JPS62145216A - Liquid crystal element and driving method thereof - Google Patents

Abstract

PURPOSE:To obtain a graded display of a liquid crystal element having bistability by using a ferroelectric liquid crystal which has changing distributions of film thickness and providing changing spacing distributions between a pair of electrodes. CONSTITUTION:The liquid crystal element 11 for the graded display has the distributions in which the film thickness of the ferroelectric liquid crystal 12 changes stepwise to d1-d4. Said element has the distribution in which the spacing between a pair of the transparent electrodes 13a (step electrode) and 13b (flat electrode) changes stepwise. A stepped insulating film 15 is formed on a substrate 14a consisting of a glass sheet or plastic film in order to form the film thickness having the changing distribution and the inter-electrode spacing having the changing distribution. Orientation controlling films 16a and 16b having the wall effect to preferentially orient the smectic molecular layer of the liquid crystal 12 in one direction can be formed on the electrodes 13a and 13b.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a liquid crystal element for gradation display using an area gradation method and a method for driving the same, and more specifically, to a liquid crystal device using a bistable ferroelectric liquid crystal. The present invention relates to a liquid crystal element for gradation display suitable for display panels such as liquid crystal televisions, and a method for driving the same.

[Conventional technology]

In LCD television panels using the conventional active matrix drive method, thin film transistors (TPT)
are arranged in a matrix for each pixel, and a gate-on pulse is applied to the TPT to make the source and drain conductive. At this time, a video image signal is applied from the source and accumulated in the capacitor, and the capacitor corresponds to the accumulated image signal. A liquid crystal (for example, twisted nematic-TN liquid crystal) is driven, and grayscale display is performed by simultaneously modulating the voltage of the video signal.

However, in active matrix drive type television panels using such TN liquid crystals, the TPT used is
Because TPT has a complicated structure, the number of structural steps is large, and high manufacturing costs are a bottleneck.In addition, the thin film semiconductors (e.g., polysilicon, amorphous silicon) that make up TPT cannot be spread over a large area. There are problems such as difficulty in forming a film over the entire area.

On the other hand, a passive matrix drive type display panel using TN liquid crystal is known as a device that can be manufactured at low manufacturing cost. 1 while scanning
The time during which an effective electric field is applied to one selection point (duty ratio) decreases at a rate of l/N, which causes crosstalk and has disadvantages such as not providing a high-contrast image. On top of being there.

When the duty ratio becomes low, it becomes difficult to control the gradation of each pixel by voltage modulation, and therefore it is not suitable for display panels with a high density of wiring, especially liquid crystal television panels.

In order to solve these fundamental problems of conventional TN liquid crystals, a ferroelectric liquid crystal element having bistability has been proposed, such as in US Pat. No. 4,367,924 by Clark and Lagerwall et al.

[Problem that the invention seeks to solve]

However, in image display using the aforementioned bistable ferroelectric liquid crystal, the shape of the ferroelectric liquid crystal molecules is 7ff.
When i is in a state with memory properties, it attempts to stabilize in either of the two bistable states and does not take an intermediate molecular position, at least ideally, so that it can adopt conventional analog molecular behavior. It was considered to be unsuitable for gradation expression. However, gradation display using the dither method lowers the resolution and cannot meet the display quality requirements.In particular, when electrodes are formed by etching, there is a limit to the size of one pixel. So I didn't like it.

[Means for Solving the Problems] and [Operations] The object of the present invention is to eliminate the above-mentioned drawbacks, and more specifically, to solve the problems in display panels having high density pixels over a wide area, especially in liquid crystal television panels. An object of the present invention is to provide a liquid crystal element capable of displaying gradations and a method for driving the same.

That is, the present invention provides a liquid crystal element having a pair of electrodes and a ferroelectric liquid crystal disposed between the pair of electrodes, in which the ferroelectric liquid crystal has a varied thickness distribution, and the ferroelectric liquid crystal has a changed thickness distribution. The distance between the electrodes has changed! 1j.

Furthermore, the present invention provides a first electrode, a second electrode, a first electrode, and a second electrode.
and a ferroelectric liquid crystal having a changed film thickness 4j, which is disposed opposite to the electrode and the second electrode, and substantially covers the entire area of the pixel. A first electrode that applies a voltage signal to the first electrode and the second electrode to bring the region into one of the first state 7g and the second state.
The predetermined area of the pixel is changed from one state in the first step to the other state by applying a pulse having a waveform according to the gradation information to the first electrode and the second electrode. A second feature of the method for driving a liquid crystal element includes a second step of inverting the liquid crystal element.

