JP2021152483A - Hydrogen gas sensitive film, coating liquid used for formation thereof, production method of coating liquid, and production method of hydrogen gas sensitive film - Google Patents

Abstract

To provide a technique with which the color of a hydrogen gas sensitive film is rendered opaque white before the film is exposed to a hydrogen gas, so that the change of the color can be easily clarified when the film is exposed to the hydrogen gas.SOLUTION: A hydrogen gas sensitive film comprises dispersed particles including tungsten, oxygen, and a platinum group metal. The hydrogen gas sensitive film has the surface roughness of 50 nm-300 nm and the porosity of 20%-50%. The hydrogen gas sensitive film becomes white when being exposed to the atmospheric air and becomes blue when being exposed to hydrogen.SELECTED DRAWING: Figure 6

Description

The present invention relates to a hydrogen gas-sensitive film, a coating liquid used for film formation thereof, a method for producing the coating liquid, and a method for producing a hydrogen gas-sensitive film.

Conventionally, a tungsten oxide film supporting a metal catalyst has been developed as a hydrogen gas sensitive film. This hydrogen gas-sensitive film usually has a low transmittance and a blue color when exposed to hydrogen gas, and a high transmittance and a return to the original colorless and transparent color when exposed to the atmosphere. Applications of the hydrogen gas sensitive film are, for example, a hydrogen gas visualization sheet, a hydrogen gas sensor, a hydrogen gas sensitive smart window, and the like.

As a method for producing a hydrogen gas-sensitive film, not only a physical vapor deposition method but also a wet method that can be produced at a lower cost has been proposed. In the wet method, the coating liquid is applied to the base material to form a coating film on the surface of the base material. In many cases, it is difficult to use a base material having low heat resistance because high-temperature firing of the coating film is required.

Recently, a process that uses ultraviolet rays instead of high-temperature firing has been developed, but in that case, ultraviolet rays are applied while exposing the coating film to a reducing harmful gas such as formaldehyde or hydrogen or a flammable gas. It was necessary to irradiate the membrane (see, for example, Patent Documents 1 to 3).

On the other hand, a new coating liquid capable of producing a hydrogen gas-sensitive film at a low temperature of room temperature to 150 ° C. without using harmful gas and flammable gas has also been developed (see, for example, Patent Documents 4 to 5).

Japanese Unexamined Patent Publication No. 2010-2346 International Publication No. 2009/154216 Japanese Unexamined Patent Publication No. 2016-161507 International Publication No. 2019/087705 International Publication No. 2019/087704

The conventional tungsten oxide-based hydrogen gas-sensitive film had a colorless and transparent color before being exposed to hydrogen gas, and it was difficult to see the color change when exposed to hydrogen gas.

One aspect of the present invention provides a technique for making a color before exposure to hydrogen gas opaque white so that a change in color can be easily seen when the hydrogen gas sensitive film is exposed to hydrogen gas.

[1] The hydrogen gas-sensitive membrane according to one aspect of the present invention is
Particles containing tungsten, oxygen, and a platinum group metal are dispersed and contained.
The surface roughness is 50 nm to 300 nm,
Porosity is 20% to 50%,
It turns white when exposed to the atmosphere and blue when exposed to hydrogen.

[2] The platinum group metal is at least one selected from the group consisting of palladium, platinum, and a palladium-platinum alloy.

[3] The coating liquid used for forming the hydrogen gas-sensitive film according to one aspect of the present invention is
Tungsten oxide precursor derived from tungsten alkoxide,
With chain or cyclic ether,
A metal catalyst precursor containing a metal ion that becomes a metal catalyst having hydrogen gas sensitivity by being reduced,
An organic solvent that dissolves the tungsten oxide precursor and the metal catalyst precursor,
It contains a carboxylic acid that reduces the metal ions contained in the metal catalyst precursor to a metal to produce the metal catalyst.

[4] Further contains an emulsifier.

[5] It is in the form of micelles.

[6] The emulsifier is an amphipathic organic solvent.

[7] The amphipathic organic solvent is methanol, ethanol, or acetone.

[8] The metal catalyst precursor contains ions of a platinum group metal.

[9] A method for producing a coating liquid used for forming a hydrogen gas-sensitive film according to one aspect of the present invention is described.
Tungsten chloride and chain ether are mixed and stirred to react to prepare a first solution containing a tungsten oxide precursor.
To prepare a second solution containing a metal catalyst precursor by dissolving a metal compound containing a metal ion that becomes a metal catalyst having hydrogen gas sensitivity by being reduced in an organic solvent.
The first solution and the second solution are mixed and stirred to prepare a third solution separated into a lower layer and an upper layer containing the tungsten oxide precursor and the metal catalyst precursor.
The present invention comprises adding a carboxylic acid that produces the metal catalyst by reducing the metal ions contained in the metal catalyst precursor to a metal with respect to the third solution.

[10] Further, an emulsifier is added to the third solution.

[11] By adding the emulsifier, the third solution is made into micelles.

[12] The emulsifier is an amphipathic organic solvent.

[13] The amphipathic organic solvent is methanol, ethanol, or acetone.

[14] The metal compound is a compound of a platinum group metal.

[15] The method for producing a hydrogen gas-sensitive film according to one aspect of the present invention is as follows.
By applying the coating liquid to the base material to form a coating film on the surface of the base material,
Drying the coating film in the air at room temperature or higher and 100 ° C. or lower
After or during the drying of the coating film, the coating film is irradiated with ultraviolet rays to form a tungsten oxide film carrying the metal catalyst.

According to one aspect of the present invention, the color before exposure to hydrogen gas can be made opaque white so that the color change can be easily seen when the hydrogen gas sensitive film is exposed to hydrogen gas.

