PRODUCTION OF OPTICAL MASTER DISK AND OPTICAL DISK SUBSTRATE

摘要

PURPOSE:To allow the exposing of very small and narrow-width pits and groove patterns for guiding for a high-density optical disk by adding a shielding plate having adequate light shielding patterns to a master disk cutting device. CONSTITUTION:The band-shaped shielding member 3 is provided on the surface of a recording lens 2 of the cutting device and the light in the central part of a light beam 1 is removed in a band shape. The intensity distribution of the light spot on a focal plane 4 of the lens 2 is such that the zero order diffracted light in the central part is narrow in the width of the distribution and in turn the first order diffracted light appears strongly on both sides of the zero order diffracted light when the light in the central part is shielded. The development processing is, therefore, increased in contrast and the effective gamma value of a photoresist is increased. The groove width is made as narrow as Rb. The optical master disk having the guide grooves and very small prepits suitable for the high-density optical disk is thus obtd. The optical master disk having the very small prepits and guide grooves is produced in this way.