JP7523232B2 - Thermal radiation light source - Google Patents

Description

The present invention relates to a thermal radiation light source in which a thermal radiation layer and a substrate that heats the thermal radiation layer are stacked.

Such a thermal radiation light source heats the thermal radiation layer to a high temperature state by means of a substrate, thereby causing the thermal radiation layer to radiate radiant light for heating an object to be heated.
As such a thermal radiation light source, there is one in which a substrate and a thermal radiation layer are arranged in a sealed state inside a sealed tube formed of a light-transmitting airtight material such as quartz glass, and the inside of the sealed tube is made into a vacuum state, or an inert gas such as nitrogen gas is sealed inside the sealed tube (see, for example, Patent Document 1).

In Patent Document 1, the substrate is made of a high-melting-point metal such as tungsten that generates heat when a current is passed through it, and the heat radiation layer is formed of a metal layer such as tantalum or molybdenum. The substrate and heat radiation layer are disposed in a sealed state inside a sealed tube, thereby preventing deterioration of the substrate and heat radiation layer due to oxidation.

JP 2015-138638 A

Conventional thermal radiation light sources have a substrate and a thermal radiation layer sealed inside a sealed tube, which makes the overall structure complicated and expensive. Therefore, there is a demand for a thermal radiation light source that can be installed with the substrate and thermal radiation layer exposed to the atmosphere.

In addition, for purposes such as heating objects with infrared rays, there is a demand for thermal radiation light sources that have a high emissivity (radiation rate) in a narrow band of wavelengths greater than 4 μm and less than 8 μm (i.e., a narrow band of wavelengths excluding the short wavelength side of mid-infrared light) and a low emissivity (radiation rate) for wavelengths greater than 8 μm (i.e., far-infrared light).

The present invention has been made in consideration of the above-mentioned circumstances, and its purpose is to provide a thermal radiation light source that can be installed with the substrate and thermal radiation layer exposed to the atmosphere, and that has a high emissivity in the wavelength range greater than 4 μm and less than 8 μm, and a low emissivity for wavelengths greater than 8 μm.

The thermal radiation light source of the present invention is a laminate of a thermal radiation layer and a substrate for heating the thermal radiation layer, and its characteristic configuration is as follows:
the thermal radiation layer is configured in a state in which the radiation control section and the radiation transparent oxide layer are laminated in the order of a radiation control section having an MIM laminate section in which a resonance transparent oxide layer formed of a transparent oxide is positioned between a pair of platinum layers arranged along the lamination direction of the thermal radiation layer and the substrate, and a radiation transparent oxide layer formed of a transparent oxide is positioned closer to the substrate,
The thickness of the resonance transparent oxide layer is 1200 nm or more and 1500 nm or less, with a resonance wavelength range being greater than 4 μm and less than 8 μm,
The transparent oxide used in the resonance transparent oxide layer is any one of aluminum oxide, tantalum pentoxide, silicon dioxide, niobium pentoxide, magnesium oxide, titanium oxide, and hafnium oxide .

In other words, the thermal radiation layer is configured by laminating the radiation control section and the transparent oxide layer for radiation in the order of the radiation control section having the MIM laminate section and the transparent oxide layer for radiation, with the radiation control section being positioned closer to the substrate. Therefore, when the thermal radiation layer is heated to a high temperature state by the substrate, the radiation control section having the MIM laminate section emits radiant light, and the radiant light is emitted from the transparent oxide layer for radiation.

The substrate, which becomes hot in order to heat the thermal radiation layer, emits radiant light, but the platinum layer adjacent to the substrate in the MIM stack of the radiation control section blocks the radiant light from the substrate and prevents the radiant light from the substrate from penetrating into the inside of the radiation control section, thereby preventing the radiant light from the substrate from affecting the radiant light emitted from the radiation control section.
In addition, since the radiation transparent oxide layer, which has a refractive index smaller than platinum and larger than air, is located adjacent to the platinum layer located on the side of the radiation transparent oxide layer in the radiation control section, the reflectance of the platinum layer located on the side of the radiation transparent oxide layer is reduced, allowing the radiated light emitted from the radiation control section to be efficiently released to the outside.

The MIM stack portion of the radiation control portion positions a resonance transparent oxide layer between a pair of platinum layers arranged along the stacking direction of the thermal radiation layer and the substrate, and the thickness of the resonance transparent oxide layer is 1200 nm or more and 1500 nm or less , with a resonant wavelength range of more than 4 μm and less than 8 μm. Furthermore, the transparent oxide used for the resonance transparent oxide layer is any one of aluminum oxide, tantalum pentoxide, silicon dioxide, niobium pentoxide, magnesium oxide, titanium oxide, and hafnium oxide. Therefore, of the radiated light emitted from the platinum layer heated to a high temperature state, the transparent oxide layer has a large emissivity (radiation rate) at wavelengths in the resonance wavelength range of more than 4 μm and less than 8 μm, and has a small emissivity (radiation rate) at wavelengths greater than 8 μm (i.e., far-infrared light). As a result, the amplified radiated light having a wavelength in the resonance wavelength range of more than 4 μm and less than 8 μm is emitted to the outside from the radiation transparent oxide layer.

To explain further, MIM stands for metal insulator metal, and the MIM stacking section amplifies the radiant light with a wavelength in the range of greater than 4 μm and less than 8 μm by repeatedly reflecting the radiant light emitted by the platinum layer, with wavelengths in the range of greater than 4 μm and less than 8 μm, between the platinum layers lined up in the stacking direction of the thermal radiation layer and the substrate (within the transparent oxide layer for resonance), and this amplified radiant light with a wavelength in the range of greater than 4 μm and less than 8 μm is emitted to the outside from the transparent oxide layer for radiation.

In other words, the radiated light with a wavelength in the resonant wavelength range of greater than 4 μm and less than 8 μm is amplified as it is repeatedly reflected between the platinum layers arranged along the stacking direction of the thermal radiation layer and the substrate, and a portion of the radiated light with a wavelength in the resonant wavelength range of greater than 4 μm and less than 8 μm passes through to the side where the transparent oxide layer for radiation is present and is emitted to the outside from the transparent oxide layer for radiation. As a result, the amplified radiated light with a wavelength in the resonant wavelength range of greater than 4 μm and less than 8 μm is emitted to the outside from the transparent oxide layer for radiation.

