Thermal radiation element and heat transport method

Abstract

To provide a heat radiation element capable of realizing heat radiation at a predetermined angle over a wide wavelength band, and a heat transportation method using the heat radiation element.SOLUTION: There is provided a heat radiation element, comprising: a first metal substrate 101; a dielectric film 102 disposed on one main surface 101a of the first metal substrate; and a plurality of second metal members 103 disposed on the dielectric film 102. The plurality of second metal members 103 are lined up at a predetermined interval Sx in a first direction, and a width Lx of the second metal members in the first direction is 4 μm or more and 50 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a thermal radiation element and a heat transport method. [Background technology]

[0002] Thermal radiation from natural light is generally broad-wavelength and isotropic. It is known that the wavelength and angle of radiation can be narrowed by coupling the thermal radiation with resonance modes resulting from the structure of the thermal radiator. Angle-selective thermal radiation obtained from conventional thermal radiators is limited to a single wavelength or a limited wavelength range (Non-Patent Literature 1). Therefore, when performing angle-selective radiative heat transport, the energy transported by radiation at each angle is limited to only a portion of the wavelength range, resulting in a very small amount. From the perspective of heat transport, achieving ideal angle-selective radiative heat transport requires generating thermal radiation across a wide wavelength range within a predetermined angular range.

[0003] The wavelength range of thermal radiation is determined by the physical properties of the thermal radiator material. Therefore, by selecting the thermal radiator material according to the required wavelength range, ideal angle-selective radiative heat transport can be achieved. However, if a material corresponding to the required wavelength range does not exist or is difficult to obtain, this method cannot be applied. Therefore, there is a need for a technology that can finely adjust the wavelength range of thermal radiation regardless of the thermal radiator material. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] S. Tsuda et al., OPTICS EXPRESS 6899, Vol.26, No. 6, 19 Mar 2018 [Overview of the project] [Problems that the invention aims to solve]

[0005] This invention has been made in view of the above circumstances, and aims to provide a thermal radiation element capable of realizing thermal radiation at a predetermined angle over a wide wavelength band, and a heat transport method using the thermal radiation element. [Means for solving the problem]

[0006] To solve the above problems, the present invention employs the following means.

[0007] (1) A thermal radiation element according to one aspect of the present invention comprises a first metal substrate, a dielectric film disposed on one main surface of the first metal substrate, and a plurality of second metal members disposed on the dielectric film, wherein the plurality of second metal members are arranged at predetermined intervals in a first direction, and the width of the second metal members in the first direction is 4 μm or more and 50 μm or less, and more preferably 15 μm or more, which is a width that produces many peaks.

[0008] (2) In the thermal radiation element described in (1) above, the width of the second metal member in the first direction is preferably 5 times or more and 10 times or less the spacing.

[0009] (3) In the thermal radiation element described in either (1) or (2) above, it is preferable that the thickness of the dielectric film is 0.02 times or less the main wavelength in the thermal radiation distribution within the dielectric film.

[0010] (4) In the thermal radiation element described in any one of (1) to (3) above, a plurality of the second metal members may be arranged at predetermined intervals in a second direction intersecting the first direction.

[0011] (5) The heat transport method according to one aspect of the present invention is a heat transport method using the heat radiation element described in any one of (1) to (4) above, wherein heat radiation is generated from the second metal member side at an angle of 80 degrees or more and less than 90 degrees with respect to the vertical direction of the main surface of the second metal member over a wavelength band of 0.3 μm or more to perform heat transport. This is a wavelength band that occupies a large proportion of the total thermal radiation emitted from an object at room temperature to about 1000 degrees, and the effect of heat radiation control is large.

Advantages of the Invention

[0012] The present invention can provide a heat radiation element capable of realizing heat radiation at a predetermined angle over a wide wavelength band, and a heat transport method using the heat radiation element.

