JPS5858522A - Electrochemical display element - Google Patents

Abstract

PURPOSE:To obtain a stable ECD having good driving performance and visibility by using display electrodes provided with iron hexacyano-ferrate films on a substrate having a conductive surface and using univalent cations as one of mobile ions of an electrolyte. CONSTITUTION:Iron hexaamino-ferrate as an electrochemical coloring material is electrolytically deposited on transparent electrodes provided with an SiO2 film on a glass substrate to provide a working electrode of an ECD. The EC film is a blue pigment known as prussian blue, and its chemical structure is expressed by the formulasI, II. Said film is a mixed valency complex wherein tervalent iron and bivalent iron exist simultaneously in the same crystal. If the tervalent iron is fully reduced to the bivalent iron, the blue color disappears without any change in crystal structure and becomes colorless. The chloride contg. univalent cations expressed by the formula II is used as an electrolyte of the ECD. The ion radii of the cations resemble and the cations go into and out from the EC film complex, thus providing the ECD having long-term stable driving performance.

Description

DETAILED DESCRIPTION OF THE INVENTION This component is an electrochromic display element that utilizes the reversible optical change of an electrochromic color substance caused by an electrochemical redox reaction. Electrolyte VrIgl when iron hexacyanoferrate is used.

In recent years, with the advancement of electronics technology, the demand for display devices as output devices for small portable information devices such as wristwatches and calculators has increased significantly. Currently, there are display devices that use liquid crystals that provide such **.

Crystalline display pupils have some advantages, such as an acceptable fast response and a somewhat proven longevity.

In general, the display is dark, viewing from an oblique direction is difficult, and there is a viewing angle dependence, and there are disadvantages that cannot be ignored, such as lack of visibility and beauty, which should be the most important characteristics of a display device and a display device. A new display that solves the drawbacks of liquid crystal display devices and a phenomenon in which a certain yuzu substance exhibits a reverse color change due to electrographic acid reduction have been developed. Research and development of elm and trochrochromic displays have been actively carried out.Such electrochemical color-forming substances and [7teri] have conventionally been mainly used with viologen, which is an alkyl quaternary conductor of γ0, T3-dipyridyl. In addition, transition metal oxides such as tungsten oxide are used.

This smart product is a new electric coloring product that was previously unknown, unlike the above. This invention relates to an electrochromic display device containing iron hexacyanoferrate.

For example, when using viologen as a conventional electrochemical coloring substance, TLR takes advantage of the reaction of formula (1) in which nine colored viologen radicals are precipitated on the cathode surface when the electrolytic amount in which viologen is dissolved is electrolytically reduced. ing.

P: Alkyl group In this way, the color shown is because the reaction occurs in the form of electrolytic surface Hellopods being deposited even from the electrolyte.

Since it is determined by the amount of precipitates deposited on the deuterium, it has the disadvantage that a constant color tone cannot be obtained unless the amount of charge in the prime area of one electrode is precisely controlled. Because it lacks stability in writing itself! ! It had the disadvantage of being susceptible to deterioration due to repeated monoxide reduction.

MafC, as a conventional acetic chemical agitating substance: II! In systems using tungsten oxide, which is a transferable metal oxide.

A layer of tungsten oxide ff fixed on the electrode surface.

Equation (2) is used to color tungsten bronze, which is produced by a reaction between electrons from the W pole and metal ions injected from the electrolyte at once.

(2) Equation 4) In order for the reaction to be electrochemically reversible,
In formula (2), X≦(1S must be satisfied, and x>1
5 cannot be used for display because the reaction is irreversible. Therefore, in a display device that uses such a non-stoichiometric reaction, the amount of electrolyte must be kept constant so that the large jump of X does not exceed the range of reversibility. The drawback was that it was difficult to drive and was not suitable for playing games.

The present invention uses iron hexacyanoferrate as a new and excellent electrochemical coloring material that does not have the drawbacks of the conventional electrochemical coloring materials described above. Hexacyanoferrate iron salt used in this invention, general V
r is basically a -1 compound with the blue pigment known as Prussian blue, and has the linear composition formula (4), (
The group of compounds shown in 5) is shaded.

F e(fall('F e(1'lF e(1)(0
14) a) s...Insoluble Prussian blue
(4) M”(V e(m)F (30I) (011)
@ ) - Soluble Prussian blue (5)
Here, M keh Li , laa , K , R
b.

Refers to monovalent metal ions such as NH4''.

