WO2019172978A2

WO2019172978A2 - Infrared reflector and method of forming same

Info

Publication number: WO2019172978A2
Application number: PCT/US2018/066729
Authority: WO
Inventors: Craig A. Miller; Thomas R. Gehring
Original assignee: 3M Innovative Properties Company
Priority date: 2017-12-27
Filing date: 2018-12-20
Publication date: 2019-09-12
Also published as: WO2019172978A3

Abstract

Various embodiments of an infrared reflector and a method of forming such reflector are disclosed. The infrared reflector includes an optical film having a first major surface, a second major surface, and optical elements disposed on the second major surface, where the optical elements are adapted to reflect at least a portion of infrared radiation incident upon the first major surface of the optical film, and where the optical film is opaque for visible radiation; a patterned visible image layer that includes reflective and transmissive regions for visible radiation; and a patterned infrared image layer that includes reflective and transmissive regions for infrared radiation. Either the patterned visible image layer is disposed between the first major surface of the optical film and the patterned infrared image layer or the patterned infrared image layer is disposed between the first major surface of the optical film and the patterned visible image layer.

Description

INFRARED REFLECTOR AND METHOD OF FORMING SAME

BACKGROUND

Various systems utilize night vision and thermal infrared systems to identify vehicles, personnel, or other objects in low-light or no-light conditions. For example, vehicle identification markings can include infrared reflective films that reflect ambient thermal energy that is then detected by a thermal or infrared imager. Such infrared reflective films can reduce emission of thermal infrared radiation from the object or person marked with the film and reflect thermal energy from another area to create a surface or region that appears cold in an infrared image. Some of these films can be designed to redirect low infrared radiation scenes such as certain parts of the sky to the observer, which is referred to as cold sky reflection.

Identification of an object or person utilizing thermal infrared imaging systems can be performed utilizing an infrared reflecting film that is deposited in a vertical orientation on the object or person such that a plane of the film is substantially normal to the Earth’s surface. The film can be adapted to reflect areas of the sky that emit little infrared radiation to a ground-based observer. The film can be connected to an object that emits greater infrared radiation than the infrared radiation emitted by the colder areas of the sky. Such infrared radiation from the object can be reflected by the film away from the observer such that the imaging system utilized by the observer sees the cold sky and not the warmer object. Portions of the film can be patterned to have different values of infrared transmission such that infrared radiation from the object can be transmitted through the film and to the observer. Such patterning can provide various identification indicia such that the observer can identify the particular object in low- to no-light conditions.

Infrared systems can also be utilized for targeting simulations in field training for police and military personnel. Such infrared systems typically include powered targets that emit thermal infrared radiation to reproduce a thermal image of an object that can be viewed by a thermal or infrared imager.

These powered systems, however, require electricity to generate the thermal image. Such electricity can be difficult to provide in the field. Further, such powered systems can be expensive to repair, especially if the system is being utilized for ballistic targeting practice as munitions can damage the electrical wiring and power systems that are connected to the target.

SUMMARY

In general, the present disclosure provides various embodiments of an infrared reflector and a method of forming same. The infrared reflector can include an optical film, a patterned visible image layer, and a patterned infrared image layer. The optical film can include one or more optical elements that are adapted to direct infrared radiation from the sky to an observer. The infrared reflector can be adapted to adjust an apparent temperature of an object. In one aspect, the present disclosure provides an infrared reflector that includes an optical film having a first major surface, a second major surface, and optical elements disposed on the second major surface. The optical elements are adapted to reflect at least a portion of infrared radiation incident upon the first major surface of the optical film. Further, the optical film is opaque for visible radiation. The infrared reflector also includes a patterned visible image layer including reflective and transmissive regions for visible radiation, and a patterned infrared image layer that includes reflective and transmissive regions for infrared radiation. Either the patterned visible image layer is disposed between the first major surface of the optical film and the patterned infrared image layer or the patterned infrared image layer is disposed between the first major surface of the optical film and the patterned visible image layer.

In another aspect, the present disclosure provides a method that includes disposing a patterned visible image layer adjacent a first major surface of an optical film, where the patterned visible image layer includes reflective and transmissive regions for visible radiation; and disposing a patterned infrared image layer either between the patterned visible image layer and the first major surface of the optical film or such that the patterned visible image layer is between the patterned infrared image layer and the first major surface of the optical film, where the patterned infrared image layer includes reflective and transmissive regions for infrared radiation. The method further includes disposing non-retroreflective optical elements on a second major surface of the optical film, and disposing a patterned infrared reflective coating on one or more of the optical elements.

All headings provided herein are for the convenience of the reader and should not be used to limit the meaning of any text that follows the heading, unless so specified.

The terms“comprises” and variations thereof do not have a limiting meaning where these terms appear in the description and claims. Such terms will be understood to imply the inclusion of a stated step or element or group of steps or elements but not the exclusion of any other step or element or group of steps or elements.

