| 摘要 |
<p>A crystallizable glass composition for producing magnetic disk substrates which precipitates a main crystalline phase consisting of at least one kind selected from the group consisting of mullite and aluminum borate crystals by a heat treatment and has a composition: SiO2: 20 to 45 % by weight, Al2O3: 25 to 45 % by weight, B2O3: 10 to 25 % by weight, MgO: 2 to 20 % by weight, Li2O: 0 to 2 % by weight, Na2O: 0 to 2 % by weight, and K2O: 0 to 3 % by weight, wherein Li2O + Na2O + K2O is 0 to 5 % by weight, and a glass-ceramic magnetic disk substrate which is prepared by forming, the following heat treating, and the following polishing the crystallizable glass composition. The glass composition can easily be formed and the disk substrate can easily be polished, have excellent mechanical strength, surface flatness, surface smoothness, chemical durability, and heat resistance, and show no deterioration of magnetic film characteristics by alkali migration.</p> |
