Title of Invention	DISCHARGE LAMP FOR DIELECTRICALLY IMPEDED DISCHARGES HAVING AN ARRANGEMENT OF SUPPORT ELEMENTS.
Abstract	A discharge lamp having a base plate (4), a top plate (3) for the light exit, which is at least partially transparent, a discharge space (6) between the base plate (4) and the top plate (3) for holding a discharge medium, and electrode set (5) for producing dielectrically impeded individual localized discharge regions (7) in the discharge medium, a dielectric layer between at least one part of the electrode set (5) and the discharge medium, and a plurality of support elements (1,2,12) which produce a connection between the base plate (4) and the top plate (3), characterized in that, the individual discharge regions (7) excepting those at the edges of the discharge space (6), are surrounded by in each case substantially identical patterns of support elements (1,2,12), wherein the support elements (1,2,12) constitute supporting projections which are constructed as unipartite components of the top plate (3).

Title of Invention

DISCHARGE LAMP FOR DIELECTRICALLY IMPEDED DISCHARGES HAVING AN ARRANGEMENT OF SUPPORT ELEMENTS.

Abstract

A discharge lamp having a base plate (4), a top plate (3) for the light exit, which is at least partially transparent, a discharge space (6) between the base plate (4) and the top plate (3) for holding a discharge medium, and electrode set (5) for producing dielectrically impeded individual localized discharge regions (7) in the discharge medium, a dielectric layer between at least one part of the electrode set (5) and the discharge medium, and a plurality of support elements (1,2,12) which produce a connection between the base plate (4) and the top plate (3), characterized in that, the individual discharge regions (7) excepting those at the edges of the discharge space (6), are surrounded by in each case substantially identical patterns of support elements (1,2,12), wherein the support elements (1,2,12) constitute supporting projections which are constructed as unipartite components of the top plate (3).

