WO2023037087A1 - Dispositifs de sécurité et leurs procédés de fabrication - Google Patents

Dispositifs de sécurité et leurs procédés de fabrication Download PDF

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Publication number
WO2023037087A1
WO2023037087A1 PCT/GB2022/050006 GB2022050006W WO2023037087A1 WO 2023037087 A1 WO2023037087 A1 WO 2023037087A1 GB 2022050006 W GB2022050006 W GB 2022050006W WO 2023037087 A1 WO2023037087 A1 WO 2023037087A1
Authority
WO
WIPO (PCT)
Prior art keywords
substrate
region
relief
machine readable
relief structure
Prior art date
Application number
PCT/GB2022/050006
Other languages
English (en)
Inventor
John Godfrey
Rebecca LOCKE
Matt SHORTELL
Original Assignee
De La Rue International Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB2112961.4A external-priority patent/GB2601037B/en
Application filed by De La Rue International Limited filed Critical De La Rue International Limited
Priority to AU2022342770A priority Critical patent/AU2022342770A1/en
Priority to CA3228736A priority patent/CA3228736A1/fr
Publication of WO2023037087A1 publication Critical patent/WO2023037087A1/fr

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Classifications

    • G—PHYSICS
    • G07—CHECKING-DEVICES
    • G07D—HANDLING OF COINS OR VALUABLE PAPERS, e.g. TESTING, SORTING BY DENOMINATIONS, COUNTING, DISPENSING, CHANGING OR DEPOSITING
    • G07D7/00—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency
    • G07D7/003—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency using security elements
    • G07D7/0032—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency using security elements using holograms
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
    • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/20—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof characterised by a particular use or purpose
    • B42D25/29—Securities; Bank notes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
    • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/30—Identification or security features, e.g. for preventing forgery
    • B42D25/324—Reliefs
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
    • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/30—Identification or security features, e.g. for preventing forgery
    • B42D25/351—Translucent or partly translucent parts, e.g. windows
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
    • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/30—Identification or security features, e.g. for preventing forgery
    • B42D25/36—Identification or security features, e.g. for preventing forgery comprising special materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
    • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/30—Identification or security features, e.g. for preventing forgery
    • B42D25/36—Identification or security features, e.g. for preventing forgery comprising special materials
    • B42D25/369—Magnetised or magnetisable materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
    • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/30—Identification or security features, e.g. for preventing forgery
    • B42D25/36—Identification or security features, e.g. for preventing forgery comprising special materials
    • B42D25/378—Special inks
    • B42D25/382—Special inks absorbing or reflecting infrared light
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
    • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/30—Identification or security features, e.g. for preventing forgery
    • B42D25/36—Identification or security features, e.g. for preventing forgery comprising special materials
    • B42D25/378—Special inks
    • B42D25/387—Special inks absorbing or reflecting ultraviolet light
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
    • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/40—Manufacture
    • B42D25/405—Marking
    • B42D25/425—Marking by deformation, e.g. embossing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
    • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/40—Manufacture
    • B42D25/45—Associating two or more layers
    • B42D25/46—Associating two or more layers using pressure
    • G—PHYSICS
    • G07—CHECKING-DEVICES
    • G07D—HANDLING OF COINS OR VALUABLE PAPERS, e.g. TESTING, SORTING BY DENOMINATIONS, COUNTING, DISPENSING, CHANGING OR DEPOSITING
    • G07D7/00—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency
    • G07D7/06—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency using wave or particle radiation
    • G07D7/12—Visible light, infrared or ultraviolet radiation
    • G—PHYSICS
    • G07—CHECKING-DEVICES
    • G07D—HANDLING OF COINS OR VALUABLE PAPERS, e.g. TESTING, SORTING BY DENOMINATIONS, COUNTING, DISPENSING, CHANGING OR DEPOSITING
    • G07D7/00—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency
    • G07D7/20—Testing patterns thereon
    • G07D7/202—Testing patterns thereon using pattern matching
    • G07D7/206—Matching template patterns

