WO2011017741A1 - Dispositifs optiquement variables et procédé de fabrication - Google Patents

Dispositifs optiquement variables et procédé de fabrication Download PDF

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Publication number
WO2011017741A1
WO2011017741A1 PCT/AU2010/001006 AU2010001006W WO2011017741A1 WO 2011017741 A1 WO2011017741 A1 WO 2011017741A1 AU 2010001006 W AU2010001006 W AU 2010001006W WO 2011017741 A1 WO2011017741 A1 WO 2011017741A1
Authority
WO
WIPO (PCT)
Prior art keywords
group
optically variable
relief elements
variable device
depth
Prior art date
Application number
PCT/AU2010/001006
Other languages
English (en)
Inventor
Robert Arthur Lee
Original Assignee
Securency International Pty Ltd
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 AU2009903695A external-priority patent/AU2009903695A0/en
Application filed by Securency International Pty Ltd filed Critical Securency International Pty Ltd
Priority to CH00193/12A priority Critical patent/CH703994B1/fr
Priority to GB1202110.1A priority patent/GB2486994B/en
Priority to DE112010003249T priority patent/DE112010003249T5/de
Publication of WO2011017741A1 publication Critical patent/WO2011017741A1/fr

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Classifications

    • 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
    • B42D25/328—Diffraction gratings; Holograms
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/04—Prisms
    • G02B5/045—Prism arrays
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/18—Diffraction gratings
    • G02B5/1828—Diffraction gratings having means for producing variable diffraction
    • 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
    • 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
    • B42D25/23—Identity cards
    • 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
    • B42D25/24—Passports
    • 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
    • B42D25/305—Associated digital information
    • 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
    • B42D25/355—Security threads
    • 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
    • B42D25/373—Metallic 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
    • B42D25/40—Manufacture
    • B42D25/45—Associating two or more layers
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/18—Diffraction gratings
    • G02B5/1847—Manufacturing methods
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/18—Diffraction gratings
    • G02B5/1861—Reflection gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/18—Diffraction gratings
    • G02B5/1866—Transmission gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/0005—Adaptation of holography to specific applications
    • G03H1/0011—Adaptation of holography to specific applications for security or authentication
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/02—Details of features involved during the holographic process; Replication of holograms without interference recording
    • G03H1/024—Hologram nature or properties
    • G03H1/0244—Surface relief holograms
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/04—Processes or apparatus for producing holograms
    • G03H1/08—Synthesising holograms, i.e. holograms synthesized from objects or objects from holograms
    • G03H1/0891—Processes or apparatus adapted to convert digital holographic data into a hologram
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
    • G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
    • B42D2035/20—
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/04—Processes or apparatus for producing holograms
    • G03H1/08—Synthesising holograms, i.e. holograms synthesized from objects or objects from holograms
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/02—Details of features involved during the holographic process; Replication of holograms without interference recording
    • G03H1/0276—Replicating a master hologram without interference recording
    • G03H2001/0288—Replicating a master hologram without interference recording by electroforming
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/04—Processes or apparatus for producing holograms
    • G03H1/0476—Holographic printer
    • G03H2001/0478—Serial printer, i.e. point oriented processing
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/22—Processes or apparatus for obtaining an optical image from holograms
    • G03H1/2202—Reconstruction geometries or arrangements
    • G03H2001/2223—Particular relationship between light source, hologram and observer
    • G03H2001/2228—Particular relationship between light source, hologram and observer adapted for reflection and transmission reconstruction
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H2223/00—Optical components
    • G03H2223/18—Prism
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H2223/00—Optical components
    • G03H2223/19—Microoptic array, e.g. lens array
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H2250/00—Laminate comprising a hologram layer
    • G03H2250/36—Conform enhancement layer
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H2250/00—Laminate comprising a hologram layer
    • G03H2250/40—Printed information overlapped with the hologram

Definitions

  • the present invention relates to security devices capable of producing multiple optically variable effects, to security documents or tokens incorporating such devices, and to methods of manufacturing such devices.
  • security document includes all types of documents and tokens of value and identification documents including, but not limited to the following: items of currency such as banknotes and coins, credit cards, cheques, passports, identity cards, securities and share certificates, driver's licenses, deeds of title, travel documents such as airline and train tickets, entrance cards and tickets, birth, death and marriage certificates, and academic transcripts.
  • items of currency such as banknotes and coins, credit cards, cheques, passports, identity cards, securities and share certificates, driver's licenses, deeds of title
  • travel documents such as airline and train tickets, entrance cards and tickets, birth, death and marriage certificates, and academic transcripts.
  • the invention is particularly, but not exclusively, applicable to security documents or tokens, such as banknotes, or identification documents such as identity cards or passports, formed from a substrate to which one or more layers of printing are applied.
  • the term substrate refers to the base material from which the security document or token is formed.
  • the base material may be paper or other fibrous material such as cellulose; a plastic or polymeric material including but not limited to polypropylene (PP), polyethylene (PE), polycarbonate (PC), polyvinyl chloride (PVC), polyethylene terephthalate (PET); or a composite material of two or more materials, such as a laminate of paper and at least one plastic material, or of two or more polymeric materials.
