Micro-optic security system and method of making it

Abstract

Micro-optic security devices (100, 200, 301) comprising colored icon matrices (217) and tinted components (317a-e) and methods (400, 500) for producing same are provided. The tinted component can, in some embodiments, be provided as part of the icon matrix, or in, or on structures adjacent to the icon matrix.

Description

CCUR02-000741MICRO-OPTIC SECURITY DEVICE WITH COEORED ICON MATRICES AND OTHER TINTED COMPONENTSTECHNICAE FIELD

[0001] The present disclosure relates to micro-optic security devices which are configured to synthetically magnify image content in an icon layer through the choreographed operation of a plurality of lenses. More specifically, the present disclosure relates to extending the functionality of micro-optic devices cast-cured focusing elements and icon structures to create multi-color displays.BACKGROUND

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

[0003] Micro-optic security features, utilizing multi-layer optical structures which magnify micro- or nano- scale features in an icon layer to visible scales through the combined operation of a plurality of micro- or nano- scale focusing elements are a leading option for providing reliable indicia of authenticity on security documents such as banknotes, passports (and other items presenting attractive duplication targets to counterfeiters and other malicious actors. This is due, without limitation to the facts that: a.) such microoptic features can present characteristic images whose presence (and equally importantly, absence) readily catches the eye of end users; and b.) by virtue of the tiny size of the lenses and icons providing the image content, manufacturing such micro-optic features present significant manufacturing challenges and tooling requirements which are insurmountable to counterfeiters.

[0004] The basics of the optical physics underlying synthetic magnification are well understood and have been described in both the patent and technical literature, including, without limitation in U.S. Patent No. 8,310,760, which is incorporated herein by reference. However, the specific micro-optic structures and methods for producing same remain in a state of ongoing evolution. Micro-optic security devices which project synthetically magnified images can be produced using a variety of techniques, including, without limitation, with lithographic printing of icon material and with cast-curing of icon material. In a cast-cure process, a thin layer of uncured radiation-curable material, such as a UV-curable resin (for example, a polyacrylate) is applied to an optical spacer (typically, a thin section of a carrier film, such as a transparent polyethylene or polyester film). The thin film of uncured material is then embossed with a die with a micrometer or nanometer scale relief structure, and, while in contact with the die, exposed to curing radiation, which stabilizes and cures the previously uncured material.

[0005] As a manufacturing technique, cast-curing offers significant performance benefits over lithographic techniques, including, the ability to produce lenses and icon structures at much smaller (and thus, even harder to reproduce) scales, and with sharper features. Still further performance benefits can be realized by tool-less manufacturing techniques, which are “tool-less” in the sense that an embossing die is not used to define the locations of icon material. According to such techniques, icons can be formed byCCUR02-000742 local (or zonal) application of light-curable material, or by “backwards” curing, wherein icon structures are formed by applying a curing light through the lenses to perfectly register the locations of the icons to intended viewing angles. Such tool-less approaches offer heightened registration control and the ability to more readily incorporate more than one color into the icon layer and, by implication, the synthetic image projected by the array of focusing elements.

[0006] Despite the possibilities of tool-less manufacturing, optical security devices with cast-cured (or tooled) icon structures are highly prevalent in the industry, as such devices are, for the most part, practically impossible for malicious actors to reproduce. As such, extending the functionality of cast-cured micro-optic security devices to incorporate additional features, including the multi-color features which can be readily realized through tool-less manufacturing, remains a source of technical challenges and opportunities for improvement in the art.SUMMARY

[0007] The present disclosure illustrates embodiments of micro-optic security devices with colored icon matrices and other tinted components, as well as methods for making same.

[0008] In a first embodiment, a micro-optic security system includes an optical spacer having a first side and a second side, an array of focusing elements disposed on the first side of the optical spacer, and an icon layer comprising an icon matrix disposed on the second side of the optical spacer. The icon matrix includes a tie layer of cured resin of a first color, wherein the tie layer comprises a first side and second side, wherein the tie layer further comprises a planar region of a first thickness contacting the second side of the optical spacer on the first side of tie layer. The icon matrix includes two or more extrusions contacting the tie layer and extending away from the optical spacer to define one or more voids bounded by the second side of the tie layer and two extrusions of the two or more extrusions. The one or more voids contain cured resin of a second color, wherein the second color contrasts with the first color.

[0009] In a second embodiment, a method of making a micro-optic security system includes providing an optical spacer, the optical spacer having a first side and a second side. The method includes providing an array of focusing elements on the first side of the optical spacer. The method includes applying, to the second side of the optical spacer, an uncured layer of light-curable resin of a first color, and embossing, at a first pressure, the uncured layer of the light-curable resin of the first color to form an icon matrix. The icon matrix includes a tie layer of cured resin of a first color, wherein the tie layer comprises a first side and second side, wherein the tie layer further comprises a planar region of a first thickness contacting the second side of the optical spacer on the first side of tie layer. The icon matrix includes two or more extrusions contacting the tie layer and extending away from the optical spacer, thereby forming one or more voids bounded by the second side of the tie layer and two extrusions of the two or more extrusions. The method includes curing the light-curable resin of the first color, adding uncured light-curable resin of a second color to the one or more voids in the icon matrix, wherein the second color contrasts with the first color to the one or more voids, and curing the light-curable resin of the second color to form an icon layer comprising icons of the first color and icons of the second color.CCUR02-000743

[0010] In a third embodiment, a micro-optic device includes an optical spacer having a first side and a second side, an array of focusing elements disposed on the first side of the optical spacer, wherein focusing elements of the array of focusing elements comprise microlenses of cured light-curable resin, an icon layer disposed on the second side of the optical spacer, the icon layer comprising icons of cured-light curable resin of a first color, wherein when viewed through the optical spacer, a synthetically magnified image of the icons is projected, and a tinted component of a second color.

