JP3054906B2 - Liquid crystal element and display device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device used for a television receiver, a viewfinder of a video camera, a monitor of a computer terminal, or a liquid crystal element used for a light valve of a liquid crystal printer. .

[0002]

2. Description of the Related Art A ferroelectric liquid crystal is sandwiched between a pair of substrates having a thin gap of about 1 μm, and a helical structure is released by a regulating force at an interface. A surface-stabilized ferroelectric liquid crystal (hereinafter, referred to as "SSFLC") cell utilizing properties is known.

[0003] It is known that there are several types of alignment states of ferroelectric liquid crystals.

FIG. 1 is a schematic diagram for explaining a twist state (a) and a uniform state (b).

In the twisted state (a), the directions of the spontaneous polarization (P _s ) of the liquid crystal molecules at the interface between the upper and lower substrates are both outward (facing the substrate side) or inward (not shown). ), And the molecules inside the liquid crystal are twisted accordingly. In this twisted state, the contrast ratio between light and dark under crossed Nicols is extremely small.

On the other hand, uniform states (b) is P _s where P _s of the molecule at the interface of the upper and lower substrates are molecules of the liquid crystal inside becomes inwardly outwardly and the other substrate interface on one substrate interface also aligned in the molecule of the interface have. FIG. 1C shows a layer of these molecules.

Although the uniform state (b) in FIG. 1 is an ideal alignment state, it is difficult to stably develop such a state. A chevron structure orientation is employed.

FIG. 2 is a schematic diagram for explaining an alignment state of liquid crystal molecules having a chevron structure. In this structure, two twist states (a) and two uniform states (b)
(See Japanese Patent Application Laid-Open No. 3-252624).
No.).

However, in the chevron structure, since the layer of the liquid crystal molecules exhibiting the smectic phase is refracted as shown in FIG. 2C, the apparent tilt angle of the liquid crystal molecules is small and the transmittance is increased. Is difficult.

In FIGS. 1 and 2, reference numeral 101 denotes a C director indicating the position of liquid crystal molecules, 102 denotes a cone indicating a motion model of liquid crystal molecules, 103 denotes a bottom surface of the cone, and 104 and 105 denote upper and lower substrates. The interface is shown.

Reference numerals 106 and 107 indicate liquid crystal molecules at the interface between the upper and lower substrates. The C director 101 shows the projection of a liquid crystal layer exhibiting a smectic phase of liquid crystal molecules (hereinafter referred to as a smectic layer) onto a surface. As shown in the twisted state and chevron structure shown in FIGS. 1 and 2, liquid crystal molecules are aligned on the upper and lower substrate interfaces at a predetermined pretilt angle.

In order to increase the contrast ratio,
Attempts have been made to improve the characteristics of the liquid crystal element by employing an oblique bookshelf structure as shown in FIG. 3 without employing a chevron structure.

[0013]

However, when one pixel takes a bright state and the other pixel takes a dark state between adjacent pixels of the liquid crystal element, the alignment state of liquid crystal molecules in each pixel is not stable. There were many things.

If the electric field applied to the liquid crystal is made much larger than the threshold value in order to improve this, new technical problems such as a decrease in the speed (switching characteristics) of the liquid crystal molecules transitioning from one stable state to another stable state will occur. Will happen.

[0015]

SUMMARY OF THE INVENTION The present invention has been made in view of the above technical problems, and has as its object to provide a liquid crystal element which produces a stable alignment state of liquid crystal molecules and does not deteriorate switching characteristics. .

According to the present invention, in a liquid crystal element, a desired twist state is formed between a uniform liquid crystal molecular layer in one stable state and a liquid crystal molecular layer in another stable state, and disclination is achieved. It is characterized by generating.

