1. Field of the Invention
The present invention generally relates to plastic glazings for automobiles and to glazings that provide functions in addition to a wind and weather barrier.
2. Description of the Known Technology
Polycarbonate is becoming widely accepted as a desirable replacement for glass glazings in the automotive industry. Due to its superior strength, optical clarity, greater freedom in vehicle styling, and excellent thermal properties, polycarbonate is used in the manufacture of automotive window systems with specific functional features. However, the properties of polycarbonate glazings create challenges non-existent in glass glazings. For example, the polycarbonate glazings preferably must be protected against abrasion and, preferably, processes must be developed to incorporate various functional elements within polycarbonate glazings. Further, designers of polycarbonate windows must ensure adequate adhesion of glazings on a polycarbonate substrate.
A current technology used for defrosters and antennas is highly conductive ink that is printed on a polycarbonate substrate or plasma-coated polycarbonate substrate. This ink is usually opaque, and usually has a color, such as black. Typical printed ink defrosters defrost in an uneven pattern, wherein the portions of the window closest to the ink design are defrosted faster than other portions. Further, such ink designs are typically visible on windows, thereby decreasing the portion of the window that is transparent.
The present invention provides a method by which functional layers may be provided on a polycarbonate substrate without the use of ink, allowing for a greater amount of transparency through a plastic panel. Further, the present invention provides a transparent functional layer having a polycarbonate substrate, while still providing the desired adhesiveness between the functional layer and the polycarbonate substrate.
In one aspect, a plastic panel or glazing suitable for use in an automobile is provided. The plastic panel has a polycarbonate substrate, a conductive layer located adjacent to the polycarbonate substrate, the conductive layer comprising carbon nanotubes, and a glazing layer located over the conductive layer. The glazing layer is formed of a material that is different from polycarbonate. The glazing layer includes one or both of a weathering layer and an abrasion resistant layer.
In another aspect, the plastic panel has a first polycarbonate substrate, a second polycarbonate substrate located adjacent to the first polycarbonate substrate, and a conductive layer disposed between the first and second polycarbonate substrates. The conductive layer comprises carbon nanotubes.
In yet another aspect, a method of creating a substrate assembly is provided. The method includes providing a first polycarbonate sheet, providing a conductive layer adjacent to the first polycarbonate sheet, and providing a second polycarbonate sheet adjacent to the conductive layer. The conductive layer comprises carbon nanotubes. The method further includes delivering heat adjacent to at least one of the first and second polycarbonate sheets to fuse the first and second polycarbonate plates together.
These and other aspects and advantages of the present invention will become apparent upon reading the following detailed description of the invention in combination with the accompanying drawings.
Referring now to
Referring now to
The substrate 16 is comprised substantially of polycarbonate and preferably has a thickness of between 3 and 6 millimeters. Further, the substrate 16 may include a privacy or solar tint resin for aesthetic purposes as well as for controlling the transmission of solar radiation through the glazing 10. The substrate 16 is formed into its desired shape using any of the various known techniques, such as molding, thermoforming, or extrusion.
The conductive layer 20 is located adjacent to the substrate 16. The conductive layer 20 may be disposed directly on the surface of the substrate 16, or the conductive layer 20 may be disposed upon other optional layers, such as a weathering layer or a decorative layer, that are disposed on the substrate 16. The conductive layer 20 of the present invention comprises carbon nanotubes and preferably has a thickness of less than 50 nm. The carbon nanotubes are used as electrically conductive particles that conduct electricity to form a functional layer. Carbon nanotubes have a higher strength, stiffness, and electrical conductivity as compared to metals. The conductive layer 20 functions as a transparent electric circuit, which may operate as a transparent defrosters/defogger, an antenna, rain sensors, light sensors, touch sensors, a photochromic light control layer, or an electroluminescent layer, among other uses.
Carbon nanotubes, of which the conductive layer 20 is comprised, may be provided in whole sheets. Typically, these sheets have about one-third of the carbon nanotubes being intrinsically conductive and about two-thirds of the carbon nanotubes being semiconducting. The sheets of carbon nanotubes are typically purified to remove large catalyst particles utilized in their formation, and the sheets may contain a dopant, such as a halogen or an alkali metal, to dope the semiconducting nanotubes with a suitable charge transfer species. Single-wall carbon nanotubes typically have an outside diameter of about 1 to 2 nm, and multi-wall carbon nanotubes typically have an outside diameter of about 8 to 12 nm. The carbon nanotubes may be layered by a manufacturer to produce a desired thickness.
While carbon nanotube sheets may be provided in any thickness desired, if the conductive layer 20 is sufficiently thin, it will remain transparent. Typically, sheets with a thickness of 100 nm or less have optical grade transparency. Thus, if the conductive layer 20 is provided having a thickness of 100 nm or less, the layer 20 may be provided over substantially the whole surface of the substrate 16 without compromising the optical transparency of the transparent area 12.
