Excimer lamp

Abstract

The invention provides an excimer lamp, which is a hollow type excimer lamp capable of realizing high illumination. The excimer lamp (10) is a hollow excimer lamp that irradiates ultraviolet rays, and is provided with a discharge tube (20) obtained by welding an inner tube (25) and an outer tube (22). Furthermore, the excimer lamp (10) has a foil-shaped inner electrode (30) and an outer electrode (40), and the cladding tube (60) is welded so as to cover the periphery of the outer tube (22) and the inner electrode (30). A foil-shaped inner electrode (30) is embedded between the cladding tube (60) and the outer tube (22). The inner electrode (30) has a flat portion (32) and is sharpened toward the tip.

Description

Technical Field

[0001] The present invention relates to an excimer lamp, and more particularly to a hollow excimer lamp having a discharge tube (discharge container) with a double tube structure and irradiating an object to be irradiated in the inner tube with ultraviolet rays. Background Art

[0002] In a hollow excimer lamp, an inner tube is fused and coaxially arranged on an outer tube. In order to irradiate ultraviolet rays to an object to be irradiated, such as a raw material gas flowing in the inner tube, a foil-shaped inner electrode is buried in the outer tube, and the outer electrode is arranged on the outer tube surface in a manner opposite to the inner electrode (see Patent Document 1).

[0003] Furthermore, by adopting a structure in which an inner electrode is buried between the discharge vessel and the covering tube covering the discharge vessel, and an outer electrode such as an aluminum film covers the covering tube, an object inside the inner tube can be irradiated with ultraviolet rays (see Patent Document 2).

[0004] Patent Document 1: Japanese Patent Application Publication No. 2016-146295

[0005] Patent Document 2: Japanese Patent Application Publication No. 2020-107424

[0006] When a high voltage is applied to achieve high illumination of an excimer lamp, it is necessary to configure an inner electrode to cope with this situation (for example, the width of the foil-shaped electrode is increased). However, in order to improve the ultraviolet irradiation efficiency in an excimer lamp (especially a small excimer lamp), the volume of the discharge space needs to be increased, and there are limitations on the diameter and thickness of the inner tube and the outer tube of the discharge tube constituting the double tube structure. Therefore, the embedded inner electrode may peel off. Summary of the invention

[0007] Therefore, there is a demand for providing a hollow excimer lamp capable of achieving higher illuminance.

[0008] The excimer lamp of the present invention is a hollow excimer lamp, wherein the excimer lamp comprises: an outer tube; an inner tube coaxially arranged in the outer tube; and a foil-shaped inner electrode buried between a covering tube covering at least a portion of the outer tube and the outer tube. In addition, the outer electrode is provided on the outer surface side of the outer tube, and the inner electrode has a flat portion with a substantially constant thickness along the electrode width direction, and is sharpened from the flat portion toward both ends.

[0009] The structure of the inner tube is various. For example, the inner tube can be configured to include: an inner tube large diameter portion, which is provided with a flange-shaped portion fused to the outer tube; and an inner tube small diameter portion, which is formed at a position closer to the discharge space side than the inner tube large diameter portion and has a smaller diameter than the inner tube large diameter portion.

[0010] The structure of the inner tube is various. For example, the outer tube may be provided with an outer tube small diameter portion, which is not covered by the covering tube, has a smaller diameter than the portion covered by the covering tube, and is opposite to at least a portion of the inner tube small diameter portion.

[0011] For example, the thickness of the inner tube may be set smaller than the thickness of the outer tube and the cladding tube. Also, the electrode width of the inner electrode may be set smaller than the outer diameter of the inner tube. With respect to the inner diameter of the outer tube, the inner diameter of the outer tube may be set to be at least 1.3 times the outer diameter of the inner tube.

[0012] For example, an ultraviolet reflection film is formed on the inner surface of the outer tube in a section facing the inner electrode.

[0013] The structure of the discharge space is various. In addition to the annular discharge space formed around the inner tube, an auxiliary discharge space may be formed. For example, the covering tube and the outer tube may be partially welded, and the auxiliary discharge space may be formed in the non-welded portion between the covering tube and the outer tube. A part of the inner electrode may be exposed in the auxiliary discharge space.

[0014] According to the present invention, a hollow excimer lamp capable of achieving high illuminance can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic cross-sectional view of the excimer lamp according to the first embodiment.

