JPH0485522A - Dispersion for optical element - Google Patents

Abstract

PURPOSE:To enhance the degree of orientation not only by the rotation but deformation as well when an electric field is impressed to a bar-shaped micell and to color this micelle to an arbitrary color so that the micelle can be colored to various kinds of color tones by using a mixture composed of the above- mentioned micelle and the solvent thereof as the dispersion for optical elements. CONSTITUTION:The bar-shaped micelle is the associate of the molecules of a surfactant and is not solid and is usually curved or twisted. This micelle changes to a straight bar shape and orients in the electric field direction when the micelle is dispersed in a medium and the electric field is impressed thereto. The coloration to the arbitrary color is executed by utilizing the phenomenon of solubilization by the micelle. The optical element formed by using this dispersion exhibits the color of the bar-shaped micelle while the electric field is not impressed thereto and is made transparent when the electric field is impressed thereto. The mixed colors of the medium and the bar-shaped micelle are exhibited by the coloration of the medium while the electric field is not impressed thereto. The color of the medium is exhibited when the electric field is impressed thereto. The optical element having various kinds of the color tones is thus obtd.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a dispersion for optical elements used in light valves, display devices, dimming windows, etc., and in particular, anisotropic particles are dispersed in a medium and an electric field is applied to orient the particles. This invention relates to a dispersion body for an optical element that changes the transmittance and refractive index of light by changing the .

[Conventional technology]

A dispersion of anisotropic particles dispersed in a medium is enclosed in a cell formed by two opposing electrodes, and when an electric field is applied to this from the outside, the orientation of the particles changes and the light transmittance increases. It has been known for a long time that optical properties such as refractive index and refractive index change. Optical elements utilizing this principle have also been proposed for a long time (see, for example, US Pat. No. 1,955,923). An optical element in which a dispersion is enclosed in a thin cell made up of two transparent electrodes is opaque when no electric field is applied because many anisotropic particles are oriented in random directions, but when an electric field is applied Then, the anisotropic particles move in the direction of the electric field,
In other words, since they are aligned in the width direction of the cell, they become transparent. Therefore, by using such optical elements, light valves, various display devices, dimming windows, etc. can be obtained. In optical elements that control optical properties by changing the orientation of particles, the particles dispersed in the dispersion are anisotropic particles whose orientation changes when an electric field is applied, and whose light transmittance and refractive index change. It is necessary to use Such particles include, for example, organic crystals such as herabasite and cinchonidine periodic sulfate, metals such as aluminum, mineral crystals such as mica, and inorganic oxides such as titanium oxide and tungsten oxide. , graphite, and various other materials have been proposed.

[Problem to be solved by the invention]

However, all of these anisotropic particles are solid particles. When an electric field is applied to a dispersion of such solid particles in a medium, the particles change orientation due to their anisotropy. In other words, particles change their orientation by rotating. For this reason, conventional devices using anisotropic solid particles have a problem in that responsiveness decreases when a medium with high viscosity is used. Furthermore, since these anisotropic particles are crystals, the degree of freedom in color selection is low. The color of the dispersion is then determined by the color of the particles. Therefore, in an optical element using a dispersion in which such particles are dispersed, the color tone is limited to pearlescent or blue-based colors. In other words, in the case of particles of aluminum, mica, or titanium oxide dispersed in a medium, the scattering of light changes depending on the orientation of the particles, so when an electric field is applied, the material becomes transparent or not. Sometimes pearl-colored. In addition, since herabasite and cinchonidine periodic sulfate exhibit blue or blue-purple color, a dispersion in which these particles are dispersed becomes transparent when an electric field is applied, and has a blue-ish color tone when no electric field is applied. In the case of optical elements that control optical properties by changing the orientation of particles, the color tone change is determined by the optical properties of the particles, so in order to obtain the desired color, It is necessary to use anisotropic particles with a tone that matches the color. In this case, the particles are required to have various functions in addition to color tone, such as shape anisotropy, specific gravity, chemical stability, and dispersion stability. It is extremely difficult to find particles that satisfy all of these functions. For this reason, conventional optical elements have a problem in that desired colors cannot be obtained. The present invention has been made in view of these circumstances, and its purpose is to provide a dispersion for optical elements that uses novel particles that are oriented in a manner different from conventional ones. Another object of the present invention is to provide a dispersion for optical elements that can be used as optical elements exhibiting various color tones.

