WO2019087705A1

WO2019087705A1 - Coating liquid, method for preparing coating liquid, and method for producing hydrogen gas sensitive film

Info

Publication number: WO2019087705A1
Application number: PCT/JP2018/037599
Authority: WO
Inventors: 西澤　かおり; 山田　保誠; 吉村　和記
Original assignee: 国立研究開発法人産業技術総合研究所; 西澤　かおり; 山田　保誠; 吉村　和記
Priority date: 2017-11-06
Filing date: 2018-10-09
Publication date: 2019-05-09
Also published as: JPWO2019087705A1; JP6892153B2

Abstract

Provided is a coating liquid characterized by including: a tungsten chloride; a monovalent alcohol which has 1-4 carbon atoms and dissolves the tungsten chloride; a carboxylic acid which is dissolved in the alcohol and has reducibility; and a metal compound which becomes a metal catalyst having sensitivity to hydrogen gas when reduced by the carboxylic acid.

Description

Coating liquid, method of manufacturing coating liquid, and method of manufacturing hydrogen gas sensitive film

The present invention relates to a coating solution for producing a hydrogen gas sensitive film, a method for producing the coating solution, and a method for producing a hydrogen gas sensitive film.

Conventionally, a hydrogen gas-sensitive film made of tungsten oxide supporting a metal catalyst has been developed. The hydrogen gas sensitive membrane has a low permeability by being exposed to hydrogen gas, and a high permeability by being exposed to the atmosphere. The application of the hydrogen gas sensitive film is, for example, a hydrogen gas visualization sheet, a hydrogen gas sensor, a hydrogen gas sensitive smart window, and the like.

Although many sputtering methods which are one of physical vapor deposition methods are proposed as a manufacturing method of a hydrogen gas sensitive film | membrane, the less expensive wet method is also proposed.

However, in many cases, it is difficult to use a substrate with low heat resistance because the wet process requires a step of baking the precursor solution of hydrogen gas sensitive film on a substrate and then baking the solution at a high temperature. The problem of being present is also pointed out (see Patent Documents 1 to 5).

Therefore, a process of irradiating ultraviolet rays instead of baking treatment has also been reported, but in that case, the ultraviolet rays had to be irradiated while being exposed to reducing harmful gases such as formaldehyde and hydrogen and combustible gases. (See Patent Documents 6 to 8).

Japanese Patent Application Laid-Open No. 2003-329592 Japanese Patent Application Laid-Open No. 2003-166938 Japanese Patent Application Laid-Open No. 2005-345338 Japanese Patent Application Laid-Open No. 2005-331364 Japanese Patent Application Laid-Open No. 2007-71866 Japanese Unexamined Patent Publication No. 2010-2346 WO 2009/154216 Japanese Patent Application Laid-Open No. 2016-161507

The present invention has been made in view of the above circumstances, and the object of the present invention is to apply a coating solution to a substrate, dry the applied film, and have a metal having sensitivity to hydrogen gas. In the process of producing a film containing a catalyst, metal ions in the coating solution can be reduced in the air at a temperature of room temperature to 150 ° C. to form a metal catalyst, without using harmful gases or flammable gases. It is in providing a coating liquid.

[1] A coating liquid according to an aspect of the present invention is
With tungsten chloride,
A C 1-4 monovalent alcohol dissolving the tungsten chloride;
A reducing carboxylic acid dissolved in the alcohol;
It is characterized in that it contains a metal compound which becomes a metal catalyst having sensitivity to hydrogen gas by being reduced by the carboxylic acid.

[2] The carboxylic acid is oxalic acid. The oxalic acid may be either an anhydride or a dihydrate.

[3] The metal compound is a platinum group metal compound.

[4] The compound of the platinum group metal is preferably at least one selected from the group consisting of palladium compounds, platinum compounds, and palladium-platinum alloy compounds.

[5] The compound of the platinum group metal is palladium dichloride (PdCl ₂ ), platinum dichloride (PtCl ₂ ), platinum tetrachloride (PtCl ₄ ), and hexachloroplatinic acid hexahydrate (H ₂ PtCl _6. It is characterized in that it is at least one selected from the group consisting of 6H ₂ O).

[6] It is characterized in that it is used for film formation of a tungsten oxide film carrying the metal catalyst.

[7] A method of producing a coating liquid according to an aspect of the present invention,
Tungsten chloride is mixed with a C 1-4 monovalent alcohol dissolving the tungsten chloride to prepare a tungsten solution,
A carboxylic acid having reducibility is dissolved in the tungsten solution to prepare a precursor solution of tungsten oxide,
It is characterized in that a compound of a metal serving as a metal catalyst having sensitivity to hydrogen gas by being reduced by the carboxylic acid is dissolved in the precursor solution to prepare a coating liquid.

[8] A method of producing a hydrogen gas-sensitive film according to an aspect of the present invention,
The coating liquid according to any one of the above [1] to [6] is coated on a substrate to form a coated film, and the coated film is dried in the air at room temperature or more and 150 ° C. or less. A tungsten oxide film carrying the metal catalyst formed by reducing metal ions contained in the raw material of the metal catalyst is formed.

According to one aspect of the present invention, the coating liquid is applied to the substrate, the coated film is dried, and in the process of producing the film containing the metal catalyst having sensitivity to hydrogen gas, the harmful gas or the combustible gas A coating solution is provided, which can reduce metal ions in the coating solution in the air at a temperature of room temperature or more and 150 ° C. or less to form a metal catalyst.

