Laser marking and printing ink therefor.

摘要

A non-destructive laser marking method comprising irradiating laser light on a thermosensitive color-forming layer formed by printing with a printing ink containing a leuco dye as a color former and an acidic substance as a color developer, and at least one background color formation inhibitor selected from the group consisting of a water-soluble amino acid, an ammonium salt of an inorganic acid, a pH buffer, and water. Laser marking can be achieved with low energy and at high speed while minimizing background color formation to provide a high-contrast color image.