TW201703102A - Discharge lamp capable of preventing lack of emitter materials and inhibiting flicker of the arc discharge - Google Patents

Abstract

Provided is a discharge lamp with an electrode formed by joining different metal members, which can prevent lack of emitter materials and inhibit flicker of the arc discharge. The discharge lamp is provided with a cathode and an anode oppositely arranged in a discharge tube. The cathode is formed by means of performing a solid state bonding on a plurality of metal members including a front end side member containing emitter materials and a rear end side member supported by a conductive electrode support bar. The heat energy that moves toward the rear end side member from the front end side member is reduced by taking the proximity of a junction surface between the at least one metal member as a boundary.

Description

Discharge lamp

The present invention relates to a discharge lamp used in an exposure apparatus or the like, and more particularly to an electrode structure of a high output discharge lamp of a short arc discharge lamp or the like.

In the past, discharge lamp tubes added an emitter material to the cathode to improve the electron emission characteristics. As the emitter, cerium oxide (ThO ₂ ) is typically used, but cerium oxide is a radioactive substance. Therefore, it should be used as cautiously as possible, and as shown in Patent Document 1, a discharge lamp tube in which only the emitter material (ruthenium oxide) is contained at the tip end of the cathode is developed.

[Prior patent documents]

[Patent Literature]

[Patent Document 1] Patent No. 5316436

However, in the conventional cathode structure, the emitter contained in the tip end of the cathode cannot be effectively utilized. In the lighting of the discharge lamp, the temperature inside the front end of the cathode is lower than the surface of the front end of the cathode, and the emitter contained in the inside of the cathode front end is not thermally diffused, and the emitter is not supplied to the surface of the front end of the cathode. Therefore, the surface emitter at the front end of the cathode is lacking because the electron emission characteristics are lowered. And flashing occurs.

Therefore, in the discharge lamp tube in which the amount of the emitter is reduced, it is also required that the electron emission characteristics are not lowered and the flicker is reduced.

The discharge lamp tube of the present invention is: a discharge tube; and a cathode and an anode are disposed opposite to each other in the discharge tube; and the cathode is supported by a rod supporting the rod before the end member containing the emitter material The plurality of metal members of the rear end side member of the support are formed by solid state joining, and the heat moved from the front end side member to the rear end side member is narrowed by the vicinity of the joint surface between the plurality of metal members.

In the lighting of the discharge lamp, the front end of the cathode becomes the highest temperature, and the heat is moved from the front end to the lower end. By reducing the amount of heat generated by the vicinity of the joint surface between the members, the temperature of the front end side member is suppressed from decreasing. As a result, the emitter inside the cathode front end side member is thermally diffused, and the emitter is supplied to the surface of the front end, reducing the shortage of the emitter. Therefore, in the discharge lamp tube in which the amount of the emitter is reduced, the electron emission characteristics are not lowered, and flicker can be reduced.

10‧‧‧Discharge lamp

12‧‧‧Light tube

20‧‧‧ cathode

22‧‧‧ front end side members

24‧‧‧ rear end side members

30‧‧‧Anode

J‧‧‧ joint surface

L‧‧‧electrode shaft

Fig. 1 is a plan view showing a short arc discharge lamp of the present embodiment in a mode.

Fig. 2 is a schematic cross-sectional view showing the vicinity of the electrode between the cathodes.

Fig. 3 is a schematic cross-sectional view showing the vicinity of a joint surface of a cathode of a second embodiment.

Fig. 4 is a schematic cross-sectional view showing a cathode of a third embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Fig. 1 is a plan view showing a short arc discharge lamp of the present embodiment in a mode.

The short arc discharge lamp 10 can be used for a discharge lamp such as a light source of an exposure device (not shown) for patterning, and is provided with a discharge tube (light-emitting tube) 12 made of transparent quartz glass. In the discharge tube 12, the cathode 20 and the anode 30 are disposed to face each other at a predetermined interval.

On both sides of the discharge tube 12, the sealed tubes 13A, 13B made of quartz glass are integrally provided in opposition to the discharge tube 12, and both ends of the sealed tubes 13A, 13B are closed by the covers 14A, 14B. Here, the discharge lamp tube 10 is disposed such that the anode 30 is on the upper side and the cathode 20 is on the lower side in the vertical direction.

