22 июля, 2015 
Malyar The leuco dyes of this new class are peculiar in that they are capped at their 10-position by another dye moiety. They are in fact colored leuco dyes which on oxidation are split into two different dye fragments: one of the dyes is destined for the receptor sheet while the oxidized leuco hopefully remains on the donor sheet. The capping dye is selected among sublimable dyes whereas the azine dyes being cationic in nature would be less mobile. They have been developed to address some problems encountered in thermographic and photothermographic systems.24 Representative examples of this class of leuco dye developers are compounds 65, 66, and 67.
|
|
The thiazine, oxazine, and phenazine leuco dyes that generate yellow, magenta, and cyan dyes are used in conjunction with an oxidant such as metal nitrate or silver halide in a multilayer construction to form the basis of a very simple multicolor imaging system. Two main drawbacks are the different reactivities of the various leuco dyes and the presence of unreacted leucos in the final image which lead to high image background caused by air oxidation. There has been a great interest in transferring the dye image to a receptor to achieve a clean and stable color image leaving behind unwanted by-products. Numerous dye developers, not necessarily related to leuco dyes, have been described whereby the three primary dyes (Y, M, C) are linked to a common type of developer to ensure that the three colors are generated at the same rate.24 The developer is immobilized with hydrophobic long ballasting groups and the transferable dyes are usually small and highly mobile.
The characteristics of the azine leuco dyes have been adapted to the development of this new class of leuco dye developers. Sublimable or diffusible dyes are used to cap the 10-position of the leuco thiazine, oxazine, or phenazine dye where the splitting takes place as a result of imaging. The leuco dye moieties are rendered less mobile with long aliphatic chains.
Опубликовано в рубрике 