TW201511080A - Discharge lamp, method for producing discharge lamp, and electrode for discharge lamp - Google Patents

Abstract

The objective of the present invention is to form electrodes with improved bonding strength in electrodes that are formed by solid-phase bonding a plurality of members. A cathode (20) comprising a distal end-side metal member (20A) and a rear end-side metal member (20B) is formed by solid-phase bonding and machining. On the tapered surface (20Q) of the cathode formed during machining, a grooved part (R) comprising fine grooves (r) and wide grooves formed by laser irradiation is formed so as to straddle the bonding surface (S1). At this time, machining is carried out in such a manner that scratches occur in the metal member (20B), but do not occur in the metal member (20A).

Description

Electrode for discharge lamp tube, discharge lamp tube having the electrode for discharge lamp tube, and method for manufacturing the same

The present invention relates to a discharge lamp used in an exposure apparatus or the like, and particularly relates to an electrode structure in which a plurality of metal members are joined.

The short arc type discharge lamp irradiates high-intensity light to an exposure target such as a substrate. In order to increase the size of the object to be exposed and to increase the throughput rate, the discharge lamp is required to have a high output, and accordingly, there is a demand for an increase in rated power consumption.

When the power is increased, an electrode structure composed of a single metal has an influence on electron emission, heat release, durability, and the like. Further, since the weight of the electrode is increased, the burden of the electrode support rod or the like is large.

Therefore, a scheme in which a plurality of metals are joined to constitute an electrode has been proposed. For example, an electrode tip end portion composed of tantalum-containing tungsten or the like is solid-phase bonded to a rear main body portion made of pure tungsten or the like to form an electrode (see Patent Documents 1 and 2).

[Advanced technical literature]

[Patent Literature]

Patent Document 1: Japanese Laid-Open Patent Publication No. 2011-154927

Patent Document 2: Japanese Patent Laid-Open Publication No. 2011-070823

When the electrodes are bonded to each other to form an electrode, the gap between the outer edges of the joint faces is likely to occur due to the difference in the coefficient of thermal expansion and the like, as the temperature rises and falls during the joining. When the lamp is lit, the temperature of the electrode becomes high, and there is a fear that the gap is enlarged and the electrode is broken. Further, even if the metal member of the same material is used as the electrode for solid phase bonding, a wedge-shaped gap is formed in the vicinity of the joint surface.

Therefore, the electrode formed by the solid phase bonding must increase the joint strength in the vicinity of the joint surface.

The discharge lamp of the present invention has a discharge tube and a pair of electrodes disposed in the discharge tube. At least one of the pair of electrodes is an electrode obtained by solid-phase joining the distal end side member and the rear end side member. The front end side member is located on the front end side of the electrode, that is, near the other electrode side. The rear end side member is located close to the electrode support rod. The rear end side member has a higher/larger ductility than the front end side member.

The front end side member and the rear end side member may be composed of a metal member. For example, the front end side member is made of tantalum tungsten, and the rear end side member is made of molybdenum which is relatively high in ductility.

In the present invention, the side surface of the electrode is formed with a groove portion that spans the joint surface between the front end side member and the rear end side member, that is, the groove portion with the joint surface interposed therebetween. The "electrode side surface" includes a tapered surface formed at the tip end portion of the electrode, and also includes a side surface (outer peripheral surface) of the main body portion.

The groove portion formed to increase the joint strength has a groove pitch and a groove depth which are smaller than the pitch and depth of the millimeter level of the heat release groove. For example, a groove having a pitch and a depth of 100 μm or less can be formed. With the formation of such a fine groove, A deeper deformation occurs near the outer edge of the joint surface of the rear end side member having high ductility.

Such a groove portion including the joint surface may have a surface roughness Ra of the side surface of the rear end side member of 1.2 μm or more. Further, the surface roughness of the side surface of the distal end side member may be Ra of 0.7 μm or less. Further, the groove portion may be formed such that the reflectance of the side surface of the rear end side member is smaller than the reflectance of the side surface of the front end side member. By satisfying the above values, the joint strength can be improved.

