Thermochromatic materials

A reversible thermochromic material comprising:

• (A) one or more electron-donating chromatic organic compounds selected from the group consisting of diaryl phthalides, indolyl phthalides, polyaryl carbinols, leuco auramines, acyl auramines, aryl auramines, Rhodamine B lactam, indolines, spiropyrans and fluorans,
• (B) one or more acidic phosphoric acid ester compounds of the following general formula (I):
• ##STR208## wherein R.sub.1 and R.sub.2, which may be the same or different, each represents hydrogen, an alkyl group having from 1 to 22 carbon atoms, a branched alkyl group having from 3 to 20 carbon atoms, an alkenyl group having from 3 to 20 carbon atoms, a cycloalkyl group having from 5 to 24 carbon atoms, or an aryl group having from 6 to 20 carbon atoms in proviso that R.sub.1 and R.sub.2 do not represent hydrogen at the same time, and M represents hydrogen, sodium, potassium, lithium, calcium, zinc, zirconium, aluminum, magnesium, nickel, cobalt, tin, copper, iron, vanadium, titanium, lead or molybdenum, and
• (C) one or more compounds selected from the group consisting of aliphatic monohydric alcohols having from 4 to 31 carbon atoms, alicyclic monohydric alcohols having from 5 to 10 carbon atoms, aromatic monohydric alcohols having from 7 to 9 carbon atoms, polyhydric alcohols having from 2 to 6 carbon atoms, polyethylene glycols having a molecular weight from 200 to 20,000, sugar alcohols, ester compounds of monocarboxylic acid having from 2 to 22 carbon atoms and aliphatic monohydric alcohols having from 1 to 22 carbon atoms, ester compounds of monocarboxylic acid having from 2 to 22 carbon atoms and phenols having from 6 to 18 carbon atoms, ester compounds of monocarboxylic acid having from 2 to 22 carbon atoms and polyhydric alcohols having from 2 to 6 carbon atoms, ester compounds of polycarboxylic acids having from 2 to 12 carbon atoms and aliphatic monohydric alcohols having from 1 to 22 carbon atoms, aromatic sulfonic acid esters having from 8 to 24 carbon atoms, aliphatic sulfonic acid esters having from 8 to 20 carbon atoms, phosphoric acid triesters of aliphatic monohydric alcohols having from 2 to 18 carbon atoms or phenols having from 6 to 15 carbon atoms, aliphatic ketones having from 5 to 35 carbon atoms, aromatic ketones having from 8 to 13 carbon atoms, fatty acid amides having from 2 to 22 carbon atoms and their N-alkyl-substituted compounds, aliphatic ethers having from 8 to 36 carbon atoms, aromatic ethers having from 12 to 20 carbon atoms, aliphatic monocarboxylic acids having from 6 to 22 carbon atoms, aliphatic polycarboxylic acids having from 3 to 12 carbon atoms, aromatic monocarboxylic acids having from 7 to 11 carbon atoms and aromatic polycarboxylic acids having from 8 to 14 carbon atoms, the ratio of Component (A):
• Component (B):
• Component (C) being 1:1/10 to 50:1 to 800 by weight, said thermochromic material undergoing reversible metachromatism at a temperature within the range from -50.degree. C. to 100.degree. C., in such a manner that said thermochromic material exhibits a high temperature side coloring type metachromatism.