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[0066] In formulae (A)-1 and (A)-2, x+ is a sulfonium cation having the formula (Aa) or ammonium cation having the formula (Ab). 

[0067] In formula (Aa), R 6 , R 7 and R 8 are each indepen› dently fluorine, chlorine, bromine, iodine, or a C$_{1 }$-C$_{20 }$ monovalent hydrocarbon group which may contain a het› eroatom. R 6 and R 7 may bond together to form a ring with the sulfur atom to which they are attached. The C$_{1 }$-C$_{20 }$ monovalent hydrocarbon group may be straight, branched or 

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cyclic, and examples thereof include C$_{1 }$-C$_{20 }$ alkyl, CcC$_{20 }$ aryl, and C$_{7}$ -C$_{20 }$aralkyl groups. In these groups, some or all hydrogen may be substituted by hydroxyl, carboxyl, halo› gen, cyano, nitro, sultone, sulfone, or sulfonium salt-con› taining moiety, or an ether bond, ester bond, amide bond, carbonyl moiety, carbonate moiety or sulfonate bond may intervene between carbon atoms. 

[0068] Preferred examples of the sulfonium cation having formula (Aa) are those having the formulae (Aa)-1 and (Aa)-2. 

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[0069] In formulae (Aa)-1 and (Aa)-2, R$^{13 }$to R$^{18 }$are each independently a C$_{1 }$-C$_{14 }$ monovalent hydrocarbon group. Examples of the monovalent hydrocarbon group include C$_{1 }$-C$_{14 }$ alkyl, C$_{2}$-C$_{14 }$ alkenyl, CcC$_{14 }$ aryl, and C$_{7}$-C$_{14 }$ aralkyl groups. In these groups, some or all hydrogen may be substituted by hydroxyl, carboxyl, halogen, cyano, nitro, sultone, sulfone, or sulfonium salt-containing moiety, or some carbon may be replaced by ether bond, ester bond, carbonyl, amide bond, carbonate or sulfonic ester bond. L is a single bond, methylene, ether bond, thioether bond, or carbonyl group. The subscripts z 1 to z 6 are each indepen› dently an integer of O to 5. Examples of the alkyl, alkenyl, aryl and aralkyl groups are as exemplified above for R 5 • 

[0070] Examples of the sulfonium cation having formula (Aa) are shown below, but not limited thereto. 

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