EP1320869B1 - Discharge lamp having capacitive field modulation - Google Patents

Abstract

The invention relates to the capacitive modulation of the field distribution in a silent discharge lamp 1 , by a structured, electrically conductive device 2 for definition of preferred locations for discharge structures in the lamp 1.

Description

Technical area

The present invention relates to a so-called silent discharge lamp, also called dielectric barrier discharge lamp, which is for dielectric disabled discharges is designed. To such a discharge lamp include a discharge vessel containing the discharge medium in which ignited and maintained via electrode discharges. silence Discharge lamps are operated with dielectrically impeded discharges, wherein at least a part of the electrodes is formed by a dielectric Layer is separated from the discharge medium. If the electrodes are specific are designed as cathodes and anodes, so for operation with are provided a uniform polarity, so must at least the anodes be separated from the discharge medium by this dielectric layer. In bipolar mode, all electrodes must be protected by a dielectric Layer separated from the discharge medium. Also a wall of the discharge vessel comes as such a dielectric layer into consideration. The discharge medium generally consists of a gas mixture and contains in usually noble gases, for example Xe.

State of the art

Incidentally, may be based on a relevant prior art and the specialist literature as far as silent discharge lamps are concerned in general are.

More specific prior art of interest to the present application is US 6,252,352 B1. This document describes silent discharge lamps with strip-shaped electrodes, in which in certain Distances projections are provided in order for individual discharge structures Defining preferred places. This should be an uncontrolled hiking or extinction and recurrence of such discharge structures avoided and the local distribution of the discharge structures in the Discharge space are arranged systematically. In the cited state of Technology is particularly concerned with increasing the homogeneity of the Luminance distribution in so-called flat radiators, so flat formed silent discharge lamps, mainly for backlighting ads various kinds of interest. It will also be on top of that older US Pat. No. 6,060,828.

However, it may also be desirable for other reasons, on the arrangement individual discharge structures in the discharge space influence to be able to.

Such individual discharge structures occur in silent discharge lamps especially when, according to the pulsed explained in WO94 / 23442 Operation is performed, with Δ-shaped single discharges arise. Depending on the operating parameters such discharges also occur widened and even form continuous "curtains", in Individual cases also be divided and the like. This is a question the electrode design and the various operating parameters of the discharge lamp. For the present invention, these details do not play any essential role. Incidentally, the invention is also directed to silent discharge lamps, which may be in circumstances other than in the mentioned WO-document also describes stable and localizable Forming discharge structures. The invention is thus not based on the teaching restricted to the W0 font.

JP 08 031386 shows a dielectrically impeded discharge lamp with three electrodes, of which a runs on the inside of the discharge vessel and to reduce the time required for the ignition of the discharge Minimum voltage is used. WO 98/26447 shows a dielectrically impeded discharge lamp a periodic structured cold cathode for generating free electrons with a ferroelectric. US 5,146,140 shows an electrodeless discharge lamp arranged in a discharge tube hollow cylindrical metal bands to prevent mercury build-up in the discharge vessel walls.

Presentation of the invention

The invention is based on the technical problem, the discharges in To influence discharge space so that an edge brightening can be achieved can. The invention is directed to such silent discharge lamps, which are extended in at least one direction, hereinafter referred to as Longitudinal direction is called. Of course, the expansion can also additionally present in a second direction, so be flat.

In general, the invention is defined as a discharge lamp for dielectric disabled discharges with one with a discharge medium filled discharge vessel and discharge electrodes, at least partially separated from the discharge medium by a dielectric layer are, wherein the discharge vessel at least along a longitudinal direction is extended, and with an electrically conductive and by the electrodes Gleichspannungsmäßig electrically insulated device that at least one of the electrodes is AC capacitively coupled, thereby in that the conductive device is outside the discharge vessel is arranged and designed by the capacitive Coupling to the electrode by the electric field between the electrodes defined equipotential lines along the longitudinal direction between Edge regions and center regions of the discharge vessel different to modulate that modulation through the capacitive Coupling to the brightening of the discharge lamp is used.

