JPH06322370A - Organic dispersed liquid crystal - Google Patents

Abstract

PURPOSE:To obtain an organic dispersed liquid crystal capable of improving characteristics as a display element. CONSTITUTION:The organic dispersed liquid crystal is obtained by using an organic substance having >=8 relative permittivity as an organic material in an organic dispersed liquid crystal in the form of carrying out the dimming by applying an electric field to an organic dispersed liquid crystal layer 3, sandwiched between electrodes in which at least either is transparent and composed of a mixture of the organic material with a liquid crystal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic dispersed liquid crystal, and more particularly to improvement of a binder and liquid crystal thereof.

[0002]

2. Description of the Related Art An organic dispersed liquid crystal performs a cloudy transmission operation by utilizing the alignment of a liquid crystal having a refractive index anisotropy by an electric field and the matching of the refractive index with a binder organic substance. Therefore, unlike a conventional liquid crystal element that is widely used for display, it has a characteristic that a viewing angle is wide because a deflecting plate is unnecessary. There is also a merit that it can be easily made into a film and can be made flexible.

[0003]

However, for display, the driving voltage is higher than that of the conventional liquid crystal element using the deflecting plate, and the change in the cloudiness transmission with respect to the voltage is gentle, so that the contrast required for the display is reduced. There are problems that the switching speed for obtaining is slow, and that the driving circuit cannot be driven by DC as in the conventional device, and the driving circuit becomes complicated.

The reason for this lies mainly in the organic material that constitutes these organic dispersed liquid crystals. That is, in such an organic dispersed liquid crystal, an acrylic resin, a urethane resin, a polyester resin, a butyral resin, a styrene resin, a vinyl resin, an acrylic silicone resin, a polycarbonate resin has been conventionally used as an organic substance for dispersing the liquid crystal. Various thermoplastic, thermosetting, or ultraviolet curable resins such as resins, alkyd resins, polyethylene resins, and epoxy resins have been used.

Since these resins have a low relative permittivity of usually 2 to 4, a high voltage is required to apply a sufficient electric field for orienting the liquid crystal dispersed therein. This was a major factor that required a high driving voltage. In addition, since these resins generally have low polarities, the interaction between the resins and the liquid crystal, which will be described later, does not occur, and therefore DC driving is impossible.

The present invention solves the drawback that the above-mentioned conventional products have a high driving voltage, improves the switching characteristic of cloudiness transmission, and further enables direct current driving, whereby a display element is provided. It is an object of the present invention to provide an organic dispersed liquid crystal capable of improving the characteristics as described above.

[0007]

In the present invention, an organic substance in which a liquid crystal is dispersed is replaced with an organic substance having a higher dielectric constant and polarity than before, and a liquid crystal having a polar group in the major axis direction of the liquid crystal material. The above problem was solved by using.

[0008]

In other words, by adopting an organic material having a high dielectric constant, the effective electric field applied to the liquid crystal portion when a voltage is applied is increased, and as a result, it becomes possible to switch the cloudiness transmission at a low voltage, and it is possible to drive at a low voltage. Become. At the same time, the above-mentioned switching can be sharply performed, which facilitates display by matrix driving or the like.

The value of the relative permittivity of the organic substance that can obtain these effects varies depending on the type of liquid crystal used and the device structure, but generally, when the value is 8 or more, a remarkable effect is obtained. It is considered that this is because the generally used liquid crystal has a relative permittivity of about 8 to 10 when it is not aligned, and the above-described effect occurs when the relative permittivity of the organic substance is higher than that.

Further, by using an organic material having a large polarity and using a liquid crystal having a polar group in the long axis direction of the molecule, it becomes possible to drive at a direct current. This is for the following reason.

When a liquid crystal having a polar group in the long axis direction of the molecule is used as the liquid crystal material, it is dispersed in a polar organic substance,
The liquid crystal trapped in the space of a capsule or its continuum is bound by its polar group to the polar group of an organic substance when it is not in an electric field, and by radially and neatly orienting from the inner wall of the capsule to the center of the capsule, The optical scattering becomes excellent, and the white turbidity increases.

