JPH0216488B2 - - Google Patents

Description

Detailed Description of the Invention The present invention relates to an electrochromic display element (hereinafter abbreviated as EC) that utilizes the electrochromic (hereinafter abbreviated as EC) phenomenon in which the color of a substance changes reversibly through oxidation and reduction reactions caused by the application of a DC voltage. (hereinafter abbreviated as ECD element).

In conventional ECD elements, organic materials such as biologe derivatives and inorganic materials such as tungsten oxide have been used as EC materials.

In a system using a biologe derivative, when a DC voltage is applied to a colorless EC solution layer obtained by dissolving the biologe derivative together with a supporting electrolyte in water or another solvent, the biologe derivative is reduced and colored on the display electrode, which is the cathode. When a voltage of opposite polarity is applied, it is oxidized and returns to its original color, causing it to disappear. This reaction proceeds reversibly. Figure 1 is a cross-sectional view of the ECD element, where 1 is a glass substrate, 2 is a transparent display electrode, and 3 is a cross-sectional view of an ECD element.
is a counter electrode, 4 is an EC solution, and 5 is a spacer.

Using conventional biologe derivative ECD solution
ECD elements had the following drawbacks.

(a) High-speed response cannot be expected because the reaction at the display electrode during coloring and decoloring is rate-determined by the process of mass transfer of biologe derivative molecules to the electrode surface.

(b) Can be used because the solubility in the solvent changes depending on the colored state and the decolored state, and the colored substance must be deposited on the display electrode.
EC substances are restricted.

This invention was made with the aim of eliminating such drawbacks of the conventional ECD element.The feature of the ECD element according to this invention is that the film-like EC material layer covering the surface of the display electrode is made of an EC material and a polymer material. A white porous film-like EC material layer obtained by mixing a white powder filler with a white porous EC material layer, or a white porous EC material layer obtained by mixing a polymer material having an EC functional group in its main chain or side chain with a white powder filler. The point is that the film-like EC material layer is used.

By using a film-like EC material layer, there is no need for the EC substance to move to the display electrode surface, and the rate of the coloring and decoloring reaction is determined by the charge transfer process.
By mixing the white powder filler, the membrane became porous and the effective surface area was expanded, resulting in high-speed response. In addition, this method essentially eliminates the shortening of life due to inhibition of reverse reactions due to crystallization of colored substances deposited on display electrodes, which was observed in ECD elements using conventional viologen-based EC solutions, resulting in a long life. achieved.

In addition, the white powder filler dispersed in the membrane-like EC material layer has a shadowing effect on the counter electrode.
Provided a good background for the display.

A cross-sectional view of the ECD element according to the present invention is shown in FIG. In the figure, 6 is a white powdery filler-containing film.
The EC material layer 7 is an electrolyte solution containing a redox component that reversibly performs a counter electrode reaction and a supporting electrolyte.

As the EC substance used in this invention, EC substances such as organic EC compounds and organometallic complex EC compounds that reversibly change color and decolor through oxidation and reduction reactions upon voltage application can be used. As the functional group, an EC functional group such as an organic EC functional group or an organometallic complex EC functional group can be used.

As the polymeric substance, a wide range of polymeric substances obtained by radical polymerization, ionic polymerization, condensation polymerization, etc., and polymeric substances capable of introducing the above-mentioned EC functional group into the main chain or side chain of the polymer can be used.

The white powder filler is a polymer substance that is white in color, powdery, and constitutes a film-like EC material layer;
It must be stable without causing chemical reactions, decomposition, or dissolution with EC substances and electrolyte solutions.

As materials satisfying these conditions, a wide range of materials can be selected from titanium oxide, calcium carbonate, zeolite, and pigments.

The present invention will be explained in more detail with reference to Examples below.

Example 1 Benzyl Viologel was used as the EC substance, a water-insoluble polymer electrolyte made of vinyl polymer and having a quaternary ammonium salt structure in the side chain was used as the polymer substance, and titanium oxide and titanium oxide were used as the white powder filler. A mixture of zeolites in a weight ratio of 1:2 was used.

