Durable low emissivity window film constructions

Abstract

Low emissivity films have a substrate layer and a multi-layer construction disposed on the substrate layer. The multi-layer construction has (layer 1) a poly-5 (meth)acrylate layer, (layer 2) a silicon compound layer, (layer 3) a zinc tin oxide layer, (layer 4) a reflective metal layer of silver or a silver alloy, (layer 5) a zinc tin oxide layer, (layer 6) a silicon compound layer, and (layer 7) a radiation-cured hardcoat layer with a thickness of from 350 to 1,200 nanometers. The hardcoat layer is either a poly- (meth)acrylate, a polyurethane, or a multi-layer construction comprising a 0 poly(meth)acrylate-based sublayer and a polyolefin-based sublayer, The film has an emissivity of less than 0.3, and the film is scratch resistant and corrosion resistant.

Description

[0001]

[0002] DURABLE LOW EMISSIVITY WINDOW FILM CONSTRUCTIONS

[0003] Summary

[0004] Disclosed herein are films. The films are durable and have a low emissivity. In some embodiments, the films are window films.

[0005] In some embodiments, the film comprises a substrate layer with a first major surface and a second major surface, where a multi-layer construction is disposed on the second major surface of the substrate layer. The multi-layer construction comprises, in sequence: a first layer comprising a first radiation-cured layer with a thickness of 500 nanometers or greater comprising a poly-(meth)acrylate; a second layer comprising a first silicon compound layer, wherein the silicon compound is chosen from silicon aluminum oxide, silicon aluminum oxynitride, silicon oxide, silicon oxynitride, silicon nitride, silicon aluminum nitride, and combinations thereof, a third layer comprising a first zinc tin oxide layer, wherein the layer has a thickness from 4 nm to 24 nm; a fourth layer comprising a reflective metal layer comprising silver or a silver alloy; a fifth layer comprising a second zinc tin oxide layer, wherein the layer has a thickness of from 4 to 24 nanometers; a sixth layer comprising a second silicon compound layer, wherein the silicon compound is chosen from silicon aluminum oxide, silicon aluminum oxynitride, silicon oxide, silicon oxynitride, silicon nitride, silicon aluminum nitride, and combinations thereof, and a seventh layer comprising a second radiation-cured layer, wherein the second radiation- cured layer comprises a hardcoat layer with a thickness of from 350 to 1,200 nanometers comprising either a poly-(meth)acrylate, a polyurethane, or a multi-layer construction comprising a poly (meth)acrylate -based sublayer and a polyolefin-based sublayer, wherein the polyolefin-based sublayer is disposed on the sixth layer. The film has an emissivity of less than 0.3, the film has a visible light transmission of greater than 65%, and the film is scratch resistant and corrosion resistant. Brief Description of the Drawings

[0006] The present application may be more completely understood in consideration of the following detailed description of various embodiments of the disclosure in connection with the accompanying drawings.

[0007] Figure 1 is a cross-sectional view of an article of this disclosure.

[0008] Figure 2 is a cross-sectional view of another article of this disclosure.

[0009] The figures are not necessarily to scale. Like numbers used in the figures refer to like components. However, it will be understood that the use of a number to refer to a component in a given figure is not intended to limit the component in another figure labeled with the same number.

[0010] Detailed Description

[0011] Low emissivity (low e) window films are becoming increasingly important as a method to reduce heating energy usage by old buildings in cold climates. Emissivity is defined as the ratio of the energy radiated from a material's surface to that radiated from a perfect emitter, known as a blackbody, at the same temperature and wavelength and under the same viewing conditions. It is a dimensionless number between 0 (for a perfect reflector) and 1 (for a perfect emitter). It is desirable for low e window films to reflect infrared radiation, or heat energy, into a room while at the same time permitting visible light from outside the room to be transmitted. Low e window films typically contain metal layers (e.g., silver) which have high reflectance in the infrared (IR) region and can thus reduce radiative heat loss from buildings. Protective materials are placed over the metal layers to impart scratch and abrasion resistance and to protect the underlying metal layers from corrosion. Examples of protective materials include acrylate-based and fluoropolymer-based polymeric coatings. An example of such a window film is described in US Patent No. 11,414,924 (Padiyath et al.).

[0012] An issue with such films is scratch resistance. If the exposed surface of a low e film is scratched, not only does the scratching adversely affect the appearance and the visible light transmission, but also it can expose the underlying metal layer and permit corrosion and loss of IR reflectivity. Thus, the issues of scratch resistance and corrosion resistance are intimately related. Increasing the thickness of the protective layers on the film will make the film more scratch and corrosion resistant. However, many polymeric materials absorb infrared radiation and when applied above the IR reflective metallic layer, they increase the overall emissivity of the window film. This means a balance must be struck to define a protective coating thickness that provides both heat insulation and durability. That thickness limit is different for different polymeric materials depending on their IR absorptivity. In addition, the protective layers can affect the appearance of the film since coating thicknesses on the order of the wavelength of light can change visible light transmission due to optical interference, resulting in low transmittance, high reflectivity, or an iridescent, multicolored appearance.

[0013] This disclosure addresses such challenges with product designs to provide good durability (e.g., good scratch and corrosion resistance) while maintaining heat insulation with emissivity values of 0.30, or even less than 0.25, and visible light transmittance of greater than 65%.

