This invention generally relates to coatings applied to metallic surfaces. In particular, the invention relates to coatings applied to a metallic surface of a portable electronic device to preserve a cosmetic finish of the portable electronic device.
Computers have long been known as ugly gray machines. Fortunately, over the last decade computer companies have put efforts into enhancing the appearance of computers. A beautiful and colorful example was the birth of the iMac by Apple Computers, Inc. In addition, computers are becoming increasingly smaller reaching the size of hand-held computers. Recent examples are the development of the Pocket PC or devices such as the OQO handheld computer.
These developments have placed an increased demand on the manufacturing process to deliver smart-looking devices with a good look-and-feel and cosmetic finish. For example, logos, emblems or other features are now an important cosmetic part of the computer casing. Unfortunately, with these developments, the production cost of these computers still needs to go down to remain competitive in the computer business.
One problem that needs to be addressed in this art relates to coating of a metallic computer case to preserve a cosmetic finish applied to the metallic surface. At present many coating techniques focus on the prevention of oxidation, such as plating, anodizing, alodining, chromating, passizating, phosphatizing, bonderizing, sputtering, physical vapor deposition (PVD), as well as painting with a variety of different paint chemistries (polyurethane, UV curing, etc.). Many of the existing techniques are applied in complex batch processing operations that can involve multiple chemical baths, multiple stages, extreme temperatures, high energy, specialized equipment, comparatively long cycle times, or otherwise complex processes. Additionally, many of these coatings, once applied, change the cosmetic appearance of the metallic surface; i.e. change the color, gloss, texture, shine, or other surfaces qualities of the underlying cosmetic finish. In the particular case of clear coatings many of the existing techniques have shortcomings, such as: (i) not providing sufficient adhesion to last over time, or (ii) not sufficiently preventing oxidation over time. Both shortcomings affect the cosmetic finish of a computer device or more generally of a portable electronic device. Accordingly, it would be considered an advance in the art to develop new ways to preserve cosmetic finishes applied to a metallic surface, especially in portable electronic devices.
The present invention provides new ways for preserving a cosmetic finish applied to a metallic surface, in particular that of a portable electronic device. The portable electronic device is made out of an aluminum alloy, a steel alloy, a titanium alloy, or a magnesium alloy, which are materials that easily oxidize and/or tarnish. A cosmetic finish is applied to the metallic surface, after which a clear adhesion promoting layer is applied. The clear adhesion promoting layers is preferably applied prior to any visible oxidation of the cosmetic finish. A clear wear resistant layer is subsequently applied over the clear adhesion promoting layer.
In one variation, the metallic surface is first painted after which a portion of the painted surface could be removed to expose the cosmetic finish. In another variation, the metallic surface has a raised portion representing e.g. a logo, emblem or other feature. In this case, the paint and a small amount of the metal substrate from the raised portion could be removed to expose the cosmetic finish.
The application of the clear adhesion layer includes mixing a primer with a catalyst reducer, The primer is based on 2-Methyl-1-propanol, Methyl Isobutyl Ketone and Methyl n-Amyl Ketone. The catalyst reducer is based on 2-Propanol, Methyl Ethyl Ketone and Phosphoric Acid. The primer is reduced with a diacetone alcohol to prepare a solution for pad printing of the clear adhesion promoting layer, or is reduced with a spray thinner to prepare a solution for spray coating of the clear adhesion promoting layer. The spray thinner is based on Toluene, 2-Propanol, 2-Methyl-1-propanol, and Methyl n-Amyl Ketone.
The application of clear wear resistant layer includes mixing a top coat with a catalyst. The top coat is based on Diisobutyl Ketone and n-Butyl Acetate. The catalyst is based on Light Aromatic Hydrocarbons, 1,3,5-Trimethylbenzene, 1,2,4-Trimethylbenzene, n-Butyl Acetate, Hexamethylene Diisocyanate, and Hexamethylene Diisocyanate Polymer, The top coat is reduced with a diacetone alcohol to prepare a solution for pad printing of the clear wear resistant layer, or reducing the top coat to prepare a solution for spray coating of the clear wear resistant layer. The reducer is based on Toluene, Isopropyl Acetate and n-Butyl Acetate.