Under a DC electric field, since the polar groups of the liquid crystal are aligned in the direction of the electric field while being bound, the hydrophobic groups and polar groups of the liquid crystals can be aligned without facing each other, so that the liquid crystal can be driven.

Under the AC electric field, the binding of the liquid crystal on the inner wall surface of the organic substance capsule is insufficient, and the liquid crystal is in a state where the hydrophobic groups and the polar groups face each other. It becomes the normal operation.

Also, when the organic bead-like substance is dispersed in the liquid crystal, the liquid crystal surrounds the organic bead in the form of a micellar body from the outer wall of the organic bead when it is not in the electric field for the above-mentioned reason. It has a high degree of white turbidity because it is beautifully oriented outward.

Similarly, under a direct current electric field, since the polar groups of the liquid crystal are aligned in the direction of the electric field while being bound, the hydrophobic groups and polar groups of the liquid crystals can be aligned without facing each other, so that driving with direct current is possible. is there.

Further, under an AC electric field, the binding of the liquid crystal on the surface of the outer wall of the organic beads is insufficient, and the liquid crystal is in a state where hydrophobic groups and polar groups face each other. It will be the normal behavior seen.

The relative permittivity that causes such a phenomenon is high,
There are several kinds of organic substances having a large polarity, and among them, it is most effective to use an organic substance having a polar cyano group.

The organic substances having at least one cyano group and having a relative dielectric constant of 8 or more include nitrile rubbers, succinic acid nitriles, cyanoethylated compounds and monomers and polymers of their modified products, and polymers with various comonomers. , But especially sialyl cellulose, cyanoethyl hydroxyethyl cellulose, cyanoethyl starches (cyanoethyl starch, cyanoethyl amylose,
Cyanoethyl dextran, cyanoethyl pullulan, etc.), cyanoethyl hydroxy starches, cyanoethyl glycidol fulculane, cyanoethyl polyvinyl alcohol, cyanoethyl biphenyl, cyanoethyl sucrose, cyanoethyl sorbitol, cyanoethyl kraft, cyanoethylated monomers such as cyanoethyl metal acrylamide, and polymers, and these The mixture containing at least one cyanoethylated compound has a large polarity due to the cyano group, and therefore has a sufficient interaction between the organic substance and the liquid crystal, and is preferably used as an excellent one in the present invention.

Further, since this organic substance has a low dielectric loss tangent of 0.1 or less, it has an advantage that the loss current component is small and the device can be stabilized.

There are various liquid crystals that can drive the organic dispersed liquid crystal in the present invention by direct current, but in general, nematic liquid crystals having polar groups in the major axis direction of molecules such as twist nematic liquid crystals and super twist nematic liquid crystals. It can be said that the liquid crystal containing as a main component is suitable for having excellent characteristics. When used as an AC low voltage drive element, it does not necessarily have to have a polar group in the long axis direction of the molecule.

The organic substance and the liquid crystal can be used in any mixing ratio, but a mixture in which the organic substance accounts for 2% or more and 90% or less by weight is particularly preferably used for the purpose of the present invention.

This is because if it is less than 2%, the white turbidity is insufficient, so that the contrast is lowered and it is difficult to form a film, and if it is more than 90%, it is difficult to obtain a sufficient white turbidity, and the contrast becomes poor. Because it will decrease.

[0023]

EXAMPLES Next, the present invention will be explained based on examples.

FIG. 1 shows an organic dispersed liquid crystal (element) according to an embodiment.
FIG.

In the figure, 1 is a PET film and 2 is an I.
A TO lower electrode, 3 is an organic dispersed liquid crystal layer, 4 is an adhesive layer, 5 is an ITO upper electrode, and 6 is a PET film, and these are laminated in order from the bottom.

(A) Preparation of Organic Dispersed Liquid Crystal Element Example 1 An organic dispersed liquid crystal element (1) having a structure shown in FIG. 1 was prepared through the steps of the following a) to c).

(A) Preparation of organic dispersion liquid crystal coating cyanoethyl pullulan (Shin-Etsu Chemical Co., Ltd. CR-S), which is an organic substance having a cyano group, and has a relative dielectric constant of 19
It was dissolved in a mixed solvent consisting of 2 parts of pyrrolidone, 1 part of cyclohexanone, and 1 part of toluene to prepare a 25% by weight organic solution. Further, a mixed liquid crystal (BDH) mainly composed of a nematic liquid crystal having a polar group in the long axis direction of the molecule in the same mixed solvent.
Company E-8) was dissolved to prepare a 25% by weight solution. Equal amounts of these two types of solutions were mixed to prepare an organic dispersed liquid crystal coating material.

