JP7337532B2 - Electrodes for discharge lamps, methods of manufacturing discharge lamps and electrodes - Google Patents

Description

The present invention relates to an electrode for a discharge lamp, the electrode having a longitudinal extension and an electrode base defining one end of the electrode in the longitudinal extension. The electrodes also have an electrode axis extending in the longitudinal direction. Furthermore, the electrode has in its longitudinal extension a first electrode portion which has a cross-section which tapers in the direction of the electrode base surface along the electrode axis. Note that the first electrode portion has a surface and a plurality of indentations provided in the surface, wherein each indentation extends at least partially about the electrode axis and the surface forms a first angle greater than 0° and less than 90° with the electrode axis in a cross-section along the electrode axis. The invention also includes a discharge lamp with such an electrode and a method of manufacturing an electrode for a discharge lamp.

The invention relates to the field of electrodes for discharge lamps, in particular for DC discharge lamps, such as in exposure apparatus or cinema projectors for the semiconductor industry. Such lamps operate with a mercury or xenon plasma formed between two opposing electrodes, an anode and a cathode, usually surrounded by a quartz glass tube. The heat load of such lamps is often very high, which leads to vaporization of the anode and cathode materials, which usually consist of tungsten and possibly contain additives. This often results in a reduction in light output due to two points. One is that electrode deformation and burning can occur which reduces the light efficiency of the lamp in the reflector. Another is that the vaporized material can adhere to the glass tube of the lamp, causing blackening and also reducing light efficiency.

By reducing the temperature of the electrode, especially in the top region near the plasma, both deformation and vaporization can be reduced. Therefore, it is desirable to reduce the electrode temperature during lamp operation. For this purpose, for example, a layer with a high transmittance can be applied to the electrodes. Examples of this are tungsten layers, for example as described in EP 1 047 109, or ceramic layers as described in US Pat. No. 8,710,743. The cathode can also be structured, for example, by producing grooves perpendicular to the surface, for example using a laser, as described for example in JP 3838110 B1. This allows for increased surface area to achieve high emissivity.

Correspondingly, such grooves are indentations that are recessed with respect to a defined surface. The electrode can also, for example, have a cylindrical portion and a conical portion, such a conical portion tapering in the direction of the electrode base surface, so that correspondingly the surface of the conical portion is In a cross section along the electrode axis, it forms an angle of 0° to 90° with the electrode axis. The grooves described herein can be formed in the conical portion near the electrode base surface or on the outer surface of the cylindrical portion of the electrode.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrode, a discharge lamp and a method for manufacturing the electrode, which makes it possible to reduce the electrode temperature during lamp operation as efficiently as possible.

This problem is solved by an electrode, a discharge lamp and a method of manufacturing an electrode with the features of the independent claims. Advantageous configurations of the invention are subject matter of the respective dependent claims, the description and the drawings.

An electrode for a discharge lamp according to the invention has a longitudinal extension and has an electrode base defining one end in the longitudinal extension of the electrode. Furthermore, the electrode has an electrode axis extending in the direction of longitudinal extension and has a first electrode portion in the direction of longitudinal extension with a cross-section that tapers in the direction of the electrode table surface along the electrode axis. Here, the first electrode portion has a surface and a plurality of indentations provided in the surface, each indentation extending at least partially about the electrode axis. Also, the surface forms a first angle greater than 0° and less than 90° with the electrode axis in a cross section along the electrode axis. Furthermore, each indentation extends in a respective main direction of extension with respect to the surface forming a respective second angle different from normal to this surface, whereby each indentation in cross-section along the electrode axis has As can be seen, it is formed asymmetrically with respect to the normal to the surface (14a).

The present invention is based on the recognition that conventional structures oriented perpendicular to the surface potentially have the disadvantage of high heat influx due to the absorption of radiation from the light arc precisely in the conical portion of the electrode. there is In contrast, if the recesses forming the structure are not perpendicular to the surface but are inclined at another angle to the surface, for example perpendicular to the electrode axis, the plasma radiation is reflected especially towards the tube. This improves the heat dissipation in the rear region of the lamp, ie in the direction of the support element and the socket. That is, each indentation extends in the main direction of extension at a second angle rather than perpendicular to the surface, whereby each indentation is asymmetrical with respect to the normal to the surface, i.e. , the grooves or structures formed by each indentation can cool the electrode significantly more efficiently. Moreover, such a structure or recess provided precisely in the conical region of the electrode also provides advantages apart from the coating, in particular for increasing the heat emission. In this case, the tungsten layer conducts heat only to a very poor extent. Ceramic layers certainly have great advantages in terms of heat dissipation, but they have the disadvantage that they do not have the same temperature stability as, for example, tungsten layers. Critical temperatures are found especially near the top of the electrodes, especially up to 2700°C. Thus, both the anode and cathode surfaces are provided with near-top regions that are not significantly coated with ceramic. This is because otherwise the ceramic will decompose or vaporize during lamp operation. In addition, layer components can adhere to the tube and reduce the transmittance there. Coatings can likewise reach critical temperatures when the lamp is on. When the coating is exposed to a hot arc having several thousand degrees Celsius, the coating may partially decompose, hence the problems mentioned above. Advantageously, therefore, structured surfaces, ie surfaces with indentations, do not exhibit such temperature sensitivity. Since the cone of the electrode is usually very close to the electrode surface, it is particularly advantageous to provide such an indentation forming a structure in the electrode portion.