  • window refers to a transparent or translucent area in the security document compared to the substantially opaque region to which printing is applied.
  • the window may be fully transparent so that it allows the transmission of light substantially unaffected, or it may be partly transparent or translucent partially allowing the transmission of light but without allowing objects to be seen clearly through the window area.
  • a window area may be formed in a polymeric security document which has at least one layer of transparent polymeric material and one or more opacifying layers applied to at least one side of a transparent polymeric substrate, by omitting least one opacifying layer in the region forming the window area. If opacifying layers are applied to both sides of a transparent substrate a fully transparent window may be formed by omitting the opacifying layers on both sides of the transparent substrate in the window area.
  • a partly transparent or translucent area hereinafter referred to as a "half- window” may be formed in a polymeric security document which has opacifying layers on both sides by omitting the opacifying layers on one side only of the security document in the window area so that the "half-window" is not fully transparent, but allows some light to pass through without allowing objects to be viewed clearly through the half-window.
  • the substrates may be formed from an substantially opaque material, such as paper or fibrous material, with an insert of transparent plastics material inserted into a cut-out, or recess in the paper or fibrous substrate to form a transparent window or a translucent half-window area.
  • Opacifying layers applied to a transparent substrate may comprise any one of more of a variety of opacifying coatings.
  • the opacifying coatings may comprise a pigment, such as titanium dioxide, dispersed with a binder or carrier of heat-activated cross-linkable polymeric material.
  • a substrate of transparent plastic material could be sandwiched between opacifying layers of paper or other substantially opaque material to which indicia may be subsequently printed or otherwise applied.
  • security element or feature includes any one of a large number of security devices, elements or features intended to protect the security document or token from counterfeiting, copying, alteration or tampering.
  • Security devices or features may be provided in or on the substrate of the security document or in or on one or more layers applied to the base substrate, and may take a wide variety of forms, such as security threads embedded in layers of the security document; security inks such as fluorescent, luminescent and phosphorescent inks, metallic inks, iridescent inks, photochrome, thermochromic, hydrochromic or piezochromic inks; printed and embossed features, including relief structures; interference layers; liquid crystal devices; lenses and lenticular structures; optically variable devices (OVDs) such as diffractive devices including diffraction gratings, holograms and diffractive optical elements (DOEs).
  • ODDs optically variable devices
  • DOEs diffractive optical elements
  • DOEs Diffractive Optical Elements
  • the term diffractive optical element refers to a numerical- type diffractive optical element (DOE).
  • DOEs Numerical-type diffractive optical elements
  • a two-dimensional intensity pattern When substantially collimated light, e.g. from a point light source or a laser, is incident upon the DOE, an interference pattern is generated that produces a projected image in the reconstruction plane that is visible when a suitable viewing surface is located in the reconstruction plane, or when the DOE is viewed in transmission at the reconstruction plane.
  • the transformation between the two planes can be approximated by a fast Fourier transform (FFT).
  • FFT fast Fourier transform
  • complex data including amplitude and phase information has to be physically encoded in the micro- structure of the DOE.
  • This DOE data can be calculated by performing an inverse FFT transformation of the desired reconstruction (i.e. the desired intensity pattern in the far field).
  • DOEs are sometimes referred to as computer-generated holograms, but they differ from other types of holograms, such as rainbow holograms, Fresnel holograms and volume reflection holograms. BACKGROUND
  • OVD diffractive optically variable device
  • DOVD diffractive optically variable device
  • a diffractive security device alone may act to discourage or prevent counterfeiting of a security document, it is desirable to provide multiple distinct optical effects within the same security device to enhance the recognisability and security effectiveness of the device.
  • the present invention provides an optically variable device, including a plurality of groups of surface relief elements, the groups being interlaced and/or stacked, wherein a first said group is characterised by a first height or depth and produces a first type of optical and/or electromagnetic effect, and a second said group is characterised by a second height or depth which is different to the first height or depth, the second group producing a second, different, type of optical and/or electromagnetic effect than that produced by the first group.
  • the relief elements By applying the relief elements in such a way that they are interlaced and/or stacked, it is possible to produce a composite structure which has one optical effect when viewed under certain conditions, and a second, distinct optical effect visible in substantially the same region of the device when the device is viewed under different conditions.
  • the first optical effect may be observable in transmission, whilst the second is visible in reflection.
  • an optically variable device including a plurality of groups of surface relief elements, the method including the steps of:
  • first said group of surface relief elements to a substrate, the first group being characterised by a first height or depth and producing a first type of optical and/or electromagnetic effect
  • the second group being characterised by a second height or depth which is different to the first height or depth
  • the second group produces a second, different, type of optical and/or electromagnetic effect than that produced by the first group.
  • the groups of surface relief elements are formed in a radiation curable material applied to a substrate.
  • the first and second groups are formed in a radiation curable material applied to a substrate.
  • the first type of optical and/or electromagnetic effect is a non- diffractive effect and the second type of optical and/or electromagnetic effect is a diffractive optically variable effect.
