Patent Description:
Conventionally, an infrared radiation device using a metamaterial structure is known. For example, Patent Literature <NUM> describes a radiation device that includes a heat source, a metamaterial structure layer disposed on a front-surface side of the heat source, and a rear-surface metal layer disposed on a rear-surface side of the heat source. The metamaterial structure layer radiates thermal energy input from the heat source as radiation energy in a specific wavelength region. Average emissivity of the rear-surface metal layer is set smaller than average emissivity of the metamaterial structure layer. According to Patent Literature <NUM>, thermal energy loss from the rear-surface side of the heat source can be made small due to the rear-surface metal layer, and therefore thermal energy loss of the radiation device can be kept small.

PTL <NUM>: International Publication No. <CIT>.

<CIT> proposes a radiation device having steep wavelength selectivity. The radiation device includes heating sources and a meta-material structure having a meta-material structure layer on a side surface. The meta-material structure layer is arranged so that radiation energy radiated from the heating sources enters its surface, and is constituted so that a specific wavelength region is removed from radiation energy reflected by the surface of the meta-material structure layer.

<CIT> proposes a spectrally-selective metamaterial emitter includes bull's eye (circular target-shaped) structures disposed on a base substrate and including concentric circular ridges separated by circular grooves and set at a fixed grating period. When the base substrate is heated to a high temperature, thermally excited surface plasmons generated on the concentric circular ridges produce a highly directional, narrow band energy beam having a peak emission wavelength that is roughly equal to the fixed grating period.

<CIT> proposes an infrared heater for radiating infrared rays from micro cavities while reducing an effect of the shape of a heating body. The infrared heater has a heating body, and a micro cavity forming body including micro cavities at least the surfaces of which are formed of conductors, and having a characteristic that infrared radiation having a peak wavelength of a non-Plank distribution is radiated by the micro cavities upon absorption of energy from the heating body.

<CIT> proposes a double-sided infrared radiation apparatus.

<CIT> proposes an infrared heating apparatus with a filament so that the infrared rays are transmitted through an inner tube to reach a reflecting layer provided at a distance from the inner tube so as to cover only a part of the surroundings of the filament. The reflecting layer can be cooled by a coolant flowing through a coolant channel so that it is possible to suppress overheating of the reflecting layer.

<CIT> proposes a heating element with a heating component having pieces of metal foil electrically connected to respective ends of the heating element and external lead wires each connected electrically to the other end of the metal foil. A tube body is provided with a sealing portion for containing the heat element in the tube body and sealing each of the metal foil areas, and holes arranged outward relative to the sealing portion; and holding members attached to the holes for holding the external lead wires.

<CIT> proposes a heating means composed of carbon-based material.

<CIT> proposes a reaction product preparation method for obtaining a reaction product from a starting raw material through a predetermined organic synthesis reaction. A target wavelength is set as the peak wavelength of a reactive site participating in an organic synthesis reaction in the infrared absorption spectrum of a starting raw material. An infrared heater emits infrared radiation having a peak at the target wavelength from a structure body comprising, layered from the exterior to the interior, a metal pattern, a dielectric layer, and a metal substrate in this order, in order to cause the organic synthesis reaction to proceed in order to obtain a reaction product.

According to the radiation device disclosed in Patent Literature <NUM>, thermal energy loss can be suppressed as described above, but further suppression of thermal energy loss in an infrared radiation device is desired.

The present invention was accomplished in order to solve such a problem, and a main purpose of the present invention is to further suppress energy loss of an infrared radiation device.

The present invention employs the following means in order to accomplish the above main purpose.

An infrared radiation device of the present invention includes a body including a heat generating part and first and second metamaterial structures that are capable of radiating infrared rays having a peak wavelength of a non-Planck distribution upon receipt of thermal energy from the heat generating part. The first metamaterial structure is disposed on a first surface side of the heat generating part and the second metamaterial structure is disposed on a second surface side opposite to the first surface side of the heat generating part.

This infrared radiation device includes not only a first metamaterial structure on a first surface side of a heat generating part, but also a second metamaterial structure on a second surface side opposite to the first surface side. Accordingly, infrared rays having a peak wavelength of a non-Planck distribution can be radiated from both of the first surface side and the second surface side. In other words, infrared rays in a specific wavelength region can be selectively radiated from both of the first surface side and the second surface side. Accordingly, radiation of infrared rays having an unnecessary wavelength other than the specific wavelength region from the second surface side can be suppressed as compared with a case where a rear-surface metal layer is present on a side opposite to the metamaterial structure (there is no metamaterial structure), for example, as in the radiation device described in Patent Literature <NUM>. This reduces thermal energy loss from the second surface side. Accordingly, this infrared radiation device can further suppress energy thermal loss.

