JPS6014785B2 - electrochromic display element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reflective electrochromic display element that displays images using a reducing electrochromic compound.

Electrochromic (hereinafter abbreviated as EC).

) Compounds undergo oxidation and reduction reactions by giving and receiving electrons, and in the acid state and the reduced state, the absorption wavelength of light is different, so they have the property of exhibiting different colors. Therefore E
Since the C compound exhibits different colors depending on the application of voltage, it can be used as a display element by being injected between a pair of electrode plates, at least one of which is transparent.

Incidentally, the term "reducible EC compound" as used in the present invention refers to an EC compound that reversibly undergoes a redox reaction and is present in the air, that is, an EC compound in an oxidized state, which is colorless and transparent or a light color close to it; An EC compound in a reduced state, in which the EC compound is reduced, refers to an EC compound that is deeply colored.

Conventionally, EC display elements using this reducing EC compound are:
This EC compound is encapsulated between the electrode plates in an oxidized state.

Therefore, when displaying an image, when a predetermined voltage is applied between the electrode plates, the EC compound is reduced to a reduced state by the electrode plate on the cathode side, and becomes deeply colored, and the pattern of the electrode is displayed. However, in a closed system with no contact with the outside, reducing EC compounds are affected by hydrogen gas generated by electrolysis of water added as a solvent, and even after the applied voltage is removed and the display is erased, A portion of the EC compound in a reduced state remains. Therefore, even after the voltage is removed, the remaining EC compound in a reduced state diffuses little by little onto the display surface, and if used for a long period of time, the entire display surface becomes colored, making display impossible.

Further, in the reflective EC display element, a masking agent is mixed into the EC composition.

As the hiding agent, a material in which the EC composition can flow, such as leaking paper, glass wool, pigment, etc., is used. However, although the EC composition mixed with the above-mentioned masking agent shows good display at first, as time passes, aggregation and precipitation of the masking agent occur, resulting in uneven display on the same display surface or masking. There was a drawback that the effect was lost and the display on the rear electrode plate became visible.

Further, this aggregation causes the masking agent to become large particles, but when this occurs on the transparent electrode, it adheres to the transparent electrode and appears as many dots on the display surface, which is a drawback. In view of the above drawbacks, the present invention enables stable display over a long period of time.
E that also prevents the mixed concealing agent from changing over time.
The object of the present invention is to provide a C display element.

That is, the present invention provides two electrodes in which at least one of them is a transparent electrode.
The feature is that an empty cell is created by arranging two electrode plates facing each other, and an EC composition containing a darkly colored reducing EC compound in a reduced state, a solvent, a masking agent, and a dispersibility as essential components is sealed in the empty cell. The present invention relates to an EC display element.

The present invention will be explained in detail below.

Examples of reducing EC compounds used in the present invention include:
Pyridine derivatives, bipyridinium derivatives, and general formulas (where Y is -CH=N1, -CH=CH-, -C3C
-, -N=N-, -N=○-, etc., R,, R2 is an alkyl group or an alkoxy group, X-
indicates a monovalent anion.

) are used. The EC compound is present in an amount of 0.1 to 1% by weight, preferably 1 to 1% by weight of the total composition weight.
It is 5% by weight.

That is, if the content is less than 0.1% by weight, the display contrast will decrease and the lifespan will be shortened. Furthermore, even if more than 1% by weight is added, the display effect will not change. As the solvent used in the present invention, for example, water or water and water-soluble solvents (alcohols) are preferably used.

Further, in order to use the EC composition as an electrolyte, an electrolyte solution such as NaCl or KBr is used. In order to improve the dispersibility and wettability of the masking agent, the amount of these solvents added should be 25% by weight or more based on the total weight of the EC composition. As a masking agent,
Any fine particles that have insulating properties and can hide the electrodes of the rear electrode plate can be used, and pigments are usually used.

As this pigment, both organic pigments and inorganic pigments can be used, but it is necessary that the pigment be stable even when mixed into the EC composition of the present invention and have a large hiding power.
Note that metal pigments and extender pigments are not preferred. The colors of these pigments are selected depending on the color of the EC compound. Examples of inorganic pigments include white pigments such as titanium oxide, zinc sulfide, and lithopone; black pigments such as carbon black and graphite:
Red pigments: lead seal, cadmium red; yellow pigments: yellow, zinc yellow, cadmium yellow; blue pigments: navy blue, ultramarine, cobalt blue; green pigments: chrome green, emerald green, zinc green; brown pigments: iron oxide, There are Bengara etc.

