Abstract: There is provided a security document (10) bearing an image (16) associated with an active substance, wherein the active substance is responsive to tactile pressure (18) in the range 0.01-1O MPa to alter the appearance of the image particularly when viewed under ultraviolet radiation (14). The active substance can be incorporated in an ink forming at least part of the image, in one or more layers associated with or beneath the image, or incorporated within a polymer, or adhesive associated with the image. The active substance comprises at least one of the following: organic or inorganic dye or dyes, chromophore(s), multi-chromophore(s), lumiphore(s). A layer incorporates a UV filter capable of being rendered inoperative in response to pressure, such that tactile pressure thins this layer so that the UV are no longer blocked and reach the lumiphore layer.

Abstract: Method and apparatus are described for determining if an optically variable material (OVM) is present in or on a surface, typically of a security document such as a banknote. In some embodiments the particular type of OVM is identified. In other embodiments a pass or fail signal is generated depending on whether a specific OVM is found on the surface. The surface is subjected to at least two different wavelengths of illuminating light at a particular angle to the surface and the intensity of the light reflected and/or scattered light from the surface is determined using photodiodes. The analogue output from the photodiodes may be digitised and the digital values processed according to one or another of different algorithms described, so as to produce an output signal whose value can be compared with one or more stored reference values in a look-up table, to produce a decision signal.

Abstract: A method of manufacturing a composite security thread, e.g. for a bank note, is produced by coating aluminium film onto a polyester film and coating selected regions with magnetic material. Photoresist characters are next printed onto the magnetic material, and a chemical applied to remove the aluminium coating except where protected by the resist. An obscuring silver coating is then applied over the magnetic material, and a final transparent material applied as a barrier to reduce the risk of damage during subsequent processing.

Abstract: A method of inspecting a pixel for tolerable variation from a corresponding selected pixel in a master image comprises establishing a data word of which the bits each indicate whether or not all the master image pixels in the neighborhood of the selected pixel all have values (i.e. brightness values) within a respective range. A data word representing the value of the inspected pixel is compared simultaneously with the ranges of values associated with the bits of the data word, which provides gating for the comparisons.

Abstract: A method of inspecting a pixel for tolerable variation from a corresponding selected pixel in a master image comprises establishing a data word of which the bits each indicate whether or not all the master image pixels in the neighborhood of the selected pixel all have values (i.e. brightness values) within a respective range. A data word representing the value of the inspected pixel is compared simultaneously with the ranges of values associated with the bits of the data word, which provides gating for the comparisons.

Abstract: A printing machine which has a printing cylinder (1) having automatically incremented numbering barrels (2) includes drive means (40-45) which normally maintain the printing cylinder in speed and phase synchronization with a train of documents on a web (11). The drive means is operable to decelerate the printing cylinder and then to cause the printing cylinder to regain its normal operating speed so that the web overtakes the printing by a selected distance before the next printing nip is formed.

Abstract: A sheet element, such as a banknote, has an incorporated authenticating device comprising a film having at least one edge which is provided with a non-rectilinear portion or portions shaped to provide coded information relating to the sheet element. The shape and proportions of said at least one edge of the shaped non-rectilinear portion or portions of said film are sensed to generate a signal dependant upon the shape and proportions of the edge of the film so as to derive the coded information.

Abstract: A sheet element, such as a banknote, having an authenticating device in the form of a strip extending across the sheet and having at least one edge provided with a non-rectilinear portion or portions providing difficulty in copying for the forger and preferably shaped to provide coded information relating to the sheet element. In the case of a banknote, one or both edges of the strip may have wavy-shaped portion or portions, of which characteristics such as amplitude and periodicity can be employed to encode such information as the issuing authority, currency, denomination and serial number. Other aspects of the invention concern a method of verification comprising providing a sheet element as above and sensing the non-rectilinear edge or edges to derive the coded information, and a method of slitting a sheet comprising operating a slitting assembly to slit the sheet along a number of slitting lines into a plurality of strips as aforesaid.

Abstract: A document is provided having thereon a legible code to distinguish the document from other similar documents, the code comprising an arrangement of alphanumeric characters. Where the document is a banknote, the code may be the serial number which is unique to that banknote, and which is one of a series of such serial numbers carried on individual members of a set of such documents, and having sequential numerical values. To enhance the security value of the serial number portion of the document and to inhibit successful forgery thereof, the alphanumeric characters are provided in reverse, or negative form. The security value derives from the complexity and cost of the apparatus necessary to print a series of successive serial numbers in reverse, rather than positive form. The code may correspond to a code provided elsewhere on the document in positive form. Another reverse code on a different background may be provided elsewhere on the document.

Abstract: A sheet element, such as a banknote or other document of intrinsic value, incorporating an optical authenticating device comprising a thin film element, preferably in the form of a strip, or thread disposed within the thickness of the sheet element and having known characteristics of spectral reflectance and transmittance, and wherein in the region of a least part of the thin film element the sheet element is formed with a pair of superposed windows between which the thin film element extends so as to be visible through each window.