Patent Application
20130293101
The present invention relates to a discharge lamp, and in particular to a low-pressure discharge lamp, having a discharge vessel and a mercury filling therein, to a method for the production of such a discharge lamp and to its use.
In the case of low-pressure discharge lamps, to which the invention is not however restricted, a filling consisting of a base gas, for example a noble gas or a noble gas mixture, and a small amount of mercury, is provided in a glass discharge vessel. The mercury, which is in the vapor phase during operation, is then ionized by means of electrodes typically introduced at opposite sides of the discharge vessel, so that light generation takes place in a low-pressure plasma. The light, primarily emitted in the ultraviolet range at 254 and 185 nm, is then generally converted into visible light by a luminescent material provided internally on the discharge vessel, or is used directly.
It is an object of the present invention to provide a particularly advantageous configuration of a discharge lamp having a discharge vessel and a mercury filling therein. According to the invention, this object is achieved by a discharge lamp having
Such a discharge lamp thus has a discharge vessel in which a mercury filling is provided, and a splinter protection layer for holding discharge vessel wall fragments together in the event of fracture, the splinter protection layer being provided externally with respect to a wall of the discharge vessel. It furthermore has a contamination protection material for binding mercury in the event of fracture, which is provided internally with respect to the splinter protection layer. Thus, for example, if a mechanical shock acts on the discharge lamp, as a result of which the discharge vessel breaks, the splinter protection layer reduces or prevents free splinter formation, and thus reduces the number of loose discharge vessel wall fragments. To this end, the splinter protection layer, which may in this case also be perforated by splinters, is for example at least locally adjacent to the discharge vessel wall and then holds fragments adhering to the splinter protection layer together or, for instance, in the case of a splinter protection layer not adjacent to the discharge vessel, or not adhering thereon, it holds the fragments together in a volume.
The contamination protection material provided internally with respect to the splinter protection layer and externally with respect to the discharge vessel wall may, for example as a layer provided over a large area, absorb the mercury generally, that is to say independently of any specific fracture geometry, or as material provided pointwise it may absorb mercury when damage to the corresponding region occurs. In particular when the splinter protection layer is then put at particular risk, for example by edge formation, the lamp is thus additionally secured (contamination protection material provided over a large area can naturally also fulfill this function). A splinter protection layer undamaged in the event of discharge vessel fracture may furthermore delimit a volume for the interaction of the mercury with the contamination protection material, which makes the use of the latter particularly effective.
In the layer system according to the invention, the contamination protection material can thus advantageously be used on the one hand for additional safety, for instance when the splinter protection layer is damaged and mercury could escape; thus, the contamination protection layer provides safety in addition to sealing by the splinter protection layer. On the other hand, in the case of an undamaged splinter protection layer, this can also hold the mercury together in a restricted space, per se directly increases the safety and can furthermore promote effective binding of the mercury by the contamination protection material.
The contamination protection material may in this case be dosed in such a way that the amount of mercury contained in the discharge lamp is fully bound by the contamination protection material.
If the discharge vessel is provided in an additional translucent vessel, for example, for instance for aesthetic reasons in a hollow bulb in the form of a conventional incandescent bulb, the splinter protection layer may also be provided externally with respect to a wall of the additional vessel (and therefore also externally with respect to the discharge vessel wall); the contamination protection material may then, for example, be arranged between the two vessels or between the splinter protection layer and the additional vessel (and therefore inside the splinter protection layer).
In general, the splinter protection layer provided externally with respect to a discharge vessel wall may also extend onto other components of the discharge lamp, which is to say, for example, it is also provided at least locally on a lamp cap. Then, either the splinter protection layer per se may adhere directly on the cap or in order to improve the adhesion, for example, an additional adhesion promoter may also be provided so that detachment of the splinter protection layer from the cap and therefore escape of mercury, or loss of contamination protection material, is counteracted.
