Thermoelectric conversion element, and method of manufacturing thermoelectric conversion element

Abstract

To provide a thermoelectric conversion element advantageous from a standpoint of an increase in sensitivity of sensing of a heat flow.SOLUTION: A thermoelectric conversion element 1a comprises a thermoelectric conversion layer 10 and a conductive layer 20. In the thermoelectric conversion layer 10, the conductive layer 20 is arranged on the thermoelectric conversion layer 10. The thermoelectric conversion layer 10 and the conductive layer 20 extend in a specific direction (Y-axis direction). A dimension W10 of the thermoelectric conversion layer 10 in a thickness direction (Z-axis direction) of the thermoelectric conversion layer 10 and a width direction (X-axis direction) perpendicular to the specific direction is smaller than a dimension W20 in the width direction of the conductive layer 20.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a thermoelectric conversion element and a method for manufacturing a thermoelectric conversion element. [Background technology]

[0002] 2. Description of the Related Art Conventionally, thermoelectric conversion elements having linearly extending thermoelectric conversion parts are known.

[0003] For example, Patent Document 1 describes a thermoelectric conversion element having a thermoelectric conversion part that includes a predetermined conductive magnetic material and extends linearly. This thermoelectric conversion element includes a connection part that includes a conductor and an extension part. In this thermoelectric conversion element, the extension part and the connection part are stacked. Alternatively, the extension part and the thermoelectric conversion part are stacked. The extension part is formed by a conductive magnetic material extending from the thermoelectric conversion part or a conductor extending from the connection part.

[0004] Non-Patent Document 1 describes a heat flow sensor that utilizes the anomalous Nernst effect. This heat flow sensor is made of a wire-shaped Fe 79 Ga 21 and Fe 79 Ga 21 and Ni 10 Cu 90 The structure is arranged on a PET substrate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2023 / 54415 [Non-patent literature]

[0006] [Non-Patent Document 1] Advanced Materials,(Germany),2023, 2303416 Summary of the Invention [Problem to be solved by the invention]

[0007] 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 is growing expectation 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).

[0008] The thermoelectric conversion element described in Patent Document 1 and the heat flow sensor described in Non-Patent Document 1 are promising technologies that meet these expectations. For example, in the thermoelectric conversion element described in Patent Document 1, height differences are unlikely to occur at the contact points for electrical connection between the thermoelectric conversion section and the connection section, making cracks less likely to occur at the contact points. In addition, the influence of the Seebeck effect of the thermoelectric conversion section on the output of the thermoelectric conversion element can be reduced. Such advantages are found in thermoelectric conversion elements having a structure in which a thermoelectric conversion layer and a conductive layer are stacked. Sensitivity is particularly important in sensing heat flow. On the other hand, the technologies described in Patent Document 1 and Non-Patent Document 1 leave room for further consideration in terms of improving heat flow sensing.

[0009] In view of the above circumstances, the present invention provides a thermoelectric conversion element that is advantageous from the viewpoint of increasing the sensitivity of heat flow sensing. [Means for solving the problem]

[0010] The present invention provides a thermoelectric conversion layer; a conductive layer disposed on the thermoelectric conversion layer, the thermoelectric conversion layer and the conductive layer extend in a specific direction, the dimensions of the thermoelectric conversion layer in a thickness direction and a width direction perpendicular to the specific direction are smaller than the dimensions of the conductive layer in the width direction; A thermoelectric conversion element is provided.

[0011] The present invention also provides forming the thermoelectric conversion layer and the conductive layer extending in a specific direction by etching a laminated structure including a first layer that is a precursor of a thermoelectric conversion layer and a second layer that is a precursor of a conductive layer disposed on the first layer, and adjusting the dimensions of the thermoelectric conversion layer in a thickness direction of the thermoelectric conversion layer and in a width direction perpendicular to the specific direction to be smaller than the dimensions of the conductive layer in the width direction; A method for manufacturing a thermoelectric conversion element is provided. [Effects of the Invention]

[0012] The above-mentioned thermoelectric conversion element is advantageous from the viewpoint of increasing the sensitivity of heat flow sensing. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a plan view showing an example of a thermoelectric conversion element. [Figure 2] FIG. 2 is a cross-sectional view of the thermoelectric conversion element taken along line II-II shown in FIG. [Figure 3] FIG. 3 is an enlarged view of a portion of the cross-sectional view shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view of a thermoelectric conversion element having a laminated structure according to a reference example. [Figure 5] FIG. 5 is a diagram illustrating an example of a method for manufacturing a thermoelectric conversion element. [Figure 6] FIG. 6 is a scanning transmission electron microscope (STEM) photograph of a cross section of the thermoelectric conversion element according to Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0014] 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 the present invention is not limited to the following embodiments. In the accompanying drawings, the X-axis, Y-axis, and Z-axis are perpendicular to one another.