In this application, terms such as“a,”“an,” and“the” are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terms “a,”“an,” and“the” are used interchangeably with the term“at least one.” The phrases“at least one of’ and“comprises at least one of’ followed by a list refers to any one of the items in the list and any combination of two or more items in the list.

The phrases“at least one of’ and“comprises at least one of’ followed by a list refers to any one of the items in the list and any combination of two or more items in the list.

As used herein, the term“or” is generally employed in its usual sense including“and/or” unless the content clearly dictates otherwise.

The term“and/or” means one or all of the listed elements or a combination of any two or more of the listed elements.

As used herein in connection with a measured quantity, the term“about” refers to that variation in the measured quantity as would be expected by the skilled artisan making the measurement and exercising a level of care commensurate with the objective of the measurement and the precision of the measuring equipment used. Herein,“up to” a number (e.g., up to 50) includes the number (e.g., 50).

Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range as well as the endpoints (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

These and other aspects of the present disclosure will be apparent from the detailed description below. In no event, however, should the above summaries be construed as limitations on the claimed subject matter, which subject matter is defined solely by the attached claims, as may be amended during prosecution.

BRIEF DESCRIPTION OF THE DRAWINGS

Throughout the specification, reference is made to the appended drawings, where like reference numerals designate like elements, and wherein:

FIG. 1 is a schematic cross-section view of one embodiment of an infrared reflector.

FIG. 2 is a schematic cross-section view of a portion of the infrared reflector of FIG. 1.

FIG. 3 is a schematic cross-section view of another embodiment of an optical film of an infrared reflector.

FIG. 4 is a schematic cross-section view of another embodiment of an optical film of an infrared reflector.

FIG. 5 is a photograph of one embodiment of a patterned visible image layer.

FIG. 6 is a photograph of one embodiment of a patterned infrared image layer.

FIG. 7 is a photograph of another embodiment of a patterned visible image layer.

FIG. 8 is a photograph of another embodiment of a patterned infrared image layer.

FIG. 9 is a flowchart of one embodiment of a method of forming an infrared reflector.

DETAILED DESCRIPTION

In general, the present disclosure provides various embodiments of an infrared reflector and a method of forming same. The infrared reflector can include an optical film, a patterned visible image layer, and a patterned infrared image layer. The optical film can include one or more optical elements that are adapted to direct infrared radiation from the sky to an observer. The infrared reflector can be adapted to adjust an apparent temperature of an object.

Various embodiments of infrared reflectors described herein can redirect an infrared image or scene from a first location to an observer at a second location. For example, in one or more embodiments, one or more portions of the infrared reflector can redirect portions of the cold sky to the observer such that these portions appear cool or cold to the observer. In one or more embodiments, one or more portions of the infrared reflector can be adapted to transmit or reflect infrared radiation to the observer such that these one or more portions appear warm or hot to the observer. By tailoring the infrared reflector to reflect or transmit differing amounts of infrared radiation, the apparent temperature of the reflector can be controlled to provide to the observer one or more selected infrared images.

The various embodiments of infrared reflectors described herein can be utilized in any suitable application. In one or more embodiments, the infrared reflector can be adapted to be oriented such that a plane of the reflector is substantially parallel to a normal to the Earth’s surface, i.e., in a vertical orientation. As used herein, the term“substantially parallel” means that an angle formed between the plane of the infrared reflector and the normal to the Earth’s surface is no greater than 10°. In such embodiments, the infrared reflector can be utilized to form a target for police or military training in any light conditions. Further, one or more embodiments of infrared reflector described herein can be adapted to be oriented such that the plane of the reflector is substantially orthogonal to the normal to the Earth’s surface, i.e., in a horizontal orientation. As used herein, the term“substantially orthogonal” means that an angle formed between the plane of the infrared reflector and the normal to the Earth’s surface is at least 80° and no greater than 100°.

In one or more embodiments, the infrared reflector can be disposed adjacent to an object to hide or camouflage the object in any lighting conditions. For example, in one or more embodiments, the patterned visible image layer of the infrared reflector can provide a visible image of an object. As used herein, the term“visible image” means an image that can be viewed by an observer without the aid of a thermal or infrared imager. Further, the patterned infrared image layer of the infrared reflector can provide an infrared image of an object. As used herein, the term“infrared image” means an image that is representative of an infrared image of the object. Such infrared image can be viewed by a thermal or infrared imager. In one or more embodiments, the object represented by the visible image of the patterned visible image layer can be the same as the object represented by the patterned infrared image layer.

FIG. 1 is a schematic cross-section view of one embodiment of an infrared reflector 10. The infrared reflector defines a plane 3. The reflector 10 includes an optical film 20 that has a first major surface 22 and a second major surface 24. The optical film 20 also includes one or more optical elements 30 disposed on the second major surface 24 of the optical film. In one or more embodiments, the optical elements 30 are adapted to reflect at least a portion of infrared radiation incident upon the first major surface 22 of the optical film 20 and transmitted through the optical film to the optical elements.

