Micro-optic device with multi-color background icon structure and corresponding manufacturing method

Abstract

A micro-optic device includes an array of focusing elements (105), having a first repeat period along a first axis (201) and a second repeat period along a second axis (203). The micro-optic device also includes an icon layer (120) including a plurality of retaining structures, a first plurality of icons in a first zone (427) of the plurality of retaining structures, and a second plurality of icons formed as regions of cured light-curable material of a second color disposed on or within retaining structures of a second zone (429) of the plurality of retaining structures. The first plurality of icons has a third repeat period along the first axis, and a fourth repeat period along the second axis. The second plurality of icons has a fifth repeat period along the first axis and a sixth repeat period along the second axis.

Description

MICRO-OPTIC DEVICE WITH MULTI-COLOR BACKGROUND ICON STRUCTURE AND CORRESPONDING MANUFACTURING METHODTECHNICAL FIELD

[0001] This disclosure relates generally to anti-counterfeiting of secure and / or high value documents, such as banknotes, passports, and tickets. More specifically, this disclosure relates to a micro-optic security device with an enhanced multi-color background icon structure and methods for making same.BACKGROUND

[0002] Micro-optic security devices, or devices comprising an array of micro-scale focusing elements and arrangements of image icons (for example, sub-micro-scale regions of colored material) in the focal plane of the focusing elements, which work together to provide one or more characteristic visual effects (for example, a synthetic image having a three-dimensional appearance) have proven heretofore generally effective in providing trustworthy visual indicia of the authenticity of value documents, such as currency notes, authentication labels, and passports.

[0003] The performance and effectiveness of micro-optic security devices as visual level (i.e., detectable with a human eye, rather than with a banknote equipment manufacturer (“BEM”) device or other specialized machinery) indicia of the authenticity of a document, can depend, at least in part, on the extent to which the micro-optic security device provides a visual effect which visually engages users, and to which the appearance of the security device or visual effects provided by the security device is flexible and amenable to updates and revisions. For example, a synthetic image with dull colors or blurry features (which can occur when the image icon layer is out of focus) may be more frequently overlooked by users, thereby increasing the likelihood of counterfeit banknotes circulating without notice.

[0004] Additionally, the challenges of making micro-optic security devices include being able to produce such devices at great scale, as certain security documents (notably, banknotes) are produced, introduced, and recycled in very large runs. Accordingly, finding ways to realize manufacturing efficiencies (both in terms of extending the functionality of existing tooling and processes) and judiciously using slower, higher-precision manufacturing techniques, while maintaining image quality and appearance of the visual effects provided by micro-optic security devices remains a source of technical challenges and opportunities for improvement in the field of micro-optic security devices and methods for manufacturing same.SUMMARY

[0005] This disclosure relates to a micro-optic security device with an enhanced multi-color background icon structure and methods for making same.

[0006] In a first embodiment, a micro-optic device includes an array of focusing elements, having a first repeat period along a first axis and a second repeat period along a second axis. The micro-optic device includes an icon layer, which comprises a plurality of retaining structures, a first plurality of icons formed as regions of cured light-curable material of a first color disposed on or within retaining structures of a first zone of the plurality of retaining structures, and a second plurality of icons formed as regions of cured light- curable material of a second color disposed on or within retaining structures of a second zone of the pluralityof retaining structures. The first plurality of icons has a third repeat period along the first axis, and a fourth repeat period along the second axis. The second plurality of icons has a fifth repeat period along the first axis and a sixth repeat period along the second axis. The first zone of the plurality of retaining structures comprises a separate portion of the icon layer from second zone of the plurality of retaining structures.

[0007] In a second embodiment, a method of making a micro-optic device includes providing an array of focusing elements, wherein the array of focusing elements has a first repeat period along a first axis and a second repeat period along a second axis and providing a plurality of retaining structures in or proximate to a focal plane of focusing elements of the array of focusing elements. The method further includes forming a first plurality of icons by inking a first zone of the plurality of retaining structures with uncured light- curable material of a first color, forming a second plurality of icons by inking a second zone of the plurality of retaining structures with uncured light-curable material of a second color, curing the uncured light- curable material of the first color, and curing the uncured light-curable material of the second color. The first plurality of icons has a third repeat period along the first axis, and a fourth repeat period along the second axis. The second plurality of icons has a fifth repeat period along the first axis and a sixth repeat period along the second axis. The first zone of the plurality of retaining structures comprises a separate portion of an icon layer from second zone of the plurality of retaining structures.

[0008] Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims.

[0009] 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 functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. 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.

[0010] 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

[0011] For a more complete understanding of this disclosure and its advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:

[0012] FIGURE 1 illustrates an example of a micro-optic system according to certain embodiments of this disclosure;

[0013] FIGURES 2A and 2B illustrate views of an example micro-optic system embodying a “deep levitate” icon structure according to various embodiments of this disclosure;

[0014] FIGURE 3 illustrates an example micro-optic system embodying a “deep levitate” icon structure according to various embodiments of this disclosure;

[0015] FIGURE 4 illustrates an image from a test of blading an over-inked set of retaining structures to obtain a clean-edged transition between zones of icon material of contrasting colors; and

[0016] FIGURE 5 illustrates operations of a method for making a micro-optic security device according to various embodiments of this disclosure.DETAILED DESCRIPTION

[0017] FIGURES 1 through 5, discussed below, and the various embodiments used to describe the principles of this disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure.

