Thermal radiation element, thermal radiation element module, and thermal radiation light source

Abstract

To increase energy efficiency compared to conventional thermal radiation elements.SOLUTION: A thermal radiation element (1) has a substrate (14), a plasmonic perfect absorber (10) comprising a first conductor layer (conductor layer 13) covering one main surface of the substrate (14), an insulator layer (12), and a second conductor layer (conductor layer 11), stacked in this order, and the first conductor layer (conductor layer 13) has electrodes (electrode pads 132, 133) that conduct current in the in-plane direction of a main surface of the first conductor layer (13).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a thermal radiation element, and also to a thermal radiation element module and a thermal radiation light source that include the thermal radiation element. [Background technology]

[0002] In recent years, there has been extensive research into technologies that can obtain material-independent optical properties by forming microstructures on the surface of materials. One type of microstructure is a plasmonic structure, and one type of plasmonic structure that has been reported is a plasmonic perfect absorber. A plasmonic perfect absorber is a plasmonic structure that has a high absorption rate in a specific wavelength band. A plasmonic perfect absorber is a resonator structure in which a conductor-insulator-conductor layer is stacked, and is also called an MIM (metal-insulator-metal) structure.

[0003] According to Kirchhoff's law, emissivity is equal to absorptivity in an opaque medium. Therefore, it has been reported that the emissivity of a material surface can be controlled using an MIM structure. Emissivity is expressed as the ratio of the radiation intensity of a real surface to that of a blackbody surface. Planck's law determines the thermal radiation of a blackbody surface, and multiplying this by the emissivity gives the thermal radiation of the real surface. Thermal radiation is the phenomenon in which the thermal energy of an object, such as a blackbody or MIM structure, is emitted as electromagnetic waves depending on the object's temperature. In the following, unless otherwise specified, radiation refers to thermal radiation.

[0004] An example of prior art literature relating to emissivity control is Patent Document 1. Patent Document 1 describes a technology for performing narrowband infrared thermal radiation by controlling the wavelength of emissivity using an MIM structure.

[0005] Furthermore, a thermal radiation light source that applies emissivity control technology using an MIM structure is known, as described in Patent Document 2. Patent Document 2 describes a technology that uses a layer that suppresses oxidation on the surface to suppress oxidation of the MIM structure that can occur when the structure is operated in the atmosphere.

[0006] Incidentally, as shown in FIG. 1(b) of Patent Document 1 and FIG. 1 of Patent Document 2, the MIM structure is laminated on a substrate (a base in Patent Document 1). Hereinafter, the substrate and the MIM structure laminated on the substrate will be collectively referred to as a thermal radiation element.

[0007] In order to utilize thermal radiation using such a thermal radiation element, it is essential to heat the MIM structure to a specified operating temperature. The higher the operating temperature, the stronger the thermal radiation and the shorter the wavelength of radiation that is emitted. Temperature is the balance of thermal energy. The greater the amount of thermal energy input relative to the amount of thermal energy lost, the higher the temperature. When the same material possesses the same energy, the amount of temperature rise varies depending on the volume. The thermal energy required to raise the temperature of an object by 1°C is determined by the heat capacity C [J / °C], specific heat c [J / kg·°C], and density ρ [kg / m 3 ], and volume V [m 3 ] is defined as in equation (1). C=c×ρ×V (1) [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2018-136576 [Patent Document 2] Japanese Patent Publication No. 2020-64820 Summary of the Invention [Problem to be solved by the invention]

[0009] The aforementioned Patent Document 2 describes methods for heating an MIM structure in a thermal radiation source, including a method of causing the substrate to self-heat by passing current through the substrate, and a method of externally heating the substrate and MIM structure using an external heating unit (e.g., a heater). In both of these methods, the heat transfer path when heating the MIM structure is via the substrate. Thus, from the perspective of the MIM structure, the substrate functions as a heat source. Therefore, in order to raise the temperature of the MIM structure to the aforementioned operating temperature, it is necessary to maintain the temperature of the substrate, which is the heat source, at or above the operating temperature.

[0010] The substrate is thicker than the MIM structure, and therefore inevitably has a larger volume. In other words, the heat capacity C of the substrate is inevitably larger than the heat capacity C of the MIM structure. Therefore, there is room for improvement in the energy efficiency of the conventional method of heating the entire MIM structure using the substrate as a heat source (for example, the method described in Patent Document 2).

[0011] One aspect of the present invention has been made in view of the above-mentioned problems, and aims to improve energy efficiency compared to the conventional heat radiation element of Patent Document 2. Another aspect of the present invention aims to provide a heat radiation element module and a heat radiation light source including a heat radiation element that has higher energy efficiency than conventional ones. [Means for solving the problem]

[0012] To solve the above-mentioned problems, a thermal radiation element according to one aspect of the present invention includes an insulating substrate having a pair of main surfaces, a first conductor layer covering at least a portion of one of the main surfaces of the substrate, an insulating layer, and a plasmonic perfect absorber formed by stacking a second conductor layer in this order. In this thermal radiation element, the first conductor layer is provided with an electrode that passes a current in an in-plane direction of the main surface of the first conductor layer.

[0013] In order to solve the above-mentioned problems, a thermal radiation element module according to one aspect of the present invention includes a thermal radiation element according to one aspect of the present invention, a cavity for accommodating the thermal radiation element, and a housing provided with power terminals for supplying power to the electrodes. In this thermal radiation element module, a configuration is adopted in which, inside the cavity, at least a portion of the substrate is fixed to the cavity using a bonding member.