Electrode support rods 17A and 17B for supporting the cathode 20 and the anode 30 of the metal are disposed inside the sealed tubes 13A and 13B, and are respectively connected to the metal foils 16A and 16B such as molybdenum via a metal ring (not shown). It is connected to the conductive lead bars 15A, 15B. The sealed tubes 13A and 13B are welded to glass tubes (not shown) provided in the sealed tubes 13A and 13B, whereby the discharge space SD in which mercury or rare gas is sealed is closed.

The lead bars 15A and 15B are connected to an external power supply unit (not shown), and a voltage is applied between the cathode 20 and the anode 30 via the lead bars 15A and 15B, the metal foils 16A and 16B, and the electrode support bars 17A and 17B. When electric power is supplied to the discharge lamp tube 10, an arc discharge is generated between the electrodes, and a bright line (ultraviolet light) by mercury is emitted.

Fig. 2 is a schematic cross-sectional view showing the vicinity of the electrodes.

The cathode 20 is composed of a metal member (front end side member) 22 having a cathode front end surface 20S and a metal member (rear end side member) 24 supported by the electrode support rod 17A. The truncated conical front end side member 22 has a front end side tapered portion 22A. The rear end side member 24 has a cylindrical portion 24B that is engaged with the electrode support rod 17A, and a rear end side tapered portion 24A that is engaged with the front end side member 22. The distal end side tapered portion 22A and the rear end side tapered portion 24A constitute a reduced diameter portion (tapered portion) 20T of the cathode 20.

The distal end side member 22 is configured as an electrode made of tungsten which is made of tungsten containing cerium oxide. On the other hand, the rear end side member 24 is composed of molybdenum (Mo) which is a metal having a thermal conductivity smaller than that of the front end side member 22.

The thermal conductivity of the front end side member 22 composed of the deposited tungsten is substantially equal to the thermal conductivity of tungsten (about 177 W/mk) because the content of yttrium oxide is minute (for example, 2 wt%). On the other hand, the thermal conductivity of the end side member 24 is 139 W/mk after the molybdenum is formed, and the thermal conductivity of the rear end side member 24 is smaller than the thermal conductivity of the distal end side member 22.

The cathode 20 is formed by joining the front end side member 22 and the rear end side member 24. Here, it is manufactured according to discharge plasma sintering (SPS). Specifically, a cylindrical front end side metal material 122 and a rear end side metal material 124 (see FIG. 2) in which the metal powder is sintered and solidified are prepared and provided in the SPS apparatus.

In the SPS device, the flat end surface (joining side end surface) 122J of the front end side metal material 122 is in close contact with the end surface 124J of the rear end side metal material 124, and both the front end side metal material 122 and the rear end side metal material 124 are faced. The terminal is pressurized, and a voltage is applied thereto, and the front end side metal material 122 and the rear end side metal material 124 are solid-bonded by plasma discharge. Voltage value, pressure, and pressure at this time The time is determined by the size of the electrode and the like. The front end side metal material 122 and the rear end side metal material 124 are the front end side member 22 and the rear end side member 24, respectively.

In the case of solid state bonding, a strong crystal structure change does not occur in the vicinity of the joint surface, and the joint surface strength can be sufficiently ensured. Both fusion bonding or welding can be joined, but in fusion bonding, because heating is required until the metal melts, the contained emitter is reduced and the emitter is deficient. Further, in the welding, the temperature flux in the lighting of the discharge lamp tube 10 is melted, and the front end side member 22 may be peeled off from the rear end side member 24.

Then, the cathode 20 having the tapered portion 20T is formed by performing a processing such as cutting processing after solid state bonding. The cathode 20 and the anode 30 made of tungsten are arranged to face each other in accordance with the distance between the predetermined electrodes.

The joint surface J of the cathode 20 is formed along a direction perpendicular to the electrode axis L (here, 90°), and substantially no gap is formed in the entire joint surface J. In other words, since the end faces 122J and 124J of the distal end side metal material 122 and the rear end side metal material 124 are both flat, a gap caused by a rough surface, unevenness, or the like which is intentionally formed in advance is not generated in the joint surface J.

According to the structure of the cathode 20, the discharge lamp tube in which only the yttrium oxide (emitter substance) is contained in the distal end side member 22 to reduce the amount of yttrium oxide can be reduced in flicker.

