Thermoelectric conversion materials and thermoelectric conversion elements

Abstract

To provide a thermoelectric conversion material with excellent thermal power conversion performance and chemical resistance.SOLUTION: A thermoelectric conversion element includes a thermoelectric conversion material containing a hydrogenation nitrile rubber (A) and a conductive material (B), a thermal power conversion film formed by containing the thermoelectric conversion material, and an electrode. The thermal power conversion film and the electrode are electrically connected. Preferably, in the thermoelectric conversion material, the hydrogenation nitrile rubber (A) contains a unit derived from acrylonitrile of 10 mass% or more and less than 50 mass%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermoelectric conversion material and a thermoelectric conversion element. [Background technology]

[0002] Thermoelectric conversion technology, which converts heat into electricity, is attracting attention as a clean energy source that can convert weak thermal energy, such as body heat and exhaust heat emitted from factories, cars, and homes, as well as various types of heat found in nature, into electricity. There are various thermoelectric effects that can be used in thermoelectric conversion technology, but the most common system uses the Seebeck effect, in which an electromotive force is generated by an electron gradient that occurs within a material made up of a combination of semiconductors and metals when two different temperatures are applied to both ends of the material.

[0003] Thermoelectric materials, which can convert thermal energy into electrical energy and vice versa, are used in thermoelectric conversion elements such as thermoelectric power generation elements and Peltier elements. Thermoelectric conversion elements are elements that convert heat into electrical power and are generally made up of a combination of semiconductors and metals. Typical thermoelectric conversion elements are classified into p-type semiconductors alone, n-type semiconductors alone, and combinations of p-type and n-type semiconductors. To obtain a larger potential difference, thermoelectric conversion elements generally use a combination of p-type and n-type semiconductors as materials.

[0004] Thermoelectric conversion elements, such as Peltier elements, are also used as thermoelectric modules, which are made up of a number of elements assembled into a plate or cylinder. Because they can directly convert thermal energy into electricity, they can be used, for example, in wristwatches that operate on body heat, and as power sources for terrestrial and satellite power generation. The performance of a thermoelectric conversion element depends on the performance of the thermoelectric conversion material and the durability of the module.

[0005] As described in Non-Patent Document 1, the dimensionless thermoelectric figure of merit ZT is used as an index representing the performance of a thermoelectric conversion material. In addition, the power factor PF (= S σ) is sometimes used as an index representing the performance of a thermoelectric conversion material. The dimensionless thermoelectric figure of merit ZT is expressed by the following formula (1). ZT=((S2·σ) / к)·T Equation (1) where S is the Seebeck coefficient (V / K), σ is the electrical conductivity (S / m), T is the absolute temperature (K), and κ is the thermal conductivity (W / (m·K)). The thermal conductivity κ is expressed by the following equation (2): к=α·ρ·C Equation (2) where α is the thermal diffusivity (m 2 / s), ρ is the density (kg / m 3 ), and C is the specific heat capacity (J / (kg·K)). That is, in order to improve the thermoelectric conversion performance (hereinafter also referred to as thermoelectric properties), it is important to improve the Seebeck coefficient or electrical conductivity while decreasing the thermal conductivity.

[0006] In recent years, research has been progressing on thermoelectric conversion elements that use organic materials instead of conventional inorganic materials. Organic materials are lightweight, have excellent moldability, and are more flexible than inorganic materials, making them highly versatile within the temperature range where they do not decompose. In addition, they are more advantageous than inorganic materials in terms of manufacturing energy and costs, as they can be easily manufactured using printing techniques.

[0007] For example, Patent Document 1 discloses a thermoelectric conversion material containing a polymer dispersant having an organic dye skeleton and carbon nanotubes (CNTs), and a thermoelectric conversion element using the same. Patent Document 2 also discloses a thermoelectric conversion material containing a conductive compound in which a polycyclic aromatic ring having carrier transport properties is bonded to a substituent containing an alkyl group, and a thermoelectric conversion element using the same. However, the invention of Patent Document 1 does not provide sufficient performance as a thermoelectric conversion element. Furthermore, the invention of Patent Document 2 also discloses a thermoelectric conversion material containing a conductive compound in which a polycyclic aromatic ring having carrier transport properties is bonded to a substituent containing an alkyl group. -8 ~10 -7 The value is low at only S / cm, and it is not possible to obtain a practical value for a thermoelectric conversion element. Furthermore, in order to improve the durability and practicality of thermoelectric conversion elements, various processes such as sealing and lamination are required for the thermoelectric conversion material. For such processes, chemical resistance is essential for the thermoelectric conversion material, but conventionally known thermoelectric conversion materials have a problem of poor chemical resistance. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2015 / 050113 [Patent Document 2] International Publication No. 2015 / 129877 [Non-patent literature]

