KR20190037102A - Discharge lamp, electrode for discharge lamp, method for producing discharge lamp, and method for producing electrode for discharge lamp - Google Patents

Abstract

Provided is a solid state bonded electrode with excellent bonding strength in a discharge lamp. In a negative electrode (20) in which a member (40) at a front side mainly composed of tungsten and a member (50) at a rear side made of molybdenum (Mo) having a purity of 99 wt% or higher are bonded in a solid state, formed is coarsened crystal grains R2 having a grain size larger than crystal grains R1 of the member (40) at the front side from the vicinity of a joint surface S of the member (50) at the rear side to the vicinity of the midpoint C of a hole of an electrode support rod.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp, an electrode for a discharge lamp, a method of manufacturing a discharge lamp, and a method of manufacturing an electrode for a discharge lamp,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp that can be used in an exposure apparatus or the like, and more particularly to a structure of an electrode to which a plurality of members are bonded.

The discharge lamp is provided with an electrode to which a member different in metal type, crystal characteristics and the like is bonded according to high output. For example, a metal member containing an emitter such as thorium or a rare earth oxide is used as an electrode tip, and a refractory metal member such as pure tungsten is used as a body, thereby joining two metal members together (for example, Patent Document 1). As the bonding method, for example, solid phase bonding such as SPS is performed. Further, it is also possible to join them through the intermediate member therebetween.

[Patent Document 1] Japanese Patent No. 4484958

Impurity gas and impurities tend to remain in crystal grain boundaries (crystal grain boundaries) of electrode materials such as metals. When the discharge lamp is assembled with the electrode remaining in an impurity gas or the like, impurity gas or the like is discharged into the discharge tube as the electrode temperature is raised by the lamp lighting, and the discharge lamp is moved to the gap (bonding interface) do. If the impurity gas remains in the vicinity of the bonding surface, the electrode bonding surface deteriorates (oxidizes) and the strength is lowered.

Therefore, it is required to prevent the strength of the bonding surface from being lowered by the impurity gas or the like to the bonded electrodes.

The discharge lamp of the present invention has a discharge tube and a pair of electrodes disposed in the discharge tube, and at least one of the electrodes has a tip side member having an electrode tip (tip end) and a rear end side And a plurality of members including a member. For example, it is also possible to join the front end side member and the rear end side member to each other in a solid phase, or to provide an intermediate member between the front end side member and the rear end side member and to solid-phase bond each other. At the rear end side member, crystal grains (crystal grains) of at least a part of the rear end side members are coarsened, and crystal grains having a larger diameter than the crystal grains of the front end side members are formed (Here, it is referred to as coarse crystal grain).

As the coarse crystal grains, for example, coarse crystal grains in which secondary recrystallized grains can be formed and the grain size is 1000 mu m or more may be formed. Or, when observing the vicinity of the joint surface of the rear end member in the axial direction of the discharge lamp in an area of 300 × 300 μm ² along the cross section in the electrode axial direction, one coarse crystal particle forms coarse crystal particles occupying an area It is possible.

The rear end side member can be configured to be made of a material having a low temperature at which the crystal grains coarser than the material of the front end side member. For example, the rear end member is made of molybdenum having a purity of 99 wt% or more.

The coarse crystal grains can be arranged in the vicinity of the joining face of the rear end side member. It is also possible that the coarse crystal grains constitute at least a part of the bonding surface. Alternatively, the coarse crystal grains may occupy a range from at least a junction surface of the rear end side member to a vicinity of an intermediate point along the electrode axis direction of the electrode support bar hole. Further, it is possible to provide a getter member on the electrode supporting bar supporting at least one of the electrodes.

The electrode for a discharge lamp in another aspect of the present invention comprises a front end side member made of an alloy having an electrode tip and containing tungsten or tungsten as a main component and a rear end member made of molybdenum having a purity of 99.9 wt% And an intermediate member made of tungsten containing rhenium interposed between the front end side member and the rear end side member, wherein the front end side member, the intermediate member, and the rear end side member are solid-phase bonded to each other, Secondary recrystallized grains having a grain size of 1000 mu m or more are formed on the side member.

