Multilayer article having a UV barrier layer

Abstract

The present disclosure provides a multilayer article comprising a substrate layer comprising a fluoropolymer or silicone polymer, a 15-60 nanometer thick metal oxide layer directly attached to the substrate layer, and an adhesive layer adjacent to the metal oxide layer on the opposite side of the substrate layer, wherein the article exhibits an average transmittance of 10% or less, 7%, 5%, or 2% or less over a wavelength band of at least 30 nanometers, having a wavelength between 200 nm and 400 nm, for light incident at angles of at least 0°, 30°, 45°, 60°, or 75°.

Description

[Technical Field]

[0001] [Summary of the Invention] In a first aspect, a multilayer article is provided. The multilayer article includes a substrate layer comprising a fluoropolymer or a silicone polymer, a metal oxide layer directly attached to a major surface of the substrate layer and having a thickness of 15 nanometers (nm) to 60 nm, and an adhesive layer adjacent to a major surface of the metal oxide layer opposite the substrate layer. The article exhibits an average transmittance of 10% or less, 7%, 5%, or 2% or less over a wavelength band of at least 30 nanometers, having a wavelength between 200 nm and 400 nm, for light incident at at least one of 0°, 30°, 45°, 60°, or 75°.

[0002] UVC irradiation has been used to disinfect surfaces contaminated with bacteria and viruses. However, exposure to UVC radiation can cause certain materials to begin to degrade. It was unexpectedly discovered that a thin layer of metal oxide can provide UV barrier properties while also enhancing the adhesion of adhesives to fluoropolymer or silicone polymer substrate layers.

[0003] The above summary of the present disclosure is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The following description more particularly exemplifies illustrative embodiments. In several places throughout the application, guidance is provided through lists of examples, which examples can be used in various combinations. In each instance, the recited list serves only as a representative group and should not be interpreted as an exclusive list. [Brief explanation of the drawings]

[0004] [Figure 1A] FIG. 1A is a schematic cross-sectional view of an exemplary article. [Figure 1B] FIG. 1B is a schematic cross-sectional view of an exemplary article. [Figure 1C] FIG. 1C is a perspective view of a Cartesian coordinate system of surfaces that can be used to describe various microstructured surfaces. [Figure 2A] FIG. 2A is a cross-sectional view of a microstructured surface. [Figure 2B] FIG. 2B is a perspective view of the microstructured surface. [Figure 3] FIG. 3 is a perspective view of a microstructured surface comprising a linear array of prisms. [Figure 4A] FIG. 4A is a perspective view of a microstructured surface including an array of cube corner elements. [Figure 4B] FIG. 4B is a perspective view of a microstructured surface comprising an array of pyramidal elements. [Figure 4C] FIG. 4C is a perspective view showing the dimensions and angles of the cube corner elements. [Figure 5] FIG. 5 is a perspective view of a microstructured surface including an array of cube corner elements of a preferred shape. [Figure 6] FIG. 6 shows cross-sectional views of peak structures with various apex angles. [Figure 7A] FIG. 7A is a three-dimensional topographical view of a microstructured surface containing an array of peak structures. [Figure 7B] FIG. 7B is a three-dimensional topographical view of a microstructured surface containing an array of peak structures. [Figure 8A] FIG. 8A is a three-dimensional topographical view of a microstructured surface containing an array of peak structures. [Figure 8B] FIG. 8B is a three-dimensional topographical view of a microstructured surface containing an array of peak structures. [Figure 8C] FIG. 8C is a three-dimensional topographical view of a microstructured surface containing an array of peak structures. [Figure 9] FIG. 9 is a plot of the complement (Fcc) of the cumulative gradient (i.e., slope) magnitude distribution. [Figure 10] FIG. 10 is a plot of the complement (Ycc) of the cumulative X slope. [Figure 11] FIG. 11 is a plot of the complement of the cumulative Y slope (Xcc). [Figure 12] FIG. 12 is a schematic side view of the structure. [Figure 13]FIG. 13 is a schematic diagram of a process for producing a substrate having a microstructured surface.

[0005] The above figures illustrate various embodiments of the present disclosure; however, other embodiments are contemplated as described in the description. In all cases, the present disclosure presents the invention by way of representation, not limitation. The figures are not necessarily to scale. Numerals frequently used in the figures refer to similar components. However, it should be understood that a particular numbered component in one figure is not intended to limit the same numbered component in another figure. DETAILED DESCRIPTION OF THE INVENTION

[0006] Glossary: As used herein, "fluoropolymer" refers to any organic polymer that contains fluorine.

[0007] As used herein, "non-fluorinated" means free of fluorine.

[0008] As used herein, "(co)polymer" or "(co)polymers" includes homo(co)polymers and (co)polymers, as well as homo(co)polymers or (co)polymers that can be formed in miscible blends (e.g., by coextrusion or reaction [including, for example, transesterification]). The term "(co)polymer" includes random, block, and star (co)polymers.

[0009] As used herein, "adjacent" encompasses both direct contact (eg, directly adjacent) and the presence of one or more intermediate layers between the adjacent materials.

[0010] As used herein, "incident" with respect to light refers to light falling or striking a material.

[0011] As used herein, a "crosslinked" (co)polymer refers to a (co)polymer in which the (co)polymer chains are joined by covalent chemical bonds, usually by crosslinking molecules or groups, to form a network (co)polymer. Crosslinked (co)polymers are generally insoluble but can swell in the presence of a suitable solvent.

[0012] As used herein, "curing" refers to a process that causes a chemical change, such as, for example, a crosslinking or other reaction that creates covalent bonds that solidify or increase the viscosity of a multilayer film layer.

[0013] As used herein, "cured (co)polymer" includes both crosslinked and uncrosslinked (co)polymers.

[0014] As used herein, "metal" includes pure metals or metal alloys.

[0015] As used herein, a "film" or "layer" refers to a single layer within a multi-layer article.

[0016] As used herein, "substrate" encompasses films and layers, including microstructured films / layers.

[0017] As used herein, the term "substantially free," in the context of a composition that is substantially free of a component, refers to a composition that contains less than 1 weight percent (wt.%), 0.5 wt.% or less, 0.25 wt.% or less, 0.1 wt.% or less, 0.05 wt.% or less, 0.001 wt.% or less, or 0.0001 wt.% or less of the component, based on the total weight of the composition.

[0018] As used herein, "thermoplastic" refers to a polymer that flows when heated sufficiently above its glass transition temperature and becomes solid when cooled.

[0019] As used herein, "thermoset" refers to a polymer that, upon curing, becomes permanently solid and does not flow upon subsequent application of heat. Thermoset polymers are typically crosslinked polymers.

[0020] As used herein, the term "glass transition temperature" (Tg) of a polymer refers to the transition of the polymer from a glassy state to a rubbery state and can be measured using differential scanning calorimetry (DSC), e.g., at a heating rate of 10°C / min in a nitrogen stream. When the Tg of a monomer is referred to, it refers to the Tg of the homopolymer of that monomer. Generally, it is understood that the Tg of a homopolymer increases with increasing molecular weight up to a limiting value, and therefore the homopolymer must have a sufficiently high molecular weight so that the Tg reaches that limiting value. It is also understood that the homopolymer is substantially free of moisture, residual monomer, solvent, and other impurities that may affect the Tg. Suitable DSC methods and analytical modes are described in Matsumoto, A. et al., J. Polym. Sci. A., Polym. Chem. 1993, 31, 2531-2539.

[0021] As used herein, "(meth)acrylic" or "(meth)acrylate" with respect to a monomer, oligomer, (co)polymer, or compound means a vinyl-functional alkyl ester formed as the reaction product of acrylic acid or methacrylic acid with an alcohol.

[0022] As used herein, "optically clear" refers to an article that is free of visible distortion, haze, or defects detectable by the naked eye at a distance of about 1 meter, preferably about 0.5 meters.

[0023] As used herein, "optical thickness" when used with respect to a layer refers to the physical thickness of that layer multiplied by its in-plane refractive index.

[0024] As used herein, "vapor coating" or "vapor deposition" refers to applying a coating to a substrate surface from the vapor phase, for example, by evaporating a coating precursor material or the coating material itself and then depositing it on the substrate surface. Exemplary vapor coating processes include, for example, physical vapor deposition (PVD), chemical vapor deposition (CVD), and combinations thereof.

[0025] The use of directional terms such as "atop," "on," "over," "covering," "uppermost," "underlying," and the like with respect to the location of various elements in the disclosed coating articles refers to the relative location of the elements with respect to a horizontally oriented, upward-facing substrate. However, unless specifically indicated, no particular orientation in space is intended for the substrate or article during or after manufacture or when interpreting the claims.

[0026] As used herein, "radiation" refers to electromagnetic radiation unless otherwise specified.

[0027] As used herein, "scattering" with respect to wavelengths of light refers to causing light to deviate from a direct path and travel in different directions with different intensities.

[0028] As used herein, "reflectance" is the measure of the proportion of light or other radiation that strikes a surface at normal incidence that is reflected. Reflectance typically varies with wavelength and is reported as the percentage of incident light that is reflected from the surface (0 percent - no light reflected, 100 - all light reflected). As used herein, reflectivity and reflectance are used interchangeably.

[0029] As used herein, "reflective" and "reflectivity" refer to the property of reflecting light or radiation, and specifically refer to reflectance measured independently of the thickness of a material.

[0030] As used herein, "average reflectance" refers to reflectance averaged over a particular wavelength range.

[0031] As used herein, "absorption" refers to a material's conversion of the energy of optical radiation into internal energy.

[0032] As used herein, "absorb" with respect to wavelengths of light includes both absorption and scattering, since scattered light is eventually absorbed. Absorbance can be measured as described in ASTM E903-12, "Standard Test Methods for Solar Absorbance, Reflectance, and Transmittance of Materials Using an Integrating Sphere." The absorbance measurements described herein were made by taking the transmittance measurements described above and then calculating absorbance using Equation 1.

[0033] As used herein, the term "absorbance," in reference to quantitative measurements, refers to the base 10 logarithm of the ratio of incident radiant power to transmitted radiant power passing through a material. This 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 the internal transmittance (T) according to Equation 1:

[0034] A=-log 10 T (1) Emissivity can be measured using an infrared imaging radiometer as described in ASTM E1933-14(2018) "Standard Practice for Measuring and Compensating for Emissivity Using an Infrared Imaging Radiometer." Kirchhoff's law of thermal radiation correlates absorbance with emittance. As used herein, absorbance, absorptivity, emissivity, and emittance are used interchangeably to refer to the same purpose of radiating infrared energy into the atmosphere. Absorb and emit are also used interchangeably herein.

[0035] As used herein, "transmittance" and "transmission" refer to the ratio of the total transmission through a layer 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 may be expressed as a percentage (T%).

[0036] As used herein, "transparent" refers to a material (eg, a film or layer) that absorbs less than 20% of light having wavelengths between 350 nm and 2500 nm.

[0037] As used herein, "bandwidth" refers to the width of a continuous band of wavelengths.

[0038] As used herein, "utilitarian" means that the discontinuity provides a positive contribution to the function of the article. For example, an utilitarian discontinuity that is easy to clean provides a positive contribution to the function of the article, making it easier to clean than an article lacking the utilitarian discontinuity. Representative examples of utilitarian discontinuities include, but are not limited to, cube corner elements and parallel linear prisms with planar facets.

[0039] The words "preferred" and "preferably" refer to embodiments of the present disclosure that may offer certain benefits, under particular circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the present disclosure.

[0040] In this application, the terms "a," "an," "the," and the like are not intended to refer to only a single entity, but include a general class for which a particular example is used for illustration. The terms "a," "an," and "the" are used synonymously with "at least one." The phrases "at least one" and "including at least one," when followed by a list, refer to any one item of the list and any combination of two or more items of the list.

[0041] As used herein, the term "or" is used in its ordinary sense to include "and / or" unless the content clearly dictates otherwise.

[0042] The term "and / or" means one or all of the listed elements or any combination of two or more of the listed elements.

[0043] As used herein, all numerical values ​​are considered to be modified by the term "about," and preferably by the term "exactly." As used herein, the term "about" in connection with a measured quantity refers to the variation in that measured quantity that would be expected by a skilled artisan who exercises caution depending on the purpose of the measurement and the precision of the measuring equipment used. Also herein, references to endpoints of numerical ranges include all numbers and endpoints subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0044] The term "generally," as used herein as a modifier of a property or attribute, unless otherwise defined, means that the property or attribute will be readily recognized by a skilled artisan, but does not require absolute precision or exact agreement (e.g., within ±20% for quantitative properties). The term "substantially," unless otherwise defined, means a high degree of approximation (e.g., within ±10% for quantitative properties), but again does not require absolute precision or exact agreement. For example, terms such as "same," "equal," "uniform," "constant," and "exactly" are understood to be within normal tolerances or measurement errors applicable to the particular situation, rather than requiring absolute precision or exact agreement.

[0045] In a first aspect, a multi-layer article is provided, the multi-layer article comprising: a substrate layer comprising a fluoropolymer or a silicone polymer; a metal oxide layer deposited directly on a major surface of the substrate layer and having a thickness of 15 nanometers (nm) to 60 nm; and an adhesion layer adjacent a major surface of the metal oxide layer opposite the substrate layer; wherein the article exhibits an average transmittance of 10% or less, 7%, 5%, or 2% or less over a wavelength band of at least 30 nanometers having a wavelength between 200 nm and 400 nm for light having an incident light angle of at least one of 0°, 30°, 45°, 60°, or 75°.

[0046] In some cases, the article exhibits an average transmittance of 10% or less, 7%, 5%, or 2% or less over a wavelength band of at least 30 nanometers having wavelengths between 200 nm and 280 nm, between 200 nm and 300 nm, or between 200 nm and 320 nm, for light having an incident light angle of at least one of 0°, 30°, 45°, 60°, or 75°.

