JP2022055818A - Discharge lamp and manufacturing method for electrodes for the same - Google Patents

Abstract

To suppress the electrode temperature in a discharge lamp by effectively dissipating heat.SOLUTION: An electrode 30 is composed of a tip side member 32 including an electrode tip surface 32D and a rear end member 34 connected to an electrode support rod 17B. A recess 40 is formed in the tip side member 32. A columnar portion 50 coaxially disposed with the recess 40 is formed in the recess 40. The columnar portion 50 is made of silver tungsten. During lamp lighting, etc., liquid silver elutes into an internal space 60 formed between the columnar portion 50 and the recess 40.SELECTED DRAWING: Figure 2

Description

The present invention relates to a discharge lamp provided with an electrode, and more particularly to an internal structure of the electrode.

In the discharge lamp, the tip of the electrode becomes hot during lighting, the electrode material such as tungsten melts and evaporates, the discharge tube becomes black, and the illuminance of the lamp is lowered. In order to prevent the tip of the electrode from overheating, the tip of the electrode made of durable metal and the body made of metal with higher thermal conductivity are separately molded, and the electrode configuration is such that they are joined by solid-phase bonding. It is known (see, for example, Patent Document 1).

Further, the configuration of the electrode in which the heat dissipation space is formed inside the electrode is also known (see Patent Document 2). There, the columnar portion is coaxially arranged in the tubular recess formed inside the electrode, and a gap is formed along the electrode axis direction and the direction perpendicular to the electrode axis.

Japanese Patent No. 5472915 Japanese Unexamined Patent Publication No. 2018-142482

In the structure in which the columnar portion is joined to the concave portion inside the electrode, the columnar portion may be peeled off from the bottom surface of the concave portion when the lamp is lit. In particular, when a columnar portion made of a material having a higher coefficient of thermal expansion than the electrode material is formed, bottom surface peeling may occur due to a difference in the amount of thermal expansion, and the heat conduction performance may deteriorate. Further, even in the electrode structure in which the columnar portion is in contact with the bottom surface of the recess, a gap may be generated in the contact surface due to electrode deformation while the lamp is lit, and the heat conduction performance along the electrode axial direction may be deteriorated.

In addition, higher output (higher power) of the lamp is required more than ever in order to increase the size of the exposed object and improve the throughput. Along with this, the electrode temperature during lighting of the lamp also rises, and an electrode structure capable of suppressing the temperature rise of the electrode more effectively than before is required.

Therefore, in a discharge lamp having an internal space formed in the electrode, an electrode structure capable of more effectively suppressing the temperature rise of the electrode is required.

The discharge lamp according to one aspect of the present invention includes a discharge tube and a pair of electrodes arranged to face each other in the discharge tube, and at least one of the electrodes is a recess along the electrode axis direction and a columnar column arranged in the recess. Has a part. For example, the columnar portion can be configured to be joined or in contact with the end surface on the tip end side of the electrode and the bottom surface of the recess. Then, when the lamp is lit, at least a part of the internal space formed between the concave portion and the columnar portion is occupied by the non-convective liquid heat transfer body.

Here, the "internal space formed between the concave portion and the columnar portion when the lamp is lit" can be formed by various space shapes, sizes, and forming locations, for example, along the electrode axial direction. A space formed between the recess and the columnar portion is included. Further, when a gap is generated in the joint portion or the contact portion between the columnar portion and the concave portion during lamp manufacturing and / or lamp lighting, the gap is also included.

On the other hand, the "non-convection liquid heat transfer body" is different from the heat transfer body that heat transfers in the direction of the electrode axis by convection of the molten liquid when the lamp is lit, and does not exert the function of heat transfer by convection. A heat transfer body that is suppressed in the internal space is defined here as a "non-convective liquid heat transfer body". The liquid heat transfer body can be configured so that substances and the like previously contained in the columnar portion are eluted, or the heat transfer body that melts when the lamp is lit is included in the internal space in advance. You may.

