| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an electron emitting source with short end cooling and large electron emitting amount. SOLUTION: A filament cathode 1 has a core wire part constituted with two core wires 2, 2 spirally wound each other and heated by passing current and an electron emitting material layer 4 attached to the surroundings of the core wire part 3. The filament cathode 1 is mounted on a fluorescent character display tube. Two tungsten core wires 2, 2 having the same diameter are faced in parallel, then twisted. An alkaline earth metal carbonate (Ba, Sr, Ca)CO3 is applied to the surroundings of the core wire part 3 together with a binder. The core wire part 3 is housed within an envelope of the fluorescent character display tube by applying specified tension. The core wire part 3 is heated by passing current in an exhausting process of the envelope. The carbonate is heat-decomposed to an oxide to form an electron emitting material layer 4. Although the electron emitting amount per area is almost the same as the conventional one, end cooling is made short, and the area of the display part of the fluorescent character display tube is enlarged.</p> |
