JP2016065786A - Infrared radiating element, manufacturing method thereof, and gas analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide, e.g., an infrared radiating element which can sufficiently narrow the band of the radiation spectrum and significantly contribute to power saving.SOLUTION: An infrared radiating element comprises: a heat generator; a radiator with a periodic microstructure in a face opposite to the heat generator side; a planarization layer with a flat face opposite to the radiator side; and a bandpass filter formed on the planarization layer; in this order. Heat generated by the heat generator is conducted to the bandpass filter by heat conduction.SELECTED DRAWING: Figure 3A

Description

  The present invention relates to an infrared radiation element, a method for manufacturing the same, and a gas analyzer using the infrared radiation element.

  Gas sensors using a non-dispersive infrared absorption method (hereinafter sometimes referred to as “NDIR gas sensors”) are widely used as air conditioning controls and various gas detection devices because of their high accuracy and stability.

A schematic diagram of a conventional NDIR gas sensor is shown in FIG.
The NDIR gas sensor shown in FIG. 1 includes a measurement cell 101, an infrared light source 102 provided in the measurement cell 101, a bandpass filter 103 provided in the measurement cell 101, and a light receiving element 104 provided in the measurement cell 101. Have. Infrared light 105 emitted from the infrared light source 102 enters a gas 106 that passes through the measurement cell 101. Various gas components contained in the gas 106 each have absorption with respect to a specific infrared ray. The infrared ray 105 from the infrared light source 101 is partially absorbed while passing through the gas 106 layer, and then is received by the light receiving element 104. Incident. On the optical path from the infrared light source 102 to the light receiving element 104, a band pass filter 103 that transmits only the infrared absorption band of the gas component to be detected is provided. And the density | concentration of the gas component to detect can be known from the quantity of the infrared rays 105 which the light receiving element 104 receives.
The light receiving element 104 is generally an element that converts infrared light intensity into an electrical signal (for example, a thermopile or a bolometer).

  In applications such as sensors that use infrared rays of a specific wavelength, some specific infrared rays that pass through a bandpass filter out of a wide band of infrared rays that are generated by radiating heat to a resistor in an infrared light source. Infrared is used. Therefore, energy efficiency is poor because infrared rays of other wavelengths are not used. Therefore, there has been a demand to increase the infrared energy of a specific wavelength emitted from the infrared light source.

The reason why some specific infrared rays are used in the infrared sensor is that the detection gas in the infrared sensor has a large absorption and a narrow absorption band at a specific infrared wavelength. As an example, an absorption spectrum of carbon dioxide (CO ₂ ) is shown in FIG.
Note that the spread of the spectrum can be considered by the Q value. The Q value is a value obtained by dividing the frequency at which the intensity is maximum (the speed of light divided by the wavelength) by the half width. The larger the Q value, the narrower the spectrum in the frequency range where the intensity becomes maximum. The Q value of the absorption spectrum of carbon dioxide (CO ₂ ) near 4.3 μm is about 26.

In response to the desire to increase the infrared energy of a specific wavelength emitted from an infrared light source, it has been proposed to increase the infrared energy of a specific wavelength due to a fine structure (see, for example, Patent Documents 1 to 5). For example, it has been proposed to increase the infrared energy of a specific wavelength by forming a microcavity on the surface of a radiator.
However, with only fine structure control, there is a limit to increasing the Q value, that is, narrowing the emission spectrum.

  Therefore, the present situation is that there is a need to provide an infrared radiation element that can sufficiently contribute to power saving by narrowing the emission spectrum sufficiently, a method for manufacturing the same, and a gas analyzer using the infrared radiation element. .

JP 2013-083478 A JP 2001-519079 JP 2005-337817 A JP 2006-520074 Gazette JP 2014-053088 A

  An object of the present invention is to solve the above-described problems and achieve the following objects. That is, an object of the present invention is to provide an infrared radiation element that can sufficiently contribute to power saving by narrowing the emission spectrum sufficiently, a manufacturing method thereof, and a gas analyzer using the infrared radiation element. .

