DE102018206770A1 - Electrode for a discharge lamp, discharge lamp and method for producing an electrode - Google Patents

Abstract

The invention relates to an electrode (10a, 10b, 10c, 10d) which has a longitudinal extension direction (L), an electrode plateau (12) delimiting the electrode (10a, 10b, 10c, 10d) in the longitudinal direction (L) and one in the longitudinal extension direction (L) extending electrode axis (A), and a first electrode portion (14) having a along the electrode axis (A) in the direction of the electrode plateau (12) tapered cross-section. In this case, the first electrode section (14) has a surface (14a) and a plurality of recesses (20) arranged in the surface (14a), the surface (14a) having a first angle (φ, φ1) in a cross section along the electrode axis (A) , φ2) greater than 0 ° and less than 90 ° with the electrode axis (A). Furthermore, a respective recess (20) extends with respect to the surface (14a) in a respective main extension direction (H, H ') which encloses with the surface (14a) a respective second angle (β) different from a right angle such that a respective recess (20) in the cross-section along the electrode axis (A) viewed asymmetrically with respect to a perpendicular to the surface (14a).

Description

The invention relates to an electrode for a discharge lamp, wherein the electrode has a longitudinal extension direction and an electrode plateau, which delimits the electrode at one end in its longitudinal direction. Furthermore, the electrode has an electrode axis extending in the longitudinal direction. In addition, in the longitudinal direction the electrode has a first electrode section with a cross section that tapers along the electrode axis in the direction of the electrode plateau. In addition, the first electrode portion has a surface and a plurality of recesses arranged in the surface, wherein a respective recess extends at least partially around the electrode axis and wherein the surface in a cross section along the electrode axis has a first angle greater than 0 ° and less than 90 ° with the Includes electrode axis. The invention also includes a discharge lamp with such an electrode and a method for producing an electrode for a discharge lamp.

The invention is in the field of electrodes for discharge lamps, in particular for DC discharge lamps, as used for example in imagesetters for the semiconductor industry or in cinema projectors. Such lamps operate with a mercury or a xenon plasma generated between two opposing electrodes, an anode and a cathode, which are usually surrounded by a quartz glass bulb. The thermal load in these lamps is often very large, so that it comes to evaporation of anode and cathode material, which is usually made of tungsten, possibly with additives. This often results in reduced light output due to two points: on the one hand, deformations and backburn of the electrodes can occur, which reduce the light output of the lamps in the reflector. On the other hand, the evaporated material can be deposited on the glass bulb of the lamp, which leads to a blackening, which also reduces the light output.

By reducing the temperature of the electrodes, especially in the near-plasma tip region, both deformation and evaporation can now be reduced. Thus, it is desirable to lower the electrode temperatures during lamp operation. For example, layers with a higher emissivity can be applied to the electrodes for this purpose. Examples of these are tungsten layers, such as in the EP 1047109 B1 described or ceramic layers, for example as in the US 8710743 B2 described. Further, for example, cathodes may be patterned, for example, by making grooves perpendicular to the surface by means of a laser, for example as shown in FIG JP 3838110 B2 described. As a result, the surface can be enlarged and increased radiation can be achieved.

Such grooves correspond to depressions which are recessed in relation to a defined surface. In addition, electrodes may for example have a cylindrical portion as well as a cone-shaped portion, wherein such a cone-shaped portion tapers in the direction of the electrode plateau, so corresponding to the surface of this conical portion in a cross section along the electrode axis an angle between 0 and 90 ° with the electrode axis includes. The grooves described can be introduced both in conical sections near the electrode plateau and on the lateral surface of cylindrical sections of electrodes.

The object of the present invention is to provide an electrode, a discharge lamp and a method for producing an electrode, which allow the most efficient possible lowering of the electrode temperature in lamp operation.

This object is achieved by an electrode, a discharge lamp and a method for producing an electrode having the features according to the respective independent patent claims. Advantageous embodiments of the invention are the subject of the dependent claims, the description and the figures.

An electrode for a discharge lamp according to the invention has a longitudinal direction of extension and an electrode plateau which delimits the electrode at one end in its longitudinal direction. In addition, the electrode has an electrode axis extending in the direction of longitudinal extent, wherein the electrode further has a first electrode section in the longitudinal direction with a cross-section that tapers in the direction of the electrode plateau along the electrode axis. In this case, the first electrode section has a surface and a plurality of recesses arranged in the surface, with a respective recess extending at least partially around the electrode axis. In addition, the surface includes in a cross section along the electrode axis a first angle greater than 0 ° and less than 90 ° with the electrode axis. Furthermore, a respective recess extends with respect to the surface in a respective main extension direction, which encloses with the surface a respective second angle different from a right angle, such that a respective depression in the cross section viewed along the electrode axis is perpendicular to the surface (FIG. 14a) is asymmetrically shaped.