That is, a first aspect of the present invention is a first liquid crystal molecular layer in a first uniform state in which molecules take one stable state, and a second liquid crystal molecular layer in a second uniform state in which molecules take another stable state. A ferroelectric liquid crystal layer having a liquid crystal molecule layer and a twisted third liquid crystal molecule layer formed therebetween is provided between a pair of substrates, and the pretilt direction of the liquid crystal molecules at the substrate interface is changed. and opposite to each other in each of the substrate, and the sign of the spontaneous polarization of the liquid crystal, the third liquid crystal component of
Direction of spontaneous polarization at the interface between the upper and lower substrates in the
Combination of spiral winding direction in laral smectic layer
(1) Spontaneous polarization is negative and spontaneous at the substrate interface
The direction of polarization is outward and the helix is wound left.
(2) The spontaneous polarization is positive and the direction of the spontaneous polarization at the substrate interface is
The maki is inward and the spiral is wound left.
(3) Spontaneous polarization is negative, and the direction of spontaneous polarization at the substrate interface is
Inward, spiral direction is right-handed.
Positive spontaneous polarization, spontaneous polarization at the substrate interface points outward
In the winding direction of the spiral is right-handed, in the liquid crystal element Ah <br/> Ru either in, that it has a disclination between <br/> of the first and second liquid crystal molecular layers A second aspect of the invention is a display device including the liquid crystal element, a driving circuit for driving the element, and a control circuit for controlling the driving circuit.

According to the present invention, in a liquid crystal element having an oblique bookshelf structure in which the directions of the pretilt angles of liquid crystal molecules are different at the interface between the upper and lower substrates, the liquid crystal molecules are aligned in one stable state (for example, a bright state). If the disclination is interposed between the portion and the portion oriented to the other stable state (for example, dark state), the respective stable states are maintained well, so that the contrast ratio between light and dark is high. Thus, the liquid crystal element is less likely to cause crosstalk in the pixel.

According to the knowledge of the present inventor, it is generally considered that in the field of liquid crystal, disclination is caused by an alignment defect, and a great effort is desirably made to create an alignment state in which disclination does not occur. Was being paid.

On the other hand, while studying the stability of the orientation state of ferroelectric liquid crystal represented by the chiral smectic C phase, the present inventor has found that a certain type of liquid crystal element has excellent stability. I found that. Therefore, liquid crystal materials,
When stability was observed using many types of liquid crystal elements manufactured by appropriately selecting an alignment treatment method and the like, when two adjacent portions (regions) have different stable states from each other, a difference between the two regions was observed. It has been found that a liquid crystal element in which the alignment state of the liquid crystal molecules does not change continuously is a relatively stable element.

Further, it has been found that the above stability is remarkably observed in the case of the oblique bookshelf structure. Therefore,
When disclinations were formed between adjacent regions having different stable states, it was found that the stability was further increased.

As a result of further study, in the liquid crystal element having the oblique bookshelf structure, the disclination changes from one stable state (one uniform state) to the other stable state (the other uniform state). It has been found that, since it works so as to prevent the continuous transition to the region, the regions having these two stable states hardly interfere with each other, and the stability is improved.

On the other hand, in a conventional device, only a twisted state that continuously connects the two stable states exists between two regions in different stable states, and an alignment state in which disclination cannot exist. Had become.

FIG. 3 is a schematic diagram for explaining an alignment state of liquid crystal molecules of a liquid crystal element according to one embodiment of the present invention.

In FIG. 3, reference numerals 601 and 602 denote disclinations in which the vectors of the spontaneous polarization of the surrounding liquid crystal molecules are maintained at substantially the same angle between adjacent ones. In this case, the adjacent uniform area 603,
A disclination exists in a line between the area 605 and the twisted area 604 (a black portion in FIG. 3, which actually exists in a line perpendicular to the paper surface). FIG. 3 shows that the left area 603 has a uniform UP,
The central area 604 represents the twist, and the right area 605 represents the uniform DOWN. Since the occurrence of disclination involves a potential barrier, in such a situation, the relaxation from the uniform state to the twisted state is suppressed, and the uniform state is stabilized. Here, 606
Denotes a liquid crystal molecule, and 607 denotes a smectic layer.

