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Product and Document Security Method: Utilizing microdrop combinatorics, ink set and ink composition used therein, and products formed

Patent Abstract: 
This technology implements trap-door printing on a substrate with combinatorial microdrop arrays to form arbitrary patterns on the substrate as a means to authenticate products and documents. One method of implementing difficult reversibility in the printing and readout relationship utilizes the combination of pigments and phosphors having non-additive color mixing characteristics to make colored microdots. These microdots are produced by microdroppers or inkjet ejectors, each having a certain proportion of pigments and, therefore, would be producing a unique spectral response. Creating and characterizing a microdot having a unique spectral response holds the “cryptographic key.” A re-measurement of the spectral response of a microdot that matches the “key” authenticates the document on which the microdot is placed. Without knowledge of the “key” and because of the non-additive color mixing characteristics of pigments behind a microdot’s spectral response, a counterfeiter, taking the spectral measurement of a microdot from an original document, and then attempting to determine from this spectral information what pigments and what proportions of each were used to make this microdot, will find it very difficult, indeed almost impossible, to replicate an illegitimate copy of the document. Furthermore, utilizing computer controlled microdrop or inkjet technology adds additional layers of security. The first is that the very small amount of material used for each microdot precludes easy, direct chemical analysis of the deposited microdots. The second security factor is that microdrop or inkjet technology can be used to create very dense two-dimensional arrays of up to tens of thousands of microdots. This means that the reverse engineering to identify the “key” to a multi-thousand element array is an intractably difficult problem in nonlinear combinatorial chemistry. Furthermore, printing marks at “secret” locations on a document—that can be a certain “secret” collection of marks on a document or “secret” marks that are integrated into other patterns or letter prints on a document—adds an extra layer of security.
Low-cost: -Consumer-grade hardware could be used to print secure documents -Economically practical to print and have archived unique security labels for each individual itemHighly resistant to counterfeiting: -Duplication of security pattern is dependent on access to the information key -Resistant to compromise by thefts of raw materials -Allows for direct printing on objects to remove the risk of label transfer -Difficult to replicate spectral patternScalable: -For both low and high security applications -Can be combined with conventional security printing methods to further enhance security -Easy authentication - potentially low cost optical reader, combined with verification of patterns over the internet can allow the average consumer or employee to check
Patent Number: 
6,786,954 (USA)
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