Aqueous dispersion of fluorine-containing copolymer

An aqueous dispersion of a fluorine-containing copolymer comprising, as copolymerization units,

• (A) a (meth)acrylate represented by the general formula:
• [CH2═CHRCOO(NH)rR1NR2R3R4]+Y− [I]
• wherein R is a hydrogen atom or a methyl group;
• R1 is a linear, branched, or alicyclic alkylene group having 1 to 30 carbon atoms or a phenylene group;
• R2, R3, and R4 are the same or different and each is a linear, branched, or alicyclic alkyl group having 1 to 30 carbon atoms or an aralkyl group;
• r is 0 or 1;
• and Y− is an anionic group;
• (B)
• a perfluoroalkylalkyl(meth)acrylate represented by the general formula:
• CmF2m+1CpH2p(NR′SO2)qOCOCR═CH2 [IIa]
• wherein R is a hydrogen atom or a methyl group, R′ is an alkyl group having 1 to 5 carbon atoms, m is an integer of 4 to 14, p is an integer of 1 to 4, and q is 0 or 1;
• a polyfluoroalkylalkyl(meth)acrylate which is prepared by replacing some of the fluorine atoms in the perfluoroalkyl group in the above perfluoroalkylalkyl(meth)acrylate with hydrogen atoms;
• or
• a polyfluoroalkyl(meth)acrylate represented by the general formula:
• CnF2n+1(CH2CF2)a(CF2CF2)b(CH2CH2)cOCOCR═CH2 [IIb]
• wherein R is a hydrogen atom or a methyl group, n is an integer of 1 to 6, a is an integer of 1 to 4, b is an integer of 1 to 3, and c is an integer of 1 to 3;
• (C) benzyl(meth)acrylate;
• (D) a fluorine-free polymerizable monomer other than components (A) and (C);
• and
• (E) a crosslinkable group-containing polymerizable monomer,
• wherein 0.1 to 1.0 wt. % of component (A), 10 to 80 wt. % of component (B), 5 to 80 wt. % of component (C), 1 to 30 wt. % of component (D), and 0.3 to 30 wt. % of component (E), each in the fluorine-containing copolymer, are copolymerized using a water-soluble polymerization initiator.