[0047] 1A, multilayer article 100a includes a substrate layer 10 comprising a fluoropolymer or a silicone polymer, a metal oxide layer 20 directly attached to a major surface 12 of the substrate layer and having a thickness of 15 nanometers (nm) to 60 nm, and an adhesive layer 30 adjacent to a major surface 22 of metal oxide layer 20 opposite substrate layer 10. In this embodiment, adhesive layer 30 is directly adjacent to (i.e., attached to) major surface 22 of metal oxide layer 20.

[0048] It is further noted that substrate layer 10 has a major surface 14 opposite major surface 12, metal oxide layer 20 has a major surface 24 opposite major surface 22, and adhesive layer has opposing major surfaces 32 and 34. In certain embodiments, major surface 12 of substrate layer 10 is directly adjacent to major surface 24 of metal oxide layer 20, and major surface 22 of metal oxide layer 20 is directly adjacent to major surface 34 of adhesive layer 30.

[0049] 1B, multilayer article 100b includes substrate layer 10 comprising a fluoropolymer or a silicone polymer, metal oxide layer 20 directly attached to major surface 12 of the substrate layer and having a thickness of 15 nanometers (nm) to 60 nm, adhesive layer 30 adjacent to major surface 22 of metal oxide layer 20 opposite substrate layer 10, and intermediate layer 40 disposed between metal oxide layer 20 and adhesive layer 30. The depiction of layer 40 in FIG. 1B may represent one or more intermediate layers.

[0050] It is further noted that intermediate layer 40 has opposing major surfaces 42 and 44. In certain embodiments, major surface 42 of intermediate layer 40 is directly adjacent to major surface 34 of adhesive layer 30, and major surface 44 of intermediate layer 40 is directly adjacent to major surface 22 of metal oxide layer 20.

[0051] One example of a suitable intermediate layer is a primer layer to improve adhesion between the metal oxide layer and the adhesive layer. In some cases, the primer layer may be formed by a pretreatment procedure including discharge pretreatment (e.g., plasma, glow discharge, corona discharge, dielectric barrier discharge, or atmospheric discharge) of the metal oxide layer in a reactive or non-reactive atmosphere, chemical pretreatment, or flame pretreatment. In some embodiments, the method may include plasma pretreatment. In some cases, the primer layer may be formed from a material such as a primer known under the tradenames "BETAPRIME" or "TYVEK," commercially available from DuPont (Wilmington, Delaware).

[0052] As discussed above, it has been discovered that a thin layer of metal oxide can provide UV barrier properties and enhance adhesion of the adhesive to a fluoropolymer or silicone polymer substrate layer. Preferably, the adhesion is such that the article exhibits a peel force of 500 grams / inch (196.9 grams / centimeter) or greater between the metal oxide layer and the adhesive layer. Preferably, the adhesion is such that the article exhibits a peel force of 500 grams / inch (196.9 grams / centimeter) or greater between the substrate layer and the metal oxide layer. One way to confirm that an article has UV barrier properties is to measure the change in light transmittance through the article after exposing the article to UVC light. For example, the inclusion of a metal oxide layer in the article can enhance the article's resistance to UVC light having a wavelength of 254 nm by 50 megajoules per square meter (MJ / m 2 ) after exposure to a dose of 100 .mu.m or less, the change in light transmittance at a wavelength of 400 nm is preferably less than 10%. <Metal oxide layer> Typically, the metal oxide layer comprises titanium oxide, aluminum oxide, zinc oxide, tantalum pentoxide, zirconium oxide, or niobium oxide. In certain embodiments, the metal oxide layer comprises titanium oxide.

[0053] It is noted that various multilayer optical films utilize at least one metal oxide layer to collectively provide at least one tailored optical property, including, for example, specific transmission of wavelengths in a desired range. However, the metal oxide layer of the present disclosure is not part of the multilayer optical film. In other words, the metal oxide layer does not constitute a single layer of the multilayer optical film. Rather, the metal oxide layer has a thickness of 15 to 60 nm and is comprised of one or more metal oxides. Thus, the metal oxide layer may be formed from a single metal oxide or a combination of two or more metal oxides.

[0054] The thickness of the metal oxide layer is 15 nm or more, 17 nm, 20 nm, 22 nm, 25 nm, 27 nm, or 30 nm or more, and 60 nm or less, 57 nm, 55 nm, 52 nm, 50 nm, 47 nm, 45 nm, 42 nm, 40 nm, 37 nm, 35 nm, 32 nm, 30 nm, 27 nm, 25 nm, 22 nm, or 20 nm. In some cases, the thickness of the metal oxide layer is 15 nm to 20 nm, 20 nm to 30 nm, or 20 nm to 40 nm. If the thickness is less than 15 nm, it is difficult to form a continuous layer; instead, the deposited metal oxide material may form discontinuous islands. If the thickness is too large, there is a risk that the metal oxide layer will impart a visible color to the article and / or reduce the transmission of visible light through the metal oxide layer.

[0055] Preferably, the metal oxide layer does not impart a yellow appearance to the article. Whether an article has a yellow appearance can be determined, for example, by measuring the transmission of light passing through the article. An article that does not have a yellow appearance exhibits an average transmittance of 70% or more for light having a wavelength range at least greater than 410 nm and at at least one of the incident light angles of 0°, 30°, 45°, 60°, or 75°. Conversely, an article that exhibits an average transmittance of less than 70% for light having a wavelength range at least greater than 410 nm and at at least one of the incident light angles of 0°, 30°, 45°, 60°, or 75° may appear yellow.

[0056] As described above, the article exhibits an average transmittance of 10% or less, 7%, 5%, or 2% or less over a wavelength band of at least 30 nanometers having wavelengths between 200 nm and 400 nm for light (e.g., overall) at least one of incident light angles of 0°, 30°, 45°, 60°, or 75°.

[0057] Metal oxide layers can typically be prepared by evaporation, reactive evaporation, sputtering, reactive sputtering, chemical vapor deposition, plasma-enhanced chemical vapor deposition, and atomic layer deposition. Preferred methods include vacuum preparation, such as sputtering and evaporation. For example, in some cases, one of two forms of physical vapor deposition (PVD) is used: evaporation or sputtering. Evaporative coating relies on heating the coating material (evaporant) to a temperature at which it evaporates. The vapor then condenses onto the substrate. For evaporative coating, the electron beam evaporation process is most commonly used. Sputtering coating uses energetic gas ions to bombard the surface of the material (the "target"), ejecting atoms that condense onto the nearby substrate. The coating method and settings used for that method strongly affect the rate and structure-property relationship of thin-film coatings. Ideally, the coating rate should be high enough to allow acceptable process throughput and film performance, characterized by a dense, low-stress, void-free, and non-optically absorbing coating layer. <Adhesive layer> Examples of suitable adhesives for the adhesive layer include pressure sensitive adhesives and hot melt adhesives. In certain embodiments, the adhesive layer comprises a pressure sensitive adhesive.

[0058] Suitable pressure-sensitive adhesive classes include acrylic, tackified rubber, tackified synthetic rubber, ethylene vinyl acetate, etc. 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 (Young et al.), and 4,181,752 (Martens et al.), which are incorporated herein by reference.

[0059] In some cases, the adhesive is transparent. In certain embodiments, the adhesive is optically clear, meaning that the adhesive has transparency and clarity (e.g., low haze). In certain embodiments, the optically clear adhesive (OCA) is selected from acrylates, polyurethanes, polyolefins (e.g., polyisobutylene (PIB)), silicones, or combinations thereof. Exemplary OCAs include those described in International Publication No. WO 2008 / 128073 (Everaerts et al.) for antistatic optically clear pressure-sensitive adhesives, U.S. Patent Application Publication No. US 2009 / 089137 (Sherman et al.) for stretch-release OCAs, US 2009 / 0087629 (Everaerts et al.) for indium tin oxide-compatible OCAs, US 2010 / 0028564 (Cheng et al.) for antistatic optical structures with optically transparent adhesives, US 2010 / 0040842 (Everaerts et al.) for adhesives compatible with corrosion-sensitive layers, US 2011 / 0126968 (Dolezal et al.) for optically clear stretch-release adhesive tapes, and U.S. Pat. No. 8,557,378 (Yamanaka et al.) for stretch-release adhesive tapes. Suitable OCAs include, for example, acrylic optically clear pressure-sensitive adhesives such as 3M OCA 8146, 8211, 8212, 8213, 8214, and 8215, all available from 3M Company, St. Paul, Minnesota. Some suitable silicone adhesives are commercially available under the trade names "3M Adhesive Transfer Tape 91022" (e.g., 2 mil thick clear roll) and "3M Adhesive Transfer Tape 96042," both of which are offered by 3M Company, St. Paul, Minnesota.

[0060] In some cases, adhesives may be resistant to damage from ultraviolet radiation. Exemplary adhesives that typically resist damage from ultraviolet radiation include silicone adhesives and acrylic adhesives containing UV stabilizing / blocking additives. For example, U.S. Pat. No. 5,504,134 (Palmer et al.) describes the use of metal oxide particles ranging in size from about 0.001 to about 0.2 microns in diameter (in some embodiments, from about 0.01 to about 0.15 microns) to attenuate degradation of polymer substrates due to ultraviolet radiation. U.S. Pat. No. 5,876,688 (Laundon) describes a method for producing micronized zinc oxide small enough to be transparent when incorporated into paints, coatings, finishes, plastic products, cosmetics, and the like as a UV blocking and / or scattering agent, which is suitable for use in the present disclosure. These fine particles, such as zinc oxide and titanium oxide, with particle sizes ranging from 10 nm to 100 nm and capable of attenuating UV radiation, are available, for example, from Kobo Products, Inc. (South Plainfield, New Jersey).

[0061] Suitable hot melt adhesives include fluoropolymer THV (e.g., THV221, available from 3M Company as 3M DYNEON THV221) as an alternative to the adhesives described above. In particular, THV221 is resistant to UV degradation and can be hot melt extruded onto an article.

[0062] In certain embodiments, the adhesive layer comprises a polyisobutylene adhesive, a silicone adhesive, or a (meth)acrylic adhesive. <Base material layer> As previously mentioned, the substrate layer comprises a fluoropolymer or a silicone polymer. In certain embodiments, the substrate layer comprises a fluoropolymer.

[0063] Many fluoropolymers are advantageously resistant to UV radiation. Examples of fluoropolymers that can be used include copolymers of tetrafluoroethylene (TFE), hexafluoropropylene (HFP), and vinylidene fluoride (e.g., available from 3M Company under the trade name "3M DYNEON THV"), copolymers of TFE, HFP, vinylidene fluoride, and perfluoropropyl vinyl ether (PPVE) (e.g., available from 3M Company under the trade name "3M DYNEON THVP"), polyvinylidene fluoride (PVDF) (e.g., available from 3M Company as "3M DYNEON PVDF 6008"), ethylene chlorotrifluoroethylene polymer (ECTFE) (e.g., available from Solvay, Brussels, Belgium as "HALAR 350LC ECTFE"), ethylene tetrafluoroethylene copolymer (ETFE) (e.g., available from 3M Company as "3M DYNEON ETFE"). 6235"), perfluoroalkoxyalkane polymers (PFA), fluorinated ethylene propylene copolymers (FEP), polytetrafluoroethylene (PTFE), TFE, HFP, and copolymers of ethylene (HTE) (e.g., available from 3M Company as "3M DYNEON HTE1705"). Combinations of fluoropolymers can also be used. In certain embodiments, the fluoropolymer comprises FEP. In certain embodiments, the fluoropolymer comprises PFA.

[0064] In certain embodiments, the substrate layer comprises a fluoropolymer (co)polymer comprising polymerized units derived from one or more monomers selected from tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, perfluoroalkoxyalkylene, or combinations thereof. A suitable fluoropolymer is available from EI DuPont de Nemours (Wilmington, Delaware) under the trade name "TEFLON FEP100," with "TEFLON FEP100 500A" currently being preferred. Exemplary suitable fluoropolymers also include copolymers of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride (THV), available from Dyneon LLC (Oakdale, Minnesota) under the trade names "DYNEON THV 220," "DYNEON THV 221," "DYNEON THV 230," "DYNEON THV 2030," "DYNEON THV 415," "DYNEON THV 500," "DYNEON THV 610," and "DYNEON THV 815."

[0065] In certain embodiments, the substrate layer comprises a silicone thermoplastic polymer. One suitable silicone is available from Dow Corning Corporation (Midland, Michigan) under the trade name "DOW CORNING 93-500 SPACE GRADE ENCAPSULANT KIT." Another suitable silicone is available from Wacker Chemie AG (Munich, Germany) under the trade name "SILPURAN FILM."

[0066] In some cases, the thickness of the substrate layer is 10 microns or more, 15, 20, 25, 30, 35, 40, 50, 60, 70, 80, 90, 100, 120, 140, 160, 180, 200, 220, or 250 microns or more, and 500 microns or less, 475, 450, 425, 400, 375, 350, 325, 300, 275, 250, 225, 200, 175, 150, 125, or 100 microns or less. In certain embodiments, the substrate layer is a single layer having the above thickness. In certain embodiments, the substrate layer is self-supporting.

[0067] Certain microstructured surfaces exhibit better bacterial removal when cleaned compared to smooth surfaces. In some cases, the substrate layer is a microstructured substrate and includes a base layer having a thickness of at least 1 micron and a plurality of microstructures extending across a first surface of the base layer.

[0068] While articles with certain microstructures are useful for inhibiting the initial formation of biofilms, particularly in medical articles, in other articles, such microstructured surfaces can be difficult to clean. This is speculated to be due, at least in part, to the fact that the bristles of brushes and wipes (e.g., nonwoven) have fibers larger than the spaces between the microstructures. It has been discovered that certain microstructured surfaces exhibit better microbial (e.g., bacterial) removal when cleaned, even compared to smooth surfaces. The articles are typically not sterile implantable medical articles. Rather, microstructured surfaces usually come into contact with humans and animals, as well as other contaminants (e.g., dirt). Representative articles include, for example, surfaces or components of medical articles, dental articles, orthodontic articles (e.g., orthodontic aligners), vehicle articles, electronic articles, personal care articles, cleaning articles, exercise articles, food preparation articles, childcare articles, or building articles.

