Optical member and far infrared sensor module

Abstract

Provided is an optical member which suitably transmits far infrared rays having a wavelength of 8-12 [mu] m and exhibits white color. In a CIE1976 (L *, a *, b *) color system measured in SCE mode on the basis of JIS-Z8772: 2009 geometric condition c, the optical member of the present invention has L * of 50 or more, a * of-15 to 15, b * of-15 to 15, and an average transmittance TFIR (%) of light having a wavelength of 8 [mu] m to 12 [mu] m of TFIR > = 20.

Description

Technical Field

[0001] This invention relates to an optical component and a far-infrared sensor module incorporating the optical component. Background Technology

[0002] There are various optical devices that utilize infrared light, such as infrared cameras and infrared temperature sensors. In these optical devices, infrared light reflected or emitted by an object is focused by an infrared optical element, and an image of the subject is formed or the temperature distribution of the object is detected based on the amount of infrared light received.

[0003] In such optical elements, surface reflection of infrared light is suppressed by providing an anti-reflective structure on its surface, thereby increasing the infrared transmittance of the optical element. Patent Document 1 discloses an infrared-transmitting substrate having an anti-reflective structure composed of multiple micro-recesses.

[0004] Patent Document 2 discloses an infrared-transmitting filter comprising a matrix and particles dispersed in the matrix. It describes that the filter has a linear transmittance of 60% or more for at least a portion of wavelengths in the wavelength range of 760 nm to 2000 nm, and can exhibit a white appearance.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2016-18081

[0008] Patent Document 2: Japanese Patent Application Publication No. 2022-78336 Summary of the Invention

[0009] Optical components are required to have a white appearance and transmit far-infrared light with wavelengths of 8μm to 12μm. However, optical components that can adequately transmit far-infrared light and have a white appearance are unknown.

[0010] Although the infrared-transmitting substrate disclosed in Patent Document 1 has excellent far-infrared transmittance, it is presumed to have weak scattering of visible light and a gray appearance.

[0011] The infrared-transmitting filter disclosed in Patent Document 2 can appear white. However, since neither the substrate nor the film constituting the filter transmits far-infrared light, it is presumed that the filter itself also does not transmit far-infrared light. The film uses a resin that absorbs far-infrared light and is quite thick, therefore it is presumed that it does not transmit far-infrared light.

[0012] The present invention was made in view of the above circumstances, and its object is to provide an optical component that appropriately transmits far-infrared light with a wavelength of 8μm to 12μm and appears white.

[0013] This disclosure provides optical components, etc., having the following configurations [1] to

[12] .

[0014] [1] An optical component, measured by SCE method under geometric condition c of JIS-Z8772:2009, according to CIE1976 (L * a * b * In the color system, L * For 50 or above, a * The range is -15 to 15, b * The average transmittance T of light with wavelengths from -15 to 15 and wavelengths from 8 μm to 12 μm is -15 to 15. FIR (%) is T FIR ≥20. [2]According to the optical components of[1], wherein, (L * +T FIR ≥115. [3] An optical component according to [1] or [2], wherein it has a white layer and a substrate, the white layer comprising a resin matrix and microparticles dispersed in the resin matrix, and the substrate comprising a support substrate. [4] An optical component according to [3], wherein the thickness of the white layer is 1 μm or more and less than 10 μm. [5] An optical component according to [3] or [4], wherein the average particle size of the microparticles in the cross section of the white layer is 0.1 μm to 1 μm. [6] An optical component according to any one of [3] to [5], wherein the volume concentration of the microparticles in the white layer is 4% to 80%. [7] An optical component according to any one of [3] to [6], wherein the microparticles comprise at least one selected from TiO2, ZrO2, Nb2O5, and Ta2O5. [8] An optical component according to any one of [3] to [7], wherein the supporting substrate comprises at least one selected from Si substrate, Ge substrate, ZnS substrate and chalcogenide glass substrate. [9] An optical component according to any one of [3] to [8], wherein the resin matrix comprises at least one selected from fluororesin and polyolefin resin.

[10] An optical component according to any one of [3] to [9], wherein the substrate has a far-infrared anti-reflective film that prevents reflection of light with wavelengths of 8 μm to 12 μm.

[11] An optical component according to

[10] , wherein the far-infrared anti-reflective film comprises at least one selected from NiO, diamond-like carbon, ZrO2, ZnS, ZnSe, Ge, Si, MgO, ZnO, YF3, MgF2.

[12] A far-infrared sensor module using an optical component according to any one of [1] to

[11] .

[0015] According to the present invention, it is possible to provide an optical component that appropriately transmits far-infrared light with wavelengths of 8μm to 12μm and appears white. Attached Figure Description

[0016] Figure 1 This is a schematic cross-sectional view of an optical component according to one embodiment of the present invention.

[0017] Figure 2 This is a schematic cross-sectional view of an optical component according to one embodiment of the present invention.

