Patent Application
20060087735
Retroreflective materials are employed for various safety and decorative purposes. Particularly, these materials are useful at nighttime when visibility is important under low light conditions. With perfect retroreflective materials, light rays are reflected essentially towards the originating light source in a substantially parallel path along an axis of retroreflectivity.
Many types of retroreflective material exist for various purposes. These retroreflective materials can be used as reflective tapes and patches for clothing, such as vests and belts. Also, retroreflective materials can be used on posts, barrels, traffic cone collars, highway signs, warning reflectors, etc. Retroreflective material can be comprised of arrays of randomly oriented micron diameter spheres or close packed cube-corner (prismatic) arrays.
A retroreflective structure or chip is provided that includes a plurality of cube-corner prisms with substantially all of the prisms including a window side and a facet side. The structure can further include a reflective coating on the facet side and a coating on the window side that absorbs visible light while allowing light having a predetermined wavelength to pass therethrough to be retroreflected by the cube-corner prisms. In one embodiment, the predetermined wavelength includes long wavelength light. In a particular embodiment, the structure has a length less than about 6.35 mm.
Retroreflective structures, which can include chips, flakes, threads, fibers, sheeting, polyhedron retroreflectors, etc., are provided in accordance with embodiments of the present invention. The corner-cube structures can utilize full square-sided or triangular-sided surfaces and/or open faced or solid cube-corner prisms.
The retroreflective structure can further include a matte coating on the reflective coating. In other embodiments, the structure can include a substrate disposed between the cube-corner prisms and the coating on the window side. Moth-eye structures can be provided on the coating for improving light transmission through the retroreflective structure.
In further embodiments, the retroreflective structure is a first retroreflective structure. A second retroreflective structure can be attached to the first retroreflective structure to form a two-sided structure in which light having the predetermined wavelength is retroreflected in at least two, for example, opposite directions. Substrates can be disposed between the cube-corner prisms and the coatings on the window sides of the first and second retroreflective structures.
A method of identifying an object is also provided, which includes attaching retroreflective structures to a surface of the object. The retroreflective structures can be configured to retroreflect light having a predetermined wavelength. The method can include directing light having the predetermined wavelength at the retroreflective structures and detecting the retroreflected light.
The retroreflective structures can be further configured to absorb visible light. In further embodiments, the retroreflective structures can be configured to retroreflect light having the predetermined wavelength in at least two directions.
In another embodiment, a retroreflective structure is provided that includes a first plurality of retroreflectors with open-faced surfaces configured to retroreflect light. A coating can be provided on the surfaces that is configured to reflect a predetermined wavelength or range of wavelengths of light while allowing a predetermined wavelength or range of wavelengths to pass therethrough. In other embodiments, the structure can include a second plurality of retroreflectors with open-faced surfaces configured to retroreflect light and a coating on the surfaces of the second plurality of open-faced surfaces configured to reflect a first predetermined wavelength or range of wavelengths of light while allowing a second predetermined wavelength or range of wavelengths to pass therethrough.
The first and second plurality of retroreflector with open-faced corner cubes can be configured to retroreflect light in at least two directions. The first and second plurality of open-faced, corner cubes can be arranged in a back-to-back relationship so as to retroreflect light in opposite directions. The coating can be configured to reflect short or long wavelengths of light while reflecting midrange wavelengths.
In other embodiments, a retroreflective structure is provided that includes a first plurality of cube-corner prisms, wherein substantially all of the prisms each include a window side and a facet side. A coating can be provided on the facet side that is configured to reflect a first predetermined wavelength or range of wavelengths of light while allowing a second predetermined wavelength or range of wavelengths to pass therethrough. The structure can further include a second plurality of cube-corner prisms, wherein substantially all of the prisms each include a window side and a facet side. A coating can be provided on the facet side that is configured to reflect a first predetermined wavelength or range of wavelengths of light while allowing a second predetermined wavelength or range of wavelengths to pass therethrough. In one embodiment, the coating is configured to reflect short and long wavelengths while allowing midrange wavelengths to pass therethrough.
In a particular embodiment, the first and second plurality of cube-corner prisms are configured to retroreflect light in at least two directions and can be arranged in a back-to-back relationship so as to retroreflect light in opposite directions.
In further embodiments, a retroreflective structure is provided that includes a plurality of cube-corner prisms, wherein substantially all of the prisms each include a window side and a facet side. The prisms can be formed from a material that is substantially transparent to specific narrow or broadband wavelengths and an optical coating can be provided on the facet side that is configured to reflect a predetermined wavelength or range of wavelengths of light. A coating can be provided on the window side that absorbs a predetermined wavelength range while allowing a second predetermined wavelength range to pass therethrough.
