Nanoimprint molds with structural color images created by nanoindentation processes

Abstract

Methods of forming a structural color image can include a surface indented using one or more dies having nanoscale or microscale features to form a macroscale image. Spatial variation in at least one of the indent depth, the feature spacing, the feature shape, the feature size, or a presence or absence of features produces regions exhibiting different structural color effects arising from diffraction, interference of light, or plasmonic effects. Grayscale images may be formed by spatially varying the indent depth to produce regions of differing color intensity or vibrancy. In some embodiments, different regions of the image are formed using different dies, by orienting a die at different rotational angles, or by indenting using different spatial repeat arrangements to produce distinct structural color effects.

Description

Patent Application Attorney Dkt. No. 056785-00012NANOIMPRINT MOLDS WITH STRUCTURAL COLOR IMAGES CREATED BY NANOINDENTATION PROCESSESCROSS-REFERNCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 746,752 filed on January 17, 2025, the contents of which are incorporated herein by reference in their entirety.FIELD

[0002] The technology described herein generally relates to methods, processes, devices, systems, and apparatus to create or generate images, icons, logos, or other patterns with structural color caused by diffraction, interference of light, and / or plasmonic effects with or utilizing a plurality of nanoscale or microscale features.BACKGROUND

[0003] Existing methods to fabricate first-generation cylindrical molds can have multiple limitations including feature resolution, seam defects, durability, cost, and scalability. Hard first-generation molds fabricated using electron-beam lithography and etching techniques result in the highest resolution pattern, yet these molds are typically limited to planar, 300 mm diameter wafers. Flexible replicas are generally used to template a cylindrical mold with a nanopattem using a combination of lithography and etching. These established methods that rely on wrapping, tiling, or joining smaller molds around a cylinder inherently form seams that will be transferred to any subsequent replicas. While some alignment and joining methods can mitigate seams, the resulting patterned cylinder will never be truly seamless (i.e. a seam size less than 50 nm).

[0004] Alternative methods instead directly pattern the outside of a cylinder to mitigate seamPatent Application Attorney Dkt. No. 056785-00012defects. These methods include optical lithography, interference lithography, diamond turning, laser ablation, embossing, casting with nanoparticles, etc. Unfortunately, several of these methods cannot create nanoscale features, while nanoparticle casting methods create irregular stochastic patterns

[0005] In contrast to conventional methods and approaches, implementations of nanocoining or nanoscale indentation uniquely produce a truly seamless first-generation cylindrical mold with ordered nanoscale features directly into a hard cylinder, whereas lithography processes typically require an additional electroforming or etching process that increase the cost, time, and complexity of formatting a durable mold.SUMMARY

[0006] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used in isolation as an aid in determining the scope of the claimed subject matter.

[0007] Embodiments of the technology described herein are generally directed towards the use of an indenting process to create images, icons, logos, designs, or other macroscale patterns with structural color caused by light interacting with a plurality of nanoscale or microscale features through diffraction, interference, or plasmonic effects. During the indenting process, a die with nanoscale or microscale features is repeatedly indented into another material to create a macroscale image comprised of nanoscale or microscale features, called the indented image.

[0008] The optical effect or color will depend on variables such as the depth of the indented features, the presence or absence of features, the spacing of the features in the die, the shape of the features in the die, the rotation angle of the die, or the spacing between individual indents, all of whichPatent Application Attorney Dkt. No. 056785-00012can vary spatially.

[0009] According to some embodiments, the depth of the indents can vary spatially to create an image with varying vibrancy. Regions with deeper indents will have more vibrant colors than regions with less deep indents. In some regions, the die may not be indented at all (zero indent depth) such that these regions do not substantially diffract light, cause interference of light, or result in plasmonic effects, and thus do not create any vibrant diffractive color.

[0010] According to some embodiments, two or more dies with different feature spacings can be used to indent regions in the same image, resulting in regions that diffract light differently. At any given incidence angle of the light and angle of the viewer, regions with repeated features spaced by different amounts will diffract different colors of light. As a result, the image will appear to be multi-colored or different regions will become vibrant at different angles. Alternatively, two or more regions can be indented with the same die that is rotated at different angles such that the regions are most vibrant at different viewing angles.

[0011] According to some embodiments, two or more regions can be indented with the same die that is indented with different repeat arrangements such that the regions have different structural color effects. For example, one region could be indented on a hexagonal repeat arrangement with a repeat distance of 10 microns, while another region could be indented with the same die on a square repeat arrangement with a repeat distance of 8 microns.

