each independently an integer of 1 to 20, and wa is an integer of 1 to 10).

R ⁵ is (C _xb F _2xb -O) _za -C _ya F
_{2ya + 1} is represented by (wherein, the formula xb is 1 to 10 independently of each _{(C xb F 2xb -O),} ya is 1
And za is 1-10).

The compound represented by the above general formula (I) is
JP-A-2-142755, U.S. Pat.
2,587.
Specific examples of such compounds are listed below.

[0063]

Embedded image

[0064]

Embedded image

[0065]

Embedded image

[0066]

Embedded image

[0067]

Embedded image

[0068]

Embedded image

[0069]

Embedded image

[0070]

Embedded image

[0071]

Embedded image

[0072]

Embedded image

[0073]

Embedded image

[0074]

Embedded image The compound represented by the above general formula (II) is disclosed in International Publication W
O93 / 22396 and JP-T-7-506368. Specific examples of such compounds are listed below.

[0075]

Embedded image

[0076]

Embedded image

[0077]

Embedded image

[0078]

Embedded image

[0079]

Embedded image In particular, a compound represented by the general formula (III) is preferably used as a chiral component used in a liquid crystal composition. The compound represented by the general formula (III) can be obtained by the method described in W96 / 33251.

[0080]

Embedded image Wherein M, N and P are each independently:

[0081]

Embedded image

[0082]

Embedded image Represents

A, b and c are such that a + b + c is at least 1
And preferably an integer of 0 to 3 independently, provided that it is not larger than 2.

Each of A and B may independently be in any direction, ie, -C (= O) -O-, -C (= O) -S
-, -C (= O) -Se-, -C (= O) -Te-,-
(CH ₂ CH ₂ ) _k- (where k is 1 to 4) -C
H = CH -, - C≡C - , - CH = N -, - CH 2 -
Represents O-, -C (= O)-, -O-.

Each of X, Y and Z is independently -H,
-Cl, -F, -Br, -I, -OH, -OCH 3,
_{-CH 3, -CF 3, -OCF 3} , -CN, -N
O ₂ to represent each of l, m, n are independently an integer of 0-4.

D can be in any direction.

[0087]

Embedded image Represents

[0088] r and r 'are independently an integer of 0 to 20, s is 1 independently of each _{(C s H 2s} O)
10, t is an integer of 1 to 6, and p is an integer of 0 to 4.

R is

[0090]

Embedded image Represents

R ′ is independently —Cl, —F, —CF _{3
, -NO 2, -CN, -H,} -C q H 2q + 1,
_{-O- (O =) C-C} q H 2q + 1, -C (= O) -
_{O-C q H 2q + 1} , -Br, -OH, -OC q H
_{2q + 1} (preferably -H, -F), and q '
Is, independently for each (C _{q ′} H _{2q ′} —O), 1 to
20, q is an integer of 1 to 20, w is 1 to 1
Is an integer of 0, v is an integer of 0 to 6, v 'is each independently an integer of 0 to 6, q is an integer of 1 to 3, and D is a group represented by the structure shown above. The direction of the ring structure including D is composed of 3 to 10 atoms. W is independently N, CR ', Si
R ′, and R ′ may be chiral or achiral.

Rf 'is -R ^* -D- (O) _x- C
Represent H _{2 -D'-R f.} Here, R ^* may be a cyclic chiral or an acyclic chiral. D and D ′ are the same as those described above, and may have any direction independently, x is 0 or 1, R _f is fluoroalkyl,
Perfluoroalkyl, fluoroether, or perfluoroether. Preferably R _f is fluoroalkyl, fluoroether or perfluoroether.

R ^* is

[0094]

Embedded image Represents

R 'is independently -Cl, -F, -CF
_{3, -NO 2, -CN, -H} , -C q
_{H 2q + 1, -O- (O} =) C-C q H 2q + 1, -
_{C (= O) -O-C} q H 2q + 1, -Br, -OH,
-OC _q H _{2q + 1} (preferably -H, -F, -C
F ₃ , —Br, —OH, and —OCH ₃ , more preferably —H, —F, and —CF ₃ ), and q ′ is ((C _{q ′} H _{2q′-v ′} — ( R ') _v' )-
O) is independently 1 to 20, q is an integer of 1 to 20, w is an integer of 0 to 10, v is an integer of 0 to 6, and each v 'is independently 0 to 0. 6 is an integer of q, q is an integer of 1 to 3, and each D has the structure shown above, independently of any direction, and the ring structure containing D is composed of 3 to 10 atoms. Is done. Each w independently represents N, CR ', SiR'. More preferably,
R _f is a perfluoroether. D 'is preferably a covalent bond.