Means for solving the problems are as follows. That is,
<1> A heating element,
A radiator having a periodic fine structure on a surface opposite to the heating element side;
A planarizing layer having a flat surface opposite to the radiator side;
A bandpass filter formed on the planarizing layer in this order,
The infrared radiation element, wherein heat generated by the heating element is transmitted to the bandpass filter by heat conduction.
<2> The infrared radiation element according to <1>, wherein the band-pass filter is an alternating laminate of a high refractive index layer and a low refractive index layer.
<3> The material of the high refractive index layer is any one of Ge, PbTe, ZnSe, ZnS, Ta ₂ O ₅ , CeO ₂ , and Si.
The infrared radiation element according to <2>, wherein the material of the low refractive index layer is any one of BaF ₂ , LaF ₂ , NdF ₃ , YF ₃ , SiO ₂ , SiO, and Y ₂ O ₃ .
<4> The infrared radiation element according to any one of <1> to <3>, wherein the material of the radiator is stainless steel.
<5> The infrared radiation element according to any one of <1> to <4>, wherein a material of the heating element is any one of tungsten, platinum, and a silicide alloy.
<6> The infrared radiation element according to any one of <1> to <5>, wherein the material of the planarizing layer is SiO ₂ .
<7> The infrared radiation element according to any one of <1> to <6>, wherein an insulating layer is provided between the heat generator and the heat radiator.
<8> The method for producing an infrared radiation element according to any one of <1> to <7>,
In the radiator precursor in which a heating element is formed on one surface and a mask layer is formed on the other surface, the radiator precursor is irradiated to the mask layer on the other surface by laser irradiation and development. A pattern forming step for forming a pattern for forming a periodic fine structure in the body;
Etching the radiator precursor using the mask layer with the pattern formed as a mask to form a periodic microstructure on the other surface of the radiator precursor to obtain a radiator A process for producing an infrared radiation element.
<9> The method for manufacturing an infrared radiation element according to <8>, wherein the pattern is formed by a three-beam interference exposure method.
<10> a heating element forming step of forming a heating element on one surface of the radiator precursor;
It is a manufacturing method of the infrared radiation element in any one of said <8> to <9> including the mask layer formation process which forms a mask layer on the other surface of the said radiator precursor.
<11> The infrared radiation according to any one of <8> to <10>, including a planarization layer forming step of forming a planarization layer by a sol-gel method on the other surface of the radiator from which the mask layer has been removed. It is a manufacturing method of an element.
<12> The method for manufacturing an infrared radiation element according to any one of <8> to <11>, further including a bandpass filter forming step of forming a bandpass filter on the planarizing layer by vapor deposition.
<13> A gas analyzer comprising the infrared radiation element according to any one of <1> to <7>.
<14> Furthermore, it has a measurement cell into which the gas to be measured is introduced, and an infrared detector that detects the infrared rays emitted from the infrared radiation element,
The infrared radiation element is provided at one end of the measurement cell,
The gas analyzer according to <13>, wherein the infrared detector is provided at the other end of the measurement cell.

  According to the present invention, the conventional problems can be solved, the object can be achieved, the radiation spectrum can be sufficiently narrowed, and the infrared radiation element that can greatly contribute to power saving, and the manufacturing method thereof, and A gas analyzer using the infrared radiation element can be provided.

FIG. 1 is a schematic cross-sectional view of a conventional NDIR gas sensor. FIG. 2 is an absorption spectrum of carbon dioxide. FIG. 3A is a schematic cross-sectional view of an example of the infrared radiation element of the present invention. 3B is a schematic diagram of a radiator of the infrared radiation element of FIG. 3A. FIG. 4 is a schematic cross-sectional view of another example of the infrared radiation element of the present invention. FIG. 5 is a graph showing an example of the transmission characteristics of the bandpass filter. FIG. 6 is a graph showing an example of the angle dependency of the emissivity of the infrared radiation element of the present invention. FIG. 7: A is a schematic sectional drawing for demonstrating an example of the manufacturing method of the infrared radiation element of this invention (the 1). FIG. 7B is a schematic cross-sectional view for explaining an example of the manufacturing method of the infrared radiation element of the present invention (part 2). FIG. 7: C is schematic sectional drawing for demonstrating an example of the manufacturing method of the infrared rays radiating element of this invention (the 3). FIG. 7D is a schematic cross-sectional view for explaining an example of the manufacturing method of the infrared radiation element of the present invention (part 4). FIG. 7E is a schematic cross-sectional view for explaining an example of the manufacturing method of the infrared radiation element of the present invention (part 5). FIG. 7F is a schematic cross-sectional view for explaining an example of the manufacturing method of the infrared radiation element of the present invention (No. 6). FIG. 7G is a schematic cross-sectional view for explaining an example of the manufacturing method of the infrared radiation element of the present invention (part 7). FIG. 7H is a schematic cross-sectional view for explaining an example of the manufacturing method of the infrared radiation element of the present invention (No. 8). FIG. 7I is a schematic cross-sectional view for explaining an example of the manufacturing method of the infrared radiation element of the present invention (No. 9). FIG. 8 is a schematic cross-sectional view of an example of the gas analyzer of the present invention. FIG. 9 is a radiation spectrum of the radiator in the first example. FIG. 10 is a radiation spectrum of the infrared radiation element of Example 1. FIG. 11 is a radiation spectrum of the infrared radiation element of Comparative Example 1. FIG. 12 is a radiation spectrum of the infrared radiation element of Example 3.