[0018] FIGURE 1 illustrates an example of a micro-optic system 100 according to certain embodiments of this disclosure.

[0019] Referring to the non-limiting example of FIGURE 1, micro-optic system 100 comprises, at a fundamental level, a planar array of focusing elements 105 (including, for example, focusing element 107), and an arrangement of image icons 120 (including, for example, image icon 121). According to various embodiments, each focusing element of planar array of focusing elements 105 has a footprint, in which one or more image icons of arrangement of image icons 120 is positioned. In certain embodiments, the locations of the image icons within arrangement of image icons 120 within the respective footprint of each focusing element correspond to spaces between retaining structures in an image icon layer. According to some embodiments, the ratio of the resolution of planar array of focusing elements 105 (for example, the number of focusing elements provided in a specified area, such as a 1x1 mm box) relative to the resolution of the arrangement of image icons 120 (for example, the number of focusing elements provided in the specified area) is 1 or greater. As a non-limiting example, each image icon within arrangement of image icons 120 may fall within the footprints of multiple focusing elements. As a further non-limiting example, there may not be image icons within the footprint of every focusing element within the specified area. Additionally, in some embodiments according to this disclosure, the ratio of the resolution of planar array of focusing elements 105 relative to the resolution of the arrangement of image icons 120 may have a value of less than 1. As a non-limiting example, there may be multiple image icons within the footprint of a particular focusing element. Put differently, zones of zonally cured pigmented material according to embodiments of this disclosure can be of sub-focusing element, and multi -focusing element scales. As used in this disclosure, “uncured pigmented material” encompasses polymeric inks, pigmented polymers, as well as dye-based inks which transition from a wet, uncured state, to a more rigid, drier state in response to a chemical reaction induced through the application of a curing light (for example, ultraviolet curing light.

[0020] According to certain embodiments, plurality of focusing elements 105 comprises a planar array of micro-optic focusing elements. In some embodiments, the focusing elements of planar array of focusing elements 105 comprise micro-optic refractive focusing elements (for example, plano-convex or GRIN lenses), with a lensing surface providing a curved interface between regions of dissimilar indices of refraction (for example, a polymer lens material and air). Refractive focusing elements of planar array of focusing elements 105 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 planar array of focusing elements 105 comprise reflective focusing elements (for example, very small concave mirrors), with diameters ranging from 5pm to 50pm. While in this illustrative example, the focusing elements of planar array of focusing elements 105 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.

[0021] 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 planar array of focusing elements 105. According to various embodiments, the individual image icons of arrangement of image icons 120 comprise regions of zonally light cured material in the spaces defined by retaining structures in 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. According to certain embodiments, arrangement of image icons 120 is constructed to facilitate dynamic redesign and reconfiguration of the image icon structure of micro-optic system 100. For example, arrangement of image icons 120 is, in some embodiments, formed by selectively filling and curing retaining structures (as shown in FIGURE 1, square wells) with uncured pigmented material of one or more colors which are then cured to create regions, or zones of color within arrangement of image icons 120. In this non-limiting example, the different colors within arrangement of image icons 120 are represented by different fill patterns on a surface of the image icons most proximate to the focusing layers. For example, image icon 121 is shown as having the same color as image icons in its row.

[0022] As shown in the illustrative example of FIGURE 1, in certain embodiments, micro-optic system100 includes an optical spacer 110. According to various embodiments, optical spacer 110 comprises a film of substantially transparent material which operates to position image icons of arrangement of image icons 120 in or around the focal plane of focusing elements of planar 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, embossed and flood cured to form retaining structures, which can then be filled or coated with pigmented light curable material and cured with light. As used in this disclosure, the expression “retaining structure” encompasses wells, posts, and other structures into, or onto which, uncured light-curable colored material can be bladed to form image icons.As used in this disclosure, the term “filled,” as used in the context of filling retaining structures of an image icon layer encompasses both filling all of the available volume of the retaining structure with uncured pigmented material, but also filling the majority (for example, 50-80 percent) of the available volume of the retaining structure with uncured material. In certain embodiments, the light-curable material used to form arrangement of image icons 120 is a pigmented, ultraviolet (UV)-curable polymer.

[0023] Because the focusing elements of plurality of focusing elements 105 are provided in a regular, repeating pattern (for example, a rectilinear or diagonal grid), the spatial density of focusing elements can be expressed in terms of a repeat period along an axis of measurement. As used in this disclosure and with reference to focusing elements, the expression “repeat period” encompasses an expression of the distance in which a predetermined number of iterations of the focusing element pattern repeats along a given axis of measurement. A lower repeat period value connotes a higher density of focusing elements than a higher repeat period value. Where focusing elements of the plurality of focusing elements are circular (as opposed to lenticular), the values of the repeat period across perpendicular axes are typically the same, thought there is no requirement that this be the case. The present disclosure contemplates achieving variations in scale ratio by changing either the repeat periods of the focusing elements or the repeat periods of icon structures.

[0024] Similarly, the spatial density of image icons of arrangement of image icons 120 can be expressed in terms of a repeat period along a measurement axis. As used in this disclosure and with reference to image icons of arrangement of image icons 120, the expression “repeat period” encompasses an expression of the distance in which a predetermined number of icons are disposed. As with focusing elements, a lower repeat period value connotes a higher density of image icons, while a higher repeat period value connotes a lower density of image icons.

