Aluminium articles having anodic oxide coatings and methods of coloring them by means of optical interference effects
AssigneeAlcan Research and Development Limited
InventorsPeter G. Sheasby, Graham Cheetham, Rainer W. M. Stuckart, Tarun K. S. Gupta
Life of this patent
Estimating the term…
Abstract
The invention provides aluminium articles having porous anodic oxide films colored by means of an optical interference effect. In FIG. 4, the article 10 carries a first anodic oxide film 12 with pores 14 enlarged at their inner ends 20 and containing deposits 22. The products may be made by growing a second anodic oxide film 26 underneath the deposits 22 which are preferably of acid-resistant material. X is at least 26 nm, Y is preferably at least 60 nm, Z is preferably 15 nm to 200 nm, (Y+Z) is preferably 75 nm to 600 nm, and W is preferably at least 15 nm.
Claims15
An aluminium article having an anodic oxide coating on its surface including a first porous oxide film having a thickness of at least 3 microns, the pores of said film having inorganic pigmentary material deposited therein, the average size of the said deposits at their outer ends, with reference to the aluminium/aluminium oxide interface, being at least 26 nm, the article being coloured by virtue of optical interference, wherein there is present a second oxide film formed between the inorganic pigmentary deposits having a height, and their outer ends being separated from said interface by a distance of from 75 nm to 600 nm, for imparting to said article surface a visually perceptible colour produced by optical interference effects.
A method of treating an aluminium article, which method comprises providing an article having an anodic oxide coating on its surface including a first porous oxide film having a thickness of at least 3 microns, the pores of said film having inorganic pigmentary material deposited therein, the average size of the said deposits at their outer ends, with reference to the aluminium/aluminium oxide interface, being at least 26 nm, the article being coloured by virtue of optical interference, and forming a second oxide film between the bottoms of the said deposits and the aluminium/aluminium oxide interface, said deposits having a height, and their outer ends being separated from said interface by a distance of from 75 to 600 nm, for imparting to said article surface a visually perceptible colour produced by optical interference effects.
A method of forming an aluminium article having an oxide coating coloured by optical interference, which method comprises the steps of
- (a) forming a porous anodic oxide film at least 3 microns thick on the surface of the article,
- (b) if the pores have an average cross-section of less than 26 nm, increasing the cross-section of the pores towards their inner ends, with reference to the aluminium/aluminium oxide interface, to an average size of at least 26 nm,
- (c) forming deposits of inorganic pigmentary material in the thus enlarged regions of the said pores so that the average size of the outer ends, with reference to the aluminium/aluminium oxide interface, of the said deposits is at least 26 nm,
- (d) effecting further aluminium oxide formation beneath the said deposits so as to increase the distance of the deposits from the aluminium/aluminium oxide interface, said deposits having a height and their outer ends being separated from said interface by a distance of from 75 nm to 600 nm, for imparting to said article surface a visually perceptible colour produced by optical interference effects.
Dependencies are inferred from the claim text.