JP2000292774A - Driving method of liquid crystal element - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To prevent deterioration of image quality due to an afterimage or a decrease in contrast. A relationship between the write voltage V _D and the reset voltage V _R applied to the liquid crystal _{2, V R = - (V D} + ΔV) , and the irrespective of the value of the value of [Delta] V V _R and the V _D Moreover, it is set to be constant regardless of the type of the pixel. Therefore, when switching the image after displaying the same image for a long time, the effect of ΔV is uniform for each pixel and does not affect the afterimage, and the image quality does not deteriorate. Even if the write voltage V _D is small, the reset voltage V _R is at least compensated for by ΔV, and the problem of a decrease in contrast due to a reset failure is solved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a liquid crystal device using a liquid crystal.

[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.

The above-described active matrix type liquid crystal element includes a TFT 5 for each pixel as shown in FIG. 8, and is driven by, for example, a method shown in FIG.

FIG. 8 is a circuit diagram showing an example of a circuit configuration of a conventional liquid crystal element, and FIG. 9 is a timing chart showing an example of a driving method of the conventional liquid crystal element.
Incidentally, FIG. 9 (a) is a diagram showing a timing of the gate voltage V _g applied to the gate electrode 5a of the TFT 5, (b)
5A is a diagram showing a voltage applied to the source electrode 5b and its timing, FIG. 5C is a diagram showing a voltage applied to the liquid crystal 2, and FIG. 5D is a diagram showing an optical response of the liquid crystal.

[0008] Such a liquid crystal element, * TFT5 applying the gate voltage V _g to the gate electrode 5a of the source electrode 5b of the TFT5 with (see Fig. 9 (a))
When a constant reset voltage VR of, for example, -10 V is applied to the liquid crystal capacitance LC, the reset voltage V _R is applied to the liquid crystal capacitance L _C.
R is held and the liquid crystal 2 is reset ((c) in FIG.
see (d)), * TFT5 applying the gate voltage V _g to the gate electrode 5a in (FIG. (a) a source electrode 5b of reference) with TFT5
When a write voltage V _D is applied to the liquid crystal capacitor L (see FIG. 3B), the write voltage V _D is held in the liquid crystal capacitor L _C and writing is performed (see FIGS. 4C and 4D). Has become.
Note that the write voltage V _D is variably controlled so as to correspond to the display gray scale, and the write voltage V _D and the reset voltage V _R are set to have opposite polarities. Also, three lines are drawn in Figure (d),
This is because the level of the optical response of the liquid crystal 2 is equal to the write voltage V _D
FIG.

[0009]

By the way, in the case of the driving method shown in FIG. 9, the reset voltage V _{R is} applied to the liquid crystal 2 of each pixel in one frame period F ₀ as shown in FIG.
And writing although the voltage V _D becomes to be applied by a predetermined period of time in order, the magnitude of the write voltage V _D while the magnitude of the reset voltage V _R is constant is changed depending on the display gradation Therefore, their integral values are not always equal, and the liquid crystal 2 has a DC component (hereinafter, “DC component”).
To be applied).

On the other hand, since the display gradation difference for each pixel is typically also different for each pixel write voltage V _D, as a result, becomes the value of the DC component is also different for each pixel (e.g., The period during which the reset voltage V _R is applied is equal to the period during which the write voltage V _D is applied, and the reset voltage V _R is −10 V and the write voltage V _D is +
For 7 V pixels, the DC component is the average value of them (-1
0V + 7V) /2=-1.5V, and the reset voltage V
_R is the DC component in the pixel of a the write voltage V _D is + 6V and -10V value of the DC component is different for each pixel becomes (-10V + 6V) / 2 = -2V). For this reason, even if an image is switched after displaying the same image for a long time, a DC component is applied to each pixel (the DC component differs for each pixel as described above, but does not change temporally for each pixel). Is applied, the effect of the DC component remains as an afterimage on a new image, and there is a problem that the image quality deteriorates.

As a method for solving such a problem,
There are methods shown in FIGS. Here, FIG.
Is a circuit diagram showing another example of a circuit configuration of a conventional liquid crystal element, and FIG. 11 is a timing chart showing another example of a driving method of the conventional liquid crystal element. FIG. 11 (a)
Is a diagram showing a timing of the gate voltage V _g applied to the gate electrode 5a of the TFT 5, (b) is a diagram showing the voltage and its timing which is applied to the source electrode 5b, (c) a liquid crystal 2 is a diagram showing a voltage applied to
(d) is a diagram showing the potential of the common electrode 3.

In this method, when writing an image, the gate electrode 5a of the TFT 5 is written in the same manner as described above.
Applying a write voltage V _D to the source electrode 5b of the TFT5 to apply a gate voltage V _g in but, in the reset of the image, rather than a constant reset voltage V _R, coincides with the write voltage V _D of the immediately preceding (See FIGS. 11A and 11B). According to this method, since the write voltage V _D and the reset voltage V _R is completely equal even in size opposite polarity DC component as described above does not occur (see FIG. (C)), due to ghosting can avoid the problem of deterioration of image quality but, contrary, not the reset voltage V _R is also smaller can sufficiently reset smaller write voltage V _D, arises a problem that the contrast is deteriorated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for driving a liquid crystal element in which deterioration of image quality due to occurrence of an afterimage is prevented.

Another object of the present invention is to provide a method of driving a liquid crystal element in which deterioration of contrast due to reset failure is prevented.

