A thermochromic ink composition is provided for use on security documents such as checks which provides a reversible color change in response to heat. The ink composition includes a thermochromic aqueous slurry and an ink vehicle comprising either a phenolic modified rosin and a compatible oil, a styrene...http://www.google.se/patents/US6413305?utm_source=gb-gplus-sharePatent US6413305 - Thermochromic ink composition
