JPH10228036A - Liquid crystal display and its driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellent display which causes neither a flicker nor a decrease in contrast by removing a state wherein a potential is unstable when a ferroelectric film is depolarized from a matrix type liquid crystal display which uses the ferroelectric film. SOLUTION: A ferroelectric film 7 between a signal electrode Y and a pixel electrode 4 is formed of two parts 7A and 7B. The parts 7A and 7B are formed of the same material, the part 7a is a half in film thickness as large as the part 7B, and the are of the part 7A is double as large as that of the part 7B. Consequently, the anti-electric field Ec and residual polarization Pr of the part 7A and the anti-electric field Ec' and residual polarization Pr' of the part 7B are so related that Ec'=2.Ec and Pr'=Pr. A specific reset pulse is applied to the ferroelectric film 7 to orient the dipoles of the parts 7A and 7B positively. Then a specific selection period pulse is applied to the ferroelectric film 7 to invert the dipoles of only the part 7A to the negative direction. Consequently, the total of remaining electric charges at the parts 7A and 7B becomes zero.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display and a driving method thereof.

[0002]

2. Description of the Related Art A liquid crystal display is mainly of a matrix type, and is divided into a simple matrix type and an active matrix type according to the driving method. Recently, the active matrix type has been widely used with an increase in display capacity. It has become

In the active matrix system, a TFT
Although the driving method using (thin film transistor) is the mainstream, the process of forming the TFT is complicated, and there is a disadvantage that the yield is deteriorated when a large-area liquid crystal display is manufactured. Therefore, a diode or MIM (metal-
An active-matrix system having a simple structure using an insulator-metal or a ferroelectric film has been studied.

FIGS. 6A and 6B show a matrix type liquid crystal display using a ferroelectric film. In this liquid crystal display, a stripe-shaped signal electrode Y is formed on one surface of a lower substrate 1 made of a transparent insulating substrate, a ferroelectric film 3 is formed on the signal electrode Y, and a transparent film is formed on the ferroelectric film 3. A pixel electrode 4 made of a conductive film is formed, and a striped scanning electrode X orthogonal to the signal electrode Y on the lower substrate 1 is formed on one surface of an upper substrate 2 made of a transparent insulating substrate.

A lower substrate 1 and an upper substrate 2 are opposed to each other at a predetermined interval with the surface on which the signal electrode Y or the scanning electrode X is formed inward, and a liquid crystal material is injected between the two. The layer 5 is formed.

FIGS. 6A and 6B show one pixel of the liquid crystal display. A large number of signal electrodes Y and scanning electrodes X are arranged in a direction orthogonal to the respective extending directions, and at each intersection position. Pixels are formed. Therefore, in each pixel, the ferroelectric film 3 and the liquid crystal layer 5 are connected in series between the signal electrode Y and the scanning electrode X.

In this liquid crystal display, SID
91DIGEST, pp. 18-21, first, during the selection period, as shown in FIG.
By applying an electric field of a certain voltage or more to the series circuit of the ferroelectric film 3 forming a capacitor having a capacitance Cf for one pixel and the liquid crystal layer 5 forming a capacitor having a capacitance Clc for one pixel by a voltage Vo. Then, spontaneous polarization is excited in the ferroelectric film 3 (capacitance Cf), and then during the holding period,
As shown in FIG. 7B, after the applied voltage Vo is removed, the electric field of the voltage Vlc is continuously applied to the liquid crystal layer 5 (capacitance Clc) by the spontaneous polarization, and the alignment state of the liquid crystal molecules in the liquid crystal layer 5 is maintained. Hold.

This is because the electric field E applied to the ferroelectric film 3 is
The relationship between the polarization P and the polarization P generated in the ferroelectric film 3 by the electric field E is based on the fact that the polarization P is not proportional to the electric field E and exhibits a hysteresis characteristic, as schematically shown in FIG. is there. Ec and -Ec are coercive electric fields, and Pr and -Pr are remanent polarizations.

That is, during the selection period, the ferroelectric film 3
By applying an electric field sufficiently larger than the coercive electric field Ec to the ferroelectric film 3, a residual polarization Pr is generated in the ferroelectric film 3 and the liquid crystal layer 5 corresponds to the residual polarization Pr in the holding period after the electric field is removed. The voltage Vlc is applied.

