The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 27, 1977
Filed:
Mar. 28, 1977
William A Thornton, Cranford, NJ (US);
Westinghouse Electric Corporation, Pittsburgh, PA (US);
Abstract
The light output of a high-presure discharge lamp that employs a mercury arc tube is selectively modified by two luminescent coatings on the inner surface of the outer protective envelope to provide color rendering and a source-color that are similar to those of an incandescent-type lamp. The coating in contact with the envelope surface comprises a blend of two selected phosphors -- one which absorbs and is excited by blue-violet radiations produced by the arc discharge and emits in the green portion of the spectrum, and another which also absorbs and is excited by the blue-violet radiations and by yellow radiations produced by the discharge and emits in the red portion of the spectrum. The second luminescent coating facing the arc tube comprises a phosphor that absorbs ultraviolet radiations produced by the mercury discharge and converts them into red radiations. The ultraviolet-converting phosphor coating is such that it transmits blue-violet and yellow radiations generated by the arc tube so that they can be absorbed and converted by the first phosphor coating. The desired color-rendering characteristics and reduction in the color temperature of the light emission are achieved with a minimum drop in light output and efficacy by using a mixture of green-emitting CaS:Ce phosphor and red-emitting CaS:Eu phosphor as the first-applied coating, and europium-activated yttrium vanadate phosphate phosphor as the second coating. Various other combinations of phosphors for the two luminescent coatings are also disclosed.