The infrared reflector 10 also includes a patterned visible image layer 40. In one or more embodiments, the patterned visible image layer 40 is disposed adjacent the first major surface 22 of the optical film 20. As used herein, the term“adjacent the first major surface” means that an element or component of the infrared reflector 10 is disposed closer to the first major surface 22 of the optical film 20 than to the second major surface 24 of such film. The patterned visible image layer 40 includes one or more reflective regions 42 that are reflective for visible radiation and one or more transmissive regions 44 that are transmissive for visible radiation. As used herein, the term“visible radiation” means

electromagnetic radiation having a wavelength of at least 350 nm and no greater than 750 nm. The infrared reflector 10 also includes a patterned infrared image layer 50. In one or more embodiments, either the patterned visible image layer 40 is disposed between the first major surface 22 of the optical film 20 and the patterned infrared image layer 50 or the patterned infrared image layer is disposed between the first major surface of the optical film and the patterned visible image layer. The patterned infrared image layer 50 includes one or more reflective regions 52 that are reflective for infrared radiation and one or more transmissive regions 54 that are transmissive for infrared radiation. As used herein, the term“infrared radiation” means electromagnetic radiation having a wavelength of at least 750 nm and no greater than 1 mm.

The infrared reflector 10 can be utilized in any suitable application. In one or more embodiments, the infrared reflector 10 can form a target for police and military training applications. For example, in one or more embodiments, the infrared reflector 10 can form a target that provides a visible image to an observer 2 as well as an infrared image to the observer that can be viewed through a thermal or infrared viewing device or imager, e.g., infrared binoculars, gun sights, etc. Further, in one or more embodiments, the infrared reflector 10 can be utilized to hide or camouflage an object such as a stationary object (e.g., building) or a moving object (e.g., truck or person).

In one or more embodiments, the infrared reflector 10 is adapted to use passive illumination to provide an infrared image to the observer. For example, the infrared reflector 10 can be adapted to reflect cold-sky radiation toward the observer to produce an infrared image that appears to have hot and cold regions. This passive illumination is in contrast to active illumination infrared reflectors such as some license plates that are adapted to utilize an infrared light source that is directed toward the reflector to provide an infrared image once illuminated. One or more embodiments of infrared reflectors described herein can provide an infrared image without the need for a separate infrared light source that is directed at the reflector.

The optical film 20 of the infrared reflector 10 can include any suitable optical film or films and have any suitable dimensions. Further, the optical film 20 can include any suitable material or materials, e.g., polymeric or inorganic materials. Suitable polymeric materials include polyethylene, polypropylene, inorganic particles, inorganic pigments, and combinations thereof.

The optical film 20 can include any suitable layer or layers disposed on one or more surfaces of the optical film. For example, in one or more embodiments, the first major surface 22 of the optical film 20 can include a structured surface that can be disposed on or in the first major surface using any suitable technique or techniques, e.g., embossing. Such structured surface can include any suitable pattern, including indicia, images, etc. In one or more embodiments, the first major surface 22 can include a matte surface or coating that can be disposed on the first major surface 22 using any suitable technique or techniques.

In one or more embodiments, the optical film 20 can be substantially transparent to visible radiation. Further, in one or more embodiments, the optical film 20 can be substantially transparent to infrared radiation. As used herein, the term“substantially transparent” means that the optical film 20 transmits at least 40%, at least 50%, or at least 80% of electromagnetic radiation having a particular wavelength or range of wavelengths in a selected range of wavelengths and that is incident upon the optical film and excludes reflections at the air-surface boundaries of the film. In one or more

embodiments, the optical film 20 is translucent to visible radiation. As used herein, the term“translucent” means that the optical film diffusely transmits visible radiation with any suitable amount of haze. In one or more embodiments, the optical film 20 can be substantially transparent for infrared radiation and substantially opaque for visible radiation. As used herein, the term“substantially opaque” means that the optical film 20 transmits no greater than 40% of visible radiation. In one or more embodiments, the optical film 20 is opaque for electromagnetic radiation having a wavelength or wavelengths in a range of 350-1100 nm. In one or more embodiments, the optical film 20 is substantially opaque for visible radiation as the optical film scatters or absorbs visible radiation. Further, in one or more embodiments, the optical film reflects no greater than 50%, 40%, 30%, or 20% of visible radiation incident upon the optical film. In one or more embodiments, the optical film 20 is viewable or visible using any suitable imager for incident electromagnetic radiation having a wavelength or wavelengths in a range of 1100 nm to 25 microns.

