JPH02294384A - Electrochromic element - Google Patents

Abstract

PURPOSE:To prevent reduction in quantity of reaction electricity in fading and allowing to stand and to improve coloring performance by covering an electrochromic layer consisting of Prussian blue film and WO3 film with a MoO3 film having specific thickness. CONSTITUTION:A first electrode of a substrate with a pair of electrodes wherein the substrate 1 and/or the electrodes 2 are transparent is provided with a Prussian blue film 3 as a first electrochromic(EC) layer and a second electrode is equipped with a tungsten oxide film 5 as an EC layer. In opposing both EC elements, the tungsten oxide film 5 on the second electrode is covered with molybdenum oxide film having 50-1,000Angstrom thickness to give the aimed EC element.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to improving the coloring performance of an electrochromic element after being left to decolor by using the electro-qchromic (EC) phenomenon.

(Prior Art) As an electrochromic element, there is one shown in FIG. 1, for example (Japanese Patent Laid-Open No. 147237/1983). This electrochromic element has a Prussian blue film 3, which is an EC material, which is colored during oxidation and discolored during reduction, on a transparent electrode 2 provided on each of the pair of transparent substrates 1.
A tungsten oxide (WO3) film 5, which is an EC material that decolorizes during oxidation and changes color during reduction, is formed and placed facing each other.
Electrolyte 7 (1.0M LiC104+
(1 to 2) Propylene carbonate solution of %H20 by weight) and an auxiliary electrode 4 coated with an insulating material 8 are sealed with a sealing material 6. By oxidizing one EC substance and reducing the other at the same time, , both EC substances color and fade at the same time. Furthermore, it includes a repair means 9 for correcting the charge balance.

(Problem to be Solved by the Invention) However, in such conventional electrochromic elements, if Prussian blue is left in a reduced and decolored state for a long time, a reaction for coloring will occur next time. The amount of electricity decreases, making it impossible to color the product in the required amount. This can be recovered by repeating coloring and decoloring or by leaving it in the colored state, but for complete recovery it is necessary to leave it in the colored state for a long period of time (several days or more). Sexuality is significantly reduced.

(Means for Solving the Problems) As a result of intensive research into the above-mentioned problems with conventional electrochromic elements, the inventors found that the cause was thought to be some kind of substance eluting from the tungsten oxide film, perhaps a type of polytungstate ion. They came to the conclusion that this causes a change in the Prussian blue film left undiscolored, causing a decrease in the amount of reaction electricity in the Prussian blue film. Regarding the electrochromic reaction of Prussian blue, there is a paper by Neff showing the EC characteristics (J. Electrochem. Soc.
+125 (197B)886. ) has been published, a considerable amount of research has been conducted, but there are still many things that are unclear regarding the basic reaction mechanism, and various methods are still being investigated. Roughly speaking, the EC reaction of Prussian blue can be considered as follows.

(Blue) + M''+e-2 (Prussian Nephite) Blue Colorless and transparent M0 is a cation such as Li' or Na''. The problem here is that when Prussian blue is reduced, cations are injected from the solution to maintain electrically neutral conditions within the membrane, resulting in Prussian white. As a result, when this Prussian white is reoxidized, the reaction becomes at least partially difficult to occur.In normal driving for several minutes, the amount of reaction electricity decreases and the degree of coloring decreases. This is thought to be due to a significant decrease. Therefore, it has been found that the problem may be solved by cutting off some of the routes by which the problematic substance released from the Woff film reaches Prussian blue. In this invention, as a result of studies based on the above knowledge, this problem is solved by covering the -03 layer with a layer of Mo03 as a layer that allows Li' ions to pass through and at the same time suppresses the permeation of the problem substance from the -03 film. Settled.

That is, the electrochromic device of the present invention includes a Prussian blue film as a first electrochromic layer on the first electrode of a pair of substrates with electrodes, at least one of which is transparent, and a Prussian blue film on the second electrode. In an electrochromic element comprising a tungsten oxide film as an electrochromic layer and an electrolyte layer disposed between two opposing electrochromic layers, the tungsten oxide film on the second electrode is coated with a tungsten oxide film having a thickness of 50 to 100 mm. It is characterized by being coated with a membrane.

Here, 10. Mo, which is thought to behave similarly to a film,
The exact reason why the 03 membrane is effective is unknown, but it is thought to be as follows. The Mo03 film shows a cyclic portamogram like the solid line in Figure 2. It reacts at about 0.4 to 0.5 V more positively than the same three films in the same figure, so it cannot be completely driven by normal driving. Since it is not oxidized and remains in a partially reduced state, it is thought that this may work favorably as a result.

(Examples) The present invention will be specifically explained below using Examples and Comparative Examples.