〔Example〕

The present invention will be explained below with reference to the drawings.

The ferroelectric liquid crystal used in the present invention takes either a first optically stable state or a second optically stable state depending on the applied electric field. That is, a substance having a bistable state with respect to an electric field, particularly a liquid crystal having such properties, is used.

As the ferroelectric liquid crystal having bistability that can be used in the driving method of the present invention, a chiral smectic C phase (SmC powder) or H phase (SmCt) liquid crystal having ferroelectric properties is suitable.

Regarding this ferroelectric liquid crystal, "LE JOURNAL
197
5th year, -G6 (L-69), "Ferroelect
Lili Liquid Fist
``Ri Lists'' (rFerroel)
etric Liquid Crystals4);
°゛Applied Physics ψ Letters'' (“Appl
ied Physics Letter” (1
980 years.

No. 36 (11), ``Submicro Second Bistiple Electrical Switching Fist in Liquid Writing Risterus J (rsubmicr.

5econd B15table Electroo
pticSwitching in Liquid C
rystals') ;11r-[=1ru! Lffll
Illran+Iw++=/+AI'+1=three colors.

The ferroelectric liquid crystal disclosed in these publications is also used in the present invention.

More specifically, an example of a ferroelectric liquid crystal compound used in the method of the present invention is decyloxyhenzylidene-p'-amino-2-methylbutylcinnamate (DOBAMB
C), hexyloxybenzylidene-p'-amino-2
-Chloropropyl cinnamate (HOBACPC) and 4-o-(2-methyl)-butylresolsiliten-4
'-octylaniline (MBRA8) and the like.

When constructing an element using these materials, in order to maintain the temperature at which the liquid crystal compound becomes the Smc main phase or the SmH* phase, the element may be placed in a copper block etc. in which a heater is embedded, as necessary. can be more supported.

In addition to the above-mentioned SmCt and SmH coatings, chiral smectic C phase (SmI*), J phase (SmJ*), and G phase (sm
It is also possible to use ferroelectric liquid crystals that appear in phases such as G (G), F, fIcsmF (F), and (SmK*).

Furthermore, the present invention can be applied to chiral smectic liquid crystals having at least two stable orientation states, in addition to the above-mentioned bistable chiral smectic liquid crystals.

FIG. 10 schematically depicts an example of a t4 ferroelectric liquid crystal cell. la and ib are In203.5n02 and ITO (Indi un-TinOxide)
It is a substrate (glass plate) coated with transparent electrodes such as
In between, a liquid crystal is sealed with an SmC crystal in which a liquid crystal molecular layer 2 is oriented perpendicular to the glass surface. A thick line 3 represents a liquid crystal molecule, and this liquid crystal molecule 3 has a dipole moment (P) 4 in a direction perpendicular to the molecule. When a voltage higher than a threshold value at one point is applied between the electrodes on the substrates 1a and ib, the helical structure of the liquid crystal molecules 3 is unraveled, and the orientation direction of the liquid crystal molecules 3 is changed so that the dipole moment (P) 4 is all directed in the direction of the electric field. can be changed.

The liquid crystal molecules 3 have an elongated shape and exhibit refractive index anisotropy in the long axis direction and the short axis direction. Therefore, for example, if polarizers are placed above and below the glass surface in a crossed nicol positional relationship, It is easily understood that this is a liquid crystal optical modulation element whose optical characteristics change depending on the polarity of applied voltage. Furthermore, when the thickness of the liquid crystal cell is made sufficiently thin (for example, L)
As shown in Figure 11, even when no electric field is applied, the helical structure of the liquid crystal molecules is removed (non-helical structure).
, its dipole moment Pa or Pb is upward (4a)
or downward (4b). As shown in FIG. 4, when an electric field Ea or Eb of different polarity above a certain threshold value is applied for a predetermined period of time to such a cell, the dipole moment will move upward 4a or downward 4b in accordance with the electric field vector of the electric field Ea or Eb. Accordingly, the liquid crystal molecules are aligned in either the first alignment state 5a or the second alignment state 5b.

There are two advantages to using such a ferroelectric liquid crystal as an optical modulation element. First, the response speed is extremely fast, and the second liquid crystal molecules have a bistable orientation. To explain the second point using, for example, FIG.
This state is stable even when the electric field is turned off.

