JP7705090B2 - Ultraviolet light irradiation device - Google Patents

Description

The present invention relates to an ultraviolet light irradiation device.

Conventionally, ultraviolet light irradiation devices that irradiate ultraviolet light for the purpose of sterilization have been known. Because ultraviolet light cannot be seen by the naked eye, it is difficult to confirm whether ultraviolet light is being irradiated from an ultraviolet light irradiation device. Therefore, in Patent Document 1, a method is known in which visible light is used to confirm that ultraviolet light is being irradiated from an ultraviolet light irradiation device by arranging a phosphor that emits visible light when ultraviolet light is incident on it in a partial area of a cover that does not transmit ultraviolet light, which constitutes part of the housing of the ultraviolet light irradiation device, or in a partial area on a board where there are no light-emitting elements.

JP 2020-167147 A

In the ultraviolet light irradiation device of Patent Document 1, a portion of the ultraviolet light that should be irradiated toward the outside of the housing for sterilization must be irradiated toward the position where the phosphor is placed, reducing the efficiency of ultraviolet light usage. Therefore, the objective of this invention is to provide an ultraviolet light irradiation device that can confirm whether ultraviolet light is being irradiated from the ultraviolet light irradiation device and has high ultraviolet light usage efficiency.

The ultraviolet light irradiation device of the present invention includes a substrate having a main surface on which a solid-state light source is disposed that emits ultraviolet light including light belonging to a first wavelength band having a wavelength of 190 nm or more and less than 240 nm and light belonging to a second wavelength band having a wavelength of 240 nm or more and 280 nm or less;
a housing that houses the solid-state light source and has a light extraction section that extracts the ultraviolet light to the outside;
a phosphor that is disposed at a position where the returning ultraviolet light is incident and emits visible light when the returning ultraviolet light is incident thereon;
The optical filter includes an optical filter that does not transmit light belonging to the second wavelength band of the ultraviolet light, but transmits light belonging to the first wavelength band and the visible light.

First, the ultraviolet light emitted by a solid-state light source includes "light belonging to a first wavelength band having a wavelength of 190 nm or more and less than 240 nm, and light belonging to a second wavelength band having a wavelength of 240 nm or more and 280 nm or less." "Light belonging to the first wavelength band having a wavelength of 190 nm or more and less than 240 nm" has the effect of sterilizing the irradiated object (including inactivating viruses; the same applies below), and has the property of being extremely low in harmfulness to the human body. On the other hand, "light belonging to the second wavelength band having a wavelength of 240 nm or more and 280 nm or less" is ultraviolet light of which there are concerns about its harmfulness to the human body.

In this specification, the expression "light belonging to a wavelength band" means that this light is emitted at at least some of the wavelengths included in the wavelength band, and does not have to have an emission spectrum over the entire wavelength band. In this specification, the light belonging to the first wavelength band may be referred to as "beneficial light." Hereinafter, the light belonging to the second wavelength band may be referred to as "harmful light."

The ultraviolet light irradiation device is provided with an optical filter that does not transmit light belonging to the second wavelength band and transmits light belonging to the first wavelength band. This allows the beneficial light emitted by the solid-state light source to reach the occupied space, while the harmful light emitted by the solid-state light source is reflected by the optical filter, preventing the harmful light from reaching the occupied space.

As used herein, "populated space" means a space that can be entered by people, regardless of whether or not people are actually present. Populated spaces include, for example, spaces inside buildings such as homes, offices, schools, hospitals, or theaters, or spaces inside vehicles such as cars, buses, trains, or airplanes. Populated spaces may also be outdoors.

Providing UV light irradiation devices corresponds to Goal 3 of the United Nations-led Sustainable Development Goals (SDGs), "Ensure healthy lives and promote well-being for all at all ages," and will also make a significant contribution to Target 3.3, "By 2030, end the epidemics of AIDS, tuberculosis, malaria and neglected tropical diseases, and combat hepatitis, water-borne and other infectious diseases."

In ultraviolet light irradiation devices, there is return ultraviolet light that is not extracted from the light extraction section. As a result of intensive research, the inventor came up with the idea of using the return light to make the phosphor emit light. The return light is made incident on the phosphor to obtain visible light, and it is confirmed whether the solid-state light source is emitting light using this visible light. In this specification, "visible light" is light that is visible to humans and has a wavelength band of 380 to 780 nm.