[0015] As shown in FIGS. 1 to 3, the thermoelectric conversion element 1a includes a thermoelectric conversion layer 10 and a conductive layer 20. The conductive layer 20 is disposed on the thermoelectric conversion layer 10. For example, in the thermoelectric conversion element 1a, a laminated structure 3 including the thermoelectric conversion layer 10 and the conductive layer 20 is configured. As shown in FIG. 1, the thermoelectric conversion layer 10 and the conductive layer 20 extend in a specific direction (Y-axis direction). As shown in FIG. 3, the dimension W of the thermoelectric conversion layer 10 in the thickness direction (Z-axis direction) of the thermoelectric conversion layer 10 and in the width direction (X-axis direction) perpendicular to the specific direction is 10 is the dimension W of the conductive layer 20 in the width direction 20 Smaller than.

[0016] In order to enhance the sensitivity of heat flow sensing using the thermoelectric conversion element 1a, the specific G 20 / (G 10 +G 20 ) is advantageous. 10 is the conductance of the thermoelectric conversion layer 10 in a specific direction, and G 20 is the conductance of the conductive layer 20 in a particular direction. 20 / (G 10 +G 20 ) is large, the current in the conductive layer 20 of the laminated structure 3 becomes large and the current in the thermoelectric conversion layer 10 becomes small. The current generated by the thermoelectric effect of the thermoelectric conversion layer 10 of the laminated structure 3 can act to cancel out the current that should be output for heat flow sensing. Therefore, in order to increase the sensitivity of heat flow sensing, it is important that a larger current is more likely to be generated in the conductive layer 20 than in the thermoelectric conversion layer 10 in a specific direction of the laminated structure 3.

[0017] In the stacked structure 3x according to the reference example shown in FIG. 4, the dimension W 10 and the width W of the conductive layer 20 20 The conductance G of the thermoelectric conversion layer 10 is equal to 10 and the conductance G of the conductive layer 20 20 are the dimensions W 10 and dimension W 20In the laminated structure 3x, unless the thickness of the conductive layer 20 is increased, the ratio G 20 / (G 10 +G 20 On the other hand, according to the thermoelectric conversion element 1a, the dimension W 10 is the dimension W 20 Since it is smaller than G 20 / (G 10 +G 20 ) tends to be large, and the sensitivity of heat flow sensing using the thermoelectric conversion element 1a tends to be high.

[0018] Dimension W 10 is the dimension W 20 As long as it is smaller than dimension W 20 Dimension W for 10 The ratio is not limited to a specific value. The ratio may be, for example, 0.95 or less, or may be 0.9 or less, or may be 0.8 or less. The ratio may be, for example, 0.2 or more, or 0.3 or more, or 0.4 or more, or 0.5 or more.

[0019] Dimension W 20 is not limited to a specific value. 20 is, for example, 500 μm or less. This allows a large number of stacked structures 3 to be arranged in the width direction of the thermoelectric conversion element 1a, for example, and tends to increase the sensitivity of heat flow sensing using the thermoelectric conversion element 1a. 20 The dimension W may be 400 μm or less, 300 μm or less, 200 μm or less, or 100 μm or less. 20 is, for example, 0.1 μm or more. This makes it difficult for disconnections to occur in the laminated structure 3, and the thermoelectric conversion element 1a is likely to exhibit high durability. 20 may be 0.5 μm or more, 1 μm or more, 2 μm or more, 5 μm or more, or 10 μm or more.

[0020] The thickness of the thermoelectric conversion layer 10 is not limited to a specific value. The thickness is, for example, 5 to 1000 nm. 20 / (G 10 +G 20) tends to fall within a desired range. The thickness of the thermoelectric conversion layer 10 may be 10 nm or more, 20 nm or more, or 30 nm or more, or may be 500 nm or less, 400 nm or less, 300 nm or less, 200 nm or less, or 100 nm or less.

[0021] The thickness of the conductive layer 20 is not limited to a specific value. The thickness is, for example, 5 to 1000 nm. 20 / (G 10 +G 20 ) tends to fall within the desired range. The thickness of the conductive layer 20 may be 10 nm or more, 20 nm or more, or 30 nm or more, or may be 500 nm or less, 400 nm or less, 300 nm or less, 200 nm or less, or 100 nm or less.

[0022] 3, the thermoelectric conversion element 1a includes a reinforcing portion 32. The reinforcing portion 32 is in contact with a first end face 10e of the thermoelectric conversion layer 10 in the width direction (X-axis direction), and is covered with the conductive layer 20. 10 is the dimension W 20 Since the thickness of the conductive layer 20 is smaller than the first end surface 10e, a part of the conductive layer 20 in the laminate structure 3 protrudes from the first end surface 10e. The part of the conductive layer 20 protruding from the first end surface 10e is supported by the reinforcing portion 32. Therefore, during the manufacture or use of the thermoelectric conversion element 1a, the laminate structure 3 is less likely to be damaged or destroyed, and the thermoelectric conversion element 1a is more likely to exhibit high durability.

