Now you see it …

 作者:章兵     |      日期:2019-03-08 04:10:03
By Barry Fox Hide and Seek Technologies of Nederland, Colorado, last year announced its plans for a digital video disc that would self-destruct after a few plays (This Week, 15 November 1997, p 7). At the time, the company would not say how it works, but now a US patent 5815484 explains all. The disc includes an extra layer made from what’s called a “spiropyran” dye, which gradually darkens as the disc is played. Eventually,