Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/08—Mirrors
  • G02B5/0816—Multilayer mirrors, i.e. having two or more reflecting layers
  • G02B5/085—Multilayer mirrors, i.e. having two or more reflecting layers at least one of the reflecting layers comprising metal
  • G02B5/0858—Multilayer mirrors, i.e. having two or more reflecting layers at least one of the reflecting layers comprising metal the reflecting layers comprising a single metallic layer with one or more dielectric layers
  • G02B5/0866—Multilayer mirrors, i.e. having two or more reflecting layers at least one of the reflecting layers comprising metal the reflecting layers comprising a single metallic layer with one or more dielectric layers incorporating one or more organic, e.g. polymeric layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B15/00—Layered products comprising a layer of metal
  • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B15/00—Layered products comprising a layer of metal
  • B32B15/20—Layered products comprising a layer of metal comprising aluminium or copper
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
  • B32B27/20—Layered products comprising a layer of synthetic resin characterised by the use of special additives using fillers, pigments, thixotroping agents
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
  • B32B27/308—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising acrylic (co)polymers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
  • B32B27/365—Layered products comprising a layer of synthetic resin comprising polyesters comprising polycarbonates
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
  • F24S23/00—Arrangements for concentrating solar-rays for solar heat collectors
  • F24S23/70—Arrangements for concentrating solar-rays for solar heat collectors with reflectors
  • F24S23/82—Arrangements for concentrating solar-rays for solar heat collectors with reflectors characterised by the material or the construction of the reflector
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2255/00—Coating on the layer surface
  • B32B2255/10—Coating on the layer surface on synthetic resin layer or on natural or synthetic rubber layer
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2255/00—Coating on the layer surface
  • B32B2255/20—Inorganic coating
  • B32B2255/205—Metallic coating
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2270/00—Resin or rubber layer containing a blend of at least two different polymers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/70—Other properties
  • B32B2307/712—Weather resistant
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/70—Other properties
  • B32B2307/714—Inert, i.e. inert to chemical degradation, corrosion
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
  • F24S23/00—Arrangements for concentrating solar-rays for solar heat collectors
  • F24S23/70—Arrangements for concentrating solar-rays for solar heat collectors with reflectors
  • F24S2023/86—Arrangements for concentrating solar-rays for solar heat collectors with reflectors in the form of reflective coatings
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/40—Solar thermal energy, e.g. solar towers

Definitions

• the present disclosure generally relates to durable solar mirror films, methods of making durable solar mirror films, and constructions including durable solar mirror films.
• renewable energy is energy derived from natural resources that can be replenished, such as sunlight, wind, rain, tides, and geothermal heat.
• the demand for renewable energy has grown substantially with advances in technology and increases in global population.
• fossil fuels provide for the vast majority of energy consumption today, these fuels are non-renewable.
• the global dependence on these fossil fuels has not only raised concerns about their depletion but also environmental concerns associated with emissions that result from burning these fuels.
• countries worldwide have been establishing initiatives to develop both large-scale and small-scale renewable energy resources.
• One of the promising energy resources today is sunlight. Globally, millions of households currently obtain power from solar photovoltaic systems.
• concentrated solar technology involves the collection of solar radiation in order to directly or indirectly produce electricity.
• the three main types of concentrated solar technology are concentrated photovoltaic, concentrated solar power, and solar thermal.
• CPV concentrated photovoltaic
• optics e.g. lenses or mirrors
• CPV systems are often much less expensive to produce than other types of photovoltaic energy generation because the concentration of solar energy permits the use of a much smaller number of the higher cost solar cells.
• CSP concentrated solar power
• concentrated sunlight is converted to heat, and then the heat is converted to electricity.
• CSP technology uses mirrored surfaces in multiple geometries (e.g., flat mirrors, parabolic dishes, and parabolic troughs) to concentrate sunlight onto a receiver. That, in turn, heats a working fluid (e.g. a synthetic oil or a molten salt) or drives a heat engine (e.g., steam turbine).
• a working fluid e.g. a synthetic oil or a molten salt
• a heat engine e.g., steam turbine
• the working fluid is what drives the engine that produces electricity.
• the working fluid is passed through a heat exchanger to produce steam, which is used to power a steam turbine to generate electricity.
