Thermoelectric conversion element and thermoelectric conversion device

Abstract

A thermoelectric conversion element 1a comprises a first sheet 10, a thermoelectric conversion part 30, and a second sheet 20. The first sheet 10, the thermoelectric conversion part 30, and the second sheet 20 are arranged in the order of the first sheet 10, the thermoelectric conversion part 30, and the second sheet 20 in the thickness direction of the first sheet 10. The thermoelectric conversion part 30 includes a magnetic body.

Description

Thermoelectric conversion element and thermoelectric conversion device

[0001] The present invention relates to a thermoelectric conversion element and a thermoelectric conversion device.

[0002] 2. Description of the Related Art Thermoelectric conversion elements using magnetic materials are known.

[0003] For example, Patent Document 1 describes a thermoelectric conversion element made of a substance represented by the composition formula FeX and exhibiting the anomalous Nernst effect. As an example of this thermoelectric conversion element, a long sheet-like (tape-like) thermoelectric conversion element is described, and a thermoelectric conversion device equipped with this sheet-like thermoelectric conversion element is also described (see FIG. 9 of the same document). In this thermoelectric conversion device, the sheet-like thermoelectric conversion element is wrapped around the outer surface of a hollow member to cover it.

[0004] International Publication No. 2020 / 218613

[0005] As the Internet of Things (IoT) society and digital transformation (DX) progress, there is a growing need for heat monitoring in technical fields such as monitoring heat generation from machines and physical conditions. Furthermore, from the perspective of protecting the global environment, it is important to suppress unnecessary heat generation and increase energy efficiency, and there are high expectations for the advancement of systems that measure heat to optimize operations in various technical fields, such as batteries, heat exchangers, and motors for electric vehicles (EVs).

[0006] Thermoelectric conversion elements using magnetic materials are a promising technology that can meet these expectations. The thermoelectric conversion element described in Patent Document 1 is intended to be used in a state in which it is wound around a hollow member. However, Patent Document 1 does not specifically consider issues that may arise when the thermoelectric conversion element is used in a bent state.

[0007] According to the study by the present inventors, it has been newly discovered that when a thermoelectric conversion element using a magnetic material is bent during use, the thermoelectric conversion performance of the thermoelectric conversion element may be reduced. Such a reduction in thermoelectric conversion performance may lead to a reduction in the accuracy of detecting physical quantities to be detected, such as the amount of power generated and the amount of heat generated.

[0008] In view of the above circumstances, the present invention provides a thermoelectric conversion element that uses a magnetic material and whose thermoelectric conversion performance is unlikely to change even when it is bent during use.

[0009] The present invention provides a thermoelectric conversion element comprising: a first sheet; a thermoelectric conversion unit; and a second sheet, wherein the first sheet, the thermoelectric conversion unit, and the second sheet are arranged in the thickness direction of the first sheet in the order of the first sheet, the thermoelectric conversion unit, and the second sheet, and the thermoelectric conversion unit includes a magnetic material.

[0010] The present invention also provides a thermoelectric conversion device including the above thermoelectric conversion element.

[0011] The thermoelectric conversion element described above is unlikely to change in thermoelectric conversion performance even when used while being bent.

[0012] Fig. 1 is a plan view showing an example of an embodiment of a thermoelectric conversion element. Fig. 2 is a cross-sectional view of the thermoelectric conversion element taken along line II-II shown in Fig. 1. Fig. 3 is a diagram for schematically explaining physics relating to bending of a laminate. Fig. 4 is a cross-sectional view of a thermoelectric conversion element according to a reference example. Fig. 5 is a graph showing the relationship between magnetization of the thermoelectric conversion unit of the thermoelectric conversion element shown in Fig. 1 and an external magnetic field. Fig. 6 is a cross-sectional view showing another example of an embodiment of a thermoelectric conversion element. Fig. 7 is a perspective view showing an example of an embodiment of a thermoelectric conversion device.

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the following description is for illustrative purposes only and is not intended to limit the scope of the present invention.

[0014] 1 and 2 , the thermoelectric conversion element 1a includes a first sheet 10, a thermoelectric conversion unit 30, and a second sheet 20. The first sheet 10, the thermoelectric conversion unit 30, and the second sheet 20 are arranged in this order in the thickness direction (Z-axis direction) of the first sheet 10. The thermoelectric conversion unit 30 includes a magnetic material. In the accompanying drawings, the X-axis, the Y-axis, and the Z-axis are perpendicular to one another.

[0015] When a thermoelectric conversion element using a magnetic material is bent during use, deformation of the magnetic material due to bending of the thermoelectric conversion element can cause changes in the properties of the magnetic material due to the magnetoelastic effect. In particular, as the deformation of the magnetic material increases, the magnetoelastic effect also increases, and the properties of the magnetic material can change significantly.

[0016] As shown in Figure 3, consider applying a bending moment M to a laminate L of n layers (n = 3 in Figure 3). Here, the direction perpendicular to one of the main surfaces of the laminate L is defined as the y-axis, and the position of that main surface is defined as y = 0. In the laminate L, a neutral axis N exists at the position y = λ. As shown in Figure 3, a bend with a radius of curvature ρ is generated in the laminate L so that a compressive stress acts on the main surface of the laminate corresponding to y = 0. In this case, the strain ε and stress σ at an arbitrary position on the y-axis are expressed by the following equations (1) and (2), respectively. In equation (2), E is the Young's modulus of the object. ε = (y - λ) / ρ Equation (1) σ = E (y - λ) / ρ Equation (2)

[0017] The position λ of the neutral axis N is expressed by the following equation (3). In equation (3), E i is the Young's modulus of the i-th layer from the layer (i=1) forming the principal surface of y=0, and h i is the maximum value of the y coordinate in the i-th layer, and h i-1 is the maximum value of the y coordinate in the i-1th layer, and t i is the thickness of the ith layer, where h0 = 0.

