Thermoelectric conversion module and production method for same

Abstract

This thermoelectric conversion module comprises: a substrate that has a first main surface and a second main surface; a thermoelectric conversion part that is positioned on the first main surface; first and second thermal conduction parts that are positioned on the second main surface; and a thermal insulation member that is positioned on the second main surface. The thermoelectric conversion part has a p-type thermoelectric conversion element and an n-type thermoelectric conversion element. A first end part of the p-type thermoelectric conversion element contacts a first end part of the n-type thermoelectric conversion element. The first thermal conduction part overlaps with a second end part of the p-type thermoelectric conversion element. The second thermal conduction part overlaps with a second end part of the n-type thermoelectric conversion element. The respective thicknesses of the n-type thermoelectric conversion element and the p-type thermoelectric conversion element are 3-30 μm. The difference in linear expansion coefficient between the first thermal conduction part and the thermal insulation member, and the difference in linear expansion coefficient between the second thermal conduction part and the thermal insulation member are each not more than 100 ppm / K.

Description

Thermoelectric conversion module and manufacturing method thereof

[0001] The present disclosure relates to a thermoelectric conversion module and a method for manufacturing the same.

[0002] Thermoelectric conversion elements are sometimes used to generate electricity using geothermal energy, factory waste heat, or the like. Patent Document 1 below discloses an embodiment in which flexible substrates having pattern layers made of a resin layer and a metal layer are provided on both sides of a thermoelectric conversion module having P-type thermoelectric element material and N-type thermoelectric element material. In Patent Document 1 below, the metal layer included in one flexible substrate overlaps one electrode included in the thermoelectric conversion module, and the metal layer included in the other flexible substrate overlaps the other electrode included in the thermoelectric conversion module. In this embodiment, one flexible substrate is kept in a high-temperature state and the other flexible substrate is kept in a low-temperature state, thereby generating a temperature difference in the surface direction of the thermoelectric conversion module. This generates an electromotive force in the thermoelectric conversion module.

[0003] Patent No. 4895293

[0004] In order to improve the output of the thermoelectric conversion module described in Patent Document 1, for example, it is possible to increase the thermoelectric conversion efficiency by widening the temperature difference. In Patent Document 1, methods for widening the temperature difference include, for example, thinning the P-type and N-type thermoelectric element materials and increasing the distance between the metal layers. However, in the former case, the thinner the thermoelectric element materials, the higher the electrical resistance of each thermoelectric element material. Furthermore, in the latter case, the greater the distance, the fewer elements per unit area. Therefore, simply widening the temperature difference may actually result in a decrease in the output of the thermoelectric conversion module per unit area.

[0005] In addition, to ensure stable output of power generated by the thermoelectric conversion module independent of the temperature of the heat source, it is necessary to maintain the shape of the thermoelectric conversion module and prevent uneven temperature differences. Here, the greater the distance is increased to widen the temperature difference, the more difficult it becomes to maintain the shape of the thermoelectric conversion module. Furthermore, in the thermoelectric conversion module described in Patent Document 1, the temperature of the low-temperature portion is particularly unstable, which tends to cause uneven temperature differences in the surface direction of the thermoelectric conversion module.

[0006] An object of one aspect of the present disclosure is to provide a thermoelectric conversion module that is capable of improving output per unit area and providing stable output, and a method for manufacturing the same.

[0007] A thermoelectric conversion module according to one aspect of the present disclosure and a method for manufacturing the same are as follows: [1] A substrate having a first main surface and a second main surface located opposite to the first main surface, a thermoelectric conversion unit located on the first main surface, a first thermal conduction unit and a second thermal conduction unit located on the second main surface and adjacent to each other along a first direction perpendicular to a thickness direction of the substrate, and a heat insulating member located on the second main surface at least between the first thermal conduction unit and the second thermal conduction unit, wherein the thermoelectric conversion unit has p-type thermoelectric conversion elements and n-type thermoelectric conversion elements aligned along the first direction, and a first end of the p-type thermoelectric conversion element in the first direction is longer than a first end of the n-type thermoelectric conversion element in the first direction. [2] A thermoelectric conversion module according to [1], wherein the first and second thermal conductive members are in contact with the first end and overlap the thermal insulating member in the thickness direction, the first thermal conductive member overlaps the second end of the n-type thermoelectric conversion element in the first direction in the thickness direction, the p-type thermoelectric conversion element and the n-type thermoelectric conversion element have thicknesses of 3 μm to 30 μm, and the difference in linear expansion coefficient between the first thermal conductive member and the thermal insulating member and the difference in linear expansion coefficient between the second thermal conductive member and the thermal insulating member are each 100 ppm / K or less. [3] The thermoelectric conversion module according to [1] or [2], wherein the width of each of the first thermally conductive portion and the second thermally conductive portion along the first direction is 0.5 mm or more and 1.5 mm or less. [4] The thermoelectric conversion module according to any of [1] to [3], wherein the thermal conductivity of each of the first thermally conductive portion and the second thermally conductive portion is 2.0 W / mK or more and 5.0 W / mK or less, and the thermal conductivity of the heat insulating member is 0.02 W / mK or more and 0.05 W / mK or less. [5] The thermoelectric conversion module according to any of [1] to [4], further comprising a heat dissipation member located on the second main surface, wherein the heat dissipation member surrounds the first thermally conductive portion, the second thermally conductive portion, and the heat insulating member when viewed in the thickness direction. [6] A thermoelectric conversion module according to any one of [1] to [5], wherein the thickness of each of the p-type thermoelectric conversion element and the n-type thermoelectric conversion element is 5 μm or more and 25 μm or less, and the distance between the first thermal conduction portion and the second thermal conduction portion in the first direction is 3 mm or more and less than 12 mm.[7] A thermoelectric conversion element further comprising: a first thermoelectric conversion group located on the first main surface and having a thermoelectric conversion unit; and a second thermoelectric conversion group located on the first main surface and adjacent to the first thermoelectric conversion group along a second direction perpendicular to the thickness direction and the first direction, wherein the second thermoelectric conversion group has a second thermoelectric conversion unit adjacent to the thermoelectric conversion unit along the second direction, the second thermoelectric conversion unit has a second p-type thermoelectric conversion element and a second n-type thermoelectric conversion element arranged along the first direction, and a first end of the second p-type thermoelectric conversion element in the first direction is [8] The thermoelectric conversion module according to any one of [1] to [6], further comprising: a first conductive part located on the first main surface and connected to one end of the first thermoelectric conversion group in the first direction; and a second conductive part located on the first main surface and connected to the other end of the first thermoelectric conversion group in the first direction and one end of the second thermoelectric conversion group in the first direction, wherein the first conductive part and the second conductive part have the same conductivity type. [9] A thermoelectric conversion module according to any one of [1] to [8], wherein the substrate, the thermoelectric conversion unit, the first thermal conduction unit, the second thermal conduction unit, and the heat insulating member each exhibit flexibility.

[10] A method for manufacturing a semiconductor device, comprising: a first step of forming a first thermally conductive portion, a second thermally conductive portion, and a heat insulating member on one main surface of a substrate; a second step of forming a first layer containing a p-type thermoelectric conversion material on the other main surface of the substrate; a third step of forming a p-type thermoelectric conversion layer by immersing the other main surface of the substrate in an organic solvent after the second step; and a fourth step of forming a p-type thermoelectric conversion element and an n-type thermoelectric conversion element in the part by dropping a dopant solution onto a part of the p-type thermoelectric conversion layer after the third step, wherein the first thermally conductive portion and the second thermally conductive portion are oriented in a first direction perpendicular to the thickness direction of the substrate. a first end of the p-type thermoelectric conversion element in a first direction contacts a first end of the n-type thermoelectric conversion element in the first direction and overlaps the insulating member in the thickness direction, the first thermal conduction portion overlaps a second end of the p-type thermoelectric conversion element in the first direction in the thickness direction, and the second thermal conduction portion overlaps a second end of the n-type thermoelectric conversion element in the first direction in the thickness direction, and a difference in linear expansion coefficient between the first thermal conduction portion and the insulating member and a difference in linear expansion coefficient between the second thermal conduction portion and the insulating member are each 100 ppm / K or less.

[0008] According to one aspect of the present disclosure, it is possible to provide a thermoelectric conversion module that is capable of improving output per unit area and providing stable output, and a method for manufacturing the same.

[0009] FIG. 1A is a schematic plan view showing a thermoelectric conversion module according to an embodiment, and FIG. 1B is a schematic bottom view showing a thermoelectric conversion module according to an embodiment. FIG. 2A is an enlarged view of a portion (the area surrounded by a dashed line) of FIG. 1A, and FIG. 2B is a cross-sectional view taken along line IIb-IIb of FIG. 2A. FIGS. 3A and 3B are diagrams illustrating a method for manufacturing a thermoelectric conversion module according to an embodiment. FIGS. 4A and 4B are diagrams illustrating a method for manufacturing a thermoelectric conversion module according to an embodiment. FIGS. 5A and 5B are diagrams illustrating a method for manufacturing a thermoelectric conversion module according to an embodiment. FIG. 6 is a schematic cross-sectional view showing a portion of a thermoelectric conversion module during deformation. FIG. 7A is a schematic bottom view of a thermoelectric conversion module according to a modified example, and FIG. 7B is a schematic cross-sectional view taken along line VIIb-VIIb of FIG. 7A.

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, identical elements or elements having the same functions will be designated by the same reference numerals, and duplicated explanations will be omitted. In this specification, the term "same" and similar words are not limited to "completely same."