• Solar thermal systems collect solar radiation to heat water or to heat process streams in industrial plants. Some solar thermal designs make use of reflective mirrors to concentrate sunlight onto receivers that contain water or the feed stream. The principle of operation is very similar to concentrated solar power units, but the concentration of sunlight, and therefore the working temperatures, are not as high.
• the solar mirror film 100 of Fig. 1 includes a premask layer 1 10, a weatherable layer 120
• a corrosion resistant layer 160 (including, for example, a polymer), a thin, sputter-coated tie layer 140, a reflective layer 150 (including, for example, a reflective metal such as silver), a corrosion resistant layer 160
• Fig. 1 (including, for example, a metal such as copper), an adhesive layer 170, and a liner 180.
• the film of Fig. 1 is typically applied to a support substrate by removing liner 180 and placing adhesive layer 170 adjacent to the support substrate.
• Premask layer 1 10 is then removed to expose weatherable layer 120 to sunlight.
• metalized polymer films used in concentrated solar power units and concentrated photovoltaic solar systems are subject to continuous exposure to the elements. Consequently, a technical challenge in designing and manufacturing metalized polymer reflective films is achieving long-term (e.g., 20 years) durability when subjected to harsh environmental conditions. There is a need for metalized polymer films that provide durability and retained optical performance (e.g., reflectivity) once installed in a concentrated solar power unit or a concentrated photovoltaic cell. Mechanical properties, optical clarity, corrosion resistance, ultraviolet light stability, and resistance to outdoor weather conditions are all factors that can contribute to the gradual degradation of materials over an extended period of operation.
• the inventors of the present disclosure recognized that many of the technical problems in forming a durable metalized polymer film capable of long-term outdoor use that retains its optical performance arise from the fundamental mismatch in the physical and chemical nature and properties of metals and polymers.
• One particular difficulty relates to ensuring good adhesion between the polymer layer and the metal reflective surface. Without good adhesion between these layers, delamination occurs. Delamination between the polymer layer and the reflective layer is often referred to as "tunneling.”
• the inventors of the present disclosure recognized that the delamination typically results from the decreased adhesion between the polymer layer and the reflective layer. This decreased adhesion can be caused by any of numerous factors - and often a combination of these factors. Some exemplary factors that the inventors of the present disclosure recognized include (1) increased mechanical stress between the polymer layer and the reflective layer; (2) oxidation of the reflective layer; (3) oxidation of an adhesive adjacent to the reflective layer; and (4) degradation of the polymer layer (this can be due to, for example, exposure to sunlight). Each of these factors can be affected by numerous external conditions, such as, for example, environmental temperature (including variations in environmental temperatures), thermal shock, humidity, exposure to moisture, exposure to air impurities such as, for example, salt and sulfur, UV exposure, product handling, and product storage.
• One of the most challenging problems is related to stress at the metal/polymer interface. Once the stress becomes too great, buckling can occur, causing the polymer layer to delaminate from the reflective layer. Further, when metalized polymer films are cut, their edges may be fractured and unprotected. Corrosion of metalized polymers begins at their edges, so this combination of fractured, exposed metal edges with the net interfacial stresses listed above can overcome adhesion strength and cause tunneling. The inventors of the present invention recognized the importance of protecting the interface between the polymer layer and the reflective layer - especially along the edges of this interface.
• the inventors of the present disclosure recognized that the reflective layer in existing solar mirror films extends across the entire weatherable layer. As discussed above, the mismatch in properties of these layers make their interface prone to delamination and tunneling - especially at the edges of the mirror film. Thus, the inventors of the present disclosure recognized that a solar mirror film with less or no silver along some or all of the edges of the solar mirror film exhibits increased durability and decreased delamination and/or tunneling.
• the inventors of the present disclosure also discovered new ways to form solar mirror films having less, minimal, or no reflective material in the edge portions. For example, the inventors of the present disclosure discovered a unique way to mechanically remove portions of reflective material to form a solar mirror film as described herein.
• One embodiment of the present disclosure relates to a method of making a solar mirror film comprising: a method of making a solar mirror film comprising: providing a weatherable layer having a first major surface and a second major surface; depositing a reflective material on the first major surface of the weatherable layer; and mechanically removing a portion of the reflective material.
• the portion of the reflective material that is removed from the weatherable layer is along one or more edge regions of the weatherable layer.
• at least one of the edge regions extends from the terminal edge of the weatherable layer to 2 mm onto the first major surface.
