Ultraviolet irradiation device

Abstract

To provide an ultraviolet light irradiation device that is easy to improve abilities to inactivate pathogen while securing high safety to human-beings and animals.SOLUTION: A ultraviolet light irradiation device has a light source that exhibits light intensity within a first wavelength band of 200 nm to 235 nm and a second wavelength band of 240 nm to 280 nm, and at least a part of a main emission wavelength band belongs to the first wavelength band and an optical filter that suppresses the intensity of light in the second wavelength band, wherein the light intensity of light of the wavelength band where the main emission wavelength band and the first wavelength band overlap is integrated by the wavelength, and from a first distribution light angle distribution where the integrated value is shown for every distribution angle and a spectrum for each distribution angle, the light intensity within the second wavelength band is integrated by wavelength, and for the second light distribution light angle distribution where the integrated is shown for each light distribution light angle, a first angle of the light ray showing a maximum intensity in the first light distribution angle distribution, and a second angle of the light ray showing the maximum intensity in the second light distribution angle distribution substantially match.SELECTED DRAWING: Figure 4

Description

[Technical Field] 【0001】 This invention relates to an ultraviolet light irradiation device. [Background technology] 【0002】 In recent years, research on the effects of ultraviolet light on humans has progressed, and it has been confirmed that ultraviolet light is easily absorbed by the surface of the skin or the corneal epithelium, and that its safety increases as the wavelength shortens. Therefore, technologies are being researched that inactivate pathogens such as bacteria, fungi, and viruses present in the space within an environment where people are present by irradiating it with ultraviolet light of a relatively short wavelength. For example, Patent Document 1 discloses an ultraviolet light irradiation device that emits ultraviolet light in a wavelength range that can inactivate pathogens and has extremely low harmfulness to humans into a space where people are present, thereby inactivating pathogens. 【0003】 Incidentally, when irradiating an environment that includes people with ultraviolet light, it is sometimes necessary to suppress the amount of ultraviolet light irradiated. For example, ACGIH (American Conference of Governmental Industrial Hygienists) or JIS Z 8812 (Methods for Measuring Harmful Ultraviolet Radiation) stipulate that the amount of ultraviolet light irradiated to a person per day (8 hours) should be below the Threshold Limit Value (TLV). [Prior art documents] [Patent Documents] 【0004】 [Patent Document 1] Patent No. 6908172 [Overview of the project] [Problems that the invention aims to solve] 【0005】 Although relatively short-wavelength ultraviolet light that can be emitted into environments containing people has been confirmed to have extremely low harmfulness to humans and animals, in order to obtain a high level of safety and peace of mind, it is desirable to set the ultraviolet light emission intensity or actual irradiation time so that the ultraviolet light irradiation amount meets the above-mentioned permissible limit value (TLV). On the other hand, increasing the ultraviolet light irradiation amount is effective in improving the inactivation capacity of ultraviolet light irradiation devices. 【0006】 The present invention aims to provide an improved ultraviolet light irradiation device that can easily enhance the ability to inactivate pathogens while ensuring high safety for humans and animals. [Means for solving the problem] 【0007】 One embodiment of the ultraviolet light irradiation apparatus according to the present invention includes a light source that emits light with light intensity in a first wavelength band of 200 nm to 235 nm and a second wavelength band of 240 nm to 280 nm, and in which at least a portion of the main emission wavelength band belongs to the first wavelength band, The optical filter includes an optical filter that suppresses the intensity of light in the second wavelength band and has transmittance characteristics corresponding to the incident angle of light emitted from the light source, From the spectrum of the light emitted from the optical filter at each beam angle, the light intensity of the wavelength band in which the main emission wavelength band and the first wavelength band overlap is integrated with respect to wavelength, and the integrated value is shown for each beam angle as the first beam angle distribution, From the spectra for each of the aforementioned beam angles, the light intensity within the second wavelength band is integrated with respect to wavelength, and the integrated value is shown for each beam angle in the second beam angle distribution, The first angle of the ray showing the maximum intensity in the first light distribution and the second angle of the ray showing the maximum intensity in the second light distribution are substantially the same. 【0008】 First, we will explain the definitions of terms used in this specification. 【0009】 In this specification, "intensity indicated" means that the light emitted from a light source is detected by a measuring instrument such as a spectrometer (spectrophotometer). 【0010】 In this specification, an optical filter that "suppresses light intensity" means an optical filter that, when comparing the light intensity of incident light incident on the optical filter at an incident angle of 0° with the light intensity of the emitted light emitted from the optical filter, reduces the light intensity of the emitted light in the target wavelength range relative to the light intensity of the incident light. Typically, an optical filter that "suppresses light intensity" is an optical filter in which, when comparing the integral value of the entire target wavelength range, the light intensity of the emitted light is 50% or less of the light intensity of the incident light, and more preferably, the light intensity of the emitted light is 30% or less of the light intensity of the incident light. An optical filter that "suppresses light intensity" may also be an optical filter in which the ratio of the intensity of light in the second wavelength band to the maximum intensity of light belonging to the first wavelength band in the emitted light is lower than the ratio of the light intensity of the incident light. 【0011】 In this specification, two angles relating to a ray are considered substantially the same, including cases where the angles are perfectly the same, as well as cases where they differ by no more than ±15 degrees. 【0012】 The reason why the above-described ultraviolet light irradiation device is a means to solve the above problems will be explained. The spectrum emitted by the light source used in the ultraviolet light irradiation device shows light intensity in a first wavelength band of 200 nm to 235 nm and a second wavelength band of 240 nm to 280 nm, and at least a part of the main emission wavelength band belongs to the first wavelength band. In this specification, when simply referred to as "spectrum," "spectrum" refers to the spectral spectrum that shows the light intensity according to the wavelength. In this specification, "main emission wavelength band" refers to the wavelength band in the spectrum of light emitted from the light source that shows a light intensity of a certain percentage or more of the maximum intensity (for example, 10% or more of the maximum intensity). Alternatively, the "main emission wavelength band" may be defined based on the wavelength that shows the maximum intensity within the first wavelength band. For example, the wavelength ±5 nm that shows the maximum intensity within the first wavelength band may be defined as the "main emission wavelength band." 