Patent ID: 7220809

Claim:
A fluorine-containing polymer (I) having functional group represented by the formula (1): M A (1) in which the structural unit M is a structural unit derived from a fluorine-containing ethylenic monomer and represented by the formula (2): wherein X 1 and X 2 are the same or different and each is H or F; X 3 is H, F, CH 3 or CF 3 ; X 4 and X 5 are the same or different and each is H, F or CF 3 ; Rf is a fluorine-containing alkylene group having 1 to 5>C═O units and 1 to 50 carbon atoms excluding carbon atoms of >C═O units or a fluorine-containing alkylene group having ether bond which has 1 to 5>C═O units and 2 to 100 carbon atoms excluding carbon atoms of >C═O units; a is 1, 2, or 3; b and c are the same or different and each is 0 or 1, the structural unit A is a structural unit derived from monomer copolymerizable with the structural unit M, and the structural unit M and the structural unit A are contained in amounts of from 0.1 to 100% by mole and from 0 to 99.9% by mole, respectively.