TWI837408B - Discharge lamp and method of manufacturing electrode for discharge lamp - Google Patents

Abstract

[Topic] In a discharge lamp, heat is effectively dissipated to suppress the electrode temperature. [Solution] A closed internal space 40 is formed inside the electrode 30 of the discharge lamp 10, and heat dissipation parts 50A and 50B are formed to face each other along the electrode axis X.

Description

Discharge lamp and method for manufacturing electrode for discharge lamp

The present invention relates to a discharge lamp having a pair of electrodes, and more particularly to the internal structure of the electrodes.

When the discharge lamp is lit, the electrode tip reaches a high temperature, the electrode material such as tungsten melts and evaporates, and the discharge tube becomes black, causing the illumination of the bulb to decrease. In order to prevent the electrode tip from overheating, for example, the electrode tip made of a durable metal and the body made of a metal with higher thermal conductivity are formed separately and joined by solid bonding or the like (see patent document 1). In addition, a gap is formed inside the electrode along the electrode axis direction, which acts as a heat dissipation space (see patent document 2). [Prior patent document] [Patent document]

[Patent document 1] Patent publication No. 5472915 [Patent document 2] Patent publication No. 2018-142482

In recent years, in order to increase the size of exposure objects and improve productivity, higher power bulbs are required. As a result, the temperature of the electrode during lamp lighting also increases, and an electrode structure that can more effectively suppress the temperature rise of the electrode than before is required.

The discharge lamp of the present invention includes: a discharge tube; and a pair of electrodes arranged opposite to each other in the discharge tube; at least one of the electrodes has an internal space. For example, the internal space is a closed vacuum space.

In the present invention, heat dissipation/heat absorption structures facing each other are set on the surface of the internal space. Here, "heat dissipation/heat absorption structure" means a structure that can radiate heat and absorb heat when the lamp is turned on. When one side acts as a heat radiation structure, the other side acts as a heat absorption structure. In addition, the heat dissipation/heat absorption structure includes surface shapes such as grooves or rough surfaces, coating materials, etc.

The heat dissipation/heat absorption structures of the present invention are facing each other. Here, "facing each other" not only means that the heat dissipation structure and the heat absorption structure face each other with the same area size, but also includes a structure in which a part of the area of the heat dissipation structure (or heat absorption structure) on one side faces the area of the heat absorption structure (or heat dissipation structure) on the other side. In addition, the heat dissipation/heat absorption structure can be set on the entire surface of the internal space facing each other, or it can be set locally.

For example, when the discharge lamp is arranged along the vertical direction of the lead, a heat dissipation structure can be provided on the surface of the electrode head end side of the internal space, and a heat absorption structure can be provided on the surface facing the electrode head end side surface (the heat absorption structure is also a heat dissipation structure, and the heat dissipation structure is a heat absorption structure).

By making the heat dissipation/absorption structures facing each other identical, the characteristics of emissivity and absorptivity can be made equal. For example, they can be made of groove shapes or coatings. In addition, not only the surface of the electrode head end side of the internal space and the surface facing it, but also the surface along the electrode axis in the internal space can be provided with side heat dissipation/absorption structures facing each other.

The length of the electrode head end side surface along the electrode axis from the electrode head end surface to the inner space where the heat dissipation structure is set is shorter than the length of the electrode head end side surface to the electrode support rod side surface of the inner space where the heat absorption structure is set along the electrode axis, which can also accelerate the transfer from heat conduction to heat radiation.

This is another method for manufacturing an electrode for a discharge lamp of the present invention, which is a method for manufacturing an electrode for a discharge lamp by solid-state bonding of a plurality of electrode components, wherein the plurality of electrode components include: a first columnar electrode component having a heat dissipation/heat absorption structure provided at one end surface; a second columnar electrode component having a heat dissipation/heat absorption structure provided at one end surface; and a cylindrical component with both ends opened; the first electrode component and the second electrode component are solid-state bonded between the end surfaces having the heat dissipation/heat absorption structure provided and the cylindrical component. For example, an intermediate component may be provided between the plurality of components.

This is another method for manufacturing an electrode for a discharge lamp of the present invention, which is to form a columnar electrode tip end side member with a heat dissipation structure on one end face, a columnar electrode support rod side member with a heat absorption structure on one end face, and a cylindrical body member with openings at both ends; the electrode tip end side member and the electrode support rod side member are solid-bonded to the cylindrical body member at the end face side where the heat dissipation/heat absorption structure is respectively provided. For example, the heat dissipation/heat absorption structure of the same structure can be formed on the electrode tip end side member and the electrode support rod side member.