The metamaterial structure may be a structure that has radiation characteristics having a maximum peak steeper than a peak of the Planck distribution. Note that "steeper than a peak of the Planck distribution" means that "a full width at half maximum (FWHM) is narrower than the peak of the Planck distribution".

The infrared radiation device according to the present invention may include an infrared rays reflecting part that can reflect infrared rays radiated from at least one of the first and second metamaterial structures toward an object. Since the infrared rays reflecting part reflects infrared rays, energy of infrared rays radiated from the body can be easily utilized.

The infrared radiation device according to the present invention may include a casing that has an infrared rays transmitting part that can transmit infrared rays radiated from the first and second metamaterial structures to an outside, and the body may be disposed in an internal space of the casing. In this case, the infrared rays reflecting part may be disposed on an inner side (e.g., an inner circumferential surface) of the casing, the infrared rays reflecting part may be disposed on an outer side (e.g., an outer circumferential surface) of the casing, or a part of the casing may also serve as the infrared rays reflecting part.

The infrared radiation device according to the present invention may be configured such that a difference between a peak wavelength of a maximum peak of infrared rays radiated by the first metamaterial structure and a peak wavelength of a maximum peak of infrared rays radiated by the second metamaterial structure is <NUM> or less. That is, the peak wavelength of the first metamaterial structure and the peak wavelength of the second metamaterial structure may be close to each other or may be the same as each other.

The infrared radiation device according to the present invention may be configured such that the body is exposed to an outer space or is disposed in an internal space of a casing in which the internal space is in a non-depressurized state. In other words, a space around the body may be non-depressurized atmosphere.

The infrared radiation device according to the present invention may be configured such that at least one of the first and second metamaterial structures includes, from the heat generating part side, a first conductor layer, a dielectric layer joined to the first conductor layer, and a second conductor layer having a plurality of individual conductor layers each of which is joined to the dielectric layer and that are periodically disposed away from one another.

The infrared radiation device according to the present invention may be configured such that at least one of the first and second metamaterial structures includes a plurality of microcavities that are configured such that at least a surface thereof is made of a conductor and that are periodically disposed away from one another.

Next, an embodiment of the present invention is described by using the drawings. <FIG> are cross-sectional views of an infrared radiation device <NUM> according to an embodiment of the present invention. <FIG> is a partial bottom view of a first metamaterial structure 30a. <FIG> is a vertical cross-sectional view taken along an axial direction (a front-rear direction in this example) of the infrared radiation device <NUM>, and <FIG> illustrates a cross section perpendicular to the axial direction of the infrared radiation device <NUM>. In the present embodiment, an up-down direction, a front-rear direction, and a left-right direction are illustrated in <FIG>. The infrared radiation device <NUM> includes a body <NUM>, a casing <NUM>, a reflective layer <NUM>, and a thermocouple <NUM>. The infrared radiation device <NUM> radiates infrared rays toward an object (not illustrated) disposed below the infrared radiation device <NUM>.

The body <NUM> is disposed in an internal space <NUM> of the casing <NUM>. The body <NUM> has a flat-plate shape. As illustrated in the enlarged view of <FIG>, the body <NUM> includes a heat generating part <NUM>, first and second support substrates 20a and 20b, first and second metamaterial structures 30a and 30b.

The heat generating part <NUM> is configured as a planar heater and includes a heat generator <NUM> obtained by curving a linear member in a zigzag manner and a protection member <NUM> that is an insulator covering the heat generator <NUM> in contact with the heat generator <NUM>. The heat generator <NUM> is, for example, made of a material such as W, Mo, Ta, an Fe-Cr-Al alloy, or an Ni-Cr alloy. In the present embodiment, the heat generator <NUM> is made of Kanthal (Registered Trademark: an alloy containing iron, chromium, and aluminum). The protection member <NUM> is, for example, made of a material such as an insulating resin (e.g., polyimide) or ceramics. A bar-shaped conductor <NUM> that is conductive with the heat generator <NUM> is attached to both ends, in a longitudinal direction (the front-rear direction in this example), of the body <NUM>. The bar-shaped conductor <NUM> is drawn out to an outside from both ends, in the axial direction, of the casing <NUM>, and electric power can be externally supplied to the heat generator <NUM> through the bar-shaped conductor <NUM>. The bar-shaped conductor <NUM> also plays a role as a support for the body <NUM> in the casing <NUM>. In this example, the bar-shaped conductor <NUM> is made of Mo. The heat generating part <NUM> may be a planar heater obtained by winding a ribbon-shaped heat generator around an insulator.

