| 摘要 |
<p>A method for producing markings (MRK1, MRK2) on a web (WEB1) comprises forming a first altered portion (DOT1) of the web (WEB1) by directing a laser beam (LB2) to the web (WEB1) so as to locally reduce the 5 fluorescence yield of the web (WEB1) at the location of the first altered portion (DOT1), wherein the web (WEB1) comprises cellulose fibers and a fluorescent substance, and wherein the visual contrast between the first altered portion (DOT1) and a reference portion (REF1) is smaller than or equal to 5% when the web (WEB1) is illuminated by substantially white 10 visible light (VIS0), which does not contain ultraviolet light (UV0).</p> |
