Glass coating for adhesion prevention

The structuring of glass in hot forming processes is accompanied by massive problems during the separation of mould and glass after the embossing process. Achieving a geometrically accurate transfer of the structure in the lowest possible embossing time requires a replication at low viscosities and isothermal annealing. Especially at high temperatures, this leads to increased adhesion and sticking effects. Tool coatings improve the long-term stability of the mould but do not prevent the glass from sticking. The conditions which cause the glass to stick to the mould were subject of numerous studies, partially with conflicting results, and hence are not completely understood. It is, however, only generally accepted that the glass viscosity has the strongest effect on the sticking behaviour, inhibiting hot embossing at low viscosities. In contrast to other studies, a new coating strategy was developed to decouple the viscosity in the glass volume from the sticking behaviour at the glass surface. Instead of the mould the glass substrate was coated with a thin, adhesive and ductile layer. The subject of the presented research activities was optimizing the layer thickness for reaching a maximum ductility and a minimum adhesion of the glass substrate to the tool. The aim was to find suitable layer systems with an optimal coating for applications in micro-optics and micro-fluidics. In addition, the influence of the coatings on the function of the embossed components was investigated.