Solar control glazing laminates

A solar control glazing laminate may include a solar control film disposed between first and second polyvinyl butyral layers and first and second glazing substrates. The solar control film may include an infrared radiation reflecting polymeric film and a polymeric binder layer disposed on the infrared radiation reflecting polymeric film. The polymeric binder layer may include a polyester and cross-linked multi-functional acrylate segments and may have infrared radiation absorbing nanoparticles dispersed therein.

BACKGROUND

The present disclosure relates generally to solar control glazing laminates and a method of forming the same.

Solar control glazing provides comfort to passengers in, for example, a vehicle, especially in the side glass when the sun is in a location that more directly hits a passenger. Solar control glazing reduces the amount of infrared energy that transmits into, for example, a vehicle. Solar control glass is commonly used as the solar control glazing, however, because of legal limits on the transmission of windshields, backlights and sidelights, only a small portion of the solar energy is adsorbed.

Another solar control technology is metal/oxide coatings on glass. This improves solar control over the absorbing glass, but the metal coating can interfere with electro magnetic frequencies utilized with cell phones, garage door openers, radar detectors, automated toll collectors, and the like.

In addition, any solar control solution must be able to meet the bending requirements of windshields and other glazing units. These bending requirements often lead to delamination of solar control glazing laminates.

SUMMARY

In one exemplary implementation, the present disclosure is directed to a solar control glazing laminate that includes a first glazing substrate and a first polyvinyl butyral layer that is disposed on the first glazing substrate. A solar control film is disposed on the first polyvinyl butyral layer and a second polyvinyl butyral layer is disposed on the solar control film. A second glazing substrate is disposed on the second polyvinyl butyral layer.

The solar control film includes an infrared radiation reflecting polymeric film and a polymeric binder layer that is disposed on the infrared radiation reflecting polymeric film. The polymeric binder layer includes polyester and cross-linked multi-functional acrylate segments. Infrared radiation absorbing nanoparticles are dispersed within the polymeric binder layer.

In another exemplary implementation, the present disclosure is directed to a method of forming a solar control glazing laminate. A solar control film is disposed between first and second polyvinyl butyral layers. The solar control film includes an infrared radiation reflecting film and a polymeric binder layer disposed thereon. The polymeric binder layer includes polyester and cross-linked multi-functional acrylate segments and includes infrared radiation absorbing nanoparticles dispersed within the polymeric binder layer.

The first and second polyvinyl butyral layers, sandwiching the solar control film, are disposed between first and second glazing substrates. Heat and pressure are applied to form a solar control glazing laminate.

These and other aspects of the solar control glazing laminates according to the subject invention will become readily apparent to those of ordinary skill in the art from the following detailed description together with the drawings.

DETAILED DESCRIPTION

The following description should be read with reference to the drawings, in which like elements in different drawings are numbered in like fashion. The drawings, which are not necessarily to scale, depict selected illustrative embodiments and are not intended to limit the scope of the disclosure. Although examples of construction, dimensions, and materials are illustrated for the various elements, those skilled in the art will recognize that many of the examples provided have suitable alternatives that may be utilized.

As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” encompass embodiments having plural referents, unless the content clearly dictates otherwise. For example, reference to “a film” encompasses embodiments having one, two or more films. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

The term “polymer” will be understood to include polymers, copolymers (e.g., polymers formed using two or more different monomers), oligomers and combinations thereof, as well as polymers, oligomers, or copolymers that can be formed in a miscible blend.

The present disclosure is directed generally to solar control glazing laminates and methods of forming the same. In particular, the present disclosure is directed to a solar control glazing laminate that includes a first glazing substrate and a first polyvinyl butyral layer that is disposed on the first glazing substrate. A solar control film is disposed on the first polyvinyl butyral layer and a second polyvinyl butyral layer is disposed on the solar control film. A second glazing substrate is disposed on the second polyvinyl butyral layer.

The solar control film includes an infrared radiation reflecting polymeric film and a polymeric binder layer that is disposed on the infrared radiation reflecting polymeric film. The polymeric binder layer includes polyester and cross-linked multi-functional acrylate segments. Infrared radiation absorbing nanoparticles are dispersed within the polymeric binder layer. While the present invention is not so limited, an appreciation of various aspects of the invention will be gained through a discussion of the examples provided below.

