US 9,164,380 B2  17  18  Examples of the substituent which may be bonded to the  naphthalene ring of the vinylnaphthalene or derivative there› fore include the same substituents as those mentioned above  for the substituent which may be bonded to the benzene ring  of an a-substituted) styrene.  In a compound in which the hydrogen atom of the hydroxyl  group of an a-substituted) vinyl(hydroxynaphthalene) has  been substituted with an organic group, there are no particular  limitations on the organic group, and examples include the  same organic groups as those described above for the organic  group of an ( a-substituted) acrylate ester.  Examples of the structural unit (al) include a structural  unit (all) derived from an acrylate ester in which the hydro› gen atom bonded to the carbon atom on the a-position may be  substituted with a substituent, and containing an acid-decom› posable group, a structural unit (al2) derived from ahydroxy› styrene in which the hydrogen atom bonded to the carbon  atom on the a-position may be substituted with a substituent,  in which the hydrogen atoms bonded to the benzene ring may  be substituted with a substituent other than a hydroxyl group,  and in which the hydrogen atom of the hydroxyl group is  substituted with an acid-dissociable group or a substituent  containing an acid-dissociable group, and a structural unit  ( al 3) derived from a vinyl(hydroxynaphthalene) in which the  hydrogen atom bonded to the carbon atom on the a-position  may be substituted with a substituent, in which the hydrogen  atoms bonded to the naphthalene ring may be substituted with  a substituent other than a hydroxyl group, and in which the  hydrogen atom of the hydroxyl group is substituted with an  acid-dissociable group or a substituent containing an acid› dissociable group.  {Structural Unit (all)}  The structural unit (all) is a structural unit derived from an  acrylate ester in which the hydrogen atom bonded to the  carbon atom on the a-position may be substituted with a  substituent and containing an acid-decomposable group.  Specific examples of the structural unit (all) include struc› tural units represented by general formula (al-0-1) shown  below and structural units represented by general formula  (al-0-2) shown below.  [Chemical Formula 6]  (al-0-1)  In the formulas, R represents a hydrogen atom, an alkyl group  of 1 to 5 carbon atoms or a halogenated alkyl group of 1 to 5  carbon atoms,  xi  represents an acid-dissociable group, Y 2  represents a divalent linking group, and X 2  represents an  acid-dissociable group.  The linear or branched aliphatic hydrocarbon group may or  may not have a substituent (a group or atom other than a  hydrogen atom) that substitutes a hydrogen atom. Examples  of the substituent include a fluorine atom, a fluorinated alkyl  group of 1 to 5 carbon atoms, and an oxo group  (=0).  Examples of the aliphatic hydrocarbon group that includes  a ring within the structure include cyclic aliphatic hydrocar› bon groups (groups in which two hydrogen atoms have been  removed from an aliphatic hydrocarbon ring) which may  As the branched aliphatic hydrocarbon group, a branched  alkylene group is preferable, and specific examples include  various alkylalkylene groups, including alkylmethylene  groups  such  as  ----CH(CH$_{3}$ )-,  ----CH(CH$_{2}$CH$_{3}$)-,  ----C(CH$_{3}$ ) 2 -,  -C(CH$_{3}$)(CH$_{2}$CH$_{3}$)-,  -C(CH$_{3}$ )  (CH$_{2}$CH$_{2}$CH$_{3}$)- and -C(CH$_{2}$CH$_{3}$ ) 2 -, alkylethylene  groups such as ----CH(CH$_{3}$)CH$_{2}$ -,  ----CH(CH$_{3}$)CH(CH$_{3}$)-,  ----C(CH$_{3}$) $_{2}$CH$_{2}$ -,  -CH(CH$_{2}$CH$_{3}$)CH$_{2}$ - and  ----C(CH$_{2}$CH$_{3}$ ) $_{2}$----CH$_{2}$ -, alkyltrimethylene groups such as  ----CH(CH$_{3}$)CH$_{2}$CH$_{2}$ - and -CH$_{2}$CH(CH$_{3}$)CH$_{2}$-, and  alkyltetramethylene  groups  such  as  -CH(CH$_{3}$ )  CH$_{2}$CH$_{2}$CH$_{2}$ - and -CH$_{2}$CH(CH$_{3}$)CH$_{2}$CH$_{2}$-. As the  alkyl group within the alkylalkylene group, a linear alkyl  group of 1 to 5 carbon atoms is preferable.  As the linear aliphatic hydrocarbon group, a linear alkylene  group is preferable, and specific examples include a methyl› ene group [----CH$_{2}$ -], an ethylene group [-(CH 2 ) 2 -], a  trimethylene group [-(CH$_{2}$ ) 3 -], a tetramethylene group  [-(CH$_{2}$) 4 -] and a pentamethylene group [-(CH 2 ) 5 -].  The linear or branched aliphatic hydrocarbon group pref› erably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon  atoms, and most preferably 1 to 5 carbon atoms.  Specific examples of the aliphatic hydrocarbon group  include a linear or branched aliphatic hydrocarbon group, and  an aliphatic hydrocarbon group that includes a ring within the  structure.  An "aliphatic hydrocarbon group" refers to a hydrocarbon  group that has no aromaticity. The aliphatic hydrocarbon  group may be either saturated or unsaturated. In general, the  aliphatic hydrocarbon group is preferably saturated.  The hydrocarbon group for the divalent linking group may  be either an aliphatic hydrocarbon group or an aromatic  hydrocarbon group.  Although there are no particular limitations on the divalent  linking group for Y 2 ,  preferred examples include divalent  hydrocarbon groups which may have a substituent, and diva› lent linking groups containing a hetero atom.  (Divalent Hydrocarbon Group which May have a Substitu- ent)  X $^{2 }$is the same as defined for  xi  in formula (al-0-1).  In general formula (al-0-2), R is the same as defined for R  in formula (al-0-1).  There are no particular limitations on  Xi as long as it is an  acid-dissociable group. Examples include the aforemen› tioned tertiary alkyl ester-type acid-dissociable groups and  acetal-type acid-dissociable groups, and of these, a tertiary  alkyl ester-type acid-dissociable group is preferable.  R is preferably a hydrogen atom, an alkyl group of 1 to 5  carbon atoms or a fluorinated alkyl group of 1 to 5 carbon  atoms, and is most preferably a hydrogen atom or a methyl  group.  In general formula (al-0-1), examples of the alkyl group  and halogenated alkyl group for R include the same groups as  the alkyl groups of 1 to 5 carbon atoms and halogenated alkyl  groups of 1 to 5 carbon atoms mentioned above for the sub- stituent bonded to the carbon atom on the a-position within  the description relating to the aforementioned a-substituted  acrylate ester. 