JP3838110B2 - Positive electrode for discharge lamp and short arc discharge lamp - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a positive electrode structure and a short arc discharge lamp of a discharge lamp such as an ultra-high pressure mercury lamp used for exposure of a semiconductor or a printed board and a xenon lamp used for video or illumination.
[0002]
[Prior art]
In recent years, short arc discharge lamps are used in, for example, a photolithography process in a manufacturing process of a liquid crystal color filter. The wavelength of light used in the photolithography process is a range including a strong emission line spectrum of about 365 nm to 436 nm. The market demands an increase in the size of the color filter or a reduction in the exposure process time, and an increase in the absolute amount of light in the wavelength range emitted from the short arc discharge lamp is desired. In particular, an increase in the absolute amount of radiation in light near the wavelength of 365 nm is desired.
[0003]
However, in the short arc discharge lamp, the radiation efficiency of light in the vicinity of a wavelength of 365 nm has little dependence on the mercury vapor pressure and the pressure of the rare gas sealed as the buffer gas. The radiation efficiency of the light having the wavelength cannot be increased to a necessary level.
[0004]
On the other hand, it has been conventionally known that the amount of light emitted from the short arc discharge lamp, including the radiation of light in the vicinity of a wavelength of 365 nm, is proportional to the electric input to the short arc discharge lamp. Increasing the electrical input to increases the absolute amount of radiation. Increasing the input current can be considered as a method of increasing the electrical input to the short arc discharge lamp.
[0005]
However, when the lamp current is increased, when the lamp current increases, the tip of the positive electrode is heated by the increase of the electron current, and the temperature of the positive electrode rises. Usually, heat generated at the positive electrode is released to the outside by the heat conduction of the positive electrode, and heat generated by the radiation from the surface of the positive electrode. However, in the method of increasing the lamp current, the heat released to the outside is insufficient compared to the heating due to the increase in the electron current, and as a result, the thermal evaporation of the positive electrode material accompanying the temperature rise of the positive electrode is promoted, There has been a problem that the inner wall of the arc tube is blackened and the lamp life is shortened.
[0006]
In order to solve the above-mentioned problem, a technique has been adopted in which the efficiency of heat release from the positive electrode is improved and the temperature of the positive electrode is lowered. For example, in the invention disclosed in Japanese Patent Publication No. 39-11128, a V-shaped groove having a depth of about 1 mm to 3 mm and an opening angle of 90 ° is provided on the side surface of the positive electrode, and the surface of the V-shaped groove is further provided. In US Pat. No. 6,057,831, it is described that heat release by radiation from the positive electrode surface is enhanced by sintering tantalum carbide. However, this method has a problem that carbon is liberated depending on the temperature of the positive electrode and the discharge vessel is blackened, or the carbon moves to the tip of the positive electrode and the positive electrode is melted.
[0007]
Furthermore, in Japanese Patent Laid-Open No. 9-231946, the amount of heat radiation from the electrode surface is improved by sintering tungsten powder on the side surface of the positive electrode without forming a V-shaped groove in the electrode to improve the emissivity ε of the electrode surface. In which the temperature of the electrode is lowered by increasing the temperature. According to this method, the emissivity on the surface of the plate-like tungsten metal is about 0.4, whereas the emissivity is improved to about 0.6 when the tungsten powder is sintered to improve the emissivity. is doing. However, even with this method, the cooling of the electrodes has been insufficient to improve the amount of light emitted by increasing the electrical input to the short arc discharge lamp.
[0008]
[Problems to be solved by the invention]
Therefore, the present applicant has replaced the conventional method in which tantalum carbide is sintered on the surface of the V-shaped groove of the positive electrode or tungsten powder is sintered on the side surface of the positive electrode. Japanese Patent Application No. 2001-213612 discloses a technique for forming a fine groove on the surface of a positive electrode in which the relationship between the depth D and the pitch P is D / P ≧ 2 within 12% of the diameter of the positive electrode. FIG. 4 shows the dimension positions of the depth D and the pitch P of the fine grooves. In the figure, 6 is a fine groove, and 13 is a fin formed by adjacent fine grooves. When such a fine groove is formed, the positive electrode surface can be regarded as a cavity radiator, and the emissivity is increased. In the formation of the groove of the electrode, when the groove depth is deeper than 12% with respect to the diameter of the electrode, the heat conduction is hindered by reducing the cross-sectional area, and the electrode temperature can be effectively lowered. Absent. In addition, the relationship between the depth D of the fine groove and the pitch P is D / P ≧ 2, in which case the opening angle of the fine groove is about 30 ° or less and the emissivity is 0.7 or more. It becomes.
