JP2016045080A - Light source and non-dispersive infrared analyzer type gas detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light source and a non-dispersive infrared analyzer type gas detector with the light source that can suppress generation of damage caused by stress due to temperature difference, while inhibiting reduction in the amount of infrared rays to be emitted to the outside.SOLUTION: A light source 11 of a non-dispersive infrared analyzer type gas detector 1 can inhibit reduction in the amount of infrared rays to be emitted to the outside since an infrared ray emitting layer 47 is deposited on a supporting layer 41 with its other surfaces being exposed to the outside. The light source 11 is formed of a heater wiring with spirally arranged heat-generating resistors 45, thereby having a temperature distribution with smaller temperature difference in a membrane region 51 than a comparison light source 111 with a comparison heat-generating resistor 145 and a plurality of heater wirings arranged in parallel and connected in series has. This configuration makes it possible to suppress damage on the infrared ray emitting layer 47 caused by stress due to temperature difference.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a light source that emits infrared rays and a non-dispersive infrared analytical gas detector that detects a specific gas contained in a measurement target gas.

A light source that emits infrared rays and a non-dispersive infrared analysis type (NDIR type) gas detector that detects a specific gas contained in a measurement target gas are known.
Examples of the light source that emits infrared rays include a substrate, a thin film portion provided on the substrate, a heat generating portion provided on the thin film portion that generates heat when energized, and a heat source provided on the thin film portion to receive heat from the heat generating portion. A light source including a radiation portion that emits infrared rays has been proposed (Patent Document 1).

The light source having such a configuration can obtain a high amount of light by radiating infrared rays from a radiation portion provided at the outermost part.
As another example of the light source, there is a configuration in which the radiating portion is arranged inside the thin film portion (insulating layer) (Patent Document 2). Further, the light source includes a plurality of filaments arranged in parallel as a heat generating portion.

In addition, as a use of the light source which radiates | emits infrared rays, the light source with which a non-dispersion type | mold infrared analytical gas detector is equipped is mentioned, for example.
The non-dispersive infrared analytical gas detector uses the characteristic that gas molecules absorb infrared rays of a specific wavelength, and it is specified by measuring the infrared intensity of this specific wavelength for the infrared rays that have passed through the measurement target gas. It detects gas. The non-dispersive infrared analytical gas detector includes a light source, a measurement cell (barrel), a wavelength selection filter (bandpass filter), and a light receiver (infrared sensor) (Patent Document 3).

Japanese Patent No. 4055697 Japanese Unexamined Patent Publication No. 09-184757 JP 2004-138499 A

  However, in the light source in which the radiating part is provided at the outermost part, the radiating part may be damaged due to stress generated due to the temperature distribution due to the heat generated by the heating element. That is, when the temperature difference in the temperature distribution becomes large, stress is generated inside the radiating portion, and the radiating portion and the thin film portion may be damaged by the stress.

  Note that if the radiating portion is a light source configured to be disposed inside the thin film portion (insulating layer), the radiating portion is covered with the thin film portion, so that damage to the radiating portion may be suppressed. However, the light source having such a configuration tends to reduce the amount of infrared rays emitted toward the outside as compared with the configuration in which the radiation portion is provided at the outermost part.

Patent Document 2 describes that a uniform temperature distribution can be obtained by gradually arranging a plurality of filaments arranged in parallel toward the edge of the silicon substrate.
However, in this configuration, there is a possibility that the temperature difference of the temperature distribution in the filament width direction (parallel arrangement direction) can be adjusted, but it is difficult to adjust the temperature difference of the temperature distribution in the longitudinal direction of the filament.

  Accordingly, the present invention provides a light source capable of suppressing damage due to stress caused by a temperature difference while suppressing a decrease in the amount of infrared radiation radiated outward, and a non-dispersive infrared analytical gas detector including such a light source. The purpose is to provide a vessel.

A light source according to one aspect of the present invention made to achieve the above object includes a substrate, a support layer, a heat generating unit, and a radiation unit, and emits infrared rays.
The substrate has a cavity that penetrates in the thickness direction.

The support layer is formed in a thin film shape that is stacked on one plate surface of the substrate and covers the cavity.
The heat generating part is provided in the membrane region of the support layer that overlaps the cavity, and generates heat when energized from the outside.