[0009] [Non-Patent Document 1] Takenobu Kajikawa, "Thermoelectric Conversion Technology Handbook (First Edition)", NTS Publishing, p. 19 Summary of the Invention [Problem to be solved by the invention]

[0010] The problem to be solved by the present invention is to provide a thermoelectric conversion material that is excellent in thermoelectric conversion performance and chemical resistance. [Means for solving the problem]

[0011] The present inventors have conducted extensive research to solve the above-mentioned problems and have arrived at the present invention. Specifically, the present invention relates to a thermoelectric conversion material comprising a hydrogenated nitrile rubber (A) and a conductive material (B).

[0012] The present invention also relates to the above thermoelectric conversion material, wherein the hydrogenated nitrile rubber (A) contains 10% by mass or more and less than 50% by mass of units derived from acrylonitrile.

[0013] The present invention also relates to the above thermoelectric conversion material, wherein the content of the hydrogenated nitrile rubber (A) is from 1% by mass to 100% by mass relative to the conductive material (B).

[0014] The present invention also relates to the above thermoelectric conversion material, further comprising at least one selected from the group consisting of inorganic metal salts, inorganic bases, and organic bases.

[0015] The present invention also relates to the above thermoelectric conversion material, wherein the conductive material (B) comprises at least one material selected from the group consisting of carbon nanotubes, fullerenes, graphene, and carbon black.

[0016] The present invention also relates to the above thermoelectric conversion element, which comprises a thermoelectric conversion film containing the above thermoelectric conversion material and electrodes, wherein the thermoelectric conversion film and the electrodes are electrically connected. [Effects of the Invention]

[0017] The present invention makes it possible to provide a thermoelectric conversion material that is excellent in thermoelectric conversion performance and chemical resistance. DETAILED DESCRIPTION OF THE INVENTION

[0018] <Thermoelectric conversion materials> The thermoelectric conversion material of the present invention contains hydrogenated nitrile rubber (A) and an electrically conductive material (B).

[0019] <Hydrogenated nitrile rubber (A)> The hydrogenated nitrile rubber (A) improves the film-forming properties of the conductive material (B) and its adhesion to the substrate, and contributes to the formation of a flexible coating film.

[0020] Hydrogenated nitrile rubber (A) refers to rubber in which some or all of the unsaturated bonds in nitrile rubber (NBR), a copolymer of acrylonitrile and 1,3-butadiene, have been hydrogenated (hydrogenated).

[0021] Specific examples of the hydrogenated nitrile rubber (A) include Zetpol (registered trademark) 0020, 1020, 1010, 2001, 2001L, 2010, 2010, 2010L, 2010H, 2020, 2020L, 2030L, 3300, 3310, and 4310 manufactured by Zeon Corporation, and Therban (registered trademark) 3406 and 3407 manufactured by Arlanxeo. 07, 3607, 3907, 4307, 4309, 3446, 3467, 3497, 3496, 3627, 3629, 3668VP, 4367, 4369, 4498VP, TLT1707VP, LT1757VP, LT2157, LT2007, LT2057, LT2568VP, AT3404, AT3443VP, AT3904VP, AT4364VP, ATLT2004VP, etc.

[0022] The content of units derived from acrylonitrile in the hydrogenated nitrile rubber (A) (acrylonitrile content in the hydrogenated nitrile rubber (A)) is preferably 10% by mass to 50% by mass, more preferably 20% by mass to 50% by mass, and even more preferably 30% by mass to 50% by mass.

[0023] The iodine value of the hydrogenated nitrile rubber (A) is preferably 5 mg / 100 mg or more and 70 mg / 100 mg or less, and more preferably 10 mg / 100 mg or more and 50 mg / 100 mg or less.