The first and second support substrates 20a and 20b are flat-plate-shaped members. The first support substrate 20a is disposed on a first surface side (a lower surface side in this example) of the heat generating part <NUM>. The second support substrate 20b is disposed on a second surface side (an upper surface side in this example) of the heat generating part <NUM>. The first support substrate 20a and the second support substrate 20b are collectively referred to as support substrates <NUM>. The support substrates <NUM> support the heat generating part <NUM> and the first and second metamaterial structures 30a and 30b. The support substrates <NUM> are, for example, made of a material that can easily keep a smooth surface, has high heat resistance, and has low thermal warpage such as an Si wafer or glass. In the present embodiment, the support substrates <NUM> are made of silica glass. The first and second support substrates 20a and 20b may be in contact with the lower surface and the upper surface of the heat generating part <NUM>, respectively as in the present embodiment or may be disposed away from the lower surface and the upper surface of the heat generating part <NUM> with a space interposed therebetween. In a case where the support substrates <NUM> and the heat generating part <NUM> are in contact with each other, the support substrates <NUM> and the heat generating part <NUM> may be joined to each other.

The first and second metamaterial structures 30a and 30b are plate-shaped members. The first metamaterial structure 30a is disposed on the first surface side (the lower surface side in this example) of the heat generating part <NUM> and is located below the first support substrate 20a. The second metamaterial structure 30b is disposed on the second surface side (the upper surface side in this example) of the heat generating part <NUM> and is located above the second support substrate 20b. The first metamaterial structure 30a and the second metamaterial structure 30b are collectively referred to as metamaterial structures <NUM>. The first metamaterial structure 30a may be directly joined to a lower surface of the first support substrate 20a or may be joined to the lower surface of the first support substrate 20a with an adhesive layer (not illustrated) interposed therebetween. Similarly, the second metamaterial structure 30b may be directly joined to an upper surface of the second support substrate 20b or may be joined to the upper surface of the second substrate 20b with an adhesive layer (not illustrated) interposed therebetween. The first metamaterial structure 30a radiates infrared rays mainly downward, and the second metamaterial structure 30b radiates infrared rays mainly upward. As illustrated in <FIG>, the first metamaterial structure 30a and the second metamaterial structure 30b have the same constituent elements and are horizontally symmetrical to each other in the present embodiment. The first metamaterial structure 30a is described below. As for the second metamaterial structure 30b, the constituent elements are given identical reference signs in <FIG> and detailed description thereof is omitted.

The first metamaterial structure 30a includes a first conductor layer <NUM>, a dielectric layer <NUM>, and a second conductor layer <NUM> having a plurality of individual conductor layers <NUM> in this order from the heat generator <NUM> side toward a lower side. Such a structure is also called a metal-insulator-metal (MIM) structure. The layers of the first metamaterial structure 30a may be directly joined to one another or may be joined to one another with an adhesive layer interposed therebetween. Exposed parts of the individual conductor layers <NUM> and a lower surface of the dielectric layer <NUM> may be coated with an oxidation prevention film (not illustrated, made of alumina, for example).

The first conductor layer <NUM> is a flat-plate-shaped member joined on a side (a lower side) of the first support substrate 20a opposite to the heat generator <NUM>. The first conductor layer <NUM> is, for example, made of a conductor (electric conductor) such as a metal. Specific examples of the metal include gold, aluminum (Al), and molybdenum (Mo). In the present embodiment, the first conductor layer <NUM> is made of gold. The first conductor layer <NUM> is joined to the first support substrate 20a with an adhesive layer (not illustrated) interposed therebetween. The adhesive layer is, for example, made of a material such as chromium (Cr), titanium (Ti), or ruthenium (Ru). The first conductor layer <NUM> and the first support substrate 20a may be directly joined to each other.

The dielectric layer <NUM> is a flat-plate-shaped member that is joined on a side (a lower side) of the first conductor layer <NUM> opposite to the heat generator <NUM>. The dielectric layer <NUM> is sandwiched between the first conductor layer <NUM> and the second conductor layer <NUM>. The dielectric layer <NUM> is, for example, made of alumina (Al<NUM>O<NUM>) or silica (SiO<NUM>). In the present embodiment, the dielectric layer <NUM> is made of alumina.