[0015]

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 liquid crystal disposed between the pair of substrates. A first electrode and a second electrode which constitute a plurality of pixels and are arranged so as to sandwich the liquid crystal; a plurality of switching elements connected to the second electrode and arranged for each pixel; What is claimed is: 1. A liquid crystal device comprising: a third electrode connected to a gate of an element; and a fourth electrode connected to a source of the switching element, wherein the switching element is applied based on application of a gate voltage to the third electrode. Is turned on to set the fourth electrode and the second electrode to the same potential, and to apply a write voltage or a reset voltage to the liquid crystal. In the method of driving a liquid crystal element, the write voltage is V _D and the reset voltage is V _R That the relationship of these voltages in the case where, V _R = - satisfied (V _D + [Delta] V), the value of the [Delta] V is a constant irrespective of the different values, independent of the pixel of the V _R and the V _D And ΔV and V
_D is the same sign.

[0016]

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 liquid crystal 2 arranged between the pair of substrates 1a and 1b, and a plurality of pixels A first electrode 3 and a second electrode 4 arranged so as to sandwich the liquid crystal 2, a plurality of switching elements 5 connected to the second electrode 4 and arranged for each pixel, Third electrode G connected to the gate of element 5
_1, G _2, ... and a fourth electrode S _1, S ₂ which is connected to the source of the switching element 5, ... and an active matrix type provided with a.

Next, a method for driving the liquid crystal element P according to the present embodiment will be described.

In this embodiment, for example, as shown in FIG. 3, a gate voltage V _{g is} applied to the third electrodes G ₁ , G _{2 ,.}
, The switching element 5 is turned on, thereby setting the fourth electrodes S ₁ , S ₂ ,... And the second electrode 4 to the same potential, and applying a write voltage or a reset voltage to the liquid crystal 2. Drive.

In the present specification, the writing voltage V _D is a voltage applied to the liquid crystal 2 for displaying an image (ie, a voltage applied between the first electrode 3 and the second electrode 4). And the reset voltage V _R is a voltage applied to the liquid crystal 2 for resetting the image (that is, the first voltage V _R) .
(The voltage applied between the electrode 3 and the second electrode 4), and the relationship between these voltages V _D and V _R in the present embodiment satisfies the following condition: V _R = − (V _D + ΔV) , the value of the ΔV is a value and regardless of the V _R and the V _D, yet is constant regardless of the different pixels, and,
The ΔV and V _D is the same sign, and so. That is, in the present embodiment, * the write voltage V _D and the reset voltage V _R have opposite polarities, and * the absolute value | V _R | of the reset voltage is greater than the absolute value | V of the write voltage. It is set to be larger than _D | by a constant value | ΔV |. In this case, the time for applying the write voltage V _D and the time for applying the reset voltage V _R may be substantially equal. Further, it is preferable to variably controlled in accordance with the display gradation of the magnitude of the write voltage V _D, variably controlled in accordance with the magnitude of the reset voltage V _R to the magnitude of the write voltage V _D.

In order for the write voltage V _D and the reset voltage V _R to satisfy the above relationship,
There are the following methods. That is, as shown in FIG. 3, the potential of the first electrode 3 to 0V (FIG. (C) see) the fourth electrode with S _1, S _2, a voltage of V _D to ... (figure (b), the write voltage V _D is applied to the liquid crystal 2 (see (d) in the figure), and the potential of the first electrode 3 is set to 0 V (see FIG.
(c) said with reference) fourth electrode S _1, S _2, a method of applying the reset voltage V _R to the liquid crystal 2 by applying a voltage of V _R to ... reference (FIG. (b)) (same As shown in FIG. 4, as shown in FIG. 4, a voltage (ΔV / 2) corresponding to half of the above ΔV is applied to the first electrode 3 (see FIG.
(c)), and a voltage having a magnitude of | V _D | + | ΔV / 2 | is applied to the fourth electrodes S ₁ , S ₂ ,... _D (= V _D + ΔV / 2
−ΔV / 2) is applied to the liquid crystal 2 (see FIG. 3D),
At the same time, a voltage (ΔV / 2) corresponding to half of the above ΔV is applied to the first electrode 3 (see FIG. 3C), and | V
_D | + | ΔV / 2 | is applied to the fourth electrode S
_1, S _2, applied to ... in (FIG. (B) refer) method (see FIG (d)) which applies a reset voltage V _R (= -V _D -ΔV) to the liquid crystal 2 by 5 As shown, the potential of the first electrode 3 is set to 0 V (see FIG. 3C), and the fourth electrodes S ₁ , S ₂ ,
... a voltage of V _D (the same see FIG (b)) by applying the write voltage V _D to the liquid crystal 2 by (the (d) of FIG
And a voltage corresponding to ΔV is applied to the first electrode 3 (see FIG. 3C), and the fourth electrode S
A method of applying the reset voltage V _R to the liquid crystal 2 by applying a voltage of −V _D to ₁ , S ₂ ,... (See FIG. 2B) (see FIG. 2D) The fourth electrode By setting the potentials of S ₁ , S ₂ ,... To 0 V, turning on the switching element 5 to set the potential of the second electrode 4 to 0 V, and applying a predetermined voltage (writing voltage or reset voltage) to the first electrode 3. FIGS. 3 to 5 are timing charts showing an example of a method for driving a liquid crystal element according to the present invention.
Is a diagram showing a timing of the gate voltage V _g applied to the gate 5a of the switching element 5, (b) is a diagram showing the voltage and its timing which is applied to the source 5b, (c) the first FIG. 4 is a diagram showing a potential of one electrode 3.

