Polymer interlayers provided with electrochromic materials

Abstract

Switchable interlayers are disclosed that include an electrochromic layer comprising a polymer matrix; and at least one poly(vinyl butyral) layer, comprising a poly(vinyl butyral) polymer and a plasticizer, in contact with the polymer matrix, wherein the plasticizer comprises esters of one or more fatty acids.

Description

POLYMER INTERLAYERS PROVIDED WITH ELECTROCHROMIC MATERIALSFIELD OF THE INVENTION

[0001] The present invention is related to the field of polymer interlayers, and more specifically to polymer interlayers that encapsulate electrochromic materials such as polymer-dispersed liquid crystals.DESCRIPTION OF RELATED ART

[0002] Multiple layer panels are panels comprised of two sheets of a substrate (such as, but not limited to, glass, polyester, polyacrylate, or polycarbonate) with one or more polymer interlayers sandwiched there between. Laminated multiple layer glass panels are commonly utilized in architectural window applications and in the windows of motor vehicles and airplanes, and in photovoltaic solar panels. The first two applications are commonly referred to as laminated safety glass. The main function of the interlayer in the laminated safety glass is to absorb energy resulting from impact or force applied to the glass, to keep the layers of glass bonded even when the force is applied and the glass is broken, and to prevent the glass from breaking up into sharp pieces. Additionally, the interlayer may also give the glass a preferential sound insulation rating, reduce UV and / or IR light transmission, and enhance the aesthetic appeal of the associated window. For example, laminated glass panels with desirable acoustic properties have been produced, resulting in quieter internal spaces.

[0003] Furthermore, laminated glass panels have been used in vehicles equipped with heads-up display (“HUD”) systems (also referred to as head-up systems), which project an image of an instrument cluster or other important information to a location on the windshield at the eye level of the vehicle operator. Such a display allows the driver to stay focused on the upcoming path of travel while visually accessing dashboard information. Generally, the HUD system in an automobile or an aircraft uses the inner surface of the vehicle windscreen to partially reflect the projected image.

[0004] Another use of laminated glass panels is to provide switching functionality in windows that can safely be darkened during use, for example sunroofs. These sunroofs use what are generically described as electrochromic, photochromic, and / or thermochromic materials, naturally depending on how the change in opacity is accomplished. One of these electrochromic materials is a class of materials called polymer-dispersed liquid crystals, or PDLCs.

[0005] In order to achieve required properties and performance characteristics for such glass panels, it has become common practice to utilize multiple layer or multilayered interlayers. As used herein, the terms “multilayer” and “multiple layers” mean an interlayer having more than one layer, and multilayer and multiple layer may be used interchangeably. For example, multiple layer acoustic interlayers typically contain at least one soft layer and at least one stiff layer.

[0006] Multilayer interlayers may also be used to provide various functionalities, such as the change in opacity just described. Unfortunately, we have found that when poly(vinyl butyral) is used to encapsulate electrochromic layers such as polymer-dispersed liquid crystals, plasticizer migration from the poly(vinyl butyral) can affect the functionality of the PDLCs. There is therefore a need in the art for the development of multilayered interlayers that incorporate PDLCs while resisting the plasticizer migration that can cause loss in functionality and visual defects.SUMMARY

[0007] In one aspect, the invention relates to switchable interlayers that include a switchable layer comprising a liquid crystal and a polymer matrix; and at least one poly(vinyl butyral) layer, comprising a poly(viny I butyral) polymer and a plasticizer, in contact with the polymer matrix. The plasticizers useful according to the invention comprise esters of one or more fatty acids.

[0008] Other aspects of the invention are as disclosed and claimed herein.DETAILED DESCRIPTION

[0009] Electrochromic materials such as polymer dispersed liquid crystal (PDLC) films are used by automakers to make switchable sunroofs. When PDLC devices are encapsulated with current PVB products, edge discoloration and degradation of the PDLC switching function is observed after the laminate undergoes weathering. This issue appears to be related to plasticizer migration from the PVB used for encapsulation into the central liquid crystal layer of the PDLC device. The current solution used by the market is an edge sealing step in which the cut edges of the PDLC device are sealed with Teflon or silicone to prevent migration. This edge sealing step is time consuming and labor intensive and is a key barrier to scaling PDLC applications beyond a high-end consumer option on premium and super premium cars.

[0010] In one aspect, the invention relates to switchable interlayers that comprise an electrochromic layer comprising a polymer matrix; and at least one poly(vinyl butyral) layer, comprising a poly(vinyl butyral) polymer and a plasticizer, in contact with the polymer matrix, wherein the plasticizer comprises esters of one or more fatty acids. In this invention, we have surprisingly discovered that plasticizers that are esters or triglycerides of one or more fatty acids migrate quite slowly towards PDLC via its open edge, and as a result, when they are in contact with PDLC film, there is less edge discoloration observed. In the current invention, we can effectively slow down plasticizer migration into PDLC film.

[0011] In one aspect, the invention thus relates to the use of plasticizers comprising fatty acid esters or triglycerides. The fatty acids will typically have from about 10 to about 24 carbon atoms, or from 10 to 20 carbon atoms, or from 12 to 18 carbon atoms, or from 16 to 20 carbon atoms, and may be saturated or unsaturated. These fatty acids may also be described as C10 to C24 fatty acids, etc. They may be straight chains or may be branched. They may contain other functionalities such as hydroxyl functionalities, epoxy functionalities, and the like, or may be unsubstituted.

[0012] Thus, the one or more fatty acids may comprise one or more unsaturated bonds; they may be provided with at least one epoxy functionality; they may be provided with at least one hydroxyl functionality; or they may be provided with at least one hydroxyl functionality and at least one unsaturated bond.

[0013] In aspects, the one or more fatty acids may comprise one or more of saturated fatty acids such as capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, or cerotic acid. Similarly, the one or more fatty acids may comprise one or more of unsaturated fatty acids that correspond to those above. Similarly, the one or more fatty acids may comprise one or more unsaturated fatty acids that are hydroxyl-substituted, and especially ricinoleic acid, oleic acid, and linoleic acid. In aspects, the esters of the invention may be triglycerides that are natural fats or oils or derived from natural fats or oils, whether from animals or vegetables.

[0014] In aspects, the esters of one or more fatty acids may be glycerides of one or more fatty acids, for example monoglycerides, diglycerides, or triglycerides of fatty acids. In other aspects, the ester functionality of the fatty acid esters may derive from alcohols containing from 1 to 20 carbon atoms, or from 2 to 12 carbon atoms, or from 2 to 8 carbon atoms, and having from 1 to 6 hydroxyl groups, or from 2 to 4 hydroxyl groups, or from 2 to 3 hydroxyl groups, or 2 hydroxyl groups, or 3 hydroxyl groups, and may comprise one or more ether functionalities within the carbon chain, for example they may be derived from ethylene glycol units.

[0015] Alcohols useful according to the invention thus include diglycerol, 2- methyl-1 ,3-propanediol (MP-diol), pentane-1 ,2,3-triol, propylene glycol, glycerol, trimethylolpropane, pentaerythritol, pentane-1 ,2,4, 5-tetraol, and the like.

[0016] Thus, in aspects, the esters of one or more fatty acids may comprise the reaction product of a fatty acid and an alcohol having from 1 to 12 carbon atoms, or may comprise the reaction product of a fatty acid and a polyol having from 2 to 12 carbon atoms. Alternatively, the esters of one ormore fatty acids may comprise the reaction product of a fatty acid and an aromatic alcohol.

[0017] In one aspect, the plasticizers of the invention may comprise esters of ricinoleic acid, castor oil, or mixtures thereof. In one aspect, the ester of ricinoleic acid may comprise propylene glycol ricinoleate, or the like.

[0018] In an aspect, the esters of one or more fatty acids useful according to the invention have a molecular weight from about 300 to about 3000, or from 300 to 2000, or from 300 to 1000. In other aspects, the molecular weight may be at least 100, or at least 200, or at least 300, or at least 350, up to about 1000, or up to about 2000, or up to about 3000.

[0019] In aspects, the esters of the invention may include those disclosed and claimed in U.S. Pat. Nos. 4,128,694, 4,563,296, 4,537,828;4,574,136, and 4,604,253, the relevant disclosures of which are incorporated herein in their entirety.

[0020] In an aspect, then, the esters of the invention may comprise at least a partial ester formed by reaction of an alcohol having from 2 to 4 hydroxyl groups and a C16 -C20 unsaturated fatty acid having a hydroxyl group attached to the acid molecule. The most common unsaturated fatty acid ester falling within the above category of plasticizers is glycerol triricinoleate which is the main component of castor oil. The use of castor oil as a plasticizer for polyvinyl acetals such as polyvinyl butyral was described in U.S. Pat. No. 2,423,565 and elsewhere but it has not been recognized as also having the properties that characterize a plasticizer that can be used to prevent migration into electrochromic polymer matrices.

[0021] While the glycerol esters are found to be very satisfactory, other esters based on for example tri-ethylene glycol, trimethylol propane and pentaerythritol can also be used.

[0022] The acids that may be used to form the esters have from 16 to 20 carbon atoms, and include, besides ricinoleic acid (12-hydroxy-oleic acid), other hydroxy-oleic acids with the hydroxyl group located on other than "12" carbon atoms such as 6-, 8-, 14-, or 16- hydroxy oleic acid, 12-hydroxyelaidic acid and acids with the same empirical formula with the hydroxyl located onother than the "12" atom. Also included are the corresponding variations of 12-hydroxy-hexadec-9-enoic acid and 12-hydroxy-eicos-9-enoic acid.

