-continued  94  US  10,031,419 B2  93  The repeating unit ( c) may be a repeating unit which has  a lactone structure as a polar group.  The repeating unit which has a lactone structure is more  preferably a repeating unit which is represented by General  Formula (All) below.  In General Formula (All), Rb$_{0 }$ represents a hydrogen  atom, a halogen atom, or an alkyl group (preferably with 1  to 4 carbon atoms) which may have a substituent group.  Examples of a preferable substituent group which the  alkyl group of Rb$_{0 }$ may have include a hydroxyl group and  a halogen atom. Examples of the halogen atom of Rb$_{0 }$ include a fluorine atom, a chlorine atom, a bromine atom,  and an iodine atom.  Rb$_{0 }$ is preferably a hydrogen atom, a methyl group, a  hydroxy methyl group, and a trifluoromethyl group and  particularly preferably a hydrogen atom and a methyl group.  Ab represents a single bond, an alkylene group, a divalent  linking group which has a monocyclic or polycyclic  cycloalkyl structure, an ether bond, an ester bond, a carbonyl  group, or a divalent linking group combining the above. Ab  is preferably a single bond or a divalent linking group which  is represented by -Ab$_{1 }$-CO$_{2}$-.  Ab$_{1 }$ is a straight-chain or branched alkylene group and a  monocyclic or polycyclic cycloalkylene group and prefer› ably a methylene group, an ethylene group, a cyclohexylene  group, an adamantylene group, and a norbomylene group.  V represents a group which has a lactone structure.  As the group which has a lactone structure, it is possible  to use any group as long as the group has a lactone structure;  however, a ring lactone structure with 5 to 7 members is  preferable and a lactone structure where another ring struc› ture is condensed in a form in which a bicyclo structure and  a spiro structure are formed in a ring lactone structure with  5 to 7 members is preferable. It is more preferable to have  a repeating unit which has a lactone structure which is  represented by any of General Formulas (LCl-1) to (LCl- 17) below. In addition, the lactone structure may be directly  bonded with the main chain. Preferable lactone structures  are (LCl-1), (LCl-4), (LCl-5), (LCl-6), (LCl-8), (LCl- 13), and (LCl-14).  OH  ~  OH  ~H  0  0  OH  OH  OH  OH  OH  OH  (All)  ,4  COO-Ab-V 