It is to be noted that a ferroelectric liquid crystal may be used as the liquid crystal 2 and an alignment control film of the same material may be disposed on both sides of the liquid crystal 2 and driven as shown in FIG. That is, one frame period F ₀
Divided into a reset period F _R and the write period F _D a, * reset period F in _R, the liquid crystal 2 by applying a reset voltage V _R to the image between the first electrode 3 and the second electrode 4 perform a reset, * in the write period F _D, may be applied to the write voltage V _D to the liquid crystal 2 between the first electrode 3 and the second electrode 4 so as to display an image.

In this case, it is preferable that the write voltage V _D and the reset voltage V _R have opposite polarities and that a DC component hardly occurs.

The application of the reset voltage V _{R and} the application of the write voltage V _D are performed by applying the gate voltage V _g to the third electrodes G ₁ , G ₂ ,. The fourth electrodes S ₁ , S ₂ ,.
The method may be performed by setting the potential of the second electrode 4 to 0 V by setting the potential of the fourth electrode S ₁ , S ₂ ,... To 0 V and turning on the switching element 5. Is set to 0 V and a predetermined voltage (reset voltage or write voltage) is applied to the first electrode 3 (the reset in FIG. 6 is performed by this method). * The fourth electrodes S ₁ and S ₂ Are applied to a predetermined potential (that is, a potential equal to a reset voltage or a write voltage) to turn on the switching element 5 to make the second electrode 4 the same potential and to reduce the potential of the first electrode 3. 0V (writing in FIG. 6 is performed by this method); * the potentials of the fourth electrodes S ₁ , S ₂ ,... of How to the fourth electrode S _1, S _2, ... and the second electrode 4 at the same potential by down, there is.

As shown in FIG. 6D, the write voltage V _D is applied only for a certain period of time, and thereafter, an image may be displayed by utilizing the memory properties of the liquid crystal 2. As shown in FIGS. 3A to 3C, the potential of the first electrode 3 and the fourth electrodes S ₁ , S ₂ ,. There is a method of turning on the switching element 5 in the state described above. According to this method, no voltage is applied to the liquid crystal 2, but an image is held using the memory properties of the liquid crystal 2.

The ferroelectric liquid crystal 2 preferably has a spontaneous polarization of 10 nC / cm ² or less.

According to this method, since the ferroelectric liquid crystal 2 is used, the response speed is high, and a good display can be obtained regardless of whether the driving frequency is high or low.

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, a green film (not shown) for preventing short circuit between these electrodes is provided on the surface of each of the electrodes 3 and 4.
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 arranged at a position in contact with the liquid crystal 2, and the alignment control film includes an inorganic substance (silicon monoxide,
Silicon dioxide, aluminum oxide, zirconia, magnesium fluoride, cesium oxide, silicon nitride, silicon carbide, boron nitride, etc., and organic substances (polyvinyl alcohol, polyimide, polyamide, polyester, polyimideamide, polyesterimide, polyparaxylene) , Polycarbonate, polyvinyl acetal, polyvinyl chloride, polystyrene, polysiloxane, cellulose resin, melanin resin, urea resin, 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.

The switching element 5 includes 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, a chiral smectic liquid crystal can be used as the liquid crystal 2. When this chiral smectic liquid crystal is used, the substrate gap is preferably set to 5 μm or less in order to exhibit bistability.

The chiral smectic liquid crystal composition used in the present invention has a structure in which a terminal portion of a fluorocarbon and a hydrocarbon portion are bonded by a central nucleus and has a smectic intermediate phase or a potential smectic intermediate phase. Those having a liquid crystal compound are preferred.

As the fluorine-containing liquid crystal compound, full
Orocarbon terminal portion is -D¹ -C_xaF_2xa Table with -X
A group represented by the formula (where xa is 1 to 20,
Represents -H or -F;¹ Is -CO-O- (CH
_Two )_ra-, -O- (CH_Two )_ra-,-(CH_Two )_ra−,
-O-SO_Two -, -SO_Two -, -SO_Two − (CH_Two )_ra
-, -O- (CH_Two )_ra-O- (CH_Two )_rb-,-(C
H_Two )_ra−N (C_paH_{2pa + 1} ) -SO_Two -Or-(C
H_Two )_ra−N (C_paH_{2pa + 1} ) Represents -CO-. ra
And rb are independently 1 to 20, pa is 0 to 4.
) Or -D^Two − (C_xbF_2xb -O)_za-C_yaF
_{2ya + 1} A group represented by the formula (where xb is each
(C_xbF_2xb -O) is independently 1 to 10, ya
Is 1 to 10; za is 1 to 10;^Two Is
-CO-OC_rcH_2rc , -OC_rcH_2rc -, -C_rc
H_2rc -, -O- (C_saH_2sa -O)_ta-C_rdH_2rd 
-, -O-SO_Two -, -SO_Two -, -SO_Two -C_rcH
_2rc -, -C_rcH_2rc −N (C_pb H_2pb+1) -SO_Two 
-, -C_rcH_2rc −N (C_pbH_{2pb + 1} ) -CO-, single bond
Rc and rd are each independently 1 to 20
And sa is the respective (C_saH_2sa -O) independently
1 to 10, ta is 1 to 6, and pb is 0 to 4.
Can be used.