In R _f , the perfluoroalkyl group is represented by the structure of —C _q F _2q X ′. Where q
Is as described above (preferably at least 5), and X ′ is hydrogen or fluorine. Fluoroalkyl and fluoroether groups are represented by the structure -Rf _" -Rh _' , where _Rf" is linear or branched and has 1 to 10 (preferably 2 to 6) A fluorinated or partially fluorinated alkyl group having carbon atoms and having one or more ether oxygen atoms attached thereto. _Rh is a straight-chain or branched alkyl group, having 1 to 14 (preferably 3 to 10) carbon atoms, and one or more ether oxygen atoms. R _{f "is} preferably is fluorinated, _{R h} and _{R f"} both are linear, _{R h} and R
_At least one of the radicals of _{f ″} has at least one ether oxygen atom. More preferably, R _h or R
_{Both h} and _{Rf "} have at least one ether oxygen atom.

Preferably, the perfluoroether group is
- _{(C x} F _{2x O)} represented by 2 _{C y F 2y + 1} structure. Here, x is the respective (C _x F
_2xO ) is independently 1 to 10, y is an integer of 1 to 10, and z is an integer of 1 to 10. Preferably, the perfluoroether group is linear, x is 1-6 independently of each _{(C x F 2x O),} y is an integer from 1 to 6, z is 1 to 6 It is an integer.

Preferably, the chiral compound is represented by the following structural formula:

R ″-(O) _j -G- (OCH ₂ ) _{j
^{-R * - (C s H 2s}} O) t C r 'H 2r' -
R _f R "represents a _{(R ') v -C q H} 2q + 1-v.
Here, q is an integer of 2 to 10, and each R ′
Is independently a hydrogen, fluorine, chlorine, methyl, or perfluoromethyl group. v is an integer of 1 to 3, j is 0 or 1, and G is

[0100]

Embedded image Represents

R ^* is

[0102]

Embedded image Represents

Here, R 'is -F, q is an integer of 1-4, v is an integer of 1-3, w is N or CH
In and, D is -C (= O) -O- or -CH ₂ -. s is an integer of 1 to 6, t is 0 or 1,
r 'is an integer from 1 to 3, _{R f is,} -C _{q F 2q
X ', - R f "-R} h, - (C x F 2x O) z C
represents _y F _{2y + 1} . Here, q is an integer of 1 to 6, and X ′ is fluorine. R _{f ″} is a linear or branched, partially fluorinated alkyl group,
It has up to 4 carbon atoms and is chained with one or more ether oxygen atoms. _Rh is a linear or branched alkyl group having 2 to 7 carbon atoms and 1
Or more ether oxygen atoms are continuous. x
Is 1 to 10 independently of each _{(C x F 2x O),} y is an integer from 1 to 8, z is an integer of 1 to 5.

[0104]

[Table 1]

[0105]

[Table 2]

[0106]

[Table 3]

[0107]

[Table 4]

[0108]

[Table 5] Next, effects of the present embodiment will be described.

According to the present embodiment, the temperature dependency of the transmittance-voltage characteristics can be reduced, and the deterioration of the image quality can be avoided even if there is some temperature fluctuation.

[0110]

The present invention will be described below in more detail with reference to examples.

Example 1 In this example, an active matrix type liquid crystal panel (liquid crystal element) P shown in FIGS. 1 and 2 was prepared and driven by the method shown in FIG.

First, the structure of the liquid crystal panel P will be described with reference to FIG.
This will be described with reference to FIG.

The liquid crystal panel P has a pair of glass substrates 1a,
A common electrode (first electrode) 3 having a uniform thickness is formed on the entire surface of one glass substrate 1a, and a surface of the common electrode 3 is formed. Was formed with an insulating film (not shown). Reference numeral 10 indicates a color filter, reference numeral 11 indicates a black matrix, and reference numeral 12 indicates a flattening film.

