WO2013165965A1 - Films de miroir solaire durables - Google Patents

Films de miroir solaire durables Download PDF

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Publication number
WO2013165965A1
WO2013165965A1 PCT/US2013/038788 US2013038788W WO2013165965A1 WO 2013165965 A1 WO2013165965 A1 WO 2013165965A1 US 2013038788 W US2013038788 W US 2013038788W WO 2013165965 A1 WO2013165965 A1 WO 2013165965A1
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WIPO (PCT)
Prior art keywords
layer
solar mirror
mirror film
hygroscopic expansion
weatherable
Prior art date
Application number
PCT/US2013/038788
Other languages
English (en)
Inventor
Mark B. O'neill
Andrew J. Henderson
Timothy J. Hebrink
Rajesh K. Katare
Naiyong Jing
Diane North
Eric M. Peterson
John L. Roche
Attila Molnar
Joseph H. Eaton
Original Assignee
3M Innovative Properties Company
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Application filed by 3M Innovative Properties Company filed Critical 3M Innovative Properties Company
Publication of WO2013165965A1 publication Critical patent/WO2013165965A1/fr

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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
    • 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
    • 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 cells 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.
  • typical solar mirror films include a polymeric layer having a coefficient of hygroscopic expansion (CHE) on the order of about 30 parts per million (ppm) per percent relative humidity (RH) adjacent to a reflective layer having a CHE of about zero ppm per RH.
  • CHE coefficient of hygroscopic expansion
  • RH percent relative humidity
  • one way to minimize or eliminate film delamination and/or tunneling involves including in the solar mirror film construction a layer between the reflective layer and the polymer layer that has a CHE that is between the CHE of the prior art weatherable layer and the CHE of the reflective layer.
  • the term “compliant layer” will be used herein to describe the layer positioned between the reflective layer and the weatherable layer and having a CHE between the CHE of the reflective layer and the weatherable layer. Use of the word “compliant" in connection with this layer is not meant to add any requirements to the term layer.
  • the compliant layer has a coefficient of hygroscopic expansion (CHE) less than about 30 parts per million per PPH and greater than about 1 part per million per PPH. In some embodiments, the compliant layer has a coefficient of hygroscopic expansion (CHE) less than about 25 parts per million per PPH and greater than about 3 part per million per PPH. In some embodiments, the compliant layer has a coefficient of hygroscopic expansion (CHE) less than about 20 parts per million per PPH and greater than about 5 part per million per PPH. In some embodiments, the compliant layer has a coefficient of hygroscopic expansion (CHE) less than about 18 parts per million per PPH and greater than about 7 part per million per PPH.
  • CHE coefficient of hygroscopic expansion
  • the solar mirror films of the present disclosure have a reduced stress differential caused by the disparity in CHEs of the polymeric layer and the reflective layer. Elimination or minimization of this stress differential eliminates or minimizes tunneling and results in increased life of solar mirror films. Increased life results in decreased cost of solar power generation, which may lead to faster and/or wider adoption of this form of green energy generation.
  • One embodiment of the present disclosure relates to a solar mirror film comprising: a weatherable layer having a weatherable layer coefficient of hygroscopic expansion; a reflective layer having a reflective layer coefficient of hygroscopic expansion; and a compliant layer between the weatherable layer and the reflective layer, the compliant layer having a compliant layer coefficient of hygroscopic expansion that is between the weatherable layer coefficient of hygroscopic expansion and the reflective layer coefficient of hygroscopic expansion.
  • the coefficient of hygroscopic expansion of the compliant layer is less than about 30 ppm per percent RH and greater than zero (0) ppm per percent RH. In some embodiments, the coefficient of hygroscopic expansion of the compliant layer is less than about 28 ppm per percent RH and greater than zero (0) ppm per percent RH. In some embodiments, the coefficient of hygroscopic expansion of the compliant layer is less than about 25 ppm per percent RH and greater than one (1) ppm per percent RH. In some
  • the coefficient of hygroscopic expansion of the compliant layer is less than about 25 ppm per percent RH and greater than three (3) ppm per percent RH. In some embodiments, the coefficient of hygroscopic expansion of the compliant layer is less than about 20 ppm per percent RH and greater than five (5) ppm per percent RH. In some embodiments, the coefficient of hygroscopic expansion of the compliant layer is between about 10 ppm per percent relative humidity and about 25 ppm per percent relative humidity. In some embodiments of the solar mirror film, the coefficient of hygroscopic expansion of the compliant layer is between about 15 ppm per percent relative humidity and about 20 ppm per percent relative humidity.
  • Some embodiments of the solar mirror film have a reflective layer as the reflective layer. Some embodiments of the solar mirror film include a reflective layer that is at least one of silver, gold, aluminum, copper, nickel, and titanium. Some embodiments of the solar mirror film include a reflective layer whose coefficient of hygroscopic expansion of the reflective layer is between 0 ppm per percent relative humidity and 3 ppm per percent relative humidity.
  • the solar mirror film further include a tie layer between the weatherable layer and the compliant layer or between the compliant layer and the reflective layer (or both).
  • the tie layer comprises titanium dioxide.
  • the solar mirror film includes a corrosion protective layer adjacent to the reflective layer.
  • the corrosion protective layer comprises at least one of copper and an inert metal alloy.
  • the solar mirror film includes an adhesive layer adjacent to the reflective layer.
  • the adhesive is a pressure sensitive adhesive.
  • the adhesive layer is between the reflective layer and a substrate.
  • the substrate is one of a photovoltaic solar panel and a concentrated solar power system.
  • Another embodiment of the present disclosure relates to a concentrated photovoltaic system including a solar mirror film as described herein, including, but not limited to, any of the embodiments described above.
