| 摘要 |
<p>A security mark has a photochromic compound covered by a controlled absorption layer comprising a saturable absorber. Light of a wavelength serving to convert the photochromic compound is at low intensity absorbed by the saturable absorber. A photochromic compound converted by UV can thus be sunlight protected. At high intensities, the absorption of the saturable absorber drops to permit conversion of the photochromic compound.</p> |
