Excimer lamp

Abstract

The invention provides an excimer lamp which is good in lighting starting performance and capable of suppressing uneven discharge. In the excimer lamp (10), a dielectric (50) covering a foil electrode (30) is welded to a discharge tube (20), and a discharge space (S) is formed between the dielectric (50) and the discharge tube (20). Furthermore, for the dielectric medium (50), a small-diameter part (52) having a relatively small distance, i.e., a relatively small dimension, from the lamp shaft (C) to the outer surface is relatively provided on the tip side of the dielectric medium (50), and a large-diameter part (54) having a relatively larger distance, i.e., a relatively larger dimension, from the lamp shaft (C) to the outer surface than the small-diameter part (52) is provided.

Description

Technical Field

[0001] The present invention relates to an excimer lamp, and in particular to the lighting start-up performance of an excimer lamp. Background Art

[0002] In a double-tube excimer lamp, a light-emitting portion is formed by two coaxial cylindrical tubes extending in the axial direction, and a discharge gas is sealed in a discharge space formed between the inner tube and the outer tube. Furthermore, by applying a high-frequency voltage between an electrode (inner electrode) covered by the inner tube as a dielectric and an electrode (outer electrode) located on the outer surface of the outer tube, the discharge generated in the discharge space radiates excimer light such as ultraviolet rays.

[0003] Excimer lamps are known in which the discharge distance (discharge gap) is adjusted in order to improve the lighting and starting properties of such excimer lamps (see Patent Document 1). Therefore, a narrow portion (convex portion) of the discharge space that is less than the average discharge gap is provided on a portion of the inner surface of the outer tube of the discharge space. Under a relatively low applied voltage, a discharge is generated in the narrow portion, and this discharge serves as a trigger to generate a discharge in the entire discharge space.

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 8-31387

[0005] In the case of a double-tube excimer lamp in which the discharge distance (discharge gap) is locally narrowed in the discharge space, the discharge is uneven due to the uneven electric field intensity distribution, making it difficult to achieve uniform illumination. In particular, in a small excimer lamp (for example, the outer diameter of the discharge vessel is several mm to several tens of mm), uniform illumination is required for efficient ultraviolet irradiation, but uneven illumination is easily caused by uneven discharge. Summary of the invention

[0006] Therefore, even in a small excimer lamp or the like, it is required to have good lighting startability and suppress uneven discharge.

[0007] An excimer lamp as one embodiment of the present invention comprises: a tubular discharge vessel; an outer electrode disposed on the outer surface side of the discharge vessel; and an inner electrode covered by a dielectric. For example, the outer electrode may be disposed on the outer surface of the discharge vessel, or may be disposed with a predetermined gap. The structure of the "tubular dielectric" herein also includes a dielectric in a columnar shape in which the inner electrode is buried, regardless of whether there is a hollow portion. For example, a part of the dielectric may be welded to the discharge vessel to form a double-tube type discharge lamp.

[0008] The dielectric has a relatively large diameter portion (hereinafter referred to as a large diameter portion) and a relatively small diameter portion (hereinafter referred to as a small diameter portion) in a range along the lamp axis where the inner electrode and the outer electrode are opposed to each other at a substantially constant inter-electrode distance (hereinafter referred to as an opposing range). The small diameter portion and the large diameter portion have different discharge distances from the discharge vessel, and the distance from the small diameter portion to the discharge vessel, i.e., the discharge distance, is longer than the discharge distance from the large diameter portion to the discharge vessel. The inter-electrode distance and the discharge distance represent distances along a predetermined lamp diameter direction.

[0009] The small diameter portion and the large diameter portion can be defined as continuous dielectric portions with a substantially constant diameter in the direction of the prescribed lamp diameter. In the case where the inner electrode is a foil-shaped electrode, the small diameter portion and the large diameter portion can be formed based on the radial direction along the electrode width direction or the electrode thickness direction. For example, the small diameter portion and the large diameter portion can be formed so that the width and thickness of the small diameter portion along the electrode thickness direction are smaller than the width and thickness of the large diameter portion along the electrode thickness direction.

