JP7836729B2 - Excimer lamp - Google Patents

Description

This invention relates to an excimer lamp, and more particularly to the discharge configuration.

For example, in a double-tube excimer lamp, a dielectric covering a foil-like inner electrode is placed inside the discharge tube, and a voltage is applied between the outer electrode, located on the outer surface of the discharge tube, and the inner electrode (see Patent Document 1). This causes excimer light, such as ultraviolet light, to be emitted from the discharge space formed between the dielectric and the discharge tube.

Furthermore, to ensure reliable ignition of high-output excimer lamps, excimer lamps equipped with a starting assist function that discharges at a voltage lower than the discharge initiation voltage are known (see Patent Document 2). In these lamps, a discharge space for starting assistance, containing a gas with a low starting voltage, is formed within the inner tube of a double-tube lamp, along the lamp axis. Ultraviolet light emitted from the starting assist discharge space irradiates the gas in the main discharge space, causing a discharge in the main discharge space.

Japanese Patent Publication No. 2012-38658 Japanese Patent Publication No. 2017-4702

There is a need to provide an excimer lamp with discharge characteristics that improve lamp ignition and starting performance, regardless of whether or not a discharge space for starting assistance is formed.

The excimer lamp of the present invention comprises a discharge container filled with discharge gas, an inner electrode disposed inside the discharge container along the lamp axis, a dielectric material welded to the discharge container at a sealing portion and covering the inner electrode, and an outer electrode disposed outside the discharge container.

The configuration of the discharge vessel, inner electrode, dielectric, and outer electrode, including their shape and arrangement, can vary. For example, the discharge vessel can be configured as a cylindrical container. The inner electrode can be configured to have the same shape across both ends, or to have different shapes connected together. The dielectric's extension length should be determined according to the discharge space area. The outer electrode can be installed on the outer surface of the discharge vessel, or at a predetermined distance from the outer surface.

In this invention, a portion (referred to here as the exposed portion) is provided at the end of the inner electrode opposite to the sealing portion, and is not covered by the dielectric material, thus being exposed within the discharge vessel. For example, on the inner electrode, the exposed portion can be provided at the end opposite to the end connected to the power supply line that connects to the power supply unit. By providing the exposed portion, it is possible to form a spatial region within the discharge vessel where electric field concentration (electric field strength distribution) and discharge concentration occur during ignition startup, and a spatial region where electric field concentration and discharge concentration occur during rated operation.

For example, by appropriately configuring the shape of the inner electrode covered by the dielectric, it is possible to form a spatial region (referred to as a separation region) between the spatial region corresponding to the exposed portion (referred to as the exposed region) and the spatial region where discharge is dominant during rated operation (referred to as the discharge region or main discharge region), where electric field concentration is less likely to occur and the electric field strength is suppressed. It should be noted that the exposed region, discharge region, and separation region are regions defined in terms of characteristics and functionality related to the discharge state, and such regions are not necessarily determined by the configuration of the present invention described above; there is no intention to limit the scope of rights.

The configuration of the inner electrode can vary; it may be an electrode structure with a uniform overall shape, or it may be configured to have different electrode shapes. In either configuration, the exposed portion can be configured to be exposed within the discharge vessel outside the section along the lamp axis where the outer and inner electrodes are arranged facing each other along the lamp's radial direction (hereinafter referred to as the "lamp axis configuration section"). Here, the "lamp axis configuration section" is defined as a section defined in at least a part of the cylindrical portion (constant diameter portion) of the discharge vessel. For example, it can be configured as the entire cylindrical portion.

Furthermore, the exposed end portion of the dielectric material can be configured to be located outside the axial arrangement of the lamp, where the outer and inner electrodes are positioned opposite each other along the lamp's radial direction.

For example, the inner electrode can be configured to include a foil-like portion and a rod-shaped portion electrically connected to the foil-like portion. A portion of the rod-shaped portion can be configured to be exposed within the discharge vessel, without being covered by the dielectric.

The exposed portion of the rod-shaped part of the inner electrode is located outside the lamp axial arrangement section where the outer and inner electrodes are positioned opposite each other along the lamp's radial direction, and is exposed within the discharge vessel.

