WO2023153242A1 - Far-infrared transmission member, far-infrared sensor, automotive sensor, smartphone-mounted sensor, and sensor for wearable terminal - Google Patents

Abstract

Through the present invention, far infrared rays are suitably transmitted, and good designability is obtained. In the present invention, the regular reflectance of visible light calculated on the basis of JIS R3106 when the light is incident at an incidence angle of 5° is 10% or less, the average transmittance of light having a wavelength of 8-12 µm is 50% or greater, and the value of ∆E as defined by expression (1) is 6.0 or less.

Description

Far-infrared transmission materials, far-infrared sensors, automotive sensors, smartphone-mounted sensors, and wearable device sensors

The present invention relates to a far-infrared transmitting member, a far-infrared sensor, a vehicle-mounted sensor, a smartphone-mounted sensor, and a wearable terminal sensor.

When installing a far-infrared sensor, when providing a far-infrared transmitting member with an antireflection film for suppressing the reflection of far-infrared rays and increasing the amount of transmitted light so that the far-infrared rays are properly incident on the far-infrared sensor There is Patent Document 1 describes an infrared transmitting film having an extinction coefficient of 0.4 or less in the far infrared region.

For example, when such a far-infrared transmitting member is exposed to the outside, it is preferable that it is inconspicuous from the viewpoint of design. Therefore, there is a demand for a far-infrared transmitting member that can appropriately transmit far-infrared rays while providing good design.

　In order to improve the design of the far-infrared transmitting member, it is necessary to suppress the reflection of visible light in the far-infrared transmitting member. Patent Literature 2 discloses an antireflection film that simultaneously prevents reflection in two wavelength ranges, the visible range and the infrared range. However, since the antireflection film of Patent Document 2 uses a multilayer film obtained by alternately laminating a high refractive layer and a low refractive index layer, the reflected color changes depending on the incident angle. There was a risk of deterioration.

JP 2017-151408 A JP-A-4-357134

The present invention provides a far-infrared transmitting member, a far-infrared sensor, a vehicle-mounted sensor, a smartphone-mounted sensor, and a wearable terminal sensor, which are capable of appropriately transmitting far-infrared rays while providing good designability regardless of the angle. for the purpose.

The far-infrared transmitting member according to the embodiment of the present invention has a regular reflectance of 10% or less for visible light calculated based on JIS R3106 when incident at an incident angle of 5°, and has a wavelength of 8 μm to 12 μm. The average transmittance of light is 50% or more, and the value of ΔE defined by the following formula (1) is 6.0 or less.

L ₁ ^* a ₁ ^* b ₁ ^* : Spectral reflectance of visible light measured at an incident angle of 5° and a detection angle of 5° and calculated based on JIS Z 8781-4, using standard illuminant D65 as illumination light Chromaticity coordinates of reflected light in the actual CIE-Lab color system L ₂ ^* a ₂ ^* b ₂ ^* : Spectral reflectance of visible light measured at an incident angle of 45° and a detection angle of 45° and JIS Z 8781-4 Chromaticity coordinates of reflected light in the CIE-Lab color system when using standard illuminant D65 for illumination light, calculated based on

A far-infrared transmitting member according to an embodiment of the present invention includes a substrate having unevenness that scatters visible light on one main surface, and a first functional film that prevents reflection of light with a wavelength of 8 μm to 12 μm on the unevenness. and a second functional film on the other main surface of the substrate, and the arithmetic mean height Sa (ISO 25178) on the surface of the first functional film is 0.030 μm or more and 1.000 μm or less. characterized by

According to the present invention, it is possible to obtain a far-infrared transmitting member that appropriately transmits far-infrared rays and that provides good designability regardless of the angle.

1 is a schematic cross-sectional view of a far-infrared transmitting member according to an embodiment; FIG. FIG. 3 is a schematic cross-sectional view showing another example of a far-infrared transmitting member; FIG. 3 is a schematic cross-sectional view showing another example of a far-infrared transmitting member; FIG. 3 is a schematic cross-sectional view showing another example of a far-infrared transmitting member; FIG. 3 is a schematic cross-sectional view showing another example of a far-infrared transmitting member; FIG. 3 is a schematic cross-sectional view showing another example of a far-infrared transmitting member; FIG. 3 is a schematic cross-sectional view showing another example of a far-infrared transmitting member; FIG. 3 is a schematic cross-sectional view showing another example of a far-infrared transmitting member; It is a graph which shows the measurement result of the regular reflectance of each example. It is a graph which shows the measurement result of the infrared transmittance|permeability of each example.

In this specification, the term "~" used to indicate a numerical range is used to include the numerical values before and after it as lower and upper limits unless otherwise specified.

In this specification, visible light means light with a wavelength of 380 nm to 780 nm unless otherwise specified. Further, the far-infrared rays are light with a wavelength of 8 μm to 12 μm unless otherwise specified, but may be light with a wavelength of 8 μm to 14 μm.

The far-infrared transmitting member according to this embodiment (hereinafter sometimes referred to as this embodiment) has a regular reflectance of 10 for visible light calculated based on JIS R3106 when incident at an incident angle of 5°. % or less, the average transmittance of light with a wavelength of 8 μm to 12 μm is 50% or more, and the value of ΔE defined by the following formula (1) is 6.0 or less.

In formula (1), L ₁ ^* a ₁ ^* b ₁ ^* is the illumination light calculated based on the spectral reflectance of visible light measured at an incident angle of 5° and a detection angle of 5° and JIS Z 8781-4. is the chromaticity coordinates of the reflected light in the CIE-Lab color system when using the standard illuminant D65 in .
In formula (1), L ₂ ^* a ₂ ^* b ₂ ^* is the illumination light calculated based on the spectral reflectance of visible light measured at an incident angle of 45° and a detection angle of 45° and JIS Z 8781-4. is the chromaticity coordinates of the reflected light in the CIE-Lab color system when using the standard illuminant D65 in .

By providing such optical characteristics, it is possible to obtain a good design regardless of the angle while properly transmitting far infrared rays. The details of each optical characteristic will be described below.

In the present embodiment, the regular reflectance of visible light incident at an incident angle of 5° is 10% or less, more preferably 5% or less, even more preferably 3% or less, and even more preferably 1%. or less, and particularly preferably 0.5% or less. When the regular reflectance of visible light falls within this range, glare can be suppressed and an appearance with good design can be obtained. Here, the regular reflectance of visible light is calculated based on JIS R3106.

In the present embodiment, the average transmittance of light with a wavelength of 8 μm to 12 μm is 50% or more, more preferably 70% or more, still more preferably 80% or more, and even more preferably 85% or more. , particularly preferably 90% or more. When the average transmittance falls within this range, far-infrared rays can be appropriately transmitted. Note that the average transmittance is the average value of the transmittance of light with wavelengths of 8 μm to 12 μm.