The above-mentioned "non-convection" state of a liquid heat transfer body is the viscous property of the liquid heat transfer body, the size and shape of the internal space formed between the recess and the columnar portion, that is, between the recess and the columnar portion. Based on the pressure loss of the flow path formed in. For example, it is possible to reduce the internal space formed between the concave portion and the columnar portion along the electrode axis, that is, to shorten the distance between the concave portion and the columnar portion along the vertical direction of the electrode axis. It is also possible to provide flow path resistance by providing a groove or the like on the columnar portion or the side surface of the concave portion. If there is a gap between the end face of the columnar portion on the electrode tip side and the bottom surface of the recess, for example, when the lamp is manufactured and / or the lamp is lit, the gap portion is a small space. It can be said that it is in a "non-convection" state.

On the other hand, the discharge lamp according to another aspect of the present invention includes a discharge tube and a pair of electrodes arranged to face each other in the discharge tube, and at least one of the electrodes is arranged in a recess along the electrode axial direction and in the recess. The columnar portion is configured so that when the lamp is lit, the liquid heat transfer body can be discharged into the internal space formed between the concave portion and the columnar portion. The columnar portion may be composed of a porous heat conductive member and may contain a substance having a melting point that becomes liquid when the lamp is lit. For example, it can be made of silver-tungsten.

In order to prevent the liquid heat transfer body from being in a non-convection state, for example, the width of the side surface of the recess and the columnar portion along the vertical direction of the electrode axis in the internal space may be smaller than the radius of the columnar portion. .. Further, in order to prevent the liquid heat transfer body from being in a non-convection state, the columnar portion can be configured to form a groove or a film at least on the side surface near the tip end side of the electrode.

As for the configuration of the electrode, for example, the columnar portion is joined to the rear end side member provided with the convex portion connected to the electrode support rod, and the concave portion is formed in the front end side member including the electrode tip surface. be able to. In this case, the position of the joint surface between the columnar portion and the convex portion along the electrode axis is located closer to the electrode tip surface side than the position along the electrode axis of the joint surface of the front end side member and the rear end side member. do it.

In another aspect of the present invention, in the method for manufacturing a discharge lamp electrode, a tubular recess is formed around the central axis of the columnar tip-side solid member, and the inside diameter of the tubular recess is formed with respect to the columnar solid member. A small convex portion is formed around the central axis, and a thermally conductive member containing a substance having a melting point that becomes liquid when the lamp is lit is formed in a columnar shape according to the height from the bottom surface of the recess. An electrode is formed by joining the front end side solid member, the heat conductive member, and the rear end side solid member so as to be coaxially arranged in the tubular recess.

According to the present invention, in a discharge lamp having an internal space formed in the electrode, the temperature rise of the electrode can be suppressed more effectively.

It is a top view of the discharge lamp which is 1st Embodiment. It is a schematic cross-sectional view of the electrode of 1st Embodiment. It is sectional drawing which showed the internal state of an electrode while a lamp is lit. It is the schematic sectional drawing of the electrode of the discharge lamp which is 2nd Embodiment.

The short arc type discharge lamp 10 is a large discharge lamp capable of outputting high-intensity light, and includes a substantially spherical discharge tube (light emitting tube) 12 made of transparent quartz glass, and the inside of the discharge tube 12 is made of tungsten. A pair of electrodes 20 and 30 are arranged to face each other (coaxially). Quartz glass sealing tubes 13A and 13B are connected to and integrally formed with the discharge tube 12 on both sides of the discharge tube 12. The discharge space DS in the discharge tube 12 is filled with mercury and a rare gas such as halogen or argon gas.

The electrode 20 which is a cathode is supported by the electrode support rod 17A. The sealing tube 13A includes a glass tube (not shown) through which the electrode support rod 17A is inserted, a lead rod 15A connected to an external power source, a metal foil 16A connecting the electrode support rod 17A and the lead rod 15A, and the like. It is sealed. Similarly, for the electrode 30 which is an anode, mounting parts such as a glass tube (not shown) through which the electrode support rod 17B is inserted, a metal foil 16B, and a lead rod 15B are sealed. Further, the bases 19A and 19B are attached to the ends of the sealing tubes 13A and 13B, respectively.

