Composition for thermoelectric conversion element, thermoelectric conversion module, and method for manufacturing thermoelectric conversion module

Abstract

To provide a composition for a thermoelectric conversion element which does not substantially contain a dopant, and enables formation of a p-type or n-type thermoelectric conversion element, and a thermoelectric conversion element and a thermoelectric conversion module using the same.SOLUTION: There are provided: a composition for a p-type or n-type thermoelectric conversion element which contains nanocarbon, an epoxy compound, and a curing agent reactive with the epoxy compound, and does not substantially contain a dopant imparting p-type or n-type semiconductor characteristics to the nanocarbon, wherein as for the epoxy compound and the curing agent, the nanocarbon exhibits p-type or n-type semiconductor characteristics in the reacted epoxy resin; and a thermoelectric conversion element and a thermoelectric conversion module using the same.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a composition for a thermoelectric conversion element, a thermoelectric conversion module, and a method for producing a thermoelectric conversion module. [Background technology]

[0002] In recent years, thermoelectric power generation elements have become known as solid-state elements that convert thermal energy into electrical energy. Thermoelectric power generation elements are also used in, for example, space power sources and thermoelectric conversion modules that operate with body heat (wristwatches, wearable devices, etc.). For this reason, various studies have been conducted on compositions for thermoelectric conversion elements, thermoelectric conversion modules, and thermoelectric conversion modules.

[0003] For example, Patent Document 1 proposes "a carbon nanotube composite containing a carbon nanotube, a conductive polymer, and a p-type dopant or an n-type dopant."

[0004] Patent Document 2 describes "a nanomaterial composite containing a thermoelectric conversion material, a basic compound, and a dopant compound." [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2019 / 021908 [Patent Document 2] International Publication No. 2018 / 142748 Summary of the Invention [Problem to be solved by the invention]

[0006] Conventional compositions for thermoelectric conversion elements, including those described in Patent Documents 1 and 2, may contain, in addition to nanocarbon such as carbon nanotubes, a dopant that imparts p-type or n-type semiconductor properties to the nanocarbon.

[0007] However, many dopants are difficult to handle industrially, for example, due to their deliquescent nature. In addition, when a dopant is used to impart n-type semiconductor properties to nanocarbon, degradation due to oxidation occurs over time, and the conductivity type of the nanocarbon often changes to p-type.

[0008] Therefore, an object of the present disclosure is to provide a thermoelectric conversion element composition that is substantially free of dopants and can form a p-type or n-type thermoelectric conversion element, and a thermoelectric conversion element and a thermoelectric conversion module that utilize the same. [Means for solving the problem]

[0009] Means for solving the problems include the following aspects. <1> Nanocarbon and An epoxy compound; A curing agent that reacts with the epoxy compound; Including, The nanocarbon is substantially free of a dopant that imparts p-type semiconductor properties; The epoxy compound and the curing agent are epoxy compounds and curing agents that cause the nanocarbon to exhibit p-type semiconductor properties in an epoxy resin after reaction. A composition for p-type thermoelectric conversion elements. <2> The epoxy compound is a cycloaliphatic epoxy compound, The curing agent is an acid anhydride type curing agent. <1> The composition for a p-type thermoelectric conversion element according to claim 1. <3> Nanocarbon and An epoxy compound; A curing agent that reacts with the epoxy compound; Including, The nanocarbon is substantially free of a dopant that imparts n-type semiconductor properties. The epoxy compound and the curing agent are epoxy compounds and curing agents that cause the nanocarbon to exhibit n-type semiconductor properties in an epoxy resin after reaction. A composition for n-type thermoelectric conversion elements. <4> The epoxy compound is at least one selected from the group consisting of cycloaliphatic epoxy compounds and glycidylamine epoxy compounds, The curing agent is at least one selected from the group consisting of an acid anhydride type curing agent, an imidazole type curing agent, an amine type curing agent, and a phenol type curing agent. <3> The composition for n-type thermoelectric conversion elements according to claim 1. <5> A substrate having a plurality of through holes formed therein; p-type thermoelectric conversion elements mounted in the plurality of through holes; n-type thermoelectric conversion elements mounted in the plurality of through holes; a conductive material that alternately connects the p-type thermoelectric conversion elements and the n-type thermoelectric conversion elements in series, The p-type thermoelectric conversion element is <1> or <2> The p-type thermoelectric conversion element composition according to claim 1, The n-type thermoelectric conversion element is <3> or <4> The composition for n-type thermoelectric conversion elements according to claim 1, Thermoelectric conversion module. <6> A preparation step of preparing a substrate having a plurality of through holes formed therein; The plurality of through holes are <1> or <2> and filling the through holes not filled with the p-type thermoelectric conversion element composition with the p-type thermoelectric conversion element composition described in the above. <3> or <4> A filling step of filling the composition for n-type thermoelectric conversion elements described in forming a p-type thermoelectric conversion element from the composition for p-type thermoelectric conversion elements, and forming an n-type thermoelectric conversion element from the composition for n-type thermoelectric conversion elements; A connection step of alternately connecting the p-type thermoelectric conversion elements and the n-type thermoelectric conversion elements in series using a conductive material. A method for manufacturing a thermoelectric conversion module. Effect of the Invention