Applying the present method to a portable electronic device results in having a portable electronic device with a cosmetic finish protected by a clear adhesion promoting layer with a thickness of 5 to 10 microns, and a clear wear resistant layer with a thickness of 25 to 35 microns.
The present invention together with its objectives and advantages will be understood by reading the following description in conjunction with the drawings, in which:
The goal of the present invention is to apply a cosmetic finish to the metallic surface of logo 106 and/or other metallic surface parts of the case 102. Such a cosmetic finish could be applied by, for instance, brushing, blasting, sanding, graining, machining, polishing, grinding, buffing, peening, cutting or etching of the metallic surface. The cosmetic finish could also be applied by removing a layer from the metallic surface, patterning the metallic surface or casting, molding, forming or rolling of the metallic surface. A person of average skill in the art would readily appreciate that various other techniques could be used to apply the cosmetic finish, all of which are part of the scope of the invention.
If left untreated the metallic surface will loose its cosmetic value due to oxidation and tarnishing. Therefore, clear coating the cosmetically finished metallic surface is crucial. The preferred methods for clear coating according to the present invention is printing (pad printing) or spray painting. The clear coating process includes the application of two layers: (i) a clear adhesion promoting layer on the metallic surface with cosmetic finish, and (ii) a clear wear resistant layer on the clear adhesion promoting layer. The coating should provide: 1) strong adhesion when applied directly to finished substrate, 2) excellent long-term surface protection and wear resistance, and 3) simple and flexible production application.
The following examples provide further details of the clear coating process, which results in the preservation of the cosmetic finish of the portable electronic device or computer case.
A fast drying, pretreatment type, 2 package acid catalyzed washcoat could be used to promote adhesion for a top clear coat. The washcoat, such as Raw Look Primer (F63VXC-20474-4365) available from the Sherwin-Williams Company (Cleveland Ohio, U.S.A.), could be used both for pad printing and for spray coating. The washcoat has excellent clarity, free of lead and chromates. The washcoat could be applied directly to the desired surface of a metallic substrate. A catalyst reducer, such as Wash Primer Catalyst Reducer (R7K44) available from the Sherwin-Williams Company, is mixed with the washcoat.
The washcoat (e.g., Raw Look Primer) and the catalyst reducer (e.g., Wash Primer Catalyst Reducer) are mixed in a ratio of 469 to 100 (e.g., 469 grams to 100 grams) by weight or 1280 to 279.4 (e.g., 640 ml to 139.7 ml) by volume before application. In the example of pad printing, the mixture of the washcoat and the catalyst reducer is then reduced 30%-50% with a Diacetone Alcohol (e.g., Diacetone Alcohol (R6K24) from the Sherwin-Williams Company). In the example of spraying, the mixture of the washcoat and the catalyst reducer can be reduced up to 150% with a spray thinner (e.g., Spray Thinner (R7XXC-20475) available from the Sherwin-Williams Company).
The washcoat (e.g., Raw Look Primer (F63VXC-20474) of the Sherwin-Williams Company) could include by weight: 64% of 2-Methyl-1-propanol, 17% of Methyl Isobutyl Ketone, and 5% Methyl n-Amyl Ketone. The catalyst reducer (e.g., Wash Primer Catalyst Reducer (R7K44) of the Sherwin-Williams Company) could include by weight: 50% of 2-Propanol, 44% of Methyl Ethyl Ketone, and 3% of Phosphoric Acid.
The spray thinner (e.g., Spray Thinner (R7XXC-20475) of the Sherwin-Williams Company) could include by weight: 44% of Toluene, 14% of 2-Propanol, 31% of 2-Methyl-1-propanol, and 11% of Methyl n-Amyl Ketone.