【0013】 Light belonging to the first wavelength band of 200 nm to 235 nm has the function of inactivating pathogens and is light that is extremely low in harmfulness to humans and animals. In this specification, "pathogens" include fungi such as bacteria and fungi (molds), and viruses. "Inactivation" is a concept that includes killing pathogens or losing infectivity and toxicity. In this specification, light belonging to the first wavelength band of 200 nm to 235 nm is used for the purpose of inactivation. Hereinafter, the light in the first wavelength band of 200 nm to 235 nm may be referred to as "target light". 【0014】 Light belonging to the second wavelength band of 240 nm to 280 nm is light that may have an adverse effect on humans and animals. In this specification, the light belonging to the second wavelength band is not light that is emitted as desired, but is light that is inevitably emitted due to the nature of the light source. Hereinafter, the light in the second wavelength band of 240 nm to 280 nm may be referred to as "harmful light". 【0015】 FIG. 17A is a graph showing the angular distribution of the light distribution of the target light emitted from a conventional ultraviolet light irradiation device by simulation. FIG. 17B is a graph showing the angular distribution of the light distribution of the harmful light emitted from a conventional ultraviolet light irradiation device by simulation. In the simulation, a KrCl excimer lamp in which krypton (Kr) and chlorine (Cl) are enclosed as a light-emitting gas in a discharge tube is used as the light source of the ultraviolet light irradiation device. 【0016】 The light distribution angle distribution is a graph showing the relative value of the light intensity for each light distribution angle. The light distribution angle and the light intensity will be described. FIG. 18 is a diagram for explaining the light distribution angle θ and the light intensity I(θ). As shown in FIG. 18, the light distribution angle θ is represented by the angle formed between an arbitrary light ray Lx emitted from the ultraviolet light irradiation device 100 and the optical axis Lc of the light beam emitted from the ultraviolet light irradiation device 100. The light intensity I(θ) is the intensity of light on an arbitrary irradiated surface 90. The light intensity I(θ) varies depending on the light distribution angle θ. The light intensity of the light ray on the optical axis Lc where θ = 0 is represented by I(0). The light intensity I(θ) is represented by a relative value with I(0) being 1. Since the light intensity I(θ) can be rephrased as relative illuminance, in this specification, the light intensity I(θ) may also be referred to as "relative illuminance". 【0017】 The light distribution angle distribution shown in FIGS. 17A / 17B has the light distribution angle (θ) shown on the horizontal axis and the light intensity I(θ) shown on the vertical axis. From the graph of FIG. 17A, it can be seen that the light intensity of the target light is maximum when the light distribution angle is 0 degrees, and it decreases as the absolute value of the light distribution angle increases. From the graph of FIG. 17B, it can be seen that the light intensity of the harmful light is maximum around the light distribution angle of +45 degrees or -45 degrees. The reason why the light distribution angles showing the maximum intensity are different between the target light and the harmful light will be described later. 【0018】 FIG. 19 is a perspective view showing the positions of the maximum intensity of the target light and the maximum intensity of the harmful light emitted from the ultraviolet light irradiation device 100 respectively. Based on FIGS. 17A / 17B, the maximum relative illuminance of the target light appears at the position P1 in FIG. 19. The maximum relative illuminance of the harmful light appears at the position P2 in FIG. 19. In this specification, since it is assumed that the light distribution angle showing the maximum intensity does not vary around the optical axis Lc, the position P2 is represented as a circle. However, in reality, since the light distribution angle showing the maximum intensity may vary around the optical axis Lc, the position P2 may not be represented as a circle. 【0019】 Incidentally, the above-mentioned permissible limit values ​​(hereinafter sometimes referred to as "TLV") are specified for each wavelength. Furthermore, TLVs are reviewed over time in line with the progress of safety research on light wavelengths. For example, in the current ACGIH, the TLV for light with a wavelength of 222 nm is 22 mJ / cm² per day (8 hours). 2 It is said that... However, it is expected that the TLV for light with a wavelength of 222 nm will be relaxed while taking into consideration safety for the human body. 【0020】 The inventors investigated increasing the emission intensity or actual irradiation time of an ultraviolet light irradiation device in response to the relaxation of the TLV (Total Life Limit). If it is possible to increase the emission intensity or actual irradiation time while satisfying the relaxed TLV, it will be possible to enhance the inactivation capacity while ensuring high safety for humans and animals. In the course of such investigations, the inventors discovered that increasing the emission intensity or actual irradiation time causes problems that had not been anticipated in the past. 【0021】 This problem will be explained with reference to Figure 20. Figure 20 is a graph showing the relationship between irradiation time ti (horizontal axis) and daily irradiation dose D (vertical axis) for target light L10 and harmful light L20. The ultraviolet light irradiation device may operate not only by continuously irradiating ultraviolet light throughout the day, but also by intermittently alternating between irradiation and non-irradiation. Irradiation time ti refers to the total time (cumulative time) of irradiation throughout the day. The longer the irradiation time ti (unit: sec), the higher the irradiation dose D (unit: mJ / cm²). 2 ) will become larger. 【0022】 Conventionally, the TLV of the target light L10 was V11 (mJ / cm²). 2 ) and the TLV of harmful light L20 is V2 (mJ / cm 2 Let's assume that it was previously defined that the irradiation dose D of the target light L10 was V11 (mJ / cm²). 2 The irradiation time was set to t1 (sec) so as not to exceed ). In other words, only region A11 was being focused on. The irradiation dose of harmful light L20 was V2 (mJ / cm²). 2Since it has nothing to do with at all, as long as the area A11 was focused on, there was no need to focus on the area A12. 【0023】 Here, consider a scenario where the TLV of the target light is relaxed and can be newly set higher from the conventional V11 (mJ / cm 2 ) to V12 (mJ / cm 2 ). When considering extending the irradiation time to t2 according to the relaxation of the TLV, it was found that the irradiation amount of the harmful light L20, which was not necessary to consider conventionally, approached V2 (mJ / cm 2 ), which is the TLV of the harmful light L20 (see area A22). 