Excimer lamp and ultraviolet illuminating apparatus

Abstract

[Project] Provides an excimer lamp or ultraviolet light irradiation device that reduces light in a wavelength band of concern regarding adverse effects on the human body. [Solution] An excimer lamp has a luminescent gas containing krypton gas and chlorine gas enclosed in a rod made of fused quartz glass having an absorption band between 240 nm and 260 nm. An ultraviolet light irradiation device includes an excimer lamp containing krypton gas and chlorine gas as luminescent gas within the rod, a housing having an extraction part that accommodates the excimer lamp and extracts ultraviolet light emitted from the excimer lamp, and fused quartz glass disposed in the extraction part and having an absorption band between 240 nm and 260 nm.

Description

Technology Field

[0001] This invention relates to an excimer lamp and an ultraviolet light irradiation device. Background Technology

[0002] It is known that DNA exhibits the highest absorption characteristics around a wavelength of 260 nm. In addition, low-pressure mercury lamps exhibit a high emission spectrum around a wavelength of 254 nm. For this reason, a technique of sterilizing by irradiating ultraviolet light from a low-pressure mercury lamp has been widely used in the past.

[0003] However, light with a wavelength of around 254 nm may cause adverse effects when irradiated onto the human body. In recent years, it has been discovered that ultraviolet light with a wavelength of 235 nm or less has significantly reduced harmfulness to the human body, and technology for sterilizing or inactivating viruses using ultraviolet light with a wavelength of 235 nm or less has become known.

[0004] A KrCl excimer lamp is known as a light source emitting light in a wavelength band of 235 nm or less (see Patent Document 1). The KrCl excimer lamp encapsulates krypton gas and chlorine gas as luminescent gases within a sealed body. Then, by imparting energy to the luminescent gases, krypton and chlorine become excited dimers (KrCl * It forms ) and, when transitioning to the ground state, emits ultraviolet light with a main peak wavelength of 222 nm. Prior art literature

[0005] Japanese Patent Publication No. 2021-114423 The problem to be solved

[0006] Figure 1 shows the emission spectrum of a KrCl excimer lamp. The KrCl excimer lamp is recognized to have a very small amount of light output even in the wavelength range of 240 nm or higher, which is a concern regarding adverse effects on the human body. In order to use the KrCl excimer lamp more safely, it is desirable to reduce light in the wavelength range of 240 nm or higher.

[0007] The present invention aims to provide an excimer lamp or ultraviolet light irradiation device that reduces light in a wavelength band that is of concern for adverse effects on the human body. means of solving the problem

[0008] As described above, KrCl excimer lamps emit ultraviolet light of very short wavelength, with a main peak wavelength of 222 nm. For this reason, synthetic quartz glass, which can achieve high transmittance even for short-wavelength ultraviolet light, has been used as a material through which the radiation from the KrCl excimer lamp passes (e.g., the lamp body). Synthetic quartz glass has the advantage of having not only high light transmittance but also excellent electrical insulation and chemical stability.

[0009] Meanwhile, fused quartz glass has generally been considered unsuitable as an optical component for use in KrCl excimer lamps and their irradiation devices because, compared to synthetic quartz glass, it has a lower transmittance of short-wavelength ultraviolet light and poorer electrical insulation and chemical stability. However, as a result of the inventors’ research, it was discovered that some parts of fused quartz glass possess a characteristic not found in synthetic quartz glass, which is an absorption band that reduces light in the wavelength range of 240 nm to 260 nm. Furthermore, an excimer lamp utilizing this discovered characteristic was devised. Although details will be described later, it is believed that oxygen defects contained in the fused quartz glass are related to the manifestation of this characteristic.

