First-side dual-layer optical data storage disk and method of manufacturing the same

A first-side optical storage medium comprising:

• a flexible single substrate having first and second principal surfaces;
• a phase-change layer overlying the first principal surface of the substrate, the first principal surface having a series of grooves and, said phase-change layer mimicking a shape of said grooves and lands;
• and,
• an oxy-nitride optical coupling layer overlying the phase-change layer, the oxy-nitride optical coupling layer having a thickness and composition adapted to optically couple the phase-change layer to a laser beam incident on the optical coupling layer and to maximize contrast, and mimicking the shape of the phase-change layer and thus to the shape of the grooves and lands, wherein no further layers overlay the oxy-nitride optical coupling layer.