KR20150060673A

KR20150060673A - Discharge lamp

Info

Publication number: KR20150060673A
Application number: KR1020157004197A
Authority: KR
Inventors: 다케노리 하야카와; 하루오 쿠리야마
Original assignee: 가부시키가이샤 오크세이사쿠쇼
Priority date: 2012-09-25
Filing date: 2013-09-20
Publication date: 2015-06-03
Also published as: WO2014050728A1; KR101986402B1; TW201423830A; JP2014067540A; CN104584186A; TWI578372B; CN104584186B; JP6180716B2

Abstract

The discharge lamp of the present invention has a discharge tube and a pair of electrodes disposed in the discharge tube, and at least one of the electrodes has a heat transfer body sealed in a closed space formed inside the electrode. The heating element is in a liquid state at the time of lighting, solidifies after being turned off, and forms a concave portion toward the electrode supporting rod side opposite to the electrode front end side. By forming the recess, the stress is reduced.

Description

DISCHARGE LAMP

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp used in an exposure apparatus or the like, and more particularly to an electrode in which a heat conductor is sealed in an electrode.

BACKGROUND ART [0002] In a discharge lamp, an electrode in which a metal having a cooling function is enclosed in a hermetically sealed space formed inside an electrode is known as the output becomes higher (see Patent Document 1). In this case, a heat conductor made of a metal having a high thermal conductivity and a relatively low melting point, such as silver, is sealed inside the positive electrode. When the electrode temperature rises due to lamp lighting, the metal is melted and liquefied. As a result, a thermal current is generated in the inner space, and the heat of the electrode tip portion is transported in the direction of the electrode support rod on the opposite side.

When the heater is sealed in the internal space, the ratio of the heater, that is, the volume ratio, affects the heat transport efficiency and the electrode strength. If the proportion of the heat transfer material is too small, the thermal flow becomes insufficient and the heat transfer efficiency deteriorates. On the other hand, if the ratio of the heat transfer element is too large, the vapor pressure in the closed space rises, excessive pressure is applied to the wall of the closed space, and electrode breakage may occur.

Therefore, an appropriate volume ratio between the heat conductive member and the internal sealed space is determined, and the amount of the heat conductive member to be sealed is adjusted (see Patent Document 2). Alternatively, the volume ratio of the projection member extending to the closed space is adjusted (see Patent Document 3).

Japanese Unexamined Patent Application Publication No. 2012-15007 Japanese Patent Application Laid-Open No. 2010-003594 Japanese Patent Application Laid-Open No. 2004-259644

When the lamp is turned on, the heat conductor is in a liquid state, but when the electrode temperature is lowered due to the lamp being turned off, the heat conductor is coagulated under heat shrinkage. At this time, stress is applied to the bottom surface and the side wall of the inner space. Further, when the lamp is turned on again, the heat transfer element melts while being thermally expanded, and becomes a liquid. At this time, stress is applied to the inner space side wall.

The stress generated at the time of phase change of the heat transfer member becomes burdensome on the inner wall of the electrode, that is, on the side wall and the bottom of the electrode inner space, and there is a fear that the inner wall of the electrode is cracked by repeatedly turning on and off the lamp . However, it is not possible to maintain the electrode strength over a long period of time merely by considering the amount of the heat transfer material at the time of lighting.

Therefore, when the lamp is switched off / on, the heat transfer element must be phase-shifted so that the stress is reduced.

The discharge lamp of the present invention has a discharge tube and a pair of electrodes disposed in the discharge tube, and at least one of the electrodes has a heat transfer element which is sealed in a closed space formed inside the electrode, And solidifies after being turned off to form a concave portion toward the electrode support bar side opposite to the electrode front end side. By forming the recess, the stress is reduced.

For example, the heat conductor forms a recess to satisfy the following expression.

1/4? A / b? 3/4

Here, a represents the distance from the proximal end of the heat transfer member to the bottom of the recess, and b represents the distance from the end of the heat transfer member to the bottom of the closed space.

The heat conductor forms a recess to satisfy the following expression.

1/10? E / f? 1/4

Here, e represents the volume of the recessed portion, and f represents the volume of the heat transfer body.