[0024] The hydrogenated nitrile rubber (A) has a Mooney viscosity (30ML(1+4)100°C) of preferably 30 or more and 120 or less, more preferably 30 or more and 100 or less, and even more preferably 30 or more and 70 or less.

[0025] From the viewpoint of achieving both thermoelectric performance and coating flexibility, the content of the hydrogenated nitrile rubber (A) is preferably from 1% by mass to 100% by mass, more preferably from 20% by mass to 100% by mass, and even more preferably from 50% by mass to 80% by mass, based on the total amount of the conductive material (B).

[0026] <Conductive material (B)> The conductive material (B) contributes to electrical conductivity. Therefore, increasing the content of the conductive material (B) can improve electrical conductivity. The conductive material (B) is not particularly limited as long as it is a conductive material (carbon material, metal material, conductive polymer, etc.). Examples of the carbon material include graphite, carbon nanotubes, carbon black, and graphene (including graphene nanoplates). Examples of the metal material include metal powders such as gold, silver, copper, nickel, chromium, palladium, rhodium, ruthenium, indium, silicon, aluminum, tungsten, molybdenum, germanium, gallium, and platinum, as well as alloys and composite powders of ZnSe, CdS, InP, GaN, SiC, and SiGe. Furthermore, examples of the conductive material include fine particles having a core coated with a material different from the core material, specifically, silver-coated copper powder, in which a copper core is coated with silver. Other examples include powders of metal oxides such as silver oxide, indium oxide, tin oxide, zinc oxide, ruthenium oxide, ITO (tin-doped indium oxide), AZO (aluminum-doped zinc oxide), and GZO (gallium-doped zinc oxide), as well as powders surface-coated with these metal oxides. Examples of conductive polymers include PEDOT / PSS (a composite of poly(3,4-ethylenedioxythiophene) and polystyrene sulfonic acid), polyaniline, polyacetylene, polypyrrole, polythiophene, and polyparaphenylene. A single conductive material may be used, or two or more may be combined. The shape of the conductive material (B) is not particularly limited, and amorphous, aggregated, scale-like, microcrystalline, spherical, flake-like, wire-like, and other shapes may be used as appropriate.

[0027] From the viewpoint of achieving both a high Seebeck coefficient and electrical conductivity, the conductive material (B) preferably contains a carbon material, more preferably contains at least one material selected from the group consisting of carbon nanotubes, fullerenes, graphene (including graphene nanoplates), and carbon black, further preferably contains carbon nanotubes, and particularly preferably contains single-walled carbon nanotubes.

[0028] Examples of carbon materials include flake graphite such as CMX, UP-5, UP-10, UP-20, UP-35N, CSSP, CSPE, CSP, CP, CB-150, CB-100, ACP, ACP-1000, ACB-50, ACB-100, ACB-150, SP-10, SP-20, J-SP, SP-270, HOP, GR-60, LEP, F#1, and F manufactured by Nippon Graphite Industries Co., Ltd. Examples of graphite include #2, F#3, BF-3AK, FBF, BF-15AK, CBR, CPB-6S, CPB-3, 96L, 96L-3, K-3, SC-120, SC-60, HLP, CP-150, and SB-1 manufactured by Chuetsu Graphite Industries Co., Ltd., EC1500, EC1000, EC500, EC300, EC100, and EC50 manufactured by Ito Graphite Industries Co., Ltd., and 10099M and PB-99 manufactured by Nishimura Graphite Co., Ltd. Examples of spherical natural graphite include CGC-20, CGC-50, CGB-20, and CGB-50 manufactured by Nippon Graphite Industries Co., Ltd. Examples of amorphous graphite include Blue P, AP, AOP, and P#1 manufactured by Nippon Graphite Industries Co., Ltd., and APR, K-5, AP-2000, AP-6, 300F, and 150F manufactured by Chuetsu Graphite Co., Ltd. Examples of artificial graphite include PAG-60, PAG-80, PAG-120, PAG-5, HAG-10W, and HAG-150 manufactured by Nippon Graphite Industries Co., Ltd.; G-4AK, G-6S, G-3G-150, G-30, G-80, G-50, SMF, EMF, SFF, SFF-80B, SS-100, BSP-15AK, BSP-100AK, and WF-15C manufactured by Chuetsu Graphite Co., Ltd.; and SGP-100, SGP-50, SGP-25, SGP-15, SGP-5, SGP-1, SGO-100, SGO-50, SGO-25, SGO-15, SGO-5, SGO-1, SGX-100, SGX-50, SGX-25, SGX-15, SGX-5, and SGX-1 manufactured by SEC Carbon Co., Ltd.

