Color cathode ray tube having a radius of curvature ratio relationship

A color cathode ray tube comprising:

• an envelope including a panel having a substantially rectangular effective portion, the effective portion including an outer surface in the form of a substantially flat surface or a curved surface having some curvature;
• a phosphor screen on the inner surface of the effective portion;
• an electron gun configured to emit electron beams toward the phosphor screen;
• and
• a shadow mask located between the phosphor screen and the electron gun, the shadow mask including a substantially rectangular effective surface opposed to the phosphor screen and formed having a number of electron beam passage apertures, the effective surface having a major axis extending at right angles to a tube axis and a minor axis extending at right angles to the tube axis and the major axis and being formed of a curved surface convexed on the phosphor screen side,
• the effective surface of the shadow mask being formed so as to fulfill relations:
• 2≦RH1/RH2≦4, and
• 1<RV1/RV2≦1.47,
• where H is the distance from the center of the effective surface of the shadow mask to the major-axis end portion of the effective surface, RH1 is an average major-axis-direction curvature radius of the effective surface on the major axis defined by a distance H/2 from the center of the effective surface to a midpoint in the major-axis direction and a fall ZH1 of the effective surface in the direction of the tube axis with respect to the center of the effective surface at the major-axis-direction midpoint, RH2 is an average major-axis-direction curvature radius on the major axis defined by a distance H and a fall ZH2 of the effective surface in the direction of the tube axis with respect to the center of the effective surface at the major-axis end portion, V is the distance from the center of the effective surface of the shadow mask to the minor-axis end portion of the effective surface, RV1 is an average minor-axis-direction curvature radius on the minor axis defined by a distance V/2 from the center of the effective surface to a midpoint in the minor-axis direction and a fall ZV1 in the direction of the tube axis with respect to the center of the effective surface at the minor-axis-direction midpoint, and RV2 is an average minor-axis-direction curvature radius on the minor axis defined by a distance V to the minor-axis end portion and a fall ZV2 in the direction of the tube axis with respect to the center of the effective surface at the minor-axis end portion.