JP2015050001A - Near-infrared heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heater comprising a filament capable of efficiently converting electric power to near-infrared light that is not absorbed into glass.SOLUTION: A provided near-infrared heater includes an airtight container 2, and a filament 3 that is arranged within the airtight container 2. The airtight container 2 is made of at least a material that allows transmission of near-infrared light with a wavelength of less than 2 μm and visible light and that absorbs infrared light with a wavelength of 2 μm or more. The filament 3 comprises an infrared light suppression structure that suppresses radiation of the infrared light.

Description

  The present invention relates to a near-infrared heater with improved energy utilization efficiency, and more particularly to a light source using a filament and a thermionic emission source.

  2. Description of the Related Art A heater that heats a filament by passing a current through a W filament or the like and uses emitted infrared light as heat is widely used. Although the conversion efficiency from electric power to light by the filament of the infrared heater is as high as 90% or more, the glass material for sealing the filament shows a transmission spectrum as shown in FIG. Absorbs light components. For this reason, the proportion of infrared light that can actually be used as a heater is low. Specifically, for example, as shown in FIG. 2, the infrared radiation component having a wavelength of 2 μm or more is present at 70% or more at a temperature of 1500 K with respect to the entire black body radiation energy. Since most of the infrared radiation component having a wavelength of 2 μm or more is absorbed by the glass, the heater efficiency is deteriorated, and at the same time, the glass is heated by absorbing the long wavelength infrared light, and the temperature is close to 1000K. In some cases, safety measures are necessary.

  In Patent Documents 1 and 2, an inert gas or a halogen gas is sealed inside a light bulb to increase the filament temperature, shorten the radiation spectrum, and reduce the emission of infrared light having a wavelength of 2 μm or more. Attempts to extend filament life have been disclosed. In this configuration, it is important to control the components of the sealed gas and the pressure in order to increase the efficiency and extend the life.

  Patent Documents 3 to 5 disclose a configuration in which an infrared reflection coating is applied to the surface of a bulb glass so that infrared light emitted from the filament is reflected, returned to the filament, and absorbed. By using this technique, infrared light having a wavelength of 2 μm or more can be used for reheating the filament.

  Patent Documents 6 to 9 propose a configuration in which a fine structure is produced in the filament itself, and infrared radiation is suppressed and the proportion of visible light radiation is increased by the physical effect of the fine structure.

JP-A-60-253146 Japanese Patent Laid-Open No. 62-10854 JP 59-58752 A JP-T 62-501109 JP 2000-123795 A JP 2001-519079 JP-A-6-5263 JP-A-6-2167 JP 2006-205332 A

F. Kusunoki et al., Jpn. J. Appl. Phys. 43, 8A, 5253 (2004).

  However, the technologies using the halogen cycle as in Patent Documents 1 and 2 can achieve a life extension effect, but it is difficult to greatly improve the conversion efficiency, and the efficiency is only improved by about 10% at present.

  In addition, as in Patent Documents 3 to 5, the technology of reflecting infrared radiation with an infrared reflecting coat and reabsorbing the filament to the filament is highly effective in reabsorption because the reflectance of infrared light by the filament is as high as 70%. It does n’t happen well. Further, the infrared light reflected by the infrared reflective coating is absorbed by other parts other than the filament, such as the filament holding part and the base, and is not used for heating the filament. For this reason, it is difficult to greatly improve the conversion efficiency by this technology.

  As described in Patent Documents 6 to 9, a technique for suppressing the infrared radiation by the fine structure is a report showing the radiation enhancement and the suppression effect for the wavelength of the extreme part of the infrared radiation spectrum as in Non-Patent Document 1. However, it is very difficult to suppress infrared radiation over a wide range of infrared light. This is because when one wavelength is suppressed, another wavelength is enhanced. For this reason, it is considered difficult to achieve significant efficiency improvements using this technology. In addition, since a fine microfabrication technique such as electron beam lithography is used for producing a fine structure, a light source using this is very expensive. Furthermore, even if a microstructure is formed on the W substrate, which is a high temperature heat-resistant member, the W substrate surface particles are recrystallized and crystal grains grow at a heating temperature of about 1000 ° C., and the microstructure portion is destroyed due to this recrystallization. There is also the problem of being done.

  The objective of this invention is providing the heater provided with the filament which can convert electric power into the near infrared light which is not absorbed by glass efficiently.

  In order to achieve the above object, the present invention provides a near-infrared heater having an airtight container and a filament disposed in the airtight container. The hermetic container is made of a material that transmits at least near infrared light and visible light having a wavelength of less than 2 μm and absorbs infrared light having a wavelength of 2 μm or more. The filament includes an infrared light suppressing structure that suppresses infrared light emission.

  According to the present invention, radiation of infrared light from the filament can be suppressed by the infrared light suppression structure, so that power can be efficiently converted to near infrared light. Since near-infrared light is not absorbed by the airtight container, a near-infrared heater with high energy conversion efficiency can be obtained.

The graph which shows the transmission spectrum of hard glass and quartz glass. Explanatory drawing which shows a black body radiation energy (A), the infrared energy (B) among which the wavelength is 2 μm or more, and the ratio (B / A) in a tabular form. Sectional drawing of the near-infrared heater of this invention. The graph which shows the ideal reflectance of the filament of this invention, the emissivity, a radiation spectrum, and the relationship of glass absorption. The graph which shows the reflectance, emissivity, and radiation spectrum of W filament of a sand surface structure. The graph which shows the reflectance, emissivity, and radiation spectrum of W filament 3 after the mirror polishing of Embodiment 1. FIG. The graph which shows the reflectance, emissivity, and radiation spectrum of W filament 3 which provided the TaC layer of Embodiment 2 on the surface. (A)-(d) Explanatory drawing which shows the manufacturing process of the filament of Embodiment 2. FIG. (A)-(c) Explanatory drawing which shows another manufacturing process of the filament of Embodiment 2. FIG. The graph which shows the reflectance of the W filament 3 provided with the visible light reflectance fall film | membrane of Embodiment 3, an emissivity, and an emission spectrum. The graph which shows the relationship between the film thickness of the visible light reflectance fall film | membrane (YSH) of the W filament 3 provided with the visible light reflectance fall film | membrane of Embodiment 3, and radiation efficiency. Sectional drawing which shows the structure of the infrared-light reflection film of Embodiment 4. The graph which shows the reflectance of the W filament 3 provided with the infrared light reflection film of Embodiment 4, an emissivity, and an emission spectrum. 6 is an electron micrograph of a white scatterer of Embodiment 5. FIG. The graph which shows the reflectance, emissivity, and radiation spectrum of W filament 3 provided with the white scatterer of Embodiment 5 (absorptive materials, such as visible light). The graph which shows the reflectance of a W filament 3, an emissivity, and an emission spectrum. The graph which shows the reflectance, emissivity, and radiation spectrum of W filament 3 provided with the white scatterer of Embodiment 5 (absorbing material addition of visible light and near-infrared light). Sectional drawing of the near-infrared heater of the linear structure of Embodiment 5. FIG.

