Polymer interlayer with reduced edge bubbles

Abstract

A polymeric interlayer that resists the formation of optical defects. The polymeric interlayer comprises a first polymeric layer, a second polymeric layer, and a third polymeric layer. The first polymeric layer is positioned between the second polymeric layer and the third polymeric layer. The first polymeric layer comprises a resin that includes an adhesion control agent in a range of about 0.1 to 15 strength.

Description

[Technical field]

[0001]

[0001] The present invention relates to the field of polymeric interlayers and multilayer panels comprising polymeric interlayers, more particularly to the field of polymeric interlayers comprising multiple polymer layers. [Background technology]

[0002]

[0002] A multi-ply panel is comprised of two sheets of substrate (such as, but not limited to, glass, polyester, polyacrylate, or polycarbonate) sandwiched between them with one or more polymer interlayers. Laminated multi-ply glass panels are commonly utilized for architectural window applications and automotive and aircraft windows, as well as photovoltaic solar panels. The first two applications are commonly referred to as laminated safety glass. The primary functions of the interlayer in laminated safety glass are to absorb energy resulting from an impact or force applied to the glass, to keep the layers of glass bonded together even if a force is applied to the glass and the glass breaks, and to prevent the glass from shattering into sharp shards. In addition, the interlayer can impart a preferential sound insulation rating to the glass, reduce UV and / or IR light transmission, and enhance the aesthetic appeal of the associated window. For example, laminated glass panels have been produced with desirable acoustic properties that result in quieter interior spaces.

[0003]

[0003] Additionally, laminated glass panels are used in vehicles equipped with head-up display ("HUD") systems (also called head-up systems) that project an image of the instrument cluster or other important information onto a location on the windshield at eye level of the vehicle operator. Such displays allow the driver to visually access dashboard information while still remaining focused on the road ahead. Typically, HUD systems in automobiles or aircraft use the inner surface of the vehicle windscreen to partially reflect the projected image. However, a secondary reflection occurs at the outer surface of the vehicle windscreen, which forms a weak secondary or "ghost" image. Because these two reflected images are offset in position, double images are often observed, which results in an undesirable viewing experience for the driver. When an image is projected onto a windshield having a uniform, constant thickness, a coherent double or reflected ghost image is formed due to the difference in the position of the projected image as it is reflected from the inner and outer surfaces of the glass.

[0004] One way to address these double or ghost images is to orient the inner and outer glass sheets at an angle to one another. This aligns the location of the reflected images to a single point, thereby forming a single image. Typically, this is done by offsetting the outer sheet relative to the inner sheet through the use of a wedge-shaped or "tapered" interlayer that contains at least one region of non-uniform thickness. Many conventional tapered interlayers contain a constant wedge angle across the entire HUD area, but more recently, some interlayers have been developed that contain multiple wedge angles across the HUD area.

[0005]

[0005] It has become common practice to utilize multiple plies or multi-layer interlayers to achieve the required properties and performance characteristics of glass panels. As used herein, the terms "multi-layer" and "multi-layer" refer to interlayers having two or more layers, and multi-layer and multi-layer may be used interchangeably. Multi-layer interlayers typically contain at least one soft layer and at least one hard layer. As mentioned above, interlayers have been designed with one soft "core" layer sandwiched between two stiffer or harder "skin" layers that have the acoustic properties of the glass panel. The reverse configuration, i.e., interlayers with one hard layer sandwiched between two softer layers, have been found to improve the impact performance of glass panels and may also be designed for acoustic insulation. In either case, the soft "core" layer is generally referred to as the acoustic layer (because the soft layer beneficially reduces sound transmission), while the hard "skin" layer is referred to as the conventional layer, or non-acoustic layer.

[0006]

[0006] The layers of the interlayer are generally manufactured by mixing a polymeric resin, such as poly(vinyl butyral), with one or more plasticizers and melt processing the mixture into a sheet by any applicable process or method known to those skilled in the art, including but not limited to extrusion, and the layers are combined by processes such as coextrusion and lamination. In a three-ply interlayer, the core layer may contain more plasticizer than the skin layers, such that the core layer is softer than the relatively harder skin layers. Other additional ingredients, described in more detail below, may optionally be added for various other purposes. After the interlayer sheet is formed, it is typically collected and rolled for shipping and storage, as well as for later use in multi-ply glass panels, as discussed below.

[0007]

[0007] The following provides a simplified description of the manner in which a multi-layer glass panel is typically manufactured in combination with an interlayer. First, a multi-layer interlayer may be coextruded using a multi-manifold coextrusion device. The device operates by simultaneously extruding a polymer melt from each manifold toward an extrusion orifice. The properties of the layers may be varied by adjusting the attributes of the die lip at the extrusion orifice (e.g., temperature and / or orifice size). Once formed, the interlayer sheet may be placed between two glass substrates, and any excess interlayer is trimmed from the edges to form 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 between two glass substrates to form a multi-layer glass panel with multiple polymer interlayers. Air is then removed from the assembly by an applicable process or method known to one skilled in the art, for example, via nip rollers, vacuum bags, or another degassing mechanism. The interlayer is then partially pressed to the substrate by any method known to one skilled in the art. In a final step, this preliminary bond is made more permanent by a high temperature and pressure lamination process or any other method known to those skilled in the art, such as, but not limited to, autoclaving, to form the final integral structure.

[0008]

[0008] Multi-layer interlayers, such as tri-ply interlayers having a soft core layer and two harder skin layers, are known to provide beneficial acoustic attenuation properties. However, such interlayers, and glass panels containing these interlayers, may develop optical defects commonly known as "bubbles." Specifically, during the manufacturing process of the interlayer and / or laminated multi-ply glass panel construction, bubbles typically appear within 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 interlayer and / or laminate panels. Specifically, edge bubbles are bubbles that form within laminated glass panels, particularly within about 5 mm of the edges of the glass sheets of the glass panel. Trim bubbles are bubbles that form in the excess trim portions of the interlayer that extend beyond the edges of the glass sheets of the glass panel. Most of these bubbles become visible once the autoclave pressure is released. It is generally understood that the number of bubbles and the bubble size may depend on the moisture level in the autoclave. For example, bubble nucleation can occur inside the core layer after the polymer pressure drops below the solution pressure. Other variables known to contribute to bubble problems include environmental contamination and the rheological properties of the interlayer.