Definitions

  • PCT/GB2021/052364 and PCT/GB2021/052365 is hereby incorporated by reference.
  • This invention relates to security devices such as may be used as a mark of authenticity associated with an object of value, such as a security document including banknotes, passports, certificates, licences and the like. Methods for manufacturing and inspecting security devices are also disclosed.
  • Objects of value, and particularly documents of value are frequently the target of counterfeiters and persons wishing to make fraudulent copies thereof and/or changes to any data contained therein.
  • Typical such objects are provided with a number of visible security devices for checking the authenticity of the object. Examples include features based on one or more patterns such as microtext, fine line patterns, latent images, Venetian blind devices, lenticular devices, moire interference devices and moire magnification devices, each of which generates a secure visual effect.
  • Other known security devices include holograms, watermarks, embossings, perforations and the use of colour-shifting or luminescent I fluorescent inks.
  • a method of manufacturing one or more relief structures for a security device comprising: forming one or more relief structures on a substrate, wherein the one or more relief structures are each formed of at least one cured material comprising a machine readable substance; generating a detection output using a detector configured to detect the machine readable substance; and analysing the detection output to determine whether the one or more relief structures meet a predetermined quality threshold.
  • machine readable substance in the cured material advantageously allows for the detection and inspection of the relief structures formed on the substrate during the manufacturing process.
  • the machine readable substance may be used for quality control during manufacture of the one or more relief structures. Counterfeit protection is also improved as the counterfeiter has to replicate both the relief structure(s) and the emission characteristics of the machine readable substance.
  • machine readable we mean that the substance is detectable by a machine which is typically capable of generating a quantitative output dependent on the amount of machine readable substance present (including simply detecting the presence or absence of the substance).
  • the machine-readable substance may be a material that absorbs and/or emits radiation within a specific wavelength band (e.g.
  • machine readable substances e.g. that react to an external stimulus
  • suitable machine readable substances include any luminescent, fluorescent or phosphorescent material, or a material which exhibits Raman scattering. Magnetic materials may be used as the machine readable substance.
  • the external stimulus required and/or the emission of the machine readable substance is outside the visible range of the electromagnetic spectrum (typically in the infra-red, IR, or ultra-violet, UV, ranges), such that detection of the machine readable substance does not occur under standard visible light conditions.
  • the detection output will vary in accordance with the amount of machine readable substance present in each region of the relief structure(s) (e.g. dependent on the dimensions of the relief structure and the concentration of the machine readable substance).
  • the machine readable substance is dispersed homogenously (“uniformly”) in the cured material(s). Therefore, preferably the concentration of the machine readable substance in the cured material(s) is substantially constant in each region of a relief structure.
  • the dimensions of the relief structures (e.g. the height and width of regions thereof) and the mean average particle size of the machine readable substance are such that each region of the relief structure is able to accommodate the machine readable substance.
  • the taggant is homogenously dispersed in the curable material prior to curing.
  • the cured material typically comprises a binder with the machine readable substance dispersed therein.
  • the binder is preferably colourless but may carry a colour (e.g. a tint).
  • the use of the machine readable substance may be utilised in order to determine the presence or absence of the relief structure on the substrate. For example, if the relief structure(s) are not present (e.g. not formed at all or miss-registered), then no machine-readable substance will be detected (e.g. the detection output displays a “zero” signal) and therefore the predetermined quality threshold is not met.
  • a particular advantage of the present invention is that typically the amount of the machine readable substance present in each region of the relief structure(s) varies according to the height of the region relative to the substrate, whereby the detection output likewise varies in accordance with the height of the relief structure(s) (e.g. relative to the substrate).
  • the amount of machine-readable substance present is dependent on the thickness of the at least one cured material in the particular region of the device.
  • regions of a relief structure having a relatively greater height relative to the substrate e.g. relatively greater thickness of cured material
  • regions of a relief structure having a relatively greater height relative to the substrate contain a greater amount of machine readable substance than regions of a relatively lower thickness, and therefore present an increased signal strength of detectable emission.
  • each relief structure has an expected emission pattern in accordance with its relief profile and therefore an expected detection output. Consequently, the generated detection output (e.g. “detection pattern”) may be analysed in order to determine detailed information about the quality of the relief structures (“micro-structure”) and whether they meet the predetermined quality threshold (in addition to a determination of whether the relief structure is present (“macro-structure”). That each relief structure will have an expected detection output as a result of local height variations allows for a straightforward and repeatable inspection of the relief structures. It is noted that the signal strength of the machine readable substance needs to be above a minimum threshold in order to be detected. The threshold is typically dependent on the amount of machine readable substance present and the detector sensitivity. In general, the expected detection output is dependent on the detection configuration.
  • the characteristics of the detector e.g. its resolution and/or aperture size
  • the orientation of the substrate and/or relief structures and their positions relative to the detector may also affect the detection output.
  • a particular detection output will be expected, and therefore the generated detection output may be analysed in order to determine whether the one or more relief structures meet a predetermined quality threshold.
  • the expected detection output is dependent on the total amount of machine readable substance present within the detectable area of the detector. Therefore, dependent on the parameters of the detector (e.g. its resolution and/or aperture size), the detection output may also vary in accordance with the lateral dimensions (e.g. “footprint”) of the surface relief structure(s). Thus, in embodiments the amount of machine readable substance present in each region of the relief structure(s) varies according to the lateral dimensions of the region, whereby the detection output likewise varies in accordance with the lateral dimensions of the relief structure(s).
  • the method further comprises providing relative movement between the substrate and the detector, whereby the detection output is generated as the substrate and detector move relative to each other.
  • the relative movement is provided by conveying the substrate in a machine direction past (e.g. “through”) the detector in a machine direction, whereby the detection output is generated as the one or more relief structures are conveyed past the detector.
  • the detector may form a part of a single note inspection machine (SNIM), whereby finished banknotes in the final step of the manufacturing process are conveyed through the SNIM.
  • the detector may be part of an in-line system for manufacturing security documents, with the relief structures conveyed past the detector at an intermediate stage of manufacture. It is envisaged that the substrate may be conveyed along different machine directions in order to generate different detection outputs and determine whether the quality threshold is met.
  • the inspection may take place “off-line”, in otherwords separately to the modules manufacturing the relief structures themselves.
  • individual sheets carrying the formed surface relief structure(s) may be inspected at random or according to a predetermined sampling regime at a separate detector.
  • a combination of in-line and off-line inspection may take place.
  • a “low resolution” inspection may take place in-line to determine the presence or absence of a structure, before a “high-resolution” inspection off-line to inspect the quality of the micro-structure.
  • the detection output is preferably in the form of a detection signal. This may be a measure of signal strength against time as the relief structure(s) are conveyed through the detector for example.
  • the detection output may be in the form of an image.
  • the detector may comprise a camera configured to record an image of the relief structure(s) in the relevant part of the spectrum corresponding to the emission and/or absorption of the machine readable substance (e.g. infra-red or UV).
  • the detection output may be continuously updated with time as the substrate is conveyed past the detector.
  • the detector may be configured to record individual discrete measurements (e.g. individual discrete images) at fixed time intervals. The different possibilities for the detection output may be considered as different detection patterns.
  • the generation of the detection output comprises providing the required stimulus (e.g. input radiation) for the machine readable substance.
  • the detection output may be generated from a stationary relief structure (“static” detection).
  • a detector may be used to generate a detection output from a stationary security document or sheet/web carrying one or more relief structures.
  • the detector may generate a detection output based on the time between excitation and response of the machine readable substance (sampling rate).
  • the detector may image a whole security document or sheet of security documents at substantially one time, for example by providing UV exposure and detection of the resulting emission from the machine readable substance.
  • the substrate forms part of a security document or security article.
  • the relief structure(s) may be formed directly on a security document substrate (such as a banknote substrate) or on a separate security article substrate (such as a thread or a stripe), typically for subsequent integration with or attachment to a security document.
  • the substrate may be in the form of an individual security document, for example in cases where the detection output is generated as a finished banknote is conveyed through a SNIM.
  • the substrate may be in the form of a sheet or a web.
  • the inspection of the relief structure(s) occurs during an intermediate step in the manufacture of the security device/document.
  • the sheet or web may typically carry a plurality of security documents (such as banknotes) at an intermediate stage of their manufacture, each document carrying a relief structure formed of the cured material containing the machine readable substance.
  • the quality control inspection of the relief structures may therefore take place “inline” as the web or sheet is conveyed past the detector. This advantageously allows for the efficient inspection of a large number or relief structures.
  • the substrate may comprise paper, polymer (e.g. biaxially oriented polypropylene, BOPP, or polycarbonate), cellulose or a combination thereof.
  • the substrate is a polymeric substrate, optionally provided with one or more opacifying layers.
  • the substrate may be fully transparent, partially transparent or fully opaque to the external stimulus and/or emission (e.g. IR or UV radiation) used to detect the machine readable substance.
  • Appropriate configuration of the detector e.g. use of one-sided, multiple or dual-sided detectors may therefore be required to form the detection output dependent on the transparency level of the substrate.
  • the generated detection output is analysed to determine whether the one or more relief structures meet a predetermined quality threshold.
  • the analysis comprises: providing reference data that is indicative of one or more relief structures that meet the predetermined quality threshold; comparing the detection output with the reference data; and determining whether the one or more relief structures meet the predetermined quality threshold based on the comparison.
  • the reference data comprises a reference value of a predetermined metric
  • the comparison comprises obtaining a value for the predetermined metric from the detection output and comparing it to the value of the reference data.
  • the predetermined metric may be an expected amplitude (“signal strength”) of the detection output (e.g. detection signal) corresponding to a particular position on a document orweb/sheet.
  • the reference data is in the form of a reference signal (e.g. in the case where the detection output is also in the form of a detection signal).
  • the reference signal typically has a varying signal strength in accordance with the (e.g. height) profile of the desired relief structure.
  • a comparison of the generated detection signal with the reference signal may be performed and the determination of whether the relief structure(s) meet the predetermined quality threshold based on the comparison. For example, if the generated detection signal and the reference signal match to within a predetermined tolerance, then this is indicative of the relied structure(s) meeting the quality threshold.
  • the reference data may be in the form of a reference image (e.g. in the case where the detection output is also in the form of a detection image).
  • the reference data (such as the reference signal or image) may be generated theoretically based on the desired form of the relief structure(s) and the corresponding expected emission from the machine readable substance within the cured material(s). In other examples, the reference data may be experimentally obtained from a relief structure that is known to meet the predetermined quality threshold (e.g. having been microscopically inspected). The reference data is typically stored in memory and accessed during the analysis of the detection output.
  • the method may comprise at least one of: rejecting the relief structure(s); marking the substrate to indicate that the relief structure(s) did not meet the predetermined quality threshold; noting the location on the substrate of the relief structure(s) that did not meet the predetermined quality threshold; and stopping the forming of the one or more relief structures.
  • rejecting the relief structure(s) marking the substrate to indicate that the relief structure(s) did not meet the predetermined quality threshold; noting the location on the substrate of the relief structure(s) that did not meet the predetermined quality threshold; and stopping the forming of the one or more relief structures.
  • the structure may be rejected, e.g. by directing the document to a reject pile.
  • web or sheet-based inspection by marking the web or sheet, or noting the location of the relief structure(s), those areas of the web or sheet may be subsequently discarded.
  • a sheet of banknotes having one or more relief structures that did not meet the predetermined quality threshold may be subsequently directed to a reject pile separate to the “good” sheets where all of the relief structures met the predetermined quality threshold.
  • the manufacturing process may be stopped in order to correct the problem.
  • the method may further comprise diverting the substrate dependent on the determination of whether the one or more relief structure(s) meet the predetermined quality threshold.
  • a sheet-based process may comprise diverting the sheets into either a “good” pile (where all the relief structure meet the quality threshold) or a “reject” pile (where at least one of the relief structures does not meet the quality threshold), based on the analysis of the detection output.
  • the method comprises updating one or more parameters used in forming the relief structure(s) on the substrate, based on the analysis of the detection output.
  • the one or more parameters may be changed until the predetermined quality threshold is reached.
  • the provision of such feedback allows efficient quality control of the formation of the relief structures on the substrate.
  • parameters that may be updated based on an analysis of the detection output include the volume of curable material, the curing time, the lateral registration of the relief structure(s), the process speed, the temperature of the curable material, the viscosity of the curable material (e.g. via temperature control or use of a diluent), the power of the curing radiation, the embossing pressure, and the embossing materials (e.g. the embossing tool or impression materials).
  • the method further comprises performing at least one of: applying one or more print workings to the substrate; applying a protective layer, preferably a varnish layer, to the substrate; cutting the substrate into individual security documents.
  • a protective layer preferably a varnish layer
  • the one or more relief structures defines any of: an optically variable structure; a diffractive structure; one or more micro-optic elements such as focussing elements (e.g. lenses or mirrors), faceted elements (e.g. prisms), or a caustic elements; or a macro-structure, preferably a tactile structure.
  • micro-optic elements such as focussing elements, faceted elements (which could operate principally on reflection or refraction) will be configured as an array of such elements.
  • a relief structure may define a continuous optical structure such as a caustic structure or Fresnel lens structure. Other relief structures such as holographic or plasmonic structures are envisaged.
  • Focussing elements e.g. lenses
  • Focussing elements typically have a pitch in the range of 5pm to 150pm, preferably 20pm to 80pm; a height of 5pm to 50pm, preferably 5pm to 30pm; and a focal length of 5pm to 100pm, preferably 5pm to 90pm.
  • An array of microprisms that may be used in the present invention typically has a pitch in the range of 2pm to 100pm, preferably 5pm to 70pm; and a structure depth in the range of 2pm to 100pm, preferably 5pm to 40pm.
  • the at least one cured material is at least semi-transparent, preferably substantially clear, the machine readable substance preferably having a sufficiently small particle size and/or sufficiently low concentration so as to cause substantially no optical scattering and/or optical absorption.
  • the one or more relief structures define microoptic structures operating principally on refraction, such that the machine readable substance does not interfere with the desired optical functionality of the optical elements.
  • the size of the machine readable substance (taggant) particles is less than 10pm, preferably less than 1 pm, more preferably less than 100nm. Most preferably the size of the machine readable substance (taggant) particles is less than 20 nm in order that the scattering is negligible.
  • the concentration can be limited through the combination of efficient particles and highly sensitive machine read sensors.
  • Many inorganic taggants are quite large and scatter light quite strongly and therefore to not interfere with the micro-optical effect a very low concentration and/or is sufficiently distributed is typically required.
  • scattering per gram of taggant decreases considerably as the particle size is decreased from 200nm down to a few nm, so a higher concentration of taggant typically requires nano-particles to offset the higher concentration.
  • the taggant particles would have to be smaller than, ideally much smaller than the micro-optical elements, or the scale of other relief structures.
  • the machine readable substance could be a pigment, dye or chemical component of the resin, for instance. For pigments, concentrations less than 50%, preferably less than 5%, more preferably less than 1%, even more preferably less than 0.01% of the pigment in the curable material are desirable.
  • the cured material of the relief structure(s) may carry a coloured tint.
  • the particle size and/or concentration of the machine readable taggant is such that the cured material of any optical elements is optically clear at least in a direction that is normal to the plane of the substrate. This is a typical intended viewing direction of the surface relief structure(s).
  • the cured material comprising the machine readable substance is optically clear in substantially all directions.
  • the at least one cured material has a haze of 50% or less, preferably 30% or less, more preferably 10% or less, and/or wherein the at least one cured material has an optical density of 0.3 or less, preferably 0.15 or less, more preferably 0.05 or less.
  • the relief structure(s) may comprise two or more machine readable substances, the two or more machine readable substances having different detection characteristics.
  • each relief structure will comprise two or more machine readable substances, although alternatively different relief structures on the substrate may comprise different machines readable substances (i.e. the cured material of one relief structure will comprise a different taggant or taggants to another relief structure).
  • the machine readable substances have different detection characteristics, and will therefore generate different detection outputs.
  • the different taggants may emit detectable signals with different signal strengths or with different wavelengths. Therefore, the different machine readable substances may be detected through the use of respective detectors.
  • a relief structure comprising two or more machine readable substances may be formed of a cured material comprising two different taggants, or formed of different cured materials, each cured material comprising a respective machine readable substance. Determination of the presence of the two or more taggants, and/or a predetermined ratio (e.g. amount) of the two or more taggants may be used to determine whether the predetermined quality threshold is met.
  • one or more of the relief structure(s) comprise first and second regions having different amounts of the machine readable substance per unit area, wherein the amount of the machine readable substance per unit area in the first region is such that the first region is optically clear in a direction that is normal to the plane of the substrate; and the amount of the machine readable substance per unit area in the second region is such that the second region is not optically clear in a direction that is normal to the plane of the substrate.
  • the relief structure(s) are cast-cured relief structure(s).
  • the relief structures are formed by a cast-curing process.
  • the relief structure(s) may be formed by microintaglio. These processes do not deform the substrate (e.g. in the same manner as the temperatures and pressures involved in conventional intaglio printing do). Therefore, the substrate may be described as a substantially flat substrate (e.g. does not comprise localised raised areas as would be present following a conventional intaglio emboss for example).
  • each of the one or more relief structures is part of a respective security device.
  • the one or more relief structures being inspected with regard to the predetermined quality threshold form or will form part of a security device on a finished security document or article.
  • the relief structure may form a security device in its own right, for example exhibiting a static or diffractive image and/or defining a tactile element or structure.
  • the security device will typically comprise a further layer configured to cooperate with the optical structures in order to generate an optically variable effect.
  • the further layer may be in the form of an image layer configured to cooperate with a relief structure defining an array of focussing lenses to form a security device that exhibits a lenticular or moire effect.
  • the further layer may be in the form of a colour shifting layer with the relief structure defining a plurality of refractive elements such as microprisms that cooperate with the colour shifting layer to provide a secure optically variable effect.
  • the inspection is performed on the relief structures that will ultimately end up in circulation.
  • At least one of the relief structure(s) does not form part of a security device.
  • Such relief structures may be referred to as “test” relief structures.
  • the method may be used to inspect a test relief structure in order to determine the quality of the process (e.g. cast-cure) used to form the test relief structure, and therefore infer the quality of the other relief structures formed in the same process.
  • the quality of the relief structures of the security devices may advantageously allow for faster running speeds during manufacture.
  • the test relief structure(s) may have substantially the same form (e.g. size, cross-sectional profile) as a relief structure of the final security device.
  • test relief structure(s) may have a different form to the relief structures of the security devices.
  • the relief structure of the security device has a particularly simple form, the resulting detection output may not produce sufficient information to infer the detailed quality of the micro-structure.
  • a test structure having a more complex form may be employed in order to perform a more detailed inspection of the quality of the cast-curing process.
  • a test relief structure is laterally spaced from the security devices.
  • a plurality of test relief structures may be produced laterally spaced from the banknotes (e.g. on the side and/or edges of the web or sheet), and subsequently discarded.
  • the test structure(s) may be produced as a continuous structure or at a predetermined repeat distance.