[0014] In order to solve the above-mentioned problems, a thermal radiation source according to an aspect of the present invention includes a thermal radiation element module according to an aspect of the present invention. [Effects of the Invention]

[0015] According to one aspect of the present invention, it is possible to improve energy efficiency compared to the conventional heat radiation element of Patent Document 2. Furthermore, according to one aspect of the present invention, it is possible to provide a heat radiation element module and a heat radiation light source that include a heat radiation element that has higher energy efficiency than conventional elements. [Brief explanation of the drawings]

[0016] [Figure 1] The upper figure is a plan view of a thermal radiation element module according to one embodiment of the present invention, and the lower figure is a cross-sectional view of the same thermal radiation element module. [Figure 2] 2 is a cross-sectional view of a thermal radiation element included in the thermal radiation element module shown in FIG. 1. FIG. [Figure 3] FIG. 3 is an enlarged perspective view of a portion of a plasmonic perfect absorber provided in the thermal radiation element shown in FIG. 2. [Figure 4] FIG. 3 is a cross-sectional view of a first modified example of the heat radiation element shown in FIG. [Figure 5] FIG. 3 is a cross-sectional view of a second modified example of the heat radiation element shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0017] A thermal radiation element module M according to one embodiment of the present invention will be described with reference to Figs. 1 to 3. The upper diagram of Fig. 1 is a plan view of the thermal radiation element module M, and the lower diagram of Fig. 1 is a cross-sectional view of the thermal radiation element module M. The plan view of the thermal radiation element module M shows an opening AP of a cavity C provided in a housing 20. C is obtained when viewed from a plane in the normal direction of the main surface of the optical window 23. The cross-sectional view of the thermal radiation element module M is obtained in a cross section along the normal direction of the main surface of the optical window 23 and including the thermal radiation element 1. FIG. 2 is a cross-sectional view of the thermal radiation element 1, and is an enlarged view of the thermal radiation element 1 in FIG. 1. Note that in FIG. 2, each component is illustrated enlarged in the thickness direction. FIG. 3 is an enlarged perspective view of a part of the plasmonic perfect absorber 10 provided in the thermal radiation element 1.

[0018] [Configuration of the thermal radiation element module] As shown in the upper and lower figures of Figure 1, the thermal radiation element module M comprises a plasmonic perfect absorber 10, a substrate 14, a housing 20, an optical window 23, a bonding member 24, a bonding member 31, a metal wire 32, and power terminals 41 and 42.

[0019] Of the components of the thermal radiation element module M, the substrate 14 and the plasmonic perfect absorber 10 constitute a thermal radiation element 1 which is one aspect of the present invention.

[0020] Furthermore, the thermal radiation element module M emits electromagnetic waves (specifically, at least one of visible light, near-infrared light, mid-infrared light, and far-infrared light) resulting from thermal radiation by applying electricity to the conductor layer 13 constituting a part of the plasmonic perfect absorber 10 using the power terminals 41 and 42. In this way, the thermal radiation element module M functions as a thermal radiation light source that emits at least one of electromagnetic waves selected from visible light, near-infrared light, mid-infrared light, and far-infrared light. In other words, a thermal radiation light source using the thermal radiation element module M is also included in the scope of the present invention. Note that the thermal radiation light source may include the thermal radiation element module M and a power supply module that supplies power to the thermal radiation element module M via the power terminals 41 and 42.

[0021] The thermal radiation element module M is configured to pass a current in the in-plane direction of the conductor layer 13 using the power terminals 41 and 42. The current flowing in the in-plane direction of the conductor layer 13 generates Joule heat. Therefore, in the thermal radiation element module M, the thermal energy is used to heat the thermal radiation element 1 to a predetermined operating temperature, thereby emitting the above-mentioned electromagnetic waves. The operating temperature of the thermal radiation element 1 can be appropriately set within a temperature range in which the eutectic reaction in the plasmonic perfect absorber 10 does not proceed. The intensity of the light emitted by the plasmonic perfect absorber 10 increases as the operating temperature increases. In the thermal radiation element 1 described in this embodiment, the operating temperature is assumed to be 300°C or higher and 1200°C or lower.

[0022] <Substrate> The substrate 14 is a plate-like member made of an insulating material and having a pair of main surfaces 14a and 14b. In the state shown in FIG. 2, the main surface 14a is located on the upper side and the main surface 14b is located on the lower side. The shape of the substrate 14 can be determined as appropriate, but is preferably rectangular or square. In this embodiment, the shape of the substrate 14 is square.

[0023] In this embodiment, quartz glass, an example of glass, is used as the material for the substrate 14. However, the glass for the substrate 14 is not limited to quartz glass. The glass for the substrate 14 preferably contains SiO2 as its main component. In this embodiment, the term "main component" refers to the component with the highest content.

[0024] The material constituting the substrate 14 may also be a ceramic made of an oxide or nitride. Examples of such ceramics include ceramics whose main component is silicon oxide (SiO), ceramics made of silicon nitride (SiN), ceramics made of zirconium oxide (ZrO), and ceramics made of a mixture of calcium silicate and lithium aluminosilicate. Ceramics made of a mixture of calcium silicate and lithium aluminosilicate are also known as Adceram (registered trademark).

[0025] The material for forming substrate 14 can be appropriately selected from the above-mentioned materials in consideration of melting point, thermal conductivity, cost, etc. A high melting point is preferable to suppress eutectic reactions that may occur at high operating temperatures. Furthermore, in order to improve the energy efficiency when heating plasmonic perfect absorber 10 using Joule heat generated in conductor layer 13 of plasmonic perfect absorber 10 (described later), the thermal conductivity of substrate 14 is preferably lower than the conductivity of the conductor that forms conductor layer 13 (described later). Furthermore, in order to suppress the manufacturing cost of thermal radiation element 1, it is preferable that substrate 14 be inexpensive.

