10  US 8,691,490 B2  9  -continued  -continued  (2-2)  (13)  (14) (15) (2-1)  (2-1)’  (In the formula, each R $^{9 }$independently represents a hydro- gen atom, a fluorine atom, a methy  1  group or a trifluoromethy  1  group; X 1  represents an acid-labile group; G represents an  oxygen atom or a carbonyloxy group (-C(=O)O-).)  As above, the polymer of the present invention can further  include any one or more kinds of repeating units represented  by the foregoing general formulae  (11)  to (15) in addition to  a repeating unit represented by the foregoing general formula  (  4),  preferably a repeating unit represented by the foregoing  general formula (5).  Further, the present invention provides a method for pro› ducing a polymer, wherein at least, the polymer is obtained by  copolymerizing a monomer represented by the following  general formula (2-1) and a monomer represented by the  following general formula (2-2).  Further, the present invention provides a method for pro- ducing a polymer, wherein the polymer is obtained by blend› ing a polymer containing a repeating unit represented by the  following general formula (2-1 )’ and a polymer containing a  repeating unit represented by the following general formula  (2-2)’.  As above, in the case that a monomer represented by the  foregoing general formula (2-1) and a monomer represented  by the foregoing general formula (2-2) are copolymerized,  there exist two kinds of anions and two kinds of cations  mixedly in the polymer matrix, and thus it is considered that  an onium salt formed of a combination of the cation in the  general formula (2-1) and the anion in the general formula  (2-2) can exist. That is, a polymer including a repeating unit  represented by the foregoing general formula (  4)  can be  obtained by copolymerizing a monomer represented by the  foregoing general formula (2-1) and a monomer represented  by the foregoing general formula (2-2).  (In the formula, xa- represents a non-nucleophilic anion;  za+ represents a lithium ion, a sodium ion, a potassium ion, an  ammonium ion, an iodonium ion or a sulfonium ion; R 4 ,  R 5 ,  R 11 , R 21 , R 31 , W 1 ,  W$^{2}$,A 1 ,  p, q, k, mandnrepresentthe same  as before.) 