[0069] The microstructured surface provides a base 10 log reduction of microorganisms (e.g., bacteria) after cleaning that is at least 2, 3, 4, 5, 6, 7, or 8. Whether the microstructured surface is mechanically cleaned with a wipe or brush and / or cleaned by applying an antimicrobial solution to the microstructured surface, the microstructured surface provides improved removal of microorganisms (e.g., bacteria) compared to a surface lacking microstructures.

[0070] Referring to Figure 1, the microstructured surface can be characterized in three-dimensional space by superimposing a Cartesian coordinate system on the structure. A first reference plane 124 is located centered between major surfaces 112 and 114. The first reference plane 124 is referred to as the yz-plane and has the x-axis as its normal vector. A second reference plane 126 is referred to as the xy-plane and extends substantially coplanar with surface 116 and has the z-axis as its normal vector. A third reference plane 128 is referred to as the xz-plane and is located centered between first end surface 120 and second end surface 122 and has the y-axis as its normal vector.

[0071] In certain embodiments, the microstructured surface is three-dimensional at the macroscale. However, at the microscale (e.g., a surface region including at least two adjacent microstructures and a valley or channel disposed between the microstructures), the base / base member can be considered planar with respect to the microstructures. The width and length of the microstructures lie in the xy plane, and the height of the microstructures lies in the z direction. Furthermore, the base is parallel to the xy plane and perpendicular to the z plane.

[0072] FIG. 2A is an exemplary cross-sectional view of a microstructured surface 200 having practical discontinuities. The cross-sectional view is representative of a plurality of discrete (e.g., post or rib) microstructures 220. The microstructure includes a base 212 adjacent to a (e.g., designed) planar surface 216 (surface 116 in FIG. 1C parallel to reference plane 126). An upper (e.g., planar) surface 208 (parallel to surface 216 and reference plane 126 in FIG. 1C) is spaced from the base 212 by the height (“H”) of the microstructure. The sidewalls 221 of the microstructure 220 are perpendicular to the planar surface 216. When the sidewalls 221 are perpendicular to the planar surface 216, the microstructure has a sidewall angle of 0 degrees. In the case of perpendicular sidewalls, the sidewalls of the peak microstructures are parallel to each other and to adjacent microstructures with perpendicular sidewalls. Alternatively, the microstructure 230 has sidewalls 231 that are angled rather than perpendicular to the planar surface 216. The sidewall angle 232 is defined by the intersection of the sidewall 231 with a reference plane 233 perpendicular to the planar surface 216 (perpendicular to reference plane 126 and parallel to reference plane 128 in FIG. 1C). For example, for privacy films, as described in U.S. Pat. No. 9,335,449 (Gaides et al.), the wall angle is typically less than 10, 9, 8, 7, 6, or 5 degrees. Because the channels in privacy films contain light-absorbing materials, a larger wall angle can reduce transmittance. However, wall angles closer to 0 degrees are more difficult to clean.

[0073] Suitable surfaces are microstructured surfaces having microstructures with sidewall angles of greater than 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 degrees. In certain embodiments, the sidewall angle is at least 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 degrees. In other embodiments, the sidewall angle is at least 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 degrees. For example, in certain embodiments, the microstructure is a cube-corner peak structure with a 30-degree sidewall angle. In other embodiments, the sidewall angle is at least 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, or 45 degrees. For example, in certain embodiments, the microstructure is a prismatic structure with a 45-degree sidewall angle. In another embodiment, the sidewall angle is at least 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, or 60 degrees. It is understood that a microstructured surface can be beneficial even if some of the sidewalls have a lower sidewall angle. For example, if half of the array of peak structures have a sidewall angle within the desired range, approximately half of the benefit of improved microbial (e.g., bacterial) removal may be achieved. Thus, in certain embodiments, less than 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, or 1% of the peak structures have a sidewall angle of less than 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 degree. In certain embodiments, less than 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, or 1% of the peak structures have a sidewall angle of less than 30, 25, 20, or 15 degrees. In certain embodiments, less than 50, 45, 40, 35, 30, 25, 20, 15, 10, 5 or 1% of the peak structures have sidewall angles less than 40, 35, or 30 degrees, and 50, 60, 70, 80, 90, 95 or 99% or more of the peak structures have sidewall angles sufficiently large as described above.

[0074] For example, as described in International Publication No. WO 2013 / 003373 (Bommarito et al.), microstructures with cross-sectional dimensions of 5 microns or less are believed to substantially impede colonization and adhesion of target bacteria that are a major cause of healthcare-associated infections and other biofouling problems (e.g., increased resistance, reduced heat transfer, clogged filtration, etc.). Referring to Figure 2A, the cross-sectional width ("W") of the microstructures shown in the figure is M ") is less than or equal to the cross-sectional width ("Wv") of the channel or valley between adjacent microstructures. Thus, the cross-sectional width (W M ) is 5 microns or less, the cross-sectional width (Wv) of the channel or valley between the microstructures is also 5 microns or less. When the microstructures on either side of the valley have a sidewall angle of zero, as shown in microstructure 220 in FIG. 2A, the channel or valley defined by the sidewalls has a width (Wv) adjacent to the top surface 208 that is the same as the width adjacent to the bottom surface 212. When a microstructure has a sidewall angle greater than zero, as shown, for example, by line 231 in microstructure 230, the valley typically has a width adjacent to the top surface 208 (e.g., maximum width) that is larger compared to the width of the channel or valley adjacent to the bottom surface 212. When the sidewall angle is too small, and / or the maximum width of the valley is too small, and / or the microstructure surface includes an excessive amount of flat surface, the microstructure surface has proven to be more difficult to clean.

[0075] Suitable microstructured surfaces include microstructures having a maximum valley width of at least 1, 2, 3, or 4 microns, and in some cases greater than 5, 6, 7, 8, 9, or 10 microns, up to a maximum of 250 microns. In certain embodiments, the maximum valley width is at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 microns. In certain embodiments, the maximum valley width is no greater than 1000, 950, 900, 850, 800, 750, 700, 650, 600, 550, 500, 450, 400, 350, 300, 250, 225, 200, 175, 150, 125, 100, 75, or 50 microns. In certain embodiments, the maximum width of the valleys is 45, 40, 35, 30, 25, 20, or 15 microns or less. It is understood that a microstructured surface can be beneficial even if some of the valleys are less than the maximum width. For example, if half of the total number of valleys in a microstructured surface are within the desired range, approximately half the benefit may be achieved. Thus, in certain embodiments, less than 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, or 1% of the valleys have a maximum width of less than 10, 9, 8, 7, 6, or 5 microns. Alternatively, 50, 60, 70, 80, 90, 95, or 99% or more of the valleys have such a maximum width.

[0076] In typical embodiments, the maximum width of the microstructures falls within the same ranges as those described for the valleys. In other embodiments, the width of the valleys may be greater than the width of the microstructures. Thus, in preferred embodiments, the microstructured surface is typically substantially free of microstructures having widths of less than 5, 4, 3, 2, or 1 micron. Here, "substantially free" means that such microstructures are absent or, if present, do not impair the cleaning properties described below.

[0077] The microstructured surface may or may not include nanostructures.

[0078] While small structures, including nanostructures, can prevent biofilm formation, the presence of numerous smaller valleys or valleys with insufficient sidewall angles can hinder cleanability, including soil removal. Thus, typically, microstructured surfaces do not have numerous structures with small valleys or valleys with insufficient sidewall angles, which can hinder cleanability, including soil removal. Furthermore, microstructured surfaces with larger microstructures and valleys can typically be manufactured at a faster rate. Thus, in typical embodiments, each dimension of the microstructures is at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 microns. Furthermore, in certain embodiments, at least 50, 60, 70, 80, 90, 95, or 99% of the microstructures have no dimension less than 5, 4, 3, 2, or 1 micron.

[0079] In certain embodiments, the microstructured surface is typically substantially free of microstructures having widths of less than 5, 4, 3, 2, or 1 micron, including nanostructures having widths of less than 1 micron. Examples of microstructured surfaces that further include nanostructures are described in WO2012 / 058605, cited above. Nanostructures typically include one or two dimensions not exceeding 1 micron (e.g., width and height), and typically one or two dimensions are less than 1 micron. In certain embodiments, all dimensions of the nanostructures are not greater than 1 micron or are less than 1 micron.

[0080] "Substantially free" means that such microstructures are absent or, if present, do not impair the properties (e.g., cleaning). Thus, the microstructured surface or its microstructures can further include nanostructures, so long as they provide a reduction in the presence of microorganisms and / or a reduction in contact transmission of microorganisms after cleaning. Furthermore, in this embodiment, the presence of smaller microstructures and / or nanostructures does not prevent or significantly reduce biofilm formation.

[0081] In some embodiments, the microstructured surface may further comprise nanostructures. Microstructured surfaces further comprising other nanostructures are known. For example, Zhang et al., US 2013 / 0216784, describes a superhydrophobic film comprising flat surfaces separated by valleys. The valleys and surfaces can be covered with nanostructures. The superhydrophobic film has a static water contact angle of at least 140, 145, or 145 degrees. Such nanostructures typically have an aspect ratio of at least 1:1, 2:1, 3:1, 4:1, 5:1, or 6:1. As shown in the figures, the ratio of nanostructures to microstructures is approximately 20:1.

[0082] In other embodiments, the microstructured surface contains little or no nanostructures, and the ratio of nanostructures to microstructures is less than 20:1, 15:1, 10:1, 5:1, 4:1, 3:1, 2:1, or 1:1.

[0083] In another embodiment, the microstructured surface may further comprise randomly distributed depressions, as described in Aronson et al., WO2009 / 079275, where the presence of the randomly distributed depressions improves diffusion compared to the same microstructured surface lacking such depressions.

[0084] The presence of the nanostructures and depressions can trap dirt, especially clay particles with particle sizes less than 1 micron. However, in embodiments where the microstructured surface is used in a display or other application where the microstructured surface is not to be cleaned, the microstructured surface can include nanostructures and randomly distributed depressions.

[0085] When the peaks and valleys are sharp or rounded but not truncated, and the microstructure facets are joined, the microstructure surface can be characterized as having no flat surfaces parallel to the planar substrate. However, when the peaks and / or valleys are truncated, the microstructure surface typically has less than 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, or 1% of its area of ​​flat surfaces substantially parallel to the planar substrate. In some embodiments, the valley has a flat surface, and only one of the peak sidewalls may be angled, as shown in FIG. 2B . However, in preferred embodiments, as previously described, both sidewalls of adjacent peaks defining the valley are angled toward each other. Thus, the sidewalls on either side of the valley are not parallel to each other.

[0086] Figure 9 of WO 2021 / 033151 shows a comparative microstructured surface with discontinuous valleys. Such surfaces have also been described as having groups of features arranged relative to one another to define a serpentine path. Rather, the valleys are intersected by walls, forming an array of individual cells, each surrounded by a wall. Some cells are approximately 3 microns in length, while others are approximately 11 microns in length.

[0087] The valleys of preferred microstructured surfaces are substantially free of intersecting sidewalls or other obstructions to the valleys. By "substantially free," we mean that there are no sidewalls or other obstructions within the valleys, or to the extent that their presence does not impair cleaning properties. The valleys are typically continuous in at least one direction, which promotes the flow of cleaning solution through the valleys. Thus, the arrangement of peaks typically does not define a tortuous path.

[0088] The peak structures typically have a height (H) ranging from 1 to 250 microns. In some embodiments, the microstructure height is at least 2, 3, 4, or 5 microns. In some embodiments, the microstructure height is at least 6, 7, 8, 9, or 10 microns. In some embodiments, the microstructure height is no greater than 225, 200, 175, 150, 125, 100, 90, 80, 70, 60, or 50 microns. In some embodiments, the microstructure height is no greater than 45, 40, 35, 30, or 25 microns. In some embodiments, the microstructure height is no greater than 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, or 5 microns. In selected embodiments, the height of each peak structure is 10 to 250 microns. In typical embodiments, the height of the valleys or channels is within the same ranges described for the peak structures. In some embodiments, the peak structures and valleys have the same height.

[0089] The aspect ratio of a valley is the valley height (which may be the same as the peak height of the microstructure) divided by the maximum width of the valley. In some embodiments, the aspect ratio of a valley is at least 0.1, 0.15, 0.2, or 0.25. In some embodiments, the aspect ratio of a valley is no greater than 1, 0.9, 0.8, 0.7, 0.6, or 0.5. Thus, in some embodiments, the height of a valley typically does not exceed the maximum width of the valley, and more typically is less than the maximum width of the valley.

[0090] The base of each microstructure may have a variety of cross-sectional shapes, including, but not limited to, a parallelogram (which may have rounded corners), a rectangle, a square, a circle, a semicircle, a semi-ellipse, a triangle, a trapezoid, other polygons (e.g., pentagons, hexagons, octagons, etc.), and combinations thereof.

[0091] A suitable microstructured surface comprises an array of peak structures and adjacent valleys. The valleys preferably have a maximum width in the range of 1 micron to 250 microns. In some embodiments (e.g., for improved cleanability), the peak structures have sidewall angles greater than 10 degrees. The peak structures may include two or more facets, such as in the case of a linear array of prisms or an array of cube-corner elements. In some embodiments, the facets of the peak structures form apex angles, typically in the range of about 20 degrees to 120 degrees. The facets form a continuous or semi-continuous surface in the same direction. The valleys typically do not intersect with the walls.