The invention is based on the recognition that the previous structures oriented perpendicular to the surface, especially in the cone-shaped part of the electrodes, have the disadvantage that the heat input is increased by absorption of the radiation from the arc. In contrast, if the plurality of patterning recesses are not inclined perpendicular to the surface but at a different angle to the surface and, for example, perpendicular to the electrode axis, the plasma radiation will be reflected to a greater extent in the direction of the bulb. This improves the heat dissipation in the rear area of the lamp, that is to say in the direction of the holding elements and the base. Thus, as the respective recesses do not extend in their main extension direction at a right angle to the surface, but at a second angle such that the respective recesses are asymmetrically shaped with respect to a normal to the surface, ie, for example, inclined with respect to that perpendicular, a significantly more efficient one can be achieved Provide cooling of the electrode by these provided by the respective recesses grooves or structures. In addition, such structures or depressions, especially in the cone-shaped region of an electrode, give rise to further advantages, in particular over coatings for increasing the heat emission. Tungsten layers dissipate the heat only to a very inadequate extent. Although the ceramic layers have great advantages in terms of heat dissipation, they have the disadvantage that they are not as temperature-stable as, for example, tungsten layers. Critical temperatures are found especially near the electrode tips, in particular up to 2,700 degrees Celsius. Thus, there is an area close to the tip on both the anode side and the cathode side, which should not be coated with a ceramic, because otherwise it decomposes or evaporates during lamp operation. In addition, layer components can precipitate on the piston and reduce the transmission here. Critical temperatures for the coating can also occur when the lamp is ignited. If the hot arc, which has several 1000 degrees Celsius, on the coating, so this can be partially destroyed, resulting in the problems described above. Structured surfaces, ie the surface having the recesses, advantageously do not show this temperature sensitivity. Since the cone part of an electrode is usually arranged very close to the electrode plateau, it is particularly advantageous to provide such a structure-providing depression in this electrode section.

The perpendicular to the surface of the first electrode portion, with respect to which a respective recess is asymmetrically shaped, may be defined to pass through the center of a connecting line between two points of the surface, the two-sided edge points or boundary points of a respective recess viewed in cross-section through the electrode axis represent, this vertical is still perpendicular to this connecting line. If, for example, the depressions in the surface directly adjoin one another, a maximum is formed between each two depressions, which defines such an edge point. The surface of the first electrode section can, seen in cross-section, in part only consist of such edge points or edge regions. The main direction of extension can for example be defined so that it extends in cross section through the electrode axis through the center defined above connecting line between two points of the surface, the two-sided edge points or boundary points of a respective depression considered in cross section through the electrode axis represent, and by the minimum of considered in this cross section, wherein the minimum represents the point or area of the recess, which has the greatest distance from the surface or to the above-defined connecting line. Furthermore, this surface of the first electrode section preferably represents a conical surface.

The electrode may be generally formed as a cathode or an anode. Furthermore, the electrode is preferably formed rotationally symmetrical about the axis of rotation extending in the longitudinal direction. Furthermore, it is advantageous if the depressions not only partially but completely circulate the electrode axis, for example annularly. Thereby, the increased surface provided by the recesses can be maximized.

In addition, the electrode or at least the main body is preferably formed largely of tungsten, in particular substantially entirely of tungsten. In particular, the electrode or its basic body can be made entirely of tungsten, except for optional dopings of the tungsten material, for example thorium oxide, lanthanum oxide, zirconium oxide, carbon and / or potassium. The doping can for Example be less than 2%. By doping, for example, the electron emission of the electrode can be increased.

Moreover, the respective recesses may be formed such that the respective main extension directions in the cross section along the electrode axis, starting from the surface in the direction of the electrode axis, are inclined in a direction toward the electrode plateau with respect to the normal to the surface. Thus, for example, this results in a sawtooth-like surface structure with teeth, which are inclined away from the electrode plateau. This structure is particularly efficient with respect to the reflection of the plasma radiation.

In a further advantageous embodiment of the invention include the respective main extension directions in their theoretical extension in a cross section along the electrode axis with the electrode axis a third angle, between 70 ° and 110 °, preferably between 80 ° and 100 °. In this case, a region around 90 ° has proven to be particularly advantageous, so that it is particularly preferred if this third angle lies between 85 ° and 95 °, better still lies between 88 ° and 92 ° and particularly preferably is 90 °. It has been shown that the heat dissipation is optimal just when the recesses extend substantially perpendicular to the electrode axis. Therefore, by such a configuration of the recesses, which extend perpendicular to the electrode axis, or at least in an angular range near a right angle, the heat dissipation can be made particularly efficient.

In a further advantageous embodiment of the invention, a respective recess has a first flank surface, which extends from the surface to a minimum of the recess, for example rectilinear or curved, and which faces away from the electrode plateau, wherein a respective recess further one of the respective first Flank surface opposite second flank surface which extends from the surface to the respective minimum of the respective recess and which faces the electrode plateau, wherein a respective first length of the first flank surface from the minimum to the surface in a cross section along the electrode axis is smaller than a respective second Length of the second flank surface from the minimum to the surface in cross section along the electrode axis. Viewed in cross-section along the electrode axis, the respective recesses can thus extend, for example, sawtooth-like, for example, zigzag, the flanks facing the electrode plateau being longer than the flanks facing away from the electrode plateau, so that the recesses or webs ultimately formed are inclined away from the electrode plateau.

In particular, the minimum represents the point or region of the depression furthest away from the surface in a cross section along the electrode axis. The minimum of a depression thus preferably forms a line running around the electrode axis or a circumferential region.

It is furthermore particularly advantageous if the ratio of the first length to the second length is at most 0.9. If the ratio is greater than 0.9, the advantage of the reduced absorption of the plasma radiation compared to depressions aligned perpendicular to the surface is only marginally significant. By an aspect ratio smaller than 0.9, a particularly efficient reduction of the absorption can be provided.