[0025] Micro-optic system 100 provides visual effects by synthetically, or collectively, magnifying a design found in an image icon (or a portion thereof) through a coordinated projection of the light directed from the icons of arrangement of image icons 120 through array of focusing elements 105. The appearance of the visual content projected through the image icons depends on a host of factors, including without limitation, the local icon-lens scale ratio. As used in this disclosure, the expression “icon-lens scale ratio” encompasses, for a given section of micro-optic system 100, along a given measurement axis, the icon repeat period divided by the focusing element repeat period. Typical icon-lens scale ratios are slightly above (for example, 1.005) or slightly below (for example, 0.995) 1.000. Along measurement axes that create stereoscopic parallax (i.e., are parallel an imaginary line separating a viewer’s eyes) an icon-lens scale ratio less than 1.000 gives the impression of a “deep” (i.e., appearing below the plane of micro-optic system 100) image. Similarly, along measurement axes creating stereoscopic parallax, an icon lens scale ratio greater than 1.000 gives the impression of an image which levitates above the plane of micro-optic system 100.

[0026] Theory predicts and practice confirms that a common lens-icon scale ratio value across more than one axis of measurement makes the appearance of “deep” or levitating image effects appear across a wider range of viewing angles than if the if the scale ratio only presents along a single axis of measurement. Similarly, theory predicts, and practice confirms that progressively modulating the lens-icon scale ratioacross the icon layer can give the appearance of three-dimensionality to images projected by micro-optic system 100, with parts of a projected image appearing at different depths relative to micro-optic system 100.

[0027] Additionally, testing has shown that “deep” effects, wherein a micro-optic device has a less than 1.000 icon-lens scale ratio are perceived by viewers as being more convincingly three-dimensional, but do not appear to move in response to changes in in viewing angle. Similarly, “float” or “levitate” effects, wherein a micro-optic device has a greater than 1.000 icon-lens scale ratio, are more readily perceived as moving in response to changes in viewing angle, but, at the same time, appear less convincingly three dimensional.

[0028] There is no real, physical-world analogue for an object which is simultaneously above a plane and below it, and the relevant theory does not point to any obvious impetus for a “deep levitate” icon construction, which locally juxtaposes a greater than 1.000 lens-icon scale ratio along a first axis with a less than 1.000 lens-icon scale ratio along a second axis.

[0029] Recognizing that human vision and perception is premised on a layer of cognitive middleware (after all, the raw visual data received by our retinas is, initially, upside down and reversed from left-to- right) which, as illusionists, artists and cognitive scientists have confirmed, can be tricked, it has been found that, by structuring an icon layer of a micro-optic to provide seemingly contradictory depth signals, the historic deficiencies of deep effects not appearing to move, and float / levitate effects appearing unconvincingly three dimensional can be overcome.

[0030] Users consistently report that, for systems in which the icon layer is configured to project an image embodying both a depth effect (i.e., appearing to be below the plane of the security device) and a motion effect (appearing to move or change in response to changes in viewing position) the juxtaposition of a scale ratio greater than 1.000 along a first axis and a scale ratio less than 1.000 along a second axis orthogonal to the first axis, the perceived motion of the image is enhanced relative to a device in which the icon-lens scale ratio is less than 1.000 across both axes of measurement. Additionally, and as discussed herein, this icon structure has been found to be particularly compatible with (i.e., the quality of the projected image remains high) coarser, faster inking techniques.

[0031] In certain embodiments according to this disclosure, micro-optic system 100 comprises 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 planar array 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 planar array of focusing elements 105.

[0032] As shown in the non-limiting example of FIGURE 1, in certain embodiments, micro-optic system 100 can be attached, for example, by an adhesive layer 130, to a substrate 150, to form a security document 160. According to various embodiments, substrate 150 can be a sheet of a thin layer paper, or a polymeric substrate. According to some embodiments, substrate 150 is a thin, flexible sheet of a polymericfilm, biaxially oriented polypropylene (BOPP). In various embodiments, substrate 150 is a section of a synthetic paper material, such as TESLIN®. According to some embodiments, substrate 150 is a section of a polymeric card material, such as a polyethylene terephthalate (PET) blank of a type suitable for making credit cards and driver’s licenses.

[0033] FIGURES 2A and 2B illustrates four views of an example micro-optic system 200 according to certain embodiments of this disclosure and constructional details regarding same. For consistency and convenience of cross-reference, figure elements common to both FIGS. 2A and 2B are numbered similarly.

[0034] Referring to the illustrative example shown in FIGURE 2A, a section of a micro-optic system 200 is shown. In this example, micro-optic system 200 embodies the construction shown with reference to micro-optic system 100 in FIGURE 1, wherein the focusing layer comprises an array of circular focusing elements (in this case, a regular array of focusing elements with the same repeat period along first axis 201 as along second axis 203). Further, micro-optic system 200 comprises an arrangement of icons formed within retaining structures (for example, cast-cured recesses and mesas formed by embossing clear, light- curable material and then curing same). In this example, the image icon layers embody a “deep levitate” icon structure, wherein the icon-lens scale ratio along first axis 201 is greater than 1.000, while the iconlens scale ratio along second axis 203 is less than 1.000. Further, the icons of the array of the icon layer are formed by coarsely over-inking stripes (for example, stripes 205a through 205f) of light curable material which alternates two or more contrasting colors, wherein, and as discussed in greater detail herein, a selflubricating interface between the still-liquid uncured light curable material and the retaining structures is formed. Interestingly, over-inking can produce cleaner color transitions (i.e., less smearing and unintended blending of colors) when excess light-curable material is bladed off of the top of the retaining structures.

