Filling behaviors of optical glass during roll-to-plate (R2P) hot embossing process with assembled rigid sheet roller mold

Efficient and high-quality continuous production of glass micro-structure elements meets significant application requirements in various fields such as electronics, architecture, medicine, automotive and optics. The roll-to-plate (R2P) hot embossing process is a promising and cost-effective manufacturing technique for the rapid fabrication of high-quality and large-area glass micro-structures. However, the filling deformation of glass during the R2P hot embossing process is complex due to the unique contact interface between mold and glass, as well as the viscoelastic characteristic of softened glass. To reveal the deformation characteristics and filling pattern of glass during R2P hot embossing process, a controlled variable method test with 3 factor 5 level was conducted in the home-made machine. The sensitivity of processing parameters (roller temperature, roller speed, and roller pressure) for the surface morphology of the rolled glass was analyzed. The deformation profiles and defect evolution of glass micro-structures under different process conditions were investigated using scanning electron microscopy (SEM) and white light interferometry. The experimental results demonstrated that the height of the micro-structures exhibited a positive correlation with the roller temperature and embossing force, and an inverse correlation with the embossing speed. The experimental results show that the interface friction behavior of the glass mold in the R2P hot embossing process can be reflected by the roller torque. The low embossing speed, high embossing temperature, and high embossing speed will all lead to interface instability. The microstructure formation types under different process parameters are summarized as flat-peak-filled pattern, curvature-peak-filled pattern, bump-filled pattern. This work provides a theoretical guidance for the efficient and high-quality production of glass microstructures.