[0014] The term "film" as used herein refers, depending on the context, to either a single layer article or to a multilayer construction, where the different layers may have been laminated, extruded, coated, or any combination thereof.

[0015] The term “(meth)acrylate” refers to monomeric acrylic or methacrylic esters of alcohols. Acrylate and methacrylate monomers or oligomers are referred to collectively herein as "(meth)acrylates”. Materials referred to as “(meth)acrylate -based” are materials that contain a majority of (meth)acrylates.

[0016] The term “olefin-based” as used herein refer to polymers or units of polymers that contain a majority olefin moieties.

[0017] The terms "room temperature" and "ambient temperature" are used interchangeably to mean temperatures in the range of 20°C to 25°C.

[0018] The term “adjacent” as used herein when referring to two layers means that the two layers are in proximity with one another with no intervening open space between them. They may be in direct contact with one another (e.g., laminated together and immediately adjacent) or there may be intervening layers.

[0019] The terms “polymer” and “macromolecule” are used herein consistent with their common usage in chemistry. Polymers and macromolecules are composed of many repeated subunits. As used herein, the term “macromolecule” is used to describe a group atached to a monomer that has multiple repeating units. The term “polymer” is used to describe the resultant material formed from a polymerization reaction.

[0020] The term "adhesive" as used herein refers to polymeric compositions useful to adhere together two components (adherents). Examples of adhesives include pressure sensitive adhesives.

[0021] The term "visible light" or "visible spectrum" as used herein refers to refers to radiation in the visible spectrum, which in this disclosure is taken to be from 400 nm to 700 nm.

[0022] The term "near infrared spectrum" or simply “infrared spectrum” as used herein refers to radiation in the range from 700 nm to 2500 nm.

[0023] The term "emissivity" as used herein is a measure of the efficiency that a surface emits thermal energy and is defined as the ratio of the radiation emitted by a surface to the radiation emited by a perfect black body at the same temperature. The emissivity is a value between 0 and 1 and is measured according to ASTM Cl 371. One such instrument for measuring emissivity is available (model AE1 emissometer) from Devices and Services Company, Dallas, TX.

[0024] The term "radiation-cured” in the context of curing a polymer refers to curing aided by the use of any type of electromagnetic radiation, including, for example, actinic radiation (radiation that is capable of producing photochemical reactions, such as ultraviolet radiation, vacuum UV (VUV), extreme UV (EUV or XUV)) or in some cases even visible light, electron beam, or UV radiation generated from plasma such as that used in a sputering process, for example.

[0025] Disclosed herein are films with low emissivity. These films are similar to the films described in US Patent No. 11,414,924 (Padiyath et al.). In some embodiments, the film comprises a substrate layer with a first major surface and a second major surface, where a multi-layer construction is disposed on the second major surface of the substrate layer. The multi-layer construction comprises, in sequence: a first layer; a second layer; a third layer; a fourth layer; a fifth layer; a sixth layer; and a seventh layer. The first layer comprises a first radiation-cured layer with a thickness of 500 nanometers or greater comprising a poly-(meth)acrylate. The second layer comprises a first silicon compound layer, wherein the silicon compound is chosen from silicon aluminum oxide, silicon aluminum oxynitride, silicon oxide, silicon oxynitride, silicon nitride, silicon aluminum nitride, and combinations thereof. The third layer comprises a first zinc tin oxide layer, wherein the layer has a thickness from 4 nm to 24 nm. The fourth layer comprises a reflective metal layer comprising silver or a silver alloy. The fifth layer comprises a second zinc tin oxide layer, wherein the layer has a thickness from 4 to 24 nanometers. The sixth layer comprises a second silicon compound layer, wherein the silicon compound is chosen from silicon aluminum oxide, silicon aluminum oxynitride, silicon oxide, silicon oxynitride, silicon nitride, silicon aluminum nitride, and combinations thereof. The seventh layer comprises a second radiation-cured layer, where the second radiation-cured layer comprises a hardcoat layer with a thickness of from 350 to 1,200 nanometers comprising either a poly-(meth)acrylate, a polyurethane, or a multi-layer construction comprising a poly (meth)acrylate -based sublayer and a polyolefin-based sublayer, wherein the polyolefin-based sublayer is disposed on the sixth layer. The film has an emissivity of less than 0.3, the film has a visible light transmission of greater than 65%, and the film is scratch resistant and corrosion resistant. The term “scratch and corrosion resistant” refers to having minimal emissivity change and little to no visible corrosion damage on the film after the film is scratched with steel wool and immersed in a salt solution, as described in the Examples section. Each of these layers is described below.

[0026] The films of this disclosure include a substrate. A wide variety of substrates are suitable. In many embodiments, the substrate comprises an optically clear film substrate. The optically clear film substrate can be prepared from a variety of materials. In some embodiments, the substrate comprises a polyester polymer or polyester co-polymers. For example, useful polyester polymers include polymers having terephthalate or naphthalate comonomer units, for example, polyethylene naphthalate (PEN), polyethylene terephthalate (PET) and copolymers and blends thereof. Examples of other suitable polyester copolymers are provided in, for example, published patent application WO 99 / 36262 and in WO 99 / 36248. Other suitable substrate materials include polycarbonates, polyacrylates, and other naphthalate and terephthalate-containing polymers, such as, for example, polybutylene naphthalate (PBN), polypropylene naphtahalate (PPN), and blends and copolymers of the above with each other or with non-polyester polymers.

