Claims
- 1. A low-pressure mercury vapour discharge lamp having a vacuum-tight, radiation-transmissive envelope, provided with a luminescent layer and a gas filling comprising mercury and a rare gas wherein mercury radiation at 254 nm is generated, and furthermore provided with means for maintaining a column discharge in the gas filling, the power consumed by the column being at least 500 W per m.sup.2 surface area of the luminescent layer, characterized in that the luminesent layer contains a luminescent material which has the property of having a 254 nm-excitation a luminous flux which, after the material has been subjected for 15 minutes to ultraviolet radiation of a wavelength of mainly 185 and 254 nm and a radiation density between 150 and 500 W/m.sup.2 and a ratio of 185 nm power to 254 nm power between 0.20 and 0.40, is not more than 5% lower than the initial luminous flux of the material also at 254 nm excitation and measured under identical circumstances, and in that the combination of cations in the luminescent material has an electronegativity of not more than 1.4.
- 2. A low-pressure mercury vapour discharge lamp as claimed in claim 1, wherein an electric field strength of 150 to 1000 V/m is maintained in the column discharge during operation of the lamp.
- 3. A low-pressure mercury vapour discharge lamp as claimed in claim 2, wherein the envelope has a tubular shape, whose cross-section perpendicular to the axis of the tube is substantially circular and whose inside diameter is from 3 to 15 mm.
- 4. A low-pressure mercury vapour discharge lamp as claimed in claim 1, characterized in that the luminescent material is a red luminescing, trivalent europium-activated rare earth oxide in accordance with the formula Ln.sub.2 O.sub.3 :pEu.sup.3+, wherein Ln represents at least one of the elements Y, Gd and Lu and wherein 0.01.ltoreq.p.ltoreq.0.20.
- 5. A low-pressure mercury vapour discharge lamp as claimed in claim 1, characterized in that the luminescent material is an aluminate activated by cerium and terbium and having a hexagonal crystal structure related to the structure of magnetoplumbite, which aluminate satisfies the formula (Ce.sub.1-p-q La.sub.p Tb.sub.q).sub.2 O.sub.3. xMgO.yAl.sub.2 O.sub.3, wherein up to 25 mol.% of the Al.sub.2 O.sub.3 may have been replaced by Ga.sub.2 O.sub.3 and/or Sc.sub.2 O.sub.3 and wherein
- 0.ltoreq.x.ltoreq.2
- 10.ltoreq.y.ltoreq.16
- 0.ltoreq.p.ltoreq.0.50
- 0.ltoreq.q.ltoreq.0.60
- p+q.ltoreq.0.90
- 6. A low-pressure mercury vapour discharge lamp as claimed in claim 1, characterized in that the luminescent material is an aluminate, activated by bivalent europium, by bivalent europium and bivalent manganese or by trivalent cerium and having a hexagonal crystal structure related to the structure of .beta.-alumina, which aluminate satisfies the formula MeO.xMgO.yAl.sub.2 O.sub.3 :pEuO.qMnO.rCe.sub.2 O.sub.3, wherein Me represents Ba and/or Sr, wherein up to 25 mol.% of the Al.sub.2 O.sub.3 may have been replaced by Ga.sub.2 O.sub.3 and/or Sc.sub.2 O.sub.3 and wherein
- 0.ltoreq.x.ltoreq.2
- 5.ltoreq.y.ltoreq.8
- 0.01.ltoreq.p.ltoreq.0.50
- 0.ltoreq.q.ltoreq.1.0
- 0.ltoreq.r.ltoreq.0.50,
- wherein Me is Ba if x=0.
- 7. A low-pressure mercury vapour discharge lamp as claimed in claim 1, characterized in that the luminescent layer comprises at least a luminescent material of the group consisting of bivalent europium-activated strontium tetraborate, lead-activated barium disilicate, bivalent europium-activated strontium chlorophosphate with apatite structure, gadolinium metaborate activated by cerium and terbium, and gadolinium borate activated by trivalent bismuth and trivalent europium.
Priority Claims (3)
Number |
Date |
Country |
Kind |
7612157 |
Nov 1976 |
NLX |
|
7612158 |
Nov 1976 |
NLX |
|
7709263 |
Aug 1977 |
NLX |
|
Parent Case Info
This is a continuation of application Ser. No. 038,616, filed May 14, 1979, which was a continuation of application Ser. No. 845,926 filed Oct. 27, 1977. Both of the earlier applications are now abandoned.
US Referenced Citations (4)
Foreign Referenced Citations (1)
Number |
Date |
Country |
2109898 |
Nov 1974 |
DEX |
Non-Patent Literature Citations (1)
Entry |
"Short-Term Initial Lumen Depreciation in Fluorescent Lamps," by Vrenken et al., Illuminating Engineering, Jan. 1964, pp. 59-66. |
Continuations (2)
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Number |
Date |
Country |
Parent |
38616 |
May 1979 |
|
Parent |
845926 |
Oct 1977 |
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