  • the first type of optical and/or electromagnetic effect is one or more of one of the following effects: reflective, refractive, diffusely scattering, electrical.
  • this reduces or substantially eliminates optical cross-talk between the optical effects produced by the device, since the diffractive effect is observable mostly in higher diffraction orders while the reflective, refractive or diffusely scattering effect is observable only in the zero-order.
  • a third group of surface relief elements is interlaced and/or stacked with the first and second groups.
  • the relief elements of the third group may be formed in a surface of the relief elements of the first group or the second group.
  • the relief elements of the third group may be interlaced with the relief elements of the first group or the second group.
  • the first type of optical and/or electromagnetic effect may be a greyscale optically invariable image.
  • the greyscale image may be visible in reflection from a first side of the device, and a negative version of the greyscale image visible in transmission from the first side of the device.
  • the grey levels of the greyscale image may be determined by the surface density of the relief elements of the first group in the plane of the device. Alternatively, the grey levels may be determined by the depths of the relief elements of the first group.
  • the first height or depth is at least five times greater, and more preferably at least 10 times greater, than the second height or depth.
  • the minimum height or depth of the relief elements of the first group is preferably greater than about 5 microns, and the maximum height or depth is preferably less than about 120 microns.
  • the relief elements of the second group preferably have a maximum height or depth which is less than about 4 microns.
  • the minimum height or depth of the relief elements of the second group is preferably greater than about 0.1 microns.
  • the relief elements of the second group may be formed at least partly in an upper or lower surface of the relief elements of the first group.
  • the relief element of the second group are formed in upper surfaces of the relief elements of the first group. This makes it possible, if desired, to preferentially coat the second, shallower, group with a patterned layer of a material, such as a metallic ink, so that the pattern is in perfect register with the second group.
  • the first and/or the second groups may be metallised.
  • at least some of the relief elements of the second group may be metallised, so that the second group produces a diffractive optically variable effect in reflection, while the first group produces a diffractive or non-diffractive effect in transmission.
  • at least some of the relief elements of the first group and the second group may be metallised so that both effects are observable in reflection.
  • the third group may also, al alternatively, be metallised.
  • the second group may be metallised in a pattern which forms at least one passive electrical component.
  • the second group is metallised in a pattern which forms a passive radio-frequency antenna, for example an RFID tag.
  • a further, non-optical, authentication means may thus be incorporated into the security device.
  • the relief elements in the second group are preferably spaced from each other at a distance which is sufficiently small that light transmitted or reflected by the second group is polarised.
  • the separation of the relief elements of the second group is preferably in the range 100 nm to 300 nm.
  • the second height or depth is preferably in the range 5 microns to 10 microns.
  • the device may further include a layer or coating applied to the first group and/or the second group and, if applicable, the third group.
  • the layer or coating may be a protective layer or coating.
  • the refractive index of the layer or coating is different from the refractive index of the material in which the relief elements are formed. If the layer or coating is applied to both groups of relief elements, each of the optical effects may be visible in transmitted light.
  • the first group includes microprisms having a lower surface, an upper surface and at least one inclined sidewalk
  • the first group includes two or more sets of microprisms, and each set of microprisms is characterised by a different angle of inclination of the inclined sidewall, whereby different images or different regions of an image can be viewed through each set of microprisms of the optically variable device.
  • the device may include an image layer bearing an image composed of two or more interleaved sub-images, with each set of microprisms viewing one of the sub-images.
  • the interleaved sub-images may be arranged in bands or stripes.
  • the image layer is preferably a printed layer.
  • Each of the microprisms may correspond to a pixel of a grayscale bitmap image, the area of each microprism being related to the gray level of the corresponding pixel.
  • the device may further include a spacing layer between the first and second group of relief elements.
  • the spacing layer has a refractive index which is substantially different to the refractive index of the material in which the relief elements are formed.
  • the first group includes microlenses.
  • the device further includes a layer of microprinting, the microprinting being viewable through the microlenses to produce the first optical effect.
  • the second group of relief elements may at least partly take the form of micrographic elements, wherein the microprinting is viewable through the microlenses from an on-axis position and micrographic elements are viewable through the microlenses from an off-axis position.
  • the device may further include a transparent or translucent substrate. If the relief elements are formed in a radiation curable material applied to the substrate, the radiation curable material is preferably applied by printing.
  • the first and second groups of relief elements are applied simultaneously.
  • the method may further include the step of applying a second layer of radiation curable material overlying the first group of relief elements, whereby the second group of relief elements is formed in the second layer of radiation curable material.
  • the second layer of radiation curable material is preferably applied by printing.
  • the layer or layers of radiation curable material are embossed to form the first and second groups of relief elements and the radiation curable material is cured substantially at the same time as the embossing step.
  • embossing method is described in WO 2008/031 170, the contents of which are incorporated herein by reference.
  • the curing step is preferably performed by means of actinic radiation, such as that selected from the group comprising X-ray, electron beam and UV radiation.
  • the method preferably further includes the step of applying the radiation curable material, for example by a printing method, to a transparent or translucent substrate.
