JP2024119061A - Resin, resist composition, and method for producing resist pattern - Google Patents

Abstract

The present invention provides a resin, resist composition, etc., capable of producing a resist pattern with good CD uniformity. The present invention provides a resin comprising at least one structural unit selected from the group consisting of structural units represented by formula (a4-2) and structural units represented by formula (a4-3), and a structural unit represented by formula (I6). TIFF2024119061000168.tif65142 [Selected Figures] None

Description

The present invention relates to a resin, a resist composition, and a method for producing a resist pattern using the resist composition.

Patent Document 1 describes a resist composition that contains a resin having the following structural unit, a resin that includes a structural unit having an acid labile group, and an acid generator.

Patent Document 2 describes a resist composition containing a resin that includes the following structural unit.

JP 2012-256011 A JP 2008-107443 A

The present invention provides a resist composition that forms a resist pattern with better CD uniformity (CDU) than the resist pattern formed by the above resist composition.

［式（ａ４－２）及び式（ａ４－３）中、
Ｒ^４１は、水素原子又はメチル基を表す。
Ｌ^４３ｈ及びＬ^４４ｈは、それぞれ独立に、ハロゲン原子を有してもよい炭素数１～２０の飽和炭化水素基を表し、該飽和炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－又は－ＣＯ－に置き換わってもよい。
Ｒ^４３ｈ及びＲ^４４ｈは、それぞれ独立に、ハロゲン原子を有してもよい炭素数１～２０の飽和炭化水素基を表し、該飽和炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－又は－ＣＯ－に置き換わってもよい。
ただし、Ｌ^４３ｈ及びＲ^４３ｈのうち少なくとも１つはハロゲン原子を有し、Ｌ^４４ｈ及びＲ^４４ｈのうち少なくとも１つはハロゲン原子を有し、Ｌ^４３ｈ及びＲ^４３ｈの合計炭素数の上限並びにＬ^４４ｈ及びＲ^４４ｈの合計炭素数の上限は、それぞれ２１である。］

［式（Ｉ６）中、
Ｑ^ｂ１及びＱ^ｂ２は、それぞれ独立に、水素原子、フッ素原子、炭素数１～６のペルフルオロアルキル基又は炭素数１～６のアルキル基を表す。
Ｌ^ｂ１は、炭素数１～２４の飽和炭化水素基を表し、該飽和炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよく、該飽和炭化水素基に含まれる水素原子は、フッ素原子又はヒドロキシ基で置換されていてもよい。
Ｙ^ｂ１は、単結合又は置換基を有していてもよい炭素数３～２４の環状炭化水素基を表し、該環状炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－、－ＣＯ－、－Ｓ－又は－ＳＯ_２－に置き換わっていてもよい。
ｍｍ１は、０又は１を表す。
Ｒ^１０は、水素原子、ハロゲン原子又はハロゲン原子を有していてもよい炭素数１～６のアルキル基を表す。
Ｘ^１０は、単結合、＊－Ｏ－＊＊、＊－ＣＯ－Ｏ－＊＊、＊－Ｏ－ＣＯ－Ｏ－＊＊又は＊－Ａｘ－Ｐｈ－Ａｙ－＊＊を表す。
Ｐｈは、置換基を有していてもよいフェニレン基を表す。
Ａｘ及びＡｙは、それぞれ独立に、単結合、エーテル結合、チオエーテル結合、エステル結合、アミド結合及び炭酸エステル結合から構成される群から選択される１種の結合種を表す。
＊、＊＊は結合部位を表し、＊は、Ｒ^１０が結合した炭素原子との結合部位を表す。
Ｌ^１０は、単結合又は置換基を有してもよい炭素数１～３６の炭化水素基を表し、該炭化水素基に含まれる－ＣＨ₂－は、－Ｏ－、－Ｓ－、－ＳＯ_２－又は－ＣＯ－に置き換わっていてもよい。
Ｒ^３、Ｒ^４、Ｒ^５及びＲ^６は、それぞれ独立に、水素原子又は置換基を有していてもよい炭素数１～２０の炭化水素基を表し、該炭化水素基に含まれる－ＣＨ₂－は、－Ｏ－、－Ｓ－、－ＮＲ^７－、－ＳＯ_２－又は－ＣＯ－に置き換わっていてもよく、Ｒ^３とＲ^４、Ｒ^３とＲ^４とＲ^５がそれぞれ結合して環状炭化水素基を形成していてもよく、該環状炭化水素基は、１以上の隣接する二つの炭素原子間で二重結合を有していてもよく、該環状炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－、－ＣＯ－又は－ＮＲ^７－に置き換わっていてもよく、該環状炭化水素基に含まれる－ＣＨ＝は、－Ｎ＝に置き換わっていてもよい。
Ｒ^７は、水素原子又は置換基を有していてもよい炭素数１～２０の炭化水素基を表し、該炭化水素基に含まれる－ＣＨ₂－は、－Ｏ－、－Ｓ－、－ＳＯ_２－又は－ＣＯ－に置き換わっていてもよい。］
〔２〕式（ａ４－２）で表される構造単位を含む〔１〕に記載の樹脂。
〔３〕式（ａ４－２）で表される構造単位を含み、
式（ａ４－２）で表される構造単位が、式（ａ４－２Ａ）で表される構造単位又は式（ａ４－２Ｂ）で表される構造単位である〔１〕又は〔２〕に記載の樹脂。

［式（ａ４－２Ａ）及び式（ａ４－２Ｂ）中、
Ｒ^４１は、式（ａ４－２）中と同じものを表す。
Ｌ^４３ｆは、フッ素原子を有してもよい炭素数１～２０の飽和炭化水素基を表し、該飽和炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－又は－ＣＯ－に置き換わってもよい。
Ｒ^４３ｆＡは、フッ素原子を有する炭素数１～２０の飽和炭化水素基を表す。
Ａ^４３ｆは、フッ素原子を有していてもよい炭素数１～１７の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－又は－ＣＯ－に置き換わってもよい。
Ｘ^４３は、＊＊－Ｏ－ＣＯ－又は＊＊－ＣＯ－Ｏ－を表し、＊＊はＡ^４３ｆとの結合部位を表す。
Ｒ^４３ｆＢは、フッ素原子を有していてもよい炭素数１～１７の飽和炭化水素基を表す。
ただし、式（ａ４－２Ａ）において、Ｌ^４３ｆ及びＲ^４３ｆＡの炭素数の合計は２１以下であり、式（ａ４－２Ｂ）において、Ｌ^４３ｆ、Ａ^４３ｆ、Ｘ^４３及びＲ^４３ｆＢの炭素数の合計は２１以下であり、Ａ^４３ｆ及びＲ^４３ｆＢのうち、少なくとも一方は、少なくとも１つのフッ素原子を有する。］
〔４〕Ｙ^ｂ１が、単結合又は置換基を有していてもよい炭素数３～１８の脂環式炭化水素基（該脂環式炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－、－ＣＯ－、－Ｓ－又は－ＳＯ_２－に置き換わっていてもよい。）である〔１〕～〔３〕のいずれかに記載の樹脂。
〔５〕Ｙ^ｂ１が、置換基を有してもよい炭素数３～１８の脂環式炭化水素基であり、
該脂環式炭化水素基が、炭素数５もしくは６のシクロアルカンジイル基、ノルボルナンジイル基、アダマンタンジイル基、アダマンタンラクトンジイル基又はノルボルナンラクトンジイル基であり、該シクロアルカンジイル基、ノルボルナンジイル基及びアダマンタンジイル基に含まれる－ＣＨ_２－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよく、該シクロアルカンジイル基、ノルボルナンジイル基、アダマンタンジイル基、アダマンタンラクトンジイル基又はノルボルナンラクトンジイル基は、置換基を有してもよい〔１〕～〔４〕のいずれかに記載の樹脂。
〔６〕Ｘ^１０が、単結合又は式（Ｘ^１０－１）～式（Ｘ^１０－１０）のいずれかで表される基である〔１〕～〔５〕のいずれかに記載の樹脂。

［式（Ｘ^１０－１）～式（Ｘ^１０－１０）中、
＊、＊＊は結合部位であり、＊はＲ^１０が結合した炭素原子との結合部位を表す。
Ｒｘは、ハロゲン原子、ヒドロキシ基、炭素数１～６のフッ化アルキル基、炭素数１～１８のアルキル基又は炭素数１～６のアルコキシ基を表す。
ｍｘは、０～４のいずれかの整数を表す。
Ｘ^２０は、－Ｏ－又は－ＮＲ^３－を表す。
Ｒ^３は、水素原子又は炭素数１～６のアルキル基を表す。］
〔７〕Ｘ^１０が、単結合又は式（Ｘ^１０－１’）、式（Ｘ１０－３’）～式（Ｘ^１０－８’）及び式（Ｘ^１０－１０’）のいずれかで表される基である〔１〕～〔６〕のいずれかに記載の樹脂。

［式（Ｘ^１０－１’）、式（Ｘ^１０－３’）～式（Ｘ^１０－８’）及び式（Ｘ^１０－１０’）中、
＊、＊＊は結合部位であり、＊はＲ^１０が結合した炭素原子との結合部位を表す。］
〔８〕Ｘ^１０が、単結合又は式（Ｘ^１０－１’）、式（Ｘ^１０－５’）、式（Ｘ^１０－６’）及び式（Ｘ^１０－１０’）のいずれかで表される基である〔７〕に記載の樹脂。
〔９〕Ｌ^１０が、単結合、炭素数１～６のアルカンジイル基、炭素数３～１８の環状炭化水素基又は炭素数１～６のアルカンジイル基と炭素数３～１８の環状炭化水素基とを組み合わせてなる基であり、
該アルカンジイル基及び該環状炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－、－Ｓ－、－ＳＯ_２－又は－ＣＯ－に置き換わっていてもよく、該環状炭化水素基は、置換基を有してもよい〔１〕～〔８〕のいずれかに記載の樹脂。
〔１０〕〔１〕～〔９〕のいずれかに記載の樹脂を含むレジスト組成物。
〔１１〕さらに、〔１〕～〔９〕のいずれかに記載の樹脂とは異なり、酸不安定基を有する構造単位を含む樹脂を含む〔１０〕に記載のレジスト組成物。
〔１２〕酸不安定基を有する構造単位が、式（ａ１－０）で表される構造単位、式（ａ１－１）で表される構造単位、式（ａ１－２）で表される構造単位及び式（ａ１－５）で表される構造単位からなる群より選ばれる少なくとも１種を含む〔１１〕に記載のレジスト組成物。

［式（ａ１－０）、式（ａ１－１）及び式（ａ１－２）中、
Ｌ^ａ０１、Ｌ^ａ１及びＬ^ａ２は、それぞれ独立に、－Ｏ－又は＊－Ｏ－（ＣＨ_２）_ｋ１－ＣＯ－Ｏ－を表し、ｋ１は１～７のいずれかの整数を表し、＊は－ＣＯ－との結合部位を表す。
Ｒ^ａ０１、Ｒ^ａ４及びＲ^ａ５は、それぞれ独立に、水素原子、ハロゲン原子又はハロゲン原子を有していてもよい炭素数１～６のアルキル基を表す。
Ｒ^ａ０２、Ｒ^ａ０３及びＲ^ａ０４は、それぞれ独立に、炭素数１～８のアルキル基、炭素数３～１８の脂環式炭化水素基、炭素数６～１８の芳香族炭化水素基又はこれらを組み合わせた基を表し、該アルキル基、該脂環式炭化水素基及び該芳香族炭化水素基は、ハロゲン原子を有してもよい。
Ｒ^ａ６及びＲ^ａ７は、それぞれ独立に、炭素数１～８のアルキル基、炭素数２～８のアルケニル基、炭素数３～１８の脂環式炭化水素基、炭素数６～１８の芳香族炭化水素基又はこれらを組合せることにより形成される基を表す。
ｍ１は、０～１４のいずれかの整数を表す。
ｎ１は、０～１０のいずれかの整数を表す。
ｎ１’は、０～３のいずれかの整数を表す。］

［式（ａ１－５）中、
Ｒ^a8は、ハロゲン原子を有していてもよい炭素数１～６のアルキル基、水素原子又はハロゲン原子を表す。
Ｚ^a1は、単結合又は＊－（ＣＨ₂）_h3－ＣＯ－Ｌ⁵⁴－を表し、ｈ３は１～４のいずれかの整数を表し、＊は、Ｌ⁵¹との結合部位を表す。
Ｌ⁵¹、Ｌ⁵²、Ｌ⁵³及びＬ⁵⁴は、それぞれ独立に、－Ｏ－又は－Ｓ－を表す。
ｓ１は、１～３のいずれかの整数を表す。
ｓ１’は、０～３のいずれかの整数を表す。］
〔１３〕さらに、酸発生剤を含み、酸発生剤が、式（Ｂ１）で表される塩又は式（Ｂ２）で表される塩を含む〔１０〕～〔１２〕のいずれかに記載のレジスト組成物。

［式（Ｂ１）中、
Ｑ^ｂ１及びＱ^ｂ２は、それぞれ独立に、水素原子、フッ素原子、炭素数１～６のペルフルオロアルキル基又は炭素数１～６のアルキル基を表す。
Ｌ^ｂ１は、炭素数１～２４の飽和炭化水素基を表し、該飽和炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよく、該飽和炭化水素基に含まれる水素原子は、フッ素原子又はヒドロキシ基で置換されていてもよい。
Ｙは、置換基を有していてもよいメチル基又は置換基を有していてもよい炭素数３～２４の環状炭化水素基を表し、該環状炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－、－Ｓ－、－ＳＯ_２－又は－ＣＯ－に置き換わっていてもよい。
Ｚ^＋は、有機カチオンを表す。］

［式（Ｂ２）中、
ｍ２１は、１～５のいずれかの整数を表し、ｍ２１が２以上のとき、複数の括弧内の基は互いに同一であっても異なってもよい。
Ｒ²¹は、炭素数３～１８の環状炭化水素基を含む炭素数３～４８の炭化水素基を表し、該環状炭化水素基は、置換基を有してもよく、該炭化水素基に含まれる－ＣＨ₂－は、－Ｏ－、－Ｓ－、－ＳＯ_２－又は－ＣＯ－に置き換わっていてもよい。
Ｒ^2２は、ハロゲン原子又は炭素数１～６のアルキル基を表し、該アルキル基に含まれる－ＣＨ_２－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよい。
ｍ２２は、０～４のいずれかの整数を表し、ｍ２２が２以上のとき、複数のＲ^2２は互いに同一であっても異なってもよい。
Ｚ^＋は、有機カチオンを表す。］
〔１４〕酸発生剤から発生する酸よりも酸性度の弱い酸を発生する塩をさらに含有する〔１３〕に記載のレジスト組成物。
〔１５〕（１）〔１０〕～〔１４〕のいずれかに記載のレジスト組成物を基板上に塗布する工程、
（２）塗布後の組成物を乾燥させて組成物層を形成する工程、
（３）組成物層に露光する工程、
（４）露光後の組成物層を加熱する工程、及び
（５）加熱後の組成物層を現像する工程、を含むレジストパターンの製造方法。 The present invention includes the following inventions.
[1] A resin containing at least one structural unit selected from the group consisting of structural units represented by formula (a4-2) and structural units represented by formula (a4-3), and a structural unit represented by formula (I6).

[In formula (a4-2) and formula (a4-3),
^R41 represents a hydrogen atom or a methyl group.
L ^43h and L ^44h each independently represent a saturated hydrocarbon group having 1 to 20 carbon atoms which may have a halogen atom, and --CH ₂ -- contained in the saturated hydrocarbon group may be replaced by --O-- or --CO--.
R ^43h and R ^44h each independently represent a saturated hydrocarbon group having 1 to 20 carbon atoms which may have a halogen atom, and --CH ₂ -- contained in the saturated hydrocarbon group may be replaced by --O-- or --CO--.
However, at least one of L ^43h and R ^43h has a halogen atom, at least one of L ^44h and R ^44h has a halogen atom, and the upper limit of the total number of carbon atoms of L ^43h and R ^43h and the upper limit of the total number of carbon atoms of L ^44h and R ^44h are each 21.]

[In formula (I6),
Q ^b1 and Q ^b2 each independently represent a hydrogen atom, a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms, or an alkyl group having 1 to 6 carbon atoms.
L ^b1 represents a saturated hydrocarbon group having 1 to 24 carbon atoms, in which -CH ₂ - may be replaced by -O- or -CO-, and in which a hydrogen atom may be replaced by a fluorine atom or a hydroxyl group.
Y ^b1 represents a single bond or a cyclic hydrocarbon group having 3 to 24 carbon atoms which may have a substituent, and --CH ₂ -- contained in the cyclic hydrocarbon group may be replaced by --O--, --CO--, --S-- or --SO ₂ --.
mm1 represents 0 or 1.
R ¹⁰ represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
^X10 represents a single bond, *-O-**, *-CO-O-**, *-O-CO-O-** or *-Ax-Ph-Ay-**.
Ph represents a phenylene group which may have a substituent.
Ax and Ay each independently represent one type of bond selected from the group consisting of a single bond, an ether bond, a thioether bond, an ester bond, an amide bond, and a carbonate bond.
* and ** represent bonding sites, and * represents the bonding site with the carbon atom to which R ¹⁰ is bonded.
L ¹⁰ represents a single bond or a hydrocarbon group having 1 to 36 carbon atoms which may have a substituent, and --CH ₂ -- contained in the hydrocarbon group may be replaced by --O--, --S--, --SO ₂ -- or --CO--.
R ³ , R ⁴ , R ⁵ , and R ⁶ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, -CH ₂ - contained in the hydrocarbon group may be replaced by -O-, -S-, -NR ⁷ -, -SO ₂ - or -CO-, R ³ and R ⁴ , and R ³ , R ⁴ and R ⁵ may each be bonded to form a cyclic hydrocarbon group, which may have one or more double bonds between two adjacent carbon atoms, -CH ₂ - contained in the cyclic hydrocarbon group may be replaced by -O-, -CO- or -NR ⁷ -, and -CH= contained in the cyclic hydrocarbon group may be replaced by -N=.
^R7 represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, and _--CH2-- contained in the hydrocarbon group may be replaced by --O--, --S--, _--SO2-- or --CO--.]
[2] The resin according to [1], which contains a structural unit represented by formula (a4-2):
[3] Contains a structural unit represented by formula (a4-2),
The resin according to [1] or [2], wherein the structural unit represented by formula (a4-2) is a structural unit represented by formula (a4-2A) or a structural unit represented by formula (a4-2B).

[In formula (a4-2A) and formula (a4-2B),
R ⁴¹ has the same meaning as in formula (a4-2).
L ^43f represents a saturated hydrocarbon group having 1 to 20 carbon atoms which may have a fluorine atom, and --CH ₂ -- contained in the saturated hydrocarbon group may be replaced by --O-- or --CO--.
R ^43fA represents a saturated hydrocarbon group having 1 to 20 carbon atoms and containing a fluorine atom.
A ^43f represents a divalent saturated hydrocarbon group having 1 to 17 carbon atoms which may have a fluorine atom, and --CH ₂ -- contained in the saturated hydrocarbon group may be replaced by --O-- or --CO--.
X ⁴³ represents **-O-CO- or **-CO-O-, and ** represents a bonding site with A ^43f .
R ^43fB represents a saturated hydrocarbon group having 1 to 17 carbon atoms which may have a fluorine atom.
provided that in formula (a4-2A), the total number of carbon atoms of L ^43f and R ^43fA is 21 or less, and in formula (a4-2B), the total number of carbon atoms of L ^43f , A ^43f , X ⁴³ and R ^43fB is 21 or less, and at least one of A ^43f and R ^43fB has at least one fluorine atom.]
[4] The resin according to any one of [1] to [3], wherein Y ^b1 is a single bond or an alicyclic hydrocarbon group having 3 to 18 carbon atoms which may have a substituent (-CH ₂ - contained in the alicyclic hydrocarbon group may be replaced by -O-, -CO-, -S- or -SO ₂ -).
[5] Y ^b1 is an alicyclic hydrocarbon group having 3 to 18 carbon atoms which may have a substituent,
The resin according to any one of [1] to [4], wherein the alicyclic hydrocarbon group is a cycloalkanediyl group, norbornanediyl group, adamantanediyl group, adamantanelactonediyl group, or norbornanelactonediyl group having 5 or 6 carbon atoms, -CH ₂ - contained in the cycloalkanediyl group, norbornanediyl group, or adamantanediyl group may be replaced by -O- or -CO-, and the cycloalkanediyl group, norbornanediyl group, adamantanediyl group, adamantanelactonediyl group, or norbornanelactonediyl group may have a substituent.
[6] The resin according to any one of [1] to [5], wherein X ¹⁰ is a single bond or a group represented by any one of formulae (X ¹⁰ -1) to (X ¹⁰ -10).

[Formula (X ¹⁰ -1) to (X ¹⁰ -10),
* and ** are bonding sites, and * represents the bonding site with the carbon atom to which R ¹⁰ is bonded.
Rx represents a halogen atom, a hydroxy group, a fluorinated alkyl group having 1 to 6 carbon atoms, an alkyl group having 1 to 18 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.
mx represents an integer of 0 to 4.
X ²⁰ represents —O— or —NR ³ —.
^R3 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.
[7] The resin according to any one of [1] to [6], wherein X ¹⁰ is a single bond or a group represented by any one of formulas (X ¹⁰ -1'), (X10-3') to (X ¹⁰ -8') and (X ¹⁰ -10').

[Formula (X ¹⁰ -1'), Formula (X ¹⁰ -3') to (X ¹⁰ -8') and Formula (X ¹⁰ -10'),
* and ** are bonding sites, and * represents the bonding site with the carbon atom to which R ¹⁰ is bonded.]
[8] The resin according to [7], wherein X ¹⁰ is a single bond or a group represented by any one of formulas (X ¹⁰ -1'), (X ¹⁰ -5'), (X ¹⁰ -6') and (X ¹⁰ -10').
[9] L ¹⁰ is a single bond, an alkanediyl group having 1 to 6 carbon atoms, a cyclic hydrocarbon group having 3 to 18 carbon atoms, or a group formed by combining an alkanediyl group having 1 to 6 carbon atoms and a cyclic hydrocarbon group having 3 to 18 carbon atoms,
The resin according to any one of [1] to [8], wherein the -CH ₂ - contained in the alkanediyl group and the cyclic hydrocarbon group may be replaced by -O-, -S-, -SO ₂ - or -CO-, and the cyclic hydrocarbon group may have a substituent.
[10] A resist composition comprising the resin according to any one of [1] to [9].
[11] The resist composition according to [10], further comprising a resin that contains a structural unit having an acid labile group, different from the resin according to any one of [1] to [9].
[12] The resist composition according to [11], wherein the structural unit having an acid labile group includes at least one selected from the group consisting of a structural unit represented by formula (a1-0), a structural unit represented by formula (a1-1), a structural unit represented by formula (a1-2), and a structural unit represented by formula (a1-5).

[In formula (a1-0), formula (a1-1) and formula (a1-2),
L ^a01 , L ^a1 and L ^a2 each independently represent --O-- or *-O--(CH ₂ ) _k1 -CO--O--, where k1 represents an integer of 1 to 7, and * represents a bonding site with --CO--.
R ^a01 , R ^a4 and R ^a5 each independently represent a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
R ^a02 , R ^a03 , and R ^a04 each independently represent an alkyl group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a combination thereof, and the alkyl group, alicyclic hydrocarbon group, and aromatic hydrocarbon group may have a halogen atom.
R ^a6 and R ^a7 each independently represent an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group formed by combining these.
m1 represents an integer of 0 to 14.
n1 represents an integer of 0 to 10.
n1′ represents an integer of 0 to 3.

[In formula (a1-5),
R ^a8 represents an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, a hydrogen atom or a halogen atom.
Z ^a1 represents a single bond or *-(CH ₂ ) _h3 -CO-L ⁵⁴ -, h3 represents an integer of 1 to 4, and * represents the bonding site to L ⁵¹ .
L ⁵¹ , L ⁵² , L ⁵³ and L ⁵⁴ each independently represent --O-- or --S--.
s1 represents an integer of 1 to 3.
s1′ represents an integer of 0 to 3.]
[13] The resist composition according to any one of [10] to [12], further comprising an acid generator, the acid generator comprising a salt represented by formula (B1) or a salt represented by formula (B2).

[In formula (B1),
Q ^b1 and Q ^b2 each independently represent a hydrogen atom, a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms, or an alkyl group having 1 to 6 carbon atoms.
L ^b1 represents a saturated hydrocarbon group having 1 to 24 carbon atoms, in which -CH ₂ - may be replaced by -O- or -CO-, and in which a hydrogen atom may be replaced by a fluorine atom or a hydroxyl group.
Y represents a methyl group which may have a substituent or a cyclic hydrocarbon group having 3 to 24 carbon atoms which may have a substituent, and -CH ₂ - contained in the cyclic hydrocarbon group may be replaced by -O-, -S-, -SO ₂ - or -CO-.
Z ⁺ represents an organic cation.

[In formula (B2),
m21 represents an integer of 1 to 5, and when m21 is 2 or greater, the groups in the parentheses may be the same or different.
R ²¹ represents a hydrocarbon group having 3 to 48 carbon atoms, including a cyclic hydrocarbon group having 3 to 18 carbon atoms, the cyclic hydrocarbon group may have a substituent, and -CH ₂ - contained in the hydrocarbon group may be replaced by -O-, -S-, -SO ₂ - or -CO-.
R ²² represents a halogen atom or an alkyl group having 1 to 6 carbon atoms, and --CH ₂ -- contained in the alkyl group may be replaced by --O-- or --CO--.
m22 represents an integer of 0 to 4, and when m22 is 2 or greater, multiple R ²² may be the same or different.
Z ⁺ represents an organic cation.
[14] The resist composition according to [13], further comprising a salt that generates an acid having a weaker acidity than the acid generated from the acid generator.
[15] (1) A step of applying the resist composition according to any one of [10] to [14] onto a substrate;
(2) A step of drying the applied composition to form a composition layer;
(3) exposing the composition layer to light;
(4) a step of heating the composition layer after exposure; and (5) a step of developing the composition layer after heating.

By using the resist composition of the present invention, it is possible to produce resist patterns with good CD uniformity (CDU).

In this specification, the term "(meth)acrylic monomer" means at least one of an acrylic monomer and a methacrylic monomer. The terms "(meth)acrylate" and "(meth)acrylic acid" have the same meaning. In the groups described in this specification, those that can have both a straight chain structure and a branched structure may have either of them. When -CH ₂ - contained in a hydrocarbon group or the like is replaced with -O-, -S-, -CO- or -SO ₂ -, the same examples are applied to each group. The term "combined group" means a group in which two or more of the exemplified groups are combined by appropriately changing their valence, bond form, etc. The terms "derived from" or "derived from" refer to a polymerizable C═C bond contained in the molecule becoming a single bond (-C-C- group) by polymerization. When stereoisomers exist, all stereoisomers are included. Depending on the number of substituents, etc., hydrogen atoms in any position and number contained in each group may be replaced with bonds. The number of carbon atoms in a substituent is not included in the number of carbon atoms of the substituted group.
In this specification, the term "acid labile group" refers to a group that has a leaving group and that is eliminated by contact with an acid to form a hydrophilic group (for example, a hydroxy group or a carboxy group). The term "solid content of a resist composition" refers to the sum of all components excluding the solvent (E), which will be described later, from the total amount of the resist composition.

〔resin〕
The resin of the present invention is a resin (hereinafter sometimes referred to as "resin (A1)") that contains at least one structural unit selected from the group consisting of a structural unit represented by formula (a4-2) (hereinafter sometimes referred to as "structural unit (a4-2)") and a structural unit represented by formula (a4-3) (hereinafter sometimes referred to as "structural unit (a4-3)"), and a structural unit represented by formula (I6) (hereinafter sometimes referred to as "structural unit (I6)").

［式（ａ４－２）中、全ての符号は、それぞれ前記と同じ意味を表す。］ <Structural unit (a4-2)>
The structural unit (a4-2) is a structural unit represented by the following formula (a4-2).

[In formula (a4-2), all symbols have the same meaning as defined above.]

