Temperature differential sensor

Abstract

To provide a temperature differential sensor which has a simple and inexpensive configuration to suppress heat generation, sparking, and electrical noise.SOLUTION: A temperature differential sensor disclosed herein comprises one or more elements having an ion-conducting membrane or liquid. The iron-conducting membrane or liquid contains a thermoelectrically convertible redox species and has a metal content of less than 1 wt.%. When used in multiple, two or less elements are connected in parallel and two or less elements are connected in series.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a differential temperature sensor. [Background technology]

[0002] Microwave heating devices are widely used for heating food, organic synthesis, etc. Temperature control is important in such microwave heating devices, so they are generally equipped with a temperature difference sensor.

[0003] For example, the microwave heating temperature sensor disclosed in Patent Document 1 includes an element portion that converts the temperature of an object being heated by microwaves into an electric signal, a conductor portion that is connected to the element portion and outputs the electric signal converted by the element portion, a cylindrical insulating portion that surrounds the outer periphery of the conductor portion, and a cylindrical conductive portion that surrounds the outer periphery of the cylindrical insulating portion and the element portion, and at least the portion of the cylindrical conductive portion that surrounds the element portion is mesh-like. Patent Document 1 lists thermocouples, platinum resistors, thermistors, etc. as the element portion.

[0004] Furthermore, the microwave baking furnace disclosed in Patent Document 2, which bakes an object to be treated by microwave heating, includes a housing that houses a heat insulating material that forms a baking area, a microwave radiating means that radiates microwaves into the baking area, a grounding means that contacts the thermocouple at a portion of the wall surface of the housing where the thermocouple is exposed to the baking area to ground the thermocouple to the microwaves, and an adjustment means that adjusts the length of the thermocouple beyond the grounding position by the grounding means.

[0005] Furthermore, Patent Document 3 discloses a drying control method for unshaped refractory, in which unshaped refractory is placed inside a metal enclosure and dielectrically heated using microwaves using the space inside the enclosure as a cavity resonator, characterized in that the temperature of one or more of the atmosphere inside the furnace, the surface of the refractory, and the inside of the refractory during drying is measured using an optical fiber temperature sensor. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 8-29263 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-278640 [Patent Document 3] Japanese Patent Application Laid-Open No. 2002-303491 Summary of the Invention [Problem to be solved by the invention]

[0007] However, temperature difference sensors using thermocouples, platinum resistors, thermistors, etc., can sometimes have difficulty accurately detecting temperature differences due to heat generation by the sensor itself, sparks on the surface of the metal wires in the sensor, electrical noise, etc. To solve these problems, it has been necessary to make complex adjustments to the sensor structure, as in Patent Documents 1 and 2. Alternatively, an optical fiber temperature sensor can be used, as in Patent Document 3, but optical fiber temperature sensors are generally expensive and require careful handling due to their mechanical strength.

[0008] An object of one aspect of the present invention is to provide a temperature difference sensor that has a simple and inexpensive configuration and that suppresses the generation of heat, sparks, and electrical noise. [Means for solving the problem]

[0009] In order to solve the above problems, a temperature difference sensor according to one embodiment of the present invention comprises one or more elements having an ion conductive membrane or liquid, the ion conductive membrane or liquid containing a redox species capable of thermoelectric conversion and having a metal content of less than 1% by weight, and when a plurality of the elements are provided, the plurality of elements are connected in parallel with no more than two elements and in series with no more than two elements. [Effects of the Invention]

[0010] According to one aspect of the present invention, it is possible to provide a temperature difference sensor that has a simple and inexpensive configuration and that suppresses the generation of heat, sparks, and electrical noise. [Brief explanation of the drawings]

[0011] [Figure 1] 1A to 1C are schematic diagrams illustrating an outline of a temperature difference sensor and a method for manufacturing the same according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] An embodiment of the present invention will be described in detail below. In this specification, unless otherwise specified, "A to B" representing a numerical range means "A or more and B or less."

