Annealing of Poly(ethylene terephthalate)-Film-Based Magnetic Recording Media for Improved Dimensional Stability

PET-film-based magnetic recording media are subject to a number of dimensional instabilities, a major one being in-plane shrinkage due to stress relaxation in the biaxially oriented substrate. Annealing the media allows stress relaxation without significantly degrading other properties and makes possible the use of higher track densities. Effects of annealing on mechanical properties, coefficients of thermal and hygroscopic expansion, and long-term dimensional stability of the media are described.