[0018] Figure 3 It represents the transmittance of optical components and L. * A diagram showing the relationships between them.

[0019] Figure 4 This represents the particle size and transmittance of the optical components, and L. * A diagram showing the relationships between them. Detailed Implementation

[0020] For clarity, the following descriptions and illustrations have been appropriately simplified, and sometimes the scales of the components in the illustrations are significantly different.

[0021] In this specification, unless otherwise specified, the “~” sign indicating a range of values ​​is used to encompass the values ​​described before and after it as the lower and upper limits.

[0022] In this specification, "average transmittance" in a specific wavelength region refers to the arithmetic mean of the transmittance per 1 nm in that wavelength region.

[0023] In this specification, the “average extinction coefficient” in a specific wavelength region refers to the arithmetic mean of the extinction coefficients per 1 nm in that wavelength region.

[0024] In this specification, unless otherwise specified, "visible light" refers to light with a wavelength of 380 nm to 780 nm. Additionally, unless otherwise specified, "far-infrared light" refers to light with a wavelength of 8 μm to 12 μm, but may also be light with a wavelength of 8 μm to 14 μm.

[0025] A. Optical components

[0026] The optical component of the present invention (hereinafter also referred to as "this component") meets the CIE 1976 (L) standard measured in SCE mode based on geometric condition c of JIS-Z8772:2009. * a * b * In the color system, L * For 50 or above, a * For values ​​between -15 and below 15, b * The value is -15 to 15. Below, we will use L obtained using the method described above. * a * b * As L *a * b * .

[0027] Through L * a * b * Within the aforementioned range, this component thus presents a white appearance. From the viewpoint of further improving the whiteness of the appearance, the L of this component... * Preferably 60 or higher, more preferably 70 or higher, and even more preferably 80 or higher. From the same viewpoint, the a of this component… * Preferably -10 to 10, more preferably -8 to 8, and even more preferably -5 to 5. From the same point of view, the b of this component... * Preferably -10 to 10, more preferably -8 to 8, and even more preferably -5 to 5.

[0028] The average transmittance T of this component for light with wavelengths from 8μm to 12μm FIR (%) is T FIR ≥20. Average transmittance T of light with wavelengths of 8μm to 12μm within the above range. FIR This allows the component to appropriately transmit far-infrared light. The average transmittance T of this component for light with wavelengths of 8μm to 12μm is... FIR Preferred T FIR ≥30, more preferably T FIR ≥40, further optimization of T FIR ≥50, T is the preferred choice FIR ≥60, optimal T FIR ≥70.

[0029] In this component, L * The average transmittance T of light with wavelengths of 8μm to 12μm FIR The sum of (L) * +T FIR Preferably, the concentration is 90 or higher; more preferably, 100 or higher; further preferably, 115 or higher; particularly preferably, 130 or higher; and most preferably, 145 or higher. (L) * +T FIR Within the aforementioned range, it is thus possible to further combine excellent whiteness and excellent far-infrared transmittance.

[0030] Figure 1 This is a schematic cross-sectional view of a preferred configuration of this component. For example... Figure 1 As shown, this component 10 may have a white layer 20 that scatters visible light and a substrate 30.

[0031] Unless otherwise specified, in this component 10, the main surface that is closer to the white layer 20 than the substrate 30 will be the light incident side, and the main surface opposite to the main surface will be the light emitting side.

[0032] From the perspective of improving the transmittance of far-infrared rays, such as Figure 2 As shown, the substrate 30 preferably has a far-infrared anti-reflective film 32.

[0033] exist Figure 2 In this embodiment, the substrate 30 includes a supporting substrate 31, a far-infrared anti-reflective film 32a existing between the substrate 30 and the white layer 20, and a far-infrared anti-reflective film 32b existing on the side of the substrate 30 away from the white layer. The substrate 30 may have only either the far-infrared anti-reflective film 32a or 32b. From the viewpoint of further improving far-infrared transmittance, this component 10 preferably has both the far-infrared anti-reflective film 32a and the far-infrared anti-reflective film 32b. Unless otherwise specified, the far-infrared anti-reflective film 32a and the far-infrared anti-reflective film 32b are appropriately referred to as far-infrared anti-reflective film 32.

[0034] Without impairing the effects of the present invention, this component 10 may further include other functional layers. Examples of other functional layers include an adhesive layer, a protective layer, and an ultraviolet absorbing layer.

[0035] The white layer 20 and the substrate 30 will be described in detail below.

[0036] A-1. White layer

[0037] The white layer 20 may contain a resin matrix and particles dispersed in the resin matrix.

[0038] By appropriately selecting the material, particle size, particle concentration, and thickness of the white layer, the white layer 20 can appropriately scatter visible light through Mie scattering and suppress the scattering of far-infrared light in the white layer 20.

