WO2025248504A1

WO2025248504A1 - Articles including a multilayer optical film and a nanostructured layer and methods of making the same

Info

Publication number: WO2025248504A1
Application number: PCT/IB2025/055614
Authority: WO
Inventors: Brandon R. PIETZ; Caleb T. NELSON; Timothy G. GARTMANN; Alexander C. ELDREDGE; Sean M. SWEETNAM; David J. TARNOWSKI; Benjamin G. SONNEK; Karl K. STENSVAD; Matthew C. DACHEL
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2024-05-31
Filing date: 2025-05-30
Publication date: 2025-12-04
Anticipated expiration: 2026-11-30

Abstract

The present disclosure provides an article including a multilayer optical film including first optical layers and second optical layers, plus a boundary layer directly attached to a major surface of the multilayer optical film. The boundary layer includes a major surface opposite the multilayer optical film that has a nanostructured anisotropic surface. A method of making the article is also provided, including attaching a boundary layer directly to a major surface of a multilayer optical film, depositing an etch mask material on a major surface of the boundary layer opposite the multilayer optical film, and subsequently or concurrently reactive ion etching to anisotropically remove material in unmasked areas.

Description

ARTICLES INCLUDING A MULTILAYER OPTICAL FILM AND A NANOSTRUCTURED LAYER AND METHODS OF MAKING THE SAME

SUMMARY

[0001] In a first aspect, an article is provided. The article comprises a multilayer optical film comprising a plurality of first optical layers and a plurality of second optical layers and a boundary layer directly attached to a major surface of the multilayer optical film. The boundary layer comprises a major surface opposite the multilayer optical film that has a nanostructured anisotropic surface.

[0002] In a second aspect, a method of making an article is provided. The method comprises providing a multilayer optical film comprising a plurality of first optical layers and a plurality of second optical layers and attaching a boundary layer directly to a major surface of the multilayer optical film. The method further comprises depositing an etch mask material on a major surface of the boundary layer opposite the multilayer optical film and subsequently or concurrently reactive ion etching to anisotropically remove material in unmasked areas, thereby forming a nanostructured anisotropic surface on the major surface of the boundary layer.

[0003] Attaching a multilayer optical film (MOF) to another layer or article can be challenging. Current approaches to try to improve adhesion between the MOF and a molded article, for instance, is to extrude the MOF with a compatible skin layer that will adhere to the molded article during converting (thermoforming, injection molding, laminating, etc.). However, there are limited material choices for such a skin layer, plus article failure may still occur between the skin layer and the MOF. Articles and methods according to at least certain embodiments of the present disclosure will enable a MOF to adhere to more materials of choice and to be integrated into more articles without needing to add on skin layers. [0004] Various aspects and advantages of exemplary embodiments of the disclosure have been summarized. The above Summary is not intended to describe each illustrated embodiment or every implementation of the present certain exemplary embodiments of the present disclosure. The Drawings and the Detailed Description that follow more particularly exemplify certain preferred embodiments using the principles disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The disclosure may be more completely understood in consideration of the following detailed description of various embodiments of the disclosure in connection with the accompanying figures, in which:

[0006] FIG. 1 is a schematic cross-sectional view of an exemplary article, according to various exemplary embodiments disclosed herein;

[0007] FIG. 2 is a schematic cross-sectional view of another exemplary article, according to various exemplary embodiments disclosed herein;

[0008] FIG. 3 is a schematic cross-sectional view of a further exemplary article, according to various exemplary embodiments disclosed herein; [0009] FIG. 4 is a schematic cross-sectional view of an additional exemplary article, according to various exemplary embodiments disclosed herein;

[0010] FIG. 5 is a scanning electron microscopy (SEM) image of a cross-section of a portion of a control article;

[0011] FIG. 6 is an SEM image of a cross-section of a portion of an exemplary article made according to various exemplary embodiments disclosed herein;

[0012] FIG. 7 is an SEM image of a cross-section of a portion of another exemplary article made according to various exemplary embodiments disclosed herein;

[0013] FIG. 8A is a schematic cross-sectional view of a nanostructured bilayer for inclusion in exemplary articles, according to various exemplary embodiments disclosed herein;

[0014] FIG. 8B illustrates top elevation schematic diagrams of four representative nanostructured bilayers for inclusion in exemplary articles, according to various exemplary embodiments disclosed herein;

[0015] FIG. 9 A is an SEM image of a cross-section of a portion of an exemplary article made according to various exemplary embodiments disclosed herein;

[0016] FIG. 9B is an SEM image of the top of a portion of the exemplary article of FIG. 9A;

[0017] FIG. 10A is an SEM image of a cross-section of a portion of the exemplary article of FIG. 9A after being thermoformed; and

[0018] FIG. 10B is an SEM image of the top of a portion of the exemplary article of FIG. 10A.

[0019] In the drawings, like reference numerals indicate like elements. While the above-identified drawings, which may not be drawn to scale, set forth various embodiments of the present disclosure, other embodiments are also contemplated, as noted in the Detailed Description. In all cases, this disclosure describes the presently disclosed disclosure by way of representation of exemplary embodiments and not by express limitations. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of this disclosure.

DETAILED DESCRIPTION

[0020] For the following Glossary of defined terms, these definitions shall be applied for the entire application, unless a different definition is provided in the claims or elsewhere in the specification.

Glossary

[0021] Certain terms are used throughout the description and the claims that, while for the most part are well known, may require some explanation. It should be understood that:

[0022] The term “boundary layer” refers to a layer that is in direct contact with an outermost optical layer of a multilayer optical film.

[0023] The term “skin layer” refers to an exterior layer. In some cases, a boundary layer also acts as a skin layer.

[0024] The term “packet” refers to a multilayer feedblock stack of optical layers. [0025] The term “fluoropolymer” refers to any organic polymer containing fluorine.

[0026] The terms “(co)polymer” or “(co)polymers” includes homo(co)polymers and (co)polymers, as well as homo(co)polymers or (co)polymers that may be formed in a miscible blend, (e.g., by coextrusion or by reaction, including, (e.g., transesterification)). The term “(co)polymer” includes random, block and star (co)polymers.

[0027] The term “adhesive” refers to pressure-sensitive adhesives and/or hot melt adhesives.

[0028] As used herein, “adjacent” encompasses both in direct contact (e.g., directly adjacent) and having one or more intermediate layers present between the adjacent materials.

[0029] As used herein, “attached” encompasses both directly attached and being attached via one or more intermediate layers present between the attached materials.

[0030] The term “anisotropic” refers to having a height to width (that is, average width) ratio of about 1.5:1 or greater (preferably, 2:1 or greater; more preferably, 5:1 or greater).

[0031] The term “nanoscale” refers to submicron (for example, between about 1 nm and about 500 nm). [0032] The term “nanostructured” refers to having at least one dimension on the nanoscale. Typically, a nanostructure is three-dimensional.

[0033] The term “plasma” refers to a partially ionized gaseous or fluid state of matter containing electrons, ions, neutral molecules, and free radicals.

[0034] As used herein, “incident” with respect to light refers to the light falling on or striking a material. [0035] The term “metal” includes a pure metal or a metal alloy.

[0036] The term “film” or “layer” refers to a single stratum within a multilayer film.

[0037] The term “substrate” encompasses films, layers, and articles (e.g., lenses).

[0038] As used herein, “thickness” refers to the smallest dimension of a film or layer, e.g., in a z-axis while a major surface of the film or layer is in the x- and y-axes. Thickness may be determined using a micrometer gauge or doing a microscopic analysis of a cross-sectional sample of a layer or an article.

[0039] The term “(methjacryl” or “(methjacrylate” with respect to a monomer, oligomer, (co)polymer or compound means a vinyl-functional alkyl ester formed as the reaction product of an alcohol with an acrylic or a methacrylic acid.

[0040] The term “optically clear” refers to an article in which there is no visibly noticeable distortion, haze or flaws as detected by the naked eye at a distance of about 1 meter, preferably about 0.5 meters. [0041] The term “optical thickness” when used with respect to a layer refers to the physical thickness of the layer times its in-plane index of refraction.

[0042] The term “metasurface” refers to a two-dimensional subwavelength spacing or array of photonic resonators or truncated waveguides, which perform one or more optical functions. Each array locally acts on one or more physical properties of light, specifically, amplitude, phase, or polarization. Photonic resonators or truncated waveguides nano-feature shapes include, but are not limited to, rectangular, triangular and trapezoidal prisms; fins, cylindrical and truncated-cone shaped pillars, etc. The features may be placed with regular, deterministic, or randomized pitch, orientation and shape, dependent on application-functionality and determined article design. [0043] The term “vapor coating” or “vapor depositing” means applying a coating to a substrate surface from a vapor phase, for example, by evaporating and subsequently depositing onto the substrate surface a precursor material to the coating or the coating material itself. Exemplary vapor coating processes include, for example, physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD) and combinations thereof.

[0044] By using terms of orientation such as “atop”, “on”, “over,” “covering”, “uppermost”, “underlying” and the like for the location of various elements in the disclosed coated articles, we refer to the relative position of an element with respect to a horizontally -disposed, upwardly -facing substrate. However, unless otherwise indicated, it is not intended that the substrate or articles should have any particular orientation in space during or after manufacture, or in interpreting the claims.

[0045] As used herein, “radiation” refers to electromagnetic radiation unless otherwise specified.

[0046] As used herein, “refracting” with respect to a wavelength of light refers to causing the light to change direction when it enters a material.

[0047] As used herein, “scattering” with respect to wavelengths of light refers to causing the light to depart from a straight path and travel in different directions with different intensities.

[0048] As used herein, “reflectance” is the measure of the proportion of light or other radiation striking a surface at normal incidence which is reflected off it. Reflectivity typically varies with wavelength and is reported as the percent of incident light that is reflected from a surface (0 percent - no reflected light, 100 - all light reflected). Reflectivity and reflectance are used interchangeably herein.

[0049] As used herein, “reflective” and “reflectivity” refer to the property of reflecting light or radiation, especially reflectance as measured independently of the thickness of a material.

[0050] As used herein, “average reflectance” refers to reflectance averaged over a specified wavelength range.

[0051] As used herein, “absorption” refers to a material converting the energy of light radiation to internal energy.

[0052] As used herein, “absorb” with respect to wavelengths of light encompasses both absorption and scattering, as scattered light also eventually gets absorbed. Absorbance can be measured with methods described in ASTM E903-12 “Standard Test Method for Solar Absorptance, Reflectance, and Transmittance of Materials Using Integrating Spheres”. Absorbance measurements described herein were made by making transmission measurements as previously described and then calculating absorbance using Equation 1.

