WO2022090901A1

WO2022090901A1 - Ultraviolet c (uv-c) light reflector including fluoropolymer films

Info

Publication number: WO2022090901A1
Application number: PCT/IB2021/059831
Authority: WO
Inventors: Timothy J. Hebrink; Matthew T. Scholz; Stephen P. Maki; James A. Phipps; Caleb T. NELSON
Original assignee: 3M Innovative Properties Company
Priority date: 2020-10-30
Filing date: 2021-10-25
Publication date: 2022-05-05

Abstract

Ultraviolet C (UV-C) light multilayer reflectors and the methods of making and using the same are provided. A UV-C light multilayer reflector includes an optical layer including a fluoropolymer material, an array of inorganic particles dispersed in or disposed on a first major surface of the optical layer, and a reflecting layer disposed on a second major surface of the optical layer.

Description

ULTRAVIOLET C (UV-C) LIGHT REFLECTOR INCLUDING FLUOROPOLYMER FILMS

BACKGROUND

Ultraviolet (UV) light is useful, for example, for initiating free radical reaction chemistries used in coatings, adhesives, and polymeric materials. Ultraviolet light is also useful, for example, for disinfecting surfaces, filters, bandages, membranes, articles, air, and liquids (e.g., water). Examples where UV-C (i.e., ultraviolet C light includes wavelengths in a range from 100 nanometers to 280 nanometers) disinfection could be applied include medical offices and supplies, airplane restrooms, hospital rooms and surgical equipment, schools, air and water purification, and consumer applications (e.g., toothbrush and cell phone disinfection). Prevention of infection and spread of disease, especially in high-risk environments and populations, has become increasingly more critical as pathogens mutate and develop antibiotic resistance. The availability and speed of global human travel elevates risks of rapidly developed epidemics/pandemics. Air and water disinfection is paramount to human health and preventing infectious disease. Benefits of UV-C disinfection include touch-free application, and the mechanical disruption of cells at non-gene specific targets is unlikely to be overcome by pathogens via mutation to develop resistance. Surfaces being disinfected with ultraviolet light other than metal, ceramic, or glass surfaces will need protection from ultra-violet light. UV-C irradiation can be applied to effectively inactivate or kill prokaryotic and eukaryotic microorganisms alike, including bacteria, viruses, fungi and molds. Bacterial strains with developed resistance to one or more antibiotics are also susceptible to UV-C light. Some examples of pathogens of heightened interest include hospital acquired infections (e.g., C. diff, E. coli, MRSA, Klebsiella, influenza, mycobacteria, and enterobacteria), water and soil borne infections (e.g., giardia, legionella, and Campylobacter) and airborne infections (e.g., influenza, pneumonia, and tuberculosis). Numerous research papers have published the effectiveness of UV-C for killing both bacteria and viruses.

SUMMARY

Briefly, in one aspect, the present disclosure describes an ultraviolet C (UV-C) light multilayer reflector including an optical layer comprising a fluoropolymer material; an array of inorganic particles dispersed in or disposed on a first major surface of the optical layer; and a reflecting layer disposed on a second major surface of the optical layer, opposite the first major surface, optionally, the reflecting layer including an aluminum layer.

In another aspect, the present disclosure describes a method of making an ultraviolet C (UV-C) light multilayer reflector. The method includes providing an optical layer comprising a fluoropolymer material; providing an array of inorganic particles dispersed in or disposed on a first major surface of the optical layer; and vapor-coating a reflecting layer on a second major surface of the optical layer, opposite the first major surface.

Various unexpected results and advantages are obtained in exemplary embodiments of the disclosure. One such advantage of exemplary embodiments of the present disclosure is that the multilayer reflector containing fluoropolymer and coated or blended with inorganic particles exhibits relatively high reflectivity in an ultraviolet C (UV-C) wavelength range from 200 to 280 nanometers and high abrasion resistance. The surface of a fluoropolymer copolymer can also be modified to reduce bacteria adhesion. In addition, various multilayer UV-C reflective materials can be used along with the fluoropolymer copolymer to further improve its UV-C reflectivity.

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

BRIEF DESCRIPTION OF THE DRAWINGS

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

FIG. 1A is a cross-sectional view of an ultraviolet C (UV-C) light multilayer reflector, according to one embodiment.

FIG. IB is a cross-sectional view of an ultraviolet C (UV-C) light multilayer reflector, according to another embodiment.

FIG. 1C is a cross-sectional view of an ultraviolet C (UV-C) light multilayer reflector, according to another embodiment.

FIG. 2A is a cross-sectional view of an ultraviolet C (UV-C) light multilayer reflector, according to another embodiment.

FIG. 2B is a cross-sectional view of an ultraviolet C (UV-C) light multilayer reflector, according to another embodiment.

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

DETAILED DESCRIPTION

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

Glossary

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

The terms “(co)polymer” or “(co)polymers” includes homopolymers and copolymers, as well as homopolymers or copolymers that may be formed in a miscible blend, e.g., by coextrusion or by reaction, including, e.g., transesterification. The term “copolymer” includes random, statistical, alternating, block and star (e.g., dendritic) copolymers.

The term “fluoropolymer” refers to long chain molecules including repeating carboncarbon units (chain links) that are fully or partially fluorinated.

The term “ultraviolet C or UV-C” refers to wavelengths of light in the wavelength range of about 190 nm to about 280 nm.

The term “reflectance” refers to the percentage of light incident on a surface interface that is reflected. Reflectance quantifies the amount of light reflected back into the half space of the incoming light.

The terms “about” or “approximately” with reference to a numerical value or a shape means +/- five percent of the numerical value or property or characteristic, but expressly includes the exact numerical value. For example, a viscosity of “about” 1 Pa-sec refers to a viscosity from 0.95 to 1.05 Pa-sec, but also expressly includes a viscosity of exactly 1 Pa-sec. Similarly, a perimeter that is “substantially square” is intended to describe a geometric shape having four lateral edges in which each lateral edge has a length which is from 95% to 105% of the length of any other lateral edge, but which also includes a geometric shape in which each lateral edge has exactly the same length.

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

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

As used in this specification, the recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.8, 4, and 5).

Exemplary embodiments of the present disclosure may take on various modifications and alterations without departing from the spirit and scope of the present disclosure. Accordingly, it is to be understood that the embodiments of the present disclosure are not to be limited to the following described exemplary embodiments, but is to be controlled by the limitations set forth in the claims and any equivalents thereof. Various exemplary embodiments of the disclosure will now be described with particular reference to the Drawings.

It is found that UV-C disinfection is more effective if the UV-C irradiation is not absorbed by ceilings, walls, cabinets, countertops, and floor materials. UV-C reflective materials on the inner surfaces of a room can minimize shadows caused by objects such as tables, beds, and instruments in the room. Most materials may absorb UV-C and/or degrade from UV-C exposure. The present disclosure provides various ultraviolet C (UV-C) light multilayer reflectors including an optical layer containing a fluoropolymer material. It is found that fluoropolymers contained in the optical layer can help the UV-C light multilayer reflector to resist UV-C degradation for thousands of hours.

FIG. 1A illustrates an ultraviolet C (UV-C) light multilayer reflector 100, according to one embodiment. The UV-C reflector 100 is in the form of multilayer film, including an optical layer 110 having opposite first major surface 112 and second major surface 114, an array of inorganic particles 140 disposed on the first major surface 112 of the optical layer, and a reflecting layer 120 disposed on the second major surface 114 of the optical layer 110, opposite the first major surface 112, to reflect incident light back to the first major surface 112.

