JP2000212565A - Display element and displaying - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a display element using a low-molecular weight liquid crystal, capable of reversibly transferring by only electric stimulation between different two states having memory property. SOLUTION: This displaying element has a hollow cell oppositely arranging transparent electrodes 53 and 54 laminating liquid crystal orienting films 55 and 56 subjected to rubbing treatment onto the surface and having substrates 51 and 52 supporting the transparent electrode, a mixture 59 packed in the hollow cell and containing low-molecular liquid crystal 60 and minute solid 61 smaller than the gap 51 between the above electrodes and a voltage applying means 58 applying voltage between the above electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device and a display method using a mixture of a liquid crystal and a fine solid.

[0002]

2. Description of the Related Art With the development of information equipment, social needs for a low power consumption thin display element are rapidly increasing. Among them, a liquid crystal display element is being actively researched and developed as one form of a display element that can meet such needs. In particular, display devices using low-molecular liquid crystals have been commercialized and widely spread in society. However, the low-molecular liquid crystal easily controls the molecular orientation electrically, but does not have a memory property (the property of maintaining the molecular orientation when the voltage is applied even after the voltage application to the liquid crystal is released). As a result, in order to continuously display images, power supply to the liquid crystal cannot be stopped, and it is difficult to decisively suppress power consumption.

In order to solve this problem, a large number of new types of liquid crystal display devices using low molecular liquid crystals and capable of exhibiting memory properties have been reported.

For example, there has been reported a display device using a liquid crystal composition containing low-molecular liquid crystal and flat particles having an affinity for the low-molecular liquid crystal (JP-A-7-31898).
No. 2). When a voltage of several tens of volts is applied to this liquid crystal composition, a state of transmittance different from that before the voltage is applied is formed. This state is maintained even after the voltage application is released. That is, the liquid crystal composition using the low-molecular liquid crystal has succeeded in expressing the memory property.

[0005]

However, the prior art described above has a problem that it is not possible to reversibly transition between states having different transmittances only by electrical stimulation. That is, in order to release the memory state formed by applying a voltage, it is necessary to apply a stimulus other than an electric field to the liquid crystal composition. Two stimuli are disclosed as stimuli other than the electric field. One is a method of heating a liquid crystal composition. By converting the liquid crystal composition into an isotropic liquid by heating, the liquid crystal structure formed by applying a voltage is destroyed. Another method is to apply a mechanical stimulus to the liquid crystal composition. By applying shearing force such as shearing, vibration, or impact, the liquid crystal structure formed by applying a voltage is destroyed.

[0006] The present invention has been made in view of such problems of the prior art, and is different from the prior art having memory characteristics.
It is an object of the present invention to provide a display element and a display method using a low-molecular liquid crystal capable of reversibly switching between states only by electric stimulation.

[0007]

That is, according to the present invention, a transparent electrode having a liquid crystal alignment film subjected to a rubbing treatment laminated on a surface thereof is arranged to face each other, and at least one of the substrates supporting the transparent electrode is transparent. A hollow cell, a mixture filled with the low-molecular liquid crystal and a fine solid having a thickness smaller than the gap between the electrodes, and a voltage applying means for applying a voltage between the electrodes; Is a display element characterized by the following.

[0008] The present invention also provides a low-molecular-weight hollow cell in which a transparent electrode having a rubbed liquid crystal alignment film laminated on the surface is opposed to each other, and at least one of the substrates supporting the transparent electrode is transparent. A mixture containing a liquid crystal and a fine solid whose thickness is smaller than the gap between the electrodes is filled, the fine solid is moved by applying a voltage between the electrodes by applying voltage, and the fine solid is released by releasing the voltage. The display method is characterized in that the movement is stopped and the light transmittance is changed to perform display.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A display element according to the present invention has a hollow structure in which a transparent electrode having a rubbed liquid crystal alignment film laminated on the surface thereof is opposed to each other, and at least one of the substrates supporting the transparent electrode is transparent. A cell, a mixture filled with the low-molecular liquid crystal and a fine solid having a thickness smaller than the gap between the electrodes, which is filled in the hollow cell, and voltage applying means for applying a voltage between the electrodes. Features.

