US Patent 7736768 Magnetic disk and manufacturing method thereof

A magnetic disk comprises a magnetic layer and a protective layer sequentially formed on a disk-shaped substrate and has a principal surface to which data is recorded, and a side surface portion both of which are coated with the protective layer. The protective layer on the side surface portion is thinner than the protective layer on the principal surface. Preferably, the side surface portion includes a side wall surface, and a chamfered surface lying between the side wall surface and the principal surface, and at least the protective layer on the chamfered surface is thinner than the protective layer on the principal surface.