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

Abstract

Disclosed is a p-type or n-type composition for thermoelectric conversion elements, which contains nanocarbons, an epoxy compound, and a curing agent that reacts with the epoxy compound, and which does not substantially contain a dopant that imparts p-type or n-type semiconductor characteristics to the nanocarbons, wherein, with respect to the epoxy compound and the curing agent, the nanocarbons exhibit p-type or n-type semiconductor characteristics in the epoxy resin after a reaction. Also disclosed are a thermoelectric conversion element and a thermoelectric conversion module, which use the composition for thermoelectric conversion elements.

Description

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

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

[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 supplies and thermoelectric conversion modules (wristwatches, wearable devices, etc.) that operate on body heat. Therefore, 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."

[0005] International Publication No. WO 2019 / 021908 International Publication No. WO 2018 / 142748

[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 industrially difficult to handle, for example, due to their deliquescent nature. Furthermore, 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 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.

[0009] Means for solving the problems include the following aspects. <1> A composition for p-type thermoelectric conversion elements comprising: nanocarbon; an epoxy compound; and a curing agent reactive with the epoxy compound, wherein the composition is substantially free of a dopant that imparts p-type semiconductor properties to the nanocarbon, and the epoxy compound and the curing agent are such that the nanocarbon exhibits p-type semiconductor properties in an epoxy resin after reaction. <2> The composition for p-type thermoelectric conversion elements according to <1>, wherein the epoxy compound is a cyclic aliphatic epoxy compound, and the curing agent is an acid anhydride curing agent. <3> A composition for n-type thermoelectric conversion elements comprising: nanocarbon; an epoxy compound; and a curing agent reactive with the epoxy compound, wherein the composition is substantially free of a dopant that imparts n-type semiconductor properties to the nanocarbon, and the epoxy compound and the curing agent are such that the nanocarbon exhibits n-type semiconductor properties in an epoxy resin after reaction. <4> The composition for an n-type thermoelectric conversion element according to <3>, wherein the epoxy compound is at least one selected from the group consisting of a cyclic aliphatic epoxy compound and a glycidyl amine epoxy compound, and the curing agent is at least one selected from the group consisting of an acid anhydride curing agent, an imidazole curing agent, an amine curing agent, and a phenol curing agent. <5> A thermoelectric conversion module comprising: 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; and a conductive material connecting the p-type thermoelectric conversion elements and the n-type thermoelectric conversion elements alternately in series, wherein the p-type thermoelectric conversion elements are formed from the composition for a p-type thermoelectric conversion element according to <1> or <2>, and the n-type thermoelectric conversion elements are formed from the composition for an n-type thermoelectric conversion element according to <3> or <4>.<6> A method for manufacturing a thermoelectric conversion module, comprising: 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 composition for p-type thermoelectric conversion elements according to <1> or <2> and filling the through holes not filled with the composition for p-type thermoelectric conversion elements with the composition for n-type thermoelectric conversion elements according to <3> or <4>; a formation step of forming p-type thermoelectric conversion elements from the composition for p-type thermoelectric conversion elements and forming n-type thermoelectric conversion elements from the composition for n-type thermoelectric conversion elements; and 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.

[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.

[0011] 1 is a diagram illustrating an example of the upper surface of a thermoelectric conversion module 10 of the present disclosure, in which p-type thermoelectric conversion elements 21 and n-type thermoelectric conversion elements 22 formed from a composition for thermoelectric conversion elements of the present disclosure are mounted. Wiring 31 is formed at the position indicated by the dotted line in FIG. 1 , and the cross-sectional view shows the cut surface when cut along line A-B.

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

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

[0014] <Composition for Thermoelectric Conversion Elements> 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 such that the nanocarbon exhibits p-type or n-type semiconductor properties in the epoxy resin after reaction. Hereinafter, the epoxy compound and curing agent will also be referred to as "epoxy resin raw materials."

[0015] The thermoelectric conversion element composition of the present disclosure, as configured above, controls the conductivity type of the nanocarbon with an epoxy resin formed by the reaction of an epoxy compound and a curing agent. This allows for the formation of p-type or n-type thermoelectric conversion elements without the substantial inclusion of a dopant. Additionally, because the composition does not substantially contain a dopant, which is difficult to handle industrially, the manufacturing process for the thermoelectric conversion element composition is simplified, resulting in reduced manufacturing costs. Furthermore, because the nanocarbon is covered with epoxy resin in the formed thermoelectric conversion element, it is less susceptible to deterioration 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, the dimensionless figure of merit ZT, which is one of the indices for evaluating the thermoelectric conversion performance of a thermoelectric conversion element, will be described. ZT is expressed by the following formula (1): Dimensionless figure of merit ZT=S2×σ×T / κ (1) In formula (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 a thermoelectric conversion element exhibits high electrical conductivity (σ) using nanocarbons, which are representative of carbon nanotubes, while the thermal conductivity (κ) can be reduced by the epoxy resin binder resin, resulting in a high dimensionless figure of merit (ZT).

