Patent ID: 7045942

Claim:
A color picture tube, comprising: a panel; a phosphor screen in a substantially rectangular shape, formed on an inner surface of the panel; and a shadow mask in which a number of electron beam passage apertures are formed, placed so as to be opposed to the phosphor screen, wherein a radius of curvature of an outer surface of the panel is 10,000 mm or more, the shadow mask is made of a material containing 95% or more of iron, assuming that a distance from a reference point to a useful area end on the shadow mask in a direction vertical to a tube axis is L, and a sagging amount at the useful area end with respect to the reference point in a tube axis direction is Ze, in a case of defining a first sagging amount curve representing a first sagging amount Z 1 at a point at a distance d from the reference point in the direction vertical to the tube axis, represented by the following Formula 1, and a second sagging amount curve representing a second sagging amount Z 2 at a point at the distance d from the reference point in the direction vertical to the tube axis, represented by the following Formula 2, a sagging amount change curve along a curve C 1 on a surface of the shadow mask, which a plane passing through a center P 0 of a useful area of the shadow mask and parallel to the tube axis and a major axis crosses, satisfies the following Condition 1, and assuming that an intersection between the curve C 1 and the useful area end of the shadow mask is a major axis end PL, a distance from the center P 0 to the major axis end PL along the major axis is W, and a point on the curve C 1 away from the center P 0 by ⅔×W in a major axis direction is P 1 , a sagging amount change curve along a curve C 2 on the surface of the shadow mask, which a plane passing through the point P 1 and parallel to the tube axis and a minor axis crosses, satisfies the following Condition 2: Z 1={( Ze ·(1− rf 1))/ L 2 }d 2 +{( Ze·rf 1)/ L 4 }·d 4 Formula 1: Z 2={( Ze ·(1− rf 2))/ L 2 }d 2 +{( Ze·rf 2)/ L 4 }·d 4 Formula 2: Condition 1: Assuming that a sagging amount at the major axis end PL with respect to the center P 0 is ZPL, at least 60% portion of the sagging amount change curve along the curve C 1 between the center P 0 and the major axis end PL is present between the first sagging amount curve represented by the Formula 1 and the second sagging amount curve represented by the Formula 2, where L=W, Ze=ZPL, rf 1 =0.7, rf 2 =1.2, Condition 2: Assuming that an intersection between the curve C 2 and the useful area end of the shadow mask is P 2 , a distance from the point P 1 to the point P 2 in a minor axis direction is H 2 , and a sagging amount at the point P 2 with respect to the point P 1 is ZP 2 , at least 60% portion of the sagging amount change curve along the curve C 2 between the point P 1 and the point P 2 is present between the first sagging amount curve represented by the Formula 1 and the second sagging amount curve represented by the Formula 2, where L=H 2 , Ze=ZP 2 , rf 1 =−0.4, rf 2 =0.