[0010] An excimer lamp of one embodiment is a KrCl excimer lamp in which a luminescent gas containing krypton gas and chlorine gas is sealed within a rod made of fused quartz glass having an absorption band between wavelengths of 240 nm and 260 nm. Although details will be described later, "fused quartz glass having an absorption band" is a fused quartz glass having two points of contact where the transmittance curve and the double tangent of the transmittance curve meet in the transmission spectrum of the fused quartz glass, and in the wavelength band between these two points of contact, the transmittance of the transmittance curve is lower than the transmittance of the double tangent. In addition, if at least a portion of the "wavelength band between the two points of contact" overlaps with a wavelength range of 240 nm or more and 260 nm or less, the fused quartz glass has "an absorption band between wavelengths of 240 nm and 260 nm." By being composed of fused quartz glass having an absorption band between wavelengths of 240 nm and 260 nm, the rod reduces light in the wavelength band of 240 nm to 260 nm emitted from a KrCl excimer lamp into the rod. As a result, sterilization or inactivation of viruses can be performed using ultraviolet light with a wavelength of less than 235 nm while minimizing adverse effects on the human body.

[0011] Sterilization and inactivation of viruses using excimer lamps contribute to United Nations-led Sustainable Development Goals (SDGs) Goal 3, "Ensure all people of all ages have a healthy life and promote their well-being," and also contribute significantly to Goal 3.3, "Eradicate infectious diseases such as AIDS, tuberculosis, malaria and neglected tropical diseases by 2030, and address hepatitis, waterborne diseases and other infectious diseases."

[0012] The minimum transmittance of the above-mentioned fused quartz glass may be between 235 nm and 250 nm. By doing so, the reduction effect of light in the wavelength band to be particularly limited, emitted from the KrCl excimer lamp, is expanded.

[0013] When the light intensity of light having a wavelength of 350 nm passing through the fused quartz glass is set to 1, the light intensity at the minimum value of the transmittance of the fused quartz glass may be 0.95 or less.

[0014] It is acceptable for the OH group concentration of the above-mentioned fused quartz glass to be 50 wt.ppm or less. In processes such as forming rods, heat is applied to the fused quartz glass. If the fused quartz glass contains a large amount of OH groups, as the fused quartz glass is heated, the OH groups may repair oxygen defects, thereby potentially reducing oxygen defects. Since oxygen defects selectively absorb light in the wavelength range of 240 to 260 nm, a reduction in oxygen defects hinders the absorption of light in the wavelength range of 240 to 260 nm. Therefore, by limiting the OH groups to 50 wt.ppm or less, it becomes difficult for oxygen defects to be repaired even when the fused quartz glass is heated.

[0015] It is acceptable to satisfy at least one of the following: the Ti concentration in the fused quartz glass is 5 wt.ppm or less, the Fe concentration in the fused quartz glass is 3 wt.ppm or less, and the Mn concentration in the fused quartz glass is 3 wt.ppm or less. Ti, Fe, and Mn degrade the transmittance of the fused quartz glass of ultraviolet light with a main peak wavelength of 222 nm emitted from a KrCl excimer lamp. By limiting the concentrations of at least one of Ti, Fe, and Mn to below the above-mentioned predetermined value, it becomes easier to maintain the transmittance of the fused quartz glass of ultraviolet light with a main peak wavelength of 222 nm at a high level.

[0016] The above-mentioned fused quartz glass may be placed not only in the rod of the excimer lamp, but also in the extraction part of the housing that accommodates the excimer lamp in the ultraviolet light irradiation device, which extracts ultraviolet light emitted from the excimer lamp.

[0017] For example, an ultraviolet light irradiation device of one embodiment comprises an excimer lamp having the features described above, and

[0018] A housing having an extraction part that accommodates the excimer lamp and extracts ultraviolet light emitted from the excimer lamp, and

[0019] The above-mentioned extraction unit is provided with fused quartz glass having an absorption band between wavelengths of 240 nm and 260 nm.

[0020] An ultraviolet light irradiation device of one embodiment comprises, in a rod body that does not necessarily have to be composed of fused quartz glass having an absorption band between a wavelength of 240 nm and 260 nm, an excimer lamp comprising krypton gas and chlorine gas as a emitting gas, and

[0021] A housing having an extraction part that accommodates the excimer lamp and extracts ultraviolet light emitted from the excimer lamp, and

[0022] The above-mentioned extraction unit is provided with fused quartz glass having an absorption band between wavelengths of 240 nm and 260 nm.