FIG. 1 is a flowchart showing a method for producing a coating liquid according to an embodiment. FIG. 2 is a flowchart showing a method for producing a hydrogen gas-sensitive film according to an embodiment. FIG. 3A is a photograph immediately after the formation of the hydrogen gas-sensitive film of Example 1-1, and FIG. 3B is immediately after exposure of the hydrogen gas-sensitive film of Example 1-1 to hydrogen gas. It is a photograph of. FIG. 4 is a diagram showing a transmission spectrum of the hydrogen gas-sensitive membrane of Example 1-1. FIG. 5 is a diagram showing a reflection spectrum of the hydrogen gas sensitive film of Example 1-1. FIG. 6 (A) is an AFM photograph of the hydrogen gas-sensitive film of Example 1-1, and FIG. 6 (B) is an enlarged AFM photograph of the white square frame of FIG. 6 (A). FIG. 7 is a bright field image obtained by observing a cross section of the hydrogen gas sensitive film of Example 1-1 with a scanning transmission electron microscope (STEM). FIG. 8 is a diagram showing an example of a measuring device for measuring the responsiveness of a hydrogen gas-sensitive film to hydrogen gas. FIG. 9 is a diagram showing the measurement results of the responsiveness of the hydrogen gas-sensitive film of Example 1-1 to hydrogen gas. FIG. 10 is a photograph of the hydrogen gas-sensitive film of Example 1-2 immediately after being exposed to hydrogen gas. FIG. 11 is a photograph of the hydrogen gas-sensitive film of Example 1-3 immediately after being exposed to hydrogen gas. FIG. 12 is a photograph of the hydrogen gas-sensitive film of Example 1-4 immediately after being exposed to hydrogen gas. FIG. 13 is a photograph of the hydrogen gas-sensitive film of Example 1-5 immediately after being exposed to hydrogen gas. FIG. 14 is a photograph of the hydrogen gas-sensitive film of Example 1-6 immediately after being exposed to hydrogen gas. FIG. 15 is a diagram showing the measurement results of the responsiveness of the hydrogen gas-sensitive film of Example 1-7 to hydrogen gas. FIG. 16 is a photograph of the hydrogen gas-sensitive film of Example 1-7 immediately after being exposed to hydrogen gas. FIG. 17 is a photograph of the hydrogen gas-sensitive film of Example 2 immediately after being exposed to hydrogen gas. FIG. 18 (A) is an AFM photograph of the hydrogen gas-sensitive film of Comparative Example 3, and FIG. 18 (B) is an enlarged AFM photograph of the white square frame of FIG. 18 (A). FIG. 19 is a bright-field image of a cross section of the hydrogen gas-sensitive film of Comparative Example 3 observed by STEM.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, the same or corresponding configurations may be designated by the same reference numerals and description thereof may be omitted. In the specification, "~" indicating a numerical range means that the numerical values described before and after the numerical range are included as the lower limit value and the upper limit value.

The method for producing the coating liquid of the present embodiment includes S101 to S105 shown in FIG. In S101, tungsten chloride A and chain ether B are mixed and stirred to react to prepare a first solution L1 containing a tungsten oxide precursor C. In S102, the second solution L2 containing the metal catalyst precursor F is prepared by dissolving the metal compound D in the organic solvent E. In S103, the first solution L1 obtained in S101 and the second solution L2 obtained in S102 are mixed and stirred to form a lower layer containing the tungsten oxide precursor C and the metal catalyst precursor F, and a lower layer. Prepare a third solution L3 separated into an upper layer formed on top of it. In S104, emulsifier G is added to the third solution L3. In S105, the carboxylic acid H is added to the third solution L3. Carboxylic acid H is dissolved in the third solution L3. The order of S104 and S105 may be reversed, or S104 and S105 may be carried out at the same time. Further, if the lower layer and the upper layer can be uniformly dispersed by mixing, stirring or the like without adding the emulsifier G, the addition of the emulsifier G is unnecessary and S104 may not be carried out. Hereinafter, details of S101 to S105 will be described.

First, in S101, tungsten chloride A and chain ether B are mixed and stirred to react to prepare a first solution L1 containing a tungsten oxide precursor C. The first solution L1 is prepared, for example, in a dry nitrogen atmosphere.

The tungsten chloride A is not particularly limited, but is, for example, tungsten hexachloride (WCl ₆ ). When tungsten hexachloride (WCl ₆ ) reacts with chain ether (ROR'), at least one molecule of _{W (OR) 6} , W (OR) ₅ Cl, W (OR) ₄ Cl _{2, etc.} An aggregate or an aggregate in which two or more molecules are networked, that is, a tungsten oxide precursor C derived from a so-called tungsten alkoxide is formed, and R'Cl or the like is generated as a by-product. R and R'are organic groups such as an alkyl group or an aryl group, respectively.

Examples of the chain ether B include diisopropyl ether, diethyl ether, and methyl t-butyl ether. Of these, diisopropyl ether is particularly suitable. A plurality of types of chain ethers may be used in combination. Further, the chain ether B is preferably a super dehydration type having a water content of 10 mass ppm or less. If the ultra-dehydration type is used, it is possible to suppress the mixing of water and prevent the tungsten oxide precursor C from precipitating as _{tungsten oxide (WO 3) before film formation (before S201).}

In S101, the chain ether B is added to the tungsten chloride A, and then the tungsten chloride A and the chain ether B are stirred at room temperature. These treatments are carried out, for example, inside a glove box and a draft, and are carried out in a dry nitrogen atmosphere. By stirring at room temperature, tungsten chloride A gradually reacts with the chain ether B. This reaction results in a suspension that is largely reddish brown and partly green or blue.

In S101, following the stirring at room temperature, further stirring at a temperature higher than room temperature is performed. Stirring at high temperature is also performed in a dry nitrogen atmosphere. Stirring at a high temperature accelerates the reaction between tungsten chloride A and the chain ether B, and vaporizes R'Cl and the like as by-products and removes them from the first solution L1. The first solution L1 may be heated while adjusting the flow rate of the dry nitrogen gas inside the draft so that the by-product R'Cl or the like is easily vaporized.

The heating temperature of the first solution L1 is appropriately selected depending on the type of the chain ether B, and specifically, for example, R'Cl which is below the boiling point of the chain ether B and is a by-product. It is set above the boiling point. When diisopropyl ether is used as the chain ether B, the boiling point of diisopropyl ether is 69 ° C., and the boiling point of isopropyl chloride, which is a by-product, is 34.8 ° C., so that the heating temperature of the first solution L1 is, for example, The temperature is 50 ° C to 55 ° C. The first solution L1 is heated, for example, by a hot water bath.

The heating time of the first solution L1 is, for example, about 30 minutes to 1 hour. The heating time of the first solution L1 is appropriately adjusted based on, for example, the remaining amount of the solvent in the first solution L1. The remaining amount of the solvent depends on the flow rate of nitrogen gas as well as the heating temperature and heating time. If the amount of solvent is too low, an appropriate amount of solvent may be added. The amount of solvent is controlled so that the solvent does not completely evaporate, that is, the tungsten oxide precursor C does not solidify.