[0035] As shown in FIGURE 2A, coarsely inked stripes 205a through 205f extend across the width of micro-optic system 200 parallel to second axis 203 and alternating between blue and red (though, other colors are naturally, possible, and within the contemplated scope of this disclosure) along first axis 201. In this illustrative example, the widths of the individual stripes of coarsely inked stripes 205a-205f are exaggerated for clarity of exposition. As used in this disclosure, the expression “coarsely inked” encompasses registration accuracies lower than what can be achieved by either through-the-lens curing of uncured material (which, theoretically, is capable of perfect registration accuracy) or with a high precision ink jet (for example, registration accuracy on the order of 0.05mm between intended and actual position). Techniques for “coarse inking” according to this disclosure include, without limitation, jetting ink at registration accuracies less than 0.05mm (for example, with a 720 dot per inch inkjet), flexographic printing, lithographic printing, or even block printing. Skilled artisans will appreciate that the aforementioned “coarse inking” techniques, while providing lower registration accuracy than precision jetting of uncured light curable-material, can be done more quickly, and offer improvements in production throughput and efficiency.

[0036] Referring to the illustrative example of FIGURE 2B, micro-optic system 200 embodies what is referred to herein as a “deep levitate” icon structure, in which the icons have a greater than 1.000 icon-lensscale ratio along one axis (in this example, first axis 201) and a less than 1.000 icon-lens scale ratio along another axis (in this example, second axis 203). While first axis 201 and second axis 203, are, in this example, fully perpendicular to one another, the present disclosure contemplates and encompasses embodiments in which the axis of repetition with an icon-lens scale ratio greater than 1.000 and the axis of repetition with an icon-lens scale ratio lens than 1.000 are disposed at non-parallel angles other than 90 degrees.

[0037] FIGURE 2B shows four views (designated I-IV) of micro-optic system 200 as it is progressive tilted further around tilt axis 207, wherein tilt axis 207 parallels second axis 203, and while not shown in the figure, a line connecting a viewer’s eyes. Put differently, when micro-optic system 200 is viewed as shown in FIGURE 2B, there is stereoscopic parallax along second axis 203. In this example, micro-optic system 200 presents two synthetically magnified visual effects. A first effect 209, comprises a background effect, wherein four-pointed stars colored according to coarsely inked stripes 205a-205f exhibit both a “deep” effect (i.e., appear to be below the plane of micro-optic system 200, and at the same time, exhibit a motion effect, wherein they appear to move up and down in response to tilting about tilt axis 207. In some embodiments, the axis of repetition of the focusing elements in the x direction may be slightly skewed relative to second axis, causing the movement of the stars in first effect 209 to exhibit orthoparallactic (i.e., perpendicular to the tilt direction, such as by moving sideways in response to up-and-down tilting) motion. Because of the “deep levitate” icon structure, wherein the icon-lens scale ratio is less than 1.000 along second axis 203, but greater than 1.000 along first axis 201, the icons first effect 209 appear to “move” in a way not observed with a “purely deep” icon structure in which the icon-lens scale ratio is less than 1.000 along first axis 201 and second axis 203. At the same time, because of the icon-lens scale ratio along second axis 203 is less than 1.000, the four-pointed stars of first effect 209 appear convincingly below the plane of micro-optic system 200.

[0038] As shown in FIG. 2B, micro-optic system 200 also presents a second visual effect 211, wherein image icons presenting the number “7” exhibit a “shimmer” effect (such as described in greater detail in United States Patent No. 10,173,453), wherein the colors within the number “7” appear to progressively and continuously change as the viewing angle is changed around tilt axis 207. Thus, the “deep levitate” icon structure described herein can be used in conjunction with icon structures providing other visual effects. Similarly, in some embodiments, only part of the retaining structures forming an array of icon elements are colored using coarse-inked icon layers, leaving other parts of the icon area to be formed using other techniques, such as through-the-lens curing (for example, as described by WIPO Publication No. W02020252507A1).

[0039] FIGURE 3 illustrates four views of another example micro-optic system 300 embodying a “deep levitate” icon structure according to embodiments of this disclosure.

[0040] Referring to the illustrative example of FIG. 3, micro-optic system 300 embodies the overall design shown and described with reference to FIG. 1 and utilizes a “deep levitate” icon structure, wherein image icons along a first axis 301 have an icon-lens scale ratio greater than 1.000 relative to the focusingelements, while image icons along second axis 303 have an icon-lens scale ratio less than 1.000. Additionally, retaining structures in the icon layer have been coarse inked in three alternating bands (bands 309A, 309B and 309C) of blue and red, as well as liminal blend zones 311A-311B, where slight mixing between uncured blue light-curable material and uncured red light-curable material occurred between inking and curing.

[0041] Four views (designated A-D in the figure) of micro-optic system 300 as it appears in response to changes in view axis 307 are shown in the figure. In this illustrative example, it is assumed that the viewer’s eyes are separated along a line paralleling tilt axis 307 and second axis 303.

[0042] Referring to the illustrative example of FIGURE 3, when viewed through its array of focusing elements (for example, array of focusing elements 105 in FIG. 1) micro-optic system 300 projects at least two synthetically magnified, optically varying image motifs, including a first image motif 313 comprising a background of waves, which, in response to changes in viewing angle around tilt axis 307 appear to both move and morph. Further, due to the “deep levitate” icon structure, wherein the icon-lens scale ratio along first axis 301 is greater than 1.000 and less than 1.000 along second axis 303 the waves of first image motif 313 both move and have the appearance of depth.