Brief Description of the Drawings

[0013] [Figure 1] (a) and (b) are perspective views and cross-sectional views of a heat radiation element according to an embodiment of the present invention. [Figure 2] It is a diagram showing a state in which a resonance mode is generated in a cross section of the heat radiation element of the embodiment. [Figure 3] It is a plan view of a heat radiation element according to Modification 1 of the embodiment. [Figure 4] It is a plan view of a heat radiation element according to Modification 2 of the embodiment. [Figure 5] (a) to (c) are cross-sectional views of the heat radiation element in the manufacturing process. [Figure 6] (a) to (c) are cross-sectional views of the heat radiation element in the manufacturing process. [Figure 7] It is a graph showing the relationship between the wavelength of irradiation light and the absorption rate in the heat radiation elements of Examples 1 and 2. [Figure 8] It is a graph showing the relationship between the wavelength of irradiation light and the absorption rate in the heat radiation elements of Examples 3 and 4. [Figure 9] It is a graph comparing the absorption rate of the heat radiation element when diffracted light is generated between the second metal members and when it is not generated. [Figure 10]This graph shows the relationship between the thickness of the dielectric film and its absorption rate. [Figure 11] This is a polar plot showing the absorption rate for different angles of incidence. [Modes for carrying out the invention]

[0014] The following will describe in detail, with reference to the drawings, a heat radiation element and a heat transport method according to an embodiment to which the present invention is applied. Note that, for the sake of clarity, the drawings used in the following description may show enlarged versions of key features, and the dimensional ratios of each component may not be the same as those in reality. Furthermore, the materials, dimensions, etc., exemplified in the following description are merely examples, and the present invention is not limited to these; it can be implemented with appropriate modifications without altering its essence.

[0015] Figure 1 is a perspective view of a thermal radiation element 100 according to one embodiment of the present invention. The thermal radiation element 100 mainly comprises a substrate (first metal substrate) 101 made of a first metal, a dielectric film 102, and a plurality of second metal members 103.

[0016] The first metal substrate 101 is made of a first metal that reflects 90% or more of light. Examples of the first metal include precious metals such as gold, silver, and platinum, as well as molybdenum, aluminum, tungsten, titanium, nickel, copper, and iron. The first metal substrate 101 only needs to have a flat main surface 101a on which the dielectric film 102 is placed, and the shape and size of other parts are not limited.

[0017] The dielectric film 102 is a film body that is arranged (formed) on one main surface 101a of the first metal substrate 101 and functions as a waveguide for the irradiated light I. The dielectric film 102 is composed of molecules having vibration modes in an in-plane direction (here, the XY in-plane direction) perpendicular to its thickness direction. Examples of molecules having vibration modes in the in-plane direction include dielectrics with low light absorption (extinction coefficient k < 1), such as ceramics such as SiO2, Al2O3, TiO2, and NiO, or polymers such as acrylic resins, epoxy resins, fluororesins, and polyimides. SiO2 is particularly preferred as a constituent material for the dielectric film 102 because it has a low extinction coefficient and high material stability.

[0018] The polymer constituting the dielectric film 102 is not specifically limited, but for example, carbon compounds such as PMMA (polymethyl methacrylate resin), PMF (poly(melamine-co-formaldehyde)), and epoxy can be used.

[0019] In conventional thermal radiation elements with a dielectric film placed on a metal substrate, the wavelength of light emitted from the dielectric film 102 differs depending on the material constituting the dielectric film 102. In other words, the dielectric film 102 has wavelength selectivity for the emitted light, and the wavelength of the emitted light is determined by appropriately selecting its constituent material.

[0020] In contrast, the thermal radiation element 100 of this embodiment, in which a second metal member 103 is placed on a dielectric film 102 on a first metal substrate 101, can induce electromagnetic resonance through its structure, thereby emitting light in a wide wavelength band of 3 μm or more, regardless of the constituent material of the dielectric film 102.

[0021] PMMA has a simple molecular structure and a small number of molecular oscillators (frequencies) that couple with the Leaky mode, making it a suitable material when it is desired to narrow the wavelength range of synchrotron radiation. In contrast, PMF has a complex molecular structure and contains multiple molecular oscillators. Therefore, PMF is a suitable material when it is desired to broaden the wavelength range of synchrotron radiation.

[0022] From the viewpoint of increasing the light absorption rate, it is preferable for the dielectric film 102 to be as thin as possible. When the dielectric film 102 is thin, the leaky mode of the irradiated light I is more likely to couple with the thermal vibrations (molecular vibrations) of molecules within the dielectric film 102, and when this coupling occurs, the radiation angle of the synchrotron radiation is limited. In other words, radiation can be directed only in the desired direction, thereby increasing the directivity of the synchrotron radiation.

