| abstract |
A forgery-proof flat article, for example, for the production of banking cards, credit cards, and the like, is provided with a security feature analogous to a watermark and is made of thermoplastic and elastomeric synthetic resins based on transparent, translucent, or colored sheets made by extrusion, calendering, blow-molding, or spread coating, or composite sheets therefrom, with an application of a colorant, capable of migrating, to the surface in the presence of a crosslinkable component in the flat article and/or in the colorant application. The colorant application, upon reaching the desired migration depth of the applied colorant, is fixed in the flat article by a crosslinking reaction. This flat article, by the use of two differently quickly migrating colorants, has a coloring showing on both sides of the flat article the security feature in congruence, this security feature appearing on the topside in the color of the more rapidly migrating colorant and, when the article is viewed while held up to the light, appearing in the form of the mixed color. n Special effects are obtained in one embodiment of a composite flat article wherein one sheet side, treated with two different colorants, is bonded by laminating to a further sheet. After penetration of the colorants and fixation, the security feature is visible on both sides of the sheet and recognizable in the mixed color when the article is held up to the light and viewed in this way. |