EP0922297B1 - Fluorescent lamp - Google Patents

Abstract

PCT No. PCT/DE98/01061 Sec. 371 Date Dec. 18, 1998 Sec. 102(e) Date Dec. 18, 1998 PCT Filed Apr. 16, 1998 PCT Pub. No. WO98/49712 PCT Pub. Date Nov. 5, 1998A fluorescent lamp (1) having a tubular discharge vessel (2), filled with inert gas, and a fluorescent layer (6) has elongated electrodes (3; 4; 12; 14a-14d) arranged parallel to the longitudinal axis of the tubular discharge vessel (2), at least one electrode (4; 12; 14a-14d) being arranged on the inner wall of the discharge vessel (2). The tubular discharge vessel (2) is sealed in a gas-tight fashion at one or at both ends with a stopper (8) and by means of solder (9), the at least one inner wall electrode (4) being guided to the outside in a gas-tight fashion through the solder (9). Alternatively or also in addition, at least one electrode (16) is arranged inside the wall of the discharge vessel (2). Up to a maximum of the entire inside diameter can be used as striking distance, depending on the positioning of the associated counterelectrode(s). High luminous densities are achieved because of the large and, at the same time, constant striking distance along the discharge tube. The lamp is provided for a pulsed, dielectrically impeded discharge.

Description

Technical field

The invention is based on a fluorescent lamp according to the preamble of claim 1. The invention also relates to a method for its Operation according to the preamble of claim 11.

These are fluorescent lamps, in which either the electrodes one polarity or all electrodes, i.e. both polarities, by means of a dielectric layer are separated from the discharge (one-sided or double-sided dielectric discharge). Such electrodes are hereinafter also abbreviated as "dielectric electrodes".

The dielectric layer can through the wall of the discharge vessel itself be formed by the electrodes outside the discharge vessel, are arranged on the outer wall. An advantage of this version with external electrodes is that there are no gas-tight feedthroughs must be passed through the wall of the discharge vessel. However, the thickness of the dielectric layer - an important parameter, which among other things the ignition voltage and the burning voltage of the discharge influenced - essentially by the requirements for the discharge vessel, especially its mechanical strength. Since the Height of the required supply voltage with the thickness of the dielectric Layer increases, there are the following disadvantages. In First of all, the power supply provided for the operation of the flat radiator must be used can be designed for the higher voltage requirements. This is usually associated with additional costs and larger external dimensions. There are also higher safety precautions to protect against contact required. Finally, undesirably high electromagnetic Radiations become problematic.

On the other hand, the dielectric layer can also be at least in the form of a partial cladding or layer of at least one within the discharge vessel arranged electrode can be realized. That has the advantage, that the thickness of the dielectric layer depends on the discharge properties can be optimized. However, inner electrodes require gas-tight Current feedthroughs. As a result, additional manufacturing steps are required which usually makes the production more expensive.

Furthermore, it is in particular fluorescent lamps with a tubular, Discharge vessel closed on both sides, its inner wall is at least partially coated with a phosphor.

Such lamps are lighting especially in equipment for office automation (OA = O ffice A utomation), such as color copiers and scanners, for the signal light, for example as brake and turn signal light in automobiles, for the auxiliary, such as the interior lighting of motor vehicles, and for the backlighting of displays, for example liquid crystal displays, is used as so-called "edge type backlights".

In these technical fields of application, both are particularly short Start-up phases, but also light currents that are as independent of temperature as possible required. That is why these lamps do not contain mercury. Much more are these lamps usually with noble gas, preferably xenon, or Noble gas mixtures filled.

For the applications mentioned, both a high luminance and uniform luminance over the length of the lamp is also necessary. To increase the luminance, the lamps are used for OA usually provided with an aperture along the longitudinal axis. To the Increasing luminance further is not enough in previous systems coupled power increase because the load of a lamp for one permanent and reliable operation cannot be increased arbitrarily can. To make matters worse, the previously in the copiers and Systems used by scanners increase the efficiency of the discharge Power coupling decreases.