In contrast, the radiated light emitted from the platinum layer with a wavelength of 4 μm or less or greater than 8 μm is emitted to the outside from the radiating transparent oxide layer with little amplification due to the resonance effect.
As a result, the radiated light emitted to the outside from the radiating transparent oxide layer has a large emissivity (radiation rate) at wavelengths in the resonant wavelength range greater than 4 μm and less than 8 μm (i.e., a narrow band of wavelengths excluding the short wavelength side of mid-infrared light), and has a small emissivity (radiation rate) at wavelengths greater than 8 μm (i.e., wavelengths of far-infrared light).

Of the multiple platinum layers provided in the MIM laminate, the platinum layer adjacent to the substrate needs to block the radiant light from the substrate, while the other platinum layers need to transmit part of the radiant light, so the platinum layer adjacent to the substrate is formed thicker than the other platinum layers.

In this way, the thermal radiation layer amplifies the radiated light with a wavelength in the resonant wavelength range of greater than 4 μm and equal to or less than 8 μm and emits it to the outside from the radiating transparent oxide layer. In addition, even when installed in air, the radiation control unit and the substrate are prevented from deteriorating due to oxidation, so that the optical characteristics can be maintained for a long time.

In other words, the platinum layer of the MIM laminate is formed from platinum, which has a positively large standard Gibbs energy of oxidation over all temperature ranges and does not oxidize in air, so it will not deteriorate due to oxidation even if placed in air.
In addition, since the emission transparent oxide layer and the resonance transparent oxide layer prevent oxygen in the air from passing through to the substrate, deterioration of the substrate due to oxidation is prevented over a long period of time, even if the substrate is made of a material that is susceptible to oxidation.
Therefore, the thermal radiation layer can maintain its optical properties for a long period of time even when placed in air.

When heated to high temperatures, the platinum that forms the platinum layer adjacent to the substrate may flow over the substrate and aggregate, but the transparent oxide layer for resonance has the effect of suppressing the movement of the platinum. Also, when heated to high temperatures, the platinum that forms the platinum layer adjacent to the side of the transparent oxide layer for emission from the transparent oxide layer for resonance may flow over the transparent oxide layer for resonance and aggregate, but the transparent oxide layer for emission has the effect of suppressing the movement of the platinum, suppressing the aggregation of platinum. From this point of view, too, the thermal radiation layer can maintain its optical properties for a long time.

In short, the characteristic configuration of the present invention provides a thermal radiation light source that can be installed with the substrate and thermal radiation layer exposed to the atmosphere, and has a high emissivity in the wavelength range of greater than 4 μm and less than or equal to 8 μm, and a low emissivity for wavelengths greater than 8 μm.

A further characteristic feature of the thermal radiation light source of the present invention is that a substrate adhesion layer is laminated between the substrate and the platinum layer adjacent to the substrate in the radiation control section.

In other words, because the substrate adhesion layer is laminated between the substrate and the platinum layer adjacent to the substrate in the radiation control section, it is possible to prevent the radiation control section from peeling off from the substrate when the radiation control section is heated by the substrate.

In other words, because the thermal expansion coefficient of the substrate differs from that of the radiation control section, which is made up of multiple thin films stacked together, there is a risk that the radiation control section will peel off from the substrate when it is heated by the substrate. However, the adhesion between the substrate and the platinum layer adjacent to the substrate in the radiation control section can be increased by the substrate adhesion layer, preventing the radiation control section from peeling off from the substrate.

In short, a further characteristic configuration of the thermal radiation light source of the present invention makes it possible to prevent the radiation control section from peeling off from the substrate.

A further characteristic feature of the thermal radiation light source of the present invention is that a platinum adhesion layer is laminated between the platinum layer and the resonance transparent oxide layer in the MIM laminate, and between the emission transparent oxide layer and the platinum layer adjacent to the emission transparent oxide layer in the radiation control section.

In other words, because the platinum adhesion layer is provided between the platinum layer and the transparent oxide layer for resonance in the MIM laminate, and between the transparent oxide layer for radiation and the platinum layer adjacent to the transparent oxide layer for radiation in the radiation control section, it is possible to prevent the platinum layer in the MIM laminate from flowing and agglomerating when the radiation control section is heated to a high temperature state on the substrate, and also to prevent the platinum layer and the transparent oxide layer for resonance from peeling off, or the transparent oxide layer for radiation from the platinum layer, due to differences in thermal expansion coefficients.

In other words, because the adhesion between platinum and the transparent oxide is low, there is a risk that the platinum layer adjacent to the resonance transparent oxide layer and the platinum layer adjacent to the emission transparent oxide layer will flow and aggregate when the radiation control section is heated to a high temperature on the substrate. However, by laminating the platinum adhesion layer, the adhesion of the platinum layer adjacent to the resonance transparent oxide layer to the resonance transparent oxide layer and the adhesion of the platinum layer adjacent to the emission transparent oxide layer to the emission transparent oxide layer are increased, so that when the radiation control section is heated to a high temperature on the substrate, it is possible to suppress the platinum layer in the MIM laminate from flowing and aggregating, and it is also possible to suppress peeling between the platinum layer and the resonance transparent oxide layer, and peeling between the emission transparent oxide layer and the platinum layer.

In short, according to a further characteristic configuration of the thermal radiation light source of the present invention, when the radiation control section is heated to a high temperature state on the substrate, it is possible to suppress the platinum layer in the MIM laminate from flowing and agglomerating.

A further characteristic feature of the thermal radiation light source of the present invention is that the substrate adhesion layer and the platinum adhesion layer are made of titanium.

In other words, titanium can effectively increase the adhesion of the platinum layer adjacent to the substrate to the substrate, the adhesion of the platinum layer adjacent to the transparent oxide layer for resonance to the transparent oxide layer for resonance, and the adhesion of the platinum layer adjacent to the transparent oxide layer for radiation to the transparent oxide layer for radiation, and furthermore, because it has a high melting point of 1668°C, it can appropriately suppress the platinum layer in the MIM laminate from flowing and agglomerating when the radiation control unit is heated to a high temperature state on the substrate.