In the present embodiment, the value of ΔE defined by the above formula (1) is 6.0 or less, more preferably 5.0 or less, still more preferably 4.0 or less, and even more preferably 3.0 or less. ΔE is a value that serves as an index of change in color tone of the far-infrared transmitting member due to the angle of incident light, and the smaller the value, the less the change in color tone due to the angle.

More specifically, ΔE represents the distance of each chromaticity coordinate in the CIE-Lab color system of reflected light when visible light is incident on the far-infrared transmitting member at incident angles of 5 ° and 45 °. value. In formula (1), L ₁ ^* a ₁ ^* b ₁ ^* corresponds to the chromaticity coordinates of reflected light when visible light is incident at an incident angle of 5°, and L ₂ ^* a ₂ ^* b ₂ ^* is visible. It corresponds to the chromaticity coordinates of the reflected light when the light is incident at an incident angle of 45°.

Therefore, the smaller ΔE is, the closer the distance of the chromaticity coordinates of the reflected light when the visible light is incident at the incident angles of 5° and 45°, and the closer color feeling can be obtained regardless of the angle. When ΔE is within the above preferable range, a far-infrared transmitting member having a constant color tone can be obtained regardless of the angle.

The specific configuration of the far-infrared transmitting member according to the present embodiment is not particularly limited as long as it satisfies the above requirements, but a configuration example applicable to the present embodiment will be described below.

Preferred configurations of the present embodiment will be described below based on the drawings, but these drawings are provided for illustration and the present invention is not limited to these drawings. In each figure, the same reference numerals are given to common parts.

FIG. 1 is a schematic cross-sectional view of a preferred configuration of the far-infrared transmitting member according to this embodiment.

As shown in FIG. 1, the far-infrared transmitting member 10 according to this embodiment preferably has a substrate 20 and a functional film 30a.

The substrate 20 has a first main surface 21 and a second main surface 22 facing each other, and the functional film 30a has a surface 31a. In this specification, unless otherwise specified, the first main surface 21 side of the substrate 20 is the light incident side, and the second main surface 22 side is the light emitting side.

The far-infrared transmitting member 10 according to the present embodiment has unevenness that scatters visible light on the first main surface 21 of the substrate 20, and a functional film 30a that prevents reflection of light with a wavelength of 8 μm to 12 μm on the unevenness. It is preferable to have In the example of FIG. 1, the substrate 20 has unevenness on the first principal surface 21, but as shown in FIG. As shown in FIGS. 3, 6 and 7, the substrate 20 has irregularities on the first main surface 21 and the second main surface 22, and has functional films 30a and 30b on the irregularities on both main surfaces, respectively. may be In addition, the functional film 30b is not limited to being formed on the uneven surface, and as shown in FIGS. It may have a functional film 30b that prevents reflection of light. Note that the functional film 30b has a surface 31b.

That is, it is preferable that the far-infrared transmitting member 10 according to the present embodiment has a base material 20 having unevenness on at least the first main surface 21 and a functional film formed on the unevenness.

(Base material)
The substrate 20 is preferably a member capable of transmitting far-infrared rays. For example, the internal transmittance for light with a wavelength of 10 μm (far-infrared rays) is preferably 50% or more, preferably 60% or more. More preferably, it is 70% or more, and particularly preferably 80% or more. In addition, the average internal transmittance of the substrate 20 for light (far infrared rays) having a wavelength of 8 μm to 12 μm is preferably 50% or more, more preferably 60% or more, and preferably 70% or more. More preferably, it is particularly preferably 80% or more. When the internal transmittance at 10 μm and the average internal transmittance at 8 μm to 12 μm of the base material 20 are within this numerical range, far infrared rays can be properly transmitted. The average internal transmittance here is the average value of the internal transmittance for light of each wavelength in the wavelength band (here, 8 μm to 12 μm).

The internal transmittance of the base material 20 is the transmittance excluding the surface reflection loss on the incident side and the exit side, and is well known in the technical field, and its measurement may also be performed by a usual method. Measurement is performed, for example, as follows.

Prepare a pair of plate-shaped samples (first sample and second sample) made of base materials of the same composition and having different thicknesses. Both surfaces of the flat sample are parallel to each other and optically polished. T1 is the external transmittance including the surface reflection loss of the first sample, T2 is the external transmittance including the surface reflection loss of the second sample, Td1 (mm) is the thickness of the first sample, and Td1 (mm) is the thickness of the second sample. is Td2 (mm), where Td1<Td2, the internal transmittance τ at the thickness Tdx (mm) can be calculated by the following equation (2).

τ = exp [-Tdx x (lnT1-lnT2)/ΔTd] (2)

The infrared external transmittance can be measured, for example, by a Fourier transform infrared spectrometer (manufactured by ThermoScientific, trade name: Nicolet iS10).

The base material 20 preferably has a refractive index of 1.5 or more and 4.0 or less, more preferably 2.0 or more and 4.0 or less, and 2.2 or more and 3.5 for light with a wavelength of 10 μm. More preferably: In addition, the average refractive index of the substrate 20 with respect to light with a wavelength of 8 μm to 12 μm is preferably 1.5 or more and 4.0 or less, more preferably 2.0 or more and 4.0 or less. More preferably, it is 2 or more and 3.5 or less. By setting the refractive index and average refractive index of the substrate 20 within this numerical range, far-infrared rays can be appropriately transmitted. Note that the average refractive index here is the average value of the refractive index for light of each wavelength in the wavelength band (here, 8 μm to 12 μm). The refractive index is determined, for example, using polarization information obtained by an infrared spectroscopic ellipsometer (JA Woollam IR-VASE-UT) and a spectral transmission spectrum obtained by a Fourier transform infrared spectrometer. It can be determined by fitting the model.

The material of the base material 20 is not particularly limited, but examples thereof include Si, Ge, ZnS, chalcogenide glass, and the like. It can be said that the substrate 20 preferably contains at least one material selected from the group consisting of Si, Ge, ZnS, and chalcogenide glass. By using such a material for the base material 20, far-infrared rays can be transmitted appropriately.
A preferable composition of the chalcogenide glass is as follows.
In atomic percent,
Ge+Ga; 7% to 25%,
Sb: 0% to 35%,
Bi; 0% to 20%,
Zn; 0% to 20%,
Sn; 0% to 20%,
Si; 0% to 20%,
La; 0% to 20%,
S + Se + Te; 55% to 80%,
Ti; 0.005% to 0.3%,
Li + Na + K + Cs; 0% to 20%,
F+Cl+Br+I; composition containing 0% to 20%. This glass preferably has a glass transition point (Tg) of 140°C to 550°C.

As the material of the base material 20, it is more preferable to use Si, ZnS, or chalcogenide glass from the viewpoint of easily forming unevenness on the base material.