In one or more embodiments, the optical film 20 can include one or more materials disposed in a matrix that forms the film, where the one or more materials can be utilized to tailor one or both of the infrared and visible transmission values of the film. Any suitable materials can be utilized, e.g., metal flakes, inorganic pigments, metal-coated glass bubbles, etc.

The materials disposed in the optical film 20 can be uniformly distributed in a matrix that forms the total film or can be deposited in a gradient within the film top to bottom, or the materials can be deposited within the film in a distinct region and absent in the balance of the film.

Disposed on the second major surface 24 of the optical film 20 are optical elements 30. Although illustrated as being disposed on the second major surface 24, the optical elements 30 can be disposed on the first major surface 22 of the optical film 20, or on both the first and second major surfaces of the optical film.

The optical film 20 can include any suitable number of optical elements 30. Further, the optical elements 30 can include any suitable optical elements, e.g., cylindrical, spherical, rectangular, concave, convex, partially concave or convex, or faceted optical elements having any suitable dimensions. For example, FIG. 3 is a schematic cross-section view of another embodiment of an optical film 100. The optical film 100 includes one or more cube comer retroreflective optical elements 102. The cube comer retroreflective optical elements 102 can have any suitable dimensions and take any suitable shape or shapes. In one or more embodiments, the cube comer retroreflective optical elements 102 can be forward canted or backward canted as described, e.g., in U.S. Patent No. 5,565,151 (Nilsen) and U.S. Patent No. 4,588,258 (Hoopman).

In one or more embodiments, the optical elements 30 of optical film 20 can include hemispherical reflective optical elements. For example, FIG. 4 is a schematic cross-section view of another embodiment of an optical film 110. The optical film 110 includes one or more hemispherical reflective optical elements 112. The hemispherical reflective optical elements 112 can have any suitable dimensions and take any suitable shape or shapes.

In one or more embodiments, the optical elements 30 of the optical film 20 can include non- retroreflective optical elements. As used herein, the term“non-retroreflective” means that one or more optical elements are not capable of returning substantial quantities of incident electromagnetic radiation back towards its source. In one or more embodiments, the optical film 20 can be non-retroreflective for incident light having a wavelength or wavelengths in a range of 350-1100 nm.

Returning to FIG. 1, the optical elements 30 can include the same optical elements or one or more optical elements that are different from one or more additional optical elements. For example, in one or more embodiments, the optical elements 30 can include first optical elements and second optical elements, where the first optical elements are different from the second optical elements. In one or more embodiments, the first optical elements can include retroreflective optical elements and the second optical elements can include non-retroreflective optical elements. In one or more embodiments, the first optical elements can include cube comer retroreflective optical elements and the second optical elements can include hemispherical reflective optical elements.

The optical elements 30 can be disposed in any suitable arrangement on the second major surface 24 of the optical film 20. Further, the optical elements 30 can have any suitable dimensions and take any suitable shape or combination of shapes. For example, FIG. 2 is a schematic cross-section view of a portion of the infrared reflector 10 of FIG. 1. As shown in FIG. 2, at least one optical element 32 includes a facet 34 having a normal 36 that forms an angle 38 with a normal 26 to the first major surface 22 of the optical film 20. Angle 38 can be any suitable angle. In one or more embodiments, angle 38 can be greater than 0° and less than 60°. In one or more embodiments, angle 38 can be at least 10° and no greater than 30°. Facet 34 can take any suitable shape or combination of shapes. In one or more embodiments, facet 34 can extend along the plane 3 of the optical film 20 in a substantially horizontal direction (orthogonal the plane of FIG. 2) when the infrared reflector 10 is in a substantially vertical orientation.

The optical elements 30 can include any suitable material or materials, e.g., the same materials described herein regarding optical film 20. In one or more embodiments, the optical elements 30 include the same or different materials as those utilized to form the optical film 20.

The optical elements 30 can be disposed on the second major surface 24 of the optical film 20 using any suitable technique or techniques. In one or more embodiments, the optical elements 30 are integral with the optical film 20. For example, the optical elements 30 can be embossed into the second major surface 24 of the optical film 20. In one or more embodiments, the optical elements 30 are manufactured separately from the optical film 20 and connected to the second major surface 24 using any suitable technique or techniques. For example, the optical elements 30 can be attached to the second major surface 24 of the optical film using an adhesive. Further, for example, the optical elements 30 can be disposed on the second major surface 24 utilizing a cast-and-cure process. One or more of the optical elements 30 can be adapted to reflect at least a portion of infrared radiation incident upon the first major surface 22 of the optical film 20 and transmitted through the optical film to the optical elements. For example, electromagnetic radiation 4 is incident upon the first major surface 22 of the optical film 20 and is transmitted through the optical film until it is incident upon one or more of the optical elements 30. As illustrated in FIG. 2, at least a portion of the electromagnetic radiation 4 is reflected by facet 37 of the optical element 35. The reflected portion of electromagnetic radiation 4 is redirected through the first major surface 22 of the optical film 20 to the observer 2.