【0024】 Then, in order to set the irradiation time according to the relaxation of the TLV, it is necessary to consider both making sure that the irradiation amount of the target light L10 does not exceed V12 (mJ / cm 2 ) (see area A21), and making sure that the irradiation amount of the harmful light L20 does not exceed V2 (mJ / cm 2 ), which is the TLV of the harmful light (see area A22). 【0025】 As shown in FIG. 19, the position P1 where the light ray indicating the maximum intensity of the target light is irradiated is different from the position P2 where the light ray indicating the maximum intensity of the harmful light is irradiated. Therefore, when setting the irradiation amount D according to the relaxation of the TLV, it is necessary to monitor the positions P1 and P2 in order to ensure that the irradiation amounts of the target light and the harmful light do not exceed their respective TLVs. In particular, when the light distribution angle indicating the maximum intensity of the harmful light is unknown, first, more effort is required to measure the light distribution angle indicating the maximum intensity. In addition, although the setting of the irradiation time according to the relaxation of the TLV was mentioned above, the same can be said for the case of setting the emission intensity according to the relaxation of the TLV. 【0026】 As stated at the beginning of the section "Means for Solving the Problem," the inventors, through diligent research, have found that the ultraviolet light irradiation device can be designed such that the beam angle (first angle) of the ray showing maximum intensity in the first beam angle distribution of the target light and the beam angle (second angle) of the ray showing maximum intensity in the second beam angle distribution of the harmful light substantially coincide. This allows both the target light and harmful light irradiation doses D to be monitored at the same location when setting the irradiation dose D in accordance with the relaxation of the TLV. As a result, the adjustment of the ultraviolet light irradiation device in accordance with the relaxation of the TLV becomes simpler. 【0027】 An example of a method for deriving the first and second beam angle distributions of light emitted from the optical filter in the ultraviolet light irradiation device described above will be described in detail in the section "Modes for Carrying Out the Invention". 【0028】 The first and second angles may both be between -10 degrees and +10 degrees. The first and second angles may both be between -5 degrees and +5 degrees. As both the first and second angles approach 0 degrees, the positions (P1, P2) for monitoring light intensity can be set near the optical axis Lc of the emitted light. As a result, adjustment of the ultraviolet light irradiation device in response to TLV relaxation becomes simpler. 【0029】 In the first beam angle distribution, the light intensity of the ray with a beam angle of 40 degrees may be less than that of the ray with the first angle, and the light intensity of the ray with a beam angle of 70 degrees may be less than that of the ray with a beam angle of 40 degrees. In the second beam angle distribution, the light intensity of the ray with a beam angle of 40 degrees may be less than that of the ray with the second angle, and the light intensity of the ray with a beam angle of 70 degrees may be less than that of the ray with a beam angle of 40 degrees. This indicates that as the absolute value of the beam angle increases in steps, the light intensity of both the target light and the harmful light decreases. When the beam angle is large, the distance from the ultraviolet light irradiation device on the irradiated plane usually increases. As a result, the relative intensity of the target light and harmful light tends to decrease as the distance from the ultraviolet light irradiation device increases, and consequently, the adjustment of the ultraviolet light emission device in response to the relaxation of TLV becomes simpler. 【0030】 From the spectrum of light emitted from the optical filter, a first integrated light intensity is obtained by integrating the light intensity in the wavelength band where the main emission wavelength band and the first wavelength band overlap, and a second integrated light intensity is obtained by integrating the light intensity within the second wavelength band. The second integrated light intensity may be 1.0% or less of the first integrated light intensity. The second integrated light intensity may be 0.1% or less of the first integrated light intensity. By suppressing the second integrated light intensity, which represents the total light intensity of harmful light, it is possible to increase the amount of ultraviolet light irradiation while protecting the TLV. 【0031】 Furthermore, a diffusion unit for diffusing the light emitted from the optical filter may be provided after the optical filter. 【0032】 The average transmittance of the optical filter for light in the wavelength band where the main emission wavelength band and the first wavelength band overlap tends to decrease as the incident angle on the optical filter increases from 20 degrees to 60 degrees. The average transmittance of the optical filter for light in the second wavelength band may show an increasing trend as the incident angle on the optical filter increases from 30 degrees to 60 degrees. 【0033】 The method for deriving the average transmittance of an optical filter for each incident angle in a specific wavelength band will be described later. [Effects of the Invention] 【0034】 This provides an improved ultraviolet light irradiation device that enhances the ability to inactivate pathogens while ensuring a high level of safety for humans. 【0035】 Providing ultraviolet light irradiation equipment aligns with United Nations Sustainable Development Goal (SDG) 3, "Ensure healthy lives and promote well-being for all at all ages," and makes a significant contribution to Target 3.3, "By 2030, eradicate AIDS, tuberculosis, malaria and neglected tropical diseases, and combat hepatitis, waterborne diseases and other infectious diseases." [Brief explanation of the drawing] 【0036】 [Figure 1] This figure shows one embodiment of an ultraviolet light irradiation device. [Figure 2] Figure 1 shows the ultraviolet light irradiation device as viewed from the +Z side. [Figure 3] An example of the spectrum of ultraviolet light emitted from a light source is shown. [Figure 4] This is a cross-sectional view of the ultraviolet light irradiation device shown in Figure 1, viewed in the X direction. [Figure 5A] This shows the average transmittance of an optical filter when the angle of incidence of ultraviolet light is varied. [Figure 5B] This shows the average transmittance of an optical filter when the angle of incidence of ultraviolet light is varied. [Figure 6] This diagram illustrates the angle of incidence of light entering an optical filter. [Figure 7A] This shows the first beam angle distribution of the emitted light from the ultraviolet light irradiation device of this embodiment. [Figure 7B] This shows the second beam angle distribution of the emitted light from the ultraviolet light irradiation device of this embodiment. [Figure 8] The transmission spectra of individual optical filters at different angles of incidence are shown. [Figure 9] An example of a measurement method for obtaining transmission spectra T(λ,θ) at different incident angles is shown. [Figure 10] These are spectra of light emitted from an optical filter at different angles of incidence. [Figure 11] This shows the incident angle characteristics of the optical filter in the second wavelength band. [Figure 12] This shows