Fuji Photo Film Co., Ltd. developed a Blu-ray Disc specification-compliant, write-once read-many (WORM) disc with a blue-violet laser light source.
It features organic dye material as the recording layer, and a spin-coat method can be used to form a layer. A 23.3GB disc already has been manufactured by way of trial, and has been tested on writing and reading at the Blu-ray specification standard speed of 36Mbps, and the double speed of 72Mbps. It says that a 25GB model also has been completed by way of trial.
The company is planning to pursue an aggressive promotion in order to reflect the results this time on the WORM Blu-ray specifications. In addition, according to the company, this technology is also applicable to the next-generation DVD system currently proposed at the DVD Forum by Toshiba Corp. and NEC Corp.
The structure of the 23.3GB sample disc is as follows: from the direction of the laser incidence to the cover layer is 0.1mm; the organic dye layer is a few tens of nanometers; and the disc substrate is 1.1mm. The company refrained from commenting on whether or not there is a protection layer for the organic dye layer.
The main physical specifications are consistent with Blu-ray specification compliant rewritable mediums. Using groove recording, it has a track pitch of 0.32 microns and a minimum recording mark length of 0.16 microns. A glued-on sheet forms a cover layer, and the error in thickness is minimized to between plus and minus 2 microns. Apparently, measures also are being taken to prevent curvature of discs. Whether or not a reflective layer will be adopted is now under examination.
Although the reflectance of the recording layer was not announced, it is said to be higher than the rewritable Blu-ray specifications. The materials for the recording layer were not revealed either. However, as in CD-R and DVD-R, the materials will become cheaper as mass-production progresses. The company plans to start mass production of WORM media in keeping pace with the market growth.