[0009] In view of the above, there is a need in the art to develop a multi-layer interlayer that resists the formation of these optical defects (i.e., bubbles) without reducing the other optical, mechanical and acoustic properties of conventional multi-layer interlayers. More specifically, there is a need in the art to develop a multi-layer interlayer having at least one soft core layer and one hard skin layer that resists the development of bubbles (e.g., trim or edge bubbles). [Brief description of the drawings]

[0010] [Figure 1]

[0010] FIG. 1 is a schematic diagram of a laminated glass panel comprising a pair of glass sheets facing a polymer interlayer, the polymer interlayer comprising three layers, a pair of skin layers facing a core layer. [Diagram 2]

[0011] 1 is another schematic diagram of a laminated glass panel comprising a pair of glass sheets facing a polymer interlayer, the polymer interlayer having a wedge shape. [Diagram 3]

[0012] 1 is a chart showing the number of bubbles found in laminated glass panels with a polymer interlayer, the number of bubbles being determined based on the amount of adhesion control agent (ACA) included in the core layer of the polymer interlayer. [Figure 4]

[0013] 1 is another chart showing the number of bubbles found in the polymer interlayer, determined based on the amount of adhesion control agent (ACA) included in the core layer of the polymer interlayer. Summary of the Invention

[0011]

[0014] One aspect of the present invention relates to a polymeric interlayer that is resistant to the formation of optical defects. The polymeric interlayer comprises a first polymeric layer, a second polymeric layer, and a third polymeric layer. The first polymeric layer is positioned between the second polymeric layer and the third polymeric layer. The first polymeric layer comprises a resin that includes an adhesion control agent in a range of about 0.1 to 15 strength.

[0012]

[0015] Another aspect of the invention relates to a polymeric interlayer that is resistant to the formation of optical defects. The polymeric interlayer comprises a core layer, a first skin layer, and a second skin layer. The core layer is positioned between the first skin layer and the second skin layer. The core layer comprises a resin that includes an adhesion control agent in the range of about 0.1 to 15 strength.

[0013]

[0016] A further aspect of the invention relates to a method of forming a polymeric interlayer that is resistant to the formation of optical defects. The method includes extruding a first polymer melt to form a first polymer layer, and extruding a second polymer melt to form a second polymer layer and a third polymer layer. During the extrusion step, the first polymer layer is positioned between the second polymer layer and the third polymer layer. The first polymer layer includes a resin that includes an adhesion control agent in the range of about 0.1 to 15 titers. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014]

[0017] The present invention relates to a multilayer panel and a method for making a multilayer panel. Generally, a multilayer panel is composed of two sheets of glass or other applicable substrate with one or more polymer interlayer sheets sandwiched between them. A multilayer panel is generally manufactured by placing at least one polymer interlayer sheet between the two substrates to form an assembly. Figure 1 shows a multilayer panel 10 comprising a pair of glass sheets 12 and a multilayer interlayer sandwiched therebetween. The multilayer interlayer is configured as a three-layer interlayer having three separate polymer interlayer sheets, including a soft core layer 14 and two relatively hard skin layers 16 positioned on either side of the core layer 14.

[0015]

[0018] In some embodiments, the intermediate layer (e.g., the core layer 14 and the skin layer 16) have a substantially constant or uniform thickness over the length of the intermediate layer. However, in alternative embodiments, as shown in FIG. 2, the intermediate layer may have at least one region of non-uniform thickness. For example, the intermediate layer, comprised of the core layer 14 and the skin layer 16, may be wedge-shaped such that the thickness of the intermediate layer varies (e.g., linearly or non-linearly) over the length of the intermediate layer. In some such embodiments, the thickness of the intermediate layer may vary due to a change in the thickness of the core layer 14 (i.e., the skin layer 16 has a substantially constant thickness). Alternatively, the thickness of the intermediate layer may vary due to a change in the thickness of the skin layer 16 (i.e., the core layer 14 has a substantially constant thickness). In a further alternative, the thickness of the intermediate layer may vary due to a change in the thickness of both the core layer 14 and the skin layer 16.

[0016]

[0019] In order to facilitate a more comprehensive understanding of the interlayers and multilayer panels disclosed herein, the meanings of certain terms used in this application are defined. These definitions should not be construed as limiting these terms to those as understood by those skilled in the art, but merely as providing an improved understanding of how certain terms are used herein.

[0017]

[0020] The terms "polymer interlayer sheet", "interlayer", "polymer layer" and "polymer melt sheet" as used herein may refer to a monolayer sheet or a multilayer interlayer. A "monolayer sheet", as the name suggests, is a single polymer layer extruded as one layer. A multilayer interlayer, on the other hand, may comprise multiple layers, including separately extruded layers, coextruded layers, or any combination of separately extruded and coextruded layers. Thus, a multilayer interlayer may comprise, for example, two or more monolayer sheets combined with each other ("multilayer sheet"), two or more layers coextruded with each other ("coextruded sheet"), two or more coextruded sheets combined with each other, a combination of at least one monolayer sheet and at least one coextruded sheet, and a combination of at least one multilayer sheet and at least one coextruded sheet. In various embodiments of the present invention, a multilayer interlayer comprises at least two polymer layers (e.g., monolayer or coextruded multilayer) arranged in direct contact with each other, each layer comprising a polymer resin. The term "resin" as utilized herein refers to the polymeric component (e.g., PVB) that is removed from the process, such as those discussed more fully below. Typically, a plasticizer, such as those discussed more fully below, is added to the resin to obtain a plasticized polymer. Additionally, as described below, the resin may have other components in addition to the polymer and plasticizer, including, for example, acetates, salts, and alcohols.

[0018]

[0021] It should also be noted that although poly(vinyl butyral) ("PVB") interlayers are often specifically discussed in this application as the polymer resin of the polymer interlayer, it should be understood that other thermoplastic interlayers other than PVB interlayers may be used. Contemplated polymers include, but are not limited to, polyurethane, polyvinyl chloride, poly(ethylene vinyl acetate), and combinations thereof. These polymers may be utilized alone or in combination with other polymers. Thus, when ranges, values, and / or methods are given in this application with respect to PVB interlayers (e.g., percentages of plasticizer components, thickness and feature-enhancing additives), those ranges, values, and / or methods also apply, where applicable, to other polymers and polymer blends disclosed herein, or may be modified to apply to different materials, as known to those skilled in the art.

[0019]

[0022] As used herein, the term "molecular weight" refers to weight average molecular weight (Mw). The molecular weight of the PVB resin may be in the range of about 50,000 to about 600,000, about 70,000 to about 450,000, or about 100,000 to about 425,000 Daltons.

[0020]

[0023] PVB resins can be produced by known aqueous or solvent acetalization processes by reacting polyvinyl alcohol ("PVOH") with butyraldehyde in the presence of an acid catalyst, isolating, stabilizing, and drying 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 disclosures of which are incorporated herein by reference in their entireties.

[0021]

[0024] Although generally referred to herein as "poly(vinyl acetal)," or "poly(vinyl butyral)," the resins described herein may contain residues of any suitable aldehyde, including, but not limited to, isobutyraldehyde, as previously discussed. In some embodiments, the one or more poly(vinyl acetal) resins comprise at least one C1-C 10 The aldehyde may include a residue of an aldehyde or at least one C4-C8 aldehyde. Examples of suitable C4-C8 aldehydes may include, but are not limited to, n-butyraldehyde, isobutyraldehyde, 2-methylvaleraldehyde, n-hexylaldehyde, 2-ethylhexylaldehyde, n-octylaldehyde, and combinations thereof.