According to the present invention, when discharging the lamp, heat is effectively dissipated, and the electrode temperature can be suppressed.

In the following, the embodiments of the present invention are described with reference to the drawings.

FIG. 1 is a plan view of a discharge lamp according to a first embodiment.

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

The cathode electrode 20 is supported by the electrode support rod 17A. In the sealed tube 13A, the glass tube (not shown) into which the electrode support rod 17A is inserted, the lead rod 15A connected to the external power source, and the metal foil 16A connecting the electrode support rod 17A and the lead rod 15A are sealed. The anode electrode 30 is similarly sealed, and the assembly components of the glass tube (not shown) into which the electrode support rod 17B is inserted, the metal foil 16B, and the lead rod 15B are sealed. In addition, at the ends of the sealed tubes 13A and 13B, caps 19A and 19B are respectively installed.

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

Fig. 2 is a schematic cross-sectional view of the electrode 30 of the first embodiment. Fig. 3 is a plan view of the heat sink viewed from above. In addition, the electrode 20 can also be made into the same structure.

The electrode 30 is an electrode having a closed space 40 therein, and is formed by joining a rear end side member 32 connected to an electrode support rod 17B, a head end side member 34 having an electrode head end surface 30S, and a body member 36 with openings at both ends. Here, the joining is performed by solid state joining such as SPS.

The rear end side member 32 is a cylindrical member with a substantially constant thickness along the axial direction X (hereinafter, also referred to as the electrode axis X), and the head end side member 34 is formed into a truncated cone. The internal space 40 surrounded by the rear end side member 32, the head end side member 34 and the body member 36 is formed as a cylindrical space here and is formed coaxially with the electrode axis X. In addition, the internal space 40 is in a vacuum state.

A heat sink (heat sink structure) 50A is provided on the electrode tip end side surface (hereinafter referred to as the bottom surface) 40S1 of the internal space 40, i.e., a portion of the end surface of the tip end side member 34. A heat sink (heat absorbing structure) 50B is also provided on the electrode support rod side surface (hereinafter referred to as the top surface) 40S2, i.e., a portion of the end surface of the rear end side member 32. The length L1 along the electrode axis X from the electrode tip end surface 30S to the bottom surface 40S1 of the internal space 40 is shorter than the length L2 along the electrode axis X from the bottom surface 40S1 to the top surface 40S2 (L1＜L2).

As shown in FIG3 , the heat sink 50A formed on the bottom surface 40S1 of the internal space 40 is composed of grooves G, which are formed concentrically at predetermined intervals in the radial direction, and the depth of the grooves is approximately fixed. The heat sink 50A can be formed by known means such as laser processing or cutting processing. The heat sink 50B formed on the top surface 40S2 on the opposite side is also composed of the same concentric grooves. The shape, depth and formation area of the grooves are the same as those of the heat sink 50A. In addition, the depth of the grooves G (the thickness of the heat sinks 50A and 50B) is exaggeratedly depicted in FIG2 .

The heat dissipation parts 50A and 50B facing each other along the electrode axis X can achieve effective heat dissipation and suppress the electrode temperature when the lamp is turned on as described below.

Generally, heat is transferred by three methods: conduction, convection (heat transfer), and thermal radiation. In conduction, heat is transferred through matter by the vibration of molecules or the movement of free electrons. Convection is transferred from a solid surface to a fluid, using the movement of the fluid caused by the temperature difference to move heat. On the other hand, thermal radiation is a phenomenon of transferring heat by electromagnetic waves, and heat is transferred without passing through matter.

The temperature of the electrode during lamp lighting is about 2000℃, and sometimes even reaches nearly 3000℃. In such a high temperature state, thermal radiation is more dominant than thermal conduction. The heat of the electrode head end surface 30S is transferred to the electrode support rod 17B side by thermal conduction, but by forming the internal space 40, the heat is radiated from the bottom surface 40S1 of the internal space 40 to the top surface 40S2.

At this time, the heat dissipation portion 50A functions as a heat dissipation structure that effectively dissipates heat to the inner space 40. Most of the heat radiated by electromagnetic waves advances along the electrode axis X and is transmitted to the heat dissipation portion 50B on the top surface 40S2 opposite to the bottom surface 40S1.

Here, according to Kirchhoff's law, an object that easily radiates heat easily absorbs heat to the same extent as an object that easily radiates heat, and the emissivity and absorptivity are equal. Since the heat sink 50B is constructed in the same manner as the heat sink 50A and forms the same formation area, it acts as a heat absorbing structure that absorbs heat with excellent absorptivity and transmits it to the rear end side member 32. A part of the transmitted heat is transported to the electrode support rod 17B by heat conduction, and a part of the heat is radiated from the outer surface of the electrode.