  When viewed along the thickness direction of the substrate, the radiating portion is stacked on the support layer in a region wider than the heat generating portion while overlapping at least the heat generating portion. Further, the radiating portion has a higher emissivity than the support layer, and radiates infrared rays when heated by the heat generating portion.

  When viewed along the thickness direction of the substrate, the heat generating portion is formed by the heater wiring arranged in a spiral shape, and the width dimension of the heater wiring becomes smaller from the center of the membrane region toward the periphery, The interval between the heater wires is reduced.

When viewed along the thickness direction of the substrate, the area of the heat generating portion is 50% or more with respect to the area of the membrane region.
First, since the radiating part is laminated on the support layer and the radiating part is arranged at the outermost part, the light source having such a configuration can suppress a reduction in the amount of infrared rays radiated outward. That is, it is possible to suppress a reduction in the amount of infrared rays radiated outward as compared to a configuration in which the radiating portion is disposed inside the insulating layer or the like.

  In addition, since the light source having such a configuration is formed by the heater wiring in which the heat generating portion is arranged in a spiral shape, a plurality of heater wirings arranged in parallel are connected in series as shown in the measurement results described later. The temperature difference in the temperature distribution in the membrane region is reduced as compared with the case where the heat generating portion having the configuration described above is provided.

  Furthermore, as the heater wire is configured such that the width of the heater wire is reduced and the distance between the heater wires is reduced from the center of the membrane region toward the outer peripheral edge, the heater wire at the center of the membrane region is configured. Is relatively lower than the density of the heater wiring at the periphery of the membrane region.

  Thereby, it is possible to suppress the temperature from becoming too low at the periphery of the membrane area where the temperature tends to be low while suppressing the temperature from becoming too high at the center of the membrane area where the temperature tends to be high. As a result, an increase in temperature difference in the temperature distribution in the membrane region can be suppressed.

  Thus, by suppressing that the temperature difference in temperature distribution becomes large, it can suppress that a stress generate | occur | produces inside a radiation | emission part, and can suppress that a radiation | emission part and a support layer are damaged by stress.

Therefore, according to the light source of the present invention, it is possible to suppress damage due to stress caused by a temperature difference while suppressing a decrease in the amount of infrared rays radiated outward.
Next, the non-dispersive infrared analytical gas detector according to another aspect of the present invention may include the above-described light source.

  Since this non-dispersive infrared analytical gas detector includes the above-mentioned light source as a light source, it suppresses a decrease in the amount of infrared rays emitted from the light source, while also suppressing a reduction in the amount of infrared rays emitted from the light source. And breakage of the support layer).

  The non-dispersive infrared analytical gas detector detects a specific gas contained in the measurement target gas, for example, a light source that emits infrared light, a measurement cell in which the measurement target gas is introduced, And an infrared sensor that outputs an infrared detection signal corresponding to the intensity of the reached infrared ray. And the infrared sensor is provided with the wavelength selection filter which permeate | transmits the infrared rays of a wavelength predetermined according to specific gas.

  In other words, in such a non-dispersive infrared analytical gas detector, sufficient infrared rays can be emitted from the light source to the infrared sensor, so that the infrared detection accuracy of the infrared sensor is improved and the detection accuracy of the specific gas is improved. improves. Moreover, since it can suppress that a light source breaks with the stress resulting from a temperature difference, the possibility of falling into a state where gas detection becomes impossible also as a non-dispersion type infrared analysis type gas detector can be reduced.

According to the light source of the present invention, it is possible to suppress damage due to stress due to a temperature difference while suppressing a decrease in the amount of infrared rays radiated outward.
Further, according to the non-dispersive infrared analytical gas detector of the present invention, it is possible to suppress the light source from being damaged due to the stress caused by the temperature difference, so that the possibility of falling into a state where gas detection is impossible can be reduced. .

It is sectional drawing which shows the internal structure of a non-dispersion type | mold infrared analysis type gas detector. It is a top view showing the light source of the state which permeate | transmitted the infrared radiation layer. It is sectional drawing showing the AA cross section in FIG. 2 of a light source. It is explanatory drawing which shows the test result of a 1st measurement test. It is a top view showing the comparative light source of the state which permeate | transmitted the infrared radiation layer. It is sectional drawing showing the BB view cross section in FIG. 5 of the light source for a comparison. It is a measurement result of the temperature distribution in the membrane area | region in CC cross section of a light source. It is a measurement result of the temperature distribution in the membrane area | region in the DD cross section of the light source for a comparison.

