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 enables formation of a thermoelectric conversion element that has high adhesion to a conductive material for alternately connecting a p-type thermoelectric conversion element and an n-type thermoelectric conversion element in series while reducing an electric resistivity and holding a Seebeck coefficient, 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, p-type or n-type inorganic thermoelectric conversion material particles, a binder resin or its raw material; and a thermoelectric conversion element and a thermoelectric conversion module using the same.SELECTED DRAWING: Figure 1

Description

[Technical field]

[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. [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 have been applied to, 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 to be used in thermoelectric conversion elements.

[0003] For example, Patent Document 1 discloses "an organic thermoelectric conversion material such as a conductive polymer or a conductive nanocarbon material." Patent Document 2 discloses "a thermoelectric conversion material containing an organic semiconductor or a carbon nanotube." Patent Document 3 describes a thermoelectric material containing a thermoelectric substance and a solvent, the vapor pressure of the solvent at 25° C. being 0 Pa or more and 1.5 Pa or less, and 1×10 1 Pa or more 4×10 6 The storage modulus G' is in the range of 5 Pa to 4 x 10 6 "A thermoelectric conversion material having a loss modulus G" in the range of 0.1 Pa or less." Patent Document 4 discloses "a thermoelectric conversion material characterized by being made of a composite material containing a thermoelectric conversion material, a carbon nanomaterial having one or more pores, and metal nanoparticles." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2017 / 038717 [Patent Document 2] Patent Publication No. 2017-135337 [Patent Document 3] International Publication No. 2019 / 017170 [Patent Document 4] International Publication No. 2020 / 255898 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional compositions for thermoelectric conversion elements, including those described in Patent Documents 1 to 4, form a p-type thermoelectric conversion element and an n-type thermoelectric conversion element, and then form a conductive material that alternately connects the p-type thermoelectric conversion elements and the n-type thermoelectric conversion elements in series. However, the adhesion between the thermoelectric conversion element and the conductive material is low, and peeling of the conductive material may occur. On the other hand, it is also possible to incorporate particles into the composition for thermoelectric conversion elements and impart unevenness to the surface of the thermoelectric conversion elements, thereby exerting an anchor effect on the surface of the thermoelectric conversion elements and improving adhesion between the thermoelectric conversion elements and conductive materials. However, when particles are blended into a composition for a thermoelectric conversion element, the electrical resistivity of the resulting thermoelectric conversion element increases and the Seebeck coefficient decreases.

[0006] Therefore, an object of the present disclosure is to provide a thermoelectric conversion element composition that can form a thermoelectric conversion element that has high adhesion to a conductive material that alternately connects p-type thermoelectric conversion elements and n-type thermoelectric conversion elements in series, while reducing electrical resistivity and maintaining the Seebeck coefficient, and to provide a thermoelectric conversion element and a thermoelectric conversion module that utilize the same. [Means for solving the problem]

[0007] Means for solving the problems include the following aspects. <1> Nanocarbon and p-type inorganic thermoelectric conversion material particles; A binder resin or a raw material thereof; A composition for a p-type thermoelectric conversion element comprising: <2> Nanocarbon and n-type inorganic thermoelectric conversion material particles; A binder resin or a raw material thereof; A composition for an n-type thermoelectric conversion element comprising: <3> 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> The p-type thermoelectric conversion element composition according to claim 1, The n-type thermoelectric conversion element is <2> The composition for n-type thermoelectric conversion elements according to claim 1, Thermoelectric conversion module. <4> A preparation step of preparing a substrate having a plurality of through holes formed therein; The plurality of through holes are <1> 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. <2> 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

[0008] According to the present disclosure, there are provided a thermoelectric conversion element composition capable of forming a thermoelectric conversion element that has high adhesion to a conductive material that alternately connects p-type thermoelectric conversion elements and n-type thermoelectric conversion elements in series while reducing electrical resistivity and maintaining the Seebeck coefficient, and a thermoelectric conversion element and a thermoelectric conversion module using the same. [Brief description of the drawings]

[0009] [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

[0010] 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.

[0011] 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.

[0012] <Composition for thermoelectric conversion element> The composition for thermoelectric conversion elements of the present disclosure is a composition for p-type or n-type thermoelectric conversion elements that contains nanocarbon, p-type or n-type inorganic thermoelectric conversion material particles, and a binder resin or a raw material thereof.

[0013] When a thermoelectric conversion element is formed from the composition for a thermoelectric conversion element of the present disclosure, the inorganic thermoelectric conversion material particles form irregularities on the conductive material-forming surface of the thermoelectric conversion element. By providing the irregularities on the conductive material-forming surface, an anchor effect is exerted, and the adhesion between the thermoelectric conversion element and the conductive material is improved. In addition, since inorganic thermoelectric conversion material particles that exhibit the anchor effect exhibit p-type or n-type conductivity, mixing them with nanocarbon at a micro-level reduces the electrical resistance of the thermoelectric conversion element and also suppresses the decrease in the Seebeck coefficient of the thermoelectric conversion element due to the nanocarbon.