Each indentation is formed asymmetrically with respect to a normal to the surface of the first electrode portion, the normal being the edge point or border point on either side of the corresponding indentation in a cross-section through the electrode axis of the surface. It can be defined to extend through the midpoint of a connecting line joining two points, the perpendicular being also perpendicular to the connecting line here. If the indentations of the surface, for example, directly touch each other, maxima are formed between every two indentations that define such edge points. The surface of the first electrode portion, viewed in cross section, may consist only of such edge points or edge regions. The main direction of extension is defined above, for example, connecting two points of the surface, seen in a section through the electrode axis, which are edge points or boundary points on both sides of the relevant indentation in a section through the electrode axis. can be defined to extend through the midpoint of the connecting line and through the minimum of the relevant invagination seen in the cross-section. Here, the local minimum is the point or region of the invagination where the distance to the surface or to the connection line defined above is the greatest. Also, said surface of the first electrode portion is preferably a conical surface.

Electrodes can generally be formed as cathodes or anodes. Furthermore, the electrodes are preferably formed rotationally symmetrical about an axis of rotation extending in the longitudinal direction. Furthermore, it is advantageous if the indentation surrounds the electrode axis not only partially but completely, for example annularly. In this way, the large surface created by the invagination can be maximized.

Furthermore, the electrode or at least the substrate is preferably made mostly of tungsten, in particular made substantially completely of tungsten. In particular, the electrode or its substrate can be formed entirely of tungsten, excluding any dopants to the tungsten material such as thorium oxide, lanthanum oxide, zirconium oxide, carbon and/or potassium. Dopants may be less than 2%, for example. Dopants can, for example, increase the electron emission rate of the electrode.

Furthermore, each indentation is formed so that each main extending direction from the surface toward the electrode axis when viewed in a cross section along the electrode axis is inclined in a direction toward the electrode base surface with respect to a line perpendicular to the surface. can be done. Thus, for example, a serrated surface structure is obtained with teeth slanted away from the electrode surface. The structure is particularly efficient with respect to reflecting plasma radiation.

In another advantageous configuration of the invention, each main direction of extension is 70° to 110°, preferably 80° to 100° from the electrode axis in theoretical extension in cross section along the electrode axis. A third angle is formed. A range around 90° has proven to be particularly advantageous here, so that the third angle is between 85° and 95°, better still between 88° and 92°, particularly preferably 90°. and particularly preferred. It has been found that heat dissipation is optimal just when the recess extends substantially perpendicular to the electrode axis. Such a configuration of the indentations extending perpendicularly to the electrode axis, or at least in the angular region close to the right angle, thus allows a particularly efficient heat dissipation.

In another advantageous configuration of the invention, each indentation has a first edge surface remote from the electrode platform surface extending from the surface to a minimum of the indentation, for example linearly or curvedly, and a second edge surface facing each first edge surface and extending from the surface to each minimum of each indentation, proximate to the electrode base surface. wherein each first length of the first edge surface from the minimum to the surface in a cross section along the electrode axis is equal to a second length from the minimum to the surface in a cross section along the electrode axis; shorter than each second length of the edge face. That is, when viewed in cross-section along the electrode axis, each indentation may extend, for example, in a sawtooth, for example, in a zigzag manner, where the edge closer to the electrode surface faces the edge farther from the electrode surface. , the indentations or webs that are ultimately formed in this way are slanted away from the electrode surface.

The minimum is in particular the point or area of the indentation furthest from the surface in a cross-section along the electrode axis. That is, the minimum portion of the indentation preferably forms a line surrounding the electrode axis or a region surrounding the electrode axis.

Particularly preferably, the ratio of the first length to the second length is at most 0.9. If the ratio exceeds 0.9, little benefit is obtained in reducing the absorption of plasma radiation compared to recesses oriented perpendicular to the surface. A length ratio of less than 0.9 can provide particularly efficient absorption reduction.

More preferably, the ratio of the first length to the second length is at least 0.6. A particularly efficient heat dissipation can thereby be achieved. This is mainly due to the fact that the region of the grooves contributes to a high heat release, where the edge surfaces of both two adjacent indentations, i.e. the mutually facing edge surfaces of two adjacent indentations It is opposed based on the blackbody radiation produced by the air gap thus formed. Thus, when the ratio is less than 0.6 and does not further increase the positive impact on the emission characteristics, many materials must be removed.