  • Another embodiment of the present disclosure relates to a concentrated solar power system including a solar mirror film as described herein, including, but not limited to, any of the embodiments described above.
  • Another embodiment of the present disclosure relates to a reflector assembly including a solar mirror film as 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 view of one exemplary embodiment of a solar mirror film in accordance with the present disclosure.
  • FIG. 3 is a schematic view of another exemplary embodiment of a solar mirror film in accordance with the present disclosure.
  • FIG. 4 is a schematic view of another exemplary embodiment of a solar mirror film in accordance with the present disclosure.
  • Some embodiments of the present application relate to the inclusion of a compliant layer having a CHE that is between the CHE of the weatherable layer and the CHE of the reflective layer.
  • the compliant layer has a CHE of less than 30 ppm per percent RH and greater than zero ppm per percent RH.
  • the compliant layer is positioned between the weatherable layer and the reflective layer of a solar mirror film. The inclusion of the compliant layer lowers the stress differential caused by the disparity in CHEs of the weatherable layer and the reflective layer.
  • Solar mirror film 200 of Fig. 2 includes a premask layer 1 10, a weatherable layer 120, a compliant layer 210, a reflective layer 150 (including, for example, a reflective metal such as silver), a corrosion resistant layer 160 (including, for example, a metal such as copper), an adhesive layer 170, and a liner 180. All layers except the weatherable layer 120, the compliant layer 220, and the reflective layer 150 are optional.
  • Solar mirror film 300 of Fig. 3 includes a premask layer 110, a weatherable layer 120, a tie layer 140, a compliant layer 210, a tie layer 220, a reflective layer 150 (including, for example, a reflective metal such as silver), a corrosion resistant layer 160 (including, for example, a metal such as copper), an adhesive layer 170, and a liner 180. All layers except the weatherable layer 120, the compliant layer 220, and the reflective layer 150 are optional.
  • Solar mirror film 400 of Fig. 4 includes a premask layer 110, a weatherable layer 120, compliant layer 210, a tie layer 140, a reflective layer 150 (including, for example, a reflective metal such as silver), a corrosion resistant layer 160 (including, for example, a metal such as copper), an adhesive layer 170, and a liner 180. All layers except the weatherable layer 120, the compliant layer 220, and the reflective layer 150 are optional.
  • 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.
  • the weatherable sheet or layer is flexible and transmissive to visible and infrared light.
  • the weatherable sheet or layer 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
  • 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.
  • a blend of polyvinylidene fluoride and polymethyl methacrylate can be used.
  • 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.
  • Weatherable sheets containing polycarbonate may have relatively high CTEs in comparison to polyesters, for example.
  • the CTE of a weatherable sheet containing a polycarbonate may be, for example, about 70 ppm/K.
  • the major surface of the weatherable sheet e.g., fluoropolymer
  • Useful surface treatments include, for example, electrical discharge in the presence of 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; or electron beam treatment.
  • 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 film is a MOF layer (see, for example, U.S. Patent Application Matter No. 69678US002, assigned to the present assignee and incorporated in its entirety herein).
  • the weatherable film include a blend of PMMA and PVDF (see, for example, U.S. Patent Application Matter No. 69680US002, assigned to the present assignee and incorporated in its entirety herein).
  • the weatherable layer has a CHE that is less than 30 ppm per percent RH (see above incorporated patent applications).
  • 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.
  • weatherable layers have a weatherable layer coefficient of hygroscopic expansion of at least about 30 ppm per percent RH.
  • the compliant layer has a coefficient of hygroscopic expansion (CHE) that is between the CHE of the reflective layer and the CHE of the weatherable layer.
  • CHE coefficient of hygroscopic expansion
  • the compliant layer has a CHE of less than 30 ppm per percent relative humidity and greater than zero ppm per percent relative humidity. In some embodiments of the solar mirror film, the CHE of the compliant layer is less than about 30 ppm per percent RH and greater than zero (0) ppm per percent RH. In some embodiments, the CHE of the compliant layer is less than about 28 ppm per percent RH and greater than zero (0) ppm per percent RH. In some embodiments, the CHE of the compliant layer is less than about 25 ppm per percent RH and greater than one (1) ppm per percent RH.
  • the CHE of the compliant layer is less than about 25 ppm per percent RH and greater than three (3) ppm per percent RH. In some embodiments, the CHE of the compliant layer is less than about 20 ppm per percent RH and greater than five (5) ppm per percent RH. In some embodiments, the CHE of the compliant layer is between about 10 ppm per percent relative humidity and about 25 ppm per percent relative humidity. In some embodiments of the solar mirror film, the CHE of the compliant layer is between about 15 ppm per percent relative humidity and about 20 ppm per percent relative humidity.
  • the CHE of the compliant layer is between about 75% and about 25% of the CHE of the weatherable layer. In some embodiments, the CHE of the compliant layer is between about 70% and about 30% of the CHE of the weatherable layer. In some embodiments, the CHE of the compliant layer is between about 60% and about 40% of the CHE of the weatherable layer.
  • the compliant layer can be any material that has the desired CHE.
  • the compliant layer includes one or both of PMMA and PVDF.
  • the compliant layer includes a multilayer optical film.
  • the compliance layer includes poly(methyl methacrylate) and a first block copolymer having at least two endblock polymeric units that are each derived from a first monoethylenically unsaturated monomer comprising a methacrylate, acrylate, styrene, or combination thereof, wherein each endblock has a glass transition temperature of at least 50 degrees Celsius; and at least one midblock polymeric unit that is derived from a second monoethylenically unsaturated monomer comprising a methacrylate, acrylate, vinyl ester, or combination thereof, wherein each midblock has a glass transition temperature no greater than 20 degrees Celsius.
