摘要:
Disclosed are a diethylenicallyunsaturated monomer represented by the following formula [Ia]: wherein n is an integer of from 1 to 10, and a and b each represent 0 or an integer of from 1 to 4, and an optical resin which is substantially insoluble and infusible and has a refractive index η D of at least 1.62, and which is obtained by polymerizing a monomer comprising 50 to 100% by weight of this diethylenically unsaturated monomer.