[0022]

[0025] In many embodiments, plasticizers are added to the polymer resin to form the polymer layer or interlayer. Plasticizers are generally added to the polymer resin to increase the flexibility and durability of the resulting polymer interlayer. The plasticizer embeds itself between the polymer chains, spacing them apart (increasing the "free volume") and thus increasing the glass transition temperature (T g ), making the material softer. In this regard, the amount of plasticizer in the interlayer is important in determining the glass transition temperature (T g The glass transition temperature (T g ) is the temperature which marks the transition from the glassy to the rubbery state of the interlayer. Generally, a higher plasticizer loading results in a lower T g In some embodiments, for example when the intermediate layer is an acoustic trilayer, the inner core layer (i.e., the soft layer) has a glass transition temperature less than about 20°C, while the outer skin layers (e.g., the hard layers) have a glass transition temperature greater than about 25°C.

[0023]

[0026] Contemplated plasticizers include, but are not limited to, esters of polybasic acids, polyhydric alcohols, triethylene glycol di-(2-ethylbutyrate), triethylene glycol di-(2-ethylhexonate) (known as "3-GEH"), triethylene glycol diheptanoate, tetraethylene glycol diheptanoate, dihexyl adipate, dioctyl adipate, hexylcyclohexyl adipate, mixtures of heptyl adipate and nonyl adipate, diisononyl adipate, heptylnonyl adipate, dibutyl sebacate, and polymeric plasticizers such as oil-modified sebacic acid alkyds, and mixtures of phosphates and adipates, and mixtures and combinations thereof. 3-GEH is particularly preferred. Other examples of suitable plasticizers may 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.

[0024]

[0027] Other suitable plasticizers may include blends of two or more different plasticizers, including but not limited to those mentioned above. Still other suitable plasticizers or blends of plasticizers may be formed from the aromatic family, such as 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-ethylhexanoate), ethoxylated nonylphenol, and mixtures thereof. In some embodiments, the plasticizer may be selected from the group consisting of dipropylene glycol dibenzoate, tripropylene glycol dibenzoate, and combinations thereof.

[0025]

[0028] Generally, the plasticizer content of the polymeric interlayers of the present application is measured in parts per hundred parts of resin ("phr") on a weight / weight basis. For example, if 30 grams of plasticizer is added to 100 grams of polymeric resin, the plasticizer content of the final plasticized polymer will be 30 phr. When the plasticizer content of polymeric layers is given in this application, the plasticizer content of a particular layer is determined with reference to the phr of plasticizer in the melt used to make that particular layer. In some embodiments, high stiffness interlayers comprise layers having a plasticizer content of less than about 35 phr and less than about 30 phr.

[0026]

[0029] According to some embodiments of the invention, one or more polymer layers described herein may 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. In some embodiments, the polymer layer may also include no more than about 100 phr, no more than about 85 phr, no more than about 80 phr, no more than about 75 phr, no more than about 70 phr, no more than about 65 phr, no more than about 60 phr, no more than about 55 phr, no more than about 50 phr, no more than about 45 phr, no more than about 40 phr, no more than about 38 phr, no more than about 35 phr, or no more than about 30 phr of one or more plasticizers. In some embodiments, the total plasticizer content of at least one polymer layer may be in the range of 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 may be in the range of about 38 to about 90 phr, about 40 to about 85 phr, or about 50 to 70 phr.

[0027]

[0030] When the intermediate layer comprises a multi-layer intermediate layer, two or more polymer layers within the intermediate layer 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 intermediate layer comprises two or more polymer layers with different plasticizer contents, the two layers may be adjacent to each other. In some embodiments, the difference in plasticizer content between adjacent polymer layers may be at least about 1 phr, at least about 2 phr, at least about 5 phr, at least about 7 phr, at least about 10 phr, at least about 20 phr, at least about 30 phr, at least about 35 phr, and / or about 80 phr or less, about 55 phr or less, about 50 phr or less, or about 45 phr or less, or in the range of about 1 to about 60 phr, about 10 to about 50 phr, or about 30 to 45 phr. If there are three or more layers in the intermediate layer, at least two of the polymer layers in the intermediate layer may have similar plasticizer contents, for example, within 10 phr, within 5 phr, within 2 phr, or within 1 phr of each other, while at least two of the polymer layers may have different plasticizer contents from each other according to the above ranges.

[0028]

[0031] In some embodiments, one or more of the polymer layers or interlayers described herein may comprise a blend of two or more plasticizers, for example, including two or more of the plasticizers listed above. When a polymer layer comprises two or more plasticizers, the total plasticizer content of the polymer layer and the difference in the total plasticizer content between adjacent polymer layers may fall within one or more of the ranges above. When the interlayer is a multi-layer interlayer, one or more of the polymer layers may comprise two or more plasticizers. In some embodiments when the interlayer is a multi-layer interlayer, at least one of the polymer layers comprising a blend of plasticizers may have a glass transition temperature higher than that of a conventional plasticized polymer layer. This may provide additional hardness in some cases to a layer that may be used, for example, as an outer "skin" layer in a multi-layer interlayer.

[0029]

[0032] In addition to the plasticizer, it is also contemplated that an adhesion control agent ("ACA") may be added to the polymer resin to form the polymer interlayer. The ACA generally functions to modify and / or improve the adhesion of the interlayer to the glass panel in forming a laminate panel. Contemplated ACAs include, but are not limited to, magnesium carboxylates / salts. Furthermore, contemplated ACAs may also include ACAs disclosed in U.S. Pat. No. 5,728,472, the entirety of which is incorporated herein by reference, such as residual sodium acetate, potassium acetate, and / or magnesium bis(2-ethylbutyrate).

[0030]

[0033] Other additives may be incorporated into the interlayer to improve its performance in the final product and to impart certain additional properties to the interlayer. Such additives include, but are not limited to, dyes, pigments, stabilizers (e.g., UV stabilizers), antioxidants, antiblocking agents, flame retardants, IR absorbers or blockers (e.g., indium tin oxide, antimony tin oxide, lanthanum hexaboride (LaB6) and cesium tungsten oxide), processing aids, flow promoters, lubricants, impact modifiers, nucleating agents, heat stabilizers, UV absorbers, UV stabilizers, dispersants, surfactants, chelating agents, coupling agents, adhesives, primers, reinforcing additives, and fillers, among other additives known to those skilled in the art.

[0031]

[0034] One parameter used to describe the polymer resin components of the polymer interlayers of this application is the 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 polymer chain after processing is completed. For example, PVB may be produced by hydrolyzing poly(vinyl acetate) to poly(vinyl alcohol) and then reacting the poly(vinyl alcohol) with butyraldehyde to form PVB. In the hydrolysis process of poly(vinyl acetate), typically not all acetate side groups are converted to hydroxyl groups. Furthermore, typically not all hydroxyl groups are converted to acetal groups by reaction with butyraldehyde. As a result, in any final PVB, typically there are residual acetate groups (e.g., vinyl acetate groups) and residual hydroxyl groups (e.g., vinyl hydroxyl groups) as side groups on the polymer chain. In general, the residual hydroxyl content of a polymer may be adjusted by controlling reaction times and reactant concentrations, among other variables in the polymer manufacturing process. As utilized herein as a parameter, residual hydroxyl content is measured on a wt.% basis according to ASTM D-1396.

