Multilayer article comprising UV barrier layer

Abstract

The present disclosure provides a multilayer article comprising: a substrate layer comprising a fluoropolymer or a siloxane polymer; a metal oxide layer having a thickness of 15 nm to 60 nm, the metal oxide layer being directly attached to the substrate layer; and an adhesive layer adjacent to the metal oxide layer opposite the substrate layer. The article exhibits an average transmittance of 10% or less, 7%, 5%, or 2% or less for light incident at at least one of an angle of incidence of 0 DEG, 30 DEG, 45 DEG, 60 DEG, or 75 DEG having a wavelength of at least 200 nm to 400 nm and a wavelength bandwidth of at least 30 nm.

Description

SUMMARY

[0001] In a first aspect, a multilayer article is provided. The multilayer article includes a base layer including a fluoropolymer or a siloxane polymer; a metal oxide layer directly attached to a major surface of the base layer, the metal oxide layer 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 base layer. The article exhibits an average transmittance of 10% or less, 7%, 5%, or 2% or less for light having a wavelength of at least 200 nm to 400 nm, a wavelength bandwidth of at least 30 nanometers, and incident at at least one of 0°, 30°, 45°, 60°, or 75° incident angle.

[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 both provide UV blocking and enhance the adhesion of an adhesive to a fluoropolymer or siloxane polymer base layer.

[0003] The above summary of the present disclosure is not intended to describe each disclosed embodiment or implementation of the present disclosure. The following detailed description more particularly exemplifies illustrative embodiments. Throughout several places in the present application, guidance is provided by way of example lists, which can be used in various combinations. In each case, the cited list is only used as a representative group and should not be interpreted as an exclusive list. BRIEF DESCRIPTION OF DRAWINGS

[0004] FIG. 1A is a schematic cross-sectional view of an illustrative article;

[0005] FIG. 1B is a schematic cross-sectional view of an illustrative article;

[0006] FIG. 1C is a perspective view of a Cartesian coordinate system of a surface that can be used to describe various microstructured surfaces;

[0007] FIG. 2A is a cross-sectional view of a microstructured surface;

[0008] FIG. 2B is a perspective view of a microstructured surface;

[0009] FIG. 3 is a perspective view of a microstructured surface including an array of linear prisms;

[0010] FIG. 4A is a perspective view of a microstructured surface including an array of cube corner elements;

[0011] FIG. 4Bis a perspective view of a microstructured surface comprising an array of pyramidal elements;

[0012] FIG. 4C is a perspective view illustrating the size and angles of a cube corner element;

[0013] FIG. 5 is a perspective view of a microstructured surface comprising an array of preferred geometric cube corner elements;

[0014] FIG. 6 is a cross-sectional view of a peak structure having various apex angles;

[0015] FIG. 7A to FIG. 7B is a three-dimensional topography map of a microstructured surface comprising an array of peak structures;

[0016] FIG. 8A to FIG. 8C is a three-dimensional topography map of a microstructured surface comprising an array of peak structures;

[0017] FIG. 9 is a plot of the complement of the cumulative gradient (i.e. slope) size distribution (Fcc);

[0018] FIG. 10 is a plot of the complement of the cumulative X-slope (Ycc);

[0019] FIG. 11 is a plot of the complement of the cumulative Y-slope (Xcc);

[0020] FIG. 12 is a schematic side view of a structure; and

[0021] FIG. 13 is a schematic of a method for making a substrate having a microstructured surface.

[0022] While the above drawings illustrate various embodiments of the present disclosure, other embodiments can also be contemplated as noted in the specification. In all cases, the present disclosure introduces the present invention by way of example and not by way of limitation. The drawings are not necessarily drawn to scale. Like numbers refer to like components throughout the figures. It should be understood, however, that the use of numbers to refer to components in a given figure is not intended to limit the components marked with the same number in another figure. DETAILED DESCRIPTION

[0023] Glossary:

[0024] As used herein, "fluoropolymer" means any organic polymer that includes fluorine.

[0025] As used herein, "non-fluorinated" means not containing fluorine.

[0026] As used herein, “(co)polymer” includes hom(co)polymers and (co)polymers, as well as hom(co)polymers or (co)polymers that can be formed in miscible blends (e.g., by co-extrusion or by reactions including, for example, transesterification reactions). The term “(co)polymer” includes random (co)polymers, block (co)polymers, and star (co)polymers.

[0027] As used herein, “adjacent” includes direct contact (e.g., directly adjacent) and the presence of one or more intervening layers between the adjacent materials.

[0028] As used herein, “incident” with respect to light refers to light falling on or impinging on a material.

[0029] As used herein, “crosslinked” (co)polymer refers to a (co)polymer whose (co)polymer chains are joined together through covalent chemical bonds, typically via crosslinked molecules or groups, to form a networked (co)polymer. Crosslinked (co)polymers are typically characterized by their insolubility but can be swellable in the presence of a suitable solvent.

[0030] As used herein, “curing” refers to a process that induces a chemical change, for example, crosslinking or other reactions that create covalent bonds to harden or increase the viscosity of a multilayer film layer.

[0031] As used herein, “cured (co)polymer” includes both crosslinked (co)polymers and uncrosslinked (co)polymers.

[0032] As used herein, “metal” includes pure metals or metal alloys.

[0033] As used herein, “film” or “layer” refers to an individual layer within a multilayer article.

[0034] As used herein, “substrate” encompasses films and layers, including microstructured films / layers.

[0035] As used herein, in the context of a composition being substantially free of a component, the term “substantially free of” means that the composition contains less than 1 percent by weight (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.

[0036] As used herein, “thermoplastic” refers to a polymer that flows when heated sufficiently above its glass transition point and becomes solid when cooled.

[0037] As used herein, “thermoset” refers to a polymer that permanently sets upon curing and does not flow upon subsequent heating. Thermoset polymers are typically crosslinked polymers.

[0038] As used herein, the term "glass transition temperature" (Tg) of a polymer refers to the transition of a polymer from a glassy state to a rubbery state and can be measured using differential scanning calorimetry (DSC) such as at a heating rate of 10 °C / minute in a stream of nitrogen. When referring to the Tg of a monomer, it is the Tg of a homopolymer of that monomer. The homopolymer must have a sufficiently high molecular weight such that the Tg reaches an asymptotic value, as it is generally accepted that the Tg of a homopolymer will increase to an asymptotic value with increasing molecular weight. The homopolymer should also be understood to be substantially free of moisture, residual monomer, solvents, and other contaminants that can affect Tg. Suitable DSC methods and analysis modes are described in Matsumoto, A. et. al., J. Polym. Sci. A., Polym. Chem. 1993, 31, 2531-2539.

[0039] As used herein, "(meth)acryloyl" or "(meth)acrylate" with respect to a monomer, oligomer, (co)polymer, or compound means a vinyl-functional alkyl ester formed as a reaction product of an alcohol and acrylic or methacrylic acid.

[0040] As used herein, "optically clear" means that the article is free of visually perceptible distortion, haze, or defects as detected by the unaided human eye at a distance of about 1 meter, preferably at a distance of about 0.5 meter.

[0041] As used herein, "optical thickness" when used in reference to a layer means the physical thickness of the layer multiplied by its in-plane refractive index.

[0042] As used herein, "vapor phase coating" or "vapor deposition" means the application of a coating to a substrate surface from the vapor phase, for example, by evaporation and subsequent deposition of a precursor material of the coating or the coating material itself onto the substrate surface. Exemplary vapor phase coating processes include, for example, physical vapor deposition (PVD), chemical vapor deposition (CVD), and combinations thereof.

[0043] By the use of orientational terms such as "on top of," "on," "over," "covering," "uppermost," "underneath," and the like with respect to the position of various elements in the coated articles disclosed herein, we mean the relative position of the elements with respect to a horizontally disposed, upwardly facing substrate. However, unless otherwise indicated, the present invention is not intended to have any particular spatial orientation of the substrate or article either during manufacture or after manufacture or when interpreting the claims.

[0044] As used herein, "radiation" means electromagnetic radiation, unless otherwise indicated.

[0045] As used herein, “scattering” with respect to light wavelengths means causing light to deviate from a straight path and travel in different directions at different intensities.

[0046] As used herein, “reflectance” is a measure of the proportion of light or other radiation that is reflected by a surface when illuminated at normal incidence angle. Reflectance generally varies with wavelength and is reported as a percentage of the incident light that is reflected from the surface (0% - no light reflected, 100 - all light is reflected). Reflectance and reflectivity are used interchangeably herein.

[0047] As used herein, “reflectance” and “reflectivity” refer to the property of reflecting light or radiation, especially measured independent of material thickness.

[0048] As used herein, “average reflectance” refers to the reflectance averaged over a specified wavelength range.

[0049] As used herein, “absorption” refers to a material that converts optical radiant energy into internal energy.

[0050] As used herein, “absorption” with respect to light wavelengths includes both absorption and scattering, as scattered light is ultimately absorbed as well. Absorptance can be determined using the method described in ASTM E903-12 “Standard Test Method for Solar Absorptance, Reflectance, and Transmittance of Materials Using Integrating Spheres.” The absorptance measurements described herein are performed by making transmittance measurements as previously described, and then calculating absorptance using Equation 1.

[0051] As used herein, the term “absorptance” with respect to quantitative measurements refers to the base-10 logarithm of the ratio of incident radiant power to transmitted radiant power through a material. The ratio can be described as the radiant flux received by a material divided by the radiant flux transmitted by the material. Absorptance (A) can be calculated based on internal transmittance (T) according to Equation 1 below:

[0052] A = -log 10 T (1)

[0053] Emissivity can be measured using an infrared imaging radiometer in the method described in ASTM E1933-14 (2018), “Standard Practice for Measuring and Compensating for Emissivity Using Infrared Imaging Radiometers.” According to Kirchhoff’s law of thermal radiation, absorbance is related to emissivity. Absorbance, absorptivity, emissivity, and emittance are used interchangeably herein for the same purpose of emitting infrared energy to the atmosphere. Absorption and emission are also used interchangeably herein.

[0054] As used herein, the terms “transmissivity” and “transmission” refer to the ratio of the total transmission of a layer of material compared to the total transmission received by the material, which accounts for the effects of absorption, scattering, reflection, etc. Transmissivity (T) can be in the range of 0 to 1 or expressed as a percentage (T%).

[0055] As used herein, “transparent” refers to a material (e.g., film or layer) that absorbs less than 20% of light having a wavelength between 350 nm and 2500 nm.

[0056] As used herein, “bandwidth” refers to the width of a continuous band of wavelengths.

[0057] As used herein, “utilitarian” refers to discontinuities that provide a positive contribution to the function of the article. For example, a utilitarian discontinuity that is easy to clean provides a positive contribution to the function of cleaning the article more easily than an article without the utilitarian discontinuity. Representative examples of utilitarian discontinuities include, but are not limited to, cube corner elements and parallel linear prisms with flat faces.

[0058] The words “preferred” and “preferably” refer to a determination of one or more embodiments of the disclosure that may, in some instances, provide certain benefits, but other embodiments can also be preferred, under the same or other circumstances. Additionally, the relative use of terms, such as “one” or “the” or “at least one” or “one or more” or “at least one or more” does not indicate that all embodiments include the same element, but rather that an embodiment can include the element or might not include the element. For example, a composition can include “one or more” of a first element or “one or more” of a second element, and the composition can include both elements or neither element.

[0059] In this application, terms such as “one,” “a,” and “the” are not intended to refer to only a singular entity, but include the general class of which a specific example can be used for illustration. The terms “one,” “a,” and “the” are used interchangeably with the term “at least one” or “one or more.” The phrases “at least one of’ and “comprises at least one of’ followed by a list of two or more items mean that at least one of the items is present from the group of items, and that any combination of the items are possible.

[0060] As used herein, the term "or" is generally used in its usual sense, to mean "and / or", unless the context clearly indicates otherwise.

[0061] The term "and / or" means one or all of the listed elements or a combination of any two or more of the listed elements.

[0062] Likewise, all numerical values herein are assumed to be modified by the term "about" and preferably by the term "exactly". As used herein, the term "about", with respect to a measured quantity, means a deviation of plus or minus ten percent (10%) from the stated value of the measured quantity, to the extent that such a deviation would be expected by a person of ordinary skill in the art exercising an appropriate degree of care. Also herein, numerical ranges are expressed in terms of being "from about X to about Y", which includes all numbers and fractions between the number X and the number Y, and also includes the numbers X and Y themselves. If the numerical values of a range are endpoints, they are included in the range; for example, 1 to 5 includes 1 and 5.

[0063] As used herein, as a modifier of a characteristic or attribute, the term "approximately" means that the characteristic or attribute would be readily recognized by a person of ordinary skill in the art as being sufficiently similar to the recited absolute standard that it is essentially equivalent for the purposes at hand (e.g., within + / - 20% for a quantifiable characteristic). Unless specifically defined otherwise, the term "substantially" means a high degree of approximation (e.g., within + / - 10% for a quantifiable characteristic), but likewise does not require absolute precision or perfect matching. Terms such as identical, equal, uniform, constant, strict, and the like should be understood to be within ordinary tolerances, or within measurement error applicable to the particular situation, rather than requiring absolute precision or perfect matching.

[0064] In a first aspect, a multilayer article is provided. The multilayer article includes:

[0065] a base layer including a fluoropolymer or a siloxane polymer;

[0066] a metal oxide layer directly attached to a major surface of the base layer, the metal oxide layer having a thickness of 15 nanometers (nm) to 60 nm; and

[0067] an adhesive layer adjacent to a major surface of the metal oxide layer opposite the base layer,

[0068] wherein the article exhibits an average transmittance of 10% or less, 7%, 5%, or 2% or less for light having a wavelength of at least 200 nm to 400 nm, a wavelength bandwidth of at least 30 nanometers, and incident at at least one of 0°, 30°, 45°, 60°, or 75° angle of incidence.

[0069] In some cases, the article exhibits an average transmittance of 10% or less, 7%, 5%, or 2% or less for light having a wavelength of 200 nm to 280 nm, 200 nm to 300 nm, or 200 nm to 320 nm, a wavelength bandwidth of at least 30 nanometers, and an angle of incidence of at least one of 0°, 30°, 45°, 60°, or 75°.