Details will be given later, but "return light" refers to light that travels from the light-emitting position of the solid-state light source to the outside of the housing and is reflected by an optical filter and returned, or light that is reflected by the entrance or reflection surface of a transmission optical system that reduces the angle of incidence on the optical filter and returned. Therefore, even if the return light is used to emit light from the phosphor, it is unlikely to affect the efficiency of use of ultraviolet light.

The optical filter may be disposed in the light extraction section, and a transmission optical system may be disposed between the solid-state light source and the optical filter to reduce the angle of incidence of the ultraviolet light and the visible light on the optical filter. This makes it easier for light belonging to the first wavelength band to pass through the optical filter, improving the efficiency of ultraviolet light irradiation.

A plurality of the solid-state light sources are arranged on the main surface,
The transmission optical system may include a lens array in which a plurality of small lenses are arranged, and each of the small lenses may be disposed opposite one of the plurality of solid-state light sources.

The phosphor may be disposed continuously in an area on the main surface excluding the plurality of solid-state light sources.

The phosphor may be disposed so as to be in contact with the outer edge of the solid-state light source.

Each of the phosphors may be in a frame shape surrounding each of the plurality of solid-state light sources. This allows the outer edge of the area irradiated with ultraviolet light to be strongly illuminated, improving the visibility of the outer edge. In particular, when the phosphor has a frame shape that contacts the outer edge of the solid-state light source, it becomes easier to determine the individual lighting state of each solid-state light source.

The phosphors may be distributed on the main surface so as to face each of the small lenses. This allows not only confirmation of whether or not ultraviolet light is being irradiated, but also visual confirmation of the position where the ultraviolet light is being irradiated with visible light.

The phosphors may be arranged so that the plurality of solid-state light sources and the plurality of phosphors are mixed. This allows the entire area irradiated with ultraviolet light to be illuminated with visible light, improving the visibility of the irradiated area.

When the plurality of solid-state light sources and the plurality of phosphors are arranged in a mixed manner, the region made up of the plurality of phosphors may surround the region made up of the plurality of solid-state light sources. Alternatively, the phosphors and the solid-state light sources may be arranged alternately.

The phosphor may have an excitation spectrum in which the minimum intensity of the excitation light in the second wavelength band is higher than the minimum intensity of the excitation light in the first wavelength band. The intensity of the excitation light can be increased by effectively using the light in the second wavelength band.

The phosphor may be a LaPO ₄ :Ce, Tb phosphor.

The phosphor may be composed of two or more types of phosphors.

The solid-state light source may be an LED.

It is possible to provide an ultraviolet light irradiation device that can effectively emit ultraviolet light and can confirm whether or not ultraviolet light is being irradiated from the ultraviolet light irradiation device.

FIG. 1 is a diagram showing a first embodiment of an ultraviolet light irradiation device. FIG. 2 is a diagram showing a substrate having a solid-state light source disposed on a main surface thereof. FIG. 2 is an enlarged view of region E1 of FIG. 1 is a graph showing the transmission spectrum of an optical filter for each angle of incidence. FIG. 2 is a diagram showing light distribution curves of ultraviolet light and visible light emitted from an ultraviolet light irradiation device. FIG. 2 is a diagram showing an example of the excitation spectrum of a phosphor (LAP). FIG. 13 is a diagram showing a modified example of the first embodiment of the ultraviolet light irradiation device. FIG. 13 is a diagram showing a second embodiment of the ultraviolet light irradiation device. FIG. 13 is a diagram showing a third embodiment of the ultraviolet light irradiation device. FIG. 13 is a diagram showing a substrate on which a solid-state light source is arranged according to a third embodiment. FIG. 13 is a diagram showing the relative light intensity distribution of ultraviolet light and visible light in the third embodiment. 13A and 13B are diagrams illustrating a modified example of a substrate on which solid-state light sources are arranged in the third embodiment. FIG. 13 is a diagram showing the relative light intensity distribution of ultraviolet light and visible light in a modified example of the third embodiment. 13A and 13B are diagrams illustrating a modified example of a substrate on which solid-state light sources are arranged in the third embodiment. FIG. 1 is a diagram showing an ultraviolet light irradiation device using a light source that is not a solid-state light source.

An embodiment of an ultraviolet light irradiation device will be described with reference to the drawings. Note that each drawing, except for the graphs, is a schematic illustration, and the dimensional ratios in the drawings do not necessarily match the actual dimensional ratios, and the dimensional ratios between the drawings do not necessarily match.