[0018]

[0019] In equation (2), a positive value of stress σ corresponds to tensile stress, and a negative value of stress σ corresponds to compressive stress. As shown in equations (1) and (2), the larger the absolute value of y-λ, the larger the absolute values ​​of strain and stress at that position. Therefore, it can be understood that the bending moment M generates large strain and large stress in the portion of the laminate L located near the outermost surface.

[0020] 4 is a cross-sectional view of a thermoelectric conversion element 1x according to a reference example. The thermoelectric conversion element 1x is configured similarly to the thermoelectric conversion element 1a, except that it does not include the second sheet 20 and the adhesive layer 40 described below. In the thermoelectric conversion element 1x, the thermoelectric conversion unit 30 including the magnetic material is disposed on the outermost surface of the thermoelectric conversion element 1x. Therefore, when the thermoelectric conversion element 1x is bent, large strains and stresses are likely to occur in the thermoelectric conversion unit 30, which may significantly change the properties of the magnetic material. This may result in a decrease in the thermoelectric conversion performance of the thermoelectric conversion element 1x.

[0021] 2, in the thermoelectric conversion element 1a, the thermoelectric conversion section 30 is disposed between the first sheet 10 and the second sheet 20 in the thickness direction (Z-axis direction) of the first sheet 10, and is disposed at a position away from the outermost surface of the thermoelectric conversion element 1a. Therefore, even if the thermoelectric conversion element 1a is bent, large strain and stress are unlikely to occur in the thermoelectric conversion section 30, and the properties of the magnetic material are also unlikely to change. As a result, even if the thermoelectric conversion element 1a is bent, the thermoelectric conversion performance of the thermoelectric conversion element 1a is unlikely to change.

[0022] The arithmetic strain generated when the thermoelectric conversion element 1a is bent is not limited to a specific value. For example, when the thermoelectric conversion element 1a is bent to have a curvature radius of 15 mm, the absolute value |ε of the arithmetic strain in the thermoelectric conversion unit 30 is 15 is not limited to a specific value. 15 | is, for example, 1.5 × 10 -3 In this case, the characteristics of the magnetic material contained in the thermoelectric conversion unit 30 are less likely to change, and the thermoelectric conversion performance of the thermoelectric conversion element 1a is less likely to change even if the thermoelectric conversion element 1a is bent.

[0023] Absolute value | ε 15 | is 1.4 × 10 -3 It may be 1.2 × 10 or less, -3 or less, 1.0 × 10 -3 or less, 5.0 × 10 -4 or less, 2.0 × 10 -4 or less, 1.0 × 10 -4 or less, 5.0 × 10 -5The absolute value |ε 15 | may be 0.

[0024] As shown in FIG. 2 , the thermoelectric conversion unit 30 is disposed away from the outermost surface on both sides of the thermoelectric conversion element 1a in the thickness direction of the first sheet 10. The position of the thermoelectric conversion unit 30 in the thickness direction of the first sheet 10 is not limited to a specific position, as long as the first sheet 10, the thermoelectric conversion unit 30, and the second sheet are disposed in this order. For example, the thermoelectric conversion unit 30 is disposed in the thickness direction of the first sheet 10 at a neutral axis N of the thermoelectric conversion element 1a or a first distance d1 from the neutral axis N. The ratio d1 / t of the first distance d1 to the thickness t of the thermoelectric conversion element 1a is 0.45 or less. The first distance d1 is the shortest distance between the neutral axis N and the thermoelectric conversion unit 30 in the thickness direction of the first sheet 10. With this configuration, the thermoelectric conversion unit 30 is located on or near the neutral axis N, and large stress and strain are less likely to occur even when the thermoelectric conversion element 1a is bent. Therefore, the thermoelectric conversion performance of the thermoelectric conversion element 1a is less likely to change.

[0025] The ratio d1 / t may be 0.43 or less, 0.40 or less, 0.38 or less, 0.35 or less, 0.30 or less, or 0.25 or less.

[0026] As shown in formula (3), the position of the neutral axis N in the laminate L is determined by the Young's modulus and thickness of each layer. Therefore, the position of the neutral axis of the thermoelectric conversion element 1 a is affected by the Young's modulus and thickness of the first sheet 10 and the second sheet 20.

[0027] In the thermoelectric conversion element 1a, the area E 10 t 10 2 The product E in the second sheet 20 20 t 20 2 The ratio E 20 t 20 2 / E 10 t 10 2 is not limited to a specific value. 10 t 10 2 is the Young's modulus E of the first sheet 1010 and the square of the thickness t 10 2 and the product E 20 t 20 2 is the Young's modulus E of the second sheet 20 20 and the square of the thickness t 20 2 It is the product of the ratio E 20 t 20 2 / E 10 t 10 2 is, for example, 0.001 to 2.0, and may be 0.002 to 2.0, 0.01 to 2.0, 0.05 to 2.0, 0.1 to 2.0, 0.2 to 2.0, 0.5 to 2.0, 0.6 to 1.5, 0.8 to 1.2, or 0.9 to 1.1.

