JP5397401B2 - Short arc type discharge lamp - Google Patents

Description

  The present invention relates to a short arc type discharge lamp, and more particularly, to a short arc type discharge lamp suitably used as a light source for a semiconductor inspection apparatus, a light source for a projector apparatus, or a light source for an exposure apparatus using ultraviolet rays.

Since the short arc type discharge lamp has advantages such as high brightness, a point light source and a small size, for example, a light source for a semiconductor inspection device, a light source for a projector device, or It is preferably used as a light source for an exposure apparatus.
Such a short arc type discharge lamp is required to be further downsized. For example, Japanese Patent Application Laid-Open No. 08-287867 of Patent Document 1 discloses a discharge vessel used as a light source for an inspection apparatus such as a microscope. Discloses a small short arc discharge lamp in which the inner volume of the arc tube portion is, for example, about 300 mm ^3, and Japanese Patent Application Laid-Open No. 2007-123140 discloses a light source for a projector apparatus. There is disclosed a small short arc type discharge lamp in which the inner volume of an arc tube portion in a discharge vessel is, for example, 214 mm ³ .

FIG. 4 is an explanatory view showing an outline of the configuration of an example of a conventional short arc type discharge lamp, and FIG. 5 is an enlarged sectional view of a region surrounded by a broken line in FIG.
The short arc type discharge lamp 40 includes a substantially spherical or substantially elliptical arc tube portion 42 that forms a discharge space therein, and sealing portions 43 that are continuous to both ends of the arc tube portion 42. A discharge vessel 41 made of, for example, quartz glass is provided. Inside the arc tube portion 42, a cathode 21 and an anode 25 are arranged to face each other, and mercury as a luminescent substance and buffer gas as A rare gas and a halogen for performing a halogen cycle are enclosed.
The cathode 21 is composed of a rod-shaped electrode shaft portion 22 having a substantially conical tip, and a coil portion 23 containing an electron-emitting substance provided on the tip side portion of the electrode shaft portion 22. And electrically connected to an external lead 27 that protrudes outward in the axial direction from the outer end of the sealing portion 43 through a metal foil 28 hermetically embedded in the sealing portion 43.
The anode 25 has a rod shape with a substantially conical tip, and protrudes axially outward from the outer end of the sealing portion 43 through a metal foil 28 hermetically embedded in the sealing portion 43. It is electrically connected to an external lead 27 that extends.

  In such a short arc type discharge lamp 40, the easy-electron emitting material contained in the coil portion 23 is usually heated as the cathode 21 is heated by energization from a lamp lighting power source (not shown). Thus, the transition from glow discharge to arc discharge is quickly performed by the action of the emitted electrons, and high lamp startability can be obtained.

Japanese Patent Laid-Open No. 08-287867 JP 2007-123140 A

However, in a small short arc type discharge lamp 40 in which the inner volume of the arc tube portion 42 in the discharge vessel 41 is, for example, 300 mm ³ or less, the outer peripheral surface of the axially rear end portion of the coil portion 23 in the cathode 21 and the arc tube. When the lamp is started, the heat of the coil portion 23 heated by energization is deprived by the arc tube portion 42 in a low temperature (cold) state when the lamp is started. Therefore, there is a problem in that the efficiency of electron emission from the easily emissive material is lowered and sufficient lamp startability may not be obtained.

  The present invention has been made based on the above circumstances, and an object of the present invention is to provide a small short arc type discharge lamp that can obtain a sufficiently high lamp startability and a long service life. .

The short arc type discharge lamp of the present invention includes a light emitting tube portion having a substantially spherical shape or a substantially elliptical spherical outer shape in which a pair of electrodes are arranged opposite to each other, and a sealing continuous to both ends of the light emitting tube portion. In a short arc type discharge lamp comprising a discharge vessel having a portion, wherein at least one of the pair of electrodes is formed with a coil portion containing an electron-emitting material at the tip of the electrode shaft portion,
The inner surface surrounding the periphery of the one electrode of the arc tube portion constitutes at least an inner surface region surrounding the arc forming region in a cross section along the tube axis of the discharge vessel. A first curved portion projecting outward in a substantially spherical shape or a substantially elliptical spherical shape along the first curved portion, and a second curved portion projecting inward that is continuous with the first curved portion . The second bending portion is positioned outward from the virtual spherical surface or the virtual elliptic spherical surface from which the first bending portion is extended, and is a boundary position between the first bending portion and the second bending portion. 1 inflection point is located in the inner surface region surrounding the periphery of the coil portion;
The inner surface surrounding the periphery of the one electrode in the arc tube portion has an outwardly projecting third curved portion continuous with the second curved portion in a cross section along the axial direction of the electrode shaft portion. And a second inflection point, which is a boundary position between the second bending portion and the third bending portion, is located closer to the sealing portion than an inner surface region surrounding the coil portion. It is characterized by being.