[0092] The microstructured surfaces described herein do not prevent microorganisms (e.g., bacteria such as Streptococcus mutans, Staphylococcus aureus, or Pseudomonas aeruginosa) from presenting on the microstructured surface, i.e., do not prevent biofilm formation. However, the microstructured surfaces are easy to clean, and have been shown to have low levels of microorganisms (e.g., bacteria) present after cleaning. Without intending to be bound by theory, scanning electron microscope images suggest that large, continuous biofilms typically form on smooth surfaces. However, biofilms are disrupted by the microstructured surface, even though the peaks and valleys are much larger than the microorganisms (e.g., bacteria). In some embodiments, biofilms (before cleaning) exist on the microstructured surface as discontinuous aggregates and small cell clusters, rather than as a continuous biofilm. After cleaning, small patches of biofilm aggregates cover the smooth surface. However, the microstructured surfaces have been observed to have only small cell clusters and individual cells after cleaning. In preferred embodiments, the microstructured surface provides a base 10 log reduction of microorganisms (e.g., bacteria such as Streptococcus mutans, Staphylococcus aureus, or Pseudomonas aeruginosa) after cleaning of at least 2, 3, 4, 5, 6, 7, or 8. In some embodiments, the microstructured surface provides an average base 10 log reduction of microbial colony forming units recovered after cleaning of less than 6, 5, 4, or 3 for highly contaminated surfaces.

[0093] In some embodiments, the microstructured surface can resist beading of aqueous or (e.g., isopropanol) alcohol-based cleaning solutions compared to a smooth surface composed of the same polymeric material. If the cleaning solution beaded, or dewets, it may not be in contact with the microorganisms long enough for the disinfectant to kill them. However, it has been found that at least 50, 60, 70, 80, or 90% of the microstructured surface can contain the cleaning solution for 1, 2, and 3 minutes after the cleaning solution is applied to the microstructured surface.

[0094] In some embodiments, the microstructured surface may have the same surface as a brightness enhancing film. For example, as described in U.S. Patent No. 7,074,463 (Jones et al.), backlit liquid crystal displays typically include a brightness enhancing film disposed between a diffuser and a liquid crystal display panel. The brightness enhancing film collimates light, increasing the brightness of the liquid crystal display panel and also allowing for reduced power consumption of the light source. Therefore, brightness enhancing films have been utilized as internal components of illuminated display devices (e.g., mobile phones, computers) that are not exposed to microorganisms (e.g., bacteria) or dirt.

[0095] Referring to FIG. 3 , in one embodiment, the microstructured surface 300 includes a linear array of regular right-angle prisms 320. Each prism has a first facet 321 and a second facet 322. The prisms are shown formed on a base member 310 having a first planar surface 331 (parallel to the reference plane 126) on which the prisms are formed and a second surface 332 opposite the first surface that is substantially flat or planar. By right-angle prisms, we mean that the apex angle θ (340) is typically about 90°. However, this angle can range from 70° to 120°, and can range from 80° to 100°. These apexes can be sharp (as shown), rounded, or truncated. The spacing between peaks (e.g., prisms) is characterized as the pitch (“P”). In this embodiment, the pitch is also equal to the maximum width of the valleys. Thus, the pitch can range from greater than 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 microns, up to 250 microns, as discussed above. The length ("L") of the microstructure (e.g., a prism) is typically the largest dimension and can span the entire dimension of the microstructured surface. The facets of the prisms need not be identical, and the prisms may be angled relative to one another, as shown in Figure 6.

[0096] In another embodiment, the microstructured surface may have the same surface as cube-corner retroreflective sheeting. Retroreflective materials are characterized by their ability to reflect light incident on the material back toward its original source. This property has led to the widespread use of retroreflective sheeting for various traffic and personal safety applications. Referring to FIG. 4A, cube-corner retroreflective sheeting typically includes a thin, transparent layer having a substantially flat front surface and a rear structured surface 410 containing a plurality of cube-corner elements 417. A sealing film (not shown) is typically applied to the backside of the cube-corner elements. See, for example, U.S. Pat. No. 4,025,159 (McGrath) and U.S. Pat. No. 5,117,304 (Huang et al.). The sealing film maintains an air interface on the backside of the cube, allowing total internal reflection at the interface and inhibiting the ingress of contaminants such as soil and / or moisture.

[0097] The microstructured surface 410 in Figure 4A is characterized as an array of cube corner elements 417 defined by three sets of parallel grooves (i.e., valleys) 411, 412, and 413. Two sets of grooves (i.e., valleys) intersect with each other at angles greater than 60 degrees, and the third set of grooves (valleys) intersects with the other two sets of grooves at angles less than 60 degrees, forming an array of matched pairs of canted cube corner elements (see U.S. Pat. No. 4,588,258 (Hoopman)). The groove angles are selected so that the dihedral angles formed at the groove intersections—e.g., 414, 415, and 416 of a representative cube corner element 417—are approximately 90 degrees. In some embodiments, the triangular bases have angles of at least 64, 65, 66, 67, 68, 69, or 70 degrees, with other angles being 55, 56, 57, or 58 degrees.

[0098] In another embodiment, as shown in FIG. 4B, the microstructured surface 400 of FIG. 4B is characterized as an array of pyramidal peak structures 420 defined by a first set of parallel grooves (i.e., valleys) in the y-direction and a second set of parallel grooves in the x-direction. The bases of the pyramidal peak structures are polygonal, typically square or rectangular, depending on the groove spacing. The apex angle θ (440) is typically about 90°; however, this angle may range from 70° to 120°, or even from 80° to 100°. In other embodiments, the apex angle is at least 20°, 30°, 40°, 50°, or 60°.

[0099] Other cube corner element structures are described as "full cubes" or "preferred shape (PG) cube corner elements" and typically include at least two non-bihedral edges that are not coplanar, as described, for example, in U.S. Pat. No. 7,188,960 (Smith). Full cubes are not truncated. In one aspect, the base of a full cube element in plan view is not triangular. In another aspect, the non-bihedral edges of a full cube element characteristically do not all lie in the same plane (i.e., are not coplanar). Such cube corner elements may be characterized as "preferred shape (PG) cube corner elements." PG cube corner elements may be defined in the context of the structured surface of the cube corner element that extends along a reference plane. PG cube corner elements refer to cube corner elements that have at least one non-bihedral edge that is (1) nonparallel to a reference plane and (2) substantially parallel to the adjacent non-bihedral edges of adjacent cube corner elements. Cube corner elements whose reflective faces include rectangles (including squares), trapezoids, or pentagons are examples of PG cube corner elements.

[0100] Referring to FIG. 5, in another embodiment, a microstructured surface 500 may include an array of preferred shape (PG) cube corner elements. An exemplary microstructured surface includes four rows (501, 502, 503, and 504) of preferred shape (PG) cube corner elements. The preferred shape (PG) cube corner elements in each row have faces formed from first and second groove sets (also referred to as "side grooves"). These side grooves range from nominally parallel to adjacent side grooves to within 1 degree of non-parallel. These side grooves are typically perpendicular to reference plane 124 in FIG. 1C. The third face of such a cube corner element preferably has a major groove surface 550. This major groove surface ranges from nominally perpendicular to the surface formed by the side grooves to within 1 degree of non-perpendicular. In some embodiments, the side grooves may form an apex angle θ of nominally 90 degrees. In another embodiment, a row of preferred shape (PG) cube corner elements includes a peak structure formed from alternating pairs of side grooves 510 and 511 (e.g., about 75 degrees and about 105 degrees), as shown in FIG. 5 . Therefore, the apex angles 540 of adjacent (PG) cube corner elements can be greater than or less than 90 degrees. In some embodiments, the average apex angle of adjacent (PG) cube corner elements in the same row is typically 90 degrees. As described in the above-cited U.S. Patent No. 7,188,960, during the fabrication of a microstructured surface containing PG cube corner elements, the side grooves may be formed independently on individual laminae (laminas), with each laminae having a single row of such cube corner elements. Pairs of oppositely oriented laminae are positioned so that their respective major groove faces form a major groove 552, minimizing the formation of vertical walls. The laminae are assembled to form the microstructured surface and then replicated to form tools of appropriate size.

[0101] In some embodiments, all of the peak structures have the same apex angle θ. For example, the microstructure surface of FIG. 3 described above shows a plurality of prism structures, each with an apex angle θ of 90 degrees. As another example, the microstructure surface of FIG. 4B described above shows a plurality of pyramidal structures, each with an apex angle θ of 60 degrees. In other embodiments, the peak structures may have apex angles that are not the same. For example, as shown in FIG. 5, some peak structures may have apex angles greater than 90 degrees and some peak structures may have apex angles less than 90 degrees. In some embodiments, the peak structures in the microstructure array have different apex angles, but the average apex angle ranges from 60 to 120 degrees. In some embodiments, the average apex angle is at least 65, 70, 75, 80, or 85 degrees. In some embodiments, the average apex angle is less than 115, 110, 100, or 95 degrees.

[0102] As yet another example, as shown in the cross-sectional view of FIG. 6 , microstructured surface 600 may include multiple peak structures 646, 648, and 650 having peaks 652, 654, and 656, respectively. If the microstructured surface does not have a flat surface (i.e., a surface parallel to reference plane 126 in FIG. 1C ), the facets of adjacent peak structures may also define valleys between adjacent peaks. In some embodiments, the facets of the peak structures form valleys with valley angles less than 90 degrees (e.g., valley 658). In some embodiments, the facets of the peak structures form valleys with valley angles greater than 90 degrees (e.g., valley 660). In some embodiments, the valleys are symmetrical, as depicted by valleys 658 and 660. In other embodiments, the valleys are symmetrical, as depicted by valley 662. When a valley is symmetrical, the sidewalls of adjacent peak structures defining the valley are substantially identical. When a valley is asymmetrical, the sidewalls of adjacent peak structures defining the valley are different. The microstructured surface can have a combination of symmetric and asymmetric valleys.

[0103] In some embodiments, the peak structures typically include at least two (e.g., the prisms of FIG. 3), three (e.g., the cube corners of FIG. 4A), or more facets. For example, if the base of the microstructure is octagonal, the peak structure includes eight sidewall facets. However, if the facets are rounded or truncated, the microstructure may not be characterized by a specific geometric shape.

[0104] When the peaks and valleys are sharp or rounded but not truncated, and the microstructure facets are joined, the microstructure surface can be characterized as having no flat surfaces parallel to the planar substrate. However, when the peaks and / or valleys are truncated, the microstructure surface typically has less than 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, or 1% of its area being flat and substantially parallel to the planar substrate. In some embodiments, the valley has a flat surface, and only one of the peak sidewalls is angled, as shown in FIG. 2B. However, in preferred embodiments, as described above, both sidewalls of adjacent peaks defining the valley are angled toward each other. Therefore, the sidewalls on either side of the valley are not parallel to each other.

[0105] In each of the embodiments shown in Figures 3-6, the facets of adjacent (e.g., prismatic or cube-corner) peak structures typically connect at the bottom of the valley, i.e., adjacent to the flat substrate. The facets of the peak structures form a continuous surface in the same direction. For example, in Figure 3, facets 321 and 322 of the (e.g., prismatic) peak structures are continuous along the length (L) of the microstructure, i.e., the y-direction. As yet another example, the major grooves 452 and 550 of the PG cube-corner elements in Figure 5 form a continuous surface in the y-direction. In other embodiments, the facets form a semi-continuous surface in the same direction. For example, in Figure 4, the facets of the (e.g., cube-corner or pyramidal) peak structures are coplanar in both the x- and y-directions. These semi-continuous and continuous surfaces aid in cleaning pathogens from surfaces.

[0106] In some embodiments, the apex angle of the peak structures is typically twice the sidewall angle, especially where the facets of the peak structures are interconnected at the valleys between the peak structures. Thus, the apex angle is typically greater than 20 degrees, more typically at least 25, 30, 35, 40, 45, 50, 55, or 60 degrees. The apex angle of the peak structures is typically less than 160 degrees, more typically less than 155, 150, 145, 140, 135, 130, 125, or 120 degrees.

[0107] The microstructured surface of a microstructured film can be created by various microreplication techniques, such as coating, injection molding, embossing, laser etching, and extrusion. For example, microstructuring of a (e.g., designed) film surface can be achieved by at least one of the following: (1) casting a molten thermoplastic resin using a tool having a microstructured pattern; (2) coating a fluid onto the tool having the microstructured pattern, solidifying the fluid, and removing the resulting film; (3) passing the thermoplastic film through nip rolls to compress it against the tool having the microstructured pattern (i.e., embossing); and / or (4) contacting the tool having the microstructured pattern with a solution or dispersion of a polymer in a volatile solvent and removing the solvent (e.g., by evaporation). The tool may be made of a metal, such as nickel, nickel-plated copper, or brass, or a thermoplastic material that is stable under process conditions and preferably has a surface energy that allows the polymerized material to be cleanly removed from the tool. It should be understood that the microstructured film should comprise a material that does not melt or otherwise deform during the thermoforming process that forms the article, so that any practical discontinuities in the microstructured surface of the film will maintain their shape and impart their inverse shape to the surface of the final article.

[0108] The tools used to prepare microstructured films can be formed using any of a number of techniques known to those skilled in the art, with the selection depending in part on the tool material and desired geometric characteristics. Exemplary techniques include etching (e.g., chemical etching, mechanical etching, or other ablative means such as laser ablation or reactive ion etching, and combinations thereof), photolithography, stereolithography, micromachining, knurling (e.g., milled knurling or acid-enhanced knurling), scoring, cutting, etc., or combinations thereof. In some embodiments, the tool is a metal tool. The tool may further include a diamond-like glass layer, as described in WO2009 / 032815 (David).

[0109] Additional information regarding materials and various processes for forming microstructured tool surfaces can be found, for example, in International Publication No. WO2007 / 070310 and U.S. Publication No. US2007 / 0134784 (Halverson et al.); U.S. Publication No. US2003 / 0235677 (Hanschen et al.); International Publication No. WO2004 / 000569 (Graham et al.); U.S. Patent No. 6,386,699 (Ylitalo et al.); U.S. Publication No. US2002 / 0128578 (Johnston et al.) and U.S. Patent Nos. 6,420,622, 6,867,342, and 7,223,364 (Johnston et al.); and U.S. Patent No. 7,309,519 (Scholz et al.).