State of the art

A noble gas discharge lamp for is already known from the document US Pat. No. 5,117,160 OA devices known. On the outer surface of the wall of a tubular Discharge vessel are two strip-shaped electrodes along the longitudinal axis of the lamp arranged. The lamp comes with an AC voltage preferred frequency operated between 20 kHz and 100 kHz. Operational the 147 nm xenon line is excited. One disadvantage is one not completely transparent due to protection against accidental contact Protective layer covering both the electrode strips and the remaining lamp surface covered. Without this protective layer, they would be electrodes alternately at high voltage potential (e.g. approx. 1600 V) namely freely accessible. The protective layer also has that Function to prevent parasitic surface discharge. Further Disadvantages result from those necessary for operation with external electrodes relatively high burning voltages. Are connected to it on the one hand namely undesirably high electromagnetic radiation. On the other hand must have an electronic ballast to operate the lamp required relatively high operating voltages to be designed, what its Manufacturing usually more expensive. After all, the one used Operating mode achievable radiation efficiency and consequently the resulting Luminance relatively low.

From US-PS 5,604,410 it is also known that the efficiency of dielectrically disabled discharges with the help of a special conditions (Stroke distance, electrode configuration, electrode geometry and Filling pressure) adapted pulse operation (pulsed, dielectric impeded discharge) compared to the dielectrically handicapped excited with AC voltage Discharges (see US Pat. No. 5,117,160) can be increased significantly.

Furthermore, a tubular discharge lamp is included in US Pat. No. 5,604,410 circular cross-section, with a strip-shaped outer electrode and a rod-shaped inner electrode is disclosed. The rod-shaped inner electrode is eccentric in the with the help of two bow-shaped power supplies Close to the inner wall and parallel to the longitudinal axis of the discharge vessel arranged. The two power supplies are each one Crushing by means of melting the plate with the discharge vessel is connected gastight, led to the outside. The outer electrode is diametrical fixed opposite on the outer wall. They are disadvantageous relatively complex and consequently expensive construction for the attachment of the metallic electrode rod inside the lamp as well as the two bruises. In addition, the metallic inner electrode rod must be relatively thick be carried out to ensure the necessary rigidity. Otherwise there is a risk that the inner electrode rod will sag and consequently the stroke length along the electrodes is not sufficiently constant. A strained wire as the inner electrode would not solve the problem because this heats up during lamp operation and therefore even more so sags. For these reasons, the lamp mentioned needs a relative large diameter, but what a use for certain purposes, especially for office automation and signal lighting in automobiles, opposes.

Presentation of the invention

It is an object of the present invention to eliminate the disadvantages mentioned and a fluorescent lamp according to the preamble of claim 1 to provide with improved luminance.

This object is achieved by the characterizing features of claim 1 solved. Particularly advantageous configurations can be found in the dependent ones Claims.

Furthermore, this task is also characterized by the characteristics of Claim 4 solved. Particularly advantageous configurations can be found in the dependent claims.

The basic idea of the invention is based on the knowledge that on the one hand the Impact range of the pulsed, dielectric barrier discharge for a high electrical power input should be as large as possible. On the other hand, should the arrangement of all electrodes on the outer wall of the discharge vessel and the associated disadvantages are avoided. In addition, one is possible for the pulsed, dielectric barrier discharge To strive for a constant stroke length along the discharge tube. This is therefore important to ensure the same ignition conditions for all individual discharges during operation (see US Pat. No. 5,604,410) along the electrodes. This ensures that the individual discharges Form lined up along the entire length of the electrode (assuming sufficient electrical input power) and consequently one Basic requirement for achieving a high and homogeneous luminance the lamp is satisfied.

A first way according to the invention to solve this problem suggests before, at least one or all of the electrodes on the inner wall of the Arrange discharge vessel. The following is such an electrode abbreviated as "inner wall electrode". Because of this Depending on the positioning of the associated counter electrode (s), the concept can up to a maximum of the entire inner diameter can be used as a striking distance. One advantage is the good thermal coupling of the Electrodes over the vascular material to the outside. This ensures that the inner wall electrodes do not move from the inner wall even in continuous operation peel off. As a result, the stroke length remains constant.

