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US-12616764-B2 - Inactivating device and optical filter

US12616764B2US 12616764 B2US12616764 B2US 12616764B2US-12616764-B2

Abstract

An inactivating device includes: an ultraviolet light source to emit ultraviolet light, a main light-emission wavelength band of the ultraviolet light being at least partly included in a range from 200 nm to 230 nm inclusive; and an optical filter including a multilayer dielectric film, wherein with respect to the ultraviolet light incident at an incidence angle of 0 degrees, the optical filter has a band in which the ultraviolet light in a range of wavelengths from 190 nm to 235 nm inclusive is transmitted, and a wavelength λ5 at which transmittance of the optical filter indicates 5% is longer than or equal to 236 nm and shorter than 245 nm.

Inventors

  • Hideaki YAGYU

Assignees

  • USHIO DENKI KABUSHIKI KAISHA

Dates

Publication Date
20260505
Application Date
20221114
Priority Date
20211118

Claims (7)

  1. 1 . An inactivating device comprising: an ultraviolet light source to emit ultraviolet light, a main light-emission wavelength band of the ultraviolet light being at least partly included in a range from 200 nm to 230 nm inclusive; and an optical filter including a multilayer dielectric film, the ultraviolet light generated by the ultraviolet light source being incident on the optical filter, wherein with respect to the ultraviolet light incident at an incidence angle of 0 degrees, the optical filter: has a band in which the ultraviolet light in a range of wavelengths from 190 nm to 235 nm inclusive is transmitted, has a transmittance greater than 5% at a wavelength of 235 nm, and has a wavelength λ5 that is longer than or equal to 237 nm and shorter than 245 nm, wherein the wavelength λ5 is defined as a wavelength at which the transmittance of the optical filter is 5%, and wherein in a distribution of a relative intensity for each angle component of radiant flux of the ultraviolet light generated by the ultraviolet light source and incident on the optical filter, the incidence angle at which the relative intensity shows a peak value is included in a range from 10 degrees to 50 degrees inclusive.
  2. 2 . The inactivating device according to claim 1 , further comprising: a housing that houses the ultraviolet light source; and a light transmissive window to extract the ultraviolet light out of the housing, wherein the optical filter is disposed on a principal surface of the light transmissive window.
  3. 3 . The inactivating device according to claim 1 , wherein the wavelength λ5 of the optical filter is longer than or equal to 238 nm and shorter than 243 nm.
  4. 4 . The inactivating device according to claim 1 , wherein the optical filter includes a member that includes a material to absorb the ultraviolet light in a wavelength range of shorter than or equal to 200 nm.
  5. 5 . The inactivating device according to claim 1 , wherein the ultraviolet light source emits the ultraviolet light that has a peak wavelength within a range from 210 nm to 235 nm inclusive.
  6. 6 . The inactivating device according to claim 1 , wherein the ultraviolet light source is an excimer lamp that includes a light-emitting tube in which a gas containing krypton (Kr) and chlorine (Cl) as a light-emitting gas is sealed.
  7. 7 . An optical filter included in an inactivating device, the inactivating device comprising an ultraviolet light source to emit ultraviolet light, a main light-emission wavelength band of the ultraviolet light being at least partly included in a range from 200 nm to 230 nm inclusive, the optical filter including: a multilayer dielectric film, the ultraviolet light generated by the ultraviolet light source being incident on the optical filter, wherein with respect to ultraviolet light incident at an incidence angle of 0 degrees on the optical filter, the optical filter: has a band in which the ultraviolet light in a range of wavelengths from 190 nm to 235 nm inclusive is transmitted, has a transmittance greater than 5% at a wavelength of 235 nm, and has a wavelength λ5 that is longer than or equal to 237 nm and shorter than 245 nm, wherein the wavelength λ5 is defined as a wavelength at which the transmittance of the optical filter is 5%, and wherein in a distribution of a relative intensity for each angle component of radiant flux of the ultraviolet light generated by the ultraviolet light source and incident on the optical filter, the incidence angle at which the relative intensity shows a peak value is included in a range from 10 degrees to 50 degrees inclusive.

