Optical Products and Concentrators

Abstract

[Problem] To provide a short wavelength selective reflection-type optical product in which deformation during manufacturing is suppressed, and a condenser whereby sensitivity of detection of light in a prescribed wavelength region can be increased. [Solution] An optical product 1 is provided with a substrate 2 and an optical multilayer film 4. The optical multilayer film 4 reflects light on a short-wavelength side and suppresses reflection of light that is more on a long-wavelength side than the light on the short-wavelength side. The first layer counted from the substrate 2 of the optical multilayer film 4 is an Al layer 10 made of Al, the second layer is a low-refractive-index layer 12 made of a low-refractive-index material, the third layer is a high-refractive-index layer 14 made of a high-refractive-index material, the fourth layer is a low-refractive-index layer 12 made of a low-refractive-index material, the fifth layer is an Al layer 10 made of Al, the sixth layer is a low-refractive-index layer 12 made of a low-refractive-index material, the seventh layer is a high-refractive-index layer 14 made of a high-refractive-index material, and the eighth layer is a low-refractive-index layer 12 made of a low-refractive-index material. A collector, wherein the optical product 1 is used.

Description

[Technical Field]

[0001] This application is based on and claims the benefit of priority from Japanese Patent Application No. 2021-031974, filed on March 1, 2021, the entire contents of which are incorporated herein by reference. The present invention relates to optical products such as concentrators with long wavelength absorbing mirrors, and concentrators that can belong to such optical products. [Background technology]

[0002] The cold mirror described in Patent Document 1 (JP 2006-259124 A) has a substrate, a dielectric multilayer film in which thin films with different refractive indices are alternately stacked, and an infrared-transmitting film having a refractive index higher than that of any of the thin films that make up the dielectric multilayer film. The infrared-transmitting film is interposed between the substrate and the dielectric multilayer film. This cold mirror allows unnecessary infrared rays to pass through, thereby dissipating heat, while the thin films that make up the dielectric multilayer film provide a high reflectance for visible light. The number of layers in the dielectric multilayer film is preferably 6 or more in

[0015] . Also, in the following examples

[0025] , the total thickness of the infrared-transmitting film and the dielectric multilayer film is 0.88 μm (micrometers). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-259124 Summary of the Invention [Problem to be solved by the invention]

[0004] If the total thickness of the cold mirror film is large, the film formation time becomes longer accordingly, and the temperature rise of the substrate during film formation becomes larger. In this case, the difference in the linear expansion coefficient between the substrate and the film may cause stress to be generated in the substrate and film, which may deform the cold mirror, or may cause the substrate to deform or melt, especially if it is made of resin.

[0005] Also, because of their ability to transmit infrared light (long wavelengths) and reflect visible light (short wavelengths), cold mirrors can be used as collectors for Cherencov Telescope Arrays (CTA). CTA is an astronomical observatory (gamma-ray observation device) that observes ultra-high energy (10 GeV to 100 TeraElectronV) gamma rays from celestial bodies from the Earth's atmosphere. When ultra-high energy gamma rays enter the Earth's atmosphere, they collide with atomic nuclei in the atmosphere, generating electron-positron pairs. These electrons and positrons then collide with other atomic nuclei, emitting further gamma rays, which exponentially multiply to produce an electromagnetic cascade (a large number of electrons, positrons, and gamma rays). These electrons and positrons travel faster than the speed of light in the atmosphere, producing Cherenkov radiation, which is observed on the ground as light concentrated in the wavelength range of 300 nm (nanometers) to 500 nm (300-500 nm, etc.). To efficiently detect Cherenkov light of such wavelengths in a terrestrial environment, it is necessary to use a photodetector that is not obscured by the light (nightglow) emitted from at least one of the night sky and stars. Conventional gamma-ray observations use photomultiplier tubes (PMTs), and the detection sensitivity of Cherenkov light can be increased by adjusting the adhesion of the PMT photocathode so that the quantum efficiency of the photocathode is high in the range of 300 to 500 nm. Meanwhile, with the recent development of semiconductor photodetector technology, there is growing momentum to use semiconductor photomultipliers (SiPMs), which have high light detection efficiency, even in gamma-ray observations. However, because silicon semiconductors have the characteristic of being highly sensitive to light of long wavelengths, they cannot selectively detect Cherenkov light, and the amount of night glow detected also increases, which can reduce the detection efficiency of Cherenkov light. To improve the detection efficiency of Cherenkov light even with SiPMs, it is possible to install a multilayer reflective low-pass filter on the front of the SiPM to selectively cut out long-wavelength light from the light that reaches the photodetector. However, SiPMs have the property of secondary emission of infrared light, which must be allowed to escape from the SiPM. If a reflective low-pass filter is installed on the front of the SiPM, the secondary emission of infrared light will be reflected back by the SiPM, so installing a low-pass filter to remove night glow will increase the amount of secondary emission of infrared light detected.

[0006] A primary object of the present disclosure is to provide a short-wavelength selective reflection optical product that is suppressed from being deformed during manufacturing. Another main objective of the present disclosure is to provide a collector that can increase the detection sensitivity of light in a predetermined wavelength range, such as Cherenkov light, in a SiPM or the like that cannot adjust the sensitivity to each wavelength range by itself and that secondary emits infrared light. [Means for solving the problem]

[0007] In order to achieve the above object, a substrate and an optical multilayer film formed directly or indirectly on a film-forming surface of the substrate are provided, and the optical multilayer film reflects light on the short wavelength side and suppresses reflection of light on the wavelength side longer than the short wavelength side, and has a first layer, a second layer, a third layer, a fourth layer, a fifth layer, a sixth layer, a seventh layer, and an eighth layer counting from the substrate side, and the first layer is a first Al layer made of Al, and the An optical product is provided in which the second layer is a first low refractive index layer made of a low refractive index material, the third layer is a first high refractive index layer made of a high refractive index material, the fourth layer is a second low refractive index layer made of a low refractive index material, the fifth layer is a second Al layer made of Al, the sixth layer is a third low refractive index layer made of a low refractive index material, the seventh layer is a second high refractive index layer made of a high refractive index material, and the eighth layer is a fourth low refractive index layer made of a low refractive index material. Also provided is an optical product comprising a substrate and an optical multilayer film formed directly or indirectly on a film-forming surface of the substrate, the optical multilayer film reflecting light on the short wavelength side and suppressing reflection of light on the wavelength side longer than the short wavelength light, the first layer of the optical multilayer film counting from the substrate side being a metal layer made of metal, the optical multilayer film further comprising one or more Al layers, at least one of a low refractive index layer made of a low refractive index material and a high refractive index layer made of a high refractive index material, disposed on the substrate side of the Al layer, and at least one of a low refractive index layer made of a low refractive index material and a high refractive index layer made of a high refractive index material, disposed on the air side of the Al layer, the physical film thickness of the metal layer being 20 nm or more, and the physical film thickness of the Al layer closest to the air being 5 nm or more and 35 nm or less. Furthermore, to achieve the above object, there is provided a light collector using the above optical product. [Effects of the Invention]

[0008] A main effect of the present disclosure is to provide a short wavelength selective reflection type optical product that is suppressed from being deformed during manufacturing. Another major advantage of the present disclosure is that a collector is provided that can enhance the detection sensitivity of light in a predetermined wavelength range, such as Cherenkov light, in a SiPM or the like that cannot adjust the sensitivity to each wavelength range by itself and that secondary emits infrared light. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view of an optical product according to an embodiment of the present invention. [Figure 2] 1 is a schematic diagram of a vapor deposition apparatus when an optical product according to an embodiment of the present invention is formed by vapor deposition. [Figure 3] FIG. 2 is a schematic perspective view of a group of concentrators and a portion of an element mounting surface according to an embodiment of the present invention. [Figure 4] 1 is a schematic central longitudinal end view of a collector according to an embodiment of the present invention; FIG. [Figure 5] 1 is a graph showing the optical constants of Al. [Figure 6]1 is a graph showing the optical constants of Ta2O5. [Figure 7] 1 is a graph showing the optical constants of SiO2. [Figure 8] 10 is a graph showing simulated spectral reflectance distribution in the visible range and its adjacent ranges according to Comparative Example 1. [Figure 9] 1 is a graph showing the spectral reflectance distribution in the visible range and its adjacent range according to Comparative Example 1 actually fabricated on a PC board. [Figure 10] FIG. 1 is a schematic side view of Comparative Example 1 actually fabricated on a glass substrate. [Figure 11] 1 is a graph showing the relationship between wavelength and various light detection efficiencies. [Figure 12] 10 is a graph showing the relationship between the angle of incidence θ of light of various wavelengths on the collector and the light collection efficiency in Comparative Example 1 in a simulation. [Figure 13] 10 is a graph showing simulated spectral reflectance distribution in the visible range and its adjacent ranges according to Comparative Example 2. [Figure 14] 10 is a graph showing the spectral reflectance distribution in the visible range and its adjacent range according to Comparative Example 2, which was actually fabricated on a PC board. [Figure 15] 10 is a graph showing the relationship between the angle of incidence θ of light of various wavelengths on the collector and the light collection efficiency in Comparative Example 2 in a simulation. [Figure 16] 1 is a graph showing simulated spectral reflectance distributions in the visible range and adjacent ranges for Examples 1 to 9 and Comparative Example 3. [Figure 17] 1 is a graph showing the relationship between the physical film thickness (nm) of the fifth Al layer and the IR / UV ratio (%) in a simulation in Examples 1 to 9 and Comparative Example 3. [Figure 18] 10 is a graph showing simulated spectral reflectance distributions in the visible range and adjacent ranges for Examples 3, 3-1, and 3-2. [Figure 19] 1 is a graph showing the spectral reflectance distribution in the visible range and its adjacent range for Examples 2 to 5 actually fabricated on a PC board. [Figure 20]1 is a graph showing the optical constants of MgF2. [Figure 21] 10 is a graph showing the spectral reflectance distribution in the visible range and its adjacent range for Examples 2 and 2-1 actually fabricated on a PC board. [Figure 22] 10 is a graph showing the relationship between the incident angle θ of light of various wavelengths to the collector and the light collection efficiency in the first example in a simulation. [Figure 23] 10 is a graph showing the relationship between the incident angle θ of light of various wavelengths to the collector and the light collection efficiency in Example 2 in a simulation. [Figure 24] 10 is a graph showing the relationship between the incident angle θ of light of various wavelengths to the collector and the light collection efficiency in Example 3 in a simulation. [Figure 25] 1 is a graph showing the optical constants of HfO2. [Figure 26] 1 is a graph showing simulated spectral reflectance distributions (reflection angle δ=65°) in the visible range and adjacent ranges for Examples 11 to 19 and Comparative Example 13. [Figure 27] 10 is a graph showing the relationship between the physical film thickness (nm) of the fifth Al layer and the IR / UV ratio (%) in a simulation in Examples 11 to 19 and Comparative Example 13. [Figure 28] 1 is a graph showing simulated spectral reflectance distributions (reflection angle δ=65°) in the visible range and adjacent ranges for Examples 21 to 29 and Comparative Example 23. [Figure 29] 10 is a graph showing the relationship between the physical film thickness (nm) of the fifth Al layer and the IR / UV ratio (%) in a simulation in Examples 21 to 29 and Comparative Example 23. [Figure 30] 1 is a graph showing the optical constants of TiO2. [Figure 31] 10 is a graph showing simulated spectral reflectance distributions (reflection angle δ=65°) in the visible range and adjacent ranges for Examples 31 to 39 and Comparative Example 33. [Figure 32] 10 is a graph showing the relationship between the physical film thickness (nm) of the fifth Al layer and the IR / UV ratio (%) in a simulation in Examples 31 to 39 and Comparative Example 33. [Figure 33] 10 is a graph showing simulated spectral reflectance distribution in the visible range and its adjacent range for Example 40. [Figure 34] 1 is a graph showing simulated spectral reflectance distributions (reflection angle δ=65°) in the visible range and adjacent ranges for Examples 51 to 56 and Comparative Examples 53 to 54. [Figure 35] 10 is a graph showing the relationship between the physical film thickness (nm) of the first Al layer and the IR / UV ratio (%) in a simulation in Examples 51 to 56 and Comparative Examples 53 to 54. [Figure 36] 10 is a graph showing simulated spectral reflectance distributions (reflection angle δ=65°) in the visible range and adjacent ranges for Examples 61 to 67 and Comparative Example 63. [Figure 37] 10 is a graph showing the relationship between the physical film thickness (nm) of the fourth second Al layer and the IR / UV ratio (%) in a simulation in Examples 61 to 67 and Comparative Example 63. [Figure 38] 1 is a graph showing simulated spectral reflectance distributions (reflection angle δ=45°) in the visible range and adjacent ranges for Examples 71 to 78 and Comparative Example 73. [Figure 39] 10 is a graph showing the relationship between the physical film thickness (nm) of the fourth second Al layer and the IR / VL ratio (%) in a simulation in Examples 71 to 78 and Comparative Example 73. [Figure 40] 10 is a graph showing simulated spectral reflectance distributions for Example 72 (fourth layer Al film thickness: 10 nm), the distributions being related to three reflection angles δ=30°, 45°, and 60°. [Figure 41] 10 is a graph showing simulated spectral reflectance distributions (reflection angle δ=65°) in the visible range and adjacent ranges for Examples 81 to 87 and Comparative Example 83. [Figure 42] 10 is a graph showing the relationship between the physical film thickness (nm) of the fourth second Al layer and the IR / UV ratio (%) in a simulation in Examples 81 to 87 and Comparative Example 83. [Figure 43]1 is a graph showing simulated spectral reflectance distributions (reflection angle δ=65°) in the visible range and adjacent ranges for Examples 91 to 97 and Comparative Example 93. [Figure 44] 10 is a graph showing the relationship between the physical film thickness (nm) of the seventh second Al layer and the IR / UV ratio (%) in a simulation in Examples 91 to 97 and Comparative Example 93. [Figure 45] 1 is a graph showing simulated spectral reflectance distributions (reflection angle δ=65°) in the visible range and adjacent ranges for Examples 101 to 107 and Comparative Example 103. [Figure 46] 10 is a graph showing the relationship between the physical film thickness (nm) of the ninth second Al layer and the IR / UV ratio (%) in a simulation in Examples 101 to 107 and Comparative Example 103. [Figure 47] 1 is a graph showing simulated spectral reflectance distributions (reflection angle δ=45°) in the visible range and adjacent ranges for Examples 111 to 117 and Comparative Example 113. [Figure 48] 10 is a graph showing the relationship between the physical film thickness (nm) of the ninth, fourth Al layer and the IR / VL ratio (%) in a simulation in Examples 111 to 117 and Comparative Example 113. [Figure 49] 10 is a graph showing simulated spectral reflectance distributions of a modified example of Example 111 (9th layer Al film thickness: 7 nm), the graph showing distributions at three reflection angles δ=30°, 45°, and 60°. [Figure 50] 1 is a graph showing simulated spectral reflectance distributions (reflection angle δ=65°) in the visible range and adjacent ranges for Examples 121 to 128. [Figure 51] 1 is a graph showing the IR / UV ratio (%) in Examples 121 to 128. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, examples of embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the following examples.