[0027] In some embodiments, the substrate may be (or comprise) a polymeric multilayer optical film (“MOF”). In general, a MOF comprises at least a core section that comprises a multilayer optical stack, which comprises series of two or more alternating polymeric layers. Exemplary multilayer optical stacks 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” and WO 2011 / 062836 entitled “Multi-layer Optical Films,”. Examples of additional layers or coatings suitable for use with exemplary multilayer optical stacks of the present disclosure are described, for example, in U.S. Patent Nos. 6,368,699, and 6,459,514 both entitled "Multilayer Polymer Film with Additional Coatings or Layers,". In some embodiments, the substrate may be a durable extruded dyed polyester fdm, such as the fdm disclosed in U.S. Patent no. US 9,630,384.

[0028] In some embodiments, the fdms of this disclosure further comprise an adhesive, such as a pressure sensitive adhesive, disposed on the first major surface of the substrate. The films comprising an adhesive layer on the first major surface of the substrate typically further comprise a suitable liner disposed on the adhesive layer.

[0029] As described above, the film comprises a multi-layer construction disposed on the second major surface of the substrate layer. The first layer of the multi-layer construction comprises a first radiation-cured layer with a thickness of 500 nanometers or greater comprising a poly-(meth)acrylate. In some embodiments, the thickness is 1,000 nanometers or greater or even 1,500 nanometers or greater. A radiation-cured layer refers to a layer in which curing is aided by the use of electromagnetic radiation, including, for example, actinic radiation, electron beam, and plasma radiation. Typically, the radiation- cured layer is cured by exposure to electron beam radiation or ultraviolet radiation.

[0030] A wide range of poly-(meth)acrylates are suitable. The poly-(meth)acrylates are formed by the polymerization of a reaction mixture that contains at least one (meth)acrylate monomer. The (meth)acrylate monomers may be mono-functional (meth)acrylates or multi-functional (meth)acrylates. Examples of suitable (meth)acrylate monomers include phenylthioethyl acrylate, hexanediol diacrylate, ethoxyethyl acrylate, phenoxyethyl acrylate, cyanoethyl (mono) acrylate, isobomyl acrylate, isobomyl methacrylate, octadecyl acrylate, isodecyl acrylate, lauryl acrylate, carboxyethyl acrylate, tetrahydrofurfuryl acrylate, dinitrile acrylate, nitrophenyl acrylate, 2-phenoxyethyl acrylate, 2-phenoxyethyl methacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tripropylene glycol diacrylate, tetraethylene glycol diacrylate, neopentyl glycol diacrylate, propoxylated neopentyl glycol diacrylate, polyethylene glycol diacrylate, tetraethylene glycol diacrylate, bisphenol A epoxy diacrylate, 1 ,6-hexanediol dimethacrylate, trimethylol propane triacrylate, ethoxylated trimethylol propane triacrylate, propylated trimethylol propane triacrylate, 2-biphenyl acrylate, tris(2-hydroxyethyl)-isocyanurate triacrylate, pentaerythritol tetraacrylate, phenylthioethyl acrylate, naphthloxyethyl acrylate, EBECRYL 130 cyclic diacrylate (available from Cytec Surface Specialties, West Paterson, N.J.), epoxy acrylate RDX80095 (available from Rad-Cure Corporation, Fairfield, N.J.), CN120E50 and CN120C60 (both available from Sartomer, Exton, Pa.), and mixtures thereof.

[0031] In some embodiments, as described above, the mixtures that form the (meth)acrylate polymers include at least one multi-functional (meth)acrylate. In yet other embodiments the first radiation-cured acrylate further comprises at least one additive. In some embodiments, the (meth)acrylate mixture further comprises a photoinitiator, an adhesion promoter, and silica nanoparticles. Examples of suitable adhesion promoters are silane coupling agents. If used, the silica nanoparticles used in the composition are typically in a range from 10 wt. % to 65 wt. % (in some embodiments, 30-40 wt. %), based on the total weight of the hardcoat. The nanoparticles have an average particle diameter in a range from 2 nm to 200 nm. The nanoparticles can also be surface modified to impart acrylate functionalities to them, using a method described in US Patent No. 11,260,592.

[0032] In some embodiments, the first layer is crosslinked in situ atop the substrate. In certain embodiments, the first layer can be formed by flash evaporation or vapor deposition of an acrylate monomer or a mixture of acrylate monomers followed by curing or crosslinking via actinic radiation. In some embodiments, the layer can be applied using other conventional coating methods such as roll coating, (e.g., gravure roll coating) die coating or spray coating (e.g., electrostatic spray coating) and cured using a method mentioned earlier.

[0033] The multi-layer construction also comprises a second layer. The second layer comprises a first silicon compound layer. As used herein the first layer comprising a silicon compound refers to a layer comprising silicon that has been deposited under a reduced pressure process (less than 1 atm) and does not refer to layers only comprising silicon as part of silica nanoparticles. In certain embodiments, the first silicon compound in this layer is chosen from silicon aluminum oxide, silicon aluminum oxynitride; silicon oxide, silicon oxynitride, silicon nitride, silicon aluminum nitride, and combinations thereof.