In a further advantageous configuration of the invention, the first edge surface and the second edge surface of each indentation extend linearly in cross-section along the electrode axis and the minimum of each indentation where the half angles of the first edge surface and the second edge surface of each indentation extend in the main extension direction in a cross-section along the electrode axis. Thus, each indentation may have a zigzag structure inclined to some extent, or may be formed with a triangular cross-section, in which case the main direction of extension of the indentation is defined by a half angle. be done. In particular, edge surfaces extending linearly with respect to the cross-section viewed along the electrode axis can be realized particularly easily from a production engineering point of view. Other shape settings are also generally possible.

Furthermore, in cross section along the electrode axis, the width of each indentation is less than the first length of the first edge surface of each indentation, in particular said width is at most 1 of the first length. /2. If the height of the elevations or the corresponding depth between the recesses is significantly greater than the structure width, advantageously this likewise enables high emissivity to be achieved. This is because a large surface can be formed thereby.

The invagination does not necessarily extend to have an apex at the minimum, but may be formed to be somewhat rounded. Thus, it is also possible for the first edge region to transition continuously into the second edge region at the minima of each indentation, so that each indentation has a radius in the region of the minima. Similarly, this may be true for maxima that exist between every two adjacently located invaginations.

In another advantageous configuration of the invention, each first edge region of each indentation directly adjoins a second edge region of each indentation. Adjacent invaginations may also be in direct contact with each other. This embodiment has the great advantage that a very large number of indentations can be placed on the smallest surface, thus making available the maximum surface area for heat dissipation from the indentations or the surface structures formed thereby. have

Further configurations are also possible here. For example, each first edge region of each indentation is spatially separated from a second edge region of the same or adjacent indentation, and in particular is straight or curved when viewed in cross-section along the electrode axis. It is also possible to connect to a second edge region of the same or adjacent indentation via an extended surface portion. However, in this case it is preferred that the section is as small as possible, eg at most as long as the width of the invagination, so as to provide the maximum surface area.

In another advantageous configuration of the invention, each electrode has a second electrode portion, in particular a cylindrical electrode portion, wherein the first electrode portion is in longitudinal extension the second electrode portion. It is arranged between the electrode base surface. Theoretically, this second electrode portion could also at least partially have corresponding ridges or recesses on its mantle, but this is less preferred for reasons explained below.

Furthermore, it is preferred that the first electrode portion is formed as a conical electrode portion, ie a cone or a truncated cone. Here, the first electrode portion may be in contact with the second electrode portion and the electrode base surface. In other words, the electrode base surface is the base surface or lid surface of the conical first electrode portion, where the first electrode portion is the only conical portion of the electrode. However, other geometries are also possible, which under certain circumstances may be meaningful for various process engineering reasons. For example, the electrode can have multiple, preferably two, conical surfaces. In other words, the electrode can have a conical third electrode portion having an opening angle different from the opening angle of the first electrode portion formed by the first angle, where the first electrode Either the portion is positioned between the second electrode portion and the third electrode portion, or the third electrode portion is positioned between the second electrode portion and the first electrode portion. That is, the electrode can have a plurality of conical portions that differ from each other in terms of opening angle. Correspondingly, in this case, the indentation described in the invention and its configuration can be provided on each of the plurality of conical portions or only on one of said plurality of conical portions. For example, only the conical first electrode portion has the described indentation, and the first electrode portion is positioned between the cylindrical second electrode portion and the conical third electrode portion. It can also be configured as In this way, for example, protection of the structure can be provided during connection with other lamp parts, for example.

Furthermore, it is advantageous if the second electrode part has, at least in some areas, a ceramic coating that increases heat emission. This makes it possible to additionally increase the heat dissipation. Ceramic coatings are also much more efficient at dissipating heat than, for example, tungsten coatings. Furthermore, it is particularly advantageous if the ceramic coating is formed, for example, as a particle composite coating consisting of a matrix layer and particles embedded in the matrix layer. The material forming the matrix layer can be formed by _ZrO2 , for example. Tungsten particles are particularly suitable as embedded particles. It is particularly preferred if the ceramic coating is formed from at least 10% by volume of ceramic material and preferably from 2% to 40% by volume of the coating of tungsten particles. Such coatings have been found to be particularly efficient with respect to increasing heat release. In addition to _ZrO2 , other substances come into consideration as matrix material. The melting point of such substances is expediently as high as possible, preferably above 2000°C, particularly preferably above 2500°C. Suitable material classes are, in particular, oxides, fluorides, carbides and nitrides, such as MgF ₂ , SiC or AlN. ZrO ₂ has been found to be particularly suitable for the oxide matrix layer. This is because ZrO ₂ achieves both high mechanical stability and high transmittance. The matrix owes its stability to the metallic structure of the embedded tungsten particles. The stability can be further enhanced by the addition of _Y2U3 and/or MgO _. Alternatively, the matrix layer may be formed from _Y2U3 or _MgO only instead of _ZrO2 .