In this case, assuming that the area of one pixel of the ferroelectric film 3, that is, the area between the signal electrode Y and the pixel electrode 4 is Sf, the voltage Vlc applied to the liquid crystal layer 5 during the holding period is: Vlc = −Sf · Pr / (Clc + Cf) (1)

By setting the voltage Vlc higher than the threshold voltage Vth of the liquid crystal layer 5, the arrangement direction of the liquid crystal molecules in the liquid crystal layer 5 can be aligned with the direction of the electric field.

On the other hand, in the next selection period, the ferroelectric film 3
, A polarization P of the ferroelectric film 3 can be reduced to almost zero, thereby removing the electric field applied to the liquid crystal layer 5 and causing the liquid crystal of the liquid crystal layer 5 to be removed. The molecule can be returned to its original state.

JP-A-6-23166 and JP-A-7-11
As shown in Japanese Patent No. 4040 or the like, conventionally, a matrix type liquid crystal display using a ferroelectric film is driven by the above-described switching operation.

[0014]

However, the depolarization of the ferroelectric film 3 by applying a coercive electric field -Ec of the opposite polarity to the ferroelectric film 3 as described above is microscopically, This causes an unstable state in which the dipoles of the ferroelectric film 3 are turned in the opposite direction by 50%. In fact, the polarization characteristics near the coercive electric field −Ec change sharply with respect to the electric field E, so that it is difficult to keep the polarization P at zero.

Therefore, as a countermeasure, the voltage characteristic of the liquid crystal layer 5 is made steep so that the polarization
In order to prevent switching, liquid crystal layer 5 is considered to use an STN (super twisted nematic) liquid crystal having a large twist angle of the liquid crystal.

However, when the STN liquid crystal is used as the liquid crystal layer 5, since the twist angle of the liquid crystal is large, responsiveness is deteriorated, and a problem such as a narrow viewing angle occurs. Moreover, even in this case, since an unstable state is used for depolarization, the voltage applied to the liquid crystal layer 5 fluctuates, causing flicker and a decrease in contrast.

Therefore, the present invention provides a matrix type liquid crystal display using a ferroelectric film and a method of driving the same, which eliminates an unstable state of the ferroelectric film when the polarization is depolarized, thereby reducing flicker and contrast. In such a case, it is possible to obtain a good display which does not cause a decrease in the image quality.

[0018]

According to the present invention, which relates to a liquid crystal display, a first electrode Y and a ferroelectric film are shown by referring to the reference numerals of one embodiment shown in FIGS. 7 on which the first electrode Y is formed.
A liquid crystal layer 5 is formed between the second electrode X and a second substrate 2 having a second electrode X intersecting with the first electrode Y and the second electrode X.
A liquid crystal display in which the ferroelectric film 7 and the liquid crystal layer 5 are connected in series between the ferroelectric film 7 and the liquid crystal layer 5.
Are different from each other in the coercive electric field in the hysteresis characteristic of the electric field-polarization, and the first ferroelectric portions 7 have the same remanent polarization.
A and the second ferroelectric portion 7B.

In this case, in the first ferroelectric portion 7A and the second ferroelectric portion 7B, the thickness of the first ferroelectric portion 7A is smaller than the thickness of the second ferroelectric portion 7B, and The area of the ferroelectric portion 7A can be larger than the area of the second ferroelectric portion 7B. Alternatively, the first ferroelectric portion 7A and the second ferroelectric portion 7B are formed of different materials, and the area of the first ferroelectric portion 7A is larger than the area of the second ferroelectric portion 7B. be able to.

According to the present invention, which relates to a method of driving a liquid crystal display, in driving the liquid crystal display according to the present invention in a matrix, the liquid crystal display is driven by two pulses of a reset pulse and a selection period pulse. The voltage applied to the liquid crystal layer 5 is controlled in three states.

In this case, it is desirable that the driving by the two pulses is performed twice in one field for both positive and negative.

[0022]

According to the liquid crystal display of the present invention constructed as described above and the driving method of the present invention according to the above method, the voltage applied to the liquid crystal layer 5 when the ferroelectric film 7 is depolarized is stabilized. The ferroelectric film 7 is
The liquid crystal layer 5 is switched using only the two stable states.

The hysteresis characteristic of the electric field E-polarization P of the first ferroelectric portion 7A is adjusted to the voltage V-charge Q
When converted into the characteristic shown schematically, it is as shown by a solid line 8A in FIG.