[0023] A single acid may provide all the esterifying acid groups, but a mixture of esterifying acids may be used, some of which need not be unsaturated, as for an example in naturally occurring castor oil provided that the esterifying acids together provide at least one unsaturation and one hydroxyl group per molecule of plasticizer.

[0024] The preferred plasticizer is castor oil which comprises a mixture of esters formed by the reaction of glycerol with the following acids, (the figure in parentheses being the approximate weight percent of esters formed from that acid): ricinoleic acid (86%), oleic acid (8.5%), linoleic acid (3.5%), stearic acid 1% and dihydroxystearic acid. Approximately 63.6% of the ricinoleate was the triester, 31 .1% the diester and 5.1% the monester.

[0025] In some aspects, the plasticizers useful according to the invention may be relatively pure, and this electronic purity may assist in long-term durability. For example, contamination with ionic species such as amides and halides, as well as other impurities, may reduce the lifetime of PDLC devices due to migration. In addition, organic impurities that can degrade in an electric field may also be undesirable. These impurities may be measured directly using common analytical methods or indirectly using measurements of volume resistivity or dielectric strength.

[0026] In aspects, it may thus be desirable for the plasticizer to have a volume resistivity greater than 1 x 104Q-cm, or greater than 1 x 1011Q-cm. We note that the castor oil used in the examples was specified to have a volume resistivity greater than 2 x 1011Q-cm at 100°C. In other aspects, the volume resistivity may thus be greater than 1 x 105Q-cm, or greater than 1 x 106Q-cm, or greater than 1 x 107Q-cm, or greater than 1 x 108Q-cm, or greater than 1 x 109Q-cm, or greater than 1 x 1010Q-cm.

[0027] In other aspects, it may be desirable for the dielectric strength of the plasticizer to be higher than the voltage applied to the electrochromic device, which may be, for example, at least 30V, or at least 100 V. Dielectric strength is measured by applying an electric field to a sample of transformer oil until itbreaks down. The breakdown voltage is a measure of the dielectric strength of the oil. The industry standard for new transformer oil is a minimum breakdown voltage of 30 kV (kilovolts) per millimeter. Thus, higher dielectric strengths, greater than 100 V per millimeter, or greater than 1000V per millimeter (1 kV / mm) may thus be preferred and materials with extremely high dielectric strengths. For example, the castor oil used in our experiments was specified to have a dielectric strength greater than 33 kV per millimeter at 25°C.

[0028] In a variation of the present invention the unsaturated acid component may be wholly or partially replaced by an acetylated hydroxy-acid. In a further variation the ester can be oxidatively polymerized or epoxidized to produce derivatives that also have utility as plasticizers in the present invention.

[0029] As further elaborated below, the amount of such plasticizer to be used according to the invention may be from 10 to 100 parts per hundred based on the resin (phr), or from 20 to 75 phr, or from 25 to 50 phr, or at least 10, 15, 20, 25, 30, 35, or 40 phr, up to 50 phr, or up to 55, 60, 65, 70, 80, 90, or up to 100 phr. These amounts may vary, as elaborated below, when interlayers such as trilayers are used that may have skin and core layers that are plasticized differently.

[0030] In general, and as further elaborated below, the polyvinyl acetal resins employed include those having, on a weight basis, of from 5 to 25 percent hydroxyl groups, calculated as polyvinyl alcohol, 0 to 4 percent acetate groups, calculated as polyvinyl acetate, and the balance substantially acetal. When the acetal is butyraldehyde acetal, the polyvinyl acetal resin will typically contain, on a weight basis, from 10 to 25 percent hydroxyl groups, calculated as polyvinyl alcohol and from 0 to 10 percent acetate groups, calculated as polyvinyl acetate, the balance being substantially butyraldehyde acetal. These figures are not however any limitation on the invention since polyvinyl butyrals outside these generally available ranges may be used if desired.

[0031] According to the invention, the plasticizer formulations used may include plasticizers other than the esters described herein, as further elaborated below, so long as these plasticizer blends do not unduly affect the desired properties when used in combination with the electrochromic layers described herein. In some cases, these blends may provide additional functionality. In other cases, they may simply be used for economic reasons, to provide desired plasticity at lower cost. Of course, blends of any of the esters described herein are likewise intended to fall within the scope of the invention.

[0032] Thus, the plasticizers of the invention may include plasticizer blends that comprise a monoester of a glycol and a C16 to C20 unsaturated fatty acid having a hydroxyl group attached to the acid molecule and a multiester of an alcohol having 2 to 4 hydroxyl groups and the unsaturated fatty acid, the monoester being present in the blend on a weight basis in an amount that may be less than, equal to, or greater than the multiester. In this aspect, a preferred monoester may be formed from propylene glycol 1 ,2 and ricinoleic acid and a preferred multiester present may be castor oil.

[0033] In another aspect, plasticizer blends may be used that comprise a multiester of an alcohol having 2 to 4 hydroxyl groups and a Ci6 to C20 unsaturated fatty acid having a hydroxyl group attached to the acid molecule, combined with an effective amount of an additional plasticizer which is a monoester of a glycol and such C16 to C20 unsaturated fatty acid. The monoester is preferably propylene 1 ,2 glycol, partially esterified with ricinoleic acid. In these aspects, the ratio of the monoester to the multiester may be, for example, from about 1 :1 to about 5:1 .Propylene glycol ricinoleate (PGR), Mw 356.5

[0034] In another aspect, the plasticizer may comprise epoxidized soybean oil and other triglycerides, whether or not functionalized.• Epoxidized soybean oil (ESO), Mw 975

[0035] By identifying plasticizers that do not migrate significantly through the polymer matrices of electrochromic materials, we have the potential of developing a new PVB product that is compatible with PDLC, and thus has the potential of eliminating the time-consuming edge sealing step from the lamination process for PDLC based switchable sunroofs, resulting in cost saving for the laminator and removing a critical barrier to the scaling of these applications.

[0036] In order to facilitate a more comprehensive understanding of the interlayers and multiple layer panels disclosed herein, the meaning of certain terms, as used in this application, will be defined. These definitions should not be taken to limit these terms as they are understood by one of ordinary skill, but simply to provide for improved understanding of how certain terms are used herein.

[0037] According to the invention, electrochromic materials are used that comprise a polymer matrix, such as an acrylic polymer matrix, that may include a liquid crystal material. Thus, in one aspect, the electrochromic materials may be polymer-dispersed liquid crystal films that are electrically ioswitchable materials that change in transmittance with application of an electric field.

[0038] We note that the use of the word “electrochromic” as used herein should not be understood in its strictest sense to encompass only materials that change color as a result of an electrochemical reaction, but rather as a broader term that encompasses a switchable material, such as a liquid crystal material, that enables a change in transmittance as a result of application of an electric field.

[0039] The electrochromic or switchable layers may include PDLCs in which 1) the polymer matrix is the predominant phase, and the liquid crystals are dispersed in it, as well as 2) materials such as polymer-network liquid crystals (PNLCs), in which the liquid crystals are the predominant phase, and the polymer matrix is the minor component. The PDLC films just described are characterized by a polymer matrix that comprises liquid crystal droplets embedded in it, while typical PNLCs are predominantly comprised of the liquid crystal material. Thus, the term PDLC is used without regard to which phase is dominant or continuous, and which phase is dispersed. Thus, the polymer matrix is referred to herein, with regard to the PDLC layer, whether or not the polymer is the continuous phase or is the dispersed phase.

[0040] The term “liquid crystals” as used herein are those materials in which electricity causes a change in orientation that changes the transmittance of light passing through it. Thus, the liquid crystal materials according to the invention are ones that change transmittance when in a cured polymer matrix and electricity is applied or removed. We are not concerned here with liquid crystals that do not behave in this manner.

[0041] The liquid crystal materials of the invention are characterized as having strong dipoles or polarizable groups, or both. Examples of functionalities providing strong dipole character include cyano, amide, imide, nitro, fluroro, chloro, ester, ether, isothiocyanate, and the like. Examples of functionalities providing polarizable character include phenyl, biphenyl, terphenyl, tetraphenyl, pyrimidine, other aromatics, and the like.

[0042] Liquid crystal materials suitable for use in the invention are typically moderate-sized organic molecules, that may be composed of flat segments like benzene rings, double bonds, strong dipoles, and easily-polarizing groups. Liquid crystal materials thus may include acetylene, amide, ester, imide, cyano, and ether linking groups that link aromatic groups, and especially phenyl, biphenyl, terphenyl, pyrimidine, and the like.

[0043] Liquid crystal materials useful according to the invention include those having aromatic functionality or cyano functionality, or both aromatic and cyano functionality. For example, an E7 liquid mixture comprising approximately: 51 weight percent of 5CB, having the chemical name [1 ,1 'Biphenyl], 4-carbonitrile,4'-pentyl; 25 weight percent of 7CB, having the chemical name [1 ,1 'Biphenyl], 4-carbonitrile,4'-heptyl; 16 weight percent of 80CB, having the chemical name [1 ,1 'Biphenyl], 4-carbonitrile,4'-octyloxy; and 8 weight percent of 5CT having the chemical name [1 , 1 ',4'-1 "-Terphenyl], 4- carbonitrile,4"pentyl, is useful according to the invention, as are other mixtures of one or more of these molecules.