In the following, some of the drawings will be described with reference to the XYZ coordinate system. In this specification, when a direction is expressed by distinguishing between positive and negative directions, it is described with a positive or negative sign, for example, "+X direction" and "-X direction". When a direction is expressed without distinguishing between positive and negative directions, it is described without a positive or negative sign, for example, "X direction". In other words, in this specification, when it is simply described as "X direction", both "+X direction" and "-X direction" are included. The same applies to the Y direction and Z direction. In the embodiment described below, the direction in which the light rays on the optical axis of the light emitted from the ultraviolet light irradiation device travel is represented as "+Z direction".

First Embodiment
[Ultraviolet light irradiation device]
A first embodiment of an ultraviolet light irradiation device will be described with reference to Fig. 1. Fig. 1 is a cross-sectional view along the XZ plane of an ultraviolet light irradiation device 10. The ultraviolet light irradiation device 10 includes a substrate 2 on which at least one solid-state light source 1 is arranged, a frame 3 surrounding the substrate 2, a phosphor 5, and an optical filter 7 that transmits useful light emitted by the solid-state light source 1 and prevents harmful light emitted by the solid-state light source 1 from passing through.

In this embodiment, the emission surface of the solid-state light source 1 and the main surface of the substrate 2 on which the solid-state light source 1 is arranged are arranged parallel to the XY plane. The substrate 2, together with the frame 3, constitutes the housing 4 that houses the solid-state light source 1. In other words, the substrate 2 functions as a part of the housing 4. As a modified example, the ultraviolet light irradiation device may include a substrate 2 that does not function as the housing 4, separate from the housing 4.

The light extraction section 6, which extracts the light emitted by the solid-state light source 1 to the outside of the housing 4, is an area where the housing 4 opens outward. An optical filter 7 is disposed in the light extraction section 6. The light beam F1 (a collection of light rays having a radiation intensity of at least half the radiation intensity of the light rays that show the maximum radiation intensity among the light rays emitted from each solid-state light source 1) that has passed through the optical filter 7 is emitted in the direction D1 along the +Z direction, and sterilizes the occupied space.

"The optical filter 7 is disposed in the light extraction section 6" means that the optical filter 7 is disposed so as to cover the light extraction section 6 (the area where the housing 4 opens) so that the light extracted from the light extraction section 6 passes through the optical filter 7. In this specification, the housing 4 composed of the substrate 2 and the frame 3, and the interior surrounded by the optical filter 7 may be referred to as the interior of the housing 4. Note that the location of the optical filter 7 is not limited to the above-mentioned position. For example, the optical filter 7 may be disposed so as to be incorporated into the solid-state light source 1, or the optical filter 7 may be disposed so as to be in contact with the solid-state light source 1.

The optical filter 7 has a function of not transmitting light belonging to the second wavelength band having a wavelength of 240 nm or more and 280 nm or less, and reflecting the light (or absorbing a portion of the light). It is preferable that the optical filter 7 not transmit the entire second wavelength band, and reflects the light (or absorbs a portion of the light).

The optical filter 7 is composed of a dielectric multilayer film in which dielectric films with different refractive indices are alternately stacked on a substrate serving as a base material. Light belonging to a specific wavelength band does not penetrate the dielectric multilayer film, but is reflected by the dielectric multilayer film. Examples of the dielectric multilayer film include a film in which HfO ₂ layers and SiO ₂ layers are alternately stacked, and a film in which SiO ₂ layers and Al ₂ O ₃ layers are alternately stacked. A dielectric multilayer film layer in which HfO ₂ layers and SiO ₂ layers are alternately stacked can reduce the number of layers to obtain the same wavelength selection characteristics compared to a dielectric multilayer film layer in which SiO ₂ layers and Al ₂ O ₃ layers are alternately stacked. Therefore, the transmittance of the selected ultraviolet light can be increased. The base material is preferably a material that exhibits transparency to ultraviolet light and visible light, such as quartz glass.

Figure 2 is a diagram showing a substrate 2 with solid-state light sources 1 arranged on its main surface. As shown in Figure 2, multiple solid-state light sources 1 are arranged at regular intervals in the X and Y directions on the main surface on the +Z side of the substrate 2. Although nine solid-state light sources 1 are shown in Figure 2, the solid-state light source 1 may have ten or more solid-state light sources 1, or may have fewer than nine, and it is preferable that the solid-state light source 1 has at least one. The solid-state light source 1 emits light in the +Z direction.

