JP2021022503A - Discharge lamp - Google Patents

Abstract

To increase the strength of a sealing portion.SOLUTION: A discharge lamp includes an outer sealing tube that is integrally connected to a discharge tube, an electrode support rod that supports an electrode in the discharge tube, a columnar glass member that holds the electrode support rod, and an inner sealing tube that is coaxially arranged between the outer sealing tube and the columnar glass member and welds to the columnar glass member, and the glass member arranged coaxially with the outer sealing tube is welded to the outside of the outer sealing tube.SELECTED DRAWING: Figure 3

Description

The present invention relates to a discharge lamp and a lighting device used for an exposure device and the like, and more particularly to a short arc type discharge lamp.

For large short arc type discharge lamps (for example, 1 kW or more), the power consumption is increasing in order to improve the production efficiency of semiconductor and liquid crystal manufacturing. If the electrode structure becomes large due to the increase in electric power, excessive stress may be applied to the sealing portion and the glass member may be damaged. In addition, the current that flows when the lamp is lit becomes a high current, and the sealing portion is affected by heat more than ever. As a countermeasure, a structure in which the sealing portion is doubled is known (see Patent Document 1). In Patent Document 1, the sealing portion into which the mount component is inserted is composed of an outer sealing tube and an inner sealing tube, the inner sealing tube and the outer sealing tube are welded, and the mounting component is internally sealed. It is welded to the tube.

Patent No. 4182900

However, even though the double-sealed structure has increased mechanical strength and thermal strength, further measures are required for the electrode structure, which is becoming larger in size.

Therefore, an object of the present invention is to provide a discharge lamp having a sealing structure having higher mechanical strength and thermal strength.

The present invention includes an outer sealing tube that is integrally connected to the discharge tube, an electrode support rod that supports the electrodes in the discharge tube, a columnar glass member that holds the electrode support rod, and an outer sealing tube and a columnar glass member. A cylindrical glass member and an inner sealing tube to be welded are provided between the two, and a glass member coaxially arranged with the outer sealing tube is welded to the outside of the outer sealing tube. It is a discharge lamp characterized by being used.

According to at least one embodiment, since the sealing portion has a triple structure of an inner sealing tube, an outer sealing tube, and a glass member, the strength of the sealing portion can be increased. The effects described here are not necessarily limited, and may be any of the effects described in the present specification or an effect different from them.

FIG. 1 is a diagram schematically showing a short arc type discharge lamp to which the present invention can be applied. FIG. 2 is a cross-sectional view showing a configuration on the cathode side of the embodiment of the present invention. FIG. 3 is a partially enlarged cross-sectional view showing the configuration of one embodiment of the present invention.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram schematically showing a short arc type discharge lamp according to an embodiment. The short arc type discharge lamp 10 is a discharge lamp that can be used as a light source of an exposure device for forming a pattern, and includes a transparent quartz glass discharge tube (light emitting tube) 11. The cathode 20 and the anode 30 are arranged to face each other at predetermined intervals in the discharge tube 11.

Sealed portions 12a and 12b made of quartz glass are integrally formed with the discharge tube 11 on both sides of the spherical discharge tube 11 so as to face each other, and both ends of the sealing portions 12a and 12b are caps. 13a and 13b are fixed. The discharge lamp 10 is arranged along the vertical direction so that the anode 30 is on the upper side and the cathode 20 is on the lower side.

Conductive electrode support rods 14a and 14b that support the metal cathode 20 and the anode 30 are arranged inside the sealing portions 12a and 12b. As will be described later, the electrode support rods 14a and 14b are electrically connected to the conductive lead rods 15a and 15b via a metal member and a sealing foil such as molybdenum, respectively. The sealing portions 12a and 12b are formed by welding a glass tube, a columnar glass member, etc. provided inside, thereby sealing a discharge space in which mercury and a rare gas are sealed.