[0070] Referring to FIG. 1A , the multilayer article 100a includes a base layer 10 including a fluoropolymer or a siloxane polymer, a metal oxide layer 20 directly attached to a major surface 12 of the base layer, the metal oxide layer 20 having a thickness of 15 nanometers (nm) to 60 nm, and an adhesive layer 30 adjacent to a major surface 22 of the metal oxide layer 20 opposite the base layer 10. In this embodiment, the adhesive layer 30 is directly adjacent (i.e., attached to) the major surface 22 of the metal oxide layer 20.

[0071] It is additionally noted that the base layer 10 has a major surface 14 opposite the major surface 12, the metal oxide layer 20 has a major surface 24 opposite the major surface 22, and the adhesive layer has opposite major surfaces 32 and 34. In certain embodiments, the major surface 12 of the base layer 10 is directly adjacent to the major surface 24 of the metal oxide layer 20, and the major surface 22 of the metal oxide layer 20 is directly adjacent to the major surface 34 of the adhesive layer 30.

[0072] Referring to FIG. 1B , the multilayer article 100b includes a base layer 10 including a fluoropolymer or a siloxane polymer, a metal oxide layer 20 directly attached to a major surface 12 of the base layer, the metal oxide layer 20 having a thickness of 15 nanometers (nm) to 60 nm, an adhesive layer 30 adjacent to a major surface 22 of the metal oxide layer 20 opposite the base layer 10, and an intermediate layer 40 disposed between the metal oxide layer 20 and the adhesive layer 30. The one or more intermediate layers can be represented by the depiction of layer 40 in FIG. 1B .

[0073] It is additionally noted that the intermediate layer 40 has opposite major surfaces 42 and 44. In certain embodiments, the major surface 42 of the intermediate layer 40 is directly adjacent to the major surface 34 of the adhesive layer 30, and the major surface 44 of the intermediate layer 40 is directly adjacent to the major surface 22 of the metal oxide layer 20.

[0074] A suitable intermediate layer is a primer layer, for example, to improve the adhesion between the metal oxide layer and the adhesive layer. In some cases, the primer layer can be formed by a pretreatment scheme of discharge pretreatment (e.g., plasma, glow discharge, corona discharge, dielectric barrier discharge, or atmospheric pressure discharge), chemical pretreatment, or flame pretreatment of the metal oxide layer in the presence of a reactive or non-reactive atmosphere. In one embodiment, the method may include plasma pretreatment. In some cases, the primer layer can be formed from primer materials such as those commercially available under the trade names “BETAPRIME” or “TYVEK” from DuPont, Wilmington, DE.

[0075] As described above, it has been found that metal oxide thin layers can provide both UV blocking properties and enhance the adhesion of adhesives to fluoropolymer or silicone polymer substrates. Preferably, this adhesion results in a peel force of 500 g / in (196.9 g / cm) or greater between the metal oxide layer and the adhesive layer. One method to determine the UV blocking properties of an article is to measure the change in transmittance through the article after exposure to UVC light. For example, the inclusion of a metal oxide layer in the article preferably results in a greater peel force after exposure to a dose of 50 megajoules / m² (MJ / m²). 2 After exposure to UVC light with a wavelength of 254 nm, the transmittance changed by less than 10% at a wavelength of 400 nm.

[0076] Metal Oxide Layer

[0077] Typically, the metal oxide layer comprises titanium oxide, aluminum oxide, zinc oxide, tantalum pentoxide, zirconium oxide, or niobium oxide. In a selected embodiment, the metal oxide layer comprises titanium oxide.

[0078] It should be noted that various multilayer optical films have employed at least one metal oxide layer to collectively provide at least one customized optical property, including, for example, transmittance at a specific wavelength within a desired range. However, the metal oxide layer of this disclosure is not part of a multilayer optical film. In other words, the metal oxide layer does not constitute a layer of the multilayer optical film. Instead, the metal oxide layer consists of one or more metal oxides with a continuous thickness of 15 nm to 60 nm. Therefore, the metal oxide layer can be formed from only one type of metal oxide, or it can be formed from a combination of two or more metal oxides.

[0079] The metal oxide layer has a thickness of 15 nm or greater, 17 nm, 20 nm, 22 nm, 25 nm, 27 nm, or 30 nm or greater; and 60 nm or less, 57 nm, 55 nm, 52 nm, 50 nm, 47 nm, 45 nm, 42 nm, 40 nm, 37 nm, 35 nm, 32 nm, 30 nm, 27 nm, 25 nm, 22 nm, or 20 nm or less. In some cases, the metal oxide layer has a thickness of 15 nm to 20 nm, 20 nm to 30 nm, or 20 nm to 40 nm. When the thickness is less than 15 nm, it can be difficult to form a continuous layer, rather than discrete islands of deposited metal oxide material. When the thickness is too great, the metal oxide layer has a risk of imparting a visible color to the article and / or reducing the transmittance of visible light through the metal oxide layer.

[0080] Preferably, the metal oxide layer does not contribute to the article having a yellow appearance. For example, by measuring the transmittance of light through the article, it can be determined whether the article has a yellow appearance. A yellow appearance is not observed when the article exhibits an average transmittance of 70% or greater for light having a wavelength range of at least 410 nm or greater, incident at at least one of 0°, 30°, 45°, 60°, or 75° incident angles. Correspondingly, the article can exhibit a yellow appearance when the article exhibits an average transmittance of less than 70% for light having a wavelength range of at least 410 nm or greater, incident at at least one of 0°, 30°, 45°, 60°, or 75° incident angles.

[0081] As described above, the article (e.g., overall) exhibits an average transmittance of 10% or less, 7%, 5%, or 2% or less for light having a wavelength of at least 200 nm to 400 nm, a wavelength bandwidth of at least 30 nanometers, incident at at least one of 0°, 30°, 45°, 60°, or 75° incident angles.

[0082] The metal oxide layer can generally 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. Evaporated coatings rely on heating the coating material (evaporant) to a temperature at which it evaporates. This is followed by condensation of the vapor on the substrate. For evaporated coatings, the most commonly used process is electron beam deposition. Sputtered coatings use high-energy gas ions to bombard a material (“target”) surface, ejecting atoms that subsequently condense on a nearby substrate. Depending on the coating method used and the settings for that method, the thin film coating rate and structure-property relationships will be strongly influenced. Desirably, the coating rate should be high enough to allow for acceptable process throughput and film properties, featuring dense, low-stress, void-free, non-optically absorbing coatings.

[0083] Adhesive Layer

[0084] Exemplary adhesives suitable for the adhesive layer include pressure sensitive adhesives and hot melt adhesives. In selected embodiments, the adhesive layer comprises a pressure sensitive adhesive.

[0085] Classes of suitable pressure sensitive adhesives include acrylic, tackified rubber, tackified synthetic rubber, ethylene vinyl acetate, and the like. Suitable acrylic adhesives are disclosed in, for example, U.S. Patent 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.

[0086] In some cases, the adhesive is transparent. In selected embodiments, the adhesive is optically clear, meaning that the adhesive has both transparency and clarity (e.g., low haze). In certain embodiments, the optically clear adhesive (OCA) is selected from acrylate, polyurethane, polyolefin such as polyisobutylene (PIB), siloxane, or combinations thereof. Exemplary OCAs include those described in International Publication No. WO 2008 / 128073 (Everaerts et al.) relating to antistatic optically clear pressure sensitive adhesives; U.S. Patent Application Publication No. US 2009 / 089137 (Sherman et al.) relating to stretch release OCAs; US 2009 / 0087629 (Everaerts et al.) relating to OCAs compatible with indium tin oxide; US 2010 / 0028564 (Cheng et al.) relating to antistatic optical constructions with light transmitting adhesives; US 2010 / 0040842 (Everaerts et al.) relating to adhesives compatible with etch sensitive layers; US 2011 / 0126968 (Dolezal et al.) relating to optically clear stretch release tapes; and U.S. Patent No. 8,557,378 (Yamanaka et al.) relating to stretch release tapes. Suitable OCAs include acrylic optically clear pressure sensitive adhesives such as, for example, 3M OCA 8146, 8211, 8212, 8213, 8214, and 8215, each commercially available from 3M Company, St. Paul, MN. Some suitable siloxane adhesives are commercially available under the trade designations “3M Adhesive Transfer Tape 91022” (e.g., 2 mil thick clear roll) and “3M Adhesive Transfer Tape 96042,” both available from 3M Company, St. Paul, MN.

[0087] In some embodiments, the adhesive can be resistant to ultraviolet radiation damage. For example, exemplary adhesives that are generally resistant to ultraviolet radiation damage include silicone adhesives and acrylic adhesives containing UV stabilizing / blocking additives. For example, U.S. Patent No. 5,504,134 (Palmer et al.) describes attenuating degradation of a polymeric substrate due to ultraviolet radiation by using metal oxide particles having a size in the range of about 0.001 microns to about 0.2 microns (in some embodiments, in the range of about 0.01 microns to about 0.15 microns). U.S. Patent No. 5,876,688 (Laundon) describes a process for producing micronized zinc oxide that is small enough to be transparent when incorporated as a UV blocker and / or scatterer in paints, coatings, finishes, plastic articles, cosmetics, and the like, and is well suited for use in the present disclosure. These fine particles (such as zinc oxide and titanium oxide) having a particle size in the range of 10 nm to 100 nm that can attenuate UV radiation are commercially available from, for example, Kobo Products, Inc., South Plainfield, NJ.

[0088] 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 the article.

[0089] In selected embodiments, the adhesive layer comprises a polyisobutylene adhesive, a silicone adhesive, or a (meth)acrylic adhesive.

[0090] Substrate Layer

[0091] As described above, the base layer comprises a fluoropolymer or a silicone polymer. In certain embodiments, the base layer comprises a fluoropolymer.

[0092] 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 under the trade designation 3M DYNEON THV from 3M Company); copolymers of TFE, HFP, vinylidene fluoride, and perfluoropropyl vinyl ether (PPVE) (e.g., available under the trade designation 3M DYNEON THVP from 3M Company); polyvinylidene fluoride (PVDF) (e.g., available under the trade designation 3M DYNEON PVDF 6008 from 3M Company); ethylene-chlorotrifluoroethylene polymer (ECTFE) (e.g., available under the trade designation HALAR 350 LC ECTFE from Solvay, Brussels, Belgium); ethylene tetrafluoroethylene copolymer (ETFE) (e.g., available under the trade designation 3M DYNEON ETFE 6235 from 3M Company); perfluoroalkoxy alkane polymer (PFA); fluorinated ethylene propylene copolymer (FEP); polytetrafluoroethylene (PTFE); copolymers of TFE, HFP, and ethylene (HTE) (e.g., available under the trade designation 3M DYNEON HTE 1705 from 3M Company). Combinations of fluoropolymers can also be used. In some embodiments, the fluoropolymer comprises FEP. In some embodiments, the fluoropolymer comprises PFA.

[0093] In certain embodiments, the base layer comprises a fluoropolymer (co)polymer comprising polymerized units derived from one or more monomers selected from tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, perfluoroalkoxy alkane, or combinations thereof. Suitable fluoropolymers are available under the trade designation “TEFLON FEP100” from E.I. DuPont de Nemours, Wilmington, DE, with “TEFLON FEP100 500A” being presently preferred. Suitable exemplary fluoropolymers also include copolymers of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride (THV) available under the trade designations “DYNEON THV 220,” “DYNEON THV 221,” “DYNEON THV 230,” “DYNEON THV 2030,” “DYNEON THV 415,” “DYNEON THV 500,” “DYNEON THV 610,” and “DYNEON THV 815” from Dyneon LLC, Oakdale, MN.

[0094] In certain embodiments, the base layer comprises a siloxane thermoplastic polymer. One suitable siloxane is available under the trade designation "DOW CORNING 93-500 SPACE LEVEL ENCAPULANT KIT" from Dow Corning Corporation, Midland, MI. Another suitable siloxane is available under the trade designation "SILPURAN FILM" from Wacker Chemie AG, Munich, Germany.

[0095] In some cases, the base layer has a thickness of 10 micrometers or greater, 15 micrometers, 20 micrometers, 25 micrometers, 30 micrometers, 35 micrometers, 40 micrometers, 50 micrometers, 60 micrometers, 70 micrometers, 80 micrometers, 90 micrometers, 100 micrometers, 120 micrometers, 140 micrometers, 160 micrometers, 180 micrometers, 200 micrometers, 220 micrometers, or 250 micrometers or greater; 500 micrometers or less, 475 micrometers, 450 micrometers, 425 micrometers, 400 micrometers, 375 micrometers, 350 micrometers, 325 micrometers, 300 micrometers, 275 micrometers, 250 micrometers, 225 micrometers, 200 micrometers, 175 micrometers, 150 micrometers, 125 micrometers, or 100 micrometers or less. In selected embodiments, the base layer is a single layer having a thickness as described above. In certain embodiments, the base layer is self-supporting.

[0096] Certain microstructured surfaces exhibit better bacterial removal upon cleaning, even compared to smooth surfaces. In some cases, the base layer is a microstructured base comprising: a base layer having a thickness of at least 1 micrometer; and a plurality of microstructures extending across a first surface of the base layer.

[0097] While articles having certain microstructural features can be used to reduce the initial formation of biofilm, particularly for medical articles; in the case of other articles, such microstructured surfaces can be difficult to clean. This is believed to be due, at least in part, to the bristles of a brush or the fibers of a (e.g., nonwoven) wipe being larger than the spaces between the microstructures. It has been found that some types of microstructured surfaces exhibit better microorganism (e.g., bacterial) removal upon cleaning, even compared to smooth surfaces. The article is not typically a sterile implantable medical article. Rather, the microstructured surface is typically in contact with humans and / or animals and other contaminants (e.g., soil). Some 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, sports articles, food preparation articles, child care articles, or building articles.

[0098] The microstructured surface generally provides at least a log 10 reduction of 2, 3, 4, 5, 6, 7, or 8 of microorganisms (e.g., bacteria) after cleaning. The microstructured surface provides improved removal of microorganisms (e.g., bacteria) compared to surfaces lacking microstructuring, whether the microstructured surface is mechanically cleaned with a wipe or brush and / or cleaned by applying an antimicrobial solution to the microstructured surface.

