| 摘要 |
A security device for use in security paper comprises a continuous fine ribbon of a width of substantially 0.75 mm. and has printed thereon a design, lettering or pattern comprising characters of a height of substantially 0.4 mm. For the Example, a continuous sheet fed from a roll of regenerated cellulose foil had a name printed upon it in parallel columns in letters 0.4 mm. high. Alternate columns were displaced vertically by half the distance between successive lines. The sheet was then slit into ribbons 0.75 mm. wide, each of which had the name repeated along its length, but separated by spaces which contained mutilated lettering. These ribbons were then incorporated into paper by the method of Patent Specification 440,421. The sheet may alternatively be of paper, metal or plastic film or a laminate, e.g. of a central layer of aluminium foil with a layer of transparent material on each side. Identical designs, lettering or patterns may be printed on both sides. The printing may be in inks of two or more different colours, of which at least one may be fluorescent or sensitive to a chemical reagent which causes it to change colour. Phenophthalein is referred to as an ink component that will change colour when exposed to ammonia vapour. |