The inner wall electrode is considered to be electrically conductive, if necessary "Line-like" strips - similar to an electrical conductor track - formed and oriented parallel to the longitudinal axis of the tubular discharge vessel. The strip can e.g. in the form of liquid conductive silver or similar on the inner wall be applied. The strip is then solidified, e.g. by baking. The inner wall electrode is also as Implementation further trained including external power supply. Is to the tubular discharge vessel at least at one of its two ends sealed with a stopper which is soldered, e.g. Glass solder, gas-tight with the inner wall of the vessel end is connected. The inner wall electrode is guided gas-tight to the outside through the solder, i.e. the inner wall electrode goes into an implementation in the range of the solder and finally into an external power supply outside the vessel. On in this way are inner wall electrode, their associated implementation and associated external power supply as functionally different Sub-areas of a single common, track-like structure educated. This structure is a key to realizing the inner wall electrode This concept can be simply put Realize wisely and with relatively few components and is about it easy to automate.

Mechanical stresses caused by different thermal expansions to keep it low and to ensure gas tightness even in continuous operation, are the materials for glass solder and discharge vessel on top of each other Voted. In addition, the thickness of the conductor track (electrode, bushing, Power supply) chosen so thin that on the one hand the thermal voltages remain low and that, on the other hand, those required in operation Current strengths can be realized.

This results in a sufficiently high current carrying capacity of the conductor track of particular importance in so far as those aimed for such lamps high light intensities ultimately require high current intensities. This problem is further exacerbated in the preferred pulsed mode Operating mode of the discharge, since during the relatively short duration of the repetitive Active power coupling particularly high currents in the conductor tracks flow. This is the only way to achieve sufficiently high medium-sized ones Coupling active power and thereby the desired on average to achieve high light intensity.

To ensure the aforementioned high current carrying capacity, at least one inner wall electrode uses a relatively thick conductor track. Too small a conductor path carries the risk of cracking due to local overheating of the conductor track. The warming of the Conductor path through the ohmic part of the conductor path current is the higher, the smaller the cross section of the conductor track. The width of the conductor tracks there are limits due to space constraints, especially in the case of very slim lamps with relatively small diameters. Therefore, sooner narrow, but rather thick conductor tracks are aimed at to solve the problem of Cracking due to heat generation due to high current densities in to solve the conductor tracks. Typical thicknesses for conductive silver strips are in the Range from approx. 5 µm to approx. 50 µm, preferably in the range from approx. 5.5 µm to approx. 30 µm, particularly preferably in the range from approx. 6 µm to approx. 15 µm.

Furthermore, according to the invention, one or more further electrodes are arranged on the outer wall or also on the inner wall. In addition, at least part of the inner wall has a phosphor layer. For OA applications, only a strip-shaped aperture remains uncoated. In addition, one or more reflection layers for visible light, for example made of Al ₂ O ₃ and / or TiO ₂ , can be applied below the phosphor layer. This may prevent some of the light emitted by the phosphor layer from being transmitted through the vessel wall. Rather, the light is essentially directed onto the aperture by reflection or multiple reflection, and consequently the luminance is increased there. Alternatively, the phosphor layer itself can also additionally be used as a reflection layer, in that the phosphor layer is applied sufficiently thick.

In a first simple embodiment, the fluorescent lamp has two electrodes on, each with a strip-shaped electrode on the outer and inner wall is arranged. If the lamp is for use with bipolar Voltage pulses is provided, the inner wall electrode is additional completely covered with a dielectric layer. For use with This double-sided dielectric impedance is unipolar voltage pulses not absolutely necessary (see US Pat. No. 5,604,410). Security of touch To ensure the inner wall electrode in the latter case associated with high voltage potential.