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

[0042]

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).

[0049]

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-.

Each of X ² , Y ² , and Z ² is A ⁴ , A ⁵ , 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.

[0057]

Embedded image

[0058]

Embedded image

[0059]

Embedded image

[0060]

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[0061]

Embedded image

[0062]

Embedded image

[0063]

Embedded image

[0064]

Embedded image

[0065]

Embedded image

[0066]

Embedded image

[0067]

Embedded image

[0068]

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.

[0069]

Embedded image

[0070]

Embedded image

[0071]

Embedded image

[0072]

Embedded image

[0073]

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.

[0074]

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

[0075]

Embedded image

[0076]

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 independently may 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) -CH = C
H -, - C≡C -, - CH = N -, - CH 2 -O -, -
Represents 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, and —NO ₂ , where 1, m and n each independently represent an integer of 0 to 4.

D may be in any direction.

[0081]

Embedded image Represents

R and r ′ each independently represent an integer of 0 to 20, and s represents 1 to 10 independently of each (C _s H _{2 s} O).
And t is an integer of 1 to 6, and p is an integer of 0 to 4.

R is

[0084]

Embedded image Represents

R 'is independently -Cl, -F, -CF
_{3, -NO 2, -CN, -H} , -C q H 2q + 1, -O-
(O =) CC _q H _{2q + 1} , -C (= O) -OC _q H
_{2q + 1, -Br, -OH,} -OC q H 2q + 1 ( preferably,
-H, -F), and q 'is the respective ( _Cq'H
2q'- O) is independently 1 to 20, q is an integer of 1 to 20, w is an integer of 1 to 10, v is an integer of 0 to 6, and v 'is each independently Is an integer of 0 to 6, q is an integer of 1 to 3, each D is the structure shown above, and the direction may be either independently, and the ring structure containing D has 3 to 10 atoms. It consists of. W is each independently N, CR ', or SiR', and R 'may be chiral or achiral.

Rf ′ is -R ^* -D- (O) _x -CH ₂
Represents -D'- _Rf . Here, R ^* may be a cyclic chiral or an acyclic chiral. D and D ′ each have the same structure as that described above, and may each independently have any direction, x is 0 or 1, and R _f is fluoroalkyl, perfluoroalkyl, fluoroether, or perfluoroether. is there. Preferably R _f is fluoroalkyl, fluoroether or perfluoroether.

R ^* is

[0088]

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, -CF 3, -Br, -OH} , is -OCH _3,
More preferably, -H, -F, a -CF _3), q '
The each - from 1 to 20 independently _{((C q 'H 2q'-} v' (R ') v') -O), q is an integer of from 1 to 20, w
Is an integer of 0 to 10, v is an integer of 0 to 6, each v 'is independently an integer of 0 to 6, q is 1 to 3
Wherein each D is the structure shown above, independently in any direction, and the ring structure containing D is 3 to 1
Consists of 0 atoms. Each w is independently N,
Represents CR 'and SiR'. More preferably, R _f is
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),
X ′ is hydrogen or fluorine. Fluoroalkyl and fluoroether groups are represented by the structure -Rf _" -Rh _' , where _Rf" is linear or branched;
A fluorinated or partially fluorinated alkyl group having 1 to 10 (preferably 2 to 6) carbon atoms and one or more ether oxygen atoms attached thereto. R _h is a linear or branched alkyl group,
Having 1 to 14 (preferably 3 to 10) carbon atoms,
One or more ether oxygen atoms are missing.
R _{f ″} is preferably fluorinated; R _h and R
Both _{f "} are linear and at least one of the groups R _h and R _f" has at least one ether oxygen atom.
More preferably, R _h , or both R _h and R _{f ″} , 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 independently 1 to 1 for each (C _x F _2x O).
0, y is an integer of 1 to 10, and z is an integer of 1 to 10. Preferably, the perfluoroether groups are straight-chain, and x is independently 1 (C _x F _2x O)
, Y is an integer of 1 to 6, and z is an integer of 1 to 6.

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

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

[0094]

Embedded image Represents

R ^* is

[0096]

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, -. It represents a _{(C x F 2x O) z} C y F 2y + 1 where, q is an integer from 1 to 6, X 'is a fluorine .R _f" is A linear or branched, partially fluorinated alkyl group having 2-4 carbon atoms,
One or more ether oxygen atoms are missing.
R _h is a linear or branched alkyl group;
It has up to 7 carbon atoms and is chained with one or more ether oxygen atoms. x is the respective (C _x F
_2xO ) is independently 1 to 10, y is an integer of 1 to 8, and z is an integer of 1 to 5.

[0098]

[Table 1]

[0099]

[Table 2]

[0100]

[Table 3]

[0101]

[Table 4]

[0102]

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

According to the present embodiment, the write voltage V _D according to the display gradation is applied to the liquid crystal 2, and V _R = − (V _D + ΔV) is applied between the write voltage V _D and the write voltage V _D. so that the reset voltage V _R which satisfies is applied. Therefore, the absolute value | V _R | of the reset voltage is a constant value | Δ than the absolute value | V _D | of the write voltage.
V | Only large, 1 the entire frame period strongly towards the influence of the reset voltage V _R, the | [Delta] V | DC voltage (DC component) corresponding to the magnitude equivalent to that applied to the liquid crystal 2 (See FIG. 3D).