• the edge region extends from the terminal edge of the weatherable layer to between about 2 mm and about 20 mm onto the first major surface.
• depositing the reflective material involves at least one of physical vapor deposition via sputter coating, evaporation via e-beam or thermal methods, ion-assisted e- beam evaporation, electro-plating, spray painting, vacuum deposition, and combinations thereof.
• the reflective material covers at least 90%, at least 95%, at least 98% of the first major surface of the weatherable layer. In some embodiments, the reflective material covers at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% of the edge regions.
• mechanically removing the reflective material involves scraping, rubbing, ablating, and/or scrubbing the reflective material off of the weatherable layer.
• the method further comprises mechanically removing a portion of at least one of the weatherable layer and the tie layer.
• the method further comprises placing a filler in the area from which the reflective material was removed.
• the filler is a polymeric material.
• the filler is a thermoplastic material.
• the weatherable layer includes at least one of PMMA,
• the reflective material includes at least one of silver, gold, aluminum, copper, nickel, and titanium.
• the method further comprises placing a tie layer between the weatherable layer and the reflective material.
• the tie layer includes an adhesive.
• the method further comprises mechanically removing a portion of the tie layer.
• the method further comprises placing a polymeric material between the weatherable layer and the reflective material. In some embodiments, the method further comprises placing a corrosion protective layer adjacent to the reflective layer. In some embodiments, the corrosion protective layer comprises at least one of copper and an inert metal alloy.
• the method further comprises placing the solar mirror film in at least one of a concentrated photovoltaic system, a concentrated solar system, or a reflector assembly.
• Another embodiment of the present disclosure relates to a concentrated solar power system including a solar mirror film made using a method described herein, including, but not limited to, any of the embodiments described above.
• Another embodiment of the present disclosure relates to a concentrated photovoltaic power system including a solar mirror film made using a method described herein, including, but not limited to, any of the embodiments described above.
• Fig. 1 is a schematic view of a prior art solar mirror film.
• Fig. 2 is a schematic top view of one exemplary embodiment of a solar mirror film in accordance with the present disclosure.
• FIG. 3 is a schematic top view of another exemplary embodiment of a solar mirror film in accordance with the present disclosure.
• FIG. 4 is a schematic top view of another exemplary embodiment of a solar mirror film in accordance with the present disclosure.
• FIG. 5 is a schematic top view of another exemplary embodiment of a solar mirror film in accordance with the present disclosure.
• Some embodiments of the present disclosure include methods of mechanically removing at least some of the reflective material on a weatherable layer.
• portions of at least one of the tie layer and the weatherable layer are also removed.
• the removed portions can form a pattern or can be random. Any pattern may be formed, including, for example, dots, lines, shapes, text, and the like. Additional information on the solar mirror film can be found in U.S. Patent Application Matter No. 69678US002, assigned the present assignee and incorporated in its entirety herein.
• Some embodiments of the present disclosure relate to methods of making solar mirror films that do not include a reflective layer material across the entire weatherable layer. Some embodiments of the present disclosure relate to methods of making a solar mirror film that does not include a reflective material on one or more of the edge portions of a solar mirror film. Some embodiments of the present disclosure relate to methods of making a solar mirror films having a reflective layer with discontinuities in the edge portion of the solar mirror film.
• the methods described herein all provide a more durable solar mirror film. This increased durability is due, at least in part, to enhanced adhesion around the edges of the film as a result of the direct contact between the weatherable layer and the adhesive layer. Consequently, the incidence of delamination or tunneling is minimized. Adhesion is enhanced for at least the reason that the weatherable layer bonds directly to a layer other than the reflective layer (i.e., an adhesive layer). The weatherable layer and the layer to which it adheres have a bond strength that is greater than the bond strength of the weatherable layer and reflective layer.
• Solar mirror film 200 of Fig. 2 includes a weatherable layer 210 including a bulk region 220 and four edge regions 230a, 230b, 230c, and 230d.
• a reflective material 240 is adjacent to bulk region 220 of weatherable layer 210. Reflective material 240 is largely (or substantially) absent from edge regions 230a, 230b, 230c, and 230d.
• Reflective material 240 is largely (or substantially) absent from edge regions 230a, 230b, 230c, and 230d.