Ceramic coatings have a particularly great advantage over providing structures or ridges, among other things, just in the cylindrical region of the electrode. For one thing, ceramic coatings are significantly lower cost. It can also provide efficient cooling of the electrodes. Furthermore, since the cylindrical electrode section has a much greater distance from the electrode base surface than the conical electrode section, the risk of coating damage due to excessively high temperatures does not arise or at least is greatly reduced. Therefore, it is preferred that as large an area of the outer surface of the cylindrical electrode part as possible, for example at least 90% of the surface area of the second electrode part, has such a ceramic coating.

Therefore also, as in the case according to another preferred embodiment of the invention, it is particularly advantageous if the second electrode part does not have a surface structure, ie a laser-cut groove structure or the like. Advantageous. This is because in this way the maximum area is available for the ceramic coating.

Furthermore, the invention relates to a discharge lamp, in particular a high-pressure discharge lamp, provided with the electrode or its configuration according to the invention. In particular, the discharge lamp can have two electrodes of the invention, or two configurations thereof, in which case each electrode is preferably formed as an anode and a cathode.

Here, the electrodes can be arranged in the gas mixture-filled lamp tube of the discharge lamp. The discharge lamp can also be formed in the same way as the lamps mentioned at the outset.

For example, the discharge lamp can be configured as a xenon short arc lamp. Such lamps, also referred to as OSRAM XBO® lamps, are generally configurable to contain gas mixtures including noble gases such as argon, xenon, krypton, and the like. OSRAM XBO® lamps emit light in the visible wavelength range and are used, for example, in conventional digital film projection. However, it is particularly advantageous if the discharge lamp is constructed as a lamp containing a gas mixture containing mercury, for example an OSRAM HBO® lamp. The discharge lamp can be configured, for example, as a mercury short arc lamp. Such lamps emit light at least partially in the ultraviolet range and can be used, for example, during lithographic patterning of semiconductors. Since OSRAM HBO ® lamps are usually in a much higher price range than OSRAM XBO ® lamps, the use of the life-enhancing electrodes or configurations thereof of the present invention is particularly profitable in this case.

Furthermore, the invention relates to a method of manufacturing an electrode for a discharge lamp. In the method, an electrode substrate is provided, the electrode substrate having a longitudinally extending direction and having an electrode base surface defining one end in the longitudinally extending direction of the electrode. Furthermore, the electrode substrate has an electrode axis extending in the longitudinal direction, and has a first electrode portion in the longitudinal direction and having a cross-section that tapers in the direction of the electrode base surface along the electrode axis. . The first electrode portion has a surface forming a first angle larger than 0° and smaller than 90° with the electrode axis in a cross section along the electrode axis, and a plurality of recesses are formed on the surface using a laser. provided, whereby each indentation extends at least partially about the electrode axis. Furthermore, each indentation having a main direction of extension is provided at a second angle to the surface that is different from normal, such that each indentation, viewed in cross-section along the electrode axis, is oriented toward the surface. It is formed asymmetrically with respect to the vertical.

The advantages mentioned for the electrode according to the invention and its construction also apply to the discharge lamp according to the invention and the manufacturing method according to the invention. The features of interest mentioned in connection with the electrode of the invention and its configuration also allow development of the manufacturing method of the invention by means of further method steps.

Particularly preferably, the recess provided in the surface of the electrode substrate is formed using an ultrashort pulse laser. An optional ceramic coating can be deposited on the cylindrical electrode portion in a subsequent step or beforehand by a suitable coating method, such as a sintering method.

Further advantages, features and details of the invention follow from the following description of preferred embodiments with reference to the drawings.

1 is a schematic diagram showing an electrode for a discharge lamp, according to one embodiment of the invention; FIG. 2 is a schematic diagram showing the electrode of FIG. 1 in cross-section along the electrode axis, according to one embodiment of the present invention; FIG. 2 is a schematic diagram showing the conical electrode portion of the electrode of FIG. 1 in cross-section along the electrode axis, according to one embodiment of the invention; FIG. FIG. 5 is a schematic diagram showing a side view of an electrode having two conical portions according to another embodiment of the invention; 5 is a schematic diagram showing a cross-section of the electrode of FIG. 4 along the electrode axis, according to one embodiment of the present invention; FIG. 5 is a schematic partial view showing one conical region of the electrode of FIG. 4, in accordance with one embodiment of the present invention; FIG. 1 is a schematic diagram showing a discharge lamp according to an embodiment of the invention; FIG. Fig. 4 is a graph showing the characteristics of the luminance depending on the duration of burning of two different discharge lamps for comparison;