[0034] Deposition of the first silicon compound layer can be accomplished by any means known in the art to deposit inorganic oxides. For example, in some embodiments, deposition occurs by sputtering (e.g., reactive sputtering, either from planar or rotary cathodes), evaporation (e.g., thermal, resistive, or electron beam evaporation), various chemical vapor depositions, ion-assisted e-beam evaporation, and variations thereof, under suitable gaseous atmospheres.

[0035] In other embodiments, the second layer has a thickness from 3 nm to 20 nm, or from 5 nm to 20 nm, or from 5 nm to 15 nm, or from 5 nm to 10 nm, or from 5 nm to 9 nm.

[0036] The multi-layer construction also comprises a third layer. The third layer comprises a first zinc tin oxide layer.

[0037] Deposition of the first zinc tin oxide layer can be accomplished by using various deposition techniques with a suitable metal target under a suitable gaseous atmosphere as required (nitrogen, oxygen, or combinations thereof), such as sputtering (e.g., reactive sputtering, for example planar or rotary magnetron sputtering), evaporation (e. g., thermal, resistive, or electron beam evaporation), various chemical vapor depositions, ion-assisted e-beam evaporation, and variations thereof. Metal oxide layer may also be deposited using an oxide target in a sputtering process. The oxygen content of the deposited layer may be different from that of the target.

[0038] Typically, the deposition process continues for a sufficient duration to build up a suitable layer thickness as needed. The thickness of the first zinc tin oxide layer is from 3 nm to 29 nm. In certain embodiments, the thickness is from 4 nm to 24 nm.

[0039] The multi-layer construction also comprises a fourth layer. The fourth layer comprises a silver layer or silver alloy layer. In some embodiments, the fourth layer comprises a metal layer. In other embodiments, the fourth layer comprises a silver alloy, including silver alloys comprising 70% or more silver, such as 80%, or even 85% silver. In certain preferred embodiments, the metal layer comprises a silver-gold alloy.

[0040] The metal layer can be deposited using the same techniques described above for the third layer. In some embodiments, the metal layer is deposited using physical vapor deposition (PVD) techniques. Typically, in a PVD technique, atoms of the target are ejected by high-energy particle bombardment so that they can impinge onto a suitable substrate to form a thin fdm. 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.

[0041] Typically, the desired optical density of the final film determines the suitable thickness of the metal layer. In some embodiments, the thickness of the fourth layer is less than 30 nm, or less than 20 nm, or less than 15 nm, or less than 14 nm, or less than 13 nm, or less than 12 nm, or less than 11 nm, or less than 10 nm, or less than 9 nm, or less than 8 nm, or less than 7 nm, that thickness can depend on the efficacy of the substrate layer. In other embodiments, the thickness of the fourth layer is from 1 to 30 nm, or from 5 to 25 nm, or from 5 to 20 nm, or from 5 to 15 nm, or from 5 to 14 nm, or from 5 to 13 nm, or from 5 to 12 nm, or from 5 to 11 nm, or from 5 to 10 nm, or from 8 to 15 nm, or from 8 to 14 nm, or from 10 nm to 12 nm.

[0042] The multi-layer construction also comprises a fifth layer. The fifth layer comprises a second zinc tin oxide layer. The second zinc tin oxide layer can be deposited as described above for the first zinc tin oxide layer. The layer has a thickness from 4 to 24 nanometers.

[0043] The multi-layer construction also comprises a sixth layer. The sixth layer comprises a second silicon compound layer, where the silicon compound is chosen from silicon aluminum oxide, silicon aluminum oxynitride, silicon oxide, silicon oxynitride, silicon nitride, silicon aluminum nitride, and combinations thereof. The second silicon compound layer can be deposited as described above for the first silicon compound layer. The layer has a thickness that can be the same as the first silicon compound layer described above.

[0044] The multi-layer construction also comprises a seventh layer. The seventh layer comprises a second radiation-cured layer, where the second radiation-cured layer comprises a hardcoat layer with a thickness of from 350 to 1,200 nanometers comprising either a poly-(meth)acrylate, a polyurethane (meth)acrylate, or a multi-layer construction comprising a poly (meth)acrylate -based sublayer and a polyolefin-based sublayer, wherein the polyolefin-based sublayer is disposed on the sixth layer. In some embodiments, the seventh layer is prepared by radiation curing a (meth)acrylate mixture comprising at least one multifunctional (meth)acrylate. Multifunctional (meth)acrylates are described above for the first layer. In some embodiments, the multifunctional (meth)acrylate comprises an aliphatic diacrylate, including urethane diacrylates. In some embodiments, the aliphatic diacrylate is tricyclodecanedimethanol diacrylate.