In one variant, both electrodes are on the inner wall of the discharge vessel arranged, at least one of the two electrodes is completely covered with a dielectric layer. Should the lamp go with bipolar voltage pulses are operated, both electrodes are corresponding dielectric coated.

Due to the two electrodes, both variants arise during operation a discharge level, which is located within the discharge vessel between extends both electrodes. There are a large number of individual discharges at this level lined up side by side along the electrodes that are in the Borderline transition into a kind of curtain-like discharge form. To the To increase the luminance of the lamp, more levels of discharge within of the discharge vessel are generated. The lamp has three or more electrodes. With three electrodes, two discharge levels can already be created generate that have a common electrode. Preferably this is the (temporary) cathode and unipolar voltage pulses the other two electrodes are connected as anodes. With four electrodes can be either two independent discharge levels or realize three discharge levels with a common electrode, depending on whether the four electrodes as two cathodes and two anodes or are connected as a cathode and three anodes. In principle, you can in this way also generate more than three discharge levels. However the number of electrode strips required for this in practice Due to space constraints.

If the lamp is intended for OA applications and therefore with a Aperture is provided, the electrodes are advantageously oriented so that in Cross section looks at the perpendicular bisectors of the respective discharge planes cut the phosphor layer. This ensures that UV (ultraviolet) radiation maximum of the discharge level on the phosphor layer falls.

A second way according to the invention to solve the above-mentioned problem suggests at least one electrode inside the wall of the Arrange discharge vessel. The following is such an electrode shortened also referred to as "vessel wall electrode". Here too, depending after positioning the associated counter electrode (s), up to a maximum of the entire inside diameter can be used as the stroke distance. The advantage of this The solution is that even when operating with bipolar voltage pulses additional dielectric is required. The effective one for unloading the dielectric layer is namely through a part of the vessel wall itself formed by the part of the wall that the electrode in Covered towards the inside of the discharge vessel. The thickness of the effective dielectric layer is determined here by the depth at which the electrode is embedded in the vessel wall. That's why it is also required the electrode, e.g. in the form of a straight wire, very much evenly let into the vessel wall. It is therefore important to ensure that the thickness of the covering of the electrode by the vessel material (Dielectric!) Over the tube length is as constant as possible. Otherwise result namely different along the inner wall electrode Layer thicknesses of the effective dielectric and consequently an undesirable and non-uniform discharge structure with lower efficiency for the Useful radiation. Otherwise, the fluorescent lamp according to the second solution in principle the same features as the fluorescent lamp according to the first solution. In particular, everyone is there too mentioned variants conceivable, only the inner wall electrode is replaced by the vessel wall electrode.

Finally, both solutions can also be combined, i.e. at least one electrode each is both on the inner wall and inside arranged the vessel wall. Furthermore, one or more can also in this case Electrodes arranged on the outer wall of the discharge vessel his.

However, the tubular discharge vessel can also be curved. There the discharge direction is substantially perpendicular to the lamp longitudinal axis runs, almost any shape can be realized, in particular also circular, without affecting the discharge.

There is a gas filling inside the discharge vessel from an inert gas, in particular xenon, or an inert gas mixture.

Description of the drawings

Fig. 1a

einen Längsschnitt durch eine erfindungsgemäße Leuchtstofflampe mit Apertur und mit einer Außen- und einer Innenwandungselektrode,

Fig. 1b

einen Querschnitt durch die Leuchtstofflampe aus Figur 1a,

Fig. 2

einen Querschnitt durch eine Leuchtstofflampe mit zwei Innenwandungselektroden,

Fig. 3

einen Querschnitt durch eine Leuchtstofflampe mit einer Innenwandungs- und zwei Außenwandungselektroden,

Fig. 4

einen Querschnitt durch eine Leuchtstofflampe mit vier Innenwandungselektroden,

Fig. 5

einen Querschnitt durch eine Leuchtstofflampe mit einer Gefäßwand- und zwei Außenwandungselektroden,

Fig. 6

ein Beleuchtungssystem mit Apertur-Leuchtstofflampe und Impulsspannungs quelle,

Fig. 7

Meßkurven der Lampe aus Figur 1 bzw. Figur 3.

