| 摘要 |
PROBLEM TO BE SOLVED: To provide a thin and low-cost information recording-reproducing device, where a flat face with an information recording medium formed thereon is rotated with accuracy, and reduced side-runout and information is recorded and reproduced with high density. SOLUTION: A disk portion having the flat face, where the information recording medium for recording information is formed in a plurality of substantially concentric tracks and a rotating shaft portion is integrally formed on the face opposite to the flat face to constitute a rotating disk. As a result, parts for jointing a disk are obviated, and cost is reduced. Furthermore, the accuracy of perpendicularity between the center of rotation and the flat face with the information recording medium formed thereon is enhanced, and a second dynamic pressured generating groove is formed on either of the open end face of a bearing sleeve or the lower face of the rotating disk opposite to the open end face to constitute a second thrust bearing portion. As a result, rigidity of the bearing is enhanced, and accurate side-runout and axial runout of the disk can be obtained for attaining high recording density.
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