Method of coating a metallic article of merchandise with a protective transparent film of abrasion-resistance material

In the manufacture of a metallic article of merchandise which has a surface that enhances the aesthetic appeal of the article but is exposed to the atmosphere and frequent human contact during normal use of the article and is susceptible to abrasion damage and/or tarnishing as a result of such exposure, the method of protecting the surface of said metallic article comprising;

• placing the article in the deposition chamber of a sputtering apparatus along with a target composed of a selected non-metallic abrasion-resistant, chemically inert material selected from the group consisting of SiO.sub.2, SiC, Si.sub.3 N.sub.4, TiO.sub.2, MgO, Al.sub.2 O.sub.3, Ta.sub.2 O.sub.5, Nb.sub.2 O.sub.5, GeO, spinel, and glasses that have a Knoop hardness of over about 400 and consist essentially of mixed oxides that when sputter-deposited, forms a protective film that is substantially transparent,
• orienting the article so that the surface thereof which is to be protected will be exposed to and be coated with sputtered material from said target when the apparatus is operated, and then
• operating said apparatus and thereby sputter-depositing a substantially-transparent protective film of the said non-metallic abrasion-resistant material between about 14,000 Angstroms and 40,000 Angstroms thick on the surface of the article, the time period which said apparatus is operated and the thickness of the resulting sputter-deposited substantially-transparent protective film of abrasion-resistant material both being so correlated with the refractive index of said material so that the sputtered film is substantially devoid of undesirable discoloration effects that would otherwise be produced by optical interference of incident light rays which enter the transparent protective film, and so that the sputtered film adhers to the article.

In the manufacture of a metallic article of merchandise that is subjected to frequent human contact during normal usage of the article and is thus exposed to abrasion, corrosion and/or tarnishing by such usage and contact, the method of coating said metallic article with a different metal that enhances the aesthetic appeal of the article but is susceptible to such abrasion damage and degradation and then providing the coated surface of the article with a substantially-transparent protective film of a selected non-metallic abrasion-resistant material which does not substantially alter the color or appearance of said coated surface, said selected abrasion-resistant material having a predetermined refractive index, which method comprises;

• placing the metallic article in the coating chamber of a radio-frequency type sputtering apparatus along with (a) a quantity of the different metal to be deposited on the article, (b) a quantity of an abrasion-resistant material selected from the group consisting of SiO.sub.2, SiC, Si.sub.3 N.sub.4, TiO.sub.2, MgO, Al.sub.2 O.sub.3, Ta.sub.2 O.sub.5, Nb.sub.2 O.sub.5, GeO, spinel, and glasses that have a Knoop hardness of over about 400 and consist essentially of mixed oxides, from which the protective film is to be formed, and (c) a quantity of a selected metallic primer material which is adapted to enhance the adhesion of the coating metal,
• evacuating said chamber and, after introducing a sputtering gas therein, operating the sputtering apparatus in a first mode for a predetermined time such that a coating of sputtered metallic primer material is deposited on said article, and
• while the primer-coated article is still in the gas-filled coating chamber, sequentially operating the sputtering apparatus in second and third modes such that a layer of sputtered coating metal and a protective film of sputtered abrasion-resistant material are sequentially deposited over the primer-coated surface of the article,
• the duration of the third sputtering operation being so correlated with the refractive index of the abrasion-resistant material that the protective film of sputtered abrasion-resistant material is substantially transparent and of a thickness between about 14,000 Angstroms and 40,000 Angstroms, to prevent undesirable discoloration of the metal-coated surface of the article due to optical interference effects that would otherwise be produced by incident light rays, and to allow adhesion to the article.