[0039] The particle size can be evaluated based on the average particle size of the particles in the cross-section of the white layer 20. The average particle size of the particles in the cross-section of the white layer 20 is preferably 0.1 μm or more, more preferably 0.12 μm or more, and even more preferably 0.15 μm or more. Because the average particle size of the particles in the cross-section of the white layer 20 is within the above-mentioned range, visible light can be appropriately scattered by Mie scattering, making it easy to obtain a white appearance.

[0040] The average particle size of the microparticles in the cross-section of the white layer 20 is preferably 1 μm or less, more preferably 0.7 μm or less, and even more preferably 0.5 μm or less. Because the average particle size of the microparticles in the cross-section of the white layer 20 is within the above-mentioned range, the scattering of far-infrared rays in the white layer 20 is suppressed, resulting in high far-infrared transmittance. Furthermore, visible light can be appropriately scattered through Mie scattering, easily achieving a white appearance.

[0041] Particles can exist as primary particles or secondary particles. When a particle exists as a secondary particle, the average particle size refers to the average particle size of the secondary particles.

[0042] The method for determining the average particle size of the microparticles in the cross-section of the white layer 20 is described later in the examples.

[0043] Inorganic microparticles can be used as microparticles. From the viewpoint of high refractive index and easy scattering of visible light, the microparticles preferably contain at least one selected from SiO2, metal oxides, Si, Ge, group II-VI semiconductors, and group III-V semiconductors. From the viewpoint of being transparent to visible light and easily obtaining a white appearance, the microparticles more preferably contain at least one of SiO2 and metal oxides. In particular, from the viewpoint of high refractive index, the microparticles further preferably contain at least one selected from TiO2, ZrO2, Nb2O5, and Ta2O5. Among these, from the viewpoint of easily obtaining ultrafine particles and high refractive index, the microparticles most preferably contain TiO2.

[0044] The volume concentration of particles in the white layer 20 is preferably 4% or more, more preferably 10% or more, more preferably 15% or more, and even more preferably 18% or more. By maintaining the particle volume concentration within the above range, sufficient scattering intensity of visible light is achieved without excessively increasing the thickness of the white layer 20, thus easily obtaining a white appearance.

[0045] The volume concentration of the particles in the white layer 20 is preferably 80% or less, more preferably 50% or less, and even more preferably 30% or less. By having the volume concentration of the particles within the above range, the particles are well dispersed in the resin matrix, and the scattering and absorption of far-infrared rays based on the particles are suppressed, making it easy to obtain high far-infrared transmittance.

[0046] The resin matrix retains the particles dispersed within it.

[0047] Since this component 10 is sometimes mounted on the surface of optical equipment as a sensor cover, a resin with excellent weather resistance is preferably used as the resin matrix. By using a resin with high weather resistance as the resin matrix, not only can deformation and deterioration of the white layer 20 be suppressed, but also the reduction in design performance caused by discoloration can be suppressed. From the viewpoint of improving far-infrared transmittance, a resin with low far-infrared absorption is preferably used as the resin matrix.

[0048] The refractive index of the resin matrix for light with a wavelength of 550 nm is preferably 1.5 or less, more preferably 1.4 or less, and even more preferably 1.3 or less. Because the refractive index of the resin matrix is ​​within the above range, the refractive index difference between the resin matrix and the microparticles easily increases, making it easier to scatter visible light.

[0049] Generally speaking, the refractive index of the resin matrix for light with a wavelength of 550nm is above 1.

[0050] The resin used as the resin matrix only needs to be able to maintain the dispersed state of the particles. The specific material is arbitrary, but when considering the refractive index, weather resistance, and far-infrared transmittance of the resin matrix, the resin matrix preferably includes at least one of fluoropolymers and polyolefin resins.

[0051] In particular, as a resin with high weather resistance, the resin matrix preferably contains a fluoropolymer. Specifically, examples of fluoropolymers include vinyl fluoride resins, vinylidene fluoride resins, ethylene-tetrafluoroethylene resins, trifluorochloroethylene resins, trifluorochloroethylene-ethylene resins, tetrafluoroethylene-hexafluoropropylene resins, and tetrafluoroethylene-perfluoro(alkyl vinyl ether) resins. From the viewpoint of particle immobilization and durability against oxidation, ethylene-tetrafluoroethylene resins, tetrafluoroethylene-hexafluoropropylene resins, and tetrafluoroethylene-perfluoro(alkyl vinyl ether) resins are preferred as fluoropolymers.

[0052] In particular, resins with high far-infrared transmittance are preferred, especially those with molecular structures that have low absorption at wavelengths of 8μm to 12μm, and preferably include polyolefin resins. Examples of polyolefin resins include polyethylene and high-density polyethylene.

[0053] From the viewpoint of obtaining a white appearance by fully scattering visible light, the thickness of the white layer 20 is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 4 μm or more. From the viewpoint of obtaining high far-infrared transmittance by suppressing the absorption of far-infrared rays based on the resin matrix, the thickness of the white layer 20 is preferably less than 10 μm, more preferably less than 8 μm, and even more preferably less than 7 μm.

