WO2019000046A1 - Dispositif micro-optique sur un substrat destiné à un document de sécurité - Google Patents

Dispositif micro-optique sur un substrat destiné à un document de sécurité Download PDF

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Publication number
WO2019000046A1
WO2019000046A1 PCT/AU2018/050668 AU2018050668W WO2019000046A1 WO 2019000046 A1 WO2019000046 A1 WO 2019000046A1 AU 2018050668 W AU2018050668 W AU 2018050668W WO 2019000046 A1 WO2019000046 A1 WO 2019000046A1
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WO
WIPO (PCT)
Prior art keywords
micro
relief layer
optic device
ink
coating
Prior art date
Application number
PCT/AU2018/050668
Other languages
English (en)
Inventor
Karlo Ivan Jolic
Original Assignee
Ccl Secure 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 AU2017902535A external-priority patent/AU2017902535A0/en
Application filed by Ccl Secure Pty Ltd filed Critical Ccl Secure Pty Ltd
Publication of WO2019000046A1 publication Critical patent/WO2019000046A1/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
    • B42D25/324—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
    • 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
    • B42D25/342—Moiré effects
    • 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
    • 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

Definitions

  • the present invention relates to a micro-optic device on a substrate for a security document and methods of producing such micro-optic devices.
  • the micro- optic device includes micro-image elements comprising protruding features in a relief layer on the substrate, the micro-image elements producing a magnified image when viewed through focusing elements disposed on the substrate.
  • Embossing techniques have previously been used to produce security features with higher resolutions than can be achieved by conventional printing techniques.
  • a radiation-curable lacquer coating is embossed with an engraved shim and simultaneously cured to produce a micro-structured layer on the security document substrate.
  • the micro-structured coatings may be designed to produce a number of optical effects, including diffractive and holographic effects. Although useful optical effects may be achieved with such micro-optic devices, the shallow diffractive formations (less than 2 microns depth) are vulnerable to contamination in circulation.
  • handling of a security document comprising the security feature can result in the embossed features being filled with sweat (or other contaminants) having a similar refractive index to the embossed coating. It is thus necessary to protect the security feature, for example by applying metallised or high- refractive coatings. This adds to the manufacturing cost, as an additional printing operation is required to apply the protective coating.
  • Embossing techniques have also been used to produce micro-images which create optical effects when viewed through an array of micro-lenses.
  • Diffractive structures have been formed in an image layer on a substrate by embossing shallow grated formations into a monochromatic UV-curable coating. Contrast in the magnified image viewed through the micro-lenses is thus created by the diffractive properties of the grated microstructures set against the non-diffractive background regions of the embossed image layer. A multi-coloured magnified image is thus observed by a viewer.
  • the magnified image should generally be viewed with point source lighting rather than diffuse lighting due to the diffractive nature of the image elements.
  • the shallow diffractive micro-images remain susceptible to contamination which degrades the optical properties, thus necessitating a protective coating.
  • a pigmented UV-curable ink may be applied directly to an embossing roller engraved with a three-dimensional microstructure. Excess ink is wiped off the roller, leaving ink retained only in the recessed regions of the engraved roller surface, and the ink is partially cured on the roller with UV-radiation. The partially cured ink micro-structures are then transferred to the substrate surface and fully cured on the surface.
  • This technique while useful for producing high resolution, colour-contrasted micro-images for certain niche applications, is nevertheless difficult to scale up for high throughput production.
  • micro-image elements comprising one or more three-dimensionally structured features that protrude by more than 2 microns from surrounding base regions of a relief layer on a substrate, produce magnified images with satisfactory contrast when viewed through focusing elements disposed on the substrate.
  • the protruding features protrude by more than 3 microns, more preferably more than 5 microns, and most preferably more than 10 microns.
  • the protruding features with a protrusion height of greater than 2 microns render the micro-image elements less susceptible to optically degrading contamination than previous embossed micro-image elements.
  • the magnified images produced when viewing the micro-image elements through an array of focusing elements are found to produce surprisingly good contrast in a wide range of lighting conditions, without relying on diffractive effects. Without wishing to be bound by theory, it is believed that greater depth of the relief layer results in improved contrast between the protruding features and the surrounding base regions of the image layer. Satisfactory image contrast can thus be achieved without the application of ink to create colour contrast in the micro-image elements.
  • one or more coatings of ink can be applied to the relief layer to provide colour contrast in the micro-image elements, with at least the first coating of ink being placed evenly and repeatably only in the base regions of the relief layer surrounding the protruding features as a result of the increased protrusion height.
  • protrude and protrusion height in relation to the “protruding features”, refer to the height of the features in the direction normal to the plane of the relief layer.
  • the invention provides a micro-optic device on a substrate for a security document, the micro-optic device comprising:
  • the relief layer comprising a plurality of protruding features that protrude from surrounding base regions of the relief layer, the protruding features having a protrusion height of greater than 2 microns, preferably greater than 3 microns, more preferably greater than 5 microns, most preferably greater than 10 microns;
  • each micro-image element comprising at least one of the protruding features; and a plurality of focusing elements disposed on the substrate,
  • the plurality of micro-image elements produce a magnified image when viewed through the plurality of focusing elements.
  • the protruding features have a width in the plane of the relief layer of less than about 40 microns, preferably less than about 30 microns, more preferably less than about 20 microns.
  • a width in the plane of the relief layer for a particular protruding feature is a distance extending between opposing side wall regions of the protruding feature, across the elevated regions, and thus correlates to the resolution of the micro-image elements.
  • the width in the plane of the relief layer of a ridged line is the line thickness.
  • the width in the plane of the relief layer is the circle diameter.
  • the width in the plane of the relief layer can be either of the rectangular dimensions.
