KR20110001904A - Positive electrode for short arc type discharge lamp and short arc type discharge lamp - Google Patents

Abstract

PURPOSE: A positive electrode for a short arc type discharge lamp and a short arc type discharge lamp are provided to concentrate electronics on the inner bottom or curved corner of an anode by including a recess part. CONSTITUTION: A concave part forms in the center shaft of an anode. The inner wall of the anode(30A) is depressed inward from the end of the anode to be formed in peripheral direction. The inner bottom of the anode is connected to the inner wall of the anode. A ring type corner(30C) is formed in the peripheral direction of the anode inner wall surface and an anode tip.

Description

Anode and short arc type discharge lamp for short arc type discharge lamps {POSITIVE ELECTRODE FOR SHORT ARC TYPE DISCHARGE LAMP AND SHORT ARC TYPE DISCHARGE LAMP}

An anode for a short arc type discharge lamp and a short arc type discharge lamp which are used as a light source for exposure apparatus which forms a fine circuit pattern by irradiating an ultraviolet-ray toward a semiconductor substrate.

The conventional short arc type discharge lamp is known to comprise a light emitting tube made of quartz glass in which a central portion has been expanded, and an anode, a cathode, and the like, which are disposed to face the inside of the bulge portion of the light emitting tube. When the discharge lamp is energized, electrons emitted from the cathode collide with the gas in the lamp to generate charged particles. The mercury or the like in which the charged particles repeatedly impinge in the interior of the light emitting tube is in a plasma state, flows through the anode, and an arc is formed between the anodes.

When the discharge lamp is turned on, an arc is formed by the collision of electrons emitted from the cathode, and the anode is heated by the collision of electrons in the arc column to become high temperature, and is evaporated and consumed. In addition, when the anode is consumed by the collision of electrons, evaporated tungsten is attached to the inner wall of the light emitting tube to blacken the inner wall surface. When the discharge lamp is used for a long time, consumption of the tip portion of the positive electrode proceeds, and the emission intensity of the discharge lamp decreases sequentially, and when the decrease in the emission intensity exceeds the use limit, the discharge lamp is replaced with a new one. I needed to.

Therefore, various measures have been conventionally considered to suppress the rise of the temperature at the time of lighting of the discharge lamp, thereby slowing down the consumption of the anode and the progress of blackening of the inner wall surface of the light emitting tube.

For example, according to Patent Document 1, a porous layer is formed by sintering a mixture made of tungsten carbide (WC), tantalum carbide (TaC), and tungsten (W) on the side surface of the positive electrode, whereby the porous layer is formed. Since the adhesion between the base material and the base material is good, it is possible to appropriately suppress the temperature rise of the anode, thereby reducing the consumption of the anode and blackening of the inner wall surface of the light emitting tube and extending the life of the discharge lamp.

However, since the anode structure is complicated by sintering three kinds of high melting point materials, i.e., a mixture of tungsten carbide, tantalum carbide, and tungsten on the surface of the anode, the manufacturing process is complicated. There was a problem that a long time was required.

In the positive electrode 43 shown in each of Patent Documents 2, 3, and 4, as shown in FIG. 5 (A), a recessed portion 43A is provided in the positive electrode tip portion facing the negative electrode 42, and the recessed portion ( 43A) is formed so as to approximate the intensity of the electric field generated at the point of receiving the electrons emitted from the cathode 42. According to these documents, it is known that the current density distribution on the surface of the anode can be dispersed, thereby reducing the consumption of the anode and extending the life of the discharge lamp.

However, in the anode structure shown in Fig. 5A, the ratio of the current drawn to the edge portion 431A of the recessed portion 43A is small as described later, so that the locality of the current near the center of the anode is small. Since the concentration cannot be sufficiently suppressed, there is a problem that the consumption of the electrode cannot be sufficiently suppressed.

In the short arc type discharge lamp shown in Patent Document 5, as described above, a recess is provided at the tip of the cathode opposite to the cathode, and the cathode is disposed at a predetermined position in relation to the recess. According to this document, it is known that the utilization efficiency of light in a discharge lamp can be improved by reflecting the light emitted from the arc bright point by the concave portion of the anode and reflecting the light reflected by the concave portion at the tip conical portion of the cathode. .