[0010] According to the present disclosure, there are provided a thermoelectric conversion element composition that is substantially free of dopants and that can form a p-type or n-type thermoelectric conversion element, and a thermoelectric conversion element and a thermoelectric conversion module that utilize the same. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating an example of the upper surface of a thermoelectric conversion module 10 according to the present disclosure, in which a p-type thermoelectric conversion element 21 and an n-type thermoelectric conversion element 22 formed from a composition for thermoelectric conversion elements according to the present disclosure are mounted. [Diagram 2] 2 is a cross-sectional view showing a cut surface when wiring 31 is formed at the position shown by the dotted line in FIG. 1 and cut along line AB. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment that is an example of the present disclosure will be described. These descriptions and examples are merely illustrative of the embodiment, and are not intended to limit the scope of the invention. In the present specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range. In addition, in the present specification, the upper or lower limit of the numerical range may be replaced with a value shown in the examples. Each component in the composition may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition, if the composition contains multiple substances corresponding to each component, the amount refers to the total amount of those multiple substances present in the composition, unless otherwise specified.

[0013] When describing the embodiments with reference to the drawings, components having substantially the same functions are given the same reference numerals throughout the drawings, and duplicated descriptions may be omitted.

[0014] <Composition for thermoelectric conversion element> The composition for thermoelectric conversion elements of the present disclosure is a p-type or n-type composition for thermoelectric conversion elements that contains nanocarbon, an epoxy compound, and a curing agent that reacts with the epoxy compound, and is substantially free of a dopant that imparts p-type or n-type semiconductor properties to the nanocarbon, and the epoxy compound and curing agent are an epoxy compound and a curing agent that cause the nanocarbon to exhibit p-type or n-type semiconductor properties in the epoxy resin after reaction. In the following, the epoxy compound and the curing agent are also referred to as "epoxy resin raw materials".

[0015] The composition for thermoelectric conversion elements of the present disclosure has the above-mentioned structure, and the conductivity type of the nanocarbon is controlled by the epoxy resin formed by the reaction of the epoxy compound and the curing agent, thereby making it possible to form a p-type or n-type thermoelectric conversion element without substantially containing a dopant. In addition, since the composition does not substantially contain a dopant that is difficult to handle industrially, the production process of the composition for thermoelectric conversion elements is simplified, and production costs can be reduced. Furthermore, since the nanocarbon in the formed thermoelectric conversion element is covered with epoxy resin, it is less likely to deteriorate due to oxidation over time, and the conductivity type of the nanocarbon can be prevented from changing from n-type to p-type.

[0016] Here, we will explain the dimensionless figure of merit ZT, which is one of the indices for evaluating the thermoelectric conversion performance of a thermoelectric conversion element. ZT is expressed by the following formula (1). Dimensionless figure of merit ZT=S2×σ×T / κ (1) In equation (1), S (V / K) represents the Seebeck coefficient, σ (S / m) represents the electrical conductivity, κ (W / mK) represents the thermal conductivity, and T (K) represents the absolute temperature. In the present disclosure, a thermoelectric conversion element formed from a composition for thermoelectric conversion elements exhibits high electrical conductivity (σ) due to the nanocarbon, which is a representative carbon nanotube, while the thermal conductivity (κ) can be reduced by the epoxy resin, which is the binder resin, and as a result, the dimensionless figure of merit (ZT) can be increased.

[0017] Hereinafter, the composition for thermoelectric conversion elements according to the present disclosure will be described in detail.

[0018] The composition for thermoelectric conversion elements of the present disclosure is a composite material that contains nanocarbon and an epoxy resin raw material and is substantially free of a dopant that imparts p-type or n-type semiconductor properties to the nanocarbon, and therefore can be made into a composition having fluidity such as a paste or ink state. This can improve the handling properties of the composition, such as facilitating filling of the composition onto a substrate. In addition, since the composition for thermoelectric conversion elements of the present disclosure is a composite material of nanocarbon, epoxy resin raw material, and the raw material, the mechanical strength of the formed thermoelectric conversion element can be improved.