[0010] The small diameter part and the large diameter part of the dielectric can be formed at various positions. For example, they can be formed to include the front end of the inner electrode. In addition, the large diameter part can be formed to include the central part of the discharge container and occupy most of the above-mentioned opposing range. Not only can the large diameter part and the small diameter part be configured to have a substantially constant diameter as a whole, but also the diameters of the small diameter part and the large diameter part can be configured to be different from each other within a range that can suppress uneven discharge. For example, when the small diameter part is formed near the front end of the dielectric, the diameter of the most front end side can be made relatively large.

[0011] The dielectric may include a portion connecting the small diameter portion and the large diameter portion (referred to as a different diameter portion here). For example, the different diameter portion may be a tapered shape having a curved surface that continuously connects the outer peripheral surfaces of the small diameter portion and the large diameter portion.

[0012] The foil electrode may have various shapes. For example, the foil electrode may have a flat portion having a substantially constant thickness in the width direction between both ends of the inner electrode in the width direction, and may have a wedge shape from both ends of the flat portion toward both ends of the inner electrode in the width direction.

[0013] The outer electrode may have various shapes, for example, the outer electrode may be provided with a spiral portion obtained by spirally winding a conductive wire around the discharge container, and the dielectric may be formed with a small diameter portion so that at least a part of the small diameter portion faces the spiral portion.

[0014] Furthermore, the outer electrode may be provided with a cylindrical member electrically connected to the spiral portion, the cylindrical member being obtained by winding a conductive plate in a cylindrical shape around the discharge container. Furthermore, the dielectric may be formed with a small diameter portion so that at least a part of the small diameter portion faces the cylindrical member.

[0015] According to the present invention, it is possible to provide an excimer lamp which has good lighting startability and suppresses non-uniform discharge. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic cross-sectional view of an excimer lamp along the electrode width direction.

[0017] Figure 2 This is a schematic cross-sectional view of an excimer lamp along the electrode thickness direction.

[0018] Figure 3 It is along Figure 1 Cross-sectional view along line III-III.

[0019] Figure 4 It is along Figure 1 A cross-sectional view taken along line IV-IV.

[0020] Figure 5 is an enlarged cross-sectional view of the foil electrode.

[0021] Figure 6 is with Figure 4 Magnified cross-sectional view of the corresponding foil electrode and dielectric.

[0022] Description of symbols

[0023] 10: Excimer lamp; 20: discharge tube (outer tube); 30: foil electrode (inner electrode); 40: outer electrode; 50: dielectric (inner tube); 52: small diameter portion; 53: different diameter portion; 54: large diameter portion. DETAILED DESCRIPTION

[0024] Hereinafter, the excimer lamp according to the present embodiment will be described with reference to the drawings.

[0025] Figure 1 This is a schematic cross-sectional view of an excimer lamp along the electrode width direction. Figure 2 This is a schematic cross-sectional view of an excimer lamp along the electrode thickness direction. Figure 3 It is along Figure 1 Cross-sectional view along line III-III. Figure 4 It is along Figure 1 A cross-sectional view taken along line IV-IV.

[0026] The excimer lamp 10 has a tubular discharge tube (discharge vessel) 20 made of a dielectric material such as quartz glass, and is here formed into a discharge tube having a circular cross section along the tube diameter (lamp diameter) direction. A rare gas such as xenon or a mixed gas thereof is sealed in the discharge tube 20 as a discharge gas.

[0027] Inside the discharge tube 20, a foil electrode (hereinafter also referred to as an inner electrode) 30 is arranged in a strip shape extending along the tube axis (lamp axis) C. The foil electrode 30 is covered by a columnar dielectric 50 made of quartz glass or the like, and is not exposed to the discharge space S, but is buried in the dielectric 50. That is, the foil electrode 30 is sealed (closed) to the dielectric 50 in a sealed state. A power supply line (power supply rod) 70 is connected to the end of the foil electrode 30 along the lamp axis C, and is connected to a power supply unit (not shown) provided outside.