The solid-state light source 1 emits light belonging to a first wavelength band having a wavelength of 190 nm or more and less than 240 nm, and light belonging to a second wavelength band having a wavelength of 240 nm or more and 280 nm or less. The solid-state light source 1 may be, for example, an LED having an emission wavelength spectrum with an emission wavelength of 235 nm showing maximum intensity, or an LED having another emission wavelength spectrum. Also, instead of an LED, other solid-state light sources such as LDs and organic ELs may be used. In this specification, the term "solid-state light source" is a concept that includes LEDs, LDs, and organic ELs, and does not include light bulbs and lamps (for example, mercury lamps or excimer lamps).

[Phosphor Arrangement]
The phosphor 5 (hatched area in FIG. 2) is a type of wavelength conversion element that is excited by ultraviolet light emitted from the solid-state light source 1 and emits visible light. Specific materials for the phosphor 5 will be described later. The phosphor 5 is continuously arranged in an area excluding the solid-state light source 1 on the main surface of the substrate 2 on which the solid-state light source 1 is arranged. The state of being continuously arranged refers to a state in which a plurality of phosphors 5 are connected to each other to form one phosphor. Note that the state in which the phosphor 5 is dispersed, which will be described later in other embodiments, refers to a state in which a plurality of phosphors 5 are not connected to each other. In the embodiment shown in FIG. 1 and FIG. 2, the phosphor 5 is arranged so as to be in contact with the outer edge of the solid-state light source 1 on the main surface of the substrate 2 on which the solid-state light source 1 is arranged, but the phosphor 5 may be arranged away from the outer edge of the solid-state light source 1.

In this embodiment, the phosphor 5 is laminated in a thin film over the entire area except for the solid-state light source 1. Such a thin film of phosphor 5 may be formed, for example, by screen printing a paste containing phosphor 5 onto the substrate 2, or by applying a slurry containing phosphor 5 and firing it.

The light emitted from the solid-state light source 1 is in the +Z direction. The phosphor 5 is disposed in an area on the substrate 2 excluding the solid-state light source 1, and is disposed in a position where the light emitted by the solid-state light source 1 is unlikely to directly enter the phosphor 5. There may be a gap between the solid-state light source 1 and the phosphor 5, or a light-shielding member may be disposed between the solid-state light source 1 and the phosphor 5. The fact that the light from the solid-state light source 1 does not directly enter the phosphor 5 means that the light emitted by the solid-state light source 1 is not consumed by the phosphor 5, and can be irradiated toward an occupied space. Therefore, the utilization efficiency of the ultraviolet light is less likely to decrease.

Figure 3 is an enlarged view of region E1 in Figure 1. Referring to Figure 3, the return light of the light emitted by the solid-state light source 1 will be described. Light ray L0 represents an example of a ray of harmful light belonging to the second wavelength band emitted by the solid-state light source 1. Light ray L0 is reflected by the optical filter 7 and becomes return light toward the phosphor 5. Details will be described later, but regardless of the angle of incidence with respect to the optical filter 7, the harmful light is reflected by the optical filter 7 and becomes return light toward the phosphor 5.

Light ray L1 and light ray L2 are both examples of useful light rays belonging to the first wavelength band emitted by the solid-state light source 1. The angles of incidence (θ1, θ2) are expressed as the angles between the light rays (L1, L2) incident on the optical filter and the normal 7N to the incident surface of the optical filter 7. Light ray L1 is a low-angle light ray with a small angle of incidence on the optical filter 7, while light ray L2 is a high-angle light ray with a large angle of incidence on the optical filter 7. In other words, the angle of incidence θ2 is larger than the angle of incidence θ1. The transmittance of useful light through the optical filter 7 depends on the angle of incidence. In FIG. 3, light ray L1, which is a low-angle light ray, passes through the optical filter 7, while light ray L2, which is a high-angle light ray, is reflected without passing through the optical filter 7, and becomes return light toward the phosphor 5.

Figure 4 is a graph showing an example of the transmittance spectrum of the optical filter 7 for each angle of incidence when ultraviolet light is incident on the optical filter 7. From the transmittance below 240 nm in Figure 4, it can be seen that even for light rays of the same wavelength, the transmittance decreases as the angle of incidence θ (deg) increases.

