Thermoelectric conversion device

Abstract

This thermoelectric conversion device comprises: a first thermoelectric layer 12a and a second thermoelectric layer 12b that have mutually opposite conductivity types and that are provided alternately in a first direction which runs parallel to the surfaces of the first thermoelectric layer and the second thermoelectric layer; a first connecting layer 14a and a second connecting layer 14b that are provided alternately in the first direction and between the first thermoelectric layer and the second thermoelectric layer so as to be electrically and thermally connected to the first and second thermoelectric layers; a first thermally conductive layer 16a that is thermally connected to the first connecting layer and that extends in a second direction intersecting the surface thereof; a first insulating layer 17a through which the first thermally conductive layer penetrates and which has a smaller thermal conductivity than that of the first thermally conductive layer; and a second insulating layer 17b through which the first thermally conductive layer penetrates, which has a smaller thermal conductivity than that of the first insulating layer, and which is provided between the first insulating layer and the first and second thermoelectric layers. The second insulating layer 17b has a thickness greater than or equal to 1 / 4 of the larger of the following distances: the distance between the edge on the first thermoelectric layer side of the first thermally conductive layer, and the center of the second connecting layer in the first direction; and the distance between the edge on the second thermoelectric layer side of the first thermally conductive layer, and the center of the second connecting layer in the first direction.　

Description

[Technical Field]

[0001] The present invention relates to a thermoelectric conversion device. [Background technology]

[0002] A transverse μTEG (μTEG: Micro Thermoelectric Generator) is known, in which thermoelectric layers made of thermoelectric material and connection layers connecting the thermoelectric layers are alternately arranged in a planar direction, and heat is extracted from the connection layers via a thermal conduction layer in a direction perpendicular to the planar direction (see, for example, Patent Document 1). The transverse μTEG can be applied to thermoelectric power generation using body temperature, which has a small temperature difference. It is known that extraction electrodes are embedded in stacked insulating layers (a base substrate and a heat-insulating substrate) with different thermal conductivities (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 042708 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-158760 Summary of the Invention [Problem to be solved by the invention]

[0004] In Figure 8 of Patent Document 2, highly insulating heat-insulating substrates (A2, B2) are provided on the thermoelectric material (5a-5h, 6a-6h) side of the base substrate (A1, B1). In cross-sectional drawings of patents, the planar and vertical scales are typically different, and Patent Document 2 does not describe the thickness of the heat-insulating substrates (A2, B2). Paragraph 0057 of Patent Document 2 addresses the issue of heat flow bypassing the thermoelectric materials (5a-5h, 6a-6h) between the heat-dissipation-side electrodes (3a-3i) and the heat-absorption-side electrodes (2a-2h, 8a-8i) arranged in the planar direction. If the heat flow in the planar direction is the problem, it is believed that even thin heat-insulating substrates (A2, B2) can suppress the bypassing of the heat flow in the planar direction. However, simply considering the heat flow in the planar direction does not suppress the heat flow bypassing the thermoelectric materials (5a-5h, 6a-6h), resulting in reduced output power of the thermoelectric converter.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to provide a thermoelectric conversion device with a large output power. [Means for solving the problem]

[0006] The present invention provides a first thermoelectric layer and a second thermoelectric layer having opposite conductivity types and alternately arranged in a first direction parallel to the surfaces of the first thermoelectric layer and the second thermoelectric layer, a first connection layer and a second connection layer electrically and thermally connected to the first thermoelectric layer and the second thermoelectric layer between the first thermoelectric layer and the second thermoelectric layer and alternately arranged in the first direction, a first thermally conductive layer thermally connected to the first connection layer and extending in a second direction intersecting the surfaces, and a second thermally conductive layer penetrating the first thermally conductive layer and extending through the first thermally conductive layer. and a second insulating layer, through which the first thermally conductive layer penetrates and which has a thermal conductivity lower than that of the first insulating layer, and which is provided between the first insulating layer and the first and second thermoelectric layers, and which has a thickness that is equal to or greater than ¼ of the larger of the distance between an end of the first thermally conductive layer facing the first thermoelectric layer and a center of the second connecting layer in the first direction and the distance between an end of the first thermally conductive layer facing the second thermoelectric layer and a center of the second connecting layer in the first direction.

[0007] In the above configuration, the configuration can include a second thermally conductive layer that is thermally connected to the second connection layer, is provided on the opposite side of the first thermally conductive layer from the first thermoelectric layer and the second thermoelectric layer, and extends in the second direction; a third insulating layer that is penetrated by the second thermally conductive layer and has a thermal conductivity lower than that of the second thermally conductive layer; and a fourth insulating layer that is penetrated by the second thermally conductive layer and has a thermal conductivity lower than that of the third insulating layer, is provided between the third insulating layer and the first thermoelectric layer and the second thermoelectric layer, and has a thickness of at least 1 / 4 of the larger distance.

[0008] In the above configuration, the thickness of the second insulating layer may be equal to or less than twice the larger distance.

[0009] In the above configuration, the thickness of the first insulating layer may be at least half the thickness of the second insulating layer.

[0010] In the above configuration, the second insulating layer may be porous, and the first insulating layer may be non-porous.

[0011] In the above configuration, the second insulating layer may be in contact with the first thermoelectric layer and the second thermoelectric layer, and in contact with the first insulating layer.

[0012] In the above configuration, the fourth insulating layer may be porous, and the third insulating layer may be non-porous.

[0013] In the above configuration, the fourth insulating layer may be in contact with the first thermoelectric layer and the second thermoelectric layer, and in contact with the third insulating layer.

[0014] In the above configuration, the second insulating layer may be in contact with the first thermoelectric layer and the second thermoelectric layer and in contact with the first insulating layer, the thickness of the second insulating layer may be equal to or less than twice the larger distance, and the thickness of the fourth insulating layer may be equal to or less than twice the larger distance.

[0015] In the above configuration, the thermal conductivity of the second insulating layer and the fourth insulating layer may be 1 / 5 or less and 1 / 100 or more of the thermal conductivity of the first insulating layer and the second insulating layer.

[0016] In the above configuration, the thermal conductivity of the second insulating layer and the fourth insulating layer can be configured to be 1 / 300 or less and 1 / 30,000 or more times the thermal conductivity of the first connecting layer, the second connecting layer, the first thermal conduction layer, and the second thermal conduction layer.

[0017] In the above configuration, the thermal conductivity of the first thermoelectric layer and the second thermoelectric layer can be 1 / 50 or less of the thermal conductivity of the first connection layer, the second connection layer, the first thermal conduction layer, and the second thermal conduction layer.

