| 摘要 |
An optically readable media ( 10 ) has an information-encoding layer ( 16 ) and at least one color-forming layer ( 12 ) that embodies an optical readout-limiting mechanism. In a first embodiment the at least one color-forming layer contains an additive that does not interfere with the optical readability of the media for a duration of a readout period. The additive, upon exposure to a source of optical radiation that is suitable for reversing the color-forming layer from an optical readout inhibiting state to an optical readout enabling state, undergoes a transformation that maintains the color-forming layer in the optical readout inhibiting state. More specifically, exposure to the source causes the color-forming layer to photobleach and the additive to oxidize, where the oxidation of the additive permanently inhibits the optical readability of the media. The additive may be a leuco dye. In one embodiment the color-forming layer is comprised of 3-[2,2-bis(4-diethylaminophenyl)vinyl]-6-dimethylaminophethalide and the additive is comprised of benzoyl leucomethylene blue. In a further embodiment the additive is placed into a protective layer ( 18 ) that overlies the color-forming layer.
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