  • the protruding features have an aspect ratio, defined as the ratio of the protrusion height to the width in the plane of the relief layer, of greater than about 0.17, preferably greater than about 0.33.
  • aspect ratio defined as the ratio of the protrusion height to the width in the plane of the relief layer
  • the protruding features of the relief layer are embossed features.
  • the protruding features may be embossed directly into the substrate to form the relief layer as a surface layer of the substrate itself, for example by hot-embossing a suitable polymeric substrate. More preferably, however, the relief layer comprises a coating applied to the substrate, with the protruding features embossed into the coating.
  • the coating may a radiation-cured coating, such as a coating formed by applying a UV-curable coating to the substrate, and simultaneously embossing and curing the coating with UV-radiation.
  • Each of the micro-image elements comprises at least one of the protruding features, and may comprise a plurality of protruding features, for example two or more discrete features or interlaced features.
  • the protruding features are generally not diffractive structures, and in some embodiments, the micro-image elements do not comprise diffractive structures.
  • the magnified image produced by these micro-image elements does not rely on a contrast between diffractive and non-diffractive regions of the relief layer.
  • the micro-image elements may optionally further comprise one or more inks applied to the relief layer to provide a colour-contrasted feature in the micro-image elements, as will described in greater detail hereafter.
  • the protruding features are not limited to any particular shape or configuration.
  • the protruding features may be raised “islands” in the form of geometrical shapes, such as squares, rectangles or circles, or in the form of a discrete picture or pattern.
  • the protruding features may also be in the form of interlaced dots.
  • the protruding features comprise ridged lines which are proud on a base surface plane of the relief layer.
  • the ridged lines may have a thickness of less than 20 microns, preferably less than 10 microns, more preferably less than 5 microns.
  • the ridged lines may define individually coherent symbols or indicia, such a letters or numerals.
  • the ridged lines may define a discrete picture or pattern, or the unit cell of a two-dimensional pattern extending over the relief layer.
  • the protruding features may be configured to produce a variety of optical effects when viewed through the focusing elements.
  • the protruding features may be micro-image "icons” which produce moire magnifying effects or integral 3D image effects, or they may form lenticular imagery that produces image flips, contrast switches, animations, morphing, interlaced 3D images and the like.
  • the side walls of the protruding features are steeply inclined relative to the plane of the relief layer, as this may provide sharp image resolution when viewing the micro-image elements through the focusing elements.
  • an offset in the inclination of the side walls from normal orientation relative to the plane may be preferred, to ensure that the protruding features are cleanly released from the embossing shim or roller during manufacture.
  • the plurality of micro-image elements comprises a repeating array of substantially identical micro-image elements.
  • the repeating array may have a pitch of less than about 100 microns, preferably less than about 70 microns.
  • a repeating array of substantially identical micro-image elements, when viewed through an array of focusing elements with offset or identical pitch, may be particularly preferred for producing magnified images such as a magnified moire image, an integral image, or a flipping image.
  • the substrate is a transparent substrate such as polypropylene, preferably bi-axially oriented polypropylene.
  • the relief layer is also transparent, such as a transparent UV-cured coating.
  • the plurality of focusing elements may be disposed either on an opposite side of the substrate or on top of the relief layer (optionally spaced apart by an interposed transparent layer). In either case, the magnified image may then be viewed through the focusing elements in transmitted or reflected light. Additionally, a magnified image may be viewed from the non-lens side of the substrate in transmitted or reflected light, although with lower contrast than produced when viewed through the focusing elements.
  • transmitted light means light transmitted through the substrate from a source on the opposite side of the substrate from the viewer
  • reflected light means light originating from a source on the same side of the substrate as the viewer and reflected back to the viewer by the micro-optic device.
  • the micro-image elements are monochromatic, including colourless.
  • the protrusion height of the protruding features is sufficient to provide visual contrast in the magnified image produced by the plurality of micro-image elements.
  • An ink or other colouration is thus not applied to the relief layer to provide visual contrast in the magnified image, via the creation of colour-contrasted features in the micro-image elements.
  • the micro-image elements consist only of three-dimensionally structured features in the relief layer. It is believed that the air-relief layer interface scatters transmitted or reflected light incident on the relief layer.
  • each surface portion that falls within the focal point of the focusing elements is then imaged as a pixel through the focusing elements, the brightness correlating with the amount of light scattered (by reflection or refraction) towards the focusing elements. It is believed that increasing the protrusion height, to a minimum protrusion height of greater than 2 microns, results in improved contrast between pixels on the surface of protruding features and those on the surface of surrounding base regions of the relief layer, because the increased protrusion height causes a greater proportion of the incident light to be scattered.
  • the relief layer is transparent and colourless, such as a clear embossed coating.
  • the magnified image is then produced as a grayscale image having the colour of the transmitted or reflected light incident on the relief layer (typically white or natural light).
  • the relief layer is semi-transparent and optionally coloured, for example a translucent coating having a colour.
  • the magnified image is then produced as a grayscale image having the colour of coating.
  • the relief layer may be metallised or filled with an overlaying coating of a transparent, high refractive index composition.
  • the interface between the metallised or high refractive index coating and the relief layer scatters transmitted and/or reflected light to produce the monochromatic micro-image elements.
  • the relief layer is not metallised or filled with an overlaying coating of a transparent, high refractive index composition, it being a potential advantage of the invention that such coatings are not required to protect the micro-image elements from optical degradation due to contamination.
  • the micro-optic device further comprises a first ink coating that covers the base regions surrounding the protruding features of the relief layer.
  • the micro-image elements thus comprise a colour- contrasted feature, with the colour contrast between the protruding features and the first ink coating providing visual contrast in the magnified image.
