JP7523874B2 - Discharge lamp - Google Patents

Description

The present invention relates to a discharge lamp and lighting device used in exposure devices and the like, and in particular to a short arc type discharge lamp.

Large short-arc discharge lamps (e.g., 1 kW or more) are becoming increasingly high-powered in order to improve the production efficiency of semiconductor and liquid crystal manufacturing. If the electrode structure becomes larger as the power increases, excessive stress is applied to the sealing portion, which may damage the glass member. In addition, the current that flows when the lamp is turned on becomes high, and the sealing portion is more susceptible to heat than ever before. As a countermeasure, a structure that doubles the sealing portion is known (see Patent Document 1). In Patent Document 1, the sealing portion into which the mounting part is inserted is composed of an outer sealing tube and an inner sealing tube, and the inner sealing tube and the outer sealing tube are welded together, and the mounting part is welded to the inner sealing tube.

Patent No. 4182900

However, even though the double sealing structure has increased mechanical and thermal strength, further measures are needed to deal with electrode structures that are becoming larger.

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

The present invention includes an outer sealed tube integrally connected to a discharge tube,
an electrode support rod for supporting an electrode in the discharge tube;
a metal member that electrically connects the sealing foil and the electrode support rod disposed along the axial direction;
An inner sealing tube is disposed closer to the lamp axis than the outer sealing tube,
A glass member is fused to the outside of the outer sealing tube in a region facing the metal member ,
This discharge lamp is characterized in that the thickness of the glass member changes midway in the longitudinal direction.
The present invention also provides an external sealing tube integrally connected to the discharge tube,
An electrode support rod for supporting an electrode in the discharge tube;
A cylindrical glass member for holding an electrode support rod;
a glass tube through which the electrode support rod is inserted;
a metal member that electrically connects the sealing foil and the electrode support rod disposed along the axial direction;
an inner sealing tube disposed coaxially between the outer sealing tube and the cylindrical glass member and fused to the cylindrical glass member;
A glass member is fused to the outside of the outer sealing tube in a region facing the metal member ,
The discharge lamp is characterized in that the outer diameter including the inner sealing tube, the outer sealing tube, and the glass member is the maximum diameter within the axial range from the glass tube to the cylindrical glass member.

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

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

One embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a short arc type discharge lamp according to one embodiment. The short arc type discharge lamp 10 is a discharge lamp that can be used as a light source for an exposure device that forms a pattern, and includes a discharge tube (light emitting tube) 11 made of transparent quartz glass. A cathode 20 and an anode 30 are arranged opposite each other with a predetermined distance between them in the discharge tube 11.

On both sides of the bulb-shaped discharge tube 11, sealing parts 12a and 12b made of quartz glass are formed integrally with the discharge tube 11 so as to face each other, and bases 13a and 13b are fixed to both ends of the sealing parts 12a and 12b. The discharge lamp 10 is arranged vertically so that the anode 30 is on the upper side and the cathode 20 is on the lower side.

Conductive electrode support rods 14a, 14b are disposed inside the sealing parts 12a, 12b to support the metallic cathode 20 and anode 30. As described below, the electrode support rods 14a, 14b are electrically connected to conductive lead rods 15a, 15b, respectively, via a metal member and a sealing foil such as molybdenum. The sealing parts 12a, 12b are constructed by welding a glass tube, a cylindrical glass member, etc., provided inside, thereby sealing the discharge space in which mercury and rare gas are enclosed.

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

The illumination device is configured by arranging a spheroidal reflecting mirror (light-collecting mirror) (not shown) around the discharge lamp 10. When the lamp is turned on, the light emitted from the discharge lamp 10 is reflected by the reflecting mirror. The reflected light is collected at a secondary focus and guided to an object to be illuminated via an illumination optical system (not shown). For example, if the illumination device is provided in an exposure device, the light is irradiated onto the photosensitive surface of a substrate.

Figure 2 is a cross-sectional view of one embodiment of the present invention, and Figure 3 is an enlarged cross-sectional view of a portion thereof. Note that Figures 2 and 3 show the internal structure of the sealing part on the cathode side, but the internal structure of the sealing part on the anode side is similar. The sealing part 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 fused to the glass tube 31 and the inner sealing tube 40.

A glass member 60 arranged coaxially with the outer sealing tube 50 is fused 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 fusing it. This triple glass tube structure (inner sealing tube 40, outer sealing tube 50, glass member 60) increases the mechanical strength and thermal strength compared to conventional double sealing structures, and can prevent cracks in the sealing portion 12a.

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

The inner sealing tube 40 is coaxially arranged between the outer sealing tube 50 and the cylindrical glass member 32, and is fused to the outer sealing tube 50, the cylindrical glass member 32, and the glass tube 31. 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 provided between the cylindrical glass member 32 and the outer glass tube 37. Note that a disk-shaped circular 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 the inner metal member 33 and the outer metal member 36 is provided along the outer surface of the cylindrical glass member 32. The seal foil 34 is a plurality of strip-shaped metal foils made of molybdenum or the like that are provided at intervals along the circumferential direction.

Furthermore, a cylindrical metal foil 35 is provided on the outer peripheral surface of the inner metal member 33 and the sealing foil 34 in the vicinity thereof. Although not shown, a metal foil is also provided on the outer metal member 36 in the same manner as the inner metal member 33. Note that the metal foil 35 may be a foil configured to be covered like a cap, so long as it can cover at least the outer peripheral surface of the inner metal member 33. The metal foil 35 may also be embossed.