[0023] The second metal member 103 is made of a secondary metal that reflects 90% or more of light. Examples of secondary metals include precious metals such as gold, silver, and platinum, as well as molybdenum, aluminum, tungsten, titanium, nickel, copper, and iron. Multiple second metal members 103 are arranged (formed) on the dielectric film 102 (on the opposite side from the first metal substrate 101), and are spaced apart from each other at a predetermined interval S in the first direction (the X direction in Figure 1). x They are arranged with a gap between them. The width L of the second metal member 103 in the first direction. x This is extremely important. The wider the width, the more modes appear in the target wavelength range, and the more peaks there are. Therefore, width L x The interval S is preferably 4 μm to 50 μm, and more preferably 15 μm to 50 μm, which is the width at which many peaks are produced. x It is better if it is narrower. 。 Width L of the second metal member 103 x is interval S x It is preferable that it is between 5 and 10 times, and more preferably between 8 and 10 times.

[0024] In order to allow light to enter the dielectric film 102, the slit 103s formed between adjacent second metal members 103 is preferably an air gap, but it may also be a state in which a member that transmits 90% or more of the light is sandwiched between them. Figure 1 illustrates the case in which the slit 103s formed between the second metal members 103 extend in a direction perpendicular to the first direction (X direction) (Y direction).

[0025] The thickness 103d of the second metal member 103 is designed so that, as shown in Figure 1(b), light I incident on the main surface 103a of the second metal member 103 at an angle θ with respect to the vertical direction passes between adjacent second metal members 103 and reaches the surface (top surface) 102a of the dielectric film 102.

[0026] Figure 2 shows the operating state of the thermal radiation element 100 as determined by simulation. Figure 2 corresponds to Figure 1(b) and shows the vibration state when light is incident at an angle θ of 89°. The mechanism of resonance mode generation in the in-plane direction (X direction) is as follows: First, electrons on the upper surface 102a of the dielectric film 102 vibrate when irradiated with light. In a chain reaction with this vibration, electrons on the lower surface 102b vibrate, causing electromagnetic resonance (Fabry-Perot type resonance) to occur between the upper surface 102a and the lower surface 102b of the dielectric film. In Figure 2, the areas where electromagnetic resonance is occurring are shown in white (in Figure 2, areas where electromagnetic resonance is particularly strong are shown in a color closer to white).

[0027] Electromagnetic resonance occurs between the upper surface 102a and the lower surface 102b of the dielectric film, causing the electrons constituting the main surface 101a of the first metal substrate 101 to vibrate and create density variations. A portion of the resulting electric field appears on the structural surface as a leaky mode when the thickness of the dielectric film 102 satisfies the condition that it is 0.02 times or less of the main wavelength in the thermal radiation distribution within the dielectric film. This results in a strong interaction with light at a large angle of 80 to 90 degrees with respect to the vertical direction of the main surface (upper surface, the surface opposite to the dielectric film 102) 103a of the second metal member 103, causing strong absorption (absorption peaks) in multiple wavelength ranges. Here, the main wavelength in the thermal radiation distribution refers to the wavelength showing a peak, for example, the wavelength showing the maximum peak.

[0028] The shape and arrangement pattern of the second metal member 103 are not limited to the stripe shape shown in Fig. 1(a). As long as the second metal member 103 has a periodic structure in which a plurality of second metal members 103 are arranged at predetermined intervals in at least one direction (the first direction) as shown in Fig. 1(b), it may have other shapes and may be arranged in other patterns. For example, in the second direction intersecting the first direction, a plurality of second metal members 103 may be arranged side by side with a predetermined interval therebetween.

[0029] Figs. 3 and 4 are plan views (top views) of the heat radiation elements 110 and 120 according to modified examples of the heat radiation element 100 shown above. The heat radiation elements 110 and 120 are the same as the heat radiation element 100 except that only the shape and arrangement pattern of the second metal member 103 are different. The same reference numerals are assigned to the corresponding portions of the heat radiation element 100.

[0030] In the heat radiation element 110 of Fig. 3, a plurality of second metal members 103 are arranged in an island shape on the upper surface of the dielectric film 102, and a periodic structure is formed not only in the first direction (X direction) but also in the second direction (Y direction). (Here, it is shown as a rectangle, but it may be a square, a circle, or other shapes.) Therefore, heat radiation can be performed in the second direction as well as in the first direction. The second metal members 103 are arranged side by side with a predetermined interval S y therebetween in the second direction. The width L y of the second metal member 103 in the second direction is preferably 4 μm or more and 50 μm or less, and more preferably 15 μm or more and 50 μm or less. The interval S x is preferably narrow 。 The width L x of the second metal member 103 y is preferably 5 times or more and 10 times or less the interval S, and more preferably 8 times or more and 10 times or less.