In the heating process of the first solution L1, the chain ether B can be replaced with another type of ether. When diisopropyl ether is used as the chain ether B, diisopropyl ether may form a peroxide on a yearly basis. Therefore, in the heating process of the first solution L1, the amount of diisopropyl ether may be reduced as much as possible and replaced with methyl t-butyl ether that can be used stably.

Next, in S102, the second solution L2 containing the metal catalyst precursor F is prepared by dissolving the metal compound D in the organic solvent E. The preparation of the second solution L2 is also carried out in a dry nitrogen atmosphere in the same manner as the preparation of the first solution L1.

The metal compound D is, for example, a compound of a platinum group metal. The platinum group metal compound may be one that is uniformly mixed with the first solution L1, 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. Two or more kinds selected from the group consisting of a palladium compound, a platinum compound, and a palladium-platinum alloy compound may be mixed and used. Among them, bis (acetylacetonato) platinum (II) is exemplified as a suitable one.

If the amount of the metal compound D added is too large, not only the metal compound D cannot be completely dissolved in the organic solvent E, but also the metal compound D cannot be uniformly mixed with the first solution L1 and may precipitate. be. On the other hand, if the amount of the metal compound D added is too small, the hydrogen gas sensitivity after the film formation is lowered. The amount of the metal compound D added is 1/10 to 1/1 in terms of the molar ratio (platinum group metal / tungsten) of the metal compound D to the metal (for example, platinum group metal) that serves as a metal catalyst for tungsten in the first solution L1. 50 is preferable, and 1/50 is more preferable.

The organic solvent E is not particularly limited as long as it is a solvent that dissolves the metal compound D and also dissolves the tungsten oxide precursor C. As the organic solvent E, ethylene glycol monomethyl ether (EGMME) is exemplified as a suitable one.

Next, in S103, the first solution L1 obtained by S101 and the second solution L2 obtained by S102 are mixed and stirred to prepare a third solution L3. Mixing / stirring of the first solution L1 and the second solution L2 is carried out at room temperature. When the third solution L3 is left in a stationary state, it separates into a lower layer containing the tungsten oxide precursor C and the metal catalyst precursor F and an upper layer formed on the lower layer. For example, the lower layer contains EGMME, which is an organic solvent E, and the upper layer contains diisopropyl ether, which is a chain ether B. The density of EGMME is higher than the density of diisopropyl ether.

Next, in S104, the emulsifier G is added to the third solution L3. By adding the emulsifier G, the lower layer and the upper layer are mixed to form micelles. It is presumed that by forming the third solution L3 into micelles, a film having large surface irregularities is obtained at the time of film formation, and light is scattered by the surface irregularities to obtain an opaque white film.

The emulsifier G is, for example, an amphipathic organic solvent having an affinity for both the upper layer and the lower layer. The emulsifier G preferably does not remain in the hydrogen gas-sensitive film after the film formation. The emulsifier G is, for example, methanol, ethanol, or acetone. The emulsifier G is preferably a super dehydration type having a water content of 10 mass ppm or less. If the ultra-dehydration type is used, it is possible to suppress the mixing of water and prevent the tungsten oxide precursor C from precipitating as _{tungsten oxide (WO 3) before film formation (before S201).}

Next, in S105, the carboxylic acid H is added to the third solution L3. The carboxylic acid H has a reducing property with respect to the metal ion contained in the metal catalyst precursor F, and reduces the metal ion to a zero-valent metal at the time of the subsequent film formation (S201 to S203). Further, along with this reduction reaction, the carboxylic acid H is oxidized to generate carbonic acid gas, and a porous hydrogen gas sensitive film is obtained.

As the carboxylic acid H, oxalic acid, formic acid, citric acid and the like can be used. The larger the molecular weight of the carboxylic acid H, the easier it is for carbon to remain in the film after film formation. Therefore, oxalic acid and formic acid having a small molecular weight are preferable. Among them, oxalic acid is more preferable because of its ease of handling.

As for oxalic acid, oxalic acid / anhydride and oxalic acid / dihydrate are available as commercial products, and either of them can be used, but it is better to use oxalic acid / anhydride as the coating liquid. It is preferable in that it improves stability.

If the amount of the carboxylic acid H added is too large or too small, it adversely affects the stability of the coating liquid and the hydrogen-sensitive characteristics after the film formation. The amount of carboxylic acid H added to the third solution L3 is the molar ratio of carboxylic acid H to tungsten in the third solution L3 (carboxylic acid H / tungsten), preferably 1/5 to 2/5, and 1 /. 5 is more preferable.

The addition of the carboxylic acid H to the third solution L3 can be carried out at room temperature. After the addition, continue stirring at room temperature as it is, and stop stirring when the solution changes to a uniform and transparent solution. In this way, the coating liquid is obtained. It is desirable to store the coating liquid in a light-shielded refrigerated space in a dry atmosphere in order to maintain a stable state for a longer period of time. The temperature of the refrigerated space is lower than room temperature, for example 4 ° C.

The coating liquid is preferably produced in a dry nitrogen atmosphere. Although it can be produced in the air, according to the production in a dry nitrogen atmosphere, it is possible to suppress the precipitation of tungsten in the solution as tungsten oxide, and it is possible to suppress the decrease in the amount of tungsten in the solution.

The coating liquid of the present embodiment contains a tungsten oxide precursor C, a chain ether B, a metal catalyst precursor F, an organic solvent E, and a carboxylic acid H. The tungsten oxide precursor C is formed by mixing and stirring tungsten chloride A and chain ether B and reacting them, and is derived from tungsten alkoxide. The chain ether B is used for forming the tungsten oxide precursor C and does not dissolve the tungsten oxide precursor C. The chain ether B may be replaced with another chain or cyclic ether as described above. Therefore, the coating liquid may contain a chain or cyclic ether different from the chain ether B. The metal catalyst precursor F contains metal ions that, when reduced, become a metal catalyst having hydrogen gas sensitivity. The organic solvent E dissolves the tungsten oxide precursor C and the metal catalyst precursor F. The carboxylic acid H reduces the metal ions contained in the metal catalyst precursor F to a metal to produce a metal catalyst.

