Indolylphthalide compound and thermal recording material using the same

A thermal recording material comprising, on a substrate, a thermal recording layer which includes an electron-donating dye precursor and an electron-accepting compound, wherein at least one kind of the electron-donating dye precursor is an indolylphthalide compound represented by general formula (1): ##STR1##

• wherein R¹ and R² each independently represent a hydrogen atom, an alkyl group or the like, provided that R¹ and R² do not represent a hydrogen atom at the same time, and R¹ and R² may form a bond therebetween to collectively represent a single cycloamino structure; R³ represents an alkyl group or the like; R⁴ and R⁵ each independently represent a hydrogen atom, an alkyl group or an aryl group; X¹, X², X³ and X⁴ each independently represent N or CH; and Y represents an oxygen atom or a sulfur atom.