Excimer lamp and ultraviolet irradiation device

Abstract

To prevent an outer tube from breaking at the end of the life of a lamp for various dual tube structure excimer lamps.SOLUTION: An excimer lamp 10 includes a discharge vessel 15 in which an outer tube 20 and an inner tube 30 are welded to each other, and a foil-like inner electrode 40 coated on the inner tube 30 is coaxially disposed along a lamp axis C. The inner tube 30 includes: a thin part 32 covering the inner electrode 40 and a flange part 31 welded to the outer tube 20. A thick part 34 partially extending from a discharge vessel 15 is formed. In a section covered by the inner electrode 40, the inner electrode 40 is configured in a flat shape, and a cross-sectional shape thereof is an oval shape or an oval shape.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an excimer lamp, and more particularly to the operation of an excimer lamp. [Background technology]

[0002] A known configuration of a double-tube excimer lamp is one in which a dielectric (inner tube) covering a foil-like inner electrode is placed inside an outer tube, and an outer electrode is placed on the outer surface of a discharge vessel made up of the inner and outer tubes (see Patent Document 1). A discharge is generated by applying a high-frequency voltage between the inner and outer electrodes, and excimer light such as ultraviolet light is emitted.

[0003] To prevent damage to such discharge vessels, for example, the inner tube is made of fused silica glass and the outer tube is made of synthetic silica glass (see Patent Document 2). In this case, damage to the discharge vessel is prevented by reducing the difference in contraction due to thermal expansion between the outer and inner tubes.

[0004] Meanwhile, in view of the difficulty of determining from the lamp's appearance that the lamp is nearing the end of its life, a method of monitoring the lamp's cumulative lighting time has been proposed (see Patent Document 3). Also known is an excimer lamp that forms a discharge space (auxiliary discharge space) between the inner electrode and the inner tube to assist in starting lighting, preventing the lamp from lighting before the discharge tube becomes weak (see Patent Document 4).

[0005] In this method, molybdenum is evaporated from the inner electrode by a sputtering phenomenon and deposited on the inner surface of the inner tube. When the lamp's cumulative operating time approaches the end of its life, the deposited molybdenum film becomes a light-blocking film, preventing the lamp from operating at its rated capacity and making it impossible to restart the lamp. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5504095 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-230867 [Patent Document 3] Japanese Patent Application Laid-Open No. 2010-027944 [Patent Document 4] Japanese Patent Publication No. 2023-087558 [Patent Document 5] Patent application No. 2023-118999 [Patent Document 6] Patent application No. 2023-149556 [Patent Document 7] Patent application No. 2023-118942 Summary of the Invention [Problem to be solved by the invention]

[0007] Abnormal lighting conditions, such as lighting beyond the rated lamp life (lighting at the end of the lamp life) or lighting at a high voltage exceeding the rated lamp voltage (overload lighting), may cause damage to the discharge tube. In such cases, if the outer tube breaks first, fragments may fly off.

[0008] On the other hand, excimer lamps with a double-tube structure do not necessarily have a lamp configuration with an auxiliary discharge space. Therefore, it is possible to determine the end of a lamp's life by managing the lamp's cumulative lighting time, but the lighting conditions of excimer lamps vary depending on the usage environment, and aging also varies from lamp to lamp. Therefore, it is difficult to accurately determine the end of a lamp's life by managing the lamp's cumulative lighting time.

[0009] Therefore, for various excimer lamps with a double-tube structure, it is necessary to prevent the outer tube from breaking when the lamp is turned on at the end of its life or under overload. [Means for solving the problem]

[0010] The present invention provides an excimer lamp comprising an inner tube covering a foil-shaped inner electrode arranged along the lamp axis, and an outer tube with an outer electrode arranged on the outside, the inner tube and the outer tube being welded together to form a discharge space; when the excimer lamp is lit under overload or at the end of its lamp life, a tear occurs in the inner tube that spatially connects the interior of the inner tube to the discharge space before the outer tube breaks.

[0011] Here, "rupture" includes cracks, fissures, fissures, crevices, and tiny gaps, and indicates a state of spatial connection (communication) with the discharge space. The occurrence of a rupture allows gas contained in the gap between the inner surface of the inner tube and the surface of the inner electrode to flow into the discharge space through the rupture. This causes the excimer lamp to enter an abnormal lighting state, preventing the outer tube from bursting.

[0012] The material of the inner tube may vary. For example, at least a portion of the inner tube may have a different material, light transmittance, shape, or structure from the outer tube so that the inner tube will experience a faster decrease in dielectric strength or embrittlement in response to the wavelength of ultraviolet light radiated than the outer tube.

[0013] For example, at least a portion of the inner tube can be configured to have lower transmittance than the outer tube for the wavelength of the emitted ultraviolet light. Also, the inner tube can be configured to include a thick-walled portion provided with a flange-shaped portion to be welded to the outer tube, and a thin-walled portion formed within the discharge space and thinner than the thick-walled portion in the width direction of the foil electrode, and tearing of the inner tube occurs in the thin-walled portion.