A schematic diagram of an electrode 10a according to one embodiment of the present invention is shown in FIG. 2 again shows the electrode 10a in cross-section along the electrode axis A. FIG. Here, the electrode 10a extends in the longitudinally extending direction L and has an electrode base surface 12 that defines one end in the longitudinally extending direction L of the electrode. The electrode axis A extends parallel to the longitudinal extension direction L. Preferably, the electrode 10a is configured rotationally symmetrical with respect to the electrode axis A. In this example, the electrode has a conical first electrode portion 14 and a cylindrical second electrode portion 16 . In this case, the conical electrode portion 14 is directly in contact with the cylindrical electrode portion 16 in the longitudinal direction L, and the electrode base surface 12 is also directly on the conical electrode portion 14 in the longitudinal direction L. in contact with A conical surface 14a (see FIG. 3) of the conical electrode portion 14 forms an angle φ with the electrode axis A. As shown in FIG. The angle φ is greater than 0° and less than 90°.

To improve heat dissipation, electrode 10a advantageously has a trench structure 18 formed from a plurality of indentations 20 (see FIG. 3). By way of example, the electrode 10a has such a groove structure on the conical electrode portion 14 and preferably not on the cylindrical electrode portion 16, although this is possible in principle. . In the region of the cylindrical electrode portion 16, which in this example extends over both a first portion length l1 and a second portion length l2 in the longitudinal direction L, there is e.g. coating, in particular a ceramic coating, for example a ZrO ₂ matrix with tungsten particles embedded therein.

The groove structure 20 of the conical electrode portion 14 will now be described with reference to FIG. In this case, FIG. 3 shows a schematic cross-sectional view of the conical electrode portion 14 . The conical electrode portion 14 has a conical surface or surface 14a with a plurality of indentations 20 provided to form the groove structure 18, although for the sake of clarity only two of the indentations 20 are referenced. not numbered. This forms between each two indentations 20 a respective ridge 21 relative to the base surface 14b extending theoretically parallel to the surface 14a, where in the cross-section shown the indentations The base surface 14b, which extends through each of the 20 minima N, is not actually an ideal conical surface. This is because the recesses 20 do not have equal depths due to manufacturing differences. In this case, the groove structure 18 is formed in the surface 14a initially formed as a conical extension of the conical surface 14a directly in contact with the electrode base surface 12 along the dashed line. , is formed using a short-pulse laser. Said initial surface 14a will in this case eventually become the enveloping surface shown in FIG. Each protuberance 21 extends away from the base surface 14b in the main direction of extension H′, or in other words each indentation extends in the main direction of extension H from the surface 14a towards the electrode axis A. , wherein the respective main directions of extension H, H' extend in parallel. Advantageously, each main direction of extension H, H' encloses with the surface 14a a respective second angle β different from the respective right angle, whereby the ridges 21 are aligned with the electrodes with respect to the normal to the surface 14a. It is inclined in a direction away from the base surface 12. - 特許庁In particular, in this example, each main direction of extension H, H' is oriented so as to form a right angle with the electrode axis A, here labeled γ. Generally, the angle γ may be between 70° and 110°, preferably between 80° and 100°, particularly preferably between 88° and 92°.

The groove structure 18, unlike structures in which such grooves are oriented perpendicular to the surface 14a, reduces heat influx during operation of a discharge lamp with such electrodes 10a due to the discharge arc running between each electrode platform 12. has the great advantage of being significantly reduced. This is because most of the radiation is reflected by the groove structure 18 and not absorbed.

Further, each recessed portion 20 has a first edge surface F1 which is a surface farther from the electrode base surface 12 and extends from the maximum portion M to the base surface 14b or from the surface 14a to the minimum portion N. The first edge surface F1 has a length from the maximum portion M to the base surface 14b in a cross section along the electrode axis A, and this length is denoted by T1. Each indented portion 20 has a surface closer to the electrode base surface 12 and similarly extends from the maximum portion M of the indented portion 20 to the base surface 14b or from the surface 14a to the minimum portion N. This second edge surface F2 has a length from the maximum M to the base surface 14b in a cross section along the electrode axis A, and this length is denoted by T2 . In this example, the groove structure 18 is configured as a serrated zigzag structure, so that each edge face F1, F2 extends linearly in cross-section along the electrode axis A and two adjacent recesses. They intersect at the maximum M of the entry 20 . In addition, the indented portion 20 has a half angle W that halves the angle between the two edge surfaces F1 and F2 in the cross section shown in the figure, along the main extending directions H and H', and thus with respect to the electrode axis A. It is formed so as to extend vertically. Accordingly, the illustrated angles α1, α2 between each edge face F1, F2 and the half angle W are of equal magnitude. It has also been found to be particularly advantageous if the ratio of the length T1 of the first edge surface F1 to the length T2 of the second edge surface F2 is in the range from 0.6 to 0.9. If the ratio is significantly greater than 0.9, the benefits of reduced absorption of plasma radiation are significantly diminished. It should be noted that the region where the two sides of the groove, that is, the edge faces F1 and F2, face each other, that is, the region that measures the length T1, contributes to an increase in heat release, so if the above ratio is greater than 0.6 Advantageous. Other values will have to remove more material if there is no positive impact on the release profile.