[0019] (Nanocarbon) An example of nanocarbon is carbon nanotube (CNT). The carbon nanotube may be a single-walled carbon nanotube (SWCNT) in which one carbon film (graphene sheet) is wound in a cylindrical shape. The carbon nanotube may be a multi-walled carbon nanotube (MWCNT) such as a double-walled carbon nanotube, a triple-walled carbon nanotube, or a four-walled carbon nanotube in which two graphene sheets are wound in a concentric shape. In consideration of the thermoelectric properties, the carbon nanotube is preferably 10 layers or less. Single-walled carbon nanotubes are preferred because they tend to provide high thermoelectric properties. Multi-walled carbon nanotubes are preferred because they are inexpensive and have excellent mass productivity. Single-walled carbon nanotubes and multi-walled carbon nanotubes can also be used in combination. In addition, the carbon nanotubes may be metallic carbon nanotubes, semiconducting carbon nanotubes, or a mixture of the two. The method for producing carbon nanotubes is not particularly limited. Carbon nanotubes can be produced by arc discharge, chemical vapor deposition (CVD), laser ablation, etc. The carbon nanotubes can be produced by a polymerization method or the like. Commercially available carbon nanotubes may also be used.

[0020] The nanocarbon may be graphene. By inserting a carrier between two layers of graphene, graphene can be used as a semiconductor material.

[0021] Other examples of nanocarbons include carbon nanorods, carbon nanowires, graphene, and fullerene.

[0022] The content of nanocarbon is, for example, 0.2 to 1.7 mass % with respect to the thermoelectric conversion element to be formed.

[0023] (epoxy resin raw material) The epoxy compound and the curing agent as the epoxy resin raw materials are raw materials of the epoxy resin that functions as a binder resin in the thermoelectric conversion element. An epoxy compound is a compound that has two or more epoxy groups in its molecule. There are two types of hardeners: one is called a polyaddition type hardener, which is a compound that has one or more functional groups that react with two or more epoxy groups of an epoxy compound, and is generally added in a stoichiometric amount to the epoxy compound. The other is called a self-polymerizing type hardener, which is a compound that has one or more functional groups that react with one or more epoxy groups of an epoxy compound, and by activating the epoxy groups, it is a compound that causes a chain reaction in the epoxy compound itself when added in small amounts. In addition, amine-type, phenol-type, and acid anhydride-type curing agents are classified as polyaddition-type curing agents, and imidazole-type curing agents are classified as self-polymerization-type curing agents.

[0024] An example of a combination of an epoxy compound and a curing agent that causes the nanocarbon to exhibit p-type semiconductor properties in an epoxy resin is a combination in which the epoxy compound is a cyclic aliphatic epoxy compound and the curing agent is an acid anhydride curing agent.

[0025] On the other hand, as a combination of an epoxy compound and a curing agent in which nanocarbon exhibits n-type semiconductor properties in an epoxy resin, a combination in which the epoxy compound is at least one selected from the group consisting of cyclic aliphatic epoxy compounds and glycidylamine epoxy compounds, and the curing agent is at least one selected from the group consisting of acid anhydride curing agents, imidazole curing agents, amine curing agents, and phenolic curing agents can be mentioned. Specific examples of such combinations are as follows. Combination of cyclic aliphatic epoxy compound and acid anhydride hardener Combination of cyclic aliphatic epoxy compound and phenolic hardener - Combination of glycidylamine type epoxy compound and phenol type hardener Combination of glycidylamine type epoxy compound and acid anhydride type hardener - Combination of glycidylamine type epoxy compound and imidazole type hardener Combination of glycidylamine type epoxy compound and amine type hardener

[0026] Here, the cycloaliphatic epoxy compound is, for example, an epoxy compound having two or more epoxy group-containing cycloaliphatic groups (such as epoxycyclohexyl groups). Examples of the cyclic aliphatic epoxy compounds include 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, bis(3,4-epoxy-6-methylcyclohexyl)adipate, and the like.

[0027] The glycidylamine type epoxy compound is an epoxy compound having a glycidyl group-substituted amino group (such as a diglycidylamino group). Examples of the glycidylamine type epoxy resin include triglycidyl-p-aminophenol, N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, N,N-(diglycidyl)-o-toluidine, and diglycidylaniline.