  • a security element including the optically variable device of the first aspect, or manufactured according to the second aspect of the invention.
  • a security document including the security element of the third aspect of the invention.
  • the optically variable device is provided in a window or half-window area of the security document.
  • an embossing tool including a plurality of groups of surface relief elements or recesses, the groups being interlaced and/or stacked, wherein a first said group is characterised by a first height or depth and a second said group is characterised by a second height or depth which is different to the first height or depth, whereby when a transparent, translucent or reflective material is embossed with the embossing tool, areas embossed with the first group of relief elements produce a first type of optical effect, and areas embossed with the second group of relief elements produce a second, different, type of optical effect.
  • the embossing tool may further include a third group of surface relief elements or recesses interlaced with the first group or the second group, whereby areas embossed with the third group produce a third type of optical effect.
  • a method of creating an embossing tool for applying a plurality of groups of surface relief elements to a transparent, translucent or reflective material including the steps of:
  • embossing a first group of surface relief elements on a substrate the first group being characterised by a first height or depth to produce a first type of optical effect
  • the material is transparent or translucent it may be a polymeric substrate or a transparent radiation curable material applied to a substrate.
  • Reflective material may include a metallized layer applied to a substrate.
  • an embossing tool manufactured according to the sixth aspect of the invention.
  • the present invention provides a method of creating an embossing tool for applying a plurality of groups of surface relief elements to a transparent, translucent or reflective material, the method including:
  • a substitute including a first group of surface relief elements, the first group being characterised by a first height or depth to produce a first type of optical effect;
  • the sacrificial material may be photoresist. If so, the second group of surface relief elements may be formed by irradiating the photoresist through a mask.
  • the mask may include apertures with a surface density corresponding to the grey levels of an input greyscale image.
  • Figures 1 (A) to 1 (B) and 2(A) to 2(C) show cross sectional views through different embodiments of the optically variable device
  • Figure 3 schematically illustrates generation of two optically variable effects by the device of Figure 2(C);
  • Figures 4(A) and 4(B) demonstrate selective metallisation of a group of relief elements in an exemplary optically variable device;
  • Figures 5(A) to 5(C) show the formation of an optical variable device in which both optical effects are visible in reflection
  • Figure 6 is a cutaway view of an optically variable device including a printed layer
  • Figure 7 illustrates an embodiment of the invention in which microlenses are used to produce one of the optical effects
  • Figure 8 shows a modification of the embodiment of Figure 7
  • Figure 9 illustrates the generation of two different optically variable effects by the device of Figure 8.
  • Figures 10(A) and 10(B) illustrate embodiments of the invention including a wire grid polariser
  • Figures 1 1 (A) and 1 1 (B) show an alternative embodiment in which groups of relief elements are stacked to produce an optically variable device
  • Figure 12 shows a yet further embodiment with an interlaced and stacked arrangement of groups of relief elements
  • Figures 13(A) to 13(C) and 14 schematically depict two preferred embodiments of a method of creating an embossing tool
  • FIG. 15 is a schematic sectional view through a security document incorporating an optically variable device in accordance with the invention.
  • Figure 16 shows another embodiment of a method for creating an embossing tool
  • Figure 17 shows a method of producing an optically variable device using the embossing tool of Figure 16.
  • Figure 18 shows a person viewing the device of Figure 17.
  • a second group of relief elements is formed by a set of microstructures 120 which are formed in upper surface of the microprisms 1 10, thereby forming a composite structure 130 in which two different groups of relief elements having different depths d and D interlaced to produce two different optically variable effects.
  • the depth of the first group is indicated in Figure 1 (A) by D, and that of the second group by d.
  • D will generally be an order of magnitude or so greater than d, and is preferably in the range from about 5 microns to about 120 microns and more preferably from about 10 microns to about 40 microns.
  • the depth d is preferably in the range from about 0.1 microns to about 4 microns, and more preferably from about 0.2 microns to about 2 microns.
  • the two group of relief elements 1 10, 120 can be formed such that the first group 1 10 produces a primarily refractive effect, while the second group 120 produces a primarily diffractive effect.
  • the second group may, for example, take the form of a diffraction grating, a hologram or a diffractive optical element (DOE).
  • DOE diffractive optical element
  • the composite structure 130 is formed on a transparent substrate 200, and is such that both the diffractive and refractive optically variable effects may be viewed in transmission from either side of the device.
  • a refractive optically variable effect may be produced by structuring the microprisms such that the slopes of the microprism sidewalls vary.
  • the first group of relief elements 1 10 thus constitutes two or more interlaced subgroups of relief elements in the form of microprism arrays, each array characterised by a particular slope.
  • Each array of microprisms will refract light at a particular range of angles, so that different regions of an input image would be observed in transmission at different angles of view of the light source or different angles of view with respect to the normal to the plane of the transparent substrate 200.
  • an image switch could be created in transmission if two groups of interlaced prism regions were created having opposite slope, with the set of prisms of one group corresponding to a first input image, and the set of prisms of opposite slope corresponding to a second input image. As the transmitted angle of view or light source angle was changed from one side of the normal to the surface to the other, an image switching effect would be observed.
