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 Li2O.
The composition is composed of 54.5-59.5 wt.% SiO2, 10-30 wt.% Al2O3, 10-30 wt.% MgO and 3-12 wt.% Li2O. In the production method of the glass, after mixing the starting material containing main component composition of a glass substrate formed lastly in a prescribed proportion, the starting material is put into a platinum crucible and fused. After fusing the mixture and after forming a general shape by casting the fused matter into a mold, the formed matter is annealed to room temp. Then 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.
MORI TOSHIHARU
YUGAME HIROSHI
KAWAI HIDEKI
SUGIMOTO AKIRA
ISHIMARU KAZUHIKO