  In the short arc type discharge lamp of the present invention, an inner diameter of the arc tube portion at the position of the second inflection point is larger than an outer diameter of a rear end of the coil portion, and the second inflection point. The axial length between the position of the arc tube and the innermost edge position where the inner surface of the arc tube portion is closest to the outer peripheral surface of the electrode shaft portion is the position of the first inflection point, and the second It is preferable that the axial length between the inflection point and the position is smaller.

  According to the short arc type discharge lamp of the present invention, a sufficiently large separation distance is ensured between the outer peripheral surface of the coil portion of one electrode and the inner surface of the arc tube portion. As a result of preventing the heat of the coil part from being transferred to the arc tube part and hindering the temperature rise of the coil part, the emission of the electrons from the easy electron emitting material contained in the coil part is performed well. The desired starting assist effect by the electron-emitting material is surely obtained, and thus excellent lamp startability is obtained. Moreover, blackening of the discharge vessel due to evaporation of the constituent members of the coil portion and adhesion to the inner surface of the arc tube portion is suppressed.

  In addition, mercury sealed in the arc tube portion accumulates in an unevaporated state while the inner surface of the arc tube portion has a shape that ensures a sufficiently large separation distance from the outer peripheral surface of the coil portion. Since such a minute space is not formed, the desired pressure (mercury vapor pressure) in the arc tube can be obtained, and the lamp can be lit stably and reliably.

It is explanatory drawing which shows the outline of a structure in an example of the short arc type discharge lamp of this invention. It is an expanded sectional view of the area | region enclosed with the broken line in FIG. It is an expanded sectional view which shows the outline of the structure in the other example of the short arc type discharge lamp of this invention. It is explanatory drawing which shows the outline of a structure in an example of the conventional short arc type discharge lamp. It is an expanded sectional view of the area | region enclosed with the broken line in FIG.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is an explanatory view showing an outline of the configuration of an example of a short arc type discharge lamp according to the present invention, and FIG. 2 is an enlarged sectional view of a region surrounded by a broken line in FIG.
A short arc type discharge lamp 10 according to this embodiment is of a direct current lighting type, and has a light emitting tube portion 12 having an outer surface shape of a substantially spherical shape or a substantially elliptic sphere shape that forms a discharge space therein, and the light emission. A discharge vessel 11 made of, for example, quartz glass having a sealing portion 13A, 13B continuous to each of both ends of the tube portion 12 is provided. Inside the arc tube portion 12, a cathode 21 and an anode 25 face each other. Are arranged. Here, the distance between the cathode 21 and the anode 25 is 2.0 mm or less, for example, 0.5 to 2.0 mm. In FIG. 1, reference numeral 29 denotes a base mounted in a state where a part of the sealing portions 13 </ b> A and 13 </ b> B in the discharge vessel 11 is received.
The short arc type discharge lamp 10 is vertically lit with, for example, a posture in which the cathode 21 is positioned above.

The cathode 21 is made of, for example, tungsten, and has a rod-shaped electrode shaft portion 22 having a substantially conical tip, and an electron-emitting material (hereinafter referred to as “emitter”) provided on the tip side portion of the electrode shaft portion 22. The base end portion of the electrode shaft portion 22 is joined to the tip end portion of a metal foil 28 made of, for example, molybdenum, hermetically embedded in the sealing portion 13A, As a result, the front end portion is joined to the rear end side portion of the metal foil 28 and is electrically connected to the external lead 27 extending outwardly in the axial direction from the outer end of the sealing portion 13A via the metal foil 28. Yes.
For example, the coil portion 23 is made of tungsten containing an emitter such as thorium oxide (ThO ₂ ) or lanthanum oxide (La ₂ O ₃ ), or a wire made of thorium tungsten (thorium content is about 2 wt%, for example). For example, the electrode shaft portion 22 is formed by being wound so as to extend along the axial direction with a uniform outer diameter in the axial direction. The emitter content is preferably, for example, 0.1 to 3.0 wt%.