However, according to the present embodiment, | Δ
The value of V | depends on the display gradation (that is, the write voltage V _D).
), And is constant regardless of the type of pixel. Therefore, when switching between images after displaying the same image for a long time, the DC voltage is applied to a new image. The effect is uniform for each pixel, does not affect the afterimage, and the image quality does not deteriorate.

As described above, the absolute value | V _R | of the reset voltage is larger than the absolute value | V _{D of the} write voltage.
| Fixed value than | [Delta] V | only increase since it is set, the write voltage V _D is small but the reset voltage V _R
Will be compensated for by at least ΔV. Therefore, even in such a case, a sufficient reset can be performed,
The problem that the contrast deteriorates can be solved.

Further, as shown in FIG. 5, the potential of the first electrode 3 is set to 0 V and the fourth electrodes S ₁ , S ₂
, The write voltage V _D is applied to the liquid crystal 2 by applying a voltage of V _D to ..., and the fourth electrode S ₁ is applied with a voltage corresponding to the ΔV to the first electrode 3, S _2, in the case of using a method of applying the reset voltage _{V R} to the liquid crystal 2 by applying a voltage of -V _D ..., the fourth electrode _{S 1, S} 2,
Can be reduced, and an inexpensive drive IC can be used.

[0107]

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

Embodiment 1 In this embodiment, 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-mentioned 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.

Note that 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.

The above-mentioned orientation 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 film thickness of 10 nm.

[0119]

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 coat method, * pre-dried at a temperature of 80 ° C. for 5 minutes, and * 200 ° C. For 1 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.

[0123]

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

[0124]

[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.

FIG. 7 shows the relationship between the applied voltage and the amount of transmitted light in the prepared liquid crystal panel P.

Next, a method of driving the above-described liquid crystal panel P will be described with reference to FIG.

In the present embodiment, one frame period F ₀
The divided into a period F _D and the reset period F _R writing, in the writing period F _D, and the potential of the common electrode 3 to 0V (see FIG (c)), the voltage V _D of the positive polarity corresponding to the display gradation
Are applied to the source lines S ₁ , S ₂ ,... (See FIG. 3B).
At the same time, a gate voltage V _g was applied to the gate lines G ₁ , G ₂ ,... (See FIG. 3A). By the application of the gate voltage V _g TFT 5 is turned on, the pixel electrode 4 is the source lines S _1,
S ₂ ,... Have the same potential V _D , and the writing voltage V _D is applied to the liquid crystal 2 between the common electrode 3 and the pixel electrode 4 to display a gradation image (see FIG. 3D). ).

In the next reset period F _R , the potential of the common electrode 3 is maintained at 0 V (see FIG. 3C), and the source line S ₁
, S _2, ... in _{the, V R = - (V D} + ΔV) becomes a negative voltage is applied to the (FIG see (b)) the gate lines G ₁ of the gate voltage V _g with, G _2, applied to ... (See Figure (a)). TF by the application of the gate voltage V _g
T5 is turned on again, the voltage V _R is applied to the pixel electrode 4 via the TFT 5, and the reset voltage V _R is applied to the liquid crystal 2 between the common electrode 3 and the pixel electrode 4 to reset the image. (See Figure (d)).

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

In this embodiment, ΔV is set to 1
And is V, the value and regardless of the V _R and the V _D, yet was constant regardless of the another pixel. It was also equal to the write period F _D and the reset period F _R. Further, in the present embodiment, variably controlled in accordance with the display gradation magnitude of the write voltage V _D, and variably controlled in accordance with the magnitude of the reset voltage V _R to the magnitude of the write voltage V _D.

On the other hand, the liquid crystal panel P formed in this embodiment
In the relationship between the write voltage V _D and transmittance was shown in the following table.

[0132]

[Table 7] Next, effects of the present embodiment will be described.

[0133] The present inventors have, 2V the write voltage V _D, respectively, while a plurality of liquid crystal panels P as 4V and 7V was examined how the ghosting driven for 100 hours at room temperature, no residual image at all satisfactory image was gotten.

The contrast at the writing voltage V _D = 7 V was 250, and an image with good contrast was obtained.

(Embodiment 2) In this embodiment, a liquid crystal panel P produced in the same manner as in Embodiment 1 was driven by the method shown in FIG. In other words, divided into periods F _D writes one frame period F ₀ and the reset period F _R, the writing period F
In _D, a voltage of 0.5V to the common electrode 3 (see FIG. (C)), the source lines S _1, S _2, ..., the voltage V _D of the positive polarity corresponding to the display gradation A voltage (V _D +0.5 V) of a magnitude obtained by adding 0.5 V is applied (see FIG. 2B), and a gate voltage V _g is applied to the gate lines G ₁ , G ₂ ,. a)). By the application of the gate voltage V _g TFT 5 is turned on, the pixel electrode 4 is the source lines S _1,
S ₂ ,... Have the same potential (V _D +0.5 V), and the write voltage V _D is applied to the liquid crystal 2 between the common electrode 3 and the pixel electrode 4.
= V _D + ΔV / 2−ΔV / 2 is applied, and a gradation image is displayed (see FIG. 3D).

