Patent ID: 7265484

Claim:
A color picture tube comprising a panel in which a phosphor screen is formed on an inner surface of a substantially rectangular useful portion, and a shadow mask, wherein the shadow mask includes a perforated region opposed to the phosphor screen and made of a substantially rectangular curved surface in which a number of electron beam passage apertures are formed, a non-perforated region placed on a periphery of the perforated region so as to surround the perforated region, and a skirt portion connected to the non-perforated region and bent with respect to the non-perforated region, wherein a radius of curvature of an outer surface of the useful portion of the panel is 10,000 mm or more, assuming that a tube axis of the color picture tube is a Z-axis, an axis orthogonal to the Z-axis and parallel to a long edge direction of the perforated region is an X-axis, an axis orthogonal to the Z-axis and parallel to a short edge direction of the perforated region is a Y-axis, a size of the perforated region on the X-axis is 2L, and s is a variable satisfying 0<s<1, assuming that sagging amounts of the curved surface of the perforated region along the Z axis, with respect to a mask center, at points of X=0, sL, L on the X-axis, are Z 00 , Z 01 (s), Z 02 respectively, and sagging amounts of the curved surface of the perforated region along the Z axis, with respect to the mask center, at points of X=0, sL, L on the long edge of the perforated region, are Z 10 , Z 11 (s), Z 12 respectively, when, using a sagging amount difference ΔZ Z 01 (s) at the point of X=sL with respect to the point of X=0 on the X-axis, defined by ΔZ 01 (s)=Z 01 (s)−Z 00 , a sagging amount difference ΔZ 02 (s) at the point of X=L with respect to the point of X=sL on the X-axis, defined by ΔZ 02 (s)=Z 02 −Z 01 (s) a sagging amount difference ΔZ 11 (s) at the point of X=sL with respect to the point of X=0 on the long edge, defined by ΔZ 11 (s)=Z 11 (s)−Z 10 , and a sagging amount difference ΔZ 12 (s) at the point of X=L with respect to the point of X=sL on the long edge, defined by ΔZ 12 (s)=Z 12 −Z 11 (s), α(s) represented by α(s)=(ΔZ 01 (s)/ΔZ 11 (s))/(ΔZ 02 (s)/ΔZ 12 (s)) is defined, dα(s)/ds≧0.4 is satisfied in at least a part of a range of 0.2≦s≦0.8.