Although the thickness of the base material 20 is arbitrary, it is preferably 0.2 mm or more and 5 mm or less, more preferably 0.5 mm or more and 2 mm or less, and further preferably 0.5 mm or more and 1 mm or less. . By having the thickness within this range, it is possible to properly transmit far-infrared rays while ensuring strength.

(Surface shape of base material)
As shown in FIGS. 1 to 7, the substrate 20 is preferably provided with unevenness that scatters visible light on at least the first major surface 21 . In this specification, the surface shape of the base material 20, specifically, the shape of the unevenness formed on the surface of the base material 20 (the first main surface 21 in FIGS. 1 to 7 and the (corresponding to the second main surface 22), the arithmetic mean height Sa, the mean length RSm of the roughness curve element, and the root-mean-square slope RΔq are used. The arithmetic mean height Sa can be measured according to ISO 25178, and the mean length RSm and the root mean square slope RΔq of the curve element can be measured according to JISB 0601.

Sa on the uneven surface of the substrate 20 is preferably 0.030 μm or more and 1.000 μm or less, more preferably 0.1 μm or more and 0.5 μm or less, and more preferably 0.15 μm or more and 0.15 μm or more. It is more preferably 4 μm or less. By forming the functional film on the unevenness that satisfies these preferable surface shapes, it is possible to obtain a surface shape of the functional film that is preferable for suppressing reflection of visible light and appropriately transmitting far-infrared rays. A preferred surface shape of the functional membrane will be described later.

The RSm on the uneven surface of the substrate 20 is preferably 15 μm or less, more preferably 10 μm or less, and even more preferably 8 μm or less. By forming the functional film on the unevenness satisfying these preferable surface shapes, it is possible to obtain a surface shape of the functional film that is preferable for properly transmitting far-infrared rays. A preferred surface shape of the functional membrane will be described later.

RΔq on the uneven surface of the substrate 20 is preferably 20° or less, more preferably 15° or less, and even more preferably 10° or less. By forming the functional film on the unevenness satisfying these preferable surface shapes, it is possible to obtain a surface shape of the functional film that is preferable for properly transmitting far-infrared rays. A preferred surface shape of the functional membrane will be described later.

The method for forming unevenness on the surface of the substrate 20 is not particularly limited, but for example, a chemical treatment method involving etching, a physical treatment method such as wet blasting and sandblasting, or a mold having a desired uneven structure. can be used. From the viewpoint of facilitating control of the unevenness structure, a chemical treatment method accompanied by an etching treatment is particularly preferable as a method for forming unevenness on Si, and a press molding method is a method for forming unevenness on ZnS or chalcogenide glass. Especially preferred.

When using a chemical treatment method that accompanies an etching treatment, for example, the surface of the base material 20 is etched with an alkaline etchant containing potassium hydroxide (KOH) at a concentration of 2 to 10% by mass, an organic solvent, and a surfactant. As a result, unevenness can be formed on the surface. The uneven shape can be controlled by changing the composition and concentration of the alkaline etchant used in the etching process, as well as the processing time and processing temperature. Thereby, Sa, RSm, and RΔq of the uneven surface can be controlled. For the etching treatment, a chemical solution in which an Si compound is mixed with an alkaline etching solution may be used.　

(Functional membrane)
The functional films 30a and 30b are preferably formed on the substrate 20 and have an effect of preventing reflection of far infrared rays (wavelength 8 μm to 12 μm here). The functional film may be formed on the unevenness provided on the surface of the substrate 20 like the functional film 30a in FIGS. It may be formed on the surface of the substrate 20 that is not coated. Further, the functional films 30a and 30b may have different specific configurations as long as they have the effect of preventing the reflection of far infrared rays.

When the functional films 30a and 30b are formed to be uneven like the functional films 30a in FIGS. 1 to 7 and the functional films 30b in FIGS. becomes a structure having When the surface shape of the functional film formed on the uneven surface satisfies the preferable conditions described later, it is possible to appropriately transmit far-infrared rays and scatter visible light on the surface of the functional film. That is, in the case where the functional films 30a and 30b are formed as uneven surfaces, the functional films 30a and 30b have an effect of preventing reflection of far-infrared rays and an effect of scattering visible light. By scattering visible light on the surface of the functional film formed on the irregularities, glare can be suppressed and a good design property can be obtained regardless of the angle.

(Surface shape of functional membrane)
A preferable surface shape of the functional film formed on the uneven surface will be described below. In this specification, as an index of the surface shape of the functional film formed on the uneven surface, specifically, the surface shape of the surface 31a in FIGS. 1 to 7 and the surface 31b in FIGS. Sa and the mean length RSm of the roughness curve element are used. The arithmetic mean height Sa can be measured according to ISO 25178, and the mean length RSm and the root mean square slope RΔq of the roughness curve element can be measured according to JISB 0601.

Sa on the surface of the functional film formed on the unevenness is preferably 0.030 μm or more, and is 0.1 μm or more from the viewpoint of scattering visible light and obtaining good design properties regardless of the angle. is more preferable, and 0.15 μm or more is even more preferable. From the viewpoint of suppressing scattering of far-infrared rays and transmitting them appropriately, the thickness is preferably 1.000 μm or less, more preferably 0.5 μm or less, and even more preferably 0.4 μm or less.

Furthermore, the effects obtained by setting Sa within the above-mentioned preferable range include improvement in antifouling properties due to a reduction in the area where dirt adheres, improvement in water repellency due to an increase in the water contact angle, and improvement in tactile sensation due to a reduction in the finger contact area. can be expected.

RSm is preferably 15 μm or less, more preferably 10 μm or less, and even more preferably 8 μm or less, from the viewpoint of suppressing scattering of far-infrared rays and properly transmitting them. RΔq is preferably 20° or less, more preferably 15° or less, and even more preferably 10° or less from the viewpoint of suppressing scattering of far-infrared rays and properly transmitting them.

In the present embodiment, the surface shape of the functional film formed on the unevenness is such that Sa satisfies the above preferable range and at least one of RSm and RΔq satisfies the above preferable range. is preferred. When the surface of the functional film formed on the uneven surface satisfies such conditions, far-infrared rays can be properly transmitted, and a good design property can be obtained regardless of the angle.

(Structure of functional membrane)
Specific preferred configurations of the functional films 30a and 30b will be described below. It is preferable that the functional films 30a and 30b according to the present embodiment include at least one far-infrared ray antireflection layer. Moreover, as shown in FIGS. 5 and 6, a configuration may be adopted in which a visible light antireflection layer is further provided outside the far infrared ray antireflection layer 32 (on the side away from the substrate 20). Moreover, as shown in FIG. 7, the structure which further has an adhesion layer in the inner side (side which touches the base material 20) of the far-infrared ray antireflection layer 32 may be sufficient. In this specification, a film including at least one far-infrared antireflection layer 32 is referred to as a functional film. That is, the functional films 30a and 30b may be single layer films or multilayer films.