  An embodiment of the present invention will be described.

  As shown in FIG. 3, the near-infrared heater of the present invention has an airtight container 2 and a filament 3 disposed in the airtight container 2, and emits near-infrared light. The hermetic container 2 is made of a material that transmits at least near-infrared light and visible light having a wavelength of less than 2 μm and absorbs infrared light having a wavelength of 2 μm or more. The filament 3 has an infrared light suppression structure that suppresses infrared radiation. Since the infrared light radiation of the filament 3 is suppressed by the infrared light suppression structure, the power supplied to the filament 3 can be efficiently converted into near infrared light. Since near-infrared light can be transmitted through the hermetic container 2, the near-infrared light is efficiently radiated to the outside and is not absorbed by the hermetic container 2.

  The hermetic container 2 is preferably made of quartz glass, silicate glass, borosilicate glass, phosphate glass, Pyrex (registered trademark) glass, or BK7 glass. These glasses transmit near infrared light and visible light having a wavelength of less than 2 μm.

  The filament 3 can be configured to have a mirror-finished surface as an infrared light suppressing structure. Filaments with a mirror-finished surface have low reflectance in the visible and near-infrared light regions and high in the infrared light region, so that infrared radiation is suppressed, and visible and near-infrared light is suppressed. The radiation efficiency is increased. The principle that the emission of infrared light is suppressed when the reflectance of the filament is low in the visible light region and near infrared light region and high in the infrared light region will be described in detail later. The surface roughness preferably satisfies at least one of a center line average roughness Ra of 1 μm or less, a maximum height Rmax of 10 μm or less, and a ten-point average roughness Rz of 10 μm or less.

  Further, the filament 3 can be configured to have a TaC layer or an HfC layer on the outermost surface as an infrared light suppressing structure. TaC and HfC have a high melting point, can be heated to a high temperature, have a radiation characteristic that radiation in the infrared wavelength region is suppressed, and radiation in the visible light region and near infrared light region is large. Therefore, the filament 3 of this embodiment provided with the TaC layer or the HfC layer on the surface can improve the radiation efficiency of near infrared light. That is, the efficiency of near-infrared light conversion can be increased by enabling high-efficiency by shortening the wavelength of radiation itself by high-temperature heating of the filament 3 and enabling thermal radiation with suppressed infrared radiation of TaC itself. . In addition, by using W or Ta as the core material of the filament 3, it is possible to relatively easily manufacture a filament having TaC which is difficult to process on the surface.

  The filament 3 includes a base formed of a metal and a visible light reflectivity lowering film that covers the base as an infrared light suppressing structure and reduces the reflectivity in the visible light region and the near infrared light region of the base. It is possible to configure. Thereby, since the reflectance of the filament 3 can be lowered by visible light and increased by infrared light, the emission of infrared light is suppressed, and the radiation efficiency of near infrared light can be increased. In this case, the film thickness of the visible light reflectance lowering film is such that the visible light and near infrared light reflected by the surface of the visible light reflectance lowering film interfere with the visible light and near infrared light reflected by the substrate, and the film thickness is reduced. By setting so as to reduce the reflectance, the reflectance of visible light and near-infrared light can be reduced using interference.

Moreover, the filament 3 can be configured to include a base formed of metal and an infrared light reflection film that covers the base as an infrared light suppressing structure. Thereby, since the reflectance of a filament can be raised in an infrared light area | region, radiation | emission of infrared light is suppressed and the radiation efficiency of near-infrared light can be improved. The infrared light reflecting film is made of a material that transmits infrared light, and can include a set of first and second layers stacked. The first layer, the refractive index _{n 1,} a thickness _{d 1,} the second layer, the refractive index _{n 2,} when the thickness _{d 2,} n ₁ · with respect to a predetermined wavelength lambda ₁ of the infrared light _{d 1 = n 2 · d 2} = λ 1/4
To satisfy the relationship. As a result, infrared light having a predetermined wavelength λ ₁ can be reflected.

  Moreover, the filament 3 can be made into the structure which has the base material formed with the metal, and the white scatterer layer which coat | covers a base | substrate as an infrared-light suppression structure. A visible light absorbing material that absorbs near-infrared light and light in the visible light region is added to the white scatterer layer. Thereby, the reflectance of the filament 3 is increased in a wide wavelength range of the infrared light region and the visible light region due to the characteristics of the white scatterer, and in the visible light region and the near infrared light region due to the characteristics of the visible light absorber. Can be reduced. Therefore, it is possible to suppress the emission of infrared light and increase the emission of near infrared light. As the visible light absorber, either an impurity element or a metal particle doped in a white scatterer can be used.

  Due to the infrared light suppression structure, the filament 3 has a reflectance of at least part of the visible light region and the near infrared light region of 40% or less and a reflectance of at least part of the infrared light region of 80% or more. It is desirable.

  Next, the principle that the filament of the present invention has a high reflectance in the infrared light region and low in the visible light region and the near infrared light region can emit visible light with high efficiency will be described with reference to the drawings.

  Ideally, the filament 3 of the present invention has a reflectance close to 100% in an infrared light region having a wavelength of 2 μm or more as shown by a solid line in FIG. In the visible light region, it is desirable that the reflectance is reduced and the material has a reflectance close to 0%. The principle that the filament 3 emits visible light and near-infrared light with high efficiency when heated by current supply or the like will be described below based on Kirchhoff's law in blackbody radiation.

The energy loss with respect to the input energy of the material (here, the filament) under conditions without natural convection heat transfer (for example, in a vacuum) is given by the following equation (1) in an equilibrium state.
(Equation 1)
P (total) = P (conduction) + P (radiation) (1)
Where P (total) is the total input energy, P (conduction) is the energy lost through the lead that supplies current to the filament, and P (radiation) is the temperature at which the filament is heated It is the energy lost by radiating light.