[0011] First, the configuration of the thermoelectric conversion module according to this embodiment will be described with reference to Figures 1 and 2. Figure 1(a) is a schematic plan view showing the thermoelectric conversion module according to this embodiment, and Figure 1(b) is a schematic bottom view showing the thermoelectric conversion module according to this embodiment. Figure 2(a) is an enlarged view of a portion (the area surrounded by the dashed line) of Figure 1(a). Figure 2(b) is a cross-sectional view taken along line IIb-IIb of Figure 2(a).

[0012] The thermoelectric conversion module 1 shown in FIGS. 1A and 1B is a device capable of generating electricity by externally supplying heat. The thermoelectric conversion module 1 is a so-called in-plane device. Therefore, the thermoelectric conversion module 1 tends to be more easily processed and flexible than, for example, π-type elements (cross-plane elements). Therefore, the thermoelectric conversion module 1 can be installed, for example, along the side of a cylindrical pipe used to recover factory exhaust heat. In other words, the thermoelectric conversion module 1 can be easily installed in various locations. Therefore, the thermoelectric conversion module 1 can be used, for example, as a power source for a plant sensor that utilizes exhaust heat. In addition, the contact resistance between the thermoelectric conversion material and electrodes included in the thermoelectric conversion module 1 also tends to be lower than that of a π-type module. Hereinafter, the temperatures of each component of the thermoelectric conversion module 1 are measured under natural air convection conditions.

[0013] The thermoelectric conversion module 1 has a substrate 2, a plurality of thermoelectric conversion groups 3, a plurality of conductive parts 4, a plurality of heat conductive parts 5, and a plurality of heat insulating members 6. At least one of the substrate 2, the plurality of thermoelectric conversion groups 3, the plurality of conductive parts 4, the plurality of heat conductive parts 5, and the plurality of heat insulating members 6 exhibits flexibility.

[0014] The substrate 2 is a sheet member made of a resin that exhibits heat resistance and flexibility, and has, for example, a substantially flat plate shape. The resin that constitutes the substrate 2 is, for example, a (meth)acrylic resin, a (meth)acrylonitrile resin, a polyamide resin, a polycarbonate resin, a polyether resin, a polyester resin, an epoxy resin, an organosiloxane resin, a polyimide resin, a polysulfone resin, or the like. The thickness of the substrate 2 is, for example, 5 μm or more and 50 μm or less. The thermal conductivity of the substrate 2 is, for example, 0.1 W / mK (0.1 watts per meter per Kelvin, and 0.1 W×m －１ ×K －１ When the thermal conductivity of the substrate 2 is 0.3 W / mK or less, a temperature difference may occur inside the thermoelectric conversion group 3. The thermal conductivity of the substrate 2 is measured by a steady-state method or a non-steady-state method.

[0015] The substrate 2 has a first main surface 2a and a second main surface 2b located on the opposite side of the first main surface 2a. The first main surface 2a and the second main surface 2b are surfaces that intersect with the direction along the thickness of the substrate 2. The shapes of the first main surface 2a and the second main surface 2b are not particularly limited, and may be, for example, polygonal, circular, elliptical, etc. Hereinafter, the direction along the thickness of the substrate 2 will be simply referred to as the thickness direction D1. Viewing from the thickness direction D1 corresponds to a planar view. Furthermore, directions perpendicular to the thickness direction D1 will be referred to as the first direction D2 and the second direction D3.

[0016] A thermoelectric conversion region R1 and two conductive regions R2 are defined on the first main surface 2a. A plurality of thermoelectric conversion groups 3 are provided in the thermoelectric conversion region R1. A plurality of conductive portions 4 are provided in each conductive region R2. The thermoelectric conversion region R1 is located between the two conductive regions R2 in the first direction D2. The larger the proportion of the first main surface 2a occupied by the thermoelectric conversion region R1, the higher the output of the thermoelectric conversion module 1 tends to be. In a plan view, the proportion of the area occupied by the thermoelectric conversion region R1 of the first main surface 2a is, for example, 50% to 90%. Furthermore, in a plan view, the proportion of the area occupied by the two conductive regions R2 of the first main surface 2a is, for example, 5% to 30%. In this case, the thermoelectric conversion module 1 can produce good output while reliably forming conductive paths connecting the thermoelectric conversion groups 3.

[0017] Each of the thermoelectric conversion groups 3 is capable of generating electricity when heat is supplied from the outside and is located on the first main surface 2a. The thermoelectric conversion groups 3 extend along the first direction D2 and are arranged along the second direction D3. Each of the thermoelectric conversion groups 3 has a strip shape when viewed from the thickness direction D1. The thermoelectric conversion groups 3 are spaced apart from each other but electrically connected to each other in series. In the first direction D2, one end of each thermoelectric conversion group 3 is connected to one of the conductive parts 4 included in one conductive region R2, and the other end of each thermoelectric conversion group 3 is connected to one of the conductive parts 4 included in the other conductive region R2. Each of the thermoelectric conversion groups 3 has multiple thermoelectric conversion units 11. In this embodiment, each thermoelectric conversion group 3 has ten thermoelectric conversion units 11, but this is not limited to this. In each thermoelectric conversion group 3, the multiple thermoelectric conversion units 11 are arranged along the first direction D2. Two thermoelectric conversion units 11 adjacent to each other in the first direction D2 are in contact with each other and are connected in series.

[0018] Hereinafter, of the two thermoelectric conversion groups 3 shown in FIG. 2A, one thermoelectric conversion group 3 may be referred to as the first thermoelectric conversion group 3a, and the other thermoelectric conversion group 3 adjacent to the first thermoelectric conversion group 3a along the second direction D3 may be referred to as the second thermoelectric conversion group 3b. Furthermore, the thermoelectric conversion units 11 included in the first thermoelectric conversion group 3a may be referred to as the first thermoelectric conversion unit 11a, and the thermoelectric conversion units 11 included in the second thermoelectric conversion group 3b may be referred to as the second thermoelectric conversion unit 11b. The first thermoelectric conversion units 11a included in the first thermoelectric conversion group 3a are arranged in order along the first direction D2, and the second thermoelectric conversion units 11b included in the second thermoelectric conversion group 3b are arranged in order along the first direction D2. The first thermoelectric conversion units 11a and the second thermoelectric conversion units 11b are adjacent to each other along the second direction D3.

[0019] Each of the multiple thermoelectric conversion units 11 is a flexible portion of the thermoelectric conversion module 1 where thermoelectric conversion is performed. The shape of the thermoelectric conversion unit 11 in a plan view is not particularly limited, and may be, for example, a polygonal, circular, or elliptical shape. The p-type thermoelectric conversion elements 21 and the n-type thermoelectric conversion elements 22 have the same shape, but are not limited to this. Each thermoelectric conversion unit 11 has the p-type thermoelectric conversion elements 21 and the n-type thermoelectric conversion elements 22 arranged along the first direction D2. In each thermoelectric conversion unit 11, the first end 21 a of the p-type thermoelectric conversion element 21 in the first direction D2 and the first end 22 a of the n-type thermoelectric conversion element 22 in the first direction D2 are in contact with each other. In each thermoelectric conversion unit 11, the second end 21b of the p-type thermoelectric conversion element 21 in the first direction D2 is located at one end of the corresponding thermoelectric conversion unit 11, and the second end 22b of the n-type thermoelectric conversion element 22 in the first direction D2 is located at the other end of the corresponding thermoelectric conversion unit 11. In two thermoelectric conversion units 11 adjacent to each other in the first direction D2, the second end 21b of the p-type thermoelectric conversion element 21 included in one thermoelectric conversion unit 11 and the second end 22b of the n-type thermoelectric conversion element 22 included in the other thermoelectric conversion unit 11 come into contact with each other.

[0020] In each of the multiple thermoelectric conversion groups 3, the p-type thermoelectric conversion elements 21 and the n-type thermoelectric conversion elements 22 are arranged alternately in the first direction D2. As shown in Fig. 2A, in this embodiment, the p-type thermoelectric conversion elements 21 of the first thermoelectric conversion unit 11a are adjacent to the n-type thermoelectric conversion elements 22 (second n-type thermoelectric conversion elements) of the second thermoelectric conversion unit 11b in the second direction D3, and the n-type thermoelectric conversion elements 22 of the first thermoelectric conversion unit 11a are adjacent to the p-type thermoelectric conversion elements 21 (second p-type thermoelectric conversion elements) of the second thermoelectric conversion unit 11b in the second direction D3.

[0021] The p-type thermoelectric conversion element 21 is provided on the first main surface 2a of the substrate 2 and is in contact with the n-type thermoelectric conversion element 22. The thickness T1 of the p-type thermoelectric conversion element 21 is, for example, 3 μm or more and 30 μm or less. When the thickness T1 is 3 μm or more, the electrical resistance of the p-type thermoelectric conversion element 21 can be effectively reduced. When the thickness T1 is 30 μm or less, a temperature gradient can be easily formed inside the p-type thermoelectric conversion element 21. The thickness T1 may be 5 μm or more, 8 μm or more, 10 μm or more, 25 μm or less, 20 μm or less, or 15 μm or less. The length L1 of the p-type thermoelectric conversion element 21 in the first direction D2 is, for example, 2 mm or more and 10 mm or less. In this case, a temperature gradient can be easily formed inside the p-type thermoelectric conversion element 21. The length of the p-type thermoelectric conversion element 21 in the second direction D3 is, for example, 5 mm or more and 30 mm or less. In this case, a sufficient number of thermoelectric conversion portions 11 can be formed on the first main surface 2a. The thermal conductivity of the p-type thermoelectric conversion element 21 in the in-plane direction is, for example, 0.01 W / mK or more and 40.0 W / mK or less. The thermal conductivity of the p-type thermoelectric conversion element 21 in the in-plane direction is measured, for example, by an optical alternating current method or a 3 omega method. The p-type thermoelectric conversion element 21 is formed, for example, by various dry or wet methods. Wet methods include, for example, a doctor blade method, a dip coating method, a spray coating method, a spin coating method, and an inkjet method.

