The Production of magnetic and optical storage systems for consumer applications (such as video tapes and audio CDs) and for data-processing applications (such as magnetic hard drives and CD-ROMs) is currently an $80-billion industry, growing at about 10% per year, with more than 80% of that in magnetic media. The storage capacity of magnetic devices has increased enormously over the past few years, with storage densities reaching on the order of 100 gigabytes per cubic inch. Increasing these densities for faster access and greater capacity will require materials with unprecedented smoothness, defect density, dimensional stability, and mechanical reliability, as well as devices with greatly improved mechanical stability, reduced dimensions, and higher speeds. This book discusses the issues associated with the reliability of magnetic storage devices, particularly flexible media such as tapes. After a brief introduction to the physics of magnetic recording and data storage, and the basics of manufacturing magnetic media, the book turns to the production, coating, and properties of magnetic media based on polyethylene terephthalate films. This is followed by discussions of the viscoelastic properties of such films, the mechanical stresses encountered by the films in actual use or storage, and the long-term properties of stressed films in storage. This second edition has been revised throughout and includes a new chapter on ultra-thin substrates.