  The important point here is that when the substrate temperature is higher than 2500K, the energy lost from the filament 3 through the lead wire is only about 5%, and the remaining 95% or more is externally emitted by light radiation. Because energy is lost, almost all of the input power can be replaced by light. However, among the radiation shown by the heated filament 3, the long wavelength infrared light region of 2 μm or longer where the absorption of the hermetic container 2 becomes significant depends on the filament heating temperature, but a considerable proportion as shown in FIG. Therefore, it is not an efficient infrared light source as it is.

By the way, the term of P (radiation) in the equation (1) can be generally described by the following equation (2).
In equation (2), ε (λ) represents the emissivity at each wavelength, and the term αλ ⁻⁵ / (exp (β / λT) −1) represents Planck's radiation law. α = 3.747 × 10 ⁸ W μm ⁴ / m ² and β = 1.4387 × 10 ⁴ μmK. Also, ε (λ) has a relationship of the reflectance R (λ) and the equation (3) according to Kirchhoff's law.
(Equation 3)
ε (λ) = 1−R (λ) (3)

  When the equations (2) and (3) are discussed in association, a material whose reflectance is 1 over all wavelengths is ε (λ) = 0 from the equation (3), and hence the equation (2). Since the integral value at becomes zero, no loss due to radiation occurs. This physical meaning means that since P (total) = P (conduction), there is no loss due to light emission even with a small amount of input energy, and the filament reaches a very high temperature. On the other hand, a material having a reflectance of 0 over all wavelengths is called a complete black body, and ε (λ) = 1 from equation (3). As a result, the integral value in the equation (2) is maximized, and consequently the amount of loss due to radiation is maximized. In ordinary materials, the emissivity ε (λ) exists between 0 <ε (λ) <1, and the wavelength dependence thereof does not change dramatically (wavelength λ, slowness with respect to temperature T). There is a major dependency). Therefore, light emission in the infrared to visible region occurs uniformly from substantially visible to the infrared region as shown by the two-dot chain line in FIG. In FIG. 4, the black body radiation spectrum is plotted with ε (λ) = 1 in the entire wavelength region in order to simplify the discussion.

On the other hand, as shown by a one-dot chain line in FIG. 4, for example, a material having an emissivity of approximately 0% in a long wavelength infrared region of 2 μm or more and an emissivity of approximately 100% in a shorter wavelength region. The heat radiation heated in vacuum can be expressed by the following equation (4).

In equation (4), θ (λ−λ ₀ ) has an emissivity of ₀ from a long wavelength to a wavelength λ ₀ of infrared light, and an emissivity of 1 in a region shorter than a certain wavelength λ _0. It is a function that shows the step function behavior. The obtained radiation spectrum has a shape obtained by convolving the stepwise emissivity and the blackbody radiation spectrum, and the calculation result is a spectrum indicated by a broken line in FIG. In other words, the physical meaning of equation (4) is that the radiation loss is suppressed in the low temperature region where the input energy to the filament is small, and the P (radiation) term of equation (4) is 0, so the energy loss is Only the P (conduction), and the filament temperature rises very efficiently. On the other hand, the filament temperature is a high temperature, the peak wavelength of black-body radiation spectrum is a temperature region as shorter than lambda _0, visible and near-like spectrum shown the energy input to the filament by a broken line in FIG. 4 Loss as infrared radiation.

  Therefore, by utilizing the above principle and providing an infrared light suppressing structure in the filament, long wavelength infrared light having a wavelength of 2 μm or more is suppressed, and near infrared light and visible light shorter than this are efficiently emitted. Can do.

(Embodiment 1) Mirror surface processing In Embodiment 1, the filament 3 which has the surface processed into the mirror surface as an infrared-light suppression structure is demonstrated.

  A tungsten filament manufactured by a general manufacturing method has a sand surface structure. The reflectance of the tungsten filament whose surface is sand is as shown in FIG. On the other hand, when the surface of the tungsten filament is mirror-polished with a plurality of kinds of diamond abrasive grains, as shown in FIG. 6, the reflectivity is higher in the infrared region having a wavelength of 2 μm or more than the filament having the sand surface structure of FIG. growing.

  Thereby, the mirror-polished tungsten filament 3 has a lower emissivity (emissivity = 1) than the emissivity of the filament having the sand surface structure shown in FIG. 5 in the long wavelength infrared region of 2 μm or more as shown in FIG. -Reflectivity) can be obtained.

  Substituting the emissivity of the mirror-polished tungsten filament 3 into the formula (2) to obtain the radiation efficiency of visible light and near-infrared light of less than 2 μm, the efficiency is 1.2 times that of the filament having the sand surface structure. I can do it. The reason for this is that by making the filament a mirror surface, the reflectivity increases (the emissivity decreases), and it becomes possible to suppress long-wavelength infrared radiation due to heating of the filament according to the rate of increase in reflectivity. Because. This is because much of the energy input to the filament 3 can be converted into near-infrared light and visible light components having a wavelength of less than 2 μm as shown in FIG.

  The mirror polishing is desirably performed so that the surface roughness satisfies at least one of a center line average roughness Ra of 1 μm or less, a maximum height Rmax of 10 μm or less, and a ten-point average roughness Rz of 10 μm or less. Thereby, the reflectance at a wavelength of 2 μm can be a value exceeding 0.9. By setting the roughness after polishing to λ / 4 (wavelength λ = 632.8 nm) or less, the maximum reflectance can be reduced to about 0.98, and near infrared light and visible light of less than 2 μm The radiation efficiency can be increased to 1.2 times or more. Since the reflectance of the long-wavelength infrared light is higher than the reflectance of the near-infrared light by mirror polishing, high radiation controllability (suppression of long-wavelength infrared light) is obtained.

  5 and 6 show the radiation efficiency at a filament temperature of 3000 K. When the filament temperature is lower than 3000 K, the effect of mirror polishing is more prominent.

  In the above description, the case where the filament 3 is a tungsten wire has been described as an example. However, the technique of the present embodiment can be applied to various metal filaments regardless of this. For example, molybdenum wire, constantan wire, tantalum wire, rhenium wire, niobium wire, iridium wire, osmium wire, chromium wire, zirconium wire, platinum wire, vanadium wire, ruthenium wire, rhodium wire, iron wire, stainless steel wire, and alloys thereof Etc. are applicable.

  In this embodiment, the reflectance of the filament surface is improved by mechanical polishing. However, the present invention is not limited to mechanical polishing, and other methods can be used as long as the reflectance of the filament surface can be improved. is there. For example, wet or dry etching, a method of contacting a smooth die during drawing, forging or rolling can be employed.