[0022] The p-type thermoelectric conversion element 21 is, for example, a p-type semiconductor layer. The p-type thermoelectric conversion element 21 includes, for example, carbon nanotubes (CNTs) and a conductive resin different from the carbon nanotubes. The carbon nanotubes are p-type. The carbon nanotubes may be single-walled, double-walled, or multi-walled. From the viewpoint of the electrical conductivity of the p-type thermoelectric conversion element 21, single-walled carbon nanotubes (SWCNTs) may be used. The proportion of single-walled carbon nanotubes relative to the total amount of carbon nanotubes may be 25% by mass or more, 50% by mass or more, or 100% by mass. The diameter of the single-walled carbon nanotubes is not particularly limited, but may be, for example, 20 nm or less, 10 nm or less, or 3 nm or less. The lower limit of the diameter of the single-walled carbon nanotubes is also not particularly limited, but may be 0.4 nm or more, or 0.5 nm or more. The thermal conductivity of the carbon nanotubes is, for example, 30 W / mK or more and 40 W / mK or less.

[0023] In this specification, the diameter of a single-walled carbon nanotube is determined by Raman spectroscopy to be 100 to 300 cm －１ The wave number of the peak that appears in －１ )), the diameter can be calculated using the formula "diameter (nm) = 248 / ω". The G / D ratio in laser Raman spectroscopy is known as a method for evaluating single-walled carbon nanotubes. In this embodiment, the single-walled carbon nanotubes may have a G / D ratio of 10 or more, or 20 or more, in laser Raman spectroscopy at a wavelength of 532 nm. By using such single-walled carbon nanotubes, a p-type thermoelectric conversion element 21 with even better electrical conductivity tends to be obtained. The upper limit of the G / D ratio is not particularly limited, and may be 500 or less, or 300 or less.

[0024] The content of carbon nanotubes in the p-type thermoelectric conversion element 21 may be, for example, 20 parts by mass or more, 30 parts by mass or more, 40 parts by mass or more, 99 parts by mass or less, 95 parts by mass or less, or 90 parts by mass or less, per 100 parts by mass of the material (p-type thermoelectric conversion material) constituting the p-type thermoelectric conversion element 21.

[0025] The conductive resin of this embodiment is not particularly limited, and known conductive resins can be used without particular limitation. Examples of conductive resins include polyaniline-based conductive resins, polythiophene-based conductive resins, polypyrrole-based conductive resins, polyacetylene-based conductive resins, polyphenylene-based conductive resins, and polyphenylene vinylene-based conductive resins. An example of a polythiophene-based conductive resin is poly(3,4-ethylenedioxythiophene) (PEDOT). In this embodiment, the conductive resin contains PEDOT and an electron acceptor. In this case, the electrical conductivity of the p-type thermoelectric conversion element 21 tends to be higher. Examples of the electron acceptor include polystyrene sulfonic acid, polyvinyl sulfonic acid, poly(meth)acrylic acid, polyvinyl sulfonic acid, toluenesulfonic acid, dodecylbenzenesulfonic acid, camphorsulfonic acid, bis(2-ethylhexyl) sulfosuccinate, chlorine, bromine, iodine, phosphorus pentafluoride, arsenic pentafluoride, boron trifluoride, hydrogen chloride, sulfuric acid, nitric acid, tetrafluoroboric acid, perchloric acid, iron(III) chloride, tetracyanoquinodimethane, etc. From the viewpoint of the electrical conductivity of the p-type thermoelectric conversion element 21, the electron acceptor may be polystyrene sulfonic acid (PSS).

[0026] The carbon nanotubes and the conductive resin may be aggregated in the p-type thermoelectric conversion element 21. The p-type thermoelectric conversion element 21 may include a porous structure in which the carbon nanotubes are bonded to each other by the conductive resin.

[0027] The n-type thermoelectric conversion elements 22 are provided on the first main surface 2a of the substrate 2 and are in contact with the p-type thermoelectric conversion elements 21. The thickness of the n-type thermoelectric conversion elements 22 is the same as or substantially the same as the thickness T1 of the p-type thermoelectric conversion elements 21. The length of the n-type thermoelectric conversion elements 22 in the first direction D2 is the same as or substantially the same as the length L1 of the p-type thermoelectric conversion elements 21. The length of the n-type thermoelectric conversion elements 22 in the second direction D3 is, for example, 2 mm or more and 10 mm or less. In this case, a sufficient number of thermoelectric conversion sections 11 can be formed on the first main surface 2a. The thermal conductivity of the n-type thermoelectric conversion elements 22 in the in-plane direction is, for example, 0.01 W / mK or more and 40.0 W / mK or less. The thermal conductivity of the n-type thermoelectric conversion elements 22 in the in-plane direction is measured, for example, by an optical alternating current method or a 3 omega method. The n-type thermoelectric conversion element 22 is formed by, for example, various dry or wet methods, similar to the p-type thermoelectric conversion element 21 .

[0028] The n-type thermoelectric conversion element 22 is, for example, an n-type semiconductor layer. The n-type thermoelectric conversion element 22 includes, for example, a composite of multiple organic materials or a composite of an inorganic material and an organic material. In this embodiment, the n-type thermoelectric conversion element 22 is a portion of the p-type thermoelectric conversion element 21 that exhibits n-type conductivity by containing a dopant. Therefore, the n-type thermoelectric conversion element 22 includes carbon nanotubes, a conductive resin, and a dopant. In this embodiment, the dopant refers to a substance that changes the Seebeck coefficient of the portion doped with the dopant. "Changing the Seebeck coefficient" refers to decreasing the Seebeck coefficient value or changing the Seebeck coefficient value from a positive value to a negative value. A thermoelectric conversion material that exhibits a positive Seebeck coefficient has p-type conductivity, and a thermoelectric conversion material that exhibits a negative Seebeck coefficient has n-type conductivity.

[0029] The dopant of this embodiment contains, for example, a coordination compound that can dissociate into an anion (hereinafter simply referred to as "anion"), which is a complex ion, and an alkali metal cation (hereinafter simply referred to as "cation"), and a cation scavenger (hereinafter simply referred to as "scavenger"). Within the n-type thermoelectric conversion element 22, at least a portion of the coordination compound may be dissociated into the anion and the cation. In this case, the cation may be captured by the scavenger. The dopant may contain multiple types of at least one of the coordination compound and the scavenger. The Seebeck coefficient changes in the portion of the p-type thermoelectric conversion element 21 that contains the dopant. This results in the formation of an n-type thermoelectric conversion element 22 in the portion.

[0030] The reason for the above-described effect is not particularly limited, but one possible reason is that the scavenger contained in the dopant captures cations, dissociating anions, and the anions convert the carriers of the carbon nanotubes from holes to electrons. In this embodiment, the anions are complex ions with a metal atom at their center, and it is believed that the interaction between the metal atom and the carbon nanotubes significantly converts the anions to n-type. Furthermore, the complex ions have a large ion size, which is believed to favorably dissociate the cations captured by the scavenger, which is another possible reason for the above-described effect. In the dopant of this embodiment, the anions are complex ions. Therefore, the n-type thermoelectric conversion element 22 contains metal atoms derived from the complex ions. Therefore, in this embodiment, the metal atoms remaining in the n-type thermoelectric conversion element 22 can function as an antioxidant.

[0031] The complex ion (anion) obtained by dissociation of the coordination compound may be selected from the group consisting of ferrocyanide ion, ferricyanide ion, tetrachloroferrate(III) ion, tetrachloroferrate(II) ion, tetracyanonickelate(II) ion, tetrachloronickelate(II) ion, tetracyanocobaltate(II) ion, tetrachlorocobaltate(II) ion, tetracyanocuprate(I) ion, tetrachlorocuprate(II) ion, hexacyanochromate(III) ion, tetrahydroxidezincate(II) ion, and tetrahydroxidealuminate(III) ion. Among these, ferrocyanide ion is preferred. When the anion is ferrocyanide ion, a material with better properties can be obtained. Furthermore, when the anion is ferrocyanide ion, the iron atoms remaining in the n-type thermoelectric conversion element 22 function favorably as an antioxidant, which tends to further suppress changes in physical properties over time and improve storage stability.

[0032] The anion may include an iron atom. That is, the coordination compound may include an iron atom. In this case, the anion may be selected from the group consisting of, for example, a ferrocyanide ion, a ferricyanide ion, a tetrachloroferrate(III) ion, and a tetrachloroferrate(II) ion. From the viewpoint of the characteristics of the n-type thermoelectric conversion element 22, the anion including an iron atom may be a ferrocyanide ion. From the viewpoint of the antioxidant effect, the content of iron atoms in the n-type thermoelectric conversion element 22 may be 0.001% by mass or more and 15% by mass or less, 0.005% by mass or more and 12% by mass or less, or 0.01% by mass or more and 10% by mass or less. The content of iron atoms in the n-type thermoelectric conversion element 22 indicates a value measured, for example, by ICP atomic emission spectrometry.