The invention will be explained in more detail below with the aid of several exemplary embodiments. Show it:

Fig. 1a

2 shows a longitudinal section through a fluorescent lamp according to the invention with an aperture and with an outer and an inner wall electrode,

Fig. 1b

3 shows a cross section through the fluorescent lamp from FIG. 1a,

Fig. 2

3 shows a cross section through a fluorescent lamp with two inner wall electrodes,

Fig. 3

3 shows a cross section through a fluorescent lamp with an inner wall and two outer wall electrodes,

Fig. 4

3 shows a cross section through a fluorescent lamp with four inner wall electrodes,

Fig. 5

3 shows a cross section through a fluorescent lamp with one vessel wall and two outer wall electrodes,

Fig. 6

a lighting system with an aperture fluorescent lamp and a pulse voltage source,

Fig. 7

Measurement curves of the lamp from FIG. 1 or FIG. 3.

Figures 1a and 1b show the longitudinal or cross section of an aperture fluorescent lamp 1 for OA applications in a schematic representation. The Lamp 1 consists essentially of a tubular discharge vessel 2 with a circular cross section and a first and a second strip-shaped electrode 3,4. The inner wall of the discharge vessel 2 has a phosphor layer 6 with the exception of a rectangular aperture 5 on. The discharge vessel 2 is at its first end with one from the vessel shaped dome 7 and gas-tight at its second end by means of plugs 8 locked. The plug 8 is gas-tight with the inner wall by means of glass solder 9 connected to the end of the vessel. Inside the discharge vessel 2 is xenon with a filling pressure of 21.3 kPa (160 torr).

The first electrode 3 provided as an anode is designed as a metal foil strip, on the outer wall of the discharge vessel 2 parallel to Pipe longitudinal axis is arranged. The other electrode intended as a cathode 4 consists of a conductive silver strip arranged diametrically to the anode, the liquid state with the help of a cannula on the inner wall of the discharge vessel 2 was applied and then baked (Inner wall electrode). The layer thickness is approx. 10 µm. The cathode 4 is in a bushing area 10 between the plug 8 and the Inner wall of the second end of the discharge vessel 2 gas-tight led to the outside and there goes into an external power supply 11 about. In this way, the cathode 4, its associated implementation 10 and associated external power supply 11 as functional different sub-areas of a single common, track-like Structure trained. The glass solder 9 enables in this area 10 the gas-tight passage of the cathode 4.

The respective width of the anode and cathode strips is 0.9 mm and 0.8 mm, respectively. The outer diameter of the tubular discharge vessel 2 made of glass is approximately 9 mm with a wall thickness of approximately 0.5 mm. The width and the length of the aperture 5 are approximately 6.5 mm and 255 mm, respectively. The phosphor layer 6 is a three-band phosphor. It consists of a mixture of the blue component BaMgAl ₁₀ O ₁₇ : Eu, the green component LaPO ₄ : Ce, Tb and the red component (Y, Gd) BO ₃ : Eu. The resulting color coordinates are x = 0.395 and y = 0.383, ie white light is generated.

In Figures 2 to 5 are further cross sections of an inventive Fluorescent lamp, similar to the lamp shown in Figure 1a, with and without Aperture is shown schematically. They differ from one another in essentially through the electrode configuration. The same characteristics designated with the same reference numerals.

The lamp in FIG. 2 has a first and a second inner wall electrode 12.4 on. Since both electrodes are located inside the discharge vessel 2 are located, the first electrode 12 is covered with a dielectric layer 13 (unilaterally dielectric discharge). This is in the unipolar pulsed operation according to US-PS 5,604,410 provided as an anode.

