| 摘要 |
PURPOSE:To decrease the starting voltage and remarkably improve the increase of lamp voltage and the luminous flux maintenance characteristic during the life performance by specifying both the pressure range of a rare gas charged in the emission tube and the ratio by weight of Sc to ScI3. CONSTITUTION:A high-power metal halide lamp has a lamp power per unit interelectrode distance of at least 100W/cm and an interelectrode distance of at least 9cm. It is charged with mercury, a rare gas and at least a scandium halide. In such a lamp, the pressure of the rare gas is adjusted to 8-16Torr (the optimum level, 10-15Torr). In addition, the ratio by weight of ScI3 charged in the emission tube to that of metallic Sc charged in the emission tube is adjusted to 0.9-0.25. When the ratio Sc/ScI3 becomes 0.25 or below, the maintenance rate of luminous flux rapidly decreases. When the ratio Sc/ScI3 exceeds 0.9, the surface area of metallic Sc adhering to the inner surface of the emission tube increases and the total luminous flux decreases because of the light-shielding effect of the Sc film. |
