Security device with enhanced machine readability and method of manufacturing it

Abstract

A micro-optic security device (200) includes an optical spacer layer (210, 305) comprising a first side and a second side, an array of focusing elements (205, 310), an array of image icons (220, 319a-319c), wherein the image icons comprise colored regions of cured resin, which when viewed with or through focusing elements of the array of focusing elements, project a synthetically magnified image and a machine-readable component (330), wherein the machine-readable component exhibits a signature variation in infrared (IR) transparency or reflection which varies according to wavelength through the near-infrared region of the electromagnetic spectrum.

Description

CCUR02-000751SECURITY DEVICE WITH ENHANCED MACHINE READABILITYTECHNICAL FIELD

[0001] The present disclosure relates to enhancing security documents, such as currency notes, passports, and other documents comprising surface-applied micro-optic security devices by providing a hard-to-reproduce machine-readable security feature with enhanced readability and methods for producing same.BACKGROUND

[0002] Manufacturing passports, banknotes, and other documents (referred to herein as “security documents”) whose constructional features include hard-to-reproduce indicia of the security documents’ authenticity against counterfeiting remains an ongoing source of technical challenges and opportunities for improvement in the field of security document design.

[0003] One of the principal and persistent challenges in the field of security document design is designing and manufacturing security features (for example, micro-optic security threads or patches) which have indicia of authenticity which are simultaneously: visually striking (for example, image content that “magically” appears to move and / or have three-dimensional depth); are difficult for malicious actors to reproduce; and are rugged enough to withstand circulation, folding, and other structural rigors of everyday use. Micro-optic security devices which comprise a first layer of lenses superimposed over a second layer of icon elements and operate through the lenses’ orchestrating, magnifying, and / or restricting a user’s view of the icon elements, have been, and continue to be, one of the best available solutions for simultaneously achieving visual distinctiveness, ruggedness, and resistance to counterfeiting.

[0004] One strategy for enhancing the visual distinctiveness of lens / icon micro-optic systems is to lengthen the focal length of the focusing elements relative to the icon. For a given icon size and pitch, lengthening the focal length of the focusing elements can have the effect of producing greater shifts in the imaged portion of the icon layer for a given shift in a viewer’s position. Skilled artisans can refer to a more pronounced shift in image content in response to a given shift in perspective as “increased motion.” All other things being equal, increased motion can make the optical effects provided by the security device more noticeable to the end user and, by implication, the absence of moving optical effects in counterfeit notes more noticeable to end-users.

[0005] However, as with many multi-component systems, implementing a performance gain in one area of functionality can impose tradeoffs with regard to other areas of functionality. One such area in which designing for greater image motion can impose tradeoffs is in the detectability of machine -readable (i.e., generally invisible to the naked eye) content disposed at locations that are coplanar with or adjacent to an icon layer.

[0006] Modem commercial banknote accepting machines, desktop counters, cash recyclers, and bill validators typically authenticate banknotes using a number of different criteria. These machines may examine a banknote’s magnetic, optical, or luminescent characteristics to determine whether the document is genuine or suspect. A large proportion of these machines examine banknotes in the near-infrared (N-IR)CCUR02-000752region of the electromagnetic spectrum. Often this is performed at multiple wavelengths, in transmission and / or in reflection. Examining banknotes in this way provides the opportunity for banknote manufacturers to deliver a highly secure, optically invisible, and easily read security feature by including this material within the construction of a security foil, thread, or other feature that is imbued with an area that has a unique absorption signature in the N-IR. This concept is described in International Patent Publication No. WO2018147966 (Al), where a security thread has a N-IR absorber that is applied to a security thread’s back side to enable a secure, optically invisible, and easily read machine-readable response.

[0007] While it can, in some embodiments, be possible to obtain a secure, optically invisible, and easily read an infrared (IR) machine -readable signal by simply adding a machine-readable IR absorber with a unique absorption profile to the back of a security device, this approach imposes its own performance tradeoffs. For example, where the machine-readable taggant is applied as part of a separate layer adjacent to the icon layer, the addition of a machine-readable taggant in this way makes the overall device thicker, which can reduce the flexibility of the security document and is generally undesirable from a performance standpoint as bill counters, bill readers, and other machinery for handling security documents which pass the security documents over one or more rollers perform better when the handled documents are thinner and more flexible. Additionally, as many machine-readable taggants have comparatively large particle sizes or are not perfectly colorless, the addition of these pigments to the focusing layer, spacer layer, or icon layer of the micro-optic construction can result in cloudiness, discoloration, user-perceptible chromatic aberration, or other optical effects associated with the presence of machine-readable taggant particulates in the device.

[0008] Beyond ensuring adequate signal strength, the technical challenges associated with providing machine-readable indicia of authenticity include, without limitation, inhibiting reverse engineering of machine-readable security document features. Choosing a N-IR absorbing pigment for addition to the micro-optic device that has an unusual and characteristic absorption response through the N-IR region of the spectrum provides a high degree of security as this characteristic absorption signature is not immediately obvious, even to those observers with an IR viewing device as these devices typically only observe the subject at one wavelength and it would not be obvious that the security feature had a characteristic signature IR absorption response that could be read by cash accepting machines.

[0009] Thus, enhancing the machine-readability of security documents with machine-readable features in ways that ensure the features’ readability in “high-motion” micro-optic security devices and are not amenable to reverse engineering remains a source of technical challenges and opportunities for improvement.SUMMARY

[0010] It is advantageous, therefore, to imbue a security feature with a secure and characteristic nearinfrared absorption response as this physical property can be highly secure and is typically scrutinized by commercial banknote accepting machines, desktop counters, cash recyclers, and bill validators. The present disclosure relates to a security device with enhanced machine readability and methods for making same.CCUR02-000753

[0011] In a first embodiment, a micro-optic security device includes an optical spacer layer comprising a first side and a second side, an array of focusing elements, an array of image icons, wherein the image icons comprise colored regions of cured resin, which, when viewed with or through focusing elements of the array of focusing elements, project a synthetically magnified image and a machine -readable component, and a machine-readable component, wherein the machine-readable component exhibits a signature variation in infrared transparency or reflection which varies according to wavelength through the near-infrared region of the electromagnetic spectrum.

