Chips of thermoelectric conversion materials

Abstract

The present invention provides a chip of a thermoelectric conversion material having a recessed portion that can achieve high bonding properties with an electrode. The chip of the thermoelectric conversion material has a recessed portion on at least one surface.

Description

Technical Field

[0001] The present invention relates to a chip of thermoelectric conversion material. Background Art

[0002] Currently, one of the effective ways to utilize energy is to use a device that directly converts thermal energy into electrical energy by using a thermoelectric conversion element having a thermoelectric effect such as the Seebeck effect or the Peltier effect.

[0003] Among these thermoelectric conversion elements, a so-called π-type thermoelectric conversion element is known. A π-type thermoelectric conversion element is generally constructed as follows: a pair of electrodes spaced apart from each other are provided on a substrate, and a P-type thermoelectric element is similarly spaced apart from each other, for example, a P-type thermoelectric element is provided on one electrode and an N-type thermoelectric element is provided on the other electrode, with the top surfaces of the two thermoelectric elements being connected to the electrodes of the opposing substrate.

[0004] In recent years, there has been a demand for improved thermoelectric performance, including thinner and more highly integrated thermoelectric conversion elements. Patent Document 1 discloses a method for directly forming a pattern of a thermoelectric element layer using a thermoelectric semiconductor composition containing a resin, etc., by screen printing or other methods, including the viewpoint of achieving thinness by thinning the thermoelectric element layer.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: International Publication No. 2016 / 104615 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] However, in the method of forming a thermoelectric element directly in the form of a pattern layer on an electrode or on a substrate by screen printing or the like using a thermoelectric semiconductor composition composed of a thermoelectric semiconductor material, a heat-resistant resin, etc., as in Patent Document 1, the shape controllability of the resulting thermoelectric element layer is insufficient, and sometimes the shape of the thermoelectric element layer is destroyed due to penetration into the end of the thermoelectric element layer at the electrode interface or the substrate interface. For example, when the shape of the thermoelectric element layer is formed into a rectangular parallelepiped (including a cube) from the perspective of thermoelectric performance and ease of manufacturing, the actual cross-sectional shape of the thermoelectric element layer will basically be a semi-elliptical or trapezoidal shape (see the following). Figure 2(a)), not only can the desired thickness not be obtained, but also the control to be uniform and flat up to the two ends of the upper surface area of ​​the thermoelectric element layer cannot be performed, and sometimes the bonding material layer will wrap around the uneven surface at both ends. Therefore, in the case of forming the aforementioned π-type thermoelectric conversion element, the interface impedance and thermal impedance may increase due to insufficient bonding area between the upper surface of the obtained thermoelectric element layer and the relative electrode, and insufficient bonding, thereby reducing the thermoelectric performance and failing to fully exert the thermoelectric performance originally possessed by the thermoelectric element layer. As such, when forming the thermoelectric element layer, it is crucial to improve the shape controllability of each thermoelectric element layer from the perspective of improving thermoelectric performance and high integration.

[0010] In view of the above circumstances, an object of the present invention is to provide a chip of a thermoelectric conversion material having a recessed portion that can achieve high bonding properties with an electrode.

[0011] Solutions to the Problem

[0012] The present inventors conducted in-depth research to solve the above-mentioned problems and found that for a chip of thermoelectric conversion material having a recess on at least one side (hereinafter also referred to as a "chip" or "thermoelectric conversion material layer"), high bonding properties relative to the electrode can be achieved by filling the recess with a bonding material layer, thereby completing the present invention.

[0013] That is, the present invention provides the following (1) to (7).

[0014] (1) A chip of a thermoelectric conversion material having a recessed portion on at least one surface.

[0015] (2) The thermoelectric conversion material chip according to (1) above, wherein the shape of the thermoelectric conversion material chip is at least one selected from a rectangular parallelepiped, a cubic shape, and a cylindrical shape.

[0016] (3) The thermoelectric conversion material chip according to (1) or (2) above, wherein the area of ​​the longitudinal section of the thermoelectric conversion material chip including the center portion in the width direction is set to S (μm 2 ), when the maximum value of the thickness in the thickness direction of the longitudinal section is set to Dmax (μm), the maximum value of the length in the width direction of the longitudinal section is set to Xmax (μm), and the maximum value of the depth of the concave portion of the longitudinal section is set to Tmax (μm), the cross section of the concave portion of the longitudinal section of the chip of the thermoelectric conversion material satisfies the following conditions (A) and (B),

[0017] (A)0<(Dmax×Xmax-S) / (Dmax×Xmax)≤0.20

[0018] (B) 0.01<Tmax / Dmax<0.30 and Tmax≥2μm

[0019] Among them, the maximum value Dmax of the thickness in the thickness direction of the longitudinal section represents: in the longitudinal section of the chip of the above-mentioned thermoelectric conversion material, when a vertical line is erected on the bottom edge of the above-mentioned longitudinal section, the maximum distance (thickness) between the two intersection points obtained when the upper and lower ends of the thickness in the thickness direction of the above-mentioned longitudinal section intersect the vertical line; the maximum value Xmax of the length in the width direction of the longitudinal section represents: when a parallel line parallel to the bottom edge of the above-mentioned longitudinal section is drawn, the maximum distance (length) between the left and right ends of the length in the width direction of the above-mentioned longitudinal section intersect the parallel line; the maximum value Tmax of the depth of the concave portion of the longitudinal section represents: the maximum distance (depth) obtained by the maximum value Dmax of the thickness in the thickness direction of the longitudinal section and the shortest distance (length) between the following intersection points, wherein the intersection point is the intersection point obtained when a vertical line hanging from the deepest part of the concave portion to the bottom edge of the above-mentioned longitudinal section intersects the bottom edge.

[0020] (4) The thermoelectric conversion material chip according to any one of (1) to (3) above, wherein the recessed portion of the thermoelectric conversion material chip has a bonding material layer.

[0021] (5) The thermoelectric conversion material chip according to any one of (1) to (4) above, wherein the bonding material layer includes a solder material, a conductive adhesive, or a sintered bond.

[0022] (6) A chip of thermoelectric conversion material according to any one of (1) to (5) above, wherein the condition (A) is 0.05<(Dmax×Xmax-S) / (Dmax×Xmax)≤0.10, and the condition (B) is 0.10<Tmax / Dmax<0.20 and 4≤Tmax≤35μm.

[0023] (7) A thermoelectric conversion module comprising a chip of the thermoelectric conversion material according to any one of (1) to (6) above.

[0024] Effects of the Invention

[0025] According to the present invention, a chip of a thermoelectric conversion material having a recessed portion that can achieve high bonding properties with an electrode can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] [ Figure 1 ] A diagram for illustrating the definition of the longitudinal section of a chip of the thermoelectric conversion material of the present invention.

[0027] [ Figure 2 ] is a cross-sectional view for illustrating the longitudinal section of a chip of a thermoelectric conversion material used in a thermoelectric conversion component of an embodiment or a comparative example of the present invention.

[0028] [ Figure 3 ] is a cross-sectional view showing an example of a thermoelectric conversion module having a longitudinal section of a chip having the thermoelectric conversion material of the present invention.

[0029] [ Figure 4 ] An explanatory diagram showing an example of a method for manufacturing a chip of a thermoelectric conversion material based on a pattern frame arrangement / peeling method adopted in the present invention in order of steps.

[0030] Explanation of symbols

[0031] 1: Thermoelectric conversion components

[0032] 2a: Substrate

[0033] 2b: Substrate

[0034] 3a: Electrode

[0035] 3b: Electrode

[0036] 4. 4u, 4v: Chips of thermoelectric conversion materials

[0037] 4a: Chip of N-type thermoelectric conversion material

[0038] 4b: Chip of P-type thermoelectric conversion material

[0039] 5a, 5b: Concave portion on the upper surface of the thermoelectric conversion material chip

[0040] 11: Substrate

[0041] 12: Pattern frame

[0042] 12': Stainless steel

[0043] 13s: Opening

[0044] 13d: Opening depth (pattern frame thickness)

[0045] 13: Opening

[0046] 14a: N-type thermoelectric conversion material layer

[0047] 14b: P-type thermoelectric conversion material layer

[0048] X: Length (width direction)

[0049] Xmax: Maximum length in the width direction (longitudinal section)

[0050] Y: Length (depth direction)

[0051] D: Thickness (thickness direction)

[0052] Dmax: Maximum thickness in the thickness direction (longitudinal section)

[0053] S: area of ​​the longitudinal section

[0054] T: Deepest part (concave part)

[0055] Tmax: Maximum depth of the concave portion (longitudinal section) DETAILED DESCRIPTION

[0056] [Chip of thermoelectric conversion material]

[0057] The thermoelectric conversion material chip of the present invention is characterized in that it has a recessed portion on at least one surface of the thermoelectric conversion material chip.