The solar control glazing laminates describes herein does not interfere with electro magnetic frequencies, provides the required visible light transmission for automotive glazings, provides improved solar control, and does not delaminate when subjected to bending requirements.

FIG. 1is a schematic cross-section of a solar control glazing laminate100. The solar control glazing laminate includes a first glazing substrate110and a second glazing substrate120. In this, first and second are arbitrary and are not intended to indicate upper or lower, inside or outside or any other particular possible orientation or configuration. A first polyvinyl butyral layer130is disposed adjacent to the first glazing substrate110and a second polyvinyl butyral layer140is disposed adjacent to the second glazing substrate120. A solar control film150is disposed between first polyvinyl butyral layer130and second polyvinyl butyral layer140.

The solar control glazing laminate100may be formed by assembling and then laminating the individual components. The first polyvinyl butyral layer130may be disposed along the first glazing substrate110. The solar control film150may be placed in contact with the first polyvinyl butyral layer130. The second polyvinyl butyral layer140may be placed in contact with the solar control film150, and the second glazing substrate120may be disposed in contact with the second polyvinyl butyral layer140.

The solar control glazing laminate100may be configured to be substantially clear in appearance, having a haze value of less than 2 or even a haze value of less than 1. In some cases, the solar control glazing laminate100may be configured to be transparent or at least substantially transparent to visible light, having a visible light transmission of greater than 70 percent or greater than 72 percent. The solar control glazing laminate100may be configured to reduce the amount of solar-induced thermal energy that passes through the solar control glazing laminate100, having a reflected energy value of greater than about 15 percent and a total solar heat transmitted value of less than about 50 percent.

FIG. 2is a schematic cross-section of the solar control film150. The solar control film150includes an infrared radiation reflecting film152and a polymeric binder layer154. Infrared radiation absorbing nanoparticles156are disposed within the polymeric binder layer154. In some instances, the polymeric binder layer154may be separately formed and then subsequently disposed along the infrared radiation reflecting film152. In some cases, the polymeric binder layer154may be coated onto the infrared radiation reflecting film152.

In some instances, as illustrated, the solar control film150may be subjected to a corona treatment, resulting in a thin surface treatment layer158. In some cases, the solar control film150may be subjected to a nitrogen corona treatment at a rate of about 1 Joule per square centimeter. This corona treatment has been found to substantially increase the adhesion of the laminate layers such that these laminate layers do not delaminate during processing or bending requirements of automotive glazing units.

The first glazing substrate110and the second glazing substrate120may be formed of any suitable glazing material. In some instances, the glazing substrates may be selected from a material that possesses desirable optical properties at particular wavelengths including visible light. In some cases, the glazing substrates may be selected from materials that transmit substantial amounts of light within the visible spectrum. In some instances, the first glazing substrate110and/or the second glazing substrate120may each be selected from materials such as glass, quartz, sapphire, and the like. In particular instances, the first glazing substrate110and the second glazing substrate120may both be glass.

In many embodiments, the first glazing substrate110and a second glazing substrate120are formed of the same material and posses the same, similar, or substantially similar physical, optical, or solar control properties. For example, the first glazing substrate110and a second glazing substrate120can both be formed of either clear glass or green tint glass. In some embodiments, the first glazing substrate110and a second glazing substrate120are formed of the different material and posses the different physical, optical, or solar control properties. For example, the first glazing substrate110can be formed of clear glass and a second glazing substrate120can both be formed of green tint glass.

The first glazing substrate110and the second glazing substrate120may be either planar or non-planar. Planar glazing substrates may be used if, for example, the solar control glazing laminate110is intended as a window glazing unit. Vehicular uses such as automotive windshields, side windows and rear windows may suggest the use of non-planar glazing substrates. If desired, and depending on the intended use of the solar control glazing laminate100, the first glazing substrate110and/or the second glazing substrate120may include additional components such as tints, scratch-resistant coatings, and the like.