The second conductor layer <NUM> is a layer made of a conductor and has a periodic structure in directions (the front-rear and left-right directions) parallel with a lower surface of the dielectric layer <NUM>. Specifically, the second conductor layer <NUM> includes a plurality of individual conductor layers <NUM>, and the plurality of individual conductor layers <NUM> are disposed away from one another in the directions (the front-rear and left-right directions) parallel with the lower surface of the dielectric layer <NUM> so as to constitute a periodic structure (see <FIG>). A plurality of individual conductor layers <NUM> are disposed away from one another at equal intervals D1 in the left-right direction (a first direction). Furthermore, a plurality of individual conductor layers <NUM> are disposed away from one another at equal intervals D2 in the front-rear direction (a second direction) orthogonal to the left-right direction. In this way, the individual conductor layers <NUM> are arranged in a grid pattern. Although the individual conductor layers <NUM> are arranged in a square grid pattern in the present embodiment as illustrated in <FIG>, the individual conductor layers <NUM> may be, for example, arranged in a hexagonal grid pattern so that each of the individual conductor layers <NUM> is located at a vertex of an equilateral triangle. Each of the plurality of individual conductor layers <NUM> has a circular shape on bottom view and has a shape of a circular column having a thickness h (a height in the up-down direction) smaller than a diameter W. A cycle of the periodic structure of the second conductor layer <NUM> is Λ1 = D1 + W in the lateral direction and is A2 = D2 + W in the vertical direction. In the present embodiment, D1 = D2, and Λ1 = A2 accordingly. A material of the second conductor layer <NUM> (the individual conductor layers <NUM>) is, for example, a conductor such as a metal and may be similar to the material of the first conductor layer <NUM>. At least one of the first conductor layer <NUM> and the second conductor layer <NUM> may be a metal. In the present embodiment, the second conductor layer <NUM> is made of gold, which is the same as the material of the first conductor layer <NUM>.

As described above, the first metamaterial structure 30a has the first conductor layer <NUM>, the second conductor layer <NUM> (the individual conductor layers <NUM>) having a periodic structure, and the dielectric layer <NUM> sandwiched between the first conductor layer <NUM> and the second conductor layer <NUM>. With this configuration, the first metamaterial structure 30a can radiate infrared rays having a peak wavelength of a non-Planck distribution upon receipt of thermal energy from the heat generating part <NUM>. The Planck distribution is a mound-shaped distribution having a specific peak on a graph whose horizontal axis represents a wavelength that becomes longer toward the right and whose vertical axis represents an irradiance intensity and is a curve whose gradient on a left side of the peak is steep and whose gradient on a right side of the peak is gradual. Radiation of a typical material complies with this curve (a Planck radiation curve). Non-Planck radiation (radiation of infrared rays having a peak wavelength of a non-Planck distribution) is radiation such that a gradient of a mound shape around a maximum peak of the radiation is steeper than the Planck radiation. That is, the first metamaterial structure 30a has radiation characteristics having a maximum peak steeper than a peak of the Planck distribution. Note that "steeper than a peak of the Planck distribution" means that "a full width at half maximum (FWHM) is narrower than the peak of the Planck distribution". With this configuration, the first metamaterial structure 30a functions as a metamaterial emitter having characteristics of selectively radiating infrared rays of a specific wavelength in an entire wavelength region (<NUM> to <NUM>) of infrared rays. The characteristics are considered to be exhibited due to a resonance phenomenon explained as magnetic polariton. The magnetic polariton is a resonance phenomenon in which an anti-parallel current is excited in two upper and lower conductors (the first conductor layer <NUM> and the second conductor layer <NUM>) and a strong magnetic confinement effect is obtained in a dielectric body (the dielectric layer <NUM>) disposed between the two upper and lower conductors. For this reason, in the first metamaterial structure 30a, locally strong electric field oscillation is excited in the first conductor layer <NUM> and the individual conductor layers <NUM>, which serve as an infrared radiation source, and thus infrared rays are radiated to a surrounding environment (especially downward in this example). Furthermore, in this first metamaterial structure 30a, a resonance wavelength can be adjusted by adjusting the materials which the first conductor layer <NUM>, the dielectric layer <NUM>, and the second conductor layer <NUM> are made of and a shape and a periodic structure of the individual conductor layers <NUM>. With this configuration, infrared rays radiated from the first conductor layer <NUM> and the individual conductor layers <NUM> of the first metamaterial structure 30a exhibits characteristics such that emissivity of infrared rays of a specific wavelength is high. That is, the first metamaterial structure 30a has characteristics for radiating infrared rays having a steep maximum peak having a relatively small full width at half maximum and relatively high emissivity. Although D1 = D2 in the present embodiment, the interval D1 and the interval D2 may be different from each other. This also applies to the cycle Λ1 and the cycle A2. Note that the full width at half maximum can be controlled by changing the cycle Λ1 and the cycle A2. The maximum peak of the predetermined radiation characteristics of the first metamaterial structure 30a may be within a wavelength range of not less than <NUM> to not more than <NUM> or may be within a wavelength range of not less than <NUM> to not more than <NUM>. Furthermore, the first metamaterial structure 30a is preferably configured such that emissivity of infrared rays in a wavelength region other than a wavelength region from rising to falling of the maximum peak is <NUM> or less. The first metamaterial structure 30a is preferably configured that the full width at half maximum of the maximum peak is <NUM> or less. The radiation characteristics of the first metamaterial structure 30a may have a shape substantially vertically symmetrical about the maximum peak. Furthermore, a height (a maximum irradiance intensity) of the maximum peak of the first metamaterial structure 30a does not exceed the curve of Planck radiation.