[0058] By providing a concave portion on the surface of the thermoelectric conversion material chip, the concave portion can be filled with a bonding material layer used, for example, when bonding to an electrode constituting a thermoelectric conversion module described later, thereby improving bonding with the electrode, which leads to improved thermoelectric performance.

[0059] The shape of the chip of the thermoelectric conversion material used in the present invention is preferably at least one selected from a rectangular parallelepiped, a cubic shape, and a cylindrical shape from the viewpoint of easily achieving high shape controllability.

[0060] Among them, from the viewpoint of improving the ease of production and increasing the degree of integration of thermoelectric conversion material chips, a rectangular parallelepiped shape or a cubic shape is more preferred.

[0061] <Longitudinal cross-section of a thermoelectric conversion material chip>

[0062] In the thermoelectric conversion material chip of the present invention, the area of ​​the longitudinal section including the center portion in the width direction of the thermoelectric conversion material chip is denoted as S (μm 2 ), when the maximum value of the thickness in the thickness direction of the longitudinal section is set to Dmax (μm), the maximum value of the length in the width direction of the longitudinal section is set to Xmax (μm), and the maximum value of the depth of the concave portion of the longitudinal section is set to Tmax (μm), the cross-section of the concave portion of the longitudinal section of the chip of the above-mentioned thermoelectric conversion material satisfies the following conditions (A) and (B).

[0063] (A)0<(Dmax×Xmax-S) / (Dmax×Xmax)≤0.20

[0064] (B) 0.01<Tmax / Dmax<0.30 and Tmax≥2μm

[0065] Among them, the maximum value Dmax of the thickness in the thickness direction of the longitudinal section represents: in the longitudinal section of the chip of the above-mentioned thermoelectric conversion material, when a vertical line is erected on the bottom edge of the above-mentioned longitudinal section, the maximum distance (thickness) between the two intersection points obtained when the upper and lower ends of the thickness in the thickness direction of the above-mentioned longitudinal section intersect the vertical line; the maximum value Xmax of the length in the width direction of the longitudinal section represents: when a parallel line parallel to the bottom edge of the above-mentioned longitudinal section is drawn, the maximum distance (length) between the left and right ends of the length in the width direction of the above-mentioned longitudinal section intersect the parallel line; the maximum value Tmax of the depth of the concave portion of the longitudinal section represents: the maximum distance (depth) obtained by the maximum value Dmax of the thickness in the thickness direction of the longitudinal section and the shortest distance (length) between the following intersection points, wherein the intersection point is the intersection point obtained when a vertical line hanging from the deepest part of the concave portion to the bottom edge of the above-mentioned longitudinal section intersects the bottom edge.

[0066] In this manual, Figure 1 The definition of “a longitudinal cross section including the center portion of a chip of a thermoelectric conversion material” will be described. Figure 1 These are diagrams illustrating longitudinal sections of a chip of a thermoelectric conversion material of the present invention, wherein (a) is a top view of a chip 4 of a thermoelectric conversion material, wherein the chip 4 of the thermoelectric conversion material has a length X in the width direction and a length Y in the depth direction, and (b) is a longitudinal section of the chip 4 of the thermoelectric conversion material, wherein the longitudinal section includes the central portion C of (a) above, and represents a slashed portion (a rectangle in the figure) having a length X and a thickness D obtained when the chip is cut between A-A' in the width direction.

[0067] The longitudinal cross-section of the thermoelectric conversion material chip used in the present invention will be described with reference to the accompanying drawings.

[0068] Figure 2 These are cross-sectional views illustrating longitudinal cross-sections of thermoelectric conversion material chips of the present invention used in thermoelectric conversion modules of embodiments or comparative examples of the present invention. (a) is a longitudinal cross-section of thermoelectric conversion material chip 4u used in Comparative Example 1. The longitudinal cross-section is formed into a roughly quadrilateral (substantially trapezoidal) shape. It is a longitudinal cross-section (cross-sectional area S) having a maximum length Xmax in the width direction and a maximum thickness Dmax in the thickness direction. The upper surface 5a of the longitudinal cross-section is composed of gently curved concave portions and convex portions, with both ends of the longitudinal cross-section having slightly steep slopes. (b) is a longitudinal cross-section of thermoelectric conversion material chip 4v used in Example 1. The longitudinal cross-section is formed into a roughly quadrilateral (rectangular) shape. It is a longitudinal cross-section (cross-sectional area S) having a maximum length Xmax in the width direction and a maximum thickness Dmax in the thickness direction. The upper surface 5b of the longitudinal cross-section is a gently curved concave portion, with both ends of the longitudinal cross-section having a slope relative to the interior of the concave portion. The maximum depth Tmax of the concave portion occurs at its deepest portion T.

[0069] The cross section of the recessed portion in the longitudinal cross section of the thermoelectric conversion material chip preferably satisfies the following conditions (A) and (B).

[0070] (A)0<(Dmax×Xmax-S) / (Dmax×Xmax)≤0.20

[0071] (B) 0.01<Tmax / Dmax<0.30 and Tmax≥2μm

[0072] In condition (A), (Dmax×Xmax-S) / (Dmax×Xmax) is the ratio of the cross-sectional area of ​​the concave portion of the longitudinal cross-section of the thermoelectric conversion material chip to the cross-sectional area of ​​the thermoelectric conversion material chip including the cross-sectional area of ​​the concave portion calculated by Dmax×Xmax (hereinafter sometimes also referred to as “concave cross-sectional occupancy rate”).

[0073] In condition (A), the concave portion cross-sectional occupancy rate is preferably 0<(Dmax×Xmax-S) / (Dmax×Xmax)≤0.20, more preferably 0.03<(Dmax×Xmax-S) / (Dmax×Xmax)≤0.15, further preferably 0.04<(Dmax×Xmax-S) / (Dmax×Xmax)≤0.13, and most preferably 0.05<(Dmax×Xmax-S) / (Dmax×Xmax)≤0.10.

[0074] When the concave cross-sectional occupancy rate is within the above range, the concave portion on the thermoelectric conversion material chip is easily filled with a bonding material layer formed from a bonding material described later for bonding the opposing electrode, thereby preventing the bonding material layer from wrapping around and adhering to the side surfaces of the two ends of the longitudinal cross-section of the thermoelectric conversion material chip. Furthermore, the efficiency of the thermoelectric performance of the thermoelectric conversion material chip can be maintained.

[0075] In the condition (B), Tmax / Dmax is preferably 0.01<Tmax / Dmax<0.30, more preferably 0.07<Tmax / Dmax<0.25, and even more preferably 0.10<Tmax / Dmax<0.20.

[0076] When Tmax / Dmax is within the above range, it is easy to maintain the efficiency of the thermoelectric performance of the thermoelectric conversion material chip and to easily form a thermoelectric conversion material chip having recessed portions thereon with excellent shape controllability.

[0077] Furthermore, Tmax is preferably 2 μm or more, more preferably 2 to 50 μm, further preferably 4 to 35 μm, and most preferably 4 to 20 μm.

[0078] When Tmax is within the above range, it is easy to ensure a bonding material layer having a sufficient thickness for bonding to the counter electrode in the recessed portion of the upper surface of the thermoelectric conversion material chip, thereby easily improving mechanical bonding strength and electrical bonding properties.

[0079] When Tmax / Dmax and Tmax are within the above ranges, bonding with the counter electrode is easily achieved, and the efficiency of the thermoelectric performance of the thermoelectric conversion material chip is easily maintained.

