| abstract |
@ A pit-forming optical recording medium comprises a substrate supporting a film of optically deformable recording material comprising an organic dye for absorbing optical signals of modulated electromagnetic radiation applied to the film and thereby causing corresponding deformations of the film when the signal intensities exceed predetermined threshold levels. The dye is a phthalocyanine compound or mixture of phtalocyanine compounds in which each of at least five of the peripheral carbon atoms in the 1, 4, 5, 8, 9, 12, 13 or 16 positions (the "3,6-positions") of the phthalocyanine nucleus, as shown in Formula 1, is linked by an atom from group VB or Group VIB of the Periodic Table to a carbon atom of an organic radical. In preferred compounds each of the eight, 3,6-positions is linked by an atom from Group VB or Group VIB, especially sulphur, selenium or nitrogen, to an organic radical. |