[Means to solve the problem]

In order to achieve this objective, in the present invention, a mixture of a solvent and rod-shaped micelles is used as a dispersion sealed in the cells of an optical element. When a surfactant is added to a medium and its concentration is gradually increased, the surfactant begins to form micelles. The critical concentration for forming micelles is called the critical micelle concentration. Typically, surfactants aggregate into spherical shapes and associate to form micelles. For example, if the medium is water, the surfactant molecules solidify with the hydrophilic groups facing outward and the hydrophobic groups facing inward. Therefore, it becomes spherical. However, in the case of a specific combination of a solvent and a surfactant, it is known that when the active agent is added above the critical micelle concentration, rod-shaped micelles are formed at a certain concentration (Author MAnge I). ,'Progr,
Co11oid & Polymer Sci, J Vol. 69 (1984), pp. 12-28). A dispersion containing such rod-shaped micelles is optically isotropic as it is, but when an electric field is applied, it exhibits birefringence (M
, by Angel, 'Ber, Bunsenges
Phys, Chem, Vol. 93 (1989), pp. 184-191). That is, the rod-shaped micelles are oriented in response to the application of an electric field. The present inventors focused on such rod-shaped micelles. In the present invention, among ionic surfactants and nonionic surfactants having long hydrocarbon chains, cetylpyridine salicylate, cetyltrimethylammonium trichloroacetate, cetyltrimethylammonium salicylate are used as surfactants that form micelles. , tetradecyltrimethylammonium salicylate, dodecyltrimethylammonium chloride, cetyltrimethylammonium bromide, hexaoxyethylenedecyl ether, hexaoxyethylene dodecyl ether, hexaoxyethylene cetyl ether, etc., but are not limited thereto. In general, most surfactants will form rod-shaped micelles in the presence of a salt if the hydrophilic groups are small and the hydrophobic groups are long chains. The critical concentration of surfactant to form rod-shaped micelles is
Although it varies depending on the type of activator, temperature, salt concentration, etc., the concentration is usually from several millimoles to several 10 millimoles or more. As a result, micelles having a length of several 100 angstroms to several 1000 angstroms are formed. For example, in the presence of 10 mmol of common salt, tetradecyltrimethylammonium salicylate has approximately 2,800 angstroms at a 2 mmolar concentration and approximately 1 angstrom at a 10 mmolar concentration.
forming rod-shaped micelles with a length of 200 angstroms,
Cetyltrimethylammonium salicylate forms rod-shaped micelles with a length of about 6500 angstroms at a 2 mmolar concentration and about 900 angstroms at a 10 mmolar concentration. A solution containing the rod-shaped micelles thus formed becomes the dispersion of the present invention. That is, the dispersion is a mixture of rod-shaped micelles and their solvent. By the way, in this state, although the dispersion exhibits birefringence, since the surfactant is nearly transparent, the change in light transmittance is small. Therefore, even if an optical element is made using the dispersion, the light control function of the optical element will not necessarily be sufficient. Therefore, in the present invention, the phenomenon of solubilization by micelles is further utilized to retain the coloring material inside the micelles. Whether or not a solute dissolves in a solvent is largely determined by whether or not the polarities of the two molecules match. Lipophilic solutes do not dissolve in hydrophilic solvents, or
Even if it does dissolve, its solubility is very small. However, when a lipophilic solute is added to a solution in which a surfactant forms micelles, the solute molecules enter the inside of the micelles.
Apparent solubility increases. This is solubilization by micelles. Therefore, by utilizing this phenomenon, the micelles can be colored by dissolving dye molecules inside the micelles. For this purpose, the oil-soluble dye may be added dropwise little by little while stirring the micelle solution obtained as described above. The water-insoluble oil-soluble dyes used here include monoazo, disazo, and anthraquinone dyes, but those with as low a molecular weight as possible are preferred since they can be added in large amounts. For example, 2,4-dihydroxyazobenzene, 4-aminoazobenzene, 1.4,5°8-tetraaminoanthraquinone, 1,4-diaminoanthraquinone, etc. are preferred. However, 1-(1'-naphthylazo)-2-
Naphthol, 1-(4'-nitrophenylazo)-2-
