Hiroshi Shingai

The Phase Change Optical Disc with the Data Recording Rate of 140 Mbps

We have been developing a new phase change optical disc on the base of the recording system (DVR) with a blue laser (405 nm) and dual objective lens with a numerical aperture (NA) of 0.85. We have achieved the data recording rate of 140 Mbps. The significant techniques to achieve the recording rate as follows: rearrangement of the AgInSbTeGe composition for the rate of 140 Mbps and controlling the re-crystallization by SRC structure (the super-rapid cooling structure) and development of Write Strategy for the high data recording. As a result of the techniques, less than 10% jitter value and more than 1,000 times overwriting possibility at 140 Mbps have been achieved.

Phase Change Disc for High Data Rate Recording

We have developed a phase change disc having a thin transparent cover layer corresponding to the new optical recording system (DVR) using a blue laser (405 nm) and a numerical aperture (NA) of 0.85. We have achieved a user capacity of 22 GB per side of the 120 mm diameter disc, and a user data recording rate of 70 Mbps by designing a highly flat transparent cover layer, a recording layer having high crystallization speed and a film structure for rapid cooling.

Triple-Layer Rewritable Disc with Sb-Based Phase-Change Material

We have been developing a triple-layer rewritable disc on the base of Blu-ray disc systems using a Mn?Sb?Te?Ge phase-change material and N/2 write strategy. The remarkable features of the Mn?Sb?Te?Ge phase-change material are the high crystallization speed and high thermal stability of amorphous marks. The N/2 write strategy can be set at a long cooling pulse period and can realize the formation of amorphous marks of sufficient size. As a result, a sufficient symbol error rate (SER) and a high read stability were achieved and we confirmed the feasibility of a triple-layer rewritable disc with 100 Gbyte and 72 Mbps recording rate.

The phase-change optical disc with the data-recording rate of 216 Mbps

New recording material with higher crystallization speed and higher thermal stability is required to realize a phase-change disc for higher data recording rate. We have developed a new phase-change material that consists of TbSbTeGe material based on eutectic composition. This new phase-change material improves the crystallization speed and the crystallization temperature simultaneously. We have achieved the practical use characteristic of data recording rate of 216 Mbps (6X-speed of Blu-ray Disc) by using TbSbTeGe new phase-change material.

Functional hard-coat for cartridge-free DVR-blue

Optical discs with larger storage capacity and higher data recording rates are required for the coming digital network society, for example, to realize non-linear editing and long term data archiving on broadcasting tasks. We have been developing a new phase change optical disc, which has much higher data recording rate of up to 140 Mbps (T. Kato et al, Tech. Dig. ISOM2001, pp. 200-201, 2001), based on the DVR system (/spl lambda/=405 nm, NA=0.85, cover layer thickness=100 /spl mu/m) (Y. Kuroda et al, 1999; M.J. Dekker et al, 2000; Y. Kasami et al, 2000). As a general rule, the smaller the laser spot size on the disc surface, the more sensitive the disc becomes to scratches or fingerprints on it. In such a system, the distance between the disc surface and objective lens (i.e. working distance) is very narrow due to a high NA. Therefore it is also feared that the objective lens hits the disc surface due to an external impact. To avoid these problems when the disc is taken out of a cartridge, we have developed a new hard-coat. The cartridge-free DVR-blue disc was expected to be accomplished by the following properties: (1) abrasion resistance; (2) scratch resistance; (3) water and oil repellency (low surface free energy). Among these properties, the abrasion resistance is considered to be the most important.

Spin-Coating Technology of the Cover Layer for Digital Video Recording-Blue Disc

We have achieved the cover layer thickness distribution of 100±1.5 µm on a disc by improving the spin-coating method and developing an original spin-coating machine. The small skew of the disc is achieved by using a newly developed UV-curable resin.