  • a third type of transmission mode refractive imaging effect could be observed if the microprisms all had the same slope, but varied in area from region to region according the greyness value of the corresponding region of an input greyscale image, such as a portrait image of a human face.
  • the overall optical behaviour of the device would be a hybrid of an optically variable diffraction effect observed from the collective behaviour of the second group of relief elements 120 which is formed in the upper surfaces of the microprisms 1 10, together with an optically variable refractive effect, both effects being observed in transmission.
  • the optically variable device in the form of bi-level microstructure 130 is formed in a radiation-curable material by an embossing process.
  • a transparent UV-curable lacquer is first applied to the polymer substrate 200 by any suitable process, such as a printing process.
  • the lacquer may then be embossed under heat and pressure (hot emboss) with a shim carrying the relief structures 1 10, 120, and cured by UV radiation to simultaneously form the relief elements in the lacquer.
  • the relief elements 1 10, 120 may be embossed into the lacquer while it is still soft, and then cured by UV radiation while the embossing shim is still in contact with the lacquer (soft emboss).
  • the embossing and curing steps may be performed substantially simultaneously.
  • the relief elements 1 10 are formed in the UV- curable lacquer, by either the hot embossing or soft embossing methods described above, using an embossing shim carrying only the first group of relief elements 1 10.
  • a further layer of UV-curable lacquer is then formed on the upper surfaces of the first relief elements 1 10, and the further layer then embossed, in register with the first group of relief elements, with a separate shim carrying only the second relief elements 120.
  • the device may optionally include a protective layer 210, as shown in
  • the protective layer should have a refractive index which is sufficiently different to the radiation-curable material, the protective layer for example comprising a high refractive index transparent ink, so as not to nullify the optically variable effects produced by the two groups of relief elements.
  • the main visual difference between the diffractive and refractive optically variable effects generated by this type of device is the appearance of multiple orders and diffraction colour effects in the case of the diffractive optically variable images.
  • the refractive optically variable images generated by the interlaced arrays of microprisms will be achromatic in colour and only the zero order effect will be active. This means that the images generated by the refractive elements will not interfere or "cross talk" with the optically variable images generated by the diffractive elements.
  • a particular benefit offered by this dual transmission effect is the possibility for designing optically variable images where the diffractive and refractive elements produce different components of the same optically variable image.
  • the refractive effect is achromatic and only occurs in the zero order, and diffractive effects are polychromatic and only occur in the non- zero orders, it is possible to design optically variable images where a central achromatic image element is surrounded by polychromatic image elements with the different elements of the composite image switching on and off as the angle of view or angle of transmission illumination is changed.
  • FIG. 2(A) A bi-level interlaced microstructure 130 is formed as before ( Figure 2(A)).
  • the microstructure 130 is then selectively metallised in diffractive regions 120 with a metallic ink 125 using, for example, a rotogravure printing process, resulting in the selectively reflective diffraction regions 120' shown in Figure 2(B).
  • the resulting microstructure is then overprinted with a transparent ink or lacquer 135 of different refractive index to the UV cured lacquer ( Figure 2(C)).
  • the device is then capable of producing a diffractive optically variable effect observable in reflection, and a refractive or diffractive optically variable effect observable in transmission.
  • the diffractive elements would each contain 10 to 50 grooves, depending on the angle of diffraction required for the diffractive effect.
  • a ten groove element would diffract at a much smaller angle than a 50 groove element.
  • an optically variable diffractive image 310 with higher-order diffraction maxima corresponding to angles ⁇ i , ⁇ 2 is observed in reflection from the metallised diffractive regions 120'.
  • the diffractive optically variable effect may include image switching, movement effects, portraiture, and so on.
  • the form, location and angle of view of the images generated by diffraction from one of the regions 120' depend on the spacings (spatial frequency) and orientation of the grooves in that region.
  • a refractive optically variable effect can be observed in transmission by looking at a light source 320 placed behind the substrate 200.
  • the second optically variable effect is produced by refraction from the arrays of microprisms 1 10 to generate the optically variable image.
  • the form, location and angle of view of the refractive images from the regions 1 10 depend on the local microprism angles and orientation in each region.
  • each diffractive region 120' and refractive region 1 10 is small (generally having maximum dimension between about 30 and 60 microns), the individual optical regions 1 10, 120' are not discernable by the naked eye, and it is the collective behaviour of a large number of these elemental regions 1 10, 120' which contribute to the observed macroscopic images, which appear to an observer to occupy substantially the same spatial region of the substrate 200.
  • FIG 4 there is shown a schematic outline of the selective metallisation process.
  • a bi-level microstructure 130 is printed with a metallic ink 125 using a printing plate 400 uniformly covered with the metallic ink to a very shallow depth d', which is approximately equal to or greater than the depth d of relief structure 120 but much less than the depth D of relief structure 1 10. Because the deep regions 1 10 of the microstructure are very much deeper than the thickness d' of the ink on the printing plate, these regions will not take up any ink. Only the relatively shallow diffractive regions 120 of the microstructure will accept ink and become reflective (Figure 3(B)).