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

[0018] The composition for thermoelectric conversion elements of the present disclosure is a composite material containing nanocarbon and an epoxy resin raw material, and is substantially free of dopants that impart p-type or n-type semiconductor properties to the nanocarbon. Therefore, it can be made into a composition with fluidity such as a paste or ink. This improves the handling properties of the composition, such as facilitating filling onto a substrate. Furthermore, because the composition for thermoelectric conversion elements of the present disclosure is a composite material of nanocarbon, an epoxy resin raw material, and the raw material, it can improve the mechanical strength of the formed thermoelectric conversion element.

[0019] (Nanocarbon) Examples of nanocarbon include carbon nanotubes (CNT). The carbon nanotube may be a single-walled carbon nanotube (SWCNT) in which one carbon film (graphene sheet) is wound into 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 concentrically. In consideration of thermoelectric properties, the carbon nanotube preferably has 10 or fewer walls. Single-walled carbon nanotubes are preferred because they are likely to achieve high thermoelectric properties. Multi-walled carbon nanotubes are preferred because they are inexpensive and easy to mass-produce. Single-walled carbon nanotubes and multi-walled carbon nanotubes can also be used in combination. Furthermore, the carbon nanotubes may be metallic carbon nanotubes, semiconducting carbon nanotubes, or a mixture thereof. 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. 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 fullerenes.

[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 Materials) Epoxy compounds and curing agents as epoxy resin raw materials are the raw materials for the epoxy resin that functions as the binder resin in thermoelectric conversion elements. Epoxy compounds are compounds with two or more epoxy groups in their molecules. There are two types of curing agents: one is called a polyaddition curing agent, which is a compound with one or more functional groups that react with two or more epoxy groups in the epoxy compound. It is generally added in a stoichiometric amount to the epoxy compound. The other is called a self-polymerizing curing agent, which is a compound with one or more functional groups that react with one or more epoxy groups in the epoxy compound. By activating the epoxy groups, it causes a chain reaction in the epoxy compound itself with the addition of a small amount. Note that amine-type, phenol-type, and acid anhydride-type curing agents are polyaddition-type curing agents, while imidazole-type curing agents are self-polymerizing curing agents.

[0024] An example of a combination of an epoxy compound and a curing agent that allows the nanocarbon to exhibit p-type semiconductor properties in the 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, examples of combinations of epoxy compounds and curing agents that will cause the nanocarbon to exhibit n-type semiconductor properties in the epoxy resin include combinations in which the epoxy compound is at least one selected from the group consisting of cycloaliphatic 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. Specific examples of such combinations are as follows: A combination of a cycloaliphatic epoxy compound and an acid anhydride curing agent A combination of a cycloaliphatic epoxy compound and a phenolic curing agent A combination of a glycidylamine epoxy compound and a phenolic curing agent A combination of a glycidylamine epoxy compound and an acid anhydride curing agent A combination of a glycidylamine epoxy compound and an imidazole curing agent A combination of a glycidylamine epoxy compound and an amine curing agent

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

[0027] Glycidylamine-type epoxy compounds are epoxy compounds having a glycidyl-substituted amino group (such as a diglycidylamino group). Examples of glycidylamine-type epoxy resins include triglycidyl-p-aminophenol, N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, N,N-(diglycidyl)-o-toluidine, and diglycidylaniline.

[0028] The acid anhydride curing agent is a curing agent made of a carboxylic acid anhydride. Examples of the acid anhydride curing agent 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, methylhimic anhydride, pyromellitic dianhydride, maleated alloocimene, benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetrabisbenzophenone 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 curing agent is a curing agent having an imidazole skeleton. Examples of the imidazole 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 curing agent is a curing agent having two or more amino groups. Examples of the amine curing agent include chain aliphatic amine compounds, cyclic aliphatic amines, and aromatic amines. Examples of the chain aliphatic amine compounds include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyoxypropylenediamine, and polyoxypropylenetriamine. Examples of the cyclic aliphatic amine compounds include menthenediamine, 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 aromatic amine compounds include m-xylylenediamine, α-(m / p-aminophenyl)ethylamine, m-phenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, and α,α-bis(4-aminophenyl)-p-diisopropylbenzene.