[0043] As shown in the figure, micro-optic system 300 projects a second, synthetically magnified image motif 315, comprising a set of ships’ helms abruptly emerging from the lower waves of first image motif 313, and changing from blue to red as they pass through blend zones 311A and 31 IB, and disappearing into the upper waves of first image motif 313. Further, when the helms (for example, helm 319) approach the edges of micro-optic system 300, they appear to disappear. In certain embodiments, the disappearance of a projected object as it approaches a physical boundary can be coordinated and enhanced through the use of a control pattern to coordinate the positioning of icon elements in the icon layer, such as described in U.S. Patents Nos. 10,434,812 and 9,482,792, which are hereby incorporated by reference herein.

[0044] Depending on embodiments, the image icons, which when projected through an array of focusing elements provide second image motif 315, can either be disposed according to a “deep levitate” icon structure, with an icon-lens scale ratio along second axis 303 which is less than 1.000 and an icon-lens scale ratio greater than 1.000 along first axis 301, or alternatively, to emphasize the depth of first image motif 313. Further, and as shown in the figure, micro-optic system 300 embodies a “slit to fit” construction, wherein first edge 317A and second edge 317 are produced by cutting micro-optic system 300 from a larger section of micro-optic material, so that second image motif can be centered within micro-optic system 300, and the disappearance of helms (for example, helm 319) approaching edges of the system can be supported.

[0045] FIGURE 4 illustrates aspects of over-inking as part of coarse inking techniques for forming icon layers (for example, arrangement of image icons 121 in FIGURE 1) according to certain embodiments of this disclosure.

[0046] FIGURE 4 is an enlarged image of a partially inked set of retaining structures 400 of an image icon layer suitable for use in micro-optic devices according to embodiments of this disclosure. As shown in the figure, retaining structures 400 comprise a series of sailboat recesses disposed at regular intervals acrosstwo axes of retaining structures 400. In this example, the individual retaining structures have a width on the order of 25 microns. A first volume 405 of uncured light-curable material (in this case, a UV-curable polyacrylate) of a first color (blue) was applied on the surface of retaining structures 400 using the tip of a toothpick, to create an initial region 410 of uncured blue light-curable material. Due to the fact that the uncured blue light-curable material was daubed on with a toothpick, and as confirmed by the fact that the individual retaining structures are not visible through initial region 410. In this regard, initial region 410 can be said have been over-inked, wherein the thickness of the uncured light curable material provides a significant surplus of material than necessary to fill the retaining structures. From the photographic evidence and “smear length” of the inked portions in FIGURE 4, the expression “significant surplus” encompasses volumes of at least 2.5 times a volume necessary to fill the retaining structures over a given area. A second volume 415 of uncured light-curable material (in this case, red-colored UV-curable polyacrylate) was applied to retaining structures 400 to create a second initial region 420 of uncured red light-curable material. Eike first volume 405, second volume 415 was likewise over-inked using a toothpick, to provide a significant surplus of uncured red light curable material.

[0047] First and second volumes 405 and 415 of uncured light-curable material were then bladed with a razor blade from start point 421 and drawn rightwards along line 425, with the razor blade held perpendicular to line 425. As expected, blading filled the retaining structures within first region 427 with blue ink and removed most of the ink from the surface of retaining structures 400 within first region 427. However, the passage of the razor blade, along with a volume of removed blue material from first region 427 into the second region 429 containing second volume did not result in immediate mixing of red and blue material. Instead, and as shown in FIGURE 4, a hard visual edge 431 between blue first region 427 and red second region 429 is observed. In this test image, mixing of red and blue uncured material only appears in third region 453.

[0048] By initially over-inking a set of retaining structures with uncured light curable material of two different colors, and then blading same it is possible to achieve sharp-lined edges between regions of the different colors. In other words, for applications in the visual effects provided by a micro-optic device depend primarily on having clean, sharp-lined transitions between regions of different colors (for example, the visual effects described with reference to FIGURES 2A-3 of this disclosure), with registration of the color transitions relative to focusing elements of an array of focusing elements being a secondary, or nonexistent manufacturing goal, over-inking as shown in FIGURE 4 provides opportunities to use coarser inking techniques to increase production speeds, while at the same time, not sacrificing sharp-lined transitions between zones of color within a set of retaining structures. Study to date indicates that by overinking and providing a significant surplus of uncured light-curable material in, at a minimum, areas of color transition, the excess uncured light-curable material provides a self-lubricating interface between the blading tool (for example, a razor blade or doctor blade) and the upper surface of the retaining structures, allowing the blading tool to glide on a thin film of uncured light-curable material, with little to no friction or turbulence along the interface between the blading tool and the retaining structures. The smooth,turbulence free passage of the blading tool across regions initially inked with material of contrasting colors (for example, initial region 410 and second initial region 420) inhibits mixing of uncured light curable material above and around the interface between the blading tool and retaining structures. However, as the supply of liquid uncured, light curable material is drawn down, turbulence around the interface increases, and mixing of colors such as shown in third region 453, is observed. Skilled artisans will appreciate that, by selectively over-inking uncured light-curable material, both sharp-edged and softer, muddied color transitions can be provided in a single icon layer.

[0049] FIGURE 5 illustrates operations of an example method 500 for making a micro-optic device (for example, the devices discussed with reference to FIGURES 1-3 herein) according to various embodiments of this disclosure.

