Patent ID: 7517548

Claim:
A method of forming a ferroelectric thin film comprising vinylidene fluoride homopolymer which comprises the following steps (i), (ii) and (iii) (i) a step for preparing a green powder product of vinylidene fluoride homopolymer comprising crystal form I alone or as main component by subjecting vinylidene fluoride to radical polymerization in the presence of a radical polymerization initiator; (ii) a step for forming a thin film on a substrate surface by using vinylidene fluoride homopolymer which comprises crystal form I alone or as main component and is obtained from the green powder product of vinylidene fluoride homopolymer comprising crystal form I alone or as main component; and (iii) a step for subjecting the thin film of vinylidene fluoride homopolymer formed in the step of above (ii) to polarization treatment, wherein in the vinylidene fluoride homopolymers comprising crystal form I alone or as main component, when attention is given to proportions of the respective vinylidene fluoride homopolymers having crystal forms I, II or III in the green powder product of vinylidene fluoride homopolymer which are calculated by IR analysis, the proportion of vinylidene fluoride homopolymers having crystal form I satisfies both of (Equation 1): 100≧I-form/(I-form+II-form)≧50% by weight (Equation 1) and (Equation 2): 100≧I-form/(I-form+III-form)≧50% by weight (Equation 2).