[0054] When the resin matrix contains a resin with particularly high far-infrared transmittance, the far-infrared transmittance is not easily reduced even if the white layer 20 is thick. Therefore, when the resin matrix contains a resin with particularly high far-infrared transmittance, the thickness of the white layer 20 is preferably less than 100 μm, more preferably less than 60 μm, even more preferably less than 40 μm, particularly preferably less than 15 μm, even more preferably less than 10 μm, and most preferably less than 7 μm. By keeping the thickness of the white layer 20 within the above-mentioned range, the absorption of far-infrared rays based on the resin matrix can be suppressed.

[0055] As a method for forming the white layer 20, for example, a method of coating a white layer precursor containing a curable resin matrix and particles onto a substrate 30 by means of spin coating, curtain coating, flow coating, dip coating, spraying, screen coating, inkjet coating, etc., can be used to form a film. The white layer precursor may contain solvents and various additives.

[0056] In the white layer precursor, the dispersion of microparticles in the resin matrix is ​​carried out, for example, by rotary stirring, homogenizing mixer, ultrasonic homogenizer, high-pressure homogenizer, or high-temperature spraying.

[0057] A-2. Substrate

[0058] The substrate 30 transmits far-infrared light. From the viewpoint of improving the far-infrared transmittance of this component, the average transmittance of light with a wavelength of 8μm to 12μm of the substrate 30 is preferably 30% or more, more preferably 40% or more, further preferably 45% or more, particularly preferably 60% or more, further preferably 70% or more, and most preferably 75% or more.

[0059] From the viewpoint of improving the strength of this component 10, the thickness of the substrate 30 is preferably 0.1 mm or more, more preferably 0.2 mm or more, and even more preferably 0.3 mm or more.

[0060] From the viewpoint of ensuring the far-infrared transmittance of this component 10 and reducing the thickness of this component 10, the thickness of the substrate 30 is preferably 5 mm or less, more preferably 2 mm or less, and even more preferably 1 mm or less.

[0061] The substrate 30 includes the supporting substrate 31. If the substrate 30 does not include films other than the supporting substrate 31, such as far-infrared anti-reflective film, the supporting substrate 31 itself can be the substrate 30.

[0062] From the perspective of excellent far-infrared transmittance, the support substrate 31 preferably comprises at least one selected from Si substrates, Ge substrates, ZnS substrates, and chalcogenide glass substrates. From the perspective of high refractive index for visible light, the support substrate 31 more preferably comprises at least one of Si substrates and Ge substrates. If the support substrate 31 has a high refractive index for visible light, visible light that passes through the white layer and reaches the support substrate 31 is easily reflected at the interface of the support substrate 31. If the visible light is reflected at the interface of the support substrate 31, the reflected visible light will re-enter the white layer and be scattered, thus making it easier to obtain a white appearance.

[0063] The refractive index of the support substrate 31 for light with a wavelength of 550 nm is preferably 2 or higher, more preferably 3 or higher, and even more preferably 4 or higher. There is no particular limitation on the refractive index of the support substrate 31, but it can generally be 4.5 or lower.

[0064] When the support substrate 31 contains chalcogenide glass, the chalcogenide glass preferably contains, in atomic percent:

[0065] Ge+Ga: 7%~25%,

[0066] Sb: 0%~35%,

[0067] Bi: 0%~20%,

[0068] Zn: 0%~20%,

[0069] Sn: 0%~20%,

[0070] Si: 0%~20%,

[0071] La: 0%~20%,

[0072] S + Se + Te: 55%–80%,

[0073] Ti: 0.005%~0.3%,

[0074] Li+Na+K+Cs: 0%~20%,

[0075] F + Cl + Br + I: 0%~20%.

[0076] Chalcogenide glasses preferably have a glass transition point (Tg) of 140℃ to 550℃.

[0077] A-2-1. Far-infrared anti-reflective film

[0078] The far-infrared anti-reflective film 32 suppresses the reflection of far-infrared rays on the main surface of the substrate away from the white layer and at the interface between the white layer and the substrate.

[0079] The extinction coefficient of the far-infrared antireflective film 32 for light with a wavelength of 10 μm is preferably 0.05 or less, more preferably 0.03 or less, even more preferably 0.025 or less, particularly preferably 0.02 or less, and most preferably 0.01 or less. By ensuring that the extinction coefficient for light with a wavelength of 10 μm is within the above-mentioned range, the reflectivity of far-infrared rays can be reduced, while allowing for appropriate transmission of far-infrared rays. The extinction coefficient of the far-infrared antireflective film 32 for light with a wavelength of 10 μm can be determined, for example, by fitting an optical model using polarization information obtained from an infrared ellipsometer (JA Woollam, IR-VASE-UT) and a spectrophotometer obtained from a Fourier transform infrared spectrometer (Thermo Scientific, Nicolet iS10).

