Abstract: An ink composition comprising a microparticulate fluorescent material which can emit a high brightness fluorescent light by ultraviolet ray and has a predetermined nanosize is provided. The ink composition comprises a microparticulate fluorescent material represented by the formula YVO4:A, wherein A is a rare earth metal other than yttrium, which can emit a fluorescent light by the excitation with ultraviolet ray. The fluorescent material has an average primary particle size of 30 to 400 nm and has not been calcined. The fluorescent material is prepared by, for example, mixing Composition (I) containing a yttrium compound, a compound of rare earth metal other than yttrium and a complex forming compound in water with Composition (II) containing a vanadium compound in water and then reacting them.

Abstract: An ink composition comprising a microparticulate fluorescent material which can emit a high brightness fluorescent light by ultraviolet ray and has a predetermined nanosize is provided. The ink composition comprises a microparticulate fluorescent material represented by the formula YVO4:A, wherein A is a rare earth metal other than yttrium, which can emit a fluorescent light by the excitation with ultraviolet ray. The fluorescent material has an average primary particle size of 30 to 400 nm and has not been calcined. The fluorescent material is prepared by, for example, mixing Composition (I) containing a yttrium compound, a compound of rare earth metal other than yttrium and a complex forming compound in water with Composition (II) containing a vanadium compound in water and then reacting them.

Abstract: Colored resin particles which are colored uniformly and densely and are excellent in fluorescence, light fastness and washing resistance are prepared by copolymerizing in an aqueous medium in the presence of a water-soluble fluorescent dye (1) a polymerizable unsaturated monomer A having a low affinity for the fluorescent dye, (2) a polymerizable unsaturated monomer B having at least one cyano group and (3) a polymerizable unsaturated monomer C having a high affinity for the fluorescent dye and being insoluble or barely soluble in water, which is represented by the following general formula ##STR1## wherein X is a hydrogen atom or a methyl group.