Electronic characterization of N,N′-bis(2-phenylethyl)perylene-3,4: 9,10-bis(dicarboximide) and its application to optical disks

The title compound is a commercial black pigment based on the perylene skeleton. As evaporated, it exhibits a brilliant red color (absorption maximum: 500 nm). However, it undergoes a color change from red to black (absorption maxima: 473 and 610 nm) when exposed to acetone vapor or heated above 100 degrees C for several seconds. The electronic spectra have been characterized on the basis of the crystal structure and intermolecular interactions. The red color (500 nm) is due to randomly oriented, individual molecules in the amorphous phase; whereas the black phase is characterized by a quasiordered system which gives two absorption bands: one is due to individual molecules (473 nm) and the other is due to exciton coupling effects (610 nm). The color change is attributed to the appearance ("on" state) or disappearance ("off" state) of the absorption band around 610 nm and is applicable to optical disk systems based on an AlGaInP diode laser of 635 nm. An information storage system has been developed in which the absorption at 635 nm is switched on (red-black) or switched off (black-red) on irradiation with laser in the presence of a hydrazone compound that induces a phase change. (C) 1998 American Institute of Physics. [S0021-8979(98)04220-0].