Characteristics of Flexible-Film Disks

To achieve high-density recording with a high numerical aperture (NA) pickup, we produced a flexible optical disk system that has a small axial runout, enabling the pickup to follow the focal servo more easily. Young's modulus, the film thickness, and the position of the radius determine the rigidity of a film. Therefore, we defined the length to which a stabilizer pushing on a disk deformed the disk as the repellent force of the film and investigated the relationship between this repellent force and the axial runout of the disk. Consequently, by developing films with a specific repellent force, the axial runout of a variety of disks was reduced to less than 10 µm and high-density recording was achieved at a linear velocity of 13 m/s.