Relatively high molecular weight dyes such as naphthylamine and the like can also be added. In this way, the dye molecules are dissolved inside the micelles, and the rod-shaped micelles are colored. Thereby, substantially rod-shaped colored particles can be obtained. In that case, the dye molecule is
It is necessary to have a polarity close to that of the surfactant forming the core of the micelles and to be dissolved in the micelles. There are certain limits to the size and amount of molecules that can be dissolved in micelles, and they vary greatly depending on the ion concentration in the solvent. In general, hydrocarbons with a chain length shorter than that of the surfactant will dissolve, but molecules with a small molecular radius will dissolve more, and the higher the ion concentration, the higher the solubility. If an attempt is made to dissolve the rod-shaped micelles at a concentration higher than their solubility, the rod-shaped micelles may not be able to withstand the internal pressure and decompose, turning into spherical micelles. Therefore, the concentration of the dye must be within a range that does not destroy the rod-shaped micelles. The limit of the amount of dye added can be determined by measuring the amount of light scattering while dropping the dye. This is because when the dye dissolves inside the micelles, the scattering rate increases, but when the dye is added in excess and the rod-shaped micelles are destroyed, the light scattering rate decreases rapidly. In the presence of salt, such destruction of rod-like micelles may not occur. In that case, the oil-soluble dye added in excess does not dissolve in water and separates, so it may be filtered through an appropriate mesh filter. In the case of the dispersion thus obtained, the salt or its ions will be contained in the medium. In this way, a dispersion in which anisotropic colored particles are dispersed in a medium is obtained. The medium can also be colored in various colors. Additionally, rod-shaped micelles are generally difficult to form in non-aqueous systems. Even if they are formed, only very short ones with a small number of associations will be obtained. On the other hand, in an aqueous solution system, the electrical conductivity of the solvent increases, so
If an optical element is created using it, a large current will be required to drive the optical element. Therefore, non-aqueous dispersions are more desirable. In order to meet these conflicting demands, an effective method is to form rod-shaped micelles containing a dye in an aqueous solution, then microcapsule them and disperse them in an organic solvent. Various conventionally known methods can be used to microcapsule the micelle solution, but interfacial polymerization is the easiest to use. Substance A involved in polymerization
is dissolved in the above-mentioned micelle solution, stirred and mixed with an organic solvent to form an emulsion, and then oil-soluble substance B is added to cause interfacial polymerization. As the organic solvent in this case, a polymeric solvent with a large molecular weight is used. Specifically, in the micelle solution formed as described above,
1. Prepare solution A by dissolving polyamines such as 6-hexamethylene diamine, piperazine, and L-lysine. Since these are water-soluble polyamines, they can be made into a solution without destroying the micelles. Next, a relatively less hydrophilic surfactant such as sorbitan acid is added as a surfactant to oil-soluble polymers such as sebacoyl chloride and terephthalic acid chloride to prepare solution B. The solutions A and B obtained in this way are stirred and mixed to form a W10 emulsion, and when stirring is continued for several hours, transparent 6
．． A 10-nylon polyamide membrane is formed. That is, microencapsulation is completed. In this case, the surfactant in solution B is not necessarily necessary, and an active agent originally contained in solution A may be substituted for forming micelles. Furthermore, the types of monomers involved in polymerization are not limited to these,
Polyurethane films can also be made using various isocyanates as oil-soluble monomers. The microcapsules obtained in this way are separated from the solution by filtration and dispersed in silicone oil, fluororesin oil, etc. using a surfactant, and the capsules of the micelle solution are created in an insulating medium. A dispersion for a dispersed optical element is obtained. Such a dispersion is a liquid, but depending on the viscosity of the medium, it can also be a pasty or solid dispersion. In that case, it is possible to simply use a medium with high viscosity, but it is also possible to first disperse it in a medium with low viscosity and then increase the viscosity through a polymerization reaction.