Generally, the ratio of length T1 to length T2, depending on angle α1 or angle α2 and angle φ, is
T1/T2=sin(90°-α1-φ)/sin(90°-α1+φ)
can be calculated by

Furthermore, it has been found to be advantageous if the ratio of length to width of each indentation 20 also has a predetermined minimum value. The width B of each invagination 20 is, for example, as shown in FIG. , can be determined. The distances are denoted by B1 and B2, respectively. In particular, it is very advantageous if the ratio of the first length T1 of the first edge face F1 to the width B is at least two.

The ratio of the first length T1 of the first edge face F1 to the width B is usually dependent on the angle α1, which is equal to the angle α2, and the angle φ:
T1/B=[sin(90°-α1-φ)・sin(90°-α1)]/[sin(90°-φ)・sin(2α1)]
can be calculated by

The following table shows various possible combinations of angle α1 or angle α2 and angle φ and the resulting ratios T1/T2 and T1/B.

The length T2 is preferably in the range 0.2 mm to 1.2 mm, preferably in the range 0.5 mm to 1 mm. Therefore, the preferred ranges for the first length T1 and width B are obtained from the above relational expressions.

Correspondingly, the structures or groove structures 18 described above are oriented perpendicularly to the electrode axis A, in particular also when more than one conical surface is present, as shown for example in FIGS. It is applicable to all faces with non-uniform normals.

In this case, FIG. 4 shows a schematic view of an electrode 10b according to another embodiment of the invention, and FIG. 5 shows a cross-sectional view of the electrode of FIG. 4 along the electrode axis A. ing. In this example, the electrode 10b has a cylindrical electrode portion 16, a first conical portion 14 following in the longitudinal direction L, and a further conical portion 22 following the first conical portion 14. FIG. The further conical portion 22 is furthermore adjoined in the direction of longitudinal extension L by the electrode base surface 12 . The two conical portions 14, 22 make two different angles φ1, φ2 with the electrode axis A. The two conical portions 14, 22 can additionally be provided with a corresponding groove structure 18 as described with reference to FIG. In this example only the central conical portion 14 located between the cylindrical electrode portion 16 and the further conical portion 22 is provided with such a groove structure 18 . The groove structure 18 is again shown in detail in FIG. Each indentation 20 forming the groove structure 18 extends in each main extension direction H, H' as in the case described above, and each main extension direction H, H' is defined as above. It corresponds to each defined half angle W and is perpendicular to the electrode axis A. Such a geometry is advantageous for various process engineering reasons, e.g. to protect the structure 18 during connection with other lamp parts.

Regarding the shape of the invaginations 20 and their mutual arrangement, there are many other advantageous and possible configurations. For example, the invaginations 20 may not directly abut each other, but may be separated from each other by, for example, rounded or straight middle sections.

FIG. 7 shows a schematic representation of a discharge lamp 24, which in this example is constructed as a high-pressure discharge lamp in short-arc technology. The discharge lamp 24 here has two electrodes 10c, 10d according to an embodiment of the invention, one of which is configured as the anode 10c and the other as the cathode 10d. Here, cathode 10d and/or anode 10c can be constructed as described with reference to FIGS. Additionally, the anode 10c is distinguished from the cathode 10d by a shape setting as can be seen from FIG. In particular, the anode 10c preferably has a larger diameter perpendicular to its electrode axis A, preferably in the range of 1 cm to 4 cm, while the cathode 10d has a As vertical diameter, it preferably has a smaller diameter in the range of less than 3 cm or up to 3 cm.

Furthermore, the discharge lamp 24 has elements normally provided in such lamps, such as a discharge vessel 26, a discharge chamber 28 filled with a gas mixture and in which the electrodes 10c, 10d are arranged, and other elements. The discharge tube 26 can be formed, for example, by a corresponding glass tube. The gas mixture filling the discharge chamber 28 may contain, for example, mercury and/or one or more noble gases such as argon, xenon, krypton. Furthermore, each electrode 10c, 10d has a corresponding electrode pedestal surface 12 facing each other, where in addition the anode 10c and the cathode 10d are arranged coaxially with each other so that the respective electrode axes of these electrodes A is located on a straight line.