[0029] Examples of commercially available conductive carbon fibers and carbon nanotubes include vapor grown carbon fibers such as VGCF manufactured by Showa Denko K.K., single-walled carbon nanotubes such as EC1.5 and EC1.5-P manufactured by Meijo Nano Carbon Co., Ltd., TUBALL manufactured by Kusumoto Chemicals Co., Ltd., and ZEONANO manufactured by Zeon Nano Technology Inc., FloTube9000, FloTube7000, and FloTube2000 manufactured by CNano, NC7000 manufactured by Nanocyl, and 100T and 200P manufactured by CNano.

[0030] Examples of commercially available carbon black include Tokablack #4300, #4400, #4500, and #5500 manufactured by Tokai Carbon Co., Ltd., Printex L manufactured by Degussa Corporation, and Raven 7000, 5750, 5250, 5000ULTRAIII, 5000ULTRA, Conductex SC ULTRA, and Conductex 975 manufactured by Colombian. Examples of suitable blacks include ULTRA, PUERBLACK 100, 115, and 205; Mitsubishi Chemical Corporation's #2350, #2400B, #2600B, #3050B, #3030B, #3230B, #3350B, #3400B, and #5400B; Cabot Corporation's MONARCH 1400, 1300, and 900, Vulcan XC-72R, and BlackPearls 2000; TIMCAL Corporation's Ensaco 250G, Ensaco 260G, Ensaco 350G, and Super P-Li furnace blacks; Lion Corporation's EC-300J and EC-600JD ketjen blacks; and Denka Black, Denka Black HS-100, and FX-35 acetylene blacks. These are not particularly limited.

[0031] <Inorganic bases, inorganic metal salts, organic bases> The thermoelectric conversion material of the present invention preferably further contains an inorganic base, an inorganic metal salt, or an organic base. This improves the coating resistance and dispersibility of the thermoelectric conversion material. The inorganic base and inorganic metal salt preferably contain an alkali metal or alkaline earth metal. Examples include chlorides, hydroxides, carbonates, nitrates, sulfates, phosphates, tungstates, vanadates, molybdates, niobates, and borates of alkali metals or alkaline earth metals. Among these, chlorides, hydroxides, and carbonates of alkali metals and alkaline earth metals are preferred in terms of easy supply of cations.

[0032] Examples of alkali metal hydroxides include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Examples of alkaline earth metal hydroxides include calcium hydroxide and magnesium hydroxide. Examples of alkali metal carbonates include lithium carbonate, lithium bicarbonate, sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate. Examples of alkaline earth metal carbonates include calcium carbonate and magnesium carbonate. Among these, lithium hydroxide, sodium hydroxide, lithium carbonate, and sodium carbonate are more preferred. The metal in the inorganic base or inorganic metal salt may be a transition metal.

[0033] Examples of the organic base include primary, secondary, or tertiary alkylamines in which some of the hydrogen atoms in the alkyl may be substituted with unsaturated aliphatic hydrocarbon groups such as hydroxyl groups, alkoxy groups, and alkenyl groups, or aromatic hydrocarbon groups such as aryl groups, as shown below, and other organic bases.

[0034] Examples of primary alkylamines include propylamine, butylamine, isobutylamine, octylamine, 2-ethylhexylamine, laurylamine, and stearylamine. Examples of primary alkylamines in which a hydrogen atom in the alkyl group is substituted with an unsaturated aliphatic hydrocarbon group include oleylamine. Examples of primary alkylamines in which a hydrogen atom in the alkyl group is substituted with a hydroxyl group include 2-aminoethanol and 3-aminopropanol. Examples of primary alkylamines in which a hydrogen atom in the alkyl group is substituted with an alkoxy group include 3-ethoxypropylamine and 3-lauryloxypropylamine.