A method of manufacturing a discharge lamp according to the present invention is a method of manufacturing a discharge lamp, comprising the steps of solid-phase bonding a plurality of members including a front-end member having an electrode tip and a rear-end member supported by an electrode support rod, And the electrode support rod is fixed to the electrode to form a mount part having an electrode support rod, a glass member, a foil and the like. After the mount part is inserted into the sealing tube to place the electrode in the discharge tube, And the lamp is turned on for a predetermined period of time so as to form coarse crystal grains having a diameter larger than that of the crystal grains of the tip side member in the rear end side member, The heating time of the lamp, and the lighting time of the lamp.

A manufacturing method of a discharge lamp electrode in another aspect of the present invention is a manufacturing method of a discharge lamp electrode for solid-state bonding a plurality of members including a front-side member having an electrode tip and a rear- At least one of the temperature of the heat treatment and the heating time is determined so that secondary recrystallized particles having a larger diameter are formed in the rear end side member than the crystal particles of the front end side member.

According to the present invention, it is possible to provide a bonded electrode having excellent bonding strength in a discharge lamp.

1 is a plan view schematically showing a short arc type discharge lamp according to the present embodiment.
2 is a schematic cross-sectional view of a cathode.
3 is an enlarged cross-sectional view of an area in the vicinity of the joint surface of FIG. 2;

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

1 is a plan view schematically showing a short arc type discharge lamp according to the present embodiment.

The short arc type discharge lamp 10 is equipped with a discharge tube (light emitting tube) 12 made of transparent quartz glass, which can be used for a light source of an exposure apparatus (not shown) for pattern formation. In the discharge tube 12, the cathode 20 and the anode 30 are disposed opposite to each other with a predetermined gap therebetween.

Sealing tubes 13A and 13B made of quartz glass are integrally provided on both sides of the discharge tube 12 so as to be opposed to each other with the discharge tube 12. Both ends of the sealing tubes 13A and 13B are made of 19A, and 19B are attached. The discharge lamp 10 here 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 17A and 17B for supporting the negative electrode 20 and the positive electrode 30 are disposed in the encapsulation pipes 13A and 13B and metal rings (not shown), molybdenum Respectively, through the metal foils 16A and 16B of the conductive lead rods 15A and 15B. The sealing tubes 13A and 13B are welded to a glass tube (not shown) provided in the sealing tubes 13A and 13B to seal the discharge space DS in which mercury and rare gas are sealed.

The lead rods 15A and 15B are connected to an external power supply unit (not shown) and are connected to the negative electrode 20 (not shown) via lead rods 15A and 15B, metal foils 16A and 16B, and electrode support rods 17A and 17B. ), And the anode 30 are applied with a voltage. When power (in this case, 1 kW or more) is supplied to the discharge lamp 10, an arc discharge occurs between the electrodes, and a bright line (ultraviolet ray) by mercury is emitted. A coil-shaped getter member 21 made of tantalum, zirconium or yttrium is provided on the electrode support rod 17A. Further, a getter member may be provided on the electrode support rod 17B and the like.

2 is a schematic sectional view of the cathode 20. Fig. Here, an electrode axial cross section passing through the electrode axis X is shown. It is also possible to configure the anode 30 in the same manner.

The cathode 20 is an electrode in which both of the front end side member 40 and the rear end side member 50 which are metal members are solidly bonded to each other and the front end side member 40 is a cone Cone) shape. The shape of the electrode tip 40S may be other shapes such as a truncated cone shape having a surface. The tip side member 40 is made of an alloy containing tungsten as a main component containing a high melting point such as pure tungsten (W) or an emitter or the like. The front end side member 40 and the rear end side member 50 are bonded in a solid state by discharge plasma sintering (SPS). However, other solid-state bonding methods such as HIP and HP and other bonding methods (for example, fusion bonding) may be applied.

The rear end side member 50 is constituted by a truncated cone portion 50A to be joined to the distal end side member 40 and a columnar portion 50B in which an electrode supporting rod hole 52 is formed. However, the electrode supporting bar 17A is not shown in Fig. The rear end side member 50 is made of molybdenum (Mo) having a purity of 99 wt% or more. In particular, the purity is preferably 99.9% by weight or more, but a molybdenum alloy containing a dopant may also be used. The temperature (secondary recrystallization temperature) at which the crystal grains of molybdenum constituting the rear end side member 50 are coarsened is a temperature (secondary recrystallization temperature) at which crystal grains of tungsten, which is the main component of the front end side member 40, .

