Discharge lamp, electrode used for discharge lamp, and method for manufacturing discharge lamp

Abstract

To provide a discharge lamp, an electrode used for the discharge lamp, and a method for manufacturing the discharge lamp, in which the inner surface of an electrode is not damaged while reducing the temperature of the tip of the electrode and suppressing temperature fluctuation.SOLUTION: In a discharge lamp having therein a pair of electrodes arranged opposite to each other in the axial direction, at least one of the pair of electrodes includes a main body having a cylindrical closed space, a heat transfer body having a melting point lower than that of the material forming the main body in the closed space, and a regulating body, which is made of the same material as the main body in the closed space and regulates the convection of the molten heat transfer body from rotating in the circumferential direction, and the regulating body is integrally molded with the main body and is connected to the inner peripheral surface of the main body that defines the sealed space.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a discharge lamp, an electrode used for the discharge lamp, and a method for manufacturing the discharge lamp.

Background Art

[0002] Conventionally, in exposure apparatuses used in manufacturing processes of semiconductor elements, liquid crystal display elements, etc., a discharge lamp, particularly a short arc type discharge lamp, has been used as a light source. In this discharge lamp, an anode and a cathode are arranged to face each other in the axial direction inside a light emitting tube, and a light emitting substance such as mercury is enclosed in the light emitting tube.

[0003] In such a discharge lamp, since the thermal load applied to the electrodes during lighting is high, evaporation of the electrode material may occur due to overheating of the anode or the like. When this evaporated substance adheres to the inner wall of the light emitting tube, the discharge lamp causes so-called blackening, and a problem occurs in that the light transmittance of the light emitting tube decreases.

[0004] To solve this problem, a discharge lamp having a structure in which a heat transfer body is enclosed in a sealed space inside the anode has been proposed (Patent Document 1 below). The heat transfer body is melted in the lamp lighting state and convects in the sealed space due to the temperature distribution of the entire anode. This convection of the heat transfer body transfers the heat at the tip (the end closest to the cathode) of the anode to the rear end (the end farthest from the cathode), thereby lowering the temperature at the anode tip and suppressing the evaporation amount of the electrode material.

[0005] However, the temperature fluctuation at the anode tip becomes large due to the rotation of the convection of the heat transfer body in the circumferential direction, and as a result, a hole may be formed at the anode tip due to creep deformation. To prevent such hole formation at the electrode tip, Patent Documents 2 and 3 describe a discharge lamp in which a restricting body that restricts the rotation of the convection of the heat transfer body in the circumferential direction is provided in the sealed space.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] By providing a restricting body in a sealed space, temperature fluctuations at the electrode tip were suppressed. However, a new problem has arisen in that the restricting body causes scratches on the inner surface of the electrode, leading to electrode breakage. This is presumably because the posture of the restricting body changes when the heat transfer body melts or solidifies, and the restricting body contacts and presses against the inner surface of the electrode.

[0008] The present invention has been made in view of the above problems, and an object thereof is to provide a discharge lamp that reduces the temperature at the electrode tip, suppresses temperature fluctuations, and does not cause scratches on the inner surface of the electrode, an electrode used in the discharge lamp, and a method for manufacturing the discharge lamp.

Means for Solving the Problems

[0009] The discharge lamp according to the present invention is a discharge lamp having a pair of axially opposed electrodes inside, at least one of the pair of electrodes has a main body having a cylindrical sealed space, a heat transfer body having a lower melting point than the material constituting the main body in the sealed space, and a restricting body that is made of the same material as the main body and restricts the convection of the melted heat transfer body from rotating in the circumferential direction in the sealed space. The restricting body is integrally formed with the main body and is connected to the inner peripheral surface of the main body that partitions the sealed space.

[0010] According to this configuration, when the lamp is lit, the heat transfer body melted inside the sealed space of the main body convects, thereby reducing the temperature at the tip of the electrode. Further, by providing a restricting body in the sealed section, it is possible to prevent the convection of the heat transfer body from rotating in the circumferential direction and suppress temperature fluctuations at the tip of the electrode. Further, since the restricting body is connected to the inner circumferential surface of the main body, the restricting body does not move and come into contact with the inner surface of the electrode to cause damage.

