PURPOSE: To manufacture at a high speed and easily an optical disk base which is superior in inside and outside diametral-accuracy and thickness accuracy, by a method wherein a difference in level for pushing up a base is provided on a casting nozzle and/or an outside circumferential ring and at the time of peeling off of a cured thing of photosetting resin, a casting nozzle and/or the outside circumferential ring is shifted in an axial direction relatively to a main space.
CONSTITUTION: A mold having a resin rich area 7 is manufactured by fitting an outside circumferential ring 3 having a stepped part 13 in the inside of a notch 8 by arranging a quartz flat sheet 1 and stamper 2 made of Ni by leaving a space between them and facing them each other. Photosetting resin 5 is cast into a mold through a casting nozzle 10 having a stepped part 12 more outside than a notch 9, casting is suspended by closing a casting valve 11 at the time when about a half of the resin rich area 7 crossed over the notch 8 is filled with the photosetting resin 5 and the photosetting resin 5 is cured by a light source 6. A cured thing is removed from the quartz flat sheet 1, then the outside circumferential ring 3 and casting nozzle 10 are lowered and removed from the stamper 2 and then the cured thing of the resin rich area 7 is removed also from the resin rich area 7. A base for an optical disk has little distortion, possesses heat resistance, is superior in mechanical strength and accuracy, has high transparency and is supplyable at a high speed and low cost.
TAJIMA TETSUO
SUDO RYOICHI
HITACHI MAXELL