[0028] The foil electrode 30 is coaxially arranged in a state where the center position of the foil electrode 30 in the width direction and the thickness direction coincides with the center position of the dielectric 50. Furthermore, the dielectric 50 is coaxially arranged with the discharge tube 20. Therefore, the foil electrode 30 is arranged at a position coaxial with the discharge tube 20 and at a position symmetrical with respect to the lamp axis C. Figure 2 In the diagram, the width direction of the foil electrode 30 is defined as the Y direction, and the direction perpendicular thereto (thickness direction) is defined as the X direction.

[0029] Here, the outer electrode 40 disposed on the outer surface 20S of the discharge tube 20 is a linear electrode portion (conductive wire) made of conductive metal wound along the outer surface of the discharge tube 20, and is arranged to be spirally wound along the lamp axis C and separated at predetermined intervals.

[0030] The outer electrode 40 is provided with such a spiral electrode portion (hereinafter referred to as the spiral portion 42) and conductive members (hereinafter referred to as the cylindrical members) 45A and 45B electrically connected to both ends 42T of the spiral portion 42. Here, the cylindrical members 45A and 45B are formed by winding a strip-shaped conductive plate covering a part of the outer surface 20S of the discharge tube 20 around the lamp axis C into a cylindrical shape. Here, the arrangement section L of the outer electrode 40 along the lamp axis C direction (hereinafter referred to as the outer electrode arrangement section) corresponds to the length of the inner electrode 30, and the entire range of the inner electrode 30 in the lamp axis C direction is opposite to the outer electrode 40 along the lamp diameter direction.

[0031] The excimer lamp 10 is formed as a double-tube type discharge lamp by fusing the enlarged diameter portion (hereinafter referred to as the welding portion) 56 of the dielectric 50 protruding in the radial direction in a flange shape with the discharge tube 20, and the dielectric 50 and the discharge tube 20 correspond to the inner tube and the outer tube of the double-tube type discharge lamp, respectively. A discharge space S in which the discharge gas is sealed is formed between the dielectric 50 and the discharge tube 20. The power supply line 70 is covered by a portion (extension portion) 57 of the dielectric 50 that is formed to extend from the welding portion 56 to the outside of the discharge tube 20.

[0032] The cross-sectional shape of the foil electrode 30 is substantially constant along the lamp axis C, and the distance between the inner surface of the outer electrode 40 corresponding to the outer surface of the discharge vessel 20 and the outer surface of the inner electrode 30 (hereinafter referred to as the inter-electrode distance) in a specified radial cross section within the outer electrode arrangement interval L of the foil electrode 30 is substantially equal regardless of the cross-sectional position.

[0033] On the one hand, the dielectric 50 has a flat appearance as described later, and on the other hand, has an appearance whose cross-sectional shape varies along the lamp axis C. Specifically, the dielectric 50 has a columnar portion (hereinafter referred to as a large diameter portion) 54 that occupies most of the arrangement interval of the inner electrode along the lamp axis C direction; and a columnar portion (hereinafter referred to as a small diameter portion) 52 that is formed at a position closer to the front end side than the large diameter portion 54, and the dielectric 50 has a front end portion (hereinafter referred to as a front end portion) 51 formed at a position closer to the front end side than the small diameter portion and deviated from the arrangement interval of the inner electrode. In addition, the dielectric 50 has a portion (hereinafter referred to as a different diameter portion) 53 that continuously connects the small diameter portion 52 and the large diameter portion 54.

[0034] The large diameter portion 54 is opposite to the spiral portion 42 of the outer electrode 40, and the cross-sectional shape of the large diameter portion 54 is substantially constant in the range of the section H along the lamp axis C. The cross-sectional shape of the small diameter portion 52 is also substantially constant in the range of the section J along the lamp axis C. Figure 3 , Figure 4 As shown, the cross-sectional shapes of the small diameter portion 52 and the large diameter portion 54 are different in size, but have the same shape, and are similar to each other. The front end portion 51 is reduced in diameter so as to become thinner toward the front end 50T of the dielectric 50.