[0011] Further, in the discharge lamp according to the present invention, the restricting body includes at least one rectangular blade extending radially outward about the central axis of the sealed space, The configuration may be such that the radially outer end of the blade is connected to the inner circumferential surface of the main body.

[0012] According to this configuration, it is possible to reliably prevent the convection of the heat transfer body from rotating in the circumferential direction by the rectangular blade.

[0013] Further, in the discharge lamp according to the present invention, the restricting body may be connected to only one location on the inner circumferential surface of the main body.

[0014] According to this configuration, the restricting body connected to the inner circumferential surface of the main body can be easily integrally formed (details will be described later).

[0015] Further, in the discharge lamp according to the present invention, the restricting body includes a plurality of independent rectangular blades extending radially outward about the central axis of the sealed space, The configuration may be such that the radially outer ends of the plurality of blades are each connected to the inner circumferential surface of the main body.

[0016] According to this configuration, since the plurality of blades are each independently connected to the inner circumferential surface of the main body, the stress applied to each connection portion is reduced and the restricting body is less likely to be damaged.

[0017] The electrode used in the discharge lamp according to the present invention is an electrode used in a discharge lamp, a main body having a cylindrical sealed space, Inside the sealed space, there is a heat transfer body with a melting point lower than that of the material constituting the main body, and inside the sealed space, there is a regulating body made of the same material as the main body and regulating the circumferential rotation of the convection of the melted heat transfer body. The regulating body is integrally formed with the main body and connected to the inner peripheral surface of the main body.

[0018] According to this configuration, the temperature at the tip of the electrode is lowered, temperature fluctuations are suppressed, and no damage occurs on the inner surface of the electrode.

[0019] The method for manufacturing a discharge lamp according to the present invention is the method for manufacturing a discharge lamp as described above, and a step of forming a cylindrical inner wall and the regulating body connected to the inner wall inside a cylindrical member by wire electrical discharge machining or cutting; a step of forming a tip member disposed at one end in the axial direction of the cylindrical member; a step of forming a lid member disposed at the other end in the axial direction of the cylindrical member; a step of forming the main body having the regulating body in the sealed space by joining the tip member and the lid member to both ends in the axial direction of the cylindrical member.

[0020] According to this configuration, a discharge lamp can be manufactured that lowers the temperature at the tip of the electrode, suppresses temperature fluctuations, and does not cause damage to the inner surface of the electrode.

Brief Description of the Drawings

[0021]

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Embodiments for Carrying Out the Invention

[0022] Embodiments of the discharge lamp according to the present invention will be described with reference to the drawings. Note that the following drawings are schematically illustrated, and the dimensional ratios on the drawings do not necessarily match the actual dimensional ratios, and the dimensional ratios also do not necessarily match between the drawings.

[0023] In the following, each drawing will be described with reference to the XYZ coordinate system. In this specification, when expressing a direction, when distinguishing between positive and negative directions, it is described with positive and negative signs such as “+X direction” and “-X direction”. When expressing a direction without distinguishing between positive and negative directions, it is simply described as “X direction”. That is, in this specification, when simply described as “X direction”, both “+X direction” and “-X direction” are included. The same applies to the Y direction and the Z direction. In the embodiments described below, the -Z direction represents the direction of gravity.

[0024] [Overview of the Discharge Lamp] Referring to FIG. 1, the outline of a discharge lamp according to an embodiment of the present invention will be described. The discharge lamp 100 is a short arc type discharge lamp including a light emitting tube 1, an anode 2 and a cathode 3 disposed to face each other in the extending direction of the central axis Z1 inside the light emitting tube 1, and lead rods 4 that support the anode 2 and the cathode 3, respectively. In the present embodiment, the discharge lamp 100 is arranged such that the anode 2 is located above the cathode 3 (+Z direction), and the discharge lamp 100 is lit.

[0025] The short arc type discharge lamp refers to a lamp in which the tip of the anode 2 and the tip of the cathode 3 are arranged with a distance of 40 mm or less (value at normal temperature without thermal expansion). As an example of such a discharge lamp, there is a discharge lamp with a rated power of 2 kW to 35 kW used in an exposure apparatus used in a manufacturing process of semiconductor elements, liquid crystal display elements, etc.