(Embodiment 2) TaC layer or HfC layer In Embodiment 2, a filament 3 having a TaC layer or HfC layer on the outermost surface as an infrared light suppressing structure will be described. TaC and HfC have a melting point temperature exceeding 4000 K and can be heated to a high temperature, and as illustrated in the radiation spectrum of TaC in FIG. 7, the emission in the infrared wavelength region is suppressed, and the visible light region and the near infrared region are suppressed. The radiation characteristic is that radiation in the optical region is large. Therefore, the filament 3 of this embodiment provided with a TaC layer or an HfC layer on the surface can enhance near infrared light emission. That is, it is possible to achieve high efficiency by shortening the wavelength of the radiation itself by heating the filament 3 at an extremely high temperature, and the radiation controllability possessed by TaC and HfC itself (allowing for thermal radiation while suppressing long wavelength infrared radiation). It is possible to produce a highly efficient infrared light source. Specifically, when a TaC single filament coil is heated to 4000 K, as shown in FIG. 7, it is possible to obtain a radiation spectrum that is not absorbed by the airtight container 2 (glass material) having an absorption characteristic at a wavelength of 2 μm or more. It becomes. Thereby, the efficiency twice as high as the present halogen heater can be obtained.

Next, the manufacturing method of the filament 3 provided with the TaC layer on the surface will be described with reference to FIGS. Since TaC is hard and brittle, it is difficult to wind TaC into a filament shape. Thus, the filament 3 having a TaC layer on the surface is manufactured using W as a core material in the following steps. First, as shown in FIG. 8A, a W-shaped W base material 30 is prepared and placed in a vacuum chamber, heated in a vacuum at 1500 to 2000 ° C., and attached to the surface of the W base material 30. The oxide film such as ₂ is removed. When the W base material 30 is heated, the thermal spectrum radiated from the surface of the W base material 30 is measured by a radiation thermometer, and the temperature of the surface of the W base material 30 is evaluated, so that all oxide films such as WO ₂ are formed. You can check if it has been removed. Specifically, the oxide film such as WO ₂ exhibits a lower temperature than the actual temperature of the W base material 30, but the surface oxide film is all removed by heating, and the W metal of the W base material 30 is exposed. Then, the surface of the W base material 30 becomes high temperature. By observing this, it can be confirmed that all of the oxide film has been removed.

  Next, using a technique such as electron beam vapor deposition or sputtering vapor deposition, a Ta metal is deposited to a thickness of 0.1 to 10 μm on the surface of the W substrate 30 to form a Ta layer 31 (FIG. 8B).

  Next, as shown in FIG. 8C, the W base material 30 on which the Ta layer 31 is formed is wound in a coil shape. Since the TaC layer 32 formed in the subsequent process is hard and brittle, the TaC layer 32 can be prevented from being cracked or peeled off by being processed into a coil before the carbonization process. Note that the W base material 30 may be wound in a coil shape before the step of forming the Ta layer 31 (FIG. 8B), and then the Ta layer 31 may be formed.

  In order to remove an oxide film such as TaO on the surface of the Ta layer 31, the W substrate 30 provided with the Ta layer 31 is placed in a vacuum chamber and heated again at 1500 to 2000 ° C. in vacuum. Thereby, an oxide film such as TaO attached to the surface of the Ta layer 31 can be removed and the Ta layer 31 can be exposed. Even during this heating, it is possible to confirm whether or not all the oxide film has been removed by measuring the surface temperature of the Ta layer 31 with a radiation thermometer.

  In succession to the oxide film removal step, the TaC layer is formed by carbonizing the surface of the Ta layer 31 as shown in FIG. Carbonization is performed by introducing a carbon source such as methane gas or ethane gas into the vacuum chamber at a temperature of 1200 to 2000 ° C. Thereby, carbon is infiltrated from the surface of the Ta layer 31 (carburizing treatment), and the surface layer of the Ta layer 31 is changed to the hydrocarbon layer 32. At this time, the degree of carbonization in the film thickness direction can be controlled by controlling the time of the carburizing treatment. Thereby, for example, the TaC layer 32 whose outermost surface is TaC and whose degree of carbonization is gradually reduced in the film thickness direction can be formed. Thus, by forming the TaC layer 32 in which the carbon concentration is distributed in the film thickness direction, the problem of causing delamination between the TaC layer 32 and the Ta layer 31 due to the thermal stress due to the difference in thermal expansion coefficient is avoided. I can do it.

  Further, in the process of FIG. 8B, the above process can also form Ta (x) Hf (y) C filaments by co-evaporating Ta and Hf metals. Ta (x) Hf (y) C is known to have the highest melting point (about 4500 K) in nature, and can form a filament that can be heated at a high temperature.

  Further, as shown in FIGS. 9A to 9C, a wire-like substrate 130 of Ta (melting point 3300 K) having a melting point similar to W (melting point 3660 K) is prepared as shown in FIG. 9A. Then, after removing the oxide film by the same process as described above, the coil is wound into a coil shape as shown in FIG. 9B, and then the step of FIG. 8D is performed as shown in FIG. Layer 32 is formed. At this time, a Ta 2 C layer 131 is formed between the TaC layer 32 and the Ta base material 130. Further, by taking a sufficiently long carburizing time (for example, at 2000 ° C., the formation of TaC is 20 μm / h), the entire Ta substrate 130 can be formed into a TaC coil.

  8 and 9, by using Hf instead of Ta, a filament having an HfC layer on the surface can be similarly produced.

In the above embodiment, TaC and HfC have been described as examples. However, various metal compounds can be disposed on the surface layer of the filament regardless of this. For example, high temperature heat resistant alloys such as B ₄ C, SiC, ZrC, AlN, BN, ZrN, HfN, TiN, LaB ₆ , ZrB ₂ , HfB ₂ , etc. can be used.

(Embodiment 3) Visible light reflectance lowering film In Embodiment 3, a base is covered as an infrared light suppression structure, and a visible light reflectance lowering film that lowers the reflectance in the visible light region and the near infrared light region of the base. FIG. 10 and FIG. 11 are described about the filament 3 provided with.

The filament 3 includes a W substrate or a W wire as a base and a low refractive index material as a visible light reflectance lowering film thereon. As the low refractive index material, for example, a YSH (Yttria Stabilized Hafnia) thin film in which Y ₂ O ₃ is mixed with HfO ₂ at a ratio of several mol% to several tens mol% is used. As a result, the reflected light of the visible light and near infrared light from the surface of the visible light reflectance lowering film interferes with the reflected light of the visible light and near infrared light from the W substrate to cancel each other. Reduce the reflectance in the infrared region. Thereby, the filament 3 which has a reflectance characteristic as shown in FIG. 10 at the temperature of 2500K can be obtained.

