PURPOSE: To enable the reproduction of a medium tone by using a recording material which is varied from a transparent state to a slightly-opaque state when heated to a prescribed temperature and is held in this state and then restored to the transparent state again when cooled down gradually, and by controlling an amount of heating of a heating body for recording.
CONSTITUTION: An image forming sheet 2 is constructed of a substrate 2a formed of a synthetic resin film and a high-molecular recording material 2b superposed thereon. A pulse current generated by a pulse generator 3 is impressed on a heating body 1, and a visible image is formed with the length and amplitude of the pulse current varied. The high-molecular recording material is constructed of a thin layer formed by blending stable polymers of two kinds or more. When the image forming sheet 2 which is in a transparent state (transmittance a1) before the start of heating is heated, the transmittance decreases at a temperature T1 or above and the material gets into a light-opaque state. At a temperature T2, the transmittance turns to be a2. When the material is heated to a temperature T3, a transmittance a3 of one medium tone can be obtained. When cooled down gradually thereafter, the material can be restored again to the transparent state of the transmittance a1.
TOYONO TSUTOMU
KUREMATSU KATSUMI
KANEKO SHUZO