[0014] The inner electrode may have various configurations. For example, the foil-shaped inner electrode has a flat portion with a substantially constant thickness along the width direction between both widthwise ends of the inner electrode, and is tapered from both ends of the flat portion toward both widthwise ends of the inner electrode. The inner tube may also have various shapes. For example, the inner tube may have a cross-sectional shape that is flattened in the thickness direction of the inner electrode.

[0015] An auxiliary discharge space can be formed in the inner tube. For example, the inner tube can include, along the lamp axis, a sealed portion sealed to the inner electrode and a tubular portion surrounding the auxiliary discharge space formed between the sealed portions. In the auxiliary discharge space, the widthwise end of the inner electrode and the inner surface of the tubular portion are separated by a distance smaller than the thickness of the tubular portion along the electrode width direction, or are in contact with each other. It is also possible to form an auxiliary discharge space inside or at the tip of the inner tube, where the inner electrode is not exposed.

[0016] Another aspect of the present invention is an ultraviolet irradiation device comprising the above-described excimer lamp, a detection unit capable of detecting a change in the lighting state of the excimer lamp when a break occurs in the spatial connection between the inside of the inner tube and the discharge space, and a control unit that stops the lighting of the excimer lamp or displays a warning message in response to the change in the lighting state of the excimer lamp detected by the detection unit.

[0017] Another aspect of the present invention is a method for controlling the lighting of an excimer lamp, which comprises an inner tube covering a foil-shaped inner electrode arranged along the lamp axis, and an outer tube with an outer electrode arranged on the outside, and the inner tube and the outer tube are welded together to form a discharge space, and when a break occurs in the spatial connection between the inside of the inner tube and the discharge space, an abnormal lighting state is detected from a change in the lighting state of the excimer lamp. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide an excimer lamp that prevents damage to the outer tube when the lamp is turned on at the end of its life or under overload for various double-tube structure excimer lamps. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic cross-sectional view of an excimer lamp according to a first embodiment. [Figure 2]2 is a schematic cross-sectional view of the excimer lamp taken along the line II-II, which is perpendicular to the cross-sectional direction of FIG. 1. [Figure 3] FIG. 1 is a block diagram of an ultraviolet irradiation device equipped with an excimer lamp. [Figure 4] FIG. 1 is a schematic cross-sectional view of an excimer lamp according to a second embodiment. [Figure 5] 4. FIG. 5 is a schematic cross-sectional view of the excimer lamp taken along the line IV-IV, which is perpendicular to the cross-sectional direction of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0020] The excimer lamp of this embodiment will be described below with reference to the drawings.

[0021] Fig. 1 is a schematic plan view of an excimer lamp according to a first embodiment, and Fig. 2 is a cross-sectional view of the excimer lamp taken along line II-II in Fig. 1.

[0022] The excimer lamp 10 is configured as a double-tube excimer lamp, and includes a tubular discharge vessel (discharge tube) 15 formed by welding an outer tube 20 and an inner tube 30 made of a dielectric material such as quartz glass. Here, the excimer lamp 10 is configured as a compact excimer lamp. For example, the axial length (light-emitting length) of the discharge vessel can be set in the range of 20 mm to 400 mm. The outer diameter of the outer tube 20 can be set in the range of 5 mm to 30 mm, preferably 8 mm to 25 mm.

[0023] An annular (cylindrical) discharge space S is formed between the outer tube 20 and the inner tube 30. A rare gas such as xenon gas, or a mixture of a rare gas and a halogen gas, is sealed in the discharge space S as a discharge gas. The inner tube 30 has a lower transmittance than the outer tube 20 for the wavelengths of ultraviolet light emitted from the discharge. For example, the outer tube 20 is made of synthetic quartz glass, and the inner tube 30 is made of fused silica glass, which has a lower transmittance than synthetic quartz glass for the wavelengths of ultraviolet light emitted from the discharge.

[0024] An outer electrode 50 is disposed on the outer surface of the outer tube 20 that constitutes the discharge vessel 15. The outer electrode 50 is configured by winding a linear electrode portion made of a conductive metal along the outer surface of the outer tube 20, spirally wound along the tube axis C, and disposed at predetermined intervals. The cross section of the outer tube 20 along the tube diameter (lamp diameter) direction is formed in a hollow circular shape here.

[0025] The electrode (hereinafter referred to as the inner electrode) 40 covering the inner tube 30 is configured as a foil electrode extending along the tube axis (hereinafter also referred to as the lamp axis) C. The inner electrode 40 is not exposed to the discharge space S, but is buried within the inner tube 30.

[0026] A power supply rod (power supply line) 70, which is connected to a power supply unit (not shown here), is connected to the inner electrode 40 near one end 40T along the lamp axis C. Power is supplied to the excimer lamp 10 via the power supply rod 70. Cylindrical ends 50T1 and 50T2 provided on the outer electrode 50 are electrically connected to the linear electrode portion.