Full Text	Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH., Munich Discharge lamp for dielectrically impeded discharges having an arrangement of support elements Technical Field The invention outlined in this application relates to discharge lamps, specifically to those in which dielectrically impeded discharges burn during operation. In such discharge lamps, which are frequently denoted as silent discharge lamps, discharges are generated in a discharge medium with the aid of a set of electrodes. Dielectric impediment is produced by a dielectric layer between at least a part of the electrode set and the discharge medium, this part consisting at least of the anodes when the distribution of the tasks of the electrodes is fixed. Prior Art The details relating to silent discharge lamps need not be set forth here, because they belong to the prior art. Silent discharge lamps have recently been given increasing attention because it is possible with the aid of a special pulsed mode of operation (WO 94/23442) to achieve relatively high UV efficiencies that permit economic generation of visible light given the use of appropriate fluorescent materials. The invention relates both to UV radiators and to lamps with visible emission. Of particular interest in this case are flat discharge lamps which can be used, for example, for backlighting displays, monitors and similar devices. Such flat discharge lamps generally have a plate-like design, that is to say they have a base plate and a top plate which define a discharge space between them for the discharge medium. At least one of the plates must be designed for light emission, the top plate being considered here as at least partially transparent. Of course, the top plate can in this case bear a fluorescent material which is not itself transparent in the true sense. Because of the flat design, problems with mechanical stability arise in the case of relatively large formats of the flat discharge lamps. Consequently, it has become established to use support elements between the base plate and top plate. These support elements connect the two plates and thereby shorten the bending length between the outer edges of the plates on the paths between the support elements. In the outer region, the plates are generally connected via a frame enclosing the discharge space, which is not denoted as a support element here, although it also connects the plates and has a supporting function. The number of support elements is determined by the requirements placed on the loadability in bending and in compression, as well as by the format of the lamp, of course. Summary of the Invention The invention is based on the technical problem of specifying a silent discharge lamp of the type described at the beginning having an improved mechanical design. The invention provides for this purpose: a discharge lamp having a base plate, a top plate for the light exit, which is at least partially transparent, a discharge space between the base plate and the top plate, for holding a discharge medium, an electrode set for producing dielectrically impeded, individual localized discharges in the discharge medium, a dielectric layer between at least one part of the electrode set and the discharge medium, and a multiplicity of support elements which produce a connection between the base plate and the top plate, characterized in that, apart from those at the edges of the discharge space, the individual discharge regions are surrounded by in each case substantially identical patterns of support elements. The invention also relates to a display device with such a discharge lamp, for example to a flat display screen, a display or a similar device using LCD technology. The essential idea of the invention resides in not, as in the prior art, using the support elements in as small a number as at all possible but, on the contrary, distributing a relatively large number of support elements over the surface of the flat discharge lamp. The inventors have verified that, given appropriately more frequent support, it is possible to use comparatively thin base plates and top plates such that it is possible to realize a substantial weight saving for the overall lamp. The overall weight of the lamp is, however, of substantial importance for many applications. Moreover, in the case of relatively light plates the mounting method and automatic mounting devices possibly required therefor can be rendered substantially more simple and less expensive. Lighter plates are, moreover, associated with lower thermal capacitances, so that thermal cycles can be traversed more quickly, thus further simplifying the production. Moreover, it is of course also possible to achieve improved stability with a larger number of support elements. In this case, the support elements, which can themselves certainly be multipartite, but are preferably unipartite, are to be arranged in an assignment relating to individual localized discharges in the discharge space. It is firstly to be stated in this regard that the individual localized discharge structures have appeared with the already mentioned pulsed operating method even without this invention and were able to be permanently located by creating preferred sites on the electrodes. However, the invention is not restricted to lamps with such preferred sites. Rather, it transpires that the invention itself results in preferred locations between the support elements for individual discharges, so that for example conventional structures, for example nose-like projections on the cathodes, can also be less strongly pronounced. To the extent that individual discharge structures can be produced between the support elements according to the invention independently of the possible pulsed operating method, the invention also relates thereto. To the extent that this application talks of individual discharges or discharge structures, these statements relate, strictly speaking, to regions prescribed by the design of the lamp, in particular of the electrodes and the supporting projections, in which such individual discharge structures can burn. Depending on the operating state of the lamp, however, variously extended discharge structures are also conceivable in this case within these regions. Thus, the regions need not necessarily be filled entirely with a discharge structure. Above all, the desire can be to influence the size of the discharge structures in conjunction with dimming functions of the lamp. The statements in this application therefore relate to the regions which can be filled to the greatest extent with discharge structures. To the extent that electrode structures are provided for fixing preferred positions of discharges, there will generally be a 1:1 correspondence with the discharge regions. The assignment between supporting projections and individual discharge regions is to be present in the invention at least in so far as the individual discharge regions are respectively surrounded by identical patterns of directly adjacent supporting projections. This excludes, of course, discharge regions in the edge region of the discharge lamp, that is to say in the vicinity of the frame or the lateral closure of the discharge vessel. The aim in this case is to design the pattern of the directly adjacent supporting projections around a discharge region together with this discharge region so as already to homogenize the luminance here as far as possible. The relatively large number of supporting projections then does not play a disadvantageous role for the homogeneity (compare the above explanations on the overall design of the discharge lamp). Of course, individual supporting projections can be directly adjacent to more than one discharge region, and this will even be the rule. It is also preferred that the supporting projections for their part are surrounded as far as possible by the same pattern of directly adjacent discharge regions in each case. Moreover, the assignment between support elements and individual discharge regions is intended in the invention preferably to be present to such an extent that it is possible to find a plane through the discharge space between the base plate and top plate and a direction in this plane along which the support elements and the discharge regions alternate. The alternating row need not be a row alternating directly one after the other (according to the pattern ababab...). Also included is a row in which two support elements or two discharge regions occur regularly one after another as long as each support element and each discharge region has at least one discharge region or at least one support element as its neighbor (that is to say, for example, abbabbabb....or aabbaabb...). They need not necessarily be strictly collinear in this direction of the alternating row, but can also be distributed in a somewhat zigzag fashion. It is preferred for a multiplicity of such rows which are parallel to one another to exist in this plane. It is also preferred for there to be in the plane a second direction which is not situated parallel to the first-named direction and along which there is likewise an alternating row of support elements and discharge regions. In this case, there is preferably both a set of parallel rows in the first direction and a further set of parallel rows in the second direction. Consequently, the overall result is a planar pattern of support elements and discharge regions of alternating design, for example a chessboard pattern. Moreover, it is preferred in the above definition that the straight line along which the alternating row results connects the centers of directly adjacent discharge regions or discharge regions which are at most situated next but one or the centers of directly adjacent support elements or support elements situated next but one. A further idea of the invention consists in no longer, as in the prior art, understanding the support elements as optical disturbances in an overall discharge structure that is otherwise designed as homogeneously as possible. Rather, according to the invention the aim is to regard the support elements in their now relatively large number as an integral component of the structure responsible for the final luminance distribution. Consequently, the overall structure of the individual discharge regions is optimized together with the support elements and the optical modifications effected by them. In this case, as long as they are surrounded by a sufficiently large number of discharge regions, regularly occurring shadings can in principle be compensated just as effectively by diffusers or other homogenizing measures as was the case conventionally for the few support elements used. Moreover, as explained in more detail further below, the support elements can, however, themselves also be used for homogenization, for which purpose they preferably consist of optically transparent material. The supporting projections can certainly also be provided with a fluorescent coating, but they can also (by contrast with the remainder of the top plate) be entirely or partially free from fluorescent material, for example be wiped free subsequently. They can additionally be brightened up thereby, because the unavoidable extinction of the fluorescent layer is eliminated. For the above reasons, the invention provides that the support elements and the individual discharges, apart from edge effects of the lamp, in each case have substantially identical surroundings, that is to say, for example, all the support points are surrounded by an identical pattern of directly adjacent discharge regions, or vice versa. In the case of electrode sets with strip-shaped electrodes which, apart from local structures (preferred points for discharge regions), run more or less rectilinearly, it is preferred that the discharge regions on a respective side of a specific electrode strip are separated in each case by support elements, for example alternate in each case with support elements, that is to say support elements are provided in each case between the discharges. A particularly simple example is chessboard-like overall arrangements of support elements and discharge structures. The exemplary embodiments illustrate this, but also show a counter example. Overall, consideration is preferably given to intermediate distances between directly adjacent support elements which are 30 mm or less. In the case of typical dimensions of discharge paths and transverse extents of individual discharge structures, optically favorable and very stable support element patterns can be formed in this region. According to a further point of view of the invention, the support elements are designed as supporting projections in the sense of a unipartite component of the top plate, the outer contour tapering toward the base plate in at least one cutting plane perpendicular to the base plate. The invention is thereby delimited from conventional support elements which, in the relevant prior art normally had the form of glass balls separating the plates. The supporting projections, according to the invention, of the top plate can already be provided during the production of the top plate as a moulded element of the top plate, for example by thermoforming, pressing or another suitable shaping method. In principle, they can also be integrally moulded subsequently, although in this case they are to be designed in one piece with the top plate when the lamp is actually mounted, so that the previous substantial outlay for the positioning and fixing of separate support elements between the plates can be eliminated. The outlay on mounting would otherwise be substantial precisely with the large number of supporting projections according to the invention. However, by way of example, it can also be sensible for the purpose of fastening the supporting projections on the base plate to provide a connecting element - for example made from solder glass - between the base plate and the supporting projections. An integral production with the top plate is, of course, most favorable in this case. An advantage of this unipartite design with the top plate by contrast with being an integral part of the base plate resides in that the contact between a supporting projection and a plate unavoidably produces certain shadows in the luminance distribution which can impair the homogeneity and must be compensated. According to the inventors' findings, this compensation is easier the further removed the contacts causing the shadows are removed from the light emitting side of the top plate. This holds, in particular, in the case of the use of diffusers and other homogenizing elements on the top side or above the top plate. The greater the distance from such homogenizing elements, the better the possibilities of optical resolution of the shadows. The already mentioned tapering contour of the supporting projections should occur in at least one cross-sectional plane, the cross sectional plane running perpendicular to the base plate. The perpendicular orientation is to be defined locally in the case of a non-planar base plate. Because of the taper, the supporting projection is narrower in the direction along the plates just above the base plate than it is further removed from the base plate. This taper preferably effects the entire height of the supporting projection. However, not all the existing supporting projections need necessarily be provided with the shape explained here. These supporting projections that are slimmer in the region of the base plate at first exhibit relatively small shadow effects. In the case when the individual localized discharge structures are produced above the base plate, it is thereby possible also to keep a space free for the discharge structures by virtue of the fact that the latter can exist largely without being influenced by the supporting projections. The discharge structures can then be moved together with a way that is favorable for the homogeneity and be arranged with a high density with the aid of which high luminances can be generated. Finally, the tapering contour can also generate favorable optical properties of the top plate, something which will be described further in more detail. The favorable optical properties lead in the way already outlined at the beginning to the fact that the larger number of supporting projections contributes to the homogenizing as an integral component of the lamp design, and need not be understood as disturbance of a structure homogenized independently of the supporting projections. In order to avoid additional shadings and to utilize possible positive optical effects of the supporting projections, the latter preferably consist of an optically transparent material. However, they can in this case be coated entirely or partially with a fluorescent material, as is also the case with the remaining top plate. The supporting projections and the remainder of the top plate preferably consist of glass. The shaping of the supporting projections is preferably designed such that not only is a cross-sectional plane with a tapering cross section produced, but, moreover, there is also no cross-sectional plane in which the supporting projection widens too substantially in the direction of the base plate. When expressed in other words, this means that the outer surface of the supporting projections faces the discharge space of the base plate, in any case the important part of the outer surface. There can also be individual regions of the outer surface which run perpendicular to the base plate, but not over an important part of the circumference of the supporting projections. In this case, the outer surface extends from the base plate up to the top plate, and so there is no talk here of a small part region of the outer surface. The outer surface of the supporting projection is intended to form, in relation to a plane that cuts the supporting projection and runs at least locally parallel to the base plate between the top plate and the base plate, an angle of preferably at least 120°, better at least 130° and, in the most favorable case, 140° or more, this angle being defined in a cutting plane perpendicular to said plane and in the direction of the base plate. The angle thus refers, as an obtuse angle, to an outer surface of the supporting projection tipped toward the base plate. With such oblique outer surfaces, space for the discharges can still be created in the vicinity of the underside of the supporting projection adjacent to the base plate, on the one hand, but on the other hand these oblique outer surfaces are important for possible optical functions of the supporting projections. Specifically, when the supporting projections according to the invention are limited by the obliquely running outer surfaces described, through refraction of light impinging from the discharge space, or through appropriate alignment of the emission characteristics, of a fluorescent layer from the outer surface, they ensure an alignment of light into the core region of the supporting projections. It is thereby possible to counteract the shadows produced by the contact with the base plate. Furthermore, together with a pattern, prescribed by the electrode structure, of individual discharges it is possible to undertake an optimization to a luminance that is as homogenous as possible in an overall design of the arrangement of supporting projections and of the discharge structure. In addition to the shading effect of the contact between the supporting projection and base plate, it has also specifically to be taken into account that the individual discharge structures typically burn not below, but between supporting projections. Consequently, the maxima of the UV generation are likewise situated between the supporting projections. As a result of the effect of optical deflection, the light can be brought partly from these regions into the regions of the supporting projections so as to produce a relatively homogenous luminance on the top side of the top plate. The aspect of the invention addressed here is brought out more vividly by the exemplary embodiments. As already touched upon, the supporting projections are to taper in the direction of the base plate. It is optimal in this case when the supporting projections are as narrow as possible in the region of the contact with the base plate, the term "narrow" being measured in relation to the other dimensions of the supporting projection. "Narrow" is in this case a path forming a small fraction, for example less than 1/3, 1/4 or 1/5 of a typical transverse dimension (along the plates) of the supporting projection, for example half the height of the discharge space. This narrowness should be present in this case in at least one direction, but preferably in two directions in the "local" plane of the base plate. In other words, it can be a linearly narrow or approximately punctiform contact surface. Very generally, even in the case of somewhat larger bearing surfaces in relation to the base plate, the supporting projections can run substantially like ribs along the top plate, or be limited to small regions in relation to the dimensions of the plates. In the first- named case, it is the linear contact surfaces that are the general concern for narrow contact surfaces, while in the second case it is the approximately punctiform ones. The rib-like supporting projections can have specific stabilization functions, for example they can provide the top plate with an improved motability in bending in one direction. Furthermore, as will be explained in still further detail in the exemplary embodiments, they can also serve to separate specific regions in the discharge space from one another, in order to influence the discharge distribution. Thus, together with the electrode structure they can define preferred locations for individual discharges and separate individual discharges from one another along identical electrodes. On the other hand, the supporting projections limited locally in two directions in the plane of the plate offer the possibility of minimized shading effects, and are generally sufficient for the support function. A preferred shape for locally limited supporting projections can therefore be formed by a cone or by a pyramid, in the case of which the vertex touches the base plate (and is in this case possibly somewhat flattened off or rounded). In principle, any desired basic shapes come into consideration for the cones and pyramids, that is to say surfaces limited with any desired curves, polygonal surfaces or mixtures thereof. However, it is largely supporting projections without edges, that is to say cones, that are preferred, because the edges can lead to certain irregularities in the light distribution. As already stated, an attempt is to be made to keep the contact surfaces between supporting projections and base plate as small as possible. Limits can exist in this case that are set by production methods (rounding in the case of glass shaping) or by the mechanical point loading of the base plate, so that rather than a supporting projection actually coming to bear "in a pointed fashion" against the base plate, there is a slight rounding or flattening off. As long as this rounding or flattening off is not of any substantial consequence in relation to the size dimensions of the supporting projection, the basic idea of the narrowness is not thereby impaired. However, the preferred feature of the invention is to keep the contact surface between the supporting projection and the base plate as small as possible by virtue of the fact that it results only from bearing by touching. In other words, instances of bonding, solder glass and the like, which would necessarily enlarge the contact surface somewhat, are to be dispensed with as far as possible. For the rest, such additions usually have the disadvantage that they release gases upon heating during lamp production so that extensive pumping operations are required to keep the discharge medium pure. Production is substantially simplified if, in accordance with the invention, such substances are dispensed with. However, it is not excluded in the case of bearing by touching that the supporting projections can be pressed slightly into other layers that are required in any case, for example into reflection layers or fluorescent layers on the base plate. A similar statement can hold for a fluorescent coating of the supporting projections themselves. This bearing purely by touching between supporting projections and base plate generally suffices for the targeted stabilization effect, because mechanical stresses pressing the plates away from one another do not occur, as a rule. This holds, in particular, for the case, which is of most interest technically in any case, in which the discharge lamp is operated