Patent ID: 6456017
Filing Date: 2002-09-24
Classification: H01J

Abstract:
An electron gun for a cathode ray tube having:a triode including a cathode structure, a control electrode, and a screen electrode, a plurality of focusing electrodes forming a pre-focusing lens unit for pre-focusing and accelerating R, G, and B electron beams emitted from the triode, and a final accelerating electrode facing the focusing electrodes, forming a main lens unit, wherein R, G, and B electron beam apertures of one pair of the focusing electrodes face each other and form a quadrupole lens unit, to which one of an AC voltage having a relatively low peak and a static voltage is applied, and respective centers of the R, G, and B electron beam apertures lie on a straight line, rims of each of the R and B electron beam apertures include respective enlargement portions having a plurality of straight line segments and respective circular portions intersecting the enlargement portions so that each of the R and B electron beam aperture rims includes straight line segments and arcs, and the enlargement portions include respective central axes passing through centers of the R and B electron beam apertures and perpendicular to the straight line, not intersecting the respective centers of the circular portions of the R and B electron beam apertures, so that the R, G, and B electron beams, respectively passing through the R, G, and B electron beam apertures, are converged to a single point even when the electron beams are deflected to a corner of a screen of a cathode ray tube including the electron gun, the G electron beam aperture has a rim including a circular portion and an enlargement portion having a plurality of straight line segments, and the enlargement portion of the G electron beam aperture has a central axis perpendicular to the straight line and intersecting the center of the circular portion of the G electron beam aperture, and each of the circular portions of the R, G, and B electron beam apertures has a respective diameter, each of the enlargement portions of the R, G, and B electron beam apertures has a respective length perpendicular to the straight line, and the respective sums of each of the diameters of the circular parts of the R and B electron beam apertures and the lengths of the enlargement portions of the R and B electron beam apertures are different from the sum of the diameter of the circular part of the G electron beam aperture and the length of the enlargement portion of the G electron beam aperture.