The first metamaterial structure 30a described above can be formed, for example, as follows. First, the adhesive layer and the first conductor layer <NUM> are formed in this order on a surface (a lower surface in <FIG>) of the first support substrate 20a by sputtering. Next, the dielectric layer <NUM> is formed on a surface (a lower surface in <FIG>) of the first conductor layer <NUM> by atomic layer deposition (ALD). Next, a layer made of the material of the second conductor layer <NUM> is formed on a surface (a lower surface in <FIG>) of the dielectric layer <NUM> by helicon sputtering after a predetermined resist pattern is formed on the surface of the dielectric layer <NUM>. Then, the second conductor layer <NUM> (the plurality of individual conductor layers <NUM>) is formed by removing the resist pattern.

The infrared radiation characteristics of the first metamaterial structure 30a and the infrared radiation characteristics of the second metamaterial structure 30b may be close to each other or may be the same as each other. For example, a maximum peak of infrared rays radiated by the second metamaterial structure 30b may be the same as or close to the maximum peak of infrared rays radiated by the first metamaterial structure 30a. Specifically, a difference between a peak wavelength of the maximum peak of infrared rays radiated by the first metamaterial structure 30a and a peak wavelength of the maximum peak of infrared rays radiated by the second metamaterial structure 30b may be <NUM> or less. Furthermore, at least part of a wavelength region of a full width at half maximum (a full width at half maximum region) of the maximum peak of the first metamaterial structure 30a and at least part of a wavelength region of a full width at half maximum (a full width at half maximum region) of the maximum peak of the second metamaterial structure 30b may overlap each other or a half or more of the wavelength region of the full width at half maximum (a full width at half maximum region) of the maximum peak of the first metamaterial structure 30a and a half or more of the wavelength region of the full width at half maximum (a full width at half maximum region) of the maximum peak of the second metamaterial structure 30b may overlap each other. In the present embodiment, the first and second metamaterial structures 30a and 30b have the same D1, D2, and W and have almost the same infrared radiation characteristics.

The thermocouple <NUM> is an example of a temperature sensor that measures a temperature of a surface of the body <NUM> and is drawn out to an outside from the surface of the body <NUM> by penetrating the casing <NUM>.

The casing <NUM> is a substantially cylindrical member. The casing <NUM> has an internal space <NUM> therein. In the internal space <NUM>, the body <NUM> is disposed. The whole casing <NUM> functions as infrared rays transmitting part that can transmit, to an outside, infrared rays radiated from the first and second metamaterial structures 30a and 30b. The casing <NUM> can transmit infrared rays in at least part of the wavelength region from rising to falling of the maximum peak of infrared rays radiated from the first metamaterial structure 30a and can transmit infrared rays in at least part of the wavelength region from rising to falling of the maximum peak of infrared rays radiated from the second metamaterial structure 30b. The casing <NUM> preferably can transmit at least a wavelength region including the maximum peaks of infrared rays radiated from the first and second metamaterial structures 30a and 30b, more preferably can transmit at least a wavelength region including the full width at half maximum regions of the maximum peaks of the infrared rays radiated from the first and second metamaterial structures 30a and 30b. The casing <NUM> may have transmittance of <NUM>% or more or may have transmittance or <NUM>% or more as for infrared rays having peak wavelengths of the maximum peaks radiated from the first and second metamaterial structures 30a and 30b. The casing <NUM> is, for example, made of infrared rays transmitting material such as silica glass (which transmits infrared rays having a wavelength of not more than <NUM>), transparent alumina (which transmits infrared rays having a wavelength of not more than <NUM>), or fluorite (calcium fluoride, CaF<NUM>, which transmits infrared rays having a wavelength of not more than <NUM>). The material of the casing <NUM> may be selected as appropriate, for example, in accordance with the maximum peaks of infrared rays radiated from the metamaterial structures <NUM>. In the present embodiment, the casing <NUM> is made of silica glass. The internal space <NUM> is in a non-depressurized state. The internal space <NUM> may be an air atmosphere or may be an inert gas atmosphere such as nitrogen or argon. Both ends, in the axial direction, of the casing <NUM> have a curved taper shape, and the bar-shaped conductor <NUM> is drawn out to an outside from these ends. Parts of the casing <NUM> where the bar-shaped conductor <NUM> and the thermocouple <NUM> are drawn out to an outside from the internal space <NUM> are sealed by providing molten parts obtained by melting the casing <NUM>. These parts may be sealed by using a sealing member different from the casing <NUM>.

