INDIRECTLY-HEATED CATHODE AND ITS MANUFACTURE

摘要

PURPOSE:To obtaine an indirectly-heated cathode whose fine heater wire cannot be in contact with the metalic electro-conductive layer even when the electric insulating layer covering the heater wire has pinholes by producing the thin film of underlying metal on the insulating layer after filling up the pinholes in the said insulating layer with organic macromolecules and then burning and evaporating the said organic macromolecular layer. CONSTITUTION:Organic macromolecules are filled up in hollow portions in the thin film insulating layer having pinholes produced on the surface of a heater wire. Thereby the pinholes are eliminated and the hollow portions are also formed to equal thickness to the upper surface fo the insulating layer. On the surface of such a state a thin film of underlying metal is constructed. Thus the thin film layer of underlying metal is formed on the organic macromolecular layer over the pinholes cylindrically. Then by burning the wire in the atmosphere the organic macromolecular layer is oxidized and made to gases and evaporated through pinholes in the thin film layer of underlying metal. Thereby the hollow portions of the insulating layer are returned to the original state and the pinholes are reproduced, but the cylindrical underlying metal contacted to the upper surface of the insulating layer and the heater wire are faced to each other through the insulating layer having pinhole spaces so that the short circuit of the heater wire to the underlying metalic layer can be prevented.