As an organic pigment, C. 1. By name, there are Yellow 2, Yellow 3, Orange 5, Red 3, Red 4, etc.
Among these pigments, titanium oxide, which is a white pigment, is preferred from the viewpoint of hiding power and display stability. The amount of the hiding agent added to the EC composition varies depending on its hiding power, but it is generally 10 to 7% by weight of the total composition weight, and when the empty cell spacing is from several tens of Angstroms to several thousand piles, A range of 30 to 7% by weight is good, and a range of 40 to 7% by weight is preferred for display stability and precipitation prevention.

A dispersant is added in order to uniformly diffuse the hiding agent and prevent its agglomeration and precipitation.

As the dispersant, anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants are used. Anionic surfactants include carboxylic acid fatty acids, rosin acid soaps, ether salts; sulfate ester alkyl sulfates, sulfate bottles, sulfate esters, sulfamides, sulfate ethers; sulfonic acid alkyl sulfones. Acids, sulfonic acid esters, alkylaryls, alkylnaphthalene sulfonic acids, sulfonated amides, sulfonated esters: hydrophilic group-based phosphate esters, etc.

Particularly effective among these anionic surfactants are alkyl polyether sulfides, alkylaryl sulfides, alkylbenzene sulfides, allylsulfonic acid condensates, higher alcohol sulfonic acid sodium salts, dialkyl sulfosuccinates, These were sulfuric acid ester sodium salt, naphthalene sulfonic acid condensate, bisnaphthalene sulfonate, alkyl allyl ether sulfonic acid sodium salt, 3-naphthalene sulfonic acid sodium salt, and lauryl alcohol sulfuric acid ester sodium salt. The cationic surfactants include simple amine salts such as primary amine salts, secondary amine salts, and tertiary amine salts; quaternary ammonium salts; and pyridinium salts; among these, alkyl Amate salts, quaternary ammonium salts, and pyridinium salts are effective.

Examples of the nonionic surfactants include ether-based alkyl ethers, alkyl allyl ethers, alkyl mercaptan ethers, ester bonds, amino bonds, and amide bonds; ester-based polyhydric alcohol esters, and ether bonds. There are block polymer systems with ester and polyoxypropylene as lipophilic groups.

Among these, particularly effective ones are cellulose glycol sorbitan monostearate, cetyl alcohol, sorbitan alkylate, sorbitan ester, polyoxyethylene alkyl allyl ether, polyethylene sorbitan alkyl ester, polyoxyethylene alkyl amide,
They were polyethylene glycol oleyl ether, polyethylene glycol ester, and polyethylene glycol polyoxyethylene alkyl phenyl ether. Among the amphoteric surfactants, those having an amino group and a carboxyl group, or those having an amino group and sulfuric acid or sulfonic acid had a dispersing effect. In the case of the above-mentioned anionic and cationic surfactants, since they are electrolytes, there is no need to mix an electrolyte solution into the composition.

Furthermore, anionic ones performed well in long-term display operation experiments. Two or more of these dispersants can be used in combination as long as they do not cause reaction or precipitation. Particularly good dispersants are alkylbenzene sulfonates, fatty acid sodas, sorpitane esters, quaternary ammonium salts. The amount of the dispersant added is 0.05 to 5% by weight, preferably 0.3 to 2% by weight based on the total amount of the EC composition.
Weight%.

If it is less than 0.05% by weight, the dispersing effect will be small, and if it is more than 5% by weight, the effect will hardly change.

The EC composition is prepared by the following procedure.

First, a masking agent and a dispersing agent are added to a solvent, and high-speed milling is performed using a bevel mill or a colloid mill. Next, a solution in which the EC compound is dissolved in a solvent and an electrolyte solution are mixed and mixed. At this time, a highly stable EC composition can be obtained by blowing a deoxidized inert gas, such as nitrogen gas, into the EC composition. Note that since EC compounds are normally stored in the atmosphere, they exist in an oxidized state, and EC
It is necessary to bring the compound into a reduced state and encapsulate it between the electrode plates, but in order to bring the EC compound in this EC composition into a deeply colored reduced state, for example, Tsubaki Gansho 51-1750 discloses the following. Such a method can be adopted. That is, for example, hydrogen gas is blown into the EC composition, or a metal having a high reduction potential such as aluminum foil is introduced to bring the EC compound into a reduced state. This EC composition is injected into an empty cell in which a front electrode plate and a rear electrode plate each having a transparent electrode formed thereon are arranged facing each other, and a spacer surrounds the spacer. This injection of the EC compound is performed in an inert gas atmosphere. E of the present invention
Since a C display element is sealed with a reducing EC compound in a reduced state, when no voltage is applied, the entire element is colored in the color of the reducing EC compound in a reduced state; When this happens, the reducing EC compound in the part that is in contact with the anode side electrode plate (front electrode plate) is oxidized and becomes colorless and transparent, and the color of the masking agent, which is a component of the EC composition, appears and is displayed. .