The first ferroelectric portion 7A and the second ferroelectric portion 7B are formed of the same material, and the thickness of the first ferroelectric portion 7A is 1 / th of the thickness of the second ferroelectric portion 7B.
k (where k> 1), and the first ferroelectric portion 7A
Is made k times larger than the area of the second ferroelectric portion 7B, and if the film thickness of the first ferroelectric portion 7A is Tf and the area is Sf, the coercive electric field Ec of the first ferroelectric portion 7A The corresponding voltage Vc and the charge Qr corresponding to the remanent polarization Pr are expressed as follows: Vc = Ec · Tf (2) Qr = Pr · Sf (3)

For the sake of simplicity, when k = 2, that is, the thickness of the second ferroelectric portion 7B is twice the thickness Tf of the first ferroelectric portion 7A, and Considering the case where the area of the body part 7B is の of the area Sf of the first ferroelectric part 7A, the coercive electric field Ec ′ of the second ferroelectric part 7B is considered.
And the charge Qr ′ corresponding to the remanent polarization Pr ′ are Pr ′ = 2 · Pr, so that Vc ′ = 2 · Vc (4) Qr ′ = Qr (5) Become.

Therefore, when the hysteresis characteristic of the electric field E-polarization P of the second ferroelectric portion 7B is schematically converted into the characteristic of the voltage V-charge Q according to the actual driving, the broken line 8B in FIG. become that way.

Then, a voltage V21 shown in FIG. 2 (in this case, 2.multidot.V11) is applied to the ferroelectric film 7 as a reset pulse.
Is applied, and the dipoles of the first ferroelectric portion 7A and the second ferroelectric portion 7B of the ferroelectric film 7 are oriented in the positive direction.

At this time, the voltage V ′ 21 applied to the whole series circuit including the liquid crystal layer 5 is determined by the capacitance of the ferroelectric film 7.
f, the capacitance of one pixel of the liquid crystal layer 5 is Clc, and V′21 = (Clc + Cf) · V21 / Clc (6)

After the reset pulse is removed, a voltage Vlc expressed by the following equation is applied to the liquid crystal layer 5: Vlc = −2 · Qr / (Clc + Cf) (7)

Further, the voltage -V11 shown in FIG. 2 is applied to the ferroelectric film 7 as a selection period pulse, and only the first ferroelectric portion 7A in the ferroelectric film 7 causes the dipole to move in the negative direction. Invert. As a result, the total residual charge of the first ferroelectric portion 7A and the second ferroelectric portion 7B becomes zero.

However, it is necessary that the second ferroelectric portion 7B does not change even when the voltage -V11 is applied to the ferroelectric film 7. That is, in FIG. 2, it is necessary that V22 ≧ V11 (8).

As a reset pulse, a voltage -V21 having a polarity opposite to that of the voltage V21 may be applied to the ferroelectric film 7. In this case, the voltage applied to the entire series circuit including the liquid crystal layer 5 is a voltage -V'21 having a polarity opposite to that of the expression (6).

By driving the pixel with the two pulses of the reset pulse and the selection period pulse as described above, the liquid crystal layer 5 is applied to the ferroelectric film 7 using only the two stable states. When the voltage is Vlc, 0, -Vlc
It is possible to switch to the following three states.

Although the method of driving only one pixel has been described above, to drive a large number of pixels, matrix driving is performed as follows.

The matrix type liquid crystal display using a ferroelectric film according to the present invention has a first electrode Y1, Y2... Yn and a second electrode X1, as shown in the equivalent circuit diagram of FIG.
Xm and Xm, respectively, the first
The ferroelectric film 7 composed of the ferroelectric portion 7A and the second ferroelectric portion 7B and the liquid crystal layer 5 are connected in series.

The pulse applied for driving the matrix has a certain degree of freedom and is not particularly limited. For example, a pulse shown in FIG. 4 is applied.

However, a voltage Vs represented by Vs = (V11 + V12) / 2 (9) is applied to the ferroelectric film 7 as a selection period pulse, and Vd = (V11-V12) as a data signal. ) / 2 (10) A voltage Vd represented by the following expression is applied.