[0080] When the longitudinal section of the thermoelectric conversion material chip is within the range of the above-mentioned conditions (A) and (B), it is easy to fill the recessed portion on the upper surface of the thermoelectric conversion material chip with a bonding material layer formed by a bonding material for bonding opposing electrodes, and the bonding material layer can be prevented from wrapping around the side surfaces of the two end portions of the longitudinal section of the thermoelectric conversion material chip. As a result, the bonding property with the electrode can be improved, and the efficiency of the thermoelectric performance of the thermoelectric conversion material chip can be maintained, so an improvement in the thermoelectric performance can be expected.

[0081] In order to achieve good bonding with opposing electrodes when constituting a thermoelectric conversion module described later, the concave portion of the chip of the thermoelectric conversion material of the present invention preferably has a bonding material layer.

[0082] The bonding material used for the bonding material layer is preferably a solder material, a conductive adhesive, or a sintered bonding agent. Each bonding material is sequentially arranged in the form of a solder layer, a conductive adhesive layer, or a sintered bonding agent layer in the recessed portion of the thermoelectric conversion material chip. From the perspective of connection reliability, solder is more preferably used as the bonding material.

[0083] As for the bonding material layer, as long as it is in the concave portion of the chip of the thermoelectric conversion material, it can be a single layer, or two or more layers can be used and stacked together. In addition, within the scope of not destroying the effect of the present invention, layers other than the bonding material layer can also be used in combination in the concave portion.

[0084] It should be noted that, in this specification, conductivity refers to a resistivity of less than 1×10 6 Properties of Ω·m.

[0085] The solder material constituting the above-mentioned solder layer can be appropriately selected by taking into account the heat resistance temperature of the material constituting the thermoelectric conversion component and the electrical conductivity and thermal conductivity when the solder layer is made. Examples include: Sn, Sn / Pb alloy, Sn / Ag alloy, Sn / Cu alloy, Sn / Sb alloy, Sn / In alloy, Sn / Zn alloy, Sn / In / Bi alloy, Sn / In / Bi / Zn alloy, Sn / Bi / Pb / Cd alloy, Sn / Bi / Pb alloy, Sn / Bi / Cd alloy, Bi / Pb alloy, Sn / Bi / Zn alloy, Sn / Bi alloy, Sn / Bi / Pb alloy, Sn / Pb / Cd alloy, Sn / Cd alloy and other known materials. From the viewpoints of lead-free and / or cadmium-free properties, melting point, electrical conductivity, and thermal conductivity, alloys such as 43Sn / 57Bi alloy, 42Sn / 58Bi alloy, 40Sn / 56Bi / 4Zn alloy, 48Sn / 52In alloy, and 39.8Sn / 52In / 7Bi / 1.2Zn alloy are preferred.

[0086] Commercially available solder materials include the following: 42Sn / 58Bi alloy (manufactured by Tamura Manufacturing Co., Ltd., product name: SAM10-401-27), 41Sn / 58Bi / Ag alloy (manufactured by Handa Co., Ltd., product name: PF141-LT7HO), and the like.

[0087] The thickness of the solder layer (after heating and cooling) is preferably 10 to 200 μm, more preferably 20 to 150 μm, further preferably 30 to 130 μm, and particularly preferably 40 to 120 μm. When the solder layer thickness is within this range, adhesion to the thermoelectric conversion material chip and electrodes is easily achieved.

[0088] Examples of methods for applying the solder material include known methods such as stencil printing, screen printing, and dispensing. The heating temperature varies depending on the solder material and resin film used, but is generally 150 to 280°C for 3 to 20 minutes.

[0089] The conductive adhesive constituting the conductive adhesive layer is not particularly limited, and examples thereof include conductive pastes, etc. Examples of the conductive pastes include copper paste, silver paste, and nickel paste. When a binder is used, examples thereof include epoxy resins, acrylic resins, and urethane resins.

[0090] Examples of a method for applying the conductive adhesive include known methods such as screen printing and a dispensing method.

[0091] The thickness of the conductive adhesive layer is preferably 10 to 200 μm, more preferably 20 to 150 μm, further preferably 30 to 130 μm, and particularly preferably 40 to 120 μm.

[0092] The sintered adhesive constituting the sintered adhesive layer is not particularly limited, and examples thereof include sintered pastes. The sintered pastes are formed, for example, from micron-sized metal powders and nanometer-sized metal particles. Unlike the conductive adhesives described above, these pastes directly bond metals by sintering, and may contain binders such as epoxy resins, acrylic resins, and urethane resins.

[0093] Examples of the sintering paste include silver sintering paste and copper sintering paste.

[0094] Examples of methods for applying the sintered adhesive layer include known methods such as screen printing, stencil printing, and dispensing. Firing conditions vary depending on the metal material used, but are generally performed at 100 to 300° C. for 30 to 120 minutes.

[0095] Commercially available products of sintered bonding agents include, for example, silver sintered paste (manufactured by Kyocera Corporation, product name: CT2700R7S) and sintered metal bonding material (manufactured by Handa Co., Ltd., product name: MAX102).

[0096] The thickness of the sintered bonding agent layer is preferably 10 to 200 μm, more preferably 20 to 150 μm, further preferably 30 to 130 μm, and particularly preferably 40 to 120 μm.

[0097] [Thermoelectric conversion component]

[0098] The thermoelectric conversion module of the present invention includes a thermoelectric conversion material chip having a recessed portion. This thermoelectric conversion material chip can provide a thermoelectric conversion module having high shape controllability and improved bonding between the thermoelectric conversion material chip and the counter electrode.

[0099] Figure 3 This is a cross-sectional diagram showing an example of a thermoelectric conversion module including chips of thermoelectric conversion material having recesses according to the present invention. Thermoelectric conversion module 1 includes chips 4a of an N-type thermoelectric conversion material and chips 4b of a P-type thermoelectric conversion material on electrodes 3a of a substrate 2a. Furthermore, a counter-electrode substrate having electrodes 3b on substrate 2b is provided above the chips 4a and 4b of the N-type thermoelectric conversion material. Alternating adjacent chips 4a and 4b of the N-type thermoelectric conversion material are arranged so as to be electrically connected in series via electrodes 3b on substrate 2b, forming a π-type thermoelectric conversion element. It should be noted that the bonding material layer is disposed in the respective recesses (not shown) above the chips 4a and 4b of the P-type thermoelectric conversion material.

[0100] (Thermoelectric Conversion Material Layer)

[0101] The thermoelectric conversion material chip used in the thermoelectric conversion element, that is, the thermoelectric conversion material layer is preferably formed of a thermoelectric semiconductor composition containing a thermoelectric semiconductor material (thermoelectric semiconductor fine particles), a heat-resistant resin, and one or both of an ionic liquid and an inorganic ionic compound.

[0102] (Thermoelectric semiconductor materials)

[0103] The thermoelectric semiconductor material contained in the chip as a thermoelectric conversion material is not particularly limited as long as it is a material that can generate thermoelectromotive force by imparting a temperature difference. For example, bismuth-tellurium thermoelectric semiconductor materials such as P-type bismuth telluride and N-type bismuth telluride; telluride-based thermoelectric semiconductor materials such as GeTe and PbTe; antimony-tellurium thermoelectric semiconductor materials; zinc-antimony-based thermoelectric semiconductor materials such as ZnSb, Zn3Sb2, and Zn4Sb3; silicon-germanium-based thermoelectric semiconductor materials such as SiGe; bismuth selenide-based thermoelectric semiconductor materials such as Bi2Se3; β-FeSi2, CrSi2, and MnSi 1.73 , Mg2Si and other metal silicide-based thermoelectric semiconductor materials; oxide-based thermoelectric semiconductor materials; Whistler materials such as FeVAl, FeVAlSi, FeVTiAl, and sulfide-based thermoelectric semiconductor materials such as TiS2, etc.

[0104] Among these materials, bismuth-tellurium-based thermoelectric semiconductor materials, telluride-based thermoelectric semiconductor materials, antimony-tellurium-based thermoelectric semiconductor materials, or bismuth selenide-based thermoelectric semiconductor materials are preferred.

[0105] Furthermore, from the viewpoint of thermoelectric performance, bismuth-tellurium-based thermoelectric semiconductor materials such as P-type bismuth telluride and N-type bismuth telluride are more preferable.