[0011] ≪First form≫ [Optical product configuration, etc.] As shown in FIG. 1, the optical product 1 according to the first embodiment includes a substrate 2 and an optical multilayer film 4 formed on a film-forming surface F of the substrate 2 via an underlayer 3.

[0012] The substrate 2 is a base on which the optical product 1 is formed, and is in the form of a plate (substrate) in this case. The shape of the substrate 2 may be a flat plate, a curved plate, or a shape other than a plate, such as a block shape. Plastic is used as the material of the substrate 2, and in this case, polycarbonate resin (PC), which is a thermosetting resin, is used. Note that the material of the substrate 2 is not limited to PC, and may be, for example, polyurethane resin, thiourethane resin, episulfide resin, polyester resin, acrylic resin, polyethersulfone resin, poly-4-methylpentene-1 resin, diethylene glycol bisallyl carbonate resin, or a combination thereof. Furthermore, the material of the substrate 2 may be glass or other materials other than plastic.

[0013] The substrate 2 has a film-forming surface F disposed on its front surface, with the optical multilayer coating 4 provided on the front surface via an underlayer 3. The optical multilayer coating 4 may be provided on both the front and back surfaces, or on three or more surfaces of a block-shaped substrate 2, for example. These optical multilayer coatings 4 may have the same configuration, or may have different configurations, such as having different film thicknesses for some or all of the surfaces. Alternatively, the underlayer 3 may be omitted, and the optical multilayer coating 4 may be provided directly on the film-forming surface F of the substrate 2. Furthermore, the underlayer 3 may be composed of multiple layers. Additionally, a surface layer such as an antifouling film (water-repellent film, oil-repellent film, or water- and oil-repellent film) may be provided on the front surface (air side, opposite the substrate 2) of the optical multilayer coating 4.

[0014] The underlayer 3 is provided to achieve at least one of the following two purposes. First, the underlayer 3 is provided to improve the adhesion of the optical multilayer film 4 (particularly the first Al layer 10 counting from the substrate 2 side (same below)) to the substrate 2 compared to when the film is formed directly on the substrate 2. Second, the underlayer 3 is provided to suppress gas release from the substrate 2 and maintain the film quality of the optical multilayer film 4 (first Al layer 10) thereon. The underlayer 3 may be provided to achieve another purpose instead of or in addition to at least one of these purposes. The underlayer 3 is made of, for example, alumina (Al2O3), chromium (Cr), or a combination thereof. The underlayer 3 may be treated as a component (first layer) of the optical multilayer film 4.

[0015] The optical multilayer film 4 is a multilayer film having a total of eight layers. The optical multilayer film 4 comprises an Al layer 10 (first Al layer) as a first layer, a low refractive index layer 12 (first low refractive index layer) as a second layer, a high refractive index layer 14 (first high refractive index layer) as a third layer, a low refractive index layer 12 (second low refractive index layer) as a fourth layer, an Al layer 10 (second Al layer) as a fifth layer, a low refractive index layer 12 (third low refractive index layer) as a sixth layer, a high refractive index layer 14 (second high refractive index layer) as a seventh layer, and a low refractive index layer 12 (fourth low refractive index layer) as an eighth layer. The optical multilayer film 4 may have a structure of these eight layers, but may also have one or more layers closer to the substrate 2 than the first layer, or one or more layers closer to the air than the eighth layer, thereby making the film have nine or more layers (for example, ten or twelve layers).

[0016] Each Al layer 10 is made of aluminum. The first Al layer 10 mainly reflects or absorbs light with wavelengths from the ultraviolet to the visible range (e.g., light with wavelengths of 300 to 750 nm). Here, the visible range is 400 to 750 nm. Therefore, the material of the underlayer 3 does not fundamentally affect the optical properties of the optical multilayer film 4. The physical thickness of the first Al layer 10 is set to, for example, 100 nm or more in order to ensure sufficient reflection and absorption. Furthermore, the physical thickness of the first Al layer 10 is set to, for example, 200 nm or less, 150 nm or less, or 130 nm or less in order to suppress a decrease in reflectance due to an increase in surface roughness and to suppress an increase in cost due to an increase in film thickness. The visible range is not limited to the above, and may have a lower limit of 410 or 420 nm, or an upper limit of 700, 720, 780, or 800 nm.

[0017] The fifth Al layer 10 contributes greatly to the increase or decrease of the reflectance mainly on the long wavelength side. If the physical film thickness of the fifth Al layer 10 is zero (if the fifth Al layer 10 does not exist), the reflectance on the long wavelength side will be higher than the reflectance on the short wavelength side. Furthermore, if the physical thickness of the fifth Al layer 10 is thin, the reflectance on the long wavelength side will be lower than the reflectance on the short wavelength side, and if the physical thickness of the fifth Al layer 10 is thick, the reflectance on the long wavelength side will be higher than the reflectance on the short wavelength side. Such properties are realized mainly by the absorption of long wavelength light in the fifth Al layer 10. Based on such properties, adjusting the physical thickness of the fifth Al layer 10 mainly adjusts the properties of the optical multilayer coating 4, which reflects short wavelength light and suppresses reflection of light longer than the short wavelength light. An optical product 1 (optical multilayer coating 4) with such properties can be said to be a long wavelength absorption mirror or a short wavelength selective reflection mirror. Furthermore, if the physical film thickness of the fifth Al layer 10 is thicker than a predetermined value, the fifth Al layer 10 itself becomes like a normal metallic mirror, and the reflectivity becomes high regardless of whether it is on the long wavelength side or the short wavelength side.

[0018] The long-wavelength band can be set anywhere between the UV and infrared ranges by adjusting the film design. For example, with Cherenkov radiation in mind, the wavelength range of 600 nm or more may be considered the long-wavelength range, and the wavelength range below 600 nm may be considered the short-wavelength range. In this case, the IR / UV ratio, defined by the following equation (1), represents the performance of the optical product 1 in terms of the low reflection of long-wavelength light relative to the reflection of short-wavelength light. In other words, the smaller the IR / UV ratio, the more the reflection of long-wavelength light is suppressed relative to the reflection of short-wavelength light, resulting in a better performance of the optical product 1, which reflects on the short-wavelength side and suppresses reflection on the long-wavelength side, like a cold mirror. Note that, hereinafter, regardless of the short-wavelength and long-wavelength bands, anything that reflects on the short-wavelength side and suppresses reflection on the long-wavelength side is referred to as a cold mirror. Furthermore, for example, an IR / UV ratio', which is an index similar to the IR / UV ratio, is defined by the following formula (2).

[0019]

number

number

[0020] The physical thickness of the fifth Al layer 10 is set to, for example, 5 nm or more and 30 nm or less in order to ensure better performance (smaller IR / UV ratio or IR / UV ratio', etc.) in the optical product 1. If the physical thickness of the fifth Al layer 10 is less than 5 nm, it becomes relatively difficult to uniformly form the fifth Al layer 10. If the physical thickness of the fifth Al layer 10 exceeds 30 nm, additional Al material is required, which increases costs.

[0021] Each low refractive index layer 12 is made of a low refractive index material, which is an inorganic dielectric, such as a metal oxide or a metal fluoride, such as silicon oxide (SiO2), calcium fluoride (CaF2), magnesium fluoride (MgF2), or a mixture of two or more of these. Each high refractive index layer 14 is made of a high refractive index material that is an inorganic dielectric and a metal oxide, such as tantalum oxide (Ta2O5), zirconium oxide (ZrO2), titanium oxide (TiO2), niobium oxide (Nb2O5), hafnium oxide (HfO2), selenium oxide (CeO2), aluminum oxide (Al2O3), yttrium oxide (YO2), or a mixture of two or more of these. At least one of the low refractive index layers 12 and the high refractive index layers 14 may be made of the same material, which simplifies film design and reduces film formation costs. The physical film thickness of each low refractive index layer 12 and each high refractive index layer 14 is a factor that mainly determines the reflection band of the optical multilayer film 4. For example, if the physical film thickness of all of the low refractive index layers 12 and each high refractive index layers 14 is increased, the reflection band shifts to the longer wavelength side, and if the physical film thickness of all of the low refractive index layers 12 and each high refractive index layers 14 is decreased, the reflection band shifts to the shorter wavelength side.

