TW201423830A - Electric discharge lamp tube - Google Patents

Abstract

An objective of the invention is to retain the strength of electrodes to obtain the electrodes having excellent cooling performance. The inside of the anode 30 is formed with a sealed space 50. A heat transfer body 40 composed of metal, such as silver, is sealed therein in a recess shape. At this time, electrode sizes, the formation position of the grooves 60 for heat discharge, and the feature of the heat transfer body are defined to satisfy equations (1) and (2). When the lamp is turned on, the heat transfer body 40 is liquefied.

Description

Discharge lamp

The present invention relates to a discharge lamp used in an exposure apparatus or the like, and particularly relates to an electrode in which a heat transfer body is sealed inside an electrode.

In the discharge lamp tube, an electrode in which a metal having a cooling function is sealed in a sealed space formed inside the electrode is known (see Patent Document 1). At this point, a heat transfer body composed of a metal having a high thermal conductivity and a relatively low melting point such as silver is sealed inside the anode. When the temperature of the lighting electrode rises, the metal melts and liquefies. Therefore, heat convection occurs in the internal space, and the heat at the tip end portion of the electrode is transported in the direction of the electrode support rod on the opposite side.

When the heat transfer body is sealed in the internal space, the proportion of the heat transfer body, that is, the volume ratio, affects the heat transfer efficiency and the electrode strength. If the ratio of the heat transfer body is too small, the heat convection is insufficient to deteriorate the heat transfer efficiency. On the other hand, when the ratio of the heat transfer body is too large, the vapor pressure inside the sealed space rises, and the wall surface of the sealed space is subjected to excessive pressure, which may cause the electrode to be damaged.

Therefore, an appropriate volume ratio between the heat transfer body and the inner sealed space is set, and the amount of the heat transfer body to be sealed is adjusted (see Patent Document 2). Alternatively, the volume ratio of the protruding members extending in the sealed space is adjusted (see Patent Document 3).

[Advanced technical literature]

[Patent Literature]

Patent Document 1: Japanese Laid-Open Patent Publication No. 2012-15007

Patent Document 2: Japanese Laid-Open Patent Publication No. 2010-003594

Patent Document 3: Japanese Laid-Open Patent Publication No. 2004-259644

When the light is turned on, the heat transfer body becomes liquid. However, when the temperature of the light-off electrode is lowered, the heat transfer body is solidified while being thermally contracted. At this time, stress is applied to the bottom surface and the side wall of the internal space. When the lamp is turned on again, the heat transfer body is melted while being thermally expanded to become a liquid. At this time, stress is applied to the side walls of the internal space.

In this way, the stress generated when the heat transfer body phase changes causes a burden on the inner wall of the electrode, that is, the side wall and the bottom surface of the internal space of the electrode, and the operation of repeatedly lighting or turning off the light may cause cracks in the inner wall of the electrode. However, it is not expected to maintain the electrode strength for a long period of time simply by considering the amount of heat transfer when lighting.

Therefore, when switching off/lighting, it is necessary to reduce the stress generated by the change in the phase of the heat transfer body.

An electrode for a discharge lamp according to the present invention includes a discharge tube; a pair of electrodes are disposed in the discharge tube, wherein at least one of the pair of electrodes has a heat transfer body and is enclosed in a sealed space formed inside the electrode; The heat transfer body forms a liquid state at the time of lighting, solidifies after the light is turned off, and forms a concave portion toward the electrode support rod side opposite to the electrode front end side. The stress can be reduced by the formation of the recess.

For example, the heat transfer body forms a recess in such a manner as to satisfy the following expression.

1/4≦a/b≦3/4

Where a represents the distance from the concave end of the heat transfer body to the bottom of the recess, and b represents the distance from the end of the heat transfer body recess to the bottom surface of the sealed space.

For example, the heat transfer body forms a recess in such a manner as to satisfy the following expression.

1/10≦e/f≦3/4

Where e denotes the volume of the recess and f denotes the volume of the heat transfer body.

The shape of the concave portion is arbitrary, and the above formula may be satisfied. In this case, at least one of the solidification shrinkage ratio, the viscosity, and the thermal conductivity of the heat transfer body can be adjusted to fix the shape of the concave portion of the heat transfer body. Further, at least one of the pair of electrodes may be provided with a heat radiating portion on the surface of the electrode.

According to the present invention, it is possible to maintain the electrode strength and obtain an electrode excellent in cooling performance.

