Resin composition for optical waveguide, dry film, optical waveguide, and photoelectric composite wiring board using same

1. A resin composition for an optical waveguide, comprising:

(A) an epoxy resin constituted by a solid epoxy resin with one or less hydroxyl group in a molecule, and a liquid epoxy resin with one or less hydroxyl group in a molecule;

(B) a curing agent with one or less hydroxyl group in a molecule; and

(C) a nanosize silica sol, and

containing no compound including two or more hydroxyl groups in a molecule as a resin component.

2. The resin composition for an optical waveguide according to claim 1 , wherein the compounding ratio of the solid epoxy resin and the liquid epoxy resin in the epoxy resin (A) is 90 to 70:10 to 30, as a mass ratio.

3. The resin composition for an optical waveguide according to claim 1 , wherein the content of the nanosize silica sol (C) is 20 mass % to 80 mass %, as converted to a solid fraction of silica, with respect to the total content of the resin components.

4. The resin composition for an optical waveguide according to claim 1 , wherein silica with an average particle size of 5 nm to 20 nm is used in the nanosize silica sol (C).

5. The resin composition for an optical waveguide according to claim 1 , wherein the curing agent (B) is a cationic curing agent, and the silica sol (C) has a pH of 4.7 to 8.5.

6. A dry film obtained by coating the resin composition for an optical waveguide according to claim 1 on a base material film followed by drying.

7. An optical waveguide constituted by the resin composition for an optical waveguide according to claim 1 or the dry film according to claim 6 .

8. A photoelectric composite wiring board comprising the optical waveguide according to claim 7 .