組み合わせにより形成される基としては、１以上のアルキル基又は１以上のアルカンジイル基と、１以上の脂環式飽和炭化水素基とを組み合わせることにより形成される基が挙げられ、－アルカンジイル基－脂環式飽和炭化水素基、－脂環式飽和炭化水素基－アルキル基、－アルカンジイル基－脂環式飽和炭化水素基－アルキル基等が挙げられる。
アルカンジイル基としては、メチレン基、エチレン基、プロパン－１，３－ジイル基、ブタン－１，４－ジイル基、ペンタン－１，５－ジイル基、ヘキサン－１，６－ジイル基等の直鎖状アルカンジイル基；プロパン－１，２－ジイル基、ブタン－１，３－ジイル基、２－メチルプロパン－１，２－ジイル基、１－メチルブタン－１，４－ジイル基、２－メチルブタン－１，４－ジイル基等の分岐状アルカンジイル基が挙げられる。分岐状のアルカンジイル基の末端は、メチル基であってもよい。
Ｒ^４３ｈに含まれる飽和炭化水素基が有するハロゲン原子としては、フッ素原子、塩素原子、臭素原子又はヨウ素原子が挙げられる。
Ｒ^４３ｈに含まれる飽和炭化水素基の－ＣＨ_２－が、－Ｏ－又は－ＣＯ－に置き換わった基としては、ヒドロキシ基（メチル基中に含まれる－ＣＨ₂－が、－Ｏ－に置き換わった基）、カルボキシ基（エチル基中に含まれる－ＣＨ₂－ＣＨ₂－が、－Ｏ－ＣＯ－に置き換わった基）、カルボニル基（メチレン基中に含まれる－ＣＨ₂－が、－ＣＯ－に置き換わった基）、オキシ基（メチレン基中に含まれる－ＣＨ₂－が、－Ｏ－に置き換わった基）、アルコキシ基（アルキル基中に含まれる任意の位置の－ＣＨ₂－が、－Ｏ－に置き換わった基）、アルコキシカルボニル基（アルキル基中に含まれる任意の位置の－ＣＨ₂－ＣＨ₂－が、－Ｏ－ＣＯ－に置き換わった基）、アルキルカルボニル基（アルキル基中に含まれる任意の位置の－ＣＨ₂－が、－ＣＯ－に置き換わった基）、アルキルカルボニルオキシ基（アルキル基中に含まれる任意の位置の－ＣＨ₂－ＣＨ₂－が、－ＣＯ－Ｏ－に置き換わった基）、アルカンジイルオキシ基（アルカンジイル基中に含まれる任意の位置の－ＣＨ₂－が、－Ｏ－に置き換わった基）、アルカンジイルオキシカルボニル基（アルカンジイル基中に含まれる任意の位置の－ＣＨ₂－ＣＨ₂－が、－Ｏ－ＣＯ－に置き換わった基）、アルカンジイルカルボニル基（アルカンジイル基中に含まれる任意の位置の－ＣＨ₂－が、－ＣＯ－に置き換わった基）、アルカンジイルカルボニルオキシ基（アルカンジイル基中に含まれる任意の位置の－ＣＨ₂－ＣＨ₂－が、－ＣＯ－Ｏ－に置き換わった基）、シクロアルコキシ基、シクロアルキルアルコキシ基これらの基のうち２種以上を組み合わせた基等が挙げられる。これらの置き換わった基は、炭素数の上限が許す範囲で、本明細書で例示した基と同様のものが挙げられる。
Ｒ^４３ｈがハロゲン原子を有する飽和炭化水素基である場合、好ましくはフッ素原子を有する飽和炭化水素基であり、より好ましくはフッ素原子を有するアルキル基、フッ素原子を有するシクロアルキル基又はこれらを組み合わせた基であり、さらに好ましくはペルフルオロアルキル基又はペルフルオロシクロアルキル基であり、さらにより好ましくは炭素数が１～６のペルフルオロアルキル基であり、特に好ましくは炭素数１～３のペルフルオロアルキル基である。ペルフルオロアルキル基としては、ペルフルオロメチル基、ペルフルオロエチル基、ペルフルオロプロピル基、ペルフルオロブチル基、ペルフルオロペンチル基、ペルフルオロヘキシル基、ペルフルオロヘプチル基及びペルフルオロオクチル基等が挙げられる。ペルフルオロシクロアルキル基としては、ペルフルオロシクロヘキシル基等が挙げられる。 Examples of the saturated hydrocarbon group for R ^43h include linear or branched chain saturated hydrocarbon groups, monocyclic or polycyclic alicyclic saturated hydrocarbon groups, and groups formed by combining these groups.
Examples of the chain saturated hydrocarbon group include linear alkyl groups such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a decyl group, a dodecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, and an octadecyl group, and branched alkyl groups such as an isopropyl group and an isobutyl group.
Examples of the alicyclic saturated hydrocarbon group include monocyclic alicyclic saturated hydrocarbon groups which are monocyclic cycloalkyl groups such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group; and polycyclic alicyclic saturated hydrocarbon groups which are polycyclic cycloalkyl groups such as a decahydronaphthyl group, an adamantyl group, a norbornyl group, and the following groups (* represents a bonding site):

Examples of groups formed by combination include groups formed by combining one or more alkyl groups or one or more alkanediyl groups with one or more alicyclic saturated hydrocarbon groups, such as -alkanediyl group-alicyclic saturated hydrocarbon group, -alicyclic saturated hydrocarbon group-alkyl group, and -alkanediyl group-alicyclic saturated hydrocarbon group-alkyl group.
Examples of the alkanediyl group include linear alkanediyl groups such as methylene, ethylene, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, and hexane-1,6-diyl groups, and branched alkanediyl groups such as propane-1,2-diyl, butane-1,3-diyl, 2-methylpropane-1,2-diyl, 1-methylbutane-1,4-diyl, and 2-methylbutane-1,4-diyl groups. The terminal of the branched alkanediyl group may be a methyl group.
Examples of the halogen atom contained in the saturated hydrocarbon group contained in R ^43h include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.
Examples of the saturated hydrocarbon group in R ^43h in which -CH ₂ - is replaced by -O- or -CO- include a hydroxy group (a group in which -CH ₂ - in a methyl group is replaced by -O-), a carboxy group (a group in which -CH ₂ -CH ₂ - in an ethyl group is replaced by -O-CO-), a carbonyl group (a group in which -CH ₂ - in a methylene group is replaced by -CO-), an oxy group (a group in which -CH ₂ - in a methylene group is replaced by -O-), an alkoxy group (a group in which -CH ₂ - at any position in an alkyl group is replaced by -O-), an alkoxycarbonyl group (a group in which -CH ₂ -CH ₂ - at any position in an alkyl group is replaced by -O-CO-), an alkylcarbonyl group (a group in which -CH 2 - at any position in an alkyl group is replaced by -O-CO-), and a carboxyl group (a group in which -CH ₂ - - is replaced with -CO-), alkylcarbonyloxy groups (groups in which -CH ₂ -CH ₂ - at any position in an alkyl group is replaced with -CO-O-), alkanediyloxy groups (groups in which -CH ₂ - at any position in an alkanediyl group is replaced with -O-), alkanediyloxycarbonyl groups (groups in which -CH ₂ -CH ₂ - at any position in an alkanediyl group is replaced with -O-CO-), alkanediylcarbonyl groups (groups in which -CH ₂ - at any position in an alkanediyl group is replaced with -CO-), alkanediylcarbonyloxy groups (groups in which -CH ₂ -CH ₂ - at any position in an alkanediyl group is replaced with -CO-), cycloalkoxy groups, cycloalkylalkoxy groups, and groups in which two or more of these groups are combined. These substituted groups include those similar to the groups exemplified in this specification, within the upper limit of the carbon number.
When R ^43h is a saturated hydrocarbon group having a halogen atom, it is preferably a saturated hydrocarbon group having a fluorine atom, more preferably an alkyl group having a fluorine atom, a cycloalkyl group having a fluorine atom, or a combination thereof, still more preferably a perfluoroalkyl group or a perfluorocycloalkyl group, still more preferably a perfluoroalkyl group having 1 to 6 carbon atoms, and particularly preferably a perfluoroalkyl group having 1 to 3 carbon atoms. Examples of perfluoroalkyl groups include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, a perfluorohexyl group, a perfluoroheptyl group, and a perfluorooctyl group. Examples of perfluorocycloalkyl groups include a perfluorocyclohexyl group.

Examples of the saturated hydrocarbon group for L ^43h include linear or branched chain saturated hydrocarbon groups, monocyclic or polycyclic alicyclic saturated hydrocarbon groups, and groups formed by combining these groups.
Examples of the chain saturated hydrocarbon group include linear alkanediyl groups such as methylene, ethylene, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, and hexane-1,6-diyl groups, and branched alkanediyl groups such as propane-1,2-diyl, butane-1,3-diyl, 2-methylpropane-1,2-diyl, 1-methylbutane-1,4-diyl, and 2-methylbutane-1,4-diyl groups. The terminal of the branched alkanediyl group may be a methyl group.
Examples of the alicyclic saturated hydrocarbon group include monocyclic cycloalkanediyl groups such as a cyclobutane-1,3-diyl group, a cyclopentane-1,3-diyl group, a cyclohexane-1,4-diyl group, a cyclohexene-3,6-diyl group, a cycloheptane-1,4-diyl group, and a cyclooctane-1,5-diyl group;
Examples of the cycloalkanediyl group include polycyclic cycloalkanediyl groups such as norbornane-1,4-diyl group, norbornane-2,5-diyl group, 5-norbornene-2,3-diyl group, adamantane-1,5-diyl group, and adamantane-2,6-diyl group.
Examples of the group formed by combining two or more types selected from monocyclic or polycyclic alicyclic saturated hydrocarbon groups and straight-chain or branched chain saturated hydrocarbon groups include the same groups as those exemplified for R ^43h .
Examples of the saturated hydrocarbon group included in L ^43h in which —CH ₂ — is replaced by —O— or —CO— include the same groups as those exemplified as the saturated hydrocarbon group included in R ^43h in which —CH ₂ — is replaced by —O— or —CO—.
Examples of the halogen atom contained in the saturated hydrocarbon group contained in L ^43h include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.
The halogen atom contained in the saturated hydrocarbon group contained in L ^43h is preferably a fluorine atom.
Examples of the saturated hydrocarbon group having a fluorine atom in L ^43h include an alkanediyl group having a fluorine atom and a cycloalkanediyl group having a fluorine atom.
Examples of the alkanediyl group having a fluorine atom in L ^43h include linear alkanediyl groups having a fluorine atom, such as a methylene group having a fluorine atom, an ethylene group having a fluorine atom, a propane-1,3-diyl group having a fluorine atom, a butane-1,4-diyl group having a fluorine atom, a pentane-1,5-diyl group having a fluorine atom, a hexane-1,6-diyl group having a fluorine atom, a heptane-1,7-diyl group having a fluorine atom, and an octane-1,8-diyl group having a fluorine atom;
Examples of branched alkanediyl groups having fluorine atoms include an ethane-1,1-diyl group having a fluorine atom, a propane-1,1-diyl group having a fluorine atom, a propane-1,2-diyl group having a fluorine atom, a propane-2,2-diyl group having a fluorine atom, a pentane-2,4-diyl group having a fluorine atom, a 2-methylpropane-1,3-diyl group having a fluorine atom, a 2-methylpropane-1,2-diyl group having a fluorine atom, a pentane-1,4-diyl group having a fluorine atom, and a 2-methylbutane-1,4-diyl group having a fluorine atom. The end of the branched alkanediyl group may be a methyl group which may have a fluorine atom.
Examples of the cycloalkanediyl group having a fluorine atom in L ^43h include monocyclic cycloalkanediyl groups having a fluorine atom, such as a cyclobutane-1,3-diyl group having a fluorine atom, a cyclopentane-1,3-diyl group having a fluorine atom, a cyclohexane-1,4-diyl group having a fluorine atom, a cyclohexene-3,6-diyl group having a fluorine atom, a cycloheptane-1,4-diyl group having a fluorine atom, and a cyclooctane-1,5-diyl group having a fluorine atom;
Examples of the fluorine atom-containing polycyclic cycloalkanediyl group include a norbornane-1,4-diyl group having a fluorine atom, a norbornane-2,5-diyl group having a fluorine atom, a 5-norbornene-2,3-diyl group having a fluorine atom, an adamantane-1,5-diyl group having a fluorine atom, and an adamantane-2,6-diyl group having a fluorine atom.
The number of fluorine atoms contained in the alkanediyl group and cycloalkanediyl group having a fluorine atom in L ^43h may be 1 or more, and is preferably 2 or more.
The alkanediyl group and cycloalkanediyl group having a fluorine atom in L ^43h are preferably a perfluoroalkanediyl group and a perfluorocycloalkanediyl group, respectively.

［式（Ｌ４３ｈ－１）中、
ｓは、０又は１を表す。
Ｌ^４５ｈ及びＬ^４６ｈは、それぞれ独立に、ハロゲン原子を有していてもよい炭素数１～５の２価の飽和炭化水素基を表す。
Ｌ^４７ｈは、単結合又はハロゲン原子を有していてもよい炭素数１～５の２価の飽和炭化水素基を表す。
Ｘ^４６ｈ及びＸ^４７ｈは、それぞれ独立に、－Ｏ－、－ＣＯ－、－ＣＯ－Ｏ－又は－Ｏ－ＣＯ－を表す。
ただし、Ｌ^４５ｈ、Ｌ^４６ｈ、Ｌ^４７ｈ、Ｘ^４６ｈ及びＸ^４７ｈの炭素数の合計は７以下である。
＊及び＊＊は結合部位であり、＊＊が－Ｏ－ＣＯ－Ｒ^４３ｈとの結合部位である。］ Examples of the perfluoroalkanediyl group in L ^43h include a difluoromethylene group, a perfluoroethylene group, a perfluoroethylfluoromethylene group, a perfluoropropane-1,3-diyl group, a perfluoropropane-1,2-diyl group, a perfluoropropane-2,2-diyl group, a perfluorobutane-1,4-diyl group, a perfluorobutane-2,2-diyl group, a perfluorobutane-1,2-diyl group, a perfluoropentane-1,5-diyl group, a perfluoropentane-2,2-diyl group, a perfluoropentane- Examples of the perfluorohexane-3,3-diyl group include perfluorohexane-1,6-diyl group, perfluorohexane-2,2-diyl group, perfluorohexane-3,3-diyl group, perfluoroheptane-1,7-diyl group, perfluoroheptane-2,2-diyl group, perfluoroheptane-3,4-diyl group, perfluoroheptane-4,4-diyl group, perfluorooctane-1,8-diyl group, perfluorooctane-2,2-diyl group, perfluorooctane-3,3-diyl group, and perfluorooctane-4,4-diyl group.
Examples of the perfluorocycloalkanediyl group in L ^43h include a perfluorocyclohexanediyl group, a perfluorocyclopentanediyl group, a perfluorocycloheptanediyl group, and a perfluoroadamantanediyl group.
The saturated hydrocarbon group for ^L43h is preferably an alkanediyl group having 1 to 6 carbon atoms or a group represented by the formula (L43h-1).

[In formula (L43h-1),
s represents 0 or 1.
L ^45h and L ^46h each independently represent a divalent saturated hydrocarbon group having 1 to 5 carbon atoms which may have a halogen atom.
L ^47h represents a single bond or a divalent saturated hydrocarbon group having 1 to 5 carbon atoms which may have a halogen atom.
X ^46h and X ^47h each independently represent -O-, -CO-, -CO-O- or -O-CO-.
However, the total number of carbon atoms in ^L45h , ^L46h , ^L47h , ^X46h and ^X47h is 7 or less.
* and ** are binding sites, and ** is the binding site with -O-CO-R ^43h .]

Examples of the divalent saturated hydrocarbon group represented by L ^45h , L ^46h and L ^47h in the group represented by formula (L43h-1) include a linear or branched alkanediyl group, a monocyclic or polycyclic divalent alicyclic saturated hydrocarbon group, and a divalent saturated hydrocarbon group formed by combining an alkanediyl group and a divalent alicyclic saturated hydrocarbon group, etc. Specific examples include a methylene group, an ethylene group, a propane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diyl group, a 1-methylpropane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, etc.
It is preferred that s is 0.

Ｌ^４３ｈは、炭素数２～４のアルカンジイル基が好ましく、エチレン基が好ましい。 Examples of the group represented by formula (L43h-1) include the following groups: In the following examples, * and ** each represent a bonding site, and ** is the bonding site to --O--CO--R ^43h .

L ^43h is preferably an alkanediyl group having 2 to 4 carbon atoms, and more preferably an ethylene group.

［式（ａ４－２Ａ）及び式（ａ４－２Ｂ）中、全ての符号は、それぞれ前記と同じ意味を表す。］
Ｌ^４３ｆの飽和炭化水素基は、炭素数の上限が許す限り、かつ、フッ素原子を有する場合はフッ素原子を有する限り、式（ａ４－２）におけるＬ^４３ｈの飽和炭化水素基と同様の飽和炭化水素基が挙げられる。
Ｒ^４３ｆＡの飽和炭化水素基は、炭素数の上限が許す限り、かつ、フッ素原子を有する限り、式（ａ４－２）におけるＲ^４３ｈで例示された飽和炭化水素基と同様の飽和炭化水素基が挙げられる。
Ｒ^４３ｆＡは、炭素数１～１３のフッ素原子を有するアルキル基、炭素数３～１２のフッ素原子を有するシクロアルキル基又はそれらを組み合わせた基であることが好ましく、＊－（ＣＦ_２）_ｎ４３ｆ－Ｒ^４３ｆ（＊はカルボニル基との結合部位を表す。ｎ４３ｆは、１～６のいずれかの整数を表す。Ｒ^４３ｆは、水素原子又はフッ素原子を表す。）又は炭素数３～１２のペルフルオロシクロアルキル基であることがより好ましい。
Ａ^４３ｆ及びＲ^４３ｆＢの飽和炭化水素基は、炭素数の上限が許す限り、式（ａ４－２）におけるＲ^４３ｈで例示された飽和炭化水素基と同様の飽和炭化水素基が挙げられる。
Ａ^４３ｆは、フッ素原子を有してもよい２価の鎖式飽和炭化水素基、２価の脂環式飽和炭化水素基又はそれらを組み合わせた基であることが好ましく、フッ素原子を有する２価の鎖式飽和炭化水素基であることがより好ましく、炭素数１～６のフッ化アルカンジイル基であることがさらに好ましい。
Ｒ^４３ｆＢのフッ素原子を有していてもよい飽和炭化水素基は、フッ素原子を有してもよい鎖式飽和炭化水素基、脂環式飽和炭化水素基又はそれらを組み合わせた基が好ましく、フッ素原子を有してもよい炭素数１～１２のアルキル基、炭素数３～１２のシクロアルキル基又はそれらを組み合わせた基がより好ましく、トリフルオロメチル基、ジフルオロメチル基、メチル基、ペルフルオロエチル基、２，２，２－トリフルオロエチル基、１，１，２，２－テトラフルオロエチル基、エチル基、ペルフルオロプロピル基、２，２，３，３，３－ペンタフルオロプロピル基、プロピル基、ペルフルオロブチル基、１，１，２，２，３，３，４，４－オクタフルオロブチル基、ブチル基、ペルフルオロペンチル基、２，２，３，３，４，４，５，５，５－ノナフルオロペンチル基、ペンチル基、ヘキシル基、ペルフルオロヘキシル基、ヘプチル基、ペルフルオロヘプチル基、オクチル基及びペルフルオロオクチル基等のフッ化アルキル基、シクロプロピルメチル基、シクロプロピル基、シクロブチルメチル基、シクロペンチル基、シクロヘキシル基、ペルフルオロシクロヘキシル基、アダマンチル基、アダマンチルメチル基、アダマンチルジメチル基、ノルボルニル基、ノルボルニルメチル基、ペルフルオロアダマンチル基、ペルフルオロアダマンチルメチル基等がさらに好ましい。 R ^43h is preferably a saturated hydrocarbon group having a fluorine atom.
Examples of the structural unit represented by formula (a4-2) include structural units represented by formula (a4-2A) or (a4-2B).

[In formula (a4-2A) and formula (a4-2B), all symbols have the same meaning as defined above.]
Examples of the saturated hydrocarbon group for L ^43f include the same saturated hydrocarbon groups as the saturated hydrocarbon group for L ^43h in formula (a4-2), provided that the upper limit of the number of carbon atoms permits and, if it has a fluorine atom, that it has a fluorine atom.
Examples of the saturated hydrocarbon group for R ^43fA include the same saturated hydrocarbon groups as those exemplified for R ^43h in formula (a4-2), as long as the upper limit of the number of carbon atoms permits and as long as it has a fluorine atom.
R ^43fA is preferably an alkyl group having a fluorine atom and having 1 to 13 carbon atoms, a cycloalkyl group having a fluorine atom and having 3 to 12 carbon atoms, or a combination thereof, and is more preferably *-(CF ₂ ) _n43f -R ^43f (* represents the bonding site with the carbonyl group, n43f represents an integer of 1 to 6, and R ^43f represents a hydrogen atom or a fluorine atom) or a perfluorocycloalkyl group having 3 to 12 carbon atoms.
As the saturated hydrocarbon group for A ^43f and R ^43fB , as long as the upper limit of the number of carbon atoms permits, there can be mentioned the same saturated hydrocarbon groups as the examples of the saturated hydrocarbon groups exemplified for R ^43h in formula (a4-2).
A ^43f is preferably a divalent chain saturated hydrocarbon group which may have a fluorine atom, a divalent alicyclic saturated hydrocarbon group, or a combination thereof, more preferably a divalent chain saturated hydrocarbon group which has a fluorine atom, and even more preferably a fluorinated alkanediyl group having 1 to 6 carbon atoms.
The saturated hydrocarbon group which may have a fluorine atom of R ^43fB is preferably a chain saturated hydrocarbon group which may have a fluorine atom, an alicyclic saturated hydrocarbon group, or a group combining these, more preferably an alkyl group having 1 to 12 carbon atoms which may have a fluorine atom, a cycloalkyl group having 3 to 12 carbon atoms, or a group combining these, and further preferably a trifluoromethyl group, a difluoromethyl group, a methyl group, a perfluoroethyl group, a 2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, an ethyl group, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, a propyl group, a perfluorobutyl group, a 1,1,2,2,3,3,4, More preferred are fluorinated alkyl groups such as 4-octafluorobutyl group, butyl group, perfluoropentyl group, 2,2,3,3,4,4,5,5,5-nonafluoropentyl group, pentyl group, hexyl group, perfluorohexyl group, heptyl group, perfluoroheptyl group, octyl group, and perfluorooctyl group, cyclopropylmethyl group, cyclopropyl group, cyclobutylmethyl group, cyclopentyl group, cyclohexyl group, perfluorocyclohexyl group, adamantyl group, adamantylmethyl group, adamantyldimethyl group, norbornyl group, norbornylmethyl group, perfluoroadamantyl group, and perfluoroadamantylmethyl group.

In formula (a4-2B), one example of a structure which the group represented by *-A ^43f -X ⁴³ -R ^43fB may take is the following structure (* is a bonding site with a carbonyl group).

Examples of the structural unit represented by formula (a4-2A) include the structural units shown below and structural units in which a methyl group corresponding to R ⁴¹ in the structural unit represented by formula (a4-2A) in the following structural units is replaced with a hydrogen atom.

Examples of the structural unit represented by formula (a4-2B) include the structural units shown below and structural units in which a methyl group corresponding to R ⁴¹ in the structural unit represented by formula (a4-2B) in the following structural units is replaced with a hydrogen atom.

［式（ａ４－３）中、全ての符号は、それぞれ前記と同じ意味を表す。］ <Structural unit (a4-3)>
The structural unit (a4-3) is a structural unit represented by the following formula (a4-3).

[In formula (a4-3), all symbols have the same meaning as defined above.]

Examples of the saturated hydrocarbon group in L ^44h and R ^44h include linear or branched chain saturated hydrocarbon groups, monocyclic or polycyclic alicyclic saturated hydrocarbon groups, and groups formed by combining these, etc. Examples of the saturated hydrocarbon group in L ^44h and R ^44h include the same groups as the exemplified saturated hydrocarbon groups as the saturated hydrocarbon group in R ^43h in formula (a4-2), as long as the upper limit of the total carbon number of L ^44h and R ^44h allows.
L ^44h is preferably an alkanediyl group having 1 to 14 carbon atoms (-CH ₂ - contained in the alkanediyl group may be replaced by -O- or -CO-), and more preferably a group represented by -(CH ₂ ) _j1 -, -(CH ₂ ) _j2 -O-(CH ₂ ) _j3 - or -(CH ₂ ) _j4 -CO-O-(CH ₂ ) _j5 - (j1 to j5 each independently represent an integer of 1 to 6). Also preferred is an alkanediyl group having 1 to 4 carbon atoms (one -CH ₂ - contained in the alkanediyl group may be replaced by -O-, and one -CH ₂ -CH ₂ - contained in the alkanediyl group may be replaced by -CO-O- or -O-CO-).
R ^44h is preferably a saturated hydrocarbon group having 1 to 10 carbon atoms and having a fluorine atom, more preferably an alkyl group having 1 to 10 carbon atoms and having a fluorine atom, an alicyclic saturated hydrocarbon group having 3 to 10 carbon atoms and having a fluorine atom, or a group combining these, still more preferably an alkyl group having 1 to 10 carbon atoms and having a fluorine atom, and even more preferably an alkyl group having 1 to 6 carbon atoms and having a fluorine atom.

Examples of the structural unit represented by formula (a4-3) include the following structural units and structural units represented by the following formulas in which a methyl group corresponding to R ⁴¹ in the structural unit (a4-3) is replaced with a hydrogen atom.

［式（Ｉ６）及び式（Ｉ６－ｓ）中、全ての符号はそれぞれ前記と同じ意味を表す。］ <Structural Unit (I6)>
The structural unit (I6) is a structural unit represented by the following formula (I6).
The structural unit (I6) is derived from, for example, a salt represented by formula (I6-s) which can function as an acid generator (hereinafter, sometimes referred to as salt (I6-s)), and is in a state in which the double bond of CH ₂ ═C—R ¹⁰ contained in the salt (I6-s) is cleaved.
In the salt (I6-s), the negatively charged side is sometimes referred to as the "anion (I6-a)" and the positively charged side is sometimes referred to as the "cation (I6-c)."

[In formula (I6) and formula (I6-s), all symbols have the same meanings as defined above.]

(Anion (I6-a))
Examples of the perfluoroalkyl group represented by Q ^b1 and Q ^b2 include a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluoroisopropyl group, a perfluorobutyl group, a perfluorosec-butyl group, a perfluorotert-butyl group, a perfluoropentyl group, and a perfluorohexyl group.
Examples of the alkyl group represented by Q ^b1 and Q ^b2 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, and an n-hexyl group. An alkyl group having 1 to 4 carbon atoms is preferable, and a methyl group or an ethyl group is more preferable.
At least one of Q ^b1 and Q ^b2 preferably contains a fluorine atom or a perfluoroalkyl group, more preferably each independently is a fluorine atom or a perfluoroalkyl group, further preferably is a fluorine atom or a trifluoromethyl group, and even more preferably is both a fluorine atom.

Examples of the saturated hydrocarbon group for L ^b1 include a linear alkanediyl group, a branched alkanediyl group, and a monocyclic or polycyclic alicyclic saturated hydrocarbon group, and may be a group formed by combining two or more of these groups.
Specific examples of such straight-chain alkanediyl groups include methylene, ethylene, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, decane-1,10-diyl, undecane-1,11-diyl, dodecane-1,12-diyl, tridecane-1,13-diyl, tetradecane-1,14-diyl, pentadecane-1,15-diyl, hexadecane-1,16-diyl, and heptadecane-1,17-diyl groups;
branched alkanediyl groups such as ethane-1,1-diyl group, propane-1,1-diyl group, propane-1,2-diyl group, propane-2,2-diyl group, pentane-2,4-diyl group, 2-methylpropane-1,3-diyl group, 2-methylpropane-1,2-diyl group, pentane-1,4-diyl group, and 2-methylbutane-1,4-diyl group;
monocyclic alicyclic saturated hydrocarbon groups such as cycloalkanediyl groups, such as cyclobutane-1,3-diyl group, cyclopentane-1,3-diyl group, cyclohexane-1,4-diyl group, and cyclooctane-1,5-diyl group;
Examples of the polycyclic alicyclic saturated hydrocarbon groups include norbornane-1,4-diyl group, norbornane-2,5-diyl group, adamantane-1,5-diyl group, adamantane-2,6-diyl group, etc. The terminal of the branched alkanediyl group may be a methyl group.

Examples of the saturated hydrocarbon group represented by L ^b1 in which -CH ₂ - is replaced by -O- or -CO- include groups represented by any of formulas (b1-1) to (b1-3). In the groups represented by formulas (b1-1) to (b1-3) and specific examples thereof represented by formulas (b1-4) to (b1-11), * and ** represent bonding sites, and * represents a bonding site with -Y ^b1 .

［式（ｂ１－１）中、
Ｌ^ｂ２は、単結合又は炭素数１～２２の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子に置換されていてもよい。
Ｌ^ｂ３は、単結合又は炭素数１～２２の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子又はヒドロキシ基に置換されていてもよく、該飽和炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよい。
ただし、Ｌ^ｂ２とＬ^ｂ３との炭素数合計は、２２以下である。
式（ｂ１－２）中、
Ｌ^ｂ４は、単結合又は炭素数１～２２の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子に置換されていてもよい。
Ｌ^ｂ５は、単結合又は炭素数１～２２の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子又はヒドロキシ基に置換されていてもよく、該飽和炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよい。
ただし、Ｌ^ｂ４とＬ^ｂ５との炭素数合計は、２２以下である。
式（ｂ１－３）中、
Ｌ^ｂ６は、単結合又は炭素数１～２３の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子又はヒドロキシ基に置換されていてもよい。
Ｌ^ｂ７は、単結合又は炭素数１～２３の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子又はヒドロキシ基に置換されていてもよく、該飽和炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよい。
ただし、Ｌ^ｂ６とＬ^ｂ７との炭素数合計は、２３以下である。］

[In formula (b1-1),
L ^b2 represents a single bond or a divalent saturated hydrocarbon group having 1 to 22 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom.
L ^b3 represents a single bond or a divalent saturated hydrocarbon group having 1 to 22 carbon atoms, a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxyl group, The --CH ₂ -- contained in the hydrocarbon group may be replaced by --O-- or --CO--.
However, the total number of carbon atoms in L ^b2 and L ^b3 is 22 or less.
In formula (b1-2),
L ^b4 represents a single bond or a divalent saturated hydrocarbon group having 1 to 22 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom.
L ^b5 represents a single bond or a divalent saturated hydrocarbon group having 1 to 22 carbon atoms, a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxyl group, The --CH ₂ -- contained in the hydrocarbon group may be replaced by --O-- or --CO--.
However, the total number of carbon atoms in L ^b4 and L ^b5 is 22 or less.
In formula (b1-3),
L ^b6 represents a single bond or a divalent saturated hydrocarbon group having 1 to 23 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group.
L ^b7 represents a single bond or a divalent saturated hydrocarbon group having 1 to 23 carbon atoms, a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxyl group, The --CH ₂ -- contained in the hydrocarbon group may be replaced by --O-- or --CO--.
However, the total number of carbon atoms in L ^b6 and L ^b7 is 23 or less.

In the groups represented by formulae (b1-1) to (b1-3), when --CH ₂ -- contained in the saturated hydrocarbon group is replaced with --O-- or --CO--, the number of carbon atoms before replacement is regarded as the number of carbon atoms of the saturated hydrocarbon group.
Examples of the divalent saturated hydrocarbon group include the same divalent saturated hydrocarbon groups as those represented by L ^b1 .

L ^b2 is preferably a single bond, a methylene group, -CH(CF ₃ )- or -C(CF ₃ ) ₂ -.
L ^b3 is preferably a divalent saturated hydrocarbon group having 1 to 4 carbon atoms.
L ^b4 is preferably a divalent saturated hydrocarbon group having 1 to 8 carbon atoms, in which a hydrogen atom may be substituted with a fluorine atom, and is preferably a methylene group, -CH(CF ₃ )-, or -C(CF ₃ ) ₂ -.
L ^b5 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^b6 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 4 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom.
L ^b7 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, in which a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group, and -CH ₂ - contained in the divalent saturated hydrocarbon group may be substituted with -O- or -CO-.

