JP2005011564A - Discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp having a large output, disusing an air-cooling mechanism arranged on the outside of the discharge lamp and a cooling equipment having a size many times as large as the discharge lamp for circulating the cooling water in a water channel formed inside the electrode, capable of flowing large current through the discharge lamp. <P>SOLUTION: This is a discharge lamp in which a pair of electrodes are arranged opposed to each other inside an arc tube and at least one of the electrodes has a heat conductor sealed in the enclosed space formed inside an electrode main body made of a bottomed principal member and a lid member, and the principal member is formed so that the bottom face of the enclosed space is formed into a curved surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a discharge lamp. In particular, the present invention relates to a short arc type discharge lamp used as a light source for a projection device, a photochemical reaction device, and an inspection device.
[0002]
[Prior art]
Discharge lamps can be classified into several lamps from the viewpoints of luminescent materials, distance between electrodes, and pressure in the arc tube. Among these, xenon lamps that use xenon gas as the luminescent material, and mercury that use mercury as the luminescent material. There are lamps and metal halide lamps that use rare earth metals other than mercury as luminescent materials. Further, there are short arc type discharge lamps and long arc type discharge lamps in terms of the distance between the electrodes, and there are low pressure discharge lamps, high pressure discharge lamps, ultra high pressure discharge lamps, etc. in terms of the vapor pressure in the arc tube. .
Among them, the short arc type high-pressure mercury lamp, for example, emits light with a wavelength of 365 nm efficiently, and an electrode made of tungsten is arranged with a gap of about 2 to 12 mm inside an arc tube made of quartz glass. Furthermore, a starting gas such as mercury and argon with a vapor pressure at the time of lighting of 10 ⁵ to 10 ⁷ Pa is sealed as a luminescent substance in the arc tube.
Such a short arc type high-pressure mercury lamp has been conventionally used as a light source for exposure of a semiconductor wafer.
On the other hand, in recent years, it has been attracting attention as a light source for exposure of liquid crystal substrates, particularly liquid crystal substrates used in large area liquid crystal displays. From the viewpoint of shortening the processing time associated with the increase in the size of products, Larger output is required.
[0003]
When the rated power consumption is increased by increasing the output of the discharge lamp, the value of the current flowing through the discharge lamp is usually increased.
For this reason, the tip of the electrode (especially the anode in direct current lighting) receives a large amount of electron collision, and easily rises in temperature and melts, resulting in a problem that the arc becomes unstable. In addition, not only the anode but also the discharge lamp arranged in the vertical direction, the upper electrode is easily affected by the heat convection in the arc tube, and easily receives heat from the arc. Resulting in.
Further, when the tip of the electrode is melted, the substance constituting the electrode evaporates and adheres to the inner wall of the arc tube, thereby reducing the transmittance of the arc tube, thereby reducing the radiation output.
[0004]
Such a problem is not limited to a short arc type high-pressure mercury lamp, but generally occurs when the discharge lamp has a large output. Conventionally, an air cooling mechanism has been provided outside the discharge lamp. A forced air cooling structure has been proposed. As a high-power discharge lamp, a so-called water-cooled discharge lamp (for example, Japanese Patent No. 3075094) has been proposed in which a water channel is provided inside an electrode to flow cooling water.
[0005]
[Patent Document 1]
Japanese Patent No. 3075094 [0006]
[Problems to be solved by the invention]
However, if a method of forcibly cooling the air by providing an air cooling mechanism outside the discharge lamp in order to increase the output of the discharge lamp, a sufficient cooling effect cannot be obtained and the discharge lamp can be thrown into the discharge lamp. Since the current value is limited, it was difficult to increase the output. This limit value varies depending on the type of discharge lamp and the environment in which the discharge lamp is disposed, but is approximately 200 A.
Further, in the case of a water-cooled discharge lamp, a water channel is formed in the electrode and the cooling water is allowed to flow, so that the discharge lamp increases in size as the electrode increases in size. Furthermore, a cooling water supply and discharge device and a circulation pump have to be provided, and a cooling facility several times larger than that of the discharge lamp is required, and the versatility of the discharge lamp is poor.
