The mechanisms of ThermoRewrite are similar to those of traditional thermal paper, which is based on the reaction between a leuco dye and the developer. However, a specially designed developer is used. Reversible coloring and reversible erasing are achieved by controlling the amount of applied thermal energy and the cooling speed.
When the mixture of leuco dye and developer is melted at around 170oC and
then cooled rapidly, the mixture changes from non-colored to a colored
state that is stable
at ordinary temperature.
When the colored state mixture is heated again for a certain period of time at
120 -140oC and then cooled slowly, the developer creates stable crystalline states,
and the mixture reverts back to the non-colored state.
The printed image is erased by heating the media for a certain period of
time at the required erasing temperature and then cooling it slowly. An
erasing bar, erasing roll,
and thermal head are used to erase the printed image.
A new image is formed by heating the media for a very short time to the melting point (170 -180oC) and subsequently cooling it rapidly. A thermal head is used to supply energy.