When the discharge lamp tube 10 is turned on, the front end surface 20S of the cathode 20 is at the highest temperature (1000 ° C or higher). Since the heat system moves from a high temperature to a low temperature, the heat of the cathode front end face 20S moves toward the electrode support rod 17A side of the rear end side member 24. At this time, in the case where the cathodes of the same type of members are joined, since the thermal conductivity of the front end side member and the rear end side member are the same, The heat that moves in the vicinity of the joint surface does not change.

On the other hand, in the present embodiment, since the thermal conductivity of the rear end side member 24 is slightly smaller than the thermal conductivity of the distal end side member 22, the amount of heat to be moved is reduced by the vicinity of the joint surface J. Therefore, the temperature of the distal end side member 22 is hard to be lowered because the heat transferred to the rear end side is smaller than the front end side member of the cathode formed by joining the same members. The temperature drop of the distal end side member 22 is suppressed, and the temperature difference between the distal end surface 20S and the inside of the distal end side member 22 becomes small, and not only the surface of the distal end side member 22 but also the inside of the distal end side member 22, the cerium oxide is also thermally diffused. .

Thereby, yttrium oxide is supplied to the cathode front end surface 20S, and the electron emission characteristics are not lowered, and flicker can be reduced.

As described above, since the end face faces of the metal materials which are flat with each other are joined to each other, no rough faces or irregularities are formed on the joint faces J. There is no difference in the amount of heat conduction due to the presence or absence of the rough surface or the unevenness, and it is uniformly moved along the joint surface J. Therefore, joining the rear end side members 24 of the metal having a small thermal conductivity also prevents local overheating of the joint surface J without fear of occurrence of intense local electrode consumption.

Further, the term "flat" here is not intentionally provided with grooves or irregularities on the joint side end faces, indicating that it is not a rough surface, and does not require a smooth surface or a strict vertical direction of the counter electrode axis L. As long as there is no difference in the amount of heat moved, the range in which local overheating does not occur is flat.

Since the discharge lamp tube 10 may also have a front end surface 20S of the cathode of about 2000 ° C, the front end side member 22 is suitable for tungsten having a high melting point. From the relationship of the thermal conductivity of the tungsten (about 177 W/mk), the rear end side member 24 is most suitable for molybdenum. When the difference in thermal conductivity between the distal end side member 22 and the rear end side member 24 is too small, the amount of heat conduction does not become small, and the effect of the present invention cannot be expected. On the other hand, if the difference in thermal conductivity between the distal end side member 22 and the rear end side member 24 is too large, the periphery of the joint surface J is in an overheated state, which causes a decrease in the strength of the joint surface or consumption of the electrode.

For example, in the case where the rear end side member 24 is made of magnesium, the thermal conductivity is suitably about 157 W/mk, but since the melting point is about 650 ° C, it cannot be applied to the cathode 20 of the discharge lamp tube 10. Further, in the case where the rear end side member 24 is constituted by ruthenium, the melting point is as high as 3,180 ° C, but the thermal conductivity is as low as about 47.9 W/mk, which cannot be applied.

Further, by forming the rear end side member 24 with molybdenum, the weight is lighter than that of an electrode integrally formed of one tungsten material, and an effect of excellent vibration resistance can be expected. Further, not only pure molybdenum but also an alloy containing molybdenum as a main component may be used.

In this manner, according to the present embodiment, the short-arc discharge lamp tube 10 including the cathode 20 and the anode 30 is formed by the front end side member 22 composed of the tungsten and the rear end side member 24 composed of molybdenum. The solid state is joined to form the cathode 20, and the heat transmitted from the distal end surface 20S to the side of the rear end side member 24 is reduced in the vicinity of the joint surface.

Next, the second embodiment will be described using Fig. 3 . In the second embodiment, the diameter reduction is formed in the vicinity of the joint surface. The components other than the above are substantially the same as in the first embodiment, and the same components are denoted by the same reference numerals, and their description is omitted.

Fig. 3 is a cross-sectional view showing the vicinity of a joint surface of a cathode of a second embodiment.

