EP4710370A1

EP4710370A1 - Wavelength-selective multilayer articles and solar arrays including the same

Info

Publication number: EP4710370A1
Application number: EP24720311.0A
Authority: EP
Inventors: Sean M. SWEETNAM; David J. Rowe; Daniel M. Pierpont; Andrew C. Smith; James A. Phipps; Kevin D. HAGEN; William B. Black; Timothy J. Hebrink
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2023-05-12
Filing date: 2024-04-09
Publication date: 2026-03-18
Also published as: CN121153358A; WO2024236377A1

Abstract

Wavelength-selective multilayer articles are provided, including a polymeric multilayer optical film and an inorganic multilayer optical film. The polymeric multilayer optical film reflects normally incident light over at least a 30-nanometer wavelength reflection bandwidth in a wavelength range from 800 nanometers (nm) to 1200 nm, 1200 nm to 1600 nm, or 800 nm to 1600 nm. The inorganic multilayer optical film reflects and absorbs normally incident light over at least a 30-nanometer wavelength bandwidth in a wavelength range from 190 nm to 400 nm. Solar arrays including wavelength-selective multilayer articles are also provided.

Description

WAVELENGTH-SELECTIVE MULTILAYER ARTICLES AND SOLAR ARRAYS INCLUDING THE SAME

BACKGROUND

[0001] Photovoltaic ("PV") panels, otherwise referred to as solar arrays or arrays of solar cells, are commonly used to generate power by converting incident light energy from the Sun into electric current. Solar cells are most frequently constructed by laminating the electrical components between two sheets of silicate glass, with the volume between the glass sheets being filled with an encapsulant material, which is often a polymeric matrix. In addition, because solar cells are typically designed to strongly absorb as much light energy as possible, the materials used in construction are often dark or black in color. These factors combined lead to a solar cell that quite readily absorbs large amounts of heat energy from the incident radiation, and which is durability -limited by the polymeric encapsulant, due to its tendency to chemically degrade under exposure to intense ultraviolet (UV) radiation and high thermal loads, and the solar cell itself, whose degradation rate is increased at higher temperatures. In addition, the efficiency of solar cells is reduced at elevated temperatures.

[0002] In some cases, solar arrays operate at altitudes ranging from 20-2000 km, where the thin atmosphere absorbs little solar radiation. High-altitude devices are thus exposed to a more intense solar spectrum and to a higher intensity of UV radiation, particularly UV-C radiation, than is present in the AMI.5 solar spectrum encountered in Earth terrestrial conditions. Further, the above-mentioned issues are intensified in the outer space environment where the amount of infrared (IR) and UV light is increased due to the absence of shielding provided by the earth’s atmosphere.

SUMMARY

[0003] In a first aspect, a wavelength-selective multilayer article is provided. The wavelength-selective multilayer article comprises a polymeric multilayer optical film having a first major surface and an opposing second major surface. The polymeric multilayer optical fdm comprises one or more alternating first and second polymeric optical layers collectively reflecting light that is normally incident to a first major surface of the wavelength-selective multilayer article, an average of at least 50, 60, 70, 80, 90, or 95 percent of incident light over at least a 30-nanometer wavelength reflection bandwidth in a wavelength range from 800 nanometers (nm) to 1200 nm, 1200 nm to 1600 nm, or 800 nm to 1600 nm. The wavelength-selective multilayer article also comprises an inorganic multilayer optical film having a first major surface and an opposing second major surface, wherein the second major surface of the inorganic multilayer optical film is attached to the first major surface of the polymeric multilayer optical film. The inorganic multilayer optical film comprises one or more alternating first and second inorganic optical layers collectively reflecting and absorbing light that is normally incident to the first major surface of the wavelength-selective multilayer article, an average of at least 50, 60, 70, 80, 90, or 95 percent of incident ultraviolet light over at least a 30-nanometer wavelength bandwidth in a wavelength range from 190 nm to 400 nm.

[0004] In a second aspect, a solar array is provided. The solar array comprises a wavelength-selective multilayer article according to the first aspect disposed on an exterior surface of the solar array. [0005] By combining the inorganic and polymeric multilayer optical films, the resultant article advantageously tends to have high transmission in the visible and near-IR wavelength regimes, while having low transmission in the UV and longer-wavelength IR regimes. In addition, at least certain embodiments of the wavelength-selective multilayer article exhibit advantageously low transmission rates for water vapor, oxygen, and/or other atmospheric gasses. These benefits, in turn, extend the lifetime of the PV cell, as such contaminants can cause corrosion and degradation to the electronics and encapsulants inside the PV cell. Another advantage of exemplary embodiments of the present disclosure is that the wavelength-selective multilayer article experiences both reduced temperature increases upon exposure to incident light wavelengths and slowed degradation, which tends to increase PV cell performance. Additionally, the optional use of a structured film improves light capture of the article by minimizing light loss due to reflection, as compared to a planar film. The inorganic and/or barrier layers can be sputter deposited or evaporated in a roll-to-roll process. The polymeric multilayer optical films can be coextruded. As such, a further advantage of exemplary embodiments is to enable a high speed, roll-to- roll continuous production process for the wavelength-selective multilayer article of the present disclosure.

[0006] Various aspects and advantages of exemplary embodiments of the disclosure have been summarized. The above Summary is not intended to describe each illustrated embodiment or every implementation of the present certain exemplary embodiments of the present disclosure. The Drawings and the Detailed Description that follow more particularly exemplify certain preferred embodiments using the principles disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The disclosure may be more completely understood in consideration of the following detailed description of various embodiments of the disclosure in connection with the accompanying figures, in which:

[0008] FIG. 1 A a schematic cross-sectional view of an exemplary wavelength-selective multilayer article 10 and an exemplary solar array 40, according to various exemplary embodiments disclosed herein; [0009] FIG. IB a schematic cross-sectional view of another exemplary wavelength-selective multilayer article 10 and another exemplary solar array 40, according to various exemplary embodiments disclosed herein;

[0010] FIG. 1C is a schematic cross-sectional view of a barrier layer for use in exemplary articles disclosed herein; [0011] FIG. 2A is a perspective view of a Cartesian coordinate system of a surface that can be utilized to describe various surfaces of multilayer articles;

[0012] FIG. 2B is a schematic cross-sectional view of a structured film for use in exemplary articles disclosed herein;

[0013] FIG. 2C is a schematic cross-sectional view of a portion of an exemplary wavelength-selective multilayer article according to various exemplary embodiments disclosed herein;

[0014] FIG. 2D is a scanning electron microscopy (SEM) image of a cross-section of a portion of an exemplary wavelength-selective multilayer article 10, according to various exemplary embodiments disclosed herein;

[0015] FIG. 3 is a perspective view of a structured surface comprising a linear array of prisms;

[0016] FIG. 4A is a perspective view of a structured surface comprising an array of cube comer elements;

[0017] FIG. 4B is a perspective view of a structured surface comprising an array of pyramid elements; [0018] FIG. 5 is a perspective view of a structured surface comprising an array of cones;

[0019] FIG. 6 is a perspective view of a structured surface comprising a diffraction grating having a bias angle;

[0020] FIG. 7 is a perspective view of a structured surface comprising an array of inverted pyramids. [0021] In the drawings, like reference numerals indicate like elements. While the above-identified drawings, which may not be drawn to scale, set forth various embodiments of the present disclosure, other embodiments are also contemplated, as noted in the Detailed Description. In all cases, this disclosure describes the presently disclosed disclosure by way of representation of exemplary embodiments and not by express limitations. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of this disclosure.

DETAILED DESCRIPTION

[0022] For the following Glossary of defined terms, these definitions shall be applied for the entire application, unless a different definition is provided in the claims or elsewhere in the specification.

Glossary

[0023] Certain terms are used throughout the description and the claims that, while for the most part are well known, may require some explanation. It should be understood that:

[0024] The term “fluoropolymer” refers to any organic polymer containing fluorine.

[0025] The term “nonfluorinated” means not containing fluorine.

[0026] The terms “(co)polymer” or “(co)polymers” includes homo(co)polymers and (co)polymers, as well as homo(co)polymers or (co)polymers that may be formed in a miscible blend, (e.g., by coextrusion or by reaction, including, (e.g., transesterification)). The term “(co)polymer” includes random, block and star (co)polymers. [0027] As used herein, “adjacent” encompasses both in direct contact (e.g., directly adjacent) and having one or more intermediate layers present between the adjacent materials.

[0028] As used herein, “attached” encompasses both directly attached and having being attached via one or more intermediate layers present between the attached materials.

[0029] As used herein, “incident” with respect to light refers to the light falling on or striking a material. [0030] The term “crosslinked” (co)polymer refers to a (co)polymer whose (co)polymer chains are joined together by covalent chemical bonds, usually via crosslinking molecules or groups, to form a network (co)polymer. A crosslinked (co)polymer is generally characterized by insolubility but may be swellable in the presence of an appropriate solvent.

[0031] The term “cure” refers to a process that causes a chemical change, (e.g., a reaction that creates a covalent bond to solidify a multilayer film layer or increase its viscosity.

[0032] The term “cured (co)polymer” includes both crosslinked and uncrosslinked (co)polymers.

[0033] The term “metal” includes a pure metal or a metal alloy.

[0034] The term “film” or “layer” refers to a single stratum within a multilayer film.

[0035] The term “substrate” encompasses films and layers, including structured films/layers.

[0036] The term “(methjacryl” or “(methjacrylate” with respect to a monomer, oligomer, (co)polymer or compound means a vinyl-functional alkyl ester formed as the reaction product of an alcohol with an acrylic or a methacrylic acid.

[0037] The term “optically clear” refers to an article in which there is no visibly noticeable distortion, haze or flaws as detected by the naked eye at a distance of about 1 meter, preferably about 0.5 meters. [0038] The term “optical thickness” when used with respect to a layer refers to the physical thickness of the layer times its in-plane index of refraction.

[0039] The term “vapor coating” or “vapor depositing” means applying a coating to a substrate surface from a vapor phase, for example, by evaporating and subsequently depositing onto the substrate surface a precursor material to the coating or the coating material itself. Exemplary vapor coating processes include, for example, physical vapor deposition (PVD), chemical vapor deposition (CVD), and combinations thereof.

[0040] By using the term “overlaying” or “overcoated” to describe the position of a layer with respect to a different layer of an article of the present disclosure, we refer to the layer as being atop the different layer, but not necessarily contiguous to or in contact with the different layer, although the layer may, in some embodiments, be in direct contact with the other layer.

[0041] By using terms of orientation such as “atop”, “on”, “over,” “covering”, “uppermost”, “underlying” and the like for the location of various elements in the disclosed coated articles, we refer to the relative position of an element with respect to a horizontally -disposed, upwardly -facing substrate. However, unless otherwise indicated, it is not intended that the substrate or articles should have any particular orientation in space during or after manufacture, or in interpreting the claims.

[0042] As used herein, “radiation” refers to electromagnetic radiation unless otherwise specified. [0043] As used herein, “refracting” with respect to a wavelength of light refers to causing the light to change direction when it enters a material.

[0044] As used herein, “scattering” with respect to wavelengths of light refers to causing the light to depart from a straight path and travel in different directions with different intensities.

[0045] As used herein, “reflectance” is the measure of the proportion of tight or other radiation striking a surface at normal incidence which is reflected off it. Reflectivity typically varies with wavelength and is reported as the percent of incident light that is reflected from a surface (0 percent - no reflected light, 100 - all tight reflected). Reflectivity and reflectance are used interchangeably herein.

[0046] As used herein, “reflective” and “reflectivity” refer to the property of reflecting light or radiation, especially reflectance as measured independently of the thickness of a material.

[0047] As used herein, “average reflectance” refers to reflectance averaged over a specified wavelength range.

[0048] As used herein, “absorption” refers to a material converting the energy of light radiation to internal energy.

[0049] As used herein, “absorb” with respect to wavelengths of light encompasses both absorption and scattering, as scattered tight also eventually gets absorbed. Absorbance can be measured with methods described in ASTM E903-12 “Standard Test Method for Solar Absorptance, Reflectance, and Transmittance of Materials Using Integrating Spheres”. Absorbance measurements described herein were made by making transmission measurements as previously described and then calculating absorbance using Equation 1.

[0050] As used herein, the term “absorbance” with respect to a quantitative measurement refers to the base 10 logarithm of a ratio of incident radiant power to transmitted radiant power through a material. The ratio may be described as the radiant flux received by the material divided by the radiant flux transmitted by the material. Absorbance (A) may be calculated based on internal transmittance (T) according to Equation 1 :

A = -log₁₀ T (1)

[0051] Emissivity can be measured using infrared imaging radiometers with methods described in ASTM E1933-14 (2018) “Standard Practice for Measuring and Compensating for Emissivity Using Infrared Imaging Radiometers.” According to Kirchhoff’s law of thermal radiation, absorbance correlates with emittance. Absorbance, absorptivity, emissivity, and emittance are used interchangeably herein for the same purpose of emitting infrared energy to the atmosphere. Absorb and emit are also used interchangeably herein.

[0052] As used herein, the terms “transmittance” and “transmission” refer to the ratio of total transmission of a layer of a material compared to that received by the material, which may account for the effects of absorption, scattering, reflection, etc. Transmittance (T) may range from 0 to 1 or be expressed as a percentage (T%).

[0053] As used herein, “transparent” refers to a material (e.g., film or layer) that absorbs less than 20% of light having wavelengths between 350 nm and 2500 nm. [0054] As used herein, “bandwidth” refers to a width of a contiguous band of wavelengths.

[0055] As used herein, the term “flexible” refers to being capable of being bent around a roll core with a radius of curvature of up to 7.6 centimeters (cm) (3 inches), in some embodiments up to 6.4 cm (2.5 inches), 5 cm (2 inches), 3.8 cm (1.5 inch), or 2.5 cm (1 inch). In some embodiments, the flexible assembly can be bent around a radius of curvature of at least 0.635 cm (! inch), 1.3 cm (!/₂ inch) or 1.9 cm (% inch).

[0056] The terms “about” or “approximately” with reference to a numerical value or a shape means +/- five percent of the numerical value or property or characteristic, but expressly includes the exact numerical value.

[0057] The term “substantially” with reference to a property or characteristic means that the property or characteristic is exhibited to a greater extent than the opposite of that property or characteristic is exhibited. For example, a substrate that is “substantially” transparent refers to a substrate that transmits more radiation (e.g., visible light) than it fails to transmit (e.g., absorbs and reflects). Thus, a substrate that transmits more than 50% of the visible light incident upon its surface is substantially transparent, but a substrate that transmits 50% or less of the visible light incident upon its surface is not substantially transparent.

[0058] As used in this specification and the appended embodiments, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. Thus, for example, reference “a compound” includes a mixture of two or more compounds. As used in this specification and the appended embodiments, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

[0059] Unless otherwise indicated, all numbers expressing quantities or ingredients, measurement of properties and so forth used in the specification and embodiments are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached listing of embodiments can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings of the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claimed embodiments, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0060] By definition, the total weight percentages of all ingredients in a composition equals 100 weight percent.

[0061] Various exemplary embodiments of the disclosure will now be described. Exemplary embodiments of the present disclosure may take on various modifications and alterations without departing from the spirit and scope of the present disclosure. Accordingly, it is to be understood that the embodiments of the present disclosure are not to be limited to the following described exemplary embodiments but is to be controlled by the limitations set forth in the claims and any equivalents thereof. Wavelength-Selective Multilayer Article

[0062] In a first aspect, a wavelength-selective multilayer article is provided. The wavelength-selective multilayer article comprises:

[0063] a polymeric multilayer optical film having a first major surface and an opposing second major surface, wherein the polymeric multilayer optical film comprises one or more alternating first and second polymeric optical layers collectively reflecting light that is normally incident to a first major surface of the wavelength-selective multilayer article, an average of at least 50, 60, 70, 80, 90, or 95 percent of incident light over at least a 30 -nanometer wavelength reflection bandwidth in a wavelength range from 800 nanometers (nm) to 1200 nm, 1200 nm to 1600 nm, or 800 nm to 1600 nm; and

[0064] an inorganic multilayer optical film having a first major surface and an opposing second major surface, wherein the second major surface of the inorganic multilayer optical film is attached to the first major surface of the polymeric multilayer optical film, wherein the inorganic multilayer optical film comprises one or more alternating first and second inorganic optical layers collectively reflecting and absorbing light that is normally incident to the first major surface of the wavelength-selective multilayer article, an average of at least 50, 60, 70, 80, 90, or 95 percent of incident ultraviolet light over at least a 30-nanometer wavelength bandwidth in a wavelength range from 190 nm to 400 nm.