The rubbing direction applied to one of the opposed liquid crystal alignment films is different from the rubbing direction applied to the other liquid crystal alignment film by 180 °. In the present invention, the rubbing treatment may be performed only on the transparent electrode without using the liquid crystal alignment film.

It is preferable that the fine solid does not dissolve in the liquid crystal in a temperature range where the liquid crystal exhibits a liquid crystal phase.

Next, the fine solid according to the present invention will be described. The minute solid according to the present invention is characterized by being composed of molecules having liquid crystal residues. Further, the molecule having the liquid crystal residue may have an amide bond. The liquid crystal residue is not particularly limited, but includes a nematic liquid crystal residue. An example of a molecule having a liquid crystal residue according to the present invention is shown in the following formula (1).

[0013]

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Further, the fine solid according to the present invention is preferably prepared by recrystallizing a molecule having a liquid crystal residue.
The method of recrystallization is not particularly limited, but includes, for example, the following four methods. (Method 1) A mixture of a powder composed of molecules having liquid crystal residues and a liquid crystal is heated until the powder melts, and then cooled to precipitate crystals composed of molecules having liquid crystal residues. (Method 2) A mixture of a powder composed of a molecule having a liquid crystal residue and a liquid crystal is dissolved in a volatile good solvent (for example, chloroform) common to both substances, and then the solvent is volatilized to form a molecule having a liquid crystal residue. A crystal consisting of

(Method 3) After heating until the powder composed of molecules having liquid crystal residues is melted, it is cooled to precipitate crystals composed of molecules having liquid crystal residues. (Method 4) A powder composed of a molecule having a liquid crystal residue is dissolved by dissolving a powder composed of a molecule having a liquid crystal residue (for example, chloroform) in a good volatile solvent of the powder, and then evaporating the solvent. .

The fine solid according to the present invention may be a fine structure having liquid crystal residues bonded to the surface.
That is, the microstructure is not composed of the molecule having the liquid crystal residue, and is characterized in that the molecule having the liquid crystal residue is bonded to the surface thereof.

The material of the microstructure is not particularly limited. For example, latex beads, metal oxide fine particles and the like can be mentioned. The shape is not particularly limited.
It may be spherical, needle-like, or flat. However, it is desirable that the microstructures have the same shape and size in the cell.

The mode of bonding of the molecule having a liquid crystal residue to the microstructure is not particularly limited. It may be a covalent bond (for example, an amide bond) or a non-covalent bond (for example, an electrostatic bond). Preferably, the liquid crystal residue is a nematic liquid crystal residue.

On the other hand, the type and structure of the low-molecular liquid crystal according to the present invention are not particularly limited. However, it is desirable that the liquid crystal be capable of exhibiting at least a nematic phase within a temperature range in which the display element is expected to operate. Therefore, a mixed liquid crystal in which two or more types of liquid crystals are mixed may be used.

The mixing ratio between the liquid crystal and the fine solid in the mixture according to the present invention is not particularly limited. The content of the fine solids in the mixture is preferably 1 to 90% by weight, more preferably 2 to 80% by weight.

Next, the display principle of the display element will be described. The principle of the display principle utilizes a phenomenon that, when a voltage is applied between electrodes sandwiching a mixture of liquid crystal and fine solid, the fine solid moves in an in-plane direction parallel to the electrode surface. This phenomenon will be described with reference to FIGS. FIG. 1 is a schematic view showing an example of a display element according to the present invention. FIG.
And FIG. 3 is a diagram showing a driving waveform of the display element.

In FIG. 1, 11 and 12 are electrodes,
Reference numerals 13 and 14 denote substrates for supporting the electrodes 11 and 12, reference numeral 15 denotes a fine solid, and reference numeral 16 denotes a voltage applying means for applying a voltage between the electrodes 11 and 12. The liquid crystal sandwiched between the substrates and between the electrodes is omitted. It is also assumed that the direction of the rubbing applied to the electrode 11 is the + direction of the x-axis shown in FIG. 1 and the direction of the rubbing applied to the electrode 12 is the-direction of the x-axis.

A rectangular wave (period = 1 / t) as shown in FIG. 2 is applied between the electrodes 11 and 12 in FIG.
₁ , when a rectangular wave with a wave height of V ₁ ) is applied, a minute solid 15
Moves in the + direction of the x-axis. When the application of the rectangular wave is released, the movement of the minute solid 15 stops and does not move from the stop position. That is, it has a memory property.