In some embodiments, the reflecting layer 120 includes an aluminum layer that can be vapor-coated on to the second major surface 114 of the optical layer 110. The second major surface 114 of the optical layer 110 may include fluoropolymer film where the reflecting layer 120 (e.g., aluminum) is disposed. The aluminum/fluoropolymer interface can substantially reflect an incident light in a broad wavelength range such as, for example, the wavelength range of about 200 nanometers to about 10,000 nanometers. The aluminum layer may have a suitable thickness, for example, about 25 to 10,000 micrometers. An aluminum reflecting layer can be polished aluminum or a vapor coated aluminum layer. Aluminum absorbs substantially less light between 200 nanometers and 380 nanometers than other metals, which can enhance the reflectance in the desired wavelength range of UV-C light.

The optical layer 110 includes a fluoropolymer material. The fluoropolymer material may include, for example, one or more copolymers of tetrafluoroethylene, hexafluoropropylene, or vinylidene fluoride (THV). Exemplary fluoropolymers for the optical layer may include those available, for example, from 3M Dyneon, Oakdale, MN, under the trade designations "FLUOROPLASTIC GRANULES THV221GZ" (39 mol% tetrafluoroethylene, 11 mol% hexafluoropropylene, and 50 mol% vinylidene fluoride), "FLUOROPLASTIC GRANULES THV2030GZ" (46.5 mol% tetrafluoroethylene, 16.5 mol% hexafluoropropylene, 35.5 mol% vinylidene fluoride, and 1.5 mol% perfluoropropyl vinylether), "FLUOROPLASTIC GRANULES THV610GZ" (61 mol% tetrafluoroethylene, 10.5 mol% hexafluoropropylene, and 28.5 mol% vinylidene fluoride), and "FLUOROPLASTIC GRANULES THV815GZ" (72.5 mol% tetrafluoroethylene, 7 mol% hexafluoropropylene, 19 mol% vinylidene fluoride, and 1.5 mol% perfluoropropyl vinylether). Another suitable fluoropolymer for the optical layer 110 is FEP (fluorinated ethylene propylene copolymer). It is to be understood that the optical layer 110 may include other suitable fluoropolymer material(s) described herein further below.

The optical layer 110 may include one or more layers of fluoropolymer material(s). In some embodiments, the optical layer 110 includes a single layer of fluoropolymer material and the array of inorganic particles 140 is disposed on or dispersed in its first major surface. The single layer of fluoropolymer material may have a thickness, for example, from about one micrometer to about 1000 micrometers.

In the embodiment depicted in FIG. 1C, the optical layer 110 includes a first fluoropolymer sublayer 110a and a second fluoropolymer sublayer 110b. The array of inorganic particles 140 is disposed on or dispersed in the major surface of the first fluoropolymer sublayer 110a. The first and second fluoropolymer sublayer each may include, for example one or more copolymers of tetrafluoroethylene, hexafluoropropylene, or vinylidene fluoride (THV). In some embodiments, the first fluoropolymer sublayer may have a lower glass transition temperature than the second fluoropolymer sublayer such that it allows to press the inorganic particles 140 into the first major surface of the first fluoropolymer sublayer when the first fluoropolymer sublayer is at a melt state while the second fluoropolymer sublayer is not. In some embodiments, the first fluoropolymer sublayer may have a thickness, for example, from about one micrometer to about 100 micrometers. The second fluoropolymer sublayer may have a thickness, for example, from about one micrometer to about 1000 micrometers. In some embodiments, the optical layer may include at least a plurality of alternating first and second optical sublayers collectively reflecting at least one of 0°, 30°, 45°, 60°, or 75° incident light angle at least 30 (in some embodiments, at least 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, or even at least 90) percent of an incident UV-C light over at least a 30-nanometer wavelength reflection bandwidth in a wavelength range from 200 nanometers to 280 nanometers. The optical layer may include, for example, about 5 to about 2000 layers of the alternating first and second optical sublayers to form a UV-C reflective optical stack.

In some embodiments, the first optical sublayers may include a high refractive index material such as, for example, at least one of hafnium dioxide, zirconium oxynitride, or aluminum oxide, and the second optical sublayers may include a low refractive index material such as, for example, at least one of silicon dioxide, silicon aluminum oxide, or magnesium fluoride. The alternating first and second optical sublayers can be sandwiched by a first fluoropolymer sublayer and a second fluoropolymer sublayer such as, for example, the first fluoropolymer sublayer 110a and the second fluoropolymer sublayer 110b in FIG. 1C.

Exemplary embodiments can be designed to have peak reflectance at 254 nm, by both physical vapor deposition (PVD) methods. For example, coating discrete substrates by electronbeam deposition method, using HfCE as the high refractive index material and SiCE as the low refractive index material. Mirror design has alternating layers of “quarter wave optical thickness” (qwot) of each material, that are coated, layer by layer until, for example, after 13 layers the reflectance at 254 nm is greater than 99%. The bandwidth of this reflection peak is around 80 nm. Quarter wave optical thickness is the design wavelength, here 254 nm, divided by 4, or 63.5 nm. Physical thickness of the high refractive index layers (HfCE) is the quotient of qwot and refractive index of HfCE at 254 nm (2.41), or 30.00 nm. Physical thickness of the low refractive index layers (MgF2), with 254 nm refractive index at 1.41, is 45.02 nm. Coating athin film stack, then, which is comprised of alternating layers of HfCE and Si CU and designed to have peak reflectance at 254 nm begins by coating layer 1 HfCE at 30.00 nm. In electron beam deposition a four-hearth evaporation source is used. Each hearth is cone-shaped and 17 cm³ volume of HfCE chunks fill it. The magnetically deflected high voltage electron beam is raster scanned over the material surface as filament current of the beam is steadily, in a pre-programmed fashion, increased. Upon completion of the pre-programmed step the HfCE surface is heated to evaporation temperature, about 2500°C, and a source shutter opens, the HfCE vapor flux emerging from the source in a cosine-shaped distribution and condensing upon the substrate material above the source. For enhancement of coating uniformity, the substrate holders rotate during deposition. Upon reaching the prescribed coating thickness (30.00 nm) the filament current shuts off; the shutter closes and the HfCE material cools. For layer 2 the evaporation source is then rotated to a hearth containing chunks of MgF₂ and a similar pre-programmed heating process begins. Here, the MgF₂ surface temperature is about 950°C when the source shutter opens and, upon reaching the prescribed coating thickness (45.02 nm), the filament current shuts off; the shutter closes and the HfO₂ material cools. This step-wise process is continued, layer by layer, until the total number of design layers is reached. With this optical design, as total layers are increased, from 3 to 13, the resulting peak reflectance increases accordingly, from 40% at 3 layers to greater than 99% at 13 layers.

In another exemplary embodiment, UV transparent films can be coated in continuous roll to roll (R2R) fashion, using ZrON as the high refractive index material and SiO₂ as the low refractive index material. The optical design is the same type of thin film stack, alternating qwot layers of the two materials. For ZrON, with refractive index at 254 nm of 2.25, the physical thickness target was 28.22 nm. For SiO₂, here sputtered from an aluminum-doped silicon sputter target, with refractive index 1.49, the target thickness was 42.62 nm. Layer one ZrON is DC sputtered from a pure zirconium sputter target in a gas mixture of argon, oxygen and nitrogen. Whereas argon is the primary sputtering gas, oxygen and nitrogen levels are set to achieve transparency, low absorptance and high refractive index. The film roll transport initially starts at a pre -determined speed, and the sputter source power is ramped to full operating power, followed by introduction of the reactive gases and then achieving steady state condition. Depending upon the length of film to coat, the process continues until total footage is achieved. Here, as the sputter source is orthogonal to and wider than the film which is being coated, the uniformity of coating thickness is quite high. Upon reaching the desired length of coated film the reactive gases are set to zero and the target is sputtered to a pure Zr surface state. The film direction is next reversed and silicon (aluminum doped) rotary pair of sputter targets has AC frequency (40 kHz) power applied in an argon sputtering atmosphere. Upon reaching steady state, oxygen reactive gas is introduced to provide transparency and low refractive index. At the pre-determined process setting and line speed the second layer is coated over the length which was coated for layer one. Again, as these sputter sources are also orthogonal to and wider than the film being coated, the uniformity of coating thickness is quite high. After reaching the desired length of coated film the reactive oxygen is removed and the target is sputtered in argon to a pure silicon (aluminum doped) surface state. Layers three to five or seven or nine or eleven or thirteen, depending upon peak reflectance target, are coated in this sequence. Upon completion, the film roll is removed for post-processing.