[0033] The coordination compound may be a complex salt. Examples of the complex salt include potassium ferrocyanide, sodium ferrocyanide, potassium ferricyanide, sodium ferricyanide, potassium tetrachloroferrate(III), sodium tetrachloroferrate(III), potassium tetrachloroferrate(II), and sodium tetrachloroferrate(II). The complex salt may be a hydrate.

[0034] Examples of alkali metal cations obtained by dissociation of the coordination compound include sodium ions, potassium ions, lithium ions, etc. The coordination compound preferably contains at least one of a ferrocyanide compound and a ferricyanide compound.

[0035] The cation scavenger is not particularly limited as long as it has the ability to capture cations. Examples of cation scavenger include crown ether compounds, cyclodextrin, calixarene, ethylenediaminetetraacetic acid, porphyrin, phthalocyanine, and derivatives thereof. In this embodiment, the cation scavenger is a crown ether compound. Examples of crown ether compounds include 15-crown-5-ether, 18-crown-6-ether, 12-crown-4-ether, benzo-18-crown-6-ether, benzo-15-crown-5-ether, and benzo-12-crown-4-ether. The ring size of the crown ether used as the scavenger can be selected according to the size of the metal ion to be captured. For example, when the metal ion is a potassium ion, the crown ether compound may be an 18-membered ring crown ether. When the metal ion is a sodium ion, the crown ether compound may be a 15-membered ring crown ether. When the metal ion is a lithium ion, the crown ether compound may be a 12-membered ring crown ether.

[0036] The crown ether compound may contain a benzene ring. In this case, the stability of the crown ether compound may be improved. Examples of crown ether compounds having a benzene ring include benzo-18-crown-6-ether, benzo-15-crown-5-ether, and benzo-12-crown-4-ether.

[0037] Cation content C １ The content of the scavenger C ２ The molar ratio (C ２ / C １ ) may be 0.1 or more and 5 or less, 0.3 or more and 3 or less, or 0.5 or more and 2 or less.

[0038] In each of the multiple thermoelectric conversion units 11, the mass ratio of carbon nanotubes to the total mass of the thermoelectric conversion units 11 is, for example, 30% or more and 70% or less. When the mass ratio is 30% or more, the thermoelectric conversion units 11 can have good electrical conductivity. When the mass ratio is 70% or less, the temperature difference within the thermoelectric conversion units 11 is likely to be large. The mass ratio may be 35% or more, 40% or more, 45% or more, or 50% or more. The mass ratio may be 65% or less, 60% or less, or 55% or less. The mass ratio of carbon nanotubes to the total mass of the p-type thermoelectric conversion elements 21 may be 30% or more and 70% or less, and the mass ratio of carbon nanotubes to the total mass of the n-type thermoelectric conversion elements 22 may be 30% or more and 70% or less. In each of the plurality of thermoelectric conversion groups 3, the mass ratio of the carbon nanotubes to the total mass of the thermoelectric conversion group 3 may be 30% or more and 70% or less, or 40% or more and 60% or less. The internal temperature difference of the thermoelectric conversion unit 11, etc. is measured using, for example, thermography.

[0039] Each of the plurality of conductive portions 4 is a conductive portion located on the first principal surface 2a and connected to a corresponding thermoelectric conversion group 3. Each conductive portion 4 may be a semiconductor rather than a conductor. The thickness of each conductive portion 4 is the same as or substantially the same as the thickness T1 of the p-type thermoelectric conversion element 21. The conductivity of each conductive portion 4 may be equal to or greater than the conductivity of the p-type thermoelectric conversion element 21. The thermal conductivity of each conductive portion 4 may be equal to or greater than the thermal conductivity of the p-type thermoelectric conversion element 21. At least some of the plurality of conductive portions 4 may have a single-layer structure or a multilayer structure. For example, at least some of the plurality of conductive portions 4 may have an organic conductive layer and a metal conductive layer located on the organic conductive layer. In this embodiment, the plurality of conductive portions 4 are formed from the same material as the p-type thermoelectric conversion element 21. Therefore, each conductive portion 4 has the same conductivity type (p-type).

[0040] The plurality of conductive parts 4 have first conductive parts 4a that function as terminals for connecting to the external device and second conductive parts 4b that function as conductive paths connecting adjacent thermoelectric conversion groups 3. The plurality of conductive parts 4 have two first conductive parts 4a, and the two first conductive parts 4a are located within one conductive region R2. The other conductive region R2 is provided with only the second conductive part 4b. The plurality of thermoelectric conversion groups 3 are connected in series with each other via the plurality of second conductive parts 4b. Therefore, when the thermoelectric conversion module 1 is performing thermoelectric conversion, current can flow in series from one first conductive part 4a to the other first conductive part 4a. For example, one first conductive part 4a located in one conductive region R2 is connected to one end of the first thermoelectric conversion group 3a in the first direction D2, and one second conductive part 4b located in the other conductive region R2 is connected to the other end of the first thermoelectric conversion group 3a and one end of the second thermoelectric conversion group 3b in the first direction D2.

[0041] The multiple heat conductive portions 5 are portions exhibiting a higher thermal conductivity than the substrate 2 and are located on the second main surface 2b. At least a portion of the multiple heat conductive portions 5 overlaps the thermoelectric conversion group 3 (i.e., the thermoelectric conversion portion 11) in the thickness direction D1. More specifically, at least a portion of the multiple heat conductive portions 5 overlaps the edges of the thermoelectric conversion portion 11. On the other hand, each heat conductive portion 5 does not overlap the center of the thermoelectric conversion portion 11. This allows for a favorable temperature gradient to be generated within the thermoelectric conversion portion 11 along the first direction D2. The multiple heat conductive portions 5 are spaced apart from one another along the first direction D2 and have a band shape extending along the second direction in plan view. The shape of each heat conductive portion 5 in plan view is not particularly limited and may be, for example, a polygonal shape, a circular shape, an elliptical shape, or the like. Each heat conductive portion 5 includes, for example, a metal (silver, copper, etc.), carbon, or a resin (e.g., silicone resin, epoxy resin, or (meth)acrylic resin). Each thermally conductive portion 5 may contain a ceramic such as boron nitride or aluminum nitride, which exhibits high thermal conductivity. From the viewpoint of manufacturing efficiency, each thermally conductive portion 5 may contain the above-mentioned resin. In this case, the thermally conductive portion 5 may be formed using the resin or a solution containing the resin.

[0042] The thermal conductivity of each heat conductive portion 5 is, for example, 1 W / mK or more and 400 W / mK or less. This allows for good heat transfer to the thermoelectric conversion portion 11 via the multiple heat conductive portions 5 when the thermoelectric conversion module 1 is heated. The thermal conductivity may be, for example, 2.0 W / mK or more, 3.0 W / mK or more, 5.0 W / mK or more, or 10.0 W / mK or more. In this embodiment, the thermal conductivity of each heat conductive portion 5 is 2.0 W / mK or more and 5.0 W / mK or less, but is not limited thereto. The thermal conductivity of each heat conductive portion 5 is measured by a steady-state method or a transient method. The linear expansion coefficient of each heat conductive portion 5 in the in-plane direction is, for example, 100 ppm / K or more and 200 ppm / K or less. The linear expansion coefficient of each heat conductive portion 5 is measured, for example, by thermomechanical analysis (TMA).

[0043] The length T2 of each heat conductive portion 5 along the thickness direction D1 is, for example, 50 μm or more and 2000 μm or less. The width L2 of each heat conductive portion 5 along the first direction D2 is, for example, 0.5 mm or more and 2.0 mm or less. In these cases, the heat conductive function of each heat conductive portion 5 can be satisfactorily exhibited. Between two adjacent heat conductive portions 5, the spacing S along the first direction D2 is greater than the length L1 of the p-type thermoelectric conversion element 21 in the first direction D2 and the length of the n-type thermoelectric conversion element 22 in the first direction D2, and is 3 mm or more and 15 mm or less. The spacing S may be 4 mm or more, 5 mm or more, 6 mm or more, 12 mm or less, 10 mm or less, or 8 mm or less. Alternatively, the spacing S may be less than 12 mm or less.

[0044] 2B, one of the two heat conductive portions 5 may be referred to as the first heat conductive portion 5a, and the other heat conductive portion 5 adjacent to the first heat conductive portion 5a along the first direction D2 may be referred to as the second heat conductive portion 5b. In this case, in the thickness direction D1, the first heat conductive portion 5a overlaps one end of the first thermoelectric conversion portion 11a in the first direction D2. Also, in the thickness direction D1, the second heat conductive portion 5b overlaps the other end of the first thermoelectric conversion portion 11a in the first direction D2. More specifically, in the thickness direction D1, the first heat conductive portion 5a overlaps the second end 22b of the n-type thermoelectric conversion element 22 included in the first thermoelectric conversion portion 11a, and the second heat conductive portion 5b overlaps the second end 21b of the p-type thermoelectric conversion element 21 included in the first thermoelectric conversion portion 11a. Also, as shown in (a) of Figure 2, in the thickness direction D1, the first thermal conduction portion 5a overlaps the second end portion 21b of the p-type thermoelectric conversion element 21 included in the second thermoelectric conversion portion 11b, and the second thermal conduction portion 5b overlaps the second end portion 22b of the n-type thermoelectric conversion element 22 included in the second thermoelectric conversion portion 11b.

