JP3080667U - Short arc lamp - Google Patents

Abstract

(57) An improved short arc lamp comprising a discharge vessel having two ends and having an anode and a cathode facing each other. An object in which abnormal arc contact is prevented at the start of lighting is provided. SOLUTION: The cathode shaft is provided with a cut area, and the cut area is provided on the shaft at a linear distance z of at least 2 mm from a metal component of a holding part, and the cut area is provided. It has a radial spacing r of at least 5 mm from all components made of quartz glass and the cut area has a spacing x from the cathode tip of at least half of the cathode length y entering the bulb. The cutting area consists of at least two circumferentially extending grooves provided in the shaft, and burrs having at least one edge in the center of these two grooves project outward.

Description

[Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

 The present invention is a short arc lamp comprising a discharge vessel having two ends, an anode and a cathode facing each other, wherein the anode and the cathode comprise a head and a shaft and are end-to-end. It is of a type that is fixed by a holding part at the part. In this case, the short arc lamp relates to a mercury high-pressure discharge lamp operated with direct current, in particular for microlithography.

[0002]

[Prior art]

 When the lamp starts to ignite, the discharge arc is not immediately formed between the electrode cusps, but extends from the anode cusp to any point other than the cathode cusp at the stage of starting the lamp. In particular, arcs tend to look for distant attachment points (Ansatzpunkt) in the area of the cathode shaft. It is often provided with components of the holding part (especially the supporting roll), for example, the end of a foil that enters the discharge space. The free end of the foil serves for fixing the support roll or for mechanical separation between the support roll and the cathode shaft. These foils are located at the cathode potential. The foil melts slightly upon contact of the arc, in which case it partially evaporates, forming a deposit on the valve wall. The transmission of the lamp bulb is reduced by this metal deposit, which reduces the light output of the lamp.

When the arc comes into contact with a support roll made of quartz glass, it causes evaporation of the quartz glass, cracking of the quartz glass and, in disadvantageous cases, even rupture of the lamp bulb.

In order to solve such a problem, the following means a, b, and c have been used.

A) Install the windings near the cathode tip of the cathode shaft. In this case, the arc contact point is provided in the form of a winding, which reduces the contact of the arc in the welding area (Einschmelzbereich) of the cathode shaft. (European Patent Publication No. 75 1548).

[0006] The disadvantage is that the provision and installation of these additional components is costly. Besides, complete security cannot be obtained. This is because, despite the installation of the winding, the arc may still be able to jump behind this winding in the unfavorable case. The windings need to be cleaned by an incandescent process (Glue hprozess) before their installation, but in this case high temperatures must be avoided. The reason is that the highly heated windings are fragile and can be easily damaged during installation.

[0007] b) A protective winding is mounted immediately before the welding area with the holding part (support roll) (see EP-A-915496). The foil on the support roll is protected from arc contact by the windings. In this case, a circumferentially extending groove provided in the cathode shaft can be provided at the height of the protective winding, which ensures a reliable holding of the winding.

[0008] Disadvantages are the high cost of the additional components, the risk of winding breakage, the necessity of cleaning the windings before installation, and the complicated shape of the windings. No.

C) High wattage lamps use cathodes with coined heads (EP 7551548). The rear edge of the head pulls the arc, which prevents parts further behind the cathode, especially the shaft contact area, from being compromised.

[0010]

[Problem to be Solved by the Invention] Accordingly, an object of the present invention is to improve a short arc lamp of the type described at the beginning to provide a lamp in which abnormal arc contact is prevented at the start of lamp lighting. That is.

[0011]

[Means for Solving the Problems]

 According to the device of the present invention for solving this problem, the cathode shaft has a cut area, and the cut area satisfies the following conditions. : That is, a. A cut area is provided on the shaft at a linear spacing z of at least 2 mm from the metallic component of the holding part, the cut area being at least 5 mm radius from all components made of quartz glass. Direction r, and b. The cut area has a distance x from the cathode tip that is at least half of the cathode length y protruding into the bulb, such that x> y / 2 holds, where x is from the cathode tip. C is the distance to the cut area, y is the length of the cathode that enters the bulb, and c. The cut area is formed of at least two circumferentially extending grooves provided on the shaft, and a burr having at least one edge at the center of the two grooves protrudes outward. ing.

[0012] Particularly advantageous configurations are set out in the dependent claims.

[0013]

[Effect of the invention]

 During the rotary cutting manufacturing process, a cut area is provided on the cathode shaft. The cutout area is formed by a circumferentially extending recess in the shaft, the center of which has at least one sharp, rounded edge projecting outward. Sharp edges (preferably having a number of edges of up to 5) serve as a destination for the arc to be directed at the start of lamp operation if the arc undesirably reaches the shaft. That is, the edges and peaks form a local elevation of the electric field, which preferentially causes an arc to the protrusion.

[0014] The attractive force of the edges for the arc contact protects the sensitive components of the holding part in the welding area, in particular the thin foil. Because the cathode is made of rugged, genuine tungsten or thorium-tungsten, the cathode provides better short-term contact of the arc than the filigranen component of the holder. To hold.