with a discharge medium at low pressure. The supporting projections are then pressed against the base plate by the external overpressure. Finally, in the case of this invention preference is given to such discharge lamps as are designed for bipolar operation, in the case of which the electrodes therefore function alternately as anodes and as cathodes. Owing to a bipolar operation, the discharge structures, which are inherently generally asymmetric, are superimposed on one another to form a symmetrical distribution on average over time, for which reason the optical homogenization can be further improved. Description of the Accompaying Drawings A more concrete description of the invention is given below with the aid of the exemplary embodiments. Individual features disclosed in this case can also be essential to the invention in combinations other than those represented. Moreover, the individual features in the present description and that which follows relate to aspects of the device and of the method of the invention. In detail: figure 1 shows a schematic plan view of an arrangement according to the invention of individual discharges and supporting projections; figure 2 shows a cross-sectional illustration of the arrangement of figure 1, along the line A-A in figure 1; figure 3 shows a plan view of an electrode set of a discharge lamp according to the invention, with symbolized contact points of the supporting projections with the base plate, specifically according to the arrangement of figures 1 and 2; figure 4 shows an illustration, corresponding to figure 1, of a second exemplary embodiment; and figure 5 shows an illustration, corresponding to figures 1 and 4, of a third exemplary embodiment. Figure 1 shows a schematic plan view of an arrangement of supporting projections and individual discharge regions that is like a chessboard. In this case, the circles denoted by 1 correspond to the circular shoulder of a supporting projection at the top plate 3 situated above in the cross-sectional view (A-A) in figure 2, which are represented as an edge in figure 2. The vertices of the conical supporting projections which point downward, that is to say toward the base plate 4, and therefore form the centers of the circles in figure 1, are denoted by 2. In this exemplary embodiment, the top plate 3 is a thermoformed glass plate. The contour of the top side of the top plate 3 is therefore shaped largely like the underside of the top plate 3. However, this is not absolutely necessary. The top side of the top plate 3 could also be flat (or have different shapes) . In addition to the points of view of the optical effect of the shape of the top plate 3, that is to say of the supporting projections, in particular, it is necessary in this case chiefly to consider criteria of favorable manufacturing capability. Figure 2 shows that the thermoformed conical supporting projections have lateral surfaces running relatively flat. In fact, the vertical dimension is illustrated in an exaggerated way in figure 2, so that the supporting projections are actually even flatter than they are portrayed to be. They define with a horizontal line an angle (to be understood toward the base plate) of substantially over 120°, for example of over 130° or even over 140°. The angle between these lateral surfaces and the base plate is therefore small, that is to say is below 60°, and preferably even below 50° or below 40°. Denoted by 5 in figure 1 are electrode strips in the case of which there is no difference between anodes and cathodes, which are therefore all separated by a dielectric layer from the discharge space formed between the top plate 3 and the base plate 4. The discharge space is denoted by 6 in figure 2. The electrode strips 5 have shapes that run in the form of zigzags or waves and are composed of rectilinear path segments. Short path segments of the electrode strips 5 between directly adjacent supporting projections are inclined relative to the main strip direction and ensure separation of the discharge regions, which are denoted by 7 in figures 1 and 2. If these segments were to be omitted, the discharge regions 7 would just touch. Between these oblique path segments, the electrode strips form indistinct saw tooth shapes in the vicinity of the discharge regions 7 themselves, the tip of the saw tooth being situated in the middle in each case. These electrode shapes are important for locating individual discharges in the region of the shortest discharge spacings, that is to say between corresponding projecting tips of the electrode strips 5. An individual discharge of variable extent which can also be divided into a plurality of discharge structures in some circumstances, will burn in each discharge region 7 in the case of this exemplary embodiment. The exemplary embodiment illustrates that both the supporting projections 1, 2, on the one hand, and the discharge structures 7, on the other hand, are surrounded in each case by identical directly adjacent arrangements (the individual discharges 7 or the supporting projections 1, 2). Positions arranged only at the edge of the discharge lamps are excluded therefrom. It is to be seen that the line of section A-A illustrated in figure 1 runs alternately through supporting projections 1, 2 and discharge structures 7. The illustration in figure 2 corresponds to this. The rectangular chessboard-like arrangement produces here a simple arrangement with a multiplicity of neighboring directions of these alternating rows, specifically four horizontal rows and seven vertical rows in the detail, drawn in figure 1, of a relatively large lamp structure. It is to be seen in figure 2 that the individual discharge structures 7 could also reach in the case of other electrode shapes as far as into the region below the supporting projections 1, 2 of the top plate 3. This also holds, in addition, for a section (not illustrated here) along a vertical line running in figure 1 through the supporting projection tips 2. The individual discharge structures 7 are reproduced in figure 1 by shapes that are almost square. In fact, the individual discharges 7 can assume other shapes. The electrode strips 5 illustrated here additionally have a course which, in addition to locally fixing the individual discharge structures, also exhibits good properties with reference to the dimming capability of the discharges, for which purpose reference is made to the two applications D 198 44 720 and DE 198 45 228. The dimming function is attended by a modification of the planar extent of the individual discharge structures 7, such that the latter can also be illustrated in a smaller fashion than in figures 1 and 2. It is to be seen, moreover, that the discharge structures 7, which are arranged between the same electrode strips 5, are separated from one another by the supporting projections 1, 2. Because of the separating function of the supporting projections 1, 2 the zigzag shape of the electrode strips 5 in this exemplary embodiment is also only comparatively slightly in evidence, specifically with reference to the discharge spacing, that is to say the spacing between the electrode strips 5. Figure 3 shows a plan view, corresponding to figure 1, of the base plate 4 with the set of electrodes 5. Illustrated here, however, is a complete discharge lamp in the case of which there are provided 21 vertical (in figure 3) and 15 horizontal (in figure 3) lines with respectively alternating rows of supporting projections 1, 2 and discharge structures 7. The plane of the base plate 4 is illustrated in figure 3, and so the supporting projections are shown only with their tips 2 in the approximate form of a point. For the sake of clarity, the discharge structures 7 are not illustrated, but are seated during operation of the discharge lamp as illustrated in figures 1 and 2. Figure 3 also shows that the electrode strips 5 are respectively alternately fed to a right-hand collective terminal 10 in figure 3 and a left-hand collective terminal 11 in figure 3, in order to be connected jointly thereby to an electronic ballast. Figure 3 also shows a frame-like structure 8 in the outer region of the base plate 4. Conventionally, use has been made here of glass frames separate from the base and top plates. In this exemplary embodiment, however, it is provided in a way similar to the design of the supporting projections 1, 2 that the * frame" 8 is likewise a projection of the top plate 3, not in the shape of a cone running down to a point, but as a rib. Here, the contact surface of the frame rib 8 with the base plate 4 has a certain width, because it is necessary there to provide a gastight connection between the top plate 3 and the base plate 4, for example by means of a solder glass. In addition, there are no disturbing shadow effects in this region, because it is in any case the edge at which the luminance is already decreasing. Situated outside the frame rib 8 in figure 3 is, moreover, a line 9 which shows the limit of the frame. The frame is bent up outside the rib 8. The electrode terminals (with bus structure) 10 and 11 illustrated outside, here, could also be accommodated in a protected fashion below the bent-up part. In addition, when dimensioning the frame rib 8 the thickness of the solder glass used for fastening must be taken into account with reference to the supporting projections, which only bear against it. The fluorescent coating is situated on the side of the top plate 3 facing the discharge space 6, that is to say on the underside of the top plate 3 in figure 2, and covers the top plate 3 completely inside the boundary illustrated in figure 3. The lateral surfaces of the supporting projections 1, 2 are therefore also covered with fluorescent material. Figure 4 shows a variant of figure 1 as a second exemplary embodiment. In this case, the same reference numerals are used for corresponding parts. The difference from the first exemplary embodiment in figures 1-3 consists in that the supporting projections have a ribbed nature, that is to say rest along a line. They are therefore denoted by 12 in this exemplary embodiment. It is shown by the auxiliary lines 13 that in this exemplary embodiment the supporting projections 12 bear in a linear fashion on the base plate 4 essentially above the electrode strips 5. The zigzag shape of the electrode strips 5 serves in this case to permit the electrode strips to look out alternately to the two sides below the respective supporting projection 12. Consequently, discharges 7 can burn between adjacent electrode strips, specifically precisely in the region of the electrode strips 5 that is not covered by the supporting projections. In this exemplary embodiment, adjacent discharge structures 7 preceding from a specific electrode strip 5 to a specific side are therefore also separated in each case by supporting projections. This feature relates, specifically, to the fact that the discharge structures cannot converge to a single discharge structure. This is ensured in the present case by virtue of the fact that the supporting projections 12 cover the electrode strips 5 between such adjacent individual discharges 7 (twice). By contrast therewith, the convergence of adjacent individual discharge structures 7 in the case of the preceding exemplary embodiment had been achieved by the spatial arrangement of the supporting projections 1, 2 between the discharge structures themselves, that is to say between their centroids. In addition, this exemplary embodiment differs from the preceding one in that the supporting projections are of corrugated design in the cross-sectional profile shown on the left in figure 4, and in this case come into contact with the base plate 4 in a somewhat rounded way. Owing to this rounded form of contact, the function of the separation between the discharge regions along the same electrode strip 5 can be better observed. In addition, in this cross-sectional illustration the vertical dimension (in the direction of a perpendicular to the base plate 4) is also illustrated in an exaggerated way. In fact, the structures run flatter. However, the minimum angle of 120° already repeatedly mentioned above is not given over the entire height of the supporting projections in this exemplary embodiment. The middle region of the supporting projections actually runs somewhat more steeply. The upper region and the lower region are, however, in the preferred angular range. Figure 5 shows a further exemplary embodiment. The lines drawn throughout with a stronger stroke represent electrode strips which are denoted, once again, by 5. Otherwise than in the first two exemplary embodiments, in this exemplary embodiment the electrode strips 5 have a shape that is slightly zigzagged, but otherwise continuously straight. Rather, after a "saw tooth period" of the electrode strips 5 intermediate segments are provided that run obliquely backwards. These intermediate segments are situated in this case in parallel and below rib-like supporting projections 12 which correspond in addition to those of the second exemplary embodiment in figure 4. The courses are once again indicated with the aid of auxiliary lines 13 and illustrated in the left-hand lower region of figure 5 in a cross-sectional profile along the line C-C. In this case, as well, the rib-like supporting projections 12 touch the base plate 4 in a somewhat rounded fashion. As a result, discharges can be effectively avoided at the pieces of the electrode strips 5 that are situated in the contact region between the supporting projection 12 and the base plate 4. This is particularly important in this exemplary embodiment, because there occur along the direction of the supporting projections 12 spaces between directly adjacent electrode strips 5 that are shorter than at the points at which the discharge structures 7 are actually intended to burn. Consequently, this somewhat rounded (or alternatively somewhat planar) bearing of the supporting projections 12 on the base plate 4 is favorable in this exemplary embodiment in order to "block" specific parts of the electrode strips 5. The vertical dimension is once again exaggerated in the sectional illustration. Here, as well, the actual structures are somewhat flatter. The statements relating to figure 4 hold for the angles defined by the supporting projections along their height. However, in the case of this embodiment the rounded lower regions of the supporting projections 12 are designed to be yet a little wider in order to be able to cover the corresponding segments of the electrode strips 5 effectively. A field of individual discharges 7 that is very dense by comparison with the chessboard arrangements of the first and of the second exemplary embodiments results from the particular shape of the electrode strips 5. In the sectional illustration in figure 5, the individual discharge 7 illustrated is cut at an oblique angle. By comparison with the sectional illustrations of the discharges in figures 2 and 4, it is therefore not raised from the substrate to the same extent. (As a rule, the invention deals not with surface discharges, but with discharges that burn in the volume of the discharge space and form arcs to some degree). In fact, however, in its middle region the discharge 7 is also spaced somewhat from the base plate 4, something which is no longer illustrated in the drawing. A common feature of all three exemplary embodiments is that a high degree of plate stability results from the arrangement of supporting projections that is exceptionally dense by comparison with conventional discharge lamps. Consequently, both the top plate 3 and the base plate 4 are of relatively thin-walled design. In addition, as illustrated in figure 3, it is provided in the exemplary embodiments that no separate frame is used between the base plate 4 and top plate 3. A drastically reduced outlay on mounting and substantially shortened processing times result from the unipartite design of the supporting projections with the base plate 3. In addition, the supporting projections illustrated in the exemplary embodiments have shapes that are essential to the invention in each case. In all the exemplary embodiments, they extend from the top plate 3 toward the base plate 4 in a tapering way, the taper taking place in the case of the rib-like supporting projections from the second and the third exemplary embodiments transverse to the rib direction, in each cross-sectional plane perpendicular to the plates in the case of the conical supporting projections 1, 2 from the first exemplary embodiment. In this case, in the first exemplary embodiment angles of 40° occur between the base plate 4 and the lateral surfaces of the supporting projections, the lateral surface of the supporting projections continuing to face the base plate 4 overall. This implies an angle of 140° between the lateral surface and the plane, already explained above, that is parallel to the base plate and runs through the discharge space, this angle of 140° being defined facing the base plate. When, as in these exemplary embodiments, the base plate 3 is coated together with the supporting projections 1, 2 and 12 with fluorescent material, the result of this is that the emission characteristics of the visible radiation are inclined so as to produce a brightening of the shadow caused by the contact with the base plate 4. Thus, light is reflected from the surroundings into the center of the supporting projection. It is also possible to provide by way of support in this case optically active structures on the top side or above the top plate 3. These optically active structures can be integrated in the top plate 3 or provided as a separate element. Even when the top plate 3 is not coated with a fluorescent material, refraction of light at the lateral surfaces, obliquely facing the base plate 4, of the supporting projections 1, 2 and 12 would produce a similar effect. In this case, the supporting projections are respectively surrounded by an arrangement, as uniform as possible, of discharge structures 7. In the case of the first exemplary embodiment, this is the case because each supporting projection 1, 2 picks up light contributions from four discharge structures 7 distributed uniformly around it and, apart from the edge of the discharge lamp, the supporting projections 1, 2 do not differ therein. In the case of the second exemplary embodiment in figure 4, the supporting projection ribs 12 are supplied with light contributions stemming from discharge structures 7 on both sides, there being an addition homogenization owing to the alternating arrangement. The third exemplary embodiment in figure 5 is further improved to the extent that in addition to the alternating arrangement the discharge structures are situated more densely, thus producing more discharge-free regions. We Claim 1. A discharge lamp having a base plate (4), a top plate (3) for the light exit, which is at least partially transparent, a discharge space (6) between the base plate (4) and the top plate (3) for holding a discharge medium, and electrode set (5) for producing dielectrically impeded individual localized discharge regions (7) in the discharge medium, a dielectric layer between at least one part of the electrode set (5) and the discharge medium, and a plurality of support elements (1, 2, 12) which produce a connection between the base plate (4) and the top plate (3), characterized in that, the individual discharge regions (7) excepting those at the edges of the discharge space (6), are surrounded by in each case substantially identical patterns of support elements (1, 2, 12), wherein the support elements (1, 2, 12) constitute supporting projections which are constructed as unipartite components of the top plate (3). 2. The discharge lamp as claimed in claim 1, wherein the support elements (1, 2, 12) are surrounded by in each case substantially identical patterns of discharge regions (7). 3. The discharge lamp as claimed in claim 1 or 2, wherein a direction (A - A, B - B, C - C) exists through the discharge space (6) in a plane between the base plate (4) and the top plate (3), and wherein the support elements (1, 2, 12), and the individual discharges (7) are disposed in alternate rows along said direction. 5. The discharge lamp as claimed in claim 3 or 4, wherein the electrode set (5) comprises a plurality of strip-shaped electrodes (5), and wherein the discharge structures (7) that are arranged on one and the same electrode strip (5) adjacent to the same side of the electrode strip (5) are separated in each case by a support element (1,2,12). 6. The discharge lamp as claimed in claim 4 and claim 5, designed in such a way that the support elements (1, 2) and the discharge structures (7) form a chessboard-tike configuration. 7. The discharge lamp as claimed in one of the preceding claims, wherein the maximum distance between directly adjacent support elements (1, 2, 12) is 30 mm. 8. The discharge lamp as claimed in one of the preceding claims, wherein the support elements (1, 2, 12) constitute supporting projections which are constructed as unipartite components of the top plate (3), and wherein the outer contour of the supporting projections taper in the direction from the top plate (3) toward the base plate (4) in at least one respective cutting plane (A - A, B - B, C - C) perpendicular to the base plate (4). 9. The discharge lamp as claimed in one of the preceding claims, wherein the supporting projections (1, 2, 12) substantially comprise transparent material. 10. The discharge lamp as claimed in claim 8 and claim 9, wherein relative to the discharge space (6), the supporting projections (1, 2, 12) have an outer surface which extends from the base plate (4) up to the top plate (3) at least substantially in a continuous fashion facing the base plate (4). 11. The discharge lamp as claimed in one of the preceding claims, wherein the outer surface of the supporting projections (1, 2, 12) forms an angle of at least 120° with a plane, wherein the plane cutting the supporting projections and running at least locally parallel to the base plate (4) between the top plate (3) and the base plate (4), and wherein the angle defined in a cutting plane being perpendicular to said plane and in the direction toward the base plate (4). 12. The discharge lamp as claimed in one of the preceding claims, wherein the contact between the base plate (4) and the supporting projections (1, 2, 12) at least in one direction is narrow in relation to the dimensions of the supporting projections. 13. The discharge lamp as claimed in claims 1 to 3, or 5 to 12, wherein the supporting projections (1,2) run like ribs along the top plate (3). 14. The discharge lamp as claimed in one of the preceding claims, wherein the supporting projections (1, 2) are limited along the top plate (3) to a respective region (1), the respective region (1) being small in relation to the dimensions of the top plate (3). 15. The discharge lamp as claimed in claim 14, wherein the supporting projections (1, 2) substantially take the form of cones of pyramids with vertices (2) touching the base plate (4). 16. The discharge lamp as claimed in one of the preceding claims, wherein the supporting projections (1, 2, 12) rest against the base plate (4). 17. The discharge lamp as claimed in one of the preceding claims, wherein the supporting projections (1, 2, 12) have a fluorescent coating on the outer surface facing the discharge space (6). 18. The discharge lamp as claimed in one of the preceding claims, wherein an optical diffusion element is provided on or above the light-emitting side. 19. The discharge lamp as claimed in one of the preceding claims, wherein the lamp is configured to be suitable for bipolar operation. 20. A display device comprising a discharge lamp as claimed in one of the preceding claims, the discharge lamp serving for backlighting the display device. A discharge lamp having a base plate (4), a top plate (3) for the light exit, which is at least partially transparent, a discharge space (6) between the base plate (4) and the top plate (3) for holding a discharge medium, and electrode set (5) for producing dielectrically impeded individual localized discharge regions (7) in the discharge medium, a dielectric layer between at least one part of the electrode set (5) and the discharge medium, and a plurality of support elements (1,2,12) which produce a connection between the base plate (4) and the top plate (3), characterized in that, the individual discharge regions (7) excepting those at the edges of the discharge space (6), are surrounded by in each case substantially identical patterns of support elements (1,2,12), wherein the support elements (1,2,12) constitute supporting projections which are constructed as unipartite components of the top plate (3).

