| 摘要 |
PROBLEM TO BE SOLVED: To obtain a composition high in productivity and improved in specific Young's modulus of glass by specifying a composition range of SiO2, Al2O3, MgO and P2O5. SOLUTION: The composition is composed of 35-60 wt.% SiO2, 10-30 wt.% Al2O3, 10-30 wt.% MgO and 0.1-1.8 wt.% P2O5. In the production method of the glass, the starting material containing main component composition of a glass substrate formed lastly is sufficiently mixed in a prescribed proportion and put into a platinum crucible and fused. After fusing the mixture, the fused matter is cast into a mold to form a general shape. After annealing the formed matter to room temp., and after forming a crystalline nucleus by holding at the primary heat treating temp. for the primary treating time, the crystalline nucleus is grown by holding at a prescribed secondary heat treating temp. for the secondary treating time, and the crystalline nucleus is cooled slowly to obtain an objective crystallized glass. The glass composition is especially suitable to a crystallized glass magnetic disk, and the glass substrate having the specific Young's modulus not less than 33 and high in productivity is obtained.
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