Incidentally, titanium forming the adhesive layer for the substrate and the adhesive layer for platinum may be gradually oxidized and changed to titanium oxide when the thermal radiation source is used in the atmosphere. In other words, when the thermal radiation source is used in the atmosphere, the adhesive layer for the substrate and the adhesive layer for platinum can be considered to be formed of titanium oxide.
However, not all of the titanium forming the substrate adhesion layer and the platinum adhesion layer is converted to titanium oxide; the titanium in the areas that adhere to the platinum layer will not be oxidized and will maintain its state (metallic state) of titanium adhering to the platinum layer.

The substrate adhesion layer and platinum adhesion layer, which are made of titanium, are formed in a thin film state to have optical transparency, and the titanium formed in this thin film state changes to titanium oxide. However, since titanium oxide has transparency, the change of titanium to titanium oxide does not adversely affect the performance of the thermal radiation layer.

In short, according to a further characteristic configuration of the thermal radiation light source of the present invention, when the radiation control section is heated to a high temperature state on the substrate, the platinum layer in the MIM laminate section can be appropriately prevented from flowing and agglomerating.

A further characteristic feature of the thermal radiation light source of the present invention is that the transparent oxide is aluminum oxide.

In other words, since aluminum oxide has a small oxygen diffusion coefficient, by using aluminum oxide as the transparent oxide that forms the emission transparent oxide layer and the resonance transparent oxide layer, the transmission of oxygen in the atmosphere is appropriately suppressed, and even if the substrate is made of a material that can be oxidized, the surface of the substrate on which the radiation control unit is laminated can be appropriately prevented from deteriorating due to oxidation.

In short, this further characteristic configuration of the thermal radiation light source of the present invention makes it possible to appropriately prevent the surface of the substrate on which the radiation control unit is stacked from deteriorating due to oxidation.

A further characteristic feature of the thermal radiation light source of the present invention is that the substrate is configured to self-heat when electricity is applied.

In other words, the substrate is configured to self-heat when electricity is passed through it, so that when electricity is passed through the substrate, the substrate can be made to self-heat, thereby heating the radiation control section. This eliminates the need to provide a special external heating section for heating the substrate, simplifying the overall configuration.

Incidentally, examples of materials that generate heat when electricity is passed through them include metal materials such as Kanthal and nichrome, and the substrate can be made of these materials.

In short, the further characteristic configuration of the thermal radiation light source of the present invention allows for the simplification of the overall configuration.

A further characteristic feature of the thermal radiation light source of the present invention is that the substrate is configured to be heated by an external heating unit.

That is, since the substrate is heated by an external heating unit, the substrate can be made of various materials such as quartz (silicon dioxide) and sapphire.
That is, by forming the substrate using a material that does not oxidize, such as quartz (silicon dioxide) or sapphire, it is possible to appropriately suppress deterioration of the substrate due to oxidation.

In short, this further characteristic configuration of the thermal radiation light source of the present invention makes it possible to appropriately suppress oxidative deterioration of the substrate.

FIG. 1 is a diagram showing a basic configuration of a thermal radiation light source. 1 is a table showing an example of a structure in a basic configuration of a thermal radiation light source. 1 is a graph showing the relationship between an example of the structure of a thermal emission light source and radiation intensity. 1 is a graph showing the relationship between the type of transparent oxide of a thermal radiation source and the radiation intensity. 11 is a table showing another example of the basic structure of the thermal radiation light source. 11 is a graph showing the relationship between another example of the structure of a thermal radiation source and radiation intensity. 1 is a graph showing the relationship between the type of transparent oxide of a thermal radiation source and the radiation intensity. FIG. 2 is a diagram showing a specific configuration of a thermal radiation light source. FIG. 13 is a diagram showing the change in the platinum adhesion layer. FIG. 2 is a perspective view showing the relationship between a thermal radiation light source and a heating electrode. FIG. 2 is a perspective view showing the relationship between a thermal radiation light source and a heating electrode. FIG. 2 is a perspective view showing the relationship between a thermal radiation light source and a thermal radiator. FIG. 2 is a perspective view showing the relationship between a thermal radiation source and a high temperature fluid source.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[Basic configuration of thermal radiation light source]
FIG. 1 shows the basic structure of a thermal radiation source Q. The thermal radiation source Q is configured in such a manner that a thermal radiation layer N and a substrate K for heating the thermal radiation layer N are laminated together.
The thermal radiation layer N is configured in a stacked state in which the radiation control portion Na and the radiation transparent oxide layer Nb formed of a transparent oxide are positioned in that order closer to the substrate K.

The radiation control section Na is configured to have an MIM stack section M that positions a resonance transparent oxide layer R formed of a transparent oxide between a pair of platinum layers P arranged along the stacking direction of the thermal radiation layer N and the substrate K.
The thickness of the resonance transparent oxide layer R is set to 1200 nm or more and 1500 nm or less, with the resonance wavelength range being greater than 4 μm and equal to or less than 8 μm.

In the basic configuration of the thermal radiation source Q shown in FIG.
In other words, in the basic configuration of the thermal radiation source Q, the platinum layer P, the resonance transparent oxide layer R, and the platinum layer P, which constitute the MIM stack M, and the emission transparent oxide layer Nb are stacked sequentially on top of the substrate K in the order listed.
In the following description, the platinum layer P adjacent to the substrate K in the MIM stack M is referred to as the first platinum layer P1, and the platinum layer P adjacent to the emitting transparent oxide layer Nb in the MIM stack M is referred to as the second platinum layer P2.

The thermal radiation layer N is heated to a high temperature (for example, 300° C.) by the substrate K, so that the thermal radiation source Q emits radiant light H from the thermal radiation layer N.
Specifically, the device is configured to emit radiant light H having a large emissivity (emissivity: for example, emissivity at 5 μm is 0.8) at wavelengths in the range greater than 4 μm and equal to or less than 8 μm (i.e., a narrow band of wavelengths excluding the short wavelength side of mid-infrared light) and a small emissivity (emissivity: for example, emissivity at 10 μm is 0.3) at wavelengths greater than 8 μm (i.e., wavelengths of far-infrared light).

