Provided herein is a process of fractionating ferroelectric, preferably vinylidene fluoride polymers using a solvent having at least one polarizable functional group, and a precipitant. The composition of the fractionated ferroelectric polymers is selected so as to adjust the properties of a ferroelectric film made from the polymers. Films formed using the fractionated vinylidene fluoride polymers have improved properties, particularly with respect to roughness and crystal domain size, and suitability for use in data processing devices.
A vinylidene fluoride-based resin film including polyvinylidene fluoride whose average spherocrystal diameter is less than 0.1 .mu.m that is a detection limit or lower by observation using a transmission electron microscope is provided, the average spherocrystal diameter being obtained by shaping a vinylidene fluoride-based resin in a molten state by sandwiching the resin between rollers or metal belts so as to let it cool down. Thereby, a vinylidene fluoride-based resin film and a vinylidene fluoride-based resin multilayered film having excellent transparency, weather resistance, chemical resistance, break resistance and formability are provided.