Preferred configurations of the invention are specified in the dependent claims. In this context, throughout the whole disclosure, distinction is not made in detail between the description of the discharge lamp and its production, or use; the disclosure is implicitly to be interpreted with respect to all categories.
In a first embodiment, the contamination protection material is at least partially provided on a cap of the discharge lamp. The cap may, for example, be fitted at the end of a tubular discharge vessel onto an electrode frame fused into the discharge vessel, in which case it allows mechanical fastening of the lamp in a light and electrical supply via contact pins or screw cap contacts.
The contamination protection material may, for example, be provided both on the discharge vessel and on the cap, which is then also covered by the splinter protection layer at least in these regions, or only on the cap (in turn correspondingly covered by the splinter protection layer), and thus, for instance, may then ensure a particularly stable splinter protection layer, and which cannot be destroyed by splinters under conventional conditions, only in the region of the cap, which can be deformed by mechanical action. Furthermore, with a contamination protection material provided on the cap, escape of mercury can also be prevented when, for instance, the electrode frame breaks and damage to the discharge vessel thus occurs close to an installation plate provided for potential separation of the contact pins, which is typically perforated for evaporation of cap cement and therefore itself does not prevent an escape of mercury.
In another configuration, a surface extent of the contamination protection material amounts to at least 25%, increasingly preferably in this order at least 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, of the discharge vessel wall outer surface; the two areas may also correspond to one another, and the surface extent of the contamination protection material may furthermore exceed the discharge vessel wall outer surface, if a cap is also coated. The contamination protection material is thus provided over a large area with a significantly greater extent in two dimensions, i.e. in the not necessarily planar surface, to which the size indications refer, than in the third dimension relating to the thickness. The contamination protection material is thus essentially distributed two-dimensionally. The surface extent is in this case considered as a sum, i.e. for example the contamination protection material may also be provided in the form of separate strips with a large area in total. Owing to the contamination protection layer provided over a large area, contact between contamination protection material and mercury, which can then be bound, takes place in the event of fracture substantially independently of the specific fracture geometry.
In another configuration, the surface extent of the contamination protection material, again configured as a sum, amounts to at most 5%, increasingly preferably in this order at most (4.5), 4, (3.5), 3, (2.5), 2, of the discharge vessel wall outer surface, so that, for instance, escape of mercury is prevented at a position with particularly high risk. On the other hand, in a volume delimited, preferably delimited in a sealed manner, by the splinter protection layer, a small area of the contamination protection material can also absorb the mercury, even fully over a prolonged period of time; by combination of the two layers, particularly sparing use of contamination protection material is therefore also possible.
In this configuration, furthermore, a contamination protection material which is not transmissive or is only partially transmissive for the light of the discharge lamp, for example, is also suitable because the light emitted in total is then scarcely affected owing to the small area.
The contamination protection material may, for example, also be applied in the form of a marking and thus additionally carry information, for instance about the lamp type, the series and/or the color temperature.
In another configuration, a splinter protection layer made of polymer material is provided, for instance of elastic silicone rubber, polyolefin, polyester, polycarbonate, crosslinked polyethylene (CPE), polymethyl methacrylate (PMMA) and/or poly(tetrafluoroethylene/hexafluoropropylene) (FEP). The polymer material may be selected as a function of the requirements so that a particularly scratch-resistant protection layer, which is therefore suitable for sealed containment of the splinters, may be formed, for instance from FEP.
In this case, in another configuration, an amalgam former and/or an oxidizing agent as a precursor of an amalgam former is provided as contamination protection material. An amalgam former is a metal which forms an alloy with mercury, with which the mercury then forms a single-phase or multiphase system.
In this case, tin and/or copper and/or silver and/or gold and/or zinc and/or indium is/are preferred as amalgam formers, in which case a gold compound and/or a silver compound may also more preferably be provided. For example, silver nitrate and/or silver carbonate may be provided as oxidizing agents, that is to say a precursor of the silver which then forms an alloy with the mercury.