As discussed above, the solar control glazing laminate100includes a first polyvinyl butyral layer130and a second polyvinyl butyral layer140. Each of the first polyvinyl butyral layer130and the second polyvinyl butyral layer140may be formed via known aqueous or solvent-based acetalization process in which polyvinyl alcohol is reacted with butyraldehyde in the presence of an acidic catalyst. In some instances, the first polyvinyl butyral layer130and/or the second polyvinyl butyral layer140may include or be formed from polyvinyl butyral that is commercially available from Solutia Incorporated, of St. Louis Mo., under the trade name BUTVAR® resin.

In some instances, the first polyvinyl butyral layer130and/or the second polyvinyl butyral layer140may be produced by mixing resin and (optionally) plasticizer and extruding the mixed formulation through a sheet die. If a plasticizer is included, the polyvinyl butyral resin may include about 20 to 80 or perhaps about 25 to 60 parts of plasticizer per hundred parts of resin.

As discussed above with respect toFIG. 2, the solar control film150includes an infrared radiation reflecting film152and a polymeric binder layer154. In many embodiments, the infrared radiation reflecting film152is a multilayer optical film. The layers have different refractive index characteristics so that some light is reflected at interfaces between adjacent layers. The layers are sufficiently thin so that light reflected at a plurality of the interfaces undergoes constructive or destructive interference in order to give the film the desired reflective or transmissive properties. For optical films designed to reflect light at ultraviolet, visible, near-infrared, or infrared wavelengths, each layer generally has an optical thickness (i.e., a physical thickness multiplied by refractive index) of less than about 1 micrometer. Thicker layers can, however, also be included, such as skin layers at the outer surfaces of the film, or protective boundary layers disposed within the film that separate packets of layers.

The reflective and transmissive properties of the infrared radiation reflecting film152are a function of the refractive indices of the respective layers (i.e., microlayers). Each layer can be characterized at least in localized positions in the film by in-plane refractive indices nx, ny, and a refractive index nzassociated with a thickness axis of the film. These indices represent the refractive index of the subject material for light polarized along mutually orthogonal x-, y-, and z-axes, respectively. In practice, the refractive indices are controlled by judicious materials selection and processing conditions. The infrared radiation reflecting film152can be made by co-extrusion of typically tens or hundreds of layers of two alternating polymers A, B, followed by optionally passing the multilayer extrudate through one or more multiplication dies, and then stretching or otherwise orienting the extrudate to form a final film. The resulting film is composed of typically tens or hundreds of individual layers whose thicknesses and refractive indices are tailored to provide one or more reflection bands in desired region(s) of the spectrum, such as in the visible, near infrared, and/or infrared. In order to achieve high reflectivities with a reasonable number of layers, adjacent layers preferably exhibit a difference in refractive index (Δnx) for light polarized along the x-axis of at least 0.05. In some embodiments, if the high reflectivity is desired for two orthogonal polarizations, then the adjacent layers also exhibit a difference in refractive index (Δny) for light polarized along the y-axis of at least 0.05. In other embodiments, the refractive index difference Δnycan be less than 0.05 or 0 to produce a multilayer stack that reflects normally incident light of one polarization state and transmits normally incident light of an orthogonal polarization state.

If desired, the refractive index difference (Δnz) between adjacent layers for light polarized along the z-axis can also be tailored to achieve desirable reflectivity properties for the p-polarization component of obliquely incident light. For ease of explanation, at any point of interest on a multilayer optical film the x-axis will be considered to be oriented within the plane of the film such that the magnitude of Δnxis a maximum. Hence, the magnitude of αnycan be equal to or less than (but not greater than) the magnitude of Δnx. Furthermore, the selection of which material layer to begin with in calculating the differences Δnx, Δny, Δnzis dictated by requiring that Δnxbe non-negative. In other words, the refractive index differences between two layers forming an interface are Δnj=nij−n2j, where j=x, y, or z and where the layer designations 1, 2 are chosen so that n1x≧n2x, i.e., Δnx≧0.