Embodiments to which the present invention is applied will be described below with reference to the drawings.
[1. First Embodiment]
[1-1. overall structure]
A light source 11 and a non-dispersive infrared analytical gas detector 1 to which the present invention is applied will be described with reference to the drawings.

FIG. 1 is a cross-sectional view showing the internal configuration of the non-dispersive infrared analytical gas detector 1 of the first embodiment.
In the non-dispersive infrared analytical gas detector 1 (hereinafter also simply referred to as a gas detector 1), the measurement target gas is human breath, and the specific gas to be detected is carbon dioxide (CO ₂ ). . That is, the gas detector 1 is used to detect carbon dioxide contained in a person's breath.

The gas detector 1 includes a light source 11, a measurement cell 13, an infrared sensor 15, and a cell heater 17.
The light source 11 emits light including infrared rays. Details of the light source 11 will be described later.

  The measurement cell 13 is a cylindrical member made of aluminum, and the light source 11 is disposed inside one end in the axial direction of the cylinder. The measurement cell 13 also serves as a lens barrel that delivers infrared rays emitted from the light source 11 to the infrared sensor 15.

  The measurement cell 13 introduces and discharges an inner wall surface 21 that reflects infrared rays radiated from the light source 11, a gas space 23 into which human exhalation is introduced, and a measurement target gas (human exhalation) into the gas space 23. Gas inlet / outlet portion 25. The inner wall surface 21 is made of aluminum.

  The infrared sensor 15 is disposed at the end of the measurement cell 13 opposite to the side where the light source 11 is disposed. The infrared sensor 15 is output from the light source 11 and passes through the gas space 23 of the measurement cell 13 or An infrared detection signal corresponding to the intensity of the infrared light that is reflected by the inner wall surface 21 of the measurement cell 13 and is reached is output.

  The infrared sensor 15 includes an infrared detection element 31, a pedestal 33, a cap 35, and two band-pass filters 37 and 38 (specifically, a detection filter 37 and a reference filter 38).

The infrared detection element 31 is a MEMS (microelectromechanical element type) thermopile, and outputs an infrared detection signal corresponding to the intensity of received infrared rays.
That is, in the infrared detecting element 31, the temperature of the detecting infrared absorbing layer (not shown) and the reference infrared absorbing layer (not shown) change depending on the intensity of the irradiated infrared rays, and a temperature difference ΔT is generated between them. Then, an electromotive force ΔV corresponding to the temperature difference ΔT is generated, and an infrared detection signal corresponding to the electromotive force ΔV is output from an electrode pad (not shown) to the outside.

  In the infrared sensor 15, infrared light that has passed through the detection filter 37 reaches the detection infrared absorption layer of the infrared detection element 31, and infrared light that has passed through the reference filter 38 reaches the reference infrared absorption layer of the infrared detection element 31. It is configured to

Here, the detection filter 37 is a bandpass filter that selectively transmits infrared light having a detection wavelength (4.3 [μm]), and infrared light having a wavelength of 4.3 [μm] is carbon dioxide (CO _2). ) Is absorbed. The reference filter 38 is a bandpass filter that selectively transmits infrared light having a reference wavelength (3.9 [μm]), and infrared light having a wavelength of 3.9 [μm] is not absorbed by gas. There are characteristics.

Therefore, it is possible to determine the CO ₂ concentration by detecting the temperature change state of the detection infrared absorption layer while using the temperature of the reference infrared absorption layer as a reference. In other words, the CO ₂ concentration can be determined based on the temperature difference between the detection infrared absorption layer and the reference infrared absorption layer.

  The pedestal 33 is a metal member that supports the infrared detection element 31. The pedestal 33 includes an insertion hole (not shown) for inserting the signal line 40 connected to the infrared detection element 31. An insulating material (not shown) is disposed on the inner wall of the insertion hole, and the insulating material electrically insulates the base 33 and the signal line 40.

  One end of the signal line 40 is electrically connected to the electrode pad of the infrared detection element 31 and the other end is electrically connected to an external device, thereby forming a signal path for outputting the infrared detection signal to the outside. To do. The signal line 40 is electrically connected to the electrode pad of the infrared detecting element 31 by bonding using a gold lead wire (not shown).

