| 摘要 |
PROBLEM TO BE SOLVED: To improve an impact resistance of a shadow mask used for a flat picture tube by making the area of a hole opened on a front side change, coping with the location where a through-hole is formed. SOLUTION: For the shadow mask 1 having through-holes 2a, 2b formed with back side hole parts 4a, 4b into which electron beam is emitted, and front side hole parts 3a, 3b from which electron beam is traveling outside, forming beam spots into a prescribed shape on a surface to be irradiated, the opening area of front side hole part 3b of the through-hole 2b located at peripheral part of the shadow mask is made smaller than the opening area of front side hole part 3a of the through-hole 2a located at the middle part of the shadow mask. This shadow mask 1 is effective, especially when it is used for flat picture tube.
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