  • the substrate and/or the relief layer may be transparent or semi-transparent.
  • the substrate and/or the relief layer may even be opaque, provided that the plurality of focusing elements is then disposed on top of the relief layer in order that the colour- contrasted micro-image elements may be viewed through the focusing elements in reflected light.
  • the first ink coating may be applied by conventional printing techniques (such as roll-to-roll-Gravure printing) to the relief layer at a loading and application pressure sufficient to ensure even coverage of the base regions, without also overlaying the protruding features.
  • the minimum protrusion height of greater than 2 microns allows the coating of ink to be deposited precisely and repeatably around the protruding features, thus creating high resolution, colour-contrasted features in the micro-image elements.
  • the increased depth of the relief layer also allows the application of ink at a loading sufficient to achieve strong colouration, without covering the entire relief layer. The ink application is thus not constrained by the need to apply a very thin layer or to wipe excess ink off the relief formation.
  • the first ink coating has a thickness of less than 70%, preferably less than 50% of the protrusion height, such as less than 30% of the protrusion height. It will be appreciated that an ink coating thickness may not be entirely uniform over a structured relief layer surface; for example it may be thicker close to the protruding features due to capillary effects. To avoid doubt, the thickness of ink coating(s), as used herein, means the thickness adjacent to the side walls regions of the protruding features. With such thicknesses of the first ink coating, the micro-image elements remain three-dimensionally structured, with the light-scattering upper surface of the uncovered protruding features and the first ink coating being disposed at different depths with respect to the substrate surface.
  • the contrast in the magnified image may be provided by a potentially synergistic combination of the three- dimensional structuring and the colour contrasting of the micro-image elements.
  • the relief formation is partially filled, the colour-contrasted feature protects the micro-optic device from optical degradation as a result of contamination in circulation.
  • the first ink coating comprises multiple layers of ink, for example layers of the same ink applied in sequential printing steps. This can improve the strength of the colouration, thereby improving colour contrast against the uncoated protruding features of the micro-image elements.
  • the first ink coating comprises areas of differently coloured inks, each of the areas covering the base regions surrounding one or more of the protruding features.
  • the areas of different coloured ink may optionally partially overlap, thereby creating a region of a third, composite colour.
  • multicoloured magnified images may be produced.
  • the areas of different coloured ink may form a separate design element viewed directly on the substrate, and may thus be distinctive from the magnified image produced by the micro-image elements when viewed through the focussing elements.
  • the micro-optic device further comprises a second ink coating having a different colour from the first ink coating, the second ink coating covering the first ink coating in the base regions surrounding the protruding features of the relief layer.
  • the second ink coating thus covers substantially only the regions of the micro-image layer already coated by the first ink coating, and does not overlay the protruding features.
  • the second ink coating is not itself substantially imaged through the focusing elements, although it will be appreciated that minor edge regions of the second ink coating may be viewed where the side walls of the protruding features are significantly tapered. Instead of being directly viewed, the second ink coating enhances the colour contrast between the protruding features and the first ink coating.
  • a second coating of a reflective light-coloured ink (such as white) will enhance the brightness of first coating of dark-coloured ink (such as red) when viewing the micro-image elements in reflected light through micro-lenses disposed on the opposite side of a transparent substrate.
  • the increased depth of the relief layer as a result of the minimum protrusion height of greater than 2 microns, provides the opportunity to produce such a colour-enhancement layer without filling and covering the protruding features; the thickness of each layer of ink typically ranges from around 0.5 to 3 microns, depending on the printing method and ink viscosity.
  • the first ink coating and the second ink coating have a combined thickness of less than 90% of the protrusion height, preferably less than 80% of the protrusion height, thereby ensuring that the protruding features are not inadvertently covered during application of the second ink coating.
  • the second ink coating comprises multiple layers of ink.
  • the micro-optic device further comprises a third ink coating having a different colour from the first ink coating, the third ink coating covering both the first ink coating and the protruding features of the relief layer.
  • the third ink coating may be directly imaged through the focusing elements in the regions above the protruding features, but the first ink coating is imaged in the base regions of the relief layer.
  • the micro-image elements thus comprise a colour-contrasted feature, with the colour contrast between the first ink coating and the third ink coating providing visual contrast in the magnified image when viewed through a plurality of focusing elements disposed on the opposite side of the substrate.
  • the third ink coating has a strongly contrasting colour to the first ink coating to ensure the production of a satisfactory magnified image.
  • the micro-image element itself remains three-dimensionally structured, since the regions of the first ink coating and the third ink coating that are imaged to produce the magnified image are disposed at different depths on the relief layer. Therefore, the contrast in the magnified image may be provided by a potentially synergistic combination of the three-dimensional structuring and the colour contrasting of the different ink coatings in the micro-image elements.
  • the minimum protrusion height of greater than 2 microns allows the first and the third coatings of ink to be deposited on the relief layer by conventional printing techniques, such that high resolution, colour- contrasted and three-dimensionally structured micro-image elements are created.
  • the first ink coating, the third ink coating (and the second ink coating, if present) have a combined thickness of greater than 1 10% of the protrusion height, preferably greater than 120% of the protrusion height. This ensures that the third ink coating completely covers the protruding features with a thickness sufficient for satisfactory colour strength in the magnified image.
  • the third ink coating comprises multiple layers of ink so as to achieve the desired thickness.
  • the micro-optic device comprises a plurality of focusing elements disposed on the substrate, through which the micro-image elements may be viewed such that a magnified image is produced.
  • the focusing elements may be disposed either on the opposite side of the substrate from the relief layer or on top of the relief layer on the same side of the substrate (optionally spaced apart by an interposed transparent layer).
  • the present invention also relates to methods of producing the micro-optic devices described herein.