The coating liquid of the present embodiment further contains an emulsifier G. By adding the emulsifier G, the lower layer and the upper layer are mixed to form micelles. It is presumed that by forming the third solution L3 into micelles, a film having large surface irregularities is obtained at the time of film formation, and light is scattered by the irregularities on the surface to obtain an opaque white film. As described above, if the lower layer and the upper layer can be uniformly dispersed by mixing, stirring, etc. without adding the emulsifier G, it is not necessary to add the emulsifier G, and the coating liquid does not contain the emulsifier G. You may.

The method for producing a hydrogen gas-sensitive film of the present embodiment includes S201 to S203 shown in FIG. In S201, the coating liquid of the present embodiment is applied to the base material to form a coating film on the surface of the base material. In S202, the coating film is dried in the air at room temperature or higher and 100 ° C. or lower. In S203, the coating film is irradiated with ultraviolet rays to form a tungsten oxide film supporting a metal catalyst. By irradiating with ultraviolet rays, the reduction of metal ions contained in the metal catalyst precursor F can be promoted. The reduction of metal ions contained in the metal catalyst precursor F is also promoted by the addition of the carboxylic acid H. After coating, the carboxylic acid H reduces the metal ions contained in the metal catalyst precursor F to a metal to produce a metal catalyst. Further, S203 may be performed at the same time as S202, not after S202. That is, the irradiation of ultraviolet rays may be performed after or during the drying of the coating film. Hereinafter, details of S201 to S203 will be described.

First, in S201, the coating liquid is applied to the base material to form a coating film on the surface of the base material. The base material may be transparent or opaque. When the base material is transparent, the change in color of the hydrogen gas-sensitive film can be visually recognized through the base material. The type, thickness, and size of the base material are appropriately selected according to the use of the hydrogen gas-sensitive film, the coating method, and the like, and are not particularly limited.

As a coating method, a method capable of uniformly applying a low-viscosity solution, for example, a spin coating method, a dip coating method, a roll coating method, or the like can be applied, and the material, size, and material of the base material to be used, and It can be appropriately selected according to the thickness and the like.

Next, in S202, the coating film is dried in the air at room temperature or higher and 100 ° C. or lower. The drying temperature of the coating film is preferably 60 ° C. or higher and 100 ° C. or lower. When the drying temperature of the coating film is 60 ° C. or higher, the reduction reaction of metal ions contained in the metal catalyst precursor F can be promoted, and the strength of the coating film or the adhesion between the coating film and the substrate can be improved. On the other hand, if the drying temperature of the coating film is 100 ° C. or lower, a resin substrate, a resin film, or the like can be used as the base material in addition to the glass substrate. The resin substrate or resin film is formed of a resin having resistance to the components of the coating liquid, for example, polyethylene terephthalate (PET), polycarbonate (PC), or the like.

Next, in S203, the coating film is irradiated with ultraviolet rays to form a tungsten oxide film carrying a metal catalyst. By irradiating with ultraviolet rays, the reduction of metal ions contained in the metal catalyst precursor F can be promoted. The wavelength of ultraviolet rays is, for example, 200 nm to 380 nm, preferably 254 nm. Ultraviolet rays can be irradiated in the atmosphere. The irradiation amount of ultraviolet rays is, for example, about 5 seconds to 10 minutes at an intensity of ^{1 mW / cm 2.} The light source of ultraviolet rays is not particularly limited as long as it emits ultraviolet rays of the above wavelengths, and is, for example, an LED lamp or a mercury lamp. The distance between the ultraviolet light source and the coating film is not particularly limited as long as the ultraviolet rays can be uniformly irradiated, and is appropriately adjusted according to the irradiation amount of the ultraviolet rays, but is preferably about 1 cm to 3 cm.

A hydrogen gas sensitive film can be obtained by the above S201 to S203. After film formation, it is opaque white before being exposed to hydrogen gas. Therefore, it is easier to see the change to blue when exposed to hydrogen gas, as compared with the case where the film is colorless and transparent after being exposed to hydrogen gas. This is because the latter is easier to recognize the color change between the case where the colorless and transparent liquid film is colored with light blue ink and the case where the opaque white liquid film is colored with light blue ink. The same thing. According to this embodiment, even when the color changes to pale blue when exposed to hydrogen gas, it is easy to recognize the color change.

Further, the hydrogen gas-sensitive film of the present embodiment takes longer to return from blue to the original color when the surrounding atmosphere changes from hydrogen gas to the atmosphere, as compared with the conventional hydrogen gas-sensitive film. , The blue colored state is easily maintained. For example, in the case of the hydrogen gas-sensitive film of Patent Document 4 or 5, the original color is restored in about a few seconds to 1 minute, but in the case of the hydrogen gas-sensitive film of the present embodiment, it takes 30 to return to the original color. It takes about a minute. Therefore, the hydrogen gas-sensitive film of the present embodiment can retain information exposed to hydrogen gas for a long time as compared with the conventional hydrogen gas-sensitive film, and is more useful as a hydrogen gas visualization sheet or a hydrogen gas sensor. be.

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

The hydrogen gas-sensitive film may be formed by performing S201 (coating) and S202 (drying) once, or may be formed by repeating S201 (coating) and S202 (drying) a plurality of times. In the latter case, a hydrogen gas-sensitive film is composed of a plurality of tungsten oxide films. The film thickness of the hydrogen gas-sensitive film is appropriately selected depending on the application and the like. As described above, S203 may be performed after S202 or at the same time as S202.

The hydrogen gas-sensitive film of the present embodiment contains particles containing tungsten, oxygen, and a platinum group metal in a dispersed manner. The particles may further contain chlorine and carbon. The hydrogen gas-sensitive film has a surface roughness Ra of 50 nm to 300 nm and a porosity of 20% to 50%. The hydrogen gas sensitive film turns white when exposed to the atmosphere and blue when exposed to hydrogen. When the surface roughness Ra of the hydrogen gas-sensitive film is 50 nm or more, light is scattered by the unevenness of the surface, and an opaque white film is obtained. The surface roughness Ra is the arithmetic mean roughness described in the Japanese Industrial Standards (JIS B0601-2013). The porosity is preferably 25% to 40%.

Hereinafter, specific examples of a method for producing a coating liquid and a method for producing a hydrogen gas-sensitive film will be described. The evaluation results of the obtained hydrogen gas-sensitive membrane will also be described.

[Example 1-1]
In S101 of FIG. 1, first, the inside of the glove box was filled with a dry nitrogen atmosphere, and then 4.96 g of tungsten hexachloride (WCl ₆ ) and 50 mL of ultra-dehydrated diisopropyl ether were weighed separately in the glove box. Then, in the draft, both were mixed at room temperature while flowing dry nitrogen gas. Then, the mixture was stirred at room temperature for about 20 hours, and then stirred in a hot water bath at 55 ° C. for 30 minutes to obtain a first solution.