[0014] In addition, when an inorganic thermoelectric conversion material is not added to the composition for thermoelectric conversion elements, in order to increase the adhesion between the thermoelectric conversion element and the conductive material, after the thermoelectric conversion element is formed, a surface treatment such as an organic coating removal treatment and a surface roughening step is required on the surface on which the conductive material is formed. However, with the composition for thermoelectric conversion elements of the present disclosure, the above-mentioned surface treatment can be omitted, and costs can be reduced.

[0015] Therefore, the composition for thermoelectric conversion elements disclosed herein can form a thermoelectric conversion element that has high adhesion to a conductive material that alternately connects p-type and n-type thermoelectric conversion elements in series, while reducing electrical resistivity and maintaining the Seebeck coefficient.

[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 has high electrical conductivity (σ) due to the nanocarbon, which is representative of carbon nanotubes, while the thermal conductivity (κ) can be reduced by 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 containing nanocarbon, p-type or n-type inorganic thermoelectric conversion material particles, and a binder resin or a raw material thereof, and therefore can be made into a composition having fluidity such as a paste or ink state, which can improve the handling properties of the composition, such as facilitating filling of the composition into a substrate. Furthermore, since the composition for thermoelectric conversion elements of the present disclosure is a composite material of nanocarbon, binder resin, and its raw materials, 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] (Inorganic thermoelectric conversion material particles) Inorganic thermoelectric conversion material particles include compounds that have either P-type or N-type properties, and compounds that can be both P-type and N-type depending on the dopant.

[0024] Examples of the p-type thermoelectric conversion material and the n-type thermoelectric conversion material include nickel and nickel alloys. Nickel alloys generate electricity by creating a temperature difference, and specific examples include nickel alloys that contain nickel with one or more components such as vanadium, chromium, silicon, aluminum, titanium, molybdenum, manganese, zinc, tin, copper, cobalt, iron, magnesium, and zirconium. A representative example of a p-type thermoelectric conversion material is chromel (a nickel alloy whose main components are Ni and Cr), and a representative example of an n-type thermoelectric conversion material is constantan (a nickel alloy whose main components are Cu and Ni).

[0025] Other examples of p-type and n-type thermoelectric conversion materials include BiTe-based materials (BiTe, SbTe, BiSe, etc.), PbTe-based materials (PbTe, SnTe, AgSbTe, GeTe, etc.), Si-Ge-based materials (Si, Ge, SiGe, etc.), silicide-based materials (FeSi, MnSi, CrSi), and skutterudite-based materials (MX 3 , or R.M. 4 X 12where M represents Co, Rh, or Ir, X represents As, P, or Sb, and R=La, Yb, or Ce), transition metal oxide materials (NaCoO, CaCoO, ZnInO, SrTiO, BiSrCoO, PbSrCoO, CaBiCoO, BaBiCoO, etc.), zinc antimony materials (ZnSb, etc.), boron materials (CeB, BaB, SrB, CaB, MgB, VB, NiB, CuB, LiB, etc.), cluster materials (B cluster, Si cluster, C cluster, AlRe, AlReSi, etc.), zinc oxide materials (ZnO), etc. The conductivity type of some of these materials can be adjusted by changing the type of dopant.

[0026] Among these, the inorganic thermoelectric conversion material particles are preferably those having a Seebeck coefficient of 20 μV / K or more (preferably 20 μV / K or more). By using an inorganic thermoelectric conversion material with a high Seebeck coefficient, it becomes easy to form a thermoelectric conversion element that has high adhesion to conductive materials while maintaining electrical resistivity and Seebeck coefficient. The Seebeck coefficient is calculated by preparing a sample to be measured, heating one end of the sample to generate a temperature difference between both ends of the sample, and measuring the generated thermoelectromotive force using a thermoelectric property measuring device.

[0027] The average particle size of the inorganic thermoelectric conversion material particles is preferably 5 to 50 μm. The average particle size is determined by obtaining a particle size distribution based on the number of particles using a laser diffraction particle size analyzer, subtracting the cumulative distribution from the small particle size side in terms of number from the obtained particle size distribution, and measuring the particle size that is 50% of the total particles as the number average particle size D50p.

[0028] The content of the inorganic thermoelectric conversion material particles is preferably 20 to 50% by volume with respect to the resulting thermoelectric conversion element.

[0029] (Binder resin or its raw material) The binder resin may be a thermosetting resin or a thermoplastic resin. When the substrate to which the thermoelectric conversion element composition is filled is a printed circuit board, a thermosetting resin that can withstand the heat generated when mounting electronic components on the printed circuit board is preferred. Examples of the thermosetting resin include epoxy resin, acrylic resin, and polyimide resin.