The abrasion resistant layer 22 is applied over the conductive layer 20 and the substrate 16. The abrasion resistant layer 22 is preferably comprised of aluminum oxide, barium fluoride, boron nitride, hafnium oxide, lanthanum fluoride, magnesium oxide, scandium oxide, silicon monoxide, silicon dioxide, silicon nitride, silicon oxy-nitride, silicon oxy-carbide, hydrogenated silicon oxy-carbide, silicon carbide, tantalum oxide, titanium oxide, tin oxide, yttrium oxide, zinc oxide, zinc selenide, zinc sulfide, zirconium oxide, zirconium titanate, or a mixture or blend thereof. More preferably, the abrasion resistant layer 22 is comprised of a composition of silicon monoxide, silicon dioxide, silicon oxy-carbide, or hydrogenated silicon oxy-carbide.
The abrasion resistant layer 60 may be applied by any vacuum deposition technique known to those skilled in the art, including but not limited to plasma enhanced chemical vapor deposition (PECVD), expanding thermal PECVD, ion assisted plasma deposition, magnetron sputtering, or electron beam evaporation. Application via expanding thermal PECVD is preferred.
Now with reference to
The weathering layer 118 is disposed adjacent to the substrate 116 and may include a single layer or multiple sub-layers. For example, the weathering layer 118 may be made of a film comprising polycarbonate (PC), polymethylmethacrylate (PMMA), a combination of PC/PMMA, polysiloxane, polyurethane, polyurethane acrylate, or any other suitable material. Further, the weathering layer 118 may be coated with a material such as acrylic, polyurethane, siloxane, or a combination of these types of material to provide a high weatherability, including long term ultraviolet (UV) protection. Further, silicone nano-particles may be blended into the weathering layer 118 or a siloxane co-polymer may be formed into the material making up the weathering layer 118 by polymerization. Preferably, the weathering layer 118 has a thickness between 10 and 40 micrometers. The weathering layer 118 may be as described in U.S. Pat. No. 6,797,384, which is hereby incorporated by reference in its entirety.
In addition to the substrate 116, the weathering layer 118, the conductive layer 120, and the abrasion resistant layer 122, the plastic glazing 110 may also optionally have a second weathering layer 124 located between the abrasion resistant layer 122 and the conductive layer 120. The weathering layer 124 has properties similar to the weathering layer 118. In addition, the plastic glazing 110 could optionally have a blackout layer or decorative print layer 126 disposed adjacent to the conductive layer 120 or disposed adjacent to any of the other layers. Further, a printed ink layer could also optionally be included (not shown), for example, a decorative ink layer, an ink layer that hides molding defects, or a resistive ink layer, such as a heater grid.
As shown in
Referring now to
The dielectric layers 136 function as a buffer layer (barrier plus adhesion interface) in order to provide an optical interference layer, for example, to redirect refracted light rays, as well as a chemical and mechanical durability layer to the carbon nanotube layers 138. Further, the dielectric layers 136 provide an excellent adhesion to the abrasion resistant layer 122 as well as the weathering layer 118.
The conductive layer 120 may be applied to the plastic glazing 110 by spray, pyrolysis or sputter deposition (R.F. sputtering, Magnetron sputtering, reactive evaporation, ion beam sputtering, PECVD), screen printing, or even dip coating, to prepare the transparent multi-layer interface coatings. The dip coating may be with alcoholic sols of surface modified 3-glycidoxypropyltrimethoxysilane, GPTS, SiOx and/or TiOx nano-particles.
In the alternative, if the conductive layer 120 may be provided as a carbon nanotube sheet or sheets, with the conductive layer 120 being attached to the substrate 116 by induction welding or any other suitable method. Induction welding may include providing a heat source, such as an electromagnetic coil, near the substrate 116 and the conductive layer 120 and activating the heat source to apply heat toward the substrate 116 and the conductive layer 120 until the surface of 128 of the substrate 116 sufficiently melts to fuse the substrate 116 to the conductive layer 120. Thereafter, the weather layer 118 and abrasion resistant layers can be applied as described above. The decorative layer 124 and additional weathering layer 126 may also be applied using the methods described herein, or by any other suitable method.
Now with reference to
A method of forming a the plastic glazing 210 of
Inasmuch as the foregoing disclosure is intended to enable one skilled in the pertinent art to practice the instant invention, it should not be construed to be limited thereby but should be construed to include such aforementioned obvious variations and be limited only by the spirit and scope of the following claims.
This application claims the benefit of U.S. Provisional Application Ser. No. 60/882,296 filed on Dec. 28, 2006, entitled “FUNCTIONAL LAYERS FOR POLYCARBONATE GLAZING,” the entire contents of which are incorporated herein by reference.
Number | Date | Country | |
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60882296 | Dec 2006 | US |