[0018] In the above configuration, the thermal conductivity of the first thermoelectric layer and the second thermoelectric layer may be greater than the thermal conductivity of the second insulating layer and the fourth insulating layer.

[0019] In the above configuration, the first insulating layer and the third insulating layer may be an HSQ layer or a silicon oxide layer, and the second insulating layer and the fourth insulating layer may be porous silica.

[0020] In the above configuration, the distance between the end of the first thermal conduction layer on the first thermoelectric layer side and the center of the second connection layer in the first direction can be the same as the distance between the end of the first thermal conduction layer on the second thermoelectric layer side and the center of the second connection layer in the first direction. [Effects of the Invention]

[0021] According to the present invention, it is possible to provide a thermoelectric converter with a large output power. [Brief explanation of the drawings]

[0022] [Figure 1]FIG. 1(a) is a plan view of a thermoelectric converter in Example 1, and FIG. 1(b) is a cross-sectional view taken along the line AA in FIG. 1(a). [Figure 2] FIG. 2 is an enlarged cross-sectional view of the thermoelectric converter according to the first embodiment. [Figure 3] FIG. 3(a) is a plan view of the thermoelectric conversion module in Example 1, and FIG. 3(b) is a cross-sectional view taken along the line AA in FIG. 3(a). [Figure 4] FIG. 4 is a diagram showing the heat flow in Comparative Example 1. As shown in FIG. [Figure 5] 5(a) and 5(b) are diagrams showing normalized heat flow versus normalized X and normalized Z, respectively. [Figure 6] FIG. 6 is a diagram showing the heat flow in Comparative Example 1. [Figure 7] 7(a) and 7(b) are diagrams showing normalized heat flow versus normalized X and normalized Z, respectively. [Figure 8] 8(a) to 8(c) are diagrams showing Pout for tins1 in Example 1. FIG. [Figure 9] 9(a) to 9(e) are diagrams showing the current I and the output power Pout relative to the output voltage Vout in each sample. [Figure 10] FIG. 10 is an enlarged cross-sectional view of a thermoelectric converter according to a first modification of the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0023] As mentioned above, Figure 8 of Patent Document 2 does not describe the thickness of the heat insulating substrates (A2, B2). If the heat insulating substrates (A2, B2) are thick and have low mechanical strength, the mechanical strength of the thermoelectric converter will be low. If the heat insulating substrates (A2, B2) are thin, the performance of the thermoelectric converter will be reduced. Furthermore, in Figure 8 of Patent Document 2, a space 15 (i.e., a gap) is provided between the thermoelectric materials (5a-5h, 6a-6h) and the heat insulating substrate (B2). If a gap is provided between the thermoelectric material and the heat insulating substrate, the strength of the thermoelectric converter will be weakened.

[0024] Therefore, the inventors conducted a simulation of a thermoelectric conversion device without voids using a highly accurate distributed constant circuit model developed by the inventors. The distributed constant circuit model allows for highly accurate simulations by taking into account the thermal conductivity of each material. As a result of the simulation, a structure that can suppress a decrease in performance such as output power while ensuring mechanical strength was revealed for the first time. An example and the simulation results are described below. [Example]

[0025] FIG. 1(a) is a plan view of a thermoelectric converter in Example 1, and FIG. 1(b) is a cross-sectional view taken along the line AA in FIG. 1(a). FIG. 2 is an enlarged cross-sectional view of the thermoelectric converter in Example 1. FIG. 1(a) illustrates thermoelectric layers, connection layers, and electrodes. The surfaces of thermoelectric layers 12a and 12b are defined as an XY plane, and the arrangement direction (width direction) and extension direction (length direction) of thermoelectric layers 12a and 12b are defined as the X and Y directions, respectively. Lamination direction is the Z direction.

[0026] As shown in FIGS. 1(a), 1(b), and 2, in the thermoelectric conversion device 30, the thermoelectric layer 12a (first thermoelectric layer) and the thermoelectric layer 12b (second thermoelectric layer) are strip-shaped and extend in the Y direction. The thermoelectric layers 12a and 12b are alternately arranged in the X direction (a first direction parallel to the surface). The thermoelectric layers 12a and 12b are n-type and p-type, respectively, and have opposite conductivity types. Adjacent thermoelectric layers 12a and 12b are electrically and thermally connected to connection layers 14a (first connection layer) and 14b (second connection layer) alternately in the X direction. The connection layers 14a and 14b extend in the Y direction. A pair of thermoelectric layers 12a and 12b forms one Seebeck element 10. A plurality of Seebeck elements 10 are connected in series between electrodes 24a and 24b.

[0027] The connecting layers 14a and 14b are thermally connected to the thermally conductive layers 16a (first thermally conductive layer) and 16b (second thermally conductive layer) in the -Z direction and the +Z direction (second direction intersecting the surface), respectively. The thermally conductive layers 16a and 16b are thermally connected to the bases 22a and 22b via the electrical insulating films 20a and 20b, respectively. The thermally conductive layers 16a and 16b penetrate the insulating layers 18a and 18b, respectively. The insulating layer 18a includes insulating layers 17a (first insulating layer) and 17b (second insulating layer). The insulating layer 17b is provided between the insulating layer 17a and the Seebeck element 10 and the connecting layers 14a and 14b. The insulating layer 18b includes insulating layers 17c (third insulating layer) and 17d (fourth insulating layer). Insulating layer 17d is provided between insulating layer 17c and the Seebeck element 10 and connecting layers 14a and 14b. Insulating layers 17b and 17d contact thermoelectric layers 12a and 12b, respectively, and thermally conductive layers 16a and 16b, respectively. Insulating layers 17a and 17c contact insulating layers 17b and 17d, respectively, insulating films 20a and 20b, respectively, and thermally conductive layers 16a and 16b. The thermal conductivities of insulating layers 17a and 17c are lower than those of connecting layers 14a and 14b and thermally conductive layers 16a and 16b, and the thermal conductivities of insulating layers 17b and 17d are lower than those of insulating layers 17a and 17c.

[0028] FIG. 3(a) is a plan view of the thermoelectric conversion module in Example 1, and FIG. 3(b) is a cross-sectional view taken along line AA of FIG. 3(a). As shown in FIGS. 3(a) and 3(b), in the thermoelectric conversion module 100, bases 22a and 22b face each other. A heat sink 33 is thermally connected to the upper surface of the base 22b. The surface of the base 22a facing the base 22b has a convex portion. The base 22a has a region 35 that protrudes toward the base 22b and a region 36 that does not protrude. The distance H between the bases 22a and 22b in the region 36 is larger than the distance H between the bases 22a and 22b in the region 35. For example, the base 22b is flat, and the base 22a has a shape in which a convex portion is provided on the flat plate. A convex portion may be provided on the lower surface of the base 22b, or a convex portion may be provided on both the upper surface of the base 22a and the lower surface of the base 22b. Although the planar shapes of the bases 22a, 22b and the region 35 are shown as squares in the drawings, these planar shapes can be selected arbitrarily.

