Effects of pre-strain applied at a polyethylene terephthalate substrate before the coating of TiO_2 film on the coating film quality and optical performance

摘要

A mold was designed to create various strains in polyethylene terephthalate (PET) substrates before the deposition of TiO_2 film to simulate deposition process on a cylindrical drum. The residual stress of the PET substrate with T1O_2 film significantly increased with increasing strain, decreasing the radius of curvature. Compared to the as-received PET substrate, there was a noticeable increase in the surface roughness in the PET/T1O_2 specimens when a large strain was applied. The formation of voids or cavities in the TiO_2 layer significantly increased the roughness of the specimen. The mean cavity size and depth increased with increasing strain. For strains ^4%, the specimen's hardness and Young's modulus factored by the voids/ cavities increased with increasing surface roughness. The optical absorption increased with increasing surface roughness before becoming asymptotic to a constant value. The strain applied to the PET substrate before TiO_2 deposition greatly affects the optical reflection, transmittance, and absorption.Crown Copyright ? 2011 Published by Elsevier B.V. All rights reserved.