(Infrared radiation element)
The infrared radiation element of the present invention includes at least a heating element, a radiator, a planarization layer, and a bandpass filter, preferably an insulating layer, and further includes other members as necessary.

The infrared radiation element includes the heating element, the radiator, the planarizing layer, and the bandpass filter in this order.
In the infrared radiation element, the heat generated by the heating element is transmitted to the bandpass filter by heat conduction.

<Heating element>
The heating element is not particularly limited as long as it generates heat and can heat the radiator, and can be appropriately selected according to the purpose.
As the material of the heating element, tungsten, a tungsten compound, tantalum, a tantalum compound, platinum, or a silicide alloy is preferable in that the deterioration is small even when heat is generated at a high temperature.

For example, two electrodes are connected to the heating element. The heating element generates heat by energizing the heating element using the two electrodes.
Heat from the heating element is conducted to the radiator. As a result, the radiator is heated. The heated radiator emits infrared rays corresponding to its temperature.

Examples of the shape of the heating element include a flat plate shape.
There is no restriction | limiting in particular as a magnitude | size and a structure of the said heat generating body, According to the objective, it can select suitably.
The resistance value of the heating element is adjusted by appropriately adjusting the shape, size, and structure of the heating element. As a result, the heating temperature of the heating element can be controlled. For example, the heating temperature of the heating element can be controlled by patterning the heating element and adjusting the thickness of the heating element.

When the heating element has a flat plate shape, the average thickness is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 50 μm to 1,000 μm, and more preferably 100 μm to 500 μm.
In the present specification, the average thickness is an arithmetic average value when the thickness of a measurement target member is measured at 10 locations.

<Heat radiator>
The heat radiator is not particularly limited as long as it has a periodic fine structure on the surface opposite to the heating element side, and can be appropriately selected according to the purpose.
Due to the periodic fine structure, the radiator can narrow the emission spectrum compared to a flat radiator made of the same material.

The periodic fine structure in the radiator is not particularly limited as long as it can narrow the infrared radiation characteristic in the material of the radiator, and can be appropriately selected according to the purpose. And a structure in which the holes are periodically arranged.
The size and depth of the circular holes and the interval (pitch) between adjacent holes can be appropriately selected according to the target resonance wavelength.

The following describes the preferred range in the case of the CO ₂ and the measurement gas.
The size of the circular hole is preferably 1.6 μm to 2.0 μm, more preferably 1.7 μm to 1.9 μm from the viewpoint that the infrared radiation characteristic can be narrowed.
The depth of the circular hole is preferably 2.8 μm to 3.2 μm, more preferably 2.9 μm to 3.1 μm, from the viewpoint that the infrared radiation characteristics can be narrowed.
As a space | interval (pitch) between adjacent holes, 1.8 micrometers-2.2 micrometers are preferable, and 1.9 micrometers-2.1 micrometers are more preferable. Here, the interval means a distance between the centers of the holes.

  The material of the radiator is not particularly limited depending on the wavelength to be radiated, and can be appropriately selected according to the purpose. However, it is easy to process and easily produces a periodic fine structure. Stainless steel is preferred.

The radiator has a flat plate shape.
There is no restriction | limiting in particular as average thickness of the said radiator, Although it can select suitably according to the objective, 50 micrometers-1,000 micrometers are preferable from the point of producibility and cost, and 100 micrometers-500 micrometers are more preferable.

<Planarization layer>
The planarizing layer has a flat surface opposite to the radiator side.
In the manufacture of the infrared radiation element, the band-pass filter is usually formed on the radiator via the planarization layer. At this time, the planarization layer is interposed between the radiator and the bandpass filter, so that the bandpass filter is not affected by the periodic fine structure formed on the surface of the radiator. , Can have flatness.

  The flatness may be flatness such that the periodic fine structure does not affect the flatness of the bandpass filter. Specifically, it is sufficient that the band-pass filter is flat enough to obtain designed characteristics.

The material of the flattening layer is not particularly limited and can be appropriately selected according to the purpose. However, when the sol-gel method is adopted as a method of flattening the surface opposite to the radiator side, the sol-gel method is used. SiO ₂ is preferable because the planarization layer can be easily formed by a method.

  There is no restriction | limiting in particular as average thickness of the said planarization layer, Although it can select suitably according to the objective, 30 nm-100 nm are preferable from the point of thermal conductivity and planarization property.

<Band pass filter>
The bandpass filter is not particularly limited as long as it has a characteristic of selectively transmitting a wavelength having a maximum intensity in the radiation spectrum radiated from the radiator, and can be appropriately selected according to the purpose. An alternating laminate of a high refractive index layer and a low refractive index layer is preferable.

