Optical filter and method for manufacturing the same, and sterilization device

Abstract

Provided is an optical filter that suppresses transmission of ultraviolet rays having a wavelength of 240 nm to 320 nm and effectively transmits ultraviolet rays having a wavelength of 220 nm to 225 nm. The optical filter 1 of the present application has a transparent substrate 2 and a dielectric multilayer film 3 containing hafnium oxide provided on the transparent substrate 2, a minimum value of spectral transmittance at a wavelength of 220 nm to 225 nm at an incident angle of 0° is 50% or more, and a maximum value of spectral transmittance at a wavelength of 240 nm to 320 nm at an incident angle of 0° is 5% or less.

Description

Technical Field

[0001] The present invention relates to an optical filter capable of selectively transmitting light in a specific wavelength range, a method for manufacturing the optical filter, and a sterilization device using the optical filter. Background Technology

[0002] Optical filters that can selectively transmit light in a specific wavelength range are widely used in various applications. Among such optical filters, bandpass filters using dielectric films are known.

[0003] For example, Patent Document 1 discloses a bandpass filter that maximizes the transmittance of specific ultraviolet light with wavelengths below 250 nm. In the bandpass filter of Patent Document 1, a cavity layer composed of a dielectric film is covered above and below by a metal thin film. Patent Document 1 describes the aforementioned metal thin film as having a transmittance of less than 10% for visible wavelengths of light in the bandpass filter. Furthermore, it is described that the cavity layer is a layer composed of a dielectric film, and silicon dioxide, lanthanum fluoride, magnesium fluoride, aluminum oxide, hafnium oxide, etc., can be used as the dielectric.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2013-068885 Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] However, in ultraviolet (UV) sterilization processes, such as those used to kill bacteria and viruses attached to the skin, excimer lamps that emit UV light with wavelengths of 220 nm to 225 nm are used. However, excimer lamps also emit some harmful UV light with wavelengths of 240 nm to 320 nm.

[0009] Even when using a bandpass filter like that in Patent Document 1, it is difficult to sufficiently suppress the transmission of ultraviolet light with wavelengths of 240nm to 320nm. In particular, when it is necessary to suppress the transmission of ultraviolet light with wavelengths of 240nm to 320nm, it is difficult to allow sufficient transmission of ultraviolet light with wavelengths of 220nm to 225nm. Therefore, there is a problem that it is difficult to achieve a high level of suppression of ultraviolet light that is harmful to the human body and high-efficiency transmission of ultraviolet light that is useful for sterilization.

[0010] The purpose of this invention is to provide an optical filter capable of suppressing ultraviolet light with a wavelength of 240nm to 320nm and effectively transmitting ultraviolet light with a wavelength of 220nm to 225nm, a method for manufacturing the optical filter, and a sterilization device using the optical filter.

[0011] Technical solutions for solving technical problems

[0012] The optical filter of the present invention is characterized by having a transparent substrate and a dielectric multilayer film containing hafnium oxide disposed on the transparent substrate, wherein the minimum spectral transmittance at wavelengths of 220 nm to 225 nm is 50% or more when the incident angle is 0°, and the maximum spectral transmittance at wavelengths of 240 nm to 320 nm is 5% or less when the incident angle is 0°.

[0013] In this invention, the dielectric multilayer film preferably contains cubic hafnium oxide crystals.

[0014] In this invention, it is preferable that, in X-ray diffraction measurements, the diffraction peaks caused by the (1 1 1) crystal plane of cubic hafnium oxide crystals are larger than the diffraction peaks caused by the (-11 1) crystal plane of monoclinic hafnium oxide crystals.

[0015] In this invention, it is preferable that the above-mentioned dielectric multilayer film has a high refractive index film with a relatively high refractive index and a low refractive index film with a relatively low refractive index, wherein the high refractive index film is a film containing hafnium oxide. More preferably, the low refractive index film is a film containing silicon oxide.

[0016] In this invention, it is preferable that the outermost layer of the dielectric multilayer film is a film containing hafnium oxide. More preferably, the thickness of the outermost layer is 1 nm or more and 10 nm or less.

[0017] In this invention, the preferred spectral transmittance T at a wavelength of 222 nm is when the incident angle is 30°. 30 The ratio of the spectral transmittance T0 at a wavelength of 222 nm when the incident angle is 0° (T) 30 / T0) is above 0.5.

[0018] In this invention, it is preferable that the above-mentioned dielectric multilayer film has a high refractive index film with a relatively high refractive index and a low refractive index film with a relatively low refractive index, and the total thickness t of the high refractive index film is... H The total thickness t of the aforementioned low refractive index film L The ratio (t) H / t L The value is 0.2 or higher. More preferably, the total thickness t of the above-mentioned high refractive index film is 0.2 or higher. H The total thickness t of the aforementioned low refractive index film L The ratio (t) H / t L The value is above 0.5.

[0019] In this invention, it is preferred that the minimum transmittance at wavelengths of 220nm to 225nm is 50% or more when the incident angle is 0°, and the maximum transmittance at wavelengths of 237nm to 280nm is 10% or less.

[0020] In this invention, it is preferable that the maximum transmittance of the spectral density at a wavelength of 237nm to 280nm is less than 20% when the incident angle is 40°.

[0021] The method for manufacturing an optical filter according to the present invention is characterized by comprising: a step of forming a hafnium oxide-containing dielectric multilayer film on a transparent substrate by sputtering to obtain a film-coated transparent substrate; and a step of heat-treating the film-coated transparent substrate at a temperature of 500°C or higher.

[0022] In this invention, it is preferable that the temperature for heat treatment of the above-mentioned transparent substrate with film is below 800°C.

[0023] The sterilization device of the present invention is a sterilization device for inactivating microorganisms of the target microorganism, characterized in that it comprises: a light source emitting light with a wavelength in the wavelength range of 190 nm to 230 nm; and an optical filter constructed according to the present invention.

[0024] The effects of the invention

[0025] According to the present invention, an optical filter capable of suppressing ultraviolet light with a wavelength of 240nm to 320nm and effectively transmitting ultraviolet light with a wavelength of 220nm to 225nm, a method for manufacturing the optical filter, and a sterilization device using the optical filter are provided. Attached Figure Description

[0026] Figure 1 This is a schematic cross-sectional view showing the optical filter according to the first embodiment of the present invention.

[0027] Figure 2 This is a diagram showing the X-ray diffraction patterns of the optical filters obtained in Example 2 and Comparative Example 1.

[0028] Figure 3 This is a graph showing the transmission spectra of the optical filters obtained in Example 2 and Comparative Example 1.

[0029] Figure 4 This is a schematic cross-sectional view showing the optical filter according to the second embodiment of the present invention.

[0030] Figure 5 This is a graph showing the transmission spectra of the optical filter obtained in Example 5 before and after hydrofluoric acid impregnation.

[0031] Figure 6 This is a graph showing the transmission spectra of the optical filter obtained in Example 8 before and after hydrofluoric acid impregnation.

[0032] Figure 7 This is a schematic diagram illustrating a sterilization device according to one embodiment of the present invention.