[0012] In a second embodiment, a method of providing a micro-optic security device includes providing an optical spacer layer comprising a first side and a second side, providing an array of focusing elements, providing an array of image icons, wherein the image icons comprise colored regions of cured resin, which, when viewed with or through focusing elements of the array of focusing elements, project a synthetically magnified image, and providing a machine-readable component, wherein the machine-readable component exhibits a signature variation in infrared transparency or reflection which varies according to wavelength through the near-infrared region of the electromagnetic spectrum.

[0013] Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims.

[0014] Before undertaking the DETAILED DESCRIPTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document. The term “couple” and its derivatives refer to any direct or indirect communication between two or more elements, whether or not those elements are in physical contact with one another. The terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation. The term “or” is inclusive, meaning and / or. The phrase “associated with,” as well as derivatives thereof, means to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, have a relationship to or with, or the like. The phrase “at least one of,” when used with a list of items, means that different combinations of one or more of the listed items may be used, and only one item in the list may be needed. For example, “at least one of: A, B, and C” includes any of the following combinations: A, B, C, A and B, A and C, B and C, and A and B and C.

[0015] Definitions for other certain words and phrases are provided throughout this patent document. Those of ordinary skill in the art should understand that in many if not most instances, such definitions apply to prior as well as future uses of such defined words and phrases.BRIEF DESCRIPTION OF THE DRAWINGS

[0016] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts:

[0017] FIG. 1 illustrates an example of a security document according to some embodiments of this disclosure;CCUR02-000754

[0018] FIGS. 2A-2C illustrate examples of security devices according to various embodiments of this disclosure;

[0019] FIGS. 3A-3D illustrate examples of micro-optic security devices with enhanced machinereadability according to this disclosure;

[0020] FIGS. 4A and 4B illustrate infrared transparency curves for machine -readable components according to this disclosure relative to the infrared transparency curves of commonly available materials; and

[0021] FIG. 5 illustrates a method of providing a micro-optic security device with enhanced machine readability according to this disclosure.DETAILED DESCRIPTION

[0022] FIGS. 1-5, discussed below, and the various embodiments used to describe the principles of the present disclosure are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged security document.

[0023] Although the present disclosure has been described with various embodiments, various changes and modifications may be suggested to one skilled in the art. It is intended that the present disclosure encompass such changes and modifications as falling within the scope of the claims.

[0024] FIG. 1 illustrates an example of a security document according to certain embodiments of this disclosure.

[0025] Referring to the non-limiting example of FIG. 1, an example of a security document 100 according to various embodiments of this disclosure is shown. In this illustrative example, security document 100 is a currency note, though other embodiments (for example, tickets, identification papers, etc.) are within the contemplated scope of this disclosure. According to some embodiments, security document 100 comprises a substrate 105, which is formed from a wet web of fibrous material (for example, wood pulp, cotton fiber, linen fiber, flax fiber, sisal fiber, hemp fiber, Abaca fiber, Kozo fiber, Mitsumata fiber, bamboo fiber, Kenaf fiber, and / or synthetic fiber) and laid down (for example, in a Fourdrinier process or in a cylinder mold papermaking process) at a first, baseline fiber density. Regions of the web in which the first fiber density is not altered while the web is wet (for example, through the use of wire rolls, electrotypes, or other watermarking tools) prior to pressing, drying, and, in some embodiments, calendering, form bulk regions 110 of security document 100. As used in this disclosure, the expression “bulk region” encompasses a portion of a fibrous substrate embodying one or more of a baseline fiber density, baseline light absorption, or baseline caliper thickness. Put differently, as used in this disclosure, the expression “bulk region” encompasses portions of a finished fibrous substrate in which the locations of the constituent fibers are not deliberately altered (for example, through the use of embossed wirecloth or electrotypes) as part of the papermaking process.

[0026] While, for many species of security documents, fibrous materials are the default material for substrate 105, the user of polymeric sheets (for example, sheets of polypropylene or variants thereof, suchCCUR02-000755as biaxially oriented polypropylene (“BOPP”)), are possible and within the contemplated scope of this disclosure. Depending on the application, there may not be any specific requirement that substrate 105 be a thin, flexible section of fibrous or polymeric material. In some applications, substrate 105 can be a rigid, smooth surface of an object that is a potential counterfeiting target (for example, the metal case back of a wristwatch or a perfume bottle) to which security feature 115 can be durably adhered to provide some indicia of authenticity.

[0027] As shown in the explanatory example of FIG. 1, security document 100 further comprises one or more security features 115 adhered to the surface of security document 100. Security feature 115 comprises a thin section of material with one or more optical structures, such as structures comprising an embossed or cast-cured outer surface that provides an optically variable effect. Examples of optical structures provided on security feature 115 include, without limitation, micro-lenses, diffractive structures, and micro-optic icons. Examples of optically variable effects provided by the optical structures of security feature 115 include, without limitation, holograms, color shift effects, and synthetic images, characterized by the synthetic projection of portions of image icons across an array of image icons by focusing elements of an array of focusing elements, wherein the scale ratio (i.e., the ratio of the repeat period of the focusing elements to the repeat period of the image icons) is approximately 1.000. As discussed elsewhere herein, security feature 115 provides, through the projection of content in a micro-optic icon layer, at least one image which is visible at a predetermined angle which is not perpendicular to the surface of security document 100.

