MEANS FOR PREVENTING COPYING AND CASUAL VIEWING OF SECURE DOCUMENTS
Original Publication Date: 1980-Dec-31
Included in the Prior Art Database: 2004-Apr-02
Xerox Disclosure Journal
This disclosure describes a method for preparing a document in such a way that it cannot be copied using any generally' available copier or copier/duplicator and can be read only if viewed in a particular direction. These objectives can be achieved by bonding a document containing secure information to a sheet of plastic material called "3M Light Control Film". This material is basically transparent, but contains a miniature louvered structure whi& allows transmission only at a particular angle such as, for example, 45 degrees from the normal to the surface. Thus, copying devices whose optical systems accept input at and near normal incidence are blocked from viewing the printed material, and a casual observer cannot read the document at other than a typical reading angle.