[0027] The inner tube 30 is formed with a flange-like portion (hereinafter also referred to as an expanded diameter portion) 31 that protrudes in the radial direction, and one end of the outer tube 20 is welded to the expanded diameter portion 31. The other end of the outer tube 20 is integrally formed with a protruding portion (exhaust pipe) 22 that is formed during the lamp manufacturing process.

[0028] The polarities of the inner electrode 40 and the outer electrode 50 are set to anode and cathode, respectively. High frequency (for example, in the range of several kHz to several tens of MHz) and high voltage (for example, in the range of several kV to several tens of kV) are supplied to the excimer lamp 10 via the power feed rod 70. This causes a dielectric barrier discharge in the discharge space S, and excimer light of a predetermined spectrum (for example, a wavelength of 172 nm) is emitted from the discharge space S.

[0029] The foil-shaped inner electrode 40 is arranged coaxially with the center of the inner tube 30, with its center in the width direction and thickness direction aligned with the center of the inner tube 30. The inner tube 30 is also arranged coaxially with the outer tube 20. Therefore, the inner electrode 40 is arranged coaxially with the outer tube 20 and symmetrically with respect to the lamp axis C. Here, the width direction of the inner electrode 40 is defined as the Y direction, and the direction perpendicular thereto (thickness direction) is defined as the X direction (see FIG. 2).

[0030] The inner electrode 40 has a flat portion 44 with a substantially constant thickness, and has wedge-shaped portions 42 that taper from both widthwise ends of the flat portion 44 to both widthwise ends E1, E2 of the inner electrode 40. However, the inner electrode 40 may have a knife-edge shape with a cross section that slopes smoothly from the center along the electrode width direction toward both widthwise ends E1, E2 of the inner electrode.

[0031] The inner tube 30 has a cross-sectional shape with a different diameter along the tube axis C. Specifically, the inner tube 30 has a portion (hereinafter referred to as a thin-walled portion) 32 that covers the inner electrode 40 in the discharge space S, and a portion (hereinafter referred to as a thick-walled portion) 34 that is provided with an expanded diameter portion 31 and covers the power feed rod 70.

[0032] The thick-walled portion 34 formed in the range L2 along the tube axis C has a portion 36 (hereinafter referred to as the exposed portion) that extends further into the discharge space S than the expanded diameter portion 31 and is exposed to the discharge space, and a portion 37 (hereinafter referred to as the extended portion) that extends beyond the outer tube 20 from the discharge vessel 15 to the outside of the discharge space S. The thick-walled portion 34 is formed to have a thickness (wall thickness), i.e., a distance T12 from the power supply line 70 to the surface of the thick-walled portion 34, and a circular cross section with an outer diameter W12.

[0033] The thin-walled portion 32 has a substantially constant radial cross-sectional shape in a range L1 formed along the tube axis C, covers the vicinity of the connection between the inner electrode 40 and the power feed rod 70, and extends to the vicinity of the end 40T of the inner electrode 40. The radial cross-sectional shape of the thin-walled portion 32 covering the inner electrode 40 is not circular but is elongated elliptical or oval.

[0034] Specifically, the inner tube 30 is flattened in the electrode thickness direction (X direction), and near the center, has an outer surface that extends along the electrode width direction (Y direction), and from near both widthwise ends E1 and E2 of the inner electrode 40 to the outside, the outline of the radial cross section is semi-elliptical or semi-circular.

[0035] By making the thin-walled portion 32 of the inner tube 30 covering the inner electrode 40 flat in this way, when lighting (including relighting) the excimer lamp 10, electric field concentration occurs near both ends E1, E2 of the foil-like inner electrode 40, making lighting easier to start. On the other hand, the electric field strength does not become excessively large, preventing uneven discharge along the circumferential direction of the lamp.

[0036] Furthermore, the outer diameter W11 of the thin-walled portion 32 of the inner tube 30 in the electrode width direction (Y direction) is larger than the outer diameter W21 in the electrode thickness direction (X direction) and is smaller than the outer diameter W12 of the thick-walled portion 34. By forming such thin-walled portion 32 according to the range L1 along the tube axis C that covers the inner electrode 40, it is possible to set the discharge distance D1 (see FIG. 1) in the electrode width direction (Y direction) and the discharge distance D2 (see FIG. 2) in the electrode thickness direction (X direction) to distances that are relatively long with respect to the outer diameter of the lamp.

[0037] In addition, it is possible to set the thickness (distance) T11 (see Figure 1) of the thin-walled portion 32 from the inner electrode 40 along the electrode width direction (Y direction) and the thickness T21 (see Figure 2) from the inner electrode 40 along the electrode thickness direction (X direction) to be relatively small compared to the discharge distances D1 and D2.

[0038] Therefore, even in a small excimer lamp 10, it is possible to ensure sufficient space for the cylindrical discharge space S, thereby improving the lighting startability and increasing the ultraviolet radiation efficiency.