[0012] According to some embodiments, indenting processes such as nanocoining or step-and-repeat indenting are used to create the macroscale patterns using a die with nanoscale or microscale features.

[0013] According to some embodiments, the indented image is directly indented into a material such as a foil, film, or sleeve that is used without additional replication processes for the purpose of creating vibrant structural color, for example as a decorative or security component.Patent Application Attorney Dkt. No. 056785-00012

[0014] According to some embodiments, the indented image is created into a mold (often called a “master mold” or a “master”) that can be used to create additional copies of the mold’s textured surface into other materials using nanoimprint lithography, thermal embossing, electroforming, or other replication processes. Replication processes such as nanoimprint lithography and thermal embossing can be performed in plate-to-plate (P2P), roll-to-plate (R2P), or roll-to-roll (R2R) configurations to rapidly create large-area copies. The replicated mold copies, which will exhibit structural color due to the nanoscale or microscale features replicated from the original mold, can be used as a decorative or security feature or can be used as a second-generation mold to create additional replicas.

[0015] According to some embodiments, an additional layer or layers of materials can be added to protect the indented image or replicated mold copies. For example, the indented image or replicated mold copies can be backfilled with a second solid material so that the top surface that is exposed to the environment remains planar while the refractive-index contrast enables the diffraction. Depositing a thin, for example 5-100 nm, layer of metal on the indented image or replicated mold can increase the amount of light reflected from the structural color image, thus increasing its vibrancy.

[0016] Additional objects, advantages, and features of the technology will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or can be learned by practice of the technology described in various aspect herein.BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Aspects of the present disclosure can be better understood with reference to the accompanying drawings or figures, which are not necessarily drawn or shown to scale, but with emphasis on clearly illustrating the various aspects or embodiments of the technology and the disclosure, wherein:Patent Application Attorney Dkt. No. 056785-00012

[0018] FIG. 1A illustrates an example method for indenting the surface of a material, in accordance with some aspects of the technology described herein;

[0019] FIG. IB illustrate an example method for indenting the surface of a material, in accordance with some aspects of the technology described herein;

[0020] FIG. 1C illustrate an example method for indenting the surface of a material, in accordance with some aspects of the technology described herein;

[0021] FIG. 2 illustrates nanocoining, a high-speed indenting process that patterns a cylinder with the features on a die, in accordance with some aspects of the technology described herein;

[0022] FIG. 3 shows photos of a seamless cylindrical drum mold, a seamless cylindrical sleeve, and a flat or flexible shim, all of which can serve as a mold for nanoimprint lithography or thermal embossing, in accordance with some aspects of the technology described herein;

[0023] FIG. 4 illustrates how spatial variations in the indent depth can create spatial variations in the indented pattern, in accordance with some aspects of the technology described herein;

[0024] FIG. 5 shows a photo of a cylindrical mold with interspaced icons and images indented into its surface, in accordance with some aspects of the technology described herein;

[0025] FIG. 6 shows two photos with different lighting conditions of a grayscale image of a baby’s face on a cylindrical mold that was created by spatially varying the indent depth during the nanocoining process, in accordance with some aspects of the technology described herein;

[0026] FIG. 7 is a schematic showing how a cylindrical drum with icons or images can be replicated using a roll-to-roll process to create a strip of images exhibiting structural color, in accordance with some aspects of the technology described herein;Patent Application Attorney Dkt. No. 056785-00012

[0027] FIG. 8 is a depiction of a metal shim mold being pressed into a polymer with heat and pressure to replicate the pattern in the shim using a thermal embossing process, in accordance with some aspects of the technology described herein;

[0028] FIG. 9 show's a photo of roll-to-roll nanoimprint lithography to replicate the images in a mold with indented structural color images into a roll of polymer film, in accordance with some aspects of the technology described herein;

[0029] FIG. 10 shows a photo of a custom structural color image replicated from an indented mold onto a transparent film using nanoimprint lithography in front of an image of the Earth from space, in accordance with some aspects of the technology described herein;

[0030] FIG. 11 shows photos of two structural color images, each created by indenting different regions with two different dies to create regions with distinct structural color effects, in accordance with some aspects of the technology described herein;

[0031] FIG. 12 shows photos of a structural color image of a dog, where the image is invisible when viewed from a normal incidence (left), but appears with different colors when viewed from other angles (mi ddl e, right), in accordance with some aspects of the technology described herein;

