9  US 7,511,179 B2  10  in which M3- l is a structural unit represented by the formula  (53):  N3-l is a structural unit derived from a monomer copolymer› izable with the monomer to introduce the structural unit  M3-l, and  the structural units M3-l and N3-l are contained in amounts  of from 0.1 to 100% by mole and from Oto 99.9% by mole,  respectively.  The ninth of the present invention relates to a fluorine› containing polymer having a number average molecular  weight of from 500 to 1,000,000 which is represented by the  formula (61):  (53)  (54)  wherein Rf5°  and Rf’ $^{1 }$are the same or different and each is a  perfluoroalkyl group having 1 to 20 carbon atoms; X$^{10 }$and  X $^{11 }$are the same or different and each is H, F, an alkyl group  having 1 to 20 carbon atoms or a fluorine-containing alkyl  group which has 1 to 20 carbon atoms and may have ether 20  bond; X$^{12 }$is hydrogen atom, fluorine atom, an alkyl group  having 1 to 20 carbon atoms, a fluorine-containing alkyl  group which has 1 to 20 carbon atoms and may have ether  bond, OH group or a group represented by the formula:  wherein Rf5°  is a perfluoroalkyl group having 1 to 20 carbon  atoms; X $^{10 }$and X $^{11 }$are the same or different and each is H, F,  an alkyl group having 1 to 20 carbon atoms or a fluorine› containing alkyl group which has 1 to 20 carbon atoms and  may have ether bond; R$^{50 }$is at least one selected from an  alkylene group or fluorine-containing alkylene group which  has 1 to 3 carbon atoms and constitutes a ring; R$^{51 }$and R$^{52 }$are  the same or different and each is at least one selected from a  divalent hydrocarbon group which has 1 to 7 carbon atoms  and constitutes a ring, oxygen atom, a divalent hydrocarbon  group having ether bond which has the sum of oxygen atoms  and carbon atoms of 2 to 7 and constitutes a ring, a divalent  fluorine-containing alkylene group which has 1 to 7 carbon  atoms and constitutes a ring or a divalent fluorine-containing  alkylene group having ether bond which has the sum of oxy- gen atoms and carbon atoms of 2 to 7 and constitutes a ring;  the sum of carbon atoms constituting a trunk chain in R$^{51 }$and  R$^{52 }$is not more than 7, and OH group or a group represented  by the formula:  wherein Rf5 $^{2 }$and Rf5 $^{3 }$are the same or different and each is a  perfluoroalkyl group having 1 to 20 carbon atoms; R$^{50 }$is at  least one selected from an alky lene group or fluorine-contain› ing alkylene group which has 1 to 3 carbon atoms and con› stitutes a ring; R$^{51 }$and R$^{52 }$are the same or different and each  is at least one selected from a divalent hydrocarbon group  which has 1 to 7 carbon atoms and constitutes a ring, oxygen  atom, a divalent hydrocarbon group having ether bond which  has the sum of oxygen atoms and carbon atoms of 2 to 7 and  constitutes a ring, a divalent fluorine-containing alkylene  group which has 1 to 7 carbon atoms and constitutes a ring or  a divalent fluorine-containing alkylene group having ether  bond which has the sum of oxygen atoms and carbon atoms of  2 to 7 and constitutes a ring; the sum of carbon atoms consti› tuting a trunk chain inR$^{51 }$and R$^{52 }$is not more than 7, and OH  group or a group represented by the formula:  wherein Rf5 $^{2 }$and Rf5$^{3 }$are as defined above, may be bonded to  any of carbon atoms in R 51 ; R $^{53 }$and R$^{54 }$are the same or  different and each is a divalent alkylene group having 1 or 2  carbon atoms or a divalent fluorine-containing alky lene group  having 1 or 2 carbon atoms; n50, n51, n52, n53 and n54 are  the same or different and each is 0 or 1,  wherein Rf5 $^{2 }$and Rf5 $^{3 }$are the same or different and each is a  perfluoroalkyl group having 1 to 20 carbon atoms, may be  bonded to any of carbon atoms in R 51 ; R $^{53 }$and R$^{54 }$are the  same or different and each is a divalent alkylene group having  1 or 2 carbon atoms or a divalent fluorine-containing alky lene  group having 1 or 2 carbon atoms; n50, n51, n52, n53 and n54  are the same or different and each is 0 or 1,  Rf52  I  -C-OH  ilrs3  Rf52  I  -C-OH  ilrs3  Rf52  I  -C-OH  ilrs3  )R50)nso-,Xll_(R54 n54  (R 53 )ns3-CX 10  (R 52 )n52  \  I  (Rs1lns1-C-OH  !rso  ( R50)  -cxII_(R54  /  n50  I  n54  (R 53 )ns3-CX 10  (R 52 )ns2  \  I  l(SO  ( R 51 )  -CX 12 -C-OH  n51  \  RJ’SI  -(M3-1)-(N-3-1)- (61)  in which M3-l is a structural unit represented by the formula  (54): 