JPS5848028A - Electrochromic display cell - Google Patents

Abstract

PURPOSE:To obtain a display cell which is fast in response speed and is low in applied voltage by using an oxidation coloring thin film consisting of iridium hydroxide or nickel hydroxide and a reduction coloring thin film consisting of tungsten oxide or molybdenum oxide. CONSTITUTION:An electrochromic display cell is constituted of an oxidation coloring thin film which permits oxidation-reduction reaction and is colorless or colors in an oxidized state, a reduction coloring thin film which permits oxidation-reduction reaction and colors in a reduced state, an electrolyte layer which is provided between these two thin films, and a pair of electrodes sandwiching these three thin films. Said oxidation coloring thin film is constituted of iridium hydroxide or nickel hydroxide, and said reduction coloring thin film is constituted of tungsten oxide or molybdenum oxide. The display cell which is improved in response speed, voltage during repetitive driving, a change in the quantity of light in that time, etc. is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrochromic display cell (hereinafter referred to as EC).

Due to its characteristics such as memory properties and coloring properties, EC is considered to be applicable to display elements, transmitted light amount control elements, memory elements, etc., and its practical use is desired. Japanese Patent Application Laid-Open No. 52-73749 discloses such an EC with improved memorability of color display.
An electrolytically reducible thin film of molybdenum oxide, tungsten oxide or niobium oxide, that is, an electrochromic substance thin film, an electrolytically oxidizable thin film of chromium oxide or vanadium oxide, and an insulating material such as titanium oxide or tantalum oxide are placed between a pair of opposing electrodes. A method in which a thin film is interposed has been proposed. This EC is the light transmittance T before color development. When 100 people, 1~
When color is developed by applying a voltage of 3.5 cm, the light transmittance T becomes 10 in a few seconds. That is, optical power (hereinafter abbreviated as 0-D. 0・D-1og-!-9!-)
It takes several seconds for 1 to 3■ to become 1. Also.

It takes more than 1 second to erase the color by applying a reverse voltage, and furthermore, it takes 1QQynsec repeated square wave pulse voltage ±10
The above-mentioned publication states that the amount of transmitted light changes by a factor of several to about 10 with the application of (2). This all-solid-state EC is superior to those previously reported, but as mentioned above, the response time, which takes several seconds to develop a color and nearly one second to erase, makes it difficult for display elements, camera shutters, and apertures. It is still not satisfactory for light amount control elements such as the above. Furthermore, the change in light amount during repeated driving is insufficient at 7-10%, and it is desirable that the driving voltage, especially the voltage during repeated driving, be as low as possible.

The purpose of the present invention is to solve the above-mentioned drawbacks and to provide an EC that can be put to practical use and has improved response speed, voltage during repeated driving, changes in light intensity, etc., by several orders of magnitude compared to the second type. It is.

The present invention provides an electrochromic display cell consisting of an oxidation-reduction thin film that is capable of redox reactions and is colorless or colored in an oxidized state, a reduction color-forming thin film that is capable of redox reactions and that develops color in a reduced state, and both of these thin films. and the electrolyte layer between.

and a pair of electrodes that sandwich these three thin films; It consists essentially of tungsten oxide, molybdenum oxide, or a mixture thereof.

Here, the above-mentioned "substantially" refers to the case where the oxidative color-forming thin film or the reduction color-forming thin film is composed only of the substance described in "-," and the effect of the substance described in "- is exerted." This means that it may contain some impurities, if any.

The electrolyte layer means the electrolyte as it is or dissolved in a solvent when the electrolyte is a liquid, and the electrolyte dissolved in a solvent when the electrolyte is a solid. Semi-solid gels made of polyvinyl alcohol, CMC, agar, gelatin, starch, etc. are also included in the present invention.

As an electrolyte.

(1) Inorganic or organic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and acetic acid.

(11) Lithium hydroxide, potassium hydroxide.