[0031] In the thermal radiation element 120 shown in Figure 4, multiple patterns of square-shaped (rectangular) second metal members 103 are arranged on the upper surface of the dielectric film 102 in a nested manner with predetermined intervals between them. In this case as well, thermal radiation can be performed in both the first direction (X direction) and the second direction (Y direction) in which the periodic structure is formed.

[0032] (Manufacturing method for thermal radiation devices) Figures 5 and 6 are cross-sectional views of each process in the manufacturing of the thermal radiation element 100. The thermal radiation element 100 is mainly manufactured through the following processes.

[0033] First, as shown in Figure 5(a), a film of the first metal (hereinafter referred to as the first metal substrate) 101 made of the aforementioned material such as gold is formed on one surface of the support member 104 using a known film deposition method such as sputtering. The thickness of the first metal substrate 101 is not particularly limited, but it is preferably around 50 nm to 1000 nm (transmission does not occur if it is 50 nm or more). When Si is used for the support member 104, it is preferable to form a thin film of Cr or the like (5 nm or less) as an adhesion layer to the first metal substrate 101 before forming the first metal substrate 101.

[0034] Next, as shown in Figure 5(b), a dielectric film (hereinafter referred to as a dielectric film) 102 made of the aforementioned material such as SiO2 is formed on the first metal substrate 101 using a known film deposition method such as sputtering. The thickness of the dielectric film 102 is not limited, but it should be 300 nm or less. However, from the viewpoint of angle selectivity and increased energy absorption, it is preferably 100 nm or less, and more preferably 30 nm or less.

[0035] Next, as shown in Figure 5(c), a resist 105 (in this case, a negative resist) is applied to the upper surface of the dielectric film 102. Subsequently, as shown in Figure 6(a), only the resist applied to the portion of the upper surface of the dielectric film 102 where the second metal member 103 is placed is selectively removed using a laser lithography method or the like.

[0036] Next, as shown in Figure 6(b), a film of a second metal (hereinafter referred to as a second metal component) 103 made of the aforementioned material such as gold is formed on the top surface of the resist 105 using a known film deposition method such as sputtering. The thickness of the second metal component 103 should be 500 nm or less, and preferably around 10 nm to 100 nm. Furthermore, it is preferable to set the width of the second metal member 103 to 4 μm or more and 50 μm or less, as this allows for obtaining multiple absorption wavelengths for a broadband wavelength range of approximately 3 μm to 10 μm, which is highly practical.

[0037] Next, as shown in Figure 6(c), the heat radiating element 100 supported by the support member 104 can be obtained by lifting off the resist 105 and the second metal member 103B on the resist 105 using ultrasonic cleaning or the like. The upper surface of the dielectric 102 will have multiple second metal members 103A arranged in a line with predetermined intervals between them. At this point, the support member 104 may be removed if it is no longer needed.

[0038] As described above, in the thermal radiation element 100 of this embodiment, a plurality of second metal members 103 are arranged at intervals on the upper surface of the dielectric film 102 that absorbs light irradiated at a predetermined angle. These second metal members 103 act as resonators, thereby artificially generating an in-plane resonance mode in the dielectric film 102. The electric field caused by the density of electrons on the surface of the first metal substrate resulting from this resonance mode appears as a leaky mode.

[0039] Therefore, the irradiated light can be strongly absorbed within the dielectric film 102 over a wide wavelength range. As a result, the thermal radiation element 100 of this embodiment can generate thermal radiation corresponding to the irradiation angle over a wide wavelength band, thereby realizing a thermal transport method with improved thermal energy transport efficiency.

[0040] Since the absorption wavelength band depends on the type of resonance mode generated in the dielectric film 102, it can be finely adjusted by changing the shape and arrangement of the second metal component 103 that generates this resonance mode. Therefore, the design flexibility of the absorption wavelength band can be greatly improved compared to adjusting it by changing the material of the dielectric film 102. [Examples]

[0041] The effects of the present invention will be further clarified by the following examples. However, the present invention is not limited to the following examples and can be implemented with appropriate modifications without altering its essence.

[0042] In the examples, the amount of radiation is shown in terms of absorptivity. However, since the energy radiated by the thermal radiation element 100 is the energy absorbed by the thermal radiation element 100, the absorptivity and the amount of radiation are equivalent. Therefore, a high absorptivity means that the amount of radiation at that wavelength is high.