[0099] Referring to FIG. 1, a microstructured surface can be characterized in three-dimensional space by superimposing a Cartesian coordinate system onto its structure. A first reference plane 124 is centered between major surfaces 112 and 114. The first reference plane 124, referred to as the y-z plane, has the x-axis as its normal vector. A second reference plane 126, referred to as the x-y plane, extends substantially coplanar with surface 116 and has the z-axis as its normal vector. A third reference plane 128, referred to as the x-z plane, is centered between first end surface 120 and second end surface 122 and has the y-axis as its normal vector.

[0100] In some embodiments, the microstructured surfaces are three-dimensional on a macroscopic scale. However, on a microscopic scale (e.g., a surface area comprising at least two adjacent microstructures with a valley or channel disposed between the microstructures), the base layer / base member can be considered planar with respect to the microstructures. The width and length of the microstructures are in the x-y plane, and the height of the microstructures is in the z-direction. Further, the base layer is parallel to the x-y plane and orthogonal to the z-plane.

[0101] FIG. 2A is an exemplary cross-section of a microstructured surface 200 of practical discontinuity. Such a cross-section represents a plurality of discrete (e.g., column or rib) microstructures 220. The microstructure includes a base 212 adjacent to a (e.g., engineered) planar surface 216 (parallel to surface 116 of reference plane 126 of FIG. 1C ). A top (e.g., planar) surface 208 (parallel to surface 216 and FIG. 1C reference plane 126 of ) is spaced from base 212 by a height (“H”) of the microstructure. Sidewalls 221 of microstructure 220 are perpendicular to planar surface 216. When sidewalls 221 are perpendicular to planar surface 216, the sidewall angle of the microstructure is zero degrees. In terms of the perpendicular sidewalls of the peak microstructure, they are parallel to each other and parallel to adjacent microstructures having perpendicular sidewalls. Alternatively, microstructure 230 has sidewalls 231 that are angled rather than perpendicular with respect to planar surface 216. Sidewall angle 232 can be defined by sidewalls 231 and perpendicular to planar surface 216 (perpendicular to FIG. 1CThe intersection of the reference plane 233 (which is parallel to the reference plane 126 and parallel to the reference plane 128) defines the intersection of the reference plane 233 with the reference plane 126 and the reference plane 128. In the case of a privacy film, for example, such as described in US 9,335,449 (Gaides et al.); the sidewall angle is typically less than 10 degrees, 9 degrees, 8 degrees, 7 degrees, 6 degrees, or 5 degrees. Since the channels of a privacy film include light-absorbing material, a larger sidewall angle can reduce transmission. However, a sidewall angle close to zero degrees is also more difficult to clean.

[0102] A suitable surface is a microstructured surface that includes microstructures having a sidewall angle greater than 1 degree, 2 degrees, 3 degrees, 4 degrees, 5 degrees, 6 degrees, 7 degrees, 8 degrees, 9 degrees, or 10 degrees. In some embodiments, the sidewall angle is at least 11 degrees, 12 degrees, 13 degrees, 14 degrees, 15 degrees, 16 degrees, 17 degrees, 18 degrees, 19 degrees, or 20 degrees. In other embodiments, the sidewall angle is at least 21 degrees, 22 degrees, 23 degrees, 24 degrees, 25 degrees, 26 degrees, 27 degrees, 28 degrees, 29 degrees, or 30 degrees. For example, in some embodiments, the microstructures are cube comer peak structures having a sidewall angle of 30 degrees. In other embodiments, the sidewall angle is at least 31 degrees, 32 degrees, 33 degrees, 34 degrees, 35 degrees, 36 degrees, 37 degrees, 38 degrees, 39 degrees, 40 degrees, 41 degrees, 42 degrees, 43 degrees, 44 degrees, or 45 degrees. For example, in some embodiments, the microstructures are prismatic structures having a sidewall angle of 45 degrees. In other embodiments, the sidewall angle is at least 46 degrees, 47 degrees, 48 degrees, 49 degrees, 50 degrees, 51 degrees, 52 degrees, 53 degrees, 54 degrees, 55 degrees, 56 degrees, 57 degrees, 58 degrees, 59 degrees, or 60 degrees. It will be appreciated that a microstructured surface will be beneficial even when some of the sidewalls have a lower sidewall angle. For example, if half of the array of peak structures has a sidewall angle within the desired range, then about half the benefit of improved microorganism (e.g., bacteria) removal can be obtained. Thus, in some embodiments, less than 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, or 1% of the peak structures have a sidewall angle less than 10 degrees, 9 degrees, 8 degrees, 7 degrees, 6 degrees, 5 degrees, 4 degrees, 3 degrees, 2 degrees, or 1 degree. In some embodiments, less than 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, or 1% of the peak structures have a sidewall angle less than 30 degrees, 25 degrees, 20 degrees, or 15 degrees. In some embodiments, less than 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, or 1% of the peak structures have a sidewall angle less than 40 degrees, 35 degrees, or 30 degrees, and at least 50%, 60%, 70%, 80%, 90%, 95%, or 99% of the peak structures have a sidewall angle that is large enough, as described above.

[0103] As described, for example, in PCT Publication No. WO 2013 / 003373 (Bommarito et al.), microstructures having cross-sectional dimensions no greater than 5 microns are believed to significantly interfere with the settling and adhesion of target bacteria responsible for medical-related infection or other biological contamination issues, such as increased drag, decreased heat transfer, filter contamination, etc. Referring to FIG. 2A , the cross-sectional width of the microstructures ("W M ") as depicted in this figure is less than or equal to the cross-sectional width of the channels or valleys between adjacent microstructures ("Wv"). Thus, as depicted (in this linear prismatic embodiment), when the cross-sectional width of the microstructures (W M ) is no greater than 5 microns, the cross-sectional width of the channels or valleys between the microstructures (Wv) is also no greater than 5 microns. When the sidewall angle of the microstructures on either side of the valley is zero, such as depicted by microstructure 220 of FIG. 2A , the channel or valley defined by the sidewalls has the same width (W V ) adjacent the top surface 208 and adjacent the bottom surface 212. When the sidewall angle of the microstructures is greater than zero, such as depicted by line 231 of microstructure 230, the valley adjacent the top surface 208 typically has a greater (e.g., maximum) width compared to the width of the channel or valley adjacent the bottom surface 212. It has been found that when the sidewall angle is too small and / or the maximum width of the valley is too small, and / or the microstructured surface includes an excessive amount of flat surface area, the microstructured surface is more difficult to clean.

[0104] Suitable microstructured surfaces include microstructures in which the valleys have a maximum width of at least 1 micron, 2 microns, 3 microns, or 4 microns, and optionally greater than 5 microns, 6 microns, 7 microns, 8 microns, 9 microns, or 10 microns, ranging up to 250 microns. In some embodiments, the valleys have a maximum width of at least 1 micron, 2 microns, 3 microns, 4 microns, 5 microns, 6 microns, 7 microns, 8 microns, 9 microns, 10 microns, 11 microns, 12 microns, 13 microns, 14 microns, 15 microns, 16 microns, 17 microns, 18 microns, 19 microns, 20 microns, 21 microns, 22 microns, 23 microns, 24 microns, or 25 microns. In some embodiments, the valleys have a maximum width of no more than 1000 microns, 950 microns, 900 microns, 850 microns, 800 microns, 750 microns, 700 microns, 650 microns, 600 microns, 550 microns, 500 microns, 450 microns, 400 microns, 350 microns, 300 microns, 250 microns, 225 microns, 200 microns, 175 microns, 150 microns, 125 microns, 100 microns, 75 microns, or 50 microns. In some embodiments, the valleys have a maximum width of no more than 45 microns, 40 microns, 35 microns, 30 microns, 25 microns, 20 microns, or 15 microns. It will be appreciated that a microstructured surface will be beneficial even if some of the valleys are less than the maximum width. For example, if half of the total number of valleys of a microstructured surface are within the desired range, then about half of the benefit can be obtained. Thus, in some embodiments, less than 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, or 1% of the valleys have a minimum width of less than 10 microns, 9 microns, 8 microns, 7 microns, 6 microns, or 5 microns. Alternatively, as described above, at least 50%, 60%, 70%, 80%, 90%, 95%, or 99% of the valleys have a maximum width.

[0105] In typical embodiments, the microstructures have a maximum width falling within the same ranges as described for the valleys. In other embodiments, the width of the valleys can be greater than the width of the microstructures. Thus, in some advantageous embodiments, the microstructured surface is generally substantially free of microstructures having a width of less than 5 microns, 4 microns, 3 microns, 2 microns, or 1 micron, including nanostructures having a width of less than 1 micron. By substantially free, it is meant that there are no such microstructures, or there can be some such microstructures, provided that the presence of such microstructures does not degrade the cleanability properties, as will be described subsequently.

[0106] The microstructured surface can or can not include nanostructures.

[0107] While smaller structures including nanostructures can prevent biofilm formation, the presence of a large number of smaller valleys and / or valleys with insufficient sidewall angles can hinder cleanability including soil removal. Thus, typically microstructured surfaces lack a large number of structures with smaller valleys and / or valleys with insufficient sidewall angles that can hinder cleanability, including soil removal. Further, microstructured surfaces with larger microstructures and valleys can typically be manufactured at a faster rate. Thus, in typical embodiments, each of the dimensions of the microstructures is at least 1 micron, 2 microns, 3 microns, 4 microns, 5 microns, 6 microns, 7 microns, 8 microns, 9 microns, 10 microns, 11 microns, 12 microns, 13 microns, 14 microns, or 15 microns. Further, in certain embodiments, at least 50%, 60%, 70%, 80%, 90%, 95%, or 99% of the microstructures have dimensions that are not less than 5 microns, 4 microns, 3 microns, 2 microns, or 1 micron.

[0108] In some embodiments, the microstructured surface is typically substantially free of microstructures having a width of less than 5 microns, 4 microns, 3 microns, 2 microns, or 1 micron, including nanostructures having a width of less than 1 micron. Some examples of microstructured surfaces further including nanostructures are described in the previously cited WO 2012 / 058605. Nanostructures typically include at least one or two dimensions (e.g., width and height) that are no more than 1 micron, and typically one or two dimensions that are less than 1 micron. In some embodiments, all dimensions of the nanostructures are no more than 1 micron or less than 1 micron.

[0109] Substantially free means that such microstructures are not present, or some such microstructures can be present, provided that their presence does not reduce (e.g., cleanability) properties as will be described subsequently. Thus, the microstructured surface or microstructures thereof can also include nanostructures, provided that the microstructured surface provides a reduction in the presence of microorganisms after cleaning and / or a reduction in microorganism touch transfer as described herein. Further, in this embodiment, the presence of smaller microstructures and / or nanostructures does not prevent or significantly reduce the formation of biofilm.

[0110] In some embodiments, the microstructured surface can also include nanostructures. Other microstructured surfaces that also include nanostructures are known. For example, US 2013 / 0216784 to Zhang et al. describes a superhydrophobic film that includes planar surfaces spaced apart by valleys. The valleys and surfaces can be covered with nanostructures. The superhydrophobic film has a static water contact angle of at least 140 degrees, 145 degrees, or 145 degrees. Such nanostructures typically have an aspect ratio of at least about 1 : 1, 2: 1, 3: 1, 4: 1, 5: 1, or 6: 1. As shown, the ratio of nanostructures to microstructures is about 20: 1.

[0111] In other embodiments, in which the microstructured surface includes few or no nanostructures, 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.

[0112] In other embodiments, the microstructured surface can also include randomly distributed recesses, as described in WO 2009 / 079275 to Aronson et al. The presence of randomly distributed recesses improves diffusion compared to the same microstructured surface without such recesses.

[0113] The presence of nanostructures and recesses can trap dirt, particularly clay having a particle size of less than 1 micron. However, for embodiments in which the microstructured surface is used inside a display or other uses in which the microstructured surface is not cleaned, the microstructured surface can include nanostructures and randomly distributed recesses.

[0114] When the facets of the microstructures are such that the peaks and valleys are sharp or rounded but not truncated, the microstructured surface can be characterized as having no flat surfaces parallel to the planar base layer. However, where the peaks and / or valleys are truncated, the microstructured surface typically includes less than 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, or 1% of flat surface area substantially parallel to the planar base layer. In one embodiment, the valleys can have flat surfaces and only one of the sidewalls of the peaks is angled, such as FIG. 2B However, in advantageous embodiments, both sidewalls of adjacent peaks defining a valley are angled toward each other, as previously depicted. Thus, the sidewalls on either side of the valley are not parallel to each other.

[0115] The FIG. 9 A comparative microstructured surface having discontinuous valleys is depicted. Such surfaces are also described as having groups of features arranged relative to each other so as to define tortuous paths. In contrast, the valleys intersect with walls, forming a single cell array, each cell surrounded by walls. Some of the cells have a length of about 3 microns; while others have a length of about 11 microns.

[0116] Suitable microstructured surfaces have valleys that are substantially free of sidewalls or other obstacles intersecting the valleys. By substantially free, it is meant that there are no sidewalls or other obstacles within the valleys, or there can be some sidewalls or other obstacles, provided that the presence of these sidewalls or other obstacles does not degrade cleanability properties. The valleys are typically continuous in at least one direction. This can facilitate the flow of cleaning solution through the valleys. Thus, the arrangement of peaks typically does not define tortuous paths.

[0117] The peak structures generally have a height (H) ranging from 1 micron to 250 microns. In some embodiments, the height of the microstructures is at least 2 microns, 3 microns, 4 microns, or 5 microns. In some embodiments, the height of the microstructures is at least 6 microns, 7 microns, 8 microns, 9 microns, or 10 microns. In some embodiments, the height of the microstructures is no greater than 225 microns, 200 microns, 175 microns, 150 microns, 125 microns, 100 microns, 90 microns, 80 microns, 70 microns, 60 microns, or 50 microns. In some embodiments, the height of the microstructures is no greater than 45 microns, 40 microns, 35 microns, 30 microns, or 25 microns. In some embodiments, the height of the microstructures is no greater than 24 microns, 23 microns, 22 microns, 21 microns, 20 microns, 19 microns, 18 microns, 17 microns, 16 microns, 15 microns, 14 microns, 13 microns, 12 microns, 11 microns, 10 microns, 9 microns, 8 microns, 7 microns, 6 microns, or 5 microns. In selected embodiments, the peak structures each have a height of 10 microns to 250 microns. In typical embodiments, the height of the valleys or channels is within the same ranges just described for the peak structures. In some embodiments, the peak structures and valleys have the same height.