[0035] The different-diameter portion 53 is a portion that continuously connects the large-diameter portion 54 and the small-diameter portion 52. The diameter is reduced from the large-diameter portion 54 toward the small-diameter portion 52 to form a curved surface that is continuous with the outer peripheral surfaces of the large-diameter portion 54 and the small-diameter portion 52. Here, it is a tapered shape with a substantially constant inclination angle in a radial cross section. Since the arrangement interval of the inner electrode 30 along the lamp axis C direction is a length corresponding to the outer electrode arrangement interval L, both the small-diameter portion 52 and the different-diameter portion 53 are set at positions facing the outer electrode 40.

[0036] A protruding portion (hereinafter referred to as an exhaust pipe) 22 is formed at one end portion 20T of the discharge tube 20. The exhaust pipe 22 is a portion formed during the lamp manufacturing process. Here, the end portion 20T of the discharge tube 20 is formed by reducing the diameter of the front end side of the glass tube as a raw material by heat deformation, and a tube smaller than the glass tube is welded, thereby integrally forming the exhaust pipe 22.

[0037] Here, the polarities of the foil electrode 30 and the outer electrode 40 are set to be an anode and a cathode. In addition, a high frequency (for example, a range of several kHz to several tens of MHz) and a high voltage (for example, a range of several kV to several tens of kV) are supplied to the excimer lamp 10 via the power supply line 70. Excimer light, that is, ultraviolet light (for example, 172 nm ultraviolet light) is radiated by discharge generated by applying the high frequency voltage.

[0038] The excimer lamp 10 of this embodiment is configured as a small excimer lamp. For example, the axial length (luminous length) of the discharge generated in the discharge tube 20 can be set in the range of 20 mm to 400 mm. In addition, the outer diameter of the discharge tube 20 can be set in the range of 5 mm to 30 mm, preferably in the range of 8 mm to 25 mm.

[0039] In consideration of suppressing the degradation of the discharge tube due to the excimer light and suppressing the increase of the discharge start voltage, the wall thickness of the discharge tube 20 can be set within a range of, for example, 0.8 mm to 1.5 mm.

[0040] In order to prevent insufficient illumination due to the narrowing of the discharge space and the instability of the discharge due to the expansion of the discharge distance, the discharge distance in the large diameter portion 54, i.e., the distance between the outer surface of the dielectric 50 and the inner surface of the discharge tube 20 along the lamp diameter direction, can be set in the range of 2 mm to 12 mm, preferably in the range of 3 mm to 10 mm.

[0041] The foil electrode 30 is formed as an extremely thin strip electrode whose thickness is suppressed relative to the electrode width. Here, the thickness of the foil electrode 30 is set to be less than 1 / 30, preferably less than 1 / 50, and more preferably less than 1 / 100 relative to the electrode width. Figure 2 to Figure 4 In FIGS. 6 and 7 , the thickness of the foil electrode 30 is exaggerated.

[0042] For example, the thickness of the foil electrode 30 may be set in the range of 20 μm to 50 μm in consideration of current capacity, ease of manufacturing, and prevention of peeling from the dielectric 50. On the other hand, the width of the foil electrode 30 may be set in the range of 1.2 mm to 10 mm in consideration of current capacity, ease of manufacturing, and prevention of interruption of discharge light due to enlarged electrode area.

[0043] The electrode material of the foil electrode 30 can be formed of a metal or alloy with high conductivity. Also, it can be made of a material that is easy to be polished by electric field. Here, molybdenum or an alloy containing molybdenum is used.

[0044] Here, the dielectric 50 is made of a dielectric material (SiO 2 The thickness of the dielectric 50 can be set in the range of 0.1 mm to 2 mm, for example, in consideration of maintaining the limit of insulation and preventing the increase of the discharge start voltage.

[0045] Figure 5 It is an enlarged cross-sectional view of the foil electrode 30 .

