Excimer lamp

Abstract

To provide an excimer lamp having good lighting start-up performance and suppressing uneven discharge.SOLUTION: There is provided an excimer lamp 10 in which 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 a discharge container 20. The dielectric 50 is provided with: a small diameter part 52 with relatively small in a distance from a lamp axis C to an external surface, i.e. relatively small in size, on a tip side of the dielectric 50; and a large diameter part 54 with the distance (size) from a lamp axis C to an external surface relatively larger than that of the small diameter part 52.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In a double-tube excimer lamp, the light-emitting section is made up of two coaxial cylindrical tubes extending in the axial direction, and a discharge gas is sealed in the discharge space formed between the inner tube and the outer tube. By applying a high-frequency voltage between an electrode (inner electrode) covering the dielectric inner tube and an electrode (outer electrode) on the outer surface of the outer tube, excimer light such as ultraviolet rays is radiated from the discharge generated in the discharge space.

[0003] In order to improve the lighting startability of such excimer lamps, an excimer lamp with an adjusted discharge distance (discharge gap) is known (see Patent Document 1). In this excimer lamp, a narrow portion (convex portion) that is less than the average discharge gap of the discharge space is provided on a part of the inner surface of the outer tube of the discharge space. A discharge occurs in the narrow portion at a relatively low applied voltage, and this discharge serves as a trigger to generate a discharge throughout the entire discharge space. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-31387 Summary of the Invention [Problem to be solved by the invention]

[0005] In the case of a double-tube excimer lamp in which the discharge distance (discharge gap) is partially narrowed in the discharge space, the uneven distribution of electric field strength causes uneven discharge, making it difficult to achieve uniform illuminance. In particular, in small excimer lamps (e.g., the outer diameter of the discharge vessel is several mm to several tens of mm), uniform illuminance is required for highly efficient ultraviolet irradiation, but uneven discharge easily results in uneven illuminance.

[0006] Therefore, even in small excimer lamps and the like, there is a demand for good lighting startability and suppression of biased discharge. [Means for solving the problem]

[0007] An excimer lamp according to one aspect of the present invention comprises a tubular discharge vessel, an outer electrode provided on the outer surface side of the discharge vessel, and an inner electrode covered with a dielectric. For example, the outer electrode can be disposed on the outer surface of the discharge vessel, and can also be disposed with a predetermined gap therebetween. The configuration of the "tubular dielectric" here includes a columnar dielectric in which the dielectric is embedded, and does not matter whether it has a hollow portion or not. For example, the dielectric can be configured so that a part of it is fused to the discharge vessel to form a double-tube 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 face each other with 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 between the small diameter portion and the discharge vessel, i.e., the discharge distance, is longer than the discharge distance between the large diameter portion and the discharge vessel. However, the inter-electrode distance and the discharge distance represent distances along a predetermined lamp radial direction.

[0009] The small diameter portion and the large diameter portion can be defined as continuous dielectric portions having a substantially constant diameter in a predetermined lamp radial direction. When the inner electrode is a foil 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 locations where the small diameter portion and the large diameter portion of the dielectric are formed may vary, and for example, they may be formed to include the tip portion of the inner electrode. The large diameter portion may be formed to occupy most of the opposing range, including the center of the discharge vessel. The large diameter portion and the small diameter portion may each be configured to have a substantially constant diameter overall, or may be configured to have different diameters from each other within a range that can suppress biased discharge. For example, when the small diameter portion is formed near the tip portion of the dielectric, the diameter closest to the tip can be made relatively large.

[0011] The dielectric may be provided with a portion (herein referred to as a different diameter portion) that connects the small diameter portion and the large diameter portion. For example, the different diameter portion may be tapered with a curved surface that continuously connects the outer circumferential 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 along the width direction between both ends of the inner electrode along the width direction, and may be wedge-shaped from both ends of the flat portion to both ends of the inner electrode along the width direction.

[0013] The shape of the outer electrode may vary, for example, the outer electrode may be provided with a spiral portion in which a conductive wire is wound in a spiral shape around the discharge vessel, and a small diameter portion may be formed with respect to the dielectric such that at least a part of the small diameter portion faces the spiral portion.

