US 20060002656 A1
A stepped surface relief structure positioned on a substrate is configured to reflect narrow-band light wavelengths and is further configured such that the substrate can be incorporated into at least one of a thread, a fiber or a flake.
1. A stepped surface relief structure positioned on a substrate, the surface relief structure configured to reflect narrow-band light wavelengths, wherein the substrate is configured to be incorporated into at least one of a thread, a fiber or a flake.
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This application claims priority to U.S. Provisional Application Ser. No. 60/574,494, filed May 25, 2004 and entitled “Surface Relief Structure,” which is herein incorporated by reference.
The present invention relates generally to replicable surface-relief structures that can be applied to threads, fibers, and flakes and which provide special color effects, including both narrow-band and wide-band color.
Stepped surface relief optical structures resonate a narrow band of color and occur in nature, for example, as in the wings of the Morpho Rhetenor butterfly. The stepped resonant structures exhibit unique performance characteristics in the use of the structures for filtering, sensing and display applications.
Structures and methods of creating the structure which duplicate the narrow band color characteristics found in nature are known. Such stepped surface relief optical structures, which produce a narrow band of color by resonance are known as Aztec structures and can be formed by holographic techniques. The holographic master can be replicated in nickel to form production tooling. The production tooling can be formed into a cylinder that is then mounted onto a continuous film casting or thermoforming machine. The machine is used to cast or thermoform a continuous film having the Aztec structure formed into or onto one side of the film. The film is flexible and has a modulus of elasticity ranging from 1.0×108 pascals to 25.0×108 pascals. The film is generally supported by a carrier. The master and tooling can be designed to provide an Aztec structure that is a single resonant color or has multiple resonant colors. The finished film can be slit to any desired width and to widths as narrow as 0.008″ (200 microns) at companies, such as Metlon Corporation, Cranston, R.I.
It is desirable to provide an Aztec structure in the form of one sided and multi sided flakes, chips, threads and fibers which may be used in or with coatings, paints, resins, polymers, fabrics, papers, adhesives, and binders, for example, to create products.
Embodiments of the invention are directed to a stepped surface relief structure positioned on a substrate, the surface relief structure configured to reflect narrow-band light wavelengths, wherein the substrate is configured to be incorporated into at least one of a thread, a fiber or a flake.
Implementations of the invention may include one or more of the following features. The stepped surface relief structure can be fabricated in photoresist by means of holographic interferometry. The stepped surface relief structure can be configured to resonate in a visible spectral region. The stepped surface relief structure can be configured to resonate in an infrared spectral region. The stepped surface relief structure can be configured to resonate in an ultraviolet spectral region. The stepped surface relief structure can be configured to be transparent in a first spectral region and reflective in a second spectral region. The stepped surface relief structure can be configured to be replicated in a nickel master plate. The nickel master plate can be configured to be replicated into a particle and electromagnetic radiation curable resin. The nickel master plate can be configured to be replicated into a thermoset plastic. The nickel master plate can be configured to be cylindrical for incorporation into at least one of an embossing, casting or thermoforming production line.
Implementations of the invention may further include one or more of the following features. A second stepped surface relief structure can be positioned on a second surface of the substrate. Liquid crystal can be incorporated around the stepped surface relief structure, whereby the structure is made conductive, and a cover plate is made conductive, such that the index of refraction of the liquid crystal can be varied electrically, thus varying the resonant color. The structure can include a transparent, conductive tube that incorporates the structure and that is filled with a liquid crystal material, and whose index of refraction can be varied electrically. An outer layer, such as a transparent tube, can be formed from a single material, such as one of thermoplastic, thermset, glass or ceramic. The transparent tube can be hollow or solid and can have a triangular, circular, rectangular, square or elliptical shape. The tube may form a thread that can be woven into a fabric, netting, or a rope. The tube can be sealed in short length to form a fiber or a flake. The fibers or flakes can be dispersed in coatings or polymers. A moth eye surface can be formed into an outer layer of the tubing.
Still further implementations of the invention may include one or more of the following features. The structure can be contained in an optical horn that concentrates light from a large opening to a small area in which the structure is positioned. The optical horn can include a liquid crystal material and the index of refraction of the liquid crystal material can be varied electrically. A corner cube reflector can contain or be positioned adjacent to a stepped surface relief structure. The corner cube reflector can allow particular colors to be reflected or retro-reflected, and be viewed at given distances. The corner cube can be coated with a reflective coating. The stepped surface relief structure can be made from flexible or elastic materials which are within a modulus of elasticity ranging from 1.0×108 pascals to 25.0×108 pascals. The invention can be used in currency, documents, fabrics, coatings, polymers, for example.
The invention may provide one or more of the following advantages. The film, thread or flake may be configured to have Aztec structures on one section of the film, thread or flake and have another micro optical structure such as a corner cube on another section of the other side of the film, thread or flake. Micro optical structures that refracts or reflects light can be used. Aztec resonant structures can be combined with Aztec filters to create remotely activated tunable materials. Selected wavelengths can provide an input to an actuator such as a solar cell that provides the power to cause the LC material to change the index of refraction and create a reflected color shift.
