JP7198611B2 - Discharge lamp and method for producing electrode for discharge lamp - Google Patents

Description

The present invention relates to a discharge lamp with electrodes, and more particularly to the internal structure of the electrodes.

When the discharge lamp is lit, the tip of the electrode reaches a high temperature, and the electrode material such as tungsten melts and evaporates, blackening the discharge tube, and lowering the illumination of the lamp. In order to prevent overheating of the tip of the electrode, the tip of the electrode made of a durable metal and the body made of a metal with higher thermal conductivity are formed separately and joined by solid phase bonding or the like. For example, electrodes can be formed by solid-phase bonding such as SPS (see Patent Document 1). By forming the electrode by joining a plurality of members, it is possible to provide the electrode with durability even when the size of the electrode is increased, and at the same time, the electrode with excellent thermal conductivity can be formed.

Japanese Patent No. 5472915 Patent application 2017-36782

In order to increase the size of an object to be exposed and improve throughput, there is a demand for a higher output (higher power) lamp. Along with this, the temperature of the electrode increases during lamp lighting, and it is difficult to effectively suppress electrode overheating simply by solid-phase bonding the tip side member and the body side member.

Therefore, there is a demand for an electrode structure that can effectively suppress the temperature rise of the electrodes during lighting of the discharge lamp.

The discharge lamp of the present invention comprises a discharge tube and a pair of electrodes arranged opposite to each other in the discharge tube, at least one of the electrodes having an inner space, the surface area of the inner space being the length of the inner space in the axial direction. larger than the surface area of the electrode side portion according to . For example, the surface area of the internal space can be made larger than the surface area of the electrode side portion along the electrode axial direction.

The electrode includes a recess along the electrode axis direction and a column located in the recess, and an internal space can be formed between the recess and the column. Here, the “columnar portion” and the “recessed portion” are portions defined including contact surfaces or joint surfaces when an electrode formed by joining a plurality of members is viewed in cross section. and the bottom surface of the recess may be in contact or not. For example, it has a first solid member having a concave portion and a second solid member joined to the first solid member or an intermediate member joined to the first solid member to form a columnar portion, and the internal space is formed by the first solid member. It is formed between a solid member and a second solid member or an intermediate member.

The internal space may include a space formed around the electrode axis. Also, the internal space can be formed in a tubular shape with a bottom. A heat radiating portion can be provided on the surface portion of the internal space.

A discharge lamp according to another aspect of the present invention includes a discharge tube and a pair of electrodes arranged opposite to each other in the discharge tube. and an internal space formed between the recess and the pillar, wherein the volume of the pillar is greater than the volume of the internal space.

According to another aspect of the present invention, there is provided a method of manufacturing an electrode for a discharge lamp, in which a cylindrical recess is formed around the center axis in a columnar tip-side solid member having an electrode tip surface, and a cylindrical recess is formed in the columnar rear-end solid member. On the other hand, a columnar portion smaller in size than the cylindrical recess is formed around the central axis, and the front end side solid member and the rear end side solid member are combined so that the columnar portion is arranged coaxially with the cylindrical recess, and solid phase bonding is performed. A manufacturing method characterized by forming an electrode including a front-end solid member and a rear-end solid member, wherein the surface area of the internal space formed between the cylindrical concave portion and the columnar portion is equal to the inner The cylindrical concave portion and the columnar portion are formed so as to be larger than the surface area of the electrode side portion corresponding to the axial length of the space.

ADVANTAGE OF THE INVENTION According to this invention, it is a discharge lamp. WHEREIN: It can heat-radiate effectively and can suppress electrode temperature.

1 is a plan view of a discharge lamp according to a first embodiment; FIG. 1 is a schematic cross-sectional view of an electrode of a first embodiment; FIG. FIG. 4 is a schematic cross-sectional view of an electrode of a second embodiment; 4 is a graph showing temperature changes from the joint surfaces of an example and a comparative example.

The short-arc discharge lamp 10 is a large-sized discharge lamp capable of outputting high-intensity light, and includes a substantially spherical discharge tube (arc tube) 12 made of transparent quartz glass. A pair of electrodes 20 and 30 are arranged facing each other (coaxially). On both sides of the discharge tube 12, quartz glass sealing tubes 13A and 13B are connected to the discharge tube 12 and integrally formed. A discharge space DS in the discharge tube 12 is filled with mercury and a rare gas such as halogen or argon gas.

An electrode 20, which is a cathode, is supported by an electrode supporting rod 17A. The sealing tube 13A includes a glass tube (not shown) through which the electrode support rod 17A is inserted, a lead rod 15A connected to an external power source, a metal foil 16A connecting the electrode support rod 17A and the lead rod 15A, and the like. Sealed. Similarly, for the electrode 30, which is the anode, mount parts such as a glass tube (not shown) through which the electrode support rod 17B is inserted, the metal foil 16B, and the lead rod 15B are sealed. In addition, caps 19A and 19B are attached to the ends of the sealing tubes 13A and 13B, respectively.