In the present invention, it is desirable that the smectic layer has an oblique bookshelf structure as shown in FIG. 3 in order to provide the above-mentioned disclination line and use a liquid crystal material having a large cone angle. To do so, the pretilts 301 and 302 of the upper and lower substrates are reversed.

By employing such a structure of the smectic layer, the apparent tilt angle increases, the transmittance improves, and the contrast increases.

The disclination used in the present invention can be formed by a combination of the following liquid crystal material and alignment treatment.

(1) The direction of the pretilt at the interface between the upper and lower substrates is opposite, the sign of the spontaneous polarization of the liquid crystal is negative, and the direction of the spontaneous polarization at the interface between the upper and lower substrates in the twisted state is outward (toward the substrate). Yes, the spiral direction of the spiral in the chiral smectic layer is left-handed. (2) The pretilt direction of the upper and lower substrate interfaces is opposite, the sign of the spontaneous polarization of the liquid crystal is positive, and the upper and lower substrate interfaces in the twisted state The direction of spontaneous polarization is inward (inside of the liquid crystal), and the spiral direction of the spiral in the chiral smectic layer is left-handed. ( 3) Pretilt at the interface between the upper and lower substrates
Are opposite, the sign of the spontaneous polarization of the liquid crystal is negative,
Direction of spontaneous polarization at the interface between upper and lower substrates in twisted state
Is inward and the spiral in the chiral smectic layer
(4) of the upper and lower substrate interfaces
The direction of the pretilt is reversed and the sign of the spontaneous polarization of the liquid crystal
Is positive, and the self-
Polarization direction is outward, chiral smectic
The spiral direction in the layer is right-handed .

The above (1) to (4) used in the present invention
Are shown in Table 1 below.

[0031]

[Table 1]

When the C directors of the upper and lower substrates are separated by nearly 180 ° and the elastic energy is no longer the dominant factor, the spiral winding determines the twist direction in the twisted state as follows.

For example, consider the case where the spontaneous polarization is negative and outward at the interface. If the spiral is wound clockwise, twist clockwise from bottom to top in the layer normal direction as shown in FIG. Therefore, even when viewed in the layer, a twist in a clockwise direction from the lower substrate 105 to the upper substrate 104 is also shown. Conversely, the reverse is true if the spiral is wound left.

FIGS. 5A to 5D are schematic diagrams for explaining the state of liquid crystal molecules in four twisted states.
Indicate the case where the sign of the spontaneous polarization is negative. (A) and (b) show cases where the direction of spontaneous polarization at the substrate interface is outward even in the twisted state, and (c) and (d) show cases where the direction is inward. (A) and (c) show the case where the spiral is wound right, and (b) and (d) show the case where the spiral is wound left.

When the interfacial molecules move on the cone and rotate inward without changing the direction of the pretilt, the continuous connection to two adjacent uniform regions is as follows: (a) Right-handed case And the discontinuity is (b)
This is the case of left-handed winding. Therefore, it can be seen that the left-handed liquid crystal can stabilize the uniform state of the adjacent region in this arrangement. On the other hand, when the spontaneous polarization is inward, (c) is a liquid crystal having a right helix and (d) is a liquid crystal having a left helix. In this arrangement, it is (c) a liquid crystal having a right helix that can stabilize the uniform state. Although the case where the spontaneous polarization is negative has been described above, the same conclusion can be obtained when the spontaneous polarization is positive only by reversing the direction.

FIG. 6 is a schematic diagram showing four twisted states when the sign of the spontaneous polarization is positive.

As can be seen from FIG. 5, the directions (arrows) of the spontaneous polarization of the liquid crystal molecules at the same position are different.

6 (e) and 6 (f) show the case where the direction of the spontaneous polarization of the liquid crystal molecules at the interface between the upper and lower substrates is outward, and FIGS. 6 (g) and 6 (h) show the case where the spontaneous polarization is inward. (E) and (g) are right-handed, and (f) and (h) are left-handed.