The shape of the concave portion is arbitrary, and it is sufficient to satisfy the above expression. In this case, at least one of the coagulation shrinkage, the viscosity and the thermal conductivity of the heat transfer member may be adjusted so as to determine the shape of the heat transfer member. It is also possible to provide a heat dissipating portion on at least one of the electrodes on the electrode surface.

According to the present invention, an electrode excellent in cooling function can be obtained while maintaining the electrode strength.

1 is a plan view schematically showing a discharge lamp according to a first embodiment;
2 is a schematic cross-sectional view of an anode.
3 is a schematic cross-sectional view of the anode during lighting.
4 is a schematic cross-sectional view of a positive electrode in which the recessed portion is excessively small in height and does not satisfy the conditional expression.
5 is a schematic cross-sectional view of an anode in which the height of the concave portion is excessively large and which does not satisfy the conditional expression.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 is a plan view schematically showing a discharge lamp according to the first embodiment.

The short arc type discharge lamp 10 is a discharge lamp which can be used for a light source of an exposure apparatus (not shown) for forming a pattern, and has a discharge tube (light emitting tube) 12 made of transparent quartz glass. In the discharge tube 12, the cathode 20 and the anode 30 are disposed opposite to each other with a predetermined gap therebetween.

Sealing tubes 13A and 13B made of quartz glass are integrally provided on both sides of the discharge tube 12 so as to be opposed to each other with the discharge tube 12. Both ends of the sealing tubes 13A and 13B are connected to the ends of the vertexes 19A and 19B ).

The discharge lamp 10 is arranged along the vertical direction so that the anode 30 is on the upper side and the cathode 20 is on the lower side. Electrically conductive electrode supporting rods 17A and 17B for supporting the metallic cathode 20 and the anode 30 are disposed in the sealing tubes 13A and 13B and a metal ring And are connected to the conductive lead rods 15A and 15B through metal foils 16A and 16B such as molybdenum.

The sealing tubes 13A and 13B are welded to a glass tube (not shown) provided in the sealing tubes 13A and 13B, whereby the discharge space DS in which the mercury and the rare gas are sealed Lt; / RTI >

The lead rods 15A and 15B are connected to an external power supply unit (not shown) and are connected to the cathode 20 through lead rods 15A and 15B, metal foils 16A and 16B, and electrode support rods 17A and 17B. , And the anode (30). When electric power is supplied to the discharge lamp 10, an arc discharge occurs between the electrodes and a bright line (ultraviolet light) by mercury is emitted.

Fig. 2 is a schematic cross-sectional view of the anode 30 when the cathode 30 is off. 3 is a schematic cross-sectional view at the time when the anode 30 is lighted.

The anode 30 is composed of a columnar body portion 32 and a frustum-shaped tip end portion 34 having a positive electrode tip end 34S. The trunk part 32 has a structure in which the sealing lid 45 to which the electrode supporting rod 17B is attached is joined to the body part 32 and the tip part 34 excluding the sealing lid 45, .

In the body part 32, a cylindrical closed space 50 is formed coaxially with the electrode shaft at the center thereof. The closed space 50 has a cross section 45S whose upper end is in contact with the sealing lid 45 and whose lower end is the electrode distal end side end face 50D. The length c of the side surface 50S of the closed space 50 is longer than the diameter d of the closed space 50. [

In the sealed space (50), the heat transfer element (40) is sealed. The heat conductor 40 is made of a metal (for example, silver) having a lower melting point than the body portion 32 and the sealing lid 45. As shown in FIG. 3, the lamp is melted to be in a liquid state during lamp lighting, and the temperature rise of the tip end portion 34 is suppressed by the thermal current.

When the lamp is turned off, the heat transfer element 40 contracts while solidifying. The temperature of the heat transfer member 40 starts to solidify from the vicinity of the side surface 50S of the closed space 50 because the temperature is rapidly lowered near the body surface 32 of the anode 30. [ As time elapses, the solidification of the heat transfer body advances to the center portion while contracting.

The heat transfer element 40 finally becomes solid near the central portion of the bottom surface 50D of the closed space 50 and finally the heat transfer element 40 becomes a concave state where the central portion is recessed and solidifies. In the vicinity of the central portion of the bottom surface 50D, the stress due to the contraction acts in multiple directions, so that the hole 70 exists. A part of the heat transfer element 40 is attached to the end face 45S of the sealing lid 45 as described later.

