OPTICAL DISK COMPATIBLE WITH TWO DIFFERENT READING SYSTEMS

摘要

The invention concerns an optical disk consisting of two elemental disks (D1, D2) glued one against the other with a layer of transparent glue (3). The first elemental disk comprises a DVD data side (4b) and the second elemental disk comprises a CD type data side (7b). The optical disk of the invention can be read by a normal CD reader for the CD data and by a DVD reader for the DVD data. Thus the problem of costly upward compatibility of DVD readers is solved while ensuring a simple transition from CD to DVD for users.