PURPOSE: To titled colorless, transparent resin having a high refractive index, prepared by copolymerizing a bis(oxyalkylenephenyl)diallyl carbonate (derivative) with an aromatic ring-containing diallyl phosphate or diallyl phosphonate.

CONSTITUTION: The copolymerization of 99W1wt% bis(oxyalkylenephenyl)diallyl carbonate (derivative) of formula I (wherein R1 is H or OH, R2 is -CH2CH2O- or a group of formula II or III, X is Cl or Br, Y is -, -O-, -CO-, -SO2-, -CH2-, -CH=CH- or a group of formula IV, m and n are each 1W4, a is 0W4, and l is 1 or 2) with 1W99wt% aromatic ring-containing diallyl phosphate or diallyl phosphonate (e.g., diallyl phenylphosphate) is started at a relatively low temperature in the presence of a radical polymerization initiator (e.g., benzoyl peroxide). The temperature is increased slowly and the product is cured at a high temperature at the end of the polymerization. The polymerization is brought to completion over 2W40hr.