Abstract: A method of forming a coating on an electron emitting cathode, in which (1) a black coating is formed on the inner surface of a cathode sleeve constituting the electron emitting cathode, (2) the cathode sleeve is filled with a suspension as a coating material, and (3) a porous absorbent member is brought into contact with or near an opening portion of the cathode sleeve at the same time or after the cathode sleeve is filled with the suspension, thereby causing the porous absorbent member to absorb an unnecessary portion of the suspension. Thereafter, the cathode sleeve to which the coating material is adhered is heat-treated. As a result, a black coating having a uniform thickness is formed, on the inner surface of the cathode sleeve, as a sintered layer obtained by mixing tungsten having an average particle diameter in a range of 0.5 .mu.m (inclusive) to 2 .mu.m (inclusive) with alumina having an average particle diameter in a range of 0.1 .mu.m (inclusive) to 1 .mu.

Abstract: A black coating having a uniform thickness is formed, on the inner surface of the cathode sleeve, as a sintered layer obtained by mixing tungsten having an average particle diameter in a range of 0.5 .mu.m (inclusive) to 2 .mu.m (inclusive) with alumina having an average particle diameter in a range of 0.1 .mu.m (inclusive) to 1 .mu.m (exclusive) at a weight ratio of the tungsten to the alumina in a range of (90:10) to (65:35).