[0026] The light emitting tube 1, the anode 2, the cathode 3, and the lead rods 4 are all arranged around the central axis Z1. The anode 2 is arranged above the cathode 3 (+Z direction). Sealing tubes 11 are provided at both ends of the light emitting tube 1 in the extending direction of the central axis Z1. A base 12 electrically connected to the lead rods 4 is attached to the sealing tube 11.

[0027] The light emitting tube 1 is formed of a glass tube. The light emitting tube 1 has a region where the inner diameter of the glass tube increases from both ends of the central axis Z1 toward the center. This region where the inner diameter increases may have a spherical or ellipsoidal shape. For example, quartz glass can be used for the glass tube. The region where the inner diameter increases functions as a light emitting space. A light emitting substance such as mercury is enclosed in the light emitting space.

[0028] [Outline of Anode] Referring to FIGS. 2 and 3, the outline of the anode 2 will be described. FIG. 2 is an enlarged cross-sectional view of the anode 2 in the discharge lamp 100 of FIG. 1. In FIG. 2, the cross-section of the anode 2 in the plane passing through the central axis Z1 is shown with the tip 2a of the anode 2 close to the opposing cathode 3 on the lower side (-Z side) and the rear end 2b to which the lead rod 4 is connected on the upper side (+Z side). FIG. 3 is a cross-sectional view taken along the line A-A of FIG. 2.

[0029] As shown in FIG. 2, the anode 2 has a rotating body shape centered on the central axis Z1. The anode 2 includes a main body 5, a heat transfer body 6, and a restricting body 7.

[0030] [Main body] The main body 5 includes a bottomed cylindrical container member 51 and a lid member 52. When the lid member 52 is attached to the container member 51, a sealed space is formed inside the main body 5. The sealed space is partitioned by the inner peripheral surface and bottom surface of the container member 51 and the lid member 52. The sealed space includes a gas space 8 that is not filled with the heat transfer body 6, the restricting body 7, the heat transfer body 6, and the restricting body 7. An inert gas (for example, argon) may be enclosed in this gas space 8 instead of air. The main body 5 is made of a high melting point material so that the main body 5 is difficult to melt when the discharge lamp 100 is lit. In the present embodiment, the main body 5 (the container member 51 and the lid member 52) is mainly made of a material containing tungsten.

[0031] [Heat transfer body] The heat transfer body 6 is made of a material that is liquid at a high temperature when the discharge lamp 100 is lit and solid at a low temperature when the discharge lamp 100 is turned off. The melting point of the heat transfer body 6 is lower than the melting point of the material constituting the main body 5. The material constituting the heat transfer body 6 is made of a heat conductive material. The heat transfer body 6 preferably exhibits a higher thermal conductivity than the main body 5. In the present embodiment, a material mainly containing silver is used for the heat transfer body 6. A material mainly containing gold may be used for the heat transfer body 6. Although details will be described later, the heat transfer body 6 melted by the lighting of the discharge lamp 100 convects mainly in the Z direction (vertical direction) in the sealed space by the restricting body 7. Such convection in the Z direction transfers the heat generated near the tip 2a of the anode 2 to the rear end 2b of the anode 2. The heat transferred to the rear end 2b is transferred to the lead bar 4. Thereby, the temperature of the tip 2a of the anode 2 decreases.

[0032] [Restricting body] The restricting body 7 is provided in a part in the Z direction within the sealed space of the main body 5. Spaces for the heat transfer body 6 to convect exist on both sides of the restricting body 7 in the Z direction.

[0033] The regulating body 7 includes at least one rectangular blade 71 extending radially outward about the central axis Z1. The regulating body 7 of the present embodiment has four rectangular blades 71 to 74 as shown in FIG. 3. The four blades 71 to 74 exhibit a cross shape extending in four directions about the central axis Z1. The four blades 71 to 74 are connected by the central axis Z1 and integrated. Two of the four blades 71 and 73 extend in the Z direction and the X direction. The remaining two blades 72 and 74 extend in the Z direction and the Y direction.