(B) Formation of Organic Dispersed Liquid Crystal Layer Using the above coating composition, a screen printing was performed on a polyethylene terephthalate (hereinafter referred to as PET) film on which an indium tin composite oxide (hereinafter referred to as ITO) to be a lower electrode was deposited. An organic dispersed liquid crystal layer was formed. Further, this was dried in vacuum at 80 ° C. for 1 hour to remove the solvent. The film thickness after drying was 50 μm.

C) Formation of Upper Electrode A PET film on which ITO is vapor-deposited is coated with cyanoethylsorbitol (Shin-Etsu Chemical Co., Ltd. CR-O), which is a liquid organic substance having a cyano group, as an adhesive layer to a thickness of about 1 μm by screen printing. Then, the organic dispersed liquid crystal element formed in (b) was bonded to the organic dispersed liquid crystal by pressure bonding to form an upper electrode, thereby manufacturing an organic dispersed liquid crystal element.

The resin used for adhesion is not limited to the resin used in this embodiment, and various commonly used adhesives can be used. This adhesive layer also serves as a dielectric layer and a buffer layer. Further, the electrodes can be formed by a method such as applying a conductive ink, heating and pressure-bonding the electrode film, and vapor deposition.

Example 2 An organic dispersed liquid crystal device (2) having the structure shown in FIG. 1 was produced by the following steps d) to f).

D) Preparation of organic dispersion liquid crystal coating cyanoethyl polyvinyl alcohol (Shin-Etsu Chemical Co., Ltd. CR-V) having a relative dielectric constant of 15 which is an organic substance having a cyano group.
1 methyl 2 pyrrolidone 2 parts, cyclohexanone 1
Parts and 1 part of toluene were dissolved in a mixed solvent to prepare a 25% organic solution by weight. In addition, a mixed liquid crystal (E-8, manufactured by BDH), which is mainly a nematic liquid crystal having a polar group in the major axis direction of the molecule, was dissolved in the same mixed solvent to prepare a 25% by weight solution. Equal amounts of these two types of solutions were mixed to prepare an organic dispersed liquid crystal coating material.

(E) Formation of Organic Dispersed Liquid Crystal Layer Using the above coating material, P on which ITO serving as a lower electrode is vapor-deposited is formed.
An organic dispersed liquid crystal layer was formed on the ET film by screen printing. Further, this was dried in vacuum at 80 ° C. for 1 hour to remove the solvent. The film thickness after drying is 50μ
It was m.

F) Formation of the upper electrode [0034] Cyanoethylsorbitol (Shin-Etsu Chemical Co., Ltd. CR-O) was applied as an adhesive layer to a PET film on which ITO was vapor-deposited by screen printing to a thickness of about 1 µm, and formed by (e). On the organic dispersed liquid crystal which was made, it stuck by pressure bonding,
An upper electrode was formed to produce an organic dispersed liquid crystal device.

Example 3 An organic dispersed liquid crystal device (3) having the structure shown in FIG. 1 was produced by the following steps g) to d).

G) Preparation of Organic Dispersed Liquid Crystal Paint A liquid organic substance having a cyano group, cyanoethylsorbitol having a relative dielectric constant of 40 (Shin-Etsu Chemical Co., Ltd. CR-O),
25% by weight dissolved in a mixed solvent consisting of 1 part methyl 2 pyrrolidone 2 parts cyclohexanone 1 part toluene 1 part
An organic solution of was prepared. In addition, a mixed liquid crystal (E-8, manufactured by BDH), which is mainly a nematic liquid crystal having a polar group in the major axis direction of the molecule, was dissolved in the same mixed solvent to prepare a 25% by weight solution. Equal amounts of these two types of solutions were mixed to prepare an organic dispersed liquid crystal coating material.