[0032] FIG. 13 shows a photo of a spider web on the surface of a watch that is transparent when viewed from a normal incidence (left) but appears in different colors when viewed from other angles (middle, right), in accordance with some aspects of the technology described herein;

[0033] FIG. 14 shows three photos of the same structural color image from the same viewing angle with three different lighting conditions to demonstrate how the lighting conditions can affect the visibility and color of the image, in accordance with some aspects of the technology described herein;Patent Application Attorney Dkt. No. 056785-00012

[0034] FIG. 15 shows two photos of metallized structural color images created by replication from an indented mold followed by metallization, in accordance with some aspects of the technology described herein;

[0035] FIG. 16 shows a scanning electron microscopy (SEM) image of a microscopic Smart Material Solutions logo, which could be used as a covert security features, in accordance with some aspects of the technology described herein; and

[0036] FIG. 17 shows a photo of the diffraction pattern produced when a polymer replica of a structural color image is illuminated with a green laser, in accordance with some aspects of the technology described herein.DETAILED DESCRIPTION

[0037] The subject matter of aspects of the present disclosure is described with specificity herein to meet statutory requirements. However, the description itself is not intended to limit the scope of this disclosure. Rather, the inventors have contemplated that the claimed subject matter might also be embodied in other ways, to include different steps or combinations of steps similar to the ones described in this document, in conjunction with other present or future technologies. Moreover, although the terms “step” and / or “block” can be used herein to connote different elements of methods employed, the terms should not be interpreted as implying any particular order among or between various steps disclosed herein unless and except when the order of individual steps is explicitly described.

[0038] Accordingly, embodiments described herein can be understood more readily by reference to the following detailed description, examples, and figures. Elements, apparatus, and methods described herein, however, are not limited to the specific embodiments presented in the detailed description, examples, and figures. It should be recognized that the exemplary embodiments herein are merelyPatent Application Attorney Dkt. No. 056785-00012illustrative of the principles of the invention. Numerous modifications and adaptations will be readily apparent to those of skill in the art without departing from the scope of the invention.

[0039] In addition, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein. For example, a stated range of “1.0 to 10.0” should be considered to include any and all subranges beginning with a minimum value of 1.0 or more and ending with a maximum value of 10.0 or less, e.g., 1.0 to 5.3, or 4.7 to 10.0, or 3.6 to 7.9.

[0040] All ranges disclosed herein are also to be considered to include the end points of the range, unless expressly stated otherwise. For example, a range of “between 5 and 10” or “5 to 10” or “5-10” should generally be considered to include the end points 5 and 10.

[0041] Further, when the phrase “up to” is used in connection with an amount or quantity; it is to be understood that the amount is at least a detectable amount or quantity. For example, a material present in an amount “up to” a specified amount can be present from a detectable amount and up to and including the specified amount.

[0042] Additionally, in any disclosed embodiment, the terms “substantially,” “approximately,” and “about” may be substituted with “within [a percentage] of’ what is specified, where the percentage includes 0.1, 1, 5, and 10 percent.

[0043] Disjunctive language such as the phrase “at least one of X, Y, or Z,” unless specifically stated otherwise, is otherwise understood with the context as used in general to present that an item, term, etc., may be either X, Y, or Z, or any combination thereof (e.g., X, Y, and / or Z). Thus, such disjunctive language is not generally intended to, and should not, imply that certain embodiments require at least one of X, at least one of Y, or at least one of Z to each be present.

[0044] As used herein, the term “surface” generally refers broadly to any surface of a material, article, or mold, including planar, cylindrical, flexible, or rigid surfaces, unless otherwise specified. InPatent Application Attorney Dkt. No. 056785-00012some aspects, a surface can be considered the surface of a substrate of any material that can be used in conjunction with various aspects set out herein. As will be appreciated, any material or surface can be used that is not inconsistent with the technical objectives of this disclosure.

[0045] Patterning a surface with nanometer- to micrometer- si zed features can offer new functionalities. This process gives rise to structured surfaces that exhibit structural color, or are anti-reflective, antimicrobial, anti-fouling, and / or superhydrophobic, among other properties. Structural color usually results in vibrant, eye-catching colors that can have interesting properties such as iridescence. Applications of patterned surfaces with structural color include graphical images for packaging, decorative images on luxury products like handbags, watch bands, watch faces, jewelry, sunglasses, pens, fake nails, apparel, shoes, water bottles, mobile phone screens or cases, packaging, labels and many more items. At the same time, these images with structural color can provide anti-counterfeit and security properties, enabling a salesperson or consumer to easily identify genuine articles. For security features, the difficulty to manufacture such images is a strength, as they become more difficult to counterfeit. Structural color can also create vibrant colors without the need for dyes, opening the door for dye-free labeling and packaging.