FIG. 1 is a flowchart showing a method of manufacturing a coating liquid according to one embodiment. FIG. 2 is a view showing a measuring device for measuring the responsiveness of the hydrogen gas sensitive film. FIG. 3 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 1-1. FIG. 4 is an enlarged view of a region A surrounded by a broken line in FIG. FIG. 5 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 1-2. 6 is an enlarged view of a region A surrounded by a broken line in FIG. FIG. 7 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 1-3. FIG. 8 is an enlarged view of a region A surrounded by a broken line in FIG. FIG. 9 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 1-4. FIG. 10 is an enlarged view of a region A surrounded by a broken line in FIG. FIG. 11 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 2. FIG. 12 is an enlarged view of a region A surrounded by a broken line in FIG. FIG. 13 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 3. FIG. 14 is an enlarged view of a region A surrounded by a broken line in FIG. FIG. 15 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 4. FIG. 16 is an enlarged view of a region A surrounded by a broken line in FIG. FIG. 17 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 5-1. FIG. 18 is an enlarged view of a region A surrounded by a broken line in FIG. FIG. 19 is an enlarged view of a region B surrounded by a broken line in FIG. FIG. 20 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 5-2. FIG. 21 is an enlarged view of a region A surrounded by a broken line in FIG. FIG. 22 is an enlarged view of a region B surrounded by a broken line in FIG. FIG. 23 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 6-1. FIG. 24 is an enlarged view of a region A surrounded by a broken line in FIG. FIG. 25 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 6-2. FIG. 26 is an enlarged view of a region A surrounded by a broken line in FIG. FIG. 27 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 6-3. FIG. 28 is an enlarged view of a region A surrounded by a broken line in FIG. FIG. 29 is an enlarged view of a region B surrounded by a broken line in FIG. FIG. 30 is an enlarged view of a region C surrounded by a broken line in FIG. FIG. 31 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 7-1. 32 is an enlarged view of a region A surrounded by a broken line in FIG. FIG. 33 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 7-2. FIG. 34 is an enlarged view of a region A surrounded by a broken line in FIG. FIG. 35 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 7-3. FIG. 36 is an enlarged view of a region A surrounded by a broken line in FIG. FIG. 37 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 8. FIG. 38 is an enlarged view of a region A surrounded by a broken line in FIG. FIG. 39 is a graph showing the responsiveness of the coating film according to Comparative Example 1-1.

Hereinafter, modes for carrying out the present invention will be described.

The coating liquid according to the present embodiment includes (1) tungsten chloride, (2) a monohydric alcohol having 1 to 4 carbon atoms which dissolves tungsten chloride, (3) a carboxylic acid having reducibility, and (4) carbonic acid. And a compound of a metal that becomes a metal catalyst having a sensitivity to hydrogen gas by reduction with an acid (hereinafter, also simply referred to as a "metal compound"). The carboxylic acid of (3) is dissolved in the alcohol of (2). The coating liquid may further contain components other than the above (1) to (4).

The coating liquid of the present embodiment is applied to a substrate to form a coating film, and the coating film is dried in the air at room temperature or more and 150 ° C. or less to obtain metal ions (eg, platinum group metal ions) contained in the metal compound. A tungsten oxide film supporting a metal catalyst formed by reducing to a zero-valent metal (for example, a platinum group metal) is formed. It is not necessary to dry the coating film of the present embodiment while exposing it to a harmful gas or a flammable gas, and can be performed in the atmosphere. This is because the carboxylic acid reduces the metal ion contained in the metal compound to a zero-valent metal during drying of the coating film.

A tungsten oxide film carrying a metal catalyst is used as a hydrogen gas sensitive film. The hydrogen gas sensitive membrane has a low permeability by being exposed to hydrogen gas, and a high permeability by being exposed to the atmosphere. The application of the hydrogen gas sensitive film is, for example, a hydrogen gas visualization sheet, a hydrogen gas sensor, a hydrogen gas sensitive smart window, and the like.

The hydrogen gas-sensitive film may be made porous by carbon dioxide gas generated inside the coating film in the reduction reaction of metal ions contained in the metal compound. Carbon dioxide gas is generated by oxidizing the carboxylic acid during the drying of the coating film. The porous hydrogen gas sensitive membrane has good gas permeability and good sensitivity to the surrounding atmosphere.

FIG. 1 is a flowchart showing a method of manufacturing a coating liquid according to one embodiment. In addition, the manufacturing method of a coating liquid is not limited to the order of FIG. For example, (2) an alcohol may be added to a mixed powder in which (1) tungsten chloride, (3) carboxylic acid, and (4) a metal compound are mixed.

First, in step S11 of FIG. 1, tungsten chloride and a C 1-4 monovalent alcohol dissolving tungsten chloride are mixed to prepare a tungsten solution. As the preparation method, for example, the method described in Patent Document 8 is used. Although tungsten chloride is not particularly limited, it is, for example, tungsten hexachloride (WCl ₆ ). Examples of monohydric alcohols having 1 to 4 carbon atoms include methanol, ethanol, n-propyl alcohol and i-propyl alcohol. You may combine and use multiple types of alcohol. The reaction of tungsten hexachloride (WCl ₆ ) with alcohol (ROH) forms W (OR) _x Cl _{6 -x} .

Next, in step S12 of FIG. 1, a carboxylic acid is added to the tungsten solution to prepare a tungsten oxide precursor solution (hereinafter, also simply referred to as a "precursor solution"). Tungsten oxide is not particularly limited, and is, for example, tungsten trioxide (WO ₃ ).

The carboxylic acid has reducibility to metal ions contained in metal compounds to be added later to the precursor solution, and reduces metal ions to zero-valent metals during film formation to be performed later. Further, along with this reduction reaction, the carboxylic acid is oxidized to generate carbon dioxide gas, and a porous hydrogen gas sensitive film is obtained. Carboxylic acid can also be expected to play a role in stabilizing the precursor of tungsten oxide because it forms a chelate structure with tungsten in the precursor solution.

