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The number of carbon atoms of each of the organic groups as R$_{20}$ i, R $_{202 }$and R$_{203 }$ is generally in the range of 1 to 30, preferably 1 to 20. Two members of R$_{201 }$ to R$_{203 }$ may be bonded to each other to form a ring structure, and the ring within the same may contain an oxygen atom, a sulfur atom, an ester bond, an amide bond, or a carbonyl group. Examples of the group formed by bonding of two members out ofR$_{201 }$ to R$_{203 }$ include an alkylene group such as a butylene group and a pentylene group. 

z- represents the acid anion generated by decomposition by irradiation with actinic rays or radiation. z- is preferably a normucleophilic anion. Examples of the normucleophilic anion include a sulfonate anion, a carboxylate anion, a sulfa- nylimido anion, a bis(alkylsulfonyl)imido anion, and a tris (alkylsulfonyl)methyl anion. 

Furthermore, the normucleophilic anion means an anion whose capability of inducing a nucleophilic reaction is extremely low. By using the nucleophilic anion, time course decomposition by intramolecular nucleophilic reaction can be inhibited. This would realize an enhancement of the time course stability of the resin and the composition. 

Moreover, examples of the structural portion capable of generating an acid by irradiation with actinic rays or radiation include the structural moiety destined for a sulfonic acid precursor that is introduced in each of the following photo› acid generators. Examples of the photo-acid generators include the following compounds (1) to (3). 

(1) Compounds photolyzed to generate a sulfonic acid whose representative is an iminosulfonate or the like, as described in M. Tunooka et al., Polymer Preprints Japan, 35(8); G. Bemer et al., J. Rad. Curing, 13( 4); W. J. Mijs et al., Coating Technol., 55(697), 45 (1983); H. Adachi et al., Poly› mer Preprints Japan, 37(3); EP0199,672B, EP84515B, EP199,672B, EP044,115B, and EP0101,122B; U.S. Pat. No. 618,564B, U.S. Pat. No. 4,371,605B and U.S. Pat. No. 4,431, 774B; JP1989-18143A (JP-S64-18143A), JP1990-245756A (JP-H02-245756A), and JP1992-365048A (JP-H04- 365048A); etc. 

(2) Disulfone compounds as described in JP1986- 166544A (JP-S61-166544A), etc. 

(3) Compounds capable of generating an acid by light, as described in V. N. R. Pillai, Synthesis, (1 ), 1 (1980); A. Abad et al., Tetrahedron Lett., (47) 4555 (1971); D. H. R. Barton et al., J. Chem. Soc., (C), 329 (1970); U.S. Pat. No. 3,779,778B, EP126,712B; etc. 

Specific examples of the repeating units (B) are shown below, but the scope of the present invention is not limited thereto. 

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-continued 