[0007]
Further, in such a discharge lamp, an encapsulated substance such as mercury may accumulate in an unevaporated state at the coldest spot formed inside the arc tube. In this case, since a predetermined mercury vapor pressure cannot be obtained, a desired amount of radiated light and luminance cannot be obtained. Further, when the temperature is excessively reduced inside the arc tube, the arc becomes unstable and the discharge lamp flickers to emit light.
[0008]
Therefore, in view of the above problems, the problem to be solved by the present invention is to provide a high-power discharge lamp that does not require a cooling facility and can flow a large current through the discharge lamp.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, a discharge lamp according to the present invention has a pair of electrodes facing each other inside an arc tube, and at least one of the electrodes is formed inside an electrode body comprising a bottomed main member and a lid member. A heat transfer body is sealed in the sealed space, and the main member is formed so that a bottom surface of the sealed space is a curved surface.
[0010]
[Action]
According to the electrode of the discharge lamp of the present invention, the heat transfer body is sealed in the sealed space formed inside the electrode body composed of the main member and the lid member, and the bottom surface corresponding to the inner side of the front end portion of the main member is It is a structure formed to be a curved surface.
According to such a structure, even when the tip of the electrode reaches a high temperature when the lamp is turned on, heat is effectively transported in the axial direction through the main member in contact with the heat transfer body due to the conductive action of the heat transfer body. be able to.
Furthermore, since the inner surface corresponding to the inside of the tip of the main member is formed to be a curved surface, the tip of the electrode is deformed for the reasons described later even if the pressure in the arc tube increases when the lamp is lit. It becomes difficult.
Furthermore, the heat of the electrode tip can be more effectively transported by utilizing the convection action of the heat transfer body that has melted into a liquid state when the lamp is lit.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a schematic configuration of a discharge lamp according to the present invention. In the discharge lamp 10, the sealing portions 2 extend at both ends of the substantially spherical light emitting portion 1. An anode 3 and a cathode 4 held by the sealing portion 2 are disposed in the light emitting portion 1 so as to face each other, and an external lead rod 5 electrically connected to the anode 3 and the cathode 4 has an external power source (not shown). Is connected. A predetermined amount of mercury, xenon, argon, or the like is sealed in the light emitting unit 1, and power is supplied from an external power source, and light is emitted by arc discharge between the anode 3 and the cathode 4. The discharge lamp is lit with the anode 3 facing up and the cathode 4 facing down, with the tube axis of the light emitting section 1 supported in the vertical direction.
[0012]
FIG. 2 shows a cross-sectional view of the anode 3 in the electrode axis direction. The electrode axis coincides with the tube axis of FIG. Hereinafter, the anode 3 is also referred to as an electrode 3.
The electrode 3 has a structure having a heat transfer body M in a sealed space 33 formed inside an electrode main body 30 including a bottomed cylindrical main member 31 and a columnar lid member 32. The electrode body 30 is formed by welding the opening edge portion 31a of the main member 31 and the opening edge portion 32a of the lid member 32 in the entire circumferential direction, and forms a sealed space 33 therein. The main member 31 is formed in a bottomed cylindrical shape, and includes an opening edge portion 31a, a body portion 31b, and a tip portion 31c, and is formed so that the bottom surface (tip side) 34 of the sealed space 33 is a curved surface. . The lid member 32 is formed in a columnar shape, and is provided with an opening edge portion 32a and a bottomed insertion hole 32b into which the internal lead bar 35 is inserted.
[0013]
The main member 31 and the lid member 32 constituting the electrode body 30 are made of a refractory metal or an alloy containing a refractory metal as a main component.
As the refractory metal, for example, a metal having a melting point of 3000 K or more, such as tungsten, rhenium, and tantalum, is employed. In particular, tungsten is preferable in that it hardly reacts with the internal heat transfer body M, and so-called pure tungsten having a purity of 99.9% or more is more preferable.
As an alloy mainly composed of a refractory metal, for example, a tungsten-rhenium alloy mainly composed of tungsten can be adopted. In this case, resistance to repetitive stress at high temperature is high, and the life of the electrode can be extended.
[0014]
The heat transfer body M uses a metal having a higher thermal conductivity than the metal constituting the electrode body 30. Specifically, when the electrode body 30 is made of tungsten, for example, gold, silver, copper, or an alloy containing these as a main component can be used as the heat transfer body M. Of these, silver and copper are preferred materials, and silver is the most preferred material. This is because, at about 2000K, the thermal conductivity of tungsten is about 100 W / mK, whereas silver is about 200 W / mK and copper is about 180 W / mK, both high. Furthermore, since silver and copper do not form an alloy with tungsten, they are also desirable metals in the sense that they function stably as heat transporters.
