Patent ID: 7098582

Claim:
A cathode ray tube, comprising: a panel having a fluorescent formed on an inner surface thereof; a funnel connected to the panel; an electron gun housed in the funnel, emitting electron beams; a deflection yoke for deflecting the electron beams in horizontal and vertical directions; a shadow mask for selecting colors of the electron beams; and a mask frame for supporting the shadow mask, wherein an outer surface of the panel is substantially flat and an inner surface has a designated curvature, wherein a radius of curvature from a center of the shadow mask in a major-axis, minor-axis and diagonal-axis direction is substantially the same, and wherein the shadow mask satisfies a curvature radius expansion expressed by Z(x, y)=ax 2 +bx 4 +cy 2 +dy 4 +ex 2 y 2 +fx 4 y 2 +gx 2 y 4 +hx 4 y 4 , b/a satisfies a condition of 2.2×10 −6 <b/a<4.4×10 −6 , x and y being a distance (mm) from the center of the shadow mask to a point respectively, and Z being a height difference (mm) between the center of the shadow mask and the point on the shadow mask.