JPS61231197A - Production of mixed film of tungsten oxide-molybdenum oxide - Google Patents

Abstract

PURPOSE:To obtain an electrochromic film of a tungsten oxide-molybdenum oxide mixture at a low cost by bringing a colloidal mixed soln. of tungstic acid and molybdic acid into contact with an electrically conductive substrate, electrodepositing a thin film on the substrate and baking the film. CONSTITUTION:The mixed soln. of tungstate and molybdate is brought into contact with a cation exchange resin to prepare the mixed soln. of tungstic acid and molybdic acid contg. mixed colloid of tungstic acid and molybdic acid by cation-hydrogen ion exchange. The molar ratio of tungstic acid to molybdic acid in the mixed soln. is 1-4. The mixed soln. is brought into contact with the substrate whose surface is at least electrically conductive to said mixture and DC voltage is applied by using the substrate as a cathode to deposit a film on the surface of the substrate. The film is then baked at about 150-350 deg.C to improve the adhesion, mechanical strength and electrochromic property.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides electrochromic properties (hereinafter referred to as E
The present invention relates to a method for manufacturing a mixed film of tungsten oxide and molybdenum oxide that has a carbon property (abbreviated as C-type).

[Conventional technology]

Inorganic material system E applied to EC display elements or EC light control bodies
Currently, tungsten oxide is the main C material. However, it has recently been reported that a mixture film of tungsten oxide and molybdenum oxide exhibits good coloring efficiency. This is because the light absorption spectrum of this coating in its colored state (blue) is closer to the visible light region than that of tungsten oxide and molybdenum oxide. This is because if a color change from transparent to blue is caused with the same amount of electricity as , an EC element using a film of the above mixture will be perceived as having a larger color change than an EC element using WO3. . (For example, J, J, A, P, JLL
(12>, /62'll (/JV)) Conventionally, vacuum methods such as vapor deposition and sputtering have been used to produce this mixture film of tungsten oxide and molybdenum oxide.

[Problem that the invention seeks to solve]

Generally speaking, the vacuum method, which is the conventional method for manufacturing the above-mentioned tungsten oxide and molybdenum oxide mixture film (hereinafter abbreviated as MOαw1-a03 film), cannot produce a uniform film over a large area. ■Requires complicated operations such as vacuum lining. ■Requires large and expensive equipment. ■This makes manufacturing costs relatively high. There were problems such as.

[Means for solving problems]

In order to solve the above problems, the present invention brings a mixed solution of tungstic acid and molybdic acid containing a mixed colloid of tungstic acid and molybdic acid into contact with a substrate having conductivity at least on the surface, and uses the substrate as a cathode. A method is used in which electrolytic deposition is performed and the deposited film is fired.

Conventional aqueous solutions of impolitungstic acid (hereinafter abbreviated as tungsten acid) readily precipitate and do not exist as stable aqueous solutions. However, it has been found that when tungstic acid is mixed with molybdic acid, it exists relatively stably in an aqueous solution, and that this solution can be used for electrolytic deposition.

The mixed solution of tungstic acid and molybdate of the present invention can be prepared by a method in which a mixed solution of tungstate and molybdate is brought into contact with a cation exchange resin to perform ion exchange of cations and hydrogen ions.

It is also possible to adjust the concentration by adding a molybdic acid solution to the solution prepared by the above method, but the concentration of tungstic acid and molybdic acid obtained by the concentration of the mixed solution of tungstate and molybdate prepared initially is Since the concentration of the mixed solution can be determined, it is preferable to initially set the concentration to an appropriate value.

Tungstates and molybdates that can be used to create the above mixed salt solution include Li, Na, K
IRblC8, Be, Mg, Cia, Sr or NH4
etc. and the salt of WO4+ M ()04 can be exemplified.

In the comparatively stable mixed solution of tungstic acid and molybdic acid, the molar ratio of tungstic acid to molybdic acid in the solution is preferably 7.

If the molar ratio of tungstic acid to molybdic acid is greater than the molar ratio of molybdic acid, it is not preferable because the solution tends to produce precipitates similar to an aqueous solution of tungstic acid alone. Furthermore, if the molar ratio of tungstic acid to molybdic acid is smaller than /, the coloring properties will be less effective when an EC element is made using a mixture film of tungsten oxide and molybdenum oxide obtained by treating the same solution. I don't like this because I can't see it.

In order to carry out the electrolytic deposition of the present invention, it is necessary to ripen a mixed solution of tungstic acid and molybdic acid to form a colloid of tungstic acid and molybdic acid in the solution.