an example of a measurement method for obtaining the radiant intensity of emitted light at different beam angles. [Figure 13] This shows the beam angle distribution of light emitted from an ultraviolet light irradiation device without an optical filter. [Figure 14] This shows the beam angle distribution of light obtained by wavelength integration with harmful light in this embodiment. [Figure 15] This shows the beam angle distribution of light obtained by wavelength integration of a portion of the target light in this embodiment. [Figure 16]A modified example of an ultraviolet light irradiation device is shown. [Figure 17A] This shows the first beam angle distribution of the emitted light from a conventional ultraviolet light irradiation device. [Figure 17B] This shows the second beam angle distribution of the emitted light from a conventional ultraviolet light irradiation device. [Figure 18] This diagram explains the beam angle and light intensity. [Figure 19] This is a perspective view showing the location where the maximum relative contrast between the target light and harmful light is measured. [Figure 20] The relationship between irradiation time and irradiation dose for both target light and harmful light is shown. [Modes for carrying out the invention] 【0037】 The drawings are shown using the XYZ coordinate system as appropriate. The specification is described with reference to the XYZ coordinate system as appropriate. In this specification, when expressing a direction, positive and negative directions are distinguished, and are indicated with a sign such as "+X direction" and "-X direction". When expressing a direction without distinguishing between positive and negative directions, it is simply described as "X direction". That is, in this specification, when simply described as "X direction", both "+X direction" and "-X direction" are included. The same applies to the Y direction and Z direction. 【0038】 [Overview of UV light irradiation device] An overview of one embodiment of the ultraviolet light irradiation device will be described with reference to Figure 1. Figure 1 is a schematic diagram showing the external appearance of one embodiment of the ultraviolet light irradiation device 1, and Figure 2 is a view of the ultraviolet light irradiation device 1 of Figure 1 from the +Z side. As shown in Figure 2, the ultraviolet light irradiation device 1 of this embodiment comprises a housing 60 and a light source 30 housed inside the housing 60. 【0039】 As shown in Figure 2, the light source 30 of this embodiment is an excimer lamp comprising a plurality of discharge tubes 30a and a pair of electrodes 30b. The direction in which the plurality of discharge tubes 30a are arranged is defined as the X direction. The direction in which the discharge tubes 30a extend is defined as the Y direction. The Z direction is perpendicular to the X and Y directions. The plurality of discharge tubes 30a are mounted on a pair of electrodes 30b, as shown in Figure 4, which will be described later. The ultraviolet light emitted by the discharge tubes 30a is extracted from the light extraction unit 20 to the outside of the housing 60. 【0040】 Figure 3 is a graph showing an example of the spectrum of ultraviolet light L1 emitted from the light source 30. The light source 30 in this embodiment is an excimer lamp in which krypton (Kr) gas and chlorine (Cl) gas are sealed as the light-emitting gas G1 in the discharge tube 30a. When a voltage is applied between the electrodes (30b, 30b), ultraviolet light L1 is emitted, as shown in Figure 3, with a wavelength of 222 nm at which the maximum intensity is observed. The wavelength of 222 nm, which shows the maximum intensity, is within the first wavelength band (200 nm to 235 nm). 【0041】 The ultraviolet light emitted from the light source 30 exhibits a spectrum with a main emission wavelength band MB of 216 nm to 223 nm. The main emission wavelength band MB is the wavelength band that exhibits a light intensity of 10% or more of the maximum intensity at the light source 30. 【0042】 As shown in Figure 3, the light source 30 emits light in the second wavelength band of 240 nm to 280 nm, albeit with a low emission intensity. Since light in the second wavelength band is harmful light, an optical filter, described later, is used to limit the light in the second wavelength band and prevent harmful light from leaking out of the housing 60 of the ultraviolet light irradiation device 1. 【0043】 In this embodiment, an excimer lamp filled with Kr gas and Cl gas is used as the light source 30, but it is not limited to this. An excimer lamp filled with other gases (for example, an excimer lamp filled with Kr gas and Br gas that exhibits maximum intensity around 207 nm) may be used as the light source 30. A solid-state light source such as an LED may also be used as the light source 30. 【0044】 In the case of an excimer lamp filled with Kr gas and Cl gas, the entire main emission wavelength band MB falls within the first wavelength band of 200 nm to 235 nm. However, the entire main emission wavelength band MB does not need to be located within the first wavelength band. It is sufficient if at least a part of the main emission wavelength band MB falls within the first wavelength band. A light source 30 in which at least a part falls within the first wavelength band includes, for example, a light source whose upper limit of the main emission wavelength band MB exceeds 235 nm. Examples of light sources whose upper limit of the main emission wavelength band MB exceeds 235 nm include solid-state light sources such as LEDs. 【0045】 Figure 4 is a cross-sectional view of the ultraviolet light irradiation device 1 shown in Figure 1, viewed in the X direction. The optical axis Lc of the ultraviolet light L1 emitted from the ultraviolet light irradiation device 1 is shown along with an arrow indicating the direction of emission. The optical axis Lc is aligned with the Z direction. An optical filter 40 is located in the light extraction unit 20. The ultraviolet light irradiation device 1 emits only the light that has passed through the optical filter 40 from the ultraviolet light exhibiting a spectrum as shown in Figure 3. 【0046】 In the case of an excimer lamp that extends in one direction (in this example, the Y direction) as shown in Figures 2 and 4, the beam angle of the emitted luminous flux appearing on a plane containing the extension direction (e.g., the YZ plane) may differ from the beam angle of the emitted luminous flux appearing on a plane perpendicular to the extension direction (e.g., the XZ plane). In this specification, when the light intensity for each beam angle is expressed as a beam angle distribution, for convenience, the "beam angle distribution" is defined using the arithmetic mean of the light intensities for each beam angle appearing on a plane containing the extension direction and for each beam angle appearing on a plane perpendicular to the extension direction. 【0047】 [Optical filters] The optical filter 40 primarily transmits light in the first wavelength band (200 nm to 235 nm) and primarily reflects light belonging to the second wavelength band (240 nm to 280 nm). In this embodiment, the optical filter 40 transmits the entire main emission wavelength band MB. However, the optical filter 40 only needs to transmit at least a portion of the main emission wavelength band MB. 