[0031] Phenol-type curing agents are curing agents having two or more phenol groups, and examples of such curing agents 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 relative to the thermoelectric conversion element to be formed is 0 to 1 mass %.

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

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

[0036] <Thermoelectric Conversion Module> The thermoelectric conversion module of the present disclosure will be described with reference to Figures 1 and 2. Figure 1 is a diagram illustrating the top surface of a thermoelectric conversion module 10 of the present disclosure, in which p-type thermoelectric conversion elements 21 and n-type thermoelectric conversion elements 22 formed from a composition for thermoelectric conversion elements of the present disclosure are mounted. Figure 2 is a cross-sectional view showing a cut surface when wiring 31 is formed at the position indicated by the dotted line in Figure 1 and cut along line A-B in Figure 1.

[0037] As shown in Fig. 1, in the thermoelectric conversion module 10 of the present disclosure, p-type thermoelectric conversion elements 21 and n-type thermoelectric conversion elements 22 are mounted in through holes formed in a substrate 11. The p-type thermoelectric conversion elements 21 and 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 extraction electrodes 41. The p-type thermoelectric conversion elements 21 and n-type thermoelectric conversion elements 22 are formed from the above-described composition for thermoelectric conversion elements.

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

[0039] An example of a rigid substrate is a glass epoxy substrate. The glass epoxy substrate can have a linear expansion coefficient close to that of the epoxy resin used as the binder resin for the thermoelectric conversion element, which can 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, and polyphenyl sulfide films.

[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 through holes may be round, rectangular (square), elongated (rectangular with rounded corners), rectangular (rectangular) or other shapes. Alternatively, polygonal holes may be used. From the viewpoint of facilitating uniform filling without gaps, round holes, i.e., cylindrical, are preferred. In the case of round holes, their diameter (φ) is 0.3 mm to 5.0 mm. In the case of rectangular holes (square holes), the length of one side may be 0.3 mm to 5.0 mm, and in the case of elongated holes (rectangular with rounded corners) or rectangular holes (rectangular holes), the average length of the two sides may be 0.3 mm to 5.0 mm. If the through holes are too narrow, there is a high possibility of Joule heat generation, while if they are too wide, a sufficient number of thermoelectric conversion elements cannot be secured.

[0042] The through holes can be arranged, for example, in a staggered or parallel pattern. FIG. 1 shows an example in which the through holes are arranged in parallel. The inner walls of the through holes formed in the substrate are preferably non-through holes that are not plated with a metal such as copper. Non-through holes can prevent electricity from flowing from the thermoelectric conversion elements mounted in the through holes to the inner walls.

[0043] The wiring 31 is formed from a conductive material that electrically connects the p-type thermoelectric conversion elements 21 and the n-type thermoelectric conversion elements 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. Forming the wiring from carbon nanotubes themselves or using the thermoelectric conversion element composition of the present application for both filling and wiring eliminates the need for subsequent plating wiring, thereby simplifying the process and reducing costs. Alternatively, wiring from carbon nanotubes and applying electrolytic plating using the carbon nanotubes as a seed layer can omit a base plating step such as an electroless copper plating step, thereby simplifying the process and reducing 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, and conductive pastes containing metal nanowires such as silver, copper, and aluminum. 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 conductivity, such as copper plating, gold plating, silver plating, or tin plating.

[0046] <Method for manufacturing a composition for a thermoelectric conversion element> In the method for manufacturing a composition for a thermoelectric conversion element, first, nanocarbon is dispersed in a solvent to prepare a nanocarbon dispersion. There are no particular limitations 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 or the like. The components may be dispersed by stirring, shaking, or the like. To improve the dispersibility of the nanocarbon, the dispersion medium may be heated to a temperature above room temperature (25°C) and below the boiling point, the dispersion time may be extended, or ultrasonic treatment may be performed.

[0047] Next, an epoxy resin raw material (a composition containing an epoxy compound and a curing agent) is added while removing the solvent from the nanocarbon dispersion, replacing the solvent with the epoxy resin raw material, thereby preparing 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 way, a composition for thermoelectric conversion elements having fluidity such as a paste or ink is prepared.

[0048] The solvent may be any solvent capable of dispersing nanocarbons, and may include water, organic solvents, and mixtures thereof. Examples of organic solvents 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 that can disperse the nanocarbon and inorganic thermoelectric conversion material particles.