[0035] Examples of secondary alkylamines include dibutylamine, diisobutylamine, N-methyl-N-hexylamine, dioctylamine, distearylamine, etc. Examples of secondary alkylamines in which a hydrogen atom in the alkyl group is substituted with a hydroxyl group include 2-methylaminoethanol, etc.

[0036] Examples of tertiary alkylamines include triethylamine, tributylamine, N,N-dimethyl-N-butylamine, N,N-diisopropyl-N-ethylamine, N,N-dimethyl-N-octylamine, trioctylamine, dimethyl-N-decylamine, N,N-dimethyl-N-laurylamine, dimethyl-N-myristylamine, N,N-dimethyl-N-palmitylamine, N,N-dimethyl-N-stearylamine, and N,N-dilauryl-N-methylamine. Examples of tertiary alkylamines in which a hydrogen atom in the alkyl group is substituted with a hydroxyl group include triethanolamine and 2-(dimethylamino)ethanol. Examples of tertiary alkylamines in which a hydrogen atom in the alkyl group is substituted with an aromatic hydrocarbon group include dimethylbenzylamine. The alkylamine preferably has 1 to 30 carbon atoms, and more preferably 1 to 20 carbon atoms.

[0037] Other examples of organic bases include nitrogen-containing heterocyclic compounds such as 1,8-diazabicyclo[5.4.0]undecene-7 (DBU), 1,5-diazabicyclo[4.3.0]nonene-5 (DBN), 1,4-diazabicyclo[2.2.2]octane (DABCO), imidazole, and 1-methylimidazole, as well as quaternary ammonium hydroxides such as tetramethylammonium hydroxide and tetraethylammonium hydroxide.

[0038] The amount of inorganic base, inorganic metal salt, or organic base to be added is preferably 0.1 to 15 parts by mass per 100 parts by mass of the hydrogenated nitrile rubber (A), which further improves the coating film resistance and dispersibility.

[0039] (dispersion medium) The dispersion medium can be used as a medium when mixing the hydrogenated nitrile rubber (A) and the conductive material (B). By containing the dispersion medium, the mixture becomes an ink or paste, which can be used to form a thermoelectric conversion film by printing or coating. The dispersion medium that can be used is preferably one that can dissolve or disperse the hydrogenated nitrile rubber (A) and the conductive material (B), and examples of such dispersion medium include organic solvents and water. One type of dispersion medium may be used alone, or two or more types may be used in combination.

[0040] Examples of organic solvents include alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol methyl ether, terpineol, dihydroterpineol, 2,4-diethyl-1,5-pentanediol, 1,3-butylene glycol, isobornylcyclohexanol, ethylene glycol, 1,3-propanediol, 1,4-butanediol, glycerin, trifluoroethanol, m-cresol, and thiodiglycol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ethers such as tetrahydrofuran, dioxane, and ethylene glycol dimethyl ether; hydrocarbons such as hexane, heptane, and octane; aromatic hydrocarbons such as benzene, toluene, xylene, and cumene; esters such as ethyl acetate and butyl acetate; and nitrogen-containing heterocycles such as N-methylpyrrolidone. N-methylpyrrolidone is particularly preferred from the viewpoints of dispersibility and solubility.

[0041] (Inorganic thermoelectric conversion materials) The thermoelectric conversion material of the present invention may contain an inorganic thermoelectric conversion material as needed to enhance thermoelectric conversion performance. The inorganic thermoelectric conversion material is not particularly limited, and materials generally known as thermoelectric conversion materials can be used.

[0042] <Thermoelectric conversion element> The thermoelectric conversion element of the present invention has a thermoelectric conversion film formed using the thermoelectric conversion material of the present invention and electrodes, and the thermoelectric conversion film and the electrodes are electrically connected. The thermoelectric conversion film is excellent in heat resistance and flexibility in addition to electrical conductivity and thermoelectric properties. Therefore, high-quality thermoelectric conversion elements can be easily produced.