[0023] Resistivity ρ of thermoelectric conversion layer 10 10 and the resistivity ρ of the conductive layer 20 20 is not limited to a specific value, and the resistivity ρ 20 Resistivity ρ 10 The ratio ρ 10 / ρ 20 is not limited to a specific value. 10 / ρ 20is, for example, 17 or less. In this case, the difference between the Seebeck coefficient in a specific direction of the thermoelectric conversion layer 10 and the Seebeck coefficient in a specific direction of the conductive layer 20 tends to be small, which makes it easier to prevent a decrease in the sensitivity of heat flow sensing due to the Seebeck effect in the laminate structure 3. In addition, from the viewpoint of imparting additional properties such as high durability during storage of the thermoelectric conversion element 1a, the scope for material selection tends to be broadened.

[0024] Ratio 10 / ρ 20 may be 15 or less, 12 or less, 10 or less, 8 or less, or 6 or less. 10 / ρ 20 is, for example, 1.5 or more. In this case, the ratio G 20 / (G 10 +G 20 ) tends to fall within the desired range.

[0025] Resistivity ρ of thermoelectric conversion layer 10 10 For example, 1 x 10 -4 This makes it easier to reduce the resistance of the element and reduce noise. 10 is 1 x 10 -5 Ωm or less, 7×10 -6 Ωm or less, 3×10 -6 Ωm or less, or 2 x 10 -6 The resistivity may be, for example, 1×10 -8 This makes it easier for the desired electromotive force to be generated in the thermoelectric conversion layer 10. 10 is 5 x 10 -8 Ωm or more, 1×10 -7 Ωm or more, or 5×10 -7 It may be Ωm or more.

[0026] Resistivity ρ of the conductive layer 20 20 For example, 1 x 10 -8 Ωm~1×10 -5 Ωm.

[0027] Seebeck coefficient S of thermoelectric conversion layer 10 10 and the Seebeck coefficient S of the conductive layer 20 20Absolute value of the difference between |S 10 -S 20 is not limited to a specific value. Its absolute value is, for example, 10 μV / K or less. In this case, even if a temperature gradient occurs in a specific direction (Y-axis direction), the thermoelectromotive force caused by the Seebeck effect occurring in that specific direction is likely to be small. Therefore, it is easy to prevent a decrease in the sensitivity of heat flow sensing due to the Seebeck effect occurring in that specific direction. The Seebeck coefficient is, for example, a value at 25 to 40°C, and can be measured according to the method described in the Examples.

[0028] Absolute value |S 10 -S 20 is preferably 8 μV / K or less, more preferably 5 μV / K or less, and even more preferably 3 μV / K or less.

[0029] The area S of the cross section perpendicular to a specific direction (Y-axis direction) of the conductive layer 20 20 The area S of the cross section perpendicular to a specific direction of the thermoelectric conversion layer 10 10 The ratio S 10 / S 20 is not limited to a specific value. 10 / S 20 is, for example, 0.95 or less. 20 / (G 10 +G 20 ) tends to be large, and the sensitivity of heat flow sensing using the thermoelectric conversion element 1a tends to be high.

[0030] ratio S 10 / S 20 The ratio S is preferably 0.92 or less, and more preferably 0.90 or less. 10 / S 20 is, for example, 0.40 or more, and may be 0.45 or more, or 0.50 or more.

[0031] The material forming the thermoelectric conversion layer 10 is not limited to a specific material. The thermoelectric conversion layer 10 includes, for example, a conductive magnetic material having ferromagnetism or antiferromagnetism that exhibits the anomalous Nernst effect. In this case, for example, when a temperature gradient occurs in the thickness direction of the thermoelectric conversion layer 10, an electromotive force is generated in a direction perpendicular to the thickness direction.

[0032] Substances that exhibit the anomalous Nernst effect are, for example, magnetic materials having a saturation magnetization of 5×10 -3 T or more or substances having a band structure with a Weyl point near the Fermi energy. The conductive magnetic material contained in the thermoelectric conversion layer 10 contains, for example, at least one substance selected from the group consisting of the following (i), (ii), (iii), (iv), and (v). (i) A stoichiometric substance having a composition represented by Fe3X (ii) An off-stoichiometric substance in which the composition ratio of Fe and X deviates from the substance of (i) above (iii) A substance in which part of the Fe site of the substance of (i) above or part of the Fe site of the substance of (ii) above is substituted with a typical metal element or transition element other than X (iv) Fe3M1 1-x M2 x (0 < x < 1), and M1 and M2 are different typical elements (v) A substance in which part of the Fe site of the substance of (i) above is substituted with a transition element other than X, and part of the X site of the substance of (i) above is substituted with a typical metal element other than X

[0033] In the substances of (i) to (v) above, 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 (iv) above, the combination of M1 and M2 is not limited to a specific combination as long as M1 and M2 are different typical elements. In (iv) above, the combination of M1 and M2 is, for example, Ga and Al, Si and Al, or Ga and B.

[0034] The conductive magnetic material included in the thermoelectric conversion layer 10 may include Co2MnGa. The conductive magnetic material included in the thermoelectric conversion layer 10 may include a conductive antiferromagnetic material such as Mn3Sn.

[0035] The material forming the conductive layer 20 is not limited to a specific material. The conductive layer 20 includes, for example, a metal or an alloy. The conductive layer 20 includes, for example, at least one metal selected from the group consisting of Cu, Ag, Au, Al, Ni, and Co. In this case, the content of these metals in the conductive layer 20 is 50% or more in terms of the number of atoms. In other words, the total content of Cu, Ag, Au, Al, Ni, and Co in the conductive layer 20 is 50% or more in terms of the number of atoms. The conductive layer 20 may be formed of a single metal or an alloy.