In accordance with other embodiments of the invention, an open-faced, two-sided retroreflective structure is provided that is configured to retroreflect light in opposite directions. The structure can be formed from a sheet of material or can be formed by injection molding, compression molding, micro-casting, injection micro-molding, and/or thermoforming processes. In a particular embodiment, the sheet of material includes metal and/or polymer. In other embodiments, the sheet of material is formed into the open-faced retroreflective structure by progressive die processes.
In particular embodiments, the corner-cube structure can include five, seven, or thirteen faces. The corner-cube structure can be formed from a material that is substantially transparent to visible light and can include a coating on at least one side that is configured to reflect a first predetermined wavelength or range of wavelengths of light while allowing a second predetermined wavelength or range of wavelengths to pass therethrough. In further embodiments, the structure is breakable into sections. An Aztec security structure can be provided on one or more surfaces of the structure. The structure can be formed into the shape of a flake or thread.
In yet other embodiments, a retroreflective structure is provided that includes a plurality of open-faced surfaces on a first side of the structure. A second side of the structure can be substantially planar and the structure can be formed from a material that is substantially clear or able to transmit a predetermined wavelength or range of wavelengths of light. A first coating can be provided on the open-faced surfaces that is configured to reflect a predetermined wavelength or range of wavelengths of light while allowing a second predetermined wavelength or range of wavelength light to pass therethrough. A second coating can be provided on the first coating that is configured to reflect a first predetermined wavelength or range of wavelengths of light while allowing a second predetermined wavelength or range of wavelengths of light to pass therethrough. In particular embodiments, the first coating is configured to reflect short or long wavelengths and the second coating is configured to reflect long or short wavelengths while allowing midrange wavelengths light to pass therethrough.
In other embodiments, a retroreflective thread is provided that includes a plurality of open-faced, square-sided cube-corner prisms that are configured to retroreflect light in at least two directions. In one embodiment, the prisms have a specular or reflective coating thereon. The prisms can have coating thereon configured to reflect a predetermined wavelength or range of wavelengths of light, such as short or long wavelength light or both. The thread can be enclosed in a substantially hollow tube or cladding. In other embodiments, the thread includes flex or break points.
In further embodiments, a one-sided full square open-faced, cube-corner prism thread is provided. In one embodiment, two open-faced surfaces are formed therein by a mold. The thread can be enclosed in a substantially hollow or solid tube or cladding. The thread can be twisted within the tube or cladding to achieve retroreflection from various angles. The tube or cladding can be filled with a liquid crystal material and an inside surface of the tube or cladding can include an indium tin oxide-transparent coating. In one embodiment, the thread can be formed from a wire. A specular or reflective coating can be provided on the cube-corner prism surfaces.
In further embodiments, an octahedron retroreflector is provided that includes eight truncated solid cube-corner prisms. The prisms can be formed and then folded into the octahedron retroreflector. A specular or reflective coating can be provided on facets of the prisms. In specific embodiments, the retroreflector includes metal or polymer and is formed by progressive die processes, thermoforming processes, stepped-casting processes, compression, compression injection, and/or injection micro-molding processes. A coating can be disposed on facets of the prisms that is configured to reflect a first predetermined wavelength or range of wavelengths of light while allowing a second predetermined wavelength or range of wavelengths to pass therethrough. Differential height locators can be provided on facets of the prisms to provide an air-backed octahedron retroreflector when formed. The retroreflector can be enclosed within a hollow or solid structure.
In other embodiments, an octahedron retroreflector is provided that includes full open-faced prism surfaces. A specular or reflective coating can be provided on the surfaces. The retroreflector can be enclosed within a hollow or solid structure.
The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of various embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.
A description of various embodiments of the invention follows.
The structure 10 can include cube-corner prisms 12, such as disclosed in U.S. Pat. No. 3,684,348, which issued to Rowland on Aug. 15, 1972, the entire teachings of which are incorporated herein by reference. A method for making retroreflective sheeting is disclosed in U.S. Pat. No. 3,689,346, which issued to Rowland on Sep. 5, 1972, the entire teachings of which are incorporated herein by reference. In other embodiments, the structure 10 can include plastic and/or glass beads or “cat's eye” retroreflective elements.
The prisms 12 can be formed from a material that is substantially transparent to a wavelength of a predetermined range, which can also be a range of wavelengths. In a particular embodiment, the prisms 12 can include polyethylene terephthalate (PET), polycarbonate, polymethyl methacrylate (PMMA), or other suitable materials. A specular or reflective coating 14 can be provided on the facets 16 of the prisms 12 for retroreflecting light. In a particular embodiment, the coating 14 can include aluminum, gold, or the like.