(Far-infrared antireflection layer)
The material used for the far-infrared antireflection layer 32 preferably has an extinction coefficient of 0.05 or less, more preferably 0.03 or less, and preferably 0.025 or less for light with a wavelength of 10 μm. It is more preferably 0.02 or less, and particularly preferably 0.01 or less. When the far-infrared light extinction coefficient of the far-infrared antireflection layer 32 falls within this numerical range, the far-infrared reflectance can be reduced and the far-infrared light can be appropriately transmitted. The extinction coefficient for light with a wavelength of 10 μm is obtained by, for example, polarization information obtained by an infrared spectroscopic ellipsometer (IR-VASE-UT manufactured by JA Woollam), Fourier transform infrared spectrometer (manufactured by ThermoScientific, It can be determined by fitting an optical model using a spectral transmission spectrum obtained by Nicolet iS10).

The material used for the far-infrared antireflection layer 32 preferably has an extinction coefficient of 0.04 or more, more preferably 0.05 or more, and more preferably 0.06 or more for light with a wavelength of 550 nm. It is more preferably 0.07 or more, particularly preferably 0.08 or more, and still more preferably 0.10 or more. The far-infrared antireflection layer 32 preferably has an average extinction coefficient of 0.04 or more, more preferably 0.05 or more, and more preferably 0.06 or more for light with a wavelength of 380 nm to 780 nm. is more preferably 0.07 or more, particularly preferably 0.08 or more, and even more preferably 0.10 or more. When the extinction coefficient and the average extinction coefficient fall within this range, it is possible to suppress the reflection of visible light and obtain good design. Note that the average extinction coefficient is the average value of the extinction coefficients of light of each wavelength in the wavelength band (here, 380 nm to 780 nm). The extinction coefficient of light with a wavelength of 550 nm can be determined, for example, by fitting an optical model using polarization information obtained by a spectroscopic ellipsometer and spectral transmittance measured based on JIS R3106.

Although the specific material of the far-infrared antireflection layer 32 is arbitrary, it is preferably composed mainly of a metal oxide. The main component here means that the content of the far-infrared antireflection layer 32 as a whole is 50% by mass or more. At least one of NiO, Al ₂ O ₃ , CuO, ZnO, ZrO ₂ , Bi ₂ O ₃ , Y ₂ O ₃ and MgO is preferable as the metal oxide used for the far-infrared antireflection layer 32 . The far-infrared antireflection layer 32 preferably contains at least one material selected from the group consisting of NiO, CuO, ZnO, ZrO ₂ , Bi ₂ O ₃ , Y ₂ O ₃ and MgO as a main component. However, the material of the far-infrared antireflection layer 32 is not limited to them, and may be, for example, Si, Ge, ZnS, YF ₃ , or diamond-like carbon. Far-infrared antireflection layer 32 preferably contains at least one material selected from the group of NiO, diamond-like carbon, ZrO ₂ , ZnS, Ge, Si, MgO, and ZnO.

Further, the far-infrared antireflection layer 32 may be a single layer or multiple layers. When the far-infrared antireflection layer 32 is multi-layered, it is preferable to alternately laminate a high refractive material and a low refractive material, and the materials can be selected from the above materials.

(Visible light antireflection layer)
The visible light antireflection layer 33 is a layer for further suppressing reflection of visible light on the far-infrared transmitting member 10 . When the functional films 30a and 30b have the visible light antireflection layer 33, the visible light antireflection layer 33 is preferably the outermost surface of the functional films 30a and 30b. However, when the functional films 30a and 30b have a water-repellent layer 35, which will be described later, the visible light antireflection layer 33 may not be the outermost surface of the functional films 30a and 30b. 5 and 6, the visible light antireflection layer 33 serves as the surface 31a of the functional film 30a, and while the visible light is scattered by the uneven structure of the surface 31a, the visible light reflection is further prevented by the visible light antireflection layer 33. It can be suppressed and the design can be improved.

The visible light antireflection layer 33 preferably has a refractive index of 2.0 or less, more preferably 1.3 or more and 1.8 or less, and 1.4 or more and 1.7 or less for light with a wavelength of 550 nm. is more preferable. In addition, the visible light antireflection layer 33 preferably has an average refractive index of 2.0 or less, more preferably 1.3 or more and 1.8 or less, and 1.4 for light with a wavelength of 380 nm to 780 nm. It is more preferable that it is not less than 1.7 and not more than 1.7. The refractive index and average refractive index for visible light of the visible light antireflection layer 33 are in this numerical range, so that the combination with the far infrared ray antireflection layer 32 suppresses the reflection of visible light, and the design of the far infrared ray transmitting member 10 can improve sexuality. The refractive index of the visible light antireflection layer 33 for light with a wavelength of 550 nm is preferably equal to or less than the refractive index of the far-infrared antireflection layer 32 for light with a wavelength of 550 nm. is preferably equal to or lower than the average refractive index of the far-infrared antireflection layer 32 for light with a wavelength of 380 nm to 780 nm.

The material of the visible light antireflection layer 33 is arbitrary, and for example, at least one selected from the group consisting of ZrO ₂ , Al ₂ O ₃ , TiO ₂ , Si ₃ N _{4 ,} AlN, SiO ₂ , MgO and diamond-like carbon. It may contain materials. Moreover, the visible light antireflection layer 33 preferably contains at least one material selected from the group consisting of Al ₂ O ₃ , SiO ₂ and MgO.

(Adhesion layer)
As shown in FIG. 7, the adhesion layer 34 is preferably formed on the inner side (the side in contact with the substrate 20) of the far-infrared antireflection layer 32 in the functional films 30a and 30b. The adhesion layer 34 is a layer that improves the adhesion of the functional films 30 a and 30 b to the substrate 20 .

The adhesion layer 34 preferably has a refractive index of 1.0 or more and 4.3 or less, more preferably 1.5 or more and 4.3 or less, and 1.5 or more and 3.8 for light with a wavelength of 10 μm. More preferably: In addition, the adhesion layer 34 preferably has an average refractive index of 1.0 to 4.3, more preferably 1.5 to 4.3, for light with a wavelength of 8 μm to 12 μm. More preferably, it is 5 or more and 3.8 or less. By setting the refractive index and average refractive index of the adhesion layer 34 to far infrared rays within this numerical range, the reflection of far infrared rays can be suppressed and the far infrared rays can be properly transmitted.