Here, the comparison of the thermal conductivity of the metal composing the electrode body 30 and the metal composing the heat transfer body M should be compared at the same temperature as a matter of course. It can be determined by comparing the thermal conductivities of both metals at a temperature level of 2000K or at room temperature.
[0015]
Further, as the heat transfer body M, a metal having a melting point lower than that of the metal constituting the electrode body 30 can be used. When the electrode body 30 is made of tungsten, gold, silver, copper, indium, tin, zinc, and lead can be used. In addition, these metals may be monoatomic metals or alloys, and may be composed of any one of them, or may be composed of a combination of two or more metals. .
When any one of gold, silver, and copper is used as the heat transfer body M, these metals have higher thermal conductivity than tungsten constituting the electrode body 30, so that the heat transport effect using the above-described conduction action is used. Is obtained. Furthermore, the heat transport effect using the above-mentioned convection action is also obtained.
When any one of indium, tin, zinc, and lead is used as the heat transfer body M, these metals have lower thermal conductivity than tungsten constituting the electrode body 30, so that the heat transport effect utilizing the conduction action Can't expect. Therefore, only the heat transport effect utilizing the convection action can be obtained.
Here, although it depends on the type of discharge lamp and the environment in which the discharge lamp is arranged, generally, when the current value to be supplied to the discharge lamp is 150 A or more, only the convection action of the heat transfer body M is used. Since the heat transport effect is not sufficient, it is desirable to employ any one of gold, silver, and copper as the heat transfer body M that can also be expected to have a conductive action.
[0016]
The heat transfer body M is preferably sealed at a ratio of 50% by volume or more with respect to the internal volume of the electrode body 30, and is preferably sealed in a range of 80% by volume to 95% by volume.
This is because if the amount of the heat transfer body M enclosed is small, the effect of conducting the heat generated at the electrode tip portion (31c) to the lid member 32 is not sufficient, leading to a temperature rise at the electrode tip portion.
It is more effective to enclose the heat transfer body M in the presence of a gap than to completely fill the sealed space 33 of the electrode body 30. The reason for this is that the current distribution flowing in the heat transfer body melted in the vicinity of the air gap changes due to the presence of the air gap, and the convection flow rate of the heat transfer body M melted by the Lorentz force generated by the change in the current distribution becomes faster. This is to increase heat transport. Even if the gap is small, it is effective, but it is desirable that the gap is at least 5% by volume with respect to the inner volume of the sealed space 33.
[0017]
A method for producing the main member 31 will be described. The cylindrical member processed into a desired shape is processed so that the bottom surface 34 becomes a curved surface by providing a bottomed hole with a drilling machine or the like.
[0018]
The reason why the electrode tip portion (31c) is less likely to be deformed even when the pressure in the arc tube is increased when the lamp is lit by forming the bottom surface 34 of the main member 31 to be a curved surface will be described with reference to the following 0019.
[0019]
FIG. 3 is a diagram for explaining the operation of the electrode of the present invention. FIG. 3A is a cross-sectional view for explaining the force generated at the tip of the electrode due to the difference between the pressure in the lamp and the pressure in the sealed space in the electrode. FIG. 3B is an enlarged view of the dotted line portion X shown in FIG.
As shown in FIG. 3B, an arbitrary 2 generated at two adjacent points on the bottom surface 34 of the sealed space 33 at the electrode tip (31c) due to the difference between the pressure in the arc tube and the pressure in the sealed space in the electrode. Think about one power. The force A generated at the first point 34X on the bottom surface 34 of the sealed space 33 at the electrode tip (31c) is decomposed into a force A ′ in the direction of the sealed space 33 and forces A1 and A2 spreading along the bottom surface 34. . In addition, the force B generated at the second point 34Y slightly separated from the first point 34X is the same magnitude as the force A. Like the force A, the force B ′ in the direction of the sealed space 33 and the bottom surface 34 are applied. It is broken down into forces B1 and B2 that spread along.