[0039] Such an excimer lamp 10 can be manufactured, for example, by the manufacturing method described below.

[0040] First, an expanded diameter portion is formed on a cylindrical glass tube (hereinafter referred to as a sealing tube) that forms the thick-walled portion of the inner tube and is integrally and hermetically sealed with the outer tube. At this time, a hollow portion with an inner diameter that allows the power feed rod to be inserted is provided in the thick-walled portion. Also, a cylindrical glass tube (hereinafter referred to as a sealing tube) that forms the thin-walled portion of the inner tube and is integrally sealed with a foil-shaped inner electrode is fused coaxially to the sealing tube. At this time, a hollow portion with an inner diameter that allows the inner electrode to be inserted is provided in the thin-walled portion, and the sealing tube has a smaller outer diameter and thickness and a larger inner diameter than the sealing tube. Note that a process of cutting the glass tube may be performed instead.

[0041] After the power feed rod (power feeder wire) is connected to the inner electrode by resistance welding or other means, it is inserted into an inner tube that has a thick and thin walled section formed as an integral part. The inner tube with the inner electrode and power feed rod inserted is evacuated and sealed, and the inner tube is heated from the outside to seal the thin walled section of the inner tube to the inner electrode and the thick walled section to the power feeder wire. At this time, the heating is adjusted so that the cross section of the thin walled section becomes an oblong shape.

[0042] For example, by rotating the glass tube and heating it with a burner or the like, the inner surface of the glass tube is uniformly circumferentially contracted (reduced in diameter) until it comes into contact with both ends (wedge-shaped portions) of the foil-shaped inner electrode, and the glass tube between the portions in contact with the both ends (wedge-shaped portions) of the foil-shaped inner electrode is contracted along the thickness direction of the foil-shaped inner electrode to be integrated with the flat portion, thereby making it possible to weld the glass tube to an oblong or elliptical cross section and to the inner electrode. Note that a step of coating the glass tube may be performed instead.

[0043] An outer tube made of quartz glass or the like is then formed with an exhaust pipe at one end and an insertion opening at the other end, and the inner tube to which the inner electrode and power supply rod are sealed is inserted into the outer tube, and the insertion opening of the outer tube is welded to the expanded diameter portion of the thick-walled part of the inner tube. The outer tube has an inner diameter corresponding to the outer diameter of the expanded diameter portion of the inner tube.

[0044] While the entire discharge vessel is heated, a vacuum is drawn through the exhaust pipe to remove impurities, and after the discharge gas is filled in, the exhaust pipe is sealed and an outer electrode is disposed on the outer surface of the outer tube.

[0045] On the other hand, in an excimer lamp 10 having a flat inner tube 30 with a thin-walled portion 32, when the lamp reaches the end of its life or is operated under overload, the inner tube 30 will suffer damage such as cracks, fissures, or chips (hereinafter referred to as "cracks, etc.") before the outer tube 30 breaks (lamp breakage) when the lamp reaches the end of its life or is operated under overload.

[0046] This damage to the inner tube 30 is not simply a crack in the surface layer (part of the thickness) of the inner tube 30, but the crack reaches the outer surface of the inner tube 30 and the outer surface of the inner electrode 40, resulting in a state in which the surface of the inner electrode 40 and the discharge space S are spatially connected (exposed). Here, this type of damage is referred to as a break in the inner tube 30. In Figure 1, the break in the inner tube 30 is indicated by the symbol "G".

[0047] The electric field concentration near both ends E1 and E2 of the foil-shaped inner electrode 40 along the width direction (Y direction) improves the lighting startability, which makes the inner tube 30 more susceptible to breakage. On the other hand, by making the thin-walled portion 32 of the inner tube 30 flat, the electric field strength near both ends E1 and E2 of the inner electrode 40 along the width direction (Y direction) does not become excessively large, which prevents uneven discharge along the circumferential direction of the lamp.

[0048] With this configuration, damage (reduction in dielectric strength and progression of embrittlement) is not concentrated near both ends E1 and E2 of the inner electrode 40 in the width direction (Y direction). This prevents the inner tube 30 from becoming excessively susceptible to breakage, and causes breakage G of the inner tube 30 when a predetermined voltage or a predetermined time is exceeded, depending on the dielectric strength, UV resistance, etc. of the outer tube 20. For example, breakage G of the inner tube 30 occurs below a predetermined voltage at which the outer tube 20 is broken when a high voltage exceeding the rated voltage is applied. Furthermore, breakage G of the inner tube 30 occurs a predetermined time before the outer tube 20 becomes brittle and breaks.

[0049] Furthermore, the deterioration of dielectric strength and the progression of embrittlement are affected by the materials (dielectric strength, UV resistance) and thickness of the inner tube 30 and outer tube 20, and the environment in which they are exposed to discharge and UV radiation. As mentioned above, the UV transmittance of the fused silica glass of the inner tube 30 is lower than that of the synthetic silica glass of the outer tube 20. This results in the accumulation of damage (deterioration of dielectric strength and progression of embrittlement) to the inner tube 30 due to UV radiation.

