Structured ultraviolet light shielding article and solar cell array including same

Abstract

Structured ultraviolet light shielding articles are provided. A structured ultraviolet light shielding article includes: a microstructured film having a first major surface and an opposing second major surface, where the first major surface includes microstructures protruding therefrom; and a plurality of layers of optical films disposed on the microstructure. At least some of the microstructures each have a surface that is sloped such that light incident perpendicularly to the first major surface of the microstructured film intersects a surface of the first major surface or at least one other microstructure after reflection. The multi-layer optical film is comprised of one or more alternating first and second inorganic optical layers that collectively reflect and absorb light incident perpendicularly to the first major surface of the microstructured film, at least 50%, 60%, 70%, 80%, 90%, or 95% of incident ultraviolet light is averagely reflected and absorbed over a wavelength reflection bandwidth of at least 30 nm in a wavelength range of 190 nm (nm) to 400 nm. Also provided is a solar cell array comprising the structured ultraviolet light shielding article.

Description

BACKGROUND OF THE INVENTION

[0001] There is a class of telecommunications networks that have an infrastructure provided by a constellation of thousands of small satellites deployed in low Earth orbit. These satellites need to be powered by solar cell arrays mounted on their frames, and these solar cell arrays in turn need to be protected from the harsh environment of low Earth orbit.

[0002] Devices typically operate at altitudes in the range of 20 km - 2000 km, where the thin atmosphere absorbs little solar radiation. Thus, compared to the radiation present in the AM1.5 solar spectrum encountered in Earth ground conditions, high-altitude devices are exposed to a more intense AM0 solar spectrum and higher-intensity ultraviolet (UV) radiation, especially UV-C radiation. SUMMARY OF THE INVENTION

[0003] In a first aspect, there is provided a structured ultraviolet light shielding article. The structured ultraviolet light shielding article comprises: a) a microstructured film comprising a first major surface and an opposite second major surface, wherein the first major surface comprises a plurality of microstructures protruding therefrom; and b) a multilayer optical film disposed on the plurality of microstructures. At least some of the plurality of microstructures each have a surface with a slope such that light incident perpendicularly to the first major surface of the microstructured film intersects the first major surface or the surface of at least one other microstructure after reflection. The multilayer optical film is composed of one or more alternating first inorganic optical layers and second inorganic optical layers that together reflect and absorb light incident perpendicularly to the first major surface of the microstructured film, reflecting and absorbing at least 50%, 60%, 70%, 80%, 90% or 95% of the incident ultraviolet light within at least a 30-nanometer wavelength reflection bandwidth in the wavelength range of 190 nanometers (nm) to 400 nm.

[0004] In a second aspect, there is provided a solar cell array. The solar cell array comprises the structured ultraviolet light shielding article according to the first aspect, the structured ultraviolet light shielding article being disposed on an outer surface of the solar cell array.

[0005] Broadband UV protection is of particular interest. Alternating layers of high refractive index and low refractive index materials have been shown to provide UV blocking, but these are typically limited to relatively narrow reflection bands. On the other hand, UV absorbers generally cannot provide sufficient absorption without thick layers, and many solutions are prepared with organic absorbers that are not always able to withstand the higher-energy UVC light and atomic oxygen present in low Earth orbit.

[0006] The ultraviolet light-shielding article according to at least some embodiments of the present disclosure provides an inorganic-based solution that combines the UV absorption of inorganic materials (e.g., titanium oxide or niobium oxide) with reflection bands generated by alternating high-refractive-index and low-refractive-index materials. This results in a broadband UV-blocking filter that is tolerant to both UV and atomic oxygen. This technology can potentially replace the existing protection solution for solar cell arrays in space, namely, the cover glass. The cost of using cover glass is high due to the fragile nature of the glass slides and the small size of the glass slides that require a large amount of trimming / lamination.

[0007] Various unexpected results and advantages are obtained in the exemplary embodiments of the present disclosure. One such advantage of the exemplary embodiments of the present disclosure is that the combination of UV absorption and reflection in the structured ultraviolet light-shielding article results in a broadband UV-blocking filter made of durable inorganic materials that can withstand low-Earth orbit conditions. Additionally, compared to planar films, using a microstructured film improves the light trapping of the article by minimizing light loss due to reflection. These layers can be sputter-deposited or evaporated in a roll-to-roll process. Thus, another advantage of the exemplary embodiments is the ability to implement a high-speed roll-to-roll continuous production process for the structured ultraviolet light-shielding article of the present disclosure.

[0008] The various aspects and advantages of the exemplary embodiments of the present disclosure have been summarized. The above Summary of the Invention is not intended to describe every illustrated embodiment or every implementation of the present disclosure's current certain exemplary embodiments. The following drawings and detailed description more particularly illustrate certain preferred embodiments that utilize the principles disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present disclosure can be more fully understood in view of the following detailed description of various embodiments of the present disclosure in conjunction with the accompanying drawings, in which:

[0010] Figure 1A is a perspective view of a Cartesian coordinate system of a surface that can be used to describe various microstructured surfaces;

[0011] Figure 1B is a schematic cross-sectional view of a microstructured film for use in the exemplary articles disclosed herein;

[0012] Figure 1C is a schematic cross-sectional view of an exemplary structured ultraviolet light-shielding article according to various exemplary embodiments disclosed herein;

[0013] Figure 1D is a scanning electron microscope (SEM) image of a cross-section of a portion of an exemplary structured ultraviolet light-shielding article 10 according to various exemplary embodiments disclosed herein;

[0014] Figure 2 are schematic cross-sectional views of an exemplary structured ultraviolet light-shielding article 10 and an exemplary solar cell array 30 in accordance with various exemplary embodiments disclosed herein;

[0015] Figure 3 is a perspective view of a microstructured surface including an array of linear prisms;

[0016] Figure 4A is a perspective view of a microstructured surface including an array of cube corner elements;

[0017] Figure 4B is a perspective view of a microstructured surface including an array of cone elements;

[0018] Figure 5 is a perspective view of a microstructured surface including an array of cones;

[0019] Figure 6 is a perspective view of a microstructured surface including a diffraction grating having a bias angle;

[0020] Figure 7 is a perspective view of a microstructured surface including an array of truncated pyramids.

[0021] In the drawings, like reference numerals indicate like elements. Although the above-described drawings, which may not be to scale, illustrate various embodiments of the present disclosure, other embodiments are also conceivable, as noted in the detailed description. In all cases, the present disclosure describes the presently disclosed subject matter in terms of representations of exemplary embodiments rather than by way of limitation. It should be understood that those skilled in the art can envision many other modifications and embodiments that fall within the scope and spirit of the present disclosure. Detailed Description

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

[0023] Glossary

[0024] Certain terms are used throughout the specification and claims, and although most are well known to those skilled in the art, some explanation may still be required. It should be understood that:

[0025] The term "fluoropolymer" refers to any organic polymer that contains fluorine.

[0026] The term "non-fluorinated" means not containing fluorine.

[0027] The term “(co)polymer” includes homopolymer(s) and copolymer(s), and homopolymer(s) or copolymer(s) that can be formed in a miscible blend (e.g., by coextrusion or by a reaction including (e.g., transesterification)). The term “(co)polymer” includes random (co)polymers, block (co)polymers, and star (co)polymers.

[0028] As used herein, “adjacent” includes direct contact (e.g., directly adjacent) and the presence of one or more intermediate layers between adjacent materials.

[0029] As used herein, “incident” with respect to light means light that falls on or irradiates a material.

[0030] The term “crosslinked” (co)polymer refers to a (co)polymer in which its (co)polymer chains are joined together by covalent chemical bonds, typically via crosslinking molecules or groups, to form a network (co)polymer. Crosslinked (co)polymers are generally characterized by their insolubility but can be swellable in the presence of a suitable solvent.

[0031] The term “curing” refers to a process that causes a chemical change (e.g., a reaction that produces covalent bonds to harden a multilayer film or increase its viscosity).

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

[0033] The term “metal” includes pure metals or metal alloys.

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

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

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

[0037] The term “optically transparent” refers to an article that shows no visually detectable distortion, haze, or defects when examined by the naked eye at a distance of about 1 meter, preferably at a distance of about 0.5 meter.

[0038] When used with respect to a layer, the term “optical thickness” means the physical thickness of the layer multiplied by its planar refractive index.

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

[0040] By using orientation terms such as "on top of", "on", "above", "covering", "uppermost", "beneath", etc. for the positions of various elements in the disclosed coated articles, we refer to the relative position of the element with respect to a horizontally disposed, upward-facing substrate. However, unless otherwise specified, the present invention is not intended for the substrate or article to have any particular spatial orientation during or after manufacture or when interpreting the claims.

[0041] As used herein, unless otherwise specified, "radiation" refers to electromagnetic radiation.

[0042] As used herein, "scattering" with respect to the wavelength of light refers to causing light to deviate from a straight path and travel in different directions with different intensities.

[0043] As used herein, "reflectivity" is a measure of the proportion of light or other radiation incident on a surface at a normal angle of incidence that is reflected by it. Reflectivity typically varies with wavelength and is reported as a percentage of the incident light reflected from the surface (0% - no reflected light, 100 - all light is reflected). Reflectivity and reflectance are used interchangeably herein.

[0044] As used herein, "reflection" and "reflectivity" refer to the property of reflected light or radiation, particularly reflectivity measured independently of the thickness of the material.

[0045] As used herein, "average reflectivity" refers to the reflectivity averaged over a specified wavelength range.

[0046] As used herein, "absorption" refers to a material that converts light radiation energy into internal energy.

[0047] As used herein, "absorption" with respect to the wavelength of light includes both absorption and scattering, since scattered light will ultimately also be absorbed. Absorbance can be measured by the method described in ASTM E903 - 12 "Standard Test Method for Solar Absorptance, Reflectance, and Transmittance of Materials Using Integrating Spheres". The absorbance measurements described herein are made by performing transmittance measurements as described above and then calculating the absorbance using Equation 1.

[0048] As used herein, the term "absorbance" with respect to a quantitative measurement refers to the base-10 logarithm of the ratio of the incident radiation power to the transmitted radiation power through a material. This ratio can be described as the radiation flux received by the material divided by the radiation flux transmitted by the material. The absorbance (A) can be calculated based on the internal transmittance (T) according to Equation 1 below:

[0049] A = -log 10 T (1)

[0050] Emissivity can be measured using an infrared imaging radiometer by the method "Standard Practice for Measuring and Compensating for Emissivity Using Infrared Imaging Radiometers" described in ASTM E1933-14 (2018). According to Kirchhoff's law of thermal radiation, absorbance is related to emissivity. Absorbance, absorptance, emissivity, and emittance can be used interchangeably herein for the same purpose of emitting infrared energy to the atmosphere. Absorption and emission can also be used interchangeably herein.

[0051] As used herein, the terms "transmittance" and "transmission rate" refer to the ratio of the total transmittance of a material layer to the total transmittance received by the material, which can account for the effects of absorption, scattering, reflection, etc. Transmittance (T) can range from 0 to 1 or be expressed as a percentage (T%).

[0052] As used herein, "transparent" refers to a material (e.g., a film or layer) that absorbs less than 20% of light with wavelengths between 350 nm and 2500 nm.

