WO2023042682A1

WO2023042682A1 - Optical filter, optical filter component, sterilizer, and optical filter production method

Info

Publication number: WO2023042682A1
Application number: PCT/JP2022/033090
Authority: WO
Inventors: 友良中室; 哲也小嶋
Original assignee: 日本電気硝子株式会社
Priority date: 2021-09-14
Filing date: 2022-09-02
Publication date: 2023-03-23
Also published as: JP2023042316A

Abstract

The present invention provides an optical filter with which it is possible to efficiently allow the passage of ultraviolet rays useful for a sterilization treatment while suppressing the passage of ultraviolet rays harmful to the human body, and also possible to increase the effective irradiation area of light discharged from a light source.　An optical filter 1 comprises: a transparent base material 2 that is composed of glass and has a thickness of 0.2 mm or less; and a dielectric multilayer film 3 that is provided on the transparent base material 2 and contains a hafnium oxide. The minimum value of the spectral transmittance at a wavelength of 220 nm to 225 nm inclusive is 50% or more, and the maximum value of the spectral transmittance at a wavelength of 240 nm to 320 nm inclusive is 5% or less.

Description

Optical filter, optical filter component, sterilizer, and method for manufacturing optical filter

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

Conventionally, optical filters capable of selectively transmitting light in a specific wavelength range have been widely used for various purposes. As such an optical filter, a bandpass filter using a dielectric film is known.

Also, in recent years, a sterilization device has been proposed that selectively inactivates the DNA in the cells of organisms to be sterilized, such as bacteria, by applying ultraviolet rays without harming human cells. In this sterilization device, among the light emitted from the light source, the light in the wavelength range of 190 nm to 230 nm is transmitted, and the light with wavelengths other than the above wavelength range is cut. A filter is used.

For example, Patent Literature 1 below discloses a microorganism inactivation apparatus that inactivates microorganisms to be treated by irradiating emitted light from a light source through an optical filter. In Patent Document 1, the optical filter filters at least part of ultraviolet rays with a wavelength of 190 nm or more and 230 nm or less and at least one of ultraviolet rays with a wavelength of more than 230 nm and 237 nm or less when emitted light from a light source is incident at an incident angle of 0°. It is described that the ultraviolet ray having a wavelength other than the wavelength range of 190 nm or more and 237 nm or less is prevented from being transmitted.

JP 2019-115525 A

By the way, in an optical filter, in order to increase the effective irradiation area of emitted light from a light source, emitted light with a large incident angle needs to be incident.

However, the present inventors have found that in an optical filter such as Patent Document 1, when emitted light with a large incident angle is incident, the ultraviolet transmittance with a wavelength of 190 nm to 230 nm that selectively inactivates the cells of the organism to be sterilized is On the other hand, it has been found that the transmittance of ultraviolet rays having a wavelength of 240 nm to 280 nm, which is harmful to the human body, increases.

Therefore, with conventional optical filters, it is necessary to reduce the incident angle of emitted light incident on the optical filter, and there is the problem that it is difficult to increase the effective irradiation area.

The object of the present invention is to efficiently transmit ultraviolet rays useful for sterilization while suppressing the transmission of ultraviolet rays harmful to the human body, and to increase the effective irradiation area of the light emitted from the light source. An object of the present invention is to provide an optical filter, an optical filter component using the optical filter, a sterilization device, and a method for manufacturing the optical filter.

An optical filter according to the present invention comprises a transparent base material made of glass and having a thickness of 0.2 mm or less, and a dielectric multilayer film provided on the transparent base material and containing hafnium oxide. , the minimum value of spectral transmittance at wavelengths of 220 nm to 225 nm is 50% or more, and the maximum value of spectral transmittance at wavelengths of 240 nm to 320 nm is 5% or less.

In the present invention, the optical filter is mutually deformable between a flat state in which the optical filter is not curved and a state in which the optical filter is curved, and can be used in the curved state. preferable.

In the present invention, the optical filter is preferably used in a curved state with a radius of curvature of 100 mm or less.

An optical filter component according to the present invention is characterized by comprising an optical filter configured according to the present invention and a holding portion for holding the optical filter in a curved state.

A sterilization device according to the present invention is a sterilization device for inactivating microorganisms to be treated, and comprises a light source emitting light having a wavelength in a wavelength range of 190 nm to 230 nm, and an optical filter configured according to the present invention. and a holding portion for holding the optical filter in a curved state, and the microorganism to be treated is inactivated by irradiating the light emitted from the light source through the optical filter. The light source and the optical filter are arranged as follows.

In the present invention, it is preferable that the optical filters are arranged concentrically around the light source in a cross-sectional view along the thickness direction.

