JPH036288A - Electrodeposited iridium oxide film - Google Patents

Abstract

PURPOSE:To obtain the subject film excellent in smoothness and suitable for use as a display electrode of an electrochromic element by conducting electrodeposition from an alkaline solution containing an Ir compound below a specified amount. CONSTITUTION:The subject film is obtained by conducting electrodeposition from an alkaline solution (e.g. a solution adjusted to pH10 by adding K2CO3) containing an Ir compound (e.g. IrCl4) in an amount of at most 6X10<-3>mol/l in terms of Ir atoms. The conventional electrodeposition solution for forming an Ir oxide film, which is obtained by preparing a solution containing 5g/l 1.5X10<-2>mol/l of IrCl4 and 5g/l 4X10<-2>mol/l of (COOH)2 and adjusting the pH to 10 by adding Na2CO3, tends to cause a precipitate (IrO2.nH2O) gradually with time after preparation thereof, resulting in the change in the composition of the solution; therefore, the reproducibility of the quality of the electrodeposited film obtained therefrom is poor, and the surface of the obtained film is not smooth so that the adhesion to a base plate is poor. The use of the electrodeposition solution of this invention makes it possible to form a film having a specular surface excellent in smoothness in s relatively simple manner; therefore, it is effective in improving the quality of and lowering the cost of a product made by using an Ir oxide film.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an iridium oxide film, and particularly to an electrodeposited film of the above oxide which has excellent smoothness and is suitable for use as a display electrode of an electrochromic device.

[Conventional technology]

The conventional electrodeposition solution for forming an iridium oxide film was disclosed in a patent application filed in 1986.
As described in No. 173653, 5g/12 tsubo 1.5X 10-"m of iridium tetrachloride (IrCQ4)
ofi/Q and oxalic acid ((COOH), ) 5 g/
A solution containing n 44 X 1 0-''moM/Q was prepared and made alkaline to pH 10 by adding sodium carbonate (NazC○,).

[Problem to be solved by the invention]

After preparation, an electrodeposition solution with such a composition gradually forms a precipitate (IrO, nH, O) over time. As a result, the composition of the electrodeposited solution changes, resulting in poor reproducibility of the quality of the resulting electrodeposited film.

In addition, the surface of the obtained electrodeposited film was not smooth but rough;
Weak adhesion to the substrate. For this reason, it has been difficult to obtain a particularly thick film with high coloring density because it tends to peel off easily.

An object of the present invention is to obtain an iridium oxide electrodeposited film free of these drawbacks.

[Means to solve the problem]

The above purpose is to use iridium salt (IrCQ) as an electrodepositing solution composition.
, , Ir(SO2), , Na2IrCI2. etc.) and the complexing agent (eg (COOH), ), as well as the selection of the atmosphere and temperature.

[Effect]

The electrodepositing solution for forming an iridium oxide thin film is unique in that there is no example other than that disclosed in the inventor's earlier invention, Japanese Patent Application No. 173653/1983.

This is an iridium salt, (COOH), Na, Go.

It consists of In this configuration, the concentration of the iridium salt and the concentration of the complexing agent (COOH) z affect the electrodeposition efficiency (deposition amount relative to the deposition current density), and (COOH)2 affects the surface state of the deposited film. was revealed as a result of the study. This is shown in Table 1.

Table 1 shows the relationship between the composition of the electrodepositing solution, the deposition efficiency (the amount of electrodeposition versus the current density: the current density and the amount of electrodeposition are listed separately in the table), and the surface condition of the film.

Here, when comparing the case where the concentration of (in the electrodepositing solution is 40 ×
It can be seen that the electrodeposition efficiency increases with L. but,
The presence of (COOH) roughens the film surface and also has the effect of making the film easier to peel off from the substrate.This phenomenon is caused by the fact that (COOH)2.11 degrees
It can be seen that it appears even at a relatively low concentration of l/l. Also (COOH).

It can be seen that in the presence of , the lower the concentration of iridium salt, the higher the electrodeposition efficiency.