[0016] Figure 2 It is along Figure 1 A schematic cross-sectional view taken along line II-II.

[0017] Figure 3 It is a partially enlarged cross-sectional view of the discharge tube 20 in the vicinity of where the foil electrodes are arranged.

[0018] Figure 4 This is a schematic cross-sectional view of an excimer lamp according to a second embodiment.

[0019] Figure 5 It is along Figure 4 A schematic cross-sectional view of line VV.

[0020] Description of symbols

[0021] 10: Excimer lamp; 20: discharge tube; 22: outer tube; 25: inner tube; 30: inner electrode (foil electrode); 40: outer electrode; 50: insulating tube; 60: covering tube. DETAILED DESCRIPTION

[0022] Hereinafter, the excimer lamp according to the present embodiment will be described with reference to the drawings.

[0023] Figure 1 This is a schematic cross-sectional view of the excimer lamp according to the first embodiment. Figure 2 It is along Figure 1 A schematic cross-sectional view taken along line II-II.

[0024] The excimer lamp 10 is a hollow excimer lamp that irradiates an object with ultraviolet rays by passing the object through a flow path R formed along a lamp axis C. Here, a fluid such as a raw material gas containing oxygen flows in the flow path R.

[0025] The excimer lamp 10 has a discharge tube (discharge container) 20 made of quartz glass or the like. The discharge tube 20 has a double tube structure in which an outer tube 22 is welded to flange-shaped portions M1 and M2 provided on an inner tube 25, and the inner tube 25 is arranged coaxially with respect to the outer tube 22. A discharge gas such as a rare gas such as xenon or a mixed gas of a rare gas and a halogen gas is sealed in a discharge space S formed in the discharge tube 20.

[0026] The covering tube 60 is a member obtained by coaxially fusing a tubular member such as quartz glass to the outer tube 22 , and covers a portion of the discharge tube 20 along the lamp axis C over the entire circumferential direction.

[0027] A foil-shaped electrode (hereinafter referred to as a foil electrode or an inner electrode as needed) 30 is provided between the covering tube 60 and the discharge tube 20. Specifically, it is welded between the outer surface of the outer tube 22 and the inner surface of the covering tube 60 to form a whole, and thus buried inside the tube wall. One end of the inner electrode 30 is connected to a power supply rod 70, and the power supply rod 70 is connected to a power supply unit (not shown).

[0028] The outer electrode 40 is provided to cover the entire circumferential direction of the outer surface of the covering tube 60. Here, the outer electrode 40 is configured as a film electrode such as an aluminum film. The outer electrode 40 is connected to the ground side via a power supply line connected to a cylindrical power supply member wound in the circumferential direction (not shown).

[0029] The outer electrode 40 is provided to be isolated from the end 60T2 of the covering tube 60 protruding from the power supply rod 70, thereby preventing insulation breakdown between the outer electrode 40 and the power supply rod 70 (inner electrode 30). In addition, by covering the end 60T2 side of the covering tube 60 with an insulating covering member (here, the insulating tube 50), the effect of preventing insulation breakdown can be improved.

[0030] Portions of the inner tube 25 having a relatively large outer diameter (hereinafter referred to as the inner tube large diameter portion) 27A, 27B are formed near the welded portions M1, M2 with the outer tube 22. A portion of the inner tube having a relatively small outer diameter (hereinafter referred to as the inner tube small diameter portion) 26 is formed in the discharge space S portion between the inner tube large diameter portions 27A, 27B. The connection portion between the inner tube large diameter portions 27A, 27B and the inner tube small diameter portion 26 has a shape in which the outer diameter continuously varies along the axial direction.

[0031] The inner diameter D0 of the inner tube 25 is substantially constant over the entire inner tube large diameter portions 27A, 27B and the inner tube small diameter portion 26. On the other hand, the thickness T11 of the inner tube large diameter portions 27A, 27B is greater than the thickness T10 of the inner tube small diameter portion 26, and the respective outer diameters D10 and D11 are different (D11>D10).

[0032] The outer tube 22 has a relatively large diameter portion (hereinafter referred to as the outer tube large diameter portion) 24 corresponding to the electrode opposing section K along the lamp axis C where the outer electrode 40 and the inner electrode 30 are opposed to each other along the lamp diameter direction, i.e., the portion where the covering tube 60 is provided.