As a carboxylic acid having reducibility, oxalic acid, formic acid, citric acid, ascorbic acid and the like can be used. As the molecular weight of the carboxylic acid increases, carbon content tends to remain in the hydrogen gas-sensitive film after film formation. Therefore, oxalic acid and formic acid, which have a small molecular weight, are preferable. Among them, oxalic acid is more preferable because of ease of handling.

As oxalic acid, oxalic acid anhydride and oxalic acid dihydrate are commercially available products, and it is possible to use either, but the precursor solution using oxalic acid anhydride is more preferable. Is preferable in that the stability of

If the amount of carboxylic acid added is too large or too small, the stability of the precursor solution and the hydrogen sensitivity of the hydrogen gas sensitive film after film formation are adversely affected. The addition amount of carboxylic acid to the amount of tungsten in the tungsten solution is preferably 1/5 to 2/5, more preferably 1/5, in molar ratio (carboxylic acid / tungsten).

The addition of the carboxylic acid to the tungsten solution can be carried out at room temperature, and can also be carried out in the atmosphere without the need for special atmosphere control. The carboxylic acid can be dissolved in the tungsten solution at room temperature in air.

Next, in step S13 of FIG. 1, a metal compound as a raw material of the metal catalyst, for example, a compound of a platinum group metal, is added to the precursor solution to prepare a coating liquid. The platinum group metal compound may be any one as long as it dissolves in the precursor solution, and is, for example, one or more selected from the group consisting of a palladium compound, a platinum compound, and a palladium platinum alloy compound. You may mix and use 2 or more types selected from the group which consists of a palladium compound, a platinum compound, and a palladium platinum alloy compound.

Any palladium compound may be used as long as it can be easily dissolved in a tungsten solution or a precursor solution of tungsten oxide, but it is easily available and effectively reduces palladium ions in the air at room temperature to 150 ° C. In order to achieve this, one having a small molecular weight is preferred, and one having a small valence is preferred. Particularly preferred is palladium dichloride (PdCl ₂ ).

Any platinum compound may be used as long as it can be easily dissolved in a tungsten solution or a precursor solution of tungsten oxide, but it is easy to obtain and effectively reduces platinum ions at room temperature or more and 150 ° C. or less in the air. In order to achieve this, one having a small molecular weight is preferred, and one having a small valence is preferred. Specifically, platinum dichloride (PtCl ₂ ), platinum tetrachloride (PtCl ₄ ), and hexachloroplatinic acid hexahydrate (H ₂ PtCl ₆ .6H ₂ O) can be given. Particularly preferred is platinum dichloride (PtCl ₂ ).

When the addition amount of the metal compound which is a raw material of the metal catalyst is too large, not only the metal compound can not be completely dissolved in the precursor solution, but also the amount of metal deposited by reduction becomes large. Transparency is reduced. On the other hand, when the addition amount of the metal compound which is a raw material of a metal catalyst is too small, the hydrogen sensitivity characteristic of the hydrogen gas sensitive film after film formation will deteriorate. The addition amount of the metal compound to the amount of tungsten in the precursor solution is preferably 1/10 to 1/50, more preferably 1/50, in molar ratio (metal serving as metal catalyst (for example, platinum group metal) / tungsten). It is suitable.

The addition to the precursor solution of the metal compound which is a raw material of a metal catalyst can be performed at room temperature, and can also be performed in air | atmosphere, without requiring special atmosphere control. The metal compound which is a raw material of the metal catalyst can be dissolved in the precursor solution at room temperature in the air.

It is desirable to store the coating solution prepared in step S13 of FIG. 1 in a light-shielded space under a dry atmosphere in order to maintain a longer and stable state.

The prepared coating solution is applied to a substrate to form a coated film. As a method of application, a method capable of uniformly applying a solution with low viscosity, such as spin coating, dip coating, roll coating, etc. can be applied, and the material, size, thickness and the like of the used substrate It can be selected accordingly.

The prepared coating solution is applied to a substrate to form a coating film, and the coating film is dried at room temperature or more and 150 ° C. or less in the air to reduce metal ions contained in the metal compound to zero-valent metal. A tungsten oxide film carrying a metal catalyst is formed. It is not necessary to dry the coating film of the present embodiment while exposing it to a harmful gas or a flammable gas, and can be performed in the atmosphere. Moreover, drying of the coating film of this embodiment can be performed at room temperature (for example, 10 degreeC or more and 35 degrees or less).

In order to accelerate the reduction reaction of metal ions contained in the metal compound, the drying temperature of the coating film is preferably 50 ° C. or more and 100 ° C. or less. If the drying temperature of a coating film is 100 degrees C or less, a resin substrate etc. can be used as a base material which apply | coats a coating liquid other than a glass substrate. The resin substrate is formed of a resin having alcohol resistance and acid resistance, such as polyethylene, polypropylene, polycarbonate and the like. The substrate is preferably transparent. The thickness and size of the substrate to which the coating solution is applied are appropriately selected according to the application of the hydrogen gas-sensitive film, the application method of the coating solution, and the like, and are not particularly limited.

In order to accelerate the reduction reaction of metal ions contained in the metal compound, ultraviolet irradiation may be performed when the coating film is dried. The wavelength of the ultraviolet light is, for example, 200 nm to 380 nm. When ultraviolet irradiation is performed, the drying temperature of the coating film may be room temperature.

A tungsten oxide film carrying a metal catalyst is used as a hydrogen gas sensitive film. The hydrogen gas sensitive membrane has a low permeability by being exposed to hydrogen gas, and a high permeability by being exposed to the atmosphere.

The hydrogen gas sensitive film may be formed by applying the coating solution and drying the applied film only once, or may be formed by repeating the application of the coating solution and drying of the applied film multiple times. In the latter case, a plurality of tungsten oxide films constitute a hydrogen gas sensitive film. The film thickness of the hydrogen gas-sensitive film is appropriately selected according to the application and the like.