[0014] The outer electrode is electrically connected to the spiral portion, and a cylindrical member formed by winding a conductive plate cylindrically around the discharge vessel can be provided. A small diameter portion can be formed in the dielectric such that at least a part of the small diameter portion faces the cylindrical member. Effect of the Invention

[0015] According to the present invention, it is possible to provide an excimer lamp that has good lighting startability and suppresses biased discharge. [Brief description of the drawings]

[0016] [Figure 1] 2 is a schematic cross-sectional view taken along the electrode width direction of the excimer lamp. [Diagram 2] 2 is a schematic cross-sectional view of an excimer lamp taken along the electrode thickness direction. [Diagram 3] FIG. 2 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Diagram 5] FIG. 2 is an enlarged cross-sectional view of a foil electrode. [Figure 6] 5 is an enlarged cross-sectional view of the foil electrode and the dielectric according to FIG. 4; FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an excimer lamp according to this embodiment will be described with reference to the drawings.

[0018] Fig. 1 is a schematic cross-sectional view along the electrode width direction of an excimer lamp. Fig. 2 is a schematic cross-sectional view along the electrode thickness direction of an excimer lamp. Fig. 3 is a cross-sectional view along III-III in Fig. 1. Fig. 4 is a cross-sectional view along IV-IV in Fig. 1.

[0019] The excimer lamp 10 includes a tubular discharge tube (discharge vessel) 20 made of a dielectric material such as quartz glass, and is configured here as a discharge tube with a circular cross section along the tube diameter (lamp diameter) direction. A rare gas such as xenon gas or a mixture of these gases is enclosed inside the discharge tube 20 as a discharge gas.

[0020] A foil electrode (hereinafter also referred to as an inner electrode) 30 is disposed inside the discharge tube 20, extending in a strip shape along the tube axis (lamp axis) C. The foil electrode 30 is covered with a columnar dielectric 50 made of quartz glass or the like, and is embedded within the dielectric 50 without being exposed to the discharge space S. In other words, the foil electrode 30 is sealed (adhered) to the dielectric 50. A power supply line (power supply rod) 70 is connected to an end of the foil electrode 30 along the lamp axis C, and is also connected to an externally installed power supply unit (not shown).

[0021] The foil electrode 30 is arranged coaxially with its center position in the width direction and thickness direction aligned with the center position of the dielectric 50. Furthermore, the dielectric 50 is arranged coaxially with the discharge tube 20. Therefore, the foil electrode 30 is arranged coaxially with the discharge tube 20, and arranged symmetrically with respect to the lamp axis C. In Fig. 2, 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.

[0022] The outer electrode 40 arranged on the outer surface 20S of the discharge tube 20 is configured by winding a linear electrode portion (conductive wire) made of a conductive metal along the outer surface of the discharge tube 20, and is wound in a spiral shape along the lamp axis C and arranged at a predetermined interval.

[0023] 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, 45B electrically connected to both ends 42T of the spiral portion 42. Here, the cylindrical members 45A, 45B are formed by winding a strip-shaped conductive plate that covers a part of the outer surface 20S of the discharge tube 20 around the lamp axis C in a cylindrical shape. Here, the arrangement section L of the outer electrode 40 along the lamp axis C (hereinafter referred to as the outer electrode arrangement section) corresponds to the length of the inner electrode 30, and the inner electrode 30 faces the outer electrode 40 along the lamp radial direction over the entire lamp axis C direction.

[0024] The excimer lamp 10 is configured as a double-tube discharge lamp by welding the discharge tube 20 to an expanded diameter portion (hereinafter referred to as a welded portion) 56 that protrudes radially of the dielectric 50 like a brim, and the dielectric 50 and the discharge tube 20 correspond to the inner tube and the outer tube of the double-tube discharge lamp, respectively. A discharge space S in which the above-mentioned 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 formed so as to extend from the welded portion 56 of the dielectric 50 to the outside of the discharge tube 20.