  • the metallised regions 120' are thus automatically in register with the second group of relief elements, avoiding the problem with known selective metallisation processes in which there is a lack of accurate registration between the printing process and the preferred regions of the microstructure that are to be metallised.
  • the method described here is thus much more accurate and has a much higher intrinsic resolution because its limitations are determined by the accuracy and resolution of the microstructure itself and not that of the printing process.
  • the metallic layer may be patterned by use of an appropriately patterned printing plate.
  • optically variable devices with an inbuilt electronic or electromagnetic capability. Examples of such effects include passive RFID antenna responses, where the metallised diffractive regions of the OVD are patterned as antenna-like images which act as conducting paths, producing a unique back response electromagnetic signature to an interrogating electromagnetic wave. Since the metallised regions are also diffractive, and can therefore carry optically variable picture information, the RFID tag and diffractive optically variable effect provide a composite security device in which an optical and non-optical security feature are combined in a single device.
  • the surrounding regions are non-metallised refractive or diffuse scattering regions which can carry a further optically variable effect viewable in transmission.
  • printed substrate electronic components can also be realized by embedding a differentially metallised bi-level microstructure within a polymer film.
  • the microstructure could be embossed directly into the film under heat and pressure, or formed by "soft embossing" a polymer precursor and curing the embossed precursor, and then selectively metallising the microstructure as described above.
  • the back of the film may also have printed metallized regions so that the resulting sandwich structure produces capacitive effects between the top and bottom surface conducting electrodes.
  • resistive components and patterns can be created using metallic inks with variable resistance properties determined by the nature of the ink's constituent particles.
  • Figure 5 there is shown an alternative embodiment in which both groups of relief elements are metallised. Beginning again with a bi-level interlaced microstructure 130 (Figure 5(A)), a much thicker layer of metallic ink 125, having depth D' equal to or greater than the depth D of the deep relief elements 1 10, is applied to the printing plate. Both types of relief elements will then be reflective ( Figure 5(B)) and the hybrid optically variable effect will be produced by a combination of reflective diffractive elements 120' and reflective microprism elements (micromirror elements) 1 10'. A protective layer 136 of an opaque or transparent material may optionally be applied (Figure 5(C)).
  • an optically invariable image 610 is printed on one side of the substrate 200 adjacent to a high refractive index film layer 210.
  • printed information 610 on the back plane of the substrate 200 may be made to appear only at certain angles of observation determined by the shape of the deep phase refracting elements 1 10.
  • the differentially metallised diffraction grating regions 120' produce an optically variable diffractive image effect, and refraction and diffuse scattering from the combined refractive and printed features 1 10, 610 produce a second optically variable effect the colour dependence of which is a function of the colours used in the printed image 610.
  • the refractive elements 1 10 are in the form of longitudinal prisms then the printed information 610 is in the form of thin stripes with the stripe axis parallel to the long axis of the microprisms 1 10.
  • the printed background 610 may consist of a uniformly metallised background achieved, for example, through printing with metallic inks.
  • the printed layer 610 may consist of printed variable information, in which case the device represents a ultra high resolution differentially metallised diffractive OVD.
  • the first group of relief elements may include one or more microlens arrays.
  • the deep level microstructures incorporate refractive part-cylindrical or part-spherical lenses 712 adjacent to shallow diffractive elements 722 in grating sections 720.
  • Each grating section 720 is preferably between 30 and 60 microns wide, with the micro-lenses 712 being similarly dimensioned to the grating sections 720.
  • the diffraction grating regions 720 may be overcoated with a metallic layer 725 using the differential printed metallisation process described earlier, or may remain unmetallised.
  • the lenslets 712 may be used as magnifying elements for microtext or micrographics 735 printed on the opposite side 730 of the polymer film 200.
  • the hybrid OVD effect therefore consists of an optically variable or image switching diffractive effect due to diffractive regions 720 superimposed on magnified printed microtext or micrographics 735 which will vary with angle due to the change in distance between the microlenses 712 and the microtext or micrographics 735 as the viewing angle is changed.
  • At least some of the diffractive regions 721 may be formed as micrographic elements 723.
  • optical magnification of the micrographic elements 723 is observed when viewing through lenses 712 from an off-axis position 801 , in addition to magnification of microtext or different micrographic elements 735 viewed through the lenses 712 from an on-axis position 802 ( Figure 9).
  • the fidelity of the magnification off-axis is much greater than that observed from the on-axis position 802 due to the fact that the optical accuracy is determined purely by the origination process for the microstructure 720, 721 , and not by any subsequent micro-printing process on the top layer 730 of the substrate, ie on top of the high refractive index (hri) protective film layer 210.
  • magnification of the micro-printing 735 occurs on-axis, so that little or no interference should occur between magnification of the micrographic elements 723 off-axis and magnification of the micro-printing elements 735 on-axis.
  • FIG. 10(A) and 10(B) Further embodiments of the invention are shown schematically in Figure 10(A) and 10(B), in which regions of relatively deep relief elements 860 having high spatial frequency are interlaced with regions of relatively shallow relief elements 850 having a lower spatial frequency.