Regarding the fine groove, deformation can be caused in the vicinity of the wedge by forming a groove thicker than the front end side member. For example, a groove that generates a tear may be formed on the side surface of the rear end side member. On the other hand, in consideration of the stability of the arc discharge, it is preferable that the groove portion form a fine groove having no tear on the side surface of the front end side member.

The fine groove may be deeper on the side surface of the rear end side member than on the side surface of the front end side member. Near the wedge, the surface of the rear end side metal member is easily deformed.

When the shape of the electrode is formed by cutting, the groove portion can be formed in the cutting process after the solid phase bonding electrode. When the cutting process is performed using a turntable or the like, the groove portion can be formed at the same time, so that the manufacturing steps do not become complicated.

The groove portion can be formed with a wide groove that spans the joint surface and is larger than the pitch and depth of the fine groove.

A method of manufacturing a discharge lamp according to another aspect of the present invention includes: solid-phase joining a front end side member and a rear end side member having higher ductility than a front end side member; and cutting a side surface of the solid phase joined electrode member. In the cutting process, a groove portion that spans the joint surface between the front end side member and the rear end side member is formed on the side surface of the electrode member. For example, in the cutting process, the side surface of the rear end side member may form a fine groove having tear.

An electrode for a discharge lamp according to another aspect of the present invention includes a front end side member and a rear end side member that is solid-engaged with the front end side member. A groove portion is formed on a side surface of the electrode, and the groove portion spans a joint surface of the front end side member and the rear end side member. It is also possible to solidly join the members of the same ductility to each other.

According to the invention, it is possible to increase the joint strength of the electrode by solid-phase joining the plurality of members.

10‧‧‧Short arc discharge lamp

12‧‧‧Discharge tube

13A, 13B‧‧‧ sealed tube

15A, 15B‧‧‧ guide bars

17A, 17B‧‧‧electrode support rod

19A, 19B‧‧‧ metal cover

20,200‧‧‧ cathode

20A, 200A‧‧‧Metal components (front end side members)

20B, 200B‧‧‧Metal components (rear side members)

20S, 200S‧‧‧ electrode front end face

20Q, 200Q‧‧‧ Cone

23A‧‧‧French table shape part

23B‧‧‧Cylindrical part

30‧‧‧Anode

30A‧‧‧Metal components (front end side members)

30B‧‧‧Metal components (rear side members)

30S‧‧‧ front end face of electrode

33A‧‧‧Fracture table shape part

33B‧‧‧ cylindrical part

D‧‧‧Deep depth

DS‧‧‧discharge space

E‧‧‧electrode shaft

P1, P2‧‧‧ spacing

R, 100R‧‧‧ Ditch

Rr‧‧‧ wide ditch

r, r1A, r1B‧‧‧ micro-ditch

S1, S2‧‧‧ joint surface

W‧‧‧Wedge

Fig. 1 is a plan view schematically showing a short arc type discharge lamp of the first embodiment.

Fig. 2 is a schematic side view showing an anode and a cathode.

Figure 3 is a partial side view of the cathode.

Fig. 4 is an enlarged view of the vicinity of the joint surface of the metal member of the cathode.

Fig. 5 is a partial side view showing the cathode of the second embodiment.

Figure 6 is a photograph of the cathode near the joint.

Fig. 7 is an enlarged view of a photograph of Fig. 6.

Fig. 8 is a photograph of the vicinity of the joint surface taken using an electron microscope.

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

Fig. 1 is a plan view schematically showing a short arc type discharge lamp of the first embodiment.

The short arc discharge lamp tube 10 is a discharge lamp that can be used as a light source or the like of an exposure device (not shown) that forms a pattern, and has a transparent quartz glass. A discharge tube (light-emitting tube) 12 made of glass. In the discharge tube 12, the cathode 20 and the anode 30 are arranged to face each other with a predetermined interval therebetween.