[0025] The foil electrode 30 has a substantially constant cross-sectional shape along the lamp axis C, and the distance between the inner surface of the outer electrode 40, which corresponds to the outer surface of the discharge vessel 20, and the outer surface of the inner electrode 30 at a given radial cross section within the outer electrode arrangement section L (hereinafter referred to as the inter-electrode distance) is substantially equal regardless of the cross-sectional position.

[0026] On the other hand, the dielectric 50 has a flat external shape as described below, but has an external shape whose cross section varies along the lamp axis C. Specifically, the dielectric 50 has a columnar portion (hereinafter referred to as a large diameter portion) 54 occupying most of the arrangement section of the inner electrode along the lamp axis C direction, a columnar portion (hereinafter referred to as a small diameter portion) 52 formed on the tip side of the large diameter portion 54, and a tip portion (hereinafter referred to as a tip portion) 51 formed outside the arrangement section of the inner electrode on the tip side of the small diameter portion. The dielectric 50 also 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.

[0027] The large diameter portion 54 faces the spiral portion 42 of the outer electrode 40, and has a substantially constant cross-sectional shape over a section H along the lamp axis C. The small diameter portion 52 also has a substantially constant cross-sectional shape over a section J along the lamp axis C. As shown in Figures 3 and 4, the small diameter portion 52 and the large diameter portion 54 have different cross-sectional shapes in size but have the same shape and are similar to each other. The tip portion 51 tapers toward the tip 50T of the dielectric 50.

[0028] The different diameter portion 53 is a portion that continuously connects the large diameter portion 54 and the small diameter portion 52, and by reducing the diameter from the large diameter portion 54 toward the small diameter portion 52, it forms a curved surface that is continuous with the outer circumferential surfaces of the large diameter portion 54 and the small diameter portion 52, and here, it has a tapered shape with a substantially constant inclination angle in the radial cross section. Since the arrangement section of the inner electrode 30 along the lamp axis C has a length corresponding to the outer electrode arrangement section L, both the small diameter portion 52 and the different diameter portion 53 are positioned to face the outer electrode 40.

[0029] A protruding portion (hereinafter, referred to as an exhaust tube) 22 is formed at one end 20T of the discharge tube 20. The exhaust tube 22 is a part formed in the lamp manufacturing process, and here, the tip side of the glass tube, which is the material for the discharge tube 20, is heated and deformed to reduce the diameter to form the end 20T of the discharge tube 20, and a tip tube smaller than the glass tube is fused to form the exhaust tube 22 as a single unit.

[0030] The foil electrode 30 and the outer electrode 40 have polarities set to anode and cathode here. 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 a power supply line 70. Discharge caused by application of the high frequency voltage causes the emission of excimer light, i.e., ultraviolet light (for example, ultraviolet light of 172 nm).

[0031] The excimer lamp 10 of this embodiment is configured as a small excimer lamp. For example, the axial length (light emission length) in which discharge occurs in the discharge tube 20 can be set in the range of 20 mm to 400 mm. 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.

[0032] The thickness of the discharge tube 20 can be set in the range of, for example, 0.8 mm to 1.5 mm, taking into consideration prevention of discharge tube deterioration due to excimer light and suppression of an increase in discharge start voltage.

[0033] In the large diameter portion 54, the discharge distance, i.e., the distance along the lamp diameter direction between the outer surface of the dielectric 50 and the inner surface of the discharge tube 20, can be set in the range of 2 mm to 12 mm, preferably in the range of 3 mm to 10 mm, taking into consideration prevention of insufficient illuminance due to narrowing of the discharge space and prevention of instability of the discharge due to expansion of the discharge distance.

[0034] The foil electrode 30 is configured as an extremely thin band-shaped electrode with a thickness suppressed relative to the electrode width. Here, the thickness of the foil electrode 30 relative to the electrode width is set to 1 / 30 or less, preferably 1 / 50 or less, and more preferably 1 / 100 or less. Note that the thickness of the foil electrode 30 is exaggerated in Figs. 2 to 4 and 6.