The optical elements 30 can be selected such that one or more of the optical elements direct incident electromagnetic radiation 4 at any suitable angle to be received by the observer 2. In one or more embodiments, one or more optical elements 30 can be selected to reflect infrared radiation in a direction that is substantially parallel to the normal 26 of the first major surface 22 of the optical film 20.

In one or more embodiments, electromagnetic radiation 4 can be representative of the cold sky 6 shown in FIGS. 1-2. Such reflected electromagnetic radiation 4 from the cold sky 6 will appear to the observer 2 utilizing a thermal imager or an infrared imager as a cold portion of the infrared reflector 10 as the cold sky will have a thermal image that is cooler than a thermal image of radiation that is directed upon the optical film 20 from the observer’s surroundings or through the infrared reflector 10 from a thermal surface disposed adjacent to the second major surface 24.

Disposed adjacent the first major surface 22 of the optical film 20 is the patterned visible image layer 40. The patterned visible image layer 40 can include one or more reflective regions 42 and one or more transmissive regions 44 for visible radiation. The reflective regions 42 can include a continuous region of material that is visible to the observer during normal light conditions. In one or more embodiments, one or more visible regions 42 can be formed as a grouping of discrete dots or portions such as an ink-jet printed image.

The patterned visible image layer 40 can have any suitable transmission value or values for visible radiation, e.g., greater than 0% and no greater than 100%. Further, the patterned visible image layer 40 can have any suitable transmission value for infrared radiation e.g., greater than 0% and no greater than 100%.

The patterned visible image layer 40 can include any suitable image or images as is further described herein. In one or more embodiments, the patterned visible image layer 40 can be disposed directly on the first major surface 22 of the optical film 20 using any suitable technique or techniques, e.g., ink-jet printing, gravure printing, thermal transfer, screen printing, and combinations thereof. In one or more embodiments, one or more additional layers can be disposed between the visible image layer 40 and the first major surface 22 of the optical film 20, e.g., one or more binder layers, tie layers, etc. For example, the patterned visible image layer 40 can be formed on a transparent substrate, and the substrate can be connected to the first major surface 22 using, e.g., an optical adhesive. Further, in one or more embodiments, a clear protective coating or primer coating can be disposed on the first major surface 22 of the optical film 20 between the first major surface and the visible image layer. The clear protective coating can include any suitable material or materials. In one or more embodiments, the clear protective coating can absorb infrared radiation. In one or more embodiments, the clear protective coating can be disposed over the visible image layer 40. Further, the first major surface 22 can be treated using any suitable technique prior to disposing the patterned visible image layer 40 on the first major surface, e.g., corona treatment.

In one or more embodiments, a white background layer that is IR translucent can be disposed between the visible image layer 40 and the first major surface 22 of the optical film 20. Such white background layer can enhance the viewability of the visible image layer 40 by reflecting light that is transmitted through the visible image layer 40 toward the optical film back through the visible image layer. Further, in one or more embodiments, an opaque layer (e.g., a black layer) that blocks both visible and infrared radiation can be disposed between the white background layer and the first major surface 22 of the substrate 20 to further enhance the viewability of the visible image layer.

The patterned visible image layer 40 can include any suitable material or materials. In one or more embodiments, the patterned visible image layer 40 includes one or more materials that are visible to the observer 2 without the aid of a thermal or infrared imager, e.g., inks, pigments, dyes, UV-cured inks, and combinations thereof. Further, the patterned visible image layer 40 can include one or more materials that have any suitable transmission values for infrared radiation. In one or more embodiments, the patterned visible image layer 40 can include one or more materials that are substantially transparent to infrared radiation such that infrared radiation reflected by the optical elements 30 is transmitted through the patterned visible image layer.

The infrared reflector 10 can also include the patterned infrared image layer 50 disposed in any suitable relationship relative to the first major surface 22 of the optical film 20 and the patterned visible image layer 40. The patterned infrared image layer 50 can include one or more reflective regions 52 and one or more transmissive regions 54 for infrared radiation. The reflective regions 52 can include a continuous region of material that is visible to the observer 2 utilizing a thermal or infrared imager. In one or more embodiments, one or more reflective regions 52 can be formed as a grouping of discrete dots or portions such as an ink-jet printed image.

The patterned infrared image layer 50 can have any suitable transmission value for infrared radiation, e.g., greater than 0% and less than 100%. Further, the patterned infrared image layer 50 can have any suitable transmission values for visible radiation.