Among them, those which exist between two adjacent regions in different uniform states and which can stabilize the uniform state are (e) and (h).

That is, in FIGS. 5 and 6, (b),
The liquid crystal material and the alignment treatment method are selected so that the twisted states (c), (e) and (h) are obtained, and the upper and lower substrates are arranged so that the pretilt directions are opposite to each other. By forming the element, disclination can be interposed between adjacent regions having two different uniform states.

Next, an explanation will be given, by way of an example, of why the above-described twisted state forms disclination and stabilizes the uniform state.

FIGS. 7 and 8 are schematic diagrams for explaining a comparative example for comparison with the present invention and an alignment state of liquid crystal molecules according to one embodiment of the present invention.

When the direction of the spontaneous polarization of the liquid crystal molecules at the substrate interface is determined to be outward, for example, the twist state is more stable than the uniform state. This is because the elastic energy due to intermolecular strain is higher in the twisted state, but is usually higher than the interface regulating force. In this situation, even if an electric field is temporarily applied to form a uniform state, when the electric field is cut off, the state is gradually relaxed to a twisted state. FIG. 7 shows this state. The two different uniform states of (a) and (c) show that the interface molecules 403 at the upper substrate interface 401 and the interface molecules 404 at the lower substrate interface 402 are arrows 405 and 406.
In the direction of (b) and shifts to the twisted state of (b). As the interfacial molecules rotate, the molecules inside rotate accordingly, resulting in a continuous transition towards the twisted state. That is, in the region 407 in the uniform state (a) side on the interface side of the upper substrate, the molecules 403 in the uniform state are shifted in the direction 405 to the other stable state, and the molecules 403 moving from the molecules on the upper substrate side to the molecules on the lower substrate side. The rotation directions 410 are opposite to each other, and the molecules in the uniform state (a) are in the same molecular position (403 ′) as the molecules in the twisted state (b) according to the rotation.
Get closer to. This is the same in the region 408. In order for the uniform state to exist stably, the opposite polarization direction must be maintained against the force that determines the direction of spontaneous polarization at the substrate interface. However,
Because molecules can rotate without any potential barrier,
This reverse interface polarization cannot be maintained.

Therefore, in the present invention, as shown in FIG. 8B, by giving a twist state in the opposite direction to that of FIG.
Even if the liquid crystal molecules are rotated in the directions of 5, 506, the liquid crystal molecules that rotate in accordance with the rotation direction do not continuously shift to (b).

That is, in the region 507, the liquid crystal molecules 4
03 is in the same direction as the direction 505 of transition to the other stable state, and the rotation direction 510 of the liquid crystal molecules in the direction from the molecules on the upper substrate side to the molecules on the lower substrate side is the same direction. It is difficult to shift to a stable state.

For simplicity, as seen in the region 407 of FIG. 7, when the molecule 403 moves to the same position (403 ′) as the molecule 413, it moves on the circumference of the cone as indicated by an arrow 405. . On the other hand, in the region 507 in FIG. 8, the moving direction of the molecule 403 is indicated by the arrow 505, so that the moving distance on the circumference of the cone in FIG. Larger than compared. That is, this means that FIG. 8 is less likely to shift to the twisted state than FIG.

By forming the twisted state as shown in FIG. 8, disclinations can be formed as shown in FIG. That is, in FIG. 8, disclination is formed between the uniform state and the twist state in the regions 507 and 508.

FIG. 9 shows another twisted state (b) different from that shown in FIG. 8 formed between the uniform states (a) and (c). In this case, between the twist state (b) and the uniform state (c) in the area 707, and in the area 70
8 twist state (b) and uniform state (a)
, A disclination line is formed.

FIGS. 10 and 11 are diagrams showing the twisted state and the area where the disclination is formed when the sign of the spontaneous polarization is positive and is different from those in FIGS.

