Electrofax®printing with gallium phosphide diodes

Experimental green-light-emitting GaP diodes are shown to be capable of adequately exposing Electrofax^®paper with exposures of 400 µs. The diodes used were prepared from nitrogen-doped epitaxial junction material; the Electrofax paper was sensitized with a rose-bengal dye. Linear arrays of seven diodes spaced 250 µm apart have been constructed and used to print characters on a moving strip of Electrofax paper developed by a reversal liquid toner system. Measured image resolution is better than 40 elements/cm. Data are given on the electrical characteristics of a single diode and an array, and on the dependence of image density and dimensions on diode currents. The observed performance of the diodes indicates the feasibility of making a high-quality printer using light-emitting diodes (LED´s) and Electrofax paper.