Insulating layer composition for substrate, and prepeg and substrate using the same

Disclosed herein are an insulating layer composition for a substrate, including a soluble type liquid crystal thermosetting oligomer, a metal alkoxide compound, and graphene oxide, and an insulating film and a substrate using the same. The insulating layer composition according to the present invention can effectively lower a coefficient of thermal expansion thereof, and thus, a dimensional change due to heat can be minimized when the insulating layer composition is used as an insulation material of the substrate, resulting in a substrate having improved thermal stability.