[0013] [1. Temperature difference sensor] A temperature difference sensor according to one embodiment of the present invention comprises one or more elements having an ion-conductive membrane or liquid, the ion-conductive membrane or liquid containing a thermoelectrically convertible redox species and having a metal content of less than 1% by weight, and when a plurality of the elements are provided, the plurality of elements are connected in parallel with no more than two elements and in series with no more than two elements.

[0014] Since the ion-conducting membrane or liquid contains a redox species capable of thermoelectric conversion, a redox reaction occurs due to a temperature difference, generating a potential difference. By detecting this potential difference, the temperature difference sensor can be used as a temperature difference sensor. Therefore, the temperature difference sensor can also be said to be a thermoelectric sensor.

[0015] The ion conductive film or liquid has a metal content of less than 1% by weight, which reduces the generation of heat, sparks, and electrical noise compared to conventional thermocouples, platinum resistors, thermistors, and the like made of metal materials. Even when multiple elements are used, the number of elements connected is small, with no more than two in parallel and no more than two in series. Therefore, there is no need to use a large number of metal conductors to connect multiple elements, which also reduces the generation of heat, sparks, and electrical noise.

[0016] Furthermore, the temperature difference sensor does not require the use of a specially designed thermocouple, etc., and can be simply constructed using one or more elements having an ion-conducting membrane or liquid. Furthermore, the temperature difference sensor can be constructed using less expensive materials than when optical fibers are used.

[0017] The temperature difference sensor can be connected to a device for detecting a potential difference. An example of a device for detecting a potential difference is a voltmeter. The temperature difference sensor may be a current application type or a non-current application type, but is preferably a non-current application type from the viewpoint of preventing interference in an environment where microwaves are irradiated. A current application type temperature difference sensor is connected to a device for applying current. A non-current application type temperature difference sensor is not connected to a device for applying current. An example of a device for applying current is a source meter.

[0018] The performance of a temperature difference sensor can be evaluated by the Seebeck coefficient (Se) below. Se=ΔE / ΔT ΔE = potential difference between the high temperature side and the low temperature side ΔT = temperature difference between the hot and cold sides The higher the Seebeck coefficient, the higher the electromotive force of the temperature difference sensor.

[0019] <1-1. Ion-conducting membrane or liquid> The ion-conductive membrane may be a membrane containing a redox species and a polymer. The redox species may be mixed in a polymer or supported by the polymer. The ion-conductive membrane may further contain a solvent. That is, the ion-conductive membrane may be a membrane in which a composition containing a redox species, a polymer, and optionally a solvent has lost its fluidity, or a membrane in which the composition is cured. The ion-conductive membrane may also be a membrane in which a liquid containing a redox species and optionally a solvent is held within the three-dimensional structure of the polymer. For example, a solvent with a large dielectric tangent can be used in combination with a polymer to suppress heat generation in an environment exposed to microwaves.

[0020] The polymer content in the ion conductive membrane is preferably 40 to 80% by weight, and particularly preferably 70 to 80% by weight. If the polymer content in the ion conductive membrane is 40% by weight or more, the molecular motion of the redox species and / or solvent contained in the ion conductive membrane is restricted, and heat generation is unlikely even in a microwave irradiation environment. Furthermore, if the polymer content in the ion conductive membrane is 80% by weight or less, the resistance of the ion conductive membrane does not become too high, making it easy to detect voltage. The ion conductive membrane may be a gel membrane containing a relatively large amount of solvent, or a non-gel membrane containing a small amount of solvent or no solvent.

[0021] Examples of such polymers include polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), N,N-dimethylacrylamide / glycidyl methacrylate copolymer, epoxy resin, styrene butadiene rubber (SBR), and polyurethane. Substituents such as sulfonic acid groups, carboxyl groups, and phosphate groups may or may not be introduced into the polymer skeleton to impart ionic conductivity. In other words, the polymer that constitutes the ion-conductive membrane itself may or may not have ionic conductivity.

[0022] The liquid may be a solution containing a redox species and a solvent, i.e., a solution in which the redox species is dissolved in a solvent, or, when the redox species is an ionic liquid (room-temperature molten salt), the liquid containing the redox species may be a liquid without a solvent.