[0009]
As shown in FIG. 1, when the fine groove 6 is formed in the entire positive electrode 2 except for the tip portion 21 of the positive electrode by processing with a YAG laser, the depth D of the groove is about 600 μm and the pitch P of the groove is about 200 μm. Thus, a fine groove with an opening angle of 30 ° or less is formed.
The fins 13 formed by the adjacent fine grooves 6 are fragile due to their thinness and are broken by a slight impact. Specifically, the fin 13 breaks if it falls in the carrying container during electrode transportation or falls during heat treatment of the electrode.
[0010]
FIG. 2 shows the positional relationship between the discharge vessel 10 and the positive electrode 2 when centering the discharge vessel 10 in the lamp manufacturing process. When manufacturing the lamp, the positive electrode 2 is placed in the side tube portion 12 when the positive electrode 2 is passed through the side tube portion 12 connected to the arc tube portion 11 of the discharge vessel 10 or to center the discharge vessel 10. When the discharge vessel 10 is rotated in a state where there is, the side surface of the positive electrode 2 comes into contact with the inner surface of the side tube portion 12 and the fin 13 is broken. Here, the discharge vessel 10 includes an arc tube portion 11 and a side tube portion 12. Reference numeral 14 denotes an exhaust pipe portion.
[0011]
Further, when the fin 13 is broken, a broken piece of the fin inside the arc tube portion 11 is mixed as a foreign substance, and the glass of the arc tube portion 11 may be damaged from the inner surface, which may be the starting point of the lamp burst. Furthermore, the fragments of the fins 13 can also become devitrification nuclei generated from the inner surface of the arc tube portion 11.
[0012]
In addition, even if the fin 13 close to the inclined portion 22 of the positive electrode 2 is not broken, as shown in FIG. 5, if the fin 13 is crushed to form a portion where adjacent fins overlap each other, the emissivity of the overlapping portion is increased. descend. As a result, the fin portion that hits the peak of the fine groove has a smaller heat capacity than the electrode portion without the fine groove, so heat is accumulated in the overlapping portion of the fin, and the tungsten, which is the electrode member of the fin portion, melts and scatters. It can happen. When the electrode member is scattered, the arc tube is blackened.
[0013]
Accordingly, an object of the present invention is to provide a positive electrode for a discharge lamp that is less likely to cause chipping or bending of fins formed when a minute groove is formed on the electrode during transportation or manufacture of the short arc discharge lamp. An object of the present invention is to provide a short arc discharge lamp that uses a positive electrode, increases the emissivity of the positive electrode to enhance the cooling effect of the positive electrode, and supports high input.
[0014]
[Means for Solving the Problems]
In order to solve the above problems, the invention of claim 1 includes a distal end portion, an inclined portion following the tip portion, the tungsten discharge lamp positive electrode comprising a body portion continuing to the inclined portion, the A portion in which the depth D is within 12% of the diameter of the positive electrode and a fine groove in which the relationship between the depth D and the pitch P is D / P ≧ 2 is formed in the body portion; There is a portion where the fine groove is not formed, the portion where the fine groove is formed is between the portions where the fine groove is not formed, and the outside of the electrode body portion of the portion where the fine groove is formed. The positive electrode for a discharge lamp is characterized in that the diameter is smaller than the maximum outer diameter of the electrode portion where the fine groove is not formed .
[0017]
According to a second aspect of the present invention, there is provided a short arc discharge lamp comprising the discharge lamp positive electrode according to the first aspect.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described. FIG.3 (d) is sectional drawing of the positive electrode 2 of this invention. One end face of the positive electrode 2 has a hole 9 into which the electrode core rod 4 is inserted, and the electrode core rod 4 is fitted into the hole 9. The tip surface of the positive electrode 2 is a flat surface, and has an inclined portion 22 following the flat surface. It becomes the trunk | drum 24 following the inclination part 22. As shown in FIG. FIG. 3D shows an example in which a fine groove is formed on the inclined portion 22 on the tip side of the positive electrode 2. A YAG laser was used for fine groove processing.
[0019]
In FIG. 3D, no groove processing is performed at the boundary between the inclined portion and the body portion and in the vicinity thereof. A region (indicated as L in FIG. 3) where fine groove processing is not performed by 1 mm or more is provided on the body side.