[0036] The conductive layer 20 may contain at least one metal selected from the group consisting of Cu, Ag, Au, and Al, and at least one element selected from the group consisting of Group 8 elements, Group 9 elements, and Group 10 elements. The Group 8 element is, for example, Fe. The Group 9 element is, for example, Co. The Group 10 element is, for example, Ni or Pt. The content of the at least one element selected from the group consisting of Group 8 elements, Group 9 elements, and Group 10 elements in the conductive layer 20 is not limited to a specific value. The content may be 1% or more, 3% or more, 5% or more, 10% or more, 20% or more, 30% or more, 40% or more, or 50% or more, based on the number of atoms.

[0037] 1, the thermoelectric conversion element 1a includes, for example, a plurality of laminate structures 3. In this case, the plurality of laminate structures 3 are arranged in parallel to each other.

[0038] The thermoelectric conversion layer 10 has, for example, a meander pattern. With this configuration, the length of the thermoelectric conversion layer 10 extending in a specific direction (Y-axis direction) becomes large, and the electromotive force generated in the thermoelectric conversion element 1a tends to become large. By connecting wiring to both ends of the meander pattern, the electromotive force generated in the thermoelectric conversion element 1a can be extracted to the outside.

[0039] When the thermoelectric conversion layer 10 has a meander pattern, the laminated structure 3 and a structure consisting of only the thermoelectric conversion layer 10 are alternately arranged in the width direction (X-axis direction), thereby forming a conductive path 15. In a structure consisting of only the thermoelectric conversion layer 10, the current generated by the thermoelectric effect is unlikely to be canceled out in the laminated structure 3.

[0040] As shown in FIG. 2 , the thermoelectric conversion element 1a further includes, for example, a substrate 5. The substrate 5 supports the thermoelectric conversion layer 10 and the conductive layer 20. The thermoelectric conversion layer 10 is in contact with, for example, the substrate 5. The substrate 5 is, for example, flexible, which allows the thermoelectric conversion element 1a to be arranged along a curved surface. The substrate 5 has elasticity that allows elastic deformation of a strip-shaped test piece made from the substrate 5 when the test piece is wound around a cylindrical mandrel with a diameter of 10 cm so that both ends in the longitudinal direction of the test piece face in the same direction. The substrate 5 may also be an inflexible substrate such as a glass substrate.

[0041] When the substrate 5 is flexible, the substrate 5 contains, for example, at least an organic polymer. This makes it easy to reduce the manufacturing cost of the thermoelectric conversion element 1a. Examples of the organic polymer are polyethylene terephthalate (PET), polyethylene naphthalate (PEN), acrylic resin (PMMA), polycarbonate (PC), polyimide (PI), or cycloolefin polymer (COP). The substrate 5 may be ultra-thin glass. An example of ultra-thin glass is G-Leaf (registered trademark) manufactured by Nippon Electric Glass Co., Ltd.

[0042] The visible light transmittance of the base material 5 is not limited to a specific value. The base material 5 has a visible light transmittance of, for example, 80% or more. This makes it easy to check for the presence or absence of foreign matter during the manufacture of the thermoelectric conversion element 1a, and can prevent the wiring of the thermoelectric conversion element 1a from opening. The visible light transmittance of the base material 5 may be 83% or more, 86% or more, or 89% or more.

[0043] 3, the thermoelectric conversion element 1a includes, for example, a protective layer 30. The protective layer 30 covers, for example, the surfaces of the base material 5, the thermoelectric conversion layer 10, and the conductive layer 20. This protects the thermoelectric conversion layer 10 and the conductive layer 20. This makes it easier for the thermoelectric conversion element 1a to exhibit high durability. A portion of the protective layer 30 forms, for example, a reinforcing portion 32.

[0044] The protective layer 30 contains, for example, a cured resin that can be cured by heating or ultraviolet irradiation, etc. Examples of the resin contained in the protective layer 30 are acrylic resin, epoxy resin, and silicone resin.

[0045] An example of a method for manufacturing the thermoelectric conversion element 1a will be described. As shown in Fig. 5, the thermoelectric conversion element 1a is manufactured by a method including forming the thermoelectric conversion layer 10 and the conductive layer 20 extending in a specific direction (Y-axis direction) by etching the laminated structure 30a. By etching the laminated structure 30a, the dimension W of the thermoelectric conversion layer 10 in the width direction (X-axis direction) is further reduced. 10 is the dimension W of the conductive layer 20 in the width direction 20 The laminated structure 30a includes a first layer 10a that is a precursor of the thermoelectric conversion layer 10 and a second layer 20a that is a precursor of the conductive layer 20 disposed on the first layer 10a.

[0046] The etching is continued for a predetermined time after the first layer 10a has been completely penetrated in the thickness direction. 10 is the dimension W 20 It is easier to adjust smaller.