  A method for manufacturing the filament 3 will be described. First, the W substrate is mirror-polished. The degree of mirror polishing is a mirror surface satisfying at least one of centerline average roughness (Ra) 1 μm or less, maximum height (Rmax) 10 μm or less, and ten-point average roughness (Rz) 10 μm or less. The reason is as described in the first embodiment.

  Next, a YSH film of about 50 nm is coated on the mirror-polished W substrate. The coating thickness of this film has an allowable range, and is set to 0 nm or more and 80 nm or less as shown in FIG. By setting within this range, the radiation efficiency can be increased more than the radiation efficiency of the substrate itself. As the film forming method, various methods such as an electron beam evaporation method, a sputtering method, and a CVD method can be used. After the film formation, an annealing treatment is performed in a temperature range of 1500 ° C. to 2500 ° C. in order to improve adhesion with the W substrate interface and film quality (crystallinity, optical characteristics, etc.).

  By heating the manufactured filament 3, the reflectance characteristic (2500 K) as shown in FIG. 10 is exhibited, long wavelength infrared radiation of 2 μm or more is suppressed, and near infrared light and visible light of less than 2 μm are enhanced. Can radiate with efficiency.

The YSH film was selected as the visible light reflectance lowering film in the third embodiment. This is because the optical phase (refractive index and extinction) of the crystal phase of the dielectric thin film layer due to high-temperature heating, and consequently the crystal phase change. The rapid change in the attenuation coefficient) can be suppressed. For example, in the case of HfO ₂ alone, the phase changes from monoclinic to tetragonal at a temperature of 1600 ° C. and from tetragonal to cubic at a temperature of 2100 ° C., but 2-30 mol% of a stabilizer such as Y ₂ O _{3 is} added. By stabilizing in this way, a dielectric thin film layer that does not change in phase from room temperature to a temperature range of 2800 ° C. (cubic) can be obtained.

In addition to the YSH thin film, any one of a metal film having a melting point of 2000K or higher, a metal carbide film, a nitride film, a boride film, or an oxide film can be used as the visible light reflectance lowering film. It is. For example, Ta, Os, Ir, Mo, Re, W, Ru, Nb, Cr, Zr, V, Rh, C, B ₄ C, SiC, ZrC, TaC, HfC, AlN, BN, TiN, ZrN, HfN, LaB ₆ , ZrB ₂ , HfB ₂ , CaO, CeO ₂ , MgO, ZrO ₂ , Y ₂ O ₃ , HfO ₂ , Lu ₂ O ₃ , Yb ₂ O ₃ , ThO ₂ , GaN or a mixture thereof The formed film can be used.

  As a method for forming the visible light reflectance lowering film, various methods can be used in addition to the above-described vapor phase growth method. For example, for GaN, SiC, etc., a high-quality substrate already exists, so GaN on a sapphire substrate grown to a desired thickness or SiC on a Si substrate is metal bonded to a W substrate, It is also possible to adopt a smart cut method in which these substrates are lifted off by etching or ion implantation.

(Embodiment 4) Infrared-light-reflecting film As Embodiment 4, the filament 3 provided with the base | substrate formed with the metal and the infrared-light reflecting film which coat | covers a base | substrate as an infrared-light suppression structure is demonstrated.
The infrared light reflection film is disposed to reflect long wavelength infrared light of 2 μm or more. The infrared light reflection film 20 is disposed to reflect infrared light. As shown in FIG. 12, each of the infrared light reflection films 20 includes a set of a first layer 21 and a second layer 22 each made of a material that transmits infrared light, for example, a high heat resistant dielectric layer. Includes at least one pair. A predetermined wavelength λ (2 μm or more) of infrared light, where n _{1 is} the refractive index of the first layer 21, d _{1 is} the thickness, n _{2 is} the refractive index of the second layer 22, and d ₂ is the thickness. In contrast, Expression (5) is satisfied.
(Equation 5)
n ₁ · d ₁ = n ₂ · d ₂ = λ / 4 (5)

By laminating the two types of layers 21 and 22 having different refractive indexes in this way, the reflectance of infrared light in a predetermined wavelength range having a predetermined wavelength λ ₁ as a central wavelength can be obtained using light interference. Can be increased.

  In Embodiment 4, in order to reflect infrared light in a wide wavelength range, the infrared light reflecting film 20 has a configuration in which a plurality of sets of two types of layers 21 and 22 are laminated as shown in FIG. . By varying the center wavelength λ of each set of reflections and reflecting infrared light of slightly different wavelengths in each of the stacked sets, infrared light in a wide wavelength range as a whole of the infrared light reflection film 20 can be obtained. Can be reflected. The greater the difference in refractive index between the first layer 21 and the second layer 22, the larger the wavelength width that can be reflected. Therefore, the material of the first layer 21 and the second layer 22 is selected according to the wavelength width to be reflected. To do.

For example, the first layer 21 is an MgO layer, and the second layer 22 is an SiC layer. The number of sets of the first layer 21 and the second layer 22 is 26 sets (set 20-1 to set 20-26), for a total of 52 layers. For example, the film thickness of the MgO layer 21 is 156 nm to 94 nm. By designing the film thickness of the SiC layer 22 from 116 nm to 70 nm gradually different values for each group, as shown in FIG. 13, the center wavelength λ _{1 to} λ ₂₆ is good in the range of 1000 nm to ₁₀ μm. Excellent infrared reflection characteristics can be obtained.

As the material of the first layer 21 and second layer 22, high-temperature resistant oxide such as _{CaO, CeO 2, Cr 2 O} 3, CoO, Dy 2 O 3, Gd 2 O 3, Ga 2 O 3, _{HfO 2, HoO 3, SnO 2} , Fe 2 O 3, La 2 O 3, MgAl 2 O 4, MgO, Nd 2 O 3, NbO, Nb 2 O 3, Os 2 O 3, ReO 3, Sm 2 O 3 , Sc ₂ O ₃ , SiO, SiO ₂ , SrO, Ta ₂ O ₅ , Tb ₂ O ₃ , ThO ₂ , TiO, Ti ₂ O ₃ , TiO ₂ , UO ₂ , VO ₂ , Yb ₂ O ₃ , Y ₃ Al ₅ O ₁₂ , Y ₂ O ₃ , ZnO, ZrO ₂ , ZrSiO ₄ , etc., and high-temperature heat-resistant nitrides such as GaN, AlN, BN, HfN, NbN, Si ₃ N ₄ , TaN, TiN, VN, ZrN, etc. High-temperature resistant carbides, for _{example, Be 2 C, B 4 C} , graphene, CNT, _{DLC, Cr 3 C 2, Mo 2} C, NbC, 4H-SiC, 6H-SiC, ThC 2, TiC, W 2 C , UC ₂ , VC, ZrC, etc., high-temperature heat-resistant sulfides such as CdS, ThS ₂ , US, ZnS, etc., high-temperature heat-resistant borides such as CrZrB ₂ , MoB, Mo ₂ BC, MoTiB ₄ , Mo _{2 TiB 2, Mo 2 ZrB 2} , MoZr 2 B 4, NbB, Nb 3 B 4, NbTiB 4, NdB 6, SiB 3, Ta 3 B 4, TiWB 2, W 2 B, WB, WB 2, YB 4 and _{ZrB 12, CrB, MoB 2,} HfB 2, NbB 2, TaB 2, TiB 2, WB 2, VB 2, ZrB 2, etc., high-temperature resistant silicate Product and phosphides, e.g., _GaP, VSi 2, ZrSi _2, any material of equal or can be composed of a mixed material containing these materials.