The refractive index of the high refractive index layer may be higher than the refractive index of the low refractive index layer. In other words, it is sufficient that the refractive index of the low refractive index layer is lower than the refractive index of the high refractive index layer.
The high refractive index in the high refractive index layer is, for example, a refractive index of 1.5 or more. The low refractive index in the low refractive index layer is, for example, less than 1.5. These are, for example, the refractive index for light in the visible light range.

There is no restriction | limiting in particular as a material of the said high refractive index layer, Although it can select suitably according to the objective, It is preferable that there is no absorption with respect to the radiation spectrum from the said radiator. As such a material, Ge, PbTe, ZnSe, ZnS, Ta ₂ O ₅ , CeO ₂ and Si are preferable.
There is no restriction | limiting in particular as a material of the said low-refractive-index layer, Although it can select suitably according to the objective, It is preferable that there is no absorption with respect to the radiation spectrum from the said radiator. Such _{material, BaF 2, LaF 2, NdF} 3, YF 3, SiO 2, SiO, Y 2 O 3 is preferred.

  There is no restriction | limiting in particular as the number of lamination | stacking in the said alternating laminated body of the said high refractive index layer and the said low refractive index layer, Although it can select suitably according to the objective, 6 layers-10 layers are preferable.

  There is no restriction | limiting in particular as average thickness of the said band pass filter, Although it can select suitably according to the objective, 1500 nm-3,500 nm are preferable and 2,000 nm-3,000 nm are more preferable.

<Insulating layer>
The insulating layer is disposed between the heating element and the radiator.
The insulating layer prevents the radiator from being energized when the heating element is conducting.

The material, shape, size, and structure of the insulating layer are not particularly limited as long as insulation between the heating element and the radiator can be secured, and can be appropriately selected according to the purpose.
Examples of the material of the insulating layer include SiO ₂ .

  There is no restriction | limiting in particular as average thickness of the said insulating layer, Although it can select suitably according to the objective, 30 nm-300 nm are preferable and 50 nm-200 nm are more preferable. When the average thickness is less than 30 nm, dielectric breakdown may occur. When the average thickness exceeds 300 nm, thermal conductivity may decrease.

<Other members>
Examples of the other members include a reflective layer, an electrode, and a support.

<< Reflection layer >>
As long as the reflective layer is a layer that reflects the infrared rays emitted from the radiator to the heating element side to the band-pass filter side, the material, shape, size, and structure are not particularly limited. It can be appropriately selected depending on the case.
The reflective layer is disposed, for example, between the heating element and the radiator.

  As the material of the reflective layer, aluminum is preferable because it does not hinder heat conduction of the heat generated by the heat generating element to the heat generating element and is excellent in infrared reflectivity.

  There is no restriction | limiting in particular as average thickness of the said reflection layer, Although it can select suitably according to the objective, 80 nm-250 nm are preferable, and 100 nm-220 nm are more preferable.

<< Electrode >>
The electrode is not particularly limited as long as it is an electrode for energizing the heating element, and can be appropriately selected according to the purpose.

There is no restriction | limiting in particular as a material of the said electrode, a shape, a magnitude | size, and a structure, According to the objective, it can select suitably.
<< Support >>
The support is not particularly limited as long as it supports a laminated body having the heating element, the radiator, the planarizing layer, and the bandpass filter in this order, depending on the purpose. Can be selected as appropriate.

Here, FIG. 3A and FIG. 3B show schematic cross-sectional views of an example of the infrared radiation element of the present invention.
The infrared radiation element shown in FIG. 3A has an insulating layer 3, a reflective layer 2, a radiator 1, a planarizing layer 5, and a bandpass filter 6 in this order on a heating element 4.
The radiator 1 has a periodic fine structure on the surface opposite to the heating element 4 side. The periodic fine structure of the radiator 1 has a structure as shown in FIG. 3B.
The planarizing layer 5 has a flat surface opposite to the radiator 1 side.
In the infrared radiating element, the heating element 4 and the bandpass filter 6 are in contact with each other through the insulating layer 3, the reflective layer 2, the radiator 1, and the planarization layer 5. Is transmitted to the band-pass filter 6.

The infrared radiation element shown in FIG. 4 is an embodiment in which the infrared radiation element shown in FIGS. 3A and 3B further includes an electrode 7 and a support 8.
In the infrared radiation element shown in FIG. 4, two electrodes 7 are connected to the lower portions of two opposing sides of the heating element 4. The two electrodes 7 are formed on the support 8. The support 8 is formed with a recess, and is not in contact with the heating element 4, and is a laminated body (on the heating element 4, the insulating layer 3, the reflective layer 2, the radiator 1, the planarization layer 5, and the band). The laminate having the pass filter 6 in this order is supported.