[0023] The ion conductive film has a surface resistivity of 10 9 It is preferable that the resistance is Ω / □ or less, and 10 6 It is more preferable that the volume resistivity of the liquid is 10 Ω / □ or less. 7 It is preferable that the resistance is Ω·cm or less, and 10 4 It is more preferable that the resistivity is Ω·cm or less.

[0024] In addition, the molecular motion of redox species and / or solvent is restricted in an ion conductive membrane more than in a liquid, and heat generation is less likely to occur even in an environment where microwaves are irradiated.

[0025] The "metal" in the metal content is not particularly limited and includes alkali metals, alkaline earth metals, transition metals, and other metals, as well as metals contained in redox species. The metal content in the ion conductive membrane or liquid can be measured by inductively coupled plasma (ICP) atomic emission spectrometry.

[0026] The metal content in the ion conductive membrane or liquid is preferably 0.2 wt% or less, and more preferably 0.1 wt% or less. The lower the metal content, the better, but the lower limit may be 0 wt% or more, or even more than 0 wt%. In this specification, a metal content of 0 wt% means that the metal content is below the detection limit when measured by ICP atomic emission spectroscopy.

[0027] The polymer preferably has a calorific value index represented by the following formula (1) of less than 0.2, more preferably 0.1 or less.

[0028]

number

[0029] (In the formula, ε r represents the relative permittivity, and tanδ represents the dielectric tangent. If the calorific value index is less than 0.2, the ion conductive membrane or liquid is less likely to generate heat, and the detection accuracy of the temperature difference sensor can be further improved. The lower limit of the calorific value index of the polymer is not particularly limited, but may be, for example, 0.001 or more. The relative permittivity and dielectric loss tangent can be measured at 25°C using an LCR meter.

[0030] <1-2. Redox species> In this specification, the thermoelectrically convertible redox species refers to a compound that forms a redox pair, which undergoes an oxidation-reduction reaction due to a temperature difference, or a compound that generates a redox pair ion and its counter ion. Examples of redox pair compounds include quinone and hydroquinone. The redox pair ion and its counter ion may be a redox pair anion and its counter ion, or a redox pair cation and its counter ion.

[0031] An example of a redox pair is the ferricyanide ion and the ferrocyanide ion [Fe(CN)6 3- ] / [Fe(CN)6 4- ], iodide ion and triiodide ion [I - ] / [I 3- ] etc.

[0032] Examples of cations that serve as counter ions include inorganic cations and organic cations. Only one type of cation may be used, or two or more types may be used in combination. In addition, only inorganic cations or organic cations may be used, or inorganic cations and organic cations may be used in combination.

[0033] Examples of inorganic cations serving as counter ions include alkali metal ions, alkaline earth metal ions, etc. Examples of alkali metal ions include lithium ions, sodium ions, and potassium ions, with potassium ions being preferred.

[0034] Examples of organic cations that serve as counter ions include imidazolium cations, ammonium cations, pyridinium cations, and pyrrolidinium cations.

[0035] Examples of imidazolium cations include 1-methylimidazolium cation, 1-ethylimidazolium cation, 1-propylimidazolium cation, 1-butylimidazolium cation, 1,3-dimethyl-imidazolium cation, 1-ethyl-3-methylimidazolium cation, 1-propyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-methyl-3-octylimidazolium cation, and 1-hexyl-3-methylimidazolium cation.

[0036] Examples of the ammonium cation include diethylmethyl-(2-methoxyethyl)ammonium cation, choline cation, tetramethylammonium cation, and triethylmethylammonium cation.

[0037] Examples of the pyridinium cation include 1-butyl-4-methylpyridinium cation.

[0038] Examples of pyrrolidinium cations include N-(2-methoxyethyl)-N-methylpyrrolidinium cations.