[0028] Stack E in the first sheet 10 10 t 10 2 is not limited to a specific value. 10 t 10 2 is, for example, 1 × 10 5 ~1 x 10 10 MPa (μm) 2 In this case, the thermoelectric conversion element 1a is easily bent and tends to have a desired strength. 10 t 10 2 is 8 x 10 5 ~5 x 10 9 MPa (μm) 2 or 4.8 x 10 6 ~1.12 x 10 8 MPa (μm) 2 may be.

[0029] Stack E in the second sheet 20 20 t 20 2 is not limited to a specific value. 20 t 20 2 is, for example, 1 × 10 4 ~1 x 10 10 MPa (μm) 2In this case, the thermoelectric conversion element 1a is easily bent and tends to have a desired strength. 20 t 20 2 is 5 x 10 4 ~1 x 10 10 MPa (μm) 2 , 1×10 5 ~1 x 10 10 MPa (μm) 2 , 8 x 10 5 ~5 x 10 9 MPa (μm) 2 , or 4.8 × 10 6 ~1.12 x 10 8 MPa (μm) 2 may be.

[0030] Young's modulus E of the first sheet 10 10 is not limited to a specific value. 10 is, for example, 1 × 10 3 ~1 x 10 5 MPa, and 2 × 10 3 ~2 x 10 4 MPa or 3 x 10 3 ~5 x 10 3 The Young's modulus E of the second sheet 20 may be MPa. 20 is not limited to a specific value. 20 is, for example, 1×10 3 ~1 x 10 5 MPa, and 2 × 10 3 ~2 x 10 4 MPa or 3 x 10 3 ~5 x 10 3 MPa.

[0031] Thickness t of the first sheet 10 10 is not limited to a specific value. 10 The thickness t of the second sheet 20 is, for example, 10 to 1000 μm, and may be 20 to 500 μm or 40 to 150 μm. 20 is not limited to a specific value. 20 is, for example, 1 to 1000 μm, and may be 5 to 1000 μm, 10 to 1000 μm, 20 to 500 μm, or 40 to 150 μm.

[0032] The material forming the first sheet 10 and the second sheet 20 is not limited to a specific material. The first sheet 10 and the second sheet 20 may contain, for example, an organic material. In this case, the thermoelectric conversion element 1a is easily bent and tends to be lightweight. Examples of the organic material include organic polymers such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), acrylic resin (PMMA), epoxy resin, polycarbonate (PC), polyimide (PI), and cycloolefin polymer (COP).

[0033] Young's modulus E of the thermoelectric conversion unit 30 30 As shown in the formula (2), the absolute value of the stress σ generated in the thermoelectric conversion unit 30 when the thermoelectric conversion element 1 a is bent is determined by the Young's modulus E 30 Young's modulus E is proportional to 30 In this case, the absolute value of the stress σ generated in the thermoelectric conversion unit 30 when the thermoelectric conversion element 1a is bent is likely to be small, and the thermoelectric conversion performance of the thermoelectric conversion element 1a is less likely to change. 30 may be 10 to 250 GPa or 50 to 200 GPa.

[0034] Thickness t of the thermoelectric conversion part 30 30 is not limited to a specific value. 30 is, for example, 1 μm or less. In this case, the thermoelectric conversion portion 30 has little effect on determining the neutral axis of the thermoelectric conversion element 1 a. Therefore, in order to adjust the position of the neutral axis, it is only necessary to take into consideration the first sheet 10 and the second sheet 20, which makes it easy to design the thermoelectric conversion element 1 a. 30 may be 0.01 to 0.5 μm or 0.02 to 0.15 μm.

[0035] The squareness ratio S0 of the thermoelectric conversion unit 30 is not limited to a specific value. The squareness ratio S0 is the ratio Mr / Ms of the remanent magnetization Mr to the saturation magnetization Ms in the M-H curve. The squareness ratio S0 of the thermoelectric conversion unit 30 is, for example, 80% or more. This makes it easier for the thermoelectric conversion element 1a to exhibit the desired thermoelectric conversion performance. The squareness ratio S0 may be 85% or more, 90% or more, or 95% or more. The squareness ratio S0 is determined when the thermoelectric conversion element 1a is placed on a flat surface.

[0036] The rate of change R of the squareness ratio of the thermoelectric conversion element 1a 15 is not limited to a specific value. 15 is expressed by the following formula (4). In formula (4), S 15 is the squareness ratio of the thermoelectric conversion part 30 determined in a state where the thermoelectric conversion element 1a is bent so as to have a radius of curvature of 15 mm. 15 = (S0 - S 15 ) / S0 formula (4)

[0037] Rate of change R 15 is, for example, 0.15 or less, preferably 0.12 or less, more preferably 0.10 or less, even more preferably 0.07 or less, and particularly preferably 0.05 or less. 15 may be 0.

[0038] The thermoelectric conversion unit 30 generates thermoelectromotive force, for example, in a direction perpendicular to the temperature gradient. With this configuration, for example, when a temperature gradient occurs in the thickness direction of the first sheet 10 in the thermoelectric conversion element 1a, thermoelectromotive force is generated in the direction along the main surface of the first sheet 10 of the thermoelectric conversion unit 30. Therefore, by adjusting the shape and dimensions of the thermoelectric conversion unit 30 in a plane parallel to the main surface of the first sheet 10, large thermoelectromotive force is likely to be generated in the thermoelectric conversion element 1a.

[0039] The thermoelectric conversion unit 30 generates thermoelectric power due to, for example, the anomalous Nernst effect. In this case, the thermoelectric conversion element 1a is likely to exhibit high thermoelectric conversion performance. The thermoelectric conversion unit 30 may be configured to generate thermoelectric power due to the spin Seebeck effect and the inverse spin Hall effect.