[0053] As used herein, "bandwidth" refers to the width of a continuous band of wavelengths.

[0054] As used herein, the term "flexible" means capable of bending around a mandrel with a radius of curvature of up to 7.6 centimeters (cm) (3 inches), up to 6.4 cm (2.5 inches), 5 cm (2 inches), 3.8 cm (1.5 inches), or 2.5 cm (1 inch) in some embodiments. In some embodiments, a flexible component can bend around a radius of curvature of at least 0.635 cm (1 / 4 inch), 1.3 cm (1 / 2 inch), or 1.9 cm (3 / 4 inch).

[0055] The term "about" or "approximately" with respect to a numerical value or shape means + / - 5% of that numerical value or property or characteristic, but explicitly includes the exact numerical value.

[0056] The term "substantially" with respect to a property or characteristic means that the degree to which the property or characteristic is exhibited is greater than the degree to which the opposite of the property or characteristic is exhibited. For example, a "substantially" transparent substrate means a substrate that transmits more radiation (e.g., visible light) compared to not transmitting (e.g., absorbing and reflecting). Thus, a substrate that transmits more than 50% of the visible light incident on its surface is substantially transparent, but a substrate that transmits 50% or less of the visible light incident on its surface is not substantially transparent.

[0057] As used in this specification and the appended embodiments, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" include plural referents. Thus, for example, reference to a fine fiber that "comprises a compound" includes a mixture of two or more compounds. As used in this specification and the appended embodiments, unless the context clearly dictates otherwise, the term "or" is generally used in its sense including "and / or".

[0058] Unless otherwise indicated, all numbers expressing quantities or ingredients, properties measurements, etc. used in this specification and the 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 are subject to change as desired by those skilled in the art utilizing the teachings of this disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the embodiments claimed, each numerical parameter should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0059] By definition, the total weight percentage of all components in a composition equals 100 weight %.

[0060] Various exemplary embodiments of the present disclosure will now be described. Without departing from the spirit and scope of the present disclosure, various modifications and changes can be made to the exemplary embodiments of the present disclosure. Accordingly, it should be understood that the embodiments of the present disclosure are not limited to the exemplary embodiments described below, but are to be controlled by the limitations set forth in the claims and any equivalents thereof.

[0061] Reference Figure 1A, by superimposing a Cartesian coordinate system onto its structure, the microstructured surface can be characterized in three-dimensional space. A first reference plane 124 is centered between the main surfaces 112 and 114. The first reference plane 124, which is referred to as the y-z plane, has the x-axis as its normal vector. A second reference plane 126, which is referred to as the x-y plane, extends substantially coplanar with the surface 116 and has the z-axis as its normal vector. A third reference plane 128, which is referred to as the x-z plane, is centered between the first end face 120 and the second end face 122 and has the y-axis as its normal vector.

[0062] In some embodiments, these microstructured surfaces are three-dimensional at the macroscopic scale. However, at the microscopic scale (e.g., a surface region including at least two adjacent microstructures with valleys or channels disposed therebetween), the substrate / base member can be considered planar relative to the microstructures. The width and length of the microstructures are in the x-y plane, and the height of the microstructures is in the z-direction. Additionally, the substrate layer is parallel to the x-y plane and orthogonal to the z-plane.

[0063] Structured Ultraviolet Light Shielding Articles

[0064] In a first aspect, a structured ultraviolet light shielding article is provided. The structured ultraviolet light shielding article includes:

[0065] a) a microstructured film including a first main surface and an opposite second main surface, wherein the first main surface includes a plurality of microstructures protruding therefrom, wherein at least some of the plurality of microstructures each have a surface with a slope such that light vertically incident on the first main surface of the microstructured film intersects the first main surface or the surface of at least one other microstructure after reflection; and

[0066] a multilayer optical film disposed on the plurality of microstructures, wherein the multilayer optical film is composed of one or more alternating first inorganic optical layers and second inorganic optical layers that together reflect and absorb light vertically incident on the first main surface of the microstructured film, and that reflect and absorb at least 50%, 60%, 70%, 80%, 90%, or 95% of the incident ultraviolet light within at least a 30-nanometer wavelength reflection bandwidth in the wavelength range of 190 nanometers (nm) to 400 nm.

[0067] Referring again to Figure 1A , "light vertically incident on the first main surface of the microstructured film" refers to light that irradiates the first main surface 116 of the microstructured film perpendicular to the reference plane 126 (and parallel to the reference plane 124).

[0068] Now referring to Figure 1B, a schematic cross-sectional view of the microstructured film 100 is provided, which includes a plurality of microstructures 140 suitable for the exemplary articles of the present disclosure. "A microstructure having a surface with a slope such that light incident perpendicularly to the first major surface of the microstructured film intersects the first major surface or the surface of at least one other microstructure after reflection" refers to incident light ("I") that irradiates the surface of the microstructure 140a perpendicularly to the first major surface 130 of the microstructured film 100, and the microstructure 140a has a slope 142 such that the reflected light ("R") intersects the first major surface of the microstructured film (not shown) or the surface of another microstructure 140b. According to the discussion above with respect to Figure 1A , the first major surface 130 of the microstructured film 100 is considered parallel to the second major surface 110 of the microstructured film 100. The slope (e.g., inclined surface) 142 of the microstructure 140a is the height 141 of the microstructure 140a divided by the width 143 between the peak (e.g., the high end of the inclined surface) 145 and the bottom (e.g., the low end of the inclined surface) 147 of the microstructure 140a. Another way to determine the slope is to use the following formula:

[0069]

[0070] where m is the slope, Δy is the height of the microstructure, Δx is the width between the peak and the bottom of the microstructure, and the angle β is the inclination angle between the inclined surface of the microstructure and the bottom of the microstructure (e.g., as Figure 1B shown). For microstructures with rounded peaks, using the tangent of the inclination angle β may be a preferred way to determine the slope. An angle alpha (α) can be drawn between the slope 142 and the height 141 of the peak 145. In some cases, the angle α is 45 degrees or less, 40 degrees, 35 degrees, 30 degrees, 25 degrees, 20 degrees, 15 degrees, or 10 degrees or less.

[0071] Figure 1C is a schematic cross-sectional view of a part of an exemplary structured ultraviolet light shielding article 10 according to at least some exemplary embodiments disclosed herein. The structured ultraviolet light shielding article 10 has a first major surface 5 and an opposite second major surface 7. The first major surface 5 includes a plurality of microstructures 40 protruding therefrom. The structured ultraviolet light shielding article 10 includes a multilayer optical film 20 located on the plurality of microstructures 40. The multilayer optical film 20 includes alternating first inorganic optical layers 13 and second inorganic optical layers 12. In this embodiment, the article 10 further includes at least one intermediate layer 14 located between the microstructured film 15 and the multilayer optical film 20.

[0072] Figure 1DA scanning electron microscope (SEM) image of a cross-section of a portion of an exemplary structured ultraviolet light-shielding article 10 in accordance with at least some exemplary embodiments disclosed herein. The structured ultraviolet light-shielding article 10 has a first major surface 5. The first major surface 5 includes a plurality of microstructures 40 protruding therefrom. The structured ultraviolet light-shielding article 10 includes a multilayer optical film 20 disposed on the plurality of microstructures 40. The multilayer optical film 20 includes alternating first inorganic optical layers and second inorganic optical layers (the individual layers are too thin to be seen in the image), and the second inorganic optical layer 12 is the outermost layer. In this embodiment, the article 10 further includes an intermediate layer 14 disposed between the microstructured film 15 and the multilayer optical film 20.

[0073] Now referring Figure 2 , the present disclosure describes a structured ultraviolet light-shielding article 10 that includes a microstructured film 15 having a first major surface 5 and a multilayer optical film 20 disposed on the first major surface 5 of the microstructured film 15. Note that in this drawing, for simplicity, the schematic depictions of the various features do not show any microstructures. In some cases, the multilayer optical film 20 is disposed directly on the first major surface 5 of the microstructured film 15 (e.g., directly attached to the microstructures of the microstructured film 15), while in other cases, at least one intermediate layer 14 is disposed between the microstructured film 15 and the multilayer optical film 20. Suitable intermediate layers 14 include, for example but not limited to, adhesive layers, organic primer layers, barrier coatings, or any combination thereof. Thus, the intermediate layer 14 depicted as Figure 2 can represent any number of intermediate layers at this location in the overall structure.

[0074] The multilayer optical film 20 includes one or more alternating first inorganic optical layers 13(A-N) and second inorganic optical layers 12(A-N).

[0075] The alternating first inorganic optical layers and second inorganic optical layers together reflect and absorb light incident perpendicularly to the first major surface of the microstructured film, and within at least a 30-nanometer wavelength reflection bandwidth in the wavelength range of 190 nanometers (nm) to 400 nm, on average reflect and absorb at least 50%, 60%, 70%, 80%, 90%, or 95% (preferably at least 80%, 90%, or 95%) of the incident ultraviolet light.

[0076] In some cases, the alternating first inorganic optical layers and second inorganic optical layers together reflect and absorb light incident perpendicularly to the first major surface of the microstructured film, and within at least a 30-nanometer wavelength reflection bandwidth in the wavelength range of 190 nm to 240 nm, 240 nm to 300 nm, 300 nm to 350 nm, 350 nm to 400 nm, or any combination thereof, on average reflect and absorb at least 60%, 70%, 80%, 90%, or 95% of the incident ultraviolet light.

[0077] Optionally, the alternating first and second inorganic optical layers together reflect and absorb light vertically incident on the first major surface of the microstructured film, and within a wavelength bandwidth greater than at least 30 nanometers (e.g., at least 50 nanometers, 75 nanometers, 100 nanometers, 125 nanometers, 150 nanometers, or 175 nanometers) in the wavelength range of 190 nm to 400 nm, they reflect and absorb on average at least 60%, 70%, 80%, 90%, or 95% of the incident ultraviolet light.

[0078] When the alternating first and second inorganic optical layers together reflect and absorb, some portions of the incident ultraviolet light are absorbed and some portions are reflected. In some cases, the alternating first and second inorganic optical layers together absorb light vertically incident on the first major surface of the microstructured film, and within a wavelength bandwidth of at least 30 nanometers in the wavelength range of 190 nm to less than 350 nm, they absorb on average at least 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 95% of the incident light. In some cases, the alternating first and second inorganic optical layers together reflect light vertically incident on the first major surface of the microstructured film, and within a wavelength bandwidth of at least 30 nanometers in the wavelength range of 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, they reflect on average at least 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 95% of the incident light.

[0079] In certain selected embodiments of the structured ultraviolet light shielding article, the alternating first and second inorganic optical layers together transmit light vertically incident on the first major surface of the microstructured film, and within the wavelength range greater than 400 nm to 700 nm, they transmit on average at least 50%, 60%, 70%, 80%, 90%, or 95% of the incident visible light.