In this way, according to this embodiment, the closed internal space 40 is formed inside the electrode 30 of the discharge lamp 10, and the heat sinks 50A and 50B are formed to face each other along the electrode axis X. By forming the internal space 40 effective for the transfer of heat mainly by thermal radiation and the heat sinks 50A and 50B, the bulb temperature can be effectively suppressed.

Because the internal space 40 is in a vacuum state, the heat can be effectively moved to the top surface 40S2 side, and because the heat dissipation parts 50A and 50B are both grooves and the forming area (size) is also the same, the heat radiation and heat absorption are at the same level, and the balance between radiation and absorption is good, so that heat can be smoothly transferred.

Furthermore, in the case where the temperature of the bulb is mainly controlled by heat conduction or convection, it is effectively transferred to the inner space 40 by the presence of the heat sink 50A, and heat conduction from the top surface 40S2 to the rear end side member 32 is also effectively performed by the heat sink 50B.

Furthermore, because the length L1 from the electrode tip end surface 30S to the bottom surface 40S1 of the internal space 40, that is, the length L1 to the heat sink 50A is shorter than the length L2 from the bottom surface 40S1 to the top surface 40S2 where the heat sink 50B is provided, the heat sink 50A is close to the arc, and heat conduction can be quickly transferred to heat radiation.

In addition, the heat dissipation parts 50A and 50B may be formed by structures other than the groove G. For example, the bottom surface 40S1 and the top surface 40S2 may be covered with a heat dissipation material (a heat dissipation layer of a carbonized film or an oxide film), and a member with a high emissivity (absorption rate) such as a carbon nanotube may be used. It is sufficient to form a shape that improves heat dissipation and to set an area for the material. In addition, the heat dissipation parts 50A and 50B may be made into different structures, and one of the heat dissipation parts 50A and 50B may be formed by a coating, etc. Furthermore, the size of the area where the heat dissipation parts 50A and 50B are set may be different.

FIG. 4 is a diagram showing a manufacturing process of the electrode 30. As shown in FIG.

First, a columnar electrode tip end side member 110 and a columnar electrode support rod side member 130 are formed, and a cylindrical body member 120 with both ends opened is formed. Heat dissipation parts 50A and 50B consisting of grooves are formed on the surface of one end of the electrode tip end side member 110 and the electrode support rod side member 130 by laser processing or the like. At this time, the heat dissipation parts 50A and 50B are processed into the same shape and area size.

Then, the electrode tip side member 110, the body member 120, and the electrode support rod side member 130 are joined to each other by solid bonding such as SPS. At this time, the end surface where the heat sinks 50A and 50B are provided are solid bonded to both ends of the body member 120, so that the heat sinks 50A and 50B face each other. After that, the desired electrode shape is formed by cutting.

By adopting the step of performing cutting after solid bonding to form the inner space 40, the heat sink can be formed before solid bonding, and the desired heat sink can be formed regardless of the shape of the electrode after bonding.

In FIG4 , the heat sinks 50A and 50B are arranged to have the same area size as the bottom surface 40S1 and the top surface 40S2 of the internal space 40, but they can also be integrally formed on the end surfaces of the electrode head end side member 110 and the electrode support rod side member 130 and solid-bonded. In addition, more components can be prepared and those components can be solid-bonded to each other.

Next, a discharge lamp according to a second embodiment will be described using Fig. 5. In the second embodiment, a heat sink is provided along the side surface of the internal space, and a columnar portion is formed on the bottom surface of the internal space.

The electrode 100 has an inner space 140, and a columnar portion 160 is coaxially arranged so as to extend from a bottom surface 140S1 of the inner space 140 along the electrode axis X. Different from the first embodiment, a heat sink 150A is formed by a coating material on a surface 160S of the columnar portion 160. Moreover, a heat sink 150B is also formed by a coating material on a top surface 140S2 opposite to the bottom surface 140S1.

The area size of the heat sink 150A is smaller than the area size of the heat sink 150B. In addition, the length L1 from the electrode head end surface 130S to the heat sink 150A, that is, the length L1 to the surface 160S of the columnar portion 160 is shorter than the length L2 from the top surface 140S2 where the heat sink 150B is set to the surface 160S of the columnar portion 160. According to this structure, for example, by making the columnar portion 160 into a different material with high thermal conductivity, both heat conduction and heat radiation can be effectively performed. In addition, because the heat sink is set on the entire top surface, heat absorption is also effective.