[0011] A method of making a micro-optic device includes providing an optical spacer having a first side and a second side, forming an array of focusing elements disposed on the first side of the optical spacer, wherein focusing elements of the array of focusing elements comprise microlenses of cast-cured light- curable resin, forming an icon layer disposed on the second side of the optical spacer, the icon layer comprising icons of cured-light curable resin of a first color, wherein when viewed through the optical spacer, a synthetically magnified image of the icons is projected, and providing a tinted component of a second color, wherein the second color contrasts with the first color.

[0012] Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims.

[0013] 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.

[0014] 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

[0015] 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:

[0016] FIGURE 1 illustrates an example of a security document including a micro-optic security device according to embodiments of this disclosure;CCUR02-000744

[0017] FIGURES 2A-2D illustrate examples of icon matrices, including colored icon matrices, according to embodiments of this disclosure;

[0018] FIGURES 3A-3E illustrate examples of micro-optic security devices incorporating tinted components according to embodiments of this disclosure;

[0019] FIGURE 4 illustrates operations of an example method for making a micro-optic security device including a colored icon matrix according to various embodiments of this disclosure; and

[0020] FIGURE 5 illustrates operations of an example method for making a micro-optic security document including one or more tinted components according to this disclosure.DETAILED DESCRIPTION

[0021] FIGURES 1 through 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.

[0022] 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.

[0023] To provide context on the improvements provided by, and technical challenges overcome by, certain embodiments according to this disclosure, FIGURE 1 illustrates an example of a known architecture for a micro-optic security device 100, which is incorporated in a security document 160.

[0024] Referring to the non-limiting example of FIGURE 1, micro-optic security device 100 comprises a focusing layer comprising an array of focusing elements 105 (including, for example, focusing element 107), and an arrangement of image icons 120 (including, for example, image icon 121. Each focusing element of array of focusing elements 105 has a footprint, in which one or more image icons of arrangement of image icons 120 is positioned. Collectively, the focusing elements of array of focusing elements 105, magnify portions of image icons 120 to produce a magnification effect (also referred to as a “synthetically magnified image” or more briefly, a “synthetic image”) wherein the individually microscopic image icons are collectively magnified by the array of focusing elements 105 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 synthetic magnification effect, many malicious actors are not able to produce counterfeit versions of micro-optic security device 100. Accordingly, micro-optic security device 100 is, in many cases, a trusted visual indicium of a security document’s (for example, security document 160) authenticity.

[0025] Array of focusing elements 105 comprises a planar array of refractive focusing elements. In some embodiments, the focusing elements of plurality of focusing elements 105 comprise micro-optic refractive focusing elements (for example, plano-convex or GRIN lenses). Refractive focusing elements of array of focusing elements 105 are, in some embodiments, produced from cured light curable resins (for example, by cast-curing), wherein the cured resin has an index of refraction ranging from 1.35 to 1.7.CCUR02-000745Variations on micro-optic security device 100 in which plurality of focusing elements 105 are reflective focusing elements (i.e. , micro-mirrors) are also possible. Materials suitable for forming plurality of focusing elements 105 include, without limitation, substantially transparent, colored, or colorless polymers such as acrylics, acrylated polyesters, acrylated urethanes, epoxies, polycarbonates, polypropylenes, and the like. Various methods of providing the layer of focusing elements can include extrusion, radiation cured casting, injection molding, reaction injection molding or reaction casting.

[0026] The focusing elements of array of focusing elements 105 (can be characterized by an F#, which may be adjusted as desired to modify the synthetic image and its optical effect. Suitable F numbers, in view of the desired thickness of the security fdm or security device, can be adjusted to be less than 10, or in some embodiments less than about 4, or in some embodiments, less than 2 or 1. The synthetic image can also be modulated by the relative arrangements and alignments of the array of focusing elements to the array of image elements and each array has respective repeat periods. The repeat periods of the respective arrays may be adjusted such that their ratios are equal to 1, slightly above or slightly below 1; though ratios substantially above and substantially below 1 are also contemplated.

[0027] As shown in the illustrative example of FIGURE 1, arrangement of image icons 120 comprises a set of image icons (including image icon 121), positioned at predetermined locations within the footprints of the focusing elements of plurality of focusing elements 105. The individual image icons of arrangement of image icons 120 comprise regions of light cured material associated with the focal path of structured light (for example, collimated UV light) passing through array of focusing elements 105 from a projection point associated with one or more predetermined ranges of viewing angles. Where arrangement of image icons 120 is formed via cast-curing of a curable resin, arrangement of image icons 120 can be said to be a structured image 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 retaining structures (for example, recesses, posts, grooves, or mesas) for positioning and retaining image icon material. As noted elsewhere in this disclosure, structured image layers can be, from a performance perspective, a significant improvement on printed image layers, and thus, remain highly relevant despite the emergence of tool-less manufacturing techniques.

[0028] According to various embodiments, the individual image icons of arrangement of image icons 120 are provided within a structured image layer, the structured image layer comprising one or more of voids, mesas, or posts, which act as retaining structures to hold micro- and nano-scale volumes of colored material. In some embodiments, an arrangement of image icons comprises icons of a single color. In other embodiments, image icons of arrangement of image icons 120 comprise icons of two or more colors.