[0026] In addition, the thickness t of the substrate 14 S (See FIG. 2) is preferably 100 μm or more and 10 mm or less.

[0027] For the sake of convenience, the substrate 14 will be divided into three parallel rectangular regions below. C is a main region including the center of the substrate 14, and is the region with the widest width (length in the left-right direction in FIGS. 1 and 2) among the three regions. E is the central region R C In this embodiment, the central region R C and a pair of edge regions R E The outlines (shapes when viewed in plan) of the central region R C and a pair of edge regions R E The outline of is not limited to this and can be determined as appropriate.

[0028] <Plasmonic perfect absorber> 3, the plasmonic perfect absorber 10 included in the thermal radiation element 1 includes a conductor layer 11, an insulator layer 12, and a conductor layer 13. The conductor layer 11 is an example of a second conductor layer, and the conductor layer 13 is an example of a first conductor layer. The conductor layer 13, the insulator layer 12, and the conductor layer 11 are stacked in this order on the main surface 14a of the substrate 14.

[0029] (First conductor film) The conductor layer 13 is a conductive film formed on a main surface 14a, which is one of the main surfaces (the upper main surface in FIG. 2), of the substrate 14 so as to cover the main surface 14a. C and a pair of edge regions R E It is formed throughout the entire.

[0030] In this embodiment, hafnium nitride (HfN) is used as the conductor constituting the conductor layer 13. However, the conductor constituting the conductor layer 13 is not limited to HfN, and any material having metallic conductive properties may be used. When forming the plasmonic perfect absorber 10 on the surface of a substrate that is expected to become hot during use, it is preferable that the material constituting the conductor layer 13 be a material with a high melting point, such as HfN. The typical melting point of HfN is 3330°C.

[0031] The region of the main surface 14a where the conductor layer 13 is formed may be the entire main surface 14a or a part of the surface of the base material, and can be determined as appropriate. In this embodiment, the conductor layer 13 is formed on the entire main surface 14a.

[0032] In this embodiment, the thickness t of the conductor layer 13 13 (See Figure 2) where 100 nm is used as the thickness t 13 is not limited to 100 nm, and can be appropriately set within the range of, for example, 10 nm or more and 10 μm or less. 13 is an example of the thickness t1 described in the claims.

[0033] (insulating film) The insulating layer 12 is an insulating film formed on a main surface 13a, which is the main surface of the conductor layer 13 opposite to the substrate 14 (the upper main surface in FIG. 2), so as to cover at least a part of the main surface 13a. In this embodiment, the insulating layer 12 is formed in a central region R CIn this embodiment, the central region R C Since the outline of the conductive layer 13 is rectangular, the outline of the conductive layer 13 is also rectangular.

[0034] In this embodiment, the central region R C The insulating layer 12 is a solid film having a uniform thickness and is formed so as to cover the entire area of ​​the central region R. C The insulating layer 12 may be formed only in an area where the plurality of conductor patterns 111 are formed. That is, similar to the conductor layer 11, the insulating layer 12 may be formed of a plurality of periodically arranged conductor patterns, each of which is a circular or regular polygonal shape.

[0035] In this embodiment, SiO2 is used as the material for the insulator layer 12. However, the material for the insulator layer 12 may be any insulator and is not limited to SiO2. Examples of such materials include insulating oxides. When the plasmonic perfect absorber 10 is formed on the main surface 14a of the substrate 14, which is expected to be heated to high temperatures during use, the material for the insulator layer 12 is preferably any of SiO2, aluminum oxide (Al2O3), aluminum nitride (AlN), and a mixture of SiO2 and Al2O3.

[0036] In this embodiment, the thickness t 12 (See Figure 2) where the thickness t 12 is not limited to 180 nm, and can be appropriately set within the range of, for example, 10 nm or more and 10 μm or less.

[0037] (Second conductor layer) The conductor layer 11 is formed on a main surface 12a of the insulator layer 12, which is the main surface opposite to the insulator layer 12 (the upper main surface in FIG. 2). CTherefore, in the plasmonic perfect absorber 10, the central region R C Only on the upper surface of the insulating layer 12 and the lower surface of the conductive layer 11 are laminated.

[0038] The conductor layer 11 is made up of a plurality of (nine in FIG. 3) circular conductor patterns 111. However, the shape of each conductor pattern 111 is not limited to a circle and may be a regular polygon. A preferred example of such a regular polygon is a regular hexagon.

[0039] Note that the reference numeral 111 is assigned to only one of the plurality of conductor patterns 111. As shown in Fig. 3, the plurality of conductor patterns 111 are two-dimensionally and periodically arranged on the main surface 12a. In this embodiment, as shown in Fig. 3, a square arrangement is adopted as the periodic two-dimensional arrangement of the conductor patterns 111. However, this periodic two-dimensional arrangement is not limited to a square arrangement, and may be, for example, a hexagonal arrangement.

[0040] 2 does not show the multiple conductor patterns 111 that make up the conductor layer 11. In reality, a periodic two-dimensional structure made up of the multiple conductor patterns 111 is formed over the entire surface of the main surface 12a.

[0041] In this embodiment, hafnium nitride (HfN) is used as the conductor constituting each conductor pattern 111 of the conductor layer 11. However, the conductor constituting each conductor pattern 111 is not limited to HfN, and any material having metallic conductive properties may be used. In this respect, the conductor constituting each conductor pattern 111 is the same as the conductor constituting the conductor layer 13.