Furthermore, it is preferred that the ratio of the first length to the second length is at least 0.6. As a result, a particularly efficient thermal emission can be achieved. This is due to the fact that substantially the region of the grooves contributes to the increased thermal emission, in which the two flank surfaces of two adjacent depressions, ie mutually facing flank surfaces of two adjacent depressions, still face each other, due to the black body radiation caused by the cavity thus formed. Thus, the smaller the ratio of the first length to the second length becomes, the more material has to be removed, without a further increasing positive influence on the emission behavior being established at a ratio smaller than 0.6.

In a further advantageous embodiment of the invention, the first and the second flank surface of a respective recess in the cross section along the electrode axis rectilinear and intersect at the minimum of the respective recess, wherein an angle bisector of the first and second flank surface of a respective recess in cross section along the electrode axis in the Main extension direction runs. The depressions can thus have a kind of inclined zigzag structure or triangular shape in their cross section, in which case the main extension direction of these depressions is defined by the bisecting line. Straight flank surfaces, in particular Considered with respect to the cross section along the electrode axis, manufacturing technology can be implemented particularly easily. In general, however, other shapes are conceivable.

Furthermore, it is particularly advantageous if, in cross section along the electrode axis, a width of a respective depression is smaller than the first length of the first flank surface of a respective depression, in particular wherein the width is at most half as large as the first length. If the height of the elevations or the corresponding depth between the depressions is significantly greater in relation to the structure width, an increased radiation can advantageously also be achieved, since an enlarged surface can thereby be provided.

However, the depressions do not necessarily have to be tapered to a minimum, but may also be more or less rounded. Therefore, it is also conceivable that the first flank region merges continuously in the minimum of the respective depression into the second flank region, so that the respective depression has a rounding in the region of the minimum. In the same way, this can also apply to the maxima located between two adjacently arranged depressions.

In a further advantageous embodiment of the invention, a respective first flank region of a respective depression directly adjoins the second flank region of the depression. In addition, adjacent wells can connect directly to each other. This embodiment has the great advantage that so many depressions can be arranged on the smallest possible surface, so that the largest possible surface for the radiation of heat is available through the depressions or through these provided structuring of the surface.

But here too, other embodiments are conceivable. For example, it can also be provided that a respective first flank region of a respective depression is spatially separated from the second flank region of the same or an adjacent depression and viewed with the second flank region of the same or adjacent depression over one, in particular in cross-section along the electrode axis straight or curved extending portion of the surface is connected. It is preferred that this section is still as short as possible, for example, as long as the width of a depression in order to provide the largest possible surface.

In a further advantageous embodiment of the invention, the electrode has a second electrode section, in particular a cylindrical electrode section, wherein the first electrode section is arranged in the longitudinal direction between the second electrode section and the electrode plateau. Theoretically, this second electrode section can also have corresponding elevations or depressions, at least in regions, on its lateral surface, which however is less preferred for reasons which will be described later.

Furthermore, it is preferred that the first electrode section is designed as a cone-shaped electrode section, that is to say as a cone or truncated cone. In this case, the first electrode section can adjoin the second electrode section and the electrode plateau. In other words, the electrode plateau represents the stump or the top surface of the cone-shaped first electrode portion, and moreover, the first electrode portion is the only cone-shaped electrode portion of the electrode. However, again other geometries are conceivable here, which may make sense for different process engineering reasons can. For example, the electrode may also have a plurality, preferably two, conical surfaces. In other words, the electrode may have a cone-shaped third electrode portion having an opening angle different from the opening angle of the first electrode portion provided by the first angle, wherein the first electrode portion is disposed either between the second electrode portion and the third electrode portion or the third electrode portion is disposed between the second electrode portion and the first electrode portion. The electrode can thus have a plurality of cone-shaped sections, which differ in their opening angle to each other. The recesses described in the context of the invention and its embodiments can be arranged in a corresponding manner on each of these several conical sections or even on a single one of these conical sections. For example, it may be provided that only the first cone-shaped electrode section has the recesses described, wherein this electrode section is arranged between the cylindrical second electrode section and the likewise cone-shaped third electrode section. In this way, for example, a protection of structuring, for example, in the connection with other lamp parts, can be provided.

Furthermore, it is advantageous if the second electrode section has a ceramic coating for increasing the heat emission, at least in one area. As a result, the heat dissipation can be further increased. In addition, the ceramic coatings are much more efficient in terms of heat dissipation than, for example, tungsten coatings. Furthermore, it is particularly advantageous if the ceramic coating, for example, a particle composite coating of a matrix layer and in the matrix layer embedded particles is formed. The substance providing the matrix layer may be provided by ZrO ₂ , for example. As embedded particles are especially tungsten particles. More preferably, the ceramic coating is at least 10% by volume formed from the ceramic substance, and the tungsten particles preferably provide between 2% and 40% by volume of the coating. Such a coating has been found to be particularly efficient in increasing heat emission. Other suitable matrix materials besides ZrO ₂ are others. The melting point of such materials should be as high as possible, preferably greater than 2,000 degrees Celsius, more preferably greater than 2,500 degrees Celsius. Suitable classes of materials include oxides, fluorides, carbides and nitrides, for example, MgF ₂ , SiC or AIN. However, ZrO _{2 has} proven to be particularly suitable for an oxidic matrix layer since it combines high mechanical stability with high transparency. The matrix gives stability to the metal structure of the embedded tungsten particles. This can be further increased by adding Y ₂ U ₃ and / or MgO. Alternatively, the matrix layer may consist only of Y ₂ U ₃ or MgO instead of ZrO ₂ .