[0040] 1 , the thermoelectric conversion unit 30 is, for example, a thin wire 31. With this configuration, for example, by magnetizing the thin wire 31 in the width direction, when a temperature gradient occurs in the thickness direction of the first sheet 10, a thermoelectromotive force due to the anomalous Nernst effect can be generated in the length direction of the thin wire 31. In this case, a thermoelectromotive force according to the length of the thin wire 31 can be generated, and the thermoelectric conversion element 1a is more likely to exhibit the desired thermoelectric conversion performance.

[0041] The width of the thin wires 31 is not limited to a specific value. The width of the thin wires 31 is, for example, 500 μm or less. This reduces the amount of material used for the thin wires 31, making it easier to reduce the manufacturing cost of the thermoelectric conversion element 1a. In addition, it is easy to arrange a large number of thin wires 31 in the thermoelectric conversion element 1a, making it easier for the thermoelectric conversion element 1a to exhibit the desired thermoelectric conversion performance. The width of the thin wires 31 is, for example, 1 μm or more. This makes it less likely for breakage to occur in the thin wires 31, making it easier for the thermoelectric conversion element 1a to have high durability.

[0042] The width of the thin wire 31 may be included in any of the ranges determined by all combinations of a lower limit value of any one of 1 μm, 2 μm, 5 μm, 10 μm, 20 μm, and 30 μm and an upper limit value of any one of 500 μm, 400 μm, 300 μm, 200 μm, 100 μm, and 50 μm.

[0043] FIG. 5 is a graph showing the relationship between the magnetization of the thermoelectric conversion unit 30 and an external magnetic field. In FIG. 5, the solid line graph shows the relationship between the magnetization of the thermoelectric conversion unit 30 in the width direction (X-axis direction) of the thin wire 31 and the external magnetic field. The dashed line graph shows the relationship between the magnetization of the thermoelectric conversion unit 30 in the length direction (Y-axis direction) of the thin wire 31 and the external magnetic field. As shown in FIG. 5, the magnetic properties of the thermoelectric conversion unit 30 have large anisotropy in the length direction and width direction of the thin wire 31. Due to such large anisotropy of the magnetic properties, the thermoelectric conversion unit 30 tends to have a hard axis of magnetization in the length direction of the thin wire 31 and an easy axis of magnetization in the width direction of the thin wire 31. This makes the thermoelectric conversion unit 30 more likely to exhibit stable behavior against an external magnetic field, and the thermoelectric conversion element 1a more likely to exhibit the desired thermoelectric conversion performance. The thermoelectric conversion unit 30 has an easy axis of magnetization in, for example, the width direction of the thin wire 31.

[0044] The magnetic material included in the thermoelectric conversion unit 30 is not limited to a specific material. This magnetic material includes, for example, a material that exhibits the anomalous Nernst effect. The material that exhibits the anomalous Nernst effect is not limited to a specific material. For example, the material that exhibits the anomalous Nernst effect is, for example, 5×10 -3 The thermoelectric conversion unit 30 is a magnetic material having a saturation magnetic susceptibility of T or more, or a material having a band structure with a Weyl point near the Fermi energy. The magnetic material may be a ferrimagnetic material. The thermoelectric conversion unit 30 contains, as a material exhibiting the anomalous Nernst effect, at least one material selected from the group consisting of the following (i), (ii), (iii), (iv), and (v): (i) a stoichiometric material having a composition represented by Fe3X; (ii) an off-stoichiometric material in which the composition ratio of Fe to X deviates from that of the material in (i) above; (iii) a material in which part of the Fe sites of the material in (i) above or part of the Fe sites of the material in (ii) above is substituted with a main group metal element or transition element other than X; (iv) Fe3M1 1-x M2 x (v) A substance having a composition expressed by (0<x<1), in which M1 and M2 are different typical group elements. (i) A substance in which a part of the Fe site of the substance (i) is substituted with a transition element other than X, and a part of the X site of the substance (i) is substituted with a typical metal element other than X.

[0045] In the above substances (i) to (v), X is a typical element or a transition element. X is, for example, Al, Ga, Ge, Sn, Si, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Sc, Ni, Mn, or Co. In the above substance (iv), the combination of M1 and M2 is not limited to a specific combination as long as M1 and M2 are different typical elements. In the above substance (iv), the combination of M1 and M2 is, for example, Ga and Al, Si and Al, or Ga and B.

[0046] The thermoelectric conversion section 30 may contain Co2MnGa or Mn3Sn as a material that exhibits the anomalous Nernst effect.

[0047] 2 , the thermoelectric conversion element 1 a includes, for example, an adhesive layer 40. The adhesive layer 40 is located between the first sheet 10 and the second sheet 20 in the thickness direction of the first sheet 10, and bonds the first sheet 10 and the second sheet 20 together.

[0048] The adhesive forming the adhesive layer 40 is not limited to a specific adhesive. This adhesive may be a thermosetting adhesive or an active energy ray-curable adhesive. The active energy ray-curable adhesive may be an ultraviolet ray-curable adhesive or a visible light-curable adhesive. Examples of thermosetting adhesives include epoxy resin-based adhesives, phenol resin-based adhesives, polyurethane-based adhesives, and cyanoacrylate-based adhesives. Examples of active energy ray-curable adhesives include acrylic-based adhesives, silicone-based adhesives, epoxy-based adhesives, and urethane-based adhesives.

[0049] Thickness t of adhesive layer 40 40 is not limited to a specific value. 40 is, for example, 5 μm or less. In this case, the adhesive layer 40 has little effect on determining the neutral axis of the thermoelectric conversion element 1 a. Therefore, in order to adjust the position of the neutral axis, it is only necessary to take into consideration the first sheet 10 and the second sheet 20, which makes it easy to design the thermoelectric conversion element 1 a. 40 may be 0.2 to 3 μm or 0.8 to 1.5 μm.