When a voltage is applied to the pair of electrodes 20 , 30 , arc discharge is generated between the electrodes 20 , 30 and light is emitted outside the discharge tube 12 . Here, power of 1 kW or more is applied. Light emitted from the discharge tube 12 is guided in a predetermined direction by a reflecting mirror (not shown). For example, when the discharge lamp 10 is incorporated in an exposure apparatus, the emitted light becomes patterned light and irradiates a substrate or the like.

FIG. 2 is a schematic cross-sectional view of electrode (anode) 30 . The electrode (cathode) 20 can also have a similar structure.

The electrode 30 is composed of a rear end member 32 (second solid member) connected to the electrode support rod 17B and a front end member 34 (first solid member) having an electrode tip surface 34D. The electrode 30 is configured by joining the members 34 . Here, the rear end side member 32 and the front end side member 34 are joined by solid phase joining such as SPS.

The rear end-side member 32 is a columnar member whose central axis is the electrode axis X (hereinafter also referred to as the axial direction X), and has a columnar portion 50 (here, columnar) that protrudes toward the electrode tip surface 34D. is formed. A tubular recessed portion 40 surrounding the columnar portion 50 is coaxially formed along the axial direction X in the distal end side member 34 . The tubular concave portion 40 faces in the opposite direction to the electrode tip surface 34D, that is, is concave in the opposite direction. The rear end member 32 is solid-phase joined to the end 34E of the front end member 34 at its end 32E. It should be noted that a columnar portion may be formed in the front end side member and a concave portion may be formed in the rear end side member.

A gap (internal space) 60 is formed in the columnar portion 50 along the axial direction X and the axis-perpendicular direction perpendicular thereto between the columnar portion 50 extending from the solid-phase bonding surface toward the tip end portion of the electrode and the cylindrical recess 40 . formed all around. Here, the clearance portion along the axial direction is 60D, and the clearance portion along the axial direction X is 60V. The gap portions 60D and 60V are spatially connected.

Both the columnar portion 50 and the tubular concave portion 40 have their central axes aligned with the electrode axis X and are symmetrical with respect to the electrode axis X. As shown in FIG. The bottom surface 40B of the cylindrical recess 40 is also symmetrical with respect to the electrode axis X, and the gap 60 also has a symmetrical spatial shape with respect to the electrode axis X. As shown in FIG.

The radial width D4 of the gap portion 60V, that is, the radial distance between the side surface 50S of the columnar portion 50 and the side surface 40S of the cylindrical recess 40 is shorter than the diameter D3 of the columnar portion 50 (D4<D3). The axial width L4 of the clearance portion 60D here is the same as the radial width D4 of the clearance portion 60V, and is shorter than the height L3 of the columnar portion 50 (L4<L3). The gap 60 is formed within the electrode 30 and forms a bottomed cylindrical space region.

Here, the radial width D4 and the axial width L4 are sufficiently shorter than the diameter D3 and the height L3 of the columnar portion 50, respectively, and the side surface 50S and the end surface 50E of the columnar portion 50 correspond to the side surface 40S of the cylindrical recess 40. , the bottom surface 40</b>B, and the volume of the space formed by the gap 60 is smaller than the volume of the columnar portion 50 . Further, the gap 60 is not provided with a member such as a heat conductor.

During lamp lighting, the temperature of the electrode tip member 34 rises, and the heat of the electrode tip member 34 is transferred to the columnar portion 50 . The heat of the columnar portion 50 is transmitted to the electrode supporting rod 17B side and radiated to the gap 60. As shown in FIG. The heat that has moved not only in the axial direction X but also in the direction perpendicular to the axis is transferred from the electrode outer surface 30M to the discharge space DS.

In this embodiment, in order to effectively suppress the temperature rise of the electrode 30, the gap 60 is formed so that the surface area of the gap 60 is larger than the surface area of the electrode side portion T corresponding to the axial length of the gap 60. It is

As described above, the volume of columnar portion 50 is greater than the volume of gap 60 . As a result, the columnar portion 50 has a large amount of heat absorption, and the heat from the cylindrical recess 40 can be absorbed and effectively transported to the electrode supporting rod side.

On the other hand, since the radial width D4 and the axial width L4 of the gap 60 are relatively small, the heat of the columnar portion 50 is transmitted to the electrode outer surface 30M and radiated to the discharge space DS. In this manner, the heat dissipation effect for the electrode side surface portion T corresponding to the axial length L1 of the gap 60 is enhanced.

Such a heat dissipation effect is realized by forming a gap 60 along the circumference of the shaft at a position as far away from the center of the shaft as possible. In that case, the surface area of the gap 60 is larger than the surface area of the electrode side portion T corresponding to the axial length L1.

