New method to improve the stability of thermal paper

Abstract

Recently direct thermal recording systems have become very popular and are increasingly used in various fields. Consequently, strong demand has arisen for a thermal paper that has good response to heat, the background and images thereon having high stability and a strong resistance to various chemicals and various solvents. Many attempts have been made to overcome the difficulties described above. However such attempts have had a tendency to lower response to heat and further to be insufficent with respect to the stability of solvents. Therefore, we have developed a new method for production of a heat sensitive layer having in itself high resistance to various solvents and also using specific new materials. The most important aspect of our new method consists in the use of specific developers with very low solubility in organic solvents and very strong developing activity. Originally, we intended to use the high developing power of zinc salicylate derivatives, these generally having a high solubility in solvents. But now our efforts have been concentrated on lowering the solubility of salicylate. Finally, we found some very specific salicylate that has a very poor solubility in almost all solvents. We have now succeeded in providing a much more reliable thermal paper which has stronger resistance to various kinds of chemicals.