[0032]

[0035] In various embodiments, the poly(vinyl butyral) resin comprises from about 8 to about 35 weight percent (wt.%) residual hydroxyl groups calculated as PVOH, from about 13 to about 30 wt.% residual hydroxyl groups calculated as PVOH, from about 8 to about 22 wt.% residual hydroxyl groups calculated as PVOH, or from about 15 to about 22 wt.% residual hydroxyl groups calculated as PVOH, and in some cases of the high stiffness intermediate layers disclosed herein, in 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.

[0033]

[0036] In some embodiments, the poly(vinyl butyral) resin used in at least one polymer layer of the intermediate layer may comprise a poly(vinyl butyral) resin having a residual hydroxyl content, measured as described above, of at least about 18 wt.%, at least about 18.5 wt.%, at least about 18.7 wt.%, at least about 19 wt.%, at least about 19.5 wt.%, at least about 20 wt.%, at least about 20.5 wt.%, at least about 21 wt.%, at least about 21.5 wt.%, at least about 22 wt.%, at least about 22.5 wt.%, and / or no more than about 30 wt.%, no more than about 29 wt.%, no more than about 28 wt.%, no more than about 27 wt.%, no more than about 26 wt.%, no more than about 25 wt.%, no more than about 24 wt.%, no more than about 23 wt.%, or no more than about 22 wt.%.

[0034]

[0037] Furthermore, one or more other polymer layers in the intermediate layer described herein may comprise another poly(vinyl butyral) resin having a lower residual hydroxyl content. For example, in some embodiments, at least one polymer layer of the intermediate layer may comprise a poly(vinyl butyral) resin having a residual hydroxyl content of at least about 8 wt.%, at least about 8.5 wt.%, at least about 9 wt.%, at least about 9.5 wt.%, at least about 10 wt.%, at least about 10.5 wt.%, at least about 11 wt.%, at least about 11.5 wt.%, at least about 12 wt.%, at least about 13 wt.%, and / or about 16 wt.% or less, about 15 wt.% or less, about 14 wt.% or less, about 13.5 wt.% or less, about 13 wt.% or less, about 12 wt.% or less, or about 11.5 wt.% or less.

[0035]

[0038] When the intermediate layer includes two or more polymer layers, the layers may include poly(vinyl butyral) resins having substantially the same residual hydroxyl content, or the residual hydroxyl content 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 content of the poly(vinyl butyral) resins in each layer may be less than about 2 wt.%, less than about 1 wt.%, 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 the difference between two given weight percentages calculated by subtracting one number from the other. For example, a poly(vinyl acetal) resin with a residual hydroxyl content of 12 wt.% has a residual hydroxyl content that differs by 2 wt.% from a poly(vinyl acetal) resin with 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 or lower than another value. Unless otherwise specified, all "differences" herein refer to the numerical value of the difference and do not refer to the particular sign of the value resulting from the order in which the numbers are subtracted. Thus, unless otherwise noted, all "differences" herein refer to the absolute value of the difference between two numbers.

[0036]

[0039] When two or more layers comprise poly(vinyl butyral) resins having different residual hydroxyl contents, the difference between the residual hydroxyl contents of the poly(vinyl butyral) resins may be at least about 2 wt.%, at least about 3 wt.%, at least about 4 wt.%, at least about 5 wt.%, at least about 6 wt.%, at least about 7 wt.%, at least about 8 wt.%, at least about 9 wt.%, at least about 10 wt.%, at least about 12 wt.%, or at least about 15 wt.%, measured as described above.

[0037]

[0040] The resin may also contain less than 35 wt.% residual ester groups, calculated as polyvinyl ester, e.g., acetate, 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.%, with the remainder being acetal, preferably butyraldehyde acetal, but optionally containing trace amounts of other acetal groups, e.g., 2-ethylhexanal groups (see, e.g., U.S. Pat. No. 5,137,954, the disclosure of which is incorporated herein by reference in its entirety). The residual acetate content of the resin may also be determined according to ASTM D-1396.

[0038]

[0041] In some embodiments, as described above, one or more of the polymer layers of the intermediate layer may be formed from a poly(vinyl acetal) resin. Such poly(vinyl acetal) resin may have a residual acetate content of at least about 1 wt.%, at least about 3 wt.%, at least about 5 wt.%, at least about 7 wt.%, and / or about 15 wt.% or less, about 12 wt.% or less, about 10 wt.% or less, about 8 wt.% or less, measured as described above. When the intermediate layer comprises a multi-layer intermediate layer, two or more polymer layers may include a resin having substantially the same residual acetate content, or one or more resins in the various layers may have substantially different acetate contents. When the residual acetate content of two or more resins is substantially the same, the difference in the residual acetate content may be, for example, less than about 3 wt.%, less than about 2 wt.%, less than about 1 wt.%, 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 multi-layer intermediate layer may be at least about 3 wt.%, at least about 5 wt.%, at least about 8 wt.%, at least about 15 wt.%, at least about 20 wt.%, or at least about 30 wt.%. When such resins are utilized in a multi-layer intermediate layer, resins having different residual acetate contents may be present in adjacent polymer layers. When the multi-layer intermediate layer is a three-layer intermediate layer including a pair of outer "skin" layers surrounding or sandwiching an inner "core" layer, for example, the core layer may include a resin having a higher or lower residual acetate content. At the same time, the resin in the inner core layer may have a residual hydroxyl content that is higher or lower than the residual hydroxyl content of the outer skin layers and falls within one or more of the ranges set forth above.

[0039]

[0042] Poly(vinyl acetal) resins with higher or lower residual hydroxyl content and / or residual acetate content may also ultimately contain different amounts of plasticizer when combined with at least one plasticizer. As a result, layers or domains formed with first and second poly(vinyl acetal) resins with 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 with the polymer is largely determined by the hydroxyl content of the polymer. A polymer with a higher residual hydroxyl content typically correlates with a reduced plasticizer compatibility or capacity. Conversely, a polymer with a lower residual hydroxyl content typically results in an increased plasticizer compatibility or capacity. As a result, poly(vinyl acetal) resins with a higher residual hydroxyl content tend to be less plasticized and exhibit higher hardness than similar resins with lower residual hydroxyl content. Conversely, poly(vinyl acetal) resins with lower residual hydroxyl content, when plasticized with a given plasticizer, may tend to incorporate a greater amount of the plasticizer, which may result in a softer polymer layer exhibiting a lower glass transition temperature than a similar resin with a higher residual hydroxyl content. Depending on the particular resin and plasticizer, these trends may be reversed.

[0040]

[0043] When two poly(vinyl acetal) resins with different levels of residual hydroxyl content are blended with a plasticizer, the plasticizer can be distributed between the polymer layers or domains such that there can be more plasticizer in the layer or domain with the lower residual hydroxyl content and less in the layer or domain with the higher residual hydroxyl content. Eventually, an equilibrium state is achieved between the two resins. In general, this correlation between the polymer's residual hydroxyl content and plasticizer compatibility / capacity can be manipulated and utilized to allow the addition of an appropriate amount of plasticizer to the polymer resin and to stably maintain the difference in plasticizer content within a multilayer interlayer. Such a correlation also stably maintains the difference in plasticizer content between two or more resins when the plasticizer would otherwise migrate between the resins.