[0035] For example, the thickness of the foil electrode 30 can be set in the range of 20 μm to 50 μm, taking into consideration the current capacity, ease of manufacture, and prevention of peeling from the dielectric 50. On the other hand, the width of the foil electrode 30 can be set in the range of 1.2 mm to 10 mm, taking into consideration the current capacity, ease of manufacture, prevention of blocking of discharge light due to an increase in the electrode area, and the like.

[0036] The electrode material of the foil electrode 30 can be formed from a highly conductive metal or alloy. It can also be made from a material that is easy to electropolish. In this example, molybdenum or an alloy containing molybdenum is used.

[0037] Here, the dielectric 50 is made of a dielectric material (such as SiO2). The thickness of the dielectric 50 can be set in the range of, for example, 0.1 mm to 2 mm, taking into consideration the limit for maintaining the insulation property and the prevention of an increase in the discharge start voltage.

[0038] FIG. 5 is an enlarged cross-sectional view of the foil electrode 30. As shown in FIG.

[0039] As described above, the foil electrode 30 is an electrode formed to be extremely thin compared to the foil electrode width w, and the thickness t of the foil electrode width w is suppressed to 1 / 30 or less. The foil electrode 30 has a flat portion 32 of constant thickness (= t), and has wedge-shaped portions 34A, 34B that taper from both widthwise ends 32A, 32B of the flat portion 32 to both widthwise ends E1, E2 of the foil electrode 30.

[0040] Here, the wedge-shaped portions 34A, 34B of the foil electrode 30 are sharply pointed to their edges. That is, the foil electrode 30 is not sharpened from the center to the edges in the width direction, but is sharpened from both widthwise ends 32A, 32B of the flat portion 32 to both widthwise ends E1, E2. Furthermore, both widthwise ends E1, E2 of the foil electrode 30 are not rounded and thick, but are sharpened to their edges at both widthwise ends E1, E2 of the flat portion 32, and the thickness increases at a constant inclination angle toward both widthwise ends 32A, 32B of the flat portion 32.

[0041] For example, the angles θ1, θ2 (angle θ of edge E) of both ends E1, E2 in the width direction of the foil electrode 30 can be set in the range of 2° to 15°, preferably 10° or less, by considering the difficulty of peeling due to gaps generated at the boundary with the dielectric to be covered, the size of the cross-sectional area of ​​the flat part according to the current capacity, and the suppression of temperature rise due to Joule heat generation. The inclination angle of the cross section of the flat part 32 can be set in the range of less than 2°. This angle θ can be determined from the angle at which the thickness increases from the edge E of the foil electrode toward the flat part 32 by enlarging and observing the cross section of the foil electrode 30 in the vicinity of a range of about 100 μm from the edge E. As a result, in the foil electrode 30, an edge-like edge E is formed over the entire electrode along the lamp axis C direction.

[0042] The flat portion 32 is formed so that its widthwise center (central portion) coincides with the lamp axis C, and the wedge-shaped portions 34A, 34B are symmetrical with respect to the flat portion 32. Furthermore, the widthwise length d1 (d1 / w) of the wedge-shaped portions 34A, 34B relative to the electrode width w of the foil electrode 30 is set to 0.2 or less. Here, the wedge-shaped portions 34A, 34B are formed so that the inclination angles θ of the cross sections from both widthwise ends toward both widthwise ends 32A, 32B of the flat portion 32 are constant.

[0043] Furthermore, the flat portion 32 is formed to have a thickness that is 70% or more of the maximum thickness T of the foil electrode 30. For example, the length d (d / w) between both ends 32A, 32B in the width direction of the flat portion 32 relative to the electrode width w of the foil electrode 30 is set to be 0.6 or more.

[0044] Such an electrode shape makes it possible to provide a compact excimer lamp 10 with excellent lighting startability while increasing the adhesion between the foil electrode 30 and the dielectric 50 and suppressing peeling.

[0045] First, electric field concentration occurs due to the sharply pointed edge E of the foil electrode 30 extending along the lamp axis C. This allows discharge light to be emitted while keeping the discharge start voltage low. In addition, because the wedge-shaped portions 34A and 34B have a sharply pointed wedge shape all the way to the edge, the cross section near the edge E of the foil electrode 30 becomes linear in the axial direction, making it possible to keep the discharge start voltage lower and also making it less likely for gaps to form at the boundary with the covering dielectric 50, making it less likely for peeling to occur.