In addition, the thickness of the resonance transparent oxide layer R is set to 1200 nm or more and 1500 nm or less, which has a resonance wavelength range of more than 4 μm and not more than 8 μm, so that the radiated light H has a small emissivity (radiation rate) at wavelengths of 4 μm or less (i.e., the short wavelength side of mid-infrared light).

In other words, when the thermal radiation layer N is heated to a high temperature (e.g., 300°C) on the substrate K, the platinum layer P (the first platinum layer P1 and the second platinum layer P2) in the MIM stack M of the radiation control unit Na emits radiant light.
Furthermore, since the thickness of the resonance transparent oxide layer R provided in the MIM stack M is set to a thickness of 1,200 nm or more and 1,500 nm or less, with the resonance wavelength range being greater than 4 μm and less than 8 μm, the wavelengths of the radiated light from the platinum layer P (first platinum layer P1 and second platinum layer P2) of the MIM stack M that are greater than 4 μm and less than 8 μm (i.e., a narrow band of wavelengths excluding the short wavelength side of mid-infrared light) are amplified by the resonance action.

Therefore, the radiation control portion Na has a large emissivity (radiation rate) at wavelengths in the range greater than 4 μm and equal to or less than 8 μm (i.e., a narrow band of wavelengths excluding the short wavelength side of mid-infrared light), and has a small emissivity (radiation rate) at wavelengths greater than 8 μm (i.e., wavelengths of far-infrared light) and wavelengths equal to or less than 4 μm (i.e., wavelengths on the short wavelength side of mid-infrared light).
As a result, radiant light H with an amplified wavelength in the range of greater than 4 μm and equal to or less than 8 μm is emitted to the outside from the radiating transparent oxide layer Nb.

To explain further, MIM stands for metal insulator metal, and the MIM stack M amplifies the radiant light in the wavelength range of greater than 4 μm and less than 8 μm by repeatedly reflecting the radiant light from the platinum layer P (first platinum layer P1 and second platinum layer P2) between a pair of platinum layers P (first platinum layer P1 and second platinum layer P2) aligned along the stacking direction of the thermal radiation layer N and the substrate K, and this amplified radiant light H is emitted to the outside from the radiation transparent oxide layer Nb.

In other words, the radiated light in the wavelength range of greater than 4 μm and equal to or less than 8 μm is repeatedly reflected and amplified between the platinum layers P (first platinum layer P1 and second platinum layer P2) arranged along the stacking direction of the thermal radiation layer N and the substrate K, and a portion of the radiated light in the wavelength range of greater than 4 μm and equal to or less than 8 μm passes through to the side where the radiation transparent oxide layer Nb is present and is emitted to the outside from the radiation transparent oxide layer Nb. As a result, the radiated light H in which the wavelength range of greater than 4 μm and equal to or less than 8 μm has been amplified is emitted to the outside from the radiation transparent oxide layer Nb.

In contrast, the radiated light emitted by the platinum layer P (the first platinum layer P1 and the second platinum layer P2) having a wavelength greater than 8 μm and a wavelength of 4 μm or less is emitted to the outside from the radiating transparent oxide layer Nb with little amplification due to the resonance effect.
As a result, the radiant light H emitted from the thermal radiation source Q (radiant light emitted to the outside from the radiation transparent oxide layer Nb) has a large emissivity (emissivity) in the wavelength range of more than 4 μm and not more than 8 μm (i.e., a narrow band of wavelengths excluding the short wavelength side of mid-infrared light), and has a small emissivity (emissivity) in the wavelength range of more than 8 μm (i.e., the wavelength of far-infrared light) and wavelength of not more than 4 μm (i.e., the short wavelength side of mid-infrared light).

By the way, radiant light is emitted from the substrate K, which becomes in a high temperature state in order to heat the thermal radiation layer N, but the first platinum layer P1 blocks the transmission of the radiant light to the radiation control portion Na. In other words, the thickness of the first platinum layer P1 is a thickness that can block the radiant light from the substrate K.

In addition, since the radiation transparent oxide layer Nb has a refractive index greater than that of platinum and less than that of air, the reflectance of the platinum layer P (second platinum layer P2) located on the side where the radiation transparent oxide layer Nb exists is reduced, and the radiant light emitted from the radiation control portion Na can be efficiently released to the outside.

In addition, of the platinum layers P (first platinum layer P1 and second platinum layer P2) provided in the MIM laminate M, the platinum layer P (first platinum layer P1) adjacent to the substrate K needs to block the radiant light of the substrate K, and the other platinum layer P (second platinum layer P2) needs to transmit a part of the radiant light. Therefore, the platinum layer P (first platinum layer P1) adjacent to the substrate K is formed thicker than the other platinum layer P (second platinum layer P2). Therefore, the radiation intensity of the platinum layer P (first platinum layer P1) adjacent to the substrate K among the platinum layers P (first platinum layer P1 and second platinum layer P2) is greater than that of the other platinum layer P (second platinum layer P2).

[Explanation of structural example of basic configuration]
Next, a structural example of the basic configuration of the thermal radiation source Q will be described. In the structural example described below, the transparent oxide forming the emission transparent oxide layer Nb and the resonance transparent oxide layer R is alumina (aluminum oxide, Al ₂ O ₃ ). Any substrate K can be used, and the details of the substrate K will be described later.

The structural examples described below are four examples, Structure 1 to Structure 4, as shown in the table of Fig. 2. Incidentally, in the table of Fig. 2, the substrate K is described as layer No. 1, the first platinum layer P1 as layer No. 2, the resonance transparent oxide layer R as layer No. 3, the second platinum layer P2 as layer No. 4, and the emission transparent oxide layer Nb as layer No. 5.
It should be noted that the structures 2 and 3 correspond to the thermal radiation source Q of the present invention, while the structures 1 and 4 are thermal radiation sources Q described for reference.
3 shows the radiation intensity (W/sr/m ² /nm) when the thermal radiation layer N in structures 1 to 4 is heated to 300° C. In addition, FIG. 3 also shows the radiation intensity of a black body at 300° C.