10‧‧‧Discharge lamp

12‧‧‧Discharge tube (light tube)

13A, 13B‧‧‧ sealed tube

15A, 15B‧‧‧ guide bars

16A, 16B‧‧‧metal foil

17A, 17B‧‧‧electrode support rod

19A, 19B‧‧‧ metal cover

20‧‧‧ cathode

30‧‧‧Anode

32‧‧‧ Body Department

34‧‧‧Conical trapezoidal front end

34S‧‧‧ anode front end face

40‧‧‧ heat transfer body

40B‧‧‧ liquid phase

40T‧‧‧ recessed end

40D‧‧‧ recessed bottom

45‧‧‧Closed cover

45S‧‧‧ end face

50‧‧‧Confined space

50D‧‧‧ front end face of the electrode

50S‧‧‧ side

60‧‧‧Ray ditch

70‧‧‧ hole

A‧‧‧ recess height

DS‧‧‧discharge space

Fig. 1 is a plan view schematically showing a discharge lamp of the first embodiment.

Fig. 2 is a schematic cross-sectional view of the anode.

Figure 3 is a schematic cross-sectional view of the anode in the lighting.

Fig. 4 is a schematic cross-sectional view of the anode which is too small in height and does not satisfy the conditional expression.

Fig. 5 is a schematic cross-sectional view of the anode in which the height of the concave portion is too large and does not satisfy the conditional expression.

Embodiments of the present invention are described below with reference to the drawings.

Fig. 1 is a plan view schematically showing a discharge lamp of the first embodiment.

The short-arc discharge lamp tube 10 is a discharge lamp tube that can be used for a light source or the like for forming an exposure device (not shown), and includes a discharge tube (light-emitting tube) 12 made of transparent quartz glass. The cathode 20 and the anode 30 in the discharge tube 12 are disposed opposite each other at a predetermined interval.

Sealing tubes 13A and 13B made of quartz glass which are opposed to each other and integrated with the discharge tube 12 are provided on both sides of the discharge tube 12, and both ends of the sealing tubes 13A and 13B are plugged by the metal covers 19A and 19B.

In the discharge lamp tube 10, the anode 30 is disposed on the upper side and the cathode 20 is disposed on the lower side in the vertical direction. Electrode support rods 17A and 17B for supporting the metallic cathode 20 and the anode 30 are disposed inside the sealed tubes 13A and 13B, and the metal foils 16A and 16B through the metal ring (not shown) and molybdenum are respectively connected to Conductive bars 15A, 15B.

The sealed tubes 13A and 13B are welded to glass tubes (not shown) provided in the sealed tubes 13A and 13B to seal the discharge space DS in which mercury and inert gas are sealed.

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

Fig. 2 is a schematic cross-sectional view showing the anode 30 at the time of turning off the light. Fig. 3 is a schematic cross-sectional view showing the anode 30 at the time of lighting.

The anode 30 is composed of a columnar body portion 32 and a conical trapezoidal tip end portion 34 having an anode tip end surface 34S. The body portion 32 is joined with electrode support The structure of the sealing cover 45 of the rod 17B is formed of the same metal material as the body portion 32 and the front end portion 34 except the sealing cover 45.

The main body portion 32 has a cylindrical sealed space 50 coaxially formed with respect to the electrode axis at the inner center. The upper boundary of the sealed space 50 is an end surface 45S to which the sealing cover 45 is attached, and the lower boundary is an electrode front end side end surface 50D. The length c of the side surface 50S of the sealed space 50 is longer than the diameter d of the sealed space 50.

The heat transfer body 40 is sealed inside the sealed space 50. The heat transfer body 40 is composed of a metal (for example, silver) having a lower melting point than the body portion 32 and the sealing cover 45. As shown in Fig. 3, the lighting is melted to a liquid state, and the temperature rise of the tip end portion 34 is suppressed by the heat convection.

When switching to the light-off, the heat transfer body 40 contracts and solidifies to become a solid. Since the temperature in the vicinity of the surface 32 of the main body portion of the anode 30 is rapidly lowered, the vicinity of the side surface 50S of the sealed space 50 starts to solidify, and as time passes, the heat transfer body contracts while being solidified toward the center portion.

Then, the heat transfer body 40 finally becomes a solid near the center portion of the bottom surface 50D of the sealed space 50, and finally, the heat transfer body 40 is solidified into a concave shape in which the center portion is recessed. Since the contraction stress acts in a plurality of directions in the vicinity of the center portion of the bottom surface 50D, the hole 70 exists. A part of the heat transfer body 40 is attached to the end surface 45S of the sealing cover 45 as will be described later.