On the other glass substrate 1b side, as shown in FIG. 2, a large number of gate lines G ₁ , G ₂ ,... Are formed in the X direction in the figure, and source lines S ₁ , S ₂ ,. Many were formed in the illustrated Y direction. Then, these gate lines G ₁ , G ₂ ,
And the pixel at each intersection of the source lines S ₁ , S ₂ ,..., A thin film transistor (amorphous SiTFT) 5 as a switching element and a pixel electrode (second electrode) 4 made of a transparent conductive film such as an ITO film The capacitor electrode 6 and the like were formed. The pixel electrode 4 had a size of 100 μm × 30 μm, and constituted a pixel together with the common electrode 3.

The storage capacitor electrode 6 is formed on the surface of the glass substrate 1b at a position overlapping the pixel electrode 4.
An insulating film 17 made of silicon nitride (SiNx) having a thickness of 0.3 μm was formed in the gap between the electrodes 6 and 4 to form the auxiliary capacitance Cs.

On the other hand, the above-described amorphous Si TFT 5
Are a gate electrode 5a and an insulating film (gate insulating film) 5c.
And an a-Si layer 5d or an n + a-Si layer 5 as a semiconductor layer.
e, 5f, a source electrode 5b, a drain electrode 5g,
It was constituted by. That is, the gate electrode 5a is formed for each pixel on the glass substrate 1b, the surface of the gate electrode 5a is covered with the insulating film 5c, and the surface of the insulating film 5c is located at the position where the gate electrode 5a is formed. The -Si layer 5d was formed. On the surface of the a-Si layer 5d, n + a-Si layers 5e and 5f are formed so as to be separated from each other.
The source electrode 5b and the drain electrode 5g were formed on the + a-Si layers 5e and 5f so as to be separated from each other.

The gate electrode 5a of the TFT 5 is connected to the gate driver 1 via the gate lines G ₁ , G ₂ ,.
5 and the source electrode 5b of the TFT 5 is connected to the source line S
_. , S ₂ ,.
The drain electrode 5g of the FT 5 was connected to the pixel electrode 4.

On the other hand, an alignment control film (not shown) was formed so as to cover the above-described TFT 5 and pixel electrode 4, and the surface thereof was subjected to a uniaxial alignment treatment (rubbing treatment).

Then, a chiral smectic liquid crystal 2 was disposed between the glass substrates 1a and 1b. Therefore, the common electrode 3 and the pixel electrode 4 are arranged so as to sandwich the liquid crystal 2.

The thickness of the glass substrates 1a and 1b is 1.
The common electrode 3 and the pixel electrode 4 were formed of a 90 nm thick ITO film.

Further, the above-mentioned alignment control film is obtained by applying * an ethanol solution of ladder type polysiloxane by a spin coating method, * pre-drying at a temperature of 80 ° C. for 5 minutes, and * applying a temperature of 200 ° C. To form a polysiloxane layer having a thickness of 300 nm. * A polyimide (precursor) having the following repeating unit is similarly applied to the surface of the polysiloxane layer by a spin coating method. * Pre-drying at a temperature of 80 ° C. for 5 minutes, and heating and baking at a temperature of 200 ° C. for 1 hour to form a polyimide film having a thickness of 10 nm.

[0122]

Embedded image The orientation control film was subjected to a rubbing treatment as a uniaxial orientation treatment. For this rubbing treatment, a rubbing roll in which a nylon cloth (NF-77, manufactured by Teijin Ltd.) was adhered to a roll having a diameter of 10 cm was used.
m, the feed speed is 1 cm / sec, and the rotation speed is 1
000 rpm, and the number of rubbing treatments was four.

Further, the insulating film of the other glass substrate 1a is coated with * an ethanol solution of ladder-type polysiloxane by a spin coating method, * pre-dried at a temperature of 80 ° C. for 5 minutes, and * 200 ° C. This was fired at the above temperature for one hour to form a polysiloxane layer having a thickness of 300 nm.

On the other hand, the bonding of the pair of glass substrates 1a and 1b was performed by spraying spacer beads having an average particle size of 2.2 μm on one glass substrate 1b at a density of 300 beads / mm ² .

The liquid crystal 2 has the following (a) to (d)
The liquid crystal compositions described above were mixed at a weight ratio of 25: 60: 10: 5.

[0126]

Embedded image The physical parameters of the liquid crystal 2 thus prepared were as follows.

[0127]

[Table 6] The injection of the liquid crystal 2 into the liquid crystal cell was performed in an isotropic state, and after the liquid crystal was injected, the liquid crystal was cooled to room temperature.

