A Study On A Novel Thermo-sensitive Imaging Material

This study is an attempet 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 system 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. The new reactive emulsifier is first made: which contains RAFT (reversible addition-fragmentation transfer), triethanolamine hydrochlorid (TEA·HCl), carboxyl and ester groups. This emulsifier has preferably emulsification capability due to the presence of hydrophobic group and hydrophilic group. This can make the latex more stable.Secondly, molecular design and synthesis of the water-soluble film-forming binder polymers were carried out. Several binder polymers were prepared, which include water soluble phenolic resin bearing tertiary amino oxide groups, phenolic resin modified with acrylic acid, the resin containing acrylic acid and ester unit and so on. These resins are all water-soluble. Results showed that the resins containing acrylic acid and ester unit have good combined properties and compatibility with different IR dyes.Selection, dispersion and modification of IR dyes were tried. Five kinds of organosoluble IR dyes were chosed and modified with surfactants in order to that could be used in the water-born imaging system. In the experiment, several methods such as the physical adsorbing method, ion exchangingmethod as well as seeded emulsion polymerization were ever used to improve the dispelrsion / solubility of the IR dyes.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. However, there still exist some problems such as the wetting and spreading properties of the coating solution on the aluminium plate, which need further improvement.