  • the relief elements are embossed into, for example, a UV lacquer layer 880 applied to substrate 900, the lacquer then being cured.
  • Both of the regions 850 and 860 can be coated with metallic ink 855, as in Figure 10(A).
  • regions 860 If the spacing between adjacent relief elements in regions 860 is less than the wavelength at which the security device is being observed, and in particular of the order of half of the wavelength, light which is incident on regions 860 will be selectively absorbed in one direction so that regions 860 form a polarising structure, sometimes known as a wire grid polariser. Regions 850 diffract incident light and so produce a diffractive optically variable effect which is visible mostly in the first and second diffraction orders.
  • the device of Figure 10(B) is similar to that shown in Figure 10(A), except that the diffractive regions 850 remain unmetallised when the thin layer of metallic ink 855 is applied.
  • the device of either Figure 10(A) or Figure 10(B) is a two-channel optically variable device, in which the first group of relief elements 860 produces a polarisation-dependent image which is observed in the zero order, while the second group 850 produces a diffractive optically variable image which is observed in the first and second propagating diffractive orders.
  • an optically variable effect may thus be observed both under uniformly diffuse lighting conditions, in which normal optically variable devices show little or no normal variation, and also under illumination by normal light sources of finite extent, under which conditions ordinary diffractive optical devices may be observed.
  • FIG. 1 (A) there is shown a further embodiment of the present invention, in which a microprism array structure 920 of relatively high surface relief has been stacked on top of, a relatively low surface relief diffractive structure 910 to form a bi-level microstructure combination.
  • the diffractive microstructure 910 is first soft embossed and UV cured onto a polymer film 900 and then covered with a layer of transparent high refractive index film 915 using, for example, a rotogravure printing process.
  • a layer of UV curable lacquer 917 is then applied, preferably by printing, on top of the high refractive index film 915 and soft embossed with a microprism array microstructure 920 and again UV cured.
  • a second high refractive index layer 925 is applied on top of the microprism array structure 920 to protect the microprism array.
  • the double soft embossed diffractive and refractive structure shown in Figure 1 1 (A) will produce optically variable refractive effects in the zero order from the microprism arrays 920, in combination with optically variable diffractive effects in the non-zero diffractive orders from the diffraction grating array 910.
  • the combination of the optically variable diffractive effect and optically variable refractive effect is generated from the same area of the multilayer film, increasing the difficulty in a counterfeiter trying to reverse engineer and reconstruct the device.
  • the refractive component comprises pairs of microprism 920, 920' having respective inclined sidewalls 922, 922' of opposite slope.
  • An image switching effect in the zero order of the transmitted beam is produced due to the image components of one image being refracted from the microprisms 920' of left leaning slope and the second image components being generated by the microprisms 920 of right leaning slope.
  • the diffractive layer 910 could also be designed as a matrix or interlaced track structure of two different spatial frequencies so that image switching with different artwork could be generated from this layer also.
  • the overall effect from the combination of refractive and diffractive layers in this instance would be of a four channel image switching device with the inner diffractive image switches being coloured (as a result of the wavelength dependence of the diffractive orders), and the outer image switches being uncoloured (or achromatic) as a result of the refractive mechanism.
  • microprisms 1 120 are again stacked on top of diffractive regions 1 1 10, but in this instance are also in interlaced relationship with the diffractive regions since the prism sidewalls 1 124 overlie non-diffractive regions 1 1 1 1 which separate diffractive regions 11 10.
  • the skilled person will also appreciate that the whole of each microprism 1 120 could overlie each corresponding non-diffractive region 1 1 1 1.
  • FIG. 13 and 14 there is shown a schematic of a process for producing an embossing tool which may be used to form an optically variable device according to the present invention.
  • First two separate and complementary embossing tools 1210, 1220 are produced (steps 1310, 1320).
  • the respective relief structures are written into a resist material using electron beam lithography, for example, or by a combination of electron beam lithography and photolithography, depending on the scale of the relief structures and hence the resolution required to produce said structures.
  • Each embossing tool or shim is then produced by electroforming or electroplating onto the respective embossed relief structures.
  • a polymer substrate for example comprising Perspex
  • a thin layer (e.g. 2 microns thick) 1215 of UV curable lacquer is then applied (step 1330) on top of the embossed structure 1 10 using, for example, a rotogravure printing plate uniformly covered with the lacquer to produce the structure 1217 shown in Figure 13(B).
  • the second relief structure 120 is then soft embossed (step 1340) in register on top of the first microstructure, for example by a nano-imprinting process, and cured (step 1350) by UV radiation 1250 as shown in Figure 13(C).
  • the resultant bi-level microstructure 130 is then formed into the final bi-level embossing tool by an electroforming or electroplating technique (step 1360).
  • the bi-level microstructure 130 could be created in a single step using direct write electron beam lithography techniques, for example by using two level electron beam resist processes.
  • the bi- level structure 130 could be created using embossing of thick electron beam resists followed by a direct write process for the diffractive relief structure.