[0110] Useful (optional) base member materials include, for example, styrene-acrylonitrile, cellulose acetate butyrate, cellulose acetate propionate, cellulose triacetate, polyethersulfone, polymethyl methacrylate, polyurethane, polyester, polycarbonate, polyvinyl chloride, polystyrene, polyethylene naphthalate, copolymers or blends based on naphthalenedicarboxylic acid, polycycloolefins, polyimides, silicone and fluorinated films, and glass. Optionally, the substrate can comprise a mixture or combination of these materials. In some embodiments, the substrate can be multilayered or comprise dispersed components suspended or dispersed in a continuous phase. Examples of useful PET films include photograde polyethylene terephthalate and MELINEX, available from DuPont Films, Wilmington, Delaware. TM PET is one example of a useful thermoforming material. An example of a useful thermoforming material is polyethylene terephthalate (a glycol-containing polyester), commercially available as VIVAK PETG. Such materials are characterized by a tensile strength ranging from 5000 to 10,000 psi (ASTM D638) and a flexural strength ranging from 5,000 to 15,000 (ASTM D-790). Such materials have a glass transition temperature of 178°F (ASTM D-3418).

[0111] It is also possible, and often preferred, to include a surface energy adjusting compound in the composition used to form the microstructure to maintain the fidelity of the microstructure. In some embodiments, bloom additives can delay or prevent crystallization of the substrate composition. Suitable bloom additives can be found, for example, in International Publication No. WO 2009 / 152345 (Scholz et al.) and U.S. Patent No. 7,879,746 (Klun et al.).

[0112] Materials for retroreflective sheeting and brightness enhancement films are selected based on their optical properties. Thus, the peak structures and adjacent valleys typically comprise materials with refractive indices of at least 1.50, 1.55, 1.60, or higher. Furthermore, visible light transmittance is typically greater than 85% or 90%. However, in many embodiments of the presently described films, methods, and articles, optical properties may not be an issue. Thus, a variety of other materials with lower refractive indices, including colored, light-transmitting, and opaque materials, can be used.

[0113] 3, a continuous land layer 360 may be present between the bottom of the channel or valley and the top surface 331 of the (e.g., flat) base member 310. In some embodiments, when the microstructured surface is fabricated by casting and curing a polymerizable resin composition, the thickness of the land layer is typically at least 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 1, 2, 3, 4, or 5 microns, and in the range of up to 50 microns. In some embodiments, the thickness of the land layer is no greater than 45, 40, 35, 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, or 0.2 microns.

[0114] In some embodiments, the microstructured surface (e.g., at least its peak structures) comprises an organic polymeric material having a glass transition temperature (as measured by differential scanning calorimetry) of at least 25° C. In some embodiments, the organic polymeric material has a glass transition temperature of at least 30, 35, 40, 45, 50, 55, or 60° C. In some embodiments, the organic polymeric material has a glass transition temperature of no greater than 100, 95, 90, 85, 80, or 75° C.

[0115] Referring again to Figures 2-4 and 6, present microstructured (e.g., tooling) films optionally include a (e.g., designed) microstructured surface (200, 300, 400, 600) disposed on a base member (210, 310, 410, 610). In some cases, the base member is flat (e.g., parallel to reference plane 126). The thickness of the base member is typically at least 10, 15, 20, or 25 microns (1 mil), and typically no greater than 500 microns (20 mils). In some embodiments, the thickness of the base member is no greater than 400, 300, 200, or 100 microns. The width of the base member (e.g., of the film) can be at least 30 inches (122 cm), preferably at least 48 inches (76 cm). The base member is continuous in length from about 50 yards (45.5 m) to 100 yards (91 m), providing the microstructured film in a conveniently handled roll good, although alternatively the base member (e.g., of film) may be in individual sheets or strips rather than in a roll good.

[0116] In certain embodiments, the microstructured surface comprises peak structures and adjacent valleys, the maximum width of the valleys being in the range of 1 micron to 250 microns, and the peak structures having sidewall angles greater than 10 degrees.

[0117] In some embodiments, the microstructured surface is three-dimensional at the macroscale. However, at the microscale (e.g., a surface region including at least two adjacent microstructures and a valley or channel disposed between the microstructures), the base / base member can be considered planar relative to the microstructures. The width and length of the microstructures lie in the xy plane, and the height of the microstructures lies in the z direction. Furthermore, the base is parallel to the xy plane and perpendicular to the z plane.

[0118] Described herein are more complex microstructured surfaces, such as those shown in Figures 7A-7B and 8A-8C. The microstructured surfaces can be fabricated using any suitable manufacturing technique. For example, the microstructures can be fabricated using microreplication from a tool. The tool can be fabricated using any suitable manufacturing method, such as engraving or diamond turning. Exemplary methods are known in the art, such as those described in U.S. Pat. No. 8,888,333, WO 2000 / 048037, U.S. Pat. No. 7,140,812, U.S. Pat. No. 7,350,442, and U.S. Pat. No. 7,328,638 (Gardiner), which are incorporated herein by reference.

[0119] The formation of such microstructured surfaces is described in detail in WO 2023 / 105372 (Jones et al.), which is incorporated herein by reference in its entirety. Briefly, a cutting tool system can be used to cut a tool to produce a film having the microstructured surface of the present disclosure. The cutting tool system employs a thread-turning process and includes a roll that can be rotated about and / or moved along a central axis by a driver, and a cutter for cutting the roll material. The cutter is attached to a servo and can be moved along the x-direction into and / or along the roll by the driver. Generally, the cutter is mounted perpendicular to the roll and central axis and can be driven into the engravable material of the roll while the roll rotates about the central axis. The cutter is then driven parallel to the central axis to create a thread cut. The cutter is simultaneously operated at high frequency and low displacement to create features in the roll that, when microreplicated, result in the microstructured surface of the present disclosure.

[0120] The servo is a fast tool servo (FTS), which can contain a solid-state piezoelectric (PZT) device, often called a PZT stack, to rapidly adjust the position of the cutter. The rotational motion generated by the driver is synchronized with the translational motion generated by the driver to precisely control the resulting microstructure shape. To prepare the tool for creating the exemplary microstructured film surfaces in Figures 7A-8C, the cutter was shaped to have a rounded tip with a radius ranging from 1 to 3 microns and an apex angle beta of 80 degrees (±5 degrees).

[0121] As the roll material is cut, the rotation of the roll along its central axis and the translation of the cutter in the x-direction define a thread path around the roll with a pitch P along the central axis. As the cutter moves perpendicular to the roll surface to cut the roll material, the width of the material cut by the cutter varies as the cutter moves in and out. The cutter is angularly adjusted and vertically displaced to create a thread path that may have overcutting that erases some of the previously created wavy, pseudo-random pattern. This process of angular adjustment and vertical displacement is repeated three to seven times, or as many times as necessary, to engrave the entire surface of the roll with a pattern. The engraved roll serves as a tool for creating a film with a microstructured surface that is a negative replication of the tool's microstructured surface.

[0122] While this cutting method is described with respect to a rotating roll, randomized y-direction displacement and / or randomized x-direction displacement can also be utilized to cut flat surfaces. Similarly, overcutting can also be utilized to cut flat surfaces. It is also understood that some of the thread paths formed by the cutting tool may not incorporate randomized displacement or overcutting. For example, some of the arrays in Figures 7A-8C may include a regular repeating pattern, such as a linear array of prisms.

[0123] In some embodiments, a single cutter is used to cut the array of microstructures. In other embodiments, multiple cutters are used to cut the array of microstructures. For example, higher peaks may be formed with a cutter having a rounded tip, and lower peaks may be formed with a cutter having a sharp or less rounded tip. The surface of the tool typically has a surface roughness of less than 50, 40, 30, or 20 nm. Therefore, the surface of the microstructure can also have the same surface roughness. It is understood that the surface roughness of the tool / microstructure surface does not include the roughness contributed by the microstructure, and therefore is not the same as the roughness of the microstructure surface.

[0124] Additionally, while this cutting method is illustrated with respect to modifying the fabrication of an array of linear prisms, these same principles of solely randomizing the y-direction displacement and / or randomizing the x-direction displacement and / or over-cutting can also be used to modify the fabrication of other microstructure arrays, such as cube corner elements comprising preferred-shape cube corner elements, as described in WO 2021 / 033151 (Connell et al.), which is incorporated herein by reference. In this embodiment, the microstructured surface may be characterized as comprising modified cube corner structures or modified preferred-shape cube corner structures.

[0125] 7A-7B and 8A-8C are perspective views of exemplary (e.g., micro) structured surfaces including an array of peak structures according to the present disclosure. Note that cross-sectional views of the peak structures show that the peak structures have triangular cross sections. In some embodiments, the surfaces of FIGS. 7A-7B and 8A-8C can be characterized as "modified" linear prisms. The peak structures include facets, i.e., planes, that form a continuous surface in the same direction. When the microstructured surface includes an array of modified cube-corner structures, the peak structures include facets that form a semi-continuous surface in the same direction, as described in WO 2021 / 033151. When the microstructured surface includes an array of modified, preferred-shape cube-corner structures, the peak structures include facets that form continuous and semi-continuous surfaces in the same direction.

[0126] When a microstructured surface contains a regular repeating pattern, various dimensions, such as peak heights and maximum valley widths, can be determined by cross-sections perpendicular to the y-axis. Various angles, such as apex angles and sidewall angles, can also be determined by cross-sections perpendicular to the y-axis. However, when the microstructured surface does not contain a regular repeating pattern, i.e., a more complex microstructured surface, multiple cross-sections can be used to determine these parameters. Furthermore, when a microstructured surface contains peaks and valleys with different peak heights, different valley depths, different angles, etc., these parameters are more commonly expressed, for example, as minimum, maximum, or average values. The (micro)structured surfaces shown in Figures 7A-7B and Figures 8A-8C can be characterized as having greater variability, i.e., greater randomness, compared to the linear prisms described in WO2021 / 033151 and above.

[0127] In contrast to the linear prisms of WO 2021 / 033151, the microstructured surfaces of each of Figures 7A-7B and 8A-8C (e.g., modified linear prisms) include peaks and / or valleys of different heights. Furthermore, the microstructured surfaces of each of Figures 7A-7B and 8A-8C (e.g., modified linear prisms) include peaks and / or valleys of different widths. The minimum and maximum valley heights, valley widths, peak heights, and peak widths of the microstructured surfaces of Figures 7A-7B and 8A-8C are reported in the table below. Samples 1-4 correspond to Examples 1-4 of WO 2023 / 105372 (Jones et al.).

[0128] [Table 1]

[0129] It is noted that the height of the valley structures varies by at least 1, 2, 3, 4, or 5 microns (difference between minimum and maximum). In some embodiments, the height of the valley structures varies by no more than 20, 10, 15, or 5 microns. It is noted that the width of the valley structures varies by at least 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 microns (difference between minimum and maximum). In some embodiments, the width of the valley structures varies by no more than 20, 10, 15, or 5 microns.

[0130] [Table 2]

[0131] It is noted that the height of the peak structures varies by at least 1, 2, 3, 4, or 5 microns (the difference between the minimum and maximum values). In some embodiments, the variation in height of the peak structures is no greater than 20, 10, 15, or 5 microns. Additionally, the width of the peak structures varies by at least 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 microns (the difference between the minimum and maximum values). In some embodiments, the variation in width of the peak structures is no greater than 20, 10, 15, or 5 microns.

[0132] It is understood that the amount of variation is a function of size. In other words, the amount of variation is typically at least 10, 15, 20, 25, 30, 35, 40, 45, or 50% of the average dimension (e.g., peak height, peak width, valley height, valley width, etc.). In some embodiments, the amount of variation is less than 45, 40, 35, 30, 25, 20, or 15%. Thus, if the average dimension of the microstructured surface is 10 microns, the amount of variation is typically in the range of 1 to 5 microns. Similarly, if the average dimension of the microstructured surface is 1 micron, the amount of variation is typically in the range of 0.1 to 0.5 microns.

[0133] Figure 8C shows a negative replica, or inverse, of the surface of Figure 8B. A negative replica can be made, for example, by casting and curing a polymerizable resin onto a metal tool such as nickel, nickel-plated copper, or brass. The tool preferably has a surface energy that allows the polymerized material to be cleanly removed from the tool.

[0134] When the cured polymerizable resin is removed from the metal tool, the resulting film has a microreplicated surface, with peak structures on the tool corresponding to valleys, or cavities, in the film and valleys on the tool corresponding to peak structures in the film. It should be understood that the microstructured film should comprise a material that does not melt or otherwise deform during the thermoforming process to form the article, so that any practical discontinuities in the microstructured surface of the film will maintain their shape and impart an inverse of that shape to the surface of the final article.

[0135] In this embodiment, the peak dimensions of the structured surface of Figure 8C are the same as the valley dimensions illustrated in Sample 4 of Figure 8B. Additionally, the valley dimensions of the structured surface of Figure 8C are the same as the peak dimensions of Sample 4 illustrated in Figure 8B.

[0136] The complex surfaces of the present disclosure were characterized using surface analysis. Topographic data were collected using a VK-200 Keyence laser scanning confocal microscope (Keyence Corporation, Itasca, IL). Stitched images were generated using the microscope's native image assembly software. Thirty-five independent images (using a 150x Nikon objective) were used to create a dataset measuring approximately 300 x 600 microns. This dataset was further analyzed using the software package Digital Surf Mountains Map (Digital Surf, Besancon, France) to measure surface roughness parameters and generate the 3D surface plots shown in Figures 7A-7B and 8A-8C.

[0137] 12 is a schematic side view of the (micro)structures 160 of the (micro)structured surface 120. The structures 160 have a gradient distribution across the surface of the structure. For example, the microstructures have a gradient θ at location 510, where θ is the angle between a normal 520 (α=90 degrees) perpendicular to the microstructured surface at location 510 and a tangent 530 that touches the microstructured surface at the same location. The gradient θ is also the angle between the tangent 530 and the major surface 142 of the mat layer.