The sealed tubes 13A and 13B made of opposite quartz glass on both sides of the discharge tube 12 are integrally provided with the discharge tube 12. Both ends of the sealed tubes 13A, 13B are plugged by the metal covers 19A, 19B. The discharge lamp tube 10 is disposed here in the vertical direction such that the anode 30 is located on the upper side and the cathode 20 is located on the lower side.

In the inside of the sealed tubes 13A and 13B, the conductive electrode support rods 17A and 17B for supporting the cathode 20 and the anode 30 are placed through a metal ring (not shown) and metal foils 16A and 16B such as molybdenum. Connected to the conductive guide bars 15A, 15B. The sealed tubes 13A and 13B are welded to glass tubes (not shown) provided in the sealed tubes 13A and 13B, thereby sealing the discharge space DS in which mercury and an inert gas are sealed.

The guide bars 15A and 15B are connected to an external power supply unit (not shown) that applies a voltage to the cathode 20 and the anode 30 through the guide bars 15A and 15B, the metal foils 16A and 16B, and the electrode support bars 17A and 17B. When electricity is supplied to the discharge lamp tube 10, an arc discharge occurs between the electrodes, and a bright line (ultraviolet light) of mercury is emitted.

Fig. 2 is a schematic side view showing an anode and a cathode.

The cathode 20 is composed of a metal member (front end side member) 20A having an electrode distal end surface 20S perpendicular to the electrode axis E, and a metal member (rear end side member) 20B joined to the metal member 20A at the rear thereof. The metal member 20B supported by the electrode supporting rod 17A is composed of a cylindrical portion 23B and a truncated cone shaped portion 23A, and the truncated cone shaped metal member 20A is joined to the truncated cone shaped portion 23A of the metal member 20B.

The anode 30 is composed of an electrode front end face 30S perpendicular to the electrode axis E. The metal member (front end side member) 30A and the metal member (rear end side member) 30B joined to the metal member 30A are comprised. The metal member 30A is composed of a truncated cone shaped portion 33A and a cylindrical portion 33B, and the cylindrical metallic member 30B is engaged with the cylindrical portion 33B of the metallic member 30A.

The metal member 20A on the distal end side is made of an alloy containing tungsten as a main component such as tantalum tungsten or a high melting point metal such as pure tungsten (W). On the other hand, the metal member 20B on the rear end side is a metal which is more ductile than the metal member 20A, or an alloy containing the metal as a main component. Here, the metal member 20B is made of molybdenum (Mo). The metal members 30A and 30B of the anode 30 are made of pure tungsten (W) and molybdenum, respectively.

Figure 3 is a partial side view of the cathode. Fig. 4 is an enlarged view of the vicinity of the joint surface of the metal member of the cathode. The grooves formed on the side faces of the cathode will now be described using Figs. 3 and 4.

The cathode 20 is obtained by solid-phase bonding a material obtained by sintering and solidifying a metal powder (to be the metal members 20A and 20B) by spark plasma sintering (SPS sintering), and then cutting it by a turntable. A tapered surface (reduced diameter surface) 20Q of the cathode 20 is formed by cutting.

In the cutting process, the metal members 20A, 20B are cut along the direction of the vertical electrode axis E, that is, along the circumferential direction. Here, the joint surface S1 is cut at an angle α of ±10° or less. Then, in the cutting step for forming the electrode having the tapered surface 20Q, the groove portion R is simultaneously formed.

The groove portion R is formed across the joint surface S1 and is composed of a fine groove (hereinafter referred to as a fine groove). The fine groove r is a groove formed at a predetermined pitch P1 at the same time as the cutting process. The pitch P1 is set in the range of 1 μm to 5 μm. This is compared to The heat release groove formed in the conventional discharge lamp tube is also much smaller. In the fourth example, the fine groove r formed in the metal member 20A is indicated by "r1A", and the fine groove formed in the metal member 20B is indicated by "r1B".