A method for manufacturing an optical filter according to the present invention is a method for manufacturing an optical filter configured according to the present invention, wherein a transparent substrate made of glass and having a thickness of 0.2 mm or less is laid flat. and forming the dielectric multilayer film on at least one main surface of the transparent substrate.

According to the present invention, it is possible to efficiently transmit ultraviolet rays useful for sterilization while suppressing the transmission of ultraviolet rays harmful to the human body, and to increase the effective irradiation area of the light emitted from the light source. It is possible to provide an optical filter, an optical filter component using the optical filter, a sterilization device, and a method for manufacturing the optical filter.

FIG. 1(a) is a schematic front view showing an uncurved flat state of an optical filter according to a first embodiment of the present invention, and FIG. 1(b) is a first optical filter according to the present invention. FIG. 4 is a schematic front view showing a curved state of the optical filter according to the embodiment; FIG. 2 is a schematic cross-sectional view showing an optical filter according to the first embodiment of the invention. FIG. 3 is a schematic cross-sectional view showing an optical filter according to a second embodiment of the invention. FIG. 4 is a schematic cross-sectional view showing a sterilization device according to one embodiment of the present invention. FIG. 5 is a schematic cross-sectional view showing a conventional sterilization device. FIG. 6 is a diagram showing the transmission spectrum of the optical filter obtained in Comparative Example 1 at each incident angle. FIG. 7 is a transmission spectrum showing an enlarged portion of the transmission spectrum of FIG. 6 where the transmittance is 10% or less.

A preferred embodiment will be described below. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. Also, in each drawing, members having substantially the same function may be referred to by the same reference numerals.

[Optical filter]
(First embodiment)
FIG. 1(a) is a schematic front view showing the optical filter according to the first embodiment of the present invention in a flat, uncurved state. FIG. 1(b) is a schematic front view showing a curved state of the optical filter according to the first embodiment of the present invention.

As shown in FIG. 1(a), the optical filter 1 includes a transparent substrate 2 and a dielectric multilayer film 3. A dielectric multilayer film 3 is provided on a transparent substrate 2 .

In this embodiment, the transparent substrate 2 has a rectangular plate shape. However, the transparent base material 2 may have, for example, a disk-like shape, and the shape is not particularly limited.

The transparent base material 2 is made of glass. Among others, the transparent substrate 2 is preferably made of glass transparent in the wavelength range used by the optical filter 1 . More specifically, the transparent base material 2 preferably has an average light transmittance of 80% or more in the ultraviolet wavelength region at a wavelength of 220 nm to 225 nm.

Examples of the glass forming the transparent substrate 2 include quartz glass and borosilicate glass. The quartz glass may be synthetic quartz glass or fused quartz glass. Borosilicate glass has a glass composition of 55% to 75% SiO _{2 ,} 1% to 10% Al ₂ O ₃ , 10% to 30% B ₂ O ₃ , 0% to 5% CaO, and 0 BaO in mass %. % to 5%, Li ₂ O + Na ₂ O + K ₂ O 1.0% to 15%, and further TiO ₂ 0% to 0.001%, Fe ₂ O ₃ 0% to 0.001% , F 0.5% to 2.0%.

In this embodiment, the transparent base material 2 has a thickness of 0.2 mm or less and has a thin plate shape. Therefore, the optical filter 1 is mutually deformable between the uncurved flat state (flat shape) shown in FIG. 1(a) and the curved state (curved shape) shown in FIG. 1(b). can be made

The thickness of the transparent substrate 2 is preferably 0.20 mm or less, more preferably 0.15 mm or less, and even more preferably 0.10 mm or less. In this case, the optical filter 1 can be more easily deformed between the uncurved flat state and the curved state. Although the lower limit of the thickness of the transparent substrate 2 is not particularly limited, it is preferably 2 μm or more, more preferably 5 μm, from the viewpoint of forming the dielectric multilayer film 3 on the transparent substrate 2 more easily. That's it.

FIG. 2 is a schematic cross-sectional view showing an optical filter according to the first embodiment of the invention. 2 is a schematic cross-sectional view of the optical filter 1 in a flat state shown in FIG. 1(a). In FIG. 2, the vertical direction is reversed from that in FIG. 1(a) in order to facilitate the explanation.

As shown in FIG. 2, the transparent substrate 2 has a first major surface 2a and a second major surface 2b facing each other. A dielectric multilayer film 3 is provided as a filter section on the first main surface 2a of the transparent base material 2 .

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, a multilayer film is configured by alternately laminating the high refractive index film 4 and the low refractive index film 5 on the first main surface 2a of the transparent substrate 2 in this order.

In the present embodiment, the high refractive index film 4 is composed of hafnium oxide, and is a film containing hafnium oxide as its main component.