[0034] The radially outer end 71a of the blade 71 is connected to the inner peripheral surface 5a of the main body 5. On the other hand, the radially outer ends 72a to 74a of the blades 72 to 74 have a gap with the inner peripheral surface 5a of the main body 5. That is, the regulating body 7 is connected to the inner peripheral surface 5a of the main body 5 only at one location of the radially outer end 71a of the blade 71.

[0035] The regulating body 7 is made of the same high melting point material as the main body 5. In the present embodiment, the regulating body 7 is mainly made of a material containing tungsten. Although details will be described later, the regulating body 7 is integrally formed with the main body 5. By integrally forming the regulating body 7 with the main body 5, the strength is increased compared to the case where the separately formed regulating body 7 and the main body 5 are joined by laser welding or the like. More specifically, for example, when laser welding is performed, in addition to the welding part becoming hot and the strength decreasing, stress is generated in the welding part when the heat transfer body 6 melts or solidifies, so that the regulating body 7 may come off from the main body 5.

[0036] FIG. 4 and FIG. 5 are diagrams showing examples of convection of the heat transfer body 6, respectively. The regulating body 7 is in a state covered by the heat transfer body 6. When the discharge lamp 100 is lit, the heat transfer body 6 melts and starts to convect. In FIGS. 4 and 5, an example of the convection direction is indicated by f1. The regulating body 7 regulates as an obstacle to the convection in the direction of rotation about the central axis Z1, and promotes the convection in the Z direction. Thereby, the regulating body 7 promotes the heat transfer from the tip 2a to the rear end 2b of the anode 2 and suppresses the turbulent flow of the heat transfer body 6. Therefore, the temperature of the tip 2a of the anode 2 decreases and the temperature fluctuation range becomes small.

[0037] Further, since the restricting body 7 is connected to the inner peripheral surface 5a of the main body 5, when the heat transfer body 6 melts or solidifies, the posture of the restricting body 7 changes, and the restricting body 7 does not contact the inner peripheral surface 5a of the main body 5. As a result, the inner peripheral surface 5a of the main body 5 is not damaged by the restricting body 7, and the anode 2 is not damaged either.

[0038] [Method for manufacturing anode] With reference to FIGS. 6A to 9B, a method for manufacturing the anode 2 will be described. The main body 5 of the present embodiment is composed of four members: a tip member 53 shown in FIGS. 6A and 6B, a central member 54 shown in FIGS. 7A and 7B, a rear end member 55 shown in FIGS. 8A and 8B, and a lid member 52 shown in FIGS. 9A and 9B. By joining the tip member 53, the central member 54, and the rear end member 55 to each other, a container member 51 is formed.

[0039] The tip member 53 has a recess 53a that serves as a space for the heat transfer body 6 to convect. The recess 53a is formed by cutting or the like. The +Z direction end face 53b of the tip member 53 is a flat surface because it is joined to the central member 54.

[0040] The central member 54 has a cylindrical shape, and a restricting body 7 is connected to the cylindrical inner side wall 54a. The Z-direction height of the inner side wall 54a and the restricting body 7 is the same. Therefore, by performing wire electrical discharge machining or cutting on a cylindrical member, the central member 54 with the restricting body 7 connected to the inner side wall 54a can be formed. The -Z direction end face 54b of the central member 54 is a flat surface because it is joined to the tip member 53. Also, the +Z direction end face 54c of the central member 54 is a flat surface because it is joined to the rear end member 55.

[0041] When forming the central member 54 with the restricting body 7 connected to the inner side wall 54a, since the restricting body 7 is connected to the inner side wall 54a at only one location, as shown by the two-dot chain line in FIG. 7A, the inner side wall 54a and the restricting body 7 can be processed in a continuous one-stroke path.

[0042] The rear end member 55 has a through hole 55a which serves as a space for the heat transfer body 6 to convect, and is cylindrical as a whole. The through hole 55a is formed by wire electrical discharge machining, cutting, or the like. The -Z direction end face 55b of the rear end member 55 is a flat surface because it is joined to the central member 54. Also, the +Z direction end face 55c of the rear end member 55 is a flat surface because it is joined to the lid member 52.

[0043] The lid member 52 has a convex portion 52a that fits into the through hole 55a of the rear end member 55. The convex portion 52a is formed by cutting or the like. Also, the annular portion 52b around the convex portion 52a is a flat surface because it is joined to the rear end member 55.