[0050] When a tear G occurs in the thin-walled portion 32 of the inner tube 30, a discharge bias occurs along the circumferential direction of the discharge vessel 15 between the inner electrode 40 and the inner surface of the outer tube 30, causing a change in irradiance.

[0051] Furthermore, the tear G in the inner tube 30 causes evaporation of the foil-like inner electrode 40 (molybdenum and trace amounts of impurities contained therein) due to a sputtering phenomenon. Impurity gases such as evaporated molybdenum flow into the discharge space S through the tear G. Furthermore, impurity gases contained in the gap between the inner surface of the inner tube 30 and the surface of the inner electrode 40 flow into the discharge space S through the tear G. In this way, the leakage of impurity gases into the discharge space S causes abnormal discharge, resulting in changes in the lamp voltage, current, and irradiance.

[0052] The uneven discharge and the outflow of impure gas into the discharge space S result in abnormal lighting of the excimer lamp 10. For example, this causes changes in the irradiance, lamp voltage, and lamp current compared to the normal lighting state of the excimer lamp 10. Therefore, when abnormal lighting is detected due to a change in the lighting state caused by a break G in the inner tube 30 of the excimer lamp 10, a warning display (alarm) is displayed or the lamp is forcibly turned off, thereby making it possible to stop lighting before the lamp is damaged, i.e., before the outer tube 20 is damaged.

[0053] FIG. 3 is a block diagram of an ultraviolet irradiation device equipped with an excimer lamp 10.

[0054] The ultraviolet irradiation device 1 is capable of irradiating ultraviolet rays and includes an excimer lamp 10, a lamp power supply unit 2 that supplies power to the lamp, and a control unit (controller) 3 that can control the power supply from the lamp power supply unit 2 to the excimer lamp 10. An illuminance sensor (detection unit) 4 that can detect the lighting state of the excimer lamp 10 is provided around the excimer lamp 10, and the control unit 3 receives a detection signal from the illuminance sensor 4. An object to be irradiated (not shown) can be placed next to the ultraviolet irradiation device 1, or the device can be configured to irradiate ultraviolet rays toward a flow path through which a fluid such as a gas flows.

[0055] In response to input operations on the control unit 3 by an operator, the lamp power supply unit 2 supplies power to the excimer lamp 10. In normal lighting, the excimer lamp 10 lights up according to the rated voltage and current. On the other hand, if the operator sets a voltage that exceeds the rated voltage depending on the intended use, etc., the lamp can be lit with a high voltage that exceeds the rated voltage (overload lighting).

[0056] The control unit 3 detects the irradiance of the excimer lamp 10 based on a detection signal from the illuminance sensor 4, and also detects either the lamp voltage or the lamp current based on a detection signal from the lamp power supply unit 2. When a change in at least one of the lamp current, lamp voltage, and irradiance is detected due to the aforementioned uneven discharge or the outflow of impure gas, the control unit 3 displays a warning (alarm) to the operator or forcibly stops the power supply to stop the lamp from lighting up.

[0057] Regarding the changes in lamp current, lamp voltage, and irradiance caused by the uneven discharge and the outflow of impure gases, a threshold value set as a normal lighting state for safety reasons is used as a reference, and when the specified threshold value is exceeded, an abnormal lighting state is detected, and a warning display (alarm) is displayed to the operator or the lighting is forcibly stopped.

[0058] The ultraviolet irradiation device 1 can also be configured as an ozone generator that irradiates ultraviolet rays having a wavelength capable of generating ozone. For example, an excimer lamp 10 can be disposed in a flow path pipe, and an oxygen-containing gas (such as air) can be configured to flow through a flow path in the flow path pipe, and ozone can be generated by ultraviolet irradiation.

[0059] As described above, the excimer lamp 10 of this embodiment includes a discharge vessel 15 formed by welding the outer tube 20 and the inner tube 30, and the foil-shaped inner electrode 40 covering the inner tube 30 is arranged coaxially along the lamp axis C. The inner tube 30 has a thin-walled portion 32 covering the inner electrode 40 and a flange-shaped portion 31 welded to the outer tube 20, and a thick-walled portion 34 partially extending from the discharge vessel 15.

[0060] On the other hand, in the section covering the inner electrode 40, including the section where the inner electrode 40 and the outer electrode 50 face each other along the lamp axis C (hereinafter referred to as the electrode facing section), the inner electrode 40 is configured to be flat, and its cross-sectional shape is oval or oblong, unlike the outer tube 20, which has a circular cross-section.

[0061] Therefore, when the lamp lighting time accumulates and the lamp reaches the end of its life, or when the lamp is lighting under overload, a break G occurs in the thin-walled portion 32 of the inner tube 30 before the outer tube 20 is damaged due to a decrease in resistance. Then, by detecting a change in irradiance, lamp voltage, or lamp current caused by the break G, a warning can be displayed or the lamp can be stopped.