[0023] In addition, regarding the fused quartz glass placed in the extraction section, it is acceptable to apply an additional composition similar to that of the fused quartz glass constituting the rod body. Effects of the invention

[0024] Accordingly, an excimer lamp or ultraviolet light irradiation device that reduces light in a wavelength band of concern regarding adverse effects on the human body can be provided. Brief explanation of the drawing

[0025] Figure 1 is a diagram showing the emission spectrum of a KrCl excimer lamp. FIG. 2 is a perspective view of a first embodiment of an ultraviolet light irradiation device. FIG. 3 is a perspective view of a first embodiment of an ultraviolet light irradiation device. Figure 4 is a cross-sectional view in the C1 plane of Figure 2. FIG. 5 is a perspective view showing only the light source and electrode block extracted from the ultraviolet light irradiation device. Figure 6a is a diagram showing the transmission spectrum of quartz glass. Figure 6b is a diagram showing the transmission spectrum of quartz glass. FIG. 7 is a cross-sectional view showing a modified example of the first embodiment. FIG. 8 is a cross-sectional view of a second embodiment of an ultraviolet light irradiation device. FIG. 9 is a cross-sectional view showing a modified example of the second embodiment. Specific details for implementing the invention

[0026] An embodiment of an ultraviolet light irradiation device will be described with reference to the drawings. Additionally, the following drawings are schematically illustrated, and the dimensional ratios in the drawings do not necessarily correspond to actual dimensional ratios, nor do the dimensional ratios between the drawings necessarily correspond to each other.

[0027] In the following, each drawing is described with appropriate reference to the XYZ coordinate system. In the XYZ coordinate system, the direction in which a ray of radiation travels along the optical axis of the emitted ultraviolet light is designated as the +X direction, and the plane orthogonal to the X direction is designated as the YZ plane. Furthermore, in this specification, when expressing a direction, if positive or negative directions are distinguished, they are indicated by assigning positive or negative signs, such as "+X direction" and "-X direction." If a direction is expressed without distinguishing between positive and negative directions, it is simply indicated as "X direction." That is, in this specification, when simply indicated as "X direction," both the "+X direction" and the "-X direction" are included. The same applies to the Y direction and the Z direction.

[0028] <First Embodiment>

[0029] [Overview of Ultraviolet Irradiation Device]

[0030] With reference to FIGS. 2, 3, and 4, an overview of one embodiment of an ultraviolet light irradiation device is described. FIGS. 2 and 3 are perspective views of an ultraviolet light irradiation device. FIG. 4 is a cross-sectional view in plane C1 of FIG. 2.

[0031] The ultraviolet light irradiation device (10) of the present embodiment has an excimer lamp (3) that emits ultraviolet light, a housing (2) that accommodates the excimer lamp (3), and an extraction part (4) for extracting ultraviolet light emitted from the excimer lamp (3) out of the housing (2) in a +X direction. As shown in FIG. 4, an ultraviolet light-transmitting material (11) that transmits ultraviolet light is arranged to be inserted into the extraction part (4). The ultraviolet light-transmitting material (11) divides the outside and inside of the housing (2). The ultraviolet light-transmitting material (11) may be composed of synthetic quartz glass.

[0032] In FIGS. 2, 3, and 4, "L1" is assigned to the optical axis of the light emitted from the extraction unit (4). An arrow indicating the direction of travel of the light ray emitted along the optical axis is attached to the optical axis (L1). The tube axis direction of each of the three excimer lamps (3) follows the Y direction, and the direction in which each excimer lamp (3) is arranged follows the Z direction.

[0033] In this embodiment, the housing (2) is composed of a first frame (2a) having an opening in the center that functions as an extraction part (4) and a second frame (2b) that does not have an opening. The second frame (2b) and the first frame (2a) are fitted together to form an internal space enclosed by the housing (2). In this internal space, an excimer lamp (3) and two electrode blocks (9a, 9b) that supply power to the excimer lamp (3) are arranged (see FIG. 4). The frames constituting the housing (2) may be composed of three or more.

[0034] Two electrode blocks (9a, 9b) are fixed to the inner surface of the second frame (2b) (see FIG. 3 or FIG. 4). Two connection terminals (8a, 8b) are installed on the outer surface of the second frame (2b) (see FIG. 3). The two connection terminals (8a, 8b) are each conductive with the electrode blocks (9a, 9b) with the second frame (2b) in between. Power supply lines (7a, 7b) supplied from an external power source (not shown) are each connected to the two connection terminals (8a, 8b).