[0029] While not shown in FIG. 1, but described elsewhere in this disclosure, the relief structures of the icon layer, can operate as the image icons. In such embodiments, the embossed material may be pigmented and semi-opaque, and the variances in thickness of the relief structures may create points of contrast which can be projected through plurality of focusing elements 105 to provide a synthetic image.CCUR02-000746

[0030] In certain embodiments, micro-optic security device 100 includes an optical spacer 110. Optical spacer 110 comprises a film of substantially transparent material (for example, polyester or polyethylene film) which operates to position image icons of arrangement of image icons 120 in or around the focal plane of focusing elements of array of focusing elements 105. In certain embodiments according to this disclosure, optical spacer 110 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 image icons 120 or array of focusing elements 105. For many real-world embodiments of lens-icon micro-optic security devices, as well as other optically-variable security devices, such as holograms and patches of color changing material, a section of a clear polymer film (such as, PET or BOPP) is part of the structure. In addition to positioning image icons in, or around, the focal plane of the focusing layer, and providing a uniformly flat surface upon which to cast-cure focusing elements and icons upon, optical spacer 110 provides micro-optic security device 100 with sufficient structural integrity to facilitate mechanized and automated handling and storage, such as in reel-to-reel processes, without stretching or tearing.

[0031] According to various embodiments, micro-optic security device 100 comprises one or more regions of light-cured protective material which occupy the spaces between the image icons of arrangement of image icons 120. In some embodiments, the arrangement of image icons 120 is first formed (for example, by selectively curing and removing liquid light-curable material on optical spacer 110), and then a layer of clear, light-curable material is applied to fill spaces between the image icons of arrangement of image icons 120 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 array of focusing elements 105. In certain embodiments, the light-curable material used to form arrangement of image icons 120 is a pigmented, ultraviolet (UV)-curable resin.

[0032] In some embodiments, arrangement of image icons 120 is affixed to a second substrate 130, which operates to protect and secure arrangement of image icons 120 and provide an interface for attaching micro-optic security device 100 to a substrate 150 as part of security document 160. In some embodiments, micro-optic security device 100 is affixed to substrate 150 during the manufacture of substrate in a papermaking machine, such as a Fourdrinier machine. According to some embodiments, micro-optic security device 100 is affixed to substrate 150 by a layer of adhesive between the arrangement of image icons and a top surface of substrate 150.

[0033] Micro-optic security device 100 can include a seal layer 140. According to certain embodiments, seal layer 140 comprises a thin (for example, a 2pm to 50pm thick) layer of substantially clear material which interfaces on a lower surface, with focusing elements of the plurality of focusing elements 105 and comprises an upper surface with less variation in curvature (for example, by being smooth, or by having a surface whose local undulations are of a larger radius of curvature than the focusing elements) than the plurality of focusing elements 105. According to various embodiments, the upper surface of seal layer 140 is formed from a thermoplastic material which can be ultrasonically welded to a surface comprising a cellulosic material.CCUR02-000747

[0034] As shown in FIGURE 1, micro-optic security device 100 can be attached to substrate 150, to form a security document 160. According to various embodiments, substrate 150 comprises a sheet of material with at least one surface. Substrate 150 can be a polymeric substrate (for example, a section of PET or BOPP fdm). Alternatively, or additionally, substrate 150 can be a fibrous substrate comprising cellulosic material, such as wood pulp, cotton fiber, linen fiber, flax fiber, sisal fiber, hemp fiber, Abaca fiber, Kozo fiber, Mitsumata fiber, bamboo fiber or Kenaf fiber. In some embodiments, substrate 150 is a blend of cotton and linen fibers, such as used for U.S. banknotes. For example, substrate 150 may be made of a fiber blend which contains between 65-80% cotton fibers and between 20-35% linen fibers. In some embodiments, the relative proportions of cotton and linen fibers may be such that the substrate contains 65- 100% cotton fibers and between 0 to 35% linen fibers.

[0035] FIGS. 2A-2D illustrate examples of security devices with colored icon matrices according to various embodiments of the present disclosure. For consistency and convenience of cross-reference, elements common to more than one of FIGS. 2A-2D are numbered similarly.

[0036] Referring to the illustrative example of FIG. 2A, the fundamental structures of a micro-optic security device (for example, micro-optic security device 100 in FIG. 1) are shown in the figure.

[0037] As shown in the illustrative example of FIG. 2A, micro-optic security system 200 comprises an optical spacer 205 (sometimes also referred to as a “base film”) having a first side (in this example, the lower side) upon which an array of focusing elements 210 is formed. Array of focusing elements 210 can be formed, for example, by cast curing a layer of transparent resin on the first side of optical spacer 205. Depending on embodiments, the transparent resin used to form array of focusing elements 210 can be clear, or it can be tinted, either through the introduction of a pigment into some or all of the material used to form array of focusing elements 210.

[0038] The focusing elements of array of focusing elements 210 are typically of uniform shape (excluding manufacturing variations) and focus light at a focal length which falls within icon layer 215, and the individual elements of array of focusing elements 210 synthetically magnify material within a focal depth A above and below points at focal length f.

[0039] As shown in FIG. 2A, icon layer 215 comprises at least two structures, an icon matrix 217 (sometimes also referred to as “retaining structures”) and a plurality of image icons (in this case, image icons 219a-219d). Icon matrix 217 comprises at least two substructures, a tie layer 217a and a plurality of extrusions (in this case, extrusions 217b-217e) extending from tie layer 217a in a direction away from optical spacer 205. As its name suggests, tie layer 217a “ties” icon matrix 217 to optical spacer 205, such that tie layer 217a provides a flat surface of a predetermined and (to the extent manufacturing variations allow) uniform thickness contacting the second side of optical spacer 205. Additionally, tie layer 217a provides a base and structural foundation for extrusions 217b-217e.