[0118] The height-to-width ratio of a valley is the height of the valley (which can be the same as the height of the peaks of the microstructures) divided by the maximum width of the valley. In some embodiments, the height-to-width ratio of a valley is at least 0.1, 0.15, 0.2, or 0.25. In some embodiments, the height-to-width 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 is generally no greater than, and more typically less than, the maximum width of the valley.

[0119] The base of each microstructure can include various cross-sectional shapes including, but not limited to, parallelogram, rectangle, square, circle, semicircle, semi-ellipse, triangle, trapezoid, other polygon (e.g., pentagon, hexagon, octagon), etc., with optional rounded corners, and combinations thereof.

[0120] Suitable microstructured surfaces include an array of peak structures and adjacent valleys. The maximum width of these valleys is preferably in the range of 1 micron to 250 microns. In some embodiments (e.g., for improved cleanability), the sidewall angle of these peak structures is greater than 10 degrees. These peak structures can include two or more facets, such as in the case of an array of linear prisms or an array of cube corner elements. In some embodiments, the facets of these peak structures form an apex angle that is generally in the range of about 20 degrees to about 120 degrees. The facets form a continuous or semi-continuous surface in the same direction. These valleys are generally free of intersecting walls.

[0121] The microstructured surfaces described herein do not prevent the presence of microorganisms (e.g., bacteria such as Streptococcus mutans, Staphylococcus aureus, or Pseuodomonas aeruginosa) on the microstructured surface, or in other words, do not prevent biofilm formation. However, such microstructured surfaces have been shown to be more easily cleanable, thereby providing a low number of microorganisms (e.g., bacteria) after cleaning. Without wishing to be bound by theory, scanning electron microscopy images suggest that large continuous biofilms are typically formed on smooth surfaces. However, even though the peaks and valleys are much larger than the microorganisms (e.g., bacteria), the biofilm is still broken up by the microstructured surface. In some embodiments, the biofilm (before cleaning) is present on the microstructured surface in the form of discrete aggregates and small groups of cells, rather than in the form of a continuous biofilm. After cleaning, the biofilm aggregates in the form of small pieces cover the smooth surface. However, the microstructured surface is observed to have only small groups of cells and individual cells after cleaning. In advantageous embodiments, the microstructured surface has a logio reduction of microorganisms (e.g., bacteria such as Streptococcus mutans, Staphyloccus aureus, or Pseuodomonas aeruginosa) of at least 2, 3, 4, 5, 6, 7, or 8 after cleaning. In some embodiments, the microstructured surface has an average logio of recovered colony forming units of microorganisms that is less than 6, 5, 4, or 3 after cleaning a highly contaminated surface.

[0122] In some embodiments, the microstructured surface can prevent the cleaning solution, which is based on water or alcohol (e.g., isopropyl alcohol), from forming beads as compared to a smooth surface composed of the same polymeric material. When the cleaning solution forms beads, or in other words, re-enters, the disinfectant can not come into contact with the microorganisms for a sufficient duration of time to kill the microorganisms. However, it has been found that at least 50%, 60%, 70%, 80%, or 90% of the microstructured surface can comprise the cleaning solution 1, 2, and 3 minutes after the cleaning solution is applied to the microstructured surface.

[0123] In one embodiment, the microstructured surface can have the same surface as a brightness enhancement film. As described in, for example, US 7,074,463 (Jones et al.), backlit liquid crystal displays typically include a brightness enhancement film positioned between a diffuser and a liquid crystal display panel. The brightness enhancement film collimates light, thereby increasing the brightness of the liquid crystal display panel, and also allows for a reduction in the power of the light source. Thus, brightness enhancement films have been used as internal components of illuminated display devices (e.g., mobile phones, computers) that are not exposed to microorganisms (e.g., bacteria) or dirt.

[0124] Referring to FIG. 3 In one embodiment, the microstructured surface 300 comprises a linear array of right rectangular prisms 320. Each prism has a first facet 321 and a second facet 322. The prisms are illustrated as formed on a base member 310 having a first planar surface 331 (parallel to the reference plane 126) on which the prisms are formed and a second surface 332 that is substantially flat or planar and opposite the first surface. The right rectangular prisms mean that their apex angle Θ, 340, is generally about 90°. However, the angle can range from 70° to 120°, and can range from 80° to 100°. The apices can be sharp (as illustrated), rounded, or truncated. The spacing between (e.g., prismatic) peaks can be characterized as a pitch (“P”). In this embodiment, the pitch is also equal to the maximum width of the valleys. Thus, as previously described, the pitch is greater than 1 micron, 2 microns, 3 microns, 4 microns, 5 microns, 6 microns, 7 microns, 8 microns, 9 microns, or 10 microns, ranging up to 250 microns. The length (“L”) of the microstructure (e.g., prismatic) is generally the maximum dimension and can span the entire dimension of the microstructured surface. The facets of the prisms need not be identical, and the prisms can also be tilted relative to one another, as FIG. 6 illustrated.

[0125] In another embodiment, the microstructured surface can have the same surface as a cube corner retroreflective sheeting. Retroreflective materials are characterized by the ability to redirect light incident on the material back toward the original light source. This property has made retroreflective sheeting widely used in a variety of traffic and personal safety applications. Referring to FIG. 4A , a cube corner retroreflective sheeting generally comprises a thin transparent layer having a substantially planar front surface and a rear structured surface 410 comprising a plurality of cube corner elements 417. A sealing film (not shown) is generally applied to the back of the cube corner elements; see, e.g., U.S. Patent No. 4,025,159 (McGrath) and U.S. Patent No. 5,117,304 (Huang et al.). The sealing film preserves an air interface on the right angle back that is capable of producing total internal reflection at the interface and inhibits the ingress of contaminants such as dirt and / or moisture.

[0126] FIG. 4AThe microstructured surface 410 can be characterized as an array of cubic corner elements 417 defined by three sets of parallel trenches (i.e., valleys) 411, 412, and 413; two sets of trenches (i.e., valleys) intersect each other at an angle greater than 60 degrees, and a third set of trenches (valleys) intersects each of the other two sets at an angle less than 60 degrees to form an array of tilted pairs of cubic corner elements (see U.S. Patent 4,588,258 (Hoopman)). The angles of the trenches are chosen such that the dihedrals formed at the linear intersections of the trenches (e.g., 414, 415, and 416 of the representative cubic corner elements 417) are approximately 90 degrees. In some embodiments, the angles of the triangular bases are at least 64, 65, 66, 67, 68, 69, or 70 degrees, and other angles are 55, 56, 57, or 58 degrees.

[0127] In another implementation, it is depicted as FIG. 4B , FIG. 4B The microstructured surface 400 can be characterized as an array of cone-shaped peak structures 420, defined by a first set of parallel grooves (i.e., valleys) in the y-direction and a second set of parallel grooves in the x-direction. The base of the cone-shaped peak structure is polygonal, typically square or rectangular, depending on the spacing of the grooves. The apex angle θ, 440°, is typically about 90°. However, this angle can range from 70° to 120°, and from 80° to 100°. In other embodiments, the apex angle is at least 20°, 30°, 40°, 50°, or 60°.

[0128] Other cubic corner element structures described as “complete cubes” or “preferred geometry (PG) cubic corner elements” typically include at least two non-dihedral edges that are not coplanar, as described, for example, in US 7,188,960 (Smith); which is incorporated herein by reference. The complete cube is not truncated. In one aspect, the base of the complete cube element in a plan view is not triangular. In another aspect, the non-dihedral edges of the complete cube element are characterized in that they are not all in the same plane (i.e., not coplanar). Such cubic corner elements can be characterized as “preferred geometry (PG) cubic corner elements.” PG cubic corner elements can be defined in the context of the structured surface of a cubic corner element extending along a reference plane. A PG cubic corner element is a cubic corner element having at least one non-dihedral edge that is: (1) not parallel to the reference plane; and (2) substantially parallel to the adjacent non-dihedral edges of adjacent cubic corner elements. Reflective surfaces including rectangular (including square), trapezoidal, or pentagonal cubic corner elements are examples of PG cubic corner elements.

[0129] refer to FIG. 5In another embodiment, the microstructured surface 500 can include an array of preferred geometry (PG) cube corner elements. The exemplary microstructured surface includes four rows (501, 502, 503, and 504) of preferred geometry (PG) cube corner elements. Each row of preferred geometry (PG) cube corner elements has a face formed by a first set of grooves, also referred to as "side grooves," and a second set of grooves. Such side grooves range from nominally parallel to an adjacent side groove to within 1 degree of being non-parallel to an adjacent side groove. Such side grooves are generally perpendicular to a reference plane 124 of the microstructured surface FIG. 1C The third face of such cube corner elements preferably includes a major groove face 550. Such major groove faces range from nominally perpendicular to the face formed by the side grooves to within 1 degree of being non-perpendicular to the face formed by the side grooves. In some embodiments, the side grooves can form a vertex angle Θ of nominally 90 degrees. In other embodiments, the row of preferred geometry (PG) cube corner elements includes a peak structure formed by an alternating pair of side grooves 510 and 511 (e.g., about 75 degrees and about 105 degrees), as depicted in FIG. 5 Thus, the vertex angle 540 of adjacent (PG) cube corner elements can be greater than or less than 90 degrees. In some embodiments, the average vertex angle of adjacent (PG) cube corner elements in the same row is nominally 90 degrees. As described in the previously cited US 7,188,960, during manufacture of a microstructured surface including PG cube corner elements, the side grooves can be formed independently on separate sheets (webs), each sheet having a single row of such cube corner elements. Pairs of sheets having opposite orientations are positioned such that their respective major groove faces form a major groove 552, thereby minimizing the formation of vertical walls. The sheets can be assembled to form the microstructured surface, which is then replicated to form a tool of suitable dimensions.

[0130] In some embodiments, all of the peak structures have the same vertex angle Θ. For example, FIG. 3 The previously described microstructured surface of FIG. 1 depicts a plurality of prism structures, each having a vertex angle Θ of 90 degrees. As another example, FIG. 4B The previously described microstructured surface of FIG. 2 depicts a plurality of pyramid structures, each having a vertex angle Θ of 60 degrees. In other embodiments, the peak structures can form different vertex angles. For example, as depicted in FIG. 5 some of the peak structures can have a vertex angle greater than 90 degrees, and some of the peak structures can have a vertex angle less than 90 degrees. In some embodiments, the peak structures of the microstructured array have peak structures with different vertex angles, but the average vertex angle ranges from 60 degrees to 120 degrees. In some embodiments, the average vertex angle is at least 65 degrees, 70 degrees, 75 degrees, 80 degrees, or 85 degrees. In some embodiments, the average vertex angle is less than 115 degrees, 110 degrees, 100 degrees, or 95 degrees.

[0131] As yet another example, as depicted in cross-section, the microstructured surface 600 can include a plurality of peak structures, such as 646, 648, and 650 having peaks 652, 654, and 656, respectively. When the microstructured surface does not contain flat surfaces (i.e., surfaces parallel to the reference plane 126 of FIG. 6 , the facets of adjacent peak structures can also define valleys between adjacent peaks. In some embodiments, the facets of a peak structure form a valley (e.g., valley 658) having a valley angle less than 90 degrees. In some embodiments, the facets of a peak structure form a valley (e.g., valley 660) having a valley angle greater than 90 degrees. In some embodiments, the valleys are symmetrical, such as depicted by valleys 658 and 660. In other embodiments, the valleys are asymmetrical, such as depicted by valley 662. When the valleys are symmetrical, the sidewalls of the adjacent peak structures defining the valley are substantially identical. When the valleys are asymmetrical, the sidewalls of the adjacent peak structures defining the valley are different. The microstructured surface can have a combination of symmetrical and asymmetrical valleys. FIG. 1C

[0132] In some embodiments, the peak structures generally include at least two (e.g., prisms of FIG. 3 ), three (e.g., cube corners of FIG. 4A ), or more facets. For example, when the base of the microstructure is octagonal, the peak structure includes eight sidewall facets. However, when the facets have a circular or truncated surface, the microstructure can not feature a particular geometry.

[0133] When the facets of the microstructure are such that the peaks and valleys are sharp or rounded but not truncated, the microstructured surface can be characterized as having no flat surfaces parallel to the planar base layer. However, where the peaks and / or valleys are truncated, the microstructured surface generally includes less than 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, or 1% of flat surface area that is substantially parallel to the planar base layer. In one embodiment, the valleys can have flat surfaces and only one of the sidewalls of the peaks is angled, such as shown in FIG. 2B . However, in advantageous embodiments, two sidewalls of adjacent peaks defining a valley are angled toward each other, as previously depicted. Thus, the sidewalls on either side of the valley are not parallel to each other.

[0134] In each of the embodiments of FIG. 3 to FIG. 6 , the facets of adjacent (e.g., prismatic or cubical) peak structures are generally connected at the bottom of the valley, i.e., proximate to the planar base layer. The facets of the peak structures form a continuous surface in the same direction. For example, in FIG. 3 , the facets 321 and 322 of the (e.g., prismatic) peak structures are continuous in the direction of the length (L) of the microstructure, or in other words, the y-direction. As yet another example,​FIG. 5 The major grooves 452 and 550 of the PG cube corner elements 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 FIG. 4, the facets of the (e.g., cube corner or pyramid) peak structures are in the same plane in both the x- and y-directions. These semi-continuous and continuous surfaces can help clean pathogens from the surface.

[0135] In some embodiments, the apex angle of the peak structures is generally twice the wall angle, particularly where the facets of the peak structures are interconnected at the valleys between the peak structures. Thus, the apex angle is generally greater than 20 degrees, and more typically at least 25, 30, 35, 40, 45, 50, 55, or 60 degrees. The apex angle of the peak structures is generally less than 160 degrees, and more typically less than 155, 150, 145, 140, 135, 130, 125, or 120 degrees.

