Injection molding technology for high speed optical disk

Recently great efforts have been made to increase the data access speed and the data storage density of the optical memory disks such as CD-ROM, DVD, ASMO disk, etc. In the viewpoint of increasing the data access speed of the optical disks, it is of great importance to characterize accurately the vi bration phenomena of the rotating disk, which is related to the critical sp eed and the characteristics of the frequency response. In this paper toward s the goal of increasing the data access speed of the optical disks, we hav e proposed a novel method for improved characteristics of disk vibration wi thout deteriorating any other specification for the optical memory disks su ch as geometrical and optical characteristics. A possible idea to improve t he vibration characteristics of the optical disk is that the tensile initia l stress in the radial direction is to be imposed within the optical disk o n purpose. By the synergy, effect from the residual (initial) tensile stres s frozen within the optical disk combined with the stress induced by the ce ntrifugal force occurring in rotating the optical disk, the stiffness of th e disk would increase to have a stronger resistance to the disturbance resu lting in increase of critical speed. With such a synergy effect in mind, mo difications related to the optical disk substrate design, injection mold de sign and processing conditions of injection molding were presented and part ially evaluated. The computer simulation and experiments indicate that the suggested ideas clearly improve the characteristics of disk vibration witho ut deteriorating any other specification for the optical memory disks.