| 摘要 |
PURPOSE:To suppress an increase of a double refraction of a variation of temperature and humidity of the environment by constituting the titled disk so that it is placed between the outside periphery of a stop ring made of plastic and a disk substrate, and a center fixture is not stuck to both the disk substrate and the stop ring. CONSTITUTION:On a disk substrate 1, a groove 7B fitted to a ring-like projection 7A of a stop ring 4 is provided in a ring shape on the surface which comes into contact with the stop ring 4. The center of the groove 7B coincides with the center of the disk substrate 1. By fitting the projection 7A and the grove 7B, centering of the stop ring 4 and the disk substrate 1 can be executed exactly and easily. A center fixture 5 is made of SUS 430 and shaped like a ring, and not stuck to both the disk substrate 1 and the stop ring 4. The stop ring 4 is joined concentrically to the outside of the disk substrate 1 by an epoxy compound adhesive agent. In such a way, a dimension variation of the disk substrate 1 at the time of variation of temperature and humidity of the environment is not detained by the center fixture, therefore, an increase of a double refraction can be suppressed. |