[Effect]

Rod-shaped micelles are made up of surfactant molecules and are not solid. The rod-shaped micelles are not necessarily straight rods;
Rather, they are usually curved or twisted. When no electric field is applied, they are oriented in random directions, and many are entangled with each other. When an electric field is applied to a dispersion in which such rod-shaped micelles are dispersed in a medium, the micelles become straight rod-shaped and are oriented in the direction of the electric field. That is, the degree of orientation of the micelles increases not only by rotation but also by deformation. Then, the micelles can be colored in any desired color by utilizing the solubilization phenomenon caused by the micelles as described above. Therefore, when an optical element is made using such a dispersion, the optical element exhibits the color of a rod-shaped micelle when no electric field is applied, and becomes transparent when an electric field is applied. Furthermore, if the medium is colored, the optical element will exhibit a mixed color of the medium and rod-shaped micelles when no electric field is applied, and the color of the medium when an electric field is applied. In this way, it is possible to obtain optical elements having various color tones. When a solution containing rod-shaped micelles is microencapsulated, the micelles become oriented or randomized inside the capsule. That is, it can be driven regardless of the viscosity of the organic solvent in which the capsules are dispersed. Therefore, by dispersing the capsules using, for example, a polymer gel as a binder, it is possible to form a paste-like or solid-like dispersion.

【Example】

The present invention will be explained in detail below. (Example 1) 100 cc of a solution was prepared by adding 2 mmol/liter of cetyltrimethylammonium salicylate to a distilled aqueous solution containing lθ mmol/liter of common salt, and the solution was stirred for 48 hours using a shaker. When 0.5 mmol/liter of 4-aminobenzene was added to this solution and the mixture was again stirred using a shaker for 48 hours, the solution turned yellow. No separation of the dye occurred, but just to be sure, this solution was diluted to 0.
The residue was removed by filtration through a 2 micron mesh filter to obtain a dispersion of rod-shaped micelles. On the other hand, two transparent electrodes of indium tin oxide were placed on the - surface.
Two glass plates sputtered to a thickness of 0.000 angstroms and on which silicon oxide was sputtered to a thickness of 2000 angstroms were placed facing each other and sealed around the periphery with mylar and adhesive to form a cell gap of 0.000 angstroms. A cell of 1 mm and 50 x 50 mm in length and width was created. Then, the dispersion described above was sealed in this cell, and an AC voltage of 5 V was applied from the outside via a transformer. As a result, the cell, which was yellow when no voltage was applied, turned transparent when voltage was applied. Furthermore, the colored state changed reversibly depending on whether the voltage was turned on or off. (Example 2) 15 mmol/l of cetyltrimethylammonium bromide was added to a distilled aqueous solution containing 0.2 mol/l of sodium bromide.
100 cc of the solution was prepared and stirred for 48 hours using a shaker. Add 1 part of surfactant to this solution.
When 0 times the molar amount of 1-methylaminoanthraquinone was added and the mixture was again stirred using a shaker for 48 hours, the solution was colored red and the excess dye was separated. Therefore, this solution was filtered through a 0.2 micron mesh,
Removed as excess dye residue. The dispersion thus obtained was sealed in the same cell as in Example 1, and the same alternating current voltage was applied. In this case, the cell was red in the off state and transparent in the on state. Furthermore, the colored state changed reversibly depending on whether the voltage was turned on or off. (Example 3) Calcium carbonate 0.3 for 5 cc of the dispersion of Example 1
mol and 0.3 mol of 1,6-hexamethylenediamine were added. Also, 4 of cyclohexane and chloroform:
50 cc of a mixed solution was prepared, and 0.2 g of sorbitan trioleate was added thereto. These two solutions were stirred and mixed in a beaker held in a water bath to form an emulsion. After stirring for 20 minutes, a solution of 0.3 mol of sebacoyl chloride dissolved in 5 cc of the same 4:1 mixed solution of cyclohexane and chloroform was gently added while stirring. 1 more
Stirring was continued for 5 minutes, and stirring was stopped after waiting for the end of the microencapsulation reaction. The formed microcapsules were then separated by centrifugation. Next, the microcapsules were dispersed in water, and unreacted substances and sodium carbonate produced by the neutralization reaction between hydrochloric acid and calcium carbonate produced during the polymerization reaction were removed by dialysis. The collected microcapsules were once washed with hexane, and then dispersed in 5 cc of fluororesin oil (Daifloil #L manufactured by Daikin Industries, Ltd.) using sorbitan tristearate as a surfactant. This dispersion was sealed in the same cell as in Example 1, and 100
An alternating current voltage of V was applied. The cell, which was yellow when sealed, became transparent when voltage was applied. In this case as well, the colored state changed reversibly by turning on and off the voltage. (Example 4) The dispersion of Example 2 was used in place of the dispersion of Example 1 in Example 3, L-lysine was used instead of 1,6-hexamethylene diamine as the water-soluble monomer, and oil The micelle dispersion was microencapsulated in the same manner as in Example 3, except that terephthaloyl dichloride was used instead of sebacoyl chloride as the soluble monomer. Then, after removing unreacted substances and reaction products by the same method as in Example 3, the obtained microcapsules were similarly dispersed in dyfloil. When this dispersion was sealed in a similar cell and a voltage was applied, the cell, which was red when no voltage was applied, turned transparent upon application of the voltage. Moreover, the colored state changed reversibly depending on whether the voltage was turned on or off. Microcapsules were collected by the same operation as in Example 3, and added to 5 cc of Herocarbon Oil (#0.8) manufactured by Herocarbon Oil Products Co., Ltd. using sorbitan monooleate as a surfactant. After dispersion, a copolymer of neopentyl acrylate and n-methylolacrylamide was added in an amount of 20% of the total weight. This dispersion was sealed in the same cell as in Example 1, and heated with a xenon lamp at an output of 700 W/rn' for 100 hours.
Irradiated with light. This cell was colored yellow, but when an AC voltage of 100V was applied, it became transparent. The colored state changed reversibly depending on whether the voltage was turned on or off. After the test, an attempt was made to remove the dispersion from the cell, but the dispersion had become a gel and could not be removed. Therefore, the cells were destroyed and it was confirmed that the dispersion had become a gel. A dispersion was prepared in the same manner as in Example 2. Then, 1-(3°-methylphenylazo)-2-naphthol, which is a water-soluble dye, was added to the dispersion for coloring. This dispersion was sealed in a cell similar to that in Example 1, and a voltage was applied. When no voltage was applied, the cell had a mixed color of the micelles and the medium, but when a voltage was applied, it took on the color of the medium.

