| 摘要 |
PURPOSE:To prevent the generation of a camber in a shadow mask after perforation by subjecting a thin sheet of an 'Invar(R)' to a cold rolling with a pair of rolls having different diameters prior to the perforation by etching at the time of producing the shadow mask for a color image receiving tube. CONSTITUTION:The ingot of the 'Invar(R)' consisting of an Fe-Ni alloy is forged and rolled to the shin sheet 1 and after large dots 11a are perforated by etching from one side face 1a, small dots 11b are perforated by etching from the opposite side face 1b to form apertures 11 as the shadow mask. The sheet is cold- rolled by two pieces of rolling rolls 21, 22 having the different diameters of 1:1.2-1:2 radius ratio prior to the above-mentioned etching treatment in this case. The surface 1a to be rolled with the large dots 11a is rolled by the smalldiameter rolling roll 21 and the surface 1b to be formed with the small dots 11b is rolled by the large-diameter rolling roll 22 to form the thin sheet, by which the internal strain larger than in the region to be formed with the small dots 11b is generated in the region to be formed with the large dots 11a. The camber of the shadow mask subjected to the perforation treatment by the etching is thus obviatd.
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