PURPOSE: To obtain a resin composition having rapid curing rate, low refractive index, excellent flexibility and good bonding to a core and suitable as clad coating of optical transmission, by containing a specific (meth)acrylic acid ester.
CONSTITUTION: 1mol. compound expressed by formula I or formula II (n and m are 4W10; l is 1 or 2) is reacted with 1W5mol. (meth)acrylic acid in an organic solvent (e.g., benzene) in the presence of a catalyst (e.g., P- toluenesulfonic acid) and polymerization inhibitor at 70W150°C to afford (meth) acrylic acid ester (A). Then 20W100wt.% component A is blended with (B) 0W80wt.% ethylenic unsaturated compound [e.g., polyurethane (meth)acrylate] and (C) 0W10wt.% photopolymerization initiator (e.g., 1-hydroxycyclohexyphenyl ketone) to provide the coating agent for optical fiber consisting of resin composition. Then clad material for optical transmission is coated with the above- mentioned coating agent having 10W300μ thickness.
SASAHARA KAZUNORI
YOKOSHIMA MINORU
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