FIG. 8 shows for comparison the characteristic of the luminance I as a function of the combustion duration t for two discharge lamps, here a first discharge lamp according to a first embodiment of the invention. The luminance characteristic of 24 is designated I1, and the luminance characteristic of the second discharge lamp 24 according to the second embodiment of the invention is designated I2. In this case, the two discharge lamps 24 are driven with a power of 13.5 kW. Also, the two discharge lamps each have one electrode 10a having a conical electrode portion 14 in which the recess 20 described above is formed. The lengths T1 and T2 of each edge face F1 and F2 in cross section along the electrode axis A are, in this example, T2=0.8 mm and T1=0.5 mm. The determined width B is 0.16 mm, and in particular the ends of the respective edge faces F1, F2 opposite the respective maxima M of the invagination 20 are, in the cross-section, at distances 0.06 and 0.06 respectively from the half angle. .1.

In addition, each electrode 10a has a cylindrical electrode portion 16. As shown in FIG. The mantle region of the electrode 10a of the first discharge lamp 24, which is associated with the first luminance characteristic I1, is coated with a ceramic paste containing ZrO ₂ as its main component in order to increase the heat emission, The envelope region of the cylindrical electrode portion 16 of the electrode 10a has no structure. In contrast, the cylindrical electrode portion 16 of the electrode 10a of the second discharge lamp 24, which is associated with the second luminance characteristic I2, has a length T1=T2=0.8 mm and a width B=0.8 mm. It has a groove of 2 mm, and this groove is arranged in a region of length l1=15 mm along the longitudinal direction L of the cylindrical electrode portion 16, and the cylindrical Another area of the electrode portion 16 is provided with the ceramic paste described above. A comparison of the brightness I during the course of the burning period t shows that the first discharge lamp 24 without mantle structure is more degraded than the second discharge lamp 24 with mantle surface structure. Weaknesses can be seen. It is therefore particularly advantageous that the cylindrical electrode part 16 has no structure and has a ceramic coating that increases the heat dissipation, which is additionally very cost-effective in production, and therefore. preferable.

All in all, the electrode, which is capable of significantly improved heat dissipation and thus increased service life of the discharge lamp, by providing one or more conical regions with structures extending substantially perpendicular to the electrode axis A, Discharge lamps and methods of manufacture are provided.

10a, 10b electrode 10c anode 10d cathode 12 electrode base surface 14 conical electrode portion 14a surface 14b base surface 16 cylindrical electrode portion 18 groove structure 20 indentation 21 raised portion 22 further conical electrode portion 24 discharge lamp 26 discharge tube 28 discharge chamber A electrode Axis B Width of indentation B1, B2 Spacing F1 First edge surface F2 Second edge surface H Main extension direction of indentation H' Main extension direction of protuberance I Luminance I1, I2 Luminance characteristic L Longitudinal extension direction l1 first length of cylindrical electrode portion l2 second length of cylindrical electrode portion M maximum N minimum T1 first length of first edge region T2 second length of second edge region t Combustion period W Half angle α, β, γ, φ, φ1, φ2 Angle

Claims (14)