  The infrared radiation element of the present invention includes a heat dissipating body having a periodic fine structure and a band-pass filter, so that the radiation spectrum can be sufficiently narrowed to greatly contribute to power saving. That is, an infrared radiation element having a large Q value in the radiation spectrum can be obtained.

In general, the characteristics of the band-pass filter are easily changed by the influence of temperature, and in general gas analyzers, it is necessary to devise a technique for suppressing the characteristic change of the band-pass filter.
However, in the infrared radiation element of the present invention, the heat generated by the heating element is transmitted to the bandpass filter by heat conduction. In the infrared radiation element, the heat radiating body is set to a constant temperature in order to make the radiation characteristics constant. At that time, the band-pass filter is also kept at a constant temperature. Therefore, the characteristic change of the bandpass filter can be suppressed without requiring any special device.

The case where an alternating layered body (total thickness 4,560 nm) of a high refractive index layer and a low refractive index layer shown in Table 1 will be described as the bandpass filter. For example, when the band-pass filter is an alternately laminated body of Ge (n = 4.0) and BaF ₂ (n = 1.35), the transmission characteristics are as shown in FIG. The Q value of the infrared radiation element of the present invention obtained by laminating this on a radiator having a periodic fine structure through, for example, a SiO ₂ film (planarization layer) formed by a sol-gel method. Becomes 20 or more, and can be close to the Q value (about 26) of the absorption spectrum of carbon dioxide.

In general, since the band pass filter has an angle dependency, the radiation angle can be controlled. If only the periodic fine structure of the radiator is used, the radiation angle is large and radiation in an unnecessary direction increases. However, it is possible to further reduce unnecessary radiation by reducing the radiation angle by the band-pass filter. As a result, the infrared radiation element of the present invention can reduce power consumption.
Here, FIG. 6 shows the angle dependency of the emissivity of 4.26 μm which is the peak wavelength of carbon dioxide absorption in an example of the infrared radiation element of the present invention. The radiation is reduced from an angle exceeding 30 ° obliquely from the normal line of the surface of the infrared radiation element, indicating that the radiation is concentrated only in front of the general infrared radiation element.

(Infrared radiation element manufacturing method)
The method for manufacturing an infrared radiation element of the present invention includes at least a pattern formation step and a radiator preparation step, and preferably includes a heating element formation step, a mask layer formation step, a planarization layer formation step, and a bandpass filter formation step It includes at least one of them, and further includes other steps as necessary.
The method for manufacturing the infrared radiation element is a method for manufacturing the infrared radiation element of the present invention.

<Pattern formation process>
In the pattern forming step, the mask layer on the other surface in the radiator precursor in which the heating element is formed on one surface and the mask layer is formed on the other surface is irradiated with laser, and There is no particular limitation as long as it is a step of forming a pattern for forming a periodic fine structure on the radiator precursor by development, and it can be appropriately selected according to the purpose.

  The radiator precursor is a precursor for producing a radiator having a periodic fine structure on the surface, and examples thereof include a flat plate made of the same material as the radiator. The flat plate has a smooth surface.

  The mask layer is not particularly limited as long as it is a layer resistant to etching of the radiator precursor described later, and can be appropriately selected depending on the purpose.

The pattern is preferably formed by a three-beam interference exposure method in terms of cost.
Here, the interference exposure method is an exposure method in which a coherent light beam is irradiated to form an interference pattern on an exposure object, and the exposure object is exposed with the interference pattern. The three-beam interference exposure method is an interference exposure method in which an interference pattern is formed by three beams.

  There is no restriction | limiting in particular as the said development method, According to the objective, it can select suitably.

<Radiator production process>
The radiator manufacturing step includes etching the radiator precursor using the mask layer on which the pattern is formed as a mask to form a periodic fine structure on the other surface of the radiator precursor. If it is the process of obtaining a radiator, there will be no restriction | limiting in particular, According to the objective, it can select suitably.
As the etching, electrolytic etching is preferable in terms of cost.

<Heat generating process>
The heating element forming step is not particularly limited as long as it is a step of forming the heating element on one surface of the radiator precursor, and can be appropriately selected according to the purpose. Can be performed.

<Mask layer forming step>
The mask layer forming step is not particularly limited as long as it is a step of forming the mask layer on the other surface of the radiator precursor, and can be appropriately selected according to the purpose. Can be performed.

<Planarization layer forming step>
The flattening layer forming step is not particularly limited as long as it is a step of forming a flattening layer by the sol-gel method on the other surface of the radiator from which the mask layer has been removed. You can choose.

