| abstract |
A method of checking the authenticity of a heat-sensitive recording material having a carrier paper with a recording layer which is arranged on one face and which contains colorant formers and organic colorant acceptors that react with one another when heated; and a security feature provided as a water-soluble dye which fluoresces under UV radiation, the dye being applied without binder in a pattern, invisible under daylight, to a surface of a face of the carrier paper opposite the face provided with the recording layer, so that the entire surface has the pattern, the water-soluble dye being applied at a mass per unit area between 0.01 and 40 mg/m 2 , the method comprising the step of wetting the surface of the layer opposite the recording layer with an alkaline substance. |