The lead rod 15a is inserted through the outer glass tube 37 and the outer metal member 36 and into the sealed end of the cylindrical glass member 32.

In addition, in the present invention, the glass member 60 is fused to at least a portion of the radially outer region of the glass tube 31 in the outer sealing tube 50, extending to at least a portion of the radially outer region of the cylindrical glass member 32. That is, the glass member 60 is fused to the outer surface of the outer sealing tube 50 in the region facing the inner metal member 33. Because the thermal expansion coefficients of metal and glass are different, cracks may occur in the sealing tube (inner sealing tube 40) near the inner metal member 33. Therefore, by fusing the glass member 60 to at least this region to form a triple structure with high mechanical and thermal strength, cracks can be prevented.

Furthermore, in one embodiment of the present invention, a glass member 60 is welded to an axial region of the metal foil 35 that covers 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. When the lamp is turned on, the inner metal member 33 thermally expands, causing a large thermal stress to be 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 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. Alternatively, the axial welding range of the glass member 60 may be shortened so that it is not positioned radially outside the outer metal member 36. In other words, the glass member 60 is not positioned on the outer surface of the outer sealing tube 50 in the area 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, and the welding work time can be shortened. In addition, there is no need to prepare a dedicated base taking into account the thickness of the glass member 60, and it is possible to use the base used in the conventional double sealing structure 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 discharge tube 11 side to the large diameter portion described later. That is, as shown in FIG. 3, it has a large diameter portion (the portion indicated by the arrow 41), a small diameter portion (the portion indicated by the arrow 43) on the cylindrical glass member 32 side, and a reduced diameter portion (the portion indicated by the arrow 42) connecting the large diameter portion and the small diameter portion, and the end of the glass member 60 is not located on the outer surface of the outer sealing tube 50 in the area facing the large diameter portion. It is sufficient to be located radially outside either the small diameter portion 43 or the reduced diameter portion 42.

This configuration increases the strength of the sealing portion 12a near the inner metal member 33 while preventing the outer diameter of the sealing portion 12a from becoming excessively large in some areas. Unlike one embodiment of the present invention, if the outer diameter of the sealing portion is large, the heat capacity also increases accordingly, causing the sealing portion to accumulate heat and increase in temperature. Therefore, by not fusing the glass member 60 to the portion facing the large diameter portion of the glass tube 31, excessive temperature increases in the sealing portion 12a can be prevented. However, in order to increase the mechanical strength and 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 cylindrical glass member 32.

In one embodiment of the present invention, the outer diameter of the triple-structured sealed portion 12a consisting of the inner sealed tube 40, the outer sealed tube 50, and the glass member 60 is smaller than the outer diameter of the discharge tube side end of the base 13a. Therefore, when the discharge lamp 10 is placed in a lighting device, the reflected light reflected by the reflecting mirror can be prevented from hitting the triple-structure portion as it travels to the secondary focus, making it possible to make maximum use of the light.

Furthermore, 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 a decrease in glass strength caused by OH groups is suppressed.

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

Although one embodiment of the present technology has been specifically described above, the present invention is not limited to the above-mentioned embodiment, and various modifications based on the technical idea of the present invention are possible. For example, the thickness and diameter of the glass member 60 do not need to be constant along the longitudinal direction. Depending on the lamp shape, the diameter of the glass member 60 may be gradually changed along the longitudinal direction, and the thickness may be changed along the longitudinal direction to match the area where it is desired to make the glass member 60 thick or not. In addition, the shape of the glass tube 31 is not limited to the above-mentioned embodiment, and it is also possible to make the large diameter part long in the axial direction or to make the glass tube 31 have a constant diameter without steps. In addition, 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, and values given in the above-mentioned embodiment are merely examples, and different configurations, methods, processes, shapes, materials, and values may be used as necessary.

DESCRIPTION OF SYMBOLS 10... Discharge lamp, 11... Discharge tube, 12a, 12b... Sealing part,
13a, 13b... metal caps, 14a, 14b... electrode support rods, 20... cathode,
30: anode; 31: glass tube; 32: cylindrical glass member;
33: inner metal member, 34: sealing foil, 35: metal foil,
36: outer metal member, 37: outer glass tube, 40: inner sealing tube,
50: outer sealing tube, 60: glass member

Claims (3)

an outer sealing tube integrally connected to the discharge tube;
an electrode support rod for supporting an electrode in the discharge tube;
a metal member electrically connecting a sealing foil disposed along the axial direction to the electrode support rod;
an inner sealing tube disposed closer to the lamp axis than the outer sealing tube;
a glass member is fused to the outside of the outer sealing tube in a region facing the metal member ;
A discharge lamp characterized in that the thickness of the glass member changes midway in the longitudinal direction. an outer sealing tube integrally connected to the discharge tube;
an electrode support rod for supporting an electrode in the discharge tube;
a cylindrical glass member for holding the electrode support rod;
a glass tube through which the electrode support rod is inserted;
a metal member electrically connecting a sealing foil disposed along the axial direction to the electrode support rod;
an inner sealing tube arranged coaxially between the outer sealing tube and the cylindrical glass member and fused to the cylindrical glass member;
a glass member is fused to the outside of the outer sealing tube in a region facing the metal member ;
A discharge lamp, characterized in that an outer diameter including the inner sealing tube, the outer sealing tube, and the glass member is the maximum diameter within an axial range from the glass tube to the cylindrical glass member. 3. The discharge lamp according to claim 1, wherein the concentration of OH groups in a 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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