  There is no restriction | limiting in particular as a removal method of the said mask layer, According to the objective, it can select suitably.

In the sol-gel method, a metal alkoxide solution is used as a starting solution, this solution is made into a colloidal solution (Sol) by hydrolysis and condensation polymerization reaction, and a solid (Gel) that loses fluidity is formed by further promoting the reaction. It is a method to make it.
Examples of the metal alkoxide include alkoxysilane, alkoxytitanium, zirconium alkoxide and the like.

In the sol-gel method, it is preferable to use SiO ₂ as the metal alkoxide to form SiO ₂ . Examples of the alkoxysilane include tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane.

<Band pass filter formation process>
The bandpass filter forming step is not particularly limited as long as it is a step of forming a bandpass filter on the planarizing layer by a vapor deposition method, and can be appropriately selected according to the purpose.

<Other processes>
Examples of the other steps include a reflective layer forming step and an insulating layer forming step.

<< Reflective layer forming process >>
The reflective layer forming step is not particularly limited as long as it is a step of forming a reflective layer on one surface of the radiator precursor, and can be appropriately selected according to the purpose. It can be carried out.

  The reflective layer forming step is preferably performed before the heating element forming step. In that case, the heating element is formed on the radiator precursor via the reflective layer.

<< Insulating layer forming process >>
The insulating layer forming step is not particularly limited as long as it is a step of forming an insulating layer on one surface of the radiator precursor, and can be appropriately selected according to the purpose. It can be carried out.

  The insulating layer forming step is preferably performed before the heating element forming step. In that case, the heating element is formed on the radiator precursor via the insulating layer.

  When the manufacturing method of the infrared radiation element includes the heating element forming step, the reflective layer forming step, and the insulating layer forming step, the order includes the reflective layer forming step, the insulating layer forming step, and the The order of the heating element forming step is preferable. In that case, the reflective layer, the insulating layer, and the heating element are formed in this order on the radiator precursor.

Here, an example of the manufacturing method of the infrared radiation element of this invention is demonstrated using FIG. 7A-FIG. 7I.
First, a stainless steel plate as a radiator precursor 1A is prepared (FIG. 7A). The stainless steel plate is polished as necessary.
Next, the reflective layer 2 is formed on the radiator precursor 1A by a vapor deposition method (reflective layer forming step, FIG. 7B).
Next, the insulating layer 3 is formed on the reflective layer 2 (insulating layer forming step, FIG. 7C).
Next, the heating element 4 is formed on the insulating layer 3 (heating element forming step, FIG. 7D).
Next, the mask layer 11 is formed on the side opposite to the heating element 4 side of the radiator precursor 1A (mask layer forming step, FIG. 7E).
Next, a pattern for forming a periodic fine structure is formed on the radiator precursor 1A by laser irradiation and development on the mask layer 11 (pattern formation step, FIG. 7F).
Next, using the mask layer 11 on which the pattern is formed as a mask, the emitter precursor 1A is etched to form a periodic fine structure on the surface of the emitter precursor 1A to obtain the emitter 1 (emitter 1). Manufacturing process, FIG. 7G).
Next, the planarizing layer 5 is formed on the radiator 1 from which the mask layer 11 has been removed by a sol-gel method (planarizing layer forming step, FIG. 7H).
Next, a band pass filter 6 is formed on the planarizing layer 5 by vapor deposition (band pass filter forming step, FIG. 7I).
Thus, an infrared radiation element is obtained.

(Gas analyzer)
The gas analyzer of the present invention includes at least the infrared radiation element of the present invention, preferably includes a measurement cell and an infrared detector, and further includes other members as necessary.

<Measurement cell>
The measurement cell is not particularly limited as long as it is a cell into which a gas to be measured is introduced, and can be appropriately selected according to the purpose. The material, shape, size, and structure are not particularly limited. Can be appropriately selected according to the purpose.
Examples of the gas to be measured include CO ₂ , CO, NO, SO _{2 and the} like.

<Infrared detector>
The infrared detector is not particularly limited as long as it is a device that can detect infrared rays emitted by the infrared emitting element, and can be appropriately selected according to the purpose. For example, a thermopile, a bolometer, a pyroelectric element, A quantum element etc. are mentioned.