[0106] For the above-mentioned P-type bismuth telluride, the carrier is a hole and the Seebeck coefficient is a positive value. For example, it is preferred to use Bi X Te3Sb 2-X In this case, X is preferably 0 < X ​​≤ 0.8, and more preferably 0.4 ≤ X ≤ 0.6. When X is greater than 0 and less than 0.8, the Seebeck coefficient and electrical conductivity increase, and the characteristics as a P-type thermoelectric element can be maintained, which is preferred.

[0107] In addition, for the above-mentioned N-type bismuth telluride, the carrier is electrons and the Seebeck coefficient is negative. For example, it is preferable to use Bi2Te 3-Y Se Y In this case, Y is preferably 0≤Y≤3 (when Y=0: Bi2Te3), and more preferably 0<Y≤2.7. When Y is greater than 0 and less than 3, the Seebeck coefficient and electrical conductivity increase, and the characteristics of an N-type thermoelectric element can be maintained, so it is preferred.

[0108] The thermoelectric semiconductor fine particles used in the thermoelectric semiconductor composition are obtained by pulverizing the above-mentioned thermoelectric semiconductor material to a predetermined size using a fine pulverization device or the like.

[0109] The amount of the thermoelectric semiconductor particles in the thermoelectric semiconductor composition is preferably 30 to 99% by mass, more preferably 50 to 96% by mass, and even more preferably 70 to 95% by mass. When the amount of the thermoelectric semiconductor particles is within this range, the Seebeck coefficient (the absolute value of the Peltier coefficient) is large, and a decrease in electrical conductivity is suppressed, with only a decrease in thermal conductivity. This is preferred because a film exhibiting high thermoelectric performance and having sufficient film strength and flexibility can be obtained.

[0110] The average particle size of the thermoelectric semiconductor fine particles is preferably 10 nm to 200 μm, more preferably 10 nm to 30 μm, further preferably 50 nm to 10 μm, and particularly preferably 1 to 10 μm. Within the above range, uniform dispersion is facilitated and electrical conductivity can be improved.

[0111] The method for pulverizing the thermoelectric semiconductor material to obtain thermoelectric semiconductor fine particles is not particularly limited, and the material can be pulverized to a predetermined size using a known pulverization device such as a jet mill, ball mill, sand mill, colloid mill, or roll mill.

[0112] The average particle size of the thermoelectric semiconductor fine particles can be measured using a laser diffraction particle size analyzer (Mastersizer 3000, manufactured by Malvern) and the median value of the particle size distribution can be obtained.

[0113] In addition, the thermoelectric semiconductor particles are preferably subjected to a heat treatment in advance (the "heat treatment" here is different from the "annealing treatment" performed in the annealing treatment step of the present invention). By performing the heat treatment, the crystallinity of the thermoelectric semiconductor particles is improved. In addition, since the surface oxide film of the thermoelectric semiconductor particles is removed, the Seebeck coefficient or Peltier coefficient of the thermoelectric conversion material is increased, which can further improve the thermoelectric performance index. The heat treatment is not particularly limited, but it is preferably carried out in an inert gas atmosphere such as nitrogen, argon, etc. with controlled gas flow, in a reducing gas atmosphere such as hydrogen, or under vacuum conditions in a manner that does not adversely affect the thermoelectric semiconductor particles before preparing the thermoelectric semiconductor composition. It is more preferably carried out in a mixed gas atmosphere of an inert gas and a reducing gas. The specific temperature conditions depend on the thermoelectric semiconductor particles used, and it is generally preferably carried out at a temperature below the melting point of the particles and at 100 to 1500°C for several minutes to tens of hours.

[0114] (Heat-resistant resin)

[0115] From the perspective of annealing the thermoelectric semiconductor material at high temperature after forming the thermoelectric conversion material layer, it is preferred to use a heat-resistant resin in the thermoelectric semiconductor composition used in the present invention. This resin can act as a binder between the thermoelectric semiconductor materials (thermoelectric semiconductor particles), improve the flexibility of the thermoelectric conversion component, and facilitate the formation of thin films by coating, etc. The heat-resistant resin is not particularly limited, but it is preferred to use a heat-resistant resin that maintains various resin properties such as mechanical strength and thermal conductivity without loss when the thin film formed from the thermoelectric semiconductor composition is subjected to annealing treatment, etc. to cause crystal growth of the thermoelectric semiconductor particles.

[0116] With regard to above-mentioned heat-resistant resin, from the viewpoint that heat resistance is higher and the crystal growth of the thermoelectric semiconductor particles in the film can not be caused to adverse effect, preferably polyamide resin, polyamide-imide resin, polyimide resin, epoxy resin, from the viewpoint of excellent bending property, more preferably polyamide resin, polyamide-imide resin, polyimide resin.When using polyimide film as the substrate described later, from the viewpoint of the adhesion of this polyimide film, as heat-resistant resin, more preferably polyimide resin.It should be noted that, in the present invention, polyimide resin is the general name of polyimide and its precursor.

[0117] The heat-resistant resin preferably has a decomposition temperature of 300° C. or higher. When the decomposition temperature is within the above range, as described below, even when a thin film formed from the thermoelectric semiconductor composition is annealed, the film can maintain flexibility without losing its adhesive function.

[0118] The heat-resistant resin preferably has a weight loss rate of 10% or less, more preferably 5% or less, and even more preferably 1% or less at 300°C as determined by thermogravimetric analysis (TG). When the weight loss rate is within the above range, as described below, the flexibility of the thermoelectric conversion material layer can be maintained without losing its binder function even when a thin film formed from the thermoelectric semiconductor composition is annealed.

[0119] The heat-resistant resin is incorporated into the thermoelectric semiconductor composition in an amount of 0.1 to 40% by mass, preferably 0.5 to 20% by mass, more preferably 1 to 20% by mass, and even more preferably 2 to 15% by mass. Within this range, the heat-resistant resin functions as a binder for the thermoelectric semiconductor material, facilitates thin film formation, and yields a film having both high thermoelectric performance and film strength.

[0120] (ionic liquid)

[0121] The ionic liquid used in this invention is a molten salt composed of a combination of cations and anions, and refers to a salt that can exist as a liquid at any temperature within the temperature range of -50 to 500°C. Ionic liquids have extremely low vapor pressure and are non-volatile, exhibit excellent thermal and electrochemical stability, have low viscosity, and exhibit high ionic conductivity. Therefore, they can effectively act as conductive additives to suppress the decrease in electrical conductivity between thermoelectric semiconductor particles. Furthermore, ionic liquids exhibit high polarity due to their aprotic ionic structure and excellent compatibility with heat-resistant resins, thus achieving uniform electrical conductivity within the thermoelectric element layer.

[0122] As the ionic liquid, known or commercially available ionic liquids can be used. Examples thereof include pyridine. Pyrimidine Pyrazole Pyrrolidine Piperidine Imidazole Nitrogen-containing cyclic cationic compounds and their derivatives; tetraalkylammonium and other ammonium cations and their derivatives; trialkyl Tetraalkyl wait Lithium cations and their derivatives; compounds formed by cationic components such as lithium cations and their derivatives and the following anionic components, the anionic components include: Cl - 、AlCl4 - 、Al2Cl7 - 、ClO4 - Chloride ions, Br - Bromide ions, I - Iodide ions, BF4 - PF6 - Fluoride ions, F(HF) n - Halide anions, NO3 - 、CH3COO - CF3COO - 、CH3SO3 - CF3SO3 - 、(FSO2)2N - 、(CF3SO2)2N - 、(CF3SO2)3C - 、AsF6 - 、SbF6 - 、NbF6 - 、TaF6 - 、F(HF)n - 、(CN)2N - 、C4F9SO3 - 、(C2F5SO2)2N- 、C3F7COO - 、(CF3SO2)(CF3CO)N - wait.

[0123] From the viewpoints of high temperature stability, compatibility with thermoelectric semiconductor particles and resins, and suppression of decrease in conductivity between thermoelectric semiconductor particles, the cationic component of the ionic liquid preferably comprises a pyridine Cations and their derivatives, imidazole At least one of cations and their derivatives. The anion component of the ionic liquid preferably comprises a halide anion, more preferably a halide anion selected from Cl - Br - and I - At least one of .

