SUBSTRATE FOR INFORMATION RECORDING DISK, AND MOLD AND STAMPER FOR ITS INJECTION MOLDING, MANUFACTURE OF STAMPER, AND INFORMATION RECORDING DISK

摘要

PROBLEM TO BE SOLVED: To form a substrate for information recording disk with superior smoothness and evenness, and an injection mold and a stamper for its manufacture. SOLUTION: Cavity face forming plates 1, 2 of a mold 20 for injection molding of a plastic substrate are polished roughly, and thereafter electroless Ni-P plating is applied to the surface for the section of a cavity 22. The surface of plating is polished by the use of abrasive grains so as to obtain a surface roughness of Ra<=2.0 nm, Rmax<=22 nm. A plastic substrate molded by the mold has a smoothness equal to the polished plating surface. The cavity 22 face can also be formed with uneven patterns for formation of pits. This allows the near contact of a magnetic head, so that a high density recording can be realized.