The infrared detection element 31 is fixed to a predetermined installation position on the pedestal 33 with an epoxy adhesive.
The cap 35 is a member that is made of a stainless alloy and forms an element arrangement space (not shown) that accommodates the infrared detection element 31 supported by the pedestal 33. The cap 35 is joined to the pedestal 33 by resistance welding to form an element arrangement space together with the pedestal 33. The cap 35 includes a first window (not shown) and a second window (not shown) for taking light into the element arrangement space from the outside.

  The detection filter 37 is fixed to the cap 35 with an epoxy adhesive so as to cover the first window portion of the cap 35, and the reference filter 38 is epoxy-based adhesive so as to cover the second window portion of the cap 35. It is fixed to the cap 35 with an agent. As described above, the infrared rays that have passed through the detection filter 37 (first window portion) reach the detection infrared absorption layer of the infrared detection element 31, and the infrared rays that have passed through the reference filter 38 (second window portion) The reference infrared absorption layer of the infrared detection element 31 is reached.

As shown in FIG. 1, the infrared sensor 15 having such a configuration is fixed to the end portion of the measurement cell 13 by an aluminum fixing jig 59.
The cell heater 17 is a silicon rubber heater and is disposed so as to surround the measurement cell 13. The cell heater 17 heats the measurement cell 13 at a specific control temperature set to 40 [° C.] or higher (in this embodiment, set to 50 [° C.]).

[1-2. light source]
Next, the light source 11 will be described.
FIG. 2 is a plan view illustrating the light source 11 in a state of being transmitted through the infrared radiation layer 47, and FIG. 3 is a cross-sectional view illustrating the light source 11 taken along the line AA in FIG.

As shown in FIGS. 2 and 3, the light source 11 includes a substrate 44, a support layer 41, a heating resistor 45, and an infrared radiation layer 47.
The substrate 44 is a silicon substrate, and includes a frame portion 44a that forms an outer peripheral portion of the substrate 44, and a hollow portion 44b that penetrates in the thickness direction of the substrate 44 while being surrounded by the frame portion 44a. Of the frame portion 44a, the inner wall surface 44c facing the cavity portion 44b is formed in a tapered shape that is inclined so that the opening area of the cavity portion 44b increases from the front surface 44d to the back surface 44e of the substrate 44.

The support layer 41 is a thin film-like member laminated on one plate surface (in the present embodiment, the surface 44d) of the substrate 44, and covers the opening of the cavity 44b that appears on the surface 44d. It is laminated on the frame part 44a). The support layer 41 has a two-layer structure of an upper support layer 41a and a lower support layer 41b, and is composed of an insulating layer such as silicon nitride (Si ₃ N ₄ ) or silicon oxide (SiO ₂ ).

  The heating resistor 45 is a heating resistor mainly composed of platinum (Pt), and is a region of the support layer 41 that overlaps the cavity 44b (hereinafter also referred to as a membrane region 51), and is connected to the upper support layer 41a and the lower layer. It arrange | positions between the side support layers 41b.

  As shown in FIG. 2, the heating resistor 45 is formed of heater wiring arranged in a spiral shape in the membrane region 51. The heating resistor 45 is configured so that the width of the heater wiring becomes smaller and the distance between the heater wirings becomes smaller from the center of the membrane region 51 toward the periphery.

  The ratio of the “formation region of the heating resistor 45” in the membrane region 51 is 71%. Note that the “formation region of the heating resistor 45” is the smallest rectangular region that can cover the entire heating resistor 45, and in the light source 11 shown in FIG. 2, the region surrounded by the sides X1 and X2. It corresponds to.

  The two end portions 45a of the heating resistor 45 are electrically connected to different contact pads 50 through lead portions 45b. The two contact pads 50 are formed so as to be exposed to the outside of the support layer 41, and are electrically connected to an external power source (not shown) to form a power supply path to the heating resistor 45. The two contact pads 50 are made of aluminum (Al) or gold (Au).

  The infrared radiation layer 47 is composed of silicon carbide (SiC) as a main component, and overlaps at least the heating resistor 45 and is wider than the heating resistor 45 when viewed along the thickness direction of the substrate 44. In FIG. The infrared radiation layer 47 is laminated on the support layer 41 so as to cover not only the region where the heating resistor 45 is disposed in the support layer 41 but also the entire membrane region 51.