[0039] Cations that form redox pairs include alkali metal cations (e.g., Li and Li + , K and K + ), Fe 2+ and Fe 3+Examples of counter ion anions include bis(fluorosulfonyl)imide (FSI) anion, bis(trifluoromethanesulfonyl)imide (TFSI) anion, hexafluorophosphate (PF6) anion, tetrafluoroborate (BF4) anion, chloride ion, and the like. For example, an alkali metal salt can also be used as the redox species. When the redox species is an alkali metal salt, it is preferable to use it in combination with a glycol ether solvent or crown ether, which will be described later, as this increases the entropy change.

[0040] The content of the redox species in the ion conductive membrane or liquid is preferably 0.01 to 2.0 wt%, more preferably 0.01 to 1.5 wt%, even more preferably 0.01 to 1.0 wt%, and particularly preferably 0.01 to 0.5 wt%. If the content of the redox species is 0.01 wt% or more, sufficient thermoelectric power is obtained. Furthermore, if the content of the redox species is 2.0 wt% or less, heat generation is suppressed even when heated by microwaves.

[0041] <1-3. Solvent> The ion-conductive membrane or liquid may contain a solvent. Examples of the solvent include non-aqueous solvents and aqueous solvents. Examples of non-aqueous solvents include ethanol (a 2:1 molar mixture of ethylene glycol (EG) and choline chloride (ChCl)), dimethyl sulfoxide (DMSO), 1-ethyl-3-methylimidazolium dicyanamide, glycerin, glycol ether solvents, and aromatic solvents. Examples of aqueous solvents include water and aqueous solutions of alcohols (e.g., ethylene glycol).

[0042] From the viewpoint of suppressing heat generation in a magnetic field environment, the dielectric loss tangent (tanδ) of the solvent is preferably 0.01 to 0.15. Such a solvent is preferably one or more selected from the group consisting of glycol ether solvents and aromatic solvents. Examples of glycol ether solvents include diglyme, triglyme, and tetraglyme. Examples of aromatic solvents include toluene, xylene, and chlorobenzene.

[0043] From the viewpoint of thermal stability, the solvents preferably have a boiling point of 150°C or higher at normal pressure. In this specification, normal pressure means 1 atmosphere. Examples of solvents having a boiling point of 150°C or higher at normal pressure include glycerin, ethylene glycol, and tetraglyme. Among these, tetraglyme, which has a boiling point of 150°C or higher at normal pressure and a small dielectric dissipation factor, is particularly preferred.

[0044] <1-4. Other ingredients> The ion-conductive membrane or liquid may contain components other than the redox species and solvent. For example, the ion-conductive membrane or liquid may further contain ions other than the anions and cations described as the redox species. From the viewpoint of improving ionic conductivity and reducing resistance, the ion-conductive membrane or liquid may contain a quaternary ammonium salt (Br salt, Cl salt, etc.) or may contain ions derived from the quaternary ammonium salt. Examples of quaternary ammonium salts include guanidinium chloride and dodecyltrimethylammonium bromide (DTAB).

[0045] The ion-conductive membrane or liquid may also contain a scavenger compound, which is a substance that selectively captures only one member of a redox pair at low temperatures and releases it at high temperatures. Examples of scavenger compounds include cyclodextrin, starch, polyvinylpyrrolidone, polyethylene oxide, and polyethylene glycol.

[0046] The ion-conductive membrane or liquid may contain a crown ether. Crown ethers capture inorganic cations. Therefore, by incorporating a crown ether into the ion-conductive membrane or liquid, redox species can be dissolved at a high concentration. When inorganic cations are captured by crown ethers, the interaction between the inorganic cations and anions is weakened. By weakening the interaction between the inorganic cations and anions, the solubility of the redox species can be improved and the ionic conductivity of the anions can be increased. As a result, the performance of the temperature difference sensor is improved.

[0047] Examples of crown ethers include 12-crown-4 ether, 15-crown-5 ether, 18-crown-6 ether, and dibenzo-18-crown-6 ether. It is preferable to use a combination of crown ethers that interact with the inorganic cation depending on the type of cation. Only one type of crown ether may be used, or two or more types may be used in combination.