[0065] Referring to FIG. 1 A, the present disclosure describes wavelength-selective multilayer articles 10 including a polymeric multilayer optical film 20 and an inorganic multilayer optical film 30. The polymeric multilayer optical film 20 comprises one or more alternating first polymeric optical layers 23 (A-N) and second polymeric optical layers 22 (A-N) collectively reflecting light that is normally incident to a first major surface 16 of the wavelength-selective multilayer article 10, an average of at least 50, 60, 70, 80, 90, or 95 percent of incident light over at least a 30-nanometer wavelength reflection bandwidth in a wavelength range from 800 nm to 1200 nm, 1200 nm to 1600 nm, or 800 nm to 1600 nm. It is to be understood that the wavelength-selective multilayer article 10 is configured/oriented that light is incident to the side of the article 10 including the first major surface 36 of the inorganic multilayer optical film. Any light source may be suitable, such as the depicted light source L that is the Sun.

[0066] The polymeric multilayer optical fdm 20 has a first major surface 26 and an opposing second major surface 28. The inorganic multilayer optical film 30 has a first major surface 36 and an opposing second major surface 38, wherein the second major surface 38 of the inorganic multilayer optical film 30 is attached to the first major surface 26 of the polymeric multilayer optical film 20. In the embodiment shown in FIG. 1 A, the polymeric multilayer optical film 20 is not directly attached to the inorganic multilayer optical film 30, but rather two optional components, a structured film 50 and an intermediate layer 60, are depicted as located between the two multilayer optical films. The (optional) structured film 50 comprises a first major surface 56 and an opposing second major surface 58, wherein the first major surface 56 comprises a plurality of structures projecting therefrom. It is noted that for simplicity in this figure, the schematic depiction of the various features does not show any structures. Suitable structured films are described in detail below. In this configuration, typically the structured film 50 is a microstructured film. The (optional) intermediate layer 60 is disposed between the second major surface 38 of the inorganic multilayer optical film 30 and the first major surface 26 of the polymeric multilayer optical film 20. Suitable intermediate layers 60 include for instance and without limitation, tie layers, barrier layers, or any combination thereof. As such, the intermediate layer 60 as depicted in FIG. 1 A may represent any number of intermediate layers in that location of the overall structure. In certain embodiments, the intermediate layer 60 is a barrier layer. Suitable barrier layers are described in detail below.

[0067] Referring to FIG. IB, the present disclosure describes additional wavelength-selective multilayer articles 10 including a polymeric multilayer optical film 20 and an inorganic multilayer optical film 30, as well as a solar array 40 including the multilayer articles 10. The embodiment depicted in FIG. IB differs from the embodiment depicted in FIG. 1A primarily in the location of the structured film 50. In FIG. IB, the optional structured film 50 is disposed adjacent to the second major surface 28 of the polymeric multilayer optical film 20, which is opposite the inorganic multilayer optical film 30. In this configuration, typically the structured film 50 is a macrostructured film. Suitable macrostructured films may be prepared using thermoforming or embossing, for instance as described in detail in PCT Publication No. WO 2014/035778 (Hebrink et al.), U.S. Patent No. 6,788,463 (Merrill et al.), or U.S. Patent No. 6,096,247 (Strobel et al.), each of which is incorporated herein by reference in their entireties. Considering both FIGS. 1 A and IB, a structured film 50 is optionally disposed either: a) between the first major surface 26 of the polymeric multilayer optical film 20 and the second major surface 38 of the inorganic multilayer optical film 30 orb) adjacent to the second major surface 28 of the polymeric multilayer optical film 20 opposite the inorganic multilayer optical film 30. When a macro structured film 50 is present adjacent to the second major surface 28 of the polymeric multilayer optical film 20, the polymeric multilayer optical film 20, overlaying the macrostructured film 50, will also be macrostructured.

[0068] With reference to FIG. 2A, a multilayered article can be characterized in three-dimensional space by superimposing a Cartesian coordinate system onto its structure. A first reference plane 224 is centered between major surfaces 212 and 214. First reference plane 224, referred to as the y-z plane, has the x- axis as its normal vector. A second reference plane 226, referred to as the x-y plane, extends substantially coplanar with surface 216 and has the z-axis as its normal vector. A third reference plane 228, referred to as the x-z plane, is centered between first end surface 220 and second end surface 222 and has the y-axis as its normal vector.

[0069] In some embodiments, the multilayered article includes a structured film and the structured surfaces of the film are three-dimensional on a macroscale. However, on a microscale (e.g., surface area that includes at least two adjacent structures with a valley or channel disposed between the structures) the base layer/base member can be considered planar with respect to the structures. The width and length of the structures are in the x-y plane and the height of the structures is in the z-direction. Further, the base layer is parallel to the x-y plane and orthogonal to the z-plane. Structured films are described in detail below.

[0070] Referring again to FIG. 2A, by “light normally incident to the first major surface of the multilayer article” is meant light that strikes the first major surface 216 of the multilayer article orthogonal to the reference plane 226 (and parallel to the reference plane 224). When the multilayer article includes a structured film, the multilayer article is oriented such that light strikes the first major surface comprising a plurality of structures projecting therefrom (instead of striking the opposing second major surface of the structured film).

Polymeric Multilayer Optical Films

[0071] Referring again to FIG. 1A, the wavelength-selective multilayer article 10 includes a polymeric multilayer optical film 20 comprising one or more alternating first polymeric optical layers 23 (A-N) and second polymeric optical layers 22 (A-N) as described further below.

[0072] Typically, the polymeric multilayer optical film has a thickness of 2.0 micrometers or greater, 10 micrometers, 20 micrometers, 30 micrometers, 40 micrometers, 50 micrometers, 60 micrometers, 70 micrometers, 80 micrometers, 90 micrometers, or 100 micrometers or greater; and 1000 micrometers or less, 950 micrometers, 900 micrometers, 850 micrometers, 800 micrometers, 750 micrometers, 700 micrometers, 650 micrometers, 600 micrometers, 550 micrometers, 500 micrometers, 450 micrometers, 400 micrometers, 350 micrometers, or 300 micrometers or less, such as a thickness of 2 micrometers to 1000 micrometers or 50 micrometers to 600 micrometers.

[0073] As noted above, the plurality of alternating first and second polymeric optical layers collectively reflect light that is normally incident to a first major surface of the wavelength-selective multilayer article, an average of at least 50, 60, 70, 80, 90, or 95 percent of incident light over at least a 30- nano meter wavelength reflection bandwidth in a wavelength range from 800 nm to 1200 nm, 1200 nm to 1600 nm, or 800 nm to 1600 nm. In some cases, light is reflected over a greater wavelength reflection bandwidth than at least 30-nanometer, for instance at least a 50-nanometer, 75-nanometer, 100- nanometer, 125 -nanometer, 150-nanometer, or 175-nanometer wavelength reflection bandwidth in the abovementioned wavelength ranges.

[0074] The use of multilayer reflective films comprising alternating layers of two or more polymers to reflect light is known and is described, for example, in U.S. Pat. No. 3,711,176 (Alfrey, Jr. et al.), U.S. Pat. No. 5,103,337 (Schrenk et al.), WO 96/19347 (Jonza et al.), and WO 95/17303 (Ouderkirk et al.). The reflection and transmission spectra of a particular multilayer film depends primarily on the optical thickness of the individual layers, which is defined as the product of the actual thickness of a layer times its refractive index. Accordingly, films can be designed to reflect infrared, visible, or ultraviolet wavelengths '/.\i of light by choice of the appropriate optical thickness of the layers in accordance with the following formula: [0076] wherein M is an integer representing the particular order of the reflected light and D_r is the optical thickness of an optical repeating unit (also called a multilayer stack) comprising two or more polymeric layers. Accordingly, D_r is the sum of the optical thicknesses of the individual polymer layers that make up the optical repeating unit. D_r is always one half lambda (X) in thickness, where lambda is the wavelength of the first order reflection peak. By varying the optical thickness of an optical repeating unit along the thickness of the multilayer film, a multilayer film can be designed that reflects light over a broad band of wavelengths. This band is commonly referred to as the reflection band or stop band. In some embodiments, a reflection band has a sharp spectral edge at the long wavelength (red) and/or short wavelength (blue) side. It may be desirable to design a reflective film or other optical body that reflects light over a selected range in the visible region of the spectrum, e.g., a reflective film that reflects only green light. In such a case, it may be desirable to have sharp edges at both the red and blue sides of the reflection band. Multilayer optical films exhibiting sharpened reflective bandedge(s) are described in detail, for instance, in U.S. Patent No. 6,967,778 (Wheatley et al.), incorporated herein by reference in its entirety.

[0077] In some embodiments, polymeric multilayer optical films described herein can be made using the general processing techniques, such as those described in U.S. Pat. No 6,783,349 (Neavin et al.), the disclosure of which is incorporated herein by reference. Desirable techniques for providing a polymeric multilayer optical film with a controlled spectrum may include, for example, 1) the use of an axial rod heater control of the layer thickness values of coextruded polymer layers as described, for example, in U.S. Pat. No. 6,783,349 (Neavin et al.); 2) timely layer thickness profile feedback during production from a layer thickness measurement tool such as, for example, an atomic force microscope (AFM), a transmission electron microscope, or a scanning electron microscope; 3) optical modeling to generate the desired layer thickness profile; and 4) repeating axial rod adjustments based on the difference between the measured layer profile and the desired layer profile.

[0078] In one embodiment, an optical polymer film or a layered optical polymer film having a first and second major surface is provided. “Film” is used to refer to planar forms of plastic that are thick enough to be self-supporting but thin enough to be flexed, folded, conformed or creased without cracking. Film thickness depends upon desired applications and manufacturing methods.

[0079] “Optical Film” is used herein to refer to any reflective or partially reflective polymer film designed to exhibit desired reflection, transmission, absorption, or refraction of light upon exposure to a specific band of wavelengths of electromagnetic energy. Thus, conventional normally transparent polymeric films, such as polyester and polypropylene, are not considered “optical films” for the purposes of the present disclosure, even though such films may exhibit some degree of reflectance, or glare, when viewed from some angles. Films that exhibit both reflective and transmissive properties, however, such as those that are partially transmissive, are considered within the scope of this disclosure. Preferred optical polymer films generally absorb less than 25 percent of the radiant energy that impacts the film’s surface. Preferably, the radiating energy absorbed is less than 10 percent and most preferably less than 5 percent. The radiant energy, typically expressed as the energy in a range of wavelengths, may be reflected either specularly or diffusely. The reflectance may be isotropic, i.e., the film has the same reflective properties along both in-plane axes, or may be anisotropic, i.e., the film has different reflective properties along the orthogonal in-plane axes. The difference in reflective properties along the in-plane axes can be varied by controlling the relationship between the indices of refraction along each axis for each of the component materials.

[0080] Optical films come in a variety of forms and are selected according to a desired application. Some suitable examples include multilayer polarizers, visible and infrared mirrors, and color films such as those described in Patent Publications WO 95/17303, WO 96/19347, and WO 97/01440; U.S. Pat. No. 6,045,894 (Jonza et al.) U.S. Pat. No. 6,531,230 (Weber et al.); U.S. Pat. No. 5,103,337 (Schrenk et al.), U.S. Pat. No. 5,122,905 (Wheatley et al.), U.S. Pat. No. 5,122,906 (Wheatley), U.S. Pat. No. 5,126,880 (Wheatley et al.), U.S. Pat. No. 5,217,794 (Schrenk), U.S. Pat. No. 5,233,465 (Schrenk et al.), U.S. Pat. No. 5,262,894 (Wheatley et al.), U.S. Pat. No. 5,278,694 (Wheatley et al.), U.S. Pat. No. 5,339,198 (Wheatley et al.), U.S. Pat. No. 5,360,659 (Arends et al.), U.S. Pat. No. 5,448,404 (Schrenk et al.), U.S. Pat. No. 5,486,949 (Schrenk et al.) U.S. Pat. No. 4,162,343 (Wilcox et al.), U.S. Pat. No. 5,089,318 (Shetty et al.), U.S. Pat. No. 5,154,765 (Armanini), and U.S. Pat. No. 3,711,176 (Alfrey, Jr. et al.); and Reissued U.S. Pat. No. RE 31,780 (Cooper et al.) and U.S. Pat. No. RE 34,605 (Schrenk et al.), all contents of which are incorporated herein by reference.

[0081] Examples of optical films comprising immiscible blends of two or more polymeric materials include blend constmctions wherein the reflective and transmissive properties are obtained from the presence of discontinuous polymeric regions having a cross-sectional diameter perpendicular to the major axis that is on the order of a fraction of the distance corresponding to a wavelength of light, and may also obtain the desired optical properties through orientation, such as the blend mirrors and polarizers as described in Patent Publications WO 97/32224 (Ouderkirk et al.), U.S. Pat. No. 6,179,948 (Merrill et al.), and U.S. Pat. No. 5,751,388 (Larson), the contents of which are all herein incorporated by reference. [0082] In some embodiments, the polymeric optical layers of the first multilayer optical film comprise a fluoropolymer, a polyethylene terephthalate (PET), a polymethyl methacrylate (PMMA), a polypropylene (PP) copolymer, a polyethylene (PE) copolymer, a copolymer of ethyl acrylate and methyl methacrylate (CoPMMA), a blend of PMMA and polyvinylidene fluoride (PVDF), an acrylate copolymer, a polyurethane, a polyethylene naphthalate (PEN), or combinations thereof.

[0083] When the first multilayer optical film comprises a fluoropolymer, the polymeric optical layers preferably comprise a fluoropolymer independently selected from the group consisting of a copolymer of tetrafluoroethylene (TFE), hexafluoropropylene (HFP), and vinylidene fluoride; a copolymer of TFE, HFP, vinylidene fluoride, and perfluoropropyl vinyl ether (PPVE); a polyvinylidene fluoride (PVDF); an ethylene chlorotrifluoroethylene (ECTFE) polymer; an ethylene tetrafluoroethylene (ETFE); a perfluoroalkoxy alkane (PF A) polymer; a fluorinated ethylene propylene (FEP) polymer; a polytetrafluoroethylene (PTFE); a copolymer of TFE, HFP, and ethylene; a polyvinyl fluoride (PVF); and combinations thereof. [0084] Referring back to FIG. 1 A, the polymeric multilayer optical film 20 includes a multilayer optical stack having alternating layers 22, 23 of at least two materials, typically comprising different polymers. An in-plane index of refraction nl in one in-plane direction of high refractive index layer 23 is higher than the in-plane index of refraction n2 of low refractive index layer 22 in the same in-plane direction. The difference in refractive index at each boundary between layers 22, 23 causes part of the incident light to be reflected. The transmission and reflection characteristics of the polymeric multilayer optical film 20 is based on coherent interference of light caused by the refractive index difference between layers 22, 23 and the thicknesses of layers 22, 23. When the effective indices of refraction (or in-plane indices of refraction for normal incidence) differ between layers 22, 23, the interface between adjacent layers 22, 23 forms a reflecting surface. The reflective power of the reflecting surface depends on the square of the difference between the effective indexes of refraction of the layers 22, 23 (e.g., (nl - n2)²). By increasing the difference in the indices of refraction between the layers 22, 23, improved optical power (higher reflectivity), thinner films (thinner or fewer layers), and broader bandwidth performance can be achieved. The refractive index difference in one in-plane direction in an exemplary embodiment is at least about 0.05, preferably greater than about 0.10, more preferably greater than about 0.15 and even more preferably greater than about 0.20.

[0085] In some embodiments, the materials of layers 22, 23 inherently have differing indices of refraction. In another embodiment, at least one of the materials of the layers 22, 23 has the property of stress induced birefringence, such that the index of refraction (n) of the material is affected by the stretching process. By stretching the polymeric multilayer optical film 20 over a range of uniaxial to biaxial orientations, films can be created with a range of reflectivities for differently oriented plane- polarized incident light.