[0033] Figure 8 This is a graph showing the transmission spectrum of the optical filter obtained in Example 18 at various incident angles. Detailed Implementation

[0034] The preferred embodiments are described below. However, these embodiments are merely illustrative, and the present invention is not limited to them. Furthermore, in the various figures, components having substantially the same function are sometimes referred to by the same symbols.

[0035] [First Implementation Method]

[0036] (Optical filters)

[0037] Figure 1 This is a schematic cross-sectional view showing the optical filter according to the first embodiment of the present invention. Figure 1 As shown, the optical filter 1 has a transparent substrate 2 and a dielectric multilayer film 3. The dielectric multilayer film 3 is disposed on the transparent substrate 2.

[0038] In this embodiment, the transparent substrate 2 has a rectangular plate shape. However, the transparent substrate 2 may also have a shape such as a circular plate, and its shape is not particularly limited.

[0039] The thickness of the transparent substrate 2 is not particularly limited and can be appropriately set according to factors such as light transmittance. The thickness of the transparent substrate 2 can be set to, for example, approximately 0.1 mm to 30 mm.

[0040] The transparent substrate 2 is preferably a substrate that is transparent in the wavelength range of the optical filter 1. More specifically, the transparent substrate 2 preferably has an average light transmittance of 80% or more in the ultraviolet wavelength range of 220 nm to 225 nm.

[0041] The material used for the transparent substrate 2 is not particularly limited, and examples include glass and resin. Examples of glass include quartz glass and borosilicate glass. The quartz glass can be synthetic quartz glass or fused silica glass. The borosilicate glass preferably contains, by mass percent, 55%–75% SiO2, 1%–10% Al2O3, 10%–30% B2O3, 0%–5% CaO, 0%–5% BaO, and 1.0%–15% Li2O+Na2O+K2O; more preferably, it also contains 0%–0.001% TiO2, 0%–0.001% Fe2O3, and 0.5%–2.0% F.

[0042] The transparent substrate 2 has a first main surface 2a and a second main surface 2b that are opposite to each other. A dielectric multilayer film 3 serving as a light filter is provided on the first main surface 2a of the transparent substrate 2.

[0043] The dielectric multilayer film 3 is a multilayer film having a high refractive index film 4 with a relatively high refractive index and a low refractive index film 5 with a relatively low refractive index. In this embodiment, the high refractive index film 4 and the low refractive index film 5 are alternately stacked sequentially on the first main surface 2a of the transparent substrate 2, thereby forming a multilayer film.

[0044] The high refractive index film 4 is a film composed of hafnium oxide, with hafnium oxide as the main component. Furthermore, in this specification, "a film with... as the main component" means a film containing 50% by mass or more of this material. Of course, it can also be a film containing 100% by mass of this material.

[0045] In this embodiment, the low refractive index film 5 is a film composed primarily of silicon oxide. However, the low refractive index film 5 may also be a film primarily composed of aluminum oxide, zirconium oxide, magnesium fluoride, or silicon nitride. These low refractive index films 5 may use a single material or a combination of multiple materials.

[0046] The thickness of each layer of the high refractive index film 4 is not particularly limited, but is preferably 5 nm or more, more preferably 10 nm or more, preferably 60 nm or less, more preferably 50 nm or less.

[0047] The thickness of each layer of the low refractive index film 5 is not particularly limited, but is preferably 5 nm or more, more preferably 10 nm or more, preferably 80 nm or less, more preferably 60 nm or less.

[0048] The thickness of the dielectric multilayer film 3 as a whole is not particularly limited, but is preferably 1000 nm or more, more preferably 1500 nm or more, more preferably 3000 nm or less, and more preferably 2000 nm or less.

[0049] Furthermore, the number of layers in the dielectric multilayer film 3 is preferably 20 or more, more preferably 30 or more, more preferably 100 or less, and more preferably 80 or less.

[0050] The optical filter 1 of this embodiment is a bandpass filter designed to selectively transmit light in a specific wavelength range by utilizing the interference of light through a dielectric multilayer film 3. Specifically, it is a bandpass filter designed to have a minimum transmittance of 50% or more in the wavelength range of 220nm to 225nm and a maximum transmittance of 5% or less in the wavelength range of 240nm to 320nm.

[0051] Furthermore, in this specification, the spectral transmittance is obtained, for example, by measuring the overall spectral transmittance of the optical filter 1 using a spectrophotometer (manufactured by Hitachi High-Tech Co., Ltd., model "UH4150"). As for the measurement conditions, for example, the measurement can be performed from the main surface 1a side of the optical filter 1, with the incident angle set to 0° and the measurement wavelength set to 190 nm to 400 nm.

[0052] Thus, the optical filter 1 of this embodiment is characterized in that a dielectric multilayer film 3 containing hafnium oxide is provided on the transparent substrate 2, and the minimum transmittance at wavelengths of 220 nm to 225 nm is 50% or more, and the maximum transmittance at wavelengths of 240 nm to 320 nm is 5% or less. Furthermore, in this case, the incident angle θ, described later, is set to 0°.

[0053] Therefore, the optical filter 1 can suppress ultraviolet rays with wavelengths of 240nm to 320nm that are transmitted, and effectively transmit ultraviolet rays with wavelengths of 220nm to 225nm.

[0054] Thus, optical filter 1 can suppress the transmission of ultraviolet rays with wavelengths of 240nm to 320nm, thereby suppressing the transmission of ultraviolet rays that are harmful to the human body. In addition, since ultraviolet rays with wavelengths of 220nm to 225nm have excellent transmittance, ultraviolet rays useful in sterilization treatments such as skin sterilization can be effectively transmitted.

[0055] Therefore, with the optical filter 1 of this embodiment, when using an ultraviolet irradiation device such as an excimer lamp, it is possible to suppress the transmission of ultraviolet rays that are harmful to the human body, and effectively transmit ultraviolet rays that are useful in sterilization treatment.

[0056] In this invention, the minimum transmittance at wavelengths of 220 nm to 225 nm is preferably 60% or more, more preferably 70% or more. In this case, ultraviolet light useful in sterilization treatments such as skin sterilization can be transmitted more effectively. Furthermore, the upper limit of the minimum transmittance at wavelengths of 220 nm to 225 nm is not particularly limited, and for example, it can be set to 95%. In this case, the incident angle θ, described later, is set to 0°.

[0057] In this invention, the maximum value of the spectral transmittance in the wavelength range of 240 nm to 320 nm is preferably 3% or less, more preferably 2.5% or less, and even more preferably 1% or less. In this case, the transmission of harmful ultraviolet radiation can be further effectively suppressed. Furthermore, the lower limit of the maximum value of the spectral transmittance in the wavelength range of 240 nm to 320 nm is not particularly limited, and for example, it can be set to 0.2%. In this case, the incident angle θ, described later, is set to 0°.