[0062] The thin-walled portion 32 of the inner tube 30 does not need to have an oval or oblong cross section, and may have a circular cross section. Furthermore, the inner tube 30 may not have the same overall cross section along the tube axis (lamp axis) C, but may be formed into an exterior shape with a different scale or aspect ratio, or different cross-sectional shape.

[0063] For example, the outer diameter W11 or thickness T11 along the electrode width direction (Y direction) may be gradually or continuously reduced toward the tip 30T of the inner tube 30. The outer diameter W11 or thickness T11 near the connection portion 35 between the thin-walled portion 32 and the thick-walled portion 34 may also be gradually or continuously increased in diameter from the thin-walled portion 32 toward the thick-walled portion 34.

[0064] Even with this configuration, it is possible to achieve a configuration in which breakage G of the inner tube 30 occurs at the thin-walled portion 32 of the inner tube 30 before damage to the outer tube 20. Furthermore, even if the thin-walled portion 32 is not provided, that is, the cross-sectional shape (outer diameter) of the inner tube 30 remains substantially constant along the lamp axis C, the flat radial cross-sectional shape of the inner tube 30 can be prevented from becoming excessively prone to breakage even when lighting startability is improved.

[0065] In the above-described excimer lamp 10, the thin-walled portion 32 of the inner tube 30 has a substantially constant outer diameter W11 in the electrode-opposing section. However, the inner tube 30 may not have the same overall cross-sectional shape along the tube axis (lamp axis) C, but may have an exterior shape with a different scale, aspect ratio, or cross-sectional shape. For example, the thin-walled portion 32 near the tip of the inner tube 30, which covers part of the inner electrode 40, may have a smaller outer diameter.

[0066] The configuration of such a thin-walled portion 32 is described in the above-mentioned Patent Document 5. Specifically, the outer diameter of the thin-walled portion 32 in the portion of the inner tube 30 that covers the vicinity of the tip of the inner electrode 40 and is surrounded by a cylindrical end portion 50T1 provided on the outer electrode 50 (see symbol B1 in FIG. 1 ) can be made smaller than that of other portions, including the vicinity of the center of the lamp. In this case, a break G of the inner tube 30 will occur in the small-diameter portion of the thin-walled portion 32.

[0067] The outer pipe 20 is not limited to a configuration in which its end is welded to the expanded diameter portion 31 of the inner pipe 30, but may be configured to extend from the expanded diameter portion 31 toward the extended portion 37 of the thick-walled portion 34. Such a configuration is described in Patent Document 6.

[0068] In this embodiment, the inner tube 30 is made of fused silica glass and the outer tube 20 is made of synthetic silica glass, but they may be made of silica glass that has the same ultraviolet transmittance.

[0069] Next, an excimer lamp 100 according to a second embodiment will be described with reference to Figures 4 and 5. In the second embodiment, an auxiliary discharge space is formed within the inner tube 130 to assist in starting lighting.

[0070] Fig. 4 is a schematic cross-sectional view of an excimer lamp according to a second embodiment of the present invention, and Fig. 5 is a schematic cross-sectional view of the excimer lamp taken along the line IV-IV, which is orthogonal to the cross-sectional direction of Fig. 4.

[0071] As in the first embodiment, the excimer lamp 100 includes a discharge vessel 115 made of quartz glass or the like, and a discharge space (hereinafter referred to as the main discharge space) S1 is formed between an outer tube 120 and an inner tube 130. A rare gas such as xenon gas or a mixture of a rare gas and a halogen gas is sealed in the main discharge space S1 as a discharge gas. The inner electrode 140 is not exposed to the main discharge space S1, and one end 140T is connected to a power feed rod (power feeder wire) 170.

[0072] In addition to the main discharge space S1, an auxiliary discharge space S2 is formed in the discharge vessel 115 along the lamp axis C. Here, the auxiliary discharge space S2 is formed in a partial section CL (hereinafter referred to as the auxiliary discharge space forming section) including the center of the lamp, within the electrode facing section where the inner electrode 140 and the outer electrode 150 face each other.

[0073] The auxiliary discharge space S2 is in a reduced pressure state below atmospheric pressure and is filled with a rare gas below atmospheric pressure, which reduces the voltage at the start of lighting (lighting start voltage). Therefore, when a high-frequency voltage is applied to the inner electrode 140 and the outer electrode 150, a discharge occurs first in the auxiliary discharge space S2 due to the lighting start voltage, which is lower than that in the main discharge space S1.

[0074] The inner tube 130 is in close contact (sealed) with the inner electrode 140 around the entire circumference except in the auxiliary discharge space forming section CL. On the other hand, in the auxiliary discharge space forming section CL, the inner tube 130 is not in contact with the inner electrode 140 except near both ends.

