Method for manufacturing glass blank for magnetic disk, method for manufacturing glass substrate for magnetic disk

摘要

A method for manufacturing a glass substrate for magnetic disk is provided in which a glass is kept from being fused to a mold during press forming and shape processing to achieve a good circularity is efficiently performed. The method includes: a forming process of forming a disk-shaped glass blank by direct-pressing a molten glass by a pair of dies; and a shape processing process of performing at least one of inner hole formation and outer shape formation for forming a disk-shaped glass substrate by forming a cutting line on the principal face of the glass blank, followed by growing the cutting line to perform cutting. In the forming process, press forming is performed while the temperature of the pair of dies, over a period of time until a molten glass is separated from the die after coming into contact with the die, is set at a temperature lower than a glass transition point (Tg) and a mold release material is not attached to the surfaces of the pair of dies.

主权项

1. A method for manufacturing a glass substrate for magnetic disk, the method comprising:
a forming process of forming a disk-shaped glass blank by direct-pressing a molten glass by a pair of dies, wherein press forming is performed while the temperature of the pair of dies, over a period of time until a molten glass is separated from the die after coming into contact with the die, is set at a temperature lower than a glass transition point (Tg) and a mold release material is not attached to the surfaces of the pair of dies; and a shape processing process including:
scribing an outside concentric circle and an inside concentric circle on the principal face of the disk-shaped glass blank to form two-concentric-circle shape cutting lines, andgrowing the circular cutting lines by partially heating the disk-shaped glass blank so that a portion outside the outside concentric circle and a portion inside the inside concentric circle are removed due to a difference in thermal expansion of the disk-shaped glass blank to form a ring-shaped glass substrate, wherein a pressing force applied to a cutting line for the outside concentric circle is higher than a pressing force applied to a cutting line for the inside concentric circle.