Abstract: An optical recording element comprising, in the following order, a transparent substrate bearing an optical recording layer containing a phthalocyanine dye and a gold reflective layer characterized in that the recording layer comprises sufficient sulfur or sulfur compound to prevent defects in the gold reflective layer.

Abstract: A method and apparatus for measuring optical retardation of a transparent material, such as the protective transparent cover sheet or substrate which protects the recording layer of an optical or magneto-optical disk. The method of the invention involves the steps of producing a beam of plane-polarized radiation in which the plane of polarization rotates continuously, directing such beam through a sample of transparent material where optical retardation is to be measured, and continuously comparing the angle of polarization of the beam entering the sample with the angle of plane polarization of the beam exiting the sample. Preferably, the beam and sample are continuously moved relative to another, whereby the optical retardation is measured at different points on the sample. The beam-producing step may be effected by passing a beam of circularly polarized radiation through a plane-polarizing filter while continuously rotating the filter.