[0022] [Manufacturing methods for optical products] The underlayer 3 and each layer of the optical multilayer film 4 in the optical product 1 are formed in sequence on the film formation surface F of the substrate 2 by physical vapor deposition (PVD), vacuum deposition, sputtering, etc. The manufacturing methods for each layer of the underlayer 3 and the optical multilayer film 4 are the same, for example, from the viewpoint of ensuring ease of manufacturing. The manufacturing method for some of the layers of the underlayer 3 and the optical multilayer film 4 may be different from the manufacturing method for the other parts.

[0023] A case where the underlayer 3 and each layer of the optical multilayer film 4 are formed by vacuum deposition in a deposition apparatus 51 will be described below. FIG. 2 is a schematic diagram of a vapor deposition device 51. As shown in FIG. The vapor deposition device 51 includes a chamber 52, a vapor deposition dome 54, a plurality of (here, two of each) evaporation source holders 56A and 56B, shutters 57A and 57B, and an ion gun 58.

[0024] The chamber 52 is a sealable container, and the inside of the chamber 52 is evacuated by a pump (not shown). The deposition dome 54 is disk-shaped. The deposition dome 54 is horizontally disposed within the chamber 52 so as to be rotatable around a vertical central axis. The deposition dome 54 holds the substrate 2. The number of substrates 2 held by the deposition dome 54 may be one, as shown in FIG. 2, or may be multiple. The evaporation source holder 56A is disposed opposite the deposition dome 54 and holds the evaporation source JA in a heatable manner. The evaporation source holder 56B is similar to the evaporation source holder 56A except that it holds an evaporation source JB separate from the evaporation source JA in a heatable manner. The shutter 57A is provided so as to be switchable between a state in which it shields the upper side (the deposition dome 54 side) of the evaporation source holder 56A and a state in which it does not shield the upper side of the evaporation source holder 56B. The shutter 57B is provided so as to be switchable between a state in which it shields the upper side of the evaporation source holder 56B and a state in which it does not shield the upper side of the evaporation source holder 56B. The ion gun 58 is provided on the evaporation source holder 56 side and irradiates the chamber 52 with an ionized gas (ion beam I) (ion source). The gases are O2 gas and Ar gas. However, other gases may be used. For example, Ar gas may be replaced with another rare gas or may be omitted. Incidentally, only one set of the evaporation source holder 56A, the evaporation source JA, and the shutter 57A may be provided, or three or more sets may be provided.

[0025] In the deposition apparatus 51, the chamber 52 is first evacuated, and as a pre-treatment, ionized O2 gas and ionized Ar gas are irradiated by the ion gun 58 under predetermined conditions to clean the substrate 2 (ion cleaning). More specifically, by irradiating the substrate 2 with the ion beam I, even if organic matter or the like is attached to the substrate 2, the organic matter or the like is decomposed and removed by the ion beam I. This cleaning improves the adhesion of a film to be formed later.

[0026] Next, with shutter 57A open and shutter 57B closed, Al2O3 as the evaporation source JA is heated, and an ion beam I is irradiated from ion gun 58 toward substrate 2 which is rotated and moved by deposition dome . The Al2O3 evaporated from the evaporation source JA by heating becomes an underlayer 3 made of Al2O3 on the deposition surface F of the substrate 2. The underlayer 3 is more stably fixed to the deposition surface F of the substrate 2 by the action of the ion beam I, etc. The physical thickness of the underlayer 3 is controlled by the deposition rate and deposition time. The physical thicknesses of the other layers are controlled in a similar manner.

[0027] Next, with shutter 57B open and shutter 57A closed, Al as evaporation source JB is heated without being irradiated with ion beam I, and the Al evaporated from evaporation source JB becomes the first Al layer 10 of the optical multilayer film 4 on the underlayer 3. Furthermore, the evaporation source JA is replaced with the evaporation material for the low refractive index layer 12, and with shutter 57A open and shutter 57B closed, the evaporation material for the low refractive index layer 12 is heated to form the second low refractive index layer 12 on the Al layer 10. Thereafter, one of the evaporation sources JA and JB is replaced with a deposition material for the high refractive index layer 14, or an ion beam I of oxygen gas (including Ar gas as appropriate) is irradiated as necessary, and the third high refractive index layer 14, the fourth low refractive index layer 12, the fifth Al layer 10, the sixth low refractive index layer 12, the seventh high refractive index layer 14, and the eighth low refractive index layer 12 are deposited in this order. In this way, the optical product 1 is completed.

[0028] [Concentrators, etc.] 3 and 4, a plurality of concentrators 101 are provided to correspond to the plurality of SiPMs, respectively. Each concentrator 101 is for a CTA. However, each concentrator 101 may also be used for other purposes. The SiPMs are arranged in a staggered manner as viewed from above in the element mounting portion E. For example, about 2000 SiPMs are provided. Each concentrator 101 has a hexagonal cylindrical shape. Each concentrator 101 is placed on the SiPM so as to surround the center of the SiPM. Each concentrator 101 tapers from the upper end to the lower end (cone-shaped). The coating of the present invention is applied to the inner surface of each concentrator 101. The shape of each concentrator 101 may be a square cylindrical shape, or may be a part of a cylinder such as a semi-cylinder, or may be a curved plate or a flat plate. The taper of each concentrator 101 may be provided only in the center in the vertical direction, or may taper from the lower end to the upper end, or may be omitted. The height of each collector 101 is, for example, about 70 mm (millimeters). The length of one side of the hexagonal opening at the top end of each collector 101 is, for example, about 50 mm.

[0029] Each surface (six surfaces) constituting each collector 101 is an optical product 1 with the film-forming surface F facing inward. Each substrate 2 in one collector 101 is arranged in a cylindrical shape and constitutes a collector body 102. In each collector 101, an optical multilayer film 4 is arranged on the inner surface of the collector body 102. Each collector 101 is formed from an optical product 1 as a cold mirror. The optical multilayer film 4 may be disposed only on a portion of the inner surface of the collector body 102. Each collector 101 may be formed by fixing the optical product 1 including the substrate 2 to the inner surface of a hexagonal cylindrical base body. In this case, the base body and the substrate 2 form the collector body 102.

[0030] Light from the sky is reflected by the parabolic mirror, selectively guided by the optical component 1, and collected on the SiPM. As shown in particular in Figure 4, light incident at an incident angle θ with respect to the normal to the SiPM (the central axis of the concentrator 101) is incident on the inner surface of the concentrator 101 at a reflection angle δ with respect to the normal to the inner surface, is reflected at the same reflection angle δ with respect to the normal, and reaches the SiPM. For example, each collector 101 selectively guides light of 300 to 500 nm to the SiPM by using an optical multilayer film 4 that has high reflectance for light of 300 to 500 nm and low reflectance for light of wavelengths beyond 500 nm. Part or all of the light of wavelengths beyond 500 nm is absorbed by the optical multilayer film 4. Moreover, the infrared rays secondarily emitted from the SiPM are light in a wavelength range exceeding 500 nm, so that the reflection of the infrared rays at the optical multilayer film 4 is suppressed, and the infrared rays are prevented from returning to the SiPM and affecting the detection of light on the short wavelength side.

[0031] The collectors 101 are arranged so that one side of each upper end opening of the adjacent collectors 101 is in contact with each other. The group of collectors 101 has a honeycomb shape when viewed from above. The upper part of the group of collectors 101 has a honeycomb structure with an outer shape of, for example, about 3 m (meters) in diameter. The CTA includes a group of collectors 101 and an element installation section E, and detects Cherenkov light concentrated in the 300 to 500 nm wavelength range from the night sky.

[0032] ≪Second form≫ [Optical product configuration, etc.] The optical product of the second embodiment is configured similarly to the optical product 1 of the first embodiment, except for the optical multilayer film. Hereinafter, parts that are similar to the optical product 1 of the first embodiment will be appropriately designated by the same reference numerals, and explanations thereof will be omitted.

[0033] Although the configuration of the optical multilayer coating of the second embodiment is different from that of the optical multilayer coating 4 of the first embodiment, it satisfies the following various conditions, just like the optical multilayer coating 4 of the first embodiment. That is, the optical multilayer film of the second embodiment includes a low refractive index layer 12 made of a dielectric material, a high refractive index layer 14 made of a dielectric material, a metal layer made of a metal, and a second Al layer made of Al. The metal layer is, for example, a first Al layer made of Al or an Ag layer made of Ag (silver). The physical film thickness of the metal layer is preferably 20 nm or more. Furthermore, a third Al layer made of Al may be further disposed closer to the air side than the second Al layer, and similarly, a fourth Al layer and subsequent Al layers may be appropriately disposed.

[0034] Furthermore, the metal layer is disposed between the second Al layer and the substrate 2, and is preferably disposed as the first layer counting from the substrate 2 side. When the metal layer is an Ag layer or the like (other than Al), the first Al layer does not exist, but for clarity, the second Al layer is still referred to as the second Al layer, and when a third Al layer is further present, the third and subsequent Al layers are also referred to as the same. Additionally, at least one of one or more low refractive index layers 12 and one or more high refractive index layers 14 is disposed between the metal layer and the second Al layer. Furthermore, at least one of one or more low refractive index layers 12 and one or more high refractive index layers 14 is disposed on the air side of the second Al layer.

[0035] Each layer of the optical multilayer coating of the second type is formed in the same manner as the corresponding layer of the optical multilayer coating 4 of the first type.

[0036] The Al layer closest to the air contributes greatly to increasing or decreasing the reflectance mainly on the long wavelength side, similar to the fifth layer (closest to the air) Al layer 10 of the first embodiment. If the physical film thickness of the fifth Al layer 10 is zero (if the fifth Al layer 10 does not exist), the reflectance on the long wavelength side will be higher than the reflectance on the short wavelength side. Furthermore, if the physical thickness of the Al layer closest to the air is thin, the reflectance on the long wavelength side will be lower than the reflectance on the short wavelength side, and if the physical thickness of the Al layer closest to the air is thick, the reflectance on the long wavelength side will be higher than the reflectance on the short wavelength side. This property is realized mainly by the absorption of long wavelength light in the Al layer closest to the air. Based on this property, by adjusting mainly the physical thickness of the Al layer closest to the air, the properties of the optical multilayer coating 4, which reflects short wavelength light and suppresses reflection of light longer than the short wavelength light, can be adjusted. Furthermore, if the physical film thickness of the Al layer closest to the air side is thicker than a predetermined value, the Al layer closest to the air side itself becomes like a normal metallic mirror, and the reflectivity becomes high regardless of whether it is on the long wavelength side or the short wavelength side.