[0080] In certain selected embodiments of the structured ultraviolet light shielding article, the outermost inorganic layer is the second inorganic optical layer (e.g., Figure 2 12A in

[0081] Figure 2 13A in and has a thickness of at least 70 nm. This has the effect of reducing the amount of light reflected from the outer surface of the light shielding article and increasing the light transmitted between 400 nm and 700 nm, which is particularly useful when the structured ultraviolet light shielding article is used in solar cell array applications to allow visible light to reach the solar cells in the array.Figure 2 The thickness of at least one first optical layer in [[13N]] is 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 from the outer surface of the structured light-shielding article between 400 nm and 700 nm, which is particularly useful when the structured ultraviolet light-shielding article is used in solar cell array applications to allow visible light to reach the solar cells in the array.

[0082] In some embodiments, the structured ultraviolet light-shielding article (e.g., as a whole) transmits at least 50%, 60%, 70%, 80%, 90%, or 95% of the vertically incident visible light in the wavelength range greater than 400 nm to 700 nm. Transmitting such amounts of incident visible light is particularly useful when the ultraviolet light-shielding article is used in solar cell array applications to allow visible light to reach the solar cells in the array. Additionally, after exposure to a certain dose (e.g., in joules per square centimeter (J / cm 2 )), the structured ultraviolet light-shielding article according to certain preferred embodiments of the present disclosure exhibits a reduction in the average transmittance at wavelengths between 400 nm and 700 nm of less than 20%, 10%, 5%, or less than 1%. For example, exposure to the doses mentioned in the following examples.

[0083] Microstructured Film

[0084] As mentioned above, a microstructured film includes a first major surface and an opposite second major surface, wherein the first major surface includes a plurality of microstructures protruding therefrom, and at least some of the plurality of microstructures each have a surface with a slope such that light vertically incident on the first major surface of the microstructured film intersects the first major surface or the surface of at least one other microstructure after reflection. Thus, various different-shaped microstructures are suitable. For example, in some cases, the microstructures have the shape of a prism, pyramid, inverted pyramid, diffraction grating, inverted cone, or cone. Such shapes will be described in further detail below. Additionally, the reverse form of any of these shapes is also suitable. There may be any number of faces of a three-dimensional shape (e.g., any one of a 4-sided pyramid, 5-sided pyramid, 6-sided pyramid, etc. will be suitable). In a selected embodiment, each of the microstructures has the same size and shape, which tends to contribute to achieving consistent optical properties of the multi-layer optical film deposited on the microstructures across the surface of the structured ultraviolet light-shielding article.

[0085] Optionally, at least some of the microstructures have a shape with a triangular cross-section, such as Figure 1B and Figure 1CThe microstructures 140 and 40 therein. Although not required, in some cases, at least some of the microstructures in the microstructure 140 include at least one angled sidewall (e.g., 142) having a spike 145. Advantageously, it has been found that a multilayer optical film can be formed on a microstructure having a spike (e.g., not domed at the peak) without having "pinholes" due to insufficient deposition of the multilayer optical film on the spike.

[0086] In some cases, as Figure 1B depicted, at least some of the microstructures in the microstructure 140 include at least one angled sidewall (e.g., 142) having the following peak angle (e.g., apex angle) theta (θ): 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 peak angle (e.g., apex angle); and 5 degrees or more, 7 degrees, 10 degrees, 12 degrees, 15 degrees, 20 degrees, 25 degrees, 30 degrees, 35 degrees, 40 degrees, 45 degrees, or 50 degrees or more. As used herein, "peak angle" refers to the angle between opposite sides of the microstructure at the vertex of the microstructure.

[0087] Optionally, the plurality of microstructures 140 may have the following aspect ratio of height H to (total) width W (i.e., H:W): not exceeding 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, or not exceeding 1:1; and at least 1:2.

[0088] Generally, each microstructure has the following height: 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.

[0089] Reference Figure 3, in one embodiment, the first major surface 300 of the microstructured film 100 includes a linear array of right-angled prisms 320. Each prism has a first face (e.g., an inclined surface) 321 and a second face 322. The prisms are illustrated as being formed on a base member 310 having a first planar surface 331 (parallel to the reference plane 126) on which the prisms are formed and a second surface 332 that is substantially flat or planar and opposite the first surface. It is contemplated that the second surface 332 can also be structured. A right-angled prism means that its peak angle θ340 is typically about 90 degrees. However, the range of this angle can be as described above. These peaks can be sharp (as shown) or domed. The spacing between the (e.g., prism) peaks can be characterized as a pitch ("P"). In this embodiment, the pitch is also equal to the maximum width of the valleys. The pitch can be greater than 1 micrometer (i.e., micron), 2 microns, 3 microns, 4 microns, 5 microns, 6 microns, 7 microns, 8 microns, 9 microns, or 10 microns, with a range up to 250 microns. The length ("L") of the (e.g., prism) microstructures is typically the largest dimension and can span the entire dimension of the microstructured surface.

[0090] In another embodiment, the first major surface of the microstructured film can have the same surface shape as a cube-corner retroreflective sheet. Refer to Figure 4A , a cube-corner retroreflective sheet typically includes a thin transparent layer having a substantially flat surface and an opposite structured surface 410 that includes a plurality of cube-corner elements 417. Figure 4A The microstructured surface 410 can be characterized as an array of cube-corner 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 the third set of grooves (valleys) intersects each of the other two sets at an angle less than 60 degrees to form an array of tilted cube-corner element mating pairs (see U.S. Patent No. 4,588,258 (Hoopman)). The angles of the grooves are selected such that the dihedral angles (e.g., 414, 415, and 416 of the representative cube-corner element 417) formed at the linear intersections of the grooves are about 90 degrees. In some embodiments, the angles of the triangular base are at least 64 degrees, 65 degrees, 66 degrees, 67 degrees, 68 degrees, 69 degrees, or 70 degrees, and the other angles are 55 degrees, 56 degrees, 57 degrees, or 58 degrees.

[0091] In another embodiment, as Figure 4B depicted, Figure 4BThe first major surface of the microstructured membrane 400 can be characterized as an array of pyramid peak structures 420 defined by a first set of parallel grooves (i.e., valleys) in the y-direction and a second set of parallel grooves in the x-direction. The base of the pyramid peak structure is polygonal, typically square or rectangular, depending on the groove spacing. The peak angle θ440 is typically about 90 degrees. However, the range of this angle can be as described above.

[0092] In some cases, the microstructures can have a conical shape. Referring to Figure 5 , the microstructured surface 500 of the microstructured membrane includes an array of cones 540. Each micro-structure of the conical shape typically has only one inclined sidewall 542. The peak 545 of each cone can be sharp or rounded.

[0093] Figure 6 A schematic view depicts the first major surface 600 of a microstructured membrane that includes a diffraction grating with an offset angle. The second major surface 610 of the microstructured membrane defines a longitudinal axis (“LA”) along its length, and a plurality of microstructures 640 extend across the first major surface 600 to define a major axis (“A”). The major axis A and the longitudinal axis LA define an offset angle (“B”) between the major axis and the longitudinal axis. In some embodiments, the offset angle B ranges between about 0 degrees and about 90 degrees (such as between about 20 degrees and about 70 degrees).

[0094] In another embodiment, as Figure 7 depicted, the first major surface 710 of the microstructured membrane 700 can be characterized as an array of chamfered pyramid structures 720. The structure 720 includes faces 722 that meet in valleys (e.g., inverted peaks) 721, and the opposing edges 724 of each face together form the base of the pyramid structure 720 (i.e., at the outermost surface of the microstructured membrane 700). The base of the pyramid is polygonal, such as square or rectangular. In this particular embodiment, adjacent rows of the structure (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 the adjacent structure 725 in row 764) have different positions along the length of the row (e.g., on the y-axis). It is expressly contemplated that such offset configurations can be employed with any of the microstructures disclosed herein.

[0095] In some cases, the microstructured film is flexible (as defined in the glossary). The advantage of using a flexible microstructured film is that it avoids the high cost of using rigid glass, especially small glass chips, which may break during handling and require a large amount of labor due to the need to apply many small glass chips. Additionally, in some embodiments according to the present disclosure, the flexible microstructured film is used in a roll-to-roll process for manufacturing structured ultraviolet light shielding articles. The advantage of roll-to-roll manufacturing is that the structured ultraviolet light shielding articles can be made in a large area format. In some cases, the area of the microstructured film (or the structured ultraviolet light shielding article) is at least 50 square centimeters, such as at least 60 square centimeters, 70 square centimeters, 80 square centimeters, 90 square centimeters, 100 square centimeters, 1,000 square centimeters or at least 10,000 square centimeters.

[0096] In any of the foregoing embodiments, the microstructured film may be composed of or comprise a polymeric material (such as a (co)polymer). In some exemplary embodiments, the microstructured film comprises polyethylene terephthalate (PET), crosslinkable silicone, cured polysiloxane, silicone thermoplastic polymer, cured polyurethane, thermoplastic polyurethane, cured (meth)acrylate, cured epoxy resin, cured vinyl ether, cured oxetane, cured thiol acrylate, cured thiol ene, polypropylene, polyethylene, PMMA, coPMMA, polyimide, cycloolefin copolymer, cycloolefin polymer, polycarbonate, polyethylene naphthalate (PEN) or a fluoropolymer (co)polymer comprising polymeric units derived from one or more monomers selected from tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, perfluoroalkoxy alkylene or vinyl fluoride, or a combination thereof. Optionally, any of the above cured polymeric materials is crosslinked.

[0097] Suitable polyimides can be purchased from E.I.DuPont de Nemours, Wilmington, DE under the trade name "KAPTON", and among them, "KAPTON CS100" is currently preferred. Suitable PMMA polymers include those PMMA polymers that can be purchased from Ineos Acrylics, Inc., Wilmington, DE as CP71 and CP80. A suitable crosslinkable silicone can be purchased from Dow Corning Corporation, Midland, MI under the trade name "DOW CORNING 93-500 Aerospace Grade Encapsulant Kit". A suitable polycarbonate can be purchased from Bayer AG, Darmstadt, Germany under the trade name "Makrofol". Suitable methyl methacrylate copolymers (CoPMMA) include, for example, CoPMMA prepared from 75 wt% methyl methacrylate (MMA) monomer and 25 wt% ethyl acrylate (EA) monomer (for example, it can be purchased from Ineos Acrylics, Inc., London, England under the trade name "PERSPEX CP63" or from Arkema Corp., Philadelphia, PA under the trade name "ATOGLAS 510"); CoPMMA formed by 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 can be purchased from DuPont Teijin, Chester, VA under the trade name "Teonex Q51".

[0098] In certain exemplary embodiments, the fluoropolymer preferably includes tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, perfluoroalkoxy alkane, or a combination thereof. Suitable fluoropolymers are available from E.I. DuPont de Nemours, Wilmington, DE under the trade name "TEFLON FEP100", where "TEFLON FEP100500A" is currently preferred. Suitable exemplary fluoropolymers also include copolymers of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride (THV) available from Dyneon LLC, Oakdale, MN under the trade names "DYNEON THV 220", "DYNEON THV 221", "DYNEON THV 230", "DYNEON THV 2030", "DYNEONTHV 415", "DYNEON THV 500", "DYNEON THV 610", and "DYNEON THV 815".

[0099] In some applications, for example, when the article will be subjected to large ambient temperature changes, it may be useful to employ a low coefficient of thermal expansion (CTE) film. Some exemplary low CTE polymers include, for example but not limited to, polyimide, heat-stable PEN, and PET. Preferably, the 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 lower. The coefficient of thermal expansion has the general meaning employed in the art, i.e., determined using ASTM E831.

