Alkaline glasses with modified glass surfaces and process for the production thereof

摘要

The invention concerns alkaline glasses with modified glass surfaces. The technical object of the invention is to stabilize the modified glass surface so that reverse sodium diffusion out of the volume is substantially avoided even at elevated temperatures and in particular in the case of post-treatment procedures using a flame. Surprisingly it was found that a modified glass surface of an alkaline glass is substantially resistant to reverse sodium diffusion from the volume at elevated temperatures if the chemism within the surface has an aluminum concentration which is markedly increased in relation to the volume. The cause can be the very high level of negative formation enthalpy of albite phases. The process according to the invention is characterized in that the surface of said glasses is brought into contact with elevated levels of aluminum concentration and is subjected to a heat treatment.