The tip side member 40 is occupied by crystal particles (recrystallized particles) R1 by an electrode manufacturing process. On the other hand, in the rear end side member 50, a range extending from the vicinity of the bonding surface (bonding interface) S to the vicinity of the midpoint C of the length of the electrode support bar hole 52 in the axial X direction is defined as a plurality of coarse crystal grains 2 The second recrystallized particles) R2. A part of the bonding surface S is composed of coarse crystal grains R2. The range from the midpoint C to the rear end surface 50T is occupied by the crystal grains (recrystallized grains) R3. In addition, the sizes of the particle sizes R1 and R3 are exaggeratedly drawn. The shape and orientation of the crystal grains can be adjusted by, for example, forging. For example, it can be aligned with or elongated in the direction of the electrode axis, and is not limited to the shape or orientation drawn.

Fig. 3 is an enlarged cross-sectional view of the area BB near the joint surface S of Fig. 2. Fig.

The coarse crystal grains R2 of molybdenum are coarsened by abnormal grain growth (secondary recrystallization), and the grain size of the coarse crystal grains R2 of the crystal grains R1 of the tip side member 40 containing tungsten as a main component or And is larger than that before processing. The particle size of the crystal grains R3 of molybdenum is approximately equal to the grain size of the crystal grains R1 of tungsten. Here, the coarse crystal grains R2 of molybdenum have a diameter of 1000 mu m or more. However, the particle size is expressed by the maximum diagonal length of the particles in the electrode axial direction crossing the electrode axis X.

The square area A shown in Fig. 3 is an arbitrary area in the vicinity of the joint surface S having a length of 300 mu m and a width of 300 mu m. The coarse crystal grains R2 exceed the area A, that is, ) Of coarse crystal grains R2. However, the area A defines the axial direction of the axial cross section passing over the electrode axis X as the longitudinal direction and the axial direction (radial direction) as the lateral direction.

The formation of the coarse crystal particles R2 in the rear end side member 50 is obtained during the manufacturing process of the discharge lamp.

First, in the electrode manufacturing process, the front end side member 40 made of pure tungsten or an alloy mainly composed of tungsten and the rear end side member 50 made of 99 wt% or more molybdenum are solid-phase bonded. The rear end side member 50 at this time is composed of crystal grains or recrystallized grains having a grain size substantially equal to the grain size of the front side member 40. The electrode obtained by the solid-phase bonding is subjected to heat treatment. Then, the electrode support rod is fixed to the electrode to constitute a mount part having a glass member, a foil and the like. After the mounting parts are inserted into the sealing tube to dispose the electrodes in the discharge tube, the sealing tube is subjected to a welding process (sealing).

When the discharge lamp is assembled, the lamp is turned on for a predetermined time. For example, aging (initial lighting) or lamp lighting property evaluation is performed for lighting stabilization. During this series of discharge lamp manufacturing processes, the electrodes become hot. In this embodiment, in order to form the coarse crystal grains R2 at the completion of the final discharge lamp, the temperature and the heating time of the heat treatment are controlled in the range of 1300 to 2200 DEG C for 5 minutes to 180 minutes, The time is set in the range of 20 minutes to 180 minutes. It is also possible to form coarse crystal grains by specifying for any one of the conditions.

As described above, the secondary recrystallization temperature of the molybdenum forming the rear end side member 50 is lower than the secondary recrystallization temperature of tungsten which is the main component of the front end side member 40. Therefore, for example, when the lamp is turned on by the lamp lighting, the rear end side member 50 starts to coarsen near the joint surface S closest to the arc (heat source). At this time, a part of the impurity gas remaining in the crystal grain system near the bonding surface S migrates and diffuses to the minute gap of the bonding surface S together with crystal grain growth (coarsening).

On the other hand, at the rear end surface 50T side occupied by the crystal grains R3 of the rear end side member 50, the impurity and impurity gas of the crystal grain system are prevented from moving toward the electrode front end due to the formation of the coarse crystal particles R2, Direction (electrode side), and is released to the outside as it is.