[0053] As used herein, the term “absorbance” with respect to a quantitative measurement refers to the base 10 logarithm of a ratio of incident radiant power to transmitted radiant power through a material. The ratio may be described as the radiant flux received by the material divided by the radiant flux transmitted by the material. Absorbance (A) may be calculated based on internal transmittance (T) according to Equation 1 :

A = -logio T (1) [0054] Emissivity can be measured using infrared imaging radiometers with methods described in ASTM E1933-14 (2018) “Standard Practice for Measuring and Compensating for Emissivity Using Infrared Imaging Radiometers.” According to Kirchhoff’s law of thermal radiation, absorbance correlates with emittance. Absorbance, absorptivity, emissivity, and emittance are used interchangeably herein for the same purpose of emitting infrared energy to the atmosphere. Absorb and emit are also used interchangeably herein.

[0055] As used herein, the terms “transmittance” and “transmission” refer to the ratio of total transmission of a layer of a material compared to that received by the material, which may account for the effects of absorption, scattering, reflection, etc. Transmittance (T) may range from 0 to 1 or be expressed as a percentage (T%).

[0056] As used herein, “transparent” refers to a material (e.g., film or layer) that absorbs less than 20% of light having wavelengths between 350 nm and 2500 nm.

[0057] As used herein, “bandwidth” refers to a width of a contiguous band of wavelengths.

[0058] The terms “about” or “approximately” with reference to a numerical value or a shape means +/- five percent of the numerical value or property or characteristic, but expressly includes the exact numerical value.

[0059] The term “substantially” with reference to a property or characteristic means that the property or characteristic is exhibited to a greater extent than the opposite of that property or characteristic is exhibited. For example, a substrate that is “substantially” transparent refers to a substrate that transmits more radiation (e.g., visible light) than it fails to transmit (e.g., absorbs and reflects). Thus, a substrate that transmits more than 50% of the visible light incident upon its surface is substantially transparent, but a substrate that transmits 50% or less of the visible light incident upon its surface is not substantially transparent.

[0060] As used in this specification and the appended embodiments, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. Thus, for example, reference “a compound” includes a mixture of two or more compounds. As used in this specification and the appended embodiments, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

[0061] Unless otherwise indicated, all numbers expressing quantities or ingredients, measurement of properties and so forth used in the specification and embodiments are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached listing of embodiments can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings of the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claimed embodiments, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. [0062] By definition, the total weight percentages of all ingredients in a composition equals 100 weight percent.

[0063] Various exemplary embodiments of the disclosure will now be described. Exemplary embodiments of the present disclosure may take on various modifications and alterations without departing from the spirit and scope of the present disclosure. Accordingly, it is to be understood that the embodiments of the present disclosure are not to be limited to the following described exemplary embodiments but is to be controlled by the limitations set forth in the claims and any equivalents thereof. [0064] In a first aspect, an article is provided. The article comprises:

[0065] a multilayer optical film comprising a plurality of first optical layers and a plurality of second optical layers; and

[0066] a boundary layer directly attached to a major surface of the multilayer optical film, wherein the boundary layer comprises a major surface opposite the multilayer optical film that has a nanostructured anisotropic surface.

[0067] Referring to FIG. 1, the present disclosure describes articles 100 including a multilayer optical film 10 comprising a plurality of first optical layers 12 (A-N) and a plurality of second optical layers 13 (A-N). The articles 100 further include a boundary layer 20 directly attached to a major surface 11 of the multilayer optical film, wherein the boundary layer 20 comprises a major surface 21 opposite the multilayer optical film 10 that has a nanostructured anisotropic surface 23.

[0068] Referring to FIG. 2, in some embodiments, an article 200 includes a multilayer film 10 and a boundary layer 20, plus one or more optional layers. Similar to the article 100 of FIG. 1, the article 200 includes a multilayer optical film 10 comprising a plurality of first optical layers 12 (A-N) and a plurality of second optical layers 13 (A-N). The article 200 further includes a boundary layer 20 directly attached to a major surface 11 of the multilayer optical film 10, wherein the boundary layer 20 comprises a major surface 21 opposite the multilayer optical film 10 that has a nanostructured anisotropic surface (not shown in FIG. 2). It is noted that for simplicity in this figure, the schematic depiction of the various features does not show any structures. Additionally, the article 200 includes an optional second boundary layer 30 directly attached to a major surface 15 of the multilayer optical film 10 opposite the (i.e., first) boundary layer 20.

[0069] In some cases, the article 200 further includes an optional skin layer 40 directly or indirectly attached to the nanostructured anisotropic surface 23 of the boundary layer 20. In the embodiment depicted in FIG. 2, the optional skin layer 40 is indirectly attached, with an optional adhesive 50 directly attached the nanostructured anisotropic surface 23 of the boundary layer 20. In such a case, the optional adhesive 50 is disposed between the skin layer 40 and the boundary layer 20, attaching the skin layer 40 to the boundary layer 20. In FIG. 2, additional major surfaces are identified, including a second major surface 25 of the boundary layer 20; a first major surface 41 and a second major surface 45 of the optional skin layer 40; and a first major surface 51 and a second major surface 55 of the optional adhesive [0070] Referring to FIG. 3, in some embodiments, an article 300 includes a multilayer film 10 and a boundary layer 20, plus an optional layer 60 that could be one of various different types of layers. Similar to the article 100 of FIG. 1, the article 300 includes a multilayer optical film 10 comprising a plurality of first optical layers 12 (A-N) and a plurality of second optical layers 13 (A-N). The article 300 further includes a boundary layer 20 directly attached to a major surface 11 of the multilayer optical film 10, wherein the boundary layer 20 comprises a major surface 21 opposite the multilayer optical film 10 that has a nanostructured anisotropic surface (not shown in FIG. 3). It is noted that for simplicity in this figure, the schematic depiction of the various features does not show any structures.

[0071] In some cases, the article 300 includes an optional polymeric substrate 60, wherein a major surface 61 of the polymeric substrate 60 is in direct contact with the nanostructured anisotropic surface of the boundary layer 20. Suitable polymeric substrates include, for instance, a substrate to which the multilayer optical film 10 can be molded (e.g., a lens), in which the nanostructured anisotropic surface of the boundary layer 20 assists in improving adhesion to the polymeric substrate 60.

[0072] In some cases, the article 300 includes an optional layer 60 that is a nano structured bilayer attached to the nanostructured anisotropic surface of the boundary layer 20.

[0073] In some cases, the article 300 includes an optional layer 60 that is a microstructured layer attached to the nanostructured anisotropic surface of the boundary layer 20.

[0074] In some cases, the article 300 includes an optional layer 60 that is a primer attached to the nanostructured anisotropic surface of the boundary layer 20.

[0075] In some cases, the article 300 includes an optional layer 60 that is a hard coat attached to the nanostructured anisotropic surface of the boundary layer 20.

[0076] In FIG. 3, additional major surfaces are identified, including a second major surface 25 of the boundary layer 20; and a first major surface 61 and a second major surface 65 of the optional layer 60. [0077] Referring to FIG. 4, in some embodiments, an article 400 includes a multilayer film 10 and a boundary layer 20, plus one or more optional layers. Similar to the article 100 of FIG. 1, the article 400 includes a multilayer optical film 10 comprising a plurality of first optical layers 12 (A-N) and a plurality of second optical layers 13 (A-N). The article 400 further includes a first boundary layer 20 directly attached to a major surface 11 of the multilayer optical film 10, wherein the first boundary layer 20 comprises a major surface 21 opposite the multilayer optical film 10 that has a nanostructured anisotropic surface (not shown in FIG. 4). It is noted that for simplicity in this figure, the schematic depiction of the various features does not show any structures. Additionally, the article 400 includes an optional second boundary layer 30 directly attached to a major surface 15 of the multilayer optical film 10 opposite the first boundary layer 20.

[0078] In some cases, the article 400 further includes an optional layer 60, that could be various different types of layers, directly or indirectly attached to the second boundary layer 30. Similar to the embodiments of FIG. 3, some suitable optional layers 60 include a nano structured bilayer, a microstructured layer, a primer, or a hard coat. In the embodiment depicted in FIG. 4, the optional layer 60 is directly attached. In FIG. 4, additional major surfaces are identified, including a second major surface 25 of the first boundary layer 20; a first major surface 31 and a second major surface 35 of the optional second boundary layer; and a first major surface 61 and a second major surface 65 of the optional layer 60.

[0079] In select embodiments, article is free of any fluoropolymers, for instance fluoropolymers used as exterior protective layers.

[0080] In a second aspect, a method of making an article is provided. The method comprises:

[0081] providing a multilayer optical film comprising a plurality of first optical layers and a plurality of second optical layers;

[0082] attaching a boundary layer directly to a major surface of the multilayer optical film;

[0083] depositing an etch mask material on a major surface of the boundary layer opposite the multilayer optical film; and

[0084] subsequently or concurrently reactive ion etching to anisotropically remove material in unmasked areas, thereby forming a nanostructured anisotropic surface on the major surface of the boundary layer. [0085] The methods and materials for each of the first and second aspects are described in detail below.

Boundary Layers

[0086] Articles according to the present application include at least one boundary layer attached to a multilayer optical film. A boundary layer may be attached directly to an outer optical layer of the multilayer optical film during preparation of the multilayer optical film (e.g., via coextrusion).

Alternatively, a boundary layer may be attached to an outer optical layer of the multilayer optical film after formation of the multilayer optical film, such as by lamination. In some embodiments, a boundary layer is formed of a thermoplastic polymer, for instance and without limitation, a thermoplastic polymer selected from the group consisting of polyethylene terephthalate (PET), polystyrene, acrylonitrile butadiene styrene, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyacrylates, thermoplastic polyurethanes, polyvinyl acetate, polyamide, polyimide, polypropylene, polyester, polyethylene, poly(methylmethacrylate), methyl methacrylate copolymers (CoPMMAs), polyethylene naphthalate (PEN), polystyrene acrylonitrile, triacetate cellulose, nylon, silicone-polyoxamide polymers, cyclic olefin copolymers, thermoplastic elastomers, and combinations thereof. In select embodiments, at least one of a first boundary layer or a second boundary layer is formed of PEN.

