Patent ID: 7944138

Claim:
A fluorescent display tube structured with: an anode substrate including an insulation substrate having phosphor segments made of electron-excited phosphors formed on the insulating substrate; a front plate; and side plates, all of which are sealed in an airtight container by low-melting-point glass, wherein filament cathodes emitting thermal electrons to excite the phosphors to emit light are provided therein, the fluorescent display tube comprising: a plurality of supporting plates arranged inside the airtight container, wherein the plurality of the supporting plates include: a first supporting plate; at least two second supporting plates arranged adjacent to the first supporting plate; and third supporting plates arranged so as to be spaced-apart from the second supporting plates, wherein the second supporting plates and the third supporting plates being same in number, wherein one of the filament cathodes is arranged between the first supporting plate and the third supporting plate by one end thereof fixed to the first supporting plate and the other end thereof fixed to the third supporting plate, wherein the other of the filament cathodes having an equal length with the filament cathode arranged between the first supporting plate and the third supporting plate is arranged between the second supporting plate and the third supporting plate by one end thereof fixed to the second supporting plate and the other end thereof fixed to the third supporting plate.