Patent Description:
<CIT> discloses a laser marked device; <CIT> discloses an optical system demonstrating improved resistance to optically degrading external effects; <CIT> discloses a micro-optic film structure that alone or together with a security document or label projects images spatially coordinated with static images and/or other projected images; <CIT> discloses an optionally transferable optical system with a reduced thickness; <CIT> discloses a security arrangement; <CIT> discloses a micro-optic security and image presentation system; <CIT> discloses a security document; <CIT> discloses a security element, security system, and production method therefor; <CIT> discloses an optical device. Polymeric security documents such as banknotes are typically made from a polymer such as biaxially oriented polypropylene (BOPP). Such documents offer unique opportunities to incorporate security elements that are designed to discourage counterfeiting.

One such security element is an optical security device that projects synthetic images and generally comprises an arrangement of focusing elements (e.g., microlenses or micromirrors) and an arrangement of image icons (e.g., micro-sized image icons) located on or within a polymeric substrate. The image icon and focusing element arrangements are configured such that when the arrangement of image icons is viewed through or with the arrangement of focusing elements, one or more synthetic images are projected. These projected images may show a number of different optical effects. Material constructions capable of presenting such effects are described in, for example, <CIT>, <CIT> et al. , and <CIT>.

The arrangements of focusing elements and image icons used in these optical security devices are formed from a variety of materials such as substantially transparent or clear, colored or colorless polymers such as acrylics, acrylated polyesters, acrylated urethanes, epoxies, polycarbonates, polypropylenes, polyesters, urethanes, and the like, using a multiplicity of methods that are known in the art of micro-optic and microstructure replication, including extrusion (e.g., extrusion embossing, soft embossing), radiation cured casting, and injection molding, reaction injection molding, and reaction casting.

By way of the present invention, innovative ways of combining these optical security devices with polymer or polymeric substrates for use in making polymeric security documents (e.g., banknotes) are provided. In particular, the present invention provides an improved polymeric sheet material as defined in claim <NUM> and methods of forming such a polymeric sheet material as defined in claims <NUM> and <NUM>.

Examples of a polymeric sheet material in the form of a polymer or polymeric substrate with either an integrated or applied optical security device are described below.

Also provided by way of the present invention is a polymeric security document (e.g., a banknote) made using the improved polymeric sheet material described above, which has printing or other identifying indicia on one or opposing sides thereof.

Other features and advantages of the invention will be apparent to one of ordinary skill from the following detailed description. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

The present disclosure may be better understood with reference to the following drawings. Matching reference numerals designate corresponding parts throughout the drawings, and components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. While exemplary embodiments are disclosed in connection with the drawings, there is no intent to limit the present disclosure to the embodiment or embodiments disclosed herein.

Particular features of the disclosed invention are illustrated by reference to the accompanying drawings in which:.

As noted above, the present invention provides an improved polymeric sheet material in the form of a polymer or polymeric substrate that has one or more integrated and/or applied optical security devices. The polymer or polymeric substrate may comprise one or more layers of transparent polymer film, preferably transparent biaxially oriented polymer film. In a more preferred embodiment, the substrate is either a single layer BOPP film, or a laminate of two or more layers of BOPP film, each of which is coated with a heat-activated adhesive layer. The polymer or polymeric substrate typically ranges from greater than or equal to about <NUM> microns (preferably, from about <NUM> to about <NUM> microns) in total thickness.

For those embodiments in which the optical security device(s) is integrated and/or applied to only part of the substrate, an opacifying coating may be used to cover remaining portions thereof. The opacifying coating is made up of a major portion (≥ <NUM>%) of pigment and a minor portion (<<NUM>%) of a cross-linked polymeric binder.

For those embodiments in which the optical security device(s) is integrated and/or applied to the entire substrate, an opacifying coating may or may not be used. As will be readily appreciated by those skilled in the art, such a sheet material would be used to make an entirely micro-optic security document or banknote, which presents a number of distinct and unique advantages.