The thermal radiation light sources Q of Structures 2 and 3 have layer No. 3 thicknesses of 1200 nm and 1500 nm, and as shown in FIG. 3, have a large emissivity (radiation rate) in the wavelength range greater than 4 μm and less than 8 μm (i.e., narrow band wavelengths excluding the short wavelength side of mid-infrared light), and have a small emissivity (radiation rate) in wavelengths greater than 8 μm (i.e., far-infrared light wavelengths) and less than 4 μm (i.e., short wavelength side wavelengths of mid-infrared light).

The thermal radiation light source Q of structures 1 and 4 has a thickness of layer No. 3 of 1000 nm, and as shown in Figure 3, has a large emissivity (radiation rate) in the wavelength range of 4 μm or less (i.e., the short wavelength side of mid-infrared light).

Structures 5 and 6 will be described as other structural examples in the basic configuration of the thermal radiation source Q. In the other structural examples described below, the transparent oxide forming the emission transparent oxide layer Nb and the resonance transparent oxide layer R is alumina (aluminum oxide, Al ₂ O ₃ ). Any substrate K can be used, and the details of the substrate K will be described later.

Another structural example will be described below. In this structural example, as shown in the table of FIG. 5, the substrate K is layer No. 1, the first platinum layer P1 is layer No. 2, the resonance transparent oxide layer R is layer No. 3, the second platinum layer P2 is layer No. 4, and the emission transparent oxide layer Nb is layer No. 5.
6 shows the radiation intensity (W/sr/ ^m2 /nm) when the thermal radiation layer N in the structures 5 and 6, which are different structural examples, is heated to 300°C. Note that FIG. 6 also shows the radiation intensity of a black body at 300°C.

The thermal radiation light sources Q of Structures 5 and 6 have layer No. 3 thicknesses of 1200 nm and 1500 nm, and as shown in FIG. 6, have a large emissivity (radiation rate) in the wavelength range greater than 4 μm and less than 8 μm (i.e., narrow band wavelengths excluding the short wavelength side of mid-infrared light), and have a small emissivity (radiation rate) in wavelengths greater than 8 μm (i.e., far-infrared light wavelengths) and less than 4 μm (i.e., short wavelength side wavelengths of mid-infrared light).

In the previously described example structure 2, the thickness of the second platinum layer P2 is 10 nm, whereas in the previously described example structure 3 and the other example structures 5 and 6, the thickness of the second platinum layer P2 is 5 nm.

The first platinum layer P1 blocks the radiant light from the substrate K and prevents the radiant light from the substrate K from penetrating into the inside of the radiation control portion Na, and therefore the preferred range of its thickness is, for example, 10 nm or more, and in particular, 50 nm is even more preferred.
Moreover, since the second platinum layer P2 controls the reflection and transmission of radiant light, the preferred range of the thickness is, for example, 1.5 nm or more and 18 nm or less, and particularly preferably 5 nm or more and 10 nm or less.

The radiation transparent oxide layer Nb exists to prevent reflection and improve durability, so the preferred range of its thickness is, for example, 100 nm or more and 800 nm or less, and even more preferably 300 nm or more and 800 nm or less.

When the thickness of the second platinum layer P2 is as thin as 10 nm or less, the reflectance of the radiant light emitted by the platinum layer P (the first platinum layer P1 and the second platinum layer P2) becomes low, so it is considered that the radiation transparent oxide layer Nb is not necessary. However, from the standpoint of durability, the radiation transparent oxide layer Nb is necessary.
In other words, when the platinum that forms the second platinum layer P2 is heated to high temperatures, there is a risk that it will flow and agglomerate on the resonance transparent oxide layer R, but the emission transparent oxide layer Nb acts to suppress the movement of platinum, thereby suppressing the aggregation of platinum.
In order to suppress the aggregation of platinum, it is preferable that the thickness of the radiation transparent oxide layer Nb is set to 100 nm or more.

However, since the radiation intensity of wavelengths greater than 8 μm (i.e., wavelengths of far-infrared light) increases as the thickness of the radiation transparent oxide layer Nb increases, it is preferable to set the thickness of the radiation transparent oxide layer Nb to 800 nm or less.

[Types of transparent oxides]
In the above-mentioned structural example, alumina (aluminum oxide, Al ₂ O ₃ ) is exemplified as the transparent oxide forming the emission transparent oxide layer Nb and the resonance transparent oxide layer R.
As the transparent oxide, tantalum pentoxide (Ta ₂ O ₅ ), silicon dioxide (SiO ₂ ), niobium pentoxide (NbO ₅ ), magnesium oxide (MgO), titanium oxide (TiO ₂ ), and hafnium oxide (HfO ₂ ) can be suitably used in place of alumina.
Incidentally, alumina (Al ₂ O ₃ ) and titanium oxide (TiO ₂ ) are particularly preferable as the transparent oxide for forming the emission transparent oxide layer Nb and the resonance transparent oxide layer R, since they have a small oxygen diffusion coefficient.

4 shows the radiation intensity (W/sr/m2/nm) when the thermal radiation layer N is heated to 300°C in a structure in which the radiation transparent oxide layer Nb is 500 nm thick, the second platinum layer P2 is 10 nm thick, the resonance transparent oxide layer R is 1200 nm thick, the first platinum layer is 100 nm thick, and an arbitrary substrate K is used, and the transparent oxides forming the radiation transparent oxide layer Nb and the resonance transparent ^oxide layer R are changed to the various materials described above. Note that FIG. 4 also shows the radiation intensity of a black body at 300°C.
Incidentally, the structural example shown in FIG. 4 is a structure similar to the above-mentioned structure 2, and while in structure 2 the thickness of the first platinum layer P1 is 50 nm, in the structural example shown in FIG. 4 the thickness of the first platinum layer P1 is 100 nm.