[0028] The acid anhydride type curing agent is a curing agent made of a carboxylic acid anhydride. Examples of acid anhydride type curing agents include 3,4-dimethyl-6-(2-methyl-1-propenyl)-1,2,3,6-tetrahydrophthalic anhydride, 1-isopropyl-4-methyl-bicyclo[2.2.2]oct-5-ene-2,3-dicarboxylic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, hexahydrophthalic anhydride, methylhymic anhydride, pyromellitic dianhydride, maleic alloocimene, benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyl tetrabisbenzophenone tetracarboxylic dianhydride, (3,4-dicarboxyphenyl) ether dianhydride, bis(3,4-dicarboxyphenyl) methane dianhydride, and 2,2-bis(3,4-dicarboxyphenyl) propane dianhydride.

[0029] The imidazole type curing agent is a curing agent having an imidazole skeleton. Examples of the imidazole type curing agent include 2-methylimidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, and an isocyanuric acid adduct of 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine (isocyanuric acid is added to the N at the 1-position of imidazole).

[0030] The amine-type curing agent is a curing agent having two or more amino groups. Examples of the amine-type curing agent include chain aliphatic amine compounds, cyclic aliphatic amines, and aromatic amines. Examples of the chain aliphatic amine compound include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyoxypropylenediamine, and polyoxypropylenetriamine. Examples of the cyclic aliphatic amine compound include benzenediamine, isophoronediamine, bis(4-amino-3-methylcyclohexyl)methane, diaminodicyclohexylmethane, bis(aminomethyl)cyclohexane, N-aminoethylpiperazine, and 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro(5,5)undecane. Examples of the aromatic amine compound include m-xylylenediamine, α-(m / p-aminophenyl)ethylamine, m-phenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, α,α-bis(4-aminophenyl)-p-diisopropylbenzene, and the like.

[0031] A phenol-type curing agent is a curing agent having two or more phenol groups. Examples of the phenol-type hardener include phenol novolac, o-cresol novolac, p-cresol novolac, t-butylphenol novolac, dicyclopentadiene cresol, and derivatives thereof.

[0032] (Dopant) The composition for p-type thermoelectric conversion elements of the present disclosure does not substantially contain a dopant that imparts p-type semiconductor properties to the nanocarbon, and the composition for n-type thermoelectric conversion elements of the present disclosure does not substantially contain a dopant that imparts n-type semiconductor properties to the nanocarbon.

[0033] Here, the phrase "the composition for thermoelectric conversion elements does not substantially contain a dopant" means that the content of the dopant in the thermoelectric conversion element to be formed is 0 to 1 mass %.

[0034] The dopant includes any of compounds, low molecular weight organic compounds and inorganic salts thereof (for example, organic compounds having a molecular weight of 1000 or less and inorganic salts thereof), and inorganic compounds that impart semiconductor properties to nanocarbon.

[0035] (Other ingredients) As other components, the composition for thermoelectric conversion elements may appropriately contain a thixotropic agent, a dispersant, a surfactant, an antioxidant, a weathering light stabilizer, a heat stabilizer, a plasticizer, etc. Examples of the surfactant include known surfactants (such as cationic surfactants and anionic surfactants). do.

[0036] <Thermoelectric conversion module> The thermoelectric conversion module of the present disclosure will be described with reference to FIGS. FIG. 1 is a diagram illustrating an example of the upper surface of a thermoelectric conversion module 10 according to the present disclosure, in which a p-type thermoelectric conversion element 21 and an n-type thermoelectric conversion element 22 formed from a thermoelectric conversion element composition according to the present disclosure are mounted. FIG. 2 is a cross-sectional view showing a cut surface when wiring 31 is formed at the position shown by the dotted line in FIG. 1 and cut along line AB in FIG.

[0037] As shown in Fig. 1, in a thermoelectric conversion module 10 of the present disclosure, a p-type thermoelectric conversion element 21 and an n-type thermoelectric conversion element 22 are mounted in through holes formed in a substrate 11. The p-type thermoelectric conversion elements 21 and the n-type thermoelectric conversion elements 22 are alternately wired in series and electrically connected as shown in Fig. 2. Note that in Fig. 1, positions (31) where wiring 31 is formed on the upper surface are indicated by dotted lines. Furthermore, the substrate 11 is provided with an extraction electrode 41. The p-type thermoelectric conversion elements 21 and the n-type thermoelectric conversion elements 22 are formed from the above-mentioned composition for thermoelectric conversion elements.