【0048】 For the spectrum of light transmitted through the optical filter 40 and emitted from the ultraviolet light irradiation device 1, the value obtained by integrating the light intensity over wavelength in the wavelength band where the main emission wavelength band MB and the first wavelength band (200 nm to 235 nm) overlap is called the first integrated light intensity. In this embodiment, where the entire main emission wavelength band MB (216 nm to 223 nm) is within the first wavelength band, the value obtained by integrating the light intensity of the main wavelength band MB over wavelength corresponds to the first integrated light intensity. The value obtained by integrating the light intensity over wavelength in the entire second wavelength band (240 nm to 280 nm) is called the second integrated light intensity. 【0049】 Comparing the maximum value of the first integrated light intensity (for example, when the emission angle of the optical filter 40 is 0°) with the second integrated light intensity, the second integrated light intensity is only slightly less than the maximum value of the first integrated light intensity. Specifically, the second integrated light intensity is 3% or less of the first integrated light intensity, more preferably 2% or less, and even more preferably 1% or less. 【0050】 The optical filter 40 is composed of a dielectric multilayer film formed on a base material. Dielectric multilayer films include, for example, those in which HfO2 layers and SiO2 layers are alternately stacked, and those in which SiO2 layers and Al2O3 layers are alternately stacked. A dielectric multilayer film layer in which HfO2 layers and SiO2 layers are alternately stacked can reduce the number of layers required to obtain the same wavelength selective characteristics as a dielectric multilayer film layer in which SiO2 layers and Al2O3 layers are alternately stacked, and thus can increase the transmittance of selected ultraviolet light. 【0051】 The base material of the optical filter 40 is made of a material capable of transmitting ultraviolet light included in the first wavelength band of 200 nm to 235 nm. Specific materials for the base material include, for example, ceramic materials such as quartz glass, borosilicate glass, sapphire, magnesium fluoride, calcium fluoride, lithium fluoride, and barium fluoride, as well as resin materials such as silicon resin and fluororesin. 【0052】 The transmittance of ultraviolet light transmitted through the optical filter 40 varies depending on the angle of incidence θ of the light incident on the optical filter 40 and the wavelength range of the transmitted ultraviolet light. The angle of incidence θ is the angle between the light ray L3 incident on the optical filter 40 and the normal N1 of the incident surface 40s of the optical filter 40 on which the light ray L3 is incident. 【0053】 One method for evaluating the transmittance characteristics of such an optical filter 40 is to determine and utilize the average transmittance in a specific wavelength band according to the angle of incidence. The average transmittance in a specific wavelength band can be determined from the transmission spectrum T(λ,θ) of the optical filter 40 at different angles of incidence. The method for obtaining the transmission spectrum T(λ,θ) at different angles of incidence will be described later. 【0054】 Figures 5A and 5B show the results of determining the transmittance characteristics of the optical filter 40 using the evaluation method described above. Figure 5A shows the incident angle characteristics of the average transmittance in the main emission wavelength band MB (in this embodiment, 216 nm to 223 nm) transmitted through the optical filter 40. In the graph of Figure 5A, the horizontal axis represents the incident angle θ at which light in the main emission wavelength band MB enters the optical filter 40, and the vertical axis represents the average transmittance in the main emission wavelength band MB. The transmittance is expressed as a relative value with the transmittance at an incident angle of 0 degrees of light in the main emission wavelength band MB set to 1. 【0055】 Figure 5B shows the incident angle characteristics of the average transmittance of harmful light (240nm~280nm) transmitted through the optical filter 40. The optical filter 40 transmits harmful light, albeit slightly, compared to the target light. In the graph of Figure 5B, the horizontal axis represents the incident angle θ at which harmful light enters the optical filter 40, and the vertical axis represents the average transmittance of harmful light. The transmittance is expressed as a relative value, with the transmittance at an incident angle of 0 degrees of harmful light set to 1. 【0056】 As shown in Figures 5A and 5B, the average transmittance of the target light tends to decrease as the incident angle θ to the optical filter 40 increases from 20 degrees to 60 degrees. In contrast to the transmission characteristics of the target light, the average transmittance of harmful light tends to increase as the incident angle θ to the optical filter 40 increases from 30 degrees to 60 degrees. The difference in transmission characteristics with respect to the incident angle θ, caused by the difference in wavelength bands, is a factor that causes the optical intensity distribution angle to differ between the target light and the harmful light, as shown in Figures 17A and 17B. 【0057】 [Distribution of target light / harmful light angle] Figure 7A shows the beam angle distribution of the target light emitted from the ultraviolet light irradiation device 1 of this embodiment. More specifically, the beam angle distribution of the target light is a figure showing the integrated light intensity for each beam angle, obtained by integrating the light intensity of the wavelength band where the main emission wavelength band MB and the first wavelength band overlap, from the spectrum of the light emitted from the optical filter 40 for each beam angle. This is called the first beam angle distribution. In this embodiment, where the entire main emission wavelength band MB (216 nm to 223 nm) is within the first wavelength band, the first beam angle distribution is a figure showing the integrated light intensity for each beam angle, obtained by integrating the light intensity of the main emission wavelength band MB with respect to wavelength. 【0058】 Figure 7B shows the beam angle distribution of harmful light emitted from the ultraviolet light irradiation device 1 of this embodiment. More specifically, it is the beam angle distribution obtained by integrating the light intensity within the second wavelength band (240 nm to 280 nm) over the wavelength for each beam angle from the spectrum of light emitted from the optical filter 40. This is called the second beam angle distribution. The first and second beam angle distributions are determined by the method described later. 【0059】 In both the first and second beam angle distributions, the beam angle (θ) is shown on the horizontal axis and the light intensity I(θ) is shown on the vertical axis. It should be understood that the beam angle θ and light intensity I(θ) are defined in the same way as those explained using Figures 18 and 19, as in Figures 17A and 17B. 【0060】 From the first beam angle distribution in Figure 7A, it can be seen that the beam angle of the ray showing the maximum intensity of the target light is 0 degrees. From Figure 7B, it can be seen that the beam angle of the ray showing the maximum intensity of the harmful light is also 0 degrees. In other words, both the maximum intensity of the target light and the maximum intensity of the harmful light appear on the optical axis Lc of the light emitted from the ultraviolet light irradiation device 1. Therefore, when setting the irradiation dose D according to the relaxation of TLV, the irradiation dose D of both the target light and harmful light can be monitored simply by measuring the light intensity (relative intensity) at the position of the optical axis Lc on the irradiated surface with a spectrometer or photosensor. 