[0048] Examples of combinations of inorganic cations and crown ethers include a combination of lithium ion and 12-crown 4 ether, a combination of sodium ion and 15-crown 5 ether, a combination of potassium ion and 18-crown 6 ether, a combination of potassium ion and dibenzo-18-crown 6 ether, etc. Among these, the combination of potassium ion and 18-crown 6 ether is preferred.

[0049] The crown ether concentration in the ion-conductive membrane or liquid is preferably equal to or greater than the concentration of inorganic cations that the crown ether can capture. When the crown ether concentration is equal to or greater than the inorganic cation concentration, there is no shortage of crown ether molecules relative to the inorganic cations, and all inorganic cations can interact with the crown ether. For example, the ratio of the crown ether concentration to the inorganic cation concentration (crown ether concentration / inorganic cation concentration) is preferably 1.0 to 2.0, more preferably 1.0 to 1.5.

[0050] <1-5.Element> The element provided in the temperature difference sensor may include, in addition to the ion conductive membrane or liquid, a first electrode and a second electrode in contact with the ion conductive membrane or liquid.

[0051] When the first and second electrodes are in contact with different materials or when the temperatures around them are different, the temperature difference between them causes an oxidation-reduction reaction to occur, creating a potential difference between the first and second electrodes. By detecting this potential difference, the device can be used as a temperature difference sensor.

[0052] The first and second electrodes preferably have a metal content of less than 1% by weight. Examples of such electrodes include carbon electrodes and resin electrodes. Examples of carbon electrodes include graphite sheets, carbon felt, and glassy carbon. Resin electrodes may contain a matrix resin such as polyolefin resin and a conductive filler such as graphite or carbon black. The lower the metal content in the first and second electrodes, the better; however, the lower limit may be 0% by weight or more, or even greater than 0% by weight.

[0053] The temperature difference sensor may include a support, and the element may be provided on the support. Examples of the support include a resin film and a resin plate (such as a Bakelite plate). Examples of resins that make up the resin film include polyethylene terephthalate (PET) and polyimide. The element may be sandwiched between a first support and a second support. The liquid may be contained in a tube, a container, or the like.

[0054] The temperature difference sensor can detect a temperature difference even when it has only one element. When a plurality of elements are provided, the elements are connected in parallel with no more than two elements and in series with no more than two elements. That is, the temperature difference sensor may have two elements connected in series, or two elements connected in parallel, or two sets of two elements connected in series connected in parallel. The two elements may be an n-type element and a p-type element. For example, a p-type element containing ferricyanide ions and ferrocyanide ions as a redox couple, and a p-type element containing Fe as a redox couple, may be used. 2+ and Fe 3+ It may be connected to an n-type element including

[0055] 2. Temperature difference sensor manufacturing method There are no particular limitations on the method for manufacturing a temperature difference sensor. An example will be described below with reference to Fig. 1. Fig. 1 is a schematic diagram illustrating an outline of a temperature difference sensor according to one embodiment of the present invention and a method for manufacturing the same. In Fig. 1, for example, the xy plane is a horizontal plane, and the y axis represents the vertical direction.

[0056] First, the first electrode 2a and the second electrode 2b are placed on the first support 3a. The ion conductive membrane 1 is then placed on top of that so as to be in contact with the first electrode 2a and the second electrode 2b. The structure including the first electrode 2a, the second electrode 2b, and the ion conductive membrane 1 can be considered as a single element 10. The second support 3b is then placed on top of that, and then, for example, heat sealed, to obtain the temperature difference sensor 100.

[0057] As described above, a plurality of elements 10 may be connected to obtain the temperature difference sensor 100. Alternatively, the temperature difference sensor 100 may be obtained by sealing a liquid instead of the ion conductive membrane 1.

[0058] [3. Uses of temperature difference sensors] The temperature difference sensor may be a temperature difference sensor for use in a high electromagnetic field environment, for example, an environment where electromagnetic waves with a frequency of 3 MHz to 30 GHz are irradiated.