  • block copolymer refers to a polymeric material that includes a plurality of distinct polymeric segments (or “blocks") that are covalently bonded to each other.
  • a block copolymer includes (at least) two different polymeric blocks, commonly referred to as the A block and the B block.
  • the A block and the B block generally have chemically dissimilar compositions with different glass transition temperatures.
  • the glass transition temperature can be determined using a method such as Differential Scanning Calorimetry (DSC) or Dynamic
  • each of the A and B blocks includes a plurality of respective polymeric units.
  • the A block polymeric units, as well as the B block polymeric units, are generally derived from monoethylenically unsaturated monomers.
  • Each polymeric block and the resulting block copolymer have a saturated polymeric backbone without the need for subsequent hydrogenation.
  • the compliance layer includes a block
  • the compliance layer may include an A-B-A triblock copolymer blended with a homopolymer that is soluble in either the A or B block.
  • the homopolymer has a polymeric unit identical to either the A or B block.
  • the addition of one or more homopolymers to the block copolymer composition can be advantageously used either to plasticize or to harden one or both blocks.
  • the block copolymer contains a poly(methyl methacrylate) A block and a poly(butyl acrylate) B block, and is blended with a poly(methyl methacrylate) homopolymer.
  • blending poly(methyl methacrylate) homopolymer with poly(methyl methacrylate)-poly(butyl acrylate) block copolymers allows the hardness to be tailored to the desired application.
  • blending with poly(methyl methacrylate) provides this control over hardness without significantly degrading the clarity or processibility of the overall composition.
  • the homopolymer/block copolymer blend has an overall poly(methyl methacrylate) composition of at least 30 percent, at least 40 percent, or at least 50 percent, based on the overall weight of the blend.
  • the homopolymer/block copolymer blend has an overall poly(methyl methacrylate) composition no greater than 95 percent, no greater than 90 percent, or no greater than 80 percent, based on the overall weight of the blend.
  • non-tacky block copolymers include poly(methyl methacrylate)- poly(n-butyl acrylate)-poly(methyl methacrylate) (25:50:25) triblock copolymers. These materials were previously available under the trade designation LA POLYMER from Kuraray Co., LTD.
  • the A block component is a thermoplastic material while the B block component is an elastomeric material.
  • thermoplastic refers to a polymeric material that flows when heated and that returns to its original state when cooled back to room temperature.
  • elastomeric refers to a polymeric material that can be stretched to at least twice its original length and then retracted to approximately its original length upon release.
  • the block copolymer has a multiphase morphology, at least at temperatures in the range of about 20 degrees Celsius to 150 degrees Celsius.
  • the compliant layer is visible light-transmissive or optically clear, exhibiting, in some exemplary embodiments, an average radiation transmission over the visible light portion of the radiation spectrum from 380 nm to 780 nm (T vis ) of at least about 90%, measured along the normal axis. In some exemplary embodiments the compliant layer exhibits an average radiation transmission of at least 90% over the solar radiation wavelength range from 380 nm to 3,000 nm (T solar ). In some embodiments, the compliant layer provides at least one of high optical transmissivity and low haze and yellowing, good weatherability, good abrasion, scratch, and crack resistance during to handling and cleaning, and good adhesion to other layers.
  • Inclusion of the compliant layer in the solar mirror film construction can, in some embodiments, be introduced as in-line processes.
  • the compliance layer has a thickness of at least 10 micrometers, at least 50 micrometers, or at least 60 micrometers. Additionally, in some embodiments, the compliance layer has a thickness no greater than 200 micrometers, no greater than 150
  • the compliance layer has a thickness no greater than 5 micrometers. In some such embodiments, the compliance layer has a thickness of from 0.1 micrometer to 3 micrometers.
  • the tie layer(s) include 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 may provide surprisingly high resistance to delamination in dry peel and wet peel testing. Further options and advantages of metal oxide tie layers are described in U.S. Patent No.
  • 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, the tie layer has 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, the tie layer has 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 layers. Besides providing a high degree of reflectivity, the reflective layer(s) can provide manufacturing flexibility. Optionally, the reflective layer may be applied onto a relatively thin organic tie layer or inorganic tie layer.
  • the reflective layer(s) have smooth, reflective metal surfaces that are specular.
  • specular surfaces refer to surfaces that induce a mirrorlike 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 elemental silver.
  • the reflective layer has a CHE of about zero ppm per percent RH. In some embodiments, the reflective layer has a CHE of between about zero ppm per percent RH and about 3 ppm per percent RH.
  • the reflective layer need not extend across the entire major surface of the compliant layer.
  • the reflective layer is deposited into the compliant layer.
  • portions of the compliant layer are masked during the deposition process such that the reflective layer is applied onto only a pre- determined portion of the compliant layer.
  • Application of the reflective layer 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.
  • PVD Physical vapor deposition
  • 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 deposition process continues for a sufficient duration to build up a suitable layer thickness of the reflective layer.
  • the reflective layer 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.
  • 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. In some
  • 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. Additionally, in some embodiments, 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. Although not shown in the figures, 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 Application 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.

