22  US 9,052,590 B2  21  -continued  (1-16)  F  F  II  II  - HO-~ F  F  ~-0~  O  0  C  O  }---1---(_r\_/  0  ~  Ar $_{2 }$represents a bivalent aromatic ring group. A substituent  may be introduced in the bivalent aromatic ring group. As  preferred examples of the bivalent aromatic ring group, there  can be mentioned, for example, an arylene group having 6 to  18 carbon atoms, such as a phenylene group, a tolylene group  or a naphthylene group, and a bivalent aromatic ring group  containing a heteroring, such as thiophene, furan, pyrrole,  benzothiophene, benzofuran, benzopyrrole, triazine, imida› zole, benzimidazole, triazole, thiadiazole or triazole.  Below, general formula (II) will be described.  In general formula (II), each ofR$_{21}$, R$_{22 }$and R$_{23 }$indepen› dently represents a hydrogen atom, an alkyl group, a monova› lent aliphatic hydrocarbon ring group, a halogen atom, a  cyano group or an alkoxycarbonyl group, provided that R$_{22 }$ may be bonded to Ar$_{2 }$ to thereby form a ring (in particular,  preferably a 5- or 6-membered ring), which R$_{22 }$ in this  instance is an alkylene group.  The alkyl group represented by each ofR$_{21}$, R$_{22 }$and R$_{23 }$is  an optionally substituted linearor branched alkyl group, pref› erably an optionally substituted alkyl group having 20 or less  carbon atoms, such as a methyl group, an ethyl group, a  propyl group, an isopropyl group, an n-butyl group, a sec› butyl group, a hexyl group, a 2-ethylhexyl group, an octyl  group or a dodecyl group.  An  alkyl group having 8 or less  carbon atoms is more preferred.  An  alkyl group having 3 or  less carbon atoms is most preferred.  X$_{21 }$ represents ---0-, -S-, --CO-, -SO$_{2}$-,  -NR- (R represents a hydrogen atom or an alkyl group), a  bivalent nitrogenous nonaromatic heterocyclic group or a  group composed of a combination of these.  Particular examples of the -NR- and bivalent nitrog› enous nonaromatic heterocyclic group represented by X$_{21 }$are  the same as mentioned above in connection with X$_{11}$. Pre› ferred examples are also the same.  Preferably, X$_{21 }$ is ---0-, -S-, --CO-, -SO$_{2}$ - or a  group composed of a combination of these. ---0-,  ---OCO- and ---OSO$_{2}$ - are especially preferred.  The alkyl group contained in the alkoxycarbonyl group is  preferably the same as the alkyl group mentioned above with  respect to R$_{21}$ , R $_{22 }$and R$_{23}$ .  As the monovalent aliphatic hydrocarbon ring group, there  can be mentioned an optionally substituted mono- or polycy› cloalkyl group.  An  optionally substituted monocyclic  monovalent aliphatic hydrocarbon ring group having 3 to 8  carbon atoms, such as a cyclopropyl group, a cyclopentyl  group or a cyclohexyl group, is preferred.  X$_{22 }$ represents a single bond, -0-, -S-, --CO-,  -SO$_{2}$ -,  -NR-(Rrepresents a hydrogen atom or an alkyl  group), a bivalent nitrogenous nonaromatic heterocyclic  group or a group composed of a combination of these.  Particular examples of the -NR- and bivalent nitrog› enous nonaromatic heterocyclic group represented by X$_{22 }$are  the same as mentioned above in connection with X$_{11}$. Pre› ferred examples are also the same.  As the halogen atom, there can be mentioned a fluorine  atom, a chlorine atom, a bromine atom or an iodine atom. A  fluorine atom is especially preferred.  As preferred substituents that can be introduced in these  groups, there can be mentioned a hydroxyl group; a halogen  atom (fluorine, chlorine, bromine or iodine); a nitro group; a  cyano group; an amido group; a sulfonamido group; any of  the alkyl groups mentioned above with respect to R$_{21 }$to R$_{23}$;  an alkoxy group, such as a methoxy group, an ethoxy group,  a hydroxyethoxy group, a propoxy group, a hydroxypropoxy  group or a butoxy group; an alkoxycarbonyl group, such as a  methoxycarbonyl group or an ethoxycarbonyl group; an acyl  group, such as a formyl group, an acetyl group or a benzoyl  group; an acyloxy group, such as an acetoxy group or a  butyryloxy group; and a carboxyl group. A hydroxyl group  and a halogen atom are especially preferred.  When R$_{22 }$ is an alkylene group and is bonded to Ar$_{2 }$ to  thereby form a ring, the alkylene group is preferably an alky› lene group having 1 to 8 carbon atoms, such as a methylene  group, an ethylene group, a propylene group, a butylene  group, a hexylene group or an octylene group.  An  alkylene  group having 1 to 4 carbon atoms is more preferred.  An  alkylene group having 1 or 2 carbon atoms is most preferred.  In general formula (II), each of R$_{21 }$ and R$_{23 }$ preferably  represents a hydrogen atom, an alkyl group or a halogen atom.  R$_{22 }$preferably represents a hydrogen atom, an alkyl group, a  halogen atom or an alkylene group which forms a ring in  cooperation withAr$_{2 }$ As the bivalent aromatic ring group represented by L$_{21}$,  there can be mentioned, for example, an optionally substi› tuted arylene group having 6 to 14 carbon atoms, such as a  phenylene group, a tolylene group or a naphthylene group, or  an optionally substituted bivalent aromatic ring group con› taining a heteroring, such as thiophene, furan, pyrrole, ben- Particular examples of the alkylene group, alkenylene  group and bivalent aliphatic hydrocarbon ring group repre› sented by L$_{21 }$are the same as the above preferred examples of  the alkylene group, alkenylene group and bivalent aliphatic  hydrocarbon ring group represented by L$_{11 }$ of general for› mula  (I).  L$_{21 }$ represents a single bond, an alkylene group, an alk- enylene group, a bivalent aliphatic hydrocarbon ring group, a  bivalent aromatic ring group or a group composed of a com› bination of two or more of these, provided that in the group  composed of a combination, two or more groups combined  together may be identical to or different from each other and  may be linked to each other through, as a connecting group,  ---0-, -S-, -CO-, -SO$_{2}$ -,  -NR- (R represents a  hydrogen atom or an alkyl group), a bivalent nitrogenous  nonaromatic heterocyclic group or a group composed of a  combination of these.  Preferably, X$_{22 }$is ---0-, -S-, --CO-, -SO$_{2}$ - or a  group composed of a combination of these.  ---0-,  ---OCO-and -OSO$_{2}$ - are especially preferred. 