• the specific embodiment shown in Fig. 2 has reflective material 240 substantially absent from all four edge regions 230, but it is within the scope of the present disclosure to have reflective material 240 absent from only one or more of the edge regions.
• the term "substantially absent" with respect to the reflective material being substantially absent from the edge region(s) refers to at least 97% of the specific edge region lacking reflective material.
• edge region refers to the area between one edge of a sheeting and the bulk region.
• the edge region can, but does not have to, run the entire length or width of the sheeting.
• the size of edge region may vary based on specific disclosures. However, the edge area may be of any size that is large enough to form a bond strength between the adhesive layer and the weatherable layer that exceeds the bond strength between the weatherable layer and the reflective layer.
• Fig. 3 shows an embodiment in which not all four edge regions of a rectangular sheet are free of reflective material.
• the schematic top view of Fig. 3 shows a solar mirror film 300 including a weatherable layer 210 including a bulk region 320 and an edge regions 330a and 330b.
• a reflective material 240 is adjacent to bulk region 320 of weatherable layer 210.
• Reflective material 240 is largely (or substantially) absent from edge regions 330a and 330b.
• Fig. 4 shows an embodiment in which the edge regions do not run the entire length of the solar mirror film.
• the schematic top view of Fig. 4 shows a solar mirror film 400 including a weatherable layer 210 including a bulk region 420 and numerous edge regions 430.
• a reflective material 240 is adjacent to bulk region 420 of weatherable layer 210.
• Reflective material 240 is largely (or substantially) absent from edge regions 430.
• the reflective material is discontinuous along the edges of the sheet.
• the edge regions where the reflective material is substantially absent can be randomly sized (as shown, for example, in Fig. 4) or sized to form a pattern (as shown, for example, in Fig. 5).
• the discontinuity can be patterned (for example, as shown in Fig. 4) or random (for example, as shown in Fig. 5).
• Fig. 5 shows an embodiment in which the edge regions do not run the entire length of the solar mirror film.
• the schematic top view of Fig. 5 shows a solar mirror film 500 including a weatherable layer 210 including a bulk region 520 and numerous edge regions 530.
• a reflective material 240 is adjacent to bulk region 520 of weatherable layer 210. Reflective material 240 is largely (or substantially) absent from edge regions 530. As such, the reflective material is discontinuous along the edges of the sheet.
• FIG. 2-5 For purposes of simplicity, the schematic views shown in Figs. 2-5 only show the weatherable layer and the reflective material. These embodiments and this disclosure, however, are meant to include other layers in the solar mirror film, including, for example, layers between the weatherable layer and the reflective layer (e.g. , a tie layer) and layers on top of or below the weatherable layer and/or the reflective layer. Each of the potential layers is described in greater detail below.
• the edge regions lacking reflective material are adjacent to (and in some cases, directly adjacent to) a tie layer or adhesive. In some embodiments, the edge regions lacking reflective material are adjacent to (and in some cases, directly adjacent to) a polymeric layer.
• Some exemplary polymeric layers include, for example, PMMA layer, PVDF layers, and blends thereof.
• removal of the reflective material creates a concave area.
• this concave area is filled with a filler material.
• the filler material is a polymer.
• the polymer is a thermoplastic material.
• Any known mechanical method can be used to remove the reflective material from the weatherable layer.
• Some exemplary mechanical processes include, for example, scraping, buffing, rubbing, scrubbing, and other similar mechanical methods.
• the premask layer is optional. Where present, the premask protects the weatherable layer during handling, lamination, and installation. Such a configuration can then be conveniently packaged for transport, storage, and consumer use. In some embodiments, the premask is opaque to protect operators during outdoor installations. In some embodiments, the premask is transparent to allow for inspection for defects. Any known premask can be used.
• Premask layer can be positioned, for example, as shown in Fig. 1.
• the weatherable layer or sheet is flexible and transmissive to visible and infrared light.
• the weatherable layer or sheet is resistant to degradation by ultraviolet (UV) light.
• UV ultraviolet
• the phrase "resistant to degradation by ultraviolet light” means that the weatherable sheet at least one of reflects or absorbs at least 50 percent of incident ultraviolet light over at least a 30 nanometer range in a wavelength range from at least 300 nanometers to 400 nanometers. Photo-oxidative degradation caused by UV light (e.g., in a range from 280 to 400 nm) may result in color change and deterioration of optical and mechanical properties of polymeric films.