【0061】 As the beam angle (first angle) of the light ray showing maximum intensity in the first beam angle distribution and the beam angle (second angle) of the light ray showing maximum intensity in the second beam angle distribution approach 0 degrees, the position (P1, P2) for monitoring light intensity can be set closer to the optical axis Lc of the emitted light. As a result, the adjustment of the ultraviolet light irradiation device 1 in response to the relaxation of TLV becomes simpler. 【0062】 As shown in Figure 7A, the light intensity of both the target light and harmful light decreases as the absolute value of the beam angle increases in steps from the first angle (near 0 degrees in the example of Figure 7A), to 40 degrees, and then to 70 degrees. As shown in Figure 7B, the light intensity of both the target light and harmful light decreases as the absolute value of the beam angle increases in steps from the second angle (near 0 degrees in the example of Figure 7B), to 40 degrees, and then to 70 degrees. This leads to the conclusion that when determining the irradiation dose D in response to TLV relaxation, as long as the light intensity at the first and second angles is taken into consideration, no problems will occur even if light rays with a beam angle of 40 degrees or 70 degrees are irradiated. Therefore, the adjustment of the ultraviolet light emitter in response to TLV relaxation becomes simpler. 【0063】 Furthermore, as shown in Figures 7A and 7B, the light intensity of both the target light and harmful light gradually decreases as the absolute value of the beam angle increases from the first or second angle to 30 degrees. This leads to the conclusion that when determining the irradiation dose D in response to TLV relaxation, as long as the light intensity at the first or second angle is taken into consideration, no problems will arise even on the irradiated surface where the beam angle is within ±30 degrees of the first (second) angle. Therefore, the adjustment of the ultraviolet light emitter in response to TLV relaxation becomes simpler. 【0064】 [How to make the second angle match the first angle] As shown in Figures 7A and 7B, the second angle, which represents the maximum value of the integrated light intensity in the second beam angle distribution obtained by integrating the emitted light from the optical filter 40 over the second wavelength band, is made to substantially coincide with the first angle, which represents the maximum value of the integrated light intensity in the first beam angle distribution obtained by integrating the light intensity of the main emission wavelength band. To achieve this, there are two main methods: (I) adjusting the incident angle of light incident on the optical filter 40, and (II) using an optical filter 40 with appropriate transmittance characteristics for the incident angle. The first and second angles can be made to substantially coincide by at least one of methods (I) and (II). 【0065】 A method for adjusting the incident angle of light incident on the optical filter 40 of (I) will be described. If the beam angle of the light emitted from the light source 30 is small, the target light is easily transmitted and harmful light is not easily transmitted. The light source 30 preferably has a beam angle of half the maximum intensity of the emitted light with an absolute value of 60 degrees or less, and more preferably with an absolute value of 40 degrees or less. 【0066】 An example of a method for adjusting the beam angle of the light source 30 is shown. For example, if the surfaces of a pair of electrodes 30b function as reflective surfaces for the light emitted from the discharge tube 30a, the angle of incidence of light incident on the optical filter 40 can be adjusted by adjusting the shape of the electrodes 30b. 【0067】 The angle of incidence of light emitted from the light source 30 into the optical filter 40 can be adjusted by arranging a transmissive optical system, such as a lens, between the light source 30 and the optical filter 40. Alternatively, the angle of incidence of light into the optical filter 40 can be adjusted by changing the shape of the light source 30 itself. 【0068】 Regarding the method of using an optical filter 40 with appropriate transmittance characteristics as described in (II), the transmittance characteristics of the optical filter 40 change depending on the incident angle when the composition, layer thickness, and number of layers of the dielectric multilayer film change. The transmittance characteristics depending on the incident angle determine the unique optical distribution angle. Therefore, by determining the optical distribution angle, an optical filter 40 with desired transmittance characteristics depending on the incident angle is designed or selected. 【0069】 [How to determine the beam angle distribution] An example of how to determine the beam angle distribution is explained below. The beam angle distribution of the optical filter 40 can be determined by performing the steps shown in (a) to (e) below. As described above, once the beam angle distribution is determined, the first angle of the ray showing the maximum value of the integrated light intensity in the first beam angle distribution is compared with the second angle of the ray showing the maximum value of the integrated light intensity in the second beam angle distribution. Then, by determining whether the difference between the first angle and the second angle is small or not, it becomes possible to determine whether the transmittance characteristics of the optical filter 40 are appropriate according to the incident angle. 【0070】 (a) Measurement of the spectrum of light emitted by the light source 30 The light intensity I(λ) emitted by the light source 30 is measured using a spectrometer to obtain a spectrum. This measurement may be performed, for example, by removing the optical filter 40 from the ultraviolet light irradiation device 1 and measuring the light emitted from the ultraviolet light irradiation device 1. The wavelength to be measured is within the wavelength range that includes the target light and harmful light (in this embodiment, the range of 200 nm to 280 nm). The measured results are shown, for example, as a graph with wavelength (nm) on the horizontal axis and relative intensity with the intensity of the wavelength showing the maximum intensity set to 100% on the vertical axis, as shown in Figure 3. 【0071】 (b) Measurement of transmission spectra of optical filter 40 at different incident angles Candidate optical filters 40 are prepared, and the transmission spectra T(λ,θ) of the optical filter 40 alone are obtained for different incident angles. The transmission spectra T(λ,θ) for different incident angles are shown as a graph with wavelength (nm) on the horizontal axis and transmittance (%) on the vertical axis, for example, as shown in Figure 8. In Figure 8, three transmission spectra T(λ,θ) are shown for optical filter 40 when the incident angle θ is 0 degrees, 20 degrees, and 40 degrees. 