JPS57162252A - Fluorescent lamp - Google Patents

Abstract

PURPOSE:To make a light-distribution controlling means such as a baffle plate unnecessary by forming a fluorescent film on the inner wall of the bulb so that the distribution of light discharged from the end parts of the lamp through the opening part of the lamp is positively higher than that of light discharged from the central part of the lamp through the opening part. CONSTITUTION:The inner wall of a straight bulb 14 except a lamp opening part 16, which extends along the axial direction of the bulb 14, is coated with a reflection film made of a metal oxide such as titanium oxide, Next, a first fluorescent film 17 made of a material such as calcium halophosphate phosphor activated with antimony and manganese is formed on the above reflection film, and the inner wall of the lamp opening part 16 which is not coated with the above reflection film is coated with a protection film made of a material such as alumina. Then, the fluorescent lamp is divided along its axial direction into a central part (m), and end parts (n) and (n) having a given width. After that, a second fluorescent film 19 is formed only on the first film 17 at the end parts (n) and (n), and the first film 17 at the central part (m) is left exposed. The second film 19 is prepared from a phosphor of a narrow emission range which has a higher quantum efficiency than the first film 17.