Sol-gel preparation of scratch-resistant Al2O3 coatings on float glass

Glass surfaces including those of automotive glazing show insufficient scratch resistance. In order to improve this, a sol-gel process has been developed by means of which scratch-resistant and transparent corundum coatings (alpha-Al2O3) may be deposited on glass surfaces. Coatings which were produced by using commercial boehmite(AlOOH) dispersions could also be completely transformed into alpha-Al2O3, but they were not dense enough at about 500 nm thickness. Coatings produced by an alkoxide-gel process from aluminium butoxide were dense at a thickness of maximal 100 nm and adhered very well to the glass surface which had been slightly roughened by HF etching. A scratch test with a quartz grain showed that the damage of the glass surfaces coated in this way was less than 2 % compared to that of uncoated surfaces. Transmission of these coated glasses was about 90 % in the visible wavelength range.