When a voltage is applied to the pair of electrodes 20 and 30, an arc discharge is generated between the electrodes 20 and 30, and light is radiated to the outside of the discharge tube 12. Here, 1 kW or more of electric power is input. The light emitted from the discharge tube 12 is guided in a predetermined direction by a reflecting mirror (not shown). For example, when the discharge lamp 10 is incorporated in the exposure apparatus, the synchrotron radiation becomes pattern light and irradiates the substrate or the like.

FIG. 2 is a schematic cross-sectional view of the electrode (anode) 30. The electrode (cathode) 20 can have the same structure.

The electrode 30 is composed of a front end side member 32 having an electrode front end surface 32D and a rear end side member 34 connected to an electrode support rod 17B, and the electrode 30 is formed by joining the front end side member 32 and the rear end side member 34. Has been done. Here, it is bonded by solid phase bonding such as SPS.

The rear end side member 34 includes a columnar member 35 provided with a convex portion 35A centered on an electrode shaft X (hereinafter, also referred to as an axial direction X), and is directed from the convex portion 35A toward the electrode tip surface 32D side. A columnar portion 50 (here, a columnar portion) is formed. A cylindrical recess 40 that surrounds the columnar portion 50 is coaxially formed in the tip side member 32 along the axial direction X, and faces (recesses) in the direction opposite to the electrode tip surface 32D.

The front end side member 32 and the rear end side member 34 are solid-phase bonded at the end portions 32E and 34E. In the columnar portion 50, the end surface 50B on the electrode support rod side is solid-phase bonded to the end surface 35D of the convex portion 35A of the columnar member 35, and the end surface 50A on the electrode tip side is solid-phase bonded to the bottom surface 40B of the concave portion 40. .. The position of the end surface 50B of the columnar portion 50 along the electrode axis X, that is, the position of the joint surface between the columnar portion 50 and the columnar member 35 is the position along the electrode axis X of the end portion 34E of the rear end side member 34 ( It is located closer to the tip surface of the electrode than the position of the joint surface).

The front end side member 32 and the columnar member 35 of the rear end side member 34 are formed of a thermally conductive metal such as tungsten or molybdenum, and are maintained as a solid while the lamp is lit. The columnar portion 50 is also a heat conductive member that is maintained as a solid while the lamp is lit, while the liquid heat transfer body is configured to elute when the temperature becomes high during the lamp lighting or the electrode heat treatment.

Here, the columnar portion 50 is made of a porous body of tungsten, and is made of an alloy (silver tungsten) impregnated with silver having a higher thermal conductivity than tungsten. When the temperature is high (about 1500 ° C. or higher) when the electrode is heat-treated or the lamp is lit, silver elutes from the surface such as the side surface 50S of the columnar portion 50.

Between the columnar portion 50 and the recess 40, a tubular internal space 60 is formed along the axial direction X over the entire circumference of the columnar portion 50. The central axis of both the columnar portion 50 and the concave portion 40 coincides with the electrode axis X, and the shape is symmetrical with respect to the electrode axis X. The bottom surface 40B of the recess 40 is also symmetrical with respect to the electrode axis X, and the internal space 60 has a spatial shape symmetrical with respect to the electrode axis X. The angle formed by the bottom surface 40B and the side surface 40S (corner of the recess 40) may be configured to have a curved surface.

The volume of the internal space 60 is smaller than the volume of the columnar portion 50. Assuming that the radius of the columnar portion 50 is r and the distance from the electrode shaft X to the side surface 40S of the recess 40 is R, the internal space 60 is formed so as to satisfy Rr <r. That is, the columnar portion 50 is formed in the recess 40 so that the width of the side surface 40S of the recess 40 and the side surface 50S of the columnar portion 50 in the internal space 60 along the vertical direction of the electrode axis is shorter than the radius r of the columnar portion 50. It is composed of a thickness that occupies most of the inner space that forms.

FIG. 3 is a cross-sectional view showing the internal state of the electrode while the lamp is lit.

The columnar portion 50 has a coefficient of thermal expansion different from that of the columnar member 35 of the rear end side member 34 and the front end side member 32. Therefore, the end face 50A of the columnar portion 50 is easily peeled off from the bottom surface 40B of the recess 40 (or the end face 50B of the columnar portion 50 is a columnar member) due to the electrode heat treatment step at the time of manufacturing the lamp or the increase in the electrode temperature due to the lighting of the lamp. It is easy to peel off from the end face 35D of 35). In FIG. 3A, a gap 60D (one of the internal spaces 60 formed during lamp manufacturing and / or lamp lighting) formed by peeling of the joint surface between the end surface 50A of the columnar portion 50 and the bottom surface 40B of the recess 40. Part) is drawn.

