Hydrogen sensor and hydrogen detection system

Abstract

To provide a hydrogen sensor which can be easily installed in an object of hydrogen leakage detection, and can remotely detect hydrogen gas.SOLUTION: A hydrogen sensor includes: a resin film; a sensitive membrane which is arranged on a first surface of the resin film, and contains a catalyst dissociating hydrogen molecules, and tungsten oxide; a pair of electrodes which are disposed on the first surface of the resin film so as to come in contact with the sensitive membrane; and a communication part which is connected to the pair of electrodes, and has a detection part for detecting change in a resistance value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to hydrogen sensors and hydrogen detection systems. [Background technology]

[0002] In recent years, there has been a desire to utilize clean and recyclable energy sources from the perspective of protecting the global environment and preventing the depletion of fossil fuels. In particular, research into the use of hydrogen gas as an energy source has been actively conducted, focusing on fuel cells. However, the explosive limit concentration of hydrogen gas ranges widely, from 4% to 75%, and in order to popularize hydrogen gas as an energy source, it is essential to handle hydrogen storage and transportation, as well as to develop safety devices to prevent hydrogen leaks.

[0003] For example, odorization, which is used in city gas, can be considered, but in the case of hydrogen gas, problems such as poisoning of fuel cells and deterioration of gas turbines arise. Therefore, safety measures that replace odorization are required. Therefore, to ensure safety, hydrogen sensors that can detect hydrogen gas leaks have become extremely important.

[0004] Conventional hydrogen sensors mainly use the semiconductor method. Semiconductor hydrogen sensors detect changes in the electrical properties of the sensitive film due to the adsorption of hydrogen gas onto the sensitive film, i.e., changes in resistance value. These semiconductor hydrogen sensors are used while heated by a heater. As such, conventional hydrogen sensors pose a risk when used with hydrogen gas that requires explosion-proofing, as they require heating.

[0005] In recent years, gasochromic hydrogen sensors have been attracting attention. Known examples of gasochromic hydrogen sensors include those that use a metal oxide, such as tungsten trioxide, that changes color upon reaction with hydrogen. These gasochromic hydrogen sensors include a metal oxide, such as tungsten trioxide, and a catalyst, such as platinum, that dissociates hydrogen gas into hydrogen atoms. They optically detect hydrogen gas by utilizing the color change of the metal oxide, such as tungsten trioxide, upon reaction with hydrogen.

[0006] Patent Document 1 proposes a gas detection tape having a substrate and a gas detection layer containing a pigment and an adhesive, in which the pigment irreversibly changes color upon contact with a reducing gas.

[0007] Another known gasochromic hydrogen sensor is one that uses a switchable mirror. This gasochromic hydrogen sensor has a switchable layer made of a magnesium alloy such as a magnesium-nickel alloy and a catalyst layer made of a catalyst such as palladium, and uses the magnesium alloy's change from a reflective state to a transparent state upon reaction with hydrogen to optically detect hydrogen gas. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 7181192 Summary of the Invention [Problem to be solved by the invention]

[0009] In conventional semiconductor hydrogen sensors, because hydrogen gas is light, multiple hydrogen sensors are installed above the object to be detected for hydrogen leaks, and hydrogen gas that moves upward is detected. In this case, the distance from the hydrogen leak location to the hydrogen sensors is long. As a result, it takes time from the occurrence of a hydrogen gas leak to its detection. It is also difficult to identify the hydrogen leak location. Furthermore, the hydrogen gas is diluted with air by the time it reaches the hydrogen sensors, making it difficult to detect.

[0010] On the other hand, the gas detection tape mentioned above is a gasochromic hydrogen sensor that can be applied directly to the object to be detected for hydrogen leaks, allowing the location of the hydrogen leak to be identified by the color change. However, since the color change must be confirmed visually, the inspector must be close to the hydrogen sensor. Furthermore, it is difficult to install the hydrogen sensor in a location that is difficult to see visually.

[0011] The present disclosure has been made in consideration of the above-mentioned circumstances, and has as its main object to provide a hydrogen sensor that can be easily installed on an object for hydrogen leak detection and that can remotely detect hydrogen gas. [Means for solving the problem]

[0012] One embodiment of the present disclosure provides a hydrogen sensor having a resin film, a sensitive membrane disposed on a first surface of the resin film and containing a catalyst that dissociates hydrogen molecules and tungsten oxide, a pair of electrodes disposed on the first surface of the resin film in contact with the sensitive membrane, and a communication unit connected to the pair of electrodes and having a detection unit that detects changes in resistance value.

