| 摘要 |
Documents with increased resistance to falsification are made by covering one or both sides of an information carrier with films, at least one of which is transparent. The films carry a radiation-curable adhesive layer and are laminated to one or both sides of the document, after which the laminate is exposed to radiation which causes crosslinking of the adhesive. The adhesives are based on radiation-curable unsatd. monomers, oligomers and polymers and opt. a photoinitiator. Typical curable materials contain vinyl gps., (meth)acrylate gps., etc. and may be based e.g. on polyesters, polyethers, polyepoxides, polyurethanes, urethane-modified polyepoxides, urethane-modified polyesters and urethane modified polyesters. The coating film is e.g. of polyethylene which is opt. subjected to corona treatment before use. The information-carrying document is e.g. of paper and the lamination is carried out at up to 150 deg.C, esp. 70-120 deg.C. The irradiation is pref. carried out whilst the laminate is still hot. The process allows documents such as credit cards to be covered with plastic film coatings which are permanently bonded to the paper surface without damaging the paper, and without any possibility of removal without destroying the paper surface, thus giving excellent security against the document being altered. |