[0028] Security document 100 may comprise one or more functional watermarks 120. According to various embodiments, functional watermarks 120 comprise one or more regions in which the fiber density of substrate 105 is deliberately altered (either increased or decreased) from the fiber density in bulk region 110 to form a visible pattern of light (i.e., allowing more light to pass in transmission through the fibrous substrate than bulk region 110) and / or dark (i.e., less light to pass in transmission through the fibrous substrate than bulk region 110) elements. Additionally, at least a portion of functional watermark 120 can be covered by part of security feature 115, wherein security feature 115 is maintained in contact with functional watermark 120 by an adhesive bond. According to various embodiments, functional watermark 120 contacting security feature 115 comprises one or more light or dark elements with edges that are substantially perpendicular to one or more peel directions 125 of security feature 115. As used in this disclosure, the expression “peel direction” encompasses a direction in which the separation of security feature 115 is propagated in a direction generally corresponding to a local minimum of a separation line between security feature 115 and substrate 105. By lifting security feature 115 away from substrate 105 in a peel direction 125 substantially perpendicular to the separation line, a total peeling force applied to substrate 105 is minimized. All other things being equal, malicious actors may be reasonably expected to attempt to harvest security feature 115 by separating security feature 115 from substrate 105 along peel direction 125 in order to minimize the force applied to security feature 115. Depending on its shape, security feature 115 may present more than one peel direction.CCUR02-000756

[0029] FIGS. 2A-2C illustrate constructional aspects of a micro-optic security device (for example, security feature 115 in FIG. 1) comprising part of a security document according to various embodiments of this disclosure. For consistency and convenience of cross-reference, part numbers common to more than one of FIGS. 2A-2C are numbered similarly.

[0030] Referring to the non-limiting example of FIG. 2A, optical security device 200 comprises a plurality of focusing elements 205 (including, for example, focusing element 207), and an arrangement of first image icons 220 (including, for example, image icon 221). According to various embodiments, each focusing element of plurality of focusing elements 205 has a footprint, in which one or more image icons of arrangement of first image icons 220 is positioned. Collectively, the focusing elements of plurality of focusing elements 205, magnify portions of first image icons 220 to produce a synthetic magnification effect (also referred to as “synthetic image”) wherein the individually microscopic image icons are collectively magnified by the plurality of focusing elements 205 to produce an image which dynamically reacts (for example, by appearing to move or change colors) in response to shifts in viewing angle. Given the small scale and tight manufacturing tolerances of the constituent structures of optical security device providing the moire magnification effect, many malicious actors are not able to produce counterfeit versions of optical security device 200.

[0031] First image icons 220 can comprise a plurality of sets of icons, wherein each set of icons occupies regions within footprints of focusing elements associated with predetermined viewing angles. For example, image content predetermined to be visible when optical security device 200 is viewed “on axis” or from a perspective completely perpendicular to the planes of plurality of focusing elements 205 and first image icons 220 can be provided at or around the center of each focusing element’s footprint. Similarly, image content predetermined only to be visible from off-axis perspectives may be provided towards the periphery of each focusing element’s footprint. Accordingly, optical security device 200 is, in many cases, a trusted visual indicium of a security document’s (for example, security document 260) authenticity.

[0032] The present disclosure encompasses a variety of construction techniques for forming the image icon layer. First image icons 220 can, in some embodiments, be directionally cured image icons formed by through-the-lens curing of uncured icon material, thereby ensuring that the range of viewing angles at which first image icons 220 project an image does not include the head-on, or top-dead-center viewing angles which flatbed scanners and other commercial imaging apparatuses utilize to obtain image data of substantially two-dimensional objects.

[0033] In some embodiments according to this disclosure, in addition to first image icons 220, the icon layer of the device includes a second icon layer, which can contain icons disposed at locations within footprints of focusing elements associated with on-axis, or head-on views. In some embodiments, such second image icons are formed using the same through-the-lens curing approaches used to generate first image icons 220. In such embodiments, the curing light source is moved between curing first image icons 220 and the second image icons, resulting in image icons that are intermingled among each other and at a substantially common distance away from plurality of focusing elements 205.CCUR02-000757

[0034] Referring to the illustrative examples of FIGS. 2B and 2C, optical security device 200 can also comprise a second strata in which second image icons are disposed. In some embodiments, optical security device 200 comprises directionally cured first image icons 220 and a second set of image icons, which can, but do not have to, be visible from on-axis viewing angles. Accordingly, additional optical effects can be realized by positioning the first and second image icons relative to each other such that directionally cured first image icons 220 occlude part of the second image icons. Alternatively, additional optical effects can be realized by positioning the first and second image icons relatively to each other such that the second image icons or retaining structures for the second image icons partially occlude the directionally cured first image icons, thereby creating a “reward image,” such as described in U.S. Patent Publication No.2020 / 0384790.

[0035] FIG. 2A illustrates an example embodiment in which a second icon layer 299 is formed closer to optical spacer 210, and which, if desired, can be configured to partially occlude directionally cured first image icons 220. FIG. 2B illustrates an example embodiment in which directionally cured first image icons 220 are formed closer to optical spacer, and which, if desired, can be configured to partially occlude second icon layer 299.

[0036] In some embodiments, second icon layer 299 can also be formed by directionally curing uncured pigmented radiation curable-material and then filling the interstitial spaces between icons to create a smooth surface upon which either directionally cured first image icons 220 can be formed, or second substrate 230 can be affixed. In some embodiments, second icon layer can be formed by first creating retaining structures (for example, by cast-curing a thin layer of (typically clear) radiation-curable material) and then filling the interstices of the retaining structures with pigmented material.

