JPH05242834

PURPOSE: To eliminate ununiformity on a screen by arranging the first acceleration electrode with a specified space from a thermion generating part in which the second acceleration electrode and a shield electrode are arranged in order with a specified space kept from a cathode, and providing an outlet for a thermion, which is separated from a thermion generating part. CONSTITUTION: A thermion generating part 101 is formed with a back plate 1 and a back electrode 2, a cathode 4 placed in parallel with them, the second acceleration electrode 51 and a shield electrode 53 with a specified space kept from the cathode 4 arranged in order. In addition, by arranging the first acceleration electrode 52 with a specified space, an outlet for a thermion 102, a surface plate 11, fluorescent layer 10, a surface plate structure 12 comprising of an anode electrode 9 and an address means 13 are formed. When a specific voltage is applied to each electrode, electron clouds 31-33 are formed, however, the electron cloud 33 is separated, and the electron clouds 31, 32 do not reach the fluorescent layer 10 since there are shielded by the electrode 53. Thereby, ununiformity of brightness does not appear on a screen and a good quality image can be obtained.