Microplastic embossing process: experimental and theoretical characterizations

A microplastic hot. embossing process is characterized by measuring both the height and radius of curvature of hot-embossed cylindrical microlenses with various process conditions. including processing pressure, temperature and time. Polycarbonate is used its the plastic material and silicon mold inserts with circular openings of 100-200 mum in diameter are used to fabricate plastic microlenses. Experimentally, the processing pressure has little effect on the radius of curvature of microlens under a fixed processing temperature. The relationship between the height of the microlens and the applied pressure can be modeled linearly and the interfacial stress is derived empirically. The height and radius of curvature of microlenses with respect to temperature changes is modeled by the Arrhenius function and empirical formulae are derived. It is found that the activation energy is a constant independent of processing temperature or size of opening holes on the mold insert. Furthermore, the processing time constants for both the height and radius of curvature of microlenses are the same that implies both parameters reach steady state simultaneously. (C) 2002 Elsevier Science B.V. All rights reserved.