Impurities and impurity gas remaining in the gap of the bonding surface S are discharged to the outside of the electrode along the bonding surface S by the high temperature. The impurity gas and impurities in the vicinity of the bonding surface S and the gap in the bonding surface S are removed because the movement of the impurity gas from the rear end surface 50T side to the electrode front end side is suppressed. The impurity gas discharged to the outside of the electrode is adsorbed by the getter member (21).

By the formation of coarse crystal grains, impurity gas or the like can be prevented from being discharged into the discharge tube at the time of lamp post-manufacturing (after shipment), deterioration of lamp onability (startability) due to impurity gas, deterioration of electrodes Can be prevented. For example, if the rear end side member 50 is formed of a material having a high temperature at which the crystal grains are coarsened, such as tungsten, it is difficult to form coarse crystal grains in advance near the joining surface S, The impurity gas moves through the particle system to the vicinity of the bonding surface S and remains in the gap for a long time or the impurity gas is released from the vicinity of the bonding surface S. However, by using the rear end side member 50 made of molybdenum, the impurity gas near the bonding surface S or the gap can be removed at the manufacturing stage, so that the strength of the bonding surface and the peeling of the bonding surface can be prevented .

Coarse crystal grains are formed in the production step. However, even in the situation where coarse crystal grains are formed (further grown) after the production (after shipment) due to the power of the discharge lamp or the like, by providing the appropriate getter member 21, Peeling of the joint surface can be prevented. Since the impurity gas is adsorbed to the getter member 21 after the production, formation of coarse crystal grains or additional growth can prevent a decrease in the bonding surface strength over a long period of time. For example, in order to adsorb an impurity gas such as oxygen, tantalum is preferably used as the getter member 21.

Further, since the rear end side member 50 is constituted by molybdenum having a purity of 99 wt% or more, impurities are reduced and impurity gas released during lighting is also reduced, and a stable lamp characteristic can be obtained. In addition, it is possible to reduce the weight of the rear end side member 50, which is suitable for a large lamp.

On the other hand, since the coarse crystal particles R 2 are present up to the midpoint C of the electrode support bar hole 52, grain boundary sliding is less likely to occur from the low number of crystal grain boundaries, .

As described above, according to the present embodiment, in the cathode 20 in which the front end side member 40 mainly composed of tungsten and the rear end side member 50 made of molybdenum having a purity of 99 wt% or more are solid- The coarse crystal grains R2 having a particle size larger than that of the crystal grains R1 of the tip side member 40 are formed from the vicinity of the joining surface S of the member 50 to the vicinity of the midpoint C of the electrode support rod.

The coarse crystal grains R2 may at least partially exist in an arbitrary area of the rear end side member. For example, it may be present only in the vicinity of the bonding surface S, and a part of the bonding surface S may be formed of coarse crystal grains R2. As a result, the impurity gas existing in the vicinity of the bonding surface S can be reliably released, and the peeling of the bonding surface can be prevented. On the other hand, the entire region of the rear end side member may be composed of a plurality of coarse crystal grains or may be in a single crystal state. The impurity gas released during lighting can be further reduced. The formation region (coarse region) of the coarse crystal particles R2 can be adjusted by doping an additive such as potassium or the like and forming a micro concave portion on the electrode surface for enhancing the heat radiation effect.

In the present embodiment, coarse crystal grains are formed by lamp lighting. However, in the method of heat treatment of the electrodes, the temperature of the rear-end side member can be increased over the whole, and coarse crystal grains can be formed in a wide range.

The rear end side member may be formed of a material other than molybdenum and may be formed of a metal, alloy, or other material different from the ceramics or the front end side member 40. Since a material containing an emitter is often used for the tip side member, if the crystal grains of the tip side member are coarsened, the emitter may be released. Therefore, it is preferable that the rear end side member is lower than the temperature at which the crystal grains of the tip side member (tungsten or the like) coarsen.

In the present embodiment, the front end side member 40 and the rear end side member 50 are bonded to each other, but an intermediate member (for example, tungsten containing rhenium) ), The intermediate member, and the rear end side member 50 may be solid-bonded to each other.

[Example]

Hereinafter, the cathode of this embodiment will be described.

