JP7507615B2 - Discharge lamp and method of manufacturing electrode for discharge lamp - Google Patents

Description

The present invention relates to a discharge lamp having a pair of electrodes, and in particular to the structure of the electrodes.

When a discharge lamp is turned on, the tip of the electrode becomes very hot, causing the electrode material, such as tungsten, to melt and evaporate, blackening the discharge tube and reducing the illuminance of the lamp. To prevent the tip of the electrode from overheating, a bonded electrode made by bonding different materials is known. For example, a material with higher thermal conductivity, such as ceramics, is bonded to the rear end (electrode support rod side) of the electrode body, which is made of tungsten, to improve heat dissipation (see Patent Document 1).

Also known is a bonded electrode in which an electrode body made of a material with a lower density than the electrode tip is bonded to the rear end of an electrode tip mainly composed of tungsten or the like (see Patent Document 2). In this case, a sintered body of molybdenum, niobium, or the like is bonded to the electrode tip, and a sintered body of silicon carbide is further bonded to the rear end of the electrode.

JP 2009-211916 A JP 2013-4397 A

When components made of different materials are joined at their end faces to form an electrode, the joint surface extends to the electrode end face. Therefore, when a component such as ceramics is joined to a component such as tungsten, the force due to the difference in thermal expansion coefficients is applied to the entire joint surface, which may cause the joint to come apart.

Therefore, there is a demand for an electrode structure that improves heat dissipation while suppressing peeling.

The discharge lamp of the present invention comprises a discharge tube and a pair of electrodes arranged opposite each other within the discharge tube, with an internal space being formed in at least one of the electrodes, and a heat transfer member made of single crystal silicon carbide being provided in the internal space. For example, the heat transfer member can be arranged so that it extends along the electrode axis and the electrode axis passes through its interior.

The heat transfer member can be configured to be in contact with the bottom surface on the tip side and the bottom surface on the electrode support rod side along the direction perpendicular to the electrode axis in the internal space. In this case, "in contact" includes bonding such as solid-state bonding, and contact.

For example, the internal space can be provided with components (herein referred to as accessory components) made of a material other than single crystal silicon carbide and arranged to sandwich the heat transfer member in the direction perpendicular to the electrode axis. For example, it is possible to sandwich a plate-shaped heat transfer member between accessory components, or to provide accessory components that concentrically cover a columnar heat transfer member.

When multiple heat transfer members are provided, the multiple heat transfer members and the multiple associated members can be arranged alternately. For example, plate-shaped heat transfer members and associated members can be arranged alternately in a row, and cylindrical heat transfer members and associated members can be arranged alternately in a concentric circle shape.

The heat transfer member and the associated member are preferably configured so that the difference in thermal expansion coefficient between the heat transfer member and the associated member is 1.0×10 ⁻⁶ /K or less. In the case of a plate-shaped heat transfer member, the thickness of the heat transfer member may be 330 μm or more.

The method for manufacturing an electrode for a discharge lamp, which is one aspect of the present invention, comprises forming a first member having a recess and a second member made of the same material as the first member, forming a heat transfer member made of single crystal silicon carbide or a third member including a heat transfer member and an associated member made of a material other than single crystal silicon carbide, placing the heat transfer member or the third member in the recess of the first member, and solid-state joining the first member, the second member, the heat transfer member, or the third member.

For example, the third member can be formed by alternately arranging multiple heat transfer members and multiple auxiliary members and solid-state bonding them.

According to the present invention, it is possible to obtain electrodes in a discharge lamp that have improved heat dissipation while suppressing peeling.

1 is a plan view of a discharge lamp according to a first embodiment; FIG. 2 is a schematic cross-sectional view taken along the electrode axis direction of an electrode. FIG. 2 is a schematic cross-sectional view taken along the radial direction of an electrode. 5 is a schematic cross-sectional view of an electrode according to a second embodiment taken along an electrode axis direction. FIG. FIG. 11 is a cross-sectional view taken along a radial direction of an electrode according to a second embodiment. 10A to 10C are diagrams illustrating a method for manufacturing a heat transfer member according to a second embodiment.