Here, an example of the gas analyzer of the present invention will be described with reference to the drawings.
FIG. 8 is a schematic cross-sectional view of an example of the gas analyzer of the present invention.
The gas analyzer shown in FIG. 8 includes an infrared radiation element 51, an infrared detector 52, and a measurement cell 53. The infrared radiation element 51 is provided at one end of the measurement cell 53. The infrared detector 52 is provided at the other end of the measurement cell 53. The measurement cell 53 is provided with a sample gas inlet 53a and an outlet 53b.
At the inlet 53a of the measurement cell 53, for example, an atmospheric gas containing CO ₂ as a measurement gas is introduced as a sample gas, and is continuously exhausted from the outlet 53b. Note that sample gas may be introduced through a sampling device or the like that removes dust with a filter or removes moisture that absorbs infrared rays with a perm pure dryer.
The infrared rays emitted from the infrared radiation element 51 are absorbed by the measurement gas when passing through the measurement cell 53. Therefore, the amount of infrared rays detected by the infrared detector 52 varies depending on the concentration of the gas to be measured in the sample gas. By this change, the concentration of the gas to be measured in the sample gas can be detected.

In a general gas analyzer, as shown in FIG. 1, a measurement cell 101 is provided with a band-pass filter 103. In a gas analyzer, it is necessary to keep the temperature of the bandpass filter constant in order to keep the light transmission characteristics of the bandpass filter constant. Therefore, a general gas analyzer requires a member for keeping the temperature of the bandpass filter constant.
In the gas analyzer of the present invention, the infrared radiation element of the present invention is provided with a band-pass filter, and the band-pass filter is heated to a constant temperature by the heat of the heating element of the infrared radiation element. . Therefore, the gas analyzer of the present invention does not require a member for keeping the temperature of the bandpass filter constant, and can reduce the number of parts. Therefore, power saving is possible, and an energy efficient gas analyzer can be realized.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1
<Formation of reflective layer, insulating layer, and heating element>
On the back surface of a mirror-polished stainless steel (SUS304, diameter 2 inch) substrate (radiant precursor) with an average thickness of 50 μm, a tungsten film (average thickness 200 nm) as a reflective layer and a silicon oxide film (average thickness 200 nm) as an insulating layer ) And a tungsten film (average thickness 300 nm) as a heating element were formed in this order by vapor deposition.

<Preparation of heat radiator>
Next, an antireflection film (BARC, average thickness 30 nm) and an i-line photoresist film (mask layer, average thickness 300 nm) were sequentially formed on the surface of the stainless steel substrate by spin coating. By the three-beam interference exposure method using a longitudinal single mode laser with a wavelength of 355 nm, holes having a hole diameter of 1.3 μm and a thickness of 250 nm are formed in the mask layer in a hexagonal close-packed state with a pitch of 2.0 μm between adjacent holes. The resist pattern arranged periodically was formed.
Next, electric field etching of the stainless steel substrate is performed using the mask layer on which the resist pattern is formed as a mask, and a hole having a depth of 3.0 μm and a hole diameter of 1.8 μm is formed on the surface of the stainless steel substrate. A fine periodic structure arranged periodically in a hexagonal close-packed state with an interval of 2.0 μm was formed to obtain a heat radiator.
The radiation characteristics of this radiator are shown in FIG. This radiation characteristic was obtained from the reflectance.

<Formation of planarization layer>
The mask layer on the heat radiator was removed. A silica film (average thickness 70 nm) as a planarizing layer was formed on the surface of the heat radiating body (the surface on the side where the fine periodic structure was formed) by a sol-gel method using TEOS (tetraethoxysilane) as a metal alkoxide. . The surface of the flattening layer (the surface opposite to the radiator side) was flat without being affected by the periodic fine structure of the radiator.

<Formation of bandpass filter>
Finally, a bandpass filter (total thickness: 2,545 nm) having a multilayer structure of Ge / BaF ₂ shown in Table 2 was formed on the planarizing layer by vapor deposition. Note that a Ge layer (267 nm) is in contact with the planarizing layer.

  Thus, an infrared radiation element was obtained.

The obtained infrared radiation element was cut into a 3 mm × 5 mm rectangular shape. It was placed on a support 8 with two electrodes 7 as shown in FIG. At that time, the two electrodes 7 were connected to the opposing short sides of the infrared radiation element so that the radiator in the infrared radiation element did not contact the support.
The distance between the electrodes of the infrared radiation element is 3 mm, and the resistance of the heating element (tungsten film) is 210Ω. When 5 V was applied to this infrared radiation element, the current value was 24 mA, and when the radiation spectrum was measured, it was confirmed that the band was narrow as shown in FIG. A Q value of 28 was obtained.

