| 摘要 |
PURPOSE: To obtain the substrate for using the area up to the outermost circumference as the data area by removing the birefringence abnormal region generated at the edge outside the substrate after the substrate is formed by introducing dissolved resin into metal dies. CONSTITUTION: A substrate for optical information recording medium can be obtained by removing the birefringence abnormal area generated at the edge outside the substrate after the substrate is formed by introducing dissolved resin into metal dies. Since a polycarbonate resin substrate widely used as the optical disk substrate shows remarkably large optical elastic constant and distinctive birefringence irregularity at the edge of the outermost circumference during the projected molding, a wider cavity is set, for the projected molding, estimating previously the amount of the part removed by cutting so that the disk diameter is specified within the regulation when external edge is removed by cutting. Thereby, the substrate obtained shows an extremely less birefringence and allows the area approximated to the outermost circumference as the data area and particularly realizes high density recording by short wavelength recording with high capacity. |