As shown in FIG. 9 to FIG.
7 and 708, the directions 706 and 705 in which the molecules in the uniform state shift to the other stable state and the twisting directions 710 and 711 in the twist state are the same, and the molecules in the uniform state are unlikely to shift to the twist state. It has become.

When the liquid crystal element used in the present invention is used as a display device, the twist state 604 and the disclinations 601 and 602 in FIG. 3 are shielded from light, and only the adjacent uniform state 603 and 605 regions are independent. The pixel may be configured as a pixel, or the three states 603, 604, and 605 may be formed in one pixel.
The former case is suitable for monochrome binary display forming a mono domain, and the latter is suitable for gradation display in which a plurality of domains are formed and the transmittance is controlled by changing the size of the domains. .

In the present invention, it has been described that it is preferable to form a smectic layer having a bookshelf structure. However, in order to obtain this structure, it is generally preferable to set the pretilt angle as follows.

When the pretilt angle is in the same direction, if a liquid crystal material having a large cone angle is used, a chevron structure in the direction opposite to that in FIG. Even if the direction of the pretilt is reverse, if the value is too small, a chevron structure will also appear. That is, as shown in FIG. 12, if the pretilt angle α has a relationship of α <Θ−δ with respect to the cone angle Θ and the inclination angle δ of the layer, a chevron structure is allowed. There must be.

As described below, if the pretilt angle is too large, the entire surface is in a twist state, and the disclination line cannot be formed.

The pretilt angle is the cone angle Θ and the layer inclination angle δ
On the other hand, it is a condition for realizing the layer structure and the orientation state of the present invention to be set in the range of Θ−δ <α <δ. In practice, if Θ is 15 ° or more, the transmittance is sufficient, and in many liquid crystals, δ
Is 0.7 to 0.9 times Θ, so Θ
In the case of = 15 °, the rubbing conditions are set so that 2 ° <α <14 °, preferably 5 ° <α <11 °.

Since the above conditions are suitable, the case where a special liquid crystal material or alignment film is used may be outside the above range.

As a method for manufacturing the liquid crystal element of the present invention, conventionally known steps are employed. The outline will be described.

First, upper and lower substrates are prepared, and electrode formation and alignment processing are performed. Then, when the element is completed, the in-plane position of the upper and lower substrates is determined in consideration of the alignment control force so that the pretilt is reversed at the upper and lower substrate interfaces, and a space of about 1 to 3 μm is provided between the upper and lower portions except for the portion serving as an injection port. The ends of the upper and lower substrates are sealed (creation of empty cells). Next, a liquid crystal material is applied to the injection port, and the liquid crystal material is injected into the empty cells. afterwards,
The phase is changed to a smectic C phase by gradually cooling. At this time, if the smectic layer bends at even-numbered locations as shown in FIG. 13, an AC electric field is applied for a predetermined period or an opportunistic strain is applied to the cell to correct the oblique bookshelf structure.

Here, an experiment for checking whether the direction of spontaneous polarization of molecules at the interface between the upper and lower substrates in a twisted state in a liquid crystal element is outward or inward will be described.

This utilizes the fact that there is a difference in the wavelength distribution of transmitted light depending on whether the twisting direction of the molecule in the twisted state is clockwise or counterclockwise as shown in FIGS. is there.

FIG. 14 shows a region in the twisted state of the liquid crystal element when the polarizer is aligned with the rubbing direction using a polarizing microscope and the analyzer is arranged at 83 ° and 97 ° with respect to the polarizer. 5 is a graph showing the transmitted light wavelength characteristics of FIG.
In this liquid crystal element, the sign of the spontaneous polarization is negative, and as described later, the molecule at the interface between the upper and lower substrates has an outward spontaneous polarization in a twisted state.

On the other hand, FIG. 15 shows the transmitted light wavelength characteristic of a liquid crystal element having an inward spontaneous polarization, which is the characteristic when the analyzer is arranged at 75 ° and 105 ° with respect to the polarizer.