［式（ｂ１－４）中、
Ｌ^ｂ８は、単結合又は炭素数１～２２の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子又はヒドロキシ基に置換されていてもよい。
式（ｂ１－５）中、
Ｌ^ｂ９は、炭素数１～２０の２価の飽和炭化水素基を表し、該２価の飽和炭化水素基に含まれる－ＣＨ_２－は－Ｏ－又は－ＣＯ－に置き換わっていてもよい。
Ｌ^ｂ１０は、単結合又は炭素数１～１９の２価の飽和炭化水素基を表し、該２価の飽和炭化水素基に含まれる水素原子は、フッ素原子又はヒドロキシ基に置換されていてもよい。
ただし、Ｌ^ｂ９及びＬ^ｂ１０の合計炭素数は２０以下である。
式（ｂ１－６）中、
Ｌ^ｂ１１は、炭素数１～２１の２価の飽和炭化水素基を表す。
Ｌ^ｂ１２は、単結合又は炭素数１～２０の２価の飽和炭化水素基を表し、該２価の飽和炭化水素基に含まれる水素原子は、フッ素原子又はヒドロキシ基に置換されていてもよい。
ただし、Ｌ^ｂ１１及びＬ^ｂ１２の合計炭素数は２１以下である。
式（ｂ１－７）中、
Ｌ^ｂ１３は、炭素数１～１９の２価の飽和炭化水素基を表す。
Ｌ^ｂ１４は、単結合又は炭素数１～１８の２価の飽和炭化水素基を表し、該２価の飽和炭化水素基に含まれる－ＣＨ_２－は－Ｏ－又は－ＣＯ－に置き換わっていてもよい。
Ｌ^ｂ１５は、単結合又は炭素数１～１８の２価の飽和炭化水素基を表し、該２価の飽和炭化水素基に含まれる水素原子は、フッ素原子又はヒドロキシ基に置換されていてもよい。
ただし、Ｌ^ｂ１３～Ｌ^ｂ１５の合計炭素数は１９以下である。
式（ｂ１－８）中、
Ｌ^ｂ１６は、炭素数１～１８の２価の飽和炭化水素基を表し、該２価の飽和炭化水素基に含まれる－ＣＨ_２－は－Ｏ－又は－ＣＯ－に置き換わっていてもよい。
Ｌ^ｂ１７は、炭素数１～１８の２価の飽和炭化水素基を表す。
Ｌ^ｂ１８は、単結合又は炭素数１～１７の２価の飽和炭化水素基を表し、該２価の飽和炭化水素基に含まれる水素原子は、フッ素原子又はヒドロキシ基に置換されていてもよい。
ただし、Ｌ^ｂ１６～Ｌ^ｂ１８の合計炭素数は１９以下である。］ The divalent saturated hydrocarbon group represented by L ^b1 in which --CH ₂ -- is replaced by --O-- or --CO-- is preferably a group represented by formula (b1-1) or formula (b1-3).
Examples of the group represented by formula (b1-1) include groups represented by formulas (b1-4) to (b1-8).

[In formula (b1-4),
L ^b8 represents a single bond or a divalent saturated hydrocarbon group having 1 to 22 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group.
In formula (b1-5),
L ^b9 represents a divalent saturated hydrocarbon group having 1 to 20 carbon atoms, and --CH ₂ -- contained in the divalent saturated hydrocarbon group may be replaced by --O-- or --CO--.
L ^b10 represents a single bond or a divalent saturated hydrocarbon group having 1 to 19 carbon atoms, and a hydrogen atom contained in the divalent saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxyl group.
However, the total number of carbon atoms in L ^b9 and L ^b10 is 20 or less.
In formula (b1-6),
L ^b11 represents a divalent saturated hydrocarbon group having 1 to 21 carbon atoms.
L ^b12 represents a single bond or a divalent saturated hydrocarbon group having 1 to 20 carbon atoms, and a hydrogen atom contained in the divalent saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group.
However, the total number of carbon atoms in L ^b11 and L ^b12 is 21 or less.
In formula (b1-7),
L ^b13 represents a divalent saturated hydrocarbon group having 1 to 19 carbon atoms.
L ^b14 represents a single bond or a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and --CH ₂ -- contained in the divalent saturated hydrocarbon group may be replaced by --O-- or --CO--.
L ^b15 represents a single bond or a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and a hydrogen atom contained in the divalent saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group.
However, the total number of carbon atoms of L ^b13 to L ^b15 is 19 or less.
In formula (b1-8),
L ^b16 represents a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and --CH ₂ -- contained in the divalent saturated hydrocarbon group may be replaced by --O-- or --CO--.
L ^b17 represents a divalent saturated hydrocarbon group having 1 to 18 carbon atoms.
L ^b18 represents a single bond or a divalent saturated hydrocarbon group having 1 to 17 carbon atoms, and a hydrogen atom contained in the divalent saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group.
However, the total number of carbon atoms of L ^b16 to L ^b18 is 19 or less.]

L ^b8 is preferably a divalent saturated hydrocarbon group having 1 to 4 carbon atoms.
L ^b9 is preferably a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^b10 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 19 carbon atoms, and more preferably a single bond or a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^b11 is preferably a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^b12 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^b13 is preferably a divalent saturated hydrocarbon group having 1 to 12 carbon atoms.
L ^b14 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 6 carbon atoms.
L ^b15 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and more preferably a single bond or a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^b16 is preferably a divalent saturated hydrocarbon group having 1 to 12 carbon atoms.
L ^b17 is preferably a divalent saturated hydrocarbon group having 1 to 6 carbon atoms.
L ^b18 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 17 carbon atoms, and more preferably a single bond or a divalent saturated hydrocarbon group having 1 to 4 carbon atoms.

［式（ｂ１－９）中、
Ｌ^b19は、単結合又は炭素数１～２３の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子に置換されていてもよい。
Ｌ^b20は、単結合又は炭素数１～２３の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子、ヒドロキシ基又はアルキルカルボニルオキシ基に置換されていてもよい。該アルキルカルボニルオキシ基に含まれる－ＣＨ₂－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよく、該アルキルカルボニルオキシ基に含まれる水素原子は、ヒドロキシ基に置換されていてもよい。
ただし、Ｌ^b19及びＬ^b20の合計炭素数は２３以下である。
式（ｂ１－１０）中、
Ｌ^b21は、単結合又は炭素数１～２１の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子に置換されていてもよい。
Ｌ^b22は、単結合又は炭素数１～２１の２価の飽和炭化水素基を表す。
Ｌ^b23は、単結合又は炭素数１～２１の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子、ヒドロキシ基又はアルキルカルボニルオキシ基に置換されていてもよい。該アルキルカルボニルオキシ基に含まれる－ＣＨ₂－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよく、該アルキルカルボニルオキシ基に含まれる水素原子は、ヒドロキシ基に置換されていてもよい。
ただし、Ｌ^b21、Ｌ^b22及びＬ^b23の合計炭素数は２１以下である。
式（ｂ１－１１）中、
Ｌ^b24は、単結合又は炭素数１～２０の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子に置換されていてもよい。
Ｌ^b25は、炭素数１～２１の２価の飽和炭化水素基を表す。
Ｌ^b26は、単結合又は炭素数１～２０の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子、ヒドロキシ基又はアルキルカルボニルオキシ基に置換されていてもよい。該アルキルカルボニルオキシ基に含まれる－ＣＨ₂－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよく、該アルキルカルボニルオキシ基に含まれる水素原子は、ヒドロキシ基に置換されていてもよい。
ただし、Ｌ^b24、Ｌ^b25及びＬ^b26の合計炭素数は２１以下である。］ Examples of the group represented by formula (b1-3) include groups represented by formulas (b1-9) to (b1-11).

[In formula (b1-9),
L ^b19 represents a single bond or a divalent saturated hydrocarbon group having 1 to 23 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom.
L ^b20 represents a single bond or a divalent saturated hydrocarbon group having 1 to 23 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom, a hydroxyl group or an alkylcarbonyloxy group. -CH ₂ - contained in the alkylcarbonyloxy group may be replaced with -O- or -CO-, and a hydrogen atom contained in the alkylcarbonyloxy group may be substituted with a hydroxyl group.
However, the total number of carbon atoms of L ^b19 and L ^b20 is 23 or less.
In formula (b1-10),
L ^b21 represents a single bond or a divalent saturated hydrocarbon group having 1 to 21 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom.
L ^b22 represents a single bond or a divalent saturated hydrocarbon group having 1 to 21 carbon atoms.
L ^b23 represents a single bond or a divalent saturated hydrocarbon group having 1 to 21 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom, a hydroxyl group or an alkylcarbonyloxy group. -CH ₂ - contained in the alkylcarbonyloxy group may be replaced with -O- or -CO-, and a hydrogen atom contained in the alkylcarbonyloxy group may be substituted with a hydroxyl group.
However, the total number of carbon atoms of L ^b21 , L ^b22 and L ^b23 is 21 or less.
In formula (b1-11),
L ^b24 represents a single bond or a divalent saturated hydrocarbon group having 1 to 20 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom.
L ^b25 represents a divalent saturated hydrocarbon group having 1 to 21 carbon atoms.
L ^b26 represents a single bond or a divalent saturated hydrocarbon group having 1 to 20 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom, a hydroxyl group or an alkylcarbonyloxy group. -CH ₂ - contained in the alkylcarbonyloxy group may be replaced with -O- or -CO-, and a hydrogen atom contained in the alkylcarbonyloxy group may be substituted with a hydroxyl group.
However, the total number of carbon atoms of L ^b24 , L ^b25 and L ^b26 is 21 or less.]

In addition, in the groups represented by formulae (b1-9) to (b1-11), when a hydrogen atom contained in the saturated hydrocarbon group is substituted with an alkylcarbonyloxy group, the number of carbon atoms before substitution is regarded as the number of carbon atoms of the saturated hydrocarbon group.
Examples of the alkylcarbonyloxy group include an acetyloxy group, a propionyloxy group, a butyryloxy group, a cyclohexylcarbonyloxy group, and an adamantylcarbonyloxy group.

Examples of the group represented by formula (b1-4) include the following.

Examples of the group represented by formula (b1-5) include the following.

Examples of the group represented by formula (b1-6) include the following.

Examples of the group represented by formula (b1-7) include the following.

Examples of the group represented by formula (b1-8) include the following.

Examples of the group represented by formula (b1-2) include the following.

Examples of the group represented by formula (b1-9) include the following.

Examples of the group represented by formula (b1-10) include the following.

Examples of the group represented by formula (b1-11) include the following.

Examples of the cyclic hydrocarbon group represented by Y ^b1 include an alicyclic hydrocarbon group, an aromatic hydrocarbon group, a heterocyclic aromatic hydrocarbon group, or a combination thereof.
Examples of the alicyclic hydrocarbon group represented by Y ^b1 in which —CH ₂ — is not replaced by —O—, —S—, —SO ₂ — or —CO— include groups represented by formulae (Y1) to (Y11) and formulae (Y36) to (Y38).
When -CH ₂ - contained in the alicyclic hydrocarbon group represented by Y ^b1 is replaced by -O-, -S-, -SO ₂ - or -CO-, the number may be 1 or 2 or more. Such groups may form an ether ring, ketone ring, lactone ring, sultone ring or acetal ring, and include groups represented by formulae (Y12) to (Y35) and (Y39) to (Y43). -O- or -CO- in the groups represented by formulae (Y12) to (Y35) and (Y39) to (Y43) may be replaced by -S- or -SO ₂ -. The bonding site may be at any position.

Ｙ^ｂ１で表される脂環式炭化水素基としては、好ましくは式（Ｙ１）～式（Ｙ２０）、式（Ｙ２６）、式（Ｙ２７）、式（Ｙ３０）、式（Ｙ３１）、式（Ｙ３９）～式（Ｙ４３）のいずれかで表される基であり、より好ましくは式（Ｙ１１）、式（Ｙ１５）、式（Ｙ１６）、式（Ｙ２０）、式（Ｙ２６）、式（Ｙ２７）、式（Ｙ３０）、式（Ｙ３１）、式（Ｙ３９）、式（Ｙ４０）、式（Ｙ４２）又は式（Ｙ４３）で表される基であり、さらに好ましくは式（Ｙ１１）、式（Ｙ１５）、式（Ｙ２０）、式（Ｙ２６）、式（Ｙ２７）、式（Ｙ３０）、式（Ｙ３１）、式（Ｙ３９）、式（Ｙ４０）、式（Ｙ４２）又は式（Ｙ４３）で表される基である。
Ｙ^ｂ１で表される脂環式炭化水素基が式（Ｙ２８）～式（Ｙ３５）、式（Ｙ３９）、式（Ｙ４０）、式（Ｙ４２）、式（Ｙ４３）等の酸素原子を含むスピロ環である場合には、２つの酸素原子間のアルカンジイル基は、１以上のフッ素原子を有することが好ましい。また、ケタール構造に含まれるアルカンジイル基のうち、酸素原子に隣接するメチレン基には、フッ素原子が置換されていないのが好ましい。
脂環式炭化水素基の炭素数は、好ましくは３～２４であり、より好ましくは３～２０であり、さらに好ましくは３～１８であり、より一層好ましくは３～１６である。

The alicyclic hydrocarbon group represented by Y ^b1 is preferably a group represented by any one of formulas (Y1) to (Y20), (Y26), (Y27), (Y30), (Y31), (Y39) to (Y43), more preferably a group represented by formula (Y11), (Y15), (Y16), (Y20), (Y26), (Y27), (Y30), (Y31), (Y39), (Y40), (Y42) or (Y43), and still more preferably a group represented by formula (Y11), (Y15), (Y20), (Y26), (Y27), (Y30), (Y31), (Y39), (Y40), (Y42) or (Y43).
When the alicyclic hydrocarbon group represented by Y ^b1 is a spiro ring containing an oxygen atom such as those of formulae (Y28) to (Y35), (Y39), (Y40), (Y42) and (Y43), the alkanediyl group between the two oxygen atoms preferably has one or more fluorine atoms. Furthermore, among the alkanediyl groups contained in the ketal structure, it is preferable that the methylene group adjacent to the oxygen atom is not substituted with a fluorine atom.
The alicyclic hydrocarbon group preferably has 3 to 24 carbon atoms, more preferably 3 to 20 carbon atoms, further preferably 3 to 18 carbon atoms, and even further preferably 3 to 16 carbon atoms.

Examples of the aromatic hydrocarbon group represented by Y ^b1 include a phenylene group, a naphthylene group, a biphenylene group, an anthrylene group, a phenanthrylene group, a binaphthylene group, etc. The number of carbon atoms in the aromatic hydrocarbon group is preferably 6 to 24, more preferably 6 to 20, still more preferably 6 to 18, still more preferably 6 to 14, and still more preferably 6 to 10.
Examples of the heterocyclic aromatic hydrocarbon group represented by Y ^b1 include groups derived from a furan ring, a thiophene ring, a benzofuran ring, a benzothiophene ring, etc. The number of carbon atoms in the heterocyclic aromatic hydrocarbon group is preferably 4 to 9, and more preferably 4 to 8.
The aromatic hydrocarbon group or heterocyclic aromatic hydrocarbon group represented by Y ^b1 is preferably a phenylene group, a naphthylene group, or a group derived from a furan ring or a thiophene ring, and more preferably a phenylene group.

Substituents of the cyclic hydrocarbon group represented by Y ^b1 include a halogen atom, a hydroxy group, a cyano group, an alkyl group having 1 to 16 carbon atoms which may be substituted with a hydroxy group (-CH ₂ - contained in the alkyl group may be replaced with -O- or -CO-), an alicyclic hydrocarbon group having 3 to 16 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, an aralkyl group having 7 to 21 carbon atoms, a glycidyloxy group, a -(CH ₂ ) _ja -CO-O-R ^b1 group, or a -(CH ₂ ) _ja -O-CO-R ^b1 group (wherein R ^b1 represents an alkyl group having 1 to 16 carbon atoms, an alicyclic hydrocarbon group having 3 to 16 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group combining these, and -CH ₂ - contained in the alkyl group and the alicyclic hydrocarbon group is -O-, -S-, -SO ₂ - or -CO-, and a hydrogen atom contained in the alkyl group, the alicyclic hydrocarbon group and the aromatic hydrocarbon group may be replaced by a hydroxy group or a fluorine atom. ja represents an integer of 0 to 4.)

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Examples of the alicyclic hydrocarbon group include a cyclopentyl group, a cyclohexyl group, a methylcyclohexyl group, a dimethylcyclohexyl group, a cycloheptyl group, a cyclooctyl group, a norbornyl group, and an adamantyl group. The alicyclic hydrocarbon group may have a chain hydrocarbon group, and examples of the chain include a methylcyclohexyl group and a dimethylcyclohexyl group. The number of carbon atoms in the alicyclic hydrocarbon group is preferably 3 to 12, and more preferably 3 to 10.
Examples of aromatic hydrocarbon groups include aryl groups such as phenyl, naphthyl, anthryl, biphenyl, and phenanthryl. The aromatic hydrocarbon group may have a chain hydrocarbon group or an alicyclic hydrocarbon group, and aromatic hydrocarbon groups having a chain hydrocarbon group of 1 to 18 carbon atoms (such as tolyl, xylyl, cumenyl, mesityl, p-methylphenyl, p-ethylphenyl, p-tert-butylphenyl, 2,6-diethylphenyl, and 2-methyl-6-ethylphenyl) and aromatic hydrocarbon groups having an alicyclic hydrocarbon group of 3 to 18 carbon atoms (such as p-adamantylphenyl and p-cyclohexylphenyl) are preferred. The number of carbon atoms in the aromatic hydrocarbon group is preferably 6 to 14, and more preferably 6 to 10.
Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, etc. The number of carbon atoms in the alkyl group is preferably 1 to 12, more preferably 1 to 6, and further preferably 1 to 4.
Examples of the alkyl group substituted with a hydroxy group include hydroxyalkyl groups such as a hydroxymethyl group and a hydroxyethyl group.
Examples of the aralkyl group include a benzyl group, a phenethyl group, a phenylpropyl group, a naphthylmethyl group, and a naphthylethyl group.
Examples of the alkyl group in which --CH ₂ -- is replaced by --O--, --S--, --SO ₂ --, --CO-- or the like include an alkoxy group, an alkylthio group, an alkylsulfonyl group, an alkoxycarbonyl group, an alkylcarbonyl group, an alkylcarbonyloxy group, or a combination thereof.
Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, an octyloxy group, a decyloxy group, a dodecyloxy group, etc. The number of carbon atoms in the alkoxy group is preferably 1 to 12, more preferably 1 to 6, and even more preferably 1 to 4.
Examples of the alkylthio group include a methylthio group, an ethylthio group, a propylthio group, etc. The number of carbon atoms in the alkylthio group is preferably 1 to 12, more preferably 1 to 6, and further preferably 1 to 4.
Examples of the alkylsulfonyl group include a methylsulfonyl group, an ethylsulfonyl group, a propylsulfonyl group, etc. The number of carbon atoms in the alkylsulfonyl group is preferably 1 to 12, more preferably 1 to 6, and further preferably 1 to 4.
Examples of the alkoxycarbonyl group include a methoxycarbonyl group, an ethoxycarbonyl group, a butoxycarbonyl group, etc. The number of carbon atoms in the alkoxycarbonyl group is preferably 2 to 12, more preferably 2 to 6, and further preferably 2 to 4.
Examples of the alkylcarbonyl group include an acetyl group, a propionyl group, and a butyryl group. The number of carbon atoms in the alkylcarbonyl group is preferably 2 to 12, more preferably 2 to 6, and further preferably 2 to 4.
Examples of the alkylcarbonyloxy group include an acetyloxy group, a propionyloxy group, a butyryloxy group, etc. The number of carbon atoms in the alkylcarbonyloxy group is preferably 2 to 12, more preferably 2 to 6, and further preferably 2 to 4.
Examples of the combined group include a group that combines an alkoxy group with an alkyl group, a group that combines an alkoxy group with an alkoxy group, a group that combines an alkoxy group with an alkylcarbonyl group, and a group that combines an alkoxy group with an alkylcarbonyloxy group.
Examples of the group formed by combining an alkoxy group with an alkyl group include alkoxyalkyl groups such as a methoxymethyl group, a methoxyethyl group, an ethoxyethyl group, an ethoxymethyl group, etc. The number of carbon atoms in the alkoxyalkyl group is preferably 2 to 12, more preferably 2 to 6, and even more preferably 2 to 4.
Examples of the group consisting of a combination of an alkoxy group and an alkoxy group include an alkoxyalkoxy group such as a methoxymethoxy group, a methoxyethoxy group, an ethoxymethoxy group, an ethoxyethoxy group, etc. The number of carbon atoms in the alkoxyalkoxy group is preferably 2 to 12, more preferably 2 to 6, and even more preferably 2 to 4.
Examples of the group combining an alkoxy group and an alkylcarbonyl group include alkoxyalkylcarbonyl groups such as a methoxyacetyl group, a methoxypropionyl group, an ethoxyacetyl group, an ethoxypropionyl group, etc. The number of carbon atoms in the alkoxyalkylcarbonyl group is preferably 3 to 13, more preferably 3 to 7, and even more preferably 3 to 5.
Examples of the group combining an alkoxy group and an alkylcarbonyloxy group include alkoxyalkylcarbonyloxy groups such as a methoxyacetyloxy group, a methoxypropionyloxy group, an ethoxyacetyloxy group, an ethoxypropionyloxy group, etc. The number of carbon atoms in the alkoxyalkylcarbonyloxy group is preferably 3 to 13, more preferably 3 to 7, and even more preferably 3 to 5.
Examples of the alicyclic hydrocarbon group in which --CH ₂ -- is replaced by --O--, --S--, --SO ₂ --, --CO-- or the like include groups represented by formulae (Y12) to (Y35) and formulae (Y39) to (Y43).

［式（ｗ１－１）～式（ｗ１－３２）中、
該基に含まれる－ＣＨ₂－は、－Ｏ－、－Ｓ－、－ＣＯ－又は－ＳＯ_２－に置き換わっていてもよい。結合部位は任意の位置である。］ The cyclic hydrocarbon group in Y ^b1 (wherein —CH ₂ — may be replaced by —O—, —CO—, —S— or —SO ₂ —) is preferably an alicyclic hydrocarbon group having 3 to 24 carbon atoms (wherein —CH ₂ — may be replaced by —O—, —CO—, —S— or —SO ₂ —) or an aromatic hydrocarbon group having 6 to 24 carbon atoms, more preferably an alicyclic hydrocarbon group having 3 to 20 carbon atoms (wherein —CH ₂ — may be replaced by —O—, —CO—, —S— or —SO 2 —) or an aromatic hydrocarbon group having 6 to 20 carbon atoms, and more preferably an alicyclic hydrocarbon group having 3 to 18 carbon atoms (wherein —CH ₂ — may be replaced by —O—, —CO—, —S— or —SO _{2 —} ). - may be substituted. ) or an aromatic hydrocarbon group having 6 to 18 carbon atoms is more preferred. Specifically, it is preferably a group represented by any one of formulas (w1-1) to (w1-32), more preferably a group represented by any one of formulas (w1-1) to (w1-6) and (w1-12) to (w1-30), and even more preferably a group represented by any one of formulas (w1-1) to (w1-3), (w1-15) to (w1-17), (w1-22), (w1-25) and (w1-27) to (w1-29). Here, the cyclic hydrocarbon group may have a substituent.

[In formulas (w1-1) to (w1-32),
The --CH ₂ -- contained in the group may be replaced by --O--, --S--, --CO-- or --SO ₂ --. The bonding site may be at any position.]

Y ^b1 is preferably a single bond, an alicyclic hydrocarbon group having 3 to 24 carbon atoms which may have a substituent, or an aromatic hydrocarbon group having 6 to 24 carbon atoms which may have a substituent, more preferably a single bond, an alicyclic hydrocarbon group having 3 to 20 carbon atoms which may have a substituent, or an aromatic hydrocarbon group having 6 to 20 carbon atoms which may have a substituent, even more preferably a single bond, an alicyclic hydrocarbon group having 3 to 18 carbon atoms which may have a substituent, or an aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent, and even more preferably a single bond, is a cycloalkanediyl group having 6 carbon atoms, a norbornanediyl group, an adamantanediyl group, a polycyclic alicyclic hydrocarbon group in which a cycloalkanediyl group having 5 or 6 carbon atoms and a cycloalkanediyl group having 5 to 8 carbon atoms are bonded together in a spiro bond, a polycyclic alicyclic hydrocarbon group in which a norbornanediyl group and a cycloalkanediyl group having 5 to 8 carbon atoms are bonded together in a spiro bond, or a polycyclic alicyclic hydrocarbon group in which an adamantanediyl group and a cycloalkanediyl group having 5 to 8 carbon atoms are bonded together in a spiro bond (-CH ₂ - contained in the cycloalkanediyl group, the norbornanediyl group and the adamantanediyl group may be replaced by -O- or -CO-, and the cycloalkanediyl group, the norbornanediyl group and the adamantanediyl group may have a substituent).
The substituent that Y ^b1 may have is preferably a hydroxy group, a halogen atom, a cyano group, an alkyl group having 1 to 12 carbon atoms which may be substituted with a hydroxy group (-CH ₂ - contained in the alkyl group may be replaced with -O- or -CO-), or an alicyclic hydrocarbon group having 3 to 12 carbon atoms, and more preferably a hydroxy group, a halogen atom, a cyano group, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. Examples of the halogen atom, alkyl group, alkoxy group, and alicyclic hydrocarbon group include the same groups as those mentioned above. Of these, a fluorine atom, a hydroxy group, a methyl group, or an ethyl group is preferable.

［式（Ｘ１０）中、
Ａｘは、Ｒ^１０が結合した炭素原子と結合する結合種を表し、単結合、エーテル結合、チオエーテル結合、エステル結合、アミド結合及び炭酸エステル結合から構成される群から選択される１種の結合種を表す。
Ａｙは、Ｌ^１０と結合する結合種を表し、単結合、エーテル結合、チオエーテル結合、エステル結合、アミド結合及び炭酸エステル結合から構成される群から選択される１種の結合種を表す。
Ｒｘは、ハロゲン原子、ヒドロキシ基、炭素数１～６のフッ化アルキル基、炭素数１～１８のアルキル基又は炭素数１～６のアルコキシ基を表す。
ｍｘは、０～４のいずれかの整数を表し、ｍｘが２以上の整数の場合、複数のＲｘは互いに同じでも異なっていてもよい。］
Ａｘ及びＡｙのどちらかの一方が、単結合である場合、他方は、エーテル結合、チオエーテル結合、エステル結合、アミド結合及び炭酸エステル結合から構成される群から選択される１種であることが好ましい。
Ａｘ及びＡｙのいずれかがアミド結合の場合、－ＣＯ－ＮＲ^３－で表される結合であることが好ましい。
フェニレン基におけるＡｙの結合位置は、Ａｘの結合位置に対して、ｍ位又はｐ位であることが好ましく、ｐ位であることがより好ましい。
Ｒｘは、フッ素原子、ヨウ素原子、トリフルオロメチル基、メチル基又はエチル基が好ましい。
ｍｘは、０、１又は２が好ましい。
Ｘ^１０としては、例えば、以下の式（Ｘ^１０－１）～式（Ｘ^１０－１０）で表される基が挙げられる。＊は－Ｒ^１０が結合する炭素原子との結合部位を表す。＊＊は、Ｌ^１０、Ｙ^ｂ１又はＬ^ｂ１との結合部位を表す。

［式（Ｘ^１０－１）～式（Ｘ^１０－１０）中、
＊、＊＊は結合部位であり、＊はＲ^１０が結合した炭素原子との結合部位を表す。
Ｒｘは、ハロゲン原子、ヒドロキシ基、炭素数１～６のフッ化アルキル基、炭素数１～１８のアルキル基又は炭素数１～６のアルコキシ基を表す。
ｍｘは、０～４のいずれかの整数を表す。
Ｘ^２０は、－Ｏ－又は－ＮＲ^３－を表す。
Ｒ^３は、水素原子又は炭素数１～６のアルキル基を表す。］
式（Ｘ^１０－１）～式（Ｘ^１０－１０）で表される基の具体例としては、以下の基が挙げられる。

なかでも、Ｘ^１０は、単結合又は式（Ｘ^１０－１’）及び式（Ｘ^１０－３’）～式（Ｘ^１０－１０’）のいずれかで表される基であることが好ましく、単結合又は式（Ｘ^１０－１’）、式（Ｘ^１０－４’）、式（Ｘ^１０－５’）、式（Ｘ^１０－６’）及び式（Ｘ^１０－１０’）のいずれかで表される基であることがより好ましく、単結合、式（Ｘ^２０－１’）で表される基、式（Ｘ^１０－５’）で表される基又は式（Ｘ^１０－６’）で表される基であることがさらに好ましい。 Examples of the halogen atom for R ¹⁰ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Examples of the alkyl group for R ¹⁰ include the same groups as Q ^b1 and Q ^b2 having 1 to 6 carbon atoms.
Examples of the alkyl group having 1 to 6 carbon atoms and having a halogen atom for R ¹⁰ include a fluorinated alkyl group having 1 to 6 carbon atoms, a chlorinated alkyl group having 1 to 6 carbon atoms, a brominated alkyl group having 1 to 6 carbon atoms, and an iodinated alkyl group having 1 to 6 carbon atoms. Specific examples of the alkyl group having a halogen atom include a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluoroisopropyl group, a perfluorobutyl group, a perfluorosec-butyl group, a perfluorotert-butyl group, a perfluoropentyl group, a perfluorohexyl group, a perchloromethyl group, a perbromomethyl group, and a periodomethyl group.
The alkyl group, fluorinated alkyl group, chlorinated alkyl group, brominated alkyl group and iodinated alkyl group each preferably have 1 to 4 carbon atoms, more preferably 1 to 3 carbon atoms, and even more preferably 1 or 2 carbon atoms.
R ¹⁰ is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, still more preferably a hydrogen atom or a methyl group, and even more preferably a methyl group.
When ^X10 is a group represented by *-Ax-Ph-Ay-**, it is preferably a linking group represented by the following formula (X10).

