To prevent damages from occurring to a gilt layer and resin-coated layers while stably reducing force required for opening of a can by a method wherein a first stage opening groove and a second stage opening groove each having specified front-end radius and groove width are formed in continuity while the remaining thickness for the bottom of the groove is set within a specified range.
Opening grooves 2 are formed respectively on the surface 1a and the reverse side 1b of a can lid 1 made of surface-treated steel plate with resin-coated layers formed on both sides thereof. The opening groove 2 is a two-stage groove that is formed in continuity of the first stage opening groove 2a and the second stage opening groove 2b. The front-end radius ρ1 and the groove width L1 of the first stage opening groove 2a and the front-end radius ρ2 and the groove width L2 of the second stage opening groove 2b shall be such that satisfies the relations represented by formulae I, II and III, and the remaining thickness tR between the bottoms of the opening grooves 2 for the can lid 1 shall be such that satisfies the relation represented by the formula IV. Therefore, corrosion resistance can be ensured without damaging resin coating while reducing force required for opening the can.
MIHARA YUTAKA
FUJIKAKE MASAHISA
YAMAZAKI YUJI
YOMURA YOSHINORI
SUGIHARA REIKO
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