[0087] In some cases, the boundary layer is a first boundary layer and the article further comprises a second boundary layer directly attached to a major surface of the multilayer optical film opposite the first boundary layer. The first and second boundary layers may be formed of the same or different materials. The second boundary layer optionally includes a major surface opposite the multilayer optical film that also has a nanostructured anisotropic surface (e.g., to improve adhesion of the second boundary layer to another material). In other cases, the second boundary layer lacks a nanostructured anisotropic surface. [0088] One suitable method for forming a nano structured surface includes applying a thin, random, discontinuous masking layer to a major surface of the boundary layer using plasma chemical vapor deposition. The random, discontinuous masking layer is the reaction product of plasma chemical vapor deposition using a reactant gas that includes a compound selected from organosilicon compounds, metal alkyls, metal isopropoxides, metal acetylacetonates and metal halides. Typically, the organosilicon compounds can include tetramethylsilane, trimethylsilane, hexamethyldisiloxane, tetraethylorthosilicate, or a polyhedral oligomeric silsesquioxane. Useful metal alkyls can comprise trimethylaluminum, tributylaluminum, tributyltin, or tetramethyl gallium. Useful metal isopropoxides can comprise titanium isopropoxide, or zirconium isopropoxide. Useful metal acetylacetonates can comprise platinum acetylacetonates, or copper acetylacetonate. Useful metal halides can comprise titanium tetrachloride, or silicon tetrachloride.

[0089] Plasma chemical vapor deposition (or plasma-enhanced chemical vapor deposition) is a process by which plasmas, typically generated by radio-frequency discharge, are formed in the space between two electrodes when that space is filled with a reacting gas or gases. Plasma chemical vapor deposition is done under vacuum to reduce side reactions from unwanted species being present in the reacting chamber. The reacting gas or gases typically deposit thin solid films on a substrate. In the provided method, a random, discontinuous masking layer is formed on the substrate using plasma chemical vapor deposition. Certain chemical species, when plasma deposited on a substrate in very short time form random, discontinuous islands of material.

[0090] Typically, when reactant gases derived from relatively small organic or organometallic compounds are plasma chemical vapor deposited on a boundary layer, they initially form small islands of reacted material. Although not wishing to be bound by theory, it is likely that this effect is similar to small amounts of liquids, such as water, initially beading up on a surface that has a different surface energy. In a similar manner, when small amounts of the product produced by plasma chemical vapor deposition initially deposit on a boundary layer, they tend to huddle together in small islands that are initially in a random, discontinuous pattern. Reaction conditions are adjusted (web speed, plasma discharge energy, time of exposure, etc.) so as to halt the deposition before any coalescence occurs. The masking layer thus deposited is random and discontinuous. The individual islands typically have average dimensions of less than about 400 nm, less than about 200 nm, less than about 100 nm, less than about 50 nm or even less than about 20 nm.

[0091] Forming a nanostructured surface further includes etching portions of the major surface not protected by the masking layer to form a nanostructure on the substrate. Typically, reactive ion etching is used for the etching. In one embodiment, the provided method can be carried out using a continuous roll- to-roll process referred to as “cylindrical reactive ion etching” (cylindrical RIE). Cylindrical RIE utilizes a rotating cylindrical electrode to provide anisotropically etched nanostructures on the surface of a substrate or article. In general, cylindrical RIE can be described as follows. A rotatable cylindrical electrode (“drum electrode”) powered by radio-frequency (RF) and a grounded counter-electrode are provided inside a vacuum vessel. The counter-electrode can comprise the vacuum vessel itself. An etchant gas is fed into the vacuum vessel, and a plasma is ignited and sustained between the drum electrode and the grounded counter-electrode. [0092] A continuous substrate (i.e., boundary layer) comprising a random, discontinuous masking layer can then be wrapped around the circumference of the drum and the substrate can be etched in the direction normal to the plane of the substrate. The exposure time of the substrate can be controlled to obtain a predetermined etch depth of the resulting nanostructure. The process can be carried out at an operating pressure of approximately 10 mTorr. Cylindrical RIE is disclosed, for example, in PCT Pat. App. No. US/2009/069662 (David et al.).

[0093] The etching gases can include, for example, oxygen, argon, chlorine, fluorine, carbon tetrafluoride, perfluoromethane, perfluoroethane, perfluoropropane, nitrogen trifluoride, sulfur hexafluoride, methane, and the like. Mixtures of gases may be used advantageously to enhance the etching process. Inert gases, particularly heavy gases such as argon can be added to enhance the anisotropic etching process.

[0094] Additional details describing forming a nano structured surface by depositing an etch mask material on a major surface of the boundary layer and reactive ion etching to anisotropically remove material in unmasked areas is disclosed, for example, in US Patent No. 8,634, 146 (David et al.). [0095] The nano structured surface made by the method of the invention can have a nanostructured anisotropic surface. The nanostructured anisotropic surface typically can comprise nanoscale features having a height to width ratio or about 2: 1 or greater; preferably about 5: 1 or greater. In some embodiments, the height to width ratio can even be 50: 1 or greater, 100: 1 or greater, or 200: 1 or greater. The nanostructured anisotropic surface can comprise nanofeatures such as, for example, one or more of nano-pillars, nano-columns, or continuous nano-walls comprising nano-pillars or nano-columns. Typically, the nanofeatures have steep side walls that are substantially perpendicular to the boundary layer. In some cases, the nanofeatures have at least one dimension of 500 nm or less. Without wishing to be bound by theory, it is believed that the inclusion of nanofeatures having such a size may strike a balance between increasing adhesion to another layer or material while minimizing effects on the optical properties of the multilayer optical film. Articles according to at least certain embodiments of the present disclosure may desirably exhibit, over a wavelength range from 400 nm to 1600 nm, an average absorbance that is no more than 2% greater than an average absorbance of the same article except that the first boundary layer lacks a nanostructured anisotropic surface. For instance, an article lacking the nanostructured anisotropic surface could be a multilayer optical film prior to being subjected to a nanostructuring process (e.g., Preparative Example 1 (PEI) described in detail in the examples below, as compared to any of the nano structured articles of Examples 1-3).

[0096] In some embodiments, the majority of the nanofeatures can be capped with mask material. The mask material can have a thickness from about 3 nm to about 150 nm or from about 5 nm to about 50 nm or from about 10 nm to about 30 nm.

[0097] Referring to FIG. 5, a scanning electron microscopy (SEM) image is provided of a cross-section of a portion of a control article 500 in which a major surface 21 of a boundary layer 20 has not been subjected to a nanostructuring process and the major surface 21 is planar. [0098] In contrast, FIG. 6 is an SEM image of a cross-section of a portion of an exemplary article 600 made according to Example 1 (EXI) described in detail below. Briefly, a major surface 21 of aboundary layer 20 was subjected to a nanostructuring process for 20 seconds at a line speed of 15.0 feet per minute, resulting in a nano structured anisotropic surface 23 formed on the major surface 21 of the boundary layer 20. FIG. 7 is an SEM image of a cross-section of a portion of an exemplary article 700 made according to Example 2 (EX2) described in detail below. This example differs from the article 500 shown in FIG. 5 in that a major surface 21 of a boundary layer 20 was subjected to a nanostructuring process for 30 seconds at a line speed of 10.0 feet per minute, also resulting in a nanostructured anisotropic surface 23 formed on the major surface 21 of the boundary layer 20.

[0099] Suitable thicknesses of a boundary layer are 0.5 micrometers or greater, 0.8 micrometers, 1.0 micrometers, 1.5 micrometers, 2.0 micrometers, 2.5 micrometers, 3.0 micrometers, 3.5 micrometers, 4.0 micrometers, 5 micrometers, 6 micrometers, 7 micrometers, or 8 micrometers or greater; and 10 micrometers or less, 9 micrometers, 8 micrometers, 7 micrometers, 6 micrometers, 5 micrometers, 4 micrometers, or 3 micrometers or less. Stated another way, in some cases a boundary layer has a thickness of between 0.5 micrometers and 10 micrometers.

Multilayer Optical Films

[00100] Referring again to FIG. 2, for instance, the article 200 includes a multilayer optical film 10 comprising one or more alternating first optical layers 12 (A-N) and second optical layers 13 (A-N) as described further below.

[00101] Typically, the multilayer optical film has a thickness of 2.0 micrometers or greater, 10 micrometers, 20 micrometers, 30 micrometers, 40 micrometers, 50 micrometers, 60 micrometers, 70 micrometers, 80 micrometers, 90 micrometers, or 100 micrometers or greater; and 1000 micrometers or less, 950 micrometers, 900 micrometers, 850 micrometers, 800 micrometers, 750 micrometers, 700 micrometers, 650 micrometers, 600 micrometers, 550 micrometers, 500 micrometers, 450 micrometers, 400 micrometers, 350 micrometers, or 300 micrometers or less, such as a thickness of 2 micrometers to 1000 micrometers or 50 micrometers to 600 micrometers.

[00102] In some embodiments, the plurality of alternating first and second optical layers collectively reflect light that is normally incident to a first major surface of the article, an average of at least 50, 60, 70, 80, 90, or 99 percent of incident light over at least a 30-nanometer wavelength reflection bandwidth in a wavelength range from 400 nm to 3000 nm, 400 nm to 1200 nm, 1200 nm to 1600 nm, or 800 nm to 1600 nm. In some cases, light is reflected over a greater wavelength reflection bandwidth than at least 30-nanometer, for instance at least a 50-nanometer, 75-nanometer, 100-nanometer, 125-nanometer, 150- nanometer, or 175-nanometer wavelength reflection bandwidth in the abovementioned wavelength ranges.

[00103] The use of multilayer reflective films comprising alternating layers of two or more polymers to reflect light is known and is described, for example, in U.S. Pat. No. 3,711,176 (Alfrey, Jr. et al.), U.S. Pat. No. 5,103,337 (Schrenk et al.), WO 96/19347 (Jonza et al.), and WO 95/17303 (Ouderkirk et al.). The reflection and transmission spectra of a particular multilayer film depends primarily on the optical thickness of the individual layers, which is defined as the product of the actual thickness of a layer times its refractive index. Accordingly, films can be designed to reflect infrared, visible, or ultraviolet wavelengths '/.\i of light by choice of the appropriate optical thickness of the layers in accordance with the following formula:

[00104] _M =(2/M)*D_r

[00105] wherein M is an integer representing the particular order of the reflected light and D_r is the optical thickness of an optical repeating unit (also called a multilayer stack) comprising two or more polymeric layers. Accordingly, D_r is the sum of the optical thicknesses of the individual polymer layers that make up the optical repeating unit. D_r is always one half lambda (X) in thickness, where lambda is the wavelength of the first order reflection peak. By varying the optical thickness of an optical repeating unit along the thickness of the multilayer film, a multilayer film can be designed that reflects light over a broad band of wavelengths. This band is commonly referred to as the reflection band or stop band. In some embodiments, a reflection band has a sharp spectral edge at the long wavelength (red) and/or short wavelength (blue) side. It may be desirable to design a reflective film or other optical body that reflects light over a selected range in the visible region of the spectrum, e.g., a reflective film that reflects only green light. In such a case, it may be desirable to have sharp edges at both the red and blue sides of the reflection band. Multilayer optical films exhibiting sharpened reflective bandedge(s) are described in detail, for instance, in U.S. Patent No. 6,967,778 (Wheatley et al.), incorporated herein by reference in its entirety.