In addition, the low refractive index film 5 is composed of silicon oxide and is a film containing silicon oxide as a main component. However, the low refractive index film 5 may be a film containing aluminum oxide, zirconium oxide, tin oxide, magnesium fluoride, or silicon nitride as a main component. One of these materials for the low refractive index film 5 may be used alone, or two or more of them may be used in combination.

In this specification, a film containing the material as a main component means a film containing 50% by mass or more of the material. The film containing the material as the main component preferably contains 80% by mass or more of the material, more preferably 90% by mass or more. Of course, the main component film may be a film containing 100% by weight of the material in the film.

The optical filter 1 of this embodiment is a band-pass filter designed to selectively transmit light in a specific wavelength range by light interference by including such a dielectric multilayer film 3 . Specifically, the band-pass filter is designed so that the minimum spectral transmittance is 50% or more at wavelengths of 220 nm to 225 nm, and the maximum spectral transmittance is 5% or less at wavelengths of 240 nm to 320 nm.

In this specification, the spectral transmittance can be obtained by measuring the spectral transmittance of the entire optical filter 1 using, for example, a spectral transmittance meter (manufactured by Hitachi High-Tech Science Co., Ltd., product number "UH4150"). . As for the measurement conditions, for example, measurement can be performed from the main surface 1a side of the optical filter 1, with an incident angle of 0° and a measurement wavelength of 190 nm to 400 nm.

A feature of this embodiment is that the thickness of the transparent base material 2 is 0.2 mm or less, whereby the optical filter 1 is mutually deformable between a flat state without bending and a curved state. It is said that Further, the optical filter 1 includes the dielectric multilayer film 3, the minimum value of the spectral transmittance of the optical filter 1 at a wavelength of 220 nm to 225 nm is 50% or more, and the maximum value of the spectral transmittance at a wavelength of 240 nm to 320 nm is 5%. It consists in the following.

Since the optical filter 1 of the present embodiment has the above configuration, it is possible to efficiently transmit ultraviolet rays useful for sterilization while suppressing the transmission of ultraviolet rays harmful to the human body. Effective irradiation area can be increased. This point will be explained in detail in the section of the sterilization apparatus described later.

In the present embodiment, the minimum spectral transmittance at wavelengths of 220 nm to 225 nm is preferably 60% or higher, more preferably 70% or higher. In this case, ultraviolet rays, which are useful for sterilization such as skin sterilization, can be transmitted more effectively. Although the upper limit of the minimum value of the spectral transmittance at wavelengths of 220 nm to 225 nm is not particularly limited, it can be set to 95%, for example.

In addition, the maximum spectral transmittance at wavelengths 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, transmission of ultraviolet rays harmful to the human body can be more effectively suppressed. Although the lower limit of the maximum spectral transmittance at wavelengths of 240 nm to 320 nm is not particularly limited, it can be set to 0.2%, for example.

In the present embodiment, the total thickness t _H of the high refractive index films 4 (total thickness of each high refractive index film 4) is preferably 250 nm or more, more preferably 300 nm or more, still more preferably 400 nm or more, and particularly preferably 500 nm. above, 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. When the total thickness _tH of the high refractive index film 4 is equal to or greater than the above lower limit, the maximum value of the spectral transmittance at wavelengths of 240 nm to 320 nm can be further reduced. On the other hand, when the total thickness t _H of the high refractive index film 4 is equal to or less than the upper limit, the minimum spectral transmittance at wavelengths of 220 nm to 225 nm can be further increased.

Although the thickness of each layer of the high refractive index film 4 is not particularly limited, it is preferably 5 nm or more, more preferably 10 nm or more, preferably 60 nm or less, and more preferably 50 nm or less.

The total thickness t _L of the low refractive index film 5 (total thickness of each low refractive index film 5) is preferably 500 nm or more, more preferably 600 nm or more, even more preferably 700 nm or more, and particularly preferably 800 nm or more. is 2000 nm or less, more preferably 1700 nm or less, still more preferably 1500 nm or less, and particularly preferably 1400 nm or less. When the total thickness t _L of the low refractive index film 5 is equal to or greater than the above lower limit, the maximum spectral transmittance at wavelengths of 240 nm to 320 nm can be further reduced. On the other hand, when the total thickness t _L of the low refractive index film 5 is equal to or less than the above upper limit, the minimum value of spectral transmittance at wavelengths of 220 nm to 225 nm can be further increased.

The thickness per 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, and more preferably 60 nm or less.