However, in the anode structure of this document, similarly to the anodes disclosed in Patent Documents 2 to 4, the ratio of the current drawn by the edge portion of the concave portion formed in the anode is small so that local concentration of the current near the center of the anode is reduced. Since it cannot fully suppress, there exists a problem that it cannot fully suppress consumption of an electrode.

In addition, as shown in FIG. 5 (B), the short arc discharge lamp shown in Patent Document 6 is located at a position exceeding 40% of the distance between electrodes from the center of the flat surface of the tip portion of the anode 43. The round strip-shaped recess 43B is provided. According to this document, even when a caldera-shaped recess is generated in the flat surface of the tip of the anode 43, the electrode constituent material moved by migration is rounded in advance on the flat surface of the tip of the anode 43. It is known that the flat surface of the tip portion of the anode can be prevented from being deformed by being deposited on the strip-shaped recess 43B.

However, in the anode structure of this document, as shown in Fig. 5 (B), since the strength of the electric field of the corner portion B on the inner circumference side is higher than that of the electric field of the corner portion A on the outer circumference side, the corner portion on the inner circumference side The current concentrates in the inner region of B. The energy flowing into the corner portion B is inhibited by the round strip-shaped recess 43B in the outflow to the outside of the anode radial direction, in the axial direction at the center portion 431B surrounded by the round strip-shaped recess 43B. Only is inverted. Therefore, since the outflow path of energy becomes substantially narrow, the temperature of center part 431B becomes higher than the temperature of another area | region. Thereby, there existed a problem that the illumination intensity retention of a discharge lamp fell as a result of the center part of an anode becoming easy to evaporate.

As described above, according to the above-described conventional discharge lamps, it was difficult to suppress the consumption of the positive electrode.

(Patent Document 1) Japanese Patent No. 3598475 (Patent Document 2) Japanese Patent No. 3136511 (Patent Document 3) Japanese Patent No. 404198 (Patent Document 4) Japanese Patent No. 4132879 (Patent Document 5) Japanese Unexamined Patent Publication No. 2004-119024 (Patent Document 6) Japanese Unexamined Patent Publication No. 2003-346709

In view of the above problems, an object of the present invention is to provide a discharge lamp capable of suppressing the consumption of the positive electrode while achieving a brightness equivalent to that of a conventional discharge lamp.

In the short arc type discharge lamp, by applying a voltage between the anode and the cathode of the discharge lamp, electrons are emitted from the cathode tip toward the anode, and an arc is formed between the anode and the cathode. In the field of the said discharge lamp, in principle, since the electric field intensity | strength is high as it approaches the anode center axis, and an electron is attracted to the anode center direction, it is known that the current density of the arc near an anode center axis is high.

Therefore, in the conventional discharge lamp, as the lighting time of the discharge lamp elapses, a portion near the center axis of the anode having a high current density of arc is consumed, and a recess is formed in the portion near the center axis of the anode. I think.

MEANS TO SOLVE THE PROBLEM This inventor acquired the following knowledge as a result of earnestly examining about the problem of the recessed part of said anode.

(1) When a region having a relatively high current density is formed at a position separated from the center axis of the anode in the radially outward direction, thereby reducing the current density near the center axis of the anode than in the related art, it leads to suppression of the consumption of the anode.

(2) By increasing the current density closer to the anode central axis and increasing the current density so that the anode is not consumed, brightness equivalent to that of a conventional discharge lamp can be obtained.

Based on this knowledge, this invention solves the said subject as follows.

The invention of claim 1 is a cathode for a short arc type discharge lamp in which a recess is formed on the anode central axis of the anode front end surface.

The anode includes an anode inner wall surface formed in a circumferential direction recessed toward the inner side from the anode front end surface, a flat anode inner bottom surface formed on the inner side of the anode front end surface and connected to the anode inner wall surface, and the anode inner wall surface and It is formed in the circumferential direction at the boundary of the said anode front end surface, and is provided with the annular edge part spaced apart radially outward from the anode central axis.

The invention of claim 2 is a short arc type discharge lamp in which an anode having a recess formed on an anode central axis of an anode front end face, and a cathode are disposed to face the inside of a light emitting tube.

The anode includes an anode inner wall surface formed in a circumferential direction recessed toward the inner side from the anode front end surface, a flat anode inner bottom surface formed on the inner side of the anode front end surface and connected to the anode inner wall surface, and the anode inner wall surface and It is formed in the circumferential direction at the boundary of the said anode front end surface, and is provided with the annular edge part spaced apart radially outward from the anode central axis.

