High output fluorescent lamp with improved phosphor layer

Abstract

A fluorescent lamp having phosphor blends to provide daylight (5500K) and tungsten (3200K) color when operated at higher current such as 250-1000 ma, to provide high light output such as for stage and studio applications.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows diagrammatically, and partially in section, a fluorescent lamp according to the present invention;

FIG. 2 is a plan view of a lighting unit holding eight fluorescent lamps; and

FIG. 3 is a cross sectional view taken along line 3-3 of FIG. 2.

Claims

1. A mercury vapor discharge fluorescent lamp comprising a light-transmissive envelope having an inner surface, a pair of electrodes mounted inside said envelope, a discharge-sustaining fill comprising inert gas sealed inside said envelope, and a phosphor layer having a phosphor blend inside the envelope and adjacent the inner surface of the envelope, said lamp adapted to operate at a current of 250-1000 ma, the phosphor blend being selected from the group consisting of (a) a blend of phosphors comprising 20-50 wt. % tin doped strontium phosphate, 5-20 wt. % calcium chlorofluoroapatite doped with antimony and manganese, 5-25 wt. % europium doped strontium aluminate, and 20-60 wt. % europium doped strontium barium chlorapatite;(b) a blend of phosphors comprising 40-70 wt. % tin doped strontium phosphate, 10-30 wt. % cerium magnesium borate, 0.2-5 wt. % lanthanum phosphate doped with terbium and cerium, and 10-35 wt. % europium doped strontium aluminate; and(c) a blend of phosphors comprising 30-50 wt. % cerium magnesium borate, 30-50 wt. % calcium chlorofluoroapatite doped with antimony and manganese, 0.2-10 wt. % manganese doped zinc silicate, and 10-30 wt. % europium doped strontium aluminate; in all cases the wt. % being based on all phosphors in the phosphor layer.

2. The lamp of claim 1, said envelope being cylindrical and having a nominal outer diameter of 1 inch.

3. The lamp of claim 2, said lamp being a T8 lamp about 4 feet long.

4. The lamp of claim 1, the inert gas in the fill being 5-80 mole % neon, balance argon, said fill having a gas pressure of 1.5-5 torr.

5. The lamp of claim 1, said lamp further comprising a barrier layer between the envelope and the phosphor layer.

6. A lighting unit comprising at least 2 lamps according to claim 2 and a lamp holder, said lamps being mounted in said lamp holder in a planar array.

7. A lighting unit comprising 2-14 lamps according to claim 2 and a lamp holder, said lamps being mounted in said lamp holder in a planar array.

8. A method of providing lighting comprising the steps of (a) providing a lamp according to claim 1, and(b) operating said lamp at a current of 250-1000 ma.

9. The method of claim 8, comprising the step of operating said lamp at a current of 400-700 ma.

10. The method of claim 8, said operated lamp providing light having a CRI of at least 89.

11. The method of claim 8, comprising the further step of dimming said lamp from more than 500 ma to less than 300 ma.

12. The method of claim 8, wherein said lamp is mounted in a lighting unit comprising at least 2 such lamps mounted in a lamp holder in a planar array.

13. The method of claim 12, further comprising the steps of operating said lighting unit so as to provide light onto an object and recording an image of said lighted object.

14. The method of claim 8, said operated lamp providing light having a color temperature of about 2900-3500K or about 5000-6000K.