The adhesion layer 34 can transmit far infrared rays. The adhesion layer 34 preferably has an extinction coefficient of 0.4 or less, more preferably 0.2 or less, and even more preferably 0.1 or less for light with a wavelength of 10 μm. The adhesion layer 34 preferably has an average extinction coefficient of 0.4 or less, more preferably 0.2 or less, and even more preferably 0.1 or less for light with a wavelength of 8 μm to 12 μm. When the extinction coefficient and the average extinction coefficient fall within this range, far-infrared rays can be properly transmitted.

Although _the material of the adhesion layer 34 is arbitrary, for example, it is selected from the group of Si, Ge, MgO, NiOx, CuOx, ZnS, _Al2O3 , _ZrO2 , _SiO2 , _TiO2 , _ZnO , and _Bi2O3 . It preferably contains at least one material that is

(Water-repellent layer)
The water repellent layer 35 is a layer for improving the water repellency of the far-infrared transmitting member 10 . When the functional films 30a and 30b have a water-repellent layer 35, the water-repellent layer 35 is preferably the outermost surface of the functional films 30a and 30b. In the example of FIG. 8, the water-repellent layer 35 serves as the surface 31a of the functional film 30a, and the water-repellent layer 35 can improve the water repellency of the surface 31a.

Although the method for forming the water-repellent layer 35 is arbitrary, it can be formed by vapor deposition, for example. Any material can be used for the water-repellent layer as long as it can transmit far infrared rays. For example, AFS-R2 (manufactured by Syncron Co., Ltd.) can be used.

(Method for forming functional film)
Next, a method for forming the functional films 30a and 30b will be described. In this embodiment, the functional films 30a and 30b are preferably formed on the surface of the substrate 20 by sputtering. By forming the functional films 30a and 30b by sputtering, the adhesion of the films can be improved. For example, when the far infrared ray antireflection layer of the functional films 30a and 30b is NiO, it is preferable to form the functional films 30a and 30b while heating the surface of the substrate 20 at 100°C or higher and 300°C or lower. However, the method of forming the functional films 30a and 30b is not limited to sputtering, and may be formed by vapor deposition, for example.

(Characteristics of far-infrared transmitting member)
Regarding the characteristics of the far-infrared transmitting member according to the present embodiment, the specular reflectance of visible light incident at an incident angle of 5°, the average transmittance of light with a wavelength of 8 μm to 12 μm, and the preferable values of ΔE The ranges are as described above. Further preferable characteristics of the far-infrared transmitting member according to this embodiment will be described below.

In the present embodiment, the total reflectance of visible light is preferably 15% or less, more preferably 12% or less, even more preferably 8% or less, even more preferably 5% or less, and particularly preferably 2%. % or less. When the total reflectance of visible light falls within this range, a black appearance with good design can be obtained. Here, the total reflectance of visible light is measured under the geometric condition d (8°: di) specified in JIS-Z8722:2009 and calculated based on JIS R3106.

(Application)
The far-infrared transmitting member according to the present embodiment appropriately transmits far-infrared rays and provides a good design regardless of the angle, so that it is suitable as a member used for a far-infrared sensor. Further, the far-infrared sensor using the far-infrared transmitting member according to the present embodiment exhibits good designability, and is particularly suitable for an environment in which the sensor is exposed to the outside. Specific applications include sensors for vehicles, sensors for drones, sensors for surveillance cameras, sensors for smartphones, sensors for wearable terminals, and motion sensors.

(Example)
EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited thereto. Tables 1, 2, and 3 show the configurations of Examples and Comparative Examples, and the measurement results and evaluation results of each characteristic.

The "roughness treatment" column in Tables 1, 2, and 3 shows the method of forming the irregularities on the base material. It is shown for each of the surfaces on the light incident side and the light emitting side, and "none" means that the surface has not been processed to form unevenness.

The "functional film" column in Tables 1, 2, and 3 shows the material of the functional film formed on the substrate. It is shown for each surface on the light incident side and the light emitting side, and "none" means that no functional film is formed on the surface.

That is, for example, in the sample of Example 1, unevenness is formed by chemical etching on both the light incident side and the light emitting side of the Si substrate that is the base material, and then a NiO single layer film is formed as the functional film. It is a sample formed on both the side and the exit side.

The method for measuring the surface shape and optical properties is described below.

(Arithmetic mean height Sa)
Based on ISO 25178, VK-X250 (manufactured by KEYENCE) was used and an objective lens of 150 times was used for measurement.

(Average length RSm of roughness curve element)
Based on JIS 0601, VK-X250 (manufactured by KEYENCE) was used and an objective lens of 150 times was used for measurement.

(root mean square slope RΔq)
Based on JIS 0601, VK-X250 (manufactured by KEYENCE) was used and an objective lens of 150 times was used for measurement.

(regular reflectance)
The specular reflection spectrum in the visible light region was measured using U4100 (manufactured by Hitachi, Ltd.) at an incident angle of 5°, and calculated based on JIS R3106.

(total reflectance)
The total reflection spectrum in the visible light region was measured using U4100 (manufactured by Hitachi) under the geometric condition d (8°: di) defined in JIS-Z8722:2009, and calculated based on JIS R3106.

(ΔE)
ΔE can be measured by the following method. Visible light at an incident angle of 5 ° detection angle of 5 ° and an incident angle of 45 ° detection angle of 45 ° using a V-770 type ultraviolet-visible near-infrared spectrophotometer, ARMN-920 type (manufactured by JASCO Corporation) The spectral reflectance of each was measured.

After that, based on the measured spectral reflectance of visible light and JIS Z 8781-4, the chromaticity coordinates L ₁ ^* a ₁ ^* of the reflected light in the CIE-Lab color system when using the standard illuminant D65 as the illumination light. b ₁ ^* and L ₂ ^* a ₂ ^* b ₂ ^* were obtained, respectively, and ΔE was calculated based on the above formula (1).

Note that Tables 1, 2, and 3 show the results of measuring Sa, RSm, RΔq, specular reflectance, total reflectance, and ΔE on the light incident surface of each sample.

(Far-infrared average transmittance (wavelength 8 μm to 12 μm))
It was measured using Nicolet iS10 (manufactured by ThermoScientific). Here, the average transmittance is the average value of the transmittance of light with wavelengths of 8 μm to 12 μm.

For the samples of Examples 13 to 16, the water contact angle was also measured to evaluate water repellency. The method for measuring the water contact angle is described below.

(water contact angle)
Based on JISR32757 (1999), it was measured using CA-X (manufactured by Kyowa Interface Science Co., Ltd.) as a contact angle meter. The measurement points were three points on the surface of the functional film on the light incident side, and the average value of the measurement results is shown in the column of "water contact angle" in Table 3.

