Abstract: Disclosed are a scratch color-developable ink comprising an electron-donating colorless or light-color dye precursor, an electron-accepting color developer and a varnish, wherein a solid particle component contained therein has an average particle diameter of 0.3 to 25 ?m, a scratch color-developable ink comprising an electron-donating colorless or light-color dye precursor, an electron-accepting color developer and a varnish, wherein an azaphthalide compound is contained as the electron-donating colorless or light-color dye precursor, and an invisible information printed sheet obtained by printing invisible information on a support with the above scratch color-developable ink.