[0050] As shown in FIG. 1 , the thermoelectric conversion unit 30 has, for example, a plurality of thin wires 31. The thermoelectric conversion element 1a has, for example, a meander pattern including the thermoelectric conversion unit 30. With this configuration, the total length of the thin wires 31 included in the thermoelectric conversion element 1a tends to be large. The electromotive force generated in the length direction of the thin wires 31 due to the temperature gradient in the thickness direction of the first sheet 10 tends to be large as the total length of the thin wires 31 increases. Therefore, when the thermoelectric conversion element 1a has a meander pattern including the thermoelectric conversion unit 30, the electromotive force generated in the thermoelectric conversion element 1a tends to be large.

[0051] 1 and 2 , the thermoelectric conversion element 1a further includes, for example, wiring 32. The wiring 32 electrically connects the thin wires 31 to each other. For example, the wiring 32 electrically connects the plurality of thin wires 31 in the thermoelectric conversion unit 30 in series. The wiring 32 includes, for example, a plurality of wires 33. The plurality of thin wires 31 and the plurality of wires 33 are electrically connected in series. With this configuration, a large electromotive force is likely to be generated in the thermoelectric conversion element 1a even if the area of ​​the surface on which the plurality of thin wires 31 and the plurality of wires 33 are arranged is small.

[0052] The wiring 32 may be made of a single metal or an alloy.

[0053] The plurality of fine wires 31 and the plurality of wirings 33 are arranged, for example, to form the meander pattern described above, thereby forming a conductive path 35. For example, by connecting one end and the other end of the conductive path 35 to external wiring, the electromotive force generated in the thermoelectric conversion element 1a can be extracted to the outside. Alternatively, by applying a voltage between one end and the other end of the conductive path 35, a heat flow can be generated in the thickness direction of the sheet 10.

[0054] The multiple thin wires 31 are, for example, spaced apart at a predetermined interval in the X-axis direction and arranged parallel to one another. The wiring 32 electrically connects, for example, one end of a thin wire 31 in the Y-axis direction to the other end in the Y-axis direction of another thin wire 31 adjacent to that thin wire 31. The one ends in the Y-axis direction of the multiple thin wires 31 are located on the same side of the thin wire 31 in the Y-axis direction, and the other ends in the Y-axis direction of the multiple thin wires 32 are located on the opposite side of the one end of the thin wire 31 in the Y-axis direction.

[0055] The thickness of the wiring 32 is not limited to a specific value and may be included in any of the ranges determined by all combinations of a lower limit value of any one of 5 nm, 10 nm, 20 nm, 30 nm, and 50 nm and an upper limit value of any one of 1000 nm, 750 nm, 500 nm, 400 nm, 300 nm, and 200 nm, for example.

[0056] The width of the wiring 32 is not limited to a specific value and may be included in any of the ranges determined by all combinations of a lower limit of any one of 0.1 μm, 0.5 μm, 1 μm, 2 μm, 5 μm, 10 μm, 20 μm, and 30 μm and an upper limit of any one of 500 μm, 400 μm, 300 μm, 200 μm, 100 μm, and 50 μm.

[0057] An example of a method for manufacturing the thermoelectric conversion element 1a is shown below. The thermoelectric conversion element 1a is manufactured, for example, by a method including the following steps (I) and (II): (I) forming a thermoelectric conversion section 30 on one main surface of the first sheet 10; (II) applying an adhesive to at least one of the first sheet 10 and the second sheet 20, and curing the adhesive to bond one main surface of the first sheet 10 and the second sheet 20 together.

[0058] In (I), a film of a precursor of the thermoelectric conversion unit 30 is formed on one main surface of the first sheet 10 by, for example, sputtering, chemical vapor deposition (CVD), pulsed laser deposition (PLD), ion plating, plating, or the like. Next, for example, a photoresist is applied to the film, a photomask is placed on the film, exposure is performed, and then wet etching is performed. This results in the formation of multiple thin wires of the precursor of the thermoelectric conversion unit 30 arranged at predetermined intervals. Next, a film of a precursor of the wiring 32 is formed on one main surface of the first sheet 10 by, for example, sputtering, CVD, PLD, ion plating, plating, or the like. Next, a photoresist is applied to the film of the precursor of the wiring 32, a photomask is placed on the film of the precursor of the wiring 32, exposure is performed, and then wet etching is performed. This results in the formation of the wiring 32, and the thin wires of the precursor of the thermoelectric conversion unit 30 are electrically connected to each other.

[0059] In (I), a predetermined heat treatment is performed as necessary. The ambient temperature of the first sheet 10 and the precursor of the thermoelectric conversion section 30 during the heat treatment is, for example, 50°C or higher. This makes it easy to adjust the internal stress of the thermoelectric conversion section 30 to a desired state from the perspective of thermoelectric conversion performance. The ambient temperature of the first sheet 10 and the precursor of the thermoelectric conversion section 30 during the heat treatment may be 100°C or higher, 150°C or higher, or 200°C or higher. The ambient temperature is, for example, 300°C or lower.

[0060] The time during which the ambient temperature of the first sheet 10 is maintained at 50° C. or higher in the heat treatment is not limited to a specific value, and is, for example, 10 minutes or more and 3 hours or less.

[0061] After the heat treatment, the precursor of the thermoelectric conversion part 30 is magnetized, and the thermoelectric conversion part 30 is obtained.