For manufacturing of these inorganic coatings, the electron beam process is best suited for coating discrete parts. Though some chambers have demonstrated R2R film coating, the layer by layer coating sequence would still be necessary. For R2R sputtering of film, it is advantageous to use a sputtering system with multiple sources located around one, or perhaps two, coating drums. Here, for a thirteen layers optical stack design, a two, or even single, machine pass process, with alternating high and low refractive index layers coated sequentially, would be feasible. How many machine passes needed would be contingent upon machine design, cost, practicality of thirteen consecutive sources, and so forth. Additionally, coating rates would need to be matched to a single fdm line speed.

In some embodiments, the first optical sublayers may include polyvinylidene fluoride or polyethylene tetrafluoroethylene, and the second optical sublayers may include a copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride, or a fluorinated ethylene propylene (FEP) polymer.

In some embodiments of multilayer optical films described herein, the at least first optical sublayer may include polymeric material (e.g., at least one of polyvinylidene fluoride (PVDF), or ethylene tetrafluoroethylene (ETFE)), and where the second optical layer includes polymeric material (e.g., at least one of a copolymer (THV,) a copolymer comprising subunits derived from tetrafluoroethylene (TFE), hexafluoropropylene (HFP), and vinylidene fluoride (VDF), a copolymer (FEP) comprising subunits derived from tetrafluoro-ethylene (TFE) and hexafluoropropylene (HFP), or perfluoroalkoxy alkane (PFA)).

In some embodiments of multilayer optical films described herein, the at least first optical sublayer may include inorganic material (e.g., at least one of titania, zirconia, zirconium oxynitride, hafhia, or alumina), and where the second optical layer includes inorganic material (e.g., at least one of silica, aluminum fluoride, or magnesium fluoride). Exemplary materials are available, for example, from Materion Corporation, Mayfield Heights, OH, and Umicore Corporation, Brussels, Belgium.

Exemplary materials for making the optical layers or sublayers that reflect UV-C light (e.g., the first and second optical sublayers) include polymers. In this context, the term “polymer” will be understood to include homopolymers and copolymers, as well as polymers or copolymers that may be formed in a miscible blend, for example, by co-extrusion or by reaction, including transesterification. The terms “polymer” and “copolymer” include both random and block copolymers.

First optical sublayers can also be isotropic high refractive index layers including at least one of poly(methyl methacrylate), copolymers of polypropylene; copolymers of polyethylene, cyclic olefin copolymers, cyclic olefin block copolymers, or miscible blends of poly(methyl methacrylate) or poly(vinylidene fluoride).

Second optical layers can also include fluorinated copolymers materials such as at least one of fluorinated ethylene propylene copolymer (FEP); copolymers of tetrafluorethylene, hexafluoropropylene, and vinylidene fluoride (THV); copolymers of tetrafluoroethylene, hexafluoropropylene, or perfluorinated propylene vinyl ether. Particularly useful are melt processible copolymers of tetrafluoroethylene and at least two, at least three, or even at least four additional different comonomers.

Exemplary melt processible copolymers of tetrafluoroethylene and other monomers discussed above include those available as copolymers of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride under the trade designations “DYNEON THV 220,” “DYNEON THV 230, ’’“DYNEON THV 2030, ’’“DYNEON THV 500, ’’“DYNEON THV 610,” and “DYNEON THV 815” from Dyneon LLC, Oakdale, MN;“NEOFLON EFEP” from Daikin Industries, Ltd., Osaka, Japan; “AFLAS” from Asahi Glass Co., Ltd., Tokyo, Japan; and copolymers of ethylene and tetrafluoroethylene available under the trade designations “DYNEON ET 6210A” and “DYNEON ET 6235” from Dyneon LLC;“TEFZEL ETFE” from E.I. duPont de Nemours and Co., Wilmington, DE; and “FLUON ETFE” by Asahi Glass Co., Ltd.

Other exemplary polymers, for the optical layers, especially for use in the first layer, include homopolymers of polymethylmethacrylate (PMMA), such as those available, for example, from Ineos Acrylics, Inc., Wilmington, DE, under the trade designations“CP71” and“CP80;” and poly ethyl methacrylate (PEMA), which has a lower glass transition temperature than PMMA. Additional useful polymers include copolymers of PMMA (CoPMMA), such as a CoPMMA made from 75 wt.% methylmethacrylate (MMA) monomers and 25 wt.% ethyl acrylate (EA) monomers, (available, for example, from Ineos Acrylics, Inc., under the trade designation “PERSPEX CP63” or Arkema, Philadelphia, PA, under the trade designation “ATOGLAS 510”), a CoPMMA formed with MMA comonomer units and n-butyl methacrylate (nBMA) comonomer units, or a blend of PMMA and poly(vinylidene fluoride) (PVDF).

Additional suitable polymers for the optical layers include polyolefin copolymers such as poly (ethylene-co-octene) (PE-PO) available, for example, under the trade designation “ENGAGE 8200” from Dow Elastomers, Midland, MI; polyethylene methyl acrylate also available, for example, under the trade designation “ELVALOY 1125” from Dow, Midland, MI; poly(propylene-co-ethylene) (PPPE) available, for example, under the trade designation“Z9470” from Atofina Petrochemicals, Inc., Houston, TX; and a copolymer of atactic polypropylene (aPP) and isotatctic polypropylene (iPP) . The multilayer optical films can also include in the second layers, a functionalized polyolefin (e.g., linear low-density polyethylene-graft-maleic anhydride (LLDPE-g-MA) such as that available, for example, under the trade designation “BYNEL 4105” from E.I. duPont de Nemours & Co., Inc.).

The selection of the polymer combinations used in creating the multilayer optical film depends, for example, upon the desired bandwidth that will be reflected. Higher refractive index differences between the first optical layer polymer and the second optical layer polymer create more optical power thus enabling more reflective bandwidth. Alternatively, additional layers may be employed to provide more optical power. Exemplary combinations of birefringent layers and second polymer layers may include, for example, the following: PVDF/THV, ETFE/THV, PVDF/FEP, ETFE/FEP, blend of PVDF/PMMA with THV and blend of PVDF/PMMA with FEP.