Further, the surface area of the gap 60 in this embodiment is larger than the surface area of the entire electrode side surface T1 along the electrode axis X. That is, the gap 60 has a large surface area.

By forming the gap 60 having a relatively large surface area in relation to the side surface portion of the electrode, it is possible to effectively suppress the increase in the electrode temperature.

By the way, in the case of the electrode structure in which the gap 60 is formed between the columnar portion 50 and the cylindrical concave portion 40 , the relatively large surface area of the gap 60 described above means that the volume of the columnar portion 50 is larger than the volume of the gap 60 . It can be said that it represents something big. Since the volume of the columnar portion 50 is relatively larger than the volume of the gap 60, it is possible to effectively suppress the increase in electrode temperature.

An electrode that realizes such electrode temperature suppression can be manufactured as follows. That is, a cylindrical recess is formed around the central axis in a columnar distal end side solid member having an electrode tip surface, and a columnar portion smaller in size than the cylindrical recess is formed around the central axis in the columnar rear end side solid member. to form. At this time, the cylindrical concave portion and the columnar portion are arranged such that the surface area of the internal space formed between the cylindrical concave portion and the columnar portion is larger than the surface area of the electrode side portion corresponding to the axial length of the internal space. to form The front solid member and the rear solid member are combined so that the columnar portion is coaxially arranged in the cylindrical recess, and an electrode including the front solid member and the rear solid member is formed by solid phase bonding such as SPS. to form

The spatial shape of the gap 60 is not limited to a bottomed tubular shape, and for example, a bottomless tubular space that does not form the axis-perpendicular direction gap 60D may be formed. Also, an internal space other than the tubular space may be formed, and a space connected to the outside through a closed state or through a hole can be formed. In this case, by forming the space around the electrode axis, the surface area can be made larger than the surface area of the electrode side surface corresponding to the length in the space axis direction. The surface area of the gap (internal space) is the surface area of the space formed closer to the center of the electrode than the outer surface of the electrode. Furthermore, a closed space provided with a heat transfer body that melts at a high temperature may be formed. In this case, the surface area of the space (gap) represents the surface area of the exposed portion and does not include the surface covered with the heat conductor.

A heat radiating portion may be provided in the columnar portion 50 . For example, it is possible to use a known structure that increases the surface area, a structure that increases the emissivity (absorption rate), a heat dissipation material (a heat dissipation layer of a carbonized film or an oxide film), or a material such as a carbon nanotube. Also, a heat radiating portion may be provided at a location other than the columnar portion 50 (cylindrical concave portion 40, electrode side surface, etc.).

Next, a second embodiment will be described with reference to FIG. In the second embodiment, through holes are formed in the side surfaces of the electrodes.

FIG. 3 is a schematic cross-sectional view of the electrode (anode) 130 in the second embodiment. As shown in FIG. 3, a plurality of through holes J1 to J4 are formed. The through holes J1 to J4 are within the axial length L3 of the columnar portion 50 here. By forming the through holes J1 to J4 in this way, the heat in the gap 60 can be released, and the temperature rise of the electrodes can be suppressed. Therefore, the surface area of the gap 60 including the surface areas of the through holes J1 to J4 is determined to be larger than the electrode side portion T or T1. The angle of the through-hole is not limited to the vertical direction (horizontal direction) of the electrode axis, and may be defined as a predetermined angle. In addition, the number, hole diameter, and position are appropriately determined according to the lamp size, electrode size, and the like. For example, a through hole may be formed in the electrode tip surface 34D. Also, a heat radiating portion may be provided in the second embodiment.

The present invention is not limited to the above-described embodiments, and various modifications are possible based on the technical idea of the present invention. The electrodes shown in the first and second embodiments can also be applied to discharge lamps other than short arc discharge lamps. Since the temperature rise of the electrode can be suppressed, it is suitable for discharge lamps with a relatively large power of 1 kW or more. The shape of the electrode can be a desired shape and size, for example, a shape without a tapered portion on the side of the electrode supporting rod. Solid phase bonding (SPS, HP, etc.) is suitable for the bonding method, but other bonding methods (for example, fusion bonding) can also be applied. At the time of joining, an intermediate member may be sandwiched between the front end side member and the rear end side member so that the joining surfaces are brought into close contact with each other. Examples of the intermediate member include rhenium, tantalum, molybdenum, tungsten, or alloys thereof.

The shape and size of the columnar portion and the recessed portion are arbitrary. can be formed to Moreover, it is possible to configure the columnar portion and the tubular recessed portion with different members. For example, it is possible to form the columnar portion (rear end side member) with a member having excellent thermal radiation and light weight, and to form the tip side member with a member having excellent heat resistance and thermal conductivity. Furthermore, the columnar portion may be configured by being joined to the rear end side member. Specifically, tungsten, molybdenum, ceramics, or the like may be used, or an emitter may be contained, or an alloy of these may be applied, and can be selected as appropriate.