  • the test structure(s) may be formed on the security documents or articles themselves, typically being designed not to be clearly perceivable by the end user.
  • a test structure formed on the security document or article may be designed to have a different purpose to the security device (e.g. a macro tactile element).
  • the detector has a (e.g. lateral spatial) resolution that is finer than a minimum feature size of the one or more relief structures in the plane of the substrate.
  • a (e.g. lateral spatial) resolution that is finer than a minimum feature size of the one or more relief structures in the plane of the substrate.
  • This advantageously allows the detector to generate a detection output in accordance with the detailed structure of the relief structure(s), thereby enabling a high level of quality control.
  • effective quality control can still be performed based on the (e.g. mean) average amount of taggant detected across the detection area.
  • the minimum feature size is typically measured in the machine direction of relative movement between the substrate and the detector, and/or in a cross direction to the machine direction.
  • the detection of the machine readable substance by the detector is typically along a direction substantially normal to the plane of the substrate (i.e. the detector is typically positioned in a plane parallel with the substrate).
  • the one or more relief structures are formed in substantially the same processing step, for example on a sheet or web carrying a plurality of bank notes.
  • the one or more relief structure are formed from the same at least one curable material.
  • the forming the one or more relief structures on the substrate comprises: providing a casting tool having a tool relief structure defined in a surface thereof, the tool relief structure corresponding to the one or more relief structures; applying the at least one curable material comprising a machine readable substance to the substrate and/or to the tool relief structure of the casting tool; bringing the substrate and the casting tool together, to thereby form the at least one curable material in accordance with the relief structure and; during and/or after bringing the substrate and casting tool together, curing the at least one curable material such that the relief structure formed of the at least one cured material is retained on the substrate.
  • This is a cast-cure process.
  • Relief structures formed by cast curing include an integral base layer between raised regions of the relief structure due to the nature of the process.
  • the mode of curing will depend on the type of curable material used.
  • the material is radiation-curable (e.g. UV-curable) and the curing step(s) will involve irradiating the material with appropriate wavelength radiation so as to cause cross-linking of the material.
  • the curable material(s) are typically applied to the substrate or alternatively to the tool relief structure of the casting tool. However, in some embodiments the curable material may be applied to a combination of both the substrate and the casting tool, particularly if more than one curable material is being used.
  • the forming the one or more relief structures on the substrate comprises providing a die form, the die form having a surface comprising an arrangement of raised areas and recessed areas defining the one or more relief structures; applying the at least one curable material comprising a machine readable substance to the surface of the die form such that said at least one curable material substantially fills the recessed areas; bringing the substrate in contact with the surface of the die form such that it covers the recessed areas; separating the substrate from the surface of the die form such that the at least one curable material in the recessed areas is removed from said recessed areas and retained on the substrate to thereby form the relief structure; and during and/or after the bringing of the substrate in contact with the surface of the die form, at least partly curing the at least one curable material in one or more curing steps.
  • Relief structures formed by a microintaglio process may not include an integral base layer formed between the raised elements, as with cast cure.
  • a tie coat is used to improve the adhesion between the at least one curable material and the substrate.
  • the tie coat may be the same curable material used to form the surface relief structure(s).
  • the machine readable substance is homogenously (“uniformly”) dispersed in the curable material(s).
  • the method of the present invention is typically performed in a web-based or sheet-based manufacturing process for manufacturing security documents or security articles having security devices located thereon are therein, wherein each security device comprises one or more relief structures.
  • each security device comprises one or more relief structures.
  • a web-based or sheet-based system for manufacturing one or more relief structures for a security device, the relief structure(s) being disposed on a substrate and being formed of at least one cured material comprising a machine readable substance
  • the system comprising: a casting module configured to form one or more relief structures on a substrate; and an inspection module comprising: a detector configured to detect the machine readable substance so as to generate a detection output; and an analysis unit configured to analyse the detection output to determine whether the one or more relief structures meet a predetermined quality threshold.
  • the casting module and the inspection module are situated in-line, for example as part of the same printing apparatus (or “press”).
  • the system preferably further comprises a conveying module configured to provide relative movement between the substrate and the detector in a machine direction, whereby the detection output is generated as the substrate and detector move relative to each other.
  • the conveying module is configured to convey the substrate in a machine direction past (e.g. “through”) the inspection module, whereby the detection output is generated as the one or more relief structures are conveyed past the inspection module.
  • the inspection module may be an inline inspection module configured to inspect a plurality of relief structures disposed on the sheet or web as it is conveyed past the inspection module and therefore past the detector (e.g. in-line on a casting machine).
  • the inspection module may be a single document inspection module (e.g.
  • the inspection module may be separate to the casting machine (e.g. for “off-line” inspection). However in other embodiments the detection may take place statically, as described above.
  • the system may further comprise a marking module configured to mark the substrate if it is determined by the analysis unit that the relief structure(s) did not meet the predetermined quality threshold.
  • the marked region(s) of the sheet or web may be subsequently discarded.
  • the system further comprises a sorting module configured to divert the substrate dependent on the determination of whether the one or more relief structure(s) meet the predetermined quality threshold. For example, if the surface relief structure(s) did not meet the predetermined quality threshold then the substrate may be diverted to a “reject” pile separate to a “good” pile where the relief structure(s) did meet the predetermined quality threshold.
  • the analysis unit is configured to analyse the detection output by: comparing the detection output with reference data that is indicative of one or more relief structures that meet the predetermined quality threshold; and determining whether the one or more relief structures meet the predetermined quality threshold based on the comparison.
  • the reference data is preferably in the form of a reference signal or reference image that is indicative of one or more surface relief structures that meet the predetermined quality threshold.
  • the detector has a resolution that is finer than a minimum feature size of the one or more relief structures in the plane of the substrate. It is noted that for asymmetrical relief structures (e.g. comprising cylindrical lenses or linear microprisms), the relevant feature size will vary depending on the orientation of the relief structure as it is conveyed through the inspection module.
  • the detector preferably comprises an integral excitation element configured to provide the required excitation for the machine readable substance.
  • the use of a machine readable substance in the present invention advantageously allows the quality of relief structures to be determined during the manufacturing process. At the same time, it is highly desirable that the machine readable substance that is present within the cured material forming the relief structure does not adversely affect any desired optical properties of the relief structure.
  • a security device comprising one or more relief structure(s) on a substrate, each formed of a first cured material comprising a machine readable substance; wherein the one or more relief structures comprise first and second regions having different amounts of the machine readable substance per unit area, wherein the amount of the machine readable substance per unit area in the first region is such that the first region is optically clear in a direction that is normal to the plane of the substrate; and the amount of the machine readable substance per unit area in the second region is such that the second region is not optically clear in a direction that is normal to the plane of the substrate.
  • the first region may provide the desired optical functionality of the device (e.g. due to the surface profile of the relief structure in the first region), and the second region may provide a machine detectable signal that can be used for inspection and quality control purposes.
  • the dimensions (e.g. height) of the first cured material in the second region are preferably chosen such that the amount of machine readable substance present within the second region is above a detection threshold (e.g. for a particular detector).
  • the machine readable substance may also be used for authentication purposes, increasing the security level of the device as the would-be counterfeiter has to replicate both the optical properties of the device as well as the emission properties of the machine readable substance.
  • the first region is optically clear in a direction that is normal to the plane of the substrate, and the second region is not optically clear in a direction that is normal to the plane of the substrate.
  • the optical clarity of the first and second regions is different.
  • the optical clarity of the first region e.g. the volume of cured material forming the first region
  • the optical clarity of the second region e.g. the volume of cured material forming the second region
  • the machine readable substance is dispersed homogenously (“uniformly”) in the first cured material.
  • the concentration of the machine readable substance in the first cured material is the same in the first and second regions.
  • the dimensions of the relief structures e.g. the height and width of regions thereof
  • the mean average particle size of the machine readable substance are such that each region of the relief structure is able to accommodate the machine readable substance.
  • regions of a relief structure having different dimensions will have different amounts of taggant present, therefore providing a variation in the detectable emission from the machine readable substance across the relief structure.
  • the taggant is homogenously dispersed in the curable material prior to curing.
  • the cured material typically comprises a binder with the machine readable substance dispersed therein.
  • the binder is preferably colourless but may carry a colour (e.g. a tint).
  • the amount of machine readable substance per unit area (e.g. per unit area in the plane of the substrate) in the first region (e.g. in the first cured material of the first region) is such that the first region is optically clear in a direction that is substantially normal to the plane of the substrate. In other words, when an observer views the device along said direction, the first region exhibits negligible optical scattering/absorption. This allows the first region to exhibit its intended optical functionality due to the profile of the relief structure.
  • the optical functionality is typically a refractive optical functionality, and could be the desired refraction of incident light by a focussing lens or microlens array or microprism for example, in order that the device exhibits the desired optical effect (taking into account any changes in refractive index due to the presence of the machine readable substance).
  • the optical functionality could be a diffractive optical functionality.
  • the intended viewing direction of the device is typically (or at least includes) the direction that is substantially normal to the plane of the substrate.
  • the device may be intended to be viewed at a range of viewing angles, for example in order to exhibit an optically variable effect on tilting. Therefore, preferably the first region is optically clear when viewed in directions between -10 degrees to +10 degrees with respect to the direction that is normal to the plane of the substrate, preferably between -30 degrees to +30 degrees and more preferably between -50 degrees to +50 degrees.
  • the first region is optically clear in substantially all directions.
  • the amount of machine readable substance per unit area is dependent on the height of the region relative of the substrate (e.g. thickness of the cured material) and the concentration of the machine readable substance.
  • a relatively thicker region of first cured material will have a greater amount of machine readable substance per unit area than a relatively thinner region of cured material, due to the differences in the amount of first cured material within the unit area.
  • the machine readable substance is homogenously dispersed in the first cured material, whereby the concentration of machine readable substance is the same in each region of the device.
  • the optical clarity of the first and second regions is different, with the optical clarity of the first region being higher than the optical clarity of the second region.
  • measurements of the haze or optical density of the first cured material in the first and second regions will be different.
  • the first cured material in the first region has a (e.g. transmission) haze of 50% or less, preferably 30% or less, more preferably 10% or less, and/or the cured material in the first region has an optical density of 0.3 or less, preferably 0.15 or less, more preferably 0.05 or less.
  • the amount of the machine readable substance per unit area in the second region is such that the second region is not optically clear in a direction that is substantially normal to the plane of the substrate.
  • the cured material in the second region has a (e.g. transmission) haze of greater than 30%, preferably greater than 50%, more preferably greater than 70% and more preferably greater than 90% and/or the second region has an optical density of greater than 0.15, preferably greater than 0.3, more preferably greater than 0.5 and even more preferably greater than 1.0.
  • the desired optical clarity of the first region will be dependent on the desired optical functionality of the region.
  • a higher optical clarity e.g. lower haze and/or lower optical density
  • non-focussing elements such as microprisms.
  • the second region does not exhibit (e.g. refractive or diffractive) optical functionality.
  • the amount of taggant present in the second region is above a minimum threshold such that a detection signal may be generated. Therefore, a quality control/authentication assessment of the device may be carried out.
  • the second region is not optically clear when viewed in directions between -10 degrees to +10 degrees with respect to the direction that is normal to the plane of the substrate, preferably between -30 degrees to +30 degrees and more preferably between -50 degrees to +50 degrees.
  • the second region is not optically clear in substantially all directions.
  • the haze and the optical density of the first cured material are dependent on the concentration of the machine readable substance in the first cured material and on the height of the first cured material relative to the substrate (the thickness of the first cured material).
  • the skilled person may choose a concentration of the machine readable substance and a thickness of the cured material in the first and second regions in order to achieve the desired optical clarity.
  • a typical concentration of the machine readable substance in the first cured material is between 0.001% and 10%, preferably between 0.001% and 5%, more preferably 0.001 % and 2.5%.
  • the concentration of the machine readable substance in the first cured material may be between 0.01 % and 10%, preferably between 0.25% and 5%.
  • the amount of machine readable substance per unit area present in each region of the relief structure(s) typically varies according to the height of the region relative to the substrate, whereby a machine readable output detectable from the security device likewise varies in accordance with the height of the relief structure(s).
  • regions of a relief structure having a greater thickness of the first cured material will have a relatively higher amount of machine readable substance per unit area.
  • a (e.g. mean average) height of the first region relative to the substrate is lower than a (e.g. mean average) height of the second region relative to the substrate, whereby the amount of machine readable substance per unit area present in the first region is lower than the amount of machine readable substance per unit area in the second region.
  • the height of the first cured material within the first region e.g. the thickness of the cured material in the first region
  • the height of the first cured material e.g. thickness of the cured material in the second region.
  • each of the first and second regions has different profiles. This is typically a cross-sectional profile.
  • the first and second regions may have different shapes or geometries, or may have substantially the same shape or geometry, but with the dimensions differing such that the amount of machine readable substance per unit area is greater in the second region.
  • each of the first and second regions comprises at least one raised protrusion (having a height greater than its surroundings) integrally formed with a base layer of the or another first cured material, the base layer having a lower height than the raised protrusions. It should be noted that there may be a different cured material present between the raised protrusions, formed by the tie coat of some preferred microintaglio processes, as will be described in more detail herein. The height of the base layer may vary if desired.
  • the first region may in general define any structure, such as an optically variable structure, a diffractive structure, reflective and refractive structures, or a macrostructure such as a tactile structure.
  • the profile of the first region in combination with its optical clarity allows the first region to exhibit a desired optical effect.
  • the first region defines one or more (preferably refractive) micro-optic elements such as focussing elements (e.g. an array of one dimensional or two dimensional lenses), faceted elements (e.g. an array of prisms), or a caustic element.
  • focussing elements e.g. an array of one dimensional or two dimensional lenses
  • faceted elements e.g. an array of prisms
  • a caustic element e.g. an array of prisms
  • the amount of taggant per unit area in the first region is such that the first region is optically clear in a direction that is normal to the plane of the substrate, such (e.g. refractive) micro-optic elements may exhibit the desired optical characteristics.
  • the device is an optically variable device, meaning that the exhibited optical effect changes dependent on the angle of viewing.
  • the device further comprises a decorative layer configured to cooperate with the first region so as to exhibit an optically variable effect.
  • a decorative layer typically comprises a printed microimage layer (e.g. formed by lithographic printing) that may be configured to interact with a first region defining an array of lenses so as to generate a lenticular or moire effect.
  • the decorative layer may be in the form of a colour shifting layer configured to interact with an array of prisms. Examples of colour shifting layers include layers incorporating liquid crystals (e.g.
  • decorative layers include diffractive structures that may be in the form of a diffractive optically variable image device (“DOVID”), such as a holographic foil or cast-cure hologram (e.g. with accompanying metallic or high refractive index layer).
  • DOE diffractive optically variable image device
  • Other examples include nano-diffractive structures and plasmonic and other sub-wavelength structures.
  • the decorative layer could comprise a (e.g. printed) plasmonic ink or a metallic ink.
  • the second region typically defines structure(s) whose functions are not dependent on being optically clear (for example they do not rely on refractive effects).
  • the second region may define any of: a macro-structure, preferably a tactile structure; an array of raised protrusions; one or more reflective elements (e.g. an array of prisms or facets acting as micro-mirrors); a diffractive structure (e.g. having a reflective metallic or high refractive index coating).
  • the raised protrusions may be in the form of raised elements defining image elements of an image, preferably a screened image.
  • the array of raised elements may vary in one or more of the size, shape, orientation, spacing and/or colour density of the raised elements so as to exhibit a multi-tonal image.
  • the raised elements in the second region are typically joined by a base layer as described above.
  • a ratio of the height of at least one raised element to the height of the base layer joining the raised element to an adjacent element is at least 10, preferably at least 20, and furthermore is preferably no greater than 400, preferably no greater than 200.
  • a ratio of the height of each raised element to the height of the base layer is at least 10, preferably at least 20, and furthermore is preferably no greater than 400, preferably no greater than 200.
  • the first and second regions are laterally offset.
  • the first and second regions may be laterally spaced apart, abutting each other or partially overlapping, or may be interlaced.
  • the one or more relief structures are each formed of a first cured material comprising a machine readable substance.
  • the relief structure(s) are formed from the same curable material.
  • a particular relief structure will comprise both first and second regions as described above.
  • the first and second regions are typically part of one and the same relief structure (e.g. formed from the same patch of the first curable material).
  • the one or more relief structures are cast-cured relief structure(s).
  • the one or more relief structures are formed by cast-curing.
  • the first and second regions are typically each part of a continuous block of the first cured material.
  • the first and second regions may be joined by a base layer of the first cured material, wherein the base layer preferably has a lower height than the height of the first and second regions.
  • a different cured material may be present between the first and second regions, formed by the tie coat of some microintaglio processes.
  • the first and second regions may be laterally separated by a region absent of cured material (although in such embodiments will be cast at the same time).
  • a further layer such as an opacifying layer may be present between the first and second regions.
  • the substrate is a substantially flat substrate.
  • the substrate has not been deformed during the formation of the relief structure(s) (as is the case in intaglio printing for example, where the temperatures and pressures involved lead to a deformation of the substrate as the intaglio print is generated).
  • the substrate may comprise paper, polymer (e.g. biaxially oriented polypropylene, BOPP, or polycarbonate), cellulose or a combination thereof.
  • the substrate is a polymeric substrate, optionally provided with one or more opacifying layers.
  • a security device comprising one or more relief structure(s) on a substrate, each formed of a first cured material comprising a machine readable substance; wherein the one or more relief structures comprise first and second regions having different amounts of the machine readable substance per unit area, wherein the amount of the machine readable substance per unit area in the first region is such that the first region exhibits optical functionality and the amount of the machine readable substance per unit area in the second region is such that the second region does not exhibit optical functionality.
  • the first region exhibits (preferably refractive) optical functionality in that its profile controls (e.g. refracts) incident light in a designed manner.
  • the optical functionality may be such that the first region cooperates with a further layer or optical plane in order to generate a variable optical effect.
  • the first region could exhibit diffractive optical functionality.
  • the further layer may be a decorative layer as described.
  • the optical plane could be a projection plane if the first region defines a caustic element for example.
  • the second region does not exhibit optical functionality as it does not control incident light in a designed manner in order to generate an optical effect.
  • Such a device may exhibit any of the preferred features described above with reference to the third aspect of the invention.
  • a security document comprising a document substrate and a security device thereon, the security device being as described above, wherein the document substrate may or may not act as the substrate of the security device.
  • the document substrate could in general be of any type, although preferably the document substrate comprises paper, polymer, cellulose or a hybrid thereof. It will be understood that the security document could therefore include a single substrate, which acts as both the document substrate (i.e. the self-supporting sheet forming the body of the document) and as the security device substrate (i.e. that carrying the surface relief structure(s)).
