Shadow mask for color cathode-ray tube and method of manufacturing the same

A method of manufacturing a color cathode-ray tube which comprises a face panel including a substantially rectangular effective portion having a long axis and a short axis which are perpendicular to each other;

• a phosphor screen formed on an inner surface of the face panel;
• a shadow mask arranged so as to face the phosphor screen;
• and an electron gun for emitting an electron beam toward the phosphor screen through the shadow mask;
• the shadow mask including a substantially rectangular mask body which is formed with a number of apertures for passing the electron beam and which has a long axis and a short axis individually corresponding to the long axis and the short axis of the face panel, and a rectangular mask frame which supports a peripheral edge portion of the mask body;
• the method comprising the steps of:
• preparing a flat plate like mask material on which a number of apertures are formed;
• plastically deforming the mask material so as to form a mask body having a curved surface such that a relation between a radius of curvature Rc in the short axis direction at the region which is in the vicinity of the long axis of the mask material and a radius of curvature Ra in the short axis direction at those regions which are in the vicinity of long sides of the mask material becomes Rc<Ra;
• elastically deforming the plastically deformed mask body so as to have a curved surface such that a radius of curvature in the short axis direction is larger than the radius of curvature Rc and is constant in the short axis direction;
• and
• fixing the elastically deformed mask body to the mask frame.