[0080] The far-infrared anti-reflective film 32 comprises, for example, at least one of Si, Ge, ZnS, ZnSe, YF3, MgF2, diamond-like carbon, and metal oxides. As the metal oxide used in the far-infrared anti-reflective film 32, from the perspective of having a low extinction coefficient for far-infrared rays, at least one of NiO, Al2O3, CuO, ZnO, ZrO2, Bi2O3, Y2O3, and MgO is preferred. From the perspective of having a low extinction coefficient for far-infrared rays, the far-infrared anti-reflective film 32 preferably comprises at least one material selected from NiO, diamond-like carbon, ZrO2, ZnS, ZnSe, Ge, Si, MgO, ZnO, YF3, and MgF2. From the viewpoint of environmental resistance and ease of manufacture, the far-infrared anti-reflective film 32 is preferably composed mainly of metal oxides. Here, "main component" refers to a content of 50% by mass or more relative to the total content of the far-infrared anti-reflective film 32. Among metal oxides, from the perspective of low extinction coefficient for far-infrared rays, the far-infrared anti-reflection film 32 preferably uses at least one material selected from NiO, CuO, ZnO, ZrO2, Bi2O3, Y2O3 and MgO as the main component.

[0081] The far-infrared anti-reflective film 32 can be formed, for example, by sputtering or vapor deposition. From the viewpoint of improving the adhesion between the far-infrared anti-reflective film 32 and the supporting substrate 31, sputtering is preferred. When the far-infrared anti-reflective film 32 is NiO, it is preferable to form the far-infrared anti-reflective film 32 by setting the surface of the supporting substrate 31 to 100°C to 300°C.

[0082] B. Purpose

[0083] The optical component 10 of the present invention appropriately transmits far-infrared light and has a white appearance, thus making it suitable as a component for a far-infrared sensor module. Furthermore, the far-infrared sensor module using the optical component 10 of this embodiment exhibits good design flexibility, making it particularly suitable for environments where it is exposed to the outside. Specific applications include automotive sensors, drone-mounted sensors, surveillance camera sensors, smartphone-mounted sensors, wearable terminal sensors, home appliance-mounted sensors, street lighting sensors, IP camera sensors, motion sensors, and the like.

[0084] Example

[0085] The present invention will now be specifically described with reference to embodiments and comparative examples, but the present invention is not limited thereto. Examples 5-13, 18, and 19 are embodiments, and Examples 1-4 and 14-17 are comparative examples. The characteristics of Examples 11-19 were calculated by simulation.

[0086] The following describes the methods for determining the characteristics of Examples 1 to 10.

[0087] (Average particle size and particle concentration of particles in the cross-section of the white layer)

[0088] The white layer was processed using CP to obtain a sample for SEM observation. The sample was observed using an SEM (SU8230, manufactured by Hitachi High-Technologies) under the following conditions.

[0089] Conductive coating: None

[0090] Detector: LA

[0091] Accelerating voltage: 2kV

[0092] Magnification:×20000

[0093] The SEM images obtained through observation were read into the image processing software ImageJ and binarized using "Threshold (Otsu, B&W)". The particle volume concentration was calculated based on the proportion of the area occupied by the particles in the binarized image. The average particle size in the cross-section of the white layer was calculated as follows: for the binarized image, the region where two or more particles were connected was cut off using "Watershed", and then the average particle size was calculated using "Analyze Particle". When calculating the average particle size, particles hanging at the ends of the image were removed to obtain the correct particle size.

[0094] 26μm was obtained from 4 regions. 2 The above SEM images of the area are used to calculate the average of the particle volume concentration and average particle size obtained from each SEM image as the particle volume concentration and the average particle size of the particles in the cross section of the white layer.

[0095] (L) * a * b * )

[0096] Based on geometric condition c of JIS-Z8772:2009, measurements were performed using a spectrophotometer (manufactured by Konica Minolta).

[0097] (Average far-infrared transmittance (wavelength 8μm~12μm) T) FIR )

[0098] Measurements were performed using an infrared spectrophotometer (Nicolet iS10, ThermoScientific). Here, the average transmittance is the average transmittance of light at each wavelength from 8 μm to 12 μm.

[0099] (Refractive index of resin matrix)

[0100] The measurements were performed using an infrared ellipsometry (JA Woollam, MD2000DI). Here, the refractive index is the refractive index of light with a wavelength of 550 nm.

[0101] (Arithmetic mean height Sa)

[0102] Based on ISO 25178, measurements were performed using a laser microscope (VK-X250, KEYENCE) at 150x objective.

[0103] (Average length RSm of roughness curve elements)

[0104] Based on JIS 0601, measurements were performed using a laser microscope (VK-X250, manufactured by KEYENCE) at 150x objective.

[0105] (Root mean square slope RΔq)

[0106] Based on JIS 0601, measurements were performed using a laser microscope (VK-X250, manufactured by KEYENCE) at 150x objective.

