Method for producing polymer compound, polymer compound, and photoresist resin composition

A method for producing a polymer compound, the method comprising the step of filtering a resin solution comprising a polymer compound through a filter,

• the filter being approximately devoid of strongly acidic cation-exchange groups and developing a positive zeta potential,
• the polymer compound comprising:
• a monomer unit (a);
• and
• a monomer unit (b) comprising a group capable of releasing a moiety thereof by an action of an acid to develop solubility in an alkali,
• the monomer unit (a) comprising at least one monomer unit selected from the group consisting of monomer units represented by Formulae (a1) to (a3):
• wherein R is, independently in each occurrence, selected from hydrogen, halogen, and optionally halogenated C1-C6 alkyl;
• A is, independently in each occurrence, selected from a single bond and a linkage group;
• X is, independently in each occurrence, selected from non-bond, methylene, ethylene, oxygen, and sulfur;
• Y is selected from methylene and carbonyl;
• and R1 to R3 are, identically or differently, selected from hydrogen, fluorine, optionally fluorinated alkyl, optionally protected hydroxyl, optionally protected hydroxyalkyl, optionally protected carboxy, and cyano.