This invention is based on the finding that the distribution of Discharge structures in the discharge space not only by an inhomogeneous Design of the electrodes can achieve even. Rather, it will According to the invention, a device for capacitive influencing of the field distribution in the discharge space proposed by the electrodes (im DC sense) is galvanically isolated. The electrodes can therefore a have completely uniform shape, for example, be straight stripes (they are but not limited to uniform configurations). As the operating frequencies of dielectrically impeded discharges anyway relatively high lie, can be achieved by a capacitive coupling of the invention Establish an AC-influencing the field distribution. It can be imagined that the invention Device for capacitive influencing (hereinafter capacitive Called device) with respect to the or the electrodes or the Discharge space forms AC taps. This distorts the capacitive means the equipotential lines in the discharge space.

This is done according to the invention preferably in one along the extent the discharge lamp in the longitudinal direction oscillating manner. there is circumscribed by the term "oscillating" that the equipotential lines distorted, so to speak, in a sense that runs "up and down" or "back and forth" become. This oscillatory distortion can but need not be periodic be. However, a periodic modulation of the equipotential lines forms a preferred case.

From the cited prior art it is already clear that the individual Arrange discharge structures depending on the field distribution. Due to the distortion of the equipotential lines according to the invention Preferred places are given for discharge structures with which themselves in the desired manner, a specific arrangement of the discharge structures make sure. The capacitive device thus forms an alternative to the structuring cited in the prior art described the electrodes themselves. The invention can thus, for example, of Be interested in avoiding electrode structuring, for example because to simplify the manufacturing process or because of bad Accessibility of the spaces provided for the electrodes homogeneously continuous Offer electrodes. Moreover, the invention requires Capacitive device, which consist of electrically conductive material must, no significant technical effort and in particular Also be mounted outside of the discharge vessel, this does not have touch once.

With the invention, therefore, special structuring of the electrodes dispensed with the generation of preferential places for discharge structures become. However, such structuring is not excluded. Especially Such structuring can be achieved by the invention Measures corrected, supplemented or, if desired, compensated.

In particular, the modulation according to the invention serves to brighten the edges, for which reference is made to the embodiments.

So it is not absolutely necessary that the modulation by the capacitive Device in a one-to-one correspondence to the discharge structure distribution is adapted. However, it is preferred that the capacitive modulation on the spacings between the discharge structures is adjusted. However, this can also be the case that, for example, the capacitive Modulation is equal to multiple of the intermediate discharge distances, where within these multiple intervals an intermediate subdivision by others Measures is provided. The adaptation of the oscillation length scale The intermediate distances should also be understood in this sense.

According to the invention, a length range of at most 6 times, better 5 times, 4 times or even more than 3 times the discharge distance as the preferred range for this oscillation length scale.

The capacitive device may be provided two or more times to Discharge Vorzugsplätze from different sides of the discharge vessel from "impress". Of course, a capacitive device (s) can also the equipotential lines in the region of two or more electrodes influence. According to the invention, it is preferred that the capacitive device is provided at least twice in the sense of two parts and the Means or parts of the device both Elektrodenpolaritäten the Capture lamp. This is especially true for bipolar operated discharge lamps advantageous because it generally offers, the cathodes or the Range of cathodes to provide with preferred places for discharges, because There the discharges are more localized than in the area of the anodes. In bipolar operation, all electrodes operate in certain phases of operation as cathodes. It also works with two capacitive devices or two parts of such a light holders for a discharge lamp construct, which would be necessary anyway and thus for the invention necessary effort on a suitable structuring of the brackets restrict. For this purpose, reference is made to the example of Figure 2.

Preferably, this modulation is over substantially the entire extent the discharge lamp is present at least in the one longitudinal direction and furthermore preferably at least over this entire length in the essential periodically. As a result, in these discharge lamps in usually substantial homogeneity of the luminance distribution can be achieved.

If according to the invention the capacitive device is arranged outside the discharge vessel and the electrodes, i. at least the electrodes in the range of capacitive Device, preferably within the discharge vessel, so it is already the previously addressed galvanic separation given. Of course, even outside the discharge vessel electrodes located between an insulation be provided of the capacitive device and the electrodes. As already mentioned, the capacitive device is preferably a discharge vessel holder or a part of such.