【0072】 Figure 9 shows an example of a measurement method for obtaining transmission spectra T(λ,θ) at different incident angles. An optical filter 40 is positioned tilted at a predetermined incident angle θ with respect to the normal N1 of the optical filter 40. Directional light L2 is then incident on the optical filter 40 from the center Q1 of the light source 30. The light intensity of the light transmitted through the optical filter 40 is measured with a spectrometer 50. By dividing the measured light intensity by the light intensity of the emitted light without the optical filter, the transmission spectrum T(λ) of the optical filter 40 is obtained. Then, by changing the incident angle θ by tilting the optical filter 40 with respect to the direction of propagation of light L2, the transmission spectrum T(λ,θ) is obtained. 【0073】 The graph in Figure 8 only shows three transmission spectra T(λ,θ) with incident angles at 20-degree intervals: 0 degrees, 20 degrees, and 40 degrees. However, the interval for obtaining transmission spectra T(λ,θ) can be narrowed. For example, measurements could be taken while changing the incident angle by 5 degrees between 0 and 70 degrees, obtaining a total of 15 transmission spectra T(λ,θ) with different incident angles θ. 【0074】 (c) Calculation of the spectrum of light emitted from the optical filter at different angles of incidence. By multiplying the light intensity I(λ) obtained in (a) by the transmission spectrum T(λ,θ) of the optical filter 40 obtained in (b), the light intensity I of the emitted light transmitted through the optical filter 40 at different incident angles can be calculated. FO (λ,θ) is obtained. In other words, the light intensity I of the light emitted from the optical filter 40 at different angles of incidence is obtained. FO (λ,θ) is expressed by equation (1) shown below. 【number】 【0075】 Figure 10 shows the light intensity I emitted from the optical filter 40. FO The (λ,θ) spectrum is shown for different incident angles (for example, three types with incident angles of 0 degrees, 20 degrees, and 40 degrees) when the optical filter 40 is hit. 【0076】 (d) Calculation of the cumulative intensity of harmful light (c) The light intensity I of the emitted light FO Using (λ,θ), the integrated intensity S in the second wavelength band (240-280 nm) that exhibits harmful light is calculated. B2 We find (θ). The integrated intensity S in the second wavelength band. B2 (θ) is expressed by equation (2) below. 【number】 【0077】 Figure 11 shows the incident angle characteristics of the optical filter 40 in the second wavelength band. The integrated intensity S in the second wavelength band for incident angles from 0 to 70 degrees. B2 By determining (θ), a graph like Figure 11 can be obtained, where the angle of incidence θ to the optical filter 40 is plotted on the horizontal axis and the integrated intensity (relative value) of the second wavelength band is plotted on the vertical axis. Looking at the graph in Figure 11, as the absolute value of the angle of incidence θ to the optical filter 40 increases, the integrated intensity S of the second wavelength band increases. B2 We can see that (θ) becomes larger. 【0078】 (e) Calculation of the beam angle distribution of light emitted from an ultraviolet light irradiation device without an optical filter 40 The beam angle distribution of light emitted from the ultraviolet light irradiation device 10 without the optical filter 40 is determined by the following procedure. First, for example, as shown in Figure 12, the spectrometer 50 is rotated in a circle around the Y-axis direction at the center Q1 of the light source 30, and the radiant intensity of the emitted light is measured with the spectrometer 50. This allows the relative radiant intensity E(θ) of the ultraviolet light irradiation device 10 for each beam angle to be determined. Then, from the relative radiant intensity E(θ), the light intensity I(θ) of the light emitted from the ultraviolet light irradiation device 10 on the irradiated plane can be determined (see Figure 1). The light intensity I(θ) is calculated by the following equation (3). 【number】 【0079】 The light intensity I(θ) of the light emitted from the ultraviolet light irradiation device 10 without the optical filter 40 is shown, for example, as shown in Figure 13, as a light distribution angle distribution with the incident angle (light distribution angle) θ to the optical filter 40 on the horizontal axis and the relative value of the light intensity when the light intensity at θ=0 is set to 1 on the vertical axis. 【0080】 Light intensity I(θ) is multiplied by the integrated intensity S in the second wavelength band. B2 By multiplying by (θ), the second beam angle distribution I is obtained, which is the light intensity distribution of the harmful light emitted from the ultraviolet light irradiation device 1 according to the beam angle. B2 (θ) is obtained. In other words, the second beam angle distribution I of harmful light is obtained. B2 (θ) can be found by equation (4) below. 【number】 【0081】 Figure 14 shows the second beam angle distribution I, with the beam angle θ on the horizontal axis and the relative value of the light intensity obtained by integrating the wavelength within 240 nm to 280 nm on the vertical axis. B2 (θ) is shown. 【0082】 The above explains how to determine the beam angle distribution using harmful light as an example. Using the same method as above, the first beam angle distribution I of the target light can be determined. B1(θ) can be determined. Figure 15 shows the first beam angle distribution I, with the beam angle θ on the horizontal axis and the integrated intensity of the target light on the vertical axis. B1 (θ) is shown. 【0083】 Figure 14 Second beam angle distribution I B2 (θ) and the first beam angle distribution I in Figure 15 B1 Comparing this with (θ), the difference between the first angle of the ray showing the maximum value of the integrated light intensity in the first beam angle distribution and the second angle of the ray showing the maximum value of the integrated light intensity in the second beam angle distribution is small, indicating that the optical filter 40 has appropriate transmittance characteristics for the ultraviolet light irradiation device. 【0084】 This concludes the description of one embodiment of an ultraviolet light irradiation device. The present invention is not limited in any way to the above-described embodiment, and various modifications or improvements can be made to the above embodiment without departing from the spirit of the present invention. 【0085】 As an example of improvement, as shown in Figure 16, a diffusion unit 70 is provided downstream of the optical filter 40 to diffuse the light emitted from the optical filter 40. This allows ultraviolet light to be spread over a wide area in a favorable state. When the diffusion unit 70 is provided, the effects obtained by the present invention become even more pronounced. 【0086】 More specifically, in the conventional ultraviolet light irradiation device shown in Figures 17A and 17B, the position P1 where the light ray indicating the maximum intensity of the target light is irradiated and the position P2 where the light ray indicating the maximum intensity of the harmful light is irradiated are significantly different (see Figure 19). Therefore, when the ratio of harmful light to the target light at position P1 is used as a reference, if the light emitted from the optical filter 40 is diffused by the diffusion unit 70, the proportion of harmful light contained in the diffused light is averaged out, making it easy for the proportion of harmful light to increase above the reference. Furthermore, the degree of this increase is difficult to predict. 