[0046] The structural colors described herein can be produced by diffraction, interference of light, or plasmonic effects. Diffraction gratings enhance the reflection or transmission of a particular color of light, among the range of colors contained within incident white light. The color that is reflected from or transmitted through a diffraction grating is determined by the spacing and shape of the features, the viewing angle, and the angle of the incident light. In the case of the presently disclosed technology, the ability to manipulate the spacing of the features results in the ability to vary the color spatially within the image. Further, this technology can create ID or 2D diffraction gratings. Rather than a series of lines with a given spacing (a ID grating), 2D gratings consist of a repeating series of posts or features that canPatent Application Attorney Dkt. No. 056785-00012diffract light in multiple directions. Using 2D diffraction gratings allow the color to be seen from multiple directions and can result in different colors from different viewing directions.

[0047] The most vibrant diffractive structural color is caused by first-order diffraction. First-order diffraction occurs when the pathlength of the light interacting with one feature is one wavelength off from the light interacting with the adjacent feature. For visible light, features spaced between about 200nm and 800nm can create interesting optical effects, because they can be somewhat transparent without substantial color such that the user can see an undisturbed image behind the surface when viewing close to normal incidence, whereas these features can result in vibrant colors caused by first-order diffraction when tilted. Such fine spacing creates a manufacturing challenge, particularly for 2D diffraction gratings. Larger diffraction gratings with spacings, for example, between 800 nm and 10 pm can also be used to create vibrant arrays of colors with first-order and higher-order diffraction that can be seen from an even broader array of viewing angles.

[0048] Plasmonic color, on the other hand, usually creates more angle-independent structural color and often relies on smaller feature spacings, for example 10 nm to 200 nm spacing. Such plasmonic effects can be produced by nanoscale features formed in or coated with conductive materials, or by hybrid dielectric-conductive structures, which can be templated with the indenting methodologies described herein.

[0049] Despite the promise of these patterned (or textured) surfaces for many fields, large-area (e.g. substrates greater than 1 m2) fabrication is either infeasible or prohibitively expensive with traditional nanofabrication techniques since it requires the formation of trillions of nanoscale features. While roll-to-roll (R2R) and roll-to-plate (R2P) nanoimprint lithography provide a method for scalable manufacturing of patterned films by pressing a textured roller into a formable material such as a polymer, the technology is largely hampered by the exorbitant cost of robust, large-area cylindricalPatent Application Attorney Dkt. No. 056785-00012molds, stamps, or photomasks. Such cylindrical molds can be in the form of a patterned hard roller or flexible sleeve (i.e. belt or tube) supported by rollers.

[0050] A first-generation mold (also referred to as a master or a master mold) is typically made of a hard, planar, and non-flexible material such as quartz, silicon, or a metal. This hard mold serves as a template for all subsequent mold and film replicas. A replica can be generated using nanoimprint lithography (NIL), where a polymer (e.g. thermoset, photopolymer, or silicone) is imprinted with a template mold before it is cured with UV light or heat. Curing causes the replica material to solidify so that one of its surfaces gains the complementary or inverse pattern of its template mold. Alternatively, thermoplastic polymer replicas can be made with a thermal embossing with the application of heat, pressure, and / or solvents while metal replicas can be made with electroforming. Replicas may be the final product, or they can further serve as a template mold in subsequent nanoimprint, embossing, electroforming, or other fabrication processes. Sometimes soft or flexible replicas such as those made form silicones or cyclic olefin polymers are used as stamps (sometimes called soft molds) for subsequent replication processes.

[0051] Accordingly, at a high level, aspects of the present technology are directed to devices, systems, and methods for forming or generating or creating macroscopic images that comprise a plurality of nanoscale and / or microscale features that give rise to structural color, vary spatially, and are created through an indenting process, such as nanocoining or step-and-repeat indenting. The optical effect or color will depend on variables such as the depth of the indented features, the spacing of the features in the die, the shape of the features in the die, the rotation angle of the die, or the spacing between individual indents, all of which can vary spatially.

