| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an indirect heated cathode which can stably be manufactured, causes no crack in an alumina-based electric insulation layer and heater deformation even at the time of practically operating in a cathode-ray tube, and has a prolonged life of the heater and to provide a cathode-ray tube employing the indirect heated cathode. SOLUTION: In this indirect heated cathode 8 comprising a heater 13 for heating and produced by forming an alumina-based electric insulation layer on the surface of a metal wire by firing an alumina particle and a cathode 9 for emitting thermoelectrons while receiving heat from the heater 13 for heating, alumina of the alumina-based electric insulation layer has purity of 99.7 wt.% or higher, the Na content of 20 ppm or lower for forming the alumina-based electric insulation layer, and the Si content in the alumina particle used for forming the alumina-based electric insulation layer of 100 ppm or lower. This cathode-ray tube employs such an indirect heated cathode 8.</p> |
