| 摘要 |
PROBLEM TO BE SOLVED: To obtain a photocurable resin composition capable of providing a cured product having a low elastic modulus, and useful as a covering material for optical fiber, and further to provide a covering material for optical fiber. SOLUTION: This ultraviolet-curable resin composition comprising a urethane acrylate oligomer and a polymerization initiator is featured in the urethane acrylate oligomer having a polyoxyalkylene ether structure branched to three branches at least in the core part, in which each of the branched chain part of the structure has 2,500-10,000 number average molecular weight. The photocurable resin composition can provide a cured product having a tensile modulus lower than that of a conventional photocurable resin composition, and thereby can achieve a low tensile modulus of <=0.1 kgf/mm2 required for the cured product in a primary covering of optical fiber, and provide the reliability to microbending or the like which is one problem. Accordingly, the composition is extremely useful as a covering material for optical fiber.
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