In summary, in this embodiment, harmful light belonging to the second wavelength band and useful light of the high-angle component belonging to the first wavelength band and having a large incident angle θ on the optical filter 7 become return light from the optical filter 7 toward the phosphor 5. When the return light enters the phosphor 5, the phosphor 5 is excited and emits visible light. Note that the optical filter 7 has a high transmittance for visible light, and so even if the incident angle of visible light on the optical filter 7 becomes large, there is little return light. Therefore, the optical filter 7 does not easily restrict the visible light emitted from the phosphor 5.

[Checking luminescence using phosphor]
FIG. 5 is a diagram showing the light distribution curves of ultraviolet light (useful light) and visible light emitted from the ultraviolet light irradiation device 10. In FIG. 5, the light distribution curve of ultraviolet light is labeled UV, and the light distribution curve of visible light is labeled VIS. The line connecting 0 degrees and 180 degrees is a line parallel to the exit surface of the optical filter 7 in the ultraviolet light irradiation device 10. The line extending in the 90-degree direction from the ultraviolet light irradiation device 10 overlaps with the normal to the exit surface of the optical filter 7 and is a line along the optical axis of the exit light. The ultraviolet light (useful light) has a high ratio of light components with small angles of incidence. Therefore, the light distribution UV of the ultraviolet light emitted from the optical filter 7 has a small light distribution angle and is light with directivity in the optical axis direction.

Visible light VIS has a small incidence angle dependency of transmittance in the optical filter 7. Therefore, visible light VIS has a light distribution that is close to circular according to Lambert's cosine law, and the directionality of visible light VIS is small.

As a result, the visible light distribution curve VIS is wider than the ultraviolet light distribution curve UV. As shown in FIG. 5, specifically, the light distribution angle at which the radiation intensity is half the peak intensity is around 53 degrees for the visible light distribution curve VIS, whereas it is around 17 degrees for the ultraviolet light distribution curve UV, making the visible light distribution curve VIS a wider light distribution angle than the ultraviolet light distribution curve UV. In this way, even if the visible light does not enter the ultraviolet light irradiated area, it is possible to know whether ultraviolet light is being emitted by recognizing whether visible light is being emitted. This makes it easy to check the operation of the ultraviolet light irradiation device. Also, the visible light emitted from the phosphor 5 can be used as normal illumination light.

[Phosphor material]
In this embodiment, a LaPO ₄ :Ce, Tb (LAP) based phosphor is used as the phosphor 5. LAP emits green light when ultraviolet light is incident on it.

Figure 6 shows the excitation spectrum of phosphor 5 of this embodiment. The higher the relative intensity, the more light at that wavelength is absorbed and converted into visible light. Looking at Figure 6, it can be seen that the minimum value P1 of the relative intensity of the excitation light in the second wavelength band WB2, which has a wavelength of 240 nm or more and 280 nm or less, is higher than the minimum value P2 of the relative intensity of the excitation light in the first wavelength band WB1, which has a wavelength of 190 nm or more and less than 240 nm. This is one indicator that the phosphor has a higher luminous efficiency due to harmful light than the luminous efficiency of useful light. Since the return light from the optical filter 7 contains a lot of harmful light, if a phosphor 5 that easily emits light in response to harmful light is used, more visible light can be emitted from the return light. Note that the excitation spectrum shown in Figure 6 is an example of LAP, and the excitation spectrum varies depending on the component ratio of Ce or Tb that constitutes the phosphor 5, etc.

The phosphor 5 is not limited to LAP. It _may be a phosphor of another color (e.g., a blue phosphor of _BaMgAl10O17 :Eu or a red phosphor of (Y,Gd) _BO3 :Eu), or two or more kinds of phosphors may be used. For example, it may be a phosphor for PDPs that mixes three wavelengths of green, red, and blue, or it may be a phosphor used in white fluorescent lamps for illumination, such as calcium halophosphate.

[Modification]
A modified example of the first embodiment will be described with reference to Fig. 7. Fig. 7 is a cross-sectional view of the ultraviolet light irradiation device 20 along the XZ plane. Note that, except for the matters described below, the description will focus on the parts that are different from the ultraviolet light irradiation device 10 described above, and the matters that are not described have the same configuration as the ultraviolet light irradiation device 10 described above. Similarly, the description will focus on the different parts for other embodiments and their modified examples described below.