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  • Mechanical Engineering (AREA)
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  • Optics & Photonics (AREA)
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Abstract

La présente invention concerne généralement des films de miroir solaire durables, des procédés de fabrication de films de miroir solaire durables, et des constructions comprenant des films de miroir solaire durables. Selon un mode de réalisation, la présente invention concerne un film de miroir solaire comprenant : une couche résistant aux intempéries ayant un coefficient d'expansion hygroscopique de couche résistant aux intempéries; une couche réfléchissante ayant un coefficient d'expansion hygroscopique de couche réfléchissante; et une couche d'accommodation entre la couche résistant aux intempéries et la couche réfléchissante, la couche d'accommodation ayant un coefficient d'expansion hygroscopique de couche d'accommodation qui est entre le coefficient d'expansion hygroscopique de couche résistant aux intempéries et le coefficient d'expansion hygroscopique de couche réfléchissante.
PCT/US2013/038788 2012-05-03 2013-04-30 Films de miroir solaire durables WO2013165965A1 (fr)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9568653B2 (en) 2012-05-03 2017-02-14 3M Innovative Properties Company Durable solar mirror films
WO2017127177A3 (fr) * 2015-12-17 2018-02-15 Corning Incorporated Miroir à revêtement réfléchissant à compensation des contraintes
JP2018191329A (ja) * 2013-10-28 2018-11-29 日本電気株式会社 モバイル通信システム、ネットワークノード、ｕｅ、及び通信方法