  • the security device is located at least in part in a window or half-window region of the document substrate, which has a lower optical density than the surroundings thereof.
  • the window region may be a half window region, in which case the optical effect of the security device may be observed in reflection, or transmission if the opacity of the non-transparent side of the half window is low enough for the transmission of light.
  • the window may be a full widow, in which case the device is intended for viewing in transmission.
  • the security device may be located at least in part in a nonwindow region of the document substrate, which is typically non-transparent and where the device is intended for viewing in reflection.
  • the document substrate comprises a core polymer substrate with at least one opacifying layer disposed on one or both surfaces of the core polymer substrate, optional gaps in one or more of the opacifiying layers forming window or half-window regions of the document substrate.
  • the security document could be a polymer banknote.
  • the opacifying layers are preferably of non-fibrous materials such as a coating of binder containing light-scatting pigments, preferably white, off-white or grey in colour (such as TiO 2 ).
  • the document substrate may further comprise an integral decorative mark.
  • “Decorative marks” (unlike the decorative layer described above) are incorporated into the substrate during its production rather than during its later processing into security documents.
  • the decorative mark may be applied during the same process as that by which the opacifying layers are applied, e.g. gravure printing.
  • the decorative mark could be a watermark in a paper substrate.
  • the decorative mark is integral to the document substrate.
  • the integral decorative mark could be unrelated to the presently disclosed security device.
  • the integral decorative mark is at least partially overlapping with at least the first region such that under at least some viewing conditions the integral decorative mark and the first region may be viewed in combination.
  • the security device substrate may be affixed to or incorporated into the document substrate, preferably over a transparent or translucent region of the document substrate optionally formed as an aperture.
  • a device may be affixed to the document substrate over a non-transparent region (e.g. over an opacifying layer region), in which case the device is designed to be viewed in reflection.
  • the security document is any of: a banknote, passport, identification document, identification card, bank card, driving licence, visa, stamp, cheque or certificate.
  • a security article comprising a security device as described above, preferably wherein the security article is a security thread, strip, insert, foil or patch.
  • the method of the first aspect of the invention may be used to manufacture security documents as described in the fourth aspect of the invention.
  • the security documents according to the fourth aspect of the invention may be manufactured using the system according to the second aspect described herein.
  • the present invention also provides a method of manufacturing a security device, comprising forming one or more relief structure(s) on a substrate, each formed of a first cured material comprising a machine readable substance; wherein the one or more relief structures comprise first and second regions having different amounts of the machine readable substance per unit area, wherein the amount of the machine readable substance per unit area in the first region is such that the first region is optically clear in a direction that is normal to the plane of the substrate; and the amount of the machine readable substance per unit area in the second region is such that the second region is not optically clear in a direction that is normal to the plane of the substrate.
  • the method therefore provides a device exhibiting all of the advantages outlined above.
  • the one or more surface relief structures are formed by: providing a casting tool having a tool relief structure defined in a surface thereof, the tool relief structure corresponding to the one or more relief structure(s); applying the first curable material comprising a machine readable substance to the substrate and/or to the tool relief structure of the casting tool; bringing the substrate and the casting tool together, to thereby form the first curable material in accordance with the one or more relief structure(s) and; during and/or after bringing the substrate and casting tool together, curing the first curable material such that the relief structure(s) formed of the first cured material is retained on the substrate.
  • This is a cast-cure process as has been described above.
  • the one or more relief structures may be formed by: providing a die form, the die form having a surface comprising an arrangement of raised areas and recessed areas defining the one or more relief structures; applying the first curable material comprising a machine readable substance to the surface of the die form such that said first curable material substantially fills the recessed areas; bringing the substrate in contact with the surface of the die form such that it covers the recessed areas; separating the substrate from the surface of the die form such that the first curable material in the recessed areas is removed from said recessed areas and retained on the substrate to thereby form the one or more relief structure(s); and during and/or after the bringing of the substrate in contact with the surface of the die form, at least partly curing the first curable material in one or more curing steps.
  • the one or more relief structures are each formed of a first cured material (e.g. in either a cast-curing process or a microintaglio process as described), the first and second regions are advantageously provided in substantially the same manufacturing step.
  • the machine readable substance is homogenously dispersed in the first cured material.
  • a method of manufacturing a security document comprising providing a document substrate and either forming a security device on the document substrate or on a security device substrate affixed to or integrated within the document substrate, or forming a security device on a security device substrate, and then applying the security device substrate to or incorporating the security device substrate into the document substrate, in each case using one or more of the methods above to manufacture the security device.
  • the method may be configured to provide a security document with any of the preferred features described above.
  • a security device comprising a relief structure on a substrate, the relief structure being formed of at least one cured material (termed “UV resin” elsewhere herein for brevity) comprising a machine readable substance.
  • the relief structure is preferably made by a cast-cure process.
  • taggant i.e. a machine readable substance
  • UV resin for detection
  • micro-optics elements themselves (or other relief structures, such as diffractive or other optically variable devices).
  • the micro-optics contain the taggant themselves not detecting other parts of device and improves inspection/detection.
  • Counterfeit protection is also improved as the counterfeiter has to replicate structure and emission not just one or the other.
  • the device is often reading a magnetic/IR signal from a printed layer (on back of thread or on polymer note). This printed layer has no level 1 identification - a static print.
  • machine readability i.e.
  • the taggant) in the level 1 optics effect means there is higher counterfeit protection for cash sorters.
  • the counterfeiter would have to produce an optical effect with machine readability rather than a single printed static layer. If this is combined with the idea of having two signals that are cross-referenced or related to one another - one in micro-optics (or other optically variable device) and one from static print - the counterfeit resistance is even higher.
  • the detection of the taggant can be performed by SNIMs and the like, or by inline inspection systems on the banknote manufacturing apparatus, e.g. in-line on a casting machine.
  • the inspection system could be of the sort disclosed in GB1914760.2, however instead of laser inspection of the micro-optics or other structure, a taggant detector would be provided in the machine to check for presence or quality of the structure. Presence could be detected through just detecting taggant signal. Quality could be determined by measuring signal strength.
  • the devices may be detected and inspected, for example by ATMs and cash processing equipment at Central Banks. Such inspection can be used to determine whether the device has been damaged or destroyed and is therefore no longer functional. Such documents can then be removed from circulation.
  • Preferred but optional features in the present invention include:
  • Embossing of the structure controls the strength of detection of the taggant in a specific area of the device, i.e. taggants homogenously dispersed in resin - if printed with no structure all regions of device would have same level of emission
  • the UV resin may be used to block taggant signal in controlled manner - pattern signal via this method as above.
  • Figures 1 (a) to 1 (d) illustrate schematic cross-sectional views of relief structures on a substrate, illustrating a concept of the invention
  • Figure 1 (e) illustrates an example of a detection output in the form of an image that may be obtained
  • Figure 1 (f) illustrates an example detection output if no machine readable substance is present
  • Figures 2 to 4 illustrate further examples of relief structures containing a machine readable substance that may be inspected in a method according to the present invention
  • Figure 5 to 7 schematically illustrate how variations in the detection configurations may alter the expected detection outputs from a relief structure
  • Figure 8 schematically illustrates an example of a device that may be inspected using the method of the present invention
  • Figures 9 and Figure 10 schematically illustrate relief structures comprising different machine readable substances and the corresponding detection outputs
  • Figure 11 (a) illustrates, in plan view, a security document carrying a relief structure that may be inspected according to the method of the present invention
  • Figures 11(b) to 11 (d) illustrate cross-sectional views through the security document and the corresponding detection signals that are expected
  • Figure 12 schematically illustrates a method of manufacturing a plurality of relief structures on a sheet according to the present invention
  • Figure 13 schematically illustrates the detection of a defective relief structure on a sheet during manufacture
  • Figure 14 schematically illustrates a further example of a method of manufacturing a plurality of relief structures on a sheet according to the present invention
  • Figure 15 schematically illustrates the detection of a defective relief structure on a sheet during manufacture
  • Figure 16 illustrates further examples of the detection of a defective relief structure, according to the invention.
  • Figure 17 schematically illustrates a single document inspection according to the present invention
  • Figure 18 schematically illustrates a method of manufacturing a plurality of relief structures on a sheet according to the present invention
  • Figure 19 schematically illustrates the detection of a defective relief structure on a sheet during manufacture
  • Figure 20(a) schematically illustrates a sheet carrying a plurality of test relief structures, and Figure 20(b) illustrates the expected detection output;
  • Figures 21 and 22 illustrate further examples where test relief structures are used in the method of the present invention.
  • Figure 23 is a flow chart setting out the main steps in a method according to a preferred embodiment of the invention.
  • Figures 24(a) and 24(b) schematically illustrate a preferred method of forming one or more relief structures according to the invention
  • Figure 25 schematically illustrates a method of forming one or more relief structures according to a further embodiment of the invention.
  • Figures 26(a) and 26(b) schematically illustrates a sheet-based printing press that may be used to manufacture security documents according to the invention
  • Figure 27 schematically illustrates a web-based printing press that may be used to manufacture security documents according to the invention
  • Figure 28 illustrates, in cross-section view, a security device according to the invention
  • Figure 29 illustrates a cross-sectional view of a security device according to a further embodiment of the invention.
  • Figures 30 and 31 show cross-sectional views of security devices according to further embodiments of the invention.
  • Figure 31 A shows a cross-sectional view through a security device according to a further embodiment of the invention, and Figure 31 B illustrates the resulting detection output;
  • Figure 31 C illustrates, in plan view, a security document carrying a security device according to a further embodiment of the invention
  • Figure 31 D illustrates the security device in cross-section together with the expected detection output
  • Figure 31 E schematically illustrates an intermediate step in the formation of a plurality of security devices according to the invention
  • Figures 32(a) to 32(e) illustrate further embodiments of security devices according to the invention, in cross-section
  • Figure 33 to 35 show further cross-sectional views of security devices according to the invention.
  • Figure 36 illustrates a further example security device
  • Figures 37(a) to 37(c) illustrate a further embodiment of the invention, in plan view and cross-section, Figure 37(d) showing a variant thereof.
  • Figure 1 schematically illustrates cross-sectional views of different relief structures formed on a substrate, illustrating a concept of the invention.
  • a layer of cured material 20a comprising a machine readable substance (a “taggant”) 30 is formed on a substrate 2.
  • the substrate 2 is formed of an inner core substrate 2a, which may be a polymer material such as BOPP, and outer opacifying layers 2b, such as white ink.
  • This is a typical construction of a polymer banknote substrate.
  • the taggant 30 emits radiation R (which could be UV or IR radiation for example) in response to excitation by input radiation (shown at E), which is typically provided by the detector.
  • the layer of curable material 20a has a constant height (thickness) across the substrate, and the taggant is homogenously dispersed throughout the cured material. Therefore, the level of emission of the taggant 30 across the device in response to excitation is substantially constant. Consequently, as the structure is conveyed past a detector 245 in a machine direction MD, the detector will generate a detection signal displaying a substantially constant signal strength, as indicated in the voltage-time graph in Figure 1 (a)(ii). The level of emission is above the minimum detection threshold of the detector 245.
  • Figure 1 (b)(i) illustrates a relief structure 20 formed by a cast-curing process on a substrate 2.
  • the cured material from which the structure 20 is cast comprises a taggant 30.
  • the structure comprises a raised protrusion 21 surrounded by a layer 29 of cured material having a lower height than the raised protrusion.
  • This layer 29 is referred to as a base layer and is an artefact from the cast curing process.
  • the base layer has a thickness that is smaller than a taggant particle size and therefore does not contain any taggant (or the amount of taggant in the base layer is negligible due to the base layer thickness and therefore the signal from the base layer is below the minimum detection threshold of the sensor).
  • the resulting detection signal as the device is transported past a detector 245 in the machine direction is shown n Figure 1 (b)(ii), which displays a signal corresponding to the position of the raised protrusion 21.
  • Figure 1 (c)(i) illustrates a similar structure to that of Figure 1 (b)(i), except in this case the relief structure 20 comprises two raised protrusions 21-1 , 21-2 joined together by a region of base layer 29.
  • the relief structure 20 is formed from a continuous body of cured material.
  • the thickness of the base layer is such that no taggant (or negligible amount of taggant) is present within the base layer.
  • the heights of the two raised protrusions 21-1 , 21-2 above the substrate are substantially the same, giving rise to the illustrated detection signal as the relief structure is conveyed along the machine direction past the detector.
  • the detection signal shown in Figure 1 (c)(ii) comprises two spaced top hat functions of the same amplitude corresponding to the position two raised protrusions 21-1 , 21-2.
  • two relief structures 20-1 , 20-2 formed of the same cured material comprising the same taggant are disposed on the substrate, laterally spaced by a region absent of cured material.
  • Both relief structures 20-1 , 20-2 comprise a single raised protrusion, with the raised protrusion 21-1 of the first structure 20-1 having a lower height than the raised protrusion 21-2 in the second structure 20- 2.
  • the base layer 29 of each structure 20-1 , 20-2 has a thickness great enough to accommodate particles of the machine readable substance 30 and the taggant has the same concentration in both structures 20-1 , 20-2.
  • regions of greater height will contain more of the machine readable substance, and the detectable signal will be of greater amplitude (“higher signal”) in the high relief region relative to the lower region.
  • the resulting detection signal trace obtained as the device is conveyed past a detector is illustrated, with the higher raised protrusion of structure 20-2 providing a greater intensity signal.
  • the variation in the amount of machine-readable substance 30 may also be detected by a detector configured to record an image in the wavelength range of the taggant’s emission and/or absorption.
  • the detector may comprise an infra-red or ultra-violet camera.
  • An example of such a detection output in the form of an image is illustrated in Figure 1 (e) which is an image (taken from above) of the relief structures in Figure 1 (d).
  • the image of each relief structure displays two concentric circles corresponding to the lateral profile of the relief structures.
  • the outer concentric circle shown at 29’ corresponds to the base layer 29 which displays the same intensity across both relief structures.
  • the inner concentric circles (shown at 21 -T and 21-2’) correspond to the raised protrusions, and display a greater intensity for the second relief structure 21-2 due to its increased height and therefore increased amount of taggant.
  • Figure 1 (f)(i) illustrates sample without a relief structure containing a machine readable substance.
  • the resulting detection output in Figure 1 (f)(ii) illustrates zero signal. This indicates the absence of a structure, for example due to a production error. Such a zero detection output will also be displayed with respect to a structure that does not contain any machine readable substance, or an amount of machine readable substance that does not provide a signal strength great enough to be detected.
  • the presence of the machine readable substance in the relief structure(s) enables a device to be detected by machine relative to its surroundings.
  • the differing signal strengths dependent on the amount of taggant present in each region of the structures can be used to create a structuredependent machine readable code.
  • the concept can be used for quality control in production of the devices, e.g. on a cast-cure production machine.
  • Figure 2 illustrates further examples of how a structure-dependent detection signal can be obtained.
  • a device is illustrated which has a relief structure 20 formed by cast-curing on a substrate 2 in which the cured material comprises a homogenously dispersed taggant.
  • the structure 20 is in the form of a continuous series of stepped platforms that increase in height (and therefore amount of taggant) from one region to the next.
  • the emission level of the machine readable taggant increases from one platform to the next.
  • the detection signal as the device moves along the machine direction MD is therefore in the form of a staircase function corresponding to the form of the relief structure, as illustrated in Figure 2(a)(ii).
  • Figure 2(b)(i) the relief structure 20 containing the taggant 30 has a continuously sloping form, resulting in a detection signal having a corresponding sloped change in signal strength, as shown in Figure 2(b)(ii).
  • Figure 3 illustrates further examples of relief structures that may generate a coded detection signal.
  • Figures 3(a)(i) and 3(b)(i) illustrate relief structures 20 defining optical elements.
  • the relief structure 20 defines a plurality of lenses 41.
  • the lenses may have one-dimensional periodicity (e.g. cylindrical lenses) or two-dimensional periodicity (e.g. spherical or aspherical lenses).
  • the variation in height of the cured material across the array of lenses 41 provides variation in the amount of taggant across the structure 20, giving rise to the illustrated detection signal in Figure 3(a)(ii) as the structure is conveyed past a detector in the machine direction.
  • the relief structure 20 defines a plurality of prismatic structures 51 (e.g. symmetrical linear microprisms as shown here), which generate a detection signal in Figure 3(b)(ii) that is distinguishable from that of Figure 3(a).
  • the amount of the machine readable substance (e.g. dependent on the size of the taggant particles and the concentration) in the cured material forming the optical elements is such that the optical elements are optically clear, particularly in a direction that is normal to the substrate). That is, the optical elements (e.g. lenses or microprisms) still provide their desired optical function, for example the focussing of light in the case of lenses.
  • the size of the taggant particles or pigments should preferably be sufficiently small and/or their concentration should be sufficiently low to avoid introducing optical scatter or absorption.
  • the optical elements preferably have a (e.g. transmission) haze of 50% or less, preferably 30% or less, more preferably 10% or less, and/or an optical density of 0.3 or less, preferably 0.15 or less, more preferably 0.05 or less.
  • a device having a relief structure comprising optical elements will typically further comprise a decorative layer or decorative mark (described in further detail herein) that is configured to interact with the optical elements to generate an optically variable effect.
  • the decorative layer may define a set of microimages that together with an array of lenses form a moire magnifier device.
  • the image layer could be configured to create a lenticular or integral imaging device.
  • a decorative layer can be formed by printing, either on the opposite side of the substrate from the relief structure (if the device is formed in a window region of the substrate) or on the same side, in which case the relief structure will be formed over the decorative layer.
  • the relief structure 20 comprises an array of raised protrusions 21 that correspond to elements of an image, such as a screened image.
  • the array of raised protrusions here referred to as raised elements, may be a regular array, or may vary across the device (e.g. in one or more of size, shape and spacing) in order to exhibit a multi-tonal image.
  • the corresponding detection signal as the device is conveyed past a detector in the machine direction comprises a plurality of peaks and troughs in accordance with the array of raised elements.
  • Figure 4 illustrates examples of relief structures that have a constant cross-sectional height, but vary in lateral areal size (“footprint”) so as to provide a coded detection signal.
  • Figure 4(a)(i) shows a plan view of a device having a relief structure 20 disposed on a substrate 2 which has, in plan view (in the x-z plane), a continually tapering form.
  • Figure 4(a)(ii) illustrates a plan view of a relief structure in which has, in the x-z plane, a sinusoidal form. As shown by the cross-sectional view of Figure 4(a), the height of the cured material in both cases is substantially constant across the domain of the relief structure.
  • Figure 4(a)(i) As the structure of Figure 4(a)(i) is conveyed past detector 245 having an aperture size (e.g. field of view) (A) in a cross direction to the machine direction MD, a detection signal is generated as shown in Figure 4(b)(i), with continuously decreasing amplitude as the amount of taggant passing the field of view of the detector decreases.
  • the device of Figure 4(a)(ii) generates a detection signal having a plurality of peaks and troughs as the device moves past the detector 245, in accordance with the amount of taggant providing a detectable signal within the field of view of the detector 245.
  • the expected detection output can be controlled through the height, shape and geometry of the structures themselves, as well as the macro footprint in which the structures are designed, arranged or positioned.
  • the expected detection output is dependent on the overall detection configuration, and may vary in accordance with parameters such as the aperture size, of the detector and/or its resolution, the orientation of the relief structure(s) and the relative (lateral) positions of the detector and relief structure(s). This will now be explained in relation to Figures 5 to 7.
  • Figures 5 schematically illustrate how the aperture size of the detector may affect the expected detection output.
  • Figure 5(a) shows a schematic cross-sectional view of a surface relief structure 20 disposed on a substrate 2.
  • a detection output is generated as the substrate is conveyed along a machine direction MD past detector 245.
  • the detector has an aperture dimension A in the cross direction to the machine direction (y-axis) that is substantially the same as the width of the structure 20.