Hereinafter, specific examples of the coating liquid, the method of manufacturing the coating liquid, and the method of manufacturing the hydrogen gas-sensitive film will be described. Moreover, the evaluation result of the responsiveness of the obtained hydrogen gas sensitive film | membrane is demonstrated.

Example 1-1
First, according to the method described in Patent Document 8, super dehydrated ethanol and super dehydrated isopropyl alcohol are added to tungsten hexachloride (WCl ₆ ) under ice-cold dry nitrogen atmosphere, and then stirring is continued at room temperature to obtain a tungsten solution Obtained. The tungsten concentration in the tungsten solution was 0.25 mol / L.

Next, 1.0 × 10 ^-3 mol of oxalic acid anhydride is measured in an eggplant flask, to which 20 ml of tungsten solution (W: 5.0 × 10 ^-3 mol) is added and stirred to obtain tungsten oxide A precursor solution was prepared. The addition amount of oxalic acid anhydride relative to the amount of tungsten in the tungsten solution was 1/5 in molar ratio (oxalic acid anhydride / tungsten).

After 1 hour, 5.0 × 10 ⁻⁴ moles of PdCl ₂ was added to the precursor solution, and the mixture was shielded from light and stirred at room temperature as it was to prepare a clear brown coating solution. The amount of PdCl ₂ added to the amount of tungsten in the precursor solution was 1/10 in molar ratio (Pd / tungsten).

Next, the coating solution was spin-coated on a cleaned glass substrate at 3000 rpm for 30 seconds to form a coated film, and the formed coated film was dried by heating for 5 minutes on a hot plate at 100 ° C. in air. . The coating and drying operations were repeated five times to obtain a hydrogen gas-sensitive film.

The responsiveness of the obtained hydrogen gas-sensitive film was measured by the measuring device A shown in FIG. The measuring apparatus A does not include the hydrogen gas-sensitive film 2 which is an object to be measured, and the glass substrate 1 on which the hydrogen gas-sensitive film 2 is formed. FIG. 2 is a view showing a measuring device for measuring the responsiveness of the hydrogen gas sensitive film. In FIG. 2, arrows indicate the flow of hydrogen-containing gas. The hydrogen-containing gas is introduced by the mass flow controller 13, passes through the gap 16 between the glass cell 11 and the hydrogen gas sensitive film 2, and is released to the outside. As a hydrogen-containing gas, a gas containing 4% by volume of hydrogen gas and 96% by volume of argon gas was used.

As shown in FIG. 2, the measuring apparatus A includes a glass cell 11, a spacer 12, a mass flow controller 13, a light source 14, and a light receiver 15. The glass cell 11 is disposed to face the hydrogen gas sensitive film 2 formed on the glass substrate 1. The spacer 12 forms a gap 16 between the glass cell 11 and the hydrogen gas sensitive film 2 as a flow path of the hydrogen-containing gas. The mass flow controller 13 controls the flow rate of the hydrogen-containing gas flowing in the gap 16. The semiconductor laser device as the light source 14 emits a laser beam having a wavelength of 670 nm. The photodiode as the light receiver 15 receives the laser beam emitted from the light source 14 and outputs a signal according to the intensity of the received laser beam. The laser light emitted from the light source 14 passes through the glass substrate 1, the hydrogen gas sensitive film 2 and the glass cell 11 in this order, and is received by the light receiver 15. The ratio of the intensity of the laser beam received by the light receiver 15 to the intensity of the laser beam emitted from the light source 14 is the transmittance.

The response of the hydrogen gas-sensitive film was determined by alternately supplying the hydrogen-containing gas to the gap 16 of FIG. 2 for 60 seconds and stopping the supply for 60 seconds, alternately, the transmittance of the laser light having a wavelength of 670 nm. It measured by measuring. The measurement results are shown in FIG. 3 and FIG. FIG. 3 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 1-1. FIG. 4 is an enlarged view of a region A surrounded by a broken line in FIG. In FIG. 4, “ON” means switching from stop to supply of hydrogen-containing gas, and “off” means switch from supply of hydrogen-containing gas to stop. When the supply of the hydrogen-containing gas is stopped, the atmosphere enters the gap 16 from the outlet of the hydrogen-containing gas. The same applies to the other drawings.

As shown in FIG. 3, after the supply and stop of the hydrogen-containing gas are repeated about 20 times (about 2400 seconds), the hydrogen gas-sensitive film is gradually colored between colorless and transparent (transparent state) and blue (colored state) A change in the color (state) of Thereafter, as shown in FIG. 4, the transmittance of the laser light changed in the range of about 16% to 60% each time the supply and stop of the hydrogen-containing gas were switched. From this result, it was confirmed that the hydrogen gas-sensitive film can be obtained only by drying at 100 ° C. in the atmosphere according to the coating liquid of Example 1-1. Also, the good response of the hydrogen gas sensitive membrane means that the hydrogen gas sensitive membrane is made porous. However, when the supply and stop of the hydrogen-containing gas were repeated, the metallic gloss derived from Pd was observed due to the reduction reaction with hydrogen gas, and the transmittance at the time of transparency tended to gradually decrease.

Example 1-2
In Example 1-2, hydrogen was applied under the same conditions as Example 1-1 except that ultraviolet irradiation at a wavelength of 365 nm was simultaneously performed during 5 minutes of heating and drying the coating film on a hot plate at 100 ° C. in the atmosphere. A gas sensitive film was deposited. The responsiveness of the resulting hydrogen gas-sensitive membrane is shown in FIGS. FIG. 5 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 1-2. 6 is an enlarged view of a region A surrounded by a broken line in FIG.