A ceramic coating has especially in the cylindrical region of the electrode particularly great advantages, especially against the provision of structuring or elevations. First, the ceramic coating is much cheaper. In addition, however, a more efficient cooling of the electrode can be provided. In addition, since the cylindrical electrode portion is significantly further away from the electrode plateau than the conical electrode portion, the risk of damage to the coating due to excessive temperatures is not given or at least significantly reduced. Therefore, it is preferred that the largest possible area of the lateral surface of the cylindrical electrode section, for example at least 90% of the surface of the second electrode section, has such a ceramic coating.

Furthermore, it is therefore also particularly advantageous if, as is the case according to a further preferred embodiment of the invention, the second electrode section has no surface structures, that is to say no lasered groove structure or the like, since in this way the largest possible area for the ceramic coating is available.

Furthermore, the invention relates to a discharge lamp, in particular a high-pressure discharge lamp, with an electrode according to the invention or one of its embodiments. In particular, the discharge lamp may also have two of the electrodes according to the invention or two of their embodiments, wherein then preferably one of the electrodes is formed as an anode and one as a cathode.

The electrodes can be arranged in a lamp envelope of the discharge lamp, this lamp envelope being filled with a gas mixture. The discharge lamp can also be designed as the lamps described above. For example, the discharge lamp may be formed as a xenon short-arc lamp. Such a lamp, which is also called an OSRAM XBO® lamp, may generally be formed, for example, with a gas mixture containing a noble gas such as argon, xenon, krypton. OSRAM XBO® lamps emit light in the visible wavelength range and are used, for example, in classical and digital film projection. However, it is particularly advantageous if the discharge lamp is designed as a lamp with a mercury-comprising gas mixture, such as OSRAM HBO® lamps. The discharge lamp may be formed, for example, as a mercury short-arc lamp. Such lamps emit light at least partially in the UV range and can be used, for example, in the lithographic patterning of semiconductors. Since OSRAM HBO® lamps are usually located in a significantly higher price segment than OSRAM XBO® lamps, the use of the lifetime-enhancing electrode according to the invention or one of its embodiments is particularly profitable here.

In addition, the invention also relates to a method for manufacturing an electrode for a discharge lamp, wherein an electrode main body is provided, which has a longitudinal extension direction and an electrode plateau, which limits the electrode at one end in its longitudinal direction. In addition, the electrode base body has an electrode axis extending in the longitudinal extension direction and a first electrode section in the longitudinal extension direction with a cross section that tapers along the electrode axis in the direction of the electrode plateau. Further points the first electrode section has a surface that encloses in a cross section along the electrode axis a first angle greater than 0 ° and less than 90 ° with the electrode axis and in which a plurality of recesses are introduced by means of a laser, so that a respective recess at least partially around the electrode axis runs. Further, the respective recesses are attached with a main extension direction at a second angle to the surface other than a right angle, so that a respective recess in the cross section along the electrode axis is asymmetrically shaped with respect to a normal to the surface.

The advantages mentioned for the electrode according to the invention and its embodiments apply in the same way to the discharge lamp according to the invention and the production method according to the invention. In addition, the subject features mentioned in connection with the electrode according to the invention and its embodiments make possible the development of the production method according to the invention by further method steps.

Particularly preferably, the recesses are produced in the surface of the electrode body by means of ultra-short-time laser. The optional ceramic coating can be applied to the cylindrical portion of the electrode in subsequent steps or else beforehand by a suitable coating method, for example by sintering.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawing.

• 1 eine schematische Darstellung einer Elektrode für eine Entladungslampe gemäß einem Ausführungsbeispiel der Erfindung;
• 2 eine schematische Darstellung der Elektrode aus 1 in einem Querschnitt entlang der Elektrodenachse gemäß einem Ausführungsbeispiel der Erfindung;
• 3 eine schematische Darstellung eines konusförmigen Elektrodenabschnitts der Elektrode aus 1 in einem Querschnitt entlang der Elektrodenachse gemäß einem Ausführungsbeispiel der Erfindung;
• 4 eine schematische Darstellung einer Elektrode mit zwei konusförmigen Abschnitten in einer Seitenansicht gemäß einem weiteren Ausführungsbeispiel der Erfindung;
• 5 eine schematische Darstellung der Elektrode aus 4 in einem Querschnitt entlang der Elektrodenachse gemäß einem Ausführungsbeispiel der Erfindung;
• 6 eine schematische Detailansicht eines der konusförmigen Bereiche der Elektrode aus 4 gemäß einem Ausführungsbeispiel der Erfindung;
• 7 eine schematische Darstellung einer Entladungslampe gemäß einem Ausführungsbeispiel der Erfindung; und
• 8 eine graphische Darstellung des Verlaufs der Intensität in Abhängigkeit von der Brenndauer für zwei verschiedene Entladungslampen im Vergleich.