In some embodiments, the plurality of alternating first and second optical sublayers can be disposed as a stack between a first fluoropolymer sublayer at the first major surface and a second fluoropolymer sublayer attached to the reflecting layer. The first and/or the second fluoropolymer sublayer may include the same or different fluoropolymers. Exemplary fluoropolymers include those available, for example, from 3M Dyneon, Oakdale, MN, under the trade designations "FLUOROPLASTIC GRANULES THV221GZ" (39 mol% tetrafluoroethylene, 1 1 mol% hexafluoropropylene, and 50 mol% vinylidene fluoride), "FLUOROPLASTIC GRANULES THV2030GZ" (46.5 mol% tetrafluoroethylene, 16.5 mol% hexafluoropropylene, 35.5 mol% vinylidene fluoride, and 1.5 mol% perfluoropropyl vinylether), "FLUOROPLASTIC GRANULES THV610GZ" (61 mol% tetrafluoroethylene, 10.5 mol% hexafluoropropylene, and 28.5 mol% vinylidene fluoride), and "FLUOROPLASTIC GRANULES THV815GZ" (72.5 mol% tetrafluoroethylene, 7 mol% hexafluoropropylene, 19 mol% vinylidene fluoride, and 1.5 mol% perfluoropropyl vinylether).

The array of inorganic particles 140 may include, for example, silica glass beads. The silica glass beads may have an average size, for example, about 1 to 100 microns. The silica glass beads may be fused silica which absorbs less than 5%, less than 3%, or less than 1% of the incident UV- C light. Exemplary silica glass beads may include those available, for example, under the trade designation “e5000” or “EMB-20” from Potter’s Industries, Muscatine, IA. Other suitable glass beads include those available, for example, under the trade designation SiLiBeads Type Q from Sigmund Lindner, fused quartz spheres from American Elements, and product number 440345 from Sigma- Aldrich.

The array of inorganic particles 140 can be provided to disperse in or dispose on the first major surface 112 of the optical layer 110 by various suitable methods. In some embodiments, the first major surface 112 of the optical layer 110 is a fluoropolymer film and the array of inorganic particles 140 can be pressed at least partially into the fluoropolymer film when the fluoropolymer film is heated at a certain temperature such as, for example, 120°C to 250°C. Glass beads can be dropped into a nip roller process where molten fluoropolymer is being extruded into the nip. In some embodiments, glass beads are spread onto a moving web (e.g., polyester film or aluminum belt) which then passes into the nip roller process where molten fluoropolymer is simultaneously being extruded into the nip.

An optical layer described herein may include, for example, 50-97 % by weight of the fluoropolymer material and 3-50 % by weight of the inorganic particles. In the embodiment of FIG. 1A, the inorganic particles 140 are at least partially embedded into the first major surface 112 of the optical layer. In the embodiments of FIGS. IB and 1C, the optical layer 110 further includes a thin fluoropolymer coating 142 over the inorganic particles 140. The thin fluoropolymer coating 142 may be substantially conformal to the surface of the inorganic particles such that the inorganic particles 140 still texture the first major surface 112 of the optical layer 110. In some embodiments, the thin fluoropolymer coating 142 may have a thickness, for example, from about 0.1 micrometers to about 100 micrometers. The thin fluoropolymer coating 142 may include one or more fluoropolymer materials the same as or different from the fluoropolymer material in the bulk of the optical layer 110.

An optional adhesive layer 130 is provided to attach to the reflecting layer 120 on the side opposite the optical layer 110. A protective liner can be provided to cover the adhesive surface of the adhesive layer 130 opposite to the reflecting layer 120. Exemplary adhesives for the optional adhesive layer may include pressure sensitive adhesives and hot melt adhesives. Extrudable hot melt adhesives can be formed into pressure sensitive adhesives by extrusion blending with tackifiers. Exemplary pressure sensitive adhesives are available, for example, under the trade designations "OCA8171" and "OCA8172" from 3M Company, St. Paul, MN. Extrudable pressure sensitive adhesives are commercially available, for example, from Kuraray, Osaka, Japan, under the trade designations "LIR-290," "LA2330," "LA2250," "LA2140E," and "LAI 1 14;" and Exxon Mobil, Irving, TX, under the trade designation "ESCORE."

In some embodiments, the optional adhesive layer 130 can include a hot melt adhesive such as, for example, under the trade designation “Nucrel” available from DOW, under the trade designation “Flexel” available from H.B. Fuller, under the trade designation “EVA” available from DuraCo, etc. An exemplary hot melt adhesive is THV221GZ available from 3M Company, St. Paul, MN.

In some embodiments, one or more photocatalytic antimicrobial materials may be provided to be disposed on the first major surface of the optical layer. The photocatalytic antimicrobial material may include, for example, at least one of titanium dioxide in rutile crystal form, or titanium oxide in anatase crystal form. Exemplary titanium dioxide may include those available, for example, under the trade designation “KRONOS 1000” from KRONOS INC, Houston, TX.

The photocatalytic antimicrobial materials can be provided to disperse in or dispose on the first major surface 112 of the optical layer 110 by various suitable methods. Photocatalytic antimicrobial materials such as TiO2 micro-powder can be applied to the optical layer 110 by the same hot melt methods described for applying glass beads to optical layer 110.

In some embodiments, discontinuous islands containing titanium can be deposited on the major surface 112 of the optical layer 110 by plasma enhanced chemical vapor deposition. The deposited species is the reaction product of plasma enhanced chemical vapor deposition derived from a gaseous species. The gaseous species may include a titanium containing compound selected from metal alkyls, metal halides, or metal isopropoxides. Useful compounds can include titanium isoproxide, titanium tetrachloride, titanium chloride, and titanium tetra-ethoxide. Exemplary deposition processes were described in U.S. Patent Nos. 10,119,190 (David et. al.) and 9,908,772 (David et. al.), which are incorporated herein by reference.

In some embodiments, discontinuous islands of TiCf can be deposited onto the major surface 112 of the optical layer 110 by, for example, vapor coating techniques. Thin films of titanium dioxide are often coated by physical vapor deposition (PVD) methods such as evaporation or sputtering. In either case, the depositing material is vaporized from a source and condenses upon the surface of a substrate. Film growth can be described as occurring in stages, from nucleation to coalescence to continuous form. For controlled island growth, initial nucleation of the material upon the substrate is energy and surface dependent. The Volmer-Weber film growth model describes that when adatom to adatom interactions are stronger than those of adatom to substrate surface, formation of islands or clusters are more likely to occur. For titanium dioxide, island growth generally occurs in the 10-30 Angstrom (1-3 nm) equivalent thickness region. The interaction between energy of the arriving material and substrate surface free energy is key to controlling adatom mobility and the stepwise film growth. Each coating scenario is unique to the equipment and process which are used. In general, deposition rate control and surface plasma pretreatment are used to create a coating scenario for low surface mobility of adatoms and the formation of islands and island clusters.

In some embodiments, the first major surface of the optical layer can include an anisotropically etched structure. The anisotropically etched structure includes a nano-on-micro surface structure. In the embodiment depicted in FIG. 2A, the UV-C reflector 200 is in the form of multilayer film, including an optical layer 210 having opposite first major surface 212 and second major surface 214, a reflecting layer 120 disposed on the second major surface 214 of the optical layer 210, and an optional adhesive layer 130 provided to attach to the reflecting layer 120 on the side opposite the optical layer 210. The first major surface 212 of the optical layer 210 may be a fluoropolymer film which includes an anisotropically etched structure. The anisotropic surface 207 has microfeatures 206 having at least one dimension in a range from 1 micrometer to 500 micrometers. Nanoscale features 202 are formed on the microfeatures 206. In the depicted embodiment of FIG. 2A, the nanoscale features 202 includes nano-pillars. The nanoscale features 202 may include various nanofeatures such as, for example, nano-columns, continuous nano-walls including nano-pillars or nano-columns, etc. The nanoscale features 202 may have steep side walls that are roughly perpendicular to the film. In some embodiments, the majority of the nanoscale features 202 are capped with a photo-catalytic material 205. Exemplary photo-catalytic materials may include titanium dioxide in rutile crystal form, or titanium oxide in anatase crystal form. The surface structuring of the fluoropolymer fdm can reduce bacteria adhesion by preventing biofilm formation.