A coating 18 can be provided on the window side 20 of the prisms 12 for absorbing visible light while allowing a predetermined wavelength of light to pass therethrough. In a particular embodiment, the coating 18 includes an acrylic-based material that is about 0.00508 mm (0.0002 inches) thick. The coating 18 can be formed by mixing the following ingredients together by weight: 2.38% QUAKER 6G157; 3.71% QUAKER GR199; 0.32% QUAKER GBE186 (which are available from Quaker Color of Quakertown, Pa.); 23.53% PARALOID™ B48N (which is available from Rohm and Haas Company of Philadelphia, Pa.); and 70.06% ethyl acetate.
In particular embodiments, the structure 10 can have a length 22 less than about 6.35 mm (0.25 inches), a thickness 24 of about 0.127 mm (0.005 inches), and a pitch 26 of about 0.152 mm (0.006 inches). The structures 10 can have any geometric shape, such as hexagonal, square, rectangular, circular, etc., depending on the application.
The resulting structures 10 can be spread on an adhesive-coated film, mixed into adhesives, polymers, paints, coatings, etc. as disclosed in U.S. patent application Ser. No. 10/731,416, filed on Dec. 9, 2003, and published as U.S. Patent Application Publication 20040169928 on Sep. 2, 2004, the entire teachings of which are incorporated herein by reference. Each structure 10 retroreflects a first wavelength of light 28 generated by a light source 30 while absorbing another wavelength of light 32.
In any of the embodiments, moth-eye structures can be provided on coating 18 that transmit a predetermined range of wavelengths of light and scatter a second predetermined wavelength of light. The moth-eye structures improve long wavelength transmission but appear matte or felt-like in appearance in mid to short wavelength light. Moth-eye structures are explained in more detail in U.S. Pat. No. 6,356,389, which issued to Nilsen et al. on Mar. 12, 2002, the entire teachings of which are incorporated herein by reference.
In a particular application for any of the embodiments disclosed herein, a plurality of structures 10 can be mixed with a paint or liquid and applied to a surface of an object. The object, for example 6, can be tracked for inventory control purposes.
The structure 110 can include open-faced, cube-corner prisms 118, such as disclosed in U.S. patent application Ser. No. 09/488,129, filed on Jan. 20, 2000, the entire teachings of which are incorporated herein by reference. The prisms 118 can be formed from a material that is substantially transparent to visible light. In particular embodiments, the prisms 118 may be formed from polycarbonate, polymethyl methacrylate (PMMA), or other suitable thermoset or thermoplastic materials. The prisms 118 can be formed on a substrate 120 that is also substantially transparent to visible light. In particular embodiments, the substrate 120 can include the same materials as the prisms 118, or can include polyester, urethane acrylate, polyester naphthalate (PEN), or other suitable materials. In other embodiments, the prisms 118 and substrate 120 can be formed in one step so as to form a one-piece construction. A substantially transparent adhesive 122 can be used to attach the structure 110 to a substrate, article of clothing, etc., whose color will show through the structure 10.
A coating 124 can be provided on the facets 126 of the prisms 118 that allows the midrange wavelengths of light 112 to pass therethrough, but reflects and thus causes retroflection of longer wavelengths of light 114. In a particular embodiment, the coating 124 is a multilayer coating that can be purchased from Precision Optical Systems, Inc. of Norwood, Mass. The coating may be made with dielectric layers, with metal layers, and with combinations of dielectric and metal layers, such as the coatings used to proportion amount of light transmitted and reflected at different wavelengths. The number of coatings layers and thicknesses of the coating layers are adjusted to provide the desired light reflective range and light transmissive range. The thicknesses of the layers are generally in the range of nanometers, less than the wavelength of light. The number of layers can be in the amount of one to greater than one hundred. In further embodiments, a fill material that is transparent or substantially transparent to midrange and long wavelengths light can be provided on the coating 124 to protect the same.
The prisms 128 can be formed from a material that is substantially transparent to midrange and long wavelength light, such as polyethylene terephthalate (PET), polycarbonate, polymethyl methacrylate, or other suitable materials. A coating 124 can be provided on the facets 126 of the prisms 128 that allows the light 112 to pass therethrough while reflecting and thus causing retroreflection of light 114. An adhesive 122 can be disposed on the coating 124 for attaching the structure 110 to a substrate.
A coating can be provided on the window side 130 of the prisms 128 for absorbing visible light while allowing a predetermined range of wavelengths of light to pass therethrough. In a particular embodiment, the coating includes an acrylic-based material that is described above for coating 118.
The resulting structures of any of the embodiments disclosed herein can be spread on an adhesive-coated film, mixed into adhesives, polymers, paints, coatings, etc. In any of the embodiments, moth-eye structures can be provided on the window side 130.
In a particular application for any of the embodiments disclosed herein, a plurality of structures 110 can be mixed with a paint or liquid and applied to a surface of an object that can be visible. The object, which for example may be merchandise or a shipping container, can be tracked for inventory control purposes.