Showing:

• 1 a schematic representation of an electrode for a discharge lamp according to an embodiment of the invention;
• 2 a schematic representation of the electrode 1 in a cross section along the electrode axis according to an embodiment of the invention;
• 3 a schematic representation of a cone-shaped electrode portion of the electrode 1 in a cross section along the electrode axis according to an embodiment of the invention;
• 4 a schematic representation of an electrode with two cone-shaped sections in a side view according to another embodiment of the invention;
• 5 a schematic representation of the electrode 4 in a cross section along the electrode axis according to an embodiment of the invention;
• 6 a schematic detail view of one of the cone-shaped portions of the electrode 4 according to an embodiment of the invention;
• 7 a schematic representation of a discharge lamp according to an embodiment of the invention; and
• 8th a graphical representation of the course of the intensity as a function of the burning time for two different discharge lamps in comparison.

1 shows a schematic representation of an electrode 10a according to an embodiment of the invention. 2 shows the electrode 10a again in a cross section along the electrode axis A , The electrode 10a extends here in a longitudinal direction L and has an electrode plateau 12 on which the electrode at one end in its longitudinal direction L limited. The electrode axis A runs parallel to the longitudinal direction L , Preferably, the electrode 10a rotationally symmetric about the electrode axis A educated. In this example, the electrode has a cone-shaped first electrode section 14 and a cylindrical second electrode section 16 on. The cone-shaped electrode section 14 closes itself directly to the cylindrical electrode section 16 in the longitudinal direction L , wherein furthermore the electrode plateau 12 directly on the cone-shaped electrode section 14 in the longitudinal direction L borders. The cone-shaped surface 14a (please refer 3 ) of the cone-shaped electrode portion 14 close an angle φ with the electrode axis A one. This angle φ is greater than 0 ° and less than 90 °.

To improve the heat dissipation, the electrode 10a advantageously a groove structure 18 on, consisting of several wells 20 (please refer 3 ) is formed. Exemplary, the electrode 10a this groove structure in the cone-shaped electrode portion 14 on, and preferably not in the cylindrical electrode section 16 although this would be possible in principle. In the region of the cylindrical electrode section 16 , which in this example is about both the first part length 11 as well as the second part length 12 in the longitudinal direction L For example, a coating may be arranged to increase the heat emission, in particular a ceramic coating, such as, for example, a coating having a matrix of ZrO ₂ with tungsten particles embedded therein.

The groove structure 20 in the conical electrode section 14 will now be based on 3 described. 3 shows a schematic cross-sectional view of the conical electrode portion 14 , The conical electrode section 14 has a cone surface, namely the surface 14a , with several the groove structure 18 forming and in the surface 14a arranged depressions 20 on, for reasons of clarity, only two are provided with a reference numeral. Between every two wells 20 is thus a respective increase 21 opposite to a theoretical parallel to the surface 14a extending base area 14b formed, with this base area 14b , That is, in the illustrated cross section through the respective minima N the wells 20 runs, real does not represent an ideal cone-shaped surface, since the depressions 20 due to manufacturing tolerances are not the same depth. This groove structure 18 is thereby by short-term lasers in the surface 14a introduced, originally along the dashed line as a conical continuation of the cone-shaped surface, extending directly to the electrode plateau 12 connects, was formed. This original surface 14a then finally puts the in 3 shown envelope and the respective maxima M the wells 20 or surveys 21 These surveys 21 each now extend in a main direction of extension H' from the base 14b away, or in other words, the respective recesses extend from the surface 14a in the main extension direction H towards the electrode axis A , where the main directions of extension H . H' run parallel. Advantageously, close now the respective main extension directions H . H' with the surface 14a each one different from a right angle respective second angle β one, so that the surveys 21 with respect to a perpendicular to the surface 14a from the electrode plateau 12 are inclined. In particular, in this example, the respective main directions of extension H . H' oriented so that this with the electrode axis A a right angle here with too γ is included. In general, this angle can γ between 70 ° and 110 °, preferably between 80 ° and 100 °, and more preferably between 88 ° and 92 °.

This groove structure 18 In contrast to structures where such grooves are perpendicular to the surface 14a are oriented, the great advantage that the heat input through the discharge arc, which in the operation of a discharge lamp with such electrodes 10a between the respective electrode plateaus 12 runs, is significantly reduced, because a larger proportion of the radiation through the groove structure 18 reflected and not absorbed.

Furthermore, has a respective recess 20 one from the electrode plateau 12 remote and from a maximum M to the base area 14b or from the surface 14a to the minimum N running first flank surface F1 which in cross section along the electrode axis A a length from the maximum M to the base area 14b which is designated T1. In addition, has a respective recess 20 a corresponding second flank surface F2 on which the electrode plateau 12 is facing and also from a respective maximum M the depression 20 to the base area 14b or from the surface 14a to the minimum N extends and in the cross section along the electrode axis A a length from the maximum M to the base area 14b which is denoted by T2. In this example, the groove structure 18 designed as a sawtooth zigzag structure, so that the respective flank surfaces F1 . F2 in the cross section along the electrode axis A run straight and in the maximum M two adjacent wells 20 to cut. Furthermore, the depressions 20 formed such that an angle bisector W that measures the angle between the two flank surfaces F1 . F2 halved in the cross section shown, along the main extension direction H . H' and thus also perpendicular to the electrode axis A runs. The illustrated angles α1 and α2, ie between the respective flank surfaces F1 and F2 and the bisector W are equal. Furthermore, it has proved to be particularly advantageous if the ratio of the length T1 the first flank surface F1 to the second length T2 the second flank surface F2 in the range between 0.6 and 0.9. If this ratio is significantly greater than 0.9, the advantage of reduced plasma radiation absorption is significantly less significant. In addition, since the region of the grooves contributes to the increased thermal emission, in which the two legs, that is, the respective flank surfaces F1 . F2 , still facing each other, so on the length T1 contribute significantly, so it is advantageous if the ratio described above is greater than 0.6. Otherwise, all the more material has to be removed without having a positive influence on the emission behavior.

