Numerical modeling method for UV imprint process simulation using thermoviscoelastic constitutive equations

A novel numerical modeling method for UV imprint process simulation using thermoviscoelastic constitutive equations is proposed. The purpose of the process simulation is to predict transfer errors caused by UV shrinkage when a soft mold such as polydimethylsiloxane (PDMS) is used. The proposed method introduces an imaginary physical quantity, “virtual temperature,” as a measure of UV reaction progress and then replaces the UV curing/shrinkage phenomenon with the thermoviscoelastic cooling solidification/contraction phenomenon. A series of rheometry experiments are conducted for a general UV resin to identify the material properties of the UV resin as a thermoviscoelastic material. For the purpose of verification, the proposed method with the identified material properties is applied to the simulation of the rheometry experiments. Moreover, for the sake of validation, it is also applied to an actual UV imprinting process for a micromirror array molding with a PDMS mold. These analysis results prove the effectiveness of the present method in predicting transfer errors caused by UV shrinkage.