PURPOSE: To ensure that a compound obtained is stable to light, preservation and heat, by incorporating a specified indolyldiphenylmethane derivative as a color former in the title paper.
CONSTITUTION: An indolyldiphenylmethane derivative of general formula (I) is incorporated as a color former in the title paper. The compound of general formula (I) forms a color through an irreversible chemical reaction on making contact with a benzoquinone derivative subst. by an electron-attractive group of general formula (II). In the formulas, each of R1 and R2 is hydrogen, an alkyl, cycloalkyl, alkylene, aryl or aralkyl, each of R3 and R4 is an alkyl, aryl or aralkyl, and the compoun of formula (I) may further has alkyl, alkoxyl, aryl or halogen as a substituent group in its molecule. Each of X1WX4 represents hydrogen, a halogen, carboalkoxyl, carboaryloxyl, carboaralkyloxyl, acyl, nitro or subst. sulfonly respectively.
AOKI MARIO
ASANO MAKOTO