[0100] By appropriate optional pretreatment of the microstructured film or an optionally applied primer coat, the smoothness and adhesion of the layers to the microstructured film can be enhanced. Methods of surface modification are known in the art. In one embodiment, the pretreatment protocol includes discharge pretreatment (e.g., plasma, glow discharge, corona discharge, dielectric barrier discharge, or atmospheric pressure discharge), chemical pretreatment, or flame pretreatment of the substrate in the presence of a reactive or non-reactive atmosphere. These pretreatments can help ensure that the surface of the microstructured film will be receptive to the subsequently applied layer. In one embodiment, the method can include plasma pretreatment. For organic surfaces, plasma pretreatment can include nitrogen or water vapor. Another pretreatment protocol includes coating the microstructured film with an inorganic or organic primer coat, optionally followed by further pretreatment using plasma or one of the other pretreatments described above.

[0101] Preferably, the microstructured film itself transmits at least 70%, 80%, 90% or 95% of the incident visible light on average in the wavelength range greater than 400 nm to 700 nm.

[0102] Optional Barrier Coating

[0103] In another embodiment, an optional barrier coating is disposed between the plurality of microstructures and the multilayer optical film, for example, at the position of the intermediate layer 14 in each of Figure 1C and Figure 2 The barrier coating includes: at least one pair of layers, the at least one pair of layers consisting of a (co)polymer layer covering the first major surface of the microstructured film and an inorganic layer covering the (co)polymer layer. The barrier coating further includes an outer (co)polymer layer covering the at least one pair of layers and optionally at least one outer inorganic layer covering the outer (co)polymer layer. As used in the context of the barrier coating, "outer" refers to the outermost layer of a particular type of layer in the barrier coating (e.g., the outer (co)polymer layer or the outer inorganic layer), rather than the outermost layer of the entire structured ultraviolet light shielding article.

[0104] The structured ultraviolet light shielding article including the barrier coating provides protection against an atomic oxygen environment. For example, advantageously, in many cases, when tested according to the atomic oxygen degradation test, the light shielding article exhibits less than 1x10 -20 mg / atom, 1x10 -21 mg / atom or 1x10 -22 mg / atom of atomic oxygen degradation. Such resistance to atomic oxygen degradation is particularly useful when the light shielding article is part of a low Earth orbit device.

[0105] The barrier coatings of at least some embodiments of the present disclosure may exhibit excellent mechanical properties such as elasticity and flexibility, but still have a low atomic oxygen degradation rate. These coatings have at least one pair of layers comprising a (co)polymer layer and an oxide layer, and may have additional inorganic or hybrid organic / inorganic layers. In one embodiment, the barrier coating may have alternating (co)polymer layers and oxide layers. In other exemplary embodiments, the disclosed barrier coatings may include one or more hybrid organic / inorganic layers. Optionally, the barrier coating includes a plurality of pairs of layers, such as when the plurality of pairs of layers are at least or exactly two pairs of layers, three pairs of layers, four pairs of layers, five pairs of layers or six pairs of layers.

[0106] Each (co)polymer layer and the outer (co)polymer layer in the at least one pair of layers include a (co)polymer selected from olefin (co)polymers, (meth)acrylate (co)polymers, urethane (co)polymers, fluoropolymers, silicone (co)polymers, or combinations thereof.

[0107] (Co)polymer layers can be formed from a variety of organic materials or compounds using a variety of processes. After application, the (co)polymer layer can be crosslinked in situ. In one embodiment, the (co)polymer layer can be formed by flash evaporation, vapor deposition, and (co)polymerization of monomers using, for example, heating, plasma, UV radiation, or an electron beam.

[0108] Exemplary monomers used in the method include volatile (meth)acrylate monomers. In a specific embodiment, a volatile acrylate monomer is used. Suitable (meth)acrylates will have a molecular weight low enough to allow flash evaporation and high enough to allow condensation on the substrate. The organic material or compound can also be evaporated using any method, such as the method described in PCT Publication WO 2022 / 243756 (Sweetnam et al.), for example, the method described with respect to evaporating metal alkoxides.

[0109] If desired, the (co)polymer layer 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 chemical composition and thickness required for the additional layer will depend in part on the nature and intended use of the light-shielding article. The coating efficiency can be increased by cooling the article.

[0110] Exemplary organic compounds include esters, vinyl compounds, alcohols, carboxylic acids, acid anhydrides, halides, thiols, amines, and mixtures thereof. Non-limiting examples of esters include (meth)acrylates, which can be used alone or in combination with other polyfunctional or monofunctional (meth)acrylates. Exemplary (meth)acrylates include hexanediol diacrylate, ethoxyethyl acrylate, phenoxyethyl acrylate, cyanoethyl acrylate, isobornyl acrylate, stearyl acrylate, isodecyl acrylate, lauryl acrylate, β-carboxyethyl acrylate, tetrahydrofurfuryl acrylate, dicyanoacrylate, pentafluorophenyl acrylate, nitrobenzyl acrylate, 2-phenoxyethyl 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, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, tris(2-hydroxyethyl) isocyanurate triacrylate, pentaerythritol triacrylate, phenylthioethyl acrylate, naphthoxyethyl acrylate, IRR-214 cyclic diacrylate from UCB Chemicals, epoxy acrylate RDX80095 from Rad-Cure Corporation, the corresponding methacrylates of the above-listed acrylates, and mixtures thereof. Exemplary vinyl compounds include vinyl ethers, styrene, vinyl naphthalene, and acrylonitrile. Exemplary alcohols include hexanediol, naphthalenediol, and 2-hydroxyethyl methacrylate. Exemplary carboxylic acids include phthalic acid, terephthalic acid, and (meth)acrylic acid. Exemplary acid anhydrides include phthalic anhydride and glutaric anhydride. Exemplary halides include adipoyl dichloride and succinyl chloride. Exemplary thiols include ethylene glycol dimercaptoacetate and phenylthioethyl acrylate. Exemplary amines include ethylenediamine and hexane 1,6-diamine.

[0111] Optionally, at least one (co)polymer layer or the outer (co)polymer layer in at least one pair of layers further comprises an additive which is an ultraviolet radiation absorber, a hindered amine light stabilizer, an antioxidant, or a combination thereof. UV absorbers (UVA), hindered amine light stabilizers (HAL), and antioxidants can help prevent photooxidative degradation of the (co)polymer layer. Suitable compounds include benzophenones, benzotriazoles, and triazines (e.g., benzotriazines). Exemplary UVA's for incorporation into the (co)polymer layer include those available under the trade names "TINUVIN 1577" and "TINUVIN 1600," from BASF Corporation, Florham Park, NJ. U.S. Patent No. 9,670,300 (Olson et al.) and U.S. Patent Application Publication 2017 / 0198129 (Olson et al.) describe exemplary UVA oligomers compatible with PVDF fluoropolymers. Exemplary HAL's for incorporation into the hard coat include those available under the trade names "CHIMMASORB944" and "TINUVIN 123" from BASF Corporation. Generally, the UVA, HAL, and / or antioxidant are incorporated into the (co)polymer layer at a concentration of 1 wt% to 10 wt%.

[0112] Each inorganic layer in the inorganic layer of at least one pair of layers and the optional at least one outer inorganic layer covering the outer (co)polymer layer comprises an inorganic material selected from the group consisting of silica, silicon aluminoxide, 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, hafnium oxide, aluminum oxide, aluminum oxide-doped silica, lanthanum fluoride, neodymium fluoride, aluminum fluoride, magnesium fluoride, calcium fluoride, or a combination thereof.

[0113] The outer (co)polymer layer covers at least one pair of layers, and the at least one pair of layers can be the plurality of pairs of layers mentioned above. Preferably, the outer (co)polymer layer is crosslinked.

[0114] In some exemplary embodiments, the outer (co)polymer layer comprises an olefin (co)polymer selected from the group consisting of low density polyethylene, linear low density polyethylene, ethylene vinyl acetate, polyethylenemethyl acrylate, polyethylenoctene, polyethylenepropylene, polyethylenebutene, polyethylenemaleic anhydride, polymethylpentene, polyisobutylene, polyisobutylene, ethylenepropylene diene, cyclic olefin (co)copolymer, and blends thereof.

[0115] In certain exemplary embodiments, at least one (co)polymer layer or an outer (co)polymer layer in at least one pair of layers further comprises an ultraviolet radiation absorber, a hindered amine light stabilizer, an antioxidant, or a combination thereof.

[0116] Preferably, the ultraviolet radiation absorber is selected from benzotriazole compounds, benzophenone compounds, triazine compounds, or a combination thereof. Currently preferred hindered amine light stabilizers are available from BASF U.S.A, Florham Park, NJ under the trade name “TINUVIN”. Preferably, the hindered amine light stabilizer is selected from TINUVIN 123, TINUVIN 144, TINUVIN 292, or a combination thereof. Currently preferred antioxidants are available from BASF under the trade names “IRGANOX” and “IRGAFOS”. Preferably, suitable antioxidants for polyolefins are selected from IRGANOX 1010, IRGANOX 1076, IRGAFOS 168, or a combination thereof.

[0117] The barrier coating can be subjected to various post-treatments, such as heat treatment, UV or vacuum UV (VUV) treatment, or plasma treatment. Heat treatment can be carried out by passing the barrier coating through an oven or directly heating the barrier coating in a coating apparatus (e.g., using an infrared heater or directly heating on a drum). For example, heat treatment can be performed at a temperature of about 30 °C to about 200 °C, about 35 °C to about 150 °C, or about 40 °C to about 70 °C.

[0118] Optional Organic Primer

[0119] In another embodiment, an optional organic undercoat, especially an undercoat based on a crosslinked acrylate (co)polymer, can be advantageously employed on the microstructured film. The undercoat can be formed by flash evaporation and vapor deposition of radiation-crosslinkable monomers (e.g., acrylate monomers) followed by in-situ crosslinking (using, for example, an electron beam device, a UV light source, a discharge device, or other suitable means), as described in U.S. Pat. Nos. 4,696,719, 4,722,515, 4,842,893, 4,954,371, 5,018,048, 5,032,461, 5,097,800, 5,125,138, 5,440,446, 5,547,908, 6,045,864, 6,231,939, and 6,214,422; in published PCT application WO 00 / 26973; in D.G. Shaw and M.G. Langlois, “A New Vapor Deposition Process for Coating Paper and (co)polymer Webs”, 6th International Vacuum Coating Conference (1992); D.G. Shaw and M.G. Langlois, “A New High Speed Process for Vapor Depositing Acrylate Thin Films: An Update”, Society of Vacuum Coaters 36th Annual Technical Conference Proceedings (1993); D.G. Shaw and M.G. Langlois, “Use of Vapor Deposited Acrylate Coatings to Improve the Barrier Properties of Metallized Film”, Society of Vacuum Coaters 37th Annual Technical Conference Proceedings (1994); D.G. Shaw, M. Roehrig, M.G. Langlois, and C.as described in Sheehan, “Use of Evaporated Acrylate Coatings to Smooth the Surface of Polyester and Polypropylene Film Substrates”, RadTech (1996); J. Affinito, P. Martin, M. Gross, C. Coronado, and E. Greenwell, “Vacuum deposited (co)polymer / metal multilayer films for optical application”, Thin Solid Films 270, 43-48 (1995); and J.D. Affinito, M.E. Gross, C.A. Coronado, G.L. Graff, E.N. Greenwell, and P.M. Martin, “Polymer-Oxide Transparent Barrier Layers”, Society of Vacuum Coaters 39th Annual Technical Conference Proceedings (1996).

