Electric lamp and discharge devices – Cathode ray tube – Ray generating or control
Patent
1998-01-16
2000-10-10
Patel, Ashok
Electric lamp and discharge devices
Cathode ray tube
Ray generating or control
313270, 313337, 313346DC, H01J 2904, H01J 0120
Patent
active
061305022
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a cathode assembly, an electron gun assembly, an electron tube, and a heater which are used for the electron guns of a color cathode ray tube, and a method of manufacturing the cathode assembly.
BACKGROUND ART
Recently, downsizing has been required for display units used for computers. With the widespread use of personal computers, in particular, a great deal of attention has been paid to flat displays, mainly liquid crystal displays. However, no flat display units have been developed, which can cope with electron tubes such as cathode ray tubes in terms of size, resolution, and cost. For this reason, electron tubes such as cathode ray tubes are in urgent need of reducing their total lengths and weights.
Similar needs are increasing with respect to traveling wave tubes designed to be mounted in satellites. With such needs, demands have arisen for compact, low-profile, lightweight electron guns including cathode assemblies as tube parts.
High-speed operations are often required for high-output traveling wave tubes. A general tube uses a hot cathode assembly as an electron source, and hence the temperature rise time in the cathode assembly dominates the time required for the stable operation of the tube. That is, quick heating of the cathode assembly is required for the quick operation of the tube.
Attempts have been made to develop low-profile, lightweight display units using electron tubes. For example, as disclosed in Jpn. Pat. Appln. KOKAI Publication No. 7-58970, a low-profile display unit using an electron tube in which a plurality of electron guns are arranged has been proposed.
A short, low-power-consumption, fast electron gun is required as each electron gun mounted in the electron tube of such a display unit to reduce the profile and weight of the display unit and improve its performance.
A conventional electron tube will be described below with reference to FIG. 67. FIG. 67 is a sectional view showing portions around the cathode assembly in the electron gun assembly used in the conventional electron tube.
The cathode assembly includes a cathode sleeve 1 consisting of an alloy such as nichrome. A base metal layer 2 consisting of nickel doped with a small amount of reducing material is fixed to one end of the cathode sleeve 1. The surface of the base metal layer 2 is coated with an emissive material 3 consisting of barium oxide (BaO), strontium oxide (SrO), calcium oxide (CaO), or the like. A cathode base member 4 is constituted by the base metal layer 2 and the emissive material 3. As the cathode base member 4, in addition to the above structure, a so-called impregnated cathode base member obtained by impregnating a porous cathode base member with an emissive material such as barium oxide (BaO), strontium oxide (SrO), or aluminum oxide (Al.sub.2 O.sub.3) is used.
The cathode sleeve 1 is fixed to a cathode holder 6 consisting of Kovar (Fe--Ni--Co-based alloy) through a strap 5 consisting of invar (Fe--Ni-based alloy) as a low-thermal-expansion alloy. The cathode holder 6 =-surrounds the cathode sleeve 1 through a reflector 7 consisting of an Ni-based refractory alloy material for blocking/reflecting heat from the cathode sleeve 1. The cathode holder 6 is fixed to a cathode support strap 9 consisting of a stainless-steel-based alloy through a cathode support cylinder 8 consisting of a stainless-steel-based alloy.
A heater 10 for heating the cathode is mounted in the cathode sleeve 1. The heater 10 is obtained by helically winding an Re--W alloy wire, and coating its surface with aluminum oxide (Al.sub.2 O.sub.3) as an insulating material. The heater 10 is an elongated member extending along the longitudinal direction of the electron gun. The heater 10 is inserted into the cathode sleeve 1 through the other end thereof such that the end portions of the heater protrude from the cathode sleeve 1. The end portions of the heater 10 are fixed to a heater tab strap 12 consisting of a stainless-steel-based alloy through a heater tab 11 consisting of a stai
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patent: 5015908 (1991-05-01), Miram et al.
patent: 5475281 (1969-03-01), Heijboer
Kuhnert, et al, "Image processing using light-sensitive chemical waves", Nature, vol. 337, No. 6204, Jan. 1989, pp. 244-247.
Fujiuchi Takumi
Higuchi Toshiharu
Kimura Sakae
Kobayashi Kazuo
Koshigoe Shinpei
Kabushiki Kaisha Toshiba
Patel Ashok
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