We developed fabrication process using "all spin method" for dual layered Blu-ray Disc ROM. All of the light transmitting layer consisting of a space layer, a cover layer and a hard coat are formed by spin-coating method. Regarding the cover layer, the cycle time is less than 15 seconds and the efficiency of usage of the UV curable resin is 59%. The fabricated disc has sufficient property of thickness variation of the light transmitting layer for all disc area. The disc also has good performances of tilt characteristics including tilt transition caused by environmental sudden change due to the moisture control layer although the substrate material is conventional poly-carbonate. We confirmed the feasibility of the dual layered BD-ROM by "all spin method" and it shows the possibility of low cost BD-ROM disc.
Multi-layer write-once optical disks with tellurium suboxide palladium-doped phase-change recording films were designed and adopted to read/write utilizing a violet laser. A dual- layer medium showed carrier to noise ratios (CNRs) of more than 50 dB within a laser power of 7 mW at a linear velocity of 5 m/s in each the condition of numerical aperture (NA) equals 0.65 and NA equals 0.85, which corresponds to a recording capacity of 27 GB and 45 GB on a dual-layer disk of (phi) 120 mm in diameter, respectively. Furthermore, a quadruple-layer medium showed CNRs of more than 48 dB within a laser power of 12 mW at a linear velocity of 5 m/s in the condition of NA equals 0.85, which corresponds to a recording capacity of 90 GB on a quadruple-layer disk of (phi) 120 mm.