In the next reset period F _R , the potential of the common electrode 3 is maintained at 0.5 V (see FIG. 13C), and −V _D −0.5 V is applied to the source lines S ₁ , S ₂ ,. the magnitude of voltage is applied (see FIG. (b)), the gate voltage V _g the gate lines G _1, G _2, was applied ... (see FIG. (a)). TFT5 by the application of the gate voltage V _g is turned on again,
The pixel electrode 4 has the same potential (−V _{D) as the} source lines S ₁ , S ₂ ,.
−0.5 V), and the reset voltage V _R (= −V _D −1 V = −V) is applied to the liquid crystal 2 between the common electrode 3 and the pixel electrode 4.
_D− ΔV) was applied to reset the image (see FIG. 3D).

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

In this embodiment, ΔV is set to 1
And is V, the value and regardless of the V _R and the V _D, yet was constant regardless of the another pixel. It was also equal to the write period F _D and the reset period F _R. Further, in the present embodiment, variably controlled in accordance with the display gradation magnitude of the write voltage V _D, and variably controlled in accordance with the magnitude of the reset voltage V _R to the magnitude of the write voltage V _D.

On the other hand, the liquid crystal panel P prepared in this embodiment
In the relationship between the write voltage V _D and transmittance was shown in the following table.

[0140]

[Table 8] According to this embodiment, the same effects as those of the first embodiment were obtained.

(Embodiment 3) In this embodiment, a liquid crystal panel P produced in the same manner as in Embodiment 1 was driven by the method shown in FIG. In other words, divided into periods F _D writes one frame period F ₀ and the reset period F _R, the writing period F
_{In D} , the potential of the common electrode 3 is set to 0 V (see FIG.
), And a positive voltage V _D according to the display gradation is applied to the source lines S ₁ , S ₂ ,... (See FIG. 3B), and the gate voltage V _{g is changed} to the gate lines G ₁ , G ₂ , ... (Fig.
(a)). TFT by the application of the gate voltage V _g
5 is turned on, the source lines S ₁ is the pixel electrode 4, S _2, ... and the same potential V _D, is applied write voltage V _D is the liquid crystal 2 between the common electrode 3 and the pixel electrode 4 A gradation image is displayed (see FIG. 4D).

[0142] In the next reset period F _R, the common electrode 3 by applying a voltage of + [Delta] V = 1V (see FIG (c)), the source lines S _1, S _2, the magnitude of -V _D to ... applying a difference in voltage (see FIG. (b)), the gate voltage V _g the gate lines G _1, G _2, was applied ... (see FIG. (a)). TFT5 by the application of the gate voltage V _g is turned on again,
The pixel electrode 4 has the same potential −V _{D as the} source lines S ₁ , S ₂ ,..., And the reset voltage V _R (= −V _D −ΔV) is applied to the liquid crystal 2 between the common electrode 3 and the pixel electrode 4. Was applied to reset the image (see (d) in the figure).

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

In this embodiment, ΔV is set to 1
And is V, the value and regardless of the V _R and the V _D, yet was constant regardless of the another pixel. It was also equal to the write period F _D and the reset period F _R. Further, in the present embodiment, variably controlled in accordance with the display gradation magnitude of the write voltage V _D, and variably controlled in accordance with the magnitude of the reset voltage V _R to the magnitude of the write voltage V _D.

On the other hand, the liquid crystal panel P prepared in this embodiment
In the relationship between the write voltage V _D and transmittance was shown in the following table.

[0146]

[Table 9] According to this embodiment, the same effects as those of the first embodiment were obtained.
Further, the voltage applied to the source lines S ₁ , S ₂ ,... Can be reduced, and an inexpensive drive IC can be used.

(Embodiment 4) In this embodiment, a liquid crystal panel P produced in the same manner as in Embodiment 1 was driven by the method shown in FIG. That is, one frame period F ₀ is divided into a reset period F _R and a write period FD, and the reset period F _{D
In R} , the potentials of the source lines S ₁ , S ₂ ,... Are set to 0 V (see FIG. 3A), and the gate voltage V _{g is changed} to the gate lines G ₁ ,
G _2, applying ... (see FIG. (B)), the common electrode 3 was applied to the reset voltage V _R (see FIG. (C)). TFT5 gate voltage is applied V _g is turned on, the pixel electrode 4
Are at the same potential 0 V as the source lines S ₁ , S ₂ ,... And the reset voltage V is applied to the liquid crystal 2 between the common electrode 3 and the pixel electrode 4.
_R was applied to reset the image ((d) (e)
reference).

[0148] In the writing period F _D, (see FIG. (C)) and the potential of the common electrode 3 to 0V, and the source lines S ₁
, S ₂ ,... Include a positive voltage V _D according to the display gradation.
(See FIG. 2B), and a gate voltage _Vg is applied to the gate lines G ₁ , G ₂ ,... (See FIG. 2B). By the application of the gate voltage V _g TFT 5 is turned on again, the pixel electrode 4 is made the source lines S _1, S _2, ... and the same potential V _D, the liquid crystal 2 between the common electrode 3 and the pixel electrode 4 gradation image is displayed write voltage V _D is applied (FIG.
(See (d) and (e)).

[0149] It should be noted that, in the writing period F _D, 8m
After the lapse of sec, the common electrode 3 and the source lines S ₁ , S ₂ ,.
With the potentials of both at 0 V (see FIGS. 3A and 3C).
The gate voltage V _g is applied to the gate lines G ₁ , G ₂ ,.
FT5 was turned on (see FIG. 3 (b)). As a result, the potential of the pixel electrode 4 becomes 0 V (see FIG. 4D), but the image display is maintained by the memory property of the liquid crystal 2 (see FIG. 4E).

