JP2025015981A - Excimer Lamp - Google Patents

Abstract

To provide an excimer lamp that is good in lighting start-up and has durability performance.SOLUTION: An excimer lamp 10 includes a discharge tube 20 and a dielectric 50 covering a foil electrode 30, and forms a main discharge space S1 therebetween. The dielectric 50 includes a sealed part 54 that is sealed with the foil electrode 30, and a non-sealed part 52 that is not sealed with the foil electrode 30, at the tip side of the sealed part 54. An auxiliary discharge space S2 is provided in the non-sealed part 52.SELECTED DRAWING: Figure 1

Description

The present invention relates to an excimer lamp, and in particular to the configuration of the discharge space in an excimer lamp.

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) that covers 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.

For example, there is a known excimer lamp equipped with a start-up assistance function that discharges at a voltage lower than the discharge start voltage in order to ensure that the excimer lamp is lit (see Patent Document 1). In this lamp, a discharge space for starting lighting is formed inside an inner tube through which an inner electrode extending along the lamp axis is inserted, and a gas with a lower starting voltage than the discharge space formed between the inner tube and the outer tube is sealed in the inner tube.

In addition, among excimer lamps equipped with an inner tube that covers a foil-shaped electrode as the inner electrode, there is known an excimer lamp in which the inner electrode and the inner tube are partially sealed (see Patent Document 2). In this case, the inner electrode that covers the inner tube is provided with a portion that is sealed (closed) by the inner tube and an unsealed portion, forming an auxiliary discharge space for starting lighting where the inner electrode is exposed.

JP 2017-4702 A JP 2022-182685 A

If an auxiliary discharge space for starting lighting is formed between the inner electrode and the inner tube along the lamp diameter direction, there is a risk that the electrode will be worn out early due to sputtering, which may lead to a decrease in the starting auxiliary function. On the other hand, forming an auxiliary discharge space for starting lighting over the entire axial direction of the lamp will increase the temperature of the main discharge space due to auxiliary discharge, reducing the efficiency of ultraviolet radiation. In particular, when constructing a small excimer lamp (for example, the outer diameter of the discharge vessel is several mm to several tens of mm), it is difficult to achieve both highly efficient ultraviolet radiation and durability.

Therefore, even in small excimer lamps, it is necessary to form a discharge space for starting lighting that allows for good lighting startup and durability.

The excimer lamp according to one aspect of the present invention comprises a dielectric that covers the inner electrode including the tip, and a discharge vessel that is fused to the dielectric to form a main discharge space. The discharge vessel can be formed into a tubular shape.

The part of the dielectric that covers the inner electrode is called the sealed part. Here, "sealed" means that the dielectric (inner tube) made of glass or some other material is tightly attached (adhered) to the entire foil electrode so that no gaps are created between the foil electrode and the dielectric.

The dielectric of the present invention forms an auxiliary discharge space in a portion (herein referred to as the non-sealed portion) that is closer to the end of the discharge vessel than the sealed portion that covers the inner electrode. The auxiliary discharge space is formed in a portion different from the portion where the tubular dielectric melts and fills the hollow portion to form a columnar mass, for example, the portion where the tip of the inner electrode is buried, and the portion where the tubular dielectric melts and fills the hollow portion to form the dielectric tip portion that has become a hemispherical mass. This means that there are portions of the dielectric that are partially unwelded and partially welded between the vicinity of the tip of the inner electrode and the tip of the dielectric.

The auxiliary discharge space can be formed as a space with a circular cross section, and can be configured so that at least a portion of the cross-sectional area of the auxiliary discharge space is larger than the cross-sectional area of the inner electrode. Also, the auxiliary discharge space can be configured to face an outer electrode provided on the outer surface of the discharge vessel.

The inner electrode can be configured as a foil electrode, and can be configured so that in a cross section along the electrode width direction of the inner electrode, the width along the electrode width direction of at least a portion of the auxiliary discharge space is greater than the width of the inner electrode.