Since the anode of the present invention has a concave portion having an anode inner bottom surface formed flat on the inner side of the anode front end face and an annular corner portion formed in the circumferential direction apart from the radially outward direction of the anode central axis, the anode is formed between the cathode and the anode. The electrons in the arc are dispersed and concentrated on each of the inner bottom surface of the anode and the annular edge portion, so that the current density near the center axis of the anode becomes so high that the anode is not consumed, which is equivalent to the brightness of a conventional discharge lamp. While the luminance is obtained, the consumption of the anode can be suppressed to extend the life of the discharge lamp.

Brief Description of Drawings [Fig. 1] Fig. 1 is a sectional view showing the outline of the configuration of a short arc type discharge lamp of the present invention.
FIG. 2 is a partially enlarged view illustrating an enlarged portion A shown in FIG. 1.
3 is a conceptual diagram showing an electron density distribution in an arc together with an anode.
4 is a graph showing data of illuminance retention measured for the discharge lamp of the present invention and the conventional discharge lamp.
5 is a cross-sectional view showing the structure of a conventional positive electrode together with the structure of a negative electrode.

1 is a cross-sectional view schematically showing the configuration of a short arc type discharge lamp of the present invention. 2 is a partially enlarged view showing enlarged front ends of a cathode and an anode.

The discharge lamp 10 is provided with the light emitting tube 1 comprised from the light emitting part 11 formed in substantially spherical shape, and the sealing part 12A and 12B of the straight tube shape which is continuous in each of both ends of the light emitting part 11, respectively. . The light emitting tube 1 is integrally formed with quartz glass, for example. Sealing parts 12A and 12B are attached with chucks 13A and 13B having a cylindrical shape, respectively.

In the discharge space S formed inside the light emitting tube 1, the cathode 2 and the anode 3 are arranged on the anode central axis X to face each other, and a light emitting material is sealed.

The luminescent material contains 0.5 MPa or more of xenon gas or argon gas and 1 mg / cc or more of mercury at room temperature. As the light emitting material, only one of these rare gases and mercury may be sealed.

The cathode 2 is formed in a cylindrical body portion 2A which is held in the sealing portion 12A and protrudes toward the discharge space S, and a conical shape that gradually decreases in outer diameter as it extends toward the tip end of the body portion 2A. Tip portion 2B is integrally formed of tungsten, for example.

The anode 3 has a cylindrical body portion 3B, and truncated portions 3A and 3C which are formed to be connected to each of the front end side and the base end side of the trunk part 3B, for example, integrally by tungsten. Formed. A rod-shaped lead portion (not shown) having a smaller diameter than the trunk portion 3B is integrally connected to the truncated cone portion 3C on the proximal side, and the lead portion is held by the sealing portion 12B.

FIG. 2 is a partially enlarged view showing an enlarged portion A shown in FIG. 1. 2A is a cross-sectional view including the anode central axis X. FIG. FIG. 2 (B) is a front view of the positive electrode end face viewed from the direction of arrow B shown in FIG. 2 (A).

As shown in FIG. 2, in the truncated conical portion 3A, a flat anode tip surface 3D is formed at the tip, and a concave portion 30 is formed on the anode tip surface 3D so as to include the anode central axis X. As shown in FIG.

The recess 30 has a spherical shape in cross section including the anode central axis X, that is, has a cylindrical shape. The concave portion 30 is not limited to a cylindrical shape, but may have a rotating truncated cone shape.

The recessed portion 30 is recessed from the positive electrode end face 3D toward the inner side of the positive electrode 3, so that the concave portion 30A is formed in the circumferential direction after the positive electrode end face 3D and the inner side of the positive electrode end face 3D (cathode) Located at the side away from the tip 2B of (2), widening in the direction perpendicular to the anode central axis X, and formed at the boundary between the anode inner bottom surface 30B formed in a flat circular shape, the anode front end surface 3D and the anode inner wall surface 30A. And an annular corner portion 30C formed over the circumferential direction. The annular edge portion 30C is formed spaced apart from the anode central axis X in the radial direction.

In the discharge lamp of the present invention, when a high voltage is applied between the cathode 2 and the anode 3, an arc is formed between the cathode 2 and the anode 3.

