Hitachi Maxell, Ltd. has developed an optical storage technology "stacked volumetric optical discs (SVOD)" that can boost per-volume capacity by using a film-type disc medium with a thickness of 92 μm. The prototyped disc is a recordable disc with a diameter of 12 cm which is equivalent to that of DVDs. It includes two 92 μm thick disc media that are bonded with each other, and the capacity on both sides totals 9.4 GB.
Based on the new technology, the company has succeeded in the development of a high-capacity optical storage system having 940 GB by accommodating 100 newly developed discs in a dedicated cartridge (thickness: 6.5 cm; width: 13.3 cm; depth: 16.1 cm). The system has an advantage that its size can be significantly reduced compared to the typical DVD library systems for the same capacity.
The company plans to commercialize SVOD as early as the beginning of 2007. The target price is set at ¥40,000 or lower for a cartridge holding 100 discs. Although the system is mainly targeted for commercial use, Norio Ota, Fellow and Chief Engineer of Hitachi Maxell commented; "It is possible that the product will be provided for consumer use, too." The technology can also be applied to the next-generation optical disc that utilizes a blue-violet laser. In that case, the capacity that can be achieved by using a cartridge with 100 discs reaches 3 to 5 TB.
Two features were stressed as key points in the development of SVOD: disc manufacturing technique with the adoption of 92 μm thin film, and thin disc record/playback technique.
CD and DVD disc media are usually manufactured by injection molding, which method cannot be employed to make a disc as thin as the one used in the new optical storage system. Thus, the company has adopted a polycarbonate sheet which is used in a protective layer of the Blu-ray discs. According to the process developed by Hitachi Maxell, the sheet is subjected to heat pressing in order to obtain land and groove pattern on its surface. This process is referred to as nanoimprint technique. Although it required 6 minutes for heat pressing at the initial stage of the development, it has been reduced to 8 seconds by now. The company claims that a yield comparable to that of DVDs is expected.
The recordable system demonstrated at a press conference was fabricated by using an optical head and driver LSI included in typical DVD systems. It enables 8x recording on recordable discs. The company boasts that the size of the prototyped system supporting two-sided recording has been reduced to less than 1/10 that of a typical DVD library system.
Yasushi Uchida, Nikkei Electronics