[0029] A support 34 is provided between the bases 22a and 22b around the periphery of the bases 22a and 22b. A thermal insulator 32 is provided between the bases 22a and 22b, surrounded by the support 34. The thermal insulator 32 is, for example, a gas or vacuum having a pressure lower than atmospheric pressure. The support 34 maintains the pressure or vacuum of the thermal insulator 32. The support 34 mechanically supports the bases 22a and 22b. The thermal conductivity of the thermal insulator 32 is lower than the thermal conductivity of the thermoelectric conversion device 30, the bases 22a and 22b, and the support 34.

[0030] The thermoelectric converter 30 has a plurality of blocks 31a to 31c. In each of the blocks 31a to 31c, a plurality of thermoelectric layers 12a and 12b are alternately arranged in the X direction. The plurality of blocks 31a to 31c are arranged in the Y direction. An electrode 24c connects the blocks 31a and 31b, and an electrode 24d connects the blocks 31b and 31c. As a result, the Seebeck element 10 is connected in series between the electrodes 24a and 24b. The rest of the configuration of the thermoelectric converter 30 is the same as that shown in FIGS. 1(a) to 2, and therefore a description thereof will be omitted.

[0031] In applications where the operating temperature is around room temperature or up to several hundred degrees Celsius, the thermoelectric material used for the thermoelectric layers 12a and 12b can be a bismuth tellurium alloy, a full Heusler alloy, or a half Heusler alloy. The bismuth tellurium alloy is, for example, Bi2Te as an n-type alloy. 3-x Se x , and p-type, e.g., Bi 2-x Sb x Te3. Full Heusler alloys include, for example, Fe2VAl 1-x Ge x , Fe2VAl 1-x Si x or Fe2VTa x Al 1-x , and p-type, for example, Fe2V 1-x W x Al, Fe2V 1-x Ti x Al or Fe2V 1-x Ti x Ga, and other materials such as Fe2NbGa, Fe2HfSi, Fe2TaIn, Fe2TiSn, or Fe2ZrGe. Half-Heusler alloys include n-type alloys such as TiPtSn, (Hf 1-x Zr x ) NiSn or NbCoSn, and p-type, for example, TiCoSn x Sb 1-x , Zr(Ni 1-x Co x )Sn, Zr(Ni 1-x In x )Sn, and HfPtSn. Using the same type of material for the n-type thermoelectric material and the p-type thermoelectric material facilitates the fabrication of the thermoelectric layers 12a and 12b. Furthermore, when the temperature range used is sufficiently higher than room temperature, Si, a SiGe alloy, or a GeSn alloy can also be used as the thermoelectric material for the thermoelectric layers 12a and 12b.

[0032] The thermoelectric layers 12a and 12b use, for example, the above-exemplified materials having n-type and p-type conductivity, respectively. The thermoelectric layers 12a and 12b may use different material systems from the above-exemplified materials. Alternatively, one of the thermoelectric layers 12a and 12b may use the above-exemplified n-type or p-type material, and the other of the thermoelectric layers 12a and 12b may be replaced with an appropriate metal that is not a thermoelectric material.

[0033] The connection layers 14a and 14b are preferably made of a material with high electrical and thermal conductivity, such as a metal layer of Cu, Al, Au, Ag, etc. The connection layers 14a and 14b may be made of different materials.

[0034] The insulating layers 17a and 17c can be made of inorganic insulators such as silicon oxide, alkyl-containing silica or similar oxides and insulators (e.g., hydrogen silsesquioxane), resins (e.g., acrylic resin, epoxy resin, vinyl chloride resin, silicone resin, fluororesin, phenolic resin, Bakelite resin, polyethylene resin, polycarbonate resin, polystyrene resin, polypropylene resin), or rubber (natural rubber, ethylene propylene rubber, chloroprene rubber, silicone rubber, butyl rubber, or polyurethane rubber). The insulating layers 17b and 17d can be made of porous insulators such as porous silicon or porous silica. Porous silicon is, for example, porous silicon made from high-resistivity silicon. Porous silica is, for example, porous silicon made electrically and thermally insulator by oxidation or the like. The insulating layers 18a and 18b can be formed using CVD (Chemical Vapor Deposition), sputtering, or spin coating.

[0035] The bases 22a and 22b are preferably made of a material with high thermal conductivity, such as a metal such as Cu, Al, Au, or Ag, or a ceramic such as Si or alumina. The electrical insulating films 20a and 20b are preferably made of a material with high electrical insulation and thermal conductivity, such as an aluminum oxide film. The insulating films 20a and 20b may be formed on the bases 22a and 22b using a sputtering method or a CVD method. If the bases 22a and 22b are electrically insulating, the insulating films 20a and 20b may not be used. At least one of the bases 22a and 22b can be formed using a sputtering method or a CVD method. This allows the bases 22a and 22b to be thin. At least one of the bases 22a and 22b can be formed by a plating method. This allows the bases 22a and 22b to have a certain thickness. When at least one of the bases 22a and 22b is an oxide film or ceramic, a coating film formed by spin coating or the like can be used. The bases 22a and 22b can be made of a structure (e.g., a fin structure or a heat sink structure) and material (e.g., a heat dissipation sheet, a heat dissipation or heat absorption material containing a volatile material, or aluminum with an anodized surface) that has high heat exchange and heat dissipation properties.

[0036] The support 34 preferably has low thermal conductivity, but is preferably made of a material harder than the thermal insulator 32 in terms of supporting the bases 22a and 22b and / or maintaining the gas layer or vacuum. Polymer organic materials such as resin or rubber can be used as the support 34. For example, when the thermal insulator 32 is solid, the support 34 preferably has a higher yield strength than the thermal insulator 32 in terms of reinforcing the thermal insulator 32.

[0037] [Comparative Example 1] First, a simulation was performed for Comparative Example 1 in which insulating layers 17b and 17d were not provided and insulating layers 18a and 18b were entirely replaced with insulating layers 17a and 17c.