An electrode (10a, 10b, 10c, 10d) for a discharge lamp,
the electrodes (10a, 10b, 10c, 10d) have a longitudinal direction (L),
The electrodes (10a, 10b, 10c, 10d) have an electrode base surface (12) defining one end in the longitudinal direction (L) of the electrodes (10a, 10b, 10c, 10d),
The electrodes (10a, 10b, 10c, 10d) have an electrode axis (A) extending in the longitudinal direction (L),
The electrodes (10a, 10b, 10c, 10d) have a cross-section tapering in the longitudinal direction (L) along the electrode axis (A) in the direction of the electrode base surface (12). having an electrode portion (14);
said first electrode portion (14) having a surface (14a) and a plurality of indentations (20) provided in said surface (14a);
each indentation (20) extends at least partially about said electrode axis (A);
the surface (14a) forms a first angle (φ, φ1, φ2) greater than 0° and less than 90° with the electrode axis (A) in a cross-section along the electrode axis (A);
At the electrodes (10a, 10b, 10c, 10d),
Each invagination (20) extends in a respective main direction of extension (H, H') forming a respective second angle (β) with respect to said surface (14a) which is different from normal to said surface (14a). so that each indentation (20) is formed asymmetrically with respect to the normal to the surface (14a) when viewed in cross-section along the electrode axis (A),
Each of said main directions of extension (H, H') forms a third angle (γ) which is 90° with said electrode axis (A) in its theoretical extension in a cross section along said electrode axis (A). and
Each indentation (20) has a first edge surface (F1 ) and
Each indentation (20) has a second edge face (F2) facing said first edge face (F1), said second edge face (F2) extending from said surface (14a) extending to each of the minimum diameter portions (N) of each of the recesses (20) and on the far side from the electrode base surface (12);
A first angle (α1) between each first edge face (F1) and each main direction of extension (H, H′), each second edge face (F2) and each Electrodes (10a, 10b, 10c, 10d) characterized in that the second angles (α2) between the main directions of extension (H, H′) are of equal magnitude. Each of the recesses (20) has a main extending direction (H, H') extending from the surface (14a) toward the electrode axis (A) when viewed in cross section along the electrode axis (A). , formed so as to be inclined in the direction in which the electrode base surface (12) is inserted with respect to the perpendicular to the surface (14a),
Electrode (10a, 10b, 10c, 10d) according to claim 1. Each first length (T1) from the minimum diameter portion (N) to the surface (14a) of the first edge face (F1) in a cross section along the electrode axis (A) is than each second length (T2) from the minimum diameter portion (N) to the surface (14a) of the second edge face (F2) in a cross section along the electrode axis (A) short,
Electrode (10a, 10b, 10c, 10d) according to claim 1 or 2. the ratio of said first length (T1) to said second length (T2) is maximum 0.9 and/or minimum 0.6;
Electrode (10a, 10b, 10c, 10d) according to claim 3. The first edge surface (F1) and the second edge surface (F2) of each indentation (20) extend linearly in a cross section along the electrode axis (A), and intersecting at the minimum diameter portion (N) of each of the invagination portions (20),
A half angle (W) between the first edge surface (F1) and the second edge surface (F2) of each indentation (20) is the main extension direction in a cross section along the electrode axis (A). extending to (H, H')
Electrode (10a, 10b, 10c, 10d) according to claim 3 or 4. In a cross section along the electrode axis (A), the width (B) of each indentation (20) is equal to the first length (T1 ) shorter,
Electrode (10a, 10b, 10c, 10d) according to any one of claims 3 to 5. each first edge face (F1) of each indentation (20) directly abuts said second edge face (F2) of each said indentation (20);
Electrode (10a, 10b, 10c, 10d) according to any one of claims 1 to 6. Each first edge face (F1) of each indentation (20) is spatially separated from said second edge face (F2) of said indentation (20) and via a predetermined portion connected to said second edge face (F2);
Electrode (10a, 10b, 10c, 10d) according to any one of claims 1 to 6. said electrodes (10a, 10b, 10c, 10d) having a second electrode portion (16),
the first electrode portion (14) is arranged in the longitudinal direction (L) between the second electrode portion (16) and the electrode table surface (12);
Electrode (10a, 10b, 10c, 10d) according to any one of claims 1 to 8. said first electrode portion (14) being formed as a conical electrode portion (14),
the first electrode portion (14) is in contact with the second electrode portion (16) and the electrode base surface (12); or
The electrodes (10a, 10b, 10c, 10d) are conical with opening angles (φ, φ1, φ2) different from the opening angle of the first electrode portion (14) formed by the first angle. having a third electrode portion (22) of
The first electrode portion (14) is positioned between the second electrode portion (16) and the third electrode portion (22), or the third electrode portion (22) is positioned between the second electrode portion (16) and the first electrode portion (14);
Electrode (10a, 10b, 10c, 10d) according to claim 9. said second electrode portion (16) has, at least in some areas, a ceramic coating that enhances heat emission;
Electrode (10a, 10b, 10c, 10d) according to claim 9 or 10. said second electrode portion does not have an indentation (20);
Electrode (10a, 10b, 10c, 10d) according to any one of claims 9 to 11. Discharge lamp (24) with electrodes (10a, 10b, 10c, 10d) according to any one of claims 1 to 12. A method of manufacturing electrodes (10a, 10b, 10c, 10d) for a discharge lamp (24), comprising providing an electrode substrate,
the electrode substrate has a longitudinal direction (L),
The electrode substrate has an electrode base surface (12) defining one end of the electrodes (10a, 10b, 10c, 10d) in the longitudinal direction (L),
The electrode substrate has an electrode axis (A) extending in the longitudinal direction (L),
The electrode base has a first electrode portion (14) having a cross-section tapered in the direction of longitudinal extension (L) along the electrode axis (A) in the direction of the electrode base surface (12). ,
The first electrode portion (14) has a surface ( 14a), said surface (14a) being provided with a plurality of indentations (20) using a laser, whereby each indentation (20) extends at least partially about said electrode axis (A). exist,
in the method
Said each invagination (20) having a main direction of extension (H, H') is provided at a second angle (β) different from normal to said surface (14a), whereby each invagination ( 20), viewed in cross-section along said electrode axis (A), asymmetrically with respect to the normal to said surface (14a),
Each of said main directions of extension (H, H') forms a third angle (γ) which is 90° with said electrode axis (A) in its theoretical extension in a cross section along said electrode axis (A). and
Each indentation (20) has a first edge surface (F1 ) and
Each indentation (20) has a second edge face (F2) facing said first edge face (F1), said second edge face (F2) extending from said surface (14a) extending to each of the minimum diameter portions (N) of each of the recesses (20) and on the far side from the electrode base surface (12);
A first angle (α1) between each first edge face (F1) and each main direction of extension (H, H′), each second edge face (F2) and each A method, characterized in that the second angles (α2) with the main directions of extension (H, H′) are of equal magnitude.

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