Alkali such as sodium hydroxide and ammonium hydroxide.

(ili) Lithium bromide, potassium bromide, sodium bromide, lithium chloride, potassium chloride.

Salts such as sodium chloride, lithium perchlorate etc. are used.

As the solvent, mainly water, γ-butyrolactone, phosphoric acid, cellosolve acetate, propylene carbonate, etc. are used.

Next, the present invention will be specifically explained by examples with reference to the drawings.

FIG. 1 is a diagram illustrating a cross-sectional structure of an electrochromic display cell showing an embodiment of the present invention.

(1) is a transparent substrate such as glass, and on this substrate (1), a transparent electrode (2) of indium oxide or the like with a thickness of 2000 OA, and an oxidation coloring film of iridium hydroxide with a thickness of 500 OA are sequentially applied. a thin film (6), an electrolyte layer (4) with a thickness of 1.500.000 mm, a film thickness of 50 mm made of tungsten oxide
A reduction coloring thin film (5) of size 0 and a transparent electrode (6) made of indium oxide or the like are layered. (7) is a transparent glass plate for protection. (8) is a spacer.

To make this cell, a transparent electrode (2) and an iridium hydroxide thin film (3) are laminated on a glass substrate (1) using known thin film forming techniques such as vacuum evaporation and sputtering. In the same way, a transparent electrode (6) and a tungsten oxide thin film (5) were laminated on a glass plate (7), and the two members were joined via a spacer (8). The electrolyte is injected through an injection port (not shown) provided in a part of the cell. Here, an r-butyllactone solution containing 1M Lic104 was used as the electrolyte.

The thickness of each thin film is not limited to the above values.

In addition, a wide range of options can be selected above and below the layer, and in particular, to increase the coloring density, it is recommended to use thick iridium hydroxide or tungsten oxide, and to improve memory properties, it is recommended to thicken the electrolyte layer.

Further, of course, when nickel hydroxide or a mixture thereof is used instead of the above-mentioned iridium hydroxide, the structure may be the same as above. The same applies to insulators such as molybdenum oxide and zirconium oxide. Furthermore, the positional relationship between the oxidation color-forming thin film and the reduction color-forming thin film with respect to the substrate may be reversed.

As described above, by using iridium hydroxide, nickel hydroxide, or a mixture thereof as the oxidative color-forming thin film, the EC of the present invention has dramatically improved performance compared to the previous all-solid EC. This is shown in a table below.

Table 1 shows the applied voltage in the EC of the present invention.

As shown in Figure 1, until the transmittance reaches %, that is, 0-D=0
．． 501, the time required for color development tc, the time required for decolorization tb, and 0·D in the saturated state are shown.

Table 1 Table 2 shows the EC of the present invention and the above-mentioned Japanese Patent Application Laid-Open No. 52-73749.
The performance is compared with that of the conventional EC.

Table 2 As is clear from Table 2, the EC according to the present invention is several times faster in the time required for color development and decolorization, that is, the response speed, than the conventional one, and the applied voltage is also very low. In this case, the change in transmittance can be increased by more than 6 times with a voltage of 1/6 or less.

[Brief explanation of drawings]

1 is a diagram illustrating a cross-sectional structure of an embodiment of the present invention. [Explanation of symbols of main parts]

Claims (1)

[Scope of Claims] An oxidative color-forming thin film that is capable of an oxidation-reduction reaction and becomes colorless or colored in an oxidized state between a pair of electrodes. An electrochromic display cell having at least a reduction color-forming thin film that is capable of an oxidation-reduction reaction and develops color in a reduced state, and an electrolyte layer sandwiched between these two thin films,
The oxidative color-forming thin film essentially consists of iridium hydroxide, nickel hydroxide, or a mixture thereof. An electrochromic display cell characterized in that the reduction color forming thin film essentially consists of tungsten oxide, molybdenum oxide, or a mixture thereof.