  The infrared radiation layer 47 is made of a material having an emissivity higher than that of the support layer 41, and emits infrared light when heated by the heating resistor 45. Since the infrared radiation layer 47 is laminated on the support layer 41 in a state of being exposed to the outside without being covered by other members, the amount of infrared radiation radiated toward the outside is reduced as compared with the configuration covered by the other members. This can be suppressed.

  In the light source 11 having such a configuration, the membrane region 51 of the support layer 41 has a diaphragm structure, and the heating resistor 45 is disposed in the membrane region 51 so that the heating resistor 45 is thermally insulated from the surroundings. For this reason, the light source 11 can be heated in a short time by energizing the heating resistor 45 and can emit infrared rays from the infrared radiation layer 47 in a short time.

Further, since the light source 11 is laminated on the support layer 41 in a state where the infrared radiation layer 47 is exposed to the outside, it is possible to suppress a reduction in the amount of infrared radiation emitted toward the outside.
[1-3. Manufacturing method of light source]
Next, a method for manufacturing the light source 11 will be described.

First, in the first step, the silicon substrate 44 is cleaned. Specifically, a cleaning process is performed by immersing the substrate 44 having a thickness of 400 [μm] in a cleaning solution.
Next, in the second step, the lower support layer 41b is formed.

In the second step, a lower support layer 41b is formed by forming a film formed of silicon nitride (Si ₃ N ₄ ) on the cleaned surface 44d of the substrate 44 by a low pressure CVD method.
Next, in the third step, the heating resistor 45 and the lead portion 45b are formed.

  In the third step, first, a metal film such as platinum (Pt) is formed on the lower support layer 41b by sputtering. Thereafter, the resist is patterned by photolithography to form the heating resistor 45. At this time, the lead portion 45 b electrically connected to the heating resistor 45 is also patterned in the same manner as the heating resistor 45.

Next, in the fourth step, the upper support layer 41a is formed.
In the fourth step, a film formed of silicon nitride (Si ₃ N ₄ ) is formed by low-pressure CVD so that the film configuration in the vertical direction (stacking direction) is symmetric about the heating resistor 45. Thus, the upper support layer 41a is formed.

Next, in the fifth step, the contact pad 50 is formed.
In the fifth step, a metal film such as gold (Au) is formed by sputtering on the contact hole provided at a predetermined position above the lead portion 45b, and then patterned to form a metal material such as gold (Au). Two contact pads 50 are formed.

Next, in the sixth step, the infrared radiation layer 47 is formed.
In the sixth step, a predetermined shape of the surface of the upper support layer 41a is formed by screen printing using a paste containing a predetermined material (a material in which glass is mainly mixed with silicon carbide (SiC)). An infrared radiation layer 47 is formed.

  In addition, the formation method of the infrared radiation layer 47 is not limited to screen printing. Various methods suitable for the material constituting the infrared radiation layer 47 can be used. For example, the infrared radiation layer 47 may be formed by ink jet printing. Alternatively, the infrared radiation layer 47 can be formed by film formation by a CVD method and patterning by a photolithography process.

Next, in the seventh step, the cavity 44b is formed.
In the seventh step, first, a silicon nitride film 46 for an etching mask is formed on the entire lower surface of the substrate 44 by, eg, plasma CVD. Then, an opening is formed in the silicon nitride film 46 by photolithography. The size and position of the opening are determined according to the formation region of the membrane region 51.

  Thereafter, the substrate 44 is etched by anisotropic etching. This etching is performed until the lower support layer 41b provided on the upper surface of the substrate 44 is exposed, whereby a cavity 44b penetrating the substrate 44 in the plate thickness direction is formed. The cavity 44 b is formed in a portion of the substrate 44 corresponding to the membrane region 51.

Next, in the eighth step, the substrate 44 is cut.
In the eighth step, the substrate 44 is diced into chips using a dicing apparatus.
Through the above steps, the light source 11 having the heating resistor 45 formed of the heater wiring arranged in a spiral shape is completed.

  In the light source 11 thus completed, the heating resistor 45 generates heat by receiving external power supply through the contact pad 50, and when the infrared radiation layer 47 is heated by the heat, the infrared radiation layer 47 emits infrared rays. Is emitted.