On the other hand, when a rectangular wave as shown in FIG. 3 (a rectangular wave having a polarity opposite to that of the rectangular wave shown in FIG. 2) is applied between the electrodes 11 and 12 by the electrode applying means 16, a minute solid Reference numeral 15 moves in the negative direction of the x-axis. When the application of the rectangular wave is released, the movement of the minute solid 15 stops and does not move from the stop position.

That is, in the display element according to the present invention, when a voltage is applied between the electrodes, the fine solid moves in a direction parallel to the rubbing direction, and the direction of the movement changes the polarity of the voltage applied between the electrodes. Reverse. When the application of the voltage is released, the movement of the minute solid 15 stops and does not move from the stop position. That is, it has a memory property.

Next, the display principle of the display device according to the present invention will be described with reference to FIG. In FIG. 4, 41 and 42 are electrodes, and 43 and 44 are electrodes 41 and 4 respectively.
Reference numeral 2 denotes a substrate that supports 2, and 45 denotes a group of fine solids. The liquid crystal sandwiched between the electrode and the substrate is omitted. The direction of the rubbing applied to the electrode 41 is the plus direction of the x-axis shown in the figure, and the direction of the rubbing applied to the electrode 42 is the minus direction of the x-axis.

In the display device according to the present invention, it is assumed that the fine solid is distributed almost uniformly between the electrodes 21 and 22 as shown in FIG. In this state, y in FIG.
When the electrode surface is observed from the axial direction, the entire surface appears cloudy.
If no voltage is applied to the element in this state, that state is maintained. That is, it has a memory property.

The display element in the state of FIG.
By applying a rectangular wave, the minute solid is moved in the + direction of the x-axis in the figure. Then, as shown in FIG. 4B, the minute solids constituting the minute solid group 45 move in the + direction of the x-axis. At this time, the fine solid that has reached the edge of the electrode stays there. Further application of the square wave
As shown in FIG. 4C, the fine solid is brought to one of the electrodes. At this time, when the display element is observed from the y-axis direction, it looks more transparent than when the element in the state of FIG. 2A is observed. Even if the application of the rectangular wave is canceled in the state of (c) in FIG. 4, the minute solid does not move from that position, and the transparent state is maintained. That is, it has a memory property.

Next, a rectangular wave is applied to the display element in the state of (c) in FIG. 4 so as to move the fine solid in the negative direction of the x-axis in the figure. Specifically, it is a rectangular wave having a polarity opposite to that of the rectangular wave used to change the minute solid from the state (a) to the state (c) in FIG. When such a rectangular wave is applied, as shown in FIG. 4D, the fine solids are again distributed almost uniformly between the electrodes. This state has a memory property.

As described above, the display element according to the present invention is characterized in that display is performed by changing the distribution state of the fine solid held between the electrodes.

[0031]

The details of the present invention will be described below with reference to production examples and examples.

Example 1 In this example, a display element using a mixture of a liquid crystal and a fine solid composed of molecules represented by the following formula (p) will be described.

[0033]

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Hereinafter, a method for synthesizing the molecule represented by the formula (p),
A method for preparing a mixture of a liquid crystal and a minute solid composed of molecules represented by the formula (p), and driving of a display element according to this embodiment will be described in detail.

<Method of synthesizing molecule represented by formula (p)> First, a compound represented by the following formula (q): lg (26.3m
mol), (1R, 2R)-(-)-diaminocyclohexane 1.5 g (13 mmol), HOBt (1-hydroxybenzotriazole) 4.3 g (31.8 mm)
ol), DCC (dicyclohexylcarbodiimide)
6.5 g (31.5 mmol) is dissolved in DMF (dimethylformamide) 60 ml and stirred overnight.

[0036]

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After filtering out the crystals precipitated in the reaction solution,
The crystals were dissolved in 500 ml of chloroform, and 1M H
Cl 200 ml, saturated NaHCO ₃ aqueous solution 200 ml,
After washing with 1200 ml of saturated NaC, column purification and drying treatment are performed to obtain the substance represented by the formula (p) in 1.
5 g were obtained.