[0058] In this embodiment, the optical filter 1 preferably has a spectral transmittance T of 222 nm at an incident angle of 30°. 30 The ratio of the spectral transmittance T0 at a wavelength of 222 nm when the incident angle is 0° (T) 30 / T0) is 0.5 or higher. Furthermore, the so-called incident angle refers to the angle of inclination relative to the normal direction when the stacking direction (thickness direction) of the dielectric multilayer film 3, which is orthogonal to the direction along the main surface 1a of the optical filter 1, is taken as the normal direction (e.g., Figure 1 Therefore, the direction along the normal direction becomes the incident angle of 0°.

[0059] In this case, the spectral transmittance can be obtained, for example, by measuring the overall spectral transmittance of the optical filter 1 using a spectrophotometer (manufactured by Hitachi High-Tech Co., Ltd., model "UH4150"). As measurement conditions, for example, the measurement can be performed from the main surface 1a side of the optical filter 1, with the measurement wavelength set to 190 nm to 400 nm.

[0060] In the optical filter 1 of this embodiment, the spectral transmittance T at a wavelength of 222nm is [not specified] when the incident angle is 30°. 30 The ratio of the spectral transmittance T0 at a wavelength of 222 nm when the incident angle is 0° (T) 30 Since the value of / T0) is above the aforementioned lower limit, even when the incident angle of the emitted light from the light source is increased, ultraviolet light useful in sterilization can be transmitted more efficiently. Therefore, the effective irradiation area of ​​the emitted light from the light source can be further increased.

[0061] In this invention, the spectral transmittance T at a wavelength of 222 nm when the incident angle is 30° is... 30The ratio of the spectral transmittance T0 at a wavelength of 222 nm when the incident angle is 0° (T) 30 The ratio of / T0) is preferably 0.6 or more, more preferably 0.7 or more, even more preferably 0.8 or more, particularly preferably 0.9 or more, and preferably 1.0 or less. In the ratio (T) 30 When the light emitted from the light source is within the range mentioned above, even with an increased incident angle, ultraviolet light, which is useful in sterilization processes, can be transmitted more efficiently.

[0062] In this invention, the spectral transmittance T0 at a wavelength of 222 nm when the incident angle is 0° is preferably 60% or more, more preferably 70% or more, even more preferably 75% or more, and particularly preferably 80% or more. In this case, ultraviolet light useful in sterilization processes can be transmitted more efficiently. Furthermore, the upper limit of the spectral transmittance T0 at a wavelength of 222 nm when the incident angle is 0° is preferably high, for example, it can be set to 95%.

[0063] Spectroscopic transmittance T at an incident angle of 30° and a wavelength of 222nm 30 Preferably, it is 40% or more, more preferably 50% or more, even more preferably 60% or more, and particularly preferably 70% or more. In this case, the effective illumination area of ​​the light emitted from the light source can be further increased. Furthermore, the spectral transmittance T at a wavelength of 222 nm at an incident angle of 30° is... 30 The upper limit value should preferably be relatively high, for example, it can be set to 93%.

[0064] Furthermore, the spectral transmittance at a wavelength of 222 nm when the incident angle is 40° is preferably 5% or more, more preferably 10% or more, even more preferably 20% or more, and particularly preferably 30% or more. In this case, the effective illumination area of ​​the light emitted from the light source can be further increased. In addition, the upper limit of the spectral transmittance at a wavelength of 222 nm when the incident angle is 40° is preferably high, for example, it can be set to 55%.

[0065] In this invention, it is preferable that the minimum transmittance at wavelengths of 220nm to 225nm is 50% or more, and the maximum transmittance at wavelengths of 237nm to 280nm is 10% or less, when the incident angle is 0°. In this case, it is possible to achieve a higher level of balance between the efficient transmission of ultraviolet light useful in sterilization treatment and the suppression of ultraviolet light harmful to the human body.

[0066] When the incident angle is 0°, the maximum value of the spectral transmittance in the wavelength range of 237 nm to 280 nm is preferably 10% or less, more preferably 5% or less, even more preferably 4% or less, particularly preferably 3% or less, and most preferably 2% or less. In this case, the transmission of harmful ultraviolet radiation can be further suppressed. Furthermore, the lower limit of the maximum value of the spectral transmittance in the wavelength range of 237 nm to 280 nm when the incident angle is 0° is preferably low, for example, it can be set to 0.01%.

[0067] When the incident angle is 30°, the maximum value of the spectral transmittance in the wavelength range of 237 nm to 280 nm is preferably 15% or less, more preferably 10% or less, even more preferably 5% or less, particularly preferably 4% or less, and most preferably 3% or less. In this case, the effective illumination area of ​​the emitted light from the light source can be further increased. In addition, the lower limit of the maximum value of the spectral transmittance in the wavelength range of 237 nm to 280 nm when the incident angle is 30° is preferably low, for example, it can be set to 0.01%.

[0068] Furthermore, when the incident angle is 40°, the maximum value of the spectral transmittance in the wavelength range of 237 nm to 280 nm is preferably 20% or less, more preferably 15% or less, even more preferably 10% or less, particularly preferably 7% or less, and most preferably 5% or less. In this case, the effective illumination area of ​​the light emitted from the light source can be further increased. Additionally, the lower limit of the maximum value of the spectral transmittance in the wavelength range of 237 nm to 280 nm when the incident angle is 40° is preferably low, for example, it can be set to 0.01%.

[0069] Furthermore, the spectral transmittance at wavelength 222nm at each incident angle and the spectral transmittance at wavelengths 237nm to 280nm at each incident angle can be adjusted, for example, by the composition of the dielectric multilayer film 3.

[0070] In this invention, the total thickness t of the high refractive index film 4 H Preferably, the wavelength is 250 nm or more, more preferably 300 nm or more, even more preferably 400 nm or more, particularly preferably 500 nm or more, preferably 1000 nm or less, more preferably 800 nm or less, even more preferably 700 nm or less, and particularly preferably 600 nm or less. The total thickness t of the high refractive index film 4... H When the value is above the aforementioned lower limit, even with an increased incident angle, the high spectral transmittance at a wavelength of 222 nm can be maintained more effectively. Furthermore, the maximum value of spectral transmittance in the wavelength range of 237 nm to 280 nm can be further reduced. On the other hand, the total thickness t of the high refractive index film 4... H Below the aforementioned upper limit, the spectral transmittance at a wavelength of 222nm can be further increased.

[0071] In addition, the thickness of each layer of the high refractive index film 4 is not particularly limited, but is preferably 5 nm or more, more preferably 10 nm or more, more preferably 60 nm or less, and more preferably 50 nm or less.

[0072] In this invention, the total thickness t of the low refractive index film 5 L Preferably, the thickness is 500 nm or more, more preferably 600 nm or more, even more preferably 700 nm or more, particularly preferably 800 nm or more, preferably 2000 nm or less, more preferably 1700 nm or less, even more preferably 1500 nm or less, and particularly preferably 1400 nm or less. The total thickness t of the low refractive index film 5... L When the value is above the aforementioned lower limit, the maximum value of the spectral transmittance in the wavelength range of 237 nm to 280 nm can be further reduced. On the other hand, in the case of the total thickness t of the low refractive index film 5... L Below the aforementioned upper limit, the spectral transmittance at a wavelength of 222nm can be further increased.

