Kabushiki Kaisha Toshiba

Toru Yakabe

Toshiharu Higuchi

Eiji Yamamoto

Shigeo Kanda

Akihito Hara

Sakae Kimura

Sadao Matsumoto

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.m (exclusive) at a weight ratio of the tungsten to the alumina in a range of (90:10) to (65:35).

Method of manufacturing a cathode assembly

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).

Cathode assembly incorporating a black layer formed from particles

An indirectly heated type cathode assembly comprises a cathode sleeve having a heater within itself and having an emitter-impregnated type cathode disc fitted at one end, a plurality of straps connected at one end to a lower end portion of the cathode sleeve, and a cylinder holder whose upper end is connected to the other end of each strap, the holder being located outside the cathode sleeve such that it is spaced a predetermined distance apart from the cathode sleeve. A heat reflecting cylinder is located between the cathode sleeve and the holder of the indirectly heated type cathode assembly such that it is coaxial with the cathode sleeve and holder. The heat reflecting cylinder is supported by the holder and each strap extends such that it is not in contact with the heat reflecting cylinder. The strap is made of a Ta-W alloy or a Ta-W-Hf alloy. An electron gun structure comprises the indirectly heated type cathode assembly, a first grid placed in front of the indirectly heated type cathode assembly and an insulation support into which the first grid and the holder of the indirectly heated type cathode assembly are embedded partially and directly through a securing piece, respectively. The cathode disc is hidden, by a heat reflecting cylinder, from view at least that portion of the insulating support which is defined between an embedded spot of the first grid and that of the securing piece.

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Yokosuka, Japan

Toru Yakabe