The fine groove r1B of the metal member 20B formed on the rear end side is a groove having tear, and the groove depth d reaches a position deeper than the position of the tool blade. However, here, the groove depth d is expressed by the distance from the line connecting the peak points of the trench to the bottom. On the other hand, on the metal member 20A having relatively low ductility, a fine groove r1A having no or almost no tear is formed. The groove depth d on the side of the metal member 20A is smaller (lighter) than the side of the metal member 20B.

The number of rotations of the turntable/rotation speed, the material of the blade, the angle of cut, the amount of cut, and the like at the time of cutting are adjusted to form a fine groove r having different surface states such as depth and roughness, in which the joint surface S1 is sandwiched. Here, the adjustment is performed during the continuous cutting process so that the groove has a difference with the joint surface S1 as a boundary.

Since the groove on the metal member 20B is a groove having tear, the depth d is relatively uneven, but the cutting amount of the blade or the like is adjusted so that the depth is 5 μm or more. On the other hand, the metal member 20A also adjusts the amount of cutting of the blade or the like to prevent the occurrence of tear.

When the surface of the metal becomes thick, the disordered reflection of light becomes strong, and the reflectance is lowered. The reflectance of the original light is larger than the surface of the tungsten on the surface of the molybdenum. However, by forming the fine grooves r (r1A, r1B), the reflectance on the side of the metal member 20B in the range of the groove portion R becomes higher than that on the side of the metal member 20A. The reflectance is small. Further, the surface roughness Ra of the metal member 20B is 1.2 μm or more by the cutting process, and the surface roughness Ra of the metal member 20A is 0.7 μm or less.

As described above, the metal structure composed of molybdenum (Mo) on the rear end side The member 20B has a higher ductility than the metal member 20A composed of tungsten (W) on the front end side, and is more easily deformed. Therefore, when the metal members 20A and 20B are solid-phase bonded, as shown in FIG. 3, the wedge W is likely to be generated in the vicinity of the outer edge of the joint surface S1. This wedge W is mostly produced in micrometer scale.

However, when the fine groove r is formed in the vicinity of the joint surface S1, the metal member 20B having a relatively high ductility is formed with the fine groove r1B to the extent that tearing occurs, so that plastic deformation occurs in the vicinity of the outer edge of the joint surface S1. This is because the force applied to the metal member 20B during cutting and the like, and the cutting work or the like along the joint surface S1 (within 10°) are adjusted. The above-described surface roughness Ra can be made to be 1.2 μm or more as a standard for forming such a fine groove r1A.

As a result, the shape of the wedge W changes to the same size as that of the fine groove r formed in the vicinity of the joint surface S1. The wedge W generated on the joint surface S1 is changed in shape from a state of being deeply cut toward the center side of the electrode, and may be in a collapsed state as the case may be. This prevents breakage of the joint starting from the wedge due to the difference in thermal expansion in the vicinity of the joint surface S1 in the lamp lighting.

In particular, the current density of the tapered surface 20Q is high, and the thermal stress caused by the difference in the coefficient of thermal expansion strongly acts from the metal member 20B toward the metal member 20A. However, since the bonding strength is high, high thermal conductivity and electrical conductivity can be maintained. . In this way, the crucible content of the distal end side metal member 20A can be restricted to the minimum necessary.

Further, when the metal member 20A on the distal end side is also formed with the fine groove r1A, when the metal member 20B is applied with thermal stress to the metal member 20A in the lamp lighting, the thermal stress is dissipated through the fine groove r1A, and the bonding surface can be prevented. Near S1 Produce defects. In order to achieve the above action, the fine groove r1A can be formed to have a surface roughness Ra of 0.7 μm or less.

Further, in the vicinity of the surface of the metal member 20B, the metal member 20B forms a fine groove r1B that is etched into the electrode center side in the vicinity of the joint surface S1 due to the plastic deformation of the cutting process, and the joint strength of the joint surface S1 in the vicinity of the outer edge can be strengthened. In particular, the use of pure molybdenum to form the metal member 20B is liable to cause tearing, and it is easy to increase the surface roughness Ra.