The optical security device of the inventive polymeric sheet material basically comprises one or more arrangements of optionally embedded cylindrical or non-cylindrical focusing elements and one or more arrangements of image icons. As noted above, these arrangements are configured such that when the arrangement of image icons is viewed through the arrangement of focusing elements, one or more synthetic images are projected.

The optionally embedded focusing elements used in the practice of this invention include, but are not limited to, refractive focusing elements, reflective focusing elements, hybrid refractive/reflective focusing elements, and combinations thereof. In one contemplated embodiment, the focusing elements are refractive microlenses. Examples of suitable focusing elements are disclosed in <CIT>, <CIT>, and <CIT>.

The focusing elements have preferred widths (in the case of cylindrical lenses) and base diameters (in the case of non-cylindrical lenses) of either (i) less than or equal to <NUM> millimeter including widths/base diameters ranging from about <NUM> to about <NUM> microns and ranging from about <NUM> to about <NUM> microns, or (ii) less than about <NUM> microns including widths/base diameters ranging from less than about <NUM> microns and ranging from about <NUM> to about <NUM> microns.

Embedment of the focusing elements serves to improve the optical security device's resistance to optically degrading external effects. In one such embodiment, the refractive index from an outer surface of the optical security device to refracting interfaces is varied between a first and a second refractive index, the first refractive index being substantially or measurably different than the second refractive index. The phrase "substantially or measurably different", as used herein, means a difference in refractive index that causes the focal length(s) of the focusing elements to change at least about <NUM> micron.

The embedding material may be transparent, translucent, tinted, or pigmented and may provide additional functionality for security and authentication purposes, including support of automated currency authentication, verification, tracking, counting and detection systems, that rely on optical effects, electrical conductivity or electrical capacitance, magnetic field detection. Suitable materials can include adhesives, gels, glues, lacquers, liquids, molded polymers, and polymers or other materials containing organic or metallic dispersions.

The image icons may be printed on the polymer or polymeric substrate or may constitute microstructured image icons that are raised or recessed relative to a surface of the substrate. In a preferred embodiment, the image icons are formed as either voids or recesses on or within the substrate, or raised relative to the substrate. In either case, the image icons may be formed by casting or heat pressure processes.

In one embodiment contemplated by the present invention, the image icons are optionally coated and/or filled voids or recesses formed on or within the polymer or polymeric substrate. The voids or recesses may each measure from about <NUM> to about <NUM> microns in total depth and greater than or equal to about <NUM> microns in total width.

Exemplary embodiments of the inventive polymeric sheet material will now be disclosed in connection with the drawings. There is no intent, however, to limit the present disclosure to the embodiments disclosed herein. On the contrary, the intent is to cover all alternatives, modifications and equivalents.

In a first example, which is best shown in <FIG>, the improved polymeric sheet material of the present disclosure <NUM> is in the form of a polymer or polymeric substrate <NUM> with an integrated optical security device <NUM>, the integrated device <NUM> made up of an arrangement of focusing elements (i.e., refractive microlenses) <NUM> and an arrangement of image icons <NUM>, which are formed directly onto opposing surfaces of the substrate <NUM>. Here, substrate <NUM> contributes to the optical functionality of the integrated optical security device <NUM>, by serving as an optical spacer.

The refractive microlenses <NUM> each have a focal length such that the image icons <NUM> on the opposing side of the substrate <NUM> substantially intersect with a portion of their depth of focus, when viewed normal to the surface. These refractive microlenses <NUM> may have cylindrical, spheric or aspheric surfaces.

As noted above, the image icons may be formed from a printing method, or from voids or solid regions in a microstructure. In a preferred example, the image icons are formed from optionally coated and/or filled voids or recesses on or within the substrate, the voids or recesses each measuring from about <NUM> to about <NUM> microns in total depth and greater than or equal to about <NUM> microns in total width. The voids or recesses may be filled or coated with a material having a different index of refraction than the surrounding or underlying material, a dyed material, a metal, or a pigmented material (e.g., a submicron particle pigmented coloring material). Such an approach has the benefit of almost unlimited spatial resolution.