Below, an embodiment of the present invention will be described with reference to the drawings.

The short arc type discharge lamp 10 is a large discharge lamp capable of outputting high-intensity light, and includes a transparent quartz glass, approximately spherical discharge tube (light emitting tube) 12, in which a pair of tungsten electrodes 20, 30 are arranged facing each other. On both sides of the discharge tube 12, quartz glass sealing tubes 13A, 13B are connected to the discharge tube 12 and formed integrally with it. Mercury and rare gases such as halogen and argon gas are sealed in the discharge space DS within the discharge tube 12.

The cathode electrode 20 is supported by an electrode support rod 17A. Sealed in the sealed tube 13A are a glass tube (not shown) through which the electrode support rod 17A is inserted, a lead rod 15A that connects to an external power source, and metal foil 16A that connects the electrode support rod 17A and the lead rod 15A. Similarly, the anode electrode 30 is sealed with mounting parts such as a glass tube (not shown) through which the electrode support rod 17B is inserted, metal foil 16B, and lead rod 15B. In addition, caps 19A and 19B are attached to the ends of the sealed tubes 13A and 13B, respectively.

When a voltage is applied to the pair of electrodes 20, 30, an arc discharge occurs between the electrodes 20, 30, and light is emitted toward the outside of the discharge tube 12. Here, a power of 1 kW or more is input. The light emitted from the discharge tube 12 is guided in a predetermined direction by a reflector (not shown). For example, when the discharge lamp 10 is incorporated in an exposure device, the emitted light becomes a pattern light and is irradiated onto a substrate, etc.

Figure 2 is a schematic cross-sectional view of electrode 30 along the electrode axis direction. Figure 3 is a schematic cross-sectional view along line III-III in Figure 2.

The electrode 30 is composed of a tapered electrode tip 42 having an electrode tip surface 30S and a columnar electrode body 44, and the electrode support rod 17B is coaxially connected to the electrode axis E. Here, the electrode 30 is composed of a metal such as tungsten or molybdenum.

An internal space 50 is formed in the electrode body 44 of the electrode 30. The internal space 50 is coaxial with the electrode axis E. Here, the internal space 50 is formed as a cylindrical space and is also formed as a sealed space.

A heat transfer member 60 is provided in the internal space 50. The heat transfer member 60 extends along the electrode axis E, and here is formed in a plate shape with a rectangular cross section, and is arranged in the internal space 50 so that its center coincides with the electrode axis E. Note that the heat transfer member 60 is not limited to being plate-shaped, and may have any shape (e.g., cylindrical) that allows it to be arranged coaxially with the internal space 50. Alternatively, it may be arranged to pass through the electrode axis E.

The heat transfer member 60 is composed of a molded body composed of single crystal silicon carbide (SiC). Single crystal silicon carbide (SiC) has a higher thermal conductivity than the materials of the electrode 30, such as tungsten and molybdenum, and also has a higher thermal conductivity than polycrystalline silicon carbide. The thickness T0 of the heat transfer member 60 is set to 330 μm or more to suppress the occurrence of cracks.

The heat transfer member 60 is not in contact with the side of the internal space 50, i.e., the inner surface 50S along the electrode axis in the electrode 30, and a gap is formed between the heat transfer member 60 and the inner surface 50S. On the other hand, in the electrode axis direction, the heat transfer member 60 is joined to both bottom surfaces of the internal space 50. In other words, the electrode support rod side end surface 60T1 of the heat transfer member 60 is connected to the inner surface 50T1 along the electrode axis perpendicular direction in the electrode, and the electrode tip side end surface 60T2 of the heat transfer member 60 is connected to the inner surface 50T2 on the opposite side (electrode tip side).