[0124] Contains pyridine as a cationic component Specific examples of ionic liquids of cations and their derivatives include 4-methylbutylpyridinium chloride, 3-methylbutylpyridinium chloride, 4-methylhexylpyridinium chloride, 3-methylhexylpyridinium chloride, 4-methyloctylpyridinium chloride, 3-methyloctylpyridinium chloride, 3,4-dimethylbutylpyridinium chloride, 3,5-dimethylbutylpyridinium chloride, 4-methylbutylpyridinium tetrafluoroborate, 4-methylbutylpyridinium hexafluorophosphate, 1-butyl-4-methylpyridinium bromide, 1-butyl-4-methylpyridinium hexafluorophosphate, and 1-butyl-4-methylpyridinium iodide. Among them, 1-butyl-4-methylpyridinium bromide, 1-butyl-4-methylpyridinium hexafluorophosphate, and 1-butyl-4-methylpyridinium iodide are preferred.

[0125] In addition, imidazole is contained as a cationic component. Specific examples of ionic liquids of cations and their derivatives include: [1-butyl-3-(2-hydroxyethyl)imidazolium bromide], [1-butyl-3-(2-hydroxyethyl)imidazolium tetrafluoroborate], 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride, 1-octyl-3-methylimidazolium chloride, 1-decyl-3-methylimidazolium chloride, 1-decyl- 3-Methylimidazole bromide, 1-dodecyl-3-methylimidazole chloride, 1-tetradecyl-3-methylimidazole chloride, 1-ethyl-3-methylimidazole tetrafluoroborate, 1-butyl-3-methylimidazole tetrafluoroborate, 1-hexyl-3-methylimidazole tetrafluoroborate, 1-ethyl-3-methylimidazole hexafluorophosphate, 1-butyl-3-methylimidazole hexafluorophosphate, 1-methyl-3-butylimidazole methanesulfonate, 1,3-dibutylimidazole methanesulfonate, etc. Among them, [1-butyl-3-(2-hydroxyethyl)imidazole bromide] and [1-butyl-3-(2-hydroxyethyl)imidazole tetrafluoroborate] are preferred.

[0126] The conductivity of the above ionic liquid is preferably 10 -7 S / cm or more, more preferably 10 -6 When the electrical conductivity is within the above range, the conductive agent can effectively suppress the decrease in electrical conductivity between the thermoelectric semiconductor particles.

[0127] The ionic liquid preferably has a decomposition temperature of 300° C. or higher. When the decomposition temperature is within the above range, the conductive additive effect can be maintained even when a thin film of a thermoelectric conversion material layer formed of the thermoelectric semiconductor composition is annealed, as described below.

[0128] Furthermore, the ionic liquid preferably has a weight loss rate of 10% or less, more preferably 5% or less, and even more preferably 1% or less at 300°C, as measured by thermogravimetric analysis (TG). When the weight loss rate is within the above range, as described below, the ionic liquid maintains its effect as a conductive additive even when a thin film of a thermoelectric conversion material layer formed from the thermoelectric semiconductor composition is annealed.

[0129] The amount of the ionic liquid in the thermoelectric semiconductor composition is preferably 0.01 to 50% by mass, more preferably 0.5 to 30% by mass, and even more preferably 1.0 to 20% by mass. When the amount of the ionic liquid is within this range, a decrease in electrical conductivity can be effectively suppressed, resulting in a film with high thermoelectric performance.

[0130] (Inorganic ionic compound)

[0131] The inorganic ionic compound used in the present invention is a compound composed of at least a cation and an anion. Inorganic ionic compounds are solid at room temperature, have a melting point anywhere in the temperature range of 400-900°C, and exhibit high ionic conductivity. Therefore, they can act as a conductive additive to suppress the decrease in electrical conductivity between thermoelectric semiconductor particles.

[0132] As the cations, metal cations are used.

[0133] Examples of the metal cation include alkali metal cations, alkaline earth metal cations, typical metal cations, and transition metal cations, with alkali metal cations and alkaline earth metal cations being more preferred.

[0134] Examples of alkali metal cations include Li + 、Na + , K + , Rb + 、Cs + and Fr + wait.

[0135] Examples of alkaline earth metal cations include Mg 2+ , Ca 2+ 、Sr 2+ And Ba 2+ wait.

[0136] Examples of the anion include: F - 、Cl - Br - , I - OH - 、CN - 、NO3 - 、NO2 - , ClO - 、ClO2 - 、ClO3 - 、ClO4 - 、CrO4 2- 、HSO4 - 、SCN - 、BF4 - PF6 - wait.

[0137] The inorganic ionic compound can be a known or commercially available compound. Examples thereof include a compound composed of a cation component such as potassium cation, sodium cation or lithium cation, and a compound containing a cation component such as Cl - 、AlCl4 - 、Al2Cl7 - 、ClO4 - Chloride ions, Br - Bromide ions, I- Iodide ions, BF4 - PF6 - Fluoride ions, F(HF) n - Halide anions, NO3 - OH - 、CN - A substance composed of anionic components.

[0138] Among the above-mentioned inorganic ionic compounds, the cation component of the inorganic ionic compound preferably contains at least one selected from potassium, sodium, and lithium from the viewpoints of high temperature stability, compatibility with thermoelectric semiconductor particles and resins, and suppression of decrease in electrical conductivity between thermoelectric semiconductor particles. In addition, the anion component of the inorganic ionic compound preferably contains a halide anion, more preferably contains a halide anion selected from Cl - Br - and I - At least one of .

[0139] Specific examples of inorganic ionic compounds containing potassium cations as a cation component include KBr, KI, KCl, KF, KOH, K2CO3, etc. Among them, KBr and KI are preferred.

[0140] Specific examples of inorganic ionic compounds containing sodium cations as cation components include NaBr, NaI, NaOH, NaF, and Na2CO3. Among them, NaBr and NaI are preferred.

[0141] Specific examples of inorganic ionic compounds containing lithium cations as a cation component include LiF, LiOH, and LiNO 3 . Among them, LiF and LiOH are preferred.

[0142] The conductivity of the inorganic ionic compound is preferably 10 -7 S / cm or more, more preferably 10 -6 When the electrical conductivity is within the above range, the conductive additive can effectively suppress the decrease in electrical conductivity between thermoelectric semiconductor particles.

[0143] The decomposition temperature of the inorganic ionic compound is preferably 400° C. or higher. When the decomposition temperature is within the above range, the effect of the conductive additive can be maintained even when the thin film of the thermoelectric conversion material layer formed of the thermoelectric semiconductor composition is annealed as described below.

[0144] Furthermore, the inorganic ionic compound preferably has a weight loss rate of 10% or less, more preferably 5% or less, and even more preferably 1% or less, at 400°C as determined by thermogravimetric analysis (TG). When the weight loss rate is within the above range, the effect of the conductive additive can be maintained even when a thin film of a thermoelectric conversion material layer formed from the thermoelectric semiconductor composition is annealed, as described later.

[0145] The amount of the inorganic ionic compound in the thermoelectric semiconductor composition is preferably 0.01 to 50% by mass, more preferably 0.5 to 30% by mass, and even more preferably 1.0 to 10% by mass. When the amount of the inorganic ionic compound is within this range, a decrease in electrical conductivity can be effectively suppressed, resulting in a film with improved thermoelectric performance.

[0146] When an inorganic ionic compound and an ionic liquid are used in combination, the total content of the inorganic ionic compound and the ionic liquid in the thermoelectric semiconductor composition is preferably 0.01 to 50 mass %, more preferably 0.5 to 30 mass %, and even more preferably 1.0 to 10 mass %.

[0147] (Other additives)

[0148] The thermoelectric semiconductor composition used in the present invention may further contain, in addition to the above-mentioned components, other additives such as dispersants, film-forming aids, light stabilizers, antioxidants, tackifiers, plasticizers, colorants, resin stabilizers, fillers, pigments, conductive fillers, conductive polymers, and curing agents, as needed. These additives may be used alone or in combination of two or more.

