High index curable photochromic composition and its process

A high refractive index core resin composition comprising

• (i) 2 to 70 parts by weight of at least one first compound corresponding to formula (I):
• 3
• wherein
• n and n′ independently are 0-30,
• R1-R4 independently represent H or C1-C6 alkyl,
• X is O, S, SO2, CO2, CH2, CH═CH, C(CH3)2 or a single bond, and
• y1-y8 independently represent H, OH, halogen, mercaptan or C1-C4 alkyl,
• (ii) 2 to 80 parts by weight of at least one second compound corresponding to formula (II):
• 4
• wherein
• m is at least 1, and
• R5-R7 independently represent H or C1-C6 alkyl;
• (iii) 2 to 60 parts by weight of a reactive diluent selected from the group consisting of 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, isobornyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, vinyl benzoate, vinyl 4-t-butyl benzoate, styrene, divinyl benzene, and mixtures thereof;
• and
• (iv) 2 to 60 parts by weight of a multi-functional (meth)acrylate or (meth)acrylate derivative with three or more acrylate functional groups selected from the group consisting of trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, glyceryl tri(meth)acrylate pentaerythritol tetra(meth)acrylate, di-trimethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, penta(meth)acrylate ester and mixtures thereof;
• per 100 total parts by weight of components (i), (ii), (iii) and (iv).