Calculation of Excimer Laser Induced Temperature Profiles in PET, PBT, and PS Polymer Films
Temperature profiles in PET (Polyethylene Terephtalate), PBT (Polybutylene Terephtalate), and PS (Polystyrene) films created due to excimer laser irradiation were estimated analytically from the model of semi-infinite heat flux and numerically from the model based on 1-D heat equation. For the analytical estimation of temperature profile, we initially assumed that all of the irradiated excimer laser energy was confined in surface, and the energy was considered as a constant heat flux during the laser irradiation period. Calculation results showed that this assumption is somewhat inadequate for polymer materials especially for the polymers with low UV absorption coefficients, because we could not exclude the absorption of excimer laser energy in bulk. In order to reduce the error from this assumption, temperature profiles were estimated from numerical solution, which included a heat generating function representing absorption of excimer laser beam in polymer. Temperature measurement results showed a good agreement with this calculation, but only when ablation was not significant (i.e., for PS).