For these reasons, (COOH)' was selected to have an optimal concentration that was low enough not to lose the smoothness of the deposited film, but also to increase the electrodeposition efficiency, and for iridium salt, a low concentration was selected from the viewpoint of electrodeposition efficiency. (A solution prepared at a high concentration of 1.5 x 10'''' m, oQ/Q will produce a precipitate, so lowering the concentration is preferable.) It has high electrodeposition efficiency and excellent smoothness. The electrodeposition solution was changed to a stable electrodeposition solution that can form a film, does not generate precipitates, and does not change over time.In other words, the iridium salt is 6.0×10-'moQ from the viewpoint of precipitate formation and electrodeposition efficiency.
/Q and below, the complexing agent (COOH) is 8.0X10-
``The concentration is 3 mol/l or less.

Furthermore, all the results shown in Table 1 were performed using the electrodeposition solution under a nitrogen atmosphere (nitrogen was also blown into the solution). The efficiency of electrodeposition is significantly improved when carried out under a nitrogen atmosphere, being about twice as high, and the smoothness of the deposited film is also good.

In addition, the influence of the electrodeposition temperature on the electrodeposition efficiency is significant.
The efficiency increases as the temperature decreases, and good results are obtained at temperatures below 15°C. All results in the table were performed at 10°C.

〔Example〕

Hereinafter, the content of the present invention will be explained in more detail with reference to specific examples.

Example 1 A 100 m QrlA solution containing 6.0 x 10-"moQ/Q of engineered rCQ4 was prepared. Potassium carbonate (
K2GO? ) was added to adjust the pH to 10. This solution was applied to a glass substrate (hereinafter referred to as an ITO substrate) coated with a transparent conductive film mainly composed of indium oxide with a sheet resistance of 10 Ω/am” as an anode and a gold wire as a cathode, and the electrodeposition current density was set to 400 μA/am. cm2 and a temperature of 10'C for 30 minutes while flowing nitrogen.

As a result, a blue-black film was electrodeposited on the transparent conductive film of the anode. This film was smooth and mirror-like.

Example 2 100ml of a solution containing IrCl24 of OXlo-3moQ/n was prepared. Thereafter, the same procedure as in Example 1 was carried out to obtain a blue-black electrodeposited film having a smooth mirror surface.

Example 3゜6, OX 10-'mof2/Q's CQ4 and 4
．． A solution containing 0×10′″3 mol/l of oxalic acid was added to 100
mQ was prepared. Add potassium carbonate to this solution and P H
was set as 10. This solution has a sheet resistance of 10Ω/cm”
The ITO substrate was used as an anode, the gold wire was used as a cathode, and the deposition current density was 2.
Electrodeposition was carried out for 30 minutes while flowing nitrogen at a temperature of 10° C. and a liquid temperature of 10° C. As a result, a blue-black film was electrodeposited on the transparent conductive film of the anode. This film was smooth and had a mirror surface.

Example 4 A solution containing 4.5 x 10-3rnoQ/Q of IrCQ and 4.0 x 10''man/Q of oxalic acid was
mQ was prepared. Hereinafter, in the same manner as in Example 3, p I (%
Preparation, using similar electrodes, current density 230 μA/c+a
"Electrification was carried out at a liquid temperature of 10° C. while nitrogen was flowing in. As a result, a blue-black film was electrodeposited on the transparent conductive film of the anode. This film was smooth and had a mirror surface.

C Effects of the Invention] As described above, by using the electrodeposition solution for forming an iridium oxide film of the present invention, a film having a mirror surface with excellent smoothness can be produced relatively easily. It is effective in improving the quality and lowering the cost of products using membranes.

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Claims (5)

[Claims] 1. An iridium oxide electrodeposited film, characterized in that it is deposited from an alkaline solution containing an iridium compound of 6×10^-^3 mol/l or less per iridium atom. 2. 6×1 per iridium atom according to claim 1 above.
An iridium oxide electrodeposited film, characterized in that it is deposited from an alkaline solution containing an iridium compound of 0^-^3 mol/l or less, to which a complexing agent is further added. 3. 3. The iridium oxide electrodeposited film according to claim 2, wherein the complexing agent is oxalic acid of 8x10^-^3 mol/l or less. 4. 4. The iridium oxide electrodeposited film according to claim 1, wherein the iridium oxide film is deposited from a solution into which nitrogen is introduced. 5. The iridium oxide electrodeposited film according to any one of claims 1 to 4, which is deposited from a solution at a temperature of 5.15° or less.