In this case, voltages applied to the entire series circuit including the liquid crystal layer 5 are expressed by the following equations (11) and (1), respectively.
2), V's = (Clc + Cf) .Vs / Clc (11) V'd = (Clc + Cf) .Vd / Clc (12) The voltages Vs 'and Vd' are expressed by the following equations.

FIG. 4 shows that the second electrodes X1, X2,..., Xm are used as scanning electrodes, a reset pulse and a selection period pulse are applied thereto, and the first electrodes Y1, Y2,. When a data signal having a voltage value of ± Vd is selectively applied to the pixel at the intersection of the scanning electrode Xi (i = 1 to m) and the signal electrode Yj (j = 1 to n). The waveform is shown as (Xi, Yj).

Here, the reset pulse Vres and the selection period pulse Vsel applied to the scan electrode Xi are represented by the following equations (13) and (14), respectively: Vres = CfV'21 / Clc (13) Vsel = Cf (−V ′s ± V′d) / Clc (14)

The first ferroelectric portion 7A and the second ferroelectric portion 7B may be selected in thickness, area and material so as to satisfy the above equations (5) and (8). Therefore, when the first ferroelectric portion 7A and the second ferroelectric portion 7B are formed of the same material, as described above,
The thickness of the first ferroelectric portion 7A is 1 / k of the thickness of the second ferroelectric portion 7B, and the area of the first ferroelectric portion 7A is k times the area of the second ferroelectric portion 7B. What should I do?

On the other hand, by forming the first ferroelectric portion 7A and the second ferroelectric portion 7B from different materials, the film thickness of the first ferroelectric portion 7A is increased as described above. This can be equivalent to 1 / k of the film thickness of the dielectric portion 7B. In this case, the first ferroelectric portion 7A
And the second ferroelectric portion 7B may have the same thickness, and the area of the first ferroelectric portion 7A may be k times the area of the second ferroelectric portion 7B.

Further, the first ferroelectric portion 7A and the second ferroelectric portion 7B are formed of different materials, and the thickness of the first ferroelectric portion 7A is made smaller than the thickness of the second ferroelectric portion 7B. It is also possible to make it smaller and make the area of the first ferroelectric portion 7A larger than the area of the second ferroelectric portion 7B.

[0044]

BEST MODE FOR CARRYING OUT THE INVENTION

[One Embodiment] FIGS. 1A and 1B show one embodiment of a liquid crystal display of the present invention. In the liquid crystal display of this embodiment, a stripe-shaped signal electrode Y is formed on one surface of a lower substrate 1 made of a transparent insulating substrate, and a first ferroelectric portion 7A and a second ferroelectric portion 7B are formed on the signal electrode Y. A ferroelectric film 7 made of a transparent conductive film is formed on the ferroelectric film 7, and a signal on the lower substrate 1 is formed on one surface of an upper substrate 2 made of a transparent insulating substrate. A scanning electrode X in a stripe shape orthogonal to the electrode Y is formed.

Then, the lower substrate 1 and the upper substrate 2 are opposed to each other at a predetermined interval with the surface on which the signal electrode Y or the scanning electrode X is formed inside, and a liquid crystal material is injected between the two. The layer 5 is formed.

In this embodiment, the ferroelectric film 7 is formed by forming a ferroelectric film 7a on the signal electrode Y, and furthermore, on a part of the ferroelectric film 7a, using the same material as the ferroelectric film 7a. The ferroelectric film 7b is formed to have the same thickness as the ferroelectric film 7a, and the portion where only the ferroelectric film 7a is formed between the signal electrode Y and the pixel electrode 4 is replaced with the first ferroelectric film. With part 7A,
A portion where the ferroelectric films 7a and 7b are formed between the signal electrode Y and the pixel electrode 4 is referred to as a second ferroelectric portion 7B.
Therefore, the thickness of the first ferroelectric portion 7A is １ ／ of the thickness of the second ferroelectric portion 7B.

The first ferroelectric portion 7A and the second ferroelectric portion 7B have the same width W, and the first ferroelectric portion 7A has the same width W.
By making the length La of the first ferroelectric portion 7A twice the length Lb of the second ferroelectric portion 7B, the area (L
a · W) is made twice as large as the area (Lb · W) of the second ferroelectric portion 7B.

Therefore, in this embodiment, the hysteresis characteristics of the electric field E-polarization P of the first ferroelectric portion 7A and the second ferroelectric portion 7B are converted into the characteristics of the voltage V-charge Q to roughly. When shown, they are as shown by a solid line 8A and a broken line 8B in FIG. 2, respectively.

