Patent ID: 8470735

Claim:
A coating solution for a thermosensitive color developing layer, which comprises a colorless or pale-colored electron-donating leuco dye, a hindered phenol compound and, as an electron-accepting developer, a diphenylsulfone derivative represented by the following formula (1): wherein R 1 is a linear or branched, saturated or unsaturated hydrocarbon group having a carbon number of 1-12, R 2 -R 7 are each independently a halogen atom, or an alkyl group or alkenyl group having a carbon number of 1-12, n, o, p, q, r and s are each an integer of 0 -4, m is an integer of 0-5, and each A is independently a linear or branched, saturated or unsaturated hydrocarbon group having a carbon number of 1-12 and optionally having an ether bond, wherein the aforementioned hindered phenol compound has an average particle size (D50) of not more than 0.5 μm, and the coating solution has a color tone a* of not less than −4.0 as measured according to JIS Z 8729 and a whiteness W of not less than 62 as measured according to JIS Z 8715.