Substantially flat surfaced emulsion particles polymerized vinyl monomer, having a concavity in at least one of the flat surfaces, a diameter D of from 0.1 to 5.0 .mu.m, and a particle diameter thickness d ratio (d/D) of 1.2 to 5.0 prepared by the step of (1) aqueous emulsion polymerizing a first vinyl monomer or mixture of monomers (a) to form vinyl polymer seed particles; and (2) aqueous emulsion polymerizing a second vinyl monomer or mixture of monomers (b) in the presence of the vinyl polymer seed particles and a non-aqueous organic solvent having a surface tention to water at 20.degree. C. of 48 dyne/cm or more, in a weight ratio of monomer (a) to monomer (b) of 0.5/99.5 to 50/50; and are useful in high performance recording material, paint compositions and paper coating compositions.