[0149] (Method for preparing thermoelectric semiconductor composition)

[0150] The method for preparing the thermoelectric semiconductor composition used in the present invention is not particularly limited. The thermoelectric semiconductor composition can be prepared by adding the above-mentioned thermoelectric semiconductor particles, the above-mentioned heat-resistant resin, the above-mentioned ionic liquid and / or inorganic ionic compound, the above-mentioned other additives as needed, and a solvent using a known method such as an ultrasonic homogenizer, a spiral stirrer, a planetary stirrer, a disperser, and a mixing stirrer, and mixing and dispersing them.

[0151] Examples of the solvent include toluene, ethyl acetate, methyl ethyl ketone, ethanol, tetrahydrofuran, N-methylpyrrolidone, and ethyl cellosolve. These solvents may be used alone or in combination of two or more. The solid content concentration of the thermoelectric semiconductor composition is not particularly limited, as long as the viscosity is suitable for coating the composition.

[0152] <Method for Manufacturing Chip of Thermoelectric Conversion Material>

[0153] In the present invention, a chip of the thermoelectric conversion material is formed on a substrate or on an electrode using a coating liquid or the like containing the above-mentioned thermoelectric semiconductor composition.

[0154] Examples of a method for producing a chip of a thermoelectric conversion material that satisfies the above-mentioned conditions (A) and (B) and constitutes the thermoelectric conversion module of the present invention include the method shown in the following (P).

[0155] (P) Pattern frame arrangement / peeling method

[0156] (Pattern frame arrangement / peeling method)

[0157] The pattern frame arrangement / peeling method is a method in which a separate pattern frame having an opening is set on a substrate, a thermoelectric semiconductor composition is filled into the opening and dried, and the pattern frame is peeled off from the substrate to form a thermoelectric conversion material layer with excellent shape controllability reflecting the shape of the opening of the pattern frame.

[0158] The manufacturing process includes the steps of providing a pattern frame having an opening on a substrate, filling the opening with the thermoelectric semiconductor composition, drying the thermoelectric semiconductor composition filled in the opening to form a thermoelectric conversion material layer, and peeling the pattern frame from the substrate.

[0159] An example of a method for producing a thermoelectric conversion material layer using a pattern frame arrangement / lift-off method will be described in detail with reference to the accompanying drawings.

[0160] Figure 4 This is an explanatory diagram showing an example of a method for producing a thermoelectric conversion material layer based on the pattern frame arrangement / peeling method adopted in the present invention in order of steps.

[0161] (a) is a cross-sectional view showing a state in which a pattern frame is placed opposite to a substrate. A pattern frame 12 made of stainless steel 12' having an opening 13s, an opening portion 13, and an opening portion depth (pattern frame thickness) 13d is prepared and placed opposite to a substrate 11.

[0162] (b) is a cross-sectional view after the pattern frame is set on the substrate, wherein the pattern frame 12 is set on the substrate 11;

[0163] (c) is a cross-sectional view after the openings of the pattern frame are filled with the thermoelectric conversion material layers. With respect to the opening 13 having the opening 13s of the pattern frame 12 made of stainless steel 12′ prepared in (b), a thermoelectric semiconductor composition containing a P-type thermoelectric semiconductor material and a thermoelectric semiconductor composition containing an N-type thermoelectric semiconductor material are respectively filled into the given opening 13. The thermoelectric semiconductor composition containing the P-type thermoelectric semiconductor material and the thermoelectric semiconductor composition containing the N-type thermoelectric semiconductor material filled in the opening 13 are dried, thereby forming a P-type thermoelectric conversion material layer 14b and an N-type thermoelectric conversion material layer 14a.

[0164] (d) is a cross-sectional view showing the form of the thermoelectric conversion material layer obtained by peeling the pattern frame from the filled thermoelectric conversion material layer, and the pattern frame 12 is peeled from the formed P-type thermoelectric conversion material layer 14b and N-type thermoelectric conversion material layer 14a to obtain the P-type thermoelectric conversion material layer 14b and N-type thermoelectric conversion material layer 14a as self-supporting layers.

[0165] As the drying method, conventionally known drying methods such as hot air drying, hot roll drying, and infrared irradiation can be used. The heating temperature is usually 80 to 150° C., and the heating time varies depending on the heating method, but is usually several seconds to several tens of minutes.

[0166] When a solvent is used in the preparation of the thermoelectric semiconductor composition, the heating temperature is not particularly limited as long as it is within a temperature range that can dry the solvent used.

[0167] Through the above-described operation, a chip of the thermoelectric conversion material of the present invention used in a thermoelectric conversion module can be obtained.

[0168] Thus, by using the pattern frame arrangement / peeling method, a chip of the thermoelectric conversion material that satisfies the above-mentioned conditions (A) and (B) can be easily obtained.

[0169] The viscosity of the coating liquid containing the above-mentioned thermoelectric semiconductor composition can be appropriately adjusted according to the amount of the thermoelectric semiconductor material, the thickness of the thermoelectric conversion material layer, and the size of the pattern. From the perspective of the shape controllability of the thermoelectric conversion material layer and the control of the shape of the concave portion and the depth of the deepest portion, for example, at 25°C for 5s -1 Under the conditions of , it is 1 Pa·s to 1000 Pa·s, preferably 5 Pa·s to 500 Pa·s, more preferably 10 Pa·s to 300 Pa·s, and further preferably 30 Pa·s to 200 Pa·s.

[0170] In addition, the thickness of the film of the thermoelectric conversion material layer formed by the above-mentioned thermoelectric semiconductor composition, when used as a π-type thermoelectric conversion element, is from the perspective of use of screen printing, template printing, etc., is 50 μm or more and 1 mm or less, preferably 80 μm or more and 1 mm or less, more preferably 100 μm or more and 700 μm or less, and further preferably 150 μm or more and 500 μm or less.

[0171] (Annealing treatment)

[0172] In the present invention, after forming the thermoelectric conversion material layer, an annealing treatment is preferably performed. Annealing can stabilize the thermoelectric performance and simultaneously cause crystal growth of the thermoelectric semiconductor fine particles in the thermoelectric conversion material layer, thereby further improving the thermoelectric performance.

[0173] The annealing treatment is not particularly limited, but is usually carried out in an inert gas atmosphere such as nitrogen, argon, etc., in which the gas flow rate is controlled, in a reducing gas atmosphere, or under vacuum conditions. As for the temperature of the annealing treatment, although it depends on the heat-resistant resin, ionic liquid, inorganic ionic compound, etc. used, it is usually carried out at 100 to 600° C. for several minutes to several tens of hours, preferably at 150 to 600° C. for several minutes to several tens of hours, more preferably at 250 to 600° C. for several minutes to several tens of hours, and further preferably at 250 to 550° C. for several minutes to several tens of hours.

[0174] (Substrate)

[0175] In the thermoelectric conversion module of the present invention, the substrate is not particularly limited. However, from the perspective of thinness and flexibility, a resin film that does not affect the decrease in electrical conductivity or increase in thermal conductivity of the thermoelectric conversion material layer can be used. Among these, polyimide films, polyamide films, polyetherimide films, polyaramid films, or polyamideimide films are preferred because they exhibit excellent flexibility, do not cause thermal deformation of the substrate even when a thin film of the thermoelectric conversion material layer formed from the thermoelectric semiconductor composition is annealed, and maintain the performance, heat resistance, and dimensional stability of the thermoelectric conversion material layer. Furthermore, polyimide films are particularly preferred because of their high versatility.

[0176] From the viewpoints of flexibility, heat resistance, and dimensional stability, the thickness of the resin film is preferably 1 to 1000 μm, more preferably 5 to 500 μm, and even more preferably 10 to 50 μm.

[0177] The 5% weight loss temperature of the resin film as measured by thermogravimetric analysis is preferably 300°C or higher, more preferably 400°C or higher. The dimensional change upon heating as measured at 200°C in accordance with JIS K7133 (1999) is preferably 0.5% or lower, more preferably 0.3% or lower. The linear expansion coefficient in the plane direction as measured in accordance with JIS K7197 (2012) is 0.1 ppm·°C. -1 ~50ppm·℃ -1 , more preferably 0.1ppm·℃ -1 ~30ppm·℃ -1 .

