METHOD FOR SECURING THE CUSTOMIZED AREA OF A SECURITY DOCUMENT AND SECURITY DEVICE COMPRISING SUCH A CUSTOMIZED AREA

The invention relates to a method for securing a customized area (120) of a security document (100), comprising the following steps: - inserting, by a first insertion method, a customized color image (122) on a first surface (121, 123) of the security document; - inserting, by a second insertion method, guilloche patterns (124, 126) in color on a second surface (121, 123, 125) of the security document, wherein the first and second surfaces are stacked on top of each other such that the guilloche patterns and the customized image at least partially overlap; and - inserting a colored marking (160) on the customized image and the guilloche patterns by at least two laser beams of different wavelengths, wherein the colored marking passes at least partially through the customized image and the guilloche patterns, and wherein, for the purpose of the colored marking, said wavelengths allow to generate colors obtained by chemical reaction with the pigments of the customized image and the guilloches such that the colors of the colored marking directly depend on the pigments used in the guilloches and the customized image.