[0136] The microstructured surface of the microstructured film can be made by various microreplication techniques such as coating, injection molding, embossing, laser etching, and extrusion. For example, microstructuring of the surface of the (e.g., engineered) film can be achieved by at least one of the following methods: (1) casting a molten thermoplastic using a tool having a microstructured pattern; (2) applying a fluid to a tool having a microstructured pattern, solidifying the fluid, and removing the resulting film; (3) passing a thermoplastic film over a compression roller to be compressed (i.e., embossed) against a tool having a microstructured pattern; and / or (4) contacting a solution or dispersion of a polymer in a volatile solvent with a tool having a microstructured pattern, and removing the solvent, e.g., by evaporation. The tool can be a metal, such as nickel, nickel-plated copper, or nickel-plated brass, or can be a thermoplastic material that is stable under the process conditions and preferably has a surface energy that allows the polymeric material to be cleanly removed from the tool. It will be appreciated that the microstructured film should comprise a material that does not melt or otherwise deform during the thermoforming process in which the article is formed, so that the useful discontinuities of the microstructured surface of the film retain their shape and impart the inverse of their shape to the surface of the final article.

[0137] The tool used to make the microstructured film can be formed using any of a variety of techniques known to those skilled in the art, the choice of technique depending in part on the tool material and the features of the desired topography. Exemplary techniques include etching (e.g., chemical etching, mechanical etching, or other etching methods such as laser etching, reactive ion etching, and the like, and combinations thereof), photolithography, stereolithography, micromachining, knurling (e.g., cutting knurls or acid-hardened knurls), scoring, cutting, and the like, or combinations thereof. In some embodiments, the tool is a metal tool. The tool can also include a diamond-like glass layer, such as described in WO 2009 / 032815 (David).

[0138] Additional information regarding materials and various methods of forming microstructured tool surfaces can be found, for example, in PCT Publication No. WO 2007 / 070310 and U.S. Publication No. US 2007 / 0134784 (Halverson et al.); U.S. Publication No. US 2003 / 0235677 (Hanschen et al.); PCT Publication No. WO 2004 / 000569 (Graham et al.); U.S. Patent No. 6,386,699 (Ylitalo et al.); U.S. Publication No. US 2002 / 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.).

[0139] Useful (optional) base member materials include, for example, styrene-acrylonitrile, cellulose acetate butyrate, cellulose acetate propionate, cellulose triacetate, polyether sulfone, polymethyl methacrylate, polyurethane, polyester, polycarbonate, polyvinyl chloride, polystyrene, polyethylene naphthalate, copolymers or blends based on naphthalene dicarboxylic acid, polynaphthenes, polyimides, silicones, and fluorinated films, and glass. Optionally, the base material can comprise a mixture or combination of these materials. In one embodiment, the base can be multilayered or can contain a dispersed component suspended or dispersed in a continuous phase. Examples of useful PET films include optical grade polyethylene terephthalate and MELINEX TM PET available from DuPont Films of Wilmington, Del. An example of a useful thermoformable material is polyethylene terephthalate glycol (a glycol bearing polyester) commercially available under the trade name VIVAK PETG. Such materials are characterized by a tensile strength ranging from 5,000 psi to 10,000 psi (ASTM D638), a flexural strength of 5,000 to 15,000 (ASTM D-790). The glass transition temperature of such materials is 178 °F (ASTM D-3418).

[0140] It is also possible, and often preferred in order to preserve fidelity of the microstructure, to include a surface energy modulating compound in the composition used to form the microstructure. In some embodiments, a spreading additive can delay or prevent crystallization of the base composition. Suitable spreading 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.).

[0141] Materials for the retroreflective sheets and brightness enhancement films have been selected based on optical properties. Therefore, the peak structure and adjacent valleys typically contain materials with a refractive index of at least 1.50, 1.55, 1.60, or greater. Furthermore, the visible light transmittance is typically greater than 85% or 90%. However, for many embodiments of the films, methods, and articles described in this invention, optical properties may not be of concern. Therefore, a variety of other materials with lower refractive indices, including colored, transparent, and opaque materials, can be used.

[0142] like FIG. 3 As shown, a continuous substrate layer 360 may exist between the bottom of the channel or valley and the top surface 331 of the (e.g., planar) base member 310. In some embodiments, such as when a microstructured surface is prepared by casting and curing a polymerizable resin composition, the thickness of the substrate layer is typically at least 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 1 μm, 2 μm, 3 μm, 4 μm, or 5 μm, and ranges up to 50 μm. In some embodiments, the thickness of the substrate layer is not greater than 45 μm, 40 μm, 35 μm, 30 μm, 25 μm, 20 μm, 15 μm, 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, 1 μm, 0.9 μm, 0.8 μm, 0.7 μm, 0.6 μm, 0.5 μm, 0.4 μm, 0.3 μm, or 0.2 μm.

[0143] In some embodiments, the microstructured surface (e.g., its at least peak structure) comprises an organic polymer material having a glass transition temperature of at least 25°C (e.g., measured by differential scanning calorimetry). In some embodiments, the glass transition temperature of the organic polymer material is at least 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, or 60°C. In some embodiments, the glass transition temperature of the organic polymer material is not greater than 100°C, 95°C, 90°C, 85°C, 80°C, or 75°C.

[0144] Refer again to Figures 2 to 4 and FIG. 6The structured (e.g., molded) films described herein optionally include an (e.g., engineered) microstructured surface (200, 300, 400, 600) disposed on a base member (210, 310, 410, 610). In some cases, the base member is planar (e.g., parallel to a reference plane 126). The thickness of the base member is typically at least 10 microns, 15 microns, 20 microns, or 25 microns (1 mil) and is typically no greater than 500 microns (20 mils) thick. In some embodiments, the thickness of the base member is no greater than 400 microns, 300 microns, 200 microns, or 100 microns. The width of the base member (e.g., of the film) can be at least 30 inches (76 cm), and preferably at least 48 inches (122 cm). The base member is typically continuous in length up to about 50 yards (45.5 m) to 100 yards (91 m) such that the microstructured film can be provided in a roll format for convenient handling. Alternatively, however, the base member (e.g., of the film) can be an individual sheet or strip rather than as a roll.

[0145] In certain embodiments, the microstructured surface includes peak structures and adjacent valleys, wherein the maximum width of the valleys is in the range of 1 micron to 250 microns, and the sidewall angle of the peak structures is greater than 10 degrees.

[0146] In some embodiments, these microstructured surfaces are three-dimensional on a macroscopic scale. However, on a microscopic scale (e.g., a surface area including at least two adjacent microstructures with a valley or channel disposed between the microstructures), the base layer / base member can be considered planar with respect to the microstructures. The width and length of the microstructures are in the x-y plane, and the height of the microstructures is in the z direction. Further, the base layer is parallel to the x-y plane and orthogonal to the z plane.

[0147] More complex microstructured surfaces are described herein, such as FIG. 7A to FIG. 7B and FIG. 8A to FIG. 8C are shown. The microstructured surfaces can be prepared using any suitable manufacturing technique. For example, the microstructures can be manufactured using microreplication from a tool. Any suitable manufacturing method can be used, such as by using engraving or diamond turning to manufacture the tool. Exemplary methods are known in the art, such as described in U.S. Patent No. 8,888,333; WO 2000 / 048037; U.S. Patent No. 7,140,812; U.S. Patent Nos. 7,350,442 and 7,328,638 (Gardiner); which are incorporated herein by reference.

[0148] 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 that can be used to produce a film having a microstructured surface of the present disclosure. The cutting tool system employs a thread cutting lathe turning process and includes a roller that can be rotated about a central axis and / or moved along the central axis by a drive, and a cutter for cutting the material of the roller. The cutter is mounted on a servo and can be moved by the drive into the roller in the x-direction and / or along the roller. Typically, the cutter can be mounted perpendicular to the roller and central axis and driven into the engravable material of the roller while the roller is rotated about the central axis. The cutter can then be driven parallel to the central axis to produce a thread cut. The cutter can be actuated simultaneously with high frequency and low displacement to produce the features of the microstructured surface of the present disclosure when microreplicating in the roller.

[0149] The servo can be a fast tool servo (FTS) and can include a solid state piezoelectric (PZT) device (also commonly referred to as a PZT stack) that rapidly adjusts the position of the cutter. The rotational motion produced by the drive is synchronized with the translational motion produced by the drive in order to precisely control the resulting shape of the microstructure. In order to prepare a mold for producing an exemplary microstructured film surface of the present disclosure, FIG. 7A to FIG. 8C The shape of the cutter has a rounded tip with a radius ranging between 1 and 3 microns and a top angle β of 80 degrees (± 5 degrees) for an exemplary microstructured film surface of the present disclosure.

[0150] When cutting the material of the roller, the rotation of the roller along the central axis and the movement of the cutter in the x-direction define a thread path having a pitch P along the central axis around the roller. As the cutter is moved in a direction perpendicular to the surface of the roller to cut the material of the roller, the width of the material cut by the cutter changes as the cutter moves in and out or cuts in and out. The cutter is angularly adjusted and vertically displaced in such a way to produce a thread path that can have some overcut elements that remove portions of one or more undulating, pseudo-random patterns previously produced. This process of angular adjustment and vertical displacement is repeated 3 to 7 times, or as many times as needed, to engrave the entire surface of the roller with the pattern. The engraved roller acts as a tool for preparing a film having a microstructured surface that is a negative replication of the microstructured surface of the tool.

[0151] Although this cutting method is described with respect to the rotation of the roller, randomized displacement in the y-direction and / or randomized displacement in the x-direction can also be used to cut a planar surface. Likewise, overcutting can also be utilized to cut a planar surface. It should also be understood that some thread paths formed by the cutting tool can not include randomized displacement or overcutting. For example, FIG. 7A to FIG. 8CThe portions of the array of peaks can comprise a regular repeating pattern, such as a linear prismatic array.

[0152] In some embodiments, a single cutter is used to cut the array of microstructures. In other embodiments, more than one cutter is used to cut the array of microstructures. For example, taller peaks can be formed by a cutter having a rounded tip, and shorter peaks can be formed by a cutter having a sharp or less rounded tip. The surface of the tool typically has a surface roughness of less than 50 nm, 40 nm, 30 nm, or 20 nm. Thus, the surface of the microstructure can have this same surface roughness. It will be appreciated that the surface roughness of the tool / microstructure surface does not include the roughness contributed by the microstructure, and thus is different from the roughness of the microstructured surface.

[0153] Furthermore, while this cutting method is exemplified for modifying the manufacture of an array of linear prisms, these same principles of individually randomizing the displacement in the y-direction and / or randomizing the displacement in the x-direction and / or overcutting can be utilized to modify the manufacture of other microstructured arrays, such as cube corner elements, including preferred geometry cube corner elements; both of which are described in WO 2021 / 033151 (Connell et al.), which is incorporated herein by reference. In this embodiment, the microstructured surface can be characterized as comprising a modified cube corner structure or a modified preferred geometry cube corner structure.

[0154] FIG. 7A to FIG. 7B and FIG. 8A to FIG. 8C is a perspective view of an exemplary (e.g., micro) structured surface comprising an array of peak structures according to the present disclosure. Notably, the cross-sectional view of the peak structures shows that the peak structures have a triangular cross-section. In some embodiments, FIG. 7A to FIG. 7B and FIG. 8A to FIG. 8C The surface of the microstructured surface can be characterized as a “modified” linear prism. The peak structures comprise facets that form a continuous surface in the same direction, or in other words, faces that form a continuous surface. When the microstructured surface comprises an array of modified cube corner structures, the peak structures comprise faces that form a semi-continuous surface in the same direction, as described in WO 2021 / 033151. When the microstructured surface comprises an array of modified preferred geometry cube corner structures, the peak structures comprise faces that form a continuous and semi-continuous surface in the same direction.

[0155] When the microstructured surface comprises a regular repeating pattern, various dimensions such as peak height and maximum valley width can be determined from a cross-section orthogonal to the y-axis. Various angles such as apex angle and sidewall angle can also be determined from a cross-section orthogonal to the y-axis. However, when the microstructured surface is not a regular repeating pattern, or in other words, is a more complex microstructured surface, multiple cross-sections can be utilized to determine these parameters. Furthermore, when the microstructured surface comprises peaks and valleys having different peak heights, different valley depths, different angles, etc., these parameters can be more commonly represented, for example, by a minimum, maximum, or average value. In contrast to the linear prisms of WO 2021 / 033151 and as described above, the (micro)structured surfaces shown in FIG. 7A to FIG. 7B and FIG. 8A to FIG. 8C can be characterized as having greater variability, or in other words, greater randomness.

[0156] In contrast to the linear prisms of WO 2021 / 033151, FIG. 7A to FIG. 7B and FIG. 8A to FIG. 8C each of the microstructured surfaces (e.g., modified linear prisms) comprises peaks and / or valleys having different heights. Furthermore, FIG. 7A to FIG. 7B and FIG. 8A to FIG. 8C the microstructured surfaces (e.g., modified linear prisms) comprise peaks and / or valleys having different widths. FIG. 7A to FIG. 7B and FIG. 8A to FIG. 8B The minimum and maximum valley heights, valley widths, peak heights, and peak widths of the microstructured surfaces of

[0157] Valley Size

[0158] Sample Minimum Valley Height Maximum Valley Height Minimum Valley Width Maximum Valley Width Sample 1 3.75 8.16 9.08 17.33 Sample 2 7.40 12.40 11.50 16.50 Sample 3 3.65 8.27 7.45 17.40 Sample 4 6.86 10.73 11.56 18.15

[0159] Notably, the height of the valley structures (difference between the minimum and maximum values) varies by at least 1 micron, 2 microns, 3 microns, 4 microns, or 5 microns. In some embodiments, the height of the valley structures varies by no more than 20 microns, 10 microns, 15 microns, or 5 microns. Notably, the width of the valley structures (difference between the minimum and maximum values) varies by at least 1 micron, 2 microns, 3 microns, 4 microns, 5 microns, 6 microns, 7 microns, 8 microns, 9 microns, or 10 microns. In some embodiments, the height of the valley structures varies by no more than 20 microns, 10 microns, 15 microns, or 5 microns.