• the weatherable sheet or layer is generally abrasion and impact resistant and can prevent degradation of, for example, solar assemblies when they are exposed to outdoor elements.
• the weatherable layer includes one or more organic film- forming polymers.
• Some exemplary polymers include, for examples, polyesters, polycarbonates, polyethers, polyimides, polyolefins, fluoropolymers, and combinations thereof.
• Assemblies according to the present disclosure include a weatherable sheet or layer, which can be a single layer (monolayered embodiments) or can include more than one layer (multilayered
• some exemplary materials for use in the weatherable layer include, for example, PMMA, polycarbonate, polyester, a multilayer optical film, a fluoropolymer, or a blend of an acrylate and a fluoropolymer.
• Some exemplary material are described, for example, in U.S. Patent Application Matter Nos. 69679US002 and 69680US002, both of which are assigned to the present assignee and incorporated in their entirety herein.
• a variety of stabilizers may be added to the weatherable sheet to improve its resistance to UV light.
• examples of such stabilizers include at least one of ultraviolet absorbers (UVA) (e.g., red shifted UV absorbers), hindered amine light stabilizers (HALS), or anti- oxidants. These additives are described in further detail below.
• UVA ultraviolet absorbers
• HALS hindered amine light stabilizers
• anti- oxidants anti-oxidants
• the UV resistance of the weatherable sheet can be evaluated, for example, using accelerated weathering studies. Accelerated weathering studies are generally performed on films using techniques similar to those described in ASTM G- 155, "Standard practice for exposing non- metallic materials in accelerated test devices that use laboratory light sources.” One mechanism for detecting the change in physical characteristics is the use of the weathering cycle described in ASTM G155 and a D65 light source operated in the reflected mode.
• the article should withstand an exposure of at least 18,700 kJ/m 2 at 340 nm before the b* value obtained using the CIE L*a*b* space increases by 5 or less, 4 or less, 3 or less, or 2 or less before the onset of significant cracking, peeling, delamination, or haze.
• the weatherable sheet includes a fluoropolymer.
• Fluoropolymers are typically resistant to UV degradation even in the absence of stabilizers such as UVA, HALS, and anti-oxidants.
• Some exemplary fluoropolymers include ethylene -tetrafluoroethylene copolymers (ETFE), ethylene-chloro-trifluoroethylene copolymers (ECTFE), tetrafluoroethylene- hexafluoropropylene copolymers (FEP), tetrafluoroethylene-perfluorovinylether copolymers (PFA, MFA) tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymers (THV), polyvinylidene fluoride homo and copolymers (PVDF), blends thereof, and blends of these and other fluoropolymers.
• ETFE ethylene -tetrafluoroethylene copolymers
• ECTFE
• Fluoropolymers typically comprise homo or copolymers of TFE, CTFE, VDF, HFP or other fully fluorinated, partially fluorinated or hydrogenated monomers such as vinyl ethers and alpa-olefms or other halogen containing monomers.
• the CTE of fluoropolymer films is typically high relative to films made from hydrocarbon polymers.
• the CTE of a fluoropolymer film may be at least 75, 80, 90, 100, 1 10, 120, or 130 ppm/K.
• the CTE of ETFE may be in a range from 90 to 140 ppm/K.
• Weatherable films including fluoropolymer can also include non-fluorinated materials.
• Useful flexible, visible and infrared light-transmissive substrates also include multilayer film substrates.
• Multilayer film substrates may have different fluoropolymers in different layers or may include at least one layer of fluoropolymer and at least one layer of a non-fluorinated polymer.
• Multilayer films can comprise a few layers (e.g., at least 2 or 3 layers) or can comprise at least 100 layers (e.g., in a range from 100 to 2000 total layers or more).
• the different polymers in the different multilayer film substrates can be selected, for example, to reflect a significant portion (e.g., at least 30, 40, or 50%) of UV light in a wavelength range from 300 to 400 nm as described, for example, in U.S. Patent No. 5,540,978 (Schrenk).
• Such blends and multilayer film substrates may be useful for providing UV resistant substrates that have lower CTEs than the fluoropolymers described above.