[0013] Another embodiment of the present disclosure provides a hydrogen detection system comprising the hydrogen sensor described above. [Effects of the Invention]

[0014] The hydrogen sensor of the present disclosure has the advantage that it can be easily installed on an object for hydrogen leak detection and can detect hydrogen gas remotely. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic plan view illustrating a hydrogen sensor according to the present disclosure. [Figure 2] 1 is a schematic plan view illustrating a hydrogen sensor according to the present disclosure. [Figure 3] FIG. 1 is a schematic diagram illustrating a hydrogen detection system according to the present disclosure. [Figure 4] FIG. 1 is a schematic diagram illustrating a hydrogen detection system according to the present disclosure. [Figure 5] FIG. 1 is a schematic diagram illustrating a hydrogen detection system according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0016] Below, embodiments of the present disclosure will be described with reference to the drawings and the like. However, the present disclosure can be implemented in many different forms, and should not be construed as being limited to the description of the embodiments exemplified below. Furthermore, to clarify the explanation, the drawings may schematically depict the width, thickness, shape, etc. of each component compared to the embodiments, but these are merely examples and do not limit the interpretation of the present disclosure. Furthermore, in this specification and each drawing, elements similar to those previously described with reference to the previous drawings will be designated by the same reference numerals, and detailed descriptions may be omitted as appropriate.

[0017] In this specification, when expressing an aspect in which another component is placed on a certain component, the term "on the surface side" or "on the surface" is used, unless otherwise specified, and includes both a case in which another component is placed directly above or below a certain component so as to be in contact with the component, and a case in which another component is placed above or below a certain component with another component in between.

[0018] Furthermore, in this specification, terms such as "sheet," "film," and "plate" are not distinguished from one another solely based on differences in name. For example, the term "sheet" is used to include members also known as films and plates.

[0019] The hydrogen sensor and hydrogen detection system of the present disclosure will be described in detail below.

[0020] A. Hydrogen sensor The hydrogen sensor of the present disclosure comprises a resin film, a sensitive membrane disposed on a first surface of the resin film and containing a catalyst that dissociates hydrogen molecules and tungsten oxide, a pair of electrodes disposed on the first surface of the resin film in contact with the sensitive membrane, and a communication unit connected to the pair of electrodes and having a detection unit that detects changes in resistance value.

[0021] FIG. 1 is a schematic plan view showing an example of a hydrogen sensor in the present disclosure. As shown in FIG. 1, the hydrogen sensor 1 includes a resin film 2, a sensing film 3 disposed on the first surface of the resin film 2 and containing a catalyst for dissociating hydrogen molecules and tungsten oxide, and a pair of electrodes 4a and 4b disposed on the first surface of the resin film 2 in contact with the sensing film 3, and a communication unit 5 connected to the pair of electrodes 4a and 4b and having a detection unit for detecting a change in resistance value. In FIG. 1, the pair of electrodes 4a and 4b are a pair of comb-shaped electrodes.

[0022] The hydrogen sensor in the present disclosure uses tungsten oxide. It is known that tungsten oxide not only changes its optical properties but also its electrical properties by reacting with hydrogen. Therefore, in the present disclosure, by using tungsten oxide, hydrogen gas can be detected electrically. On the other hand, in a hydrogen sensor using a conventional dimming mirror, although magnesium alloy reacts with hydrogen and its optical properties change, its electrical properties do not change.

[0023] The hydrogen sensor in the present disclosure is a hydrogen sensor that utilizes the fact that the resistance value of a sensing film containing a catalyst and tungsten oxide decreases when it reacts with hydrogen. The operating principle of the hydrogen sensor in the present disclosure will be described.

[0024] Tungsten oxide (WO3) has a high resistance value. Therefore, in an atmosphere where hydrogen is absent, the sensing film has a high resistance value and is insulating. At this time, the pair of electrodes are insulated and in a non-conductive state.

[0025] On the other hand, when hydrogen molecules come into contact with the catalyst, the hydrogen molecules dissociate and adsorb to generate hydrogen atoms. These hydrogen atoms reduce tungsten oxide (WO3) to produce a non-stoichiometric compound (H x WO3 (0 < x < 1)). The non-stoichiometric compound (H x WO3) is W 5+ and W 6+Since the tungsten oxide is in a mixed valence state, its resistance is low. Therefore, in an atmosphere where hydrogen is present, the reduction reaction of the tungsten oxide occurs, causing the resistance of the sensitive film to decrease and become conductive. At this time, the pair of electrodes is short-circuited, resulting in a conductive state.

[0026] A communication unit having a detection unit that detects changes in resistance is connected to the pair of electrodes, so that hydrogen gas can be detected by detecting changes in resistance with the detection unit.In addition, hydrogen gas can be detected from a remote location using the communication unit.

[0027] As described above, conventional semiconductor hydrogen sensors require heating. In contrast, the reduction reaction of tungsten oxide described above does not require the supply of electricity. Therefore, the hydrogen sensor disclosed herein can be made large-area and can detect hydrogen gas over a relatively wide area at low cost. Therefore, by using the hydrogen sensor disclosed herein, hydrogen gas leaks can be detected not only in small devices such as fuel cells, but also in large facilities such as hydrogen production facilities, hydrogen pipelines, transport tankers, storage tanks, hydrogen power generation facilities, and hydrogen stations.

[0028] Furthermore, as described above, conventional gasochromic hydrogen sensors optically detect hydrogen gas by using a metal oxide such as tungsten trioxide, which changes color upon contact with hydrogen, and a catalyst such as platinum, which dissociates hydrogen gas into hydrogen atoms. Since the color change must be visually confirmed, an inspector must approach the hydrogen sensor. Furthermore, it is difficult to install a hydrogen sensor in a location that is difficult to visually inspect. In contrast, the hydrogen sensor disclosed herein includes a communication unit with a detection unit that detects changes in resistance, allowing hydrogen gas leaks to be detected from remote locations.