[0086] Referring again to FIG. 1 A, in this embodiment, an optional third polymeric optical layer 24 (A- N) is included in between the first polymeric optical layer 23 (A-N) and the second polymeric optical layer 22 (A-N) of at least one pair of the alternating first polymeric optical layers 23 (A-N) and second polymeric optical layers 22 (A-N). In certain cases, the third polymeric optical layer 24 (A-N) can be chosen to increase an interlayer adhesion between the layers of the polymeric multilayer optical film. In some embodiments, the third polymeric optical layer is an isotropic polymeric layer.

[0087] Some polymeric multilayer optical films may include an optical repeating unit having optical polymeric layers A, B and C arranged in an order ABCB. Exemplary optical films with an ABCB layer construction are described in U.S. Pat. No. 6,667,095 (Wheatley et al.), which is incorporated herein by reference.

[0088] In some cases, an optical model described as the 4x4 transfer matrix method using the Berreman algorithm can be used to model a 711 constructive interference stack having 330 alternating optical layers (55 optical repeating units) of PET (polyethylene terephthalate) as polymer A and CoPMMA (available under the tradename Altuglas 510 A from Arkema, Prussia, PA) as polymer B. The optical modeling predicts average reflectivity of about 45% over a reflection band of 850 nm to 1850 nm. The optical modeling also predicts average visible light transmission of 92% over a light transmission band of 400 nm to 750 nm. Transmitted CIE color chromacity values were calculated to be a*= -0.036 and b*= 0.208. Reflected CIE color chromacity values were calculated to be a*= 0.174 and b*= -0.769.

[0089] The Berreman algorithm was also used to model a 711 constructive interference stack having 1290 alternating optical layers (215 optical repeating units) of PET as Polymer A and CoPMMA as Polymer B. The optical modeling predicts average reflectivity of 79% over a reflection band of 850 nm to 1850 nm. The optical modeling also predicts average visible light transmission of 91% over a light transmission band of 400 nm to 750 nm. Transmitted CIE color chromacity values were calculated to be a*= -0.082 and b*= 0.382. Reflected CIE color chromacity values were calculated to be a*= 0.334 and b*= -1.382.

[0090] Additionally, 711 optical designs are also described in PCT Publication No. WO 2002/061469 (Liu et al.), incorporated herein by reference.

[0091] In some embodiments, each third polymeric optical layer comprises styrenic block copolymer, acrylic block copolymer, glycol-modified polyethylene terephthalate, glycol-modified polyethylene naphthalate, polymethylmethacrylate, a copolymer of methyl methacrylate and ethyl acrylate, anhydride- modified ethylene vinyl acetate polymer, ketone ethylene ester terpolymer, polycarbonate, polyolefin thermoplastic elastomer or copolyethylene naphthalate terephthalate copolymer. Typically, each third polymeric optical layer has a different composition than each of the first and second polymeric optical layers.

[0092] In some cases where one of the first and second polymeric optical layers comprises a fluoropolymer, a third polymeric optical layer may comprise polymethylmethacrylate (PMMA) or a copolymer of methyl methacrylate and ethyl acrylate (coPMMA), for example. Acrylates (e.g., PMMA or coPMMA or acrylic block copolymer or blends thereof) have been found be particularly useful in providing a high bond strength with fluoropolymers (e.g., THV). Interlayer adhesion between fluoropolymers (e.g., THV) and acrylates or other materials is described in U.S. Pat. Appl. Pub. Nos. 2019/0369314 (Hebrink et al.) and 2019/0111666 (Hebrink et al.), for example.

[0093] In some embodiments, each of the third polymeric optical layers has an average thickness of less than about 300 nm, 250 nm, 200 nm, 150 nm, 100 nm, 50 nm, 40 nm, 30 nm, 20 nm, 15 nm, 10 nm, or less than about 7.5 nm. In some such embodiments, or in other embodiments, each of the third polymeric optical layers has an average thickness of at least about 0.5 nm, 1 nm, 2 nm, or at least about 3 nm. For example, in some embodiments, each of the third polymeric optical layers has an average thickness in a range of about 1 nm to about 300 nm, or about 3 nm to about 200 nm.

[0094] According to some embodiments, third polymeric optical layers formed from a polymer having a low glass transition temperature, or a block copolymer containing a (e.g., soft) polymeric block with a low glass transition temperature, or blends thereof, have been found to provide improved bonding with the first and second polymeric optical layers described herein. The glass transition temperature of the third polymeric optical layers or of the soft blocks of the third polymeric optical layers can be less than 105 °C, 100 °C, 90 °C, 80 °C, 70 °C, 60 °C, 50 °C, 40 °C, 30 °C, 20 °C, 10 °C, 0 °C, -10 °C, -20 °C, -30 °C, -40 °C, or less than -50 °C, for example. The glass transition temperature of a polymeric block of a copolymer can be determined as the glass transition temperature of a homopolymer of the monomeric units of the polymeric block. The block copolymer may also include other (e.g., hard) blocks for mechanical properties (e.g., for material handling and/or low creep), for example. A (e.g., hard) block for mechanical properties can have a glass transition temperature greater than 50 °C, 60 °C, 70 °C, 80 °C, 90 °C, 100 °C, or greater than 105 °C, for example. In some embodiments, each third polymeric optical layer is a chemically inert, or substantially chemically inert, polymeric layer. That is, in some embodiments, the polymer does not create covalent bonds with the material of the other polymeric optical layers, or creates so few covalent bonds as to negligibly affect the bonding with either of the adjacent layers.

[0095] Atactic polystyrene (aPS) can optionally be blended with sPS (e.g., at about 5 to about 30 weight percent aPS) to adjust the refractive indices of the resulting layer and/or to reduce the haze of the layer (e.g., by reducing a crystallinity of the layer). Suitable THV polymers are described in U.S. Pat. Appl. Pub. No. 2019/0369314 (Hebrink et al.), for example, and include those available under the DYNEON THV tradename from 3M Company (St. Paul, MN). In some embodiments, THV can contain about 35 to about 75 mole percent tetrafluoroethylene, about 5 to about 20 mole percent hexafluoropropylene, and about 15 to about 55 mole percent vinylidene fluoride. Suitable styrenic block copolymers include KRATON G1645 and KRATON G1657 available from KRATON Polymers (Houston, TX). Suitable acrylic block copolymers include those available under the KURARITY tradename from Kuraray Co., Ltd. (Tokyo, JP). PETG can be described as PET with some of the glycol units of the polymer replaced with different monomer units, typically those derived from cyclohexanedimethanol. PETG can be made by replacing a portion of the ethylene glycol used in the transesterification reaction producing the polyester with cyclohexanedimethanol, for example. Suitable PETG copolyesters include GN071 available from Eastman Chemical Company (Kingsport, TN). PEN and coPEN can be made as described in U.S. Pat. No. 10,001,587 (Liu), for example. Low melt PEN is a coPEN including about 90 mole percent naphthalene dicarboxylate groups based on total carboxylate groups and is also known as coPEN 90/10. Another useful coPEN is coPEN 70/30 which includes about 70 mole percent naphthalene dicarboxylate groups and about 30 mole percent terephthalate dicarboxylate groups based on total carboxylate groups. More generally, coPEN Z/100-Z may be used where coPEN Z/100-Z includes Z mole percent naphthalene dicarboxylate groups (typically greater than 50 mole percent and no more than about 90 mole percent) and 100-Z mole percent terephthalate dicarboxylate groups based on total carboxylate groups. Glycol-modified polyethylene naphthalate (PENG) can be described as PEN with some of the glycol units of the polymer replaced with different monomer units and can be made by replacing a portion of the ethylene glycol used in the transesterification reaction producing the polyester with cyclohexanedimethanol, for example. PHEN can be made as described for PEN in U. S. Pat. No. 10,001,587 (Liu), for example, except that a portion of the ethylene glycol (e.g., about 40 mole percent) used in the transesterification reaction is replaced with hexanediol. Suitable PET can be obtained from Nan Ya Plastics Corporation, America (Lake City, SC), for example. Suitable sPS can be obtained from Idemitsu Kosan Co., Ltd. (Tokyo, Japan), for example. Suitable PMMA can be obtained from Arkema Inc., Philadelphia, PA., for example. Suitable anhydride-modified ethylene vinyl acetate polymers include those available from Dow Chemical (Midland, MI) under the BYNEL tradename, for example. Suitable ketone ethylene ester terpolymers include those available from Dow Chemical (Midland, MI) under the BYNEL tradename, for example. Suitable polyolefin thermoplastic elastomers include those available from Mitsui Chemicals (Tokyo, Japan) under the ADMER tradename.

[0096] PEN, PET, and PHEN are examples of positively birefringent thermoplastic polymers, while sPS is an example of a negatively birefringent thermoplastic polymer. As described in U.S. Pat. No.

9,069,136 (Weber et al.), for example, whether a polymer will exhibit positive or negative birefringence can depend on the geometry of crystallites formed when the polymer is oriented. Suitable positively birefringent thermoplastic polymers include those forming crystallites having a symmetry axis substantially aligned with a stretch direction, while suitable negatively birefringent thermoplastic polymers include those forming crystallites having discotic unit cell structure with the smallest unit cell dimension substantially aligned with a stretch direction. Styrenic block copolymers, PMMA, coPMMA, THV, acrylic block copolymer, coPEN, and PETG are examples of thermoplastic polymers that can be substantially isotropic after orientation. Substantially isotropic polymers typically either substantially do not form crystallites when oriented or form crystallites that are melted out when a film containing the polymer is heat set. Further examples of positively and negatively birefringent thermoplastic polymers and of isotropic thermoplastic polymers, are described in U.S. Pat. No. 9,069, 136 (Weber et al.), for example. Other suitable materials for the various layers in the multilayer optical film 300 include those described in U.S. Pat. Nos. 5,103,337 (Schrenk et al.); 5,540,978 (Schrenk); 5,882,774 (Jonza et al.); 6,179,948 (Merrill et al.); 6,207,260 (Wheatley et al.); 6,783,349 (Neavin et al.); 6,967,778 (Wheatley et al.); 9,069,136 (Weber et al.); and 9,162,406 (Neavin et al.), for example.

[0097] The number of layers in the polymeric multilayer optical film 20 is selected to achieve the desired optical properties using the minimum number of layers for reasons of film thickness, flexibility and economy. In the case of reflective films such as mirrors, the number of layers is preferably less than about 2,000, more preferably less than about 1,000, and even more preferably less than about 750. In some embodiments, the number of layers is at least 150 or 200. In other embodiments, the number of layers is at least 250.

[0098] The various constituent layers of polymeric multilayer optical film may be resistant to ultraviolet radiation. Many fluoropolymers are resistant to UV-radiation. Examples of fluoropolymers that may be used include copolymers of tetrafluoroethylene (TFE), hexafluoropropylene (HFP), and vinylidene fluoride (e.g., available from 3M Company under the trade designation 3M DYNEON THV); a copolymer of TFE, HFP, vinylidene fluoride, and perfluoropropyl vinyl ether (PPVE) (e.g., available from 3M Company under the trade designation 3M DYNEON THVP); a polyvinylidene fluoride (PVDF) (e.g., 3M DYNEON PVDF 6008 from 3M Company); ethylene chlorotrifluoroethylene polymer (ECTFE) (e.g., available as HALAR 350LC ECTFE from Solvay, Brussels, Belgium); an ethylene tetrafluoroethylene copolymer (ETFE) (e.g., available as 3M DYNEON ETFE 6235 from 3M Company); perfluoroalkoxyalkane polymers (PF A); fluorinated ethylene propylene copolymer (FEP); a polytetrafluoroethylene (PTFE); copolymers of TFE, HFP, and ethylene (HTE) (e.g., available as 3M DYNEON HTE1705 from 3M Company). Combinations of fluoropolymers can also be used. In some embodiments, the fluoropolymer includes FEP. In some embodiments, the fluoropolymer includes PFA. In some embodiments, the fluoropolymer includes PVF.

[0099] Examples of non-fluorinated polymers that may be used in at least one layer of the polymeric multilayer optical film include at least one of: PET, polypropylene copolymers, polyethylene copolymers, polyethylene methacrylate copolymers, polymethyl methacrylate, methyl methacrylate copolymers (e.g., copolymers of ethyl acrylate and methyl methacrylate), polyurethanes, acrylate copolymers, extended chain polyethylene polymers (ECPEs), polyethylene naphthalate (PEN), or combinations thereof. In general, combinations of non-fluorinated polymers can be used. Exemplary nonfluorinated polymers, especially for use in high refractive index optical layers, may include homopolymers of polymethyl methacrylate (PMMA), such as those available as CP71 and CP80 from Ineos Acrylics, Inc., Wilmington, DE; and polyethyl methacrylate (PEMA), which has a lower glass transition temperature than PMMA. Suitable polyethylene naphthalate (PEN) polymers are available under the tradename “Teonex Q51” from DuPont Teijin, Chester, VA. Additional useful polymers include: copolymers of methyl methacrylate such as, for example, a copolymer made from 75 wt.% methyl methacrylate and 25 wt.% ethyl acrylate, for example, as available from Ineos Acrylics, Inc. as PERSPEX CP63, or as available from Arkema, Philadelphia, PA as ALTUGLAS 510, and copolymers of methyl methacrylate monomer units and n- butyl methacrylate monomer units. Blends of PMMA and PVDF may also be used.

[00100] Suitable triblock acrylic copolymers are available, for example, as KURARITY LA4285 from Kuraray America Inc., Houston, TX. Additional suitable polymers for the optical layers, especially for use in the refractive index optical layers, may include at least one of: polyolefin copolymers such as poly(ethylene-co-octene) (e.g., available as ENGAGE 8200 from Dow Elastomers, Midland, MI), polyethylene methacrylate (e.g., available as ELVALOY from Dow Elastomers), poly (propylene-co- ethylene) (e.g., available as Z9470 from Atofina Petrochemicals, Inc., Houston, TX); and a copolymer of atactic polypropylene and isotactic polypropylene. Materials may be selected based on absorbance or transmittance properties described herein, as well as on refractive index. In general, the greater the refractive index between two materials, the thinner the film can be.

[00101] Multilayer optical films can be made by coextrusion of alternating polymer layers having different refractive indices, for example, as described in U.S Pat. Nos. 5,882,774 (Jonza et al.); 6,045,894 (Jonza et al.); 6,368,699 (Gilbert et al.); 6,531,230 (Weber et al.); 6,667,095 (Wheatley et al.); 6,783,349 (Neavin et al.); 7,271,951 B2 (Weber et al); 7,632,568 (Padiyath et al.); 7,652,736 (Padiyath et al.); and 7,952,805 (McGurran et al.); and PCT Publications WO 95/17303 (Ouderkirk et al.) and WO 99/39224 (Ouderkirk et al.).

[00102] In certain embodiments, the polymeric multilayer optical film comprises a third order harmonic that reflects at least 80, 90, or 95 percent of light that is normally incident to a first major surface of the wavelength-selective multilayer article over at least a 30 nm wavelength bandwidth in a wavelength range from 340 nm to 400 nm, 350 nm to 400 nm, or 365 nm to 400 nm. As described in U.S. Pat. No. 6,667,095 (Wheatley et al.) and U.S. Pat. No. 5,360,659 (Arends et al.), multilayer optical films, made with two alternating materials in a quarter-wave type interference filter, generate higher-order reflections at integer divisions of the primary reflection band, with the 3rd order harmonic appearing at wavelength ranges equal to 1/3 the wavelength range of the primary reflection band, the 5th order appearing at 1/5 the wavelength range of the primary band, and so forth. For example, the “Example 16” IR film made from PET and poly(ethylene-co-octene) (PE-PO) described in U.S. Pat. No. 6,744,561 (Condo et al.), which has a primary reflection band reflecting light between 1020 nm and 1200 nm, would have a third order harmonic reflection band reflecting light between 340 nm and 400 nm, or 1/3 of the wavelength range of the primary wavelength band. Some suitable polymer pairs for the first and second optical layers to employ to achieve the third order harmonic include for instance and without limitation, polyethylene terephthalate (PET)/coPMMA, PMMA/polydimethyl siloxane oxamide based segmented copolymer (SPOX), thermoplastic polyurethane (TPU)/SPOX, ethylene vinyl acetate (EVA)/SPOX, ethylene methyl acrylate (EMA)/SPOX, and cyclic olefin copolymers (COC)/SPOX. Advantageously, by reflecting wavelengths in these ranges, less UV reflection/absorption is required to be achieved by the inorganic multilayer optical film, which may result in a lower cost article due to containing fewer inorganic layers. [00103] Typically, the polymeric multilayer optical film has an average thickness of 50 micrometers to 250 micrometers, such as 50 micrometers or greater, 55 micrometers, 60 micrometers, 65 micrometers, 70 micrometers, 75 micrometers, 80 micrometers, 85 micrometers, 90 micrometers or 95 micrometers or greater; and 250 micrometers or less, 225 micrometers, 200 micrometers, 175 micrometers, 150 micrometers, 125 micrometers, 100 micrometers, 90 micrometers, 80 micrometers, 70 micrometers, or 60 micrometers or less.