By doing so, it is possible to prevent the fins that form the fine grooves from touching other parts, jigs, or work benches from being bent or bent when handling the electrodes in the manufacturing process. In FIG. 3D, the outer diameter (A1 in the drawing) of the electrode body portion where the fine groove is formed is larger than the maximum outer diameter (A2 in the drawing) of the electrode portion where the fine groove is not formed. Is also small.
[0020]
In this way, the fin forming the fine groove does not come into contact with, for example, the side tube at all, and the effect of being protected from destruction is further ensured.
[0021]
In addition to the processing by the YAG laser, the microgroove processing can be performed by a diamond cutter blade or an electron beam. The fine groove may be one in which each groove is independent, or a groove formed continuously in a spiral shape.
[0022]
FIG. 6 shows an overall view of the short arc discharge lamp 1 of the present invention. Similar to the positive electrode 2 made of tungsten, the negative electrode 3 made of tungsten is disposed opposite to the arc tube portion 11 of the discharge vessel 10 with a tip distance of about 10 mm.
The positive electrode 2 and the negative electrode 3 are each embedded in the side tube portion 12 and electrically connected to the external terminal 15. The arc tube 11 is filled with a noble gas such as xenon, argon, krypton or a mixture thereof, and a luminescent material such as mercury. The pressure of the sealing gas is, for example, 0.1 to 10 atm at the time of sealing, and the mercury sealing amount is 10 to 60 mg / cc by weight per inner volume of the arc tube portion 11. For example, the discharge lamp is lit at a rating of 50 V and a rating of 5 kW.
[0023]
【The invention's effect】
According to the present invention, it is possible to provide a positive electrode for a discharge lamp that is less prone to chipping or bending of fins formed by fine groove processing on the electrode during transportation or manufacture of a short arc discharge lamp. Is free and the discharge vessel is blackened, or the carbon moves to the tip of the positive electrode and the positive electrode melts.
[0024]
Also, the electrode can be sufficiently cooled to improve the amount of light emitted by increasing the electrical input to the short arc discharge lamp. In addition, if the positive electrode is used and the emissivity of the positive electrode is increased to make a lamp with the same input as the conventional one, the positive electrode can be made smaller than before, and the lamp itself can be reduced in size to be a short arc discharge lamp. Can do.
[0025]
Further, since the fin formed by the fine groove does not break, the broken pieces of the fin are mixed as foreign matter in the arc tube, and the glass of the arc tube portion is not damaged from the inner surface. In addition, the fin fragments cannot become devitrification nuclei generated from the inner surface of the arc tube portion.
[0026]
Further, the fins are crushed and the adjacent fins are not overlapped, so that tungsten as an electrode member is not melted and scattered, and the arc tube is not blackened due to melting and scattering of tungsten.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a positive electrode on which laser grooving has been performed over substantially the entire region excluding the tip.
FIG. 2 shows the positional relationship between the discharge vessel and the electrode when centering the discharge vessel.
FIG. 3 (d) shows a cross-sectional view of the positive electrode of the present invention.
4 shows dimensional positions of groove depth D and groove pitch P. FIG.
FIG. 5 shows a state in which fins formed by fine grooves are crushed and the fins overlap each other.
FIG. 6 shows an overall view of a short arc discharge lamp of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Short arc discharge lamp 2 Positive electrode 21 Tip part 22 Inclined part 23 Boundary 24 Body part 3 Negative electrode 4 Electrode core rod 6 Fine groove 9 Hole 10 Discharge vessel 11 Light emitting tube part 12 Side tube part 13 Fin 14 Exhaust pipe part 15 External Terminal

Claims (2)

In a positive electrode for a discharge lamp made of tungsten, comprising a tip, an inclined part following the tip, and a trunk following the inclined part,
A portion in which the depth D is within 12% of the diameter of the positive electrode and a fine groove in which the relationship between the depth D and the pitch P is D / P ≧ 2 is formed in the trunk portion; A portion where the fine groove is not formed, the portion where the fine groove is formed is between the portions where the fine groove is not formed, and the electrode body portion of the portion where the fine groove is formed A positive electrode for a discharge lamp, wherein an outer diameter is smaller than a maximum outer diameter of an electrode portion in which the fine groove is not formed .  A short arc discharge lamp comprising the positive electrode for a discharge lamp according to claim 1.

Images