The lead rods 15a and 15b are connected to an external power supply unit, and a voltage is applied between the cathode 20 and the anode 30 via the metal member, the seal foil and the electrode support rods 14a and 14b. When electric power is supplied to the discharge lamp 10, an arc discharge is generated between the electrodes, and a bright line (ultraviolet light) due to mercury is emitted.

A spheroidal reflection mirror (condensing mirror) (not shown) is arranged around the discharge lamp 10 to form an illumination device. When the lamp is lit, the light emitted from the discharge lamp 10 is reflected by the reflection mirror. The reflected light is focused on the secondary focus and guided to the object to be irradiated through an illumination optical system (not shown). For example, when the lighting device is provided in the exposure device, the photosensitive surface of the substrate is irradiated with light.

FIG. 2 is a cross-sectional view of an embodiment of the present invention, and FIG. 3 is a partially enlarged cross-sectional view. Although FIGS. 2 and 3 show the structure inside the sealing portion on the cathode side, the inside of the sealing portion on the anode side has the same structure. The sealing portion 12a has a triple glass tube structure consisting of an inner sealing tube 40, an outer sealing tube 50, and a glass member 60. The outer sealing tube 50 is integrally connected to the discharge tube 11, and is welded to the glass tube 31 and the inner sealing tube 40.

A glass member 60 arranged coaxially with the outer sealing tube 50 is welded to the outside of the outer sealing tube 50. That is, the glass member 60 is provided by covering the outer surface of the outer sealing tube 50 with a tubular glass member (quartz glass) and welding the glass member 60. With such a triple glass tube structure (inner sealing tube 40, outer sealing tube 50, glass member 60), the mechanical strength and thermal strength are increased as compared with the conventional double sealing structure, and the sealing portion 12a Cracks can be prevented.

The electrode support rod 14a that supports the cathode 20 in the discharge tube 11 is inserted through the inner metal member 33 that is an annular member, and further extends to the columnar glass member 32. The electrode support rod 14a is held by a glass tube 31, an inner metal member 33, and a columnar glass member 32 along the lamp axis.

The inner sealing tube 40 is arranged coaxially between the outer sealing tube 50 and the cylindrical glass member 32, and is welded to the outer sealing tube 50, the cylindrical glass member 32, and the glass tube 31. Further, the annular inner metal member 33 is provided between the glass tube 31 and the cylindrical glass member 32, and the annular outer metal member 36 is located between the cylindrical glass member 32 and the outer glass tube 37. Is provided. A disk-shaped disc foil may be provided between each member such as between the glass tube 31 and the inner metal member 33. A seal foil 34 that electrically connects between the inner metal member 33 and the outer metal member 36 is provided along the outer surface of the columnar glass member 32. The seal foil 34 is a plurality of strip-shaped metal foils made of molybdenum or the like provided apart from each other along the circumferential direction.

Further, a tubular metal foil 35 is provided on the outer peripheral surface of the inner metal member 33 and the seal foil 34 in the vicinity thereof. Although not shown, a metal foil is provided on the outer metal member 36 as well as the inner metal member 33. The metal foil 35 may be a foil having a structure such as a cap as long as it can cover at least the outer peripheral surface of the inner metal member 33. Further, the metal foil 35 may be embossed.

The lead rod 15a is inserted through the outer glass tube 37 and the outer metal member 36, and is inserted into the sealing end side of the columnar glass member 32.

Further, in the present invention, the glass member 60 is welded from at least a part of the radial outer region of the glass tube 31 in the outer sealing tube 50 to at least a part of the radial outer region of the cylindrical glass member 32. There is. That is, the glass member 60 is welded to the outer surface of the outer sealing tube 50 in the region facing the inner metal member 33. Since the coefficient of thermal expansion differs between metal and glass, cracks may occur in the sealing tube (inner sealing tube 40) near the inner metal member 33. Therefore, cracks can be prevented by welding the glass member 60 to at least this region to form a triple structure having high mechanical strength and thermal strength.