[0038] [Simulation of Comparative Example 1] The structural parameters shown in FIGS. 1 to 3 are defined as follows. D: Widths of the bases 22a and 22b in the X and Y directions D': width of region 35 in the X and Y directions D0: Length of the thermoelectric converter 30 in the X direction (total length of the blocks 31a to 31c) H: Distance between bases 22a and 22b in region 36 x: width of the support 34 in the X and Y directions d: pitch of thermoelectric layers 12a and 12b in the X direction γ: trade-off parameter, parameter for which the width occupied by the thermoelectric layers 12a and 12b is γd γd: width of the thermoelectric layers 12a and 12b in the X direction (1-γ)d: distance between thermoelectric layers 12a and 12b in the X direction L: length of the thermoelectric layers 12a and 12b in the Y direction t s : Thickness of the thermoelectric layers 12a and 12b in the Z direction t ins1 : Thickness of insulating layers 17b and 17d in the Z direction, in Comparative Example 1 tins1 is 0. t ins2 : Thickness of insulating layers 17a and 17c in the Z direction t C =t C1 +t C2 : Thickness of insulating layers 18a and 18b in the Z direction t C1 The larger of the distance in the X direction between the end of the thermally conductive layer 16a and the center of the thermally conductive layer 16b and the distance in the X direction between the end of the thermally conductive layer 16b and the center of the thermally conductive layer 16a t PI : Thickness of the insulating films 20a and 20b in the Z direction m0: number of pairs of thermoelectric layers 12a and 12b (i.e., number of Seebeck elements 10) ΔT S : Temperature difference between the bottom surface of the base 22a and the top surface of the base 22b P out : Output power of thermoelectric converter

[0039] When the thermoelectric conversion module 100 is used as a power source for a wearable device, the thermoelectric conversion module 100 generates electricity using the temperature difference between the body temperature of the human body and the temperature of the atmosphere. Therefore, a homeothermic animal model was used for the body temperature of the human body. Details of the simulation are described in IEEE Transactions on Electron Devices, doi: 10.1109 / TED.2020.3006168. In the simulation, the output power P out γ, γd, (1-γ)d, m0, L and t are chosen so that C1 The model inside the thermoelectric converter 30 uses a highly accurate distributed parameter circuit model.

[0040] The simulation conditions for each dimension and material were as follows: D×D=10mm×10mm D´×D´=3mm×3mm D0=9mm H=5mm x=0.5mm t S =1000nm t PI =100nm Thermoelectric layers 12a and 12b Material: BiTe Seebeck coefficient = S p -S n :434μV / K Thermal conductivity λ=(λ p +λ n ) / 2:1.43W / (m·K) Electrical resistivity ρ=(ρ p +ρ n ) / 2:8.11μΩ·m λ n and ρ n are the thermal conductivity and electrical resistivity of the thermoelectric layer 12a, respectively, and λ p and ρ p are the thermal conductivity and electrical resistivity of the thermoelectric layer 12b, respectively. Connection layers 14a, 14b, thermally conductive layers 16a and 16b Material: Cu Thermal conductivity λ C:386W / (m·K) Electrical resistivity ρ C :17nΩ·m Insulating films 20a and 20b Material: AlO x Thermal conductivity λ PI :1.5W / (m·K) Support 34 Material: Organic material Thermal conductivity λ WL :0.15W / (m·K) Thermal Insulator 32 vacuum contact resistance BiTe and Cu Contact electrical resistance r PC :1.0Ω·μm 2 Contact thermal resistance k PC :140μm 2 K / mW Cu and AlO x Contact thermal resistance k C-PI :3.4μm 2 K / mW The temperature difference between the body temperature of the human body and the temperature of the atmosphere was set to 10 K. Note that contact electrical resistance is the electrical resistance per unit area at the surface where two materials come into contact, and contact thermal resistance is the thermal resistance per unit area at the surface where two materials come into contact.

[0041] Simulations were performed using the following three materials for the insulating layers 18a and 18b. Sample PS Material: Porous silica Thermal conductivity λ PS :35.7mW / (m·K) Sample HSQ Material: Hydrogen silsesquioxane Thermal conductivity λ HSQ :0.3W / (m·K) Sample SiO2 Material: SiO2 Thermal conductivity λ SiO2 :0.9W / (m·K) PS has low thermal conductivity but is brittle, which makes it difficult to form thick layers. SiO2 has high mechanical strength and can be easily formed thickly, but has high thermal conductivity. HSQ (hydrogen silsesquioxane) is a molecule in which hydrogen is doped into silsesquioxane, an intermediate material between silica and silicon, and has weaker mechanical strength than SiO2 but lower thermal conductivity than SiO2.

[0042] Table 1 shows the t C2 +t C1 When the insulating layers 18a and 18b each have a single layer structure, t C2 = 30 μm, the optimized output power P out 1 is a table showing each parameter. [Table 1] As shown in Table 1, the output power P out is 16.15μW, but the output power P out is less than half of the sample PS, and the output power P out is 1 / 5 or less of that of sample PS. Since the thermal conductivity of the insulating layers 18a and 18b differs for each sample, the output power P out Each parameter when optimized varies for each sample.

[0043] In Comparative Example 1, when PS was used as the insulating layers 18a and 18b, the output power P out When HSQ and SiO2 are used as the insulating layers 18a and 18b, the mechanical strength is sufficient and the process is easy, but the output power P out will decrease significantly.

[0044] The leakage of heat flow from the thermoelectric layers 12a and 12b and the thermal conduction layers 16a and 16b to the insulating layers 18a and 18b in the samples PS and HSQ of Comparative Example 1 was simulated using a highly accurate distributed parameter circuit model.

[0045] FIG. 4 is a diagram showing heat flows in Comparative Example 1. The lower surface of the insulating film 20a was set to a high temperature, and the upper surface of the insulating film 20b was set to a low temperature. A simulation was performed to determine a heat flow 54 leaking from the thermally conductive layer 16a to the insulating layer 18a and a heat flow 53 flowing from the insulating layer 18a into the thermoelectric layers 12a and 12b. The X coordinate positions X of the thermoelectric layers 12a and 12b were normalized. The positions X where the thermoelectric layers 12a and 12b contact the connection layer 14b were set to 0, and the positions X where the thermoelectric layers 12a and 12b contact the connection layer 14a were set to 1. The Z coordinate position Z of the thermally conductive layer 16a was normalized. The positions Z where the thermally conductive layer 16a contact the insulating film 20a were set to 0, and the positions Z where the thermally conductive layer 16a contact the connection layer 14a were set to 1.