[0041]

[0044] As a result of migration of plasticizer within the interlayer, the glass transition temperature of one or more polymer layers may differ when measured alone or as part of a multi-layer interlayer. In some embodiments, the interlayer may include at least one polymer layer having a glass transition temperature of at least about 33°C, at least about 34°C, at least about 35°C, at least about 36°C, at least about 37°C, at least about 38°C, at least about 39°C, at least about 40°C, at least about 41°C, at least about 42°C, at least about 43°C, at least about 44°C, at least about 45°C, or at least about 46°C outside the interlayer. In some embodiments, the same layer may have a glass transition temperature of at least about 34°C, at least about 35°C, at least about 36°C, at least about 37°C, at least about 38°C, at least about 39°C, at least about 40°C, at least about 41°C, at least about 42°C, at least about 43°C, at least about 44°C, at least about 45°C, at least about 46°C, or at least about 47°C within the polymer layer.

[0042]

[0045] In the same or other embodiments, at least one other polymer layer of a multi-layer interlayer may have a glass transition temperature of less than 30° C. measured when the interlayer is not part of the interlayer, and may have a glass transition temperature of, for example, about 25° C. or less, about 20° C. or less, about 15° C. or less, about 10° C. or less, about 9° C. or less, about 8° C. or less, about 7° C. or less, about 6° C. or less, about 5° C. or less, about 4° C. or less, about 3° C. or less, about 2° C. or less, about 1° C. or less, about 0° C. or less, about −1° C. or less, about −2° C. or less, or about −5° C. The same polymer layer may have a glass transition temperature of about 25° C. or less, about 20° C. or less, about 15° C. or less, about 10° C. or less, about 9° C. or less, about 8° C. or less, about 7° C. or less, about 6° C. or less, about 5° C. or less, about 4° C. or less, about 3° C. or less, about 2° C. or less, about 1° C. or less, or about 0° C. or less measured outside the interlayer.

[0043]

[0046] According to some embodiments, the difference between the glass transition temperatures of two polymer layers, typically adjacent polymer layers in an interlayer, may be at least about 5° C., at least about 10° C., at least about 15° C., at least about 20° C., at least about 25° C., at least about 30° C., at least about 35° C., at least about 40° C., or at least about 45° C.; in other embodiments, two or more polymer layers may have glass transition temperatures within about 5° C., within about 3° C., within about 2° C., or within about 1° C. of each other. Generally, a lower glass transition temperature layer will have a lower hardness than a higher glass transition temperature layer in an interlayer, and may be located between higher glass transition temperature polymer layers in the final interlayer structure.

[0044]

[0047] For example, in some embodiments of the present application, the increased acoustic damping properties of the soft layer are combined with the mechanical strength of the hard / rigid layer to form a multi-layer interlayer. In these embodiments, a central soft layer is sandwiched between two hard / rigid outer layers. This (hard) / / (soft) / / (hard) configuration forms a multi-layer interlayer that is easy to handle, can be used in conventional lamination methods, and can be constructed with relatively thin and lightweight layers. The soft layer is generally characterized by a lower residual hydroxyl content (e.g., 16 wt.% or less, 15 wt.% or less, or 12 wt.% or less, or any of the ranges disclosed above), a higher plasticizer content (e.g., about 48 phr or more, or about 70 phr or more, 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).

[0045]

[0048] It is contemplated that the polymer interlayer sheets described herein may be manufactured by any suitable process known to those skilled in the art for manufacturing polymer interlayer sheets that may be used in multi-layer panels (e.g., glass laminates). For example, it is contemplated that the polymer interlayer sheets may be formed by solution casting, compression molding, injection molding, melt extrusion, melt blowing, or any other procedure for the production and manufacture of polymer interlayer sheets known to those skilled in the art. Furthermore, in embodiments in which multiple polymer interlayers are utilized, it is contemplated that these multiple polymer interlayers may be formed by coextrusion, blown film, dip coating, solution coating, blade, paddle, air knife, printing, powder coating, spray coating, or other processes known to those skilled in the art. While all methods for the manufacture of polymer interlayer sheets known to those skilled in the art are contemplated as possible methods for manufacturing the polymer interlayer sheets described herein, the present application focuses on polymer interlayer sheets manufactured by extrusion and / or coextrusion processes. The final multi-layer glass panel laminates of the present disclosure are formed using processes known in the art.

[0046]

[0049] In the extrusion process, the thermoplastic resin and plasticizer, including any of the resins and plasticizers mentioned above, are generally premixed and fed into the extruder device. Additives such as colorants and UV inhibitors (liquid, powder or pellet form) may be used and may be mixed into the thermoplastic resin or plasticizer before reaching the extruder device. These additives are incorporated into the thermoplastic polymer resin and into the final polymer interlayer sheet by extrusion to enhance certain properties of the polymer interlayer sheet and its performance in the final multi-ply glass panel product.

[0047]

[0050] In the extruder device, the particles of thermoplastic raw materials and plasticizers, including any of the resins, plasticizers and other additives mentioned above, are further mixed and melted to produce a melt that is generally uniform in temperature and composition. An embodiment of the present invention may provide a melt temperature of about 200°C. Once the melt reaches the end of the extruder device, it is forced into an extruder die. The extruder die is the part of the extruder device that gives the final polymer interlayer sheet product its shape. The die generally has an opening defined by a lip, one dimension of which is significantly larger than the vertical dimension. Generally, the die is designed so that the melt flows uniformly from a cylindrical shape to the final product shape as it exits the die. The die may impart multiple shapes to the final polymer interlayer sheet, as long as there is a continuous profile. Generally, in its most basic sense, extrusion is a process used to form an object of a fixed cross-sectional profile. This is accomplished by pushing or drawing the material through a die of the desired cross-section of the final product.

[0048]

[0051] In some embodiments, a coextrusion process may be utilized. Coextrusion is a process in which multiple layers of polymeric materials are extruded simultaneously. Generally, this type of extrusion utilizes two or more extruders to melt a steady processing volume of different thermoplastic melts of different viscosities or other properties and deliver them as a desired final form through a coextrusion die. For example, the multilayer interlayer of the present invention (e.g., in the form of a three-layer interlayer) may be coextruded preferably using a multi-manifold coextrusion device including a first die manifold, a second die manifold, and a third die manifold. The coextrusion device may operate by simultaneously extruding the polymer melt from each manifold through the die and out of the opening, and the multilayer interlayer is extruded as a composite of three individual polymer layers. The polymer melt may flow through the die such that the core layer is positioned between the skin layers to result in the production of a three-layer interlayer in which the core layer is 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 melt, the skin layers may contact the lips. In either case, the interlayer thickness can be varied by adjusting the distance between the die lips located at the die opening.