[0046] Furthermore, the foil electrode 30 is arranged coaxially with the dielectric 50, the discharge tube 20 and the outer electrode 40, the inter-electrode distances, which are the distances from both edges E of the foil electrode 30 to the inner surface of the outer electrode 40 corresponding to the outer surface of the discharge tube 20 in a specified radial cross section in the outer electrode arrangement section L, are equal, and the discharge distance, which is the distance between the outer surface of the large diameter part 54 of the dielectric 50 and the inner surface of the discharge tube 20, is equal. Therefore, light is emitted from the discharge tube 20 in an overall well-balanced manner.

[0047] 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 increased, 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 60% or more of the foil electrode 30, the generation of Joule heat in the foil electrode 30 is suppressed by the current flowing through the flat portion 32 with a relatively large cross-sectional area during lamp lighting.

[0048] As a result, thermal expansion of the foil electrode 30 in the thickness direction (X direction) and width direction (Y direction) can be suppressed. That is, there is no need to make the foil electrode 30 particularly long in the width direction to ensure a large cross-sectional area, and large thermal expansion along the width direction can be prevented. In addition, there is no need to particularly increase the thickness of the foil electrode 30, and therefore large thermal expansion along the thickness direction can be prevented.

[0049] Furthermore, by forming the wedge-shaped portions 34A, 34B with a constant inclination angle of the cross section, it becomes easy to polish the surfaces of the wedge-shaped portions 34A, 34B by electrolytic polishing, etc. This makes it possible to suppress the occurrence of peeling at the boundary portion with the dielectric 50.

[0050] The shape of the foil electrode 30 may be a knife-edge shape with a cross section that is smoothly inclined from the center to both ends along the electrode width direction, and may be a foil electrode without a flat portion. Also, the foil electrode may have a shape other than a knife-edge shape.

[0051] FIG. 6 is an enlarged cross-sectional view of the foil electrode 30 and the dielectric material 50 covering the foil electrode 30 in the large diameter portion 54 according to FIG.

[0052] In this embodiment, the dielectric 50 has a cross-sectional shape that minimizes the difference in the distance (thickness to the foil electrode) from any surface of the foil electrode 30 to the outer surface 50S of the dielectric 50, in accordance with the arrangement and shape of the foil electrode 30 shown in Figure 5.

[0053] Dielectric 50 has a flat shape with a substantially constant thickness along the width direction (Y direction) of foil electrode 30 (see Figs. 3, 4, and 6), and is formed to be flat over the entire section in which foil electrode 30 is disposed. It can also be said that dielectric 50 is composed of a rectangular columnar portion with a substantially constant thickness along the width direction (Y direction) of foil electrode 30, and semi-cylindrical portions formed at one end at both ends of the rectangular columnar portion.

[0054] The cross-sectional shape of such dielectric 50, which is oblong or elliptical, is a cross-sectional shape that matches the arrangement and shape of foil electrode 30 shown in Figure 5, and minimizes the difference in the distance from any surface of foil electrode 30 to outer surface 50S of dielectric 50 (thickness to the foil electrode).

[0055] Here, the portion of section M0 where a planar (flat surface) outer surface 50S1 of a quadrangular columnar portion approximately parallel to the flat portion 32 of the foil electrode 30 is formed is defined as a central portion (flat portion) 50M0. Also, the portions of section M1 where a curved (semi-ellipsoid) outer surface 50S2 of a semi-cylinder portion that is convex from both ends of the central portion 50M0 toward the outside in the electrode width direction (Y direction) is formed are defined as end portions (curved portions) 50M1.

[0056] The quadrangular columnar portion has a cross section along the lamp radial direction that approximates a quadrangle such as a square or a rectangle, and is a columnar body with a uniform cross-sectional shape along the lamp axial direction that is approximately parallel to the flat portion 32 of the foil electrode. A pair of these quadrangular columnar portions cover the vicinity of the center in the width direction of the foil electrode from both sides in the electrode thickness direction so that the thickness T2 is approximately constant.