On the other hand, when the columnar portion 50 is heated by the heat from the tip side member 32 while the lamp is lit and exceeds the melting point of silver 70, the impregnated silver 70 elutes from the columnar portion 50 into the internal space 60. Then, the liquid silver 70 enters the gap 60D formed between the columnar portion 50 and the recess 40 (see FIG. 3B). As a result, heat from the bottom surface 40B side of the recess 40 is transferred to the columnar portion 50 via the silver occupying the gap 60D. The thermal conductivity is maintained by the silver 70 entering the gap 60D, and the intervention of the silver 70 having a high thermal conductivity results in further enhancement of the thermal conductivity performance.

As described above, the internal space 60 is formed so that the volume of the internal space 60 is smaller than the volume of the columnar portion 50 or extremely smaller than the inner space formed by the recess 40. This means that the side surface 40S of the recess 40 and the side surface 50S of the columnar portion 50 facing the recess 40 are convected by the liquid silver 70 at least in the electrode axial direction in the internal space 60, that is, the fluid heated in the electrode axial direction is on the upper side. It rises to and imparts flow path resistance that suppresses the inflow of surrounding low-temperature fluid.

The liquid silver 70 that enters the gap 60D generated between the columnar portion 50 and the recess 40 is also suppressed from moving along the electrode axis X direction. The liquid silver 70 whose movement is suppressed occupies a part of the internal space 60 (including the gap 60D) in a non-convection manner, thereby reducing the heat from the tip side member 32 side and the thermal conductivity. It can be transported to the columnar portion 50 without causing it. The columnar portion 50 made of silver tungsten having high thermal conductivity efficiently transfers heat to the electrode support rod 17B side, and can more effectively suppress the temperature rise of the electrode.

As described above, according to the present embodiment, the electrode 30 is composed of a front end side member 32 including the electrode front end surface 32D and a rear end side member 34 connected to the electrode support rod 17B, and the front end side member 32 has a recess 40. A columnar portion 50 formed and coaxially arranged with the recess 40 is formed in the recess 40. The columnar portion 50 is made of silver tungsten, and when the lamp is lit, liquid silver elutes into the internal spaces 60 and 60D formed between the columnar portion 50 and the recess 40.

By arranging the columnar portion 50 made of silver tungsten in the electrode 30, two heat transfer bodies, that is, the columnar portion 50 functioning as a heat conductive member and the liquid silver 70 having high thermal conductivity are formed while the lamp is lit. It can be configured to be provided.

The electrode 30 can be manufactured as follows. That is, a cylindrical recess is formed around the central axis with respect to the solid member on the tip side having a columnar thermal conductivity that has the tip surface of the electrode. Further, for a columnar solid member having thermal conductivity, a convex portion smaller than the inner diameter of the concave portion is formed around the central axis thereof. Then, a columnar member made of porous silver tungsten is formed into a columnar shape according to the diameter of the convex portion and the height from the bottom surface of the concave portion.

After that, the tip side solid member, the columnar member, and the member including the rear end side solid member are combined so that the columnar member is coaxially arranged in the concave portion, and solid-phase bonding such as SPS is performed to perform solid-phase bonding. An electrode including a member and a solid member on the rear end side is formed.

By such a manufacturing method, it is possible to manufacture the electrode 30 in which the liquid silver 70 is eluted from the columnar portion 50 during the heat treatment of the electrode or when the lamp is lit, without including the step of separately enclosing the liquid heat transfer body. The discharge lamp manufacturing process other than the electrode 30 (arrangement of the electrode 30 on the discharge tube 12, sealing step, etc.) may be performed by a conventionally known manufacturing method.