  • the detector aperture is wider than the width of the structure.
  • Figure 6(a)(i) illustrates a cross-sectional view of a device having a relief structure 20 comprising sets of lenses laterally separated by a region of base layer 29.
  • the expected detection output dependsent on the orientation of the device on the substrate (or the orientation of the substrate), and the aperture size of the detector, the expected detection output varies.
  • the dimension of the detector aperture A in the y direction (cross direction to the machine direction) and the positioning of the detector relative to the relief structure 20 is such that no detection signal is generated as no taggant is present within the detector aperture.
  • the detector location and aperture size are the same as for Figure 6(b) but the relief structure 20 is rotated 90 degrees. Consequently, the detection signal displaying increased amplitude corresponding to the two sets of lenses is generated.
  • the aperture size is larger than the dimension of the relief structure 20 in the cross direction to the machine direction, and the resulting detection signal displays an amplitude corresponding to the averaged amount of taggant detected within the aperture dimensions.
  • the form of the detection signal will be dependent on the resolution of the detector.
  • the resolution of the detector is finer than a minimum feature size (e.g. pitch of the lenses in Figure 3(a)) of the relief structure in the plane of the substrate.
  • a minimum feature size e.g. pitch of the lenses in Figure 3(a)
  • Such a detector may be described as a “high” or “fine” resolution detector. Therefore, the detector signals depicted in Figures 3(a)(ii) to 3(c)(ii) convey the detailed structure (“micro-structure”) of the relief structures 20.
  • each of the devices illustrated in Figures 3(a)(i), 3(b)(i) and 3(c)(i) would generate a “smoothed” or “averaged” detection signal as now explained schematically with reference to Figure 7.
  • Figures 7(a)(i) to 7(c)(i) illustrate the same surface relief structure 20 (here comprising an array of lenses) on a substrate 2, with the cured material of the surface relief structure comprising a machine readable substance.
  • the detector 245a used in Figure 7 has a resolution finer than the pitch of the lenses, and consequently a high resolution detection signal is generated as illustrated in Figure 7(a)(ii) showing the full profile of the lenses.
  • the detector 245b in Figure 7(b) has a coarser resolution than detector 245a and a lower resolution signal is displayed which does not represent the full structure detail of the lenses.
  • Detector 245c in Figure 7(c) has a lower resolution again, giving rise to the lower resolution signal displayed in Figure 7(c).
  • the relief structures 20 have each been disposed in a non-windowed region of the substrate.
  • the substrate has opacifying layers on both sides in the region of the relief structure.
  • Figure 8 illustrates an example of a device that is located within a windowed region of the substrate, here a “full” window 51 defined by an absence of opacifying material on both sides of the core substrate 2a.
  • Figure 8(a) illustrates in intermediate step in the formation of the device, with two laterally spaced uncured patches of curable resin 205-1 , 205-2 being disposed on the substrate 2 within the window region 51.
  • the uncured resin 205 is preferably provided by screen printing, although other suitable forms of printing may be used such as flexographic, gravure, offset or inkjet printing. As schematically shown, first resin patch 205-1 does not comprise any machine readable substance, whereas second resin patch 205-2 comprises a machine readable substance 30 homogenously dispersed within the uncured material.
  • Figure 8(b) illustrates the finished device following a cast-curing process (described in more detail herein), where the two uncured resin patches are embossed and cured so as to form two laterally spaced relief structures 20-1 , 20- 2 each comprising a plurality of raised elements.
  • the two surface relief structures may appear to be substantially identical, the resulting detection signal highlighting the presence or absence of the taggant in the structures across the device is shown in Figure 8(c).
  • a “low resolution” detector was used, having a coarse resolution with respect to the size of the individual raised elements such that the detection signal does not show the microstructure of the relief structure.
  • the two uncured resin patches 205-1 (not comprising machine readable substance) and 205-2 (containing machine readable substance) may be applied to the substrate in a laterally offset but partially overlapping manner.
  • the resulting dispersion of taggant in the cured material of the surface relief structure will be non-uniform, generating a varying detection signal .
  • the two uncured resin patches 205-1 and 205-2 may both comprise the same machine readable substance, but with different concentrations, generating a detection signal displaying a variation in amplitude.
  • the uncured resin patches could be applied to the substrate in a laterally spaced or a partially overlapping manner.
  • Figures 9 and 10 schematically illustrate examples in which different machine readable substances with different emission characteristics may be used.
  • Both Figures 9(a) and 10(a) illustrate relief structures 20 (here in the form of lens arrays) comprising two different taggants schematically shown at 30- 1 and 30-2.
  • the second taggant 30-2 emits a higher signal strength than the first taggant 30-1 upon excitation.
  • Figure 9(a) illustrates the case where the taggants are detected by a common detector 245, with the higher signal strength of the second taggant emission visible in the higher amplitude detection signal shown in Figure 9(b).
  • two detectors are used that are tuned to the respective taggants (e.g.
  • Detector 245-1 is configured to detect the first taggant 30-1 and detector 245-2 is configured to detect the second taggant 30-2.
  • the resulting combined detection signal is illustrated in Figure 10(b), again with the second taggant 30-2 exhibiting a higher signal strength.
  • the presence of both detection signals from the respective taggants can indicate the presence of the relief structure, with a measured ratio of the signals indicating a quality of the microstructure.
  • the different taggants 30-1 and 30-2 have substantially the same particle size. However, the different taggants may have different particles sizes, which may give rise to different optical appearances as well as differences in the detection signals.
  • the machine readable substances used in the surface relief structure(s) of a device may vary through at least one of signal level, required excitation, and emission characteristics (e.g. wavelength). This allows for different detection signals to be generated for different relief structures.
  • the detection signal for a particular structure may be unique.
  • taggants include any luminescent, fluorescent or phosphorescent material, or a material which exhibits Raman scattering, for example. Magnetic materials may be used as a machine readable substance.
  • Exemplary phosphors can be any compound that is capable of emitting IR- radiation upon excitation with light. Suitable examples of phosphors include, but are not limited to, phosphors that comprises one or more ions capable of emitting IR radiation at one or more wavelengths, such as transition metal-ions including Ti-, Fe-, Ni-, Co-and Cr-ions and lanthanide-ions including Dy-, Nd-, Er-, Pr-, Tm- , Ho-, Yb- and Sm-ions.
  • the exciting light can be directly absorbed by an IR- emitting ion.
  • Acceptable phosphors also include those that use energy transfer to transfer absorbed energy of the exciting light to the one or more IR-emitting ions such as phosphors comprising sensitizers for absorption (e.g. transition metalions and lanthanide-ions), or that use host lattice absorption or charge transfer absorption.
  • Acceptable infrared emitting phosphors include Er-doped yttrium aluminium garnet, Nd-doped yttrium aluminium garnet, or Cr-doped yttrium aluminium garnet.
  • a direct bandgap semiconductor for example a group ll-VI (e.g. ZnO, ZnS, ZnSe, CdS, CdTe, CdSe etc ) or a group I l-V (eg GaN, GaAs, AIN, InN etc) semiconductor can show strong luminescence.
  • a group ll-VI e.g. ZnO, ZnS, ZnSe, CdS, CdTe, CdSe etc
  • a group I l-V eg GaN, GaAs, AIN, InN etc
  • nanostructured materials e.g. such as metallic, semiconductor and dielectric materials and combinations thereof, which can show many different types of luminescence such as fluorescence, phosphorescence, elastic and inelastic scattering.
  • a particularly preferred substance suitable for use in implementations of the invention is Er-Yb-KGd(PO3)4 (also known as Er-Yb-KGP).
  • Er-Yb-KGP strongly absorbs in the infra-red portion of the electromagnetic spectrum between about 960 nm and 990 nm.
  • This substance can thus be regarded as having a waveband for absorption with a width of about 30 nm, and the predetermined input radiation for a security print medium incorporating it can be defined as radiation that falls within this waveband.
  • Er-Yb-KGP After being excited by the predetermined input radiation, Er-Yb-KGP emits radiation across a range of wavelengths. The emission is also in the infra-red portion of the electromagnetic spectrum and is strongest between about 1520 nm and 1560 nm.
  • the predetermined output radiation to be detected when authenticating or inspecting a security device incorporating this substance can be regarded as that falling within the output waveband which has a width of about 40 nm.
  • the wavebands of the input and output radiation of Er-Yb-KGP are thus relatively narrow. This is advantageous.
  • the machine readable substance may take the form of particles, pigments or a dye which can be either incorporated into the curable material (examples of such provided herein).
  • the size of the particles or pigments for optically functional elements should preferably be sufficiently small and/or their concentration should be sufficiently low to avoid introducing optical scatter.
  • FIG 11 (a) illustrates, in plan view, a security document 100, in this case a banknote.
  • the banknote 100 has a substrate 2 comprised of a transparent core polymer substrate 2a (e.g. BOPP) and opacifying layers 2b on both sides thereof as discussed previously and as shown clearly in the cross-section view of Figure 11 (b).
  • a security device 10 is provided in a full window region 51 of the document substrate 2, the full window region being defined by the localised absence of the opacifying layers 2b.
  • Figure 10(b) is a cross-sectional view of the document 100 along the line Q-Q’.
  • the security device 10 comprises a cast-cured relief structure 20 formed of a cured material containing a homogenously dispersed machine readable taggant 30, the relief structure being formed on the document substrate 2.
  • the relief structure 20 is in the form of an array of raised protrusions 21 spaced by recessed areas of base layer 29.
  • the array of raised protrusions preferably correspond to elements of a (e.g. screened) image.
  • the raised protrusions may be optically functional structures such as lenses.
  • the quality of the cast relief structure 20 can be determined by passing the banknote 100 past (“through”) a detector that is operable to detect the taggant 30 present in the relief structure, and analysing the generated detection signal.
  • the detector may be positioned in a single note inspection machine (SNIM) for example, located at the end of a printing press for manufacturing the banknotes.
  • SNIM single note inspection machine
  • the orientation of the relief structure 20 as the banknote passes through the SNIM will affect the profile of the detection signal (dependent on the aperture size of the detector). If the banknote 100 is conveyed along a machine direction that is parallel to Q-Q’, then the expected detection signal generated by detector 245-1 will have a square wave profile in accordance with the cross-sectional profile of the relief structure 20, as shown in Figure 11(c). Here, the detection signal displays a square wave function having regions of greater signal strength corresponding to the raised elements 21 that contain increased amounts of the taggant.
  • Figure 11 (d) displays the detection signal obtained by conveying the banknote along a machine direction MD parallel to P-P’ past detector 245-2 differing from the detection signal obtained from detector 245-1 due to the difference in relative orientation.
  • Figure 12 schematically illustrates the inspection of a plurality of relief structures 20 disposed on a substrate 2 in the form of a sheet 90.
  • the sheet carries a number of banknotes 100 (herein, “banknote” refers to banknotes in all stages of their manufacture), arranged in an mxn matrix of rows and columns. In this example the sheet carries 32 banknotes arranged in four columns (or “tracks”).
  • the sheet is conveyed in a machine direction MD past an inspection module 240 comprising an inline detector 247 that comprises an individual detector element 247a, 247b, 247c, 247d for each sheet track.
  • the detector may measure all positions on the sheet (e.g. with a single detector element), rather than comprising individual detector elements for each track.
  • Each banknote carries a security device 10 comprising a cast-cured relief structure 20 with the curable material comprising a machine-readable substance (“taggant”).
  • the relief structures are formed on the sheet upstream of the inspection module 240, as will be described in more detail herein.
  • each detector element 247a, 247b, 247c, 247d generates a detection signal as illustrated in Figure 12(b).
  • each relief structure 20 is in the form of a raised protrusion having a constant height, and therefore each detector element generates a detection signal having a square-wave profile as illustrated in Figure 12(b).
  • each track of banknotes on the sheet may be inspected by analysing the detection signal and comparing it to its expected form.
  • the square wave profile could also be produced from a relief structure having a varying height, but with a detector having a coarse resolution.
  • Figure 13 illustrates a scenario where the casting of the relief structure 20 on banknote 100X is absent. This may have been caused by a fault in the casting process upstream of the inspection module 240. As no relief structure (and therefore no taggant) is present on banknote 100X, the detection signal generated by detector element 247c displays a “missing” square wave section (as indicated in Figure 13(b) as compared to the expected detection signal. Therefore, it can be determined that one of the banknotes on the sheet 90 does not meet a predetermined quality threshold. The sheet can be marked as such, or diverted to a reject pile for subsequent discarding.
  • the sheet 90 of banknotes is orientated in a portrait manner, and therefore the inline detector 247 comprises eight detector elements 247a...247h that each generate a detection signal for their respective column (i.e. track) of banknotes.
  • the expected detection signal for each track is illustrated in Figure 14(b), showing a square wave profile in accordance with the presence of each relief structure 20 as it is conveyed through the inspection module 240.
  • Figure 15 illustrates the detection of a defective sheet in which the relief structure on banknote 100X is absent.
  • the detection signal generated by sensor element 247c displays a missing square wave element corresponding to the expected position of the relief structure on document 100X, as shown in Figure 15(b). Therefore the sheet may be marked as such, or can be diverted to a reject pile for discarding.
  • Figure 16 highlights how the present invention may be used to detect a relief structure that has been cast incorrectly (rather than being completely missing as previously discussed).
  • banknote 100X on the sheet 90 carries an improperly cast relief structure 20X.
  • the improper casting may have an incorrect planar area (“footprint”) as shown in Figure 16(a)(i), or an incorrect resin volume (e.g. height) as shown in Figure 16(a)(ii).
  • the casting may be miss-registered, for example not being completely located within a window region of the substrate.
  • the defects can be detected through analysis of the detection signal from detector 247, as shown in Figures 16(b) and 16(c).
  • Figure 16(b) shows the detection signal generated from detector element 247c due to an incorrect resin area on banknote 100X as in Figure 16(a)(i).
  • the detection signal displays an incomplete square-wave section due to the incorrect footprint of the cast structure
  • Figure 16(c) illustrates the detection signal obtained from detector element 247c as a result of a structure being cast with an incomplete volume of resin as in Figure 16(a)(ii).
  • the square wave profile displays a region of reduced amplitude as compared to the expected signal, due to the recued amount of taggant present in the structure.
  • the detection signal will display an irregular spacing between the square wave regions.
  • the sheet is rejected upon analysis of the detection signal to determine the casting that does not meet the predetermined quality threshold, the sheet is rejected.
  • a banknote 100 is illustrated carrying a security device 10 having a cast-cured relief structure 20 defining an array of raised protrusions 21 as shown in the cross-sectional view of Figure 17(b).
  • the cast-cured relief structure may define a lens array.
  • the curable material forming the relief structure comprises a machine readable substance 30.
  • Such a relief structure 20 may be inspected by conveying the banknote along a machine direction past a detector 245 in a SNIM.
  • the expected detection signal is illustrated in Figure 17(c). Deviation from the expected detection signal shown in Figure 17(c) is indicative of a defective casting and the banknote (or other security document carrying such a structure) can be rejected.
  • Figure 18(a) illustrates a sheet 90 carrying a plurality of banknotes 100 each carrying a relief structure as described in Figure 17.
  • the expected detection signal for each of the tracks of banknotes passing through the inspection module 240 is shown in Figure 18(b).
  • Figure 19(a) illustrates an incorrectly cast sheet with the relief structure missing from banknote 100X.
  • the resulting detection signal from track 3 (as generated from detector element 247c) is shown in Figure 19(b), indicating that the sheet should be rejected.
  • Figure 19(c) illustrates the detection signal for Track 3 where the relief structure on banknote 100X is defective (rather than missing completely), with the detection signal displaying a reduced amplitude in the expected position of banknote 100X.
  • the cured material may be present by the structure is only partially replicated (e.g. due to an issue with the casting tool, such as dirt or a blocked structure).
  • a defective casting may be due to insufficient curable material being applied to the substrate or tool prior to casting.
  • a corresponding expected detection output e.g. a detection signal or detection image
  • the aperture size and resolution of the detector used may also affect the expected detection output.
  • the relief structure comprising a machine readable substance to be inspected may not form part of a security device.
  • Figure 20(a) illustrates a sheet 90 carrying a plurality of banknotes 100 as before, each banknote having a relief structure 20 designed to form part of a security device in the final banknote.
  • the sheet 90 also carries a plurality of relief structures 20’ that are formed on the sheet laterally separate from the banknotes 100; in other words the relief structures 20’ are not deigned to form part of a security device in the finished banknote.
  • the relief structures 20’ may be inspected as described herein, and the quality of the relief structures formed on the banknotes themselves may be inferred from the inspection result of structures 20’.
  • the relief structures 20’ may be referred to as a “test” relief structures. Such “test” relief structure(s) may be cut off and discarded when the sheet is cut into single banknotes.
  • the test relief structures 20’ are arranged around the perimeter of the sheet 90 such that orientations of the test relief structures varies. As the sheet 90 passes through inline sheet detector 247, individual detector elements S1 , S2 and S3 generate respective detection signals resulting from the test relief structures 20’. These detection signals are shown in Figure 20(b). If each of the three detection signals from detector elements S1 , S2 and S3 match the expected detection signal then it can be inferred the all of the relief structures formed on the security devices themselves meet the predetermined quality threshold.
  • test structures 20’ are formed in the same process as the device structure 20 (e.g. from the same taggant-containing curable material, applied and casted at the same time), and may have the same structure.
  • the “test” relief structures 20’ may have a structure that is specifically designed to infer the quality of the casting process, which is different to the device structure formed on the banknotes.
  • test relief structures are laterally separate from the banknotes, in alternative embodiments, test relief structure(s) may be located on the banknotes themselves, as shown in Figure 21.
  • test relief structures formed on the security documents themselves may be designed to not be overtly noticeable by the end user, or could provide further security features, such as provision of a macro tactile structure.
  • the expected detection signal for each track of test relief structure on sheet 90 illustrated in Figure 21 is displayed in Figure 22.
  • Figure 23 illustrates the principal steps of a method for manufacturing one or more relief structures according to a preferred embodiment of the invention.
  • one or more relief structures are formed on a substrate.
  • the relief structure(s) are typically formed as part of a method of manufacturing a plurality of security documents or security articles, with the relief structures forming a part of a security device carried by the document or article.
  • the substrate could be of any type, including fibrous substrates such as paper or non-fibrous substrates such as polymer (or a hybrid of both).
  • the relief structure(s) may be formed in a window region or non-window region of the substrate (or a combination) as will be described in more detail herein.
  • the one or more relief structures are each formed of a cured material comprising a machine readable substance.
  • Suitable apparatus, materials and methods for forming the relief structures disclosed herein are described in WO-A-2018/153840 and WO-A-2017/009616.
  • the relief structures can be formed by the in-line casting devices detailed in WO-A-2018/153840 (e.g. that designated 80 in Figure 4 thereof), using an embossing tool 85 carrying an appropriately designed micro-optical structure from which can be cast the desired relief structure shape.
  • the castcuring apparatuses and methods disclosed in section 2.1 of WO-A-2017/009616 (e.g. in Figures 4 to 8 thereof) can also be used to form the presently disclosed relief structures, by replacing the relief 225 carried on casting tool 220 with an appropriate relief from which can be cast the desired shapes.
  • WO-A-2017/009616 describes the use of the apparatus to form focussing elements, the same apparatus can be used to form any desired relief structure by appropriate reconfiguration the relief 225, including that envisaged herein.
  • the curable material(s) from which the relief structure is cast may be applied either directly to the tool carrying the desired relief shape (e.g. to the embossing tool 85 of WO-A-2018/153840 or to the casting tool 220 of WO-A-2017/009616), or the curable material(s) may be applied directly to the substrate on which the relief structure is to be formed, and then brought into contact with the tool (e.g. by impressing the tool onto the deposited curable material). Both options are described in the aforementioned documents. Preferably, the latter option is employed and the curable material(s) are applied to the substrate by screen printing as detailed in WO-A-2018/153840, before being formed into the desired relief structure.
  • Suitable curable materials are disclosed in WO-A-2017/009616, section 2.1 . UV- curable materials are most preferred. Curing of the material(s) preferably takes place while the casting tool is in contact with the curable material, against the substrate.
  • the resulting relief structure will typically include a base layer of material on top of the substrate, connecting the protrusions of the relief at their base.
  • this base layer is integral with the relief structure and formed of the same curable material(s), resulting from either the shape of the casting relief and/or the manner in which the curable material is pressed between the substrate and the casting tool during processing.
  • An example of such a base layer and its formation is disclosed in WO-A- 2017/009619, Figure 8. It is also possible to provide (alternatively or in addition) a base layer in the form of a pedestal layer, applied in a preceding step.
  • WO-A-2018/153840 and WO-A-2017/009616 also disclose print stations, which may be disposed downstream of the above-described casting apparatus (but alternatively could be located upstream). Print stations such as these are suitable for applying any print elements mentioned herein, to the same side of the substrate as the cast relief structure, or to the opposite side.
  • the apparatus disclosed in WO-A-2018/153840 can achieve particularly high registration between such cast relief structures and the printed elements.
  • Suitable substrates on which the relief structures can be formed are disclosed in WO-A-2017/009616, section 1 , and apparatus/methods for applying opacifying layers thereto in section 4, including the formation of window regions.
  • the opacifying layers are applied before formation of the presently disclosed security devices on the substrate.
  • the sheet material supplied to the apparatus of WO-A-2018/153840 may comprise a polymer substrate of the sort disclosed in WO-A-2017/009616, already provided with one or more opacifying layers.