[0075] The auxiliary discharge space S2 can be formed in the lamp manufacturing process by sealing a glass tube, which serves as the material for the dielectric (inner tube) that is transparent to the light (electromagnetic waves) emitted from the discharge formed in the auxiliary discharge space, to the inner electrode 140 not all around the circumference in the auxiliary discharge space forming section CL, but only partly around the circumference to the inner electrode 140 along the lamp axis.

[0076] The cross-sectional shape of the inner tube 130 in the auxiliary discharge space forming section CL is different from the cross-sectional shape of the other portions. The sealed portion 130F where the inner tube 130 is in close contact with the inner electrode 140 is flat, as in the first embodiment, and is flattened in the electrode thickness direction (X direction).

[0077] On the other hand, in the auxiliary discharge space forming section CL, the inner tube 130 is configured as a tubular portion 130G. The tubular portion 130G is not flattened in the electrode width direction (Y direction) or the electrode thickness direction (X direction), and its cross section is formed in a hollow circular (ring-like) shape. Therefore, in the auxiliary discharge space forming section CL, the distance D10 along the electrode width direction (Y direction) shown in FIG. 4 is approximately equal to the distance D20 along the electrode thickness direction (X direction) shown in FIG. 5. Near both ends of the auxiliary discharge space forming section CL, i.e., at the boundary between the sealed portion 130F of the inner tube 130 and the tubular portion 130G, the cross section of the inner tube 130 gradually flattens and has a complex curved shape.

[0078] The foil-shaped inner electrode 140 has, as in the first embodiment, a wedge-shaped portion 142 that tapers at the tips near the width-direction ends E1 and E2 along the electrode width direction (Y direction), and has a flat portion 144 with a constant thickness therebetween. However, it may be in the form of a knife-edge shape that smoothly slopes from the center along the electrode width direction toward the width-direction ends E1 and E2, respectively. Alternatively, an inner electrode 140 with a constant thickness along the electrode width direction may be configured.

[0079] In the auxiliary discharge space S2, both ends E1 and E2 of the inner electrode 140 along the electrode width direction are close to the inner surface of the tubular portion 130G of the inner tube 130. That is, the inner electrode 140 extends along the electrode width direction (Y direction) close to the inner surface of the tubular portion 130G.

[0080] The distance interval (hereinafter also referred to as the separation distance) D1 between both ends E1 and E2 in the width direction of the inner electrode 140 and the inner surface of the tubular portion 130G of the inner tube 130 along the electrode width direction (Y direction) is determined to be shorter than the thickness T10 (=T20) of the tubular portion 130G (D1<T10). That is, the separation distance D1 is shorter than the wall thickness of the tubular portion 130G.

[0081] Also, in the auxiliary discharge space formation section CL, the separation distance D1 is shorter than the distance interval D10 between the outer surface of the tubular portion 130G and the inner surface of the outer tube 120 in the main discharge space S1. Therefore, the high-frequency voltage applied between the inner electrode and the outer electrode is dominated by the voltage applied between the separation distance D10 in the main discharge space S1 rather than between the separation distance D1 in the auxiliary discharge space S2, and power is supplied mainly to the main discharge rather than the auxiliary discharge. As a result, the lighting startability can be improved and the ultraviolet radiation efficiency can be enhanced. In the discharge vessel 115, the main discharge space S1 is formed as the dominant discharge space, and the auxiliary discharge space S2 is formed along the lamp axis C direction as a discharge space where a slight auxiliary discharge is formed.

[0082] On the other hand, in a cross section of the inner tube 130 taken along the electrode width direction (Y direction), the width (outer diameter) between the tubular portion 130G and the sealed portion 130F is approximately equal (W10 ≈ W11), and there is no substantial difference in outer diameter throughout the entire electrode-mounted section BL. Therefore, in the main discharge space S1, the distance D10 between the outer surface of the tubular portion 130G and the inner surface of the outer tube 120 along the electrode width direction (Y direction) and the distance D11 between the outer surface of the sealed portion 130F and the inner surface of the outer tube 120 along the electrode width direction (Y direction) are approximately constant throughout the entire electrode-facing section along the lamp axis C.

[0083] In the configuration of the inner tube 130 in which such an auxiliary discharge space S2 is formed inside the tube, both ends E1, E2 of the inner electrode 140 along the electrode width direction are close to each other, and the thickness is determined taking into consideration the decrease in dielectric strength and ultraviolet resistance when exposed to the main discharge generated in the main discharge space S1 and the auxiliary discharge generated in the auxiliary discharge space S2, thereby adjusting the susceptibility of the tubular portion 130G of the inner tube 130 to tear, so that tear G occurs in the tubular portion 130G of the inner tube 130 before the outer tube 120 is damaged (see Figure 4).

[0084] As a result, the auxiliary discharge space S2 and the main discharge space S1 are spatially connected, causing an abnormal discharge and resulting in changes in the irradiance, lamp voltage, or lamp current. As in the first embodiment, by detecting such changes in the lighting state and displaying a warning or forcibly stopping the lighting, damage to the outer tube 120 can be prevented.

