JPS57187854A - Bent tube type fluorescent lamp - Google Patents

Abstract

PURPOSE:To improve the characteristics of a fluorescent lamp and the strength of a sealed container by changing the constitution of a phosphor material film coated on the inner face of the sealed container. CONSTITUTION:A phosphor material film coated on the inner face 2 of a sealed container has the first phosphor material layer 7 which contains a binding agent of 0.5- 7.0%, by weight, of the phosphor material and is coated with a phosphor material having an average particle size of 5.5mu or less as measured by a gas permeation method at a rate of 0.4X10<-3>-2.0X10<-3>g per 1cm<2> of the area of the inner face of the sealed container and in contact with its inner wall, and the second phosphor material layer which is coated in contact with the first phosphor material layer and contains the binding agent of 0.1-4.0%, by weight, of the phosphor material having the average particle size of 6.0mu or more as measured by the gas permeation method. Since the first phosphor material layer is made of a fine phosphor material with the average particle size of 5.5mu or less, the phosphor material particles do not sink into the inner wall of the container during the softening and molding process of the sealed container, therefore the strength of the sealed container is not deteriorated. Furthermore, the flux of light emitted from the bent tube type fluoresent lamp is maintained at a high value due to the phosphor material of the second phosphor material layer.