A salt having a group represented by the formula (aa):

##STR00001##

wherein X.sup.a and X.sup.b independently each represent an oxygen atom or a sulfur atom,
the ring W represents a C3-C36 heterocyclic ring which has an ester bond or a thioester bond, said heterocyclic ring optionally further having an oxygen atom, a sulfur atom, a carbonyl group or a sulfonyl group each by which a methylene group has been replaced, and said heterocycilic ring optionally having a hydroxyl group, a cyano group, a carboxyl group, a C1-C12 alkyl group, a C1-C12 alkoxy group, a C2-C13 alkoxycarbonyl group, a C2-C13 acyl group, a C2-C13 acyloxy group, a C3-C12 alicyclic hydrocarbon group, a C6-C10 aromatic hydrocarbon group or any combination of these groups each by which a hydrogen atom has been replaced, and
* represents a binding position.

A fluorine-containing polymer includes at least one repeating unit represented by any of General Formulae (I) to (III):

##STR00001##

A fluorine-containing polymer includes at least one repeating unit represented by any of General Formulae (I) to (III):

##STR00001##

The present invention relates to a piezoelectric material, comprising: a vinylidene fluoride/trifluoroethylene copolymer; and a (meth)acrylic polymer which contains a structural unit derived from a (meth)acrylic monomer represented by Formula (I):

##STR00001## [wherein, R.sub.1 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, wherein at least one hydrogen atom of R.sub.1 is optionally substituted with a halogen atom; and R.sub.2 represents a linear or branched alkyl group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 3 to 12 carbon atoms which contains an alicyclic structure having 3 to 6 carbon atoms, a phenyl group, or a phenylalkylene group which contains an alkylene group having 1 to 4 carbon atoms, wherein, at least one carbon atom of the alkyl group, the alicyclic hydrocarbon group, the phenyl group, and the phenylalkylene group is optionally substituted with —O—, —N—, or —S—, at least one hydrogen atom of the alkyl group, the alicyclic hydrocarbon group, and the alkylene group is optionally substituted with a hydroxy group, an alkyl group having 1 to 6 carbon atoms, and/or an alkoxy group having 1 to 6 carbon atoms, at least one hydrogen atom on the phenyl rings of the phenyl group and the phenylalkylene group is optionally substituted with a hydroxy group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and/or a cyano group, and at least one hydrogen atom of R.sub.2 is optionally substituted with a halogen atom, with a proviso that at least one hydrogen atom of R.sub.1 and/or R.sub.2 is substituted with a halogen atom.

The present invention relates to a piezoelectric material, comprising: a vinylidene fluoride/trifluoroethylene copolymer; and a (meth)acrylic polymer which contains a structural unit derived from a (meth)acrylic monomer represented by Formula (I):

##STR00001## [wherein, R.sub.1 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, wherein at least one hydrogen atom of R.sub.1 is optionally substituted with a halogen atom; and R.sub.2 represents a linear or branched alkyl group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 3 to 12 carbon atoms which contains an alicyclic structure having 3 to 6 carbon atoms, a phenyl group, or a phenylalkylene group which contains an alkylene group having 1 to 4 carbon atoms, wherein, at least one carbon atom of the alkyl group, the alicyclic hydrocarbon group, the phenyl group, and the phenylalkylene group is optionally substituted with —O—, —N—, or —S—, at least one hydrogen atom of the alkyl group, the alicyclic hydrocarbon group, and the alkylene group is optionally substituted with a hydroxy group, an alkyl group having 1 to 6 carbon atoms, and/or an alkoxy group having 1 to 6 carbon atoms, at least one hydrogen atom on the phenyl rings of the phenyl group and the phenylalkylene group is optionally substituted with a hydroxy group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and/or a cyano group, and at least one hydrogen atom of R.sub.2 is optionally substituted with a halogen atom, with a proviso that at least one hydrogen atom of R.sub.1 and/or R.sub.2 is substituted with a halogen atom.

The present invention is directed to a purification method for purifying a fluorine-containing polymerizable monomer of the formula (1), in which the fluorine-containing polymerizable monomer is purified by distillation in the coexistence of a phenolic compound A such as 6-tert-butyl-2,4-xylenol and a phenolic compound B such as 2,2′-methylene-bis(4-methyl-6-tert-butylphenol).

##STR00001##

By the combined use of the phenolic compound A and the phenolic compound B, it is possible to significantly suppress polymerization or oligomerization of the fluorine-containing polymerizable monomer even during industrial-production-scale distillation and efficiently purify the fluorine-containing polymerizable monomer by distillation.

The present invention is directed to a purification method for purifying a fluorine-containing polymerizable monomer of the formula (1), in which the fluorine-containing polymerizable monomer is purified by distillation in the coexistence of a phenolic compound A such as 6-tert-butyl-2,4-xylenol and a phenolic compound B such as 2,2′-methylene-bis(4-methyl-6-tert-butylphenol).

##STR00001##

By the combined use of the phenolic compound A and the phenolic compound B, it is possible to significantly suppress polymerization or oligomerization of the fluorine-containing polymerizable monomer even during industrial-production-scale distillation and efficiently purify the fluorine-containing polymerizable monomer by distillation.

Chain scission resist compositions suitable for EUV lithography applications may include monomer functional groups that improve the kinetics and/or thermodynamics of the scission mechanism. Chain scission resists may include monomer functional groups that reduce the risk that leaving groups generated through the scission mechanism may chemically corrode processing equipment.

Chain scission resist compositions suitable for EUV lithography applications may include monomer functional groups that improve the kinetics and/or thermodynamics of the scission mechanism. Chain scission resists may include monomer functional groups that reduce the risk that leaving groups generated through the scission mechanism may chemically corrode processing equipment.

Metal-oxide composite particles are used as a toner additive.