[0050] <Method for Manufacturing Thermoelectric Conversion Module> A method for manufacturing a thermoelectric conversion module by filling through holes in a substrate with a thermoelectric conversion element composition 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 through holes in the substrate, or a step of preparing a substrate with through holes already formed therein. The through holes may be formed using a known method. Next, the plurality of through holes are filled with a p-type thermoelectric conversion element composition so as to be arranged so that p-type thermoelectric conversion elements and n-type thermoelectric conversion elements can be alternately connected in series, and through holes not filled with the p-type thermoelectric conversion element composition are filled with an n-type thermoelectric conversion element composition. The filling of the p-type or n-type thermoelectric conversion element composition may be performed in either order. For example, on the first surface of the substrate, 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 of the substrate opposite the first surface, the through-holes that are not to be 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. Filling may be performed using a squeegee or a vacuum hole-filling machine. Next, p-type thermoelectric conversion elements are formed from the p-type thermoelectric conversion element composition, and n-type thermoelectric conversion elements are formed from the n-type thermoelectric conversion element composition. For example, the epoxy resin raw material is heated to its curing temperature to harden the epoxy resin raw material, forming the thermoelectric conversion element. The curing temperature and time are appropriately selected depending on the type of epoxy resin raw material used. Any cured or solidified material that protrudes from the through-holes is removed by polishing. Next, the p-type thermoelectric conversion elements and n-type thermoelectric conversion elements are connected alternately 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 FIG. 2, the p-type thermoelectric conversion elements and n-type thermoelectric conversion elements are electrically connected by plating. In this way, 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. Covering the front and back surfaces with solder resist allows for the mounting of electronic components and ensures insulation. The solder resist is preferably made of a material with high heat dissipation properties.

[0051] Another method for manufacturing a thermoelectric conversion module involves stacking two substrates. First, an upper substrate, which is placed on the upper side, and a lower substrate, which is placed on the lower side, are prepared. Two extraction electrodes are formed on one of the upper and lower substrates by copper plating or the like. Furthermore, multiple wirings are formed on each of the upper and lower substrates by copper plating or the like. When the upper and lower substrates are stacked with their wiring-bearing surfaces facing each other (for the sake of explanation, assuming that the respective wirings are designated as Wire 1 and Wire 2), the wirings are arranged so that a portion of Wire 1 on the upper substrate overlaps a portion of Wire 2 on the lower substrate, another portion of Wire 2 on the lower substrate overlaps a portion of Wire 3 on the upper substrate, and another portion of Wire 3 on the upper substrate overlaps a portion of Wire 4 on the lower substrate (same applies hereinafter). In other words, the wirings are arranged so that, starting from one electrode and ending at the other electrode, the multiple wirings on the upper substrate and the multiple wirings on the lower substrate can be electrically connected in series. The wiring shapes can be rectangular, oval, racetrack, elliptical, or the like. For example, if the wiring is racetrack-shaped, one circular portion of Wire 1 on the upper substrate overlaps one circular portion of Wire 2 on the lower substrate, the other circular portion of Wire 2 on the lower substrate overlaps one circular portion of Wire 3 on the upper substrate, and the other circular portion of Wire 3 on the upper substrate overlaps one circular portion of Wire 4 on the lower substrate (similarly described below). Next, an insulating layer is prepared. The insulating layer is the middle layer between the upper and lower substrates, and the thermoelectric conversion module has three layers in the order of upper substrate / insulating layer / lower substrate. The insulating layer has multiple holes, and their shapes can be circular, square, etc. The holes are formed in positions such that the overlapping portions of the wiring on the upper substrate and the wiring on the lower substrate can be electrically connected when the upper substrate / insulating layer / lower substrate are stacked in this order. Next, a paste (or ink) of a thermoelectric conversion element composition is placed on the wiring on the upper and lower substrates. For ease of explanation, the wiring shape will be described as being racetrack-shaped. An appropriate amount of paste (or ink) of the composition for n-type thermoelectric conversion elements is placed on one of the two circular portions of the racetrack on the upper substrate, and an appropriate amount of paste (or ink) of the composition for p-type thermoelectric conversion elements is placed on one of the two circular portions of the racetrack on the lower substrate.When the upper and lower substrates are stacked, the n-type thermoelectric conversion element composition on the upper substrate contacts the circular portion of the lower substrate where no composition is applied, and the p-type thermoelectric conversion element composition on the lower substrate contacts the circular portion of the upper substrate where no composition is applied. Next, the upper and lower substrates are stacked with the insulating layer sandwiched between them, with the wiring surfaces facing each other. In this manner, 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 contacts the circular portion of the lower substrate where no composition is applied. 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 contacts the circular portion of the upper substrate where no composition is applied. Next, the thermoelectric conversion module comprising the three layers of upper substrate / insulating layer / lower substrate is pressed from above and below, and the thermoelectric conversion element composition is cured or solidified by heating or the like. In this manner, a thermoelectric conversion module can also be produced from two substrates and an insulating layer.