  • the invention provides a method of producing a micro-optic device on a substrate for a security document, the method comprising:
  • embossing a plurality of protruding features to produce a relief layer on the substrate wherein the protruding features protrude from surrounding base regions of the relief layer with a protrusion height of greater than 2 microns, preferably greater than 3 microns, more preferably greater than 5 microns, most preferably greater than 10 microns;
  • each micro-image element comprising at least one of the protruding features
  • the plurality of micro-image elements produce a magnified image when viewed through the plurality of focusing elements.
  • the method further comprises applying an embossable coating to the substrate, wherein embossing the protruding features to produce the relief layer comprises embossing the coating.
  • the embossable coating may be transparent, semi-transparent or opaque, and may be colourless or coloured.
  • the coating is a transparent radiation-curable coating, such as a UV-curable coating.
  • the protruding features may be simultaneously embossed into the embossable coating and cured with radiation.
  • the protruding features may be embossed into the embossable coating with an engraved shim or an engraved roller having recesses corresponding to the shapes of the protruding features to be embossed into the coating.
  • the recesses in the embossing tool are tapered (i.e. the side walls are offset from the normal) to allow clean release of the embossed protruding features. This may be particularly preferred where the embossed protruding features have high aspect ratios, such as above about 0.17, or above about 0.33.
  • the method excludes a step of applying an ink or other colouration to the embossed relief layer to create a colour-contrasted feature in the micro-image elements.
  • the micro-image elements produced by these method embodiments are thus monochromatic, including colourless.
  • the protrusion height of the protruding features is sufficient to provide visual contrast in the magnified image produced by the plurality of micro-image elements.
  • the method may however include a step of metallising the entire relief layer surface or filling the relief layer with an overlaying coating of a transparent, high refractive index composition.
  • the method may alternatively exclude a step of metallising the entire relief layer surface or filling the relief layer with an overlaying coating of a transparent, high refractive index composition.
  • the method further comprises applying a first ink to the relief layer at a loading and pressure sufficient to form a first ink coating which covers only the base regions surrounding the protruding features of the relief layer. A colour contrast between the protruding features and the first ink coating provides visual contrast in the magnified image.
  • the method further comprises applying a second ink having a different colour from the first ink at a loading and pressure sufficient to form a second ink coating which covers substantially only the first ink coating in the base regions surrounding the protruding features of the relief layer.
  • the second ink coating enhances the colour contrast between the protruding features and the first ink coating, for example by enhancing the brightness of the first ink coating when viewing the microimage elements in reflected light through micro-lenses disposed on the opposite side of a transparent substrate.
  • the method further comprises applying a third ink having a different colour from the first ink at a loading and pressure sufficient to form a third ink coating which covers both the first ink coating and the protruding features of the relief layer.
  • a colour contrast between the first ink coating and the third ink coating provides visual contrast in the magnified image, since the third ink coating, in the regions above the protruding features, will be imaged in the magnified image, while the first ink coating, in the base regions of the relief layer, will be imaged through focusing elements disposed on the opposite side of the substrate.
  • the third ink has a strongly contrasting colour to the first ink to ensure the production of a multi-coloured magnified image with satisfactory colour contrast.
  • the first, second and third inks may be solvent-based inks with solids content varying between 10% and 60%, depending on the desired printing viscosity.
  • the viscosity of the inks may be in the range of from 16 to 25 seconds (10 to 50 centipoise) as measured using a Zahn Cup #2.
  • the first, second and third ink coatings may be formed by applying the first, second and third inks respectively at a mass loading of from about 1 g/m 2 to about 10 g/m 2 , and at an impression pressure from about 0.5 bar to about 8 bar, using conventional printing techniques (such as roll-to-roll-Gravure printing). After application, the ink coatings may be dried with heater ovens that blow warm air onto the substrate.
  • the plurality of focusing elements may be disposed on the substrate either before, after, or simultaneously to embossing the plurality of protruding features and forming the micro-image elements.
  • the focusing elements may be embossed into an embossable coating on an opposite side of the substrate from the relief layer.
  • the invention provides a micro-optic device on a substrate for a security document, produced by the method of any one of the embodiments described herein.
  • the invention provides a security document comprising a micro-optic device according to any of the embodiments described herein, as a security feature.
  • first, second, third etc in relation to various features of the disclosed devices are arbitrarily assigned and are merely intended to differentiate between two or more such features that the device may incorporate in various embodiments. The terms do not of themselves indicate any particular orientation or sequence. Moreover, it is to be understood that the presence of a “first” feature does not imply that a “second” feature is present, the presence of a “second” feature does not imply that a "first” feature is present, etc.
  • Figure 1 depicts in plan view a cut-out section of a micro-optic device with micro-image units consisting of a protruding feature on a relief layer, in accordance with an embodiment of the invention
  • Figure 2 depicts in side view (not to scale) the micro-optic device of Figure 1 , taken through section line A-B indicated in Figure 1 ;
  • Figure 3 depicts in side view (not to scale) a micro-optic device with microimage units comprising a protruding feature on a relief layer and a first ink coating on surrounding base regions of the relief layer, in accordance with an embodiment of the invention
  • Figure 4 depicts in side view (not to scale) a micro-optic device with microimage units comprising a protruding feature on a relief layer and a double-layered first ink coating on surrounding base regions of the relief layer, in accordance with an embodiment of the invention
  • Figure 5 depicts in side view (not to scale) a micro-optic device with microimage units comprising a protruding feature on a relief layer, a first ink coating on surrounding base regions of the relief layer, and a second colour-contrasting ink coating covering only the first ink coating, in accordance with an embodiment of the invention
  • Figure 6 depicts in side view (not to scale) a micro-optic device with microimage units comprising a protruding feature on a relief layer, a first ink coating on surrounding base regions of the relief layer, and a third colour-contrasting ink coating covering both the first ink coating and the protruding feature, in accordance with an embodiment of the invention
  • Figure 7 is a scanning electron microscope image of a relief layer comprising rectangular pyramidal protruding features with a protrusion height of 12 microns embossed into a transparent coating on a substrate;
  • Figure 8 is an optical microscope image taken of a cross-section (cross- sectional line C-D indicated in Figure 7) through the relief layer comprising 12 micron protruding features;
  • Figure 9 is a scanning electron microscope image of the relief layer comprising 12 micron protruding features, over-printed with a 2 micron thick first ink coating;
  • Figure 10 is an optical microscope image taken of a cross-section (cross- sectional line E-F indicated in Figure 9) through the relief layer comprising 12 micron protruding features with over-printed 2 micron first ink coating;
  • Figure 1 1 is a plan view optical microscope image of the relief layer comprising uncoated 12 micron height protruding features surrounded by 2 micron thick first ink coating.
