To provide a hot cathode for a CRT which can restrain evaporation of an electron emitting substance and whose electric current density is high and which has a high definition, high luminance and a long service life by using a substance composed of a boride of a rare earth element composed of the specific atomic combination ratio as a thermoelectron emitting source.
A thermoelectron emitting source 1 is installed on a metallic column 3 through a heater 2, and these are installed on an insulator 4, and a hot cathode for a CRT is obtained. A substance composed of a boride of a rare earth element is used as the thermoelectron emitting source 1. In this case, a hexaboride on which the atomic ratio of boron in the boride to a rare earth element is 6.02 to 6.3, preferably, 6.10 to 6.3 is used. La and/or Ce is preferable as the rare earth element.
TERUI YOSHINORI
SAITO TSUNENARI
SUMI KOICHIRO
SONY CORP
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