Excimer Laser Ablation and Morphology of Uniaxially Stretched Poly(ethylene-2,6-naphthalate) Films

Microstructures formed by excimer laser ablation of uniaxially stretched poly(ethylene-2,6-naphthalate) (PEN) films were analyzed as a function of draw ratio, laser fluency, and number of pulses. Before ablation, stretched films with draw ratio higher than 3 exhibit band like structure on the surface running perpendicular to the drawing direction. By TEM observation of the cross section, this structure was found to extend into the bulk region. Upon laser pulse irradiation, microstructures are formed on the surface whose pattern and pitch are similar to those for the original band like structure. With further irradiation of pulses, pleated structures were formed with pitch larger than that for the original band like structure. Spectroscopic analysis of the pleated structure was conducted on the particles scratched off from the ablated surface. It was indicated that the pleated parts were amorphous but partially elongated.