Optical recording medium with high absorption and high reflectivity

Abstract

A thin film is formed on a plastic substrate that is preformed with recording tracks, either continuous or discontinuous, formed of a metal containing film on a thermoplastic substrate. Individually-identifiable recording elements arranged in rows are preferred. Initial reflection of the recording elements are reduced by etching or microscopically roughing the surface to produce discontinuities with dimensions less than one wavelength of the light being used to record on and read from the media. The rough surface may be created on the plastic before the application of the metallic film or the film itself may be roughened after application to the plastic. The resulting micromirrors can have about equal initial reflectivity and absorption of about fifty percent with little or no transmission. The location of the individual recording elements can be determined prior to recording and used as a gauge to permit compensation for changes in the scanning velocity of the reading or writing beam. One bit of digital information is recorded on each recording element either by leaving the reflectivity unchanged or by applying focused energy of sufficient intensity to melt or distort the plastic beneath the metal-containing film and thereby further decrease the reflectivity.