PURPOSE: To enable a high resistance film with a given size to be formed in a given position by vapor deposition without deteriorating interelectrode insulation by attaching a ribbon-like metallic piece, which is used as an evaporation source for the high resistance film, to a low voltage electrode in such a manner as to locate the middle portion of the metallic piece outside an insulating strut for supporting the electrode of the electron gun.
CONSTITUTION: The ends of a ribbon-like metallic piece 13 made of a nonmagnetic metal such as a nickel-chromium alloy are fixed to the two projections 6a of a focusing electrode 6. And, the middle portion of the metallic piece 13 is located outside an insulating strut 12. During or after the process of evacuating the encircling case, the metallic piece 13 is subjected to high frequency dielectric heating to produce an evaporated conductive substance. The thus produced evaporated conductive substance is deposited on the inner surface of a bulb neck 1 as a thin film, thereby forming a high resistance film 14. Consequently, it is possible to almost completely prevent any spark from occuring in the bulb neck.
MURANISHI HIDEO
FUJISAWA HIDEKUNI
TANABE KEIICHI