[0040] Icons 219a-219d comprise regions of cured light-curable resin of one or more non-transparent colors disposed in the voids between extrusions 217b-217e and the top side 221 of tie layer 217a. Light passing through focusing elements of array of focusing elements 210 is selectively directed to icons 219a-CCUR02-000748219d, partially absorbed according to the color of cured-light curable resin and is reflected back through array of focusing elements 210 to present a synthetically magnified image which includes the colors and shapes of the icons.

[0041] Icon matrix 217 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 217b-217e. In embodiments where the light-curable resin is colorless, the thickness of tie layer 217a is not necessarily a critical dimension, provided the colored material of icons 219a-219d falls within the focal depth A of the focusing elements of array of focusing elements 210.

[0042] However, and as shown by FIG. 2A, tie layer 217a lies on the optical path between icon layer 215 and array of focusing elements 210, as do extrusions 217b-217e. Historically, tie layer 217a and extrusions 217b-217e have been formed from colorless, transparent material, and have not been used to contribute to the colored components of icon designs or synthetic images produced by micro-optic security system 200. Producing micro-optic security films with thicknesses on the order of 100 microns (i.e., 1 / 10 of a millimeter), focusing elements with diameters on the order of 25 microns, and sub-micron size image icons presents such significant technical challenges that coloring the components of icon matrix 217 to provide additional colored elements of the synthetically magnified image projected by the system was thought impossible or unconsidered.

[0043] Research has shown that, through careful tuning and control of the thickness of tie layer 217a and the concentration of pigment added to the resin used to produce icon matrix 217, icon matrix 217 can advantageously be colored, and that tie layer 217a and extrusions 217b-217e can appear in, and impart color to, the synthetically magnified image projected by micro-optic security system 200. In this way, the functionality of cast-cured, or structured icon layers which incorporate icon matrices, such as icon matrix 217 can be extended to include some of the multi-color images provided by tool-less manufacturing techniques.

[0044] With the correct thickness and concentration of pigment in the resin, a colored icon matrix 217 can be formed, such that tie layer 217a functions as a colored filter, which tints the space between the icons and, if desired, can alter the color of the icons. At the same time, extrusions 217b-217e can function as pseudo-icons. In this way, a micro-optic security device with a structured icon layer, such as micro-optic security system 200 can project a synthetic image having similar multi-color characteristics of a device made using tool-less manufacturing techniques.

[0045] Referring to the illustrative example of FIG. 2B, a second example micro-optic device 250 is shown in the figure. In this illustrative example, the thickness of tinted tie layer 251 has been reduced from the thickness of tie layer 217a in FIG. 2A. In some embodiments, tinted tie layer 251 is less than 2 microns in thickness. In some embodiments, tinted tie layer 251 can be less than 1 micron in thickness. Where tinted tie layer 251 is less than two microns in thickness, the tint may be provided as a powdered pigment mixed with the uncured resin at a 1: 1 ratio by weight. In some embodiments, the ratio of powdered pigment to uncured resin may be closer to a 1:2 ratio. In some embodiments, the ratio of powdered pigment to uncuredCCUR02-000749 resin can be on the order of 1 :9. While the pressure needed to achieve tinted tie layer 251 can vary according to a host of factors, including the temperature, the relief structure of the embossing tool, and the choice of curable resin used, in some embodiments, a tool pressure on the order of 70 p.s.i. (as measured by the gas feed on a pneumatic press) can produce a tinted tie layer 251 of suitable thickness, and, at the same time, ensure that extrusions 217b-217e are properly cast.

[0046] In the illustrative example of FIG. 2B, icons 219a-219d are formed by fdling the voids in icon matrix 217 with colored resin of a color which contrasts with the pigment added to the resin forming icon matrix 217.

[0047] While it is possible in some embodiments, to uniformly fill the voids within icon matrix 217 with resin of a second color to just below the tips of extrusions 217b-217e, thereby avoiding a thin tint film (“tonungsfilme”) of resin of the same color as icons 219a-219d on the portion of icon layer 215 furthest away from optical spacer 205, other embodiments are possible, and within the contemplated scope of this disclosure.

[0048] Referring to the illustrative example of FIG. 2C, a tinted icon matrix that includes tinted tie layer 251 may be selectively (also referred to as “zonally”) inked with uncured material of a color which contrasts with the tinted icon matrix, and selectively cured with actinic energy, such as described in U.S. Patent No. 11,685,180, the contents of which are incorporated by reference herein. As shown in the figure, zonal application and curing of light-curable resin allows the voids in icon matrix 217 to be selectively filled with resin of a second color. In the example of FIG. 2C, volumes of icon material are present in voids in left-side voids and form image icons 219a and 219b but the adjacent void 260 is empty. When viewed through array of focusing elements 210 (see FIGS. 2A and 2B), image icons 219a and 219b appear as regions of a second color and void 260 appears as a region of a lighter shade of the first color, due to tinted tie layer 251 acting as a colored filter. Depending on the configuration, icon geometry and concentration of pigment of the first color in the tinted icon matrix, intermediate shades blending the first and second color can appear in the synthetically magnified image.

