ELECTRIC GAS-DISCHARGE LAMP PROVIDED WITH LUMINESCENT COATING

• Main Authors: WANMAKER,WILLEM L.,NL, MANDERS,WILHELMUS J.,NL, TER VRUGT,JOHANNES W.,NL
• Format: Patent
• Language: English
• Published: 28.06.1982
• Subjects: BASIC ELECTRIC ELEMENTS; ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS; ELECTRICITY

1496438 Luminescent materials PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 2 May 1975 [6 May 1974] 18431/75 Heading C4S [Also in Division H1] To maintain visible or long wavelength UV emission by phosphors excited by UV of 240 nm. upward from a discharge lamp with reduced requirement for phosphors, the phosphors mixture is applied in two or more layers either on the inner wall of the discharge tube, e.g. in a low pressure Hg lamp or on the inner wall of an outer envelope in, e.g. a high pressure Hg lamp. The layer nearest the discharge contains only phosphors, while deeper layers contain additionally successively higher proportions of a white pigment. The UV specific absorption of the pigment is less than 20% and preferably less than 10% of that of the least absorbent phosphor component. Suitable phosphors for good colour rendering are 1-5 micron grains of Alternatively Mn and Sb activated Ca halophosphates may be used. For the pigment preferably somewhat finer grains of C a P 2 O 7 or BaSO 4 are suitable. In an example with the stratum nearest the discharge containing 3 grams of phosphor and the deeper stratum containing controlled proportions of phosphor and pigment, curves (Fig. 2, not shown) show that compared with a single phosphor layer containing 6À5 grams of phosphor, a slight increase in brightness is achieved with, e.g. only 5 grams of total phosphor (2 gm. in deeper layer) and 4À5 grams of pigment. Beyond 6 grams of pigment adhesion fails.