MAGNETIC DISK SUBSTRATE WITH OFFSET PORTION ON A MAIN SURFACE WITHIN A RANGE OF 92.0 to 97.0% IN A RADIAL DIRECTION FROM A CENTER, MAGNETIC DISK WITH SUBSTRATE AND MAGNETIC DISK DEVICE

摘要

A magnetic disk substrate having a flat main surface, an end face, and a chamfered face formed between the main surface and the end face. The substrate has an offset portion, present on the main surface within a range of 92.0 to 97.0% in a radial direction from a center of the substrate. A distance from the center of the substrate to the end face of the substrate in a radial direction is 100%, the offset portion being raised or lowered with respect to a virtual straight line connecting two points on the main surface, set at positions of 92.0% and 97.0%. A maximum distance from the virtual straight line to the offset portion in a direction perpendicular to the virtual straight line is a “maximum offset value.”

主权项

1. A magnetic disk substrate being a disk-shaped substrate for use in a magnetic disk to be mounted to a magnetic disk device and having a main surface, an end face, and a chamfered face formed between the main surface and the end face,
the main surface having a flat surface and an offset portion, the offset portion being located at a periphery of the main surface and formed between the flat surface and the chamfered surface, the offset portion being raised with respect to the flat surface, wherein: when a distance from a center of the disk-shaped substrate to the end face is 100%, an extreme portion where rising is maximum in a radial direction in said offset portion is located in a range of 92.0 to 97.0% from the center, and when measuring the extreme portion at 12 points per 30° in a circumferential direction of said substrate, a change in radial position of adjacent extreme portions is 0.3 mm or less.