There are many requirements for glasses used as displays, touch screens, as well as in solar, transport and security applications. In addition to transparency and scratch resistance, weight optimisation is especially aspired. Achieving constant mechanical properties while reducing the glass thickness, the strength of the glass must be increased. While the theoretical glass strength is very high, the strength in applications is one to two orders of magnitude lower. During the life span new contact damage in the order of several micrometers constantly arise and act as cracks in the sense of the stability theory of Griffith. Therefore, an active protection against unstable crack growth is required. The method of chemical strengthening may be used to introduce compressive stresses near the surface of the glass via ion exchange processes. The current state of the art provides the immersion of a sodium-containing glass in a potassium salt melt. Hence crack growth is only possible by overcoming these additional compressive stresses. A technological alternative to using a salt bath is presented. After spraying an aqueous salt solution on the pre-heated glass surface, the ion exchange between the glass and the salt layer can be realised in conventional annealing furnaces. The mechanical strength of the prepared ion exchanged glasses are compared with conventionally chemical strengthened glasses.