Full Text

Patent-Treuhand-Gesellschaft
für elektrische Glühlampen mbH., Munich
Discharge lamp for dielectrically impeded discharges
having an arrangement of support elements
Technical Field
The invention outlined in this application relates to
discharge lamps, specifically to those in which
dielectrically impeded discharges burn during
operation. In such discharge lamps, which are
frequently denoted as silent discharge lamps,
discharges are generated in a discharge medium with the
aid of a set of electrodes. Dielectric impediment is
produced by a dielectric layer between at least a part
of the electrode set and the discharge medium, this
part consisting at least of the anodes when the
distribution of the tasks of the electrodes is fixed.
Prior Art
The details relating to silent discharge lamps need not
be set forth here, because they belong to the prior
art. Silent discharge lamps have recently been given
increasing attention because it is possible with the
aid of a special pulsed mode of operation (WO 94/23442)
to achieve relatively high UV efficiencies that permit
economic generation of visible light given the use of
appropriate fluorescent materials. The invention
relates both to UV radiators and to lamps with visible
emission. Of particular interest in this case are flat
discharge lamps
which can be used, for example, for backlighting
displays, monitors and similar devices. Such flat
discharge lamps generally have a plate-like design,
that is to say they have a base plate and a top plate
which define a discharge space between them for the
discharge medium. At least one of the plates must be
designed for light emission, the top plate being
considered here as at least partially transparent. Of
course, the top plate can in this case bear a
fluorescent material which is not itself transparent in
the true sense.
Because of the flat design, problems with mechanical
stability arise in the case of relatively large formats
of the flat discharge lamps. Consequently, it has
become established to use support elements between the
base plate and top plate. These support elements
connect the two plates and thereby shorten the bending
length between the outer edges of the plates on the
paths between the support elements. In the outer
region, the plates are generally connected via a frame
enclosing the discharge space, which is not denoted as
a support element here, although it also connects the
plates and has a supporting function. The number of
support elements is determined by the requirements
placed on the loadability in bending and in
compression, as well as by the format of the lamp, of
course.
Summary of the Invention
The invention is based on the technical problem of
specifying a silent discharge lamp of the type
described at the beginning having an improved
mechanical design.
The invention provides for this purpose: a discharge
lamp having a base plate, a top plate for the light
exit, which is at least partially transparent, a
discharge space between the base plate and the top
plate, for holding a discharge medium, an electrode set
for producing dielectrically impeded, individual
localized discharges in the discharge medium, a
dielectric layer between at least one part of the
electrode set and the discharge medium, and a
multiplicity of support elements which produce a
connection between the base plate and the top plate,
characterized in that, apart from those at the edges of
the discharge space, the individual discharge regions
are surrounded by in each case substantially identical
patterns of support elements.
The invention also relates to a display device with
such a discharge lamp, for example to a flat display
screen, a display or a similar device using LCD
technology.
The essential idea of the invention resides in not, as
in the prior art, using the support elements in as
small a number as at all possible but, on the contrary,
distributing a relatively large number of support
elements over the surface of the flat discharge lamp.
The inventors have verified that, given appropriately
more frequent support, it is possible to use
comparatively thin base plates and top plates such that
it is possible to realize a substantial weight saving
for the overall lamp. The overall weight of the lamp
is, however, of substantial importance for many
applications. Moreover, in the case of relatively light
plates the mounting method and automatic mounting
devices possibly required therefor can be rendered
substantially more simple and less expensive. Lighter
plates are, moreover, associated with lower thermal
capacitances, so that thermal cycles can be traversed
more quickly, thus further simplifying the production.
Moreover, it is of course also possible to achieve
improved stability with a larger number of support
elements.
In this case, the support elements, which can
themselves certainly be multipartite, but are
preferably unipartite, are to be arranged in an
assignment relating to individual
localized discharges in the discharge space. It is
firstly to be stated in this regard that the individual
localized discharge structures have appeared with the
already mentioned pulsed operating method even without
this invention and were able to be permanently located
by creating preferred sites on the electrodes. However,
the invention is not restricted to lamps with such
preferred sites. Rather, it transpires that the
invention itself results in preferred locations between
the support elements for individual discharges, so that
for example conventional structures, for example
nose-like projections on the cathodes, can also be less
strongly pronounced. To the extent that individual
discharge structures can be produced between the
support elements according to the invention
independently of the possible pulsed operating method,
the invention also relates thereto.
To the extent that this application talks of individual
discharges or discharge structures, these statements
relate, strictly speaking, to regions prescribed by the
design of the lamp, in particular of the electrodes and
the supporting projections, in which such individual
discharge structures can burn. Depending on the
operating state of the lamp, however, variously
extended discharge structures are also conceivable in
this case within these regions. Thus, the regions need
not necessarily be filled entirely with a discharge
structure. Above all, the desire can be to influence
the size of the discharge structures in conjunction
with dimming functions of the lamp. The statements in
this application therefore relate to the regions which
can be filled to the greatest extent with discharge
structures. To the extent that electrode structures are
provided for fixing preferred positions of discharges,
there will generally be a 1:1 correspondence with the
discharge regions.
The assignment between supporting projections and
individual discharge regions is to be present in the
invention at least in so far as the individual
discharge regions are respectively surrounded by
identical patterns of directly adjacent supporting
projections. This excludes, of course, discharge
regions in the edge region of the discharge lamp, that
is to say in the vicinity of the frame or the lateral
closure of the discharge vessel. The aim in this case
is to design the pattern of the directly adjacent
supporting projections around a discharge region
together with this discharge region so as already to
homogenize the luminance here as far as possible. The
relatively large number of supporting projections then
does not play a disadvantageous role for the
homogeneity (compare the above explanations on the
overall design of the discharge lamp). Of course,
individual supporting projections can be directly
adjacent to more than one discharge region, and this
will even be the rule. It is also preferred that the
supporting projections for their part are surrounded as
far as possible by the same pattern of directly
adjacent discharge regions in each case.
Moreover, the assignment between support elements and
individual discharge regions is intended in the
invention preferably to be present to such an extent
that it is possible to find a plane through the
discharge space between the base plate and top plate
and a direction in this plane along which the support
elements and the discharge regions alternate. The
alternating row need not be a row alternating directly
one after the other (according to the pattern
ababab...). Also included is a row in which two support
elements or two discharge regions occur regularly one
after another as long as each support element and each
discharge region has at least one discharge region or
at least one support element as its neighbor (that is
to say, for example, abbabbabb....or aabbaabb...).
They need not necessarily be strictly collinear in this
direction of the alternating row, but can also be
distributed in a somewhat zigzag fashion. It is
preferred for a multiplicity of such rows which are
parallel to one another
to exist in this plane. It is also preferred for there
to be in the plane a second direction which is not
situated parallel to the first-named direction and
along which there is likewise an alternating row of
support elements and discharge regions. In this case,
there is preferably both a set of parallel rows in the
first direction and a further set of parallel rows in
the second direction. Consequently, the overall result
is a planar pattern of support elements and discharge
regions of alternating design, for example a chessboard
pattern.
Moreover, it is preferred in the above definition that
the straight line along which the alternating row
results connects the centers of directly adjacent
discharge regions or discharge regions which are at
most situated next but one or the centers of directly
adjacent support elements or support elements situated
next but one.
A further idea of the invention consists in no longer,
as in the prior art, understanding the support elements
as optical disturbances in an overall discharge
structure that is otherwise designed as homogeneously
as possible. Rather, according to the invention the aim
is to regard the support elements in their now
relatively large number as an integral component of the
structure responsible for the final luminance
distribution. Consequently, the overall structure of
the individual discharge regions is optimized together
with the support elements and the optical modifications
effected by them. In this case, as long as they are
surrounded by a sufficiently large number of discharge
regions, regularly occurring shadings can in principle
be compensated just as effectively by diffusers or
other homogenizing measures as was the case
conventionally for the few support elements used.
Moreover, as explained in more detail further below,
the support elements can, however, themselves also be
used for homogenization, for which purpose they
preferably consist of optically transparent material.
The supporting projections
can certainly also be provided with a fluorescent
coating, but they can also (by contrast with the
remainder of the top plate) be entirely or partially
free from fluorescent material, for example be wiped
free subsequently. They can additionally be brightened
up thereby, because the unavoidable extinction of the
fluorescent layer is eliminated. For the above reasons,
the invention provides that the support elements and
the individual discharges, apart from edge effects of
the lamp, in each case have substantially identical
surroundings, that is to say, for example, all the
support points are surrounded by an identical pattern
of directly adjacent discharge regions, or vice versa.
In the case of electrode sets with strip-shaped
electrodes which, apart from local structures
(preferred points for discharge regions), run more or
less rectilinearly, it is preferred that the discharge
regions on a respective side of a specific electrode
strip are separated in each case by support elements,
for example alternate in each case with support
elements, that is to say support elements are provided
in each case between the discharges. A particularly
simple example is chessboard-like overall arrangements
of support elements and discharge structures. The
exemplary embodiments illustrate this, but also show a
counter example.
Overall, consideration is preferably given to
intermediate distances between directly adjacent
support elements which are 30 mm or less. In the case
of typical dimensions of discharge paths and transverse
extents of individual discharge structures, optically
favorable and very stable support element patterns can
be formed in this region.
According to a further point of view of the invention,
the support elements are designed as supporting
projections in the sense of a unipartite component of
the top plate, the outer contour tapering toward the
base plate in at least one cutting plane perpendicular
to the base plate. The invention is thereby delimited
from conventional support elements which, in the
relevant prior art normally had the form of glass balls
separating the plates. The supporting projections,
according to the invention, of the top plate can
already be provided during the production of the top
plate as a moulded element of the top plate, for
example by thermoforming, pressing or another suitable
shaping method. In principle, they can also be
integrally moulded subsequently, although in this case
they are to be designed in one piece with the top plate
when the lamp is actually mounted, so that the previous
substantial outlay for the positioning and fixing of
separate support elements between the plates can be
eliminated. The outlay on mounting would otherwise be
substantial precisely with the large number of
supporting projections according to the invention.
However, by way of example, it can also be sensible for
the purpose of fastening the supporting projections on
the base plate to provide a connecting element - for
example made from solder glass - between the base plate
and the supporting projections.
An integral production with the top plate is, of
course, most favorable in this case. An advantage of
this unipartite design with the top plate by contrast
with being an integral part of the base plate resides
in that the contact between a supporting projection and
a plate unavoidably produces certain shadows in the
luminance distribution which can impair the homogeneity
and must be compensated. According to the inventors'
findings, this compensation is easier the further
removed the contacts causing the shadows are removed
from the light emitting side of the top plate. This
holds, in particular, in the case of the use of
diffusers and other homogenizing elements on the top
side or above the top plate. The greater the distance
from such homogenizing elements, the better the
possibilities of optical resolution of the shadows.
The already mentioned tapering contour of the
supporting projections should occur in at least one
cross-sectional plane, the cross sectional plane
running perpendicular to the base plate. The
perpendicular orientation is to be defined locally in
the case of a non-planar base plate. Because of the
taper, the supporting projection is narrower in the
direction along the plates just above the base plate
than it is further removed from the base plate. This
taper preferably effects the entire height of the
supporting projection. However, not all the existing
supporting projections need necessarily be provided
with the shape explained here.
These supporting projections that are slimmer in the
region of the base plate at first exhibit relatively
small shadow effects. In the case when the individual
localized discharge structures are produced above the
base plate, it is thereby possible also to keep a space
free for the discharge structures by virtue of the fact
that the latter can exist largely without being
influenced by the supporting projections. The discharge
structures can then be moved together with a way that