When the inner electrode is a foil electrode, the width of the auxiliary discharge space can be configured to be larger than the width of the sealed portion along the electrode thickness direction of the inner electrode. Here, the "width of the auxiliary discharge space" corresponds to the cross-sectional width along the electrode thickness direction in the space portion that occupies most of the auxiliary discharge space.

In addition, when the inner electrode is a foil electrode, the distance between the outer surface of the dielectric and the inner surface of the discharge vessel along the electrode width direction of the inner electrode can be configured to be approximately constant along the lamp axis direction. The "distance" here corresponds to the cross-sectional width along the electrode thickness direction in the space portion that occupies most of the auxiliary discharge space.

The sealed portion can be configured to have an oval or oblong cross section, and can be configured so that the width of the sealed portion is approximately equal to the width of the non-sealed portion along the electrode width direction of the inner electrode. Also, the thickness of the non-sealed portion can be configured to be smaller than the thickness of the sealed portion along the electrode thickness direction of the inner electrode.

The outer electrode provided on the outer surface of the discharge vessel can be configured in various ways, and can be configured to have a spiral portion in which a conductive wire is wound in a spiral shape around the discharge vessel. For example, it can be configured so that the auxiliary discharge space does not face the spiral portion.

It is possible to provide a cylindrical section that is electrically connected to the spiral section and has a conductive plate wound around the discharge vessel in a cylindrical shape, and it is possible to configure the auxiliary discharge space so that at least a part of it is formed closer to the end of the discharge vessel than the cylindrical section (the side where the outer electrode is not provided).

The present invention makes it possible for an excimer lamp to have good lighting start-up and durability.

2 is a schematic cross-sectional view taken along the electrode width direction of the excimer lamp. 2 is a schematic cross-sectional view of an excimer lamp taken along the electrode thickness direction. FIG. 2 is a cross-sectional view taken along line III-III in FIG. FIG. 2 is a cross-sectional view taken along line IV-IV in FIG. FIG. 2 is an enlarged cross-sectional view of a foil electrode. 5 is an enlarged cross-sectional view of a foil electrode and a dielectric covering the foil electrode in a sealed portion according to FIG. 4 .

The following describes this embodiment of the excimer lamp with reference to the drawings.

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

The excimer lamp 10 is equipped with 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 sealed inside the discharge tube 20 as a discharge gas.

Inside the discharge tube 20, a foil electrode (hereinafter also referred to as the inner electrode) 30 is arranged in a band 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 embedded within the dielectric 50 without being exposed to the discharge space S1. 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 the end of the foil electrode 30 along the lamp axis C, and is also connected to an externally installed power supply unit (not shown).

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. The dielectric 50 is also arranged coaxially with the discharge tube 20. Therefore, the foil electrode 30 is arranged coaxially with the discharge tube 20 and 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.

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.

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 that are electrically connected to both ends 42T of the spiral portion 42. The cylindrical members 45A, 45B are formed by wrapping 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 direction (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.

The excimer lamp 10 is configured as a double-tube discharge lamp by welding the discharge tube 20 to the enlarged diameter portion (hereinafter referred to as the welded portion) 56 that protrudes radially from 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 S1 (hereinafter referred to as the main discharge space) 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 to extend from the welded portion 56 of the dielectric 50 to the outside of the discharge tube.

As described above, the dielectric 50 is sealed to the inner electrode 30, while an unsealed portion 55 that is not sealed to the inner electrode 30 is provided between the tip 30T of the inner electrode 30 and the tip 50T of the dielectric 50. Furthermore, the unsealed portion 55 can be divided into a welded portion 53 where the hollow portion of the tubular dielectric is filled by welding during the manufacturing process to embed (seal) the tip 30T of the inner electrode 30 along the tube axis C direction, a welded portion 51 where the tubular dielectric is welded during the manufacturing process to form the tip 50T of the dielectric 50 with the hollow portion filled, and a portion (hereinafter referred to as the unsealed portion) 52 between the welded portion 53 and the welded portion 51 where the hollow portion is maintained with the dielectric remaining tubular without being welded during the manufacturing process.