Since single crystal silicon carbide is a dissimilar material that does not match the material of the electrode 30, such as tungsten, in terms of thermal expansion coefficient, there is a possibility that the joint may come apart due to the difference in thermal expansion coefficient while the lamp is turned on. However, in this embodiment, the electrode 30 is made of the same material, such as tungsten, while a heat transfer member 60 made of single crystal silicon carbide, which has higher thermal conductivity, is provided in the internal space 50.

Unlike conventional electrode structures in which a member such as tungsten and a member made of silicon carbide are joined at their end faces, the joint between the electrode members such as silicon carbide and tungsten is not exposed on the outer surface of the electrode, and the joint is not across the entire end face between the members. This allows the energy applied during joining to be concentrated, suppressing peeling of the joint.

The heat transfer member 60, which has high thermal conductivity and extends along the electrode axis E, is joined inside the electrode to connect the electrode tip side and the electrode support rod side, so that heat from the electrode tip side can be effectively transported to the electrode support rod side. In addition, because the heat transfer member 60 is made of single crystals that have a higher thermal conductivity than polycrystalline silicon carbide, heat can be transported more effectively.

By arranging the heat transfer member 60 coaxially with respect to the internal space 50 so that it passes through the electrode axis E, heat can be efficiently transferred from the electrode tip side to the electrode support rod side even when a heat transfer member 60 that is small in size relative to the internal space 50 is prepared due to cost or other constraints, for example.

Single crystal silicon carbide has inferior bonding strength compared to polycrystalline silicon carbide, and is prone to peeling at the bonded portion. However, because the heat transfer member 60 is bonded in the internal space 50, even if peeling occurs between the heat transfer member 60 and the electrode 30, there is no risk of it falling.

Furthermore, the thermal expansion coefficient of single crystal silicon carbide (approximately 4.6×10 ^-6 /K) is smaller than that of polycrystalline silicon carbide (approximately 4.0×10 ^-6 /K), and has a smaller difference from the thermal expansion coefficients of tungsten and molybdenum. Therefore, even if there is thermal expansion of heat transfer member 60 during lighting, it is possible to prevent a large force from being applied to the joint between electrode tip portion 42 and body portion 44 of electrode 30.

An electrode 30 having a heat transfer member 60 in such an internal space 50 can be manufactured as follows. First, a member (first member) that will become the electrode body portion with a recess and a member (second member) that will become the electrode tip portion are formed to prepare the heat transfer member. Then, after placing the heat transfer member in the recess, the first member and the second member are solid-state bonded by setting a predetermined pressure, temperature, and pressurization time. For example, solid-state bonding can be performed by SPS.

After solid-state bonding, machining and other processing is performed to produce electrodes of the desired size and shape. After the electrodes are manufactured, the discharge lamp can be manufactured by conventional methods such as mounting and sealing. Note that bonding can also be done by methods other than those described above, and is not limited to bonding the electrode body and electrode tip, as long as the electrode is configured to form an internal space, and the electrode may be configured with an insert member interposed. The internal space is not limited to being an enclosed space, and it is also possible to provide a through hole that communicates with the internal space, for example.

Next, a discharge lamp electrode according to a second embodiment will be described with reference to Figures 4 to 6. In the second embodiment, instead of disposing a heat transfer member alone in the internal space, a member made of the same material as the electrode and bonded to the heat transfer member is provided in the internal space.

Figure 4 is a schematic cross-sectional view of an electrode of a discharge lamp according to a second embodiment. Figure 5 is a schematic cross-sectional view of the electrode taken along line V-V in Figure 4.

As in the first embodiment, the electrode 130 is composed of an electrode tip portion 42 and an electrode body portion 44, and an internal space 50 is formed inside the electrode. In the internal space 50, a columnar member 160 is provided, which is composed of multiple heat transfer members 60A-60C and multiple members (hereinafter referred to as accessory members) made of the same material as the electrode, and is joined to the electrode 130 at the internal space 50.