[0043] The thermoelectric conversion film may be a film obtained by applying a thermoelectric conversion material to a substrate. Because thermoelectric conversion materials have excellent formability, it is easy to obtain a good film by coating or printing. The method for producing the thermoelectric conversion film is not particularly limited as long as it can obtain the desired thermoelectric conversion film, and can be appropriately selected depending on the properties of the thermoelectric conversion material, such as viscosity, and the required film thickness, area, shape, and other conditions. Examples of methods include spin coating, spray coating, roll coating, gravure coating, flexo coating, die coating, lip coating, knife coating, blade coating, comma coating, roll coating, curtain coating, bar coating, dip coating, dispenser coating, screen coating, and inkjet printing.

[0044] The thickness of the thermoelectric conversion film is not particularly limited and can be set according to the required electrical properties such as current value, voltage value, and resistance, as well as the thermoelectric properties, but as will be described later, it is preferable that the thermoelectric conversion film be formed to have a certain thickness or more so that a temperature difference can be generated and transmitted in the thickness direction or in the plane direction of the thermoelectric conversion film. From the viewpoint of thermoelectric properties and flexibility, the thickness of the thermoelectric conversion film is preferably in the range of 0.1 to 200 μm, more preferably in the range of 1 to 100 μm, and particularly preferably in the range of 1 to 60 μm.

[0045] The substrate is not particularly limited, and examples thereof include nonwoven fabric, paper, plastic films made of materials such as polyethylene, polyethylene terephthalate (PET), polyethylene naphthalate, polyethersulfone, polypropylene, polyimide, polycarbonate, and cellulose triacetate, and glass. These substrates may have an aluminum vapor deposition layer or a barrier layer on the surface of the substrate to prevent deterioration of the thermoelectric conversion material due to the effects of water and oxygen.

[0046] In order to improve the adhesion between the substrate and the thermoelectric conversion film, various treatments can be performed on the substrate surface. Specifically, prior to application of the thermoelectric conversion material, UV ozone treatment, corona treatment, plasma treatment, or adhesion-enhancing treatment can be performed.

[0047] The thermoelectric conversion film may be laminated with a substrate or may be a free-standing film without a substrate. There are no particular limitations on how to prepare a free-standing film, and it can be obtained, for example, by forming the thermoelectric conversion film on a release sheet and then removing the release coating.

[0048] Examples of the release sheet include release-treated plastic films such as polyester film, polyethylene film, polypropylene film, and polyimide film.

[0049] The thermoelectric conversion element can be constructed using techniques well known in the art, except that it is constructed using the above-mentioned thermoelectric conversion material. A more specific configuration of the thermoelectric conversion element and a manufacturing method thereof will be described below.

[0050] In a thermoelectric conversion element, the thermoelectric conversion film and the electrodes are electrically connected. Here, "electrically connected" means that they are joined to each other or can conduct electricity via other components such as wires.

[0051] The material of the electrode is not particularly limited as long as it functions as an electrode, and can be selected from metals, alloys, and semiconductors. In one embodiment, metals and alloys are preferred because they have high conductivity and low contact resistance of the thermoelectric conversion film. For example, the electrode preferably contains at least one selected from the group consisting of gold, silver, copper, platinum, nickel, and aluminum. The electrode more preferably contains silver.

[0052] The method for forming the electrodes is not particularly limited, and they can be formed by methods such as vacuum deposition, thermocompression bonding of an electrode material foil or a film having an electrode material film, coating of a paste in which fine particles of the electrode material are dispersed, etc. From the viewpoint of process simplicity, methods using thermocompression bonding of an electrode material foil or a film having an electrode material film, and coating of a paste in which the electrode material is dispersed are preferred.

[0053] Typical examples of the structure of thermoelectric conversion elements can be broadly classified into (1) a structure in which electrodes are formed on both ends of the thermoelectric conversion film of the present invention, and (2) a structure in which the thermoelectric conversion film of the present invention is sandwiched between two electrodes, based on the positional relationship between the thermoelectric conversion film and a pair of electrodes. A thermoelectric conversion element having the structure (1) above can be obtained, for example, by forming a thermoelectric conversion film on a substrate and then applying silver paste to both ends of the film to form first and second electrodes. A thermoelectric conversion element having electrodes formed on both ends of the thermoelectric conversion film in this way can easily increase the distance between the two electrodes. Therefore, a large temperature difference can be generated between the two electrodes, making it easy to perform efficient thermoelectric conversion.