Even if electrolytic deposition is attempted by immersing the electrode substrate in the mixed solution in which no colloid is produced, a film cannot be obtained on the surface of the substrate. (Although tungsten blue is partially reduced and produced, a film is not formed because it is diffused into the solution.) When a mixed solution of tungstic acid and molybdic acid is aged, a colloid is produced in the solution. This aging means maintaining the solution at a certain temperature for a certain amount of time, and the temperature during aging is preferably less than 60"C, and the aging time is preferably longer than 72 hours. If the temperature of the mixed solution of tungstic acid and molybdic acid exceeds 10"C, precipitation will easily occur in the solution during aging, and even if electrolytic deposition is attempted within 72 hours, colloid formation will be insufficient, resulting in a film failure. is difficult to form.

When a mixed solution of tungstic acid and molybdic acid, which has been sufficiently aged to form a colloid of tungstic acid and molybdic acid, is brought into contact with an electrode and a DC voltage is applied, a film is deposited on the surface of the cathode.

The deposited film has poor adhesion to the electrode substrate, lacks mechanical strength, and also has poor EC characteristics, requiring a firing operation. The temperature during firing is preferably 750 to 350°C. If the firing temperature is higher than 350° C., the crystallization of the film will progress and the reversibility of the EC device made using the obtained film will deteriorate, which is not preferable. Furthermore, if the firing temperature is lower than /j O'C, the strength cannot be improved much by firing, and
This is not preferable because the decoloring speed of the C element becomes slow.

〔Example〕

First, a potassium tungstate aqueous solution of 0.1 mol/l and a potassium molybdate aqueous solution of the same concentration were prepared.

Next, a potassium tungstate aqueous solution and a potassium molybdate aqueous solution were mixed in a ratio of 7=3, and this solution was passed through a column dripped with a cation exchange resin to convert it into a free tungstate-molybdenum mixed aqueous solution. Next, this solution was aged for 72 hours in a constant temperature bath at ≠o'C to obtain a stable cotetraid solution with an appropriate viscosity.

Next, a glass plate with a 5n02 transparent conductive film was immersed in this solution, and a constant voltage current was applied from a DC power supply using the glass plate as a cathode to electrolytically deposit a film on the glass plate. In order to improve the adhesion of the deposited film to the glass plate and the reversibility of the EC characteristics of the resulting film, the glass plate was coated with 2°C. ; O'C,/hour heat treatment was performed.

FIG. 1 shows the light absorption spectrum of the EC device produced using the thin film thus obtained.

The absorption spectrum peak of the colored state of the EC element created using the film obtained in this example is closer to the visible region than the absorption spectrum peak of the +C element using tungsten oxide or molybdenum oxide, The coloring efficiency of the EC element using the film obtained in this example is impressive.

Table 1 shows the results of compositional analysis of the obtained coating.

Next, as in the above example, a potassium tungstate aqueous solution and a potassium molybdate aqueous solution were added at 6=4c and /:l.
A mixed thin film of tungsten oxide and molybdenum oxide was obtained by the same operation. The composition of the obtained film is shown in Table 1. From Table 1, it can be seen that the composition of the resulting film can be controlled by controlling the precipitation solution (there is approximately a correspondence between the precipitation solution and the composition of the film obtained).

ta1 Expression [Effects of the Invention] According to the present invention, it is possible to apply a piezoelectric deposition method for creating a mixed film of tungsten oxide and molybdenum oxide.

Therefore, a uniform film can be formed over a large area at low cost, and furthermore, by controlling the conditions of electrolytic deposition, it is possible to accurately control the thickness of the resulting film.

In addition, the present invention does not require large-scale equipment and has high productivity compared to conventional manufacturing methods such as vacuum methods, so that a tungsten oxide and molybdenum oxide mixed film can be obtained at low cost.

In addition, the light absorption spectrum of the EC device made using this mixture film is shifted to the visible light region compared to the EC device made using conventional tungsten oxide or molybdenum oxide, so it is difficult to color the EC device when colored. The blue color tone is different from the conventional one, and it provides diversity in the color tone of the EC element.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the spectral transmittance of an electrochromic film created using a mixed film of tungsten oxide and molybdenum oxide created according to an example of the present invention.

Claims (2)

[Claims] (1) A mixed solution of tungstic acid and molybdic acid containing a mixed colloid of tungstic acid and molybdic acid is brought into contact with a substrate having conductivity at least on the surface, and electrolytic deposition is performed using the substrate as a cathode to perform electrolytic deposition on the surface of the substrate. A method for producing a mixed film of tungsten oxide and molybdenum oxide, in which a film is deposited on the substrate, and then the film is fired to obtain a mixed film of tungsten oxide and molybdenum oxide. (2) The molar ratio of tungstic acid to molybdic acid in the mixed solution of tungstic acid and molybdic acid is 1
4. A method for producing a mixed film of tungsten oxide and molybdenum oxide according to claim 1.