[0035] FIG. 5 is a perspective view showing only the excimer lamp (3) and electrode blocks (9a, 9b) removed from the ultraviolet light irradiation device. The excimer lamp (3) is equipped with a hollow rod (5) and has a luminescent gas sealed inside. The rod (5) comes into contact with each of the two electrode blocks (9a, 9b), thereby supplying power to each excimer lamp (3).

[0036] The luminescent gas is a mixture of krypton gas and chlorine gas. When a high voltage is applied to the electrode blocks (9a, 9b), a dielectric barrier discharge occurs within the rod (5), and inside the rod (5), an excited dimer of krypton and chlorine (KrCl₂) is formed. * ) is formed. When this excited dimer returns to the ground state, it emits ultraviolet light with a main peak wavelength of 222 nm. The emitted ultraviolet light passes through the rod (5) and is radiated out of the excimer lamp (3). Furthermore, the excimer lamp (3) shown in FIGS. 2 to 5 is merely an example of an embodiment, and the shape of the rod (5), the arrangement or shape of the electrodes, and other details other than the krypton gas and chlorine gas being sealed in the rod (5) are not particularly limited.

[0037] [Bongche]

[0038] In this embodiment, fused quartz glass is used in the rod body (5) that transmits ultraviolet light. The reason for this is explained with reference to FIGS. 6a and FIGS. 6b. FIGS. 6a and FIGS. 6b each show the transmission spectrum of quartz glass. In FIGS. 6a, transmittance curve S1 shows an example of the transmission spectrum of fused quartz glass. In FIGS. 6b, transmittance curve S2 shows an example of the transmission spectrum of fused quartz glass having an absorption band, transmittance curve S3 shows an example of the transmission spectrum of fused quartz glass not having an absorption band, and transmittance curve S4 shows an example of the transmission spectrum of synthetic quartz glass. The vertical axes of FIGS. 6a and FIGS. 6b each represent the relative transmittance at each wavelength when the transmittance of quartz glass transmitting 350 nm light is set to 100%.

[0039] Referring to the transmittance curve S1 in Fig. 6a, the change in transmittance of the fused quartz glass having said transmittance curve S1 is explained from the larger wavelength to the smaller wavelength. As the wavelength moves from 350 nm to 262 nm, the transmittance decreases. From 262 nm, the transmittance begins to drop suddenly, and the decrease in transmittance continues until 242 nm. At 242 nm, it becomes a minimum value. As the wavelength moves from 242 nm to 226 nm, the transmittance increases. At 226 nm, it becomes a maximum value. When the wavelength becomes smaller than 226 nm, the transmittance begins to decrease, and when the wavelength falls below 215 nm, the transmittance falls below 80%.

[0040] When drawing a tangent to the transmittance curve S1, a double tangent T1 can be drawn at two points (Cp1, Cp2) that is tangent to the transmittance curve S1. The wavelength band A1 between the points of contact (Cp1, Cp2) of the transmittance curve S1 and the double tangent T1 is the absorption band of the fused quartz glass having the transmittance curve S1. The absorption band A1 of the fused quartz glass shown in FIG. 6a is 226 nm to 262 nm.

[0041] Since the absorption band A1 overlaps with the wavelength range of 240 nm to 260 nm, the fused quartz glass having this absorption band A1 is "fused quartz glass having an absorption band between wavelengths 240 nm and 260 nm." By transmitting radiant light from a KrCl excimer lamp through this fused quartz glass, a reduction effect can be obtained for light in the wavelength range of 240 nm to 260 nm, which is likely to have adverse effects on the human body. Also, the main peak wavelength of 222 nm is close to the maximum value of the transmittance curve S1 and is not between wavelengths 240 nm and 260 nm, so it transmits a large amount of light compared to the wavelengths to be limited.

[0042] In addition, it is known that ultraviolet light with a wavelength of 200 nm or less generates ozone from oxygen in the atmosphere. When ozone is at a high concentration, there is a concern that it may have adverse effects on the human body. Since the transmittance curve S1 shows that the transmittance of ultraviolet light with a wavelength of 200 nm or less is low, transmitting radiation from a KrCl excimer lamp through this fused quartz glass leads to a reduction in the probability of ozone generation. This effect is one that cannot be obtained with the synthetic quartz glass described later.