[0059] For example, the temperature difference sensor may be a temperature difference sensor for a microwave heating device. Microwave heating devices are used for cooking, sterilizing, and drying food; drying wood, printed materials, textiles, and paper; and for hyperthermia in medical settings. An example of a microwave heating device is a microwave oven. One embodiment of the present invention also includes a microwave heating device equipped with the temperature difference sensor.

[0060] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0061] An embodiment of the present invention may include the following features. <1> A temperature difference sensor comprising one or more elements having an ion-conducting membrane or liquid, the ion-conducting membrane or liquid containing a redox species capable of thermoelectric conversion and having a metal content of less than 1% by weight, and when a plurality of the elements are provided, the plurality of elements are connected in parallel in a number of not more than two and in series in a number of not more than two. <2> The content of the redox species in the ion conductive membrane or liquid is 0.01 to 2.0% by weight. <1> The temperature difference sensor according to claim 1. <3> the ion conductive membrane or liquid contains a solvent, and the dielectric tangent (tanδ) of the solvent is 0.01 to 0.15; <1> or <2> The temperature difference sensor according to claim 1. <4> The solvent is at least one selected from the group consisting of glycol ether solvents and aromatic solvents. <3> The temperature difference sensor according to claim 1. <5> The polymer content in the ion conductive membrane is 40 to 80% by weight. <1> ~ <4> 10. The temperature difference sensor according to claim 9, wherein: <6> For use in environments exposed to electromagnetic waves with frequencies between 3MHz and 30GHz. <1> ~ <5> 10. The temperature difference sensor according to claim 9, wherein: <7> It is a non-current-applied type. <1> ~ <6> 10. The temperature difference sensor according to claim 9, wherein: [Example]

[0062] An embodiment of the present invention will be described below.

[0063] [Evaluation method] (1) Temperature sensing capability The terminals of a voltmeter were contacted with the graphite sheet portions located at both ends of the temperature difference sensor produced in the examples. One of the graphite sheets was heated to 75°C using a commercially available Peltier element. After confirming that the other, unheated graphite sheet was at 24°C, the voltage displayed on the voltmeter was checked and found to be 105 mV. The Seebeck coefficient of the temperature difference sensor produced in the examples was calculated from the obtained voltage value and the temperature difference between the graphite sheets located at both ends of the temperature difference sensor. If the absolute value of the Seebeck coefficient was 0.1 mV / K or more, it was rated as A; if it was greater than 0 mV / K and less than 0.1 mV / K, it was rated as B; and if it was 0 mV / K, it was rated as C.

[0064] (2) Confirmation of the effects of microwave irradiation environment 4.0 g of the ion conductive membrane or liquid for the temperature sensor of each manufacturing example was placed in a No. 7 screw tube and the product temperature (°C) was measured using a thermometer. The product was then heated for 10 seconds using an IRIS OHYAMA microwave oven "PMG-T179-W" at a frequency of 2.45 GHz and a microwave output of 200 W. A thermometer was inserted into the ion conductive membrane or liquid for the temperature difference sensor immediately after heating to monitor the product temperature and confirm the temperature change before and after heating. The product temperature (°C) after heating was defined as the temperature at which no further temperature increase was observed. A temperature change of less than 60°C was rated as A; a temperature change of 60°C to less than 80°C was rated as B; a temperature change of 80°C or higher was rated as C; and a temperature change of less than 60°C was rated as D if measurement was not possible due to the risk of sparks.

[0065] [Production Example 1] (1) Preparation of PVA aqueous solution 95 parts by weight of ion-exchanged water was added to 5 parts by weight of polyvinyl alcohol (hereinafter sometimes referred to as "PVA") (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., degree of polymerization 1000), and the mixture was heated and stirred at 90°C for 6 hours to obtain a 5 wt% PVA aqueous solution. The calorific value index of PVA, expressed by formula (1), was 0.196.