Here, the forces A1, A2, B1, and B2 spreading along the bottom surface 34 are all the same magnitude, and the forces A1 and B2, and the forces A2 and B1 are in opposite directions, so the forces A1 and B2 cancel each other. Accordingly, the force A2 and the force B1 are also canceled, and the force A ′ and the force B ′ having the same magnitude are generated on the bottom surface 34 in the direction of the sealed space 33.
Although the distance between the first point 341 and the second point 342 is very small, it is exaggerated in FIG. Furthermore, although the force generated on the bottom surface 34 actually exists infinitely, only two arbitrary forces are described in FIG. Then, all the forces along the bottom surface 34 are canceled as described above, and the same amount of force acts concentrically in the direction of the sealed space 33 on the bottom surface 34, so that the force for locally deforming the bottom surface 34 is applied. Does not occur, and the force to deform the electrode tip (31c) is relaxed.
[0020]
For the above reasons, the electrode according to the present invention can be applied to a lamp having a higher lamp pressure without causing deformation of the electrode tip (31c). Specifically, when the thickness of the electrode tip (31c) in FIG. 2 is 4.5 mm, the electrode does not have the structure (the bottom of the sealed space in which the heat transfer body is sealed is not curved) Can be used only up to about 1.5 MPa, but up to 2.5 MPa can be used if the electrode of the present invention is used.
[0021]
Further, the shape of the bottom surface 34 is d-1... Where the inner diameter of the electrode main body 30 in FIG. Preferably it is part of a sphere having a diameter of 5d.
[0022]
Further, the main member 31 preferably has a minimum thickness t1 at the intersection 34a between the electrode shaft and the bottom surface 34. According to such a structure, heat generated at the electrode tip (31c) is easily transferred to the heat transfer body, so that heat can be transported more effectively.
[0023]
FIG. 4 shows a cross-sectional view of an electrode according to another embodiment of the present invention cut along the electrode axis direction. The electrode according to the present invention is not limited to the structure shown in FIG. 2, and a structure as shown in FIG. 4 can also be adopted. 4, the same components as those described in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted.
As illustrated in FIG. 4, the bottom surface 340 of the sealed space 330 may have a shape in which a first sphere 341 and a second sphere 342 having a smaller diameter than the first sphere 341 are overlapped. If the diameter of the second sphere 342 is too small, a place where the molten heat transfer body M stays is formed and a turbulent flow is generated, so that the heat transport effect by the convection action of the heat transfer body M is achieved. Since it may become inadequate, it is preferable that it is d / 4-d / 2.
[0024]
As described above, according to the electrode of the present invention, by forming the electrode having a novel structure in which the heat transfer body is sealed in the sealed space formed inside the electrode body, the electrode tip portion is formed by the conductive action of the heat transfer body. The heat generated in can be transported effectively.
Furthermore, since the bottom surface of the main member constituting the electrode body is formed to be a curved surface, the force for deforming the electrode tip can be relaxed.
Furthermore, the molten heat transfer material does not stay when the lamp is lit, and the occurrence of turbulent flow is suppressed, and the convection of the molten heat transfer material is performed smoothly, so that the heat at the electrode tip can be transported more effectively. Can do.
For this reason, it is possible to solve problems such as melting and evaporation due to the high temperature of the electrode tip at the time of lamp lighting, without using a large cooling facility like a conventional water-cooled discharge lamp, A large output discharge lamp can be manufactured by applying a large current.
[0025]
Note that the electrode structure of the present invention is used for an electrode arranged on the upper side in a vertically lit discharge lamp in which the tube axis of the discharge lamp is arranged in the vertical direction because the heat transfer material melts when the lamp is lit. preferable. Since the electrode disposed on the upper side is likely to be heated to a high temperature, an anode having a larger volume than that of the cathode is usually used. However, this does not exclude the arrangement of the cathode employing the electrode structure of the present invention on the upper side. Absent.
Further, in an AC lighting type discharge lamp, the electrode structure of the present invention can be adopted for both electrodes.
[0026]
The discharge lamp of the present invention is not limited to a short arc type high-pressure mercury lamp, but a xenon lamp using xenon gas as a luminescent material, a metal halide lamp using a rare earth metal other than mercury as a luminescent material, and a discharge enclosing halogen. It can employ | adopt without being limited to luminescent substances, such as a lamp | ramp. Further, the present invention is not limited to short arc type discharge lamps, but can be used for middle arc type discharge lamps and long arc type discharge lamps, and can be applied to various discharge lamps such as low pressure discharge lamps, high pressure discharge lamps, and ultra high pressure discharge lamps.