The ratio ( _tH / _tL ) of the total thickness _tH of the high refractive index film 4 to the total thickness _tL of the low refractive index film 5 is preferably 0.2 or more, more preferably 0.3 or more, and further 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, still more preferably 0.8 or less, particularly preferably 0 0.75 or less. When the ratio (t _H /t _L ) is equal to or greater than the above lower limit, the minimum value of spectral transmittance at wavelengths of 220 nm to 225 nm can be further increased. Further, when the ratio (t _H /t _L ) is equal to or less than the upper limit, the maximum spectral transmittance at wavelengths of 240 nm to 320 nm can be further reduced.

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, still more preferably 1100 nm or more, particularly preferably 1200 nm or more, preferably 2500 nm or less, more preferably 2200 nm. Below, more preferably 2000 nm or less, particularly preferably 1900 nm or less. When the total thickness of the dielectric multilayer film 3 is equal to or greater than the above lower limit, the maximum value of the spectral transmittance at wavelengths of 240 nm to 320 nm can be further reduced. On the other hand, when the total thickness of the dielectric multilayer film 3 is equal to or less than the upper limit, the minimum spectral transmittance at wavelengths of 220 nm to 225 nm can be further increased.

The number of layers of the films constituting the dielectric multilayer film 3 is preferably 20 layers or more, more preferably 25 layers or more, still more preferably 30 layers or more, particularly preferably 35 layers or more, and preferably 100 layers or less. , more preferably 80 layers or less, still more preferably 60 layers or less, and particularly preferably 45 layers or less. When the number of layers of the films constituting the dielectric multilayer film 3 is equal to or greater than the above lower limit value, the maximum value of the spectral transmittance at wavelengths of 240 nm to 320 nm can be further reduced. Moreover, when the number of layers of the films constituting the dielectric multilayer film 3 is equal to or less than the above upper limit, the minimum value of the spectral transmittance at wavelengths of 220 nm to 225 nm can be further increased.

In this embodiment, the dielectric multilayer film 3 preferably contains hafnium oxide crystals. More specifically, the high refractive index film 4 constituting the dielectric multilayer film 3 preferably contains hafnium oxide crystals, and more preferably contains cubic hafnium oxide crystals. In this case, the transmittance of ultraviolet rays with a wavelength of 240 nm to 320 nm can be further suppressed, while the transmittance of ultraviolet rays with a wavelength of 220 nm to 225 nm can be further enhanced.

In this specification, whether or not a cubic hafnium oxide crystal is contained is determined by observing a diffraction peak due to a (1,1,1) crystal plane derived from a cubic hafnium oxide crystal in X-ray diffraction measurement. It can be confirmed by whether it is done or not.

Also, in this specification, the X-ray diffraction measurement can be measured by a wide-angle X-ray diffraction method. As the X-ray diffractometer, for example, product number "SmartLab" manufactured by Rigaku Corporation can be used. Moreover, CuKα rays can be used as the radiation source. In the X-ray diffraction measurement, the entire optical filter 1 is measured from the main surface 1a side.

In the present invention, in the X-ray diffraction measurement, the diffraction peak due to the (1,1,1) crystal plane derived from the cubic hafnium oxide crystal is derived from the monoclinic hafnium oxide crystal (-1,1, 1) It is preferably larger than the diffraction peak due to the crystal plane. In this case, the transmittance of ultraviolet rays with a wavelength of 240 nm to 320 nm can be further suppressed, while the transmittance of ultraviolet rays with a wavelength of 220 nm to 225 nm can be further enhanced.

In the present invention, the peak area intensity Ic of the diffraction peak due to the (1,1,1) crystal plane derived from the cubic hafnium oxide crystal and the (-1,1,1 ) The ratio Ic/Im of the diffraction peak due to the crystal plane to the peak area intensity Im is preferably 0.1 or more, more preferably 1 or more, still more preferably 2 or more, particularly preferably 2.5 or more, and most preferably 3 That's it. When the ratio Ic/Im is equal to or higher than the above lower limit, it is possible to further suppress the transmission of ultraviolet rays having a wavelength of 240 nm to 320 nm while further increasing the transmittance of ultraviolet rays having a wavelength of 220 nm to 225 nm. Although the upper limit of the ratio Ic/Im is not particularly limited, it can be set to 10,000, for example.

In the present invention, an antireflection film may be provided on the second main surface 2b of the transparent substrate 2. In this case, it is possible to further increase the transmittance of ultraviolet light having a wavelength of 220 nm to 225 nm.

The antireflection film is not particularly limited, and for example, a multilayer film having 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 may be configured by alternately providing a high refractive index film and a low refractive index film in this order. As the high refractive index film, for example, a film containing hafnium oxide as a main component can be used. Examples of the low refractive index film include films containing silicon oxide, aluminum oxide, zirconium oxide, tin oxide, magnesium fluoride, silicon nitride, or the like as a main component. Further, the number of layers of films constituting the multilayer film can be, for example, 4 or more and 100 or less.