The diameter of the columnar portion 50 and the diameter of the convex portion 35A do not have to be the same. The rear end side member 34 may be configured so that the columnar member 35 is not provided with the convex portion 35A. The columnar portion 50 does not have to have both end faces 50A and 50B solid-phase bonded to the end face 35D of the convex portion 35A of the columnar member 35 and the bottom surface 40B of the concave portion 40, respectively, and either end face or both end faces thereof. , May be configured to simply touch. In the above-described embodiment, the gap 60D is formed, but of course, the gap 60D may not be provided. On the other hand, the axial length of the columnar portion 50 is designed to be slightly shorter, and the electrode is manufactured. A gap (gap 60D) along the direction perpendicular to the electrode axis may be formed at the stage.

A solid phase bonding (SPS, HP, etc.) is preferable as the bonding method, but other bonding methods (for example, melt bonding) can also be applied. At the time of joining, an intermediate member may be sandwiched between the front end side member and the rear end side member to bring the joint surfaces into close contact with each other. Further, an intermediate member may be sandwiched between both end faces 50A and 50B of the columnar portion 50 and the end faces 35D of the columnar member 35 and the bottom surface 40B of the recess 40. As the intermediate member, for example, rhenium, tantalum, molybdenum, tungsten, or an alloy thereof can be applied.

The shape and size of the columnar portion and the concave portion are arbitrary. For example, a columnar portion 50 having a diameter changing (diameter expansion or contraction) along the axial direction X is formed, and a concave portion having a corresponding (complementary) shape is formed. Is possible to form. Further, a convex portion, a concave portion, a curved surface, or the like may be provided on the bottom surface 40B of the concave portion 40, or the shape of the end portion of the (complementary) columnar portion 50 on the electrode tip side may be formed. It is also possible to make the cross-sectional shape of the recess 40 and the columnar portion 50 into a shape other than a circular shape.

In the present embodiment, the columnar portion 50 extends toward the tip end side of the electrode, but the opposite configuration may be made, that is, a columnar portion may be formed on the tip end side member and a recess may be formed on the rear end side member. Further, an internal space may not be provided along the electrode shaft X, and the columnar portion may be configured to fit in the recess so that a substantially gap does not occur.

On the contrary, the internal space is not limited to the tubular internal space along the electrode axis X, but has a U-shaped axial cross section in which a gap is formed between the columnar portion and the concave portion along the vertical direction of the electrode axis. An internal space may be formed. Further, it is also possible to reduce the diameter of the columnar portion so that most (more than half) of the inner space of the recess is formed in the inner space.

The columnar portion 50 may have a configuration other than the porous silver tungsten impregnated with silver, and the liquid heat transfer body may be eluted from the columnar portion during lamp manufacturing and / or lamp lighting. All you need is. For example, copper tungsten, copper molybdenum, silver diamond, etc. may be used.

Next, the discharge lamp according to the second embodiment will be described with reference to FIG. In the second embodiment, a heat transfer body that becomes liquid when the lamp is lit is provided in advance in the internal space.

FIG. 4 is a schematic cross-sectional view of the electrode of the discharge lamp according to the second embodiment.

Similar to the first embodiment, the electrode (anode) 30'is composed of a front end side member 32'and a rear end side member 34', and a columnar portion 50'is arranged in the recess 40'. Further, the columnar portion 50'is joined to the recess 40'and the columnar member 35'of the rear end side member 34'.

Here, the columnar portion 50'does not contain a substance that elutes at the lamp lighting temperature, and is made of the same material as the front end side member 32'and the rear end side member 34'. For example, it can be composed of a metal such as tungsten or molybdenum or an alloy thereof. Alternatively, a boride such as zirconium borohydride or a member having high thermal conductivity such as ceramic may be applied.

A granular heat transfer body 70'is previously sealed in the internal space 60'formed between the recess 40'formed in the tip side member 32'and the columnar portion 50'. The heat transfer body 70'is solid in the state before the start of lighting (normal temperature), and a liquid that melts when the lamp is lit can be applied. For example, fluoride such as magnesium fluoride and calcium fluoride, tungsten oxide, bismuth oxide and the like can be applied. Fluoride is applicable. Here, copper is used. On the side surface 50'S of the columnar portion 50', fine grooves M along the circumferential direction are formed over the entire length of the columnar portion 50'. The fine groove M can be formed by, for example, laser processing.