[0038] An example of the substrate 11 is a printed circuit board. When a printed circuit board is used, the printed circuit board itself can be used as a thermoelectric conversion module. Furthermore, the use of a printed circuit board makes it easy to connect to the outside, and a control circuit can be formed on the same substrate as needed. The printed circuit board may be a flexible substrate or a rigid substrate. A rigid substrate is preferable because it allows thermoelectric conversion elements to be mounted at a higher density. Furthermore, the use of a rigid substrate allows soldering and electronic components to be mounted, so that the control circuit can be formed on the same surface. In this way, a thermoelectric conversion module is formed in part of the ECU (Electronic Control Unit), and a mechanism for directly cooling the area directly below the heat-generating components is formed. It is possible.

[0039] An example of a rigid substrate is a glass epoxy substrate. Since the substrate is a glass epoxy substrate and the linear expansion coefficient of the substrate can be made close to that of the epoxy resin used as the binder resin of the thermoelectric conversion element, it is possible to prevent the thermoelectric conversion element from peeling off from the substrate due to thermal contraction of the resin.

[0040] Other substrates that can be used include glass, transparent ceramics, metals, plastic films, etc. Examples of plastic films include polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate, polybutylene terephthalate, poly(1,4-cyclohexylene dimethylene terephthalate), polyethylene-2,6-phthalenedicarboxylate, polyester films such as polyester films of bisphenol A and iso- and terephthalic acid, polycarbonate films, polyether ether ketone films, polyphenyl sulfide films, etc.

[0041] The thickness of the substrate is 0.1 mm to 6.5 mm. The gap between the through holes formed in the substrate is 0.1 mm to 3.0 mm. The shape of the through holes can be a round hole, a rectangular hole (square hole), an elongated round hole (rectangle with rounded corners), an oblong hole (rectangle hole), or the like. Alternatively, the through holes may be polygonal. From the viewpoint of easiness of filling uniformly without gaps, a round hole, i.e., a cylindrical shape, is preferable. In the case of a round hole, its diameter (φ) is 0.3 mm to 5.0 mm. In the case of a rectangular hole (square hole), the length of one side may be 0.3 mm to 5.0 mm, and in the case of an elongated round hole (rectangle with rounded corners) or an oblong hole (rectangle hole), the average length of two sides may be 0.3 mm to 5.0 mm. If the through hole is too thin, the possibility of Joule heat generation increases, and conversely, if it is too thick, the number of thermoelectric conversion elements cannot be sufficiently secured.

[0042] The through holes can be arranged, for example, in a staggered fashion or in parallel. FIG. 1 shows an example in which the through holes are arranged in parallel. The inner walls of the through holes formed in the board are preferably non-through holes that are not plated with a metal such as copper. If the through holes are non-through holes, the components mounted in the through holes can be mounted without any problems. This can prevent electricity from flowing from the attached thermoelectric conversion element to the inner wall.

[0043] The wiring 31 is formed from a conductive material that electrically connects the p-type thermoelectric conversion element 21 and the n-type thermoelectric conversion element 22. For example, the wiring 31 may be formed from copper plating or copper foil. Alternatively, the wiring 31 may be formed from a conductive paste of carbon nanotubes. By forming the wiring from carbon nanotubes themselves or using the thermoelectric conversion element composition of the present application for both filling and wiring, subsequent plating wiring becomes unnecessary, which makes it possible to simplify the process and reduce costs. Alternatively, by wiring from carbon nanotubes and applying electrolytic plating using the carbon nanotubes as a seed layer, it is possible to omit a base plating step such as an electroless copper plating step, which makes it possible to simplify the process and reduce costs. The thickness of the wiring 31 is, for example, 1 μm to 50 μm.

[0044] Other conductive materials that may be used to form the wiring 31 include transparent electrode materials such as indium tin oxide (ITO) and zinc oxide (ZnO), metal electrode materials such as silver, copper, gold and aluminum, carbon materials such as CNT and graphene, organic materials such as PEDOT (poly(3,4-ethylenedioxythiophene)) / PSS (poly(4-styrenesulfonic acid)), conductive pastes in which conductive fine particles such as silver and carbon are dispersed, conductive pastes containing metal nanowires such as silver, copper and aluminum, etc. Among these, metal electrode materials such as aluminum, gold, silver or copper, or conductive pastes containing these metals are preferred.

[0045] The extraction electrode 41 may be formed by any known method as long as it is a plated film having excellent electrical conductivity, for example, copper plating, gold plating, silver plating, or tin plating.

