Laser marking method, laser marking composition and articles having color developing layer made of said composition

摘要

This invention relates to a laser marking method which comprises coating a laser marking composition containing as essential components a color former, a color developer and an inorganic compound having the absorption peak on the infrared absorption spectrum in the region of 900-1,000 cm-1 on a substrate to form a color developing layer, and irradiating laser light to the color developing layer; the laser marking composition; and articles having a color developing layer made of the laser marking composition. The method of this invention is capable of forming a mark with vivid color development even when the color developing layer is a thin film of less than 5 mu m in thickness or when marking is carried out at high speed.