[0042] In this embodiment, the thickness t 11 (See FIG. 2, that is, the thickness of each conductive pattern 111) is 100 nm. 13is not limited to 40 nm, and can be appropriately set within the range of, for example, 10 nm or more and 10 μm or less. 11 is an example of the thickness t2 described in the claims.

[0043] In addition, the thickness t of the conductor layer 13 13 , and the thickness t of the insulator layer 12 11 is t 13 >1.5×t 11 It is preferable that the following relationship is satisfied.

[0044] (a pair of electrode pads) As shown in FIGS. 1 and 2, one edge region R E In the edge region R 1 , a base layer 131 and an electrode pad 132 are laminated in this order on the conductor layer 13. In the edge region R 2 , the base layer 131 and the electrode pad 132 are laminated in this order on the conductor layer 13. E , a base layer 131 and an electrode pad 133 are laminated in this order on a conductor layer 13.

[0045] The pair of underlayers 131 and the pair of electrode pads 132 and 133 are formed in the edge region R E The pair of underlayers 131 and the pair of electrode pads 132 and 133 are an example of a pair of electrodes as defined in the claims.

[0046] By connecting wires of opposite polarities to the electrode pads 132 and 133 and supplying power to them, a current flows from one of the electrode pads 132 and 133 to the other. That is, a current flows in the in-plane direction of the main surface 13a of the conductor layer 13. Therefore, the pair of base layer 131 and electrode pads 132 and 133 provided on the main surface 13a of the conductor layer 13 are an example of electrodes that pass a current in the in-plane direction of the main surface of the conductor layer 13.

[0047] In this embodiment, a pair of strip-shaped base layers 131 and electrode pads 132 and 133 are formed in the central region R CThat is, each of the pair of base layers 131 and electrode pads 132, 133 has a rectangular (square in this embodiment) central region R C , the contacts are provided along each of the pair of opposite sides.

[0048] In this embodiment, gold is used as the material for the electrode pads 132 and 133. However, this material is not limited to gold, and can be appropriately determined taking into consideration high conductivity, low reactivity, high melting point, etc.

[0049] In this embodiment, the pair of underlayers 131 are formed of a Cr / Pt double-layer film, in which chromium (Cr) and platinum (Pt) are laminated in this order. The thicknesses of the Cr and Pt are not limited, but in this embodiment, they are both 50 nm. The pair of underlayers 131 may be formed of a single layer or a multilayer film of three or more layers. The materials of each film constituting the pair of underlayers 131 can also be selected appropriately. In consideration of the compatibility and reactivity between the material constituting the substrate 14 and the material constituting the electrode pads 132 and 133, the pair of underlayers 131 may be omitted in some cases.

[0050] <Case> The housing 20 is a rectangular parallelepiped block. In this embodiment, the material constituting the housing 20 is aluminum, which is an example of a metal. However, the metal constituting the housing 20 is not limited to aluminum and can be selected as appropriate. Furthermore, the material constituting the housing 20 is not limited to metal, but may be an alloy, an inorganic compound such as ceramic, or an organic compound such as resin. However, when the operating temperature of the thermal radiation element 1 is set to 150°C or higher, the material constituting the housing 20 is preferably any one of metal, alloy, and ceramic.

[0051] Of the pair of main surfaces of the housing 20, the main surface located on the upper side in the state shown in Fig. 1 is referred to as main surface 20a, and the main surface located on the lower side in the state shown in Fig. 1 is referred to as main surface 20b. A cavity C is formed in the main surface 20a. The depth of the cavity C is smaller than the thickness of the housing 20. Therefore, the cavity C does not penetrate all the way to the main surface 20b.

[0052] The cavity C is composed of two sub-cavities C1 and C2.

[0053] The sub-cavity C1 is formed in a region close to the main surface 20a (i.e., a shallow region). The sub-cavity C2 is formed in a region farther from the main surface 20a (i.e., a deep region) than the sub-cavity C1. An opening AP of the sub-cavity C1 C The size of the heat radiation element 1 is determined so that it can be enclosed in a plan view. C However, in the lower part of Figure 1, AP C is omitted from the illustration.

[0054] On the other hand, the opening of the sub-cavity C2, which is formed on the bottom surface of the sub-cavity C1, is sized so that it is encompassed by the thermal radiation element 1 in plan view. The cavity C configured in this way is formed in a stepped shape.

[0055] The thermal radiation element 1 is accommodated in the sub-cavity C1 of the cavity C. The edge region R of the substrate 14 that constitutes the thermal radiation element 1 E At least a part of them is fixed to the bottom wall of the sub-cavity C1 by using a bonding member 31. In this embodiment, sintered silver (Ag) is used as the bonding member 31. Sintered silver like this is preferable as the bonding member 31 because it has heat resistance that can withstand the operating temperature of the thermal radiation element 1 (for example, any temperature between 300°C and 1200°C).

[0056] As described above, since the thermal radiation element 1 has a high operating temperature, in order to improve energy efficiency, it is preferable to suppress the thermal energy dissipated by heat conduction from the thermal radiation element 1 to the housing 20. In the thermal radiation element module M, by forming the sub-cavity C2 in the housing 20 in addition to the sub-cavity C1, it is possible to limit the thermal conduction paths that may occur between the thermal radiation element 1 and the housing 20.