  • the present invention relates to a micro-optic device on a substrate for a security document, the micro-optic device comprising: a relief layer on the substrate, the relief layer comprising a plurality of protruding features that protrude from surrounding base regions of the relief layer, the protruding features having a protrusion height of greater than 2 microns, preferably greater than 3 microns, more preferably greater than 5 microns, most preferably greater than 10 microns; a plurality of microimage elements, each micro-image element comprising at least one of the protruding features; and a plurality of focusing elements disposed on the substrate, wherein the plurality of micro-image elements produce a magnified image when viewed through the plurality of focusing elements.
  • the present invention also relates to a method of producing a micro-optic device on a substrate for a security document, the method comprising: embossing a plurality of protruding features into a relief layer on the substrate, wherein the protruding features protrude from surrounding base regions of the relief layer with a protrusion height of greater than 2 microns, preferably greater than 3 microns, more preferably greater than 5 microns, most preferably greater than 10 microns; forming a plurality of micro-image elements, each micro-image element comprising at least one of the protruding features; and disposing a plurality of focusing elements on the substrate, wherein the plurality of micro-image elements produce a magnified image when viewed through the plurality of focusing elements.
  • security document includes all types of documents of value and identification documents including, but not limited to the following: items of currency such as bank notes and coins, credit cards, cheques, passports, identity cards, securities and share certificates, driver's licences, 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 bank notes and coins, credit cards, cheques, passports, identity cards, securities and share certificates, driver's licences, deeds of title
  • travel documents such as airline and train tickets, entrance cards and tickets, birth, death and marriage certificates, and academic transcripts.
  • the micro-optic device of to the invention is typically a security or authentication feature for a security document.
  • the security document may be additionally provided with one or more of a large number of other security devices, elements or features intended to protect the security document against counterfeiting, copying, alteration or tampering.
  • Security features 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, photochromic, 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
  • the substrate may be any suitable substrate for security documents.
  • the substrate 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.
  • PP polypropylene
  • PE polyethylene
  • PC polycarbonate
  • PVC polyvinyl chloride
  • PET polyethylene terephthalate
  • 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.
  • the use of plastic or polymeric materials in the manufacture of security documents pioneered in Australia has been very successful because polymeric banknotes are more durable than their paper counterparts and can also incorporate new security features (such as micro-optic devices).
  • the substrate is a transparent or translucent material.
  • Transparent substrates are particularly preferred as micro-image elements produced on one surface of the substrate may then be viewed through an array of focusing elements disposed on the opposite surface of the substrate.
  • the thickness of the transparent substrate is preferably above 50 pm, to allow the micro-image elements to be placed at, or just within, the focal length of focusing elements on the opposite surface.
  • the substrate is from 60 to 100 pm thick, preferably from 65 to 90 pm thick.
  • a particularly suitable transparent substrate is polypropylene and in particular bi-axially oriented polypropylene.
  • the micro- optic device of the invention is produced on a window region of a transparent substrate.
  • the substrate may then include one or more opacifying layers over other regions of the substrate surface.
  • the transparent substrate may be an insert into a cutout region of a substantially opaque material, such as paper or fibrous material.
  • the relief layer may be a layer integrally formed in or embossed into the substrate itself. More typically, however, the relief layer is an embossed coating, produced by applying a coating layer to the substrate, and embossing and hardening the coating.
  • the embossed coating may be a hot-embossed coating, or an embossed and cured coating formed by embossing and simultaneously curing with radiation such as ultraviolet (UV), electron beams or X-ray radiation.
  • the coating is formed from a radiation-curable coating comprising an acrylic based UV-curable clear embossable lacquer.
  • a radiation-curable coating comprising an acrylic based UV-curable clear embossable lacquer.
  • Such UV curable lacquers can be obtained from various manufacturers, including Kingfisher Ink Limited, product ultraviolet type UVF-203 or similar. These coatings have been reported to be particularly suitable for embossing microstructures, including diffractive structures such as DOEs, diffraction gratings and holograms, microlenses and lens arrays, and non-diffractive optically variable devices.
  • the radiation curable embossable coating may be based on other compounds, e.g. nitro-cellulose.
  • the radiation-curable coating when applied to the substrate, has a viscosity falling in the range of from about 20 to about 175 centipoise, and more preferably from about 30 to about 150 centipoise.
  • the viscosity may be determined by measuring the time to drain the lacquer from a Zahn Cup #2. A sample which drains in 20 seconds has a viscosity of 30 centipoise, and a sample which drains in 63 seconds has a viscosity of 150 centipoise. Viscosities in this range may allow the coating to be applied by roll-to-roll gravure printing techniques.