H) Formation of Organic Dispersed Liquid Crystal Layer Using the above coating material, P on which ITO serving as a lower electrode is vapor-deposited is formed.
An organic dispersed liquid crystal layer was formed on the ET film by screen printing. Further, this was dried in vacuum at 80 ° C. for 1 hour to remove the solvent. The film thickness after drying is 50μ
It was m.

(I) Formation of upper electrode A PET film having ITO deposited thereon was coated with cyanoethylsorbitol (Shin-Etsu Chemical Co., Ltd. CR-O), which is a liquid organic substance having a cyano group, as an adhesive layer to a thickness of about 1 μm by screen printing. Then, the organic dispersed liquid crystal element formed in (4) was bonded to the organic dispersed liquid crystal by pressure bonding to form an upper electrode, thereby manufacturing an organic dispersed liquid crystal element.

Example 4 An organic dispersed liquid crystal element (4) having the structure shown in FIG. 1 was produced by the following steps (n) to (n).

(4) Preparation of organic dispersion liquid crystal coating cyanoethyl pullulan (Shin-Etsu Chemical Co., Ltd. CR-S), which is a liquid organic substance having a cyano group, and sialethyl polyvinyl alcohol (Shin-Etsu Chemical Co., Ltd. CR-V) are mixed in equal amounts to obtain a dielectric constant. An organic substance with a rate of 17 is 1 methyl 2 pyrrolidone 2
Parts, cyclohexanone 1 part, and toluene 1 part were dissolved in a mixed solvent to prepare a 25% by weight organic solution. Further, a mixed liquid crystal mainly composed of a nematic liquid crystal having a polar group in the long axis direction of the molecule in the mixed solvent (B-8 E-8).
Was dissolved to prepare a 25% by weight solution. Equal amounts of these two types of solutions were mixed to prepare an organic dispersed liquid crystal coating material.

Le) Formation of Organic Dispersed Liquid Crystal Layer Using the above coating material, ITO which is a lower electrode is vapor-deposited on P
An organic dispersed liquid crystal layer was formed on the ET film by screen printing. Further, this was dried in vacuum at 80 ° C. for 1 hour to remove the solvent. The film thickness after drying is 50μ
It was m.

W) Formation of upper electrode A PET film on which ITO was vapor-deposited was coated with cyanoethylsorbitol (Shin-Etsu Chemical Co., Ltd. CR-O), which is a liquid organic substance having a cyano group, as an adhesive layer to a thickness of about 1 μm by screen printing. Then, the organic dispersed liquid crystal element formed in (1) was attached to the organic dispersed liquid crystal formed by (1) by pressure bonding to form an upper electrode, thereby manufacturing an organic dispersed liquid crystal element.

Comparative Example An organic dispersed liquid crystal device (5) having the structure shown in FIG. 1 was produced by the following steps (a) to (e).

(5) Preparation of Organic Dispersion Liquid Crystal Paint Acrylic resin having a relative dielectric constant of 3 (Dainippon Ink A-95
40) was dissolved in a mixed solvent consisting of 2 parts of 1-methyl-2-pyrrolidone, 1 part of cyclohexanone and 1 part of toluene to prepare a 25% by weight organic solution. Further, a mixed liquid crystal mainly composed of a nematic liquid crystal having a polar group in the molecular long axis direction (E-8 manufactured by BDH Co.) was dissolved in the same mixed solvent to give a weight ratio of 25.
% Solution was made. Mix equal amounts of these two solutions,
An organic dispersed liquid crystal paint was prepared.

F) Formation of organic dispersed liquid crystal layer P formed by vapor-depositing ITO serving as a lower electrode using the above coating material.
An organic dispersed liquid crystal layer was formed on the ET film by screen printing. Further, this was dried in vacuum at 80 ° C. for 1 hour to remove the solvent. The film thickness after drying is 50μ
It was m.

(I) Formation of upper electrode A PET film having ITO deposited thereon was coated with cyanoethylsorbitol (Shin-Etsu Chemical Co., Ltd. CR-O), which is a liquid organic substance having a cyano group, as an adhesive layer to a thickness of about 1 μm. Then, the organic dispersed liquid crystal element formed in step (a) was bonded to the organic dispersed liquid crystal by pressure bonding, and an upper electrode was formed to produce an organic dispersed liquid crystal element.