[0049]

[0052] The thickness of the multiple polymer layers exiting the extrusion die in the coextrusion process can generally be controlled by adjusting the relative speed of the melt through the extrusion die and the size 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 mils, at least about 25 mils, at least about 27 mils, at least about 30 mils, at least about 31 mils, and / or about 75 mils or less, about 70 mils or less, about 65 mils or less, about 60 mils or less, or can be within the range of about 13 to about 75 mils, about 25 to about 70 mils, or about 30 to 60 mils. When the intermediate layer comprises two or more polymer layers, each of the layers may have a thickness of at least about 2 mils, at least about 3 mils, at least about 4 mils, at least about 5 mils, at least about 6 mils, at least about 7 mils, at least about 8 mils, at least about 9 mils, at least about 10 mils, and / or not more than about 50 mils, not more than about 40 mils, not more than about 30 mils, not more than about 20 mils, not more than about 17 mils, not more than about 15 mils, not more than about 13 mils, not more than about 12 mils, not more than about 10 mils, not more than about 9 mils. In some embodiments, each of the layers may have about the same thickness, while in other embodiments, one or more layers may have a different thickness than one or more other layers in the intermediate layer.

[0050]

[0053] In some embodiments where the intermediate layer comprises at least three polymer layers, one or more of the inner layers may be relatively thin compared to the other outer layers. For example, in some embodiments where the multi-layer intermediate layer is a three-layer intermediate layer, the innermost layer may have a thickness of about 12 mils or less, about 10 mils or less, about 9 mils or less, about 8 mils or less, about 7 mils or less, about 6 mils or less, about 5 mils or less, or may have a thickness in the range of 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 may be at least about 4 mils, at least about 5 mils, at least about 6 mils, at least about 7 mils, and / or about 15 mils or less, about 13 mils or less, about 12 mils or less, about 10 mils or less, about 9 mils or less, about 8 mils or less, or may be in the range of about 2 to about 15 mils, about 3 to about 13 mils, or about 4 mils to about 10 mils. When the intermediate layer includes two outer layers, the layers may have a combined thickness of at least about 9 mils, at least about 13 mils, at least about 15 mils, at least about 16 mils, at least about 18 mils, at least about 20 mils, at least about 23 mils, at least about 25 mils, at least about 26 mils, at least about 28 mils, or at least about 30 mils, and / or no more than about 73 mils, no more than about 60 mils, no more than about 50 mils, no more than about 45 mils, no more than about 40 mils, no more than about 35 mils, or in the range of about 9 to about 70 mils, about 13 to about 40 mils, or about 25 to about 35 mils.

[0051]

[0054] According to some embodiments, the ratio of the thickness of one of the outer layers to one of the inner layers in a multi-layer intermediate layer may 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 intermediate layer is a three-layer intermediate layer 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 above ranges. In some embodiments, the ratio of the total thickness of the outer layer 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 no more than about 30:1, no more than about 20:1, no more than about 15:1, no more than about 10:1, no more than about 9:1, or no more than about 8:1.

[0052]

[0055] The multi-layer interlayer described herein may comprise a generally flat interlayer having substantially the same thickness along the length or longest dimension and / or width or second longest dimension of the sheet. However, in some embodiments, the multi-layer interlayer of the present invention may be a tapered or wedge-shaped interlayer comprising at least one tapered zone having a wedge-shaped profile. A tapered interlayer has a thickness profile that varies along at least a portion of the length and / or width of the sheet, for example, such that at least one end of the interlayer has a greater thickness than the other end. When the interlayer is a tapered interlayer, at least one, at least two, at least three or more of the individual resin layers may include at least one tapered zone. Tapered interlayers may be particularly useful, for example, in head-up display (HUD) panels in automotive and aviation applications.

[0053]

[0056] In view of the above, embodiments of the present invention include a polymeric interlayer that resists the formation of optical defects. The polymeric interlayer may comprise a core layer, a first skin layer, and a second skin layer. The core layer is generally positioned between the first skin layer and the second skin layer such that the skin layers sandwich the core layer. Notably, the core layer includes a resin that includes an adhesion control agent in the range of about 0.1 to 15 strength.

[0054]

[0057] Beneficially, in such embodiments, the polymer interlayer has lower bubble formation than prior art polymer interlayers. For example, the polymer interlayer can have no more than two bubbles formed throughout the polymer interlayer, no more than one bubble, and / or no bubbles. In some particular embodiments, the polymer interlayer can have no more than two edge bubbles formed throughout the polymer interlayer (e.g., when laminated between a pair of glass sheets to form a laminated glass panel), no more than one edge bubble, and / or no edge bubbles. In particular, when the polymer interlayer of the present invention is laminated between a pair of glass sheets to form a laminated glass panel, such glass panel can have no bubbles formed within the glass panel. In some embodiments, the glass panel can have no more than two bubbles or no more than one bubble. In some particular embodiments, the laminated glass panel can have no more than two edge bubbles, no more than one edge bubble, and / or no edge bubbles. Determining the presence of edge bubbles is described in more detail in Example 1 below.

[0055]

[0058] To facilitate the reduction of such bubbles within the interlayer and / or laminate panel, the core layer of the interlayer may comprise a polyimide resin having a strength of about 0.1-15, 0.1-13, 0.1-12, 0.1-11, 0.1-10, 0.1-9, 0.1-8, 0.1-6, 0.1-5, 0.5-18, 0.5-15, 0.5-13, 0.5-12, 0.5-11, 0.5-10, 0.5-9, 0.5-8, 0.5-6, 0.5-5. The adhesion modifier may comprise a strength ranging from 1×10 to 18×15, 5×13, 5×12, 5×11, 5×10, 5×9, 5×8, 5×6, 8×18, 8×15, 8×13, 8×12, 8×11, 8×10, 8×9, 10×18, 10×15, 10×13, 10×12, 10×11, 12×18, 12×15, 12×13, 13×18, and / or 13×15. In certain embodiments, the adhesion modifier in the first polymer layer comprises a magnesium salt. As used herein, a strength of ACA is 1×10 per gram of resin. -7 is defined to mean a molar adhesion control agent (ACA) (e.g., magnesium salt).

[0056]

[0059] The above-mentioned polymeric interlayer, which resists the formation of optical defects (e.g., bubbles), may be formed by extruding a first polymer melt to form a core layer and a second polymer melt to form a first and second skin layer. In some embodiments, the first polymer melt is fed by a first extruder (e.g., a core extruder), while the second polymer melt is fed by a second extruder (e.g., a skin extruder), and then split into two streams to form the skin layer. In either case, the core layer and the skin layer are generally coextruded 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 includes a resin containing an adhesion control agent in the range of about 0.1 to 15 titers.

[0057]

[0060] Thus, the polymer interlayer has lower bubble formation than prior art polymer interlayers. For example, the polymer interlayer can have no more than two bubbles formed throughout the polymer interlayer, no more than one bubble, and / or no bubbles. In some particular embodiments, the polymer interlayer can have no more than two edge bubbles formed throughout the polymer interlayer, no more than one edge bubble, and / or no edge bubbles (e.g., when the interlayer is laminated between a pair of glass sheets to form a laminated glass panel).