[0066] (2) Mixing of redox species and solvents with aqueous PVA solution To 68.97 parts by weight of the above 5 wt% PVA (degree of polymerization 1000) aqueous solution, 30.91 parts by weight of glycerin (Fujifilm Wako Pure Chemical Industries, Ltd., special grade), 0.07 parts by weight of potassium hexacyanilide ferrate(II) trihydrate (Fujifilm Wako Pure Chemical Industries, Ltd., special grade), and 0.06 parts by weight of potassium hexacyanilide ferrate(III) (Fujifilm Wako Pure Chemical Industries, Ltd., special grade) were added, and the mixture was stirred at room temperature for 3 hours to obtain a mixed solution.

[0067] (3) Preparation of gel by drying 50 mL of the mixture obtained above was poured into a container approximately 10 cm square and air-dried for two days. The resulting gel (residual water content approximately 10 wt%) was air-dried in a thermostatic chamber at 45°C for one day to obtain a gel for a temperature difference sensor with a residual water content of less than 1 wt%. This was used as an ion-conductive membrane.

[0068] [Production Examples 2 to 5] A redox species-containing liquid was prepared by mixing the solvent and redox species (potassium hexacyanilide ferrate (II) trihydrate and potassium hexacyanilide ferrate (III) in a molar ratio of 1:1) shown in Table 1 with stirring.

[0069] The solvents in Table 1 are as follows: Water: Ion-exchanged water Ethylene glycol (Fujifilm Wako Pure Chemical Industries, purity >99.0%) [Production Example 6] A redox species-containing liquid was prepared by mixing and stirring 99.98 parts by weight of tetraglyme (Tokyo Chemical Industry Co., Ltd., purity >98.0%) and 0.02 parts by weight of LiFSI (lithium bis(fluorosulfonyl)imide, Kishida Chemical Co., Ltd., purity >90.0%).

[0070] [Production Example 7] A redox species-containing liquid was prepared by stirring and mixing 99.96 parts by weight of xylene, 0.022 parts by weight of potassium hexacyanidoferrate(II) trihydrate, 0.018 parts by weight of potassium hexacyanidoferrate(III), and 0.10 parts by weight of 18-crown-6 ether (Tokyo Chemical Industry Co., Ltd., purity >98.0%).

[0071] [Production Example 8] An ion-conductive membrane was obtained in the same manner as in Production Example 1, except that PVA (degree of polymerization 1000) was changed to PVA (degree of polymerization 1700) and the compositional ratio of each component in the ion-conductive membrane was changed to the compositional ratio shown in Table 2. The ratio of redox species (K4[Fe(CN)6] 3H2O / K3[Fe(CN)6]) was adjusted to be the same as in Production Example 1.

[0072] [Production Example 9] SBR (styrene-butadiene rubber, manufactured by JSR Corporation, model number "TRD104A," 45 wt% aqueous solution) was diluted with ion-exchanged water to obtain a 20 wt% SBR aqueous solution. An ion-conductive membrane was obtained in the same manner as in Production Example 1, except that the 5 wt% PVA (degree of polymerization 1000) aqueous solution was replaced with the above 20 wt% SBR aqueous solution, and the compositional ratio of each component in the ion-conductive membrane was changed to the compositional ratio shown in Table 2. The ratio of redox species (K4[Fe(CN)6]·3H2O / K3[Fe(CN)6]) was adjusted to be the same as in Production Example 1. The calorific value index of SBR, expressed by equation (1), was 0.001.

[0073] [Production Example 10] A two-component curing epoxy resin precursor (50.0 parts by weight, Huntsman Japan, product name "ARALDITE RAPID RT30") (total of two components), 49.63 parts by weight of glycerin, 0.21 parts by weight of potassium hexacyanidoferrate(II) trihydrate (Fujifilm Wako Pure Chemical Industries, Ltd., special grade), and 0.17 parts by weight of potassium hexacyanidoferrate(III) (Fujifilm Wako Pure Chemical Industries, Ltd., special grade) were mixed thoroughly at room temperature, then the mixture was quickly poured into a container and allowed to stand and cure to obtain an ion-conductive membrane. The calorific value of the resulting epoxy resin, expressed by Equation (1), was 0.042.

