| 摘要 |
PURPOSE:To obtain a high production yield by forming a recording layer and a protective coating layer on a substrate and then forming a warpage-correcting groove in a specified area in the inner circumference part of the substrate to correct warpage of the substrate. CONSTITUTION:After a recording layer and a polymer protective coating layer comprising an org. polymer material not shown in the figure are formed on the substrate of an optical disk 1, a warpage correcting groove 3 having 0.01-0.5mm depth and 0.01-1.0mm width is formed in the inner area from the most inner circumference part 2a of the signal region 2 of the optical disk 1. Further, a hub 4 is attached to the center part. Thereby, tensile stress in the protective coating layer comprising a UV-curing resin is relaxed to decrease warpage of the optical medium. Or, the warpage correcting groove 3 may be formed on the hard coating layer or the protective coating layer, or plural warpage correcting grooves may be formed with 18, 19, and 20mm radii according to the degree of warpage. |