[00106] In some embodiments, multilayer optical films described herein can be made using the general processing techniques, such as those described in U.S. Pat. No 6,783,349 (Neavin et al.), the disclosure of which is incorporated herein by reference. Desirable techniques for providing a polymeric multilayer optical film with a controlled spectrum may include, for example, 1) the use of an axial rod heater control of the layer thickness values of coextruded polymer layers as described, for example, in U.S. Pat. No. 6,783,349 (Neavin et al.); 2) timely layer thickness profile feedback during production from a layer thickness measurement tool such as, for example, an atomic force microscope (AFM), a transmission electron microscope, or a scanning electron microscope; 3) optical modeling to generate the desired layer thickness profile; and 4) repeating axial rod adjustments based on the difference between the measured layer profile and the desired layer profile.

[00107] In one embodiment, an optical polymer film or a layered optical polymer film having a first and second major surface is provided. “Film” is used to refer to planar forms of plastic that are thick enough to be self-supporting but thin enough to be flexed, folded, conformed or creased without cracking. Film thickness depends upon desired applications and manufacturing methods.

[00108] “Optical Film” is used herein to refer to any reflective or partially reflective polymer film designed to exhibit desired reflection, transmission, absorption, or refraction of light upon exposure to a specific band of wavelengths of electromagnetic energy. Thus, conventional normally transparent polymeric films, such as polyester and polypropylene, are not considered “optical films” for the purposes of the present disclosure, even though such films may exhibit some degree of reflectance, or glare, when viewed from some angles. Films that exhibit both reflective and transmissive properties, however, such as those that are partially transmissive, are considered within the scope of this disclosure. Preferred optical polymer films generally absorb less than 25 percent of the radiant energy that impacts the film’s surface. Preferably, the radiating energy absorbed is less than 10 percent and most preferably less than 5 percent. The radiant energy, typically expressed as the energy in a range of wavelengths, may be reflected either specularly or diffusely. The reflectance may be isotropic, i.e., the film has the same reflective properties along both in-plane axes, or may be anisotropic, i.e., the film has different reflective properties along the orthogonal in-plane axes. The difference in reflective properties along the in-plane axes can be varied by controlling the relationship between the indices of refraction along each axis for each of the component materials.

[00109] Optical films come in a variety of forms and are selected according to a desired application. Some suitable examples include multilayer polarizers, visible and infrared mirrors, and color fdms such as those described in Patent Publications WO 95/17303, WO 96/19347, and WO 97/01440; U.S. Pat. No. 6,045,894 (Jonza et al.) U.S. Pat. No. 6,531,230 (Weber et al.); U.S. Pat. No. 5,103,337 (Schrenk et al.), U.S. Pat. No. 5,122,905 (Wheatley et al.), U.S. Pat. No. 5,122,906 (Wheatley), U.S. Pat. No. 5,126,880 (Wheatley et al.), U.S. Pat. No. 5,217,794 (Schrenk), U.S. Pat. No. 5,233,465 (Schrenk et al.), U.S. Pat. No. 5,262,894 (Wheatley et al.), U.S. Pat. No. 5,278,694 (Wheatley et al.), U.S. Pat. No. 5,339,198 (Wheatley et al.), U.S. Pat. No. 5,360,659 (Arends et al.), U.S. Pat. No. 5,448,404 (Schrenk et al.), U.S. Pat. No. 5,486,949 (Schrenk et al.) U.S. Pat. No. 4,162,343 (Wilcox et al.), U.S. Pat. No. 5,089,318 (Shetty et al.), U.S. Pat. No. 5,154,765 (Armanini), and U.S. Pat. No. 3,711,176 (Alfrey, Jr. et al.); and Reissued U.S. Pat. No. RE 31,780 (Cooper et al.) and U.S. Pat. No. RE 34,605 (Schrenk et al.), all contents of which are incorporated herein by reference.

[00110] Examples of optical films comprising immiscible blends of two or more polymeric materials include blend constmctions wherein the reflective and transmissive properties are obtained from the presence of discontinuous polymeric regions having a cross-sectional diameter perpendicular to the major axis that is on the order of a fraction of the distance corresponding to a wavelength of light, and may also obtain the desired optical properties through orientation, such as the blend mirrors and polarizers as described in Patent Publications WO 97/32224 (Ouderkirk et al.), U.S. Pat. No. 6,179,948 (Merrill et al.), and U.S. Pat. No. 5,751,388 (Larson), the contents of which are all herein incorporated by reference.

[00111] Referring back to FIG. 2, the multilayer optical film 10 includes a multilayer optical stack having alternating layers 12, 13 of at least two materials, typically comprising different polymers. An in-plane index of refraction nl in one in-plane direction of high refractive index layer 13 is higher than the inplane index of refraction n2 of low refractive index layer 12 in the same in-plane direction. The difference in refractive index at each boundary between layers 12, 13 causes part of the incident light to be reflected. The transmission and reflection characteristics of the multilayer optical fdm 10 is based on coherent interference of light caused by the refractive index difference between layers 12, 13 and the thicknesses of layers 12, 13. When the effective indices of refraction (or in-plane indices of refraction for normal incidence) differ between layers 12, 13, the interface between adjacent layers 12, 13 forms a reflecting surface. The reflective power of the reflecting surface depends on the square of the difference between the effective indexes of refraction of the layers 12, 13 (e.g., (nl - n2)²). By increasing the difference in the indices of refraction between the layers 12, 13, improved optical power (higher reflectivity), thinner films (thinner or fewer layers), and broader bandwidth performance can be achieved. The refractive index difference in one in-plane direction in an exemplary embodiment is at least about 0.05, preferably greater than about 0.10, more preferably greater than about 0.15 and even more preferably greater than about 0.20.

[00112] In some embodiments, the materials of layers 12, 13 inherently have differing indices of refraction. In another embodiment, at least one of the materials of the layers 12, 13 has the property of stress induced birefringence, such that the index of refraction (n) of the material is affected by the stretching process. By stretching the polymeric multilayer optical film 10 over a range of uniaxial to biaxial orientations, films can be created with a range of reflectivities for differently oriented plane- polarized incident light.

[00113] The number of layers in the polymeric multilayer optical film 10 is selected to achieve the desired optical properties using the minimum number of layers for reasons of film thickness, flexibility and economy. In the case of reflective films such as mirrors, the number of layers is preferably less than about 2,000, more preferably less than about 1,000, and even more preferably less than about 750. In some embodiments, the number of layers is at least 150 or 200. In other embodiments, the number of layers is at least 250.

[00114] In some cases, the first and second optical layers are independently selected from a polycarbonate, an epoxy -containing polymer, a poly(epoxy -containing monomer), a vinyl polymer, a cyclic olefin polymer, a poly(phenylene oxide), a polysulfone, a polyamide, a polyurethane, a polyethylene, a polypropylene, a polyamic acid, a polyimide, a polyester, a fluoropolymer, a polydimethylsiloxane, a poly(alkylene terephthalate), a polyalkylene napthalate), poly(methylmethacrylate), a methyl methacrylate copolymer (CoPMMA), a silicone polymer, a cellulose derivative, an ionomer, or a copolymer thereof. In select embodiments, the first optical layer is formed of PEN and the second optical layer is formed of polymethylmethacrylate (PMMA).

[00115] The first and second polymeric optical layers can independently include, for example, at least one of polycarbonate) (PC); syndiotactic or isotactic poly(styrene) (PS); (Cl-C8)alkyl styrenes; alkyl, aromatic, or aliphatic ring-containing acrylates or (methjacrylates, including polymethylmethacrylate) (PMMA) or PMMA copolymers; ethoxylated or propoxylated acrylate or (methjacrylates; multifunctional acrylates or (methjacrylates; acrylated epoxies; epoxies; or other ethylenically unsaturated materials; cyclic olefins or cyclic olefinic copolymers; acrylonitrile butadiene styrene (ABS); styrene acrylonitrile copolymers (SAN); epoxies, poly (viny Icy clohexane), PMMA/poly(vinylfluoride) blends; poly(phenylene oxide) alloys; styrenic block copolymers; polyimide; polysulfone; poly(vinyl chloride); poly(dimethyl siloxane) (PDMS); polyurethanes; unsaturated polyesters; poly(ethylene), including low birefringence polyethylene; poly(propylene) (PP); poly(alkylene terephthalates), such as polyethylene terephthalate) (PET); polylalkylene napthalates), such as polyethylene naphthalate)(PEN); polyamide, ionomers; vinyl acetate/polyethylene copolymers; cellulose acetate; cellulose acetate butyrate; fluoropoiymers; poly(styrene)-poly(ethylene) copolymers; PET or PEN copolymers, including polyolefinic PET or PEN; or poly(carbonate)/aliphatic PET blends.

[00116] Exemplary polymers, especially for use in high refractive index optical layers, may include homopolymers of polymethyl methacrylate (PMMA), such as those available as CP71 and CP80 from Ineos Acrylics, Inc., Wilmington, DE; and polyethyl methacrylate (PEMA), which has a lower glass transition temperature than PMMA. Suitable polyethylene naphthalate (PEN) polymers are available under the tradename “Teonex Q51” from DuPont Teijin, Chester, VA. Additional useful polymers include: copolymers of methyl methacrylate such as, for example, a copolymer made from 75 wt.% methyl methacrylate and 25 wt.% ethyl acrylate, for example, as available from Ineos Acrylics, Inc. as PERSPEX CP63, or as available from Arkema, Philadelphia, PA as ALTUGLAS 510, and copolymers of methyl methacrylate monomer units and n-butyl methacrylate monomer units. Blends of PMMA and PVDF may also be used.

[00117] Suitable triblock acrylic copolymers are available, for example, as KURARITY LA4285 from Kuraray America Inc., Houston, TX. Additional suitable polymers for the optical layers, especially for use in the low refractive index optical layers, may include at least one of: polyolefin copolymers such as poly(ethylene-co-octene) (e.g., available as ENGAGE 8200 from Dow Elastomers, Midland, MI), polyethylene methacrylate (e.g., available as ELVALOY from Dow Elastomers), poly (propylene-co- ethylene) (e.g., available as Z9470 from Atofina Petrochemicals, Inc., Houston, TX); and a copolymer of atactic polypropylene and isotactic polypropylene. Materials may be selected based on absorbance or transmittance properties described herein, as well as on refractive index. In general, the greater the refractive index between two materials, the thinner the film can be.