The shape of the recessed portion opened toward the sealing lid 45 of the heat conductive member 40 fulfills the role of reducing the stress caused by the lighting. That is, the stress caused by the thermal expansion of the heat conductor 40 at the time of lighting is placed at the central portion, whereby the stress associated with the bottom surface 50D and the side surface 50S of the closed space 50 can be reduced . Each time the light is turned on / off repeatedly, the heat transfer element 40 repeats solidification and liquefaction in a recessed shape as shown in Figs.

Since the heat conductive member attached to the sealing lid 45 by the light off is isolated from the heat conductive member 40 having the concave shape, when it is switched to the light, it melts prematurely and flows down to the surface of the recess, Advances liquefaction.

A laser groove 60 having a heat radiation function is formed in the vicinity of the anode tip end portion 34 in the circumferential direction on the body side surface 32S of the anode 30. [ The anode tip 32 is prevented from becoming excessively hot during the lamp lighting and the solidification of the heater 40 inside the closed space 50 is accelerated.

The shape of the concave portion of the heat transfer element 40 shown in Fig. 2 is determined by the heat dissipation characteristics of the anode 30, the characteristics of the heat transfer element 40, the volume ratio of the heat transfer element 40 to the closed space 50, And the like. Particularly, the depth of the concave portion varies depending on the heat radiation characteristic of the laser groove 60 of the anode 30 and the characteristics of the heat transfer member 40. Here, the characteristics of the heat transfer element (40) indicate the coagulation shrinkage rate, viscosity and thermal conductivity.

In this embodiment, the amount and characteristics of the enclosure 40 and the position of the laser groove 60 are determined so that the height of the concave portion, which is a feature of the concave portion, satisfies predetermined conditions. The height of the concave portion is defined as the distance from the concave portion 40T to the concave bottom 40D in contact with the side surface 50S of the closed space 50 and the highest position of the heat transfer member 40 at the highest position.

Preferably, the recess height a satisfies the following conditional expression.

1/4? A / b? 3/4 ... (One)

Where a represents the distance from the heat transfer member proximal end 40T to the concave bottom 40D and b represents the distance from the heat transfer member concave end 40T to the bottom surface 50D of the closed space.

More preferably, the following conditional expression is satisfied.

1/10? E / f? 1/4 ... (2)

Here, e represents the volume of the recess of the heat transfer element 40, and f represents the volume of the heat transfer element 40.

If the height of the concave portion is excessively small, the stress generated at the time of lighting off lowers the electrode strength. More specifically, when the lamp is turned off, the solidification of the heat transfer element 40 starts from above the sealing lid 45 with a relatively low temperature. Therefore, by lowering the temperature at the lower portion close to the anode tip portion 32, it is necessary to accelerate the drop of the liquid level due to shrinkage at the time of the phase change.

In order to make the height of the recessed portion sufficient, the heat radiation effect by the groove 60 is effective. In addition, the characteristics of the heat conductor 40 must be taken into account. When the solidification shrinkage ratio is low, since the volume reduction ratio is small, the drop of the liquid level is suppressed. If the viscosity is small, the portion remaining in the vicinity of the upper side of the closed space 30S by the viscosity decreases and the height of the recessed portion becomes small. When the thermal conductivity is high, since the temperature difference between the central portion and the vicinity of the side surface is small, there is no difference in the liquid surface height at the time of starting solidification and the height of the recessed portion is reduced.

In addition, when the heater 40 is re-melted due to switching to lighting in a cow or the like, if the height of the recessed portion is small, the greatest stress occurring in the vicinity of the closed space bottom surface 50D can not be released, I can not.

Conversely, when the height of the concave portion is excessively large, an excessive stress is applied to the inner surface of the anode, that is, the bottom surface 50D and the side surface 50S of the closed space 50. If the solidification reduction ratio of the heat transfer member 40 is high, the viscosity is high, and the thermal conductivity is high, the height of the recessed portion becomes large. However, if the recessed portion becomes too high, the concave bottom 40D becomes close to the closed space bottom face 50D, and solidification accompanied by a strong stress acts on the bottom face 50D, which may cause cracks in the anode inner wall.