[0178] Insulating materials such as glass and ceramics can be used as the substrate used in the present invention. From the perspective of process and dimensional stability, the thickness of the substrate is preferably 5 to 1200 μm, more preferably 10 to 800 μm, and even more preferably 30 to 700 μm.

[0179] (electrode)

[0180] Examples of the metal material of the electrode of the thermoelectric conversion element used in the present invention include copper, gold, nickel, aluminum, rhodium, platinum, chromium, palladium, stainless steel, molybdenum, tin, and alloys containing any of these metals.

[0181] The thickness of the electrode layer is preferably 10 nm to 200 μm, more preferably 30 nm to 150 μm, and even more preferably 50 nm to 120 μm. When the thickness of the electrode layer is within the above range, the electrical conductivity is high, the resistance can be low, and sufficient strength can be obtained when the electrode is manufactured.

[0182] The electrodes are formed using the above-mentioned metal materials.

[0183] Methods for forming electrodes include: providing an unpatterned electrode on a resin film and then processing it into a given pattern shape through known physical or chemical treatments such as photolithography, or a combination thereof; or directly forming an electrode pattern by screen printing, inkjet printing, or the like.

[0184] As methods for forming unpatterned electrodes, there are listed: dry processes such as PVD (physical vapor deposition) such as vacuum evaporation, sputtering, and ion plating, or CVD (chemical vapor deposition) such as thermal CVD and atomic layer evaporation (ALD), or various coatings such as dip coating, spin coating, spray coating, gravure coating, die coating, and blade coating, wet processes such as electrodeposition, silver salt method, electrolytic plating, chemical plating, and lamination of metal foils, etc., which can be appropriately selected according to the material of the electrode.

[0185] The electrodes used in the present invention require high electrical conductivity and high thermal conductivity from the perspective of maintaining thermoelectric performance, and therefore electrodes formed by plating or vacuum film forming are preferably used. From the perspective of being able to easily achieve high electrical conductivity and high thermal conductivity, vacuum film forming methods such as vacuum evaporation and sputtering, as well as electrolytic plating and chemical plating are preferred. Although it also depends on the size and dimensional accuracy requirements of the pattern to be formed, it is also possible to easily form a pattern through a hard mask such as a metal mask.

[0186] (Jointing material layer)

[0187] In the thermoelectric conversion module used in the present invention, a bonding material layer can be used to bond the thermoelectric conversion material layer to the electrode. In the configuration of the thermoelectric conversion module of the present invention, the bonding material layer is disposed in the recessed portion of the thermoelectric conversion material chip. The bonding material layer is as described above.

[0188] By ensuring that the longitudinal cross-section of the thermoelectric conversion material layer, including the recessed portion, satisfies conditions (A) and (B), a thermoelectric conversion module can be obtained that exhibits high bonding between the thermoelectric conversion material layer and the electrodes and excellent thermoelectric performance. Furthermore, this can contribute to achieving high integration of the thermoelectric conversion material layer.

[0189] Example

[0190] Hereinafter, the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples at all.

[0191] The resistance values ​​and the recessed portion cross-sectional occupancy rates of the thermoelectric conversion modules produced in Examples and Comparative Examples were evaluated by the following methods.

[0192] (a) Resistance evaluation

[0193] The resistance value between the extraction electrodes of the thermoelectric conversion module including the obtained thermoelectric conversion material layer (chip) was measured using a digital multimeter (manufactured by Hioki Electric Co., Ltd., model: 3801-50) in an environment of 25°C and 50% RH.

[0194] (b) Concave section occupancy rate

[0195] The longitudinal section including the center portion of the thermoelectric conversion material layer (chip) of the obtained thermoelectric conversion module (see FIG. 1 ) was observed using a digital microscope (Keyence, Model: VHX-5000). Figure 2 (b)) was observed and the area S (μm) of the longitudinal section was measured. 2), the maximum thickness Dmax (μm) in the thickness direction of the longitudinal section, the maximum length Xmax (μm) in the width direction of the longitudinal section, the maximum depth Tmax (μm) of the concave portion of the longitudinal section, and the shortest distance (μm) between the intersection point Z where a perpendicular line drawn from the deepest portion T to the bottom edge of the longitudinal section intersects the bottom edge. The concave cross-section occupancy ratio (Dmax × Xmax - S) / (Dmax × Xmax) was calculated and evaluated using the measured Dmax, Xmax, and S.

[0196] (Example 1)

[0197] The thermoelectric semiconductor material constituting the thermoelectric semiconductor composition is used in the form of thermoelectric semiconductor fine particles.

[0198] (Fabrication of Thermoelectric Semiconductor Particles)

[0199] P-type bismuth telluride (Bi) as a bismuth-tellurium-based thermoelectric semiconductor material was milled using a planetary ball mill (FRITSCH Japan, Premium line P-7). 0.4 Te3Sb 1.6 (manufactured by Kojun Chemical Research Institute, particle size: 180 μm) was pulverized in a nitrogen atmosphere to produce thermoelectric semiconductor fine particles T1 with an average particle size of 1.2 μm. The particle size distribution of the pulverized thermoelectric semiconductor fine particles was measured using a laser diffraction particle size analyzer (manufactured by Malvern, Mastersizer 3000).

[0200] In addition, N-type bismuth telluride Bi2Te3 (produced by Kojundo Chemical Research Institute, particle size: 180 μm) as a bismuth-tellurium-based thermoelectric semiconductor material was pulverized in the same manner as above to produce thermoelectric semiconductor fine particles T2 with an average particle size of 1.4 μm.

[0201] (Preparation of coating liquid)

[0202] Coating liquid (P)

[0203] A coating liquid (P) was prepared, consisting of a thermoelectric semiconductor composition containing 90 parts by mass of the obtained P-type bismuth-tellurium thermoelectric semiconductor material microparticles T1, 5 parts by mass of polyamic acid (a poly(pyromellitic dianhydride-co-4,4'-diaminodiphenyl ether) amic acid solution, manufactured by Sigma-Aldrich, solvent: N-methylpyrrolidone, solids concentration: 15% by mass), and 5 parts by mass of 1-butyl-3-(2-hydroxyethyl)imidazole bromide as an ionic liquid. The viscosity of the coating liquid (P) was 170 Pa·s.

[0204] Coating liquid (N)

[0205] A coating liquid (N) was prepared, consisting of a thermoelectric semiconductor composition containing 90 parts by mass of the obtained N-type bismuth-tellurium thermoelectric semiconductor material fine particles T2, 5 parts by mass of polyamic acid (a polyimide precursor, manufactured by Sigma-Aldrich, a poly(pyromellitic dianhydride-co-4,4'-diaminodiphenyl ether) amic acid solution, solvent: N-methylpyrrolidone, solids concentration: 15% by mass), and 5 parts by mass of 1-butyl-3-(2-hydroxyethyl)imidazole bromide as an ionic liquid. The viscosity of the coating liquid (N) was 170 Pa·s.

[0206] <Formation of Thermoelectric Conversion Material Layer>

[0207] The thermoelectric conversion material layer was formed by the following pattern frame arrangement / lift-off method, and a π-type thermoelectric conversion module was produced.

[0208] <Forming the thermoelectric element layer using pattern frame alignment / lift-off method>

[0209] A pattern frame with a thickness of 200 μm was set on the electrode of the lower polyimide film substrate (manufactured by DuPont Toray, Kapton 200H, 100 mm × 100 mm, thickness: 50 μm) in a separated manner and designed with openings. The above-mentioned coating liquids (P) and (N) were printed in the above-mentioned openings and dried. The above-mentioned pattern frame was peeled off from the substrate, thereby setting a total of 100 pairs of 1.5 mm × 1.5 mm P-type thermoelectric conversion material layers and N-type thermoelectric conversion material layers.

[0210] After application, the coating liquid was dried at 150°C in an argon atmosphere for 10 minutes. The resulting thermoelectric conversion material thin film was annealed in a mixture of hydrogen and argon (hydrogen:argon = 3 vol%:97 vol%) at a heating rate of 5K / min and held at 325°C for 1 hour to allow crystal growth of thermoelectric semiconductor material particles. This resulted in a P-type and an N-type thermoelectric conversion material layer. The thickness of the thermoelectric conversion material layer was 180 μm at both ends of the upper recess and 5 μm at the deepest portion of the recess, with a recess cross-sectional area occupancy ratio of 0.05.