The exposed end of the foil-like portion of the inner electrode can be configured to be located outside the axial arrangement section where the outer electrode and inner electrode are positioned opposite each other along the lamp's radial direction. Similarly, the exposed end of the outer electrode can be configured to be located outside the axial arrangement section where the foil-like portions of the outer electrode and inner electrode are positioned opposite each other along the lamp's radial direction.

When a foil-like portion is provided on the inner electrode, it is possible to form an auxiliary discharge space by sealing a portion of the dielectric material along the lamp axis direction with the foil-like portion. This auxiliary discharge space can be formed outside the lamp axis arrangement section where the outer and inner electrodes are positioned opposite each other along the lamp radial direction.

As for the configuration of the discharge vessel, a small-diameter section can be provided on the exposed side of the lamp-axial arrangement section where the outer and inner electrodes of the discharge vessel are arranged facing each other along the lamp radial direction. This section has an inner diameter smaller than the inner diameter of the lamp-axial arrangement section where the outer and inner electrodes are arranged facing each other along the lamp radial direction. In this case, at least a portion of the exposed area can be configured to be located within the small-diameter section. For example, the exposed end of the dielectric material may be configured to be located within the small-diameter section.

According to the present invention, the lamp's starting performance can be improved regardless of whether or not a discharge space for starting assistance is formed.

This is a schematic cross-sectional view of the excimer lamp, which is the first embodiment, as seen from the side. This is a schematic cross-sectional view showing a modified example of the excimer lamp, which is the first embodiment. This is a schematic cross-sectional view of an excimer lamp, which is a second embodiment. This figure shows a modified example of the excimer lamp, which is the second embodiment. This is a schematic cross-sectional view showing an excimer lamp, which is a third embodiment. This is a schematic cross-sectional view showing a modified example of the excimer lamp, which is a third embodiment. This is a schematic cross-sectional view of an excimer lamp, which is a fourth embodiment.

The embodiments of the present invention will be described below with reference to the drawings.

Figure 1 is a schematic cross-sectional view of the excimer lamp, which is the first embodiment, as seen from the side.

The excimer lamp 10 comprises a discharge container 20 with a substantially cylindrical cross-section, made of a dielectric material such as quartz glass. Inside the discharge container 20, an electrode (hereinafter referred to as the inner electrode) 30 is provided, extending along the direction of the lamp axis (tube axis) C. On the outer surface 20S of the discharge container 20, an electrode (hereinafter referred to as the outer electrode) 40 is arranged, facing the inner electrode 30 along the lamp radial direction.

The inner electrode 30 is covered by a columnar dielectric 50 extending along the lamp axis C. The dielectric 50 is arranged coaxially with respect to the discharge vessel 20. Furthermore, the inner electrode 30 is arranged coaxially with respect to the discharge vessel 20 such that its center in both its width and thickness directions aligns with the lamp axis C. Alternatively, the inner electrode 30 may be embedded in the dielectric 50.

A sealing portion 21 is formed at one end 20T1 of the discharge container 20, where the dielectric 50 is integrally heated and welded to the discharge container 20. Inside the discharge container 20, a space S1 is formed between the dielectric 50 and the inner surface of the discharge container 20 (hereinafter, for convenience, this space, including the portion that does not discharge, will be referred to as the discharge space or main discharge space). A rare gas such as xenon gas, or a mixed gas of a rare gas and a halogen gas, is sealed in the discharge space S1 as the discharge gas. The sealing pressure of the discharge gas (at room temperature) is set, for example, to 5 kPa to 150 kPa.

The outer electrode 40, in this case, is configured by winding a linear electrode portion made of conductive metal along the outer surface 20S of the discharge container 20. It is wound spirally so that it is spaced apart at predetermined intervals along the lamp axis C. Note that electrode shapes other than linear are also possible. Alternatively, the electrode may not be placed on the outer surface 20S of the discharge container 20, but rather at a position spaced apart from the outer surface 20S along the radial direction of the lamp.

