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different from each other. Further, the plurality of present substituents (Rb$_{2}$ ) may be bonded to each other to thereby form a ring. 

The repeating unit having a lactone group is generally present in the form of optical isomers. Any of the optical isomers may be used. It is both appropriate to use a single type of optical isomer alone and to use a plurality of optical iso› mers in the form of a mixture. When a single type of optical isomer is mainly used, the optical purity thereof is preferably 90% ee or higher, more preferably 95% ee or higher. 

Particular examples of the repeating units each having a lactone structure contained in the resin are shown below, which in no way limit the scope of the present invention. In the following formulae, Rx represents H, CH$_{3}$ , CH$_{2}$0H or CF$_{3}$ • 

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-continued 

