| 主权项 |
1. A method for manufacturing a glass substrate by employing a down-draw process in which a molten glass is made to overflow from a forming member and formed into a sheet glass and the sheet glass is then cooled while being drawn in a downward-flow direction, the method comprising:
after the sheet glass has separated from the forming member and when a temperature of the sheet glass is within a temperature region ranging from a temperature higher than the softening point to a temperature near the annealing point, cooling the sheet glass by maintaining a viscosity of side sections of the sheet glass within a range of 109.0-1014.5 poise while applying a tension toward said side sections, wherein, in said temperature region, a thickness-equalizing step of equalizing a thickness of the sheet glass along a width direction and a warpage-reducing step of reducing warpage of the sheet glass after the thickness-equalizing step are performed, and wherein: in the thickness-equalizing step, a widthwise temperature distribution in a central region of the sheet glass is kept uniform, and a temperature in both the side sections of the sheet glass is made lower than a temperature in the central region; and in the warpage-reducing step, the widthwise temperature distribution of the sheet glass is set to temperatures lower than the widthwise temperature distribution in the thickness-equalizing step, and a temperature gradient is formed in the width direction of the sheet glass from a center section of the central region toward said side sections. |