[0045] The multiple heat insulating members 6 are portions exhibiting a thermal conductivity equal to or lower than that of the substrate 2 and are located on the second main surface 2b. Each of the multiple heat insulating members 6 is located between the corresponding first heat conducting portion 5a and second heat conducting portion 5b. The multiple heat insulating members 6 are spaced apart from one another along the first direction D2. The shape of each heat insulating member 6 in plan view is not particularly limited, and may be, for example, a polygonal, circular, or elliptical shape. In this embodiment, each heat insulating member 6 has a strip shape extending along the second direction in plan view and contacts both the corresponding first heat conducting portion 5a and second heat conducting portion 5b. Therefore, in this embodiment, the width of each heat insulating member 6 along the first direction D2 corresponds to the interval S. The length T3 of each heat insulating member 6 along the thickness direction D1 is shorter than the length T2 of each heat conducting portion 5. For example, the length T3 is 80% or less, or 70% or less, of the length T2. In this case, the heat insulating member 6 is less likely to peel off from the substrate 2 when the thermoelectric conversion module 1 deforms.

[0046] At least a portion of each of the multiple heat insulating members 6 overlaps the center of the corresponding thermoelectric conversion unit 11 in the thickness direction D1. In other words, in each thermoelectric conversion unit 11, the first end 21a of the p-type thermoelectric conversion element 21 and the first end 22a of the n-type thermoelectric conversion element 22 overlap at least a portion of each of the multiple heat insulating members 6 in the thickness direction D1. This stabilizes the temperature at the center of each thermoelectric conversion unit 11, which tends to stabilize the temperature gradient inside the thermoelectric conversion unit 11 along the first direction D2. Therefore, the range of variation in the temperature difference inside each thermoelectric conversion unit 11 over a predetermined period can be, for example, 2.5°C or less, 2.0°C or less, or 1.0°C or less. The range of variation in the temperature difference of the thermoelectric conversion unit 11 can be obtained by measuring the changes over time in each of the high-temperature region of the thermoelectric conversion unit 11 (e.g., both ends of the thermoelectric conversion unit 11 in the first direction D2) and the low-temperature region of the thermoelectric conversion unit 11 (e.g., the center of the thermoelectric conversion unit 11 in the first direction D2). The predetermined period is not particularly limited, but is, for example, from 10 seconds to 100 hours.

[0047] Each heat insulating member 6 includes, for example, cellulose nanofiber (CNF), silica aerogel, resin (e.g., silicone), etc. Each heat insulating member 6 may be a foam. The thermal conductivity of each heat insulating member 6 is, for example, 0.01 W / mK or more and 0.1 W / mK or less. The thermal conductivity may be 0.02 W / mK or more, 0.03 W / mK or more, 0.08 W / mK or less, or 0.05 W / mK or less. In this embodiment, the thermal conductivity of each heat insulating member 6 is, for example, 0.02 W / mK or more and 0.05 W / mK or less, but is not limited thereto. The linear expansion coefficient of each heat insulating member 6 is, for example, 200 ppm / K or less. The linear expansion coefficient of each heat insulating member 6 is measured, for example, by thermomechanical analysis (TMA). The difference between the linear expansion coefficient of each heat conductive portion 5 and the linear expansion coefficient of each heat insulating member 6 is, for example, 100 ppm / K or less. As a result, even if the thermoelectric conversion module 1 is attached to a heat source in a deformed state, the thermoelectric conversion module 1 will not come off the heat source and can generate electricity while maintaining a stable temperature gradient. The difference may be 80 ppm / K or less, 50 ppm / K or less, or 10 ppm / K or less.

[0048] The thermoelectric conversion module 1 may further include configurations other than those described above. For example, the thermoelectric conversion module 1 may include wiring for electrically connecting other thermoelectric conversion modules, wiring for extracting power to an external circuit, and the like.

[0049] Next, an example of a method for manufacturing the thermoelectric conversion module 1 according to this embodiment will be described with reference to Figures 3 to 5. Figures 3(a) and 3(b), Figures 4(a) and 4(b), and Figures 5(a) and 5(b) are diagrams for explaining the method for manufacturing the thermoelectric conversion module according to this embodiment.

[0050] First, as shown in Figures 3(a) and 3(b), a plurality of thermally conductive portions 5 and a plurality of thermal insulating members 6 are formed on the second main surface 2b (one of the main surfaces) of a substrate 2 prepared in advance (first step). In the first step, a highly thermally conductive material and a thermal insulating material are applied to the second main surface 2b by a known method, such as an inkjet method, a dispensing method, a doctor blade method, or a screen printing method. The highly thermally conductive material and the thermal insulating material may be applied simultaneously or at different times. Next, the highly thermally conductive material and the thermal insulating material are cured by heating, thereby forming a plurality of thermally conductive portions 5 and a thermal insulating member 6 on the second main surface 2b.

[0051] Next, as shown in FIG. 4A , a first layer 41 is formed on the first main surface 2 a (the other main surface) (second step). In the second step, a dispersion is first dropped onto the first main surface 2 a by a known method, such as an inkjet method, a dispensing method, a doctor blade method, a screen printing method, a casting method, a dip coating method, or a spray coating method. The dispersion is then dried to form the first layer 41. For example, the substrate 2 is heated by placing it in a blower dryer set to a temperature of 25° C. to 90° C. for 10 minutes to 21,600 minutes. This dries the dispersion to form the first layer 41.

[0052] The dispersion liquid used in the second step is, for example, a liquid in which a p-type thermoelectric conversion material is dispersed. In this embodiment, the dispersion liquid is a liquid in which carbon nanotubes and a conductive resin are dispersed. The content of carbon nanotubes in the dispersion liquid is, for example, 25% by mass or more, 30% by mass or more, 35% by mass or more, or 40% by mass or more, and 80% by mass or less, 75% by mass or less, 70% by mass or less, or 60% by mass or less, based on the total amount of the conductive resin and the carbon nanotubes. In this case, a temperature difference is likely to occur in the first layer 41, and the electrical conductivity of the first layer 41 tends to be increased. Furthermore, in each of the multiple thermoelectric conversion units 11 described below, the mass ratio of carbon nanotubes to the total mass of the thermoelectric conversion units 11 is easily adjusted to 30% by mass or more and 70% by mass or less. The total mass concentration of the carbon nanotubes and the conductive resin in the dispersion is, for example, 0.05% by mass or more, 0.06% by mass or more, 0.07% by mass or more, 0.10% by mass or more, 0.12% by mass or more, or 0.15% by mass or more. The total mass concentration of the carbon nanotubes and the conductive resin in the dispersion may be 10% by mass or less, or 2% by mass or less. The dispersion used in the second step is, for example, a mixed liquid formed by mixing a first liquid containing carbon nanotubes with a second liquid containing a conductive resin. Note that the content of carbon nanotubes in the dispersion based on the total amount of the conductive resin and the carbon nanotubes is substantially equal to the mass ratio of carbon nanotubes to the total mass of the thermoelectric conversion unit 11. Therefore, in this specification, the content of carbon nanotubes in the dispersion based on the total amount of the conductive resin and the carbon nanotubes can be considered to be the mass ratio of carbon nanotubes to the total mass of the thermoelectric conversion unit 11.

[0053] The first liquid contains, for example, carbon nanotubes and a first solvent. The concentration of carbon nanotubes in the first liquid is, for example, 0.01% by mass or more and 10% by mass or less. The first solvent may be any solvent capable of dispersing carbon nanotubes, such as a polar liquid or an aqueous solvent. The aqueous solvent is water or a mixed solvent of water and an organic solvent. The first solvent may be a protic solvent or an aprotic solvent. Specific examples of the first solvent include water, alcohols (e.g., methanol, ethanol), amides (e.g., N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone), ketones (e.g., acetone, methyl ethyl ketone), glycols (e.g., ethylene glycol, diethylene glycol), dimethyl sulfoxide, acetonitrile, etc. Among these, one or more members of the group consisting of water, methanol, ethanol, N-methylpyrrolidone, and dimethyl sulfoxide are preferred, and water is more preferred. The first liquid may further contain additives such as a surfactant and an organic binder.

[0054] The second liquid includes, for example, a conductive resin (PEDOT / PSS) composed of PEDOT and PSS, and a second solvent. The PEDOT / PSS content ratio is not particularly limited. The PSS to PEDOT ratio (mass ratio) is, for example, 1 or more, 1.25 or more, or 1.5 or more, and 30 or less, or 20 or less. The second solvent may be any solvent capable of dispersing PEDOT / PSS, such as a polar liquid or an aqueous solvent. The second solvent may be a protic solvent or an aprotic solvent. Specific examples of the second solvent are the same as those of the first solvent. Among these, one or more solvents from the group consisting of water, methanol, and ethanol are preferred, with water being more preferred. In one embodiment, the second liquid may be an aqueous dispersion of PEDOT / PSS. The second solvent may be used singly or in combination. The second liquid may further contain various additives.