[0058]

[0061] Additionally, embodiments may further include a method of forming a laminated glass panel with reduced optical defects. Such a method may include laminating the above-described polymer interlayer between a pair of glass sheets to form a laminated glass panel. Such a glass panel, in certain embodiments, has no bubbles (e.g., edge or trim bubbles) formed within the glass panel. In some embodiments, the glass panel can have no more than two bubbles (e.g., edge or trim bubbles) formed within the glass panel, or no more than one bubble (e.g., edge or trim bubble). In some specific embodiments, the laminated glass panel can have no more than two edge bubbles, no more than one edge bubble, and / or no edge bubbles. EXAMPLES

[0059] Example 1

[0062] Four sets of laminated glass panels were formed, as described in more detail below. Each of the glass panels included a polymer interlayer sandwiched between a pair of glass sheets, with each polymer interlayer having a core layer sandwiched between a pair of skin layers. Each set included eight glass panels with a specific amount of adhesion control agent (ACA) in the corresponding core layer. Specifically, a first set of eight laminated glass panels was formed with a 26 strength ACA in the core layer. A second set of eight laminated glass panels was formed with a 22 strength ACA in the core layer. A third set of eight laminated glass panels was formed with an 18 strength ACA in the core layer. A fourth set of eight laminated glass panels was formed with a 12 strength ACA in the core layer. One strength is equivalent to approximately 1.37 ppm of magnesium salt. The number of bubbles identified in each of the glass panels was counted, as shown in Table 1 below.

[0060]

[0063] More specifically, each of the polymer interlayers was formed with PVB by coextrusion. The amount of ACA included in the core layer was as discussed in the paragraph above. Upon formation of the polymer interlayer, the interlayer was conditioned at 40° C. and 25% relative humidity (RH) for 4 hours. The polymer interlayer was then laminated between a pair of glass sheets such that each resulting laminated glass panel was approximately square with dimensions of 15 cm×15 cm. The laminated glass panels were then autoclaved according to the following conditions: First, the laminated glass panel was inserted into an autoclave at atmospheric pressure and a temperature of about 20° C. The pressure in the autoclave was increased to 13 bar for the remainder of the autoclave process for about 1 minute. Once the autoclave pressure was reached, the temperature was increased to 143° C. at a rate of 6° C. / min. The temperature was held at 143° C. for 20 minutes, at which point the pressure was reduced at a rate of 4.5° C. / min until an end temperature of 45° C. was reached. At such time the pressure was reduced to atmospheric pressure and the autoclaving process was terminated. The laminated glass panels were allowed to cool at room temperature for 1 hour and then placed in a 100° C. oven for 16 hours.

[0061]

[0064] Each of the laminated glass panels was then counted for bubbles. Specifically, an edge bubble test was used to count the number of edge bubbles present at each of the four edges of the glass panel. Following the test, the number of edge bubbles was visually counted for each laminated glass panel. An edge bubble is a bubble formed within a glass panel adjacent to an edge of the glass panel. Specifically, as used herein, an edge bubble forms within a glass panel and / or polymer interlayer within about 5 mm of an edge of the glass panel and / or polymer interlayer. Edge bubbles are typically circular and have a diameter of a few tenths of a millimeter to about a millimeter. The results of the edge bubble test are reproduced below in Table 1, which shows the number of edge bubbles counted for each glass panel.

[0062] [Table 1]

[0063]

[0065] As shown by the data from Table 1, the number of bubbles identified in the glass panels was found to be generally proportional to the amount of ACA included in the core layer of the polymer interlayer. More generally, lower levels of ACA were found to correspond to fewer edge bubbles, or the absence of edge bubbles. For example, a first set of laminated glass panels (each having an ACA amount of 26 strength in the associated core layer) was found to have an average of 3.0 edge bubbles per glass panel. A second set of laminated glass panels (each having an ACA amount of 22 strength in the associated core layer) was found to have an average of 1.5 edge bubbles per glass panel. A third set of laminated glass panels (each having an ACA amount of 18 strength in the associated core layer) was found to have an average of 1.0 edge bubble per glass panel. Finally, a fourth set of laminated glass panels (each having an ACA amount of 12 strength in the associated core layer) was found to have an average of 0.75 edge bubbles per glass panel. Figure 3 presents the data from Table 1 in chart form. The diamond associated with each data set is used to illustrate the average number of edge bubbles (i.e., with a center line extending across the middle of the diamond), as well as the 95% confidence interval (i.e., with upper and lower lines extending across the upper and lower portions of the diamond) for a particular set of laminated glass panels.

[0064]

[0066] It is noted that the discovery of such a proportional relationship between the amount of ACA in the interlayer core layer and the number of identified bubbles in the interlayer and / or laminated glass panel was unexpected. This is because, as previously explained, it is generally preferred that ACA be used in laminate panels to promote adhesion between the layers of the laminate panel. Thus, reduction of ACA in the interlayer was previously thought to be undesirable. However, it has been found that interlayers and / or glass panels formed in accordance with embodiments of the present invention unexpectedly maintain the required adhesive properties while reducing bubbles.

[0065] Example 2

[0067] A plurality of polymer interlayers were formed according to an embodiment of the present invention. Each polymer interlayer was formed as a trilayer with a core layer sandwiched between a pair of skin layers. The polymer interlayers contained various amounts of adhesion control agent (ACA) in their respective core layers, as shown by the graph in FIG. 4 (note that in FIG. 4, some points are uniformly shifted left or right to represent individual data points for eleven ACA levels discussed below). More specifically, eleven groups of polymer interlayers were formed, each group having 0.1, 6.0, 9.0, 10.0, 11.0, 12.0, 13.0, 15.0, 18.0, 22.0, and 23.0 titers of ACA in each core layer of the polymer interlayer from the group, respectively. Each polymer interlayer was exposed to high pressure and high temperature, after which the number of bubbles formed in the polymer interlayer was determined. The average number of bubbles and standard deviation (based on ACA level) for each group of polymer interlayers is shown in Table 2 below.

[0066] [Table 2]

[0067]

[0068] As shown by the data from Table 2 and Figure 4, the number of bubbles determined in the polymer interlayer of this example was found to be generally proportional to the amount of ACA included in the core layer of the polymer interlayer. More generally, lower levels of ACA were found to correspond to fewer bubbles.

[0068]

[0069] Additionally, individual groups of polymer interlayers from this example were assigned to qualitative categories, such categories having been developed by the inventors of the present application. Specifically, groups of polymer interlayers having an average bubble count of 3.0 or greater were deemed to be of "unacceptable" quality, since such a large number of bubbles would result in a polymer interlayer having significant optical defects. Groups of polymer interlayers having an average bubble count of less than 3.0 were deemed to be of "acceptable" quality, since such a number of bubbles would result in acceptable or tolerable optical defects. Additionally, groups of polymer interlayers having an average bubble count of less than 2.0 were deemed to be of "excellent" quality.