To maintain high reflectivity of p-polarized light at oblique angles of incidence, the z-index mismatch Δnzbetween layers can be controlled to be substantially less than the maximum in-plane refractive index difference Δnx, such that Δnz≦0.5*Δnx. More preferably, Δnz≦0.25*Δnx. A zero or near zero magnitude z-index mismatch yields interfaces between layers whose reflectivity for p-polarized light is constant or near constant as a function of incidence angle. Furthermore, the z-index mismatch Δnzcan be controlled to have the opposite polarity compared to the in-plane index difference Δnx, i.e. Δnz<0. This condition yields interfaces whose reflectivity for p-polarized light increases with increasing angles of incidence, as is the case for s-polarized light.

The infrared radiation reflecting film152can be formed by any useful combination of alternating polymer type layers. In many embodiments, at least one of the alternating polymer layers is birefringent and oriented. In some embodiments, one of the alternating polymer layer is birefringent and orientated and the other alternating polymer layer is isotropic. In one embodiment, the multilayer optical film is formed by alternating layers of a first polymer type including polyethylene terephthalate (PET) or copolymer of polyethylene terephthalate (coPET) and a second polymer type including poly(methyl methacrylate) (PMMA) or a copolymer of poly(methyl methacrylate) (coPMMA). In another embodiment, the multilayer optical film is formed by alternating layers of a first polymer type including polyethylene terephthalate and a second polymer type including a copolymer of poly(methyl methacrylate and ethyl acrylate). In another embodiment, the multilayer optical film is formed by alternating layers of a first polymer type including cyclohexanedimethanol (PETG) or a copolymer of cyclohexanedimethanol (coPETG) and second polymer type including polyethylene naphthalate (PEN) or a copolymer of polyethylene naphthalate (coPEN). In another embodiment, the multilayer optical film is formed by alternating layers of a first polymer type including polyethylene naphthalate or a copolymer of polyethylene naphthalate and a second polymer type including poly(methyl methacrylate) or a copolymer of poly(methyl methacrylate). Useful combination of alternating polymer type layers are disclosed in U.S. Pat. No. 6,352,761, which is incorporated by reference herein.

As discussed above with respect toFIG. 2, the solar control film150also includes a polymeric binder layer154. In many embodiments, the polymeric binder layer154may include both polyester and multi-functional acrylate, curable acrylate, and/or acrylate/epoxy materials.

It has been found that the inclusion of a multi-functional acrylate, curable acrylate, and/or acrylate/epoxy material reduces plasticizer migration from the infrared radiation reflecting film152to the polymeric binder layer154. Preventing this plasticizer migration improves (i.e., decreases) the haze value of the solar control glazing laminate100.

Polyesters that are suitable for use in forming the polymeric binder layer154may include carboxylate and glycol subunits and may be generated by reactions of carboxylate monomer molecules with glycol monomer molecules. Each carboxylate monomer molecule has two or more carboxylic acid or ester functional groups and each glycol monomer molecule has two or more hydroxy functional groups. The carboxylate monomer molecules may all be the same or there may be two or more different types of molecules. The same applies to the glycol monomer molecules. Also included within the term “polyester” are polycarbonates derived from the reaction of glycol monomer molecules with esters of carbonic acid.

A useful polyester is polyethylene terephthalate (PET). A PET having an inherent viscosity of 0.74 dL/g is available from Eastman Chemical Company of Kingsport, Tenn. A useful PET having an inherent viscosity of 0.854 dL/g is available from E. I. DuPont de Nemours & Co., Inc.

The polymeric binder layer154also includes multi-functional acrylate segments. Specific examples include those prepared from free-radically polymerizable acrylate monomers or oligomers such as described in U.S. Pat. No. 5,252,694 at col. 5, lines 35-68, and U.S. Pat. No. 6,887,917, col. 3, line 61 to col. 6, line 42, which are incorporated by reference herein.

The polymeric binder layer154can also include curable acrylate and acrylate/epoxy material, such as those described in U.S. Pat. No. 6,887,917 and U.S. Pat. No. 6,949,297, which are incorporated by reference herein.

The polymeric binder layer154includes infrared radiation absorbing nanoparticles156dispersed through the polymeric binder layer154. The infrared radiation absorbing nanoparticles may include any material that preferentially absorbs infrared radiation. Examples of suitable materials include metal oxides such as tin, antimony, indium and zinc oxides and doped oxides.

