CRYSTALLIZED GLASS FOR SUBSTRATE OF INFORMATION RECORDING DISK

摘要

PROBLEM TO BE SOLVED: To obtain crystallized glass for the substrate of an information recording disk excellent in meltability, moldability, mechanical strength and chemical durability, deposing fine crystals and ensuring such surface smoothness as <=10Åsurface roughness after polishing. SOLUTION: Starting material for glass contg., by weight, 55-85% SiO2 , 5-20% Li2 O, 0-10% K2 O+Na2 O, 0-10% MgO, 0-20% CaO, 0-10% SrO, 0-10% BaO, 0-10% ZnO, 0-10% Al2 O3 , 0-15% B2 O3 , 0-6% P2 O5 , 0-3%TiO2 , 0-3% ZrO2 , 0-3% SnO2 and 0-1% As2 O3 +Sb2 O3 as components expressed in terms of oxides and further contg. 0.1-10wt.% F and 0.1-20wt.% Cl is melted, molded, vitrified and crystallized to obtain the objective crystallized glass contg. at least 0.05wt.% Cl.