Both (4) and (5) generally exist as three-dimensional complexes exhibiting an insoluble cubic structure, and the cyano group is Fe(
Basic upper F that bridges TIJ and Fe (I[)
, in (4) the ferric ion and in (5) the gold ion M+ have an interstitial crystal structure, such that divalent iron and trivalent iron exist in the same Vr crystal. Iron exists at the same time. Because it is a so-called mixed valence complex, it exhibits the beautiful blue color characteristic of Prussian blue. If all the trivalent iron in the crystal formation is reduced to divalent iron, there will be no major change in KFi, the crystal structure, but the blue color will be lost and it will turn colorless. do.

This idea is based on the principle Vr of changing the color tone by reversibly changing the trivalent iron in the above-mentioned mixed valence complex between trivalent and divalent through electric reduction and oxidation. The reaction is shown by formula (6) and formula (6Y).

In an electrochromic display device using hexacyanoiron as an electrochemical color separation substance, the color tone is changed by electrochemical reaction of a layer fixed in advance on the surface of one display electrode as a thin film of an insoluble three-dimensional complex. Since it uses a modified iron and does not involve repeating precipitation and dissolution from VrlW like the viologen mentioned above, it is determined by the thickness of the combined 1r material and hexacyanoferrate iron salt. It can be held at a certain concentration #If@. In addition, one reaction formula (6
) As is clear from the reaction of F and tungsten oxide, the reaction is not non-stoichiometric as in the case of formula (2), but is an electronic reaction based on the writing theory.1 When driving a display device, There is no need to closely control the amount of electrolysis.

Is it driving or flattering? In addition, the blue pigment known as Prussian blue has been widely used as a pigment in paints and printing inks since ancient times. As described above, the present invention allows the display to be easily driven with a color tone of a constant density.
The chemical stability of colored species has been scientifically proven. The present invention realizes a beautiful, dark blue (Prussian blue) electrochromic display device.

Next, when using iron hexacyanoferrate used in this invention as an electrochemical coloring substance, we will discuss how the selection of electrolytes is a matter of superposition.

Iron hexadi-7-ferrate has an insoluble pull as shown by formula (4).
) Whether it is cyan blue or the soluble Prussian blue shown in equation (5), Vr in the coloring substance changes due to the oxidation and reduction between the color state and the colorless state. In order to compensate for the negative charge, the entry and exit of positively charged cations is also essential. Formation N6 As far as formulas (6) and (6)l are concerned, Vr can be used so that the reaction formula formally holds true with any cation. But 7.
Prussian blue is a mixed valence complex with a three-dimensional structure as shown in the diagram.

It is a crystal belonging to the cubic system with a lattice constant IQ of 2A.

The plane 14j1 interval is 51st, but each ion forming the lattice has a large bottleneck considering the size of the atom.
As shown in the figure, it is 55s. The size of this bottleneck ζ is expected to limit the size of ions that enter and exit during oxidation and reduction of Prussian blue.

Based on the above reasons, this wisdom is based on Hexaji 7.
The electrolyte for electrochromic displays using iron ferrate as a color separation substance, %ff cation, was properly selected.

I will give a concrete explanation of Ippon Wise based on DJ Shimosaise fullff.

Example 1 Iron hexacyanoferrate, a color separation substance, was formed on the surface of one display electrode by an electrochemical method. first.

+111f20ξ mol/liter of 7 Elysian and potassium, rum (KsIFe ((3N)@) aqueous solution,
Hydrochloric acid () I (?!/) is mixed with a volume of ferric chloride aqueous droplets dissolved in a 102N aqueous solution to give a concentration of 20 mmol liter to give a brownish-transparent solution.This brownish-brown transparent solution A platinum electrode with an area of 11% (snow) having electron conductivity on the surface of which hexacyanoferric acid ridges are to be formed is immersed in the solution.・The transparent electrode is used as a cathode, the platinum electrode is used as an anode, and a current of 10 μm is electrolyzed at 1
It lasted 0 minutes. After the electrolysis was completed, blue iron hexacyanoferrate was formed on the transparent electrode.

Next, an experiment was conducted to select an optimal electrolyte using the thus formed transparent electrode coated with iron hexacyanoferrate as a working electrode. First, the above-mentioned action voltage &1 area 10
A 5-electrode electrolytic cell is formed using a 0- platinum counter electrode and a saturated Amagi electrode as a reference, and the potential of the working electrode is set between 1=, -(L2V and +〇, 6V on the reference electrode) in one type of electrolyte. The working electrode, which is the 0-display W pole, is driven by a rectangular wave pulse to perform color development and decolorization, and is colorless at a potential of -α2V and blue at +0.6'V with respect to the reference electrode. .

The electrolyte cation was selected by performing many cycles of color development and decolorization.