As also noted above, the arrangements of focusing elements <NUM> and image icons <NUM> may be formed from a variety of materials such as substantially transparent or clear, colored or colorless polymers such as acrylics, acrylated polyesters, acrylated urethanes, epoxies, polycarbonates, polypropylenes, polyesters, urethanes, and the like.

In an exemplary method of manufacture, the image icons are formed as voids in a radiation cured liquid polymer (e.g., acrylated urethane) that is cast from an icon mold against the substrate <NUM>. The image icon voids are then filled with a submicron particle pigmented coloring material by gravure-like doctor blading against the polymeric icon surface. The fill is then solidified by suitable means (e.g., solvent removal, radiation curing, or chemical reaction). Then, the lenses are cast against an opposing side of the substrate <NUM> by bringing that side against a lens mold filled with radiation curable polymer. The polymer is then solidified by application of ultraviolet (UV) light or other actinic radiation.

The integrated optical security device <NUM> in this example and the integrated or applied optical security devices of the following examples and embodiments may adopt any size or shape. For example, they may be formed in the shape of a patch, stripe (band or thread), or co-extensive layer.

In a second example, which is best shown in <FIG>, the arrangement of refractive microlenses <NUM> and the arrangement of image icons <NUM> are transferred onto all or part of opposing surfaces of the substrate <NUM>.

An exemplary method of forming these transferable focusing element and image icon layers comprises:.

Once prepared, the transferable layers may be handled like a traditional transfer foil, that is, the material can be wound and unwound from a roll and further converted into a suitable final shape such as a patch, stripe (band or thread), or sheet by converting methods common in the security printing and packaging industries. In order to transfer the focusing element layer <NUM> and image icon layer <NUM> from the release liners, the adhesive side of each transferable layer is placed in contact with opposing sides of the polymer or polymeric substrate <NUM>. Heat and/or pressure is applied causing the adhesive in adhesive layer <NUM> to bond securely to substrate <NUM>. Then, the release liner with "lens mold" layer and the other release liner are peeled away, leaving behind the desired focusing element and image icon layers.

In a third example, which is best shown in <FIG>, the inventive polymeric sheet material <NUM> employs an integrated optical security device in the form of a film material <NUM> made up of an arrangement of image icons and an overlying optionally embedded arrangement of focusing elements that are located on a top surface of the polymer or polymeric substrate <NUM>, and a reflective layer <NUM> (e.g., a vapor deposited metal layer) that is located directly below on a bottom surface of the substrate <NUM>. As noted above, in this example, the reflective layer <NUM> serves to provide a reflection of the image icons beyond the reflective surface so that the focusing elements can focus on the reflection of the image icons, thus allowing for the use of focusing elements with a focal length that extends beyond the arrangement(s) of image icons.

The film material <NUM> may be formed in place on the substrate <NUM> or the film material (with one or more adhesive layers) may be transferred to the substrate as a transfer film using previously noted techniques including mechanical, chemical, thermal and photo-induced separation techniques. The concept of separation of desired components from a carrier substrate is known in the art of holographic foil transfer, whereby a film with a release coating (i.e., release liner) is provided with optical coatings and adhesives, such that the optical coatings and adhesives can be transferred to a final substrate with application of heat and pressure.

Reflective layer <NUM> may be a vapor deposited metal layer. Metallization may be achieved, for example, by evaporated or sputtered aluminum, gold, rhodium, chromium, osmium, depleted uranium or silver, by chemically deposited silver, or by multi-layer interference films. This layer may contain image icons formed from patterned demetallization, or holographic features. In this exemplary embodiment, the focusing elements focus on the reflection of icons.