In the ultraviolet light irradiation device 20, the phosphor 5 is not only provided on the substrate 2, but also on the inner wall surface of the frame 3 and the inner surface of the optical filter 7. The inner wall surface of the frame 3 on which the phosphor 5 is arranged and the inner surface of the optical filter 7 are located outside the light beam F2. The light beam F2 represents a collection of light rays composed of light rays having a radiation intensity of at least half of the light beam showing the maximum radiation intensity among the light rays emitted from each solid light source 1. The light emitted by the solid light source 1 is unlikely to directly enter the phosphor 5 located outside the light beam F2. However, the return light reflected by the optical filter 7 enters the phosphor 5 arranged on the inner wall surface of the frame 3 and the inner surface of the optical filter 7. By increasing the formation area of the phosphor 5 in this way, stronger visible light can be emitted from the phosphor 5.

Second Embodiment
A second embodiment of the ultraviolet light irradiation device will be described with reference to Fig. 8. Fig. 8 is a cross-sectional view of the ultraviolet light irradiation device 30 along the XZ plane. In the ultraviolet light irradiation device 30, an optical filter 7 is disposed in the light extraction unit 6, and a transmission optical system that reduces the angle of incidence of ultraviolet light and visible light on the optical filter 7 is disposed between the solid-state light source 1 and the optical filter 7. The transmission optical system is composed of at least one optical lens. In this embodiment, a single lens array 15 in which a plurality of small lenses are arranged is used as the transmission optical system, but it does not have to be a lens array, and a plurality of lenses may be used.

Each of the small lenses constituting the lens array 15 is arranged opposite each of the solid-state light sources 1 in a one-to-one relationship. Each small lens deflects the light beam F2 from each solid-state light source 1 so that it approaches parallel light, thereby reducing the angle of incidence of the light beam incident on the optical filter 7. This makes it easier for useful light to pass through the optical filter 7, improving the efficiency of ultraviolet light irradiation. Furthermore, in this embodiment, a portion of the ultraviolet light emitted from the solid-state light source 1 is reflected not only by the optical filter 7, but also by the entrance surface or exit surface of the lens array 15. Therefore, the ultraviolet light reflected by the entrance surface or exit surface of the lens array 15 becomes return light that causes the phosphor 5 to emit light.

Third Embodiment
A third embodiment of the ultraviolet light irradiation device will be described with reference to Fig. 9. Fig. 9 is a cross-sectional view along the XZ plane of an ultraviolet light irradiation device 40. In the ultraviolet light irradiation device 40, an optical filter 7 is disposed in a light extraction unit 6, and a lens array 15 in which a plurality of small lenses are arranged is disposed between the solid-state light source 1 and the optical filter 7, as in the second embodiment.

Figure 10 is a diagram showing a substrate 22 used in an ultraviolet light irradiation device 40, on whose main surface a solid-state light source 1 is arranged. A plurality of solid-state light sources 1 are arranged in the X and Y directions on the main surface on the +Z side of the substrate 22. The phosphors 5 (hatched areas in Figure 10) are arranged in a dispersed manner, and each of the dispersed phosphors 5 has a frame shape surrounding each solid-state light source 1. The visible light emitted by the frame-shaped phosphors 5 is refracted by each small lens that constitutes the lens array 15, similar to the ultraviolet light emitted from each solid-state light source 1, and is made closer to parallel light.

In particular, in Figures 9 and 10, the phosphor 5 is arranged so as to contact the outer edge of the solid-state light source 1 on the main surface of the substrate 2 on which the solid-state light source 1 is arranged. This makes it easier to determine the individual lighting state of each solid-state light source.

The effect of the ultraviolet light irradiation device 40 having the substrate 22 will be described with reference to Figure 11. Figure 11 is a diagram showing the relative light intensity distribution of the ultraviolet light (useful light) UV and the visible light VIS of the ultraviolet light irradiation device on the irradiated surface 200 mm away from the optical filter 7 in the +Z direction. The horizontal axis represents the distance from the optical axis position of the emitted light (position 0 mm). The vertical axis represents the relative value of the light intensity when the maximum light intensity is set to 1. This relative light intensity distribution is obtained by simulation.

As can be seen from Figure 11, the relative intensity of the ultraviolet light UV decreases from +20 mm to +50 mm, and decreases from -20 mm to -50 mm. The area irradiated with ultraviolet light UV where the relative light intensity is 0.5 or more is from -35 mm to +35 mm.

