| 摘要 |
PURPOSE:To prevent the crazing and peeling of the coated film in an outer peripheral part and to well maintain the appearance of the optical disk substrate by rounding the sectional shape of an end part which is the boundary part between a main surface and an outer peripheral surface and providing a shoulder part projecting toward the outer side on the outer peripheral surface. CONSTITUTION:The surface of the disk substrate 1 slopes continuously downward while gently drawing an arc in the outer peripheral end part when the sectional shape in the outer peripheral end part of the substrate 1 is rounded to >=0.3mm radius of curvature. The film material falling down along this surface is shaken off and splashed by centrifugal force without stagnating at all. The build up of the film material in the outer peripheral end part of the substrate 1 is thereby decreased and the coated film having a uniform thickness is formed. The cracking and peeling by stresses are, therefore, obviated. The shoulder part 9 projecting >=0.1mm and <=5mm is formed on the outer side of the substrate in succession to the round end part, by which the film material beginning to fall down without being completely shaken off in the round end part 3 is stagnated and retained in this shoulder part. As a result, the spread of the film material to the rear side 11 of the coated surface is obviated and, therefore, the good appearance of the substrate is maintained. |