Inorganic Multilayer Optical Films

[00104] Referring again to FIG. 1A, the wavelength-selective multilayer article 10 includes an inorganic multilayer optical film 30 comprising one or more alternating first inorganic optical layers 33 (A-N) and second inorganic optical layers 32 (A-N). The inorganic multilayer optical film 30 has a first major surface 36 and an opposing second major surface 38, wherein the second major surface 38 of the inorganic multilayer optical film 30 is (directly or indirectly) attached to the first major surface 26 of the polymeric multilayer optical film 20.

[00105] The alternating first and second inorganic optical layers collectively reflect and absorb light that is normally incident to the first major surface of the wavelength-selective multilayer article, an average of at least 50, 60, 70, 80, 90, or 95 percent (preferably at least 80, 90, or 95 percent) of incident ultraviolet light over at least a 30-nanometer wavelength reflection bandwidth in a wavelength range from 190 nanometers (nm) to 400 nm.

[00106] In some cases, the alternating first and second inorganic optical layers collectively reflect and absorb light that is normally incident to the first major surface of the wavelength-selective multilayer article, an average of at least 60, 70, 80, 90, or 95 percent of incident ultraviolet light over at least a 30- nanometer wavelength reflection bandwidth in a wavelength range from 190 nm to 240 nm, 240 nm to 300 nm, 300 nm to 350 nm, 350 nm to 400 nm, or any combination thereof.

[00107] Optionally, the alternating first and second inorganic optical layers collectively reflect and absorb light that is normally incident to the first major surface of the wavelength-selective multilayer article, an average of at least 60, 70, 80, 90, or 95 percent of incident ultraviolet light over a greater wavelength reflection bandwidth than at least 30-nanometer, for instance at least a 50-nanometer, 75-nanometer, 100- nanometer, 125-nanometer, 150-nanometer, or 175-nanometer wavelength reflection bandwidth in a wavelength range from 190 nm to 400 nm.

[00108] As the alternating first and second inorganic optical layers collectively reflect and absorb, some portion of the incident ultraviolet light may be absorbed and some portion reflected. In some cases, the alternating first and second inorganic optical layers collectively absorb light that is normally incident to the first major surface of the wavelength-selective multilayer article, an average of at least 30, 40, 50, 60, 70, 80, 90, or 95 percent of incident light over at least a 30-nanometer wavelength bandwidth in a wavelength range from 190 nm to less than 350 nm. In some cases, the alternating first and second inorganic optical layers collectively reflect light that is normally incident to the first major surface of the wavelength-selective multilayer article, an average of at least 30, 40, 50, 60, 70, 80, 90, or 95 percent of incident light over at least a 30-nanometer wavelength bandwidth in a wavelength range from 190 nm to less than 400 nm, 190 nm to 240 nm, 240 nm to 300 nm, 300 nm to 350 nm, 350 nm to less than 400 nm, or any combination thereof.

[00109] In select embodiments of the wavelength-selective multilayer article, the alternating first and second inorganic optical layers collectively transmit light that is normally incident to the first major surface of the wavelength-selective multilayer article, an average of at least 50, 60, 70, 80, 90, or 95 percent of incident visible light in a wavelength range from greater than 400 nm to 700 nm, greater than 400 nm to 1100 nm, or greater than 400 nm to 1350 nm.

[00110] In select embodiments of the wavelength-selective multilayer article, the outermost inorganic layer is a second inorganic optical layer (e.g., 32A in FIG. 1 A) and has a thickness of at least 70 nm. This has the effect of reducing the amount of light reflected off the outer surface of the article and increases the light transmitted between 400 nm and 700 nm, which is particularly useful when the wavelength- selective multilayer article is used in a solar array application, to allow visible light to reach the solar cells of the array.

[00111] In select embodiments, at least one of the first optical layers nearest to the exterior of the film (e.g., 33A in FIG. 1A) or nearest to the polymeric multilayer optical film (e.g., 33N in FIG. 1A) has a thickness of at most 95%, 90%, 85%, or at most 80% of the other first optical layers. This has the effect of reducing the amount of light reflected off the outer surface of the wavelength-selective multilayer article between 400 nm and 700 nm, which is particularly useful when the wavelength-selective multilayer article is used in a solar array application, to allow visible light to reach the solar cells of the array. [00112] In some embodiments, the wavelength-selective multilayer article (e.g., as a whole) transmits an average of at least 50, 60, 70, 80, 90, or 95 percent of normally incident visible light in a wavelength range from greater than 400 nm to 700 nm, greater than 400 nm to 1100 nm, or greater than 400 nm to 1350 nm. Transmitting such amounts of incident visible light is particularly useful when the wavelength- selective multilayer article is used in a solar array application, to allow visible light to reach the solar cells of the array. Additionally, wavelength-selective multilayer articles according to certain preferred embodiments of the present disclosure exhibit an average transmission of wavelengths between greater than 400 nm and 700 nm, greater than 400 nm to 1100 nm, or greater than 400 nm to 1350 nm, through the article being reduced by less than 20%, 10%, 5%, or less than 1% after exposure to a certain dose of ultraviolet light (e.g., in units of Joules per square centimeter (J/cm²)). Similarly, in some cases wavelength-selective multilayer articles according to the present disclosure exhibit an average reflection of wavelengths between 800 nm to 1200 nm, 1200 nm to 1600 nm, or 800 nm to 1600 nm, off the article that is reduced by less than 20%, 10%, 5%, or less than 1% after exposure to a certain dose of ultraviolet light. For instance, exposed to a dose of 425 megajoules per square centimeter (MJ/cm²), 470 MJ/cm², or 850 MJ/cm².

[00113] Typically, the inorganic multilayer optical film has a thickness of 200 nm or greater, 250 nm, 300 nm, 350 nm, 400 nm, 500 nm, or 550 nm or greater; and 1500 nm or less, 1400 nm, 1300 nm, 1200 nm, 1100 nm, 1000 nm, 900 nm, 850 nm. 800 nm, 750 nm, 700 nm, 650 nm, or 600 nm or less, such as a thickness of 200 nm to 1500 nm.

[00114] In some cases, the first optical layer of the inorganic multilayer optical film comprises at least one of niobium oxide, titanium oxide, silicon oxynitride, molybdenum oxide, tungsten oxide, silicon nitride, indium tin oxide, hafnium oxide, tantalum oxide, zirconium oxynitride, zirconium oxide, aluminum zinc oxide, or zinc oxide. Alloys of oxides may be suitable, as known to those skilled in the art. In some cases, the second optical layer of the inorganic multilayer optical film comprises at least one of silicon oxide, silicon aluminum oxide, N type- or P type-doped silicon oxide, aluminum oxide, aluminum fluoride, magnesium fluoride, calcium fluoride, indium tin oxide, or zinc oxide. In select embodiments of the inorganic multilayer optical film, the first optical layer comprises at least one of niobium oxide or titanium oxide, and the second optical layer comprises silicon aluminum oxide. Similarly, in select embodiments of the inorganic multilayer optical film, the first optical layer comprises at least one of niobium oxide or titanium oxide, and the second optical layer comprises silicon oxide. Advantageously, such inorganic multilayer optical films can also provide some antistatic properties to the wavelength-selective multilayer article.

[00115] When a photoactive inorganic material such as titanium oxide is employed, typically a nonphotoactive material (e.g., silicon oxide, aluminum oxide, etc.) may be disposed between the photoactive inorganic material and any organic layers to minimize degradation of the organic layer. For instance, referring again to FIG. 1 A, a layer of a non-photoactive material could be an intermediate layer 60 located between the first optical layer 33N and (optionally) a structured film 50 or a polymeric multilayer optical film 20. [00116] It was unexpectedly discovered that wavelengths of light in each of UVA, UVB, and UVC regions could be shielded from additional layers (e.g., a solar array 70) using just the combined reflectance and absorbance of a plurality of alternating first inorganic optical layers and second inorganic optical layers, typically while still maintaining an acceptable amount of transmission of visible light (e.g., at least 50% of incident visible light).

[00117] Optical thin film stack designs comprised of alternating thin layers of inorganic dielectric materials with refractive index contrast, are particularly suited for the inorganic multilayer optical film. In recent decades they have been used for applications in UV, Visible, NIR and IR spectral regions. Depending upon the spectral region of interest, there are specific materials suitable for that region. Also, for coating these materials, one of two forms of physical vapor deposition (PVD) are used: evaporation or sputtering. Evaporated coatings rely upon heating the coating material (evaporant) to a temperature at which it evaporates. This is followed by condensation of the vapor upon a substrate. For evaporated dielectric mirror coatings, the electron-beam deposition process is most commonly used. Sputtered coatings use energetic gas ions to bombard a material (“target”) surface, ejecting atoms which then condense on the nearby substrate. Depending upon which coating method is used, and the settings used for that method, thin film coating rate and structure-property relationships will be strongly influenced. Ideally, coating rates should be high enough to allow acceptable process throughput and film performance, characterized as dense, low stress, void free, non-optically absorbing coated layers.

[00118] The number of optical layers is selected to achieve the desired optical properties using the minimum number of layers for reasons of film thickness, flexibility and economy. One skilled in the art could extend such deposition techniques to include CVD, ALD, and other vapor depositions. Typically, the total number of layers is preferably 21 or less, 19, 17, 15, or 13 optical layers or less; and 3 optical layers or more, 5, 7, 9, or 11 optical layers or more, may be needed. In select embodiments, the inorganic multilayer optical film is formed of at least 1 first optical layer and 2 second optical layers.

[00119] The thickness of each of the first and second optical layers can vary substantially. For instance, in some cases each of the first optical layers and each of the second optical layers independently has a thickness of 5 nm or greater, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, or 70 nm or greater; and a thickness of 2000 nm or less, 500 nm, 145 nm, 140 nm, 135 nm, 130 nm, 125 nm, 120 nm, 115 nm, 110 nm, 105 nm, 100 nm, 95 nm, 90 nm, 85 nm, 80 nm, or 75 nm or less. In select embodiments, each of the first and second optical layers of the inorganic multilayer optical film independently has a thickness of 20 nm to 400 nm.

[00120] Inorganic multilayer optical films described herein can be made using general processing techniques, such as those described in U.S. Pat. No 6,783,349 (Neavin et al.), the entire disclosure of which is incorporated herein by reference in its entirety.

[00121] For manufacturing inorganic coatings, the electron beam process is best suited for coating discrete parts. Optionally, ultraviolet light shielding articles can be prepared in continuous roll-to-roll (R2R) fashion for larger articles. Though some chambers have demonstrated R2R film coating, the layer by layer coating sequence would still be necessary. For R2R sputtering of inorganic layers of ultraviolet light shielding articles 10, it is advantageous to use a sputtering system with multiple sources located around one, or perhaps two, coating dmms. Here, for a thirteen layers optical stack design, a two, or even single, machine pass process, with alternating high and low refractive index layers coated sequentially, would be feasible. How many machine passes needed would be contingent upon machine design, cost, practicality of thirteen consecutive sources, and the like. Additionally, coating rates would need to be matched to a single film line speed.

[00122] The film roll transport initially starts at a pre -determined speed, and the sputter source power is ramped to full operating power, followed by introduction of the reactive gases and then achieving steady state condition. Depending upon the length of film to coat, the process continues until total footage is achieved. Here, as the sputter source is orthogonal to and wider than the film which is being coated, the uniformity of coating thickness is quite high. Upon reaching the desired length of coated film the reactive gases are set to zero and the target is sputtered to a pure metal surface state. The film direction is next reversed and a rotary pair of sputter targets has AC frequency (40 kHz) power applied in an argon sputtering atmosphere. Upon reaching steady state, oxygen reactive gas is introduced to provide transparency and low refractive index. At the pre-determined process setting and line speed the second layer is coated over the length which was coated for layer one. Again, as these sputter sources are also orthogonal to and wider than the film being coated, the uniformity of coating thickness is quite high. After reaching the desired length of coated film the reactive oxygen is removed and the target is sputtered in argon to a pure metal surface state. Layers three to five (or seven or nine, eleven or thirteen, etc.) depending upon optical targets, are coated in this sequence. Upon completion, the film roll is removed for post-processing.

Structured Films

[00123] Referring again to FIG. 1A, in some embodiments, a wavelength-selective multilayer article 10 further comprises a structured film 50 disposed between the first major surface 26 of the polymeric multilayer optical film 20 and the second major surface 38 of the inorganic multilayer optical film 30. Referring now to FIG. 2B, a schematic cross-sectional view is provided of a structured film 200 comprising a plurality of structures 240 suitable for use in exemplary articles of the present disclosure. By “a structure that has a surface whose slope causes light that is normally incident to the first major surface of the structured film to intercept the first major surface or the surface of at least one other structure after reflection” is meant that incident light (“I”) that strikes a surface of a structure 240a normal to the first major surface 230 of the structured film 200, and the structure 240a has a slope 242 that causes reflected light (“R”) to intercept either the first major surface of the structured film (not shown) or the surface of another structure 240b. Similar to the discussion above with respect to the article depicted in FIG. 2A, the first major surface 230 of the structured film 200 is considered parallel to a second major surface 210 of the structured film 200. The slope (e.g., sloped surface) 242 of the structure 240a is the height 241 of the structure 240a divided by the width 243 between the peak (e.g., high end of the sloped surface) 245 and the bottom (e.g., low end of the sloped surface) 247 of the structure 240a. Another way to determine slope is using the following formula:

Ay m = -T— = tan B

Lx wherein m is the slope, Ay is the height of the structure, Ax is the width between the peak and the bottom of the structure, and angle 0 is the angle of incline between the sloped surface of the structure and the bottom of the structure (e.g., as shown in FIG. 2B). For structures having a rounded peak, using the tangent of the angle of incline 0 may be a preferable way to determine the slope. An angle alpha (a) can be drawn between the slope 242 and the height 241 of the peak 245. In some cases, the angle a is 45 degrees or less, 40 degrees, 35 degrees, 30 degrees, 25 degrees, 20 degrees, 15 degrees, or 10 degrees or less.

[00124] FIG. 2C is a schematic cross-sectional view of a portion of an exemplary wavelength-selective multilayer article 10 according to at least some exemplary embodiments disclosed herein. The portion of wavelength-selective multilayer article 10 includes a structured film 50 that has a first major surface 56 and an opposing second major surface 58. The first major surface 56 comprises a plurality of structures 57 projecting therefrom. The wavelength-selective multilayer article 10 comprises an inorganic multilayer optical film 30 positioned on the plurality of structures 57. The inorganic multilayer optical film 30 comprises alternating first inorganic optical layers 33 and second inorganic optical layers 22. In this embodiment, the article 10 further includes at least one intermediate layer 60 positioned between the structured film 50 and the inorganic multilayer optical film 30.

[00125] FIG. 2D is a scanning electron microscopy (SEM) image of a cross-section of a portion of an exemplary wavelength-selective multilayer article 10 according to at least some exemplary embodiments disclosed herein. The wavelength-selective multilayer article 10 includes a structured film 50 having a first major surface 56. The first major surface 56 comprises a plurality of structures 57 projecting therefrom. An inorganic multilayer optical film 30 is positioned on the plurality of structures 57. The inorganic multilayer optical film 30 comprises alternating first and second inorganic optical layers (the individual layers are too thin to see in the image); a second inorganic optical layer 32 is an outer layer. In this embodiment, the article 10 further includes an intermediate layer 60 positioned between the structured film 50 and the inorganic multilayer optical film 30.