The welded portion 51, the unwelded portion 52, and the welded portion 53 that make up the unsealed portion 55 are continuously connected to the portion 54 where the dielectric 50 is sealed to the inner electrode 30 (hereinafter referred to as the sealed portion). A discharge space (hereinafter referred to as the auxiliary discharge space) S2 for starting lighting is formed in the unwelded portion 52. The auxiliary discharge space S2 is formed on the tip side of the dielectric 50 along the lamp axis C, that is, on the end 20T side of the discharge tube 20, rather than the tip 30T of the inner electrode 30.

As shown in FIG. 3, the auxiliary discharge space S2 has a circular cross section near the center in the lamp axis direction, and the spatial distance (inner diameter) D1 along the width direction (Y direction) of the foil electrode 30 and the spatial distance (inner diameter) D2 along the thickness direction (X direction) of the foil electrode 30 are approximately the same. In addition, the thickness T10 along the width direction (Y direction) of the thick foil electrode 30 and the thickness T20 along the thickness direction (X direction) of the foil electrode 30 are also approximately the same. The inner surface of the auxiliary discharge space S2 is formed so that the size of its cross-sectional area (inner diameter) smoothly decreases from near the center in the lamp axis C direction toward both ends (welded portions 51, 53).

Here, the non-welded portion 52 is formed closer to the end 20T of the discharge tube 20 than the outer electrode arrangement section L, and the auxiliary discharge space S2 here is formed entirely at a position along the lamp axis C that is outside the outer electrode arrangement section L.

The auxiliary discharge space S2 is in a reduced pressure state lower than atmospheric pressure. It is also possible to fill the auxiliary discharge space S2 with a rare gas at or below atmospheric pressure to lower the voltage at the start of lighting.

A protruding portion (hereafter referred to as the exhaust tube) 22 is formed at one end 20T of the discharge tube 20. The exhaust tube 22 is a part formed during the lamp manufacturing process, in which the tip side of the glass tube, which is the material for the discharge tube 20, is reduced in diameter by heating and deforming to form the end 20T of the discharge tube 20, and a tip tube with a smaller diameter than the glass tube is fused to form the exhaust tube 22 as a single unit.

The foil electrode 30 and the outer electrode 40 are set to have anode and cathode polarities. High frequency (e.g., in the range of several kHz to several tens of MHz) and high voltage (e.g., in the range of several kV to several tens of kV) are supplied to the excimer lamp 10 via the power supply line 70.

When high-frequency voltage is applied, the auxiliary discharge space S2 is in a reduced pressure state, so that a discharge occurs first in the auxiliary discharge space S2 due to a lower lighting start voltage than in the main discharge space S1. Then, part of the excimer light, i.e., ultraviolet light, emitted from the auxiliary discharge space S2 in the lamp diameter direction is irradiated through the dielectric 50 to the main discharge space S1.

In addition, a portion of the ultraviolet light generated in the auxiliary discharge space S2 and radiated in the direction of the lamp axis C is transmitted to the expanded portion 56 of the discharge tube 20 and to the entire wall of the discharge tube 20 by the so-called fiber effect, which causes repeated reflections within the tube wall of the dielectric 50 (the boundary surface of the tube wall), and the ultraviolet light is irradiated toward the main discharge space S1. Here, a dielectric barrier discharge is generated, and excimer light (ultraviolet light) of a specified spectrum (for example, a wavelength of 172 nm) is radiated from the main discharge space S1.

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 within 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.

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

In the outer electrode arrangement section L, the discharge distance, i.e., the distance between the outer surface of the sealed portion 54 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 the prevention of insufficient illuminance due to narrowing of the discharge space and the prevention of instability of the discharge due to the expansion of the discharge distance.

The foil electrode 30 is configured as an extremely thin strip-shaped electrode with a thickness that is 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 Figures 2, 4, and 6.

