19  US 9 904 167 B2  20  Examples of the organic onium ion (countercation) which  is represented by M$_{1 }$ +  and M$_{2 }$ +  include onium ions such as  iodonium  sulfonium  phosphonium  diazonium  ammo› nium  pyridinium  quinolinium  acridinium  oxonium  sele› nonium  and arsonium  among which onium ions such as  iodonium  sulfonium  phosphonium  diazonium  quino› linium  and acridinium are preferable  and onium ions such  as iodonium and sulfonium are even more preferable.  In addition  examples thereof include cations such as  onium ions of onium salts of group 15 to 17 elements  described in JP1994-184170A (JP-H06-184170A)  and the  like  diazonium ions of diazonium salts described in S. I.  Schlesinger  Photogr. Sci. Eng.  18  387 (1974)  T. S. Bal et  al.  Polymer  21  423 (1980)  and the like  ammonium ions  of ammonium salts described in U.S. Pat. No. 4 069 055A   U.S. Pat. No. 4 069 056A  US RE27992E  JP1991-140140A  (JP-H03-140140A)  and the like  phosphonium ions of phos› phonium salts described in D.C. Necker et al.  Macromol› ecules  17  2468 (1984)  C. S. Wen et al.  Teh  Proc. Conf.  Rad. Curing ASIA  p. 478 Tokyo  October (1988)  U.S. Pat.  No. 4 069 055A  U.S. Pat. No. 4 069 056A  JP1997- 202873A (JP-H09-202873A)  and the like  iodonium ions of  iodonium salts described in J. V. Crivello et al.  Macromol› ecules  10 (6)  1307 (1977)  Chem. & Eng. News  November  28  p. 31 (1988)  EP104143B  EP339049B  EP410201B   JP1990-150848A  (JP-H02-150848A)   JP1990-296514A  (JP-H02-296514A)  and the like  sulfonium ions of sulfo› nium salts described in J. V. Crivello et al.  Polymer J. 17   73 (1985)  J.  V. Crivello et al.  J. Org. Chem.  43  3055  (1978)   W.  R. Watt et al.  J. Polymer Sci.  Polymer Chem.  Ed.  22  1789 (1984)  J. V. Crivello et al.  Polymer Bull.  14   279 (1985)  J. V. Crivello et al.  Macromolecules  14(5)   1141 (1981)  J.  V. Crivello et al.  J. Polymer Sci.  Polymer  Chem. Ed.  17  2877 (1979)  EP370693B  EP161811B   EP410201B   EP339049B   EP233567B   EP297443B   EP297442B  U.S. Pat. No. 3 902 114A  U.S. Pat. No. 4 933   377A  U.S. Pat. No. 4 760 013A  U.S. Pat. No. 4 734 444A   U.S. Pat. No. 2 833 827A  DE2904626B  DE3604580B   DE3604581B  JP! 995-28237 A (JP-807-28237 A)  JP! 996- 27102A (JP-H08-27102A)  and the like  quinolinium ions of  quinolinium salts described in JP1997-221652A (JP-H09- 221652A) and the like  selenonium ions of selenonium salts  described in J.  V. Crivello et al.  Macromolecules  10 (6)   1307 (1977)  J.  V. Crivello et al.  J. Polymer Sci.  Polymer  Chem. Ed.  17  1047 (1979)  and the like  and arsonium ions  of arsonium salts described in C. S. Wen et al.  Teh  Proc.  Conf. Rad. Curing ASIA  p. 478 Tokyo  October (1988)  and  the like; however  the present invention is not limited  thereto.  In addition  preferable examples of the countercation  described above include cations having the structure repre- sented by any one of Formulae (II) to (VII) below.  R 1 -W::::N  +  R 2 -I-R 3  R4  I  s+  Rs/ ’-R6  R7  I  RS-p+-RIO  I  R9  (II)  (III)  (IV)  (V)  -continued  (VI)  (VII)  In Formulae (II) to (VII) above  R 1  to R 3  each indepen› dently represent an aryl group  R 4  to R 6  each independently  represent an alkyl group  an alkenyl group  an alkynyl group   an aryl group  a cyclic hydrocarbon group  or a heterocyclic  group  R 7  to R 11  each independently represent an alkyl  group  an alkenyl group  an alkynyl group  an aryl group  a  cyclic hydrocarbon group  a heterocyclic group  an alkoxy  group  or an aryloxy group  and R$^{12 }$to R$^{17 }$each indepen› dently represent a hydrogen atom  a halogen atom  or a  monovalent organic group.  The alkyl groups denoted by R 4  to R$^{11 }$preferably have 1  to 30 carbon atoms  more preferably 1 to 20 carbon atoms   and particularly preferably 1 to 8 carbon atoms  and may be  straight-chain and may have a substituent group.  The alkenyl groups denoted by R $^{4 }$to R $^{11 }$preferably have  2 to 30 carbon atoms  more preferably 2 to 20 carbon atoms   and particularly preferably 2 to 8 carbon atoms  and may  further have a substituent group.  The alkynyl groups denoted by R $^{4 }$to R $^{11 }$preferably have  2 to 30 carbon atoms  more preferably 2 to 20 carbon atoms   and particularly preferably 2 to 8 carbon atoms  and may  further have a substituent group.  The aryl groups denoted by R $^{1 }$to R $^{11 }$preferably have 6 to  30 carbon atoms  more preferably 6 to 20 carbon atoms  and  particularly preferably 6 to 10 carbon atoms  and may  further have a substituent group.  The cyclic hydrocarbon groups denoted by R 4  to R 11  preferably have 3 to 30 carbon atoms  more preferably 3 to  20 carbon atoms  and particularly preferably 3 to 10 carbon  atoms  and may further have a substituent group.  The heterocyclic groups denoted by R 4  to R$^{11 }$preferably  have 4 to 30 carbon atoms  more preferably 4 to 20 carbon  atoms  and particularly preferably 4 to 10 carbon atoms  and  may further have a substituent group. In addition  the hetero  atom included in the heterocyclic group is preferably a  nitrogen atom  an oxygen atom  or a sulfur atom.  The alkoxy groups denoted by R $^{7 }$to R $^{11 }$preferably have  1 to 30 carbon atoms  more preferably 1 to 20 carbon atoms   and even more preferably 1 to 8 carbon atoms. In addition   the alkoxy groups may have a substituent group described  below  and the alkyl moiety of the alkoxy groups may be an  alkenyl group  an alkynyl group  a cyclic hydrocarbon  group  or a heterocyclic group other than an aromatic group.  The aryloxy groups denoted by R $^{7 }$to R $^{11 }$preferably have  6 to 30 carbon atoms  more preferably 6 to 20 carbon atoms   and even more preferably 6 to 10 carbon atoms. In addition   the aryloxy groups may have a substituent group described  below  and the aryl moiety of the aryloxy groups may be an  aromatic heterocyclic group.  In Formula (III)  R 2  and R 3  may be bonded with each  other to form a ring if this is possible.  In Formula (IV)  two or more ofR 4  to R$^{6 }$may be bonded  with each other to form a ring if this is possible. 