In the present embodiment, the radiation characteristics of the first and second metamaterial structures 30a and 30b are set so that the peak wavelength of the maximum peak is <NUM> since the casing <NUM> is made of silica glass, which transmits infrared rays having a wavelength of not more than <NUM> (absorbs infrared rays of more than <NUM>). These radiation characteristics can be realized, for example, by setting the thickness of the first conductor layer <NUM> to <NUM>, setting the thickness of the dielectric layer <NUM> to <NUM>, setting the thickness of the second conductor layer <NUM> (the individual conductor layers <NUM>) to <NUM>, setting the diameter W of the individual conductor layers <NUM> to <NUM>, and setting the cycles A1 and A2 to <NUM>.

The reflective layer <NUM> is an example of infrared rays reflecting part and is disposed so as to cover a part of an outer circumferential surface of the casing <NUM>. Accordingly, the reflective layer <NUM> is provided so as to cover only part of surroundings of the body <NUM>. The reflective layer <NUM> is disposed in a direction perpendicular to a longitudinal direction of the casing <NUM> when viewed from the body <NUM> (above the body <NUM> in this example). The reflective layer <NUM> is disposed on a side (an upper side in this example) of the second metamaterial structure 30b opposite to the heat generating part <NUM>. The reflective layer <NUM> is disposed on an outer upper surface of the casing <NUM>. In this example, it is assumed that the reflective layer <NUM> covers all of an upper half of the outer circumferential surface of the casing <NUM> (see <FIG>). The reflective layer <NUM> has an arc shape (in particular, a semi-circular shape in this example) on a cross-sectional view perpendicular to the longitudinal direction of the infrared radiation device <NUM> as illustrated in <FIG>. The reflective layer <NUM> is disposed so as to face the second metamaterial structure 30b and is located in a direction (an upward direction in this example) of main infrared radiation from the second metamaterial structure 30b. The reflective layer <NUM> reflects downward infrared rays radiated from the second metamaterial structure 30b. The reflective layer <NUM> is, for example, made of a material such as gold, platinum, or aluminum. In this example, the reflective layer <NUM> is made of gold. The reflective layer <NUM> may be formed on a surface of the casing <NUM> by using a film formation method such as coating and drying, sputtering, CVD, or thermal spraying.

An example of use of the infrared radiation device <NUM> described above is described below. First, electric power is supplied from a power source (not illustrated) to the heat generator <NUM> through the bar-shaped conductor <NUM>. The electric power is supplied so that a temperature of the heat generator <NUM> reaches a preset temperature (not limited in particular but is set to <NUM> in this example). Energy is transmitted to surroundings from the heat generator <NUM> that has reached the predetermined temperature mainly through conduction among three forms of heat transmission (conduction, convection, and radiation), and thus the metamaterial structures <NUM> are heated. As a result, a temperature of the metamaterial structures <NUM> rises to a predetermined temperature (for example, <NUM> in this example), and the metamaterial structures <NUM> serve as radiators that radiate infrared rays. Since the metamaterial structures <NUM> have the first conductor layer <NUM>, the dielectric layer <NUM>, and the second conductor layer <NUM> as described above, the body <NUM> radiates infrared rays having a peak wavelength of a non-Planck distribution. More specifically, the body <NUM> selectively radiates infrared rays in a specific wavelength region from the first conductor layer <NUM> and the individual conductor layers <NUM> of the metamaterial structures <NUM>. The infrared rays in the specific wavelength region radiated from the first metamaterial structure 30a passes through the casing <NUM> and is radiated to a region below the infrared radiation device <NUM>. Furthermore, infrared rays in the specific wavelength region radiated mainly upward from the second metamaterial structure 30b is reflected downward by the reflective layer <NUM> and is radiated to a region below the infrared radiation device <NUM>. This allows the infrared radiation device <NUM> to selectively radiate infrared rays in the specific wavelength region from the first and second metamaterial structures 30a and 30b to an object disposed below the infrared radiation device <NUM>. It is therefore possible to perform infrared processing such as heating process, drying processing, or chemical reaction, for example, on an object having a high rate of absorption of infrared rays in the specific wavelength region by efficiently radiating the infrared rays toward the object.

The infrared radiation device <NUM> according to the present embodiment described in detail above includes not only the first metamaterial structure 30a on a first surface side (a lower surface side) of the heat generating part <NUM>, but also the second metamaterial structure 30b on a second surface side (an upper surface side) opposite to the first surface side. Accordingly, infrared rays having a peak wavelength of a non-Planck distribution can be radiated from both of the first surface side and the second surface side of the heat generating part <NUM>. In other words, infrared rays in a specific wavelength region can be selectively radiated from both of the first surface side and the second surface side of the heat generating part <NUM>. Accordingly, for example, radiation of infrared rays having an unnecessary wavelength other than the specific wavelength region from the second surface side of the heat generating part <NUM> can be suppressed as compared with a case where the second metamaterial structure 30b is not present or a case where the rear-surface metal layer described in Patent Literature <NUM> is present instead of the second metamaterial structure 30b. This reduces thermal energy loss from the second surface side. Accordingly, the infrared radiation device <NUM> can further suppress energy thermal loss.