[0055] Next, as shown in FIG. 4B , the substrate 2 is immersed in an organic solvent to form a p-type thermoelectric conversion layer 42 (third step). In this embodiment, after the second step, the first main surface 2 a of the substrate 2 is immersed in dimethyl sulfoxide (DMSO), which is the organic solvent (immersion treatment). For example, the first main surface 2 a of the substrate 2 is immersed in dimethyl sulfoxide set to room temperature for 1 minute to 7,200 minutes. After the immersion treatment, the substrate 2 may be heated in a blower dryer. For example, the substrate 2 is heated by placing it in a blower dryer set to 25° C. to 90° C. for 10 minutes to 21,600 minutes. This results in a patterned p-type thermoelectric conversion layer 42. A portion of the p-type thermoelectric conversion layer 42 will later become the n-type thermoelectric conversion elements 22. Another portion of the p-type thermoelectric conversion layer 42 will later become the p-type thermoelectric conversion elements 21. Yet another part of the p-type thermoelectric conversion layer 42 will later become the conductive portion 4 .

[0056] Next, as shown in FIG. 5A , after the third step, a dopant-containing solution (dopant solution 51) is dropped onto a portion 42a of the p-type thermoelectric conversion layer 42 to form p-type thermoelectric conversion elements 21 and n-type thermoelectric conversion elements 22 in the portion 42a (fourth step). In the fourth step, the portion 42a of the p-type thermoelectric conversion layer 42 is impregnated with the dopant solution 51 by a known method, such as an inkjet method or a dispensing method. In this embodiment, regions of the p-type thermoelectric conversion layer 42 to which the dopant solution 51 has been dropped alternate with regions to which the dopant solution 51 has not been dropped. Next, the dopant solution 51 is dried to convert the portion 42a into the n-type thermoelectric conversion elements 22. For example, the substrate 2 is heated by placing it on a hot plate set to a temperature of 25° C. to 90° C. for 10 minutes to 21,600 minutes. This dries the dopant solution 51. The solvent contained in the dopant solution 51 is, for example, water, acetonitrile, ethanol, ethylene glycol, dimethyl sulfoxide (DMSO), N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, etc. Furthermore, the portions of the p-type thermoelectric conversion layer 42 onto which the dopant solution 51 has not been dropped become the p-type thermoelectric conversion elements 21 or the conductive portions 4, as shown in FIG. 5(b). In this manner, a thermoelectric conversion module 1 having a plurality of thermoelectric conversion portions 11 formed thereon is formed.

[0057] Next, the effects achieved by the thermoelectric conversion module 1 formed by the manufacturing method according to the present embodiment described above will be described.

[0058] The thermoelectric conversion module 1 according to this embodiment has a first thermally conductive portion 5a and a second thermally conductive portion 5b located on the second main surface 2b. In the thickness direction D1, the first thermally conductive portion 5a overlaps the second end portion 22b of the n-type thermoelectric conversion element 22 included in the first thermoelectric conversion unit 11a, and the second thermally conductive portion 5b overlaps the second end portion 21b of the p-type thermoelectric conversion element 21 included in the first thermoelectric conversion unit 11a. Furthermore, a heat insulating member 6 is provided on the second main surface 2b and is located between the first thermally conductive portion 5a and the second thermally conductive portion 5b. As a result, the first thermally conductive portion 5a and the second thermally conductive portion 5b overlap both ends of the first thermoelectric conversion unit 11a in the thickness direction D1, but do not overlap the center of the first thermoelectric conversion unit 11a. Therefore, for example, by heating the first thermally conductive portion 5a and the second thermally conductive portion 5b, an internal temperature difference can be effectively generated between the p-type thermoelectric conversion element 21 and the n-type thermoelectric conversion element 22. Here, the thickness T1 of the p-type thermoelectric conversion element 21 (and the thickness of the n-type thermoelectric conversion element 22) is 3 μm or more and 30 μm or less. By keeping the thickness T1 within this range, an increase in the number of elements per unit area and the internal resistance of the elements can be suppressed. Additionally, at least a portion of the heat insulating member 6 overlaps the center of the thermoelectric conversion unit 11 in the thickness direction D1. This allows the temperature of the center of the thermoelectric conversion unit 11, which becomes relatively low during heating, to be stabilized. Therefore, uneven temperature differences within the thermoelectric conversion unit 11 are less likely to occur. Furthermore, the difference in linear expansion coefficient between the first thermally conductive portion 5a and the second thermally conductive portion 5b and the heat insulating member 6 is 100 ppm / K or less. As a result, even when the thermoelectric conversion module 1 is attached to a heat source in a deformed state, the thermoelectric conversion module 1 can generate power while maintaining a stable temperature gradient without peeling off from the heat source. Therefore, by adopting the thermoelectric conversion module 1 according to this embodiment, it is possible to achieve an improved output per unit area and a stable output, regardless of the temperature of the heat source.

[0059] In this embodiment, the linear expansion coefficients of the first thermally conductive portion 5 a and the second thermally conductive portion 5 b are each 100 ppm / K or more and 200 ppm / K or less, and the linear expansion coefficient of the heat insulating member 6 may be 200 ppm / K or less. In this case, even if the thermoelectric conversion module 1 is attached to a heat source in a deformed state, the thermoelectric conversion module 1 will not peel off from the heat source and can generate electricity while maintaining a more stable temperature gradient.

[0060] In the present embodiment, the width L2 of each heat conductive portion 5 along the first direction D2 may be 0.5 mm or more and 1.5 mm or less. In this case, the heat conductive portion 5 exhibits excellent heat transfer performance, and the internal temperature difference of the thermoelectric conversion portion 11 can be increased.

[0061] In this embodiment, the thermal conductivity of each of the first thermally conductive portion 5 a and the second thermally conductive portion 5 b may be 2.0 W / mK or more and 5.0 W / mK or less, and the thermal conductivity of the heat insulating member 6 may be 0.01 W / mK or more and 0.05 W / mK or less. In this case, the internal temperature difference of the thermoelectric conversion portion 11 can be more effectively generated.

[0062] In this embodiment, the thickness T1 of the p-type thermoelectric conversion elements 21 may be 5 μm or more and 25 μm or less, and the spacing S may be 3 mm or more and less than 12 mm. In these cases, it is possible to further improve the output per unit area of ​​the thermoelectric conversion module 1.

[0063] In this embodiment, the substrate 2, the thermoelectric conversion unit 11, the heat conduction unit 5, and the heat insulating member 6 may each be flexible. In this case, the thermoelectric conversion module 1 can be easily provided along the surface of a cylindrical pipe, for example. In other words, restrictions on the location where the thermoelectric conversion module 1 can be attached can be alleviated.

[0064] In this embodiment, the dopant solution 51 is dripped onto a portion 42a of the p-type thermoelectric conversion layer 42, thereby converting the portion 42a into the n-type thermoelectric conversion element 22. In this case, the contact resistance between the p-type thermoelectric conversion element 21 and the n-type thermoelectric conversion element 22 can be effectively reduced. In addition, the dripping of the dopant solution 51 is performed after the thermal conduction portion 5 is formed. This makes it difficult for the material contained in the dopant solution 51 to deteriorate due to heating or the like.

[0065] In this embodiment, the length T3 of each heat insulating member 6 along the thickness direction D1 is shorter than the length T2 of each heat conductive portion 5, and for example, the length T3 is 80% or less, or 70% or less of the length T2. In this case, as shown in Fig. 6 , each heat insulating member 6 is less likely to interfere with the deformation of the substrate 2. This makes it less likely that excessive compressive stress will be applied to the boundary between the heat conductive portion 5 and the heat insulating member 6, for example, and therefore makes it less likely that the heat insulating member 6 will peel off from the substrate 2 when the thermoelectric conversion module 1 deforms.

[0066] The thermoelectric conversion module and the manufacturing method thereof according to the present disclosure are not limited to the above-described embodiment and modified examples, and various other modifications are possible.

[0067] FIG. 7A is a schematic bottom view of a thermoelectric conversion module according to a modified example. FIG. 7B is a schematic cross-sectional view taken along line VIIb-VIIb in FIG. 7A. The components provided on the first main surface 2a are omitted in FIG. 7B. The thermoelectric conversion module 1A shown in FIGS. 7A and 7B differs from the thermoelectric conversion module 1 of the above embodiment in that it further includes a heat dissipation member 7 located on the second main surface 2b. Additionally, the shape of the heat insulating member 6A included in the thermoelectric conversion module 1A differs from the shape of the heat insulating member 6 of the above embodiment. The heat dissipation member 7 is a member for dissipating heat accumulated in the thermoelectric conversion module 1A and has a frame shape surrounding the heat conduction sections 5 and the heat insulating member 6A in a plan view. In this modified example, the heat dissipation member 7 has a rectangular frame shape, but is not limited thereto. The heat insulating member 6A is provided to fill the area surrounded by the heat dissipation member 7. Therefore, the heat insulating member 6A is in contact with not only each heat conducting portion 5 but also the heat dissipation member 7, and each heat conducting portion 5 is surrounded by the heat insulating member 6A in a plan view.

[0068] The thermal conductivity of the heat dissipation member 7 is at least higher than that of the substrate 2, for example, 1 W / mK to 400 W / mK. The thermal conductivity of the heat dissipation member 7 is measured by a steady-state method or a transient method. The difference between the in-plane linear expansion coefficient of the heat dissipation member 7 and the linear expansion coefficient of the heat insulating member 6 is, for example, 100 ppm / K or less. As a result, even if the thermoelectric conversion module 1A is attached to a heat source in a deformed state, the thermoelectric conversion module 1A will not peel off from the heat source and can generate electricity while maintaining a stable temperature gradient. The above-described modified example can also achieve the same effects as the above-described embodiment. In addition, the provision of the heat dissipation member 7 makes it difficult for heat to accumulate in the thermoelectric conversion module 1A, making it easier to maintain the temperature difference within the thermoelectric conversion unit 11.

