US Patent 7354640 Hard coating and its production method

A hard coating formed by a physical vapor deposition method, comprising metal elements comprising Si and at least one selected from the group consisting of transition metal elements of Groups 4a, 5a and 6a in the Periodic Table, Al and B, and at least one non-metal element selected from the group consisting of C, N and O, the hard coating having a columnar structure comprising a multi-layer structure composed of pluralities of layers with Si content differences, crystal lattice stripes being continuous in the interlayer boundary regions, and each layer having a thickness of 0.1-100 nm.