[0050] Referring to the non-limiting example of FIGURE 5, at operation 505, an array of focusing elements (for example, array of focusing elements 105 in FIG. 1) is provided. In some embodiments, the array of focusing elements can be provided by cast-curing a matrix of spherical micro lenses on an optical spacer or other substrate. In some embodiments, the array of focusing elements (for example, an array of reflective focusing elements), may be pre-formed. The focusing elements of the array of focusing elements can be provided in a repeating pattern, with one or more axes of repetition. Further, the array of focusing elements can have a first repeat period along a first axis (for example, first axis 201 in FIGURE 2A) and a second repeat period along a second axis (for example, second axis 203 in FIGURE 2A).

[0051] At operation 510, a plurality of retaining structures is provided. Providing retaining structures (for example, retaining structures 400) can be performed by cast curing a relief pattern of recesses, posts, and mesas which, collectively, define spaces to be filled or coated with uncured light-curable material of one or more colors, which, once cured, become the image icons of the finished micro-optic device. The spaces defined by the relief pattern of the retaining structures, like the focusing elements of the array of focusing elements provided at operation 505, can have first and second repeat periods across first and second axes of measurement. When divided by the repeat periods of focusing elements of the array of focusing elements, an icon-lens scale ratio can be determined. In some embodiments, the retaining structures define an icon structure with a “deep levitate” construction, wherein an icon-lens scale ratio greater than 1.000 is provided on a first axis (for example, first axis 201 in FIGURE 2A) and a less than 1.000 scale ratio is provided on a second axis (for example, second axis 203) enabling stereoscopic parallax.

[0052] At operation 515, a first zone of icons is formed by inking a first region of the retaining structures (for example, stripe 205a) with uncured light-curable material of a first color. According to some embodiments, the first region can be over-inked (for example, as described with reference to FIG. 4) and the uncured light-curable material of the first color coarsely inked, for example, by a low-resolution inkjet, lithographic printing, flexographic printing, or block printing. As noted in this disclosure, sharp lines between zones of colors can be achieved by providing a significant surplus of light-curable material to provide a self-lubricating, low-turbulence interface between a blading tool and retaining structures.

[0053] At operation 520, a second zone of icons is formed by inking a second region (for example, stripe 205b) with uncured light-curable material of a second color. According to some embodiments, the second region can be over-inked or coarsely inked. Depending on the inking technique used, operations 515 and 520 can be performed simultaneously.

[0054] At operation 525, the first zone of icons is bladed and cured to form a first set of icons. Depending on embodiments, and what optically variable effects are provided, blading and curing the first zone of icons at operation 525 can be performed simultaneously with blading and curing the second zone of icons at operation 530. Additionally, or alternatively, some or all of either the first or second zones of icons may be locally, or zonally, cured, such as described in U.S. Patent No. 11,685,180.

[0055] Examples of micro-optic security devices according to this disclosure include micro-optic devices comprising an array of focusing elements, having a first repeat period along a first axis and a second repeat period along a second axis, and an icon layer, the icon layer comprising a plurality of retaining structures, a first plurality of icons formed as regions of cured light-curable material of a first color disposed on or within retaining structures of a first zone of the plurality of retaining structures, a second plurality of icons formed as regions of cured light-curable material of a second color disposed on or within retaining structures of a second zone of the plurality of retaining structures. The first plurality of icons has a third repeat period along the first axis, and a fourth repeat period along the second axis, the second plurality of icons has a fifth repeat period along the first axis and a sixth repeat period along the second axis, and wherein the first zone of the plurality of retaining structures comprises a separate portion of the icon layer from second zone of the plurality of retaining structures.

[0056] Examples of micro-optic security devices according to this disclosure include micro-optic devices comprising a first edge extending parallel to the first axis, and a second edge extending parallel to the first axis. The second axis is perpendicular, or substantially perpendicular, to the first axis, the third repeat period is greater than the first repeat period, wherein the fourth repeat period is less than the second repeat period, wherein the fifth repeat period is greater than the first repeat period, and wherein the sixth repeat period is less than the second repeat period.

[0057] Examples of micro-optic security devices according to this disclosure include micro-optic devices wherein the third repeat period is the same as the fifth repeat period, and wherein the fourth repeat period is the same as the sixth repeat period.

[0058] Examples of micro-optic security devices according to this disclosure include micro-optic devices comprising a third plurality of icons formed between the first and second edges, wherein, when viewed through the array of focusing elements, the third plurality of icons projects a first synthetically magnified image of at least one icon of the third plurality of icons, which when viewed across a first range of viewing angles, appears to move along the second axis.

[0059] Examples of micro-optic security devices according to this disclosure include micro-optic devices wherein the first synthetically magnified image becomes invisible before contacting at least one of the first edge or the second edge.

[0060] Examples of micro-optic security devices according to this disclosure include micro-optic devices wherein the first synthetically magnified image becomes invisible just before, just after or while contacting at least one of the first or second edge.

[0061] Examples of micro-optic security devices according to this disclosure include micro-optic devices comprising a fourth plurality of icons formed between the first and second edges, wherein, when viewed through the array of focusing elements, the fourth plurality of icons projects a second synthetically magnified image of at least one icon of the fourth plurality of icons, which appears to float between the first and second edges, wherein, when viewed through the array of focusing elements, the second synthetically magnified image does not appear to contact at least one of the first edge or the second edge.