[0138] The gradient of the microstructure, the gradient of the microstructure surface 120 was taken first along the x direction and then along the y direction:

[0139]

number

[0140] where H(x,y) is the height profile of the surface.

[0141] The average x- and y-tilts were evaluated at the center of each pixel at 2-micron intervals. In different embodiments, the micron interval can be selected to be smaller or larger, as long as a constant interval with sufficient resolution relative to the size of the microstructures is used. The selected interval is smaller than the minimum peak width of the structures. In some embodiments, the ratio of interval to minimum peak width is at least 3:1, 4:1, or 5:1. Thus, smaller intervals are selected for smaller structures, and larger intervals are typically selected for larger structures. Each pixel has a slope, and each structure typically has multiple sets of x,y coordinates and therefore multiple calculated slope values. If micron-sized intervals are selected to evaluate the slope of a microstructured surface, the presence of nanostructures typically does not significantly change the Fcc of the microstructured surface. For example, a 200-nm nanostructure will change the coordinates of a 10-micron microstructure by only 2%. From the x-tilt and y-tilt data, the magnitude of the gradient can be determined using Equation 3:

[0142]

number

[0143] The average gradient magnitude could be estimated at the center of each pixel within a 6 μm × 6 μm box. The gradient magnitude was generated within a bin size of 0.5 degrees. The gradient magnitude distribution was N G It should be understood that to find the degree values ​​of the x slope, y slope, and gradient magnitude angles corresponding to the above values, it is necessary to take the arc tangent of the values ​​in Equations 1, 2, and 3. Another characterization of the surface is the complementary cumulative distribution (F CC (θ)) and is defined as the percentage of gradient magnitudes greater than or equal to a certain angle θ (or the percentage multiplied by 100%). The complementary cumulative distribution (FCC(θ)) is defined as:

[0144]

number

[0145] Thus, if a certain percentage of the structured surface is stated to have a slope magnitude less than a certain number of degrees, this characterization is expressed as F in Eq. CC (θ). The gradient magnitude corresponds to the combination of the x and y slopes, and therefore the gradient magnitude can be understood as the general slope magnitude. The terms "gradient magnitude" and "gradient magnitude" may be used interchangeably throughout this specification, and these terms should be understood to have the same meaning. For example, as shown in Figures 7A-7B and 8A-8C, if the entire surface is microstructured and the selected spacing is smaller than the minimum peak width of the microstructure, the Fcc of the entire surface is both the Fcc of the microstructured surface and the Fcc of the microstructure.

[0146] For the embodiment microstructured surfaces shown in Figures 7A-7B and 7A-7C, the x-gradient distribution (Xcc), y-gradient distribution (Ycc), and F(cc) were calculated.

[0147] FIG. 9 is a plot of the cumulative gradient (i.e., slope) magnitude distribution complement (Fcc) calculated from the surface topography data of FIGS. 7A-7B and 8A-8B, compared with comparative examples. Comparative example A is a representative brightness enhancement film (e.g., Example 1 of WO 2021 / 033162). Comparative example B is a representative cube-corner film (e.g., Example 20 of WO 2021 / 033162). Note that the microstructures of these comparative microstructured surfaces have a narrow slope distribution. 90% of the microstructures on the surfaces of Comparative examples A and B have a slope of at least 30 degrees. 80% of the microstructures on the surface of Comparative example A have a slope of at least 45 degrees (i.e., half the apex angle). Meanwhile, 80% of the microstructures on the microstructured surface of Comparative example B have a slope of at least 40 degrees (i.e., half the apex angle). Less than 5% of the microstructures in both Comparative examples A and B have a slope of less than 20 degrees. Furthermore, less than 5% of the microstructures have a slope greater than 50 degrees. For regular repeating patterns such as Comparative Examples A and B, the slope calculated from the topographical data obtained from surface analysis can be substantially the same as the sidewall angle calculated from the cross section.

[0148] It is noted that the surfaces shown in Figures 7A-7B and 8A-8C have a much broader distribution of slopes. In particular, the structured surfaces include a plurality of structures having a complementary cumulative slope magnitude distribution (Fcc) such that at least 30, 40, 50, 60, 70, 80, or 90% of the structures have a slope greater than 10 degrees. Furthermore, in some embodiments, less than 80% of the structures have a slope greater than 35 degrees. In some embodiments, the structured surfaces described herein and shown in Figures 7A-7B and 8A-8C include a plurality of structures having a complementary cumulative slope magnitude distribution (Fcc) that meets one or more of the following criteria: a) At least 10, 20, 30, 40, 50, 60, 70 or 80% of the structure has a slope greater than 20 degrees; b) At least 10, 20, 30, 40, 50, 60, or 70% of the structure has a slope greater than 30 degrees; c) At least 10, 20, 30, 40, or 50% of the structure has a slope greater than 40 degrees; d) At least 10, 20, or 30% of the structure has a slope greater than 50 degrees; e) At least 10 or 20% of the structure has a slope of more than 60 degrees; f) 20, less than 10% of the structure has a slope greater than 70 degrees; g) Less than 50, 40, 30, or 20% of the structure has a slope greater than 60 degrees; h) Less than 50 or 40% of the structure has a slope greater than 50 degrees; i) Less than 70, 60, or 50% of the structure has a slope greater than 40 degrees; j) Less than 90 or 80% of the structure has a slope greater than 30 degrees; k) Less than 90% of the structure has a slope greater than 20 degrees.

[0149] The complementary cumulative gradient magnitude distribution (Fcc) of Figure 8C, i.e., the negative replica of Figure 8B, may also be characterized by the same complementary cumulative gradient magnitude distribution (Fcc) criteria described above. The structured surfaces shown in Figures 7A-7B and 8A-8C may be characterized by various combinations of the complementary cumulative gradient magnitude distribution (Fcc) criteria described above, and in some embodiments may meet all of the criteria described above.

[0150] 10 is a plot of the complement of the cumulative gradient (i.e., tilt) magnitude distribution (Ycc) of the structured surfaces shown in FIGS. 7A-7B and 8A-8B. These surfaces include a plurality of structures having a complement cumulative tilt magnitude distribution (Ycc) such that at least 20, 25, 30, 35, 40, 45, or 50% of the structures have a tilt greater than 10 degrees and less than 55, 50, 45, 40, 35, 30, 25, or 20% of the structures have a tilt greater than 30 degrees. In some embodiments, the structured surfaces described herein and shown in FIGS. 7A-7B and 8A-8B include a plurality of structures having a complement cumulative tilt magnitude distribution (Ycc) that meets one or more of the following criteria: a) At least 10 or 20% of the structure has a slope of more than 20 degrees; b) at least 10 or 20% of the structure has a slope of more than 30 degrees; c) at least 10 or 15% of the structure has a slope of more than 40 degrees; d) at least 10% of the structure has a slope greater than 50 degrees; e) At least 5% of the structure has a slope greater than 60 degrees; f) Less than 10 or 5% of the structure has a slope greater than 70 degrees; g) Less than 10% of the structure from 20 has a slope greater than 60 degrees; h) Less than 50, 40, 30, 20 or 10% of the structure has a slope greater than 50 degrees; i) Less than 90, 80, 70, 60, 50, 40, 30 or 20% of the structure has a slope greater than 40 degrees; j) Less than 90, 80, 70, 60, 50, 40, or 30% of the structure has a slope greater than 20 degrees; k) Less than 90, 80, 70, 60, 50, 40, or 30% of the structure has a slope greater than 10 degrees.

[0151] 11 is a plot of the complementary cumulative gradient (i.e., slope) magnitude distribution (Xcc) of the structured surfaces shown in FIGS. 7A-7B and 8A-8B. These surfaces include a plurality of structures having a complementary cumulative slope magnitude distribution (Xcc) such that at least 45, 50, or 60% of the structures have a slope greater than 30 or 35 degrees, and less than 85 or 80% of the structures have a slope greater than 40 degrees. In some embodiments, the structured surfaces described herein and shown in FIGS. 7A-7B and 8A-8B include a plurality of structures having a complementary cumulative slope magnitude distribution (Xcc) that meets one or more of the following criteria: a) At least 10, 20, 30, 40, 50, 60, 70, or 80% of the structure has a slope greater than 10 degrees; b) At least 10, 20, 30, 40, 50, 60, or 70% of the structure has a slope greater than 20 degrees; c) At least 10, 20, 30, 40, 50, or 60% of the structure has a slope greater than 40 degrees; d) at least 10 or 20% of the structure has a slope of more than 50 degrees; e) At least 10% of the structure has a slope greater than 60 degrees; f) Less than 20 or 10% of the structure has a slope greater than 70 degrees; g) Less than 50, 40, 30 or 20% of the structure has a slope greater than 60 degrees; h) Less than 50, 40, or 30% of the structure has a slope greater than 50 degrees; i) Less than 90, 80, or 70% of the structure has a slope greater than 30 degrees; j) Less than 90 or 80% of the structure has a slope greater than 20 degrees.

[0152] It will be appreciated that the structured surface of FIG. 8C can also be characterized by the same complementary cumulative gradient magnitude distribution (Xcc) and (Ycc) criteria described above.

[0153] Various other surface roughness parameters, Sa (roughness average), Sq (root mean square), Sku (surface kurtosis), Sbi (surface support index), and Svi (valley fluid retention index), were calculated from the topographic images (3D). Before calculating the roughness, a planar correction was performed using "plane subtraction" (first-order plane fit shape removal).

[0154] The following table shows the S-parameters of some representative examples and comparative examples. Note that some comparative examples are also described in WO2021 / 033151.

[0155] [Table 3]

[0156] Topography maps can be obtained using a confocal laser scanning microscope (CLSM), such as the Keyence VK-X200. CLSM is an optical microscopy technique that uses a focused laser beam to scan a surface and map its topography. CLSM works by passing a laser beam through an aperture in the light source, focusing it onto a small area of ​​the surface with an objective lens, and collecting photons emitted from the sample to build an image pixel by pixel. A pinhole is used to block out-of-focus light during imaging. Dimensional analysis can be used to measure various parameters using SPIP6.7.7 Image Metrology software according to the manual (see https: / / www.imagemet.com / media-library / support-documents).

[0157] Surface roughness parameters Sa (Roughness Average), Sq (Root Mean Square), Sbi (Surface Bearing Index), Svi (Valley Fluid Retention Index) can be calculated from the topographic images (3D). Before calculating the roughness, a plane correction is performed using "Subtract Plane" (1st order planefit form removal).

[0158] The roughness average Sa is defined as follows:

[0159]

number

[0160] where M and N are the number of X and Y data points.

[0161] While smooth surfaces may have an Sa approaching zero, comparative smooth surfaces that were found to have insufficient microbial removal after cleaning had an average surface roughness Sa of at least 10, 15, 20, 25, or 30 nm. The comparative smooth surfaces had an average surface roughness Sa of less than 1000 nm (1 micron). In some embodiments, the comparative smooth surfaces had an Sa of at least 50, 75, 100, 125, 150, 200, 250, 300, or 350 nm. In some embodiments, the comparative smooth surfaces had an Sa of no more than 900, 800, 700, 600, 500, or 400 nm.

[0162] The microstructured surfaces that exhibited improved microbial removal after cleaning had an average surface roughness Sa of 1 micron (1000 nm) or greater. In some embodiments, Sa was at least 1100 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm, 1600 nm, 1700 nm, 1800 nm, 1900 nm, or 2000 nm (2 microns). In some embodiments, the microstructured surfaces had an Sa of at least 2500 nm, 3000 nm, 3500 nm, 4000 nm, or 5000 nm. In some embodiments, the microstructured surfaces had an Sa of at least 10,000 nm, 15,000 nm, 20,000 nm, or 25,000 nm. In some embodiments, the microstructured surfaces that exhibit improved microbial removal after cleaning have a Sa of 40,000 nm (40 microns), 35,000 nm, 30,000 nm, 15,000 nm, 10,000 nm, or 5,000 nm or less.

[0163] In some embodiments, the Sa of the microstructured surface is at least 2 or 3 times that of the smooth surface. In other embodiments, the Sa of the microstructured surface is at least 4, 5, 6, 7, 8, 9, or 10 times that of the smooth surface. In other embodiments, the Sa of the microstructured surface is at least 15, 20, 25, 30, 35, 40, 45, or 50 times that of the smooth surface. In other embodiments, the Sa of the microstructured surface is at least 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 times that of the smooth surface.

[0164] The root mean square (RMS) parameter Sq is defined as:

[0165]

number

[0166] where M and N are the number of X and Y data points.

[0167] Although the Sq value is slightly higher than the Sa value, the Sq value also falls within the same range as described above for the Sa value.

[0168] Surface kurtosis Sku describes the "sharpness" of the surface topography and is defined as:

[0169]

number

[0170] [Table 4]

[0171] Notably, Samples 1-4 have higher Sku than Comparative Examples A, B, and D. In some embodiments, the Sku is greater than 2.40, 2.45, 2.50, 2.55, 2.60, 2.65, 2.70, or 2.75. In some embodiments, the Sku is less than 3.00, 2.95, 2.90, 2.85, 2.80, 2.75, 2.70, 2.65, 2.60, 2.55, 2.50, or 2.45.

[0172] The surface support index Sbi is defined as:

[0173]

number

[0174] where Z 0.05 refers to the surface height at 5% of the support area.

[0175] The valley fluid retention index, Svi, is defined as:

[0176]

number

[0177] where V V (h0.80 ) refers to the void volume in the valley region at 80-100% bearing area.