<Method of adjusting mixture of fine solid and liquid crystal>
After dissolving 500 mg of the substance obtained by the above method and 500 mg of nematic liquid crystal (trade name: BL6, manufactured by Merck) in chloroform, chloroform was gradually evaporated at room temperature. Then, a fine solid composed of the molecule represented by the formula (p) that is not compatible with the liquid crystal is deposited in the liquid crystal. Ultrasonic treatment was performed on the mixture comprising the liquid crystal and the fine solid to uniformly disperse the fine solid in the liquid crystal. The mixture composed of the liquid crystal and the fine solid was used as a mixture for a display element in this example.

<Driving of Display Element> FIG. 5 is a schematic view of a display element according to this embodiment. In FIG. 5, 51 and 52
Is a transparent substrate, and 53 and 54 are transparent electrodes (electrode width = 5).
00 μm). Numerals 55 and 56 are liquid crystal alignment films made of a rubbed polyimide thin film. Reference numeral 57 denotes a spacer (diameter = 10 μm), and reference numeral 58 denotes voltage applying means for applying a voltage between the electrodes 53 and 54. In addition,
The directions of the rubbing applied to the liquid crystal alignment films 55 and 56 are the + direction and the − direction of the x-axis shown in FIG. 4, respectively.
59 is a liquid crystal 60 and a fine solid 61 adjusted by the method described above.
Is a mixture consisting of

Next, a display state of the display element was changed by applying a voltage between the electrodes 53 and 54. First,
A rectangular wave as shown in FIG. 6 was applied for 5 seconds to a display element in which fine solids were uniformly distributed between the electrodes. Then, the display element which had become cloudy before the rectangular wave was applied became transparent. Even when the application of the rectangular wave was canceled, the transparent state was maintained. Next, when a rectangular wave as shown in FIG. 7 was applied for 5 seconds, it became cloudy again. Even when the application of the rectangular wave was canceled, this cloudy state was maintained.

FIG. 8 shows the results of measuring the process of changing from the cloudy state to the transparent state and from the transparent state to the cloudy state by the light transmittance of the display element. The transmittance in the state where the fine solids are uniformly dispersed between the electrodes and cloudy is 0%,
The transmittance in the transparent state reached after applying the rectangular wave shown in FIG. 6 for 5 seconds was defined as 100%. Further, at the time point of 5 seconds shown in FIG. 8, the rectangular wave shown in FIG.
The rectangular wave was released at a time of 9 seconds. Then, the rectangular wave shown in FIG. 7 was applied at a time of 16 seconds, and the rectangular wave was released at a time of 20 seconds.

When the minute solid was observed with a microscope when the rectangular wave was applied, it was observed that the minute solid moved in one direction. Moreover, the direction of movement of the minute solid when the rectangular wave shown in FIG. 7 was applied was opposite to the direction of movement of the minute solid when the square wave shown in FIG. 6 was applied. .

Next, an operation of applying a rectangular wave as shown in FIG. 6 for 1 second to a display element in which fine solids are uniformly dispersed between the electrodes, and then canceling the application for 3 seconds 5 times. Repeated. The transmittance of the display element in the course of this operation was measured. FIG. 9 shows the result. As a result, the transmittance required for gradation display could be changed stepwise.

The operation of applying a rectangular wave as shown in FIG. 7 for 1 second to the device thus made transparent and then releasing the application for 3 seconds was repeated five times. The transmittance of the display element in the course of this operation was measured. As a result, the transmittance decreased stepwise.

Embodiment 2 The configuration of the display element in this embodiment is the same as that of Embodiment 1 except that the minute solid sandwiched between the electrodes is changed.

In this embodiment, a liquid crystal residue bonded to the surface of a microstructure was mixed with liquid crystal as a fine solid.
Microbeads having an amino group (—NH ₂ ) on the surface (diameter 5 μm, manufactured by Wako Pure Chemical Industries, Ltd.) were used as the microstructures. The amino group on the bead surface is reacted with the substance represented by the formula (q) (see Example 1) in the same manner as in Example 1 (condensation reaction using DCC) to leave a liquid crystal residue on the bead surface. A microsolid with attached groups was made.

50 mg of this fine solid was placed in 500 mg of nematic liquid crystal (trade name: BL6, manufactured by Merck), and then subjected to ultrasonic treatment to disperse the fine solid in the liquid crystal. The mixture composed of the liquid crystal and the fine solid was used as a mixture for a display element in this example.