On the other hand, the fine groove r1A on the side surface of the metal member 20A does not substantially tear, and thus a groove having a uniform pitch or depth is formed. Therefore, the metal member 20A composed of tungsten having low ductility does not cause cracking or defects, and the arc discharge at the time of lamp lighting is stabilized. Since the fine groove r is formed at the same time as the cutting process, the electrode manufacturing steps are not complicated.

Although the groove portion R formed on the tapered surface 20Q of the cathode 20 has been described above, the anode 30 also has the same groove portion as the cathode 20. As a result, the metal member 30A composed of tungsten and the metal member 30B composed of molybdenum are formed with a groove portion which is formed with the joint surface S2 interposed therebetween, and the metal member 30B is formed with a fine groove which is torn. Thereby, joint strength, thermal conductivity, and electrical conductivity can be improved.

According to the present embodiment, the metal member 20A on the distal end side is solid-phase bonded to the metal member 20B on the rear end side, and is cut to form the cathode 20. On the tapered surface 20Q of the cathode 20 formed during the cutting process, a groove portion R including the fine groove r is further formed. At this time, the cutting process performed causes the metal member 20B to be torn, but the metal member 20A is not torn.

Next, a short arc type discharge lamp of the second embodiment will be described using FIG. In the second embodiment, a heat generating groove portion is further formed.

Fig. 5 is a side view showing the cathode of the second embodiment.

The cathode 200 is composed of a front end side metal member 200A including a front end surface 200S and a rear end side metal member 200B. At the time of the cutting process of forming the tapered surface 200Q, the groove portion 100R composed of the fine groove is further formed.

After the formation of the fine groove r, a groove rr (hereinafter referred to as a wide groove) having a large pitch is formed by laser irradiation. The wide groove rr has a pitch P2 and a depth d' (not shown) of a larger order (millimeter level) than the fine groove. Here, the pitch P2 is set in the range of 0.1 mm to 1.0 mm, and the depth d' is set in the range of 0.1 to 0.5 mm. In particular, the pitch P2 is set in the range of 0.2 mm to 0.5 mm, and the depth d' is preferably in the range of 0.2 to 0.5 mm.

The wide groove rr formed in the groove portion R by the laser irradiation after the cutting increases the heat radiation effect of the electrode, and at the same time, a part of the metal melted by the laser irradiation is buried in the wedge W, and the joint strength is further improved.

The fine groove may be formed by a method other than cutting, and a fine groove/concave surface which does not cause tearing may be formed. A groove having an appropriate depth and pitch can be formed in a range in which the strength of the joint surface rises. In particular, it is preferable that the groove portion having the groove depth on the rear end side is deeper than the groove on the front end side.

For example, the fine groove can be formed at a pitch of 100 μm or less, and the depth of the fine groove can be made 100 μm or less when cutting the rear end side metal member. This is because the wedge W is mostly generated on the order of micrometers, and the wedge W cannot be sufficiently buried even if it is larger than the above range.

The formation of the groove portion may be only a part of the vicinity of the joint surface, or may be the entirety of the tapered surface 20Q. In addition, a method other than laser irradiation (cutting or the like) can also form a wide groove having a large pitch, and can also be shaped only. Form a fine groove or only form a wide groove.

The metal material of the metal member 20A on the distal end side and the metal member 20B on the rear end side are selected such that the ductility of the metal member 20B is relatively higher than that of the metal member 20A. For example, the metal member 20B may be formed of bismuth/molybdenum or an alloy containing bismuth/molybdenum as a main component.

Further, three or more metal members may be used to form the electrodes. The electrode of only one of the pair of electrodes may be formed in the vicinity of the joint surface, and the groove portion may be formed even on the joint surface formed on either the tapered surface or the cylindrical surface. It is also possible to use a member other than the metal member for solid phase bonding, and it is also applicable to a discharge lamp tube other than the short arc type discharge lamp.