[0046] As described above, the foil electrode 30 is an electrode formed to be very thin relative to the width w, and the thickness t of the foil electrode is suppressed to be less than 1 / 30 relative to the width w. The foil electrode 30 has a flat portion 32 with a 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.

[0047] Here, the wedge-shaped portions 34A and 34B of the foil electrode 30 are wedge-shaped and sharp until the edge. 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 in the width direction of the flat portion 32 to the ends E1 and E2 in the width direction. Moreover, the ends E1 and E2 in the width direction of the foil electrode 30 are not rounded and have thickness, but the ends E1 and E2 in the width direction of the foil electrode 30 are sharpened, and the thickness increases at a constant inclination angle toward the ends 32A and 32B in the width direction of the flat portion 32.

[0048] For example, the angles θ1 and θ2 (angle θ of the edge E) at the two ends E1 and E2 in the width direction of the foil electrode 30 can be set within a range of 2° to 15°, preferably within a range of 10° or less, by considering the difficulty of peeling caused by the gap generated in the boundary portion with the covered dielectric, 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. In addition, the inclination angle of the cross section of the flat portion 32 can be set within a range of less than 2°. The angle θ can be set according to the following angle: when the cross section near the range of about 100 μm away from the edge E of the foil electrode 30 is magnified and observed, the thickness increases from the edge E of the foil electrode toward the flat portion 32. As a result, in the foil electrode 30, the edge-shaped edge E is formed on the entire electrode along the tube axis C direction.

[0049] The flat portion 32 is formed so that the center (central portion) in the width direction coincides with 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 less than 0.2 with respect to the electrode width w (d1 / w) of the foil electrode 30. Here, the inclination angle θ of the cross section from the width direction ends of the wedge-shaped portions 34A and 34B toward the width direction ends 32A and 32B of the flat portion 32 is formed to be constant.

[0050] The flat portion 32 is formed to have a thickness that accounts for 70% or more of the maximum thickness T of the foil electrode 30. For example, the length d between the widthwise ends 32A and 32B of the flat portion 32 is set to be 0.6 or more relative to the electrode width w of the foil electrode 30 (d / w).

[0051] With such an electrode shape, it is possible to provide a small excimer lamp 10 that improves the adhesion between the foil electrode 30 and the dielectric 50 to suppress separation and has excellent lighting startability.

[0052] First, the edge E of the foil electrode 30 extending along the lamp axis C is sharp, which generates electric field concentration. As a result, discharge light emission can be performed while suppressing the discharge start voltage to a low level. In addition, since the wedge-shaped portions 34A and 34B are wedge-shaped with sharp edges, 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 likely to be generated at the boundary portion with the covered dielectric 50, and peeling is not likely to occur.

[0053] Furthermore, the foil electrode 30 is coaxially arranged with the dielectric 50, the discharge tube 20, and the outer electrode 40, and the distance between the edges E of the foil electrode 30 on both sides and the inner surface of the outer electrode 40 corresponding to the outer surface of the discharge tube 20 in a predetermined radial cross section within the outer electrode arrangement section L, i.e., the inter-electrode distance, is equal, and the distance between the outer surface of the large diameter portion 54 of the dielectric 50 and the inner surface of the discharge tube 20, i.e., the discharge distance, is equal. Therefore, light can be radiated from the discharge tube 20 in a well-balanced manner as a whole.

[0054] On the other hand, by forming the flat portion 32 on the foil electrode 30, the adhesion between the foil electrode 30 and the dielectric 50 can be improved and peeling can be suppressed. That is, by providing the flat portion 32 with a 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.

[0055] As a result, the thermal expansion of the foil electrode 30 in the thickness direction (X direction) and the width direction (Y direction) can be suppressed. That is, it is not necessary to make the foil electrode 30 particularly long in the width direction in order to ensure a larger cross-sectional area, and the increase of thermal expansion along 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 along the thickness direction can be prevented.

[0056] Furthermore, by forming the wedge-shaped portions 34A and 34B with a constant inclination angle in the cross section, the surfaces of the wedge-shaped portions 34A and 34B can be easily polished by electrolytic polishing, etc. This can suppress the occurrence of peeling at the boundary portion with the dielectric 50 .