First, the structure of the electrochromic device will be explained using FIG. 1. 1 is the board (100mm x 100
mm x 1.2 mm glass), 2 has a surface resistance of approximately 20Ω/
Nesa film (transparent electrode) at the mouth, 3 is a Prussian blue film with a thickness of approximately 4000 mm formed by electrodeposition, and 5 is a film formed by vacuum evaporation method (degree of vacuum: 5 XIO-'torr) with a thickness of approximately 4000 mm. Human tungsten oxide film (Woff), 4
is an auxiliary electrode for reducing the Prussian blue film that is in an oxidized state during film formation to bring the cell to its initial state, and for compensating for the charge balance shift between both electrochromic layers. 4#-}liphenylamine) (Japanese Unexamined Patent Publication No. 60-212420), carbon, and a Teflon binder. 6 is a sealing material. As the electrolyte 7 in this cell (1.OMLiC10a
+ 1.2% by weight H20) propylene carbonate solution was injected, and using the auxiliary electrode covered with the insulating paper 8 of 4 as a counter electrode, Prussian blue, which was in an oxidized state immediately after fabrication, was reduced to a reduced state and its color was erased. Coloring and decoloring can be achieved by setting the potential of Prussian blue to 1.0 and -0.5, respectively, relative to tungsten oxide. The area of the display part of this cell was 60 cm.The ratio of the amount of electricity in the first reaction after leaving this cell in a decolorized state for a certain period of time to that before leaving it is shown by the broken line in Figure 3. The cell almost completes the reaction in around 20 seconds, but in order to clarify the phenomenon, the amount of electricity flowing in the cell for 3 minutes after setting each voltage was used as the amount of reaction electricity.Similarly, Although there are some variations among the cells manufactured using the same method, the broken line in FIG. 3 is an average value.

A cell was constructed in the same manner as in Comparative Example 1, except that the film was replaced with a MoO 3 film with a thickness of approximately 4000 nm made by vacuum evaporation, and the Prussian blue was reduced and decolored. Also, coloring and decoloring was attempted in the same manner as in Comparative Example 1. the result,
Similarly, the color was colored, but even when the voltage was set to -0.5V, the color could not be completely removed. Even if the voltage was further increased to a negative value, the color could not be completely erased. Therefore, it is considered difficult to use a combination of Prussian blue and Mob without causing side reactions that lead to deterioration.

A cell was fabricated in the same manner as above, except that the A03 film in Comparative Example 1 was covered with a MoO film of about 100 mm thick (deposited at the same degree of vacuum as the WOs film) by vacuum evaporation. The solid line in FIG. 3 shows the ratio of the amount of reaction electricity when the sample was constructed and left to decolor. As can be seen from the figure, in Comparative Example 1, the amount of reaction electricity decreases considerably when left to decolor, but in this example, there is almost no change.

Although it was observed that the response speed was slightly slower, the transmittance when decoloring was visually observed to be almost the same as normal.

Implementation I The same procedure was followed as in Comparative Example 1, except that the 10 film in Comparative Example 1 was covered with a Mob film of about 200 people in thickness (deposited at the same degree of vacuum as the WO 3 film) by vacuum evaporation. A cell was constructed. The decolorized state was a little darker than normal when visually observed, indicating that the MOO and J films were in a shallow reduced state. As in Example 1, almost no decrease in the amount of reaction electricity was observed when the color was left to stand.

(Effect of the invention) As explained above, the Prussian blue membrane and the WO.
The electrochromic device consists of a film, the film is Mo.
b. According to this invention, which prevents substances that cause problems with Prussian blue from reaching the Prussian blue film by coating with a thin film, the required amount is sufficient due to the small amount of reaction electricity after decolorization seen in conventional electrochromic devices. This can solve the problem of not being able to be colored, and has the effect of significantly improving the quality of electrochromic devices.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the electrochromic device, Figure 2 is a cyclic voltammogram diagram of Mob, membrane and -03 membrane in 1.0M LiClOa propylene carbonate solution, Figure 3 is Example 1 and Comparative Example 1. FIG. 3 is a diagram showing a change in the amount of reaction electricity when the cell is left to decolor. 1...Substrate 2...Transparent electrode 3...
・Prussian blue membrane 4...Auxiliary electrode 5...Tungsten oxide film 6...Sealing material 7...Electrolyte solution
8... Insulating paper 9... Repair means

Claims (1)

[Claims] 1. A Prussian blue film is provided as the first electrochromic layer on the first electrode of a pair of substrates with electrodes in which at least one of the substrates and the electrode is transparent, and a tungsten oxide film is provided as the electrochromic layer on the second electrode. In an electrochromic element comprising: an electrolyte layer disposed between two opposing electrochromic layers,
The thickness of the tungsten oxide film on the second electrode is 50 to 100.
An electrochromic device characterized by being coated with a 0 Å film of molybdenum oxide.