JPS60262139A - Electrochromic display element - Google Patents

Abstract

PURPOSE:To increase response speed and to improve display life by forming a transparent display electrode to one of two sheets of substrates facing each other and a counter electrode on the other and forming the counter electrode in such a manner that an insulating layer sandwiched by the 1st conductive layer and the 2nd conductive layer faces the display electrode. CONSTITUTION:The display electrode 2 consisting of a transparent electrode of In2O3 or SnO2 is provided on a glass plate 1 and the counter electrode 3 facing the electrode 2 is provided on the plate 1. The electrode 3 is formed by providing the insulating film 7 between the 1st conductive film 6 and the 2nd conductive film 8 in the position facing the electrode 2. Both substrates facing each other are sealed 4 by an epoxy resin or low-melting glass and a non-displayable material 5 is sealed between said substrates. The films 6, 8 are formed of the transparent conductive films consisting essentially of In2O3 or SnO2. A metallic oxide (SiO2, Al2O3), etc., metallic fluoride (CaF2, MgF2, etc.) or metallic nitride (Si3N4, etc.) is used for the film 7.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electrochromic display element used for various displays such as watches, measuring instruments, and home appliances.

Conventional Structures and Problems Compared to liquid crystals, which are one type of light-receiving display, electrochromic displays have no viewing angle dependence and are characterized by bright and clear colors. Electrochromic materials are classified into two types: inorganic materials and organic materials. Transition metal oxides, especially WO3, are well known as inorganic materials. As organic substances, dyes such as viologen, anthraquinone, pyrazoline, and styryl-based compounds are known. In addition, the use of complexes such as lidded cyanide and Prussian blue, or thin films of conductive polymers has recently been announced.

A thin film is formed on a transparent electrode of WO2 by vapor deposition or the like, and an electrolytic solution, a dielectric film, etc. are provided between counter electrodes to form an element. Practical problems with WO2 include, in addition to the display life, color unevenness between display segments and the fact that the coloring is only one blue color.

Unfortunately, in connection with improving display life, there is a problem in that in order to stabilize the counter electrode reaction, the counter electrode material must be improved and reflectors and the like must also be incorporated into the device.

On the other hand, compared to inorganic materials, organic dyes have the possibility of diversifying coloring types, but generally have a problem with display life.

Viologen dyes are subject to the phenomenon of insolubility and solubility in solvents depending on whether the color develops or fades, and this problem of reversibility greatly affects display life.

However, oxidation-reduction reactions of dyes still cause decolorization, but since ions are involved in these reactions, ions may have an adverse effect on transparent electrodes, etc.
Another problem is that the power consumption is large. Similar problems exist with other organic dyes and complexes.

The characteristics that current electrochromic displays are inferior to liquid crystal displays are display life and response speed. The present applicant previously proposed an electrochromic display element using a dye, which is a type of styryl-like compound, as an electrochromic material. The basic structure of the electrochromic display element is shown in Figure 1. 1 is a glass substrate, 2 is a display electrode, 3 is a counter electrode, 4 is a sealing material, and 5 is a displayable substance. The glass substrate 1 may be made of a material in which at least one side is transparent. As the electrode material for the display electrode 2 and the counter electrode 3, transparent electrodes such as N2O3 and 5N02 are used. In terms of area, the display electrode 2 is smaller than the counter electrode 3. As the sealing material 4, epoxy resin, low melting point glass, solder, etc. are used. The displayable substance 6 is a solution in which a dye is dissolved in a non-aqueous organic solvent together with a supporting electrolyte. In such an element structure, there are several factors that determine the display life, such as impurities contained in the displayable substance 6, etc., but deterioration due to electrochemical reactions of the counter electrode 3 material is also one factor. There is. In other words, since the transparent electrodes forming the display electrode 2 and the counter electrode 3 are made of metal oxides such as In2O3, they are susceptible to reduction reactions. This may adversely affect display life. The larger the current value, the more easily the electrode is subject to reduction. In particular, the alteration of the counter electrode 3 becomes a problem. Therefore, when we investigated the current density distribution of the counter electrode 3, we found that when it is divided into regions A, B, and C as shown in Figure 1, the ratio of region A to the total current is 7.
0%, region B, 20%, region C became about 1Q, and region A was significantly reduced and the display life deteriorated.

In order to eliminate this drawback, an electrochromic display element having the structure shown in FIG. 2 was proposed. This configuration basically has the same structure as that shown in FIG. The structure is different. In this example, the display life was improved by reducing the current and improving the color density. However, it seems that there are still areas near the insulating film 7 where the current density is locally high, and the conductive film 6 itself may be attacked by the reaction, so the display life is still not sufficient.

In addition, in these electrochromic display elements, when a DC voltage is applied between the display electrode 2 and the counter electrode 3 so that the display electrode 2 is on the + side, the color density and the current change with respect to time are as shown in FIG. 3. (a) shows the applied voltage, (b) shows the color density, and (C) shows the temporal change in current value. Figure 3 (b
) shows the time t1 until the color density reaches saturation.
It is also necessary to shorten the response speed to increase the response speed.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional problems and aims to improve the response speed and display life of an electrochromic display element.

Structure of the Invention The present invention achieves the above object, and consists of two substrates, at least one of which is transparent and provided facing each other, a display electrode is provided on one side and a counter electrode is provided on the other, and the counter electrode is insulated. An electrochromic display element having a structure in which a film is sandwiched between first and second conductive films is provided.