[0033] The outer tube large diameter portion 24 has a flange-shaped portion (outer tube flange portion) M3 having a relatively larger thickness than other portions near one end portion 60T1 of the covering tube 60, and has a relatively smaller diameter portion (hereinafter referred to as the outer tube small diameter portion) 23 formed on the end side of the discharge tube 20 toward the welded portion M1 than the outer tube flange portion M3. The outer tube large diameter portion 24 is continuously and smoothly connected to the outer tube small diameter portion 23. The introduction tube 21 provided in the outer tube small diameter portion 23 is configured to be opposed to the inner tube large diameter portion 27A but to be opposed to a part of the inner tube small diameter portion 26.

[0034] The spatial region of the discharge space S formed in the discharge tube 20, particularly the spatial region of the discharge space S within the electrode opposing section K where the outer electrode 40 and the inner electrode 30 generating the discharge are opposed to each other along the lamp diameter direction, is determined in accordance with the illumination intensity and irradiation amount (light amount) of ultraviolet rays required for the fluid passing through the flow path R in the inner tube 25, and accordingly the size and axial length of the inner diameter D20 of the outer tube 22 (outer tube large diameter portion 24) and the outer diameter D10 of the inner tube (inner tube small diameter portion 26) are set.

[0035] Here, the inner diameter D20 of the outer tube 22 is set to be 1.3 times or more the outer diameter D10 of the inner tube small diameter portion 26 facing it. Preferably, the inner diameter D20 of the outer tube 22 is set to be 3 times or more the outer diameter D10 of the inner tube small diameter portion 26 .

[0036] The thickness T10 (of the tube wall) of the inner tube small diameter portion 26 is smaller than the thickness T30 of the cladding tube 60 and the thickness T20 of the outer tube 22 (outer tube large diameter portion 24) added together. However, the thickness of the inner electrode 30 is very small compared to the cladding tube 60 and the outer tube 22, and therefore is considered to be included in the above thickness. In addition, the thickness T20 of the outer tube 22 is smaller than the thickness T30 of the cladding tube 60. However, the thickness T20 of the outer tube 22 may be larger than the thickness T30 of the cladding tube 60. In either case, the thickness T10 of the inner tube is set smaller than the thickness T30 of the cladding tube 60, and smaller than the thickness T20 of the outer tube 22.

[0037] A reflective film 95 that reflects ultraviolet rays is formed on the inner surface of the outer tube 22. Here, the reflective film 95 is formed corresponding to the electrode opposing section K along the lamp axis C, and is formed in a range including the connecting portion where the outer tube large diameter portion 24 and the outer tube small diameter portion 23 are connected continuously and smoothly in inner diameter, but is not formed near the flange-shaped portions M1 and M2 and the introduction tube 21. The reflective film 95 is made of SiO2, for example. The lighting auxiliary light passes through the reflective film 95 and is irradiated to the inside of the outer tube 22.

[0038] Next, use Figure 3 The inner electrode 30 (used in the following Figure 3 The shape of the electrode (referred to as a foil electrode in the description) is described below.

[0039] Figure 3 This is a partial enlarged cross-sectional view of the discharge tube 20, in which the vicinity of the arrangement foil electrode 30 is enlarged. Here, the boundary between the discharge container and the covering tube and the arc-shaped (curved) bend of the foil electrode are omitted, and are represented as straight lines (flat surfaces), and the width direction of the foil electrode 30 is set as the X direction, and the thickness direction is set as the Y direction.

[0040] The foil electrode 30 is an electrode formed to be very thin relative to the electrode width (electrode width) w, and the thickness t is suppressed to less than 1 / 30 relative to the electrode width w. The foil electrode 30 has a flat portion 32 with a substantially constant thickness t, and has wedge-shaped portions 34A and 34B, and the front ends of the wedge-shaped portions 34A and 34B become thinner in a wedge shape from the width direction ends 32A and 32B of the flat portion 32 to the width direction ends E1 and E2 of the foil electrode 30.

[0041] Here, the wedge-shaped portions 34A and 34B of the foil electrode 30 are wedge-shaped and sharp to the edge E. That is, the foil electrode 30 is not sharpened from the center to the edge in the width direction, but is sharpened from the ends 32A and 32B of the flat portion 32 in the width direction to the ends E1 and E2 of the entire foil electrode 30 in the width direction.