[0047] As shown in FIG. 5, first, a first layer 10a is formed on a substrate 5. Next, a second layer 20a is formed on the first layer 10a. The first layer 10a and the second layer 20a can be formed successively, for example, while being isolated from the atmosphere. This allows a laminated structure 30a to be obtained without the interface between the first layer 10a and the second layer 20a being affected by the atmosphere. This makes it easier for the contact portion for electrical connection between the thermoelectric conversion layer 10 and the conductive layer 20 to have high durability.

[0048] The method for forming the first layer 10a and the second layer 20a is not limited to a specific method. The first layer 10a and the second layer 20a are formed by, for example, magnetron sputtering. In this case, the first layer 10a and the second layer 20a are less likely to peel off from each other, and cracks are less likely to occur in the contact portion for electrical connection between the thermoelectric conversion layer 10 and the conductive layer 20. The first layer 10a and the second layer 20a may each be formed by other methods such as sputtering, chemical vapor deposition (CVD), pulsed laser deposition (PLD), ion plating, and plating.

[0049] Photoresist is applied to the surface of the laminated structure 30a, and a photomask is placed on the laminated structure 30a for exposure. Next, the exposed portion of the photoresist is removed by a developer. Next, the laminated structure 30a is immersed in an etching solution capable of selectively etching the material constituting the second layer 20a for wet etching. As a result, the second layer 20a is etched so as to have, for example, a meander pattern 22 in plan view. Next, the laminated structure 30a is immersed in an etching solution capable of selectively etching the material constituting the first layer 10a for wet etching. As a result, the first layer 10a is etched so as to have, for example, a meander pattern 12 in plan view. The wet etching of the first layer 10a is continued for a predetermined time after the penetration of the first layer 10a is completed. For example, the time from the start to the end of the wet etching of the first layer 10a is adjusted to be at least two times but not more than six times the time from the start of the wet etching of the first layer 10a to the completion of the penetration of the first layer 10a. As a result, the dimension W 10 The dimension W 20Next, the photoresist is removed by washing with a predetermined organic solvent.

[0050] Next, photoresist is applied to the second layer 20a forming the meander pattern 22, and a photomask is placed on the laminated structure 30a to expose areas other than the area where the laminated structure 3 will be formed. The exposed portions of the photoresist are then removed using a developer. Next, the laminated structure 30a is immersed in an etching solution capable of selectively etching the material of the second layer 20a, performing wet etching. This exposes a portion of the first layer 10a forming the meander pattern 12, resulting in a structure consisting of only the first layer 10a and a laminate of the first layer 10a and the second layer 20a alternately arranged in the width direction. Next, the photoresist is removed by washing with a predetermined organic solvent. In this manner, the conductive layer 20 is obtained from the second layer 20a. The first layer 10a is magnetized, for example, in the width direction. This results in a thermoelectric conversion layer 10.

[0051] Next, a liquid that is a precursor of the protective layer 30 is applied onto the substrate 5, and a coating film of this liquid is formed. This coating film is cured by a method such as heating or ultraviolet irradiation to form the protective layer 30. As a result, the space that contacts the first end face 10e in the width direction of the thermoelectric conversion layer 10 and is covered by the conductive layer 20 is filled with resin to form the reinforcing portion 32. In this manner, for example, a thermoelectric conversion element 1a can be obtained.

[0052] The viscosity of the liquid precursor of the protective layer 30 is not limited to a specific value. The viscosity is, for example, 0.2 to 1000 mPa·sec at 20° C. In this case, the liquid easily enters the space in contact with the first end face 10e and covered by the conductive layer 20, and the reinforcing portion 32 is easily formed in the desired state.

[0053] The thermoelectric conversion element 1a may be provided together with, for example, an adhesive layer. In this case, the base material 5 is disposed between the thermoelectric conversion layer 10 and the adhesive layer in the thickness direction of the base material 5. This allows the adhesive layer to be pressed against an article, thereby attaching the thermoelectric conversion element 1a to the article.

[0054] 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 strength of the adhesive layer while 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 1a to be attached to an article. [Example]

[0055] 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.

[0056] Example 1 An iron alloy film having a thickness of 40 nm was formed on a polyethylene terephthalate (PET) film having a thickness of 50 μm by DC magnetron sputtering using a target material containing Fe and Ga. The Fe content:Ga content in the target material used in this DC magnetron sputtering was 3:1 based on the number of atoms. Next, a copper alloy film having a thickness of 40 nm was formed on the iron alloy film by DC magnetron sputtering using a target material containing Cu and Ni. The Cu content:Ni content in the target material used in this DC magnetron sputtering was 9:1 based on the number of atoms. In this way, a PET film with an alloy film according to Example 1 was obtained.