[0043] Referring to the transmittance curve S2 in FIG. 6b, just like the transmittance curve S1, the transmittance curve S2 can have a double tangent line drawn and has two points of contact with the double tangent line. Then, the absorption band A2, which is the wavelength band between the two points of contact, overlaps with the wavelength range of 240 nm or more and 260 nm or less. Therefore, the fused quartz glass having this absorption band A2 is a "fused quartz glass having an absorption band between wavelengths of 240 nm and 260 nm."

[0044] Referring to the transmittance curve S3 in FIG. 6b, the change in transmittance of the fused quartz glass having the transmittance curve S3 is explained from the larger wavelength side to the smaller wavelength side. As the wavelength approaches 350 nm to 233 nm, the transmittance gradually decreases. From 233 nm, the transmittance begins to drop abruptly. The abrupt drop in transmittance continues until around 200 nm. There are no maximum or minimum values ​​in the transmittance curve S3. When drawing a tangent to the transmittance curve S3, a tangent with only one point of contact can be drawn, but a double tangent that touches the transmittance curve S3 at two points cannot be drawn. The fused quartz glass having the transmittance curve S3 does not have an absorption band.

[0045] Referring to the transmittance curve S4 in FIG. 6b, the change in transmittance of the synthetic quartz glass having said transmittance curve S4 is explained from the larger wavelength side to the smaller wavelength side. As the wavelength approaches 350 nm to 200 nm, the transmittance decreases. There are no maximum or minimum values ​​in the transmittance curve S4. When drawing a tangent line to the transmittance curve S4, a tangent line with only one point of contact can be drawn, but a double tangent line that touches the transmittance curve S4 at two points cannot be drawn. Therefore, the synthetic quartz glass having the transmittance curve S4 does not have an absorption band. The synthetic quartz glass having the transmittance curve S4 has a transmittance of 95% or more across the entire wavelength band of 200 to 350 nm.

[0046] The maximum extent of the decrease in transmittance appears at the minimum value of the transmittance curve. As described above, the minimum value of the transmittance curve S1 is when the wavelength is 242 nm. When the minimum value is between 240 nm and 250 nm, the reduction effect of light in the absorption band A1, specifically the wavelength band to be limited, is amplified. In addition, it is acceptable to use the minimum value of the transmittance curve S1 in the wavelength band between 235 nm and 250 nm, which includes the wavelength band to be limited. In Fig. 6a, the minimum value of the transmittance curve S1 is 92 (%). When the light intensity of light having a wavelength of 350 nm passing through the fused quartz glass is set to 1 (transmittance 100%), the light intensity at the minimum value of the transmittance curve of the fused quartz glass must be 0.95 or less (transmittance 95% or less).

[0047] In FIG. 6a, the transmittance of the absorption band A1 of the transmittance curve S1 exhibits a maximum decrease d1 of 3% compared to the double tangent transmittance. While a larger decrease d1 is preferable, it is acceptable for the decrease d1 of the transmittance of the absorption band A1 to be small. For example, the decrease d1 of the transmittance of the absorption band A1 relative to the double tangent transmittance may be 1% or more. Additionally, the difference in transmittance between the maximum and minimum values ​​may be 1% or more, preferably 2% or more, and more preferably 3% or more.

[0048] [Oxygen defect]

[0049] The existence of absorption bands (A1, A2) overlapping with the aforementioned wavelength range of 240–260 nm is attributed to the fact that the fused quartz glass contains a large amount of oxygen defects. Quartz glass is typically a structure formed by the irregular bonding of SiO4 tetrahedra as units. However, in the parts referred to as oxygen defects, SiO4 is not formed, and a defect structure is formed where O is not bonded to Si. Consequently, the defect structure absorbs light of a specific wavelength. The transmittance curves of fused quartz glass and synthetic quartz glass with low oxygen defects do not have absorption bands. Examples of fused quartz glass containing oxygen defects include GE214 manufactured by MOMENTIVE and PQ871 manufactured by PACIFIC QUARTZ. In addition, fused quartz glass produced by the electro-melting method is prone to retaining desired oxygen defects, making it easy to apply as the fused quartz glass of the present invention.