[0042] Furthermore, the ends E1 and E2 in the width direction are not rounded and thick, but the ends E1 and E2 in the width direction of the foil electrode 30 are sharp, and the ends E1 and E2 in the width direction are in the shape of edges to the extent indicated by dots in the cross section. Furthermore, the thickness of the foil electrode 30 decreases at constant inclination angles θ1 and θ2 (the angle θ of the edge E with respect to the X direction is not shown here) from the ends 32A and 32B in the width direction of the flat portion 32 toward the ends E1 and E2 in the width direction.

[0043] Here, the angles θ1 and θ2 of the two ends E1 and E2 in the width direction of the foil electrode 30 are determined in consideration of the difficulty of peeling caused by the gap generated at the boundary portion of the buried coating tube 60 and the outer tube 22, the size of the cross-sectional area of ​​the flat portion corresponding to the current capacity, and the suppression of the temperature rise caused by the generation of Joule heat. Here, the angles θ1 and θ2 are both set in the range of 2° to 15°, preferably in the range of 2° to 10°, and are set to the same angle (hereinafter, also represented as θ).

[0044] However, when the cross section of the area about 100 μm away from the edge E of the foil electrode 30 is observed in an enlarged manner, the angles θ1 and θ2 are defined as angles at which the thickness increases from the edge E of the foil electrode toward the widthwise ends 32A and 32B of the flat portion 32. In the foil electrode 30, the edge-shaped edge E having such angles θ1 and θ2 is formed along the tube axis C direction on the entire electrode.

[0045] The center (central portion) of the flat portion 32 in the width direction is formed along the tube axis C, and the wedge-shaped portions 34A and 34B are symmetrical with respect to the flat portion 32. In addition, regarding the wedge-shaped portions 34A and 34B, the width direction length d1 of the wedge-shaped portions 34A and 34B is set to be 0.2 or less relative to the electrode width w of the foil electrode 30 (d1 / w).

[0046] Accordingly, the length d of the two ends 32A and 32B in the width direction of the flat portion 32 is set to be greater than 0.6 relative to the electrode width w (d / w) of the foil electrode 30. As described above, the inclination angles θ1 and θ2 of the cross section from the two ends E1 and E2 in the width direction toward the two ends 32A and 32B in the width direction of the flat portion 32 are equal and constant, but the angles θ1 and θ2 may be different angles.

[0047] The flat portion 32 does not have a constant thickness t in a strict sense, and may be a structure that can be considered as substantially flat within a range where there are slight bends, slight bumps, etc. when observed under magnification. Here, the flat portion 32 is formed such that the thickness of any portion of the flat portion 32 along the electrode width direction has a thickness that accounts for a ratio of 0.7 or more to the maximum thickness of the foil electrode 30 (flat portion 32).

[0048] By adopting such an electrode shape, it is possible to provide a small excimer lamp 10 which has improved adhesion with the covering tube 60 and the outer tube 22, suppresses peeling, and has excellent lighting startability. Figure 2 The shape of the foil electrode 30 shown is schematic and does not Figure 3 The shapes are different.

[0049] First, the edge E extending along the tube axis C of the foil electrode 30 is sharply pointed, so that electric field concentration is generated. As a result, discharge can be made while suppressing the discharge start voltage to a low level. In addition, since the wedge-shaped portions 34A and 34B are sharply pointed up to the edge E, the cross section near the edge E of the foil electrode 30 is linear in the axial direction, and the discharge start voltage can be suppressed to a lower level, and a gap is not easily generated at the boundary portion between the covering tube 60 and the outer tube 22, and peeling is not easily generated.

[0050] On the other hand, by forming the flat portion 32 on the foil electrode 30, the adhesion with the covering tube 60 and the outer tube 22 can be improved and peeling can be suppressed. That is, by providing the flat portion 32 with a substantially constant thickness t, a relatively large cross-sectional area is ensured for the foil electrode 30 with an extremely thin thickness t. In particular, since the flat portion 32 occupies more than 60% of the foil electrode 30, during the lighting of the lamp, the current flows through the flat portion 32 with a relatively large cross-sectional area, thereby suppressing the generation of Joule heat in the foil electrode 30.

[0051] As a result, the thermal expansion of the foil electrode 30 in the thickness direction (Y direction) and the width direction (X direction) can be suppressed. That is, it is not necessary to increase the length of the foil electrode 30 in the width direction in order to ensure a large cross-sectional area, and the increase of thermal expansion in the width direction can be prevented. In addition, it is not necessary to increase the thickness of the foil electrode 30, so the increase of thermal expansion in the thickness direction can be prevented.

