PURPOSE: To reduce the warpage and reggedness of the titled substrate and to improve the flatness by completely curing the cross-linking plastic plate of vinyl ester resin, polyester resin, etc., which has been primarily cured in a mold and released from the mold in an inert liq. such as fluorocarbon.
CONSTITUTION: A soln. (6%) of cobalt naphthenate in naphthenic acid is added by 0.5% to a phenyol novolak type resinous soln. contg. 36% styrene monomer as a curing accelerator, and then 1.5% org. peroxide is added as a curing agent. The soln. is defoamed, charged into a mold, and then allowed to stand at 25°C for 20min to primarily cure the resin. The obtained plastic substrate is released from the mold, and worked into a specified size to obtain an optical disk substrate. The optical disk substrate 1 and a substrate holder 2 are immersed in an inert liq. 4 such as fluorocarbon which is stored in a liq. container 3. The liq. is heated at the rate of 10°C/min from 25°CW90°C, and kept at 90°C for 1hr to completely cure the plastic of the substrate 1.
YASHIRO MITSURU
YAMAMOTO KAZUMASA
