| 摘要 |
PURPOSE:To improve the productivity of a disk of high quality which is not affected by ambient temperature by forming a hub for attraction of a material obtained by mixing magnetic metallic powder with a plastic material which has a coefficient of thermal expansion nearly equal to that of a disk substrate. CONSTITUTION:A resin layer 2, pre-pit projection/recess pattern 3, and a recording film 4 are formed on one-surface sides of two disk substrates 1 and 1 made of plastic materials and spacers 6 and 7 are stuck on the inner and outer peripheral parts of the substrates 1 and 1 to form a specific gap between the films 4 and 4. Then, a projection part 5b which is fitted closely in the center hole 1a of the substrate 1 and a through hole 5c are provided and hubs 5 and 5 molded out of the material obtained by mixing ferromagnetic metallic powder with a plastic material having the coefficient of thermal expansion nearly equal to that of the material of the substrate 1 are bonded to the substrates 1 and 1. Consequently, birefringence due to thermal strain which is generated when the ambient temperature varies is eliminated to prevent an error in reading from occurring and deterioration in C/N from being caused. |