In some embodiments, a fluoropolymer film containing microstructures can be used to generate a nanostructure on top of the microstructure by plasma treatment. In some embodiments, the top skin layer (e.g., a fluoropolymer film) of an optical layer can be sputtered with islands of photo-catalytic materials such as, for example, titanium dioxide in rutile crystal form, or titanium oxide in anatase crystal form. The fluoropolymer film is then reactive ion etched with plasma using the sputtered islands of material as masks to create nanoscale features having caps of the photo-catalytic materials. Exemplary anisotropically-etching processes were described in U.S. Patent Nos. 10,119,190 (David et. al.) and 9,908,772 (David et. al.), which are incorporated herein by reference.

In the embodiment depicted in FIG. 2B, the optical layer 210’ of the UV-C reflector 200’ further includes an array of inorganic particles 240 dispersed in the first major surface 212 of the optical layer. The anisotropic surface 207 having the microfeatures 206 and the nanoscale features 202 are formed to at least partially cover the array of inorganic particles 240, where the nanoscale features 202 are capped with the photo-catalytic material 205. FIG. 2B shows randomly spaced glass beads 240 in the thickness direction of the first optical whereas FIG. 1 A-B show a mono- layer of glass beads on or near the surface of the first optical layer.

Exemplary embodiments of the present disclosure may take on various modifications and alterations without departing from the spirit and scope of the disclosure. Accordingly, it is to be understood that the embodiments of the present disclosure are not to be limited to the following described exemplary embodiments, but are to be controlled by the limitations set forth in the claims and any equivalents thereof. Listing of Exemplary Embodiments Embodiment 1 is an ultraviolet C (UV-C) light multilayer reflector comprising: an optical layer comprising a fluoropolymer material; an array of inorganic particles dispersed in or disposed on a first major surface of the optical layer; and a reflecting layer disposed on a second major surface of the optical layer, opposite the first major surface, optionally, the reflecting layer comprising an aluminum layer.

Embodiment 2 is the UV-C light multilayer reflector of embodiment 1, wherein the fluoropolymer material comprises one or more copolymers of tetrafluoroethylene, hexafluoropropylene, or vinylidene fluoride (THV). Embodiment 3 is the UV-C light multilayer reflector of embodiment 1 or 2, wherein the array of inorganic particles comprises silica glass beads.

Embodiment 4 is the UV-C light multilayer reflector of embodiment 3, wherein the silica glass beads have an average size of about 1 to 100 microns.

Embodiment 5 is the UV-C light multilayer reflector of any of embodiments 1-4, wherein the optical layer comprises 50-97 % by weight of the fluoropolymer material and 3-50 % by weight of the inorganic particles.

Embodiment 6 is the UV-C light multilayer reflector of any of embodiments 1-5, further comprising a photocatalytic antimicrobial material disposed on the first major surface of the optical layer, optionally, the photocatalytic antimicrobial material comprising at least one of titanium dioxide in rutile crystal form, or titanium oxide in anatase crystal form.

Embodiment 7 is the UV-C light multilayer reflector of any of embodiments 1-6, wherein the first major surface of the optical layer comprises an anisotropically etched structure.

Embodiment 8 is the UV-C light multilayer reflector of embodiment 7, wherein the anisotropically etched structure includes a nano-on-micro surface structure.

Embodiment 9 is the UV-C light multilayer reflector of any of embodiments 1-8, wherein the optical layer comprises a first fluoropolymer sublayer at the first major surface to receive the array of inorganic particles and a second fluoropolymer sublayer attached to the reflecting layer. Embodiment 10 is the UV-C light multilayer reflector of embodiment 9, wherein the first and second fluoropolymer sublayer each comprises one or more copolymers of tetrafluoroethylene, hexafluoropropylene, or vinylidene fluoride (THV), and the first fluoropolymer sublayer has a lower glass transition temperature than the second fluoropolymer sublayer.

Embodiment 11 is the UV-C light multilayer reflector of any of embodiments 1-10, wherein the optical layer further comprises a plurality of alternating first and second optical sublayers collectively reflecting at least 50%, 60%, 70%, 80%, or at least 90% of an incident UV-C light over at least a 30-nanometer wavelength reflection bandwidth in a wavelength range from 200 nanometers to 280 nanometers.

Embodiment 12 is the UV-C light multilayer reflector of embodiment 11, wherein the first optical sublayers comprise at least one of hafnium dioxide, zirconium oxynitride, or aluminum oxide, and the second optical sublayers comprise at least one of silicon dioxide, silicon aluminum oxide, or magnesium fluoride.

Embodiment 13 is the UV-C light multilayer reflector of embodiment 11, wherein the first optical sublayers comprise polyvinylidene fluoride or polyethylene tetrafluoroethylene, and the second optical sublayers comprise a copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride, or a fluorinated ethylene propylene (FEP) polymer. Embodiment 14 is the UV-C light multilayer reflector of any of embodiments 11-13, wherein the plurality of alternating first and second optical sublayers are disposed as a stack between a first fluoropolymer sublayer at the first major surface and a second fluoropolymer sublayer attached to the reflecting layer.

Embodiment 15 is the UV-C light multilayer reflector of any of embodiments 1-14, further comprising an adhesive layer attached to the reflecting layer on the side opposite the transparent layer.

Embodiment 16 is the UV-C light multilayer reflector of any of embodiments 1-15, which having an average reflectance of at least 30%, 40% or 50% in an ultraviolet C (UV-C) wavelength range from 200 to 280 nanometers.

Embodiment 17 is a method of making an ultraviolet C (UV-C) light multilayer reflector, the method comprising: providing an optical layer comprising a fluoropolymer material; providing an array of inorganic particles dispersed in or disposed on a first major surface of the optical layer; and vapor-coating a reflecting layer on a second major surface of the optical layer, opposite the first major surface.

Embodiment 18 is the method of embodiment 17, wherein the fluoropolymer material comprises one or more copolymers of tetrafluoroethylene, hexafluoropropylene, or vinylidene fluoride (THV).

Embodiment 19 is the method of embodiment 17 or 18, wherein the array of inorganic particles comprises silica glass beads.

Embodiment 20 is the method of any of embodiments 17-19, further comprising providing a photocatalytic antimicrobial material disposed on the first major surface of the optical layer, optionally, the antimicrobial material comprising at least one of titanium dioxide in rutile crystal form or titanium oxide in anatase crystal form.

Embodiment 21 is the method of any of embodiments 17-20, further comprising anisotropically etching the first major surface of the optical layer using plasma to form an anisotropic surface. Embodiment 22 is the method of embodiment 21, wherein the anisotropically etched structure includes a nano-on-micro surface structure.

Embodiment 23 is the method of any of embodiments 17-22, wherein providing the optical layer comprises coextruding a first fluoropolymer sublayer and a second fluoropolymer sublayer. Embodiment 24 is the method of any of embodiments 17-23, wherein providing the optical layer comprises providing a plurality of alternating first and second optical sublayers collectively reflecting at least 50%, 60%, 70%, 80%, or at least 90% of an incident UV-C light over at least a 30-nanometer wavelength reflection bandwidth in a wavelength range from 200 nanometers to 280 nanometers.

Embodiment 25 is the method of embodiment 24, wherein the first optical sublayers comprise at least one of hafnium dioxide, zirconium oxynitride, or aluminum oxide, and the second optical sublayers comprise at least one of silicon dioxide, silicon aluminum oxide, or magnesium fluoride. Embodiment 26 is the method of embodiment 24, wherein the first optical sublayers comprise polyvinylidene fluoride or polyethylene tetrafluoroethylene, and the second optical sublayers comprise a copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride, or a fluorinated ethylene propylene (FEP) polymer.

