| 摘要 |
A flat glass bulb for a cathode ray tube, which is light weight and provides good productivity, is realized. The external shape of a cross section of a body portion 3 near the yoke portion, perpendicular to the bulb axis, is made to be a substantially rhombic shape or a substantially bobbin shape, the maximum diameter direction of the substantially rhombic cross section is made to be the same as the long axis direction of a funnel, maximum-diameter portions are provided between the long axis and diagonal axes when the cross sectional shape is the substantially bobbin shape, and the body portion is made to be constituted by a smooth continuous surface without having a step, a protrusion or recess, in which the minimum value of the differential value h=f(s) is made to be at least 0 provided that the distance from the yoke end in the direction perpendicular to the bulb axis is s, whereby the stress formed in the yoke portion is reduced to realize a flat cathode ray tube having high reliability.
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