[0057] Electrode pads 21 and 22 are provided on the bottom wall of sub-cavity C1 so as to run parallel to electrode pads 132 and 133. Electrode pad 21 and electrode pad 132 are electrically connected by metal wire 32 (see the lower diagram in FIG. 1). Similarly, electrode pad 22 and electrode pad 133 are electrically connected by a metal wire (reference numeral omitted) (see the lower diagram in FIG. 1).

[0058] In this embodiment, the electrode pads 21 and 22 are also extended in a strip shape, similar to the electrode pads 132 and 133. Since the electrode pads 21 and 22 and the electrode pads 132 and 133 are all extended in a strip shape, a plurality of metal wires 32 can be used to establish electrical continuity between the electrodes. This reduces the resistance that can occur between the electrode pads 21 and 132 and between the electrode pads 22 and 133, and also ensures redundancy when establishing electrical continuity between the electrode pads.

[0059] As shown in the lower diagram of Fig. 1, power terminals 41 and 42 are provided on the housing 20. The power terminal 41 is drawn from the outside to the inside of the housing 20. The tip of the power terminal 41 is electrically connected to the electrode pad 21. Similarly, the power terminal 42 is drawn from the outside to the inside of the housing 20. The tip of the power terminal 42 is electrically connected to the electrode pad 22. The portions of the power terminals 41 and 42 adjacent to the inside of the housing 20 are sealed to maintain hermeticity.

[0060] As shown in the upper and lower figures in Figure 1, the opening AP Cis covered with an optical window 23. The material constituting the optical window 23 is preferably light-transmitting and heat-resistant enough to withstand the operating temperature of the thermal radiation element 1 (for example, a temperature of 300°C or higher and 1200°C or lower), and in this embodiment, a plate-shaped member made of quartz glass is used.

[0061] The optical window 23 is joined to the main surface 20a of the housing 20 using a joining member 24. In this embodiment, the joining member 24 is made of gold (Au) tin (Sn) solder.

[0062] Furthermore, the thermal radiation element module M is configured so that the pressure inside the cavity C is lower than the pressure outside the cavity C (for example, atmospheric pressure). This configuration can be realized, for example, by sealing the cavity C in a reduced pressure environment that is lower than atmospheric pressure. The pressure inside the cavity C is, but is not limited to, 1×10 3 It is preferable that the pressure inside the cavity C is equal to or less than 100 Pa. The lower the pressure inside the cavity C, the higher the heat insulating property of the cavity C can be.

[0063] 〔summary〕 A thermal radiation element 1 according to one aspect of the present invention includes an insulating substrate 14, a plasmonic perfect absorber 10 including a conductor layer 13 (first conductor layer) covering at least a portion (all of the principal surface 14a in this embodiment), an insulating layer 12, and a conductor layer 11 (second conductor layer) stacked in this order. In the plasmonic perfect absorber 10, a base layer 131 and electrode pads 132 and 133 are provided on the conductor layer 13, which are electrodes that pass a current in the in-plane direction of the principal surface 13a.

[0064] According to this configuration, when viewed from the perspective of plasmonic perfect absorber 10, conductor layer 13 is used as a heat source. In other words, when viewed from the perspective of plasmonic perfect absorber 10, substrate 14, which has a larger volume than plasmonic perfect absorber 10, is not a heat source. Therefore, when heating plasmonic perfect absorber 10 to an operating temperature, substrate 14, which has a larger volume, does not need to be heated to a temperature above the operating temperature. Therefore, thermal radiation element 1 can have higher energy efficiency than the thermal radiation element of Patent Document 2, which is a conventional thermal radiation element.

[0065] Furthermore, the thermal radiation element 1 is configured such that the thermal conductivity of the insulator that constitutes the substrate 14 is lower than the thermal conductivity of the conductor that constitutes the conductor layer 13.

[0066] This configuration can prevent the thermal energy generated by the conductor layer 13, which is a heat source, from escaping to the substrate 14, thereby further improving energy efficiency.

[0067] Furthermore, in the thermal radiation element 1, the conductor layer 11 is configured to consist of a plurality of conductor patterns 111 arranged two-dimensionally and periodically, each of which has a circular or regular polygonal shape.

[0068] According to this configuration, by adjusting the size and periodic arrangement of the plurality of conductor patterns 111, the wavelength range of light emitted from the plasmonic perfect absorber 10 can be adjusted.

[0069] In the thermal radiation element 1, the thickness t 13 (thickness t1 of the first conductor layer) and thickness t 11 (thickness t2 of the second conductor layer) is t 13 >1.5×t 11 A configuration is adopted that satisfies the relationship (t1>1.5×t2).

[0070] According to this configuration, the resistance value of the conductor layer 13 is appropriately reduced, which makes it easier to pass a large current through the conductor layer 13. Therefore, the thermal energy generated in the conductor layer 13 can be increased.

[0071] In the thermal radiation element 1, the thickness t S The thickness of the insulating film is 100 μm or more and 10 mm or less.

[0072] According to this configuration, the strength of the substrate 14 supporting the plasmonic perfect absorber 10 can be increased to a strength sufficient for practical use. S is significantly thicker than the total thickness of the plasmonic perfect absorber 10. Therefore, the thermal radiation device 1 can reliably achieve higher energy efficiency than conventional thermal radiation devices.

[0073] In addition, in the thermal radiation element 1, t 13 (thickness t1 of the first conductor layer), thickness t 12 (thickness of the insulating layer td), and t 11 The thickness t2 of the second conductor layer is in the range of 10 nm to 10 μm.

[0074] This configuration prevents the total thickness of the plasmonic perfect absorber 10 from becoming excessively thick, and the total thickness of the plasmonic perfect absorber 10 is kept within the thickness t S Therefore, the heat radiation element 1 can reliably improve the energy efficiency compared to conventional heat radiation elements.

