JP2003223865A - Positive electrode for discharge lamp and short arc discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive electrode for a discharge lamp where fins, formed when a electrode is subjected to a fine groove processing, are hard to chip or bend in transporting or manufacturing a short arc discharge lamp, and to provide the short arc discharge lamp where the positive electrode is used and the cooling effect of the positive electrode is improved by increasing the emissivity of the positive electrode and which supports a high input. <P>SOLUTION: The positive electrode for the discharge lamp made of tungsten, comprising a tip, an inclined part continued to the tip, and a barrel part continued to the inclined part, is characterized in that fine grooves, where the depth D is within 12% of the diameter of the positive electrode and the relation between the depth D and the pitch P is D/P≥2, are formed on the surface of the barrel part except the boundary region between the inclined part and the barrel part and the neighborhood. In addition, the short arc discharge lamp comprises the positive electrode for the discharge lamp. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive electrode structure of a discharge lamp such as an ultra-high pressure mercury lamp used for exposure of semiconductors and printed circuit boards and a xenon lamp used for image and illumination, and a short arc discharge lamp.

[0002]

2. Description of the Related Art In recent years, short arc discharge lamps have been used in, for example, a photolithography process in the manufacturing process of liquid crystal color filters. The wavelength of light used in the photolithography process is in 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, it is desired to increase the absolute amount of radiation in the light near the wavelength of 365 nm.

However, in the short arc discharge lamp, the radiation efficiency of light near the wavelength of 365 nm has little dependence on the mercury vapor pressure and the pressure of the rare gas filled as the buffer gas, and the amount of the filled material is changed. By doing so, the radiation efficiency of the light of the wavelength cannot be increased to the required level.

On the other hand, it is conventionally known that the amount of light emitted from the short arc discharge lamp, including the emission of light having a wavelength near 365 nm, is proportional to the electrical input to the short arc discharge lamp. Increasing the electrical input to the arc discharge lamp will also increase the absolute amount of radiation. As a method of increasing the electric input to the short arc discharge lamp, increasing the input current can be considered.

However, when increasing the lamp current, the tip of the positive electrode is heated by the increase in the electron flow and the temperature of the positive electrode rises as the lamp current increases. Usually, heat generated in the positive electrode is radiated to the outside by heat conduction of the positive electrode and radiated from the surface of the positive electrode to the outside. However, in the method of increasing the lamp current, the heat released to the outside is insufficient as compared with the heating by increasing the electron flow, and as a result, the thermal evaporation of the positive electrode material accompanying the temperature rise of the positive electrode is promoted, There was a problem that the inner wall of the arc tube was blackened and the lamp life was shortened.

In order to solve the above-mentioned problems, a method of improving the efficiency of heat release from the positive electrode and lowering the temperature of the positive electrode has been taken. For example, in the invention disclosed in Japanese Examined Patent Publication No. 39-11128, the side surface of the positive electrode is 1 mm to 3 m.
A V-shaped groove having a depth of about m and an opening angle of 90 ° is provided, and tantalum carbide is sintered on the surface of the V-shaped groove, whereby heat release by radiation from the positive electrode surface can be enhanced. Have been described. However, this method has a problem that carbon is liberated to blacken the discharge vessel depending on the temperature of the positive electrode, or the carbon moves to the tip of the positive electrode to melt the positive electrode.

Further, in JP-A-9-231946, without forming a V-shaped groove in the electrode, tungsten powder is sintered on the side surface of the positive electrode to improve the emissivity ε of the electrode surface to improve the emissivity ε of the electrode surface. It is disclosed that the amount of heat radiation is increased to lower the temperature of the electrode. According to this method, the emissivity on the surface of the plate-shaped tungsten metal is about 0.4, but when the emissivity is improved by sintering the tungsten powder, the emissivity is improved to about 0.6. is doing. However, even with this method, the cooling of the electrodes was insufficient to improve the amount of light emission by increasing the electric input to the short arc discharge lamp.