[00118] Multilayer optical films can be made by coextrusion of alternating polymer layers having different refractive indices, for example, as described in U.S Pat. Nos. 5,882,774 (Jonza et al.); 6,045,894 (Jonza et al.); 6,368,699 (Gilbert et al.); 6,531,230 (Weber et al.); 6,667,095 (Wheatley et al.); 6,783,349 (Neavin et al.); 7,271,951 B2 (Weber et al); 7,632,568 (Padiyath et al.); 7,652,736 (Padiyath et al.); and 7,952,805 (McGurran et al.); and PCT Publications WO 95/17303 (Ouderkirk et al.) and WO 99/39224 (Ouderkirk et al.). Additionally, in some embodiments the boundary layer is attached to a major surface of (an outer layer of) the multilayer optical film by coextrusion of the boundary layer with the multilayer optical film.

Adhesives

[00119] In some embodiments, an article according to the present disclosure may include one or more optional adhesives. For instance, an article may include an adhesive directly attached the nanostructured anisotropic surface of the boundary layer to adhere a skin layer or a substrate to the boundary layer. Adhesives are not particularly limited and may include pressure-sensitive adhesives and/or hot melt adhesives. Typically, an adhesive is transparent to minimize affecting the optical properties of the multilayer optical film.

[00120] Classes of suitable pressure sensitive adhesives include acrylics, tackified rubber, tackified synthetic mbber, ethylene vinyl acetate and the like. Suitable acrylic adhesives are disclosed, for example, in U.S. Pat. Nos. 3,239,478 (Harlan); 3,935,338 (Robertson); 5,169,727 (Boardman); 4,952,650 (Y oung et al.) and 4,181,752 (Martens et al.), incorporated herein by reference.

[00121] In select embodiments, the adhesive is optically clear, which means that the adhesive has both transparency and clarity (e.g., low haze). In certain embodiments, an optically clear adhesive (OCA) is selected from an acrylate, a polyurethane, a polyolefin (such as a polyisobutylene (PIB)), a silicone, or a combination thereof. Illustrative OCAs include those described in International Pub. No. WO 2008/128073 (Everaerts et al.) relating to antistatic optically clear pressure sensitive adhesives, U.S. Pat. App. Pub. Nos. US 2009/089137 (Sherman et al.) relating to stretch releasing OCA, US 2009/0087629 (Everaerts et al.) relating to indium tin oxide compatible OCA, US 2010/0028564 (Cheng et al.) relating to antistatic optical constructions having optically transmissive adhesive, US 2010/0040842 (Everaerts et al.) relating to adhesives compatible with corrosion sensitive layers, US 2011/0126968 (Dolezal et al.) relating to optically clear stretch release adhesive tape, and U.S. Pat. No. 8,557,378 (Yamanaka et al.) relating to stretch release adhesive tapes. Suitable OCAs include acrylic optically clear pressure sensitive adhesives such as, for example, 3M OCA 8146, 8211, 8212, 8213, 8214, and 8215, each available from 3M Company, St. Paul, MN.

[00122] In some cases, some of the (optional) adhesive may interpenetrate the nanofeatures of the nanostructured anisotropic surface of the boundary layer. In other cases, the adhesive may only come into contact with the tops of the nanofeatures of the nanostructured anisotropic surface of the boundary layer. Exemplary thicknesses of a layer of adhesive layer may be in the range from about 0.05 to about 100 micrometers.

Skin Layer

[00123] In some embodiments, an article according to the present disclosure may include one or more optional skin layers. A skin layer is an exterior layer of the article. In some cases, the skin layer provides protection during handling or other use of the article, and/or dimensional stability to the overall article. [00124] Optionally, a skin layer may be affixed to an article by extruding a thermoplastic polymer layer onto the nanostructured anisotropic surface of the boundary layer. Suitable thermoplastic polymers include for instance and without limitation, a polyethylene, a polypropylene, 1 -octene, styrene, a polyolefin copolymer, a polyamide, poly- 1 -butene, poly-4-methyl-l-pentene, a polyethersulfone, a polysulfone, a polyacrylonitrile, a polyamide, a cellulose acetate, a cellulose nitrate, a regenerated cellulose, a polyvinyl chloride, a polycarbonate, a polyethylene terephthalate, a polyimide, an epoxycontaining polymer, a poly(epoxy -containing monomer), a vinyl polymer, a cyclic olefin polymer, a poly(phenylene oxide), a polyurethane, a polyamic acid, a polyester, a fluoropolymer, a polydimethylsiloxane, a poly(alkylene terephthalate), a polyalkylene napthalate), poly(methylmethacrylate), a methyl methacrylate copolymer (CoPMMA), a silicone polymer, an ionomer, or combinations thereof.

[00125] In some embodiments, a skin layer is indirectly attached to the nanostructured anisotropic surface of the boundary layer, such as by using an adhesive such as the adhesives described in detail above.

[00126] Suitable thicknesses of a skin layer are between 1 micrometer and 50 micrometers.

Substrate

[00127] In some embodiments, an article according to the present disclosure may include an optional substrate to which the multilayer optical film is attached. In certain embodiments, a substrate may be thermoformed, injection molded, or laminated to an article according to the present disclosure. For instance, a method of making an article may include molding the article to a polymeric substrate, wherein the nanostructured anisotropic surface of the boundary layer is in direct contact with the polymeric substrate. Advantageously, the presence of the nanostructured anisotropic surface of the boundary layer enhances the adhesion of the article to the substrate.

[00128] The substrate is not particularly limited and may include various objects that would benefit from the addition of a multilayer optical film attached to a surface of the object, such as a lens.

Nanostructured Bilayer

[00129] In some embodiments, an article according to the present disclosure may include a nanostructured bilayer attached to a boundary layer opposite the multilayer optical film - the first boundary layer and/or the second boundary layer. The nano structured bilayer comprises a patterned layer having a nanostructured surface and a refractive index contrast layer comprising a refractive index contrast material adjacent to the nano structured surface of the patterned layer.

[00130] Often, the nano structured bilayer acts as a metasurface feature, and when in optical communication with the multilayer optical film, may alter, enhance, or improve one or more optical properties of the MOF.

[00131] As depicted in FIG. 8A, a nano structured bilayer 60 comprises a patterned layer 62 having a nanostructured surface 63 and a refractive index contrast layer 66 comprising a refractive index contrast material adjacent to the nanostructured surface 63 of the patterned layer 62. FIG. 8B illustrates top elevation schematic diagrams of four representative nanostructured bilayers, showing different patterns of patterned layers 62 of the nanostructured surfaces 63. The nanostructured bilayers may include one or more aspects of the representative nanostructured bilayers illustrated in FIG. 8B; however, these are nonlimiting illustrative nanostructure topography.

[00132] The patterned layer 62 has a first surface proximate to a boundary layer and has a second nanostructured surface opposite the first surface. A refractive index contrast layer 66 comprising a refractive index contrast material is adjacent to the nanostructured surface of the patterned layer 62, forming a nano structured bilayer 60 having a nano structured interface 67. The nano structured bilayer 60 is disposed on an article, such as by laminating the nanostructured bilayer and the article together. In some cases, a pressure-sensitive adhesive interface between the nanostructured bilayer and the boundary layer of the article is used, and/or a curing step to bond the nanostructured bilayer to the boundary layer of the article. The nanostructured bilayer acts locally on an amplitude, phase, or polarization of light, or a combination thereof and imparts a light phase shift that varies as a function of position of the nanostructured bilayer on the article, and the light phase shift of the nanostructured bilayer defines a predetermined operative phase profile of the article.

[00133] The nano structured bilayer may have a nominal height or nominal thickness in a range from about 50 to 5000 nanometers, or from 100 to 3000 nanometers.

[00134] The patterned layer may be formed of thermoplastic material. The patterned layer may be formed of poly(methyl methacrylate), polycarbonate, polypropylene, polyethylene, polystyrene, polyester, or polyamide. The patterned layer may be formed of polymerizable compositions comprising acrylate or methacrylate components. The patterned layer may include a fluoropolymer, (meth)acrylate (co)polymer, or silica containing polymers. The patterned layer may include a metal oxide. The patterned layer may include silica or alumina.

[00135] The refractive index contrast material may have a first refractive index value and the patterned layer has a second refractive index value being at least 0.25 different than, 0.5 different than, 0.75 different than, 1.0 different than, or even at least 1.4 different than the first refractive index value. The refractive index contrast material may have a first refractive index value in a range from 1.7 to 4.5. The patterned layer may have a second refractive index value in a range from 1.2 to 1.7.

[00136] The refractive index contrast material may include a metal, a metal oxide or metal nitride. The refractive index contrast material may include at least one of titanium, zirconium, tantalum, hafnium, niobium, zinc, or cerium; an oxide of titanium, zirconium, tantalum, hafnium, niobium, zinc, or cerium; a nitride of titanium, zirconium, tantalum, hafnium, niobium, zinc, or cerium; a sulfide of titanium, zirconium, tantalum, hafnium, niobium, zinc, silicon, or cerium; or a combination thereof.

[00137] In select embodiments, the patterned layer may include (meth)acrylate and the refractive index contrast material may include titanium dioxide.

[00138] The nanostructured bilayer may be defined by a plurality of nanostructures embedded into the refractive index contrast layer. The nanostructures forming the nano structured surface may have an aspect ratio of at least about 1: 1, 2: 1, 5: 1, 10:1 or 15: 1. The nanostructures forming the nanostructured surface preferably may have an aspect ratio in a range of about 2 : 1 to about 20 : 1 , or from about 4 : 1 to about 15: 1. [00139] The nanostructures forming the nano structured surface may define a tapered sidewall having an angle in a range from about 1 to 10 degrees, 2 to 10 degrees, 3 to 10 degrees, 4 to 10 degrees, 1 to 6 degrees, 2 to 6 degrees, or 3 to 6 degrees, or 2 to 4 degrees. The nanostructures forming the nanostructured surface may define a tapered sidewall having an angle in a range from about 0 to 10 degrees, 0 to 6 degrees, 0 to 3 degrees, 0 to 2 degrees, 0 to 1 degree, or 0 degrees.

[00140] The nanostructures forming the nanostructured surface may have a height of 5 micrometer or less, or in a range from about 50 to about 5000 nanometers, or 100 nanometers to about 3000 nanometers, or from about 500 nanometers to about 3000 nanometers. [00141] The nanostructures forming the nanostructured surface has a nominal pitch (center-to-center distance between adjacent nanostructures) that is subwavelength with respect to the shortest wavelength contained in the interrogating electromagnetic radiation.

