Low pressure mercury discharge fluorescent lamp utilizing multilayer phosphor combination for white color illumination

摘要

A low pressure mercury discharge fluorescent lamp is disclosed utilizing a particular phosphor blend deposited on a calcium haloapatite phosphor base layer to achieve white color lamp illumination efficiently with improved color rendition. The surface phosphor layer is a blended mixture of a first phosphor which is divalent europium barium and/or strontium magnesium aluminate having a hexagonal crystalline structure and which further includes coactivation by divalent manganese ion sufficient to produce substantial green color emission with a second phosphor which is trivalent europium activated rare earth oxide having a rare earth ion selected from yttrium, gadolinium and lutetium, including mixtures of these rare earth ions. The underlying calcium haloapatite layer also exhibits emission at approximately the same color point as achieved with the surface phosphor layer.