Issued: January 7, 1997
Also Canadian patent 2,201,397 issued July 2, 2002
Inventors: Lyle D. Small, Ithaca, NY and Gerald Highberger, Linden, NJ
Assignee: Chromatic Technologies, Inc., 4320 Northpark Drive, Suite B, Colorado Springs, CO 80907
The present invention comprises a series of discoveries related to the problems associated with formulations that destroy the color change properties of thermochromic encapsulated dyes. One aspect of the present invention is the discovery of a method of correcting these formulations to allow the addition of thermochromic dyes. Certain solvents destroy the dye, therefore any aldehydes, ketones, and diols, and most aromatic compounds should be removed from the formulation and if needed they should be replaced with solvents preferably having a large molecular weight (i.e. greater than 100 and low reactivity). Secondly, the formulation should be adjusted to be neutral (i.e. 6.5-7.5 pH) or have a low acid value. These two adjustments will allow the thermochromic dyes to added to the formulation without a loss of its color change properties.
See also Patent Nos. 5,997,849 and 6,139,779 for other thermochromic ink patents from CTI.
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