Electron gun with improved withstand voltage for color-picture tube

A color cathode ray tube comprising:

• an electron gun assembly for generating in-line electron beams;
• a phosphor screen for emitting light rays when said electron beams land thereon;
• a vacuum envelope having a face where said phosphor screen is formed and which accommodates said electron gun assembly;
• deflecting means for deflecting said electron beams in vertical and horizontal directions in said vacuum envelope;
• said electron gun assembly having an electron-beam generating section, for generating a plurality of in-line electron beams, and a main electronic lens section for converging said plurality of in-line electron beams, generated by said electron-beam generating section, on said phosphor screen,
• said main electronic lens section including a plurality of grids each having electron-beam through holes and securely supported by a plurality of insulating supports, at least one of said grids having a portion with a substantially rectangular cross section for commonly enclosing said plurality of in-line electron beams and a face having electron-beam through holes formed at one or more ends and substantially perpendicular to said portion having a substantially rectangular cross section, said substantially rectangular portion having an outside length L.sub.H in a long-axial direction and an outside length L.sub.S in a short-axial direction such that a ratio of said outside length L.sub.H to said outside length L.sub.S, L.sub.H /L.sub.S, is
• 2.5<L.sub.H /L.sub.S <4.4
• and a ratio of said outside length L.sub.S in said short-axial direction to a length D.sub.V of said electron-beam through holes in the same short-axial direction, L.sub.S /D.sub.V, is
• 1.0<L.sub.S /D.sub.V <2.1.