Incidentally, the aspect ratio can be T1 to T2 as follows depending on the angles α1 and α2 and φ to calculate: $$\text{T1 / T2}=\text{sin}\left(90°-\mathrm{\alpha }1-\mathrm{\phi }\right)/\text{sin}\left(90°-\mathrm{\alpha }1+\mathrm{\phi }\right),$$

In addition, it has proved to be advantageous, although the length-width ratio of a respective recess 20 has a certain minimum size. The width B a respective recess 20 can, for example, as in 3 shown, defined as the sum of the vertical distances of the respective maximum M opposite ends of the flank surfaces F1 . F2 from the bisector W , These distances are denoted by B1 and B2 respectively. It is particularly advantageous in particular if the ratio of the first length T1 the first flank surface F1 to the width B is at least 2.

The ratio of the first length T1 the first flank surface F1 to the width B can be, moreover, as follows depending on the angles α1, which is equal to the angle α2, and φ to calculate: $$\text{T1 / B}=\left[\text{sin}\left(90°-\mathrm{\alpha }1-\mathrm{\phi }\right)\cdot \text{sin}\left(90°-\mathrm{\alpha }1\right)\right]/\left[\text{sin}\left(90°-\mathrm{\phi }\right)\cdot \text{sin}\left(2\mathrm{\alpha }1\right)\right],$$

The following table shows various possible combinations of the angles α1 or α2 and φ , as well as the resulting conditions T1 / T2 and T1 / B illustrates: φ α1 = α2 T1 / T2 T1 / B 30 5 0.90 5.43 40 5 0.86 5.30 50 5 0.81 5.12 60 5 0.74 4.85 30 7.5 0.86 3.51 40 7.5 0.80 3.38 50 7.5 0.73 3.20 60 7.5 0.63 2.93 30 10 0.82 2.55 40 10 0.74 2.42 50 10 0.65 2.24 60 10 0.53 1.97 30 12.5 0.77 1.97 40 12.5 0.69 1.84 50 12.5 0.58 1.66 60 12.5 0.45 1.39

The length T2 is preferably in the range of 0.2 mm to 1.2 mm, preferably in the range of 0.5 mm to 1 mm. The preferred ranges for the first length T1 and the width B arise in accordance with the above-mentioned relationships.

The described structuring or groove structure 18 can be applied in a similar way for any surface whose normal is not perpendicular to the electrode axis A is oriented, ie in particular even if there is more than one conical surface, such as in 4 and 5 shown.

4 shows a schematic representation of an electrode 10b according to a further embodiment of the invention and 5 a cross section through this electrode 4 along the electrode axis A , In this example, the electrode points 10b So again a cylindrical electrode section 16 on, one in the longitudinal direction L subsequent first conical section 14 . as well as to this subsequent further conical section 22 , At this further conical section 22 In turn, the electrode plateau closes 12 in the longitudinal direction L at. These two conical sections 14 . 22 now close two different angles φ1 . φ2 with the electrode axis 1 one. In both of these conical sections 14 . 22 can turn corresponding groove structures 18 , how to 3 described, be arranged. This example is only in the middle conical section 14 between the cylindrical electrode section 16 and the further conical section 22 is arranged, such a groove structure 18 intended. This is in 6 shown again in a detail view. The respective depressions 20 that this groove structure 18 provide, in turn, extend in respective main directions of extension H , the respective bisectors W , as defined above, and which are perpendicular to the electrode axis A stand. Such a geometry may be useful for various process engineering reasons, for example structuring 18 to protect when connecting with other lamp parts.

Regarding the shaping of the depressions 20 As well as their arrangements to each other, there are many other advantageous possible embodiments. For example, the pits must be 20 not directly adjoin one another, but may for example also be separated from each other by a round or straight intermediate piece.

7 shows a schematic representation of a discharge lamp 24 , which is formed in this example as a high pressure discharge lamp in short arc technique. The discharge lamp 24 also has two electrodes 10c . 10d according to embodiments of the invention, one of which as an anode 10c and one as a cathode 10d is trained. This can be the cathode 10d and / or the anode 10c , how to 1 up to 6 described, be trained. The anode 10c is different from the cathode 10d in addition, by their shape, like out 7 is apparent. In particular, the anode has 10c preferably a larger diameter perpendicular to its electrode axis A which is preferably in the range between 1 and 4 centimeters, while the cathode 10d a smaller diameter perpendicular to the corresponding electrode axis A which is preferably in the range of less than or equal to 3 centimeters.

