Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
  • H02S40/00—Components or accessories in combination with PV modules, not provided for in groups H02S10/00 - H02S30/00
  • H02S40/20—Optical components
  • H02S40/22—Light-reflecting or light-concentrating means
• • 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
• • 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
  • B32B33/00—Layered products characterised by particular properties or particular surface features, e.g. particular surface coatings; Layered products designed for particular purposes not covered by another single class
• • 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
  • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
• • 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
  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/04—Interconnection of layers
  • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
• • 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
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
  • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
  • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
  • G02B1/14—Protective coatings, e.g. hard coatings
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/08—Mirrors
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/08—Mirrors
  • G02B5/0808—Mirrors having a single reflecting layer
• • 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
  • G02B5/0875—Multilayer mirrors, i.e. having two or more reflecting layers at least one of the reflecting layers comprising metal the reflecting layers comprising two or more metallic layers
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F19/00—Integrated devices, or assemblies of multiple devices, comprising at least one photovoltaic cell covered by group H10F10/00, e.g. photovoltaic modules
• • 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
  • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
  • B32B37/14—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers
  • B32B37/24—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers with at least one layer not being coherent before laminating, e.g. made up from granular material sprinkled onto a substrate
  • B32B2037/246—Vapour deposition
• • 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
  • B32B38/00—Ancillary operations in connection with laminating processes
  • B32B38/0012—Mechanical treatment, e.g. roughening, deforming, stretching
  • B32B2038/0028—Stretching, elongating
• • 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
  • B32B38/00—Ancillary operations in connection with laminating processes
  • B32B2038/0052—Other operations not otherwise provided for
  • B32B2038/0092—Metallizing
• • 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
  • B32B2307/40—Properties of the layers or laminate having particular optical properties
• • 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
  • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
  • B32B37/14—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers
  • B32B37/15—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers with at least one layer being manufactured and immediately laminated before reaching its stable state, e.g. in which a layer is extruded and laminated while in semi-molten state
  • B32B37/153—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers with at least one layer being manufactured and immediately laminated before reaching its stable state, e.g. in which a layer is extruded and laminated while in semi-molten state at least one layer is extruded and immediately laminated while in semi-molten state
• • 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
• • 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
  • Y02E10/50—Photovoltaic [PV] energy
  • Y02E10/52—PV systems with concentrators

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 (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 (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 surfaces/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 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 metal reflective layer. Further, when metalized polymer films are cut, their edges may be fractured and unprotected. Corrosion of metalized polymers typically begins at their edges. So, the 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 metal reflective layer - especially along the edges.
• polymeric weatherable layers e.g., acrylic
• CHE coefficient of hygroscopic expansion
• ppm parts per million
• RH percent relative humidity
• the inventors of the present disclosure recognized that one way to minimize or eliminate film delamination and/or tunneling involves including in the mirror film construction a multilayer optical film as the weatherable layer.
• the multilayer optical film has a CHE that is between the CHE of the prior art weatherable layer and the CHE of the reflective layer.
• the multilayer optical film as the weatherable layer lowers the stress differential caused by the disparity in CHEs of the prior art weatherable layer and the metal reflective layer. Elimination or minimization of this stress differential eliminates or minimizes tunneling and/or delamination and results in solar mirror films having an increased life. Increased life results in decreased cost of solar power generation, which may lead to faster and/or wider adoption of this valuable form of green energy generation.
• One embodiment of the present disclosure relates to a solar mirror film comprising: a multilayer optical film layer having a coefficient of hygroscopic expansion of less than about 30 ppm per percent relative humidity; and a reflective layer.
• the solar mirror film include a multilayer optical film having a CHE that is between about 25 ppm per percent RH and about 5 ppm per percent RH. In some embodiments of the solar mirror film, the CHE of the multilayer optical film layer is between about 10 ppm per percent RH and about 25 ppm per percent RH. In some embodiments of the solar mirror film, the CHE of the multilayer optical film layer is between about 15 ppm per percent RH and about 20 ppm per percent RH.
• Some embodiments of the solar mirror film have a metal 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 CHE is between 0 ppm per percent RH and 3 ppm per percent RH.
• the solar mirror film further include a tie layer between the multilayer optical film layer and the reflective layer.
• the tie layer includes titanium dioxide.
• the multilayer optical film layer is a weatherable layer.
• Some embodiments of the solar mirror film include a weatherable layer.
• the solar mirror film include a compliance layer between the multilayer optical film layer and the reflective layer.