[0160] Peak Size

[0161] Sample Minimum Peak Height Maximum Peak Height Average Peak Height Minimum Peak Width Maximum Peak Width Sample 1 11.3 15.0 11.7 9.1 19 Sample 2 10.7 11.2 9.8 9.9 18.2 Sample 3 10.8 15.6 10.9 10.8 16.5 Sample 4 15.1 19.7 13.3 10.1 17.8

[0162] Notably, the height of the peak structure (the difference between the minimum and maximum) varies by at least 1 micron, 2 microns, 3 microns, 4 microns, or 5 microns. In some embodiments, the height of the peak structure varies by no more than 20 microns, 10 microns, 15 microns, or 5 microns. Notably, the width of the peak structure (the difference between the minimum and maximum) varies by at least 1 micron, 2 microns, 3 microns, 4 microns, 5 microns, 6 microns, 7 microns, 8 microns, 9 microns, or 10 microns. In some embodiments, the height of the peak structure varies by no more than 20 microns, 10 microns, 15 microns, or 5 microns.

[0163] It is recognized that the amount of variation can be a function of the size. Unless otherwise specified, 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%, 15%. Thus, when the average dimension of the microstructured surface is 10 microns, the amount of variation is typically in the range of 1 micron to 5 microns. Likewise, when the average dimension of the microstructured surface is 1 micron, the amount of variation is typically in the range of 0.1 micron to 0.5 microns.

[0164] FIG. 8C is a negative replica of the surface of FIG. 8B or, in other words, is the inverse of the surface. For example, a negative replica can be made by casting and curing a polymerizable resin onto a metal tool (e.g., 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.

[0165] When the cured polymerizable resin is removed from the metal tool, the resulting film will have a microreplicated surface in which the peak structures of the tool correspond to valleys, or in other words, cavities, in the film, and the valleys of the tool correspond to peak structures in the film. It will be appreciated that the microstructured film should comprise a material that does not melt or otherwise deform during the thermoforming process in which the article is formed, such that the useful discontinuities of the microstructured surface of the film retain their shape and impart the inverse of their shape to the surface of the final article.

[0166] For this embodiment, FIG. 8C the peak size of the structured surface of FIG. 8B Sample 4 described above. In addition, FIG. 8C the valley size of the structured surface of FIG. 8B Sample 4 described above.

[0167] Surface analysis is used to characterize the complex surfaces of the present disclosure.

[0168] Topography data was collected using a VK-200 Keyence laser scanning confocal microscope (Keyence Corporation, Itasca, IL). Stitched images were generated using native image assembly software provided with the microscope. An array of 35 individual images (using a 150X Nikon objective) was used to produce approximately 300 microns x 600 microns data sets. Data sets were further analyzed using the software package Digital Surf Mountains Map (Digital Surf, Besancon, France) to measure surface roughness parameters and produce 3-dimensional surface maps of FIG. 7A to FIG. 7B and FIG. 8A to FIG. 8C

[0169] FIG. 12 is a schematic side view of a (micro)structure 160 of the (micro)structured surface 120. The structure 160 has a distribution of tilt across the structure surface. For example, the microstructure has a tilt Θ at location 510, where Θ is the angle between a normal 520 to the microstructure surface at location 510 (a = 90 degrees) and a tangent 530 to the microstructure surface at the same location. The tilt Θ is also the angle between the tangent 530 and the major surface 142 of the matte layer.

[0170] The tilt of the (micro)structure is first obtained along the x-direction (the tilt of the (micro)structured surface 120), and then the tilt is obtained along the y-direction, such that:

[0171] Equation 1: and

[0172] Equation 2:

[0173] where H(x,y) = height profile of the surface.

[0174] ​The average x- and y-tilt is evaluated at 2-micron intervals centered on each pixel. In different embodiments, the micron intervals can be chosen to be smaller or larger, as long as a constant interval is used for microstructure sizes with sufficient resolution. The chosen interval is smaller than the smallest peak width of the structure. In some embodiments, the ratio of the interval to the smallest peak width is at least 3: 1, 4: 1, or 5: 1. Thus, for smaller structures, a smaller interval will be chosen, while for larger structures a larger interval is typically chosen. Each pixel has a tilt, and each structure typically has more than one set of x, y coordinates, and thus more than one calculated tilt value. When micron-sized intervals are chosen to evaluate the tilt of a microstructured surface, the presence of nanoscale structures typically does not significantly change the Fcc of the microstructured surface. For example, a 200 nm nanoscale structure changes the coordinates of a 10 micron microstructure by 2%. From the x- and y-tilt data, it is possible to determine the gradient size according to Equation 3.

[0175] Equation 3:

[0176] Subsequently, the average gradient size can be evaluated by a 6 pm x 6 pm box centered on each pixel. The gradient size is obtained within a 0.5 degree bin size. The gradient size distribution can be written as N G It will be appreciated that to obtain the angle values for the x-tilt, y-tilt, and the gradient size angle corresponding to the above values, the arctangent of these values in Equations 1, 2, and 3 should be taken. Another characterization of the surface is the complement cumulative distribution (F CC (0)) which is defined as the fraction (or percentage by multiplying the fraction by 100%) of gradient sizes that are greater than or equal to a particular angle 0. The complement cumulative distribution (F CC (0)) is defined as

[0177] Equation 4:

[0178] Thus, when it is stated that a certain percentage of the structured surface has a tilt size less than a certain number of degrees, this characterization is obtained from F CC (0) in Equation 4. The gradient size corresponds to the combination of the x- and y-tilts, and thus the gradient size can be understood as the total tilt size. It will be appreciated that the terms "gradient size" and "tilt size" are used interchangeably in this specification and these terms should be understood to have the same meaning. When the entire surface is microstructured (such as depicted in FIG. 7A to FIG. 7B and FIG. 8A to FIG. 8C , and the chosen interval is smaller than the smallest peak width of the microstructure as described previously, the Fcc of the entire surface is also the Fcc of the microstructured surface and the Fcc of the microstructure.

[0179] The X-tilt distribution (Xcc), Y-tilt distribution (Ycc), and F(cc) of a particular microstructured surface were calculated as FIG. 7A to FIG. 7B and FIG. 7A to FIG. 7C.

[0180] FIG. 9 are plots of the complement of the cumulative gradient (i.e., tilt) magnitude distribution (Fcc) calculated from topography data of the surfaces according to FIG. 7A to FIG. 7B and FIG. 8A to FIG. 8B 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). Notably, the microstructures of these comparative microstructured surfaces have narrow tilt distributions. 90% of the microstructures of the surfaces of Comparative Example A and Comparative Example B have a tilt of at least 30 degrees. 80% of the microstructures of the surface of Comparative Example A have a tilt of at least 45 degrees (i.e., half of the apex angle); while 80% of the microstructures of the microstructured surface of Comparative Example B have a tilt of at least 40 degrees (i.e., half of the apex angle). Less than 5% of the microstructures of Comparative Example A and Comparative Example B have a tilt of less than 20 degrees. Furthermore, less than 5% of the microstructures have a tilt of greater than 50 degrees. For regular repeating patterns, such as Comparative Example A and Comparative Example B, the tilt calculated from topography data obtained from surface analysis can be substantially the same as the sidewall angle calculated from cross-sections.

[0181] Notably, FIG. 7A to FIG. 7B and FIG. 8A to FIG. 8C the surfaces shown in FIGS. 7A and 7B have much wider tilt distributions. Notably, the structured surfaces include a plurality of structures having a complement cumulative tilt magnitude distribution (Fcc) such that at least 30%, 40%, 50%, 60%, 70%, 80%, or 90% of the structures have a tilt of greater than 10 degrees. Furthermore, in some embodiments, less than 80% of the structures have a tilt of greater than 35 degrees. In some embodiments, as shown in FIG. 7A to FIG. 7B and FIG. 8A to FIG. 8C the structured surfaces described herein include a plurality of structures having a complement cumulative tilt magnitude distribution (Fcc) that satisfies one or more of the following criteria:

[0182] a) at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, or 80% of the structures have a tilt of greater than 20 degrees;

[0183] b) at least 10%, 20%, 30%, 40%, 50%, 60%, or 70% of the structures have a tilt of greater than 30 degrees;

[0184] c) At least 10%, 20%, 30%, 40%, or 50% of the structure has an inclination greater than 40 degrees;

[0185] d) At least 10%, 20%, or 30% of the structure has an inclination greater than 50 degrees;

[0186] e) At least 10% or 20% of the structure has an inclination greater than 60 degrees;

[0187] f) Less than 20% or 10% of the structure has an inclination greater than 70 degrees;

[0188] g) Structures with less than 50%, 40%, 30%, or 20% of the material have an inclination greater than 60 degrees;

[0189] h) Less than 50% or 40% of the structure has an inclination greater than 50 degrees;

[0190] i) Less than 70%, 60%, or 50% of the structure has an inclination greater than 40 degrees;

[0191] j) Less than 90% or 80% of the structure has an inclination greater than 30 degrees; and

[0192] k) Less than 90% of the structures have an inclination greater than 20 degrees.

[0193] FIG. 8C The complement cumulative slope magnitude distribution (Fcc) (i.e. FIG. 8B The negative copy can also be characterized by the same complement cumulative slope magnitude distribution (Fcc) criterion as just described. FIG. 7A to FIG. 7B and FIG. 8A to FIG. 8C The structured surface shown can be characterized by various combinations of the complement cumulative tilt magnitude distribution (Fcc) criteria just described, and all the criteria just described in some embodiments.

[0194] FIG. 10 Is it like this? FIG. 7A to FIG. 7B and FIG. 8A to FIG. 8B The diagram shows a complement curve of the cumulative gradient (i.e., tilt) magnitude distribution (Ycc) of the structured surface. These surfaces include multiple structures with complement cumulative tilt magnitude distributions (Ycc), wherein at least 20%, 25%, 30%, 35%, 40%, 45%, or 50% of the structure has a tilt greater than 10 degrees, and less than 55%, 50%, 45%, 40%, 35%, 30%, 25%, or 20% of the structure has a tilt greater than 30 degrees. In some embodiments, such as FIG. 7A to FIG. 7B and FIG. 8A to FIG. 8B As shown, the structured surfaces described herein include multiple structures having a complement cumulative tilt magnitude distribution (Ycc) that satisfies one or more of the following criteria:

[0195] a) at least 10% or 20% of the structures have a tilt greater than 20 degrees;

[0196] b) at least 10% or 20% of the structures have a tilt greater than 30 degrees;

[0197] c) at least 10% or 15% of the structures have a tilt greater than 40 degrees;

[0198] d) at least 10% of the structures have a tilt greater than 50 degrees;

[0199] e) at least 5% of the structures have a tilt greater than 60 degrees;

[0200] f) less than 10% or 5% of the structures have a tilt greater than 70 degrees;

[0201] g) less than 20% to 10% of the structures have a tilt greater than 60 degrees;

[0202] h) less than 50%, 40%, 30%, 20%, or 10% of the structures have a tilt greater than 50 degrees;

[0203] i) less than 90%, 80%, 70%, 60%, 50%, 40%, 30%, or 20% of the structures have a tilt greater than 40 degrees;

[0204] j) less than 90%, 80%, 70%, 60%, 50%, 40%, or 30% of the structures have a tilt greater than 20 degrees; and

[0205] k) less than 90%, 80%, 70%, 60%, 50%, 40%, or 30% of the structures have a tilt greater than 10 degrees.

[0206] FIG. 11 are graphs of the complement of the cumulative gradient (i.e., tilt) size distribution (Xcc) of the structured surfaces as shown in FIG. 7A to FIG. 7B and FIG. 8A to FIG. 8B The structured surfaces described herein include a plurality of structures having a complement cumulative tilt size distribution (Xcc) that satisfies one or more of the following criteria: FIG. 7A to FIG. 7B FIG. 8A to FIG. 8B

[0207] a) at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, or 80% of the structures have a tilt greater than 10 degrees;​​

[0208] b) at least 10%, 20%, 30%, 40%, 50%, 60%, or 70% of the structures have a tilt greater than 20 degrees;

[0209] c) at least 10%, 20%, 30%, 40%, 50%, or 60% of the structures have a tilt greater than 40 degrees;

[0210] d) at least 10% or 20% of the structures have a tilt greater than 50 degrees;

[0211] e) at least 10% of the structures have a tilt greater than 60 degrees;

[0212] f) less than 20% or 10% of the structures have a tilt greater than 70 degrees;

[0213] g) less than 50%, 40%, 30%, or 20% of the structures have a tilt greater than 60 degrees;

[0214] h) less than 50%, 40%, or 30% of the structures have a tilt greater than 50 degrees;

[0215] i) less than 90%, 80%, or 70% of the structures have a tilt greater than 30 degrees; and

[0216] j) less than 90% or 80% of the structures have a tilt greater than 20 degrees.

[0217] It is understood that FIG. 8C The structured surface of Formula (I) can also be characterized by the same complement cumulative tilt magnitude distribution (Xcc) and (Ycc) criteria as just described.

[0218] Various other surface roughness parameters were calculated from the topography images (3D): Sa (average roughness), Sq (root mean square), Sku (surface peakiness), and Sbi (surface bearing index), Svi (valley fluid retention index). Prior to calculating roughness, a plane correction “subtract plane” (first order planar surface fit form removal) was used.

[0219] The following table describes the S parameters for some representative and comparative examples. It is noted that some comparative examples are also described in WO 2021 / 033151.

[0220]

[0221] Topography maps can be obtained using a confocal laser scanning microscope (CLSM) (e.g., Keyence VK-X200). CLSM is an optical microscopy technique that uses a focused laser beam to scan a surface to map the topography of the surface. CLSM works by passing a laser beam through a light source aperture and then focusing that laser beam into a small area on the surface through an objective lens, and builds an image pixel by pixel by collecting emitted photons from the sample. The CLSM uses a pinhole to block out-of-focus light in the image formation. Size analysis can be used to measure various parameters using SPIP 6.7.7 image metrology software according to the manual (see https: / / www.imagemet.com / media-library / support-documents

[0222] Surface roughness parameters: Sa (roughness average), Sq (root mean square), Sbi (surface bearing index), and Svi (valley fluid retention index) can be calculated from the topography images (3D). Prior to calculating roughness, a plane correction “subtract plane” (first order flat plane fit form removal) is used.

[0223] Roughness average Sa, is defined as:

[0224]

[0225] where M and N are the number of data points X and Y.