[0069] In the above embodiment and modified example, the thermoelectric conversion elements are exposed on the first main surface, but this is not limited thereto. For example, the thermoelectric conversion elements may be covered with a sealing layer made of resin. Also, an insulator may be provided between two adjacent thermoelectric conversion groups. In this case, it is preferable that the thermal conductivity of the insulator be low in order to maintain the internal temperature difference of the thermoelectric conversion unit.

[0070] In the above embodiment and modified example, the heat insulating member is formed by drying the heat insulating material applied to the substrate, but this is not limiting. For example, a pre-formed heat insulating member may be fixed onto the substrate.

[0071] One aspect of the present disclosure will be described in more detail by the following examples, but one aspect of the present disclosure is not limited to these examples.

[0072] Example 1 <Insulating Component> An insulating sheet (Sumitomo Riko Co., Ltd., "Fineshrite (registered trademark) Standard Type," thickness: 0.63 mm) was cut into a 10 mm wide x 96 mm long piece to prepare an insulating component. <Dispersion> 80 g of a carbon nanotube dispersion (concentration: 0.2% by mass, G / D ratio: 41, aqueous dispersion, single-walled carbon nanotubes, diameter: 0.9-1.7 nm, thermal conductivity: 30 W / mK) was concentrated by vacuum drawing until the carbon nanotube concentration reached 0.4% by mass. Next, 5.7 g of a PEDOT / PSS aqueous dispersion (Heraeus K.K., "Clevious PH1000," solids concentration: 1.2% by mass) and the concentrated carbon nanotube dispersion were thoroughly stirred with a Three-One Motor (AS ONE Corporation, "PM203" model) for 30 minutes. This resulted in a dispersion liquid in which the content of carbon nanotubes relative to the total amount of PEDOT / PSS and carbon nanotubes was 75% by mass. －１ The viscosity of the dispersion was measured using a rheometer (product name "MCR302" manufactured by Anton Paar). The measurement conditions were: temperature: 25°C, plate: φ25 mm parallel plate, gap: 1 mm.

[0073] <Dopant solution> A dopant solution was prepared by dissolving 0.32 g of potassium ferrocyanide trihydrate and 0.94 g of benzo-18-crown-6-ether in 15 mL of ultrapure water. In the dopant solution, the concentrations of potassium ions and benzo-18-crown-6-ether were each 0.2 M. The molar ratio (C ２ / C １ ) is 1.

[0074] <Substrate> A 100 mm square polyimide film (Kapton H type, film thickness 25 μm, thermal conductivity 0.16 W / mK, manufactured by DuPont-Toray Co., Ltd.) was prepared as a substrate. The polyimide film was washed with acetone.

[0075] <Thermoelectric Conversion Module> Spray glue (3M Japan Ltd., Regular Series S / N 55) was applied to one side of the heat insulating member and attached to the polyimide film with a 1.0 mm gap. Next, a high thermal conductivity material (Shin-Etsu Chemical Co., Ltd., G-789) was applied to the gap using an Iwashita Engineering dispenser "AD3000C" and a desktop robot "EzROBO-5GX." At this time, the spacing along the first direction of the nozzle position from which the high thermal conductivity material was discharged was set to 11 mm, and the nozzle was moved along a second direction perpendicular to the first direction while applying the material. This resulted in multiple band-shaped high thermal conductivity materials being applied to the second main surface. After application, the substrate was placed on a hot plate set to 120°C for 60 minutes. This formed multiple thermally conductive portions. The thickness and width of the thermally conductive portions were each 1 mm, and the spacing between the thermally conductive portions in the first direction was 10 mm. Furthermore, a heat insulating member was placed and fixed so as to fill the 10 mm gap.

[0076] The dispersion was applied to the first main surface of a polyimide film using a jet dispenser "AeroJet®" manufactured by Musashi Engineering and a desktop robot "SHOTMASTER 400ΩX." The laminate coated with the dispersion was then placed in a blower dryer set at 60°C for 3 hours. This resulted in a composite film with a thickness of 62 μm being formed on the polyimide film. The composite film had both a thermoelectric conversion region and a conductive portion on the polyimide film. The direction in which the thermoelectric conversion region extended was perpendicular to the direction in which the heat conductive portion and the heat insulating member extended.

[0077] The thickness of the composite film was measured using a high-precision digimatic micrometer (MDH-25MB, manufactured by Mitutoyo Corporation). Specifically, the thickness of the portion where the composite film was provided and the thickness of the portion where the composite film was not provided (portion with only polyimide film) were measured, and the difference between the thicknesses was taken as the thickness of the composite film.

[0078] Next, the first main surface of the polyimide film was immersed in DMSO (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) at room temperature for 30 minutes. Subsequently, the polyimide film was removed from the DMSO and placed on a hot plate set to 60°C for 120 minutes. This resulted in a p-type thermoelectric conversion layer being formed on the first main surface of the polyimide film. In Example 1, the thickness of the p-type thermoelectric conversion layer was 14.7 µm.

[0079] Next, a dopant solution was dripped onto a portion of the p-type thermoelectric conversion layer that functioned as a thermoelectric conversion element using a Fujifilm inkjet printer, the "Material Printer DMP2850." In Example 1, the dopant solution was first dripped onto an area 10 mm wide and 5.5 mm long. Subsequently, the dopant solution was similarly dripped onto an area 10 mm wide and 5.5 mm long, with 5.5 mm intervals. This dripping operation was repeated to alternate between areas where the dopant solution was dripped and areas where it was not. As a result, 48 p-type thermoelectric conversion elements and 48 n-type thermoelectric conversion elements were formed on the polyimide film. In other words, a total of 96 thermoelectric conversion elements were formed on the polyimide film. Thus, a total of 48 thermoelectric conversion units, each containing one p-type thermoelectric conversion element and one n-type thermoelectric conversion element, were formed. Here, the thickness of the n-type thermoelectric conversion elements was substantially the same as the thickness of the p-type thermoelectric conversion elements. The end of each thermoelectric conversion unit overlaps the heat conductive unit, and at least the center of each thermoelectric conversion unit does not overlap the heat conductive unit. The area of ​​the thermoelectric conversion element on the polyimide film is 52.8 cm. ２ The area occupied by the two conductive regions R2 on the polyimide film was 17.4 cm ２ The mass ratio of the carbon nanotubes to the total mass of the thermoelectric conversion section was 30% or more and 70% or less. The content of iron atoms in the n-type thermoelectric conversion element was 0.01% or more and 10% or less by mass.

[0080] Next, the polyimide film on which the thermoelectric conversion elements were provided was left on a hot plate and dried for 30 minutes. The polyimide film was then placed in a fan dryer set to 100°C for 60 minutes. This resulted in the production of a thermoelectric conversion module in which p-type thermoelectric conversion elements and n-type thermoelectric conversion elements were alternately arranged in series. The in-plane thermal conductivity of the p-type thermoelectric conversion elements was 32 W / mK. The parameters of the thermoelectric conversion module according to Example 1 are shown in Table 1 below.

[0081] Comparative Example 1 A thermoelectric conversion module was formed in the same manner as in Example 1, except that no heat insulating member was provided on the second main surface of the substrate. Therefore, a space was provided between two adjacent heat conductive portions. The parameters of the thermoelectric conversion module according to Comparative Example 1 are shown in Table 1 below. The thermal conductivity of the space (air) was set to 0.02 W / mK.

[0082] (Comparative Example 2) A thermoelectric conversion module was formed in the same manner as in Example 1, except that the heat insulating member was a foamed silicone "KE-521" manufactured by Shin-Etsu Chemical Co., Ltd. The parameters of the thermoelectric conversion module according to Comparative Example 2 are shown in Table 1 below.

[0083] (Comparative Example 3) A thermoelectric conversion module was formed in the same manner as in Example 1, except that the heat conductive portion was an aluminum square bar. The parameters of the thermoelectric conversion module according to Comparative Example 3 are shown in Table 1 below.

[0084] (Method for measuring linear expansion coefficient) A test piece measuring 3 cm square and 1 mm thick was prepared from the same material as the heat conductive portion of Example 1. Next, the test piece was sandwiched between 2 mm thick anti-adhesion plates and placed on a 10 mm quartz standard sample, and the linear expansion coefficient in the in-plane direction of the test piece was measured using a thermomechanical analyzer "TMA-4000SA" manufactured by Brugger Japan Co., Ltd. In addition, the test piece made from the same material as the heat conductive portion of Comparative Example 3, the test piece made from the same material as the heat insulating member of Example 1, and the test piece made from the same material as the heat insulating member of Comparative Example 2 were prepared, and the linear expansion coefficient in the in-plane direction of each test piece was measured. The measurement results of the linear expansion coefficient of each test piece are shown in Table 1 below.

[0085]

[0086] (Evaluation of power generation of thermoelectric conversion modules) The thermally conductive portions of the thermoelectric conversion modules of Example 1 and Comparative Examples 1 to 3 were wound around and brought into contact with a 76 mm diameter SUS pipe heated to 100°C with a silicone rubber heater. This created a temperature difference within each thermoelectric conversion element, putting the thermoelectric conversion module into a power generating state (hereinafter simply referred to as the "power generating state"). The resistance, open circuit voltage, short circuit current, maximum output, and maximum power density per unit area of ​​the thermoelectric conversion element of each thermoelectric conversion module were evaluated using a source meter ("Keithley 2612B" manufactured by Tektronix). The temperature difference within the thermoelectric conversion unit was measured using a thermograph ("InfRec R550Pro" manufactured by Nippon Avionics Co., Ltd.). When the resistance value, open circuit voltage, short circuit current, and maximum output of the thermoelectric conversion module of Comparative Example 1 are each set to 100, the evaluation results of Example 1 and Comparative Examples 1 to 3 are shown in Table 2 below.

