Fluorescent lamp

Details Fluorescent lamp Fluorescent lamp

1998-12-18

2000-08-01

Philogene, Haissa

Electric lamp and discharge devices: systems

Combined load device or load device temperature modifying...

Discharge device load

315DIG1, 313234, H01J 744

Patent

active

06097155&

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The invention relates to a fluorescent lamp and a lighting system using the fluorescent lamp.
Under discussion here are fluorescent lamps in which either the electrodes of one polarity or all the electrodes, that is to say those of either polarity, are separated from the discharge by means of a dielectric layer (unilaterally or bilaterally dielectrically impeded discharge). Such electrodes are also denoted below as "dielectric electrodes" for short.
The dielectric layer can be formed by the wall of the discharge vessel itself by arranging the electrodes outside the discharge vessel, for example on the outer wall. One advantage of this design with external electrodes is that no gas-tight electrical feedthroughs need be guided through the wall of the discharge vessel. However, the thickness of the dielectric layer--an important parameter which influences, inter alia, the starting voltage and the operating voltage of the discharge--is essentially fixed by the requirements placed on the discharge vessel, in particular its mechanical strength. Since the level of the required supply voltage increases with the thickness of the dielectric layer, there are the following disadvantages, inter alia. Firstly, the voltage supply provided for operating the flat radiator must be designed for the higher voltage requirement. As a rule, this is associated with additional costs and larger outside dimensions. Moreover, more stringent safety preparations are required for shock protection. Finally, undesirably high electromagnetic radiations can become problematical.
On the other hand, the dielectric layer can also be implemented in the form of an at least partial covering or layer of at least one electrode arranged inside the discharge vessel. This has the advantage that the thickness of the dielectric layer can be optimized to the discharge characteristics. However, internal electrodes require gas-tight electrical feedthroughs. Additional production steps are required as a result, and this generally means more expensive production.
Of particular concern here, moreover, are fluorescent lamps with a tubular discharge vessel which is sealed at both ends and whose inner wall is coated at least partially with a fluorescent material.
Such lamps are used, in particular, in equipment for office automation (OA), for example colour copiers and colour scanners, for signal lighting, for example as brake indicator lights and direction indicator lights in automobiles, for auxiliary lighting, for example the interior lighting of automobiles, and for background lighting of displays, for example liquid crystal displays, as so-called edge type backlights.
These technical fields of application require both particularly short starting phases, but also luminous fluxes which are as independent as possible of temperature. These lamps therefore contain no mercury. Rather, these lamps are usually filled with an inert gas, preferably xenon, or mixtures of inert gases.
The said applications require both a high luminous density and a luminous density which is uniform over the length of the lamp. In order to increase the luminous density, lamps for use in OA are usually provided with an aperture along the longitudinal axis. It is not sufficient for the purpose of raising the luminous density further to increase the power input into previous systems, since it is impossible to raise the loading of a lamp arbitrarily for permanent and reliable operation. A further complication is that the efficiency of the discharge decreases with increasing power input in the systems previously used in copiers and scanners.


PRIOR ART

An inert gas discharge lamp for OA equipment is already known from publication U.S. Pat. No. 5,117,160. Two strip-shaped electrodes are arranged along the lamp longitudinal axis on the outer surface of the wall of a tubular discharge vessel. The lamp is operated with AC voltage at a preferred frequency of between 20 kHz and 100 kHz. The 147 nm xenon line is excited in operation. A disadvantage is an incompletely transparent

REFERENCES:
patent: 5757132 (1998-05-01), Matsuno et al.
patent: 5763999 (1998-06-01), Matsuno et al.
patent: 5886468 (1999-03-01), Terada et al.
patent: 5932960 (1999-08-01), Terada et al.

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