[0226] While the Sa of a smooth surface can approach zero, it was found that the average surface roughness Sa of a comparative smooth surface that had poor microbial removal after cleaning was at least 10 nm, 15 nm, 20 nm, 25 nm, or 30 nm. The average surface roughness Sa of a comparative smooth surface was less than 1000 nm (1 micron). In some embodiments, the Sa of a comparative smooth surface was at least 50 nm, 75 nm, 100 nm, 125 nm, 150 nm, 200 nm, 250 nm, 300 nm, or 350 nm. In some embodiments, the Sa of a comparative smooth surface was not greater than 900 nm, 800 nm, 700 nm, 600 nm, 500 nm, or 400 nm.

[0227] ​The average surface roughness Sa of the microstructured surface with improved microbial removal after cleaning is 1 micron (1000 nm) or greater. In some embodiments, the Sa is 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 Sa of the microstructured surface is at least 2500 nm, 3000 nm, 3500 nm, 4000 nm, or 5000 nm. In some embodiments, the Sa of the microstructured surface is at least 10,000 nm, 15,000 nm, 20,000 nm, or 25,000 nm. In some embodiments, the Sa of the microstructured surface with improved microbial removal after cleaning is no greater than 40,000 nm (40 microns), 35,000 nm, 30,000 nm, 15,000 nm, 10,000 nm, or 5,000 nm.

[0228] In some embodiments, the Sa of the microstructured surface is at least 2 or 3 times the Sa 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 the Sa of the smooth surface. In other embodiments, the Sa of the microstructured surface is at least 15, 20, 25, 30, 35, 40, 45, 50 times the Sa 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 the Sa of the smooth surface.

[0229] The root mean square (RMS) parameter Sq is defined as:

[0230]

[0231] where M and N are the number of data points X and Y.

[0232] While the Sq value is slightly higher than the Sa value, the Sq value also falls within the same ranges just described for the Sa value.

[0233] The surface kurtosis Sku describes the "peakedness" of the surface topography and is defined as:

[0234]

[0235] Sample / Example Sku Sample 2 2.424 Sample 3 2.796 Sample 4 2.565 Sample 1 2.490 Comparative Example D 2.390 Comparative Example B 1.924 Comparative Example A 1.786

[0236] Notably, Samples 1-4 have a Sku greater than Comparative Example A, Comparative Example B, and Comparative Example 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, or 2.55, or 2.50, or 2.45.

[0237] The surface bearing index, Sbi, is defined as:

[0238]

[0239] where Z 0.05 is the surface height at 5% bearing area.

[0240] The valley fluid retention index, Svi, is defined as:

[0241]

[0242] where Vv(h0.80) is the void volume at the valley region within 80% to 100% bearing area.

[0243] As described above in the S parameter table, the Sbi / Svi ratio for the comparative smooth sample is 1 and 3. The microstructured surface having improved microbial removal after cleaning has an Sbi / Svi ratio greater than 3. The microstructured surface has an Sbi / Svi ratio of at least 4, 5, or 6. In some embodiments, the microstructured surface having improved microbial removal after cleaning has an Sbi / Svi ratio of at least 7, 8, 9, or 10. In some embodiments, the microstructured surface having improved microbial removal after cleaning has an Sbi / Svi ratio of at least 15, 20, 25, 30, 35, 40, or 45. The microstructured surface having improved microbial removal after cleaning has an Sbi / Svi ratio less than the comparative square wave microstructured surface. Thus, the microstructured surface having improved microbial removal after cleaning has an Sbi / Svi ratio less than 90, 85, 80, 75, 70, or 65. In some embodiments, the microstructured surface having improved microbial removal after cleaning has an Sbi / Svi ratio less than 60, 55, 50, 45, 40, 35, 30, 25, 20, or 10.

[0244] The topography map can also be used to measure other features of the microstructured surface. For example, peak height (particularly of repeating peaks of the same height) can be determined from the height histogram function of the software. To calculate the percentage of "flat areas" of a square wave film, the particle hole analysis feature of SPIP can be used to identify "flat areas", which identifies certain shapes (in this case, "flat areas" of the microstructured square wave film).

[0245] In certain embodiments, the microstructured surface comprises peak structures and adjacent valleys having a distribution of cumulative slope magnitude of the complement (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.

[0246] In particular cases, the microstructured surface comprises less than 30% of flat surface areas parallel to the planar base layer.

[0247] In alternative embodiments, the base layer is planar such that it exhibits an average surface roughness Sa of less than 1000 nm. The planar base layer does not have a microstructured surface as described in detail above.

[0248] Optional Additives and Coatings

[0249] Optionally, a low surface energy coating can be applied to the base layer. Exemplary low surface energy coating materials that can be used include the following materials: such as hexafluoropropylene oxide (HFPO); or organosilanes such as alkylsilanes, alkoxysilanes, acryloylsilanes, polyhedral oligomeric silsesquioxanes (POSS), and fluorine-containing organosilanes, to name a few. Examples of particular coatings known in the art can be found, for example, in U.S. Publication No. 2008 / 0090010 (Zhang et al.) and commonly owned published document U.S. Publication No. 2007 / 0298216 (Jing et al.). The coating can be applied by any appropriate coating method, such as sputtering, vapor deposition, spin coating, dip coating, roll coating, or any other suitable method.

[0250] In some embodiments, the base layer can be modified to make the major surface opposite the metal oxide layer more hydrophilic. The microstructured surface can generally be modified such that a flat organic polymer film surface identical to the modified microstructured surface material exhibits 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 identical to the microstructured surface material generally exhibits an advancing or receding contact angle with deionized water of greater than 45 degrees, 50 degrees, 55 degrees, or 60 degrees.

[0251] The hydrophilic substrate layer surface can be achieved using any suitable known method. Surface treatments such as plasma treatment, vacuum deposition, polymerization of hydrophilic monomers, grafting of hydrophilic moieties to the film surface, corona or flame treatment, and the like can be employed. For certain embodiments, the hydrophilic surface treatment comprises a zwitterionic silane, and for certain embodiments, the hydrophilic surface treatment comprises a non-zwitterionic silane. Non-zwitterionic silanes include, for example, non-zwitterionic anionic silanes.

[0252] In other embodiments, the hydrophilic surface treatment further comprises at least one silicate, such as, but not limited to, lithium silicate, sodium silicate, potassium silicate, silicon dioxide, tetraethyl orthosilicate, poly(diethoxysiloxane), or combinations thereof. The one or more silicates can be mixed into a solution containing the hydrophilic silane compound for application to the (e.g., microstructured) surface.

[0253] Article

[0254] As a useful purpose is to provide an article having a surface with increased microbial (e.g., bacterial) removal upon cleaning, the article is generally not a (e.g., sterile) medical article, such as a nasogastric tube, wound contact layer, blood flow catheter, stent, pacemaker housing, heart valve, orthopedic implant (such as hip, knee, shoulder, etc.), periodontal implant, denture, crown, contact lens, intraocular lens, soft tissue implant (breast implant, penile implant, facial and hand implant, etc.), surgical tool, suture (including degradable sutures), cochlear implant, tympanoplasty tube, shunt (including for hydrocephalus), post-surgical drainage tube and drainage device, urinary catheter, endotracheal tube, heart valve, wound dressing, other implantable device, and other indwelling device. The just-described medical articles can be characterized as single-use articles, i.e., the article is used once and then discarded. The above-described articles can also be characterized as single-person (e.g., patient) articles. Thus, such articles are generally not cleaned (as opposed to sterilized) and reused by other patients.

[0255] In contrast, the articles and surfaces described herein include those in which the microstructured surface is exposed to the ambient (e.g., indoor or outdoor) environment and subjected to being touched or otherwise contacted by multiple humans and / or animals, as well as other contaminants (e.g., dirt).

[0256] In some embodiments, the microstructured surface of the article comes into direct (e.g., skin) contact with (e.g., multiple) people and / or animals during normal use of the article. In other embodiments, in the absence of direct (e.g., skin) contact, the microstructured surface may be in close proximity to (e.g., multiple) people and / or animals. However, due to the close proximity of the microstructured surfaces, such article surfaces can be easily contaminated by microorganisms (e.g., bacteria) and are therefore cleaned to prevent the spread of microorganisms to other places.

[0257] Representative articles that will be cleaned during normal use and / or used on curved surfaces suitable for integrating microstructured surfaces into articles include various internal or external surfaces or components of medical articles, dental articles, orthodontic articles, vehicle articles, electronic articles, personal care articles, cleaning articles, sporting articles, food preparation articles, child care articles, or building articles. More specifically, some embodiments of representative articles in these categories may include the following:

[0258] a) Vehicle products (e.g., automobiles, buses, trains, airplanes, ships, ambulances, etc.)

[0259] (Ships), such as headrests, dashboards, door panels, (e.g., airplane) blinds,

[0260] Gear shift lever, seat belt buckle, instrument panel and button panel, armrests, railings, luggage compartment,

[0261] Steering wheel, handlebars, etc.;

[0262] b) Medical or dental products, including medical, dental, or laboratory facilities or medical...

[0263] Surfaces of dental or laboratory equipment (e.g., defibrillators, ventilators and CPAPs (especially their masks), protective face shields, canes, wheelchairs, bed rails, breast pumps, IV stands and bags, dental tools (e.g., hand tools used in dental cleaning and restoration), curing lamps (e.g., for dental materials), and examination tables (e.g., non-sterile).

[0264] c) Orthodontic products, including braces (e.g., clear tray braces), retainers, night protection devices, splints, Class II and Class III braces, sleep apnea devices, bite openers, bands, brackets, buccal tubes, traction hooks, buttons, and other attachment devices.

[0265] d) electronic articles including housings and enclosures for electronic devices (e.g., telephones, laptops, tablets, or computers) and keyboards, mice, projectors, printers, remote controls, locks, chargers (including cords and docking stations), electronic keys, video and arcade games, automated teller machines; and point-of-sale electronic devices such as credit card readers, keypads, styluses, cash registers, bar code scanners, payment terminals, and the like;

[0266] e) personal care articles including toothbrushes, eyeglass frames, shoes, clothing, handbags, and the like;

[0267] f) cleaning articles including vacuum cleaners, mops, scrub brushes, dusters, toilet bowl cleaners, toilet bowl brushes, brooms, and the like;

[0268] g) sports articles including helmets, protective gear, balls, and hand-held devices for various sports including baseball, lacrosse, tennis, football, basketball, soccer, and golf, and the like;

[0269] h) food preparation article appliances (e.g., microwaves, stoves, ovens, blenders, toasters, coffee makers, refrigerators), grills, utensils (e.g., especially their handles), condiment bottles, salt and pepper shakers, kitchen carts, cutting boards, lunch boxes, thermoses, tables, and chairs especially for public dining in restaurants, delis, nursing homes, and prisons, and the like;

[0270] i) child care articles including toys, pacifiers, bottles, tooth picks, car seats, cribs, changing tables, playground equipment, and the like; and

[0271] j) building articles including railings, countertops, table tops, cabinets, storage cabinets, window sills, electrical modulators such as light switches, dimmers, and outlets, components of furniture (e.g., desks, tables, chairs, seats, and armrests); furniture, building doors, revolving doors, appliances, vehicles, shopping carts and baskets, bathroom surfaces and components (e.g., sinks, toilet surfaces (e.g., levers), drain covers, shower walls, bathtubs, vanities, countertops), and the like.

[0272] Microstructured surfaces are particularly advantageous for common living facilities such as military housing, prisons, dormitories, nursing homes, apartments, hotels; public locations such as offices, schools, arenas, bowling alleys, golf courses, arcades, gyms, hair salons, spas, shopping centers, airports, train stations; and public transportation.

[0273] The term "microorganism" is generally used to refer to any prokaryotic or eukaryotic microorganism, including but not limited to one or more of a bacterium (e.g., a motile or non-motile bacterium, vegetative or non-viable bacterium, gram-positive bacterium or gram-negative bacterium, planktonic or living in a biofilm, bacterial spore or endospore, algae, fungus (e.g., yeast, filamentous fungus, fungal spore), mycoplasma, and protozoa, and combinations thereof. In some cases, microorganisms of particular interest are those that are pathogenic, and the term "pathogen" is used to refer to any pathogenic microorganism. Examples of pathogens can include, but are not limited to, both gram-positive and gram-negative bacteria, fungi, and viruses, including members of the Enterobacteriaceae or Micrococaceae or Staphylococcus spp., Streptococcus spp., Pseudomonas spp., Acinetobacter spp., Enterococcus spp., Salmonella spp., Legionella spp., Shigella spp., Yersinia spp., Enterobacter spp., Escherichia spp., Bacillus spp., Listeria spp., Campylobacter spp., Acinetobacter spp., Vibrio spp., Clostridium spp., Klebsiella spp., Proteus spp., Aspergillus spp., Candida spp, and Corynebacterium spp., and particular examples of pathogens can include, but are not limited to: Escherichia coli (including enterohemorrhagic E. coli), Staphylococcus aureus, Streptococcus pyogenes, Pseudomonas aeruginosa, Acinetobacter baumannii, Enterococcus faecalis, Salmonella enterica, Listeria monocytogenes, Clostridium difficile, Klebsiella pneumoniae, Candida albicans, and Corynebacterium diphtheriae.E. coli), for example, serotypes 0157:H7, 0129:H11); Pseudomonas aeruginosa; Bacillus cereus; Bacillus anthracis; Salmonella enteritidis; Salmonella enterica serotype 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 pnuemoniae; Proteus mirabilus; and Enterobacter [Cronobacter] sakazakii.

[0274] Exemplary Embodiments

[0275] In a first embodiment, the present disclosure provides a multilayer article. The multilayer article includes: a base layer including a fluoropolymer or a siloxane polymer; a metal oxide layer directly attached to a major surface of the base layer, the metal oxide layer 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 base layer. The article exhibits an average transmittance of 10% or less, 7%, 5%, or 2% or less for light having a wavelength of at least 200 nm to 400 nm, a wavelength bandwidth of at least 30 nanometers, and an angle of incidence of at least one of 0°, 30°, 45°, 60°, or 75°.

[0276] In a second embodiment, the present disclosure provides the multilayer article of the first embodiment, further comprising at least one intermediate layer disposed between the metal oxide layer and the adhesive layer.