Further, in one embodiment of the present invention, the glass member 60 is welded to the axially extending region of the metal foil 35 covering the inner metal member 33 in the outer sealing tube 50. That is, the glass member 60 is welded to the outer surface of the outer sealing tube 50 in the region facing the metal foil 35. While the lamp is lit, the inner metal member 33 thermally expands and a large thermal stress is applied to the metal foil 35, which also acts toward the sealing tube (inner sealing tube 40). Therefore, by welding the glass member 60 to this region, the mechanical strength and the thermal strength of the sealing portion 12a in the vicinity where a large thermal stress is applied can be increased.

In the configuration shown in FIG. 2, the glass member 60 is provided up to the position of the outer glass tube 37. Unlike this, the axial welding range of the glass member 60 may be shortened so as not to be located radially outside the outer metal member 36. That is, the glass member 60 is not positioned on the outer surface of the outer sealing tube 50 in the region facing the outer metal member 36. By shortening the axial length of the glass member 60 in this way, the welding range can be shortened, so that the welding work time can be shortened. Further, it is not necessary to prepare a special base in consideration of the thickness of the glass member 60, and the base used in the conventional double sealing structure can be used as it is.

As shown in FIG. 3, the glass tube 31 has a cross-sectional shape in which the diameter gradually decreases from the side of the discharge tube 11 with a large diameter portion described later as a boundary. That is, as shown in FIG. 3, the large diameter portion (the portion indicated by the arrow 41), the small diameter portion on the columnar glass member 32 side (the portion indicated by the arrow 43), and the reduced diameter portion (arrow) connecting the large diameter portion and the small diameter portion. 42), and the end of the glass member 60 is not located on the outer surface of the outer sealing tube 50 in the region facing the large diameter portion. It may be located on the outer side in the radial direction of either the small diameter portion 43 or the reduced diameter portion 42.

With such a configuration, the strength of the sealing portion 12a near the inner metal member 33 is increased, and the outer diameter of the sealing portion 12a is not partially increased more than necessary. Unlike one embodiment of the present invention, if the outer diameter of the sealing portion is large, the heat capacity is also increased by that amount, and the sealing portion stores heat and the temperature rises. Therefore, by not welding the glass member 60 to the portion of the glass tube 31 facing the large diameter portion, it is possible to prevent an excessive temperature rise of the sealing portion 12a. However, in order to increase the mechanical strength and the thermal strength, the outer diameter of the triple structure may be the maximum diameter in the axial range from the glass tube 31 to the outer end of the columnar glass member 32.

In one embodiment of the present invention, the outer diameter of the triple-structured sealing portion 12a composed of the inner sealing pipe 40, the outer sealing pipe 50, and the glass member 60 is smaller than the outer diameter of the discharge pipe side end of the base 13a. It is supposed to be. Therefore, when the discharge lamp 10 is arranged in the lighting device, it is possible to prevent the reflected light reflected by the reflecting mirror from hitting the portion of the triple structure when it travels to the secondary focus, and the light can be used to the maximum extent.

Further, in one embodiment of the present invention, the OH group concentration in the radial range from the inner surface of the inner sealing tube 40 to the outer surface of the glass member 60 is set to 30 ppm or less. By setting the OH group concentration to a low value such as 30 ppm, the occurrence of cracks in the sealing portion 12a due to the decrease in glass strength due to the OH group is suppressed.

Since the amount of glass used in the triple structure increases, the total OH group content in the sealing portion 12a inevitably increases. Further, as described above, cracks are likely to occur from the inner surface of the inner sealing tube 40 due to the thermal expansion of the inner metal member 33. Therefore, it has been empirically found that cracks can be suppressed more effectively by defining the OH group concentration in the radial range from the inner surface of the inner sealing tube 40, which tends to be the starting point of cracks, to the outer surface of the glass member 60. It was. The content of this OH group can be controlled by heat-treating the glass (dehydration treatment, high-temperature vacuum treatment, etc.), and is measured by, for example, FTIR (Fourier transform infrared spectrophotometer).