The effect of the invention is particularly pronounced when the Capacitive means a capacitive coupling between the coupled with her Electrode and an associated counter electrode closer Parts of the discharge space causes. Then there is an effective one Electrode broadening comparable effect.

In an earlier patent application (DE-A 199 55 108) of the same applicant has been explained that with an external thermal device of Heat transport in the discharge lamp or from the discharge lamp out in an inhomogeneous way. That should be that in itself Inhomogeneous self-temperature behavior of the discharge lamp counteracted be as homogeneous as possible discharge conditions and thus to produce a homogeneous luminance distribution.

The present invention is related to those treated with the invention there Problems in the following context: By the capacitive device For the purposes of the present application, a certain temperature homogenization along the at least one longitudinal direction of the discharge lamp be effected. This depends in detail on how well the thermal contact between the capacitive device and the discharge vessel is. The necessary by the modulation of the field distribution Structuring the capacitive device is this temperature homogenization not necessarily in the way, because of this Modulation with a matched to the Zwischenentladungsabstände Length scale should be made. The temperature inhomogeneities in the discharge lamp However, they usually occur on a larger length scale; the discharge lamp is usually warmer in the middle than on the Rand, with a steady course between them. The for the modulation the field distribution necessary structuring can therefore theoretically Although lead to a slight modulation of the temperature distribution, if the thermal contact with the discharge vessel is good. However, temperature fluctuations on the length scale of the intermediate discharge distances, but repeating the extension of the lamp with this modulation, insignificant, because of that the discharge structures essentially all are equally affected.

In addition, the defined in the cited application thermal Device, however, be combined with the present invention. It can therefore the thermal device according to the cited application and the capacitive device according to the present application simultaneously be provided, in particular, they can also be combined. To can the thermal / capacitive device on the self-temperature behavior adapted to the lamp thermally inhomogeneous effect, for example by different thermal conductivity. When doing so for the capacitive effect does not use crucial properties can, the field modulation of it remain completely untouched. For example The material thickness or the material itself could be chosen this way be that the device in the middle of the lamp cools more than on the Edge. Similarly, only in the middle could a thermally conductive Connection to a cooling device may be provided and the like. In particular, inhomogeneously arranged cooling fins can be used become. Among the various design options for the thermal Institution is referred to the cited advance notification.

When the thermally inhomogeneous influence of the lamp by insulation measures is made by the tend to be too cold ends the lamp can be isolated, so this can be independent of the capacitive anyway Establishment done.

Preferably, the discharge lamp according to the invention with a ballast provided on the already mentioned pulsed operating method is tailored. According to current knowledge can be with this Method in a particularly efficient way localized discharge structures produce.

Particular application of the invention in rod-shaped elongated Discharge lamps. On the one hand, these are a preferred application for the explained "thermal homogenization", on the other hand it can be all in such discharge lamps difficult to patterned electrodes to install, especially if they are within the discharge vessel should. However, electrodes within the discharge vessel are for reduction the voltages required for starting and operating often desired. Unlike flat opener situations in which For example, can be used with screen printing, is within a glass tube as a discharge tube difficult one with protrusions or other geometric elements for the definition of preferred sites for Discharges provided electrode. Here is the invention an easy way out, especially if the already necessary Holder is designed in accordance with the invention.

Such flashlights are of particular interest to copiers or scanning devices in which a flashlight on a visually scanned Field, about a paper surface, must be performed.

However, the invention is also suitable for flat radiators, which, as mentioned, in particular for the backlighting of display devices an essential Field of application for silent discharge lamps form.

Description of the drawings

Figur 1

eine schematisierte Ansicht einer stillen Stabentladungslampe zur Veranschaulichung;

Figur 2

eine Variante zu Figur 1, und zwar im Schnitt entlang der Längsachse;

Figur 3

eine schematische Ansicht einer Variante zu Figur 2 als erstes Ausführungsbeispiel;

Figur 4

eine schematische Ansicht einer weiteren Variante zu Figur 3 als zweites Ausführungsbeispiel;

Figur 5

eine schematische Ansicht einer erfindungsgemäßen stillen Stabentladungslampe als drittes Ausführungsbeispiel.

