| abstract |
A monophase solid solution comprising a plurality of color formers selected from the group consisting essentially of the fluoran type, phthalide type, phenoxazine type, phenothiazine type, rhodamine lactam type, leuco-auramine type, triphenylmethane type, spiropyran type, benzoxazine type, quinazoline type of color formers and mixtures thereof, preferably wherein the color forming materials are selected from the fluoran and phthalide type of color former and mixtures thereof. |