[0075] In the thermal radiation element 1, the region where the conductor layer 13 (first conductor layer) is formed (the central region R C ) has a rectangular shape (square in this embodiment), and the electrodes are composed of a pair of base layers 131, which are a pair of electrodes, and a pair of electrode pads 132, 133. In the thermal radiation element 1, each of the pair of electrodes has the rectangular region (central region R C) is provided on each of a pair of opposite sides.

[0076] This configuration makes it possible to uniformize the current distribution of the current flowing in the in-plane direction of the main surface 13a of the conductor layer 13. Therefore, it is possible to uniformize the distribution of Joule heat generated in the conductor layer 13, and therefore it is possible to uniformize the temperature distribution on the main surface 13a.

[0077] Moreover, in the thermal radiation element 1, a configuration is adopted in which the substrate 14 is made of glass or ceramic.

[0078] According to this configuration, the thermal conductivity of the insulator constituting the substrate 14 can be reliably made lower than the thermal conductivity of the conductor constituting the conductor layer 13, which reliably prevents the thermal energy generated by the conductor layer 13 from escaping to the substrate 14. Therefore, the energy efficiency can be reliably improved.

[0079] In the thermal radiation element 1, the conductor layer 13 (first conductor layer) and the conductor layer 11 (second conductor layer) are made of hafnium nitride (HfN).

[0080] According to this configuration, since HfN has a high melting point, it is possible to suppress the eutectic reaction that may occur between HfN and at least one of the insulators that constitute the substrate 14 and the insulators that constitute the insulator layer 12. Therefore, the operating temperature of the thermal radiation element 1 can be increased.

[0081] In the thermal radiation element 1, the insulating layer 12 is made of at least one of SiO2, Al2O3, and AlN.

[0082] According to this configuration, the insulator layer 12 having high insulating properties can be easily formed.

[0083] A thermal radiation element module M according to one embodiment of the present invention includes a thermal radiation element 1, a cavity C that houses the thermal radiation element 1, and a housing 20 that is provided with power terminals 41, 42 that supply power to a pair of base layers 131 that are electrodes and a pair of electrode pads 132, 133. The thermal radiation element module M employs a configuration in which, inside the cavity C, at least a portion of the substrate 14 is fixed to the cavity C using a bonding member 31.

[0084] The thermal radiation element module M has the same effects as the thermal radiation element 1. Furthermore, the thermal radiation element constituting the thermal radiation element module M is not limited to the thermal radiation element 1, but may be the thermal radiation element 1A shown in Fig. 4 or the thermal radiation element 1B shown in Fig. 5. The thermal radiation elements 1A and 1B will be described later.

[0085] In the thermal radiation element module M, the opening AP of the cavity C C When viewed from above (see the top of Figure 1), the opening AP C contains the thermal radiation element 1, and has an opening AP C is sealed by a light-transmitting optical window 23, and the pressure inside the cavity C is lower than the pressure outside the cavity C.

[0086] According to this configuration, the heat insulation of the cavity C can be improved compared to when the pressure inside the cavity C is equal to or higher than the pressure outside, and therefore it is possible to reduce the dissipation of the thermal energy generated by the conductor layer 13 to the outside of the cavity C. Therefore, it is possible to improve the energy efficiency of the thermal radiation element module M as a whole.

[0087] Furthermore, in the thermal radiation element module M, the thermal energy is used to heat the thermal radiation element 1 to a predetermined operating temperature, thereby emitting electromagnetic waves resulting from thermal radiation (specifically, at least one of visible light, near-infrared light, mid-infrared light, and far-infrared light). In this way, the thermal radiation element module M functions as a thermal radiation light source that emits at least one of electromagnetic waves among visible light, near-infrared light, mid-infrared light, and far-infrared light. In other words, a thermal radiation light source equipped with the thermal radiation element module M is also included in the scope of the present invention.

[0088] Here, the effects of one aspect of the present invention have been explained using the thermal radiation element 1 shown in Figures 1 and 2. However, the effects of the thermal radiation element 1 described above can also be obtained in the thermal radiation elements 1A and 1B described below.

[0089] [First Modification] A heat radiation element 1A, which is a first modified example of the heat radiation element 1, will be described with reference to Fig. 4. Fig. 4 is a cross-sectional view of the heat radiation element 1 corresponding to Fig. 2, and is a cross-sectional view of the heat radiation element 1A.

[0090] The thermal radiation element 1A is obtained by replacing the pair of base layer 131 and electrode pads 132, 133 provided in the thermal radiation element 1 with a pair of base layer 131A and electrode pads 132A, 133A. Therefore, in this modification, the pair of base layer 131A and electrode pads 132A, 133A will be described.

[0091] In the thermal radiation element 1, the width of the electrode pads 132 and 133 (the length in the left-right direction in FIG. 2) is E Therefore, as shown in FIG. 2, in one cross section of the thermal radiation element 1, the electrode pads 132 and 133 are located at the edge region R E It is formed to cover a part of the

[0092] On the other hand, in the thermal radiation element 1A, the width (length in the left-right direction in FIG. 4) of the pair of base layers 131A and electrode pads 132A and 133A is equal to or less than the width of the annular edge region R E4, in one cross section of the thermal radiation element 1A, the pair of base layers 131A and electrode pads 132A and 133A are arranged in the edge region R E It is formed to cover the entire

[0093] As is clear from the electrode pads 132, 133 and the electrode pads 132A, 133A, the width of the pair of electrode pads for passing current through the conductor layer 13 can be determined appropriately, and they may be electrically connected to a part of the conductor layer 11 in addition to the conductor layer 13. The same applies to the pair of base layers 131A. Note that in the thermal radiation element 1A, parts of the electrode pads 132A, 133A near their upper ends may overlap the outer edge of the conductor layer 11.