In some instances, the metal oxide nanoparticles include, tin oxide, antimony oxide, indium oxide, indium doped tin oxide, antimony doped indium tin oxide, antinomy tin oxide, antimony doped tin oxide or mixtures thereof. In some embodiments, the metal oxide nanoparticles include antimony oxide (ATO) and/or indium tin oxide (ITO). In some cases, the infrared radiation absorbing nanoparticles may include or be made of lanthanum hexaboride, or LaB6.

Lanthanum hexaboride is an effective near IR (NIR) absorber, with an absorption band centered on 900 nm. The infrared radiation absorbing nanoparticles156can be sized such that they do not materially impact the visible light transmission of the polymeric binder layer154. In some instances, the infrared radiation absorbing nanoparticles156may have any useful size such as, for example, 1 to 100, or 30 to 100, or 30 to 75 nanometers.

EXAMPLES

These examples are merely for illustrative purposes only and are not meant to be limiting on the scope of the appended claims. All parts, percentages, ratios, etc. in the examples and the rest of the specification are by weight, unless noted otherwise. Solvents and other reagents used were obtained from Sigma-Aldrich Chemical Company; Milwaukee, Wis. unless otherwise noted.

Test Methods

The haze of each sample was measured following ASTM-D1003, using a Haze Guard Plus Haze meter (available from BYK-Gardner, Columbia Md.), prior to and after lamination. The visible transmission (Tvis according to ANSI-Z26), reflected energy (Re according to ISO-9050) and total solar heat transmitted (TSHT according to ISO-9050) were measured using a Perkin Elmer Lambda 19 Spectrophotometer. Compressive shear of laminated samples was also tested using an Instron Tensile tester configured to shear a laminated sample mounted at 45 degrees to the compressive force.

This combination was then mixed in a roller mill for approximately 1 hour, and then coated on Solar Reflecting Film 1200 (available from 3M Company, St. Paul Minn.) using a meyer rod resulting in a dry thickness of 0.35 mils (9 micrometers). The samples were oven dried at 70° C. for approximately 10 minutes and then UV cured at 67 feet/minute using a Fusion Systems processor (UV Systems Inc. Gaithersberg, Md.) fitted with a D-bulb. The sample was then nitrogen corona treated at 1.0 J/cm2to improve adhesion of the laminate.

A laminated stack was prepared by sandwiching a coated film sample between 2 sheets of 0.38 mm Saflex RK 11 (or BUTVAR) PVB (polyvinylbutyral available from Solutia, St. Louis Mo.), and then placing the sandwich between 2 pieces of 2.0 mm clear glass (available from PPG). The laminated stack was then heated to 90° C. for 15 minutes, and then nip rolled to remove air. They were then autoclaved (autoclave available from Lorimer Corporation) in the following cycle: ramp from 0 psig and 21° C. (70° F.) to 140 psig and 138° C. (280° F.) in 25 minutes, hold for 30 minutes, cool to 38° C. (100° F.) in 40 minutes using an external fan, vent pressure to 0 psig.

Comparative Example 1

A sample was prepared in the same manner as that discussed with respect to Example 1, except that no corona treatment was applied.

Table 1 lists both films (before lamination) and laminate haze values, as well as providing compressive shear values. It can be seen that corona treatment provides a significant increase in adhesion, as indicated by a significant difference in compressive shear. Table 2 lists optical properties for Example 1.

Two pieces of 2.1 mm thick green tint glass (available from PPG) and 0.76 mm RK11 PVB were laminated together using the lamination process described in Example 1. The visible transmission (Tvis), reflected energy (Re) and total solar heat transmitted (TSHT) of laminated samples were measured. The results are in the table below.

Comparative Example 2

A solution was prepared in the same manner as Example 1, with the following differences: the materials in the coating solution were KHF-7A (13%), Vitel 2200 (22%) and MEK (65%), the resulting dry coating thickness was 0.15 mils (4 micrometers), and no UV curing was required (since the multi-functional acrylate was not present). The laminated stack was prepared, and the haze measured as in Example 1.