[0029] Furthermore, because the hydrogen sensor of the present disclosure has a resin film as a substrate supporting the sensitive membrane and pair of electrodes, it has good conformability to curved surfaces, unevenness, and steps. Therefore, the hydrogen sensor can be installed directly on the object of hydrogen leak detection, regardless of the shape of the object. Furthermore, as described above, because hydrogen gas can be detected remotely, the hydrogen sensor can be installed anywhere on the object of hydrogen leak detection.

[0030] The hydrogen sensor according to the present disclosure will be described in detail below with respect to each of its components.

[0031] 1. Resin film The resin film in the present disclosure is an insulating member that supports the sensitive membrane and the pair of electrodes.

[0032] The resin film is not particularly limited as long as it has insulating properties. Examples of resins contained in the resin film include polyimide, polyamideimide, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyphenylene sulfide, polyolefins such as polyethylene and polypropylene, fluororesins, nylon, and ethylene-vinyl alcohol copolymers. Examples of fluororesins include perfluoroethylene propylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), polytetrafluoroethylene (PTFE), and perfluoroalkoxyalkane (PFA).

[0033] It is preferable that the resin film has low thermal expansion. As described below, the sensitive film can be formed by a sol-gel method. Specifically, the sensitive film is formed by applying a composition containing raw materials for tungsten oxide to a first surface of the resin film, drying it, and heating it. In this case, by using a resin film with low thermal expansion, it is possible to prevent cracks from occurring in the sensitive film. If cracks occur in the sensitive film, they will act as a physical barrier, leading to an unintended increase in the resistance value. Therefore, by using a resin film with low thermal expansion, it is possible to prevent cracks from occurring in the sensitive film and stably detect changes in the resistance value.

[0034] The resin film preferably has a small linear expansion coefficient in each of a first direction and a second direction that are perpendicular to each other. The average linear expansion coefficient of the resin film in the first direction at 70° C. or more and 80° C. or less is 2.00×10 -4 / K or less is preferable, and 1.00 × 10 -4 Similarly, the average linear expansion coefficient of the resin film in the second direction at 270° C. or more and 80° C. or less is more preferably 2.00×10 -4 / K or less is preferable, and 1.00 × 10 -4 / K or less is more preferable. The average linear expansion coefficient is preferably small, and there is no particular lower limit for the average linear expansion coefficient.

[0035] The first direction and the second direction are both in-plane directions of the resin film. In this specification, "perpendicular" means that the angle between the first direction and the second direction is 90±2°. The angle between the first direction and the second direction may be 90±1° or 90°.

[0036] The linear expansion coefficient is measured using the following method. First, a hydrogen sensor is cut into a 5 mm wide piece to serve as a test piece. Note that the thickness of the sensitive film and the electrodes are usually very thin compared to the thickness of the resin film, so the sensitive film and electrodes do not have a significant effect on the linear expansion coefficient. Therefore, the test piece can be taken from the hydrogen sensor, rather than the resin film alone. Next, a thermomechanical analyzer is used to measure the displacement due to thermal expansion of the test piece under the conditions below, and the linear expansion coefficient is determined from the TMA curve. The average linear expansion coefficient is the average value of the linear expansion coefficients at temperatures between 70°C and 80°C. Specifically, the average linear expansion coefficient α is calculated using the following formula: α = (1 / L) × (ΔL / ΔT) In the above formula, L is the initial length of the test piece, ΔL is the change in length, and ΔT is the change in temperature. L is the distance between the jigs, which is 10 mm. ΔL is the change in length from 70°C to 80°C. Also, ΔT is 80°C - 70°C = 10°C. The above measurement is carried out three times, and the average value of the three measurements is used.

[0037] <Measurement conditions> Load: 50mN Distance between jigs: 10mm Temperature program: Starting temperature 10°C, target temperature 100°C, heating rate 5°C / min, holding time 0 min

[0038] Examples of methods for adjusting the average linear expansion coefficient of a resin film include a method of incorporating a resin having the above average linear expansion coefficient into the resin film, and a method of incorporating a filler into the resin film.

[0039] Examples of resins that satisfy the above average linear expansion coefficient include polyimide, polyamideimide, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, nylon, and ethylene-vinyl alcohol copolymer.

[0040] The filler is not particularly limited as long as it has insulating properties and can produce a resin film that satisfies the above-mentioned average linear expansion coefficient, and both inorganic and organic fillers can be used. Examples of inorganic fillers include silica, alumina, zirconia, magnesium oxide, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, silicon nitride, aluminum nitride, boron nitride, barium sulfate, aluminum borate, barium titanate, calcium titanate, magnesium titanate, bismuth titanate, barium zirconate, calcium zirconate, talc, clay, and mica. Examples of organic fillers include cellulose fiber and aramid fiber. One type of filler may be used alone, or two or more types may be used in combination.

[0041] The content of the filler in the resin film is not particularly limited as long as a resin film satisfying the above average linear expansion coefficient can be obtained, and is appropriately selected within a range that does not impair the properties of the resin film.