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 manufacturing, 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 manufacturing, and prevention of blocking of discharge light due to an increase in the electrode area.

The electrode material of the foil electrode 30 can be made of a highly conductive metal or alloy. It can also be made of a material that is easy to electropolish. Here, molybdenum or an alloy containing it is used.

Here, the dielectric 50 is made of a dielectric material (such as _SiO2 ). The thickness of the dielectric 50 can be determined to be 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.

Figure 5 is an enlarged cross-sectional view of the foil electrode 30.

As described above, the foil electrode 30 is an electrode formed with a very thin thickness 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 with a 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.

The wedge-shaped portions 34A, 34B of the foil electrode 30 are sharply pointed all the way to the 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 are not rounded and thick, but the widthwise ends E1, E2 of the foil electrode 30 are sharpened and the thickness increases at a constant angle toward both widthwise ends 32A, 32B of the flat portion 32.

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 taking into consideration 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.

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. 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 angle θ of the cross section from both widthwise ends toward both widthwise ends 32A, 32B of the flat portion 32 is constant.

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.

This 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 preventing peeling.

First, the edge E of the foil electrode 30 extending along the lamp axis C is sharply pointed, which creates an electric field concentration. This allows discharge light to be emitted while keeping the discharge start voltage low. In addition, because the wedge-shaped portions 34A and 34B are sharply pointed 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 even lower, and also making it less likely for gaps to form at the boundary with the covering dielectric 50, which makes it less likely for peeling to occur.

Furthermore, the foil electrode 30 is arranged coaxially with the dielectric 50, the discharge tube 20 and the outer electrode 40, and the inter-electrode distance, which is the distance from both edges E of the foil electrode 30 to the inner surface of the outer electrode 40, which corresponds to the outer surface of the discharge tube 20, in a given radial cross section within the outer electrode arrangement section L, is equal, and the discharge distance, which is the distance between the outer surface of the sealed portion 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 balanced manner.

On the other hand, by forming a 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. In other words, by providing a 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 accounts for more than 60% of the foil electrode 30, when the lamp is turned on, the generation of Joule heat in the foil electrode 30 is suppressed by current flowing through the flat portion 32 with a relatively large cross-sectional area.

As a result, thermal expansion of the foil electrode 30 in the thickness direction (X direction) and width direction (Y direction) can be suppressed. In other words, 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, so large thermal expansion along the thickness direction can be prevented.

In addition, by forming the wedge-shaped portions 34A and 34B with a constant cross-sectional inclination angle, it becomes easier to polish the surfaces of the wedge-shaped portions 34A and 34B by electrolytic polishing or the like. This makes it possible to suppress peeling at the boundary with the dielectric 50.

The shape of the foil electrode 30 can be a knife-edge shape with a cross section that slopes smoothly from the center to both ends along the electrode width direction, and the foil electrode can be configured without a flat portion. Also, the foil electrode can be shaped in a way other than a knife-edge shape.

Figure 6 is an enlarged cross-sectional view of the foil electrode 30 and the dielectric 50 covering the foil electrode 30 at the sealed portion 54 according to Figure 4.

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 FIG. 5.

The dielectric 50 is flat and has a substantially constant thickness along the width direction (Y direction) of the foil electrode 30 (see Figures 4 and 6), and is formed to be flat over the entire installation section along the lamp axis C direction of the foil electrode 30. It can also be said that the dielectric 50 is composed of a rectangular 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 rectangular columnar portion.

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

Here, the portion of section M0 where the planar (flat) outer surface 50S1 of the rectangular columnar portion approximately parallel to the flat portion 32 of the foil electrode 30 is formed is referred to as the central portion (flat portion) 50M0. In addition, the portions of section M1 where the curved (semi-ellipsoidal) outer surface 50S2 of the semi-cylinder portion that is convex from both ends of the central portion 50M0 toward the outside in the electrode width direction (Y direction) are formed are referred to as the end portions (curved portions) 50M1.