Thermoplastic polymer sheets, such as polycarbonate (PC), polymethyl methacrylate, cyclic olefin copolymers (COCs), or other suitable polymers, can be formed into cube-corner prism structures using thermoforming processes. Thermoplastic polymers can also be molded into a desired cube-corner prism shape using appropriate compression, compression injection or injection micro-molding processes. Micro-molding techniques can produce as many as 500 flakes from one pellet of thermoplastic. In addition, thermoset polymers, such as ultraviolet-curable acrylic acrylates and urethane acrylates can be cast into the desired cube-corner prism shapes using a stepped micro-casting process.
In any of the embodiments, a predetermined wavelength reflecting coating that is substantially transparent to a second predetermined wavelength range of light can be provided on the reflecting facets of flake 146, which is formed from a resin that is substantially transparent to a predetermined range of wavelengths of light. The flake 146 of this size or larger lands flat and functions as a retroreflecting dust. The flake 146 retroreflects a predetermined wavelength range of light upside down and right side up. Additionally, a substantially transparent adhesive can be applied to one side of the flake 146 to bond it to an article, object, garment, etc.
In other embodiments, a predetermined wavelength range reflecting coating that is substantially transparent to a second predetermined wavelength range of light can be applied to both sides of the flake 146, which is configured to be substantially black or colored. The flake 146 of this size or larger lands flat and functions as a black retroreflecting dust. The flake 146 retroreflects one predetermined wavelength range of light upside down and right side up. In further embodiments, a black or colored adhesive can be applied to one side to bond the flake 146 to an article, object, garment, etc.
Thin-walled cube-corner prism retroreflecting octahedrons 182 can be made by forming metal or polymers. Thin polished metal such as polished aluminum sheet can be formed into cube-corner prism flakes using progressive die processes. Thermoplastic polymer sheets, such as polycarbonate, polymethyl methacrylate, cyclic olefin copolymers, or other suitable materials, can be formed into cube-corner prism structures using thermoforming processes. Thermoplastic polymers can also be molded into the desired cube-corner prism shapes using appropriate compression, compression injection or injection micro-molding processes. Micro-molding techniques can be used to produce as many as 500 octahedrons from one pellet of thermoplastic. In addition, thermoset polymers, such as ultraviolet-curable acrylic acrylates and urethane acrylates, can be cast into the desired cube-corner prism shapes using a stepped micro-casting process.
After forming the cube-corner prism pattern shown in
In other embodiments, an octahedron can be formed by providing bumps or differential height locators, as disclosed in U.S. application Ser. No. 10/830,701, filed on Apr. 23, 2004, and published as U.S. Patent Application Publication 20040246599 on Dec. 9, 2004, the entire teachings of which are incorporated herein by reference, on the facets of the cube-corner prisms. When the cube-corner prisms are folded into an octahedron, an air-space is provided between the prism facets to form an air-backed structure.
In any of the embodiments, coatings can be used to create a colored appearance. Flakes, chips, or fibers of the present application can be of any shape such as square, triangular, hexagonal, rectangular, circular, and the like. The shape can be chosen to suit the application. The flakes can be used individually to mark objects or can 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, offset printed, painted, and the like onto any surface. The surface can be a fabric, a metal, a glass, a ceramic, a stone, a cement, a polymer and the like.
Any combination of retroreflected light performance can be created by mixing flakes having different cube-corner prism features or making the flakes to have more than one design of cube-corner prism structures on a single flake.
One side of the flake can be configured with a specific cube-corner prism size structure or combination of cube-corner prism structures and the other side of the flake can be configured with a second cube-corner prism size structure or combination of cube-corner prism size structures.
In general, any object can be made to have a covering of cube-corner prism structures. The covering can be in the form of a fabric, a coating, a sheet, a paste, a tape, or the like. The cube-corner prism structures can be tunable to create varying entrance angle performance. The cube-corner prism structures can be arranged to create multiple colors in any arrangement of color. In other embodiments, the cube-corner prism structures can be invisible at predetermined wavelengths.
The film, thread or flake of the present application can be configured to have Aztec structures on one side of the film, thread or flake and have another micro-optical structure, such as an open-faced, cube-corner prism structure, on the other side of the film, thread or flake. Micro-optical structures can include open-faced, cube-corner prisms, gratings, moth-eye structures, lens arrays, lenticular prisms or lenses, and the like. Any micro-optical structure that refracts or reflects light can be used.
The thread or flake can be configured to have cube-corner prism structures on one section of the thread or flake and have another micro-optical structure, such as an Aztec structure, on another section of the other side of the thread or flake. Any micro-optical structure that refracts or reflects light can be used.
While this invention has been particularly shown and described with references to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.
This application claims the benefit of U.S. Provisional Application Nos. 60/570,411 filed May 12, 2004 and 60/616,819, filed Oct. 7, 2004. The entire teachings of the above applications are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60570411 | May 2004 | US | |
| 60616819 | Oct 2004 | US |
