| 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 contai ns an additive that does not interfere with the optical readability of hte medi a for a duration of a readout period. The additive, upon eyposure to a source of optical radiation that is suitable for reversing the color-forming layer fro m an optical radiaiton that is suitable for reversing the color-forming layer from an optical readout inhibiting state to an optical readout enabling stat e, 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 athe 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-[2,3-bis(4-diethylaminophenyl)viny l]- 6-dimethylaminophthalide 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. |