The columnar member 160 has an integral structure in which the heat transfer members 60A-60C and the associated members 70A-70D are arranged alternately and in contact with each other. The heat transfer members 60A, 60B, and 60C are sandwiched between the associated members 70A and 70B, the associated members 70B and 70C, and the associated members 70C and 70D, respectively.

By providing such a columnar member 160 in the internal space 50, the heat capacity of the electrode is ensured, and because the material of the auxiliary members 70A-70D is the same material (tungsten) as that of the electrode 130, the bond of the columnar member 160 inside the electrode is strong. Furthermore, by arranging the heat transfer member 60B so that the electrode axis E passes through it, the heat of the electrode tip 42 can be transferred more effectively to the electrode support rod side.

The material of the auxiliary members 70A to 70D is not limited to the same material as that of the electrode 130, and any material may be selected so that the difference in thermal expansion coefficient from that of single crystal silicon carbide is equal to or less than a predetermined value, for example, the material may be selected so that the difference in thermal expansion coefficient is 1.0×10 ^-6 /K. This allows the electrode 130 and the columnar member 160 to have a more integrated structure, and makes it possible to suppress peeling from the joint.

The thickness T of the heat transfer members 60A to 60C is set to the same thickness of 330 μm or more, and the thickness T1 of the associated members 70A to 70D is also equal to the thickness T of the heat transfer members 60A to 60C. Note that the thickness T of the heat transfer members 60A to 60C does not have to be the same for all of them, and the heat transfer member may be thicker at the position where the electrode axis E passes, and the thickness of the associated members 70A to 70D does not have to be uniform as well.

Figure 6 shows the manufacturing process for the columnar member 160.

Plate-shaped materials made of single crystal silicon carbide and plate-shaped materials made of tungsten are arranged so that they are in contact with each other, and solid-phase bonding such as SPS is performed. Then, a columnar member (third member) is formed by cutting. Note that it is not limited to being formed into a columnar shape, and it may be cut into a plate shape. Furthermore, it is also possible to have a configuration in which an annular heat transfer member and an annular auxiliary member are arranged concentrically and alternately to be joined.

Three heat transfer members are used here, but more than three may be used, or a single heat transfer member may be configured with associated members on either side. Also, an insert member made of another material may be interposed between the heat transfer member and the associated member.

In the first and second embodiments, the heat transfer member is joined to the electrode in the internal space, but it may be configured so that it is only in contact with the electrode without being joined. It is also possible to configure it so that it is joined to or in contact with only one of the end face on the electrode tip side or the end face on the electrode support rod side.

10 Discharge lamp 30 Anode (electrode)
50 Internal space 60 Heat transfer member

Claims (5)

A discharge tube;
A pair of electrodes disposed opposite each other within the discharge tube,
An internal space is formed in at least one of the electrodes,
The internal space is provided with a plurality of heat transfer members made of single crystal silicon carbide and a plurality of auxiliary members made of a material other than single crystal silicon carbide and arranged to sandwich the heat transfer members in a direction perpendicular to the electrode axis;
A discharge lamp, characterized in that the plurality of heat transfer members and the plurality of associated members are arranged alternately. The difference in thermal expansion coefficient between the heat transfer member and the associated member is 1.0×10 ^-6 2. The discharge lamp according to claim 1, wherein the temperature is 0.15 to 1.5° C. The heat transfer member is plate-shaped,
3. The discharge lamp according to claim 1, wherein the heat transfer member has a thickness of 330 [mu]m or more. forming a first member having a recess and a second member made of the same material as the first member;
forming a heat transfer member made of single crystal silicon carbide, or a third member including the heat transfer member and an associated member made of a material other than single crystal silicon carbide;
The heat transfer member or the third member is disposed in a recess of the first member;
A method for manufacturing an electrode for a discharge lamp, comprising solid-state joining the first member, the second member, the heat transfer member or the third member. 5. The method for manufacturing an electrode for a discharge lamp according to claim 4, wherein the third member is formed by alternately arranging a plurality of heat transfer members and a plurality of auxiliary members and solid-state bonding the members.

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