• the compliance layer comprises butyl acrylate.
• Some embodiments of the solar mirror film include 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.
• Some embodiments of the solar mirror film include an adhesive layer adjacent to the reflective layer. In some embodiments, the adhesive is a pressure sensitive adhesive. In some embodiments, the adhesive layer is between the reflective layer and a substrate
• 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
• 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
• 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.
• FIG. 5 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 multilayer optical film as the weatherable layer of a solar mirror film.
• the multilayer optical film has a CHE that is between the CHE of typically used weatherable layers (e.g., acrylics) and the CHE of the reflective layer. As such, the multilayer optical film lowers the stress differential caused by the disparity in CHEs of the weatherable layer and the reflective layer.
• One exemplary embodiment is shown schematically in Fig. 2.
• a premask layer 1 10 includes a premask layer 1 10, a MOF weatherable layer 220, 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 (including, for example, a metal such as copper), an adhesive layer 170, and a liner 180.
• Solar mirror film 300 includes a premask layer 1 10, a MOF weatherable layer 220, a compliance layer 310 (including, for example, an butyl acrylate), 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 (including, for example, a metal such as copper), an adhesive layer 170, and a liner 180.
• Solar mirror film 400 includes a premask layer 1 10, a PMMA layer 410, an adhesive layer 420, a MOF weatherable layer 220, 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 (including, for example, a metal such as copper), an adhesive layer 170, and a liner 180.
• a compliance layer as shown schematically in Fig. 3 and described below.
• Solar mirror film 500 includes a premask layer 1 10, a compliance layer 310, a MOF weatherable layer 220, 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 (including, for example, a metal such as copper), an adhesive layer 170, and a liner 180.
• 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. One exemplary commercially available premask is ForceField® 1035 sold by Tredegar of Richmond, Virginia.
• Exemplary multilayer optical films of the present disclosure may be prepared, for example, using the apparatus and methods disclosed in U.S. Patent No. 6,783,349, entitled “Apparatus for Making Multilayer Optical Films," U.S. Patent No. 6,827,886, entitled “Method for Making Multilayer Optical Films,” and PCT Publication Nos.
• WO 2009/140493 entitled “Solar Concentrating Mirror”
• WO 201 1/062836 entitled “Multi-layer Optical Films,” all of which are incorporated herein by reference in their entireties.
• PMMA/PVDF skin layers are described.
• the weatherable MOF layer may have spectral regions of high reflectivity (>90%) and other spectral regions of high transmissivity (>90%).
• the weatherable layer provides high optical transmissivity over a portion of the solar spectrum and low haze and yellowing, good weatherability, good abrasion, scratch, and crack resistance during to handling and cleaning, and good adhesion to other layers, for example, other (co)polymer layers, metal oxide layers, and metal layers applied to one or both major surfaces of the films when used as substrates, for example, in compact electronic display and/or solar energy applications.
• Inclusion of the multilayer optical film in the solar mirror film construction can, in some embodiments, be introduced as in-line processes.
• the multilayer optical film has a coefficient of hygroscopic expansion that is between the coefficient of hygroscopic expansion of prior art weatherable layers and the reflective layer. In some embodiments, the multilayer optical film has a coefficient of hygroscopic expansion that is less than 30 ppm per percent RH. In some embodiments, the multilayer optical film has a coefficient of hygroscopic expansion of between about 10 ppm per percent relative humidity and about 25 ppm per percent relative humidity. In some embodiments, the multilayer optical film has a coefficient of hygroscopic expansion of between about 15 ppm per percent relative humidity and about 20 ppm per percent relative humidity.
• Prior art weatherable films have a coefficient of hygroscopic expansion of at least about 30 ppm per percent RH.
• the coefficient of hygroscopic expansion of the multilayer optical film is between about 75% and about 25% of the coefficient of hygroscopic expansion of the prior art weatherable layers.
• the coefficient of hygroscopic expansion of the multilayer optical film is between about 70% and about 30% of the coefficient of hygroscopic expansion of the prior art weatherable layers.
• the coefficient of hygroscopic expansion of the multilayer optical film is between about 60% and about 40% of the coefficient of hygroscopic expansion of the prior art weatherable layers.
• 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 and wet peel testing. Further options and advantages of metal 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 film includes a compliance layer. Compliance layers are preferably non-tacky at ambient temperatures.
• 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.
• 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 block copolymer may be combined with a suitable ultraviolet light absorber to enhance the stability.
• the block copolymer contains an ultraviolet light absorber.