[0057] Next, the alloy film-coated PET film of Example 1 was fixed to the surface of a glass plate measuring 10 cm on a side in plan view using thermally peelable double-sided tape. Next, a spin coater was used to apply photoresist OFPR-800 LB (Tokyo Ohka Kogyo Co., Ltd.) to a thickness of approximately 1 μm onto the copper alloy film, and the resulting coating was prebaked at 110°C. Next, a photomask was placed on the prebaked coating, and the photoresist was exposed to light. The exposed portions of the photoresist were removed using developer NMD-3 (Tokyo Ohka Kogyo Co., Ltd.). The alloy film-coated PET film was then immersed in etching solution A, which can selectively etch the material constituting the copper alloy film, to etch the copper alloy film. Etching solution A was obtained by diluting a copper selective etching solution (Nippon Chemical Industry Co., Ltd.) 20 times by volume with pure water. Etching using etching solution A was stopped once penetration in the thickness direction of the portion of the copper alloy film corresponding to the removed exposed portion was confirmed. This resulted in a meander pattern of the copper alloy film. Next, the PET film with the alloy film was immersed in etching solution B, which can selectively etch the material that makes up the iron alloy film, to etch the iron alloy film. Etching solution B was obtained by diluting Kanto Chemical's mixed acid Al etching solution twice by volume with pure water. Etching using etching solution B was continued for a predetermined time after penetration in the thickness direction of the iron alloy film portion corresponding to the removed exposed portion was confirmed. The time from the start to the end of etching using etching solution B was 60 seconds, and the time from the start of etching to penetration in the thickness direction of the iron alloy film was 30 seconds. This resulted in a meander pattern of the iron alloy film. Next, the photoresist was removed by washing with an organic solvent.

[0058] Next, using a spin coater, the photoresist was applied to a copper alloy film with a meander pattern approximately 1 μm thick, and the resulting coating was prebaked at 110°C. Next, a photomask was placed on the prebaked coating, and the photoresist was exposed to light. The exposed portions of the photoresist were removed using the developer. The PET film with the alloy film was then immersed in etching solution A, which can selectively etch the material constituting the copper alloy film, to etch the copper alloy film. This etched a portion of the meander patterned copper alloy film, resulting in a conductive layer. A pattern was obtained in which linear portions consisting of only the iron alloy film and linear portions consisting of a laminated structure of the iron alloy film and the copper alloy film serving as the conductive layer were alternately arranged. The iron alloy film had a meander pattern. Using an electromagnet with a central magnetic flux density of 0.5 T, the iron alloy film was magnetized in the width direction, parallel to the main surface of the PET film and perpendicular to the direction of the linear portions consisting of only the iron alloy film, to obtain a thermoelectric conversion layer.

[0059] Next, a liquid coating agent was applied using a spin coater so that it covered the thermoelectric conversion layer and conductive layer, forming a coating film. The liquid coating agent was obtained by diluting SU-8 3005 manufactured by Nippon Kayaku Co., Ltd. with 2-methoxy-1-methylethyl acetate manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., at a volume ratio of 7:3. The viscosity of the coating agent at 20°C was 5 mPa·sec. Next, the coating film was heated in an environment of 95°C for 90 seconds. Next, ultraviolet light with a peak wavelength of 365 nm was applied at 100 mJ / cm. 2 The coating agent was cured by irradiation under the conditions of (a) to (c) to obtain a protective layer. Next, the thermally peelable double-sided tape was peeled off from the glass by heat treatment in a 150°C environment for 30 minutes, and then the double-sided tape was peeled off from the PET film. In this way, the thermoelectric conversion element according to Example 1 was obtained.

[0060] <Example 2> A thermoelectric conversion element according to Example 2 was obtained in the same manner as in Example 1, except for the following points: The time from the start to the end of etching using etchant B was changed to 120 seconds.

[0061] Example 3 A thermoelectric conversion element according to Example 3 was obtained in the same manner as in Example 1, except that no protective layer was formed.

[0062] Example 4 A thermoelectric conversion element according to Example 4 was obtained in the same manner as in Example 2, except that no protective layer was formed.

[0063] <Comparative Example 1> A thermoelectric conversion element according to Comparative Example 1 was obtained in the same manner as in Example 1, except for the following points. Etching using etchant B was terminated immediately after penetration in the thickness direction of the iron alloy film from the start of the etching. The time from the start to the end of etching using etchant B was 30 seconds.

[0064] <Comparative Example 2> A thermoelectric conversion element according to Comparative Example 2 was obtained in the same manner as in Example 1, except for the following points: A pure copper target material was used instead of the target material containing Cu and Ni, and a pure copper film was formed instead of the copper alloy film.

[0065] [Observation of layered structure] Samples for optical microscope observation were prepared from the thermoelectric conversion elements according to each Example and Comparative Example, and optical microscope observation was performed. From the results of this optical microscope observation, the width of the thermoelectric conversion layer and the width of the conductive layer in the laminated structure were determined. The results are shown in Table 1. Samples for scanning transmission electron microscope (STEM) observation were prepared from the thermoelectric conversion elements according to each Example and Comparative Example. These samples were prepared so that a cross section of the laminated structure perpendicular to the direction in which the thermoelectric conversion layer and the conductive layer extend could be observed. From the results of observation using these samples, the thickness of the thermoelectric conversion layer and the thickness of the conductive layer in the laminated structure were determined. In addition, the ratio of the cross-sectional area of the conductive layer to the cross-sectional area of the thermoelectric conversion layer was determined. The results are shown in Table 1. FIG. 6 shows a STEM photograph of the sample obtained from the thermoelectric conversion element according to Example 1.