Moreover, when an electric field Eb in the opposite direction is applied, the liquid crystal molecules are aligned to the second alignment state 5b and the orientation of the molecules is changed.
It remains in this state even if the electric field is turned off. Further, as long as the applied electric field Ea does not exceed a certain threshold value, each orientation state is maintained. In order to effectively realize such fast response speed and bistability, it is preferable for the cell to be as thin as possible, and in general, 0.5L to 20g, especially lp to 5JL is suitable. . Liquid crystal with matrix electrode structure using this type of ferroelectric liquid crystal
Electro-optical devices, for example by Clark and Ragaval.

The present invention, proposed in U.S. Pat. No. 4,367,924, proposes a modification to the cell structure when used in a ferroelectric liquid crystal having at least two stable states, especially under the bistability state of the ferroelectric liquid crystal described above. Specifically, the layer thickness of the ferroelectric liquid crystal is changed continuously or stepwise,
By changing the distance between the pair of electrodes continuously or stepwise in accordance with this change in layer thickness, desired gradation display can be achieved.

As described above, a ferroelectric liquid crystal element having bistability can change the alignment direction of the liquid crystal by applying two different polar electric fields, thereby performing optical modulation.

In the present invention, an element using ferroelectric liquid crystal is generally driven by applying a rectangular pulse to the liquid crystal layer from between a pair of electrodes. Ferroelectric liquid crystals have sharp threshold characteristics for electric fields given by rectangular pulses. That is, there is no response below a certain electric field, but a transition between one, for example, two stable states occurs above a certain electric field. In the present invention, - the liquid crystal layer film and electrode spacing within a pixel are given a variation distribution;

When a voltage pulse is applied within a pixel, a difference is generated in the electric field strength, and this electric field strength creates regions within the pixel that are inverted and regions that are not, and the gradation is controlled by the ratio of the inverted regions. It can be made possible.

FIG. 1 is a sectional view showing a typical example of the liquid crystal element of the present invention.

In the gradation display liquid crystal element 11 shown in FIG. 1, the thickness of the ferroelectric liquid crystal 12 is gradually increased by dl and ct2.

It has a distribution that changes from d3 to d4, and corresponding to this changing distribution, the distance between the pair of transparent electrodes 13a (step electrode) and 13b (flat electrode) has a distribution that changes stepwise. A step insulation 11U15 is formed on a substrate 14a such as a glass plate or a plastic film in order to form a film thickness having a varied distribution and an electrode spacing having a varied distribution as described above. Further, alignment control films 16a and 16b having a wall effect for orienting the smectic molecular layer of the ferroelectric liquid crystal 12 in one direction can be formed on the transparent electrodes 13a and 13b, respectively.

As mentioned above, the film thicknesses di, d2. Since the electric field strength applied to the ferroelectric liquid crystals 12 of d3 and d4 is different in each film thickness region, a pulse signal with a voltage peak value depending on the gradation, or a pulse signal with a pulse width or pulse number depending on the gradation is generated. Gradation can be expressed by applying a signal and forming regions in a pixel in which the inversion threshold voltage is exceeded and regions in which the inversion threshold voltage is not exceeded according to the film thicknesses d1 to d4.

In addition, in the present invention, prior to applying the above-mentioned gradation signal,
After going through an erasing step that puts the pixel into either a bright state or a dark state, an inversion voltage that reverses that state is controlled according to the gray scale and applied to the ferroelectric liquid crystal. That is reassuring.

Further, preferred specific examples of the present invention will be described.

FIG. 2 schematically shows a method of applying electrical signals, and FIGS. 3 and 4 show electrical signals. 3 shows the waveform of the signal (a) generated in the drive circuit 23 of FIG. 2, and FIGS. 4(a) to (e) show the waveform of the signal (b) generated in the drive circuit 23 of FIG. It represents.

Now, the signal (a) is a 12V 1m5ec pulse, and the signal (b) is -8V 1 +n s e
An erasing step is provided in which c pulses are applied in advance in synchronization (this is called an erasing pulse). Then, the liquid crystal
The light is switched to a stable state, and the entire pixel A becomes a bright state (the cross polarizing plates are arranged in this way). From this state, gradation signals having various pulses as shown in FIGS. 4(a) to (e) are used as signals (b) to be applied to the transparent step electrode 13a in synchronization with the pulses shown in FIG. 13b, the optical state of pixel A is expressed as the fifth
Shown in Figures (a) to (e).