In S102, bis (acetylacetonato) platinum (II) (Pt (acac) ₂ ) is separately dissolved in ethylene glycol monomethyl ether (EGMME), and the concentration of the metal catalyst precursor is 0.016 mol / L. Two solutions were prepared.

In S103, 10 mL of the second solution was added to the first solution and stirred to prepare a third solution separated into a blue lower layer and a colorless and transparent upper layer.

In S104, 45 mL of ultra-dehydrated ethanol was added as an emulsifier to the third solution, and the mixture was stirred. The lower layer and the upper layer were mixed to form micelles, and a dark blue uniform solution was obtained.

If the amount of liquid in the upper layer is small immediately before S104, an appropriate amount of super-dehydrated diisopropyl ether may be added. Further, instead of the super-dehydrated diisopropyl ether, an appropriate amount of methyl t-butyl ether may be added.

In S105, about 0.1 g of oxalic acid was added to the micellar solution. After the addition, stirring was continued at room temperature as it was, and stirring was stopped when the color of the solution changed from dark blue to pale yellowish green. A transparent and uniform coating liquid colored in pale yellowish green was obtained.

The obtained coating liquid contained a tungsten oxide precursor, super-dehydrated diisopropyl ether, a metal catalyst precursor, ethylene glycol monomethyl ether (EGMME), oxalic acid, and super-dehydrated ethanol.

In S201 of FIG. 2, a coating liquid is applied to the surface of a polycarbonate (PC) substrate (wetting contact angle of water: about 65 °, hereinafter referred to as substrate 1-1-1) by a spin coating method, and a coating film is applied. Formed. The surface of the polycarbonate substrate was a square with a length of 3 cm and a width of 3 cm. The rotation speed of the substrate was 3000 rpm, and the coating time of the coating liquid was 30 seconds.

In S202, the coating film was heated on a hot plate at 80 ° C. in the air for 5 minutes to dry the coating film. S201 and S202 were repeated 5 times in total. The color of the coating film was opaque white. Then, S203 was carried out.

In S203, the dried coating film was irradiated with ultraviolet light having a wavelength of 254 nm for 10 minutes. The color of the coating film temporarily changed from opaque white to blue by irradiation with ultraviolet rays, but the color of the coating film slowly returned to the original white after irradiation with ultraviolet rays.

The hydrogen gas sensitive film 2-1-1 was obtained by the above S201 to S203. The color of the hydrogen gas-sensitive film immediately after the film formation was opaque white.

A photograph of the hydrogen gas-sensitive film 2-1-1 immediately after the film formation is shown in FIG. 3 (A). The hydrogen gas-sensitive film 2-1-1 immediately after the film formation was a dull white film. When hydrogen gas was sprayed onto this white film, the color of the hydrogen gas sensitive film 2-1-1 changed to blue, as shown in FIG. 3 (B).

FIG. 4 shows the transmission spectrum of the hydrogen gas-sensitive film 2-1-1 of Example 1-1. In FIG. 4, the broken line LA shows the transmission spectra of the hydrogen gas-sensitive film 2-1-1 and the substrate 1-1-1 immediately after the film formation, and the solid line LB shows the hydrogen gas-sensitive film 2-1 immediately after the hydrogen gas spraying. The transmission spectrum of -1 and the substrate 1-1-1 is shown, and the alternate long and short dash line LC shows the transmission spectrum of only the substrate 1-1-1.

As shown by the broken line LA in FIG. 4, the light transmittance in the visible light region having a wavelength of 400 nm to 800 nm was about 20% to 50% immediately after the film formation. On the other hand, as shown by the solid line LB in FIG. 4, immediately after the hydrogen gas spraying, the light transmittance of the hydrogen gas sensitive film 2-1-1 decreased, and a peak occurred in the blue wavelength region of 450 nm to 500 nm. This indicates that the color of the hydrogen gas-sensitive film 2-1-1 changed from opaque white to blue by spraying hydrogen gas.

FIG. 5 shows the reflection spectrum of the hydrogen gas sensitive film 2-1-1 of Example 1-1. In FIG. 5, the broken line LA shows the reflection spectra of the hydrogen gas-sensitive film 2-1-1 and the substrate 1-1-1 immediately after the film formation, and the solid line LB shows the hydrogen gas-sensitive film 2-1 immediately after the hydrogen gas spraying. The reflection spectrum of -1 and the substrate 1-1-1 is shown, and the alternate long and short dash line LC shows the reflection spectrum of only the substrate 1-1-1.

As shown by the broken line LA in FIG. 5, the reflectance in the visible light region having a wavelength of 400 nm to 800 nm was about 35% to 45% immediately after the film formation. On the other hand, as shown by the solid line LB in FIG. 5, the light reflectance of the hydrogen gas sensitive film 2-1-1 decreased immediately after the hydrogen gas spraying.

FIG. 6 shows an atomic force microscope (AFM) photograph of the hydrogen gas sensitive film 2-1-1 of Example 1-1. The surface roughness Ra of the hydrogen gas-sensitive film 2-1-1 was 109 nm as measured by an AFM (trade name: Nanoscale Hybrid microscope VN-8010) manufactured by KEYENCE CORPORATION. It is presumed that light was scattered due to the large surface irregularities, and an opaque white hydrogen gas-sensitive film 2-1-1 was obtained.

FIG. 7 shows a bright field image obtained by observing a cross section of the hydrogen gas sensitive film 2-1-1 of Example 1-1 with a scanning transmission electron microscope (STEM). In FIG. 7, 1-1-1 is a PC substrate, 2-1-1 is a hydrogen gas sensitive film, 21 is a grain containing tungsten, oxygen and platinum, 22 is a void, and 3 is a carbon protective film for observation. Reference numeral 4 denotes a tungsten protective film for observation. As is clear from FIG. 7, the grains 21 were dispersed, there were many voids 22, a porous structure was obtained, and the surface unevenness was large. The void ratio of the hydrogen gas sensitive film 2-1-1 was about 30% when measured by image processing a bright field image acquired by STEM (trade name: HD-2700) manufactured by Hitachi High-Technologies Corporation. rice field. The porosity is the ratio of the area of the void 22 to the total area of the grain 21 and the void 22. The chemical composition of the grain 21 was measured by STEM (trade name: HD-2700) manufactured by Hitachi High-Technologies Corporation, and the tungsten content was 16.9 atomic%, the oxygen content was 43.1 atomic%, and platinum. The content of was 0.4 atomic%, the content of chlorine was 0.4 atomic%, and the content of carbon was 39.3 atomic%.