Examples according to the second embodiment will be described below.

The discharge lamp of the example is a discharge lamp provided with eight through-holes on the side surface of the electrode and an electrode provided with a through-hole also on the tip surface of the electrode. L4=3 mm, D1=38 mm, D2=26 mm, D3=22 mm, D4=2 mm, through hole diameter=3 mm, and electrode tip hole diameter=3 mm. The surface area of the gap is greater than the surface area of the electrode side portion depending on the axial length of the gap (5552.3>3286.1).

Predetermined electric power was applied to such a discharge lamp to light it, and the temperature of the electrodes in a stable lighting state was measured. The temperature was measured with a thermotracer set to an emissivity of ε0.68 and a measurement wavelength range of 2.2 to 2.6 μm. On the other hand, as a discharge lamp of a comparative example, temperature measurement was performed in the same manner for a discharge lamp incorporating the same electrodes as those of the example except for the configuration in which no gaps and through holes were provided.

FIG. 4 is a graph showing temperature changes toward the electrode tip side in the example and the comparative example. This is obtained by measuring a plurality of points in a region corresponding to the electrode tip side from the joint surface, ie, the electrode side portion T, and plotting the plot to approximate a straight line. The same is true for the comparative examples. As shown in FIG. 4, it was confirmed that the temperature of the electrode of the example was lower than that of the comparative example, and that temperature suppression was maintained even toward the tip of the electrode.

10 discharge lamp 30 electrode (anode)
32 Rear end side member 34 Tip side member 40 Cylindrical recess (recess)
50 columnar portion 60 gap (internal space)

Claims (10)

a discharge tube;
A pair of electrodes arranged oppositely in the discharge tube,
at least one electrode has an interior space;
The internal space has a symmetrical spatial shape with respect to the electrode axis,
A discharge lamp, wherein the surface area of the internal space is larger than the surface area of the electrode side portion corresponding to the axial length of the internal space. 2. The discharge lamp according to claim 1, wherein the surface area of said internal space is larger than the surface area of the electrode side portion along the electrode axial direction. a discharge tube;
A pair of electrodes arranged oppositely in the discharge tube,
at least one electrode has an interior space;
The internal space has a space formed along the entire circumference around the electrode axis ,
A discharge lamp, wherein the surface area of the internal space is larger than the surface area of the electrode side portion corresponding to the axial length of the internal space. a discharge tube;
A pair of electrodes arranged oppositely in the discharge tube,
at least one electrode has an interior space;
the electrode includes a recess along the electrode axis direction and a columnar portion located in the recess,
the internal space is formed to have a width between the concave portion and the columnar portion ;
A discharge lamp, wherein the surface area of the internal space is larger than the surface area of the electrode side portion corresponding to the axial length of the internal space. 5. The discharge lamp according to any one of claims 1 to 4, wherein the inner space is formed in a tubular shape with a bottom. 6. The discharge lamp according to any one of claims 1 to 5, wherein said internal space has a through hole along the direction perpendicular to the electrode axis. 7. The discharge lamp according to any one of claims 1 to 6, wherein a heat radiating portion is provided on a surface portion of said internal space. The at least one electrode is
a first solid member having the recess and a second solid member bonded to the first solid member or an intermediate member bonded to the first solid member and having the columnar portion;
5. The discharge lamp of claim 4 , wherein said internal space is formed between said first solid member and said second solid member or said intermediate member. a discharge tube;
A pair of electrodes arranged oppositely in the discharge tube,
at least one electrode
a recess along the axial direction of the electrode; a columnar portion located in the recess;
An internal space formed between the recess and the columnar portion,
The internal space has a space formed along the entire circumference around the electrode axis,
The discharge lamp, wherein the volume of the columnar portion is larger than the volume of the internal space. A cylindrical recess is formed around a central axis in a columnar tip-side solid member having an electrode tip surface,
forming a columnar portion having a size smaller than that of the cylindrical concave portion around the central axis in the columnar rear end side solid member;
The tip-side solid member and the rear end are arranged so that the columnar portion is coaxially arranged in the cylindrical recess and forms an internal space extending all around the electrode axis between the columnar portion and the cylindrical recess. Combined with the side solid member,
A manufacturing method characterized by forming an electrode including the front-end solid member and the rear-end solid member by solid phase bonding,
The cylindrical concave portion and the columnar portion are arranged such that the surface area of the internal space formed between the cylindrical concave portion and the columnar portion is larger than the surface area of the electrode side portion corresponding to the axial length of the internal space. A method of manufacturing a discharge lamp electrode, comprising forming a columnar portion.

Images