[0085] In addition, the inner tube 130 may be configured so that the width (outer diameter) differs between the tubular portion 130G and the sealed portion 130F, with the outer diameter of the tubular portion 130G being relatively larger, thereby adjusting the ease with which the inner tube 130 breaks.

[0086] In the excimer lamp 100 of the second embodiment, the inner electrode 140 is configured to be exposed to the auxiliary discharge space S2, but it is also possible to configure the inner electrode 140 so that it is not exposed to the auxiliary discharge space S2. For example, as in the first embodiment, the inner tube in which the inner electrode is embedded can be covered with a dielectric such as quartz glass so that the auxiliary discharge space is formed, and the main discharge space can be formed between the dielectric and the outer tube.

[0087] Alternatively, an auxiliary discharge space can be formed near the tip of the inner tube 130 along the lamp axis C. Such a configuration is described in Patent Document 7. The tip of the inner electrode is not exposed to the auxiliary discharge space formed further toward the tip, but is separated from it by a predetermined distance along the lamp axis C. When the lamp is turned on at the end of its life or under overload, the inner tube breaks between the auxiliary discharge space and the inner electrode. As a result, impure gas leaks into the auxiliary discharge space, which deteriorates the starting ability of the lamp and ultimately makes it difficult to restart, and damage to the outer tube 120 can be prevented. [Explanation of symbols]

[0088] 10 Excimer Lamp 15 Discharge vessel 20 Outer tube 30 inner tube 32 Thin wall part (sealed tube) 34 Thick wall part (sealed tube) 40 inner electrode 50 outer electrode 70 Power supply rod (power supply line)

Claims

1. an inner tube covering a foil-shaped inner electrode disposed along the lamp axis; an outer tube having an outer electrode disposed on the outside thereof; The excimer lamp has a discharge space formed by welding the inner tube and the outer tube, When the excimer lamp is lit under overload or at the end of its life, Before the outer tube breaks, An excimer lamp characterized in that the inner tube generates a break that spatially connects the inside of the inner tube with the discharge space.

2. 2. The excimer lamp according to claim 1, wherein gas contained in a gap between the inner surface of the inner tube and the surface of the inner electrode flows out into the discharge space through the break.

3. 2. The excimer lamp according to claim 1, wherein at least a portion of said inner tube is more susceptible to a decrease in dielectric strength or embrittlement at a wavelength of ultraviolet light emitted therefrom than said outer tube.

4. 2. The excimer lamp according to claim 1, wherein at least a portion of said inner tube has a lower transmittance than said outer tube for the wavelength of the ultraviolet light emitted.

5. 2. The excimer lamp according to claim 1, wherein the foil-shaped inner electrode has a flat portion having a substantially constant thickness along the width direction between both widthwise ends of the inner electrode, and is tapered from both ends of the flat portion toward both widthwise ends of the inner electrode.

6. 2. The excimer lamp according to claim 1, wherein the inner tube has a cross-sectional shape that is flattened in the thickness direction of the inner electrode.

7. the inner tube has a thick-walled portion provided with a flange-shaped portion to be welded to the outer tube, and a thin-walled portion formed in the discharge space and having a thickness in the width direction of the foil electrode smaller than that of the thick-walled portion, 2. The excimer lamp according to claim 1, wherein the breakage of the inner tube occurs at the thin-walled portion.

8. the inner tube has, along the lamp axial direction, a sealed portion sealed to the inner electrode and a tubular portion surrounding an auxiliary discharge space formed between the sealed portions, 2. The excimer lamp of claim 1, wherein in the auxiliary discharge space, the widthwise end of the inner electrode and the inner surface of the tubular portion are spaced apart by a distance smaller than the thickness of the tubular portion along the electrode width direction, or are in contact with each other.

9. 2. The excimer lamp according to claim 1, wherein an auxiliary discharge space is formed inside or at the tip of the inner tube, where the inner electrode is not exposed.

10. an excimer lamp comprising an inner tube covering a foil-shaped inner electrode disposed along the lamp axis, and an outer tube having an outer electrode disposed on the outside, the inner tube and the outer tube being welded together to form a discharge space; a detection unit capable of detecting a change in the lighting state of the excimer lamp when a break occurs in the spatial connection between the inside of the inner tube and the discharge space; and a control unit that stops the excimer lamp from lighting or displays a warning message in response to a change in the lighting state of the excimer lamp detected by the detection unit.

11. an inner tube covering a foil-shaped inner electrode disposed along the lamp axis; an outer tube having an outer electrode disposed on the outside thereof; A lighting control method for an excimer lamp in which the inner tube and the outer tube are welded together to form a discharge space, comprising: A method for controlling the lighting of an excimer lamp, characterized in that an abnormal lighting state is detected by a change in the lighting state of the excimer lamp when a break occurs in the spatial connection between the inside of the inner tube and the discharge space.

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