[00126] The structured film comprises a first major surface and an opposing second major surface, wherein the first major surface comprises a plurality of structures projecting therefrom, wherein at least some of the plurality of structures each has a surface whose slope causes light that is normally incident to the first major surface of the structured film to intercept the first major surface or the surface of at least one other structure after reflection. As such, various different shapes of structures are suitable. For example, in some cases, the structures have a shape that is a prism, a pyramid, an inverted pyramid, a diffraction grating, an inverted cone, or a cone. Such shapes will be described in further detail below. Additionally, the inverse of any of these shapes are also suitable. Any number of facets of a three- dimensional shape may be present (e.g., any of a 4-sided pyramid, a 5-sided pyramid, a 6-sided pyramid, etc., would be suitable.). In select embodiments, each of the structures has the same size and shape, which tends to assist in achieving consistent optical performance of the multilayer optical film deposited on the structures across the surface of the structured film.

[00127] Optionally, at least some of the structures have a shape with a triangular cross-section, such as the structures 240 and 57 in FIGS. 2B and 2C, respectively. While not required, in some cases, at least some of the structures 240 comprise at least one angled sidewall (e.g., 242) that has a peak 245 that comes to a point. Advantageously, it was discovered that it is possible to form the multilayer optical film on structures that have peaks that come to a point (e.g., that are not rounded at the peak) without having “pinholes” due to inadequate deposition of the multilayer optical film on the points of the peaks.

[00128] In some cases, as depicted in FIG. 2B, at least some of the structures 240 comprise at least one angled sidewall (e.g., 242) having a peak angle (e.g., apex angle) theta (0) of 90 degrees or less, 85 degrees, 80 degrees, 75 degrees, 70 degrees, 65 degrees, 60 degrees, 55 degrees, 50 degrees, or 45 degrees or less; and 5 degrees or greater, 7 degrees, 10 degrees, 12 degrees, 15 degrees, 20 degrees, 25 degrees, 30 degrees, 35 degrees, 40 degrees, 45 degrees, or 50 degrees or greater. As used herein, the “peak angle” refers to the angle between opposing sides of a structure at the vertex of the structure.

[00129] Optionally, the plurality of structures 240 may have an aspect ratio of height H to (total) width W (i.e., H : W) of no more than 10 : 1, 9 : 1, 8 : 1, 7 : 1, 6 : 1, 5 : 1, 4 : 1, 3 : 1, 2 : 1, or no more than 1 : 1; and at least 1 : 2.

[00130] In some cases, the structures are macrostructures. Typically, macro structures each have a height of greater than 500 micrometers, 600 micrometers, 700 micrometers, 800 micrometers, 900 micrometers, or 1000 micrometers or greater; and 10 millimeters (mm) or less, 9.5 mm, 9 mm, 8.5 mm, 8 mm, 7.5 mm, 7 mm, 6.5 mm, 6 mm, 5.5 mm, 5 mm, 4.5 mm, 4 mm, 3.5 mm, 3 mm, 2.5 mm, 2 mm, or 1.5 mm or less. [00131] In some cases, the structures are microstructures. Typically, micro structures each have a height of 0.5 micrometers or greater, 1 micrometer, 2 micrometers, 3 micrometers, 4 micrometers, 5 micrometers, 6 micrometers, 7 micrometers, 8 micrometers, 9 micrometers, 10 micrometers, 12 micrometers, 15 micrometers, 17 micrometers, 20 micrometers, 25 micrometers, 30 micrometers, 35 micrometers, 40 micrometers, 45 micrometers, 50 micrometers, 60 micrometers, 70 micrometers, 80 micrometers, 90 micrometers, 100 micrometers, 110 micrometers, 120 micrometers, 150 micrometers, 175 micrometers, 200 micrometers, 225 micrometers, or 250 micrometers or greater; and 500 micrometers or less, 475 micrometers, 450 micrometers, 425 micrometers, 400 micrometers, 375 micrometers, 350 micrometers, 325 micrometers, 300 micrometers, 275 micrometers, 250 micrometers, 225 micrometers, 200 micrometers, 175 micrometers, 150 micrometers, 125 micrometers, 100 micrometers, 75 micrometers, 50 micrometers, or 25 micrometers or less.

[00132] Referring to FIG. 3, in one embodiment, the first major surface 300 of a structured film 100 comprises a linear array of regular right prisms 320. Each prism has a first facet (e.g., sloped surface) 321 and a second facet 322. The prisms are illustrated as formed on a base member 310 that has a first planar surface 331 (parallel to reference plane 126) on which the prisms are formed and a second surface 332 that is substantially flat or planar and opposite first surface. It is envisioned that the second surface 332 could also be structured. By right prisms it is meant that the peak angle 0, 340, is typically about 90 degrees. However, this angle can range as described above. These peaks can be sharp (as shown) or rounded. The spacing between (e.g., prism) peaks may be characterized as pitch (“P”). In this embodiment, the pitch is also equal to the maximum width of the valley. The pitch may be greater than 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 microns ranging up to 250 microns. The length (“L”) of the (e.g., prism) structures is typically the largest dimension and can span the entire dimension of the structured surface. [00133] In another embodiment, the first major surface of the structured film may have the same surface shape as cube comer retroreflective sheeting. With reference to FIG. 4A, cube comer retroreflective sheeting typically comprises a thin transparent layer having a substantially planar surface and an opposing stmctured surface 410 comprising a plurality of cube comer elements 417. The structured surface 410 of FIG. 4A may be characterized as an array of cube comer elements 417 defined by three sets of parallel grooves (i.e., valleys) 411, 412, and 413; two sets of grooves (i.e., valleys) intersect each other at an angle greater than 60 degrees and a third set of grooves (valleys) intersects each of the other two sets at an angle less than 60 degrees to form an array of canted cube comer element matched pairs (see U.S. Pat. No. 4,588,258 (Hoopman)). The angles for the grooves are chosen such that the dihedral angle formed at the linear of intersection of the grooves, e.g., 414, 415, and 416 for representative cubecomer element 417 are about 90 degrees. In some embodiments, the triangular base has angle of at least 64, 65, 66, 67, 68, 69, or 70 degrees and the other angles are 55, 56, 57, or 58 degrees.

[00134] In another embodiment, depicted in FIG. 4B, the first major surface of the stmctured film 400 of FIG. 4B may be characterized as an array of pyramidal peak structures 420 defined by a first set of parallel grooves (i.e., valleys) in the y direction and a second set of parallel groves in the x direction. The base of the pyramidal peak stmctures is a polygon, typically a square or rectangle depending on the spacing of the grooves. The peak angle 0, 440, is typically about 90 degrees. However, this angle can range as described above.

[00135] In some cases, the stmctures may have a shape of a cone. Referring to FIG. 5, a stmctured surface 500 of a stmctured film comprises an array of cones 540. Each structure of a cone shape typically has just one angled sidewall 542. The peak 545 of each cone can be pointed or rounded.

[00136] FIG. 6 depicts a schematic of a first major surface 600 of a stmctured fdm comprising a diffraction grating having a bias angle. A second major surface 610 of the stmctured film defines a longitudinal axis (“LA”) along its length and the plurality of stmctures 640 extends across the first major surface 600 to define a primary axis (“A”). The primary axis A and the longitudinal axis LA define a bias angle (“B”) therebetween. In some embodiments, the bias angle B is in a range of between about 0 degrees and about 90 degrees, such as between about 20 degrees and about 70 degrees.

[00137] In another embodiment, depicted in FIG. 7, the first major surface 710 of the stmctured film 700 may be characterized as an array of inverted pyramid stmctures 720. The stmctures 720 include facets 722 that meet in a valley (e.g., inverted peak) 721, and the opposing edge 724 of each facet together form a base of the pyramid stmcture 720 (i.e., at the outermost surface of the stmctured film 700). The base of the pyramid is a polygon, such as a square or rectangle. In this particular embodiment, adjacent rows of stmctures (e.g., end row 762 is adjacent to row 764) are offset from each other such that the bottoms of the valleys of adjacent structures (e.g., 723 in row 762 and an adjacent structure 725 in row 764) have different positions along the length of the rows (e.g., in a y-axis). It is expressly contemplated that such an offset configuration may be employed with any of the structures disclosed herein.

[00138] Advantageously, in certain embodiments, the structures refract light that is incident at an angle other than normal to the first major surface of the wavelength-selective multilayer article to exit the structured film at an angle that is closer to normal than the incident angle (e.g., in some cases to be directed towards the polymeric multilayer optical film at an angle that is closer to normal to the first major surface of the polymeric multilayer optical film than the incident angle of the incident light). [00139] In some cases, the stmctured film is flexible (as defined in the Glossary). An advantage to employing a flexible structured film is avoiding the high cost of working with rigid glass, particularly small pieces of glass, which can break during handling and require significant labor due to the need to apply many small pieces of glass. Additionally, in some embodiments according to the present disclosure flexible structured film are used in roll-to-roll processing of manufacturing the wavelength-selective multilayer article. An advantage to roll-to-roll manufacturing is that the wavelength-selective multilayer article can be made in large area form factors. In some cases, a structured fdm (or the wavelength- selective multilayer article) has an area of at least 50 square centimeters, such as at least 60, 70, 80, 90, 100, 1,000, or at least 10,000 square centimeters.

[00140] In any of the foregoing embodiments, the structured film may be comprised of or consist of a polymeric material, such as a (co)polymer. In some exemplary embodiments, the structured film comprises polyethylene terephthalate (PET), a crosslinkable silicone, a cured polysiloxane, a silicone thermoplastic polymer, a cured urethane, a thermoplastic urethane, a cured (meth)acrylate, a cured epoxy, a cured vinyl ether, a cured oxetane, a cured thiol-acrylate, a cured thiol-ene, a polypropylene, a polyethylene, PMMA, coPMMA, a polyimide, a cyclic olefin copolymer, a cyclic olefin polymer, a polycarbonate, a polyethylene naphthalate (PEN), or a fluoropolymer (co)polymer comprising polymerized units derived from one or more monomers selected from tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, a perfluoroalkoxy alkylene, or a vinyl fluoride, or a combination thereof. Optionally, any of the cured polymeric materials mentioned above are crosslinked. [00141] Suitable polyimides are available under the trade name “KAPTON” from E. I. DuPont de Nemours, Wilmington, DE, of which “KAPTON CS100” is currently preferred. Suitable PMMA polymers include those available as CP71 and CP80 from Ineos Acrylics, Inc., Wilmington, DE. One suitable crosslinkable silicone is available under the trade name “DOW CORNING 93-500 SPACE GRADE ENCAPSULANT KIT” from Dow Coming Corporation, Midland, MI. One suitable polycarbonate is available under the trade name “Makrofol”, from Bayer AG (Darmstadt, Germany). Suitable methyl methacrylate copolymers (CoPMMA) include, for instance, a CoPMMA made from 75 wt.% methylmethacrylate (MMA) monomers and 25 wt.% ethyl acrylate (EA) monomers, (available, for example, from Ineos Acrylics, Inc. (London, England) under the trade designation “PERSPEX CP63” or Arkema Corp., (Philadelphia, PA) under the trade designation “ATOGLAS 510”), a CoPMMA formed with MMA comonomer units and n-butyl methacrylate (nBMA) comonomer units, or a blend of PMMA and poly(vinylidene fluoride) (PVDF). Suitable polyethylene naphthalate (PEN) polymers are available under the tradename “Teonex Q51” from DuPont Teijin, Chester, VA.

[00142] In certain exemplary embodiments, the fluorinated (co)polymer preferably comprises tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, a perfluoroalkoxy alkane, or a combination thereof. Suitable fluoropolymers are available under the trade name “TEFLON FEP100” from E. I. DuPont de Nemours, Wilmington, DE, or which “TEFLON FEP100 500 A is currently preferred.

Suitable exemplary fluoropolymers also include copolymers of tetrafluorethylene, hexafluoropropylene, and vinylidene fluoride (THV) under the trade designations “DYNEON THV 220,” “DYNEON THV 221,” “DYNEON THV 230,” “DYNEON THV 2030,” “DYNEON THV 415”, “DYNEON THV 500”, “DYNEON THV 610”, and “DYNEON THV 815” from Dyneon LLC, Oakdale, MN.

[00143] In some applications, it may be useful to employ a low coefficient of thermal expansion (CTE) film, for instance when the article will be subjected to large variations in ambient temperature. Some exemplary low CTE polymers include for instance and without limitation, polyimide, heat stabilized PEN, and PET. Preferably, a low CTE material has a CTE of 80 parts per million per kelvin (ppm/K) or lower, 70 ppm/K, 60 ppm/K, 50 ppm/K, 40 ppm/K, 30 ppm/K, or even 25 ppm/K or less. The coefficient of thermal expansion has tire general meaning as emplo ed in the art, i.e., as determined using ASTM E831.

[00144] The smoothness and adhesion of layers to the structured film can be enhanced by appropriate optional pretreatment of the structured film or optional application of a priming layer. Methods for surface modification are known in the art. In one embodiment, a pretreatment regimen involves electrical discharge pretreatment of the substrate in the presence of a reactive or non-reactive atmosphere (e.g., plasma, glow discharge, corona discharge, dielectric barrier discharge or atmospheric pressure discharge), chemical pretreatment, or flame pretreatment. These pretreatments can help ensure that the surface of the structured film will be receptive to the subsequently applied layers. In one embodiment, the method can include plasma pretreatment. For organic surfaces, plasma pretreatments can include nitrogen or water vapor. Another pretreatment regimen involves coating the structured film with an inorganic or organic base coat layer optionally followed by further pretreatment using plasma or one of the other pretreatments described above.

[00145] Preferably, the structured film itself transmits an average of at least 70, 80, 90, or 95 percent of incident visible light in a wavelength range from greater than 400 nm to 700 nm.

Optional Barrier Layer

[00146] In another embodiment, an optional barrier layer is included in the wavelength-selective multilayer article. For instance, at the locations of intermediate layers 60 and/or 80 in FIG. 1 A and/or intermediate layer 60 in FIG. 2C. The barrier layer 60 is disposed between the second major surface 38 of the inorganic multilayer optical film 30 and the first major surface 26 of the polymeric multilayer optical film 20. In cases where the wavelength-selective multilayer article 10 includes a structured film 50, the barrier layer 60 is disposed between the first major surface 56 of the structured film 50 and the second major surface 38 of the inorganic multilayer optical film 30. The barrier layer 80 is disposed between the second major surface 28 of the polymeric multilayer optical film 20 and a substrate 70 (e.g., a solar array described in detail below).

[00147] Referring to FIG. 1C, a schematic cross-sectional view of a barrier layer 90 is provided. The barrier layer 90 may include a single layer or more than one layer. In some embodiments, the barrier layer 90 comprises an inorganic layer 92. Suitable inorganic layer(s) comprise an inorganic material selected from silicon oxide, silicon alumina oxide, silicon oxynitride, gallium oxide, magnesium oxide, niobium oxide, titanium dioxide, yttrium oxide, zinc oxide, tin oxide, nickel oxide, tungsten oxide, aluminum doped zinc oxide, indium tin oxide, zirconium oxide, zirconium oxynitride, hafnia, aluminum oxide, alumina doped silicon oxide, lanthanum fluoride, neodymium fluoride, aluminum fluoride, magnesium fluoride, calcium fluoride, or a combination thereof.

[00148] In certain embodiments, the inorganic layer is a metal oxide layer. Typically, such a metal oxide layer comprises titanium oxide, aluminum oxide, zinc oxide, tantalum pentoxide, zirconium oxide, or niobium oxide. In select embodiments, a metal oxide layer comprises titanium oxide. A suitable inorganic layer is composed of a continuous 15-60 nm thickness of one or more inorganic materials. Accordingly, the inorganic layer could be formed of just one metal oxide or could be formed of a combination of two or more metal oxides.

[00149] Often, a thickness of the inorganic layer is 15 nm or greater, 17 nm, 20 nm, 22 nm, 25 nm, 27 nm, or 30 nm or greater; and 60 nm or less, 57 nm, 55 nm, 52 nm, 50 nm, 47 nm, 45 nm, 42 nm, 40 nm, 37 nm, 35 nm, 32 nm, 30 nm, 27 nm, 25 nm, 22 nm, or 20 nm or less. In some cases, a thickness of the inorganic layer is 15 nm to 20 nm, 20 nm to 30 nm, or 20 nm to 40 nm. When the thickness is less than 15 nm it can be difficult to form a continuous layer instead of discontinuous islands of deposited inorganic material. When the thickness is too great, the inorganic layer risks imparting a visible color to the article and/or decreasing transmission of visible light through the inorganic layer.

