The present invention relates to specific pentamethine cyanine azo complex dye compounds and their use as dyes in optical layers for optical data recording, preferably for optical data recording using a laser with a wavelength from 630 to 670 nm. The invention further relates to an optical layer comprising said dyes and to a write only read many (WORM) type optical recording medium capable of recording and reproducing information with radiation of a red laser, which employs said pentamethine cyanine azo complex type dye in the optical layer.