[0094] [Second Modification] A heat radiation element 1B, which is a second modified example of the heat radiation element 1, will be described with reference to Fig. 5. Fig. 5 is a cross-sectional view of the heat radiation element 1 corresponding to Fig. 2, and is a cross-sectional view of the heat radiation element 1B.

[0095] The thermal radiation element 1B is obtained by replacing the insulator layer 12, the conductor layer 11, the pair of base layers 131, and the electrode pads 132 and 133 of the thermal radiation element 1 with an insulator layer 12B, a conductor layer 11B, a pair of base layers 131B, and electrode pads 132B and 133B, respectively. Therefore, in this modification, the insulator layer 12B, the conductor layer 11B, the pair of base layers 131B, and the electrode pads 132B and 133B will be described.

[0096] In the thermal radiation element 1, the insulating layer 12 and the conductor layer 11 are formed in a central region R C It is formed to cover the

[0097] On the other hand, in the heat radiation element 1B, the insulating layer 12B and the conductor layer 11B are formed so as to cover the entire main surface 13a.

[0098] In addition, the pair of base layers 131B and electrode pads 132B, 133B are formed so as to cover the side surfaces of the substrate 14, the conductor layer 13, the insulator layer 12B, and the conductor layer 11B (i.e., the side surfaces of the heat radiation element 1B) in one cross section of the heat radiation element 1B, as shown in Fig. 5. One base layer 131B and the electrode pad 132B are laminated in this order on one side surface of the heat radiation element 1B (the left side surface in Fig. 5), and the other base layer 131B and the electrode pad 133B are laminated in this order on the side surface opposite to the one side surface (the right side surface in Fig. 5).

[0099] In the heat radiation element 1B, a portion of the pair of base layers 131B and the electrode pads 132B, 133B near their lower ends is also formed in an area near the edge of the main surface 14b, which is the lower main surface of the substrate 14. In the heat radiation element 1B, the pair of base layers 131B and the electrode pads 132B, 133B formed in an area near the edge of the main surface 14b are bonded to the electrode pads 21, 22 using a bonding member 31 (see the lower diagram in FIG. 1 ). In this manner, in this modification, the bonding member 31 fixes the heat radiation element 1B to the bottom wall of the sub-cavity C1 inside the cavity C and ensures electrical continuity between the electrode pads 132B, 133B and the electrode pads 21, 22.

[0100] The pair of underlayers 131B may be a single-layer film, a two-layer film, or a multi-layer film of three or more layers, similar to the pair of underlayers 131 and the pair of underlayers 131A. Furthermore, each film constituting the pair of underlayers 131B can be configured similarly to each film constituting the pair of underlayers 131 and the pair of underlayers 131A. [Example]

[0101] [First Example] A thermal radiation element module M according to a first embodiment of the present invention will be described below. In this embodiment, the configuration of the thermal radiation element 1A shown in FIG. 4 was adopted as the thermal radiation element, and each component was designed as follows. It was confirmed that the thermal radiation element module M of this embodiment stably emits near-infrared light of 1.0 μm or more and 2.0 μm or less when 500°C is used as an example of the operating temperature of the thermal radiation element 1A. In other words, the thermal radiation element module M of this embodiment can be suitably used as a thermal radiation light source that stably emits near-infrared light of 1.0 μm or more and 2.0 μm or less when 500°C is used as the operating temperature.

[0102] <Substrate> The substrate 14 is made of quartz glass and has a thickness t S The plate-shaped member used was a square with a side length of 5 mm and a diameter of 500 μm.

[0103] <Plasmonic perfect absorber> The conductor layer 13 has a thickness of t 13 The HfN film used was 100 nm thick.

[0104] The insulating layer 12 has a thickness t 12 The SiO2 film used was 180 nm thick.

[0105] The conductor layer 11 has a thickness of t 11 The HfN film used had a diameter of 40 nm. The conductive patterns 111 constituting the conductive layer 11 were circular in shape with a diameter of 400 nm. The conductive patterns 111 were periodically arranged in a square pattern with a period of 650 nm.

[0106] A Cr / Pt double-layer film was used as the pair of underlayers 131A, and the thickness of each of the Cr and Pt layers was 50 nm.

[0107] The electrode pads 132A and 133A were made of strip-shaped gold films having a thickness of 400 nm, a width (length in the left-right direction in FIG. 4) of 200 μm, and a length (length in the depth direction in FIG. 4) of 5 mm.

[0108] The electrical resistivity of the HfN used in this example is approximately 1×10 -3 (Ω·mm), and the electrical resistivity of SiO2 used in this example is approximately 1×10 15 (Ω·mm). In thermal radiation element 1A of this example, plasmonic perfect absorber 10A has a total thickness of 220 nm.

[0109] <Thermal radiation element module> A gold wire having a diameter φ of 25 μm was used as the metal wire 32 for electrically connecting the electrode pad 21 and the electrode pad 132, and as the metal wire for electrically connecting the electrode pad 22 and the electrode pad 133 (see the lower diagram of FIG. 1).

[0110] The pressure inside cavity C is 1×10 0 Pa was adopted.