[In formula (X10),
Ax represents a bond bonded to the carbon atom to which R ¹⁰ is bonded, and represents one type of bond selected from the group consisting of a single bond, an ether bond, a thioether bond, an ester bond, an amide bond and a carbonate bond.
Ay represents a bond bonded to L ¹⁰ and represents one type of bond selected from the group consisting of a single bond, an ether bond, a thioether bond, an ester bond, an amide bond and a carbonate bond.
Rx represents a halogen atom, a hydroxy group, a fluorinated alkyl group having 1 to 6 carbon atoms, an alkyl group having 1 to 18 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.
mx represents an integer of 0 to 4, and when mx is an integer of 2 or more, the multiple Rx's may be the same or different.
When either Ax or Ay is a single bond, the other is preferably one selected from the group consisting of an ether bond, a thioether bond, an ester bond, an amide bond, and a carbonate ester bond.
When either Ax or Ay is an amide bond, it is preferably a bond represented by --CO--NR ³ --.
The bonding position of Ay in the phenylene group is preferably the m-position or p-position relative to the bonding position of Ax, and more preferably the p-position.
Rx is preferably a fluorine atom, an iodine atom, a trifluoromethyl group, a methyl group or an ethyl group.
mx is preferably 0, 1 or 2.
Examples of X ¹⁰ include groups represented by the following formulae (X ¹⁰ -1) to (X ¹⁰ -10). * represents the bonding site with the carbon atom to which -R ¹⁰ is bonded. ** represents the bonding site with L ¹⁰ , Y ^b1 or L ^b1 .

[Formula (X ¹⁰ -1) to (X ¹⁰ -10),
* and ** are bonding sites, and * represents the bonding site with the carbon atom to which R ¹⁰ is bonded.
Rx represents a halogen atom, a hydroxy group, a fluorinated alkyl group having 1 to 6 carbon atoms, an alkyl group having 1 to 18 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.
mx represents an integer of 0 to 4.
X ²⁰ represents —O— or —NR ³ —.
^R3 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.
Specific examples of the groups represented by formulae (X ¹⁰ -1) to (X ¹⁰ -10) include the following groups.

Among these, X ¹⁰ is preferably a single bond or a group represented by any one of formulas (X ¹⁰ -1') and formulas (X ¹⁰ -3') to (X ¹⁰ -10'), more preferably a single bond or a group represented by any one of formulas (X ¹⁰ -1'), (X ¹⁰ -4'), (X ¹⁰ -5'), (X ¹⁰ -6') and (X ¹⁰ -10'), and further preferably a single bond, a group represented by formula (X ²⁰ -1'), a group represented by formula (X ¹⁰ -5') or a group represented by formula (X ¹⁰ -6').

Examples of the hydrocarbon group having 1 to 36 carbon atoms for ^L10 include aliphatic hydrocarbon groups (chain hydrocarbon groups and alicyclic hydrocarbon groups such as alkanediyl groups, alkenediyl groups, and alkynediyl groups), aromatic hydrocarbon groups, and the like, and may be a hydrocarbon group formed by combining two or more of these groups.

具体的に、単環式の脂環式炭化水素基としては、シクロブタン－１，３－ジイル基、シクロペンタン－１，３－ジイル基、シクロヘキサン－１，４－ジイル基、シクロヘキセン－３，６－ジイル基、シクロオクタン－１，５－ジイル基等の単環式シクロアルカンジイル基が挙げられ、多環式の脂環式炭化水素基としては、ノルボルナン－１，４－ジイル基、ノルボルナン－２，５－ジイル基、５－ノルボルネン－２，３－ジイル基、アダマンタン－１，５－ジイル基、アダマンタン－２，６－ジイル基等の多環式シクロアルカンジイル基が挙げられる。
脂環式炭化水素基の炭素数は、好ましくは３～１８であり、より好ましくは３～１６であり、さらに好ましくは３～１２である。
芳香族炭化水素基としては、フェニレン基、ナフチレン基、アントリレン基、ビフェニレン基、フェナントリレン基等が挙げられる。芳香族炭化水素基の炭素数は、好ましくは６～１８であり、より好ましくは６～１４であり、さらに好ましくは６～１０である。
２種以上を組み合わせた炭化水素基としては、アルカンジイル基と脂環式炭化水素基及び／又は芳香族炭化水素基とを組み合わせた基等が挙げられ、－脂環式炭化水素基－アルカンジイル基－、－アルカンジイル基－脂環式炭化水素基－、－アルカンジイル基－脂環式炭化水素基－アルカンジイル基－、－アルカンジイル基－芳香族炭化水素基－、－芳香族炭化水素基－アルカンジイル基－等が挙げられる。また、脂環式炭化水素基もしくは芳香族炭化水素基とアルカンジイル基を組み合わせた基の場合、アルカンジイル基の末端は、メチル基であってもよい。 Examples of the alkanediyl group include linear alkanediyl groups such as a methylene group, an ethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, an octane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diyl group, an undecane-1,11-diyl group, and a dodecane-1,12-diyl group;
Examples of branched alkanediyl groups include ethane-1,1-diyl group, propane-1,1-diyl group, propane-1,2-diyl group, propane-2,2-diyl group, pentane-2,4-diyl group, 2-methylpropane-1,3-diyl group, 2-methylpropane-1,2-diyl group, pentane-1,4-diyl group, and 2-methylbutane-1,4-diyl group. The terminal of the branched alkanediyl group may be a methyl group.
Examples of the alkenediyl group include an ethenediyl group, a propenediyl group, an isopropenediyl group, a butenediyl group, an isobutenediyl group, a tert-butenediyl group, a pentenediyl group, a hexenediyl group, a heptenediyl group, an octenediyl group, an isooctenediyl group, and a nonenediyl group.
Examples of the alkynediyl group include an ethynediyl group, a propynediyl group, an isopropynediyl group, a butynediyl group, an isobutynediyl group, a tert-butynediyl group, a pentynediyl group, a hexynediyl group, an octynediyl group, and a nonynediyl group.
The chain hydrocarbon group preferably has 1 to 12 carbon atoms, more preferably 1 to 9 carbon atoms, even more preferably 1 to 6 carbon atoms, still more preferably 1 to 4 carbon atoms, and even more preferably 1 to 3 carbon atoms.
The alicyclic hydrocarbon group may be any of monocyclic, polycyclic and spirocyclic. Examples of the alicyclic hydrocarbon group include the groups shown below. The bonding site may be any position.

Specific examples of the monocyclic alicyclic hydrocarbon group include monocyclic cycloalkanediyl groups such as a cyclobutane-1,3-diyl group, a cyclopentane-1,3-diyl group, a cyclohexane-1,4-diyl group, a cyclohexene-3,6-diyl group, and a cyclooctane-1,5-diyl group. Examples of the polycyclic alicyclic hydrocarbon group include polycyclic cycloalkanediyl groups such as a norbornane-1,4-diyl group, a norbornane-2,5-diyl group, a 5-norbornene-2,3-diyl group, an adamantane-1,5-diyl group, and an adamantane-2,6-diyl group.
The alicyclic hydrocarbon group preferably has 3 to 18 carbon atoms, more preferably 3 to 16 carbon atoms, and even more preferably 3 to 12 carbon atoms.
Examples of the aromatic hydrocarbon group include a phenylene group, a naphthylene group, an anthrylene group, a biphenylene group, a phenanthrylene group, etc. The number of carbon atoms in the aromatic hydrocarbon group is preferably 6 to 18, more preferably 6 to 14, and further preferably 6 to 10.
Examples of hydrocarbon groups combining two or more types include groups combining an alkanediyl group with an alicyclic hydrocarbon group and/or an aromatic hydrocarbon group, such as -alicyclic hydrocarbon group-alkanediyl group-, -alkanediyl group-alicyclic hydrocarbon group-, -alkanediyl group-alicyclic hydrocarbon group-, -alkanediyl group-alicyclic hydrocarbon group-alkanediyl group-, -alkanediyl group-aromatic hydrocarbon group-, -aromatic hydrocarbon group-alkanediyl group-, etc. In the case of a group combining an alicyclic hydrocarbon group or an aromatic hydrocarbon group with an alkanediyl group, the terminal of the alkanediyl group may be a methyl group.

The --CH ₂ -- contained in the hydrocarbon group having 1 to 36 carbon atoms of L ¹⁰ may be replaced by --O--, --S--, --CO-- or --SO ₂ --.
When the hydrocarbon group having 1 to 36 carbon atoms of ^L10 has a substituent, or when _--CH2-- contained in the hydrocarbon group is replaced with --O--, --S--, --CO-- or _--SO2-- , the number of carbon atoms before replacement is regarded as the number of carbon atoms of the hydrocarbon group.
Examples of groups in which --CH ₂ -- in a hydrocarbon group is replaced by --O--, --S--, --SO ₂ -- or --CO-- include a hydroxy group (a group in which --CH ₂ -- in a methyl group is replaced by --O--), a carboxy group ( _{a group in which --CH 2 --} in an ethyl group is replaced by --O--CO--), a thiol group (a group in which --CH ₂ -- in a methyl group is replaced by --S--), a carbonyl group (a group in which --CH ₂ -- in a methylene group is replaced by --CO--), a sulfonyl group (a group in which --CH ₂ -- in a methylene group is replaced by --SO ₂ --), an oxy group (a group in which --CH ₂ -- in a methylene group is replaced by --O--), a thio group (a group in which --CH ₂ -- in a methylene group is replaced by --S--), an alkoxy group (a group in which --CH at any position in an alkyl group is replaced by --O--), and ₂ -- is replaced by --O--), alkoxycarbonyl group (a group in which --CH ₂ -- at any position contained in an alkyl group is replaced by --O--CO--), alkylcarbonyl group (a group in which --CH ₂ -- at any position contained in an alkyl group is replaced by --CO--), alkylcarbonyloxy group (a group in which --CH ₂ -- at any position contained in an alkyl group is replaced by --CO--O--), alkanediyloxy group (a group in which --CH ₂ -- at any position contained in an alkanediyl _group is replaced by --O--), alkanediyloxycarbonyl group (a group in which --CH ₂ -- _at any position contained in an alkanediyl group is replaced by --O--CO--), alkanediylcarbonyl group (a group in which --CH _{2 --} at any position contained in an alkanediyl group is replaced by --O--CO--), - is replaced with -CO-), alkanediylcarbonyloxy group (a group in which -CH ₂ -CH ₂ - at any position contained in an alkanediyl group is replaced with -CO-O-), alkylthio group (a group in which -CH ₂ - at any position contained in an alkyl group is replaced with -S-), alkylsulfonyl group (a group in which -CH ₂ - at any position contained in an alkyl group is replaced with -SO ₂ -), alkanediylsulfonyl group (a group in which -CH ₂ - at any position contained in an alkanediyl group is replaced with -SO ₂ -), alkanediylthio group (a group in which -CH ₂ - at any position contained in an alkanediyl group is replaced with -S-), cycloalkoxy group, cycloalkylalkoxy group, alkoxycarbonyloxy group, aromatic hydrocarbon group-carbonyloxy group, aromatic hydrocarbon group-carbonyl group, aromatic hydrocarbon group-oxy group, and groups combining two or more of these groups.
Examples of the alkoxy group include alkoxy groups having 1 to 35 carbon atoms, such as a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, an octyloxy group, a 2-ethylhexyloxy group, a nonyloxy group, a decyloxy group, an undecyloxy group, etc. The number of carbon atoms in the alkoxy group may be 1 to 17, preferably 1 to 11, more preferably 1 to 6, even more preferably 1 to 4, and even more preferably 1 to 3.
Examples of the alkoxycarbonyl group include alkoxycarbonyl groups having 2 to 35 carbon atoms, such as a methoxycarbonyl group, an ethoxycarbonyl group, and a butoxycarbonyl group. Examples of the alkylcarbonyl group include alkylcarbonyl groups having 2 to 36 carbon atoms, such as an acetyl group, a propionyl group, and a butyryl group. Examples of the alkylcarbonyloxy group include alkylcarbonyloxy groups having 2 to 35 carbon atoms, such as an acetyloxy group, a propionyloxy group, and a butyryloxy group. The number of carbon atoms in the alkoxycarbonyl group, the alkylcarbonyl group, and the alkylcarbonyloxy group may be 2 to 17, preferably 2 to 11, more preferably 2 to 6, even more preferably 2 to 4, and even more preferably 2 to 3.
The alkanediyloxy group includes an alkanediyloxy group having 1 to 35 carbon atoms, such as a methyleneoxy group, an ethyleneoxy group, a propanediyloxy group, a butanediyloxy group, a pentanediyloxy group, etc. The number of carbon atoms in the alkanediyloxy group may be 1 to 17, preferably 1 to 11, more preferably 1 to 6, even more preferably 1 to 4, and even more preferably 1 to 3.
Examples of the alkanediyloxycarbonyl group include alkanediyloxycarbonyl groups having 2 to 35 carbon atoms, such as a methyleneoxycarbonyl group, an ethyleneoxycarbonyl group, a propanediyloxycarbonyl group, and a butanediyloxycarbonyl group. Examples of the alkanediylcarbonyl group include alkanediylcarbonyl groups having 2 to 36 carbon atoms, such as a methylenecarbonyl group, an ethylenecarbonyl group, a propanediylcarbonyl group, a butanediylcarbonyl group, and a pentanediylcarbonyl group. Examples of the alkanediylcarbonyloxy group include alkanediylcarbonyloxy groups having 2 to 35 carbon atoms, such as a methylenecarbonyloxy group, an ethylenecarbonyloxy group, a propanediylcarbonyloxy group, and a butanediylcarbonyloxy group. The number of carbon atoms in the alkanediyloxycarbonyl group, alkanediylcarbonyl group, and alkanediylcarbonyloxy group may be 2 to 17, preferably 2 to 11, more preferably 2 to 6, even more preferably 2 to 4, and still more preferably 2 to 3.
The alkylthio group includes alkylthio groups having 1 to 35 carbon atoms, such as a methylthio group, an ethylthio group, a propylthio group, etc. The number of carbon atoms in the alkylthio group may be 1 to 17, preferably 1 to 11, more preferably 1 to 6, even more preferably 1 to 4, and even more preferably 1 to 3.
The alkylsulfonyl group includes alkylsulfonyl groups having 1 to 35 carbon atoms, such as a methylsulfonyl group, an ethylsulfonyl group, a propylsulfonyl group, etc. The number of carbon atoms in the alkylsulfonyl group may be 1 to 17, preferably 1 to 11, more preferably 1 to 6, even more preferably 1 to 4, and even more preferably 1 to 3.
The alkanediylsulfonyl group includes an alkanediylsulfonyl group having 1 to 35 carbon atoms, such as a methylenesulfonyl group, an ethylenesulfonyl group, a propylenesulfonyl group, etc. The number of carbon atoms in the alkanediylsulfonyl group may be 1 to 17, preferably 1 to 11, more preferably 1 to 6, even more preferably 1 to 4, and even more preferably 1 to 3.
The alkanediylthio group includes an alkanediylthio group having 1 to 35 carbon atoms, such as a methylenethio group, an ethylenethio group, a propylenethio group, etc. The number of carbon atoms in the alkanediylthio group may be 1 to 17, preferably 1 to 11, more preferably 1 to 6, even more preferably 1 to 4, and even more preferably 1 to 3.
Examples of the cycloalkoxy group include cycloalkoxy groups having 3 to 35 carbon atoms, such as a cyclohexyloxy group. Examples of the cycloalkylalkoxy group include cycloalkylalkoxy groups having 4 to 35 carbon atoms, such as a cyclohexylmethoxy group. Examples of the alkoxycarbonyloxy group include alkoxycarbonyloxy groups having 2 to 34 carbon atoms, such as a butoxycarbonyloxy group. The number of carbon atoms in the cycloalkoxy group or cycloalkylalkoxy group may be 3 to 17, preferably 3 to 11, and more preferably 3 to 6. The number of carbon atoms in the alkoxycarbonyloxy group may be 2 to 17, preferably 2 to 11, more preferably 2 to 6, even more preferably 2 to 4, and even more preferably 2 to 3. Examples of the aromatic hydrocarbon group-carbonyloxy group include aromatic hydrocarbon group-carbonyloxy groups having 7 to 35 carbon atoms, such as a benzoyloxy group. Examples of the aromatic hydrocarbon group-carbonyl group include aromatic hydrocarbon group-carbonyl groups having 7 to 36 carbon atoms, such as a benzoyl group, etc. Examples of the aromatic hydrocarbon group-oxy group include aromatic hydrocarbon group-oxy groups having 6 to 35 carbon atoms, such as a phenyloxy group, etc.
Examples of groups in which --CH ₂ -- contained in an alicyclic hydrocarbon group is replaced by --O--, --S--, --CO-- or --SO ₂ -- include the groups shown below. --O-- or --CO-- in the groups shown below may be replaced by --S-- or --SO ₂ --. The bonding site may be at any position.

Examples of the substituent that the hydrocarbon group of L ¹⁰ may have include a halogen atom, a cyano group, and a carbon nitro group.
When L ¹⁰ contains an alicyclic hydrocarbon group or an aromatic hydrocarbon group, the alkyl group or alkanediyl group (the terminal of the alkanediyl group may be an alkyl group such as a methyl group) bonded to the alicyclic hydrocarbon group or aromatic hydrocarbon group can be regarded as substantially a substituent of the alicyclic hydrocarbon group or aromatic hydrocarbon group. Due to a group in which --CH ₂ -- contained in the hydrocarbon group of L ¹⁰ is replaced by --O-- or --CO--, L ¹⁰ can substantially have a substituent such as a hydroxy group, a carboxy group, an alkoxy group, an alkoxycarbonyl group, an alkylcarbonyl group or an alkylcarbonyloxy group.
Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
The hydrocarbon group having 1 to 36 carbon atoms represented by L ¹⁰ may have one or more substituents.

L ¹⁰ is a single bond, an alkanediyl group having 1 to 6 carbon atoms (provided that -CH ₂ - contained in the alkanediyl group may be replaced by -O- or -CO-), a cyclic hydrocarbon group having 3 to 18 carbon atoms (provided that the cyclic hydrocarbon group may have a substituent and the -CH ₂ - contained in the cyclic hydrocarbon group may be replaced by -O-, -S-, -SO ₂ - or -CO-), or a group formed by combining an alkanediyl group having 1 to 6 carbon atoms with a cyclic hydrocarbon group having 3 to 18 carbon atoms (provided that the cyclic hydrocarbon group may have a substituent and the -CH ₂ - contained in the alkanediyl group may be replaced by -O- or -CO- and the -CH ₂ - contained in the cyclic hydrocarbon group may be replaced by -O-, -S-, -SO _{2 -} or -CO-). - or -CO-), and examples thereof include a single bond, an alkanediyl group having 1 to 4 carbon atoms (wherein -CH ₂ - contained in the alkanediyl group may be replaced by -O- or -CO-), an alicyclic hydrocarbon group having 3 to 18 carbon atoms (wherein -CH ₂ - contained in the alicyclic hydrocarbon group may be replaced by -O-, -S-, -SO ₂ - or -CO-), an aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent, and a group formed by combining an alkanediyl group having 1 to 4 carbon atoms and an alicyclic hydrocarbon group having 3 to 18 carbon atoms (wherein -CH ₂ - contained in the alkanediyl group may be replaced by -O- or -CO- and -CH ₂ - contained in the alicyclic hydrocarbon group may be replaced by -O-, -S-, -SO ₂ - or -CO-). - or -CO-), or a group formed by combining an alkanediyl group having 1 to 4 carbon atoms and an aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent (provided that -CH ₂ - contained in the alkanediyl group may be replaced by -O- or -CO-), is more preferred, and examples thereof include a single bond, an alkanediyl group having 1 to 4 carbon atoms (provided that -CH ₂ - contained in the alkanediyl group may be replaced by -O- or -CO-), an alicyclic hydrocarbon group having 3 to 18 carbon atoms (provided that -CH ₂ - contained in the alicyclic hydrocarbon group may be replaced by -O- or -CO-), a phenylene group which may have a substituent, a group formed by combining an alkanediyl group having 1 to 4 carbon atoms and an alicyclic hydrocarbon group having 3 to 18 carbon atoms (provided that -CH ₂ - contained in the alkanediyl group may be replaced by -O- or -CO-), - may be replaced by -O- or -CO-, and -CH ₂ - contained in the alicyclic hydrocarbon group may be replaced by -O- or -CO-, or a group formed by combining an alkanediyl group having 1 to 4 carbon atoms with a phenylene group which may have a substituent (provided that -CH ₂ - contained in the alkanediyl group may be replaced by -O- or -CO-), and even more preferably a single bond or an alkanediyl group having 1 to 4 carbon atoms (provided that -CH ₂ - contained in the alkanediyl group may be replaced by -O- or -CO-).

Examples of the anion (I6-a) include the following anions:

Specific examples of the anion (I6-a) include anions in which the methyl group corresponding to R ¹⁰ in formula (I6) is replaced with a hydrogen atom in the anions represented by formulas (I-a-1) to (I-a-19). Among these, the anions represented by formulas (I-a-1) to (I-a-6) and (I-a-16) to (I-a-19) are preferred.

具体的には、単環式の脂環式炭化水素基としては、シクロプロピル基、シクロブチル基、シクロペンチル基、シクロヘキシル基シクロヘプチル基、シクロオクチル基、シクロノニル基、シクロデシル基等の単環式シクロアルキル基が挙げられる。多環式の脂環式炭化水素基としては、デカヒドロナフチル基、アダマンチル基、ノルボルニル基等の多環式シクロアルキル基が挙げられる。脂環式炭化水素基の炭素数は、好ましくは３～１８であり、より好ましくは３～１６であり、さらに好ましくは３～１２である。
芳香族炭化水素基としては、フェニル基、ナフチル基、ビフェニル基、アントリル基、フェナントリル基、ビナフチル基等が挙げられる。芳香族炭化水素基の炭素数は、好ましくは６～１８であり、より好ましくは６～１４であり、さらに好ましくは６～１０である。
鎖式炭化水素基、脂環式炭化水素基、芳香族炭化水素基のうち、２種以上の基を組み合わせることにより形成される基としては、芳香族炭化水素基と鎖式炭化水素基とを組み合わせた基（例えば、芳香族炭化水素基－アルカンジイル基－＊、アルキル基－芳香族炭化水素基－＊、アルキル基－芳香族炭化水素基－アルカンジイル基－＊、該アルカンジイル基及び該アルキル基に含まれる－ＣＨ_２－は、－Ｏ－、－ＣＯ－、－Ｓ－又は－ＳＯ_２－に置き換わってもよい。）、脂環式炭化水素基と鎖式炭化水素基とを組み合わせた基（例えば、脂環式炭化水素基－アルカンジイル基－＊、アルキル基－脂環式炭化水素基－＊、アルキル基－脂環式炭化水素基－アルカンジイル基－＊、該脂環式炭化水素基、該アルカンジイル基及び該アルキル基に含まれる－ＣＨ_２－は、－Ｏ－、－ＣＯ－、－Ｓ－又は－ＳＯ_２－に置き換わってもよい。）、芳香族炭化水素基と脂環式炭化水素基とを組み合わせた基（例えば、芳香族炭化水素基－脂環式炭化水素基－＊、脂環式炭化水素基－芳香族炭化水素基－＊、該脂環式炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－、－ＣＯ－、－Ｓ－又は－ＳＯ_２－に置き換わってもよい。）が挙げられる。＊は結合部位を表す。
芳香族炭化水素基－アルカンジイル基－＊としては、ベンジル基、フェネチル基等のアラルキル基が挙げられる。
アルキル基－芳香族炭化水素基－＊としては、トリル基、キシリル基、クメニル基等が挙げられる。
脂環式炭化水素基－アルカンジイル基－＊としては、シクロヘキシルメチル基、シクロヘキシルエチル基、１－（アダマンタン－１－イル）メチル基、１－（アダマンタン－１－イル）－１－メチルエチル基等のシクロアルキルアルキル基等が挙げられる。
アルキル基－脂環式炭化水素基－＊としては、メチルシクロヘキシル基、ジメチルシクロヘキシル基、２－アルキルアダマンタン－２－イル基等のアルキル基を有するシクロアルキル基等が挙げられる。
芳香族炭化水素基－脂環式炭化水素基－＊としては、フェニルシクロヘキシル基等が挙げられる。
脂環式炭化水素基－芳香族炭化水素基－＊としては、シクロヘキシルフェニル基等が挙げられる。
なお、組み合わせにおいて、脂環式炭化水素基、芳香族炭化水素基、鎖式炭化水素基は、それぞれ２種以上を組み合わせてもよい。また、いずれの基がベンゼン環に結合していてもよい。 (Cation (I6-c))
Examples of the hydrocarbon group having 1 to 20 carbon atoms for ^R3 , ^R4 , ^R5 , ^R6 , and ^R7 include chain hydrocarbon groups such as alkyl groups and alkanediyl groups, alicyclic hydrocarbon groups, aromatic hydrocarbon groups, and groups formed by combining these.
The alkyl group is a straight-chain or branched alkyl group, and examples thereof include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a hexyl group, an octyl group, a nonyl group, and a decyl group.
The alkanediyl group is a linear or branched alkanediyl group, and examples thereof include linear alkanediyl groups such as a methylene group, an ethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, an octane-1,8-diyl group, a nonane-1,9-diyl group, and a decane-1,10-diyl group; and branched alkanediyl groups such as an ethane-1,1-diyl group, a propane-1,1-diyl group, a propane-1,2-diyl group, a propane-2,2-diyl group, a pentane-2,4-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group, and a 2-methylbutane-1,4-diyl group.
The chain hydrocarbon group preferably has 1 to 12 carbon atoms, more preferably 1 to 9 carbon atoms, even more preferably 1 to 6 carbon atoms, still more preferably 1 to 4 carbon atoms, and even more preferably 1 to 3 carbon atoms.
The alicyclic hydrocarbon group may be either monocyclic or polycyclic, and examples thereof include the groups shown below. The bonding site may be any position.

Specifically, examples of the monocyclic alicyclic hydrocarbon group include monocyclic cycloalkyl groups such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, and a cyclodecyl group. Examples of the polycyclic alicyclic hydrocarbon group include polycyclic cycloalkyl groups such as a decahydronaphthyl group, an adamantyl group, and a norbornyl group. The number of carbon atoms in the alicyclic hydrocarbon group is preferably 3 to 18, more preferably 3 to 16, and even more preferably 3 to 12.
Examples of the aromatic hydrocarbon group include a phenyl group, a naphthyl group, a biphenyl group, an anthryl group, a phenanthryl group, a binaphthyl group, etc. The number of carbon atoms in the aromatic hydrocarbon group is preferably 6 to 18, more preferably 6 to 14, and even more preferably 6 to 10.
Groups formed by combining two or more of the chain hydrocarbon group, alicyclic hydrocarbon group, and aromatic hydrocarbon group include a group formed by combining an aromatic hydrocarbon group with a chain hydrocarbon group (for example, aromatic hydrocarbon group-alkanediyl group-*, alkyl group-aromatic hydrocarbon group-*, alkyl group-aromatic hydrocarbon group-alkanediyl group-*, where the -CH ₂ - contained in the alkanediyl group and the alkyl group may be replaced with -O-, -CO-, -S-, or -SO ₂ -), a group formed by combining an alicyclic hydrocarbon group with a chain hydrocarbon group (for example, alicyclic hydrocarbon group-alkanediyl group-*, alkyl group-alicyclic hydrocarbon group-*, alkyl group-alicyclic hydrocarbon group-alkanediyl group-*, where the -CH ₂ - contained in the alicyclic hydrocarbon group, the alkanediyl group, and the alkyl group may be replaced with -O-, -CO-, -S-, or -SO _{2 -)} , -), and groups combining an aromatic hydrocarbon group with an alicyclic hydrocarbon group (for example, aromatic hydrocarbon group-alicyclic hydrocarbon group-*, alicyclic hydrocarbon group-aromatic hydrocarbon group-*, -CH ₂ - contained in the alicyclic hydrocarbon group may be replaced by -O-, -CO-, -S- or -SO ₂ -). * represents a bonding site.
The aromatic hydrocarbon group -alkanediyl group-* includes aralkyl groups such as benzyl group and phenethyl group.
Examples of the alkyl group-aromatic hydrocarbon group-* include a tolyl group, a xylyl group, and a cumenyl group.
Examples of the alicyclic hydrocarbon group -alkanediyl group-* include cycloalkylalkyl groups such as a cyclohexylmethyl group, a cyclohexylethyl group, a 1-(adamantan-1-yl)methyl group, and a 1-(adamantan-1-yl)-1-methylethyl group.
Examples of the alkyl group-alicyclic hydrocarbon group-* include cycloalkyl groups having an alkyl group such as a methylcyclohexyl group, a dimethylcyclohexyl group, and a 2-alkyladamantan-2-yl group.
Examples of the aromatic hydrocarbon group-alicyclic hydrocarbon group-* include a phenylcyclohexyl group.
Examples of the alicyclic hydrocarbon group-aromatic hydrocarbon group-* include a cyclohexylphenyl group.
In addition, in the combination, two or more of each of the alicyclic hydrocarbon groups, aromatic hydrocarbon groups and chain hydrocarbon groups may be combined. In addition, any of the groups may be bonded to a benzene ring.