  • the plurality of focusing elements may include any devices previously reported to be suitable for viewing micro-image elements on a substrate, particularly a substrate of a security document.
  • the focusing elements comprise refractive micro-lens structures, including conventional micro-lenses and Fresnel lenses.
  • diffractive focusing elements such as zone plates or photon sieves, may be employed. Fresnel lenses and diffractive focusing elements may be particularly suited for integration into a security feature of a security document, because such focusing elements are thinner than conventional micro-lens structures for a given focal length.
  • the plurality of focusing elements are generally in an ordered, repeating array, such as lenticular, rectangular or hexagonal configurations.
  • the focusing elements may be registered in exact or offset alignment with the array of micro-image elements on the substrate, depending on the nature of the optical effect to be produced.
  • the plurality of focusing elements may be produced as a separate sheet which is adhered to the substrate. However, in preferred embodiments, the plurality of focusing elements is produced by applying a transparent radiation-curable coating to the substrate, and embossing and curing the coating with radiation to form the focusing elements.
  • the transparent coating into which the focusing elements are embossed may optionally have the same composition as the embossed coating of the relief layer.
  • the focusing elements are generally disposed at a distance from the microimage elements that is equal to or within the focal length of the focusing elements. For use in security documents, the focal lengths of the focusing elements are preferably in the range of from 20 to 200 pm, more preferably from 65 to 90 pm, corresponding with or exceeding the typical thickness of transparent substrates for security documents.
  • FIG. 1 schematically depicts in plan view a cut-out section of micro- optic device 10 in accordance with an embodiment of the invention.
  • Figure 2 schematically depicts micro-optic device 10 in side view (not to scale), taken through section line A-B as indicated in Figure 1 .
  • Micro-optic device 10 comprises a plurality of substantially identical micro-image elements 1 1 , including micro-image elements H and as seen in Figure 1.
  • Micro-image elements 1 1 are in the form of O"-shapes, and are arranged in a rectangular array on substrate 12, the repeating array consisting of rows of micro-image elements 1 1 with a constant pitch.
  • micro-optic device 10 comprises relief layer 13 on a surface of transparent substrate 12.
  • Relief layer 13 is a transparent embossed and UV-cured coating.
  • Relief layer 13 comprises a plurality of protruding features 14, including protruding features 14a and 14b depicted in Figure 2, which protrude from surrounding base regions 15 of relief layer 13.
  • Protruding features 14 have a protrusion height, marked "h” in Figure 2, of greater than 2 microns (for example, 5 or 10 microns).
  • Protruding features 14 are ridged lines having a width in the plane of the relief layer marked "w" in Figure 2.
  • the aspect ratio, defined as the ratio of h:w, of protruding features 14 is greater than 0.33.
  • Micro-image elements 1 1 each include one protruding feature 14. As depicted in Figure 2, micro-image element 1 1 a includes protruding feature 14a and micro-image element 1 1 b includes protruding feature 14b.
  • Micro-image elements 1 1 are monochromatic, since both the protruding features 14 and surrounding base regions 15 of relief layer 13 are transparent and colourless, and no ink or other colouration is applied to relief layer 13 to create a colour-contrasted feature. In the embodiment depicted in Figure 2, micro-image elements 1 1 thus consist only of the three-dimensionally structured formations of relief layer 13.
  • micro-optic device 10 further comprises a plurality of focusing elements 16, including focusing elements 16z, 16a and 16b, disposed on substrate 12.
  • Focusing elements 16 are refractive micro-lenses formed by applying a radiation curable transparent coating to substrate 12, and then simultaneously embossing and curing the lenses into the coating.
  • Focusing elements 16 have a focal length that is at least equal to the combined thickness of substrate 12 and relief layer 13, such that micro-image elements 1 1 lie at or within the focal length.
  • Focusing elements 16 are in register (optionally offset) with micro-image elements 1 1 , with each micro-image element 1 1 or part thereof generally being imaged through one superimposed focusing element 16.
  • the plurality of micro-image elements 1 1 When viewed through the plurality of focusing elements 16 by observer 17 in either transmitted or reflected light, the plurality of micro-image elements 1 1 produce magnified, grayscale image 100 having the colour of the light incident on the surface of relief layer 13.
  • the pitch or rotational alignment of focusing elements 16 with respect to micro-image elements 1 1 may be the same or offset so as to produce optical effects such as a magnified moire image, an integral image or a flipping image.
  • relief layer 13 is coloured, while retaining sufficient transparency for the surface of protruding features 14 to be imaged through focusing elements 16, magnified grayscale image 100 will have the colour of the coating when viewed in white light.
  • the scattering of the incident light on the surface of relief layer 13, via refraction and/or reflection at the air-relief layer interface, allows micro-image elements 1 1 to be imaged, with the depth of the three- dimensionally structured formations providing the necessary image contrast.
  • Protruding features 14 having a protrusion height of greater than 2 microns are sufficient to provide visual contrast in the magnified image.
  • the increased depth of relief layer 14 as a result of the minimum protrusion height protects the optical effects against contamination by sweat and other contaminants, which would rapidly fill shallower relief formations in circulation.
  • a magnified image may also be viewed in transmitted or reflected light when viewed by an observer from the side of embossed relief layer 13.
  • Focusing elements 16 transform the incoming light into an array of light sources at the plane of relief layer 13, which sample micro-image elements 1 1 to construct and project the magnified image to the observer.
  • the magnified image has lower contrast, because the array of light sources is produced by the small amount of light that is internally reflected at the lens- air interface of focusing elements 16, back through transparent substrate 14.
  • FIG. 3 schematically depicts micro-optic device 20 in side view (not to scale), in accordance with another embodiment of the invention.