[0044] Thus, 4-alkyl-4’-cyanobiphenyls are useful according to the invention, for example, one or more of 4-pentyl-4’-cyanobiphenyl, 4-heptyl-4’- cyanobiphenyl, and 4-octyloxy-4’-cyanobiphenyl, or other 4-alkyl-4’-cyano- biphenyls in which the alkyl group has from 2 to 10 carbon atoms.

[0045] Another useful mixture is E63 liquid crystal mixture, which is similar to the E7 mixture, with added cyclohexanes. It contains 5CB, having the chemical name [1 ,1 'Biphenyl], 4-carbonitrile,4'-pentyl; 7CB, having the chemical name [1 ,1 'Biphenyl], 4-carbonitrile,4'-heptyl; a lesser amount of 5CT, having the chemical name [1 ,1',4'-1 "-Terphenyl], 4-carbonitrile,4"pentyl; a lesser amount of PCH3, having the chemical name Benzonitrile, 4-(4 propyl-1 - cyclohexen-1-yl); a lesser amount of BCH5, having the chemical name [1 ,1'Biphenyl]-4-carbonitrile,4'(4-pentyl-1-cyclohexen-1 -yl); and a still lesser amount of DB71 , having the chemical name [1 ,1'-Biphenyl]-4-carboxylic acid, 4'-heptyl-4'-cyano[1 ,1'-biphenyl]-4-yl ester. Other mixtures of one or more of these molecules may likewise be used.

[0046] Another mixture suitable for use according to the invention is ROTN404, a liquid crystal mixture similar to the E7 mixture, with added pyrimidines. It contains approximately: 30 weight percent of 50CB, having the chemical name [1 ,1 'Biphenyl], 4-carbonitrile,4'-pentyloxy; 15 weight percent of 80CB, having the chemical name [1 ,1'Biphenyl],4-carbonitrile,4'-octyloxy; 10 weight percent of 5CT, having the chemical name [1 ,1',4'-1"-Terphenyl],4- carbonitrile,4-pentyl; 10 weight percent of RO-CP-7035, having the chemical name Benzonitrile, 4-(5-pentyl-2-pyrimidimyl)-; 20 weight percent of RO-CP- 7037, having the chemical name Benzonitrile, 4-(5-heptyl-2-pyrimidimyl)-; and 15 weight percent of the commonly known liquid crystal component RO-CM- 7334 having the chemical name Benzonitrile, 4-[5-(4-butylphenyl)-2- pyrimidimyl]-. Other useful materials are disclosed in U.S. Pat. No. 5,021 ,188, the relevant portions of which are disclosed herein by reference.

[0047] Another group of useful liquid crystal materials includes cholesteryl salts, such as acetate, benzoate, miristate, and the like.

[0048] Other suitable materials include n-(4-methoxybenzylidene)-4- butylaniline and 4-pentylphenyl 2-chloro-4-(4-pentylbenzoyloxy)benzoate, and mixtures thereof.

[0049] Suitable liquid crystals include those crystals exhibiting a nematic phase, smectic phase, cholesteric phase, columnar phase, and the like.

[0050] Liquid crystals useful according to the invention thus include cholesteric phase liquid crystals, nematic phase liquid crystals, chiral nematic liquid crystals, twisted nematic, and super twisted nematic. Any given liquid cyrstals may be used alone or in mixtures withother liquid crystals. They may be used with dichroic dyes or without dichroic dyes.

[0051] Polymer matrix layers of electrochromic materials are typically protected on each side, that is on the top and on the bottom of the layers, by a relatively impermeable film such as polyethylene terephthalate typically coated with a single or multi-layer transparent conductive material made up of a dielectric material such as indium tin oxide (ITO), fluorine doped tin oxide (FTO) or aluminum-doped zinc oxide (AZO) or thin metal layers or metal nano-particles made up of Ag, Au, or combinations of these materials or thelike that also serve as the electrodes for the device. Upon application of an electric field to the matrix, the liquid crystal droplets in the polymer matrix align along the electric field, which typically results in reduced light scattering, although certain liquid crystal materials, reverse phase materials, actually increase light scattering on application of the electric field. The light scattering is a function of the difference between the refractive index of the liquid crystal when charged compared with that of the polymer matrix, which typically does not change with application of an electric field. The liquid crystal, however, exhibits a different refractive index when an electric field is applied than when the charge is absent.

[0052] Common polymers used in electrochromic polymer matrices are acrylic polymers, although other polymer matrices may be used, such as polyvinyl alcohols such as formals, acetals, and the like; cured epoxies; cured polyurethanes; cured thiol-ene based polymers, siloxanes, and the like. Other include, for example, polystyrene, poly(methylmethacrylate), or poly(dimethylsiloxane).

[0053] According to one aspect of the invention, we have found that PDLC films comprising an acrylic polymer matrix with a dispersed nematic phase liquid crystal droplets layer and two protective layers, exhibit a loss in functionality when encapsulated or placed adjacent at least one poly(vinyl butyral) layer, which appears to be a function of the nature of the plasticizer used in the poly(vi nyl butyral) polymer. This acrylic polymer matrix material typically comprises such monomers as acrylates and methacrylates generally, and specifically n-butyl acrylate, acrylonitrile, lauryl acrylate and methacrylate, hydroxypropyl methacrylate, 3,5,5-trimethylhexyl acrylate, glycidyl methacrylate, tetrahydrofurfuryl acrylate and methacrylate, benzyl methacrylate, cyclohexyl methacrylate, and the like.

[0054] Thus, the electrical properties of the plasticizer and the switchable material may be important to preserve switching functionality. For example, the ionic or organic impurities or their degradation products in the matrix may allow for an increase in parasitic current in a device, which can both negatively affect power efficiency for the device and give rise to an increase tovarious defects and durability issues in the PDLC devices. These may include undesired redox reactions of the matrix or liquid crystal, change of color, picture framing or other known defects.

[0055] The terms “polymer interlayer sheet,” “interlayer,” “polymer layer”, and “polymer melt sheet” as used herein, may designate a single-layer sheet or a multilayered interlayer. A “single-layer sheet,” as the names implies, is a single polymer layer extruded as one layer. A multilayered interlayer, on the other hand, may comprise multiple layers, including separately extruded layers, co-extruded layers, or any combination of separately and co-extruded layers. Thus, the multilayered interlayer could comprise, for example: two or more single-layer sheets combined together (“plural-layer sheet”); two or more layers co-extruded together (“co-extruded sheet”); two or more co-extruded sheets combined together; a combination of at least one single-layer sheet and at least one co-extruded sheet; and a combination of at least one plurallayer sheet and at least one co-extruded sheet. In various embodiments of the present invention, a multilayered interlayer comprises at least two polymer layers (e.g., a single layer or multiple layers co-extruded) disposed in direct contact with each other, wherein each layer comprises a polymer resin. The term “resin,” as utilized herein refers to the polymeric component (e.g., PVB) removed from the processes, such as those discussed more fully below. Generally, plasticizer, such as those discussed more fully below, is added to the resins to result in a plasticized polymer. Additionally, as described below, resins may have other components in addition to the polymer and plasticizer including; e.g., acetates, salts and alcohols.

[0056] It should also be noted that while poly(vinyl butyral) (“PVB”) interlayers are often specifically discussed as the polymer resin of the polymer interlayers in this application, it should be understood that other thermoplastic interlayers besides PVB interlayers may be used. Contemplated polymers include, but are not limited to, polyurethane, polyvinyl chloride, polyethylene vinyl acetate) and combinations thereof. These polymers can be utilized alone, or in combination with other polymers. Accordingly, it should be understood that when ranges, values and / or methods are given for a PVBinterlayer in this application (e.g., plasticizer component percentages, thickness and characteristic-enhancing additives), those ranges, values and / or methods also apply, where applicable, to the other polymers and polymer blends disclosed herein or could be modified, as would be known to one of ordinary skill, to be applied to different materials.

[0057] As used herein, the term “molecular weight” as applied to PVB or other polymers refers to weight average molecular weight (Mw). The molecular weight of the PVB resin can be in the range of from about 40,000 to about 600,000, about 70,000 to about 450,000, or about 100,000 to about 425,000 Daltons.

[0058] The PVB resin may be produced by known aqueous or solvent acetalization processes by reacting polyvinyl alcohol (“PVOH”) with butyraldehyde in the presence of an acid catalyst, separation, stabilization, and drying of the resin. Such acetalization processes are disclosed, for example, in U.S. Pat. Nos. 2,282,057 and 2,282,026 and Wade, B. (2016), “Vinyl Acetal Polymers”, Encyclopedia of Polymer Science and Technology, pp. 1-22 (John Wiley & Sons, Inc.), the entire disclosures of which are incorporated herein by reference.

[0059] While generally referred herein as “poly(viny I acetal)” or “poly(vinyl butyral)”, the resins described herein may include residues of any suitable aldehyde, including, but not limited to, isobutyraldehyde, as previously discussed. In some embodiments, one or more poly(vinyl acetal) resin can include residues of at least one Ci to C10 aldehyde, or at least one C4 to Cs aldehyde. Examples of suitable C4 to Cs aldehydes can include, but are not limited to, n-butyraldehyde, isobutyraldehyde, 2-methylvaleraldehyde, n-hexyl aldehyde, 2-ethylhexyl aldehyde, n-octyl aldehyde, and combinations thereof.