Description of examples Embodiments of the present invention will be described below with reference to the drawings.

FIG. 4 shows a cross-sectional view of an electrochromic display element according to an embodiment of the present invention.

In the figure, 1 is a glass plate, 2 is a display electrode made of a transparent electrode such as N2O3 or Sn○2, 3 is a counter electrode which is a characteristic part of this embodiment, and 4 is made of epoxy resin, low melting point glass, solder, etc. A sealing material 5 is a solution containing an electrochromic substance or a displayable material made of a combination of an electrochromic film and an electrolyte provided on the surface of the display electrode 2; 6 is formed on a glass 4.1' plate 1''2; 7 is an insulating film formed to cover a region facing the display electrode 2 of the first conductive film 6; 8 is an insulating film 7
and a second conductive film formed to cover the surface of the first conductive film 8, and in this embodiment, the first conductive film 6 and the insulating film 7.
The counter electrode 3 is composed of the second conductive film 8 and the second conductive film 8 .

The characteristics of the electrochromic display element having such a configuration are that the rise time t1 of the color density shown in FIG. 3(b) is shortened, that is, the response characteristics are improved, and the erosion of the counter electrode material due to electrochemical reaction is reduced. The display life can be improved. Current value 1 in Figure 3 (C)
1 increases slightly by providing the second conductive film 8, but since the effect of making the current density distribution uniform is large,
Display life can be improved.

The first conductive film 6 of this embodiment has a diameter of n203° and a diameter of n2.
A transparent conductive film containing 03Sn○2 or Sno2 as a main component is easy to use in terms of ease of film formation and cost. The insulating film 7 is made of metal oxide (for example, SiO2,
At203. BaTiO3, etc.), metal fluorides (e.g. C
aF 2 , MqF2, etc.), metal nitrides (Si3N4, etc.), and the like, and it is desirable that the insulating film 7 has the same shape as the display electrode 2.

As the second conductive film 8, the same transparent conductive film as the first conductive film 6 can be used. Although it is somewhat difficult to control the metal color due to cost and film thickness, it is preferable to use Au, which is a noble metal, from the standpoint of stability of electrochemical reactions upon contact with solutions, etc.
, P t , Ag, etc. are more advantageous. Let me be more specific.

It has the structure shown in FIG. 4, and the first conductive film 6 constituting the counter electrode 3 is In2O3-8n02 and the insulating film 7 is 8102 and is 500 people;
It was provided with a thickness of 500 in 20s-8no2.

The electrochromic material of displayable substance 5 is 3,3-dimethyl-2-, which is one of the dyes of styryl-like compounds.
(P-dimethylstyryl)indolino(21-b)oxazoline, the supporting electrolyte was te]butylammonium perchlorate, and the solvent was acetonitrile.

The concentrations of the dye and supporting electrolyte are o, o2M/l, respectively.
o, 1M/l.

The table below shows a comparison of the display characteristics of the device having such a structure and the device shown in FIGS. 1 and 2.

table .

The applied voltage for decolorization was 1.3V.

As can be seen from the table, this example shows a remarkable improvement in responsiveness. The responsiveness was compared at the time t1 at which the saturation concentration was reached as shown in FIG. 3(b).

The concentration was measured at 550 nm, which is the absorption peak of colored light, and the saturation concentration was higher when the insulating film was covered, and the color density was about twice as high in terms of absorption rate.

Although the power consumption of this example was slightly higher than that of the device shown in FIG. 2, it was not a problem, and the repeated lifespan was improved by more than one order of magnitude.

As another embodiment of the present invention, the second conductive film 8 is made of Au.
A device similar to that of the previous example was fabricated except that the number of layers was 300, and the display characteristics were investigated.

Responsiveness is 20% compared to the case of N203-8nO2 film.
~30% were excellent. Similar results were obtained for other properties.

Effects of the Invention In short, the present invention provides two substrates, at least one of which is transparent and which are provided facing each other, a display electrode is provided on one of the substrates, and a counter electrode is provided on the other, and the counter electrode is provided with an insulating film on the first and second substrates. The present invention provides an electrochromic display element having a structure sandwiched between two conductive films, which can significantly improve response speed and display life.

[Brief explanation of drawings]

FIG. 4 is a cross-sectional view showing an electrochromic display element according to an embodiment of the present invention.・1[1...Glass substrate, 2...Display electrode,
3...Counter electrode, 4...Sealing material, 5...Displayable substance, 6...
...First conductive film, 7...--Insulating film, 8...
Second conductive film. Figure 1 Figure 2 Figure 3 Figure 4 Figure 2

Claims (4)

[Claims] (1) Two substrates, at least one of which is transparent, are provided facing each other, a display electrode is provided on one side, and a counter electrode is provided on the other, and the counter electrode is connected to a first conductive film provided on the substrate. , comprising an insulating film provided on the first conductive film in a region facing the two display electrodes, and a second conductive film formed to cover the first conductive film and the insulating film. An electrochromic display element. (2) The first and second conductive films of the counter electrode are In2o3°In2O3-8n02. Alternatively, the first claim is characterized in that it is made of a material whose main component is SnO2.
The electrochromic display element described in . (3) The first conductive film of the counter electrode is In2O3, ■n2o
The electrochromic display element according to claim 1, characterized in that the second conductive film is made of Au, Ag, or Pt, and the second conductive film is made of Au, Ag, or Pt. . (4) The electrochromic display element according to claim 1, wherein the insulating film constituting the counter electrode is made of metal oxide, metal fluoride, or metal nitride.