[0054] A thermoelectric conversion element having the structure (2) above can be obtained, for example, by applying silver paste to a substrate to form a first electrode, forming the thermoelectric conversion film of the present invention on top of that, and then applying silver paste to form a second electrode on top of that. A thermoelectric conversion element having the thermoelectric conversion film of the present invention sandwiched between two electrodes in this way can utilize the temperature difference in the thickness direction of the thermoelectric conversion film, i.e., in the direction perpendicular to the substrate, and can therefore be used in a form attached to a heat source. This is preferable because it has the advantage of being able to extract heat from a wide range from the heat source. In a thermoelectric conversion element having the structure (2) above, it is also possible to increase the distance between the two electrodes by increasing the film thickness, thereby ensuring a sufficient temperature difference.

[0055] Thermoelectric conversion elements can generate a high voltage when connected in series, and can generate a large current when connected in parallel. The thermoelectric conversion element may be one in which two or more thermoelectric conversion elements are connected. According to the present invention, the thermoelectric conversion element has excellent flexibility, and therefore can be well-installed on a heat source having a shape that is not flat. The thermoelectric conversion element may have a heat absorption layer or a heat storage layer for efficient heat transfer from the heat source, or may have a heat insulation layer or a heat dissipation layer for ensuring a temperature difference. Furthermore, depending on the application and the amount of power required, the extracted electricity can be boosted using a boost circuit, or the extracted electrical energy can be temporarily stored in a condenser, capacitor, secondary battery, or the like for use. [Example]

[0056] The present invention will be described in more detail below with reference to experimental examples, but is not limited to these examples. In the examples, "parts" means "parts by mass" and "%" means "% by mass." Furthermore, "NMP" refers to N-methylpyrrolidone.

[0057] <Production of a dispersion containing a thermoelectric conversion material> [Example 1] (Dispersion 1) 0.2 parts of hydrogenated nitrile rubber (A), 0.4 parts of SWCNT (single-walled carbon nanotubes "TUBALL" manufactured by OCSiAl Corporation), and 79.3 parts of NMP were weighed and mixed. Beads were then added, and the mixture was shaken in a Scandex for 4 hours. The beads were then removed by filtration, and thermoelectric conversion material dispersion 1 was obtained.

[0058] [Examples 2 to 13, 22, 24, 25, 29 to 31, Comparative Examples 1 and 2] (Dispersions 2~13, 22, 24, 25, 29~31, 101, 102) Thermoelectric conversion material dispersions 2 to 13, 22, 24, 25, 29 to 31, 101, and 102 were obtained in the same manner as dispersion 1, except that the types and amounts of materials were changed as shown in Table 1.

[0059] [Example 14] (Dispersion 14) 0.4 parts of hydrogenated nitrile rubber (A), 0.4 parts of SWCNT (single-walled carbon nanotubes "TUBALL" manufactured by OCSiAl), 0.0004 parts of NaOH, and 79.3 parts of NMP were weighed and mixed. Beads were then added, and the mixture was shaken in a Scandex for 4 hours. The beads were then removed by filtration, yielding a thermoelectric conversion material dispersion liquid 14.

[0060] [Examples 15 to 21, 23, 26 to 28] (Dispersion 15~21, 23, 26~28) Thermoelectric conversion material dispersions 15 to 21, 23, and 26 to 28 were obtained in the same manner as dispersion 14, except that the types and amounts of materials were changed as shown in Table 2.

[0061] The abbreviations for the materials listed in Table 2 are as follows: <Hydrogenated nitrile rubber (A)> LT1757 VP: Therban (registered trademark) LT1757VP (manufactured by Arlanxeo) LT2007: Therban (registered trademark) LT2007 (manufactured by Arlanxeo) AT3404: Therban (registered trademark) AT3404 (manufactured by Arlanxeo) Zetpol2020: Zetpol (registered trademark) 2020 (manufactured by Zeon Corporation) AT4364: Therban (registered trademark) AT4364 (manufactured by Arlanxeo)

