85  US 9,360,753 B2  86  -continued  Herein R 26 - 1  and R 26 - 2  each are hydrogen, a C$_{1}$-C$_{4 }$ alkyl,  alkoxy, alkanoyl or alkoxycarbonyl, hydroxyl, nitro, C$_{6}$-C$_{10 }$ aryl, halogen or cyano group, R is as defined above, and m26  and n26 are an integer of 1 to 4.  Examples of the monomer from which recurring units (al)  having an acid labile group of formula (A-3)-26 substituted  thereon are derived are shown below.  The acid labile group R $^{2 }$in recurring units (al) may be a  group having the general formula (A-3)-26.  Ar"ir--?-x  VZ-0<  (A-3)-26  X  0  X  0  0 