High color rendering index fluorescent lamp with multi-layer phosphor coating

摘要

Described are methods and apparatus for providing fluorescent lamps having a two-layer phosphor coating that includes a base coating and a top coating that economically provides a high color rendering index (CRI) of at least 87 with improved brightness. In an embodiment, a low-pressure discharge lamp includes a light transmissive envelope having a basecoat phosphor layer disposed on an inner surface, wherein the basecoat phosphor layer includes less than ten percent weight of a rare earth phosphor. Also included is a topcoat phosphor layer on a surface of the base coat phosphor layer that includes a blend of at least red, green, green-blue and blue emitting rare earth phosphors, and a fill gas composition within the light transmissive envelope.