The quadrangular columnar portion has a cross section along the lamp radial direction that approximates a quadrangle such as a square or 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 foil electrode near the center in the width direction from both sides in the electrode thickness direction so that the thickness T2 is approximately constant.

The semi-cylindrical portion has a cross section along the lamp radial direction that is approximating a semicircle, such as a semi-ellipse, and is a semi-cylindrical body with a uniform cross-sectional shape along the lamp axial direction. A pair of semi-cylindrical 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 at the center.

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 of the foil electrode 30 in the width direction (lamp axis C) 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 section M0 along the foil electrode's width direction (Y direction) is set to be smaller than w, and preferably smaller than d. Also, the length of section M1 is formed to be greater than T1.

As described above, in the excimer lamp 10 of this embodiment, a main discharge space S1 is formed between the discharge tube 20 and the dielectric 50 covering the foil electrode 30. The dielectric 50 has a sealed portion 54 that is sealed to the foil electrode 30, and a non-welded portion 52 that is located on the tip side of the sealed portion 54 and is not welded to the foil electrode 30. In the non-welded portion 52, an auxiliary discharge space S2 is provided in the non-welded portion 52 that is between the welded portion 51 and the welded portion 53. By forming the auxiliary discharge space S2 in the non-welded portion 52 of the dielectric 50 (inner tube), an excimer lamp 10 that has good lighting startability and excellent durability can be provided.

First, as described above, the auxiliary discharge space S2 has a circular cross section near its center, and the discharge distance (inner diameter) D1, D2 (D1 ≒ D2) along the width direction (Y direction) and thickness direction (X direction) of the foil electrode 30 near the center of the non-welded portion 52 is greater than the width W1, W2 of the inner electrode 30. Therefore, even if the auxiliary discharge space S2 is located outside the section L along the lamp axis C of the outer electrode arrangement section, discharge in the auxiliary discharge space S2 will occur first. This leads to increased reliability in lighting startability.

On the other hand, the tip 30T of the foil electrode 30 does not extend to the auxiliary discharge space S2, but is buried in the welded portion 53 of the dielectric 50 and is not exposed to the auxiliary discharge space S2. Therefore, the inner electrode 30 is not consumed by the sputtering phenomenon, and the lamp durability can be improved.

Since no sputtering phenomenon occurs, it is possible to prevent the temperature rise in the main discharge space S1 due to the auxiliary discharge, and to prevent uneven distribution of electric field strength and uneven discharge during the main discharge while the lamp is on. This improves the uniformity of the illuminance distribution. In addition, the fact that the auxiliary discharge space S2 has a circular cross section also contributes to suppressing uneven discharge.

The above-mentioned configuration of the dielectric 50 covering the foil electrode 30 can increase the ultraviolet radiation efficiency and prevent biased discharge during the main discharge. That is, since the outer diameter (width) W11x of the non-welded portion 52 is approximately equal to the outer diameter W1 of the sealed portion 54, the discharge distance D10 between the non-welded portion 52 and the discharge tube 20 and the discharge distance D11 between the sealed portion 54 and the discharge tube 20 are approximately equal. Since the discharge distance is approximately constant in the width direction (Y direction) of the foil electrode 30 along the lamp axis C, biased discharge can be suppressed.

In addition, the thickness T20 of the non-welded portion 52 along the electrode thickness direction (X direction) is smaller than the thickness T2 of the sealed portion 54 along the electrode thickness direction (X direction). Therefore, the discharge from the auxiliary discharge space S2 does not hinder the generation of discharge in the main discharge space S1 in the electrode thickness direction (X direction), and the occurrence of biased discharge can be suppressed.

The auxiliary discharge space S2, including the conductive member 45, does not face the outer electrode 40 along the lamp diameter direction, so the electric field strength in the auxiliary discharge space S2 does not become greater than necessary, and the impact on the electric field strength distribution in the outer electrode arrangement section L, i.e., the bias of the discharge, can be suppressed.