[0042] The thickness of the resin film is not particularly limited, but is preferably 10 μm or more and 500 μm or less from the viewpoint of flexibility.

[0043] The thickness of the resin film is the value measured from a cross section of the hydrogen sensor in the thickness direction observed with a scanning electron microscope (SEM), and is the average value of the thicknesses of 10 randomly selected locations. The same method applies to the measurement of the thickness of each layer.

[0044] 2. Sensitive membrane The sensitive film in the present disclosure includes a catalyst that dissociates hydrogen molecules and tungsten oxide.

[0045] The sensitive film may be a single layer containing a catalyst and tungsten oxide, or may have, in order from the substrate side, a tungsten oxide layer containing tungsten oxide and a catalyst layer containing a catalyst.

[0046] When the sensitive film has a tungsten oxide layer and a catalyst layer, the catalyst layer may be a continuous film or a discontinuous film.

[0047] The catalyst is not particularly limited as long as it can dissociate hydrogen molecules into hydrogen ions (protons), and examples thereof include noble metals such as palladium, platinum, iridium, etc. The catalyst may be used alone or in combination of two or more.

[0048] Tungsten oxide is tungsten trioxide (WO3).

[0049] The position of the sensitive film is not particularly limited as long as it is disposed in contact with the pair of electrodes. For example, the pair of electrodes and the sensitive film may be disposed in this order on the first surface of the resin film, or the sensitive film and the pair of electrodes may be disposed in this order on the first surface of the resin film.

[0050] When the sensitive film is a single layer containing a catalyst and tungsten oxide, the thickness of the sensitive film is not particularly limited as long as it is thick enough to detect changes in the resistance value of the sensitive film, and may be, for example, 50 nm to 3000 nm, 100 nm to 2000 nm, or 200 nm to 1000 nm. When the thickness of the sensitive film is relatively thin within the above range, the occurrence of cracks can be further suppressed.

[0051] On the other hand, when the sensitive film has a tungsten oxide layer and a catalyst layer, the thickness of the tungsten oxide layer is not particularly limited as long as it is thick enough to detect changes in the resistance value of the tungsten oxide layer, and may be, for example, 50 nm to 3000 nm, 100 nm to 2000 nm, or 200 nm to 1000 nm. By keeping the thickness of the tungsten oxide layer relatively thin within the above range, the occurrence of cracks can be further suppressed. Furthermore, the thickness of the catalyst layer is, for example, 1 nm to 10 nm.

[0052] When the sensitive film is a single layer containing a catalyst and tungsten oxide, the sensitive film can be formed by, for example, a sol-gel method. For examples of methods for forming sensitive films using the sol-gel method, see Japanese Patent Nos. 5152797 and 5540248.

[0053] On the other hand, when the sensitive film has a tungsten oxide layer and a catalyst layer, the method for forming the tungsten oxide layer is not particularly limited, and examples thereof include a sol-gel method, a vacuum deposition method, a sputtering method, and an ion plating method.The method for forming the catalyst layer is also not particularly limited, and examples thereof include a vacuum deposition method, a sputtering method, and an ion plating method.

[0054] 3. A pair of electrodes In the present disclosure, the pair of electrodes is disposed on the first surface of the resin film in contact with the sensitive film.

[0055] The pair of electrodes is preferably a pair of comb-shaped electrodes. Specifically, as shown in Fig. 2, the pair of electrodes 4a, 4b includes a plurality of first sensor electrodes 11 and a plurality of second sensor electrodes 12, a first bus electrode 13 connected to the first sensor electrodes 11, and a second bus electrode 14 connected to the second sensor electrodes 12. The plurality of first sensor electrodes and the plurality of second sensor electrodes are preferably arranged on the first surface of the resin film in contact with the sensitive membrane and alternately spaced at intervals that allow detection of changes in the resistance value of the sensitive membrane. Electrode 4a includes a plurality of first sensor electrodes 11 and a first bus electrode 13 connected to the first sensor electrodes 11. Electrode 4b includes a plurality of second sensor electrodes 12 and a second bus electrode 14 connected to the second sensor electrodes 12.

[0056] 2, the pair of electrodes 4a, 4b are usually arranged at a distance d1 at which a change in the resistance value of the sensitive film 3 can be detected. In this specification, the "distance at which a change in the resistance value of the sensitive film can be detected" refers to a distance at which the pair of electrodes can be short-circuited when the reduction reaction of the tungsten oxide described above occurs and the resistance value of the sensitive film decreases.

[0057] The distance between the pair of electrodes, i.e., the distance between the first sensor electrode and the second sensor electrode, may be any distance that allows detection of changes in the resistance value of the sensitive film. The distance may be, for example, 100 μm or more, or 500 μm or more. The distance may be, for example, 10 mm or less, or 5 mm or less. That is, the distance may be, for example, 100 μm or more and 10 mm or less, or 500 μm or more and 5 mm or less.

[0058] The distance between the first sensor electrode 11 and the second sensor electrode 12 is the distance from the edge of the first sensor electrode to the edge of the second sensor electrode. For example, in Figure 2, the distance between the first sensor electrode 11 and the second sensor electrode 12 is indicated by d1.