[00142] The nanostructures forming the nanostructured surface are each separated from each other (edge to edge) by a subwavelength lateral distance. The nanostructures forming the nanostructured surface are each separated from each other by about 4000 nanometers or less, or in a range from about 20 nanometers to about 4000 nanometers, or from about 50 nanometers to about 300 nanometers. The nanostructures forming the nano structured surface have a lateral dimension orthogonal to a nanostructure feature height that is subwavelength. The nanostructures forming the nanostructured surface may have a lateral dimension orthogonal to a nanostructure feature height of about 6000 nanometers or less, or in a range from about 10 nanometers to about 6000 nanometers, or from about 30 nanometers to about 350 nanometers.

[00143] The nanostructures forming the nano structured surface may have a varying orientation that depends on the location of the individual nanostructure on the article. The nanostructures forming the nanostructured surface may have a varying spatial arrangement that depends on the location of the individual nanostructure on the article. The nanostructures forming the nanostructured surface may have a varying shape that depends on the location of the individual nanostructure on the article. The nanostructures forming the nanostructured surface may have a varying aspect ratio that depends on the location of the individual nanostructure on the article. The nanostructures forming the nano structured surface may be geometrically anisotropic in a planar direction. The nanostructures forming the nanostructured surface may be geometrically isotropic in a planar direction.

[00144] Nanostructured bilayers and how to manufacture them are described in additional detail in PCT Publication No. WO 2021/220089 (Wolk et al.), incorporated herein by reference.

Microstructured Layer

[00145] In some embodiments, an article according to the present disclosure may include a microstructured layer attached to a boundary layer opposite the multilayer optical film - the first boundary layer and/or the second boundary layer. A micro structured layer comprises a first major surface and an opposing second major surface, wherein the first major surface comprises a plurality of microstructures projecting therefrom. In some cases, a microstructured surface comprises adjacent peaks and valleys, forming a series of prisms across the surface. Further details regarding microstructured substrates having peak structure arrays and how to form them are described in US 2021/0187819 (Connell et al.), incorporated herein by reference. Prisms are just one example of suitable microstructures for inclusion on a microstructured surface. Microstructured films/layers are well known in the art and can include for instance and without limitation, louver structures (see, e.g., WO 2019/118685 (Schmidt et al.) and WO 2020/026139 (Schmidt et al.), each incorporated herein by reference); facet structures (see, e.g., WO 2020/250180 (Kenney et al.), incorporated herein by reference); and projection array structures (see, e.g., WO 2020/097319 (Wolk et al.), incorporated herein by reference). [00146] A microstructured layer may be attached to a boundary layer of an article either directly or indirectly. When indirectly attached, lamination using an adhesive (e.g., a pressure-sensitive adhesive) interface may be performed. When directly attached, a curing step may be needed to bond the microstructured layer to the boundary layer of the article.

Primer

[00147] In some embodiments, an article according to the present disclosure may include a primer attached to a boundary layer opposite the multilayer optical film - the first boundary layer and/or the second boundary layer. The primer may assist in a user attaching the article to another layer or object. A primer may be applied to the boundary layer using conventional coating methods such as roll coating (for example, gravure roll coating) or spray coating (for example, electrostatic spray coating). Often, a primer will be in a form of a solution, emulsion, or dispersion, and require removal of a solvent and optionally also curing of the primer coating.

[00148] In some cases, the primer may be chosen to be hydrophilic or hydrophobic. As used herein, the term “hydrophilic” refers to a surface that is wet by aqueous solutions and does not express whether or not the material absorbs aqueous solutions. By “wet” it is meant that the surface exhibits an advancing (maximum) water contact angle of less than 90°, preferably 45° or less. As used herein, the term “hydrophobic” refers to a surface that exhibits an advancing water contact angle of 90° or greater. Some suitable hydrophilic primer polymers include for instance and without limitation, a polyester, a polyamide, a polyurethane, a poly(vinyl alcohol) (e.g., ethylene vinyl alcohol), a poly(alkylene glycol), a poly(alkylene oxide), a poly(vinyl pyrrolidone), a rubber elastomer, or any combination thereof. Some suitable hydrophobic primer polymers include for instance and without limitation, a polyethylene, a polydimethylsiloxane (PDMS), a polystyrene, a silicone polyoxamide, or any combination thereof.

Hard Coat

[00149] In some embodiments, an article according to the present disclosure may include a primer attached to a boundary layer opposite the multilayer optical film - the first boundary layer and/or the second boundary layer. A hard coat is typically an outer layer of the article and configured to protect the multilayer optical film from degradation due to issues such as handling during converting processes, corrosion, weathering, dirt, scratches, and the like.

[00150] A hard coat generally should be as thin as possible to minimize adverse effects on the optical properties of the article. If desired, the hard coat may be applied using conventional coating methods such as roll coating (for example, gravure roll coating) or spray coating (for example, electrostatic spray coating). The hard coat preferably is crosslinked. The hard coat may be formed using flash evaporation, vapor deposition, and crosslinking of a monomer or oligomer. Examples of monomers or oligomers for use in such a protective layer includes volatilizable (methjacrylates. Some suitable polymeric materials for the hard coat include for instance and without limitation, crosslinked acrylate polymers, urethane polymers, or vinyl polymers. The hard coat may also contain adhesion-promoting additives. [00151] Listing of Exemplary Embodiments

[00152] In a first embodiment, the present disclosure provides an article. The article comprises a multilayer optical film comprising a plurality of first optical layers and a plurality of second optical layers and a boundary layer directly attached to a major surface of the multilayer optical film. The boundary layer comprises a major surface opposite the multilayer optical film that has a nanostructured anisotropic surface.

[00153] In a second embodiment, the present disclosure provides an article according to the first embodiment, wherein the multilayer optical film reflects an average of at least 50, 60, 70, 80, 90, or 99 percent of light over a wavelength bandwidth of at least 30 nanometers (nm) within a wavelength range of 400 nm to 3000 nm.

[00154] In a third embodiment, the present disclosure provides an article according to the first embodiment or the second embodiment, wherein the boundary layer is formed of a thermoplastic polymer.

[00155] In a fourth embodiment, the present disclosure provides an article according to any of the first through third embodiments, wherein the boundary layer is formed of a thermoplastic polymer selected from the group consisting of polyethylene terephthalate (PET), polystyrene, acrylonitrile butadiene styrene, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyacrylates, thermoplastic polyurethanes, polyvinyl acetate, polyamide, polyimide, polypropylene, polyester, polyethylene, poly (methylmethacrylate), methyl methacrylate copolymers (CoPMMAs), polyethylene naphthalate (PEN), polystyrene acrylonitrile, triacetate cellulose, nylon, silicone-polyoxamide polymers, cyclic olefin copolymers, thermoplastic elastomers, and combinations thereof.

[00156] In a fifth embodiment, the present disclosure provides an article according to any of the first through fourth embodiments, wherein the boundary layer is a first boundary layer and the multilayer optical film further comprises a second boundary layer directly attached to a major surface of the multilayer optical film opposite the first boundary layer.

[00157] In a sixth embodiment, the present disclosure provides an article according to the fifth embodiment, wherein the second boundary layer comprises a major surface opposite the multilayer optical film that has a nanostructured anisotropic surface.

[00158] In a seventh embodiment, the present disclosure provides an article according to the fifth embodiment or the sixth embodiment, further comprising a nano structured bilayer attached to the second boundary layer opposite the multilayer optical film, wherein the nanostructured bilayer comprises a patterned layer having a nanostructured surface and a refractive index contrast layer comprising a refractive index contrast material adjacent to the nanostructured surface of the patterned layer.

[00159] In an eighth embodiment, the present disclosure provides an article according to the fifth embodiment or the sixth embodiment, further comprising a microstructured layer attached to the second boundary layer opposite the multilayer optical film. [00160] In a ninth embodiment, the present disclosure provides an article according to the fifth embodiment or the sixth embodiment, further comprising a primer attached to the second boundary layer opposite the multilayer optical film.

[00161] In a tenth embodiment, the present disclosure provides an article according to the fifth embodiment or the sixth embodiment, further comprising a hard coat attached to the second boundary layer opposite the multilayer optical film.

[00162] In an eleventh embodiment, the present disclosure provides an article according to any of the first through tenth embodiments, wherein at least one of the first boundary layer or the second boundary layer comprises nanoscale features having a height to width ratio or about 2:1 or greater.

[00163] In a twelfth embodiment, the present disclosure provides an article according to any of the first through eleventh embodiments, wherein at least one of the first boundary layer or the second boundary layer comprises nanoscale features comprising at least one of nano-pillars, nano-columns, or continuous nano-walls comprising nano-pillars or nano-columns.

[00164] In a thirteenth embodiment, the present disclosure provides an article according to any of the first through twelfth embodiments, wherein at least one of the first boundary layer or the second boundary layer is formed of PEN.

[00165] In a fourteenth embodiment, the present disclosure provides an article according to any of the first through thirteenth embodiments, wherein the first and second optical layers are independently selected from a polycarbonate, an epoxy-containing polymer, a poly(epoxy -containing monomer), a vinyl polymer, a cyclic olefin polymer, a poly(phenylene oxide), a polysulfone, a polyamide, a polyurethane, a polyethylene, a polypropylene, a polyamic acid, a polyimide, a polyester, a fluoropolymer, a polydimethylsiloxane, a poly(alkylene terephthalate), a polyalkylene napthalate), poly(methylmethacrylate), a methyl methacrylate copolymer (CoPMMA), a silicone polymer, a cellulose derivative, an ionomer, or a copolymer thereof.

[00166] In a fifteenth embodiment, the present disclosure provides an article according to any of the first through fourteenth embodiments, wherein the first optical layer is formed of PEN and the second optical layer is formed of polymethylmethacrylate (PMMA).

[00167] In a sixteenth embodiment, the present disclosure provides an article according to any of the first through fifteenth embodiments, wherein the article is free of any fluoropolymers.

[00168] In a seventeenth embodiment, the present disclosure provides an article according to any of the first through sixteenth embodiments, further comprising an adhesive directly attached the nanostructured anisotropic surface of the boundary layer.

[00169] In an eighteenth embodiment, the present disclosure provides an article according to any of the first through seventeenth embodiments, further comprising a skin layer directly or indirectly attached to the nanostructured anisotropic surface of the boundary layer.

