| 摘要 |
PURPOSE:To obtain electrodes for a low-pressure mercury vapor discharge lamp of high quality, in which coloring around its electrodes does not occur even in its long-term lighting, by improving a shape of tungsten filament holding oxide. CONSTITUTION:An inner diameter of a primary winding is made to be 2-5 times a diameter of a tungsten wire, a pitch of the primary winding being two or less times the diameter of the tungsten wire, an inner diameter of a secondary winding being the outer diameter or smaller of the primary winding, and a pitch of the secondary winding being two or less times the outer diameter of the primary winding. Because electrodes like these are put as not only oxide 3 in the primary winding but also oxide 4 in the secondary winding, their surface area can be made to 2-3 times as large as that in case they are put only in the primary winding. Besides, because of coating carbonate being no distant from tungsten serving as a heating source, oxidation of the carbonate can be facilitated by heating, with the amount of intermediate product being small compared with the oxide.
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