(evaluation)
Each sample of Examples 1 to 16 was evaluated for designability and far-infrared transmission performance. For the evaluation of designability, the specular reflectance, total reflectance and ΔE on the light incident surface of the sample were used. With respect to the specular reflectance and ΔE, which are particularly important indicators, the samples satisfying the specular reflectance of 10% or less and ΔE of 6.0 or less were evaluated as round and passed. On the other hand, when the measurement result of at least one of the specular reflectance and ΔE did not meet the above criteria, it was marked as crossed out and rejected.

In evaluating the far-infrared transmission performance, the average transmittance of light with a wavelength of 8 μm to 12 μm was used. An average transmittance of 80% or more is indicated by a double circle, an average transmittance of 50% or more and less than 80% is indicated by a circle, and an average transmittance of less than 50% is indicated by a cross.

In the present specification, samples in which the evaluation results of both the designability and far-infrared transmission performance are circled or double-circled are used as examples, and the evaluation results of at least one of the designability and far-infrared transmission performance are crossed. Let the sample which became become a comparative example. That is, Examples 1, 2, 6, 9, 11, 12, 13, 14 and 15 correspond to Examples, and Examples 3, 4, 5, 7, 8, 10 and 16 correspond to Comparative Examples.

The samples of Examples 13 to 16 were further evaluated for water repellency. In the evaluation of water repellency, the water contact angle of the sample was used. A sample with a water contact angle of 120° or more was evaluated as a circle, and a sample with a water contact angle of less than 120° was evaluated as a cross, and a circle was evaluated as a pass.

(Examples 1-4)
Examples 1 to 4 are examples of the far-infrared transmitting member 10 shown in FIG. In Examples 1-4, both sides of the substrate 20 were chemically etched to form unevenness. Using KOH, an organic solvent, and a surfactant as the chemical liquid, the composition was appropriately adjusted, and four types of substrates having different surface shapes were prepared. After that, functional films 30a and 30b were formed on both sides of the base material by sputtering to obtain a far-infrared transmitting member. In Examples 1 to 4, a Si substrate having a thickness of 0.5 mm was used as the base material, and the functional films 30a and 30b were single-layer films of NiO, which are far-infrared antireflection layers. Further, in this example, the first main surface 21 of the substrate 20 corresponds to the light incident side.

In Examples 1 to 4, the functional film was formed on the main surface of the base material by a post-oxidation sputtering method using a load-lock type sputtering apparatus (RAS-1100BII, manufactured by Synchron Co., Ltd.) to a film thickness of about A 1.2 μm NiO film was formed. The conditions for forming the NiO film are as follows.

(NiO deposition conditions)
Target: NiO (70% by mass) + Ni (30% by mass) mixed target Sputtering gas: Ar gas (flow rate: 150 sccm)
Input power: 6 kW
Reactive gas: Ar (flow rate: 70 sccm) + O ₂ (flow rate: 10 sccm)
RF power: 2kW
Substrate temperature: normal temperature Film formation pressure: 0.19 Pa

(Example 5)
In Example 5, the functional films were formed on both sides of the base material 20 by sputtering without forming unevenness on the surface of the base material 20 . In Example 5, a Si substrate having a thickness of 0.5 mm was used as the base material 20, and the functional films 30a and 30b were single-layer films of NiO for the anti-reflection layers of far-infrared rays. The method of forming the NiO film is the same as in Examples 1-4.

(Evaluation results of Examples 1 to 5)
Table 1 shows the evaluation results of the samples of Examples 1-5. It can be seen that Examples 1 to 4, which have functional films formed on the uneven surface on the light incident side, have better design properties than Example 5. From this, by forming a functional film on the uneven surface and scattering visible light on the surface of the functional film, the regular reflectance and total reflectance of visible light are reduced, and a constant color tone is obtained regardless of the angle. It can be seen that a far-infrared transmitting member with good design can be obtained.

FIG. 9 shows the measurement results of the specular reflectance of the samples of Examples 1 and 5. Comparing Example 1 and Example 5, it can be seen that Example 1 has a lower regular reflectance over the entire visible light range. From this, it can be seen that by forming a functional film on the unevenness to scatter visible light, the specular reflectance can be lowered and the design can be improved.

On the other hand, when comparing Examples 1 and 2 with Examples 3 and 4, it can be seen that Examples 3 and 4 have lower far-infrared transmission performance than Examples 1 and 2. This is probably due to the scattering of far-infrared rays on the surface of the functional film on the light incident side of Examples 3 and 4, since Sa and RSm are larger than those of Examples 1 and 2. . Therefore, as in Examples 1 and 2, by setting Sa and RSm on the surface of the functional film on the light incident side to the above-mentioned preferred ranges, far-infrared rays can be properly transmitted, and good designability can be achieved regardless of the angle. It is considered possible to obtain a far-infrared transmitting member with

Fig. 10 shows the measurement results of the far-infrared transmittance of the samples of Examples 1, 3, and 5. It can be seen that the sample of Example 3 has a good design property, but the transmittance of far infrared rays is lower than those of Examples 1 and 5. This is presumably due to the scattering of far-infrared rays on the surface of the functional film on the light incident side, as described above. On the other hand, in Example 1, far-infrared rays can be appropriately transmitted by setting Sa and RSm on the surface of the functional film on the light incident side to the above-mentioned preferred ranges. In Example 5, since the functional film was not formed on the uneven surface, the far-infrared rays were not scattered on the surface of the functional film and could be properly transmitted, but the sample had poor design.

From these facts, it can be seen from FIG. 10 that by setting the Sa and RSm of the functional film surface on the light incident side within the above-mentioned preferable ranges, it is possible to appropriately transmit far infrared rays and achieve good designability regardless of the angle. It is considered possible to obtain a far-infrared transmitting member with

(Examples 6-8)
Examples 6 to 8 are examples of the far-infrared transmitting member 10 shown in FIG. In Examples 6 to 8, unevenness was formed using a wet blasting device (Jr. Type II, manufactured by Maco Co., Ltd.) on the first main surface 21 of the substrate, which is the light incident side. Wet blasting is a technique for imparting irregularities to the surface of a workpiece by injecting slurry, which is a mixture of a liquid and an abrasive, onto the workpiece using compressed air. White alumina WA#6000, WA#4000, and WA#2500 manufactured by Fujimi Incorporated were used as abrasives. By adjusting the slurry concentration, air pressure, slurry pressure, distance between the injection nozzle and the workpiece, sweep speed, and number of treatments, three types of substrates with different surface shapes were prepared.

After that, functional films 30a and 30b were formed on both sides of the base material by sputtering to form a far-infrared transmitting member. In Examples 6 to 8, a Si substrate having a thickness of 0.5 mm was used as the base material 20, and the functional films 30a and 30b were NiO films of far-infrared antireflection layers. The method of forming the NiO film is the same as in Examples 1-5.

