JPS56106360A - Double-structured fluorescent light discharge tube - Google Patents

Abstract

PURPOSE:To enhance brightness of the light source of a fluorescent discharge tube, by means of a double-structured tube including both transparent outer and inner glass tubes to be arranged in such a way as spreading phosphor film over the external circumferential surface of the inner tube and the internal circumferential surface of the outer tube, while providing a reflecting film over the internal wall of the inner tube. CONSTITUTION:An outer tube 10 and inner tube 5 respectively made of transparent glass tubes of large and small diameters are arranged in a double-structured concentric configuration with those central axes coinciding with each other. The space (p) between both tubes is sealed in vaccum while in vicinity of both right and left ends of the space (p) are provided filaments 19, 19' connected to external electrode terminals 21, 21' respectively. Phosphor films 9, 12 are spread over the external wall of inner tube 5 and the internal wall of outer tube 10 and further a thin film 7 is formed on the internal wall of inner tube 5 through process of vacuum evaporation or the like, so that a fluorescent light can be reflected on the surface toward the outside of tube 5. Therefore, a quite intense fluorescent beam can be irradiated because a part of fluorescent light generated from phosphor film 9 on inner tube 5 may be relected at reflecting film 7 as an additional intensity.