As shown in FIG. 5, the color of the hydrogen gas-sensitive film changes between colorless and blue on the entire surface of the film immediately after the start of repeated supply and stop of the hydrogen-containing gas, and the color of the laser light changes as shown in FIG. The transmittance varied in the range of about 16% to 58%. From this result, it was confirmed that the time until response start (start of change of transmittance) can be shortened by using ultraviolet irradiation when drying the coating film.

Example 1-3
In Example 1-3, a hydrogen gas-sensitive film was formed under the same conditions as in Example 1-2 except that ultraviolet irradiation with a wavelength of 254 nm was performed instead of ultraviolet irradiation with a wavelength of 365 nm. The responsiveness of the obtained hydrogen gas sensitive membrane is shown in FIGS. 7 and 8. FIG. 7 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 1-3. FIG. 8 is an enlarged view of a region A surrounded by a broken line in FIG.

As shown in FIG. 7, the color of the hydrogen gas-sensitive film changes between colorless and transparent and blue immediately after the start of repeated supply and stop of the hydrogen-containing gas, but the response portion is only the center of the film, and the film outer periphery Remained dark blue and did not respond. At the central part of the membrane where the response was confirmed, the laser light transmittance changed in the range of about 40% to 60% as shown in FIG. 8, but for the switching from stop to supply of hydrogen-containing gas The response speed (hereinafter also referred to as "coloring response speed") and the response speed to switching from supply of hydrogen-containing gas to stop (hereinafter also referred to as "decoloring response speed") were slow.

Example 1-4
In Example 1-4, drying of the coating film is performed at room temperature (25 ° C.) in the air, and the coating film during the drying is irradiated with ultraviolet light of wavelength 365 nm for 5 minutes, and hydrogen is used under the same conditions as Example 1-2. A gas sensitive film was deposited. The responsiveness of the obtained hydrogen gas-sensitive membrane is shown in FIGS. FIG. 9 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 1-4. FIG. 10 is an enlarged view of a region A surrounded by a broken line in FIG.

As is apparent from FIGS. 9 and 10, it is possible to produce a hydrogen gas-sensitive film whose color changes depending on ON and OFF even when the drying temperature of the coating film is room temperature when irradiated with ultraviolet light having a wavelength of 365 nm. Was confirmed.

Example 2
Example 2 is an example except that the addition amount of oxalic acid anhydride relative to the amount of tungsten in the tungsten solution is increased from 1/5 to 2/5 in molar ratio (oxalic acid / tungsten) to prepare a precursor solution. A hydrogen gas sensitive film was formed under the same conditions as 1-2. The responsiveness of the obtained hydrogen gas sensitive membrane is shown in FIGS. FIG. 11 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 2. FIG. 12 is an enlarged view of a region A surrounded by a broken line in FIG.

As shown in FIG. 11, the color of the hydrogen gas-sensitive film changes between colorless and blue on the entire surface of the film immediately after the start of repeated supply and stop of the hydrogen-containing gas, as shown in FIG. The permeability changed in the range of about 22% to 62%, and it was confirmed that the film showed good sensitivity to hydrogen gas. As apparent from comparison between FIG. 12 and FIG. 6 of Example 1-2, the response speed upon coloring and the response speed upon discoloring become slower by increasing the molar ratio (oxalic acid / tungsten). I understand. In addition, as the number of repetitions of supply and stop of the hydrogen-containing gas increases, the transmittance at the time of coloring and the transmittance at the time of decoloring deteriorate (the transmittance at the time of coloring increases and the transmittance at the time of decoloring decreases) ) Also confirmed.

[Example 3]
In Example 3, the coating liquid was prepared except that the addition amount of PdCl ₂ with respect to the amount of tungsten in the precursor solution was reduced from 1/10 to 1/25 in molar ratio (Pd / tungsten). A hydrogen gas sensitive film was formed under the same conditions. The responsiveness of the obtained hydrogen gas sensitive membrane is shown in FIGS. 13 and 14. FIG. 13 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 3. FIG. 14 is an enlarged view of a region A surrounded by a broken line in FIG.

As shown in FIG. 13, the color of the hydrogen gas-sensitive film changes between colorless and blue on the entire surface of the film immediately after the start of repeated supply and stop of the hydrogen-containing gas, and the color of the laser light changes as shown in FIG. It was confirmed that the permeability changed in the range of about 34% to 70%, and showed good sensitivity to hydrogen gas. As apparent from the comparison between FIG. 14 and FIG. 6 of Example 1-2, the response speed at coloring and the response speed at decoloring become slower by reducing the molar ratio (Pd / tungsten). It was found that the transmissivity at the time of transparency was improved by about 10%. However, a slight metallic sheen from Pd was expected, which was expected to be overcome by the reduction of the molar ratio (Pd / tungsten).

Example 4
In Example 4, a hydrogen gas-sensitive film was prepared under the same conditions as in Example 1-2 except that a precursor solution was prepared using citric acid instead of oxalic acid anhydride as the carboxylic acid to be added to the tungsten solution. Was deposited. As in Example 1-2, the amount of citric acid added to the amount of tungsten in the tungsten solution was 1/5 in molar ratio (citric acid / tungsten). The responsiveness of the obtained hydrogen gas sensitive membrane is shown in FIGS. FIG. 15 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 4. FIG. 16 is an enlarged view of a region A surrounded by a broken line in FIG.

As shown in FIG. 15, after the supply and stop of the hydrogen-containing gas were repeated about 40 times (about 4800 seconds), the color of the hydrogen gas-sensitive film gradually changed between colorless and transparent and blue over the entire surface of the film. . As apparent from comparison between FIG. 15 and FIG. 5 of Example 1-2, when citric acid having a large molecular weight is used as the carboxylic acid, it takes time for the response to start (start of change in transmittance) all right. After that, as shown in FIG. 16, the change in the transmittance of the laser light with ON and OFF was about 30%, but as the number of repetitions of the supply and stop of the hydrogen-containing gas increases, the transmittance when transparent It went down.