[0107] The following describes the manufacturing methods of the optical components in Examples 1 to 10.

[0108] (Example 1)

[0109] A 0.5mm thick Si support substrate was used as the substrate. No white layer was formed.

[0110] (Example 2)

[0111] NiO films were deposited as far-infrared anti-reflection films on both sides of the support substrate in Example 1. No white layer was formed. For film formation, a load-locked sputtering apparatus (RAS-1100BII, manufactured by SHINCRON) was used to form a NiO film with a thickness of approximately 1.2 μm by post-oxidation sputtering. The NiO film formation conditions are as follows.

[0112] (NiO film formation conditions)

[0113] Target: NiO (70 wt%) + Ni (30 wt%) mixed target

[0114] Sputtering gas: Ar gas (flow rate: 150 sccm)

[0115] Input power: 6kW

[0116] Reactive gas: Ar (flow rate 70 sccm) + O2 (flow rate: 10 sccm)

[0117] RF power: 2kW

[0118] Support substrate temperature: room temperature

[0119] Film-forming pressure: 0.19 Pa

[0120] (Example 3)

[0121] Chemical etching was performed on both sides of a 0.5 mm thick Si substrate to create uneven surfaces. The etching solution used consisted of KOH, an organic solvent, and a surfactant. The composition of the etching solution was adjusted to obtain the arithmetic mean height Sa, the average length RSm of the roughness curve elements, and the root mean square slope RΔq as shown in Table 1. No white layer was formed.

[0122] (Example 4)

[0123] The composition of the etching solution was adjusted in a way that could obtain the arithmetic mean height Sa, the average length RSm of the roughness curve elements, and the root mean square slope RΔq as shown in Table 1. Otherwise, the part was fabricated using the same method as in Example 3.

[0124] (Example 5)

[0125] A white layer containing TiO2 as microparticles and fluoropolymer as resin matrix was formed on the substrate of Example 1. The white layer was formed by spin-coating a white layer precursor onto the substrate and then drying it in an electric furnace at 190°C for 9 minutes. The white layer precursor consisted of a fluoropolymer coating containing TiO2 microparticles (Bonflon GT#2000, manufactured by AGC Coat Tech), a fluoropolymer coating (Bonflon#2050 clear, manufactured by AGC Coat Tech), and xylene. The composition was adjusted to achieve the white layer thickness and microparticle concentration shown in Table 1. The TiO2 microparticles existed in the white layer in the form of secondary particles.

[0126] (Examples 6 and 7)

[0127] The composition of the white layer precursor and the rotation speed of the spin coater were adjusted in such a way that the thickness of the white layer in Table 1 could be obtained. Otherwise, the optical components were fabricated using the same method as in Example 5.

[0128] (Examples 8~10)

[0129] The substrate was changed to that of Example 2, and the composition of the white layer precursor and the rotation speed of the spin coater were adjusted in such a way that the thickness of the white layer in Table 1 could be obtained. Otherwise, the optical component was manufactured using the same method as in Example 5.

[0130] The simulation methods of Examples 11 to 19 are described below.

[0131] (Examples 11~19)

[0132] To obtain the correction and scaling factors described later, a reference white layer (hereinafter referred to as the reference white layer) was actually prepared. 100 parts by mass of 1,11-dodecadiene (manufactured by Tokyo Chemical Industry Co., Ltd.), 125 parts by mass of 3-functional alkyl thiol (ACTOCURE SS32, manufactured by Kawaguchi Chemical Industry Co., Ltd.), and 2.2 parts by mass of azo polymerization initiator (V-65, manufactured by Fujifilm and Koko Pure Chemical Industries Co., Ltd.) were dissolved in methyl ethyl ketone. TiO2 particles were added, and the mixture was stirred by rotation. The resulting substance was used as the white layer precursor. The white layer precursor was dropped onto a substrate and then cured by UV irradiation using an exposure machine to form a reference white layer with a polyolefin resin matrix.

[0133] The following details the verification methods for each characteristic.

[0134] (L) * a * b * )

[0135] The refractive index *n* and extinction constant *k* of the particles and substrate were obtained using values ​​from well-known databases such as RefractiveIndex.INFO (https: / / refractiveindex.info / ). The refractive index *n* and extinction constant *k* of the resin matrix were measured values. Using these optical constants and particle size as input values, the scattering cross-section σ was calculated based on Mie's scattering theory. sca and absorption cross-sectional area σ abs Here, the scattering cross-section σ is calculated in such a way that the spectrum of scattered reflection obtained under conditions for reproducing the reference white layer is consistent with the spectrum of scattered reflection obtained from the reference white layer. sca The correction factor is used. The scattering cross-section σ obtained below by multiplying by the above correction factor will be... sca As the scattering cross-section σ sca The scattering cross-section σ sca Calculate the extinction coefficient K and the scattering coefficient μ.