The inner electrode 30 may be configured as something other than a foil electrode. For example, it may be configured as a rod-shaped electrode with a circular or rectangular cross section. The outer electrode 40 may also have an electrode structure other than a spiral shape, and may have an electrode structure in which cylindrical members are not provided at both ends of the outer electrode. The sealed portion 54 may also have a shape other than a flat or elliptical shape, with an elliptical or oblong cross section.

It is also possible to arrange the auxiliary discharge space S2 so that it faces the outer electrode 40 along the lamp radial direction (see symbols 40'T and 45'T in FIG. 1). By arranging the position where the auxiliary discharge space S2 of the non-sealed portion 55 is formed so that it faces the outer electrode 40 partially along the lamp radial direction, the electric field strength in the auxiliary discharge space S2 can be increased, that is, auxiliary discharge can be easily performed. By adjusting the position where the auxiliary discharge space S2 of the non-sealed portion 55 is formed along the lamp axis C direction, it is possible to adjust the electric field strength distribution, the voltage at the start of lighting by auxiliary discharge, etc., and conversely, the position where the auxiliary discharge space S2 of the non-sealed portion 55 is formed or the arrangement positions of both ends of the outer electrode (cylindrical member) may be adjusted according to the lighting start voltage. In this case, the electrode structure of the outer electrode can be a configuration with a spiral portion or conductive member as described above, or other configurations. The external shape of the dielectric and the cross-sectional shape of the inner electrode are also arbitrary.

Adjusting the relationship between the position where the auxiliary discharge space is formed and the position where the outer electrode is arranged can meet the demands of small excimer lamps and the like to increase the efficiency of UV radiation while suppressing the applied voltage, as well as the demands of precisely emitting UV rays at the desired UV intensity.

10 Excimer lamp 20 Discharge tube (outer tube)
30 Foil electrode (inner electrode)
40 Outer electrode 50 Dielectric (inner tube)
70 Power supply rod (power supply line)

Claims (10)

a dielectric covering the inner electrode including the tip;
a discharge vessel that is fused to the dielectric to form a main discharge space,
2. An excimer lamp according to claim 1, wherein the dielectric defines an auxiliary discharge space in an unsealed portion closer to an end of the discharge vessel than a sealed portion covering the inner electrode. The auxiliary discharge space has a circular cross section,
2. The excimer lamp of claim 1, wherein a cross-sectional area of at least a portion of the auxiliary discharge space is greater than a cross-sectional area of the inner electrode. The inner electrode is a foil electrode,
3. The excimer lamp according to claim 2, wherein in a cross section of the inner electrode in the electrode width direction, a width of at least a part of the auxiliary discharge space in the electrode width direction is larger than a width of the inner electrode. The inner electrode is a foil electrode,
3. The excimer lamp according to claim 2, wherein a width of the auxiliary discharge space is greater than a width of the sealed portion along a thickness direction of the inner electrode. The inner electrode is a foil electrode,
3. The excimer lamp according to claim 2, wherein a distance between an outer surface of the dielectric body and an inner surface of the discharge vessel along a width direction of the inner electrode is approximately constant along the lamp axis. The sealing portion has an oval or oblong cross section,
3. The excimer lamp according to claim 2, wherein the width of the sealed portion and the width of the unsealed portion are substantially equal along the electrode width direction of the inner electrode. The sealing portion has an oval or oblong cross section,
3. The excimer lamp according to claim 2, wherein the thickness of the unsealed portion is smaller than the thickness of the sealed portion along the electrode thickness direction of the inner electrode. an outer electrode provided on the outer surface of the discharge vessel has a spiral portion in which a conductive wire is wound in a spiral shape around the discharge vessel,
2. The excimer lamp according to claim 1, wherein the auxiliary discharge space does not face the spiral portion. 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 part of the auxiliary discharge space is formed closer to the end of the discharge vessel than the cylindrical portion. The excimer lamp according to claim 1, characterized in that the auxiliary discharge space faces an outer electrode provided on the outer surface of the discharge vessel.

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