Embodiment 27 is the method of any of embodiments 24-26, further comprising disposing the plurality of alternating first and second optical sublayers as a stack between a first fluoropolymer sublayer at the first major surface and a second fluoropolymer sublayer attached to the reflecting layer.

Embodiment 28 is the method of any of embodiments 17-27, further comprising attaching an adhesive layer to the reflecting layer on the side opposite the optical layer.

The operation of the present disclosure will be further described with regard to the following detailed examples. These examples are offered to further illustrate the various specific and preferred embodiments and techniques. It should be understood, however, that many variations and modifications may be made while remaining within the scope of the present disclosure.

EXAMPLES

These Examples are merely for illustrative purposes and are not meant to be overly limiting on the scope of the appended claims. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the present disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

MEK Rub Test Method

The MEK Rub Test Method utilized an automated machine (obtained under the trade designation “MEK RUB TEST MACHINE” from DJH Designs Inc., Oakville, Ontario, Canada) which was used to determine scratch resistance to cleaning of fdms with a common cleaning product (obtained under the trade designation “WINDEX MULTI-SURFACE CLEANER” from S.C. Johnson, Racine, WI). The MEK reservoir was fdled with Windex Multi-Surface Cleaner and 1000 grams of weight were applied to the rubbing block. Fresh cotton pads (obtained under the trade designation “PN#1963” from DJH Designs Inc., Oakville, Ontario, Canada) were applied to the bottom of the rubbing block and saturated with the Windex Multi-Surface Cleaner. A 4 inch by 10 inch (10.2 cm by 25.4 cm) test specimen of a fdm to be tested was taped, using a clear polyester-backed adhesive tape (obtained under the trade designation “SCOTCH BOX SEALING TAPE 355” from 3M, St. Paul, MN), along its perimeter, to the rub table. The number of strokes was set at 25. Test specimens were examined for scratching before and after 25 rub strokes with the saturated cotton pad.

Example 1 - Aluminum vapor coated THV 815/THV 221 bi-layer film with glass beads pressed into THV 221

Fluoropolymer (obtained under the trade designation “3M DYNEON THV 815GZ” from 3M Dyneon, Oakdale, MN) was coextruded with another fluoropolymer (obtained under the trade designation “3M DYNEON THV 221GZ” from 3M Dyneon, Oakdale, MN) using two 25 mm twin screw extruders and a flat film extrusion die onto a film casting wheel chilled to 70 °F (21 °C) to create a 50-micrometer thick bi-layer fluoropolymer (“THV 815/THV 221”) film . This bi-layer fluoropolymer film was then vapor coated with 100 nm of aluminum on the “THV 815” side of the bi-layer film. Then 0. 1 grams of glass beads having mean particle size of 10 microns (low alkaline borosilicate solid glass microspheres available under the trade designation “SPHERIGLASS EMB- 20” from Potters Industries LLC, Valley Forge, PA) was dusted onto 25 cm2 of the “THV 221” side of the bi-layer fluoropolymer film. The dusted film was then sandwiched between two aluminum plates with a 5kg weight on the top plate and placed into an oven at 150 °C for 24hrs. When removed from the oven, the glass beads were embedded in the THV 221 layer of the aluminum vapor coated bi-layer film. Reflectance was measured with a spectrophotometer (obtained under the trade designation “LAMBDA 1050” from Perkin-Elmer, Waltham, MA), and averaged 53% over a wavelength range from 200nm to 280nm. Rub testing was conducted on the glass bead side of the bi-layer film according to the MEK Rub Test Method described above and no scratching of the film was observed.

Example 2 - Aluminum vapor coated THV 815/THV 221 bi-layer film with TiCh powder pressed into THV 221

Fluoropolymer (obtained under the trade designation “3M DYNEON THV 815GZ” from 3M Dyneon, Oakdale, MN) was coextruded with another fluoropolymer (obtained under the trade designation “3M DYNEON THV 221GZ” from 3M Dyneon, Oakdale, MN) using two 25 mm twin screw extruders and a flat film extrusion die onto a film casting wheel chilled to 70 °F (21 °C) to create a 50-micrometer thick bi-layer fluoropolymer “THV 815/THV 221” film. This bi -layer fluoropolymer film was then vapor coated with 100 nm of aluminum on the “THV 815” side of the bi-layer film. 0.1 grams of TiCE powder obtained under the trade designation “KRONOS 1000” from KRONOS Worldwide, Inc., Dallas, TX) was dusted onto 25 cm2 “THV 221” side of the of the bi-layer fluoropolymer film. The dusted film was then sandwiched between 2 aluminum plates with a 5kg weight on the top plate and placed into an oven at 150 °C for 24hrs. When removed from the oven, the TiO2 was embedded in the THV221 layer of the aluminum vapor coated bi- layer film. Reflectance was measured with a spectrophotometer (obtained under the trade designation “LAMBDA 1050” from Perkin-Elmer, Waltham, MA) and averaged 40% reflectance over a wavelength range from 200 nm to 280 nm. Rub testing was conducted on the TiCE side of the bi-layer film according to the MEK Rub Test Method described above and no scratching of the film was observed.

Example 3 - Aluminum vapor coated UVC dielectric mirror made with HfCL High Index Optic Lavers and SiO2 Low Index Optic Lavers

A UV-C mirror was made by vapor coating an inorganic optical stack having first optical layers comprising HfCE and second optical layers comprising SiO2 onto 100 micrometer thick fluoropolymer film (obtained under the trade designation “NOWOFLON THV 815” from Nowofol Kunststoffprodukte GmbH & Co. KG, Siegsdorf, Germany). More specifically, a thin film stack comprised of alternating layers of HfCE and SiCE and designed to have peak reflectance at 280 nm. The stack began by coating layer 1 of HfCE at 30.00 nm. For electron beam deposition, a four-hearth evaporation source was used. Each hearth was cone-shaped and 17 cm³ volume of HfCE chunks filled it. The magnetically deflected high voltage electron beam was raster scanned over the material surface as filament current of the beam was steadily, in a pre-programmed fashion, increased. Upon completion of the pre-programmed step, the HfCE surface was heated to evaporation temperature, about 2500 °C, and a source shutter opened, the HfCE vapor flux emerging from the source in a cosine-shaped distribution and condensing upon the substrate material above the source. For enhancement of coating uniformity, the substrate holders rotated during deposition. Upon reaching the prescribed coating thickness (30.00 nm) the filament current was shut off; the shutter was closed and the HfO2 material cooled. For the second layer, the evaporation source was then rotated to a hearth containing chunks of Si O2 and a similar preprogrammed heating process began. Here, the SiCE surface temperature was about 950 °C when the source shutter opened and, upon reaching the prescribed coating thickness (45.02 nm), the filament current was shut off; the shutter closed and the Si O2 material cooled. This step-wise process was continued, layer by layer, until a total number of 13 layers was reached. The resulting peak reflectance was measured with a spectrophotometer (obtained under the trade designation “SHIMADZU 2550 UV-VIS” from Shimadzu Corp., Kyoto, Japan) and found to be 79% at 254 nm, with greater than 70% reflectance averaged over a wavelength range from 220 nm to 280 nm. The UV-C mirror film was then vapor coated with 100 nm of aluminum. UV light transmission was also measured with the “SHIMADZU 2550 UV-VIS” to be 0% over a wavelength range of 200nm to 400nm. Glass beads were then pressed into an additional “THV 221” layer (which had been heat laminated onto the surface of the UV-C mirror film) by the same method used in Example 1. Rub testing was then conducted on the glass bead embedded surface according to the MEK Rub Test Method described above and no scratches were observed on the film surface.