[0052] Methods of forming a structural color image can include a surface that is indented using one or more dies having nanoscale or microscale features to form a macroscale image. Spatial variation in atPatent Application Attorney Dkt. No. 056785-00012least one of the indent depth, the feature spacing, the feature shape, the feature size, or a presence or absence of features produces regions exhibiting different structural color effects arising from diffraction, interference of light, or plasmonic effects. Grayscale images may be formed by spatially varying the indent depth to produce regions of differing color intensity or vibrancy. Tn some embodiments, different regions of the image are formed using different dies, by orienting a die at different rotational angles, or by indenting using different spatial repeat arrangements to produce distinct structural color effects. The indented surface may be used directly as a decorative or security feature or may serve as a mold for forming one or more generations of replicas using replication processes including nanoimprint lithography, thermal embossing, or electroforming. Replicated surfaces may be used as decorative or authentication features or as molds for further replication

[0053] Turning to the figures, FIG. 1A, FIG. IB, and FIG. 1C illustrate side views of several steps of an indenting process in which a material 100 is indented with a die 102 with a nanoscale or microscale pattern 104 to convert the unpatterned surface 122 into a patterned surface 124. FIG. 1A shows the die 102 and the mold 100 before indenting. FIG. IB shows the die 102 and the mold 100 during an indent, which deforms the unpatterned mold surface 122 to create a patterned mold surface 124. FIG. 1C shows the patterned surface 124 that is left behind after two side-by-side indents with the patterned die surface 104 of the die 102.

[0054] Some examples of indenting processes include step-and-repeat indenting and nanocoining. Step-and-repeat indenting occurs when a die is indented into a mold, removed, translated laterally with respect to the mold, and indented again. This process can be repeated to cover large areas with repeated features. FIG. 2 illustrates the nanocoining process in which a rotating cylinder 200 is indented with a die 202, which vibrates along an elliptical path such that it indents the unpatterned surface 222 to create a patterned surface 224 without smearing the indented features. As will be appreciated, the cylinder 200Patent Application Attorney Dkt. No. 056785-00012can take many forms including a solid cylinder, a tube, or a sleeve. FIG. 3 shows photos of a cylindrical mold, a cylindrical sleeve, and a flexible or flat foil, shim, or sleeve that can be created using indenting processes.

[0055] In some aspects, in order to create, form or generate images or icons using an indenting process, a die with nanoscale and / or microscale features is repeatedly indented into the surface of another material with varying indent depths to create a macroscale image that is comprised of a plurality of nanoscale or microscale features that give rise to a structural color effect, such as diffraction. The spatial variation in the indent depth causes selective reflection or transmission of different colors of light that vary spatially over the surface of the mold in a controlled way, revealing a macroscale icon or image. FIG. 4 illustrates how different regions of a material 400 can be indented with the same die to different indent depths. The unpatterned surface 422 will be smooth. The deeply indented surface 424 will have taller features, whereas the shallowly indented surface will have shorter features. FIG. 5 shows a photo of an example cylindrical mold with several icons and images that were created using the nanocoining indenting process. FIG. 6 shows two photos under different lighting conditions of a cylindrical mold with a grayscale image that was created by varying the depth of the indented features during the nanocoining process.

[0056] In some instances, the mold, can be, for example, created through mechanical indenting, is typically metal, but it can also be other materials, including polymers or ceramics. Diffraction is created by the repeated pattern on the die being indented or by the spacing of adjacent indents. When the spacing of the features in these patterns is similar to the wavelength of visible light, 400 nm to 790 nm, brilliant colors can appear due to diffraction of light off of the repeated features. In some embodiments, feature spacings may extend beyond 10 micrometers, for example up to approximately 20 micrometers, while still producing visible structural color effects. In some embodiments, repeated nanoscale featuresPatent Application Attorney Dkt. No. 056785-00012may have characteristic dimensions or spacings as small as approximately 10 nanometers, particularly for plasmonic structural color effects. The indented pattern can be controlled either by increasing or decreasing the depth of the indented features on the mold, or leaving void spaces where there are no features at all.