Example 5-1
In Example 5-1, a hydrogen gas-sensitive film was prepared under the same conditions as Example 1-1 except that PtCl ₂ was used instead of PdCl ₂ as the metal compound to be added to the precursor solution. The film was formed. As in Example 1-1, the amount of PtCl ₂ added to the amount of tungsten in the precursor solution was 1/10 in molar ratio (Pt / tungsten). The responsiveness of the obtained hydrogen gas-sensitive film is shown in FIGS. FIG. 17 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 5-1. FIG. 18 is an enlarged view of a region A surrounded by a broken line in FIG. FIG. 19 is an enlarged view of a region B surrounded by a broken line in FIG.

As shown in FIGS. 17 and 19, unlike in the case of Example 1-1 (see FIG. 3), it is between about colorless and transparent and blue on the entire surface almost immediately after the start of repetition of supply and stop of hydrogen-containing gas. The color of the hydrogen gas sensitive membrane has changed. In addition, as shown in FIG. 18, it was confirmed that the transmittance of the laser light changed in the range of about 16% to 55%, and showed good sensitivity to hydrogen gas. Further, as apparent from comparison between FIG. 18 and FIG. 4 of Example 1-1, by using Pt as the metal catalyst instead of Pd, the response speed at the time of coloring and the response speed at the time of decoloring can be improved. It became faster. However, similar to Example 1-1, when the supply and stop of the hydrogen-containing gas are further repeated, the metallic gloss derived from Pt is observed by the reduction reaction with hydrogen gas, and the transmittance at the time of transparency tends to gradually decrease. there were.

Example 5-2
In Example 5-2, hydrogen was applied under the same conditions as in Example 5-1 except that ultraviolet irradiation at a wavelength of 365 nm was simultaneously performed during 5 minutes of heating and drying the coated film on a hot plate at 100 ° C. in the atmosphere. A gas sensitive film was deposited. That is, in Example 5-2, a hydrogen gas-sensitive film was formed under the same conditions as in Example 1-2 except that PtCl ₂ was used instead of PdCl ₂ as the metal compound added to the precursor solution. The responsiveness of the obtained hydrogen gas-sensitive film is shown in FIGS. FIG. 20 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 5-2. FIG. 21 is an enlarged view of a region A surrounded by a broken line in FIG. FIG. 22 is an enlarged view of a region B surrounded by a broken line in FIG.

As shown in FIG. 20 and FIG. 22, the color of the hydrogen gas-sensitive film changes between colorless and transparent and blue over the entire surface of the film immediately after the start of repeated supply and stop of hydrogen-containing gas, as shown in FIG. It was confirmed that the transmittance of the laser light changed in the range of about 14% to 46% and showed a good sensitivity to hydrogen gas. As apparent from comparison between FIG. 22 and FIG. 19 of Example 5-1, it is possible to shorten the time until response start (start of change of transmittance) by using ultraviolet irradiation together with heat drying. confirmed. Further, as apparent from comparison between FIG. 21 and FIG. 6 of Example 1-2, by using Pt as the metal catalyst instead of Pd, the response speed at the time of coloring and the response speed at the time of decoloring can be improved. It became faster.

Example 6-1
In Example 6-1, the amount of PtCl ₂ added to the amount of tungsten in the precursor solution was reduced by 1/10 to 1/50 in the molar ratio (Pt / tungsten) to prepare a coating solution, except for A hydrogen gas-sensitive film was formed under the same conditions as in 2. The responsiveness of the obtained hydrogen gas sensitive membrane is shown in FIG. 23 and FIG. FIG. 23 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 6-1. FIG. 24 is an enlarged view of a region A surrounded by a broken line in FIG.

As shown in FIG. 23, even if the molar ratio (Pt / Tungsten) is reduced from 1/10 to 1/50, as in Example 5-2, the inside of the film is immediately after the start of the repetition of the supply and stop of the hydrogen-containing gas. The color of the hydrogen gas sensitive film changed between colorless and transparent and blue over the entire surface. In addition, as shown in FIG. 24, it was confirmed that the transmittance of the laser light changed in the range of about 18% to 55%, and showed good sensitivity to hydrogen gas. Further, as in Example 5-2, the response speed at the time of coloring and the response speed at the time of decoloring were fast. In addition, the metallic luster derived from Pt observed in Example 5-2 was not observed.

Example 6-2
In Example 6-2, a hydrogen gas-sensitive film was formed under the same conditions as in Example 6-1 except that the drying temperature of the coating film was lowered from 100 ° C. to 80 ° C. The responsiveness of the obtained hydrogen gas sensitive membrane is shown in FIGS. 25 and 26. FIG. 25 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 6-2. FIG. 26 is an enlarged view of a region A surrounded by a broken line in FIG.

As shown in FIG. 25, the color of the hydrogen gas-sensitive film changes between colorless and blue on the entire surface of the film immediately after the start of repeated supply and stop of the hydrogen-containing gas, as shown in FIG. It was confirmed that the permeability changes in the range of about 20% to 65%, and shows good sensitivity to hydrogen gas. However, as apparent from comparison of FIG. 26 with FIG. 24 of Example 6-1, the response speed at the time of coloring and the response speed at the time of decoloring were reduced due to the lowering of the drying temperature. Further, when the supply and stop of the hydrogen-containing gas were further repeated, a region which did not return to the transparent state while remaining blue-colored was observed in the outer peripheral portion of the film.