Aztec structures can be combined with corner cube structures to create a film, thread, fiber, flake and the like that will retro-reflect a predetermined color from a long distance but will reflect plus retro-reflect a different color form a short distance. The structures may also be tunable to create any desired color shifts using an electrical potential difference. The film, thread or flake can be configured to have Aztec structures on one side of the film, thread or flake and have another micro optical structure such as a corner cube on the other side of the film, thread or flake. Micro optical structures include corner cubes, gratings, moth eye, lens arrays, lenticular prisms or lenses, for example. Micro optical structures that refract or reflect light can be used.
For a better understanding of the present invention, reference is made to the figures which are incorporated herein by reference and in which:
Embodiments of the invention provide a stepped surface relief structure. In embodiments of the invention, the stepped surface relief structures resonate in a narrow band of color and are known as Aztec structures. In embodiments of the invention, replication of the stepped structures by casting or thermoform can be done on one or both sides of a film. In still further embodiments of the invention, slitting can be done to form threads. Embodiments of the invention can be used on or with coatings, paints, resins, polymers, fabrics, papers, adhesives and binders. Embodiments of the invention can be used for other applications that will be apparent according to the following figures and description.
Aztec structures are made using holographic processes and replicated into nickel masters that are made into production tooling. Such structures can be formed into thread for various uses, for example, the thread can be woven into products or enclosed in a transparent tubing to make a smooth outer surface thread. The transparent tubing can be extruded around the slit Aztec structure thread using a cross head extrusion die. A thread can be adjusted to resonate or reflect different narrow bands of color by having the electric potential shift the index of refraction of a liquid crystal material. The standard and tunable threads can be woven into fabrics to provide unique narrow band iridescent colored fabrics. In one form, the fabrics are tunable to create a change in color. Applications include, but are not limited to, camouflage fabrics and intelligent garments that change color as the environment changes or as the mode of a person or object changes.
In addition to filters, the Aztec structures can be used in other structures, such as threads. In
The Aztec thread 90, 99 can include high reflectivity in a part of the spectrum that is not in the visible, but rather in some other part of the spectrum. Aztec structures are configured with step heights appropriate for creating resonance or constructive interference of light that is to be reflected. The light reflected can be from any portion of the electromagnetic spectrum. An Aztec step structure can be configured to create constructive interference at any wavelength from about 1.0 nm up to or greater than several thousand nanometers. Referring to
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When an Aztec structure is exposed to rain, water or some other medium that has an index of refraction different than that in which the Aztec structure is configured to operate, the wavelength that is resonated is shifted to a different wavelength. The different index of refraction causes the effective optical path between the steps to change. The effective optical path is the index of refraction times the distance that the light is traveling in a medium, where the distance is the distance from one step to the next lower or higher step on the Aztec structure. As the index of refraction of the medium that fills the Aztec structure changes, the resonate wavelength changes. Thus, Aztec structures and threads can be enclosed in transparent tubing to prevent changes in performance.
In embodiments of the invention, Aztec threads as discussed with respect to
A one-sided or two-sided Aztec structure film can also be made into flakes, chips or fibers that are of any shape such as square, triangular, hexagonal, rectangular, circular, and the like. The shape can be chosen to maximize the yield from the film. Companies such as Glitterex in Cranford, N.J. have the capability to make these shapes out of film into sizes ranging from 0.002″ (50 microns) to 0.250″ (6250 microns). These flakes may be used individually to mark objects or may be mixed into paints, coatings, resins, polymers, binders, adhesive, paste and the like to create a medium that can be sprayed, painted, screen printed, gravure coated, off set printed, painted, and the like onto any surface. The surface may be a fabric, a metal, a glass, a ceramic, a stone, a cement, or a polymer, for example.
Combinations of colors can be created by mixing flakes having different Aztec structure features or making the flakes to have more than one design of Aztec structure on a single flake. The coating can be designed to be tunable by providing a conductive coating on the surface of the Aztec structures and an enclosure to enclose an LC material above the flake with the enclosing structure including a transparent conductive coating and a connection to connect an electrical potential difference. One side of the flake may be configured with a specific Aztec structure or combination of Aztec structures and the opposite side of the flake may be configured with a second Aztec structure or combination of Aztec structures.
Aztec structure threads, fibers, flakes and chips can be made with reflective coatings which are transparent in one part of the electromagnetic spectrum and reflect in another part of the electromagnetic spectrum. For example, Aztec structures may be visible in the short wavelength or long wavelength part of the spectrum and transparent in the mid-range part of the spectrum. A suitable light source and detector will allow observing the color reflected, otherwise the material is transparent. The materials may also be tunable such that the material is transparent to defined wavelengths until an electrical potential difference is applied and then the material reflects a chosen color. Examples of coatings include coatings developed by Precision Optical Systems of Norwood, Mass.
In embodiments of the invention, the Aztec structure that is embossed into the film/substrate or cast onto the film/substrate can have a modulus of elasticity that is the same as the substrate film or higher or lower than the substrate film. For example, for an elastic material, the substrate film has a low modulus of elasticity (below 7×108 pascals) and the Aztec structure has a high modulus of elasticity (above 15×108 pascals), such that the Aztec structure is rigid and retains its shape as the relatively elastic substrate is stretched. An Aztec structure with a low modulus of elasticity positioned on a substrate with a high modulus of elasticity creates a reboundable (elastic) Aztec structure on a rigid substrate film.
Having thus described at least one illustrative embodiment of the invention, various alterations, modifications and improvements will readily occur to those skilled in the art. Such alterations, modifications and improvements are intended to be within the scope and spirit of the invention. Accordingly, the foregoing description is by way of example only and is not intended as limiting.