  • the security devices disclosed herein may be disposed in a window region defined by the opacifying layers, or in a non-window region.
  • Figures 24(a) and 24(b) schematically illustrate a cast-cure process by which the relief structure(s) may be formed.
  • the process is shown as applied to a support layer 201 which may be the document (e.g. banknote) substrate or could be another substrate which is either attached to or incorporated within the document substrate, or is later applied to the document substrate.
  • Figure 24(a) depicts the apparatus from a side view
  • Figure 24(b) shows the support layer in a perspective view, the manufacturing apparatus itself being removed for clarity.
  • a curable material 205 comprising a homogenous dispersion of machine readable substance is first applied to the support layer 201 using an application module 210 which here comprises a patterned print cylinder 211 which is supplied with the curable material from a doctor chamber 213 via an intermediate roller 212.
  • an application module 210 which here comprises a patterned print cylinder 211 which is supplied with the curable material from a doctor chamber 213 via an intermediate roller 212.
  • the components shown could form part of a screen printing system. Other printing techniques such as lithographic, flexographic, offset or inkjet printing could also be used. Print processes such as these are preferred since the curable material 205 can then be laid down on the support 201 only in selected regions 202 thereof, the size, shape and location of which can be selected by control of the print process, e.g. through appropriate configuration of the pattern on cylinder 211.
  • an all over coating method could be used, e.g. if the surface relief structure is to be formed all over the support 201.
  • the curable material 205 is applied to the support 201 in an uncured (or at least not fully cured) state and therefore may be fluid or a formable solid.
  • the support 201 is then conveyed to a casting module 220 which here comprises a casting tool 221 in the form of a cylinder carrying a surface relief 225 defining the shape of the relief structure which is to be cast into the curable material 205.
  • a casting module 220 which here comprises a casting tool 221 in the form of a cylinder carrying a surface relief 225 defining the shape of the relief structure which is to be cast into the curable material 205.
  • a casting tool 221 in the form of a cylinder carrying a surface relief 225 defining the shape of the relief structure which is to be cast into the curable material 205.
  • the curable material 205 is cured by exposing it to appropriate curing energy such as radiation R from a source 222. This preferably takes place while the curable material is in contact with the tool surface relief 225 although if the material is already sufficiently viscous this could be performed after separation.
  • the material is irradiated through the support layer 201 (e.g. the paper or polymer substrate is sufficiently transparent to the curing radiation for the curing to take place) although the source 222 could alternatively be positioned above the support layer 201 , e.g. inside cylinder 221 if the cylinder is formed from a suitable transparent material such as quartz.
  • the curable material 205 could be applied directly onto casting tool 221 rather than on to the substrate 201 . This could be done in an all-over or patternwise manner.
  • the relief structure(s) may be formed by a microintaglio process. Exemplary “microintaglio” processes which can alternatively be used to form the relief structures disclosed herein, and suitable curable materials, are disclosed in WO-A-2017/009616, section 3.1 , Figures 12 to 15.
  • the surface relief structures are formed on a support layer 301 , which is preferably transparent, and which could be the polymer substrate 2a ultimately forming the basis of the security document substrate 2, or could be another carrier film 2’ which is then affixed to the document substrate 2.
  • the support layer 301 is preferably pre-primed, e.g. by applying a primer layer such as a thin, optically clear UV adhesive layer (not shown) or by raising its surface energy e.g. by corona treatment.
  • the desired pattern of the relief structure 20 is defined by recessed areas in the surface 303 of a die form 302. The recessed areas are separated by raised areas of that surface 303.
  • the die form preferably takes the form of a cylinder, but this is not essential.
  • the recessed areas of the die form are filled with a curable material 305 comprising a machine readable substance.
  • An exemplary first application module for applying the material 305 into the recessed areas is shown at 310a.
  • This includes a slot die 312a configured to supply the curable material 305 to a transfer roller 311 a from which it is applied to the die form surface 303.
  • the shore hardness of the transfer roller 311a is preferably sufficiently low that some compression/compliance is achieved to improve the transfer of material to the die form 302, which is typically relatively rigid such as a metal print cylinder.
  • the applied layer of curable material should match or exceed the depth of the recessed areas.
  • the viscosity of the curable material may be configured so that the material 305 transfers substantially only into the recessed areas of the die form and not onto the raised surfaces but in case any of the material 305 remains on the raised surfaces it is preferred to provide a removal means such as doctor blade 315a to remove any such excess material 305 from outside the recessed areas.
  • the material 305 in the recessed areas is preferably then at least partially cured by exposing the material 305 to appropriate curing energy, e.g. radiation, from a source 320a, although this curing could be performed at a later stage of the process.
  • a second application module 310b is provided downstream of the first (and preferably of curing source 320a) for applying more of the same material 305 to the die form.
  • the second application module 310b is of the same configuration as the first, comprising a slot die 312b for supplying the curable material 305 onto a transfer roller 311b which applies the curable material 305 into the partially-filled recessed areas on the die form surface.
  • the viscosity of the material could be adjusted so that it only fills those recessed areas and is not substantially applied to the raised areas, but preferably another removal means such as doctor blade 315b is provided to remove any such excess material 305 from outside the recessed areas.
  • the transferred material 305 is then at least partially cured by second curing source 320b although as discussed below this is not essential, or the degree of curing of the additional material applied by second application module 310b may be lower than that of the material applied first.
  • third and subsequent application modules 310 can be provided as necessary.
  • a tie coat 307 formed of a second curable material is optionally applied over substantially the whole surface of the die form 303, i.e. coating both the filled recessed areas and the raised areas of the surface 303.
  • the second curable material may or may not be of the same composition as the first curable material.
  • the tie coat composition may be selected so as to improve the adhesion between the first curable material and the support layer 301 .
  • the tie coat 307 is applied by a tie coat application module 330 which here comprises a slot die 332 and a transfer roller 331. It is desirable for the tie coat to be applied in a continuous, homogenous manner at the micron level hence it is preferably applied in a metered way via a slot die and transfer roller combination.
  • the tie coat may be partially cured at this point by a further radiation source (not shown).
  • the die form surface carrying the filled recesses and tie coat is then brought into contact with the support layer 301 , either at a nip point or, more preferably, along a partial wrap contact region between two rollers 309a, 309b as shown.
  • the combination is then exposed to curing energy, e.g. from radiation source 335, preferably while the support layer 301 is in contact with the die form surface.
  • the support layer 301 is then separated from the die form at roller 309b, carrying with it the tie coat 307 and the elements of material 305 removed from the recessed areas of the die form surface 303 by the tie coat 307.
  • the material 305 is therefore present on the support layer 301 in accordance with the desired pattern, forming the surface relief structures 20.
  • the tie coat 307 is preferably at least partially cured before the die form 302 leaves contact with the support layer 301 at roller 309b, hence the preferred use of a partial wrap contact via lay on and peel off rollers 309a, b as shown which tension the web around the die form cylinder. If the material is not fully cured in this step, an additional curing station may be provided downstream (not shown) to complete the cure.
  • a removal means such as a further doctor blade could be provided to remove the tie coat 307 from the raised portions of the die form surface 303 such that the regions of the tie coat 307 are confined to the surface relief structures. These tie coat regions will most likely not be proud of the die form surface.
  • the support layer 301 in this embodiment is preferably primed with a compliant adhesive layer which may be partly cured prior to contacting the die form but should still be compliant before entering the curing wrap.
  • tie-coat 307 is optional. Hence the tie coat and its application steps may be omitted from the above-described method. This is particularly the case where the last application of material 305 is not fully cured, since this incompletely cured material can take on the function of the tie coat, helping to affix the material 305 onto the support 301. In many cases, the tie coat 307, if provided, will be a transparent material.
  • a detection output is generated. This may preferably be generated by conveying the substrate in a machine direction past a detector that is configured to detect the machine readable substance in the cured material forming the surface relief structures and generate a detection signal.
  • a detection image may be generated using a suitably configured camera system.
  • different detectors may be employed, each configured to detect a respective taggant. The generation of the detection output may occur at different stages of the manufacturing process.
  • the inspection of the relief structure(s) takes place at the end of the manufacturing process, i.e. the substrate having all the desired security features and print workings thereon and having been cut into individual notes.
  • the inspection takes place during manufacture of the document, for example by in-line inspection of a plurality of relief structures carried by a web or a sheet before the final print workings are applied and the web/sheet is cut into individual documents.
  • the generated detection output is compared with reference data corresponding to the type of detection output generated.
  • the reference data is typically in the form of a reference detection signal if the detector generates a detection signal.
  • the reference data may comprise a quantitative value or values that may indicate an expected signal strength due to the taggant.
  • the reference detection signal may either be theoretically generated based on the expected structure of the relief structures, or may be experimentally generated from one or more relief structures that are known to meet a predetermined quality threshold.
  • the reference data is stored in memory and accessed at step S307.
  • the reference data e.g. reference signal
  • step S313a the surface relief structure(s) are rejected.
  • the banknote (or other document) carrying the relief structure(s) will be discarded, for example by directing the note to a reject pile.
  • the sheet carrying the defective relief structure will be marked as such and/or diverted into a reject pile for discarding.
  • the region of the web carrying the defective structure may be marked, and the subsequent sheet containing the structure (following cutting of the web into sheets) may be discarded.
  • feedback may be communicated to the application and casting modules forming the relief structures.
  • Such feedback may be inferred from the position and form of the discrepancies in the generated detection ouput and could indicate problems such as:
  • the relief structure is missing (e.g. indicated by a lack of signal).
  • Voids in the curable material e.g. formed by air bubbles. This could be indicated by a low amplitude signal.
  • Miss-registration e.g. indicated by an incorrect positioning of the detection signal or low amplitude signal, for example due to only part of the structure passing the detector.
  • FIG 26(a) schematically illustrates an in-line printing press 2000 that may be used to manufacture security documents carrying relief structures according to the invention.
  • the press 2000 is configured to manufacture polymer-based banknotes in a sheet-based process.
  • the sheet-based printing press 2000 comprises an inspection module 240 according to the invention.
  • sheets 90 comprising an mxn matrix of banknotes 100 are introduced to the printing press 2000 at feed module 200.
  • the sheets are conveyed through the press along the machine direction MD.
  • the sheet substrate i.e. the banknote substrate
  • the sheet substrate already comprises opacifying layer(s) defining windowed and non-windowed regions of the banknotes.
  • the opacifying layers are typically applied using gravure printing, although other suitable printing techniques may be used.
  • cast-cured relief structures containing a machine readable substance are formed on the banknotes by application module 210 and casting module 220 in the manner described above.
  • the relief structures may be formed within the lateral confines of the window regions, or within non-window regions on the substrate.
  • printing module 230 may then apply such a decorative layer (e.g. an image layer applied by lithographic printing) to the substrate sheet in order to form the security device incorporated into the banknote.
  • a decorative layer e.g. an image layer applied by lithographic printing
  • the decorative layer may be applied at other stages in the formation of the device, for example in the case of a colour shifting layer this may be applied prior to or following this casting process.
  • the relief structures and decorative layers are formed substantially simultaneously; in other words the relief structures are cast in substantially the same process step as the formation of the decorative layer.
  • An example of such a simultaneous casting and printing technique is disclosed in WO-A-2018/153840.
  • the sheets of polymer substrate, now comprising the cast relief structures and decorative layers, are then conveyed through in-line inspection module 240 where it is determined whether or not the cast relief structures meet a predetermined quality threshold. In the case where a defect is detected, the respective sheet is diverted to a reject pile as indicated at 245. After the inspection of the relief structures has occurred at inspection module 240, the remaining “good” sheets are collected at collection module 250. The remaining “good” sheets may then be provided to further finishing machines for application of print works (e.g. lithographic, intaglio and screen workings), numbering, varnishing and finally cutting into individual banknotes.
  • print works e.g. lithographic, intaglio and screen workings
  • FIG. 26(b) A variation of the press 2000 is shown in Figure 26(b), where the inspection takes place “off-line”.
  • the press 2000 will continuously form casted and printed sheets as described above, with the sheets collected into stacks at the collection module 250. While the press is still running, an operator will take a sheet from a stack (at random or in a defined sampling regime) and perform inspection at an off-line inspection module 240. Dependent on the result of the inspection, feedback may be provided to the press to rectify any issues.
  • the press 2000 may comprise both an in-line inspection module (e.g. configured to perform a “low” or “coarse” resolution inspection of the relief structures) as well as an offline inspection module that may be used to perform more detailed inspection.
  • Figure 27 schematically illustrates an example of an in-line web-based printing press 4000 configured to manufacture polymer banknotes.
  • the web-based printing press 4000 comprises an inspection module 440 according to an aspect of the invention and may be, for example, any inspection module as previously described herein.
  • a reel 15 of transparent polymer substrate is introduced to unwind module 400.
  • the web 95 of substrate comprises an mxn matrix of banknotes 100.
  • the unwind module 400 conveys the web 95 through the press 4000 along the machine direction MD.
  • An opacifying layer module 410 applies opacifying layers 2b to the recto and verso sides of the substrate web.
  • the opacifying layers are omitted in localised areas so as to define window region(s) of the banknotes as is known in the art.
  • the opacifying layer module 410 may also be used to apply an electrically conductive layer to the banknotes.
  • application module 420 applies curable material containing taggant to the substrate, preferably in the window regions of the banknotes.
  • the curable material is then embossed and cured at casting module 430 in order to form the relief structures on the banknotes.
  • the opacifying layers may be applied at different points in the process.
  • the infeed material on reel 15 already comprises opacifying layers defining window region(s) of the banknotes with the light control layers registered to the window regions.
  • the opacifying layers are formed after the relief structures are formed.
  • the substrate web 95 is conveyed to inspection module 440 where the formed relief structures are inspected as described above, and a determination is made as to whether or not they meet the predetermined quality threshold. If it is determined that the relief structures do not meet the predetermined quality threshold, then that area of the web may be marked (or the position thereof noted) for subsequent removal of that banknote; or the printing process may be stopped and action taken to correct the defect.
  • a decorative layer is formed (e.g. printed) on the respective banknotes for optical cooperation with the applied relief structures.
  • a decorative layer may typically be a printed image layer (e.g. for lenticular devices) or a colour shifting layer (e.g. for light control layers comprising prismatic microstructures).
  • the decorative layer is typically applied to the opposing side of the substrate web to the side on which the light control layer was cast if the device is formed in a window region of the substrate.
  • the printing of the decorative layer may be performed substantially simultaneously with the casting of the relief structures, or may be performed prior to the application and casting steps.
  • the substrate web is then re-wound at rewind module 460.
  • the web may then be provided to a cutting machine for cutting into sheets.
  • banknotes having relief structures that did not meet the predetermined quality threshold at inspection module 440 may be discarded.
  • the sheets of “good” banknotes may then pass through further finishing machine(s) for application of print workings (e.g. lithographic, intaglio and screen workings), numbering, varnishing and finally cutting into individual bank notes.
  • the inspection module may be positioned at different locations within the press subsequent to the application and casting modules.
  • the inspection of the relief structures may occur before the application of a decorative layer by the printing module if the casting and printing are not performed simultaneously.
  • the inspection module 240, 440 may be located after the finishing processes and the cutting of the web or sheet into individual banknotes (e.g. as a single note inspection machine).
  • Figure 28 illustrates a security device 10 according to an embodiment of the invention.
  • the security device is formed directly on a document substrate ultimately used as the basis for security documents such as banknotes, passports, certificates, licences, ID cards and the like.
  • all embodiments of the security device could alternatively be formed on a separate substrate (e.g. the substrate of a security article such as a security thread or stripe) for later application to, or incorporation into, a security document.
  • the device 10 is formed in a full window region 51 of the substrate 2, which is defined by the registered absence of opacifying layers 2b on opposing sides of clear core polymer substrate 2a.
  • the device 10 comprises a surface relief structure 20 disposed on a first surface 3a of the substrate, and a decorative layer 35 formed on the opposing surface 3b in the form of a printed image layer.
  • the relief structure 20 defines a plurality of cylindrical lenses 41 forming a lens array 40.
  • the dimensions of the lenses and the substrate are such that the image layer lies substantially within the focal plane of the lens array.
  • the lens array 40 and the image layer 35 cooperate such that the device 10 provides an optically variable effect when viewed along viewing direction D, for example a lenticular “image switch” effect or a moire magnification effect upon tilting.
  • the surface relief structure 20 is formed of a cured material comprising a machine readable substance (“taggant”) as has been described herein. In this way, the relief structure 20 may be analysed for quality control during manufacture.
  • the taggant is preferably homogenously dispersed within the cured material such that each region of the relief structure has the same concentration of taggant
  • the lenses 41 are desired to refract incident light in the designed manner so as to focus on the image array 35, as indicated by the ray arrows in Figure 28. Therefore, the amount of taggant per unit area (i.e.
  • the direction D is a typical intended viewing direction of the device.
  • the device is intended to be viewed at a range of viewing angles 0 (measured from the direction D), for example so as to exhibit an optically variable effect.
  • the lenses are preferably optically clear and exhibit their intended (refractive) optical functionality when viewed at a range of viewing angles 0, typically within a range of -50 degrees to +50 degrees.
  • the lenses are optically clear in all directions.
  • the amount of taggant present is such that the (e.g. transmission) haze of the cured material forming the lenses 41 is 50% or less, preferably 30% or less, more preferably 10% or less and/or the optical density is 0.3 or less, preferably 0.15 or less, more preferably 0.05 or less.
  • the amount of taggant present within the relief structure needs to be above a minimum threshold in order that a detection output may be obtained.
  • the surface relief structure 20 further comprises raised protrusions 21 that have a height above the substrate 2 that is higher than the height of the lenses 41. In this manner, the amount of taggant present within the region of the raised protrusions 21 is greater than that present in the lenses.
  • the dimensions of the raised protrusions e.g.
  • the amount of taggant per unit area within the raised protrusions is such that they are not optically clear in the direction D normal to the plane of the substrate.
  • the optical clarity of the raised protrusions 21 is less than the optical clarity of the lenses 41. However, this does not adversely affect the optically variable effect generated by the cooperation of the lens array 40 and the image layer 30.
  • the transmission haze of the raised protrusions 21 is greater than 30%, preferably greater than 50%, more preferably greater than 70% and more preferably greater than 90% and/or the optical density is greater than 0.15, preferably greater than 0.3, more preferably greater than 0.5 and even more preferably greater than 1.0.
  • the raised protrusions 21 are typically not optically clear when viewed within a range of viewing angles 0 at least between -10 degrees and +10 degrees.
  • the optically clear lenses 41 define a first region of the device 10 (shown at A) and the optically non-clear raised protrusions 21 define a second region (shown at B).
  • the first and second regions may be laterally separate as shown in Figure 28, where the raised protrusions are located at the periphery of the lens array 40 (e.g. surrounding the lens array).
  • the first and second regions may be laterally spaced or may abut each other.
  • Figure 29 illustrates an alternative embodiment similar to that shown in Figure 28 but in which the first and second regions are interlaced with each other.
  • the optical clarity of the cured material in the first and second regions of the device is dependent on the concentration of the machine readable substance in the cured material, and the thickness of the cured material.
  • the optical clarity generally decreases with increased thickness of cured material and concentration of the machine readable substance.
  • suitable materials e.g. varying thicknesses of cured material and concentrations of machine readable substance
  • they are then able to use this relationship to choose a height (“thickness”) of the cured material and concentration of the machine readable substance in the first and second regions so as to achieve the desired levels of optical clarity.
  • Atypical thickness of the cured material in the first and second regions is in the range of between 1 m and 200pm, preferably between 5pm and 100pm, more preferably 5pm and 80pm.
  • Figure 30 illustrates, in cross-sectional view, a further example of a security device 10 according to an embodiment of the invention, comprising a relief structure 20 that is formed from a cured material comprising a homogenously dispersed machine readable substance, disposed on a first surface 3a of a substrate 2.
  • the device is located within a full window region 51 of the substrate 2, which again here is a document substrate.
  • the relief structure 20 comprises an array of lenses 41 , in which the amount of taggant per unit area (in the x-z plane) is low enough such that that array the lenses are optically clear in the direction D, thus forming optically clear region A.