The other end 20T2 of the discharge container 20 is provided with a projection-like portion (hereinafter referred to as the small-diameter portion) 22 that protrudes along the lamp axis C from the constant-diameter portion (hereinafter referred to as the cylindrical portion) 20T0 surrounding the discharge space S1. The diameter (inner diameter) D of the small-diameter portion 22 is formed during the lamp manufacturing process and is smaller than the diameter (inner diameter) D0 of the cylindrical portion 20T0 of the discharge container. Here, the small-diameter portion 22 is integrally formed by heating and deforming the tip side of the outer tube of the discharge container 20 to reduce its diameter, and then welding a tip tube with a smaller diameter than the discharge container 20 to it.

The section L of the cylindrical portion 20T0 of the discharge vessel in which the outer electrode 40 is arranged along the lamp axis (hereinafter referred to as the lamp axis arrangement section) is defined here as the range along the lamp axis of the cylindrical portion 20T0, that is, the range along the lamp axis between the two ends 20T1 and 20T2 where the outer diameter of the discharge vessel 20 tapers. The power supply line 70, connected to the sealing end 30T1 of the inner electrode 30, is connected to an externally installed power supply unit (not shown), and power is supplied to the excimer lamp 10 via the power supply line 70.

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 tens of kVp-p (peak to peak)) are applied to the inner electrode 30 and outer electrode 40, causing excimer light to be emitted from the discharge space S1. Here, discharge gas is sealed within the discharge container 20 so that ultraviolet light with a wavelength capable of generating ozone (e.g., wavelength 172 nm) is emitted from the excimer lamp 10 to the outside of the discharge container 20. Therefore, the excimer lamp 10 can be used as an ozone generator for sterilization and deodorization, and can also be used as an ultraviolet irradiation device that directly irradiates objects with ultraviolet light for sterilization and deodorization purposes.

As shown in Figure 1, the inner electrode 30 is composed of a foil-shaped electrode portion (hereinafter referred to as the foil portion) 32 having a width along the tube diameter direction (hereinafter also referred to as the lamp diameter direction) and a rod-shaped electrode portion (hereinafter referred to as the rod portion) 34 extending along the lamp axis C. Here, the metal foil portion 32 and the rod portion 34 are directly connected, but a conductive member may be interposed between them. The aforementioned lamp axial arrangement section L represents the section where the inner electrode 30 and the outer electrode 40, including the rod portion 34, face each other along the lamp diameter direction.

The foil-like portion 32 is entirely covered with dielectric 50 along the lamp axis C. One end of the rod-shaped portion 34 is connected to the end 32T of the foil-like portion 32, and the other end extends toward the small-diameter portion 22 along the lamp axis C. The dielectric 50 has an axial length at its end 50T that aligns with the position of the lamp axial-axis arrangement section L. A portion of the rod-shaped portion 34 toward the small-diameter portion 22 is not covered by the dielectric 50 and is exposed within the discharge container 20 (hereinafter, the exposed portion of the rod-shaped portion 34 will be referred to as the exposed portion 35).

This configuration of the inner electrode 30 and dielectric 50 allows for the definition of three spatial regions within the discharge vessel 20. First, in the lamp axial arrangement section L, where the inner electrode 30 and outer electrode 40 are positioned opposite each other along the lamp radial direction, the spatial region M1 where the foil-like portion 32 of the inner electrode 30 and the outer electrode 40 face each other along the lamp radial direction is defined here as the "discharge region" (hereinafter also referred to as the main discharge region).

On the other hand, the spatial region M2 in which the exposed portion 35 of the rod-shaped portion 34 is exposed is defined here as the "exposed region." In the exposed region M2, the outer electrode 40 and the exposed portion 35 are not in a positional relationship facing each other, and a part of the exposed portion 35 is contained within the spatial region 22W of the small-diameter portion 22. The spatial region M3 interposed between the discharge region M1 and the exposed region M2 is defined here as the "separated region."

