▎ 摘　　要

NOVELTY - A composite film comprises a functionalized graphene bonded with a polymer. The graphene is functionalized with functional group(s) configured to bond with the polymer. USE - Composite film is used for substrate sheet of printed circuit board of electronic device (all claimed). ADVANTAGE - The composite film has excellent flexibility. The device using the film is lightweight and has excellent reliability. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: (1) production of composite film; and (2) electronic device, which comprises a printed circuit board comprising substrate sheet(s) which comprises functionalized graphene bonded with a polymer.