| 摘要 |
1476681 Security paper DASY INTER SA 9 May 1974 [11 May 1973 6 June 1973 10 April 1974] 20587/74 Heading D2B [Also in Divisions B5 B6 and G4] A document is authenticated by embedding in at least a portion thereof a predetermined number of ferromagnetic particles per unit area of the document or portion thereof, the ferromagnetic particles having been formed by providing a fibrous substance with a coating of ferromagnetic material, the number of ferromagnetic particles per unit area of the document or portion thereof classifying the document. The fibrous substance may be organic e.g. cotton fibres, plastics, or carbon fibres. The ferromagnetic material may be Fe, Co, Ni, a chrome-Ni alloy or chromium-nickel dioxide. The coating of ferromagnetic material may be applied galvanically, or by vapour deposition, spraying, dipping, or printing, and may cover a part or the whole of the fibrous substance. The ferromagnetic particles may be incorporated into paper during its manufacture, and may be arranged therein in strips. Fibres coated with a non-magnetic metal e.g. Al, Sn may be located between strips of the ferromagnetic particles so that there is no optically recognizable difference. The ferromagnetic particles may be aligned vertically to the plane of the paper. |