Example 4 - Aluminum vapor coated MOF UV mirror made with ZrON High Index Optic Lavers and SiO2 Low Index Optic Lavers

The 4x4 matrix method using the Berreman algorithm was used for modeling the spectra of constructive and destructive interference generated from layer interfaces of materials having different refractive indices. The Berreman 4x4 matrix methodology is described in the Journal of the Optical Society of America (Volume 62, Number 4, April 1972) and the Journal of Applied Physics (Volume 85, Number 6, March 1999), the disclosures of which are incorporated herein by reference. Input parameters for this optical model were individual layer refractive indices, layer thicknesses, number of layers, and reflection bandwidth including a left band edge and a right band edge. The Berreman methodology calculated the percent light reflected at each layer interface and the percent light transmitted at each layer interface and calculated a reflection spectrum and transmission spectrum. The Berreman methodology was used to calculate %Reflectance of UV-C multilayer optical film having 10 alternating optical layers of ZrON high refractive index layers and SiO2 low refractive index layers for a peak reflectance wavelength target of 254 nm.

The following is a description of a method by which the modelled UV-C mirror can be created. UV-C mirror is created by sputter coating an inorganic optical stack having first optical layers of ZrON and second optical layers of SiO2 onto 100 microns thick fluoropolymer film (available under the trade designation “NOWOFLON THV 815” from Nowofol Kunststoffprodukte GmbH & Co. KG, Siegsdorf, Germany). A UV transparent film is coated in continuous roll to roll (R2R) fashion, using ZrON as the high refractive index material and SiO2 as the low refractive index material. The optical design is alternating quarter wave thickness layers of the two materials tuned to start reflecting at 200nm with a gradient of layer thickness to end reflecting at 300 nm. For ZrON, with refractive index of 2.25 at 222 nm, the physical thickness target is 24.66 nm. For SiCh, here sputtered from an aluminum-doped silicon sputter target, with refractive index 1.49, the target thickness is 37.23 nm. Layer one ZrON is DC sputtered from a pure zirconium sputter target in a gas mixture of argon, oxygen and nitrogen. Whereas argon is the primary sputtering gas, oxygen and nitrogen levels are set to achieve transparency, low absorptance and high refractive index. The film roll transport initially starts at a pre -determined speed, and the sputter source power is ramped to full operating power, followed by introduction of the reactive gases and then achieving steady state condition. The sputter source is orthogonal to and wider than the film which is being coated. Upon reaching the desired length of coated film the reactive gases are set to zero and the target is sputtered to a pure Zr surface state. The film direction is next reversed and silicon (aluminum doped) is deposited using a rotary pair of sputter targets using AC frequency (40 kHz) power applied in an argon sputtering atmosphere. Upon reaching steady state, oxygen reactive gas is introduced to provide transparency and low refractive index. At the pre-determined process setting and line speed the second layer is coated over the length which was coated for the first layer. The sputter sources are orthogonal to and wider than the film being coated. After reaching the desired length of coated film the reactive oxygen is removed and the target is sputtered in argon to a pure silicon (aluminum doped) surface state. This step-wise process is continued, layer by layer, until a total number of 13 layers is reached. Resulting peak reflectance is expected to be 95% at 222 nm when measured with a spectrophotometer (“SHIMADZU 2550 UV-VIS”). This UVC mirror film is then vapor coated with 100 nm of aluminum. UV-C light transmission is then measured with the spectrophotometer (“SHIMADZU 2550 UV-VIS”) to be 0% over a wavelength range of 200nm to 400nm. Glass beads are then pressed into an additional “THV 221” layer (which is heat laminated onto the surface of the UVC mirror film by the same method used in Example 1). Rub testing is then conducted on the glass bead embedded surface according to the MEK Rub Test Method described above and it is expected that no scratches would be observed on the film surface.

Example 5 - Aluminum vapor coated MOF UV mirror made with PVDF High Index Optic Lavers and THV Low Index Optic Lavers

The 4x4 matrix method using the Berreman algorithm was used for modeling the spectra of constructive and destructive interference generated from layer interfaces of materials having different refractive indices. The Berreman 4x4 matrix methodology is described in the Journal of the Optical Society of America (Volume 62, Number 4, April 1972) and the Journal of Applied Physics (Volume 85, Number 6, March 1999), the disclosures of which are incorporated herein by reference. Input parameters for this optical model were individual layer refractive indices, layer thicknesses, number of layers, and reflection bandwidth including a left band edge and a right band edge. The Berreman methodology calculated the percent light reflected at each layer interface and the percent light transmitted at each layer interface and calculated a reflection spectrum and transmission spectrum. The Berreman methodology was used to calculate %Reflectance spectra of UV-C multilayer optical film having 275 alternating optical layers of Poly( vinylidene fluoride) (PVDF) high refractive index layers and “THV 221” low refractive index layers, for a peak reflectance wavelength target of 254 nm.

Such a film as the modelled UV-C mirror can be created by methods well known in the art, by utilizing a multilayer feedblock and film die. Resulting reflectance is expected to be 97% over a wavelength range of 200nm to 280nm when measured with a spectrophotometer (“SHIMADZU 2550 UV-VIS”). This UVC mirror film is then vapor coated with 100 nm of aluminum. UV-C light transmission is then measured with the spectrophotometer (“SHIMADZU 2550 UV-VIS”) to be 0% over a wavelength range of 200nm to 400nm. Glass beads are then pressed into an additional “THV 221” layer (which is heat laminated onto the surface of the UVC mirror film by the same method used in Example 1). Rub testing is then conducted on the glass bead embedded surface according to the MEK Rub Test Method described above and it is expected that no scratches would be observed on the film surface.

Example 6 - Aluminum vapor coated MOF UV mirror made with ZrON High Index Optic Layers and SiO2 Low Index Optic Layers, where a THV815 top skin layer is deposited with islands of TiOx and reactive ion etched with plasma to create nano-pillars having TiOx caps.

UV-C mirror film made as described in Example 4 could be modified with nano-pillars having TiOx caps as described in U.S. Patent No. 10,119,190 (David, et al.), U.S. Patent No. 10,134,566 (David, et al.) or U.S. Patent No. 8,634,146 (David, et al.) , which are incorporated herein by reference. The UVC mirror film made as described in Example 4 may be mounted onto a powered electrode. The reactor chamber may then be pumped down to a base pressure of less than 2 mTorr (2.6 Pa). A mixture of titanium isopropoxide and oxygen may then be introduced into the chamber. Subsequently, 13.56 Mhz RF power can be coupled into the reactor. The ratio of the gases may be advantageously chosen to deposit discontinuous islands of TiOx, while simultaneously reactive ion etching the THV815 top skin layer. The film may then be carried through the reaction zone at a rate of 10 ft/min (3 meter/min) resulting in an approximate exposure time of 10 seconds. At the end of this treatment time, the RF power and the gas supply may be stopped and the chamber returned to atmospheric pressure.

