PURPOSE: To obtain a capsular ink having an excellent suitability for optical reading, in the near-infrared region by incorporating microcapsules containing a specified compound as an electron-donating color former.

CONSTITUTION: The capsular ink comprises microcapsules containing a compound of the formula [wherein R1 to R4 are each lower aliphatic alkyl such as CH3, C2H5 or C3H7, lower aliphatic haloalkyl such as chloromethyl or bromomethyl, (substituted) benzyl (the substituent is one not making the compound water-soluble) or (substituted) phenyl (the substituent is one not making the compound water-soluble); X is H or lower aliphatic alkyl such as CH3, C2H5 or C3H7, lower aliphatic alkoxy such as methoxy or ethoxy, halogen or haloalkyl such as chloromethyl or CF3, alkylamino such as (di)methylamino or (di)ethylamine, phenoxy, nitro or lower aliphatic alkylthio such as methylthio or ethylthio; and n is 1-2].