FLUORESCENT LAMP WITH ZINC SILICATE PHOSPHOR AND PROTECTIVE PHOSPHOR LAYER

摘要

A fluorescent lamp comprises a glass envelope that is light transmitting. Also included is means for providing a discharge inside the envelope. A discharge-sustaining fill includes mercury and an inert gas sealed inside the envelope. An underlying phosphor- containing layer is disposed inside the envelope. The underlying layer includes zinc silicate phosphor. A protective phosphor-containing layer is disposed over the underlying layer at a location that is more distal from the glass than the underlying layer. A ratio of a surface density of the protective layer to a surface density of the underlying layer is at least 0.4: 1.