In a preferred example, the reflective layer <NUM> is a patterned metal layer in which image icons (secondary image icons), which are positive or negative in relation to their background, are formed by patterned demetallization. The demetalized pattern or secondary image icons may adopt any form including, but not limited to, positive text, negative text, imagery, line work, and the like. These secondary image icons control which focusing elements will see a reflection and which focusing elements will not. By providing this control, a second image - one which blocks light and allows a clear image to be seen in transmitted light, is provided. This will be a static image, and not a synthetic image (e.g., a moving or three dimensional synthetic image).

The visual effect achieved by this example will be described in conjunction with <FIG>. In <FIG>, reflective layer <NUM> is adjusted to include demetalized "holes" (only one demetalized "hole" is shown in <FIG>). As a result, light passes straight through the optics in those areas. When looking at the inventive sheet material, one would see one or more synthetic images with missing bits where the "holes" are located. Depending on the color of the underlying substrate (or its transparency), the missing bits may appear to be light "missing" areas, or dark "missing" areas. By way of example, and as best shown in <FIG>, the reflective layer is adjusted to include the words "DEMET TEXT". In <FIG>, these words are shown as light "missing" areas, which is indicative of the polymeric sheet material being placed over a white surface (e.g., a white polymeric surface) or over a paper substrate. This effect may also be indicative of the sheet material being viewed in a combination of reflected and transmitted light. In <FIG>, these words are shown as dark "missing" areas, which is indicative of the sheet material being placed over a transparent polymer or polymeric substrate that is held against a dark background (shown in reflected light). As shown in <FIG>, when the sheet material is viewed in transmitted light, the micro-optic areas will be opaque (due to the presence of the metal reflective layer) and the demetalized areas (i.e., the words "DEMET TEXT") will appear light.

In a fourth example, one version of which is shown in <FIG>, the inventive polymeric sheet material <NUM> employs an integrated optical security device made up of a first arrangement of focusing elements <NUM> and a first arrangement of image icons <NUM>, which are formed directly or applied onto all or part of one surface of the substrate <NUM>, and a second arrangement of focusing elements <NUM> and a second arrangement of the same or different image icons <NUM>, which are formed directly or applied onto all or part of an opposing surface of the substrate <NUM>. Here, the focusing elements on one surface of the substrate <NUM> focus on the image icons on an opposing surface of the substrate. This example is a two-sided example displaying a different and/or different color image 36a, 36b on the front and back. In <FIG>, the focusing elements are embedded focusing elements.

If one were to make this sheet material using the same focusing elements or lenses (lenses in arrangement <NUM> and in arrangement <NUM>), then these lenses would image one another, forming a moiré pattern of the lenses themselves, which would be visible from both sides. In order to avoid this effect, the polymeric sheet material <NUM> shown in <FIG> includes:.

In the above cases, having a different pitch may be difficult to achieve as an "only" solution, because changing the pitch inevitably either spaces out the lenses further from one another (causing loss in optical efficiency), or it requires a change in the radius of curvature of the lenses (which isn't always a parameter that can be changed dramatically). When considering this problem, the present inventors arrived at an example, which is shown in <FIG>. By way of this example, the polymeric sheet material <NUM> employs an arrangement of non-embedded or open lenses on one side of the substrate, and embedded or sealed lenses on the other side. This arrangement greatly changes the pitch difference between the two focusing element systems. It also has the interesting consequence that one side of the sheet material <NUM> will be slightly "textured" while the other side will be perfectly smooth. This effect constitutes a useful secondary (semi-forensic) authentication feature.

In a fifth example, which is best shown in <FIG>, the inventive polymeric sheet material <NUM> is in the form of polymer or polymeric substrate <NUM> with an applied optical security device that is made up of an arrangement of image icons <NUM> and an underlying arrangement of concave reflective focusing elements <NUM>, that are transferred onto one surface of the substrate <NUM>.

The sheet material <NUM> in this fifth example, is engineered around the bond strength between the arrangement of image icons <NUM> and a release liner. This bond strength must be less than the bond strength between an adhesive which would be located between the arrangement of concave reflective focusing elements <NUM> and the substrate <NUM>. The reason for the different bond strength requirements is that for some embodiments of the present invention the release liner must "release" from the sheet material <NUM> once the sheet material has been applied to the substrate <NUM>. For other embodiments where more abrasion resistance is desired, the release liner would remain in place on the applied polymeric sheet material <NUM> and therefore would not need to "release" from the sheet material <NUM>.