When —CH ₂ — contained in the hydrocarbon group represented by R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁷ is replaced by —O—, —CO—, —S— or —SO ₂ —, the number of carbon atoms before replacement is taken as the total number of carbon atoms in the hydrocarbon group. In addition, the number may be 1 or 2 or more.
Examples of groups in which -CH ₂ - in a hydrocarbon group is replaced by -O-, -CO-, -S- or -SO ₂ - include a hydroxy group (a group in which -CH ₂ - in a methyl group is replaced by -O-), a thiol group (a group in which -CH ₂ - in a methyl group is replaced by -S-), a carboxy group (a group in which -CH ₂ -CH ₂ - in an ethyl group is replaced by -O-CO-), an alkoxy group (a group in which -CH ₂ - at any position in an alkyl group is replaced by -O-), an alkoxycarbonyl group (a group in which -CH ₂ -CH ₂ - at any position in an alkyl group is replaced by -O-CO-), an alkylcarbonyl group (a group in which -CH ₂ - at any position in an alkyl group is replaced by -CO-), and an alkylcarbonyloxy group (a group in which -CH ₂ -CH _{2 -} at any position in an alkyl group is replaced by -CO-). - is replaced by -CO-O-), an alkylthio group (a group in which -CH ₂ - at any position contained in an alkyl group is replaced by -S-), an alkylsulfonyl group (a group in which -CH ₂ - at any position contained in an alkyl group is replaced by -SO ₂ -), an oxy group (a group in which -CH ₂ - contained in a methylene group is replaced by -O-), a carbonyl group (a group in which -CH ₂ - contained in a methylene group is replaced by -CO-), a thio group (a group in which -CH ₂ - contained in a methylene group is replaced by -S-), a sulfonyl group (a group in which -CH ₂ - contained in a methylene group is replaced by -SO ₂ -), an alkanediyloxy group (a group in which -CH _{2 -} at any position contained in an alkanediyl group is replaced by -SO 2 -), - is replaced by -O-), an alkanediyloxycarbonyl group (a group in which -CH ₂ -CH ₂ - at any position contained in an alkanediyl group is replaced by -O-CO-), an alkanediylcarbonyl group (a group in which -CH ₂ - at any position contained in an alkanediyl group is replaced by -CO-), an alkanediylcarbonyloxy group (a group in which -CH ₂ -CH ₂ - at any position contained in an alkanediyl group is replaced by -CO-O-), an alkanediylthio group (a group in which -CH ₂ - at any position contained in an alkanediyl group is replaced by -S-), an alkanediylsulfonyl group (a group in which -CH ₂ - at any position contained in an alkanediyl group is replaced by -SO ₂ -substituted), a cycloalkoxy group, a cycloalkylalkoxy group, an alkoxycarbonyloxy group, an aromatic hydrocarbon group-carbonyloxy group, an aromatic hydrocarbon group-carbonyl group, an aromatic hydrocarbon group-oxy group, or a group in which two or more of these groups are combined.
Examples of the alkoxy group include alkoxy groups having 1 to 19 carbon atoms, such as a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, an octyloxy group, a 2-ethylhexyloxy group, a nonyloxy group, a decyloxy group, an undecyloxy group, etc. The number of carbon atoms in the alkoxy group is preferably 1 to 11, more preferably 1 to 6, even more preferably 1 to 4, and even more preferably 1 to 3.
Examples of the alkoxycarbonyl group include alkoxycarbonyl groups having 2 to 19 carbon atoms, such as methoxycarbonyl, ethoxycarbonyl, and butoxycarbonyl groups. Examples of the alkylcarbonyl group include alkylcarbonyl groups having 2 to 20 carbon atoms, such as acetyl, propionyl, and butyryl groups. Examples of the alkylcarbonyloxy group include alkylcarbonyloxy groups having 2 to 19 carbon atoms, such as acetyloxy, propionyloxy, and butyryloxy groups. The number of carbon atoms in the alkoxycarbonyl group is preferably 2 to 11, more preferably 2 to 6, even more preferably 2 to 4, and even more preferably 2 or 3. The number of carbon atoms in the alkylcarbonyl group is preferably 2 to 12, more preferably 2 to 6, even more preferably 2 to 4, and even more preferably 2 or 3. The alkylcarbonyloxy group preferably has 2 to 11 carbon atoms, more preferably 2 to 6 carbon atoms, even more preferably 2 to 4 carbon atoms, and even more preferably 2 or 3 carbon atoms.
The alkylthio group includes alkylthio groups having 1 to 19 carbon atoms, such as a methylthio group, an ethylthio group, a propylthio group, a butylthio group, a pentylthio group, a hexylthio group, an octylthio group, a 2-ethylhexylthio group, a nonylthio group, a decylthio group, an undecylthio group, etc. The number of carbon atoms in the alkylthio group is preferably 1 to 11, more preferably 1 to 6, even more preferably 1 to 4, and even more preferably 1 to 3.
Examples of the alkylsulfonyl group include alkylsulfonyl groups having 1 to 19 carbon atoms, such as a methylsulfonyl group, an ethylsulfonyl group, a propylsulfonyl group, a butylsulfonyl group, a pentylsulfonyl group, a hexylsulfonyl group, an octylsulfonyl group, a 2-ethylhexylsulfonyl group, a nonylsulfonyl group, a decylsulfonyl group, an undecylsulfonyl group, etc. The number of carbon atoms in the alkylsulfonyl group is preferably 1 to 11, more preferably 1 to 6, even more preferably 1 to 4, and even more preferably 1 to 3.
The alkanediyloxy group includes an alkanediyloxy group having 1 to 19 carbon atoms, such as a methyleneoxy group, an ethyleneoxy group, a propanediyloxy group, a butanediyloxy group, a pentanediyloxy group, etc. The number of carbon atoms in the alkanediyloxy group is preferably 1 to 11, more preferably 1 to 6, even more preferably 1 to 4, and even more preferably 1 to 3.
Examples of the alkanediyloxycarbonyl group include alkanediyloxycarbonyl groups having 2 to 19 carbon atoms, such as a methyleneoxycarbonyl group, an ethyleneoxycarbonyl group, a propanediyloxycarbonyl group, and a butanediyloxycarbonyl group. Examples of the alkanediylcarbonyl group include alkanediylcarbonyl groups having 2 to 20 carbon atoms, such as a methylenecarbonyl group, an ethylenecarbonyl group, a propanediylcarbonyl group, a butanediylcarbonyl group, and a pentanediylcarbonyl group. Examples of the alkanediylcarbonyloxy group include alkanediylcarbonyloxy groups having 2 to 19 carbon atoms, such as a methylenecarbonyloxy group, an ethylenecarbonyloxy group, a propanediylcarbonyloxy group, and a butanediylcarbonyloxy group. The number of carbon atoms in the alkanediyloxycarbonyl group is preferably 2 to 11, more preferably 2 to 6, even more preferably 2 to 4, and even more preferably 2 or 3. The number of carbon atoms in the alkanediylcarbonyl group is preferably 2 to 12, more preferably 2 to 6, even more preferably 2 to 4, and even more preferably 2 or 3. The number of carbon atoms in the alkanediylcarbonyloxy group is preferably 2 to 11, more preferably 2 to 6, even more preferably 2 to 4, and even more preferably 2 or 3.
The alkanediylthio group includes an alkanediylthio group having 1 to 19 carbon atoms, such as a methylenethio group, an ethylenethio group, a propylenethio group, etc. The number of carbon atoms in the alkanediylthio group is preferably 1 to 11, more preferably 1 to 6, even more preferably 1 to 4, and still more preferably 1 to 3.
The alkanediylsulfonyl group includes an alkanediylsulfonyl group having 1 to 19 carbon atoms, such as a methylenesulfonyl group, an ethylenesulfonyl group, a propylenesulfonyl group, etc. The number of carbon atoms in the alkanediylsulfonyl group is preferably 1 to 11, more preferably 1 to 6, even more preferably 1 to 4, and even more preferably 1 to 3.
Examples of the cycloalkoxy group include cycloalkoxy groups having 3 to 19 carbon atoms, such as a cyclohexyloxy group. Examples of the cycloalkylalkoxy group include cycloalkylalkoxy groups having 4 to 19 carbon atoms, such as a cyclohexylmethoxy group. Examples of the alkoxycarbonyloxy group include alkoxycarbonyloxy groups having 2 to 16 carbon atoms, such as a butoxycarbonyloxy group. Examples of the aromatic hydrocarbon group-carbonyloxy group include aromatic hydrocarbon group-carbonyloxy groups having 7 to 18 carbon atoms, such as a benzoyloxy group. Examples of the aromatic hydrocarbon group-carbonyl group include aromatic hydrocarbon group-carbonyl groups having 7 to 20 carbon atoms, such as a benzoyl group. Examples of the aromatic hydrocarbon group-oxy group include aromatic hydrocarbon group-oxy groups having 6 to 19 carbon atoms, such as a phenyloxy group.

Ｒ^３とＲ^４及びＲ^３とＲ^４とＲ^５が、それぞれ結合して形成する環状炭化水素基は、窒素原子を含む環状アンモニウムカチオンが挙げられ、該環状アンモニウムカチオンに含まれる－ＣＨ_２－は、－Ｏ－、－ＣＯ－又は－ＮＲ^７－に置き換わっていてもよく、該環状アンモニウムカチオンに含まれる－ＣＨ＝は、－Ｎ＝に置き換わっていてもよい。該環状アンモニウムカチオンとしては、窒素原子を含む単環式もしくは多環式の複素環式脂環式炭化水素環、窒素原子を含む複素環式芳香族炭化水素環に由来するカチオン等が挙げられる。窒素原子を含む複素環式脂環式炭化水素環は、ピロリジン環、イミダゾリジン環、ピラゾリジン環、オキサゾリジン環、イソキサゾリジン環、ピリジン環、ピペラジン環、モルホリン環、スクシンイミド環、２－オキサゾリドン環、キヌクリジン環、１－アザアダマンタン環等が挙げられる。窒素原子を含む複素環式芳香族炭化水素環は、ピロール環、ピラゾール環、イミダゾール環、オキサゾール環、イミダゾリジン環、トリアゾール環、ピラジン環、ピリミジン環、インドール環、イソインドール環、キノリン環、イソキノリン環、カルバゾール環等が挙げられる。環状アンモニウムカチオンについては、以下で表されるアンモニウムカチオンが例示される。
Ｒ^３とＲ^４、Ｒ^３とＲ^４とＲ^５が、それぞれ結合して形成する環の炭素数は、３～１２であることが好ましく、４～１２であることがより好ましく、例えば、以下の式で表される環状アンモニウムカチオンであることが好ましい。

Ｒ^３とＲ^４、Ｒ^３とＲ^４とＲ^５がそれぞれ結合して環状炭化水素基を形成している場合も、炭化水素基として、鎖式炭化水素基等が結合していてもよく、置換基を有していてもよい。
Ｒ^３、Ｒ^４、Ｒ^５、Ｒ^６及びＲ^７の炭化水素基が有していてもよい置換基としては、ハロゲン原子、シアノ基、ニトロ基が挙げられる。
ハロゲン原子としては、フッ素原子、塩素原子、臭素原子及びヨウ素原子等が挙げられる。
炭化水素基は、１つの置換基又は複数の置換基を有していてもよい。
Ｒ^３、Ｒ^４及びＲ^５は、それぞれ独立に、水素原子、炭素数１～１２の鎖式炭化水素基、炭素数３～１２の環状炭化水素基もしくは炭素数１～８の鎖式炭化水素基と炭素数３～１２の環状炭化水素基とを組み合わせた基であるか、又は、Ｒ^３とＲ^４、Ｒ^３とＲ^４とＲ^５がそれぞれ結合して環状炭化水素基を形成していることが好ましく、水素原子、炭素数１～４のアルキル基、炭素数３～１０の環状炭化水素基もしくは炭素数１～３のアルキル基と炭素数３～１０の環状炭化水素基とを組み合わせた基であるか、又は、Ｒ^３とＲ^４、Ｒ^３とＲ^４とＲ^５がそれぞれ結合して環状炭化水素基を形成していることがより好ましく、水素原子もしくは炭素数１～４のアルキル基であるか、又は、Ｒ^３とＲ^４が結合し、炭素数４～１２の環状炭化水素基を形成していることがさらに好ましい。ここで、上記の基において、該鎖式炭化水素基及び該環状炭化水素基に含まれる－ＣＨ₂－は、－Ｏ－、－Ｓ－、－ＮＲ^７－、－ＳＯ_２－又は－ＣＯ－に置き換わっていてもよい。また、該環状炭化水素基は、１以上の隣接する二つの炭素原子間で二重結合を形成していてもよく、該環状炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－、－ＣＯ－又は－ＮＲ^７に置き換わっていてもよく、該環状炭化水素基に含まれる－ＣＨ＝は、－Ｎ＝に置き換わっていてもよい。また、いずれの基も、置換基を有していてもよい。
Ｒ^６は、水素原子、炭素数１～１２の鎖式炭化水素基、炭素数３～１２の環状炭化水素基又は炭素数１～８の鎖式炭化水素基と炭素数３～１２の環状炭化水素基とを組み合わせた基であることが好ましく、水素原子、炭素数１～４のアルキル基、炭素数３～１０の環状炭化水素基又は炭素数１～３のアルキル基と炭素数３～１０の環状炭化水素基とを組み合わせた基であることがより好ましい。ここで、上記の基において、該鎖式炭化水素基及び該環状炭化水素基に含まれる－ＣＨ₂－は、－Ｏ－、－Ｓ－、－ＮＲ^７－、－ＳＯ_２－又は－ＣＯ－に置き換わっていてもよい。また、いずれの基も、置換基を有していてもよい。
Ｒ^７は、水素原子又は炭素数１～４のアルキル基であることが好ましい。 Examples of the group in which --CH ₂ -- contained in the alicyclic hydrocarbon group is replaced by --O--, --CO--, --S-- or --SO ₂ -- include the groups shown below. The bonding site can be any position.

The cyclic hydrocarbon group formed by the bonding of R ³ and R ⁴ , and R ³ , R ⁴ and R ⁵ , respectively, includes a cyclic ammonium cation containing a nitrogen atom, in which -CH ₂ - contained in the cyclic ammonium cation may be replaced by -O-, -CO- or -NR ⁷ -, and -CH= contained in the cyclic ammonium cation may be replaced by -N=. Examples of the cyclic ammonium cation include a monocyclic or polycyclic heterocyclic alicyclic hydrocarbon ring containing a nitrogen atom, and a cation derived from a heterocyclic aromatic hydrocarbon ring containing a nitrogen atom. Examples of the heterocyclic alicyclic hydrocarbon ring containing a nitrogen atom include a pyrrolidine ring, an imidazolidine ring, a pyrazolidine ring, an oxazolidine ring, an isoxazolidine ring, a pyridine ring, a piperazine ring, a morpholine ring, a succinimide ring, a 2-oxazolidone ring, a quinuclidine ring, and a 1-azaadamantane ring. Examples of the heterocyclic aromatic hydrocarbon ring containing a nitrogen atom include a pyrrole ring, a pyrazole ring, an imidazole ring, an oxazole ring, an imidazolidine ring, a triazole ring, a pyrazine ring, a pyrimidine ring, an indole ring, an isoindole ring, a quinoline ring, an isoquinoline ring, a carbazole ring, etc. Examples of the cyclic ammonium cation include the ammonium cations represented by the following.
The number of carbon atoms in the ring formed by bonding between ^R3 and ^R4 , and between ^R3 , ^R4 and ^R5 , is preferably 3 to 12, and more preferably 4 to 12. For example, the ring is preferably a cyclic ammonium cation represented by the following formula:

When ^R3 and ^R4 , and ^R3 , ^R4 and ^R5 are bonded to each other to form a cyclic hydrocarbon group, the hydrocarbon group may be bonded to a chain hydrocarbon group or may have a substituent.
Substituents that the hydrocarbon groups of R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁷ may have include a halogen atom, a cyano group and a nitro group.
Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
The hydrocarbon group may have one substituent or multiple substituents.
R ³ , R ⁴ and R ⁵ are each independently a hydrogen atom, a chain hydrocarbon group having 1 to 12 carbon atoms, a cyclic hydrocarbon group having 3 to 12 carbon atoms, or a group formed by combining a chain hydrocarbon group having 1 to 8 carbon atoms with a cyclic hydrocarbon group having 3 to 12 carbon atoms, or preferably R ³ and R ⁴ , and R ³ , R ⁴ and R ⁵ are each bonded to form a cyclic hydrocarbon group, more preferably a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyclic hydrocarbon group having 3 to 10 carbon atoms, or a group formed by combining an alkyl group having 1 to 3 carbon atoms with a cyclic hydrocarbon group having 3 to 10 carbon atoms, or more preferably R ³ and R ⁴ , and R ³ , R ⁴ and R ⁵ are each bonded to form a cyclic hydrocarbon group, and even more preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, or even more preferably R ³ and R ⁴ are bonded to form a cyclic hydrocarbon group having 4 to 12 carbon atoms. In the above groups, -CH ₂ - contained in the chain hydrocarbon group and the cyclic hydrocarbon group may be replaced by -O-, -S-, -NR ⁷ -, -SO ₂ - or -CO-. Furthermore, the cyclic hydrocarbon group may form one or more double bonds between two adjacent carbon atoms, -CH ₂ - contained in the cyclic hydrocarbon group may be replaced by -O-, -CO- or -NR ⁷ , and -CH= contained in the cyclic hydrocarbon group may be replaced by -N=. Furthermore, any of the groups may have a substituent.
R ⁶ is preferably a hydrogen atom, a chain hydrocarbon group having 1 to 12 carbon atoms, a cyclic hydrocarbon group having 3 to 12 carbon atoms, or a group combining a chain hydrocarbon group having 1 to 8 carbon atoms with a cyclic hydrocarbon group having 3 to 12 carbon atoms, and more preferably a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyclic hydrocarbon group having 3 to 10 carbon atoms, or a group combining an alkyl group having 1 to 3 carbon atoms with a cyclic hydrocarbon group having 3 to 10 carbon atoms. Here, in the above groups, -CH ₂ - contained in the chain hydrocarbon group and the cyclic hydrocarbon group may be replaced by -O-, -S-, -NR ⁷ -, -SO ₂ - or -CO-. Furthermore, any of the groups may have a substituent.
^R7 is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

Examples of the cation of the salt (I6) include cations represented by the following formulae (I6-c-1) to (I6-c-24).

The salt (I6-s) is a combination of the above-mentioned anion (I6-a) and the above-mentioned cation (I6-c), which can be combined in any desired manner. As the salt (I6-s), a combination of an anion represented by any one of formulas (I-a-1) to (I-a-6) and formulas (I-a-16) to (I-a-19) and a cation (I6-c-1) to (I6-c-24) is preferably used.

中でも、塩（Ｉ－ｓ）は、式（Ｉ－ａ－１）～式（Ｉ－ａ－６）、式（Ｉ－ａ－１６）～式（Ｉ－ａ－１９）のいずれかで表されるアニオンと式（Ｉ６－ｃ－１）～式（Ｉ６－ｃ－２４）のいずれかで表されるカチオンとを組み合わせた塩が好ましい。
また、化合物（Ｉ６－ｓ）は、特開２００８－１０７４４３号公報に開示される製造方法によって、入手することができる。 Examples of the salt (I6-s) include salts listed in Table 1. In the table below, each symbol represents the symbol attached to the structure representing the above-mentioned anion or cation, and "-" indicates that the salt (I6-s) corresponds to the anion (I6-a) or cation (I6-c), respectively. For example, the salt (I6-s-1) means a salt consisting of the anion represented by formula (I1-a-1) and the cation represented by formula (I6-c-1), and represents the salt shown below.

Among them, the salt (I-s) is preferably a salt obtained by combining an anion represented by any one of formulas (I-a-1) to (I-a-6), and (I-a-16) to (I-a-19) with a cation represented by any one of formulas (I6-c-1) to (I6-c-24).
In addition, compound (I6-s) can be obtained by the production method disclosed in JP-A-2008-107443.

Resin (A1) may be a copolymer containing one structural unit represented by formula (a4-2) and one structural unit (I6) selected from the group consisting of structural units represented by formula (a4-3), or a copolymer containing one structural unit represented by formula (a4-2) and one structural unit represented by formula (a4-3) and two or more structural units (I6), or a copolymer containing a structural unit selected from the group consisting of two or more structural units represented by formula (a4-2) and one structural unit (I6), or a copolymer containing a structural unit selected from the group consisting of two or more structural units represented by formula (a4-2) and one structural unit (I6), or a copolymer containing a structural unit selected from the group consisting of two or more structural units represented by formula (a4-3) and two or more structural units (I6).
The content of the structural unit represented by formula (a4-2) and/or the structural unit represented by formula (a4-3) is 30 mol% or more, preferably 50 mol% or more, more preferably 70 mol% or more, and even more preferably 85 mol% or more, based on 100 mol% of all structural units in the resin (A1). Also, 99.9 mol% or less, preferably 99 mol% or less, more preferably 98 mol% or less, even more preferably 97 mol% or less, even more preferably 95 mol% or less, and even more preferably 93 mol% or less. Specifically, 30 to 99.9 mol% is mentioned, preferably 30 to 99 mol%, more preferably 50 to 98 mol%, even more preferably 70 to 97 mol%, and even more preferably 85 to 97 mol%.
The content of the structural unit (I6) is 0.1 mol% or more, preferably 0.5 mol% or more, more preferably 0.8 mol% or more, and even more preferably 1 mol% or more, based on the total structural units of the resin (A1). It may also be 30 mol% or less, preferably 25 mol% or less, more preferably 20 mol% or less, and even more preferably 15 mol% or less. Specifically, it may be 0.1 to 30 mol%, preferably 0.5 to 25 mol%, more preferably 0.8 to 20 mol%, and even more preferably 1 to 15 mol%.
In resin (A1), the content ratio of the structural unit selected from the group consisting of structural units represented by formula (a4-2) and structural units represented by formula (a4-3) to the structural unit (I6) is preferably 50:50 to 99.9:0.1, more preferably 70:30 to 99.5:0.5, even more preferably 80:20 to 99.2:0.8, and still more preferably 85:15 to 99:1.

Resin (A1) may further contain a structural unit having an acid labile group (hereinafter sometimes referred to as "structural unit (a1)"), in addition to the structural unit (I6) and the structural unit selected from the group consisting of structural units represented by formula (a4-2) and structural units represented by formula (a4-3).
The resin (A1) may further contain a structural unit other than the structural unit (a1).
Examples of structural units other than the structural unit (a1) include structural units not having an acid labile group (hereinafter sometimes referred to as "structural unit (s)") and structural units known in the art.

［式（１）中、Ｒ^ａ１、Ｒ^ａ２及びＲ^ａ３は、それぞれ独立に、炭素数１～８のアルキル基、炭素数２～８のアルケニル基、炭素数３～２０の脂環式炭化水素基、炭素数６～１８の芳香族炭化水素基又はこれらを組み合わせた基を表すか、Ｒ^a1及びＲ^a2は互いに結合してそれらが結合する炭素原子とともに炭素数３～２０の脂環式炭化水素基を形成し、該アルキル基、該アルケニル基、該芳香族炭化水素基及び該脂環式炭化水素基は、ハロゲン原子を有してもよい。
ｍａ及びｎａは、それぞれ独立して、０又は１を表し、ｍａ及びｎａの少なくとも一方は１を表す。
＊は結合部位を表す。］

［式（２）中、Ｒ^ａ１’及びＲ^ａ２’は、それぞれ独立に、水素原子又は炭素数１～１２の炭化水素基を表し、Ｒ^ａ３’は、炭素数１～２０の炭化水素基を表すか、Ｒ^ａ２’及びＲ^ａ３’は互いに結合してそれらが結合する炭素原子及びＸとともに炭素数３～２０の複素環基を形成し、該炭化水素基及び該複素環基に含まれる－ＣＨ_２－は、－Ｏ－又は－Ｓ－で置き換わってもよく、該炭化水素基及び該複素環基は、ハロゲン原子を有してもよい。
Ｘは、酸素原子又は硫黄原子を表す。
ｎａ’は、０又は１を表す。
＊は結合部位を表す。］ <Structural Unit (a1)>
The structural unit (a1) is derived from a monomer having an acid labile group (hereinafter, may be referred to as "monomer (a1)").
The acid labile group contained in the resin (A1) is preferably a group represented by formula (1) (hereinafter also referred to as group (1)) and/or a group represented by formula (2) (hereinafter also referred to as group (2)).

[In formula (1), R ^a1 , R ^a2 , and R ^a3 each independently represent an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a combination of these, or R ^a1 and R ^a2 are bonded to each other to form an alicyclic hydrocarbon group having 3 to 20 carbon atoms together with the carbon atom to which they are bonded, and the alkyl group, alkenyl group, aromatic hydrocarbon group and alicyclic hydrocarbon group may have a halogen atom.
ma and na each independently represent 0 or 1, and at least one of ma and na represents 1.
* indicates a binding site.]

[In formula (2), R ^a1' and R ^a2' each independently represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms; R ^a3' represents a hydrocarbon group having 1 to 20 carbon atoms; or R ^a2' and R ^a3' are bonded to each other to form a heterocyclic group having 3 to 20 carbon atoms together with the carbon atom to which they are bonded and X, and -CH ₂ - contained in the hydrocarbon group and the heterocyclic group may be replaced by -O- or -S-, and the hydrocarbon group and the heterocyclic group may have a halogen atom.
X represents an oxygen atom or a sulfur atom.
na′ represents 0 or 1.
* indicates a binding site.]

Ｒ^ａ１、Ｒ^ａ２及びＲ^ａ３における芳香族炭化水素基としては、フェニル基、ナフチル基、アントリル基、ビフェニル基、フェナントリル基等のアリール基が挙げられる。
組み合わせた基としては、上述したアルキル基と脂環式炭化水素基とを組み合わせた基（例えば、メチルシクロヘキシル基、ジメチルシクロへキシル基、メチルノルボルニル基、シクロヘキシルメチル基、アダマンチルメチル基、アダマンチルジメチル基、ノルボルニルエチル基等のアルキルシクロアルキル基又はシクロアルキルアルキル基）、ベンジル基等のアラルキル基、アルキル基を有する芳香族炭化水素基（ｐ－メチルフェニル基、ｐ－ｔｅｒｔ－ブチルフェニル基、トリル基、キシリル基、クメニル基、メシチル基、２，６－ジエチルフェニル基、２－メチル－６－エチルフェニル基等）、脂環式炭化水素基を有する芳香族炭化水素基（ｐ－シクロヘキシルフェニル基、ｐ－アダマンチルフェニル基等）、フェニルシクロヘキシル基等のアリール－シクロアルキル基等が挙げられる。
好ましくは、ｍａは０であり、ｎａは１である。
Ｒ^a1及びＲ^a2が互いに結合して脂環式炭化水素基を形成する場合の－Ｃ（Ｒ^a1）（Ｒ^a2）（Ｒ^a3）としては、下記の環が挙げられる。脂環式炭化水素基は、好ましくは炭素数３～１２である。＊は－Ｏ－との結合部位を表す。

Examples of the alkyl group for R ^a1 , R ^a2 and R ^a3 include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group and an octyl group.
Examples of the alkenyl group for R ^a1 , R ^a2 and R ^a3 include an ethenyl group, a propenyl group, an isopropenyl group, a butenyl group, an isobutenyl group, a tert-butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an octenyl group, an isooctenyl group and a nonenyl group.
The alicyclic hydrocarbon group in R ^a1 , R ^a2 and R ^a3 may be either monocyclic or polycyclic. Examples of the monocyclic alicyclic hydrocarbon group include cycloalkyl groups such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group and a cyclooctyl group. Examples of the polycyclic alicyclic hydrocarbon group include a decahydronaphthyl group, an adamantyl group, a norbornyl group and the following groups (* represents a bonding site). The number of carbon atoms in the alicyclic hydrocarbon group in ^{R a1} , R ^a2 and R ^a3 is preferably 3 to 16.

Examples of the aromatic hydrocarbon group for R ^a1 , R ^a2 and R ^a3 include aryl groups such as a phenyl group, a naphthyl group, an anthryl group, a biphenyl group and a phenanthryl group.
Examples of the combined group include a group in which the above-mentioned alkyl group and an alicyclic hydrocarbon group are combined (for example, an alkylcycloalkyl group or a cycloalkylalkyl group such as a methylcyclohexyl group, a dimethylcyclohexyl group, a methylnorbornyl group, a cyclohexylmethyl group, an adamantylmethyl group, an adamantyldimethyl group, or a norbornylethyl group), an aralkyl group such as a benzyl group, an aromatic hydrocarbon group having an alkyl group (a p-methylphenyl group, a p-tert-butylphenyl group, a tolyl group, a xylyl group, a cumenyl group, a mesityl group, a 2,6-diethylphenyl group, a 2-methyl-6-ethylphenyl group, or the like), an aromatic hydrocarbon group having an alicyclic hydrocarbon group (a p-cyclohexylphenyl group, a p-adamantylphenyl group, or the like), and an aryl-cycloalkyl group such as a phenylcyclohexyl group.
Preferably, ma is 0 and na is 1.
When R ^a1 and R ^a2 are bonded to each other to form an alicyclic hydrocarbon group, examples of -C(R ^a1 )(R ^a2 )(R ^a3 ) include the following rings. The alicyclic hydrocarbon group preferably has 3 to 12 carbon atoms. * represents the bonding site with -O-.

Ｒ^a1、Ｒ^a２、Ｒ^a3、Ｒ^ａ１、Ｒ^ａ２’及びＲ^ａ３’が有してもよいハロゲン原子は、フッ素原子、塩素原子、臭素原子又はヨウ素原子が挙げられる。
Ｒ^ａ１’及びＲ^ａ２’のうち、少なくとも１つは水素原子であることが好ましい。
ｎａ’は、好ましくは０である。 Examples of the hydrocarbon group for R ^a1′ , R ^a2′ and R ^a3′ include an alkyl group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group and a group formed by combining these groups.
Examples of the alkyl group, the alicyclic hydrocarbon group, the aromatic hydrocarbon group, and the group formed by combining these groups include the same groups as those exemplified for R ^a1 , R ^a2 , and R ^a3 .
When R ^a2' and R ^a3' are bonded to each other to form a heterocyclic group together with the carbon atom to which they are bonded and X, -C(R ^a1' )(R ^a2' )-X-R ^a3' includes the following groups: * represents a bonding site.

The halogen atom which may be possessed by R ^a1 , R ^a2 , R ^a3 , R ^a1 , R ^a2′ and R ^a3′ includes a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.
At least one of R ^a1' and R ^a2' is preferably a hydrogen atom.
na′ is preferably 0.

Examples of the group (1) include the following groups.
A group in which R ^a1 , R ^a2 and R ^a3 in the formula (1) are alkyl groups, ma = 0 and na = 1. As the group, a tert-butoxycarbonyl group is preferable.
A group in which R ^a1 and R ^a2 together with the carbon atom to which they are bonded form an adamantyl group, R ^a3 is an alkyl group, ma=0, and na=1 in the formula (1).
A group represented by formula (1), in which R ^a1 and R ^a2 each independently represent an alkyl group, R ^a3 represents an adamantyl group, ma=0, and na=1.
Specific examples of the group (1) include the following groups: * represents a binding site.

Specific examples of the group (2) include the following groups: * represents a bonding site.

Monomer (a1) is preferably a monomer having an acid labile group and an ethylenically unsaturated bond, more preferably a (meth)acrylic monomer having an acid labile group.

Among the (meth)acrylic monomers having an acid labile group, those having an alicyclic hydrocarbon group having 5 to 20 carbon atoms are preferred. If a resin (A1) having a structural unit derived from a monomer (a1) having a bulky structure such as an alicyclic hydrocarbon group is used in a resist composition, the resolution of the resist pattern can be improved.

