VARYING TONE SECURING DOCUMENT

摘要

An improved security document which protects documents from copying on color copying machines. The document has cancellation terms and background pattern in two tones. If the copier is adjusted to obscure the cancellation term on reproduced copies at one tone, the cancellation at the other tone will appear. In an alternative embodiment, the density of the cancellation term and the background pattern vary across the face of the document. In this case, the cancellation term will appear somewhere on the copy no matter what copier adjustments are made.