[0046] <Method of manufacturing composition for thermoelectric conversion element> In the method for producing the composition for thermoelectric conversion elements, first, nanocarbon is dispersed in a solvent to prepare a nanocarbon dispersion. There is no particular limitation on the method for preparing the nanocarbon dispersion, and it can be carried out at room temperature and normal pressure using a normal mixing device, etc. Each component can be dispersed by stirring, shaking, etc. In order to improve the dispersibility of the nanocarbon, the dispersion medium may be heated to a temperature between room temperature (25°C) and the boiling point, the dispersion time may be extended, or ultrasonic treatment may be performed.

[0047] Next, while removing the solvent from the nanocarbon dispersion, an epoxy resin raw material (a composition containing an epoxy compound and a curing agent) is added, and the solvent is replaced with the epoxy resin raw material to prepare a composition for thermoelectric conversion elements. A known method can be used to remove the solvent. For example, the solvent may be removed by evaporating it by heating. In this manner, a composition for thermoelectric conversion elements having flowability such as a paste or ink form is prepared.

[0048] The solvent may be any solvent capable of dispersing nanocarbon, and may be water, an organic solvent, or a mixture thereof. Examples of the organic solvent include methyl ethyl ketone (MEK), alcohol, chloroform, dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), chlorobenzene, dichlorobenzene, benzene, toluene, xylene, mesitylene, tetralin, tetramethylbenzene, pyridine, cyclohexanone, acetone, diethyl ether, tetrahydrofuran (THF), t-butyl methyl ether, dimethoxyethane, and diglyme. The solvent may be used alone or in combination of two or more.

[0049] The amount of the solvent is not particularly limited as long as it is an amount capable of dispersing the nanocarbon and inorganic thermoelectric conversion material particles.

[0050] <Method of manufacturing thermoelectric conversion module> As a method for producing a thermoelectric conversion module, a method for filling a through hole in a substrate with a composition for a thermoelectric conversion element will be described. First, a substrate having a plurality of through holes formed therein is prepared. The preparation step may include a step of forming the through holes in the substrate, or a step of preparing a substrate having through holes already formed therein. The through holes may be formed by a known method. Next, the p-type thermoelectric conversion element composition is filled into the multiple through holes so that the p-type thermoelectric conversion elements and the n-type thermoelectric conversion elements can be alternately connected in series, and the through holes not filled with the p-type thermoelectric conversion element composition are filled with the n-type thermoelectric conversion element composition. Either the p-type or n-type thermoelectric conversion element composition may be filled first. For example, on the first surface of the substrate, the through holes not filled with the p-type thermoelectric conversion element composition are masked, and the unmasked through holes are filled with the p-type thermoelectric conversion element composition. Similarly, on the second surface opposite to the first surface of the substrate, the through holes not filled with the n-type thermoelectric conversion element composition are masked, and the unmasked through holes are filled with the n-type thermoelectric conversion element composition. The filling may be performed by filling with a squeegee, or a vacuum filling machine may be used. Next, a p-type thermoelectric conversion element is formed from the composition for p-type thermoelectric conversion elements, and an n-type thermoelectric conversion element is formed from the composition for n-type thermoelectric conversion elements. For example, the epoxy resin raw material is heated to its curing temperature to cure the epoxy resin raw material to form a thermoelectric conversion element. The curing temperature and time are appropriately selected depending on the type of epoxy resin raw material used. The cured or solidified material protruding from the through hole is removed by grinding. Next, the p-type thermoelectric conversion elements and the n-type thermoelectric conversion elements are alternately connected in series on the first surface of the substrate and the second surface opposite the first surface of the substrate using a conductive material. For example, as shown in Figure 2, the p-type thermoelectric conversion elements and the n-type thermoelectric conversion elements are electrically connected by plating. In this manner, a thermoelectric conversion module is produced that includes a plurality of p-type thermoelectric conversion elements and a plurality of n-type thermoelectric conversion elements mounted in the through holes of the substrate. The front and back surfaces of the thermoelectric conversion module may be covered with solder resist. By covering the front and back surfaces with solder resist, electronic components can be mounted and insulation can be ensured. The solder resist is preferably made of a material with high heat dissipation properties.