A film other than an antireflection film may be laminated on the second main surface 2b of the transparent substrate 2 as long as the effects of the present invention are not impaired. Further, a film other than the dielectric multilayer film 3 may be provided on the first main surface 2a of the transparent substrate 2 as long as the effects of the present invention are not impaired. 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 the dielectric multilayer film 3 .

An example of the method for manufacturing the optical filter 1 will be described in detail below.

(Manufacturing method of optical filter)
film-coated transparent substrate forming step;
First, the transparent base material 2 is prepared, and the transparent base material 2 is arranged in a flat state. Next, a dielectric multilayer film 3 is formed on the first main surface 2a of the transparent substrate 2. As shown in FIG. Thereby, a film-coated transparent substrate is obtained. Note that the dielectric multilayer film 3 may be formed on the second main surface 2 b of the transparent substrate 2 . Also, the dielectric multilayer film 3 may be formed on both the first principal surface 2a and the second principal surface 2b of the transparent base material 2 .

The dielectric multilayer film 3 can be formed by alternately laminating a high refractive index film 4 and a low refractive index film 5 on the first main surface 2a of the transparent substrate 2 in this order. The high refractive index film 4 and the low refractive index film 5 can each be formed by a sputtering method.

The temperature of the substrate when forming the high refractive index film 4 is preferably 300° C. or less, more preferably 270° C. or less. In this case, the obtained optical filter 1 can more effectively transmit ultraviolet rays in the wavelength range of 220 nm to 225 nm while further suppressing transmission of ultraviolet rays in the wavelength range of 240 nm to 320 nm. The lower limit of the temperature of the substrate when forming the high refractive index film 4 can be set to 20° C., for example.

The high refractive index film 4 is formed by, for example, using a target of the material constituting the high refractive index film 4, setting the flow rate of an inert gas such as argon gas as a carrier gas to 50 sccm to 500 sccm, and applying an electric power of 0.5 sccm. It can be performed as 5 kW to 40 kW.

The low refractive index film 5 is formed by, for example, using a target of the material constituting the low refractive index film 5, setting the flow rate of an inert gas such as argon gas as a carrier gas to 50 sccm to 500 sccm, and applying an electric power of 0.5 sccm. It can be performed as 5 kW to 40 kW.

heat treatment process;
Next, the obtained film-coated transparent substrate is heat-treated. Thereby, the optical filter 1 can be obtained. The temperature of the heat treatment can be, for example, 450° C. or higher. In particular, when the film-coated transparent substrate is heated at a temperature of 450° C. or higher, the content of cubic hafnium oxide crystals can be relatively increased. Therefore, in the obtained optical filter 1, the transmittance of ultraviolet rays with a wavelength of 240 nm to 320 nm can be further suppressed, and the transmittance of ultraviolet rays with a wavelength of 220 nm to 225 nm can be further enhanced.

The temperature of the heat treatment for the film-coated transparent substrate is preferably 450°C or higher, more preferably 500°C or higher, still more preferably 550°C or higher, preferably 800°C or lower, and more preferably 750°C or lower. When the temperature of the heat treatment is within the above range, it is possible to further suppress the transmission of ultraviolet rays having a wavelength of 240 nm to 320 nm and further increase the transmittance of ultraviolet rays having a wavelength of 220 nm to 225 nm.

The heat treatment time for the film-coated transparent substrate is not particularly limited, but can be, for example, 10 minutes or more and 120 minutes or less.

In the present embodiment, in the X-ray diffraction measurement of the film-coated transparent substrate before heat treatment, the intensity of the diffraction peak due to the (−1,1,1) crystal plane derived from the monoclinic hafnium oxide crystal is Small is preferred. The intensity of the diffraction peak due to the (−1,1,1) crystal plane derived from the monoclinic hafnium oxide crystal is preferably at the microcrystal level, and the height of the peak intensity is higher than the peak intensity of the amorphous halo. It is more preferably within three times the height. In this case, by the heat treatment, the peak area intensity Ic of the diffraction peak due to the (1,1,1) crystal plane derived from the cubic hafnium oxide crystal and the (−1,1 1) The ratio Ic/Im of the diffraction peak due to the crystal plane to the peak area intensity Im can be further increased. Therefore, in the obtained optical filter 1, the transmittance of ultraviolet rays with a wavelength of 240 nm to 320 nm can be further suppressed, and the transmittance of ultraviolet rays with a wavelength of 220 nm to 225 nm can be further enhanced.