Description

CROSS-REFERENCE TO RELATED APPLICATION The present invention claims the benefit of priority to Japanese Patent Application No. 2021-187813 filed on Nov. 18, 2021 with the Japanese Patent Office, the entire contents of which are incorporated herein by reference in its entirety. BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an inactivating device for bacteria or viruses and particularly to a device for inactivating bacteria or viruses using ultraviolet light. The present invention also relates to an optical filter used in a device for inactivating bacteria or viruses using ultraviolet light. Description of the Related Art Technologies for inactivating bacteria or viruses by irradiating them with ultraviolet light have been known. Since DNA exhibits the highest absorption characteristics around a light wavelength of 260 nm, ultraviolet light with wavelengths around 254 nm emitted from light sources such as low-pressure mercury lamp is used in many cases. Methods for inactivating bacteria or viruses by ultraviolet light are characterized by being able to sterilize a target space or a target object only by irradiating the target space or the target object with ultraviolet light without spraying with chemicals or the like. It is known that ultraviolet light in a wavelength band has high risk of affecting the human body and ultraviolet light in another wavelength band has low risk of affecting the human body. Thus, in recent years, methods or devices for inactivating bacteria or viruses present in a room by ultraviolet light in a wavelength band with low risk of affecting the human body have been considered. For instance, Patent Document 1 shown below gives a description of a sterilizing device (an inactivating device) that uses ultraviolet light in a wavelength range of 190 nm to 230 nm, which has an extremely small influence on the human body. Prior Art Document Patent Document Patent Document 1: JP-B-6025756 Non-Patent Document Non-Patent Document 1: Sachiko Kaidzu et al. “Re-Evaluation of Rat Corneal Damage by Short-Wavelength UV Revealed Extremely Less Hazardous Property of Far-UV-C†” Photochemistry and Photobiology, 2021, 97: 505-516 SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved inactivating device by suppressing an increase in intensity of ultraviolet light in a wavelength band that affects the human body while increasing intensity of the ultraviolet light in a wavelength band that has a small influence on the human body. An inactivating device according to the present invention includes: an ultraviolet light source to emit ultraviolet light, a main light-emission wavelength band of the ultraviolet light being at least partly included in a range from 200 nm to 230 nm inclusive; andan optical filter including a multilayer dielectric film,wherein with respect to the ultraviolet light incident at an incidence angle of 0 degrees, the optical filter has a band in which the ultraviolet light in a range of wavelengths from 190 nm to 235 nm inclusive is transmitted, and a wavelength λ5 at which transmittance of the optical filter indicates 5% is longer than or equal to 236 nm and shorter than 245 nm. In the present specification, “inactivation” refers to a concept that includes killing bacteria or viruses and weakening infectivity or toxicity. And “bacteria” refer to microorganisms such as bacteria and fungi (molds). The “bacteria or viruses” may be hereinafter collectively referred to as “pathogens”. In the present specification, a “main light-emission wavelength band” refers to a wavelength band across which an intensity spectrum of light emitted from a light source shows a light intensity higher than or equal to 10% of a peak intensity of the intensity spectrum. For the ultraviolet light source described above, a peak wavelength of the ultraviolet light is preferably within a range from 190 nm to 235 nm and is more preferably within a range from 210 nm to 235 nm. In recent years, the influence of ultraviolet light on the human body has been researched and verified in a progressive manner. It is proved that ultraviolet light is apt to be absorbed in a skin surface layer and ectocornea and is characterized as improving in safety with a decrease in wavelength. In particular, it is proved that ultraviolet light with a wavelength of shorter than 240 nm has low risk of affecting the human body. It is proved that ultraviolet light with a wavelength of shorter than or equal to 230 nm has extremely low risk of affecting the human body. For instance, Non-Patent Document 1 above gives a report about results obtained by verification of the generation of cyclobutane pyrimidine dimers (CPD), which is DNA damage induced by radiation of ultraviolet light and is a factor in the incidence of cancer. According to Non-Patent Document 1, ultraviolet light of wavelengths 207 nm and 222 nm ultraviolet light, when irradiated to the cornea of an organism, o