  The anode 25 is made of, for example, tungsten and has a rod-like shape having a substantially conical tip, and a base end portion of a metal foil 28 made of, for example, molybdenum, hermetically embedded in the sealing portion 13B. As a result, the front end portion is joined to the rear end side portion of the metal foil 28 and is electrically connected to the external lead 27 extending outwardly in the axial direction from the outer end of the sealing portion 13B via the metal foil 28. It is connected to the.

Further, inside the arc tube portion 12, mercury as a luminescent substance, a rare gas as a buffer gas, and a halogen for performing a halogen cycle are enclosed.
Amount of enclosed mercury is a by 0.20 mg / mm ³ or less, such as 0.10 mg / mm ^3.
The rare gas is, for example, argon gas, and the enclosed amount is, for example, 13 kPa.
Halogen is, for example, a bromine, its added amount, in the range of ^{2.0 × 10- 4 μmol / mm 3} ~7.0 × 10 -3 μmol / mm 3, for example, 3.0 × 10- ⁴ μmol / mm ³ . Note that the amount of enclosed halogen is not limited to the above range.

Thus, in the short arc type discharge lamp 10 described above, the inner surface of the arc tube portion 12 in the discharge vessel 11 has the following shape.
That is, the inner surface R1 surrounding the periphery of the cathode 21 in the arc tube portion 12 is at least around the arc formation region (interelectrode region) in the cross section along the tube axis direction of the discharge vessel 11, as shown in FIG. An outwardly convex first curved portion 15 that constitutes an inner surface region that surrounds, an inwardly convex second curved portion 16 that is continuous with the first curved portion 15, and the second curved portion 16. A third curved portion 17 that is convex outward and continuous inward, and a bent portion 18 that is convex inward and continuous with the third curved portion 17. The first inflection point P1, which is the boundary position between the first bending portion 15 and the second bending portion 16, is located in the inner surface region surrounding the coil portion 23, and the second bending portion. A second inflection point P <b> 2, which is a boundary position between the portion 16 and the third bending portion 17, is located closer to the sealing portion 13 </ b> A than the inner surface region surrounding the coil portion 23.
Further, the inner surface R <b> 2 that surrounds the periphery of the anode 25 in the arc tube portion 12 is configured by the first curved portion 15 that constitutes the inner surface that surrounds the periphery of the cathode 21.

The first curved portion 15 has, for example, a substantially spherical shape or a substantially elliptic spherical shape along the outer surface of the arc tube portion 12, and the second curved portion 16 has, for example, a substantially spherical shape or a substantially elliptic spherical shape. Has been. Here, the radius of curvature of the first curved portion 15 and the radius of curvature of the second curved portion 16 may be either the same size or different sizes.
In addition, the third bending portion 17 has, for example, a substantially spherical shape or a substantially elliptic spherical shape having a smaller radius of curvature than the first bending portion 15 and the second bending portion 16.

  The position of the first inflection point P <b> 1 is preferably located in an inner surface region that surrounds a portion within a range of 1.0 to 2.0 mm from the tip edge of the coil portion 23. Thereby, a sufficiently large separation distance can be reliably ensured between the outer peripheral surface of the coil portion 23 in the cathode 21 and the inner surface of the arc tube portion 12.

  At the position of the second inflection point P <b> 2 on the inner surface of the arc tube portion 12, the cathode 21 has an inner diameter that is larger than the outer diameter of the rear end of the coil portion 23. A substantially annular space G is formed around the electrode shaft portion 22 on the rear side in the axial direction, and a sufficiently large separation distance is secured between the outer peripheral surface of the rear end of the coil portion 23 and the inner peripheral surface of the arc tube portion 12. It is said that it was in the state.