Looking at the characteristics at 90 ° or more, ie, 97 ° in FIG. 14, and the characteristics at 90 ° or more, ie, 105 °, in FIG. 15, it can be seen from FIG. On the other hand, FIG. 15 shows substantially the same (macroscopic) transmittance in almost the entire wavelength region.
That is, the former (FIG. 14) exhibits blue, and the latter (FIG. 15) exhibits white.

On the other hand, when the angle is smaller than 90 °, the former exhibits white and the latter exhibits blue. In other words, cross Nicol (90
°), the wavelength characteristic of the transmitted light at a position shifted from the twisted direction reflects the twist direction of the twist.
225).

Therefore, it can be seen that the direction of the twist is opposite between FIG. 14 and FIG.

Next, in order to specify the direction of the twist, as shown in FIG. 16, the rubbing directions RD are not parallel to the upper and lower substrates, but the upper and lower substrates are shifted by 10 ° from each other, and the ferroelectric A racemic liquid crystal exhibiting no properties was injected, and two kinds of reference samples of a liquid crystal cell were prepared.

Since the racemic body does not have spontaneous polarization, the molecules are oriented in the rubbing direction at the interface between the substrates. Therefore, the twist in the rubbing direction as shown in FIGS. Become. When the wavelength characteristics of the reference sample thus obtained were measured under the arrangement of the polarizer and the analyzer as described above, the characteristics in FIG. 14 were roughly the same as those in the left-handed reference sample, and those in FIG. Matched.

From this, it can be seen that, in a liquid crystal having a negative sign of spontaneous polarization, the liquid crystal having the characteristic shown in FIG. 14 is outward at the interface between the upper and lower substrates, and the liquid crystal having the characteristic shown in FIG. 15 is inward.

When the sign of the spontaneous polarization is positive, the direction of the spontaneous polarization of the molecules at the interface between the upper and lower substrates is reversed.

According to the present invention, as described above, a new combination of a liquid crystal material and an alignment treatment
When the regions in two uniform states are in different stable states, the above-mentioned twist state is created during the period, thereby forming disclination.

[0071]

【Example】

(Example 1) Indium tin oxide (I)
TO) and a transparent electrode stripe pattern of width 22
It was formed to have a thickness of 0 μm, a space of 10 μm, and a thickness of 700 °.

On a substrate on which a transparent electrode is formed, a thickness of 200
Å with polyimide (LQ1802; manufactured by Hitachi Chemical Co., Ltd.)
Was coated.

Next, a rubbing treatment was performed using a rubbing roller around which a nylon cloth was wound. The conditions of the rubbing treatment were a roller pushing amount of 0.3 mm and a rotation speed of 1000 RPM.

The above-mentioned substrates were opposed to each other in such a manner that the rubbing directions of the two substrates were opposite to each other and the crossing angle of the rubbing directions was not more than 3 °. The ends of the upper and lower substrates are sealed, and the following ferroelectric liquid crystal material (sample A)
Was injected.

[0075]

Embedded image

In this liquid crystal material, the spiral winding was left-handed and the sign of spontaneous polarization was negative.

After injecting the liquid crystal material (sample A) in an isotropic phase, the temperature was lowered to cause a phase transition to a smectic C phase, and an AC voltage was applied to produce a liquid crystal element.

Next, it was examined whether the twisted state of the manufactured liquid crystal element was outward or inward at the interface between the upper and lower substrates.

The results show spectral characteristics as shown in FIG. 14, in which the direction of spontaneous polarization of molecules at the interface between the upper and lower substrates is outward.

When a predetermined voltage is applied to the transparent electrode to make two adjacent pixels bright and dark, a twist state and a disclination line occur between them.

Example 2 Next, sample B represented by the following formula was used as a liquid crystal material.

[0082]

Embedded image

A liquid crystal element was produced using nylon having a thickness of 250 ° as an alignment film. Other manufacturing conditions are the same as those in the first embodiment.

