JP2013020703A - Short arc type discharge lamp - Google Patents

Abstract

Provided is a short arc type discharge lamp in which an emitter material contained in an emitter member can be efficiently used, and thus a long service life can be obtained.
A short arc type discharge lamp of the present invention comprises an arc tube, and an anode and a cathode disposed opposite to each other in the arc tube, the cathode comprising an electrode head and the electrode head. An emitter member embedded and held at the distal end, and a communicating path is formed at the distal end of the electrode head in the cathode from the outer surface of the electrode head to the surface of the emitter member. Features.
[Selection] Figure 2

Description

  The present invention relates to a short arc type discharge lamp in which an anode and a cathode are arranged opposite to each other in an arc tube.

For example, a short arc type discharge lamp is used as a light source in an exposure apparatus used in a manufacturing process of a semiconductor element, a liquid crystal display element, and the like and various projectors. This short arc type discharge lamp is configured such that an anode and a cathode are arranged opposite to each other in an arc tube, and a luminous substance such as mercury or xenon gas is enclosed in the arc tube.
In such a short arc type discharge lamp, an emitter material such as thorium oxide (ThO ₂ ) is used for the cathode in order to facilitate the emission of electrons from the cathode. Such an emitter material is contained in a refractory metal constituting the cathode, such as tungsten, but thorium (Th) is a radioactive element, and therefore, it is required to suppress its use amount. Proposed is a short arc discharge lamp in which a columnar emitter member containing an emitter substance is embedded and held at the tip of the electrode head in such a manner that the tip surface is exposed on the tip of the electrode head. (See Patent Document 1).
In such a short type discharge lamp, when the cathode is heated by the lighting, the emitter material contained in the emitter member is reduced and metal atoms are taken out, and these metal atoms are used as the base constituting the emitter member. The material diffuses in the material and is supplied to the surface of the emitter member to act as an emitter.

However, the short arc type discharge lamp having the above configuration has the following problems.
The peripheral surface of the emitter member in the cathode is covered with the tip of the electrode head, that is, only the tip surface of the emitter member is exposed to the discharge space. Since the temperature decreases from the front end toward the rear end, the emitter material contained in a portion other than the front end portion of the emitter member does not function effectively. Therefore, when the emitter material contained in the front end portion of the emitter member disappears. Because of flickering, a long service life cannot be obtained.

Japanese Patent Publication No. 36-20994

  The present invention has been made based on the above circumstances, and the object thereof is to efficiently use the emitter material contained in the emitter member, and thus a short circuit that can provide a long service life. An object is to provide an arc-type discharge lamp.

The short arc type discharge lamp of the present invention comprises an arc tube, and an anode and a cathode arranged opposite to each other in the arc tube,
The cathode comprises an electrode head and an emitter member containing an emitter material embedded and held at the tip of the electrode head,
The tip of the electrode head in the cathode is formed with a communication path that leads from the outer surface of the electrode head to the surface of the emitter member.

In the short arc type discharge lamp of the present invention, the tip portion of the electrode head in the cathode has a large number of holes, and the air permeability at 20 ° C. is 0.001 to 10 cm ³ · cm / (cm ² · sec. It is preferable that the communicating path is formed by holes of the sintered metal body (cmH ₂ O).
Further, the emitter member is preferably made of triated tungsten.
Moreover, it is preferable that the tip part of the electrode head in the cathode contains carbon or carbide.

  According to the short arc type discharge lamp of the present invention, a communicating path that communicates from the outer surface of the electrode head to the surface of the emitter member is formed at the tip of the cathode electrode head located around the emitter member. Thus, the metal atoms taken out from the emitter material contained in the portion other than the tip portion of the emitter member are supplied to the surface of the electrode head through the communication path formed in the electrode head, thereby acting as an emitter. Therefore, the emitter material contained in the emitter member can be used efficiently, and thus a long service life can be obtained.

It is sectional drawing for description which shows the structure in an example of the short arc type discharge lamp of this invention. It is sectional drawing for description which shows the structure of the cathode in the short arc type discharge lamp shown in FIG. It is explanatory drawing which shows the manufacturing process of the cathode shown in FIG.