FIG. 9 shows the responsiveness of the hydrogen gas-sensitive film 2-1-1 to hydrogen gas measured by the measuring device 5 shown in FIG. First, the measuring device 5 will be described with reference to FIG. In FIG. 8, the thin arrow indicates the flow of the hydrogen-containing gas, and the thick arrow indicates the path of the laser beam.

As shown in FIG. 8, the measuring device 5 includes a glass cell 51, a spacer 52, a mass flow controller 53, a light source 54, and a receiver 55. The measuring device 5 does not include the hydrogen gas-sensitive film 2-1-1 and the substrate 1-1-1 on which the hydrogen gas-sensitive film 2-1-1 is formed, which are the objects to be measured.

The glass cell 51 is arranged to face the hydrogen gas sensitive film 2-1-1. The spacer 52 forms a gap 56 that serves as a flow path for the hydrogen-containing gas between the glass cell 51 and the hydrogen gas-sensitive film 2-1-1. The gap 56 is, for example, 1 mm or less, preferably about 0.1 mm to 0.5 mm.

The mass flow controller 53 controls the flow rate of the hydrogen-containing gas flowing through the gap 56. The hydrogen-containing gas is introduced by the mass flow controller 53, passes through the gap 56 between the glass cell 51 and the hydrogen gas-sensitive film 2-1-1, and is discharged to the outside. On the other hand, when the mass flow controller 53 stops the introduction of the hydrogen-containing gas, the atmosphere enters the gap 56. As the hydrogen-containing gas, a gas containing 4% by volume of hydrogen gas and 96% by volume of nitrogen gas is used.

The semiconductor laser device as the light source 54 irradiates a laser beam having a wavelength of 670 nm. The photodiode as the receiver 55 receives the laser beam emitted from the light source 54 and outputs a signal corresponding to the intensity of the received laser beam.

As shown by a thick arrow in FIG. 8, the laser light emitted from the light source 54 passes through the substrate 1-1-1, the hydrogen gas sensitive film 2-1-1, and the glass cell 51 in this order, and receives a receiver. Received light at 55. The ratio of the intensity of the laser light received by the receiver 55 to the intensity of the laser light emitted from the light source 54 is the transmittance.

The responsiveness of the hydrogen gas-sensitive film 2-1-1 to hydrogen gas is determined by alternately repeating supplying a hydrogen-containing gas to the gap 56 in FIG. 8 for 1 minute and stopping the supply for a predetermined time. It was measured by measuring the transmittance of laser light at 670 nm.

FIG. 9 shows the measurement results of the responsiveness of the hydrogen gas-sensitive film 2-1-1 of Example 1-1 to hydrogen gas. In FIG. 9, “ON” means switching from the supply stop of the hydrogen-containing gas to the supply, and “OFF” means switching from the supply of the hydrogen-containing gas to the supply stop. The same is true in FIG.

As shown in FIG. 9, the light transmittance gradually decreased by the supply of the hydrogen-containing gas, and the color of the hydrogen gas-sensitive film 2-1-1 changed from opaque white to blue. Immediately after the start of measurement, the responsiveness of the hydrogen gas-sensitive film 2-1-1 to hydrogen gas was slow, but by repeating switching several times, sufficient responsiveness was obtained by supplying hydrogen gas for about 1 minute. The color of the hydrogen gas sensitive film 2-1-1 changed from white to deep blue.

As shown in FIG. 9, after the color of the hydrogen gas sensitive film 2-1-1 has changed to deep blue, when the supply of hydrogen gas is stopped, it takes about 30 minutes to complete the hydrogen gas sensitive film 2-1. The color of -1 slowly returned from blue to white. About 1 minute after the supply of hydrogen gas was stopped, the color of the hydrogen gas sensitive film 2-1-1 remained blue and hardly changed. Therefore, the information exposed to hydrogen gas could be retained for a long time.

[Example 1-2]
In Example 1-2, the same conditions as in Example 1-1 except that a glass substrate (wetting contact angle of water: about 10 °, hereinafter referred to as substrate 1-1-2) was used instead of the PC substrate. A hydrogen gas-sensitive film 2-1-2 was produced in the above. In Example 1-2, the coating liquid prepared in Example 1-1 was used.

FIG. 10 shows a photograph of the hydrogen gas-sensitive film 2-1-2 of Example 1-2 immediately after being exposed to hydrogen gas. In FIG. 10, a part of the hydrogen gas sensitive film 2-1-2 was exposed to hydrogen gas using the measuring device 5 shown in FIG. As shown in FIG. 10, the change in color of the hydrogen gas-sensitive film 2-1-2 could be visually recognized via the substrate 1-1-2.

[Example 1-3]
In Examples 1-3, a hydrophilized polyethylene terephthalate (PET) film (wetting contact angle of water: about 2 °, hereinafter referred to as substrate 1-1-3) was used instead of the PC substrate. A hydrogen gas-sensitive film 2-1-3 was produced under the same conditions as in Example 1-1 except. In Examples 1-3, the coating liquid prepared in Example 1-1 was used.

FIG. 11 shows a photograph of the hydrogen gas-sensitive film 2-1-3 of Example 1-3 immediately after being exposed to hydrogen gas. In FIG. 11, a part of the hydrogen gas-sensitive film 2-1-3 was exposed to hydrogen gas using the measuring device 5 shown in FIG. As shown in FIG. 11, the change in color of the hydrogen gas-sensitive film 2-1-3 could be visually recognized via the substrate 1-1-3.

[Example 1-4]
In Example 1-4, a hydrogen gas-sensitive film 2-1-4 was produced under the same conditions as in Example 1-1 except that the wavelength of ultraviolet rays was changed from 254 nm to 365 nm. In Examples 1-4, the coating liquid prepared in Example 1-1 was used.

