Color cathode ray tube

A color cathode ray tube comprising:

• a vacuum envelope including a substantially rectangular panel having a substantially flat outer surface, an inner surface provided with a phosphor screen, and a long axis and a short axis perpendicular to each other and also to a tube axis;
• a shadow mask arranged in the vacuum envelope and opposed to the phosphor screen, the shadow mask including a mask main body that has a substantially rectangular mask surface and a skirt portion extending along a periphery of the mask surface, and a substantially rectangular mask frame attached to the skirt section of the mask main body, the mask surface including an effective portion opposed to the phosphor screen and provided with a plurality of electron beam passage apertures;
• and
• an electron gun provided in the vacuum envelope for emitting electron beams onto the phosphor screen through the shadow mask,
• wherein:
• the inner surface of the panel has an effective section with a curvature, the inner surface of the panel being formed to satisfy at least one of the following relationships:
• ZPH/LPH≦0.050,
• and
• ZPV/LPV≦0.050
• where LPH represents a distance from a center of the effective section to a long axis end of the effective section, LPV represents a distance from the center of the effective section to a short axis end of the effective section, ZPH represents a fall of the effective section at the long axis end along the tube axis with respect to a level of the center of the effective section, and ZPV presents a fall of the effective section at the short axis end along the tube axis with respect to the level of the center of the effective section;
• and
• the mask frame has a pair of long side walls situated symmetrical with respect to the long axis, and a pair of short side walls situated symmetrical with respect to the short axis, at least one of each long side wall and each short side wall having a convex curved shape such that a central portion thereof projects outwardly, and satisfying at least corresponding one of the following relationships:
• YFL/LFL≦0.015,
• and
• XFS/LFS≦0.015
• where LFL represents a distance from the short axis of the effective section of the mask surface to each corner of the effective section, LFS represents a distance from the long axis of the effective section of the mask surface to each corner of the effective section, YFL represents a fall, along the short axis, between a point of each long side wall of the mask frame on the short axis and a point of said each long side wall which is apart from the short axis by LFL, and XFS represents a fall, along the long axis, between a point of each short side wall of the mask frame on the long axis and a point of said each short side wall which is apart from the long axis by LFS.