JPS6471036A - Manufacture of cathode-ray tube - Google Patents

Abstract

PURPOSE:To prevent the generation of the stray emission or the grid emission deteriorating the insulation characteristics of a CRT by applying a negative voltage to anode electrode or some grid electrodes not being used for the activation during the activation process of the cathode with electron beam. CONSTITUTION:The 1st. grid electrode 1 of a CRT is connected to the ground, and the 2nd. grid electrode 2 and the 3rd. grid electrode 3 are connected to a DC source of about 300V. To the anode electrode 5 DC voltage of -400V is supplied from the anode 7 through the inner conductive film 8. The 4th. grid electrode 9 is connected to the anode electrode 5 with a connector 10 to be kept in the same voltage, therefore the electron beam 12 emitted from the cathode 11 is cut off by the said electrode 9 not to access to the 5th. grid electrode 13. At this time, a voltage necessary to obtain adequate electron beam is applied to the heater 14, but it has no effect on the decomposition of barium oxide adhered on the 5th. grid electrode 13. As described above, by applying a negative voltage to the anode electrode or the grid electrode not to be used for the electron beam activation in the activation process of the cathode the access of the electron beam to some of the electrodes applied with positive voltage can be prevented. Thereby barium oxide on the said electrodes cannot be decomposed, so that the generation of the stray emission or the grid emission can be prevented to obtain good insulation characteristics.