[0043] (Example 1) A simulation was performed in which light was irradiated onto the thermal radiation element of the above embodiment from the second metal member 103 side at an incident angle of 80 degrees, and the absorption intensity of TE-polarized and TM-polarized light contained in the irradiated light was calculated for each wavelength. The material of both the first metal substrate and the second metal member was Au (gold). The material of the dielectric film was SiO2. In the first direction, the width of the second metal member was set to 13 μm, and the distance between the second metal members was set to 2 μm. The thickness of the second metal member was set to 0.1 μm, and the thickness of the dielectric film was set to 0.15 μm.

[0044] (Example 2) A thermal radiation element was fabricated and prepared under the same conditions as in Example 1. Light was irradiated onto it, and the absorption intensity of TE-polarized and TM-polarized light contained in the irradiated light was measured for each wavelength.

[0045] (Example 3) The same simulation as in Example 1 was performed, with the angle of incidence of light on the thermal radiation element set to 10 degrees and all other conditions unchanged.

[0046] (Example 4) The incident angle of light on the thermal radiation element was set to 10 degrees, and the same measurements as in Example 2 were performed without changing any other conditions.

[0047] Figure 7 is a graph showing the simulation results (thin dashed line) and TM polarization simulation results (thick dashed line) for Example 1 (incidence angle 80 degrees) and the measurement results (thin solid line) and TM polarization (thick solid line) for Example 2 (incidence angle 80 degrees). Figure 8 is a graph showing the simulation results (thin dashed line) and TM polarization simulation results (thick dashed line) for Example 3 (incidence angle 10 degrees) and the measurement results (thin solid line) and TM polarization (thick solid line) for Example 4 (incidence angle 10 degrees). In all graphs, the horizontal axis represents the wavelength of the irradiated light (μm), and the vertical axis represents the absorption intensity. The solid lines in the graphs correspond to the measured results, and the dashed lines correspond to the simulation results. It can be seen that the measured results and simulation results tend to be in close agreement regardless of the incident angle and type of polarization of the light.

[0048] As shown in the graphs in Figures 7 and 8, there is almost no absorption for TE polarization, but strong absorption is observed for TM polarization across multiple wavelength bands over a wide range of wavelengths from 3 to 10 μm. This difference is due to the fact that the vibration direction of TE polarization is perpendicular to the extension direction of the slit, while the vibration direction of TM polarization is parallel to the extension direction of the slit, thus enabling the generation of a Fabry-Perot type resonance mode.

[0049] When the incident angle is 80 degrees, the TM polarization (Figure 7) is absorbed approximately four times more strongly than when the incident angle is 10 degrees (Figure 8). From this result, it can be seen that, with the above-mentioned thermal radiation element in which the second metal members are arranged in a stripe pattern, thermal radiation (heat transport) with a large amount of energy can be realized from the second metal member side over a limited angular range of 80 degrees or more and less than 90 degrees with respect to the vertical direction of the main surface of the second metal member, and over a wide wavelength band of 3 μm or more.

[0050] The broad wavelength range of 3 μm and above accounts for a large proportion of the total thermal radiation emitted from objects ranging from room temperature to approximately 1000 degrees Celsius, making it a highly effective area for controlling thermal radiation. Furthermore, since thermal radiation can be performed within a limited angular range of 80 degrees to less than 90 degrees, it increases the design options for thermal equipment used in heat transport.

[0051] The absorptivity in the above measurement results is (1-R), which is calculated by measuring the reflectance R of light irradiated onto the thermal radiation element and subtracting only that reflectance R from the total probability of 1. The calculated (1-R) ​​may include the probability that the light is emitted as diffracted light without being absorbed by the dielectric film. Therefore, the calculated result of (1-R) ​​"Normal°" for a thermal radiation element with a structure that is not affected by diffraction was compared with the calculated result "Total°" in the above example. Figure 9 is a graph showing the results of the comparison. The horizontal and vertical axes of the graph are the same as in Figures 7 and 8. The results of the comparison show that the two calculated absorptivity values ​​are of approximately the same magnitude, indicating that the absorptivity can be evaluated correctly.

[0052] (Example 5) The dielectric film thickness was set to 0 to 0.1 μm, and the same simulation as in Example 1 was performed without changing any other conditions, and the absorption rate for each thickness was calculated.