[0136] The refractive index *n* and extinction constant *k* of the white layer at various particle concentrations were calculated using Bruggeman's effective medium approximation. The Fresnel reflectance *r* at the interface between the white layer and the atmosphere was then calculated using the calculated refractive index *n* and extinction constant *k*. 21 Fresnel reflectance r at the interface between the white layer and the substrate 23 Transmittance t from the atmosphere to the white layer 12 After calculating r 23 In this case, the values ​​on the substrate side are the experimental values ​​obtained from Examples 1 and 2.

[0137] Equation (1) is an example of a formula for expressing the intensity of the scattered electric field. Here, δ is the phase difference between the incident wave and the reflected wave, and L is the length (optical path length) of the incident light from the atmosphere-white layer interface to the white layer-substrate interface.

[0138]

[0139] For equation (1), the scattered reflection spectrum is calculated by integrating the scattering intensity over the entire region with respect to the incident angle using the spectrum of the D65 light source as the incident light source. Following the mathematical transformations of CIE 1976, the scattered reflection spectrum is converted to CIE XYZ space, and further transformed to calculate L. * a * b * .

[0140] (Average transmittance of far-infrared rays)

[0141] And calculate L * a * b * Similarly, considering the effective medium approximation and Mie scattering, the refractive index n and scattering cross-section σ are calculated. sca and absorption cross-sectional area σ sbs Next, the extinction constant k is calculated so that the transmittance calculated under conditions reproducing the reference white layer is consistent with the transmittance of the reference white layer. At this point, the refractive index is calculated as if the film has a visible monodisperse structure. The extinction coefficient κ is related to the scattering cross-section σ. sca and absorption cross-sectional area σ sbs Based on the proportional relationship, if the scattering cross-section σ sca and absorption cross-sectional area σ sbs Dividing by the extinction coefficient κ yields the proportionality constant. This proportionality constant is then used in conjunction with the scattering cross-section σ of each particle size. sca and absorption cross-sectional area σ sbs Simulated n and k for the white layer relative to each particle size were obtained. Using optical thin film simulation software (TFCalc, Software Spectra), the average far-infrared transmittance under the following conditions was calculated based on the simulated n and k.

[0142] Field of view: 2 degrees

[0143] Polarized light: p and s mixture

[0144] Angle of incidence: 0 degrees

[0145] The values ​​of the characteristics for Examples 1-19 are shown in Tables 1 and 2. In the case of a far-infrared anti-reflective film, the column for "Far-infrared anti-reflective film" is set to "0". For L... * a * b* T FIR Sa, RSm, and RΔq were measured on the light incident side of each sample. The results are shown in Tables 1-2.

[0146] [Table 1]

[0147]

[0148] [Table 2]

[0149]

[0150] As shown in Tables 1 and 2, it can be seen that in components with a white layer, by appropriately adjusting the material, concentration, and particle size of the microparticles, the material of the resin matrix, the thickness of the white layer, and the application of a far-infrared anti-reflective film, it is possible to achieve both high far-infrared transmittance and a white appearance. Specifically, in Examples 5 to 13, 18, and 19 as embodiments, by setting L* to 50 or more, a* to -15 to 15, b* to -15 to 15, and T... FIR The transmittance is 20% or more, thus achieving both high far-infrared transmittance and a white appearance. On the other hand, it can be seen that in Examples 1-4 and 14-17, which are comparative examples, at least one of them is not satisfied, and it is impossible to achieve both high far-infrared transmittance and a white appearance.

[0151] Examples 3 and 4 are comparative examples of optical components having multiple micro-unfolds on their surface. Example 3, through a suitable unfolding structure that scatters visible light and transmits far-infrared light, displays a higher L than Example 1. * However, the values ​​are not sufficient to achieve a white appearance. Example 4 is an example with a rough, uneven texture of scale 3. Example 4's L * It is similar to Example 3 in degree, but it hardly transmits far-infrared rays.

[0152] Examples 5-7 are examples where the resin matrix is ​​fluororesin, the microparticles are TiO2, and there is no far-infrared anti-reflective film. In Examples 5-7, the microparticle concentration and microparticle size are constant; only the thickness of the white layer differs.

[0153] Examples 8-10 are examples of far-infrared anti-reflective films with a fluororesin matrix, TiO2 particles, and a resin matrix. In Examples 8-10, the particle concentration and particle size are constant; only the thickness of the white layer differs.

[0154] Figure 3 The far-infrared transmittance of Examples 5-7 and Examples 8-10 is expressed as a function of L. * The relationship. In examples 5-7 and 8-10, L *The greater the thickness of the white layer, the lower the far-infrared transmittance. This is believed to be because as the film thickness of the white layer increases, the amount of particles in the white layer increases, leading to increased visible light scattering. On the other hand, the amount of resin matrix absorbing far-infrared rays also increases, resulting in greater absorption of far-infrared radiation. Furthermore, according to... Figure 3 It is known that by applying a far-infrared anti-reflective film, the same level of L* can be displayed as that of a component without a far-infrared anti-reflective film, and a higher far-infrared transmittance can be obtained.

