Read-only optical data card

Abstract

A data card comprising a self-supporting, wallet size plastic card base upon which is disposed a film substrate layer, a highly reflective layer and an optical storage layer which is a selected photosensitive layer which has been exposed at an actinic wavelength and developed to be substantially opaque over a portion of its extent, except for an imagewise exposure pattern of clear and partially clear data marks revealing to varying extends reflectivity in the underlying reflective layer. Data spots may have one of four different reflectivities thereby representing a quadrinary digit 0, 1, 2 or 3 replacing two binary digits. The reflective layer is matched to the selected optical storage layer so that the reflective layer is highly reflective at a read beam wavelength in the red or near infrared and less reflective at actinic wavelengths either in the blue/green range or in the ultraviolet. A double-sided data card with a transparent card base and two film substrate layers, two reflective layers and two optical storage layers is also disclosed. A method for forming the data cards comprises vacuum or vapor deposition of the reflective layer over the substrate layer, disposing the photosensitive layer over the reflective layer, making an imagewise exposure of the emulsion at actinic wavelengths through a multilevel opacity mask, developing the photosensitive layer opaque and disposing the resulting strip onto the card base. The photosensitive layers may be silver-halide, diazo or vesicular film emulsions.