The display state shown in Fig. 5(a) is the JI-function when the pulse (OV) shown in Fig. 4(a) is applied.
Prison Step Nth Floor III J-R No. 51 is kept as it is. In the display states shown in FIGS. 5(b) to 5(d), the pulses shown in FIGS. 4(b) to 4(d) corresponding to halftone signals are applied, and the bright state 51 changes to the film thickness d1 to d4. The state is accordingly inverted to a dark state 52.

In other words, FIG. 5(b) shows the -2V shown in FIG. 4(b).
, the film thickness d within one pixel A when a pulse of 1 m5ec is applied
The area corresponding to 1 represents a display state inverted to a dark state. FIG. 5(c) shows the 14V shown in FIG. 4(c).

When a pulse of 1 m5ec is applied, the film thickness d in pixel A is
The areas corresponding to 1 and d2 represent a display state inverted to a dark state, and FIG. 5(d) shows the -6V shown in FIG. 4(d),
When a pulse of 1 m5ec is applied, the film thickness in pixel A is ct
1. This shows a display state in which the areas corresponding to d2 and d3 are inverted to a dark state.

The display state in FIG. 5(e) is the film thickness dl in pixel A.
, d2. The area corresponding to ci3 and d4, that is, the entire pixel A is in a dark state 52.

The present invention also provides a transparent flat electrode 13. shown in FIG. d
is formed into a stripe shape, and the transparent step electrode 13a is similarly formed.
have a stripe shape, and each transparent electrode 13a and 1
3b can be made into a matrix electrode structure in which they intersect with each other.

In the driving method of the present invention, gradation can be reproduced by changing the frequency according to the gradation. FIG. 6 shows a concrete example thereof.

That is, as shown in FIGS. 6(a) to 6(e), a signal with a pulse width corresponding to the gradation is generated, for example, as shown in FIGS.
The fifth pulse can also be applied in place of the pulse in (e).
It is possible to display the gradations shown in the figure. At this time, the pulses shown in FIGS. 6(b) to 6(C) correspond to halftone signals. Furthermore, according to the present invention, similar gradation display can be performed by changing the number of pulses.

Furthermore, in the liquid crystal element shown in FIGS. 1 and 2, only the transparent electrode on one side is used as a transparent step electrode, but in the liquid crystal element of the present invention, two transparent electrodes forming a pair on both sides are used as transparent step electrodes. It can be done.

FIG. 7 is a sectional view showing another embodiment of the liquid crystal element of the present invention. The liquid crystal element shown in FIG. 7 has a wedge-shaped insulating film 72 and a transparent electrode formed thereon in order to form a distribution in which both the distance between a pair of electrodes and the film thickness of the ferroelectric liquid crystal change continuously. 71 is provided.

The alignment control films 16a and 16b used in the present invention include, for example, silicon oxide, silicon dioxide, aluminum oxide, zirconia, magnesium fluoride, cerium oxide, cerium fluoride, silicon nitride, silicon carbide, boron nitride, etc. Inorganic insulation materials and organic insulation such as polyvinyl alcohol, polyimide, polyamideimide, polyesterimide, polyparaxylerin, polyester, polycarbonate, polyvinyl acetal, polyvinyl chloride, polyamide, polystyrene, cellulose resin, melamine resin, urea resin, and acrylic resin. An alignment control film can be used in which a film formed using a substance is subjected to a uniaxial alignment treatment such as a rubbing treatment.

Further, the step insulating film 15 used in the liquid crystal element of the present invention is
It can be obtained by repeating photolithography technology, and photoresist resin is suitable as the insulating material used at this time, but other resins such as polyvinyl alcohol, polystyrene, cellulose resin, polyamide, and polyimide can also be used. be.

FIG. 8 shows a specific example when the gradation expression method according to the present invention is applied to matrix driving.

The display panel shown in FIG. 8 has a striped transparent step electrode 81 (81a) on a glass substrate.

8 l b , --- 81g) are arranged.

A striped transparent flat electrode 82 (82a, 82b--82f) facing the transparent step electrode 81 is
The wiring is arranged to intersect with the transparent step electrode 81, and a ferroelectric liquid crystal is arranged between the pair of transparent electrodes 81 and 82.