[0027]
An experimental example for confirming the effect of the present invention will be described.
<Example>
An electrode according to the present invention as shown in FIG. 2 was produced. Ten discharge lamps having the following specifications, in which this electrode was incorporated on the anode side of the discharge lamp as shown in FIG. 1, were manufactured.
[Xenon mercury lamp]
The inner volume of the arc tube: 1830 cm ³
Distance between electrodes: 12mm
Xenon sealing pressure: 100kPa
Mercury amount: 28.2 mg / cm ³
[Anode electrode]
Material: Tungsten Dimensions: Length in the axial direction of electrode: 55 mm, Body outer diameter: 25 mm
Internal volume: 6700mm ³
Heat transfer material: Silver heat transfer capacity: 6000 mm ³
Internal lead bar material: Tungsten internal lead bar outer diameter: 6mm
(Cathode side electrode)
Material: Triated tungsten (Tria: 2wt.%)
Internal lead bar material: Tungsten internal lead bar outer diameter: 6mm
<Comparative example>
When a final shape is adopted, a discharge lamp in which a conventional electrode composed entirely of tungsten is incorporated on the anode side of the discharge lamp as shown in FIG. Made this book.
<Experimental example>
The discharge lamps according to the above examples and comparative examples were lit with a lamp current of 200 A and with the anode side electrode facing upward, with the lamps supported in the vertical direction. Then, 600 seconds after the lamp was turned on, the surface temperature at the tip of the anode electrode was measured with a micropyrometer.
As a result, the temperature in the vicinity of the tip of the electrode was 2130 ° C. for the discharge lamp according to the comparative example, whereas it was 2025 ° C. for the discharge lamp according to the example, which was lower in the discharge lamp according to the present invention. It was confirmed that
That is, according to the discharge lamp according to the present invention, the temperature of the electrode tip can be made lower than that of the conventional discharge lamp. As a result, a large current can be allowed to flow through the discharge lamp without providing a forced cooling mechanism, so that high output can be achieved.
[0028]
【The invention's effect】
According to the discharge lamp of the present invention, since the heat transfer body is sealed in the sealed space formed inside the electrode main body composed of the bottomed cylindrical main member and the columnar lid member, it is generated at the electrode tip. It is possible to efficiently transport heat toward the rear of the electrode. Thereby, even if it does not comprise a forced cooling mechanism, a high output discharge lamp can be provided.
Furthermore, since the electrode according to the present invention is formed so that the bottom surface corresponding to the inside of the tip end portion of the main member is a curved surface, the tip end portion of the electrode is not easily deformed even if the inside of the arc tube becomes high pressure when the lamp is turned on. Structure.
Furthermore, since the convection of the heat transfer material melted when the lamp is lit is smoothly performed without stagnation, it is possible to transport the heat generated at the electrode tip toward the rear of the electrode more efficiently. .
[Brief description of the drawings]
FIG. 1 is a view showing an entire discharge lamp according to the present invention.
FIG. 2 is a cross-sectional view of the anode according to the present invention cut in the electrode axis direction.
FIG. 3 is a view for explaining the operation of the electrode of the present invention.
FIG. 4 is a cross-sectional view of an electrode according to another embodiment of the present invention cut in the electrode axis direction.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Light emission part 2 Sealing part 3 Anode 4 Cathode 5 External lead rod 10 Discharge lamp 30 Electrode main body 31 Main member 31a Opening edge part 31b Body part 31c Tip part 32 Lid member 32a Opening edge part 32b Bottomed insertion hole 33 Sealed space 34 Bottom surface 34a Intersection 34X between electrode axis and bottom surface 34X First point 34Y on bottom surface 34 Second point 35 on bottom surface 34 Internal lead bar 330 Sealed space 340 Bottom surface 341 First sphere 342 Second sphere M Heat transfer Thickness d of body t1 34a Inner diameter of electrode body 30

Claims (1)

In a discharge lamp in which a pair of electrodes are arranged facing each other inside the arc tube,
At least one of the electrodes has a heat transfer member sealed in a sealed space formed inside an electrode body composed of a bottomed main member and a lid member,
The discharge lamp according to claim 1, wherein the main member is formed such that a bottom surface of the sealed space is a curved surface.

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