Example 6-3
In Example 6-3, a hydrogen gas-sensitive film was formed under the same conditions as in Example 6-2, except that ultraviolet irradiation was not performed at the time of drying of the coated film. The response of the obtained hydrogen gas-sensitive film is shown in FIGS. FIG. 27 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 6-3. FIG. 28 is an enlarged view of a region A surrounded by a broken line in FIG. FIG. 29 is an enlarged view of a region B surrounded by a broken line in FIG. FIG. 30 is an enlarged view of a region C surrounded by a broken line in FIG.

As shown in FIG. 27, the coloring phenomenon from colorless and transparent to blue was observed immediately after the start of the repetition of the supply and stop of the hydrogen-containing gas, and the change was also fast, but the time until the decoloring phenomenon was observed I needed it. The response speed at the time of coloring and the response speed at the time of decoloring became faster (see FIG. 29) when the number of repetitions of supply and stop of the hydrogen-containing gas exceeded 100 times (12000 seconds). The response speed gradually decreased as the number of repetitions exceeded 400 times (48000 seconds) (see FIG. 30). In addition, the film outer peripheral portion did not return to the transparent state while it was colored blue since about the time the number of repetitions exceeded 400 times. However, it was also confirmed that the transmittance of the laser light changed in the range of 20% to 70% even if it was dried at 80 ° C. without ultraviolet irradiation, showing good sensitivity to hydrogen gas.

Example 7-1
In Example 7-1, a precursor solution is prepared using oxalic acid dihydrate instead of oxalic acid anhydride as the carboxylic acid added to the tungsten solution, and the metal added to the precursor solution Hydrogen gas sensitization under the same conditions as in Example 5-1 except that H ₂ PtCl ₆ · 6H ₂ O was used instead of PtCl ₂ as the compound and the coating solution was prepared with a molar ratio (Pt / tungsten) of 1/26. Film was deposited. As in Example 5-1, the amount of oxalic acid dihydrate added was 1/5 in molar ratio (oxalic acid dihydrate / tungsten) with respect to the amount of tungsten in the tungsten solution. The responsiveness of the hydrogen gas sensitive membrane is shown in FIGS. 31 and 32. FIG. 31 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 7-1. 32 is an enlarged view of a region A surrounded by a broken line in FIG.

As shown in FIG. 31, after the supply and stop of the hydrogen-containing gas are repeated about 110 times (about 13200 seconds), the hydrogen gas-sensitive film is gradually colored between colorless and transparent (transparent state) and blue (colored state) A color change began to occur. It took H ₂ PtCl ₆ · 6 H ₂ O containing tetravalent Pt ion to take longer to start response (start of change of transmittance) compared to the case of Example 5-1 (see FIG. 17). It is considered that the reduction reaction to zero valent Pt is insufficient at the time of film formation as compared with PtCl ₂ containing divalent Pt ions. After that, as shown in FIG. 32, it was confirmed that the transmittance of the laser light changed in the range of about 20% to 70%, and it showed good sensitivity to hydrogen gas. Further, as in the case of Example 5-1 (see FIG. 18), the response speed upon coloring and the response speed upon decoloring were fast.

Example 7-2
In Example 7-2, hydrogen was applied under the same conditions as in Example 7-1, except that ultraviolet irradiation at a wavelength of 365 nm was simultaneously performed during 5 minutes of heating and drying the coated film on a hot plate at 100 ° C. in the atmosphere. A gas sensitive film was deposited. The responsiveness of the obtained hydrogen gas sensitive membrane is shown in FIG. 33 and FIG. FIG. 33 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 7-2. FIG. 34 is an enlarged view of a region A surrounded by a broken line in FIG.

As shown in FIG. 33, after the supply and stop of the hydrogen-containing gas are repeated about 80 times (9,600 seconds), the color of the hydrogen gas-sensitive film gradually between colorless and transparent (transparent state) and blue (colored state) Change began to take place. As apparent from comparison between FIG. 33 and FIG. 31 of Example 7-1, it was confirmed that response start (start of change of transmittance) is quickened by using ultraviolet irradiation together with heating and drying. . After that, as shown in FIG. 34, it was confirmed that the transmittance of the laser light changed in the range of about 22% to 76%, and showed a good sensitivity to hydrogen gas. As apparent from the comparison between FIG. 34 and FIG. 32 of Example 7-1, by using ultraviolet irradiation together with heat drying, the response speed at coloring and the response speed at decoloring became faster.

Example 7-3
In Example 7-3, a hydrogen gas-sensitive film was formed under the same conditions as in Example 7-1 except that the coating film was dried by heating on a hot plate at 150 ° C. in the atmosphere. The responsiveness of the obtained hydrogen gas sensitive membrane is shown in FIGS. 35 and 36. FIG. 35 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 7-3. FIG. 36 is an enlarged view of a region A surrounded by a broken line in FIG.

As shown in FIG. 35, after the supply and stop of the hydrogen-containing gas are repeated about 25 times (3000 seconds), the color of the hydrogen gas-sensitive film gradually between colorless and transparent (transparent state) and blue (colored state) Change began to take place. As apparent from the comparison between FIG. 35 and FIG. 31 of Example 7-1, it was confirmed that the response start (the start of the change of the transmittance) is quickened by the increase of the drying temperature. After that, as shown in FIG. 36, it was confirmed that the transmittance of the laser light changed in the range of about 35% to 70%, and it showed good sensitivity to hydrogen gas. As apparent from a comparison between FIG. 36 and FIG. 32 of Example 7-1, it was also found that the response speed at coloring and the response speed at decoloring become slower as the drying temperature becomes higher.