[0057] The semi-cylinder portion is a semi-cylinder whose cross section along the lamp radial direction is approximating a semicircle such as a semi-ellipse and has a uniform cross-sectional shape along the lamp axial direction. A pair of semi-cylinder portions cover the vicinity of the edge in the width direction of the foil electrode from both sides in the electrode width direction, with a thickness T1 in the electrode width direction and a thickness T2 in the electrode thickness direction, so as to surround the vicinity of the edge from the center.

[0058] The boundaries between the central portion (flat portion) 50M0 and both end portions (curved portions) 50M1 of the dielectric 50 are located along the width direction (Y direction) of the foil electrode 30 closer to the center in the width direction (lamp axis C) of the foil electrode 30 than both ends E1, E2 of the foil electrode 30, preferably the width direction ends 32A, 32B of the flat portion 32. 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. Moreover, the length of the section M1 is formed to be larger than T1.

[0059] 3 has a similar cross-sectional shape, and is homothetic (having the same shape but different size) with the cross-sectional shape of the large diameter portion 54. 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). Furthermore, 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).

[0060] Here, thickness T20 represents the distance along the electrode width direction (Y direction) between flat portion 32 of foil electrode 30 in small diameter portion 52 and outer surface 50S1 of dielectric 50, and thickness T10 represents the distance along the electrode thickness direction (X direction) between both ends E1, E2 (E) of foil electrode 30 in small diameter portion 52 and outer surface 50S2 of dielectric 50. Different diameter portion 53 also has a cross-sectional shape similar to large diameter portion 54, and like small diameter portion 52, has similar characteristics with respect to the width along the electrode width direction (Y direction) and the thickness along the electrode thickness direction (X direction).

[0061] Here, the cross-sectional shape of the discharge tube 20 along the lamp axis C is approximately constant in the outer electrode arrangement section L. Due to the configuration of the dielectric 50 having the above-mentioned small diameter section 52 and large diameter section 54, the discharge distance D10 along the electrode width direction (Y direction) of the radial cross section in the small diameter section 52 is longer than the discharge distance D11 along the electrode width direction (Y direction) of the radial cross section in the large diameter section 54 (see FIG. 1). Also, the discharge distance D20 along the electrode thickness direction (X direction) of the small diameter section 52 is longer than the discharge distance D21 along the electrode thickness direction (X direction) of the large diameter section 54 (see FIG. 2).

[0062] Furthermore, 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.

[0063] On the other hand, since the cross-sectional shape of the foil electrode 30 along the lamp axis C is approximately constant, the distance between both ends E1, E2 of the foil electrode 30 and the inner surface 20M of the discharge tube 20, and the distance between the flat portion 32 of the foil electrode 30 and the inner surface 20M of the discharge tube 20 are approximately equal among the small diameter portion 52, the different diameter portion 53, and the large diameter portion 54. Therefore, by making the discharge distances between the small diameter portion 52 and the large diameter portion 54 different, uneven discharge can be suppressed and the illuminance can be made uniform.

[0064] In other words, since the thickness T10 (see FIG. 3) of the small diameter portion 52 along the electrode width direction (Y direction) relative to the dielectric 50 is thinner than the thickness T1 of the large diameter portion 54 along the electrode width direction (Y direction), discharge is more likely to occur in the small diameter portion 52 due to electric field concentration, thereby improving the lighting startability.

[0065] On the other hand, in the small diameter portion 52, 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 are longer than the discharge distances (including D11 and D21) in the corresponding directions of the large diameter portion 54. Therefore, after lighting starts, a biased discharge state in which the electric field strength along the lamp axis C becomes large is suppressed in the small diameter portion 52, and the illuminance during lamp lighting can be made uniform.

[0066] Furthermore, a different diameter portion 53 is provided between small diameter portion 52 and large diameter portion 54, continuously and smoothly connecting the outer circumferential surfaces of small diameter portion 52 and large diameter portion 54. This makes it possible to suppress uneven discharge between small diameter portion 52 and large diameter portion 54 and cracks in dielectric 50. In particular, since different diameter portion 53 has a tapered shape with a constant cross-sectional inclination angle, it is possible to suppress unevenness in the electric field strength distribution along lamp axis C and easily prevent peeling of dielectric 50 covering foil electrode 30.