[0060] According to the present invention, as already described, we have found that certain plasticizers work especially well in combination with electrochromic materials that comprise polymer matrices.

[0061] More generally, plasticizers are added to the polymer resin to form polymer layers or interlayers. Plasticizers are generally added to the polymer resin to increase the flexibility and durability of the resultant polymerinterlayer. Plasticizers function by embedding themselves between chains of polymers, spacing them apart (increasing the “free volume”) and thus significantly lowering the glass transition temperature (Tg) of the polymer resin, making the material softer. In this regard, the amount of plasticizer in the interlayer can be adjusted to affect the glass transition temperature (Tg). The glass transition temperature (Tg) is the temperature that marks the transition from the glassy state of the interlayer to the rubbery state. In general, higher amounts of plasticizer loading can result in lower Tg. In some embodiments, such as when the interlayer is an acoustic trilayer, the inner core layer (i.e., the soft layer) will have a glass transition temperature less than about 20°C, while the outer skin layers (e.g., the stiff layer) will have a glass transition temperature greater than about 25°C.

[0062] Conventional plasticizers generally include, but are not limited to, esters of a polybasic acid, a polyhydric alcohol, triethylene glycol di-(2- ethylbutyrate), triethylene glycol di-(2-ethylhexonate) (known as “3-GEH”), triethylene glycol diheptanoate, tetraethylene glycol diheptanoate, dihexyl adipate, dioctyl adipate, hexyl cyclohexyladipate, mixtures of heptyl and nonyl adipates, diisononyl adipate, heptylnonyl adipate, dibutyl sebacate, and polymeric plasticizers such as oil-modified sebacic alkyds and mixtures of phosphates and adipates, and mixtures and combinations thereof. 3-GEH is particularly preferred. Other examples of suitable plasticizers can include, but are not limited to, tetraethylene glycol di-(2-ethylhexanoate) (“4-GEH”), di(butoxyethyl) adipate, and bis(2-(2-butoxyethoxy)ethyl) adipate, dioctyl sebacate, nonylphenyl tetraethylene glycol, and mixtures thereof.

[0063] Other suitable plasticizers may include blends of two or more distinct plasticizers, including but not limited to those plasticizers described above. Still other suitable plasticizers, or blends of plasticizers, may be formed from aromatic groups, such polyadipates, epoxides, phthalates, terephthalates, benzoates, toluates, mellitates and other specialty plasticizers. Further examples include, but are not limited to, dipropylene glycol dibenzoate, tripropylene glycol dibenzoate, polypropylene glycol dibenzoate, isodecyl benzoate, 2-ethylhexyl benzoate, diethylene glycol benzoate,propylene glycol dibenzoate, 2,2,4-trimethyl-1 ,3-pentanediol dibenzoate, 2,2,4-trimethyl-1 ,3-pentanediol benzoate isobutyrate, 1 ,3-butanediol dibenzoate, diethylene glycol di-o-toluate, triethylene glycol di-o-toluate, dipropylene glycol di-o-toluate, 1 ,2-octyl dibenzoate, tri-2-ethylhexyl trimellitate, di-2-ethylhexyl terephthalate, bis-phenol A bis(2-ethylhexaonate), ethoxylated nonylphenol, and mixtures thereof. In some embodiments, the plasticizer can be selected from the group consisting of dipropylene glycol dibenzoates, tripropylene glycol dibenzoates, and combinations thereof.

[0064] Generally, the plasticizer content of the polymer interlayers of this application are measured in parts per hundred resin parts (“phr”), on a weight per weight basis. For example, if 30 grams of plasticizer is added to 100 grams of polymer resin, the plasticizer content of the resulting plasticized polymer would be 30 phr. When the plasticizer content of a polymer layer is given in this application, the plasticizer content of the particular layer is determined in reference to the phr of the plasticizer in the melt that was used to produce that particular layer. In some embodiments, the high rigidity interlayer comprises a layer having a plasticizer content of less than about 35 phr and less than about 30 phr.

[0065] According to some embodiments of the present invention, one or more polymer layers described herein can have a total plasticizer content of at least about 20 phr, at least about 25 phr, at least about 30 phr, at least about 35 phr, at least about 38 phr, at least about 40 phr, at least about 45 phr, at least about 50 phr, at least about 55 phr, at least about 60 phr, at least about 65 phr, at least about 67 phr, at least about 70 phr, at least about 75 phr of one or more plasticizers. In some embodiments, the polymer layer may also include not more than about 100 phr, not more than about 85 phr, not more than 80 phr, not more than about 75 phr, not more than about 70 phr, not more than about 65 phr, not more than about 60 phr, not more than about 55 phr, not more than about 50 phr, not more than about 45 phr, not more than about 40 phr, not more than about 38 phr, not more than about 35 phr, or not more than about 30 phr of one or more plasticizers. In some embodiments, the total plasticizer content of at least one polymer layer can be in the rangeof from about 20 to about 40 phr, about 20 to about 38 phr, or about 25 to about 35 phr. In other embodiments, the total plasticizer content of at least one polymer layer can be in the range of from about 38 to about 90 phr, about 40 to about 85 phr, or about 50 to 70 phr.

[0066] When the interlayer includes a multiple layer interlayer, two or more polymer layers within the interlayer may have substantially the same plasticizer content and / or at least one of the polymer layers may have a plasticizer content different from one or more of the other polymer layers. When the interlayer includes two or more polymer layers having different plasticizer contents, the two layers may be adjacent to one another. In some embodiments, the difference in plasticizer content between adjacent polymer layers can be at least about 1 , at least about 2, at least about 5, at least about 7, at least about 10, at least about 20, at least about 30, at least about 35 phr and / or not more than about 80, not more than about 55, not more than about 50, or not more than about 45 phr, or in the range of from about 1 to about 60 phr, about 10 to about 50 phr, or about 30 to 45 phr. When three or more layers are present in the interlayer, at least two of the polymer layers of the interlayer may have similar plasticizer contents falling for example, within 10, within 5, within 2, or within 1 phr of each other, while at least two of the polymer layers may have plasticizer contents differing from one another according to the above ranges.

[0067] In some embodiments, one or more polymer layers or interlayers described herein may include a blend of two or more plasticizers including, for example, two or more of the plasticizers listed above. When the polymer layer includes two or more plasticizers, the total plasticizer content of the polymer layer and the difference in total plasticizer content between adjacent polymer layers may fall within one or more of the ranges above. When the interlayer is a multiple layer interlayer, one or more than one of the polymer layers may include two or more plasticizers. In some embodiments when the interlayer is a multiple layer interlayer, at least one of the polymer layers including a blend of plasticizers may have a glass transition temperature higher than that of conventional plasticized polymer layer. This may provide, in some cases,additional stiffness to layer which can be used, for example, as an outer “skin” layer in a multiple layer interlayer.

[0068] In addition to plasticizers, it is also contemplated that adhesion control agents (“ACAs”) can also be added to the polymer resins to form polymer interlayers. ACAs generally function to alter and / or improve the adhesion of the interlayer to the glass panels when forming a laminated panel. Contemplated ACAs include, but are not limited to, magnesium carboxylates / salts. In addition, contemplated ACAs may also include those ACAs disclosed in U.S. Patent 5,728,472, incorporated by reference herein in its entirety, such as residual sodium acetate, potassium acetate, and / or magnesium bis(2-ethyl butyrate).

[0069] Other additives may be incorporated into the interlayer to enhance its performance in a final product and impart certain additional properties to the interlayer. Such additives include, but are not limited to, dyes, pigments, stabilizers (e.g., ultraviolet stabilizers), antioxidants, anti-blocking agents, flame retardants, IR absorbers or blockers (e.g., indium tin oxide, antimony tin oxide, lanthanum hexaboride (LaB6) and cesium tungsten oxide), processing aides, flow enhancing additives, lubricants, impact modifiers, nucleating agents, thermal stabilizers, UV absorbers, UV stabilizers, dispersants, surfactants, chelating agents, coupling agents, adhesives, primers, reinforcement additives, and fillers, among other additives known to those of ordinary skill in the art.

[0070] One parameter used to describe the polymer resin components of the polymer interlayers of this application is residual hydroxyl content (as vinyl hydroxyl content or poly(vinyl alcohol) (“PVOH”) content). Residual hydroxyl content refers to the amount of hydroxyl groups remaining as side groups on the chains of the polymer after processing is complete. For example, PVB can be manufactured by hydrolyzing poly(vinyl acetate) to poly(vinyl alcohol), and then reacting the poly(vinyl alcohol) with butyraldehyde to form PVB. In the process of hydrolyzing the poly(vinyl acetate), typically not all the acetate side groups are converted to hydroxyl groups. Further, the reaction with butyraldehyde typically will not result in all the hydroxyl groups beingconverted into acetal groups. Consequently, in any finished PVB, there will typically be residual acetate groups (such as vinyl acetate groups) and residual hydroxyl groups (such as vinyl hydroxyl groups) as side groups on the polymer chain. Generally, the residual hydroxyl content of a polymer can be regulated by controlling the reaction times and reactant concentrations, among other variables in the polymer manufacturing process. When utilized as a parameter herein, the residual hydroxyl content is measured on a wt. % basis per ASTM D-1396.

