US 2019/0196326 Al  15  Jun.27,2019  [0103]  R$_{2 }$ and R$_{3 }$ each independently represent a hydrogen  atom, an alkyl group, a cycloalkyl group, and an aryl group,  and R$_{2 }$ and R$_{3 }$ may be linked to each other to form a ring,  [0102]  R$_{1 }$represents an alkyl group, a cycloalkyl group, an  alkoxy group, a cycloalkoxy group, an aryl group, and an  alkenyl group,  [0101]  In Formula (ZI-3),  [0112]  R$_{2 }$ and R$_{3 }$ represent a hydrogen atom, an alkyl  group, a cycloalkyl group, or an aryl group, and R$_{2 }$ and R$_{3 }$ may be linked to each other to form a ring.  It  is preferable  that at least one of R$_{2 }$ or R$_{3 }$ represents an alkyl group, a  [0111]  Examples of the alkenyl group as R$_{1 }$include a vinyl  group and an ally! group.  [0110]  The aryl group as R$_{1 }$ is preferably an aryl group  having 6 to 14 carbon atoms, and examples thereof include  a phenyl group, a naphthyl group, and a biphenyl group. The  aryl group of R$_{1 }$ may have a substituent, and preferable  examples of the substituent include an alkyl group, a  cycloalkyl group, an alkoxy group, a cycloalkoxy group, an  aryloxy group, an alkylthio group, and an arylthio group. In  a case where the substituent is an alkyl group, a cycloalkyl  group, an alkoxy group, or a cycloalkoxy group, examples  thereof include the same groups as the alkyl group, the  cycloalkyl group, the alkoxy group, and the cycloalkoxy  group described above as R$_{1}$ .  [0109]  The cycloalkoxy group as R$_{1 }$ is preferably a  cycloalkoxy group having 3 to 20 carbon atoms, and  examples thereof include a cyclohexyloxy group, a norbor› nyloxy group, and an adamantyloxy group. The cycloalkoxy  group of R$_{1 }$ may have a substituent, and examples of the  substituent include an alkyl group and a cycloalkyl group.  [0100]  Preferable examples of the cation represented by  Formula (ZI) include cations represented by Formula (ZI-3)  or (ZI-4) described below. First, a cation represented by  Formula (ZI-3) is described.  [0099]  Examples of the preferable structure in a case  where at least one ofR$_{201}$, R 202 , or R $_{203 }$is not an aryl group  include cation structures such as compounds disclosed in  paragraphs 0046 and 0047 of JP2004-233661A and para› graphs 0040 to 0046 of JP2003-035948A, compounds  exemplified as  Formulae (I-1) to (I-70) in US2003/  0224288Al, and compounds exemplified as Formulae (IA- 1) to (IA-54) and Formulae (IB-1) to (IB-24) in US2003/  0077540Al.  [0108]  The alkoxy group as R$_{1}$is preferably an alkoxy  group having 1 to 20 carbon atoms. Specific examples  thereof include a methoxy group, an ethoxy group, an  isopropyloxy group, a t-butyloxy group, a t-amyloxy group,  and an n-butyloxy group. The alkoxy group ofR$_{1 }$ may have  a substituent, and examples of the substituent include an  alkyl group and a cycloalkyl group.  [0107]  The cycloalkyl group as R$_{1 }$ is preferably a  cycloalkyl group having 3 to 20 carbon atoms and may have  an oxygen atom, or a sulfur atom in the ring. Specific  examples thereof include a cyclopropyl group, a cyclopentyl  group, a cyclohexyl group, a norbomyl group, and an  adamantyl group. The cycloalkyl group of R$_{1 }$ may have a  substituent, and examples of the substituent include an alkyl  group and an alkoxy group.  [0098]  Two selected from R$_{20}$ i,  R$_{202}$, and R 203  may be  bonded to each other via a single bond or a linking group.  Examples of the linking group include an alkylene group  (preferably having 1 to 3 carbon atoms),  -0-, -S-,  -CO- and but the present invention is not limited to these.  [0097]  An aryl group, an alkyl group, and a cycloalkyl  group as R$_{201}$ , R 202 , and R 203  each may further have a  substituent. Examples the substituent include a halogen  atom such as a nitro group and a fluorine atom, a carboxy  group, a hydroxyl group, an amino group, a cyano group, an  alkoxy group (preferably having 1 to 15 carbon atoms), a  cycloalkyl group (preferably having 3 to 15 carbon atoms),  an aryl group (preferably having 6 to 14 carbon atoms), an  alkoxycarbonyl group (preferably having 2 to 7 carbon  atoms), an acyl group (preferably having 2 to 12 carbon  atoms), and an alkoxycarbonyloxy group (preferably having  2 to 7 carbon atoms), and the present invention is not limited  to these.  [0106]  The alkyl group in R$_{1 }$ is preferably a linear and  branched alkyl group having 1 to 20 carbon atoms and may  have an oxygen atom, a sulfur atom, or a nitrogen atom in  an alkyl chain. Specific examples thereof include a linear  alkyl group such as a methyl group, an ethyl group, an  n-propyl group, an n-butyl group, an n-pentyl group, an  n-hexyl group, an n-octyl group, an n-dodecylgroup, an  n-tetradecyl group, and an n-octadecyl group, and a  branched chain alkyl group such as an isopropyl group, an  isobutyl group, a t-butyl group, a neopentyl group, and a  2-ethylhexyl group. The alkyl group of R$_{1 }$ may have a  substituent, and examples of the alkyl group having a  substituent include a cyanomethyl group, a 2,2,2-trifluoro› ethyl group, a methoxycarbonylmethyl group, and an  ethoxycarbonylmethyl group.  [0105]  Rx  and  RY  each independently represent an alkyl  group, a cycloalkyl group, an alkenyl group, an aryl group,  a 2-oxoalkyl group, a 2-oxocycloalkyl group, an alkoxycar› bonylalkyl group, and an alkoxycarbonyl cycloalkyl group,  Rx  and  RY  may be linked to each other to form a ring, and this  ring structure may include an oxygen atom, a nitrogen atom,  a sulfur atom, a ketone group, an ether bond, an ester bond,  or an amide bond.  [0104]  R$_{1 }$ and R$_{2 }$ may be linked to each other to form a  ring, and  [0096]  It  is preferable that at least one of R$_{201 }$ R$_{202}$, or  R$_{203 }$ an aryl group, and it is more preferable that $^{0}$all of the  three are acyl groups. In addition to a phenyl group and a  naphthyl group, as the aryl group, a heteroaryl group such as  an indole residue, a pyrrole residue is also possible.  [0095]  Examples of the organic group ofR$_{201}$, R 202 , and  R$_{203 }$include an aryl group (preferably having 6 to 15 carbon  atoms), a linear or branched alkyl group (preferably having  1 to 10 carbon atoms), and a cycloalkyl group (preferably  having 3 to 15 carbon atoms)  [0094]  The acid generator may be a compound having a  plurality of structures represented by Formula  (ZI).  For  example, the acid generator may be a compound having a  structure in which at least one of R$_{20}$ i, ... ,  or R$_{203 }$ of the  compound represented by Formula  (ZI)  is bonded to at least  one of R$_{201}$ , ... , or R $_{203 }$of another compound represented  by Formula  (ZI)  via a single bond or a linking group.  (ZI-3)  0  Rx  Jl  ,J+-Ry  R(’  y~  R 2  R3 