  The axial length X1 between the second inflection point P2 and the innermost edge position Q in the axial direction in which the inner surface of the arc tube portion 12 is closest to the outer peripheral surface of the electrode shaft portion 22 is the first length X1. The axial direction length between the inflection point P1 and the second inflection point P2 (the axial length of the second bending portion 16) is smaller than X2. With such a configuration, unevaporated mercury is accumulated between the inner surface of the arc tube portion 12 and the outer surface of the electrode shaft portion 22 on the rear side in the axial direction from the rear end of the coil portion 23. Formation of a minute space is suppressed.

When showing a configuration example of a short arc type discharge lamp 10 described above, for example, the internal volume of the arc tube portion 12 is 300 mm ³ or less, for example 150 to 200 mm ^3, the maximum outer diameter of the arc tube portion 12 Fai8～fai11mm, the arc tube The maximum inner diameter of the portion 12 is φ5 to φ8 mm, the inner diameter at the position of the first inflection point P1 is φ4 to φ7 mm (<the maximum inner diameter of the arc tube portion 12), and the inner diameter at the position of the second inflection point P2 is φ3−3. φ6 mm (maximum outer diameter of coil portion <inner diameter at second inflection point P <b> 2 <inner diameter at first inflection point P <b> 1), outer diameter of electrode shaft portion 22 in cathode 21 is φ0.5 to φ0.9 mm, cathode The axial length of the coil portion 23 at 21 is 2 to 5 mm, the maximum outer diameter is φ1.2 to φ1.8 mm, and the axial length between the first inflection point P1 and the second inflection point P2 (X2). ) Is 2 to 4 mm, the second inflection point P2, and the arc tube portion 1 The inner surface axial length between the innermost edge position Q that closest to the outer peripheral surface of the electrode shaft portion 22 of the cathode 21 (X1) is 1~3mm (<X2), the rated power is 95～105W.

  Thus, according to the short arc type discharge lamp 10 having the above configuration, the inner surface R1 surrounding the periphery of the cathode 21 of the arc tube portion 12 is at least in the arc forming region in the cross section along the tube axis of the discharge vessel 11. An outwardly convex first curved portion 15 constituting an inner surface region surrounding the periphery, an inwardly convex second curved portion 16 continuous with the first curved portion 15, and the second curved shape An outwardly convex third curved portion 17 that is continuous with the portion 16, and the first inflection point P1 is located in the inner surface region surrounding the coil portion 23 in the cathode 21, Since the second inflection point P2 has a shape positioned on the side of the sealing portion 13A related to the cathode 21 from the inner surface region surrounding the periphery of the coil portion 23, the second bending portion 16 becomes the discharge vessel. 11 is formed so as to extend substantially parallel to the tube axis of 11 And the outer peripheral surface of the coil portion 23 in 1, the distance is large enough is ensured between the inner surface of the arc tube portion 12. Thereby, at the time of starting the lamp, the heat of the coil part 23 heated by the cathode 21 being heated by energization is prevented from being transferred to the arc tube part 12 and the temperature rise of the coil part 23 is prevented. As a result, the emission of electrons from the emitter contained in the coil portion 23 can be performed satisfactorily, and the desired starting assisting effect can be reliably obtained by the emitter. It becomes. In addition, since it is possible to reliably suppress the blackening of the discharge vessel 11 due to evaporation of the constituent members of the coil portion 23 and adhesion to the inner surface of the arc tube portion 12, the desired illuminance can be reduced for a long time. It can be maintained for a long time and has a long service life.

  Further, the inner diameter of the position of the second inflection point P2 in the arc tube portion 12 is larger than the outer diameter at the rear end of the coil portion 23, and the second inflection point P2 and the inner surface of the arc tube portion 12 are the cathode 21. The axial length X1 between the innermost edge position Q closest to the outer peripheral surface of the electrode shaft portion 22 and the axial length X2 between the first inflection point P1 and the second inflection point P2 is Due to the small configuration, the arc tube portion 12 is sealed in the arc tube portion 12 while having a sufficiently large separation distance between the inner surface of the arc tube portion 12 and the outer peripheral surface of the coil portion 23. In this way, a minute space in which the mercury is accumulated in an unevaporated state is not formed, so that the desired pressure (mercury vapor pressure) in the arc tube portion 12 can be obtained and the short arc type discharge lamp. 10 can be lighted stably and reliably.