[0053] (Examples 6-10) The dielectric film thickness was set to 0.01 μm (Example 6), 0.02 μm (Example 7), 0.03 μm (Example 8), 0.1 μm (Example 9), and 0.5 μm (Example 10), and the same measurements as in Example 2 were performed without changing any other conditions.

[0054] (Reference example) Using a thermal radiation element with a dielectric film thickness of 0 to 0.5 μm and a structure that does not generate diffracted light, the same simulation as in Example 1 was performed to calculate the absorption rate for each thickness.

[0055] Figure 10 is a graph summarizing the simulation results for Example 5, the measured results for Examples 6, 7, and 9, and the results for the reference example. The horizontal axis of the graph shows the relative thickness of the dielectric film (d / 5: the actual thickness d normalized by the wavelength of molecular vibrations within the dielectric film (SiO2 film) of 5 μm). The vertical axis of the graph shows the relative absorptivity (A) of the dielectric film. 80 / A 10 : Average absorption rate of light at an incident angle of 10 degrees (absorption rate per unit area) A 10 The average absorption rate A of light with an incident angle of 80 degrees 80 This ratio indicates the strength of the dielectric film's (incident) angle selectivity with respect to incident light. In Figure 10, the calculation results in the example are shown as black circles, the fitting function as a solid line, the experimental results in the example as squares, and the calculation results for a thermal radiation element with a structure unaffected by diffraction as white circles.

[0056] Figure 11 shows polar plots of absorption rates for each angle of incidence, using the measured results from Examples 8-10.

[0057] Figures 10 and 11 show that the thickness of the dielectric film 102 is very important in the mechanism of resonance mode generation. As is clear from Figures 10 and 11, the relative absorption rate (A 80 / A 10 The value increases as the dielectric film thins. This means that the thinner the dielectric film, the higher the angular selectivity, and light incident at large angles of 80 degrees or more is selectively and strongly absorbed. Furthermore, the measured results and simulation results tend to be in close agreement regardless of the angle of incidence of light and the type of polarization. Note that the deviation in measurement results due to the generation of diffracted light is almost eliminated when the relative absorptivity is 0.02 or less.

[0058] The angular selectivity changes exponentially with respect to the thickness of the dielectric film, suggesting that it includes modes related to evanescent waves. When generating thermal radiation, these modes are thought to be caused by the density of electrons on the surface of the first metal substrate due to Fabry-Perot resonance.

[0059] From the results in Figure 10, it is estimated that the angle selectivity becomes significantly better when the thickness d of the dielectric film 102 is 300 nm or less. The absorption rate at high angles is more than three times higher than at low angles when the thickness d of the dielectric film 102 is 300 nm or less, and more than 5.5 times higher when it is 30 nm or less. This leads to an increase in angle selectivity and the amount of energy absorbed (i.e., radiation), and it is more practically preferable to use such a thin film thickness. [Explanation of symbols]

[0060] 100... Thermal radiation element 101...First metal substrate 101a...One main surface of the first metal substrate 102... Dielectric film 102d...Thickness of the dielectric film 103...Second metal component 103d...Thickness of the second metal component 103s...Slit 104...Support member 105... Resist I...Light L x , L y ...width of the second metal member S x S y ···interval θ...Angle of incidence

Claims

1. First metal substrate and A dielectric film disposed on one main surface of the first metal substrate, The system comprises a plurality of second metal members disposed on the dielectric film, The multiple second metal members are arranged at predetermined intervals in the first direction. The width of the second metal member in the first direction is 4 μm or more and 50 μm or less. The thickness of the dielectric film is 0.02 times or less the main wavelength in the thermal radiation distribution within the dielectric film. A thermal radiation element characterized in that the main wavelength is the wavelength that shows the largest peak in the thermal radiation distribution.

2. The thermal radiation element according to claim 1, characterized in that the width of the second metal member in the first direction is 5 times or more and 10 times or less the spacing.

3. The thermal radiation element according to either claim 1 or 2, characterized in that a plurality of the second metal members are arranged at predetermined intervals in a second direction intersecting the first direction.

4. A heat transport method using a heat radiation element according to any one of claims 1 to 3, A heat transport method characterized by generating thermal radiation from the second metal member side at an angle of 80 degrees or more and less than 90 degrees with respect to the vertical direction of the main surface of the second metal member, over a wavelength band of 0.3 μm or more, and performing heat transport.

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