[0062] Next, proceeding to (II), an adhesive is applied to at least one of the first sheet 10 and the second sheet 20. The adhesive is applied by, for example, spin coating. Next, one main surface of the first sheet 10 and one main surface of the second sheet 20 are bonded together with the adhesive. Next, the adhesive is cured by heating or irradiating the adhesive with active energy rays such as ultraviolet light, thereby obtaining the adhesive layer 40. For example, in this manner, a thermoelectric conversion element 1a is manufactured.

[0063] The thermoelectric conversion element 1a may be modified as shown in Fig. 6 as a thermoelectric conversion element 1b. The thermoelectric conversion element 1b has the same configuration as the thermoelectric conversion element 1a, except for portions that will be particularly described. The same reference numerals are used to designate components of the thermoelectric conversion element 1b that are the same as or correspond to the components of the thermoelectric conversion element 1a, and detailed descriptions thereof will be omitted. The description of the thermoelectric conversion element 1a also applies to the thermoelectric conversion element 1b, unless technically inconsistent.

[0064] 6 , in the thermoelectric conversion element 1b, the adhesive layer 40 is omitted, and the second sheet 20 is in contact with the thermoelectric conversion section 30. Even with this configuration, the thermoelectric conversion performance of the thermoelectric conversion element 1b is unlikely to change even if the thermoelectric conversion element 1b is bent. A portion of the second sheet 20 is in contact with, for example, one main surface of the first sheet 10.

[0065] The thermoelectric conversion element 1b can be manufactured, for example, by applying a fluid precursor of the second sheet 20 to a predetermined thickness onto one main surface of the first sheet 10 on which the thermoelectric conversion section 30 is formed, and then curing the precursor to obtain the second sheet 20, instead of the above-mentioned step (II). Examples of precursors of the second sheet 20 include precursors of acrylic resin and epoxy resin. The precursor of the second sheet 20 can be cured by irradiation with active energy rays such as ultraviolet rays or by heating.

[0066] The thermoelectric conversion element 1a or 1b may be provided together with, for example, an adhesive layer. In this case, the adhesive layer is in contact with the first sheet 10 or the second sheet 20, and the first sheet 10 or the second sheet 20 is disposed between the thermoelectric conversion unit 30 and the adhesive layer in the thickness direction of the first sheet 10. This allows the thermoelectric conversion element 1a to be attached to an article by pressing the adhesive layer against the article.

[0067] The adhesive layer contains, for example, a rubber-based adhesive, an acrylic-based adhesive, a silicone-based adhesive, or a urethane-based adhesive. The thermoelectric conversion element 1a may be provided together with an adhesive layer and a release liner. In this case, the release liner covers the adhesive layer. The release liner is typically a film that can maintain the adhesive force of the adhesive layer when covering the adhesive layer and can be easily peeled off from the adhesive layer. The release liner is, for example, a film made of a polyester resin such as PET. By peeling off the release liner, the adhesive layer is exposed, allowing the thermoelectric conversion element 100 to be attached to an article.

[0068] As shown in FIG. 7 , for example, a thermoelectric conversion device 3 including a thermoelectric conversion element 1a can be provided. This thermoelectric conversion device 3 is, for example, a sensor that detects heat in an object 5. For example, when a temperature gradient occurs in the thickness direction of the first sheet 10, an electromotive force is generated in the length direction of the thin wires 31. The thermoelectric conversion device 3 can sense heat by processing an electrical signal output to the outside of the thermoelectric conversion element 1a based on this electromotive force. The thermoelectric conversion device 3 further includes, for example, a signal processing device 2. The electrical signal output to the outside of the thermoelectric conversion element 1a is processed in the signal processing device 2. The thermoelectric conversion device 3 may be configured as a device other than a sensor. The thermoelectric conversion device 3 may include a thermoelectric conversion element 1b.

[0069] 7, the thermoelectric conversion element 1a is arranged along a curved surface. Even when the thermoelectric conversion element 1a is used in a bent state like this, the thermoelectric conversion element 1a is likely to exhibit the desired thermoelectric conversion performance, and the thermoelectric conversion device 3 is likely to have the desired performance. The curved surface may be, for example, a cylindrical surface, a spherical surface, another quadratic surface, or a curved surface other than a quadratic surface.

[0070] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples. First, the evaluation methods used in the examples will be described.

[0071] Example 1: A 0.1 μm-thick thin film was formed on a 50 μm-thick polyethylene terephthalate (PET) film first sheet by DC magnetron sputtering using a target material containing Fe and Ga. In the DC magnetron sputtering, argon gas was supplied as the process gas at a pressure of 0.1 Pa. The target material satisfied the Fe content:Ga content = 3:1 atomic ratio. The ambient temperature of the first sheet was adjusted to 100°C. The first sheet on which the thin film was formed was heat-treated in an environment of 150°C for 30 minutes. Next, a photoresist was applied to the thin film, and a photomask was placed on the thin film to perform exposure, followed by wet etching. This resulted in the formation of 115 FeGa-containing thin wires arranged at predetermined intervals. Each FeGa-containing thin wire had a width of 40 μm and a length of 1.5 cm. Then, a Cu thin film having a thickness of 0.1 μm was formed on the first sheet by DC magnetron sputtering using a Cu-containing target material. A photoresist was applied to the Cu thin film, and a photomask was placed on the Cu thin film to perform exposure, followed by wet etching. This resulted in the formation of Cu-containing thin wires having a width of 40 μm. A pair of adjacent FeGa-containing thin wires was electrically connected by the Cu-containing thin wires, forming a conductive path with a meander pattern.