[0071] In various embodiments, the poly(vinyl butyral) resin comprises about 8 to about 35 wt. % (wt. %) residual hydroxyl groups calculated as PVOH, about 13 to about 30 wt. % residual hydroxyl groups calculated as PVOH, about 8 to about 22 wt. % residual hydroxyl groups calculated as PVOH, or about 15 to about 22 wt. % residual hydroxyl groups calculated as PVOH; and for some of the high rigidity interlayers disclosed herein, for one or more of the layers, the poly(vinyl butyral) resin comprises greater than about 19 wt. % residual hydroxyl groups calculated as PVOH, greater than about 20 wt. % residual hydroxyl groups calculated as PVOH, greater than about 20.4 wt. % residual hydroxyl groups calculated as PVOH, and greater than about 21 wt. % residual hydroxyl groups calculated as PVOH.

[0072] In some embodiments, the poly(vinyl butyral) resin used in at least one polymer layer of an interlayer may include a poly(vinyl butyral) resin that has a residual hydroxyl content of at least about 18, at least about 18.5, at least about 18.7, at least about 19, at least about 19.5, at least about 20, at least about 20.5, at least about 21 , at least about 21 .5, at least about 22, at least about 22.5 wt. % and / or not more than about 30, not more than about 29, not more than about 28, not more than about 27, not more than about 26, not more than about 25, not more than about 24, not more than about 23, or not more than about 22 wt. %, measured as described above.

[0073] Additionally, one or more other polymer layers in the interlayers described herein may include another po ly (vinyl butyral) resin that has a lower residual hydroxyl content. For example, in some embodiments, at least one polymer layer of the interlayer can include a poly(vinyl butyral) resin having aresidual hydroxyl content of at least about 8, at least about 8.5, at least about 9, at least about 9.5, at least about 10, at least about 10.5, at least about 11 , at least about 11 .5, at least about 12, at least about 13 wt. % and / or not more than about 16, not more than about 15, not more than about 14, not more than about 13.5, not more than about 13, not more than about 12, or not more than about 11 .5 wt. %, measured as described above.

[0074] When the interlayer includes two or more polymer layers, the layers may include poly(vinyl butyral) resins that have substantially the same residual hydroxyl content, or the residual hydroxyl contents of the poly(vinyl butyral) resins in each layer may differ from each other. When two or more layers include poly(vinyl butyral) resins having substantially the same residual hydroxyl content, the difference between the residual hydroxyl contents of the poly(vinyl butyral) resins in each layer may be less than about 2, less than about 1 , or less than about 0.5 wt. %. As used herein, the terms “weight percent different” and “the difference between ... is at least ... weight percent” refer to a difference between two given weight percentages, calculated by subtracting one number from the other. For example, a poly(vinyl acetal) resin having a residual hydroxyl content of 12 wt. % has a residual hydroxyl content that is 2 wt. % different than a poly(vinyl acetal) resin having a residual hydroxyl content of 14 wt. % (14 wt. % - 12 wt. % = 2 wt. %). As used herein, the term “different” can refer to a value that is higher than or lower than another value. Unless otherwise specified, all “differences” herein refer to the numerical value of the difference and not to the specific sign of the value due to the order in which the numbers were subtracted. Accordingly, unless noted otherwise, all “differences” herein refer to the absolute value of the difference between two numbers.

[0075] When two or more layers include poly(vinyl butyral) resins having different residual hydroxyl contents, the difference between the residual hydroxyl contents of the poly(vinyl butyral) resins can be at least about 2, at least about 3, at least about 4, at least about 5, at least about 6, at least about 7, at least about 8, at least about 9, at least about 10, at least about 12, at least about 15 wt. %, measured as described above.

[0076] The resin can also comprise less than 35 wt. % residual ester groups, less than 30 wt. %, less than 25 wt. %, less than 15 wt. %, less than 13 wt. %, less than 11 wt. %, less than 9 wt. %, less than 7 wt. %, less than 5 wt. %, or less than 1 wt. % residual ester groups calculated as polyvinyl ester, e.g., acetate, with the balance being an acetal, preferably butyraldehyde acetal, but optionally including other acetal groups in a minor amount, for example, a 2 -ethyl hexanal group (see, for example, U.S. Patent No. 5,137,954, the entire disclosure of which is incorporated herein by reference). The residual acetate content of a resin may also be determined according to ASTM D-1396.

[0077] In some embodiments, as described above, one or more of the polymer layers of the interlayer may be formed from poly(viny I acetal) resin. Such poly(vinyl acetal) resin may have a residual acetate content of at least about 1 , at least about 3, at least about 5, at least about 7 wt. % and / or not more than about 15, not more than about 12, not more than about 10, not more than about 8 wt. %, measured as described above. When the interlayer comprises a multiple layer interlayer, two or more polymer layers can include resins having substantially the same residual acetate content, or one or more resins in various layers can have substantially different acetate contents. When the residual acetate contents of two or more resins are substantially the same, the difference in the residual acetate contents may be, for example, less than about 3, less than about 2, less than about 1 , or less than about 0.5 wt. %. In some embodiments, the difference in residual acetate content between two or more poly(vinyl butyral) resins in a multiple layer interlayer can be at least about 3, at least about 5, at least about 8, at least about 15, at least about 20, or at least about 30 wt. %. When such resins are utilized in a multiple layer interlayer, the resins having different residual acetate contents may be located in adjacent polymer layers. When the multiple layer interlayer is a three-layer interlayer including a pair of outer “skin” layers surrounding, or sandwiching, an inner “core” layer, for example, the core layer may include a resin having higher or lower residual acetate content. At the same time, the resin in the inner core layer can have a residual hydroxyl content that is higheror lower than the residual hydroxyl content of the outer skin layer and fall within one or more of the ranges provided previously.

[0078] Poly(vinyl acetal) resins having higher or lower residual hydroxyl contents and / or residual acetate contents may also, when combined with at least one plasticizer, ultimately include different amounts of plasticizer. As a result, layers or domains formed of first and second poly(vinyl acetal) resins having different compositions may also have different properties within a single polymer layer or interlayer. Notably, for a given type of plasticizer, the compatibility of the plasticizer in the polymer is largely determined by the hydroxyl content of the polymer. Polymers with a greater residual hydroxyl content are typically correlated with reduced plasticizer compatibility or capacity. Conversely, polymers with a lower residual hydroxyl content typically will result in increased plasticizer compatibility or capacity. As a result, poly(vinyl acetal) resins with higher residual hydroxyl contents tend to be less plasticized and exhibit higher stiffness than similar resins having lower residual hydroxyl contents. Conversely, poly(vinyl acetal) resins having lower residual hydroxyl contents may tend to, when plasticized with a given plasticizer, incorporate higher amounts of plasticizer, which may result in a softer polymer layer that exhibits a lower glass transition temperature than a similar resin having a higher residual hydroxyl content. Depending on the specific resin and plasticizer, these trends could be reversed.

[0079] When two poly(vinyl acetal) resins having different levels of residual hydroxyl content are blended with a plasticizer, the plasticizer may partition between the polymer layers or domains, such that more plasticizer can be present in the layer or domain having the lower residual hydroxyl content and less plasticizer may be present in the layer or domain having the higher residual hydroxyl content. Ultimately, a state of equilibrium is achieved between the two resins. Generally, this correlation between the residual hydroxyl content of a polymer and plasticizer compatibility / capacity can be manipulated and exploited to allow for addition of the proper amount of plasticizer to the polymer resin and to stably maintain differences in plasticizer content within multilayered interlayers. Such a correlation also helps to stablymaintain the difference in plasticizer content between two or more resins when the plasticizer would otherwise migrate between the resins.

[0080] As a result of the migration of plasticizer within an interlayer, the glass transition temperatures of one or more polymer layers may be different when measured alone or as part of a multiple layer interlayer. In some embodiments, the interlayer can include at least one polymer layer having a glass transition temperature, outside of an interlayer, of at least about 33, at least about 34, at least about 35, at least about 36, at least about 37, at least about 38, at least about 39, at least about 40, at least about 41 , at least about 42, at least about 43, at least about 44, at least about 45, or at least about 46°C. In some embodiments, the same layer may have a glass transition temperature within the polymer layer of at least about 34, at least about 35, at least about 36, at least about 37, at least about 38, at least about 39, at least about 40, at least about 41 , at least about 42, at least about 43, at least about 44, at least about 45, at least about 46, or at least about 47°C.

[0081] In the same or other embodiments, at least one other polymer layer of the multiple layer interlayer can have a glass transition temperature less than 30°C and may, for example, have a glass transition temperature of not more than about 25, not more than about 20, not more than about 15, not more than about 10, not more than about 9, not more than about 8, not more than about 7, not more than about 6, not more than about 5, not more than about 4, not more than about 3, not more than about 2, not more than about 1 , not more than about 0, not more than about -1 , not more than about -2°C, or not more than about -5°C, measured when the interlayer is not part of an interlayer. The same polymer layer may have a glass transition temperature of not more than about 25, not more than about 20, not more than about 15, not more than about 10, not more than about 9, not more than about 8, not more than about 7, not more than about 6, not more than about 5, not more than about 4, not more than about 3, not more than about 2, not more than about 1 , or not more than about 0°C, when measured outside of the interlayer.