An EC substance and a polymer substance were mixed at a molar ratio of 1:2, and a methanol solution was prepared by mixing this with a white powder filler at a weight ratio of 1:3. This solution was applied using a spindle onto a SuO ₂ display electrode provided on a transparent glass plate to form a porous film-like EC material layer containing a white powdery filler. ECD shown in Figure 2 using this glass substrate
Assemble the element and place it between the display electrode and the counter electrode.
Filled with K ₂ SO ₄ aqueous solution. When a DC voltage of about 1 V was applied to this ECD element with the display electrode set as negative, the film-like EC layer on the display electrode turned purple, and when the polarity of the applied voltage was reversed, it returned to its original white color. The response speed during coloring was 60 msec, which was a high-speed response, and the repeated display life was 107 times or more.

Example 2 Dioxane, hydrochloric acid, and an aqueous solution were prepared by mixing titanium oxide as a white powder filler in a weight ratio of 1:5 with a polymer EC material synthesized by the reaction of polystyrene sulfonic acid and viologen as an EC material. . This solution was applied using a spinner onto a SuO ₂ display electrode provided on a transparent glass plate to form a filler-containing porous film-like EC material layer.
Thereafter, an ECD element was assembled in the same manner as in Example 1. When a DC voltage of about 1 V was applied to this ECD element with the display electrode set as negative, the film-like EC layer on the display electrode turned purple, and when the polarity of the applied voltage was reversed, it returned to its original white color. The response speed during coloring was as fast as 50 msec, and the repeated display life was 107 times or more.

The present invention provides a display element comprising an electrochromic material layer formed in the form of a film containing an organic electrochromic substance covering the surface of a transparent display electrode, wherein the electrochromic material layer is formed of a white powder filler. The material is characterized by being porous and containing a large amount of silica, providing high-speed response and a long service life. Furthermore, Japanese Patent Application Laid-open No. 52-6546 discloses a porous thin film impregnated with a display chemical, which is a display material. It disappears easily. In addition, although there are some substances that develop color and become insolubilized, it is necessary to select a display substance that can be insolubilized, which narrows the selection range of display substances.
On the other hand, since the electrochromic material of the electrochromic device of the present invention is not liquid, it is possible to eliminate the disadvantages of the liquid display materials. In addition, Japanese Patent Application Laid-open No. 149047/1983 discloses a porous copolymer resin in which a molecular electrochromic substance having electrochromic properties is bonded.
Generally, porous polymers have high transparency, and when used in display devices, they are used to obtain high contrast display.
It is necessary to provide a shield plate on the counter electrode. or,
The electrochromic material must have a reactive group capable of reacting with the porous copolymer resin, which narrows the range of choices. On the other hand, since the electrochromic device of the present invention uses a white powder filler, it is opaque and can provide a high contrast display without using a shielding plate. Furthermore, since the electrochromic substance and the white powder filler are not reacted, the range of electrochromic substances to be selected is widened.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional electrochromic display element, and FIG. 2 is a sectional view of an embodiment of the present invention. In the figure, 1 is a glass substrate, 2 is a transparent display electrode, 3 is a counter electrode, 5 is a spacer, 6 is a porous membrane electrochromic layer, and 7 is an electrolyte solution. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A display element comprising an electrochromic material layer formed in the form of a film containing an organic electrochromic substance covering the surface of a transparent display electrode,
An electrochromic display element characterized in that the electrochromic material layer contains a white powder filler and is porous. 2. The porous electrochromic material layer is a mixture of an organic electrochromic material, a white powder filler, and a polymeric material serving as a binder;
The electromic display element according to claim 1, wherein the electrochromic display element is formed of a mixture of a polymer material having an organic electrochromic functional group in its main chain and a white powder filler. 3. The electrochromic display element according to claim 2, wherein an electrolyte solution is filled between both electrodes.