Furthermore, the discharge lamp 24 the usual for such a lamp components such as a discharge vessel 26 , a discharge room 28 , which is filled with a gas mixture and in which the electrodes 10c . 10d and other components. The discharge vessel 26 may for example be provided by a corresponding glass bulb. The gas mixture with which the discharge space 28 is filled, may contain, for example, mercury and / or one or more noble gases such as argon, xenon, krypton. Furthermore, the respective electrodes 10c . 10d corresponding electrode plateaus 12 on, which face each other, wherein further the anode 10c and the cathode 10d are arranged coaxially with each other so that their respective electrode axes A lie on a line.

8th time the course of the intensity I depending on the burning time t for two discharge lamps in comparison, wherein the intensity profile of a first discharge lamp 28 is designated according to a first embodiment of the invention with I1 and the intensity profile of a second discharge lamp 28 is designated by a second embodiment of the invention with I2. Both discharge lamps 28 were operated with an output of 13.5 kW. Also, the two discharge lamps each have an electrode 10a on, which has a cone-shaped electrode section 14 having, with recesses 20 as described above. The lengths T1 . T2 the respective flank surfaces F1 . F2 in cross section along the electrode axis A in this example T2 = 0.8 mm and T1 = 0.5 mm, and the width B as above 3 is defined as 0.16 mm, in particular wherein the respective maximum M a depression 20 opposite ends of the respective flank surfaces T1 . T2 in cross section of the bisectors have the respective distance 0.06 and 0.1.

In addition, the respective electrodes have 10a a cylindrical electrode section 16 on. In the jacket area of the electrode 10a the first discharge lamp 28 which the first intensity course I1 is assigned a Keramikbepastung to increase the heat emission, which contains ZrO2 as the main component, but has the cladding region of the cylindrical electrode portion 16 this electrode 10a no structuring on. In contrast, the cylindrical electrode section 16 the electrode 10a the second discharge lamp 10a which the second intensity curve I2 is assigned, grooves with lengths T1 = T2 = 0.8 mm and a width B of 0.2 mm in a portion of the cylindrical electrode portion 16 with an area length of 11 = 15mm along the longitudinal direction L are arranged, and in a wider region of the cylindrical electrode portion 16 the longitudinal direction L above-mentioned Keramikbepastung. Comparing the intensities I during the burning period t , it can be seen that the first discharge lamp 28 less structuring of the shell heavily degraded as the second discharge lamp 28 with structuring of the lateral surface. Accordingly, it is particularly advantageous, and therefore preferred, that the cylindrical electrode section 16 no structuring but a ceramic coating to increase the heat emission, which is also significantly cheaper to manufacture in addition.

Overall, such an electrode, a discharge lamp and a manufacturing method are provided by providing it substantially perpendicular to the electrode axis A extending structuring in one or more conical areas a significantly improved heat dissipation and thus allow an increase in the life of the discharge lamp.

LIST OF REFERENCE NUMBERS

10a

electrode

10b

electrode

10c

anode

10d

cathode

12

electrodes plateau

14

conical electrode section

14a

surface

14b

Floor space

16

cylindrical electrode section

18

groove structure

20

deepening

21

survey

22

another conical electrode section

24

discharge lamp

26

discharge vessel

28

discharge space

A

electrode axis

B

Width of the recess

B1

distance

B2

distance

F1

first flank surface

F2

second flank surface

H

Main extension direction of a depression

H'

Main extension direction of a survey

I

intensity

I1

intensity curve

I2

intensity curve

L

Longitudinal extension

11

first length of the cylindrical electrode portion

12

second length of the cylindrical electrode portion

M

maximum

N

minimum

T1

first length of the first flank area

T2

second length of the second flank area

t

burning time

W

bisecting

α

angle

β

angle

γ

angle

φ

angle

φ1

angle

φ2

angle

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1047109 B1 [0003]
• US 8710743 B2 [0003]
• JP 3838110 B2 [0003]

Claims (15)

