Color cathode ray tube having an improved electron gun

Abstract

A color cathode ray tube includes a three-color phosphor screen, a shadow mask spaced from the phosphor screen and a three-beam type electron gun. The main lens section includes a focus electrode and an anode facing the focus electrode, each of the focus electrode and the anode has an electrode having a single opening common for three electron beams in an end thereof facing each other and a plate electrode disposed therein. The focus electrode is formed of at least one first sub-electrode adapted to be supplied with a first focus voltage and at least one second sub-electrode adapted to be supplied with a second focus voltage, one of the at least one first sub-electrode and the at least one second sub-electrode faces the anode. The second focus voltage is a fixed voltage superposed with a dynamic voltage varying with beam deflection, and an electrostatic quadrupole lens is formed between a first one of the at least one first sub-electrode and a first one of the at least one second sub-electrode. An inequality V >H−2×S is satisfied, where V and H are vertical and horizontal diameters of the single opening, respectively, S is P×L/Q, P is a horizontal center-to-center spacing between adjacent phosphor elements at a center of the phosphor screen, Q is an axial spacing between the phosphor screen and the shadow mask at the center of the phosphor screen, and L is an axial distance between the shadow mask and the single opening in the focus electrode.