The exposed portion 35, not covered by the dielectric 50, is part of the inner electrode 30, where electric field concentration occurs, forming an exposed region M2 with high electric field strength. Therefore, it has the function of lowering the ignition start voltage, improving ignition performance (startup). On the other hand, because the exposed portion 35 is not covered by the dielectric 50, the electrode material of the inner electrode 30, such as tungsten, is susceptible to sputtering (melting and evaporation) during lamp operation. However, because the exposed portion 35 of the rod-shaped portion 34 is cylindrical, electric field concentration is suppressed compared to the knife-edge portion of the foil-shaped portion 32, thus suppressing sputtering. Because it is a cylindrical shape with a smaller diameter compared to the width of the foil-shaped portion 32, electric field concentration is less likely to occur compared to when the foil-shaped portion 32 is exposed.

However, the exposed region M2 is defined as a spatial region separate from the discharge region M1, with a separation region M3 interposed between them. The discharge region M1 is a spatial region corresponding to the axial arrangement section L where the foil-like portion 32 of the inner electrode 30 and the outer electrode 40 are arranged opposite each other along the lamp's radial direction. Both edges of the foil-like portion 32 along the lamp axis are formed in a knife-edge shape, becoming thinner towards the edges, and its width is larger than the diameter of the cylindrical rod-shaped portion 34. Therefore, electric field concentration occurs in the knife-edge-shaped portion, forming a region of high electric field strength in the discharge region M1. In the discharge space S1 during stable (rated) operation after the lamp starts ignition, discharge concentration in the exposed region M2 is suppressed, and discharge in the discharge region M1 becomes dominant.

The separation region M3 is a spatial region where the outer electrode 40 and the rod-shaped portion 34 face each other along the radial direction of the lamp. However, unlike the foil-shaped portion 32, the rod-shaped portion 34 does not have a knife-edge-shaped portion and has a cylindrical shape with a smaller diameter compared to the width of the foil-shaped portion 32. Therefore, electric field concentration is less likely to occur compared to the discharge region M1. Furthermore, although it has the same cylindrical shape as the exposed portion 35 of the exposed region M2, the separation region M3 is covered with a dielectric, making electric field concentration less likely compared to the exposed region M2. Therefore, a region with high electric field strength is not formed, and discharge concentration in the separation region M3 is suppressed.

By interposing a separation region M3, where a region with a low electric field strength is formed, between the discharge region M1 and the exposed region M2, where regions with high electric field strength are formed, it is possible to reliably suppress the occurrence of discharge concentration where discharge becomes dominant in the exposed region M2 during stable (rated) operation after the lamp is started. As a result, during stable operation, melting and evaporation of the rod-shaped portion 34 are suppressed, and the accumulation of blackening components and the formation of a light-shielding film on the inner surface of the discharge container 20, which would otherwise cause a decrease in illuminance, can be suppressed.

Furthermore, the dielectric 50 extends along the lamp axis C direction such that its end 50T aligns with the end 40T of the outer electrode 40, i.e., with the lamp axis axial arrangement section L. The exposed portion 35 is located in the exposed region M2, which is outside the lamp axis axial arrangement section L, and does not face the outer electrode 40 in the lamp radial direction. This arrangement of the dielectric 50 suppresses electric field concentration in the exposed region M2, thereby suppressing sputtering.

When the excimer lamp 10 is lit for an extended period, some degree of sputtering may be unavoidable depending on the characteristics of the electrode material of the inner electrode 30. However, as described above, the small-diameter portion 22 is provided on the end 20T2 side of the discharge container 20, and a portion of the exposed portion 35 is contained within the spatial region 22W formed by the small-diameter portion 22. Since the spatial region 22W is at a lower temperature than the discharge region M1, even if the blackening component evaporates from the exposed portion 35, most of it will adhere to the inner surface of the small-diameter portion 22. Therefore, it is possible to prevent the formation of a light-shielding film on the inner surface of the discharge container 20 in the discharge region M1 where a stable discharge occurs.

Furthermore, the discharge region M1, the exposed region M2, and the separation region M3 do not have strictly defined boundary lines, and it is possible that spatial region characteristics and functionalities may coexist near the boundary lines.

Figure 2 is a schematic cross-sectional view showing an excimer lamp, which is a modified example of the first embodiment. Here, the end portion 50T of the dielectric 50 is located on the sealing portion 21 side of the lamp axial arrangement section L. Since a portion of the exposed portion 35 faces the outer electrode 40 along the lamp radial direction, a region with a higher electric field strength is formed in the exposed region M2 compared to the excimer lamp 10 shown in Figure 1. However, because a separation region M3 is provided between the discharge region M1 and the exposed region M2, it is possible to suppress the adhesion of blackening components due to sputtering in the exposed portion 35 to the inner surface of the discharge container 20 surrounding the discharge region M1.