[0049] In addition to icon layers which include negative space in the form of selectively unfilled voids in a fined icon matrix, embodiments according to the present disclosure also include embodiments in which the extrusions in the tinted icon matrix are proportioned and positioned to create icons of blended color as well as regions of a second color of equal color density to icons (for example, icons 219a & 219b) formed by filling voids in an icon matrix.

[0050] Referring to the illustrative example of FIG. 2D, an example icon layer 270 is shown in the figure. Example icon layer 270 comprises two regions. In a first region, 271, the extrusions of icon matrix 217 are of approximately equal width and height as the filled voids comprising the image icons. As such, first region 271, when synthetically magnified by array of focusing elements 210, appears as a region of a color which comprises a blend of the color used in the icons and the color of the icon matrix. For example, if the icon matrix is of a blue color, and the filled icons are red, first region 271 will appear a purple color.CCUR02-0007410In a second region, 281, the extrusions are of greater width than the fdled voids. As such, second region 281 appears predominantly blue.

[0051] In addition to, or as an alternative to using a tinted icon matrix to realize some of the multicolor structures and image functionality of devices made using tool-less manufacturing, in some embodiments according to this disclosure, multi-colored functionality can be achieved by selectively tinting other parts of the micro-optic device.

[0052] Referring to the illustrative example of FIGS. 3A through 3E, five examples of micro-optic security devices utilizing colored structures to create multi-color synthetic images are shown in the figure. For consistency and convenience of cross-reference, elements common to more than one of FIGS. 3A-3E are numbered similarly.

[0053] Referring to the illustrative example of FIG. 3A, a first example of a multi-color micro-optic security device 301 according to the present disclosure is shown in the figure . As shown in the figure, microoptic security device 301 comprises optical spacer 305, which like optical spacer 205 in FIGS. 2A and 2B, comprises a transparent section of a base film providing a structural support for cast-cured icon and lens structures. Optical spacer 305 includes a first side 306a and a second side 306b. Further, an array of focusing elements 310 is, in some embodiments, disposed on first side 306a of the optical spacer 305. Like array of focusing elements 210 in FIGS. 2A and 2B, array of focusing elements 310 can be cast-cured from a transparent resin. As shown in the figure, micro-optic security device further comprises an icon layer 315, which in this example is a “structured” icon layer comprising an icon matrix (for example, icon matrix 217) which operates as a retaining structure that defines voids and other structures which can be filled with colored curable resin of a specified color. As discussed with reference to the examples of FIGS. 2A-2D, the resin used to form the icon matrix can itself be tinted, and the thickness of the tie layer of the icon matrix tuned to provide a colored layer that acts as a transparent, tilted filter.

[0054] Referring to the illustrative example of FIG. 3A, micro-optic security device further includes one or more tinted components (for example, tinted component 317a). As used in this disclosure, the expression “tinted component” encompasses structures other than image icons, which are formed of substantially transparent material to which a pigment has been added, and which operate as light filters, selectively imparting a colored component to synthetic images projected by the micro-optic system. In the example of FIG. 3 A, tinted component 317a is provided by adding tint to the resinous material used to form a subset of the focusing elements of array of focusing elements 310. In this regard, tinted component 317a acts as a chromatic filter and imparts a colored tint to portions of the synthetically magnified image.

[0055] Other embodiments and locations for a tinted component operating as a colored filter to add additional colors to synthetic images projected by micro-optic security device 301 are possible and within the contemplated scope of this disclosure. For example, and as shown in FIG. 3B, a tinted component 317b can be provided as a thin layer of tinted material disposed between array of focusing elements and first side 306a of optical spacer 305. According to some embodiments, tinted component 317b can be provided as aCCUR02-0007411 layer of ink printed onto optical spacer 305, or a separate application of a tinted, curable resin applied to first side of 306a of optical spacer 305.

[0056] Still further embodiments of a micro-optic security device 301 with a tinted component are possible and within the contemplated scope of this disclosure. FIG. 3C illustrates a further example configuration, wherein tinted component 317c is provided as a thin film between icon layer 315 and second side 306b of optical spacer 305. Similar to tinted component 317b in FIG. 3B, tinted component 317c can be provided as a layer of ink printed onto optical spacer 305, or as a separate application of a tinted, curable resin applied to second side of 306b of optical spacer 305. Additionally, or alternatively, tinted component 317 can be provided as an ink or dispersion of pigment in a material providing an icon matrix.

[0057] FIG. 3D illustrates another example of a micro-optic security device 301 incorporating a tinted component 317d as a colored sub-region of optical spacer 305. According to certain embodiments, tinted component 317d may be formed by adding a pigment to the resin used to form optical spacer 305, or by using a multi-layered optical spacer, wherein one of the layers is colored or includes colored regions.

[0058] FIG. 3E illustrates a still further example of a micro-optic security device 301 incorporating a tinted component 317e, which is provided as a coating on a subset of focusing elements of array of focusing elements 310. Depending on embodiments, tinted component 317e may be provided as a pigment or ink added to a mold used for cast curing of array of focusing elements 310. Tinted component 317e may be provided as a thin, insoluble layer of resin. Additionally, or alternatively, tinted component 317e may be provided as a thin layer of water (or other solvent) soluble ink, whose presence or absence can be indicative of a wear state of micro-optic security device 301, or whether micro-optic security device 301 has been soaked in an attempt to be harvested or otherwise separated from a substrate.

[0059] FIGURE 4 illustrates operations of an example method 400 for making a micro-optic security device with a colored icon matrix according to certain embodiments of this disclosure.