(Evaluation results of Examples 6 to 8)
Table 2 shows the evaluation results of the samples of Examples 6-8. Comparing Example 6 with Examples 7 and 8, it can be seen that Examples 7 and 8 are inferior to Example 6 in designability. This is probably because the surface Sa of the functional film formed on the uneven surface of Examples 7 and 8 is smaller than that of Example 6, and visible light is not sufficiently scattered on the surface. . Therefore, it is believed that by setting Sa within the above-mentioned preferable range as in Example 6, it is possible to obtain a far-infrared transmitting member that appropriately scatters visible light and has a good design regardless of the angle. .

(Example 9)
Example 9 is an example of the far-infrared transmitting member 10 shown in _{FIG .} This is a configuration in which a single layer film is further formed. In Example 9, under the same conditions as in Example 1, both sides of the substrate 20 were subjected to chemical etching treatment to form unevenness. After that, on the first main surface 21, which is the light incident side, as the functional film 30a, a single layer of NiO as a far-infrared antireflection layer and a single layer of Al ₂ O ₃ as a visible light antireflection layer are formed. A single-layer film of NiO was formed as the functional film 30b on the second main surface 22, which is the light emitting side, on which the unevenness is not formed on the substrate. The method of forming the NiO film is the same as in Examples 1-8.

In Example 9, when forming Al ₂ O ₃ , an Al ₂ O ₃ film having a thickness of about 0.1 μm was formed on the NiO single layer film by reactive sputtering using a transport type sputtering apparatus. formed. The deposition conditions for the Al ₂ O ₃ film are as follows.

(Al ₂ O ₃ deposition conditions)
Target: Al
Sputtering gas: Ar 70 sccm
Reactive gas: O2 10 sccm
Input power: 500W
Substrate temperature: Room temperature Film formation pressure: 0.5 Pa

(Example 10)
Example 10 has a structure in which a single-layer film of Al ₂ O ₃ as a visible light antireflection layer is further formed on the surface of the functional film, which is the light incident side, of the sample of Example 5. Specifically, it was produced as follows. Under the same conditions as in Example 5, without forming unevenness on the surface of the substrate, a single layer film of NiO, which is a far-infrared antireflection layer, was formed as a functional film on the light incident side of the substrate, A monolayer film of Al ₂ O ₃ as a visible light antireflection layer was laminated in this order, and a monolayer film of NiO was formed as a functional film on the surface of the substrate from which light was emitted. The method for forming the NiO film is the same as in Examples 1 to 9, and the method for forming the Al ₂ O ₃ film is the same as in Example 9.

(Evaluation result of Example 9)
Table 2 shows the evaluation results of the samples of Example 9. From Table 2, it can be seen that the sample of Example 9 exhibits good results in terms of both designability and far-infrared transmission performance. Compared to the sample of Example 1, which was produced under the same conditions except that an Al ₂ O ₃ film, which is a visible light antireflection layer, was formed on the functional film, Example 9 has a lower total reflectance, and is more designable. is improved.

(Evaluation result of Example 10)
Table 2 shows the evaluation results of the samples of Example 10. Compared to the sample of Example 5, which was produced under the same conditions except that the Al ₂ O ₃ film, which is a visible light antireflection layer, was formed on the functional film, Example 10 had lower regular reflectance and total reflectance. , it can be seen that the designability is improved. On the other hand, compared with the sample of Example 9, ΔE was increased, confirming a change in color tone depending on the angle. From this, it can be seen that the change in color tone depending on the angle can be suppressed by scattering visible light with the unevenness of the surface of the functional film.

(Example 11)
Example 11 is an example of the far-infrared transmitting member 10 shown in FIG. A sample was produced under the same conditions as in Example 1, except that the functional film 30b was not formed.

(Evaluation result of Example 11)
Table 2 shows the evaluation results of the samples of Example 11. Since the functional film is formed only on the light incident side, compared with Example 1, Example 11 shows a decrease in far-infrared transmittance, but sufficient transmittance is obtained as a far-infrared transmitting member. It is understood that In addition, it was confirmed that good design properties were exhibited as in Example 1.

(Example 12)
Example 12 is an example of the far-infrared transmitting member 10 shown in FIG. In Example 12, both sides of substrate 20 were chemically etched to form irregularities. Samples were prepared under the same conditions as in Examples 1 to 4, except that the composition of the chemical solution was adjusted and the surface shape of the substrate after unevenness formation was different from those of Examples 1 to 4.

(Evaluation result of Example 12)
Table 3 shows the evaluation results of the samples of Example 12. From Table 3, it can be seen that the sample of Example 12 exhibits good results in terms of both design and far-infrared transmission performance. In Example 12, as in Examples 1 and 2, the Sa and RSm of the functional film surface on the light incident side are within the above-described preferred ranges, so far-infrared rays are appropriately transmitted, and good design is achieved regardless of the angle. It is considered to have sexuality.

(Example 13)
Example 13 is an example of the far-infrared transmitting member 10 shown in FIG. 8, and has a configuration in which a water-repellent layer is further formed on the surface of the functional film in addition to the sample of Example 1. FIG. In Example 13, under the same conditions as in Example 1, both sides of the substrate 20 were subjected to chemical etching to form unevenness. After that, on the first main surface 21, which is the light incident side, as the functional film 30a, a single layer film of NiO, which is a far-infrared antireflection layer, and a water-repellent layer are laminated in this order to emit light. As the functional film 30b, a single layer film of NiO, which is a far-infrared antireflection layer, and a water-repellent layer were laminated in this order on the second main surface 22, which is the side. The method of forming the NiO film is the same as in Examples 1-12.

In Example 13, when the water-repellent layer was formed, it was formed on the NiO single-layer film by vapor deposition using a load-lock type sputtering apparatus (RAS-1100BII, manufactured by Synchron Co., Ltd.). The deposition conditions for the water-repellent layer are as follows.

(Water-repellent layer deposition conditions)
Vapor deposition temperature: 300 degrees Vapor deposition time: 5 minutes Vapor deposition material: AFS-R2 (manufactured by Syncron)

(Evaluation result of Example 13)
Table 3 shows the evaluation results of the samples of Example 13. From Table 3, it can be seen that the sample of Example 13 exhibits good water repellency. This is probably because Sa on the functional film surface on the light incident side of Example 13 was within the preferred range described above.

Furthermore, it can be seen that the sample of Example 13 exhibits good results in terms of both designability and far-infrared transmission performance. Example 13 has a configuration in which a water-repellent layer is formed on the surface of the functional film in comparison with the sample of Example 1, which is an embodiment. However, it can be seen that good design and far-infrared transmission performance can be maintained.

(Examples 14 and 15)
Examples 14 and 15 are examples of the far-infrared transmitting member 10 shown in FIG. It is a structure in which a water-repellent layer is further formed. The method for forming the NiO film is the same as in Examples 1 to 13, and the method for forming the water-repellent layer is the same as in Example 13.