[1-4. Gas detection]
The gas detector 1 having the above-described configuration introduces / exhales human exhalation (measurement target gas) into the gas space 23 of the measurement cell 13 via the gas inlet / outlet unit 25, and then converts the breath into the exhaled gas introduced into the gas space 23. The concentration of carbon dioxide (specific gas) contained is detected.

  That is, since the infrared rays emitted from the light source 11 are absorbed by carbon dioxide contained in the exhaled breath introduced into the gas space 23 of the measurement cell 13, the intensity of infrared rays reaching the infrared sensor 15 is equal to the concentration of carbon dioxide. Will change accordingly. And since the infrared detection signal output from the infrared sensor 15 (infrared detection element 31) changes according to the concentration of carbon dioxide, the concentration of carbon dioxide contained in human breath can be detected based on the infrared detection signal. . The infrared sensor 15 corresponds to the transmission center wavelength (4.3 [μm]) of the detection filter 37 based on the infrared rays corresponding to the transmission center wavelength (3.9 [μm]) of the reference filter 38. Detect infrared rays.

  In the gas detector 1, the cell heater 17 heats the measurement cell 13 and prevents the inner wall surface 21 of the measurement cell 13 from dew condensation, so that the infrared light emitted from the light source 11 is emitted from the inner wall surface of the measurement cell 13. The amount of attenuation at the time of reflection at 21 is reduced.

  As described above, since the infrared detection signal output from the infrared sensor 15 (infrared detection element 31) changes according to the concentration of carbon dioxide, the concentration of carbon dioxide contained in human breath based on the infrared detection signal. Can be detected.

  That is, in the gas detector 1, the infrared light emitted from the light source 11 passes through the measurement cell 13 and reaches the infrared sensor 15, and is based on the intensity of the infrared light received by the infrared detection element 31 of the infrared sensor 15. Detecting gas (carbon dioxide) corresponding to the infrared of the detection wavelength.

Therefore, by using this gas detector 1, it is possible to detect the concentration of carbon dioxide contained in human breath based on the infrared detection signal.
[1-5. Measurement test]
In the light source to which the present invention is applied, the test result of the first measurement test in which the relationship between the ratio of the region where the heating resistor 45 is formed to the membrane region 51 and the amount of infrared rays radiated will be described.

  Note that the “formation region of the heating resistor 45” is the smallest rectangular region that can cover the entire heating resistor 45, and in the light source 11 shown in FIG. 2, the region surrounded by the sides X1 and X2. It corresponds to.

  In this test, four types of light sources having different membrane area sizes were used. In each light source, the ratio of the area where the heating resistor 45 was formed to the membrane area 51, the amount of light (the amount of emitted infrared rays), and The relationship was measured. In addition, the dimension (DP size) of one side of the membrane region in the four types of light sources is 2.0 mm, 2.5 mm, 3.0 mm, and 4.0 mm, respectively.

  According to the measurement results shown in FIG. 4, all of the four types of light sources set the ratio of the formation region of the heating resistor 45 to the membrane region 51 to 50% or more, so that the heating resistor 45 to the membrane region 51 is set. It can be seen that the amount of light (the amount of infrared rays radiated) is increased as compared with the case where the ratio of the formation region is 30% or less.

In particular, it can be seen that if the ratio of the region where the heating resistor 45 is formed to the membrane region 51 is 60% or more, the amount of light (the amount of emitted infrared rays) increases significantly.
Therefore, according to the first measurement test, it can be seen that the reduction in the amount of infrared rays emitted from the light source toward the outside can be suppressed by setting the ratio of the region where the heating resistor 45 is formed to the membrane region 51 to 50% or more. .

  Next, the temperature distribution in the membrane region is measured for each of the light source to which the present invention is applied and the comparative light source in which the shape of the heating resistor (specifically, the heater wiring arrangement shape) is different from the present invention. The test results of the second measurement test will be described.

  The comparative light source 111 includes a substrate 44, a support layer 41, a comparative heating resistor 145, and an infrared radiation layer 47, as shown in FIGS. Among these, the configuration other than the comparative heating resistor 145 is the same as that of the light source 11 and is denoted by the same reference numeral.

  The comparative heating resistor 145 is a heating resistor mainly composed of platinum (Pt), and is configured by connecting a plurality of heater wires arranged in parallel in series. The two end portions 145a of the comparative heating resistor 145 are electrically connected to different contact pads 50 through lead portions 145b.