An exemplary method of manufacturing an exampleof this transferable thin (reflective) optical security device comprises:.

The resulting film-like structure can be handled/converted/transferred like a traditional transfer film. In other words, the converted structure may be brought into contact with the polymer or polymeric substrate <NUM>, and upon the application of heat and pressure, the release liner can be completely peeled away, leaving only the thin (reflective) transfer product on one side of the substrate <NUM>.

In a sixth example, which is best shown in <FIG>, the polymeric sheet material is a "fold-over" polymeric sheet material <NUM> in the form of polymer or polymeric substrate <NUM> with an integrated optical security device made up of an embedded or sealed arrangement of two different sized focusing elements <NUM> and a first arrangement of image icons <NUM>, which are formed directly or applied onto remote portions of one surface of the substrate <NUM>, and a second arrangement of different image icons <NUM>, which is formed directly or applied on an opposing surface of the substrate <NUM> directly opposite the first arrangement of image icons <NUM>. This example, which makes use of different sized focusing elements with different focal lengths, allows for both arrangements of image icons (<NUM>, <NUM>) to be viewed simultaneously. When the portion of the substrate containing the embedded arrangement of focusing elements <NUM> is positioned directly over the portion of the substrate containing the first and second arrangements of image icons <NUM>, <NUM>, two different images <NUM>, <NUM> will be projected. Here, the "same side" image <NUM> would be seen from "farther away", and the "opposite side" image <NUM> would be seen "more closely".

In a similar example shown in <FIG>, similarly sized focusing elements are used, some of which are embedded or sealed while others are not. This particular example has the advantage of being able to "print" the embedding or sealing material after (and not during) production of the sheet material, in a defined pattern, perhaps with a varnish or transparent material in a silkscreen. This printing can be done on a printing press at the same time the rest of substrate <NUM> (e.g., a banknote) is printed.

In another similar example, which is best shown in <FIG>, the focusing elements have a focal length that is tuned to image the image icons on the same side of the substrate <NUM> (e.g., banknote) when the banknote is folded tightly, and to image the icons on the opposite side of the banknote when it is folded loosely. That is, there is an ability of the user to control the placement of the image icons by folding the banknote and pressing the folded part directly against the other half, versus loosely folding the banknote, and allowing some air gap to exist such that the nearer image icons are placed in the focal plane of the focusing elements or lenses. This example can be combined with any of the aforementioned combination lenses, where some of the lenses (the longer focal length lenses) can exhibit this squeeze-fold effect.

In a seventh example, which is best shown in <FIG>, the polymeric sheet material <NUM> is in the form of a "two-ply" polymer or polymeric substrate 12a, 12b with an integrated optical security device in which an arrangement of focusing elements is positioned between the two plies, and first and second arrangements of the same or different image icons are formed or applied to all or part of opposing surfaces of the two-ply substrate. Here, one or more images are projected from opposing surfaces of the substrate. In another example (not shown), one or more arrangements (e.g., first and second arrangements) of the same or different image icons are positioned between the two plies, and an optionally embedded arrangement of focusing elements is formed or applied to all or part of one or opposing surfaces of the two-ply substrate.

In one embodiment, the inventive polymeric sheet material <NUM> has a hybrid refractive/reflective optical security device formed or applied onto a surface of the substrate <NUM>.

