| 摘要 |
PURPOSE:To prevent ununiformity of luminous brightness by constructing the cathode side closing member of the two closing members of a luminous tube with cermet. CONSTITUTION:The high pressure sodium lamp of high color output for DC lighting is an alumina luminous tube, and its diameter is narrowed down at both end parts, and the electrode conductor 2 consisting of niobium tube is sealed in the inside surface of one end part of the tube by glass cement and the cermet 5 is sealed in the inside surface of the other end part of the tube by glass cement. the cermet 5 holds the cathode 6 on itself and plays a role of conductor, and works as a heater, though only slightly, during the discharge current is flowing in the cerment 5. Therefore, the temperature of the end part of the cathode side of the luminous tube 1 is kept adequately, hence the point of lowest temperature of the luminous tube 1 is created in the end part of the anode side of the tube, so the cataphoretic phenomenon associated with DC lighting is not induced in the inside space of the luminous tube 1, and almost constant discharge condition is realized independently to the lighting directions. By this, the almost constant lighting characteristic without ununiformity of luminous brightness can be obtained.
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