  In addition, although the case where the combination of the material which comprises the 1st layer 21 and the 2nd layer 22 was the same in each set 20-1 to 20-26 was demonstrated here, this invention is limited to this structure. Of course, the combination of the materials of the first layer 21 and the second layer 22 may be different for each set.

  The difference in refractive index between the first layer 21 and the second layer 22 is preferably 0.1 or more because good reflectance characteristics can be obtained. The greater the difference in refractive index, the wider the wavelength range that can be reflected by one set of the first layer 21 and the second layer 22, and the total number of thin film stacks can be reduced. It is desirable.

  In the lamination of the set of the first layer 21 and the second layer 22, good reflectance characteristics can be obtained when the total number of the laminations is 3 to 200 layers. When the number of layers is 200 or more, cracks and peeling occur due to stress and the like, and it becomes difficult to maintain good reflectance characteristics. Therefore, it is desirable to employ a film formation technique for preventing these.

(Embodiment 5) White scatterer As Embodiment 5, a filament 3 having a base formed of metal and a white scatterer layer covering the base as an infrared light suppressing structure will be described. A visible light absorbing material that absorbs light in the visible light region and near infrared light region is added to the white scatterer layer.

  The base of the filament 3 is a metal having a high melting point, for example, HfC (melting point 4160K), TaC (melting point 4150K), ZrC (melting point 3810K), C (melting point 3800K), W (melting point 3680K), Re (melting point 3453K), Os (melting point 3327K), Ta (melting point 3269K), Mo (melting point 2890K), Nb (melting point 2741K), Ir (melting point 2683K), Ru (melting point 2583K), Rh (melting point 2239K), V (melting point 2160K), Cr (melting point 2160K) And a material containing any one of Zr (melting point 2125K).

Examples of the white scatterer include yttria (Y ₂ O ₃ ), hafnia (HfO ₂ ), lutecia (Lu ₂ O ₃ ), tria (ThO ₂ ), magnesia (MgO), zirconia (ZrO ₂ ), ytterbia (Yb ₂ O ₃ ), strontia (SrO), calcium oxide (CaO), beryllium oxide (BeO), holmium oxide (Ho ₂ O ₃ ), terbium oxide (Tb ₂ O ₃ ), dysprosium oxide (Dy ₂ O ₃ ), oxidation Holmium (Ho ₂ O ₃ ), Erbium oxide (Er ₂ O ₃ ), Thulium oxide (Tm ₂ O ₃ ), Promethium oxide (Pm ₂ O ₃ ), Samarium oxide (Sm ₂ O ₃ ), Europium oxide (Eu ₂ O _3), gadolinium oxide _{(Gd 2 O} 3), cerium oxide _{(Ce 2 O} 3), praseodymium oxide (P ₂ O _3), neodymium oxide _{(Nd 2 O} 3), zirconia nitride (ZrN), titanium nitride (TiN), aluminum nitride (AlN) and boron nitride (BN), used those containing any of the . This is because these white scatterers show very high reflection characteristics with little absorption from the infrared to the visible region. Among the many white scatterers, the white scatterer has heat resistance under vacuum and maintains high reflection characteristics even in a temperature range of 2300K or more where the filament emits light efficiently. It is. The particles of the white scatterer desirably have a particle size of 50 nm or more and 50 μm or less. The shape of the particles is preferably a shape that allows a large filling rate in terms of light scattering efficiency. Considering the coating method on the substrate, it is desirable that the spherical particles have good symmetry. The white scatterer is more preferably subjected to at least one of surface dangling bond removal treatment and surface crystal defect recovery treatment.

  As the visible light absorbing material, for example, an impurity element doped into a white scatterer can be used. Examples of impurity elements include Ce, Eu, Mn, Ti, Sn, Tb, Au, Ag, Cu, Al, Ni, W, Pb, As, Tm, Ho, Er, Dy, Pr, Nd, Pm, and Sm. , Gd, Yb, or the like can be used. The doping concentration of the impurity element into the white scatterer is set to 0.0001% to 50%, for example. As a doping method, a method in which a white scatterer and these impurity elements are mixed and doped using a solid-phase reaction (firing), or a white scatterer oxide and an impurity are both dissolved in concentrated nitric acid. A method of co-precipitation with an acid salt and firing it can be taken.

  Metal particles can also be used as the visible light absorbing material. Examples of the metal particles include W, Ta, Mo, Au, Ag, Cu, Al, Ti, Ni, Co, Cr, Si, V, Mn, Fe, Nb, Ru, Pt, Pd, Hf, Y, Particles such as Zr, Re, Os, and Ir can be used. In this case, the particle size of the metal particles is preferably 2 nm or more and 5 μm or less. The concentration of the metal particles added to the white scatterer is set to 0.0001% to 50%, for example. As an addition method, a white scatterer and these impurity elements are mixed and co-deposited, and then fired to grow metal fine crystal crystals in the white scatterer, or the above metal ions are added to the white scatterer. , Using an ion implantation apparatus, and then firing and growing a crystal of metal fine particles in a white scatterer. The metal particles added to the white scatterer form various absorption bands because the absorption wavelength and the amount of absorption in the visible light region can be controlled according to the type and particle size of the metal, as in the stained glass of a church. It becomes possible. For example, by changing the particle size of Au fine particles from 2 nm to 5 nm, the stained glass color can be changed from pink to deep green. This is due to a change in transmitted light (complementary color) due to the local resonance absorption effect of the. That is, when the particle size is small, it absorbs short wavelength light, and as the particle size increases, it absorbs long wavelength light. Absorption by adding fine metal particles to a white scatterer is also based on this principle.