In the matrix driving method of the present invention, prior to writing, all or a predetermined portion of the pixel formed at the intersection of the striped transparent step electrode 81 and the striped transparent flat electrode 82 is placed in either a bright state or a dark state at once. It is possible to use a method of writing a gradation image by sequentially applying a write signal with a gradation signal to the pixel for each row after one state is written. After setting all or a predetermined portion of the pixels on the top of the screen to either a bright state or a dark state, the step of applying a write signal accompanied by a gradation signal to the pixels on the top of the top of the screen is sequentially performed row by row, thereby creating a gradation pixel. A method of writing can be used. These driving methods are disclosed in, for example, Japanese Unexamined Patent Publication Nos. 59-193427 and 60-156047, and are preferred examples of driving in the present invention.

In the driving method of the present invention, the striped transparent step electrode 8
1 as a scanning electrode group, to which a scanning signal is applied, and the opposing striped transparent flat electrode 82 as a signal electrode group, to which a gradation signal shown in FIG. 4 or 6 is selectively applied. In addition, conversely, a scanning signal can be applied to the strip-shaped transparent flat electrode 82, and a gradation signal can be selectively applied to the other strip-shaped transparent step electrode 81. Writing can also be performed by

Hereinafter, the present invention will be explained by giving detailed specific examples.

Example 1 A step insulating film shown in Fig. 1 was formed on a glass plate using acrylic negative resist resin (RFG” from Building Blocks Fine Chemicals).
On the step insulating film, an ITO film that becomes a striped transparent step electrode is provided, and a polyimide film with an I film thickness of 1000 nm is further applied over the negative side (the polyimide film consists of pyromellitic dianhydride and 4 .It was formed by coating a 5% by weight N-methylpyrrolidone solution of polyamic acid, which is a dehydration condensate with 4'-diaminodiphenyl ether, and causing a dehydration ring-closing reaction by heating at a temperature of 180°C.) A rubbing process was performed along the longitudinal direction of the striped pole. This was designated as the A' electrode plate.

Next, another glass plate was prepared, and after forming striped ITOII on it, a 1,000-layer polyimide film similar to that used when creating the A electrode plate was applied. Rubbing treatment was performed in a direction perpendicular to the longitudinal direction of the flat electrode. This was designated as the B electrode plate.

Next, the A
The electrode plate and the B electrode plate were stacked on top of each other, and the periphery thereof was sealed with epoxy adhesive except for the injection port to create a cell. Thereafter, the following composition was injected into the cell under vacuum, and the injection port was sealed. Then 0
．． A bistable chiral smectic phase ferroelectric liquid crystal device was prepared by slow cooling at a rate of 5°C/hour.

The phase transition mode of the aforementioned composition is as follows:
It was.

In the table, ch is the cholesteric phase, SmA is the smectic A phase, and SmB is the smectic B phase.) The electric field response characteristics of this composition in the chiral smectic phase are shown in Figure 9. The thickness was 1.0 gm).

The characteristic curve shown in FIG.
This was obtained by measuring the amount of transmitted light when a rectangular pulse with a pulse width of c was applied.

According to FIG. 9, it can be seen that when a rectangular pulse with a pulse width of 1 m5 ec is applied, the first stable orientation state IE is reversely switched to the second stable orientation state with an electric field strength of 13 V/μm.

In addition, the thickness of the liquid crystal in the ferroelectric liquid crystal element described above and 1
The electric field strength during reverse switching was measured for this one thickness. The results are shown in Table 1.

Table 1 Strong M Yubisuke ν also has σ film thickness λ switching y 7 pieces! d 1 = 0.9 gm
l 1.7Vd 2 = 1.1 pm
14.3Vd 3-1.3 gm
16.9VcL4=1.5gm
19.5V A rectangular pulse of 1 m5ec at 12V was applied to all of the striped transparent flat electrodes on the B' electrode plate in the ferroelectric liquid crystal element thus created, and at the same time, a 1m5ec rectangular pulse was applied to the striped transparent flat electrodes on the A electrode plate. By applying a rectangular pulse of 1 m5 ec for 18 sec to all of the electrode groups, all pixels were cleared to a bright state. Next, a rectangular pulse of 1 m5 ec at 12 V as shown in FIG. 3 was sequentially applied to each row as a scanning selection signal to the striped flat electrode of the B electrode plate, and Ov was applied when scanning was not selected. A fourth striped transparent step electrode on the A electrode plate is synchronized with the scanning selection signal.
OV shown in the figure, 1m5ec at -2V, 1m5e at -4V
When a rectangular pulse of 1 m5 ec at -6 V and 1 m5 ec at -8 V was applied according to the gradation information, an image with good gradation could be displayed.