【Effect of the invention】

As is clear from the above description, according to the present invention, a mixture of rod-shaped micelles and their solvent is used as a dispersion for optical elements, so when an electric field is applied,
The optical properties change due to the orientation of the rod-shaped micelles. In that case, the rod-shaped micelles are not oriented only by rotation like conventional anisotropic solid particles;
The degree of orientation also increases through deformation. therefore,
This eliminates the problems encountered with solid particles. Since the rod-shaped micelles can be colored in any color, by using the dispersion in an optical element, an optical element exhibiting a desired color can be obtained. Patent applicant Japan Steel Works Co., Ltd. Patent attorney Yu Morishita Hata

Claims (6)

[Claims] (1) A dispersion in which anisotropic particles are dispersed in a medium is enclosed in a cell in which electrodes are arranged on each of two opposing sides,
By applying an external electric field through the electrode,
A dispersion used in an optical element in which the optical properties are changed by changing the orientation of the particles; characterized in that the anisotropic particles are rod-shaped micelles, and the medium is a solvent thereof. Dispersion for optical elements. (2) The dispersion for an optical element according to claim 1, wherein the rod-shaped micelles contain a dye. (3) the medium is colored; The dispersion for optical elements according to claim 1 or 2. (4) the medium contains salt or its ions; The dispersion for optical elements according to any one of claims 1 to 3. (5) The dispersion for an optical element according to any one of claims 1 to 4, wherein the rod-shaped micelles and the solvent are microencapsulated, and the microcapsules are dispersed in an organic solvent. (6) the organic solvent is a gel-like substance; The dispersion for optical elements according to claim 5.