As shown in Figure 4, when the transparent oxide is changed to various materials, even if the thickness of _the resonance transparent oxide layer R is the same (1,200 nm), the resonating peak wavelength shifts to the longer wavelength side in the following order: silicon dioxide ( _SiO2 ), alumina (aluminum oxide, _Al2O3 ), magnesium oxide (MgO), hafnium oxide ( _HfO2 ), niobium pentoxide ( _NbO5 ), and _tantalum pentoxide ( _Ta2O5 ).
Tantalum pentoxide (Ta ₂ O ₅ ) and titanium oxide (TiO ₂ ) have substantially the same resonant peak wavelength.

Incidentally, the peak wavelength of silicon dioxide (SiO ₂ ) is 4.1 μm, the peak wavelength of alumina (aluminum oxide, Al ₂ O ₃ ) is 4.5 μm, the peak wavelength of magnesium oxide (MgO) is 4.7 μm, the peak wavelength of hafnium oxide (HfO ₂ ) is 5.4 μm, the peak wavelength of niobium pentoxide (NbO ₅ ) is 5.8 μm, the peak wavelength of titanium oxide (TiO ₂ ) is 6.1 μm, and the peak wavelength of tantalum pentoxide (Ta ₂ O ₅ ) is 6.1 μm.

7 shows the radiation intensity (W/sr/m2/nm) when the thermal radiation layer N is heated to 300°C in a structure in which the radiation transparent oxide layer Nb is 100 nm thick, the second platinum layer P2 is 5 nm thick, the resonance transparent oxide layer R is 1200 nm thick, the first platinum layer is 100 nm thick, and an arbitrary substrate K is used, and the transparent oxides forming the radiation transparent oxide layer Nb and the resonance transparent ^oxide layer R are changed to the various materials described above. Note that FIG. 7 also shows the radiation intensity of a black body at 300°C.
Incidentally, the structural example shown in FIG. 7 corresponds to the above-mentioned structure 5.

As shown in Figure 7, when the transparent oxide is changed to various materials, even if the thickness of _the resonance transparent oxide layer R is the same (1,200 nm), the resonating peak wavelength shifts to the longer wavelength side in the following order: silicon dioxide ( _SiO2 ), alumina (aluminum oxide, _Al2O3 ), magnesium oxide (MgO), hafnium oxide ( _HfO2 ), niobium pentoxide ( _NbO5 ), titanium oxide ( _TiO2 ), titanium oxide ( _TiO2 ), and _tantalum pentoxide ( _Ta2O5 ).

Incidentally, the peak wavelength of silicon dioxide ( _SiO2 ) is 4.4 μm, the peak wavelength of alumina ( _aluminum oxide, _Al2O3 ) is 4.8 μm, the peak wavelength of magnesium oxide (MgO) is 5.1 μm, the peak wavelength of hafnium oxide ( _HfO2 ) is 5.8 μm, the peak wavelength of niobium pentoxide ( _NbO5 ) is 6.2 μm, the peak wavelength of titanium oxide ( _TiO2 ) is 6.4 μm, and the peak wavelength of tantalum _pentoxide ( _Ta2O5 ) is 6.5 μm.

[Specific configuration of thermal radiation light source]
As shown in FIG. 8, the specific configuration of the thermal radiation source Q is such that a substrate adhesion layer S1 is laminated between the substrate K and the platinum layer P (first platinum layer P1) adjacent to the substrate K in the radiation control section Na, and platinum adhesion layers S2 are laminated respectively between the platinum layer P (first platinum layer P1 and second platinum layer P2) in the MIM laminate section M and the resonance transparent oxide layer R, and between the emission transparent oxide layer Nb and the platinum layer P (second platinum layer P2) adjacent to the emission transparent oxide layer Nb in the radiation control section Na.

In other words, since the substrate adhesion layer S1 is laminated between the substrate K and the platinum layer P (first platinum layer P1) in the radiation control portion Na that is adjacent to the substrate K, peeling of the radiation control portion Na from the substrate K is suppressed when the radiation control portion Na is heated by the substrate K.

In other words, since the thermal expansion coefficient of the substrate K is significantly different from that of the radiation control portion Na, which is made up of multiple thin films stacked together, there is a risk that the radiation control portion Na will peel off from the substrate K when it is heated by the substrate K. However, the adhesion between the substrate K and the platinum layer P (first platinum layer P1) in the radiation control portion Na adjacent to the substrate K is increased by the substrate adhesion layer S1, which prevents the radiation control portion Na from peeling off from the substrate K.

In addition, the platinum adhesion layer S2 is provided between the platinum layer P (first platinum layer P1 and second platinum layer P2) and the resonance transparent oxide layer R in the MIM laminate M, and between the emission transparent oxide layer Nb and the platinum layer P (second platinum layer P2) adjacent to the emission transparent oxide layer Nb in the radiation control unit Na. Therefore, when the radiation control unit Na is heated to a high temperature state on the substrate K, the platinum layer P (first platinum layer P1 and second platinum layer P2) in the MIM laminate M is prevented from flowing and coagulating, and the platinum layer P and the resonance transparent oxide layer R are prevented from peeling off, and the platinum layer P and the emission transparent oxide layer Nb are prevented from peeling off.

In other words, because the adhesion between platinum and the transparent oxide is low, there is a risk that the platinum layer P adjacent to the resonance transparent oxide layer R and the platinum layer P adjacent to the emission transparent oxide layer Nb will flow and aggregate when the radiation control unit Na is heated to a high temperature on the substrate K. However, by laminating the platinum adhesion layer S2, the adhesion of the platinum layer P adjacent to the resonance transparent oxide layer R to the resonance transparent oxide layer R and the adhesion of the platinum layer P adjacent to the emission transparent oxide layer Nb to the emission transparent oxide layer Nb are increased, so that the platinum layer P in the MIM laminate M is prevented from flowing and agglomerating when the radiation control unit Na is heated to a high temperature on the substrate K.

Titanium (Ti) and chromium (Cr) are excellent materials for forming the substrate adhesion layer S1 and platinum adhesion layer S2 in terms of melting point and adhesion. Titanium (Ti) is particularly desirable. In the following description, the substrate adhesion layer S1 and platinum adhesion layer S2 will be described as being formed from titanium (Ti).