• Some exemplary weatherable sheets comprising a fluoropolymer can be commercially obtained, for example, from E.I. duPont De Nemours and Co., Wilmington, DE, under the trade designation “TEFZEL ETFE” and “TEDLAR,” and films made from resins available from Dyneon LLC, Oakdale, MN, under the trade designations "DYNEON ETFE”, “DYNEON THV”, “ DYNEON FEP”, and " DYNEON PVDF", from St.
• Some useful weatherable sheets are reported to be resistant to degradation by UV light in the absence of UVA, HALS, and anti-oxidants.
• certain resorcinol for example, certain resorcinol
• isophthalate/terephthalate copolyarylates for example, those described in U. S. Patent Nos.
• the major surface of the weatherable sheet e.g., fluoropolymer
• a suitable reactive or non-reactive atmosphere e.g., plasma, glow discharge, corona discharge, dielectric barrier discharge or atmospheric pressure discharge
• chemical pretreatment e.g., using alkali solution and/or liquid ammonia
• flame pretreatment e.g., using alkali solution and/or liquid ammonia
• electron beam treatment e.g., using alkali solution and/or liquid ammonia
• a separate adhesion promotion layer may also be formed between the major surface of the weatherable sheet and the PSA.
• the weatherable sheet may be a fluoropolymer that has been coated with a PSA and subsequently irradiated with an electron beam to form a chemical bond between the substrate and the pressure sensitive adhesive; (see, e.g., U. S. Pat. No. 6,878,400 (Yamanaka et al.).
• Some useful weatherable sheets that are surface treated are commercially available, for example, from St. Gobain Performance Plastics under the trade designation "NORTON ETFE".
• the weatherable sheet has a thickness from about 0.01 mm to about 1 mm. In some embodiments, the weatherable sheet has a thickness from about 0.05 mm to about 0.25 mm. In some embodiments, the weatherable sheet has a thickness from about 0.05 mm to about 0.15 mm.
• the tie layer includes a metal oxide such as aluminum oxide, copper oxide, titanium dioxide, silicon dioxide, or combinations thereof.
• a metal oxide such as aluminum oxide, copper oxide, titanium dioxide, silicon dioxide, or combinations thereof.
• titanium dioxide was found to provide surprisingly high resistance to delamination in dry peel testing. Further options and advantages ofmetal oxide tie layers are described in U.S. Patent No. 5,361, 172 (Schissel et al.), incorporated by reference herein.
• the tie layer has a thickness of equal to or less than 500 micrometers. In some embodiments, the tie layer has a thickness of between about 0.1 micrometer and about 5 micrometers. In some embodiments, it is preferable that the tie layer have an overall thickness of at least 0.1 nanometers, at least 0.25 nanometers, at least 0.5 nanometers, or at least 1 nanometer. In some embodiments, it is preferable that the tie layer have an overall thickness no greater than 2 nanometers, no greater than 5 nanometers, no greater than 7 nanometers, or no greater than 10 nanometers.
• the solar mirror films described herein include one or more reflective including one or more reflective materials.
• the reflective layer(s) (including reflective material) provide reflectivity.
• the reflective layer(s) have smooth, reflective metal surfaces that are specular.
• specular surfaces refer to surfaces that induce a mirror- like reflection of light in which the direction of incoming light and the direction of outgoing light form the same angle with respect to the surface normal. Any reflective metal may be used for this purpose, although preferred metals include silver, gold, aluminum, copper, nickel, and titanium.
• the reflective layer includes silver.
• Prior art reflective layers extend across the entire major surface of the weatherable layer.
• the reflective layer(s) do not extend across the entire major surface of the weatherable layer. Any method can be used to create a reflective layer that does not extend across the entire major surface of the weatherable layer.
• the reflective layer is deposited onto or otherwise positioned adjacent to the weatherable layer such that the reflective material does not extend across the entire major surface of the weatherable layer. In some embodiments, portions of the weatherable layer are masked during the deposition process such that the reflective layer is applied onto only a predetermined portion.
• U.S. Patent Disclosure Matter No. 69866US002 (assigned to the assignee of the present disclosure) provides more detail on these methods and is incorporated herein by reference.
• the reflective material may be deposited or positioned adjacent to the weatherable layer such that the reflective material extends across all or substantially all of the major surface of the weatherable layer and then portions of the reflective material are removed to form a reflective layer that does not extend across the entire major surface.