Hereinafter, embodiments of the present invention will be described in detail.
[First Embodiment]
FIG. 1 is an explanatory cross-sectional view showing a configuration of a short arc type discharge lamp according to a first embodiment of the present invention.
The arc tube 10 of this short arc type discharge lamp is made of, for example, quartz glass, and has a substantially spherical light-emitting portion 11 that forms a discharge space S therein, and is integrated with both ends of the light-emitting portion 11. One rod-like sealing portion 12 and the other sealing portion 13 that extend outward along the tube axis.

In the light emitting portion 11 of the arc tube 10, an anode 20 in which a substantially columnar electrode head 21 made of a refractory metal is held at the tip of an electrode core rod 25 made of a refractory metal, and made of a refractory metal. An electrode core rod 35 is disposed at the tip of the electrode core bar 35 so as to face each other with a cathode 30 on which an electrode head 31 made of a refractory metal is held. The electrode core rod 25 in the anode 20 is supported by the one sealing portion 12 by having a base end portion embedded in the one sealing portion 12. Further, the electrode core bar 35 in the cathode 30 is supported by the other sealing portion 13 by burying the base end portion in the other sealing portion 13.
In addition, a light emitting material such as a rare gas such as mercury or xenon gas is enclosed in the light emitting portion 11 of the arc tube 10.

  In each of the one sealing portion 12 and the other sealing portion 13 in the arc tube 10, metal foils 14 and 15 made of molybdenum are embedded in an airtight manner by, for example, a shrink seal. One end of the metal foil 14 embedded in one sealing portion 12 is welded and electrically connected to the base end of the electrode core rod 25 in the anode 20, and the other end of the metal foil 14 is An external lead 16 protruding outward from the outer end of one sealing portion 12 is welded and electrically connected. Further, the base end of the electrode core bar 35 in the cathode 30 is welded and electrically connected to one end of the metal foil 15 embedded in the other sealing portion 13, and the other end of the metal foil 15 is connected to the other end of the metal foil 15. The external lead 17 protruding outward from the outer end of the other sealing portion 13 is welded and electrically connected. Further, in the short arc type discharge lamp of this example, caps 18 and 19 are provided at the end portions of one sealing portion 12 and the other sealing portion 13.

  In the anode 20, the electrode head 21 has a tapered tip portion 21T having a small diameter toward the tip. As the refractory metal constituting the electrode head 21 and the electrode core rod 25 in the anode 20, it is preferable to use tungsten.

  In the cathode 30, the electrode head 31 has a tapered tip portion 31T having a smaller diameter toward the tip, and a columnar emitter member 32 is embedded in the tip portion 31T. More specifically, the emitter member 32 has a tapered tip portion 32T, and is embedded and held in the tip portion 31T of the electrode head 31 with the surface of the tip portion 32T exposed.

  In addition, a communication path 31H that communicates from the outer surface of the electrode head 31 to the surface of the emitter member 32 is formed at the tip 31T of the electrode head 31 in the cathode 30. More specifically, the electrode head 31 is composed of a sintered metal body having a large number of holes, and a communication path 31H is formed by the numerous holes of the sintered metal body.

The sintered metal constituting the electrode head 31 preferably has an air permeability of 0.001 to 10 cm ³ · cm / (cm ² · sec · cm H ₂ O), more preferably 0.00. 01 to ⁵ cm ³ · cm / (cm ² · sec · cm H ₂ O). If this air permeability is too low, the velocity of the gas from the emitter material passing through the communicating hole, for example thorium gas, becomes extremely slow. As a result, the supply of thorium to the tip of the cathode 30 becomes insufficient, and arc stabilization It will cause a decline in sex. On the other hand, when the air permeability is excessive, the porosity of the electrode head 31 is increased and the strength of the electrode head 31 is decreased. The electrode head 31 may be deformed due to high temperature.
Here, the gas permeability (20 ° C. air) passed through the sample is Q (cm ³ ), the sample thickness (gas passage distance) is D (cm), and the sample is perpendicular to the gas passage direction. The cross-sectional area when cut on a flat surface is A (cm ² ), the gas pressure difference between the gas introduction surface and the gas discharge surface of the sample is P (cmH ₂ O), and the volume Q gas is required to pass through the sample When the time taken is T (sec), it is obtained by the following equation.
Formula: Air permeability = (Q × D) / (A × P × T)