［式（ａ１－０）、式（ａ１－１）及び式（ａ１－２）中、全ての符号は、それぞれ前記と同じ意味を表す。］ Examples of the structural unit derived from a (meth)acrylic monomer having the group (1) include a structural unit represented by formula (a1-0) (hereinafter, sometimes referred to as structural unit (a1-0)), a structural unit represented by formula (a1-1) (hereinafter, sometimes referred to as structural unit (a1-1)), or a structural unit represented by formula (a1-2) (hereinafter, sometimes referred to as structural unit (a1-2)). Preferably, it is at least one structural unit selected from the group consisting of the structural unit (a1-0), the structural unit (a1-1) and the structural unit (a1-2), more preferably at least one structural unit selected from the group consisting of the structural unit (a1-1) and the structural unit (a1-2). These may be used alone, or two or more of them may be used in combination.

[In formula (a1-0), formula (a1-1) and formula (a1-2), all symbols have the same meaning as defined above.]

R ^a01 , R ^a4 and R ^a5 are preferably a hydrogen atom or a methyl group, more preferably a methyl group.
L ^a01 , L ^a1 and L ^a2 are preferably an oxygen atom or *-O-(CH ₂ ) _k01 -CO-O- (wherein k01 is preferably an integer of 1 to 4, more preferably 1), and more preferably an oxygen atom.
Examples of the alkyl group, alicyclic hydrocarbon group, aromatic hydrocarbon group and combinations thereof in R ^a02 , R ^a03 and R ^a04 include the same groups as those exemplified for R ^a1 , R ^a2 and R ^a3 in the group (1).
Examples of the alkyl group, alkenyl group, alicyclic hydrocarbon group, aromatic hydrocarbon group and combinations thereof for R ^a6 and R ^a7 include the same groups as those exemplified for R ^a1 , R ^a2 and R ^a3 in formula (1).
The alkyl group in R ^a02 , R ^a03 , and R ^a04 is preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group or an ethyl group, and even more preferably a methyl group.
The alkyl group for R ^a6 and R ^a7 is preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group, an ethyl group, an isopropyl group or a t-butyl group, and even more preferably an ethyl group, an isopropyl group or a t-butyl group.
The alkenyl group for R ^a6 and R ^a7 is preferably an alkenyl group having 2 to 6 carbon atoms, and more preferably an ethenyl group, a propenyl group, an isopropenyl group or a butenyl group.
The alicyclic hydrocarbon group of R ^a02 , R ^a03 , R ^a04 , R ^a6 and R ^a7 preferably has 5 to 12 carbon atoms, and more preferably 5 to 10 carbon atoms.
The aromatic hydrocarbon groups of R ^a02 , R ^a03 , R ^a04 , R ^a6 and R ^a7 preferably have 6 to 12 carbon atoms, and more preferably 6 to 10 carbon atoms.
In the group in which an alkyl group and an alicyclic hydrocarbon group are combined, the total number of carbon atoms in the combination of the alkyl group and the alicyclic hydrocarbon group is preferably 18 or less.
In the group in which an alkyl group and an aromatic hydrocarbon group are combined, the total number of carbon atoms in the combination of the alkyl group and the aromatic hydrocarbon group is preferably 18 or less.
R ^a02 and R ^a03 are preferably an alkyl group having 1 to 6 carbon atoms or an aromatic hydrocarbon group having 6 to 12 carbon atoms, and more preferably a methyl group, an ethyl group, a phenyl group or a naphthyl group.
R ^a04 is preferably an alkyl group having 1 to 6 carbon atoms or an alicyclic hydrocarbon group having 5 to 12 carbon atoms, and more preferably a methyl group, an ethyl group, a cyclohexyl group or an adamantyl group.
R ^a6 and R ^a7 are each independently preferably an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an aromatic hydrocarbon group having 6 to 12 carbon atoms, more preferably a methyl group, an ethyl group, an isopropyl group, a t-butyl group, an ethenyl group, a phenyl group, or a naphthyl group, and even more preferably an ethyl group, an isopropyl group, a t-butyl group, an ethenyl group, or a phenyl group.
m1 is preferably an integer of 0 to 3, and more preferably 0 or 1.
n1 is preferably an integer of 0 to 3, and more preferably 0 or 1.
n1' is preferably 0 or 1.

Examples of the structural unit (a1-0) include structural units represented by any one of formulas (a1-0-1) to (a1-0-18) and structural units in which the methyl group corresponding to R ^a01 in the structural unit (a1-0) is replaced with a hydrogen atom, a halogen atom, a haloalkyl group or another alkyl group. Of these, structural units represented by any one of formulas (a1-0-1) to (a1-0-10), (a1-0-13) and (a1-0-14) are preferred.

Examples of the structural unit (a1-1) include structural units derived from monomers described in JP-A-2010-204646. Among these, structural units represented by any one of formulas (a1-1-1) to (a1-1-7) and structural units in which the methyl group corresponding to R ^a4 in the structural unit (a1-1) is replaced with a hydrogen atom, a halogen atom, a haloalkyl group or another alkyl group are preferred, and structural units represented by any one of formulas (a1-1-1) to (a1-1-4) are more preferred.

Examples of the structural unit (a1-2) include structural units represented by any one of formulas (a1-2-1) to (a1-2-14) and structural units in which the methyl group corresponding to R ^a5 in the structural unit (a1-2) is replaced with a hydrogen atom, a halogen atom, a haloalkyl group, or another alkyl group. Of these, structural units represented by any one of formulas (a1-2-2), (a1-2-5), (a1-2-6), and (a1-2-10) to (a1-2-14) are preferred.

When the resin (A1) contains the structural unit (a1-0), the content thereof is 5 mol % or more, preferably 10 mol % or more, based on the total structural units of the resin (A1). The content is 80 mol % or less, preferably 75 mol % or less, and more preferably 70 mol % or less. Specifically, the content is 5 to 80 mol %, preferably 5 to 75 mol %, and more preferably 10 to 70 mol %.
When the resin (A1) contains the structural unit (a1-1) and/or the structural unit (a1-2), the total content of these units is 10 mol% or more, preferably 15 mol% or more, more preferably 20 mol% or more, even more preferably 25 mol% or more, and even more preferably 30 mol% or more, based on the total structural units of the resin (A1). Also, 95 mol% or less, preferably 90 mol% or less, more preferably 85 mol% or less, even more preferably 80 mol% or less, even more preferably 75 mol% or less, and even more preferably 70 mol% or less. Specifically, 10 to 90 mol% is mentioned, preferably 15 to 85 mol%, more preferably 20 to 80 mol%, even more preferably 20 to 75 mol%, and even more preferably 20 to 70 mol%.

［式（ａ１－４）中、
Ｒ^a32は、水素原子、ハロゲン原子、又は、ハロゲン原子を有していてもよい炭素数１～６のアルキル基を表す。
Ｒ^a33は、ハロゲン原子、ヒドロキシ基、カルボキシ基、ハロゲン原子を有していてもよい炭素数１～６のアルキル基、炭素数１～６のアルコキシ基、炭素数２～１２のアルコキシアルキル基、炭素数２～１２のアルコキシアルコキシ基、炭素数２～４のアルキルカルボニル基、炭素数２～４のアルキルカルボニルオキシ基、アクリロイルオキシ基又はメタクリロイルオキシ基を表す。
Ａ^a30は、単結合又は＊－Ｘ^a31－（Ａ^a32－Ｘ^a32）_nc－を表し、＊は－Ｒ^a32が結合する炭素原子との結合部位を表す。
Ａ^a32は、炭素数１～８のアルカンジイル基を表す。
Ｘ^a31及びＸ^a32は、それぞれ独立に、－Ｏ－、－ＣＯ－Ｏ－又は－Ｏ－ＣＯ－を表す。
ｎｃは、０又は１を表す。
ｌａは、０～４のいずれかの整数を表す。ｌａが２以上のいずれかの整数である場合、複数のＲ^a33は互いに同一であっても異なっていてもよい。
Ｒ^a34及びＲ^a35は、それぞれ独立に、水素原子又は炭素数１～１２の炭化水素基を表し、Ｒ^a36は、炭素数１～２０の炭化水素基を表すか、Ｒ^a35及びＲ^a36は互いに結合してそれらが結合する－Ｃ－Ｏ－とともに炭素数２～２０の２価の炭化水素基を形成し、該炭化水素基及び該２価の炭化水素基に含まれる－ＣＨ₂－は、－Ｏ－又は－Ｓ－で置き換わってもよい。］ An example of the structural unit (a1) having a group (2) is a structural unit represented by formula (a1-4) (hereinafter, sometimes referred to as "structural unit (a1-4)").

[In formula (a1-4),
R ^a32 represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
R ^a33 represents a halogen atom, a hydroxy group, a carboxy group, an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, an alkoxy group having 1 to 6 carbon atoms, an alkoxyalkyl group having 2 to 12 carbon atoms, an alkoxyalkoxy group having 2 to 12 carbon atoms, an alkylcarbonyl group having 2 to 4 carbon atoms, an alkylcarbonyloxy group having 2 to 4 carbon atoms, an acryloyloxy group, or a methacryloyloxy group.
A ^a30 represents a single bond or *-X ^a31 -(A ^a32 -X ^a32 ) _nc -, where * represents the bonding site with the carbon atom to which -R ^a32 is bonded.
A ^a32 represents an alkanediyl group having 1 to 8 carbon atoms.
X ^a31 and X ^a32 each independently represent —O—, —CO—O—, or —O—CO—.
n c represents 0 or 1.
la represents an integer of 0 to 4. When la is an integer of 2 or more, multiple R ^a33 may be the same or different.
R ^a34 and R ^a35 each independently represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, R ^a36 represents a hydrocarbon group having 1 to 20 carbon atoms, or R ^a35 and R ^a36 are bonded to each other to form a divalent hydrocarbon group having 2 to 20 carbon atoms together with the -C-O- to which they are bonded, and the -CH ₂ - contained in the hydrocarbon group and the divalent hydrocarbon group may be replaced by -O- or -S-.]

Examples of the halogen atom in R ^a32 and R ^a33 include a fluorine atom, a chlorine atom, and a bromine atom.
Examples of the alkyl group having 1 to 6 carbon atoms which may have a halogen atom in R ^a32 and R ^a33 include a trifluoromethyl group, a difluoromethyl group, a methyl group, a perfluoroethyl group, a 2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, an ethyl group, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, a propyl group, a perfluorobutyl group, a 1,1,2,2,3,3,4,4-octafluorobutyl group, a butyl group, a perfluoropentyl group, a 2,2,3,3,4,4,5,5,5-nonafluoropentyl group, a pentyl group, a hexyl group, and a perfluorohexyl group.
R ^a32 is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom, a methyl group or an ethyl group, and even more preferably a hydrogen atom or a methyl group.
Examples of the alkyl group for R ^a33 include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, and a hexyl group. The alkyl group is preferably an alkyl group having 1 to 4 carbon atoms, more preferably a methyl group or an ethyl group, and further preferably a methyl group.
Examples of the alkoxy group in R ^a33 include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxy group, and a hexyloxy group. The alkoxy group is preferably an alkoxy group having 1 to 4 carbon atoms, more preferably a methoxy group or an ethoxy group, and further preferably a methoxy group.
Examples of the alkoxyalkyl group for ^R include a methoxymethyl group, an ethoxyethyl group, a propoxymethyl group, an isopropoxymethyl group, a butoxymethyl group, a sec-butoxymethyl group, and a tert-butoxymethyl group. The alkoxyalkyl group is preferably an alkoxyalkyl group having 2 to 8 carbon atoms, more preferably a methoxymethyl group or an ethoxyethyl group, and further preferably a methoxymethyl group.
Examples of the alkoxyalkoxy group for ^R include a methoxymethoxy group, a methoxyethoxy group, an ethoxymethoxy group, an ethoxyethoxy group, a propoxymethoxy group, an isopropoxymethoxy group, a butoxymethoxy group, a sec-butoxymethoxy group, and a tert-butoxymethoxy group. The alkoxyalkoxy group is preferably an alkoxyalkoxy group having 2 to 8 carbon atoms, and more preferably a methoxyethoxy group or an ethoxyethoxy group.
Examples of the alkylcarbonyl group for R ^a33 include an acetyl group, a propionyl group, a butyryl group, etc. The alkylcarbonyl group is preferably an alkylcarbonyl group having 2 to 3 carbon atoms, and more preferably an acetyl group.
The alkylcarbonyloxy group for R ^a33 includes an acetyloxy group, a propionyloxy group, and a butyryloxy group. The alkylcarbonyloxy group is preferably an alkylcarbonyloxy group having 2 to 3 carbon atoms, and more preferably an acetyloxy group.
R ^a33 is preferably a halogen atom, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxyalkoxy group having 2 to 8 carbon atoms, more preferably a fluorine atom, an iodine atom, a hydroxy group, a methyl group, a methoxy group, an ethoxy group, an ethoxyethoxy group, or an ethoxymethoxy group, and still more preferably a fluorine atom, an iodine atom, a hydroxy group, a methyl group, a methoxy group, or an ethoxyethoxy group.

Examples of *-X ^a31 -(A ^a32 -X ^a32 ) _nc - include *-O-, *-CO-O-, *-O-CO-, *-CO-O-A ^a32 -CO-O-, *-O-CO-A ^a32 -O-, *-O-A ^a32 -CO-O-, *-CO-O-A ^a32 -O-CO- and *-O-CO-A ^a32 -O-CO-. Among these, *-CO-O-, *-CO-O-A ^a32 -CO-O- or *-O-A ^a32 -CO-O- are preferred.

Examples of the alkanediyl group include a methylene group, an ethylene group, a propane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group, and a 2-methylbutane-1,4-diyl group.
A ^a32 is preferably a methylene group or an ethylene group.

A ^a30 is preferably a single bond, *-CO-O- or *-CO-O-A ^a32 -CO-O-, more preferably a single bond, *-CO-O- or *-CO-O-CH ₂ -CO-O-, further preferably a single bond or *-CO-O-.

芳香族炭化水素基としては、フェニル基、ナフチル基、アントリル基、ビフェニル基、フェナントリル基等のアリール基等が挙げられる。
組み合わせた基としては、上述したアルキル基と脂環式炭化水素基とを組み合わせた基（例えば、メチルシクロヘキシル基、ジメチルシクロへキシル基、メチルノルボルニル基、シクロヘキシルメチル基、アダマンチルメチル基、アダマンチルジメチル基、ノルボルニルエチル基等のアルキルシクロアルキル基又はシクロアルキルアルキル基）、ベンジル基等のアラルキル基、アルキル基を有する芳香族炭化水素基（ｐ－メチルフェニル基、ｐ－ｔｅｒｔ－ブチルフェニル基、トリル基、キシリル基、クメニル基、メシチル基、２，６－ジエチルフェニル基、２－メチル－６－エチルフェニル基等）、脂環式炭化水素基を有する芳香族炭化水素基（ｐ－シクロヘキシルフェニル基、ｐ－アダマンチルフェニル基等）、フェニルシクロヘキシル基等のアリール－シクロアルキル基等が挙げられる。特に、Ｒ^a36としては、炭素数１～１８のアルキル基、炭素数３～１８の脂環式炭化水素基、炭素数６～１８の芳香族炭化水素基又はこれらを組み合わせることにより形成される基が挙げられる。 la is preferably 0, 1 or 2, more preferably 0 or 1, and even more preferably 0.
Examples of the hydrocarbon group for R ^a34 , R ^a35 and R ^a36 include an alkyl group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group and a group formed by combining these groups.
Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, and an octyl group.
The alicyclic hydrocarbon group may be either monocyclic or polycyclic. Examples of the monocyclic alicyclic hydrocarbon group include cycloalkyl groups such as cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Examples of the polycyclic alicyclic hydrocarbon group include decahydronaphthyl, adamantyl, and norbornyl groups, as well as the following groups (* indicates a bonding site):

Examples of the aromatic hydrocarbon group include aryl groups such as a phenyl group, a naphthyl group, an anthryl group, a biphenyl group, and a phenanthryl group.
Examples of the combined group include a group in which the above-mentioned alkyl group and alicyclic hydrocarbon group are combined (e.g., an alkylcycloalkyl group or a cycloalkylalkyl group such as a methylcyclohexyl group, a dimethylcyclohexyl group, a methylnorbornyl group, a cyclohexylmethyl group, an adamantylmethyl group, an adamantyldimethyl group, or a norbornylethyl group), an aralkyl group such as a benzyl group, an aromatic hydrocarbon group having an alkyl group (e.g., a p-methylphenyl group, a p-tert-butylphenyl group, a tolyl group, a xylyl group, a cumenyl group, a mesityl group, a 2,6-diethylphenyl group, or a 2-methyl-6-ethylphenyl group), an aromatic hydrocarbon group having an alicyclic hydrocarbon group (e.g., a p-cyclohexylphenyl group, a p-adamantylphenyl group), and an aryl-cycloalkyl group such as a phenylcyclohexyl group. In particular, R ^a36 may be an alkyl group having 1 to 18 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group formed by combining these.

R ^a34 is preferably a hydrogen atom.
R ^a35 is preferably a hydrogen atom, an alkyl group having 1 to 12 carbon atoms or an alicyclic hydrocarbon group having 3 to 12 carbon atoms, and more preferably a methyl group or an ethyl group.
The hydrocarbon group of R ^a36 is preferably an alkyl group having 1 to 18 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group formed by combining these, and more preferably an alkyl group having 1 to 18 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, or an aralkyl group having 7 to 18 carbon atoms. The alkyl group and alicyclic hydrocarbon group in R ^a36 are preferably unsubstituted. The aromatic hydrocarbon group in R ^a36 is preferably an aromatic ring having an aryloxy group having 6 to 10 carbon atoms.
The --OC(R ^a34 )(R ^a35 )--O--R ^a36 in the structural unit (a1-4) is eliminated on contact with an acid (eg, p-toluenesulfonic acid) to form a hydroxy group.
--OC(R ^a34 )(R ^a35 )--O--R ^a36 is preferably bonded to the m-position or p-position of the benzene ring.

Examples of the structural unit (a1-4) include structural units derived from monomers described in JP-A-2010-204646. Preferred examples include structural units represented by formulas (a1-4-1) to (a1-4-24) and structural units in which the hydrogen atom corresponding to R ^a32 in the structural unit (a1-4) is replaced with a halogen atom, a haloalkyl group, or an alkyl group, and more preferred examples include structural units represented by formulas (a1-4-1) to (a1-4-5), (a1-4-10), (a1-4-13), (a1-4-14), (a1-4-19), and (a1-4-20).

When resin (A1) contains structural unit (a1-4), its content is preferably 3 to 80 mol %, more preferably 5 to 75 mol %, even more preferably 7 to 70 mol %, even more preferably 7 to 65 mol %, and even more preferably 10 to 60 mol %, based on the total of all structural units in resin (A1).

［式（ａ１－５）中、全ての符号は、それぞれ前記と同じ意味を表す。］ Examples of the structural unit derived from a (meth)acrylic monomer having the group (2) include a structural unit represented by formula (a1-5) (hereinafter, may be referred to as "structural unit (a1-5)").

[In formula (a1-5), all symbols have the same meaning as defined above.]

Examples of the halogen atom include a fluorine atom and a chlorine atom, with a fluorine atom being preferred.
Examples of the alkyl group having 1 to 6 carbon atoms which may have a halogen atom include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a fluoromethyl group, and a trifluoromethyl group.
In formula (a1-5), R ^a8 is preferably a hydrogen atom, a methyl group or a trifluoromethyl group.
L ⁵¹ is preferably an oxygen atom.
It is preferable that one of L ⁵² and L ⁵³ is —O— and the other is —S—.
It is preferable that s1 is 1.
s1' is preferably an integer of 0 to 2.
Z ^a1 is preferably a single bond or *--CH ₂ --CO--O--.

Examples of the structural unit (a1-5) include structural units derived from monomers described in JP-A-2010-61117. Among these, the structural units represented by formulae (a1-5-1) to (a1-5-4) are preferred, and the structural unit represented by formula (a1-5-1) or (a1-5-2) is more preferred.

When resin (A1) contains structural unit (a1-5), its content is preferably 1 to 50 mol %, more preferably 3 to 45 mol %, even more preferably 5 to 40 mol %, and even more preferably 5 to 30 mol %, based on the total structural units of resin (A1).

Further, examples of the structural unit (a1) include the following structural units.

When resin (A1) contains structural units represented by formulae (a1-3-1) to (a1-3-7), the content thereof is preferably 10 to 95 mol%, more preferably 15 to 90 mol%, even more preferably 20 to 85 mol%, even more preferably 20 to 70 mol%, and particularly preferably 20 to 60 mol%, based on the total structural units of resin (A1).

樹脂（Ａ１）が、式（ａ１－６－１）～（ａ１－６－３）で表される構造単位を含む場合、その含有率は、樹脂（Ａ１）の全構造単位に対して、１０～６０モル％が好ましく、１５～５５モル％がより好ましく、２０～５０モル％がさらに好ましく、２０～４５モル％がさらにより好ましく、２０～４０モル％が特に好ましい。 Further, examples of the structural unit (a1) include the following structural units.

When resin (A1) contains structural units represented by formulas (a1-6-1) to (a1-6-3), the content thereof is preferably 10 to 60 mol %, more preferably 15 to 55 mol %, even more preferably 20 to 50 mol %, still more preferably 20 to 45 mol %, and particularly preferably 20 to 40 mol %, based on all structural units in resin (A1).

<Structural unit (s)>
The structural unit (s) is derived from a monomer having no acid labile group (hereinafter, may be referred to as "monomer (s)"). As the monomer from which the structural unit (s) is derived, a monomer having no acid labile group known in the resist field can be used.
The structural unit (s) preferably has a hydroxy group, a carboxy group, or a lactone ring. The use of the resin of the present invention, which contains a structural unit having a hydroxy group or a carboxy group and no acid labile group (hereinafter sometimes referred to as "structural unit (a2)") and/or a structural unit having a lactone ring and no acid labile group (hereinafter sometimes referred to as "structural unit (a3)"), in a resist composition can improve the resolution of the resist pattern and the adhesion to the substrate. In addition to the above-mentioned structural units, the structural unit (s) can also include a structural unit having a non-leaving hydrocarbon group (hereinafter sometimes referred to as structural unit (a5)), a structural unit having a sultone structure (hereinafter sometimes referred to as structural unit (a6)), or a structural unit that decomposes upon exposure to generate an acid (hereinafter sometimes referred to as structural unit (a7)).

［式（ａ２）中、
Ｒ^a２は、水素原子、ハロゲン原子又はハロゲン原子を有していてもよい炭素数１～６のアルキル基を表す。
Ａ^ａ２１は、単結合又は炭素数１～１２のアルカンジイル基を表し、該アルカンジイル基に含まれる－ＣＨ_２－は、－Ｏ－、－ＣＯ－又は－ＮＲ^ａ２８－に置き換わっていてもよい。
Ｒ^ａ２８は、水素原子又は炭素数１～４のアルキル基を表す。
Ｌ^ａ２１は、単結合又は炭素数１～２８の炭化水素基を表し、該炭化水素基は、置換基を有してもよく、該炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－、－ＣＯ－、－Ｓ－又は－ＳＯ_２－に置き換わっていてもよい。
Ｌ^ａ２２は、単結合又はフッ素原子を有してもよい炭素数１～１２の鎖式炭化水素基を表し、該鎖式炭化水素基に含まれる－ＣＨ₂－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよい。
ｎａ２は、１～５のいずれかの整数を表し、ｎａ２が２以上のとき、複数のＬ^ａ２２は、互いに同一であっても異なっていてもよい。］ <Structural unit (a2)>
The structural unit (a2) is a structural unit represented by formula (a2) and has an alcoholic hydroxy group, a phenolic hydroxy group, a phenolic carboxy group, or the like.

[In formula (a2),
R ^a2 represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
A ^a21 represents a single bond or an alkanediyl group having 1 to 12 carbon atoms, and --CH ₂ -- contained in the alkanediyl group may be replaced by --O--, --CO-- or --NR ^a28 --.
R ^a28 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
L ^a21 represents a single bond or a hydrocarbon group having 1 to 28 carbon atoms, the hydrocarbon group optionally having a substituent, and —CH ₂ — contained in the hydrocarbon group optionally being replaced by —O—, —CO—, —S— or —SO ₂ —.
L ^a22 represents a single bond or a chain hydrocarbon group having 1 to 12 carbon atoms which may have a fluorine atom, and --CH ₂ -- contained in the chain hydrocarbon group may be replaced by --O-- or --CO--.
na2 represents an integer of 1 to 5, and when na2 is 2 or more, the multiple L ^a22 may be the same or different.

Examples of the halogen atom in R ^a2 include a fluorine atom, a chlorine atom, and a bromine atom.
Examples of the alkyl group having 1 to 6 carbon atoms which may have a halogen atom in R ^a2 include a trifluoromethyl group, a difluoromethyl group, a methyl group, a perfluoroethyl group, a 2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, an ethyl group, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, a propyl group, a perfluorobutyl group, a 1,1,2,2,3,3,4,4-octafluorobutyl group, a butyl group, a perfluoropentyl group, a 2,2,3,3,4,4,5,5,5-nonafluoropentyl group, a pentyl group, a hexyl group, a perfluorohexyl group, a chloromethyl group, a bromomethyl group, an iodomethyl group, etc. The number of carbon atoms in the alkyl group is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2.
R ^a2 is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom, a methyl group or an ethyl group, and even more preferably a hydrogen atom or a methyl group.

例えば、シクロアルカンジイル基、シクロアルカントリイル基、シクロアルカンテトライル基、シクロアルカンペンタイル基、シクロアルカンヘキサイル基等の２～６価の脂環式炭化水素基等が挙げられる。
具体的には、シクロブタン－１，３－ジイル基、シクロペンタン－１，３－ジイル基、シクロヘキサン－１，４－ジイル基、シクロオクタン－１，５－ジイル基、シクロプロパントリイル基、シクロブタントリイル基、シクロペンタントリイル基、シクロヘキサントリイル基、シクロヘプタントリイル基、シクロオクタントリイル基、シクロデカントリイル基、シクロプロパンテトライル基、シクロブタンテトライル基、シクロペンタンテトライル基、シクロヘキサンテトライル基、シクロヘプタンテトライル基、シクロオクタンテトライル基、シクロデカンテトライル基等の単環式の脂環式炭化水素基及び
ノルボルナン－１，４－ジイル基、ノルボルナン－２，５－ジイル基、アダマンタン－１，５－ジイル基、アダマンタン－２，６－ジイル基、デカヒドロナフタレンジイル基、ビシクロ[３．３．０]オクタンジイル基、ノルボルナントリイル基、アダマンタントリイル基、デカヒドロナフタレントリイル基、ビシクロ[３．３．０]オクタントリイル基、ノルボルナンテトライル基、アダマンタンテトライル基、デカヒドロナフタレンテトライル基、ビシクロ[３．３．０]オクタンテトライル基等の多環式の脂環式炭化水素基が挙げられる。
また、上述した基の水素原子の１つ以上を結合部位に置き換えた基等も挙げられる。
脂環式炭化水素基の炭素数は、好ましくは３～２０であり、より好ましくは３～１８であり、さらに好ましくは３～１６であり、さらにより好ましくは３～１２である。
Ｌ^ａ２１における芳香族炭化水素基としては、アリーレン基、アレーントリイル基、アレーンテトライル基、アレーンペンタイル基、アレーンヘキサイル基等の２～６価の芳香族炭化水素基等が挙げられる。
具体的には、フェニレン基、ナフチレン基、アントリレン基、ビフェニレン基、フェナントリレン基、ベンゼントリイル基、ナフタレントリイル基、アントラセントリイル基、ビフェニレントリイル基、フェナントレントリイル基、ベンゼンテトライル基、ナフタレンテトライル基、アントラセンテトライル基、ビフェニレンテトライル基、フェナントレンテトライル基等の芳香族炭化水素基が挙げられる。
また、上述した基の水素原子の１つ以上を結合部位に置き換えた基等も挙げられる。
芳香族炭化水素基の炭素数は、好ましくは６～２０であり、より好ましくは６～１８であり、さらに好ましくは６～１４であり、さらにより好ましくは６～１０である。
２種以上を組み合わせた基としては、脂環式炭化水素基と鎖式炭化水素基とを組み合わせた基、芳香族炭化水素基と鎖式炭化水素基とを組み合わせた基、脂環式炭化水素基と芳香族炭化水素基とを組み合わせた基、脂環式炭化水素基と鎖式炭化水素基と芳香族炭化水素基とを組み合わせた基等が挙げられる。組み合わせにおいて、脂環式炭化水素基、芳香族炭化水素基、鎖式炭化水素基は、それぞれ２種以上を組み合わせてもよい。また、いずれの基がＡ^ａ２１及びＬ^ａ２２に結合していてもよい。
炭化水素基に含まれる－ＣＨ₂－が、－Ｏ－、－Ｓ－、－ＳＯ_２－又は－ＣＯ－に置き換わった基としては、ヒドロキシ基（メチル基中に含まれる－ＣＨ₂－が、－Ｏ－に置き換わった基）、カルボキシ基（エチル基中に含まれる－ＣＨ₂－ＣＨ₂－が、－Ｏ－ＣＯ－に置き換わった基）、チオール基（メチル基中に含まれる－ＣＨ₂－が、－Ｓ－に置き換わった基）、アルコキシ基（アルキル基中に含まれる任意の位置の－ＣＨ₂－が、－Ｏ－に置き換わった基）、アルキルチオ基（アルキル基中に含まれる任意の位置の－ＣＨ₂－が、－Ｓ－に置き換わった基）、アルコキシカルボニル基（アルキル基中に含まれる任意の位置の－ＣＨ₂－ＣＨ₂－が、－Ｏ－ＣＯ－に置き換わった基）、アルキルスルホニル基（アルキル基中に含まれる任意の位置の－ＣＨ₂－が、－ＳＯ_２－に置き換わった基）、アルキルカルボニル基（アルキル基中に含まれる任意の位置の－ＣＨ₂－が、－ＣＯ－に置き換わった基）、アルキルカルボニルオキシ基（アルキル基中に含まれる任意の位置の－ＣＨ₂－ＣＨ₂－が、－ＣＯ－Ｏ－に置き換わった基）、オキシ基（メチレン基中に含まれる－ＣＨ₂－が、－Ｏ－に置き換わった基）、カルボニル基（メチレン基中に含まれる－ＣＨ₂－が、－ＣＯ－に置き換わった基）、チオ基（メチレン基中に含まれる－ＣＨ₂－が、－Ｓ－に置き換わった基）、スルホニル基（メチレン基中に含まれる－ＣＨ₂－が、－ＳＯ_２－に置き換わった基）、アルカンジイルオキシ基（アルカンジイル基中に含まれる任意の位置の－ＣＨ₂－が、－Ｏ－に置き換わった基）、アルカンジイルオキシカルボニル基（アルカンジイル基中に含まれる任意の位置の－ＣＨ₂－ＣＨ₂－が、－Ｏ－ＣＯ－に置き換わった基）、アルカンジイルカルボニル基（アルカンジイル基中に含まれる任意の位置の－ＣＨ₂－が、－ＣＯ－に置き換わった基）、アルカンジイルカルボニルオキシ基（アルカンジイル基中に含まれる任意の位置の－ＣＨ₂－ＣＨ₂－が、－ＣＯ－Ｏ－に置き換わった基）、アルカンジイルスルホニル基（アルカンジイル基中に含まれる任意の位置の－ＣＨ₂－が、－ＳＯ_２－に置き換わった基）、アルカンジイルチオ基（アルカンジイル基中に含まれる任意の位置の－ＣＨ₂－が、－Ｓ－に置き換わった基）、シクロアルコキシ基、シクロアルキルアルコキシ基、アルコキシカルボニルオキシ基、芳香族炭化水素基－カルボニルオキシ基、芳香族炭化水素基－カルボニル基、芳香族炭化水素基－オキシ基、これらの基のうち２種以上を組み合わせた基等が挙げられる。また、これらの基の水素原子の１つ以上を結合部位に置き換えた基等も挙げられる。これらの置き換わった基としては、本明細書において例示したものと同様のものが挙げられる。
また、脂環式炭化水素基に含まれる－ＣＨ_２－が、－Ｏ－、－Ｓ－、－ＣＯ－又は－ＳＯ_２－で置き換わった基も、本明細書において例示したものと同様のものが挙げられる。
組み合わせた基に含まれる－ＣＨ_２－が、－Ｏ－、－Ｓ－、－ＣＯ－又は－ＳＯ_２－で置き換わった基としては、以下の基等も挙げられる。結合部位は任意の位置とすることができる。