[0037] In the second embodiment, the long wavelength and short wavelength bands can be arbitrarily set between the UV region and the infrared region by adjusting the film design, as in the first embodiment. In the second embodiment, similarly to the first embodiment, the short wavelength side is set to 300 to 500 nm and the long wavelength side is set to 600 to 800 nm, and performance can be evaluated by various IR / UV ratios. In the second embodiment, with periscope cameras and the like in mind, the short wavelength side can be 400 to 600 nm and the long wavelength side can be 700 to 900 nm. In this case, the IR / VL ratio, which is similar to the IR / UV ratio and is defined by the following formula (3), represents the performance of the low reflectance of light on the long wavelength side relative to the reflectance of light on the short wavelength side. Note that, even in the first embodiment, the short wavelength side can be 400 to 600 nm and the long wavelength side can be 700 to 900 nm, and performance can be evaluated by the IR / VL ratio. Furthermore, at least one of the upper and lower limits of the wavelength range on the short wavelength side and the upper and lower limits of the wavelength range on the long wavelength side can be changed. A periscope camera captures images by reflecting visible light (VL) from a lens using a mirror like a periscope and directing it toward an image sensor installed at a different angle (e.g., 90°) from the lens. Because it is compact considering its optical path length, it is often built into mobile devices. Image sensors are sensitive to near-infrared (IR) light in addition to visible light. Near-infrared light, which is nearly invisible, can adversely affect the image. Therefore, image quality can be improved by using a mirror to reflect visible light toward the image sensor and transmit and block near-infrared light. According to the characteristics of typical image sensors, image quality improves when light with wavelengths above 700 nm is blocked. Furthermore, blocking near-infrared light from reaching the image sensor reduces temperature rise, resulting in more stable operation.

[0038]

number

[0039] The physical film thickness of the second Al layer closest to the air is preferably 5 nm to 35 nm, more preferably 5 nm to 30 nm, from the viewpoint of ensuring better performance (smaller IR / UV ratio, IR / UV ratio, IR / UVL ratio, etc.) in optical products. Similarly, when a third Al layer or a fourth Al layer, etc., is present, the physical film thickness of the Al layer closest to the air is preferably 5 nm to 35 nm, more preferably 5 nm to 30 nm. If the physical thickness of the air-side Al layer is less than 5 nm, it becomes relatively difficult to form a uniform Al layer on the air side.If the physical thickness of the air-side Al layer exceeds 35 nm, additional Al material is required, which increases costs.

[0040] [2-1 form ~ 2-7 form, etc.] The optical multilayer film of type 2-1, which belongs to the second type, has a total of six layers, which are, from the first layer onwards, a first Al layer (metal layer), a low refractive index layer 12, a high refractive index layer 14, a second Al layer, a low refractive index layer 12, and a high refractive index layer 14. The physical film thickness of the first Al layer, which is the first layer, is 20 nm or more. The physical film thickness of the second Al layer, which is the fourth layer, is 5 nm or more and 30 nm or less. The optical multilayer film of type 2-1 is expressed as "MLHALH", where the metal layer is "M", the Al layer is "A", the low refractive index layer 12 is "L", and the high refractive index layer 14 is "H". Furthermore, the optical multilayer film of type 2-2, which belongs to type 2, has a total of six layers, which are, from the first layer onwards, a first Al layer (metal layer), a low refractive index layer 12, a high refractive index layer 14, a second Al layer, a low refractive index layer 12, and a high refractive index layer 14. The physical film thickness of the first Al layer, which is the first layer, is 20 nm or more. The physical film thickness of the second Al layer, which is the fourth layer, is 5 nm or more and 30 nm or less. The optical multilayer film of type 2-2 is expressed as "MLHALH", just like type 2-1. Furthermore, the optical multilayer film of type 2-3, which belongs to type 2, has a total of six layers, which are, from the first layer onwards, an Ag layer (metal layer), a low refractive index layer 12, a high refractive index layer 14, a second Al layer, a low refractive index layer 12, and a high refractive index layer 14. The physical film thickness of the first Ag layer is 20 nm or more. The physical film thickness of the fourth second Al layer is 5 nm or more and 30 nm or less. The optical multilayer film of type 2-3 is expressed as "MLHALH" ​​in the same way as type 2-1.

[0041] In addition, the optical multilayer film of type 2-4, which belongs to type 2, has a total of five layers, which are, from the first layer onwards, a first Al layer (metal layer), a low refractive index layer 12, a high refractive index layer 14, a second Al layer, and a high refractive index layer 14. The physical film thickness of the first Al layer, which is the first layer, is 20 nm or more. The physical film thickness of the second Al layer, which is the fourth layer, is 5 nm or more and 30 nm or less. The optical multilayer film of type 2-4 is expressed as "MLHAH". The optical multilayer film of type 2-5, which belongs to type 2, has a total of nine layers, which are, starting from the first layer, a first Al layer (metal layer), a low refractive index layer 12, a high refractive index layer 14, a second Al layer, a low refractive index layer 12, a high refractive index layer 14, a third Al layer, a low refractive index layer 12, and a high refractive index layer 14. The physical film thickness of the first Al layer, which is the first layer, is 20 nm or more. The physical film thickness of the third Al layer, which is the seventh layer, is 5 nm or more and 30 nm or less. The optical multilayer film of type 2-5 is expressed as "MLHALHALH". Furthermore, the optical multilayer film of type 2-5 is expressed as "M(LHA)" when the number of repetitions of "LHA" is written to the upper right of each "LHA". 2 It is expressed as "LH". Furthermore, the optical multilayer film of type 2-6, which belongs to type 2, has a total of 11 layers, which are, from the first layer onwards, a first Al layer (metal layer), a low refractive index layer 12, a high refractive index layer 14, a low refractive index layer 12, a high refractive index layer 14, a second Al layer, a low refractive index layer 12, a high refractive index layer 14, a third Al layer, a low refractive index layer 12, and a high refractive index layer 14. The physical film thickness of the first Al layer, which is the first layer, is 20 nm or more. The physical film thickness of the third Al layer, which is the ninth layer, is 5 nm or more and 30 nm or less. The optical multilayer film of type 2-6 is called "MLHLHALHALH" ​​or "MLH(LHA) 2 It is expressed as "LH". Furthermore, the optical multilayer film of type 2-7 belonging to type 2 has a total of 11 layers, which are, from the first layer, a first Al layer (metal layer), a high refractive index layer 14, a second Al layer, a low refractive index layer 12, a high refractive index layer 14, a third Al layer, a low refractive index layer 12, a high refractive index layer 14, a fourth Al layer, a low refractive index layer 12, and a high refractive index layer 14. The physical film thickness of the first Al layer, the first layer, is 20 nm or more. The physical film thickness of the ninth layer, the fourth Al layer, is 5 nm or more and 30 nm or less. The optical multilayer film of type 2-7 is called "MHALHALHALH" ​​or "MHA (LHA) 2 It is expressed as "LH".

[0042] ≪Third form≫ [3rd-1st form ~ 3rd-8th form, etc.] The optical product of the third form is similar to the optical product of the second form. The optical multilayer film of type 3-1, which belongs to the third type, has a total of four layers and has the "MHAL" structure. The optical multilayer film of type 3-2, which belongs to the third type, has a total of four layers and has an "MLAL" configuration. The optical multilayer film of type 3-3, which belongs to the third type, has a total of five layers and has the "MLHAH" structure.

[0043] The optical multilayer coating of the third type, type 3-4, has a total of eight layers and has a structure of "MLHALHAH". The optical multilayer coating of the third type, type 3-4, has two adjacent sets of "LHA" in the optical multilayer coating of type 3-3, that is, "M(LHA) 2 The name is "H". The optical multilayer coating of type 3-5, which belongs to type 3, has a total of 11 layers and has the structure of "MLHALHALHAH". The optical multilayer coating of type 3-5 is structured by dividing one set of "LHA" in the optical multilayer coating of type 3-3 into three consecutive sets, that is, "M(LHA) 3 The name is "H". The optical multilayer coating of type 3-6, which belongs to type 3, has a total of 14 layers and has the structure of "MLHALHALHALHAH". The optical multilayer coating of type 3-6 is structured by dividing one set of "LHA" in the optical multilayer coating of type 3-3 into four consecutive sets, that is, "M(LHA) 4The name is "H". The optical multilayer film of type 3-7, which belongs to type 3, has a total of 17 layers and has the structure of "MLHALHALHALHALHAH". The optical multilayer film of type 3-7 is structured by dividing one set of "LHA" in the optical multilayer film of type 3-3 into five consecutive sets, that is, "M(LHA) 5 The name is "H".

[0044] The optical multilayer film of type 3-8 belonging to the third type has a total of eight layers and has a "MLHLALHL" structure. Incidentally, the 3rd to 8th forms are the same as the 1st form. [Example]

[0045] Next, preferred examples of the present invention and comparative examples not belonging to the present invention will be described. The present invention is not limited to the following examples. Depending on how the present invention is interpreted, the following examples may essentially be comparative examples, and vice versa.

[0046] [Comparative Example 1] As Comparative Example 1, an optical multilayer film with a good IR / UV ratio was designed as follows. That is, Ta2O5 was selected as the high refractive index material and SiO2 was selected as the low refractive index material, and an optical multilayer film with a total physical thickness of 4275.4 nm was designed with 66 layers. In the design, the optical constants (refractive index and extinction coefficient) of Al, Ta2O5, and SiO2 were used as shown in Figures 5, 6, and 7, respectively. The extinction coefficient of SiO2 is zero throughout the entire wavelength range (horizontal axis) in Figure 7. The layer number (counted from the substrate 2 side), material and physical film thickness (nm) of each layer are shown in Table 1 below. Moreover, the simulated spectral reflectance distribution (reflection angle δ=65°) of Comparative Example 1 is shown in Fig. 8. The IR / UV ratio calculated based on Fig. 8 was 0.089 (8.9%).

[0047] [Table 1]

[0048] Furthermore, based on the design of Comparative Example 1, Comparative Example 1 was actually produced on a substrate using a vapor deposition apparatus 51. The substrate here was a PC substrate having a shape in which the collector 101 was vertically divided into three (120° opening pieces). The deposition conditions for Comparative Example 1 (PC substrate) were set as shown in the top two rows of Table 2. When ion assistance was used (Ta2O5 deposition in Comparative Example 1), the ion assistance conditions were set as shown in the corresponding rows of Table 3. The ion cleaning conditions were set as shown in the top row of Table 3. The ion cleaning time was set to 60 seconds.

[0049] [Table 2] [Table 3]

[0050] During deposition of Comparative Example 1 (PC substrate), the substrate temperature rose to 120°C, generating thermal stress and deformation in the substrate. In addition, the total physical film thickness of the optical multilayer film was relatively thick at 4275.4 nm, and the film stress caused cracks in the optical multilayer film. The spectral reflectance distribution (reflection angle δ=65°) of the produced Comparative Example 1 (PC substrate) is shown in Figure 9. The IR / UV ratio calculated based on Figure 9 was 0.202 (20.2%), which was higher than the simulated value.

[0051] Furthermore, instead of the PC substrate, a glass substrate (D263Teco manufactured by Schott Nippon K.K.) with a square shape of 76 mm on each side and a thickness of 0.1 mm was used, and Comparative Example 1 (glass substrate) was actually produced in the same manner as the PC substrate. 10, Comparative Example 1 (glass substrate) was curved so as to be convex toward the optical multilayer film side, with the maximum height difference H being 2 mm. If an optical multilayer film is formed flat on such a thin substrate, a cold mirror can be easily introduced by cutting it to fit a base body or the like and attaching it. However, Comparative Example 1 (glass substrate) is curved and therefore cannot be easily introduced.