[0059] The width of the first sensor electrode 11 and the width of the second sensor electrode 12 may be any width that allows detection of changes in the resistance value of the sensitive film. The width may be, for example, 100 μm to 10 mm, or 500 μm to 5 mm. For example, in FIG. 2, the width of the first sensor electrode 11 is indicated by b1, and the width of the second sensor electrode 12 is indicated by b2.

[0060] The lengths of the first and second sensor electrodes may be any lengths that allow for detection of changes in the resistance value of the sensitive membrane. The lengths may be, for example, 10 mm to 500 mm, or 50 mm to 100 mm. For example, in FIG. 2, the length of the first sensor electrode 11 is indicated by a1, and the length of the second sensor electrode 12 is indicated by a2.

[0061] The overlap length between the first sensor electrode 11 and the second sensor electrode 12 may be any length that allows detection of changes in the resistance value of the sensitive film. The overlap length may be, for example, 9 mm to 450 mm, or 45 mm to 90 mm. For example, in FIG. 2, the overlap length between the first sensor electrode 11 and the second sensor electrode 12 is indicated by c.

[0062] The number of first sensor electrodes and the number of second sensor electrodes are set appropriately depending on the size of the hydrogen sensor, the arrangement of the first bus electrodes, the arrangement of the second bus electrodes, and the like.

[0063] The shapes of the first sensor electrode 11 and the second sensor electrode 12 are not particularly limited and may be, for example, linear, polygonal, or curved. For example, in Fig. 2, the shapes of the first sensor electrode 11 and the second sensor electrode 12 are linear.

[0064] The width of the first bus electrode and the second bus electrode may be any width that allows them to function as electrodes. The width may be, for example, 1 mm to 50 mm, or 5 mm to 10 mm. For example, in FIG. 2, the width of first bus electrode 13 is indicated by e1, and the width of second bus electrode 14 is indicated by e2.

[0065] The distance between the first bus electrode and the second bus electrode that face each other with the first sensor electrode and the second sensor electrode sandwiched therebetween may be any distance that allows the first sensor electrode and the second sensor electrode to be arranged. The distance may be, for example, 11 mm or more and 550 mm or less, or may be 55 mm or more and 110 mm or less. For example, in FIG. 2, the distance between the first bus electrode 13 and the second bus electrode 14 that face each other with the first sensor electrode 11 and the second sensor electrode 12 sandwiched therebetween is indicated by f.

[0066] Examples of conductive materials used for the pair of electrodes include carbon and metal materials. Of these, carbon is preferred. Carbon is inactive to hydrogen gas and inexpensive. As described above, when the sensitive film and the pair of electrodes are arranged in this order on the first surface of the resin film, the conductive material used for the pair of electrodes is preferably inactive to hydrogen gas. On the other hand, when the pair of electrodes and the sensitive film are arranged in this order on the first surface of the resin film, the conductive material used for the pair of electrodes is not exposed to hydrogen gas, and therefore may be active or inactive to hydrogen gas.

[0067] The thickness of the pair of electrodes is not particularly limited as long as it is a thickness that allows them to function as electrodes, and is, for example, 0.1 μm or more and 2 μm or less.

[0068] The method for forming the pair of electrodes is not particularly limited, and examples thereof include a method of forming a conductive film and patterning it, a mask vapor deposition method, and a printing method. Examples of the method for forming the conductive film include a vacuum vapor deposition method, a sputtering method, an ion plating method, and a plating method. Examples of the patterning method include an etching method and a lift-off method.

[0069] 4. Communications Department The communication unit in the present disclosure has a detection unit that is connected to a pair of electrodes and detects changes in resistance value.

[0070] The communication unit may be, for example, a unit that performs wireless communication. Specific examples include short-range wireless communication such as IC tags, Bluetooth (registered trademark), and Wi-Fi (registered trademark), and long-range wireless communication such as LPWA. Note that IC tags are also called RF tags, RFID tags, electronic tags, wireless tags, etc.

[0071] The detection unit may be any unit that can detect a change in resistance value, and may be appropriately selected depending on the type of communication unit.

[0072] In an IC tag, an IC chip that detects changes in resistance value is used as a detection unit. An open-short type IC chip can be used as the IC chip. The open-short type IC chip detects changes in resistance value by entering a high-resistance state and setting flag information to "0" when the inter-terminal resistance is equal to or greater than a first threshold, and entering a low-resistance state and setting flag information to "1" when the inter-terminal resistance is equal to or less than a second threshold that is smaller than the first threshold. Alternatively, a capacitive type IC chip can be used. A capacitive type IC chip typically detects changes in impedance when the antenna is detuned by contact with water droplets or the like. In the present disclosure, when a capacitive type IC chip is used, the above-mentioned sensitive film is separately disposed in contact with the antenna of the IC tag (described later) to detect the changes in impedance. Among these, an open-short type IC chip is preferred. An example of an open-short type IC chip is the UCODE G2iM+ from NXP.

[0073] The IC tag has the above-mentioned IC chip as a detection unit and also has an antenna. Any IC tag can be used as long as it has the above-mentioned IC chip and antenna, and a general IC tag can be used. If it is an IC tag, hydrogen gas can be detected using RFID.