In the manufacture of a metallic article of merchandise that is subjected to frequent human contact during normal usage of the article and is thus exposed to abrasion and/or corrosion damage by such usage and contact, the method of protecting the surface of said metallic article from such abrasion and/or corrosion damage during use without materially altering the color or appearance of said surface, which method comprises;

• placing the metallic article in the deposition chamber of a sputtering apparatus along with (a) a first target composed of a selected non-metallic inert material which has a thermal expansion coefficient smaller than that of the metallic article, is selected from the group consisting of SiO.sub.2, SiC, Si.sub.3 N.sub.4, TiO.sub.2, MgO, Al.sub.2 O.sub.3, Ta.sub.2 O.sub.5, Nb.sub.2 O.sub.5, GeO, spinel and glasses that have a Knoop hardness of at least about 400 and consist essentially of mixed oxides, and is adapted to form a sputter-deposited protective film of controlled thickness that is abrasion-resistant and substantially colorless and transparent and (b) a second target composed of another selected non-metallic inert material that has a thermal expansion coefficient greater than that of the protective film material and less than that of the metallic article and is also adapted to form a sputter-deposited layer that is substantially colorless and transparent,
• evacuating said chamber and, after introducing a sputtering gas therein, operating the sputtering apparatus in a first mode such that a sputtered layer of material from the second target is deposited on the metallic article and thereby provides a buffer layer which is substantially colorless and transparent and reduces thermally-induced stresses caused by the difference in the thermal expansion coefficients of the metallic article and the protective film material, and
• while the metallic article is still in the gas-filled coating chamber, operating the sputtering apparatus in a second mode such that a sputtered protective film of material from the first target is deposited over the said buffer layer,
• the operation of the sputtering apparatus being of such duration that the combination of the deposited buffer layer plus protective film of abrasion-resistant material is substantially transparent and of a thickness between about 14,000 Angstroms and 40,000 Angstroms, to prevent undesirable discoloration effects due to optical interference produced by incident light rays, to provide the desired protection against abrasion and/or corrosion damage when the metallic article is in use, and to allow both to adhere to the article.

In the manufacture of a metallic article of merchandize that is subjected to abrasion damage during normal use which progressively degrades the aesthetic appearance and quality of the article, the method of coating said metallic article with a composite coating which automatically restores the aesthetic appearance of the article during the course of such use and resulting abrasion and consists essentially of a plurality of overlapping alternately-arranged thin films of (a) a metal that enhances the aesthetic appearance of the metallic article and (b) a selected non-metallic material which is substantially transparent in thin-film form and is also of sufficient hardness to constitute an abrasion-resistant material, said films being of such thickness that they are adapted to be worn away sequentially by abrasion during normal usage of the article, which method comprises;

• placing the metallic article in the coating chamber of a sputtering apparatus along with a quantity of the metal to be deposited on the article and a quantity of said non-metallic abrasion-resistant material selected from the group consisting of SiO.sub.2, SiC, Si.sub.3 N.sub.4, TiO.sub.2, MgO, Al.sub.2 O.sub.3, Ta.sub.2 O.sub.5, Nb.sub.2 O.sub.5, GeO, spinel and glasses that have a Knoop hardness over about 400 and consist essentially of mixed oxides,
• evacuating said coating chamber and, after introducing a sputtering gas therein, sequentially operating the sputtering apparatus in first and second modes for predetermined times such that a thin film of sputtered metal of predetermined thickness is first deposited on said article and then coated with a thin film of sputtered non-metallic abrasion-resistant material which is also of predetermined thickness,
• the operation of the sputtering apparatus in said second mode being of such duration that the film of sputtered non-metallic abrasion-resistant material is not only substantially transparent but is also substantially colorless and thus protects the underlying film of sputtered metal without substantially altering the aesthetic appearance of the sputtered metal film, and then
• repeating the sequential operation of said sputtering apparatus in said first and second modes for said predetermined times until a predetermined number of overlapping alternately-arranged thin films of sputtered metal and adherent, substantially colorless and transparent protective thin films of sputtered non-metallic abrasion-resistant material are deposited on the metallic article and thus form said composite coating.