[0120] If desired, the primer coat can also be applied using conventional coating methods such as roll coating (e.g., gravure roll coating) or spray coating (e.g., electrostatic spray coating), and then crosslinked using, for example, heat, ultraviolet radiation, or electron beam. The chemical composition and thickness required for the primer coat will depend in part on the nature of the microstructured film. For example, for PET, the primer coat can be formed from acrylate monomers and can have a thickness of, for example, only a few nanometers to about 7 microns.

[0121] Multilayer Optical Film

[0122] Referring again to Figure 2 , the structured ultraviolet light shielding article 10 includes a multilayer optical film 20 that includes one or more alternating first inorganic optical layers 13(A-N) and second inorganic optical layers 12(A-N), the one or more alternating first inorganic optical layers and second inorganic optical layers being located on a first major surface 5 of the microstructured film 15, as further described below.

[0123] Typically, the multi-layer optical film has the following thicknesses: 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 200 nm to 1500 nm.

[0124] InorganicLayers = Inorganic Layers

[0125] In some cases, the first optical layer includes 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. As is known to those skilled in the art, alloys of oxides may be suitable. In some cases, the second optical layer includes 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 a selected embodiment, the first optical layer includes at least one of niobium oxide or titanium oxide, and the second optical layer includes silicon aluminum oxide. When a photoactive inorganic material (such as titanium oxide) is employed, a non-photoactive material (e.g., silicon oxide, aluminum oxide, etc.) is typically provided between the photoactive inorganic material and any organic layer to minimize degradation of the organic layer. For example, referring again to Figure 2 , the non-photoactive material layer may be the intermediate layer 14 located between the first optical layer 13N and the microstructured film 15.

[0126] It has been unexpectedly found that by using only the combination of multiple alternating first inorganic optical layers and second inorganic optical layers, light of each wavelength within each of the UVA, UVB and UVC regions can be shielded from the microstructured film, while generally still maintaining an acceptable amount of visible light transmission (e.g., at least 50% of the incident visible light).

[0127] Optical thin film stacks are composed of alternating thin layers of inorganic dielectric materials with refractive index contrast and are particularly suitable for multi-layer optical films. In recent decades, these designs have been used in applications in the UV, visible, NIR, and IR spectral regions. Depending on the spectral region of interest, there are specific materials suitable for that region. Additionally, for coating these materials, one of two forms of physical vapor deposition (PVD) is used: evaporation or sputtering. Evaporated coatings rely on heating the coating material (evaporant) to its evaporation temperature. Then there is the condensation of the vapor on the substrate. For evaporated dielectric mirror coatings, the electron beam deposition process is most commonly used. Sputtered coatings use high-energy gas ions to bombard the surface of the material ("target"), thereby ejecting atoms that then condense on a nearby substrate. Depending on the coating method used and the settings for that method, the thin film coating rate and the structure-property relationships will be strongly affected. Desirably, the coating rate should be high enough to allow for an acceptable process throughput and film properties, characterized by a dense, low-stress, void-free, non-optically absorbing coating.

[0128] For reasons of film thickness, flexibility, and economy, the number of optical layers is chosen to obtain the desired optical properties using the minimum number of layers. Those skilled in the art can extend such deposition techniques to include CVD, ALD, and other vapor depositions. Generally, preferably, the total number of layers is 21 or fewer, 19, 17, 15, or 13 or fewer optical layers; and 3 or more optical layers, 5, 7, 9, or 11 or more optical layers may be required. In a selected embodiment, the multi-layer optical film is formed from at least 1 first optical layer and 2 second optical layers.

[0129] The thickness of each of the first optical layer and the second optical layer can vary significantly. For example, in some cases, each of the first optical layers in the first optical layer and each of the second optical layers in the second optical layer 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 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 a selected embodiment, each of the first optical layer and the second optical layer independently has a thickness of 20 nm to 400 nm.

[0130] The multi-layer optical films described herein can be prepared using conventional processing techniques, such as those described in U.S. Patent No. 6,783,349 (Neavin et al.), the entire disclosure of which is incorporated herein by reference in its entirety.

[0131] For the fabrication of inorganic coatings, electron beam processes are most suitable for coating discrete components. Optionally, the ultraviolet light shielding article can be prepared in a continuous roll-to-roll (R2R) manner for larger articles. Although some chambers have demonstrated R2R film coating, a layer-by-layer coating sequence is still necessary. For R2R sputtering of the inorganic layers of the ultraviolet light shielding article 10, it is advantageous to use a sputtering system having multiple sources located around one or possibly two coating cylinders. Here, for a thirteen-layer optical stack design, a dual or even single-pass machine with alternating high and low refractive index layers would be feasible. How many machine passes will be required will depend on machine design, cost, availability of thirteen consecutive sources, etc. Additionally, the coating rate will need to match the single film line speed.

[0132] The film roll conveyance initially starts at a predetermined speed, and the sputtering source power ramps up to full operating power, then a reactive gas is introduced, and then steady state conditions are achieved. Depending on the length of the film to be coated, the process continues until the total footprint is achieved. Here, since the sputtering source is orthogonal to and wider than the film being coated, the uniformity of the coating thickness is quite high. When the desired length of coated film is reached, the reactive gas is set to zero and the target is sputtered to a pure metal surface condition. Next, the film direction is reversed, and the pair of sputtering targets has AC frequency (40 kHz) power applied in an argon sputtering atmosphere. When steady state is reached, an oxygen reactive gas is introduced to provide transparency and a low refractive index. At a predetermined process setting and line speed, the second layer is coated over the length coated for layer one. Again, since these sputtering sources are also orthogonal to and wider than the film being coated, the uniformity of the coating thickness is quite high. After the desired length of coated film is reached, the reactive oxygen is removed and the target is sputtered to a pure metal surface condition in argon. Depending on the optical target, three to five (or seven or nine, eleven or thirteen, etc.) layers are coated in this sequence. After completion, the film roll is removed for post-processing.

[0133] The examples describe in more detail an exemplary method for preparing an exemplary structured ultraviolet light shielding article 10.

[0134] Solar Array

[0135] In a second aspect, a solar cell array is provided. The solar cell array includes a structured ultraviolet light shielding article according to any embodiment of the first aspect described in detail above.

[0136] One of the energy resources with good prospects today is sunlight. Generating power using sunlight can be achieved by using photovoltaic (PV) cells (also known as solar cells) for the photovoltaic conversion of sunlight into electric current. Solar cells are relatively small in size and are typically combined into physically integrated solar modules (or PV modules) that have a correspondingly greater power output compared to a single solar cell in the module. Solar modules are typically formed from two "strings" or more of solar cells, which are surrounded by encapsulants and enclosed by a front panel and a back panel, with at least one panel being transparent to sunlight.

[0137] Accordingly, the ultraviolet light shielding article according to the present disclosure can be used to protect a solar cell array by being included on an outer surface of the solar cell array.

[0138] Referring again to Figure 2 , the present disclosure describes a solar cell array 30, each of which includes a structured ultraviolet light shielding article 10 located on an outer surface 16 of the solar cell array. In some cases, the structured ultraviolet light shielding article 10 can be directly attached to the surface 16 of the solar cell array, for example, by using thermal lamination. Instead, there may be one or more optional intermediate layers (not shown) between the structured ultraviolet light shielding article 10 and the solar cell array surface 16, such as a transparent adhesive bonding layer or an encapsulant. The structured ultraviolet light shielding article 10 includes a microstructured film 15 having a first major surface 5 and a multilayer optical film 20 located on the first major surface 5 of the microstructured film 15.

[0139] List of Exemplary Embodiments

[0140] In a first embodiment, a structured ultraviolet light shielding article is provided. The ultraviolet light shielding article includes: a) a microstructured film that includes a first major surface and an opposite second major surface, wherein the first major surface includes a plurality of microstructures protruding therefrom; and b) a multilayer optical film disposed on the plurality of microstructures. At least some of the plurality of microstructures each have a surface with a slope such that light perpendicularly incident on the first major surface of the microstructured film intersects the first major surface or the surface of at least one other microstructure after reflection. The multilayer optical film is composed of one or more alternating first inorganic optical layers and second inorganic optical layers, and the one or more alternating first inorganic optical layers and second inorganic optical layers together reflect and absorb light perpendicularly incident on the first major surface of the microstructured film, and within at least a 30-nanometer wavelength reflection bandwidth in the wavelength range of 190 nanometers (nm) to 400 nm, on average reflect and absorb at least 50%, 60%, 70%, 80%, 90%, or 95% of the incident ultraviolet light.

[0141] In a second embodiment, there is provided a structured ultraviolet light shielding article according to the first embodiment, wherein the aspect ratio of the height to the width of the plurality of microstructures is no greater than 10:1, 8:1, 6:1, 4:1, 2:1, or 1:1.

[0142] In a third embodiment, there is provided a structured ultraviolet light shielding article according to the first embodiment or the second embodiment, wherein the microstructured film comprises polyethylene, polyethylene terephthalate (PET), crosslinkable silicone, silicone thermoplastic polymer, cured polyurethane, thermoplastic polyurethane, cured (meth)acrylate, cured epoxy resin, cured vinyl ether, cured oxetane, cured thiol acrylate, cured thiol ene, polypropylene, polyethylene, PMMA, coPMMA, polyimide, cycloolefin copolymer, cycloolefin polymer, polycarbonate, PEN, or fluoropolymer (co)polymer, the fluoropolymer (co)polymer comprising polymerized units derived from one or more monomers selected from tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, perfluoroalkoxy alkylene, or vinyl fluoride, or a combination thereof.

[0143] In a fourth embodiment, there is provided a structured ultraviolet light shielding article according to any one of the first to third embodiments, wherein at least some of the microstructures in the microstructures include at least one angled sidewall having a spike.

[0144] In a fifth embodiment, there is provided a structured ultraviolet light shielding article according to any one of the first to fourth embodiments, wherein at least some of the microstructures in the microstructures include at least one angled sidewall having a peak angle of 90 degrees or less.

[0145] In a sixth embodiment, there is provided a structured ultraviolet light shielding article according to any one of the first to fifth embodiments, wherein at least some of the microstructures in the microstructures have a shape with a triangular cross-section.

[0146] In a seventh embodiment, there is provided a structured ultraviolet light shielding article according to any one of the first to sixth embodiments, wherein the microstructures have the shape of a prism, pyramid, inverted pyramid, diffraction grating, inverted cone, or cone.

[0147] In an eighth embodiment, there is provided a structured ultraviolet light shielding article according to any one of the first to seventh embodiments, wherein each of the microstructures in the microstructures has the same size and shape.