[00170] In a nineteenth embodiment, the present disclosure provides an article according to the eighteenth embodiment, wherein the skin layer is directly attached to the nanostructured anisotropic surface of the boundary layer. [00171] In a twentieth embodiment, the present disclosure provides an article according to any of the first through sixteenth embodiments, further comprising a polymeric substrate, wherein a major surface of the polymeric substrate is in direct contact with the nanostructured anisotropic surface of the boundary layer. [00172] In a twenty -first embodiment, the present disclosure provides an article according to any of the first through sixteenth embodiments, further comprising a nanostructured bilayer attached to the nanostructured anisotropic surface of the first boundary layer, wherein the nanostructured bilayer comprises a patterned layer having a nanostructured surface and a refractive index contrast layer comprising a refractive index contrast material adjacent to the nanostructured surface of the patterned layer.

[00173] In a twenty-second embodiment, the present disclosure provides an article according to any of the first through sixteenth embodiments, further comprising a microstructured layer attached to the nanostructured anisotropic surface of the first boundary layer.

[00174] In a twenty -third embodiment, the present disclosure provides an article according to any of the first through sixteenth embodiments, further comprising a primer attached to the nano structured anisotropic surface of the first boundary layer.

[00175] In a twenty -fourth embodiment, the present disclosure provides an article according to any of the first through sixteenth embodiments, further comprising a hard coat attached to the nano structured anisotropic surface of the first boundary layer.

[00176] In a twenty -fifth embodiment, the present disclosure provides an article according to any of the first through twenty -fourth embodiments, exhibiting, over a wavelength range from 400 nm to 1600 nm, an average absorbance that is no more than 2% greater than an average absorbance of the same article except that the first boundary layer lacks a nanostructured anisotropic surface.

[00177] In a twenty-sixth embodiment, the present disclosure provides a method. The method comprises providing a multilayer optical film comprising a plurality of first optical layers and a plurality of second optical layers and attaching a boundary layer directly to a major surface of the multilayer optical film. The method further comprises depositing an etch mask material on a major surface of the boundary layer opposite the multilayer optical film and subsequently or concurrently reactive ion etching to anisotropically remove material in unmasked areas, thereby forming a nano structured anisotropic surface on the major surface of the boundary layer.

[00178] In twenty -seventh embodiment, the present disclosure provides a method according to the twenty-sixth embodiment, the present disclosure provides a method, wherein the multilayer optical film reflects an average of at least 50, 60, 70, 80, 90, or 99 percent of light over a wavelength bandwidth of at least 30 nanometers (nm) within a wavelength range of 400 nm to 3000 nm.

[00179] In a twenty-eighth embodiment, the present disclosure provides a method according to the twenty-sixth embodiment or the twenty-seventh embodiment, wherein the boundary layer is attached to the major surface of the multilayer optical film by coextrusion of the boundary layer with the multilayer optical film. [00180] In a twenty -ninth embodiment, the present disclosure provides a method according to the twentysixth embodiment or the twenty-seventh embodiment, wherein the boundary layer is attached to the major surface of the multilayer optical film after formation of the multilayer optical film.

[00181] In a thirtieth embodiment, the present disclosure provides a method according to any of the twenty-sixth through twenty -ninth embodiments, wherein the etch mask material is the reaction product of plasma chemical vapor deposition using a reactant gas that includes a compound selected from organosilicon compounds, metal alkyls, metal isopropoxides, metal acetylacetonates and metal halides. [00182] In a thirty -first embodiment, the present disclosure provides a method according to any of the twenty-sixth through thirtieth embodiments, wherein an etching gas used in the reactive ion etching is selected from the group consisting of oxygen, argon, chlorine, fluorine, carbon tetrachloride, perfluoromethane, perfluoroethane, perfluoropropane, nitrogen trifluoride, sulfur hexafluoride, methane, and combinations thereof.

[00183] In a thirty-second embodiment, the present disclosure provides a method according to any of the twenty-sixth through thirty -first embodiments, wherein the nanofeatures have at least one dimension of 500 nm or less.

[00184] In a thirty -third embodiment, the present disclosure provides a method according to any of the twenty-sixth through thirty -second embodiments, further comprising extruding a thermoplastic polymer layer onto the nano structured anisotropic surface of the boundary layer.

[00185] In a thirty -fourth embodiment, the present disclosure provides a method according to any of the twenty-sixth through thirty -third embodiments, further comprising disposing an adhesive directly on the nanostructured anisotropic surface of the boundary layer.

[00186] In a thirty -fifth embodiment, the present disclosure provides a method according to any of the twenty-sixth through thirty -fourth embodiments, further comprising molding the article to a polymeric substrate, wherein the nanostructured anisotropic surface of the boundary layer is in direct contact with the polymeric substrate.

[00187] In a thirty-sixth embodiment, the present disclosure provides a method according to any of the twenty-sixth through thirty -second embodiments, further comprising attaching a nanostructured bilayer onto the nano structured anisotropic surface of the boundary layer, wherein the nanostructured bilayer comprises a patterned layer having a nanostructured surface and a refractive index contrast layer comprising a refractive index contrast material adjacent to the nanostructured surface of the patterned layer.

[00188] In a thirty-seventh embodiment, the present disclosure provides a method according to any of the twenty-sixth through thirty -second embodiments, further comprising attaching a microstructured layer onto the nano structured anisotropic surface of the boundary layer.

[00189] In a thirty -eighth embodiment, the present disclosure provides a method according to any of the twenty-sixth through thirty-second embodiments, further comprising applying a primer to the nanostructured anisotropic surface of the boundary layer. [00190] In a thirty -ninth embodiment, the present disclosure provides a method according to any of the twenty-sixth through thirty -eighth embodiments, further comprising applying a hard coat to the nanostructured anisotropic surface of the boundary layer.

[00191] In a fortieth embodiment, the present disclosure provides a method according to any of the twenty-sixth through thirty -eighth embodiments, wherein the article comprises the article of any of the first through twenty -fourth embodiments.

EXAMPLES

[00192]Unless otherwise noted or readily apparent from the context, all parts, percentages, ratios, etc. in the Examples and the rest of the specification are by weight.

Materials

[00193]Preparative Example 1 (PEI)

[00194] Multilayer optical films described herein can be made using general processing techniques, such as those described in U.S. Pat. No. 6,783,349 (Neavin et al.) and U.S. Pat. No. 9,459,386 (Hebrink et al.), the disclosures of which are incorporated herein by reference. A multilayer optical film was made with first optical layers of polyethylene 2,6 naphthalate (PEN) and second optical layers of PMMA. The polyethylene 2,6 naphthalate (PEN) was synthesized in a batch reactor with the following raw material charge: 2,6 dimethyl naphthalene dicarboxylate (136 kg), ethylene glycol (73 kg), manganese (II) acetate (27 grams), cobalt (II) acetate (27 grams) and antimony (III) acetate (48 grams). Under a pressure of 1520 torr or 2*105 N/m² (2 atm.), this mixture was heated to 254° C while removing methanol (a transesterification reaction by-product). After 35 kg of methanol was removed, 49 grams of triethyl phosphonoacetate was charged to the reactor and the pressure was gradually reduced to (131 N/m²) (1 ton) while heating to 290° C. The condensation reaction by-product, ethylene glycol, was continuously removed until a polymer with an intrinsic viscosity of 0.48 dL/g (as measured in 60/40 wt. % phenol/o- dichlorobenzene) was produced.

[00195] The PEN and PMMA were coextruded through a multilayer polymer melt manifold to create a multilayer melt stream having 650 alternating first and second optical layers. This multilayer coextruded melt stream was cast onto a chilled roll at 22 meters per minute creating a multilayer cast web about 1250 micrometers (50 mils) thick.

[00196] The multilayer cast web was then heated by infrared heaters in a length orienter prior to being oriented in the machine direction to a draw ratio of 3.5, and then heated in a tenter oven at 145° C for 10 seconds prior to being oriented in the transverse direction to a draw ratio of 3.5. The oriented multilayer film was further heated to 225° C for 10 seconds to increase crystallinity of the PEN layers. Reflectivity of this multilayer visible mirror film was measured with a spectrophotometer (obtained from Perkin- Elmer, Inc., Waltham, Mass., under the trade designation “LAMBDA 1050”) to have an average reflectivity of 98.5% over a bandwidth of 400-1600 nm.

[00197] Preparative Example 2 (PE2)

[00198] The multilayer optical film of PE2 was a reflective polarizer comprised of a plurality of polymeric layers, including a boundary layer comprising polyester, co-polyester, and polycarbonate.

General Method for Nanostructuring

[00199] Plasma processing was performed in a home-built parallel plate capacitively coupled plasma reactor. The chamber has a central cylindrical powered electrode with a surface area of about 1.70 m². After loading the designated mask/amorphous silicon sample into the chamber, the reactor chamber was pumped down to a base pressure of less than 1 mtorr. Process gas was introduced into the chamber at the flow rates detailed in the example section below. Treatment was performed by coupling RF power into the reactor at a frequency of 13.56 MHz and an applied power detailed in the example section below. The treatment time was controlled by translating the film samples through the reaction zone at speeds detailed in the example section below. The operating pressure during treatment is detailed in the example section below. Following the treatment(s), the process gas flow, applied power, and film translation were stopped, and the chamber was returned to atmospheric pressure. Additional information regarding materials and processes for applying cylindrical RIE and further details around the reactor used can be found in U.S. Pat. No. 8460568.

Thermoforming Method

[00200] Thermoforming was performed in a Hytech AccuForm Thermoformer (Hy-Tech Forming Systems USA, Inc., Phoenix, AZ). A sample (e.g., EX4) was loaded into the forming mold, then a platen clamped the sample in place and created an airtight seal. Next, an infrared heater applied a temperature of 560°F (293°C) for 30 seconds. High pressure air of about 500 psi (3.4 megapascals) flooded the mold cavity above the sample, forming the sample onto a convex mold. After exhaustion of the high pressure air from the mold cavity, the mold was opened and the sample removed.

[00201] Examples 1-3

[00202] The surface of Preparative Example 1 (PEI) was nanostructured according to the General Method for Nanostructuring, thereby forming Examples 1-3 (EXI, EX2, and EX3). The surface of Preparative Example 2 (PE2) was nano structured according to the General Method for Nano structuring, thereby forming Example 4 (EX4). Detailed in Table 1 are the various samples made and the conditions at which they were run.

[00203] Table 1

Preparation of Film Insert Molded Samples

[00204] Film insert molding samples were prepared using an EM 310/180 T WP US 231040 from ENGEL MACHINERY INC. 3740 Board Road York, PA 17406 USA with a 40 mm general purpose screw. A plaque with the dimensions of 0.1” x 4.02” x 4.02” was used to demonstrate adhesion to various substrates during film insert molding. Film samples of PEI and EX3 were cut out to the approximate dimensions of 3.9” x 3.9” to ensure they would fit in the mold cavity. Films were inserted into instruments and held in place with static pinning during molding. Injection molding conditions for ABS Cheimei 757, Exxon 1024PP and Polycarbonate Makrolon 2207 were reported in Table 2 below. Samples were collected with and without a 1-inch tab between the top of the film and the molded article using 3M 5413 Or 3M 8403 tape.

