| 摘要 |
PROBLEM TO BE SOLVED: To obtain a novel leuco dye in which hydrogen transferable by isomerization is substituted with a group which can be eliminated by the action of heat or acid and which develops a color irreversibly with high sensitivity by the action of heat or an acid. SOLUTION: This novel leuco dye is a leuco dye of formula II in which a hydrogen atom transferable by isomerization in the dye represented by formula I and its isomer is substituted with a group P which can be eliminated by the action of heat or an acid. In the formulae, (A) is an atomic group necessary to form a nitrogen-containing hetero ring and a five- or six-membered nitrogen- containing hetero ring, especially a five-membered nitrogen-containing hetero ring is preferably formed. (B) is an atomic group necessary to form a six- membered nitrogen-containing hetero ring. These hetero rings may have possible substituents and the substituents may be linked to each other to form a fused ring. X is O, S or N (wherein X may have H or a possible substituent) and O is preferred. When X is N, it may form a fused ring together with (A). |
