| 摘要 |
PROBLEM TO BE SOLVED: To improve sealing performance when preserved in a magnetic disk cartridge which is constituted by rotatably accommodating a disk-shaped magnetic disk medium having a center core in a flat cartridge case provided with a window part for inserting a magnetic head and a shutter member for opening/ closing the window part and forming a hole part which makes a bottom surface of a cylindrical hub of the center core face to an outside at the lower surface of a cartridge case. SOLUTION: At a lower plate part 52 of the shutter member 5, a plate part 52a extending till the hole part 27 which makes the bottom surface of the cylindrical hub of the center core face to the outside is extendingly provided and the hole part 27 is opened/closed by the plate part 52a.
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