FIGS. 1A and 1B show one pixel of the liquid crystal display. A large number of signal electrodes Y and scanning electrodes X are arranged in a direction orthogonal to the respective extending directions, and at each intersection position. Pixels are formed. Therefore, as shown in FIG. 3, the signal electrodes Y1, Y2,.
, Xm, and scanning electrodes X1, X2,.
The first ferroelectric portion 7A and the second ferroelectric portion 7
The ferroelectric film 7 made of B and the liquid crystal layer 5 are connected in series.

Then, as shown in FIG. 4 and described above, a large number of pixels of the liquid crystal display are driven in a matrix.

Example 1 A glass substrate (7059, manufactured by Corning Incorporated) is used as the lower substrate 1 of the liquid crystal display shown in FIGS. 1A and 1B, and the signal electrode Y is formed of Cr. The ferroelectric films 7a and 7b are each formed of PZT (lead zirconate titanate). The pixel electrode 4
A glass substrate (7059, manufactured by Corning Incorporated) with an electrode made of an ITO film is used as the scanning electrode X and the upper substrate 2 formed of an ITO film.

The thickness of the first ferroelectric portion 7A is 0.4 μm.
m, the area (La · W) is 12 μm × 10 μm, the film thickness of the second ferroelectric portion 7B is 0.8 μm, and the area (Lb · W) is 6 μm × 10 μm.

At this time, the characteristics of the first ferroelectric portion 7A include a dielectric constant of 50, a coercive electric field Ec of 250 kV / cm, a residual polarization Pr of 4 μC / cm ² , and a characteristic of the second ferroelectric portion 7B. Has a dielectric constant of 50 and a coercive electric field Ec ′ of 500 k
V / cm and the residual polarization Pr ′ is 4 μC / cm ² . The characteristic of the ferroelectric film 7 is that the capacitance Cf is 0.27
pF, and voltages V11, V12, V21, and V22 are V11 =
13V, V12 = 7V, V21 = 26V, V22 = 14
V.

The liquid crystal material of the liquid crystal layer 5 has a dielectric constant of 1
0 nematic liquid crystal is used, the area of one pixel of the liquid crystal layer 5 is 300 μm × 300 μm, and the cell gap is 5 μm. At this time, the capacitance Clc for one pixel of the liquid crystal layer 5 is:
It becomes 1.6 pF.

The actual driving voltages V'21, V's, and V'd represented by the equations (6), (11), and (12) are expressed as V'21 = 30.
4 V, V's = 11.7 V, and V'd = 4.8 V are set. At this time, the voltages Vlc, Vres, and Vsel expressed by the equations (7), (13), and (14) are Vlc = −5.14.
V, Vres = 5.13V, Vsel = −2.78, −
1.16V. This value is an effective voltage of 3.0 V at a light transmittance of 90% in the electro-optical characteristics of the liquid crystal material.
Is satisfied enough.

The liquid crystal display is configured as described above,
By driving, a state in which the potential of the ferroelectric film at the time of depolarization is unstable is removed, and a favorable display free from flicker and reduction in contrast can be obtained. Further, unlike the case where STN liquid crystal having a large twist angle of liquid crystal is used, problems such as poor response and a narrow viewing angle do not occur.

Example 2 In a matrix type liquid crystal display using a ferroelectric film, a voltage is continuously applied to the liquid crystal cell, so that image sticking is likely to occur. Therefore,
In the second embodiment, the liquid crystal display is driven so that burn-in is prevented.

The liquid crystal display itself is the same as that of the first embodiment.
Is the same as In the second embodiment, as shown in FIG. 5, the driving clock frequency is doubled compared to that in the first embodiment shown in FIG. 4, and the driving by the reset pulse and the selection period pulse is performed by one field. Is performed twice in positive and negative directions.

In the example of FIG. 5, when the pixel is turned on, as shown by (X1, Y1) or (X2, Y2), the pixel is turned on twice in one field by the pulse of the opposite polarity, and the pixel is turned on. When turning off, (X
As shown by (1, Y2) or (X2, Y1), the pulse is turned off twice within one field by a pulse of the opposite polarity. However, when the pixel is turned off, it may be turned off only once in one field.

