Hidetake Itoh

150 GB, 6-Layer Write Once Disc for Blu-ray Disc System

This report is on a 50 GB 6-layer write once disc with the newly developed recording materials for blu-ray disc system. We achieved the optimum recording powers and the jitter values less than 160 mW and 8.0% for each layer at the user data recording rate of 72 Mbps. This result shows feasibility of realization of 6-layered recordable blu-ray disc

High-Performance Hard Coat for Cartridge-Free Blu-ray Disc

A practical way of realizing cartridge-free Blu-ray disc using nanocomposite UV-curable resin as a hard coat on a laser incident surface of the disc is described. The hard coat is a composite material of UV-curable acrylic resin and nanoparticles of silica. A lubricant that exhibits oil repellency as well as low friction coefficient was added to the hard coat in order to facilitate the removal of fingerprints. It effectively prevents abrasions, scratches and problems of fingerprints on the disc surface. Abrasion and scratch resistances, and ease of fingerprint removal were evaluated and compared with those of a polycarbonate surface and a conventional UV-curable hard coat.

Antifingerprint property of the hard coat for cartridge-free Blu-ray Disc

We made improvements on the previously reported hard-coat for cartridge-free Blu-ray disc from a viewpoint of an anti-fingerprint property. As a result of this study, two types of the hard-coat have been obtained. One is for Blu-ray discs of ROM and write-once types, and the other is for that of rewritable type. The former well inhibited a deterioration of bit error rate (bER) of the signal written prior to the fingerprint adhesion. The later exhibited low bER for the data signals written both before and after the fingerprint adhesion. These results are attributable to the area ratio of drops of fingerprint-ingredient on the disc surface, and the low area ratio resulted in a low bER. Moreover, it was confirmed that the disc with higher contact angle of oily compound exhibited the lower area ratio of the fingerprint.