In the positive electrode 3, in accordance with the principle of the above-described discharge lamp, the electric field strength increases as it approaches the positive electrode central axis X, but the annular edge portion 30C is provided at a position separated radially outward from the positive electrode central axis X. For this reason, the electric field strength becomes high even at this position.

That is, the positive electrode 3 is in a state where both of the electric field strength near the anode center axis X and the electric field strength of the annular edge portion 30C are high, so that electrons emitted from the cathode 2 are near the anode center axis X and the annular edge portion 30C. Since it is attracted by being dispersed in each of, the amount of electrons attracted near the anode central axis X is reduced.

In addition, the anode 3 has the anode inner bottom surface 30B on the inner side of the anode rather than the anode front end surface 3D, and the anode inner bottom surface 30B is formed flat. On the anode inner bottom surface 30B, according to the principle of the above-described discharge lamp, The current density near the anode central axis X becomes high.

In other words, the anode 3 includes both the anode inner bottom surface 30B and the annular edge portion 30C, so that some of the electrons emitted from the cathode 2 are located at the annular edge portion 30C in the radially outward direction of the anode central axis X. The remaining electrons which are attracted and not attracted to the annular edge portion 30C gather near the anode central axis X of the anode inner bottom surface 30B, and the current density near the anode central axis X becomes high so that the anode is not consumed.

FIG. 3 shows simulation results of the electric field intensity distribution in the arc for each of the discharge lamp of the present invention having the anode shown in FIG. 2 and the conventional discharge lamp having the anode shown in FIG. 5A. 3 represents the electric field intensity, and the abscissa represents the distance from the anode center axis X. FIG. The solid line of FIG. 3 shows the electric field strength of the anode of this invention, and the broken line shows the electric field strength of the conventional anode (shown in FIG. 5 (A)).

As shown by the solid line in FIG. 3, the anode of this invention shows the sharp peak of the electric field intensity in the position corresponding to the annular edge part 30C of the recessed part 30 around the anode center axis X, and has an annular edge part. It is assumed that electrons in the arc concentrate at 30C. Therefore, the anode of this invention is guessed that the ratio of the electric current attracted to the annular edge part 30C becomes large.

On the other hand, in the conventional anode (shown in Fig. 5A), such a peak is not seen, and it is estimated that the ratio of the electric current drawn to the edge portion 431A of the recessed portion 43A is small.

Thus, the discharge lamp provided with the anode 3 of this invention has the annular edge part 30C formed so that it may space apart in the radial direction outward of the anode center axis X, and is located in both the vicinity of the anode center axis X and the annular edge part 30C. Since the current is distributed, the concentration of local current near the center axis X of the anode is relaxed, and by having the anode inner bottom surface 30B, the current density near the center axis X of the anode is appropriately high so that the anode is not consumed.

Therefore, while the discharge lamp provided with the anode 3 of this invention is able to obtain the brightness equivalent to the brightness of the conventional discharge lamp, compared with the discharge lamp provided with the conventional anode, it is possible to surely suppress consumption of the anode. Can be.

In addition, the depth H (distance between the positive electrode end surface 3D and the positive electrode inner bottom surface 30B) of the concave portion 30 provided in the anode 3 is appropriately determined according to the specification of the discharge lamp, but is in the range of 0.1 mm to 0.5 mm. It is preferable.

If the depth H of the concave portion 30 is less than 0.1 mm, since the electric field strength at the annular edge portion 30C does not increase, it is not possible to sufficiently attract electrons emitted from the negative electrode 2, so that consumption of the positive electrode can be suppressed. none.

Moreover, when the depth H of the recessed part 30 exceeds 0.5 mm, the distance between the cathode 2 and the anode 3 will become long, and the lamp voltage of a discharge lamp will rise, and a lamp current will fall by this (this way) Since a discharge lamp of a kind is generally lit by a constant power supply for lighting, when one of the lamp voltage and the lamp current rises, the other decreases), and the luminance of radiation decreases. In addition, when the depth H of the concave portion 30 exceeds 0.5 mm, since the arc is widened in the radial direction, the light condensing efficiency is lowered and the exposure surface roughness of the exposure apparatus or the like is lowered.

Below, the experiment and the result of the experiment which were performed in order to confirm the effect of this invention are demonstrated.

In performing the experiment, the discharge lamps of the present invention, Comparative Example 1 and Comparative Example 2 were produced in accordance with the configuration shown in FIG. 1. The detail of each discharge lamp is as follows.