When the lamp is lit, the molten heat transfer body 70'enters the gap (not shown in FIG. 4) formed by peeling the columnar portion 50'from the bottom surface 40'B of the recess 40', and even if peeling occurs, the electrode Thermal conductivity along axis X is maintained. Further, since the heat transfer body 70'existing in the internal space 60'is in a non-convection state in which convection that causes a flow in which the fluid rises at least along the electrode axis direction is suppressed, the internal space (including the gap) is present. It stays at 60'and has better thermal conductivity along the electrode axis X.

On the other hand, as in the first embodiment, the position of the end surface 50'B of the columnar portion 50'along the electrode axis X, that is, the position of the joint surface is the electrode of the end portion 34E'of the rear end side member 34'. Since the liquid heat transfer body 70'is located closer to the electrode front surface side than the position of the joint surface along the axis X, it prevents the liquid heat transfer body 70'from leaking from the joint surface between the front end side member 32' and the rear end side member 34'. be able to.

Since the fine groove M is formed on the side surface 50'S of the columnar portion 50', the side surface 50'S of the columnar portion 50'has an uneven shape, which contributes to increasing the flow path resistance. As a result, the movement of the liquid heat transfer body 70'can be suppressed to create non-convection. In addition, heat can be easily absorbed inward in the vertical direction of the electrode axis, and heat can be easily transported from the columnar portion 50'to the electrode support rod side. Instead of forming the groove M on the side surface 50'S of the columnar portion 50', a film having radioactivity may be formed. Further, it is possible to form the fine groove M or the like also in the first embodiment, and it may be formed at least in the vicinity of the electrode tip side (bottom surface 40B of the recess 40).

10 Discharge lamp 30 Electrode 32 Front end side member 34 Rear end side member 40 Recessed part 50 Columnar part 60 Internal space 70 Silver (heat transfer body)

Claims (9)

With the discharge tube
It is provided with a pair of electrodes arranged to face each other in the discharge tube.
At least one electrode has a recess along the electrode axial direction and a columnar portion arranged in the recess.
A discharge lamp characterized in that at least a part of an internal space formed between the recess and the columnar portion is occupied by a non-convection liquid heat transfer body when the lamp is lit. With the discharge tube
It is provided with a pair of electrodes arranged to face each other in the discharge tube.
At least one electrode has a recess along the electrode axial direction and a columnar portion arranged in the recess.
The discharge lamp is characterized in that the columnar portion is configured so that a liquid heat transfer body can be eluted into an internal space formed between the recess and the columnar portion when the lamp is lit. The discharge lamp according to claim 1 or 2, wherein the width of the concave side surface and the columnar portion in the internal space along the direction perpendicular to the electrode axis is smaller than the radius of the columnar portion. The discharge lamp according to any one of claims 1 to 3, wherein the columnar portion forms a groove or a film on a side surface near the tip end side of the electrode. The discharge lamp according to any one of claims 1 to 4, wherein the columnar portion is joined or in contact with the end surface on the tip end side of the electrode and the bottom surface of the recess. The columnar portion is joined to a rear end side member provided with a convex portion connecting to the electrode support rod.
The recess is formed in the tip side member including the electrode tip surface, and is formed.
The position of the joint surface between the columnar portion and the convex portion along the electrode axis is closer to the electrode tip surface side than the position along the electrode axis of the joint surface between the front end side member and the rear end side member. The discharge lamp according to any one of claims 1 to 5. The discharge lamp according to any one of claims 1 to 6, wherein the columnar portion is a porous heat conductive member and contains a substance having a melting point that becomes liquid when the lamp is lit. The discharge lamp according to any one of claims 1 to 7, wherein the columnar portion includes silver tungsten. A cylindrical recess is formed around the central axis for the solid member on the tip side of the columnar shape.
For a cylindrical solid member, a convex portion smaller than the inner diameter of the tubular concave portion is formed around the central axis thereof.
A thermally conductive member containing a substance having a melting point that becomes liquid when the lamp is lit is formed in a columnar shape according to the height from the bottom surface of the recess.
An electrode is formed by joining the front end side solid member, the heat conductive member, and the rear end side solid member so that the heat conductive member is coaxially arranged in the tubular recess. A method for manufacturing an electrode for a discharge lamp, which comprises the above.

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