[0052] The fabricated thermoelectric conversion module can be used to recover industrial waste heat as electrical energy. Furthermore, the heat generated by power elements and packaged components, such as IGBTs (insulated gate bipolar transistors), can be recovered as electrical energy, improving the fuel efficiency of electric vehicles (EVs). Furthermore, electricity can be passed through the thermoelectric conversion module, allowing it to function as a Peltier element for heating and cooling. For example, a thermoelectric conversion module can be locally formed under an IC packaged component that requires heat dissipation, serving as a cooling mechanism for the packaged component. It can also be applied to heaters and coolers in vehicle steering wheels and seats. It can also be used as a heat flow sensor by reading the thermoelectromotive force, or as a sensor power source in places without a power source. A heat dissipation material, a water-cooled cooler, or the like can be placed in close contact with the thermoelectric conversion module.

[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 Compositions for thermoelectric conversion elements containing carbon nanotubes (CNTs) and epoxy resin raw materials (epoxy compound and curing agent) were prepared according to the formulations shown in Table 1. The resulting compositions for thermoelectric conversion elements were then applied to glass substrates, and the coatings were cured under the curing conditions shown in Table 1 to produce thermoelectric conversion element samples with a thickness of 50 μm. The resulting thermoelectric conversion element samples were evaluated as follows.

[0055] (Electrical Resistivity) The electrical resistivity of the thermoelectric conversion element sample was measured. The measurement method was as follows. Four electrodes were brought into contact with the sample, and the resistance value was measured using a four-terminal measurement method. Then, the distance between the electrodes and the cross-sectional area of ​​the sample were 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. The measurement method is as follows. 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 property measuring device. The conductivity type was then determined from the Seebeck coefficient.

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

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

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

[0060]

[0061] From the above results, it is clear 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.

[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

[0063] The disclosure of Japanese Patent Application No. 2023-200020 is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A composition for p-type thermoelectric conversion elements comprising: nanocarbon; an epoxy compound; and a curing agent that reacts with the epoxy compound, wherein the composition is substantially free of a dopant that imparts p-type semiconductor properties to the nanocarbon, and the epoxy compound and the curing agent are such that the nanocarbon exhibits p-type semiconductor properties in an epoxy resin after reaction.

2. The composition for p-type thermoelectric conversion elements according to claim 1, wherein the epoxy compound is a cyclic aliphatic epoxy compound, and the curing agent is an acid anhydride curing agent.

3. A composition for n-type thermoelectric conversion elements comprising: nanocarbon; an epoxy compound; and a curing agent that reacts with the epoxy compound, wherein the epoxy compound and the curing agent are substantially free of a dopant that imparts n-type semiconductor properties to the nanocarbon, and the epoxy compound and the curing agent are such that the nanocarbon exhibits n-type semiconductor properties in an epoxy resin after reaction.

4. The composition for n-type thermoelectric conversion elements according to claim 3, wherein the epoxy compound is at least one selected from the group consisting of cyclic aliphatic epoxy compounds and glycidyl amine type epoxy compounds, and the curing agent is at least one selected from the group consisting of acid anhydride type curing agents, imidazole type curing agents, amine type curing agents, and phenol type curing agents.

5. A thermoelectric conversion module comprising: 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; and a conductive material that alternately connects the p-type thermoelectric conversion elements and the n-type thermoelectric conversion elements in series, wherein the p-type thermoelectric conversion elements are formed from a composition for p-type thermoelectric conversion elements as defined in claim 1 or claim 2; and the n-type thermoelectric conversion elements are formed from a composition for n-type thermoelectric conversion elements as defined in claim 3 or claim 4.

6. A method for manufacturing a thermoelectric conversion module, comprising: 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 composition for p-type thermoelectric conversion elements according to claim 1 or claim 2, and filling through holes not filled with the composition for p-type thermoelectric conversion elements with the composition for n-type thermoelectric conversion elements according to claim 3 or claim 4; a formation step of 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; and 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.

Images