[0082] According to some embodiments, the difference between the glass transition temperatures of two polymer layers, typically adjacent polymerlayers within an interlayer, can be at least about 5, at least about 10, at least about 15, at least about 20, at least about 25, at least about 30, at least about 35, at least about 40, or at least about 45°C, while in other embodiments, two or more polymer layers can have a glass transition temperature within about 5, about 3, about 2, or about 1 °C of each other. Generally, the lower glass transition temperature layer has a lower stiffness than the higher glass transition temperature layer or layers in an interlayer and may be located between higher glass transition temperature polymer layers in the final interlayer construction.

[0083] For example, in some embodiments of this application, the increased acoustic attenuation properties of soft layers are combined with the mechanical strength of stiff / rigid layers to create a multilayered interlayer. In these embodiments, a central soft layer is sandwiched between two stiff / rigid outer layers. This configuration of (stiff) / / (soft) / / (stiff) creates a multilayered interlayer that is easily handled, can be used in conventional lamination methods and that can be constructed with layers that are relatively thin and light. The soft layer is generally characterized by a lower residual hydroxyl content (e.g., less than or equal to 16 wt. %, less than or equal to 15 wt. %, or less than or equal to 12 wt. % or any of the ranges disclosed above), a higher plasticizer content (e.g., greater than or equal to about 48 phr or greater than or equal to about 70 phr, or any of the ranges disclosed above) and / or a lower glass transition temperature (e.g., less than 30°C or less than 10°C, or any of the ranges disclosed above).

[0084] It is contemplated that polymer interlayer sheets as described herein may be produced by any suitable process known to one of ordinary skill in the art of producing polymer interlayer sheets that are capable of being used in a multiple layer panel (such as a glass laminate). For example, it is contemplated that the polymer interlayer sheets may be formed through solution casting, compression molding, injection molding, melt extrusion, melt blowing or any other procedures for the production and manufacturing of a polymer interlayer sheet known to those of ordinary skill in the art. Further, in embodiments where multiple polymer interlayers are utilized, it iscontemplated that these multiple polymer interlayers may be formed through co-extrusion, blown film, dip coating, solution coating, blade, paddle, air-knife, printing, powder coating, spray coating or other processes known to those of ordinary skill in the art. While all methods for the production of polymer interlayer sheets known to one of ordinary skill in the art are contemplated as possible methods for producing the polymer interlayer sheets described herein, this application will focus on polymer interlayer sheets produced through extrusion and / or co-extrusion processes. The final multiple layer glass panel laminate of the present disclosure are formed using processes known in the art.

[0085] In the extrusion process, thermoplastic resin and plasticizers, including any of those resins and plasticizers described above, are generally pre-mixed and fed into an extruder device. Additives such as colorants and UV inhibitors (in liquid, powder, or pellet form) may be used and can be mixed into the thermoplastic resin or plasticizer prior to arriving in the extruder device. These additives are incorporated into the thermoplastic polymer resin, and by extension the resultant polymer interlayer sheet, to enhance certain properties of the polymer interlayer sheet and its performance in the final multiple layer glass panel product.

[0086] In the extruder device, the particles of the thermoplastic raw material and plasticizers, including any of those resins, plasticizers, and other additives described above, are further mixed and melted, resulting in a melt that is generally uniform in temperature and composition. Embodiments of the present invention may provide for the melt temperature to be approximately 200°C. Once the melt reaches the end of the extruder device, the melt is propelled into the extruder die. The extruder die is the component of the extruder device which gives the final polymer interlayer sheet product its profile. The die will generally have an opening, defined by a lip, that is substantially greater in one dimension than in a perpendicular dimension. Generally, the die is designed such that the melt evenly flows from a cylindrical profile coming out of the die and into the product’s end profile shape. A plurality of shapes can be imparted to the end polymer interlayersheet by the die so long as a continuous profile is present. Generally, in its most basic sense, extrusion is a process used to create objects of a fixed cross-sectional profile. This is accomplished by pushing or drawing a material through a die of the desired cross-section for the end product.

[0087] In some embodiments, a co-extrusion process may be utilized. Coextrusion is a process by which multiple layers of polymer material are extruded simultaneously. Generally, this type of extrusion utilizes two or more extruders to melt and deliver a steady volume throughput of different thermoplastic melts of different viscosities or other properties through a coextrusion die into the desired final form. For example, the multiple layer interlayers of the present invention (e.g., in the form of a trilayer interlayer) may be preferably co-extruded using a multiple manifold co-extrusion device which includes a first die manifold, a second die manifold, and a third die manifold. The co-extrusion device may operate by simultaneously extruding polymer melts from each manifold through a die and out of an opening, where the multiple layer interlayer is extruded as a composite of three individual polymer layers. The polymer melts may flow through the die such that the core layer is positioned between the skin layers, to result in the manufacture of a trilayer interlayer with the core layer sandwiched between the skin layers. The die opening may include a pair of lips positioned on either side of the opening. Given the positional orientation of the polymer melts, the skin layers may come into contact with the lips. Regardless, the interlayer thickness can be varied by adjusting the distance between die lips located at the die opening.

[0088] The thickness of the multiple polymer layers leaving the extrusion die in the co-extrusion process can generally be controlled by adjustment of the relative speeds of the melt through the extrusion die and by the sizes of the individual die lips. According to some embodiments, the total thickness of the multiple layer interlayer can be at least about 13 mils, at least about 20, at least about 25, at least about 27, at least about 30, at least about 31 mils and / or not more than about 75, not more than about 70, not more than about 65, not more than about 60 mils, or it can be in the range of from about 13 toabout 75 mils, about 25 to about 70 mils, or about 30 to 60 mils. When the interlayer comprises two or more polymer layers, each of the layers can have a thickness of at least about 2, at least about 3, at least about 4, at least about 5, at least about 6, at least about 7, at least about 8, at least about 9, at least about 10 mils and / or not more than about 50, not more than about 40, not more than about 30, not more than about 20, not more than about 17, not more than about 15, not more than about 13, not more than about 12, not more than about 10, not more than about 9 mils. In some embodiments, each of the layers may have approximately the same thickness, while in other embodiments, one or more layers may have a different thickness than one or more other layers within the interlayer.

[0089] In some embodiments wherein the interlayer comprises at least three polymer layers, one or more of the inner layers can be relatively thin, as compared to the other outer layers. For example, in some embodiments wherein the multiple layer interlayer is a three-layer interlayer, the innermost layer can have a thickness of not more than about 12, not more than about 10, not more than about 9, not more than about 8, not more than about 7, not more than about 6, not more than about 5 mils, or it may have a thickness in the range of from about 2 to about 12 mils, about 3 to about 10 mils, or about 4 to about 9 mils. In the same or other embodiments, the thickness of each of the outer layers can be at least about 4, at least about 5, at least about 6, at least about 7 mils and / or not more than about 15, not more than about 13, not more than about 12, not more than about 10, not more than about 9, not more than about 8 mils, or can be in the range of from about 2 to about 15, about 3 to about 13, or about 4 to about 10 mils. When the interlayer includes two outer layers, these layers can have a combined thickness of at least about 9, at least about 13, at least about 15, at least about 16, at least about 18, at least about 20, at least about 23, at least about 25, at least about 26, at least about 28, or at least about 30 mils, and / or not more than about 73, not more than about 60, not more than about 50, not more than about 45, not more than about 40, not more than about 35 mils, or in the range of from about 9 to about 70 mils, about 13 to about 40 mils, or about 25 to about 35 mils.

[0090] According to some embodiments, the ratio of the thickness of one of the outer layers to one of the inner layers in a multiple layer interlayer can be at least about 1 .4:1 , at least about 1 .5:1 , at least about 1 .8:1 , at least about 2:1 , at least about 2.5:1 , at least about 2.75:1 , at least about 3:1 , at least about 3.25:1 , at least about 3.5:1 , at least about 3.75:1 , or at least about 4:1 . When the interlayer is a three-layer interlayer having an inner core layer disposed between a pair of outer skin layers, the ratio of the thickness of one of the skin layers to the thickness of the core layer may fall within one or more of the ranges above. In some embodiments, the ratio of the combined thickness of the outer layers to the inner layer can be at least about 2.25:1 , at least about 2.4:1 , at least about 2.5:1 , at least about 2.8:1 , at least about 3:1 , at least about 3.5:1 , at least about 4:1 , at least about 4.5:1 , at least about 5:1 , at least about 5.5:1 , at least about 6:1 , at least about 6.5:1 , or at least about 7:1 and / or not more than about 30:1 , not more than about 20:1 , not more than about 15:1 , not more than about 10:1 , not more than about 9:1 , or not more than about 8:1 .

[0091] Multiple layer interlayers as described herein can comprise generally flat interlayers having substantially the same thickness along the length, or longest dimension, and / or width, or second longest dimension, of the sheet. In some embodiments, however, the multiple layer interlayers of the present invention can be tapered, or wedge-shaped, interlayers that comprise at least one tapered zone having a wedge-shaped profile. Tapered interlayers have a changing thickness profile along at least a portion of the length and / or width of the sheet, such that, for example, at least one edge of the interlayer has a thickness greater than the other. When the interlayer is a tapered interlayer, at least 1 , at least 2, at least 3, or more of the individual resin layers may include at least one tapered zone. Tapered interlayers may be particularly useful in, for example, heads-up display (HUD) panels in automotive and aircraft applications.