[0008]

Therefore, the applicant of the present invention is
Sintering tantalum carbide on the surface of the V-shaped groove of the positive electrode,
Instead of the conventional method of sintering tungsten powder on the side surface of the positive electrode, the depth D is within 12% of the diameter of the positive electrode, and the relationship between the depth D and the pitch P is D / P ≧ Two
Japanese Patent Application No. 2001-213612 discloses a technique for forming fine grooves on the surface of the positive electrode. Fine groove depth D
The dimensional positions of the pitch P and the pitch P are shown in FIG. In the figure, 6 is a fine groove, and 13 is a fin formed by adjacent fine grooves. When such fine grooves are formed, the surface of the positive electrode can be regarded as a hollow radiator, and the emissivity is increased. When the groove depth is set to be 12% or more deeper than the electrode diameter in forming the groove of the electrode, the inhibition of heat conduction due to the reduction of the cross-sectional area becomes larger and the temperature of the electrode can be effectively lowered. Absent. Further, the relationship between the depth D of the fine grooves and the pitch P is D / P ≧ 2, which means that the opening angle of the fine grooves is about 30 ° or less and the emissivity is 0.7 or more in this relation. It becomes.

As shown in FIG. 1, a fine groove 6 is formed on the entire positive electrode 2 except for the tip 21 of the positive electrode by machining with a YAG laser.
When the groove is formed, the groove depth D is about 600 μm, the groove pitch P is about 200 μm, and the groove becomes an opening angle of 30 ° or less. Fins 13 formed by adjacent fine grooves 6
Due to its thinness, it is fragile and breaks with a little impact.
Specifically, the fins 13 may be broken if they fall down in the carrying container during electrode transportation or during heat treatment of the electrodes.

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 making a lamp, discharge vessel 1
The discharge vessel 10 with the positive electrode 2 inside the side tube portion 12 in order to pass the positive electrode 2 through the side tube portion 12 connected to the zero arc tube portion 11 or to center the discharge vessel 10. When rotating, 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. The discharge vessel 10 is composed of an arc tube portion 11 and a side tube portion 12. 14 is an exhaust pipe part.

When the fins 13 are broken, the broken pieces of the fins enter the arc tube portion 11 as foreign matter,
The glass of the arc tube portion 11 may be damaged from the inner surface, which may be a starting point of the lamp rupture, and the fragments of the fins 13 may also serve as nuclei of devitrification generated from the inner surface of the arc tube portion 11.

Even if the fin 13 near the inclined portion 22 of the positive electrode 2 is not broken, as shown in FIG.
If a part is formed by overlapping the adjacent fins due to crushing, the emissivity of the overlapping part decreases. When that happens,
The fin portion that hits the crest 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 that is the electrode member of the fin portion is melted and scattered. Can happen.
When the electrode members scatter, the arc tube is blackened.

Therefore, an object of the present invention is to provide a positive electrode for a discharge lamp, in which the fins formed when the electrodes are finely grooved are not easily chipped or bent when the short arc discharge lamp is transported or manufactured. , And using the positive electrode, the emissivity of the positive electrode is increased to enhance the cooling effect of the positive electrode, thereby providing a short arc discharge lamp compatible with high input.

[0014]

In order to solve the above-mentioned problems, the invention according to claim 1 is made of tungsten, which comprises a tip portion, an inclined portion continuing to the tip portion, and a body portion continuing to the inclined portion. In the positive electrode for the discharge lamp, the fine groove having the depth D within 12% of the diameter of the positive electrode and the relationship between the depth D and the pitch P is D / P ≧ 2 is The discharge electrode positive electrode is characterized in that it is formed on the surface of the body except the boundary with the body and the vicinity thereof.

According to the second aspect of the present invention, the outer diameter of the electrode body portion where the fine groove is formed is smaller than the maximum outer diameter of the electrode portion where the fine groove is not formed. The positive electrode for a discharge lamp according to claim 1.

According to a third aspect of the present invention, the positive electrode for a discharge lamp according to the first or second aspect is characterized in that the body portion following the boundary has a smooth peripheral surface of 1 mm or more. It is a thing.

According to a fourth aspect of the present invention, there is provided a short arc discharge lamp comprising the positive electrode for a discharge lamp according to any one of the first to third aspects.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described. 3 (a) to 3 (d) are sectional views of the positive electrode 2 of the present invention. A hole 9 into which the electrode core rod 4 is inserted is provided on one end surface of the positive electrode 2, 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. The slope portion 22 is followed by the body portion 24. 3B, 3C, and 3D are examples in which the inclined portion 22 on the tip side of the positive electrode 2 is finely grooved. A YAG laser was used for fine groove processing.