[0155] Examples 11-15 are examples where the resin matrix is ​​a polyolefin resin, the particulates are TiO2, and there is no far-infrared anti-reflective film. Example 13 has the same level of particulate concentration, particulate size, and white layer thickness as Example 5, but differs in that the resin matrix is ​​a polyolefin resin instead of a fluororesin. Example 13 shows the same level of L as Example 5. * However, the far-infrared transmittance of Example 13 was significantly higher than that of Example 5. It is believed that high far-infrared transmittance can be obtained by using a resin with low far-infrared absorption as the resin matrix.

[0156] Figure 4 Examples 11-15 show the particle size and far-infrared transmittance and L. * The relationship. According to Figure 4 The study shows a trend where the larger the particle size, the lower the far-infrared transmittance. It is believed that if the particle size is too large, the far-infrared transmittance decreases due to increased scattering of far-infrared radiation based on the particles.

[0157] according to Figure 4 Display L * The light intensity increases with increasing particle size, then decreases. It is believed that by keeping the particle size within an appropriate range to fully scatter visible light, a high Lo can be obtained. * .

[0158] Examples 16 and 17 are examples where the material of the particles in Example 12 has been changed. Examples 16 and 17 show significantly lower L values ​​than in Example 12. * It is believed that SiO2 and MgO have lower scattering coefficients for visible light compared to TiO2, making it difficult to obtain high L values ​​when used as particulate matter. * However, even when SiO2 and MgO are used as particulates, for example, compared to the compositions of Examples 16 and 17, higher L can be obtained by appropriately increasing the thickness of the white layer and the particulate concentration. * However, increasing the thickness of the white layer and the concentration of particles reduces the far-infrared transmittance.

[0159] Regarding far-infrared transmittance, among Examples 12, 16, and 17, Example 17 shows the highest value. It is believed that the high far-infrared transmittance of Example 17 is due to the high far-infrared transmittance of MgO.

[0160] Examples 18 and 19 are examples of far-infrared anti-reflective films with a polyolefin resin matrix, TiO2 particles, and the same degree of far-infrared anti-reflective properties as Example 12. * However, the far-infrared transmittance is higher than that of Example 12. It can be seen that even in examples where the resin matrix is ​​a polyolefin resin, higher far-infrared transmittance can be obtained by applying a far-infrared anti-reflective film.

[0161] Example 19 is an example of a particularly thick white layer. As can be seen from Example 19, by using a resin with low far-infrared absorption in the resin matrix, a high far-infrared transmittance can be obtained even with a thick white layer.

[0162] Example 15 shows b values ​​less than -25. * It is believed that Example 15 shows a large absolute value of b through Mie resonance. * .

[0163] Symbol Explanation

[0164] 10 Optical Components

[0165] 20 White Layers

[0166] 30 Substrate

[0167] 31 Support substrate

[0168] 32a, 32b Far-infrared anti-reflective film

Claims

1. An optical member, in CIE 1976 (L * , a * , b * ) color system measured in SCE mode based on JIS-Z 8772:2009 geometric condition c, L * is 50 or more, a * is -15 to 15, and b * is -15 to 15. The average transmittance T of light having a wavelength of 8 μm to 12 μm FIR (%) is T FIR ≥ 20.

2. The optical component of claim 1, wherein, (L * + T FIR ≥ 115.

3. The optical component of claim 1, wherein, A white layer containing a resin matrix and microparticles dispersed in the resin matrix, and a substrate containing a support substrate.

4. The optical component of claim 3, wherein, The thickness of the white layer is 1 μm or more and less than 10 μm.

5. The optical component of claim 3, wherein, The average particle diameter of the microparticles in the cross section of the white layer is 0.1 μm to 1 μm.

6. The optical component of claim 3, wherein, The volume concentration of the microparticles in the white layer is 4% to 80%.

7. The optical component of claim 3, wherein, The microparticles contain at least one selected from TiO2, ZrO2, Nb2O5, and Ta2O5.

8. The optical component of claim 3, wherein, The support substrate contains at least one selected from Si-based substrates, Ge-based substrates, ZnS-based substrates, and chalcogenide glass substrates.

9. The optical component of claim 3, wherein, The resin matrix contains at least one of a fluororesin and a polyolefin resin.

10. The optical component of claim 3, wherein, The substrate is provided with a far infrared antireflection film that prevents reflection of light having a wavelength of 8 μm to 12 μm.

11. The optical component of claim 10, wherein, The far infrared antireflection film contains at least one selected from NiO, diamond-like carbon, ZrO2, ZnS, ZnSe, Ge, Si, MgO, ZnO, YF3, and MgF2.

12. A far infrared sensor module using the optical member described in any one of claims 1 to 11.

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