Process for preparing film positive sheets for forging-by-copying-proof prints and prints therefrom
Security, information document
Varying tone securing document Patent #: 5197765
ApplicationNo. 926692 filed on 08/10/1992
US Classes:283/93, Having dot pattern283/902ANTI-PHOTOCOPY
ExaminersPrimary: Bell, Paul A.
Attorney, Agent or Firm
Foreign Patent References
International ClassB42D 015/00
Foreign Application Priority Data1991-12-07 GB
AbstractA security document that provides an indication it is a copy when copied by a photocopy machine has printed background pattern and warning printer matter interspersed with blank areas of a substrate to provide a distinct intermeshed pattern so that the warning printed matter is indistinguishable from the printed background by the human eye. The printed background comprises a number of parallel lines of a size such that they will be resolved by a photocopy machine, while the warning printed matter comprises geometric elements (typically circular dots) of a size less than that which can be resolved by a photocopy machine. The dots are disposed in a geometric continuation of at least some of the lines from the printed background, and are configured to form invalidating indicia of the document is copied by a photocopy machine. The printed background pattern and warning printed matter typically have a density of less than 20%, such as about 7-11%. The warning printed matter may be in the form of at least one outline letter configuration, in which case second lines, making an angle of about 20-70% with respect to the first lines, are provided within the outline letter configuration.