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Proceedings Paper

Direct thermal dyes
Author(s): Edward Ehlinger
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Paper Abstract

Direct thermal dyes are members of a class of compounds referred to in the imaging industry as color formers or leuco dyes. The oldest members of that class have simple triarylmethane structures, and have been employed for years in various dyeing applications. More complex triarylmethane compounds, such as phthalides and fluorans, are now used in various imaging systems to produce color. Color is derived from all of these compounds via the same mechanism, on a molecular level. That is, an event of activation produces a highly resonating cationic system whose interaction with incident light produces reflected light of a specific color. The activation event in the case of a direct thermal system is the creation of a melt on the paper involving dye and an acidic developer. The three major performance parameters in a thermal system are background color, image density, and image stability. The three major dye physical parameters affecting thermal performance are chemical constituency, purity, and particle size. Those dyes having the best combination of characteristics which can also be manufactured economically dominate the marketplace. Manufacturing high performance dyes for the thermal market involves multi-step, convergent reaction sequences performed on large scale. Intermediates must be manufactured at the right time, and at the right quality to be useful.

Paper Details

Date Published: 1 July 1990
PDF: 8 pages
Proc. SPIE 1253, Hard Copy and Printing Materials, Media, and Processes, (1 July 1990); doi: 10.1117/12.19827
Show Author Affiliations
Edward Ehlinger, Hilton Davis Co. (United States)


Published in SPIE Proceedings Vol. 1253:
Hard Copy and Printing Materials, Media, and Processes
Joseph Gaynor, Editor(s)

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