Although one embodiment of the present invention has been specifically described above, the present invention is not limited to the above-mentioned one embodiment, and various modifications based on the technical idea of the present invention are possible. .. For example, the wall thickness and diameter of the glass member 60 do not have to be constant along the longitudinal direction. Depending on the shape of the lamp, the diameter of the glass member 60 may be gradually changed in the middle of the longitudinal direction, or the wall thickness may be changed in the middle of the longitudinal direction according to a region to be thickened or not to be thickened. Further, the shape of the glass tube 31 is not limited to the above-described embodiment, and it is also possible to have a shape in which the large diameter portion is long in the axial direction or a shape having a constant diameter without a step. Further, the present invention may be applied to a sealing structure on either the cathode side or the anode side. In addition, the configurations, methods, processes, shapes, materials, numerical values, etc. mentioned in the above-described embodiments are merely examples, and different configurations, methods, processes, shapes, materials, numerical values, etc. may be used as necessary. May be good.

10 ... Discharge lamp, 11 ... Discharge tube, 12a, 12b ... Sealing part,
13a, 13b ... Mouthpiece, 14a, 14b ... Electrode support rod, 20 ... Cathode,
30 ... Anode, 31 ... Glass tube, 32 ... Cylindrical glass member,
33 ... Inner metal member, 34 ... Seal foil, 35 ... Metal leaf,
36 ... outer metal member, 37 ... outer glass tube, 40 ... inner sealing tube,
50 ... outer sealing tube, 60 ... glass member

Claims (7)

The outer sealing tube that is integrally connected to the discharge tube,
An electrode support rod that supports the electrodes in the discharge tube and
A columnar glass member that holds the electrode support rod and
It is provided with an inner sealing tube coaxially arranged between the outer sealing tube and the cylindrical glass member and welded to the columnar glass member.
A discharge lamp characterized in that a glass member coaxially arranged with the outer sealing tube is welded to the outer side of the outer sealing tube. The glass tube through which the electrode support rod is inserted and
A metal member for electrically connecting the seal foil arranged along the axial direction and the electrode support rod is provided.
The glass member is characterized in that it is welded from at least a part of the radial outer region of the glass tube in the outer sealing tube to at least a part of the radial outer region of the cylindrical glass member. The discharge lamp according to claim 1. A metal foil covering at least the outer peripheral surface of the metal member is provided.
The discharge lamp according to claim 1 or 2, wherein the glass member is welded to a radial outer region of the metal foil in the outer sealing tube along the axial direction. It is provided with an outer metal member that electrically connects the lead rod electrically connected to external power and the seal foil.
The discharge lamp according to any one of claims 1 to 3, wherein the glass member is not located radially outside the outer metal member in the outer sealing tube. The glass tube has a large diameter portion, a small diameter portion having a diameter smaller than that of the large diameter portion on the columnar glass member side, and a reduced diameter portion connecting the large diameter portion and the small diameter portion.
The discharge lamp according to any one of claims 1 to 4, wherein the end portion of the glass member is located at one of the small diameter portion and the reduced diameter portion. A mouthpiece is fixed to the outer end of the outer sealing tube,
The outer diameter including the inner sealing tube, the outer sealing tube, and the glass member is the maximum diameter in the axial range from the glass tube to the cylindrical glass member, and the base is the base. The discharge lamp according to any one of claims 1 to 5, wherein the discharge lamp is smaller than the outer diameter of the arc tube side end portion of the above. The discharge lamp according to any one of claims 1 to 6, wherein the OH group concentration in the radial range from the inner surface of the inner sealing tube to the outer surface of the glass member is 30 ppm or less.

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