Thermal expansion and flow model for pit formation in laser marking of polymeric film optical disks

Abstract

A mechanism for the formation of a pit by laser marking of a polymer/dye medium is proposed. The absorbed radiation melts the medium and increases its volume, causing formation of a protruding bulge of molten polymer. This protrusion flows out and levels under the driving force of surface tension. Subsequent cooling and contraction leave a depression surrounded by a rim. Approximate calculations to support the plausibility of the proposed mechanism are presented.