| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a cathode electrode which, even when a large current is input, can maintain a highly luminous and stable arc discharge. <P>SOLUTION: A cathode 14 is composed of high melting point metal containing an electron radioactive material and comes in a tapered-off shape. On an outer edge of the tip part is formed an annular high work function region 14B. The high work function region 14B consists of larger crystal grains than crystal grains in the middle of the tip part. For this reason, discharging of an emitter begins from a low work function region 14A which is surrounded by the high work function region 14B. Since the tip of the cathode 14 can be made to be a large diameter D1, heat transfer from the tip of the cathode 14 to a bulk region is improved. Therefore, even when a large current is input, the tip part of the cathode 14 can be prevented from becoming excessively hot. <P>COPYRIGHT: (C)2012,JPO&INPIT |