[0050] There are multiple types of oxygen defects based on differences in defect structure, such as SLPC defects, NBOHC defects, or ODC defects. Each of these defect structures has a different absorption band peak, and as a result, absorbs light of a specific wavelength. For example, SLPC defects have an energy absorption band peak of 5.15 eV and absorb light of a wavelength of 241 nm. NBOHC defects have an energy absorption band peak of 4.8 eV and absorb light of a wavelength of 258 nm. ODC defects have an energy absorption band peak of 5.02 eV and absorb light of a wavelength of 247 nm. These various oxygen defects selectively absorb light in the wavelength band of 240 to 260 nm. As the oxygen defect content increases, the amount of absorption of light of a specific wavelength increases. The extent to which oxygen defects exist in quartz glass can be estimated by analyzing the transmittance spectrum or absorption spectrum of the fused quartz glass. In FIG. 6a, the absorption band A1 of the transmittance curve S1 is 226 to 262 nm, and by adjusting the amount of defects or the thickness of the glass, the wavelength width of the absorption band can be expanded, contracted, or shifted, or the amount of absorption (transmittance) can be increased or decreased.

[0051] Some of the fused quartz glass contains OH groups. When the fused quartz glass is heated and activated, the OH groups in the fused quartz glass function as a source of oxygen atoms to repair oxygen defects. In this embodiment, if oxygen defects are reduced by repairing these oxygen defects, it becomes difficult to selectively absorb light in the wavelength band of 240 to 260 nm. Therefore, it is preferable that the concentration of OH groups in the fused quartz glass be below a specified value.

[0052] The OH group concentration in the fused quartz glass should be 50 wt.ppm or less, more preferably 30 wt.ppm or less, and even more preferably 20 wt.ppm or less. Among fused quartz glass with a low OH group concentration, there is a relatively large amount of electro-fused quartz produced by the electro-melting method. The fused quartz glass is heated in a process of processing the fused quartz glass, for example, in a process of processing the fused quartz glass into the shape of the rod (5) of an excimer lamp (3). In addition, by intentionally performing heat treatment on the fused quartz glass, oxygen defects can be restored so that the amount of oxygen defects can be brought close to a desired value.

[0053] The concentration of OH groups contained in quartz glass can be calculated from the infrared absorption spectrum. The procedure for calculating the OH group concentration is explained. Infrared radiation is irradiated onto quartz glass of thickness t [mm] to be measured, and the infrared radiation transmitted through the quartz glass is measured using an infrared spectrophotometer. In this way, an infrared absorption spectrum can be obtained. Then, regarding the infrared absorption band at a wavelength of 2.73 μm caused by OH groups (hydroxyl groups) in the quartz glass in the infrared absorption spectrum, the transmittance (Tb [%]) at the wavelength of the infrared absorption peak in the said absorption band and the transmittance (Ta [%]) at a wavelength not affected by infrared absorption (here, the transmittance [%] at a wavelength of 2.60 μm) are read. The concentration of OH groups (C [wt.ppm]) in the quartz glass is calculated based on the following equation (1).

[0054] OH group concentration (C) = (1 / t) × (Log 10 (Ta / Tb))×997 … (1)

[0055] The impurities contained in the above-mentioned fused quartz glass reduce the transmittance of ultraviolet light, which has a main peak wavelength of 222 nm and is emitted from a KrCl excimer lamp. Among the impurities, in particular, Ti, Fe, or Mn are likely to be contained in the fused quartz glass as impurities and are likely to cause a reduction in transmittance. Therefore, it is sufficient if the concentration of at least one of Ti, Fe, and Mn contained in the fused quartz glass is below a specified value.

[0056] For example, the concentration of Ti should be 5 wt.ppm or less, and more preferably 3 wt.ppm or less. This makes it easier to maintain a high level of transmittance of ultraviolet light with a main peak wavelength of 222 nm.

[0057] For example, the concentration of Fe contained in the fused quartz glass should be 3 wt.ppm or less, and more preferably 1.5 wt.ppm or less. By doing so, it becomes easier to maintain a high level of transmittance of ultraviolet light with a main peak wavelength of 222 nm.

