Patent ID: 8867885

Claim:
An optical waveguide forming epoxy resin composition comprising: (A) a liquid epoxy resin; and (B) a photoacid generator; wherein the liquid epoxy resin (A) comprises a liquid epoxy resin represented by the following general formula (I) as a major component thereof in a proportion of 50 to 75 wt % based on the overall amount of a resin component: wherein R 1 and R 2 are each a hydrogen atom or a methyl group; wherein R 3 to R 6 are each a hydrogen atom, a methyl group, a chlorine atom or a bromine atom; wherein X is a C 2 to C 15 alkylene group, an ethyleneoxy group, a di(ethyleneoxy) group, a tri(ethyleneoxy) group, a propyleneoxy group, a propyleneoxypropyl group, a di(propyleneoxy)propyl group or a tri(propyleneoxy)propyl group; wherein n is a natural number and has an average value of 1.2 to 5, wherein the optical waveguide forming epoxy resin composition is free from a diluent component irrelevant to a curing reaction, wherein the optical waveguide forming epoxy resin composition is free from a solid epoxy resin component, and wherein the optical waveguide forming epoxy resin composition has a viscosity satisfying the following conditions: (x) the viscosity is 12.6 to 99.7 Pa·s as measured at 25° C.; and (y) the viscosity is 1.2 to 5.2 Pa·s as measured at 50° C. with heating.