Abstract: The invention is to improvements in signature panels for credit cards or similar instruments. The signature panel is made from a foil having a carrier layer with a transferable signature panel layer having a coating composition incorporating a polymeric material. The signature panel layer can be transferred in response to heat and pressure onto a plastic substrate from the carrier layer providing a signature space. A security indicia is placed on or in the signature accepting surface, of the signature panel layer, using an ink to define a rainbow pattern.

Abstract: A transfer film for use, for example, with security documents includes a pattern defining layer having concavities defining an inverted relief pattern, and a retaining layer overlying and releasably filling the concavities of the pattern defining layer. The pattern defining layer is removable from the retaining layer to transfer the relief pattern from the pattern defining layer to the retaining layer.

Abstract: Raman-active compounds such as polydiacetylenes are provided in the form of particles whose maximum dimension is 40 .mu.m. They can be formulated into inks, for the purpose of printing on security documents which are thus readily capable of authentication.

Abstract: This invention relates to documents, such as banknotes, which are produced and used in large numbers and which, for a given series, are identical one with another except for a unique multi-digit number upon each individual document, the number thus uniquely identifying that document within the series. According to the present invention, to render unauthorized reproduction of the document more difficult, on each document, at least two characters in the identifying number differ from each other (in addition to any differences in the letters or digits which they represent) in one or more visible characteristics. Thus the differing characters may have different heights or widths or be in different styles of type. Preferably, the identifying number appears twice on each document, in diagonally opposite corners, and preferably the variation of physical characteristics of the characters along the length of one of the numbers is reversed in direction in the other of the numbers.

Abstract: In a method of detecting sheets which do not have a genuine watermark (i.e. watermarks which result from variations in fibre distribution introduced during manufacture) the absorption of ultra-violet radiation is measured for each sheet in the area in which the watermark is expected to be present, and the transmittance of light by this area of the sheet is also measured. Sheets for which the absorption measurement does not show a substantially constant value, and sheets for which the light-transmittance shows a substantially constant value over the said area, are rejected. The absorption measurement is preferably effected by measuring the reflectance of ultra-violet radiation by the sheet, but the transmittance of ultra-violet radiation or the fluorescence of the sheet in the presence of ultra-violet radiation can also be measured. The measured value for the area can be compared with a reference value obtained by a measurement of the same parameter outside the watermark area.