The cathode 20 is constructed by the front end side member 22 and the rear end side member 24 The joint surface J is formed along the vertical direction of the electrode axis L. Further, in the vicinity of the joining-side end surface of the rear end side member 24, the reduced diameter portion 26 which is recessed toward the electrode axis L side is formed. The diameter of the electrode shaft L of the reduced diameter portion 26 in the vertical direction is smaller than the diameter of the joint side end surface of the distal end side member 22.

The reduced diameter portion 26 is formed over the entire circumference of the joint side end surface of the rear end side member 24, and can be formed by cutting processing after solid state joining. Further, the recess may be initially provided on the rear end side material 124.

By forming the reduced diameter portion 26 in this manner, the diameter of the vicinity of the joint side end surface of the end side member 24 after the diameter reducing portion 26 is provided is smaller than the diameter of the vicinity of the joint side end surface of the distal end side member 22. From the cathode front end surface 20S toward the electrode support rod 17A side, the cross-sectional area is reduced, and the amount of heat of movement is reduced. Thereby, it contributes to suppressing the temperature fall of the front-end side member 22. Therefore, the cerium oxide is also thermally diffused from the inside of the front end side member 22, and yttrium oxide is supplied to the front end surface 20S of the cathode, so that the electron emission characteristics are not lowered, and flicker can be reduced.

The position at which the reduced diameter portion 26 is formed should be appropriately selected in accordance with the size of the cathode 20 by experiment or the like. However, when the formation position of the reduced diameter portion 26 is more excessively distant from the electrode support rod 17A side than the joint surface J, and the deep reduction diameter is not formed, the diameter of the electrode axis L of the reduced diameter portion 26 in the vertical direction cannot be made larger than the front end side. The diameter of the joint side end face of the member 22 is smaller. As a result, the cutting process becomes complicated. On the other hand, if the formation position of the reduced diameter portion 26 is excessively close to the joint surface J, there is a possibility that the strength of the joint surface is lowered. Therefore, the reduced diameter portion 26 may be provided at a position where the processing does not become complicated and the strength of the joint surface can be maintained.

In the present embodiment, the reduced diameter portion 26 is formed over the entire circumference of the joint side end surface of the rear end side member 24. However, as long as the diameter ratio of the reduced diameter portion 26 can be made The diameter of the joint side end surface of the distal end side member 22 is smaller, and the reduced diameter portion 26 may be formed at least a part of the vicinity of the joint side end surface of the rear end side member 24, or may not be the entire circumference. Further, the reduced diameter portion 26 may be a thread groove for increasing the surface area of the cathode 20.

Next, a discharge lamp of the third embodiment will be described using Fig. 4 . In the third embodiment, the taper angle of the rear end side member is smaller than the taper angle of the front end side member. The components other than the above are substantially the same as in the first embodiment, and the same components are denoted by the same reference numerals, and their description is omitted.

Fig. 4 is a schematic cross-sectional view showing a cathode of a third embodiment.

The cathode 20 is composed of the distal end side member 22 and the rear end side member 24, and forms a joint surface J along the vertical direction of the electrode axis. Further, the taper angle θ2 of the rear end side member 24 is smaller than the taper angle θ1 of the distal end side member.

The desired taper angle can be formed by performing processing such as cutting processing after solid state bonding. Further, the front end side metal material 122 and the rear end side metal material 124 which have originally formed the desired taper angle may be solid-bonded. For example, the taper angle θ1 of the distal end side member can be made 70°, and the taper angle θ2 of the rear end side member 24 can be made 50°.

According to this configuration, the taper angle θ2 of the rear end side member 24 is smaller than the taper angle θ1 of the distal end side member 22, and the taper angle of the distal end side member 22 and the taper angle of the rear end side member 24 are equal to each other. The cross-sectional area of the heat conductive portion is reduced, which contributes to suppressing the temperature drop of the front end side member 22. Therefore, the cerium oxide is also thermally diffused from the inside of the front end side member 22, and yttrium oxide is supplied to the front end surface 20S of the cathode, so that the electron emission characteristics are not lowered, and flicker can be reduced.

Further, the configuration is not limited to the second and third embodiments, and only At least a part of the end side member 24 after the vicinity of the joint surface J may be disposed on the side of the axis L of the cathode 20 more than the taper angle of the front end side member 22. The amount of heat moved from the cathode front end face 20S can be limited, resulting in a decrease in flicker. Further, the rear end side member 24 may be made of tungsten as long as the amount of heat to be moved is reduced.

