Patent ID: 8622436

Claim:
A security document incorporating a chemically reactive security ink, comprising: a document substrate, a message printed on said document substrate in a solvent-resistant message ink, and a solvent-soluble masking ink printed in a pattern over said message so that said pattern obscures or hides said message until said solvent-soluble masking ink is removed by exposure of said solvent-soluble masking ink to solvent, wherein: the solvent-soluble masking ink comprises a solvent-soluble dye and a non-drying vehicle or ink base; the solvent-soluble dye is selected from the group consisting of azo dyes, xanthene dyes, anthraquinone dyes, triarylmethane dyes, azine dyes, thiazine dyes, phthalocyanine dyes, and metal complexes of the same; the non-drying vehicle or ink base comprises from 10% to 60% by weight resin and from 30% to 90% by weight oil, based on the total weight of the non-drying vehicle or ink base; the solvent-soluble masking ink comprises from 0.1% to 20% by weight said solvent-soluble dye, based on the total weight of the solvent-soluble masking ink.