is favorable for the homogeneity and be arranged with a
high density with the aid of which high luminances can
be generated. Finally, the tapering contour can also
generate favorable optical properties of the top plate,
something which will be described further in more
detail. The favorable optical properties lead in the
way already outlined at the beginning to the fact that
the larger number of supporting projections contributes
to the homogenizing as an integral component of the
lamp design, and need not be understood as disturbance
of a structure homogenized independently of the
supporting projections.
In order to avoid additional shadings and to utilize
possible positive optical effects of the supporting
projections, the latter preferably consist of an
optically transparent material. However, they can in
this case be coated entirely or partially with a
fluorescent material, as is also the case
with the remaining top plate. The supporting
projections and the remainder of the top plate
preferably consist of glass.
The shaping of the supporting projections is preferably
designed such that not only is a cross-sectional plane
with a tapering cross section produced, but, moreover,
there is also no cross-sectional plane in which the
supporting projection widens too substantially in the
direction of the base plate. When expressed in other
words, this means that the outer surface of the
supporting projections faces the discharge space of the
base plate, in any case the important part of the outer
surface. There can also be individual regions of the
outer surface which run perpendicular to the base
plate, but not over an important part of the
circumference of the supporting projections. In this
case, the outer surface extends from the base plate up
to the top plate, and so there is no talk here of a
small part region of the outer surface.
The outer surface of the supporting projection is
intended to form, in relation to a plane that cuts the
supporting projection and runs at least locally
parallel to the base plate between the top plate and
the base plate, an angle of preferably at least 120°,
better at least 130° and, in the most favorable case,
140° or more, this angle being defined in a cutting
plane perpendicular to said plane and in the direction
of the base plate. The angle thus refers, as an obtuse
angle, to an outer surface of the supporting projection
tipped toward the base plate. With such oblique outer
surfaces, space for the discharges can still be created
in the vicinity of the underside of the supporting
projection adjacent to the base plate, on the one hand,
but on the other hand these oblique outer surfaces are
important for possible optical functions of the
supporting projections.
Specifically, when the supporting projections according
to the invention are limited by the obliquely running
outer surfaces described, through refraction of light
impinging from the discharge space, or through
appropriate alignment of the emission characteristics,
of a fluorescent layer from the outer surface, they
ensure an alignment of light into the core region of
the supporting projections. It is thereby possible to
counteract the shadows produced by the contact with the
base plate.
Furthermore, together with a pattern, prescribed by the
electrode structure, of individual discharges it is
possible to undertake an optimization to a luminance
that is as homogenous as possible in an overall design
of the arrangement of supporting projections and of the
discharge structure. In addition to the shading effect
of the contact between the supporting projection and
base plate, it has also specifically to be taken into
account that the individual discharge structures
typically burn not below, but between supporting
projections. Consequently, the maxima of the UV
generation are likewise situated between the supporting
projections. As a result of the effect of optical
deflection, the light can be brought partly from these
regions into the regions of the supporting projections
so as to produce a relatively homogenous luminance on
the top side of the top plate. The aspect of the
invention addressed here is brought out more vividly by
the exemplary embodiments.
As already touched upon, the supporting projections are
to taper in the direction of the base plate. It is
optimal in this case when the supporting projections
are as narrow as possible in the region of the contact
with the base plate, the term "narrow" being measured
in relation to the other dimensions of the supporting
projection. "Narrow" is in this case a path forming a
small fraction, for example less than 1/3, 1/4 or 1/5
of a typical transverse dimension (along the plates) of
the supporting projection, for example half the height
of the discharge space. This narrowness should be
present in this case in at least one direction, but
preferably in two directions in the "local" plane of
the base plate. In other words, it can be a linearly
narrow or approximately punctiform contact surface.
Very generally, even in the case of somewhat larger
bearing surfaces in relation to the base plate, the
supporting projections can run substantially like ribs
along the top plate, or be limited to small regions in
relation to the dimensions of the plates. In the first-
named case, it is the linear contact surfaces that are
the general concern for narrow contact surfaces, while
in the second case it is the approximately punctiform
ones. The rib-like supporting projections can have
specific stabilization functions, for example they can
provide the top plate with an improved motability in
bending in one direction. Furthermore, as will be
explained in still further detail in the exemplary
embodiments, they can also serve to separate specific
regions in the discharge space from one another, in
order to influence the discharge distribution. Thus,
together with the electrode structure they can define
preferred locations for individual discharges and
separate individual discharges from one another along
identical electrodes. On the other hand, the supporting
projections limited locally in two directions in the
plane of the plate offer the possibility of minimized
shading effects, and are generally sufficient for the
support function.
A preferred shape for locally limited supporting
projections can therefore be formed by a cone or by a
pyramid, in the case of which the vertex touches the
base plate (and is in this case possibly somewhat
flattened off or rounded). In principle, any desired
basic shapes come into consideration for the cones and
pyramids, that is to say surfaces limited with any
desired curves, polygonal surfaces or mixtures thereof.
However, it is largely supporting projections without
edges, that is to say cones, that are preferred,
because the edges can lead to certain irregularities in
the light distribution.
As already stated, an attempt is to be made to keep the
contact surfaces between supporting projections and
base plate as small as possible. Limits can exist in
this case that are set by production methods (rounding
in the case of glass shaping) or by the mechanical
point loading of the base plate, so that rather than a
supporting projection actually coming to bear "in a
pointed fashion" against the base plate, there is a
slight rounding or flattening off. As long as this
rounding or flattening off is not of any substantial
consequence in relation to the size dimensions of the
supporting projection, the basic idea of the narrowness
is not thereby impaired.
However, the preferred feature of the invention is to
keep the contact surface between the supporting
projection and the base plate as small as possible by
virtue of the fact that it results only from bearing by
touching. In other words, instances of bonding, solder
glass and the like, which would necessarily enlarge the
contact surface somewhat, are to be dispensed with as
far as possible. For the rest, such additions usually
have the disadvantage that they release gases upon
heating during lamp production so that extensive
pumping operations are required to keep the discharge
medium pure. Production is substantially simplified if,
in accordance with the invention, such substances are
dispensed with. However, it is not excluded in the case
of bearing by touching that the supporting projections
can be pressed slightly into other layers that are
required in any case, for example into reflection
layers or fluorescent layers on the base plate. A
similar statement can hold for a fluorescent coating of
the supporting projections themselves.
This bearing purely by touching between supporting
projections and base plate generally suffices for the
targeted stabilization effect, because mechanical
stresses pressing the plates away from one another do
not occur, as a rule. This holds, in particular, for
the case, which is of most
interest technically in any case, in which the
discharge lamp is operated with a discharge medium at
low pressure. The supporting projections are then
pressed against the base plate by the external
overpressure.
Finally, in the case of this invention preference is
given to such discharge lamps as are designed for
bipolar operation, in the case of which the electrodes
therefore function alternately as anodes and as
cathodes. Owing to a bipolar operation, the discharge
structures, which are inherently generally asymmetric,
are superimposed on one another to form a symmetrical
distribution on average over time, for which reason the
optical homogenization can be further improved.
Description of the Accompaying Drawings
A more concrete description of the invention is given
below with the aid of the exemplary embodiments.
Individual features disclosed in this case can also be
essential to the invention in combinations other than
those represented. Moreover, the individual features in
the present description and that which follows relate
to aspects of the device and of the method of the
invention. In detail:
figure 1 shows a schematic plan view of an arrangement
according to the invention of individual discharges and
supporting projections;
figure 2 shows a cross-sectional illustration of the
arrangement of figure 1, along the line A-A in figure
1;
figure 3 shows a plan view of an electrode set of a
discharge lamp according to the invention, with
symbolized contact points of the supporting projections
with the base plate, specifically according to the
arrangement of figures 1 and 2;
figure 4 shows an illustration, corresponding to figure
1, of a second exemplary embodiment; and
figure 5 shows an illustration, corresponding to
figures 1 and 4, of a third exemplary embodiment.
Figure 1 shows a schematic plan view of an arrangement
of supporting projections and individual discharge
regions that is like a chessboard. In this case, the
circles denoted by 1 correspond to the circular
shoulder of a supporting projection at the top plate 3
situated above in the cross-sectional view (A-A) in
figure 2, which are represented as an edge in figure 2.
The vertices of the conical supporting projections
which point downward, that is to say toward the base
plate 4, and therefore form the centers of the circles
in figure 1, are denoted by 2.
In this exemplary embodiment, the top plate 3 is a
thermoformed glass plate. The contour of the top side
of the top plate 3 is therefore shaped largely like the
underside of the top plate 3. However, this is not
absolutely necessary. The top side of the top plate 3
could also be flat (or have different shapes) . In
addition to the points of view of the optical effect of
the shape of the top plate 3, that is to say of the
supporting projections, in particular, it is necessary
in this case chiefly to consider criteria of favorable
manufacturing capability.
Figure 2 shows that the thermoformed conical supporting
projections have lateral surfaces running relatively
flat. In fact, the vertical dimension is illustrated in
an exaggerated way in figure 2, so that the supporting
projections are actually even flatter than they are
portrayed to be. They define with a horizontal line an
angle (to be understood toward the base plate) of
substantially over 120°, for example of over 130° or
even over 140°. The angle between these lateral
surfaces and the base plate is therefore small, that is
to say is below 60°, and preferably even below 50° or
below 40°.
Denoted by 5 in figure 1 are electrode strips in the
case of which there is no difference between anodes and
cathodes, which are therefore all separated by a
dielectric layer from the discharge space formed
between the top plate 3 and the base plate 4. The
discharge space is denoted by 6 in figure 2. The
electrode strips 5 have shapes that run in the form of
zigzags or waves and are composed of rectilinear path
segments. Short path segments of the electrode strips 5
between directly adjacent supporting projections are
inclined relative to the main strip direction and
ensure separation of the discharge regions, which are
denoted by 7 in figures 1 and 2. If these segments were
to be omitted, the discharge regions 7 would just
touch. Between these oblique path segments, the
electrode strips form indistinct saw tooth shapes in
the vicinity of the discharge regions 7 themselves, the
tip of the saw tooth being situated in the middle in
each case. These electrode shapes are important for
locating individual discharges in the region of the
shortest discharge spacings, that is to say between
corresponding projecting tips of the electrode strips
5. An individual discharge of variable extent which can
also be divided into a plurality of discharge
structures in some circumstances, will burn in each
discharge region 7 in the case of this exemplary
embodiment.
The exemplary embodiment illustrates that both the
supporting projections 1, 2, on the one hand, and the
discharge structures 7, on the other hand, are
surrounded in each case by identical directly adjacent
arrangements (the individual discharges 7 or the
supporting projections 1, 2). Positions arranged only
at the edge of the discharge lamps are excluded
therefrom.
It is to be seen that the line of section A-A
illustrated in figure 1 runs alternately through
supporting projections 1, 2 and discharge structures 7.
The illustration in figure 2 corresponds to this. The
rectangular chessboard-like
arrangement produces here a simple arrangement with a
multiplicity of neighboring directions of these
alternating rows, specifically four horizontal rows and
seven vertical rows in the detail, drawn in figure 1,
of a relatively large lamp structure. It is to be seen
in figure 2 that the individual discharge structures 7
could also reach in the case of other electrode shapes
as far as into the region below the supporting
projections 1, 2 of the top plate 3. This also holds,
in addition, for a section (not illustrated here) along
a vertical line running in figure 1 through the
supporting projection tips 2. The individual discharge
structures 7 are reproduced in figure 1 by shapes that
are almost square. In fact, the individual discharges 7
can assume other shapes.
The electrode strips 5 illustrated here additionally
have a course which, in addition to locally fixing the
individual discharge structures, also exhibits good
properties with reference to the dimming capability of
the discharges, for which purpose reference is made to
the two applications D 198 44 720 and DE 198 45 228.
The dimming function is attended by a modification of
the planar extent of the individual discharge
structures 7, such that the latter can also be
illustrated in a smaller fashion than in figures 1 and
2. It is to be seen, moreover, that the discharge
structures 7, which are arranged between the same
electrode strips 5, are separated from one another by
the supporting projections 1, 2. Because of the
separating function of the supporting projections 1, 2
the zigzag shape of the electrode strips 5 in this
exemplary embodiment is also only comparatively