In the first and second embodiments, solid phase bonding is performed using different metal members, but solid phase bonding may be performed using the same type of metal member. Even if the ductility of the metal member is the same, the joint surface is likely to form a minute wedge, and the wedge can be prevented from expanding by forming the fine groove.

Embodiments of the present invention will be described below using Figs. 6-8.

[Examples]

The cathode of a short-arc discharge lamp having a rated power of 5 kW is a solid member formed by a metal member composed of tantalum tungsten and a metal member composed of molybdenum by SPS sintering, and then formed into a cathode shape by cutting. The anode is obtained by solid-phase joining a metal member having a tip end side composed of tungsten and a metal member having a rear end side composed of molybdenum, and performing a pass-through cutting process. The total length of the cathode was 20 mm, the distance from the front end surface of the cathode to the joint surface was 5 mm, and the diameter of the joint surface was 16 mm.

Figure 6 is a photograph of the cathode near the joint surface. Fig. 7 is an enlarged photograph of Fig. 6. Fig. 8 is a photograph of the vicinity of the joint surface taken by an electron microscope.

As shown in Fig. 6, the groove portion is formed along the direction of the joint surface and spans the joint surface. Further, as shown in Figs. 7 and 8, the metal member on the rear end side is torn.

Since the cutting process is formed such that the groove portion is formed along the joint surface and the rear end side member is torn, no wedge-shaped gap is formed at the end of the joint surface, and the joint portion is not broken during lighting.

20‧‧‧ cathode

20A‧‧‧Metal components (front end side members)

20B‧‧‧Metal components (rear side members)

20S‧‧‧ front end face of electrode

20Q‧‧‧ Cone

R‧‧‧Ditch Department

R‧‧‧micro-ditch

S1‧‧‧ joint surface

Claims (11)

A discharge lamp tube comprising: a discharge tube; a pair of electrodes disposed in the discharge tube, wherein at least one of the pair of electrodes is more malleable than the front end side member and the front end side member An electrode formed by solid-phase joining of the end member has a groove formed on a side surface of the electrode, and the groove portion spans a joint surface of the front end side member and the rear end side member. The discharge lamp according to claim 1, wherein the groove portion on the side surface of the rear end side member is formed with a fine groove having a tear. The discharge lamp according to any one of claims 1 to 2, wherein the fine groove is deeper on a side surface of the rear end side member than a side surface of the front end side member. A discharge lamp according to any one of claims 1 to 3, wherein the groove portion is formed in a cutting process after solid phase bonding. The discharge lamp according to any one of claims 1 to 4, wherein the structure is further formed with a wide groove spanning the joint surface and having a larger pitch and depth than the fine groove. The discharge lamp according to any one of claims 1 to 5, wherein a surface roughness Ra of the groove portion on a side surface of the rear end side member is 1.2 μm or more. The discharge lamp according to any one of claims 1 to 6, wherein a surface roughness Ra of the groove portion on a side surface of the front end side member is 0.7 μm or less. The discharge lamp according to any one of claims 1 to 7, wherein a reflectance of the groove portion on a side surface of the rear end side member is larger than a side surface of the front end side member The reflectance is small. A method of manufacturing a discharge lamp, comprising: solid-phase joining a front end side member and a rear end side member having a higher ductility than the front end side member; and cutting a side surface of the solid phase joined electrode member, wherein the cutting In the processing, a groove portion that spans a joint surface between the front end side member and the rear end side member is formed on the side surface of the electrode member. The method of manufacturing a discharge lamp according to claim 9, wherein in the cutting process, a side surface of the rear end side member is formed with a fine groove having tear. An electrode for a discharge lamp, comprising: a front end side member; and a rear end side member engaged with the front end side member, wherein a side surface of the electrode is formed with a groove portion spanning the front end side member and the rear end side member Joint surface.