Sep. 10,2020  6  US 2020/0285152 Al  as ally! and 3-cyclohexenyl, aryl groups such as phenyl,  1-naphthyl and 2-naphthyl, and aralkyl groups such as  benzyl and diphenylmethyl. In these groups, some hydrogen  may be substituted by a moiety containing a heteroatom  such as oxygen, sulfur, nitrogen or halogen, or some carbon  may be replaced by a moiety containing a heteroatom such  as oxygen, sulfur or nitrogen, so that the group may contain  a hydroxyl, cyano, carbonyl, ether bond, ester bond, sulfonic  acid ester bond, carbonate bond, lactone ring, sultone ring,  carboxylic  anhydride  (-C(=0)---0-C(=O)-)  or  haloalkyl moiety.  [0059]  The preferred cations in the onium salts having  formula  (1)  are those having the formulae (la) to (ld).  [0061]  In formula (le), R 3  is a C$_{1}$-C$_{40 }$monovalent hydro› carbon group which may contain a heteroatom. The mon› ovalent hydrocarbon group may be straight, branched or  cyclic and examples thereof are shown below, but not  limited thereto.  [0060]  In formula  (1),  z- is an organic anion. The pre› ferred organic anion has the formula (le).  (le)  (la)  (lb)  (le)  (ld)  Herein m$^{1 }$and m$^{2 }$are each independently an integer of  1  to  4. 