<Discharge lamp of the present invention>

(lamp)

Inter electrode distance: 10mm

Mercury Loading: 25mg / cc

Rare Gas Encapsulation: 0.15MPa

Input power: 10kW

(anode)

With recess

Diameter D of the recessed portion 30: 5 mm

Depth of the recess 30 H: 0.4mm

Shape of anode inner bottom surface 30B: flat

<Discharge Lamp of Comparative Example 1>

(lamp)

Same as the discharge lamp of the present invention

(anode)

No recess

<Discharge Lamp of Comparative Example 2>

(lamp)

Same as the discharge lamp of the present invention

(anode)

With recess

Diameter D of the recess 43A: 5mm

Depth of the recess 43A H: 0.4mm

Shape of anode inner bottom: spherical surface (shown in Fig. 5 (A))

<Discharge Lamp of Comparative Example 3>

(lamp)

Same as the discharge lamp of the present invention

(anode)

With recess: round strip recess

Diameter D of the round strip-shaped recess (edge A side of 43B): 5 mm

Width of the strip-shaped recess 43B (distance between edges AB): 1 mm

Depth H of the round strip-shaped recess 43B: 0.4 mm

Shape of the anode round strip-shaped recess: round strip-shaped groove (shown in Fig. 5 (B))

Each said discharge lamp was made to light using the electrostatic power supply for lighting, and the irradiance retention of each discharge lamp was measured. The result is shown in FIG. The vertical axis of FIG. 4 represents the irradiance retention, and the horizontal axis represents the lighting time.

The irradiance retention is closely related to the consumption of the anode. In other words, high irradiance retention indicates that consumption of the positive electrode is suppressed.

As shown in Fig. 4, the irradiance retention after 800 hours from the start of lighting is 95% in the discharge lamp of the present invention, 84% in the discharge lamp of Comparative Example 1, 92% in the discharge lamp of Comparative Example 2, and the comparative example. It was confirmed that the discharge lamp of 3 was 86%.

From the above result, it was confirmed that the discharge lamp of this invention can suppress consumption of a positive electrode compared with the discharge lamp of the comparative example 1, the comparative example 2, and the comparative example 3.

As described above, according to the positive electrode 3 of the present invention, an annular edge formed in the circumferential direction with a positive electrode inner bottom surface 30B formed on the inner side of the positive electrode end face 3D and spaced apart from the positive electrode central axis X radially outward. Since the concave portion 30 having the portion 30C is provided, electrons in the arc formed between the cathode 2 and the anode 3 are dispersed and concentrated in each of the anode inner bottom surface 30B and the annular edge portion 30C. Therefore, since the current density near the anode center axis X is so high that the anode is not consumed, the brightness equivalent to that of the conventional discharge lamp can be obtained, while the consumption of the anode is suppressed and the discharge lamp 10 ) Can extend the life.

10: discharge lamp 1: light emitting tube
11: light emitting part 12A, 12B: sealing part
13A, 13B: Chuck 2: Cathode
2A: fuselage 2B: tip
3: anode 3A: conical portion
3B: fuselage part 3C: conical part
3D: anode front end 30: recess
30A: anode inner wall surface 30B: anode inner wall surface
30C: annular corner

Claims (2)

An anode for a short arc type discharge lamp in which a recess is formed on an anode central axis of an anode end surface,
The anode,
An anode inner wall surface recessed inward from the anode front end surface and formed in a circumferential direction;
A flat anode inner bottom surface having a depth of 0.1 mm to 0.5 mm formed on an inner side of the anode front end surface after the anode inner wall surface;
And an annular corner portion formed in a circumferential direction at a boundary between the anode inner wall surface and the anode tip surface and spaced apart from the anode central axis in a radially outward direction. In a short arc discharge lamp in which an anode having a concave portion formed on an anode central axis of an anode end face and a cathode are disposed to face the inside of a light emitting tube,
The anode,
An anode inner wall surface recessed inward from the anode front end surface and formed in a circumferential direction;
A flat anode inner bottom surface having a depth of 0.1 mm to 0.5 mm formed on an inner side of the anode front end surface after the anode inner wall surface;
And an annular corner portion formed in a circumferential direction at a boundary between the anode inner wall surface and the anode front end surface and spaced apart from the anode central axis in a radially outward direction.

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