  • Micro-optic device 20 comprises relief layer 13 having protruding features 14 and base regions 15, and focusing elements 16, these elements being the same as those of micro-optic device 10 depicted in Figure 2.
  • Micro-optic device 20 further comprises first ink coating 28 that covers only base regions 15 of relief layer 13, and therefore does not cover protruding features 14.
  • First ink coating 28 is formed by applying a coloured ink to relief layer 13 with gravure printing, at a loading and pressure sufficient to form first ink coating 28 selectively covering only recessed base regions 15.
  • First ink coating 28 has a thickness of less than the protrusion height, such as approximately 25% of the protrusion height.
  • Micro-image elements 21 of micro-optic device 20, including micro-image elements 21 a and 21 b depicted in Figure 3, comprise a colour-contrasted feature, since colourless protruding features 14 contrast against coloured first ink coating 28.
  • micro-image elements 21 also remain three-dimensionally structured, since both the light-scattering upper surface of protruding features 14 and first ink coating 28, located at different depths with respect to the surface of substrate 12, may be imaged through focusing elements 16.
  • the plurality of micro-image elements 21 When viewed through the plurality of focusing elements 16 by an observer, the plurality of micro-image elements 21 produce a magnified image. The colour contrast between colourless protruding features 14 and first ink coating 28 provides visual contrast in the magnified image.
  • the magnified image may best be viewed in reflected light to obtain bright colouration corresponding to the colour of first ink coating 28.
  • the image may also be viewed in transmitted light, with the magnified image appearing in colour if first ink coating 28 is sufficiently translucent, or appearing in black and white if first ink coating 28 is substantially opaque.
  • micro-optic device 30 is identical to micro- optic device 20, except that first ink coating 38 comprises two layers of ink, layers 38a and 38b.
  • First ink coating 38 is formed by first applying a coloured ink to relief layer 13 with gravure printing, at a loading and pressure sufficient to form first layer 38a selectively in the recessed base regions 15, and then applying the same coloured ink in a second gravure printing step to form second layer 38b on top of first layer 38a.
  • first ink coating 38 has improved colour strength, which enhances the colour contrast against uncoated protruding features 14 of microimage elements 31.
  • micro-optic device 40 in accordance with another embodiment of the invention.
  • Micro-optic device 40 comprises the same relief layer 13 and focusing elements 16 as do micro-optic devices 10, 20 and 30.
  • micro-optic device 40 comprises first ink coating 48 having layers 48a and 48b only in recessed base regions 15 of relief layer 13.
  • first ink coating 48 may instead comprise only a single layer of ink.
  • Micro-optic device 40 further comprises second ink coating 49 having a different colour from first ink coating 48.
  • Second ink coating 49 covers first ink coating 48 substantially only in base regions 15, and does not also cover protruding features 14. To ensure that protruding features 14 remain uncovered, first ink coating 48 and second ink coating 49 have a combined thickness of less than the protrusion height, for example less than 80% of the protrusion height.
  • Second ink coating 49 is formed by applying a coloured ink on top of first ink coating 48 with gravure printing, at a loading and pressure sufficient to form second ink coating 49 selectively in the recessed ink- coated base regions 15.
  • Second ink coating 49 is reflective and/or light-coloured, and thus enhances the brightness of first ink coating 48 when imaged through the plurality of focusing elements 16 in reflected light. For example, a white second coating 49 will enhance the brightness of a red first coating 48. Since second ink coating 49 covers only first ink coating 48, it is not imaged directly through focusing elements 16 by the observer, but instead enhances the colour contrast in micro-image elements 41 between uncovered protruding features 14 and first ink coating 48.
  • micro-optic device 50 in accordance with another embodiment of the invention.
  • Micro-optic device 50 comprises the same relief layer 13 and focusing elements 16 as do micro-optic devices 10, 20 and 30.
  • micro-optic device 50 comprises first ink coating 58 in recessed base regions 15 only of relief layer 13.
  • first ink coating 58 may instead comprise only a single layer of ink.
  • Micro-optic device 50 further comprises third ink coating 59 having a different colour from first ink coating 58, preferably a strongly contrasting colour.
  • Third ink coating 59 is of sufficient thickness that it covers both first ink coating 58 and protruding features 14 of relief layer 13, including protruding features 14a and 14b depicted in Figure 6.
  • First ink coating 58 and third ink coating 59 thus have a combined thickness of greater than the protrusion height of protruding features 14, such as about 125% of the protrusion height.
  • Third ink coating 59 is formed by applying a coloured ink on top of first ink coating 58 with gravure printing, at a loading sufficient to form third ink coating 59 such that it fills and covers entire relief layer 13.
  • third ink coating may comprise two or more layers of ink so as to achieve the required thickness.
  • Micro-image elements 51 of micro-optic device 50 comprise a colour-contrasted feature, since coloured third ink coating 59 (as imaged above protruding features 14) contrasts against coloured first ink coating 28 (as imaged above base regions 15).
  • micro-image elements 51 remain three-dimensionally structured, since the regions of the first and third coating imaged through focusing elements 16 are at different depths with respect to the surface of substrate 12 (as well as being of different colours).
  • a transparent relief layer comprising an array of rectangular pyramid protruding structures was produced by applying a transparent UV-curable coating (1 1 microns thick) to a 75 micron thick transparent substrate, and then simultaneously embossing and irradiating the coating through the substrate with UV-light.
  • a roller having tapered rectangular recesses ablated into the surface with a laser was used as the embossing tool.
  • the rectangular pyramid structures on the relief layer had a protrusion height of 12 microns (corresponding to the depth of the recesses in the roller), and in-plane dimensions of approximately 25 microns (horizontal) and 30 microns (vertical). The structures thus had an aspect ratio of between 0.4 and 0.5.