• Disclosure of the reflective layer / the reflective material can be achieved using numerous coating methods including, for example, physical vapor deposition via sputter coating, evaporation via e-beam or thermal methods, ion-assisted e-beam evaporation, electro-plating, spray painting, vacuum deposition, and combinations thereof.
• the metallization process is chosen based on the polymer and metal used, the cost, and many other technical and practical factors.
• Physical vapor deposition (PVD) of metals is very popular for some disclosures because it provides the purest metal on a clean interface. In this technique, atoms of the target are ejected by high-energy particle bombardment so that they can impinge onto a substrate to form a thin film.
• the high- energy particles used in sputter-deposition are generated by a glow discharge, or a self-sustaining plasma created by applying, for example, an electromagnetic field to argon gas.
• the reflective layer and/or reflective material is applied to a weatherable layer.
• the reflective layer of reflective material is applied onto a tie layer.
• Subsequent removal of portions of the reflective material can be effected in numerous ways including, for example, ultrasonically, using mechanical removal methods (including, for example, physical removal and laser removal), and using thermal removal methods.
• U.S. Patent Disclosure Matter No. 69677US002 (assigned to the assignee of the present disclosure) provides more detail on these methods and is incorporated herein by reference.
• the reflective material or layer(s) is preferably thick enough to reflect the desired amount of the solar spectrum of light.
• the preferred thickness can vary depending on the composition of the reflective layer and the specific use of the solar mirror film.
• the reflective layer is between about 75 nanometers to about 100 nanometers thick for metals such as silver, aluminum, copper, and gold.
• the reflective layer has a thickness no greater than 500 nanometers.
• the reflective layer has a thickness of from 80 nm to 250 nm.
• the reflective layer has a thickness of at least 25 nanometers, at least 50 nanometers, at least 75 nanometers, at least 90 nanometers, or at least 100 nanometers.
• the reflective layer has a thickness no greater than 100 nanometers, no greater than 1 10 nanometers, no greater than 125 nanometers, no greater than 150 nanometers, no greater than 200 nanometers, no greater than 300 nanometers, no greater than 400 nanometers, or no greater than 500 nanometers.
• two or more reflective layers may be used.
• the corrosion resistant layer is optional. Where included, the corrosion resistant layer may include, for example, elemental copper. Use of a copper layer that acts as a sacrificial anode can provide a reflective article with enhanced corrosion-resistance and outdoor weatherability. As another approach, a relatively inert metal alloy such as Inconel (an iron-nickel alloy) can also be used.
• a relatively inert metal alloy such as Inconel (an iron-nickel alloy) can also be used.
• the corrosion resistant layer is preferably thick enough to provide the desired amount of corrosion resistance.
• the preferred thickness can vary depending on the composition of the corrosion resistant layer. In some exemplary embodiments, the corrosion resistant layer is between about 75 nanometers to about 100 nanometers thick. In other embodiments, the corrosion resistant layer is between about 20 nanometers and about 30 nanometers thick. Although not shown in the figures, two or more corrosion resistant layers may be used.
• the corrosion resistant layer has a thickness no greater than 500 nanometers. In some embodiments, the corrosion resistant layer has a thickness of from 80 nm to 250 nm. In some embodiments, the corrosion resistant layer has a thickness of at least 25 nanometers, at least 50 nanometers, at least 75 nanometers, at least 90 nanometers, or at least 100 nanometers. Additionally, in some embodiments, the corrosion resistant layer has a thickness no greater than 100 nanometers, no greater than 1 10 nanometers, no greater than 125 nanometers, no greater than 150 nanometers, no greater than 200 nanometers, no greater than 300 nanometers, no greater than 400 nanometers, or no greater than 500 nanometers.
• the adhesive layer is optional. Where present, the adhesive layer adheres the multilayer construction to a substrate (not shown in the figures).
• the adhesive is a pressure sensitive adhesive.
• the term "pressure sensitive adhesive” refers to an adhesive that exhibits aggressive and persistent tack, adhesion to a substrate with no more than finger pressure, and sufficient cohesive strength to be removable from the substrate.
• Exemplary pressure sensitive adhesives include those described in PCT Publication No. WO 2009/146227 (Joseph, et al.), incorporated herein by reference.
• the liner is optional. Where present, the liner protects the adhesive and allows the solar mirror film to be transferred onto and another substrate. Such a configuration can then be conveniently packaged for transport, storage, and consumer use.