FIG. 12 shows a photograph of the hydrogen gas-sensitive film 2-1-4 of Example 1-4 immediately after being exposed to hydrogen gas. In FIG. 12, a part of the hydrogen gas-sensitive film 2-1-4 was exposed to hydrogen gas using the measuring device 5 shown in FIG. As shown in FIG. 12, the change in color of the hydrogen gas-sensitive film 2-1-4 could be visually recognized via the substrate 1-1-4 (the same PC substrate as the substrate 1-1-1). However, as compared with Example 1-1 irradiated with ultraviolet rays of 254 nm, the darkness of blue immediately after exposure to hydrogen gas was lighter.

[Example 1-5]
In Example 1-5, the coating liquid produced in Example 1-1 is spin-coated on the surface of a glass substrate (the same glass substrate as substrate 1-1-2, hereinafter referred to as substrate 1-1-5). It was applied by the method to form a coating film. The surface of the glass substrate was a square with a length of 3 cm and a width of 3 cm. The rotation speed of the substrate was 3000 rpm, and the coating time of the coating liquid was 30 seconds. Then, the coating film was dried in the air at 40 ° C. for 10 minutes. Further, forming the coating film by the spin coating method under the same conditions and drying the coating film in the air at 60 ° C. for 5 minutes were repeated a total of 4 times. Then, the dried coating film was irradiated with ultraviolet rays having a wavelength of 254 nm for 10 minutes.

FIG. 13 shows a photograph of the hydrogen gas-sensitive film 2-1-5 of Example 1-5 immediately after being exposed to hydrogen gas. In FIG. 13, a part of the hydrogen gas sensitive film 2-1-5 was exposed to hydrogen gas using the measuring device 5 shown in FIG. As shown in FIG. 13, the change in color of the hydrogen gas-sensitive film 2-1-5 could be visually recognized via the substrate 1-1-5.

[Example 1-6]
In Example 1-6, the coating liquid produced in Example 1-1 is spin-coated on the surface of a glass substrate (the same glass substrate as substrate 1-1-2; hereinafter referred to as substrate 1-1-6). It was applied by the method to form a coating film. The surface of the glass substrate was a square with a length of 3 cm and a width of 3 cm. The rotation speed of the substrate was 3000 rpm, and the coating time of the coating liquid was 30 seconds. Then, the coating film was dried at room temperature (26 ° C.) in the air for 15 minutes. The formation of the coating film and the drying of the coating film were repeated 5 times in total. Then, the dried coating film was irradiated with ultraviolet rays having a wavelength of 254 nm for 10 minutes.

FIG. 14 shows a photograph of the hydrogen gas-sensitive film 2-1-6 of Example 1-6 immediately after being exposed to hydrogen gas. In FIG. 14, a part of the hydrogen gas sensitive film 2-1-6 was exposed to hydrogen gas using the measuring device 5 shown in FIG. As shown in FIG. 14, the change in color of the hydrogen gas-sensitive film 2-1-6 could be visually recognized via the substrate 1-1-6.

[Example 1-7]
In Example 1-7, the coating liquid produced in Example 1-1 is spin-coated on the surface of a glass substrate (the same glass substrate as substrate 1-1-2; hereinafter referred to as substrate 1-1-7). It was applied by the method to form a coating film. The surface of the glass substrate was a square with a length of 3 cm and a width of 3 cm. The rotation speed of the substrate was 3000 rpm, and the coating time of the coating liquid was 30 seconds. Then, the coating film was dried on a hot plate at 100 ° C. in the air for 10 minutes, and at the same time, the coating film was irradiated with ultraviolet rays having a wavelength of 254 nm for 10 minutes. The formation of this coating film and the drying of the coating film while irradiating with ultraviolet rays were repeated a total of 5 times.

FIG. 15 is a diagram showing the measurement results of the responsiveness of the hydrogen gas sensitive film 2-1-7 of Example 1-7 to hydrogen gas. As shown in FIG. 15, the responsiveness of the hydrogen gas-sensitive film 2-1-7 to hydrogen gas is fast immediately after the start of measurement, and sufficient responsiveness can be obtained by supplying hydrogen gas for about 1 minute, and the hydrogen gas-sensitive film is sensitive to hydrogen gas. The color of the gas membrane 2-1-7 changed from white to deep blue.

As shown in FIG. 15, after the color of the hydrogen gas sensitive film 2-1-7 has changed to deep blue, when the supply of hydrogen gas is stopped, the hydrogen gas sensitive film 2-1 takes about 30 minutes. The color of -7 slowly returned from blue to white. About 1 minute after the supply of hydrogen gas was stopped, the color of the hydrogen gas sensitive film 2-1-7 remained blue and hardly changed. Therefore, the information exposed to hydrogen gas could be retained for a long time.

FIG. 16 shows a photograph of the hydrogen gas-sensitive film 2-1-7 of Example 1-7 immediately after being exposed to hydrogen gas. In FIG. 16, a part of the hydrogen gas sensitive film 2-1-7 was exposed to hydrogen gas using the measuring device 5 shown in FIG. As shown in FIG. 16, the change in color of the hydrogen gas-sensitive film 2-1-7 could be visually recognized via the substrate 1-1-7.

[Example 2]
In Example 2, the coating liquid was prepared under substantially the same conditions as in Example 1-1, except that the coating liquid was prepared in an air atmosphere without using nitrogen gas. However, the bathing time at 55 ° C. was extended from 30 minutes to 1 hour. Therefore, it takes a long time to prepare the coating liquid. In addition, since a gray precipitate was formed in the finally obtained solution, a work of removing the gray precipitate was added.

In Example 2, the prepared coating liquid was applied to the surface of a PC substrate (the same PC substrate as substrate 1-1-1; hereinafter referred to as substrate 1-2) by a spin coating method to form a coating film. .. The surface of the PC substrate was a square with a length of 3 cm and a width of 3 cm. The rotation speed of the substrate was 3000 rpm, and the coating time of the coating liquid was 30 seconds. Then, the coating film was dried on a hot plate at 80 ° C. in the air for 5 minutes. The formation of the coating film and the drying of the coating film were repeated 5 times in total. The color of the coating film was opaque white. Then, the dried coating film was irradiated with ultraviolet light having a wavelength of 254 nm for 10 minutes.

FIG. 17 shows a photograph of the hydrogen gas-sensitive film 2-2 of Example 2 immediately after being exposed to hydrogen gas. In FIG. 17, a part of the hydrogen gas sensitive film 2-2 was exposed to hydrogen gas using the measuring device 5 shown in FIG. As shown in FIG. 17, the change in color of the hydrogen gas-sensitive film 2-2 could be visually recognized via the substrate 1-2. However, as compared with Example 1-1, the darkness of white after film formation and before exposure to hydrogen gas was lighter, and the darkness of blue immediately after exposure to hydrogen gas was also lighter.