[0037] According to certain embodiments, plurality of focusing elements 205 comprises a planar array of micro-optic focusing elements. In some embodiments, the focusing elements of plurality of focusing elements 205 comprise micro-optic refractive focusing elements (for example, plano-convex or GRIN lenses). Refractive focusing elements of plurality of focusing elements 205 are, in some embodiments, produced from light cured resins with indices of refraction ranging from 1.35 to 1.7, and have diameters ranging from 5pm to 200pm. In various embodiments, the focusing elements of plurality of focusing elements 205 comprise reflective focusing elements (for example, very small concave mirrors), with diameters ranging from 5 pm to 50pm. While in this illustrative example, the focusing elements of plurality of focusing elements 205 are shown as comprising circular plano-convex lenses, other refractive lens geometries, for example, lenticular lenses, are possible and within the contemplated scope of this disclosure.

[0038] Arrangement of first image icons 220 comprises a set of image icons (including image icon 221), positioned at predetermined locations within the footprints of the focusing elements of plurality of focusing elements 205. According to various embodiments, the individual image icons of arrangement of first image icons 220 comprise regions of light cured material associated with the focal path of structured light (for example, collimated UV light) passing through plurality of focusing elements 205 from a projection point associated with one or more predetermined ranges of viewing angles. In someCCUR02-000758embodiments, the individual image icons of arrangement of first image icons 220 are not provided within a structured image icon layer. As used in this disclosure, the term “structured image layer” encompasses a layer of material (for example, a light-curable resin) which has been embossed, or otherwise formed to comprise structures (for example, recesses, posts, grooves, or mesas) for positioning and retaining image icon material. These structures - posts, grooves and mesas can be referred to as an “icon matrix.” According to various embodiments, the individual image icons of arrangement of first image icons 220 are provided within an icon matrix comprising one or more of voids, mesas, or posts, which act as retaining structures to hold micro- and nano-scale volumes of colored material.

[0039] In certain embodiments, optical security device 200 includes an optical spacer 210. According to various embodiments, optical spacer 210 comprises a film of substantially transparent material (for example, polyethylene terephthalate (“PET”), or BOPP) which operates to position image icons of arrangement of first image icons 220 in or around the focal plane of focusing elements of plurality of focusing elements 205. In certain embodiments according to this disclosure, optical spacer 210 comprises a manufacturing substrate upon which one or more layers of light curable material can be applied, to form one or more of arrangement of first image icons 220 or plurality of focusing elements 205.

[0040] According to various embodiments, optical security device 200 comprises one or more regions of light-cured protective material which occupy the spaces between the image icons of arrangement of first image icons 220. In some embodiments, the arrangement of first image icons 220 is first formed (for example, by selectively curing and removing liquid light-curable material on optical spacer 210), and then a layer of clear, light-curable material is applied to fill spaces between the image icons of arrangement of first image icons 220 and then flood-cured to create a protective layer, which protects the image icons from being moved from their positions within the footprints of focusing elements of plurality of focusing elements 205. In certain embodiments, the light-curable material used to form arrangement of first image icons 220 is a pigmented, ultraviolet (UV)-curable polymer.

[0041] In some embodiments, arrangement of first image icons 220 is affixed to a second substrate 230, which operates to protect and secure arrangement of first image icons 220 and provide an interface for attaching optical security device 200 to a substrate 250 as part of security document 260. In some embodiments, optical security device 200 is affixed to substrate 250 during the manufacture of substrate in a paper-making machine, such as a Fourdrinier machine or a cylinder mold paper machine. According to some embodiments, optical security device 200 is affixed to substrate 250 by a layer of adhesive between the arrangement of image icons and a top surface of substrate 250.

[0042] In certain embodiments according to this disclosure, optical security device 200 comprises a seal layer 240. According to certain embodiments, seal layer 240 comprises a thin (for example, 2pm to 50pm thick) layer of substantially clear material which interfaces on a lower surface, with focusing elements of the plurality of focusing elements 205 and comprises an upper surface with less variation in curvature (for example, by being smooth or having a surface whose local undulations are of a larger radius of curvature than the focusing elements) than the plurality of focusing elements 205.CCUR02-000759

[0043] While FIGS. 2A-2C provide three examples of optical security devices according to various embodiments, the present disclosure is not so limited. Other optical security devices which can be configured provide enhanced machine readability are possible and contemplated by the present disclosure.

[0044] FIGS. 3A-3D provide four illustrative examples of micro-optic security devices which provide enhanced machine readability, according to various embodiments of this disclosure. For consistency and convenience of cross-reference, figure elements shown in more than one of FIGS. 3A-3D are numbered consistently.

[0045] Referring to the illustrative example of FIG. 3 A, a first example of a micro-optic security device 300 (for example, security feature 115 in FIG. 1) with enhanced machine-readability is shown in the figure.

[0046] As shown in the illustrative example of FIG. 3A, micro-optic security device 300 comprises an optical spacer 305 (sometimes also referred to as a “base film”) having a first side upon which an array of focusing elements 310 is formed. Array of focusing elements 310 can be formed, for example, by cast curing a layer of transparent resin on the first side of optical spacer 305. Depending on embodiments, the transparent resin used to form array of focusing elements 310 can be clear, or it can be slightly tinted, either through the introduction of a pigment into some or all of the material used to form array of focusing elements 310.

[0047] The focusing elements of array of focusing elements 310 are typically of uniform shape (excluding manufacturing variations) and focus light at a focal length f, which falls within icon layer 315, and the individual elements of array of focusing elements 310 synthetically magnify material within a focal depth above and below points at focal length f. As noted elsewhere in this disclosure, to enhance the “motion” of synthetically magnified images projected by micro-optic security device 300, focal length f can be lengthened (for example, by modifying one or more of the geometry or index of refraction of the individual focusing elements of array of focusing elements 310).