[00150] Preferably, an inorganic layer does not contribute to the wavelength-selective multilayer article having a yellow appearance. Whether or not an article has a yellow-colored appearance can be determined, for instance, by measuring the transmission of light through the wavelength-selective multilayer article. A lack of a yellow-colored appearance is found in an article that exhibits an average transmission of at least one of 0°, 30°, 45°, 60°, or 75° incident light angle of light having a wavelength range of at least above 410 nm of 70% or greater. Concomitantly, an article that exhibits an average transmission of at least one of 0°, 30°, 45°, 60°, or 75° incident light angle of light having a wavelength range of at least above 410 nm of less than 70% is likely to appear yellow.

[00151 ] An inorganic layer can typically be prepared by evaporation, reactive evaporation, sputtering, reactive sputtering, chemical vapor deposition, plasma enhanced chemical vapor deposition, and atomic layer deposition. Preferred methods include vacuum preparations such as sputtering and evaporation.

For instance, in some cases one of two forms of physical vapor deposition (PVD) are used: evaporation or sputtering. Evaporated coatings rely upon heating the coating material (evaporant) to a temperature at which it evaporates. This is followed by condensation of the vapor upon a substrate. For evaporated coatings, the electron-beam deposition process is most commonly used. Sputtered coatings use energetic gas ions to bombard a material (“target”) surface, ejecting atoms which then condense on the nearby substrate. Depending upon which coating method is used, and the settings used for that method, thin film coating rate and structure-property relationships will be strongly influenced. Ideally, coating rates should be high enough to allow acceptable process throughput and film performance, characterized as dense, low stress, void free, non-optically absorbing coated layers.

[00152] In some embodiments, the barrier layer 90 comprises both an inorganic layer 92 and a (e.g., first) (co)polymer layer 94 overlaying the inorganic layer 90. In some embodiments, the barrier layer 90 further comprises a (e.g., second) (co)polymer layer 96 disposed opposite the first (co)polymer layer 94. Such a configuration provides a three-layer barrier layer 90 of an inorganic layer 92 disposed between two (co)polymer layers 94, 96. Considering the barrier layer positioned in a wavelength-selective multilayer article, the second (co)polymer layer would be located between the inorganic layer and the first major surface of the polymeric multilayer optical fdm. Stated another way, referring back to FIG.

1 A, the barrier layer 60 optionally comprises a (co)polymer layer disposed adjacent to the first major surface 26 of the polymeric multilayer optical film 20.

[00153] Wavelength-selective multilayer articles that include a barrier layer provide protection from atomic oxygen environments. For instance, advantageously, in many cases the wavelength-selective multilayer article exhibits an atomic oxygen degradation, when tested according to the Atomic Oxygen Degradation Test, of less than 1 x IO'²⁰ mg/atom, 1 x 10'²¹ mg/atom, or 1 x 10'²² mg/atom. Such resistance to degradation by atomic oxygen is particularly useful when the light shielding article is part of a low earth orbit device.

[00154] Barrier layers, according to at least certain embodiments of the present disclosure, can exhibit superior mechanical properties such as elasticity and flexibility yet still have low atomic oxygen degradation rates.

[00155] Each optional (co)polymer layer in the barrier layer comprises a (co)polymer selected from an olefinic (co)polymer, a (methjacrylate (co)polymer, a urethane (co)polymer, a fluoropolymer, a silicone (co)polymer, or a combination thereof. (Co)polymeric layers can be formed from a variety of organic materials or compounds using a variety of processes. The (co)polymeric layer may be crosslinked in situ after it is applied. In one embodiment, the (co)polymeric layer can be formed by flash evaporation, vapor deposition and (co)polymerization of a monomer using, for example, heat, plasma, UV radiation or an electron beam.

[00156] Exemplary monomers for use in such a method include volatilizable (methjacrylate monomers. In a specific embodiment, volatilizable acrylate monomers are employed. Suitable (methjacrylates will have a molecular weight that is sufficiently low to allow flash evaporation and sufficiently high to permit condensation on the substrate. The organic materials or compounds also can be vaporized using any methods like those described in PCT Publication No. WO 2022/243756 (Sweetnam et al.) for example the methods described with respect to vaporizing a metal alkoxide. [00157] If desired, the one or more (co)polymeric layers can alternatively be applied using conventional methods such as plasma deposition, solution coating, extrusion coating, roll coating (e.g., gravure roll coating), or spray coating (e.g., electrostatic spray coating), and if desired crosslinked or (co)polymerized, (e.g., as described above. The desired chemical composition and thickness of the additional layer will depend in part on the nature and desired purpose of the wavelength-selective multilayer article. Coating efficiency can be improved by cooling the article.

[00158] Exemplary organic compounds include esters, vinyl compounds, alcohols, carboxylic acids, acid anhydrides, acyl halides, thiols, amines and mixtures thereof. Non-limiting examples of esters include (meth)acrylates, which can be used alone or in combination with other multifunctional or monofunctional (meth)acrylates. Exemplary (meth)acrylates include hexanediol diacrylate, ethoxyethyl acrylate, phenoxyethyl acrylate, cyanoethyl (mono)acrylate, isobomyl acrylate, octadecyl acrylate, isodecyl acrylate, lauryl acrylate, beta-carboxyethyl acrylate, tetrahydrofurfuryl acrylate, dinitrile acrylate, pentafluorophenyl acrylate, nitrophenyl acrylate, 2 -phenoxy ethyl acrylate, 2,2,2-trifluoromethyl acrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tripropylene glycol diacrylate, tetraethylene glycol diacrylate, neopentyl glycol diacrylate, propoxylated neopentyl glycol diacrylate, polyethylene glycol diacrylate, tetraethylene glycol diacrylate, bisphenol A epoxy diacrylate, trimethylol propane triacrylate, ethoxylated trimethylol propane triacrylate, propylated trimethylol propane triacrylate, tris(2- hydroxyethyl)-isocyanurate triacrylate, pentaerythritol triacrylate, phenylthioethyl acrylate, naphthloxyethyl acrylate, IRR-214 cyclic diacrylate from UCB Chemicals, epoxy acrylate RDX80095 from Rad-Cure Corporation, the corresponding methacrylates of the acrylates listed above and mixtures thereof. Exemplary vinyl compounds include vinyl ethers, styrene, vinyl naphthylene and acrylonitrile. Exemplary alcohols include hexanediol, naphthalenediol and hydroxyethylmethacrylate. Exemplary carboxylic acids include phthalic acid and terephthalic acid, (meth)acrylic acid). Exemplary acid anhydrides include phthalic anhydride and glutaric anhydride. Exemplary acyl halides include hexanedioyl dichloride, and succinyl dichloride. Exemplary thiols include ethyleneglycol- bisthioglycolate, and phenylthioethylacrylate. Exemplary amines include ethylene diamine and hexane 1,6-diamine.

[00159] Optionally, at least one (co)polymer layer, if present in the barrier layer, further comprises an additive that is an ultraviolet radiation absorber, a hindered amine light stabilizer, an antioxidant, or a combination thereof. UV absorbers (UVAs), Hindered Amine Light Stabilizers (HALs), and antioxidants can help prevention of photo-oxidation degradation of the (co)polymer layer. Suitable compounds include benzophenones, benzotriazoles, and triazines (e.g., benzotriazines). Exemplary UVAs for incorporation into a (co)polymer layer include those available under the trade designations “TINUVIN 1577” and “TINUVIN 1600,” from BASF Corporation, Florham Park, NJ. U.S. Pat. No. 9,670,300 (Olson et al.) and U.S. Pat. App. Pub. No. 2017/0198129 (Olson et al.) describe exemplary UVA oligomers that are compatible with PVDF fluoropolymers. Exemplary HALs for incorporation into a (co)polymer layer include those available under the trade designations “CHIMMASORB 944” and “TINUVIN 123,” from BASF Corporation. Typically, UVAs, HALs, and/or antioxidants are incorporated in the (co)polymer layer at a concentration of 1-10 wt.%.

[00160] The first (co)polymer layer, if present, is preferably crosslinked. In some exemplary embodiments, the first (co)polymer layer comprises an olefinic (co)polymer selected from low density polyethylene, linear low density polyethylene, ethylene vinyl acetate, polyethylene methyl acrylate, polyethylene octene, polyethylene propylene, polyethylene butene, polyethylene maleic anhydride, polymethyl pentene, polyisobutene, polyisobutylene, polyethylene propylene diene, cyclic olefin (co)polymers, and blends thereof.

[00161] In certain exemplary embodiments, the at least one optional (co)polymer layer further comprises an ultraviolet radiation absorber, a hindered amine light stabilizer, an antioxidant, or a combination thereof. The ultraviolet radiation absorber is preferably selected from a benzotriazole compound, a benzophenone compound, a triazine compound, or a combination thereof. Presently preferred hindered amine light stabilizers are available from BASF U.S.A (Florham Park, NJ) under the trade name “TINUVIN”. The hindered amine light stabilizer is preferably selected from TINUVIN 123, TINUVIN 144, TINUVIN 292, or a combination thereof. Presently preferred anti-oxidants are available from BASF under the trade name “IRGANOX” and “IRGAFOS”. Suitable antioxidants for polyolefins are preferably selected from IRGANOX 1010, IRGANOX 1076, IRGAFOS 168, or a combination thereof.

[00162] The optional barrier layer can be subjected to various post-treatments such as heat treatment, UV or vacuum UV (VUV) treatment, or plasma treatment. Heat treatment can be conducted by passing the barrier layer through an oven or directly heating the barrier layer in the coating apparatus, (e.g., using infrared heaters or heating directly on a drum. Heat treatment may for example be performed at temperatures from about 30°C to about 200°C, about 35°C to about 150°C, or about 40°C to about 70°C.

Solar Arrays

[00163] In a second aspect, a solar array is provided. The solar array includes a wavelength-selective multilayer article according to any embodiments of the first aspect described in detail above disposed on an exterior surface of the solar array.

[00164] One of the promising energy resources today is sunlight. Harnessing sunlight may be accomplished by the use of photovoltaic (PV) cells (also referred to as solar cells), which are used for photovoltaic conversion of sunlight to electrical current. Solar cells are relatively small in size and typically combined into a physically integrated solar module (or PV module) having a correspondingly greater power output than the individual solar cells of the module. Solar modules are generally formed from two or more “strings” of solar cells surrounded by an encapsulant and enclosed by front and back panels, wherein at least one panel is transparent to sunlight.

[00165] Wavelength-selective multilayer articles according to the present disclosure may thus be used to protect an array of solar cells by being included on an exterior surface of the solar array.

[00166] Referring again to FIG. 1 A, the present disclosure describes solar arrays 40 each including a wavelength-selective multilayer article 10 positioned on an exterior surface 76 of a solar cell array 70. The wavelength-selective multilayer article 10 includes an inorganic multilayer optical film 30 and a polymeric multilayer optical film 20. In some cases, the wavelength-selective multilayer article 10 may be directly attached to the surface 76 of the solar array 70, e.g., by using heat lamination. There may instead be one or more optional intermediate layers 80 between the wavelength-selective multilayer article 10 and the solar array surface 76, such as a barrier layer, transparent adhesive tie layer or an encapsulant. When an intermediate layer 80 is present, in some embodiments, the intermediate layer 80 is a barrier layer according to any of the embodiments described above in detail with respect to the first aspect. In such cases, the solar array 40 further comprises a barrier layer 80 disposed between the solar array 70 and the wavelength-selective multilayer article 10.

[00167] Listing of Exemplary Embodiments

[00168] In a first embodiment is provided a wavelength-selective multilayer article. The wavelength- selective multilayer article comprises a polymeric multilayer optical film having a first major surface and an opposing second major surface. The polymeric multilayer optical film comprises one or more alternating first and second polymeric optical layers collectively reflecting light that is normally incident to a first major surface of the wavelength-selective multilayer article, an average of at least 50, 60, 70, 80, 90, or 95 percent of incident light over at least a 30-nanometer wavelength reflection bandwidth in a wavelength range from 800 nanometers (nm) to 1200 nm, 1200 nm to 1600 nm, or 800 nm to 1600 nm. The wavelength-selective multilayer article also comprises an inorganic multilayer optical film having a first major surface and an opposing second major surface, wherein the second major surface of the inorganic multilayer optical film is attached to the first major surface of the polymeric multilayer optical film. The inorganic multilayer optical film comprises one or more alternating first and second inorganic optical layers collectively reflecting and absorbing light that is normally incident to the first major surface of the wavelength-selective multilayer article, an average of at least 50, 60, 70, 80, 90, or 95 percent of incident ultraviolet light over at least a 30-nanometer wavelength bandwidth in a wavelength range from 190 nm to 400 nm.

[00169] In a second embodiment is provided a wavelength-selective multilayer article according to the first embodiment, further comprising a structured film comprising a first major surface and an opposing second major surface, wherein the first major surface comprises a plurality of structures projecting therefrom, wherein at least some of the plurality of structures each has a surface whose slope causes light that is normally incident to the first major surface of the stmctured film to intercept the first major surface or the surface of at least one other structure after reflection, wherein the structured film is disposed either: a) between the first major surface of the polymeric multilayer optical film and the second major surface of the inorganic multilayer optical film or b) adjacent to the second major surface of the polymeric multilayer optical film opposite the inorganic multilayer optical film.

[00170] In a third embodiment is provided a wavelength-selective multilayer article according to the first embodiment or the second embodiment, wherein at least some of the stmctures comprise at least one angled sidewall having a peak angle of 90 degrees or less and the peak angle is 5, 15, 25, 35, or 45 degrees or greater.

[00171] In a fourth embodiment is provided a wavelength-selective multilayer article according to the second embodiment or the third embodiment, wherein at least some of the structures have a shape with a triangular cross-section.

[00172] In a fifth embodiment is provided a wavelength-selective multilayer article according to any of the second through fourth embodiments, wherein the structures have a shape that is a prism, a pyramid, an inverted pyramid, a diffraction grating, an inverted cone, or a cone.

[00173] In a sixth embodiment is provided a wavelength-selective multilayer article according to any of the second through fifth embodiments, wherein the structured film is flexible.

[00174] In a seventh embodiment is provided a wavelength-selective multilayer article according to any of the second through sixth embodiments, wherein the structures refract light that is incident at an angle other than normal to the first major surface of the wavelength-selective multilayer article to exit the structured film at an angle that is closer to normal than the incident angle.

[00175] In an eighth embodiment is provided a wavelength-selective multilayer article according to any of the first through seventh embodiments, further comprising a barrier layer disposed between the second major surface of the inorganic multilayer optical film and the first major surface of the polymeric multilayer optical film.

[00176] In a ninth embodiment is provided a wavelength-selective multilayer article according to the eighth embodiment, wherein the structured film is present between the first major surface of the polymeric multilayer optical fdm and the second major surface of the inorganic multilayer optical film and the barrier layer is disposed between the first major surface of the structured film and the second major surface of the inorganic multilayer optical film.

[00177] In a tenth embodiment is provided a wavelength-selective multilayer article according to the eighth embodiment or the ninth embodiment, wherein the barrier layer comprises an inorganic layer. [00178] In an eleventh embodiment is provided a wavelength-selective multilayer article according to the tenth embodiment, wherein the inorganic layer has a thickness of 15 to 60 nm.

[00179] In a twelfth embodiment is provided a wavelength-selective multilayer article according to any of the eighth through eleventh embodiments, wherein the barrier layer further comprises a (co)polymer layer overlaying the inorganic layer.

[00180] In a thirteenth embodiment is provided a wavelength-selective multilayer article according to the twelfth embodiment, wherein the barrier layer further comprises a (co)polymer layer disposed between the inorganic layer and the first major surface of the polymeric multilayer optical film.

[00181] In a fourteenth embodiment is provided a wavelength-selective multilayer article according to any of the first through thirteenth embodiments, wherein the polymeric multilayer optical film further comprises a third polymeric optical layer disposed between the first polymeric optical layer and the second polymeric optical layer of at least one pair of the alternating first and second polymeric optical layers. [00182] In a fifteenth embodiment is provided a wavelength-selective multilayer article according to any of the first through fourteenth embodiments, which transmits light that is normally incident to the first major surface of the wavelength-selective multilayer article, an average of at least 50, 60, 70, 80, 90, or 95 percent of normally incident light in a wavelength range from greater than 400 nm to 700 nm, greater than 400 nm to 1100 nm, or greater than 400 nm to 1350 nm.

