Importance

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Abstract

A method is disclosed for making an optically readable media (20) unreadable. The method includes steps of providing the media having a readout layer (22, 23) having features that encode information; forming over the readout layer a reactive layer (302) that inhibits a readout device from reading the information; and forming over the reactive layer a reaction inhibiting layer (304) comprising a volatile substance that inhibits transport through the reaction inhibiting layer until the volatile substance is lost to the environment. The reactive layer may contain a solvent and a dye and may be a color-forming layer that is responsive to a loss of the solvent. The solvent of the color-forming layer may comprise 1,5-dimethyl-2-pyrrolidinone (DMP), or it may comprise N-methyl-pyrrolidinone (NMP). The reaction inhibiting layer may also contain a solvent, such as any transparent, non-absorbing solvent. Glycerol is one suitable example. The reaction inhibiting layer could also comprise water that evaporates to the environment. Also disclosed is an optically readable media that includes means for rendering the optically readable media unreadable, and that further includes an inhibit layer that contains a first substance that slows the passage of a second substance through the inhibit layer while the first substance is present in the inhibit layer. The second substance is one involved in a chemical reaction that results in the optically readable media becoming unreadable.

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First Claim