The patterned infrared image layer 50 can be disposed in any suitable relationship relative to the patterned visible image layer 40. As shown in FIGS. 1-2, the patterned visible image layer 40 is disposed between the first major surface 22 of the optical film 20 and the patterned infrared image layer 50. In one or more embodiments, one or more portions of the patterned infrared image layer 50 can be disposed such that these portions are between the first major surface 22 of the optical film 20 and the one or more portions of patterned visible image layer 40. In one or more embodiments, one or more portions of the patterned infrared image layer 50 can be disposed on the first major surface 22 of the optical film 20. In one or more embodiments, one or more portions of the patterned infrared image layer 50 can be disposed on one or more portions of the patterned visible image layer 40. For example, in one or more

embodiments, at least one reflective region 53 of the pattern infrared image layer is disposed on at least one reflective region 43 of the pattern visible image layer 40. In one or more embodiments, one or more additional layers can be disposed between the patterned visible image layer 40 and the patterned infrared image layer 50, e.g., binder layers, tie layers, etc.

The patterned infrared image layer 50 can be disposed in any suitable pattern or patterns. In one or more embodiments, the patterned infrared image layer 50 is disposed such that it is in registration with the patterned visible image layer 40, i.e., the reflective regions 42 of the pattern visible image layer are registered with the reflective regions 52 of the pattern infrared image layer in a direction normal to the plane 3 of the infrared reflector.

The patterned infrared image layer 50 can include any suitable material or materials such that reflective regions 52 of the image layer are reflective for infrared radiation. For example, the patterned infrared image layer 50 can include one or more of UV-cured inks, carbon black in a polymer matrix, polyethylene terephthalate (PET), poly-methyl methacrylate (PMMA), and poly-vinyl chloride (PVC). In one or more embodiments, the properties of one or more reflective regions 52 can be chosen such that these reflective regions have varying transmission values for any suitable infrared wavelength or wavelengths. For example, the reflective region 53 can have a first reflectivity, and a second reflective region 55 can have a second reflectivity that is different from the first reflectivity. Such varying reflectivity of the reflective regions 52 can be provided using any suitable technique or techniques. For example, the reflective region 53 can include a first material that exhibits a first transmission value for infrared, and the second reflective region 55 can include a second transmission value for infrared. In one or more embodiments, one or more of the thickness, pigment concentration, particle diameter, and polymer composition of the one or more reflective regions 52 can be selected to provide a desired transmissivity of infrared radiation.

The transmissive regions 44, 54 of each of the patterned visible image layer 40 and the patterned infrared image layer 50 can be openings or gaps in the respective layers. In one or more embodiments, one or both of the visible image layer 40 and the patterned infrared image layer 50 can be a continuous layer that has reflective regions 42, 52 formed in the continuous layer, and the transmissive regions 44, 54 are portions of the continuous layers that are not reflective for visible and infrared radiation respectively. Further, in one or more embodiments, the patterned visible image layer 40 and the patterned infrared image layer 50 can be combined into a single layer that includes reflective and transmissive regions 42,

44 for visible radiation and reflective and transmissive regions 52, 54 for infrared radiation.

The patterned visible image layer 40 and the patterned infrared image layer 50 can be adapted such that a first portion 12 of the infrared reflector includes a first infrared reflectivity, and a second portion 14 of the infrared reflector includes a second infrared reflectivity. In one or more embodiments, the first infrared reflectivity is greater than the second infrared reflectivity. In one or more embodiments, the first infrared reflectivity is less than the second infrared reflectivity.

Any suitable technique or techniques can be utilized to provide the first and second portions 12, 14. For example, the first portion 12 can have a first density of coverage of infrared reflective regions 52 of the patterned infrared image layer 50, and the second portion 14 can have a second density of coverage of infrared reflective regions. As used herein, the term“density of coverage” refers to a percentage of the surface area of the first major surface 22 of the optical film 20 that is covered by the infrared reflective regions 52 from 0% (i.e., no coverage) to 100% (i.e., total coverage) of the surface area of the first major surface.

The patterned infrared reflective coating 60 is disposed on one or more of the optical elements 30. In one or more embodiments, the infrared reflective coating 60 can be disposed on all of the optical elements 30. In one or more embodiments, the infrared reflective coating 60 can be patterned such that it is disposed on fewer than all of the optical elements 30.

The infrared reflective coating 60 can be disposed in any suitable pattern on the one or more optical elements 30. For example, the reflective coating 60 can include a first reflective region 62 and a second reflective region 64. The coating 60 can also include one or more transmissive or uncoated regions 66 between the first and second reflective regions 62, 64. Electromagnetic radiation 8 is transmitted through the second major surface 24 and first major surface 22 where it can be observed by the observer 2. In one more embodiments, radiation 8 can include infrared radiation from objects adjacent the second major surface 24 of the infrared reflector 10 that is transmitted through the reflector to the observer 2. Such infrared radiation 8 can be detected by an infrared detector as a high infrared radiation region.