[0148] In a ninth embodiment, there is provided a structured ultraviolet light shielding article according to any one of the first to eighth embodiments, wherein the microstructured film is flexible.

[0149] In a tenth embodiment, there is provided a structured ultraviolet light shielding article according to any one of the first to ninth embodiments, wherein the microstructure has a height of 0.5 micrometers to 500 micrometers.

[0150] In an eleventh embodiment, there is provided a structured ultraviolet light shielding article according to any one of the first to tenth embodiments, wherein the peak angle is 5 degrees, 15 degrees, 25 degrees, 35 degrees or 45 degrees or greater.

[0151] In a twelfth embodiment, there is provided a structured ultraviolet light shielding article according to any one of the first to eleventh embodiments, wherein each of the first optical layer and the second optical layer independently has a thickness of 20 nm to 400 nm.

[0152] In a thirteenth embodiment, there is provided a structured ultraviolet light shielding article according to any one of the first to twelfth embodiments, wherein the alternating first inorganic optical layer and second inorganic optical layer together absorb light incident perpendicularly to the first major surface of the microstructured film, and absorb at least 30%, 40%, 50%, 60%, 70%, 80%, 90% or 95% of the incident light on average within at least a 30-nanometer wavelength bandwidth in the wavelength range of 190 nm to less than 350 nm.

[0153] In a fourteenth embodiment, there is provided a structured ultraviolet light shielding article according to any one of the first to thirteenth embodiments, wherein the alternating first inorganic optical layer and second inorganic optical layer together reflect light incident perpendicularly to the first major surface of the microstructured film, and reflect at least 30%, 40%, 50%, 60%, 70%, 80%, 90% or 95% of the incident light on average within at least a 30-nanometer wavelength bandwidth in the wavelength range of 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.

[0154] In a fifteenth embodiment, there is provided a structured ultraviolet light shielding article according to any one of the first to fourteenth embodiments, wherein the alternating first inorganic optical layer and second inorganic optical layer together transmit light incident perpendicularly to the first major surface of the microstructured film, and transmit at least 50%, 60%, 70%, 80%, 90% or 95% of the incident visible light on average in the wavelength range greater than 400 nm to 700 nm.

[0155] In a sixteenth embodiment, there is provided a structured ultraviolet light shielding article according to any one of the first to fifteenth embodiments, wherein in the wavelength range greater than 400 nm to 700 nm, the microstructured film transmits at least 70%, 80%, 90% or 95% of the incident visible light on average.

[0156] In a seventeenth embodiment, there is provided a structured ultraviolet light shielding article according to any one of the first to sixteenth embodiments, wherein the first optical layer 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 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.

[0157] In an eighteenth embodiment, there is provided a structured ultraviolet light shielding article according to any one of the first to seventeenth embodiments, wherein the first optical layer comprises at least one of niobium oxide or titanium oxide, and wherein the second optical layer comprises silicon aluminum oxide.

[0158] In a nineteenth embodiment, there is provided a structured ultraviolet light shielding article according to any one of the first to eighteenth embodiments, wherein the outermost optical layer is the second optical layer and has a thickness of at least 70 nm.

[0159] In a twentieth embodiment, there is provided a structured ultraviolet light shielding article according to any one of the first to nineteenth embodiments, wherein the thickness of at least one first optical layer in the first optical layer closest to the outside of the film or closest to the microstructure is at most 95%, 90%, 85% or at most 80% of the other first optical layers.

[0160] In a twenty-first embodiment, there is provided a structured ultraviolet light shielding article according to any one of the first to twentieth embodiments, wherein the multi-layer optical film has a thickness of 200 nm to 1500 nm.

[0161] In a twenty-second embodiment, there is provided a structured ultraviolet light shielding article according to any one of the first to twenty-first embodiments, wherein the multi-layer optical film is formed of at least 1 first optical layer and 2 second optical layers.

[0162] In a twenty-third embodiment, there is provided a structured ultraviolet light-shielding article according to any one of the first to twenty-second embodiments, wherein the alternating first inorganic optical layer and second inorganic optical layer together reflect and absorb light perpendicularly incident on the first major surface of the microstructured film, and within at least a 30-nanometer wavelength reflection bandwidth in the wavelength range of 190 nm to 400 nm, on average reflect and absorb at least 80%, 90%, or 95% of the incident ultraviolet light.

[0163] In a twenty-fourth embodiment, there is provided a structured ultraviolet light-shielding article according to any one of the first to twenty-third embodiments, wherein the alternating first inorganic optical layer and second inorganic optical layer together reflect and absorb light perpendicularly incident on the first major surface of the microstructured film, and within at least a 30-nanometer wavelength reflection bandwidth in the wavelength range of 190 nm to 240 nm, 240 nm to 300 nm, 300 nm to 350 nm, 350 nm to 400 nm, or any combination thereof, on average reflect and absorb at least 60%, 70%, 80%, 90%, or 95% of the incident ultraviolet light.

[0164] In a twenty-fifth embodiment, there is provided a structured ultraviolet light-shielding article according to any one of the first to twenty-fourth embodiments, wherein the alternating first inorganic optical layer and second inorganic optical layer together reflect and absorb light perpendicularly incident on the first major surface of the microstructured film, and within at least a 50-nanometer, 75-nanometer, 100-nanometer, 125-nanometer, 150-nanometer, or 175-nanometer wavelength reflection bandwidth in the wavelength range of 190 nm to 400 nm, on average reflect and absorb at least 60%, 70%, 80%, 90%, or 95% of the incident ultraviolet light.

[0165] In a twenty-sixth embodiment, there is provided a structured ultraviolet light-shielding article according to any one of the first to twenty-fifth embodiments, the structured ultraviolet light-shielding article transmitting light perpendicularly incident on the first major surface of the microstructured film, and on average transmitting at least 50%, 60%, 70%, 80%, 90%, or 95% of the incident visible light in the wavelength range greater than 400 nm to 700 nm.

[0166] In a twenty-seventh embodiment, there is provided a structured ultraviolet light-shielding article according to any one of the first to twenty-sixth embodiments, the structured ultraviolet light-shielding article further comprising a barrier coating disposed between the plurality of microstructures and the multilayer optical film, the barrier coating comprising: at least one paired layer composed of a (co)polymer layer covering the first major surface of the microstructured film and an inorganic layer covering the (co)polymer layer; and an outer (co)polymer layer covering the at least one paired layer; and optionally at least one outer inorganic layer covering the outer (co)polymer layer.

[0167] In a twenty-eighth embodiment, there is provided a structured ultraviolet light-shielding article according to any one of the first to twenty-seventh embodiments, which exhibits a reduction in the average transmittance at wavelengths between 400 nm and 700 nm of less than 20%, 10%, 5% or less than 1% after exposure to a certain dose of ultraviolet light.

[0168] In a twenty-ninth embodiment, there is provided a solar cell array. The solar cell array includes a structured ultraviolet light-shielding article according to any one of the first to twenty-eighth embodiments, the structured ultraviolet light-shielding article being disposed on the outer surface of the solar cell array.

[0169] Examples

[0170] Unless otherwise specified or readily apparent from the context, all parts, percentages, ratios, etc. in the examples and the remainder of the specification are by weight.

[0171] Materials Used in Examples

[0172]

[0173]

[0174] Test Methods

[0175] Spectral Property Modeling Test: Before manufacturing the structured ultraviolet light-shielding article, the optical properties (transmission, reflection, and absorption) of the intended coating are modeled to precisely determine the necessary thickness of the optical coating. For this modeling, an ellipsometer (purchased from J.A. Woolam Co., Inc. (J.A. Woolam; Lincoln, NE) under the trade name "RC2 Ellipsometer") is used to measure Test Samples 1 and 2 to determine the spectral refractive index (n) and extinction coefficient (k) values of the evaporated TiO2 and SiO2 samples. Then, the n and k obtained above are input into optical modeling software (purchased from The Thin Film Center (The Thin Film Center; Tucson, AZ) under the trade name "Essential Macleod") and used to calculate the reflection, transmission, and absorption spectra of the multi-layer optical film prepared as described below. All structures are modeled using a PET substrate with an incident angle of 45 degrees.

[0176] Test Samples

[0177] Test Sample 1: A 70-nm-thick TiO2 layer was deposited on a silicon chip in the following manner: The vapor coater used was an optical coater from Denton Vacuum, which consists of a 5-planet gear drive system located approximately 30" (76.2 cm) above a 4-bag Temescal electron beam gun (purchased from Ferro Tec Corporation, Livermore, CA). The planetary gears are designed to keep the substrate perpendicular to the evaporation source and move the disk into and out of the evaporation plume in a planetary motion during deposition. The actual coating process includes: a) vent the vapor coater to the atmosphere and remove one of the five planets. Prepare the substrate for coating by adhering / wrapping the substrate to the planet using a polyimide tape. b) Reinstall the planet and, if necessary, construct the other 4 planets in a similar manner and also reinstall them in the coater. c) Seal the chamber and pump it down to a vacuum level of <2 x 10 -5 torr (2.7 x 10 -3 Pa). d) When the vapor coater is at a low enough vacuum, use a Kaufman-type ion source to ion beam treat the material at a voltage of 400 V for approximately 10 minutes as a pre-treatment of the substrate to adhere the vapor-deposited coating to the substrate before applying the oxide film. e) Add oxygen via an MKS mass flow controller (purchased from MKS Instruments, Inc., Andover, MA) to obtain 4.0 x 10 -5 torr (5.3 x 10-3 The pressure of Pa). The oxygen added is typically about 10 standard cubic centimeters per minute (sccms). f) Start the planetary gears and move them around the coater at a rotational speed of 60 rpm to prepare for coating and achieve a high level of uniformity on the attached substrates. g) Power on the Temescal electron beam gun power supply. Apply a voltage of 10 kV and a current of a few milliamperes to the filament of the electron gun to heat the source material in the electron gun. Heat and control the source via the OMS (Optical Monitoring System) of Eddy Company (purchased from Eddy Company, Apple Valley, CA). Heat the source until the deposition rate required for the material is reached; in the case of TiO2, this rate is 2 angstroms per second (A / s), and in the case of SiO2, this rate is 4 A / s. When the deposition rate required for the material is reached and stabilized, open the gate valve that separates the source from the planetary gears, and maintain this rate via the OMS until the desired optical thickness is reached, at which point the gate valve is closed and the OMS cuts off the power supply to the electron beam source. h) Turn off the main power supply of the power and allow the source to cool for about 10 minutes. i) Repeat this process for additional layers / types of materials until all the required multi-layer optical films are deposited. j) Then, evacuate the chamber back to atmospheric pressure via N2 gas, remove each planetary gear, and remove the substrates from each planetary gear.

[0178] Test Sample 2: Deposit 115 nm thick SiO2 on a silicon chip in the same manner as Test Sample 1.

[0179] Examples

[0180] Unless otherwise specified or readily apparent from the context, all parts, percentages, ratios, etc. in the examples and the remainder of the specification are by weight.