[0092] In view of the above, embodiments of the present invention include a polymer interlayer that resists formation of optical defects. The polymer interlayer may comprise a core layer, a first skin layer, and a second skinlayer. The core layer will generally be positioned between the first and second skin layers, such that the skin layers sandwich the core layer. Notably, the core layer comprises a resin including an adhesion control agent in the range of about 0.1 to 15 titers.

[0093] Beneficially, in such embodiments, the polymer interlayer will have a lower bubble formation than prior art polymer interlayers. For example, the polymer interlayer may have no more than two bubbles, no more than one bubble, and / or no bubbles formed throughout the polymer interlayer. In some specific embodiments, the polymer interlayer may have no more than two edge bubbles, no more than one edge bubble, and / or no edge bubbles formed throughout the polymer interlayer (e.g., when laminated between a pair of glass sheets to form a laminated glass panel). In particular, when the inventive polymer interlayer is laminated between a pair of glass sheets to form a laminated glass panel, such glass panel may have no bubbles formed in the glass panel. In some embodiments, the glass panel may have no more than two bubbles or no more than one bubble. In some specific embodiments, the laminated glass panel may have no more than two edge bubbles, no more than one edge bubble, and / or no edge bubbles. The determination of the presence of edge bubbles will be described in more detail below in Example 1.

[0094] To facilitate such reduction in bubbles within the interlayer and / or the laminated panel, the core layer of the interlayer may include an adhesion control agent in the range of about 0.1 to 15 titers 0.1 to 13 titers, 0.1 to 12 titers, 0.1 to 11 titers, 0.1 to 10 titers, 0.1 to 9 titers, 0.1 to 8 titers, 0.1 to 6 titers, 0.1 to 5 titers, 0.5 to 18 titers, 0.5 to 15 titers, 0.5 to 13 titers, 0.5 to 12 titers, 0.5 to 11 titers, 0.5 to 10 titers, 0.5 to 9 titers, 0.5 to 8 titers, 0.5 to 6 titers, 0.5 to 5 titers, 5 to 18 titers, 5 to 15 titers, 5 to 13 titers, 5 to 12 titers, 5 to 11 titers, 5 to 10 titers, 5 to 9 titers, 5 to 8 titers, 5 to 6 titers, 8 to 18 titers, 8 to 15 titers, 8 to 13 titers, 8 to 12 titers, 8 to 11 titers, 8 to 10 titers, 8 to 9 titers, 10 to 18 titers, 10 to 15 titers, 10 to 13 titers, 10 to 12 titers, 10 to 11 titers, 12 to 18 titers, 12 to 15 titers, 12 to 13 titers, 13 to 18 titers, and / or 13 to15 titers. In certain embodiments, the adhesion control agent in the firstpolymer layer comprises magnesium salt. As used herein, one titer of ACA is defined to mean 1 x 10-7mole of adhesion control agent (ACA) (e.g., magnesium salt) per gram of resin.

[0095] The above-described polymer interlayer, which resists formation of optical defects (e.g., bubbles) may be formed by extruding a first polymer melt to form the core layer and extruding a second polymer melt to form the first and second skin layers. In some embodiments, the first polymer melt will be fed by a first extruder (e.g., a core extruder), while the second polymer melts will be fed by a second extruder (e.g., a skin extruder) and then split into two streams to form the skin layers. Regardless the core layer and the skin layers will generally be co-extruded, such that the core layer is positioned between the first and second skin layers. Notably, the first polymer melt, from which the core layer is formed, comprises a resin that includes an adhesion control agent in the range of about 0.1 to 15 titers.

[0096] As such, the polymer interlayer will have a lower bubble formation than prior art polymer interlayers. For example, the polymer interlayer may have no more than two bubbles, no more than one bubble, and / or no bubbles formed throughout the polymer interlayer. In some specific embodiments, the polymer interlayer may have no more than two edge bubbles, no more than one edge bubble, and / or no edge bubbles formed throughout the polymer interlayer (e.g., when the interlayer is laminated between a pair of glass sheets to form a laminated glass panel).

[0097] Furthermore, embodiments may additionally include a method of forming a laminated glass panel with reduced optical defects. Such method may include laminating the above-described polymer interlayer between a pair of glass sheets to form a laminated glass panel. Such glass panel may, in certain embodiments, have no bubbles (e.g., edge bubbles or trim bubbles) formed in the glass panel. In some embodiments, the glass panel may have no more than two bubbles (e.g., edge bubbles or trim bubbles) or no more than one bubble (e.g., edge bubbles or trim bubbles) formed in the glass panel. In some specific embodiments, the laminated glass panel may have nomore than two edge bubbles, no more than one edge bubble, and / or no edge bubbles.

[0098] The following offers a simplified description of the manner in which multiple layer glass panels are generally produced in combination with the interlayers. First, a multiple layer interlayer may be co-extruded using a multiple manifold co-extrusion device. The device operates by simultaneously extruding polymer melts from each manifold toward an extrusion opening. Properties of the layers can be varied by adjusting attributes (e.g., temperature and / or opening dimensions) of the die lips at the extrusion opening. Once formed, the interlayer sheet can be placed between two glass substrates and any excess interlayer is trimmed from the edges, creating an assembly. It is not uncommon for multiple polymer interlayer sheets or a polymer interlayer sheet with multiple layers (or a combination of both) to be placed within the two glass substrates creating a multiple layer glass panel with multiple polymer interlayers. Then, air is removed from the assembly by an applicable process or method known to one of skill in the art; e.g., through nip rollers, vacuum bag or another deairing mechanism. Additionally, the interlayer is partially press-bonded to the substrates by any method known to one of ordinary skill in the art. In a last step, in order to form a final unitary structure, this preliminary bonding is rendered more permanent by a high temperature and pressure lamination process, or any other method known to one of ordinary skill in the art such as, but not limited to, autoclaving.

[0099] Multilayer interlayers such as a trilayer interlayer having a soft core layer and two stiffer skin layers are known to provide beneficial acoustic damping properties. However, such interlayers, as well as glass panels containing these interlayers, can develop optical defects commonly known as “bubbles.” Specifically, during the manufacturing process of interlayers and / or laminated multiple layer glass panel constructs, bubbles commonly appear in the soft core of the interlayer. Often, such bubbles are in the form of trim or edge bubbles, which appear near the edges of the interlayers and / or the laminated panels. Specifically, edge bubbles are bubbles that form within a laminated glass panel, and particularly, within about 5 mm from edges of theglass sheets of the glass panel. Trim bubbles are bubbles that form in excess trim portions of the interlayers that extend beyond the edges of the glass sheets of the glass panel. Most of these bubbles become visible when the autoclave pressure is released. It is commonly understood that bubble counts and bubble sizes can depend upon the moisture level in the autoclave. For instance, bubble nucleation may occur inside the core layer after the pressure of the polymer drops below the solubility pressure. Other variables that are known to contribute to the bubble problem include environmental contaminates and the rheology characteristics of the interlayers.

[0100] While the invention has been disclosed in conjunction with a description of certain embodiments, including those that are currently believed to be the preferred embodiments, the detailed description is intended to be illustrative and should not be understood to limit the scope of the present disclosure. As would be understood by one of ordinary skill in the art, embodiments other than those described in detail herein are encompassed by the present invention. Modifications and variations of the described embodiments may be made without departing from the spirit and scope of the invention.

[0101] It will further be understood that any of the ranges, values, or characteristics given for any single component of the present disclosure can be used interchangeably with any ranges, values or characteristics given for any of the other components of the disclosure, where compatible, to form an embodiment having defined values for each of the components, as given herein throughout. For example, a polymer layer can be formed comprising plasticizer content in any of the ranges given in addition to any of the ranges given for residual hydroxyl content, where appropriate, to form many permutations that are within the scope of the present invention but that would be cumbersome to list.EXAMPLESExample 1 — PDLC squares testing in plasticizer

[0102] During this testing, PDLC film was cut into 1 inch x 1 inch squares, which were then placed in a glass jar filled with plasticizer liquid. The PDLC sample was fully immersed into the plasticizer. The following plasticizers are tested with PDLC film:Castor oil, Mw 927Aurorium LLC DB Castor oilPropylene glycol ricinoleate (PGR), Mw 356.5 CASPOL 5001Dibutyl sebacate (DBS), Mw 314

[0103] Epoxidized soybean oil (ESO), Mw 975, , (Soybean Oil, Epoxidized, SpectrumChemical• Blend of PGR and Castor oil at a ratio of 2.5:1

[0104] Once plasticizer started to migrate into PDLC film through its open edge, we observed edge discoloration, turning from white opaque to transparent and causing the formation of a transparent band around the PDLC film. By comparing the width of this transparent band after a given period at a certain temperature (in this study, we used room temperature), we can estimate the relative migration rate of plasticizers into PDLC. A plasticizer that is most compatible with PDLC in switchable sunroof application will have slowest migration rate into PDLC via its edge.