In contrast, the visible light VIS emitted by the frame-shaped phosphor 5 surrounding the solid-state light source 1 has a high light intensity between +30 mm and +50 mm and between -30 mm and -50 mm, which are near the outer edge of the area irradiated with the ultraviolet light UV. Then, the visible light VIS is irradiated to the irradiated surface so as to form the outer edge of the area irradiated with the ultraviolet light UV. This makes it possible to visually confirm the position irradiated with the ultraviolet light using the visible light VIS. In other words, in this embodiment, by using visible light, not only can it be confirmed whether or not ultraviolet light is being emitted, but also the position irradiated with the ultraviolet light that cannot be seen with the naked eye can be visually confirmed. In particular, the vicinity of the outer edge of the irradiated area, which is the boundary between the area irradiated with ultraviolet light and the area not irradiated, is strongly illuminated, so that the visibility of the outer edge of the irradiated area is high.

[Modification]
A modified example of the third embodiment will be described below. In this modified example, a substrate 32 (see FIG. 12) is used. The configuration of the ultraviolet light irradiation device 40 except for the substrate 32 is the same as that of the third embodiment.

As shown in FIG. 12, phosphors 5 (hatched areas in FIG. 12) are dispersedly arranged on the substrate 32. The phosphors 5 have a shape and size similar to the solid-state light source 1. A plurality of solid-state light sources 1 and a plurality of phosphors 5 are arranged in a mixed manner on the substrate 32. Region 5a made up of a plurality of phosphors 5 surrounds region 1a made up of a plurality of solid-state light sources 1.

Figure 13 shows the relative light intensity distribution of ultraviolet light (useful light) UV and visible light VIS from an ultraviolet light irradiation device 40 using a substrate 32 on an irradiated surface 200 mm away from the optical filter 7 in the +Z direction. The horizontal axis represents the distance from the optical axis position of the emitted light (position 0 mm). The vertical axis represents the relative value of the light intensity when the maximum light intensity is set to 1. This relative light intensity distribution is obtained by simulation.

In FIG. 13, the area irradiated with visible light VIS roughly coincides with the area irradiated with ultraviolet light UV. In other words, when substrate 32 is used, the area in which visible light VIS is visible can be said to be the area irradiated with ultraviolet light UV. In other words, in this modified example as well, by using visible light, not only can it be confirmed whether ultraviolet light is being emitted, but the irradiated position of ultraviolet light that cannot be seen with the naked eye can be seen with visible light. Since the area irradiated with visible light roughly overlaps with the area irradiated with ultraviolet light, people can intuitively understand the area irradiated with ultraviolet light.

The relative light intensity distribution in FIG. 13 can be obtained not only with the substrate 32 shown in FIG. 12, but also with a substrate 42 in which phosphors 5 and solid-state light sources 1 are arranged alternately, as shown in FIG. 14.

The above describes the various embodiments and variations of the ultraviolet light irradiation device. The present invention is not limited to the above-described embodiments, and the above-described embodiments and variations can be combined or various changes or improvements can be made to the above-described embodiments without departing from the spirit of the present invention. For example, the lens array 15 (transmission optical system) can be removed from the ultraviolet light irradiation device 40 of the third embodiment or the variation of the third embodiment.

In addition, although an example of using a solid-state light source as an ultraviolet light irradiation device has been described, a phosphor may also be arranged in an ultraviolet light irradiation device using a light source that is not a solid-state light source (for example, a mercury lamp or an excimer lamp). That is, for an ultraviolet light irradiation device with an unspecified light source, the ultraviolet light irradiation device may be characterized by comprising a light source that emits ultraviolet light including light belonging to a first wavelength band having a wavelength of 190 nm or more and less than 240 nm, and light belonging to a second wavelength band having a wavelength of 240 nm or more and 280 nm or less, a housing that houses the light source and has a light extraction part that extracts the ultraviolet light to the outside, a phosphor that is arranged at a position where the return light of the ultraviolet light is incident and emits visible light when the return light is incident, and an optical filter that does not transmit light belonging to the second wavelength band among the ultraviolet light, and transmits light belonging to the first wavelength band and the visible light.

In the configuration of the ultraviolet light irradiation device in the previous paragraph, it is desirable to place the phosphor at a position where the ultraviolet light emitted from the light source does not directly enter, but where the return light enters. As described above, "return light" refers to light that travels from the light source's emission position to the outside of the housing and is reflected by an optical filter and returns, or light that is reflected by the entrance surface or reflection surface of a transmission optical system that reduces the angle of incidence at the optical filter and returns. In particular, it is desirable to place the phosphor at a position where harmful light reflected by the optical filter enters as "return light". In addition, the configuration of the ultraviolet light irradiation device using the above-mentioned solid-state light source can also be applied to an ultraviolet light irradiation device using a light source that is not a solid-state light source.