  • the device further comprises an image layer 35 on the opposing side 3b of the substrate 2 to the lens array 40, with the array of lenses and the image layer cooperating so as to exhibit an optically variable effect to the viewer when viewing the device along the direction D and upon tilting.
  • a raised protrusion 21 In a second region of the device (B), laterally spaced from the array of lenses 41 , is a raised protrusion 21 having a greater height above the substrate than the array of lenses.
  • the amount of taggant contained within the cured material forming the raised protrusion 21 is greater than in the lenses 41 and is such that the relief structure of the device 10 generates a detection signal when passed through a detector configured to detect the taggant.
  • a quality level of the relief structure 20 may be determined during manufacture. For example, the device can be inspected for the presence of the relief structure, and/or for the correct amount of cured material present.
  • the optical clarity of the first region A is different to the optical clarity of the second region B.
  • the amount of taggant per unit area within the raised protrusion 21 is such that it is not optically clear in the direction D.
  • the raised protrusion 21 may still contribute to the security level of the device 10, for example by acting as a tactile element or defining an image or indicia such as an alphanumerical character or code.
  • the optically clear array of lenses 40 and the optically non-clear raised protrusion 21 are part of the same relief structure 20 and are joined by a region of base layer 29.
  • the optically clear region and the non-optically clear region are formed from a continuous block of the first cured material.
  • the first A and second B regions may be laterally spaced by a region absent of base layer, such that the device 10 comprises separate relief structures 20-1 , 20-2.
  • the separate relief structures of the device are formed from the same curable material in the same casting step.
  • Figure 31 A illustrates a security device 10 according to a further embodiment of the invention
  • Figure 31 B displays the detection signal obtained by detector 247 as the device is moved along the machine direction MD.
  • the device 10 comprises a surface relief structure 20 formed of a first cured material containing a homogenously dispersed taggant, and comprises a raised protrusion 21 adjacent to an array 40 of lenses 41 , with the raised protrusion having a greater height with respect to the substrate 2 than the lens array. Due to the thickness of the cured material forming the raised protrusion, the amount of taggant per unit area present in the raised protrusion is such that it is not optically clear in a direction substantially normal to the plane of the substrate.
  • the thickness of the cured material forming the lens array is thin enough such that the lenses are optically clear in a direction normal to the plane of the substrate, and preferably optically clear in all directions.
  • the device therefore comprises an optically clear first region A that is optically functional due to the focussing effect of the lenses, and a non-optically clear second region B that is not optically functional.
  • the optical clarity of the first region A is greater than the optical clarity of the second region B.
  • the cured material of the raised protrusion 21 in region B contains enough machine readable substance such that the resulting emission (e.g. upon excitation) is above the minimum detection threshold of the detector and a quality control assessment of the device may be performed.
  • the cured material forming the lenses contains machine readable taggant, there is still a response from the taggant in the lenses; however, in this example this is below the minimum detection threshold of the detector.
  • Figure 31 C illustrates, in plan view, a security document 100 (here in the form of a banknote) carrying a security device according to an embodiment of the invention.
  • the device comprises an array of lenses 41 and a raised protrusion 21 , each formed of a cured material comprising a homogenously dispersed taggant.
  • the array of lenses 41 defines a first region A which is optically clear in a direction normal to the plane of the substrate, and the raised protrusion defines a second region B which in not optically clear in the direction normal to the plane of the substrate.
  • the first and second regions are spaced apart by a region absent of cured material, with a region of opacifying layer 2b present between the first and second regions.
  • each region of the device is present within a window region (here a full window region 51 although it will be appreciated that the regions of the device could be present within a half window region).
  • the regions of the device may be joined by a base layer that extends over the opacifying layer between the first and second regions.
  • Figure 31 D shows the expected detection signal as the document is conveyed through a SNIM.
  • the amount of taggant present in the raised protrusion 21 is such that the emission from this region of the device exceeds the minimum detection threshold and a detection output may be generated.
  • the emission from the taggant present in the lenses 41 is not great enough to reach the minimum detection threshold.
  • Figure 31 E illustrates a sheet 90 carrying a plurality of banknotes 100, each carrying a security device 10 as described with reference to Figures 31 C and 31 D.
  • the expected detection output as the sheet is conveyed through inline detector 247 is also shown in Figure 31 E, illustrating how the machine readable emissions from the raised elements 21 on the sheet exceed the minimum detection threshold for the detector, thereby allowing an determination of the quality of the relief structures to be made.
  • the amount of taggant present within the optically clear regions is such that the emission is below the minimum detection threshold of the detector, in other examples the emission from the optically clear regions may exceed the detection threshold (for example if a particularly sensitive sensor is employed).
  • the optically clear elements are in the form of lenses 41 configured to cooperate with an image layer 30 in order to generate an optically variable effect such as a lenticular or moire effect.
  • the optically clear region of the relief structure may define alternative optical elements and generate different effects.
  • the optically clear region of the device 10 may define optical elements in the form of microprisms, with the refractive function of the microprisms designed to cooperate with a decorative layer in the form of a colour shifting coating to generate a designed effect.
  • the decorative layer is disposed on the opposing surface of the substrate to the relief structure.
  • the decorative layer and the relief structure may be provided on the same surface.
  • the optically clear region may define a caustic structure configured to project an image upon illumination, in which case the decorative layer may not be present.
  • the security device 10 of the present invention may be provided within a window region, half-window region or a non-window region of the substrate (or a combination thereof), Similarly, the inspection method of the present invention may be performed on relief structures provided within a window region, halfwindow region or a non-window region of the substrate.
  • the substrate 2 is depicted as a multilayer substrate comprising a transparent core substrate 2a of a polymer such as BOPP with opacifying layers 2b arranged on each side thereof.
  • Figure 32(a) depicts a security device 10 arranged in a window region 51 of the substrate 2, i.e. where both opacifying layers 2b are absent so that the substrate is locally transparent. Regions of the substrate 2 having its standard, base level of opacity are referred to as non-window regions 50. In the examples shown, this corresponds to regions where both the opacifying layers 2b on the two sides 3a, 3b of the substrate are uniformly present.
  • the window region 51 is surrounded by nonwindow regions 50. In these non-window regions the substrate 2 has its highest level of opacity.
  • the device 10 is located in a half-window 52, i.e. where one of the opacifying layers 2b is absent and the other present.
  • the half-window region 52 is translucent rather than transparent, and has a lower opacity than the surrounding non-window regions 50.
  • the half window region 52 is formed by locally omitting the opacifying layer 2b on the first surface 3a of the substrate so that the surface relief structure is formed directly on the surface of transparent core substrate 2a (optionally via a primer layer or other surface treatment).
  • the reverse arrangement is shown in Figure 32(c), where the halfwindow is formed by retaining the opacifying layer on the first surface 3a of the substrate and omitting it from the second surface 3b.
  • Figure 32(d) illustrates a security device located within a non-window region 50 of the substrate 2.
  • the non-window region may be opaque if desired, in which case the visual effect exhibited by the surface relief structure will be visible in reflected light only.
  • it may be desirable that the non-window region 50 in which the security device is located has a sufficiently low level of opacity such that the security device 10 may be viewed in transmitted light.
  • Standard polymer banknote substrates and conventional paper banknote substrates typically meet this requirement.
  • Figure 32(e) schematically illustrates a more complex example, in which the same surface relief structure 20 is formed across different regions of the substrate 2.
  • the surface relief structure in the form of a continuous block of cured material comprises three laterally separate regions of raised elements (shown generally at A, B and C), joined by the base layer 29.
  • the raised elements of region A are disposed in half-window region 52; the raised elements of region B are disposed in window region 51 ; and the raised elements of region C are disposed in non-window region 50.
  • the security device 10 could be formed on a conventional document substrate 2.
  • substrates are typically fibrous in nature, comprising for instance paper or regenerated cellulose as described in W02020/156655.
  • Suitable document substrates include polymer document substrates of the type already referred to above, where the substrate 2 comprises a core substrate of a transparent polymeric material such as polypropylene (PP) (most preferably bi-axially oriented PP (BOPP)), polyethylene terephthalate (PET), polyethylene (PE), polycarbonate (PC), polyvinyl chloride (PVC), nylon, acrylic, Cyclic Olefin Polymer (COP) or Cyclic Olefin Copolymer (COC), or any combination thereof.
  • PP polypropylene
  • BOPP bi-axially oriented PP
  • PET polyethylene terephthalate
  • PE polyethylene
  • PC polycarbonate
  • PVC polyvinyl chloride
  • nylon acrylic, Cyclic Olefin Polymer (COP) or Cyclic Olefin Copolymer (COC), or any combination thereof.
  • the polymer substrate 2a may be monolithic, e.g.
  • polymer substrate 2a is substantially visually clear, although it may carry a coloured tint.
  • a primer layer may be applied to all or part of either surface of the polymer substrate 2a, e.g. by printing or coating.
  • the primer layer is preferably also transparent and again could be tinted or carry another optically detectable material.
  • Suitable primer layers include compositions comprising polyethylene imine, hydroxyl terminated polymers, hydroxyl terminated polyester based co-polymers, crosslinked or uncross-lined hydroxylated acrylates, polyurethanes and UV curing anionic or cationic acrylates.
  • the surface of the polymer substrate 2a may be prepared for onward processing by controlling its surface energy. Suitable techniques for this purpose include plasma or corona treatment.
  • the opacifying layer(s) 2b each comprise a non-transparent material, the primary purpose of which is usually to provide a suitable background for later printing of graphics thereon.
  • the opacifying layers comprise polymeric, non-fibrous material containing at least a light scattering substance such as a pigment.
  • the opacifying layers 2b are preferably light in colour, most preferably white or another light colour such as off-white or grey so that a later-applied graphics layer will contrast well against it.
  • the opacifying layers each have a brightness L* in CIE L*a*b* colour space of at least 70, preferably at least 80 and more preferably at least 90.
  • each opacifying layer may comprise a resin such as a polyurethane based resin, polyester based resin or an epoxy based resin and an opacifying pigment such as titanium dioxide (TiO2), silica, zinc oxide, tin oxide, clays or calcium carbonate.
  • a resin such as a polyurethane based resin, polyester based resin or an epoxy based resin
  • an opacifying pigment such as titanium dioxide (TiO2), silica, zinc oxide, tin oxide, clays or calcium carbonate.
  • Two or more opacifying layers may be applied to each surface of the polymer substrate 2a, in order to achieve the necessary opacity.
  • the optical density of each layer by itself may typically be around 0.2 to 0.5.
  • three or more layers are applied to each surface, overlapping one another.
  • At least one of the opacifying layers (preferably one on each surface of the polymer substrate 2a) is made electrically conductive, e.g. by the addition of a conductive pigment thereto. This reduces the effect of static charges which may otherwise build up on the security document during handling.
  • the opacifying layers 2b are preferably applied to the polymer substrate 2a before the formation of the relief structure(s) using a printing process such as gravure printing, although in other cases the opacifying layers could be coated onto the substrate, or applied by offset, flexographic, lithographic or any other convenient method.
  • the opacifying layers may be omitted across gaps on one or both surfaces of the polymer substrate to form window regions (which may be full windows or half windows, or a mixture of both) as described above. This can be achieved through appropriate patterning of the opacifying layers during the application process.
  • the opacifying layers 2b could comprise self-supporting pre-formed layers (optionally including apertures to later form windows) which are then laminated to the polymer substrate 2a.
  • the opacifying layers could be polymeric or could be of fibrous construction, such as paper, thus rendering the security document a “hybrid” paper/polymer construction.
  • an integral decorative mark 60 in the substrate 2 can be additionally provided in the substrate 2, as schematically shown in Figure 34.
  • Decorative marks are formed during manufacture of a document substrate, rather than being applied to the substrate during later processing thereof (as with the decorative layers described previously).
  • a decorative mark may be integrated into a multilayer polymer document substrate during the same process as that which applies the opacifying layer 2b to the core substrate 2a, e.g. via gravure printing.
  • the integral decorative mark 60 will be in precise register with the opacifying layers 2b and particularly any window regions or half-window regions they define.
  • Such decorative marks can be incorporated into security devices of the sort herein disclosed, by arranging the surface relief structure(s) to partially or fully overlap the decorative mark 60 or otherwise interact with it (e.g.
  • the security device 10 can be formed on a substrate other than the document substrate 2.
  • the security device 10 can be formed on its own substrate, resulting in a security article 1 such as a security thread, strip, foil or patch.
  • the security article can then be affixed to or incorporated into a security document 100, e.g. by adhesive or via hot or cold stamping.
  • a secondary substrate 2’ such as a transparent polymer film (e.g. PET).
  • PET transparent polymer film
  • the surface relief structure 20 is formed on a first surface of the substrate 2’.
  • the security article 1 is shown to be affixed to a first surface 3a of the security document substrate 2 with the security device 10 (or at least a part thereof) over a window region 51 of the document formed by an aperture through the document substrate 2, as may typically be the case where the document substrate 2 is paper or similar. It is also possible to locate a security article 1 of this sort with the security device 10 in a non-window region 50 of the document substrate 2. Security articles 1 can alternatively be applied to polymer type document substrates, in window regions, half-window regions and/or non-window regions thereof.
  • the secondary substrate 2’ may be affixed to the document substrate 2 and then the surface relief structure 20 formed over the secondary substrate.
  • the surface relief structure may be disposed only on the secondary substrate 2’, or over a combination of the secondary substrate (fully or partially) and the document substrate.
  • Suitable substrates on which the disclosed devices can be formed are disclosed in WO-A-2017/009616, section 1 , and apparatus/methods for applying opacifying layers thereto in section 4, including the formation of window regions.
  • the opacifying layers are applied before formation of the presently disclosed security devices on the substrate.
  • the sheet material supplied to the apparatus of WO-A-2018/153840 may comprise a polymer substrate of the sort disclosed in WO-A-2017/009616, already provided with one or more opacifying layers.
  • the security devices disclosed herein may be disposed in a window region defined by the opacifying layers, or in a non-window region, or a combination thereof.
  • Figure 36 shows a further security device.
  • a relief structure 20, here an array of lenses 41 is formed by cast-curing on a substrate 2.
  • the substrate could be a banknote substrate or the substrate of a security article such as a security thread or stripe.
  • the curable material from which the lenses are cast (commonly termed “UV resin”) comprises a taggant (i.e. a machine readable substance) 30.
  • the structure comprises regions of different heights. Since the region of greater height will contain a greater volume of the curable material (and hence more of the machine readable substance), the detectable signal resulting from that substance will be of greater intensity in the high relief region of the structure relative to the lower region of the structure. This can be used to create a structure-dependent machine readable code. It should be noted that the variation in height/thickness could alternatively or in addition be achieved by varying the thickness of the base layer 29 rather than the optical elements (e.g. lenses 41) themselves.
  • the presence of the machine readable substance 30 in the relief structure 20 enables the device to be detected by machine relative to its surroundings.
  • the concept can be used for inspection/detection of the device for level 3 machinery (such as SNIM/cash sorters), quality control in production (on the cast-cure production machine) and authentication in circulation (certain taggants can have UV/IR properties that can be verified by members of the public who have access readers - level 2).
  • the device may further comprise an image layer configured to interact with the relief structure, such as an image array.
  • the relief structure may define an array of focussing elements and the image layer may define a set of microimages such that together they form a moire magnifier device.
  • the image layer could be configured to create a lenticular or integral imaging device.
  • the image layer can be formed by printing, either on the opposite side of the substrate from the relief structure or on the same side, in which case the relief structure will be formed over the image layer.
  • the relief structure could be any form of optically variable structure, such as a diffractive relief.
  • Figure 37 shows an embodiment of a security device in accordance with another aspect of the invention.
  • the security device comprises one or more relief structure(s) on a substrate, each formed of a first cured material comprising a machine readable substance wherein the one or more relief structures comprise first and second regions having different amounts of the machine readable substance per unit area.
  • the first curable material in this case typically comprises a visible pigment (e.g. a visible colour or a scattering substance) as well as a machine readable substance.
  • the machine readable substance could be any of the types mentioned above, but is preferably either an IR absorbing substance, or a substance which emits visible or invisible wavelength(s) when illuminated in a certain manner.
  • the relief structure(s) in this case are spatially configured to exhibit an image, made up of image elements formed by raised elements 21 of the relief structure, such as line elements or dot elements.
  • the image will typically be a multitonal image at least when viewed under first viewing conditions such as standard lighting conditions (i.e. white light).
  • Figure 37(a) shows an example of the device 10 in plan view under standard lighting and it will be seen that here the image is of the currency symbol constituted by an array of curvilinear line elements which are spaced apart from one another.
  • the image elements In a first region A of the image, the image elements have a first appearance, whereas in the second region B, the image elements have a second appearance which is different from the first.
  • the image elements may differ in tone (i.e.
  • each raised element in the first region A contains less of the pigment(s) or other substances contained in the cured material than does each of the raised elements 21-2 in the second region B. Therefore if the curable material contains a visible pigment (e.g. a green pigment), the image elements in the first region will contain less pigment than the image elements in the second region with the result that the first region A appears lighter in tone (e.g. light green) than does the second region B (e.g. dark green).
  • a visible pigment e.g. a green pigment
  • the machine readable substance in the cured material will similarly be present in greater amount in the image elements 21-2 in the second region B than in the image elements 21-1 of the first region A, for the same reason.
  • the relative volumes of the image elements in the two regions are selected such that in the first region the amount of the machine readable substance present is below a detection threshold, whereas in the second region the amount of the machine readable substance present is above the detection threshold.
  • the machine readable substance is an IR-absorbing material
  • the security device 10 is illuminated with IR and viewed (by a suitable camera) in the IR spectrum, as shown in Figure 37(b)
  • only the second region B of the device 10 is visible. In other words, the image is incomplete.
  • the two regions A and B need not be two halves of an image but could be more complex shapes and could in some cases be interlaced with one another. What is required is that under first viewing conditions, the whole image is detectable (preferably visible to the naked eye) whereas under second viewing conditions which are different from the first, the detectable image is incomplete.
  • the demarcation between the two regions corresponds to the configuration of the surface relief, with the image elements 20- 2 that contain more of the machine readable substance per unit area of the substrate remaining detectable under the second viewing conditions (e.g. by machine). Those elements 20-1 which contain less of the machine readable substance per unit area of the substrate are detectable under the first viewing conditions but not the second.
  • the precise threshold amount of machine readable substance will depend on the type of machine readable substance in use and the method/apparatus by which it will be detected.
  • the widths of the elements 21-1 , 21-2 may be uniform across both regions while the height may vary instead, the elements 21- 2 in the second region B having a greater height than those in the first region A.
  • the appearance of the device will be as shown in Figures 37(a) and (b). It is also possible to vary both the width and the height of the elements between regions.
  • a security device comprising a relief structure on a substrate, the relief structure being formed of at least one cured material comprising a machine readable substance.
  • Numbered Clause 2 A security device according to numbered clause 1 , wherein the machine readable substance is dispersed substantially homogeneously in the at least one cured material.
  • Numbered Clause 3 A security device according to numbered clause 1 or numbered clause 2, wherein the amount of the machine readable substance present in each region of the device varies according to the height of the region relative to the substrate, whereby the machine readable signal detectable from the security device likewise varies in accordance with the height of the relief structure.
  • a security device according to any of the preceding numbered clauses, wherein the relief structure defines any of: an optically variable structure; a diffractive structure; a micro-optic structure, preferably comprising an array of focussing elements such as lenses or mirrors, or an array or prisms; or a macro-structure, preferably a tactile structure.
  • Numbered Clause 5 A security device according to any of the preceding numbered clauses, wherein the cured material is at least semi-transparent, preferably substantially clear, the machine readable substance preferably having a sufficiently small particle size and/or sufficiently low concentration so as to cause substantially no optical scattering.
  • Numbered Clause 6 A security device according any of the preceding numbered clauses, wherein the relief structure is a cast-cured relief structure.
  • Numbered Clause 7 A method of manufacturing a security device, comprising cast-curing a curable material to form a relief structure, the curable material comprising a machine readable substance.
  • Numbered Clause 8 A method according to numbered clause 7, configured to provide the security device with any of the features of numbered clauses 1 to 6.