[0074] There are two types of IC tags: active, which have a built-in power source (battery), and passive, which do not. Of these, passive tags are preferred because they do not have their own power source (battery) but instead operate by receiving externally supplied radio waves via an antenna.

[0075] An example of the operating principle of the hydrogen sensor of the present disclosure when the communication unit is an IC tag will be described. As described above, in an atmosphere without hydrogen, the sensitive film has a high resistance and is insulating. At this time, the pair of electrodes are insulated and non-conductive. Therefore, even when power is supplied to the IC tag from an external device, no current flows between the pair of electrodes via the sensitive film. On the other hand, in an atmosphere with hydrogen, the above-mentioned tungsten oxide reduction reaction occurs, causing the sensitive film to have a lower resistance and become conductive. At this time, the pair of electrodes are short-circuited and become conductive. Therefore, when power is supplied to the IC tag from an external device, current flows between the pair of electrodes via the sensitive film. The IC chip measures the resistance value, detects information from the resistance value, and transmits a signal corresponding to that information to the external device. The external device detects hydrogen leakage based on the information.

[0076] In Bluetooth (registered trademark), Wi-Fi (registered trademark), and LPWA, a microcomputer is used as the detection unit. Hereinafter, the microcomputer may be referred to as a "micon." Any microcomputer with an A / D converter function can be used, and a general-purpose microcomputer can be used. The microcomputer converts the analog signal into a digital signal and compares the digital signal with a preset reference value to determine whether a hydrogen leak has occurred.

[0077] The number of communication units is at least one. The number of communication units may be one or more.

[0078] The communication unit may be disposed on one side of the resin film, or may be separate from the resin film on which the sensitive film and pair of electrodes are disposed. In FIG. 1, the communication unit 5 is disposed on one side of the resin film 2. When the communication unit is disposed on one side of the resin film, the hydrogen sensor can be made smaller, allowing it to be installed in a smaller space. On the other hand, when the communication unit is separate from the resin film on which the sensitive film and pair of electrodes are disposed, the resin film on which the sensitive film and pair of electrodes are disposed can be disposed directly on the object to be detected for hydrogen leak detection, while the communication unit can be disposed in a position that makes it easier to send and receive radio waves, such as by being away from metal or the like that blocks radio waves, or by facing the device that transmits and receives radio waves.

[0079] 5. Cracked area In the present disclosure, as described above, when cracks occur in the sensitive film, they act as physical barriers, leading to an unintended increase in resistance. Therefore, when the sensitive film is viewed from above, the ratio of the area occupied by the cracks to the entire area of ​​the sensitive film is preferably 1.50% or less, more preferably 1.00% or less, and even more preferably 0.50% or less. When the area ratio of the cracks is within the above range, changes in resistance can be stably detected. It is preferable that the area ratio of the cracks is small, and there is no particular lower limit for the area ratio of the cracks.

[0080] When the sensitive film is viewed in plan, the ratio of the area occupied by the cracked portion to the area of ​​the entire sensitive film is measured by observing the surface of the sensitive film under transmitted illumination using an optical microscope and analyzing the image. When observing using an optical microscope, the observation area is selected so that the electrodes of the hydrogen sensor are not included in the image used to determine the area ratio of the cracked portion. A specific measurement method will be described in the Examples below.

[0081] B. Hydrogen Detection System The hydrogen detection system of the present disclosure includes the hydrogen sensor described above.

[0082] Figure 3 is a schematic diagram showing an example of a hydrogen detection system according to the present disclosure. In Figure 3, hydrogen detection system 20 comprises multiple hydrogen sensors 1, a device 21 that transmits and receives radio waves, and multiple antennas 22 connected to device 21 that transmits and receives radio waves. Hydrogen sensor 1 is attached to a hydrogen pipeline 30 installed underground. Device 21 that transmits and receives radio waves and antenna 22 are installed at any location near the ground and are fixed in place.

[0083] Figure 4 is a schematic diagram showing another example of a hydrogen detection system according to the present disclosure. In Figure 4, hydrogen detection system 20 includes multiple hydrogen sensors 1, a device 21 that transmits and receives radio waves, and an antenna 22 connected to device 21 that transmits and receives radio waves. Hydrogen sensor 1 is attached to hydrogen pipeline 30 installed underground. Device 21 that transmits and receives radio waves and antenna 22 are installed on a mobile object 23 and are therefore mobile.

[0084] Figure 5 is a schematic diagram showing another example of a hydrogen detection system according to the present disclosure. In Figure 5, hydrogen detection system 20 is used in a hydrogen station. Hydrogen detection system 20 includes multiple hydrogen sensors 1, a device 21 that transmits and receives radio waves, and an antenna 22 connected to device 21 that transmits and receives radio waves. Hydrogen sensor 1 is attached to dispenser 31 that supplies hydrogen to automobiles and the like. Device 21 that transmits and receives radio waves and antenna 22 are installed in canopy (roof) 32 and are fixed in place.

