Kishimura Akihiro, Yamashita Takashi, Yamaguchi Kentaro, Aida Takuzo
Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
Nat Mater. 2005 Jul;4(7):546-9. doi: 10.1038/nmat1401. Epub 2005 Jun 19.
Security inks have become of increasing importance. They are composed of invisible substances that provide printed images that are not able to be photocopied, and are readable only under special environments. Here we report a novel photoluminescent ink for rewritable media that dichroically emits phosphorescence due to a structural bistability of the self-assembled luminophor. Long-lasting images have been developed by using conventional thermal printers, which are readable only on exposure to ultraviolet light, and more importantly, are thermally erasable for rewriting. Although thermally rewritable printing media have already been developed using visible dyes and cholesteric liquid crystals, security inks that allow rewriting of invisible printed images are unprecedented. We realized this unique feature by the control of kinetic and thermodynamic processes that compete with one another in the self-assembly of the luminophor. This strategy can provide an important step towards the next-generation security technology for information handling.
防伪油墨变得越来越重要。它们由不可见物质组成，这些物质能提供无法被影印的印刷图像，并且只能在特殊环境下才能被读取。在此，我们报告一种用于可重写介质的新型光致发光油墨，由于自组装发光体的结构双稳性，该油墨会二向色性地发射磷光。通过使用传统热敏打印机已生成了持久图像，这些图像仅在暴露于紫外光下时才可读取，更重要的是，它们可通过加热擦除以进行重写。尽管已经使用可见染料和胆甾相液晶开发出了热可重写打印介质，但允许重写不可见印刷图像的防伪油墨却是前所未有的。我们通过控制在发光体自组装过程中相互竞争的动力学和热力学过程实现了这一独特特性。这一策略可为下一代信息处理安全技术迈出重要一步。