  Moreover, it is preferable that the surface of the filament substrate is polished to a mirror surface. The conditions are as described in the first embodiment.

A method for manufacturing the filament 3 will be described. A high-temperature heat-resistant wire such as a W filament or a substrate is used as a base, and yttria (Y ₂ O ₃ ), zirconia (ZrO ₂ ), hafnia (HfO ₂ ), lutecia (Lu ₂ ) having a shape as shown in FIG. O ₃ ), tria (ThO ₂ ), or a mixture thereof, and a high-temperature heat-resistant white scatterer stabilized so as not to cause a phase change at a high temperature is applied. The reason for applying the white scatterer is that, as shown in FIG. 15, the white scatterer has no absorption from the infrared region to the visible region and exhibits a very high reflectance characteristic. The reason why the white scatterer is selected from among many white scatterers is that it is a material having heat resistance in a temperature range of 2500K or higher.

  The filament coated with the white scatterer emits near-infrared light with high efficiency when heated by current supply or the like. This physical process is divided into two stages. The first stage creates a situation that once suppresses all radiation by a white scatterer. If a material whose reflectance is 1 over all wavelengths is ε (λ) = 0 from equation (3), and the integrated value in equation (2) is 0, no loss due to radiation occurs. This physical meaning means that since P (total) = P (conduction), there is no loss due to light emission even with a small amount of input energy, and the filament reaches a very high temperature. (If the heated object is seen from the outside, there is no radiation, so the temperature is not known until it is touched, whether it is hot or cold.) Very high without absorption in a wide range of wavelengths from the infrared to the visible region A characteristic of the white scatterer is that it exhibits reflectance characteristics (very low emissivity characteristics). By coating or forming the white scatterer closely on the filament, it is possible to suppress a decrease in reflectance in the long wavelength infrared region, which is a defect of the metal filament.

FIG. 16 shows the reflectivity of the mirror-polished W substrate and the emission spectrum when heated to 2500K. FIG. 15 shows the reflectance shown when a Lu ₂ O ₃ white scatterer is coated on a mirror-polished W substrate and the emission spectrum shown when heated to 2500K. In FIG. 15, the low reflectivity portion of the infrared region and the infrared region at a wavelength of 7 μm or more are the conduction band energy absorption of Lu ₂ O ₃ (ultraviolet portion) and the optical phonon absorption of Lu ₂ O ₃ (infrared portion: 1TO phonon, 1LO phonon, 2TO phonon, 2LO phonon, etc.).

However, as is apparent from FIG. 15, when only the white scatterer is coated, the visible light and near infrared light are not efficiently emitted because the reflectance in the visible light and near infrared light regions is high. Therefore, in order to reduce the reflectivity in the near infrared region (increase the emissivity), techniques such as addition of impurities and addition of metal fine particles are used to create absorption in the visible light and near infrared light regions. As an example, doping the Lu ₂ O ₃ white scatterer with Ta fine particles of about 2% can reduce the reflectance in the visible light and near infrared light regions as shown in FIG. The emissivity of external light and visible light can be increased.

Here, the particle diameter and the white scatterer thickness are optimized using the light scattering theory: light diffusion equation.
The above equation (6-1), in (6-2) n (r, t) is the light intensity at any time in the scatterer, D is the diffusion coefficient, t _a is the decay time due to absorption of the sample, l * Is the mean free path, and c is the speed of light. By solving equations (6-1) and (6-2), the light transmittance T (L) when there is no absorption can be simply described as equation (7).
(Equation 7)
T (L) = (l * / L) (7)
Here, L is the thickness of the white scatterer.

  When there is no absorption, T (L) + R (L) = 1. Therefore, when the reflectance R is desired to be about 99.9%, the transmittance T needs to be about 0.1%. Here, assuming that the white scatterer must be applied to a volume and thickness that does not impair the thermal energy stored in the filament, the filament radii is 1 mm, and this white scatterer is approximately 1/10 of this 1 mm. It is necessary to make it thick. By the way, from the calculation of the scattering cross section, the mean free path of l * and the particle radius of the white scatterer are estimated to be approximately the same, so the thickness L = 100 mm and the white scatterer radius R = 100 nm. You can ask. By selecting a particle size smaller than this, radiation control can be performed without energy loss.

(Embodiment 6)
As a sixth embodiment, a near infrared heater using the filament of the present invention will be described.

  FIG. 3 is a sectional view of the near-infrared heater of the present embodiment. The near infrared heater includes an airtight container 2, a filament 3 disposed inside the airtight container 2, a pair of lead wires 4 and 5 electrically connected to both ends of the filament 3 and supporting the filament 3, And an anchor 6 that supports the filament 3. The lead wires 4 and 5 and the anchor 6 are supported by an insulating mount 7 disposed in the hermetic container 2. The base portion of the mount 7 is supported by the sealing portion 8 of the airtight container 2. Sealing metals (metal foils) 14 and 15 and lead bars 16 and 17 are arranged in the sealing portion 8.

  As described above, the hermetic container 2 is made of a material that transmits at least near-infrared light and visible light having a wavelength of less than 2 μm and absorbs infrared light having a wavelength of 2 μm or more.

  The lower ends of the lead wires 4 and 5 are welded to metal foil sealing metals 14 and 15. The upper ends of the lead bars 16, 17 are welded to the sealing metals 14, 15, and the lower ends are drawn out from the sealing portion 8. The sealing portion 8 has a structure in which the sealing metals 14 and 15, the lower ends of the lead wires 4 and 5, and the upper ends of the lead rods 16 and 17 are pinch-sealed (melted and sealed by melting glass). Thereby, current can be supplied from the lead rods 16 and 17 to the filament 3 from the outside. The reason why the sealing metals 14 and 15 are arranged in the sealing portion to perform pinch sealing is to prevent the hermetic container 2 from being broken (breaking the glass) when the filament is used at a high temperature of 3000K or higher. It is. That is, the material of the airtight container 2 has a low coefficient of thermal expansion, whereas the metal lead wires 4 and 5 and the metal lead rods 16 and 17 generally have a high coefficient of thermal expansion. However, the sealing metals 14 and 15 relieve the stress caused by the difference in thermal expansion depending on their thickness and material.

As the filament 3, the filament 3 of Embodiments 1 to 5 is used. In FIG. 3, as an example, filaments in the form of wire rods are spirally wound. However, the filament shape is not limited to this shape, and may be a desired shape such as a rod shape or a plate shape. Moreover, the inside of the airtight container 2 is in a pressure state of 10 ⁻³ to 10 ⁺⁷ Pa.

