(19)
(11) EP 1 067 572 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
21.08.2002 Bulletin 2002/34

(43) Date of publication A2:
10.01.2001 Bulletin 2001/02

(21) Application number: 00114001.1

(22) Date of filing: 04.07.2000
(51) International Patent Classification (IPC)7: H01J 1/20, H01J 29/04
(84) Designated Contracting States:
AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE
Designated Extension States:
AL LT LV MK RO SI

(30) Priority: 05.07.1999 JP 19015499

(71) Applicant: Hitachi, Ltd.
Chiyoda-ku, Tokyo 101-8010 (JP)

(72) Inventors:
  • Koizumi, Sachio, c/o Hitachi Ltd., IP Group
    Chiyoda-ku, Tokyo 100-8220 (JP)
  • Komiya, Toshifumi, c/o Hitachi Ltd., IP Group
    Chiyoda-ku, Tokyo 100-8220 (JP)
  • Iwamura, Norio, c/o Hitachi Ltd., IP Group
    Chiyoda-ku, Tokyo 100-8220 (JP)

(74) Representative: Beetz & Partner Patentanwälte 
Steinsdorfstrasse 10
80538 München
80538 München (DE)

   


(54) Cathode ray tube with indirectly heated cathode


(57) A cathode ray tube has a vacuum envelope formed of a panel portion (11), a neck portion (12) and a funnel portion (13) for connecting the panel portion and the neck portion, a phosphor screen (14) formed on an inner surface of the panel portion, and an electron gun (19) housed in the neck portion and including a cathode (40) and a heater (31a). The cathode includes a disk-shaped cathode base metal (41) having an oxide coating (42) thereon and a cylindrical cathode sleeve (43) housing the heater. The cylindrical cathode sleeve includes a small-diameter portion (43c) having the disk-shaped cathode base metal fitted within an end thereof and housing a top portion of the heater and a large-diameter portion housing leg portions (31) of the heater, and an axial length SL (mm) of the small-diameter portion and an outside diameter DD (mm) of the disk-shaped cathode base metal satisfies the following inequation:0.5 ≤ SL/DD ≤ 4.0.






Search report