[00205] Table 2 Scanning Electron Microscopy (SEM) Imaging

[00206] For imaging, cross-sections of a sample were cut. Samples were mounted on aluminum examination stubs and coated with AuPd by DC sputtering in a coater (Denton Vacuum Desk IV from Denton Vacuum, Moorestown, NJ) to ensure conductivity. Examinations were performed in a Hitachi S4700 Field Emission Scanning Electron Microscope. Where applicable, feature dimensions were measured in ImageJ using the reference scale bar generated by the S4700 microscope.

[00207] Results for Example 4 (EX4)

[00208] FIG. 9 A is an SEM image of a cross-section of a portion of an exemplary article 900 made according to Example 4 (EX4). A major surface 21 of a boundary layer 20 was subjected to a nanostructuring process at a line speed of 6.7 feet per minute, resulting in a nanostructured anisotropic surface 23 formed on the major surface 21 of the boundary layer 20. Next, the article of EX4 was subjected to thermoforming as described above in the Thermoforming Method. FIG. 10A is an SEM image of a cross-section of a portion of the exemplary article of FIG. 9A after being thermoformed, making it thermoformed article 1000. FIG. 10A shows that the thermoforming process did not destroy the nanostructured anisotropic surface 23 present on the major surface 21 of the boundary layer 20, going from article 900 to article 1000. Additionally, FIG. 9B is an SEM image of the top of a portion of the exemplary article 900 of FIG. 9A and FIG. 10B is an SEM image of the top of a portion of the exemplary article 1000 of FIG. 10A. The major surfaces 21 of the boundary layer 20 of each of articles 900 and 1000 have a consistent appearance, further demonstrating that the thermoforming process did not substantially change the major surfaces 21, going from article 900 to article 1000.

Description of Peel Adhesion Test

[00209] To conduct the 180 degree peel testing using the iMass SP2000 Slide Peel Tester, the samples were prepared and tested as follows. Film insert molded samples were prepared as described above. A 1- inch tab was created between the top of the film and the molded article using 3M 5413 or 3M 8403 tape. The film stack was cut into 1-inch strips and the molded article was adhered to the test apparatus using 3M double coated urethane foam tape 4206. The force application rate was set to a constant rate of 12 inches per minute, providing a controlled and consistent peeling speed. A 2-second delay was introduced before initiating the test to allow for any necessary adjustments or stabilization. The test duration was set to 5 seconds, providing sufficient time to measure the peel strength accurately. The peel strength was calculated by measuring the average force required to separate the materials and dividing it by the bond area. Additionally, the maximum force was calculated. All data is reported as an average of 4 measurements. Type of adhesive bond failure was also recorded. Results are shown in Table 3 below. [00210] Results for Examples 5-7 (EX5, EX6, and EX7) and Comparative Examples 1-3 (CE1, CE2, and

CE3)

[00211] Table 3 *CE examples the film fell off prior to testing on iMass SP2000 Slide Peel Tester.

[00212] Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.

[00213] Furthermore, all publications and patents referenced herein are incorporated by reference in their entirety to the same extent as if each individual publication or patent was specifically and individually indicated to be incorporated by reference. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description prevails. Various exemplary embodiments have been described. These and other embodiments are within the scope of the following claims.

Claims

What is claimed is:

1. An article comprising: a multilayer optical film comprising a plurality of first optical layers and a plurality of second optical layers; and a boundary layer directly attached to a major surface of the multilayer optical film, wherein the boundary layer comprises a major surface opposite the multilayer optical film that has a nanostructured anisotropic surface.

2. The article of claim 1, wherein the multilayer optical film reflects an average of at least 50, 60, 70, 80, 90, or 99 percent of light over a wavelength bandwidth of at least 30 nanometers (nm) within a wavelength range of 400 nm to 3000 nm.

3. The article of claim 1 or claim 2, wherein the boundary layer is formed of a thermoplastic polymer.

4. The article of any of claims 1 to 3, wherein the boundary layer is formed of a thermoplastic polymer selected from the group consisting of polyethylene terephthalate (PET), polystyrene, acrylonitrile butadiene styrene, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyacrylates, thermoplastic polyurethanes, polyvinyl acetate, polyamide, polyimide, polypropylene, polyester, polyethylene, poly(methylmethacrylate), methyl methacrylate copolymers (CoPMMAs), polyethylene naphthalate (PEN), polystyrene acrylonitrile, triacetate cellulose, nylon, silicone-polyoxamide polymers, cyclic olefin copolymers, thermoplastic elastomers, and combinations thereof.

5. The article of any of claims 1 to 4, wherein the boundary layer is a first boundary layer and the multilayer optical film further comprises a second boundary layer directly attached to a major surface of the multilayer optical film opposite the first boundary layer.

6. The article of claim 5, wherein the second boundary layer comprises a major surface opposite the multilayer optical film that has a nanostructured anisotropic surface.

7. The article of claim 5 or claim 6, further comprising a nano structured bilayer attached to the second boundary layer opposite the multilayer optical film, wherein the nanostructured bilayer comprises a patterned layer having a nanostructured surface and a refractive index contrast layer comprising a refractive index contrast material adjacent to the nanostructured surface of the patterned layer.

8. The article of claim 5 or claim 6, further comprising a microstructured layer attached to the second boundary layer opposite the multilayer optical film.

9. The article of claim 5 or claim 6, further comprising a primer attached to the second boundary layer opposite the multilayer optical film.

10. The article of claim 5 or claim 6, further comprising a hard coat attached to the second boundary layer opposite the multilayer optical film.

11. The article of any of claims 1 to 10, wherein at least one of the first boundary layer or the second boundary layer comprises nanoscale features having a height to width ratio or about 2:1 or greater.

12. The article of any of claims 1 to 11, wherein at least one of the first boundary layer or the second boundary layer comprises nanoscale features comprising at least one of nano-pillars, nanocolumns, or continuous nano-walls comprising nano-pillars or nano-columns.

13. The article of any of claims 1 to 12, wherein the first and second optical layers are independently selected from a polycarbonate, an epoxy -containing polymer, a poly(epoxy -containing monomer), a vinyl polymer, a cyclic olefin polymer, a poly(phenylene oxide), a polysulfone, a polyamide, a polyurethane, a polyethylene, a polypropylene, a polyamic acid, a polyimide, a polyester, a fluoropolymer, a polydimethylsiloxane, a poly(alkylene terephthalate), a polyalkylene napthalate), poly(methylmethacrylate), a methyl methacrylate copolymer (CoPMMA), a silicone polymer, a cellulose derivative, an ionomer, or a copolymer thereof.

14. The article of any of claims 1 to 13, wherein the article is free of any fluoropolymers.

15. The article of any of claims 1 to 14, further comprising an adhesive directly attached the nano structured anisotropic surface of the boundary layer.

16. The article of any of claims 1 to 15, further comprising a skin layer directly or indirectly attached to the nanostructured anisotropic surface of the boundary layer.

17. The article of claim 16, wherein the skin layer is directly attached to the nanostructured anisotropic surface of the boundary layer.

18. The article of any of claims 1 to 14, further comprising a polymeric substrate, wherein a major surface of the polymeric substrate is in direct contact with the nanostructured anisotropic surface of the boundary layer.

19. The article of any of claims 1 to 14, further comprising a nano structured bilayer attached to the nanostructured anisotropic surface of the first boundary layer, wherein the nanostructured bilayer comprises a patterned layer having a nanostructured surface and a refractive index contrast layer comprising a refractive index contrast material adjacent to the nanostructured surface of the patterned layer.

20. The article of any of claims 1 to 14, further comprising a micro structured layer attached to the nanostructured anisotropic surface of the first boundary layer.

21. The article of any of claims 1 to 14, further comprising a primer attached to the nanostructured anisotropic surface of the first boundary layer.

22. The article of any of claims 1 to 14, further comprising a hard coat attached to the nano structured anisotropic surface of the first boundary layer.

23. The article of any of claims 1 to 22, exhibiting, over a wavelength range from 400 nm to 1600 nm, an average absorbance that is no more than 2% greater than an average absorbance of the same article except that the first boundary layer lacks a nanostructured anisotropic surface.

24. A method of making an article, the method comprising: providing a multilayer optical film comprising a plurality of first optical layers and a plurality of second optical layers; attaching a boundary layer directly to a major surface of the multilayer optical film; depositing an etch mask material on a major surface of the boundary layer opposite the multilayer optical film; and subsequently or concurrently reactive ion etching to anisotropically remove material in unmasked areas, thereby forming a nanostructured anisotropic surface on the major surface of the boundary layer.

25. The method of claim 24, wherein the boundary layer is attached to the major surface of the multilayer optical film by coextrusion of the boundary layer with the multilayer optical film.

26. The method of claim 24, wherein the boundary layer is attached to the major surface of the multilayer optical film after formation of the multilayer optical film.

27. The method of any of claims 24 to 26, wherein the etch mask material is the reaction product of plasma chemical vapor deposition using a reactant gas that includes a compound selected from organosilicon compounds, metal alkyls, metal isopropoxides, metal acetylacetonates and metal halides.

28. The method of any of claims 24 to 27, wherein an etching gas used in the reactive ion etching is selected from the group consisting of oxygen, argon, chlorine, fluorine, carbon tetrachloride, perfluoromethane, perfluoroethane, perfluoropropane, nitrogen trifluoride, sulfur hexafluoride, methane, and combinations thereof.

29. The method of any of claims 24 to 28, wherein the nanofeatures have at least one dimension of 500 nm or less.

30. The method of any of claims 24 to 29, further comprising extruding a thermoplastic polymer layer onto the nanostructured anisotropic surface of the boundary layer.

31. The method of any of claims 24 to 30, further comprising disposing an adhesive directly on the nano structured anisotropic surface of the boundary layer.

32. The method of any of claims 24 to 29, further comprising molding the article to a polymeric substrate, wherein the nanostructured anisotropic surface of the boundary layer is in direct contact with the polymeric substrate.

33. The method of any of claims 24 to 30, further comprising attaching a nanostructured bilayer onto the nanostructured anisotropic surface of the boundary layer, wherein the nano structured bilayer comprises a patterned layer having a nanostructured surface and a refractive index contrast layer comprising a refractive index contrast material adjacent to the nanostructured surface of the patterned layer.

34. The method of any of claims 24 to 30, further comprising attaching a microstructured layer onto the nanostructured anisotropic surface of the boundary layer.