  • the bi-level microstructure could be created by using the first embossing tool 1210 to form the relief structure 1 10 in a layer of a UV-curable lacquer (step 1325), and curing the lacquer (step 1327). This is followed by soft embossing, in register, of a thin layer of UV curable lacquer applied to the relief structure 1 10 by the second embossing tool 1220 as before.
  • FIG 15 there is shown a cross-section through part of a security document, indicated generally by 1400, including a security device in the form of a bi-level interlaced microstructure 100 substantially as shown in Figure 2(C).
  • the security document includes a transparent substrate 200 on which the security device 100 having refractive elements 1 10 and metallised diffractive relief structures 120' is formed.
  • a high refractive index material 210 is applied over the microstructure 100.
  • the security document includes at least one opacifying coating 1410 applied on one or both sides, apart from in window areas 1420a, 1420b in which the opacifying coating(s) 1410 is omitted.
  • An observer viewing the window area 1420b of security document 1400 will see a combination of a refractive effect due to the relief elements 1 10 and a diffractive effect due to the metallised diffractive relief structures 120'.
  • FIG 16 there is shown a substrate 1500 in which a first group of surface relief elements 1510 is formed.
  • the surface relief elements 1510 may be embossed directly into the substrate 1500, or the substrate 1500 may be a preformed structure such as the embossing shim 1220 shown in Figure 13.
  • the substrate 1500 is then coated with a relatively thick (for example, 30 micron thick) layer of photoresist 1520.
  • the photoresist 1520 is then exposed through a mask 1530 having apertures 1531 formed therein.
  • the radiation source 1525 may be any source suitable for exposing the photoresist 1520, for example, a source of UV radiation.
  • the exposure step leaves a second group of relief elements in the form of pillars of photoresist 1542 which overlie the first group of surface relief elements 1510.
  • the tops of pillars 1542 are then embossed with a second embossing shim 1550 which may carry a surface relief structure which is the same as or different than the surface relief structure 1510 carried by substrate or embossing shim 1500.
  • This step leaves embossed photoresist pillars 1552 having a third group of surface relief elements 1543 formed in their upper surface.
  • Embossing shim 1600 includes a first group 1601 , a second group 1602, and a third group 1603 of surface relief structures.
  • Figure 17 shows fabrication of an optically variable device using the shim 1600 of Figure 16.
  • Shim 1600 is brought into contact with embossing medium 1710 (for example, an embossable radiation curable ink) to create first, second and third groups of surface relief structures 1701 , 1702 and 1703.
  • embossing medium 1710 for example, an embossable radiation curable ink
  • a printing roller carrying a thin layer of metallic ink 1710 is then brought into contact with the tops of pillars 1702 in order to create metalized surface relief structures 1713 which can be viewed in reflection.
  • the surface relief structures are then overcoated with a transparent lacquer 1720 having a different refractive index to embossing medium 1710.
  • a person 1800 viewing the device 1700 from a first side 1810 will see an optically variable image from metalized regions 1713 of the device 1700. If the light source 1805 is placed on the opposite side 1820 to the first side 1810, the viewer 1800 sees a second optically variable image in transmission from regions 1701 of the device 1700.
  • the apertures 1531 in photomask 1530 may advantageously be arranged to have a surface density corresponding to the grey levels of an input greyscale image.
  • the viewer 1800 will then see a greyscale image (for example, a dithered portrait) in reflection, corresponding to the pattern of the second group of surface relief elements 1702, whilst in transmission, a negative version of the greyscale image will be apparent to the viewer 1800.
  • the security document shown in Figure 15 may have printing or other matter, including further security elements, applied to either or both of the opacifying coatings.
  • the coating on the top surface could be applied over the whole surface of the security document, so that the omitted region 1420b forms a half-window area.
  • the security document of Figure 15 may include any of the various types of security device described herein.

Abstract

L'invention porte sur un dispositif optiquement variable, lequel dispositif comprend une pluralité de groupes d'éléments de relief de surface. Les groupes sont entrelacés et/ou empilés. Un premier groupe d'éléments de relief est caractérisé par une première hauteur ou profondeur, et produit un premier type d'effet optique et/ou électromagnétique. Un deuxième groupe d'éléments de relief est caractérisé par une deuxième hauteur ou profondeur qui est différente de la première hauteur ou profondeur. Le deuxième groupe produit un deuxième type d'effet optique et/ou électromagnétique différent de celui produit par le premier groupe.
PCT/AU2010/001006 2009-08-10 2010-08-09 Dispositifs optiquement variables et procédé de fabrication WO2011017741A1 (fr)

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CH00193/12A CH703994B1 (fr) 2009-08-10 2010-08-09 Dispositifs à effet optique variable et méthode de fabrication.
GB1202110.1A GB2486994B (en) 2009-08-10 2010-08-09 Optically variable devices and method of manufacture
DE112010003249T DE112010003249T5 (de) 2009-08-10 2010-08-09 Optisch variable Vorrichtungen und Verfahren zur Herstellung

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GB201202110D0 (en) 2012-03-21
GB2486994B (en) 2017-03-22
DE112010003249T5 (de) 2013-05-02
CH703994B1 (fr) 2016-09-15

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