When the voltage is removed, the oxidized reducing EC compound quickly diffuses in the solvent, so the display is immediately erased and the entire device returns to the original color of the reducing EC compound in the reduced state. As described above, since the EC display element of the present invention has a reducing EC compound sealed in the cell in a reduced state, it is similar to the conventional EC display element in which a reducing EC compound is sealed in the cell in an oxidized state. It is possible to prevent the display from becoming impossible to display, and since the concealing agent is stably dispersed, the display can be displayed stably over a long period of time.

This will be explained below with reference to examples.

Example 1 Two glass plates provided with 100/Sakaki indium oxide transparent electrodes were ultrasonically cleaned with Freon solvent, and a low melting point glass frit was applied to one of the glass plates by silk screen printing, and after drying, The other glass plate was placed on top of the other glass plate, and the temperature was raised to 510° C. over about 60 minutes, and this temperature was maintained for about 10 minutes to create an empty cell with an electrode plate spacing of 200 degrees.

5% by weight of titanium oxide (Ti02), 34% by weight of deoxidized distilled water, and one of dodecylbenzenesulfonate sodium salt, sodium oleate, sorbitan monolaurate, and lecithin as a dispersant were mixed. , or five types of liquid A were made without mixing at all.

These mixtures were performed using a ball mill in a nitrogen gas atmosphere. Solution B was prepared by mixing 1% by weight of distilled water and 5% by weight of 4,4-dimethylpipyridinium bromide. EC compositions {11 to {5) were prepared by mixing the above-mentioned five types of A liquids with this B liquid. For the EC composition leg, a certain amount of electrolyte solution KBr was added. Hydrogen gas was blown into the EC compositions m to ① thus prepared to color them blue. This colored EC composition {1} to {5
' was injected into the empty cell under pressure in a nitrogen gas atmosphere, and after injection, the injection port and exhaust port were sealed with resin and ln-Sn metal solder to create EC display elements {1--'5''. .
When a DC voltage of 0.9 V was applied under conditions of 25° C., the white color of titanium oxide in the EC composition appeared on the anode side.

When the voltage was removed, the anode immediately returned to its original blue color. By turning the DC voltage on and off in this manner, the display could also be turned on and off. In addition, the EC display element {11~'51 is held vertically and the voltage is 0.2Hz, 1.8V.
It was driven by applying an alternating current pulse. In the EC display element {51 to which no dispersant was added, flocculation and precipitation occurred after 1 hour, resulting in uneven display. On the other hand, the EC display elements [1' to '4' to which the dispersant was added gave an extremely uniform display and remained stable even after 100 hours had elapsed. In particular, EC display elements using anionic surfactants [11, [2 female 20]
Even after 0q hours had passed, extremely good display could be achieved. Here, ◎, 0, △, and × mean the following. ◎
: Do something abnormal. ○: A slight white color of titanium oxide was generated on the display surface.

Δ: A slight white color of titanium oxide was generated on the display surface, and the contrast was slightly non-uniform. ×: Bad example 0 In the same manner as in Example 1, 50% by weight of titanium oxide, 3% by weight of distilled water, 10% by weight of ethylene glycol, 4,4'
An EC display element was prepared in the same manner as in Example 1 using an EC composition consisting of 5% by weight of dibutyl bipyridinium bromide and 5% by weight of sodium oleate, and when driven, this EC display element also showed good display. Indicated.

As described above, in the present invention, since a dispersant is added, agglomeration and precipitation of the shielding agent are prevented, and a uniform display can be provided for a long time.

Claims (1)

[Scope of Claims] 1. Two electrode plates, at least one of which is a transparent electrode, are placed opposite each other to form an empty cell, in which a darkly colored reducing electrochromic compound in a reduced state, a solvent, and a masking agent are placed. and an electrochromic display element containing an electrochromic composition comprising one or more dispersants. 2. The electrochromic display element according to claim 1, wherein the dispersant is an anionic surfactant. 3. The electrochromic display element according to claim 2, wherein the anionic surfactant is an alkylbenzene sulfonate. 4. The electrochromic display element according to claim 2, wherein the anionic surfactant is fatty acid soda. 5. The electrochromic display element according to claim 1, wherein the dispersant is a cationic surfactant. 6. The electrochromic display element according to claim 5, wherein the cationic surfactant is a quaternary ammonium salt. 7. The electrochromic display element according to claim 1, wherein the dispersant is a nonionic surfactant. 8. The electrochromic display element according to claim 7, wherein the nonionic surfactant is a sorbitan ester.