| 摘要 |
A high-density optical data disc consists of two basic discs (D1, D2) joined together with a transparent adhesive coating (3). Each disc comprises a transparent substrate (4, 7) with a data surface (4b, 7b) created by a series of micro-projections (6, 8) in spiral or concentric tracks, designed to be read by a laser beam (5a, 5b). The data surface of the first basic disc is coated with a semi-reflective layer (6a) adjacent to the adhesive coating, while the data surface (7b) of the second disc has a reflective metal layer (9) on the opposite side to the adhesive coating. The two data surfaces are produced to two different standards - Compact Disc (CD) and Digital Video Disc (DVD), and the semi-reflective layer has a transmission coefficient which is at least equal to a first predetermined valve for a laser wavelength at least as high as a first threshold. Its reflection coefficient is at least as high as a second predetermined value for a laser wavelength below a second threshold, with the first threshold being at least 100 Nm above the first. |
