| 摘要 |
PURPOSE:To maintain a starting characteristic until the end of the life together with preventing the decrease of a light flux by sealing a particular amount of a radioactive substance such as a sodium 22 or the like inside a light emission tube. CONSTITUTION:Together with sealing a rare gas for starting such as scandium iodide or the like inside a bulb 1 of a light emission tube, an radioactive substance such as a sodium 22 or the like having more than 0.5 years and less than 10 years of a half-life is sealed by less than 100 microcuries of amount of radioactivity per a light emission tube. Further, at sealing, the radioactive substance 10 is made to be a sealing line source by coating it will a cover 11 composed of a nonradioactive substance such as a light emission metal, halogenide or the like, and after putting it into the bulb 1, the flashing is performed by applying the voltage to an electrode 3. Then, the cover 11 is broken by the heat to diffuse the radioactive substance into the bulb. Accordingly, the starting characteristic is not damaged until the end of the life even if the amount of sealing is poor and the decrease of an optical flux by a chemical reaction can be prevented. |