Example 7 - Aluminum vapor coated MOF UV mirror made with PVDF High Index Optic Layers and THV Low Index Optic Layers, where a PVDF top skin layer is deposited with islands of TiOx and reactive ion etched with plasma to create nano-pillars having TiO2 caps. UV-C mirror film made as described in Example 5 could be modified with nano-pillars having TiOx caps as described in U.S. Patent No. 10,119,190 (David, et al.), U.S. Patent No. 10,134,566 (David, et al.) or U.S. Patent No. 8,634,146 (David, et al.), which are incorporated herein by reference. The UVC mirror film made as described in Example 5 may be mounted onto a powered electrode with the PVDF skin layer facing away from the electrode. The reactor chamber may then be pumped down to a base pressure of less than 2 mTorr (2.6 Pa). A mixture of titanium isopropoxide and oxygen may then be introduced into the chamber. Subsequently, 13.56 Mhz RF power can be coupled into the reactor. The ratio of the gases may be advantageously chosen to deposit discontinuous islands of TiOx, while simultaneously reactive ion etching the PVDF top skin layer. The film may then be carried through the reaction zone at a rate of 10 ft/min (3 meter/min) resulting in an approximate exposure time of 10 seconds. At the end of this treatment time, the RF power and the gas supply may be stopped, and the chamber returned to atmospheric pressure.

Reference throughout this specification to "one embodiment," "certain embodiments," "one or more embodiments" or "an embodiment," whether or not including the term "exemplary" preceding the term "embodiment," means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the certain exemplary embodiments of the present disclosure. Thus, the appearances of the phrases such as "in one or more embodiments," "in certain embodiments," "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily referring to the same embodiment of the certain exemplary embodiments of the present disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.

While the specification has described in detail certain exemplary embodiments, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing, may readily conceive of alterations to, variations of, and equivalents to these embodiments. Accordingly, it should be understood that this disclosure is not to be unduly limited to the illustrative embodiments set forth hereinabove. Furthermore, all publications and patents referenced herein are incorporated by reference in their entirety to the same extent as if each individual publication or patent was specifically and individually indicated to be incorporated by reference. Various exemplary embodiments have been described. These and other embodiments are within the scope of the following claims.

Claims

What is claimed is:

1. An ultraviolet C (UV-C) light multilayer reflector comprising: an optical layer comprising a fluoropolymer material; an array of inorganic particles dispersed in or disposed on a first major surface of the optical layer; and a reflecting layer disposed on a second major surface of the optical layer, opposite the first major surface, optionally, the reflecting layer comprising an aluminum layer.

2. The UV-C light multilayer reflector of claim 1, wherein the fluoropolymer material comprises one or more copolymers of tetrafluoroethylene, hexafluoropropylene, or vinylidene fluoride (THV).

3. The UV-C light multilayer reflector of claim 1 or 2, wherein the array of inorganic particles comprises silica glass beads.

4. The UV-C light multilayer reflector of claim 3, wherein the silica glass beads have an average size of about 1 to 100 microns.

5. The UV-C light multilayer reflector of any of claims 1-4, wherein the optical layer comprises 50-97 % by weight of the fluoropolymer material and 3-50 % by weight of the inorganic particles.

6. The UV-C light multilayer reflector of any of claims 1-5, further comprising a photocatalytic antimicrobial material disposed on the first major surface of the optical layer, optionally, the photocatalytic antimicrobial material comprising at least one of titanium dioxide in rutile crystal form, or titanium oxide in anatase crystal form.

7. The UV-C light multilayer reflector of any of claims 1-6, wherein the first major surface of the optical layer comprises an anisotropically etched structure.

8. The UV-C light multilayer reflector of claim 7, wherein the anisotropically etched structure includes a nano-on-micro surface structure.

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9. The UV-C light multilayer reflector of any of claims 1-8, wherein the optical layer comprises a first fluoropolymer sublayer at the first major surface to receive the array of inorganic particles and a second fluoropolymer sublayer attached to the reflecting layer.

10. The UV-C light multilayer reflector of claim 9, wherein the first and second fluoropolymer sublayer each comprises one or more copolymers of tetrafluoroethylene, hexafluoropropylene, or vinylidene fluoride (THV), and the first fluoropolymer sublayer has a lower glass transition temperature than the second fluoropolymer sublayer.

11. The UV-C light multilayer reflector of any of claims 1-10, wherein the optical layer further comprises alternating first and second optical sublayers collectively reflecting at least 50%, 60%, 70%, 80%, or at least 90% of an incident UV-C light over at least a 30-nanometer wavelength reflection bandwidth in a wavelength range from 200 nanometers to 280 nanometers.

12. The UV-C light multilayer reflector of claim 11, wherein the first optical sublayers comprise at least one of hafnium dioxide, zirconium oxynitride, or aluminum oxide, and the second optical sublayers comprise at least one of silicon dioxide, silicon aluminum oxide, or magnesium fluoride.

13. The UV-C light multilayer reflector of claim 11, wherein the first optical sublayers comprise polyvinylidene fluoride or polyethylene tetrafluoroethylene, and the second optical sublayers comprise a copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride, or a fluorinated ethylene propylene (FEP) polymer.

14. The UV-C light multilayer reflector of any of claims 11-13, wherein the alternating first and second optical sublayers are disposed as a stack between a first fluoropolymer sublayer at the first major surface and a second fluoropolymer sublayer attached to the reflecting layer.

15. The UV-C light multilayer reflector of any of claims 1-14, further comprising an adhesive layer attached to the reflecting layer on the side opposite the transparent layer.

16. The UV-C light multilayer reflector of any of claims 1-15, which having an average reflectance of at least 30%, 40% or 50% in an ultraviolet C (UV-C) wavelength range from 200 to 280 nanometers.

17. A method of making an ultraviolet C (UV-C) light multilayer reflector, the method comprising: providing an optical layer comprising a fluoropolymer material; providing an array of inorganic particles dispersed in or disposed on a first major surface of the optical layer; and vapor-coating a reflecting layer on a second major surface of the optical layer, opposite the first major surface.

18. The method of claim 17, wherein the fluoropolymer material comprises one or more copolymers of tetrafluoroethylene, hexafluoropropylene, or vinylidene fluoride (THV).

19. The method of claim 17 or 18, wherein the array of inorganic particles comprises silica glass beads.

20. The method of any of claims 17-19, further comprising providing a photocatalytic antimicrobial material disposed on the first major surface of the optical layer, optionally, the antimicrobial material comprising at least one of titanium dioxide in rutile crystal form or titanium oxide in anatase crystal form.

21. The method of any of claims 17-20, further comprising anisotropically etching the first major surface of the optical layer using plasma to form an anisotropic surface.

22. The method of claim 21, wherein the anisotropically etched structure includes a nano-on-micro surface structure.

23. The method of any of claims 17-22, wherein providing the optical layer comprises coextruding a first fluoropolymer sublayer and a second fluoropolymer sublayer.

24. The method of any of claims 17-23, wherein providing the optical layer comprises providing alternating first and second optical sublayers collectively reflecting at least 50%, 60%, 70%, 80%, or at least 90% of an incident UV-C light over at least a 30-nanometer wavelength reflection bandwidth in a wavelength range from 200 nanometers to 280 nanometers.

25. The method of claim 24, wherein the first optical sublayers comprise at least one of hafnium dioxide, zirconium oxynitride, or aluminum oxide, and the second optical sublayers comprise at least one of silicon dioxide, silicon aluminum oxide, or magnesium fluoride.

26. The method of claim 24, wherein the first optical sublayers comprise polyvinylidene fluoride or polyethylene tetrafluoroethylene, and the second optical sublayers comprise a copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride, or a fluorinated ethylene propylene (FEP) polymer.

27. The method of any of claims 24-26, further comprising disposing the alternating first and second optical sublayers as a stack between a first fluoropolymer sublayer at the first major surface and a second fluoropolymer sublayer attached to the reflecting layer.

28. The method of any of claims 17-27, further comprising attaching an adhesive layer to the reflecting layer on the side opposite the optical layer.

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