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[Chemical Formula 58] 

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As the -SO$_{2}$ - containing cyclic group, a group repre› sented by the aforementioned general formula (3-1) is pref› erable, at least one member selected from the group consist- 

-continued 

ing of groups represented by the aforementioned chemical formulas (3-1-1 ), (3-1-18), (3-3-1) and (3-4-1) is more pref› erable, and a group represented by chemical formula (3-1-1) is most preferable. 

The term "lactone-containing cyclic group" refers to a cyclic group including a ring containing a ---0----C(=O)› structure (lactone ring). The term "lactone ring" refers to a single ring containing a -O----C(=O)- structure, and this ring is counted as the first ring. A lactone-containing cyclic group in which the only ring structure is the lactone ring is referred to as a monocyclic group, and groups containing other ring structures are described as polycyclic groups regardless of the structure of the other rings. The lactone› containing cyclic group may be either a monocyclic group or a polycyclic group. 

The lactone-containing cyclic group for the structural unit (a2L) is not particularly limited, and an arbitrary structural unit may be used. Specific examples of lactone-containing monocyclic groups include a group in which one hydrogen atom has been removed from a 4-to 6-membered lactonering, such as a group in which one hydrogen atom has been removed from ~-propionolactone, a group in which one hydrogen atom has been removed from y-butyrolactone, and a group in which one hydrogen atom has been removed from 1\-valerolactone. Further, specific examples of lactone-con› taining polycyclic groups include groups in which one hydro› gen atom has been removed from a lactone ring-containing bicycloalkane, tricycloalkane or tetracycloalkane. 

With respect to the structural unit (a2), there is not particu› lar limitation to the structure of the other portion, as long as the structural unit has a -SO$_{2}$ - containing cyclic group or a lactone-containing cyclic group. The structural unit (a2) is preferably at least one structural unit selected from the group consisting of a structural unit (a2s) derived from an acrylate ester which may have the hydrogen atom bonded to the car› bon atom on the a-position substituted with a substituent and contains an -SO$_{2}$-containing cyclic group, and a structural unit (a2L) derived from an acrylate ester which may have the hydrogen atom bonded to the carbon atom on the a-position substituted with a substituent and contains a lactone-contain› ing cyclic group. 

Structural Unit (a2s): 

More specific examples of the structural unit (a2s) include structural units represented by general formula (a2-0) shown below. 

[Chemical Formula 59] 

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In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; A 0 represents ---0- or -NH-; R 28 represents an -SO$_{2}$ - containing cyclic group; and R $^{29 }$rep› resents a single bond or a divalent linking group. 