Figure 3 is a schematic cross-sectional view of an excimer lamp according to the second embodiment. In the excimer lamp 200 of the second embodiment, the end portion 50T of the dielectric 50 is located on the smaller diameter portion 22 side of the lamp axial arrangement section L, and the outer electrode 40 faces the foil-like portion 32 of the inner electrode 30 along the lamp radial direction. Since the rod-shaped portion 34 of the inner electrode 30 in the separation region M3 does not face the outer electrode 40 along the lamp radial direction, a region with a lower electric field strength is formed in the exposed region M2 compared to the excimer lamp 10 shown in Figure 1. Therefore, the configuration of interposing the separation region M3 between the discharge region M1 and the exposed region M2 is more effective, and it is possible to reliably suppress the adhesion of blackening components due to sputtering in the exposed portion 35 to the inner surface of the discharge container 20 surrounding the discharge region M1.

Figure 4 shows a modified example of the excimer lamp, which is a second embodiment. In the excimer lamp 300 shown in Figure 4, the length of the outer electrode 40, i.e., the lamp axial arrangement section L, is approximately half the lamp axial length of the discharge container 20, and a separation region M3 is defined extending from the center of the discharge container 20 to the vicinity of the small diameter section 22. Compared to the excimer lamp 200 shown in Figure 3, a larger gap is secured between the discharge region M1 and the exposed region M2, thus more effectively suppressing the adhesion of blackening components due to sputtering to the inner surface of the discharge container 20 surrounding the discharge region M1.

Figure 5 is a schematic cross-sectional view showing an excimer lamp according to the third embodiment. In the excimer lamp 400 of the third embodiment, the end 32T of the foil-like portion 32 of the inner electrode 30 and the end 50T of the dielectric 50 are positioned approximately at the same location along the lamp axis, and the entire rod-shaped portion 34 corresponds approximately to the exposed portion 35. The lamp axial arrangement section L also covers up to near the end 32T of the foil-like portion 32 of the inner electrode 30, and the separation region M3 interposed between the discharge region M1 and the exposed region M2 is smaller compared to the first and second embodiments.

However, the end portion 50T of the dielectric 50 is close to the small-diameter portion 22, and most of the exposed portion 35 is contained within the spatial region 22W formed by the small-diameter portion 22. Therefore, after the lamp is lit, the electrode material that melts and evaporates from the exposed portion 35 adheres to the inner surface of the small-diameter portion 22, preventing it from adhering to the inner surface of the discharge container 20 surrounding the discharge region M1.

Figure 6 is a schematic cross-sectional view showing a modified example of the excimer lamp, which is a third embodiment. In Figure 6, the end portion 50T of the dielectric 50 is located on the smaller diameter portion 22 side of the lamp axial arrangement section L, and the foil-like portion 32 and a part of the rod-shaped portion 34 located in the separation region M3 are covered by the dielectric 50. The exposed portion 35 of the rod-shaped portion 34 is contained within the spatial region 22W formed by the smaller diameter portion 22.

Thus, because a portion of the separation region M3 exists within the spatial region 22W formed by the small-diameter portion 22, the electrode material melting and evaporating from the exposed portion 35 can be more reliably adhered to the inner surface of the small-diameter portion 22.

Figure 7 is a schematic cross-sectional view of an excimer lamp according to the fourth embodiment. In Figure 7, a discharge space S2 for assisting ignition (hereinafter referred to as the auxiliary discharge space) is formed in a portion of the space between the inner electrode 30 and the dielectric 50.

Similar to the excimer lamp 300 shown in Figure 4, the axial arrangement section L of the lamp is defined to the left of the center of the discharge container 20. On the other hand, the dielectric 50 and the inner electrode 30 are not partially sealed together from the center of the discharge container 20 towards the smaller diameter section 22. This creates an auxiliary discharge space S2.