[0057] The foil electrode 30 may have a knife-edge shape with a cross section that smoothly slopes from the center toward both ends of the electrode along the electrode width direction and may be a foil electrode without a flat portion.

[0058] Figure 6 is with Figure 4 An enlarged cross-sectional view of the foil electrode 30 and the dielectric 50 covering the foil electrode 30 at the corresponding large diameter portion 54 .

[0059] The dielectric 50 of this embodiment has Figure 5 The configuration and shape of the foil electrode 30 shown match the cross-sectional shape of, and reduce the difference in, the distance from any surface of the foil electrode 30 to the outer surface 50S of the dielectric 50 (to the thickness of the foil electrode).

[0060] The dielectric 50 is a flat material having a substantially constant thickness along the width direction (Y direction) of the foil electrode 30 (see Figure 3 , Figure 4 , Figure 6 ), and is formed to be flat in the entire range of the section where the foil electrode 30 is arranged. It can also be said that the dielectric 50 is composed of a quadrangular columnar portion having a substantially constant thickness along the width direction (Y direction) of the foil electrode 30 and semi-cylindrical portions integrally formed at both ends of the quadrangular columnar portion.

[0061] The cross-sectional shape of the dielectric 50 is long oval or long circle. Figure 5 The configuration and shape of the foil electrode 30 shown match the cross-sectional shape of, and reduce the difference in, the distance from any surface of the foil electrode 30 to the outer surface 50S of the dielectric 50 (to the thickness of the foil electrode).

[0062] Here, the section M0 is defined as the central section (planar section) 50M0, and the section M0 has a planar (flat surface) outer surface 50S1 of a quadrangular columnar section substantially parallel to the flat section 32 of the foil electrode 30. The section M1 is defined as the two end sections (curved section sections) 50M1, and the section M1 has a curved (semi-elliptical) outer surface 50S2 of a semi-cylindrical section convex from both ends of the central section 50M0 toward the outside in the electrode width direction (Y direction).

[0063] The quadrangular columnar portion is a columnar body whose cross section along the lamp diameter direction is approximately a quadrilateral such as a square or a rectangle, and whose cross-sectional shape is the same along the lamp axis direction which is approximately parallel to the flat portion 32 of the foil electrode. The quadrangular columnar portion is a pair, and covers the vicinity of the center portion in the width direction of the foil electrode from both sides in the electrode thickness direction so that the thickness T2 is approximately constant.

[0064] The semi-cylindrical portion is a semi-cylindrical body whose cross section along the lamp diameter direction is approximately a semicircular shape such as a semi-ellipse, and whose cross-sectional shape is the same along the lamp axis direction. The semi-cylindrical portion is a pair, and covers the vicinity of the edge in the width direction of the foil electrode from both sides in the electrode width direction in a manner of surrounding the vicinity of the edge with the vicinity of the edge as the center, with a thickness T1 in the electrode width direction and a thickness T2 in the electrode thickness direction.

[0065] The boundary between the central portion (flat portion) 50M0 and the two end portions (curved portion) 50M1 of the dielectric 50 is located closer to the center (tube axis C) of the width direction of the foil electrode 30 than the two ends E1 and E2 of the foil electrode 30, preferably the two ends 32A and 32B of the flat portion 32 in the width direction. That is, the length of the section M0 along the width direction (Y direction) of the foil electrode is set to be smaller than w, preferably smaller than d. In addition, the length of the section M1 is formed to be larger than T1.

[0066] Figure 3 The small diameter portion 52 shown also has the same cross-sectional shape, and is similar to the cross-sectional shape of the large diameter portion 54 (same shape but different size). The width W20 of the dielectric 50 along the electrode thickness direction (X direction) is smaller than the width W10 along the electrode width direction (Y direction). In addition, the thickness T20 of the dielectric 50 along the electrode thickness direction (X direction) is smaller than the thickness T10 along the electrode width direction (Y direction).