[0062] Examples of micro-optic security devices according to this disclosure include micro-optic devices wherein the first zone of the plurality of retaining structures abuts the second zone of the plurality of retaining structures along a border paralleling the second axis, or wherein the first zone of the plurality of retaining structures abuts a blend zone along a second border paralleling the second axis and the second zone of the plurality of retaining structures abuts the blend zone along a third border paralleling the second axis.

[0063] Examples of methods according to this disclosure include methods comprising providing an array of focusing elements, wherein the array of focusing elements has a first repeat period along a first axis and a second repeat period along a second axis, providing a plurality of retaining structures in or proximate to a focal plane, of focusing elements of the array of focusing elements, forming a first plurality of icons by inking a first zone of the plurality of retaining structures with uncured light-curable material of a first color, forming a second plurality of icons by inking a second zone of the plurality of retaining structures with uncured light-curable material of a second color, curing the uncured light-curable material of the first color, and curing the uncured light-curable material of the second color, wherein the first plurality of icons has a third repeat period along the first axis, and a fourth repeat period along the second axis, wherein the second plurality of icons has a fifth repeat period along the first axis and a sixth repeat period along the second axis, wherein the first zone of the plurality of retaining structures comprises a separate portion of an icon layer from second zone of the plurality of retaining structures.

[0064] Examples of micro-optic security devices according to this disclosure include micro-optic devices comprising, forming a first edge extending parallel to the first axis; and forming a second edge extending parallel to the first axis, wherein the second axis is perpendicular to the first axis, wherein the third repeat period is greater than the first repeat period, wherein the fourth repeat period is less than the second repeat period, wherein the fifth repeat period is greater than the first repeat period, and wherein the sixth repeat period is less than the second repeat period.

[0065] Examples of micro-optic security devices according to this disclosure include micro-optic devices wherein the first zone of the plurality of retaining structures and the second zone of the plurality of retaining structures are inked at the same time, wherein inking the first zone of the plurality of retaining structures comprises over-inking the first zone of the plurality of retaining structures at a layer thicknesssufficient to create a first self-lubricating interface between the uncured light-curable material of the first color and the retaining structures, wherein inking the second zone of the plurality of retaining structures comprises over-inking the second zone of the plurality of retaining structures at a layer thickness sufficient to create a second self-lubricating interface between the uncured light-curable material of the second color and the retaining structures, and further comprising blading excess light curable material from the first zone and second zone of the plurality of retaining structures.

[0066] Examples of micro-optic security devices according to this disclosure include micro-optic devices wherein over-inking the first zone comprises applying uncured light-curable material of the first color by at least one of: ink jetting, lithographic printing, flexographic printing, gravure, spraying, offset printing or block printing.

[0067] Examples of micro-optic security devices according to this disclosure include micro-optic devices wherein the first zone extends from the first edge to the second edge, wherein the second zone extends from the first edge to the second edge, wherein the excess light curable material is bladed from the first edge to the second edge in a direction not parallel to the second axis.

[0068] Examples of micro-optic security devices according to this disclosure include micro-optic devices wherein the third repeat period is the same as the fifth repeat period, and wherein the fourth repeat period is the same as the sixth repeat period.

[0069] Examples of micro-optic security devices according to this disclosure include micro-optic devices comprising providing a third plurality of icons formed between the first and second edges, wherein, when viewed through the array of focusing elements, the third plurality of icons projects a first synthetically magnified image of at least one icon of the third plurality of icons, which when viewed across a first range of viewing angles, appears to move along the second axis.

[0070] Examples of micro-optic security devices according to this disclosure include micro-optic devices wherein the first synthetically magnified image becomes invisible before contacting at least one of the first edge or the second edge.

[0071] Examples of micro-optic security devices according to this disclosure include micro-optic devices comprising providing a fourth plurality of icons formed between the first and second edges, wherein, when viewed through the array of focusing elements, the fourth plurality of icons projects a second synthetically magnified image of at least one icon of the fourth plurality of icons, which appears to float between the first and second edges, wherein, when viewed through the array of focusing elements, the second synthetically magnified image does not appear to contact at least one of the first edge or the second edge.

[0072] Examples of micro-optic security devices according to this disclosure include micro-optic devices wherein the first zone of the plurality of retaining structures abuts the second zone of the plurality of retaining structures along a border paralleling the second axis, or wherein the first zone of the plurality of retaining structures abuts a blend zone along a second border paralleling the second axis and the secondzone of the plurality of retaining structures abuts the blend zone along a third border paralleling the second axis.

[0073] None of the description in this application should be read as implying that any particular element, step, or function is an essential element that must be included in the claim scope. The scope of patented subject matter is defined only by the claims. Moreover, none of the claims is intended to invoke35 U.S.C. § 112(f) unless the exact words “means for” are followed by a participle.

Claims

WHAT IS CLAIMED IS:

1. A micro-optic device comprising : an array of focusing elements, having a first repeat period along a first axis and a second repeat period along a second axis; and an icon layer, comprising: a plurality of retaining structures; a first plurality of icons formed as regions of cured light-curable material of a first color disposed on or within retaining structures of a first zone of the plurality of retaining structures; and a second plurality of icons formed as regions of cured light-curable material of a second color disposed on or within retaining structures of a second zone of the plurality of retaining structures, wherein the first plurality of icons has a third repeat period along the first axis, and a fourth repeat period along the second axis, wherein the second plurality of icons has a fifth repeat period along the first axis and a sixth repeat period along the second axis, and wherein the first zone of the plurality of retaining structures comprises a separate portion of the icon layer from second zone of the plurality of retaining structures.