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US5361172A (en) * 1993-01-21 1994-11-01 Midwest Research Institute Durable metallized polymer mirror
US6120901A (en) * 1996-12-09 2000-09-19 3M Innovative Properties Company UV protected syndiotactic polystyrene overlay films
US20060181765A1 (en) * 2001-02-09 2006-08-17 Jorgensen Gary J Advanced ultraviolet-resistant silver mirrors for use in solar reflectors
US20110226234A1 (en) * 2008-09-22 2011-09-22 Saint-Gobain Glass France Corrosion-resistant mirror
US20110303277A1 (en) * 2009-01-28 2011-12-15 Evonik Roehm Gmbh Transparent, weathering-resistant barrier film, production by lamination, extrusion lamination or extrusion coating

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5361172A (en) * 1993-01-21 1994-11-01 Midwest Research Institute Durable metallized polymer mirror
US6120901A (en) * 1996-12-09 2000-09-19 3M Innovative Properties Company UV protected syndiotactic polystyrene overlay films
US20060181765A1 (en) * 2001-02-09 2006-08-17 Jorgensen Gary J Advanced ultraviolet-resistant silver mirrors for use in solar reflectors
US20110226234A1 (en) * 2008-09-22 2011-09-22 Saint-Gobain Glass France Corrosion-resistant mirror
US20110303277A1 (en) * 2009-01-28 2011-12-15 Evonik Roehm Gmbh Transparent, weathering-resistant barrier film, production by lamination, extrusion lamination or extrusion coating

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9568653B2 (en) 2012-05-03 2017-02-14 3M Innovative Properties Company Durable solar mirror films
US9998070B2 (en) 2012-05-03 2018-06-12 3M Innovative Properties Company Durable solar mirror films
JP2018191329A (ja) * 2013-10-28 2018-11-29 日本電気株式会社 モバイル通信システム、ネットワークノード、ｕｅ、及び通信方法
WO2017127177A3 (fr) * 2015-12-17 2018-02-15 Corning Incorporated Miroir à revêtement réfléchissant à compensation des contraintes

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