content_image/935976.jpg content_image/935977.jpg
The aryl group is preferably an aryl group having 6 to 10 carbon atoms because it can be synthesized at a low cost. Specific examples thereof include a phenyl group and a naph› thyl group. Of these, a phenyl group is particularly desirable. 

As examples of the alkyl group, alkoxy group and halogen atom with which the hydrogen atoms of the aryl group may be substituted, the same alkyl group, alkoxy group and halogen atom as those with which the arylene group for R 2 may be substituted can be given. 

The alkyl group for R 3 and R 4 is not particularly limited and includes, for example, a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms. In terms of achieving excellent resolution, the alkyl group preferably has 1 to 5 carbon atoms. Specific examples include a methyl group, an ethyl group, ann-propyl group, anisopropyl group, ann-butyl group, an isobutyl group, an n-pentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, a nonyl group and a decyl group. Among these, a methyl group is preferable because it is excellent in resolution and can be synthesized at a low cost. 

In general formula (a0-2’), R 3 and R 4 may be mutually bonded to form a ring with the sulfur atom. 

In such a case, the ring including the sulfur atom is prefer- ably a 3- to IO-membered ring, and more preferably a 5- to 7-membered ring. 

The ring structure formed with the sulfur atom may include a hetero atom such as a sulfur atom or an oxygen atom (---0-, =0). 

Specific examples of the ring formed include a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a fluorene ring, a triphenylene ring, a naphthacene ring, a biphenyl ring, a pyrrole ring, a furan ring, a thiophene ring, an imidazole ring, an oxazole ring, a thiazole ring, a pyridine ring, a pyrazine ring, a pyrimidine ring, a pyridazine ring, an indolizine ring, an indole ring, a benzofuran ring, a ben- zothiophene ring, an isobenzofuran ring, a quinolizidine ring, a quinoline ring, a phthalazine ring, a naphthyridine ring, a quinoxaline ring, a quinoxazoline ring, an isoquinoline ring, a carbazole ring, a phenanthridine ring, an acridine ring, a phenanthroline ring, a thianthrene ring, a chromene ring, a xanthene ring, a phenoxathiin ring, a phenothiazine ring and a phenazine ring. 

In the present invention, with respect to the structural unit (a0-2), examples of the cation moiety of the group repre- sented by general formula (a0-2’) include groups represented by the formulas shown below. 

[Chemical Formula 6] 

<img src='content_image/935976.jpg'>

<img src='content_image/935977.jpg'>

-continued 