[0058] For example, the concentration of Mn contained in the fused quartz glass should be 3 wt.ppm or less, and more preferably 1 wt.ppm or less. By doing so, it becomes easier to maintain a high level of transmittance of ultraviolet light with a main peak wavelength of 222 nm.

[0059] The concentration of impurities in fused quartz glass, such as Ti, Fe, or Mn, can be measured using inductively coupled plasma mass spectrometry (ICP-MS).

[0060] The absorption coefficient of fused quartz glass for ultraviolet light with a wavelength of 240 nm can be, for example, 0.05 to 5 / mm, preferably 1 to 5 / mm, and more preferably 2 to 5 / mm.

[0061] The thickness of the rod should be 5 mm or less, preferably 2 mm or less. By doing so, the decrease in transmittance of ultraviolet light with a main peak wavelength of 222 nm can be suppressed, and a large radiant intensity can be obtained even when using fused quartz glass. The thickness of the rod should be 0.5 mm or more, preferably 1 mm or more. As the thickness of the rod increases, the reduction effect of light in the wavelength band of 240 to 260 nm becomes greater.

[0062] Referring to FIG. 7, a modified example of an ultraviolet light irradiation device is described. The ultraviolet light irradiation device (15) is equipped with an optical filter (6) that transmits ultraviolet light belonging to a wavelength band of 190 nm to 235 nm and inhibits the transmission of ultraviolet light in a wavelength band of 240 nm to 280 nm. For example, when emitted light from a light source is incident on the optical filter at an angle of incidence of 0 degrees, an optical filter may be employed that attenuates the light intensity of the ultraviolet light in the wavelength band of 240 nm to 280 nm after transmission to 3% or less and 1% or less, with respect to the light intensity of the peak wavelength in the wavelength band of 190 nm to 235 nm among the ultraviolet light emitted from the light source. In addition to using molten quartz glass in the rod (5) of the excimer lamp (3), by placing an optical filter (6) in the extraction part (4), ultraviolet light of 240 nm to 280 nm can be further reduced, thereby further improving the safety of the ultraviolet light irradiation device (15) for the human body. Furthermore, it is preferable that the optical filter (6) is an optical filter that inhibits the transmission of a wavelength range of 280 to 320 nm in addition to the aforementioned wavelength range, as this increases safety.

[0063] The optical filter (6) is not limited in its placement location or shape. In addition to the optical filter (6) being formed spaced apart from the excimer lamp (3) as shown in FIG. 7, it is acceptable for the optical filter (6) to be formed in contact with the excimer lamp (3) (as a specific example, the optical filter (6) may be laminated on the surface of the rod (5).

[0064] The optical filter (6) is formed by alternately stacking dielectric films with different refractive indices on a substrate, for example, composed of quartz glass. As for the dielectric multilayer film, for example, there are films in which an HfO2 layer and a SiO2 layer are alternately stacked, and films in which a SiO2 layer and an Al2O3 layer are alternately stacked. Since the dielectric multilayer film in which an HfO2 layer and a SiO2 layer are alternately stacked can reduce the number of layers required to obtain the same wavelength selection characteristics compared to the dielectric multilayer film in which a SiO2 layer and an Al2O3 layer are alternately stacked, the transmittance of selected ultraviolet light can be increased.

[0065] <Second Embodiment>

[0066] Referring to FIG. 8, a second embodiment of the ultraviolet light irradiation device is described. Except for the details shown below, it is the same as the first embodiment. In the ultraviolet light irradiation device (20), fused quartz glass (12) having an absorption band between wavelengths of 240 nm and 260 nm is disposed in the extraction part (4). By doing so, the amount of light with a wavelength band of 240 nm to 260 nm emitted from the excimer lamp (3) that is emitted to the ultraviolet light irradiation device (20) can be reduced.

[0067] Since fused quartz glass (12) having an absorption band between 240 nm and 260 nm is disposed in the extraction part (4) of the ultraviolet light irradiation device (20), the rod body (5) of the excimer lamp (3) in the ultraviolet light irradiation device (20) does not need to be composed of fused quartz glass having an absorption band between 240 nm and 260 nm. That is, the rod body (5) may be composed of fused quartz glass or synthetic quartz glass without an absorption band. If the rod body (5) of the excimer lamp (3) is composed of fused quartz glass having an absorption band between 240 nm and 260 nm, light in the wavelength band of 240 nm to 260 nm can be further reduced.

