US Patent 10391806 Permanent staining of varnished security documents

The disclosure relates to the field of the protection of security documents, especially banknotes, against illegal actions such as robbery or theft. In particular, the present disclosure relates to the field of ink-stained documents that are resistant to chemicals. The disclosed security documents are covered on at least one side by from about 70% to about 90% of a protective varnish and have from about 10% to about 30% of one or more varnish-free areas with one or more varnish-free indentations, the percentages being based on the total surface of the one side of the security document.