A front end side member made of tungsten containing thorium having an outer diameter of 16 mm and a rear end side member having an outer diameter of 20 mm made of 99.9 wt% of molybdenum and having a columnar portion, And the negative electrode which has been bonded and formed into a predetermined shape is subjected to heat treatment at a temperature of 1,600 캜 and a heating time of 10 minutes. The electrodes are arranged in the discharge tube and sealed. For the assembled discharge lamp, aging is carried out for 1 hour.

A cross section of the negative electrode having undergone such a process is observed with a scanning electron microscope. From the junction plane to the vicinity of the midpoint of the electrode support bar hole, a coarse crystal having a particle size larger than the particle size of the recrystallized particles of the tip- It was confirmed that particles were formed.

10: discharge lamp
20: cathode
30: anode
40:
50: rear end side member
S: joint surface

Claims (13)

A discharge tube,
A pair of electrodes disposed in the discharge tube,
Wherein at least one of the electrodes is constituted by a plurality of members including a front end side member having an electrode front end and a rear end side member supported by the electrode supporting bar,
Wherein at least a part of the crystal grains of the rear end side member are coarsened in the rear end side member and crystal grains having a larger diameter than the crystal grains of the front end side member are formed, . The method according to claim 1,
Wherein at least one of the electrodes is constituted by the front end side member and the rear end side member or an intermediate member is provided between the front end side member and the rear end side member, ) Of the discharge lamp. 3. The method according to claim 1 or 2,
Wherein the rear end side member is made of a material having a low temperature at which crystal grains are coarsened as compared with a material of the front end side member. 3. The method according to claim 1 or 2,
Wherein the rear end side member is made of molybdenum having a purity of 99 wt% or more. 3. The method according to claim 1 or 2,
And the coarsely grained crystal grains are present in the vicinity of the joint surface of the rear end side member. 3. The method according to claim 1 or 2,
And the coarsely grained crystal grains constitute at least a part of the bonding surface. 3. The method according to claim 1 or 2,
Wherein the coarsely grained crystal particles occupy at least a range from a junction surface of the rear end side member to a vicinity of an intermediate point along the electrode axis direction of the electrode supporting bar hole. 3. The method according to claim 1 or 2,
Wherein a getter member is provided on the electrode supporting bar supporting at least one of the electrodes. 3. The method according to claim 1 or 2,
And the particle size of the coarsely grained crystal grains is 1000 mu m or more. 3. The method according to claim 1 or 2,
Wherein one coarse crystal grain occupies the area when observed in an area of 300 x 300 mu m ² along the axial direction of the electrode in the axial cross section of the discharge lamp near the joint surface of the rear end side member Discharge lamp. A front end side member made of an alloy having an electrode tip and containing tungsten or tungsten as a main component,
A rear end side member supported by the electrode support rod and made of molybdenum having a purity of 99.9 wt% or more,
An intermediate member interposed between the front end side member and the rear end side member and made of tungsten containing rhenium,
The distal end side member, the intermediate member, and the rear end side member are solid-
Wherein secondary recrystallized particles having a particle size of 1000 mu m or more are formed in the rear end side member. A plurality of members including a tip side member having an electrode tip end and a rear end side member supported by the electrode support rods are bonded in a solid phase,
The electrode obtained by the solid-phase bonding was subjected to heat treatment,
Wherein the electrode support rod is fixed to the electrode so as to be a mount component having at least one of the electrode support rod, the glass member, and the foil,
The mount part is inserted into an encapsulation tube to dispose the electrode in the discharge tube, and then the encapsulation tube is subjected to a bonding treatment,
A method of manufacturing a discharge lamp in which lamp lighting is performed over a predetermined period of time,
Characterized in that at least one of the temperature of the heat treatment, the heating time, and the lighting time of the lamp is determined so that coarse crystal particles having a larger diameter are formed in the rear end side member than the crystal particles of the front end side member Of the discharge lamp. A method of manufacturing an electrode for a discharge lamp in which a plurality of members including a front-end member having an electrode tip and a rear-end member supported by the electrode support are solid-
Characterized in that at least one of a temperature and a heating time of the heat treatment is determined so that secondary recrystallized particles having a larger diameter are formed in the rear end side member than crystal particles of the front end side member Gt;

Images