Example 3 Sample C represented by the following formula as a liquid crystal material:

[0085]

Embedded image

A liquid crystal element was manufactured using nylon having a thickness of 200 ° as an alignment film. Other manufacturing conditions are the same as those in the first embodiment.

Example 4 Sample D represented by the following formula as a liquid crystal material:

[0088]

Embedded image

A liquid crystal element was manufactured using polyimide having a thickness of 250 ° as an alignment film. Other manufacturing conditions are the same as those in the first embodiment.

Comparative Example 1 A liquid crystal element was manufactured using the liquid crystal material of Sample A and nylon having a thickness of 200 mm as an alignment film. Other manufacturing conditions are the same as those in the first embodiment.

(Comparative Example 2) A liquid crystal element was manufactured using the liquid crystal material of Sample B and polyimide having a thickness of 250 ° as an alignment film. Other manufacturing conditions are the same as those in the first embodiment.

Comparative Example 3 A liquid crystal element was manufactured using the liquid crystal material of Sample C and polyimide having a thickness of 200 ° as an alignment film. Other manufacturing conditions are the same as those in the first embodiment.

Comparative Example 4 A liquid crystal element was manufactured using the liquid crystal material of Sample D and nylon having a thickness of 250 ° as an alignment film. Other manufacturing conditions are the same as those in the first embodiment.

Examples 1-4 and Comparative Examples 1-4 produced as described above
+10 V and -10 with respect to the reference voltage
V binary DC voltage is applied to each different pixel,
Two adjacent pixels are in a uniform state in which light and darkness are different from each other.

Thereafter, the application of the voltage was stopped and the device was left in a memory state for 148 hours.

Table 2 shows the characteristics of the liquid crystal device thereafter.

[0097]

[Table 2]

As shown in Table 2, the devices of Examples 1 to 4 also
Immediately after the DC voltage application was cut off, the pixels of Comparative Examples 1 to 4 each took a bright or dark state, a uniform state in the pixel, and a twisted state between the two bright and dark pixels. As the time elapses, in the devices of Comparative Examples 1 to 4, the uniform state in the pixel gradually collapsed and gradually shifted to the twisted state.

On the other hand, the devices of Examples 1 to 4
A twist state and a disclination have occurred between the two dark pixels, and a favorable oblique bookshelf structure has been exhibited in a memory state even when left without an electric field for a long time.

After that, a DC voltage was applied so as to change the dark pixel to the bright state and the bright pixel to the dark state.
The device of No. 4 was quickly switched.

(Comparative Example 5) When the empty cell (the structure before liquid crystal injection) of Example 1 was manufactured, the rubbing direction was the same for both the upper and lower substrates, and otherwise the liquid crystal element was manufactured in the same manner as in Example 1. Produced. When the element thus obtained was left in the memory state for a long period of time, the uniform state collapsed and the element was twisted.

(Comparative Example 6) When the empty cell of Example 1 was manufactured, the rubbing directions were crossed by 5 ° between the upper and lower substrates so that they were opposite to each other. Thereafter, a liquid crystal element was manufactured in the same manner as in Example 1. The element thus obtained also became twisted due to collapse of the uniform state after being left for a long time.

Embodiment 5 In manufacturing the liquid crystal device of Embodiment 1, a liquid crystal capable of forming fine irregularities on an ITO film and applying a signal for gradation display to the ITO electrode to perform gradation display. An element was formed.

The gradation display method is described in US Pat. No. 4,796,980 invented by Kaneko et al.

The other manufacturing steps are the same as in the first embodiment.

FIG. 17 is a schematic diagram for explaining the present embodiment. The liquid crystal element FLCDP is provided with two drive circuits connected to the ITO electrodes on the upper and lower substrates, and generates a gradation signal. These circuits are controlled by a control circuit. The control circuit is controlled by an external host computer.

