CATHODE FOR ELECTRONIC TUBE, MANUFACTURE THEREOF, AND ELECTRON EMISSION CONTROLLING METHOD

摘要

PROBLEM TO BE SOLVED: To improve an electron beam convergent characteristic without requiring any processing such as installation of a metallic cap by constructing a cathode of base metal, an electron emissive material layer formed on the base metal, and an electron emission area limiting coating formed on the electron emissive material layer. SOLUTION: A coating is arranged in an area, in which no electron is emitted, for limiting an electron emission area so as to be formed into a coating layer 1 in a cathode. In this cathode, the coating layer 1, which is made of metal or insulating material and provided with a thickness of 0.05-3μm approximately, is formed on an electron emissive material layer 2. In the coating layer 1, an openingϕ1 with a diameter of about 20-200μm is arranged so that the electron emissive material layer 2 can emit electrons. In this way, beams can be focused, and efficiency in beam radiation to phosphor can be increased. As a material for the coating layer 1, metal with a high work function and excellent heat resistance such as Pt, Mo, W, or Ni is used.