In one or more embodiments, the infrared reflective coating 60 can be disposed such that it is in registration with the transmissive regions 44, 54 of the patterned visible image layer 40 and the patterned infrared reflective layer 50 in a direction orthogonal to the plane 3 of the infrared reflector 10. In one or more embodiments where the reflective coating 60 is registered with the visible image layer 40, electromagnetic radiation from the cold sky 6 can be reflected by the reflective coating 60 and directed through the one or more transmissive regions 44 of the patterned visible image layer 40. In one or more embodiments, the reflective coating 60 can be patterned to be in registration with the patterned visible image layer 40 in a direction orthogonal to the plane 3 of the infrared reflector 10 such that at least a portion of radiation reflected by the reflective coating is transmitted through transmissive regions 44 of the patterned visible image layer.

The infrared reflective coating 60 can include any suitable material or materials. For example, the infrared reflective coating 60 can be opaque, or can be a metal such as silver, chromium, nickel, aluminum, titanium, aluminum-titanium alloy, gold, zirconium, platinum, palladium, aluminum- chromium alloy, rhodium, or combinations thereof.

The infrared reflector 10 can also include a backing layer 70 disposed over the optical elements 30 such that the optical elements are disposed between the backing layer and the optical film 20. In one or more embodiments, the backing layer 70 is disposed on one or more optical elements 30. The backing layer 70 can include any suitable material or materials. In one or more embodiments, the backing layer 70 includes any suitable adhesive that can be utilized to attach the infrared reflector to the substrate 80. The substrate 80 can include any suitable substrate, e.g., a stationary object or a moving object.

The patterned visible image layer 40 can form any suitable visual image. In one or more embodiments, the pattern visible image layer 40 can form a visible image of an object. Any suitable object can be imaged by the visible image layer 40. For example, FIG. 5 is a photograph of an image 200 of a truck 202. The image 200 can be acquired using any suitable technique or techniques, e.g., photography. The image 200 can be disposed adjacent the first major surface 22 of the optical film 20 as the visible image layer 40 using any suitable technique or techniques.

In one or more embodiments, the patterned visible image layer 40 can form a camouflage image that can be applied any suitable object such as a vehicle. For example, FIG. 7 is a photograph of one embodiment of a camouflage visible image layer 300. The camouflage visible image layer 300 can include any suitable pattern or patterns and can be formed using any suitable technique or techniques. The camouflage visible image layer 300 can be disposed adjacent the first major surface 22 of optical film 20 using any suitable technique or techniques.

As mentioned herein, patterned infrared image layer 50 can also include any suitable image. For example, FIG. 6 is an infrared photograph of the truck 202 of FIG. 5. Any suitable technique or techniques can be utilized to form the infrared image 204 of the truck 202. For example, in one or more embodiments, an infrared photograph of the truck 202 (or any suitable object) can be taken, and the infrared image of the truck can be disposed, e.g., on the second major surface 24 of the optical film 20, e.g., by inkjet printing the infrared image onto the optical film utilizing infrared reflective materials such that the infrared image is viewable by the observer 2 using any suitable thermal or infrared imager.

One or more reflective regions 52 of the patterned infrared image layer 50 can be utilized to form one or more portions of the image 204 that appear warm or hot when viewed with a thermal or infrared imager. For example, one or more reflective regions 52 can be provided to block electromagnetic radiation from the cold sky 6 that is reflected by optical elements 30 to provide hot region 206 of image 204. By blocking the electromagnetic radiation from the cold sky 6, the reflective region 52 can increase the apparent temperature of the region 206 such that it appears to be warm compared to region 208 of image 204. Region 208 can include transmissive regions 54 that are disposed to allow reflective cold-sky radiation 6 to be directed to the observer 2.

In one or more embodiments, the patterned infrared image layer 50 can form an infrared image of an object (e.g., infrared image 204 of truck 202 of FIG. 6), and the patterned visible image layer 40 can form a visible image of the same object (e.g., image 200 of truck 202 of FIG. 5). In one or more embodiments, such infrared image of the object can be in registration with the visible image of the object. In such embodiments, the infrared reflector 10 can provide a visible image and an infrared image of the same object such that the object is viewable both in the visible spectrum as well as in the infrared by the observer 2 using any suitable thermal or infrared imager.

In one or more embodiments of infrared reflectors (e.g., infrared reflector 10 of FIG. 1) that include a camouflage visible image layer 400, the patterned infrared image layer 50 can also include a camouflage image in the infrared. For example, FIG. 8 is a photograph of a camouflage patterned infrared image layer 302. Such reflector can include the camouflage patterned visible image layer 300 of FIG. 7 and the camouflage patterned infrared image layer 302 of FIG. 8. The reflector can provide camouflage to an object as viewed in the visible and also in the infrared as viewed through a thermal or infrared imager to obscure or hide the object associated with the reflector or to provide a decoy.