[0068] FIG. 9 shows a further modified example of the second embodiment. The ultraviolet light irradiation device (25) has an optical filter (13) in which a dielectric multilayer film is laminated on fused quartz glass having an absorption band between 240 nm and 260 nm, which is the substrate, in the extraction part (4). The optical filter (13) can obtain both the light reduction effect in the wavelength band between 240 nm and 260 nm by the fused quartz glass having an absorption band between 240 nm and 260 nm and the light reduction effect in the wavelength band between 240 nm and 260 nm by the dielectric multilayer film. Explanation of the symbols

[0069] 2 : Housing 2a : 1st frame 2b : 2nd frame 3 : Excimer Lamp 4 : Extraction part 5 : Sealed body 6 : Optical filter 10, 15, 20, 25: Ultraviolet light irradiation device 11 : UV light-transmitting material 12: Fused Quartz Glass 13: Optical filter A1 : Absorption band L1 : Optical axis

Claims

Claim 1 An excimer lamp characterized in that a luminescent gas comprising krypton gas and chlorine gas is sealed within a body composed of fused quartz glass having an absorption band between 240 nm and 260 nm wavelengths, wherein the fused quartz glass has a transmittance at a wavelength of 222 nm that is higher than the transmittance corresponding to the minimum value of the absorption band, and when the light intensity of light having a wavelength of 350 nm passing through the fused quartz glass is set to 1, the light intensity at the minimum value of the transmittance of the fused quartz glass is 0.95 or less. Claim 2 An excimer lamp according to claim 1, characterized in that the minimum value of the transmittance of the fused quartz glass is 235 nm or more and 250 nm or less. Claim 3 An excimer lamp according to claim 1 or claim 2, characterized in that the OH group concentration of the fused quartz glass is 50 wt.ppm or less. Claim 4 An excimer lamp according to claim 1 or claim 2, characterized in satisfying at least one of the following: the Ti concentration contained in the fused quartz glass is 5 wt.ppm or less, the Fe concentration contained in the fused quartz glass is 3 wt.ppm or less, and the Mn concentration contained in the fused quartz glass is 3 wt.ppm or less. Claim 5 An ultraviolet light irradiation device characterized by comprising: an excimer lamp as described in claim 1 or claim 2; a housing having an extraction unit that accommodates the excimer lamp and extracts ultraviolet light emitted from the excimer lamp; and fused quartz glass disposed in the extraction unit and having an absorption band between a wavelength of 240 nm and 260 nm. Claim 6 An ultraviolet light irradiation device comprising, in a rod body, an excimer lamp including krypton gas and chlorine gas as luminescent gases, a housing having an extraction unit that accommodates the excimer lamp and extracts ultraviolet light emitted from the excimer lamp, and a fused quartz glass disposed in the extraction unit and having an absorption band between a wavelength of 240 nm and 260 nm, wherein the fused quartz glass has a transmittance at a wavelength of 222 nm that is higher than the transmittance corresponding to the minimum value of the absorption band, and when the light intensity of light having a wavelength of 350 nm passing through the fused quartz glass is set to 1, the light intensity at the minimum value of the transmittance of the fused quartz glass is 0.95 or less. Claim 7 An ultraviolet light irradiation device according to claim 6, characterized in that the minimum value of the transmittance of the fused quartz glass is 240 nm or more and 250 nm or less. Claim 8 An ultraviolet light irradiation device according to claim 6 or claim 7, characterized in that the OH group concentration of the molten quartz glass is 50 wt.ppm or less. Claim 9 An ultraviolet light irradiation device according to claim 6 or claim 7, characterized in satisfying at least one of the following: the Ti concentration contained in the fused quartz glass is 5 wt.ppm or less, the Fe concentration contained in the fused quartz glass is 3 wt.ppm or less, and the Mn concentration contained in the fused quartz glass is 3 wt.ppm or less. Claim 10 delete Claim 11 delete

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