The shape of the concave portion in which the heat transfer body 40 is opened toward the sealing cover 45 has an effect of reducing the stress generated at the time of lighting. In other words, the stress generated by the thermal expansion of the heat transfer body 40 at the time of lighting is moved toward the center portion, and the stress applied to the bottom surface 50D and the side surface 50S of the sealed space 50 can be reduced. Each time the lighting is turned on/off, the heat transfer body 40 repeats the solid phase and liquefaction of the recessed shape as shown in Figs. 2 and 3 .

Since the heat transfer body adhering to the sealing cover 45 due to the light-off is isolated from the heat-transfer body 40 having a recess shape, it can be melted early upon switching to the lighting, and then dripped onto the surface of the concave portion to accelerate the liquefaction of the heat transfer body 40.

Further, on the main body side surface 32S of the anode 30, a laser beam 60 having a heat releasing function is formed in the circumferential direction in the vicinity of the anode tip end portion 34. During the lighting, the anode front end portion 32 is prevented from being excessively heated, and the solidification of the heat transfer body 40 inside the sealed space 50 is accelerated.

The shape of the concave portion of the heat transfer body 40 shown in Fig. 2 depends on the heat release characteristics of the anode 30, the characteristics of the heat transfer body 40, the volume ratio of the heat transfer body 40 to the sealed space, the size of the sealed space 50, and the like. In particular, the depth of the recess of the recess varies depending on the heat release characteristics of the laser beam 60 of the anode 30 and the characteristics of the heat transfer body 40. Here, the characteristics of the heat transfer body 40 are the solidification shrinkage ratio, the viscosity, and the thermal conductivity.

In the present embodiment, the amount and characteristics of the heat transfer body 40, the position of the laser beam 60, and the like are set, and the height of the concave portion which is a feature of the shape of the concave portion satisfies a predetermined condition. Here, the height of the concave portion is defined as a distance from the side surface 50S of the sealed space 50, and the distance between the both ends 40T of the concave portion 40D of the heat transfer body 40 at the highest position to the concave bottom portion 40D.

The height a of the recess preferably satisfies the following conditional expression.

1/4≦a/b≦3/4.....(1)

Where a represents the distance from the heat transfer body concave end portion 40T to the concave portion bottom portion 40D, and b represents the distance from the heat transfer body concave end portion 40T to the bottom surface 50D of the sealed space.

It is better to satisfy the following conditional formula 1/10≦e/f≦1/4....(2)

Wherein e represents the volume of the concave portion of the heat transfer body 40, and f represents the volume of the heat transfer body 40.

If the height of the concave portion is too small, the stress generated when the light is turned off may lower the strength of the electrode. Specifically, when the lighting state is switched to the light-off state, the solidification of the heat transfer body 40 is started from the vicinity of the vicinity of the sealing cover 45 having a relatively low temperature. Therefore, it is necessary to accelerate the temperature drop below the anode front end portion 32 to accelerate the liquid level reduction caused by the shrinkage in the phase change.

In order to ensure a sufficient recess height, the heat release effect of the groove 60 is quite effective. In addition to this, the characteristics of the heat transfer body 40 must also be considered. When the solidification shrinkage rate is low, the proportion of volume reduction is small, so that the drop of the liquid level is suppressed. Further, when the viscosity is small, the portion remaining in the vicinity of the upper side 30S of the sealed space due to the viscosity is reduced, and the height of the concave portion is reduced. Further, when the thermal conductivity is high, the temperature difference between the center portion and the side surface is small, so that there is no height difference between the liquid surface at the start of solidification, and the height of the concave portion is reduced.

When the heat transfer body 40 is re-melted by switching off the light to the lighting, if the height of the concave portion is small, the maximum stress generated in the vicinity of the bottom surface 50D of the sealed space cannot be released, and the stress can not be expected to be alleviated.

Conversely, if the height of the concave portion is too large, excessive stress is applied to the inner wall of the anode, that is, the bottom surface 50D and the side surface 50S of the sealed space 50. When the heat transfer body 40 has a high solidification reduction ratio, a large viscosity, and a high thermal conductivity, the height of the concave portion becomes large. However, if the concave portion becomes too high, the concave bottom portion 40D approaches the bottom surface 50D of the sealed space, so that solidification with strong stress acts on the bottom surface 50D, and the inner wall of the anode may be cracked.

