The present invention provides a moulding composition, which includes: a plurality of bead polymers dispersed in at least one matrix polymer; wherein the bead polymers: have an average particle size of 5 to 40 &mgr;m, and have a refractive index nD at 20° C. which is different from a refractive index nD at 20° C. of said matrix polymer; and wherein the bead polymers are prepared by a process, which includes: contacting: at least one polymerizable mix which includes at least 50% by weight of at least one (meth)acrylate monomer, at least one aluminum compound, and an aqueous phase, to prepare a mixture; dispersing the mixture at a shear rate ≧103 s−1 to form a dispersion, wherein the dispersion is stabilized by the aluminum compound; and polymerizing to produce the bead polymers having an average particle size of 5 to 40 &mgr;m.