[0067] The thickness T20 indicates the distance between the flat portion 32 of the foil electrode 30 at the small diameter portion 52 and the outer surface 50S1 of the dielectric 50 along the electrode thickness direction (X direction), and the thickness T10 indicates the distance between the two ends E1 and E2 (E) of the foil electrode 30 at the small diameter portion 52 and the outer surface 50S2 of the dielectric 50 along the electrode width direction (Y direction). The cross-sectional shape of the different diameter portion 53 is also similar to that of the large diameter portion 54, and similarly to the small diameter portion 52, the width along the electrode width direction (Y direction) and the thickness along the electrode thickness direction (X direction) have the same characteristics.

[0068] Here, the cross-sectional shape of the discharge tube 20 along the lamp axis C is substantially constant in the outer electrode arrangement section L. Due to the structure of the dielectric 50 provided with the small diameter portion 52 and the large diameter portion 54, the discharge distance D10 along the electrode width direction (Y direction) of the radial cross section of the small diameter portion 52 is longer than the discharge distance D11 along the electrode width direction (Y direction) of the radial cross section of the large diameter portion 54 (refer to Figure 1 ). In addition, the discharge distance D20 of the small diameter portion 52 along the electrode thickness direction (X direction) is longer than the discharge distance D21 of the large diameter portion 54 along the electrode thickness direction (X direction) (refer to Figure 2 ).

[0069] Moreover, since the small diameter portion 52 and the large diameter portion 54 are in a similar relationship, the discharge distance of the small diameter portion 52 is longer than the corresponding discharge distance of the large diameter portion 54 not only in the electrode width direction (Y direction) and the electrode thickness direction (X direction), but also in any direction in the radial cross section.

[0070] On the other hand, since the cross-sectional shape of the foil electrode 30 along the lamp axis C is substantially constant, the distances between the two ends E1 and E2 of the foil electrode 30 and the inner surface 20M of the discharge tube 20 and the distances between the flat portion 32 of the foil electrode 30 and the inner surface 20M of the discharge tube 20 are substantially equal between the small diameter portion 52, the different diameter portion 53, and the large diameter portion 54. Therefore, the discharge distances between the small diameter portion 52 and the large diameter portion 54 are different, so that uneven discharge can be suppressed and illumination can be made uniform.

[0071] That is, for the dielectric 50, the thickness T10 (see Figure 3 ) is thinner than the wall thickness T1 of the large diameter portion 54 along the electrode width direction (Y direction), so it is easy to generate discharge in the small diameter portion 52 through electric field concentration, which can improve the lighting start-up performance.

[0072] On the other hand, the discharge distance D10 in the electrode width direction (Y direction), the discharge distance D20 in the electrode thickness direction (X direction) and other discharge distances of the small diameter portion 52 are longer than the discharge distances (including D11 and D21) in the corresponding directions of the large diameter portion 54. Therefore, it is possible to suppress the uneven discharge state in which the electric field intensity along the lamp axis C in the small diameter portion 52 increases after lighting startup, and achieve uniform illumination during lamp lighting.

[0073] Furthermore, a different diameter portion 53 is provided between the small diameter portion 52 and the large diameter portion 54 to continuously and smoothly connect the outer peripheral surfaces of the small diameter portion 52 and the large diameter portion 54. Thus, it is possible to suppress uneven discharge between the small diameter portion 52 and the large diameter portion 54 and cracks in the dielectric 50. In particular, since the different diameter portion 53 is a tapered shape with a constant cross-sectional inclination angle, it is possible to suppress uneven distribution of electric field intensity along the lamp axis C, and it is easy to prevent the dielectric 50 covering the foil electrode 30 from peeling off.

[0074] Thus, in the excimer lamp 10 of the present embodiment, the dielectric 50 covering the foil electrode 30 is welded to the discharge tube 20, and a discharge space S is formed between the dielectric 50 and the discharge tube 20. In addition, the small diameter portion 52 of the dielectric 50, which is relatively small in distance from the lamp axis C to the outer surface, is provided at the front end side of the dielectric 50, and the large diameter portion 54 is provided, which is relatively large in distance (size) from the lamp axis C to the outer surface compared with the small diameter portion 52. In addition, the dielectric 50 may be provided in an external shape other than a flat shape or an elliptical shape with an elliptical or oblong cross section.