On the other hand, heat dissipation parts (side heat dissipation/heat absorption structures) 250A and 250B facing each other are provided on the side surface 140T of the internal space 140. The heat dissipation parts 250A and 250B are formed into an arc shape here, for example, and are composed of a coating material. By also providing a heat dissipation part on the side surface 140T of the internal space 140, heat dissipation in a direction perpendicular to the electrode axis X is also effective. In addition, the internal space can be configured not as a closed space, but as a space enclosed with a rare gas or the like.

It can be applied to discharge lamps other than short arc type discharge lamps, but because the temperature rise of the electrode can be suppressed, it is suitable for discharge lamps with a relatively large power of more than 1kW. In addition, the solid state bonding (SPS, HP, etc.) is suitable for the bonding method, but other bonding methods (such as melting bonding) can also be applied. During bonding, an intermediate member can be inserted between the head end side member and the rear end side member (between the first electrode member and the second electrode member) to make the bonding surfaces close. Furthermore, the head end side member and the rear end side member can also be tungsten or molybdenum, or alloys of these metals, ceramics, etc., and can also contain an emitter, which can be appropriately selected.

10: discharge lamp 30: electrode (anode) 32: rear end side member 34: head end side member 40: internal space 50A, 50B: heat dissipation part (heat dissipation/heat absorption structure)

[Fig. 1] is a plan view of a discharge lamp according to the first embodiment. [Fig. 2] is a schematic cross-sectional view of an electrode according to the first embodiment. [Fig. 3] is a view showing a heat dissipation/heat absorption structure. [Fig. 4] is a view showing a method for manufacturing an electrode. [Fig. 5] is a schematic cross-sectional view of an electrode according to the second embodiment.

17B: Electrode support rod

30: Electrode (anode)

30S: electrode head end face

32: Rear side member

34: Head end side member

36: Body components

40:Inner Space

40S1: Bottom

40S2: Top

50A, 50B: Heat dissipation (heat dissipation/heat absorption structure)

X:Electrode axis

L1: Length from the end surface 30S of the electrode head to the bottom surface 40S1 of the inner space 40 along the electrode axis X

L2: Length from bottom surface 40S1 to top surface 40S2 along electrode axis X

Claims (9)

A discharge lamp, characterized by: comprising: a discharge tube; and a pair of electrodes, arranged opposite to each other in the discharge tube; at least one of the electrodes has an internal space; on the surface of the internal space, heat dissipation/heat absorption structures facing each other are arranged; on the surface of the electrode head end side of the internal space, a heat dissipation structure is arranged, and on the surface facing the surface of the electrode head end side, a heat absorption structure is arranged. As in claim 1, the discharge lamp, wherein the heat dissipation/heat absorption structures facing each other are of the same structure. For example, in the discharge lamp of claim 1, side heat dissipation/heat absorption structures facing each other are provided on the surface along the electrode axis of the internal space. The discharge lamp of claim 1, wherein the length along the electrode axis from the end surface of the electrode head to the end side surface of the electrode head in the internal space where the heat dissipation structure is arranged is shorter than the length along the electrode axis from the end side surface of the electrode head to the side surface of the electrode support rod in the internal space where the heat absorption structure is arranged. A discharge lamp as claimed in claim 1, wherein the internal space is a closed vacuum space. A discharge lamp as claimed in claim 1, wherein the lamp is lit at a temperature at which the heat dissipation/absorption structure is dominated by thermal radiation. A method for manufacturing an electrode for a discharge lamp is a method for manufacturing an electrode for a discharge lamp by solid-state bonding of a plurality of electrode components, wherein the plurality of electrode components include: a first columnar electrode component having a heat dissipation/heat absorption structure provided on one end face; a second columnar electrode component having a heat dissipation/heat absorption structure provided on one end face; and a cylindrical component with both ends being opened; the first electrode component and the second electrode component are solid-state bonded between the end face side where the heat dissipation/heat absorption structure is provided and the cylindrical component. A method for manufacturing an electrode for a discharge lamp, characterized by: forming a columnar electrode tip end side component with a heat dissipation structure on one end face, a columnar electrode support rod side component with a heat absorption structure on one end face, and a cylindrical body component with openings at both ends; and solid-state bonding the electrode tip end side component and the electrode support rod side component to the cylindrical body component at the end face side where the heat dissipation/heat absorption structure is provided. As in claim 8, the manufacturing method of the electrode for the discharge lamp, wherein the side member at the end of the electrode head and the side member of the electrode support rod form the same heat dissipation/heat absorption structure.

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