| 摘要 |
PURPOSE:To prevent unnecessary fluorescent screen emission due to electron beam reflection on an aperture part by specifying a clearance between a stamping type punch and a die in process of stamping the aperture part so that a rough cut shape is formed. CONSTITUTION:A clearance between a stamping type punch 4 and a dice 5 in process of stamping an aperture in a shadow mask frame 1 is specified to be 1% to 2% or 25% to 40% of plate thickness. In the case of either clearances, a discrepancy in cracks occurs between the punch 4 side and the die 5 side, and the second shear 6 is generated to form a rough cut shape. Therefore, electron beams are deflected in every direction and so the reflected electron beams are not collected on the side of a fluorescent screen, and fluorescent screen emission sensitive to eyes does not occur.
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