[0105] Table 1 shows the edge discoloration width in ‘mm’ for different plasticizers after one, two and eight days of plasticizer immersion.TABLE 1PGR Castor Oil ESO DBS PGR: Castor Oil =2.5:1Day 1 0.16 0.16 0.12 1.73 0.33Day 2 0.32 0.31 0.34 2.58 0.31Day 8 0.47 0.47 0.69 5.76 0.46

[0106] As we can see from table 1 , PGR migrates into PDLC at a much slower rate than DBS, even though its molecular weight is slightly lower. Without wishing to be bound by any theory, this may be because the C-C double bond makes the plasticizer molecule more rigid and bulkier, thus less labile for migration. The same is also true for castor oil, which shows much slower migration into PDLC due to its complicated and bulky molecular structure. It is also possible that partial dehydration of the castor oil may lead to crosslinking to a certain extent.Example 2 — PDLC lamination

[0107] Two commercial Saflex products, DB and SX, were used to laminate with PDLC film. DB contains 32 phr DBS as plasticizer, while SX contains 42 phr of a mixture of PGR and Castor oil (P:C = 2.5:1 ) as plasticizer. The stack structure was as follows, from top to bottom: a glass layer, a PVB layer, a PDLC patch framed on four sides with the same PVB, another PVB layer of the same material, and glass.

[0108] SX PVB showed 0.5mm edge discoloration in PDLC films after 40 days in ambient condition whereas DB PVB showed 4.58mm edge discoloration after 70 days under the same conditions. This clearly indicatesthe plasticizer (PGR and Castor oil) in SX migrated to PDLC at a much slower rate than the one (DBS) in DB.

[0109] We also tested the effect of PVB resin on the edge discoloration of PDLC films. We brabendered different PVB resin with Castor oil with following formulations and laminated them with PDLC films, in the manner just described. It has been shown that the effect of PVB resin on plasticizer migration is not obvious. However, PVB resin with lower OH% may lead to slower flow under autoclave, thus LH and NZ type of PVB resin exhibited an air gap between PVB layers. This may also be a function of molecular weight.

[0110] Table 2 shows the formulation for castor oil in different PVB resin.TABLE 2

[0111] We also tested the effect of plasticizer mixture on the edge discoloration of PDLC films. We brabendered PVB ZB resin with castor oil and TEG-EH mixture or castor oil and DBS mixture with following formulation, then laminated them with PDLC films as already described. It has been shown that laminates with higher fraction of castor oil in plasticizer mixture can lead to less edge discoloration of PDLC films.TABLE 3

[0112] We also tested the effect of plasticizer loading on the edge discoloration of PDLC films. We brabendered PVB resin with castor oil at 40phr and 20phr loadings, then laminated them with PDLC films (same stack structure as already described). It has been shown that laminates with lower castor oil loading can lead to less edge discoloration of PDLC films. After 13 months, the laminate with 20 phr Castor Oil has 0.2mm edge discoloration of PDLC sample whereas the laminate with 40 phr Castor Oil has 0.7mm edge discoloration.

[0113] Selected above laminates were placed in the oven at 95°C for 240 hours. The laminate with 42phr castor oil had 3mm edge discoloration after this thermal soak test, while the laminate with 38phr TEGEH had 8.5mm edge discoloration. PVB sheets made with 42phr Castor oil, UV stabilizer, adhesion control agent, optionally colorant, were successfully extruded.Example 3 - PNLC lamination

[0114] Polymer network liquid crystal (PNLC) sample was supplied by Kyusyu Nanotec Optics Co., Ltd. We laminated it with our commercial SX PVB product that contains 42 phr of a mixture of PGR and Castor oil (P:C = 2.5:1) as plasticizer with the stack structure already described (replaced PDLC with PNLC film). After stored at room temperature for a year, the edge discoloration was 0.5mm and PNLC’s switching function has been validated as the same as prior to lamination.

Claims

We claim:1 . A switchable interlayer comprising: a. a switchable layer comprising a liquid crystal and a polymer matrix; and b. at least one poly(vinyl butyral) layer, comprising a poly(vinyl butyral) polymer and a plasticizer, in contact with the polymer matrix, wherein the plasticizer comprises esters of one or more fatty acids.

2. The switchable interlayer of claim 1 , wherein the esters of one or more fatty acids comprise the reaction product of an alcohol having from 1 to 6 hydroxyl groups and a fatty acid having from 12 to 20 carbon atoms.

3. The switchable interlayer of claim 1 , wherein the esters of one or more fatty acids comprise at least a partial ester formed by the reaction of an alcohol having from 2 to 4 hydroxyl groups and a C16 to C20 unsaturated fatty acid having a hydroxyl group attached to the acid molecule.

4. The switchable interlayer of claim 1 , wherein the esters of one or more fatty acids comprise propylene glycol ricinoleate.

5. The switchable interlayer of claim 1 , wherein the esters of one or more fatty acids comprise a blend of a multiester of an alcohol having 2 to 4 hydroxyl groups and a C16 to C20 unsaturated fatty acid having a hydroxyl group attached to the acid molecule, and a monoester of a glycol and the C16 to C20 unsaturated fatty acid.

6. The switchable interlayer of claim 1 , wherein the one or more fatty acids have from 10 to 20 carbon atoms.

7. The switchable interlayer of claim 1 , wherein the esters of one or more fatty acids comprise castor oil.

8. The switchable interlayer of claim 1 , wherein the one or more fatty acids include branched fatty acids.

9. The switchable interlayer of claim 2, wherein the alcohol comprises one or more of diglycerol, 2-methyl-1 ,3-propanediol, pentane-1 ,2,3-triol, propylene glycol, glycerol, trimethylolpropane, pentaerythritol, or pentane-1 ,2,4,5-tetraoL10. The switchable interlayer of claim 1 , wherein the esters of one or more fatty acids are glycerides of one or more fatty acids.11 . The switchable interlayer of claim 1 , wherein the esters of one or more fatty acids comprise the reaction product of a fatty acid and an alcohol having from 1 to 12 carbon atoms.

12. The switchable interlayer of claim 1 , wherein the esters of one or more fatty acids comprise the reaction product of a fatty acid and a polyol having from 2 to 12 carbon atoms.

13. The switchable interlayer of claim 1 , wherein the polymer matrix comprises an acrylic matrix.

14. The switchable interlayer of claim 1 , wherein the one or more fatty acids comprise one or more unsaturated bonds.

15. The switchable interlayer of claim 1 , wherein the one or more fatty acids are provided with at least one epoxy functionality.

16. The switchable interlayer of claim 1 , wherein the one or more fatty acids are provided with at least one hydroxyl functionality.

17. The switchable interlayer of claim 1 , wherein the one or more fatty acids are provided with at least one hydroxyl functionality and at least one unsaturated bond.

18. The switchable interlayer of claim 1 , wherein the esters of one or more fatty acids comprise the reaction product of a fatty acid and an aromatic alcohol.

19. The switchable interlayer of claim 2, wherein the plasticizer comprises one or more of: castor oil, propylene glycol ricinoleate, or epoxidized soybean oil.

20. The switchable interlayer of claim 1 , wherein the esters of one or more fatty acids do not contain aromatic functionality.21 . The switchable interlayer of claim 1 , wherein the esters of one or more fatty acids have a molecular weight from about 300 to about 3000.

22. The switchable interlayer of claim 1 , wherein the esters of one or more fatty acids have a molecular weight from 300 - 2000.

23. The switchable interlayer of claim 1 , wherein the plasticizer has a volume resistivity greater than 1 x 104 Q-cm, or greater than 1 x 1011 Q-cm.

24. The switchable interlayer of claim 1 , wherein the plasticizer has a dielectric strength greater than 1000V per millimeter (1 kV / mm).

25. The switchable interlayer of claim 1 , wherein the liquid crystal comprises one or more of the following functionalities: cyano, amide, imide, nitro, fluroro, chloro, ester, ether, isothiocyanate.

26. The switchable interlayer of claim 1 , wherein the liquid crystal comprises one or more of the following functionalities: phenyl, biphenyl, terphenyl, tetraphenyl, pyrimidine.

27. The switchable interlayer of claim 1 , wherein the liquid crystal comprises one or more of: [1 ,1 'Biphenyl], 4-carbonitrile,4'-pentyl;[1 , 1 'Biphenyl], 4-carbonitrile, 4'-heptyl; [1 , 1 'Biphenyl], 4-carbonitrile, 4'- octyloxy; [1 ,1 ',4'-1 "-Terphenyl], 4-carbonitrile, 4"pentyl; 4-pentyl-4’- cyanobiphenyl; 4-heptyl-4’-cyanobiphenyl; 4-octyloxy-4’-cyanobiphenyl; [1 ,1 ',4'-1 "-Terphenyl], 4-carbonitrile, 4"pentyl; Benzonitrile, 4-(4 propyl-1 - cyclohexen-1 -yl); [1 ,1 'Biphenyl]-4-carbonitrile,4'(4-pentyl-1 -cyclohexen- 1 -yl); [1 ,1 '-Biphenyl]-4-carboxylic acid, 4'-heptyl-4'-cyano[1 ,1 ’-biphenyl]- 4-yl ester; [1 ,1 'Biphenyl], 4-carbonitrile, 4'-pentyloxy; [1 ,1 'Biphenyl], 4- carbonitrile,4'-octyloxy; [1 ,1 ',4'-1 "-Terphenyl], 4-carbonitrile, 4-pentyl;Benzonitrile, 4-(5-pentyl-2-pyrimidimyl)-; Benzonitrile, 4-(5-heptyl-2- pyrimidimyl)-; Benzonitrile, 4-[5-(4-butylphenyl)-2-pyrimidimyl],

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