Furthermore, the infrared radiation device <NUM> includes the reflective layer <NUM> that can reflect infrared rays radiated from the second metamaterial structure 30b toward an object. This makes it easy to use energy of the second metamaterial structure 30b radiated from the body <NUM>. For example, in the present embodiment, the reflective layer <NUM> is located above the second metamaterial structure 30b, and the reflective layer <NUM> reflects downward infrared rays radiated upward from the second metamaterial structure 30b. With this configuration, energy of infrared rays radiated from the second metamaterial structure 30b can be used for infrared processing of an object even in a case where there is no object irradiated with infrared rays on the second surface side of the body <NUM> (an upper side of the body <NUM> in this example).

The present invention is not limited to the above-described embodiments, and can be carried out by various modes as long as they belong to the technical scope of the invention.

For example, although each of the metamaterial structures <NUM> has the first conductor layer <NUM>, the dielectric layer <NUM>, and the second conductor layer <NUM>, i.e., an MIM structure in the above embodiment, this configuration is not restrictive. The metamaterial structures <NUM> may be any structures that can radiate infrared rays having a peak wavelength of a non-Planck distribution upon receipt of thermal energy from the heat generating part <NUM>. For example, the metamaterial structures may be configured as microcavity structures each having a plurality of microcavities. <FIG> is a partial cross-sectional view of a body <NUM> according to a modification. <FIG> is a partial bottom perspective view of a first metamaterial structure 30a according to the modification. Each of the first and second metamaterial structures 30a and 30b of the body <NUM> according to the modification has a plurality of microcavities 41A that are configured such that at least surfaces (side surfaces 42A and bottom surfaces 44A in this example) thereof are a conductor layer 35A and that constitute a periodic structure in the front-rear and left-right directions. The first metamaterial structure 30a and the second metamaterial structure 30b have the same constituent elements and are horizontally symmetrical to each other. The following describes the first metamaterial structure 30a in detail. As for the second metamaterial structure 30b, the constituent elements are given identical reference signs in <FIG> and detailed description thereof is omitted. The first metamaterial structure 30a includes a body layer 31A, a recess formation layer 33A, and a conductor layer 35A in this order from a heat generating part <NUM> side of the body <NUM> toward a lower side. The body layer 31A is, for example, a glass substrate. The recess formation layer 33A is, for example, made of a resin or an inorganic material such as ceramics or glass and is formed on a lower surface of the body layer 31A so as to form recesses each having a shape of a circular column. The recess formation layer 33A may be made of the same material as the second conductor layer <NUM>. The conductor layer 35A is disposed on a surface (a lower surface) of the first metamaterial structure 30a and covers surfaces (a lower surface and side surfaces) of the recess formation layer 33A and a lower surface of the body layer 31A (a part where the recess formation layer 33A is not disposed). The conductor layer 35A is a conductor and is, for example, made of a material such as a metal (e.g., gold or nickel) or an electrically conductive resin. Each of the microcavities 41A is a substantially circular columnar space that is surrounded by a side surface 42A (a part that covers the side surface of the recess formation layer 33A) and a bottom surface 44A (a part that covers the lower surface of the body layer 31A) of the conductor layer 35A and is opened on a lower side. As illustrated in <FIG>, the plurality of microcavities 41A are arranged in the front-rear and left-right directions. Note that the lower surface of the first metamaterial structure 30a serves as a radiation surface 38A that radiates infrared rays toward an object. Specifically, when the first metamaterial structure 30a absorbs energy from the heat generating part <NUM>, infrared rays having a specific wavelength is strongly radiated from the radiation surface 38A toward an object below the first metamaterial structure 30a due to a resonance effect between an incident wave and a reflected wave in the space formed by the bottom surface 44A and the side surface 42A. With this configuration, the first metamaterial structure 30a can radiate infrared rays having a peak wavelength of a non-Planck distribution. Note that radiation characteristics of the first metamaterial structure 30a can be adjusted by adjusting a diameter and a depth of a circular column of each of the plurality of microcavities 41A. Note that the shape of each of the microcavities 41A is not limited to a circular column and may be a polygonal column. The depth of each of the microcavities 41A may be, for example, not less than <NUM> and not more than <NUM>. Since an infrared radiation device that has the body <NUM> illustrated in <FIG> is also configured such that the body <NUM> includes the first and second metamaterial structures 30a and 30b as in the above embodiment, thermal energy loss from the second surface side of the body <NUM> is reduced. The first metamaterial structure 30a illustrated in <FIG> can be formed, for example, as follows. First, the recess formation layer 33A is formed the lower surface of the body layer 31A by known nanoimprint. Then, the conductor layer 35A is formed, for example, by sputtering so as to cover a surface of the recess formation layer 33A and a surface of the body layer 31A. It is also possible to employ a configuration in which one of the first and second metamaterial structures 30a and 30b has an MIM structure and the other one of the first and second metamaterial structures 30a and 30b has microcavities.