The cut area is economically considered during the cathode fabrication process and does not require additional fabrication steps such as cleaning and mounting of additional components (windings). Furthermore, the risk of error functions such as winding cuts is avoided.

In this case, care must be taken that the cut area is not too close to the sensitive area of the shaft appendage near the sealing area (implemented advantageously as a weld). A spacing z of at least 2 mm is sufficient to prevent heating of the foil edge or another metallic component of the holding part. In addition, it is necessary to maintain a spacing of at least 5 mm for all components made of quartz glass, especially for narrow valve necks. This prevents the quartz glass from overheating, even if the arc contacts near the sealing area.

Basically, the cathode is formed of a head or point and a shaft (cylindrical bar), which can be integrally formed (for low power) and have the same diameter. Alternatively, it can be formed from separate parts, in which case the head in particular has a larger diameter than the shaft.

The interval between the cut regions provided on the outer peripheral surface of the cathode or a bar (shaft) including the cathode needs to be sufficiently large from the cathode tip. This allows the cut area to effectively attract (ie, capture) the arc contact in the event that the arc does not touch the cathode tip. Such a catching mechanism is then ensured if the distance from the cathode tip to the cutting area (start of the cutting area) corresponds to at least half the length of the cathode which freely enters the bulb.

The present invention is a short arc lamp having a discharge vessel having two ends, wherein an anode and a cathode are opposed, the anode and cathode comprising a head and a shaft, and having an end. In this case, it is fixed by a holding part, in which case the cathode shaft is provided with a cut area, in which case the following conditions are satisfied. That is, a. A notch area is provided on the shaft with a linear spacing z of at least 2 mm from the metallic component of the holding part and a radial spacing of at least 5 mm from all components made of quartz glass. r. The cut area has at least half the length y of the cathode projecting into the bulb and a distance x from the tip of the cathode, so that x> y / 2 holds, in which case: x = the distance from the cathode tip to the cut area, and y = the length of the cathode entering the bulb. The condition is fulfilled that the cut-out area consists of at least two circumferentially extending grooves provided in the shaft, the burr having at least one edge in the center protruding outward.

Advantageously, the burr is formed in a v-shape and has sharp, non-rounded edges, the edge angles of which are in particular 90 degrees or less than 90 degrees. Since the burrs can alternatively be formed in steps, the burrs have two edges, the edge angles of which are in particular between 90 and 120 degrees.

The holding part is often provided with metal and dielectric components. This means in particular a component made of quartz glass, for example a support roll. As a metal component of the holding part, a foil having a free end part which enters the discharge volume is a problem.

The following dimensions have emerged as particularly effective geometric conditions: According to this dimension, x is in the range of 0.6y to 0.8y, the extended portion a of the cut area is in the range of 2mm to 15mm, and z is in the range of 2mm to 20mm.

In order to obtain even higher electric field strengths, the cut areas need to be formed with sharp, ie non-rounded edges.

[0024]

[Embodiment of the invention]

 Next, an embodiment of the present invention will be described in detail with reference to the illustrated embodiment.

FIG. 1 shows a mercury high-pressure discharge lamp having an average output of 1.5 kW. The mercury high-pressure discharge lamp comprises an oval, barrel or similar bulb 2 made of quartz glass. Opposite sides of this valve 2 are connected two ends 3, which are configured as valve necks 4 and each hold a holding part 8. The neck 4 has a conical front edge 4a and a cylindrical rear edge 4b, the front edge 4a comprising a small support roll 5 made of quartz glass as the main component of the holding part 8. The rear edge 4b forms a dense weld. The front part 4a is provided with a recess 6 with a length of 5 mm. The conical supporting rolls 5 each having a central hole are connected to the drawn-in portions 6. The inner diameter of the support roll 5 is 7 mm, and the outer diameter is 11 mm at the front end and 15 mm at the rear end. The wall thickness of the valve in this region is about 4 mm. The axial length of the support roll 5 is 17 mm.

A bar or shaft 10 of the cathode 7 having a diameter of 6 mm is guided in the hole of the first support roll 5 in the axial direction, this bar or shaft 10 reaching the discharge volume. And a head 11 formed integrally therewith. The bar 10 is guided backwards beyond the support roll 5 and terminates in a first dish 12. A cylindrical quartz block 13 is connected to the first dish 12. Behind the quartz block 13 is a second dish 14 which, in the center, holds an outer current supply in the form of a molybdenum bar 15. Along the outer peripheral surface of the quartz block 13, four foils 16 of molybdenum are guided in a known manner and are sealed to the wall of the valve neck 4. The shaft 10 of the cathode 7 has a cut area 20.

In a manner analogous to the cathode 7, an anode consisting of a separate head 18 and a shaft 19 is held in a hole in the second support roll 5.

FIG. 2 shows the cathode 7 and the holding unit 8 in detail. The head 11 is formed as a pointed end. The shaft 10 is an integral component of the cathode and has the same outer diameter as the head 11. The cut area 20 is formed of two grooves 21, and a burr 22 is located at the center of these grooves 21. The burr 22 has a sharp edge having an angle α of 60 degrees. The holding unit 8 is formed of a support roll 5 and a plurality of foils provided in holes of the support roll 5.