[0045] In some embodiments, the (meth)acrylate mixture further comprises at least one multi-functional (meth)acrylate, and at least one additive selected from metal oxide nanoparticles, a surfactant, a photoinitiator, UV absorbers, or a combination thereof. Examples of suitable multi-functional (meth)acrylates include those described above for the first layer. Examples of suitable metal oxide nanoparticles include silica nanoparticles as described above. Examples of suitable surfactants include TEGORAD 2250, TEGORAD 2500 from Evonik, UV3505 from BYK, and KR4000G from Shin-Etsu.. A photoinitiator is an initiator that is activated by light, typically ultraviolet (UV) light. Photoinitiators are well understood by one of skill in the art of (meth)acrylate polymerization. Examples of suitable free radical photoinitiators include OMNIRAD 184, OMNIRAD 819, OMNIRAD 4265, OMNIRAD TPO, and ESACURE One from IGM Resins. In these embodiments, the (meth)acrylate mixture is disposed on the sixth layer by solvent coating or vapor coating.

[0046] In other embodiments, the seventh layer comprises two sublayers, a polyolefin- based sublayer disposed on the sixth layer and a poly (meth)acrylate -based sublayer disposed on the polyolefin-based sublayer.

[0047] A wide range of polyolefin-based sublayers are suitable. In some embodiments, the polyolefin-based sublayer is formed by radiation curing of a curable mixture comprising: cyclic olefin polymer (COC), cyclic olefin co-polymer (COP), or combinations thereof; photoinitiator; silane coupling agents; and multi-functional (meth)acrylate monomers, as described above.

[0048] In some embodiments, the curable mixture comprises at least one polyolefin with pendant vinyl groups such as those described in PCT Publication No. WO 2024 / 100476.

[0049] In some embodiments, the curable mixture of the polyolefin-based sublayer further comprises a silane coupling agent, and up to 5 weight % acrylate monomers. A wide range of silane coupling agents are suitable. Particularly suitable are acrylate functional silane coupling agents such as KR-513 and KB-5103 from Shin-Etsu.

[0050] The curable mixture in many embodiments also comprises at least one photoinitiator. Suitable photoinitiators are described above.

[0051] In some embodiments, the curable mixture of the polyolefin-based sublayer is a solvent-borne mixture. Suitable solvents include alkanes such as heptane and cyclohexane, and aromatics such as toluene and xylene.

[0052] In these embodiments, the seventh layer also comprises a poly(meth)acrylate-based sublayer. In some embodiments, the poly(meth)acrylate-based sublayer is formed by radiation curing of a curable mixture comprising: a mixture of (meth)acrylate monomers; metal oxide nanoparticles such as silica nanoparticles; at least one surfactant; and at least one photoinitiator. Each of these components is described above.

[0053] The films of this disclosure have a variety of desirable properties. In some embodiments, the combined thickness of layer two, layer three, layer five and layer six has a thickness of greater than 40 nanometers. In some embodiments, the film has an emissivity of less than 0.30 or even 0.25.

[0054] As was mentioned above, a desirable property of the current films is the scratch resistance and corrosion resistance of the films. These properties can be measured in a variety of ways. For example, resistance to scratches can be measured using an abrasion test with steel wool and measuring any change in emissivity. Resistance to corrosion can be measured by soaking the article in a saltwater solution and measuring any change in emissivity. Among the particularly suitable methods for measuring these properties include the scratch and salt soak test methods described in the Examples section below. Changes in emissivity of less than 0.05 after a scratch test, a saltwater soak test, or a combination of the tests are indicative of scratch and corrosion resistance. In some embodiments, the change in emissivity is less than 0.02 after a scratch test, a saltwater soak test, or a combination of the tests.

[0055] In some embodiments, the films of this disclosure are window films that may be attached to glazing substrates to provide articles, such as windows or glazing articles with low emissivity properties. Examples of suitable glazing substrates may be prepared from a variety of different materials including, for example, a variety of different types of glass or from polymeric materials such as polyolefins, polyimides, polycarbonates or polymethyl methacrylates. In some embodiments, the glazing substrate may also comprise additional layers or treatments. Examples of additional layers include, for example, additional layers of fdm designed to provide glare reduction, tinting, shatter resistance and the like. Examples of additional treatments that may be present on glazing substrates include, for example, coatings or various types such as hardcoats, and etchings such as decorative etchings.

[0056] As mentioned previously, in some embodiments, the films contain an adhesive layer on a suitable surface of the film to laminate the film to a first glazing substrate. The adhesive layer may be protected by a release liner.

[0057] Adhesive compositions suitable to be used with or in window films are well known to those of ordinary skill in the art. In certain embodiments, the adhesives used in the films of the present disclosure include heat activated adhesives and pressure sensitive adhesives (PSAs). Heat activated adhesives are non-tacky at room temperature but become tacky and capable of bonding to a substrate at elevated temperatures. These adhesives usually have a glass transition temperature (7g) or melting point (Tm) above room temperature. When the temperature is elevated above the Tg or Tm, the storage modulus usually decreases and the adhesive becomes tacky.

[0058] Pressure sensitive adhesives suitable to be used in the instant films possess properties at room temperature including the following: (1) aggressive and permanent tack, (2) adherence with no more than finger pressure, (3) sufficient ability to hold onto an adherend, and (4) sufficient cohesive strength to be cleanly removable from the adherend. Materials that have been found to function well as pressure sensitive adhesives are polymers designed and formulated to exhibit the requisite viscoelastic properties resulting in a desired balance of tack, peel adhesion, and shear holding power.