As the refractory metal constituting the electrode head 31 and the electrode core bar 35 in the cathode 30, it is preferable to use tungsten.
Further, the tip portion 31T of the electrode head 31 in the cathode 30 preferably contains carbon or carbide at a rate of 1 to 10% by mass, for example. Specific examples of carbon include carbon black, and specific examples of carbide include WC, W ₂ C, TaC, Ta ₂ C, HfC, NbC, ZrC, MoC, and Mo ₂ C.
When carbon or carbide is contained in the tip portion 31T of the electrode head 31, the oxide constituting the emitter material evaporated from the emitter member 32 is subjected to a reduction action while passing through the communication path 31H of the electrode head 31 and is activated. Or the carbide C diffuses into the emitter member 32 and reduces the oxide that constitutes the emitter material, thereby diffusing and moving to the surface as metal atoms, thereby obtaining a lamp with a longer service life. It is done.

The emitter member 32 includes an emitter material contained in a base material. The emitter member 32 is made of thorium oxide (ThO ₂ ), lanthanum oxide (La ₂ O ₃ ), cerium oxide (CeO ₂ ), yttrium oxide (Y ₂ O ₃ ) in a high melting point metal such as tungsten. ), An emitter material such as a barium compound, an aluminate compound, or a zirconate compound can be used. Among these, in the tungsten, it is preferable to use a thoriated tungsten ThO ₂ is formed by containing.
The content ratio of the emitter material in the emitter member 32 is preferably 0.5 to 5% by mass.

Further, the surface of the emitter member 32 is preferably carbonized, so that metal atoms are extracted from the metal compound constituting the emitter material with high efficiency and stably supplied to the surface of the emitter member 32. can do.
Further, grooves or protrusions may be formed on the surface of the emitter member 32. According to such a configuration, since the surface area of the emitter member 32 is increased, metal atoms extracted from the emitter material in the emitter member 32 can be efficiently supplied to the surface of the emitter member 32, and the emitter member. It is possible to prevent 32 from falling off the electrode head 31.

Such a cathode 30 can be manufactured as follows, for example.
First, as shown in FIG. 3A, a cathode manufacturing mold 40 having a molding recess 41 corresponding to the shape of the cathode 30 to be formed is prepared, and the molding recess 41 of the cathode manufacturing mold 40 is prepared. An emitter member 32 is disposed therein. Next, as shown in FIG. 3B, an electrode head forming material 31B containing a metal powder such as tungsten powder and a binder is put into the molding recess 41 of the cathode manufacturing mold 40, for example. In addition to the deposition, the tip of the electrode core bar 35 is caused to enter the deposited electrode head forming material 31B, and then pressed by the pressing member 45 as shown in FIG. And the compacting body 31A formed by holding the electrode core 35 is formed.
And after performing the degreasing process by heating with respect to the compacting body 31A as needed under a hydrogen gas atmosphere, the cathode 30 shown in FIG. 2 is obtained by performing a baking process.

In the above, it is preferable to use a metal powder having an average particle diameter of 1 to 10 μm as the metal powder constituting the electrode head forming material 31B.
As the binder contained in the electrode head forming material 31B, stearic acid, polyvinyl alcohol, or the like can be used.
Moreover, the processing temperature in the degreasing process of 31 A of compacting bodies is 500-1000 degreeC, for example.
Moreover, although the processing temperature in the sintering process of the compacted body 31A depends on the material of the metal powder used, it is preferably 1500 to 2500 ° C. when using tungsten powder. When this process temperature is less than 1500 degreeC, there exists a possibility that the intensity | strength of the metal sintered compact obtained may become low. On the other hand, when this processing temperature exceeds 2500 degreeC, there exists a possibility that the metal sintered body obtained may have a low air permeability.

  According to such a short arc type discharge lamp, the communicating path 31H that communicates from the outer surface of the electrode head 31 to the surface of the emitter member 32 is provided at the tip of the electrode head 31 of the cathode 30 located around the emitter member 32. As a result, the metal atoms taken out from the emitter material contained in the portion other than the tip portion of the emitter member 32 are transferred to the surface of the electrode head 31 via the communication path 31H formed in the electrode head 31. Therefore, the emitter material contained in the emitter member 32 can be used efficiently, so that a long service life can be obtained.