Although the reflective layer <NUM> is disposed on an outer circumferential surface of the casing <NUM> in the above embodiment, the reflective layer <NUM> may be disposed at a position on an outer side of the casing <NUM> other than the outer circumferential surface. For example, infrared rays reflecting part that is an independent member may be disposed on an outer side of the casing <NUM> instead of the reflective layer <NUM>. Alternatively, the reflective layer <NUM> may be disposed on an inner side (e.g., an inner circumferential surface) of the casing <NUM>. Furthermore, a part of the casing <NUM> may also serve as infrared rays reflecting part instead of the configuration in which the infrared radiation device <NUM> includes the reflective layer <NUM>. In this case, the casing <NUM> need just have infrared rays transmitting part and infrared rays reflecting part instead of the configuration in which the whole casing <NUM> functions as infrared rays transmitting part as in the above embodiment. For example, the casing <NUM> may include a casing body that functions as infrared rays reflecting part and infrared rays transmitting plate that plays a role as a window that transmits infrared rays radiated from the metamaterial structures <NUM> to an outside of the casing <NUM>. The infrared rays transmitting plate is, for example, disposed so as to face the lower surface of the first metamaterial structure 30a. In this case, the casing body is, for example, made of a material such as stainless steel. The infrared rays transmitting plate is, for example, made of the aforementioned infrared rays transmitting material. The casing <NUM> need not entirely be infrared rays transmitting part and need just include at least infrared rays transmitting part irrespective of whether or not the casing <NUM> includes infrared rays reflecting part.

The reflective layer <NUM> has an arc shape (in particular, a semi-circular shape in this example) on a cross-sectional view as illustrated in <FIG> but is not limited to this. For example, the reflective layer <NUM> may be a hemisphere shape or may be a flat-plate shape.

Although the reflective layer <NUM> is disposed on a side (an upper side in this example) of the second metamaterial structure 30b opposite to the heat generating part <NUM>, this configuration is not restrictive. The infrared rays reflecting part provided in the infrared radiation device <NUM> need just reflect infrared rays radiated from at least one of the first metamaterial structure 30a and the second metamaterial structure 30b toward an object. Furthermore, although the reflective layer <NUM> reflects downward infrared rays radiated from the second metamaterial structure 30b, a direction in which the infrared rays are reflected is not limited to this. For example, the infrared radiation device <NUM> may include a reflective layer <NUM> located on at least one of left and right sides of the casing <NUM> in <FIG> instead of the reflective layer <NUM> of <FIG>. The reflective layer <NUM> in this case may reflect downward infrared rays radiated from the first metamaterial structure 30a and reflect upward infrared rays radiated from the second metamaterial structure 30b.

Although the reflective layer <NUM> reflects infrared rays toward an object in the above embodiment, the reflective layer <NUM> may reflect part of the infrared rays toward the body <NUM>. Note, however, that the reflective layer <NUM> preferably reflect infrared rays toward the object as much as possible.

In the above embodiment, the infrared radiation device <NUM> need not include the reflective layer <NUM>. Even in a case where the infrared rays reflecting part such as the reflective layer <NUM> is not present, energy of infrared rays radiated from the first and second metamaterial structures 30a and 30b can be utilized in a case where an object is present above and below the infrared radiation device <NUM>. In this case, the object below the infrared radiation device <NUM> and the object above the infrared radiation device <NUM> may be different, and the first and second metamaterial structures 30a and 30b may have different radiation characteristics in accordance with the respective objects.

Although the internal space <NUM> of the casing <NUM> is in a non-depressurized state in the above embodiment, this configuration is not restrictive, and the internal space <NUM> of the casing <NUM> may be in a depressurized state or may be in a vacuum state. Furthermore, the infrared radiation device <NUM> need not include the casing <NUM>, and the body <NUM> may be exposed to an outer space. Even in this case, a space (an outer space) around the body <NUM> may be in a non-depressurized state such as atmosphere.

The present application claims priority from <CIT>. Industrial Applicability.

The present invention is applicable to industries that need infrared processing such as heating, drying, and chemical reaction of an object.

Claim 1:
An infrared radiation device (<NUM>) comprising a body (<NUM>) including a heat generating part (<NUM>) and first and second metamaterial structures (30a, 30b) that are capable of radiating infrared rays having a peak wavelength of a non-Planck distribution upon receipt of thermal energy from the heat generating part (<NUM>),
wherein the first metamaterial structure (30a) is disposed on a first surface side of the heat generating part (<NUM>) and the second metamaterial structure (30b) is disposed on a second surface side opposite to the first surface side of the heat generating part (<NUM>).