In the above, the short arc type discharge lamp of the DC lighting system has been described, but the present invention can also be applied to the AC lighting system.
FIG. 3 is an enlarged cross-sectional view showing an outline of the configuration of another example of the short arc type discharge lamp of the present invention.
In the short arc type discharge lamp according to this embodiment, each of the pair of electrodes 31, 31 disposed opposite to each other inside the arc tube portion 12 in the discharge vessel 11 has a substantially conical tip. It is composed of a rod-shaped electrode shaft portion 32 and a coil portion 33 containing an emitter provided at the tip side portion of the electrode shaft portion 32. The inner surface of the arc tube portion 12 has the following shape. The short arc type discharge lamp 10 shown in FIG. 1 and FIG.
The inner surface of the peripheral region R1 of each of the electrodes 31 and 31 in the arc tube portion 12 protrudes outward in a cross section along the tube axis direction of the discharge vessel 11 to constitute at least an inner surface region surrounding the arc forming region. The first curved portion 15, the inwardly convex second curved portion 16 continuous with the rear end of the first curved portion 15, and the outer side continuous with the rear end of the second curved portion 16. A third curved portion 17 that is convex to the rear, and an inwardly convex bent portion 18 that is continuous to the rear end of the third curved portion 17, and the first inflection point P 1 is around the coil portion 23. And the second inflection point P2 is positioned closer to the sealing portion 13 than the inner surface region surrounding the periphery of the coil portion 23.

  Also in the short arc type discharge lamp according to this embodiment, the same effect as that of the short arc type discharge lamp 10 shown in FIGS. 1 and 2 can be obtained.

Hereinafter, experimental examples performed for confirming the effects of the present invention will be described.
<Experimental example 1>
50 short arc discharge lamps (hereinafter simply referred to as “lamps”) according to the present invention were produced in accordance with the configuration shown in FIGS. The specifications of each lamp are as follows. Note that the positions of the first and second inflection points on the inner surface of the discharge vessel are obtained by taking an X-ray photograph in a state in which the electrodes are focused, and the arc tube in the photograph obtained thereby. This was confirmed by observing the inner shape of the part.
[Lamp specification]
Discharge vessel: material: quartz glass, maximum outer diameter of arc tube portion; φ10 mm, maximum inner diameter of arc tube portion; φ6 mm, radius of curvature of first curved portion; R12 mm, radius of curvature of second curved portion; R10 mm, first The radius of curvature of the curved portion 3; R4 mm, the inner diameter of the arc tube portion at the position of the first inflection point is φ5 mm, the inner diameter of the arc tube portion at the position of the second inflection point is φ4 mm, and the axial center of the discharge vessel Axial distance from the position to the first inflection point position: 5.0 mm, Axial distance from the axial center position of the discharge vessel to the second inflection point position: 7.0 mm, the first inflection point Axial length (X2) between the position of the inflection point and the position of the second inflection point; 2.0 mm, the position of the second inflection point, and the outer peripheral surface of the electrode shaft portion at the cathode of the bent portion Length in the axial direction (X1) between the closest position to the tube; 1.0 mm, inner volume of the arc tube portion; 18 mm ^3,
Cathode (21): Material of electrode shaft portion: tungsten, outer diameter: φ1,0 mm, coil portion: a wire rod made of thorium tungsten (thorium content: 2 wt%) having a wire diameter of φ0.4 mm is wound Configuration, axial length of the coil part: 5.0 mm, outer diameter of the rear end of the coil part: φ1.6 mm, axial distance from the center of the discharge vessel to the leading edge of the coil part; 3.0 mm,
Anode (25): Material: Tungsten, Maximum outer diameter: φ3.0 mm,
Distance between electrodes: 2.0 mm,
Mercury encapsulation amount: 0.10 mg / mm ³ Argon (rare gas) encapsulation amount: 13 kPa Bromine (halogen) encapsulation amount: 3.0 × 10 ⁻⁴ μmol / mm ³

  Further, in the lamp according to the present invention manufactured as described above, the inner surface of the arc tube portion has a substantially elliptical spherical shape along the outer surface of the arc tube portion as the discharge vessel (the first curved portion and the second curved portion). 50 comparative lamps having the same configuration as that of the lamp according to the present invention described above, except that the first and second curved portions are not included.