[0059] The pressure sensitive adhesives may be (meth)acrylate-based pressure sensitive adhesives. Useful alkyl (meth)acrylates (i.e., acrylic acid alkyl ester monomers) include linear or branched monofunctional unsaturated acrylates or methacrylates of non-tertiary alkyl alcohols, the alkyl groups of which have from 4 to 14 and, in particular, from 4 to 12 carbon atoms. Poly(meth)acrylic pressure sensitive adhesives are derived from, for example, at least one alkyl (meth)acrylate ester monomer such as, for example, isooctyl acrylate, isononyl acrylate, 2-methyl-butyl acrylate, 2-ethyl-n-hexyl acrylate and n-butyl acrylate, isobutyl acrylate, hexyl acrylate, n-octyl acrylate, n-octyl methacrylate, n-nonyl acrylate, isoamyl acrylate, n-decyl acrylate, isodecyl acrylate, isodecyl methacrylate, isobomyl acrylate, 4-methyl-2-pentyl acrylate and dodecyl acrylate; and at least one optional co-monomer component such as, for example, (meth)acrylic acid, vinyl acetate, N-vinyl pyrrolidone, (meth)acrylamide, a vinyl ester, a fumarate, a styrene macromer, alkyl maleates and alkyl fumarates (based, respectively, on maleic and fumaric acid), or combinations thereof.

[0060] The articles of this disclosure may be better understood by referring to the Figures. Figure 1 is a cross-sectional view of an article of this disclosure. In Figure 1, Layer 100 is a substrate. Layer 102 is the first layer comprising a first radiation-cured layer comprising a poly-(meth)acrylate, layer 104 is the second layer comprising a first silicon compound layer, layer 106 is the third layer comprising a first zinc tin oxide layer, the layer 108 is the fourth layer comprising a reflective metal layer comprising silver or a silver alloy, layer 110 is the fifth layer comprising a second zinc tin oxide layer, layer 112 is the sixth layer comprising a second silicon compound layer,, and layer 114 is the seventh layer comprising a second radiation-cured layer that is a hardcoat layer.

[0061] Figure 2 is a cross-sectional view of another article of this disclosure. In Figure 2, Layer 200 is a substrate. Layer 202 is the first layer comprising a first radiation-cured layer comprising a poly-(meth)acrylate, layer 204 is the second layer comprising a first silicon compound layer, layer 206 is the third layer comprising a first zinc tin oxide layer, the layer 208 is the fourth layer comprising a reflective metal layer comprising silver or a silver alloy, layer 210 is the fifth layer comprising a second zinc tin oxide layer, layer 212 is the sixth layer comprising a second silicon compound layer,, and layer 214 is the seventh layer comprising a second radiation-cured layer that is a hardcoat layer, and includes sublayers 214a and 214b. Sublayer 214a is a polyolefin-based sublayer and sublayer 214b is a poly(meth)acrylate-based sublayer.

[0062] Examples

[0063] These examples are merely for illustrative purposes only and are not meant to be limiting on the scope of the appended claims. All parts, percentages, ratios, etc. in the examples and the rest of the specification are by weight, unless noted otherwise. Solvents and other reagents used were obtained from Sigma-Aldrich Chemical Company; Milwaukee, Wisconsin unless otherwise noted. The following abbreviations are used: cm = centimeters; nm = nanometers; in = inch; g = grams; mTorr= millitorr; Pa = Pascals; min = minutes; W = Watts; mA = milliAmperes; kV = kilovolts; mJ = milliJoules. The terms “weight %”, “% by weight”, and “wt%” are used interchangeably. Table of Abbreviations

[0064] Test Methods

[0065] Emissivity

[0066] Emissivity was measured in accordance with ASTM C1371 using an emissometer, model AE1 and read directly from model RD1 scaling digital voltmeter, both available from Devices and Services Company, Dallas, TX.

[0067] Visible Light Transmission

[0068] Spectral properties of films were measured in accordance with ASTM E903 in a Perkin Elmer Lambda 1050 spectrophotometer. The transmission and reflectance spectra were formatted for software compatibility and the data imported into Optics 6, which is publicly available glazing analysis software available from Lawrence Berkeley National Laboratories, Berkeley, CA (http: / / windows.lbl.gov / software / Optics / optics.html, last accessed on April 14, 2017). NFRC_300_2003 was chosen as the standard for the calculation of visible light transmission. Visible Light Reflection

[0069] Spectral properties of films were measured in accordance with ASTM E903 in a Perkin Elmer Lambda 1050 spectrophotometer. The transmission and reflectance spectra were formatted for software compatibility and the data imported into Optics 6, which is publicly available glazing analysis software available from Lawrence Berkeley National Laboratories, Berkeley, CA (http: / / windows.lbl.gov / software / Optics / optics.html, last accessed on 02 February, 2017. NFRC_300_2003 was chosen as the standard for the calculation of visible light reflection.

[0070] Film Scratch and Soak Test Method

[0071] Film samples of 3 in x 5 in (7.6 cm x 12.7 cm) were measured to determine initial emissivity. The film samples were then abraded on the low-e surface of the film (Layer 7) using a Taber 5750 Linear Abraser with 650g of additional weight on the shaft (1000g total including the spline, shaft and support assembly) and a 1.25 in (3.2 cm) diameter pad of very fine grade steel wool such as Magic Sand -00 grade from HUT products for 5 cycles at 30 cycles per minute. After surface abrasion the samples were submerged in a 20% weight salt water solution and left to soak for 72 hours. At the conclusion of the soaking period the samples were removed from the solution and not rinsed, but allowed to air dry for 4 hours before rinsing with tap water and patting dry. Once dry a final emissivity measurement was made and the change in emissivity from initial to final was recorded.