【0087】 On the other hand, as described above, in the present invention, the beam angle (first angle) of the ray showing the maximum intensity in the first beam angle distribution and the beam angle (second angle) of the ray showing the maximum intensity in the second beam angle distribution both approach 0 degrees. In other words, the position P1 where the ray showing the maximum intensity of the target light is irradiated and the position P2 where the ray showing the maximum intensity of the harmful light is irradiated are close together. Therefore, when the light emitted from the optical filter 40 is diffused by the diffusion section 70, the proportion of harmful light contained in the diffused light is maintained at or below the standard. As a result, safety management is easier and ultraviolet light can be spread over a wide area in a more favorable state. The diffusion section 70 is, for example, a plate or film-shaped optical member. 【0088】 The optical filter 40 does not have to be placed in the light extraction unit 20, but may be placed near the light source 30. Alternatively, the optical filter 40 may be placed, for example, in the lamp enclosure as part of the light source 30. [Explanation of symbols] 【0089】 1,100: Ultraviolet light irradiation device 10: Ultraviolet light irradiation device (without optical filter) 20: Light extraction section 30:Light source 30a: Discharge tube 30b: Electrode 40: Optical filter 50: Spectrometer 60: Enclosure 70: Diffusion section 90:Irradiated plane

Claims

[Claim 1] A light source that exhibits light intensity within a first wavelength band of 200 nm to 235 nm and a second wavelength band of 240 nm to 280 nm, and emits light in which at least a portion of the main emission wavelength band belongs to the first wavelength band, The optical filter includes an optical filter that suppresses the intensity of light in the second wavelength band and has transmittance characteristics corresponding to the incident angle of light emitted from the light source, From the spectrum of the light emitted from the optical filter at each beam angle, the light intensity of the wavelength band in which the main emission wavelength band and the first wavelength band overlap is integrated with respect to wavelength, and the integrated value is shown for each beam angle as the first beam angle distribution, From the spectra for each of the aforementioned beam angles, the light intensity within the second wavelength band is integrated with respect to wavelength, and the integrated value is shown for each beam angle in the second beam angle distribution, The first angle of the ray showing the maximum intensity in the first beam angle distribution and the second angle of the ray showing the maximum intensity in the second beam angle distribution are substantially the same. Both the first angle and the second angle are between -10 degrees and +10 degrees. In the first beam angle distribution, the light intensity of the light ray with a beam angle of 40 degrees is less than the light intensity of the light ray at the first angle, and the light intensity of the light ray with a beam angle of 70 degrees is less than the light intensity of the light ray with a beam angle of 40 degrees. An ultraviolet light irradiation device characterized in that, in the second beam angle distribution, the light intensity of the light ray with a beam angle of 40 degrees is smaller than the light intensity of the light ray at the second angle, and the light intensity of the light ray with a beam angle of 70 degrees is smaller than the light intensity of the light ray with a beam angle of 40 degrees. [Claim 2] The ultraviolet light irradiation apparatus according to claim 1, characterized in that, with respect to the first integrated light intensity obtained by integrating the light intensity in the wavelength band in which the main emission wavelength band and the first wavelength band overlap from the spectrum of light emitted from the optical filter, and the second integrated light intensity obtained by integrating the light intensity in the second wavelength band, the second integrated light intensity is 1.0% or less of the first integrated light intensity. [Claim 3] The ultraviolet light irradiation device according to claim 2, characterized in that the second integrated light intensity is 0.1% or less of the first integrated light intensity. [Claim 4] A light source that emits light with light intensity in a first wavelength band of 200 nm to 235 nm and a second wavelength band of 240 nm to 280 nm, wherein at least a portion of the main emission wavelength band belongs to the first wavelength band, The optical filter includes an optical filter that suppresses the intensity of light in the second wavelength band and has transmittance characteristics corresponding to the incident angle of light emitted from the light source, From the spectrum of the light emitted from the optical filter at each beam angle, the light intensity of the wavelength band in which the main emission wavelength band and the first wavelength band overlap is integrated with respect to wavelength, and the integrated value is shown for each beam angle as the first beam angle distribution, From the spectra for each of the aforementioned beam angles, the light intensity within the second wavelength band is integrated with respect to wavelength, and the integrated value is shown for each beam angle in the second beam angle distribution, The first angle of the ray showing the maximum intensity in the first beam angle distribution and the second angle of the ray showing the maximum intensity in the second beam angle distribution are substantially the same. An ultraviolet light irradiation device characterized by having a diffusion unit for diffusing the light emitted from the optical filter located downstream of the optical filter. [Claim 5] A light source that emits light with light intensity in a first wavelength band of 200 nm to 235 nm and a second wavelength band of 240 nm to 280 nm, wherein at least a portion of the main emission wavelength band belongs to the first wavelength band, The optical filter includes an optical filter that suppresses the intensity of light in the second wavelength band and has transmittance characteristics corresponding to the incident angle of light emitted from the light source, From the spectrum of the light emitted from the optical filter at each beam angle, the light intensity of the wavelength band in which the main emission wavelength band and the first wavelength band overlap is integrated with respect to wavelength, and the integrated value is shown for each beam angle as the first beam angle distribution, From the spectra for each of the aforementioned beam angles, the light intensity within the second wavelength band is integrated with respect to wavelength, and the integrated value is shown for each beam angle in the second beam angle distribution, The first angle of the ray showing the maximum intensity in the first beam angle distribution and the second angle of the ray showing the maximum intensity in the second beam angle distribution are substantially the same. The average transmittance of the optical filter for light in the wavelength band where the main emission wavelength band and the first wavelength band overlap tends to decrease as the incident angle on the optical filter increases from 20 degrees to 60 degrees. An ultraviolet light irradiation device characterized in that the average transmittance of the optical filter to light in the second wavelength band tends to increase as the angle of incidence to the optical filter increases from 30 degrees to 60 degrees.

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