Any suitable technique or techniques can be utilized to form the various embodiments of infrared reflectors described herein. For example, FIG. 9 is a flowchart of one embodiment of a method 400 for forming an infrared reflector 10. Although described in reference to the infrared reflector 10 of FIGS. 1- 2, the method 400 can be utilized to form any suitable infrared reflector.

At 402, the patterned visible image layer 40 can be disposed adjacent the first major surface 22 of the optical film 20 using any suitable technique or techniques. As mentioned herein, the pattern visible image layer 40 can include any suitable number of reflective regions 42 disposed in any suitable pattern and any suitable number of transmissive regions 44 also disposed in any suitable pattern. In one or more embodiments, the patterned visible image layer 40 can be disposed on the first major surface 22 of the optical film 20.

The patterned infrared image layer 50 can be disposed either between the patterned visible image layer 40 and the first major surface 22 of the optical film 20 or such that the patterned visible image layer is between the patterned infrared image layer and the first major surface of the optical film using any suitable technique or techniques at 404. As also mentioned herein, the patterned infrared image layer 50 can include any suitable number of reflective and transmissive regions 52, 54 disposed in any suitable pattern or patterns.

At 406, the optical elements 30 can be disposed on the second major surface 24 of the optical film 20 using any suitable technique or techniques. Further, the patterned infrared reflective coating 70 can be disposed on one or more of the optical elements at 408 using any suitable technique or techniques.

All references and publications cited herein are expressly incorporated herein by reference in their entirety into this disclosure, except to the extent they may directly contradict this disclosure.

Illustrative embodiments of this disclosure are discussed and reference has been made to possible variations within the scope of this disclosure. These and other variations and modifications in the disclosure will be apparent to those skilled in the art without departing from the scope of the disclosure, and it should be understood that this disclosure is not limited to the illustrative embodiments set forth herein. Accordingly, the disclosure is to be limited only by the claims provided below.

Claims

What is claimed is:

1. An infrared reflector, comprising:

an optical film comprising a first major surface, a second major surface, and optical elements disposed on the second major surface, wherein the optical elements are adapted to reflect at least a portion of infrared radiation incident upon the first major surface of the optical film, wherein the optical film is opaque for visible radiation;

a patterned visible image layer comprising reflective and transmissive regions for visible radiation; and

a patterned infrared image layer comprising reflective and transmissive regions for infrared radiation;

wherein either the patterned visible image layer is disposed between the first major surface of the optical film and the patterned infrared image layer or the patterned infrared image layer is disposed between the first major surface of the optical film and the patterned visible image layer.

2. The infrared reflector of claim 1, wherein a first portion of the infrared reflector comprises a first infrared reflectivity and a second portion of the infrared reflector comprises a second infrared reflectivity that is less than the first infrared reflectivity.

3. The infrared reflector of claim 2, wherein the first portion comprises a first density of coverage of infrared reflective regions of the patterned infrared image layer and the second portion comprises a second density of coverage of infrared reflective regions of the patterned infrared image layer, wherein the first density is greater than the second density.

4. The infrared reflector of any one of claims 1-3, wherein the optical elements comprise retroreflective optical elements.

5. The infrared reflector of claim 4, wherein the retroreflective optical elements comprise cube corner retroreflective optical elements.

6. The infrared reflector of any one of claims 1-3, wherein the optical elements comprise hemispherical reflective optical elements.

7. The infrared reflector of any one of claims 1-6, wherein the optical film is substantially transparent for infrared radiation.

8. The infrared reflector of any one of claims 1-7, further comprising a patterned infrared reflective coating disposed on one or more optical elements of the optical film.

9. The infrared reflector of any one of claims 1-8, further comprising a backing layer disposed over the optical elements such that the optical elements are disposed between the backing layer and the optical film.

10. The infrared reflector of any one of claims 1-9, wherein the optical elements are integral with the optical film.

11. The infrared reflector of any one of claims 1-10, wherein the patterned visible image layer is in registration with the patterned infrared image layer.

12. The infrared reflector of any one of claims 1-11, wherein the patterned visible image layer forms a camouflage image.

13. The infrared reflector of claim 12, wherein the patterned infrared image layer forms an infrared image of an object.

14. The infrared reflector of any one of claims 1-11, wherein the patterned infrared image layer forms an infrared image of an object and the patterned visible image layer forms a visible image of the object, wherein the infrared image of the object is in registration with the visible image of the object.

15. The infrared reflector of any one of claims 1-14, wherein the patterned visible image layer is disposed between the first major surface of the optical film and the patterned infrared image layer.

16. The infrared reflector of any one of claims 1-14, wherein the patterned infrared image layer is disposed between the first major surface of the optical film and the patterned visible image layer.

17. The infrared reflector of any one of claims 1-16, wherein the optical elements are adapted to reflect at least a portion of infrared radiation having a wavelength of at least 1100 nm and no greater than 25 microns that is incident upon the first major surface of the optical film.