• the block copolymer contains an amount of the ultraviolet light absorber ranging from 0.5 percent to 3.0 percent by weight, based on the total weight of the block copolymer and absorber. It is to be noted, however, that the block copolymer need not contain any ultraviolet light absorbers. Using a composition free of any ultraviolet light absorbers can be advantageous because these absorbers can segregate to the surfaces and interfere with adhesion to adjacent layers.
• the block copolymer may be combined with one or more nanofillers to adjust the modulus of the compliance layer.
• a nanofiller such as silicon dioxide or zirconium dioxide can be uniformly dispersed in the block copolymer to increase the overall stiffness or hardness of the solar mirror film.
• the nanofiller is surface-modified as to be compatible with the polymer matrix.
• the compliance layer includes a random copolymer having a first polymeric unit with a relatively high T g and second polymeric unit with a relatively low T g .
• the first polymeric unit derives from a first monoethylenically unsaturated monomer comprising a methacrylate, acrylate, styrene, or combination thereof and associated with a glass transition temperature of at least 50 degrees Celsius and the second polymeric unit derived from a second monoethylenically unsaturated monomer comprising a methacrylate, acrylate, vinyl ester, or combination thereof and associated with a glass transition temperature no greater than 20 degrees Celsius.
• the first polymeric unit is methyl methacrylate and the second polymeric unit is butyl acrylate. It is preferable that the random copolymer has a methyl methacrylate composition of at least 50 percent, at least 60 percent, at least 70 percent, or at least 80 percent, based on the overall weight of the random copolymer. It is further preferable that the random copolymer has a methyl methacrylate composition of at most 80 percent, at most 85 percent, at most 90 percent, or at most 95 percent, based on the overall weight of the random copolymer.
• 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 micrometers or no greater than 100 micrometers. In some embodiments, 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 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, which is in turn situated on a weatherable layer.
• 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 elemental silver.
• the reflective layer has a coefficient of hygroscopic expansion of about zero ppm per percent RH. In some embodiments, the reflective layer has a coefficient of hygroscopic expansion 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 weatherable layer. If desired, the weatherable layer can be masked during the deposition process such that the reflective layer is applied onto only a pre-determined portion of the weatherable layer.
• Patterned deposition of the reflective layer onto the multilayer optical film or weatherable layer is also possible. Exemplary ways of creating a pattern in the reflective layer are described, for example, in matter numbers 69678US002, 69677US002, and 69681US002, all assigned to the present applicant and all incorporated herein in their entirety.
• Application of the metal to the polymer 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 on the weatherable layer, thereby forming 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.
• metals such as silver, aluminum, copper, and gold.
• two or more reflective layers may be used.
• the reflective layer has a thickness no greater than 500 nanometers. In some embodiments, the reflective layer has a thickness of from 80 nm to 250 nm. In some embodiments, 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.
• 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.
• 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).
• 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.).
• exemplary substrates include metals, such as, for example, aluminum, steel, glass, or composite materials.
• metals such as, for example, aluminum, steel, glass, or composite materials.
• Those of skill in the art will appreciate that the embodiments described herein can include additional materials or layers.
• some embodiments may include a compliant layer as is described in U.S. Patent Application Matter No. 69682US002, assigned to the present assignee and incorporated herein by reference in its entirety.
• Some embodiments may have less or no silver on the edge regions of the solar mirror film, as is described in U.S. Patent Application Matter No.
• 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.
• Hygroscopic expansion was measured using a dynamic mechanical analyzer (DMA) (model "Q800" obtained from TA Instruments) coupled with a DMA-RH accessory (obtained from TA Instruments). Displacement (in m/m) was measured over a ramp of varying relative humidities, ranging from about 20% to about 80% at a constant temperature of 25°C. Changes in the sample dimensions caused by humidity changes are used to calculate the CHE. Results are expressed in parts per million (ppm) per percent relative humidity (% RH).
• Corrosion of the comparative 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 visual observations after various times.
• a silver metallized acrylic film (“ECP-305+” manufactured by 3M Company, St. Paul, MN) was provided. This film looked substantially the same as the film shown in Fig. 1 except that it did not include tie layer 140.
• the silver metallized acrylic film had a CHE of 30 ppm per percent RH.
• the ECP-305+ film was laminated to a painted aluminum substrate using the PSA included in the product. The sample was cut to 4" x 4" using a shear cutter. The sample was weather tested according to the NSS described above and was found to exhibit tunneling in less than 72 hours.