[0051] As another method for manufacturing a thermoelectric conversion module, a method for manufacturing the module by stacking two substrates will be described. First, an upper substrate to be placed on the upper side and a lower substrate to be placed on the lower side are prepared. Two lead electrodes are formed on either the upper substrate or the lower substrate by copper plating or the like. Furthermore, a plurality of wirings are formed on each of the upper substrate and the lower substrate by copper plating or the like. When the upper substrate and the lower substrate are stacked such that the surfaces having the wirings face each other, the wirings are arranged so that (when the wirings are distinguished as wirings 1 and 2 for the sake of explanation) a part of the wiring 1 of the upper substrate overlaps with a part of the wiring 2 of the lower substrate, another part of the wiring 2 of the lower substrate overlaps with a part of the wiring 3 of the upper substrate, and another part of the wiring 3 of the upper substrate overlaps with a part of the wiring 4 of the lower substrate (hereinafter the same). That is, the wirings are arranged so that the plurality of wirings of the upper substrate and the plurality of wirings of the lower substrate can be electrically connected in series with one electrode as the starting point and the other electrode as the end point. The shape of the wirings can be a rectangle, an oval, a racetrack shape, an ellipse, or the like. For example, if the wiring is racetrack shaped, the wiring is arranged so that one circular portion of wire 1 on the upper substrate overlaps with one circular portion of wire 2 on the lower substrate, the other circular portion of wire 2 on the lower substrate overlaps with one circular portion of wire 3 on the upper substrate, and the other circular portion of wire 3 on the upper substrate overlaps with one circular portion of wire 4 on the lower substrate (and so on). Next, an insulating layer is prepared. The insulating layer is a middle layer between the upper substrate and the lower substrate, and the thermoelectric conversion module has three layers in the order of upper substrate / insulating layer / lower substrate. The insulating layer has a plurality of holes, and its shape The shape of the hole can be a circle, a square, etc. The hole is formed at a position where the overlapping portion of the wiring of the upper substrate and the wiring of the lower substrate can be electrically connected when the upper substrate / insulating layer / lower substrate are laminated in this order. Next, a paste (or ink) of the composition for thermoelectric conversion elements is placed on the wiring of the upper substrate and the lower substrate. For ease of explanation, the shape of the wiring is described as a racetrack shape. An appropriate amount of the paste (or ink) of the composition for n-type thermoelectric conversion elements is placed on one of the two circular parts of the racetrack shape on the upper substrate. An appropriate amount of the paste (or ink) of the composition for p-type thermoelectric conversion elements is placed on one of the two circular parts of the racetrack shape on the lower substrate. When the upper substrate and the lower substrate are stacked, the composition for n-type thermoelectric conversion elements on the upper substrate should be in contact with the circular part of the lower substrate where no composition is placed, and the composition for p-type thermoelectric conversion elements on the lower substrate should be in contact with the circular part of the upper substrate where no composition is placed. Next, the upper and lower substrates are stacked with the insulating layer between them so that the surfaces having wiring face each other. In this way, the n-type thermoelectric conversion element composition arranged on one circular portion of the upper substrate passes through the holes in the insulating layer and comes into contact with the composition-free circular portion of the lower substrate. The p-type thermoelectric conversion element composition arranged on one circular portion of the lower substrate passes through the holes in the insulating layer and comes into contact with the composition-free circular portion of the upper substrate. Next, the thermoelectric conversion module having three layers of upper substrate / insulating layer / lower substrate is pressed from above and below, and the composition for thermoelectric conversion elements is cured or solidified by heating or the like. In this way, a thermoelectric conversion module can be made from two substrates and an insulating layer.

[0052] The fabricated thermoelectric conversion module can be used to recover waste heat from the industry as electrical energy. In addition, the heat generated by power elements such as IGBTs (insulated gate bipolar transistors) and packaged components can be recovered as electrical energy, improving the fuel efficiency of EVs (electric vehicles). Furthermore, it is possible to pass electricity through the thermoelectric conversion module and use it as a Peltier element for heating and cooling. For example, a thermoelectric conversion module can be formed locally under an IC packaged component that requires heat dissipation, and used as a cooling mechanism for the packaged component. It may also be applied to heaters and coolers for steering wheels and seats in vehicles. It may be used as a heat flow sensor by reading the thermoelectromotive force, or as a sensor power source in a place where there is no power source. A heat dissipation material, a water-cooled cooler, or the like may be placed in close contact with the thermoelectric conversion module. EXAMPLES

[0053] Examples will be described below, but the present disclosure is not limited to these examples. In the following description, unless otherwise specified, all "parts" and "%" are based on mass.

[0054] <Examples 1 to 7> A composition for a thermoelectric conversion element containing carbon nanotubes (CNTs) and epoxy resin raw materials (epoxy compound and curing agent) was prepared according to the composition shown in Table 1. The obtained composition for thermoelectric conversion elements was then applied onto a glass substrate and the coating was cured under the curing conditions shown in Table 1 to prepare a sample of a thermoelectric conversion element having a thickness of 50 μm. The obtained thermoelectric conversion element samples were subjected to the following evaluations.