The lamp in FIG. 3 has two outer wall electrodes 3a, 3b and one Inner wall electrode 4. The outer wall electrodes 3a, 3b are as the anode and the inner wall electrode 4 is provided as the cathode. Consequently, two are formed in the pulsed operation according to US Pat. No. 5,604,410 Layers with single discharges that are dielectrically impeded from one side (not ) Shown. A first level of discharge extends between the cathode strips 4 and the first anode strip 3a. The other level of discharge extends between the cathode strip 4 and the second Anode strips 3b. The electrodes 3a, 3b, 4 are viewed in cross section arranged at the corner points of an imaginary isosceles triangle.

The lamp in FIG. 4 has four inner wall electrodes 14a-14d. Each of the inner wall electrodes 14a-14d is covered with a dielectric layer 15a-15d. A first 14a of the four electrodes 14a-14d is provided for a first polarity of a supply voltage, while the three other electrodes 14b-14d are provided for the second polarity. In pulsed operation, a total of three discharge levels are formed, namely between the first electrode 14a and one of the three remaining electrodes 14b-14d. Since the discharge is dielectrically impeded on both sides, operation is not only possible with unipolar voltage pulses but also with bipolar voltage pulses. With the exception of aperture 5, the inner wall of the discharge vessel 2 is provided with a reflection double layer 16 made of Al ₂ O ₃ and TiO ₂ . A phosphor layer 6 is applied to the reflection double layer 16. The reflection double layer 16 reflects the light generated by the phosphor layer 6. In this way, the luminance of the aperture 5 is increased.

The lamp in FIG. 5 has two outer wall electrodes 3a, 3b and one Vessel wall electrode 4. The vessel wall electrode 4 consists of a Wire made of Vacovit® (from Vacuumschmelze GmbH) with a diameter of approx. 100 µm, which is melted into the vessel wall. Since here as well as in Figure 4 all electrodes are dielectrically impeded, is next unipolar and bipolar pulse operation possible. The inner wall of the discharge vessel 2 is with a Phosphor layer 17, i.e. she knows unlike the previous ones Do not illuminate an aperture. The lamp of Figure 5 is for automotive lighting provided, for example, depending on the phosphor as brake light or flashing light.

FIG. 6 shows a lighting system for OA devices. The aperture fluorescent lamp 1 from FIG. 1 additionally points at its second end a base 18. The base 18 consists essentially of a Socket pot 19 and two connecting pins 20a, 20b. The base pot 19 is primarily used to hold the lamp 1. In addition, inside the Base pot 19, the outer wall electrode 3 and the inner wall electrode 4 or the outer power supply section 11 (see FIG. 1) with connected to the two pins 20a, 20b (not shown). The connector pins 20a, 20b are in turn connected via electrical lines 21a, 21b the two poles 22a and 22b of a pulse voltage source 23 connected.

The pulse voltage source 23 supplies a series of unipolar voltage pulses with a repetition frequency of 66 kHz. The pulse duration is approx. 1.1 µs each.

FIG. 7 shows the luminance L in cd / m ² measured by the aperture as a function of the time-averaged electrical power P in W. The measurement curve 24 relates to an illumination system according to FIG. 6 with the operating parameters specified there. As can be seen, approximately 40,000 cd / m ^{2 are} achieved with a power of almost 20 W. A comparable conventional lamp according to the teaching of US Pat. No. 5,117,160, on the other hand, delivers only 20,000 cd / m ² with the same electrical power. The lamp according to the invention consequently produces twice the luminance with the same electrical power; this corresponds to a 100% increase over the prior art.

The measurement curve 25 is obtained by replacing the lamp according to FIG. 1 with the lamp according to FIG. 3, ie a lamp with two instead of only one anode strips. Two discharge levels thus arise during operation (see also description of FIG. 3). As can be seen, from an electrical power of approx. 10 W, even higher luminance levels are achieved than with the measurement curve 24. With a power of 20 W, just under 50,000 cd / m ² can be achieved. This corresponds to 2.5 times the luminance compared to the state of the art or an increase of 150%.

These results document the advantageous effect of the invention.

The invention is not limited to the exemplary embodiments specified. In particular, combinations of features are different Embodiments included.