Moreover, in order to increase the joint strength between the front end side member 22 and the rear end side member 24, the intermediate member is interposed between the front end side member 22 and the rear end side member 24, and the front end side member 22, the intermediate member, and the rear end side member are sandwiched. 24 is solid-state bonding, whereby it is suitable when the joint surfaces are in close contact. Since the amount of heat conduction is small, the joint strength can be maintained even if heat is accumulated in the vicinity of the joint surface J.

The intermediate member is preferably a thickness of about 1 mm or less in order to suppress the influence of the magnitude relationship of the heat transfer between the distal end side member 22 and the rear end side member 24. For example, tantalum, niobium, molybdenum, or alloys of these can be used. Further, in the case of using the intermediate member having the thickness, in order to restrict the temperature drop of the front end side member 22, it is necessary to move the boundary between the front end side member and the intermediate member or the joint surface of the intermediate member and the rear end side member. Less heat.

According to the structure of the cathode 20 of the present invention, since the cerium oxide (emitter substance) contained in the inside of the distal end side member 22 can be effectively utilized, the amount of cerium oxide contained in the distal end side member 22 itself can be reduced. In the first to third embodiments, the distal end side member 22 contains 2% by weight of cerium oxide, but can be reduced to 1% by weight. The front end member 22, which is composed of tungsten-coated tungsten containing 1% by weight of cerium oxide, is also configured as described in the first to third embodiments, and the electron emission characteristics are not lowered, and flicker can be reduced.

Further, in the first to third embodiments, the cathode 20 is formed in a tapered shape, but may be a so-called bullet-shaped circular arc shape. Furthermore, it can also be applied to short arc type A discharge lamp other than a lamp. Further, the emitter material is not limited to cerium oxide, and may be a substance which enhances electron emission characteristics such as cerium oxide or a rare earth element.

17A‧‧‧electrode support rod

20‧‧‧ cathode

20S‧‧‧ front end

20T‧‧‧Reducing section (taper)

22‧‧‧ front end side members

22A‧‧‧ front side taper

24‧‧‧ rear end side members

24A‧‧‧Rear end taper

24B‧‧‧ cylindrical part

30‧‧‧Anode

122‧‧‧ front end metal material

122J‧‧‧ end face

124‧‧‧Back end side metal materials

124J‧‧‧ end face

L‧‧‧electrode shaft

Claims (7)

A discharge lamp tube comprising: a discharge tube; and a cathode and an anode disposed in opposite directions in the discharge tube; wherein the cathode is made of a pair of front side members containing an emitter material, and is electrically conductive a plurality of metal members of the rear end side member supported by the electrode support rod are formed by solid state joining; heat transferred from the front end side member to the rear end side member is bordered by a vicinity of a joint surface between the at least one metal member Become smaller. The discharge lamp of claim 1, wherein the front end side member contains ruthenium oxide coated with ruthenium, and the rear end side member is molybdenum or an alloy containing molybdenum as a main component. The discharge lamp of claim 1 or 2, wherein the cathode has a tapered portion formed by at least a tapered portion of the front end side member and a tapered portion of the rear end side member; At least a portion of the tapered portion of the end side member is disposed on the cathode axis side more than the taper angle of the front end side member. The discharge lamp according to any one of claims 1 to 3, wherein the reduced diameter portion is formed in at least a portion of the vicinity of the joint side end surface of the rear end side member. A discharge lamp according to any one of claims 1 to 4, wherein the rear end side member has a taper angle smaller than a taper angle of the front end side member. A discharge lamp according to any one of claims 1 to 5, wherein The cathode system is formed by interposing an intermediate member between the front end side member and the rear end side member, and solidifying the front end side member, the intermediate member, and the rear end side member in solid state. A discharge lamp tube comprising: a discharge tube; and a cathode and an anode disposed opposite to each other in the discharge tube; wherein the cathode is made of tantalum containing tungsten containing less than 1% by weight of cerium oxide The front end side member and the plurality of metal members of the rear end side member made of molybdenum are solid-solid joined; the heat moved from the front end side member to the rear end side member is bounded by the joint surface between the members Become smaller.