| 摘要 |
PROBLEM TO BE SOLVED: To obtain a leuco dye which can develop a color monomolecularly without the aid of an excessive color developer and has improved color development. SOLUTION: Ethyl 3-oxobutanoate is reacted with 2-hydroxy-1-naphthaldehyde in a stream of a hydrogen chloride gas to obtain the corresponding ethyl ester. This ester is hydrolyzed into a carboxylic acid, and this acid is treated with dihydropyran in the presence of a p-toluenesulfonic acid to obtain a leuco dye monomer. This monomer is polymerized at 0-100 deg.C, desirably, 30-100 deg.C in the presence of a radical initiator to obtain a leuco dye of the formula: LD-(A-P1)n. In the formula, LD is an acid-sensitive leuco parent nucleus; -A is an acidic group (-AH) residue selected from among -SO3H, -CO2H, and -p(=O)(OH)xRy; R is H or a substituent; x and y are such that x=1 and y=1 or that x=2 and y=0; P1 is a protective group which can leave under the action of light, heat, or an acid. |
