JPS61166526A - Electrochromic display element - Google Patents

Abstract

PURPOSE:To improve a productivity and to depress the production cost in the production of the title element by coating an EC material layer composed of hexacyanoferrate prepared by the well-known electrolytic film forming method with a mixture composed of an inorganic pigment having an electrochromisum, conductive powders and a binding agent, followed by drying. CONSTITUTION:The EC material layer is prepared by coating the mixture composed of the inorg. pigment having the electrochromisum, the conductive powders and a binder, and then by drying. As the EC material layer is prepared by coating said mixture and drying, the preparation of the title element makes easily whereby the productivity of the title element is enhased, and the production cost thereof is reduced. As for the inorg. pigment having the electrochromisum hexacyanoferrate is used, and as for the conductive powder white one is preferble. The preferable compounding ratio of the components capable of forming the EC material is for example, 5-40wt% inorg. pigment having the electrochromisum, 10-70wt% conductive powders and 10-80wt% binding agent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an electrochromic display element (hereinafter abbreviated as ECD) using an inorganic pigment exhibiting electrochromism as an electrochromic substance.

"Prior art and its problems" In recent years, ECUs have no viewing angle dependence and can display large areas.
It has been attracting attention as a display element for reasons such as its display having memory properties. A variety of organic and inorganic materials are used as display materials for EOD, but unlike organic materials that mainly use a single dye, inorganic materials are stable for long periods of time due to their simple molecular structure. Be expected. The most common inorganic materials are transition metal oxides such as tungsten oxide and iridium oxide, but recently transition metal mixed-valence complexes, typified by iron hexacyanoferrate, have been attracting attention.

Iron hexadipenferrate is a type of pigment known as Prussian blue or Berlin blue.
It has a basic structure in which a cyano group bridges Fe(m) and Fe(II). And Fe(I) in the crystal structure
When II) is electrochemically reduced to Fe (■), it becomes colorless, and when it is oxidized back to Fe (m), it exhibits a beautiful blue color. This redox reaction can be performed reversibly.

Since the ECD using iron hexacyanoferrate has a stoichiometric coloring/decoloring reaction, it can be expected to have a long operating life.

Conventionally, when forming an electrochromic material layer (hereinafter abbreviated as EC material layer) made of iron hexadipenferrate on a display electrode, a mixed solution of, for example, aqueous potassium cyanide solution and ferric chloride solution was used. A so-called electrolytic film formation method was used in which a display electrode and a platinum electrode were immersed, and electrolysis was performed using the transparent electrode side as a cathode and the platinum electrode side as an anode to deposit iron hexacyanoferrate on the display electrode.

However, when forming an EC material layer by the electrolytic film formation method described in J: above, it is necessary to pass current to each display electrode, and the current application time is also required to be approximately several hundred to 1000 seconds, which reduces productivity. There was a problem that the manufacturing cost was high.

"Objective of the Invention" The object of the present invention is to facilitate the formation of an EC material layer and to enable it to be manufactured at low cost and with high productivity when an inorganic pigment exhibiting electrochromism such as iron hexacyanoferrate is used as an EC material. The objective is to provide EG [I that has been improved.

"Structure of the Invention" The present inventor has discovered that iron hexacyanoferrate, which has conventionally been produced and supplied in large quantities at low cost as a pigment under the name of Prussian blue or Berlin blue, and iron hexacyanoferrate obtained by electrolytic deposition method (7) iron ferrate. Noting that they are the same substance, the present invention was developed as a result of various studies on methods of fixing pigments on transparent electrodes so as to make them electrochemically active.

That is, in the HCD of the present invention, an electrolytic solution is interposed between a display electrode and a counter electrode, an EC material layer is formed at least inside the display electrode, and the EC material layer is an inorganic pigment exhibiting electrochromism. It is characterized by consisting of a coated and dried layer of a mixture of conductive powder and binder.

1' Therefore, the formation of the EC material layer is extremely easy since it is only necessary to apply and dry the above-mentioned mixture, thereby increasing productivity and reducing manufacturing costs.

Although the structure of the ECD of the present invention is not particularly limited, it can be, for example, the following structure. That is, a transparent display electrode made of indium oxide, tin oxide, etc. is formed on a transparent insulating substrate such as glass, and then an EC material layer is formed by coating and drying the above mixture on this display electrode. Ru. In this case, the display electrodes and the EC material layer are patterned. On the other hand, a counter electrode made of a transparent electrode or a metal thin film similar to the above is formed on another insulating substrate. Then, the insulating substrate on which the display electrode is formed and the insulating substrate on which the counter electrode is formed are bonded together via a spacer, and the peripheral portion is adhesively sealed with epoxy resin or the like. An electrolytic solution is injected into the cells thus formed to form an ECU. Note that an ion-permeable white background plate or the like may be provided between both substrates, and further,
If white conductive powder is used as the conductive powder, the white background plate can be omitted. Furthermore, the EC material layer may be formed on both the display electrode and the counter electrode.