[0072] Using an electromagnet with a central magnetic flux density of 0.5 T, the FeGa-containing thin wires were magnetized in a width direction parallel to the main surface of the first sheet and perpendicular to the length direction of the FeGa-containing thin wires. Next, an epoxy-based thermosetting adhesive was applied to the main surface of a second sheet, which was another PET film with a thickness of 50 μm, and this main surface was bonded to the main surface of the first sheet on which the FeGa-containing thin wires were formed. In this state, the adhesive was heated in an environment of 120°C for 1 hour to harden the adhesive, thereby obtaining an adhesive layer. The thickness of the adhesive layer was 1 μm. In this way, a thermoelectric conversion element according to Example 1 was obtained.

[0073] Example 2 A thermoelectric conversion element according to Example 2 was obtained in the same manner as Example 1, except for the following points: Instead of the PET film, a polyimide (PI) sheet having a thickness of 50 μm was used as the second sheet.

[0074] Example 3 A thermoelectric conversion element according to Example 3 was obtained in the same manner as Example 1, except for the following points. Epoxy-based photoresist SU-8 manufactured by Nippon Kayaku Co., Ltd. was used as the precursor for the second sheet. After magnetizing the FeGa-containing thin wire, the epoxy-based photoresist SU-8 was applied to the main surface of the first sheet by spin coating to a predetermined thickness to form a coating film. This coating film was irradiated with ultraviolet light containing light with a wavelength of 365 nm to harden the coating film, thereby obtaining a second sheet containing an epoxy resin. The thickness of the second sheet was 20 μm. In this way, a thermoelectric conversion element according to Example 3 was obtained.

[0075] Example 4 A thermoelectric conversion element according to Example 4 was obtained in the same manner as in Example 3, except for the following points: A coating of epoxy photoresist SU-8 was formed on the main surface of the first sheet by spin coating so that the thickness of the second sheet would be 10 μm.

[0076] Example 5 A thermoelectric conversion element according to Example 5 was obtained in the same manner as in Example 3, except for the following points: A coating of epoxy photoresist SU-8 was formed on the main surface of the first sheet by spin coating so that the thickness of the second sheet would be 5 μm.

[0077] Example 6 A thermoelectric conversion element according to Example 6 was obtained in the same manner as in Example 3, except for the following points: A coating of epoxy photoresist SU-8 was formed on the main surface of the first sheet by spin coating so that the thickness of the second sheet was 2 μm.

[0078] Comparative Example 1 A thermoelectric conversion element according to Comparative Example 1 was obtained in the same manner as in Example 1, except that the application of adhesive and the bonding of the second sheet were not performed.

[0079] [Young's Modulus of Sheet] Test pieces prepared from the cured PET film, PI film, and SU-8 coating film used in each Example and Comparative Example were used to measure the tensile modulus (Young's modulus) of these sheets in accordance with Japanese Industrial Standards (JIS) K7161-1. A testing machine TCM-1kNB manufactured by Minebea Co., Ltd. was used for this measurement. The test speed was set to 300 mm / min. The results are shown in Table 1.

[0080] [Young's Modulus of FeGa-Containing Thin Wires] Using a nanoindenter (TI-950) manufactured by Hysitron, the tensile modulus (Young's modulus) of the material constituting the FeGa-containing thin wires in the thermoelectric conversion elements according to each example and comparative example was measured by nanoindentation. In this measurement, a triangular pyramidal Berkovich indenter made of diamond was pressed into the sample. The diagonal angle of this indenter was 115°. The results are shown in Table 1.

[0081] [Bending strain and stress] The arithmetic strain ε in the FeGa-containing thin wire when each thermoelectric conversion element was bent to have a curvature radius of 15 mm 15 Absolute value of and stress σ 15 was calculated according to the above formulas (1) to (3). In addition, the ratio of the distance (first distance) between the neutral axis and the FeGa-containing thin wire in the thickness direction of the first sheet to the thickness of each thermoelectric conversion element was calculated. The results are shown in Table 1. Note that, as a result of this calculation, in each example, the FeGa-containing thin wire was present in a range away from the neutral axis in the thickness direction of the first sheet by a distance equivalent to 45% of the thickness of the thermoelectric conversion element.

[0082] [Magnetic Properties] The magnetic properties of the FeGa-containing thin wires of the thermoelectric conversion elements according to each example and each comparative example were measured using a physical property measuring device PPMS-versalab from Quantum Design. Measurement samples were prepared by cutting out 2 mm squares from the portions of the modules according to each example and each comparative example where the conductive paths were arranged. Additionally, a vibrating sample magnetometer (VSM) was used for the measurements, and a magnetic field of ±800 [kA / m] was swept parallel to the magnetization direction of the magnetized FeGa-containing thin wire. An M-H curve was obtained at a temperature of 300 K, taking into account the thickness of the FeGa-containing thin wire and the area of ​​the FeGa-containing thin wire in the measurement sample. The ratio Mr / Ms of the magnetization Ms value at ±800 [kA / m] to the magnetization Mr value at 0 [kA / m] during the magnetic field sweep was defined as the squareness ratio S0 or S1. 15 The squareness ratio S0 was determined when the measurement sample was placed on a flat surface, and the squareness ratio S 15 The squareness ratios S and S were determined in a state where the measurement sample was arranged so that compressive stress was generated in the first sheet and the sample had a radius of curvature of 15 mm. 15 According to the formula (4), the rate of change R 15 The results are shown in Table 1.

