A security paper is provided for incorporation in a security document, or other document having intrinsic value. The security paper includes a resinous substrate sheet on which indicia are printed. Paper sheets are laminated on either side of the resinous substrate sheet using a suitable adhesive. In...http://www.google.es/patents/US5449200?utm_source=gb-gplus-sharePatente US5449200 - Security paper with color mark