• a multilayer optical film was prepared as following: a multilayer optical stack (described below) was prepared by coextruding first and second polymer layers through a multilayer polymer melt manifold to create a multilayer melt stream having five-hundred and fifty alternating layers. Two skin layers each having a thickness of approximately 4 microns were also co-extruded as protective layers on each side of the optical layer stack.
• the multilayer melt stream was cast onto a chilled roll creating a multilayer cast web.
• the multilayer cast web was then heated in a tenter oven to a temperature of about 105° C prior to being biaxially oriented to a draw ratio of 3.8 by 3.8.
• a silver reflective layer approximately 100 nm thick was vapor deposited onto the film substrate.
• a copper layer approximately 80 nm thick was coated onto the silver layer.
• a 25 micron acrylic adhesive was coated onto the copper layer.
• the resulting multilayer optical film was bonded to an epoxy coated aluminum substrate having a thickness of about 0.5 mm.
• the laminated sample was cut to 4" x 4" using a shear cutter.
• the first polymer layer of the multilayer stack was a birefringent layer including polyethylene terephtalate (PET) (obtained under the trade designation “PET 9921 ,” sold by Eastman Chemical Company), and an ultraviolet absorber (obtained under the trade designation "SUKANO UV
• MASTERBATCH TA07-07 sold by Sukano Polymers Corporation, Duncan, South Carolina compounded at about 10 weight percent (wt%).
• the second polymer layer included a copolymer of polymethylmethacrylate (co-PMMA) (obtained under the trade designation "ATOGLAS 51 OA,” sold by Arkema, King of Prussia, Pennsylvania).
• the skin layers included a polymer blend comprising 35% polyvinylidene fluoride (PVDF) (obtained under the trade designation “DYNEON PVDF 6008,” sold by 3M Company) and 65% polymethylmethacrylate (PMMA) (obtained under the trade designation "CP-82,” sold by Plaskolite, Columbus, Ohio), and which included 2.5 wt% of a second ultraviolet absorber
• PVDF polyvinylidene fluoride
• PMMA polymethylmethacrylate
• the hygroscopic expansion of the multilayer MOF film was measured as described above and determined to be about 15 ppm per percent RH.
• a multilayer optical film was prepared as following: a multilayer optical stack (described below) was prepared by coextruding first and second polymer layers through a multilayer polymer melt manifold to create a multilayer melt stream having one hundred and fifty alternating layers. Two skin layers each having a thickness of approximately 4 microns were also co-extruded as protective layers on each side of the optical layer stack.
• the multilayer melt stream was cast onto a chilled roll creating a multilayer cast web.
• the multilayer cast web was then heated in a tenter oven to a temperature of about 105° C prior to being biaxially oriented to a draw ratio of 3.8 by 3.8.
• a silver reflective layer approximately 100 nm thick can be vapor deposited onto the film substrate.
• a copper layer approximately 80 nm thick can be coated onto the silver layer.
• a 25 micron acrylic adhesive can be coated onto the copper layer.
• the resulting multilayer optical film can be bonded to an epoxy coated aluminum substrate having a thickness of about 0.5 mm.
• the first polymer layer of the multilayer stack was a non-birefringent layer including a polymer blend comprising 80 wt% polymethylmethacrylate (PMMA) (obtained under the trade designation "CP- 82,” sold by Plaskolite, Columbus, Ohio) and 20wt% polyvinylidene fluoride (PVDF) (obtained under the trade designation "DYNEON PVDF 6008,” sold by 3M Company) .
• PMMA polymethylmethacrylate
• PVDF polyvinylidene fluoride
• the second polymer layer included a polymer blend comprising 20 wt% polymethylmethacrylate (PMMA) (obtained under the trade designation "CP-82,” sold by Plaskolite, Columbus, Ohio) and 80wt% polyvinylidene fluoride (PVDF) (obtained under the trade designation "DYNEON PVDF 6008,” sold by 3M
• PMMA polymethylmethacrylate
• PVDF polyvinylidene fluoride
• the skin layers included a polymer blend comprising polyvinylidene fluoride (PVDF) (obtained under the trade designation "DYNEON PVDF 6008,” sold by 3M Company) and polymethylmethacrylate (PMMA) (obtained under the trade designation "CP-82,” sold by PVDF)
• PVDF polyvinylidene fluoride
• PMMA polymethylmethacrylate
• the hygroscopic expansion of the multilayer MOF film measured as described above is expected to be about 15 ppm per percent RH.
• the film weather tested as described above is not expected to exhibit tunneling after 1500 hours.

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