[0178] As shown in the S-parameter table above, the comparative smooth samples had Sbi / Svi ratios of 1 and 3. Microstructured surfaces that exhibited improved microbial removal after cleaning had Sbi / Svi ratios greater than 3. Such microstructured surfaces had Sbi / Svi ratios of at least 4, 5, or 6. In some embodiments, microstructured surfaces that exhibited improved microbial removal after cleaning had Sbi / Svi ratios of at least 7, 8, 9, or 10. In some embodiments, microstructured surfaces that exhibited improved microbial removal after cleaning had Sbi / Svi ratios of at least 15, 20, 25, 30, 35, 40, or 45. The microstructured surfaces that exhibited improved microbial removal after cleaning had lower Sbi / Svi ratios than the comparative square wave microstructured surfaces. Thus, the microstructured surfaces that exhibited improved microbial removal after cleaning had Sbi / Svi ratios of less than 90, 85, 80, 75, 70, or 65. In some embodiments, the microstructured surfaces that exhibited improved microbial removal after cleaning had an Sbi / Svi ratio of less than 60, 55, 50, 45, 40, 35, 30, 25, 20, or 10.

[0179] Topography maps can also be used to measure other features of the microstructured surface. For example, peak heights (especially repeating peaks of the same height) can be determined from the software's height histogram function. To calculate the percentage of "flat area" in a square wave film, the "flat area" can be identified using SPIP's particle pore analysis function, which identifies a specific shape (in this case, the "flat top" of a microstructured square wave film).

[0180] In certain embodiments, the microstructured surface comprises peak structures and adjacent valleys having a complementary cumulative slope magnitude distribution (Fcc) such that at least 30, 40, 50, 60, 70, 80, or 90% of the structures have a slope greater than 10 degrees and less than 80% of the structures have a slope greater than 35 degrees.

[0181] In certain cases, the microstructured surface has less than 30% planar surface area parallel to the planar substrate.

[0182] In another embodiment, the substrate layer is flat and has an average surface roughness Sa of less than 1000 nm. A flat substrate layer lacks the microstructured surface described in detail above. <Optional additives and coatings> Optionally, a low surface energy coating can be applied to the substrate layer. Exemplary low surface energy coating materials that may be used include hexafluoropropylene oxide (HFPO), organosilanes such as alkylsilanes, alkoxysilanes, acrylicsilanes, polyhedric oligomeric silsesquioxanes (POSS), and fluorine-containing organosilanes, to name a few. Examples of specific coatings known in the art can be found, for example, in U.S. Publication No. 2008 / 0090010 (Zhang et al.) and commonly owned U.S. Publication No. 2007 / 0298216 (Jing et al.). The coating can be applied by any suitable coating method, such as sputtering, vapor deposition, spin coating, dip coating, roll-to-roll coating, or many others.

[0183] In some embodiments, the substrate layer can be modified to make the major surface opposite the metal oxide layer more hydrophilic. The microstructured surface can generally be modified so that a flat organic polymer film surface made of the same material as the modified microstructured surface has an advancing or receding contact angle with deionized water of 45 degrees or less. In the absence of such modification, a flat organic polymer film surface made of the same material as the microstructured surface typically has an advancing or receding contact angle with deionized water of greater than 45, 50, 55, or 60 degrees.

[0184] Any suitable known method can be used to achieve a hydrophilic substrate layer surface. Surface treatments can include plasma treatment, vacuum deposition, polymerization of hydrophilic monomers, grafting of hydrophilic moieties onto the film surface, corona or flame treatment, etc. In certain embodiments, the hydrophilic surface treatment comprises a zwitterionic silane, and in certain embodiments, the hydrophilic surface treatment comprises a non-zwitterionic silane. Non-zwitterionic silanes include, for example, non-zwitterionic anionic silanes.

[0185] In another embodiment, the hydrophilic surface treatment further comprises at least one silicate, such as, but not limited to, lithium silicate, sodium silicate, potassium silicate, silica, tetraethyl orthosilicate, poly(diethoxysiloxane), or a combination thereof. The one or more silicates can be mixed into a solution containing a hydrophilic silane compound and applied to the (e.g., microstructured) surface. <Goods> Because one useful purpose is to provide an article with a surface that enhances microbial (e.g., bacterial) removal upon cleaning, the article is typically not a (e.g., sterile) medical article, such as a nasogastric tube, wound contact layer, blood flow catheter, stent, pacemaker shell, heart valve, orthopedic implant (e.g., hip, knee, shoulder), periodontal implant, dentures, dental crown, contact lens, intraocular lens, soft tissue implant (e.g., breast implant, penile implant, facial and hand implant), surgical tool, suture (including degradable suture), cochlear implant, tympanoplasty tube, shunt (including hydrocephalus shunt), postoperative drainage tube and drainage device, urinary catheter, endotracheal tube, heart valve, wound dressing, other implanted device, or other indwelling device. The above medical articles may be characterized as disposable articles, i.e., articles that are used once and then discarded. The above articles may also be characterized as articles for a single person (e.g., patient). Therefore, such articles are typically cleaned (rather than sterilized) and not reused for another patient.

[0186] In contrast, the articles and surfaces described herein include those in which the microstructured surface is exposed to the surrounding (e.g., indoor or outdoor) environment and may come into contact with or come into contact with multiple people and / or animals, as well as other contaminants (e.g., dirt).

[0187] In some embodiments, the microstructured surface of the article comes into direct contact (e.g., via skin) with human(s) and / or animal(s) during normal use of the article. In other embodiments, the microstructured surface may be in close proximity to human(s) and / or animal(s) without direct (e.g., skin) contact. However, due to the proximity of the microstructured surface, such article surfaces can easily become contaminated with microorganisms (e.g., bacteria) and are cleaned to prevent the spread of microorganisms to others.

[0188] Representative articles that are cleaned during normal use or suitable for integrating a microstructured surface into the curved surface of the article include various interior or exterior surfaces or components of medical, dental, orthodontic, vehicular, electronic, personal care, cleaning, athletic, food preparation, child care, or architectural articles. More specifically, examples of representative articles in these categories include the following: a) Vehicle articles (e.g., automobiles, buses, trains, airplanes, boats, ambulances, ships) include headrests, dashboards, door panels, window shutters (e.g., in airplanes), gear shifters, seat belt buckles, instrument and button panels, armrests, handrails, luggage compartments, steering wheels, handlebars, etc.; b) Medical or dental items include (e.g., non-sterile) surfaces in medical, dental, or research facilities and medical, dental, or research equipment (e.g., defibrillators, ventilators and CPAPs (especially their masks), face shields, crutches, wheelchairs, bed rails, breast pumps, IV poles and bags, dental tools (e.g., hand tools used in dental cleaning and restorative procedures), curing lights (e.g., for dental materials), examination tables, etc.); c) Orthodontic articles include aligners (e.g., clear tray aligners), retainers, night guards, splints, Class II and Class III orthodontic appliances, sleep apnea appliances, bite openers, bands, brackets, buccal tubes, cleats, buttons, and other attachment devices; d) Electronic goods include housings and cases for electronic devices (e.g., phones, laptops, tablets, or computers), keyboards, mice, projectors, printers, remote controls, locks, chargers (including cords and docking stations), fabs, video and arcade games, slot machines, automated teller machines, and point-of-sale electronic devices such as credit card readers, keypads, stylists, cash registers, barcode scanners, and payment kiosks; e) Personal care items include toothbrushes, eyeglass frames, shoes, clothing, handbags, etc.; f) Cleaning items include vacuum cleaners, mops, scrub brushes, dusters, toilet cleaners, plungers, brooms, etc.; g) Athletic articles include helmets, guards, balls and handheld equipment for various sports such as baseball, lacrosse, tennis, football, basketball, soccer, golf, etc.; h) Food preparation items include appliances (e.g., microwave ovens, stoves, ovens, blenders, toasters, coffee makers, refrigerators), grills, cooking utensils (especially their handles), condiment bottles, salt and pepper shakers, galleys, carts, cutting boards, lunch boxes, thermoses, tables and chairs (especially for public dining in restaurants, dormitories, nursing homes, and prisons); i) Childcare items include toys, pacifiers, bottles, teethers, car seats, cribs, changing tables, play equipment, etc.; j) Building articles include handrails, countertops, desktops, cabinets, lockers, window sills, electrical modulators (e.g., switches, dimmers, outlets), furniture components (e.g., desks, tables, chairs, seats, armrests), furniture, building doors, turnstiles, appliances, vehicles, shopping carts and baskets, washroom surfaces and components (e.g., sinks, toilet surfaces (e.g., levers), drain caps, shower walls, bathtubs, vanities, countertops), and the like.

[0189] Microstructured surfaces are particularly advantageous in multi-dwelling facilities such as military housing, prisons, dormitories, nursing homes, apartments, and hotels, as well as public places such as offices, schools, arenas, casinos, bowling alleys, golf courses, arcades, gyms, salons, spas, shopping centers, airports, train stations, and public transportation.

[0190] The term "microorganism" is generally used to refer to any prokaryotic or eukaryotic microscopic organism, including bacteria (e.g., motile or non-motile, vegetative or dormant, Gram-positive or Gram-negative, living in plankton or biofilms), bacterial spores or endospores, algae, fungi (e.g., yeast, filamentous fungi, fungal spores), mycoplasma, protozoa, and combinations thereof. In some cases, microorganisms of particular interest are pathogenic, and the term "pathogen" is used to refer to any pathogenic microorganism. Examples of pathogens include, but are not limited to, gram-positive and gram-negative bacteria, fungi, viruses, members of the Enterobacteriaceae family, members of the Micrococaceae family, or species of the genera Staphylococcus, Streptococcus, Pseudomonas, Acinetobacter, Enterococcus, Salmonella, Legionella, Shigella, Yersinia, Enterobacter, Escherichia, Bacillus, Listeria, Campylobacter, Acinetobacter, Vibrio, Clostridium, Klebsiella, Proteus, Aspergillus, Candida, Corynebacterium, and the like.Specific examples of pathogens include Escherichia coli (including enterohemorrhagic E. coli, e.g., serovars O157:H7, O129:H11), Pseudomonas aeruginosa, Bacillus cereus, Bacillus anthracis, Salmonella enteritidis, Salmonella enterica serovar Typhimurium, Listeria monocytogenes, Clostridium botulinum, Clostridium perfringens, Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, carbapenem-resistant Enterobacteriaceae, Campylobacter jejuni, Yersinia enterocolitica, Vibrio vulnificus, Clostridium difficile, vancomycin-resistant Enterococcus, Klebsiella pneumoniae, Proteus mirabilis, and Enterobacter [Cronobacter]. These include, but are not limited to, S. sakazakii. Exemplary Embodiments In a first embodiment, the present disclosure provides a multilayer article. The multilayer article includes a substrate layer comprising a fluoropolymer or a silicone polymer; a metal oxide layer directly attached to a major surface of the substrate layer and having a thickness of 15 nanometers (nm) to 60 nm; and an adhesive layer adjacent to the major surface of the metal oxide layer opposite the substrate layer. The article exhibits an average transmittance of 10% or less, 7%, 5%, or 2% or less over a wavelength band of at least 30 nanometers, having a wavelength between 200 nm and 400 nm, for light incident at at least one of 0°, 30°, 45°, 60°, or 75°.

[0191] In a second embodiment, the present disclosure provides a multi-layer article according to the first embodiment, further comprising at least one intermediate layer disposed between the metal oxide layer and the adhesive layer.

[0192] In a third embodiment, the present disclosure provides a multi-layer article according to the first or second embodiment, wherein the adhesion layer is directly attached to the metal oxide layer.

[0193] In a fourth embodiment, the present disclosure provides a multilayer article according to any of the first to third embodiments, wherein the metal oxide layer comprises at least one of titanium oxide, aluminum oxide, zinc oxide, tantalum pentoxide, zirconium oxide, or niobium oxide.

[0194] In a fifth embodiment, the present disclosure provides a multi-layer article according to any of the first to fourth embodiments, wherein the metal oxide layer comprises titanium oxide.

[0195] In a sixth embodiment, the present disclosure provides a multilayer article according to any of the first to fifth embodiments, wherein the metal oxide layer has a thickness of 15 nm to 20 nm, 20 nm to 30 nm, or 20 nm to 40 nm.

[0196] In a seventh embodiment, the present disclosure provides a multilayer article according to any of the first to sixth embodiments, exhibiting an average transmittance of 70% or greater for light having a wavelength range greater than at least 410 nm for incident light angles of at least one of 0°, 30°, 45°, 60°, or 75°.

[0197] In an eighth embodiment, the present disclosure provides a multilayer article according to any of the first to seventh embodiments, exhibiting an average transmittance of 10% or less, 7%, 5%, or 2% or less over a wavelength band of at least 30 nanometers having a wavelength of 200 nm to 280 nm, 200 nm to 300 nm, or 200 nm to 320 nm for light having an incident light angle of at least one of 0°, 30°, 45°, 60°, or 75°.

[0198] In a ninth embodiment, the present disclosure provides a multilayer article according to any of the first to eighth embodiments, wherein the metal oxide layer is not part of a multilayer optical film.

[0199] In a tenth embodiment, the present disclosure provides a multi-layer article according to any of the first to ninth embodiments, wherein the adhesive layer comprises a pressure sensitive adhesive or a hot melt adhesive.

[0200] In an eleventh embodiment, the present disclosure provides a multi-layer article according to any of the first to tenth embodiments, wherein the adhesive layer comprises a pressure-sensitive adhesive.

[0201] In a twelfth embodiment, the present disclosure provides a multi-layer article according to any of the first to eleventh embodiments, wherein the adhesive layer comprises a polyisobutylene adhesive, a silicone adhesive, or a (meth)acrylic adhesive.

[0202] In a thirteenth embodiment, the present disclosure provides a multilayer article according to any of the first to twelfth embodiments, wherein the peel force between the metal oxide layer and the adhesive layer is 500 grams / inch (196.9 grams / centimeter) or greater.

[0203] In a fourteenth embodiment, the present disclosure provides a multilayer article according to any of the first to thirteenth embodiments, wherein the peel force between the substrate layer and the metal oxide layer is 500 grams / inch (196.9 grams / centimeter) or greater.