[0046] 5(a) and 5(b) are diagrams showing the normalized heat flow for normalized X and normalized Z, respectively. In the simulation, the range of 0 to 1 for normalized X and the range of 0 to 1 for normalized Z were divided into 10 and 15 ranges, respectively. The dots in FIGS. 5(a) and 5(b) indicate the sum of the normalized heat flow within the divided ranges. The straight lines connect the dots. FIG. 5(a) shows the normalized heat flow 53 flowing from the insulating layer 18a to the thermoelectric layers 12a and 12b. The normalized heat flow is a heat flow obtained by normalizing each heat flow by the total heat flow flowing from the outside into the insulating film 20a. As shown in FIG. 5(a), in the sample HSQ, the normalized heat flow in the region 51 was X The normalized heat flow 53 is large when X is near 0, and the normalized heat flow 53 decreases as the normalized X increases. This corresponds to the fact that the temperature of the thermoelectric layers 12a and 12b increases as the normalized X increases. As the temperatures of the thermoelectric layers 12a and 12b decrease, the heat flow flowing in from the insulating layer 18a increases. In the region 50, the normalized heat flow 53 increases as the normalized X increases.

[0047] FIG. 5(b) shows the normalized heat flow 54 leaking from the thermally conductive layer 16a to the insulating layer 18a. As shown in FIG. 5(b), in sample HSQ, the normalized heat flow 54 is almost zero in region 52. In region 50, the normalized heat flow 54 increases as the normalized Z increases. Thus, in region 50 of FIG. 4, it was found that there is a heat flow from the thermally conductive layer 16a through the insulating layer 18a to the thermoelectric layers 12a and 12b. This is due to the thermal contact resistance k between the thermally conductive layer 16a and the thermoelectric layers 12a and 12b. PC This may be because the heat flow from the connection layer 14a to the thermoelectric layers 12a and 12b is less likely to flow through the region 50 due to the contact thermal resistance k PC is sufficiently small, it is believed that the heat flow through region 50 is due to the high thermal conductivity of insulating layer 18a. In sample PS, normalized heat flows 53 and 54 in Figures 5(a) and 5(b) are smaller than those in sample HSQ. This is believed to be because in sample PS, the thermal conductivity of insulating layer 18a is low, so the amount of heat passing through insulating layer 18a is small.

[0048] FIG. 6 is a diagram showing heat flows in Comparative Example 1. The lower surface of insulating film 20a was set to a high temperature, and the upper surface of insulating film 20b was set to a low temperature. Simulations were performed on heat flows 58 leaking from thermoelectric layers 12a and 12b to insulating layer 18b, and heat flows 59 flowing from insulating layer 18b to thermally conductive layer 16b. Normalization X is the same as in FIG. 4. The position Z where thermally conductive layer 16b and connection layer 14b contact was set to 0, and the position Z where thermally conductive layer 16b and insulating film 20b contact was set to 1.

[0049] 7(a) and 7(b) are graphs showing the normalized heat flow versus normalized X and normalized Z, respectively. FIG. 7(a) shows the normalized heat flow 58 flowing from the thermoelectric layers 12a and 12b to the insulating layer 18b. As shown in FIG. 7(a), in sample HSQ, in region 56, the normalized heat flow 58 is large when the normalized X is near 1, and the normalized heat flow 58 decreases as the normalized X decreases. This is due to the temperature distribution of the thermoelectric layers 12a and 12b. In region 55, the normalized heat flow 58 increases as the normalized X decreases.

[0050] Figure 7(b) shows the normalized heat flow 59 flowing from the insulating layer 18b to the thermally conductive layer 16b. As shown in Figure 7(b), in sample HSQ, the normalized heat flow 59 is nearly zero in region 57. In region 55, the normalized heat flow 59 increases as the normalized Z decreases. Thus, in region 55 of Figure 6, heat flow from the thermoelectric layers 12a and 12b to the thermally conductive layer 16b via the insulating layer 18b is evident. The heat flow through region 55 is believed to be due to the high thermal conductivity of the insulating layer 18b. In Figures 7(a) and 7(b), the normalized heat flows 58 and 59 of sample PS are also smaller than those of sample HSQ. This is believed to be due to the low thermal conductivity of the insulating layer 18b in sample PS, resulting in a small heat flow through the insulating layer 18b.

[0051] As described above, there are two types of heat flows passing through the insulating layers 18a and 18b: a heat flow that depends on the temperature distribution of the thermoelectric layers 12a and 12b, and a heat flow that passes through the regions 50 and 55 and is caused by the high thermal conductivity of the insulating layers 18a and 18b. The existence of these two heat flows with different mechanisms is not suggested in Patent Document 2. Due to the leakage of heat flow into the insulating layers 18a and 18b due to these two mechanisms, the output power P out It is believed that the output power of Example 1 when the above two mechanisms exist was simulated.

[0052] [Simulation of Example 1] The sample HSQ / PS is a sample in which HSQ is used for the insulating layers 17a and 17c, and PS is used for the insulating layers 17b and 17d. The sample SiO2 / PS is a sample in which SiO2 is used for the insulating layers 17a and 17c, and PS is used for the insulating layers 17b and 17d. C1 = 7 μm and t C2 = 1 μm, t C1 = 8 μm and t C2 = 10 μm, t C1 = 9.4 μm and t C2 For the three conditions of t = 30 μm, the thickness t of the insulating layers 17b and 17dins1 The optimized output power P out was simulated.

[0053] 8(a) to 8(c) show the t ins1 P for out 1 shows samples HSQ / PS and SiO2 / PS as Example 1, and sample PS as Comparative Example 1. In sample PS, t ins1 =t C1 +t C2 However, to compare with the samples HSQ / PS and SiO2 / PS, out A ins1 The dotted line shows a constant value regardless of the value of t ins1 When is near 0, the output power P out is less than half of the sample PS. ins1 When becomes larger, the output power P out approaches the sample PS, and t ins1 =t C1 When , the output power P of the samples HSQ / PS and SiO2 / PS out is approximately the output power of the sample PS P out It will be almost the same as

[0054] Table 2 shows the sample PS output. electric power P out Sample HSQ / PS output to PS electric power P out The ratio P indicates HSQ out HSQ / P out 1 is a table showing PS. [Table 2]

[0055] Table 3 shows a sample PS output. electric power P out Output of sample SiO2 / PS to PS electric power P out The ratio P indicates SiO2 outSiO2 / P out 1 is a table showing PS. [Table 3]

[0056] In Tables 2 and 3, t C2 When is 1 μm, 10 μm and 30 μm, t ins1 t C1 and t C1 / 2 When P out HSQ / P out PS and P out SiO2 / P out As shown in Tables 2 and 3, ins1 =t C1 So, t C2 Regardless, P out HSQ and P out SiO2 is almost P out It is the same as PS. ins1 =t C1 In / 2, t C2 Regardless, P out HSQ and P out SiO2 is P out As shown in Figures 8(a) to 8(c), t ins1 =t C1 In / 4, P out HSQ and P out SiO2 is P out It is almost 75% of PS, and t ins1 =t C1 In / 3, P out HSQ and P out SiO2 is P out Thus, the thickness t ins1 If the value is not increased to a certain value, the output power P out cannot be made larger.