2. The micro-optic device of claim 1, further comprising: a first edge extending parallel to the first axis; and a second edge extending parallel to the first axis, wherein the second axis is perpendicular to the first axis, wherein the third repeat period is greater than the first repeat period, wherein the fourth repeat period is less than the second repeat period, wherein the fifth repeat period is greater than the first repeat period, and wherein the sixth repeat period is less than the second repeat period.

3. The micro-optic device of claim 2, wherein: the third repeat period is the same as the fifth repeat period, and the fourth repeat period is the same as the sixth repeat period.

4. The micro-optic device of claim 2, further comprising a third plurality of icons formed between the first and second edges, wherein, when viewed through the array of focusing elements, the third plurality of icons projects a first synthetically magnified image of at least one icon of the third plurality of icons, which when viewed across a first range of viewing angles, appears to move along the second axis.

5. The micro-optic device of claim 4, wherein the first synthetically magnified image becomes invisible before contacting at least one of the first edge or the second edge.

6. The micro-optic device of claim 2, further comprising a fourth plurality of icons formed between the first and second edges, wherein, when viewed through the array of focusing elements, the fourth plurality of icons projects a second synthetically magnified image of at least one icon of the fourth plurality of icons, which appears to float between the first and second edges, and wherein, when viewed through the array of focusing elements, the second synthetically magnified image does not appear to contact at least one of the first edge or the second edge.

7. The micro-optic device of claim 1, wherein: the first zone of the plurality of retaining structures abuts the second zone of the plurality of retaining structures along a border paralleling the second axis, or the first zone of the plurality of retaining structures abuts a blend zone along a second border paralleling the second axis and the second zone of the plurality of retaining structures abuts the blend zone along a third border paralleling the second axis.

8. A method of making a micro-optic device, the method comprising: providing an array of focusing elements, wherein the array of focusing elements has a first repeat period along a first axis and a second repeat period along a second axis; providing a plurality of retaining structures in or proximate to a focal plane of focusing elements of the array of focusing elements; forming a first plurality of icons by inking a first zone of the plurality of retaining structures with uncured light-curable material of a first color; forming a second plurality of icons by inking a second zone of the plurality of retaining structures with uncured light-curable material of a second color; curing the uncured light-curable material of the first color; and curing the uncured light-curable material of the second color, wherein the first plurality of icons has a third repeat period along the first axis, and a fourth repeat period along the second axis, wherein the second plurality of icons has a fifth repeat period along the first axis and a sixth repeat period along the second axis, and wherein the first zone of the plurality of retaining structures comprises a separate portion of an icon layer from second zone of the plurality of retaining structures.

9. The method of claim 8, further comprising: forming a first edge extending parallel to the first axis; and forming a second edge extending parallel to the first axis, wherein the second axis is perpendicular to the first axis, wherein the third repeat period is greater than the first repeat period, wherein the fourth repeat period is less than the second repeat period, wherein the fifth repeat period is greater than the first repeat period, and wherein the sixth repeat period is less than the second repeat period.

10. The method of claim 8, wherein the first zone of the plurality of retaining structures and the second zone of the plurality of retaining structures are inked at a same time, wherein inking the first zone of the plurality of retaining structures comprises over-inking the first zone of the plurality of retaining structures at a layer thickness sufficient to create a first self-lubricating interface between the uncured light-curable material of the first color and the retaining structures, wherein inking the second zone of the plurality of retaining structures comprises over-inking the second zone of the plurality of retaining structures at a layer thickness sufficient to create a second selflubricating interface between the uncured light-curable material of the second color and the retaining structures; and further comprising blading excess light curable material from the first zone and second zone of the plurality of retaining structures.

11. The method of claim 10, wherein over-inking the first zone comprises applying uncured light-curable material of the first color by at least one of: ink jetting, lithographic printing, flexographic printing, gravure, spraying, offset printing, or block printing.

12. The method of claim 10, wherein: the first zone extends from the first edge to the second edge, the second zone extends from the first edge to the second edge, and the excess light curable material is bladed from the first edge to the second edge in a direction not parallel to the second axis.

13. The method of claim 9, wherein: the third repeat period is the same as the fifth repeat period, and the fourth repeat period is the same as the sixth repeat period.

14. The method of claim 9, further comprising providing a third plurality of icons formed between the first and second edges, wherein, when viewed through the array of focusing elements, the third plurality of icons projects a first synthetically magnified image of at least one icon of the third plurality of icons, which when viewed across a first range of viewing angles, appears to move along the second axis.

15. The method of claim 14, wherein the first synthetically magnified image becomes invisible before contacting at least one of the first edge or the second edge.

16. The method of claim 9, further comprising providing a fourth plurality of icons formed between the first and second edges, wherein, when viewed through the array of focusing elements, the fourth plurality of icons projects a second synthetically magnified image of at least one icon of the fourth plurality of icons, which appears to float between the first and second edges, and wherein, when viewed through the array of focusing elements, the second synthetically magnified image does not appear to contact at least one of the first edge or the second edge.

17. The method of claim 8, wherein: the first zone of the plurality of retaining structures abuts the second zone of the plurality of retaining structures along a border paralleling the second axis, or the first zone of the plurality of retaining structures abuts a blend zone along a second border paralleling the second axis and the second zone of the plurality of retaining structures abuts the blend zone along a third border paralleling the second axis.

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