[0073] In addition, the thickness of each layer of the low refractive index film 5 is not particularly limited, but is preferably 5 nm or more, more preferably 10 nm or more, more preferably 80 nm or less, and more preferably 60 nm or less.

[0074] In this invention, the total thickness t of the high refractive index film 4 H The total thickness t of the low refractive index film 5 L The ratio (t) H / t L The value is preferably 0.2 or more, more preferably 0.3 or more, even more preferably 0.4 or more, particularly preferably 0.5 or more, most preferably 0.6 or more, preferably 1 or less, more preferably 0.9 or less, even more preferably 0.8 or less, and particularly preferably 0.75 or less. In the ratio (t) H / t L When the value is above the aforementioned lower limit, even with an increased incident angle, the high spectral transmittance at a wavelength of 222 nm can be maintained even more effectively. Furthermore, compared to (t... H / t L When the value is below the upper limit mentioned above, the maximum value of the spectral transmittance in the wavelength range of 237nm to 280nm can be further reduced.

[0075] The total thickness of the dielectric multilayer film 3 is not particularly limited, but is preferably 800 nm or more, more preferably 1000 nm or more, even more preferably 1100 nm or more, particularly preferably 1200 nm or more, preferably 2500 nm or less, more preferably 2200 nm or less, even more preferably 2000 nm or less, and particularly preferably 1900 nm or less. When the total thickness of the dielectric multilayer film 3 is at or above the aforementioned lower limit, the maximum value of the spectral transmittance in the wavelength range of 237 nm to 280 nm can be further reduced. On the other hand, when the total thickness of the dielectric multilayer film 3 is at or below the aforementioned upper limit, the spectral transmittance in the wavelength range of 222 nm can be further increased.

[0076] Furthermore, the number of layers constituting the dielectric multilayer film 3 is preferably 20 or more, more preferably 25 or more, even more preferably 30 or more, particularly preferably 35 or more, preferably 100 or less, more preferably 80 or less, even more preferably 60 or less, and particularly preferably 45 or less. When the number of layers constituting the dielectric multilayer film 3 is at or above the aforementioned lower limit, the maximum value of the spectral transmittance at wavelengths of 237 nm to 280 nm can be further reduced. Furthermore, when the number of layers constituting the dielectric multilayer film 3 is at or below the aforementioned upper limit, the spectral transmittance at wavelength of 222 nm can be further increased.

[0077] In this invention, the dielectric multilayer film 3 contains hafnium oxide crystals. More specifically, it is preferable that the high refractive index film 4 constituting the dielectric multilayer film 3 contains hafnium oxide crystals, and more preferably, it contains cubic hafnium oxide crystals. In this case, it is possible to further suppress the transmission of ultraviolet light with wavelengths of 240 nm to 320 nm, and further improve the transmittance of ultraviolet light with wavelengths of 220 nm to 225 nm.

[0078] Furthermore, whether cubic hafnium oxide crystals are present in this specification can be confirmed by observing diffraction peaks caused by the (1 1 1) crystal plane of cubic hafnium oxide crystals in X-ray diffraction measurements.

[0079] Furthermore, in this specification, X-ray diffraction measurements can be performed using wide-angle X-ray diffraction. For example, the "SmartLab" model manufactured by Rigaku Corporation can be used as the X-ray diffraction apparatus. Additionally, CuKα rays can be used as the radiation source. Moreover, in the X-ray diffraction measurement, the optical filter 1 as a whole is measured from the first principal surface 2a side.

[0080] In this invention, during X-ray diffraction measurements, it is preferable that the diffraction peaks originating from the (1 1 1) crystal plane of cubic hafnium oxide crystals are larger than those originating from the (-11 1) crystal plane of monoclinic hafnium oxide crystals. In this case, the transmission of ultraviolet light with wavelengths of 240 nm to 320 nm can be further suppressed, and the transmittance of ultraviolet light with wavelengths of 220 nm to 225 nm can be further improved.

[0081] In this invention, the ratio Ic / Im of the peak area intensity Ic of the diffraction peak caused by the (1 1 1) crystal plane of cubic hafnium oxide crystal and the peak area intensity Im of the diffraction peak caused by the (-1 1 1) crystal plane of monoclinic hafnium oxide crystal is preferably 0.1 or more, more preferably 0.3 or more, even more preferably 1 or more, more preferably 2 or more, particularly preferably 2.5 or more, and most preferably 3 or more. When the ratio Ic / Im is at or above the lower limit mentioned above, the transmission of ultraviolet light with wavelengths of 240 nm to 320 nm can be further suppressed, and the transmittance of ultraviolet light with wavelengths of 220 nm to 225 nm can be further improved. In addition, the upper limit of the ratio Ic / Im is not particularly limited, for example, it can be set to 10000.

[0082] Alternatively, in this invention, an anti-reflective film may be provided on the second main surface 2b of the transparent substrate 2. In this case, the transmittance of ultraviolet rays with wavelengths of 220nm to 225nm can be further improved.

[0083] There are no particular limitations on the antireflective coating; for example, a multilayer film consisting of a high-refractive-index film with a relatively high refractive index and a low-refractive-index film with a relatively low refractive index can be used. The multilayer film can also be constructed by alternately setting high-refractive-index and low-refractive-index films sequentially. For example, a film with hafnium oxide as the main component can be used as the high-refractive-index film. Examples of low-refractive-index films include films with silicon oxide, aluminum oxide, zirconium oxide, tin oxide, or silicon nitride as the main components. Furthermore, the number of layers constituting the multilayer film can be, for example, 4 or more and 100 or less.

[0084] Furthermore, as long as it does not impede the effect of the present invention, a film other than an anti-reflective film may be laminated on the second main surface 2b of the transparent substrate 2. Additionally, as long as it does not impede the effect of the present invention, a film other than a dielectric multilayer film 3 may also be provided on the first main surface 2a of the transparent substrate 2. In this case, a film may be provided between the transparent substrate 2 and the dielectric multilayer film 3, or a film may be provided on top of the dielectric multilayer film 3.

[0085] The following is a detailed description of an example of the manufacturing method of optical filter 1.

[0086] (Manufacturing method of optical filters)

[0087] Transparent substrate forming process with film:

[0088] First, a transparent substrate 2 is prepared. Then, a dielectric multilayer film 3 is formed on the first main surface 2a of the transparent substrate 2. The dielectric multilayer film 3 can be formed by sequentially and alternately stacking a high refractive index film 4 and a low refractive index film 5 on the first main surface 2a of the transparent substrate 2. The high refractive index film 4 and the low refractive index film 5 can be formed by sputtering.

[0089] When forming the high refractive index film 4, the substrate temperature is preferably 300°C or lower, more preferably 270°C or lower. In this case, the resulting optical filter 1 can further suppress light with wavelengths of 240nm to 320nm and further effectively transmit ultraviolet light in the wavelength range of 220nm to 225nm. In addition, the lower limit of the substrate temperature when forming the high refractive index film 4 can be set, for example, to 20°C.

[0090] The high refractive index film 4 can be formed, for example, by using a target material that constitutes the high refractive index film 4, setting the flow rate of an inert gas such as argon as a carrier gas to 50 sccm to 500 sccm, and setting the applied power to 0.5 kW to 40 kW.

[0091] The low refractive index film 5 can be formed, for example, by using a target material that constitutes the low refractive index film 5, setting the flow rate of an inert gas such as argon as a carrier gas to 50 sccm to 500 sccm, and setting the applied power to 0.5 kW to 40 kW.

[0092] Heat treatment process:

[0093] Then, the obtained transparent substrate with film is heat-treated at a temperature of, for example, 450°C or higher. This yields optical filter 1. In particular, heating the transparent substrate with film at a temperature of 450°C or higher allows for a relatively further increase in the content of cubic hafnium oxide crystals. Therefore, in the obtained optical filter 1, the transmission of ultraviolet light with wavelengths of 240 nm to 320 nm can be further suppressed, and the transmittance of ultraviolet light with wavelengths of 220 nm to 225 nm can be further improved.

[0094] The heat treatment temperature for the transparent substrate with film is preferably 500°C or higher, more preferably 550°C or higher, more preferably 800°C or lower, and more preferably 750°C or lower. When the heat treatment temperature is within the above range, it is possible to further suppress the transmission of ultraviolet rays with wavelengths of 240nm to 320nm and further improve the transmittance of ultraviolet rays with wavelengths of 220nm to 225nm.

[0095] There is no particular limitation on the heat treatment time for the transparent substrate with film; for example, it can be set to more than 10 minutes or less than 120 minutes.

[0096] Furthermore, in this invention, it is preferable that the intensity of the diffraction peak caused by the (-1 1 1) crystal plane of monoclinic hafnium oxide crystal is relatively low in X-ray diffraction measurements of the transparent substrate before heat treatment. The intensity of the diffraction peak caused by the (-1 1 1) crystal plane of monoclinic hafnium oxide crystal is preferably at the microcrystalline level, and the height of the peak intensity is more preferably within three times the height of the halo peak intensity of the amorphous crystal. In this case, by heat treatment, the ratio Ic / Im of the peak area intensity Ic of the diffraction peak caused by the (1 1 1) crystal plane of cubic hafnium oxide crystal to the peak area intensity Im of the diffraction peak caused by the (-1 1 1) crystal plane of monoclinic hafnium oxide crystal can be further increased. Therefore, in the obtained optical filter 1, the transmission of ultraviolet light with wavelengths of 240 nm to 320 nm can be further suppressed, and the transmittance of ultraviolet light with wavelengths of 220 nm to 225 nm can be further improved.

[0097] In this invention, the transmittance of ultraviolet light in the wavelength range of 240 nm to 320 nm and the transmittance of ultraviolet light in the wavelength range of 220 nm to 225 nm can be adjusted, for example, by adjusting the total number of films constituting the dielectric multilayer film 3, the film thickness and material, and the heat treatment temperature of the transparent substrate with film. In particular, by adjusting the heat treatment temperature of the transparent substrate with film, the transmittance of ultraviolet light in the wavelength range of 240 nm to 320 nm can be further suppressed in the obtained optical filter 1, and the transmittance of ultraviolet light in the wavelength range of 220 nm to 225 nm can be further effectively improved.

[0098] Furthermore, the spectral transmittance at wavelength 222 nm and in the wavelength range of 237 nm to 280 nm at various incident angles can be adjusted, for example, by adjusting the total number of films constituting the dielectric multilayer film 3, the film thickness and material, and the heat treatment temperature of the transparent substrate with the film. In particular, by adjusting the heat treatment temperature of the transparent substrate with the film, the spectral transmittance at wavelength 222 nm can be further increased, and the maximum value of the spectral transmittance in the wavelength range of 237 nm to 280 nm can be further decreased in the obtained optical filter 1.

[0099] [Second Implementation]

[0100] Figure 4 This is a schematic cross-sectional view showing the optical filter according to the second embodiment of the present invention. Figure 4 As shown, in the optical filter 21, the outermost layer 26 of the dielectric multilayer film 23 is a high refractive index film 4 made of hafnium oxide. Other aspects are the same as in the first embodiment.

[0101] Similarly, in optical filter 21, the minimum transmittance in the wavelength range of 220nm to 225nm is 50% or more, and the maximum transmittance in the wavelength range of 240nm to 320nm is 5% or less. Therefore, it is possible to suppress the transmission of ultraviolet light in the wavelength range of 240nm to 320nm and effectively allow ultraviolet light in the wavelength range of 220nm to 225nm to pass through.

[0102] However, when using excimer lamps or similar devices that emit ultraviolet light in the range of 220nm to 225nm, the irradiated light can sometimes degrade the device components and generate acidic gases. These gases can corrode the film of optical filters, thereby altering their optical properties and sometimes preventing them from meeting the required characteristics.

[0103] In contrast, when the outermost layer 26 is made of hafnium oxide, such as in optical filter 21, corrosion caused by acidic gases can be further suppressed, and changes in optical properties can be further suppressed.

[0104] Furthermore, the thickness of the outermost layer 26 is preferably 1 nm or more, more preferably 2 nm or more, preferably 10 nm or less, more preferably 7 nm or less. When the thickness of the outermost layer 26 is at or above the aforementioned lower limit, corrosion caused by acidic gases can be further suppressed, and changes in optical properties can be further suppressed. On the other hand, when the thickness of the outermost layer 26 is below the aforementioned upper limit, the transmission of ultraviolet light with wavelengths of 240 nm to 320 nm can be further suppressed, and ultraviolet light with wavelengths of 220 nm to 225 nm can be effectively transmitted.

[0105] [Sterilization device]

[0106] Figure 7 This is a schematic diagram illustrating a sterilization device according to one embodiment of the present invention. Figure 7 As shown, the sterilization device 31 includes a housing 32, a light source 33, and an optical filter 1. The light source 33, which emits light with a wavelength in the range of 190 nm to 230 nm, is disposed inside the housing 32. The light source 33 is positioned facing the optical filter 1. Preferably, a dielectric multilayer film 3 is disposed on the side of the light source 33. In the sterilization device 31, the emitted light from the light source 33 irradiates the object to be sterilized 34 via the optical filter 1.

[0107] As the light source 33, an excimer lamp can be used, for example. Preferably, an excimer lamp emitting ultraviolet light in the wavelength range of 220 nm to 225 nm is used. For example, a KrCl excimer lamp can be used as such an excimer lamp. A KrBr excimer lamp can also be used.

[0108] The sterilization apparatus 31 of this embodiment uses the aforementioned optical filter 1, thus enabling efficient transmission of ultraviolet light useful in sterilization processes. Therefore, ultraviolet sterilization can be efficiently performed on the target organism 34. Furthermore, ultraviolet sterilization allows ultraviolet light to act on the intracellular DNA of bacteria and other target organisms, selectively inactivating them. Additionally, ultraviolet sterilization can also allow ultraviolet light to act on viruses, selectively inactivating them. More preferably, the sterilization apparatus 31 is used for inactivating target microorganisms.

[0109] The present invention will be further described in detail below based on specific embodiments. The present invention is not limited to any of the following embodiments, and appropriate modifications can be made without changing its essence.

[0110] (Manufacturing Example 1)

[0111] First, a synthetic quartz glass substrate (manufactured by USTRON) is prepared as a transparent substrate. Then, a dielectric multilayer film is formed on one main surface of the prepared transparent substrate by sputtering. Specifically, first, a hafnium target is sputtered using argon and oxygen as carrier gases to form a hafnium oxide film (HfO2 film) on one main surface of the transparent substrate. At this time, the flow rates of argon and oxygen are each set to 100 sccm, and the target power (film formation power) is set to 4 kW. Then, a silicon target is sputtered using argon and oxygen as carrier gases to form a silicon oxide film (SiO2 film) on the HfO2 film. Again, the flow rates of argon and oxygen are set to 100 sccm, and the target power (film formation power) is set to 4 kW. By repeating this operation, a dielectric multilayer film of 38 layers with alternating HfO2 and SiO2 films is formed on one main surface of the transparent substrate, thereby obtaining a transparent substrate with a film. In addition, the substrate temperature was set to room temperature (20°C) during film formation.

[0112] (Manufacturing Example 2)

[0113] Except for setting the substrate temperature to 270°C during film formation, the same operation as in Manufacturing Example 1 was performed to obtain a transparent substrate with a film.

[0114] (Manufacturing Example 3)

[0115] Except that a fused silica glass substrate (manufactured by USTRON) is used as a transparent substrate and a film is formed so that the film thickness of each layer is as shown in Table 1 below, the same operation as in Manufacturing Example 1 is performed to obtain a film-coated transparent substrate.

[0116] (Manufacturing Example 4)

[0117] Except that a borosilicate glass substrate (manufactured by Nippon Electric Glass Co., Ltd., model "BU-41") is used as a transparent substrate and a film is formed so that the film thickness of each layer is as shown in Table 1 below, the same operation as in Manufacturing Example 1 is performed to obtain a transparent substrate with a film.

[0118] The thicknesses of each layer in the transparent substrate with film produced in Examples 1 to 4 are shown in Table 1 below.

[0119] [Table 1]

[0120]

[0121] (Manufacturing Example 5)

[0122] First, a synthetic quartz glass substrate (manufactured by USTRON) is prepared as a transparent substrate. Then, a dielectric multilayer film is deposited on one main surface of the prepared transparent substrate by sputtering. Specifically, argon and oxygen are used as carrier gases to sputter a hafnium target, forming a hafnium oxide film (HfO2 film) on one main surface of the transparent substrate. The flow rates of argon and oxygen are set to 100 sccm each, and the target power (film deposition power) is set to 4 kW. Next, argon and oxygen are used as carrier gases to sputter a silicon target, forming a silicon oxide film (SiO2 film) on the HfO2 film. Again, the flow rates of argon and oxygen are set to 100 sccm, and the target power (film deposition power) is set to 4 kW.

[0123] By repeatedly performing this operation, a dielectric multilayer film with a total of 39 layers, consisting of alternating layers of HfO2 and SiO2 films with the outermost layer being an HfO2 film, is formed on one side of the main surface of the transparent substrate, thereby obtaining a transparent substrate with a film. In addition, the substrate temperature is set to room temperature (20°C) during film formation.

[0124] The thickness of each layer in the transparent substrate with film produced in Manufacturing Example 5 is shown in Table 2 below.

[0125] [Table 2]

[0126]

[0127] (Manufacturing Example 6)

[0128] Except that a fused silica glass substrate (manufactured by USTRON) is used as a transparent substrate and a film is formed so that the film thickness of each layer is as shown in Table 1 above, the same operation as in manufacturing example 1 is performed to obtain a film-coated transparent substrate.

[0129] (Examples 1-17 and Comparative Examples 1-4)

[0130] In Example 1, the transparent substrate with film obtained in Manufacturing Example 1 was heated at 500°C for 60 minutes in an atmospheric atmosphere to obtain an optical filter. Similarly, in Examples 2-17, the transparent substrate with film obtained in each manufacturing example was heated in an atmospheric atmosphere at the temperatures and times shown in Table 3 below to obtain optical filters. Furthermore, as shown in Table 3 below, in Comparative Examples 1-4, the transparent substrate with film obtained in each manufacturing example was not heated and was directly used as an optical filter.

[0131] [evaluate]

[0132] (X-ray diffraction measurement)

[0133] X-ray diffraction measurements were performed on the optical filters of Examples 1-7, 9-17 and Comparative Examples 1-4 using wide-angle X-ray diffraction. The X-ray diffraction apparatus used was a "SmartLab" model manufactured by Rigaku Corporation. CuKα rays (wavelength...) were used as the X-ray source. The X-ray diffraction pattern of the optical filter was measured under the following conditions: scanning axis: 2θ / ω, measurement range: 10°~65°, scanning speed: 2° / min, tube current: 200mA, and tube voltage: 45kV. An example of the obtained X-ray diffraction pattern of the optical filter is shown below. Figure 2 .

[0134] Figure 2 This is a diagram showing the X-ray diffraction patterns of the optical filters obtained in Example 2 and Comparative Example 1. (As shown) Figure 2 As shown, in the X-ray diffraction pattern of Example 2, a diffraction peak caused by the (11 1) crystal plane of cubic hafnium oxide was observed near 2θ = 30.7°, and a diffraction peak caused by the (-1 1 1) crystal plane of monoclinic hafnium oxide was observed near 2θ = 28.4°. On the other hand, in Comparative Example 1, no diffraction peak caused by the (1 11) crystal plane of cubic hafnium oxide was observed.

[0135] Similarly, X-ray diffraction measurements were performed on the optical filters of Examples 1, 3-7, 9-17 and Comparative Examples 2-4, and the ratio Ic / Im of the peak area intensity Ic of the diffraction peak caused by the (1 1 1) crystal plane of cubic hafnium oxide crystal and the peak area intensity Im of the diffraction peak caused by the (-1 11) crystal plane of monoclinic hafnium oxide crystal was obtained. The results are shown in Table 3 below.

[0136] (Spectroscopic transmittance)

[0137] The optical filters of Examples 1-17 and Comparative Examples 1-4 were subjected to spectrophotometer transmittance measurement using a Hitachi High-Tech Co., Ltd. model "UH4150". Specifically, the incident angle was set to 0°, and the measurement wavelength was set to 190 nm to 400 nm. An example of the transmission spectrum of the obtained optical filters is shown below. Figure 3 .

[0138] Figure 3 This is a graph showing the transmission spectra of the optical filters obtained in Example 2 and Comparative Example 1. (As shown) Figure 3 As shown, in Example 2, it was confirmed that the minimum value of the spectral transmittance in the wavelength range of 220 nm to 225 nm was improved. On the other hand, in Comparative Example 1, the minimum value of the spectral transmittance in the wavelength range of 220 nm to 225 nm was not sufficiently improved. Furthermore, it was found that in both Example 2 and Comparative Example 1, the maximum value of the spectral transmittance in the wavelength range of 240 nm to 320 nm was reduced.