• the liner is a release liner. In some embodiments, the liner is a silicone-coated release liner.
• the films described herein can be applied to a substrate by removing liner 180 (where present) and placing adhesive layer 170 (where present) adjacent to the substrate. Premask layer 1 10 (where present) is then removed to expose weatherable layer 120 to sunlight.
• Suitable substrates generally share certain characteristics. Most importantly, the substrate should be sufficiently rigid. Second, the substrate should be sufficiently smooth that texture in the substrate is not transmitted through the adhesive/metal/polymer stack. This, in turn, is advantageous because it: (1) allows for an optically accurate mirror, (2) maintains physical integrity of the metal reflective layer by eliminating channels for ingress of reactive species that might corrode the metal reflective layer or degrade the adhesive, and (3) provides controlled and defined stress concentrations within the reflective film-substrate stack. Third, the substrate is preferably nonreactive with the reflective mirror stack to prevent corrosion. Fourth, the substrate preferably has a surface to which the adhesive durably adheres.
• Exemplary substrates for reflective films are described in PCT Publication Nos. WO041 14419 (Schripsema), and WO03022578 (Johnston et al.); U.S. Publication Nos. 2010/0186336 (Valente, et al.) and 2009/0101 195 (Reynolds, et al.); and U.S. Patent No. 7,343,913 (Neidermeyer), all of which are incorporated in their entirety herein.
• the article can be comprised in one of the many mirror panel assemblies as described in co-pending and co-owned provisional U.S. Patent Disclosure No. 13/393,879 (Cosgrove, et al.), incorporated herein in its entirety.
• Other exemplary substrates include metals, such as, for example, aluminum, steel, glass, or composite materials.
• each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Also, in these examples, all percentages, proportions and ratios are by weight unless otherwise indicated.
• Corrosion of the comparative examples and examples was evaluated following the procedure outlined on ISO 9227:2006, "Corrosion tests in artificial atmospheres - Salt spray tests" with the exception that results are reported as either % reflective area after various times or simply as visual observation failure.
• Visual observation failure means the first visual sign of corrosion.
• a reflective mirror film comprising a polymer layer and a metallized layer (obtained under the trade designation "SOLAR MIRROR FILM SMF-1 100" from 3M Company, St. Paul, MN) was laminated onto a painted aluminum substrate having a thickness of approximately 0.02 in (0.05 cm) after removing the pressure sensitive adhesive liner on the metallized side. The aluminum substrate was then cut into 10.2 cm x 10.2 cm samples using a shear cutter. The premask was removed. The three samples were tested according to the Neutral Salt Spray test described above. Test results are provided in Table 1.
• a single (0.9 m x 1.2 m) sample was exposed to the Neutral Salt Spray test described above for a week and was then placed on a rooftop in StPaul, MN and exposed to sun and weathering. After 2 months of outdoor exposure, 80% of the surface was covered with 1.3 cm (0.5 in) tunnels.
• a reflective mirror film comprising a polymer layer and a metallized layer (obtained under the trade designation "SOLAR MIRROR FILM SMF-1 100" from 3M Company, St. Paul, MN) was laminated onto a painted aluminum substrate having a thickness of approximately 0.02 in (0.05 cm) after removing the pressure sensitive adhesive liner on the metallized side.
• the aluminum substrate was then cut into 10.2 cm x 10.2 cm samples using a shear cutter. The premask was removed. All four edges of the sample were taped with 0.5 in wide "3M Weather Resistant Film Tape 838" by adhering 0.25 inch of the tape to the front side of the sample and around the edge face and tightly folding the remaining edge tape over the sample.
• the sample was tested according to the Neutral Salt Spray test described above and showed signs of corrosion after two weeks (14 days).
• a sample of the (10.2 cm x 10.2 cm) laminate as described in Example 1 was made.
• the sample without the PSA and liner had all four metal edges manually mechanically scraped from the metal side of the laminate with a silicon carbide hand tool (0.5 in wide blade with square edge). The tool was used to remove 0.125 inch of the silver from all 4 edges. Following this mechanical removal, an equivalent PSA was coated onto the scraped metal side of the laminate and the laminate was then adhered to the aluminum substrate as described under "Aluminum Substrate Preparation.”
• the sample was tested as described in the "Neutral Salt Spray Test" and showed no signs of corrosion after 1600 hrs (67 days).

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