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: The in-line type electron gun of this invention is formed so that a depression, which is formed at the lower voltage electrode face opposing to the higher electrode of the two electrodes for forming a common main focusing lens in the opposing gap thereof and has three lens holes for individual electron beams arrayed in-line at the bottom thereof, is formed so that the width in the direction perpendicular to the lens hole array direction is smaller at the central part in the lens hole array direction as compared with the other parts. Also the center lens hole of the three lens holes at the bottom of the depression is smaller in diameter than the other two. Accordingly, the focus voltages of the three beams passing through the three lens holes and the shapes of beam spots are made more uniform as compared with the prior art.

Abstract: A color cathode ray tube comprises a first fluorescent part on a part of an inner surface of a face plate and said first fluorescent part imparting a luminescence of a predetermining reference white color by irradiation of electron beams; a second fluorescent part on the remained part of the face plate and said second fluorescent part imparting red, green and blue fluorescent dots or stripes wherein the first fluorescent part for the reference white color is formed by a mixture or tricolor fluorescent materials for the second fluorescent part or a mixture of tricolor fluorescent materials which imparts a luminous spectrum being similar to that of the tricolor fluorescent materials for the second fluorescent part.