[0060] Referring to the non-limiting example of FIG. 4, at operation 405 an optical spacer (for example, optical spacer 205 in FIG. 2A) is provided. The optical spacer comprises a section of a transparent material (for example, polyester fdm or biaxially-oriented polypropylene fdm) of a thickness which is less than a focal length of focusing elements of a subsequently-applied array of focusing elements (for example, array of focusing elements 210).

[0061] At operation 410, an array of focusing elements (for example, array of focusing elements 210) is provided on the first side of the optical spacer. The array of focusing elements may be provided by applying a layer of transparent, uncured, light-curable resin (for example, a UV-curable acrylate) and embossing same with a tool carrying the relief structure of an array of micro-lenses and, with the tool still contacting the uncured resin, applying curing energy (for example, UV light) to cure the layer of light curable resin.

[0062] At operation 415, a layer of light curable resin of a first color is applied to the second side of the optical spacer. The color in the light curable resin can be provided by adding particles of a colored pigment to the uncured resin.CCUR02-0007412

[0063] At operation 420, the layer of light curable resin of the first color is embossed with a tool whose relief structure comprises recesses defining extrusions of an icon matrix, and whose lands define the flat portions of a tie layer, wherein the tie layer comprises a planar region of a first thickness contacting the second side of the tie optical spacer (for example, tie layer 217a). The thickness of the tie layer can be controlled by modulating the pressure with which the embossing tool is pushed into the layer of uncured material. Experimentation has shown that a tie layer thickness of less than 2pm can be effective for producing a synthetic image which contains colored components of both a first and second color, and wherein both components of the first and second colors are in focus. Of course, other thicknesses are possible and within the contemplated scope of this disclosure. Further, at operation 420, the layer of light curable resin of the first color, once embossed, is subjected to curing energy (for example, UV light) to produce a colored icon matrix.

[0064] At operation 425, uncured light curable resin of a second color, wherein the second color contrasts with the first color, is added to voids in the icon layer. Depending on embodiments, the uncured light curable resin of the second color can be zonally applied (for example, using a jetting device) to a selected subset of the voids in the colored icon matrix. In some embodiments, the uncured light curable resin of the second color can be applied across a full area of the icon matrix and the excess bladed off.

[0065] At operation 430, the light curable resin of the second color is cured (for example, either zonally or flood cured) to produce an icon layer (for example, icon layer 215) which includes icons of the first color and icons of the second color.

[0066] FIGURE 5 illustrates operations of an example method 500 for making a micro-optic device with a tinted component (for example, micro-optic security device 301) according to various embodiments of this disclosure.

[0067] Referring to the non-limiting example of FIG. 5, at operation 505, an optical spacer (for example, optical spacer 305 in FIG. 3A) is provided. The optical spacer comprises a section of a transparent material (for example, polyester film or biaxially-oriented polypropylene film) of a thickness which is less than a focal length of focusing elements of a subsequently-applied array of focusing elements (for example, array of focusing elements 310).

[0068] At operation 510, an array of focusing elements (for example, array of focusing elements 310) is provided on the first side of the optical spacer. The array of focusing elements may be provided by applying a layer of transparent, uncured, light-curable resin (for example, a UV-curable acrylate) and embossing same with a tool carrying the relief structure of an array of micro-lenses and, with the tool still contacting the uncured resin, applying curing energy (for example, UV light) to cure the layer of light curable resin.

[0069] At operation 515, an icon layer (for example, icon layer 315) is formed on the second side of the optical spacer. The icon layer can be formed by cast-curing an icon matrix (for example, a colored or clear) icon matrix and completely or selectively filling the voids in the icon matrix with cured pigmented material of a first color.CCUR02-0007413

[0070] At operation 520, one or more tinted components (for example, tinted components 317a-317e in FIGS. 3A-3E) of a second color, wherein the second color contrasts with the first color, are provided.

[0071] Examples of micro-optic security systems according to this disclosure include micro-optic security systems wherein the first thickness is less than 5 microns.

[0072] Examples of micro-optic security systems according to this disclosure include micro-optic security systems, wherein the first thickness is less than 2 microns.

[0073] Examples of micro-optic security systems according to this disclosure include micro-optic security systems, wherein the cured resin of the first color comprises a UV curable monomer with a dispersion of a powdered pigment of the first color.

[0074] Examples of micro-optic security systems according to this disclosure include micro-optic security systems, wherein the cured resin of the second color comprises a UV curable monomer with a dispersion of a powdered pigment of the second color.

[0075] Examples of micro-optic security systems according to this disclosure include micro-optic security systems, wherein the cured resin of the second color does not form a cap or tint film on the two or more extrusions.

[0076] Examples of micro-optic security systems according to this disclosure include micro-optic security systems comprising a second void bounded by the second side of the tie layer and two extrusions of the two or more extrusions, wherein the second void is not filled with cured resin of the second color.

[0077] Examples of micro-optic security systems according to this disclosure include micro-optic security systems wherein the one or more extrusions comprise at least one low-aspect ratio protrusion, and wherein a width of the at least one low-aspect ratio protrusion is at least five times greater than a height of the low-aspect ratio protrusion.

[0078] Examples of micro-optic security systems according to this disclosure include micro-optic security systems, wherein the width of the low-aspect ratio protrusion is at least ten times greater than the height of the protrusion.

[0079] Examples of micro-optic security systems according to this disclosure include micro-optic security systems, wherein, when viewed through the array of focusing elements, the micro-optic security system projects a synthetically magnified image of the icon layer, and wherein the synthetically magnified image of the icon layer comprises elements of the first color and elements of the second color.