[0052] In addition, for a CTA collector with Comparative Example 1 applied to its inner surface, the above-mentioned incident angle θ and the collection efficiency (%) of light of various wavelengths (6 wavelengths in 100 nm increments from 300 to 800 nm) were simulated. The collector was similar to the above-mentioned collector 101 except for the type of optical multilayer film on the inner surface. Figure 11 is a graph showing the relationship between wavelength (280-820 nm) and various photon detection efficiencies (Photon Detection Efficiency, PDE, %). In Figure 11, the top curve at 500 nm, "SiPM (75-μm cell size)," indicates a SiPM with a cell size of 75 μm. The second curve at 500 nm, "SiPM (50-μm cell size)," indicates a SiPM with a cell size of 50 μm. The bottom curve (dotted line) at 500 nm, "PMT (QE x 90% Col. Eff.)," indicates a PMT with a light collection efficiency of 90%. "PMT Spread" indicates a PMT in a normal state with a range of photon detection efficiencies. The third curve (dotted line) at 500 nm, "Cherenkov Spectrum," indicates the intensity distribution of Cherenkov light. While the PMT tuned for Cherenkov radiation exhibits a drop in light detection efficiency in the wavelength range above 500 nm, the SiPM maintains a relatively high light detection efficiency even at 800 nm. As mentioned above, it is difficult to tune the SiPM itself for Cherenkov radiation. Fig. 12 is a graph showing the relationship between the incident angle θ (horizontal axis) and the collection efficiency (vertical axis) of light of various wavelengths onto the collector in Comparative Example 1. As shown in Fig. 12, with this collector, the collection efficiency exceeds 70% in the range of 300 to 500 nm, but is suppressed to 40% or less at 600 nm or above, which makes this collector suitable for SiPMs. However, in Comparative Example 1, which was actually fabricated on a PC board, as described above, thermal stress, substrate deformation, film stress, and cracks were observed, and therefore the concentrator of Comparative Example 1 may be relatively inferior in terms of durability and precision.

[0053] Comparative Example 2 As Comparative Example 2, the following optical multilayer film was designed based on the optical multilayer film (enhanced reflection mirror) applied to the inner surface of the collector in the conventional CTA using a PMT. That is, Comparative Example 2, in which an Al layer as the first layer, an SiO2 layer made of SiO2 as the second layer, and a Ta2O5 layer made of Ta2O5 as the third layer were stacked on an adhesion layer made of Al2O3, was designed as shown in Table 4 below.

[0054] [Table 4]

[0055] The simulated spectral reflectance distribution (reflection angle δ=65°) of Comparative Example 2 is shown in Fig. 13. The reflectance of Comparative Example 2 is similarly high in both the 300 to 500 nm and 600 to 800 nm wavelengths, and the IR / UV ratio of Comparative Example 2 is relatively high at 0.81 (81%), making Comparative Example 2 difficult to call a cold mirror and difficult to use for SiPMs.

[0056] Furthermore, based on the design of Comparative Example 2, Comparative Example 2 was actually produced on a substrate using the vapor deposition apparatus 51. The substrate here was the same as that of Comparative Example 1 (PC substrate). The deposition conditions and ion cleaning (60 seconds) conditions for Comparative Example 2 (PC substrate) were set as shown in Tables 2 and 3 above. The spectral reflectance distribution (reflection angle δ=65°) of the produced Comparative Example 2 (PC board) is shown in Fig. 14. This spectral reflectance distribution is not significantly different from the simulated spectral reflectance distribution of Comparative Example 2.

[0057] In addition, for the case where Comparative Example 2 was applied to the inner surface of the collector, the above-mentioned incident angle θ and the light collection efficiency of light of various wavelengths were simulated in the same manner as in Comparative Example 1. Fig. 15 is a graph showing the relationship between the incident angle θ (horizontal axis) and the collection efficiency (vertical axis) of light of various wavelengths on the collector in Comparative Example 2. According to Fig. 15, with this collector, the collection efficiency exceeds approximately 70% not only for wavelengths of 300 to 500 nm but also for wavelengths of 600 nm or more, which makes this collector unsuitable for SiPMs.

[0058] [Examples 1 to 9, Comparative Example 3] As Examples 1 to 9, optical products 1 according to the above-described embodiment (first form) were designed and simulated. In Examples 1 to 9, the physical thicknesses of the optical multilayer film 4 are the same except for the physical thickness of the fifth Al layer 10. The physical thicknesses of the underlayers 3 are also the same. Furthermore, Comparative Example 3 was also designed and simulated, in which the physical film thickness of the fifth Al layer 10 of the optical multilayer film 4 was set to zero (the Al layer 10 was omitted), and the physical film thicknesses of the other layers were the same as those of Examples 1 to 9. The layer number, material, and physical film thickness (nm) of each layer in Examples 1 to 9 and Comparative Example 3, as well as the total physical film thickness and IR / UV index, are shown in Table 5. The various optical constants used in the design of Examples 1 to 9 and Comparative Example 3 are shown in Figures 5 to 7. Moreover, the simulated spectral reflectance distributions (reflection angle δ=65°) of Examples 1 to 9 and Comparative Example 3 are shown in FIG. Furthermore, the relationship between the physical film thickness (Al film thickness, nm) of the fifth Al layer 10 and the IR / UV ratio (%) in the simulation in Examples 1 to 9 and Comparative Example 3 is shown in FIG.

[0059] [Table 5]

[0060] In Comparative Example 3, which does not have the fifth Al layer 10, the IR / UV ratio is nearly 90%, whereas in Examples 1 to 9, which have the fifth Al layer 10, the IR / UV ratio is 75% or less. In particular, in Examples 1 to 7 in which the physical film thickness of the fifth Al layer 10 is 5 nm or more and 30 nm or less, the IR / UV ratio is 70% or less.

[0061] Furthermore, Example 3-1 was designed and simulated by multiplying the physical film thickness of all SiO2 low refractive index layers 12 in Example 3 by 0.95 and multiplying the physical film thickness of all Ta2O5 high refractive index layers 14 by 0.95. Also, Example 3-2 was designed and simulated by multiplying the physical film thickness of all SiO2 low refractive index layers 12 in Example 3 by 1.05 and multiplying the physical film thickness of all Ta2O5 high refractive index layers 14 by 1.05. 18 is a graph showing the spectral reflectance distribution (reflection angle δ=65°) in the visible range and its adjacent range for Examples 3, 3-1, and 3-2. From the transitions in Examples 3-1, 3, and 3-2, it can be seen that the reflection band shifts toward longer wavelengths as the physical film thicknesses of both the low refractive index layer 12 and the high refractive index layer 14 increase.

[0062] Furthermore, based on the designs of Examples 2 to 5, the optical multilayer films 4 of Examples 2 to 5 were actually formed on a substrate using a vapor deposition apparatus 51. The substrate here was the same substrate as Comparative Example 1 (PC substrate). For spectroscopic measurement, test pieces were also prepared in which the optical multilayer films 4 of Examples 2 to 5 were vapor-deposited on each of the substrates made of white plate glass. The deposition conditions and ion cleaning (60 seconds) conditions for Examples 2 to 5 (PC substrate) were set as shown in Tables 2 and 3 above. During deposition of each optical multilayer film 4 in Examples 2 to 5 (PC substrate), the temperature rise of the substrate was suppressed to below 80°C, no deformation of the substrate occurred, stress was suppressed due to the thin total physical film thickness, and no cracks occurred in the optical multilayer film 4. The various conditions for Examples 2 to 5 (white glass substrates) were set to be the same as those for Examples 2 to 5 (PC substrates). In addition, the appearance of each optical multilayer film 4 during and after deposition for Examples 2 to 5 (white glass substrates) was the same as that for Examples 2 to 5 (PC substrates).

[0063] The spectral reflectance distributions (reflection angle δ=65°) of the produced Examples 2 to 5 (white glass substrates) are shown in FIG. The spectral reflectance distribution is basically not significantly different from the simulated spectral reflectance distribution of Examples 2 to 5. Examples 2 to 5 (white glass substrates) exhibit a relatively low IR / UV ratio and have higher performance. Furthermore, in Examples 2 to 5 (white glass substrates), unlike Comparative Example 1 (PC substrate), thermal stress, substrate deformation, film stress, and crack occurrence are suppressed, and Examples 2 to 5 (white glass substrates) have superior durability and precision.

[0064] However, in Example 2 (white glass substrate) in which the physical film thickness of the fifth Al layer 10 is 10 nm, the reflectance in the range of 300 to 500 nm is lower than the reflectance in the simulation. This is thought to be because the physical film thickness of the fifth Al layer 10 is small and it is actually a discontinuous film or a patchy film. Furthermore, if a vapor deposition apparatus 51 with improved performance is used or the design of the optical multilayer film 4 is adjusted, the fifth Al layer 10 with a thin physical film thickness, as in Examples 1 and 2 (white glass substrate) and Examples 1 and 2 (PC substrate), can be produced as a continuous film or a uniform film.

[0065] Furthermore, the fifth Al layer 10 is sandwiched between low refractive index layers 12 made of SiO2, and depending on the state of the interface between the Al layer 10 and the low refractive index layers 12, it may become a discontinuous film or a patchy film. Therefore, Example 2-1 (white glass substrate) was further produced in which the low refractive index layers 12, except for the eighth layer, of the optical multilayer film 4 of Example 2 were made of MgF2 while maintaining the physical film thickness. The optical constants of MgF2 are shown in Figure 20. The extinction coefficient of MgF2 is zero throughout the entire wavelength range (horizontal axis) in Figure 20. The spectral reflectance distribution (reflection angle δ=65°) of the produced Example 2, 2-1 (white glass substrate) is shown in FIG. The reflectance of Example 2-1 (white glass substrate) in the range of 300 to 500 nm is greater than that of Example 2 (white glass substrate) and is equivalent to that of Examples 3 to 5. Furthermore, the reflectance of Example 2-1 (white glass substrate) in the range of 600 to 800 nm is slightly greater than that of Example 2 (white glass substrate), but is less than that of Examples 3 to 5. Therefore, Example 2-1 (white glass substrate) exhibits an excellent IR / UV ratio and is a cold mirror with higher performance.

[0066] Furthermore, Example 3 (glass substrate) was prepared in the same manner as Comparative Example 1 (glass substrate). In Example 3 (glass substrate), no warping occurred and the substrate was flat (maximum height difference H=0). Therefore, Example 3 (glass substrate) can be easily introduced into the base body by fixing it to the base body without significantly changing the shape (thickness) of the base body. Furthermore, in Examples 1 to 9 (excluding Example 3), the stress is relatively small due to the thin total physical film thickness, and therefore it is believed that warping does not occur in the case of a thin glass substrate.

[0067] In addition, for the light collector 101 in which Examples 1 to 3 were applied to the inner surface, the incident angle θ and the light collection efficiency of light of various wavelengths were simulated in the same manner as in Comparative Example 1. 22 to 24 are graphs showing the relationship between the incident angle θ (horizontal axis) of light of various wavelengths onto the collector 101 and the light collection efficiency (vertical axis) in Examples 1 to 3, respectively. 22 to 24, the collectors 101 of Examples 1 to 3, unlike the collector of Comparative Example 2, have a collection efficiency of approximately 60% to 80% in the 300 to 500 nm wavelength range, while the collection efficiency is suppressed to approximately 10% to 40% above 600 nm. In this respect, these collectors 101 are suitable for SiPMs. That is, the collectors 101 of Examples 1 to 3 improve the signal-to-noise ratio of atmospheric Cherenkov light relative to night glow, enabling highly efficient observation of gamma rays, improved accuracy in determining gamma-ray energy, and improved accuracy in determining the direction of gamma-ray arrival. In light of the simulation results, the collectors 101 of Examples 4 to 9 can also achieve the same performance improvements as the collectors 101 of Examples 1 to 3.

[0068] Furthermore, in consideration of the manufacturing results of Examples 2 to 5 (PC substrate) and Examples 2 to 5 (white glass substrate), it can be said that, unlike the concentrator of Comparative Example 1, each of the concentrators 101 of Examples 1 to 9 has a long life without cracks, etc., and can maintain relatively high performance for a long period of time.

[0069] Here, various values ​​and the like for Examples 1 to 9 and Comparative Examples 1 to 3 are summarized in Table 6 below.

[0070] [Table 6]

[0071] [Examples 11 to 19, Comparative Example 13] Examples 11 to 19 and Comparative Example 13 were designed and simulated by partially changing the material and physical film thickness of the optical multilayer film 4 in Examples 1 to 9 and Comparative Example 3. Example 10 and Comparative Examples 4 to 12 are omitted. In Examples 11 to 19 and Comparative Example 13, all of the low refractive index layers 12 were made of MgF2, and all of the high refractive index layers 14 were made of HfO2. The physical film thicknesses of the substrate, underlayer 3, and fifth Al layer 10 in Examples 11 to 19 and Comparative Example 13 were the same as those in Examples 1 to 9 and Comparative Example 3, respectively. The layer number, material, and physical film thickness (nm) of each layer in Examples 11 to 19 and Comparative Example 13, as well as the total physical film thickness and IR / UV index, are shown in Table 7. The optical constants of HfO2 are shown in Figure 25. The optical constants of Al and MgF2 are shown in Figures 5 and 20, respectively. Moreover, the simulated spectral reflectance distributions (reflection angle δ=65°) of Examples 11 to 19 and Comparative Example 13 are shown in FIG. Furthermore, the relationship between the physical film thickness (Al film thickness, nm) of the fifth Al layer 10 and the IR / UV ratio (%) in the simulation in Examples 11 to 19 and Comparative Example 13 is shown in FIG.

[0072] [Table 7]

[0073] In Comparative Example 13, which does not have the fifth Al layer 10, the IR / UV ratio reaches nearly 90%, whereas in Examples 1 to 9, which have the fifth Al layer 10, the IR / UV ratio is 77% or less. In particular, in Examples 11 to 17 in which the physical film thickness of the fifth Al layer 10 is 5 nm or more and 30 nm or less, the IR / UV ratio is 72% or less. In Examples 11 to 19, higher performance cold mirrors are provided, and the collector 101 formed using at least one of these guides light of 300 to 500 nm, which is the object of observation, to the photodetector, and suppresses, mainly by absorption, the introduction of light of 600 nm or more, which is not the object of observation, into the photodetector.

[0074] [Examples 21 to 29, Comparative Example 23] Examples 21 to 29 and Comparative Example 23 were designed and simulated by partially changing the material and physical film thickness of the optical multilayer film 4 in Examples 1 to 9 and Comparative Example 3. Example 20 and Comparative Examples 14 to 22 are omitted. In Examples 21 to 29 and Comparative Example 23, all low refractive index layers 12 were made of SiO2, and all high refractive index layers 14 were made of HfO2. The physical film thicknesses of the substrate, underlayer 3, and fifth Al layer 10 in Examples 21 to 29 and Comparative Example 23 were the same as those in Examples 1 to 9 and Comparative Example 3, respectively. The layer number, material, and physical film thickness (nm) of each layer in Examples 21 to 29 and Comparative Example 23, as well as the total physical film thickness and IR / UV index, are shown in Table 8. The optical constants of Al, SiO2, and HfO2 are shown in Figures 5, 7, and 25, respectively. Moreover, the simulated spectral reflectance distributions (reflection angle δ=65°) of Examples 21 to 29 and Comparative Example 23 are shown in FIG. Furthermore, the relationship between the physical film thickness (Al film thickness, nm) of the fifth Al layer 10 and the IR / UV ratio (%) in the simulation in Examples 21 to 29 and Comparative Example 23 is shown in FIG.

[0075] [Table 8]

[0076] In Comparative Example 23, which does not have the fifth Al layer 10, the IR / UV ratio exceeds 90%, whereas in Examples 21 to 29, which have the fifth Al layer 10, the IR / UV ratio is 75% or less. In particular, in Examples 21 to 27 in which the physical film thickness of the fifth Al layer 10 was 5 nm or more and 30 nm or less, the IR / UV ratio was 70.1% or less. In Examples 21 to 29, higher performance cold mirrors are provided, and the collector 101 formed using at least one of these guides light of 300 to 500 nm, which is the object of observation, to the photodetector, and suppresses the introduction of light of 600 nm or more, which is not the object of observation, into the photodetector.

[0077] [Examples 31 to 39, Comparative Example 33] Examples 31 to 39 and Comparative Example 33 were designed and simulated by partially changing the material and physical film thickness of the optical multilayer film 4 in Examples 1 to 9 and Comparative Example 3. Example 30 and Comparative Examples 24 to 32 are omitted. In Examples 31 to 39 and Comparative Example 33, all low refractive index layers 12 were made of SiO2, and all high refractive index layers 14 were made of TiO2. The physical film thicknesses of the substrate, underlayer 3, and fifth Al layer 10 in Examples 31 to 39 and Comparative Example 33 were the same as those in Examples 1 to 9 and Comparative Example 3, respectively. The layer number, material, and physical film thickness (nm) of each layer in Examples 31 to 39 and Comparative Example 33, as well as the total physical film thickness and IR / UV ratio are shown in Table 8 below. The optical constants of TiO2 are shown in Figure 30. The optical constants of Al and SiO2 are shown in Figures 5 and 7, respectively. Moreover, the simulated spectral reflectance distributions (reflection angle δ=65°) of Examples 31 to 39 and Comparative Example 33 are shown in FIG. Furthermore, the relationship between the physical film thickness (Al film thickness, nm) of the fifth Al layer 10 and the IR / UV ratio′ (%) in the simulation in Examples 31 to 39 and Comparative Example 33 is shown in FIG.

[0078] [Table 9]

[0079] In Comparative Example 33, which does not have the fifth Al layer 10, the IR / UV ratio' is 84.5%, whereas in Examples 31 to 39, which have the fifth Al layer 10, the IR / UV ratio' is 74% or less. In particular, in Examples 31 to 37 in which the physical film thickness of the fifth Al layer 10 was 5 nm or more and 30 nm or less, the IR / UV ratio' was 68% or less. In Examples 31 to 39, higher performance cold mirrors are provided, and the collector 101 formed using at least one of these guides light of 350 to 500 nm, which is the object of observation, to the photodetector, and suppresses the introduction of light of 600 nm or more, which is not the object of observation, into the photodetector.

[0080] [Example 40] As Example 40, a material that reflects visible light (mainly light with wavelengths of 400 to 700 nm) and suppresses reflection of near-infrared light was designed and simulated. The layer number, material, and physical film thickness (nm) of each layer in Example 40 are shown in Table 10. The various optical constants used in the design of Example 40 are shown in FIGS. FIG. 33 shows a simulated spectral reflectance distribution for light incident in a direction perpendicular to the substrate in Example 40.

[0081] [Table 10]

[0082] According to Example 40 (short wavelength side wavelength range with high reflectance: visible range, long wavelength side wavelength range with low reflectance: near-infrared range), a high-performance, long-life cold mirror is provided for a band different from that of Examples 1 to 39 (short wavelength side: 300 to 500 nm, long wavelength side: 600 to 800 nm). That is, at least one of the shape and use of the film structure of the present invention is not limited to the shape and use of the Cherenkov light collector as in Example 40, but can be applied to various shapes and uses.

[0083] [Summary of Examples 1 to 40] Examples 1 to 40 each include a substrate 2 and an optical multilayer film 4 indirectly formed on the film-forming surface F of the substrate 2. The optical multilayer film 4 reflects light on the short wavelength side and suppresses reflection of light on the wavelength side longer than the short wavelength side. Counting from the substrate 2 side, the optical multilayer film 4 has a first layer, a second layer, a third layer, a fourth layer, a fifth layer, a sixth layer, a seventh layer, and an eighth layer. The first layer is a first Al layer 10 made of Al, and the second layer is The second layer is a low refractive index layer 12 made of a low refractive index material, the third layer is a third high refractive index layer 14 made of a high refractive index material, the fourth layer is a fourth low refractive index layer 12 made of a low refractive index material, the fifth layer is a fifth Al layer 10 made of Al, the sixth layer is a sixth low refractive index layer 12 made of a low refractive index material, the seventh layer is a seventh high refractive index layer 14 made of a high refractive index material, and the eighth layer is an eighth low refractive index layer 12 made of a low refractive index material. Therefore, a short wavelength selective reflection type optical product 1 is provided that is suppressed from being deformed during manufacturing.

[0084] Furthermore, in Examples 1 to 7, 11 to 17, 21 to 27, 31 to 37, and 40, the physical film thickness of the fifth Al layer 10 is 5 nm or more and 30 nm or less, thereby providing an optical product 1 with better performance. In Examples 1 to 39, the light on the short wavelength side exhibiting a higher reflectance than the light on the long wavelength side is light in the wavelength range of less than 600 nm (300 nm to 500 nm), which makes it more suitable for the collector 101 of a gamma ray observation device such as CTA. In addition, in Example 40, the light on the short wavelength side that exhibits a higher reflectance than the light on the long wavelength side is light in the wavelength range of 400 nm to 700 nm, which makes it more suitable for cold mirrors and the like related to visible light.

[0085] Furthermore, in Examples 1 to 40, an underlayer 3 is provided between the substrate 2 and the first Al layer 10 to improve adhesion of the first Al layer 10 to the substrate 2. This allows the optical multilayer film 4 to be provided more stably, and the performance of the optical product 1 to be exhibited more stably. In addition, in Examples 1 to 40, the low refractive index material is at least one of SiO2, CaF2, and MgF2, and the high refractive index material is at least one of Ta2O5, ZrO2, TiO2, Nb2O5, HfO2, CeO2, Al2O3, and YO2, so that the optical product 1 can be formed more easily.

[0086] Furthermore, if any of the first to fortieth embodiments is used in the collector 101, the collector 101 can be provided which can enhance the detection sensitivity of light in a predetermined wavelength range such as Cherenkov light. Furthermore, if the collector 101 has a collector body 102 having the shape of a tube or a part thereof, and the optical multilayer film 4 of Examples 1 to 40 is arranged on the inner surface of the collector body 102, it becomes easier to provide a collector 101 that can increase the detection sensitivity of light in a specified wavelength range. In addition, the collector 101 on which the optical multilayer film 4 of Examples 1 to 39 is arranged is used for a gamma ray observation device, and a collector 101 for a gamma ray observation device having superior performance is provided.

[0087] [Examples 51 to 56, Comparative Examples 53 to 54] Optical products conforming to the above-mentioned 2-1 mode were designed for UV reflection and IR transmission (such as a light collector) and simulated as Examples 51 to 56. Examples 41 to 50 and Comparative Examples 34 to 52 are omitted. In Examples 51 to 56, the physical thicknesses of the layers other than the first metal layer (first Al layer) in the optical multilayer coating (MLHALH) of 2-1 embodiment are the same, and the physical thickness of the underlying layer 3 is the same (10 nm). Furthermore, comparative examples 53 and 54 were also designed and simulated, in which the physical film thickness of the first Al layer of the optical multilayer film was set to 0 and 10 nm, respectively, and the physical film thicknesses of the other layers were the same as in examples 51 to 56. The layer number, material, and physical film thickness (nm) of each layer, as well as the total physical film thickness and IR / UV rate in Examples 51 to 56 and Comparative Examples 53 to 54, are shown in Table 11 below. Moreover, the simulated spectral reflectance distributions (reflection angle δ=65°) of Examples 51 to 56 and Comparative Examples 53 to 54 are shown in FIG. Furthermore, the relationship between the physical film thickness of the first Al layer (first layer Al film thickness, nm) and the IR / UV ratio (%) in the simulation for Examples 51 to 56 and Comparative Examples 53 and 54 is shown in Figure 35. Note that Figure 35 also shows the IR / UV ratios for Examples in which the physical film thickness of the first layer is 130, 150, and 200 nm.

[0088] [Table 11]

[0089] In comparison example 53, which does not have a first Al layer, the IR / UV ratio is 40% or more, whereas in examples 51 to 56, in which the physical film thickness of the first Al layer is 20 nm or more, and comparison example 54, in which the physical film thickness of the first Al layer is 10 nm, the IR / UV ratio is 25% or less. Furthermore, in Comparative Examples 53 and 54, sufficient reflectance is not obtained in the short wavelength region. In view of this situation, it is clear that the physical film thickness of the first Al layer (metal layer) is preferably 20 nm or more.

[0090] [Examples 61 to 67, Comparative Example 63] Optical products conforming to the above-mentioned 2-2 mode were designed for UV reflection and IR transmission (such as a light collector) and simulated as Examples 61 to 67. Examples 57 to 60 and Comparative Examples 55 to 62 are omitted. In Examples 61 to 67, the physical thicknesses of the layers other than the fourth Al layer in the optical multilayer coating (MLHALH) of the 2-2 embodiment are the same, and the physical thicknesses of the underlayers 3 are the same (10 nm). Furthermore, Comparative Example 63 was also designed and simulated, in which the physical film thickness of the second Al layer, the fourth layer in the optical multilayer film, was set to 0 nm, and the physical film thicknesses of the other layers were the same as in Examples 61 to 67. The layer number, material, and physical film thickness (nm) of each layer, as well as the total physical film thickness and IR / UV rate in Examples 61 to 67 and Comparative Example 63, are shown in Table 12 below. Moreover, the simulated spectral reflectance distributions (reflection angle δ=65°) of Examples 61 to 67 and Comparative Example 63 are shown in FIG. Furthermore, the relationship between the physical film thickness of the fourth second Al layer (fourth Al film thickness, nm) and the IR / UV ratio (%) in the simulation for Examples 61 to 67 and Comparative Example 63 is shown in FIG.

[0091] [Table 12]

[0092] In Comparative Example 63, which does not have a fourth second Al layer, the IR / UV ratio is 90% or more, whereas in Examples 61 to 67, in which the physical thickness of the fourth second Al layer is 5 nm or more and 35 nm or less, the IR / UV ratio is 70% or less. In particular, in Examples 61 to 66, in which the physical thickness of the fourth second Al layer is 5 nm or more and 30 nm or less, the IR / UV ratio is 65% or less. From this situation, it is clear that the physical film thickness of the second Al layer (the Al layer closest to the air) is preferably 5 nm or more and 35 nm or less, and more preferably 5 nm or more and 30 nm or less.

[0093] [Examples 71 to 78, Comparative Example 73] As Examples 71 to 78, optical products conforming to the above-mentioned 2-3 embodiment were designed and simulated for VL reflection and IR transmission (such as a periscope camera). In the 2-3 embodiment, the first layer (metal layer) of the optical multilayer film of the 2-2 embodiment was changed from the first Al layer to an Ag layer. Examples 68 to 70 and Comparative Examples 64 to 72 are omitted. In Examples 71 to 78, the physical thicknesses of the layers other than the second Al layer as the fourth layer in the optical multilayer coating (MLHALH) of the second-third embodiment are the same, and the physical thicknesses of the underlying layers 3 are the same (10 nm). Furthermore, Comparative Example 73 was also designed and simulated, in which the physical film thickness of the second Al layer, the fourth layer in the optical multilayer film, was set to 0 nm, and the physical film thicknesses of the other layers were the same as in Examples 71 to 78. The layer number, material, and physical film thickness (nm) of each layer, as well as the total physical film thickness and IR / VL ratio in Examples 71 to 78 and Comparative Example 73, are shown in Table 13 below. Moreover, the simulated spectral reflectance distributions (reflection angle δ=45°) of Examples 71 to 78 and Comparative Example 73 are shown in FIG. Furthermore, the relationship between the physical film thickness of the fourth second Al layer (fourth Al film thickness, nm) and the IR / VL ratio (%) in the simulation for Examples 71 to 78 and Comparative Example 73 is shown in Figure 39. Note that Figure 39 also shows the IR / VL ratios for Examples in which the physical film thickness of the fourth layer is 40, 50, and 60 nm. In addition, to investigate the incidence angle dependency, simulated spectral reflectance distributions for Example 72 (fourth layer Al film thickness: 10 nm), for three reflection angles δ = 30°, 45°, and 60°, are shown in Figure 40.

[0094] [Table 13]

[0095] In Comparative Example 73, which does not have a fourth second Al layer, the IR / VL ratio exceeds 100%, whereas in Examples 71 to 78, in which the physical thickness of the fourth second Al layer is 5 nm or more and 35 nm or less, the IR / VL ratio is 60% or less. In particular, in Examples 71 to 77, in which the physical thickness of the fourth second Al layer is 5 nm or more and 30 nm or less, the IR / VL ratio is 55% or less. From this situation, it is clear that the physical film thickness of the second Al layer (the Al layer closest to the air) is preferably 5 nm or more and 35 nm or less, and more preferably 5 nm or more and 30 nm or less. Furthermore, for example, in the case of a mirror for a periscope camera, since the imaging element has a wide area, it is preferable that the basic reflection angle δ is set to, for example, 45°, and that the spectral reflection (transmission) performance on the short wavelength side and the long wavelength side be stable even within a certain range of the reflection angle δ (for example, 45°±15°). In this regard, if we focus on the short wavelength side (400 to 600 nm) and the long wavelength side (700 to 900 nm) in Figure 40, we can see that in Example 72, the spectral reflectance distribution is similar whether the reflection angle δ is 45-15=30°, 45°, or 45+15=60°. In other words, Example 72 has a low incidence angle dependency of the spectral reflectance distribution, resulting in a mirror with better performance. Note that, like Example 72, Examples 71, 73 to 77 also have a low incidence angle dependency of the spectral reflectance distribution.

[0096] [Examples 81 to 87, Comparative Example 83] Optical products conforming to the above-mentioned second to fourth embodiments were designed for UV reflection and IR transmission (such as a light collector) and simulated as Examples 81 to 87. Examples 79 to 80 and Comparative Examples 74 to 82 are omitted. In Examples 81 to 87, the physical thicknesses of the layers other than the second Al layer, which is the fourth layer, of the optical multilayer coating (MLHAH) of the second-fourth embodiment are the same, and the physical thickness of the underlayer 3 is the same (10 nm). Furthermore, Comparative Example 83 was also designed and simulated, in which the physical film thickness of the second Al layer, the fourth layer in the optical multilayer film, was set to 0 nm, and the physical film thicknesses of the other layers were the same as in Examples 81 to 87. The layer number, material, and physical film thickness (nm) of each layer in Examples 81 to 87 and Comparative Example 83, as well as the total physical film thickness and IR / UV rate, are shown in Table 14 below. Moreover, the simulated spectral reflectance distributions (reflection angle δ=65°) of Examples 81 to 87 and Comparative Example 83 are shown in FIG. Furthermore, the relationship between the physical film thickness of the fourth second Al layer (fourth Al film thickness, nm) and the IR / UV ratio (%) in the simulation for Examples 81 to 87 and Comparative Example 83 is shown in FIG.

[0097] [Table 14]

[0098] In Comparative Example 83, which does not have a fourth second Al layer, the IR / UV ratio is 95% or more, whereas in Examples 81 to 87, in which the physical thickness of the fourth second Al layer is 5 nm or more and 35 nm or less, the IR / UV ratio is 75% or less. In particular, in Examples 81 to 86, in which the physical thickness of the fourth second Al layer is 5 nm or more and 30 nm or less, the IR / UV ratio is 70.2% or less. From this situation, it is clear that the physical film thickness of the second Al layer (the Al layer closest to the air) is preferably 5 nm or more and 35 nm or less, and more preferably 5 nm or more and 30 nm or less.

[0099] [Examples 91 to 97, Comparative Example 93] Optical products conforming to the above-mentioned second to fifth embodiments were designed for UV reflection and IR transmission (such as a light collector) and simulated as Examples 91 to 97. Examples 88 to 90 and Comparative Examples 84 to 92 are omitted. In Examples 91 to 97, the physical thicknesses of the seventh and third Al layers in the optical multilayer coating (MLHALHALH) of the second-fifth embodiment are the same, and the physical thicknesses of the underlying layers 3 are the same (10 nm). Furthermore, Comparative Example 93 was also designed and simulated, in which the physical film thickness of the third Al layer, the seventh layer of the optical multilayer film, was set to 0 nm, and the physical film thicknesses of the other layers were the same as in Examples 91 to 97. The layer number, material, physical film thickness (nm) and IR / UV rate of each layer in Examples 91 to 97 and Comparative Example 93 are shown in Table 15 below. Due to space limitations, the physical film thickness of the underlayer 3 and the total physical film thickness are omitted from Table 15 onwards, and "Examples" are indicated as "Actual" and "Comparative Examples" are indicated as "Comparative". Moreover, the simulated spectral reflectance distributions (reflection angle δ=65°) of Examples 91 to 97 and Comparative Example 93 are shown in FIG. Furthermore, the relationship between the physical film thickness of the seventh third Al layer (seventh Al film thickness, nm) and the IR / UV ratio (%) in the simulation for Examples 91 to 97 and Comparative Example 93 is shown in FIG.

[0100] [Table 15]

[0101] In Comparative Example 93, which does not have a seventh third Al layer, the IR / UV ratio is 90% or more, whereas in Examples 91 to 97, in which the physical thickness of the seventh third Al layer is 5 nm or more and 35 nm or less, the IR / UV ratio is 72% or less. In particular, in Examples 91 to 96, in which the physical thickness of the seventh third Al layer is 5 nm or more and 30 nm or less, the IR / UV ratio is 70% or less. From this situation, it is clear that the physical film thickness of the third Al layer (the Al layer closest to the air) is preferably 5 nm or more and 35 nm or less, and more preferably 5 nm or more and 30 nm or less.

[0102] [Examples 101 to 107, Comparative Example 103] Optical products conforming to the above-mentioned second to sixth embodiments were designed for UV reflection and IR transmission (such as a light collector) and simulated as Examples 101 to 107. Examples 98 to 100 and Comparative Examples 94 to 102 are omitted. In Examples 101 to 107, the physical thicknesses of the layers other than the third Al layer as the ninth layer in the optical multilayer coating (MLHLHALHALH) of the second-sixth embodiment are the same, and the physical thicknesses of the underlying layers 3 are the same (10 nm). Furthermore, Comparative Example 103 was also designed and simulated, in which the physical film thickness of the third Al layer, the ninth layer of the optical multilayer film, was set to 0 nm, and the physical film thicknesses of the other layers were the same as those of Examples 101 to 107. The layer number, material, physical film thickness (nm) and IR / UV rate of each layer in Examples 101 to 107 and Comparative Example 103 are shown in Table 16 below. Moreover, the simulated spectral reflectance distributions (reflection angle δ=65°) of Examples 101 to 107 and Comparative Example 103 are shown in FIG. Furthermore, the relationship between the physical film thickness of the ninth third Al layer (9th Al film thickness, nm) and the IR / UV ratio (%) in the simulation for Examples 101 to 107 and Comparative Example 103 is shown in FIG.

[0103] [Table 16]

[0104] In Comparative Example 103, which does not have a ninth third Al layer, the IR / UV ratio is 90% or more, whereas in Examples 101 to 107, in which the physical thickness of the ninth third Al layer is 5 nm or more and 35 nm or less, the IR / UV ratio is 72% or less. In particular, in Examples 101 to 106, in which the physical thickness of the ninth third Al layer is 5 nm or more and 30 nm or less, the IR / UV ratio is 70% or less. From this situation, it is clear that the physical film thickness of the third Al layer (the Al layer closest to the air) is preferably 5 nm or more and 35 nm or less, and more preferably 5 nm or more and 30 nm or less.

[0105] [Examples 111 to 117, Comparative Example 113] Optical products conforming to the above-mentioned second to seventh embodiments were designed and simulated for VL reflection and IR transmission (such as a periscope camera) as Examples 111 to 117. Examples 108 to 110 and Comparative Examples 104 to 112 are omitted. In Examples 111 to 117, the physical thicknesses of the layers other than the fourth Al layer as the ninth layer in the optical multilayer coating (MHALHALHALH) of the second-seventh embodiment are the same, and the physical thicknesses of the underlying layers 3 are the same (10 nm). Furthermore, Comparative Example 113 was also designed and simulated, in which the physical film thickness of the fourth Al layer, the ninth layer of the optical multilayer film, was set to 0 nm, and the physical film thicknesses of the other layers were the same as in Examples 111 to 117. The layer number, material, physical film thickness (nm) and IR / VL ratio of each layer in Examples 111 to 117 and Comparative Example 113 are shown in Table 17 below. Moreover, the simulated spectral reflectance distributions (reflection angle δ=45°) of Examples 111 to 117 and Comparative Example 113 are shown in FIG. Furthermore, the relationship between the physical film thickness of the ninth fourth Al layer (9th Al film thickness, nm) and the IR / VL ratio (%) in the simulation for Examples 111 to 117 and Comparative Example 113 is shown in Fig. 48. Note that Fig. 48 also shows the IR / VL ratio for Examples in which the physical film thickness of the 9th layer is 9 nm. In addition, in order to investigate the incidence angle dependency, the simulated spectral reflectance distribution of a modified example of Example 111 (9th layer Al film thickness: 7 nm), which is the distribution for three reflection angles δ = 30°, 45°, and 60°, is shown in Figure 49.

[0106] [Table 17]

[0107] In Comparative Example 113, which does not have a ninth fourth Al layer, the IR / VL ratio exceeds 85%, whereas in Examples 111 to 117, in which the physical thickness of the ninth fourth Al layer is 5 nm or more and 35 nm or less, the IR / VL ratio is 63% or less. In particular, in Examples 111 to 117, in which the physical thickness of the ninth fourth Al layer is 5 nm or more and 30 nm or less, the IR / VL ratio is 60% or less. From this situation, it is clear that the physical film thickness of the fourth Al layer (the Al layer closest to the air) is preferably 5 nm or more and 35 nm or less, and more preferably 5 nm or more and 30 nm or less. Furthermore, regarding the incidence angle dependence, if we focus on the short wavelength side (400 to 600 nm) and the long wavelength side (700 to 900 nm) in Figure 49, we can see that in the modified example of Example 111, the spectral reflectance distribution is similar whether the reflection angle δ is 45-15 = 30°, 45°, or 45+15 = 60°. In other words, in the modified example of Example 111, the incidence angle dependence of the spectral reflectance distribution is low, resulting in a mirror with better performance. Note that, in Examples 111 to 117, the incidence angle dependence of the spectral reflectance distribution is also low, as in the modified example of Example 111.

[0108] [Examples 121 to 128] As Examples 121 to 128, optical products conforming to the above-mentioned embodiments 3-1 to 3-8 were designed for UV reflection and IR transmission (such as a collector) and simulated. Examples 118 to 120 are omitted. In Examples 121 to 127, the physical film thickness of the Al layer closest to the air side was 10 nm. In Example 128, the physical film thickness of the Al layer closest to the air side was 5 nm. In Examples 121 to 128, the physical film thickness of the underlayer 3 was the same (10 nm). The layer number, material and physical film thickness (nm) of each layer in Examples 121 to 128 are shown in Table 18 below. Moreover, the simulated spectral reflectance distributions (reflection angle δ=60°) of Examples 121 to 128 are shown in FIG. Furthermore, the IR / UV ratios (%) in Examples 121 to 128 are shown in FIG.

[0109] [Table 18]

[0110] In all of Examples 121 to 128, UV reflection and IR transmission were achieved, and the IR / UV ratio was 70% or less. From this situation, it can be seen that sufficient UV reflection and IR transmission can be achieved in any of the film structures according to the 3-1 to 3-8 forms. The film structures of the 3-1 to 3-8 modes are listed below.

[0111] 3-1 Form Example 121 MHAL 3-2nd Form Example 122 MLAL 3-3rd Form Example 123 MLHAH Third and fourth forms Example 124 MLHALHAH 3rd-5th Form Example 125 MLHALHALHAH 3rd-6th Form Example 126 MLHALHALHALHAH 3rd-7th Form Example 127 MLHALHALHALHALHAH 3rd-8th Form Example 128 MLHLALHL

[0112] [Summary of Examples 51 to 128] Examples 51 to 128 include a substrate 2 and an optical multilayer film indirectly formed on the deposition surface F of the substrate 2, which reflects light on the short wavelength side and suppresses reflection of light on the longer wavelength side than the short wavelength light. The first layer of the optical multilayer film, counting from the substrate 2 side, is a metal layer M made of metal. The optical multilayer film further includes one or more Al layers A, and at least one of a low refractive index layer L made of a low refractive index material and a high refractive index layer H made of a high refractive index material, which are arranged on the substrate 2 side of the Al layer A, and at least one of a low refractive index layer L made of a low refractive index material and a high refractive index layer H made of a high refractive index material, which are arranged on the air side of the Al layer A. The physical film thickness of the metal layer M is 20 nm or more, and the physical film thickness of the Al layer A closest to the air is 5 nm or more and 35 nm or less. Therefore, a short wavelength selective reflection type optical product is provided that is suppressed from being deformed during manufacturing.

[0113] Furthermore, in Examples 51 to 78 and 91 to 121, a high refractive index layer H is disposed adjacent to the substrate 2 side of the Al layer A closest to the air, and a low refractive index layer L is disposed adjacent to the air side of the Al layer A closest to the air, i.e., the Al layer A closest to the air is "HAL." Therefore, optical products with better performance are provided. Furthermore, in Examples 51 to 128, an underlayer 3 is provided between the substrate 2 and the metal layer M to improve adhesion of the metal layer M to the substrate 2. This allows the optical multilayer film to be provided more stably, and the performance of the optical product can be exhibited more stably. Additionally, in Examples 51 to 128, the metal is at least one of Al and Ag, so that optical products can be formed more easily.

[0114] Furthermore, if any of Examples 51 to 128 (particularly Examples 51 to 67, 81 to 107, and 121 to 128) is used in the collector 101, a collector capable of increasing the detection sensitivity of light in a predetermined wavelength range such as Cherenkov light can be provided. [Explanation of symbols]

[0115] 1··Optical product, 2··Substrate, 3··Undercoat layer, 4··Optical multilayer film, 10··Al layer (1st layer: first Al layer, 5th layer: second Al layer), 12··Low refractive index layer (2nd layer: first low refractive index layer, 4th layer: second low refractive index layer, 6th layer: third low refractive index layer, 8th layer: fourth low refractive index layer), 14··High refractive index layer (3rd layer: first high refractive index layer, 7th layer: second high refractive index layer), 101··Concentrator, 102··Concentrator body, F··Coating surface.

Claims

1. A substrate; an optical multilayer film formed directly or indirectly on the film-forming surface of the substrate; It is equipped with the optical multilayer film reflects light on the short wavelength side and suppresses reflection of light on the wavelength side longer than the short wavelength side light, and includes a first layer, a second layer, a third layer, a fourth layer, a fifth layer, a sixth layer, a seventh layer, and an eighth layer counted from the substrate side, the first layer is a first Al layer made of Al, the second layer is a first low refractive index layer made of a low refractive index material, the third layer is a first high refractive index layer made of a high refractive index material, the fourth layer is a second low refractive index layer made of a low refractive index material, the fifth layer is a second Al layer made of Al, the sixth layer is a third low refractive index layer made of a low refractive index material, the seventh layer is a second high refractive index layer made of a high refractive index material, The eighth layer is a fourth low refractive index layer made of a low refractive index material. An optical product characterized by:

2. The physical thickness of the second Al layer is 5 nm or more and 30 nm or less.

2. The optical product according to claim 1.

3. An underlayer is provided between the substrate and the first Al layer to enhance adhesion of the first Al layer to the substrate.

3. The optical product according to claim 1 or 2.

4. The refractive indexes of the first low refractive index layer, the second low refractive index layer, the third low refractive index layer, and the fourth low refractive index layer are lower than the refractive indexes of the first high refractive index layer and the second high refractive index layer.

4. The optical product according to claim 1, wherein the optical product is a glass substrate.

5. A substrate; an optical multilayer film formed directly or indirectly on the film-forming surface of the substrate; It is equipped with the optical multilayer film reflects light on the short wavelength side and suppresses reflection of light on the longer wavelength side than the light on the short wavelength side, the first layer counting from the substrate side in the optical multilayer film is a metal layer made of metal, Furthermore, the optical multilayer film is one or more Al layers; At least one of a low refractive index layer made of a low refractive index material and a high refractive index layer made of a high refractive index material, which is disposed on the substrate side of the Al layer; At least one of a low refractive index layer made of a low refractive index material and a high refractive index layer made of a high refractive index material, which is disposed on the air side of the Al layer; It has the physical film thickness of the metal layer is 20 nm or more; The physical film thickness of the Al layer closest to the air is 5 nm or more and 35 nm or less. An optical product characterized by:

6. the high refractive index layer is disposed adjacent to the substrate side of the Al layer closest to the air, The low refractive index layer is disposed adjacent to the air side of the Al layer closest to the air.

6. The optical product according to claim 5.

7. A base layer is provided between the substrate and the metal layer to enhance adhesion of the metal layer to the substrate.

7. The optical product according to claim 5 or 6.

8. The metal is at least one of Al and Ag.

8. The optical product according to claim 5, wherein the optical product is a glass substrate.

9. The short wavelength light is light in a wavelength range of less than 600 nm.

9. The optical product according to claim 1.

10. The light on the short wavelength side is light in a wavelength range of 300 nm or more and 500 nm or less.

10. The optical product according to claim 9.

11. The light on the short wavelength side is light in a wavelength range of 400 nm or more and 700 nm or less.

11. The optical product according to claim 1.

12. The low refractive index material is SiO ２ , CaF ２ , MgF ２ At least one of 12. The optical product according to claim 1.

13. The high refractive index material is Ta ２ O ５ , ZrO ２ , TiO ２ , Nb ２ O ５ , HfO ２ , CeO ２ , Al ２ O ３ , Y.O. ２ At least one of 13. The optical product according to claim 1.

14. The optical product according to any one of claims 1 to 13 is used. A concentrator characterized by:

15. The concentrator body has a shape of a tube or a part thereof, The optical multilayer film is disposed on the inner surface of the collector body.

15. The concentrator of claim 14.

16. It is for gamma ray observation equipment.

16. A collector according to claim 14 or claim 15.

Images