(Example 2)
Table 3 shows a prospective calculation for improving the power consumption efficiency of the infrared radiation element according to the present invention.
In the trial calculation, the following conditions (1) to (3) were used.
Condition (1) 100% of the input power is converted to light Condition (2) Only the portion of the radiation spectrum that coincides with carbon dioxide absorption is incident on the light receiver.
Condition (3) Only the range of 10 ° from the normal of the radiation surface is incident on the light receiver.
In the infrared radiating element of the present invention, the utilization efficiency is improved from 4% to 84% by improving the spectral component, and the utilization efficiency of the radiation angle component is 2.5%, compared with the conventional black body radiation type emitter. Therefore, the total utilization efficiency is improved about 60 times from 0.1% to 6.6%. Further, as shown in Table 3, all of the spectrum utilization efficiency, the radiation angle component utilization efficiency, and the total utilization efficiency are improved as compared with the case where the light source is an infrared LED.
Therefore, in the infrared radiation element of the present invention, the power consumption of the infrared gas sensor can be reduced by narrowing the emission spectrum and narrowing the radiation angle distribution.

(Comparative Example 1)
In Example 1, except that no bandpass filter was formed, an infrared radiation element was produced in the same manner as in Example 1, and the radiation characteristic was measured. The results are shown in FIG.

(Example 3)
In Example 1, except that the structure of the bandpass filter was changed to the structure shown in Table 4 (total thickness: 2,201 nm), an infrared radiation element was produced in the same manner as in Example 1, and the radiation characteristics were measured. . The results are shown in FIG. The infrared radiation element had a Q value of 13.

  Comparing Examples 1 and 3, depending on the transmission characteristics of the bandpass filter, the Q value of the radiation characteristic of the infrared radiation element of Example 1 is more than the Q value of the radiation characteristic of the infrared radiation element of Example 3. Was also big.

DESCRIPTION OF SYMBOLS 1 Heat radiator 1A Radiator precursor 2 Reflective layer 3 Insulating layer 4 Heat generating body 5 Flattening layer 6 Band pass filter 7 Electrode 8 Support body 11 Mask layer 51 Infrared radiation element 52 Infrared detector 53 Measurement cell 53a Inlet 53b Outlet 101 Measurement Cell 102 Infrared light source 103 Band pass filter 104 Light receiving element 105 Infrared ray 106 Gas

Claims (14)

A heating element;
A radiator having a periodic fine structure on a surface opposite to the heating element side;
A planarizing layer having a flat surface opposite to the radiator side;
A bandpass filter formed on the planarizing layer in this order,
An infrared radiation element, wherein heat generated by the heating element is transmitted to the bandpass filter by heat conduction.   The infrared radiation element according to claim 1, wherein the band-pass filter is an alternately laminated body of a high refractive index layer and a low refractive index layer. The material of the high refractive index layer is one of Ge, PbTe, ZnSe, ZnS, Ta ₂ O ₅ , CeO ₂ , and Si;
The material of the low refractive index _{layer, BaF 2, LaF 2, NdF} 3, YF 3, SiO 2, SiO, and is either _Y 2 _{O 3,} the infrared radiation element according to claim 2.   The infrared radiation element according to any one of claims 1 to 3, wherein a material of the radiator is stainless steel.   The infrared radiation element according to any one of claims 1 to 4, wherein a material of the heating element is any one of tungsten, platinum, and a silicide alloy. The infrared radiation element according to claim 1, wherein the material of the planarizing layer is SiO ₂ .   The infrared radiation element according to claim 1, further comprising an insulating layer between the heat generator and the heat radiator. It is a manufacturing method of the infrared radiation element according to any one of claims 1 to 7,
In the radiator precursor in which a heating element is formed on one surface and a mask layer is formed on the other surface, the radiator precursor is irradiated to the mask layer on the other surface by laser irradiation and development. A pattern forming step for forming a pattern for forming a periodic fine structure in the body;
Etching the radiator precursor using the mask layer with the pattern formed as a mask to form a periodic microstructure on the other surface of the radiator precursor to obtain a radiator A process for producing an infrared radiation element.   The method of manufacturing an infrared radiation element according to claim 8, wherein the pattern is formed by a three-beam interference exposure method. A heating element forming step of forming a heating element on one surface of the radiator precursor;
A method for manufacturing an infrared radiation element according to claim 8, further comprising: a mask layer forming step of forming a mask layer on the other surface of the radiator precursor.   The manufacturing method of the infrared rays radiating element in any one of Claim 8 to 10 including the planarization layer formation process of forming a planarization layer by the sol-gel method on the other surface of the radiator from which the mask layer was removed.   The manufacturing method of the infrared radiation element in any one of Claim 8 to 11 including the band pass filter formation process which forms a band pass filter by a vapor deposition method on a planarization layer.   A gas analyzer comprising the infrared radiation element according to claim 1. Furthermore, it has a measurement cell into which the gas to be measured is introduced, and an infrared detector that detects infrared rays emitted from the infrared radiation element,
The infrared radiation element is provided at one end of the measurement cell,
The gas analyzer according to claim 13, wherein the infrared detector is provided at the other end of the measurement cell.