The Raw Look Primer (F63VXC-20474) promotes excellent adhesion for clear coats, is exceptionally fast for air dry, has excellent pad printing or spray capability, clear aesthetic design capability, excellent clarity and excellent flow capability, and is free of lead and chromates. Typically, the Raw Look Primer has a specific gravity of 0.83, 14% of solids in weight, 11% of solid in volume, and has a viscosity of 3100 centipoise.
Polane Falling Sand Clear (F63VXC-17924) of the Sherwin-Williams Company could be used as the clear wear resistant layer. The Polane Falling Sand Clear could include by weight: 15% of Diisobutyl Ketone and 30% of n-Butyl Acetate. Before application, a catalyst for the wear resistant coat, such as POLANE* HS Plus Exterior Catalyst (V66V55) of the Sherwin-Williams Company, is mixed with the clear wear resistant coat material (e.g., Polane Falling Sand Clear) a ratio of 231 to 50 by volume or 838 to 203 by weight.
The catalyst, such as POLANE* HS Plus Exterior Catalyst (V66V55) of the Sherwin-Williams Company, could include by weight: 1% of Light Aromatic Hydrocarbons, 1% of 1,3,5-Trimethylbenzene, 2% of 1,2,4-Trimetbylbenzene, 5% of n-Butyl Acetate, 0.2% of Hexamethylene Diisocyanate (max.), and 90% of Hexamethylene Diisocyanate Polymer.
In the example of pad printing, the mixture of the clear wear resistant coat and the catalyst is reduced with a Diacetone Alcohol (e.g., Diacetone Alcohol (R6K24) from the Sherwin-Williams Company). In the example of spraying, the mixture of the clear wear resistant coat and the catalyst can be reduced (e.g., using POLANE* 66 Reducer (R7K84) of the Sherwin-Williams Company).
An example of a reducer for the wear resistant coat is e.g. POLANE* 66 Reducer (R7K84) of the Sherwin-Williams Company, and could include by weight: 20% Toluene, up to 36% of Isopropyl Acetate, and up to 45% of 123-86-4 n-Butyl Acetate. Polane Falling Sand Clear has exceptional falling sand resistance (35 liters/mil avg. #16 silicon carbide) and rub resistance (900-1000 CDI8900 Rub Resistance). Typically, the Falling Sand Clear has a specific gravity of 0.99, a viscosity of 1300 centipoise, 62.6% of Solids in Weight, 60° Gloss of over 90, and a pencil hardness of 2H.
The clear coating process could distinguish the following method steps:
The result is a tough anti-oxidant coating that preserves the look of the substrate underneath. A cure time of about 12 hours in a well-ventilated area at room temperature conditions (e.g., 25 degree Celsius) is preferred prior to quality control and packaging for shipment. The coated parts can continue to cure and release volatile compounds for up to one month after the final cure. Therefore, the packaging of the portable electronic device with the coatings of the present invention should preferably be breathable. For example, if the devices are individually wrapped in bags, bags could then be perforated with slits or holes to allow out-gassing. Open trays that allow airflow can also be used.
The present invention has now been described in accordance with several exemplary embodiments, which are intended to be illustrative in all aspects, rather than restrictive. Thus, the present invention is capable of many variations in detailed implementation, which may be derived from the description contained herein by a person of ordinary skill in the art. All such variations are considered to be within the scope and spirit of the present invention as defined by the following claims and their legal equivalents.
This application is cross-referenced to and claims the benefit from U.S. Provisional Application 60/612,890 filed on Sep. 24, 2004, which is hereby incorporated by reference.
Number | Date | Country | |
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60612890 | Sep 2004 | US |
Number | Date | Country | |
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Parent | 11234860 | Sep 2005 | US |
Child | 12245108 | US |