[0062] <Conductive material (B)> SWCNT: OCSiAl's single-walled carbon nanotubes "TUBALL" MWCNT: (Kumho Petrochemical's multi-walled carbon nanotubes "Knanos100P") Fullerene: Fullerene C60, 99.5% (Fujifilm Wako Pure Chemical Industries, Ltd.) Graphene: Graphene powder (Stem Chemicals) CB: (Lion Ketjenblack "EC-300J") <Other materials> NMP: 1-methyl-2-pyrrolidone TMAOH: tetramethylammonium hydroxide Ethylene vinyl acetate: Ethylene vinyl acetate copolymer, Ultrathene 630 (manufactured by Tosoh Corporation)

[0063] <Evaluation of thermoelectric conversion materials> The obtained dispersions 1 to 31 and 101 to 102 were each applied to a 75 μm thick PET film substrate using an applicator, and then dried at 120°C for 30 minutes to obtain laminates each having a thermoelectric conversion film with a thickness of 5 μm. Furthermore, the electrical conductivity and Seebeck coefficient of the obtained laminates having the thermoelectric conversion film (hereinafter also referred to as the coating film) were measured and the flexibility was evaluated according to the following methods. The results are shown in Table 1.

[0064] (Electrical conductivity (resistivity)) Immediately after production, the laminate was cut into a piece measuring 2.5 cm × 5 cm, and its conductivity was measured by the four-probe method using a Loresta GX MCP-T700 (manufactured by Mitsubishi Chemical Analytech Co., Ltd.) in accordance with JIS-K7194. The conductivity is shown in Table 2 as a relative value when the conductivity of Comparative Example 1 is set to 1.

[0065] (Seebeck coefficient) Immediately after production, the laminate was cut into a size of 3 mm × 10 mm, and the Seebeck coefficient (μV / K) at 80°C was measured using a ZEM-3LW manufactured by Advance Riko Co., Ltd. Table 2 shows the relative values ​​when the Seebeck coefficient of Comparative Example 1 was set to 1.

[0066] (chemical resistance) Chemical resistance was evaluated by rubbing the thermoelectric conversion film surface of the laminate immediately after production with a cotton swab soaked in toluene 30 times, then visually inspecting the condition and rating it on a 5-point scale according to the following criteria: A usable level is "3" or higher. 5: No change in surface. 4: Dissolution is observed on part of the surface (less than 10% of the area). 3: Dissolution is observed on part of the surface (less than 10% to 30% of the area). 2: Dissolution is observed on part of the surface (less than 30% to 50% of the area). 1: Dissolution is observed on part of the surface (more than 50% of the area) or the entire surface.

[0067] <Manufacturing of thermoelectric conversion elements> The dispersions were each applied to a 50 μm-thick PET film to produce five thermoelectric conversion layers, each 20 μm thick and measuring 5 mm × 30 mm, spaced 10 mm apart. Next, four silver circuits (electrodes) each measuring 10 μm thick and 5 mm × 33 mm were fabricated using silver paste so that the thermoelectric conversion layers were connected in series, thereby producing thermoelectric conversion elements. The silver paste used was REXALPHA® RA-FS 074 manufactured by Toyo Ink Co., Ltd. The electromotive force of each thermoelectric conversion element was measured, and it was confirmed that the thermoelectric conversion elements produced using the dispersions produced in the examples all had a superior Seebeck coefficient to the thermoelectric conversion elements produced using the dispersions produced in the comparative examples.

[0068] [Table 1]

Claims

1. A thermoelectric conversion material comprising a hydrogenated nitrile rubber (A) and a conductive material (B), wherein the hydrogenated nitrile rubber (A) contains 10% by mass or more and less than 50% by mass of units derived from acrylonitrile.

2. 2. The thermoelectric conversion material according to claim 1, wherein the content of the hydrogenated nitrile rubber (A) is 1% by mass or more and 100% by mass or less relative to the conductive material (B).

3. 2. The thermoelectric conversion material according to claim 1, further comprising at least one selected from the group consisting of inorganic metal salts, inorganic bases, and organic bases.

4. 2. The thermoelectric conversion material according to claim 1, wherein the conductive material (B) comprises at least one material selected from the group consisting of carbon nanotubes, fullerenes, graphene, and carbon black.

5. A thermoelectric conversion element comprising a thermoelectric conversion film containing the thermoelectric conversion material according to any one of claims 1 to 4 and electrodes, wherein the thermoelectric conversion film and the electrodes are electrically connected.

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