  • the rectangular pyramid structures were arranged in a rectangular array, with a horizontal pitch of 30 microns and a vertical pitch of 63.5 microns.
  • the relief layer was approximately 8 microns thick in the base regions (between the protruding structures) after embossing and curing.
  • FIG. 7 A scanning electron microscope image of the embossed relief layer is shown in Figure 7. It is evident that the rectangular pyramid micro-structures are produced in high resolution and regularity, without the dot skip, drying-in, feathering and/or screening defects that would be expected for conventionally printed image features with similar dimensions.
  • Figure 8 depicts an optical microscope image of the embossed relief layer cross-section (section C-D as indicated in Figure 7), and shows substrate 100 and relief layer 101 , with one rectangular pyramid protruding feature 102 having a protrusion height of 12 microns (marked "h").
  • a transparent embossed relief layer on a transparent substrate was produced identically to that of Example 1 .
  • the relief layer was then overprinted with white ink, using a loading sufficient to produce a 2 micron thick first ink coating on the relief layer.
  • the ink used had a solids content of 30% and a viscosity of 20 seconds @ Zahn Cup #2, and was gravure printed using an impression pressure of 2 bar and a mass loading of 6 g/m 2 .
  • the ink coating was then dried using heater ovens.
  • Example 1 An array of cylindrical micro-lenses was then placed on the opposite side of the substrate to the relief layer, as for Example 1 .
  • a contrast switch (flipping) optical effect was produced.
  • the effect observed was similar to that of Example 1 , except the colour of the magnified image viewed in reflection was now the colour of the first ink coating i.e. white.
  • FIG. 9 A scanning electron microscope image of the embossed and overprinted relief layer is shown in Figure 9.
  • the recessed base regions of the over-printed relief structure in Figure 9 have high surface roughness, due to deposition of the first ink coating in these regions.
  • Figure 10 depicts an optical microscope image of the over-printed relief layer cross-section (section E-F as indicated in Figure 9), and shows substrate 200 and relief layer 201 (the dotted line indicating the interface), with one rectangular pyramid protruding feature 202 having a protrusion height of 12 microns, and surrounding base regions. It is evident that the first ink coating 203 has covered the recessed base regions of the relief structure, and partially covered the tapered side walls of the rectangular pyramid feature 202.
  • the top of the pyramid feature 202 is uncoated with ink in an area 204 about 10 microns wide.
  • the resulting regular array of 10 micron dots, shown in plan view in the optical microscope image of Figure 1 1 and consisting of the colourless pyramid upper surfaces set against a coated white background, would not have been possible to produce with conventional printing techniques.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Credit Cards Or The Like (AREA)
  • Diffracting Gratings Or Hologram Optical Elements (AREA)
  • Printing Methods (AREA)

Abstract

L'invention concerne un dispositif micro-optique (10) sur un substrat (12) destiné à un document de sécurité, le dispositif micro-optique comprenant : une couche en relief (13) disposée sur le substrat, la couche en relief comprenant une pluralité d'éléments saillants (14) qui font saillie depuis des régions de bases circonvoisines (15) de la couche en relief, les éléments saillants présentant une hauteur de saillie (h) supérieure à 2 microns, de préférence supérieure à 3 microns, plus préférentiellement supérieure à 5 microns, idéalement supérieure à 10 microns ; une pluralité d'éléments de micro-image (11), chaque élément de micro-image comprenant au moins l'un des éléments saillants ; et une pluralité d'éléments de focalisation (16) disposés sur le substrat, la pluralité d'éléments de micro-image produisant une image agrandie (100) lorsqu'elle est vue à travers la pluralité d'éléments de focalisation.
PCT/AU2018/050668 2017-06-30 2018-06-29 Dispositif micro-optique sur un substrat destiné à un document de sécurité WO2019000046A1 (fr)

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AU2017902535A AU2017902535A0 (en) 2017-06-30 Micro-optic device on a substrate for a security document
AU2017902535 2017-06-30

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CN113645790A (zh) * 2021-08-12 2021-11-12 Oppo广东移动通信有限公司 壳体与电子设备
WO2021228573A3 (fr) * 2020-05-14 2021-12-30 Leonhard Kurz Stiftung & Co. Kg Procédé de fabrication d'un corps multicouche et corps multicouche
CN116338976A (zh) * 2023-03-06 2023-06-27 苏州大学 一种相位调制莫尔成像器件

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US20140306441A1 (en) * 2011-10-11 2014-10-16 De La Rue International Limited Security devices and methods of manufacture thereof
US20140312606A1 (en) * 2011-10-11 2014-10-23 De La Rue International Limited Security devices
US20170129272A1 (en) * 2015-07-13 2017-05-11 Wavefront Technology, Inc. Optical products, masters for fabricating optical products, and methods for manufacturing masters and optical products

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Publication number Priority date Publication date Assignee Title
US20140306441A1 (en) * 2011-10-11 2014-10-16 De La Rue International Limited Security devices and methods of manufacture thereof
US20140312606A1 (en) * 2011-10-11 2014-10-23 De La Rue International Limited Security devices
US20170129272A1 (en) * 2015-07-13 2017-05-11 Wavefront Technology, Inc. Optical products, masters for fabricating optical products, and methods for manufacturing masters and optical products

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021228573A3 (fr) * 2020-05-14 2021-12-30 Leonhard Kurz Stiftung & Co. Kg Procédé de fabrication d'un corps multicouche et corps multicouche
CN113645790A (zh) * 2021-08-12 2021-11-12 Oppo广东移动通信有限公司 壳体与电子设备
CN116338976A (zh) * 2023-03-06 2023-06-27 苏州大学 一种相位调制莫尔成像器件

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