slightly in evidence, specifically with reference to
the discharge spacing, that is to say the spacing
between the electrode strips 5.
Figure 3 shows a plan view, corresponding to figure 1,
of the base plate 4 with the set of electrodes 5.
Illustrated here, however, is a complete discharge lamp
in the case of which there are provided 21 vertical (in
figure 3) and 15 horizontal (in figure 3) lines with
respectively alternating rows of supporting projections
1, 2
and discharge structures 7. The plane of the base plate
4 is illustrated in figure 3, and so the supporting
projections are shown only with their tips 2 in the
approximate form of a point. For the sake of clarity,
the discharge structures 7 are not illustrated, but are
seated during operation of the discharge lamp as
illustrated in figures 1 and 2. Figure 3 also shows
that the electrode strips 5 are respectively
alternately fed to a right-hand collective terminal 10
in figure 3 and a left-hand collective terminal 11 in
figure 3, in order to be connected jointly thereby to
an electronic ballast.
Figure 3 also shows a frame-like structure 8 in the
outer region of the base plate 4. Conventionally, use
has been made here of glass frames separate from the
base and top plates. In this exemplary embodiment,
however, it is provided in a way similar to the design
of the supporting projections 1, 2 that the * frame" 8
is likewise a projection of the top plate 3, not in the
shape of a cone running down to a point, but as a rib.
Here, the contact surface of the frame rib 8 with the
base plate 4 has a certain width, because it is
necessary there to provide a gastight connection
between the top plate 3 and the base plate 4, for
example by means of a solder glass. In addition, there
are no disturbing shadow effects in this region,
because it is in any case the edge at which the
luminance is already decreasing.
Situated outside the frame rib 8 in figure 3 is,
moreover, a line 9 which shows the limit of the frame.
The frame is bent up outside the rib 8. The electrode
terminals (with bus structure) 10 and 11 illustrated
outside, here, could also be accommodated in a
protected fashion below the bent-up part. In addition,
when dimensioning the frame rib 8 the thickness of the
solder glass used for fastening must be taken into
account with reference to the supporting projections,
which only bear against it. The fluorescent coating is
situated on the side of the top plate 3 facing the
discharge space 6, that is to say
on the underside of the top plate 3 in figure 2, and
covers the top plate 3 completely inside the boundary
illustrated in figure 3. The lateral surfaces of the
supporting projections 1, 2 are therefore also covered
with fluorescent material.
Figure 4 shows a variant of figure 1 as a second
exemplary embodiment. In this case, the same reference
numerals are used for corresponding parts. The
difference from the first exemplary embodiment in
figures 1-3 consists in that the supporting projections
have a ribbed nature, that is to say rest along a line.
They are therefore denoted by 12 in this exemplary
embodiment. It is shown by the auxiliary lines 13 that
in this exemplary embodiment the supporting projections
12 bear in a linear fashion on the base plate 4
essentially above the electrode strips 5. The zigzag
shape of the electrode strips 5 serves in this case to
permit the electrode strips to look out alternately to
the two sides below the respective supporting
projection 12. Consequently, discharges 7 can burn
between adjacent electrode strips, specifically
precisely in the region of the electrode strips 5 that
is not covered by the supporting projections.
In this exemplary embodiment, adjacent discharge
structures 7 preceding from a specific electrode strip
5 to a specific side are therefore also separated in
each case by supporting projections. This feature
relates, specifically, to the fact that the discharge
structures cannot converge to a single discharge
structure. This is ensured in the present case by
virtue of the fact that the supporting projections 12
cover the electrode strips 5 between such adjacent
individual discharges 7 (twice). By contrast therewith,
the convergence of adjacent individual discharge
structures 7 in the case of the preceding exemplary
embodiment had been achieved by the spatial arrangement
of the supporting projections 1, 2 between the
discharge structures themselves, that is to say between
their centroids.
In addition, this exemplary embodiment differs from the
preceding one in that the supporting projections are of
corrugated design in the cross-sectional profile shown
on the left in figure 4, and in this case come into
contact with the base plate 4 in a somewhat rounded
way. Owing to this rounded form of contact, the
function of the separation between the discharge
regions along the same electrode strip 5 can be better
observed. In addition, in this cross-sectional
illustration the vertical dimension (in the direction
of a perpendicular to the base plate 4) is also
illustrated in an exaggerated way. In fact, the
structures run flatter. However, the minimum angle of
120° already repeatedly mentioned above is not given
over the entire height of the supporting projections in
this exemplary embodiment. The middle region of the
supporting projections actually runs somewhat more
steeply. The upper region and the lower region are,
however, in the preferred angular range.
Figure 5 shows a further exemplary embodiment. The
lines drawn throughout with a stronger stroke represent
electrode strips which are denoted, once again, by 5.
Otherwise than in the first two exemplary embodiments,
in this exemplary embodiment the electrode strips 5
have a shape that is slightly zigzagged, but otherwise
continuously straight. Rather, after a "saw tooth
period" of the electrode strips 5 intermediate segments
are provided that run obliquely backwards. These
intermediate segments are situated in this case in
parallel and below rib-like supporting projections 12
which correspond in addition to those of the second
exemplary embodiment in figure 4. The courses are once
again indicated with the aid of auxiliary lines 13 and
illustrated in the left-hand lower region of figure 5
in a cross-sectional profile along the line C-C. In
this case, as well, the rib-like supporting projections
12 touch the base plate 4 in a somewhat rounded
fashion. As a result, discharges can be effectively
avoided at the pieces of the electrode strips 5 that
are situated in the contact region between the
supporting projection 12 and the
base plate 4. This is particularly important in this
exemplary embodiment, because there occur along the
direction of the supporting projections 12 spaces
between directly adjacent electrode strips 5 that are
shorter than at the points at which the discharge
structures 7 are actually intended to burn.
Consequently, this somewhat rounded (or alternatively
somewhat planar) bearing of the supporting projections
12 on the base plate 4 is favorable in this exemplary
embodiment in order to "block" specific parts of the
electrode strips 5.
The vertical dimension is once again exaggerated in the
sectional illustration. Here, as well, the actual
structures are somewhat flatter. The statements
relating to figure 4 hold for the angles defined by the
supporting projections along their height. However, in
the case of this embodiment the rounded lower regions
of the supporting projections 12 are designed to be yet
a little wider in order to be able to cover the
corresponding segments of the electrode strips 5
effectively.
A field of individual discharges 7 that is very dense
by comparison with the chessboard arrangements of the
first and of the second exemplary embodiments results
from the particular shape of the electrode strips 5. In
the sectional illustration in figure 5, the individual
discharge 7 illustrated is cut at an oblique angle. By
comparison with the sectional illustrations of the
discharges in figures 2 and 4, it is therefore not
raised from the substrate to the same extent. (As a
rule, the invention deals not with surface discharges,
but with discharges that burn in the volume of the
discharge space and form arcs to some degree). In fact,
however, in its middle region the discharge 7 is also
spaced somewhat from the base plate 4, something which
is no longer illustrated in the drawing.
A common feature of all three exemplary embodiments is
that a high degree of plate stability results from the
arrangement of supporting projections that is
exceptionally dense by comparison with conventional
discharge lamps. Consequently, both
the top plate 3 and the base plate 4 are of relatively
thin-walled design. In addition, as illustrated in
figure 3, it is provided in the exemplary embodiments
that no separate frame is used between the base plate 4
and top plate 3. A drastically reduced outlay on
mounting and substantially shortened processing times
result from the unipartite design of the supporting
projections with the base plate 3.
In addition, the supporting projections illustrated in
the exemplary embodiments have shapes that are
essential to the invention in each case. In all the
exemplary embodiments, they extend from the top plate 3
toward the base plate 4 in a tapering way, the taper
taking place in the case of the rib-like supporting
projections from the second and the third exemplary
embodiments transverse to the rib direction, in each
cross-sectional plane perpendicular to the plates in
the case of the conical supporting projections 1, 2
from the first exemplary embodiment. In this case, in
the first exemplary embodiment angles of 40° occur
between the base plate 4 and the lateral surfaces of
the supporting projections, the lateral surface of the
supporting projections continuing to face the base
plate 4 overall. This implies an angle of 140° between
the lateral surface and the plane, already explained
above, that is parallel to the base plate and runs
through the discharge space, this angle of 140° being
defined facing the base plate.
When, as in these exemplary embodiments, the base plate
3 is coated together with the supporting projections 1,
2 and 12 with fluorescent material, the result of this
is that the emission characteristics of the visible
radiation are inclined so as to produce a brightening
of the shadow caused by the contact with the base plate
4. Thus, light is reflected from the surroundings into
the center of the supporting projection. It is also
possible to provide by way of support in this case
optically active structures on the top side or above
the top plate 3.
These optically active structures can be integrated in
the top plate 3 or provided as a separate element.
Even when the top plate 3 is not coated with a
fluorescent material, refraction of light at the
lateral surfaces, obliquely facing the base plate 4, of
the supporting projections 1, 2 and 12 would produce a
similar effect. In this case, the supporting
projections are respectively surrounded by an
arrangement, as uniform as possible, of discharge
structures 7. In the case of the first exemplary
embodiment, this is the case because each supporting
projection 1, 2 picks up light contributions from four
discharge structures 7 distributed uniformly around it
and, apart from the edge of the discharge lamp, the
supporting projections 1, 2 do not differ therein. In
the case of the second exemplary embodiment in figure
4, the supporting projection ribs 12 are supplied with
light contributions stemming from discharge structures
7 on both sides, there being an addition homogenization
owing to the alternating arrangement. The third
exemplary embodiment in figure 5 is further improved to
the extent that in addition to the alternating
arrangement the discharge structures are situated more
densely, thus producing more discharge-free regions.
We Claim
1. A discharge lamp having a base plate (4), a top plate (3) for the light exit,
which is at least partially transparent, a discharge space (6) between the
base plate (4) and the top plate (3) for holding a discharge medium, and
electrode set (5) for producing dielectrically impeded individual localized
discharge regions (7) in the discharge medium, a dielectric layer between
at least one part of the electrode set (5) and the discharge medium, and a
plurality of support elements (1, 2, 12) which produce a connection
between the base plate (4) and the top plate (3), characterized in that,
the individual discharge regions (7) excepting those at the edges of the
discharge space (6), are surrounded by in each case substantially identical
patterns of support elements (1, 2, 12), wherein the support elements (1,
2, 12) constitute supporting projections which are constructed as
unipartite components of the top plate (3).
2. The discharge lamp as claimed in claim 1, wherein the support elements
(1, 2, 12) are surrounded by in each case substantially identical patterns
of discharge regions (7).
3. The discharge lamp as claimed in claim 1 or 2, wherein a direction (A - A,
B - B, C - C) exists through the discharge space (6) in a plane between
the base plate (4) and the top plate (3), and wherein the support
elements (1, 2, 12), and the individual discharges (7) are disposed in
alternate rows along said direction.
5. The discharge lamp as claimed in claim 3 or 4, wherein the electrode set
(5) comprises a plurality of strip-shaped electrodes (5), and wherein the
discharge structures (7) that are arranged on one and the same electrode
strip (5) adjacent to the same side of the electrode strip (5) are separated
in each case by a support element (1,2,12).
6. The discharge lamp as claimed in claim 4 and claim 5, designed in such a
way that the support elements (1, 2) and the discharge structures (7)
form a chessboard-tike configuration.
7. The discharge lamp as claimed in one of the preceding claims, wherein
the maximum distance between directly adjacent support elements (1, 2,
12) is 30 mm.
8. The discharge lamp as claimed in one of the preceding claims, wherein
the support elements (1, 2, 12) constitute supporting projections which
are constructed as unipartite components of the top plate (3), and
wherein the outer contour of the supporting projections taper in the
direction from the top plate (3) toward the base plate (4) in at least one
respective cutting plane (A - A, B - B, C - C) perpendicular to the base
plate (4).
9. The discharge lamp as claimed in one of the preceding claims, wherein
the supporting projections (1, 2, 12) substantially comprise transparent
material.
10. The discharge lamp as claimed in claim 8 and claim 9, wherein relative to
the discharge space (6), the supporting projections (1, 2, 12) have an
outer surface which extends from the base plate (4) up to the top plate
(3) at least substantially in a continuous fashion facing the base plate (4).
11. The discharge lamp as claimed in one of the preceding claims, wherein
the outer surface of the supporting projections (1, 2, 12) forms an angle
of at least 120° with a plane, wherein the plane cutting the supporting
projections and running at least locally parallel to the base plate (4)
between the top plate (3) and the base plate (4), and wherein the angle
defined in a cutting plane being perpendicular to said plane and in the
direction toward the base plate (4).
12. The discharge lamp as claimed in one of the preceding claims, wherein
the contact between the base plate (4) and the supporting projections (1,
2, 12) at least in one direction is narrow in relation to the dimensions of
the supporting projections.
13. The discharge lamp as claimed in claims 1 to 3, or 5 to 12, wherein the
supporting projections (1,2) run like ribs along the top plate (3).
14. The discharge lamp as claimed in one of the preceding claims, wherein
the supporting projections (1, 2) are limited along the top plate (3) to a
respective region (1), the respective region (1) being small in relation to
the dimensions of the top plate (3).

15. The discharge lamp as claimed in claim 14, wherein the supporting
projections (1, 2) substantially take the form of cones of pyramids with
vertices (2) touching the base plate (4).
16. The discharge lamp as claimed in one of the preceding claims, wherein
the supporting projections (1, 2, 12) rest against the base plate (4).
17. The discharge lamp as claimed in one of the preceding claims, wherein
the supporting projections (1, 2, 12) have a fluorescent coating on the
outer surface facing the discharge space (6).
18. The discharge lamp as claimed in one of the preceding claims, wherein an
optical diffusion element is provided on or above the light-emitting side.
19. The discharge lamp as claimed in one of the preceding claims, wherein
the lamp is configured to be suitable for bipolar operation.
20. A display device comprising a discharge lamp as claimed in one of the
preceding claims, the discharge lamp serving for backlighting the display
device.
A discharge lamp having a base plate (4), a top plate (3) for the light exit, which
is at least partially transparent, a discharge space (6) between the base plate (4)
and the top plate (3) for holding a discharge medium, and electrode set (5) for
producing dielectrically impeded individual localized discharge regions (7) in the
discharge medium, a dielectric layer between at least one part of the electrode
set (5) and the discharge medium, and a plurality of support elements (1,2,12)
which produce a connection between the base plate (4) and the top plate (3),
characterized in that, the individual discharge regions (7) excepting those at the
edges of the discharge space (6), are surrounded by in each case substantially
identical patterns of support elements (1,2,12), wherein the support elements
(1,2,12) constitute supporting projections which are constructed as unipartite
components of the top plate (3).

Documents:

IN-PCT-2002-471-KOL-(09-03-2010)-FORM-15.pdf

IN-PCT-2002-471-KOL-CORRESPONDENCE-1.1.pdf

IN-PCT-2002-471-KOL-CORRESPONDENCE.pdf

IN-PCT-2002-471-KOL-FORM 15.pdf

in-pct-2002-471-kol-granted-abstract.pdf

in-pct-2002-471-kol-granted-claims.pdf

in-pct-2002-471-kol-granted-correspondence.pdf

in-pct-2002-471-kol-granted-description (complete).pdf

in-pct-2002-471-kol-granted-drawings.pdf

in-pct-2002-471-kol-granted-examination report.pdf

in-pct-2002-471-kol-granted-form 1.pdf

in-pct-2002-471-kol-granted-form 18.pdf

in-pct-2002-471-kol-granted-form 2.pdf

in-pct-2002-471-kol-granted-form 3.pdf

in-pct-2002-471-kol-granted-gpa.pdf

in-pct-2002-471-kol-granted-priority document.pdf

in-pct-2002-471-kol-granted-reply to examination report.pdf

in-pct-2002-471-kol-granted-specification.pdf

in-pct-2002-471-kol-granted-translated copy of priority document.pdf

IN-PCT-2002-471-KOL-PA.pdf

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Patent Number

223422

Indian Patent Application Number

IN/PCT/2002/471/KOL

PG Journal Number

37/2008

Publication Date

12-Sep-2008

Grant Date

10-Sep-2008

Date of Filing

12-Apr-2002

Name of Patentee

PATENT-TREUHAND GESELLSCHAFT FUR ELEKTRISCHE GLUHLAMPEN MBH.

Applicant Address

HELLABRUNNER STR.1, D-81543 MUNCHEN

Inventors:

#	Inventor's Name	Inventor's Address
1	HITZSCHKE, LOTHAR	THEODOR-ALT-STR.6,D-81737 MUNCHEN
2	VOLLKOMMER FRANK	NEURIEDERSTR. 18, D-82131 BUCHENDORF, DEUTSCHLAND

PCT International Classification Number

H01J 61/30

PCT International Application Number

PCT/DE01/03408

PCT International Filing date

2001-09-05

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	100 44 186.8	2000-09-29	Germany