Fig. 4 is a schematic cross-sectional view of the anode which is too small in height and does not satisfy the conditional expression. In this case, when the lamp is turned on again, the stress near the bottom surface 50D is not sufficiently released to the concave portion, so that the inner wall of the anode may be cracked.

Fig. 5 is a schematic cross-sectional view of the anode in which the height of the concave portion is too large and does not satisfy the conditional expression. The portion of the liquid phase 40B that is finally solidified undergoes a strong stress in a complicated direction, and thus the hole 70 is generated. That is to say, in the case of Fig. 5, this stress occurs in the vicinity of the bottom surface 50D, and the bottom surface 50D may be cracked.

Moreover, in the case of lighting again, it takes time to advance the melting of the heat transfer body 40 upward. Therefore, it is quite time consuming until the start of the heat convection, causing the electrode front end portion 34 to overheat.

Furthermore, the location at which the grooves 60 are formed affects the height of the recesses. When the groove 60 is formed until the vicinity of the sealing cover 45, the solidification in the upper portion becomes faster, and the concave portion is formed in a state in which the unsolidified liquid phase portion remains. On the other hand, if only the groove 60 is formed in the vicinity of the lower side, the height of the concave portion becomes excessively large because the solidification in the vicinity of the lower side is promoted.

Therefore, it is necessary to prevent the extreme height of the concave portion from being generated when the heat transfer body is solidified. In the present embodiment, the groove 60 is formed, and the characteristics of the heat transfer body 40 are set to satisfy the conditional expression (1).

According to the present embodiment, the sealed space 50 is formed inside the anode 30, and the heat transfer body 40 made of a metal such as silver is sealed in the shape of a recess. At this time, the conditional expressions (1) and (2) are satisfied by setting the electrode size, the position at which the groove 60 for heat release is formed, the characteristics of the heat transfer body 40, and the like. When switching to lighting, the heat transfer body 40 is liquefied.

As the heat releasing means, in addition to the formation of the grooves, it is also possible to apply a structure such as spraying of fine particles or alumina processing as a heat releasing portion having a heat releasing property different from that of other electrode surfaces. In addition, the cathode can also adopt the same configuration.

Further, when the conditional expressions (1) and (2) are not satisfied, the heat transfer body is prevented from filling the entire closed space in a liquid state, or after the solidification is avoided The bottom of the concave portion of the heat transfer body reaches a state near the bottom surface of the sealed space, that is, an extreme state in which the concave portion cannot be formed, and the electrode strength can be improved.

17B‧‧‧electrode support rod

30‧‧‧Anode

32‧‧‧ Body Department

32S‧‧‧ body side

34‧‧‧Conical trapezoidal front end

34S‧‧‧ anode front end face

40‧‧‧ heat transfer body

40D‧‧‧ recessed bottom

40J‧‧‧ recess surface

40T‧‧‧ recessed end

45‧‧‧Closed cover

45S‧‧‧ end face

50‧‧‧Confined space

50D‧‧‧ front end face of the electrode

50S‧‧‧ side

60‧‧‧Ray ditch

70‧‧‧ hole

Claims (5)

A discharge lamp tube comprising: a discharge tube; a pair of electrodes disposed in the discharge tube, wherein at least one of the pair of electrodes has a heat transfer body enclosed in a sealed space formed inside the electrode, wherein the The heat transfer body is in a liquid state at the time of lighting, solidifies after the light is turned off, and a concave portion is formed toward the electrode support rod side opposite to the tip end side of the electrode. A discharge lamp according to claim 1, wherein the heat transfer body forms a concave portion in such a manner as to satisfy the following formula, 1/4 ≦ a / b ≦ 3 / 4 wherein a represents a concave end portion of the heat transfer body The distance from the bottom of the recess to the bottom of the recess indicates the distance from the end of the recess of the heat transfer body to the bottom surface of the sealed space. A discharge lamp according to claim 1, wherein the heat transfer body forms a concave portion in such a manner as to satisfy the following formula, 1/10≦e/f≦3/4, wherein e represents the volume of the concave portion, f Indicates the volume of the heat transfer body. The discharge lamp according to any one of claims 1 to 3, wherein at least one of a solidification shrinkage ratio, a viscosity, and a thermal conductivity of the heat transfer body is adjusted to fix a concave shape of the heat transfer body. . A discharge lamp according to any one of claims 1 to 4, wherein at least one of the pair of electrodes has a heat release portion on the electrode surface.