In the present embodiment, the transmittance of ultraviolet rays at a wavelength of 240 nm to 320 nm and the transmittance of ultraviolet rays at a wavelength of 220 nm to 225 nm are, for example, the total number, film thickness, and material of the films constituting the dielectric multilayer film 3, and the transparent film with the film. It can be adjusted by the heat treatment temperature of the substrate. In particular, in the obtained optical filter 1, the transmission of ultraviolet rays at a wavelength of 240 nm to 320 nm is further suppressed, and the transmission of ultraviolet rays at a wavelength of 220 nm to 225 nm is further effectively improved by the heat treatment temperature of the transparent substrate with the film. can be enhanced.

(Second embodiment)
FIG. 3 is a schematic cross-sectional view showing an optical filter according to a second embodiment of the invention. As shown in FIG. 3, in the optical filter 21, the outermost layer 26 of the dielectric multilayer film 23 is the high refractive index film 4 made of hafnium oxide. Other points are the same as in the first embodiment.

Also in the second embodiment, the thickness of the transparent base material 2 is 0.2 mm or less, so that the optical filter 21 is mutually deformed between the uncurved flat state and the curved state. It is possible. In addition, the optical filter 21 includes a dielectric multilayer film 23, the minimum value of the spectral transmittance of the optical filter 21 at a wavelength of 220 nm to 225 nm is 50% or more, and the maximum value of the spectral transmittance at a wavelength of 240 nm to 320 nm is 5%. % or less. Therefore, the optical filter 21 can efficiently transmit ultraviolet rays useful for sterilization while suppressing the transmission of ultraviolet rays harmful to the human body, and can increase the effective irradiation area of the emitted light from the light source. .

By the way, when an excimer lamp or the like that emits ultraviolet light with a wavelength of 220 nm to 225 nm is used, the irradiated light may deteriorate the device members and generate acidic gas. The gas corrodes the film of the optical filter, which changes the optical characteristics and may not satisfy the required characteristics.

On the other hand, like the optical filter 21, when the outermost layer 26 of the dielectric multilayer film 23 is composed of hafnium oxide, it is possible to further suppress the erosion due to the acidic gas, and the change in optical characteristics is suppressed. can be further suppressed.

Further, 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 equal to or greater than the above lower limit, erosion due to 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 equal to or less than the above upper limit, it is possible to further suppress the transmission of ultraviolet rays with a wavelength of 240 nm to 320 nm, and more effectively transmit the ultraviolet rays with a wavelength of 220 nm to 225 nm.

[Optical filter parts and sterilizer]
FIG. 4 is a schematic cross-sectional view showing a sterilization device according to one embodiment of the present invention.

The sterilization device 30 shown in FIG. 4 is a sterilization device for inactivating the object to be processed. The sterilization device 30 comprises a light source 32 , a reflector 33 , a housing 34 and an optical filter component 31 . The optical filter component 31 includes the optical filter 1 of the first embodiment and a holding portion 35 that holds the optical filter 1 in a curved state.

In the sterilization device 30, the optical filter 1 is provided in a curved state. A dielectric multilayer film 3 is positioned on the concave side of the optical filter 1, and a transparent substrate 2 is positioned on the convex side. In the sterilization device 30 , the emitted light emitted from the light source 32 is applied to the sterilization target P through the optical filter 1 . The transparent substrate 2 may be positioned on the concave surface side of the optical filter 1, and the dielectric multilayer film 3 may be positioned on the convex surface side, and the positional relationship therebetween is not particularly limited.

A light source 32 and a reflector 33 are arranged inside the housing 34 . The light source 32 is a light source that emits light in a wavelength range of 190 nm to 230 nm. The reflector 33 can widely diffuse the light emitted from the light source. The light source 32 is arranged to face the concave surface of the optical filter 1 .

For example, an excimer lamp can be used as the light source 32 . As the excimer lamp, it is preferable to use an excimer lamp that emits ultraviolet light having a wavelength of 220 nm to 225 nm. As such an excimer lamp, for example, a KrCl excimer lamp can be used. The excimer lamp may be a KrBr excimer lamp.

The configuration such as the shape of the holding portion 35 is not particularly limited. The holding portion 35 may hold the optical filter 1 in a predetermined curved shape. Examples of the shape of the holding portion 35 include a frame shape and a box shape. Note that the holding portion 35 may be configured as an independent part, and may be provided as part of the housing 34, for example. Aluminum, for example, can be used as the material of the holding portion 35 .