[0048] As shown in FIG. 3 A, icon layer 315 comprises at least two structures, an icon matrix 317 (sometimes also referred to as “retaining structures”) and a plurality of image icons (in this case, image icons 319a-319c). Icon matrix 317 comprises at least two substructures, a tie layer 317a and a plurality of extrusions, also referred to as “posts” (in this case, extrusions 317b-317e) extending from tie layer 317a in a direction away from optical spacer 305. As its name suggests, tie layer 317a “ties” icon matrix 317 to optical spacer 305, such that tie layer 317a provides a flat surface of a predetermined and (to the extent manufacturing variations allow) uniform thickness contacting the second side of optical spacer 305. Additionally, tie layer 317a provides a base and structural foundation for extrusions 317b-317e.

[0049] Icons 319a-319c comprise regions of cured resin of one or more non-transparent colors disposed in the voids between extrusions 317b-317e and the top side 321 of tie layer 317a. The resin may be cured using various methods, such via light, radiation, heat, and / or electron beams. Light passing through focusing elements of array of focusing elements 310 can be selectively directed to icons 319a-319c, partially absorbed according to the color of cured resin and is reflected back through array of focusing elements 310 to present a synthetically magnified image which includes the colors and shapes of the icons.CCUR02-0007510

[0050] Icon matrix 317 can be formed by cast-curing a light-curable resin (for example, a polyacrylate) by applying an uncured layer of the light-curable resin and embossing same with a tool defining the relief structures of extrusions 317b-317e. In many embodiments, the thickness of tie layer 317a is not necessarily a critical dimension, provided the colored material of icons 319a-319c falls within the focal depth f of the focusing elements of array of focusing elements 310.

[0051] As noted herein, increasing the focal distance f of micro-optic security device 300 to enhance the apparent motion of the synthetic images projected by the device can, by itself, impose tradeoffs in terms of the signal strength of a machine-readable taggant provided in the lower layers of the device, for which simply increasing the concentration of taggant is an imperfect solution, which imposes its own tradeoffs in terms of image quality and device thickness.

[0052] To avoid the above-mentioned performance tradeoffs, embodiments according to the present disclosure can include a small-particle sized machine-readable taggant disposed in locations which do not add to the overall thickness of the device. Referring to the illustrative example of FIG. 3 A, a fine-particled machine-readable taggant 330 (also shown in the figures as circled “m”s) can be provided in the resin (for example, a UV-curable polyacrylate) used to form icon matrix 317. As shown in the figures, the fine-particled machine-readable taggant can be disposed in at least one of the tie layer 317a or plurality of extrusions 317b and 317c. The fine-particled machine -readable taggant 330 can be a machine-readable component which exhibits a signature variation in transparency across one or more ranges within the infrared spectrum. The machine-readable component can, in some embodiments, comprise sub-micron particulates within the cured resin used to form icon matrix 317.

[0053] In some embodiments, the machine-readable component has a characteristic and unusual absorption response between 810 and 940nm. The machine -readable component can, in some embodiments, be provided at a concentration of 10 percent by weight of the total uncured polymer / machine-readable component mixture. In some embodiments, the machine-readable component can be provided at concentrations covering the ranges between 20, 25 and 30 percent by weight of the total uncured polymer / machine-readable component mixture. Further examples of suitable concentrations of the sub-micron sized particulates relative to the curable polymer include 10-35% particulates by weight, 5-40% particulates by weight, or 10-30% particulates by weight.

[0054] FIG. 3B illustrates a second example micro-optic security device 391 according to various embodiments of this disclosure. Micro-optic security device 391 builds upon the base device of micro-optic security device 300 by incorporating a seal layer 325 (for example, an instance of seal layer 240 in FIG.2A) on top of array of focusing elements 310, wherein seal layer 325 is formed of a polymer with a different refractive index than used for array of focusing elements 310. The refractive index of seal layer 325 can, in some embodiments, be tuned through the addition of nanoparticles (for example, nano-sized particles of titanium oxide). Additionally, or alternatively, machine-readable component 330 may be provided in seal layer 325 to provide enhanced machine-readability, as well as to effect minor adjustments in the refractive index of seal layer 325. In some embodiments, the machine -readable component 330 may be provided inCCUR02-0007511the array of focusing elements 310. For example, the material from which the focusing elements are formed may contain particles or molecules of the machine-readable component 330.

[0055] FIG. 3C illustrates another example micro-optic security device 397 according to various embodiments of this disclosure. Example micro-optic security device 397 builds upon the example of the device shown in FIG. 3B by introducing further icon structures in icon layer 315. As shown in the illustrative example of FIG. 3C, in addition to icon structures provided by filling voids in icon matrix 317, micro-optic security device 397 includes “cap” style icons 327a and 327b, wherein cured colored pigmented material is provided on the surfaces of extrusions 317c and 317d parallel to optical spacer 305. Additionally, and as shown in the example of FIG. 3C, particulate matter with the characteristic IR transparency variation can also be provided in optical spacer layer 305.

[0056] FIG. 3D illustrates another example micro-optic security device 395 according to various embodiments of this disclosure. While the previously-discussed examples have comprised micro-optic systems in which array of focusing elements 310 is an array of refractive focusing elements (for example, micro-lenses), the present disclosure is not so limited, and encompasses embodiments wherein array of focusing elements 310 comprises reflective focusing elements (for example, embedded micromirrors). As shown in the non-limiting example of FIG. 3D, icon layer 315 is disposed closer to aviewer’s eye 389 than array of focusing elements 310. In this example, seal layer 325 contacts the substantially flat surface provided by icon matrix 317 and icons 319a-319c. Accordingly, seal layer 325 can be comparatively thinner than in embodiments in which seal layer 325 is provided on top of an array of refractive focusing elements, as the need for the seal layer to fdl in the recesses between curved refractive focusing elements is eliminated.