In this embodiment, a change in the display state of the display element was examined by applying the same rectangular wave as in the first embodiment. As a result, it was possible to make a transition between states having different transmittances using only a rectangular wave. Further, the transmittance could be changed stepwise.

[0049]

As described above, according to the present invention,
It is possible to provide a display element and a display method capable of changing reversibly between states having different transmittances and having a memory property only by electric stimulation and changing the transmittance stepwise. Was.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a display element according to the present invention.

FIG. 2 is a diagram showing a driving waveform of a display element.

FIG. 3 is a diagram showing a driving waveform of a display element.

FIG. 4 is an explanatory diagram showing a display principle of a display element.

FIG. 5 is a schematic view showing a display element in Examples 1 and 2 of the present invention.

FIG. 6 is a diagram showing drive waveforms of a display element in Examples 1 and 2.

FIG. 7 is a diagram showing a driving waveform of a display element in Examples 1 and 2.

FIG. 8 is a diagram illustrating a measurement example of the transmittance of the display element according to the first embodiment.

FIG. 9 is a diagram illustrating a measurement example of the transmittance of the display element according to the first embodiment.

[Explanation of symbols]

 11, 12, 41, 42, 53, 54 Electrode 13, 14, 43, 44, 51, 52 Substrate 15, 61 Micro solid 16, 58 Voltage applying means 45 Group of micro solid 55, 56 Liquid crystal alignment film 57 Spacer 59 Mixture 60 liquid crystal

Claims (19)

[Claims] 1. A hollow cell in which transparent electrodes each having a liquid crystal alignment film subjected to a rubbing treatment laminated on the surface thereof are opposed to each other, and at least one of substrates supporting the transparent electrodes is transparent; A display element comprising: a mixture containing a low-molecular liquid crystal and a minute solid having a thickness smaller than the gap between the electrodes; and a voltage applying means for applying a voltage between the electrodes. 2. The rubbing direction applied to one of the opposing liquid crystal alignment films is different from the rubbing direction applied to the other liquid crystal alignment film by 180 °. Display element. 3. The display device according to claim 1, wherein the fine solid does not dissolve in the liquid crystal in a temperature region where the liquid crystal exhibits a liquid crystal phase. 4. The display device according to claim 1, wherein the fine solid is composed of a molecule having a liquid crystal residue. 5. The display device according to claim 4, wherein the molecule having a liquid crystal residue has an amide bond. 6. The display device according to claim 5, wherein the liquid crystal residue is a nematic liquid crystal residue. 7. The display device according to claim 6, wherein the molecule having the liquid crystal residue has a structure represented by the following formula (1). Embedded image 8. The display device according to claim 1, wherein the minute solid is a minute structure having liquid crystal residues bonded to the surface. 9. The display device according to claim 8, wherein the bond is a covalent bond. 10. The display device according to claim 9, wherein the bond is an amide bond. 11. The display device according to claim 8, wherein the bond is a non-covalent bond. 12. The display element according to claim 11, wherein the coupling is an electrostatic coupling. 13. The display device according to claim 8, wherein the liquid crystal residue is a nematic liquid crystal residue. 14. The display device according to claim 8, wherein the shape of the microstructure is spherical. 15. The display device according to claim 8, wherein the shape of the microstructure is needle-like. 16. The display device according to claim 8, wherein the shape of the microstructure is flat. 17. The display device according to claim 1, wherein the low-molecular liquid crystal is a low-molecular nematic liquid crystal. 18. The display device according to claim 17, wherein the low-molecular nematic liquid crystal is a mixed liquid crystal composed of at least two kinds of low-molecular liquid crystals. 19. A low-molecular liquid crystal and a thin film in a hollow cell in which transparent electrodes each having a liquid crystal alignment film subjected to a rubbing treatment laminated on the surface thereof are opposed to each other, and at least one of the substrates supporting the transparent electrodes is transparent. Is filled with a mixture containing fine solids smaller than the gap between the electrodes, the fine solids are moved by applying a voltage between the electrodes by applying voltage, and the movement of the fine solids is stopped by releasing the voltage. A display method in which the light transmittance is changed to perform display.