[0052] Moreover, since the wedge-shaped portions 34A and 34B formed from the widthwise ends 32A and 32B of the flat portion 32 toward the widthwise ends E1 and E2 of the foil electrode 30 are sharp wedge-shaped up to the edge E, the electrolytic strength can be concentrated on the edge E of the foil electrode 30, and peeling of the foil electrode 30 relative to the covering tube 60 and the outer tube 22 can be suppressed.

[0053] Furthermore, by forming the wedge-shaped portions 34A and 34B with constant inclination angles θ1 and θ2 of the cross section, it is easy to grind the surfaces of the wedge-shaped portions 34A and 34B by electrolytic grinding, etc. Thus, it is possible to suppress the occurrence of peeling at the boundary between the covering tube 60 and the outer tube 22, and to achieve high illumination of the hollow excimer lamp 10.

[0054] The width w of the foil electrode 30 is smaller than the outer diameter D10 of the inner tube 25 (the inner tube small diameter portion 26). That is, the width of the inner tube 25 along the width direction of the foil electrode 30 is wider than the foil electrode 30. Therefore, when a discharge is generated in the discharge space S, due to the characteristics of the wedge shape of the foil electrode 30, it is easy to form a discharge near the outer surface of the inner tube 25 close to the flow path R in the inner tube 25, and the ultraviolet rays can be effectively irradiated to the fluid passing through the flow path R.

[0055] In the excimer lamp 10, the diameters of the inner tube 25 and the outer tube 22 constituting the discharge tube 20 are set to sizes suitable for high illumination. If the inner diameter D0 of the inner tube 25 is too large, the proportion of the fluid passing through the state without being irradiated by ultraviolet rays increases, and the ultraviolet irradiation efficiency decreases. On the other hand, if the inner diameter D0 of the inner tube 25 is too small, the ultraviolet irradiation efficiency decreases due to a decrease in flow rate or an increase in flow velocity.

[0056] In the present embodiment, as described above, the inner diameter D20 of the outer tube 22 (outer tube large diameter portion 24) is set to be 1.3 times or more the outer diameter D10 of the inner tube 25 (inner tube small diameter portion 26). Thus, when the inner diameter D0 of the inner tube 25 is set to a certain size or more so as not to be too small, the volume of the discharge space S that is appropriate for the volume of the flow path R and does not reduce the ultraviolet irradiation efficiency can be ensured.

[0057] In order to improve the ultraviolet irradiation efficiency, it is preferable to suppress the size of the inner tube small diameter portion 26 so as not to increase relative to the volume of the discharge space S. Such a reduction in the size of the inner tube small diameter portion 26 may reduce the mechanical strength of the discharge tube 20 having a double tube structure and cause damage.

[0058] However, by providing the inner tube large diameter portions 27A and 27B near both ends of the discharge tube 20, the mechanical strength of the discharge tube 20 can be maintained. Also, regarding the outer tube 22, the introduction tube 21 is provided at the outer tube small diameter portion 23 away from the electrode facing section K and facing the inner tube small diameter portion 26 formed near the inner tube large diameter portion 27A. Thus, the introduction tube 21 can be configured not to protrude more than the covering tube 60 in the lamp diameter direction, and the exhaust efficiency of the impurity gas in the discharge tube 20 through the introduction tube 21 and the sealing efficiency through the introduction tube 21 can be improved.

[0059] Even in the inner tube 25 provided with the inner tube small diameter portion 26 and the inner tube large diameter portions 27A and 27B, at least in the electrode facing section K, the inner tube small diameter portion 26 is not subjected to heat forming, and the inner diameter D0 is substantially constant. That is, in the electrode facing section K where discharge is generated and ultraviolet rays are irradiated, the state of the tube blank with small errors is maintained, and the error of each lamp is suppressed. Therefore, the error of the ultraviolet irradiation efficiency of the fluid flowing in the flow path R of each lamp can be suppressed, and the reliability can be prevented from being reduced.

[0060] The excimer lamp 10 described above can be manufactured by the following manufacturing method, for example.