That is, titanium (Ti) can effectively increase the adhesion of the platinum layer P (first platinum layer P1) adjacent to the substrate K to the substrate K, the adhesion of the platinum layer P (first platinum layer P1 and second platinum layer P2) adjacent to the resonance transparent oxide layer R to the resonance transparent oxide layer R, and the adhesion of the platinum layer P (second platinum layer P2) adjacent to the radiation transparent oxide layer Nb to the radiation transparent oxide layer Nb, and further, since it has a high melting point of 1668°C, it can appropriately suppress the platinum layer P (first platinum layer P1 and second platinum layer P2) in the MIM laminate M from flowing and agglomerating when the radiation control unit Na is heated to a high temperature state on the substrate K.

[Thickness of adhesive layer for substrate]
When the substrate adhesion layer S1 becomes hot, it emits radiant light with a wavelength greater than 4 μm (i.e., far-infrared light). However, since the radiant light emitted from the substrate adhesion layer S1 is blocked by the first platinum layer P1, in this regard, it does not matter if the thickness (film thickness) of the substrate adhesion layer S1 is large.
However, if the substrate adhesion layer S1 is too thick, when the radiation control part Na is heated to a high temperature state on the substrate K, titanium (Ti) may move around due to heat and appear on the surface of the first platinum layer P1 on the side where the resonance transparent oxide layer R is present. If such a phenomenon occurs, the thermal radiation control structure of the radiation control part Na will collapse, making it difficult to control the thermal radiation.

Furthermore, if the substrate adhesion layer S1 is too thin, it will not be able to accommodate the difference in thermal expansion coefficient between the radiation control portion Na having multiple thin films and the substrate K, and there is a risk that the radiation control portion Na will peel off from the substrate K when the radiation control portion Na is heated to a high temperature state on the substrate K.
From this viewpoint, the thickness of the substrate adhesion layer S1 (the thickness of titanium) is preferably 2 nm or more and 15 nm or less.

[Thickness of platinum adhesion layer]
The thickness (film thickness) of the platinum adhesion layer S2 needs to be set from the two standpoints of optical properties and durability.
That is, if the thickness (film thickness) of the platinum adhesion layer S2 is too thick, it is not optically good. That is, when the platinum adhesion layer S2 is in a high temperature state, it emits radiant light of a large wavelength (i.e., far-infrared light), so if the thickness (film thickness) of the platinum adhesion layer S2 is too thick, the intensity of the radiant light from the platinum adhesion layer S2 increases, which adversely affects the radiant light from the radiation control portion Na to have a small emissivity (emissivity) at a wavelength (i.e., far-infrared light) greater than 8 μm.

Furthermore, if the thickness (film thickness) of the platinum adhesion layer S2 is too thick, it will block radiant light, so it is necessary to avoid the thickness (film thickness) of the platinum adhesion layer S2 being too thick.
However, since the platinum adhesion layer S2 does not adhere to the substrate K and the thin film but adheres thin films to each other, an adhesion effect is obtained even if it is thinner than the substrate adhesion layer S1.
In view of this, it is desirable for the thickness (film thickness) of the platinum adhesion layer S2 to be 0.1 nm or more and 10 nm or less.

[On the oxidation of titanium]
There is a high possibility that titanium (Ti) forming the substrate adhesion layer S1 and the platinum adhesion layer S2 will be gradually oxidized and changed to titanium oxide (TiO ₂ ) by using the thermal radiation source Q in the atmosphere. In other words, when the thermal radiation source Q is used in the atmosphere, the substrate adhesion layer S1 and the platinum adhesion layer S2 can be regarded as being formed of titanium oxide (TiO ₂ ).

However, as shown in FIG. 9, not all of the titanium forming the platinum adhesion layer S2 is converted to titanium oxide, but the titanium in the portion in contact with the platinum layer P (second platinum layer P2) remains in the state of titanium in contact with the platinum layer P (second platinum layer P2) (metallic state) without being oxidized.
Although not shown in the figure, not all of the titanium forming the substrate adhesion layer S1 is converted to titanium oxide; the titanium in the area in contact with the platinum layer P (first platinum layer P1) is not oxidized and maintains the state of titanium in contact with the platinum layer P (first platinum layer P1) (metallic state).

In other words, the titanium forming the substrate adhesion layer S1 and the platinum adhesion layer S2 does not all change to titanium oxide, but the titanium in the area that adheres to the platinum layer P does not oxidize and continues to be in the form of titanium that adheres to the platinum layer P, and continues to function as the substrate adhesion layer S1 and the platinum adhesion layer S2.

To explain further, platinum (Pt) does not react with oxygen because its standard oxidation Gibbs energy change is +200 k/mol/ _O2 (chemical reactions proceed in the direction of a negative Gibbs energy change. A positive Gibbs energy change means that there is no reaction). This means that it is difficult to use an oxide as an adhesive layer for platinum (Pt) due to the bond energy relationship. For this reason, there is a concern that when titanium is oxidized to titanium oxide, it will no longer function as an adhesive layer for platinum (Pt). However, in reality, even if titanium is oxidized, the titanium at the interface with platinum (Pt) maintains its bond with platinum, so it continues to function as the substrate adhesive layer S1 and the platinum adhesive layer S2.

Incidentally, the substrate adhesion layer S1 and platinum adhesion layer S2, which are made of titanium, are formed in a thin film state so as to have optical transparency, and the titanium formed in a thin film state is changed into titanium oxide. However, since titanium oxide has transparency, the change of titanium into titanium oxide does not adversely affect the performance of the thermal radiation layer N.
In addition, taking into consideration the oxidation of the materials forming the substrate adhesion layer S1 and the platinum adhesion layer S2, chromium (Cr) turns black when oxidized, and therefore chromium, which turns black when oxidized, is unsuitable as an adhesion layer from the standpoint of radiation control, whereas titanium (Ti), which forms titanium oxide (TiO ₂ ), which turns transparent when oxidized, is superior from the standpoint of radiation control.