  FIG. 7 shows the measurement result of the temperature distribution in the membrane area in the CC section of the light source 11, and FIG. 8 shows the measurement result of the temperature distribution in the membrane area in the DD section of the comparative light source 111.

  In the light source 11, in the formation region of the heating resistor 45 (corresponding to the coordinate region of −800 to +800 [μm]), the minimum temperature is about 420 ° C. and the maximum temperature is about 460 ° C. The temperature difference is about 40 ° C., and the temperature difference of the temperature distribution is within a relatively small range (within 50 ° C.). When the temperature difference of the temperature distribution is within 50 ° C., the stress generated inside the infrared radiation layer 47 is suppressed to be small, and the damage of the infrared radiation layer 47 and the support layer 41 due to thermal stress can be suppressed.

  In the comparative light source 111, the minimum temperature is about 370 ° C. and the maximum temperature is about 500 ° C. in the region where the comparative heating resistor 145 is formed (corresponding to the coordinate region of −800 to +800 [μm]). The temperature difference of the temperature distribution is about 130 ° C., and the temperature difference of the temperature distribution is large (the temperature difference is 100 ° C. or more). When the temperature difference of the temperature distribution is 100 ° C. or more, the stress generated inside the infrared radiation layer 47 is increased, and the infrared radiation layer 47 and the support layer 41 are easily damaged by thermal stress.

  According to these measurement results, the light source 11 has a smaller temperature difference in the temperature distribution in the membrane region than the comparative light source 111, and the stress generated between the infrared radiation layer 47 and the support layer 41 can be suppressed to be small. Thus, it is possible to prevent the infrared radiation layer 47 from being damaged due to thermal stress. That is, by providing the heating resistor formed of the heater wiring arranged in a spiral shape, the membrane region is more than in the case of including the heating resistor having a configuration in which a plurality of heater wirings arranged in parallel are connected in series. The temperature difference of the temperature distribution in can be reduced, and the breakage of the infrared radiation layer due to thermal stress can be suppressed.

[1-6. effect]
As described above, the light source 11 provided in the non-dispersive infrared analytical gas detector 1 of the present embodiment includes the infrared radiation layer 47 laminated on the support layer 41.

The infrared radiation layer 47 is provided in a state of being exposed to the outside without being covered by other members, and radiates infrared rays by heating by the heating resistor 45.
Thus, since the infrared radiation layer 47 is laminated on the support layer 41 in a state of being exposed to the outside without being covered by another member, the infrared radiation radiated toward the outside as compared with the configuration covered by the other member. It can suppress that quantity falls.

Further, the light source 11 includes a heating resistor 45 formed by heater wiring arranged in a spiral shape.
The heating resistor 45 is disposed in the membrane region 51, and is configured such that the width dimension of the heater wiring is reduced and the interval between the heater wirings is reduced from the center of the membrane region 51 toward the periphery. Further, the ratio of the “formation region of the heating resistor 45” in the membrane region 51 is 71%.

  Since the light source 11 is formed by the heater wiring in which the heating resistor 45 is arranged in a spiral shape, as shown in the above measurement result, a plurality of heater wirings arranged in parallel are connected in series. The temperature difference in the temperature distribution in the membrane region 51 is smaller than that of the comparative light source 111 including the comparative heating resistor 145.

  Furthermore, as the heating resistor 45 is configured so that the width dimension of the heater wiring is reduced and the distance between the heater wirings is reduced from the center of the membrane area 51 toward the outer peripheral edge, the center of the membrane area 51 is configured. The density of the heater wiring in FIG. 2 is relatively lower than the density of the heater wiring in the periphery of the membrane region 51.

  Thereby, it is possible to suppress the temperature from being excessively low at the periphery of the membrane region 51, which tends to be low, while suppressing the temperature from being excessively high at the center of the membrane region 51, where the temperature is likely to be high. As a result, an increase in temperature difference in the temperature distribution in the membrane region 51 can be suppressed.

  By suppressing the temperature difference in the temperature distribution from increasing in this way, it is possible to suppress the generation of stress inside the infrared radiation layer 47 and to prevent the infrared radiation layer 47 and the support layer 41 from being damaged by the stress. Can be suppressed.