A foil 24 is wound around the shaft 10 a plurality of times (two to four layers) for mechanical separation between the support roll 5 and the shaft 10. The foil 24 does not have an end near the bent discharge volume (although the foil 24 may overhang the support roll 5 in another embodiment). Several narrow foils 23 located on opposite sides of the rolled foil 24 serve to fix the support roll 5. To this end, the foil 23 extends beyond the support roll 5 on the discharge side and is bent outward. In this case, the projecting end of the foil 23 is a problem in the present invention (in another embodiment, the problem is the end of both foil types 23, 24). The protruding end of the foil 23 is protected against arcing by the cut 20.

The free total length y of the cathode 7 from the free end of the foil 23 to the tip of the cathode 7 is 39 mm in the present embodiment, and the tip of the cathode 7 and the starting position of the cut region 20 The length x between is about 28 mm, measured at the start of the first groove. The distance z from the end position of the second groove from the top to the start position of the foil 23 is 7 mm, and the extension a of the cut area 20 is 4 mm. In this case, y = x + z + a holds. The foil 23 protrudes into the discharge volume by about 2-3 mm.

FIG. 3 shows another embodiment of a cut area 26 having two edges 27 with an edge angle α = 45 degrees. The smaller the edge angle, the higher the resulting electric field strength. Of course, if the edge angle is extremely small, it becomes technically difficult, so the applicable area is between about 30 degrees and 90 degrees.

FIG. 4 shows another embodiment of a cut area 30 comprising five meandering steps 31 having an edge angle α = 90 degrees. . Here, a large edge angle is selected. This is because the number of edges is larger than in the case of the V-shape, and it is particularly easy to manufacture the case of an angle of 90 degrees. Overall, the applicable area is about 80-120 degrees.

In the notch area 34 of another embodiment (FIG. 5), a mixed shape consisting of a V-shape and a step-shape, such as a burr 35 formed in a W-shape, may be used. . In this case, many edges and small edge angles are obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a mercury high-pressure discharge lamp.

FIG. 2 is a sectional view showing details of a cathode.

FIG. 3 is a diagram illustrating a cut area according to another embodiment.

FIG. 4 is a diagram showing a cut area according to another embodiment.

FIG. 5 is a diagram illustrating a cut area according to another embodiment.

[Explanation of symbols]

1 mercury high pressure discharge lamp, 2 bulb, 3 end,
4 valve neck, 4a front part, 4b rear part, 5 support roll, 6 retraction part, 7 cathode,
8 holding part, 10 bar or shaft, 11
Head, 12 1st dish, 13 Quartz block, 1
4 second dish, 15 molybdenum bar, 16 foil,
18 head, 19 shaft, 20 cut area, 21 groove, 22 burr, 23 foil, 24
Foil, 26 cut area, 27 edge, 30 cut area, 31 steps, 34 cut area, 35 burr

Claims (9)

[Utility model registration claims] 1. A short arc lamp comprising a discharge vessel having two ends, an anode and a cathode facing each other, wherein the anode and cathode comprise a head and a shaft. And of the form fixed at the end by a holding part, wherein the shaft of the cathode comprises a notch area,
The cut area has the following conditions: The cut area is provided on the shaft at a linear distance z of at least 2 mm from the metal component of the holding part, and the cut area is at least 5 mm from all components made of quartz glass. Radial spacing r
And b. The cut area is a cathode length y that protrudes into the bulb.
At least half of the distance x from the cathode tip, where x> y / 2 holds, where x is the distance from the cathode tip to the cut area, and y enters the bulb. C. The cut area comprises at least two circumferentially extending grooves provided in the shaft;
A short arc lamp, which satisfies a condition that a burr having at least one edge in the center of one groove projects outward. 2. The method according to claim 1, wherein the burr is formed in a V-shape, the burr has a sharp, non-rounded edge, and the angle of the edge is, for example, 90 degrees or 90 degrees.
The short arc lamp according to claim 1, wherein the short arc lamp is smaller than a degree. 3. The short arc according to claim 1, wherein the burr is formed in a step shape and has two edges, and the angle of the edges is, for example, between 90 degrees and 120 degrees. lamp. 4. The short arc lamp according to claim 1, wherein the holding portion has a component made of quartz glass, for example, a support roll. 5. The short arc lamp according to claim 1, wherein the metal component of the holding part is a foil, and the foil has a free end which projects into the discharge volume from behind. 6. The short arc lamp according to claim 1, wherein the cut area has a plurality of grooves and a plurality of edges. 7. The distance x from the cathode tip to the cut area is equal to 0.
The short arc lamp according to claim 1, wherein the short arc lamp is between 6 and 0.8 times. 8. The short arc lamp according to claim 1, wherein an extension a of the cut area is between 2 mm and 15 mm. 9. The short arc lamp according to claim 1, wherein a distance z from a metal component of the holding portion to the cut region is between 2 mm and 20 mm.