Ｌ^ａ２１における炭化水素基は、１又は複数の置換基を有していてもよい。該置換基としては、ハロゲン原子、炭素数１～１２のハロアルキル基、炭素数１～１６のアルキル基（該アルキル基に含まれる－ＣＨ₂－は、－Ｏ－又は－ＣＯ－で置き換わっていてもよい。）、アクリロイルオキシ基又はメタクリロイルオキシ基等が挙げられる。
ハロゲン原子としては、フッ素原子、塩素原子、臭素原子、ヨウ素原子等が挙げられる。
Ｌ^ａ２１における炭化水素基は、置換基としてハロゲン原子を有することで、実質的に、ハロアルキル基等の置換基を有することができる。ハロアルキル基は、フッ化アルキル基、塩化アルキル基、臭化アルキル基、ヨウ化アルキル基等が挙げられ、例えば、クロロメチル基、ブロモメチル基、ヨードメチル基、フルオロメチル基、ジフルオロメチル基、トリフルオロメチル基、ペルフルオロエチル基、ペルフルオロプロピル基、ペルフルオロブチル基等が挙げられる。ハロアルキル基の炭素数は、好ましくは１～８であり、より好ましくは１～６であり、さらに好ましくは１～４であり、さらにより好ましくは１～３である。
Ｌ^ａ２１の炭化水素基は、分岐状の構造を含むことにより、Ｌ^ａ２１は、実質的に、アルキル基等の置換基を有することができる。アルキル基は、メチル基、エチル基、ｎ－プロピル基、イソプロピル基、ｎ－ブチル基、ｓｅｃ－ブチル基、ｔｅｒｔ－ブチル基、ペンチル基、ヘキシル基、ヘプチル基、２－エチルヘキシル基、オクチル基、ノニル基、デシル基、ウンデシル基及びドデシル基等が挙げられる。アルキル基の炭素数は、好ましくは１～１２であり、より好ましくは１～１０であり、さらに好ましくは１～８であり、より一層好ましくは１～６であり、さらに一層好ましくは１～４であり、さらにより好ましくは１～３である。
Ｌ^ａ２１の炭化水素基に含まれる－ＣＨ₂－が－Ｏ－又は－ＣＯ－に置き換わった基により、Ｌ^ａ２１は、実質的に、ヒドロキシ基、カルボキシ基、アルコキシ基、アルコキシカルボニル基、アルキルカルボニル基、アルキルカルボニルオキシ基、アルコキシアルキル基、アルコキシアルコキシ基、アクリロイルオキシ基、メタクリロイルオキシ基等の置換基を有することができる。アルコキシ基の炭素数は、好ましくは１～１２であり、より好ましくは１～６であり、さらに好ましくは１～４であり、さらにより好ましくは１～３である。アルコキシカルボニル基、アルキルカルボニル基、アルキルカルボニルオキシ基の炭素数は、好ましくは２～１２であり、より好ましくは２～６であり、さらに好ましくは２～４であり、さらにより好ましくは２～３である。アルコキシアルキル基、アルコキシアルコキシ基の炭素数は、好ましくは２～１２であり、より好ましくは２～８であり、さらに好ましくは２～６であり、さらにより好ましくは２～４である。
上記の基としては、本明細書において例示したものと同様のものも挙げられる。
Ｌ^ａ２１における炭化水素基が有していてもよい置換基としては、ハロゲン原子、炭素数１～８のハロアルキル基又は炭素数１～１２のアルキル基（該アルキル基に含まれる－ＣＨ₂－は、－Ｏ－又は－ＣＯ－で置き換わっていてもよい。）が好ましく、ハロゲン原子、炭素数１～６のハロアルキル基又は炭素数１～１０のアルキル基（該アルキル基に含まれる－ＣＨ₂－は、－Ｏ－又は－ＣＯ－で置き換わっていてもよい。）がより好ましく、ハロゲン原子、炭素数１～４のハロアルキル基、炭素数１～４のアルキル基、ヒドロキシ基、炭素数１～４のアルコキシ基又は炭素数２～８のアルコキシアルコキシ基がさらに好ましく、フッ素原子、ヨウ素原子、トリフルオロメチル基、メチル基、ヒドロキシ基、メトキシ基、エトキシ基、エトキシエトキシ基又はエトキシメトキシ基がより一層好ましく、フッ素原子、ヨウ素原子、トリフルオロメチル基、メチル基、ヒドロキシ基、メトキシ基又はエトキシエトキシ基がさらに一層好ましい。
また、Ｌ^ａ２１のアルカンジイル基が、－Ｏ－又は－ＣＯ－に置き換わっている場合、例えば、＊－Ｌ^ａ２３－Ｘ^ａ２１－（Ｌ^ａ２３は、炭素数１～８のアルカンジイル基を表し、Ｘ^ａ２１は、－Ｏ－、－Ｏ－ＣＯ－、－ＣＯ－Ｏ－又は－Ｏ－ＣＯ－Ｏ－を表し、＊は、Ａ^ａ２１との結合部位を表す。）であることも好ましい。
Ｌ^ａ２１は、単結合、置換基を有していてもよい炭素数１～１２の鎖式炭化水素基（但し、該鎖式炭化水素基に含まれる－ＣＨ₂－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよい。）、置換基を有していてもよい炭素数３～２０の環状炭化水素基（但し、該環状炭化水素基に含まれる－ＣＨ₂－は、－Ｏ－、－Ｓ－、－ＣＯ－又は－ＳＯ_２－に置き換わっていてもよい。）又は置換基を有していてもよい炭素数１～８の鎖式炭化水素基と置換基を有していてもよい炭素数３～２０の環状炭化水素基とを組み合わせてなる基（但し、該鎖式炭化水素基に含まれる－ＣＨ₂－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよく、該環状炭化水素基に含まれる－ＣＨ₂－は、－Ｏ－、－Ｓ－、－ＳＯ_２－又は－ＣＯ－に置き換わっていてもよい。）であることが好ましく、置換基を有していてもよい炭素数１～１０の鎖式炭化水素基（但し、該鎖式炭化水素基に含まれる－ＣＨ₂－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよい。）、置換基を有していてもよい炭素数３～１８の環状炭化水素基（但し、該環状炭化水素基に含まれる－ＣＨ₂－は、－Ｏ－、－Ｓ－、－ＣＯ－又は－ＳＯ_２－に置き換わっていてもよい。）又は置換基を有していてもよい炭素数１～６の鎖式炭化水素基と置換基を有していてもよい炭素数３～１８の環状炭化水素基とを組み合わせてなる基（但し、該鎖式炭化水素基に含まれる－ＣＨ₂－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよく、該環状炭化水素基に含まれる－ＣＨ₂－は、－Ｏ－、－Ｓ－、－ＳＯ_２－又は－ＣＯ－に置き換わっていてもよい。）であることがより好ましい。 Examples of the alkanediyl group of A ^a21 include a methylene group, an ethylene group, a propane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, an octane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diyl group, an undecane-1,11-diyl group, a dodecane-1,1 Examples of the alkanediyl group include linear alkanediyl groups such as a 2-diyl group, and branched alkanediyl groups such as a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group, a 2-methylbutane-1,4-diyl group, a heptane-1,6-diyl group, an octane-1,7-diyl group, a nonane-1,8-diyl group, and a decane-1,9-diyl group.
The number of carbon atoms in the alkanediyl group is preferably 1 to 10, more preferably 1 to 8, even more preferably 1 to 6, still more preferably 1 to 4, even more preferably 1 to 3, and still more preferably 1 or 2. In addition, A ^a21 is also preferably a methylene group or an ethylene group.
Examples of the alkyl group for R ^a28 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and a tert-butyl group.
When --CH ₂ -- contained in the alkanediyl group of A ^a21 is replaced with --O--, --CO-- or --NR ^a28 --, the number of carbon atoms before replacement is regarded as the number of carbon atoms of the alkanediyl group.
Examples of the group in which -CH ₂ - in the alkanediyl group of A ^a21 is replaced by -O-, -CO- or -NR ^a28 - include a hydroxy group (a group in which -CH ₂ - in a methyl group is replaced by -O-), a carboxy group (a group in which -CH ₂ -CH ₂ - in an ethyl group is replaced by -O-CO-), a carbonyl group (a group in which -CH ₂ - in a methylene group is replaced by -CO-), an oxy group (a group in which -CH ₂ - in a methylene group is replaced by -O-), an amino group (a group in which -CH ₂ - in a methyl group is replaced by -NR ^a28 -), an alkoxy group (a group in which -CH ₂ - at any position in an alkyl group is replaced by -O-), an alkoxycarbonyl group (a group in which -CH ₂ -CH ₂ at any position in an alkyl group is replaced by -O-), and - is replaced with -O-CO-), alkylcarbonyl group (a group in which -CH ₂ - at any position contained in an alkyl group is replaced with -CO-), alkylamino group (a group in which -CH ₂ - at any position contained in an alkyl group is replaced with -NR ^a28 -), peptide group (a group in which -CH ₂ -CH ₂ - in an ethylene group is replaced with -CO-NR ^a28 -), alkanediylamino group (a group in which -CH ₂ - at any position contained in an alkanediyl group is replaced with -NR ^a28 -), etc. Examples of these replaced groups include the same as those exemplified in this specification.
The alkylamino group includes alkylamino groups having 1 to 11 carbon atoms, such as a methylamino group, an ethylamino group, a propylamino group, a butylamino group, a pentylamino group, a hexylamino group, an octylamino group, etc. The number of carbon atoms in the alkylamino group is preferably 1 to 8, more preferably 1 to 6, even more preferably 1 to 4, and even more preferably 1 to 3.
The alkanediylamino group includes an alkanediylamino group having 1 to 11 carbon atoms, such as a methyleneamino group, an ethyleneamino group, a propyleneamino group, etc. The number of carbon atoms in the alkanediylamino group is preferably 1 to 8, more preferably 1 to 6, even more preferably 1 to 4, and still more preferably 1 to 3.
Among these, examples of groups in which —CH ₂ — contained in the alkanediyl group of A ^a21 is replaced with —O—, —CO— or —NR ^a28 include *-O-, *-CO-O-, *-O-CO-, *-CO-O-A ^a22 -CO-O-, *-O-CO-A a22 -O-, *-O-A ^a22 -CO-O-, *-CO-O-A ^a22 -O-CO-, *-O-CO-A ^{a22 -O} -CO- and *-CO-NR ^a28 -. Among these, *-CO-O-, *-CO-O-A ^a22 -CO-O- or *-O-A ^a22 -CO-O- and *-CO-NR ^a28 - are preferred. Here, A ^a22 represents an alkanediyl group having 1 to 8 carbon atoms, and * represents a bonding site with the carbon atom to which R ^a2 is bonded. The alkanediyl group of A ^a22 may be the same as A ^a21 , within the range permitted by the upper limit of the number of carbon atoms.
A ^a21 is preferably a single bond, *-CO-O- or *-CO-O-A ^a22 -CO-O-, more preferably a single bond, *-CO-O- or *-CO-O-CH ₂ -CO-O-, further preferably a single bond or *-CO-O-.
The hydrocarbon group in L ^a21 is a (na2+1)-valent hydrocarbon group, and examples of such cyclic hydrocarbon groups include linear or branched chain hydrocarbon groups, monocyclic or polycyclic (including spiro rings, fused rings, or bridged rings) alicyclic hydrocarbon groups, and aromatic hydrocarbon groups, and may be a group formed by combining two or more of these groups (for example, a hydrocarbon group formed from an alicyclic hydrocarbon group or an aromatic hydrocarbon group and a chain hydrocarbon group).
Examples of the chain hydrocarbon group represented by L ^a21 include divalent to hexavalent chain hydrocarbon groups such as an alkanediyl group, an alkanetriyl group, an alkanetetrayl group, an alkanepentyl group, and an alkanehexyl group.
Examples of the alkanediyl group include the same alkanediyl groups as those represented by A ^a21 .
Examples of the alkanetriyl group include a methanetriyl group, an ethanetriyl group, a propanetriyl group, a butanetriyl group, a pentanetriyl group, a hexanetriyl group, a heptanetriyl group, an octanetriyl group, a nonanetriyl group, a decanetriyl group, an undecanetriyl group, a dodecanetriyl group, a tridecanetriyl group, a tetradecanetriyl group, a pentadecanetriyl group, a hexadecanetriyl group, and a heptadecanetriyl group.
Examples of the alkanetetrayl group include a methanetetrayl group, an ethanetetrayl group, a propanetetrayl group, a butanetetrayl group, a pentanetetrayl group, a hexanetetrayl group, a heptanetetrayl group, an octanetetrayl group, a nonanetetrayl group, a decanetetrayl group, an undecanetetrayl group, a dodecanetetrayl group, a tridecanetetrayl group, a tetradecanetetrayl group, a pentadecanetetrayl group, a hexadecanetetrayl group, and a heptadecanetetrayl group.
Further, examples include groups in which one or more hydrogen atoms of the above groups are replaced with bonding sites.
The number of carbon atoms in the chain hydrocarbon group is preferably 1 to 18, more preferably 1 to 12, even more preferably 1 to 10, still more preferably 1 to 9, even more preferably 1 to 8, still more preferably 1 to 6, even more preferably 1 to 5, and particularly preferably 1 to 4.
Examples of the monocyclic and polycyclic alicyclic hydrocarbon groups for L ^a21 include the following alicyclic hydrocarbon groups: The binding site may be any position.

For example, there may be mentioned divalent to hexavalent alicyclic hydrocarbon groups such as a cycloalkanediyl group, a cycloalkanetriyl group, a cycloalkanetetrayl group, a cycloalkanepentyl group, and a cycloalkanehexyl group.
Specifically, monocyclic alicyclic hydrocarbon groups such as cyclobutane-1,3-diyl group, cyclopentane-1,3-diyl group, cyclohexane-1,4-diyl group, cyclooctane-1,5-diyl group, cyclopropanetriyl group, cyclobutanetriyl group, cyclopentanetriyl group, cyclohexanetriyl group, cycloheptanetriyl group, cyclooctanetriyl group, cyclodecanetriyl group, cyclopropanetetrayl group, cyclobutanetetrayl group, cyclopentanetetrayl group, cyclohexanetetrayl group, cycloheptanetetrayl group, cyclooctanetetrayl group, and cyclodecanetetrayl group; Examples of polycyclic alicyclic hydrocarbon groups include norbornane-1,4-diyl group, norbornane-2,5-diyl group, adamantane-1,5-diyl group, adamantane-2,6-diyl group, decahydronaphthalenediyl group, bicyclo[3.3.0]octanediyl group, norbornanetriyl group, adamantanetriyl group, decahydronaphthalenetriyl group, bicyclo[3.3.0]octanetriyl group, norbornanetetrayl group, adamantanetetrayl group, decahydronaphthalenetetrayl group, and bicyclo[3.3.0]octanetetrayl group.
Further, examples include groups in which one or more hydrogen atoms of the above groups are replaced with bonding sites.
The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, more preferably 3 to 18 carbon atoms, even more preferably 3 to 16 carbon atoms, and even more preferably 3 to 12 carbon atoms.
Examples of the aromatic hydrocarbon group for L ^a21 include divalent to hexavalent aromatic hydrocarbon groups such as an arylene group, an arenetriyl group, an arenettetrayl group, an arenetyl group, and an arenehexyl group.
Specific examples of aromatic hydrocarbon groups include a phenylene group, a naphthylene group, an anthrylene group, a biphenylene group, a phenanthrylene group, a benzenetriyl group, a naphthalenetriyl group, an anthracenetriyl group, a biphenylenetriyl group, a phenanthrenetriyl group, a benzenetetrayl group, a naphthalenetetrayl group, an anthracenetetrayl group, a biphenylenetetrayl group, and a phenanthrenetetrayl group.
Further, examples include groups in which one or more hydrogen atoms of the above groups are replaced with bonding sites.
The aromatic hydrocarbon group preferably has 6 to 20 carbon atoms, more preferably 6 to 18 carbon atoms, even more preferably 6 to 14 carbon atoms, and even more preferably 6 to 10 carbon atoms.
Examples of the group combining two or more types include a group combining an alicyclic hydrocarbon group and a chain hydrocarbon group, a group combining an aromatic hydrocarbon group and a chain hydrocarbon group, a group combining an alicyclic hydrocarbon group and an aromatic hydrocarbon group, and a group combining an alicyclic hydrocarbon group, a chain hydrocarbon group and an aromatic hydrocarbon group. In the combination, two or more types of alicyclic hydrocarbon groups, aromatic hydrocarbon groups, and chain hydrocarbon groups may each be combined. In addition, any group may be bonded to A ^a21 and L ^a22 .
Examples of groups in which -CH ₂ - in a hydrocarbon group is replaced by -O-, -S-, -SO ₂ - or -CO- include a hydroxy group (a group in which -CH ₂ - in a methyl group is replaced by -O-), a carboxy group (a group in which -CH ₂ -CH ₂ - in an ethyl group is replaced by -O-CO-), a thiol group (a group in which -CH ₂ - in a methyl group is replaced by -S-), an alkoxy group (a group in which -CH ₂ - at any position in an alkyl group is replaced by -O-), an alkylthio group (a group in which -CH ₂ - at any position in an alkyl group is replaced by -S-), an alkoxycarbonyl group (a group in which -CH ₂ -CH ₂ - at any position in an alkyl group is replaced by -O-CO-), an alkylsulfonyl group (a group in which -CH ₂ - at any position in an alkyl group is replaced by -SO ₂ -), alkylcarbonyl group (a group in which -CH ₂ - at any position contained in an alkyl group is replaced with -CO-), alkylcarbonyloxy group (a group in which -CH ₂ -CH ₂ - at any position contained in an alkyl group is replaced with -CO-O-), oxy group (a group in which -CH ₂ - contained in a methylene group is replaced with -O-), carbonyl group (a group in which -CH ₂ - contained in a methylene group is replaced with -CO-), thio group (a group in which -CH ₂ - contained in a methylene group is replaced with -S-), sulfonyl group (a group in which -CH ₂ - contained in a methylene group is replaced with -SO 2 -), alkanediyloxy group (a group in which -CH ₂ - at any position contained in an alkanediyl group is replaced with -SO ₂ -), - is replaced by -O-), an alkanediyloxycarbonyl group (a group in which -CH ₂ -CH ₂ - at any position contained in an alkanediyl group is replaced by -O-CO-), an alkanediylcarbonyl group (a group in which -CH ₂ - at any position contained in an alkanediyl group is replaced by -CO-), an alkanediylcarbonyloxy group (a group in which -CH ₂ -CH ₂ - at any position contained in an alkanediyl group is replaced by -CO-O-), an alkanediylsulfonyl group (a group in which -CH ₂ - at any position contained in an alkanediyl group is replaced by -SO 2 -), an alkanediylthio group (a group in which -CH _{2 -} at any position contained in an alkanediyl group is replaced by -SO ₂ -), Examples of the substituted groups include a cycloalkoxy group, a cycloalkylalkoxy group, an alkoxycarbonyloxy group, an aromatic hydrocarbon group-carbonyloxy group, an aromatic hydrocarbon group-carbonyl group, an aromatic hydrocarbon group-oxy group, and a group combining two or more of these groups. Examples also include groups in which one or more hydrogen atoms of these groups are replaced with a bonding site. Examples of these substituted groups include the same as those exemplified in this specification.
Furthermore, examples of groups in which --CH ₂ -- contained in an alicyclic hydrocarbon group is replaced by --O--, --S--, --CO-- or --SO ₂ -- include the same as those exemplified in this specification.
Examples of the groups in which --CH ₂ -- contained in the combined groups is replaced by --O--, --S--, --CO-- or --SO ₂ -- include the following groups: The bonding site may be any position.

The hydrocarbon group in L ^a21 may have one or more substituents, such as a halogen atom, a haloalkyl group having 1 to 12 carbon atoms, an alkyl group having 1 to 16 carbon atoms (-CH ₂ - contained in the alkyl group may be replaced by -O- or -CO-), an acryloyloxy group, or a methacryloyloxy group.
Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
The hydrocarbon group in L ^a21 can have a halogen atom as a substituent, and thus can substantially have a substituent such as a haloalkyl group. Examples of the haloalkyl group include a fluorinated alkyl group, a chlorinated alkyl group, a brominated alkyl group, and an iodinated alkyl group, and examples thereof include a chloromethyl group, a bromomethyl group, an iodomethyl group, a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, and a perfluorobutyl group. The number of carbon atoms in the haloalkyl group is preferably 1 to 8, more preferably 1 to 6, even more preferably 1 to 4, and even more preferably 1 to 3.
The hydrocarbon group of L ^a21 contains a branched structure, and thus L ^a21 can substantially have a substituent such as an alkyl group. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, and a dodecyl group. The number of carbon atoms in the alkyl group is preferably 1 to 12, more preferably 1 to 10, still more preferably 1 to 8, still more preferably 1 to 6, still more preferably 1 to 4, and still more preferably 1 to 3.
Due to the group in which -CH ₂ - contained in the hydrocarbon group of L ^a21 is replaced with -O- or -CO-, L ^a21 can substantially have a substituent such as a hydroxy group, a carboxy group, an alkoxy group, an alkoxycarbonyl group, an alkylcarbonyl group, an alkylcarbonyloxy group, an alkoxyalkyl group, an alkoxyalkoxy group, an acryloyloxy group, or a methacryloyloxy group. The number of carbon atoms of the alkoxy group is preferably 1 to 12, more preferably 1 to 6, still more preferably 1 to 4, and even more preferably 1 to 3. The number of carbon atoms of the alkoxycarbonyl group, the alkylcarbonyl group, and the alkylcarbonyloxy group is preferably 2 to 12, more preferably 2 to 6, still more preferably 2 to 4, and even more preferably 2 to 3. The number of carbon atoms of the alkoxyalkyl group and the alkoxyalkoxy group is preferably 2 to 12, more preferably 2 to 8, still more preferably 2 to 6, and even more preferably 2 to 4.
The above groups also include those exemplified in this specification.
The substituent that the hydrocarbon group in L ^a21 may have is preferably a halogen atom, a haloalkyl group having 1 to 8 carbon atoms, or an alkyl group having 1 to 12 carbon atoms (-CH ₂ - contained in the alkyl group may be replaced by -O- or -CO-), more preferably a halogen atom, a haloalkyl group having 1 to 6 carbon atoms, or an alkyl group having 1 to 10 carbon atoms (-CH ₂ - contained in the alkyl group may be replaced by -O- or -CO-), still more preferably a halogen atom, a haloalkyl group having 1 to 4 carbon atoms, an alkyl group having 1 to 4 carbon atoms, a hydroxy group, an alkoxy group having 1 to 4 carbon atoms, or an alkoxyalkoxy group having 2 to 8 carbon atoms, still more preferably a fluorine atom, an iodine atom, a trifluoromethyl group, a methyl group, a hydroxy group, a methoxy group, an ethoxy group, an ethoxyethoxy group, or an ethoxymethoxy group, and still more preferably a fluorine atom, an iodine atom, a trifluoromethyl group, a methyl group, a hydroxy group, a methoxy group, or an ethoxyethoxy group.
In addition, when the alkanediyl group of L ^a21 is replaced with —O— or —CO—, for example, it is also preferable that the formula is *-L ^a23 -X ^a21 - (L ^a23 represents an alkanediyl group having 1 to 8 carbon atoms, X ^a21 represents —O—, —O—CO—, —CO—O— or —O—CO—O—, and * represents the bonding site with A ^a21 ).
L ^a21 is preferably a single bond, an optionally substituted chain hydrocarbon group having 1 to 12 carbon atoms (provided that -CH ₂ - contained in the chain hydrocarbon group may be replaced by -O- or -CO-), an optionally substituted cyclic hydrocarbon group having 3 to 20 carbon atoms (provided that -CH ₂ - contained in the cyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or -SO ₂ -), or a group formed by combining an optionally substituted chain hydrocarbon group having 1 to 8 carbon atoms with an optionally substituted cyclic hydrocarbon group having 3 to 20 carbon atoms (provided that -CH ₂ - contained in the chain hydrocarbon group may be replaced by -O- or -CO- and that -CH ₂ - contained in the cyclic hydrocarbon group may be replaced by -O-, -S-, -SO ₂ - or -CO-), and is preferably a optionally substituted chain hydrocarbon group having 1 to 10 carbon atoms (provided that -CH ₂ -may be replaced by -O- or -CO-), a cyclic hydrocarbon group of 3 to 18 carbon atoms which may have a substituent (provided that -CH ₂ - contained in the cyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or -SO ₂ -), or a group formed by combining a chain hydrocarbon group of 1 to 6 carbon atoms which may have a substituent and a cyclic hydrocarbon group of 3 to 18 carbon atoms which may have a substituent (provided that -CH ₂ - contained in the chain hydrocarbon group may be replaced by -O- or -CO- and -CH ₂ - contained in the cyclic hydrocarbon group may be replaced by -O-, -S-, -SO ₂ - or -CO-).

Examples of the chain hydrocarbon group having 1 to 12 carbon atoms for L ^a22 include linear alkane dialkyl groups such as methylene, ethylene, propane-1,3-diyl, propane-1,2-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, decane-1,10-diyl, undecane-1,11-diyl, and dodecane-1,12-diyl. Examples of branched alkanediyl groups include ethane-1,1-diyl, propane-1,1-diyl, propane-1,2-diyl, propane-2,2-diyl, 1-methylpropane-1,3-diyl, 2-methylpropane-1,3-diyl, 2-methylpropane-1,2-diyl, 1-dimethylpropane-1,3-diyl, pentane-2,4-diyl, pentane-1,4-diyl, and 2-methylbutane-1,4-diyl. The number of carbon atoms in the chain hydrocarbon group is preferably 1 to 10, more preferably 1 to 8, even more preferably 1 to 6, and even more preferably 1 to 4.
Examples of the chain hydrocarbon group in which --CH ₂ -- is replaced by --O-- or --CO-- include the same as those exemplified in this specification.
The number of fluorine atoms contained in L ^a22 may be one or more.
na2 is preferably an integer of 1 to 4, and more preferably an integer of 1 to 3.
Examples of the structural unit (a2) when L ^a21 is a single bond or a chain hydrocarbon group include the following structural units: Among the following structural units, structural units in which the methyl group corresponding to R ^a2 is replaced with a hydrogen atom or the like are also suitable structural units for the structural unit (a2) like the following structural units.

When producing a resist pattern from the resist composition of the present invention, if a high-energy ray such as a KrF excimer laser (248 nm), an electron beam, or EUV (extreme ultraviolet light) is used as the exposure light source, the structural unit (a2) having a phenolic hydroxyl group is preferred, and it is more preferable to use the structural unit (a2-A) described below. Furthermore, if an ArF excimer laser (193 nm) or the like is used, the structural unit (a2) having an alcoholic hydroxyl group is preferred, and it is more preferable to use the structural unit (a2-1) described below. The structural unit (a2) may contain one type alone or two or more types.

［式（ａ２－Ａ）中、
Ｒ^a50は、水素原子、ハロゲン原子又はハロゲン原子を有していてもよい炭素数１～６のアルキル基を表す。
Ｒ^a51は、ハロゲン原子、ヒドロキシ基、カルボキシ基、炭素数１～６のアルキル基、炭素数１～６のアルコキシ基、炭素数２～１２のアルコキシアルキル基、炭素数２～１２のアルコキシアルコキシ基、炭素数２～４のアルキルカルボニル基、炭素数２～４のアルキルカルボニルオキシ基、アクリロイルオキシ基又はメタクリロイルオキシ基を表す。
Ａ^a50は、単結合又は＊－Ｘ^a51－（Ａ^a52－Ｘ^a52）_nb－を表し、＊は－Ｒ^a50が結合する炭素原子との結合部位を表す。
Ａ^a52は、炭素数１～８のアルカンジイル基を表す。
Ｘ^a51及びＸ^a52は、それぞれ独立に、－Ｏ－、－ＣＯ－Ｏ－又は－Ｏ－ＣＯ－を表す。
ｎｂは、０又は１を表す。
ｍｂは、０～４のいずれかの整数を表す。ｍｂが２以上のいずれかの整数である場合、複数のＲ^a51は互いに同一であっても異なっていてもよい。］ In the structural unit (a2), an example of a structural unit having a phenolic hydroxy group is a structural unit represented by formula (a2-A) (hereinafter, may be referred to as "structural unit (a2-A)").