[0057] In some embodiments, the icons or images can be written around a cylindrical drum or sleeve, into a flat, or into a foil or shim that is wrapped over a flat or cylinder. These indented surfaces can be used without additional replication steps or become a mold for mass replication through molding, nanoimprint lithography, thermal embossing, electroforming, or other replication processes. FIG. 7 shows how a cylindrical drum with icons or images can be replicated using a roll-to-roll replication process to create a strip of images exhibiting structural color. As will be appreciated, FIG. 7 illustrates nanocoining to rapidly nanopattem roll-to-roll molds, roll-to-roll processes which can be implemented for low cost and high-throughput manufacturing, and large-area nanopatterns that can exhibit advanced optical and wetting properties. FIG. 8 shows how a patterned mold can be used to replicate the mold features into another material using processes like thermal embossing of a polymer by bringing the mold in contact with a polymer film, applying heat and pressure, and removing the film to reveal an inverted copy of the mold’s pattern. FIG. 9 shows a photo of roll-to-roll nanoimprint lithography to create a roll of polymer film with structural color images from a cylindrical mold with macroscale images that were created with nanocoining. FIG. 10 shows a photo of a structural color image replicated into a transparent film from a cylindrical mold with nanoimprint lithography. The film is held with tweezers in front of a picture of the Earth from space to illustrate the transparency of the smooth film.

[0058] In some embodiments, the patterns may be created by indenting with several different dies with different repeating patterns. The regions indented with different dies will diffract different colors, and these colors can be mixed or interspaced to create a multi-color image. FIG. 11 shows two photos ofPatent Application Attorney Dkt. No. 056785-00012polymer replicas of structural color images created by indenting different regions with two different dies, resulting in regions with distinct structural color effects. The photo on the left shows a shield indented with one die and a lock indented with a second die. The image on the right shows a photo of a butterfly with the outline indented with the first die and the details indented with a second die. Both structural color images in FIG. 11 make it clear that there are two distinct structural color effects created by indenting two different regions with two different dies.

[0059] In some embodiments, the patterns may be created by indenting different regions with the same die that is rotated to different angles. The regions indented with different die-rotation angles will be most vibrant at different viewing angles, and these die-rotation-angles can be mixed or interspaced to create a multi-color image. Alternatively, different regions can be indented with the same die that is indented with different repeat arrangements such that the regions have different structural color effects. For example, one region could be indented on a hexagonal repeat arrangement with a repeat distance of 10 microns, while another region could be indented with the same die on a square repeat arrangement with a repeat distance of 8 microns. Such use of multiple dies, differing die orientations, or different indent repeat conditions enables spatially selective control of color, visibility, or optical response within a single macroscale image.

[0060] In some embodiments, the visibility or apparent color of the structural color image varies in response to viewing angle, illumination angle, illumination spectrum, or illumination intensity.Transparent polymer replicas consisting of features that are spaced less than the wavelength of visible light will appear optically clear at a normal viewing angle for many incident light angles, but can create vibrant colors at other incident and viewing angles. Larger features will create first-order and higher-order diffraction that is visible from more viewing angles, but the replicated transparent films will also appear hazy to a viewer seeking to look through the replica since these larger features can scatter visiblePatent Application Attorney Dkt. No. 056785-00012light. FIG. 12 shows photos a structural color image of a dog created by nanocoining a cylindrical mold and replicating that mold into a polymer film. The image of the dog is barely visible when viewed from a normal incidence (photo on the left), but appears with different colors when viewed from other angles (photos in the middle and on the right).

[0061] In some embodiments, the first indented surface can be the final product in and of itself. For example, the indenting process can be applied to write icons, images, or text directly into a surface like the back cover of a watch, a wedding band, pens, phone cases, or multitude of other surfaces to create a decorative, customization, or security effect. These surfaces may be made from stainless steel, steel, copper, aluminum, titanium, platinum, gold, silver, or other metal or non-metal material that can accept the mechanical indent from the patterned die.

[0062] The replicated features can be used as a final product or be used to create additional replicas. The replicated features can be used as components in watches, clothing, apparel, shoes, sunglasses, nail polish or fake nails, pens, phone cases, or a multitude of other surfaces to impart decorative or security features. FIG. 13 shows photos of a watch with a structural color image of a spider web on its surface created by laminating a polymer replica of a mold created with nanocoining onto the surface of a watch. This image was also created with nanocoining and has the same features spacing as the features that make up the structural color image of the dog in FIG. 12. The watch in FIG. 13 exhibits very little structural color when viewed from normal incidence (photo on the left), but stronger diffractive color appears at other incidence angles as can be seen in the middle photo and the photo on the right. FIG. 14 further demonstrates how lighting can affect the visible appearance of a structural color image. This figure shows three photos of a polymer replica with a structural color image created by nanocoining and roll-to-roll nanoimprint lithography under three different lighting conditions. The photo on the left was taken with only ambient indoor lighting. In this photo, the structural color image is barely visible. ThePatent Application Attorney Dkt. No. 056785-00012other two photos were taken with colored LEDs illuminating the side of the film, resulting in increased visibility of the image.