The embodiment of the short arc type discharge lamp of the present invention has been described above. However, the present invention is not limited to the above embodiment, and various modifications can be made.
For example, the emitter member 32 does not need to contain the same emitter material throughout, for example, the emitter material contained in the front end portion of the emitter member 32 and the emitter material contained in the rear end portion are different. There may be.
Further, the emitter member 32 is not limited to a columnar one, and may be a bundle of a plurality of wires made of, for example, triated tungsten.

  Specific examples of the short arc type discharge lamp of the present invention will be described below, but the present invention is not limited to these examples.

[Production of cathode]
<Production Example 1>
According to the process shown in FIG. 3, a cathode was produced as follows.
A cathode manufacturing mold (40) having a molding recess (41) corresponding to the shape of the cathode to be formed is prepared, and an emitter member (41) is placed in the molding recess (41) of the cathode manufacturing mold (40). 32), and in this state, a material for forming an electrode head (containing a tungsten powder having an average particle size of 3 μm and stearic acid in a molding recess (41) of the cathode manufacturing mold (40)) ( 31B) is charged and deposited, and the tip of the electrode core rod (35) made of tungsten having a diameter of 8 mm is entered into the deposited electrode head forming material (31B), and then the pressing member (45). Was pressed to form a green compact (31A) in which the emitter member (32) and the electrode core rod (35) were held.
In the above, the emitter member (32) is made of triated tungsten (ThO ₂ content is 2% by mass), has a total length of 4 mm, a diameter of 2.5 mm, and a tapered tip. A cylindrical one was used.
And after performing a degreasing process on the conditions of 1000 degreeC under hydrogen gas atmosphere with respect to the obtained compacting body (31A), a sintering process is performed on conditions of 1500 degreeC under reduced pressure for 3 hours. Thus, a cathode (30) having the configuration shown in FIG. 2 was produced. The obtained cathode (30) has a length from the rear end of the electrode head (31) to the tip of the emitter member (32) of 20 mm, and a diameter of the portion excluding the tip (31T) of the electrode head (31) is 12 mm. The angle formed by the taper at the tip of each of the electrode head (31) and the emitter member (32) is 60 °.
Further, when the air permeability of air at 20 ° C. was measured for the sintered metal constituting the electrode head (31) in the obtained cathode (30), 10 cm ³ · cm / (cm ² · sec · cmH ₂ O )Met. This cathode is referred to as “cathode A”.

<Production Example 2>
A cathode was produced in the same manner as in Production Example 1 except that the temperature condition in the sintering treatment of the green compact was changed from 1500 ° C to 2000 ° C. The metal sintered body constituting the electrode head in the obtained cathode was measured for air permeability by air at 20 ° C. and found to be 1 cm ³ · cm / (cm ² · sec · cmH ₂ O). This cathode is referred to as “cathode B”.

<Production Example 3>
A cathode was produced in the same manner as in Production Example 1 except that the temperature condition in the sintering treatment of the green compact was changed from 1500 ° C to 2500 ° C. The sintered metal body constituting the electrode head in the obtained cathode was measured for air permeability by air at 20 ° C. and found to be 0.001 cm ³ · cm / (cm ² · sec · cm H ₂ O). This cathode is referred to as “cathode C”.

<Production Example 4>
A cathode was produced in the same manner as in Production Example 1 except that the temperature condition in the sintering treatment of the green compact was changed from 1500 ° C. to 2800 ° C. The sintered metal body constituting the electrode head of the obtained cathode was measured for air permeability at 20 ° C. and found to be 0.0001 cm ³ · cm / (cm ² · sec · cm H ₂ O). This cathode is referred to as “cathode D”.

<Production Example 5>
A cathode was produced in the same manner as in Production Example 1 except that the temperature condition in the sintering treatment of the green compact was changed from 1500 ° C to 1300 ° C. The sintered metal body constituting the electrode head in the obtained cathode was measured for air permeability at 20 ° C. and found to be 50 cm ³ · cm / (cm ² · sec · cmH ₂ O). This cathode is referred to as “cathode E”.

