Improvement of the photo-polymer sheet for the multi-layer disk with the high NA objective lens and blue-violet laser

In ODS2000, we reported experimental results for the triple-layer disk using the photo-polymer (2P) sheet (N. Shida et al, ODS 2000 Tech. Dig., pp. 27-29, 2000). The subjects of the 2P sheet were the high transmittance, low variation of thickness and duplicate performance. Therefore, we developed a new 2P sheet which has sufficiently high transmittance of over 95% and sufficiently small thickness variation of less than ±0.5 μm to realize the multi-layer read-only disk. We evaluated the duplicate performance of an improved 2P sheet as the layer 0 (L0) in a dual-layer read-only disk. The disk had 25 Gbyte capacity on each information layer. We measured the jitter value of a sample disk using the reproduction system with a numerical aperture (NA) of 0.85 and a blue-violet laser and the limit equalizer (Y. Tomita, Jpn. J. Appl. Phys. vol. 40, pp. 1716-1722, 2001). As a result, the jitter values were 8.0% on L0 and 7.8% on layer 1 (L1).