The evaluation standard used a numerical value called residual film rate.

The residual film rate was defined using the amount of electricity possessed by one working electrode, an electrode covered with iron hexacyanoferrate, as follows.

The amount of electricity was measured by connecting a coulometer (coulomb meter) to the five-electrode electrolytic cell.

The reduction in the residual film rate is due to the color-forming substance Hexacyano & IP! ! #This is thought to be an indicator of membrane destruction due to electrolyte cations entering and exiting iron.

As electrolytes to be evaluated, HC/, LiCff, NaO
f.

K,Of,'BbCl, and080/ (')61
The vehicle test described above was carried out once using a 11N aqueous solution. Outside HC/μj, PH4 and [)VrM were adjusted. The results are shown in Figure 5.

As is clear from Fig. 95, it was found that ff, KcI Rt+O/ and C-5ol stably drive the iron hexacyanoferrate display electrode.

Example 2　Method for forming a display electrode using iron hexacyanoacetate, which is a color-forming substance,
The test method is as follows: 1 and (b).

As the electrolyte to be evaluated* BeCt m + Mg O
/ Proverb TOak/@ and SrC! /m of saturated alkaline earth chloride droplets were used. A glance at PHti4.0,
When we tested Example 1 and one IW machine, B! Lc
/'l only.

A residual film rate of 20% was obtained after 10 cycles. I didn't mind doing 10 cycles with other electrolytes.

Banjos could not be put to practical use after 10 cycles, and divalent alkaline earth gold Kaede was found to be unsuitable.

Examples & Method of forming a display electrode using iron hexacyanoferrate, which is a color-forming substance,
The test method is the same as the 11th test.

As an electrolyte to evaluate* NH4C/ NM and NM
@aCI NKtaCl, NPr101 and NBuaG/@4 class ammonium salts were used. Dark 1
hNH*oe was [L I N h et al. used saturated aqueous oil.

PI (adjusted to 4.0).

As a result, as shown in Figure S, the cycle test for NHaC/ was found to be completely stable, and it was found to be suitable as an electrolyte for the iron hexacyanoferrate covered electrode. Sen's body quaternary ammonium salt is t) Zuka I
FNMe4Cl caused 20% thinning in Lie/ and -sheath 1, ie 10 m cycles, but otherwise was completely inadequate.

Summarizing 1.2.5 in simple IIL, hexacyanoferrate-accumulated lightning pole** K"0wb", cg" and N
This is due to stable f-drive by only Ha-valent cations. This fact can be rationally clarified from Table 1 shown below and the naivety of the bottleneck shown in Figure 2. Table 1 shows the Stocks radius, which is one indication of the ion ml and the irrigated ion radius.

Furthermore, the crystal ionic radius is shown. There is a surprisingly good correspondence between the types of ions that can stably enter and exit the hexacyanoferrate IF and the Stokes ion radius of 11-t.

Surface type Ion type and ion radius According to the present invention, iron hexacyanoferrate can be stabilized by Vr.
Fi that we were able to select a cation that could be driven;
Its value in terms of longevity of electrocrocism display is baking soda.

The industrial value is great.

4. One plane of sharp contrast. Figure 1 shows the crystal lattice of iron hexacyanoferrate.
The circle indicates the iron ion, and the one that matches the charcoal is Fe.
(II), I! Fe(
2)). Saraff, Interstitial Fe
(2) Monovalent cations for fc are omitted for simplicity.

Figure 2 is a diagram showing the magnitude of the bottleneck of iron hexacyanoferrate. FIG. 5 is a graph showing the residual film perforation and cycle number of the iron hexacyanoferrate-coated electrode for the case where various cations were mixed with IIr solute and 17 times.

Fishing Applicant: Daini Kozue Kosha Co., Ltd.

Claims (1)

[Claims] (1) An iron hexacyanoferrate film in close contact with a base material having electron conductivity on at least 9 sides is used as an indicator, and an electrolyte and a strong electrode are used to generate #I electricity. An electrochemical display element in which one mobile ion in the electrolyte is a monovalent cation. (2. An electrochemical display element characterized in that the monovalent cation described in claim 1 is an alkali metal ion. (5) The alkali metal ion described in claim 2 is potassium ion, rubidium ion. %lr!f#I which is a cesium ion
The electrochemical display element according to the first and second terms of the range of lf requirements. (4) - An electrochemical display element characterized in that the monovalent cation according to claim 1 is an ammonium ion. (5) An electrochemical display element characterized in that the monovalent cation described in claim 1 is a combination of at least two of potassium ions, rubidium ions, cesium ions, and ammonium ions.