[0044] Next, the tip member 53, the central member 54, and the rear end member 55 are assembled and joined to each other by diffusion bonding, welding, or the like. Thereby, a bottomed cylindrical member with one end open is formed. In order to integrate the respective members, it is preferable to perform diffusion bonding.

[0045] Diffusion bonding is a method in which the base materials are heated and pressure is maintained without melting them, atoms at the bonding interface are diffused across the bonding surface, and a metallurgically perfect joint is obtained. When electric current heating is performed under a predetermined pressure, crystal grains grow across the bonding interface over time and the base materials are joined together. As processing conditions for diffusion bonding, examples include pressure: 20 to 50 MPa, heating temperature: 1400 to 2200 °C, and processing time: 1 to 20 minutes.

[0046] Finally, the heat transfer body 6 is inserted through the opening of the bottomed cylindrical container, and the remaining member, that is, the lid member 52, is joined by diffusion bonding, welding, or the like to form the main body 5 having the regulating body 7 in the sealed space. Also, after joining the central member 54, the rear end member 55, and the lid member 52, the heat transfer body 6 may be inserted through the opening of the bottomed cylindrical container and the tip member 53 may be joined.

[0047] Note that, at the stage of assembling each of the tip member 53, the central member 54, the rear end member 55, and the lid member 52, the heat transfer body 6 may be inserted and the tip member 53, the central member 54, the rear end member 55, and the lid member 52 may be joined together at once.

[0048] As described above, the embodiments of the present invention have been described with reference to the drawings. However, the specific configuration should be considered not to be limited to these embodiments. The scope of the present invention is shown not only by the description of the above embodiments but also by the scope of claims, and further includes all modifications within the meaning and scope equivalent to the scope of claims.

[0049] It is possible to adopt the structure employed in each of the above embodiments in any other embodiment. The specific configuration of each part is not limited to only the above-described embodiments, and various modifications are possible without departing from the gist of the present invention. Further, one or more of the configurations and methods according to the following various modification examples may be arbitrarily selected and adopted in the configurations and methods according to the above-described embodiments.

[0050] (1) In the above embodiment, the restricting body 7 has four rectangular blades 71 to 74 extending radially outward about the central axis Z1, and the four blades 71 to 74 show an example of presenting a cross shape extending in four directions about the central axis Z1, but it is not limited thereto.

[0051] Figs. 10 to 13 show cross-sectional views of the anode 2 according to another embodiment. The restricting body 7 shown in Fig. 10 has three rectangular blades 71, 72, 74 extending radially outward about the central axis Z1. The restricting body 7 shown in Fig. 11 has two rectangular blades 71, 73 extending radially outward about the central axis Z1.

[0052] (2) In the above-described embodiment, an example was shown in which the radially outer end 71a of the blade 71 is connected to the inner peripheral surface 5a of the main body 5, while the radially outer ends 72a to 74a of the blades 72 to 74 are not connected to the inner peripheral surface 5a of the main body 5. However, the present invention is not limited to this. In the example shown in FIG. 12, all of the radially outer ends 71a to 74a of the four blades 71 to 74 are connected to the inner peripheral surface 5a of the main body 5. Similarly, in FIGS. 10 and 11, the radially outer ends of all the blades may be connected to the inner peripheral surface 5a of the main body 5. According to this configuration, since there are a plurality of connection portions between the restricting body 7 and the main body 5, the restricting body 7 is less likely to be damaged.

[0053] (3) In the above-described embodiment, an example was shown in which the four blades 71 to 74 of the restricting body 7 are connected by the central axis Z1 and integrated. However, the present invention is not limited to this. That is, the four blades 71 to 74 do not necessarily have to extend radially outward from the central axis Z1 of the sealed space, and may extend radially outward from a position away from the central axis Z1. In the example shown in FIG. 13, the restricting body 7 includes a plurality of independent rectangular blades 71 to 74 that extend radially outward about the central axis Z1 of the sealed space, and the radially outer ends 71a to 74a of the plurality of blades 71 to 74 are respectively connected to the inner peripheral surface 5a of the main body 5. According to this configuration, since the plurality of blades 71 to 74 are independently connected to the main body 5, the stress applied to each connection portion is reduced, and the restricting body 7 is less likely to be damaged. In addition, the inner peripheral surface 5a and the plurality of blades 71 to 74 can be processed in a continuous and single stroke path.