[0277] In a third embodiment, the present disclosure provides the multilayer article of the first or second embodiment, wherein the adhesive layer is directly attached to the metal oxide layer.

[0278] In a fourth embodiment, the present disclosure provides the multilayer article of any one of the first through 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.

[0279] In a fifth embodiment, the present disclosure provides the multilayer article of any one of the first through fourth embodiments, wherein the metal oxide layer comprises titanium oxide.

[0280] In a sixth embodiment, the present disclosure provides the multilayer article of any one of the first through 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.

[0281] In a seventh embodiment, the present disclosure provides the multilayer article of any one of the first through sixth embodiments, exhibiting an average transmittance of 70% or more for light incident at at least one of 0°, 30°, 45°, 60°, or 75° incident angle, for a wavelength range of at least 410 nm or more.

[0282] In an eighth embodiment, the present disclosure provides the multilayer article of any one of the first through seventh embodiments, exhibiting an average transmittance of 10% or less, 7%, 5%, or 2% or less for light incident at at least one of 0°, 30°, 45°, 60°, or 75° incident angle, for a wavelength of 200 nm to 280 nm, 200 nm to 300 nm, or 200 nm to 320 nm, with a wavelength bandwidth of at least 30 nm.

[0283] In a ninth embodiment, the present disclosure provides the multilayer article of any one of the first through eighth embodiments, wherein the metal oxide layer is not part of a multilayer optical film.

[0284] In a tenth embodiment, the present disclosure provides the multilayer article of any one of the first through ninth embodiments, wherein the adhesive layer comprises a pressure sensitive adhesive or a hot melt adhesive.

[0285] In an eleventh implementation, the present disclosure provides the multilayer article of any of the first through tenth implementations, wherein the adhesive layer comprises a pressure sensitive adhesive.

[0286] In a twelfth implementation, the present disclosure provides the multilayer article of any of the first through eleventh implementations, wherein the adhesive layer comprises a polyisobutylene adhesive, a silicone adhesive, or a (meth)acrylic adhesive.

[0287] In a thirteenth implementation, the present disclosure provides the multilayer article of any of the first through twelfth implementations, exhibiting a peel force of 500 grams per inch (196.9 grams per centimeter) or more between the metal oxide layer and the adhesive layer.

[0288] In a fourteenth implementation, the present disclosure provides the multilayer article of any of the first through thirteenth implementations, exhibiting a peel force of 500 grams per inch (196.9 grams per centimeter) or more between the substrate layer and the metal oxide layer.

[0289] In a fifteenth implementation, the present disclosure provides the multilayer article of any of the first through fourteenth implementations, wherein the substrate layer comprises a fluoropolymer.

[0290] In a sixteenth implementation, the present disclosure provides the multilayer article of any of the first through fifteenth implementations, wherein the substrate layer comprises a fluoropolymer (co)polymer comprising polymerized units derived from one or more monomers selected from tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, perfluoroalkoxyalkane, or combinations thereof.

[0291] In a seventeenth implementation, the present disclosure provides the multilayer article of any of the first through sixteenth implementations, wherein the substrate layer comprises a silicone thermoplastic polymer.

[0292] In an eighteenth implementation, the present disclosure provides the multilayer article of any of the first through seventeenth implementations, wherein the substrate layer is a monolayer having a thickness of 10 micrometers to 500 micrometers.

[0293] In a nineteenth implementation, the present disclosure provides the multilayer article of any of the first through eighteenth implementations, wherein the substrate layer is a microstructured substrate comprising: a base layer having a thickness of at least 1 micrometer; and a plurality of microstructures extending across a first surface of the base layer.

[0294] In a twentieth embodiment, the present disclosure provides the multilayer article of any of the first through nineteenth embodiments, wherein the microstructured surface comprises peak structures and adjacent valleys, wherein the maximum width of the valleys is in a range from 1 micrometer to 250 micrometers, and the sidewall angle of the peak structures is greater than 10 degrees.

[0295] In a twenty-first embodiment, the present disclosure provides the multilayer article of any of the first through nineteenth embodiments, wherein the microstructured surface comprises peak structures and adjacent valleys having a complement cumulative facet size distribution (Fcc) such that at least 30%, 40%, 50%, 60%, 70%, 80%, or 90% of the structures have a facet size greater than 10 degrees; and less than 80% of the structures have a facet size greater than 35 degrees.

[0296] In a twenty-second embodiment, the present disclosure provides the multilayer article of any of the first through nineteenth embodiments, wherein the microstructured surface comprises less than 30% of flat surface area parallel to the planar base layer.

[0297] In a twenty-third embodiment, the present disclosure provides the multilayer article of any of the first through twenty-second embodiments, which exhibits less than 10% change in light transmittance at 400 nm wavelength after exposure to UVC light at a dose of 50 megajoules per square meter (MJ / m 2 ), wavelength of 254 nm.

[0298] In a twenty-fourth embodiment, the present disclosure provides the multilayer article of any of the nineteenth through twenty-third embodiments, wherein the microstructured surface is capable of a log10 reduction of microorganisms of at least 2, 3, 4, 5, 6, 7, or 8 after cleaning.

[0299] Example

[0300] The following examples are merely illustrative and are not intended to limit the scope of the appended claims.

[0301] Unless otherwise indicated or otherwise apparent from context, all parts, percentages, ratios, etc. in the examples and the rest of the specification are provided on a weight basis.

[0302] Materials Used in the Examples

[0303]

[0304] Interlayer Adhesion Strength Test :

[0305] The interlayer adhesive strength of samples prepared according to the examples and comparative examples described below was tested. For each example or comparative example sample, two 1" × 10" (2.54cm × 25.4cm) strips were prepared. The two strips were then further laminated together with an adhesive-to-adhesive construction. The interlayer adhesive strength of the resulting samples was determined using an IMASS tape peel tester (model SP-2000, purchased from IMASS, Inc., Accord, MA) according to ASTM International, West Conshohocken, PA, “Standard Test Method for Peel Resistance of Adhesives (T-Peel Test)”.

[0306] Light Transmission Loss Test :

[0307] Samples prepared according to the following examples and comparative examples were exposed to 100 megajoules per square meter (MJ / m²) emitted at a wavelength of 254 nm by a germicidal lamp (118VRRD-30-8S germicidal lamp, manufactured by Atlantic Ultraviolet Corporation, Hauppauge, NY). 2 Before and after UVC radiation exposure, the transmittance of the light from the samples was measured at 400 nm using a Shimadzu spectrometer (trade name "SHIMADZU 2550UV-VIS", purchased from Shimadzu Corporation, Kyoto, Japan). The percentage of transmittance loss after UVC radiation exposure was calculated. The transmittance loss at 400 nm indicates photo-oxidative degradation.

[0308] Preparation of Example 1 (PE1) Preparation of THV815GZ fluoropolymer substrate with microstructured surface

[0309] use FIG. 13 The method illustrated herein is used to prepare a THV815GZ fluoropolymer substrate of PE1 with a microstructured surface using a three-roll vertical stack molding apparatus. This apparatus includes an extruder and an extrusion die suitable for extruding one or more layers of molten thermoplastic material into a mold. The mold is a microstructured film, marketed under the trade name "3M". TMBrightness Enhancement Film BEF4-DT-90 (24”) was purchased from 3M Company, St. Paul, MN, and was wrapped around a cylindrical casting roll to provide the desired surface pattern for transfer from the extruder to the molten THV815GZ fluoropolymer as it passed over the cylindrical surface of the roll. The mold surface had a linear prism microstructure. The casting roll had a surface temperature of 76.6 °C and a casting roll speed of 18.8 meters / minute. A roll gap force of 7600 pounds (33806 N) was applied to the fluoropolymer as it contacted the mold on the casting roll. The resulting THV815GZ fluoropolymer substrate of PE1 was 2 mils (50 microns) thick and had a surface comprising a microstructure in the form of linear prisms. The detailed features of the microstructured surface of the PE1 substrate were determined by confocal laser scanning microscopy (CLSM) and are summarized in the table of microstructure features below.

[0310] Microstructure Feature

[0311]

[0312] Preparation of Example 2 (PE2) : Vapor coated the bottom surface of the PE1 substrate with a UV blocking layer (Ti02)

[0313] The bottom surface (opposite the microstructured surface) of the PE1 substrate was coated with a UV blocking coating comprising Ti02using a Denton Vacuum optical coater (purchased from Denton Vacuum, Moorestown, NJ) consisting of a 5 planetary rack planetary drive system located about 30” (76.2 cm) above a 4-chamber Temescal e-beam gun (purchased from Ferro Tec Corporation, Livermore, CA). The planetary system was designed to hold the substrate perpendicular to the evaporation source and to move in and out of the evaporation plume in planetary motion during deposition.

[0314] The actual coating process was as follows: a) vent the vapor coater to atmosphere and remove one of the five planetary racks. The substrate to be coated was adhered to the planetary rack by polyimide tape. The sample was oriented so that the bottom surface of PE1 was exposed for coating. b) Reinstall the planetary rack and, if necessary, similarly configure the other 4 planetary racks and they are also reinstalled in the coater. c) Close the chamber and pump down to <2 x 10 -5 Torr (2.7 x 10 -3d) Turn on the power to the Temescal e-beam gun power supply. Apply a voltage of 10 kV and a current of a few milliamps to the filament of the e-beam gun, thereby heating the Ti02 source material in the e-beam gun. The Ti02 source is heated and controlled via an Eddy Company Optical Monitoring System (OMS) (Eddy Company, Apple Valley, CA). The source is heated until the desired deposition rate of 4 Angstroms per second is achieved and stabilized, the shutter separating the source from the planet carrier is opened, and the rate is maintained via the OMS until the desired thickness is achieved, at which point the shutter is closed and the OMS cuts power to the e-beam source. e) Turn off the main power to the power supply and allow the source to cool for about 10 minutes. h) Then, backfill the chamber to atmospheric pressure via N2 gas, remove each planet carrier and remove the resulting coated PE2 substrate from the coater.

[0315] The Ti02 UV barrier layer formed above has a thickness of about 40 nm.

[0316] Comparative Examples 1-3 (CE1-CE3)

[0317] CE1 samples were prepared by manually laminating the PE1 fluoropolymer substrate with FSA 1250 acrylic pressure sensitive transfer adhesive. The adhesive was laminated on the surface of the PE1 fluoropolymer opposite the microstructured surface.

[0318] CE2 and CE3 samples were prepared in the same manner as 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.

[0319] The CE1-CE3 samples were then tested for interlayer adhesion strength (adhesive to PE1 fluoropolymer substrate interlayer adhesion strength) and transmission loss using the tests described above. The test results are summarized in the Test Results table below.

[0320] Examples 4-6 (E4-E6)

[0321] E4-E6 samples were prepared in the same manner as CE1 described above, except that a PE2 fluoropolymer substrate was used and the selected adhesive was laminated on the UV barrier (Ti02) coated side of the PE2 fluoropolymer substrate.

[0322] ​​The adhesive was FSA 1250 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.

[0323] The samples of E4-E6 were then tested for intercoat adhesion strength (adhesive strength to the UV-blocked side of the PE2 fluoropolymer substrate) and loss of transmission using the tests described above. The test results are summarized in the Test Results table below.

[0324] Test Results

[0325]

Claims

1. A multilayer article comprising: a base layer comprising a fluoropolymer or a siloxane polymer; a metal oxide layer directly attached to a major surface of the base layer, the metal oxide layer 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 base layer, wherein the article exhibits an average transmittance of 10% or less, 7%, 5%, or 2% or less for light incident at at least one of 0°, 30°, 45°, 60°, or 75° angle of incidence having a wavelength of at least 200 nm to 400 nm, a wavelength bandwidth of at least 30 nanometers.

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. The multilayer article of any of claims 1 to 3, 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. The multilayer article of any of claims 1 to 5, 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. The multilayer article of any of claims 1 to 6, exhibiting an average transmittance of 70% or more for light incident at at least one of 0°, 30°, 45°, 60°, or 75° angle of incidence having a wavelength range of at least 410 nm or more.

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 for light incident at at least one of 0°, 30°, 45°, 60°, or 75° angle of incidence having a wavelength of 200 nm to 280 nm, 200 nm to 300 nm, or 200 nm to 320 nm, a wavelength bandwidth of at least 30 nanometers.

9. The multilayer article of any of claims 1 to 8, wherein the metal oxide layer is not part of a multilayer optical film.

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. The multilayer article of any of claims 1 to 11, wherein the adhesive layer comprises a polyisobutylene adhesive, a siloxane adhesive, or a (meth)acrylic adhesive. ​ 13. The multi-layer article of any one of claims 1 to 12, exhibiting a peel force of 500 grams / inch (196.9 grams / cm) or more between the metal oxide layer and the adhesive layer.

14. The multi-layer article of any one of claims 1 to 13, exhibiting a peel force of 500 grams / inch (196.9 grams / cm) or more between the substrate layer and the metal oxide layer.

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

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

17. The multi-layer article of any one of claims 1 to 16, wherein the substrate layer comprises a siloxane thermoplastic polymer.

18. The multi-layer article of any one of claims 1 to 17, wherein the substrate layer is a single layer having a thickness of 10 micrometers to 500 micrometers.

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

20. The multi-layer article of claim 19, wherein the microstructured surface comprises peak structures and adjacent valleys, wherein the valleys have a maximum width in the range of 1 micrometer to 250 micrometers and the peak structures have a sidewall angle greater than 10 degrees.

21. The multi-layer article of claim 19, wherein the microstructured surface comprises peak structures and adjacent valleys having a distribution of cumulative complement slope magnitude (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. The multi-layer article of claim 19, wherein the microstructured surface comprises less than 30% of flat surface area parallel to the planar base layer.

23. The multilayer article according to any one of claims 1 to 22, wherein the multilayer article is exposed to a dose of 50 megajoules / m² (MJ / m²). 2 After exposure to UVC light with a wavelength of 254 nm, the transmittance changed by less than 10% at a wavelength of 400 nm.

24. The multi-layer article of any one of claims 19 to 23, wherein the microstructured surface has a log10 reduction of microorganisms after cleaning of at least 2, 3, 4, 5, 6, 7, or 8.

Images