As the inorganic pigment exhibiting electrochromism that forms the EC material layer, for example, iron hexadi-7ferrate can be used. Further, as the conductive powder, as mentioned above, white powder is preferable, and for example, "To 10" (trade name, manufactured by Mitsubishi Metals Corporation) can be used. Note that in the case of the EC material layer formed on the counter electrode, non-white powder such as carbon can also be used as the conductive powder. Furthermore, various resins, solvents, or mixtures thereof can be used as binders, such as 3% polymethyl methacrylate resin.
Carpitol acetate solution etc. can be used.

The blending ratio of the components forming the EC material layer is not particularly limited, but for example, an inorganic pigment exhibiting electrochromism 5
~40% by weight, conductive powder 10-70% by weight, binder 1
The EC material layer is formed by mixing these components, preferably about 0 to 80% by weight, and applying the mixture in a predetermined pattern by means such as screen printing, followed by drying.

Furthermore, various electrolytes such as potassium chloride, rubidilam chloride, cesium chloride, and potassium sulfate can be used as the electrolyte.

"Embodiments of the Invention" FIG. 2 shows the structure of a display electrode portion employed in an ECD according to the present invention. That is, commercially available insoluble Berlin Blue pigment powder (ferric hexacyanoferrate powder) (F
! ! (manufactured by German Chroma) 9 and conductive white powder rW-10
J (trade name, manufactured by Mitsubishi Metals Corporation) 10 in a mortar. A 3% calpitol acetate solution of polymethyl methacrylate resin (abbreviated as PMMA, trade name "Acrypet", manufactured by Mitsubishi Rayon Co., Ltd.) as a binder 11 is added to this and further mixed. The dispersion liquid thus obtained is collected with a dropper and dropped onto a transparent electrode 2 of an insulating substrate 1 made of transparent glass. And 100℃
Dry for 15 minutes to form an EC material layer 4.

Using the thus obtained insulating substrate 1 on the display electrode side,
A cyclic portamogram was measured by the three-electrode method as shown in FIG. 3, and the electrochromism characteristics were investigated. In Figure 3, 12 is a silver silver chloride reference electrode, 13 is a platinum mesh counter electrode, 14 is a 0.5 molar potassium sulfate aqueous solution,
15 is a beaker, IB is a potentiostat, 17 is an X
-Y recorder. The obtained cyclic portamogram is shown in FIG. 4. As shown in FIG. 4, a clear redox peak was obtained, and at the same time, a clear blue-white color change was obtained in the EC material layer 4. Furthermore, in FIG. 5, which shows the absorption spectrum of the EC material layer 4, A and B correspond to points A and B in FIG.

FIG. 1 shows an ECU made using the display electrode portion shown in FIG. 2. That is, a counter electrode 7 is formed on an insulating substrate 8 made of glass, and a layer 6 similar to the EC material layer 4 is further formed on this counter-type aiT. This calendar 6 was formed in the same manner as the EC material layer 4 by using graphite powder (trade name rAUP J, manufactured by Nippon Graphite Co., Ltd.) instead of the white conductive powder 10 of the EC material layer 4. 1. Then, the insulating substrate 1 on the display electrode side and the insulating substrate 8 on the counter electrode side are bonded together with the spacer 3 interposed therebetween.

The periphery is sealed with epoxy resin. Roughly speaking, an electrolytic solution 5 consisting of a 0.5 molar potassium sulfate aqueous solution is injected into the inside of the cell. This ECD has a counter electrode 7
When +0.2V was applied to the display electrode 2, the color became blue, and when -0.8V was applied to the display electrode 2, the color became white, showing a clear color change.

Although the above examples use iron hexacyanoferrate, it is clear that the present invention can be applied to other inorganic pigments exhibiting electrochromism.

"Effects of the Invention" As explained above, according to the present invention, an EC material layer made of iron hexadipenferrate, which was conventionally formed by an electrolytic deposition method, is replaced by an inorganic pigment exhibiting electrochromism.
It can be formed by coating and drying using a conductive powder and a binder. Therefore, productivity can be improved and manufacturing costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the ECD according to the present invention, and FIG. 2 is a partially enlarged sectional view showing the display electrode portion of the ECD.
Fig. 3 is a block diagram showing a circuit for investigating the electrochromic characteristics of the display electrode portion, Fig. 4 is a cyclic portammogram obtained by the method shown in Fig. 3, and Fig. 5
The figure is a chart showing the absorption spectra of the display electrodes mentioned in section 1. In the figure, 1 is an insulating substrate, 2 is a display electrode, 4 is an electrochromic material layer, 5 is an electrolytic solution, 7 is a counter electrode, 8 is an insulating substrate, 3 is iron hexacyanoferrate powder, IO is a white conductive material powder, 11 is a binder. Figure 4 Figure 5 Waves

Claims (2)

[Claims] (1) An electrolyte is interposed between the display electrode and the counter electrode,
In an electrochromic display element comprising an electrochromic material layer formed inside at least the display electrode, the electrochromic material layer is formed of a layer formed by coating and drying a mixture of an inorganic pigment exhibiting electrochromism, a conductive powder, and a binder. An electrochromic display element characterized by: (2) The electrochromic display element according to claim 1, wherein the inorganic pigment exhibiting electrochromism is iron hexacyanoferrate.