Super high density optical disc by using multi-layer structure

To realize a super high density optical disc, the authors made basic researches into a space layer by using a photopolymer sheet owing to the uniformity of each space layer thickness. Then a prototype disc was manufactured. Thickness variation on each sheet was within 1.3 /spl mu/m. The transcription characteristic was verified. The data-to-clock jitter of the disc was measured. The recording capacity was 27.4 GB on a 12 cm disc. The capacity of each layer was 13.7 GB. As a result of these basic researches, we realized a super high density optical disc by using multi-layer structure, it is very important to utilize a photopolymer sheet for the space layer. It then will be possible to realize the recording capacity of 50 GB or over on a 12 cm disc having a four layered structure.