Each of the lamp according to the present invention and the comparative lamp is in a state where the lamp lighting time is 0 hour (initial state), a state where 100 hours have elapsed since the start of lamp lighting, and a state where 300 hours have elapsed since the start of lamp lighting. The dielectric breakdown voltage at the start of lamp lighting was measured. The results are shown in Table 1 below. Here, the lighting conditions of the lamp are as follows, and the numerical value of the dielectric breakdown voltage in Table 1 is an average value of 50 lamps.
[Lamp lighting conditions]
Input power: 100W, lamp voltage: 20V, lamp current: 5A, vertical lighting (cathode is upward),

  As is clear from the above results, it was confirmed that the average value of the breakdown voltage of the lamp according to the present invention was lower than the average value of the breakdown voltage of the comparative lamp, and excellent lamp startability was obtained. . The reason for this is considered to be that the emitter contained in the coil portion of the cathode was successfully heated at the start of lamp lighting.

<Experimental example 2>
50 lamps according to the present invention and comparative lamps having the same specifications as those produced in Experimental Example 1 were produced, and the lamp lighting time was 0 hour (initial state) for each lamp. The illuminance was measured in a state where 100 hours had elapsed since the start of lamp lighting and in a state where 300 hours had elapsed since the start of lamp lighting, and the illuminance maintenance ratio was calculated based on the illuminance in the initial state. The results are shown in Table 2 below. Here, the lighting conditions of the lamp are the same as the lighting conditions in Experimental Example 1, and the numerical value of the illuminance maintenance rate in Table 2 is an average value of 50 lamps.

  As is clear from the above results, it was confirmed that the average value of the illuminance maintenance ratio of the lamp according to the present invention is higher than the average value of the illuminance maintenance ratio of the comparative lamp. The reason for this is considered to be that, in the lamp according to the present invention, it was possible to suppress a problem such that the constituent members of the coil portion in the cathode evaporated and adhered to the inner surface of the arc tube portion to cause blackening.

DESCRIPTION OF SYMBOLS 10 Short arc type discharge lamp 11 Discharge vessel 12 Arc tube part 13, 13A, 13B Sealing part 15 1st bending part 16 2nd bending part 17 3rd bending part 18 Bending part P1 1st inflection point P2 Second inflection point 21 Cathode 22 Electrode shaft portion 23 Coil portion 25 Anode 27 External lead 28 Metal foil 29 Base 31 Electrode 32 Electrode shaft portion 33 Coil portion 40 Short arc type discharge lamp 41 Discharge vessel 42 Arc tube portion 43 Sealing Part

Claims (2)

A discharge vessel having a pair of electrodes opposed to each other inside, a discharge tube portion having a substantially spherical shape or a substantially elliptical spherical outer shape, and a sealing portion continuous to each of both ends of the discharge tube portion; In a short arc type discharge lamp in which at least one of the electrodes is formed with a coil part containing an electron-emitting substance at the tip of the electrode shaft part,
The inner surface surrounding the periphery of the one electrode of the arc tube portion constitutes at least an inner surface region surrounding the arc forming region in a cross section along the tube axis of the discharge vessel. A first curved portion projecting outward in a substantially spherical shape or a substantially elliptical spherical shape along the first curved portion, and a second curved portion projecting inward that is continuous with the first curved portion . The second bending portion is positioned outward from the virtual spherical surface or the virtual elliptic spherical surface from which the first bending portion is extended, and is a boundary position between the first bending portion and the second bending portion. 1 inflection point is located in the inner surface region surrounding the periphery of the coil portion;
The inner surface surrounding the periphery of the one electrode in the arc tube portion has an outwardly projecting third curved portion continuous with the second curved portion in a cross section along the axial direction of the electrode shaft portion. And a second inflection point, which is a boundary position between the second bending portion and the third bending portion, is located closer to the sealing portion than an inner surface region surrounding the coil portion. The short arc type discharge lamp characterized by the above-mentioned. The inner diameter of the arc tube portion at the position of the second inflection point is larger than the outer diameter of the rear end of the coil portion, and the position of the second inflection point and the inner surface of the arc tube portion are the electrodes. The axial length between the innermost edge position closest to the outer peripheral surface of the shaft portion is smaller than the axial length between the position of the first inflection point and the position of the second inflection point. The short arc type discharge lamp according to claim 1.

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