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  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Physics & Mathematics (AREA)
  • Toxicology (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Computer Security & Cryptography (AREA)
  • Computer Vision & Pattern Recognition (AREA)
  • Business, Economics & Management (AREA)
  • Accounting & Taxation (AREA)
  • Finance (AREA)
  • Inspection Of Paper Currency And Valuable Securities (AREA)

Abstract

L'invention concerne un procédé de fabrication d'une ou de plusieurs structures en relief pour un dispositif de sécurité. Le procédé consiste à former une ou plusieurs structures en relief sur un substrat, la ou les structures en relief étant chacune constituée d'au moins un matériau durci comprenant une substance lisible par machine ; à générer une sortie de détection à l'aide d'un détecteur configuré pour détecter la substance lisible par machine ; et à analyser la sortie de détection pour déterminer si la ou les structures en relief satisfont un seuil de qualité prédéfini. L'invention concerne également un système de fabrication d'une ou de plusieurs structures en relief, ainsi que des dispositifs de sécurité comprenant de telles structures en relief.
PCT/GB2022/050006 2021-09-10 2022-01-05 Dispositifs de sécurité et leurs procédés de fabrication WO2023037087A1 (fr)

Priority Applications (2)

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AU2022342770A AU2022342770A1 (en) 2021-09-10 2022-01-05 Security devices and methods of manufacture thereof
CA3228736A CA3228736A1 (fr) 2021-09-10 2022-01-05 Dispositifs de securite et leurs procedes de fabrication

Applications Claiming Priority (12)

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GB2112961.4A GB2601037B (en) 2020-09-11 2021-09-10 Security documents and methods of manufacture thereof
GB2112959.8 2021-09-10
GB2112959.8A GB2601036B (en) 2020-09-11 2021-09-10 Security devices and methods of manufacture thereof
GBGB2112955.6A GB202112955D0 (en) 2020-09-11 2021-09-10 Security devices and methods of manufacture thereof
GB2112961.4 2021-09-10
GB2112956.4 2021-09-10
GB2112982.0A GB2601038B (en) 2020-09-11 2021-09-10 Security devices and methods of manufacture thereof
GB2112955.6 2021-09-10
GB2112958.0 2021-09-10
GB2112982.0 2021-09-10
GB2112958.0A GB2601035B (en) 2020-09-11 2021-09-10 Security devices and methods of manufacture thereof
GB2112956.4A GB2601034B (en) 2020-09-11 2021-09-10 Security devices and methods of manufacture thereof

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007137744A2 (fr) * 2006-05-31 2007-12-06 Giesecke & Devrient Gmbh Élément de sécurité transparent à réfraction
WO2008098753A1 (fr) * 2007-02-14 2008-08-21 Giesecke & Devrient Gmbh Laque d'impression pour éléments de sécurité micro-optiques
US20100148050A1 (en) * 2007-03-09 2010-06-17 Mazhar Ali Bari Security mark
WO2017009616A1 (fr) 2015-07-10 2017-01-19 De La Rue International Limited Procédés de fabrication de documents de sécurité et de dispositifs de sécurité
WO2018109035A2 (fr) * 2016-12-16 2018-06-21 Ovd Kinegram Ag Procédé de vérification d'un document de sécurité et document de sécurité, dispositif et élément de sécurité
WO2018153840A1 (fr) 2017-02-22 2018-08-30 Kba-Notasys Sa Presse à imprimer avec dispositif de coulée en ligne pour la réplication et la formation d'une structure micro-optique
WO2020156655A1 (fr) 2019-01-30 2020-08-06 Kba-Notasys Sa Articles de sécurité polymères

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007137744A2 (fr) * 2006-05-31 2007-12-06 Giesecke & Devrient Gmbh Élément de sécurité transparent à réfraction
WO2008098753A1 (fr) * 2007-02-14 2008-08-21 Giesecke & Devrient Gmbh Laque d'impression pour éléments de sécurité micro-optiques
US20100148050A1 (en) * 2007-03-09 2010-06-17 Mazhar Ali Bari Security mark
WO2017009616A1 (fr) 2015-07-10 2017-01-19 De La Rue International Limited Procédés de fabrication de documents de sécurité et de dispositifs de sécurité
WO2017009620A1 (fr) 2015-07-10 2017-01-19 De La Rue International Limited Procédés de fabrication de documents de sécurité et de dispositifs de sécurité
WO2017009619A1 (fr) 2015-07-10 2017-01-19 De La Rue International Limited Procédés de fabrication de documents de sécurité et de dispositifs de sécurité
WO2018109035A2 (fr) * 2016-12-16 2018-06-21 Ovd Kinegram Ag Procédé de vérification d'un document de sécurité et document de sécurité, dispositif et élément de sécurité
WO2018153840A1 (fr) 2017-02-22 2018-08-30 Kba-Notasys Sa Presse à imprimer avec dispositif de coulée en ligne pour la réplication et la formation d'une structure micro-optique
WO2020156655A1 (fr) 2019-01-30 2020-08-06 Kba-Notasys Sa Articles de sécurité polymères

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