[0087] Furthermore, a durability test was conducted in which the thermoelectric conversion module was wrapped around the SUS pipe and maintained in an atmospheric state for 100 hours. The thermoelectric conversion modules of Example 1 and Comparative Example 1 remained wrapped around the SUS pipe without deformation even after 100 hours. On the other hand, the thermoelectric conversion module of Comparative Example 2 peeled off from the SUS pipe before the end of the durability test, but no damage was observed in the thermoelectric conversion element. Furthermore, the thermoelectric conversion module of Comparative Example 3 was warped after the durability test, and cracks were observed in some of the thermoelectric conversion elements. From this, it can be said that the thermoelectric conversion modules of Example 1 and Comparative Examples 1 and 2 are flexible, while the thermoelectric conversion module of Comparative Example 3 is not flexible.

[0088] After 100 hours had passed, the source meter and thermography were used to measure the power generation amount and temperature difference between Example 1 and Comparative Example 1. The values ​​obtained by dividing the power generation amount and temperature difference after 100 hours by the initial power generation amount and temperature difference, respectively, were taken as "retention rates," and the results of these calculations are shown in Table 3. In Table 3, the power generation retention rates for Comparative Examples 2 and 3 were set to 0%, and the temperature difference retention rate was not measurable.

[0089]

[0090] As shown in Table 2, the open-circuit voltage of Example 1 was about 1.8 times higher than that of Comparative Example 1. The short-circuit current of Example 1 was also about 1.8 times higher than that of Comparative Example 1. The temperature difference variation range of Example 1 was smaller than that of Comparative Example 1. Specifically, the temperature difference variation range of Example 1 was about 1 / 7 to 1 / 3 of that of Comparative Example 1. On the other hand, the open-circuit voltage and short-circuit current of Comparative Examples 2 and 3 were both higher than that of Comparative Example 1. As described above, the thermoelectric conversion module of Comparative Example 3 is not flexible and therefore cannot be said to be practical as a power source. From the above, it can be seen that Example 1 and Comparative Example 2 are more practical as power sources than Comparative Examples 1 and 3.

[0091] The maintenance rate of the power generation amount and the temperature difference after the durability test in Example 1 were both 100%, which were higher than those in Comparative Example 1. On the other hand, as described above, the thermoelectric conversion module in Comparative Example 2 peeled off from the SUS pipe before the end of the durability test, and the thermoelectric conversion module in Comparative Example 3 had cracks in part of the thermoelectric conversion element after the durability test. Therefore, in Comparative Examples 2 and 3, the thermoelectric conversion module was unable to maintain power generation. These results show that Example 1 is more useful as a thermoelectric conversion module than Comparative Examples 1 to 3.

[0092] 1, 1A... thermoelectric conversion module, 2... substrate, 2a... first main surface, 2b... second main surface, 3... thermoelectric conversion group, 3a... first thermoelectric conversion group, 3b... second thermoelectric conversion group, 4... conductive portion, 5... heat conductive portion, 5a... first heat conductive portion, 5b... second heat conductive portion, 6, 6A... heat insulating member, 7... heat dissipation member, 11... thermoelectric conversion portion, 11a... first thermoelectric conversion portion, 11b... second thermoelectric conversion portion, 21... p-type thermoelectric conversion element, 21a... first end portion, 21b... second end portion, 22... n-type thermoelectric conversion element, 22a... first end portion, 22b... second end portion, D1... thickness direction, D2... first direction, D3... second direction, L1... length, L2... width, S... spacing, R1... thermoelectric conversion region, R2... conductive region, T1... thickness, T2, T3... length.

Claims

1. a substrate having a first major surface and a second major surface opposite the first major surface; A thermoelectric conversion portion located on the first main surface; a first thermal conductive portion and a second thermal conductive portion located on the second main surface and adjacent to each other along a first direction perpendicular to a thickness direction of the substrate; a heat insulating member located on the second main surface and at least between the first heat conductive portion and the second heat conductive portion, The thermoelectric conversion unit has p-type thermoelectric conversion elements and n-type thermoelectric conversion elements arranged along the first direction, a first end portion of the p-type thermoelectric conversion element in the first direction contacts a first end portion of the n-type thermoelectric conversion element in the first direction and overlaps the heat insulating member in the thickness direction; In the thickness direction, the first thermal conductive portion overlaps a second end of the p-type thermoelectric conversion element in the first direction, In the thickness direction, the second thermal conductive portion overlaps a second end of the n-type thermoelectric conversion element in the first direction, The thickness of each of the p-type thermoelectric conversion element and the n-type thermoelectric conversion element is 3 μm or more and 30 μm or less, a difference in linear expansion coefficient between the first thermal conductive portion and the heat insulating member, and a difference in linear expansion coefficient between the second thermal conductive portion and the heat insulating member are each 100 ppm / K or less; Thermoelectric conversion module.

2. The first thermally conductive portion and the second thermally conductive portion each have a linear expansion coefficient of 100 ppm / K or more and 200 ppm / K or less, The thermoelectric conversion module according to claim 1 , wherein the thermal insulation member has a linear expansion coefficient of 200 ppm / K or less.

3. 3 . The thermoelectric conversion module according to claim 1 , wherein the first thermal conductive portion and the second thermal conductive portion each have a width along the first direction of 0.5 mm to 1.5 mm.

4. The thermal conductivity of each of the first thermal conductive portion and the second thermal conductive portion is 2.0 W / mK or more and 5.0 W / mK or less, The thermoelectric conversion module according to claim 1 , wherein the thermal conductivity of the heat insulating member is 0.02 W / mK or more and 0.05 W / mK or less.

5. Further comprising a heat dissipation member located on the second main surface, The thermoelectric conversion module according to claim 1 , wherein the heat dissipation member surrounds the first thermal conductive portion, the second thermal conductive portion, and the heat insulating member when viewed in the thickness direction.

6. The thickness of each of the p-type thermoelectric conversion element and the n-type thermoelectric conversion element is 5 μm or more and 25 μm or less, The thermoelectric conversion module according to claim 1 , wherein a distance between the first thermal conductive portion and the second thermal conductive portion in the first direction is equal to or greater than 3 mm and less than 12 mm.

7. a first thermoelectric conversion group located on the first main surface and having the thermoelectric conversion unit; a second thermoelectric conversion group located on the first main surface and adjacent to the first thermoelectric conversion group along a second direction perpendicular to the thickness direction and the first direction, The second thermoelectric conversion group includes a second thermoelectric conversion unit adjacent to the thermoelectric conversion unit along the second direction, the second thermoelectric conversion unit has a second p-type thermoelectric conversion element and a second n-type thermoelectric conversion element arranged along the first direction, a first end portion of the second p-type thermoelectric conversion element in the first direction contacts a first end portion of the second n-type thermoelectric conversion element in the first direction and overlaps the heat insulating member in the thickness direction; Each of the first thermal conductive portion and the second thermal conductive portion extends along the second direction, In the thickness direction, the first thermal conduction portion overlaps a second end portion of the second p-type thermoelectric conversion element included in the second thermoelectric conversion portion in the first direction, The thermoelectric conversion module according to claim 1 or 2, wherein in the thickness direction, the second thermal conduction portion overlaps with a second end portion of the second n-type thermoelectric conversion element included in the second thermoelectric conversion portion in the first direction.

8. a first conductive portion located on the first main surface and connected to one end of the first thermoelectric conversion group in the first direction; a second conductive portion located on the first main surface and connected to the other end of the first thermoelectric conversion group in the first direction and one end of the second thermoelectric conversion group in the first direction, The thermoelectric conversion module according to claim 7 , wherein the first conductive portion and the second conductive portion have the same conductivity type.

9. The thermoelectric conversion module according to claim 1 , wherein each of the substrate, the thermoelectric conversion section, the first thermal conductive section, the second thermal conductive section, and the heat insulating member exhibits flexibility.

10. A first step of forming a first thermal conductive portion, a second thermal conductive portion, and a heat insulating member on one main surface of a substrate; a second step of forming a first layer including a p-type thermoelectric conversion material on the other main surface of the substrate; a third step of forming a p-type thermoelectric conversion layer by immersing the other main surface of the substrate in an organic solvent after the second step; and a fourth step of, after the third step, dropping a dopant solution onto a portion of the p-type thermoelectric conversion layer to form a p-type thermoelectric conversion element and an n-type thermoelectric conversion element on the portion, the first thermal conductive portion and the second thermal conductive portion are adjacent to each other along a first direction perpendicular to a thickness direction of the substrate, a first end portion of the p-type thermoelectric conversion element in the first direction contacts a first end portion of the n-type thermoelectric conversion element in the first direction and overlaps the heat insulating member in the thickness direction; In the thickness direction, the first thermal conductive portion overlaps a second end of the p-type thermoelectric conversion element in the first direction, In the thickness direction, the second thermal conductive portion overlaps a second end of the n-type thermoelectric conversion element in the first direction, a difference in linear expansion coefficient between the first thermal conductive portion and the heat insulating member, and a difference in linear expansion coefficient between the second thermal conductive portion and the heat insulating member are each 100 ppm / K or less; A method for manufacturing a thermoelectric conversion module.

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