Signaling lamp with phosphor excitation in the VUV range and...

Details Signaling lamp with phosphor excitation in the VUV range and... Signaling lamp with phosphor excitation in the VUV range and...

1999-08-11

2002-04-30

Patel, Vip (Department: 2879)

Electric lamp and discharge devices

With luminescent solid or liquid material

With gaseous discharge medium

C313S483000, C313S485000, C313S486000, C313S635000, C252S30140R, C252S30160R

Reexamination Certificate

active

06380669

ABSTRACT:

TECHNICAL FIELD
The present invention relates to signaling lamps, in particular in the area of traffic signals and traffic signs. From a particular point of view, it relates to signaling lamps for traffic lights.
In general, lamp technology is not only applied in illumination tasks. The area of signaling lamps is also an important field in lamp technology. The term signaling lamp should in this case be understood primarily to be a lamp which provides information to the observer (informs) about an event or a state. This information is generally already imparted to the observer by the on or off state of the lamp. Furthermore, the lamp may impart additional information content to the observer, for example by means of its shape, color or a legend.
Signaling lamps are used in very many areas of daily life, for example in road traffic, in marine transport and in railroads. Furthermore, they play a role in virtually all forms of technical equipment to be operated or monitored by an operator, be it in the area of household appliances or in entertainment electronics. Furthermore, safety signs for buildings or traffic, commercial or industrial installations should be mentioned, for example airports, train stations, cinemas, public buildings and the like. For example, signaling lamps are being used more and more for indicating escape routes, for drawing attention to hazards, and for drawing attention to particular situations for example, a fire alarm and the like.
PRIOR ART
Typical of the area of signaling lamps are particular requirements on reliability, which are based on the one hand on safety viewpoints and, on the other hand, are necessitated by their widespread uses in terms of numbers and location and the associated considerable effort for servicing and maintenance. Furthermore, in many applications it is necessary or desirable to be able to use particular physical shapes, for example particularly flat signaling lamps.
Conventionally, normal incandescent lamps or incandescent halogen lamps are generally used in signaling lamps. This applies in particular to the numerous signaling lamps which have to be switched on and off during operation.
Incandescent lamps, including incandescent halogen lamps, have significant disadvantages, however: as a result of the use of a more or less fine incandescent filament, they are basically relatively sensitive to vibration, which leads to restrictions in their use, in particular in the traffic sector.
Furthermore, their operating service life is restricted to a few thousand hours, depending on the lamp type and the operating voltage used. However, an early end to this operating service life is very disadvantageous, in exactly the same way as any other type of susceptibility to defects, because of the frequently high numbers and very widespread uses of signaling lamps, as mentioned.
In many applications, the incandescent lamps have to be installed in an optical system, for example one having a reflector and/or with lenses. Such systems are sensitive to misadjustment of a lamp base or other elements. Furthermore, a certain amount of internal soiling, above all in the traffic sector, is basically unavoidable, so that it is generally not possible, even following expensive internal cleaning operations, to reproduce the initial output of the lamp.
Above all in the case of incandescent lamp applications which have an optical system with reflectors or lenses, for example for illuminating a relatively large signaling area or for controlling the radiation direction of the signaling lamps, a relatively cumbersome overall size and shape or a corresponding weight is inevitable, but in many cases is very undesirable.
In addition, LEDs, that is to say light-emitting diodes, are known in the signaling lamp sector. However, they have the disadvantage that the color locus, which is important for signaling lamp applications and often standardized, cannot be adjusted. Occasionally, they are also unsuitable because of the radiation characteristic.
DESCRIPTION OF THE INVENTION
This invention is therefore based on the technical problem of specifying a new signaling lamp having new possibilities for avoiding the abovementioned difficulties. Furthermore, the invention relates to preferred means for producing a signaling lamp according to the invention, to be specific the use of specific phosphors or phosphor mixtures as described below.
According to the invention, provision is made for a signaling lamp as claimed in claim
1
and its uses as claimed in claims
14
,
15
and
16
. In addition, in claims
3
,
4
,
10
and
12
, the invention specifies phosphors or phosphor mixtures for use in a green, a yellow or a red signaling lamp.
According to the invention, therefore, a fluorescent lamp is provided, in specific terms a fluorescent lamp having a particularly short-wavelength excitation in the VUV range (Vacuum Ultra Violet range), that is to say that a wavelength below 200 nm. Particularly preferred in this case are excitation wavelengths below 185 nm or below 180 nm. Fluorescent lamps have significant advantages over incandescent lamps with regard to their operational service life, reliability and also with regard to the achievable physical shapes and sizes. VUV fluorescent lamps are a technically relatively novel and particularly interesting sector.
This relates primarily to dielectric barrier discharges, above all of noble gases, and primarily also to the dielectric barrier Xe excimer lamp. In relation to the constructional and electrical details of dielectric barrier gas discharge lamps, reference is made to the applications DE-P 43 11 197.1 (WO 94/23442), DE 195 26 211.5 (WO 97/04625), DE 196 36 965.7 and, with regard to the specific applications of a traffic light, primarily to the European parallel application “Flat signaling lamp with dielectric barrier discharge” (97122798:8), the respective disclosure content of the abovementioned applications being included by reference in this application. This applies above all to the pulse technique in electrical operation, the electrode configuration for particularly uniformly illuminated lamps and special, primarily flat, overall shapes as well as, as mentioned, the construction of a traffic light from dielectric barrier gas discharge lamps.
In the signaling lamp sector, the colors red, green and yellow have a particular significance, for example in traffic lights, motor-vehicle signaling lamps (yellow and red), marine lamps (green and red for starboard and port) and so on. The invention therefore relates in particular to phosphors and phosphor mixtures with which appropriate signaling lamps can be implemented with VUV excitation. In many cases, standards also have to be complied with, for example in motor-vehicle rear lamps or traffic lights.
To begin with green signaling lamps, according to the invention, the phosphors listed in the claims: BaMgAl
10
O
17
:Mn, Zn
2
SiO
4
:Mn, Sr
4
Al
14
O
25
:Eu, BaMgAl
10
O
17
:Eu, BaCaAl
28
O
45
:Eu, LaPO
4
:Ce,Tb and Y
3
Al
5
O
12
:Ce have been shown to be phosphors which can be used in the VUV excitation range and from which a signal green may be produced by an appropriate mixture. In particular, green signaling lamps can be produced in a particularly simple and thus advantageous way in many applications merely by using the phosphor Sr
4
Al
14
O
25
:Eu. This is because, according to the invention, it has been shown that the corresponding color locus with VUV excitation—see the exemplary embodiment—is located particularly favorably.
Furthermore, it has been shown that signal green tones may be mixed in a flexible manner by using a mixture of BaMgAl
10
O
17
:Mn and/or Zn
2
SiO
4
:Mn on the one hand, and Sr
4
Al
14
O
25
:Eu and/or BaMgAl
10
O
17
:Eu and/or BaCaAl
28
O
45
:Eu on the other hand, it being possible to meet appropriate standards, for example for traffic-light green (as shown in the exemplary embodiment for the case of the German DIN Standard).
Additional freedom is obtained by adding a third component of LaPO
4
:Ce,Tb and/or Y
3
Al
5
O
12
:Ce, which are located at consid

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