PURPOSE: To enhance a color forming property, raw preservability and the stability of a developed color image, in a recording material using an electron donating leuco dye and an electron acceptive compound, by using p- diarylaminophenylindolylphthalide derivative as the leuco dye.

CONSTITUTION: A phthalide derivative represented by formula (I) (wherein Ar and Ar' are an aryl group, R1 and R2 are an alkyl group or an aryl group, X is a hydrogen atom, an alkyl group, an alkoxy group, an aryloxy group or a halogen atom and Y and Z are a hydrogen atom, an alkyl group or an alkoxy group) is used as an electron donating leuco dye. This electron donating leuco dye is a colorless or light-colored crystal and also has high solubility to an org. solvent and rapidly develops a blue color upon contact with an electron acceptive substance. The developed color is extremely stable and advantageous from the aspect of the long-term preservation of recording.