IMPROVEMENT IN DURABILITY AGAINST THE REPETITION OF IMAGE-FORMATION AND DELETION BY CROSS-LINKING OF THE POLYMER IN THERMOREVERSIBLE RECORDING MEDIA

We studied the durability against the repetition of image formation an d deletion by crosslinking of the polymer in thermoreversible recordin g media composed of a polymeric film with dispersed long-chain molecul es. These media have two different optical states, transparent or ligh t scattering, depending on the thermal history. However, the media hav e the problem that the densities of the images change and the images b ecome invisible as the number of repetitions of image formation and de letion increases. By observation of the internal structures in the rec ording layers, it was clarified that the deterioration of the image is caused by the particle growth of long-chain molecules in the recordin g layer; the particles grow by the heat and shear stress applied from the thermal printhead. Next, the properties of the recording layer cro sslinked with electron beam irradiations were investigated, and it was clarified that the crosslinked recording layer did not soften very mu ch at a high temperature. A high degree of crosslinking of the layer w as obtained by applying multifunctional monomers, and the durability a gainst the repetition was improved to 1000 times, at which the image c ontrast hardly changed from that before the repetitive experiment by t he crosslinking.