[0085] In such a hydrogen detection system, the IC chip that constitutes the detection section of the communication section of the hydrogen sensor is driven in a non-contact manner, and changes in the resistance value of the sensitive film can be detected, thereby making it possible to detect hydrogen gas.

[0086] The hydrogen detection system of the present disclosure is not particularly limited as long as it uses a hydrogen sensor, but is preferably a system that uses short-range wireless communication. Specifically, the hydrogen detection system of the present disclosure includes a hydrogen sensor, a device that transmits and receives radio waves, and an antenna connected to the device that transmits and receives radio waves.

[0087] The equipment that transmits and receives radio waves can be either fixed or mobile. Fixed equipment allows for continuous monitoring. Mobile equipment, on the other hand, allows for trace inspection, making trace inspection more advanced, smarter, and less manpower-intensive.

[0088] The hydrogen detection system disclosed herein can be used not only in small devices such as fuel cells, but also in large facilities such as hydrogen production facilities, hydrogen pipelines, transport tankers, storage tanks, hydrogen power generation facilities, hydrogen stations, etc. As hydrogen pipelines, not only underground pipelines but also aerial pipelines can be used.

[0089] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure. [Example]

[0090] The present disclosure will be described in more detail below with reference to examples.

[0091] [Example 1] A 50 μm-thick polyethylene terephthalate (PET) film ("A4160" manufactured by Toyobo Co., Ltd.) was used as the resin film. A pair of electrodes was formed on the resin film by printing. In the pair of electrodes, the length a1 of the first sensor electrode and the length a2 of the second sensor electrode were 4.5 mm, the number of first sensor electrodes and the number of second sensor electrodes were four, the width b1 of the first sensor electrode and the width b2 of the second sensor electrode were 0.5 mm, the distance d1 between the first sensor electrode and the second sensor electrode was 0.5 mm, and the width e1 of the first bus electrode and the width e2 of the second bus electrode were 3.0 mm. The thickness of the pair of electrodes was 0.15 μm.

[0092] Next, a sensitive film was formed on the PET film by a sol-gel method to cover the pair of electrodes. Specifically, first, sodium tungstate dihydrate manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. was used as the tungsten oxide raw material. The tungsten oxide raw material was dissolved in pure water to form an aqueous solution with a concentration of 0.5 mol / L, and sodium was removed using AMBERLITE® IR120B H manufactured by Organo Corporation as the ion exchange resin. Hexachloroplatinic(IV) acid hexahydrate manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. was used as the catalyst. The catalyst was dissolved in pure water to form an aqueous solution with a concentration of 0.289 mol / L. The sodium-removed tungstic acid aqueous solution, hexachloroplatinic(IV) acid aqueous solution, and ethanol were mixed in a ratio of 13:2:20 to prepare a precursor composition. Next, the precursor composition was coated on the PET film and dried by heating at 80°C for 1 hour. Thereafter, the substrate was irradiated with ultraviolet light for 1 hour using a Handy UV Lamp SUV-16 manufactured by AS ONE in a formaldehyde gas environment to obtain a sensitive film with a thickness of 300 nm.

[0093] Next, an IC tag was fabricated that had an IC chip (NXP UCODE G2iM+) and an antenna. Specifically, copper foil was attached to a glass epoxy substrate, and the copper foil was patterned according to a design drawing to form the antenna. The copper foil was patterned by etching and grinding. Next, the IC chip was mounted so that the antenna terminal was connected to the antenna, and an IC tag was fabricated. The antenna was designed to be sensitive to UHF radio waves. Next, the IC tag was connected to a pair of electrodes to obtain a hydrogen sensor.

[0094] [Example 2] A hydrogen sensor was produced in the same manner as in Example 1, except that a 50 μm thick polyimide (PI) film (Kapton 500H manufactured by Panac Corporation) was used as the resin film.

[0095] [Example 3] A hydrogen sensor was fabricated in the same manner as in Example 1, except that a 50 μm thick polyethylene (PE) film ("TUX-HCE" manufactured by Mitsui Chemicals Tohcello Inc.) was used as the resin film.

[0096] [Example 4] A hydrogen sensor was fabricated in the same manner as in Example 1, except that a 50 μm thick polypropylene (PP) film ("RXC22" manufactured by Mitsui Chemicals Tocello Inc.) was used as the resin film.

[0097] [evaluation] (1) Hydrogen gas detection A UHF-band RFID reader / writer was used to transmit readout radio waves to the hydrogen sensors of Examples 1 to 4, and it was confirmed that the reflected and transmitted radio waves could be detected. Furthermore, when radio waves were transmitted in the same manner as above while the hydrogen sensors were exposed to hydrogen gas, the signal level of the reflected and transmitted radio waves changed. This confirmed that hydrogen gas can be detected without the hydrogen sensor itself being equipped with a power source.

[0098] (2) Average linear expansion coefficient For the resin films used in Examples 1 to 4, the average linear expansion coefficient in a first direction from 70°C to 80°C and the average linear expansion coefficient in a second direction perpendicular to the first direction from 70°C to 80°C were determined using the method described above in the section "A. Hydrogen Sensor 1. Resin Film." The thermomechanical analyzer used was a "TMA7100" manufactured by Hitachi High-Tech Science Corporation.