Next, a method of driving the above-described liquid crystal panel P will be described with reference to FIG. Here, FIG. 3 is a timing chart showing an example of a method for driving a liquid crystal panel according to the present invention. FIG.
FIG. 4 is a diagram showing the timing of a gate voltage V _g applied to a
(b) is a diagram showing the voltage applied to the source electrode 5b and its timing, (c) is a diagram showing the voltage applied to the liquid crystal 2, and (d) is a diagram showing the optical response of the liquid crystal.

In the present embodiment, one frame period F ₀
Divided into a reset period F _R and the write period F _D and, in a reset period F _R, and applies a gate voltage V _g1 to the gate electrode 5a of the TFT 5 TF with (see FIG. 3 (a))
A reset voltage V _{R of} −10 V was applied to the source electrode 5b of T5 (see FIG. 3B). The TFT 5 is turned on by the application of the gate voltage V _g1 , and the pixel electrode 4 is connected to the source line S
_1, S _2, ... and the same potential 0V, the liquid crystal 2 between the common electrode 3 and the pixel electrode 4 is applied the reset voltage V _R is the reset of the image is performed (FIG. (C) (d)).

[0130] In addition, in the writing period F _D, TF
A gate voltage V _g2 is applied to the gate electrode 5a of T5 (see FIG. 7A), and a positive write voltage V _D according to the display gradation is applied to the source electrode 5b (see FIG. 8B). ). By applying the gate voltage V _g2, the TFT 5 is turned on again, and the pixel electrode 4 becomes the same potential V _{D as the} source lines S ₁ , S ₂ ,..., And the liquid crystal 2 between the common electrode 3 and the pixel electrode 4 gradation image is displayed is applied write voltage V _D is (see Fig. (c) (d)). Although drawn three lines in FIG. (D), which shows a state in which the level of the optical response of the liquid crystal 2 changes in accordance with the write voltage V _D.

[0131] It should be noted that, in the writing period F _D, 3m
After the elapse of sec, the potentials of the source lines S ₁ , S ₂ ,.
In this state (see FIG. 2B), a gate voltage V _g3 is applied to the gate lines G ₁ , G ₂ ,... To turn on the TFT 5 (see FIG. 2A). As a result, the potential of the pixel electrode 4 became 0 V (see FIG. 3C).

Such driving was repeated for each frame period to perform display.

[0133] Incidentally, when the reset period F _R starts, and the pulse width of the write period F _D starting gate voltage V _g1, V _g2 is a 7Myusec, pulse width of the voltage applied to the source electrode 5b was 8 .mu.sec. Also, one frame period F
₀ was set to about 16 msec, and the potential of the common electrode 3 was maintained at 0V.

The writing voltage-transmittance characteristics of the liquid crystal panel P prepared in this embodiment are as shown in the following table and FIG. 5, and are substantially the same in the temperature range of 10 ° C. to 50 ° C. , The temperature dependency can be reduced), and deterioration of the image quality can be avoided even if there is some temperature fluctuation.

[0135]

[Table 7] FIG. 6 shows that the memory domain amount (T _d / T) is equal to 0.
FIG. 4 is a diagram showing the relationship between the write voltage and the write voltage application time Δt at 1 for each temperature. Specifically, the lower part of each curve indicates “the memory domain amount (T _{d at} that temperature)”.
/ T) is less than 0.1. In this embodiment, the write voltage application time Δt is 3 msec and the write voltage is 8 V or less.
The memory domain amount (T
_d / T) is smaller than 0.1.

Embodiment 2 In this embodiment, the liquid crystal panel P produced in Embodiment 1 was driven by the method shown in FIG.
That is, the reset voltage V _D and the write voltage V _D are alternately applied to the liquid crystal 2 with the write voltage application time Δt set to 8 msec, and the write voltage V _D shown in FIGS. _D removal (ie, pixel electrode 4
To 0 V).

The rest of the structure and the driving method were the same as in the first embodiment.

According to the present embodiment, the memory domain amount (T _d / T) becomes smaller than 0.1 at a temperature of 40 ° C. or lower (see FIG. 6).

The writing voltage-transmittance characteristics of the liquid crystal panel P prepared in this embodiment are as shown in the following table, and are almost the same within the temperature range of 10 ° C. to 40 ° C. (that is, the temperature dependence). ), And the image quality could be prevented from deteriorating even if there was some temperature fluctuation.