[0063] The visibility of the structural color images can also be enhanced by metallizing the surface to increase reflection without substantially altering the underlying feature geometry, resulting in a more visible and often more vibrant image. FIG. 15 shows two photos of structural color images replicated into a polymer using nanoimprint lithography and then metallized with approximately 80nm of aluminum.

[0064] As will be appreciated, One issue with structural color can be the durability of the imprinted polymer replica. This can be remedied in some embodiments by performing a backfdling step in which the structural color image is filled with a second solid material.

[0065] In some embodiments, the structural color image and / or patterned surface may serve as an anti-counterfeiting or brand authentication feature and may include covert features, such as microscale logos observable under magnification or diffractive patterns observable upon illumination with coherent light, such as laser light. FIG. 16 shows a scanning electron microscopy image of a microscale Smart Material Solutions logo. FIG. 17 shows an example diffraction pattern produced when a polymer replica of a structural color image is illuminated with a laser, for example a green laser, thereby enabling authentication based on the observed diffractive response.EXAMPLE EMBODIMENTS

[0066] Aspects of the present technology can be further illustrated by way of the following nonlimiting example embodiments.

[0067] Embodiment 1. A method of forming a structural color image, comprising indenting a surface with at least one die having a plurality of nanoscale or microscale features, wherein the at least one die is indented into the surface at a plurality of locations to form a macroscale image defined byPatent Application Attorney Dkt. No. 056785-00012spatial variation in at least one of: the indent depth, the presence or absence of features indented into the surface, the size of the nanoscale or microscale features on the die and / or the shape of the nanoscale or microscale features on the die, wherein the nanoscale or microscale features are configured to interact with incident light such that the macroscale image exhibits structural color.

[0068] Embodiment 2. The method of embodiment 1, wherein the indenting process is nanocoining or step-and-repeat indenting.

[0069] Embodiment 3. The method of embodiments 1 or 2, wherein the structural color arises from at least one of diffraction of light, interference of light, or plasmonic effects.

[0070] Embodiment 4. The method of embodiments 1 to 3, wherein the spatial variation in the indent depth produces regions of differing color intensity or vibrancy within the macroscale image.

[0071] Embodiment 5. The method of any previous embodiment, wherein the nanoscale or microscale features on the die are arranged in a repeating pattern with a center-to-center spacing between approximately 10 nanometers and 20 micrometers.

[0072] Embodiment 6. The method of any previous embodiment, wherein different regions of the macroscale image are formed by indenting the surface using at least one of: two or more dies having different nanoscale or microscale features, a single die oriented at different rotational angles, and / or a single die indented with different spatial repeat arrangements on the surface, such that the different regions exhibit different structural color effects.

[0073] Embodiment 7. The method of any previous embodiment, wherein visibility or apparent color of the structural color image varies in response to at least one of a viewing angle, an illumination angle, or illumination conditions.Patent Application Attorney Dkt. No. 056785-00012

[0074] Embodiment 8. The method of any previous embodiment, further comprising backfilling the indented surface with a transparent or translucent material to protect the nanoscale or microscale features.

[0075] Embodiment 9. The method of any previous embodiment, wherein the structural color image is formed as a decorative feature on a consumer product or branded article.

[0076] Embodiment 10. The method of any previous embodiment, wherein the structural color image is formed as an authentication or anti-counterfeit feature for verifying authenticity of an article.

[0077] Embodiment 11. The method of any previous embodiment, wherein the structural color image comprises microscale features configured to be observable under magnification for authentication.

[0078] Embodiment 12. The method of any previous embodiment, further comprising illuminating the structural color image with coherent light to observe a diffractive response for authentication.

[0079] Embodiment 13. The method of any previous embodiment, wherein the surface is configured for use as a decorative or security feature on a finished product without further replication.

[0080] Embodiment 14. The method of any previous embodiment, wherein the surface comprises a mold configured for use in a subsequent replication process.

[0081] Embodiment 15. The method of any previous embodiment, wherein the mold comprises a cylindrical drum, a cylindrical sleeve, or a shim.

[0082] Embodiment 16. The method of any previous embodiment, wherein the mold comprises a cylindrical drum or cylindrical sleeve, and wherein the macroscale image is formed continuously around a circumference of the cylindrical mold without a seam.

