JPH0352554B2 - - Google Patents

Description

[Detailed description of the invention]

a. Field of Industrial Application The present invention relates to a method for producing a molybdenum oxide film, and in particular to an electrochromic device (hereinafter referred to as
This paper relates to an electrolytic deposition method for a molybdenum oxide film that is suitable as a film for EC devices. b. Prior Art Molybdenum oxide is known to exhibit EC characteristics, and many EC elements using this have been proposed. The so-called PVD method (Physical Vapor Deposition), such as the sputtering method and vapor deposition method, is used to form molybdenum oxide films, but in general, with the PVD method, it is difficult to create a uniform film over a large area, and productivity is low. It had the drawback of being bad. c Problems to be Solved by the Invention The present invention solves the drawbacks of the conventional method in which a uniform coating cannot be obtained over a large area, and obtains a uniform molybdenum oxide coating over a large area.
The purpose is to obtain a molybdenum oxide film particularly suitable for use in EC devices. d Means for Solving the Problems The present invention for solving the above problems is a method in which a substrate having conductivity at least on the surface is immersed in an aqueous molybdate solution, and electrolytic deposition is performed using the substrate as a cathode. is used. The molybdate aqueous solution used in the present invention preferably contains 0.005 to 2 mol/molybdate ion. If the concentration is less than 0.005 mol/ml, the resistance of the aqueous solution will increase, requiring a higher voltage, or side reactions other than the desired electrolytic deposition reaction will become more intense, resulting in poor electrolytic efficiency or gas formation on the electrode. This is a drawback that may occur. Furthermore, if the concentration is greater than 2 mol/mol, it becomes difficult to adjust the liquid pH. In addition, in order to obtain a uniform film with good adhesion,
The molybdate aqueous solution is preferably acidic, particularly preferably at a pH of 5 or less. Furthermore, when the pH of the molybdate aqueous solution is set to 0.8 to 1.5, a blue molybdenum oxide film having an absorption maximum in the near-infrared region can be obtained, and by setting the pH to 2 or higher, an absorption band can be obtained between 400 and 500 nm. A brown molybdenum oxide film is obtained. As the molybdate used to prepare the molybdate aqueous solution, salts with various metals can be used. Among them, it is preferable to use cationic salts with a small ionic radius, such as lithium salts, sodium salts, and potassium salts, because an EC element with a quick response can be obtained using the molybdenum oxide film obtained by this manufacturing method. . As a voltage application method for electrolytic deposition, constant current electrolysis is preferable in terms of controlling the deposited film thickness.
If electrolytic deposition is performed at a current density higher than 5 A/m ² , the uniformity and adhesion of the resulting film will deteriorate, so it is desirable to perform electrolytic deposition at a current density of 5 A/m ² or less. Further, the substrate on which the molybdenum oxide film of the present invention can be manufactured may be of any material or shape as long as it can serve as an electrode during electrolytic deposition, and any material having conductivity on at least the surface may be used. If so, even metal or oxide substrates can be used. Furthermore, in order to use the film produced by this manufacturing method as a film for an EC device, it is preferable that the substrate be transparent, and a glass plate with a conductive film is particularly desirable. e Example 100 ml of each 0.07 mol/aqueous lithium molybdate aqueous solution whose pH value was adjusted to 1.0, 1.5, 2.0, 3.0, and 4.0 using sulfuric acid was prepared. Each of these electrolytes was placed in a thermostat and maintained at 25°C, while glass with a SnO ₂ transparent conductive film (vertical) was added to the electrolyte.
20mm, width 50mm, thickness 1.1mm) and a platinum plate (vertical 20mm, width 50mm, thickness 0.3mm) were immersed, and the platinum plate was used as an anode and the glass with transparent conductive film was used as a cathode, and a current density of 3A/ ^m2 was applied. Constant current electrolysis was performed for 90 seconds each. Approximately 2,000 cells each are placed on the transparent conductive film by the above operation.
Å molybdenum oxide coating (hereinafter abbreviated as coating)
However, all of the above five types of coatings had good uniformity and adhesion. The coatings obtained with electrolyte pH of 1 and 1.5 were blue, and the coatings obtained with electrolyte pH of 2.0, 3.0, and 4.0 were brown. Afterwards, five types of glass substrates with coatings and Pt plates (vertical 16cm, width 2cm, thickness
0.3 mm) was immersed in a 1 mol/LiClO ₄ propylene carbonate solution to prepare a simple EC element.
The coated glass substrate and Pt of this simple EC element
Using the plate as both electrodes, a DC voltage of ±2V is applied between the two electrodes, and the optical density at that time (hereinafter referred to as optical
density OD) was measured. Table 1 shows the OD values OD (+), OD (-) and the difference ΔOD between these OD values when a voltage was applied using the coated glass side as an anode and a cathode, respectively. Here, each OD value is the OD value at the point when the OD becomes almost constant after applying the voltage (λ = 600 nm)
shows. The coatings prepared under the conditions of PH1.0 and 1.5 showed colorless-blue color development and fading in the above procedure,
The film created under these conditions is brown (light) - brown (dark).
A reversible change in OD occurred between PH1.0
Fig. 1 shows the visible light absorption spectrum of the film prepared under the conditions of pH 3.0, and Fig. 2 shows the visible absorption spectrum of the film prepared under the conditions of pH 3.0.

[Table] In the above results, it is preferable for the EC characteristics to have a large difference in absorbance △OD when coloring and decoloring. Therefore, as a coating for blue-colored EC elements, a coating prepared at PH1.0 is preferable, and a coating prepared at PH1.0 is also suitable for brown-coloring. It can be seen that the film prepared at PH3.0 is suitable as the EC element film in the above examples. f Effects of the Invention According to the present invention, a uniform molybdenum oxide film can be formed over a large area on any substrate having conductivity at least on the surface. The molybdenum oxide film thus obtained exhibits electrochromic properties and is suitable for manufacturing electrochromic devices. In addition, according to the present invention, brown (light)-brown (dark) which could not be obtained conventionally.
It is possible to obtain a molybdenum oxide film that can be used to create an electrochromic device that exhibits color development and fading. It also has the advantage that coatings for electrochromic devices that exhibit different colors, blue and brown, can be obtained by simply changing the pH of a solution containing molybdate ions. Furthermore, since the present invention utilizes electrolytic deposition, the thickness of the produced film can be accurately controlled by the amount of electrolysis.

[Brief explanation of drawings]

Figure 1 shows the visible light absorption spectrum showing the color development and fading of a simple EC element using a molybdenum oxide film prepared under the conditions of PH 1.0, and Figure 2 shows the visible light absorption spectrum showing the color development and fading of a simple EC element using a molybdenum oxide film prepared under PH 1.0 conditions.
FIG. 2 is a diagram of the visible light absorption spectrum of a simple EC device using the film prepared in FIG.

Claims (1)

[Claims] 1. A substrate having conductivity at least on the surface is immersed in an aqueous molybdate solution, and electrolytic deposition is performed using the substrate as a cathode to form a molybdenum oxide film on the base surface of the substrate. A method for producing a characteristic molybdenum oxide film. 2. The method for producing a molybdenum oxide film according to claim 1, wherein the molybdate aqueous solution has a pH of 0.8 to 1.5, and the formed molybdenum oxide film is blue in color. 3. The method for producing a molybdenum oxide film according to claim 1, wherein the molybdate aqueous solution has a pH of 2 or more, and the molybdenum oxide film formed is brown.