[0140]

[Table 8] (Embodiment 3) In this embodiment, the write voltage application time Δt
Was set to 12 msec, and the upper limit of the writing voltage was set to 8V. Other configurations and driving methods were the same as those in the first embodiment.

According to the present embodiment, the memory domain amount (T _d / T) becomes smaller than 0.1 at a temperature of 30 ° C. or lower (see FIG. 6).

The writing voltage-transmittance characteristics of the liquid crystal panel P prepared in this embodiment are as shown in the following table, and are almost the same within the temperature range of 10 ° C. to 30 ° C. (that is, the temperature dependence). ), And the image quality could be prevented from deteriorating even if there was some temperature fluctuation.

[0143]

[Table 9] Comparative Example 1 In this comparative example, the write voltage application time Δt
Was set to 16 msec, and the upper limit of the writing voltage was set to 8V. Other configurations and driving methods were the same as those in the first embodiment.

According to this comparative example, the memory domain amount (T _d / T) became smaller than 0.1 at a temperature of 20 ° C. or lower (see FIG. 6).

The writing voltage-transmittance characteristics of the liquid crystal panel P prepared in this comparative example are as shown in the following table, and are the same only within the temperature range of 10 ° C. to 20 ° C. If the temperature fluctuates above 20 ° C., the image quality deteriorates.

[0146]

[Table 10] (Embodiment 4) In this embodiment, the liquid crystal 2 is the same as that of the first embodiment.
(A) to (d) used in 25: 6
The mixture was prepared by mixing at a weight ratio of 3: 10: 2, and spontaneous polarization was controlled so that T _d / T was smaller than 0.1. Other configurations were the same as those of the first embodiment.

The spontaneous polarization and other physical parameters of the prepared liquid crystal 2 were as follows.

[0148]

[Table 11] The created liquid crystal panel P is used in a method shown in FIG.
When the writing voltage application time Δt was driven at about 8 msec), the writing voltage-transmittance characteristics and the transmittance 9
The temperature characteristics of the memory domain amount at 0% are as shown in the following table, and can be almost the same (that is, the temperature dependency is small) within the temperature range of 10 ° C. to 40 ° C., and there is some temperature fluctuation. Also prevented the deterioration of image quality.

[0149]

[Table 12]

[0150]

[Table 13] Comparative Example 2 In this comparative example, the write voltage application time Δt
Was set to 16 msec, and other configurations and driving methods were the same as those in the fourth embodiment.

According to this comparative example, the temperature dependence of the writing voltage-transmittance characteristic was increased, and the image quality was degraded due to the temperature fluctuation.

[0152]

As described above, according to the present invention,
The temperature dependence of the transmittance-voltage characteristics can be reduced, and the image quality can be prevented from deteriorating even if there is some temperature fluctuation.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure of a liquid crystal panel driven by the present invention.

FIG. 2 is a circuit diagram showing a circuit configuration of a liquid crystal panel driven by the present invention.

FIG. 3 is a timing chart showing an example of a method for driving a liquid crystal panel according to the present invention.

FIG. 4 is a schematic diagram for explaining a state in which a liquid crystal is inverted.

FIG. 5 is a diagram showing characteristics of writing voltage-transmittance in a liquid crystal panel.

FIG. 6 is a diagram showing a relationship between a write voltage at which a memory domain amount (T _d / T) becomes 0.1 and a write voltage application time for each temperature.

FIG. 7 is a timing chart showing another example of the method for driving a liquid crystal panel according to the present invention.

FIG. 8 is a diagram showing an appropriate range of the present invention in a relationship between a writing voltage application time and spontaneous polarization of liquid crystal.

[Explanation of symbols]

1a, 1b Glass substrate (substrate) 2 Smectic liquid crystal 3 Common electrode (first electrode) 4 Pixel electrode (second electrode) 5 TFT (switching element) 5a Gate electrode (gate) 5b Source electrode (source) G ₁ ,. Line (third electrode) P Liquid crystal panel (liquid crystal element) S ₁ ,... Source line (fourth electrode) V _D write voltage V _R reset voltage Δt Write voltage application time

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yukio Hanyu 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Tsuneki Nobuno 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Non-corp. AA16 AC15 BA12 BA13 BB16 FA19 FA21 FA56 GA02 GA03 5C080 AA10 BB05 DD05 DD20 EE29 FF11 JJ02 JJ04 JJ05 JJ06

Claims (19)