In the following, various embodiments of the invention are explained in detail. The features disclosed in this case can also be essential to the invention in combinations other than those shown. In detail shows:

FIG. 1

a schematic view of a silent rod discharge lamp for illustration;

FIG. 2

a variant of Figure 1, in section along the longitudinal axis;

FIG. 3

a schematic view of a variant of Figure 2 as a first embodiment;

FIG. 4

a schematic view of a further variant of Figure 3 as a second embodiment;

FIG. 5

a schematic view of a silent rod discharge lamp according to the invention as a third embodiment.

Figure 1 illustrates a device for capacitive modulation on a simple example. However, it is not an embodiment. 1 with a silent rod discharge lamp is called, consisting essentially of an elongated glass tube. The details of the electrode structure are not shown here, but to some extent in Figure 2 can be seen. For details of such silent rod discharge lamps reference is made to the document US Pat. No. 6,097,155.

The by the in this rod discharge lamp 1 internal electrodes generated potential distribution within the discharge vessel, namely the Glass tube, can be modulated by the designated 2 metal sheet. This metal sheet has a comb-like shape extending vertically in FIG Structure, wherein the upper ends of the tines 3 of this comb structure abut the rod discharge lamp 1.

Figure 2 also shows no embodiment and illustrates that the Tines 3, the lamp 1 can also partially enclose. Otherwise shows Figure 2 in cross section the internal electrodes 4 of the rod discharge lamp.

In the manner already explained, the tines 3 couple to the interior of the discharge vessel the rod discharge lamp 1 at. This is a purely capacitive Effect in which between the electrodes 4 and the tines 3 and between the interior of the discharge vessel and the tines 3 a complete galvanic Separation is present. When structuring the sheet metal 2, this results in a modulation of the result of the homogeneous strip-shaped Design of the electrode strips 4 otherwise along the longitudinal extent the rod discharge lamp 1 substantially undisturbed Equipotential lines. This characterizes the comb structure of the sheet 2 of the Field distribution within the rod discharge lamp 1, a structure with the same Oszillationslänge, in this example, practically over the entire Length of the rod discharge lamp 1 is a periodic oscillation. Accordingly, the discharge structures are distributed within the rod discharge lamp 1. They are preferably located at the points of the tines 3 inside the discharge vessel. In the second example in FIG. 2 occurs this effect over the first example in Figure 1 amplified on that the tines 3 to the rod discharge lamp 1 each about a Quadrant circumference are guided around. You can also do this modulation clearly understand as effective electrode broadening.

Moreover, Figure 1 shows that the sheet 2 only in one in the longitudinal extension the rod discharge lamp 1 middle area over a wider Sheet metal part 5 and two screws is mounted. Here, the assembly can also take place on a heat sink, whereby the sheet 2 as a whole as a cooling device acts. If the tines 3 run slightly wider than drawn and a relatively good thermal contact with the rod discharge lamp 1, for example by having a part as shown in FIG abut the cross-sectional circumference at this, the sheet 2 forms an inhomogeneous Cooling device in the sense of the previously mentioned earlier invention, without thereby the capacitive coupling inhomogeneous in the same way would.

FIG. 3 shows very schematically a first embodiment of the invention, and an alternative arrangement of tines one in the rest comparable comb structure, wherein the tines are designated here with 6. The tines are in a left edge region of the rod discharge lamp in FIG 1 arranged denser than in a middle right in Figure 3 shown Area, which also results in a denser array of discharge structures in the rod discharge lamp 1 results. From this follows an inventive Brightening of the edge area. Such edge brightening can be useful for a variety of reasons, in particular it can be used for Compensation of an otherwise occurring edge darkening can be selected So basically only serve for homogenization of the luminance distribution. For brightening the rest, reference is made to the already cited US Pat. No. 6,252,352 B1.

