Study On Affinity-changeable Thermo-sensitive Imaging Material

This study is an attempt to develop a new thermal-sensitive imaging material based on the core-shell latex particle which possessed a hydrophobic core and a hydrophilic shell. This imaging material typically consists of core-shell latex particle, water-soluble film-forming binder polymer, infrared sensitizing dye and other additives. The imaging mechanism is that the core-shell particles will undergo affinity switchment (i.e. from the hydrophilic state to the hydrophobic one) at elevated temperatures when exposed to IR laser beam. The exposed area would become water insoluble whereas the the unexposed area could be developed with neutral water. So, the imaging material is environment friendly. This work mainly contains the following parts:Further improvement of the preparation of core-shell latex particles was made according to the previous work. In this research, two kinds of oligomers which have a thiocarbonothioylthio group and a carboxy group were synthesized and used as the reactive surfactant to prepare core-shell microcapsules through soap-free emulsion polymerization. The microcapsule is amphiphilic, which had a hydrophobic core and a hydrophilic charged shell. Through the comparison of the core-shell microcapsules which were polymerized with two kinds of reactive surfactant, we can conclude that the size of latex particles is closely related to molecular weight. The results of angle contact show that these kinds of core-shell microcapsules (latex particles) are affinity changeable after being heated at a suitable temperature.Secondly, we focused on the synthesis of two kinds of water soluble phenolic resin which possessed tertiary amine oxide side groups. These polymers are not only have good hydrophilic and coating properties ,but also have the behavior of solubility change under different thermal treatment conditions.It was found that the modified epoxy phenol-formaldehyde resin can still dissolve in the water after being heated at 80℃for a long time, and the solubility remained almost unchanged. But upon being heated at the temperature of 140℃or above, the solubility gradually became poor or even completely insoluble in water . The decomposed modified epoxy phenolic resin had good adhesive strength and excellent film forming property.A kind of organosoluble IR dyes is synthesized and modified with surfactants in order to that could be used in the water-born imaging system. Preparation and properties of the coating solution were also attempted. The contents of the main ingredients (latex particles, IR dyes and film forming binder polymers, etc) and their effects on the properties of the coating solutions were studied. The recipes of the coating solution were investingated and optimized.Finally, the thermo-induced imaging properties were investingated. The coating solution was casted on aluminum substrates and dried to afford uniform films. Then the films were exposed by IR laser beams and developed with neutral water to give the clear images with high resolution and contract.