Example 8
In Example 8, a precursor solution is prepared using citric acid instead of oxalic acid dihydrate as the carboxylic acid added to the tungsten solution, and H ₂ PtCl ₆ ··· relative to the amount of tungsten in the precursor solution. A hydrogen gas-sensitive film was formed under the same conditions as in Example 7-2, except that the amount of addition of 6H ₂ O was increased from 1/26 to 1/10 in molar ratio (Pt / tungsten) to prepare a coating solution. . As in Example 7-2, the addition amount of citric acid to the amount of tungsten in the tungsten solution was 1/5 in molar ratio (citric acid / tungsten). The responsiveness of the obtained hydrogen gas sensitive membrane is shown in FIG. 37 and FIG. FIG. 37 is a graph showing the responsiveness of the hydrogen gas-sensitive film according to Example 8. FIG. 38 is an enlarged view of a region A surrounded by a broken line in FIG.

As shown in FIG. 37, after the supply and stop of the hydrogen-containing gas were repeated about 80 times (9600 seconds), the color of the hydrogen gas-sensitive film gradually changed between colorless and transparent and blue. As shown in FIGS. 37 and 38, the change in the transmittance of the laser light with ON and OFF was about 40% to 45%.

Comparative Example 1-1
In Comparative Example 1-1, the addition of _H ₂ PtCl ₆ · 6H 2 O in the precursor solution prepared without the addition of carboxylic acids such as oxalic acid tungsten solution, _H 2 PtCl for tungsten amount in the precursor solution Coating and drying were carried out under the same conditions as in Example 7-1 except that the amount of the added ₆ · 6H ₂ O was increased from 1/26 to 29/500 in molar ratio (Pt / tungsten) to prepare a coating solution. A film was formed. The responsiveness of the obtained coating film is shown in FIG. FIG. 39 is a graph showing the responsiveness of the coating film according to Comparative Example 1-1.

As apparent from FIG. 39, although the molar ratio (Pt / tungsten) was higher than that of Example 7-1, the carboxylic acid was not added, and thus the tetravalent Pt ion had zero valent Pt. No response was observed even if the hydrogen-containing gas was repeatedly supplied and stopped for 10 hours.

Comparative Example 1-2
In Comparative Example 1-2, coating was performed under the same conditions as Comparative Example 1-1 except that ultraviolet irradiation at a wavelength of 365 nm was simultaneously performed during 5 minutes of heating and drying the coated film on a hot plate at 100 ° C. in the atmosphere. A film was formed.

In Comparative Example 1-2, since the ultraviolet irradiation was used in combination with the heating and drying, the supply and stop of the hydrogen-containing gas were repeated 100 times (12000 seconds) even if the carboxylic acid was not added. A change in color began to occur between the transparent state) and the blue color (colored state), but the change in the transmittance of the laser light was small. In addition, the area where the color changed was limited to the vicinity of the outlet of hydrogen-containing gas (that is, the inlet of the atmosphere), and no response was seen on the entire surface of the film. It was also found that the response speed at the time of decoloring was slow.

[Summary]
The experimental conditions and the like of the above example and the above comparative example are summarized in Table 1.

As shown in Table 1, in the above-mentioned example, unlike the above-mentioned comparative example, the coating liquid containing carboxylic acid was used. As a result, in the above example, unlike the above comparative example, in the process of applying the coating liquid to the base material and drying the applied film to produce a film containing a metal catalyst having sensitivity to hydrogen gas, The metal ion in the coating solution was able to be reduced in the air at a temperature of room temperature to 150 ° C. to form a metal catalyst without using harmful gas or flammable gas.

Although the embodiments of the coating liquid, the method of manufacturing the coating liquid, and the method of manufacturing the hydrogen gas-sensitive film have been described above, the present invention is not limited to the above embodiments and the like, and the present invention is described in the claims. Within the scope of the invention, various modifications and improvements are possible.

This application claims the priority based on Japanese Patent Application No. 2017-214050 filed on Nov. 6, 2017 to the Japanese Patent Office, and the entire contents of Japanese Patent Application No. 2017-214050 are incorporated into the present application. Do.

S11 Step of preparing tungsten solution S12 step of preparing tungsten oxide precursor solution step S13 of preparing coating solution

Claims

With tungsten chloride,
A C 1-4 monovalent alcohol dissolving the tungsten chloride;
A reducing carboxylic acid dissolved in the alcohol;
What is claimed is: 1. A coating liquid comprising: a compound of a metal serving as a metal catalyst having sensitivity to hydrogen gas by being reduced by the carboxylic acid.
The coating liquid according to claim 1, wherein the carboxylic acid is oxalic acid.
The coating liquid according to claim 1, wherein the metal compound is a platinum group metal compound.
The coating liquid according to claim 3, wherein the compound of the platinum group metal is one or more selected from the group consisting of a palladium compound, a platinum compound, and a palladium-platinum alloy compound.
The compound of the platinum group metal is palladium dichloride (PdCl 2 ), platinum dichloride (PtCl 2 ), platinum tetrachloride (PtCl 4 ), and hexachloroplatinic acid hexahydrate (H 2 PtCl 6 · 6H 2 O) It is 1 or more types selected from the group which consists of, The coating liquid of Claim 3 characterized by the above-mentioned.
The coating liquid according to claim 1, which is used for forming a tungsten oxide film supporting the metal catalyst.
Tungsten chloride is mixed with a C 1-4 monovalent alcohol dissolving the tungsten chloride to prepare a tungsten solution,
A carboxylic acid having reducibility is dissolved in the tungsten solution to prepare a precursor solution of tungsten oxide,
A method of producing a coating liquid, comprising: dissolving a compound of a metal serving as a metal catalyst having sensitivity to hydrogen gas by reduction with the carboxylic acid in the precursor solution to prepare a coating liquid.
A coating solution according to claim 1 is applied to a substrate to form a coating film, and the coating film is dried in the air at room temperature or more and 150 ° C. or less to obtain metal ions contained in the raw material of the metal catalyst. A method for producing a hydrogen gas sensitive film, comprising forming a tungsten oxide film carrying the metal catalyst formed by reduction.