US 10,005,868 B2  43  44  -continued  -continued  (A-2)-31  (A-2)-18  (A-2)-19  (A-2)-20  (A-2)-21  (A-2)-22  (A-2)-23  (A-2)-24  (A-2)-25  (A-2)-26 40  (A-2)-27  (A-2)-28  (A-2)-29  (A-2)-30  (A-2b)  In the above formulae,  RL $^{40 }$and RL $^{41 }$represent a hydro- gen atom or a linear, branched, or cyclic alkyl group having  1  to 8 carbon atoms. Alternatively,  RL $^{40 }$and RL 41  may be  bonded to form a ring together with the carbon atoms to  which these groups are bonded; and when the ring is formed,  RL 40  and RL 41 , which participate in the ring formation,  represent a linear or branched alkylene group having  1  to 8  carbon atoms.  RL $^{42 }$represents a linear, branched, or cyclic  alkylene group having  1  to  10  carbon atoms; Bl and Dl  represent an integer of Oto  10,  preferably Oto 5; and Cl  RL4o  RL4o  I  I  -C-0- RL4l_  B-A-t-B--f-RL4 2 -0-t;;,C--t;::,  I  DI  I  Cl  RL41  RL41  Among the acid-labile groups shown by the formula  (A-2), illustrative examples of the cyclic one include a  tetrahydrofuran-2-yl group, a 2-methyltetrahydrofuran-2-yl  group, a tetrahydropyran-2-yl group, and a 2-methyltetra› hydropyran-2-yl group.  The base resin may be linked through an acid-labile group  shown by the general formula (A-2a) or (A-2b) to form  intermolecular or intramolecular crosslinking.  (A-2)-35  (A-2)-34  (A-2)-33  (A-2)-32  -CH2-0 