Fig. 4 is a schematic cross-sectional view of the anode in which the recessed portion height is excessively small and the conditional expression is not satisfied. In this case, the stress in the vicinity of the bottom surface 50D can not be sufficiently released to the recesses at the time of re-exposure, and there is a fear that cracks may occur in the inner wall of the anode.

5 is a schematic cross-sectional view of the anode in which the height of the recess is excessively large and which does not satisfy the conditional expression. In the portion where the liquid phase 40B finally coagulates, a strong stress is generated in a complicated direction, so that a hole 70 is formed. That is, in the case of Fig. 5, this stress occurs near the bottom surface 50D, and there is a fear that the bottom surface 50D is cracked.

Further, in the case of being turned on again, it takes time for the melting of the heat transfer member 40 to move upward. Therefore, it takes time until the start of the thermal flow and the electrode tip portion 34 is overheated.

Further, the position of the groove 60 affects the height of the concave portion. When the grooves 60 are formed up to the vicinity of the sealing lid 45, the solidification at the upper side is accelerated, and the recessed portion is formed with the liquid phase portion which is not solidified left. On the other hand, if the grooves 60 are formed only in the vicinity of the bottom, solidification in the vicinity of the bottom is promoted, so that the height of the recesses becomes excessively large.

In this embodiment, the grooves 60 are formed so as to satisfy the conditional expression (1), and the characteristics of the heat transfer element 40 .

As described above, according to the present embodiment, the sealed space 50 is formed inside the anode 30, and the heat transfer body 40 made of metal such as silver is enclosed in the hollow space. At this time, the electrode size, the formation position of the heat dissipating groove 60, the characteristics of the heat conductor 40, and the like are determined so as to satisfy the conditional expressions (1) and (2). When the lamp is turned on, the heat transfer element 40 liquefies.

As the heat dissipation mechanism, in addition to the formation of the grooves, the heat dissipation portion having a different heat dissipation characteristic from the other electrode surface portion may be applied with fine particle spraying, alumina processing, or the like. The cathode may have the same structure.

Even when the equations (1) and (2) are not satisfied, a state in which the heat transfer element is filled with the liquid phase so as to fill the closed space, or a state in which the bottom of the heat transfer element concave reaches the vicinity of the bottom of the closed space It is possible to improve the electrode strength by avoiding an extreme state in which the recesses are not formed.

With regard to the present invention, various changes, substitutions and substitutions are possible without departing from the spirit and scope of the present invention as defined by the appended claims. In addition, the present invention is not intended to be limited to the processes, apparatuses, manufacture, compositions, means, methods and steps of the specific embodiments described in the specification. Those skilled in the art will recognize from the disclosure of the present invention that the devices, means and methods leading to substantially the same functions as those brought about by the embodiments described herein, or substantially resulting in equivalent actions and effects. Accordingly, the appended claims are intended to be included within the scope of such devices, means, and methods.

The present application is based on a Japanese patent application (Japanese Patent Application No. 2012-211104, filed on September 25, 2012), which claims priority, and the disclosure contents including the specification, drawings and claims of the basic application are incorporated herein by reference Are incorporated herein by reference.

10 discharge lamp
30 Anode
40 electric heater
a waist height

Claims

A discharge tube,
And a pair of electrodes disposed in the discharge tube,
Wherein at least one of the electrodes has an electrothermal element enclosed in a closed space formed inside the electrode,
Wherein the heat transfer member is in a liquid state at the time of lighting and solidifies after being turned off to form a concave portion toward the electrode support rod side opposite to the electrode front end side.

The method according to claim 1,
Wherein said heat conductor forms a concave portion so as to satisfy the following expression.
1/4? A / b? 3/4
Here, a represents the distance from the proximal end of the heat transfer member to the bottom of the recess, and b represents the distance from the end of the heat transfer member to the bottom of the closed space.

The method according to claim 1,
Wherein said heat conductor forms a concave portion so as to satisfy the following expression.
1/10? E / f? 1/4
Here, e represents the volume of the recessed portion, and f represents the volume of the heat transfer body.

4. The method according to any one of claims 1 to 3,
Wherein at least one of the coagulation shrinkage ratio, the viscosity, and the thermal conductivity of the heat transfer member is adjusted so as to determine the shape of the recess of the heat transfer member.

5. The method according to any one of claims 1 to 4,
Wherein at least one of the electrodes has a heat radiation portion on an electrode surface.