In the above examples, the PET film was used as the support of the organic dispersed liquid crystal film and ITO was used as the electrode material. However, since it is sufficient that at least one of the organic dispersed liquid crystal films is transparent, it is possible to use the transparent side. The support may be PET, PES, or other transparent polymer glass,
It may be omitted. Various transparent conductive materials other than ITO are used for the electrodes. Also, the other side is not necessarily transparent and various supports are conceivable but not necessary. In addition to the transparent conductive material, a material having conductivity such as metal or carbon can be widely used for the electrode.

(B) Evaluation of Organic Dispersed Liquid Crystal Device FIG. 2 shows devices (1) to (1) manufactured in Examples 1 to 4.
It is a voltage-visible light reflectance characteristic graph of (4).

The measurement was carried out by injecting a light beam having a wavelength of 500 nm at an incident angle of 45 ° into a sample having an ITO vapor-deposited PET film on the back surface, and measuring the intensity of reflected light due to scattering above the vertical direction. The drive voltage is 0 to 50 V and is 100 Hz alternating current. In order to see the contrast, the reflected light intensity when no voltage is applied is set to 100%.

For comparison, the characteristics of the device (5) manufactured according to the comparative example are also shown. When a voltage is applied, the reflectance of element (4) decreases more rapidly than that of element (5).
The voltage at which the respective reflectance values were halved was 12 V in the device (4), whereas it was 30 V in the device (5).

As a result of visual examination, the voltage for obtaining a sufficient contrast was about 40 V for the device (5), while it was about 15 V for the device (4) of the present invention.

At an applied voltage of 0 V, the reflectance of the device (4) of the present invention was higher by about 10%. This is because the liquid crystal is neatly and radially aligned in the capsule of the binder, and the difference in the refractive index between the organic material used in this example and the liquid crystal at the time of random alignment is larger than that of the conventional product. Next, it is also a factor for improving contrast.

The elements (1) to (3) also show the same tendency as the characteristics of the element (4) described above, but in this embodiment, the element (4) changes from cloudiness to transmission with respect to voltage. It is most excellent in the balance of the three conditions of the steepness of the change, the high opacity when no voltage is applied, and the high transparency when 50 V is applied.

Then, the elements (1) to (1) according to Examples 1 to 4
A DC voltage was applied to the element (5) according to (4) and the comparative example, and the contrast with that when no voltage was applied was visually examined.

As a result, at 27 V, the devices (1)-
In (4), while sufficient contrast was obtained,
The device (5) remained opaque even at 120 V and could not be driven.

Thus, the devices (1) to (1) according to the present invention
In (4), it was confirmed that lower voltage driving and improvement of switching characteristics were achieved, and that DC driving was possible.

[0057]

As described above, when the liquid crystal having a polar group is used, the organic dispersed liquid crystal according to the present invention can be driven by a direct current or an alternating current of a low frequency, and in normal alternating current driving. Also, the driving voltage is reduced. Further, there is an effect that the switching characteristic of cloudiness transmission is improved, and an element suitable for display such as matrix driving is obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of an organic dispersed liquid crystal device according to the present invention.

FIG. 2 shows an organic dispersed liquid crystal device according to each embodiment of the present invention,
It is a characteristic view which shows the relationship between an applied voltage and relative reflection intensity.

[Explanation of symbols]

 1 PET film 2 ITO lower electrode 3 organic dispersed liquid crystal layer 4 adhesive layer 5 ITO upper electrode 6 PET film

Claims (3)

[Claims] 1. An organic dispersed liquid crystal of a system in which an electric field is applied to an organic dispersed liquid crystal film composed of a mixture of an organic material and a liquid crystal sandwiched between electrodes, at least one of which is transparent, to obtain an organic dispersed liquid crystal. An organic dispersed liquid crystal characterized by using an organic material having a relative dielectric constant of 8 or more. 2. The organic dispersed liquid crystal according to claim 1, wherein the organic material contains an organic substance having a cyano group. 3. The liquid crystal material according to claim 1, wherein the liquid crystal material is a single liquid crystal having a polar group in the direction of the long axis of the molecule, or a mixed liquid crystal mainly containing the polar group. Organic dispersed liquid crystal.