By using the sterilization device 30, the objects to be treated (microorganisms, viruses, etc.) adhering to the object P to be sterilized can be inactivated. In the sterilization device 30, since ultraviolet rays useful for sterilization treatment can be efficiently transmitted, the object P to be sterilized can be sterilized with ultraviolet rays efficiently. For example, in ultraviolet sterilization, ultraviolet rays can be applied to the DNA in the cells of microorganisms such as bacteria to selectively inactivate the microorganisms, or viruses can be selectively inactivated by the application of ultraviolet rays. . Therefore, the object to be treated is preferably a microorganism or virus, more preferably a microorganism. That is, the sterilization device 30 is preferably used for inactivating microorganisms or viruses to be treated, and more preferably used for inactivating microorganisms to be treated.

Since the sterilization device 30 of the present embodiment includes the optical filter 1, it is possible to efficiently transmit ultraviolet rays useful for sterilization while suppressing transmission of ultraviolet rays harmful to the human body. The effective irradiation area of emitted light can be increased. This point can be explained as follows.

FIG. 5 is a schematic cross-sectional view for explaining a conventional sterilization device. As shown in FIG. 5, in the conventional sterilizer 100, an optical filter 101 is placed flat on a housing 104. As shown in FIG. Therefore, near the center of the optical filter 101 located above the light source 102, emitted light with a small incident angle is incident. On the other hand, emitted light with a large incident angle is incident on a portion located obliquely above the light source 102 and away from the center of the optical filter 101 . At this time, when emitted light with a large incident angle is incident, the transmittance of ultraviolet rays with a wavelength of 190 nm to 230 nm that selectively inactivates the cells of the object to be treated is reduced, while ultraviolet rays with a wavelength of 240 nm to 280 nm that are harmful to the human body are reduced. There is a problem of high transmittance. As shown in FIG. 5, the angle of incidence means an angle θ inclined with respect to the direction perpendicular to the main surface 101a of the optical filter 101 as the normal direction. and Therefore, the direction along the normal direction has an incident angle of 0°.

On the other hand, in the sterilization device 30 of this embodiment, the optical filter 1 is provided in a curved state. Therefore, the radiant light with a small incident angle θ is made incident not only near the center of the optical filter 1 located above the light source 32, but also at a portion located obliquely above the light source 32 and away from the center of the optical filter 1. be able to. Therefore, according to the sterilization device 30, even when the effective irradiation area of the emitted light from the light source 32 is increased, it is possible to efficiently transmit ultraviolet rays useful for sterilization while suppressing the transmission of ultraviolet rays harmful to the human body. can be done. When the optical filter 1 is provided in a curved state as in this embodiment, the incident angle .theta. In addition, the direction perpendicular to the main surface 1a is taken as the normal direction, and the angle is inclined with respect to the normal direction. For example, in FIG. 4, the direction perpendicular to the upper surfaces (horizontal planes) of the housing 34 and the holding portion 35 is the normal direction.

In the sterilization device 30 of the present embodiment, as shown in FIG. 4, the optical filters 1 are preferably arranged concentrically around the light source 32 in a cross-sectional view along the thickness direction. In this case, it is possible to more efficiently transmit ultraviolet rays useful for sterilization, while further suppressing the transmission of ultraviolet rays harmful to the human body. can.

Also, the optical filter 1 is preferably used in a curved state with a radius of curvature of 100 mm or less. In this case, it is possible to more efficiently transmit ultraviolet rays useful for sterilization, while further suppressing the transmission of ultraviolet rays harmful to the human body. can.

The optical filter 1 is preferably used in a curved state with a radius of curvature of preferably 100 mm or less, more preferably 10 mm or less.

In addition, from the viewpoint of making it more difficult for the dielectric multilayer film 3 to separate from the transparent base material 2, the optical filter 1 is curved so that the radius of curvature is preferably 1 mm or more, more preferably 5 mm or more. It is preferably used in

Hereinafter, the present invention will be described in more detail based on specific examples. The present invention is by no means limited to the following examples, and can be modified as appropriate without changing the gist of the invention.

(Example 1)
First, a 0.1 mm-thick borosilicate glass substrate (manufactured by Nippon Electric Glass Co., Ltd., product number “BU-41”, dimensions: 70 mm×52 mm×0.1 mm) was prepared as a transparent substrate. Next, a dielectric multilayer film was formed by sputtering on one main surface of the prepared transparent substrate. Specifically, first, using argon gas and oxygen gas as carrier gases, a hafnium target was sputtered to form a hafnium oxide film (HfO ₂ film) on one main surface of the transparent substrate. At this time, the flow rates of argon gas and oxygen gas were each set to 100 sccm, and the power applied to the target (film formation power) was set to 4 kW. Next, using argon gas and oxygen gas as carrier gases, a silicon target was sputtered to form a silicon oxide film (SiO ₂ film) on the HfO ₂ film. At this time, the flow rates of argon gas and oxygen gas were set to 100 sccm, and the power applied to the target (film formation power) was set to 4 kW. By repeating this operation, a dielectric multilayer film having a total of 38 layers, in which HfO ₂ films and SiO ₂ films are alternately laminated one by one, is formed on one main surface of the transparent substrate. to obtain a film-coated transparent substrate. The substrate temperature was set at room temperature (20° C.) during film formation. Next, an optical filter was obtained by heat-treating the film-coated transparent substrate at a temperature of 500° C. for 60 minutes in an air atmosphere.