[0139] Similarly, the spectral transmittance at wavelengths of 220 nm to 225 nm and at wavelengths of 240 nm to 320 nm was also measured for the optical filters of Examples 1, 3 to 17 and Comparative Examples 2 to 4. In addition, the incident angle was set to 0°C as described above.

[0140] The results are shown in Table 3 below.

[0141] [Table 3]

[0142]

[0143] As shown in Table 3, the optical filters of Examples 1 to 17 can suppress the transmission of ultraviolet light in the wavelength range of 240 nm to 320 nm, and effectively allow ultraviolet light in the wavelength range of 220 nm to 225 nm to pass through. On the other hand, the optical filters of Comparative Examples 1 to 4 failed to sufficiently allow ultraviolet light in the wavelength range of 220 nm to 225 nm to pass through.

[0144] (Erosion test)

[0145] The optical filters obtained in Examples 5 and 8 were immersed in 0.5% by weight hydrofluoric acid (HF) for etching tests. An example of the transmission spectra before and after etching is shown below. Figure 5 and Figure 6 .

[0146] Figure 5 This is a graph showing the transmission spectra of the optical filter obtained in Example 5 before and after hydrofluoric acid impregnation. Figure 6 This is a graph showing the transmission spectra of the optical filter obtained in Example 8 before and after hydrofluoric acid impregnation. Additionally, in Figure 5 and Figure 6In this case, the immersion time in hydrofluoric acid was set to 240 seconds.

[0147] according to Figure 5 and Figure 6 It can be seen that in Example 8, where the outermost layer is an HfO2 film, compared with Example 5 where the outermost layer is a SiO2 film, the transmittance variation at wavelengths of 220nm to 225nm can be suppressed.

[0148] Furthermore, Table 4 below shows the relationship between the amount of erosion at each immersion time selection and the change in transmittance at wavelengths of 220 nm to 225 nm for the optical filters obtained in Examples 5 and 8.

[0149] [Table 4]

[0150]

[0151] As shown in Table 4, in Example 8, where the outermost layer is an HfO2 film, compared with Example 5 where the outermost layer is a SiO2 film, the amount of erosion can be reduced and the transmittance variation in the wavelength range of 220nm to 225nm can be suppressed.

[0152] (Example 18)

[0153] First, a synthetic quartz glass substrate (manufactured by USTRON) is prepared as a transparent substrate. Then, a dielectric multilayer film is formed on one main surface of the prepared transparent substrate by sputtering. Specifically, first, a hafnium target is sputtered using argon and oxygen as carrier gases to form a hafnium oxide film (HfO2 film) on one main surface of the transparent substrate. At this time, the flow rates of argon and oxygen are each set to 100 sccm, and the target power (film formation power) is set to 4 kW. Then, a silicon target is sputtered using argon and oxygen as carrier gases to form a silicon oxide film (SiO2 film) on the HfO2 film. Again, the flow rates of argon and oxygen are set to 100 sccm, and the target power (film formation power) is set to 4 kW. By repeating this operation, a dielectric multilayer film of 38 layers with alternating HfO2 and SiO2 films is formed on one main surface of the transparent substrate, thus obtaining a transparent substrate with a film. In addition, the substrate temperature was set to room temperature (20°C) during film formation. Then, the transparent substrate with the film was heated at 500°C for 60 minutes in an atmospheric atmosphere to obtain the optical filter.

[0154] (Example 19)

[0155] Except for changing the thickness of each layer and the number of film layers as shown in Table 5 below when making the transparent substrate with film, the optical filter is made in the same manner as in Example 18.

[0156] (Example 20)

[0157] Except for changing the thickness of each layer and the number of film layers as shown in Table 5 below when making the transparent substrate with film, and heating the obtained transparent substrate with film at 550°C for 60 minutes in an atmospheric atmosphere, the optical filter was made in the same manner as in Example 18.

[0158] (Example 21)

[0159] Except for changing the thickness of each layer and the number of film layers as shown in Table 5 below when making the transparent substrate with film, and heating the obtained transparent substrate with film at 600°C for 60 minutes in an atmospheric atmosphere, the optical filter was made in the same manner as in Example 18.

[0160] (Example 22)

[0161] Except for changing the thickness of each layer and the number of film layers as shown in Table 5 below when making the transparent substrate with film, and heating the obtained transparent substrate with film at 450°C for 60 minutes in an atmospheric atmosphere, the optical filter was made in the same manner as in Example 18.

[0162] (Example 23)

[0163] Except for changing the thickness of each layer and the number of film stacks as shown in Table 5 below when fabricating the transparent substrate with film, and setting the target power (film forming power) when forming the hafnium oxide film (HfO2 film) to 3.5kW, the optical filter was fabricated in the same manner as in Example 22.

[0164] (Example 24)

[0165] Except for changing the thickness of each layer and the number of film stacks as shown in Table 5 below when fabricating the transparent substrate with film, and setting the power applied to the target (film forming power) when forming the hafnium oxide film (HfO2 film) to 3kW, the optical filter was fabricated in the same manner as in Example 22.

[0166] (Example 25)

[0167] Except for changing the thickness of each layer and the number of film stacks when making the transparent substrate with film as shown in Table 5 below, the optical filter is obtained by operating in the same manner as in Example 23.

[0168] [Table 5]

[0169]

[0170] (Comparative Example 5)

[0171] On one side of a transparent substrate prepared in the same manner as in Example 18, a dielectric multilayer film is formed by sputtering. Specifically, firstly, using argon and oxygen as carrier gases, an aluminum target is sputtered to form an alumina film (Al2O3 film) on one side of the transparent substrate. At this time, the argon flow rate is set to 100 ccm, the oxygen flow rate is set to 20 ccm, and the target power (film formation power) is set to 4 kW. Then, using argon and oxygen as carrier gases, a silicon target is sputtered to form a silicon oxide film (SiO2 film) on the Al2O3 film. At this time, the argon and oxygen flow rates are each set to 100 sccm, and the target power (film formation power) is set to 4 kW. By repeatedly performing this operation, a dielectric multilayer film with a total thickness of 10 μm and alternating layers of Al2O3 and SiO2 films is formed on one side of the main surface of the transparent substrate, thereby obtaining a transparent substrate with a film (optical filter). In addition, the substrate temperature is set to room temperature (20°C) during film formation.

[0172] (Comparative Example 6)

[0173] On one main surface of a transparent substrate prepared in the same manner as in Example 18, a dielectric multilayer film is formed by sputtering. Specifically, firstly, argon and oxygen are used as carrier gases to sputter a hafnium target, forming a hafnium oxide film (HfO2 film) on one main surface of the transparent substrate. At this time, the flow rates of argon and oxygen are each set to 100 ccm, and the target power (film formation power) is set to 3 kW. Then, argon and oxygen are used as carrier gases to sputter a silicon target, forming a silicon oxide film (SiO2 film) on the HfO2 film. At this time, the flow rates of argon and oxygen are set to 100 sccm, and the target power (film formation power) is set to 4 kW. By repeating this operation, a dielectric multilayer film with 33 layers of alternating HfO2 and SiO2 films and a total thickness of 1700 nm is formed on one main surface of the transparent substrate, thereby obtaining a transparent substrate with a film. In addition, the substrate temperature was set to room temperature (20°C) during film formation. Then, the transparent substrate with film was heated at 425°C for 60 minutes in an atmospheric atmosphere to obtain the optical filter.

