| 摘要 |
This invention converts commercially available plastic ID cards, usually made of PVC, and/or electronically printed documents, e.g., laser printed documents, photo copier printed documents, dye-sublimation printed documents, ink jet printed documents, into time dependant, self-expiring badges or documents that display a visual indicia, e.g., change of color, appearance of a word, e.g., VOID after a specified or predetermined period of time. Broadly, a pressure sensitive security sticker is applied to these commercially available plastic ID cards and/or electronically printed documents. The sticker changes color, typically from white to red, after a predetermined period of time. This change in color is caused by the toner/dye/color pigment contained in these documents. The sticker provides a time dependent indicator for these documents. These security stickers can also display words like "VOID' after the expiration of the document or card so that security personnel will readily recognize that the ID credential or document is no longer valid.
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