Coating composition for optical fiber

摘要

In the coating composition for a optical fiber of the present invention, a polyurethane (meth)acrylate oligomer (A), which is based on a urethane prepolymer having an equivalent ratio of NCO group in a polyisocyanate (a) to OH group in a polyol (b) of more than 3.0, is used and the oligomer (A) has a mixing weight ratio of an oligomer (d) having a number average molecular weight of 800 or less to an oligomer (e) having a number average molecular weight of 1,000 or more of 30/70 - 70/30. The coating composition of this invention has a low viscosity, and therefore, is suitable for a rapid fiber-drawing in a production of an optical fiber. Further, a cured material obtained from the coating composition of the present invention has both a high elastic modulus and a high elongation, which properties are required for a hard material, and has a slight change of elastic modulus with a change of temperature to improve a long-term reliability of an optical fiber.