FIG. 4 shows a variant of FIG. 3 with the tines 7 illustrated there second embodiment. Here are the tines 7 in the left to be recognized Edge region of the rod discharge lamp, although not arranged denser, but wider. As a result, the discharge structures burn in Edge area brighter than in the middle right in Figure 4 center area Bar discharge lamp 1. To both figures 3 and 4 it should be noted that the Heterogeneity of the tine structure 6 or 7 towards the edge a bit exaggerated is shown. In a practical embodiment, the heterogeneity in usually only be so pronounced that overall as homogeneous as possible Luminance distribution is achieved.

Figure 5 shows the third embodiment, also in a highly schematic Presentation. With 1 is again the already explained rod discharge lamp designated. On this a designated 8 metal strip is applied, in the left and right outer area relatively wide and in the middle Area is made relatively narrow, with continuous between Transitions are given. In this third embodiment is assumed that the electrode strips within the rod discharge lamp 1 are not structured, but because of a high lamp power a continuous curtain-like discharge burns. (However, you can the electrode strips also be structured, as is known from the prior art Technology is already known.) Here, the present invention has only the Task to provide for the already explained edge brightening. Accordingly Although the capacitive device 8 modulates the field lines over in essentially the entire length of the rod discharge lamp 1, but independently of intermediate discharge distances. This modulation could also only available in the edge area. However, according to the invention, at least in the edge region of the longitudinal extent of the silent discharge lamp or over substantially its entire length in the longitudinal direction of the invention Modulation present.

This modulation is oscillating in the sense that it is a "back and forth" or "up and down shift" with an intermediate maximum or minimum equivalent. That would apply even if the middle range of the metal strip 8 would be missing.

Of course, the third embodiment of Figure 5 could also with the first or second example, so that on a structuring the electrode strip 4 itself can be dispensed with.

Claims (12)

1. Discharge lamp for dielectric barrier discharges having a discharge vessel (1) which is filled with a discharge medium and
   discharge electrodes (4), which are at least partially isolated from the discharge medium by means of a dielectric coating,
   with the discharge vessel (1) extending along at least one longitudinal direction,
   and having a device (2, 3, 5, 6-8) which is electrically conductive, is electrically DC-decoupled from the electrodes but is capacitively AC-coupled to at least one of the electrodes (4) and is arranged outside the discharge vessel (1),
   characterized in that the conductive device (2, 3, 5, 6-8) is designed, by means of the capacitive coupling to the electrode (4), to differently modulate the equipotential lines, which are defined by the electric field between the electrodes (4), along the longitudinal direction between edge regions and central regions of the discharge vessel (1) such
   that the modulation by means of the capacitive coupling is used for edge brightening in order to compensate for any edge darkening which would otherwise occur and for homogenization of the light intensity distribution in the discharge lamp.
2. Discharge lamp according to Claim 1, in which the modulation is oscillatory in three dimensions.
3. Discharge lamp according to Claim 2, in which the oscillatory modulation is periodic.
4. Discharge lamp according to one of the preceding claims, in which the conductive device (3) is provided in duplicated form, with each of the conductive devices (3) being capacitively coupled to in each case at least one electrode (4) of a respectively different polarity.
5. Discharge lamp according to one of the preceding claims, in which the electrodes (4) are arranged in the interior of the discharge vessel (1).
6. Discharge lamp according to one of the preceding claims, in which the conductive device (3, 6, 7) is a holder, or a part of a holder, for the discharge vessel.
7. Discharge lamp according to one of the preceding claims having a thermal device for controlling the heat transport to/from the lamp in an inhomogeneous manner along the longitudinal direction, and which is designed such that the temperature in the lamp is homogenized along the longitudinal direction during operation, with this thermal device having cooling ribs which are arranged inhomogeneously with regard to their presence, their extent and/or their density along the longitudinal direction.
8. Discharge lamp according to one of the preceding claims, in which the electrically conductive device (3) produces capacitive coupling between the electrode (4) coupled to it and those parts of the discharge area which are located closer to the opposite electrode (4).
9. Discharge lamp according to one of the preceding claims, in which the discharge vessel (1) is elongated in the form of a rod.
10. Discharge lamp according to one of Claims 1 to 9, which is designed as a flat lighting element.
11. Discharge lamp according to one of the preceding claims, having a ballast which is designed for a pulsed operating method.
12. Use of a discharge lamp according to Claim 9 for a copying device or a scanning device.

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