[0211] Next, recesses on the P-type thermoelectric conversion material layer and the N-type thermoelectric conversion material layer were filled with solder material (PF141-LT7HO F=10, manufactured by Handa Co., Ltd., Japan) and bonded to electrodes on an upper polyimide film substrate (which had the same specifications as the lower polyimide film substrate except for the arrangement of the electrodes, in which 100 pairs of P-type thermoelectric conversion material layers and N-type thermoelectric conversion material layers were arranged alternately in series and electrically connected in series). This produced a π-type thermoelectric conversion module (Peltier cooling element) in which 100 pairs of P-type thermoelectric conversion material layers and N-type thermoelectric conversion material layers were arranged alternately in series and electrically connected in series.

[0212] It should be noted that the distance between the centers of the P-type thermoelectric conversion material layer and the N-type thermoelectric conversion material layer formed on the electrode of the lower polyimide film substrate is set to 2.5 mm, and the distance between the centers of the P-type thermoelectric conversion material layer and the N-type thermoelectric conversion material layer on the electrode of the upper polyimide film substrate is set to 2.5 mm.

[0213] (Example 2)

[0214] A π-type thermoelectric conversion module according to Example 2 was produced in the same manner as in Example 1, except that the viscosities of the coating liquids (P) and (N) were adjusted to 120 Pa·s by adding N-methylpyrrolidone. The thickness of the thermoelectric conversion material layer after annealing was 170 μm at both ends of the upper recess and 8 μm at the deepest portion of the recess, with a recess cross-sectional area occupancy ratio of 0.07.

[0215] (Example 3)

[0216] A π-type thermoelectric conversion module according to Example 3 was produced in the same manner as in Example 1, except that the viscosities of the coating liquids (P) and (N) were adjusted to 70 Pa·s by adding N-methylpyrrolidone. The thickness of the thermoelectric conversion material layer after annealing was 160 μm at both ends of the upper recess and 10 μm at the deepest portion of the recess, with a recess cross-sectional occupancy ratio of 0.10.

[0217] (Comparative Example 1)

[0218] A π-type thermoelectric conversion module for Comparative Example 1 was produced in the same manner as in Example 1, except that the P-type and N-type thermoelectric conversion material layers were formed by pattern printing using a 235 μm thick stencil, rather than by the pattern frame alignment / stripping method. The thickness of the thermoelectric conversion material layer after annealing was 180 μm.

[0219] (Comparative Example 2)

[0220] A π-type thermoelectric conversion module of Comparative Example 2 was produced in the same manner as in Example 1, except that the viscosities of the coating liquids (P) and (N) were adjusted to 30 Pa·s by adding N-methylpyrrolidone. The thickness of the thermoelectric conversion material layer after annealing was 130 μm at both ends of the upper recess and 30 μm at the deepest portion of the recess, with a recess cross-sectional occupancy ratio of 0.30.

[0221] The thermoelectric conversion modules obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were evaluated for resistance value, recessed portion cross-sectional occupancy, deepest portion Tmax, Dmax, and Dmax / Xmax. The evaluation results are shown in Table 1.

[0222]

[0223] As is clear from Table 1, when comparing the configuration of π-type thermoelectric conversion elements, the thermoelectric conversion modules of Examples 1 to 3, which were equipped with a thermoelectric conversion material layer (chip) having recessed portions, exhibited lower resistance values ​​between the electrodes at both ends of the thermoelectric conversion module, compared to the thermoelectric conversion module of Comparative Example 1, which was equipped with a thermoelectric conversion material layer without recessed portions, demonstrating that high thermoelectric performance was achieved. Furthermore, the thermoelectric conversion modules of Examples 1 to 3, which were equipped with a thermoelectric conversion material layer (chip) having a longitudinal cross-section that did not satisfy condition (A), exhibited lower resistance values ​​between the electrodes at both ends of the thermoelectric conversion module, demonstrating that high thermoelectric performance was achieved, compared to the thermoelectric conversion module of Comparative Example 2, which was equipped with a thermoelectric conversion material layer (chip) having a longitudinal cross-section that did not satisfy condition (A).

[0224] Industrial Applicability

[0225] According to the thermoelectric conversion material chip of the present invention, a thermoelectric conversion module equipped with a thermoelectric conversion material chip having a longitudinal cross-section that satisfies conditions (A) and (B) has a substantially rectangular parallelepiped shape with a specific recess formed thereon. Therefore, the bonding material used to bond the thermoelectric conversion material chip to the electrode can be filled into the recess without flowing around the side of the thermoelectric conversion material chip. Therefore, the resistance value of the thermoelectric conversion material chip can be controlled to a low level, and improved thermoelectric performance can be expected. Furthermore, the thermoelectric conversion module using the thermoelectric conversion material chip of the present invention can be expected to achieve high integration because the shape of the thermoelectric conversion material chip is excellently controllable.

[0226] The above-mentioned thermoelectric conversion components are considered to be suitable for power generation purposes by converting waste heat from various combustion furnaces such as factories, waste incinerators, cement incinerators, etc., waste heat from automobile combustion gases, and waste heat from electronic equipment into electrical energy. As cooling applications, they are considered to be suitable for temperature control of various sensors such as CPUs (Central Processing Units) used in smartphones and various computers, as well as image sensors such as CMOS (Complementary Metal Oxide Semiconductor Image Sensors) and CCDs (Charge Coupled Devices), as well as MEMS (Micro Electro Mechanical Systems) and other light receiving elements in the field of electronic equipment.

Claims

1. A chip of a thermoelectric conversion material, having a recess on at least one side thereof, In the longitudinal section of the thermoelectric conversion material chip including the center portion in the width direction, the area of ​​the longitudinal section is denoted as S (μm 2 ), when the maximum value of the thickness in the thickness direction of the longitudinal section is set to Dmax (μm), the maximum value of the length in the width direction of the longitudinal section is set to Xmax (μm), and the maximum value of the depth of the concave portion of the longitudinal section is set to Tmax (μm), the cross section of the concave portion of the longitudinal section of the chip of the thermoelectric conversion material satisfies the following conditions (A) and (B), (A)0<(Dmax×Xmax-S) / (Dmax×Xmax)≤0.20 (B) 0.01<Tmax / Dmax<0.30 and Tmax≥2μm in, The maximum value Dmax of the thickness in the thickness direction of the longitudinal section represents the maximum distance (thickness) between the two intersection points of the longitudinal section of the thermoelectric conversion material chip when a perpendicular line is drawn on the bottom of the longitudinal section and the upper and lower ends of the thickness in the thickness direction of the longitudinal section intersect the perpendicular line. The maximum value Xmax of the width direction of the longitudinal section is the maximum distance (length) between the two intersection points obtained when the left and right ends of the width direction of the longitudinal section intersect with a parallel line drawn parallel to the bottom side of the longitudinal section. The maximum value Tmax of the depth of the concave portion of the longitudinal section is represented by: the maximum distance (depth) obtained by subtracting the shortest distance (length) between the deepest part of the concave portion and the following intersection point from the maximum value Dmax of the thickness in the thickness direction of the longitudinal section, wherein the intersection point is the intersection point obtained when a perpendicular line descending from the deepest part of the concave portion to the bottom edge of the longitudinal section intersects the bottom edge.

2. The chip of thermoelectric conversion material according to claim 1, wherein The shape of the thermoelectric conversion material chip is at least one selected from a rectangular parallelepiped, a cube, and a cylinder.

3. The thermoelectric conversion material chip according to claim 1 or 2, wherein: The concave portion of the thermoelectric conversion material chip has a bonding material layer.

4. The thermoelectric conversion material chip according to claim 3, wherein: The bonding material layer includes a solder material, a conductive adhesive, or a sintered bond.

5. The thermoelectric conversion material chip according to claim 1 or 2, wherein: The condition (A) is 0.05<(Dmax×Xmax−S) / (Dmax×Xmax)≤0.10, and the condition (B) is 0.10<Tmax / Dmax<0.20 and 4≤Tmax≤35 μm. A thermoelectric conversion module comprising a chip of the thermoelectric conversion material according to any one of claims 1 to 5.

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