Irreversibly erasable ink composition having a discoloration agent

A thermochromic ink composition comprising core-shell microcapsules, an aqueous dispersion medium and a decolorization agent,

• wherein the core-shell microcapsules comprise a core component and a shell component, wherein the core component comprises (a) an electron-donative organic compound, (b) an electron-accepting compound, and (c) a reaction medium for causing a color-forming electron transfer reaction between the components (a) and (b) above the melting or softening point of the core component, and wherein the shell component comprises an organic polymer;
• wherein the decolorization agent is capable of irreversibly decoloring a colorant formed by the electron transfer reaction between the components (a) and (b);
• and
• wherein the decolorization agent is a polyether amine comprising a polyether backbone comprising one or more primary or secondary amino groups attached to the end of the polyether backbone.