Cathode-ray tube

A cathode-ray tube comprising an electron gun assembly having an electron beam generating section that generates an electron beam, a prefocus lens section that prefocuses the electron beam generated from the electron beam generating section, a main lens section that focuses the electron beam, which is prefocused by the prefocus lens section, onto a phosphor screen, and an insulation support member that supports and fixes cathodes and electrodes, which constitute said sections,

• wherein the prefocus lens section includes at least a first prefocus electrode that is disposed on the electron beam generating section side, a second prefocus electrode that is disposed on the main lens section side, and an auxiliary electrode that is disposed between the first prefocus electrode and the second prefocus electrode,
• the auxiliary electrode is a cup-shaped electrode with a side wall that surrounds an outer peripheral part of the second prefocus electrode, which part is located on the first prefocus electrode side, and extends in parallel to a tube axis, and the auxiliary electrode has a bottom surface disposed to face the first prefocus electrode and has an open portion disposed to face the second prefocus electrode,
• the cathode-ray tube includes an electrically conductive ribbon that surrounds the insulation support member in the vicinity of the auxiliary electrode, the electrically conductive ribbon being connected to the auxiliary electrode, and electrically conductive films that are formed, in the vicinity of the electrically conductive ribbon, on a surface of the insulation support member, which is opposed to a neck, and on a surface of the neck, which is opposed to the insulation support member, and
• a relationship, E1<Es<E2, is established, where E1 is a potential applied to the first prefocus electrode, E2 is a potential applied to the second prefocus electrode, and Es is a potential applied to the auxiliary electrode.