JP4998840B2 - Short arc type discharge lamp - Google Patents

Description

  The present invention relates to a short arc type discharge lamp, and more particularly to a short arc type discharge lamp having an electrode in which a heat transfer body is sealed in a sealed space of an electrode body.

Conventionally, the output of a short arc type discharge lamp used as an ultraviolet irradiation light source of an exposure apparatus that exposes a semiconductor substrate, a liquid crystal substrate for a liquid crystal display, a printed circuit board and the like has been increased. When the rated power consumption increases due to this increase in output, the value of the current flowing through the lamp usually increases, which causes the problem that the amount of the electrode subjected to electron collision increases, and the temperature easily rises and melts. .
In addition, the material constituting the electrode, such as tungsten, evaporates and adheres to the inner surface of the arc tube, resulting in blackening, resulting in a problem that the radiation ability of the lamp is reduced.

In order to solve such problems of melting and evaporation of the electrode material, for example, a short arc type discharge lamp having an electrode structure as disclosed in Japanese Patent Application Laid-Open No. 2004-6246 has been proposed.
In this short arc type discharge lamp, an electrode in which a heat transfer coefficient higher than that of an electrode material and which melts when the lamp is lit is enclosed in a sealed internal space formed in the electrode body.

This prior art will be described with reference to FIGS.
In FIG. 7, a short arc type discharge lamp 1 having a pair of electrodes 11, 12 disposed opposite to each other in an arc tube 10 is shown, and at least one of the electrodes (in this example, an anode) 12 is shown. As shown in FIG. 8, the electrode body 15 includes a container member 16 and a lid member 17, and a sealed space 18 is formed therein.
The sealed space 18 encloses an electric heating element M made of a material that has a higher thermal conductivity than that of the material constituting the electrode 12, such as tungsten, and melts when the lamp is turned on, such as gold or silver. The sealed space 18 is filled with an inert gas.
The heat transfer body M melts when the lamp is turned on, convects in the sealed space 18, and transfers the heat at the front end of the electrode main body 15 to the rear end side of the electrode main body 15. As a result, the temperature at the tip can be decreased, and as a result, the temperature at the tip can be lowered, and thereby, the melting and evaporation at the tip of the electrode can be suppressed.

However, when the short arc type discharge lamp having such an electrode structure is lit for a long time, a phenomenon called “high temperature creep deformation” occurs in a part of the inner wall of the tip of the electrode body, and the tip of the electrode is deformed. Eventually, a hole may open at the tip, leading to rupture.
This high temperature creep deformation is a deformation phenomenon peculiar to an electrode structure having a sealed space inside.
The mechanism is presumed to occur when the inner wall of the electrode receives a high pressure from the heat transfer body and the inert gas and receives extremely high temperature heat from the outside of the electrode when the lamp is lit. In particular, the tip where the discharge arc occurs is exposed to a high temperature of, for example, 2000 ° C. In high temperature creep deformation, a part of the bottom part (wall on the electrode tip side) forming the container member is deformed into a concave shape from the inside, and if it proceeds as it is, it will eventually puncture and burst. It might be.

This phenomenon will be described in detail below.
As shown in FIG. 8, the heat transfer body M in the sealed space 18 of the electrode 12 is a metal such as gold or silver having a higher heat transfer coefficient and a lower melting point than the electrode material, and melts at a high temperature when the lamp is lit. Liquid state. When the lamp is vertically lit by arranging the longitudinal direction of the electrodes along the vertical direction, the molten heat transfer body M is vertically moved within the container member 16 mainly in the vertical direction and receiving buoyancy and Lorentz force. A convection motion F is performed, where an upward flow Fu and a downward flow Fd are generated.
Inside the container member 6, there is a portion where the upward flow Fu and the downward flow Fd approach each other, and the upper and lower flows face each other, thereby increasing the pressure of this portion. In order to relieve this pressure, the fluid is dispersed in the horizontal direction, and a horizontal acceleration is applied to the convection.
As a result, as shown in FIG. 9, the upward flow Fu and the downward flow Fd receive a force in the horizontal direction and move in the circumferential direction (rotation direction). Therefore, the positions where the upward flow and the downward flow are generated are sealed. It moves relative to the container member 16 and changes every moment.

Here, the upward flow Fu receives heat from the bottom portion (electrode tip) 16a of the sealed container member 16, so the temperature thereof is high, and the downward flow Fd descends after transporting this heat to the inner wall near the lid portion 17. Therefore, the temperature is low. In particular, in the vicinity of the bottom portion 16a, since the upward flow Fu has just received heat, the temperature difference from the downward flow Fd is large.
When such convection rotates in the circumferential direction as described above and changes with time, the temperature of the wall near the bottom 16a of the container member 16 is observed at a fixed point, as shown in FIGS. It was confirmed that a drastic temperature change occurred as in the graph shown as a conventional example in FIG.