[0074] [Production Example 11] A 20 wt % SBR aqueous solution was obtained in the same manner as in Production Example 9. An ion conductive membrane was obtained in the same manner as in Production Example 9, except that the contents of glycerin and polymer (SBR) in the ion conductive membrane were changed to have the composition ratios shown in Table 2.

[0075] [Comparative Production Example 1] Ion-exchanged water was used as a comparative liquid.

[0076] [Examples 1, 8 to 11] As shown in FIG. 1, a temperature difference sensor 100 was fabricated by combining an ion conductive membrane 1, a first electrode 2a, a second electrode 2b, a first support 3a, and a second support 3b. The ion conductive membrane 1 consisted of one gel film sheet obtained in Production Examples 1, 8, and 11, cut to a size of 20 mm x 80 mm. Two sheets of graphite sheet "PERMA-FOIL" (1000 μm thick) manufactured by Toyo Tanso Co., Ltd., cut to a size of 20 mm x 50 mm, were used as the first electrode 2a and the second electrode 2b. Two sheets of transparent laminate film (100 μm thick) manufactured by Dai Nippon Printing Co., Ltd., cut to a size of 30 mm x 100 mm, were used as the first support 3a and the second support 3b. These were stacked as shown in FIG. 1, and the four edges of the laminated PET film were heat-sealed in a vacuum environment to obtain a device. This device was used as a temperature difference sensor.

[0077] [Examples 2 to 7, Comparative Example 1] A device was produced by filling a PTFE tube (manufactured by AS ONE, inner diameter 2 mm) between two graphite sheets with the redox species-containing liquids produced in Production Examples 2 to 7 above or the ion-exchanged water of Comparative Production Example 1, and then sealing the space between the tube and the graphite sheets with an adhesive. The device (temperature difference sensor) was subjected to "(1) Confirmation of temperature sensing ability" by heating one of the graphite sheets.

[0078] Comparative Example 2 "(1) Temperature sensing capability confirmation" was performed using a thermocouple (K type).

[0079] [Evaluation results] The evaluation results of the examples and comparative examples are shown in Tables 1 and 2.

[0080] [Table 1]

[0081] [Table 2]

[0082] In Examples 1 to 11, which used an ion conductive membrane or liquid containing redox species and with a metal content of less than 1 wt %, the temperature difference was judged to be A to C, and the temperature sensing ability was judged to be A. In Comparative Example 1, which used water not containing redox species, the temperature sensing ability was judged to be C. In Comparative Example 2, which used a thermocouple, the temperature difference was judged to be D. [Industrial Applicability]

[0083] One aspect of the present invention can be used, for example, in a temperature difference sensor for a microwave heating device. [Explanation of symbols]

[0084] 1. Ion-conducting membrane 2a 1st electrode 2b 2nd electrode 3a 1st support 3b Second support 10 elements 100 Temperature difference sensor

Claims

1. one or more elements having an ion-conducting membrane or liquid; the ion-conducting membrane or liquid contains a thermoelectrically convertible redox species and has a metal content of less than 1 wt. %; When a plurality of the elements are provided, the plurality of elements are connected in parallel with no more than two elements and in series with no more than two elements.

2. 2. The temperature difference sensor according to claim 1, wherein the content of the redox species in the ion conductive membrane or liquid is 0.01 to 2.0% by weight.

3. the ion-conducting membrane or the liquid contains a solvent; 3. The temperature difference sensor according to claim 1, wherein the solvent has a dielectric loss tangent (tan δ) of 0.01 to 0.

15.

4. 4. The temperature differential sensor according to claim 3, wherein the solvent is at least one selected from the group consisting of glycol ether solvents and aromatic solvents.

5. 3. The temperature difference sensor according to claim 1, wherein the content of the polymer in the ion conductive membrane is 40 to 80% by weight.

6. 3. The temperature difference sensor according to claim 1, which is for use in an environment where it is irradiated with electromagnetic waves having a frequency of 3 MHz to 30 GHz.

7. 3. The temperature difference sensor according to claim 1, which is of a non-current-applied type.

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