Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
2000-04-03
2002-08-27
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C427S250000, C427S405000, C427S409000, C427S412300, C427S412400, C427S412500, C428S031000, C428S425500, C428S425800, C428S450000
Reexamination Certificate
active
06440541
ABSTRACT:
BACKGROUND OF THE INVENTION
Electrically continuous thin metal layers or films, formed on rigid dielectric substrates by vacuum metallization, have been long used to give substrates a reflective metallic appearance. To slow corrosion of the metal layer, the layer was typically top coated with a clear, colorless dielectric polymeric coating. However, once the top coats are damaged or experience water infiltration, these metal films have experienced widespread corrosion of the metal layer.
More recently, electrically discontinuous metal layers have been developed which appear as continuous metal layers to the naked eye, which are less susceptible to widespread corrosion and which can be applied to flexible substrates. These electrically discontinuous layers consist of discrete metallic islands, which are vacuum deposited on the substrate, wherein the islands are separated by channels. These islands and channels are then topcoated with a dielectric polymeric coating to separately encapsulate each island and to prevent corrosion of the metal islands. However, under weathering conditions the topcoat has experienced a loss of adhesion (e.g., peel) from the metal islands and substrate in the channels allowing water infiltration.
To provide adequate adhesion of the top coat to the discontinuous layer, the metal layer has been etched with a caustic (e.g., sodium hydroxide solution) to remove metal deposited in the channels between the islands to provide a larger substrate surface area for bonding with the top coat. However, caustic etching has resulted in the formation of blackened areas in the metal layer.
Therefore, a need exists for a means of vacuum metallization of rigid and flexible substrates wherein the top coat will adhere to the metallized layer without etching and etch side effects, and wherein the top coat is less susceptible to water infiltration and the loss of adhesion over time and weathering.
SUMMARY OF THE INVENTION
This invention relates to a metallized article comprising a substrate having a layer of electrically discrete metallic islands of a corrosion prone metal disposed on the substrate. Prefrerably a polyurethane basecoat layer is formed on the substrate prior to forming the metallic islands thereon. A crosslinked polyurethane top coat, bound to an organosilane, preferably an epoxy silane, is disposed on and encapsulates the discrete metallic islands. The organosilane is also is is bound to the metallic islands.
The advantage of this invention is that it improves the bonding of polyurethane top coat to the basecoat or substrate, and to the metal layer deposited on the substrate, without caustic etching of the metal layer. This invention also increases the water resistance (hydrophobicity) of the top coat by increasing polymeric crosslinking within the top coat, thereby enhancing corrosion resistance.
DETAILED DESCRIPTION
The substrates of the present invention include any substrate upon which a reflective metallic coating is desirable. These substrates can be rigid or flexible. Further, these substrates and may or may not be electrically conductive.
Typically, substrates used in the present invention include vehicular/automotive trim applications, sheet stock, sports equipment, clothing and any other items suitable for decoration by inclusion of a reflective metallic surface.
Examples of suitable nonconductive (dielectric) substrates include a wide variety of plastic substrates which are dielectric materials (non-conductive) including thermoplastic materials, thermosetting materials and elastomeric materials, such as thermoset polyurethane, flexible elastomers which may be a natural or synthetic thermoplastic or thermoset polymer having an elongation of at least 30%, polyolefins, as polyethylene, polypropylene, polybutylene or a rubber/polypropylene blend, ABS (polyacrylonitrile-butadiene-styrene), thermoplastics as polyvinyl chloride, Surlyn (DuPont), polyester, polyester elastomer, and the like. Articles made of plastic substrates include, for example, automobile parts such as exterior moldings, bumper guards, dual pulls, mirror housings, grill headers, light bezels, gear shift bezels, door pulls, steering wheel emblems and other exterior and interior automotive trim components. Other plastic articles can be used, for example in the plumbing trade, for household hardware applications, for home decoration, trucks, motor cycles and marine parts.
Examples of suitable conductive substrates include metals, such as aluminum, aluminum alloy, carbon steel, cast iron, brass, copper, nickel, nickel alloy, stainless steel, magnesium alloy and zinc based materials. Articles comprising metal substrates include, for example, faucets, knobs, handles, cutlery, files and blades, golf clubs and irons, hammers, jet blades, rifle barrels, skate blades, camera components and luggage. Preferably, the metal substrate is a vehicle wheel.
It is to be understood with respect to many of the metallic substrates used in the present invention, in particular for wheels, that these substrates may be pretreated prior to the present application process. Such pretreatment may optionally include pickling and/or the application of corrosion resistant coatings. Those corrosion resistant coatings can be phosphate corrosion resistant coatings or epoxy primers such as “E-coat”, i.e., a cathodic electrocoat or a coating utilizing powder particles. With respect to aluminum and magnesium alloys, such a corrosion resistant coating may include well known chromium conversion coatings and the like.
It is also understood that an adhesion promoter may be applied to non-metallic substrates, such as chlorinated polyolefin to thermoplastic olefins. Typically, a coating thickness of about 0.1 mils to about 0.4 mils is applied.
The preferred substrates for the present invention are flexible substrates.
The metals that are used to form the layer of metallic islands are metals, or surface oxidized metals that will give a bright surface. Suitable metals are corrosion prone metals including tantalum, copper, silver, nickel, chromium, tin and aluminum and alloys thereof, and the like. Preferably, the metallic islands contain indium, indium alloys and/or indium oxides.
The layer of metallic islands is formed by depositing metal on the substrate, or coated substrate, by thermal evaporization, sputtering, ion plating, induction heating, electron beam evaporization and like methods. More uniform coverage is obtained, particularly around corners, edges or recesses if the metallization occurs in a chamber containing an inert gas such as argon.
The method for forming a layer of metallic islands, on a substrate, a treated substrate or a coated substrate, is described in U.S. Pat. Nos. 4,407,871 and 4,431,711 which are incorporated herein by reference.
Metallization produces a substrate that has a layer of discrete metallic islands deposited thereon. The discrete metallic islands are round in nature and have a thickness, or diameter, small enough to make the metallic film electrically non-conductive, as there are channels between the islands such that there is typically no conductivity between the islands, and alternately large enough to reflect enough light to make the coated article appear as a metal article to the naked eye. Typically, the thickness of the metallic islands will be between about 25 and about 4000 Angstroms (Å), preferably 500-3000 Å. Most preferably, the thickness is between about 500 Å-1200 Å.
In the present invention the layer of metallic islands on the substrate is encapsulated by a top coat. Preferably, a prime coat and/or basecoat was also applied to the substrate prior to metallization.
Typically, the coating composition for the prime coat, basecoat and/or top coat, after curing is a polyurethane or a polyester polyurethane. A resin suitable for forming basecoats and top coats useful in the present invention is described in Example 1.
To increase the adhesion of the polymeric top coat to the metal layer, particularly the metallic islands, and typically, to at least partially cr
Humphrey William M.
Murano Adam
Grossman Tucker Perreault & Pfleger PLLC
Nakarani D. S.
Textron Automotive Company Inc.
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