[0066] [Resistivity measurement] The sheet resistance of the thermoelectric conversion layer and the conductive layer for each example and comparative example was measured using a non-contact resistance measuring device NC-80MAP manufactured by Napson Corporation according to the eddy current measurement method in accordance with Japanese Industrial Standard JIS Z 2316-1:2014. The product of the sheet resistance of each layer measured in this way and the thickness of each layer was calculated to determine the resistivity ρ of the thermoelectric conversion layer and the conductive layer. The results are shown in Table 1.

[0067] [Conductance ratio] In the laminated structure of the thermoelectric conversion layer and the conductive layer, the conductance G of each layer was determined according to the following formula (1). In formula (1), w is the width of the layer [m], t is the thickness of the layer [m], l is the length of the laminated structure [m], and ρ is the specific resistance of the layer [Ω·m]. The ratio of the conductance of the conductive layer to the sum of the conductance of the thermoelectric conversion layer and the conductance of the conductive layer was determined to be the conductance ratio. The results are shown in Table 1. G=w×t×l / ρ Equation (1)

[0068] [Sensitivity evaluation] The thermoelectric conversion elements according to each Example and Comparative Example 1 were fixed between a pair of Cu plates measuring 30 mm, 30 mm, and 5 mm using silicone grease KS609 manufactured by Shin-Etsu Chemical Co., Ltd. to prepare samples for sensitivity evaluation. The samples were placed on a cooling plate SCP-125 manufactured by AS ONE Corporation. A film heater manufactured by Shinwa Measuring Instruments Co., Ltd. was fixed on top of the upper Cu plate using double-sided tape No. 5000NS manufactured by Nitto Denko Corporation. This heater had dimensions of 30 mm square and an electrical resistance of 20 Ω. With the temperature of the cooling plate maintained at 25°C, the film heater was heated under constant voltage control of 10 V, and the heat output from the film heater was 0.52 W / cm. 2 The temperature was adjusted to 100°C. At this time, the electromotive force generated in each sample was measured using a data logger. The electromotive force was measured by measuring the voltage across both ends of the meander pattern. The sensitivity of each thermoelectric conversion element was calculated by dividing the electromotive force by the amount of heat output from the film heater. The results are shown in Table 1.

[0069] [Check for disconnection] For each example and comparative example 1, 20 thermoelectric conversion elements were fabricated, and each element was checked for the presence of a disconnection in the thermoelectric conversion layer, the conductive layer, or the boundary between the thermoelectric conversion layer and the conductive layer. A tester was used to measure the electrical resistance at both ends of the meander pattern in each element, and if the resistance value was unmeasurable, it was evaluated as having a disconnection. The number of elements evaluated as having a disconnection among the 20 thermoelectric conversion elements is shown in Table 1.

[0070] [Seebeck coefficient measurement] Using a small, refrigerant-free physical property measurement system, PPMS VersaLab, manufactured by Quantum Design, the Seebeck coefficients of the thermoelectric conversion layer and conductive layer of the thermoelectric conversion elements in each example and comparative example were measured at 27 to 37°C using separately prepared samples. Each Seebeck coefficient was determined based on the electromotive force and temperature difference induced between two thermometers attached to the sample when a heat flow was generated by a heater attached to one end of the sample. The Seebeck coefficients of the individual materials constituting each thermoelectric conversion layer and conductive layer at 27 to 37°C are shown in Table 1.

[0071] As shown in Table 1, the sensitivity of the thermoelectric conversion elements according to each Example was higher than that of the thermoelectric conversion element according to Comparative Example 1. This suggests that in the laminated structure of the thermoelectric conversion layer and the conductive layer, a smaller width of the thermoelectric conversion layer than the conductive layer is advantageous for increasing the sensitivity of the thermoelectric conversion element. In the thermoelectric conversion elements according to each Example, the difference between the Seebeck coefficient of the conductive layer and the Seebeck coefficient of the thermoelectric conversion layer was small, and it is believed that even if a thermal gradient occurs in the length direction of the meander pattern, the electromotive force associated with the Seebeck effect is small. On the other hand, in the thermoelectric conversion element according to Comparative Example 2, the difference between the Seebeck coefficient of the conductive layer and the Seebeck coefficient of the thermoelectric conversion layer was large. Comparing Examples 1 and 2 with Examples 3 and 4, the number of thermoelectric conversion elements that experienced disconnections was higher in Examples 3 and 4 than in Examples 1 and 2. It is believed that disconnections are likely caused by peeling off the PET film from the thermally peelable double-sided tape. This suggests that the formation of a protective layer can suppress the occurrence of such disconnections. 6, it was confirmed that the space in contact with the end face in the width direction of the thermoelectric conversion layer and covered by the conductive layer was filled with the resin forming the protective layer. It is believed that this resin filling reinforces the laminated structure of the thermoelectric conversion layer and the conductive layer, making disconnection less likely to occur.

