Improved high-density phase-change recording

By using a simple write strategy we have found that a wide range of linear velocities can be covered for direct overwrite in high-density phase-change recording. This is especially advantageous for data recording where the application of constant angular velocity facilitates fast seek and short random-access times. In the case of repeated overwriting, material flow will limit the number of cycles, particularly if a fixed pseudo-random data pattern is used: We studied how a random bit shift can reduce this problem and found that a relatively large shift of up to 100 bytes was required. Using these techniques in an optimized disc structure we achieved more than 100,000 overwrite cycles on a 2.6 Gbyte 12 cm phase-change disc.