As described above, when a severe temperature change occurs on the inner surface of the container member 16, a deformation in which a protrusion protrudes from the inner surface due to a high temperature creep deformation occurs.
Specifically, as shown in FIG. 10, when the inner surface of the container member 16 is changed from a low temperature to a high temperature, a compressive thermal stress is generated and protrudes from the inner surface of the container member 16 to relieve the stress. Creep deformation 20 in the direction to relieve stress. At this time, the tungsten atoms that move to the protruding region 20 are supplied mainly from the bottom surface central portion 21 that is at the highest temperature, so that the peripheral portion 20 on the bottom surface is thick as shown in FIG. As a result, the bottom center portion 21 becomes thinner.
When the thickness of the bottom portion (electrode tip) 16a of the container member 16 progresses in this way, as shown in FIG. 10 (B), the hole 22 is finally opened so that the bottom 16a of the container member 16 penetrates, so There was a problem that the heat element M leaked.

JP 2004-6246 A

  In view of the above-mentioned problems of the prior art, the present invention provides a short arc type discharge lamp in which a heat transfer body is enclosed in a sealed space of an electrode. Therefore, it is intended to provide a structure in which a hole is not opened at the tip of an electrode even if it is lit for a long time by suppressing rotation in the circumferential direction in a sealed space.

In order to solve the above-described problems, in the present invention, a regulating body is provided in the sealed space of the electrode enclosing the heat transfer body to restrict the convection of the molten heat transfer body melted at the time of lighting from rotating in the circumferential direction. It is characterized by being.
Further, the regulation body is made of a plate material extending in the longitudinal direction of the electrode and traversing in the radial direction.

  According to the present invention, since the plate-shaped restricting body is provided in the sealed space of the electrode, the convection in the sealed space of the molten heat transfer body melted at the time of lighting is restricted / prevented from rotating in the circumferential direction. Since the temperature change at the same location of the electrode due to the movement of the convection is less likely to occur, high temperature creep deformation based on the temperature change does not occur, and no hole is formed at the electrode tip.

Sectional drawing of the electrode of the discharge lamp which concerns on this invention. Sectional drawing of another Example. Sectional drawing of another Example. FIG. 2 is an operation explanatory diagram of the embodiment of FIG. 1. FIG. 4 is a diagram illustrating the operation of the embodiment of FIG. The graph which shows the effect of this invention. Sectional drawing of the conventional short arc type discharge lamp. Sectional drawing which shows the conventional electrode structure. Explanatory drawing of the behavior of the convection of the molten heat transfer body shown in FIG. Explanatory drawing of the malfunction of the conventional electrode.

FIG. 1 shows an electrode structure of a short arc type discharge lamp according to the present invention. FIG. 1 (A) is a longitudinal sectional view thereof, and FIG. 1 (B) is a transverse sectional view thereof.
In the figure, the electrode 12 has an electrode body 15 composed of a container member 16 and a lid member 17, and a sealed space 18 is formed in the electrode body 15. In the sealed space 18, a heat transfer body M having a higher thermal conductivity than that of an electrode material such as tungsten is enclosed. The heat transfer body M is made of, for example, a metal such as gold or silver, has a lower melting point than the electrode material, and melts in the sealed space 18 when the lamp is lit.
A plate-shaped regulating body 2 is inserted into the sealed space 18 of the electrode 12. The restricting body 2 is provided so as to extend in the longitudinal direction on the substantially central axis of the sealed space 18 and to traverse in the radial direction, and has substantially the same size as the inner diameter of the sealed space 18 of the electrode 12. The restricting body 2 does not have to be positioned on the central axis of the electrode 12 in a strict sense.

  By the way, the regulation body 2 does not necessarily have a size substantially equal to the inner diameter of the sealed space 18 of the electrode 12, and may be shorter than this, as shown in FIGS. In such a case, it is necessary to hold the regulating body 2 in a predetermined posture or position in the sealed space 18, and as shown in FIG. 2B, an arc-shaped support piece along the internal shape of the sealed space 18 2a is provided, and the regulating body 2 is supported by the arcuate support piece 2a. The support of the restriction body 2 is not limited to this, and may be directly fixed to the electrode body 15 by laser welding or the like.

  FIG. 3 shows a different embodiment, and the restricting body 2 includes a pair of plate members 3 and 4 that intersect each other. The plate members 3 and 4 in this case also have a shape extending in the longitudinal direction of the electrode 12 and crossing in the radial direction. In the case of this embodiment, the longitudinal dimension of at least one of the plate members 3 and 4 is set to be shorter than the height of the enclosed heat transfer body M.

