ELECTRODE FOR HIGH PRESSURE METALLIC VAPOR ELECTRIC-DISCHARGE LAMP

摘要

PURPOSE:To reduce the dissociation of an electron-discharging substance from the electrode coil by using an inner and an outer electrode coil to form the main electrode of the emission tube having a double-coil structure and specifying the distance between the inner and the outer electrode coils. CONSTITUTION:The main electrode of a light emitting tube for a metal halide lamp or similar lamp is formed by winding an inner electrode coil 31 around a core wire 25 before winding an outer electrode coil 32 around the inner coil 31 and then fixing their ends to the core wire 25; the inner electrode coil 31 is prepared by winding a secondary coil 42 having a diameter smaller than that of a primary coil 41 around it. When the outer diameter of the inner electrode coil 31 is supposed to be D, the distance (l) between the coil elements is adjusted to within the range of 0.4D-0.75D. And, an electron-discharging substance 27 such as Sc is packed into the space between the coil elements. Therefore it is possible to prevent any deterioration of the luminous characteristic by reducing the dissociation of the electron-discharging substance 27 from the electrode. Furthermore it is possible to improve the starting performance of the electrode.