[0111] [Second Example] A thermal radiation element module M according to a second embodiment of the present invention will now be described. In this embodiment, the configuration of the thermal radiation element 1B shown in FIG. 5 was adopted as the thermal radiation element, and each component was designed as follows. It was confirmed that the thermal radiation element module M of this embodiment stably emits near-infrared light of 1.0 μm or more and 2.0 μm or less when 700°C was used as an example of the operating temperature of the thermal radiation element 1B. In other words, the thermal radiation element module M of this embodiment can be suitably used as a thermal radiation light source that operates at 700°C and stably emits near-infrared light of 1.0 μm or more and 2.0 μm or less.

[0112] <Substrate> The substrate 14 is made of quartz glass and has a thickness t S The plate-shaped member used was a square with a diameter of 500 μm and a side length of 10 mm.

[0113] <Plasmonic perfect absorber> The conductor layer 13 has a thickness of t 13 The HfN film used was 200 nm thick.

[0114] The insulating layer 12 has a thickness t 12 The SiO2 film used was 320 nm thick.

[0115] The conductor layer 11 has a thickness of t 11 The HfN film used was 40 nm thick. The shapes of the plurality of conductor patterns 111 constituting the conductor layer 11 were the same as the shapes of the plurality of conductor patterns 111 used in the first example.

[0116] A double-layer film of Cr / Pt was used as the pair of underlayers 131B, with the Cr layer having a thickness of 100 nm and the Pt layer having a thickness of 200 nm.

[0117] A gold film having a thickness (length in the left-right direction in FIG. 5) of 500 nm was used as the electrode pads 132B and 133B. One base layer 131B and an electrode pad 132B were laminated in this order over the entire surface of one side of the substrate 14 and the plasmonic perfect absorber 10B, and the other base layer 131B and an electrode pad 133B were laminated in this order over the entire surface of the side opposite to the one side.

[0118] The electrical resistivity of the HfN used in this example is approximately 1×10 -3 (Ω·mm), and the electrical resistivity of SiO2 used in this example is approximately 1×10 15 (Ω·mm). In thermal radiation element 1B of this example, plasmonic perfect absorber 10B has a total thickness of 580 nm.

[0119] <Thermal radiation element module> In this embodiment, sintered silver is used as the joining member 31 that joins and provides electrical continuity between one of the base layer 131B and a portion of the electrode pad 132B (a portion near the lower end in the state shown in FIG. 5) and the electrode pad 21, and as the joining member 31 that joins and provides electrical continuity between the other of the base layer 131B and a portion of the electrode pad 133B (a portion near the lower end in the state shown in FIG. 5) and the electrode pad 22.

[0120] The pressure inside cavity C is 1×10 0 Pa was adopted.

[0121] [Additional Notes] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0122] M Thermal radiation element module (part of thermal radiation light source) 1. Heat radiation element 10 Plasmonic perfect absorber 11 Conductor layer (second conductor layer) 111 Conductor pattern 12 Insulator layer 13 Conductor layer (first conductor layer) 131 Underlayer (constitutes an electrode together with electrode pads 132 and 133) 132, 133 electrode pads (forming electrodes together with the base layer 131) 14 PCB 14a, 14b Main surfaces (pair of main surfaces) R C Central region (region where the first conductor layer is formed) R E Edge Area 20 Case 23 Optical window C cavity AP C opening 41,42 Power terminal 31 Joint materials

Claims

1. a substrate made of an insulating material and having a pair of main surfaces, the substrate having a thickness of 100 μm or more and 10 mm or less; a plasmonic perfect absorber including a first conductor layer covering at least a portion of one main surface of the substrate, an insulator layer, and a second conductor layer stacked in this order; an electrode for passing a current in an in-plane direction of a main surface of the first conductor layer is provided on the first conductor layer; the thermal conductivity of the insulator constituting the substrate is lower than the thermal conductivity of the conductor constituting the first conductor layer; The substrate is made of a single material. Heat radiation element.

2. the second conductor layer is made up of a plurality of conductor patterns that are two-dimensionally and periodically arranged, each of which has a circular or regular polygonal shape; The thermal radiation element according to claim 1 .

3. a thickness t1 of the first conductor layer and a thickness t2 of the second conductor layer satisfy the relationship t1>1.5×t2; The thermal radiation element according to claim 1 or 2.

4. a thickness t1 of the first conductor layer, a thickness td of the insulator layer, and a thickness t2 of the second conductor layer are all 10 nm or more and 10 μm or less; The thermal radiation element according to any one of claims 1 to 3.

5. the region in which the first conductor layer is formed is rectangular, The electrode is composed of a pair of electrodes, Each of the pair of electrodes is provided on a pair of opposite sides of the rectangular region. The thermal radiation element according to any one of claims 1 to 4.

6. The substrate is made of glass or ceramic. The thermal radiation element according to any one of claims 1 to 5.

7. the first conductor layer and the second conductor layer are made of HfN; The thermal radiation element according to any one of claims 1 to 6.

8. The insulating layer is made of SiO ２ , Al ２ O ３ and AlN, The thermal radiation element according to any one of claims 1 to 7.

9. A thermal radiation element according to any one of claims 1 to 8, a housing provided with a cavity for accommodating the thermal radiation element and a power terminal for supplying power to the electrode; At least a portion of the substrate is fixed to the cavity using a bonding member inside the cavity. Thermal radiation element module.

10. When the opening of the cavity is viewed from above, the opening includes the thermal radiation element, the opening is sealed with a light-transmitting optical window, the pressure inside the cavity is lower than the pressure outside the cavity; The thermal radiation element module according to claim 9 .

11. A thermal radiation element module according to claim 9 or 10, Thermal radiant light source.

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