[00183] In a sixteenth embodiment is provided a wavelength-selective multilayer article according to any of the first through fifteenth embodiments, wherein the first optical layer of the inorganic multilayer optical film comprises at least one of niobium oxide, titanium oxide, silicon oxynitride, molybdenum oxide, tungsten oxide, silicon nitride, indium tin oxide, hafnium oxide, tantalum oxide, zirconium oxynitride, zirconium oxide, aluminum zinc oxide, or zinc oxide and wherein the second optical layer of the inorganic multilayer optical film comprises at least one of silicon oxide, silicon aluminum oxide, N type- or P type-doped silicon oxide, aluminum oxide, aluminum fluoride, magnesium fluoride, calcium fluoride, indium tin oxide, or zinc oxide.

[00184] In a seventeenth embodiment is provided a wavelength-selective multilayer article according to any of the first through sixteenth embodiments, wherein the first optical layer of the inorganic multilayer optical film comprises at least one of niobium oxide or titanium oxide, and wherein the second optical layer of the inorganic multilayer optical film comprises silicon aluminum oxide.

[00185] In an eighteenth embodiment is provided a wavelength-selective multilayer article according to any of the first through seventeenth embodiments, wherein the first optical layer of the inorganic multilayer optical film comprises at least one of niobium oxide or titanium oxide, and wherein the second optical layer of the inorganic multilayer optical film comprises silicon oxide.

[00186] In a nineteenth embodiment is provided a wavelength-selective multilayer article according to any of the first through eighteenth embodiments, exhibiting an average transmission of wavelengths between 400 nm and 700 nm, 400 nm to 1100 nm, or 400 nm to 1350 nm, through the article that is reduced by less than 20%, 10%, 5%, or less than 1% after exposure to a certain dose of ultraviolet light. [00187] In a twentieth embodiment is provided a wavelength-selective multilayer article according to any of the first through nineteenth embodiments, exhibiting an average reflection of wavelengths between 800 nm to 1200 nm, 1200 nm to 1600 nm, or 800 nm to 1600 nm, off the article that is reduced by less than 20%, 10%, 5%, or less than 1% after exposure to a certain dose of ultraviolet light.

[00188] In a twenty -first embodiment is provided a wavelength-selective multilayer article according to any of the first through twentieth embodiments, wherein the polymeric multilayer optical film comprises a third order harmonic that reflects at least 80, 90, or 95 percent of light that is normally incident to a first major surface of the wavelength-selective multilayer article over at least a 30 nm wavelength bandwidth in a wavelength range from 340 nm to 400 nm, 350 nm to 400 nm, or 365 nm to 400 nm.

[00189] In a twenty-second embodiment is provided a solar array. The solar array comprises a wavelength-selective multilayer article according to any of the first through twenty -first embodiments disposed on an exterior surface of the solar array. [00190] In a twenty-third embodiment is provided a solar array according to the twenty-second embodiment, further comprising a barrier layer disposed between the solar array and the wavelength- selective multilayer article.

EXAMPLES

[00191]Unless otherwise noted or readily apparent from the context, all parts, percentages, ratios, etc. in the Examples and the rest of the specification are by weight.

Materials Used in the Examples

Test Methods

\GGl91\Spectral Properties Modelin Test. Prior to fabricating the structured ultraviolet light shielding articles, we modeled the optical properties (transmission, reflection, and absorption) of the intended inorganic multilayer optical film coatings to precisely determine the necessary thicknesses of the optical coating layers. To perform this modeling, Test Samples 1 and 2 were measured with an ellipsometer (obtained under tradename “RC2 Ellipsometer” from J. A. Woolam; Lincoln, NE) to determine the spectral index of refraction (n) and extinction coefficient (k) values of the evaporated TiCh and SiCh samples. Then the n and k obtained above were input into optical modeling software (obtained under tradename “Essential MaCleod” from The Thin Film Center; Tucson, AZ) and used to compute the reflection, transmission, and absorption spectra for the inorganic multilayer optical films detailed in the Comparative Examples Structure Table, Example Structure Table, and Prophetic Example Structure Table below. All structures were modeled with a PET substrate except Comparative Example 4 which was modeled with a glass substrate. Comparative Examples 2 and 4 and Examples 1 and 2 were modeled with normally incident light, and Examples 3 and 4 and Prophetic Examples 5, 6, and 7 were modeled with an incident angle of 45 degrees.

[00193] The total transmission, reflection, and absorption spectra of Prophetic Examples 5 and 6 were modeled in the following way. First, the spectra of the inorganic multilayer optical film was modeled as described in the preceding paragraph. Next a measured spectra of a film of Comparative Example 1 was collected. These prophetic examples would have structured inorganic multilayer optical films and structured polymeric multilayer optical films, and these structures would cause incident reflected light to strike a second surface of the film, so it was necessary to model the effect of two passes of the light through the film. The total transmission, reflectance, and absorption after two passes through the film was calculated as (all units in %):

[00194] where Rtotai/Ttotai/Atotai are the total effective reflection/transmission/absorption of light after two passes through the film, Ri is the reflected light after a single reflection off of the film, Rm/Tin/Am are the reflection/transmission/absorption of the inorganic vapor coated mirror, and Rp/Tp/A_p are the reflection/transmission/absorption of the polymeric multilayer optical film. [00195] The total transmission, reflection, and absorption spectra of Prophetic Example 7 was modeled in the following way. First, the spectra of the inorganic multilayer optical film coating was modeled as described previously. Next, the spectra of the 3rd order harmonic IR light reflecting multilayer optical mirror film was calculated from figure 12 (i.e., FIG. 12) of U.S. Pat. No. 6,744,561 (Condo et al.), assuming no absorption of light in the film above 360 nm and 100% absorption of light below 360 nm as an approximation of the absorption of PET and poly(ethylene-co-octene) (PE-PO) in these wavelength ranges. The Prophetic Example 7 film would have a structured inorganic multilayer optical film which causes incident light reflected by the inorganic multilayer optical film to strike an additional surface of the film, so it was necessary to model the effect of the second bounce of the light reflected by the inorganic multilayer optical film. The total transmission, reflectance, and absorption through the film was calculated as (all units in %):

^Rtotal = (^Rtn + Tin * ^Rp) + ^RIn * (^Rtn + T_in * Rp) Ttotal = ( in * Tp) + R_irl * (T_in * T_p) ^total 100 — Rt_ot_ai T_tota

[00196] Note that all of these are spectrally resolved quantities, though in the result tables below they are reported as average quantities over selected spectral wavelength ranges.

\00l9T\Spectral Properties Measurement Test: The spectral transmission and reflection of freestanding examples of ultraviolet light shielding articles were measured using a spectrophotometer (obtained under the trade designation “LAMBDA 1050” from PerkinElmer, Inc., Waltham, MA). Absorption was calculated (in units of percentage) as 100 - Reflection -Transmission. The measured spectral reflection, absorption, and transmission are reported as an average percent over a wavelength range in the in the Infrared Reflection Results Table, the Ultraviolet Reflection and Absorption Results Table, and the Transmission Results Table.

[00198] Solar Aging Test'. Samples were exposed in an Atlas Ci5000 Weather-Ometer (obtained from AMETEK, Berwyn, PA) using a xenon arc lamp equipped with quartz inner and outer filters. The quartz filter set provides minimal attenuation to the spectral power distribution of the xenon lamp, which gives a close approximation to the shape of solar output (ASTM E490). To increase the rate at which dosage is accumulated, the samples were exposed on custom-made stainless steel and aluminum extended holders. The extended holders move the exposure plane from 19 inches (48.3 cm) away from the core of the lamp to 13.5 inches (34.3 cm) from the core of the lamp. Irradiance was controlled at 1.5 W/m² at 340 nm at the rack plane and was measured to be 2.6 W/m² at 340 nm at the extended sample plane. Ambient air temperature inside the Weatherometer was controlled at 48 °C, a black-panel thermometer (BPT) was controlled at 75 °C at the rack plane and measured to be approximately 95 °C at the sample plane, and relative humidity was controlled at 30%. Samples were exposed without any backing. Samples were exposed to a dose of at least 470 MJ/m² cumulative irradiance from 250-385 nm.

[00199] The reduction in sample spectral properties after solar aging was calculated as % reduction in spectra = Sf_resh — S_aged

[00200] where Sf_resh is the average value of a particular spectra (e.g., transmission or reflectance) over a spectral range (e.g., 400-700 nm) before solar aging, and S_aged is the average spectral value over the same spectral range after the above exposure. The results of the Solar Aging Test are summarized in the Solar Aging Results Tables.

1002011 Flexibility Test: Samples were tested for flexibility by wrapping the films around a metal mandrel with a diameter of 0.5” (1.27 cm), with the coated side facing away from the mandrel. The Spectral Properties Test was performed both before and after wrapping the samples around the mandrel. The change in spectral value in units of absolute percent was calculated as

% change in spectra = S_unwrapped ’ wrapped

[00202] where Sunwrapped and Swrappe are the average value of a particular spectra (e.g., transmission, reflectance, or absorption) and spectral range (e.g., 400-700 nm), in units of percentage, for the same sample before and after wrapping, respectively. This calculation was performed separately for the transmission, reflection, and absorption spectra. The calculated percent difference in spectra after wrapping are reported below in the Flexibility Test Results Table below.

Test

[00203] Test Sample 1 : A 70 nm-thick TiCh layer was deposited on a silicon chip in the following manner: the vapor coater used was a Denton Vacuum Optical Coater consisting of a 5-planet planetary drive system located ~ 30” (76.2 cm) above a 4-pocket Temescal Electron Beam gun (obtained from Ferro Tec Corporation, Livermore, CA). The planetary system was designed to hold the substrate perpendicular to the evaporation source and to move that disk in a planetary type motion in and out of the evaporation plume during the deposition. The actual process for the coating consisted of: a) The vapor coater was vented to atmosphere and one the five planets was removed. The substrate was prepared for coating by adhering/taping it to the planet by a poly imide tape, b) The planet was reinstalled, and the other 4 planets were configured similarly, if needed, and they too were reinstalled in the coater, c) The chamber was closed and pumped to a vacuum level of < 2xl0'⁵ Torr (2.7xl0‘³ Pa), d) When the vapor coater was at a low enough vacuum, the material was ion beam treated using a Kaufman-type ion source for ~ 10 minutes at a voltage of 400V as a pretreatment to the substrate for adhesion of the vapor deposited coating to the substrate prior to applying the oxide films, e) Oxygen gas was added via a MKS mass flow controller (obtained from MKS Instruments, Inc., Andover, MA) to obtain a pressure of 4.0xl0'⁵ Torr (5.3xl0‘³ Pa). This was usually about 10 standard cubic centimeters per minute (seems) for added oxygen gas. f) The planetary was started and moved around the coater at a rotational speed of ~60 rpm to prepare for coating and to achieve a high level of uniformity on the attached substrates, g) A Temescal electron beam gun power supply was energized. A voltage of WkV and a current of a few milliamps was applied to the e-gun’s filament, heating the source material in the e-gun. The source was heated and controlled via an Eddy Company Optical Monitoring System (OMS) (from Eddy Company, Apple Valley, CA). The source was heated until the desired deposition rate of the material was achieved; in the case of TiO₂ this rate was 2 angstroms per second (A/s), and in the case of SiCf this was 4 A/s. When the desired deposition rate of the material was achieved and steady, a shutter that separates the source from the planets was opened and the rate was maintained via the OMS until the desired optical thickness was achieved, at which point the shutter closed and the OMS shut power off to the e-beam source, h) The main power to the power supply was turned off and the source allowed to cool for about 10 minutes, i) This process was repeated for additional layers/types of material until the full desired multilayer optical film had been deposited, j) The chamber was then vented back to atmospheric pressure via N₂ gas and each planet was removed and the substrate was removed from each planet.

[00204] Test Sample 2: a 115 nm-thick SiO₂ layer was deposited on a silicon chip in the same manner as Test Sample 1.

Comparative Examples

[00205] Comparative Example 1 : An infrared (IR) light reflecting multilayer optical mirror film was made with alternating layers in an ABCB configuration with the A optical layers made from PET resin, B optical layers made with PETG resin, and C optical layers made from CoPMMA resin. Exemplary optical films with an ABCB layer construction were described in U.S. Pat. No. 6,667,095 (Wheatley et al), which is incorporated herein by reference. This film was prepared by coextrusion and biaxial orientation as described in U.S. Pat. Appl. Pub. No. 2001/0013668 (Neavin et al.) with exceptions as follows. The PET, PETG, and CoPMMA were coextruded through a multilayer polymer melt manifold to form a stack of 425 optical layers. The optical layer thickness profile of this IR reflecting mirror film was adjusted to be approximately a linear profile with the optical layers adjusted to reflect 1200 mu to 1800 mu light. Layer thickness profiles of such films can be adjusted to provide for improved spectral characteristics using the axial rod apparatus taught in U.S. Pat. No. 6,783,349 (Neavin et al.) combined with layer profile information obtained with microscopic techniques. In addition to these optical layers, non-optical protective boundary layers of PET were coextmded on both sides of the optical layer stack. The multilayer melt was then cast through a film die onto a chill roll, in the conventional manner for polyester films, upon which it was quenched. The cast web was then stretched in a commercial scale biaxial tenter at temperatures and draw profiles similar to those described in U.S. Pat. Appl. Pub. No. 2001/0013668 (Neavin et al.).

[00206] Comparative Example 2: A vapor coated multilayer optical film was prepared in the same manner as Test Sample 1, except a PET film was used for the substrate, and the structure deposited on the PET film substrate is summarized in the Comparative Examples Structure Table below. The PET film substrate used for these samples was pretreated by the supplier on one side to promote adhesion of other materials to the substrate; the substrate was taped to the planet such that the non-pretreated side of the PET film would be coated by the vapor coating process.

[00207] Comparative Example 3 : Comparative Example 3 was a piece of BEF4 film. [00208] Comparative Example 4: Comparative Example 4 was prepared in the same manner as Comparative Example 2, except a piece of BK7 was used as the substrate, and the coating layers deposited are as described in the Comparative Examples Structure Table.

Preparatory Examples

[00209] Preparatory Example 1 : Preparatory Example 1 was prepared by covering a piece of Comparative Example 1 infrared mirror film substrate with a stack of a base polymer layer (Layer 1), an inorganic silicon aluminum oxide (SiAlOx) barrier layer (Layer 2), and a protective polymeric layer (Layer 3) in a vacuum coater similar to the coater described in U.S. Pat. No. 5,440,446 (Shaw et al.) and U.S. Pat. No. 7,018,713 (Padiyath, et al.), both of which are incorporated herein by reference. The individual layers were formed as follows:

[00210] Layer 1 (a base polymer layer): 300 mm x 300 mm sheets of Comparative Example 1 infrared mirror film were taped to the surface of a 356 mm wide roll of PET film of indefinite length. A length of at least 150 feet of PET film was left without sheet samples both before and after the samples to ensure adequate length for the coating equipment to warm up and stabilize before the sheet samples were exposed, and cool down after coating was complete. This film roll was loaded into a roll-to-roll vacuum processing chamber. The chamber was pumped down to a pressure of 2xl0'⁵ Torr. A web speed of 3.4 meters/minute was held while maintaining the backside of the film in contact with a coating drum chilled to -10° C. With the backside in contact with the drum, the film frontside surface was treated with a nitrogen plasma at 0.02 kW of plasma power. The sheet samples’ microstructured frontside surfaces were then coated with SR833S. The monomer was degassed under vacuum to a pressure of 20 mTorr prior to coating, loaded into a syringe pump, and pumped at a flow rate of 0.89 mL/min and N₂ carrier gas flow rate of 60 seem through an ultrasonic atomizer operating at a frequency of 60 kHz into a heated vaporization chamber maintained at 260° C. The resulting monomer vapor stream condensed onto the film surface and was electron beam crosslinked using a multi-filament electron-beam cure gun operating at 7.0 kV and 4 mA to form a 500 nm thick base polymer layer.

