Hitachi, Ltd.

Other

Hitachi Nisshin Electronics Co., Ltd.

Terutoshi Ichihara

Sachio Koizumi

Norio Iwamura

Toshio Kawashima

A cathode ray tube includes a phosphor screen and an electron gun. The electron gun includes an indirectly heated cathode structure and plural grid electrodes in axially spaced relationship. The cathode structure includes a base metal having an electron emissive material coating and a heater for heating the base metal. The heater includes a major heating portion having a spirally wound heating wire and leg portions disposed at ends of the major heating portion, and each of the leg portions includes a first multilayer winding portion having heating wires wound spirally in plural layers and a second multilayer winding portion disposed intermediate between the major heating portion and the first multilayer winding portion and having heating wires wound in plural layers. The major heating portion and at least a portion of the second multilayer winding portion are covered with an insulating coating, the heater is welded to electrical conductors for applying a voltage thereto at the first multilayer winding portion, and the number of layers in the second multilayer winding portion is at least three and the number of layers in the first multilayer winding portion is larger than that in the second multilayer winding portion.

Cathode ray tube having an improved indirectly heated cathode

In a heater for an indirectly-heated cathode having a double helical structure, a film which can be removed by heating at the temperature of 250.degree. to 350.degree. C. is disposed between adjacent portions in a vertical direction, of a helical core wire coated with an insulating layer. Since this film is disposed, the occurrence of cracks in the insulating layer can be prevented so that the insulating property between the heater and a cathode sleeve do not gel deteriorated and clogging of an electron beam aperture of a shadow mask can be prevented, too.

Heater for indirectly-heated cathode

A dark heater is produced by a method which comprises coating the first coating layer made of an insulating material with a suspension containing heat-resistant particles having a high thermal emissivity, such as W particles, while 0.5 to 1.5 wt. % of a volatile matter such as water remains in the first coating layer to form a dark coating layer. Since the suspension having a low viscosity can be used, the thickness of the dark coating layer can be made highly uniform and the emission characteristics of the heater can be stabilized.

Growing community of inventors

Isumi-gun, Japan

Terutoshi Ichihara