JPS5778764A - Single-base type low pressure vapor discharge lamp - Google Patents

Abstract

PURPOSE:To reduce the usage of expensive material by applying the inexpensive phosphor subsistance on the inside glass tube of a discharge lamp comprising double glass bulb while applying the expensive phosphor subsistance which dominates the color of the light emitted from the discharge lamp on the outside glass tube. CONSTITUTION:An outside glass tube 1 and an inside glass tube 2 are arranged coaxially then the cathode 6 is located in the inside glass tube 2 while a plurality of anodes 7, 7' are located between said glass tubes 1, 2 to form a fountain- shaped discharge path. Then an inexpensive halo-calcium phosphate phosphor subsistance 3 is applied on the inner and outer faces of the inside glass tube 2 while an expensive blue, green, red phosphor subsistance 4 is applied on the inner face of the outside glass tube 1 thus to convert the ultra-violet ray produced from a discharge plasma into the visible beam. Consequently the light emission color depending on the chromaticity of an expensive phosphor substance 4 can be obtained irrespective of the fact that the real coating mount of the expensive mono- color phosphor subsistance 4 is 37-54wt% of inexpensive phosphor subsistance 3 resulting in the considerable reduction of the material cost.