| abstract |
Successive areas of recording medium, having a precursor (methylene blue) reduceable with a low level of energy, are exposed to monochromatic (red) laser output for forming a record. The precursor is carried in a thin thermoplastic film from a substrate, has a color complementary to the color of the laser output, and is opaque to the wave length of energy to be used for sensing the record. A latent reducing agent included in the recording medium is carried in a thin thermoplastic film supported from the substrate. It releases a reducing agent which react with the precursor upon exposure of the medium to the laser output to reduce the precursor to a state (leuco form) which is permeable (transparent) to the wave length of the record sensing energy. Spontaneous reduction of the precursor is prevented, according to a modified embodiment of the disclosure, by an inert barrier comprised of a thermoplastic film sandwiched in the recording medium between the films containing the precursor and the reducing agent. |