[0054] (4) In the above-described embodiment, an example was shown in which the main body 5 is composed of four members, namely, the tip member 53, the central member 54, the rear end member 55, and the lid member 52. However, the present invention is not limited to this. The main body 5 may be composed of three members, namely, the tip member 53 shown in FIGS. 6A and 6B, the body portion 56 shown in FIG. 14, and the lid member 52 shown in FIGS. 9A and 9B. That is, the body portion 56 also serves as the central member 54 shown in FIGS. 7A and 7B and the rear end member 55 shown in FIGS. 8A and 8B.

[0055] As a method for forming the body portion 56 shown in FIG. 14, first, a cylindrical member is machined by an end mill to form a round hole 56a corresponding to the through hole 55a of the rear end member 55. Next, the body portion 56 having the regulating body 7 connected to the inner wall 56b can be formed by wire electrical discharge machining or cutting. Since the -Z direction end face 56c of the body portion 56 is joined to the tip member 53, it is made into a flat surface. Further, since the +Z direction end face 56d of the body portion 56 is joined to the lid member 52, it is made into a flat surface.

[0056] In the above embodiment, the example in which the anode 2 has the heat transfer body 6 and the regulating body 7 has been described. However, similar to the anode 2, the cathode 3 may have the heat transfer body 6 and the regulating body 7. The discharge lamp 100 may be arranged such that the cathode 3 is located above the anode 2.

Explanation of Signs

[0057] 1: Discharge tube 2: Anode 2a: Tip 2b: Rear end 3: Cathode 4: Lead rod 5: Body 5a: Inner peripheral surface 6: Heat transfer body 7: Regulating body 51: Container member 52: Lid member 53: Tip member 54: Central member 55: Rear end member 56: Body portion 71: Blade 71a: Radial outer end of the blade 72: Blade 72a: Radial outer end of the blade 73: Blade 73a: Radial outer end of the blade 74: Blade 74a: Radial outer end of the blade 100: Discharge lamp Z1: Central axis

Claims

1. In a discharge lamp having a pair of electrodes arranged to face each other in the axial direction, at least one of the pair of electrodes has a main body having a cylindrical sealed space, a heat conductor having a melting point lower than that of the material constituting the main body, within the sealed space, and a restricting body, within the sealed space, which is made of the same material as the main body and restricts the convection of the melted heat conductor from rotating in the circumferential direction, wherein the restricting body is integrally formed with the main body and is connected to the inner peripheral surface of the main body partitioning the sealed space, a discharge lamp.

2. The restricting body includes at least one rectangular blade extending radially outward about the central axis of the sealed space, and the radially outer end of the blade is connected to the inner peripheral surface of the main body. The discharge lamp according to claim 1.

3. The restricting body is connected to the inner peripheral surface of the main body at only one location. The discharge lamp according to claim 1.

4. The restricting body includes a plurality of independent rectangular blades extending radially outward about the central axis of the sealed space, and the radially outer ends of the plurality of blades are each connected to the inner peripheral surface of the main body. The discharge lamp according to claim 1.

5. An electrode used in a discharge lamp, comprising a main body having a cylindrical sealed space, a heat conductor having a melting point lower than that of the material constituting the main body, within the sealed space, and a restricting body, within the sealed space, which is made of the same material as the main body and restricts the convection of the melted heat conductor from rotating in the circumferential direction, wherein the restricting body is integrally formed with the main body and is connected to the inner peripheral surface of the main body, an electrode.

6. A method for manufacturing the discharge lamp according to claim 1, comprising a step of forming, by wire electrical discharge machining or cutting, a cylindrical inner wall and the restricting body connected to the inner wall inside a cylindrical member, a step of forming a tip member disposed at one axial end of the cylindrical member, a step of forming a lid member disposed at the other axial end of the cylindrical member, and a step of joining the tip member and the lid member to both axial ends of the cylindrical member to form the main body having the restricting body within the sealed space. A method for manufacturing a discharge lamp.

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