[0174] [evaluate]

[0175] (X-ray diffraction measurement)

[0176] X-ray diffraction measurements were performed on the optical filters of Examples 18-25 and Comparative Examples 5-6 using wide-angle X-ray diffraction. The X-ray diffraction apparatus used was a "SmartLab" model manufactured by Rigaku Corporation. CuKα rays (wavelength...) were used as the radiation source. The measurements were performed under the following conditions: scanning axis: 2θ / ω, measurement range: 10°~65°, scanning speed: 2° / minute, tube current: 200mA, tube voltage: 45kV.

[0177] In the obtained X-ray diffraction pattern, the case where the diffraction peak caused by the (1 1 1) crystal plane of cubic hafnium oxide crystal is larger than the case where the diffraction peak caused by the (-1 1 1) crystal plane of monoclinic hafnium oxide crystal is evaluated as "0", and the case where it is smaller is evaluated as "×".

[0178] Furthermore, using the obtained X-ray diffraction spectrum, the ratio Ic / Im of the peak area intensity Ic of the diffraction peak caused by the (1 1 1) crystal plane of cubic hafnium oxide crystal and the peak area intensity Im of the diffraction peak caused by the (-1 1 1) crystal plane of monoclinic hafnium oxide crystal was obtained.

[0179] (Spectroscopic transmittance)

[0180] The spectral transmittance of the optical filters of Examples 18-25 and Comparative Examples 5-6 was measured using a spectrophotometer (Hitachi Hitachi, model "UH4150"). Specifically, the incident angle (AOI) was set to 0°, 25°, 30°, 40°, or 50°, and the measurement wavelength was set to 190 nm to 400 nm. An example of the transmission spectrum of the obtained optical filters is shown below. Figure 8 .

[0181] Figure 8 This is a graph showing the transmission spectrum of the optical filter obtained in Example 18 at various incident angles. For example... Figure 8 As can be seen, in Example 18, even with an increased incident angle, the high spectral transmittance at a wavelength of 222 nm can be maintained more effectively, and the maximum value of spectral transmittance at wavelengths of 237 nm to 280 nm can be further reduced.

[0182] Similarly, the spectral transmittance at a wavelength of 222 nm and the spectral transmittance (maximum transmittance) at wavelengths of 237 nm to 280 nm were also measured for the optical filters of Examples 18 to 25 and Comparative Examples 5 to 6 at various incident angles.

[0183] The results are shown in Table 6 below. Additionally, Table 6 also shows the spectral transmittance T at a wavelength of 222 nm when the incident angle is 30°. 30 The ratio of the spectral transmittance T0 at a wavelength of 222nm when the incident angle is 0° (T... 30 / T0). Table 6 below also shows the minimum transmittance at wavelengths of 220 nm to 225 nm. The total thickness t of the high refractive index film is also shown. H (HfO2 thickness), total thickness t of the low refractive index filmL (SiO2 thickness), film thickness ratio (t) H / t L ).

[0184] [Table 6]

[0185]

[0186] As shown in Table 6, in the optical filters of Examples 18 to 25, compared with Comparative Examples 5 to 6, even when the incident angle is increased, the high spectral transmittance at wavelength 222 nm can be maintained more effectively, and the maximum value of spectral transmittance at wavelengths of 237 nm to 280 nm can be further reduced.

[0187] Furthermore, in the optical filters of Examples 18-25, the maximum value of the spectral transmittance in the wavelength range of 240 nm to 320 nm was measured using the same method as in Example 1, and the result was less than 5%. In addition, the values ​​were 17.8% and 21.5% in Comparative Examples 5 and 6, respectively.

[0188] Symbol Explanation

[0189] 1, 21… Optical filter; 1a… Main surface; 2… Transparent substrate; 2a… First main surface; 2b… Second main surface; 3, 23… Dielectric multilayer film; 4… High refractive index film; 5… Low refractive index film; 26… Outermost layer; 31… Sterilization device; 32… Housing; 33… Light source; 34… Sterilization target.

Claims

1. An optical filter, characterized by have: Transparent substrate; and A dielectric multilayer film containing hafnium oxide disposed on the transparent substrate The dielectric multilayer film has a high refractive index film with a relatively high refractive index and a low refractive index film with a relatively low refractive index. The total thickness t of the high refractive index film H The ratio t L of the total thickness t of the low refractive index film H to the total thickness t of the high refractive index film L is 0.2 to 0.75, The high refractive index film is a film containing 100% hafnium oxide. The total thickness t of the high refractive index film H is 503 nm or more and 1000 nm or less, In X-ray diffraction measurements, the ratio of the diffraction peak Ic from the (1 1 1) crystal plane of cubic hafnium oxide crystal to the diffraction peak Im from the (-1 1 1) crystal plane of monoclinic hafnium oxide crystal, Ic / Im, is greater than 2. When the incident angle is 0°, the minimum transmittance in the wavelength range of 220nm to 225nm is greater than 50%. When the incident angle is 0°, the maximum transmittance of the spectral density in the wavelength range of 240nm to 320nm is less than 5%.

2. The optical filter as described in claim 1, characterized in that: The low-refractive-index film is a film containing silicon oxide.

3. The optical filter as described in claim 1 or 2, characterized in that: The outermost layer of the dielectric multilayer film is a film containing hafnium oxide.

4. The optical filter as described in claim 3, characterized in that: The thickness of the outermost layer is greater than 1 nm and less than 10 nm.

5. The optical filter as described in claim 1 or 2, characterized in that: Spectroscopic transmittance T at an incident angle of 30° and a wavelength of 222nm 30 The ratio of the spectral transmittance T0 at a wavelength of 222 nm to the transmittance at an incident angle of 0° (T 30 / T0) is above 0.

5.

6. The optical filter as described in claim 1 or 2, characterized in that: When the angle of incidence is 0°, The minimum transmittance in the wavelength range of 220nm to 225nm is above 50%. The maximum transmittance at wavelengths of 237 nm to 280 nm is less than 10%.

7. The optical filter as described in claim 1 or 2, characterized in that: When the incident angle is 40°, the maximum transmittance of the spectral density at wavelengths of 237nm to 280nm is less than 20%.

8. A method for manufacturing an optical filter, used to manufacture the optical filter according to any one of claims 1 to 7, the method being characterized by comprising: The process of forming a hafnium oxide-containing dielectric multilayer film on a transparent substrate by sputtering to obtain a transparent substrate with a film. and The process of heat-treating the film-coated transparent substrate at a temperature above 500°C.

9. The method for manufacturing an optical filter as described in claim 8, characterized in that: The heat treatment temperature for the film-coated transparent substrate is below 800°C.

10. A sterilization device, characterized in that: It is a sterilization device used to inactivate microorganisms in the target organism. The sterilization device has the following features: A light source that emits light in the wavelength range of 190 nm to 230 nm; and The optical filter according to any one of claims 1 to 7.

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