No abstract

High-density recording four times that of a current DVD-RAM has been achieved by applying Domain Wall Displacement Detection (DWDD) technology using a conventional optical head which has the same wavelength of 660 nm and NA of 0.6 as the DVD head. It has been confirmed by using a sampled servo and PRML that a recording density of 15 Gbit/inch2 with a track pitch of 540 nm and bit length of 80 nm has sufficient system margin. This means that a capacity of 3 GB on a two-inch-diameter disk is now available for portable use. If applied to a digital video camera, one hour of MPEG2 video contents can be recorded at a transfer rate of 6 Mbps.

To achieve low-cost Blu-ray disc (BD) media, a test line for dual layer media based on the “All Spin Method”, which we have previously proposed, was fabricated. All transparent layers (the space layer, the cover layer, and the hard coat) were made of inexpensive UV resin by spin coating. Dual-layer BD read-only memory (BD-ROM) media were manufactured with a cycle time of 4 s, and the characteristics of the media were observed. The results indicated that (1) the variation in total thickness of the transparent layers was within ±2 µm; (2) tilt properties after sudden environmental change and storage at high temperatures were good; (3) reproduced signals showed good jitter values and symbol error rate (SER); (4) reproduced signals were not degraded even after a storage test of 200 h at 80 °C and 85% relative humidity (RH). We have thus confirmed that the manufacturing line employing the All Spin Method has potential for mass production of low cost BD media. The All Spin Method is adaptable not only to the manufacture of BD-ROM but also BD-R (recordable) and BD-RE (rewritable), so it can contribute to decreasing the costs of all types of BD media.