content_image/886469.jpg content_image/886470.jpg content_image/886471.jpg content_image/886472.jpg content_image/886468.jpg content_image/886474.jpg
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). 

<img src='content_image/886469.jpg'>

<img src='content_image/886470.jpg'>

<img src='content_image/886471.jpg'>

<img src='content_image/886472.jpg'>

Herein m$^{1 }$and m$^{2 }$are each independently an integer of 1 to 4. 

[0060] In formula (1), z- is an organic anion. The pre› ferred organic anion has the formula (le). 

<img src='content_image/886468.jpg'>

[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. 

<img src='content_image/886474.jpg'>

