Patent ID: 7332109

Claim:
A thermally color-developing reversibly thermochromic pigment which shows a colored state upon heating from a discolored state and returns to the discolored state upon cooling from the colored state, said thermally color-developing thermochromic pigment consisting essentially of at least (a) an electron-donating chromic organic compound, (b) an electron-accepting compound selected from gallic acid esters and (c) a reaction medium which reversibly generates color reactions of both of the compounds within a specified temperature range, which has a melting point of less than 50° C., and which comprises one or more alcohols and one or more esters, and the weight ratio of alcohols/esters is from 80/20 to 20/80, wherein these three essential components are contained in microcapsules having an average particle diameter of from 0.5 to 50 μm, and has a ΔH value within a range of from 3 to 40° C.