[0099] (3) Observation of cracks The sensitive films of the hydrogen sensors in Examples 1 to 4 were visually inspected for the presence or absence of cracks.

[0100] (4) Area ratio of cracked areas For the sensitive membranes of the hydrogen sensors in Examples 1 to 4, the ratio of the area occupied by the cracked portion to the entire area of ​​the sensitive membrane was determined when the sensitive membrane was viewed in plan view using the method described in the section "A. Hydrogen Sensor 5. Cracked Portion" above. A Carl Zeiss Axio Imager M1m optical microscope was used. The surface of the sensitive membrane was photographed at 20x magnification to obtain Image A. ImageJ (National Institutes of Health) was used for image analysis. Image A was cropped to obtain Image B, measuring 685 μm × 482 μm (1280 × 900 pixels). Image B was converted to grayscale image C by selecting "Image → Type → 8 bit." Brightness and contrast were not adjusted. Grayscale image C was binarized by selecting "Image → Adjust → Auto Local Threshold," setting Method to Bernsen, Radius to 100, Parameter 1 to 10, and Parameter 2 to 0, to obtain binarized image D. Select "Analyze → Analyze Particles", set Size (pixel^2) to 0-Infinity, and Circularity to 0.00-1.00, and calculate the ratio of the total area of ​​the white areas (cracks) to the total area of ​​the binarized image D. In binarized image D, minute white areas may appear due to the resin film. Therefore, when calculating the area ratio of the white areas (cracks), the area of ​​one white area must be 50 μm 2 A white area with an area of ​​50 μm or more was considered to be a crack. 2 The white areas where the crack area was less than 100% were not included in the crack area. This procedure was repeated five times, and the arithmetic mean value was taken as the crack area ratio.

[0101] (5) Resistance value The resistance between the pair of electrodes of the hydrogen sensor was measured in air and in a hydrogen atmosphere. For the hydrogen atmosphere, the hydrogen concentration was set to 100%. The resistance between the pair of electrodes was measured using the following method. First, the IC tag was removed from the hydrogen sensor. Next, the resistance between the pair of electrodes was measured using a CUSTOM digital multimeter CDM-36. The measurement was performed five times, and the maximum and minimum values ​​were excluded from the five measurements, and the average of the three measurements was used as the resistance between the pair of electrodes.

[0102] [Table 1]

[0103] In all of Examples 1 to 4, it was confirmed that the resistance value between the pair of electrodes changed before and after exposure to hydrogen. This suggested that hydrogen gas could be detected. Furthermore, in Examples 1 and 2, visual observation revealed no cracks and the area ratio of the cracked portions was small, so the resistance value between the pair of electrodes after hydrogen exposure decreased significantly. A large change in resistance value before and after hydrogen exposure is preferable for a hydrogen sensor. The occurrence of cracks was suppressed due to the low average linear expansion coefficient of the resin film.

[0104] In the present disclosure, the following inventions are provided: [1] A resin film; a sensitive film disposed on a first surface of the resin film, the sensitive film including a catalyst that dissociates hydrogen molecules and tungsten oxide; a pair of electrodes arranged on the first surface of the resin film in contact with the sensitive film; a communication unit having a detection unit connected to the pair of electrodes and detecting a change in resistance value; A hydrogen sensor comprising: [2] The resin film has an average linear expansion coefficient in a first direction at 70°C or more and 80°C or less of 2.00 x 10 -4 / K or less, The resin film has an average linear expansion coefficient of 2.00×10 at 70° C. or more and 80° C. or less in a second direction perpendicular to the first direction.-4 / K or less. [3] The hydrogen sensor according to [1] or [2], wherein, when the sensitive film is viewed in plan, the ratio of the area occupied by the cracked portion to the area of ​​the entire sensitive film is 1.50% or less. [4] A hydrogen detection system comprising the hydrogen sensor according to any one of [1] to [3]. [Explanation of symbols]

[0105] 1... Hydrogen sensor 2... Substrate 3... Sensitive membrane 4a, 4b ... a pair of electrodes 5. Communications Department 20... Hydrogen detection system

Claims

1. A resin film; a sensitive film disposed on a first surface of the resin film, the sensitive film including a catalyst that dissociates hydrogen molecules and tungsten oxide; a pair of electrodes arranged on the first surface of the resin film in contact with the sensitive membrane; a communication unit having a detection unit connected to the pair of electrodes and detecting a change in resistance value; A hydrogen sensor comprising:

2. The average linear expansion coefficient of the resin film in the first direction at 70°C or more and 80°C or less is 2.00 × 10 －４ / K or less, The resin film has an average linear expansion coefficient of 2.00 × 10 at 70 ° C. or more and 80 ° C. or less in a second direction perpendicular to the first direction. －４ 2. The hydrogen sensor according to claim 1, wherein the hydrogen concentration is 0.15 kJ / K or less.

3. 2. The hydrogen sensor according to claim 1, wherein, when the sensitive film is viewed from above, the ratio of the area occupied by the cracked portion to the entire area of ​​the sensitive film is 1.50% or less.

4. A hydrogen detection system comprising the hydrogen sensor according to any one of claims 1 to 3.

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