Therefore, according to the light source 11, the damage by the stress resulting from a temperature difference can be suppressed, suppressing the fall of the amount of infrared rays radiated | emitted toward the exterior.
The non-dispersive infrared analytical gas detector 1 including such a light source 11 suppresses a decrease in the amount of infrared rays emitted from the light source 11 and also suppresses a decrease in the amount of infrared rays emitted from the light source 11 (specifically, the infrared light source 11 Damage to the radiation layer 47) can be suppressed.

  In the non-dispersive infrared analytical gas detector 1, sufficient infrared rays can be emitted from the light source 11 to the infrared sensor 15, so that the infrared ray detection accuracy of the infrared sensor 15 is improved and a specific gas (dioxide dioxide) is obtained. Carbon) detection accuracy is improved. Further, since it is possible to suppress the light source 11 from being damaged by the stress due to the temperature difference, the possibility that the non-dispersive infrared analytical gas detector 1 is incapable of gas detection can be reduced.

[1-7. Correspondence with Claims]
Here, the correspondence of the words in the claims and the present embodiment will be described.
The light source 11 corresponds to an example of a light source, the substrate 44 corresponds to an example of a substrate, the support layer 41 corresponds to an example of a support layer, the heating resistor 45 corresponds to an example of a heat generating portion, and the infrared radiation layer 47 includes The non-dispersive infrared analytical gas detector 1 corresponds to an example of a radiation part, and corresponds to an example of a non-dispersive infrared analytical gas detector.

[2. Other Embodiments]
As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, it is possible to implement in various aspects.

  For example, in the above-described embodiment, as the heat generating portion (heat generating resistor) formed by the heater wiring arranged in a spiral shape, the heat generating portion in which three heater wirings are arranged from the center to the periphery of the membrane region has been described. The heat generating part is not limited to such a configuration. That is, the heat generating part may have a configuration in which four or more heater wires are arranged from the center to the periphery of the membrane region.

  In addition, the ratio of the heating resistor forming region in the membrane region is not limited to 71% as in the above embodiment, and if it is 50% or more, the amount of infrared radiation emitted from the radiation portion (infrared radiation layer) Can be suppressed.

  Further, the non-dispersive infrared analytical gas detector 1 is not limited to a gas detector for measuring carbon dioxide in exhaled breath, and other gas detectors can be detected by changing the detection wavelength of the detection filter. Can be used. For example, by using a band-pass filter that selectively transmits infrared light having a wavelength of 9.4 [μm] as the detection filter, the alcohol concentration in exhaled breath can be determined.

Next, in the above embodiment, the radiating portion (infrared radiating layer 47) has been described with silicon carbide (SiC) as the main component, but the radiating portion is limited to silicon carbide (SiC) as the main component. CuO (copper oxide), Fe ₂ O ₃ (iron oxide), blackened Pt (platinum black), blackened Au (gold black), C (carbon), etc. You may comprise as a component.

  DESCRIPTION OF SYMBOLS 1 ... Non-dispersion type infrared analytical gas detector (gas detector), 11 ... Light source, 13 ... Measurement cell, 15 ... Infrared sensor, 17 ... Cell heater, 41 ... Support layer, 41a ... Upper support layer, 41b ... Lower support layer, 44 ... substrate, 44a ... frame part, 44b ... hollow part, 44c ... inner wall surface, 44d ... front surface, 44e ... back surface, 45 ... heating resistor, 45a ... end part, 45b ... lead part, 46 ... Silicon nitride film, 47 ... infrared radiation layer, 50 ... contact pad, 51 ... membrane region.

Claims (2)

A light source that emits infrared light,
A substrate having a hollow portion penetrating in the thickness direction;
A thin film-like support layer laminated on one plate surface of the substrate and covering the cavity,
Provided in the membrane region that overlaps the cavity portion of the support layer, a heat generating portion that generates heat by energization from the outside,
When viewed along the plate thickness direction of the substrate, it is stacked on the support layer in a region wider than the heat generating part while overlapping at least the heat generating part, and has a higher emissivity than the support layer, A radiating portion that radiates the infrared rays by heating by the heat generating portion;
With
When viewed along the thickness direction of the substrate,
The heat generating portion is formed of a heater wiring arranged in a spiral shape, and the width dimension of the heater wiring is reduced and the interval between the heater wirings is reduced from the center to the periphery of the membrane region. It is configured as
The area of the heat generating part is 50% or more with respect to the area of the membrane region,
A light source characterized by   A non-dispersive infrared analytical gas detector comprising the light source according to claim 1.