Patent ID: 6853788

Claim:
A resin composition for a coating for an optical fiber comprising a radical polymerizable oligomer (A) and a radical polymerizable monomer (B), wherein said radical polymerizable oligomer (A) comprises: a radical polymerizable oligomer (A1) with a number average molecular weight of 600 to 1600 formed by reacting compounds (1) to (3) below: (1) an aliphatic polyol compound (a1) with a chain structure which may contain branch chains, with a number average molecular weight of 50 to 600, (2) a polyisocyanate compound (a2) with a ring structure, and (3) a compound (a3) with a hydroxyl group and a radical polymerizable unsaturated group within a single molecule; and a radical polymerizable oligomer (A2) formed by reacting compounds (4) to (6) below: (4) an aliphatic polyol compound (a4) with a chain structure which may contain branch chains, with a number average molecular weight of 800 to 10,000, (5) a polyisocyanate compound (a5), and (6) a compound (a3) with a hydroxyl group and a radical polymerizable unsaturated group within a single molecule; a mass ratio (A1)/(A2) of said radical polymerizable oligomer (A1) and said radical polymerizable oligomer (A2) is within a range from 20/80 to 80/20, and a concentration of urethane linkages within said resin composition for a coating for an optical fiber is within a range from 1.85 to 3.00 mol/kg.