[0080] Examples of micro-optic security systems according to this disclosure include micro-optic security systems, wherein focusing elements of the array of focusing elements have a focal length, and wherein the focal length extends into the tie layer.

[0081] Examples of methods of making micro-optics security systems according to this disclosure include methods wherein the first thickness is less than 5 microns.

[0082] Examples of methods of making micro-optics security systems according to this disclosure include methods, wherein the first thickness is less than 2 microns.CCUR02-0007414

[0083] Examples of methods of making micro-optics security systems according to this disclosure include methods, wherein the cured resin of the first color comprises a UV curable monomer with a dispersion of a powdered pigment of the first color.

[0084] Examples of methods of making micro-optics security systems according to this disclosure include methods, wherein the cured resin of the second color comprises a UV curable monomer with a dispersion of a powdered pigment of the second color.

[0085] Examples of methods of making micro-optics security systems according to this disclosure include methods, wherein the cured resin of the second color does not form a cap or tint film on the two or more extrusions.

[0086] Examples of methods of making micro-optics security systems according to this disclosure include methods, wherein the light-curable resin of the second color is zonally cured.

[0087] Examples of methods of making micro-optics security systems according to this disclosure include methods, further comprising a second void bounded by the second side of the tie layer and two extrusions of the two or more extrusions, and wherein the second void is not filled with cured resin of the second color.

[0088] Examples of methods of making micro-optics security systems according to this disclosure include methods, wherein the one or more extrusions comprise at least one low-aspect ratio protrusion, wherein a width of the at least one low-aspect ratio protrusion is at least five times greater than a height of the low-aspect ratio protrusion.

[0089] Examples of methods of making micro-optics security systems according to this disclosure include methods, wherein the width of the low-aspect ratio protrusion is at least ten times greater than the height of the protrusion.

[0090] Examples of methods of making micro-optics security systems according to this disclosure include methods, wherein when viewed through the array of focusing elements, the micro-optic security system projects a synthetically magnified image of the icon layer, and wherein the synthetically magnified image of the icon layer comprises elements of the first color and elements of the second color.

[0091] Examples of methods of making micro-optics security systems according to this disclosure include methods, wherein focusing elements of the array of focusing elements have a focal length, and wherein the focal length extends into the tie layer.

[0092] Examples of micro-optic devices according to this disclosure include micro-optic devices, wherein the tinted component is provided as a subset of the array of focusing elements, wherein focusing elements of the subset comprise light-curable resin with a pigment of the second color.

[0093] Examples of micro-optic devices according to this disclosure include micro-optic devices, wherein the tinted component is provided as a layer of tinted material of the second color disposed between the first side of the optical spacer and the array of focusing elements.CCUR02-0007415

[0094] Examples of micro-optic devices according to this disclosure include micro-optic devices, wherein the tinted component is provided as a layer of tinted material of the second color disposed between the second side of the optical spacer and the icon layer.

[0095] Examples of micro-optic devices according to this disclosure include micro-optic devices wherein the icon layer comprises a structured icon layer comprising retaining structures holding the light- curable resin of the first color; and wherein the tinted component is provided as a pigment of the second color in a material forming the retaining structures.

[0096] Examples of micro-optic devices according to this disclosure include micro-optic devices wherein the tinted component is provided as a sub-region of the optical spacer containing pigment of the second color.

[0097] Examples of micro-optic devices according to this disclosure include micro-optic devices wherein the tinted component is provided as a colored coating on a subset of focusing elements of the array of focusing elements.

[0098] Examples of micro-optic devices according to this disclosure include micro-optic devices wherein the tinted component comprises a powder provided as a dispersion in a light-curable resin.

[0099] Examples of micro-optic devices according to this disclosure include micro-optic devices wherein the tinted component is provided as a conformal coating to a curved portion of focusing elements of the subset of focusing elements.

[0100] Examples of micro-optic devices according to this disclosure include micro-optic devices wherein the tinted component has an infrared (IR) signature.

[0101] Examples of micro-optic devices according to this disclosure include micro-optic devices wherein the tinted component is a wear indicator for the micro-optic device.

[0102] Examples of micro-optic devices according to this disclosure include micro-optic devices wherein the tinted component is provided as a tamper-evident water-soluble ink.

[0103] Examples of micro-optic devices according to this disclosure include micro-optic devices wherein the tinted component is provided as tamper-evident meltable resin.

[0104] Methods of making micro-optic devices according to this disclosure include methods wherein the tinted component is provided as a subset of the array of focusing elements, wherein focusing elements of the subset comprise light-curable resin with a pigment of the second color.

[0105] Methods of making micro-optic devices according to this disclosure include methods wherein the tinted component is provided as a layer of tinted material of the second color disposed between the first side of the optical spacer and the array of focusing elements.

[0106] Methods of making micro-optic devices according to this disclosure include methods wherein the tinted component is provided as a layer of tinted material of the second color disposed between the second side of the optical spacer and the icon layer.

[0107] Methods of making micro-optic devices according to this disclosure include methods wherein the icon layer comprises a structured icon layer comprising retaining structures holding the light-curableCCUR02-0007416 resin of the first color; and wherein the tinted component is provided as a pigment of the second color in a material forming the retaining structures.

[0108] Methods of making micro-optic devices according to this disclosure include methods wherein the tinted component is provided as a sub-region of the optical spacer containing pigment of the second color.

[0109] Methods of making micro-optic devices according to this disclosure include methods wherein the tinted component is provided as a colored coating on a subset of focusing elements of the array of focusing elements.

[0110] Methods of making micro-optic devices according to this disclosure include methods wherein the tinted component comprises a powder provided as a dispersion in a light-curable resin.