As contamination protection material, however, it is also possible to provide an oxidizing agent which, after its reduction, does not constitute an amalgam former but itself forms a compound with the mercury. Sulfur, with which mercury forms stable mercury sulfides, is preferred as an oxidizing agent.
In another configuration, the contamination protection material is in particle form with an average particle size of less than 50 μm, increasingly preferably in this order less than 40, 30, 20, 10, 5, 3, 2, 1 μm. Owing to the particularly preferred particle size lying in the nanocrystalline range, for example, on the one hand the area available for the interaction with the mercury can be increased and, on the other hand, for instance, contamination protection layers which are improved in respect of their optical properties can also be produced. Thus, the transmission properties can be improved by reducing the average particle size, which for example also permits large-area application of the contamination protection material.
The invention also relates to a method for producing a corresponding discharge lamp, wherein the contamination protection material is provided on the discharge lamp in a first step, and the splinter protection layer is applied in a second step. In this way, in particular, it is also possible to facilitate the application of the contamination protection material, which for instance in the simplest case may be sprayed or spread on as a suspension; elaborate embedding of the contamination protection material in a matrix is not necessary.
The contamination protection material is then provided as a layer separate from the splinter protection layer, for instance as a layer in powder form between the discharge vessel and the splinter protection layer, and can thus be released or exposed in the event of discharge vessel fracture, and in this way can interact particularly effectively with the mercury.
The splinter protection layer may, for example, be produced by an extrusion method, which is suitable for instance for polycarbonate or FEP.
In another configuration, the contamination protection material is applied by an indirect printing method, in particular by a pad printing method. In this case, a pad takes a printing image, for instance a type designation to be applied, from an image plate and then adapts to the shape of the discharge lamp during the printing owing to its elastic properties. As printing material, for example, varnish with suspended particles, preferably suspended nanoparticles, may be provided.
The invention also relates to the use of a corresponding discharge lamp for the illumination of foodstuffs, for instance illumination in food production, and/or illumination in installations which are associated with food production, for example producing packaging material for foodstuffs.
Furthermore, the invention also relates to the use of a corresponding discharge lamp in an earthquake-proof building.
The invention will be explained in more detail below with the aid of exemplary embodiments; the individual features may also be essential to the invention in another combinations, and they implicitly refer to all categories of the invention.
The low-pressure discharge lamp 1 formed as a fluorescent lamp is constructed from a discharge vessel 2, which in this case is linearly tubular, into which electrode frames 3 are fused at two opposite end sides. The fluorescent lamp 1 is then held in a light by means of caps 4, likewise provided on the end side, and the electrode frames 3 are electrically contacted via contact pins 5 emerging from the caps 4.
A filling of noble gases and about 2 mg of mercury is provided in the volume 6 delimited in part by the inner wall surface 2a of the discharge vessel 2.
Adjacent to the outer wall surface 2b of the discharge vessel 2, there is a contamination protection layer 7 made of silver nitrate and silver carbonate particles with an average particle size of less than 1 μm. If fracture of the discharge vessel 2 occurs, the contamination protection layer 7 comes in contact with the volume 6 at least locally at fracture points; the silver nitrate or silver carbonate is reduced to silver, which then binds the mercury as an amalgam.
By an FEP splinter protection layer 8 adjacent to the outer side 7b of the silver nitrate/carbonate layer 7 and extending over the caps as far as their end sides, the individual splinters are held inside the volume delimited by the caps 4 and the splinter protection layer 8 in the event of fracture. The silver nitrate/carbonate present in excess with respect to the mercury can then likewise fully absorb the mercury restricted to this volume. During disposal, on the one hand the splinters are held together and, on the other hand, the mercury is bound. In order to improve the sealing by the splinter protection layer 8, an additional adhesion promoter may also be provided between the latter and the caps 4.
As an alternative to
In
In the discharge lamp according to
In the embodiment according to
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2011 002 634.7 | Jan 2011 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2011/073123 | 12/16/2011 | WO | 00 | 7/11/2013 |