[0083] As shown in Table 1, the arithmetic strain ε in the FeGa-containing thin wire when the thermoelectric conversion element according to each example was bent to have a curvature radius of 15 mm 15 Absolute value of and stress σ 15 was smaller than that of the thermoelectric conversion element according to Comparative Example 1. In addition, the rate of change in squareness ratio R 15 is the rate of change R of the squareness ratio of the thermoelectric conversion element according to Comparative Example 1 15 By configuring the thermoelectric conversion element so that the FeGa-containing thin wire is disposed between the first sheet and the second sheet, it is expected that the thermoelectric conversion performance will be less likely to change even if the thermoelectric conversion element is bent.

[0084]

[0085] A first aspect of the present invention provides a thermoelectric conversion element comprising: a first sheet; a thermoelectric conversion unit; and a second sheet, wherein the first sheet, the thermoelectric conversion unit, and the second sheet are arranged in the following order in a thickness direction of the first sheet: the first sheet, the thermoelectric conversion unit, and the second sheet; and the thermoelectric conversion unit includes a magnetic material.

[0086] In a second aspect of the present invention, when the thermoelectric conversion element is bent to have a curvature radius of 15 mm, the absolute value of the arithmetic strain in the thermoelectric conversion part is 1.5×10 -3 The present invention provides a thermoelectric conversion element according to a first aspect, which comprises:

[0087] In a third aspect of the present invention, when the thermoelectric conversion element is bent to have a curvature radius of 15 mm, the absolute value of the arithmetic strain in the thermoelectric conversion part is 1.0×10 -3 The present invention provides a thermoelectric conversion element according to a first aspect, which comprises:

[0088] A fourth aspect of the present invention provides a thermoelectric conversion element according to any one of the first to third aspects, in which the thermoelectric conversion portion is located on the neutral axis of the thermoelectric conversion element or a first distance away from the neutral axis in a thickness direction of the first sheet, and the ratio of the first distance to a thickness of the thermoelectric conversion element is 0.45 or less.

[0089] A fifth aspect of the present invention provides a thermoelectric conversion element according to the first or second aspect, in which the thermoelectric conversion portion is located on the neutral axis of the thermoelectric conversion element or a first distance away from the neutral axis in a thickness direction of the first sheet, and the ratio of the first distance to a thickness of the thermoelectric conversion element is 0.25 or less.

[0090] A sixth aspect of the present invention provides the thermoelectric conversion element according to any one of the first to fifth aspects, wherein the thermoelectric conversion portion has a squareness ratio of 80% or more.

[0091] A seventh aspect of the present invention provides the thermoelectric conversion element according to any one of the first to sixth aspects, in which the first sheet and the second sheet contain an organic material.

[0092] An eighth aspect of the present invention provides the thermoelectric conversion element according to any one of the first to seventh aspects, wherein the thermoelectric conversion portion generates a thermoelectromotive force in a direction perpendicular to a temperature gradient.

[0093] A ninth aspect of the present invention provides the thermoelectric conversion element according to any one of the first to eighth aspects, wherein the thermoelectric conversion portion generates a thermoelectromotive force by the anomalous Nernst effect.

[0094] A tenth aspect of the present invention provides a thermoelectric conversion device including the thermoelectric conversion element according to any one of the first to ninth aspects.

[0095] An eleventh aspect of the present invention provides the thermoelectric conversion device according to the tenth aspect, in which the thermoelectric conversion elements are arranged along a curved surface.

Claims

1. A thermoelectric conversion element comprising: a first sheet; a thermoelectric conversion unit; and a second sheet, wherein the first sheet, the thermoelectric conversion unit, and the second sheet are arranged in the thickness direction of the first sheet in the following order: the first sheet, the thermoelectric conversion unit, and the second sheet, and the thermoelectric conversion unit includes a magnetic material.

2. The absolute value of the arithmetic strain in the thermoelectric conversion unit when the thermoelectric conversion element is bent to have a curvature radius of 15 mm is 1.5 x 10 -3 The thermoelectric conversion element according to claim 1 , wherein:

3. When the thermoelectric conversion element is bent to have a curvature radius of 15 mm, the absolute value of the arithmetic strain in the thermoelectric conversion unit is 1.0 x 10 -3 The thermoelectric conversion element according to claim 1 , wherein:

4. A thermoelectric conversion element as described in claim 1, wherein the thermoelectric conversion portion is located on the neutral axis of the thermoelectric conversion element or a first distance away from the neutral axis in the thickness direction of the first sheet, and a ratio of the first distance to a thickness of the thermoelectric conversion element is 0.45 or less.

5. A thermoelectric conversion element as described in claim 1, wherein the thermoelectric conversion portion is located on the neutral axis of the thermoelectric conversion element or a first distance away from the neutral axis in the thickness direction of the first sheet, and a ratio of the first distance to a thickness of the thermoelectric conversion element is 0.25 or less.

6. The thermoelectric conversion element according to claim 1, wherein the thermoelectric conversion section has a squareness ratio of 80% or more.

7. The thermoelectric conversion element according to claim 1, wherein the first sheet and the second sheet contain an organic material.

8. The thermoelectric conversion element according to claim 1, wherein the thermoelectric conversion section generates a thermoelectromotive force in a direction perpendicular to a temperature gradient.

9. The thermoelectric conversion element according to claim 1, wherein the thermoelectric conversion section generates a thermoelectromotive force due to the anomalous Nernst effect.

10. A thermoelectric conversion device comprising the thermoelectric conversion element according to any one of claims 1 to 9.

11. The thermoelectric conversion device according to claim 10, wherein the thermoelectric conversion elements are arranged along a curved surface.

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