Abstract: A frame (3) for supporting a color selection electrode body (2) under tension includes a pair of first frames (10) arranged in the horizontal direction and a pair of second frames (20) arranged in the vertical direction. The first frames (10) are each formed by bending a sheet material into a substantially triangular sectional shape, whose three side faces are formed by a first support part (12), a second support part (14) and a third support part (16). Projections (30) each having a shear plane (32) are formed in an inner position of the one side edge of the first support part (12). The other side edge (16a)) of the third support part (16) is arranged to be in contact with a main surface of the first support part (12) and the shear plane (32) of each of the projections (30). Shearing force acting between the other side edge (16a)) of the third support part (16) and first support part (12) is received by the projections (30).

Abstract: A strip-type mask assembly includes a strip-type mask having slits and strips. The strip-type mask further has perforations aligned with at least one of the slits and is disposed in at least one of regions between the extreme ends of the slits and the weld lines. The distance between the perforation and the extreme end of the slit is less than or equal to 2 mm. The dimensions and the positions of the perforations, and the number of the perforations aligned with one slit are determined so as to reduce the difference among the widths of the slits resulting from the local variation of the distribution of the tension on the slits or the difference among the lengths of the slits.

Abstract: An electron gun of a multi-stage convergence type includes a plurality of focusing electrodes, wherein a quadrupole lens nearest to a cathode has a diverging function in the horizontal scanning direction and a converging function in the vertical scanning direction, and a quadrupole lens in the next stage has a converging function in the horizontal scanning direction and a diverging function in the vertical scanning direction. In this structure, even when a voltage synchronized with a deflection current is superposed on a constant focus voltage, applied to the focusing electrode, the operation of the quadrupole lenses is not influenced significantly.

Abstract: In an electron gun, and a color cathode-ray tube and an image display device using the electron gun, each of two pairs of convergence electrodes is disposed in a focusing electrode for focusing three electron beams in a manner to pass the respective side beam of the three electron beams. Since an alternating current voltage synchronized with a deflection current is superposed to one of each pair of the convergence electrodes, such forces are exerted to the side beams as to separate the side beams from each other in the vicinity of the peripheral edge of a screen having a fluorescent body, so that the converging point of the electron beams is positioned on the screen. The focusing function of a main electron lens is weakened in the vicinity of the peripheral edge of the screen, whereby the electron beams are correctly focused.

Abstract: An electron gun for a cathode-ray tube has, in addition to its main lens, a triode with first and second grids as control electrodes. The thickness of the second grid, and the separation between the first and second grids, is at most one-half the diameter of the beam aperture in the second grid. These dimensions lead to formation of a prefocus lens with no concave lens component, hence with no beam diverging effect. The resulting triode aberration corrects spherical aberration in the main lens, so that the size of the beam spot focused on the screen has little tendency to increase with increasing beam current.

Abstract: A cathode ray tube apparatus comprises three cathodes arranged in line with each other in a first direction for emission of respective electron beams therefrom, a focusing electrode having first to third apertures defined therein for the passage of the respective electron beams therethrough, a quadrupole electrode structure including first to third quadrupole electrodes one for each electron beam, each of the quadrupole electrode being comprised of a pair of horizontal electrode pieces spaced a predetermined distance from each other in a second direction perpendicular to the first direction and positioned upwardly and downwardly, respectively, with respect to the associated electron beam, and a pair of vertical electrode pieces spaced a predetermined distance from each other in a direction aligned with the first direction and positioned leftwards and rightwards with respect to such associated electron beam, and a power source circuit for applying a predetermined voltage to the quadrupole electrode structure.