Oct. 21, 2010  7  US 2010/0266955 Al  [0097]  In general formula. (a0-1), R $^{2 }$represents a divalent  hydrocarbon group which may have a substituent.  [0098]  With respect to R 2 ,  the hydrocarbon group "has a  substituent" means that part or all of the hydrogen atoms  within the hydrocarbon group has been substituted with a  group or an atom other than a hydrogen atom.  [0099]  The hydrocarbon group may be either an aliphatic  hydrocarbon group or an aromatic hydrocarbon group. An  "aliphatic hydrocarbon group" refers to a hydrocarbon group  that has no aromaticity.  [0100]  The aliphatic hydrocarbon group may be saturated  or unsaturated. In general, the aliphatic hydrocarbon group is  preferably saturated,  [0101]  As specific examples of the aliphatic hydrocarbon  group, a linear or branched aliphatic hydrocarbon group, and  an aliphatic hydrocarbon group containing a ring in the struc› ture thereof can be given.  [0102]  The linear or branched aliphatic hydrocarbon group  preferably has 1 to 10 carbon atoms, more preferably 1 to 8,  still more preferably 1 to 5, and most preferably 1 or 2.  [0103]  As the linear aliphatic hydrocarbon group, a linear  alkylene group is preferable, Specific examples thereof  include a methylene group  [----CH$_{2}$-],  an ethylene group  [-(CH$_{2}$ ) 2 -], a trimethylene group  [-(CH$_{2}$k],  a tetrameth› ylene group  [-(CH$_{2}$ ) 4 -] and a pentamethylene group  [-(  CH$_{2}$ )s-]. Among these, a methylene group or an ethylene  group is preferable.  [0104]  As the branched aliphatic hydrocarbon group,  branched alkylene groups are preferred, 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 -; alkyl› ethylene 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.  [0105]  The linearor branched aliphatic hydrocarbon group  (chain-like aliphatic hydrocarbon group) may or may not  have a substituent. Examples of substituents include a fluo› rine atom, a fluorinated alkyl group of 1 to 5 carbon atoms,  and an oxygen atom  (=0).  [0106]  As examples of the hydrocarbon group containing a  ring in the structure thereof, a cyclic aliphatic hydrocarbon  group (a group in which two hydrogen atoms have been  removed from an aliphatic hydrocarbon ring), a group in  which the cyclic aliphatic hydrocarbon group is bonded to the  terminal of the aforementioned chain-like aliphatic hydrocar› bon group, and a group in which the cyclic aliphatic hydro› carbon group is interposed within the aforementioned chain› like aliphatic hydrocarbon group, can be given.  [0107]  The cyclic aliphatic hydrocarbon group preferably  has 3 to 20 carbon atoms, and more preferably 3 to 12 carbon  atoms.  [0108]  The cyclic aliphatic hydrocarbon group may be  either a polycyclic group or a monocyclic group.  [0109]  As the monocyclic group, a group in which two  hydrogen atoms have been removed from a monocycloalkane  of3 to 6 carbon atoms is preferable. Examples of the mono› cycloalkane include cyclopentane and cyclohexane.  [0110]  As the polycyclic group, a group in which two  hydrogen atoms have been removed from a polycycloalkane  of7 to 12 carbon atoms is preferable. Examples of the poly› cycloalkane include adamantane, norbomane, isobomane,  tricyclodecane and tetracyclododecane.  [0111]  The cyclic aliphatic hydrocarbon group may or may  not have a substituent.  [0112]  Examples of the substituent include an alkyl group  of 1 to 5 carbon atoms, a fluorine atom, a fluorinated alkyl  group of 1 to 5 carbon atoms, and an oxygen atom  (=0).  [0113]  Examples of the aforementioned aromatic hydro› carbon group include a divalent aromatic hydrocarbon group  in which one hydrogen atom has been removed from a ben› zene ring of a monovalent aromatic hydrocarbon group such  as a phenyl group, a biphenyl group, a fluorenyl group, a  naphthyl group, an anthryl group or a phenanthryl group; an  aromatic hydrocarbon group in which part of the carbon  atoms constituting the ring of the aforementioned divalent  aromatic hydrocarbon group has been substituted with a het› ero atom such as an oxygen atom, a sulfur atom or a nitrogen  atom; and an aromatic hydrocarbon group in which one  hydrogen atom has been removed from a benzene ring of an  arylalkyl group such as a benzyl group, a phenethyl group, a  1-naphthylmethyl group, a 2-naphthylmethyl group, a  1-naphthylethyl group or a 2-naphthylethyl group.  [0114]  The aromatic hydrocarbon group may or may not  have a substituent. Examples of the substituent include an  alkyl group of 1 to 5 carbon atoms, a fluorine atom, a fluori› nated alkyl group of 1 to 5 carbon atoms, and an oxygen atom  (=0).  [0115]  Among the aforementioned examples, as R 2 ,  an ali› phatic hydrocarbon group which may have a substituent is  preferable, a linear or branched aliphatic hydrocarbon group  is more preferable, a linear or branched alkylene group is still  more preferable, and a linear alkylene group is particularly  desirable.  [0116]  In the present invention, as the structural unit (a0), a  structural unit represented by general formula (a0-1-10)  shown below is particularly desirable.  [Chemical Formula 9]  (a0-1-10)  In general formula ( a0-1-10), 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;  R  la  represents an aliphatic  cyclic group-containing acid dissociable, dissolution inhibit› ing group; and A2c represents an alkylene group of 1 to 12  carbon atoms.  [0117]  In general formula ( a0-1-10), R represents a hydro› gen atom, an alkyl group of 1 to 5 carbon atoms or a haloge› nated alkyl group of 1 to 5 carbon atoms, and the same groups  as those described above for R in general formula ( a0-1) can  be used.  [0118]  In general formula (a0-1-10), R$^{1$_{a }$}$represents an ali› phatic cyclic group-containing acid dissociable, dissolution 