The operation of the above embodiment will be described with reference to FIGS.
FIG. 4 is a schematic explanatory diagram of the operation of the embodiment of FIG. 1. The convection F of the molten heat transfer body M is suppressed from moving in the circumferential direction in the sealed space 18 by the plate-like regulating body 2, Convection in a plane along the body 2.
Note that the embodiment of FIG. 2 is easily understood to be the same as the operation description of FIG.
FIG. 5 is a schematic explanatory view of the operation of the embodiment of FIG. 3. The convection F1 of the molten heat transfer body M is transferred from the space A surrounded by the two plate members 3 and 4 constituting the regulating member 2 to the plate member 3. It rises along it, flows into the space B beyond the plate material 4, and becomes a downward flow. The convection F <b> 1 is restricted from moving in the circumferential direction by the plate material 3 and is maintained as the convection F <b> 1 along the plate material 3.
The same convection F2 is also formed in the space regions C and D on the opposite side with respect to the plate material 3.
In this embodiment, the convection direction is not limited to the convection direction as shown in the figure, and there may be convection flowing from the space A to the space C and convection flowing from the space B to the space D. Depending on the state of convection of the molten heat transfer body M in FIG. However, in any case, once the convection is determined, the convection is maintained by the plate members 3 and 4 constituting the regulating body 2 and is not rotated in the circumferential direction in the sealed space 18. .

In order to demonstrate the effect of the present invention, the following experiment was conducted.
The specifications of the lamp are as follows.
<Luminescent tube>
Material: Quartz glass Internal volume: 550cm ³
Distance between electrodes: 6mm
Inclusion material: mercury 2.0 mg / cc, argon 100 kPa
<Anode>
Material: Tungsten trunk (container) outer diameter: 25mm
Electrode body volume: 6 cm ³
Wall thickness: 5.5mm
Heat transfer body: Silver 4.7cm ³
Filled gas: Argon 100 kPa
<Cathode>
Material: Thorium-containing tungsten (tritan) Thorium-containing 2% by weight
<Rating>
Rated current: 150A
Rated power: 5kW

Next, a lamp having a conventional electrode structure, a lamp A having the electrode structure of FIG. 1, and a lamp B having the electrode structure of FIG.
<Regulatory body>
Material: Tungsten Dimensions: Thickness 200μm, Height 15mm

These lamps are vertically lit with the anode facing upward, the electrode surface temperature at a location 10 mm above the anode tip surface along the electrode axis is measured with a radiation thermometer for 3 minutes, and the temperature fluctuation range (maximum value) -Minimum value) was recorded. The result is shown in FIG.
As can be seen from the graph, the temperature variation width of the lamp A of the present invention is 9 ° C. and the temperature variation of the lamp B is 6 ° C. Both lamps are greatly reduced from the temperature variation width of 60 ° C. of the conventional lamp.

表１で分かるように、初期において５．５ｍｍであった肉厚が、従来ランプでは３．０ｍｍとなり、その肉厚減少量は２．５ｍｍであったのに対して、本発明ランプＡでは肉厚減少量が１．２ｍｍ、本発明ランプＢでは１．０ｍｍとなり、大幅な改善が見られた。 Further, these lamps were turned on for 750 hours, and then cut along a section passing through the central axis of the anode, and the thickness at the center of the tip was measured with a microscope. The results are shown in Table 1 together with the temperature fluctuation range.
<Table 1>

As can be seen from Table 1, the thickness of 5.5 mm in the initial stage was 3.0 mm in the conventional lamp, and the thickness reduction amount was 2.5 mm, whereas in the lamp A of the present invention, the thickness was reduced. The thickness reduction amount was 1.2 mm, and the lamp B of the present invention was 1.0 mm, showing a significant improvement.

  As described above, according to the present invention, in the short arc type discharge lamp having the electrode in which the heat transfer body is sealed in the sealed space of the electrode body, the regulating body is disposed in the sealed space of the electrode, so that it melts during lighting. Therefore, the convection of the heat transfer body is prevented from rotating in the circumferential direction of the electrode sealed space, the convection is always maintained at the same position, and the temperature does not change locally at the electrode, and high temperature creep deformation occurs. Therefore, an unexpected situation where a hole is opened at the electrode tip is avoided.

DESCRIPTION OF SYMBOLS 1 Short arc type discharge lamp 2 Regulating body 3, 4 Plate material 10 Arc tube 11, 12 Electrode 15 Electrode body 16 Container member 17 Cover member 18 Sealed space M Heat transfer body F Convection Fu Upflow Fd Downflow

Claims (4)

In a short arc type discharge lamp having a pair of electrodes inside the arc tube, and a heat transfer body sealed in a sealed space of at least one of the electrodes,
A short arc type discharge lamp characterized in that a regulating body for regulating rotation of the convection of the molten heat transfer body in the circumferential direction is provided in the sealed space.   2. The short arc type discharge lamp according to claim 1, wherein the restricting body is made of a plate material extending in a longitudinal direction of the electrode in the sealed space and traversing in a radial direction.   The short arc type discharge lamp according to claim 2, wherein the plate member is disposed so as to pass on a central axis of the electrode. The short arc type discharge lamp according to claim 2, wherein the regulating body is made of two plate members intersecting each other.

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