[0069]

[0070] In view of the above, and in view of Table 2 and Figure 4, it should be noted that both groups of polymer interlayers containing ACA at 22.0 and 23.0 strengths had an average unacceptable number of bubbles. In contrast, groups of polymer interlayers containing ACA at 0.1, 6.0, 9.0, 10.0, 11.0, 12.0, 13.0, and 15.0 strengths each had an average acceptable number of bubbles. Furthermore, groups of polymer interlayers with ACA at 0.1, 6.0, 9.0, 10.0, 11.0, 12.0, 13.0, and 15.0 strengths each were identified as being of excellent quality.

[0070]

[0071] Although the present invention has been disclosed in conjunction with the description of certain specific embodiments, including those currently considered to be preferred embodiments, the detailed description is intended to be illustrative and should not be understood to limit the scope of the disclosure. As will be understood by those skilled in the art, embodiments other than those specifically described 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 present invention.

[0071]

[0072] Furthermore, it is understood that any range, value, or characteristic set forth for any single component of the present disclosure may be used interchangeably with any range, value, or characteristic set forth for any of the other components of the present disclosure to form embodiments having the defined values ​​for each of the components as set forth throughout this specification, where compatible. For example, a polymer layer may be formed that includes any of the ranges set forth for residual hydroxyl content, as well as any of the ranges set forth for plasticizer content, where appropriate, forming many permutations that are within the scope of the present invention but too cumbersome to enumerate.

Claims

1. A polymer interlayer that is resistant to the formation of optical defects, comprising: a first polymer layer; a second polymer layer; and Third Polymer Layer Equipped with the first polymer layer is positioned between the second polymer layer and the third polymer layer; A polymeric interlayer, wherein the first polymeric layer comprises a resin containing an adhesion control agent in the range of about 0.1 to 15 strength.

2. The polymer interlayer of claim 1 , wherein the resin of the first polymer layer comprises PVB.

3. The polymeric interlayer of claim 1 , wherein the adhesion control agent in the first polymer layer comprises a magnesium salt.

4. The adhesive modification in the first polymer layer is about 0.1-13 strength, 0.1-12 strength, 0.1-11 strength, 0.1-10 strength, 0.1-9 strength, 0.1-8 strength, 0.1-6 strength, 0.1-5 strength, 0.5-15 strength, 0.5-13 strength, 0.5-12 strength, 0.5-11 strength, 0.5-10 strength, 0.5-9 strength, 0.5-8 strength, 0.5-6 strength, 0.5-5 strength, 5-15 strength 10. The polymeric interlayer of claim 1, wherein the polymeric interlayer is in the range of 10-15, 10-13, 10-12, 10-11, 10-15, 10-13, 10-12, 10-11, 12-15, and / or 12-13 strength.

5. The polymer interlayer of claim 1 , wherein the first polymer layer is softer than the second and third polymer layers.

6. A polymer interlayer that is resistant to the formation of optical defects, comprising: Core layer; a first skin layer; and Second Skin Layer Equipped with the core layer is positioned between the first skin layer and the second skin layer; A polymeric interlayer wherein the core layer comprises a resin containing an adhesion control agent in the range of about 0.1 to 15 strength.

7. The polymeric interlayer of claim 6 , wherein the resin of the core layer comprises PVB.

8. The polymeric interlayer of claim 6 , wherein the adhesion control agent in the core layer comprises a magnesium salt.

9. The adhesive adjustment in the core layer is about 0.1-13 strength, 0.1-12 strength, 0.1-11 strength, 0.1-10 strength, 0.1-9 strength, 0.1-8 strength, 0.1-6 strength, 0.1-5 strength, 0.5-15 strength, 0.5-13 strength, 0.5-12 strength, 0.5-11 strength, 0.5-10 strength, 0.5-9 strength, 0.5-8 strength, 0.5-6 strength, 0.5-5 strength, 5-15 strength, 7. The polymeric interlayer of claim 6, wherein the strength is within the range of 5-13 strength, 5-12 strength, 5-11 strength, 5-10 strength, 5-9 strength, 5-8 strength, 5-6 strength, 8-15 strength, 8-13 strength, 8-12 strength, 8-11 strength, 8-10 strength, 8-9 strength, 10-15 strength, 10-13 strength, 10-12 strength, 10-11 strength, 12-15 strength, and / or 12-13 strength.

10. 10. The polymer interlayer of claim 1, wherein when the polymer interlayer is laminated between a pair of glass sheets to form a laminated glass panel, such glass panel contains no more than two edge bubbles, no more than one edge bubble, and / or no edge bubbles as determined using an edge bubble test.

11. The polymer interlayer of claim 1 , wherein the thickness of the polymer interlayer is substantially constant along the length of the polymer interlayer.

12. 10. The polymer interlayer of claim 1, wherein the thickness of the polymer interlayer varies along the length of the polymer interlayer such that the polymer interlayer has a wedge shape.

13. 13. The polymer interlayer of claim 6, wherein the core layer is softer than the first and second skin polymer layers.

14. 1. A method for forming a polymer interlayer that is resistant to the formation of optical defects, comprising: (a) extruding a first polymer melt to form a first polymer layer; (b) extruding the second polymer melt to form a second polymer layer and a third polymer layer; Including, During the extrusion of steps (a) and (b), a first polymer layer is positioned between the second polymer layer and the third polymer layer; The method wherein the first polymer layer comprises a resin containing an adhesion control agent in the range of about 0.1 to 15 strength.

15. 15. The method of claim 14, wherein the extrusion of steps (a) and (b) is performed by coextrusion, the resin of the first polymer layer comprises PVB, and the adhesion control agent in the first polymer layer comprises a magnesium salt.

16. The adhesive modification in the first polymer layer is about 0.1-13 strength, 0.1-12 strength, 0.1-11 strength, 0.1-10 strength, 0.1-9 strength, 0.1-8 strength, 0.1-6 strength, 0.1-5 strength, 0.5-15 strength, 0.5-13 strength, 0.5-12 strength, 0.5-11 strength, 0.5-10 strength, 0.5-9 strength, 0.5-8 strength, 0.5-6 strength, 0.5-5 strength, 5-1 strength 15. The method of claim 14, wherein the titer is within the range of 5, 5-13, 5-12, 5-11, 5-10, 5-9, 5-8, 5-6, 8-15, 8-13, 8-12, 8-11, 8-10, 8-9, 10-15, 10-13, 10-12, 10-11, 12-15, and / or 12-13.

17. (c) laminating the polymer interlayer between a pair of glass sheets to form a laminated glass panel; 15. The method of claim 14, wherein upon lamination in step (c), the laminated glass panel contains no more than two edge bubbles, no more than one edge bubble, and / or no edge bubbles as determined using an edge bubble test.

18. The method of claim 14 , wherein the thickness of the polymer interlayer is substantially constant along the length of the polymer interlayer.

19. The method of claim 14 , wherein the thickness of the polymer interlayer varies along the length of the polymer interlayer such that the polymer interlayer has a wedge shape.

20. 20. The method of any one of claims 14 to 19, wherein the first polymer layer is softer than the second and third polymer layers.

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