15 shows an ultraviolet light irradiation device 50 using an excimer lamp 11. The ultraviolet light irradiation device 50 includes a cylindrical excimer lamp 11 (for example, a KrCl excimer lamp with a main emission peak wavelength of 222 nm) extending in the Y direction, a housing 4, an electrode block 19, a phosphor 5, an optical filter 7, and a diffusion plate 13 that diffuses ultraviolet light. The electrode block 19 not only functions as an electrode of the excimer lamp 11, but also functions as a reflector that reflects part of the ultraviolet light emitted from the excimer lamp 11. The phosphor 5 is disposed on the surface of the electrode block 19 at a position where it is not used as a reflector (i.e., a position where light from the excimer lamp 11 does not directly enter). Return light from the optical filter 7 enters the phosphor 5. A transmission optical system may be disposed in the ultraviolet light irradiation device 50. In that case, for example, a lens array with cylindrical type small lenses can be used as the transmission optical system.

1: Solid-state light source 2, 22, 32, 42: Substrate 3: Frame 4: Housing 5: Phosphor 6: Light extraction section 7: Optical filter 10, 20, 30, 40, 50: Ultraviolet light irradiation device 11: Excimer lamp 13: Diffuser 15: Lens array 19: Electrode block

Claims (14)

A substrate having a solid-state light source disposed on a main surface thereof, the solid-state light source emitting ultraviolet light including light belonging to a first wavelength band having a wavelength of 190 nm or more and less than 240 nm and light belonging to a second wavelength band having a wavelength of 240 nm or more and 280 nm or less;
a housing that houses the solid-state light source and has a light extraction section that extracts the ultraviolet light to the outside;
a phosphor that is disposed at a position where the returning ultraviolet light is incident and emits visible light when the returning ultraviolet light is incident thereon;
An ultraviolet light irradiation device comprising: an optical filter that does not transmit light belonging to the second wavelength band among the ultraviolet light, and transmits light belonging to the first wavelength band and the visible light. The ultraviolet light irradiation device according to claim 1, characterized in that the optical filter is disposed in the light extraction section, and a transmission optical system is disposed between the solid-state light source and the optical filter, which reduces the angle of incidence of the ultraviolet light and the visible light on the optical filter. A plurality of the solid-state light sources are arranged on the main surface,
3. The ultraviolet light irradiation device according to claim 2, wherein the transmission optical system includes a lens array in which a plurality of small lenses are arranged, and each of the small lenses is disposed opposite each of the plurality of solid-state light sources in a one-to-one relationship. The ultraviolet light irradiation device according to claim 3, characterized in that the phosphor is continuously arranged in an area on the main surface excluding the plurality of solid-state light sources. The ultraviolet light irradiation device according to claim 1, characterized in that the phosphor is disposed on the outer edge of the solid-state light source. The ultraviolet light irradiation device according to claim 5, characterized in that each of the phosphors has a frame shape surrounding each of the plurality of solid-state light sources. The ultraviolet light irradiation device according to claim 3, characterized in that the phosphors are distributed and arranged on the main surface so as to face each of the small lenses. The ultraviolet light irradiation device according to claim 7, characterized in that each of the phosphors is arranged so that the plurality of solid-state light sources and the plurality of phosphors are mixed. The ultraviolet light irradiation device according to claim 8, characterized in that an area made up of a plurality of phosphors surrounds an area made up of a plurality of the solid-state light sources. The ultraviolet light irradiation device according to claim 8, characterized in that the phosphors and the solid-state light sources are arranged alternately. The ultraviolet light irradiation device according to any one of claims 1 to 10, characterized in that the phosphor has an excitation spectrum in which the minimum intensity of the excitation light in the second wavelength band is higher than the minimum intensity of the excitation light in the first wavelength band. 11. The ultraviolet light irradiation device according to claim 1, wherein the phosphor is a LaPO ₄ :Ce, Tb-based phosphor. The ultraviolet light irradiation device according to any one of claims 1 to 10, characterized in that the phosphor is composed of two or more types of phosphors. The ultraviolet light irradiation device according to any one of claims 1 to 10, characterized in that the solid-state light source is an LED.