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

The liquid crystal panel P produced in this embodiment
In the relationship between the write voltage V _D and transmittance was shown in the following table.

[0152]

[Table 10] According to this embodiment, the same effects as those of the first embodiment were obtained.

Comparative Example 1 In this comparative example, a liquid crystal panel P prepared in the same manner as in Example 1 was driven by the method shown in FIG.

[0154] That is, dividing one frame period F ₀ in the reset period F _R and the write period F _D, a reset period F
In _R, a gate voltage is applied to V _g the gate electrode 5a of the TFT5 applying a voltage of -10V to the source electrode 5b of the TFT5 with (see Fig. 9 (a)) (see FIG. (B)). As a result, the reset voltage V is applied to the liquid crystal capacitance L _C.
R is held and the liquid crystal 2 is reset ((c) in FIG.
(d)).

[0155] In addition, in the writing period F _D, TF
T5 applying the gate voltage V _g to the gate electrode 5a of applying a write voltage V _D to the source electrode 5b of the TFT5 with (FIG. (A) see) (see FIG. (B)). Thereby, the write voltage V _D to the liquid crystal capacitance L _C has been performed the writing is maintained (see FIG. (C) (d)).

The liquid crystal panel P prepared in this comparative example
In the relationship between the write voltage V _D and transmittance was shown in the following table.

[0157]

[Table 11] The inventor of the present invention has driven the plurality of liquid crystal panels P at room temperature for 100 hours at a write voltage V _D of 3 V, 5 V, and 8 V, respectively.
About 10% image sticking was observed when a halftone was displayed. Note that the contrast at the writing voltage V _D = 8 V was 250.

(Comparative Example 2) In this comparative example, a liquid crystal panel P prepared in the same manner as in Example 1 was driven by the method shown in FIG.

[0159] That is, when the writing of the image, the source electrode 5b of the TFT5 to apply a gate voltage V _g to the gate electrode 5a of the TFT5 by the same method as above
To While applying a write voltage V _D, during reset of the image, rather than a constant reset voltage V _R, and variably controlled so as to coincide with the write voltage V _D immediately before (FIG. 11 (a) (b )).

According to this method, the write voltage V _D = 8
The contrast at V was as low as 70.

(Comparative Example 3) On one glass substrate 1b,
A TFT 5, a pixel electrode 4, an alignment control film, and the like were formed in the same manner as in Example 1, and a common electrode and an insulating film were formed on the other glass substrate 1a. The surface of the insulating film of the other glass substrate 1a was washed twice with IPA (isopropanol). Other configurations and manufacturing conditions were the same as in Example 1. Then, were examined how the residual image occurs a plurality of liquid crystal panels P driven for 100 hours at room temperature by varying the write voltage V _D in the manner shown in FIG. 6 were obtained excellent images without any afterimage . However, the memory property when displaying halftones was unstable.

The liquid crystal panel P prepared in this comparative example
In the relationship between the write voltage V _D and transmittance was shown in the following table.

[0163]

[Table 12]

[0164]

As described above, according to the present invention,
The liquid crystal is applied write voltage V _D corresponding to the display gray scale, between the write voltage V _D, V _R = - that (V _D + [Delta] V) reset voltage V _R which satisfies is applied and Become.
Therefore, the absolute value | V _R | of the reset voltage is larger than the absolute value | V _D | of the write voltage by a constant value | ΔV |, and the reset voltage V _R for the entire frame period.
Is more intense, which is equivalent to applying a DC voltage (DC component) corresponding to the magnitude of | ΔV | to the liquid crystal.

[0165] However, according to the present invention, the | [Delta] V | values display gradation (i.e., the write voltage magnitude V _D) is a constant independent of the, so as to be constant irrespective of the different pixel Therefore, when switching the image after displaying the same image for a long time, the effect of the DC voltage on the new image is uniform for each pixel and does not affect the afterimage, and the image quality is low. It doesn't get worse.

Further, as described above, since the absolute value | V _R | of the reset voltage is set to be larger than the absolute value | V _D | of the write voltage by a constant value | ΔV |, the write voltage V _D is the reset voltage V _R be small so that the ΔV alone is at least compensated. Therefore, even in such a case, a sufficient reset can be performed, and the problem that the contrast deteriorates can be solved.

Further, by setting the potential of the first electrode to 0 V and applying a voltage of V _{D to} the fourth electrode, the write voltage V _D is applied to the liquid crystal, and a voltage corresponding to ΔV is applied. when using the method for applying the reset voltage V _R to the liquid crystal by applying a voltage of -V _D to the fourth electrode while applying to the first electrode, the voltage applied to the fourth electrode Drive IC
Inexpensive one can be used.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure of a liquid crystal element driven by the present invention.

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

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

FIG. 4 is a timing chart illustrating an example of a method for driving a liquid crystal element according to the present invention.

FIG. 5 is a timing chart illustrating an example of a method for driving a liquid crystal element according to the present invention.

FIG. 6 is a timing chart illustrating an example of a method for driving a liquid crystal element according to the present invention.

FIG. 7 is a diagram showing an applied voltage-transmitted light amount characteristic of a liquid crystal.

FIG. 8 is a circuit diagram showing an example of a circuit configuration of a conventional liquid crystal element.

FIG. 9 is a timing chart illustrating an example of a conventional method for driving a liquid crystal element.