[Claims] 1. A pair of substrates arranged with a predetermined gap therebetween, a smectic liquid crystal arranged between the pair of substrates, and a plurality of pixels arranged so as to sandwich the smectic liquid crystal. A first electrode and a second electrode, a plurality of switching elements connected to the second electrode and arranged for each pixel, a third electrode connected to the gate of the switching element, and a source of the switching element. And turning on the switching element based on application of a gate voltage to the third electrode in a state where the fourth electrode and the first electrode are maintained at a predetermined potential. Accordingly, in a liquid crystal element driven by setting the fourth electrode and the second electrode to the same potential, the transmittance (%) of the liquid crystal when a voltage is applied is set to T, and the voltage is removed. Transmittance of the liquid crystal in the case and the (%) in the case of the T _d, their transmittance, [Formula 1] A liquid crystal element characterized by being set so as to be: 2. Adjusting the spontaneous polarization of the smectic liquid crystal, The liquid crystal element according to claim 1, wherein the liquid crystal element is set to be: 3. The liquid crystal device according to claim 2, wherein the above expression is satisfied at a temperature of 50 ° C. or less. 4. The liquid crystal device according to claim 3, wherein the above expression is satisfied at a temperature of 40 ° C. or less. 5. The liquid crystal device according to claim 4, wherein the above expression is satisfied at a temperature of 30 ° C. or lower. 6. The liquid crystal device according to claim 1, wherein the smectic liquid crystal is a chiral smectic liquid crystal. 7. The smectic liquid crystal has a structure in which a terminal portion of a fluorocarbon and a hydrocarbon portion are bound by a central nucleus, and has a fluorine-containing liquid crystal compound having a smectic intermediate phase or a potential smectic intermediate phase. The liquid crystal device according to claim 6, wherein 8. The smectic liquid crystal has a spontaneous polarization of 1
The liquid crystal element according to claim 6, wherein the liquid crystal element is 0 nC / cm ² or less. 9. The liquid crystal device according to claim 1, wherein the switching element is a transistor. 10. A pair of substrates disposed with a predetermined gap therebetween, a smectic liquid crystal disposed between the pair of substrates, and a plurality of pixels arranged so as to sandwich the smectic liquid crystal. First electrode and second electrode
An electrode, a plurality of switching elements connected to the second electrode and arranged for each pixel, a third electrode connected to the gate of the switching element, and a fourth electrode connected to the source of the switching element And wherein the switching element is turned on based on application of a gate voltage to the third electrode while the fourth electrode and the first electrode are maintained at a predetermined potential. 4th
In a method for driving a liquid crystal element in which an electrode and the second electrode are set to the same potential and a writing voltage is applied to the liquid crystal, a case where T is a transmittance (%) of the liquid crystal when a voltage is applied and the voltage is removed In the case where the transmittance (%) of the liquid crystal in the above is _Td , the transmittances thereof are expressed by the following formula: A method for driving a liquid crystal element, characterized in that: 11. Equation 4 The method for driving a liquid crystal element according to claim 10, wherein the application time of the writing voltage is adjusted so as to satisfy the following condition. 12. The method according to claim 10, wherein the above expression is satisfied at a temperature of 50 ° C. or less. 13. The method according to claim 12, wherein the above expression is satisfied at a temperature of 40 ° C. or less. 14. The method according to claim 13, wherein the above expression is satisfied at a temperature of 30 ° C. or lower. 15. The method for adjusting the application time of the write voltage includes: turning on the switching element at a predetermined timing with the potentials of the fourth electrode and the first electrode both set to 0 V; The method according to any one of claims 10 to 14, wherein the driving is performed by removing a voltage applied to the liquid crystal device. 16. The driving method of a liquid crystal element according to claim 10, wherein a reset voltage is applied before applying a writing voltage to the smectic liquid crystal. 17. The method according to claim 10, wherein the application of the write voltage to the smectic liquid crystal is performed while applying the write voltage to the fourth electrode and setting the potential of the first electrode to 0V. 17. The method for driving a liquid crystal element according to any one of items 16. 18. The method according to claim 10, wherein the application of the write voltage to the smectic liquid crystal is performed while the potential of the fourth electrode is set to 0 V and the write voltage is applied to the first electrode. 17. The method for driving a liquid crystal element according to any one of items 16. 19. The method according to claim 10, wherein the magnitude of the write voltage is variably controlled in accordance with a display gradation.