Incidentally, if titanium (Ti) of the platinum adhesion layer S2 oxidizes over time, even if the platinum adhesion layer S2 is thick, it is considered that the thermal radiation will eventually approach that of the case where the thickness (film thickness) of FIG. 9 is thin. However, if the thickness (film thickness) is thick, when the radiation control portion Na is heated to a high temperature state on the substrate K, there is a risk that the titanium (Ti) will move around due to heat and come out onto the surface of the second platinum layer P2. If such a phenomenon occurs, the thermal radiation control structure of the radiation control portion Na will collapse, making it difficult to control the thermal radiation. In particular, since the platinum of the second platinum layer P2 is thin, the movement of titanium (Ti) will have a large effect on the collapse of the thermal radiation control structure.
Therefore, it is desirable to set the thickness (film thickness) of the platinum adhesion layer S2 to about sub-nm (about 1 nm or less).

[About the board]
Considering that the thermal radiation light from the substrate K, which becomes in a high temperature state, is blocked by the first platinum layer P1 and does not transmit to the radiation control portion Na, various materials can be used as the material (base material) of the substrate K, such as quartz (SiO ₂ ), sapphire, stainless steel (SUS), Kanthal, nichrome, aluminum, silicon, etc.

When using a substrate K made of an oxide-based material, there is no particular problem. However, when using a substrate K made of a metal-based material, oxidation deterioration of the substrate K becomes a problem when it is heated in the atmosphere for use. However, the presence of the resonance transparent oxide layer R and the radiation transparent oxide layer Nb prevents oxidation deterioration of the surface of the substrate K on the side where the thermal radiation layer N is present.
The surface of the substrate K on the side where the heat radiation layer N is present is formed into a mirror surface to the extent that diffuse reflection is not caused.

The substrate K may be configured to generate heat by itself when electricity is applied, or may be configured to be heated by an external heating unit U.
That is, when the substrate K is made of a material that generates heat when electricity is passed through it, such as Kanthal or Nichrome, the substrate K can be configured to generate heat by itself when electricity is passed through it.
When the substrate K is made of quartz (SiO ₂ ), sapphire, stainless steel (SUS), or the like, it is configured to be heated by an external heating unit U, as shown in Figures 10 to 13. When the substrate K is heated by the external heating unit U, a light absorber (heat absorber) may be provided on the surface of the substrate K facing the external heating unit U.

10 and 11 show the case where the external heating unit U is configured as a plate-shaped heating electrode Ud equipped with a heater wire that generates heat when electricity is passed through it, and the substrate K of the thermal radiation source Q is disposed in close contact with the heating electrode Ud.
11 illustrates a case where the thermal radiation light source Q is disposed on one side of the heating electrode Ud, and FIG. 12 illustrates a case where the thermal radiation light source Q is disposed on both sides of the heating electrode Ud.

Figure 12 shows a case where the external heating unit U is configured as a thermal radiation source Ug that emits thermal radiation light G whose wavelength is not controlled, and the substrate K of the thermal radiation light source Q is arranged facing the thermal radiation source Ug.
FIG. 13 shows a case where the external heating unit U is configured as a fluid supply source Ut that supplies a high-temperature fluid T, and a substrate K of the thermal radiation source Q is disposed so as to face the fluid supply source Ut.

[Another embodiment]
Other embodiments are listed below.
(1) In the above embodiment, even if the back surface of the substrate K opposite the surface on which the thermal radiation layer N is stacked is oxidized, the back surface of the substrate K opposite the surface on which the thermal radiation layer N is stacked is exposed in consideration of the fact that the thermal radiation layer N is not adversely affected if the substrate K is thick. However, an anti-oxidation film that suppresses oxidation may be stacked on the back surface.

(2) In the above embodiment, the radiation control portion Na includes one MIM stack portion M. However, the radiation control portion Na may include two or more MIM stack portions M.
Incidentally, provision of multiple MIM stacked portions M means that three or more platinum layers P are arranged along the stacking direction of the thermal radiation layer N and the substrate K, and a resonance transparent oxide layer R is positioned between adjacent platinum layers P.

The configurations disclosed in the above embodiment (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, so long as no contradiction arises. Furthermore, the embodiments disclosed in this specification are merely examples, and the present invention is not limited to these embodiments. They can be modified as appropriate within the scope of the purpose of the present invention.

K: Substrate N: Thermal radiation layer Na: Radiation control portion Nb: Radiation transparent oxide layer M: MIM laminate portion P: Platinum layer R: Resonance transparent oxide layer S1: Adhesion layer for substrate S2: Adhesion layer for platinum

Claims (7)

A thermal radiation light source in which a thermal radiation layer and a substrate for heating the thermal radiation layer are laminated,
the thermal radiation layer is configured in a state in which the radiation control section and the radiation transparent oxide layer are laminated in the order of a radiation control section having an MIM laminate section in which a resonance transparent oxide layer formed of a transparent oxide is positioned between a pair of platinum layers arranged along the lamination direction of the thermal radiation layer and the substrate, and a radiation transparent oxide layer formed of a transparent oxide is positioned closer to the substrate,
The thickness of the resonance transparent oxide layer is 1200 nm or more and 1500 nm or less, with a resonance wavelength range of more than 4 μm and 8 μm or less,
A thermal radiation light source , wherein the transparent oxide used in the resonance transparent oxide layer is any one of aluminum oxide, tantalum pentoxide, silicon dioxide, niobium pentoxide, magnesium oxide, titanium oxide, and hafnium oxide . The thermal radiation light source according to claim 1, wherein a substrate adhesion layer is laminated between the substrate and the platinum layer adjacent to the substrate in the radiation control section. The thermal radiation light source according to claim 2, wherein a platinum adhesion layer is laminated between the platinum layer and the resonance transparent oxide layer in the MIM laminate, and between the emission transparent oxide layer and the platinum layer adjacent to the emission transparent oxide layer in the radiation control section. The thermal radiation light source according to claim 3, wherein the substrate adhesion layer and the platinum adhesion layer are formed of titanium. The thermal radiation light source according to any one of claims 1 to 4, wherein the transparent oxide is aluminum oxide. The thermal radiation light source according to any one of claims 1 to 5, wherein the substrate is configured to generate heat by itself when electricity is applied. The thermal radiation light source according to any one of claims 1 to 5, wherein the substrate is configured to be heated by an external heating unit.

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