[0181] Materials Used in Examples

[0182]

[0183]

[0184] Test Methods

[0185] Spectral Property Modeling Test: Before manufacturing the structured ultraviolet light shielding article, the optical properties (transmission, reflection, and absorption) of the intended coating are modeled to precisely determine the necessary thickness of the optical coating. To perform this modeling, an ellipsometer (purchased from J.A. Woolam Co., Inc. (J.A. Woolam; Lincoln, NE) in Lincoln, Nebraska under the trade name "RC2 Ellipsometer") is used to measure Test Samples 1 and 2 to determine the spectral refractive index (n) and extinction coefficient (k) values of the evaporated TiO2 and SiO2 samples. Then, the n and k obtained above are input into optical modeling software (purchased from The Thin Film Center (The Thin Film Center; Tucson, AZ) in Tucson, Arizona under the trade name "Essential MaCleod") and used to calculate the reflection, transmission, and absorption spectra of the multi-layer optical film prepared as described below. Except that Comparative Example 1 uses vertically incident light for modeling, all structures are modeled using a PET substrate with an incident angle of 45 degrees.

[0186] Spectral Property Measurement Test : A spectrophotometer (purchased from PerkinElmer, Inc. (PerkinElmer, Inc., Waltham, MA) in Waltham, Massachusetts under the trade name "LAMBDA 1050") is used to measure the spectral transmission and reflection of independent embodiments of the ultraviolet light shielding article. The absorbance (in percentage) is calculated as 100 - reflectance - transmittance. In the reflection and absorption result tables and the transmission result tables, the measured spectral reflection, absorption, and transmission are reported as the average percentage within the wavelength range.

[0187] Sun Aging Test : The sample is exposed in an Atlas Ci5000 weathering tester (purchased from AMETEK, Inc. (AMETEK, Berwyn, PA) in Berwyn, Pennsylvania) using a xenon arc lamp equipped with quartz inner and outer filters. The quartz filter set provides minimal attenuation of the spectral power distribution of the xenon lamp, thus closely approximating the shape of solar output (ASTM E490). To increase the dose accumulation rate, the sample is exposed on a custom stainless steel and aluminum extension bracket. The extension bracket moves the exposure plane from 19 inches (48.3 cm) from the lamp core to 13.5 inches (34.3 cm) from the lamp core. On the bracket plane, the irradiance at 340 nm is controlled at 1.5 W / m 2 and on the extended sample plane, the irradiance at 340 nm is measured as 2.6 W / m 2. The ambient air temperature inside the aging test machine is controlled at 48 °C, the black panel thermometer (BPT) is controlled at 75 °C on the support plane and measured at approximately 95 °C at the sample plane, and the relative humidity is controlled at 30%. The sample is exposed without any backing. The sample is exposed to a cumulative irradiance of 250 nm - 385 nm at a dose of at least 425 megajoules per square meter (MJ / m 2 ).

[0188] The change in transmittance is calculated as:

[0189]

[0190] where T fresh is the average transmittance from 400 nm - 700 nm before solar aging, and T aged is the average transmittance from 400 nm - 700 nm after the above exposure. The results of the solar aging test are summarized in the solar aging results table.

[0191] Flexibility Test : The flexibility of the sample is tested by winding the film around a metal mandrel with a diameter of 0.5" (1.27 cm), with the coated side facing away from the mandrel. Spectral property tests are performed both before and after winding the sample around the mandrel. The change in spectral values in absolute percentage is calculated as the percentage spectral change = S unwrapped -S wrapped

[0192] where S unwrapped and S wrapped are the average values (in percentage) of a specific spectrum (e.g., transmittance, reflectance, or absorbance) in the average range of 200 nm - 700 nm for the same sample before and after winding, respectively. This calculation is performed separately for the transmittance, reflectance, and absorbance spectra. The percentage spectral difference calculated after winding is reported in the flexibility test results table below.

[0193] Test Samples

[0194] Test Sample 1: A 70 nm thick TiO2 layer was deposited on a silicon chip in the following manner: The vapor coater used was an optical coater from Denton Vacuum, which consists of a 5 - planetary gear drive system located approximately 30" (76.2 cm) above a 4 - pocket Temescal electron beam gun (purchased from Ferro Tec Corporation, Livermore, CA). The planetary gear drive system is designed to keep the substrate perpendicular to the evaporation source and move the disk into and out of the evaporation plume in a planetary motion during deposition. The actual coating process includes: a) vent the vapor coater to the atmosphere and remove one of the five planets. Prepare the substrate for coating by adhering / wrapping the substrate to the planet using a polyimide tape. b) Re - install the planet and, if needed, construct the other 4 planets in a similar manner and also re - install them in the coater. c) Close the chamber and pump it down to a vacuum level of <2x10 -5 Torr (2.7x10 -3 Pa). d) When the vapor coater is at a sufficiently low vacuum, use a Kaufman - type ion source to ion - beam treat the material at a voltage of 400 V for approximately 10 minutes as a pre - treatment of the substrate for adhering the vapor - deposited coating to the substrate before applying the oxide film. e) Add oxygen via an MKS mass flow controller (purchased from MKS Instruments, Inc., Andover, MA) to obtain 4.0x10 -5 Torr (5.3x10 -3The pressure of (Pa). The oxygen added is typically about 10 standard cubic centimeters per minute (sccms). f) Start the planetary gears and move them around the coater at a rotational speed of 60 rpm to prepare for coating and achieve a high level of uniformity on the attached substrates. g) Power on the Temescal electron beam gun power supply. Apply a voltage of 10 kV and a current of a few milliamperes to the filament of the electron gun to heat the source material in the electron gun. Heat and control the source via the OMS (Optical Monitoring System) of Eddy Company (purchased from Eddy Company, Apple Valley, CA). Heat the source until the deposition rate required for the material is reached; in the case of TiO2, this rate is 2 angstroms per second (A / s), and in the case of SiO2; and this rate is 4 A / s. When the deposition rate required for the material is reached and stabilized, open the gate valve that separates the source from the planetary gears, and maintain this rate via the OMS until the desired optical thickness is reached, at which point the gate valve is closed and the OMS cuts off the power supply to the electron beam source. h) Turn off the main power supply and allow the source to cool for about 10 minutes. i) Repeat this process for additional layers / types of materials until all the required multi-layer optical films are deposited. j) Then, evacuate the chamber back to atmospheric pressure via N2 gas, remove each planetary gear, and remove the substrates from each planetary gear.

[0195] Test sample 2: Deposit 115 nm thick SiO2 on a silicon chip in the same manner as test sample 1.

[0196] Preparation Examples

[0197] Preparation Example 1

[0198] Preparation Example 1 is a THV815 film having microstructured linear prisms, which are prepared as follows: Obtain a microstructured film BEF4 to be used as a mold / tool film. The process uses a three-roll vertical stack forming device similar to that described in U.S. Patent Application No. 2015 / 9108349 (Clarke et al.), which includes an extruder and an extrusion die head adapted to extrude one or more layers of molten thermoplastic material into the mold. In this case, the mold is a microstructured tool film (BEF4), which has been unwound onto a cylindrical roller to provide the desired surface pattern to transfer it to the molten thermoplastic material as it passes over the cylindrical surface of the roller. The casting roller has a surface temperature of 76.6 °C and a casting roller speed of 18.8 meters per minute. When the polymer contacts the BEF4 film on the casting roller, a nip force of 7600 pounds (300 pounds per linear inch) is applied to the polymer to prepare the THV815 linear prism microstructured film (2 mils (50.8 microns) thick). The characteristics of the microstructured film are reported in the following table of prismatic THV815 structures.

[0199] Prismatic THV815 Structure Table

[0200] Peak Height (μm) Peak Pitch (μm) Angle (degrees) Sidewall Angle (degrees) Tip Radius (μm) 6-12 24 90 45 2-10

[0201] Preparation Example 2

[0202] In a vacuum coater similar to the coater described in U.S. Patent Nos. 5,440,446 (Shaw et al.) and 7,018,713 (Padiyath et al.), Preparation Example 2 is prepared by covering the microstructured surface of the BEF4 substrate with a stack of the following: a matrix polymer layer (Layer 1), an inorganic silicon aluminum oxide (SiAlOx) barrier layer (Layer 2), and a protective polymer layer (Layer 3), all of which patents are incorporated herein by reference. Each layer is formed as follows:

[0203] Layer 1 (matrix polymer layer): A BEF4 film 356 mm wide and of indefinite length is loaded into a roll-to-roll vacuum processing chamber. The chamber is evacuated to a pressure drop of 2×10 -5Support. Maintain a web speed of 3.4 m / min while keeping the back side of the film in contact with the coating drum cooled to -10°C. With the back side in contact with the drum, treat the front side surface of the film with nitrogen plasma at a plasma power of 0.02 kW. Then coat the microstructured front side surface of the film with SR833S. Degas the monomer to a pressure of 20 mTorr under vacuum before coating, load it into an injection pump, and pump it through an ultrasonic nebulizer operating at a frequency of 60 kHz and into a heated vaporization chamber maintained at 260°C at a flow rate of 0.89 mL / min and an N2 carrier gas flow rate of 60 sccm. The resulting monomer vapor stream condenses onto the film surface and is electron beam crosslinked using a multi-wire electron beam curing gun operating at 7.0 kV and 4 mA to form a 360 nm thick matrix polymer layer.

[0204] Layer 2 (inorganic layer): Immediately after depositing the matrix polymer layer and while the back side of the film is still in contact with the drum, sputter deposit a SiAlOx layer on top of the matrix polymer layer. Two alternating current (AC) 40 kHz power supplies are used to control two pairs of cathodes; each cathode houses two 90% Si / 10% Al sputtering targets. During the sputter deposition process, the voltage signal of each power supply is used as an input to a proportional-integral-derivative control loop to maintain a predetermined oxygen flow rate to each cathode. The sputtering conditions are: AC power of 16 kW, where at a sputtering pressure of 3.5 mTorr, the gas mixture contains 350 sccm of argon and 213 sccm of oxygen. This provides an 18 nm thick SiAlOx layer deposited on top of the matrix polymer layer (layer 1).

[0205] Layer 3 (protective polymer layer): Immediately after depositing the SiAlOx layer and while the film is still in contact with the drum, coat and crosslink a second acrylate using the same conventional conditions as layer 1 with the following exceptions: (1) Electron beam crosslinking is carried out using a multi-wire electron beam curing gun operating at 7 kV and 10 mA. Additionally, increase the monomer flow rate to 1.33 mL / min to provide a 535 nm thick acrylate layer on top of layer 3. (2) The protective polymer layer contains 3 wt% of DYNASYLAN 1189, and the rest is SR833S.

[0206] Examples

[0207] Example 1

[0208] The preparation of Example 1 is as follows: A vapor-coated multilayer optical film is prepared on a BEF4 substrate in the same manner as Test Sample 1, except that a BEF4 film is used for the substrate, and the structures deposited on this BEF4 substrate are summarized in the following Example Structure Table. The BEF4 substrate is adhered to the planet with tape such that the structured side of the BEF4 will be coated by the vapor coating process.

[0209] An important factor to consider when preparing a vapor coating on a microstructured substrate is the geometry of the substrate. The inclined surfaces of the structure increase the surface area of the microstructured substrate relative to a planar substrate. Due to the increased surface area, the same material deposition process on the microstructured substrate and the planar substrate produces a thinner coating on the surface of the microstructured substrate than on the planar substrate. In other words, a fixed deposition process deposits a fixed volume of material onto the substrate, so the substrate with the higher surface area overall obtains a thinner coating (coating thickness equals the volume of deposited material divided by the surface area of the substrate).

