| abstract |
A method for forming a document includes the steps of (1) selecting a marking medium that has a pre-determined machine-readable characteristic, and (2) selecting a document substrate that is compatible with the pre-determined machine-readable characteristic of the selected marking medium. An information symbol is secured to the selected document substrate. A security layer which includes the selected marking medium is also affixed to the document substrate so that the security layer is in at least partial register with the information symbol. The method can further include the step of affixing a blocking layer to the document substrate in at least partial register with the information symbol. The blocking layer can be affixed to the document substrate so that blocking layer is intermediate the information symbol and the security layer or so that the security layer is intermediate the information symbol and the blocking layer. Inks that can be printed with conventional printing methods, such as intaglio printing, screen printing, relief printing, planographic printing, letterpress printing, and flexographic printing, are especially useful as any of the selected marking media. The ink used is chosen for a particular machine-readable characteristic such as dry-state conductance, fluorescence, optical density, reflectance, and scattering. For example, an ink which has a known, measurable conductance in a dry-state can be used to print conductive layers on the document which serve as security layers. |