〔Effect of the invention〕

As described above, it is possible to provide a liquid crystal display element that realizes gradation display using a liquid crystal element having bistability, which has been considered difficult until now.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a liquid crystal element of the present invention. FIG. 2 is an explanatory diagram showing a specific embodiment of the liquid crystal element of the present invention. FIG. 3 and FIGS. 4(a) to 4(e) are explanatory diagrams showing a scanning selection signal and a gradation signal, respectively, used in the driving method of the present invention. FIGS. 5(a) to 5(e) are explanatory diagrams schematically showing gradation display states appearing in pixels. Figure 6 (a
) to (e) are explanatory diagrams showing other gradation signals used in the driving method of the present invention. FIG. 7 is a sectional view showing another embodiment of the liquid crystal element of the present invention. FIG. 8 is a plan view of a matrix electrode used in the liquid crystal element of the present invention. FIG. 9 is an explanatory diagram showing the relationship between the electric field strength and the amount of transmitted light in the ferroelectric liquid crystal used in the present invention. 10 and 11 are perspective views schematically showing a ferroelectric liquid crystal used in the present invention.

Claims (16)

[Claims] (1) In a liquid crystal element having a pair of electrodes and a ferroelectric liquid crystal disposed between the pair of electrodes, the ferroelectric liquid crystal has a varied thickness distribution, and the ferroelectric liquid crystal has a varied thickness distribution, and A liquid crystal element characterized in that it has a varying interval distribution. (2) The pair of electrodes is composed of a scanning electrode group and a signal electrode group, and the intersection of the scanning electrode group and the signal electrode group has a ferroelectric film thickness distribution that changes at each intersection. A liquid crystal element according to claim 1, comprising a liquid crystal and a pair of electrodes having a varied spacing distribution. (3) The liquid crystal element according to claim 1 or 2, wherein the change in the film thickness distribution is continuous or stepwise. (4) The liquid crystal element according to claim 1 or 2, wherein the changed interval distribution is continuous or stepwise. (5) The liquid crystal device according to claim 1, wherein the ferroelectric liquid crystal is a chiral smectic liquid crystal having at least two stable states. (6) A liquid crystal device according to claim 1, wherein the ferroelectric liquid crystal is a chiral smectic liquid crystal having bistability. (7) The liquid crystal device according to claim 1, wherein the ferroelectric liquid crystal is a chiral smectic liquid crystal with a non-helical structure. (8) A first electrode, a second electrode, a first electrode and a second electrode, and a first electrode and a second electrode.
a pixel formed by a ferroelectric liquid crystal disposed opposite to the electrode and having a varied thickness distribution;
A first voltage signal that brings substantially the entire area of the pixel into one of the first state and the second state.
A predetermined area area of a pixel is divided into a predetermined area of a pixel by applying a pulse having a waveform corresponding to the gradation information to the first electrode and the second electrode. 1. A method for driving a liquid crystal element, comprising a second step of reversing one state in the first step to the other state. (9) The driving method according to claim 8, wherein the changed film thickness distribution is continuous or stepwise. (10) The first electrode and the second electrode correspond to a first striped electrode group and a second striped electrode group, respectively, and have a matrix structure composed of these electrode groups,
In the second step, a scanning signal is sequentially applied to the first striped electrode group, and a grayscale signal is applied to the second striped electrode group in synchronization with the scanning selection signal in accordance with the grayscale information. The driving method according to claim 8, which is a driving method. (11) The driving method according to claim 10, wherein the first striped electrode is a step electrode. (12) The driving method according to claim 10, wherein the second striped electrode is a step electrode. (13) The driving method according to claim 10, wherein the first and second striped electrodes are both step electrodes. (14) The driving method according to claim 10, wherein the ferroelectric liquid crystal is a chiral smectic liquid crystal having at least two stable states. (15) The driving method according to claim 10, wherein the ferroelectric liquid crystal is a chiral smectic liquid crystal having bistability. (16) The driving method according to claim 10, wherein the ferroelectric liquid crystal is a chiral smectic liquid crystal with a non-helical structure.