(Evaluation results of Examples 14 and 15)
Table 3 shows the evaluation results of the samples of Examples 14 and 15. From Table 3, it can be seen that the samples of Examples 14 and 15 exhibit good water repellency. It is considered that this is because the Sa on the functional film surface on the light incident side in Examples 14 and 15 was within the preferred range described above.

Furthermore, it can be seen that the samples of Examples 14 and 15 show good results in terms of both designability and far-infrared transmission performance. Example 14 is a sample of Example 12, and Example 15 is a sample of Example 2, in which a water-repellent layer is formed on the surface of the functional film. From this result, it can be seen that, as in Example 13, good design and far-infrared transmission performance can be maintained even when a water-repellent layer is formed on the outermost surface of the functional film.

(Example 16)
Example 16 has a structure in which a water-repellent layer is further formed on the surface of the functional film in addition to the sample of Example 5. The method of forming the NiO film is the same as in Examples 1-15, and the method of forming the water-repellent layer is the same as in Examples 13-15.

(Evaluation result of Example 16)
Table 3 shows the evaluation results of the samples of Example 16. From Table 3, it can be seen that Example 16 has lower water repellency than the samples of Examples 13-15. In Example 16, since the surface of the base material was not subjected to the unevenness treatment, the Sa of the functional film surface on the light incident side of Example 16 was outside the above-mentioned preferred range. For this reason, compared with Examples 13-15, it is considered that the water repellency was lowered.

Although the embodiment of the present invention has been described above, the embodiment is not limited by the content of this embodiment. In addition, the components described above include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those within the so-called equivalent range. Furthermore, the components described above can be combined as appropriate. Furthermore, various omissions, replacements, or modifications of components can be made without departing from the gist of the above-described embodiments.

The present invention can be suitably used for various devices that use far infrared rays. INDUSTRIAL APPLICABILITY The present invention is particularly suitable for installation exposed to the outside, since good design properties can be obtained regardless of the angle.

REFERENCE SIGNS LIST 10 far-infrared transmitting member 20 substrate 21 first main surface 22 second main surface 30a, 30b functional film 31a, 31b surface 32 far-infrared antireflection layer 33 visible light antireflection layer 34 adhesion layer 35 water-repellent layer

Claims (23)

1. The specular reflectance of visible light calculated based on JIS R3106 when incident at an incident angle of 5° is 10% or less, and the average transmittance of light with a wavelength of 8 μm to 12 μm is 50% or more. A far-infrared transmitting member, wherein the value of ΔE defined by the formula (1) is 6.0 or less.
   

   

   L ₁ ^* a ₁ ^* b ₁ ^* : Spectral reflectance of visible light measured at an incident angle of 5° and a detection angle of 5° and calculated based on JIS Z 8781-4, using standard illuminant D65 as illumination light Chromaticity coordinates of reflected light in the actual CIE-Lab color system L ₂ ^* a ₂ ^* b ₂ ^* : Spectral reflectance of visible light measured at an incident angle of 45° and a detection angle of 45° and JIS Z 8781-4 Chromaticity coordinates of reflected light in the CIE-Lab color system when using standard illuminant D65 for illumination light, calculated based on
2. The far-infrared transmitting member according to claim 1, which has an average transmittance of 80% or more for light with a wavelength of 8 μm to 12 μm.
3. The far-infrared transmitting member according to claim 1 or 2, wherein the regular reflectance is 5% or less.
4. Claims 1 to 3, wherein the total reflectance of visible light calculated based on JIS R3106 is 15% or less when measured under the geometric condition d (8°: di) defined in JIS-Z8722:2009. The far-infrared transmitting member according to any one of .
5. 5. The substrate according to any one of claims 1 to 4, comprising a base material provided with unevenness for scattering visible light on at least one main surface, and a functional film for preventing reflection of light having a wavelength of 8 μm to 12 μm on the unevenness. The far-infrared transmitting member according to the item.
6. The far-infrared transmitting member according to claim 5, wherein both main surfaces of the base material are provided with the unevenness, and the first functional film and the second functional film are formed on the unevenness.
7. 6. The method according to claim 5, wherein one main surface of the base material is provided with the unevenness, the first functional film is formed on the unevenness, and the second functional film is formed on the other main surface of the base material. The far-infrared transmitting member as described.
8. The far-infrared transmitting member according to any one of claims 5 to 7, wherein the arithmetic mean height Sa (ISO 25178) on the surface of the uneven functional film is 0.030 µm or more and 1.000 µm or less.
9. The far-infrared transmitting member according to claim 8, wherein the average length RSm (JISB 0601) of the roughness curve elements on the surface of the functional film on the unevenness is 15 µm or less.
10. The far-infrared transmitting member according to claim 8 or 9, wherein a root-mean-square slope RΔq (JISB 0601) on the surface of the uneven functional film is 20° or less.
11. The far-infrared transmitting member according to any one of claims 5 to 10, wherein the functional film has one or more far-infrared antireflection layers.
12. The far-infrared transmitting member according to claim 11, wherein the far-infrared antireflection layer contains at least one material selected from the group of NiO, diamond-like carbon, _ZrO2 , ZnS, Ge, Si, MgO, and ZnO.
13. The far-infrared transmitting member according to claim 11 or 12, wherein the functional film has a visible light antireflection layer on the outermost surface.
14. The far-infrared transmitting member according to claim 13, wherein the visible light antireflection layer contains at least one material selected from the group of _Al2O3 , _SiO2 and _MgO .
15. The far-infrared transmitting member according to any one of claims 5 to 14, wherein the base material contains at least one material selected from the group consisting of Si, Ge, ZnS, and chalcogenide glass.
16. The far-infrared transmitting member according to claim 11 or 12, wherein the functional film has a water-repellent layer on its outermost surface.
17. A substrate provided with unevenness for scattering visible light on one main surface, a first functional film on the unevenness for preventing reflection of light with a wavelength of 8 μm to 12 μm, and on the other main surface of the substrate A far-infrared transmitting member having a second functional film, wherein the surface of the first functional film has an arithmetic mean height Sa (ISO 25178) of 0.030 μm or more and 1.000 μm or less.
18. The far-infrared transmitting member according to claim 17, wherein the average length RSm (JISB 0601) of the roughness curve elements on the surface of the first functional film is 15 µm or less.
19. The far-infrared transmitting member according to claim 17 or 18, wherein the root-mean-square slope RΔq (JISB 0601) on the surface of the first functional film is 20° or less.
20. A far-infrared sensor using the far-infrared transmitting member according to any one of claims 1 to 19.
21. An in-vehicle sensor using the far-infrared sensor according to claim 20.
22. A smartphone-mounted sensor using the vehicle-mounted sensor according to claim 21.
23. A wearable terminal sensor using the smartphone-mounted sensor according to claim 22.

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