Method of rendering documents resistant to photocopying, and anti-copying paper and ink therefor

摘要

Confidential information is printed, typed or otherwise applied to paper with a color having a reflection spectral response or less than about 10% for light with a wave-length below about 600 millimicrons. The color is sufficiently contrasting with the information to enable the information to be read by the human eye when the document is viewed under white light, but the document cannot be successfully photocopied.