Patent ID: 6137217
Filing Date: 2000-10-24
Classification: C09K,H01J

Abstract:
A fluorescent lamp comprising a glass envelope having electrodes at its ends, a mercury and inert gas filling within said envelope which produces ultraviolet radiation, a coating comprising at least one layer of a quad-phosphor blend for converting a substantial portion of said ultraviolet radiation to visible illumination, said blend comprising a first and second red-emitting phosphor components, each red-emitting phosphor component having different visible emission spectrum principally in the 590 to 630 nm wavelength range, a third blue-emitting phosphor component having an emission spectrum principally in the 430 to 490 nm wavelength range, and a fourth green-emitting phosphor component having an emission spectrum principally in the 500 to 570 nm wavelength range, said first red-emitting phosphor being a rare-earth activated phosphor and said second red-emitting component being a non-rare-earth containing phosphor wherein the relative proportions of the phosphor components are such that an enhanced color rendering index is produced as compared to tri-component blends formed from a three-phosphor blend consisting of the said first red-emitting component and said third and fourth components.