Patent ID: 7538177

Claim:
A crosslinkable fluorinated aromatic prepolymer which is obtained by subjecting either one or both of a compound (Y-1) having a polymerizable double bond (A) and a phenolic hydroxyl group and a compound (Y-2) having a polymerizable double bond (A) and a fluorinated aromatic ring, to a condensation reaction in the presence of a HF-removing agent, with a fluorinated aromatic compound (B) represented by the following formula (1): (wherein n is an integer of from 0 to 3, each of a and b which are independent of each other, is an integer of from 0 to 3, each of Rf 1 and Rf 2 which may be the same or different from each other, is a fluorinated alkyl group having at most 8 carbon atoms, and F in the aromatic ring represents that hydrogen atoms of the aromatic ring are all substituted by fluorine atoms), and a compound (C) having at least 3 phenolic hydroxyl groups, the respective phenolic hydroxyl groups not being present in the same aromatic ring, and which has polymerizable double bonds (A) and ether bonds and has a number average molecular weight of from 1×10 3 to 5×10 5 , wherein a cured film having a thickness of about 3 μm on a glass substrate, formed from a wet film of a coating composition comprising said prepolymer and a solvent on the substrate, removing the solvent and curing, exhibits a light transmittance at a wavelength of 400 nm of at least 98%.