Patent ID: 8008397

Claim:
A rubber latex formed from a copolymer of a conjugated diene, an ethylenically unsaturated aromatic compound and optionally, a crosslinking agent, said crosslinking agent being selected from the group consisting of divinylbenzene, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, aryl methacrylate, and 1,3-butylene glycol diacrylate, wherein the rubber latex has a multi-layer structure with an inner-layer rubber latex having a refractive index of 1.54-1.59 and an outer-layer rubber latex having a refractive index of 1.51-1.54, and wherein the monomeric ratio averaged over the entirety of said rubber latex is about conjugated diene : (ethylenically unsaturated aromatic compound + crosslinking agent) =3:1 by weight, wherein a difference between the refractive index of the inner-layer rubber latex and that of the outer-layer rubber latex is greater than or equal to 0.0222.