Mar. 26, 2015  28  US 2015/0086912 Al  [0238]  Each ofRs 1  and Rs$_{3 }$ in formula (a) more preferably  represents a hydrogen atom, an alkyl group or a halogen atom,  and especially preferably a hydrogen atom, a methyl group,  an ethyl group, a trifluoromethyl group (-CF  3 ),  a hydroxym› ethyl group (----CH$_{2}$---0H), a chloromethyl group (----CH$_{2}$- Cl), or a fluorine atom (-F). Rs$_{2 }$ more preferably represents  a hydrogen atom, an alkyl group, a halogen atom, or an  alkylene group (forming a ring together with Ls), and espe› cially preferably a hydrogen atom, a methyl group, an ethyl  group, a trifluoromethyl group (-CF$_{3}$ ),  a hydroxymethyl  group (-CH$_{2}$-OH), a chloromethyl group (----CH$_{2}$----Cl), a  fluorine atom (-F), a methylene group (forming a ring  together with Ls), or an ethylene group (forming a ring  together with Ls)- [0239]  As the divalent linking group represented by Ls, an  alkylene group, a divalent aromatic cyclic group, -COO› L1-, -O-L 1 -, -L 1 -O-, and a group formed by combining  two or more of these groups are exemplified, wherein L 1  represents an alkylene group, a divalent aliphatic hydrocar› bon cyclic group, a divalent aromatic cyclic group, or a group  obtained by combining an alkylene group and a divalent  aromatic cyclic group, which may further be substituted with  a fluorine atom or the like.  [0240]  Ls preferably represents a single bond, ----COO-L 1  - (L 1  is preferably an alkylene group having 1 to 5 carbon  atoms, and more preferably a methylene group or a propylene  group), or a group represented by a divalent aromatic cyclic  group.  [0241]  The alkyl group ofRs$_{4 }$ to Rs$_{6 }$ is preferably an alkyl  group having 1 to 20 carbon atoms, more preferably an alkyl  group having 1 to 10 carbon atoms, and especially preferably  an alkyl group having 1 to 4 carbon atoms, such as a methyl  group, an ethyl group, an n-propyl group, an isopropyl group,  an n-butyl group, an isobutyl group, or at-butyl group.  [0242]  The monovalent aliphatic hydrocarbon cyclic group  represented by  Rss  and Rs$_{6 }$ is preferably a monovalent ali› phatic hydrocarbon cyclic group having 3 to 20 carbon atoms,  which group may be monocyclic such as a cyclopentyl group  or a cyclohexyl group, or may be polycyclic such as a norbo› nyl group, an adamantyl group, a tetracyclodecanyl group, or  a tetracyclododecanyl group.  [0243]  The ring formed by bonding  Rss  to Rs$_{6 }$to each other  is preferably a ring having 3 to 20 carbon atoms, which may  be monocyclic such as a cyclopentyl group or a cyclohexyl  group, or may be polycyclic such as a norbonyl group, an  adamantyl group, a tetracyclodecanyl group, or a tetracy› clododecanyl group. When  Rss  and Rs$_{6 }$ form a ring by bond› ing to each other, Rs$_{4 }$ preferably represents an alkyl group  having 1 to 3 carbon atoms, and more preferably a methyl  group or an ethyl group.  [0244]  The monovalent aromatic cyclic group represented  by  Rss  and Rs$_{6 }$is preferably an aromatic cyclic group having  6 to 20 carbon atoms, e.g., a phenyl group and a naphtyl group  are exemplified. When eitherone ofRss and Rs$_{6 }$is a hydrogen  atom, the other is preferably a monovalent aromatic cyclic  group.  [  0245]  A monomer corresponding to the repeating unit rep› resented by formula (a) can be synthesized according to an  ordinary synthesizing method of a polymerizable group-con› taining ester without any restriction.  [0246]  The specific examples of the repeating units repre› sented by formula (a) are shown below, but the invention is  not restricted thereto.  (V-1)  --+  H2  H  +- C -C  )---0+  (V-2)  j  cj  H2  I  C -C  )---0+  (V-3)  CH20H  --+  H2  I+- C -C  )---0+  (V-4)  j  c:j  H2  I  C -C  OAO+  (V-5)  --+  H2  H  +- C -C  oAof-!  (V-6)  j  cj  H2  I  C -C  OAO+<  (V-7)  j  cj  H2  I  ::tot-a  (V-8)  j  cj  H2  I  C -C  OAO+o 