[0057] The thickness t of the insulating layers 17b and 17d ins1 If the output power P outThe reason why it is not possible to increase the normalized X is as follows. First, in FIG. 4, when the normalized X is near 0, the heat flow 53 flowing from the insulating layer 18a to the thermoelectric layers 12a and 12b flows from the thermoelectric layers 12a and 12b in the insulating layer 18a to the C1 Furthermore, the region 50 where the heat flow 54 leaking from the thermally conductive layer 16a to the insulating layer 18a exists is the region from the thermoelectric layers 12a and 12b to t C1 6, the heat flow 58 leaking from the thermoelectric layers 12a and 12b to the insulating layer 18b when the normalized X is near 1 flows from the thermoelectric layers 12a and 12b in the insulating layer 18b to the C1 Furthermore, the region 55 where the heat flow 59 flows from the insulating layer 18b to the thermally conductive layer 16b is located is the region from the thermoelectric layers 12a and 12b to t C1 This is thought to be because the area has expanded to a certain extent.

[0058] The thickness t of the insulating layers 17b and 17d is ins1 Output power P out This behavior is not suggested in the description of Patent Document 2, but is knowledge that was obtained by starting to perform simulations using highly accurate distributed constant circuit models, as shown in FIGS. 4 to 7(b).

[0059] According to the first embodiment, the thickness t ins1 A C1 This will increase the output power P out The output power P of the sample PS out It can be 75% or more of t C1 is the longer of the distance between the end of the thermal conduction layer 16a on the thermoelectric layer 12a side and the center of the thermal conduction layer 16b in the X direction, or the distance between the end of the thermal conduction layer 16a on the thermoelectric layer 12b side and the center of the thermal conduction layer 16b in the X direction. ins1 is t C1 / 3 or more is more preferable, and t C1 The thickness t of the insulating layers 17b and 17d is more preferably 1 / 2 or more. int1 A C1By setting the thickness to 1 / 2, an output power of about 90% of the output power of the sample PS can be obtained, and the thickness t int1 A C1 This is because a highly accurate distributed constant circuit model simulation showed that by setting the output power to 1 / 3 of the value, an output power of about 85% of the output power of the sample PS could be obtained.

[0060] Thickness t ins1 t C1 Even if it is thicker, the output power P out Therefore, in order to increase the mechanical strength of the insulating layers 18a and 18b, the thickness t ins1 is 2 x t C1 Less than 1.5 x t is preferred C1 The following is more preferable: C1 The following is more preferable. ins1 A preferred range of (e.g., t C1 / 2 or more and t C1 8(a) to 8(c), the materials of the insulating layers 17b and 17d and t C2 In addition, the thickness t ins1 A C1 / 4 or more and 2×t C1 The following may also be used.

[0061] In order to increase the mechanical strength of the insulating layers 18a and 18b, the thickness t ins2 Therefore, t ins2 is t ins1 / 2 or more is preferable, and t ins1 More preferably, 1.5 x t ins1 The above is even more preferable.

[0062] The thermal conductivity of insulating layers 18a and 18b should be lower than that of thermally conductive layers 16a and 16b. The thermal conductivity of insulating layers 17a and 17c should preferably be 1 / 300 or less, more preferably 1 / 1000 or less, of that of thermally conductive layers 16a and 16b. The thermal conductivity of insulating layers 17b and 17d should be lower than that of insulating layers 17a and 17c, but should preferably be 1 / 5 or less, more preferably 1 / 10 or less, and even more preferably 1 / 50 or less, of that of insulating layers 17a and 17c. To make the thermal conductivity of insulating layers 17b and 17d lower than that of insulating layers 17a and 17c, insulating layers 17b and 17d may be porous, and insulating layers 17a and 17c may be non-porous. When the insulating layers 17b and 17d are porous, the porosity (void ratio) of the insulating layers 17b and 17d is preferably 10% or more, more preferably 50% or more. This allows the thermal conductivity of the insulating layers 17b and 17d to be low. When the insulating layers 17a and 17c are non-porous, the porosity of the insulating layers 17a and 17b is preferably 1% or less, more preferably 0.1% or less. below This is more preferable, as it increases the mechanical strength of the insulating layers 17a and 17b.

[0063] Table 4 shows the output power P of the sample HSQ / PS relative to the sample HSQ. out The increase rate of the output power P of the sample SiO2 / PS relative to the sample SiO2 out This is a table showing the growth rate of t C2 = 30 μm, t ins1 =t C1 is. [Table 4] As shown in Table 4, sample HSQ / PS has a higher P out The P value of sample SiO2 / PS increased by 125% compared to that of sample SiO2. out increases by 426%.

[0064] Figures 9(a) to 9(e) show the output voltage V out current I and output power P out9(a) shows sample PS, FIG. 9(b) shows sample HSQ, FIG. 9(c) shows sample SiO2, FIG. 9(d) shows sample HSQ / PS, and FIG. 9(e) shows sample SiO2 / PS. The areas of the bases 22a and 22b are D × D = 1 cm 2 By connecting multiple modules in series and / or parallel, the mounting area S A 20cm 2 From 120cm 2 Up to 20cm 2 The sample is changed in steps. C2 = 30 μm, and for samples HSQ / PS and SiO2 / PS, t ins1 =t C1 is.

[0065] As shown in Figure 9(a) to Figure 9(e), the output voltage V out When is approximately 1V, the output power P out As shown in Figure 9(a), the mounting area S A is 120cm 2 In this case, the output power P out However, the insulating layers 18a and 18b of the sample PS have low mechanical strength. As shown in Figs. 9(b) and 9(c), the insulating layers 18a and 18b of the samples HSQ and SiO2 have high mechanical strength, but the mounting area S A 120cm 2 Even if out As shown in Fig. 9(d) and Fig. 9(e), in the HSQ / PS and SiO2 / PS samples, S A is 120cm 2 In this case, the output power P out The power dissipation is about 2 mW, which is almost the same as that of sample PS. Since the insulating layers 17a and 17c are made of HSQ or SiO2, mechanical strength can be ensured.