As a result, the charge is prevented from being shifted to one side in the liquid crystal layer 5, and the image sticking is prevented.

[Other Embodiments] As described above, the first ferroelectric portion 7A and the second ferroelectric portion 7B are formed of different materials, and the first ferroelectric portion 7A and the second ferroelectric portion 7A are formed. The thickness of the portion 7B is equal, or the first ferroelectric portion 7
The thickness of A may be smaller than the thickness of the second ferroelectric portion 7B, and the area of the first ferroelectric portion 7A may be larger than the area of the second ferroelectric portion 7B.

In the above embodiment, the electrode Y on the substrate 1 on which the ferroelectric film 7 is formed is used as a signal electrode, and the electrode X on the other substrate 2 is used as a scanning electrode. To
The electrode Y may be a scanning electrode and the electrode X may be a signal electrode.

[0063]

As described above, according to the present invention, the state where the potential of the ferroelectric film at the time of depolarization is unstable is removed.
It is possible to obtain a favorable display which does not cause flicker or decrease in contrast. Furthermore, when driving by two pulses of the reset pulse and the selection period pulse is performed twice in one field for both positive and negative, the burn-in can be prevented. Further, since the voltage when the pixel is turned off becomes stable, the NCAP (Nematic Curve)
It is also possible to use a liquid crystal having a gentle electro-optical characteristic, such as a liquid crystal having a vignetized alignment (nematic curve type alignment phase).

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a liquid crystal display of the present invention.

FIG. 2 is a diagram illustrating a voltage of a ferroelectric film of the liquid crystal display of FIG. 1;
FIG. 4 is a diagram illustrating characteristics of electric charges.

FIG. 3 is a diagram showing an equivalent circuit of the liquid crystal display of FIG.

FIG. 4 is a diagram showing an example of a driving method according to the present invention.

FIG. 5 is a diagram showing another example of the driving method of the present invention.

FIG. 6 is a diagram showing a conventional example of a matrix type liquid crystal display using a ferroelectric film.

FIG. 7 is a diagram provided for explanation of the liquid crystal display of FIG. 6;

8 is an electric field of the ferroelectric film of the liquid crystal display of FIG. 6;
It is a figure showing the hysteresis characteristic of polarization.

[Explanation of symbols]

 Reference Signs List 1 lower substrate (first substrate) 2 upper substrate (second substrate) Y signal electrode (first electrode) X scanning electrode (second electrode) 4 pixel electrode 5 liquid crystal layer 7 ferroelectric film 7A first ferroelectric Part 7B Second ferroelectric part

Claims (5)

[Claims] 1. A liquid crystal layer is formed between a first substrate on which a first electrode and a ferroelectric film are formed, and a second substrate on which a second electrode intersecting the first electrode is formed. In a liquid crystal display in which the ferroelectric film and the liquid crystal layer are connected in series between a first electrode and the second electrode, the ferroelectric films differ from each other in a coercive electric field in electric field-polarization hysteresis characteristics. And the first to make the remanent polarization the same
A liquid crystal display comprising a ferroelectric part and a second ferroelectric part. 2. The liquid crystal display according to claim 1, wherein said first ferroelectric part and said second ferroelectric part are:
The thickness of the first ferroelectric portion is smaller than the thickness of the second ferroelectric portion, and the area of the first ferroelectric portion is larger than the area of the second ferroelectric portion. Liquid crystal display. 3. The liquid crystal display according to claim 1, wherein said first ferroelectric part and said second ferroelectric part are:
A liquid crystal display formed of a different material, wherein an area of the first ferroelectric portion is larger than an area of the second ferroelectric portion. 4. A liquid crystal layer is formed between a first substrate on which a first electrode and a ferroelectric film are formed and a second substrate on which a second electrode crossing the first electrode is formed. The ferroelectric film and the liquid crystal layer are connected in series between the first electrode and the second electrode, and the ferroelectric films have different coercive electric fields in electric field-polarization hysteresis characteristics, and
In driving a liquid crystal display composed of a first ferroelectric portion and a second ferroelectric portion having the same remanent polarization in a matrix, the liquid crystal display is driven by two pulses of a reset pulse and a selection period pulse, and Controlling the voltage applied to the layer to three states,
Driving method of liquid crystal display. 5. The driving method according to claim 4, wherein the driving with the two pulses is performed twice in one field for both positive and negative.