High quality optical disc stampers with round edge grooves

We describe a deep groove having round edges in the optical disc substrate as one of solutions for difficulty in injection molding. The round edge deeper grooves were actually made and tested. Stampers with the round edge grooves can be easily made by modified directly engraved glass mastering. Replication separability from the stamper is markedly improved. No cloud problem, shorter cycle time at replication process and longer lifetime of stampers were confirmed.