[0067] In this manner, in the excimer lamp 10 of this embodiment, the dielectric 50 covering the foil electrode 30 is welded to the discharge vessel 20, and a discharge space S is formed between the dielectric 50 and the discharge vessel 20. A small diameter section 52 having a relatively small distance from the lamp axis C to the outer surface, i.e., a relatively small size, is provided at the tip side of the dielectric 50, and a large diameter section 54 having a relatively large distance (size) from the lamp axis C to the outer surface than the small diameter section 52 is provided. Note that the dielectric 50 can also have an external shape other than a flat or elliptical shape with an elliptical or oblong cross section.

[0068] In this embodiment, the dielectric 50 extends along the lamp axis C so as to correspond to the outer electrode section L, and the tip portion 51 including the tip 50T of the dielectric 50 is configured to deviate from the outer electrode section L (cylindrical member 45A) to the end 20T of the discharge tube 20 along the lamp axis C, but the tip portion 51 may be adjusted to enter the center (spiral portion 42) of the outer electrode 40 in the outer electrode section L along the lamp axis C and face the cylindrical member portion 45A. Also, the inner electrode 30 may be configured to extend along the lamp axis C toward the end 20T of the discharge tube 20 beyond the outer electrode section L (cylindrical member 45A), and further, the different diameter portion 53 may be adjusted to face the cylindrical member portion 45A. Also, instead of the small diameter portion having a substantially constant cross-sectional shape, the small diameter portion may be tapered so that the diameter decreases from the large diameter portion 54 toward the tip portion 51 over the section J along the lamp axis C. In this manner, at least a portion of the small diameter portion 52 covering the inner electrode 30 can be included in the outer electrode arrangement section L.

[0069] Such adjustment of the position of the small diameter portion 52 of the dielectric 50 and the outer electrode 40 can satisfy the requirements for good lighting startability, suppression of uneven discharge, and uniform illuminance in small excimer lamps, etc. As for the outer electrode 40, the electrode structure may be configured to include the spiral portion 42 and cylindrical members 45A and 45B as described above, or may have other configurations. [Explanation of symbols]

[0070] 10 Excimer Lamp 20 Discharge tube (outer tube) 30 Foil electrode (inner electrode) 40 outer electrode 50 Dielectric (inner tube) 52 Small diameter section 53 Different diameter section 54 Large diameter section

Claims

1. A tubular discharge vessel; an outer electrode provided on an outer surface of the discharge vessel; an inner electrode covered with a tubular dielectric; the dielectric body has a large diameter portion and a small diameter portion in a facing area along the lamp axis where the inner electrode and the outer electrode face each other with a substantially constant inter-electrode distance, 13. An excimer lamp comprising: a discharge vessel having a small diameter portion and a discharge distance therebetween that is longer than a discharge distance therebetween that is between the large diameter portion and the discharge vessel.

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

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

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

5. 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 outer circumferential surfaces of the small diameter portion and the large diameter portion.

6. The dielectric material is flat, 2. The excimer lamp according to claim 1, wherein the small diameter portion has a radial cross-sectional shape similar to that of the large diameter portion.

7. The inner electrode is a foil electrode, 2. The excimer lamp according to claim 1, characterized in that the inner electrode has a flat portion having a substantially constant thickness along the width direction between both ends along the width direction, and the flat portion is wedge-shaped from both ends of the flat portion to both ends along the width direction of the inner electrode.

8. the outer electrode has a spiral portion in which a conductive wire is wound in a spiral shape around the discharge vessel, 8. The excimer lamp according to claim 1, wherein at least a portion of the small diameter portion faces the spiral portion.

9. a cylindrical portion electrically connected to the spiral portion and formed by winding a conductive plate around the discharge vessel in a cylindrical shape; 9. The excimer lamp according to claim 8, wherein at least a portion of the small diameter portion faces the cylindrical portion.

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