Method of strengthening glass and increasing the scratch resistance of the surface thereof

Abstract

Abstract A combined treatment for newly formed glass bodies for increasing the mechanical strength thereof, and for increasing the scratch resistance of the glass surface. Newly formed glass bodies at elevated temperatures, usually somewhat above 800* F. are sprayed or otherwise coated with stannic chloride, or a compound of titanium or zirconium which pyrolyzes to form a metal oxide film on the glass surface. While still at elevated temperatures the glass bodies are sprayed with an aqueous solution of a potassium compound which volatilizes and deposits potassium salt which acts through the previously deposited tin, titanium or zirconium coating to effect exchange of larger potassium ions for smaller sodium ions in a surface layer of the glass to produce a compressive stress layer. The glass is held at elevated temperature below its strain point, or cooled relatively slowly in a lehr, whereby this ion exchange proceeds to a sufficient degree while the glass is still at elevated temperature. When the glass has cooled it is washed to remove excess unexchanged potassium from the glass surface to expose the tin, titanium or zirconium coating at the exterior of the glass surface, and a final coating of an olefin polymer, such as polyethylene is applied to bond with and coact with the metal oxide coating to substantially improve the scratch resistance of the glass surface. Various transparent organic coatings may be employed in the final coating.

Inventors

• 👤 J Poole
• 👤 H Snyder
• 👤 M Boschini

Bibliographic Details