[Comparative Example 1]
In Comparative Example 1, a hydrogen gas-sensitive film was attempted under the same conditions as in Example 1-1 except that the coating film was not irradiated with ultraviolet rays, but the obtained film was sprayed with hydrogen gas. The color of the film did not change from white to blue. It is probable that the reduction of platinum ions did not proceed sufficiently because the ultraviolet rays were not irradiated.

[Comparative Example 2]
In Comparative Example 2, a hydrogen gas-sensitive film was attempted under the same conditions as in Example 1-1 except that oxalic acid was not added when the coating liquid was prepared, but hydrogen gas was sprayed onto the obtained film. However, the color of the film did not change from white to blue. It is probable that the reduction of platinum ions did not proceed sufficiently because oxalic acid was not added.

[Comparative Example 3]
In Comparative Example 3, a hydrogen gas-sensitive film 2-3 was prepared by the method of Example 1-1 of Patent Document 5. The hydrogen gas-sensitive film 2-3 was colorless and transparent after the film was formed and before it was exposed to hydrogen gas.

FIG. 18 shows an AFM photograph of the hydrogen gas sensitive film 2-3 of Comparative Example 3. The surface roughness Ra of the hydrogen gas sensitive film 2-3 was 3 nm. From this result, it was found that the surface was smooth, so that light was not scattered and the film was a colorless and transparent hydrogen gas-sensitive film.

FIG. 19 shows a bright field image of the cross section of the hydrogen gas sensitive film 2-3 of Comparative Example 3 observed by STEM. In FIG. 19, 1-3 is a substrate, 2-3 is a hydrogen gas sensitive film, 122 is a void, 103 is a carbon protective film for observation, and 104 is a tungsten protective film for observation. The porosity of the hydrogen gas sensitive film 2-3 was about 10%.

From the comparison of FIGS. 7 and 19, the cross-sectional structure of the hydrogen gas-sensitive film 2-1-1 produced in Example 1-1 of the present invention and the method of Example 1-1 of Patent Document 5 were produced. It was found that the hydrogen gas-sensitive membranes 2-3 were clearly different.

[Comparative Example 4]
In Comparative Example 4, a hydrogen gas-sensitive film 2-4 was formed by the method of Example 1-1 of Patent Document 5. The color of the film after the film formation and before exposure to hydrogen gas was colorless and transparent. An attempt was made to roughen the surface of this colorless and transparent film with a file to obtain an opaque white film such as frosted glass, but rubbing the film with a file did not result in a cloudy film. Moreover, even if hydrogen gas was exposed to this film, it did not turn blue. It is presumed that this is because the film was damaged by rubbing with a file.

The time required for producing the coating liquid used in Comparative Examples 3 and 4 was four times or more the time required for producing the coating liquid of Example 1-1 of the present invention. Therefore, according to the present invention, it is possible to shorten the production time of the coating liquid.

The hydrogen gas-sensitive film according to the present invention, the coating liquid used for film formation thereof, the method for producing the coating liquid, and the method for producing the hydrogen gas-sensitive film have been described above. Not limited. Within the scope of the claims, various changes, modifications, replacements, additions, deletions, and combinations are possible. Naturally, they also belong to the technical scope of the present invention.

2-1-1 Hydrogen gas sensitive film 21 grains 22 voids

Claims (15)

Particles containing tungsten, oxygen, and a platinum group metal are dispersed and contained.
The surface roughness is 50 nm to 300 nm,
Porosity is 20% to 50%,
A hydrogen gas-sensitive film that turns white when exposed to the atmosphere and blue when exposed to hydrogen. The hydrogen gas-sensitive film according to claim 1, wherein the platinum group metal is at least one selected from the group consisting of palladium, platinum, and a palladium-platinum alloy. A coating liquid used for forming a hydrogen gas-sensitive film.
Tungsten oxide precursor derived from tungsten alkoxide,
With chain or cyclic ether,
A metal catalyst precursor containing a metal ion that becomes a metal catalyst having hydrogen gas sensitivity by being reduced,
An organic solvent that dissolves the tungsten oxide precursor and the metal catalyst precursor,
A coating liquid containing a carboxylic acid that reduces the metal ions contained in the metal catalyst precursor to a metal to produce the metal catalyst. The coating liquid according to claim 3, further comprising an emulsifier. The coating liquid according to claim 4, which is in the form of micelles. The coating liquid according to claim 4 or 5, wherein the emulsifier is an amphipathic organic solvent. The coating liquid according to claim 6, wherein the amphipathic organic solvent is methanol, ethanol, or acetone. The coating liquid according to any one of claims 3 to 7, wherein the metal catalyst precursor contains ions of a platinum group metal. A method for producing a coating liquid used for forming a hydrogen gas-sensitive film.
Tungsten chloride and chain ether are mixed and stirred to react to prepare a first solution containing a tungsten oxide precursor.
To prepare a second solution containing a metal catalyst precursor by dissolving a metal compound containing a metal ion that becomes a metal catalyst having hydrogen gas sensitivity by being reduced in an organic solvent.
The first solution and the second solution are mixed and stirred to prepare a third solution separated into a lower layer and an upper layer containing the tungsten oxide precursor and the metal catalyst precursor.
A method for producing a coating liquid, which comprises adding a carboxylic acid for producing the metal catalyst by reducing the metal ions contained in the metal catalyst precursor to a metal to the third solution. The method for producing a coating liquid according to claim 9, further comprising adding an emulsifier to the third solution. The method for producing a coating liquid according to claim 10, wherein the third solution is made into micelles by adding the emulsifier. The method for producing a coating liquid according to claim 10 or 11, wherein the emulsifier is an amphipathic organic solvent. The method for producing a coating liquid according to claim 12, wherein the amphipathic organic solvent is methanol, ethanol, or acetone. The method for producing a coating liquid according to any one of claims 9 to 13, wherein the metal compound is a compound of a platinum group metal. The coating liquid according to any one of claims 3 to 8 is applied to a base material to form a coating film on the surface of the base material.
Drying the coating film in the air at room temperature or higher and 100 ° C. or lower
A method for producing a hydrogen gas-sensitive film, which comprises irradiating the coating film with ultraviolet rays after or during drying of the coating film to form a tungsten oxide film carrying the metal catalyst.

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