[0057] As shown in the figure, machine-readable component 330 can, in embodiments with reflective focusing elements, be disposed in one or more of icon matrix 317 or seal layer 325. Additionally, in some embodiments, machine-readable component 330 can be provided as a dispersion in the pigmented, light-curable resin from which icon 319a is formed. In some embodiments, machine-readable component 330 can be provided as a dispersion in anon-light curable formulation. In some embodiments, machine-readable component 330 can be provided as a dispersion within surface-effect Raman particles that can be used with Raman spectroscopy to determine vibrational modes of the particles.

[0058] FIGS. 4A and 4B illustrate examples of the IR transparency response of machine -readable components (for example, machine-readable component 330 in FIGS. 3A-3D) according to this disclosure. For consistency and convenience of cross-reference, elements common to both FIGS. 4A and 4B are numbered similarly.

[0059] FIG. 4A provides a first plot 400, showing representative IR absorption curves for the overwhelming bulk of IR absorbent and IR transmissive inks suitable for use in micro-optic security devices.

[0060] In first plot 400, the y-axis shows percentage transparency, and the x-axis shows wavelength. Boxes showing the approximate range of human-visible wavelengths (400-700nm) and machine-readable wavelengths (400-1000nm) are provided below the x-axis.CCUR02-0007512

[0061] FIG. 4A shows two transparency / absorption curves. A first curve 401, shows the transparency response for an ink that skilled artisans refer to as “IR transparent.” As shown in the figure, the ink providing first curve displays variable transparency of wavelengths within the visible spectrum, and from 750-800nm, its response curve jumps to approximately 100%, where it remains between approximately 800 and lOOOnm.

[0062] In practical terms, the ink providing first curve 401 will appear “bright” in an IR camera view, and the presence of such an ink can be easily detected by malicious actors scanning a single wavelength in the IR range. Further, inks exhibiting the IR transparent response of first curve 401 are readily available.

[0063] A second curve 403, shows the transparency response for an ink with what skilled artisans refer to as an “IR absorbing” response. Similar to first curve 401, second curve exhibits variable, and slightly increasing transparency across increasing wavelengths in the visible spectrum. However, unlike first curve 401, second curve 403 remains substantially flat across the range of wavelengths between 750- lOOOnm. In practical terms, the ink providing second curve 403 appears “dark” in an IR camera view, and the presence of such an ink can reliably be detected by malicious actors scanning a single wavelength in the IR range. Like the inks exhibiting the IR transparent response, inks exhibiting the IR absorbent response of second curve 403 are also readily available. As skilled artisans will appreciate, the inks exhibiting first and second curves 401 and 403 can be less than ideal in that they are both readily detectible (i.e., can be found by applying light at only a single frequency in the IR range), and can be reproduced with readily available materials.

[0064] FIG. 4B shows a second plot 450 along the same x- and y- axes as first plot 400, but of an actual machine-readable taggant exhibiting a signature variation in IR transparency, according to embodiments of this disclosure. Second plot 450 shows a third transmission curve 405 for a machine-readable feature according to the present disclosure. As shown in the figure, third curve 405 fluctuates between approximately 20-40 units of transparency in the visible spectrum. However, within the IR spectrum, third curve 405 displays unique characteristics which can significantly assist in providing reliable machine-readable indicia of authenticity.

[0065] As shown in FIG. 4B, at shorter wavelengths within the IRband, such as between 730-780nm, third curve 405 appears similar to first curve 401 in FIG. 4A, and for malicious actors only sampling at frequencies within this portion of the IR waveband, could be mistaken for an IR transparent ink.

[0066] At randomly chosen wavelengths between 950nm and lOOOnm, third curve 405 is exhibits a similar IR absorbent response to second curve 403 in FIG. 4A, and for malicious actors only sampling at frequencies within this portion of the IR waveband, third curve 405 could be mistaken for an IR absorbent ink. However, from wavelengths between approximately 800nm to 925nm, third curve 405 displays a variation in IR transparency not seen in either the IR transparent response of first curve 401 or IR absorbent response of second curve 403, wherein, the IR transparency drops by a specified amount 407 over a specified range of wavelengths 409, third curve 405 exhibits a variation in IR transparency not seen in either first curve 401 or second curve 403.CCUR02-0007513

[0067] From a security and authentication perspective the IR transparency response of third curve 405 is more advantageous, in that, with uninformed sampling and measurement, taggants providing IR transparency curves like third curve 405 could be mistaken for commonly available IR transparent or IR absorbent response inks, making counterfeits using such commonly available taggants easily detectible.

[0068] Only by examining IR transparency across the correct range of wavelengths (for example, range of wavelengths 409) can the indicia of authenticity provided by taggants according to this disclosure be detected. Put simply, third curve 405 provides a security feature which, if one did not know to look for it, would probably be overlooked. The advantages of taggants providing third curve 405 further include the fact that the IR transparency response of third curve 405 cannot readily be obtained or reverse engineered using commonly available IR responsive materials.

[0069] FIG. 5 illustrates operations of an example method 500 for creating a micro-optic security device with enhanced machine-readability (for example, the devices described with reference to FIGS. 3A-3D of this disclosure) according to this disclosure.

[0070] Referring to the illustrative example of FIG. 5, at operation 505, an array of focusing elements is provided (for example, array of focusing elements 310 as shown in FIGS. 3A-3D). The focusing elements can be reflective or refractive focusing elements, and the focusing elements may be provided on an exterior surface of the security device (for example, as shown in FIG. 3A) or embedded under a seal layer, such as shown in FIG. 3B).

[0071] At operation 510, an optical spacer (for example, optical spacer 305 in FIGS. 3A-3D) is provided. The optical spacer can be a stand-alone section of a transparent fdm, such as polyester or BOPP, or it can be a larger section of material (for example, a polymeric substrate for a polymeric security document, such as a polymeric banknote).