<Example 1>
Using the cathode A, a short arc type discharge lamp having the following specifications was manufactured according to the configuration shown in FIGS.
[Luminescent tube (10)]
Material: quartz glass, axial length of light emitting part (11): 225 mm, maximum inner diameter of light emitting part (11): 175 mm, inner volume of light emitting part (11): 2800 cm ³
[Anode (20)]
Material of electrode head (21) and electrode core rod (25): tungsten, total length of electrode head (21): 65mm, body diameter of electrode head (21): 35mm, tip diameter of electrode head (21): 18mm, electrode Diameter of core rod (25): 10mm
[Others]
Distance between electrodes of anode (20) and cathode (30): 7.5 mm
Inclusion material: Xenon gas

  The above-mentioned short arc type discharge lamp is turned on under the conditions of a lamp power of 25 kW and a lamp voltage of 53 V, and the lighting time until the fluctuation value of the amount of light emitted from the short arc type discharge lamp exceeds the range of ± 2%. Was measured as the service life. The results are shown in Table 1 below.

<Example 2>
A short arc type discharge lamp having the same configuration and specifications as in Example 1 except that the cathode B was used in place of the cathode A was manufactured, and its service life was measured in the same manner as in Example 1. The results are shown in Table 1 below.

<Example 3>
A short arc type discharge lamp having the same configuration and specifications as in Example 1 except that the cathode C was used in place of the cathode A was manufactured, and its service life was measured in the same manner as in Example 1. The results are shown in Table 1 below.

<Example 4>
A short arc discharge lamp having the same configuration and specifications as in Example 1 was used except that the cathode D was used instead of the cathode A, and the service life was measured in the same manner as in Example 1. The results are shown in Table 1 below.

<Comparative example 1>
Instead of the cathode A, a cathode obtained by cutting a cylindrical body of large-diameter triated tungsten (having a ThO ₂ content of 2 mass%) having the same shape and dimensions as the cathode A Hereinafter, a short arc type discharge lamp having the same configuration and specifications as in Example 1 except that this was used as “cathode F”) was manufactured, and its service life was measured in the same manner as in Example 1. . The results are shown in Table 1 below.

  As is clear from the results in Table 1, it was confirmed that the short arc discharge lamps according to Examples 1 to 4 can provide a long service life.

<Reference example>
In the cathode (30), a short arc type discharge lamp having the same configuration and specifications as in Example 1 was manufactured except that the cathode E was used instead of the cathode A, and this short arc type discharge lamp was the same as in Example 1. When lighting was performed under the conditions of the above, since a part of the electrode head was missing and dropped out, lighting was stopped within a few hours after starting lighting.

DESCRIPTION OF SYMBOLS 10 Light emission tube 11 Light emission part 12 One sealing part 13 The other sealing part 14, 15 Metal foil 16, 17 External lead 18, 19 Base 20 Anode 21 Electrode head 21T End part 25 Electrode core rod 30 Cathode 31 Electrode head 31T Tip portion 31H Communication path 31A Compact body 31B Electrode head forming material 32 Emitter member 32T Tip portion 35 Electrode core rod 40 Cathode manufacturing die 41 Molding recess 45 Press member S Discharge space

Claims (4)

An arc tube, and an anode and a cathode arranged opposite to each other in the arc tube, the cathode containing an electrode head and an emitter material embedded and held at the tip of the electrode head And an emitter member
A short arc type discharge lamp characterized in that a communicating path is formed at the tip of the electrode head in the cathode from the outer surface of the electrode head to the surface of the emitter member. The tip of the electrode head in the cathode is made of a sintered metal having a large number of holes and an air permeability of 20 ° C. by air of 0.001 to 10 cm ³ · cm / (cm ² · sec · cm H ₂ O). The short arc type discharge lamp according to claim 1, wherein the communication path is formed by a hole of the sintered metal body.   3. The short arc type discharge lamp according to claim 1, wherein the emitter member is made of tritated tungsten.   The short arc type discharge lamp according to any one of claims 1 to 3, wherein carbon or carbide is contained in a tip portion of the electrode head in the cathode.

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