[00211]Layer 2 (an inorganic layer): immediately after the base polymer layer deposition and with the backside of the film still in contact with the drum, a SiAlOx layer was sputter-deposited atop the base polymer layer. Two alternating current (AC) 40 kHz power supplies were used to control two pairs of cathodes; with each cathode housing two 90% Si/10% Al sputtering targets. During sputter deposition, the voltage signal from each power supply was used as an input for a proportional-integral-differential control loop to maintain a predetermined oxygen flow to each cathode. The sputtering conditions were: AC power 16 kW, with a gas mixture containing 350 standard cubic centimeter per minute (seem) argon and 213 seem oxygen at a sputter pressure of 3.5 mTorr. This provided a 25 nm thick SiAlOx layer deposited atop the base polymer layer (Layer 1).

[00212]Layer 3 (a protective polymeric layer): immediately after the SiAlOx layer deposition and with the film still in contact with the drum, a second acrylate was coated and crosslinked using the same general conditions as for Layer 1, but with these exceptions: (1) Electron beam crosslinking was carried out using a multi-filament electron-beam cure gun operated at 7 kV and 10 mA. Also, the monomer flow rate was increased to 1.33 mL/min to provide a 750 nm acrylate layer atop Layer 3. (2) The protective polymeric layer contained 3 wt. % of DYNASYLAN 1189 with the remainder SR833S.

[00213] Preparatory Example 2: Preparatory Example 2 was a THV815 film with microstructured linear prisms prepared as follows. A microstructured film, BEF4, was obtained to use as a mold/tooling film. The process used a three-roll vertical stack molding apparatus similar to the one described in U.S. Patent Application No. 2015/9108349 (Clarke et al.), which includes an extruder and extrusion die adapted for extruding one or more layers of molten thermoplastic material into a mold. In this case, the mold is a microstructured tooling film (BEF4), which has been unwound onto a cylindrical roll to provide a desired surface pattern for transference to the molten thermoplastic material as it passes over the cylindrical surface of the roll. The casting roll had a surface temperature of 76.6 °C and a casting roll speed of 18.8 meters/minute. A nip force of 7600 pounds (300 pounds per linear inch) was applied to the polymer as it contacted the BEF4 film on the casting roll to produce the THV815 linear prism microstructured film (2 mil thick). The features of the micro structured film are reported in the Prismatic THV815 Structure Table below.

[00214] Preparatory Example 3 : Preparatory Example 3 was prepared in the same manner as Comparative Example 2, except a piece of Preparatory Example 2 prismatic TH V815 film was used for the substrate, and the structure deposited on the prismatic THV815 substrate is summarized in the Preparatory Examples Structure Table below. The prismatic THV815 film substrate was taped to the planet such that the structured side of the prismatic THV815 film would be coated by the vapor coating process.

[00215] One important factor to consider when preparing vapor coatings on micro structured substrates was the geometry of the substrate. The sloped surface of the structure resulted in an increased surface area for a microstructured substrate relative to a planar substrate. As a result of this increased surface area, the same deposition process of material onto a microstructured substrate and a planar substrate resulted in a thinner coating on the surface of the micro structured substrate than on the planar substrate. In other words, the fixed deposition process deposited a fixed volume of material onto the substrates, so the substrate with higher surface area received a thinner coating overall (coating thickness equals volume of material deposited divided by surface area of substrate).

[00216] Therefore, to achieve the desired thickness on a microstructured substrate, it was necessary to increase the total volume of material deposited relative to a deposition on a planar substrate. The volume of material was increased by a factor equal to the ratio of the surface area of the microstructured substrate and the planar substrate. In the case of a prismatic THV815 film substrate, which had one-dimensional prisms with a peak angle of 90 degrees, and therefore a slope of 45 degrees, it was necessary to increase the volume of material deposited by a factor equal to l/SIN(peak angle/2) = 1/SIN(45°) = 1.414.

[00217] Preparatory Example 4: Preparatory Example 4 was prepared first by coating pieces of Preparatory Example 2 prismatic THV815 film with a stack of a base polymer layer (Layer 1), an inorganic silicon aluminum oxide (SiAlOx) barrier layer (Layer 2), and a protective polymeric layer (Layer 3) in the same manner as Preparatory Example 1, except sheets of Preparatory Example 2 prismatic THV815 film were used instead of sheets of Comparative Example 1 IR mirror film, and the thicknesses of Layers 1/2/3 were 360 nm/18 nm/536 nm, respectively.

[00218] The sheet samples were then removed from the PET film roll. Then a vapor coated multilayer optical film was deposited on top of the protective polymer layer (Layer 3) in the same manner as Preparatory Example 3. The coating layers deposited are as described in the Preparatory Examples Stmcture Table.

[00219] Examples

[00220] Example 1 : Example 1 was prepared in the same manner as Comparative Example 2, except a piece of Comparative Example 1 IR mirror film was used as the substrate instead of PET film. The coating layers deposited are as described in the Examples Structure Table.

[00221] Example 2: Example 2 was prepared in the same manner as Comparative Example 2, except a piece of Preparatory Example 1 was used as the substrate instead of PET film. The coating layers deposited are as described in the Examples Structure Table.

[00222] Example 3 : Example 3 was prepared by placing a piece of Preparatory Example 3 on top of a piece of Comparative Example 1. The coating layers deposited are as described in the Examples Structure Table.

[00223] Example 4: Example 4 was prepared by placing a piece of Preparatory Example 4 on top of a piece of Comparative Example 1. The coating layers deposited are as described in the Examples Structure Table.

[00224] Prophetic Example 5 : A macrostructured version of Example 2 could be fabricated via multiple macrostructuring approaches. One way to produce such a film would be to first thermoform a piece of Comparative Example 1 into the desired structured shape, for example a 1 dimensional array of prisms with a triangular cross section, 90 degree apex angle, and height of 12 micrometers, then coat the macrostructured film with a stack of a base polymer layer (Layer 1), an inorganic silicon aluminum oxide (SiAlOx) barrier layer (Layer 2), and a protective polymeric layer (Layer 3) in the same manner as Preparatory Example 4, and then deposit a vapor coated multilayer optical film on top of the protective polymer layer (Layer 3) in the same manner as Preparatory Example 4. Note that the vapor coated layers deposited on these macrostructured films should be optimized for non-normally incident light. The hypothetical coating layers deposited could be as described in the Prophetic Examples Structure Table. [00225] Prophetic Example 6 : A macrostructured version of Example 1 could be fabricated via multiple macrostructuring approaches. One way to produce such a film would be to perform the same process described for preparing Prophetic Example 5, but to omit the deposition of the base polymer layer, the SiAlOx barrier layer, and the protective polymer layer. The hypothetical coating layers deposited could be as described in the Prophetic Examples Structure Table.

[00226] Prophetic Example 7: aversion of Example 4 could be made with similar optical properties, with the addition of a third order harmonic reflection band that reflects at least 80, 90, or 95 percent of light that is normally incident to a first major surface of the wavelength-selective multilayer article over at least a 30 nm wavelength bandwidth in a wavelength range from 340 nm to 400 nm, 350 nm to 400 nm, or 365 nm to 400 nm, by replacing the IR light reflecting multilayer optical mirror film Comparative Example 1 used in Example 4 with a 3^rd order harmonic IR light reflecting multilay er optical mirror film. An example of an appropriate 3^rd order harmonic IR light reflecting multilayer optical mirror film would be the “Example 16” IR film made from PET and poly(ethylene-co-octene) (PE-PO) described in U.S. Pat. No. 6,744,561 (Condo et al.), which has a primary reflection band reflecting >90-99% of light between 1020 nm and 1200 nm, and a third order harmonic reflection band reflecting >80-95% of light between 340 nm and 400 nm. The transmission, reflection, and absorption values for such a film were calculated using the spectrum in figure 12 (FIG. 12) of U.S. Pat. No. 6,744,561 (Condo et al.) and assuming reflection (%) is equal to 100 % - transmission (%) for the range 360-1500 nm, and that the PET component of the film absorbed all light below 360 nm, which are good approximations given the strong absorption below 340 nm and minimal absorption above 360 nm of PET and PE-PO materials. The optical properties of Prophetic Example 7 were calculated by modeling the optical structures of Example 4 on top of a film with the optical properties of “Example 16” described in U.S. Pat. No. 6,744,561 (Condo et al.), accounting for second reflections caused by the structured surface of the film, and are reported in the tables below.

Comparative Examples Structure Table

Preparatory Examples Structure Table

Examples Structure Table Prophetic Examples Structure Table

Infrared Reflection Results Table Ultraviolet Reflection and Absorption Results Table

Transmission Results Table Flexibility Test Results Table

[00227] Prophetic Examples 5-7 : these examples are expected to behave similarly in a bend test to Examples 1-4 because they have similar architectures, with the only major difference being the presence of macrostructuring of the underling polymeric multilayer optical film, which is not expected to affect the response to the bend test.

Solar Aging Test Tables [00228] Prophetic Examples 5-7: these examples are predicted to behave similarly to Examples 1-4 in the Solar Aging Test because the dominant factor will be the composition of the underlying polymeric multilayer optical film. In the case of Prophetic Examples 5-6, the underlying polymeric multilayer optical film is the same as that used in Examples 1-4 so no differences in the solar Aging Test are expected. In the case of Prophetic Example 7, PE-PO replaces the use of PETG and CoPMMa in the underling polymeric multilayer film, and PE-PO is not expected to increase the reduction in transmission or reflection caused by the Solar Aging Test.

[00229] Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.

[00230] Furthermore, all publications and patents referenced herein are incorporated by reference in their entirety to the same extent as if each individual publication or patent was specifically and individually indicated to be incorporated by reference. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description prevails. Various exemplary embodiments have been described. These and other embodiments are within the scope of the following claims.

Claims

What is claimed is:

1. A wavelength-selective multilayer article comprising: a polymeric multilayer optical film having a first major surface and an opposing second major surface, wherein the polymeric multilayer optical film comprises one or more alternating first and second polymeric optical layers collectively reflecting light that is normally incident to a first major surface of the wavelength-selective multilayer article, an average of at least 50, 60, 70, 80, 90, or 95 percent of incident light over at least a 30- nanometer wavelength reflection bandwidth in a wavelength range from 800 nanometers (nm) to 1200 nm, 1200 nm to 1600 nm, or 800 nm to 1600 nm; and an inorganic multilayer optical fdm having a first major surface and an opposing second major surface, wherein the second major surface of the inorganic multilayer optical film is attached to the first major surface of the polymeric multilayer optical film, wherein the inorganic multilayer optical film comprises one or more alternating first and second inorganic optical layers collectively reflecting and absorbing light that is normally incident to the first major surface of the wavelength-selective multilayer article, an average of at least 50, 60, 70, 80, 90, or 95 percent of incident ultraviolet light over at least a 30-nanometer wavelength bandwidth in a wavelength range from 190 nm to 400 nm.

2. The wavelength-selective multilayer article of claim 1, further comprising a structured film comprising a first major surface and an opposing second major surface, wherein the first major surface comprises a plurality of structures projecting therefrom, wherein at least some of the plurality of structures each has a surface whose slope causes light that is normally incident to the first major surface of the structured film to intercept the first major surface or the surface of at least one other structure after reflection, wherein the structured film is disposed either: a) between the first major surface of the polymeric multilayer optical film and the second major surface of the inorganic multilayer optical film or b) adjacent to the second major surface of the polymeric multilayer optical film opposite the inorganic multilayer optical film.

3. The wavelength-selective multilayer article of claim 1 or claim 2, wherein at least some of the structures comprise at least one angled sidewall having a peak angle of 90 degrees or less and the peak angle is 5, 15, 25, 35, or 45 degrees or greater.

4. The wavelength-selective multilayer article of claim 2 or claim 3, wherein at least some of the structures have a shape with a triangular cross-section.

5. The wavelength-selective multilayer article of any of claims 2 to 4, wherein the structures have a shape that is a prism, a pyramid, an inverted pyramid, a diffraction grating, an inverted cone, or a cone.

6. The wavelength-selective multilayer article of any of claims 2 to 5, wherein the structured film is flexible.

7. The wavelength-selective multilayer article of any of claims 2 to 6, wherein the structures refract light that is incident at an angle other than normal to the first major surface of the wavelength- selective multilayer article to exit the structured film at an angle that is closer to normal than the incident angle.

8. The wavelength-selective multilayer article of any of claims 1 to 7, further comprising a barrier layer disposed between the second major surface of the inorganic multilayer optical film and the first major surface of the polymeric multilayer optical film.

9. The wavelength-selective multilayer article of claim 8, wherein the structured film is present between the first major surface of the polymeric multilayer optical film and the second major surface of the inorganic multilayer optical film and the barrier layer is disposed between the first major surface of the structured film and the second major surface of the inorganic multilayer optical film.

10. The wavelength-selective multilayer article of claim 8 or claim 9, wherein the barrier layer comprises an inorganic layer.

11. The wavelength-selective multilayer article of claim 10, wherein the inorganic layer has a thickness of 15 to 60 nm.

12. The wavelength-selective multilayer article of any of claims 8 to 11, wherein the barrier layer further comprises a (co)polymer layer overlaying the inorganic layer.

13. The wavelength-selective multilayer article of claim 12, wherein the barrier layer further comprises a (co)polymer layer disposed between the inorganic layer and the first major surface of the polymeric multilayer optical film.

14. The wavelength-selective multilayer article of any of claims 1 to 13, wherein the polymeric multilayer optical film further comprises a third polymeric optical layer disposed between the first polymeric optical layer and the second polymeric optical layer of at least one pair of the alternating first and second polymeric optical layers.

15. The wavelength-selective multilayer article of any of claims 1 to 14, which transmits light that is normally incident to the first major surface of the wavelength-selective multilayer article, an average of at least 50, 60, 70, 80, 90, or 95 percent of normally incident light in a wavelength range from greater than 400 nm to 700 nm, greater than 400 nm to 1100 nm, or greater than 400 nm to 1350 nm.

16. The wavelength-selective multilayer article of any of claims 1 to 15, wherein the first optical layer of the inorganic multilayer optical film comprises at least one of niobium oxide, titanium oxide, silicon oxynitride, molybdenum oxide, tungsten oxide, silicon nitride, indium tin oxide, hafnium oxide, tantalum oxide, zirconium oxynitride, zirconium oxide, aluminum zinc oxide, or zinc oxide and wherein the second optical layer of the inorganic multilayer optical film comprises at least one of silicon oxide, silicon aluminum oxide, N type- or P type-doped silicon oxide, aluminum oxide, aluminum fluoride, magnesium fluoride, calcium fluoride, indium tin oxide, or zinc oxide.

17. The wavelength-selective multilayer article of any of claims 1 to 16, wherein the first optical layer of the inorganic multilayer optical film comprises at least one of niobium oxide or titanium oxide, and wherein the second optical layer of the inorganic multilayer optical film comprises silicon aluminum oxide.

18. The wavelength-selective multilayer article of any of claims 1 to 17, wherein the first optical layer of the inorganic multilayer optical film comprises at least one of niobium oxide or titanium oxide, and wherein the second optical layer of the inorganic multilayer optical film comprises silicon oxide.

19. The wavelength-selective multilayer article of any of claims 1 to 18, exhibiting an average transmission of wavelengths between 400 nm and 700 nm, 400 nm to 1100 nm, or 400 nm to 1350 nm, through the article that is reduced by less than 20%, 10%, 5%, or less than 1% after exposure to a certain dose of ultraviolet light.

20. The wavelength-selective multilayer article of any of claims 1 to 19, exhibiting an average reflection of wavelengths between 800 nm to 1200 nm, 1200 nm to 1600 nm, or 800 nm to 1600 nm, off the article that is reduced by less than 20%, 10%, 5%, or less than 1% after exposure to a certain dose of ultraviolet light.

21. The wavelength-selective multilayer article of any of claims 1 to 20, wherein the polymeric multilayer optical film comprises a third order harmonic that reflects at least 80, 90, or 95 percent of light that is normally incident to a first major surface of the wavelength-selective multilayer article over at least a 30 nm wavelength bandwidth in a wavelength range from 340 nm to 400 nm, 350 nm to 400 nm, or 365 nm to 400 nm.

22. A solar array comprising the wavelength-selective multilayer article of any of claims 1 to 21 disposed on an exterior surface of the solar array.

23. The solar array of claim 22, further comprising a barrier layer disposed between the solar array and the wavelength-selective multilayer article.