[0111] Methods of making micro-optic devices according to this disclosure include methods wherein the tinted component is provided a conformal coating to a curved portion of focusing elements of the subset of focusing elements.

[0112] Methods of making micro-optic devices according to this disclosure include methods wherein the tinted component has an infrared (IR) signature.

[0113] Methods of making micro-optic devices according to this disclosure include methods wherein the tinted component is a wear indicator for the micro-optic device.

[0114] Methods of making micro-optic devices according to this disclosure include methods wherein the tinted component is provided as a tamper-evident water-soluble ink.

[0115] Methods of making micro-optic devices according to this disclosure include methods wherein the tinted component is provided as tamper-evident meltable resin.

[0116] 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.

[0117] 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

CCUR02-0007417WHAT IS CLAIMED IS:

1. A micro-optic security system comprising: an optical spacer having a first side and a second side; an array of focusing elements disposed on the first side of the optical spacer; and an icon layer comprising an icon matrix disposed on the second side of the optical spacer, wherein the icon matrix comprises: a tie layer of cured resin of a first color, wherein the tie layer comprises a first side and second side, wherein the tie layer further comprises a planar region of a first thickness contacting the second side of the optical spacer on the first side of tie layer; and two or more extrusions contacting the tie layer and extending away from the optical spacer to define one or more voids bounded by the second side of the tie layer and two extrusions of the two or more extrusions, wherein the one or more voids contain cured resin of a second color, wherein the second color contrasts with the first color.

2. The micro-optic security system of claim 1, wherein the first thickness is less than 5 microns.

3. The micro-optic security system of claim 1, wherein the first thickness is less than 2 microns.

4. The micro-optic security system of claim 1, wherein the cured resin of the first color comprises a UV curable monomer with a dispersion of a powdered pigment of the first color.

5. The micro-optic security system of claim 4, wherein the cured resin of the second color comprises a UV curable monomer with a dispersion of a powdered pigment of the second color.

6. The micro-optic security system of claim 1, wherein the cured resin of the second color does not form a cap or tint film on the two or more extrusions.

7. The micro-optic security system of claim 1, further comprising a second void bounded by the second side of the tie layer and two extrusions of the two or more extrusions, wherein the second void is not filled with cured resin of the second color.

8. The micro-optic security system of claim 1, wherein the one or more extrusions comprise at least one low-aspect ratio protrusion, wherein a width of the at least one low-aspect ratio protrusion is at least five times greater than a height of the low-aspect ratio protrusion.CCUR02-00074189. The micro-optic security system of claim 8, wherein the width of the low-aspect ratio protrusion is at least ten times greater than the height of the protrusion.

10. The micro-optic security system of claim 1, wherein, when viewed through the array of focusing elements, the micro-optic security system projects a synthetically magnified image of the icon layer, and wherein the synthetically magnified image of the icon layer comprises elements of the first color and elements of the second color.

11. The micro-optic security system of claim 1, wherein focusing elements of the array of focusing elements have a focal length, and wherein the focal length extends into the tie layer.

12. A method of making a micro-optic security system, the method comprising: providing an optical spacer, the optical spacer having a first side and a second side; providing an array of focusing elements on the first side of the optical spacer; applying, to the second side of the optical spacer, an uncured layer of light-curable resin of a first color; embossing, at a first pressure, the uncured layer of the light-curable resin of the first color to form an icon matrix, wherein the icon matrix comprises: a tie layer of cured resin of a first color, wherein the tie layer comprises a first side and second side, wherein the tie layer further comprises a planar region of a first thickness contacting the second side of the optical spacer on the first side of tie layer; and two or more extrusions contacting the tie layer and extending away from the optical spacer, thereby forming one or more voids bounded by the second side of the tie layer and two extrusions of the two or more extrusions; curing the light-curable resin of the first color; adding uncured light-curable resin of a second color to the one or more voids in the icon matrix, wherein the second color contrasts with the first color to the one or more voids; and curing the light-curable resin of the second color to form an icon layer comprising icons of the first color and icons of the second color.

13. The method of claim 12, wherein the first thickness is less than 5 microns.

14. The method of claim 13, wherein the first thickness is less than 2 microns.CCUR02-000741915. The method of claim 12, wherein the cured resin of the first color comprises a UV curable monomer with a dispersion of a powdered pigment of the first color.

16. The method of claim 15, wherein the cured resin of the second color comprises a UV curable monomer with a dispersion of a powdered pigment of the second color.

17. The method of claim 12, wherein the cured resin of the second color does not form a cap or tint film on the two or more extrusions.

18. The method of claim 12, wherein the light-curable resin of the second color is zonally cured.

19. The method of claim 12, further comprising a second void bounded by the second side of the tie layer and two extrusions of the two or more extrusions, wherein the second void is not filled with cured resin of the second color.

20. The method of claim 12, wherein the one or more extrusions comprise at least one low- aspect ratio protrusion, wherein a width of the at least one low-aspect ratio protrusion is at least five times greater than a height of the low-aspect ratio protrusion.

21. The method of claim 20, wherein the width of the low-aspect ratio protrusion is at least ten times greater than the height of the protrusion.

22. The method of claim 12, wherein when viewed through the array of focusing elements, the micro-optic security system projects a synthetically magnified image of the icon layer, and wherein the synthetically magnified image of the icon layer comprises elements of the first color and elements of the second color.

23. The method of claim 12, wherein focusing elements of the array of focusing elements have a focal length, and wherein the focal length extends into the tie layer.

Images