Electrode (10a, 10b, 10c, 10d) for a discharge lamp, - wherein the electrode (10a, 10b, 10c, 10d) has a longitudinal direction of extension (L); - wherein the electrode (10a, 10b, 10c, 10d) has an electrode plateau (12) which bounds the electrode (10a, 10b, 10c, 10d) at one end in its longitudinal direction (L); - Wherein the electrode (10a, 10b, 10c, 10d) in the longitudinal direction (L) extending electrode axis (A) has; - wherein the electrode (10a, 10b, 10c, 10d) in the longitudinal direction (L) has a first electrode section (14) with a along the electrode axis (A) in the direction of the electrode plateau (12) tapered cross-section; - wherein the first electrode portion (14) has a surface (14a) and a plurality of recesses arranged in the surface (14a); - Wherein a respective recess extends at least partially around the electrode axis (A); and - wherein the surface (14a) in a cross-section along the electrode axis (A) includes a first angle (φ, φ1, φ2) greater than 0 ° and less than 90 ° with the electrode axis (A); characterized in that a respective recess (20) extends with respect to the surface (14a) in a respective main extension direction (H, H ') which encloses with the surface (14a) a respective second angle (β) different from a right angle, such that a respective depression in the cross-section along the electrode axis (A) is asymmetrically shaped as viewed perpendicular to the surface (14a). Electrode (10a, 10b, 10c, 10d) after Claim 1 characterized in that the respective recesses are shaped such that the respective main extension directions (H, H ') in the cross section along the electrode axis (A) viewed from the surface (14a) in the direction of the electrode axis (A) in one of the Electrode plateau (12) pointing direction relative to the perpendicular to the surface (14 a) are inclined. Electrode (10a, 10b, 10c, 10d) according to one of the preceding claims, characterized in that the respective main extension directions (H, H ') in their theoretical extension in a cross section along the electrode axis (A) with the electrode axis (A) has a third Include angle (γ) which is between 70 ° and 110 °, preferably between 80 ° and 100 °, and particularly preferably 90 °. Electrode (10a, 10b, 10c, 10d) according to one of the preceding claims, characterized in that a respective recess (20) has a first flank surface (F1) which extends from the surface (14a) to a minimum (N) of the recess (14). 20), and which faces away from the electrode plateau (12), and wherein a respective recess (20) has a second flank face (F2) opposite the respective first flank face (F1), which extends from the surface (14a) to the respective minimum (20). N) of the respective recess, and which faces the electrode plateau (12), wherein a respective first length (T1) of the first flank surface (F1) from the minimum (N) to the surface (14a) in a cross section along the electrode axis (A ) is smaller than a respective second length (T2) of the second flank surface (F2) from the minimum (N) to the surface (14a) in cross section along the electrode axis (A). Electrode (10a, 10b, 10c, 10d) after Claim 4 , characterized in that the ratio of the first length to the second length is at most 0.9 and / or at least 0.6. Electrode (10a, 10b, 10c, 10d) according to one of Claims 4 to 5 characterized in that the first and second flank surfaces (F1, F2) of a respective recess (20) are rectilinear in cross section along the electrode axis (A) and intersect at the minimum (M) of the respective recess (20), and wherein an angle bisector (W) of the first and second flank surface (F1, F2) of a respective recess (20) extends in cross section along the electrode axis (A) in the main extension direction (H, H '). Electrode (10a, 10b, 10c, 10d) according to one of Claims 3 to 6 characterized in that in cross-section along the electrode axis (A), a width (B) of a respective recess (20) is smaller than the first length (T1) of the first flank surface (F1) of a respective recess (20), in particular wherein the width (B) is at most half the size of the first length (T1). Electrode (10a, 10b, 10c, 10d) according to one of Claims 3 to 7 , characterized in that a respective first flank surface (F1) of a respective recess (20) immediately adjoins the second flank surface (F2) of the respective recess (20). Electrode (10a, 10b, 10c, 10d) according to one of Claims 3 to 8th , characterized in that a respective first flank surface (F1) of a respective recess (20) of the second flank surface (F2) of the recess (20) is spatially separated and with the second flank surface (F2) over a, in particular in cross-section along the electrode axis (A) rectilinear, section is connected. Electrode (10a, 10b, 10c, 10d) according to one of the preceding claims, characterized in that the electrode (10a, 10b, 10c, 10d) has a second electrode portion (16), in particular a cylindrical electrode portion (16), wherein the first Electrode portion (14) in the longitudinal direction (L) between the second electrode portion (16) and the electrode plateau (12) is arranged. Electrode (10a, 10b, 10c, 10d) after Claim 10 characterized in that the first electrode portion (14) is formed as a cone-shaped electrode portion (14) and wherein - the first electrode portion (14) adjoins the second electrode portion (16) and the electrode plateau (12); or - wherein the electrode (10a, 10b, 10c, 10d) has a cone-shaped third electrode portion (22) having an opening angle (φ, φ1, φ2), which is the opening angle of the first electrode portion (14) through the first Angle is provided, wherein the first electrode portion (14) between the second electrode portion (16) and the third electrode portion (22) is arranged or the third electrode portion (22) between the second electrode portion (16) and the first electrode portion (14 ) is arranged. Electrode (10a, 10b, 10c, 10d) according to one of Claims 10 or 11 in that the second electrode section (16) has a ceramic coating for increasing the heat emission at least in one area, in particular wherein the at least one area provides at least 90% of the surface area of the second electrode section (16). Electrode (10a, 10b, 10c, 10d) according to one of Claims 10 to 12 , characterized in that the second electrode section has no surface structures (18). Discharge lamp (28), in particular high-pressure discharge lamp, with an electrode (10a, 10b, 10c, 10d) according to one of the preceding claims. A method for producing an electrode (10a, 10b, 10c, 10d) for a discharge lamp (28), wherein an electrode base body is provided, - which has a longitudinal extension direction (L); - Having an electrode plateau (12) which limits the electrode (10 a, 10 b, 10 c, 10 d) at one end in its longitudinal direction (L); - Having in the longitudinal direction (L) extending electrode axis (A); - In the longitudinal direction of extension (L) has a first electrode section (14) with a along the electrode axis (A) in the direction of the electrode plateau (12) tapered cross-section; - wherein the first electrode section (14) has a surface (14a) which in a cross section along the electrode axis (A) includes a first angle (φ1, φ2) greater than 0 ° and less than 90 ° with the electrode axis (A) and in which a plurality of recesses (20) are introduced by means of a laser, so that a respective recess extends at least partially around the electrode axis (A); characterized in that the respective recesses are introduced with a main extension direction (H, H ') at a second angle (β) to the surface (14a) different from a right angle such that a respective recess in the cross section along the electrode axis (A) viewed asymmetrically with respect to a perpendicular to the surface (14a).

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