One of the main parameters controlling durability of optical disks such as CD-R is the stability of the dye layer. Ambient light exposure contributes to degrdn. of the light-sensitive dye used in recordable media. Our study focuses how light irradn. influences the dye layer on a polycarbonate (PC) substrate before and after CD-R engraving. The dye layer surface was characterized by at. force microscopy (AFM) to measure dye degrdn., which, in turn, can be used to assess CD-R readability. For a blank CD-R, pre-groove height is a major degrdn. indicator. For a recorded CD-R, however, pit and land size and depth can be used to show degrdn. For long irradn. times, coded areas completely disappear, leading to the loss of stored information