Reference numeral 900 denotes a gray scale display state in a pixel. Reference numeral 901 denotes a dark domain in one stable state;
Reference numeral 3 denotes a bright domain in the other stable state, reference numeral 902 denotes the twist state described above, and the twist states 902 and 2
A disclination line is formed between the two stable states 901 and 903 to stably maintain the halftone display state.

[0108]

As described above, in the liquid crystal device of the present invention, the display state of each pixel is stable, and the switching to the other display state is prompt, and high-quality image display is realized. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a twisted state and a uniform state of a ferroelectric liquid crystal.

FIG. 2 is a schematic diagram of a chevron structure of a ferroelectric liquid crystal.

FIG. 3 is a schematic diagram of an alignment state of a liquid crystal element according to an embodiment of the present invention.

FIG. 4 is a schematic diagram showing a helix of liquid crystal molecules.

FIG. 5 is a schematic diagram of a twisted state of a liquid crystal in which the sign of spontaneous polarization is negative.

FIG. 6 is a schematic diagram of a twisted state of a liquid crystal in which the sign of spontaneous polarization is positive.

FIG. 7 is a schematic diagram illustrating an alignment state of a liquid crystal element according to a comparative example.

FIG. 8 is a schematic diagram illustrating an example of an alignment state of the liquid crystal element of the present invention.

FIG. 9 is a schematic view showing another example of the alignment state of the liquid crystal element of the present invention.

FIG. 10 is a schematic view showing another example of the alignment state of the liquid crystal element of the present invention.

FIG. 11 is a schematic view showing another example of the alignment state of the liquid crystal element of the present invention.

FIG. 12 is a schematic diagram for explaining a relationship between a pretilt angle of liquid crystal molecules and a tilt angle of a smectic layer.

FIG. 13 is a schematic diagram showing an alignment state of a liquid crystal in which a smectic layer is bent at two places.

FIG. 14 is a graph showing spectral characteristics of transmitted light of a liquid crystal element.

FIG. 15 is a graph showing spectral characteristics of transmitted light of a liquid crystal element.

FIG. 16 is a schematic diagram of a configuration of a reference sample used when measuring the twist of molecules in a twisted state.

FIG. 17 is a schematic view of an example of a liquid crystal element of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/1337 G02F 1/141 G02F 1/13 101 G09F 9/30

Claims (4)

(57) [Claims] 1. A first liquid crystal molecular layer in a first uniform state in which molecules take one stable state, a second liquid crystal molecular layer in a second uniform state in which molecules take another stable state, and And a third liquid crystal molecule layer in a twisted state formed between the two substrates. A ferroelectric liquid crystal layer having a twisted third liquid crystal layer is provided between the pair of substrates, and the pretilt directions of the liquid crystal molecules at the substrate interface are opposite to each other in each substrate. Direction and spontaneous liquid crystal
Signs of polarization and upper and lower substrates in the third liquid crystal molecular layer
Direction of spontaneous polarization at the interface and chiral smectic layer
Winding direction, the combination of the helix in the (1) in the spontaneous polarization is negative the direction of spontaneous polarization of the substrate interface
Outward, spiral direction is left-handed. (2) Spontaneous polarization is positive, and the direction of spontaneous polarization at the substrate interface is
Inward, spiral direction is left-handed. (3) Spontaneous polarization is negative, and the direction of spontaneous polarization at the substrate interface is
In inward, the winding direction of the spiral is right-handed, (4) in the spontaneous polarization is positive, the direction of spontaneous polarization of the substrate interface
A liquid crystal element, which is outward and has a spiral winding direction of right-handed , characterized in that the liquid crystal element has disclination between the first and second liquid crystal molecular layers . 2. The liquid crystal device according to claim 1, wherein the disclination is between pixels. 3. The liquid crystal device according to claim 1, wherein the disclination is in the pixel. 4. A display device comprising: the liquid crystal element according to claim 1; a driving circuit for driving the element; and a control circuit for controlling the driving circuit.