[0055] (Electrical resistivity) The electrical resistivity of the thermoelectric conversion element sample was measured by the following method. The four electrodes were placed in contact with the sample, and the resistance was measured using the four-terminal measurement method.The distance between the electrodes and the cross-sectional area of ​​the sample were then measured, and the electrical resistivity was calculated using these values.

[0056] (Seebeck coefficient / conductivity type) The Seebeck coefficient of the thermoelectric conversion element sample was measured by the following method. One end of the sample was heated to generate a temperature difference between both ends of the sample, and the generated thermoelectromotive force was measured and calculated using a thermoelectric characteristic measuring device. The conductivity type was determined by the Seebeck coefficient.

[0057] (Materials used) Details of the epoxy compounds and curing agents used in each example are as follows:

[0058] -Epoxy compounds- Cycloaliphatic epoxy compound: The following compound (3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate) [ka] Glycidylamine type epoxy compound: The following compound (triglycidyl-p-aminophenol) [ka]

[0059] - Hardener - · Acid anhydride type hardener: The following compound (methylhexahydrophthalic anhydride) [ka] Imidazole type hardener: The following compound (1-cyanoethyl-2-ethyl-4-methylimidazole) [ka] Amine type hardener: The following compound (triethylenetetramine) [ka] Phenol-type hardener: The following compound (phenol novolac) [ka]

[0060] [Table 1]

[0061] From the above results, it is understood that the composition for thermoelectric conversion elements of this example does not substantially contain a dopant and can form a p-type or n-type thermoelectric conversion element. [Explanation of symbols]

[0062] 10 thermoelectric conversion module, 11 substrate, 21 p-type thermoelectric conversion element, 22 n-type thermoelectric conversion element, (31) wiring position, 31 wiring, 41 extraction electrode

Claims

1. Nanocarbon and An epoxy compound; A curing agent that reacts with the epoxy compound; Including, The nanocarbon is substantially free of a dopant that imparts p-type semiconductor properties; The epoxy compound and the curing agent are epoxy compounds and curing agents that cause the nanocarbon to exhibit p-type semiconductor properties in an epoxy resin after reaction. A composition for p-type thermoelectric conversion elements.

2. The epoxy compound is a cycloaliphatic epoxy compound, The curing agent is an acid anhydride type curing agent. The composition for a p-type thermoelectric conversion element according to claim 1 .

3. Nanocarbon and An epoxy compound; A curing agent that reacts with the epoxy compound; Including, The nanocarbon is substantially free of a dopant that imparts n-type semiconductor properties. The epoxy compound and the curing agent are epoxy compounds and curing agents that cause the nanocarbon to exhibit n-type semiconductor properties in an epoxy resin after reaction. A composition for n-type thermoelectric conversion elements.

4. the epoxy compound is at least one selected from the group consisting of cycloaliphatic epoxy compounds and glycidylamine epoxy compounds, The curing agent is at least one selected from the group consisting of an acid anhydride type curing agent, an imidazole type curing agent, an amine type curing agent, and a phenol type curing agent. The composition for an n-type thermoelectric conversion element according to claim 3 .

5. A substrate having a plurality of through holes formed therein; p-type thermoelectric conversion elements mounted in the plurality of through holes; n-type thermoelectric conversion elements mounted in the plurality of through holes; a conductive material that alternately connects the p-type thermoelectric conversion elements and the n-type thermoelectric conversion elements in series, The p-type thermoelectric conversion element is formed from the composition for p-type thermoelectric conversion elements according to claim 1 or 2, The n-type thermoelectric conversion element is formed from the composition for n-type thermoelectric conversion elements according to claim 3 or 4. Thermoelectric conversion module.

6. A preparation step of preparing a substrate having a plurality of through holes formed therein; a filling step of filling the plurality of through holes with the p-type thermoelectric conversion element composition according to claim 1 or 2, and filling the through holes not filled with the p-type thermoelectric conversion element composition with the n-type thermoelectric conversion element composition according to claim 3 or 4; forming a p-type thermoelectric conversion element from the composition for p-type thermoelectric conversion elements, and forming an n-type thermoelectric conversion element from the composition for n-type thermoelectric conversion elements; A connection step of alternately connecting the p-type thermoelectric conversion elements and the n-type thermoelectric conversion elements in series using a conductive material. A method for manufacturing a thermoelectric conversion module.

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