3A, 3B, 3C and 3D,
Grooves were not formed on the boundary between the inclined part and the body and its vicinity. A region (indicated by L in FIG. 3) where 1 mm or more of the fine groove is not formed is provided on the body side. By doing so, it is possible to prevent the fins that form the fine grooves from directly touching other parts, jigs or worktables and bending or bending during handling of the electrodes in the manufacturing process. Figure 3
In (d), the outer diameter (A1 in the figure) of the electrode body portion where the fine groove is further formed is smaller than the maximum outer diameter (A2 in the figure) of the electrode portion where the fine groove is not formed. I'm making it small.

In this way, the fins that form the fine grooves never come into contact with, for example, the side tube,
The effect of being protected from destruction becomes more certain.

The fine grooves can be processed by using a YAG laser, a diamond cutter blade, or an electron beam. The fine grooves may be independent grooves, or may be grooves formed continuously in a spiral shape.

FIG. 6 shows an overall view of the short arc discharge lamp 1 of the present invention. In the arc tube portion 11 of the discharge vessel 10, a tungsten positive electrode 2 and a tungsten negative electrode 3 are arranged to face each other with a tip distance of about 10 mm. Each of the positive electrode 2 and the negative electrode 3 is embedded in the side tube portion 12 and electrically connected to the external terminal 15. Arc tube section 11
A noble gas such as xenon, argon, krypton or a filled gas made of a mixture thereof and a luminescent substance such as mercury are filled therein. The pressure of the enclosed gas is, for example, 0.1 to 10 atm at the time of enclosure, and the enclosed amount of mercury is 10 to 60 mg in terms of weight per internal volume of the arc tube portion 11.
/ Cc. This discharge lamp is lit at a rated voltage of 50 V and a rated voltage of 5 kW, for example.

[0023]

According to the present invention, it is possible to provide a positive electrode for a discharge lamp in which the fins formed by fine groove processing on the electrode are less likely to be chipped or bent when the short arc discharge lamp is transported or manufactured. In the present invention, there is no problem that the carbide is liberated and the discharge vessel is blackened, or the carbon moves to the tip of the positive electrode and the positive electrode is melted.

Further, the electrode can be sufficiently cooled in order to improve the light emission amount by increasing the electric input to the short arc discharge lamp. Further, if the positive electrode is used and the emissivity of the positive electrode is increased to make a lamp having the same input as the conventional one, the positive electrode can be downsized as compared with the conventional one, and the lamp itself can be made a short arc discharge lamp. You can

Furthermore, since the fins formed by the fine grooves are not broken, the fragments of the fins do not enter the arc tube as foreign matter and damage the glass of the arc tube portion from the inner surface. Further, the fin fragments cannot serve as the core of devitrification generated from the inner surface of the arc tube portion.

Further, there is no part where the fins are crushed and adjacent fins overlap each other, the tungsten that is the electrode member is not melted and scattered, and the arc tube is blackened due to the melting and scattering of tungsten. Does not happen.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a positive electrode in which laser groove processing is applied to almost the entire region except a tip portion.

FIG. 2 shows a positional relationship between a discharge vessel and an electrode when the discharge vessel is centered.

FIG. 3 shows a cross-sectional view of a positive electrode of the present invention.

FIG. 4 shows dimensional positions of a groove depth D and a groove pitch P.

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]

1 Short arc discharge lamp 2 Positive electrode 21 Tip 22 Inclined part 23 boundary 24 torso 3 negative electrode 4 electrode core rod 6 fine groove 9 holes 10 discharge vessel 11 arc tube 12 Side tube 13 fins 14 Exhaust pipe section 15 External terminal

Claims (4)

[Claims] 1. A positive electrode for a discharge lamp made of tungsten, comprising a tip portion, an inclined portion continuing to the tip portion, and a body portion continuing to the inclined portion, and the depth D is 12% of the diameter of the positive electrode.
And the relationship between the depth D and the pitch P is D / P ≧
2. A positive electrode for a discharge lamp, wherein the fine groove 2 is formed on the surface of the body except the boundary between the inclined portion and the body and the vicinity thereof. 2. The outer diameter of the electrode body portion where the fine groove is formed is smaller than the maximum outer diameter of the electrode portion where the fine groove is not formed. Positive electrode for discharge lamp. 3. The positive electrode for a discharge lamp according to claim 1, wherein the body portion following the boundary has a smooth peripheral surface of 1 mm or more. 4. A short arc discharge lamp comprising the positive electrode for a discharge lamp according to any one of claims 1 to 3.