The thickness of each layer in the dielectric multilayer film is as shown in Table 1 below.

(Comparative example 1)
An optical filter was obtained in the same manner as in Example 1, except that a 1 mm-thick quartz glass plate (manufactured by USTRON, product number "FLH311", dimensions: 70 mm x 52 mm x 1 mm) was used as the transparent substrate.

[evaluation]
(spectral transmittance)
The spectral transmittance of the optical filters of Example 1 and Comparative Example 1 was measured using a spectral transmittance meter (manufactured by Hitachi High-Tech Science, product number "UH4150"). In addition, in the measurement of the spectral transmittance, in Example 1, the optical filter was bent so as to have a radius of curvature of 24 mm and was placed in the folder. Also, in Comparative Example 1, the optical filter was placed in the folder in a flat state without being curved.

Specifically, the angle of incidence (AOI) was set to 0° or 40°, and the measurement wavelength was set to 200 nm to 320 nm. The incident angle was adjusted by rotating the folder in which the sample was placed.

FIG. 6 is a diagram showing the transmission spectrum of the optical filter obtained in Comparative Example 1 at each incident angle. 7 is a diagram showing a transmission spectrum obtained by enlarging a portion of the transmission spectrum shown in FIG. 6 where the transmittance is 10% or less.

As shown in FIGS. 6 and 7, in Comparative Example 1, when the incident angle is 40°, the minimum spectral transmittance at wavelengths of 220 nm to 225 nm is reduced. Also, in Comparative Example 1, when the incident angle is 40°, the maximum value of the spectral transmittance at wavelengths of 240 nm to 320 nm is high.

Similarly, for the optical filter of Example 1, the minimum value of spectral transmittance at wavelengths of 220 nm to 225 nm and the maximum value of spectral transmittance at wavelengths of 240 nm to 320 nm were measured.

As is clear from Table 2, in the optical filter of Example 1, compared with Comparative Example 1, even when the incident angle is increased, the minimum value of the spectral transmittance at wavelengths of 220 nm to 225 nm can be increased. , the maximum value of the spectral transmittance at wavelengths of 240 nm to 320 nm can be reduced.

Therefore, in the optical filter of Example 1, it is possible to efficiently transmit ultraviolet rays useful for sterilization while suppressing the transmission of ultraviolet rays harmful to the human body, and increase the effective irradiation area of the emitted light from the light source. I have confirmed that it is possible.

Reference Signs List

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 30 ... Sterilization device 31 ... Optical filter component 32 ... Light source 33 ... Reflector 34 ... Housing 35 ... Holding part P ... Object to be sterilized

Claims

a transparent substrate made of glass and having a thickness of 0.2 mm or less;
a dielectric multilayer film provided on the transparent substrate and containing hafnium oxide;
with
The minimum spectral transmittance at a wavelength of 220 nm to 225 nm is 50% or more,
An optical filter having a maximum spectral transmittance of 5% or less at a wavelength of 240 nm to 320 nm.
the optical filter is mutually deformable between a flat state in which the optical filter is not curved and a state in which the optical filter is curved;
2. The optical filter of claim 1, used in a curved state.
The optical filter according to claim 2, wherein the optical filter is used in a curved state with a radius of curvature of 100 mm or less.
an optical filter according to any one of claims 1 to 3;
a holding part for holding the optical filter in a curved state;
An optical filter component, comprising:
A sterilization device for inactivating microorganisms to be treated,
a light source whose emitted light has a wavelength in the wavelength range of 190 nm to 230 nm;
an optical filter according to any one of claims 1 to 3;
a holding part for holding the optical filter in a curved state;
with
The sterilization device, wherein the light source and the optical filter are arranged so that the microorganisms to be treated are inactivated by irradiating the light emitted from the light source through the optical filter.
The sterilization device according to claim 5, wherein the optical filters are arranged concentrically around the light source in a cross-sectional view along the thickness direction.
A method for manufacturing an optical filter according to any one of claims 1 to 3,
Placing a transparent base material made of glass and having a thickness of 0.2 mm or less in a flat state;
forming the dielectric multilayer film on at least one main surface of the transparent substrate;
A method of manufacturing an optical filter, comprising: