Electric lamp and discharge devices – With luminescent solid or liquid material – With gaseous discharge medium
Reexamination Certificate
2002-04-15
2004-07-13
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
With gaseous discharge medium
C313S491000, C313S484000, C313S483000
Reexamination Certificate
active
06762549
ABSTRACT:
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.
BACKGROUND 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 (U.S. Pat. No. 5,604,410) 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.
DISCLOSURE 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 pl
Hitzschke Lothar
Vollkommer Frank
Clark Robert F.
Harper Holly
Patel Nimeshkumar D.
Pätent-Treuhand-Gesellschaft fuer elektrische Gluehlampen mbH
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