[0066] [Modification 1 of Example 1] 10 is an enlarged cross-sectional view of a thermoelectric converter according to a first modification of the first embodiment. As shown in FIG. 10, in the first modification of the first embodiment, the lengths of the thermoelectric layers 12a and 12b in the X direction are different. The distance between the end of the thermal conduction layer 16b on the thermoelectric layer 12b side and the center of the thermal conduction layer 16a in the X direction is d1, and the distance between the end of the thermal conduction layer 16b on the thermoelectric layer 12a side and the center of the thermal conduction layer 16b in the X direction is d2. The pitch in the X direction is d.

[0067] When the distances d1 and d2 are different, as in the first modification of the first embodiment, it is necessary to suppress both the heat flow bypassing the insulating layer 18a and the heat flow bypassing the insulating layer 18b. Therefore, the larger of the distances d1 and d2, d2, is used as the reference. That is, t ins1 is preferably d2 / 4 or more, more preferably d2 / 3 or more, and even more preferably d2 / 2 or more. ins1 is preferably 2×d2 or less, more preferably 1.5×d2 or less, and even more preferably d2 or less. As in Example 1, distances d1 and d2 may be the same to the extent of manufacturing tolerance, or as in Modification 1 of Example 1, distances d1 and d2 may differ by more than the extent of manufacturing tolerance. In the above-described example, insulating layers 18a and 18b, the cross section of which is shown in FIG. 10, are repeatedly arranged at a pitch d in the X direction. Since pitch d is a constant value, there are two distances, d1 and d2. Note that pitch d does not have to be constant. In this case, the largest distance among the multiple distances d1 and the multiple distances d2 may be used as the reference.

[0068] In the above-described embodiment, the second insulating layer, which is penetrated by the first thermally conductive layer, has a thermal conductivity lower than that of the first insulating layer, is provided between the first insulating layer and the first and second thermoelectric layers, and has a thickness of at least 1 / 4 of the larger of the distance between the end of the first thermally conductive layer facing the first thermoelectric layer and the center of the second connecting layer in the first direction and the distance between the end of the first thermally conductive layer facing the second thermoelectric layer and the center of the second connecting layer in the first direction, is insulating layer 17b, 17d made of a porous insulator as shown in FIG. 2 or FIG.

[0069] 1(a) to 2, when insulating layer 17b contacts thermoelectric layers 12a and 12b and insulating layer 17a, and insulating layer 17d contacts thermoelectric layers 12a and 12b and insulating layer 17a, spaces 15 (i.e., voids) as shown in FIG. 8 of Patent Document 2 are not formed between base 22a and thermoelectric layers 12a and 12b, and between base 22b and thermoelectric layers 12a and 12b. This is because base 22a, thermoelectric layers 12a and 12b, and base 22b are produced by a fine lamination process such as a semiconductor formation process. This makes it possible to provide a very high-density, compact thermoelectric conversion device at low manufacturing cost and further increase the strength of the thermoelectric conversion device.

[0070] In a thermoelectric converter without voids, the thermal conductivity of the insulating layers 17b and 17d is set to be smaller than that of the insulating layers 17a and 17c, so that the results of the simulations shown in Figures 8(a) to 8(c) can be applied. That is, the thicknesses of the insulating layers 17b and 17d with low thermal conductivity are set to t C1 By setting the value to 1 / 4 or more, the output power P out 8(a) to 8(c), when insulating layers 17b and 17d are porous silica and insulating layers 17a and 17c are HSQ or SiO2, the output power can be increased to, for example, 75% or more compared to when insulating layers 18a and 18b are all made of HSQ or SiO2.

[0071] As shown in FIGS. 8(a) to 8(c), the thicknesses of the insulating layers 17b and 17d are set to t C1 Therefore, the insulating layers 17a and 17c having high thermal conductivity and high mechanical strength are provided, and the thickness of the insulating layers 17b and 17d having low mechanical strength is set to t C1 By setting the thickness to be equal to or less than two times the thickness of the insulating layers 18a and 18b, the mechanical strength of the thermoelectric converter can be increased compared to when all of the insulating layers 18a and 18b are made of a material with low mechanical strength, such as porous silica. P outThis can suppress the decline in

[0072] 8(a) to 8(c), for the HSQ / PS and SiO2 / PS samples, the thermal conductivities of the insulating layers 17b and 17d (porous silica) are 1 / 8.4 and 1 / 25.2 times that of the insulating layers 17a and 17c (HSQ and SiO2), respectively. The thermal conductivities of the insulating layers 17b and 17d (porous silica) are also 1 / 10800 times that of the connecting layers 14a and 14b and the thermally conductive layers 16a and 16b (Cu).

[0073] To achieve the same effects as those shown in the simulation results of FIGS. 8(a) to 8(c), the thermal conductivity of insulating layers 17b and 17d is preferably in the range of 1 / 5 or less and 1 / 100 or more than that of insulating layers 17a and 17c. By setting the thermal conductivity of insulating layers 17b and 17d to 1 / 5 or less than that of insulating layers 17a and 17c, the heat flow through insulating layers 17b and 17d can be suppressed to a range similar to that of the simulation results. This suppresses a decrease in output power. Furthermore, by setting the thermal conductivity of insulating layers 17b and 17d to 1 / 100 or more than that of insulating layers 17a and 17c, materials with high mechanical strength can be used for insulating layers 17a and 17c. This allows the mechanical strength of the thermoelectric converter to be ensured while suppressing the heat flow through insulating layers 17b and 17d to a range similar to that of the simulation results.

[0074] Furthermore, the thermal conductivity of the insulating layers 17b and 17d preferably ranges from 1 / 300 to 1 / 30,000 times that of the connecting layers 14a and 14b and the thermally conductive layers 16a and 16b. By setting the thermal conductivity of the insulating layers 17b and 17d to 1 / 300 or less that of the connecting layers 14a and 14b and the thermally conductive layers 16a and 16b, the thermal conductivity of the connecting layers 14a and 14b and the thermally conductive layers 16a and 16b can be increased, thereby suppressing heat flow through the insulating layers 17b and 17d. This reduces a decrease in output power. Setting the thermal conductivity of the insulating layers 17b and 17d to 1 / 30,000 or more that of the connecting layers 14a and 14b and the thermally conductive layers 16a and 16b allows the insulating layers 17b and 17d to be made of a practical material, such as porous silica, which is applicable to fine layering processes, such as semiconductor fabrication processes. Therefore, costs can be reduced. Furthermore, when the thermal conductivity of the insulating layers 17b and 17d is within the above range, the thickness of each of the insulating layers 17b and 17d can be set to t C1 It is preferable that the value is 1 / 4 or more and 2 or less.