[0083] Embodiment 17. A method of replicating a structural color image, comprising providing a mold formed according to any of the previous embodiments, forming a replica of the macroscale imagePatent Application Attorney Dkt. No. 056785-00012from the mold such that the replica comprises nanoscale or microscale features corresponding to the macroscale image, and replicating the structural color image in a substate.

[0084] Embodiment 18. The method of embodiment 17, wherein the replicated surface is used as a mold to form one or more additional replicas of the structural color image.

[0085] Embodiment 19. The method of embodiments 17 or 18, further comprising depositing a metal layer on the replicated surface to increase reflectivity or vibrancy of the structural color image.

[0086] Embodiment 20. The method of any of embodiments 17 to 19, further comprising backfilling the replicated surface with a transparent or translucent material to protect the nanoscale or microscale features.

[0087] Many different arrangements of the various components and / or steps depicted and described, as well as those not shown, are possible without departing from the scope of the claims below.Embodiments of the present technology have been described with the intent to be illustrative rather than restrictive. Alternative embodiments will become apparent from reference to this disclosure. Alternative means of implementing the aforementioned can be completed without departing from the scope of the claims below. Certain features and subcombinations are of utility and can be employed without reference to other features and subcombinations and are contemplated within the scope of the claims.

Claims

Patent Application Attorney Dkt. No. 056785-00012CLAIMS1. A method of forming a structural color image, the method comprising:indenting a surface with at least one die having a plurality of nanoscale or microscale features;wherein the at least one die is indented into the surface at a plurality of locations to form a macroscale image defined by spatial variation in at least one of:(i) the indent depth,(ii) the presence or absence of features indented into the surface,(iii) the size of the nanoscale or microscale features on the die, or(iv) the shape of the nanoscale or microscale features on the die; andwherein the nanoscale or microscale features are configured to interact with incident light such that the macroscale image exhibits structural color.

2. The method of claim 1, wherein the indenting process is nanocoining or step-and-repeat indenting.

3. The method of claim 1, wherein the structural color arises from at least one of diffraction of light, interference of light, or plasmonic effects.

4. The method of claim 1, wherein the spatial variation in the indent depth produces regions of differing color intensity or vibrancy within the macroscale image.

5. The method of claim 1, wherein the nanoscale or microscale features on the die are arranged in a repeating pattern with a center-to-center spacing between approximately 10 nanometers and 20 micrometers.

6. The method of claim 1, wherein different regions of the macroscale image are formed by indenting the surface using at least one of:(i) two or more dies having different nanoscale or microscale features,(ii) a single die oriented at different rotational angles, orPatent Application Attorney Dkt. No. 056785-00012(iii) a single die indented with different spatial repeat arrangements on the surface, such that the different regions exhibit different structural color effects.

7. The method of claim 1, wherein visibility or apparent color of the structural color image varies in response to at least one of a viewing angle, an illumination angle, or illumination conditions.

8. The method of claim 1, further comprising backfdling the indented surface with a transparent or translucent material to protect the nanoscale or microscale features.

9. The method of claim 1, wherein the structural color image is formed as a decorative feature on a consumer product or branded article.

10. The method of claim 1, wherein the structural color image is formed as an authentication or anticounterfeit feature for verifying authenticity of an article.

11. The method of claim 10, wherein the structural color image comprises microscale features configured to be observable under magnification for authentication.

12. The method of claim 10, further comprising illuminating the structural color image with coherent light to observe a diffractive response for authentication.

13. The method of claim 1, wherein the surface is configured for use as a decorative or security feature on a finished product without further replication.

14. The method of claim 1, wherein the surface comprises a mold configured for use in a subsequent replication process.

15. The method of claim 14, wherein the mold comprises a cylindrical drum, a cylindrical sleeve, or a shim.Patent Application Attorney Dkt. No. 056785-0001216. The method of claim 14, wherein the mold comprises a cylindrical drum or cylindrical sleeve, and wherein the macroscale image is formed continuously around a circumference of the cylindrical mold without a seam.

17. A method of replicating a structural color image, comprising:providing a mold formed according to the method of claim 14; andforming a replica of the macroscale image from the mold such that the replica comprises nanoscale or microscale features corresponding to the macroscale image.

18. The method of claim 17, wherein the replicated surface is used as a mold to form one or more additional replicas of the structural color image.

19. The method of claim 17, further comprising depositing a metal layer on the replicated surface to increase reflectivity or vibrancy of the structural color image.

20. The method of claim 17, further comprising backfilling the replicated surface with a transparent or translucent material to protect the nanoscale or microscale features.

Images