[0061] The inner tube small diameter portion 26, the inner tube large diameter portions 27A and 27B, the flange portions M1 and M2 of the inner tube 25, the introduction tube 21, the outer tube small diameter portion 23, the outer tube large diameter portion 24, and the outer tube flange portion M3 of the outer tube 22 are heat-formed from a tubular member made of a dielectric material such as quartz glass. In the discharge tube 20, both ends of the outer tube 22 are heated to reduce their diameters and are welded to the flange portions M1 and M2 provided on the inner tube 25, thereby forming a discharge space S.

[0062] The discharge tube 20 having foil electrodes arranged on its outer circumferential surface is inserted into a tubular member made of a dielectric material such as quartz glass and having an inner diameter larger than the outer diameter of the discharge tube 20. The cladding tube 60 is coaxially heated and reduced in diameter while the end 60T1 of the cladding tube 60 and the outer tube flange portion M3 are in contact with each other in the axial direction, thereby fusing the cladding tube 60 and at least a portion of the outer circumferential surface of the outer tube large diameter portion 24 into one body.

[0063] The discharge tube 20 is evacuated through the introduction tube 21 to remove impurities. Then, a discharge gas is filled in the discharge tube 20, and the introduction tube 21 is heated and melted to hermetically seal the discharge tube 20.

[0064] Next, use Figure 4 , Figure 5 An excimer lamp according to a second embodiment will be described. In the second embodiment, an auxiliary discharge space is formed in a discharge tube.

[0065] Figure 4 This is a schematic cross-sectional view of an excimer lamp according to a second embodiment. Figure 5 It is along Figure 4 A schematic cross-sectional view of line VV.

[0066] As in the first embodiment, the excimer lamp 100 is configured as a hollow excimer lamp having a discharge tube 20 obtained by fusing an outer tube 22 and an inner tube 25. A non-fusing portion is partially present between the covering tube 160 and the outer tube 22, forming an auxiliary discharge space S1. One end 30T of the inner electrode 30 is exposed in the auxiliary discharge space S1.

[0067] Lighting startability can be improved by forming the auxiliary discharge space S1 in the discharge tube 20. The excimer lamp 100 having the auxiliary discharge space S1 can be manufactured by the following manufacturing method, for example.

[0068] In the manufacturing method of the excimer lamp of the first embodiment, when the covering tube 160, the end portion 160T1 and the outer tube flange portion M3 are coaxially heated and shrunk in a state where they are axially abutted, the covering tube 60 and the outer tube 22 are not welded in the entire circumferential direction near the end portion 30T on one side of the inner electrode 30, thereby manufacturing an excimer lamp 100 having an auxiliary discharge space S1.

Claims

1. An excimer lamp, characterized in that: The excimer lamp has: lateral tube; an inner tube coaxially disposed within the outer tube; and a foil-shaped inner electrode embedded between a covering tube covering at least a portion of the outer tube and the outer tube, An outer electrode is provided on the outer surface side of the outer tube, The inner electrode has a flat portion having a substantially constant thickness along the electrode width direction, and is sharpened from the flat portion toward both ends.

2. The excimer lamp according to claim 1, characterized in that: The inner tube has: an inner tube large diameter portion provided with a flange-shaped portion welded to the outer tube; and The inner tube small diameter portion is formed at a position closer to the discharge space than the inner tube large diameter portion and has a smaller diameter than the inner tube large diameter portion.

3. The excimer lamp according to claim 2, characterized in that: The outer tube has an outer tube small diameter portion, which is not covered by the covering tube and has a smaller diameter than the portion covered by the covering tube. The outer tube small diameter portion faces at least a portion of the inner tube small diameter portion.

4. The excimer lamp according to claim 1, characterized in that: The thickness of the inner tube is smaller than the thickness of the outer tube and the cladding tube.

5. The excimer lamp according to claim 1, characterized in that: The electrode width of the inner electrode is smaller than the outer diameter of the inner tube.

6. The excimer lamp according to claim 1, characterized in that: The inner diameter of the outer tube is 1.3 times or more the outer diameter of the inner tube.

7. The excimer lamp according to claim 1, characterized in that: An ultraviolet reflection film is formed on the inner surface of the outer tube in a section facing the inner electrode.

8. The excimer lamp according to claim 1, characterized in that: The cladding tube and the outer tube are partially welded, An auxiliary discharge space is formed in a non-welded portion between the cladding tube and the outer tube.

9. The excimer lamp according to claim 8, characterized in that: A portion of the inner electrode is exposed in the auxiliary discharge space.

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