As best shown in <FIG>-(c), an arrangement of "lightly metalized" hybrid refractive/reflective focusing elements <NUM> is positioned below a first arrangement of image icons <NUM> and above a second arrangement of image icons <NUM>. The focusing elements <NUM> are "lightly metalized" so that they are partially reflective and partially transparent. In other words, the focusing element or lens surfaces have been given a vapor deposition of a reflective metal. The layer thickness of the material chosen will have an impact on the reflectance and transmittance of light with respect to the lens. When using silver, if the layer thickness is high, say above <NUM> nanometers (nm), the transmittance will be quite low, making the device nearly completely opaque. The desired layer thickness of the metal is below <NUM>, preferably around <NUM>, to provide a balance of reflectance and transmittance. The right balance is found, for a particular metal, when the reflected synthetic images can be clearly seen in normal "room" lighting conditions, and the transmitted synthetic images can be seen clearly when the material is backlit using readily available environmental light, such as a fluorescent light used in a building or home. This readily available light, such as a lightbulb or tube light, is considered to be a relatively bright light source, and will overwhelm the reflected mode and allow the user to see the transmitted mode. This is the same principle by which a one-way mirror operates. As previously noted, metallization may be achieved, for example, by evaporated or sputtered aluminum, gold, rhodium, chromium, osmium, depleted uranium or silver, by chemically deposited silver, or by multi-layer interference films.

By way of this embodiment, a different optical effect may be viewed in reflected and transmitted light. Referring to <FIG>, in reflection mode (i.e., no bright light coming from the "top" or "back" of substrate <NUM>), "lightly metalized" hybrid refractive/reflective focusing elements <NUM> act as reflective focusing elements. The image icon layer containing the first arrangement of image icons <NUM> lies between the viewer's eyes (not shown) and the "lightly metalized" focusing elements <NUM>. Light scattered from the image icons is reflected from/projected by the "lightly metalized" focusing element layer, passing through the icon layer toward the viewer. The icon layer is maintained at a distance equal to the focal length of the "lightly metalized" focusing elements <NUM>.

As shown in <FIG>, relatively bright light used in transmission mode will overwhelm the reflective mode. In <FIG>, relatively bright light (similar to that used to view a watermark) is directed toward the "back" of the substrate <NUM>. The light is bright enough to "pass through" the substrate <NUM> and the "lightly metalized" focusing elements <NUM>, which now act like refractive focusing elements. These focusing elements focus on the second arrangement of image icons <NUM> located on the "back" of substrate <NUM>. In <FIG>, relatively bright light is directed toward the "top" of the substrate <NUM>. Here, the "lightly metalized" focusing elements <NUM> are again acting like refractive focusing elements but the focal point or focal plane now lies beyond or above the "top" of the substrate. This embodiment may be used as a fold-over feature by using remotely placed image icons on the "top" of the substrate. The substrate may then be folded so as to place these image icons on or within the focal plane that now lies beyond the "top" of the substrate, the resulting projected images being viewable from the "back" of the substrate.

In <FIG>, an embodiment is depicted that is similar to that shown in <FIG>. Two different color images are projected by the inventive polymeric sheet material <NUM>, a reflected light view <NUM> and a transmitted light view <NUM>. Opaque overprint as well as a clear window is shown on the arrangement of image icons in this drawing, with the clear window allowing for a transmitted light view, which can overwhelm the reflected light view.

Visual effects demonstrated by each of the above described embodiments include, but are not limited to, motion or movement, orthoparallactic motion (OPM), Deep, Float, Levitate, Morph, and <NUM>-D. These effects are fully described in <CIT>et al. , <CIT>et al. , and <CIT>et al.

Claim 1:
An improved polymeric sheet material (<NUM>) for use in making polymeric security documents such as banknotes, which is made up of a polymer or polymeric substrate (<NUM>) and one or more integrated optical security devices which project one or more synthetic images,
wherein the one or more integrated optical security devices is made up of an arrangement of metalized hybrid refractive/reflective focusing elements positioned below a first arrangement of image icons on an upper surface of the substrate, characterized by a second arrangement of different image icons positioned directly below the first arrangement of image icons and the metalized hybrid refractive/reflective focusing elements on a lower surface of the substrate and further characterized in that the polymer or polymeric substrate (<NUM>) has a thickness greater than or equal to about <NUM>, wherein different synthetic images are viewed in reflected and transmitted light.