[0072] Samples were rated as follows:

[0073] 0 = No damage

[0074] 1 = Scratches visible, but no corrosion

[0075] 2 = Minimal corrosion affecting small percentage of test area

[0076] 3 = Significant corrosion throughout test area

[0077] 4 = Catastrophic corrosion throughout test area and / or entire sample

[0078] Examples

[0079] Preparation of a 6-Layer Construction (Comparative Example CE1)

[0080] A multilayer optical stack comprising zinc tin oxide, a silver alloy, silicon oxide or oxynitride, and a radiation cured acrylate layer was deposited on a PET film substrate. All individual layers were formed using a vacuum coating apparatus similar to the one described in Figure 3 of PCT Publication No. WO 2009 / 085741 without breaking the vacuum. The sequence of layers deposited are as follows:

[0081] Layer 1: The substrate roll was loaded into a vacuum coater and the chamber pumped down to a base pressure of less than 1x10"4Torr. The film was exposed to a N2 plasma pre-treatment process using a titanium target run at 200 W. An acrylate monomer mixture comprising Acrylate-2 and SCA-1 in the ratio 94:6, respectively, was flash evaporated, condensed on the PET film substrate and cured with an electron beam source. The electron beam source was operated at 7kV acceleration voltage and 7 mA beam current. The monomer flow rate, and web speed were chosen to result in a cured polymer layer thickness of approximately 1.25 micrometers.

[0082] Layer 2: A silicon aluminum oxynitride layer, approximately 30 nm thick was deposited using a reactive magnetron sputtering process on layer 1. A silicon-aluminum target consisting of 90% Si and 10% Al was used for the deposition of this layer. Gas flow consisting of 85% nitrogen (balance oxygen) was used in the deposition process. Pressure in the sputtering zone was maintained at less than approximately 3 mTorr.

[0083] Layer 3: A zinc tin oxide layer was deposited on layer 2 using a reactive magnetron sputtering process. Sputtering power settings, oxygen flow rate and line speed chosen resulted in a coating thickness less than 6 nm.

[0084] Layer 4: A gold-silver alloy layer, approximately 12 nm thick, was deposited on zinc tin oxide layer using a magnetron sputtering process. The alloy target consisted of approximately 85% Silver and 15% Gold. The sheet resistance of the as-deposited film was approximately 12 ohms / sq.

[0085] Layer 5 : A second zinc tin oxide layer was deposited over the gold-silver alloy layer using the same process conditions as for layer 3.

[0086] Layer 6: A silicon aluminum oxide layer was sputter deposited on layer 5 using a silicon aluminum target consisting of 90% silicon and 10% aluminum. An oxygen atmosphere was maintained during the deposition process. The coating thickness obtained under the process conditions was approximately 6 nm.

[0087] The resultant 6 layer construction is called Comparative Example 1 (CE1) in the following sections.

[0088] Other exemplary constructions of the 6-layer stack Preparation of Coating Formulations for Preparing Layer 7

[0089] A series of Formulations were prepared for use in the preparing Layer 7. The composition of these formulations is shown in the Composition Tables below: Formulation 1

[0090] Formulation 2

[0091] Composition of Formulation 3 (Acrylate layer of Olefin / Acrylate)

[0092]

[0093] Examples Exl and Ex2 (Olefin / (meth)acrylate layers)

[0094] Example Exl was prepared by first coating Formulation 1 on the Layer 6 of the 6 Layer Construction described above in a roll-to-roll die coating process operating at 25 ft / min with a coating width of 4 inches and a solution flow rate of 3.5 cm3 / min. The dried coating was UV cured using an H-bulb (Fusion UV Systems Inc.) operating at 300 W / in (118 W / cm) power. The coated film was then passed through the die coating process again and Formulation 3 was coated on top of the UV-cured Formulation 1 at a web speed of 10 ft / min and a solution flow rate of 2.5 cm3 / min. Similar UV condition as mentioned earlier was used for curing Formulation 3.

[0095] Example Ex2 was prepared by first coating Formulation 2 on the Layer 6 of the 6 Layer Construction described above in a roll-to-roll die coating process at a web speed of 10 ft / min, coating width of 4 inches, and solution flow rate of 2.5 cm3 / min. The coated film was cured using similar UV processing conditions as above. The coated film was then passed through the die coating process again and Formulation 3 was coated on top of the UV-cured Formulation 2 at a web speed of 10 ft / min and a solution flow rate of 2.5 cm3 / min. Similar UV condition as mentioned earlier was used for curing Formulation 3.