[0072] At operation 515, one or more arrays of image icons (for example, image icons 319a-319c or 327a-327b in FIG. 3C) are provided. According to certain embodiments, the image icons are contained in, or supported by an icon matrix, wherein the icon matrix comprises at least one of voids or posts for retaining pigmented image icon material. Further, at operation 520, a machine-readable component, having a signature variation in transparency in the IR spectrum (for example, as discussed with reference to FIGS.4A and 4B) is provided, such as in a dispersion in a UV-curable resin. In some embodiments, the machine-readable component is configured to exhibit a characteristic and unusual absorption response to light radiation in the IR spectrum. In some embodiments, the machine-readable component is provided in a spacer layer of the security document. In some embodiments, the machine -readable component is provided in one or more portions of an icon matrix, such as tie layer 317a or protrusion / post 317b. In some embodiments, the machine -readable component is provided in a seal layer (for example, seal layer 325). In some embodiments, the machine -readable component is provided in an icon layer of a device with reflective focusing elements.

[0073] Examples of micro-optic security devices according to this disclosure include micro-optic security devices comprising an optical spacer layer comprising a first side and a second side, an array ofCCUR02-0007514focusing elements, an array of image icons, wherein the image icons comprise colored regions of cured resin, which when viewed with or through focusing elements of the array of focusing elements, project a synthetically magnified image, and a machine-readable component, wherein the machine-readable component exhibits a signature variation in infrared (IR) transparency or reflection which varies according to wavelength through the near-infrared region of the electromagnetic spectrum.

[0074] Examples of micro-optic security devices according to this disclosure include micro-optic security devices wherein the array of focusing elements is an array of refractive focusing elements disposed on a first side of the optical spacer layer, and wherein the array of image icons is disposed on a second side of the optical spacer layer.

[0075] Examples of micro-optic security devices according to this disclosure include micro-optic security devices wherein the array of image icons comprises an icon matrix of cured resin comprising voids, wherein the image icons are disposed within the voids of the icon matrix, and wherein the machine-readable component is comprised in the cured resin of the icon matrix or the machine-readable component is comprised in inked areas of the icon matrix.

[0076] Examples of micro-optic security devices according to this disclosure include micro-optic security devices, wherein the array of image icons comprises an icon matrix of cured resin comprising posts, and wherein the image icons are the posts of the icon matrix.

[0077] Examples of micro-optic security devices according to this disclosure include micro-optic security devices, wherein the machine-readable component is comprised in the posts or in the surrounding resin.

[0078] Examples of micro-optic security devices according to this disclosure include micro-optic security devices comprising a seal layer comprising a layer of cured, clear resin disposed over focusing elements of the array of focusing elements.

[0079] Examples of micro-optic security devices according to this disclosure include micro-optic security devices wherein the machine-readable component is comprised in the cured, clear resin of the seal layer.

[0080] Examples of micro-optic security devices according to this disclosure include micro-optic security devices wherein the array of focusing elements comprises an array of reflective focusing elements disposed on a first side of the optical spacer layer and wherein the image icons are disposed within a seal layer covering the array of focusing elements.

[0081] Examples of micro-optic security devices according to this disclosure include micro-optic security devices wherein the machine-readable component is provided within the seal layer covering the array of focusing elements.

[0082] Examples of micro-optic security devices according to this disclosure include micro-optic security devices wherein the machine-readable component is provided within at least one of the image icons.CCUR02-0007515

[0083] Examples of micro-optic security devices according to this disclosure include micro-optic security devices wherein the machine-readable component does not cause a user-perceptible chromatic aberration in the synthetically magnified image.

[0084] Examples of micro-optic security devices according to this disclosure include micro-optic security devices comprising sub-micron particulates exhibiting the signature variation in IR transparency provided by itself or in a dispersion.

[0085] Examples of micro-optic security devices according to this disclosure include micro-optic security devices wherein the machine-readable component creates a variation in reflection or absorption in response to IR light at different wavelengths.

[0086] Examples of micro-optic security devices according to this disclosure include micro-optic security devices wherein the machine-readable component is comprised in the optical spacer layer or in the array of focusing elements.

[0087] Examples of micro-optic security devices according to this disclosure include micro-optic security devices wherein the machine-readable component is comprised in the array of focusing elements.

[0088] Examples of micro-optic security devices according to this disclosure include micro-optic security devices comprising surface-effect Raman particles, wherein the machine -readable component is comprised in the surface-effect Raman particles.

[0089] Examples of methods of providing micro-optic security devices according to this disclosure include methods that comprise providing an optical spacer layer comprising a first side and a second side, providing an array of focusing elements, providing an array of image icons, wherein the image icons comprise colored regions of cured resin, which when viewed with or through focusing elements of the array of focusing elements, project a synthetically magnified image, and providing a machine-readable component, wherein the machine-readable component exhibits a signature variation in IR transparency or reflection which varies according to wavelength through the near-infrared region of the electromagnetic spectrum.

[0090] Examples of methods of providing micro-optic security devices according to this disclosure include methods wherein the array of image icons comprises an icon matrix of cured resin comprising voids, wherein the image icons are disposed within the voids of the icon matrix, and wherein the machine-readable component is comprised in the cured resin of the icon matrix or the machine-readable component is comprised in inked areas of the icon matrix.

[0091] Examples of methods of providing micro-optic security devices according to this disclosure include methods wherein the array of image icons comprises an icon matrix of cured resin comprising posts, wherein the image icons are the posts of the icon matrix, and wherein the machine-readable component is comprised in at least one of the posts or in surrounding resin.

[0092] Examples of methods of providing micro-optic security devices according to this disclosure include methods comprising providing a seal layer comprising a layer of cured, clear resin disposed overCCUR02-0007516focusing elements of the array of focusing elements, and wherein the machine -readable component is comprised in the cured, clear resin of the seal layer.