[0210] Therefore, in order to achieve the desired thickness on a microstructured substrate, the total volume of deposited material must be increased relative to the deposition on a planar substrate. The factor by which the material volume is increased equals the ratio of the surface areas of the microstructured substrate and the planar substrate. In the case of the BEF4 substrate, which has a one-dimensional prism with a 90-degree peak angle and thus a slope of 45 degrees, the volume of deposited material needs to be increased by a factor equal to 1 / SIN(peak angle / 2) = 1 / SIN(45°) = 1.414.

[0211] Example 2

[0212] Example 2 is prepared in the same manner as Example 1, except that a piece prepared in Example 1 is used instead of BEF4 as the substrate.

[0213] Example 3

[0214] Example 3 is prepared in the same manner as Example 1, except that a piece prepared in Example 2 is used instead of BEF4 as the substrate.

[0215] Comparative Examples

[0216] Comparative Example 1

[0217] Comparative Example 1 is prepared in the same manner as Example 1, except that a piece of BK7 is used as the substrate, and the deposited coating is as described in the Comparative Example Structure Table.

[0218] Comparative Example 2

[0219] Comparative Example 2 is a piece of BEF4 film.

[0220] Preparation Example Structure Table

[0221] Layer 1 is in contact with the substrate.

[0222] Samples Preparation Example 1 Preparation Example 2 Substrate Prismatic THV815 BEF4 Layer 1 SR833S / 360nm Layer 2 SiAlOx / 18nm Layer 3 SR833S + 3% DYNASYLAN 1189 / 535nm

[0223] Example Structure Table

[0224] Layer 1 is in contact with the substrate.

[0225] Samples Example 1 Example 2 Example 3 Substrate BEF4 Prismatic THV815 BEF4 Layer 1 <![CDATA[SiO2 / 55.1nm]]> <![CDATA[SiO2 / 55.1nm]]> SR833S / 360nm Layer 2 <![CDATA[TiO2 / 31.6nm]]> <![CDATA[TiO2 / 31.6nm]]> SiAlOx / 18nm Layer 3 <![CDATA[SiO2 / 55.1nm]]> <![CDATA[SiO2 / 55.1nm]]> SR833S + 3% DYNASYLAN 1189 / 535nm Layer 4 <![CDATA[TiO2 / 37.2nm]]> <![CDATA[TiO2 / 37.2nm]]> <![CDATA[SiO2 / 55.1nm]]> Layer 5 <![CDATA[SiO2 / 55.1nm]]> <![CDATA[SiO2 / 55.1nm]]> <![CDATA[TiO2 / 31.6nm]]> Layer 6 <![CDATA[TiO2 / 37.2nm]]> <![CDATA[TiO2 / 37.2nm]]> <![CDATA[SiO2 / 55.1nm]]> Layer 7 <![CDATA[SiO2 / 55.1nm]]> <![CDATA[SiO2 / 55.1nm]]> <![CDATA[TiO2 / 37.2nm]]> Layer 8 <![CDATA[TiO2 / 37.2nm]]> <![CDATA[TiO2 / 37.2nm]]> <![CDATA[SiO2 / 55.1nm]]> Layer 9 <![CDATA[SiO2 / 55.1nm]]> <![CDATA[SiO2 / 55.1nm]]> <![CDATA[TiO2 / 37.2nm]]> Layer 10 <![CDATA[TiO2 / 31.6nm]]> <![CDATA[TiO2 / 31.6nm]]> <![CDATA[SiO2 / 55.1nm]]> Layer 11 <![CDATA[SiO2 / 140.8nm]]> <![CDATA[SiO2 / 140.8nm]]> <![CDATA[TiO2 / 37.2nm]]> Layer 12 <![CDATA[SiO2 / 55.1nm <!-- 23 -->]]> Layer 13 <![CDATA[TiO2 / 31.6nm]]> Layer 14 <![CDATA[SiO2 / 140.8nm]]>

[0226] Comparative Example Structure Table

[0227] Samples Comparative Example 1 Comparative Example 2 Substrate BK7 BEF4 Layer 1 <![CDATA[SiO2 / 58.8nm]]> Layer 2 <![CDATA[TiO2 / 36.1nm]]> Layer 3 <![CDATA[SiO2 / 58.8nm]]> Layer 4 <![CDATA[TiO2 / 36.1nm]]> Layer 5 <![CDATA[SiO2 / 58.8nm]]> Layer 6 <![CDATA[TiO2 / 36.1nm]]> Layer 7 <![CDATA[SiO2 / 58.8nm]]> Layer 8 <![CDATA[TiO2 / 36.1nm]]> Layer 9 <![CDATA[SiO2 / 58.8nm]]> Layer 10 <![CDATA[TiO2 / 36.1nm]]>

[0228] Reflection and Absorption Results Table

[0229]

[0230] Transmission Results Table

[0231]

[0232] Flexibility Test Results Table

[0233]

[0234]

[0235] Sun Aging Results Table

[0236] Samples Measured Transmittance Change (%) from 400nm - 700nm <![CDATA[Dose (MJ / m 2 )]]> Example 1 9.4 479 Example 2 0.4 479 Example 3 5.3 479 Comparative Example 1 NA NA Comparative Example 2 22.6 479

[0237] Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art will recognize that many alternative and / or equivalent specific embodiments may be used in place of the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any modifications or variations of the specific embodiments discussed herein. Accordingly, the present disclosure is intended to be limited only by the claims and their equivalents.

[0238] In addition, all publications and patents cited herein are hereby incorporated by reference in their entirety as if each individual publication or patent were specifically and individually indicated to be incorporated by reference. In the event of inconsistencies or contradictions between the incorporated reference section and this application, the information in the foregoing description shall control. The various exemplary embodiments have been described. These embodiments, as well as other embodiments, are within the scope of the following claims.

Claims

1. A structured ultraviolet light shielding article, the structured ultraviolet light shielding article comprising: a) A microstructured film, the microstructured film comprising a first major surface and an opposite second major surface, wherein the first major surface comprises a plurality of microstructures protruding therefrom, wherein at least some of the plurality of microstructures each have a surface, the slope of the surface being such that light vertically incident on the first major surface of the microstructured film intersects the first major surface or the surface of at least one other microstructure after reflection; and b) A multilayer optical film, the multilayer optical film disposed on the plurality of microstructures, wherein the multilayer optical film is composed of one or more alternating first inorganic optical layers and second inorganic optical layers, the one or more alternating first inorganic optical layers and second inorganic optical layers together reflect and absorb light vertically incident on the first major surface of the microstructured film, and within at least a 30 nanometer wavelength reflection bandwidth in the wavelength range of 190 nanometers (nm) to 400 nm, on average reflect and absorb at least 50%, 60%, 70%, 80%, 90% or 95% of the incident ultraviolet light.

2. The structured ultraviolet light shielding article according to claim 1, wherein the aspect ratio of the height to the width of the plurality of microstructures is not greater than 10:1, 8:1, 6:1, 4:1, 2:1 or 1:

1.

3. The structured ultraviolet light shielding article according to claim 1 or 2, wherein at least some of the microstructures comprise at least one angled sidewall having a spike.

4. The structured ultraviolet light shielding article according to any one of claims 1 to 3, wherein at least some of the microstructures comprise at least one angled sidewall having a peak angle of 90 degrees or less.

5. The structured ultraviolet light shielding article according to any one of claims 1 to 4, wherein at least some of the microstructures have a shape with a triangular cross-section.

6. The structured ultraviolet light shielding article according to any one of claims 1 to 5, wherein the microstructures have the shape of a prism, pyramid, inverted pyramid, diffraction grating, inverted cone or cone.

7. The structured ultraviolet light shielding article according to any one of claims 1 to 6, wherein each of the microstructures has the same size and shape.

8. The structured ultraviolet light shielding article according to any one of claims 1 to 7, wherein the microstructured film is flexible.

9. The structured ultraviolet light shielding article according to any one of claims 1 to 8, wherein the microstructures have a height of 0.5 micrometers to 500 micrometers.

10. The structured ultraviolet light shielding article according to any one of claims 1 to 9, wherein the peak angle is 5 degrees, 15 degrees, 25 degrees, 35 degrees or 45 degrees or greater.

11. The structured ultraviolet light shielding article according to any one of claims 1 to 10, wherein each of the first optical layer and the second optical layer independently has a thickness of 20 nm to 400 nm.

12. The structured ultraviolet light shielding article according to any one of claims 1 to 11, wherein the alternating first inorganic optical layer and second inorganic optical layer together transmit light perpendicularly incident on the first major surface of the microstructured film, and in the wavelength range greater than 400 nm to 700 nm, transmit at least 50%, 60%, 70%, 80%, 90% or 95% of the incident visible light on average.

13. The structured ultraviolet light shielding article according to any one of claims 1 to 12, wherein the first optical layer 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 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.

14. The structured ultraviolet light shielding article according to any one of claims 1 to 13, wherein the first optical layer comprises at least one of niobium oxide or titanium oxide, and wherein the second optical layer comprises silicon aluminum oxide.

15. The structured ultraviolet light shielding article according to any one of claims 1 to 14, wherein the outermost optical layer is the second optical layer and has a thickness of at least 70 nm.

16. The structured ultraviolet light shielding article according to any one of claims 1 to 15, wherein the thickness of at least one first optical layer in the first optical layer closest to the outside of the film or closest to the microstructure is at most 95%, 90%, 85% or at most 80% of the other first optical layers.

17. The structured ultraviolet light shielding article according to any one of claims 1 to 16, wherein the multilayer optical film is formed of at least 1 first optical layer and 2 second optical layers.

18. The structured ultraviolet light shielding article according to any one of claims 1 to 17, the structured ultraviolet light shielding article transmits light perpendicularly incident on the first major surface of the microstructured film, and in the wavelength range greater than 400 nm to 700 nm, transmits at least 50%, 60%, 70%, 80%, 90% or 95% of the perpendicularly incident visible light on average.

19. The structured ultraviolet light-shielding article according to any one of claims 1 to 18, wherein the structured ultraviolet light-shielding article further comprises a barrier coating disposed between the plurality of microstructures and the multilayer optical film, and the barrier coating comprises: At least one pair of layers, the at least one pair of layers being composed of a (co)polymer layer covering the first major surface of the microstructured film and an inorganic layer covering the (co)polymer layer; and an outer (co)polymer layer, the outer (co)polymer layer covering the at least one pair of layers; and optionally at least one outer inorganic layer, the at least one outer inorganic layer covering the outer (co)polymer layer.

20. The structured ultraviolet light shielding article according to any one of claims 1 to 19, after being exposed to a certain dose of ultraviolet light, the structured ultraviolet light shielding article exhibits a reduction in the average transmittance at wavelengths between 400 nm and 700 nm of less than 20%, 10%, 5% or less than 1%.

21. A solar cell array, the solar cell array comprising a structured ultraviolet light shielding article according to any one of claims 1 to 20, the structured ultraviolet light shielding article being disposed on an outer surface of the solar cell array.

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