  The shape of the near-infrared heater is not limited to the tube structure, and can be a desired shape corresponding to the shape of the object to be heated. For example, FIG. 18 is a cross-sectional view of a linear infrared near-infrared heater using the filament 3. In FIG. 18, the same components as those of the near-infrared heater of FIG. In the near-infrared heater of FIG. 18, the airtight container 2 is a straight tube, and the filament 3 is arranged along the axis of the tubular airtight container 2. Sealing portions 8 and 9 are respectively disposed at both ends of the annular airtight container 2. The hermetic container 2 is made of a material that transmits at least near-infrared light and visible light having a wavelength of less than 2 μm and absorbs infrared light having a wavelength of 2 μm or more.

  One end of a pair of lead wires 4 and 5 is connected to both ends of the filament 3. The other ends of the lead wires 4 and 5 are connected to sealing metals (metal foils) 14 and 15 disposed in the sealing portions 8 and 9. One end of the lead rods 16 and 17 is connected to the sealing metals 14 and 15, and the other ends of the lead rods 16 and 17 are drawn out from the sealing portions 8 and 9. The sealing portions 8 and 9 have a structure in which the end portions of the sealing metals 14 and 15, the lead wires 4 and 5, and the end portions of the lead rods 16 and 17 are welded to each other in the same manner as the tube structure of FIG. .

  In the near-infrared heater having a linear structure shown in FIG. 18, the filament 3 may be a wire-shaped filament wound in a spiral shape or a desired shape such as a rod shape or a plate shape. be able to. The pressure inside the airtight container 2 is set in the same manner as the tube structure in FIG.

  As described in the first to fifth embodiments, the filament 3 of the present invention has a high reflectance in the infrared wavelength region of 2 μm or more and a low reflectance in the near infrared light region and the visible light region. Radiation can be suppressed. Therefore, a near-infrared heater having high near-infrared light emission efficiency and high energy conversion efficiency can be obtained.

The filament 3 of each embodiment described above may cause sublimation of the visible light reflectance lowering film 11 or the like when the hermetic container 2 is in a high vacuum state such as 10 ⁻³ Pa, but in that case, An inert gas such as Ar may be sealed in the hermetic container 2 at a high pressure of about 10 ⁵ to 10 ⁷ Pa to suppress sublimation of the film. Further, in place of an inert gas such as Ar, the film can be sublimated as appropriate by using about several percent oxygen gas, nitrogen gas, halogen gas, carbon-based gas, or a mixed gas thereof. Therefore, it is possible to achieve a long life.

  In the present embodiment, the near-infrared heater of the present invention is suitable as a heater for heating, a heater for automobile heating, a heat source for melting snow, a heater for fixing toner in a copying machine, and the like.

2 ... Airtight container, 3 ... Filament, 4 ... Lead wire, 5 ... Lead wire, 6 ... Anchor, 8 ... Sealing part, 9 ... Base

Claims (14)

A near-infrared heater having an air-tight container and a filament disposed in the air-tight container and emitting near-infrared light,
The airtight container is made of a material that transmits at least near infrared light and visible light having a wavelength of less than 2 μm and absorbs infrared light having a wavelength of 2 μm or more,
The near-infrared heater, wherein the filament includes an infrared light suppression structure that suppresses radiation of the infrared light absorbed by the airtight container.   2. The near-infrared heater according to claim 1, wherein the hermetic container is made of quartz glass, silicate glass, borosilicate glass, phosphate glass, Pyrex (registered trademark) glass, or BK7 glass. A near-infrared heater. A near-infrared heater having an air-tight container and a filament disposed in the air-tight container and emitting near-infrared light,
The airtight container is composed of quartz glass, silicate glass, borosilicate glass, phosphate glass, Pyrex (registered trademark) glass, BK7 glass,
The near-infrared heater, wherein the filament includes an infrared light suppression structure that suppresses radiation of the infrared light absorbed in the hermetic container and emits near-infrared light and visible light.   The near-infrared heater according to any one of claims 1 to 3, wherein the filament has a mirror-finished surface as an infrared light suppressing structure.   The near-infrared heater according to any one of claims 1 to 3, wherein the filament includes a TaC layer or an HfC layer on the outermost surface as the infrared light suppression structure. .   4. The near-infrared heater according to claim 1, wherein the filament covers the base formed of a metal and the base as the infrared light suppressing structure, and the visible light of the base and A near-infrared heater comprising a visible light reflectance lowering film that lowers the reflectance of near-infrared light.   4. The near-infrared heater according to claim 1, wherein the filament includes a base formed of a metal and an infrared light reflection film that covers the base as the infrared light suppression structure. 5. A near-infrared heater characterized by that. The near-infrared heater according to any one of claims 1 to 3, wherein the filament has a base formed of metal and a white scatterer layer that covers the base as the infrared light suppressing structure. ,
The near-infrared heater, wherein a visible light absorbing material that absorbs light in a visible light region and a near-infrared light region is added to the white scatterer layer.   The near-infrared heater according to claim 4, wherein the surface roughness is such that a center line average roughness Ra is 1 μm or less, a maximum height Rmax is 10 μm or less, and a ten-point average roughness Rz is 10 μm or less. A near-infrared heater characterized by satisfying at least one of them.   The near-infrared heater according to claim 5, wherein the filament has a core material of W or Ta.   The near-infrared heater according to claim 6, wherein the visible light reflectance lowering film has a thickness of visible light and near infrared light reflected by the surface of the visible light reflectance lowering film and visible light reflected by the substrate. A near-infrared heater, which is set to reduce intensity by causing interference with light and near-infrared light. The near-infrared heater according to claim 7, wherein the infrared light reflection film includes a set of first and second layers each made of a material that transmits infrared light and laminated. When the first layer has a refractive index n ₁ and a thickness d ₁ , and the second layer has a refractive index n ₂ and a thickness d ₂ , n _{1 with} respect to a predetermined wavelength λ ₁ of infrared light _{· d 1 = n 2 · d} 2 = λ 1/4
The near-infrared heater is characterized in that the infrared light having the predetermined wavelength λ ₁ is reflected.   The near-infrared heater according to claim 8, wherein the visible light absorber includes any one of an impurity element and metal particles doped in the white scatterer.   The near-infrared heater according to any one of claims 1 to 3, wherein the filament has a reflectance of 40% or less in at least a part of the visible light region and the near-infrared light region, and at least in the infrared light region. A near-infrared heater, wherein a part of the reflectance is 80% or more.