[0093] Examples of methods of providing micro-optic security devices according to this disclosure include methods, wherein the array of focusing elements comprises an array of reflective focusing elements disposed on a first side of the optical spacer layer, and wherein the image icons are disposed within a seal layer covering the array of focusing elements.

[0094] Examples of methods of providing micro-optic security devices according to this disclosure include methods wherein the machine-readable component does not cause a user-perceptible chromatic aberration in the synthetically magnified image.

[0095] Examples of methods of providing micro-optic security devices according to this disclosure include methods wherein the machine-readable component comprises sub-micron particulates exhibiting the signature variation in IR transparency or reflection which varies according to wavelength, provided by itself or in a dispersion.

[0096] Examples of methods of providing micro-optic security devices according to this disclosure include methods wherein the machine-readable component is comprised in the optical spacer layer or in the array of focusing elements.

[0097] Examples of methods of providing micro-optic security devices according to this disclosure include methods wherein the machine-readable component is comprised in the array of focusing elements.

[0098] Although the present disclosure has been described with various embodiments, various changes and modifications may be suggested to one skilled in the art. It is intended that the present disclosure encompass such changes and modifications as falling within the scope of the claims.

[0099] The present disclosure should not be read as implying that any particular element, step, or function is an essential element, step, or function that must be included in the scope of the claims. Moreover, the claims are not intended to invoke 35 U.S.C. § 112(f) unless the exact words “means for” are followed by a participle.

Claims

1. CCUR02-0007517WHAT IS CLAIMED IS:

1. A micro-optic security device comprising:an optical spacer layer comprising a first side and a second side;an array of focusing elements;an array of image icons, wherein the image icons comprise colored regions of cured resin, which, when viewed with or through focusing elements of the array of focusing elements, project a synthetically magnified image; anda machine-readable component, wherein the machine-readable component exhibits a signature variation in infrared (IR) transparency or reflection which varies according to wavelength through the nearinfrared region of the electromagnetic spectrum.

2. The micro-optic security device of claim 1, wherein the array of focusing elements is an array of refractive focusing elements disposed on a first side of the optical spacer layer, andwherein the array of image icons is disposed on a second side of the optical spacer layer.

3. The micro-optic security device of claim 1, wherein the array of image icons comprises an icon matrix of cured resin comprising voids,wherein the image icons are disposed within the voids of the icon matrix, andwherein the machine-readable component is comprised in the cured resin of the icon matrix or the machine-readable component is comprised in inked areas of the icon matrix.

4. The micro-optic security device of claim 1, wherein the array of image icons comprises an icon matrix of cured resin comprising posts,wherein the image icons are the posts of the icon matrix, andwherein the machine-readable component is comprised in at least one of the posts or in surrounding resin.

5. The micro-optic security device of claim 1, wherein the machine -readable component is comprised in the optical spacer layer or in the array of focusing elements.

6. The micro-optic security device of claim 1, further comprising a seal layer comprising a layer of cured, clear resin disposed over focusing elements of the array of focusing elements, wherein the machine-readable component is comprised in the cured, clear resin of the seal layer.

7. The micro-optic security device of claim 1, further comprising surface-effect Raman particles, wherein the machine-readable component is comprised in the surface-effect Raman particles.CCUR02-00075188. The micro-optic security device of claim 1, wherein the array of focusing elements comprises an array of reflective focusing elements disposed on a first side of the optical spacer layer; and wherein the image icons are disposed within a seal layer covering the array of focusing elements.

9. The micro-optic security device of claim 8, wherein the machine-readable component is provided within the seal layer covering the array of focusing elements.

10. The micro-optic security device of claim 8, wherein the machine-readable component is provided within at least one of the image icons.

11. The micro-optic security device of claim 1, wherein the machine-readable component does not cause a user-perceptible chromatic aberration in the synthetically magnified image.

12. The micro-optic security device of claim 1, wherein the machine-readable component comprises sub-micron particulates with the signature variation in IR transparency provided by itself or in a dispersion.

13. The micro-optic security device of claim 12, wherein the machine-readable component creates a variation in reflection or absorption in response to IR light at different wavelengths.

14. A method of providing a micro-optic security device, the method comprising: providing an optical spacer layer comprising a first side and a second side;providing an array of focusing elements;providing an array of image icons, wherein the image icons comprise colored regions of cured resin, which, when viewed with or through focusing elements of the array of focusing elements, project a synthetically magnified image; andproviding a machine-readable component, wherein the machine-readable component exhibits a signature variation in infrared (IR) transparency or reflection which varies according to wavelength through the near-infrared region of the electromagnetic spectrum.

15. The method of claim 14, wherein the array of image icons comprises an icon matrix of cured resin comprising voids,wherein the image icons are disposed within the voids of the icon matrix, andwherein the machine-readable component is comprised in at least one of the cured resin of the icon matrix or the machine-readable component is comprised in inked areas of the icon matrix.CCUR02-000751916. The method of claim 14, wherein the array of image icons comprises an icon matrix of cured resin comprising posts,wherein the image icons are the posts of the icon matrix, andwherein the machine-readable component is comprised in at least one of the posts or in surrounding resin.

17. The method of claim 14, further comprising providing a seal layer comprising a layer of cured, clear resin disposed over focusing elements of the array of focusing elements, wherein the machine-readable component is comprised in the cured, clear resin of the seal layer, in the optical spacer layer, or in the array of focusing elements.

18. The method of claim 14, wherein the array of focusing elements comprises an array of reflective focusing elements disposed on a first side of the optical spacer layer, andwherein the image icons are disposed within a seal layer covering the array of focusing elements.

19. The method of claim 14, wherein the machine-readable component does not cause a user-perceptible chromatic aberration in the synthetically magnified image.

20. The method of claim 14, wherein the machine-readable component comprises sub-micron particulates exhibiting the signature variation in IR transparency or reflection which varies according to wavelength, provided by itself or in a dispersion.

Images