[0096] Example Ex3 ((meth)acrylate layer)

[0097] A solution of SCA-1 (1 wt.% in MEK) was first coated on the Layer 6 of the 6 Layer Construction described above using a #3 Mayer rod and the coated sample was placed in 150°F oven for 180 seconds. After it was taken out of oven and allowed cool to room temperature, Formulation 4 was applied using #3 Mayer rod. After the coated sample was placed in 150 °F oven for 180 seconds to drive off the solvent, it was cured with a H-bulb at a UVA+B+C light intensity of 1778 mW / cm2(871 mJ / cm2)

[0098] Comparative Example CE2 and Example Ex4 ((meth)acrylate Layer)

[0099] Formulation 5 acrylate mixture was flash evaporated and deposited on layer 6 and cured with an e-beam source

[0100] Examples Ex5-Ex7 (Other 6 layer constructions)

[0101] Additional 7-layer constructions were prepared using the 6-layer constructions A-C shown above with layer 7 the same as for Ex4.

[0102] Results and Testing

[0103] The coatings resulting from the above tests are described in Table 1 below. Testing was carried out according to the Test Methods described above. The results of the testing are shown in Table 2. In the Tables, T is luminous transmission, H is haze, e is emissivity

[0104] Table 1

[0105] Table 2

Claims

What is claimed is:

1. A film comprising: a substrate layer with a first major surface and a second major surface, wherein a multilayer construction is disposed on the second major surface of the substrate layer, the multilayer construction comprising, in sequence: a first layer comprising a first radiation-cured layer with a thickness of 500 nanometers or greater comprising a poly-(meth)acrylate; a second layer comprising a first silicon compound layer, wherein the silicon compound is chosen from silicon aluminum oxide, silicon aluminum oxynitride, silicon oxide, silicon oxynitride, silicon nitride, silicon aluminum nitride, and combinations thereof, a third layer comprising a first zinc tin oxide layer, wherein the layer has a thickness from 4 nm to 24 nm; a fourth layer comprising a reflective metal layer comprising silver or a silver alloy; a fifth layer comprising a second zinc tin oxide layer, wherein the layer has a thickness from 4 to 24 nanometers; a sixth layer comprising a second silicon compound layer, wherein the silicon compound is chosen from silicon aluminum oxide, silicon aluminum oxynitride, silicon oxide, silicon oxynitride, silicon nitride, silicon aluminum nitride, and combinations thereof, and a seventh layer comprising a second radiation-cured layer, wherein the second radiation-cured layer comprises a hardcoat layer with a thickness of from 350 to 1,200 nanometers comprising either a poly-(meth)acrylate, a polyurethane, or a multi-layer construction comprising a poly(meth)acrylate-based sublayer and a polyolefin-based sublayer, wherein the polyolefin-based sublayer is disposed on the sixth layer, and wherein the film has an emissivity of less than 0.3, the combined thickness of the second layer and the third layer is greater than 15 nanometers, and wherein the film is scratch resistant and corrosion resistant.. The film of claim 1, wherein the film has an emissivity of less than 0.25.

3. The film of claim 1, wherein the combined thickness of layer two, layer three, layer five and layer six has a thickness of greater than 40 nanometers.

4. The film of claim 1, wherein the reflective metal layer comprises a silver-gold alloy.

5. The film of claim 1, wherein the first layer is prepared by radiation curing of a (meth)acrylate mixture comprising (meth)acylate monomers.

6. The film of claim 5, wherein the (meth)acrylate mixture further comprises: at least one multi-functional (meth)acrylate, at least one adhesion promoter, 30-40 weight % of silica nanoparticles, or a combination thereof.

7. The film of claim 5, wherein the (meth)acrylate mixture is disposed on the film substrate by solvent coating or vapor coating.

8. The film of claim 1, wherein the seventh layer is prepared by radiation curing a (meth)acrylate mixture comprising at least one multi-functional (meth)acrylate.

9. The film of claim 8, wherein the (meth)acrylate mixture comprises tricyclodecanedimethanol diacrylate.

10. The film of claim 8, wherein the (meth)acrylate mixture is disposed on the sixth layer by solvent coating or vapor coating.

11. The film of claim 1, wherein the seventh layer comprises two sublayers, a polyolefin- based sublayer disposed on the sixth layer and a poly (meth)acrylate -based sublayer disposed on the polyolefin-based sublayer.

12. The film of claim 11, wherein the polyolefin-based sublayer is formed by radiation curing of a curable mixture comprising: cyclic olefin polymer (COC), cyclic olefin co-polymer (COP), or combinations thereof; and multi-functional (meth)acrylate monomers.

13. The film of claim 12, wherein the curable reaction mixture comprises at least one polyolefin with pendant vinyl groups.

14. The film of claim 12, wherein the curable mixture of the polyolefin-based sublayer further comprises a silane coupling agent and up to 5 weight % acrylate monomer, and at least one photoinitiator.

15. The film of claim 12, wherein the curable mixture of the polyolefin-based sublayer is a solvent-borne mixture.

16. The film of claim 11, wherein the poly(meth)acrylate-based sublayer is formed by radiation curing of a curable mixture comprising: a mixture of (meth)acrylate monomers; metal oxide nanoparticles; at least one surfactant; and at least one photoinitiator.

17. The film of claim 1, wherein the substrate layer comprises an optically clear film.

18. The film of claim 1, further comprising a pressure sensitive adhesive disposed on the first major surface of the substrate layer.

19. The film of claim 1, wherein the film comprises a window film.

20. The film of claim 1, wherein the film has a change in the emissivity of less than 0.05 after a scratch test, a saltwater soak test, or a combination of the tests.

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