[0072] [Table 1]

[0073] A first aspect of the present invention is a thermoelectric conversion layer; a conductive layer disposed on the thermoelectric conversion layer, the thermoelectric conversion layer and the conductive layer extend in a specific direction, the dimensions of the thermoelectric conversion layer in a thickness direction and a width direction perpendicular to the specific direction are smaller than the dimensions of the conductive layer in the width direction; A thermoelectric conversion element is provided.

[0074] A second aspect of the present invention is a reinforcing portion in contact with a first end surface of the thermoelectric conversion layer in the width direction and covered with the conductive layer; A thermoelectric conversion element according to a first aspect is provided.

[0075] A third aspect of the present invention is The ratio of the resistivity of the thermoelectric conversion layer to the resistivity of the conductive layer is 17 or less. A thermoelectric conversion element according to a first or second aspect is provided.

[0076] A fourth aspect of the present invention is the absolute value of the difference between the Seebeck coefficient of the thermoelectric conversion layer and the Seebeck coefficient of the conductive layer is 10 μV / K or less; The present invention provides a thermoelectric conversion element according to any one of the first to third aspects.

[0077] A fifth aspect of the present invention is a ratio of a cross-sectional area of the thermoelectric conversion layer perpendicular to the specific direction to a cross-sectional area of the conductive layer perpendicular to the specific direction is 0.95 or less; The present invention provides a thermoelectric conversion element according to any one of the first to fourth aspects.

[0078] A sixth aspect of the present invention is The thermoelectric conversion layer further includes a flexible substrate that supports the thermoelectric conversion layer and the conductive layer. The present invention provides a thermoelectric conversion element according to any one of the first to fifth aspects.

[0079] A seventh aspect of the present invention is The thermoelectric conversion layer has a meander pattern. The present invention provides a thermoelectric conversion element according to any one of the first to sixth aspects.

[0080] An eighth aspect of the present invention is forming the thermoelectric conversion layer and the conductive layer extending in a specific direction by etching a laminated structure including a first layer that is a precursor of a thermoelectric conversion layer and a second layer that is a precursor of a conductive layer disposed on the first layer, and adjusting the dimensions of the thermoelectric conversion layer in a thickness direction of the thermoelectric conversion layer and in a width direction perpendicular to the specific direction to be smaller than the dimensions of the conductive layer in the width direction; A method for manufacturing a thermoelectric conversion element is provided.

[0081] A ninth aspect of the present invention is The etching is continued for a predetermined time after the first layer has been completely penetrated in the thickness direction. According to an eighth aspect, there is provided a manufacturing method.

[0082] A tenth aspect of the present invention is The method further includes filling a space that is in contact with a first end surface in the width direction of the thermoelectric conversion layer and is covered by the conductive layer with a resin to form a reinforcing portion. A manufacturing method according to the eighth or ninth aspect is provided. [Explanation of symbols]

[0083] 1a Thermoelectric conversion element 5 Base material 10 Thermoelectric conversion layer 10a First layer 10e First end surface 20 Conductive layer 20a Second layer 30a laminated structure 32 Reinforcement

Claims

1. a thermoelectric conversion layer; a conductive layer disposed on the thermoelectric conversion layer, the thermoelectric conversion layer and the conductive layer extend in a specific direction, the dimensions of the thermoelectric conversion layer in a thickness direction and a width direction perpendicular to the specific direction are smaller than the dimensions of the conductive layer in the width direction; Thermoelectric conversion element.

2. a reinforcing portion in contact with a first end surface of the thermoelectric conversion layer in the width direction and covered with the conductive layer; The thermoelectric conversion element according to claim 1 .

3. a ratio of the resistivity of the thermoelectric conversion layer to the resistivity of the conductive layer is 17 or less; The thermoelectric conversion element according to claim 1 .

4. the absolute value of the difference between the Seebeck coefficient of the thermoelectric conversion layer and the Seebeck coefficient of the conductive layer is 10 μV / K or less; The thermoelectric conversion element according to claim 1 .

5. a ratio of an area of a cross section of the thermoelectric conversion layer perpendicular to the specific direction to an area of a cross section of the conductive layer perpendicular to the specific direction is 0.95 or less; The thermoelectric conversion element according to claim 1 .

6. The thermoelectric conversion layer further includes a flexible substrate that supports the thermoelectric conversion layer and the conductive layer. The thermoelectric conversion element according to claim 1 .

7. The thermoelectric conversion layer has a meander pattern. The thermoelectric conversion element according to claim 1 .

8. forming the thermoelectric conversion layer and the conductive layer extending in a specific direction by etching a laminated structure including a first layer that is a precursor of a thermoelectric conversion layer and a second layer that is a precursor of a conductive layer disposed on the first layer, and adjusting the dimensions of the thermoelectric conversion layer in a thickness direction of the thermoelectric conversion layer and in a width direction perpendicular to the specific direction to be smaller than the dimensions of the conductive layer in the width direction; A method for manufacturing a thermoelectric conversion element.

9. The etching is continued for a predetermined time after the first layer has been completely penetrated in the thickness direction. The method of claim 8.

10. The method further includes filling a space that is in contact with a first end surface in the width direction of the thermoelectric conversion layer and is covered by the conductive layer with a resin to form a reinforcing portion. The method of claim 8.

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