[0075] 8(a) to 8(c), the thermal conductivity of insulating layers 17b and 17d is preferably 1 / 10 or less, and more preferably 1 / 20 or less, of the thermal conductivity of insulating layers 17a and 17c. The thermal conductivity of insulating layers 17b and 17d is preferably 1 / 1000 or less, and more preferably 1 / 5000 or less, of the thermal conductivity of connecting layers 14a and 14b and thermally conductive layers 16a and 16b.

[0076] In Comparative Example 1, when the thermal conductivity of the thermoelectric layers 12a and 12b is low, a temperature distribution occurs within the thermoelectric layers 12a and 12b. This increases the heat flow from the insulating layer 18a to the thermoelectric layers 12a and 12b, as indicated by heat flow 53 in FIG. 4, and the heat flow from the thermoelectric layers 12a and 12b to the insulating layer 18b, as indicated by heat flow 58 in FIG. 6. In the simulations of FIGS. 8(a) to 8(c), the thermal conductivity of the thermoelectric layers 12a and 12b (BiTe) is 1 / 270 times that of the connection layers 14a and 14b and the thermal conduction layers 16a and 16b (Cu). Therefore, to apply the results of the simulations of FIGS. 8(a) to 8(c), the thermal conductivity of the thermoelectric layers 12a and 12b is preferably 1 / 50 or less of that of the connection layers 14a and 14b and the thermal conduction layers 16a and 16b.

[0077] 8(a) to 8(c), the thermal conductivity of the thermoelectric layers 12a and 12b is preferably 1 / 100 or less of the thermal conductivity of the connection layers 14a and 14b and the thermal conduction layers 16a and 16b. The thermal conductivity of the thermoelectric layers 12a and 12b is, for example, 1 / 1000 or more of the thermal conductivity of the connection layers 14a and 14b and the thermal conduction layers 16a and 16b.

[0078] If the thermal conductivity of the thermoelectric layers 12a and 12b is too low, the heat flow through the thermoelectric layers 12a and 12b will be reduced. In the simulations of FIGS. 8(a) to 8(c), the thermal conductivity of the thermoelectric layers 12a and 12b (BiTe) is 40 times that of the insulating layers 17b and 17d (porous silica). Therefore, to achieve the same effects as those in the simulations of FIGS. 8(a) to 8(c), the thermal conductivity of the thermoelectric layers 12a and 12b is preferably greater than that of the insulating layers 17b and 17d. To apply the results of the simulations of FIGS. 8(a) to 8(c), the thermal conductivity of the thermoelectric layers 12a and 12b is preferably at least 10 times that of the insulating layers 17b and 17d. The thermal conductivity of the thermoelectric layers 12a and 12b is, for example, 100 times or less that of the insulating layers 17b and 17d.

[0079] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as set forth in the claims. [Explanation of symbols]

[0080] 10 Seebeck element 12a, 12b thermoelectric layer 14a, 14b Connection layer 16a, 16b Thermally conductive layer 17a to 17d, 18a, 18b Insulating layers 22a, 22b base 24a~24d electrode

Claims

1. the first thermoelectric layer and the second thermoelectric layer having opposite conductivity types and alternately arranged in a first direction parallel to the surfaces of the first thermoelectric layer and the second thermoelectric layer; a first connection layer and a second connection layer that are electrically and thermally connected to the first thermoelectric layer and the second thermoelectric layer between the first thermoelectric layer and the second thermoelectric layer and that are alternately provided in the first direction; a first thermally conductive layer thermally connected to the first connection layer and extending in a second direction intersecting the surface; a second thermal conduction layer that is thermally connected to the second connection layer, is provided on the opposite side of the first thermal conduction layer from the first thermoelectric layer and the second thermoelectric layer, and extends in the second direction; a first insulating layer through which the first thermally conductive layer passes and which has a thermal conductivity lower than that of the first thermally conductive layer; a second insulating layer through which the first thermally conductive layer penetrates, has a thermal conductivity lower than that of the first insulating layer, and is provided between the first insulating layer and the first thermoelectric layer and the second thermoelectric layer; a third insulating layer through which the second thermally conductive layer passes and which has a thermal conductivity lower than that of the second thermally conductive layer; a fourth insulating layer through which the second thermally conductive layer penetrates, has a thermal conductivity lower than that of the third insulating layer, and is provided between the third insulating layer and the first thermoelectric layer and the second thermoelectric layer; Equipped with A thermoelectric conversion device, wherein the thickness of the second insulating layer and the fourth insulating layer is at least 1 / 4 of the longer distance between the center of the first thermal conduction layer and the edge of the adjacent second thermal conduction layer in the first direction.

2. 2. The thermoelectric converter according to claim 1, wherein the thickness of the second insulating layer is equal to or less than twice the larger distance.

3. 3. The thermoelectric converter according to claim 1, wherein the thickness of the first insulating layer is at least half the thickness of the second insulating layer.

4. The thermoelectric converter according to claim 1 , wherein the second insulating layer is porous and the first insulating layer is non-porous.

5. The thermoelectric converter according to claim 1 , wherein the second insulating layer is in contact with the first thermoelectric layer and the second thermoelectric layer, and is in contact with the first insulating layer.

6. The thermoelectric converter according to claim 1 , wherein the fourth insulating layer is porous and the third insulating layer is non-porous.

7. The thermoelectric conversion device according to claim 1 , wherein the fourth insulating layer is in contact with the first thermoelectric layer and the second thermoelectric layer, and is in contact with the third insulating layer.

8. 8. The thermoelectric conversion device according to claim 1, wherein the thermal conductivity of the second insulating layer and the fourth insulating layer is 1 / 5 or less and 1 / 100 or more of the thermal conductivity of the first insulating layer and the third insulating layer.

9. The thermoelectric conversion device according to claim 8, wherein the thermal conductivity of the second insulating layer and the fourth insulating layer is 1 / 300 or less and 1 / 30,000 or more of the thermal conductivity of the first connection layer, the second connection layer, the first thermal conduction layer, and the second thermal conduction layer.

10. 10. The thermoelectric conversion device according to claim 9, wherein the thermal conductivity of the first thermoelectric layer and the second thermoelectric layer is 1 / 50 or less of the thermal conductivity of the first connection layer, the second connection layer, the first thermal conduction layer, and the second thermal conduction layer.

11. The thermoelectric conversion device according to claim 10 , wherein the thermal conductivity of the first thermoelectric layer and the second thermoelectric layer is greater than the thermal conductivity of the second insulating layer and the fourth insulating layer.

12. 12. The thermoelectric conversion device according to claim 1, wherein the first insulating layer and the third insulating layer are HSQ layers or silicon oxide layers, and the second insulating layer and the fourth insulating layer are porous silica.

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