| 摘要 |
A security document is produced from a paper substrate having invisible hydrophobic toner blended into the paper. The clear toner is produced by milling and classifying a polyester resin, mixing it with silica flowing agent, and then electrostatically imaging the toner onto the paper substrate, as a spot that can be overprinted, or preferably as indicia that is not visible to the naked eye or color copiers. An infra-red absorbing or UV responsive dye may be added to the toner so that it is visible under infra-red/ultraviolet light respectively, or without that dye it is not visible when eliminated by light of any wavelength. When applied to the paper the toner is snow white, but after infra-red heat fusing it blends into the paper and is substantially invisible. The security indicia is easily made visible by passing a conventional marker nib over it, or other mechanism for applying a water based low concentrate colored ink which is readily absorbed by the surrounding paper, but not by the hydrophobic security indicia. |