FIG. 10 is a circuit diagram showing another example of the circuit configuration of a conventional liquid crystal element.

FIG. 11 is a timing chart showing another example of a conventional method for driving a liquid crystal element.

[Explanation of symbols]

1a, 1b Glass substrate (substrate) 2 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 ,. (Third electrode) P liquid crystal panel (liquid crystal element) S ₁ , ... source line (fourth electrode)

Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court II (Reference) G09G 3/20 621 G09G 3/20 641C 641 3/36 3/36 G02F 1/137 510 (72) Inventor Yukio Hanyu Tokyo 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Tsuneki Nadanobu 3-30-2 Shimomaruko 3-chome, Ota-ku, Tokyo Inside Canon Inc. (72) Minato Yagyu Ota, Tokyo 3-30-2 Kushita Maruko F-term (reference) in Canon Inc. BF31 FA34 FA54 GA02 GA03 GA04 5C080 AA10 BB05 CC03 DD03 DD29 EE29 FF11 GG08 JJ02 JJ03 JJ04 JJ05 JJ06

Claims (12)

[Claims] A pair of substrates disposed with a predetermined gap therebetween, a liquid crystal disposed between the pair of substrates,
A first electrode and a second electrode that constitute a plurality of pixels and are arranged so as to sandwich the liquid crystal, and a plurality of switching elements that are connected to the second electrodes and arranged for each pixel;
A third electrode connected to the gate of the switching element;
A fourth electrode connected to the source of the switching element;
A switching element that is turned on based on application of a gate voltage to the third electrode to bring the fourth electrode and the second electrode to the same potential, and to change a writing voltage or a reset voltage to the liquid crystal. a method of driving a liquid crystal element to be applied to the relationship of these voltages in a case where the reset voltage the write voltage V _D was V _{R is, V R = - (V D} + ΔV) satisfy, the [Delta] V value, the V _R and the set constant regardless of the different values and pixels regardless of V _D, and the ΔV and V _D is the same sign, the driving method of the liquid crystal element, characterized in that. 2. The write voltage V _D and the reset voltage V _R have opposite polarities, and the absolute value | V _R | of the reset voltage is greater than the absolute value | V _D | of the write voltage. The method according to claim 1, wherein the driving voltage is larger by a constant value | ΔV |. 3. The magnitude of the write voltage V _D is variably controlled in accordance with a display gradation, and the magnitude of the reset voltage V _R is adjusted to the magnitude of the write voltage V _D.
3. The method according to claim 1, wherein the control is variably performed according to the size of _{D. 4} . 4. The potential of the first electrode is set to 0 V, and a voltage of V _D is applied to the fourth electrode, so that the write voltage V _D is applied to the liquid crystal, and the potential of the first electrode is adjusted. the reset voltage V _R by applying a voltage of V _R to the fourth electrode while a 0V to
Is applied to the liquid crystal, the method for driving a liquid crystal element according to any one of claims 1 to 3. 5. The write operation by applying a voltage corresponding to half of the ΔV to the first electrode and applying a voltage of | V _D | + | ΔV / 2 | to the fourth electrode. A voltage V _D is applied to the liquid crystal, a voltage corresponding to half of ΔV is applied to the first electrode, and a voltage of magnitude | V _D | + | ΔV / 2 | is applied to the fourth electrode. To the reset voltage V _R
Is applied to the liquid crystal, the method for driving a liquid crystal element according to any one of claims 1 to 3. 6. The potential of the first electrode is set to 0 V, and a voltage of V _D is applied to the fourth electrode to apply the write voltage V _D to the liquid crystal, and a voltage corresponding to ΔV. and applies the reset voltage V _R to the liquid crystal by applying a voltage of -V _D to the fourth electrode and applies to the first electrode, any one of claims 1 to 3, characterized in that 1 13. A method for driving a liquid crystal element according to item 9. 7. The method according to claim 1, wherein a time for applying the write voltage and a time for applying the reset voltage are substantially equal to each other. 8. The method for driving a liquid crystal element according to claim 1, wherein the switching element is a transistor. 9. A chiral liquid containing a fluorine-containing liquid crystal compound having a smectic intermediate phase or a potential smectic intermediate phase, wherein the liquid crystal comprises a fluorocarbon terminal chain and a hydrocarbon terminal chain, both terminal chains being linked by a central nucleus. The method for driving a liquid crystal element according to any one of claims 1 to 8, wherein the method is a smectic liquid crystal. 10. A pair of substrates disposed with a predetermined gap therebetween, a liquid crystal disposed between the pair of substrates, and a second liquid crystal disposed between the pair of substrates and arranged to sandwich the 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 connected to the switching element A liquid crystal element comprising: a fourth electrode that has been subjected to a gate voltage applied to the third electrode, and turns on the switching element to bring the fourth electrode and the second electrode into the same potential and write data. In a method for driving a liquid crystal element applying a voltage or a reset voltage to the liquid crystal, the liquid crystal is a liquid crystal exhibiting ferroelectricity, and the writing voltage and the reset voltage have opposite polarities, and a DC component is Tondo no method for driving a liquid crystal element, characterized in that. 11. The driving method for a liquid crystal element according to claim 10, wherein the writing voltage is applied only for a certain period of time, and thereafter, an image is displayed using the memory property of the liquid crystal. . 12. The liquid crystal has a spontaneous polarization of 10 nC / c.
The method for driving a liquid crystal element according to claim 10, wherein m ² or less.