[0030] The raw material of the binder resin is not particularly limited as long as it is a raw material from which the desired binder resin can be formed. For example, when the binder resin is an epoxy resin, the raw material may be a composition containing an epoxy compound and a curing agent having a functional group that reacts with the epoxy group of the epoxy compound. When the binder resin is a polyimide resin, the raw material may be polyamic acid.

[0031] The content of the binder resin and its raw materials is not particularly limited as long as the composition for thermoelectric conversion elements can maintain the fluidity of a paste or ink, and the resulting thermoelectric conversion element can ensure the desired electrical conductivity.

[0032] (Other ingredients) As other components, the composition for thermoelectric conversion elements may appropriately contain dopants (onium salts, etc.) that impart semiconductor properties to nanocarbon, thixotropic agents, dispersants, surfactants, antioxidants, weathering and light stabilizers, heat stabilizers, plasticizers, etc. Examples of surfactants include known surfactants (cationic surfactants, anionic surfactants, etc.). do.

[0033] <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.

[0034] 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.

[0035] 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.

[0036] An example of a rigid substrate is a glass epoxy substrate. When the substrate is a glass epoxy substrate and the binder resin of the composition for thermoelectric conversion elements is an epoxy resin, the linear expansion coefficients of the substrate and the binder resin can be made close to each other, so that the thermoelectric conversion element can be prevented from peeling off from the substrate due to thermal contraction of the resin.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] <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.

[0044] Next, either p-type inorganic thermoelectric conversion material particles or n-type inorganic thermoelectric conversion material particles are added to the nanocarbon dispersion liquid. Next, the binder resin or its raw material is added while removing the solvent from the nanocarbon dispersion, and the solvent is replaced with the binder resin or its raw material to prepare a composition for thermoelectric conversion elements. The method for removing the solvent can be a known method. 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.

[0045] The solvent may be any solvent capable of dispersing nanocarbon and inorganic thermoelectric conversion material particles, 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.

[0046] 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.

[0047] <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, when the binder resin is a thermosetting resin, the binder resin is cured by heating to the curing temperature of the resin to form a thermoelectric conversion element. The curing temperature and time are appropriately selected depending on the type of binder resin used. When the binder resin is a thermoplastic resin, the binder resin is solidified by a method that solidifies the resin (cooling, drying, etc.) to form a thermoelectric conversion element. 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.

[0048] 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.

[0049] 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

[0050] 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.

[0051] <Examples and Comparative Examples> A composition for thermoelectric conversion elements was prepared according to the composition shown in Table 1, containing carbon nanotubes (CNTs), an epoxy resin raw material (a 50 / 50 mass ratio mixture of a glycidylamine-type epoxy compound and an acid anhydride-type curing agent), and p-type or n-type inorganic thermoelectric conversion material particles. However, in the comparative example, a composition for a thermoelectric conversion element that did not contain p-type or n-type inorganic thermoelectric conversion material particles was prepared.

[0052] 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.

[0053] (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.

[0054] (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.

[0055] (Adhesion to conductive materials) The adhesion between the thermoelectric conversion element sample and the conductive thin film material was evaluated as follows. First, a conductive thin film material was formed on the surface of a sample of a thermoelectric conversion element. Next, two cuts were made in the conductive thin film material with a utility knife so that an intersection would be created, cellophane tape was applied to cover the area around the intersection, and then the tape was forcefully peeled off for the test. And it was evaluated according to the following criteria. "Good": No peeling of the conductive thin film material. "Fail": Peeling of conductive thin film material has occurred.

[0056] (Materials used) Details of the epoxy compounds and curing agents used in each example are as follows: -Epoxy compounds- Glycidylamine type epoxy compound: The following compound (triglycidyl-p-aminophenol) [ka]

[0057] - Hardener - · Acid anhydride type hardener: The following compound (methylhexahydrophthalic anhydride) [ka]

[0058] [Table 1]

[0059] The above results show that the composition for thermoelectric conversion elements of this example can form a thermoelectric conversion element that has high adhesion to a conductive material that alternately connects p-type and n-type thermoelectric conversion elements in series, while reducing the electrical resistivity and maintaining the Seebeck coefficient. [Explanation of symbols]

[0060] 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 P-type inorganic thermoelectric conversion material particles; A binder resin or a raw material thereof; A composition for a p-type thermoelectric conversion element comprising:

2. Nanocarbon and n-type inorganic thermoelectric conversion material particles; A binder resin or a raw material thereof; A composition for an n-type thermoelectric conversion element comprising:

3. 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 , The n-type thermoelectric conversion element is formed from the composition for n-type thermoelectric conversion elements according to claim 2. Thermoelectric conversion module.

4. 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 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 claim 2; 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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