[0075] In the present embodiment, the dielectric 50 is configured to extend along the lamp axis C in a manner corresponding to the outer electrode arrangement section L, and the front end portion 51 including the front end 50T of the dielectric 50 is offset from the outer electrode arrangement section L (cylindrical member 45A) to the end portion 20T of the discharge tube 20 along the lamp axis C. However, the front end portion 51 may be adjusted to enter the center (spiral portion 42) side of the outer electrode 40 in the outer electrode arrangement section L along the lamp axis C and face the cylindrical member 45A. In addition, the inner electrode 30 may be configured to extend toward the end portion 20T of the discharge tube 20 along the lamp axis C beyond the outer electrode arrangement section L (cylindrical member 45A), and the different diameter portion 53 may be adjusted to face the cylindrical member 45A. In addition, instead of the small diameter portion having a substantially constant cross-sectional shape, a small diameter portion having a tapered shape that decreases in diameter from the large diameter portion 54 toward the front end portion 51 in the range of the section J along the lamp axis C may be provided. In this way, at least a part of the small diameter portion 52 covering the inner electrode 30 may be included in the outer electrode arrangement section L.

[0076] Such adjustment of the arrangement position of the small diameter portion 52 of the dielectric 50 and the outer electrode 40 can meet the requirements of good lighting start-up, suppression of uneven discharge, and uniform illumination in a small excimer lamp, etc. In addition, regarding the outer electrode 40, its electrode structure can adopt the structure provided with the spiral portion 42 and the cylindrical parts 45A and 45B as described above, or other structures.

Claims

1. An excimer lamp, characterized in that: The excimer lamp has: Tubular discharge vessel; an outer electrode disposed on an outer surface of the discharge vessel; and The inner electrode, which is covered by a tubular dielectric, The dielectric has a large diameter portion and a small diameter portion in a range along the lamp axis where the inner electrode and the outer electrode face each other at a substantially constant inter-electrode distance. A discharge distance between the small diameter portion and the discharge container is longer than a discharge distance between the large diameter portion and the discharge container.

2. The excimer lamp according to claim 1, wherein: The inner electrode is a foil electrode, The width and thickness of the small diameter portion along the electrode width direction are smaller than the width and thickness of the large diameter portion along the electrode width direction.

3. The excimer lamp according to claim 1, wherein: The inner electrode is a foil electrode, The width and thickness of the small diameter portion along the electrode thickness direction are smaller than the width and thickness of the large diameter portion along the electrode thickness direction.

4. The excimer lamp according to claim 1, wherein: The dielectric body includes a different diameter portion between the small diameter portion and the large diameter portion.

5. The excimer lamp according to claim 4, wherein: The different-diameter portion has a tapered shape having a curved surface that continuously connects the small-diameter portion and the outer peripheral surface of the large-diameter portion.

6. The excimer lamp according to claim 1, wherein: The dielectric is flat. The radial cross-sectional shape of the small diameter portion is similar to the radial cross-sectional shape of the large diameter portion.

7. The excimer lamp according to claim 1, wherein: The inner electrode is a foil electrode, A flat portion having a substantially constant thickness in the width direction is provided between both ends of the inner electrode in the width direction, and a wedge shape is formed from both ends of the flat portion toward both ends of the inner electrode in the width direction.

8. The excimer lamp according to any one of claims 1 to 7, wherein: The outer electrode has a spiral portion formed by spirally winding a conductive wire around the discharge container. At least a portion of the small diameter portion faces the spiral portion.

9. The excimer lamp according to claim 8, wherein: The excimer lamp further comprises a cylindrical portion obtained by winding a conductive plate in a cylindrical shape around the discharge container, the cylindrical portion being electrically connected to the spiral portion. At least a portion of the small diameter portion faces the cylindrical portion.

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