Claims (12)

1. Fluorescent lamp (1) having an at least partially transparent closed, tubular discharge vessel (2) which is filled with a gas filling, has a round cross-section and is made from an electrically nonconducting material, which discharge vessel (2) has on its inner wall at least partially a layer of a fluorescent material or mixture of fluorescent materials (6), and having elongated electrodes (3; 4; 12; 14a-14d) arranged parallel to the longitudinal axis of the tubular discharge vessel (2), at least the electrodes which are dedicated to the same operating polarity being separated by a dielectric (2; 13; 15a-15d) from the interior of the discharge vessel, characterized in that

   at least one electrode (4; 12; 14a-14d) is arranged on the inner wall of the discharge vessel (2),

   the at least one inner wall electrode (4; 12; 14a-14d) is additionally further constructed as a feedthrough (10) and the latter, in turn, is further constructed as an external supply lead (11), that is to say that each inner wall electrode (4), the associated feedthrough (10) thereof and associated external supply lead (11) are constructed in each case as functionally differing subregions of a unilateral common structure (4, 10, 11) resembling a conductor track.
2. Fluorescent lamp according to Claim 1, characterized in that the tubular discharge vessel (2) is sealed in a gas-tight fashion at one or at both ends with a stopper (8) and by means of solder (9), the at least one inner wall electrode (4) being guided to the outside in a gas-tight fashion through the solder (9), that is to say that the inner wall electrode (4) merges into a feedthrough (10) in the region of the solder (9) and, finally, into an external supply lead (11) outside the vessel (2).
3. Fluorescent lamp according to Claim 1, characterized in that the inner wall electrode(s) (12; 14a-14d) is (are) covered additionally (in each case) with a dielectric layer (13; 15a-15d).
4. Fluorescent lamp (1) having an at least partially transparent closed, tubular discharge vessel (2) which is filled with a gas filling, has a round cross-section and is made from an electrically nonconducting material, which discharge vessel (2) has on its inner wall at least partially a layer of a fluorescent material or mixture of fluorescent materials (17), and having elongated electrodes (3a; 3b; 16) arranged parallel to the longitudinal axis of the tubular discharge vessel (2), at least the electrodes which are dedicated to the same operating polarity being separated by a dielectric (2) from the interior of the discharge vessel, characterized in that at least one electrode (16) is arranged inside the wall of the discharge vessel (2).
5. Fluorescent lamp having the features of Claims 1 and 4.
6. Fluorescent lamp according to one or more of the preceding claims, characterized in that the number of the electrodes of one polarity (4; 14a; 16) is different from the number of the electrodes of the other polarity (3a,3b; 14b-14d).
7. Fluorescent lamp according to one or more of the preceding claims, characterized in that the inner wall of the discharge vessel (2) has an aperture (5) which is excepted from the fluorescent layer (6) and, if appropriate, a reflective layer (16).
8. Fluorescent lamp according to Claim 7, characterized in that the electrodes are arranged asymmetrically with respect to the aperture (5).
9. Fluorescent lamp according to Claim 8, characterized in that at least one electrode pair of differing polarity (3,5; 4,12; 3a,4; 14a,14d) is arranged in such a way that seen in cross-section the mid-vertical on the connecting line of an electrode pair (3,5; 4,12; 3a,4; 14a,14d) intersects the fluorescent layer (6), that is to say meets the inner wall outside the aperture (5).
10. Fluorescent lamp according to one or more of the preceding claims, characterized in that the width of the electrodes is less than 2 mm, in particular less than 1 mm.
11. Method for operating a fluorescent lamp according to one or more of the preceding claims, characterized in that the fluorescent lamp (1) is connected to an electric pulsed voltage source (23) which supplies voltage pulses separated from one another by pauses.
12. Method according to Claim 11, characterized by the following operating parameters:

    a repetition frequency of the voltage pulses of higher than 60 kHz

    a pulse duration of the voltage pulses of less than 2 µs.

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