[0204] In a fifteenth embodiment, the present disclosure provides a multi-layer article according to any of the first to fourteenth embodiments, wherein the substrate layer comprises a fluoropolymer.

[0205] In a sixteenth embodiment, the present disclosure provides a multilayer article according to any of the first to fifteenth embodiments, wherein the substrate layer comprises a fluoropolymer (co)polymer comprising polymerized units derived from one or more monomers selected from tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, perfluoroalkoxyalkylene, or a combination thereof.

[0206] In a seventeenth embodiment, the present disclosure provides a multi-layer article according to any of the first to sixteenth embodiments, wherein the substrate layer comprises a silicone thermoplastic polymer.

[0207] In an eighteenth embodiment, the present disclosure provides a multi-layer article according to any of the first to seventeenth embodiments, wherein the substrate layer is a single layer having a thickness of from 10 microns to 500 microns.

[0208] In a nineteenth embodiment, the present disclosure provides a multilayer article according to any of the first to eighteenth embodiments, wherein the substrate layer is a microstructured substrate comprising a base layer having a thickness of at least 1 micron and a plurality of microstructures extending across a first surface of the base layer.

[0209] In a twentieth embodiment, the present disclosure provides a multilayer article according to any of the first to nineteenth embodiments, wherein the microstructured surface comprises peak structures and adjacent valleys, the valleys having a maximum width in the range of 1 micron to 250 microns, and the peak structures having a sidewall angle greater than 10 degrees.

[0210] In a twenty-first embodiment, the present disclosure provides a multilayer article according to any of the first to nineteenth embodiments, wherein the microstructured surface comprises peak structures and adjacent valleys and has a complementary cumulative slope magnitude distribution (Fcc) such that at least 30, 40, 50, 60, 70, 80 or 90% of the structures have a slope greater than 10 degrees and less than 80% of the structures have a slope greater than 35 degrees.

[0211] In a twenty-second embodiment, the present disclosure provides a multi-layer article according to any of the first to nineteenth embodiments, wherein the microstructured surface has less than 30% of its planar surface area parallel to the planar substrate.

[0212] In a twenty-third embodiment, the present disclosure provides a multi-layer article according to any of the first to twenty-second embodiments, wherein the multi-layer article is irradiated with UVC light having a wavelength of 254 nm at a dose of 50 megajoules per square meter (MJ / m 2 ) the change in light transmittance at a wavelength of 400 nm is less than 10% after exposure to a dose of

[0213] In a 24th embodiment, the present disclosure provides a multi-layer article according to any of the 19th to 23rd embodiments, wherein the microstructured surface is capable of providing a base 10 log reduction in microorganisms of at least 2, 3, 4, 5, 6, 7, or 8 after cleaning. [Example]

[0214] The following examples are for illustrative purposes only, and are not intended to unduly limit the scope of the appended claims.

[0215] Unless otherwise stated or apparent from the context, all parts, percentages, ratios, etc. in the examples and elsewhere in the specification are provided by weight.

[0216] [Table 5]

[0217] <Interlayer adhesive strength test> The samples prepared according to the examples and comparative examples described below were tested for interlayer adhesive strength. Two 1-inch by 10-inch (2.54 cm by 25.4 cm) strips were prepared for each example or comparative example sample. The two strips were then further laminated together in an adhesive-to-adhesive configuration. The interlayer adhesive strength of the resulting samples was measured using an IMASS tape peel tester (Model SP-2000) obtained from IMASS, Inc. (Accord, Massachusetts) in accordance with ASTM-D1876-08(2015)e1, "Standard Test Method for Peel Resistance of Adhesives (T-Peel Test)," available from ASTM International (West Consahocken, Pennsylvania). <Light transmittance degradation test> The samples prepared according to the Examples and Comparative Examples described below were measured for light transmittance at 400 nm of 100 megajoules per square meter (MJ / m) using a Shimadzu spectrophotometer obtained from Shimadzu Corporation (Kyoto, Japan) under the trade name "SHIMADZU 2550 UV-VIS." 2The samples were tested before and after exposure to UVC radiation at a wavelength of 254 nm. The percent loss in transmittance due to UVC radiation after exposure was calculated. A decrease in light transmittance at 400 nm indicates that photooxidative degradation has occurred. <Preparation Example 1 (PE1)>: Preparation of THV815GZ fluoropolymer substrate with microstructured surface PE1 THV815GZ fluoropolymer substrates with microstructured surfaces were prepared using a three-roll vertical stack molding apparatus including an extruder and extrusion die adapted to extrude one or more layers of molten thermoplastic material into a mold using the process shown schematically in Figure 13. The mold was purchased from 3M Company (St. Paul, MN) as "3M TM The microstructured film, available under the trade name "Brightness Enhancement Film BEF4-DT-90(24)," was wrapped around a cylindrical casting roll to provide the desired surface pattern for transfer to the molten THV815GZ fluoropolymer from the extruder as it passed over the cylindrical surface of the roll. The mold surface had a linear prism microstructure. The surface temperature of the casting roll was 76.6°C, and the casting roll speed was 18.8 meters / min. A nip force of 7,600 pounds (33,806 N) was applied to the THV815GZ fluoropolymer as it contacted the mold on the casting roll. The resulting THV815GZ fluoropolymer substrate, PE1, was 2 mils (50 micrometers) thick and had a surface containing microstructures in the form of linear prisms. Detailed characteristics of the microstructured surface of the PE1 substrate were determined by confocal laser scanning microscopy (CLSM) and are summarized in the microstructure characteristics table below.

[0218] [Table 6]

[0219] <Preparation Example 2 (PE2)>: Vapor deposition coating of a UV barrier layer (TiO2) on the bottom surface of the PE1 substrate The bottom side of the PE1 substrate (the side opposite the microstructured surface) was coated with a UV barrier coating containing TiO2. This was done using a Denton Vacuum Optical Coater obtained from Denton Vacuum Corporation (Moorestown, New Jersey), which consisted of a five-planet planetary drive system positioned approximately 30 inches (76.2 cm) above a four-pocket Temescal electron beam gun obtained from Ferrotec Corporation (Livermore, California). The planetary system was designed to hold the substrate perpendicular to the evaporation source and allow it to move in and out of the evaporation plume during deposition in a planet-like motion.

[0220] The actual coating process is as follows: a) The evaporation coater was vented to the atmosphere and one of the five planets was removed. The substrate to be coated was secured to the planet with polyimide tape. The sample was positioned so that the bottom surface of PE1 was exposed for coating. b) The planet was reinstalled, and if necessary the other four planets were similarly positioned and reinstalled in the coater. c) Close the chamber and vacuum the chamber until the vacuum level is 2 x 10 -5 Torr (2.7 x 10 -3 The atmosphere was then pumped down to below 100 Pa, which was typically about 10 sccm of additional oxygen gas. d) The planetary was started and moved around the coater at a rotational speed of approximately 60 rpm, preparing the coating to achieve high uniformity on the attached substrate. e) The Temescal electron beam gun was powered on. A voltage of 10 kV and a few milliamps of current were applied to the e-gun filament, heating the TiO2 source material within the e-gun. The TiO2 source was heated and controlled via an Eddy Company Optical Monitoring System (OMS) (from Eddy Company, Apple Valley, CA). The source was heated until the desired deposition rate of 4 Å / s was achieved and stabilized, at which point the shutter separating the source from the planet was opened, maintaining the rate via the OMS until the desired thickness was achieved, at which point the shutter was closed and the OMS turned off power to the e-beam source. f) The power supply was turned off at the mains and the sauce was allowed to cool for approximately 10 minutes. h) The chamber was then returned to atmospheric pressure by passing N2 gas through it, each planet was removed, and the resulting coated PE2 substrate was removed from the coater.

[0221] The thickness of the TiO2 UV barrier layer formed above was about 40 nm. <Comparative Examples 1~3 (CE1~CE3)> The CE1 sample was prepared by manually laminating FSA1250 acrylic pressure-sensitive transfer adhesive to the PE1 fluoropolymer substrate. The adhesive was laminated to the surface of the PE1 fluoropolymer opposite the microstructured surface.

[0222] The CE2 and CE3 samples were prepared in a similar manner to CE1, except that the adhesive used was 91022 silicone acrylic pressure-sensitive transfer adhesive for CE2 and 81504 polyisobutylene pressure-sensitive transfer adhesive for CE3.

[0223] The CE1-CE3 samples were then tested for interlayer bond strength (adhesion between the adhesive and the PE1 fluoropolymer substrate) and loss of light transmission using the tests described above. The test results are summarized in the test results table below. <Examples 4 to 6 (E4 to E6)> Samples E4–E6 were prepared in a similar manner to CE1 above, except that a PE2 fluoropolymer substrate was used and the selected adhesive was laminated to the UV barrier (TiO2) coated side of the PE2 fluoropolymer substrate.

[0224] The adhesives were FSA1250 acrylic pressure sensitive transfer adhesive for E4, 91022 silicone acrylic pressure sensitive transfer adhesive for E5, and 81504 polyisobutylene pressure sensitive transfer adhesive for E63.

[0225] Samples E4-E6 were then tested for interlayer adhesion strength (the bond between the adhesive and the UV barrier coating side of the PE2 fluoropolymer substrate) and loss of light transmission using the tests described above. The test results are summarized in the Test Results table below.

[0226] [Table 7]

Claims

1. a substrate layer comprising a fluoropolymer or a silicone polymer; a metal oxide layer deposited directly on a major surface of the substrate layer and having a thickness of 15 nanometers (nm) to 60 nm; an adhesion layer adjacent to a major surface of the metal oxide layer opposite the substrate layer; 1. A multilayer article that exhibits an average transmittance of 10% or less, 7%, 5%, or 2% or less over a wavelength band of at least 30 nanometers having a wavelength between 200 nm and 400 nm for light having an incident light angle of at least one of 0°, 30°, 45°, 60°, or 75°.

2. The multilayer article of claim 1 further comprising at least one intermediate layer disposed between the metal oxide layer and the adhesive layer.

3. The multilayer article of claim 1 , wherein the adhesive layer is directly attached to the metal oxide layer.

4. 4. The multilayer article of claim 1, wherein the metal oxide layer comprises at least one of titanium oxide, aluminum oxide, zinc oxide, tantalum pentoxide, zirconium oxide, or niobium oxide.

5. The multilayer article of any of claims 1 to 4, wherein the metal oxide layer comprises titanium oxide.

6. 6. The multilayer article of claim 1, wherein the metal oxide layer has a thickness of 15 nm to 20 nm, 20 nm to 30 nm, or 20 nm to 40 nm.

7. 7. The multilayer article of any one of claims 1 to 6, which exhibits an average transmittance of 70% or greater for light having a wavelength range greater than 410 nm at at least one of incident light angles of 0°, 30°, 45°, 60°, or 75°.

8. 8. The multilayer article of any of claims 1 to 7, exhibiting an average transmittance of 10% or less, 7%, 5%, or 2% or less over a wavelength band of at least 30 nanometers having wavelengths between 200 nm and 280 nm, between 200 nm and 300 nm, or between 200 nm and 320 nm, for light at an incident light angle of at least one of 0°, 30°, 45°, 60°, or 75°.

9. The multilayer article of claim 1 , wherein the metal oxide layer is not part of a multilayer optical film.

10. 10. The multilayer article of any of claims 1 to 9, wherein the adhesive layer comprises a pressure sensitive adhesive or a hot melt adhesive.

11. The multilayer article of any of claims 1 to 10, wherein the adhesive layer comprises a pressure sensitive adhesive.

12. 12. The multilayer article of any of claims 1 to 11, wherein the adhesive layer comprises a polyisobutylene adhesive, a silicone adhesive, or a (meth)acrylic adhesive.

13. 13. The multilayer article of any of claims 1 to 12, wherein the peel force between the metal oxide layer and the adhesive layer is 500 grams / inch (196.9 grams / centimeter) or greater.

14. 14. The multilayer article of any of claims 1 to 13, wherein the peel force between the substrate layer and the metal oxide layer is 500 grams / inch (196.9 grams / centimeter) or greater.

15. The multilayer article of any of claims 1 to 14, wherein the substrate layer comprises a fluoropolymer.

16. 16. The multilayer article of any of claims 1 to 15, wherein the substrate layer comprises a fluoropolymer (co)polymer having polymerized units derived from one or more monomers selected from tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, perfluoroalkoxyalkylene, or combinations thereof.

17. 17. The multilayer article of any of claims 1 to 16, wherein the substrate layer comprises a silicone thermoplastic polymer.

18. 18. The multilayer article of any of claims 1 to 17, wherein the substrate layer is a single layer having a thickness of from 10 microns to 500 microns.

19. 19. The multilayer article of any of claims 1 to 18, wherein the substrate layer is a microstructured substrate comprising a base layer having a thickness of at least 1 micron and a plurality of microstructures extending across a first surface of the base layer.

20. 20. The multilayer article of claim 19, wherein the microstructured surface comprises peak structures and adjacent valleys, the valleys having a maximum width in the range of 1 micron to 250 microns, and the peak structures having sidewall angles greater than 10 degrees.

21. 20. The multilayer article of claim 19, wherein the microstructured surface comprises peak structures and adjacent valleys and has a complementary cumulative slope distribution (Fcc) such that at least 30%, 40%, 50%, 60%, 70%, 80%, or 90% of the structures have a slope greater than 10 degrees and less than 80% of the structures have a slope greater than 35 degrees.

22. 20. The multilayer article of claim 19, wherein the microstructured surface has less than 30% of its planar surface area parallel to the planar substrate.

23. UVC light with a wavelength of 254 nm at 50 megajoules per square meter (MJ / m ２ 23. The multilayer article of any of claims 1 to 22, wherein the change in light transmission at a wavelength of 400 nm is less than 10% after exposure to a dose of 100 ppm or less.

24. 24. The multilayer article of any of claims 19-23, wherein the microstructured surface is capable of providing a base 10 log reduction in microorganisms of at least 2, 3, 4, 5, 6, 7, or 8 after cleaning.

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