By forming such an auxiliary discharge space S2, it is possible to improve ignition and starting performance even if the separation region M3 between the discharge region M1 and the exposed region M2 of the main discharge space S1 is wide.

10 Excimer lamp 20 Discharge vessel 30 Inner electrode 32 Foil-like portion 34 Rod-like portion 35 Exposed portion 40 Outer electrode 50 Dielectric

Claims (7)

A discharge container filled with discharge gas,
An inner electrode is disposed inside the discharge vessel along the lamp axis,
The discharge vessel and the sealing portion are welded together, and the dielectric covering the inner electrode,
The discharge vessel comprises an outer electrode disposed on the outside of the discharge vessel,
An exposed portion is provided at the end of the inner electrode opposite to the sealing portion, which is not covered by the dielectric and is exposed to the inside of the discharge container .
The inner electrode has a foil-like portion and a rod-like portion electrically connected to the foil-like portion.
An excimer lamp characterized in that a portion of the rod-shaped part is not covered by the dielectric and is exposed within the discharge container as the exposed portion . The excimer lamp according to claim 1, characterized in that the exposed portion of the rod-shaped part of the inner electrode is exposed inside the discharge container outside the lamp axial arrangement section in which the outer electrode and the inner electrode are arranged opposite each other along the lamp radial direction. The excimer lamp according to claim 2, characterized in that the exposed end of the foil-like portion of the inner electrode is located outside the lamp axial arrangement section in which the outer electrode and the inner electrode are arranged opposite each other along the lamp radial direction. The excimer lamp according to claim 2, characterized in that the exposed end of the outer electrode is located outside the lamp axial arrangement section in which the outer electrode and the foil-like portion of the inner electrode are arranged opposite each other along the lamp radial direction. A discharge container filled with discharge gas,
An inner electrode is disposed inside the discharge vessel along the lamp axis,
The discharge vessel and the sealing portion are welded together, and the dielectric covering the inner electrode,
The discharge vessel comprises an outer electrode disposed on the outside of the discharge vessel,
An exposed portion is provided at the end of the inner electrode opposite to the sealing portion, which is not covered by the dielectric and is exposed to the inside of the discharge container.
The exposed portion is exposed inside the discharge container outside the lamp axial arrangement section in which the outer electrode and the inner electrode are arranged facing each other along the radial direction of the lamp,
The inner electrode has a foil-like portion,
An auxiliary discharge space is formed by sealing a portion of the dielectric along the lamp axis with the foil-like portion.
An excimer lamp characterized in that the auxiliary discharge space is formed outside the lamp axial arrangement section in which the outer electrode and the inner electrode are arranged opposite each other along the lamp radial direction. A discharge container filled with discharge gas,
An inner electrode is disposed inside the discharge vessel along the lamp axis,
The discharge vessel and the sealing portion are welded together, and the dielectric covering the inner electrode,
The discharge vessel comprises an outer electrode disposed on the outside of the discharge vessel,
An exposed portion is provided at the end of the inner electrode opposite to the sealing portion, which is not covered by the dielectric and is exposed to the inside of the discharge container.
A small-diameter portion is provided on the exposed side of the lamp axial arrangement section in which the outer electrode and the inner electrode of the discharge container are arranged facing each other along the lamp radial direction, having an inner diameter smaller than the inner diameter of the lamp axial arrangement section in which the outer electrode and the inner electrode of the discharge container are arranged facing each other along the lamp radial direction.
At least a portion of the exposed portion is located within the small diameter portion,
An excimer lamp characterized in that the exposed end of the dielectric material is located within the small diameter portion. A discharge container filled with discharge gas,
An inner electrode is disposed inside the discharge vessel along the lamp axis,
The discharge vessel and the sealing portion are welded together, and the dielectric covering the inner electrode,
The discharge vessel comprises an outer electrode disposed on the outside of the discharge vessel,
An exposed portion is provided at the end of the inner electrode opposite to the sealing portion, which is not covered by the dielectric and is exposed to the inside of the discharge container.
An excimer lamp characterized in that the exposed end of the dielectric material is located outside the lamp axial arrangement in which the outer electrode and the inner electrode are arranged opposite each other along the lamp radial direction.