[In formula (a2-A),
R ^a50 represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
R ^a51 represents a halogen atom, a hydroxy group, a carboxy group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkoxyalkyl group having 2 to 12 carbon atoms, an alkoxyalkoxy group having 2 to 12 carbon atoms, an alkylcarbonyl group having 2 to 4 carbon atoms, an alkylcarbonyloxy group having 2 to 4 carbon atoms, an acryloyloxy group, or a methacryloyloxy group.
A ^a50 represents a single bond or *-X ^a51 -(A ^a52 -X ^a52 ) _nb -, where * represents the bonding site with the carbon atom to which -R ^a50 is bonded.
A ^a52 represents an alkanediyl group having 1 to 8 carbon atoms.
X ^a51 and X ^a52 each independently represent —O—, —CO—O— or —O—CO—.
nb represents 0 or 1.
mb represents an integer of 0 to 4. When mb is an integer of 2 or more, multiple R ^a51 may be the same or different.

Examples of R ^a50 include the same groups as those exemplified as R ^a2 in formula (a2).
Examples of the halogen atom in R ^a51 include a fluorine atom, a chlorine atom, and a bromine atom.
Examples of the alkyl group in R ^a51 include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, and a hexyl group. The alkyl group is preferably an alkyl group having 1 to 4 carbon atoms, more preferably a methyl group or an ethyl group, and further preferably a methyl group.
Examples of the alkoxy group for R ^a51 include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, a sec-butoxy group, and a tert-butoxy group. The alkoxy group is preferably an alkoxy group having 1 to 4 carbon atoms, more preferably a methoxy group or an ethoxy group, and even more preferably a methoxy group.
Examples of the alkoxyalkyl group for R ^a51 include a methoxymethyl group, an ethoxyethyl group, a propoxymethyl group, an isopropoxymethyl group, a butoxymethyl group, a sec-butoxymethyl group, and a tert-butoxymethyl group. The alkoxyalkyl group is preferably an alkoxyalkyl group having 2 to 8 carbon atoms, more preferably a methoxymethyl group or an ethoxyethyl group, and further preferably a methoxymethyl group.
Examples of the alkoxyalkoxy group in R ^a51 include a methoxymethoxy group, a methoxyethoxy group, an ethoxymethoxy group, an ethoxyethoxy group, a propoxymethoxy group, an isopropoxymethoxy group, a butoxymethoxy group, a sec-butoxymethoxy group, and a tert-butoxymethoxy group. The alkoxyalkoxy group is preferably an alkoxyalkoxy group having 2 to 8 carbon atoms, and more preferably a methoxyethoxy group or an ethoxyethoxy group.
Examples of the alkylcarbonyl group for R ^a51 include an acetyl group, a propionyl group, a butyryl group, etc. The alkylcarbonyl group is preferably an alkylcarbonyl group having 2 to 3 carbon atoms, and more preferably an acetyl group.
The alkylcarbonyloxy group for R ^a51 includes an acetyloxy group, a propionyloxy group, and a butyryloxy group. The alkylcarbonyloxy group is preferably an alkylcarbonyloxy group having 2 to 3 carbon atoms, and more preferably an acetyloxy group.
R ^a51 is preferably a halogen atom, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxyalkoxy group having 2 to 8 carbon atoms, more preferably a fluorine atom, an iodine atom, a hydroxy group, a methyl group, a methoxy group, an ethoxy group, an ethoxyethoxy group, or an ethoxymethoxy group, and even more preferably a fluorine atom, an iodine atom, a hydroxy group, a methyl group, a methoxy group, or an ethoxyethoxy group.

Examples of the alkanediyl group of A ^a52 in A ^a50 include a methylene group, an ethylene group, a propane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, an octane-1,8-diyl group, a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group, and a 2-methylbutane-1,4-diyl group, etc. The number of carbon atoms in the alkanediyl group is preferably 1 to 6, more preferably 1 to 4, even more preferably 1 to 3, and even more preferably 1 or 2.
A ^a52 is preferably a methylene group or an ethylene group.
Examples of *-X ^a51 -(A ^a52 -X ^a52 ) _nb - include *-O-, *-CO-O-, *-O-CO-, *-CO-O-A ^a52 -CO-O-, *-O-CO-A ^a52 -O-, *-O-A ^a52 -CO-O-, *-CO-O-A ^a52 -O-CO-, and *-O-CO-A ^a52 -O-CO-. Of these, *-CO-O-, *-CO-O-A ^a52 -CO-O- or *-O-A ^a52 -CO-O- are preferred.
A ^a50 is preferably a single bond, *-CO-O- or *-CO-O-A ^a52 -CO-O-, more preferably a single bond, *-CO-O- or *-CO-O-CH ₂ -CO-O-, further preferably a single bond or *-CO-O-.

mb is preferably 0, 1 or 2, and more preferably 0 or 1.
At least one hydroxy group is preferably bonded to the m-position or p-position of the benzene ring. When the phenylene group contains two or more hydroxy groups, the two hydroxy groups are preferably bonded to the m-position and p-position, respectively.

Examples of the structural unit (a2-A) include structural units derived from monomers described in JP-A-2010-204634 and JP-A-2012-12577.
Examples of the structural unit (a2-A) include structural units represented by formulas (a2-2-1) to (a2-2-32) and structural units in which the methyl group corresponding to R ^a50 in the structural unit (a2-A) is replaced with a hydrogen atom, a halogen atom, a haloalkyl group, or another alkyl group in the structural units represented by formulas (a2-2-1) to (a2-2-32). The structural unit (a2-A) is a structural unit represented by formulas (a2-2-1) to (a2-2-4), a structural unit represented by formula (a2-2-6), a structural unit represented by formula (a2-2-8), a structural unit represented by formulas (a2-2-12) to (a2-2-18), and a structural unit represented by formulas (a2-2-1) to (a2-2-4), a structural unit represented by formula (a2-2-6), a structural unit represented by formula (a2-2-8), and a structural unit represented by formulas (a2-2-12) to (a2-2-18). It is preferable that the structural unit (a2-A) is a structural unit in which the methyl group corresponding to ^a50 is replaced with a hydrogen atom, and in the structural unit represented by formula (a2-2-3), the structural unit represented by formula (a2-2-4), the structural unit represented by formula (a2-2-8), the structural unit represented by formula (a2-2-12) to formula (a2-2-14), the structural unit represented by formula (a2-2-18), and the structural unit represented by formula (a2-2-3), the structural unit represented by formula (a2-2-4), the structural unit represented by formula (a2-2-8), the structural unit represented by formula (a2-2-12) to formula (a2-2-14), and the structural unit represented by formula (a2-2-18), A structural unit in which a methyl group corresponding to ^a50 in the structural unit (a2-A) is replaced with a hydrogen atom is more preferable, and a structural unit represented by formula (a2-2-3), a structural unit represented by formula (a2-2-4), a structural unit represented by formula (a2-2-8), and a structural unit in which a methyl group corresponding to R ^a50 in the structural unit (a2-A) is replaced with a hydrogen atom is even more preferable.

When the structural unit (a2-A) is contained in the resin (A1), the content of the structural unit (a2-A) is preferably 5 mol% or more, more preferably 10 mol% or more, even more preferably 15 mol% or more, and even more preferably 20 mol% or more, based on the total structural units. It is also preferably 80 mol% or less, more preferably 70 mol% or less, and even more preferably 65 mol% or less. Specifically, it is preferably 5 to 80 mol%, more preferably 10 to 70 mol%, even more preferably 15 to 65 mol%, and even more preferably 20 to 65 mol%.
The structural unit (a2-A) can be incorporated into the resin (A1) by, for example, polymerizing the structural unit (a1-4) and then treating with an acid such as p-toluenesulfonic acid. Alternatively, the structural unit (a2-A) can be incorporated into the resin (A1) by polymerizing the structural unit (a1-4) and then treating with an alkali such as tetramethylammonium hydroxide.

［式（ａ２－Ａ１）及び式（ａ２－Ａ２）中、
Ｒ^a50及びＡ^a50は、それぞれ式（ａ２）と同じ意味を表す。
ｍｂ１は、０～４のいずれかの整数を表す。
Ｒ^ａ５２は、ハロゲン原子を表す。
Ｒ^ａ５３は、炭素数１～６のアルキル基、炭素数１～６のアルコキシ基、炭素数２～１２のアルコキシアルキル基、炭素数２～１２のアルコキシアルコキシ基、炭素数２～４のアルキルカルボニル基、炭素数２～４のアルキルカルボニルオキシ基、アクリロイルオキシ基又はメタクリロイルオキシ基を表す。
ｍｂ２及びｍｂ３は、それぞれ独立に、０～４のいずれかの整数を表し、ｍｂ２が２以上の場合、複数のＲ^ａ５２は互いに同一であっても異なってもよく、ｍｂ３が２以上の場合、複数のＲ^ａ５３は互いに同一であっても異なってもよく、１≦ｍｂ２＋ｍｂ３≦４を満たす。］
Ｒ^ａ５２のハロゲン原子は、Ｌ^ａ２１の炭化水素基の置換基及びＲ^ａ５１におけるハロゲン原子と同じものが挙げられる。Ｒ^ａ５２のハロゲン原子としては、フッ素原子又はヨウ素原子が好ましい。
Ｒ^ａ５３の炭素数１～６のアルキル基、炭素数１～６のアルコキシ基、炭素数２～１２のアルコキシアルキル基、炭素数２～１２のアルコキシアルコキシ基、炭素数２～４のアルキルカルボニル基、炭素数２～４のアルキルカルボニルオキシ基、アクリロイルオキシ基又はメタクリロイルオキシ基としては、それぞれ、Ｌ^ａ２１の炭化水素基の置換基及びＲ^ａ５１におけるアルキル基、アルコキシ基、アルコキシアルキル基、アルコキシアルコキシ基、アルキルカルボニル基、アルキルカルボニルオキシ基、アクロイルオキシ基、メタクリロイルオキシ基と同じものが挙げられ、メチル基、メトキシ基、エトキシ基、エトキシエトキシ基又はエトキシメトキシ基がより好ましく、メトキシ基又はエトキシエトキシ基がさらに好ましい。
ｍｂ１は、０～３のいずれかの整数が好ましく、０～２のいずれかの整数がより好ましく、０又は１がさらに好ましい。
ｍｂ２は、０～３のいずれかの整数が好ましく、１～３のいずれかの整数がより好ましく、１又は２がさらに好ましい。
ｍｂ３は、０～３のいずれかの整数が好ましく、０～２のいずれかの整数がより好ましく、０又は１がさらに好ましい。 Examples of the structural unit (a2-A) include a structural unit represented by the following formula (a2-A1) (hereinafter may be referred to as “structural unit (a2-A1)”) and a structural unit represented by the following formula (a2-A2) (hereinafter may be referred to as “structural unit (a2-A2)”).

[In formula (a2-A1) and formula (a2-A2),
R ^a50 and A ^a50 each have the same meaning as in formula (a2).
mb1 represents an integer of 0 to 4.
R ^a52 represents a halogen atom.
R ^a53 represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkoxyalkyl group having 2 to 12 carbon atoms, an alkoxyalkoxy group having 2 to 12 carbon atoms, an alkylcarbonyl group having 2 to 4 carbon atoms, an alkylcarbonyloxy group having 2 to 4 carbon atoms, an acryloyloxy group, or a methacryloyloxy group.
mb2 and mb3 each independently represent an integer of 0 to 4, and when mb2 is 2 or greater, multiple R ^a52 may be the same as or different from each other, and when mb3 is 2 or greater, multiple R ^a53 may be the same as or different from each other, and 1≦mb2+mb3≦4 is satisfied.
Examples of the halogen atom of R ^a52 include the same as the substituent of the hydrocarbon group of L ^a21 and the halogen atom of R ^a51 . The halogen atom of R ^a52 is preferably a fluorine atom or an iodine atom.
Examples of the ^alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, the alkoxyalkyl group having 2 to 12 carbon atoms, the alkoxyalkoxy group having 2 to 12 carbon atoms, the alkylcarbonyl group having 2 to 4 carbon atoms, the alkylcarbonyloxy group having 2 to 4 carbon atoms, the acryloyloxy group or the methacryloyloxy group of R a53 include the same as the substituent of the hydrocarbon group of L ^a21 and the alkyl group, alkoxy group, alkoxyalkyl group, alkoxyalkoxy group, alkylcarbonyl group, alkylcarbonyloxy group, acryloyloxy group or methacryloyloxy group of R ^a51 , respectively. A methyl group, a methoxy group, an ethoxy group, an ethoxyethoxy group or an ethoxymethoxy group is more preferable, and a methoxy group or an ethoxyethoxy group is even more preferable.
mb1 is preferably an integer of 0 to 3, more preferably an integer of 0 to 2, and further preferably 0 or 1.
mb2 is preferably an integer of 0 to 3, more preferably an integer of 1 to 3, and further preferably 1 or 2.
mb3 is preferably an integer of 0 to 3, more preferably an integer of 0 to 2, and further preferably 0 or 1.

［式（ａ２－１）中、
Ｌ^a3は、－Ｏ－又は＊－Ｏ－（ＣＨ₂）_k2－ＣＯ－Ｏ－を表し、
ｋ２は、１～７のいずれかの整数を表す。＊は－ＣＯ－との結合部位を表す。
Ｒ^a14は、水素原子又はメチル基を表す。
Ｒ^a15及びＲ^a16は、それぞれ独立に、水素原子、メチル基又はヒドロキシ基を表す。
ｏ１は、０～１０のいずれかの整数を表す。］ An example of the structural unit (a2) having an alcoholic hydroxy group is a structural unit represented by formula (a2-1) (hereinafter sometimes referred to as "structural unit (a2-1)").

[In formula (a2-1),
L ^a3 represents —O— or *—O—(CH ₂ ) _k2 —CO—O—;
k2 represents an integer of 1 to 7. * represents a bonding site with —CO—.
R ^a14 represents a hydrogen atom or a methyl group.
R ^a15 and R ^a16 each independently represent a hydrogen atom, a methyl group or a hydroxy group.
o1 represents an integer of 0 to 10.

In formula (a2-1), L ^a3 is preferably --O--, --O--(CH ₂ ) _f1 --CO--O-- (wherein f1 represents an integer of 1 to 4), and more preferably --O--.
R ^a14 is preferably a methyl group.
R ^a15 is preferably a hydrogen atom.
R ^a16 is preferably a hydrogen atom or a hydroxy group.
o1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

Examples of the structural unit (a2-1) include structural units derived from monomers described in JP 2010-204646 A. A structural unit represented by any one of formulas (a2-1-1) to (a2-1-6) is preferred, a structural unit represented by any one of formulas (a2-1-1) to (a2-1-4) is more preferred, and a structural unit represented by formula (a2-1-1) or formula (a2-1-3) is even more preferred.

When resin (A1) contains structural unit (a2-1), the content thereof is 1 mol% or more, preferably 2 mol% or more, based on the total structural units of resin (A1). Alternatively, the content may be 45 mol% or less, preferably 40 mol% or less, more preferably 35 mol% or less, even more preferably 20 mol% or less, and even more preferably 10 mol% or less. Specifically, the content may be 1 to 45 mol%, preferably 1 to 40 mol%, more preferably 1 to 35 mol%, even more preferably 1 to 20 mol%, and even more preferably 1 to 10 mol%.

［式（ａ２－Ｂ）中、
Ｒ^a50及びＡ^a50は、それぞれ式（ａ２－Ａ）と同じ意味を表す。
Ｒ^ａ５４及びＲ^ａ５５は、それぞれ独立に、炭素数１～４のフッ化アルキル基を表す。
Ｌ^ａ５１は、単結合又は炭素数１～３のアルカンジイル基を表し、該アルカンジイル基はフッ素原子が置換されていてもよい。
Ｒ^ａ５６は、ハロゲン原子、ヒドロキシ基、炭素数１～４のハロアルキル基又は炭素数１～１２のアルキル基を表し、該アルキル基に含まれる－ＣＨ₂－は、－Ｏ－又は－ＣＯ－で置き換わっていてもよい。
ｍｂ４は、１～３のいずれかの整数を表し、ｍｂ４が２以上のとき、複数のＲ^ａ５４、Ｒ^ａ５５及びＬ^ａ５１は、それぞれ互いに同一であっても異なってもよい。
ｍｂ５は、０～４のいずれかの整数を表し、ｍｂ５が２以上のとき、複数のＲ^ａ５６は互いに同一であっても異なってもよい。但し、１≦ｍｂ４＋ｍｂ５≦５である。］
Ｒ^ａ５４及びＲ^ａ５５の炭素数１～４のフッ化アルキル基としては、それぞれ独立に、トリフルオロメチル基、２，２，２－トリフルオロエチル基、３，３，３－トリフルオロプロピル基、４，４，４－トリフルオロブチル基等が挙げられる。Ｒ^ａ５４及びＲ^ａ５５としては、トリフルオロメチル基が好ましい。
Ｌ^ａ５１の炭素数１～３のアルカンジイル基としては、メチレン基、エタン－１，１－ジイル基、プロパン－１，１－ジイル基、プロパン－２，２－ジイル基等が挙げられる。Ｌ^ａ５１としては、単結合又はメチレン基が好ましい。
Ｒ^ａ５６のハロゲン原子としては、フッ素原子、塩素原子、臭素原子及びヨウ素原子等が挙げられる。
Ｒ^ａ５６における炭素数１～４のハロアルキル基とは、ハロゲン原子を有する炭素数１～４のアルキル基を表し、クロロメチル基、ブロモメチル基、フルオロメチル基、ジフルオロメチル基、トリフルオロメチル基、ペルフルオロブチル等が挙げられである。
Ｒ^ａ５６における炭素数１～１２のアルキル基としては、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基、イソブチル基、ｔｅｒｔ－ブチル基、ペンチル基、ヘキシル基、オクチル基、ノニル基等のアルキル基が挙げられる。アルキル基の炭素数は、好ましくは１～９であり、より好ましくは１～６であり、さらに好ましくは１～４である。
Ｒ^ａ５６で表されるアルキル基に含まれる－ＣＨ₂－は、－Ｏ－又は－ＣＯ－に置き換わっている場合、置き換わる前の炭素数を該アルキル基の総炭素数とする。また、Ｒ^ａ５６は、ヒドロキシ基（メチル基中に含まれる－ＣＨ₂－が、－Ｏ－に置き換わった基）、カルボキシル基（エチル基中に含まれる－ＣＨ₂－ＣＨ₂－が、－Ｏ－ＣＯ－に置き換わった基）、炭素数１～１１のアルコキシ基（炭素数２～１２のアルキル基中に含まれる－ＣＨ₂－が、－Ｏ－に置き換わった基）、炭素数２～１１のアルコキシカルボニル基（炭素数３～１２のアルキル基中に含まれる－ＣＨ₂－ＣＨ₂－が、－Ｏ－ＣＯ－に置き換わった基）、炭素数２～１２のアルキルカルボニル基（炭素数２～１２のアルキル基中に含まれる－ＣＨ₂－が、－ＣＯ－に置き換わった基）、炭素数２～１１のアルキルカルボニルオキシ基（炭素数３～１２のアルキル基中に含まれる－ＣＨ₂－ＣＨ₂－が、－ＣＯ－Ｏ－に置き換わった基）を有していてもよい。
Ｒ^ａ５６としては、なかでも、ハロゲン原子、炭素数１～４のハロアルキル基又は炭素数１～１２のアルキル基（該アルキル基に含まれる－ＣＨ₂－は、－Ｏ－又は－ＣＯ－で置き換わっていてもよい。）であることが好ましい。
ｍｂ４は、好ましくは、１又は２であり、より好ましくは１である。さらに好ましくは、ｍｂ４が１であり、かつ括弧内の基がパラ位に結合するものである。
ｍｂ５は、好ましくは０～２のいずれかの整数であり、より好ましくは０又は１であり、さらに好ましくは０である。
構造単位（ａ２－Ｂ）としては、以下の式（ａ２－Ｂ１）で表される構造単位（以下、「構造単位（ａ２－Ｂ１）」という場合がある。）であることがより好ましい。

［式（ａ２－Ｂ１）中、
Ｒ^ａ５７は、水素原子又はメチル基を表す。
Ａ^ａ５３は、単結合又は＊－ＣＯ－Ｏ－を表し、＊は－Ｒ^ａ５７が結合する炭素原子との結合部位を表す。
Ｒ^ａ５６、ｍｂ４及びｍｂ５は、それぞれ式（ａ２－Ｂ）と同じ意味を表す。］ An example of the structural unit (a2) having an alcoholic hydroxy group is a structural unit represented by formula (a2-B) (hereinafter, may be referred to as "structural unit (a2-B)").

[In formula (a2-B),
R ^a50 and A ^a50 have the same meanings as in formula (a2-A).
R ^a54 and R ^a55 each independently represent a fluorinated alkyl group having 1 to 4 carbon atoms.
L ^a51 represents a single bond or an alkanediyl group having 1 to 3 carbon atoms, and the alkanediyl group may be substituted with a fluorine atom.
R ^a56 represents a halogen atom, a hydroxy group, a haloalkyl group having 1 to 4 carbon atoms or an alkyl group having 1 to 12 carbon atoms, and --CH ₂ -- contained in the alkyl group may be replaced by --O-- or --CO--.
mb4 represents an integer of 1 to 3, and when mb4 is 2 or greater, a plurality of R ^a54 , R ^a55 and L ^a51 may be the same or different.
mb5 represents an integer of 0 to 4, and when mb5 is 2 or more, multiple R ^a56 may be the same or different from each other, provided that 1≦mb4+mb5≦5.
Examples of the fluorinated alkyl group having 1 to 4 carbon atoms for R ^a54 and R ^a55 each independently include a trifluoromethyl group, a 2,2,2-trifluoroethyl group, a 3,3,3-trifluoropropyl group, a 4,4,4-trifluorobutyl group, etc. R ^a54 and R ^a55 are preferably a trifluoromethyl group.
Examples of the alkanediyl group having 1 to 3 carbon atoms for L ^a51 include a methylene group, an ethane-1,1-diyl group, a propane-1,1-diyl group, a propane-2,2-diyl group, etc. L ^a51 is preferably a single bond or a methylene group.
Examples of the halogen atom for R ^a56 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
The haloalkyl group having 1 to 4 carbon atoms for R ^a56 represents an alkyl group having 1 to 4 carbon atoms and a halogen atom, and examples thereof include a chloromethyl group, a bromomethyl group, a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, and a perfluorobutyl group.
Examples of the alkyl group having 1 to 12 carbon atoms in R ^a56 include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a hexyl group, an octyl group, a nonyl group, etc. The number of carbon atoms in the alkyl group is preferably 1 to 9, more preferably 1 to 6, and further preferably 1 to 4.
When --CH ₂ -- contained in the alkyl group represented by R ^a56 is replaced by --O-- or --CO--, the number of carbon atoms before replacement is regarded as the total number of carbon atoms in the alkyl group. In addition, R ^a56 may have a hydroxy group (a group in which -CH ₂ - in a methyl group is replaced with -O-), a carboxyl group (a group in which -CH ₂ -CH ₂ - in an ethyl group is replaced with -O-CO-), an alkoxy group having 1 to 11 carbon atoms (a group in which -CH ₂ - in an alkyl group having 2 to 12 carbon atoms is replaced with -O-), an alkoxycarbonyl group having 2 to 11 carbon atoms (a group in which -CH ₂ -CH ₂ - in an alkyl group having 3 to 12 carbon atoms is replaced with -O-CO-), an alkylcarbonyl group having 2 to 12 carbon atoms (a group in which -CH ₂ - in an alkyl group having 2 to 12 carbon atoms is replaced with -CO-), or an alkylcarbonyloxy group having 2 to 11 carbon atoms (a group in which -CH ₂ -CH ₂ - in an alkyl group having 3 to 12 carbon atoms is replaced with -CO-O-).
Among these, R ^a56 is preferably a halogen atom, a haloalkyl group having 1 to 4 carbon atoms, or an alkyl group having 1 to 12 carbon atoms (-CH ₂ - contained in the alkyl group may be replaced by -O- or -CO-).
mb4 is preferably 1 or 2, and more preferably 1. Even more preferably, mb4 is 1 and the group in the parentheses is bonded to the para position.
mb5 is preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0.
The structural unit (a2-B) is more preferably a structural unit represented by the following formula (a2-B1) (hereinafter, sometimes referred to as “structural unit (a2-B1)”).

[In formula (a2-B1),
R ^a57 represents a hydrogen atom or a methyl group.
A ^a53 represents a single bond or *--CO--O--, and * represents the bonding site with the carbon atom to which -R ^a57 is bonded.
R ^a56 , mb4 and mb5 each have the same meaning as in formula (a2-B).

In formula (a2-B1), R ^a57 is preferably a hydrogen atom.
A ^a53 is preferably a single bond.

Examples of the structural unit (a2-B) include the structural units shown below.

Specific examples of the structural unit (a2-B) include structural units represented by formulae (a2-B-1) to (a2-B-8) in which the hydrogen atom corresponding to R ^a57 is replaced with a methyl group, etc., and structural units represented by formulae (a2-B-9) to (a2-B-16) in which the methyl group corresponding to R ^a57 is replaced with a hydrogen atom, etc. Among these, the structural units represented by formulae (a2-B-1) to (a2-B-8) are preferred, the structural units represented by formulae (a2-B-1) to (a2-B-4) are more preferred, and the structural unit represented by formula (a2-B-1) is even more preferred.

When resin (A1) contains structural unit (a2-B), its content is preferably 3 mol% or more, more preferably 5 mol% or more, and even more preferably 10 mol% or more, based on the total structural units of resin (A1). It is also preferably 80 mol% or less, more preferably 75 mol% or less, even more preferably 70 mol% or less, and even more preferably 65 mol% or less. Specifically, it is preferably 3 to 80 mol%, more preferably 5 to 75 mol%, even more preferably 10 to 70 mol%, and even more preferably 10 to 65 mol%.

<Structural unit (a3)>
The lactone ring of the structural unit (a3) may be a monocyclic ring such as a β-propiolactone ring, a γ-butyrolactone ring, or a δ-valerolactone ring, or may be a condensed ring of a monocyclic lactone ring with another ring. Preferred examples include a γ-butyrolactone ring, an adamantanelactone ring, or a bridged ring containing a γ-butyrolactone ring structure (for example, a structural unit represented by the following formula (a3-2)).

［式（ａ３－１）、式（ａ３－２）、式（ａ３－３）及び式（ａ３－４）中、
Ｌ^ａ４、Ｌ^ａ５及びＬ^ａ６は、それぞれ独立に、－Ｏ－又は＊－Ｏ－（ＣＨ_２）_k3－ＣＯ－Ｏ－（ｋ３は１～７のいずれかの整数を表す。）で表される基を表す。
Ｌ^ａ７は、－Ｏ－、＊－Ｏ－Ｌ^ａ８－Ｏ－、＊－Ｏ－Ｌ^ａ８－ＣＯ－Ｏ－、＊－Ｏ－Ｌ^ａ８－ＣＯ－Ｏ－Ｌ^ａ９－ＣＯ－Ｏ－又は＊－Ｏ－Ｌ^ａ８－Ｏ－ＣＯ－Ｌ^ａ９－Ｏ－を表す。
Ｌ^ａ８及びＬ^ａ９は、それぞれ独立に、炭素数１～６のアルカンジイル基を表す。
＊は、カルボニル基との結合部位を表す。
Ｒ^ａ１８、Ｒ^ａ１９、Ｒ^ａ２０及びＲ^ａ２４は、それぞれ独立に、ハロゲン原子を有していてもよい炭素数１～６のアルキル基、水素原子又はハロゲン原子を表す。
Ｘ^ａ３は、－ＣＨ_２－又は酸素原子を表す。
Ｒ^ａ２１は、炭素数１～４の脂肪族炭化水素基を表す。
Ｒ^ａ２２、Ｒ^ａ２３及びＲ^ａ２５は、それぞれ独立に、カルボキシ基、シアノ基又は炭素数１～４の脂肪族炭化水素基を表す。
ｐ１は、０～５のいずれかの整数を表す。
ｑ１は、０～３のいずれかの整数を表す。
ｒ１は、０～３のいずれかの整数を表す。
ｗ１は、０～８のいずれかの整数を表す。
ｐ１、ｑ１、ｒ１及び／又はｗ１が２以上のとき、複数のＲ^ａ２１、Ｒ^ａ２２、Ｒ^ａ２３及び／又はＲ^ａ２５は互いに同一であっても異なっていてもよい。］ The structural unit (a3) is preferably a structural unit represented by formula (a3-1), formula (a3-2), formula (a3-3) or formula (a3-4). One of these may be contained alone, or two or more of them may be contained.

[In formula (a3-1), formula (a3-2), formula (a3-3) and formula (a3-4),
L ^a4 , L ^a5 and L ^a6 each independently represent a group represented by —O— or *-O—(CH ₂ ) _k3 —CO—O— (k3 represents an integer of 1 to 7).
L ^a7 represents -O-, *-OL ^a8 -O-, *-OL ^a8 -CO-O-, *-OL ^a8 -CO-OL ^a9 -CO-O- or *-OL ^a8 -O-CO-L ^a9 -O-.
L ^a8 and L ^a9 each independently represent an alkanediyl group having 1 to 6 carbon atoms.
* indicates the bonding site with the carbonyl group.
R ^a18 , R ^a19 , R ^a20 and R ^a24 each independently represent an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, a hydrogen atom or a halogen atom.
X ^a3 represents —CH ₂ — or an oxygen atom.
R ^a21 represents an aliphatic hydrocarbon group having 1 to 4 carbon atoms.
R ^a22 , R ^a23 and R ^a25 each independently represent a carboxy group, a cyano group or an aliphatic hydrocarbon group having 1 to 4 carbon atoms.
p1 represents an integer of 0 to 5.
q1 represents an integer of 0 to 3.
r1 represents an integer of 0 to 3.
w1 represents an integer of 0 to 8.
When p1, q1, r1 and/or w1 is 2 or more, a plurality of R ^a21 , R ^a22 , R ^a23 and/or R ^a25 may be the same or different from each other.]

Examples of the aliphatic hydrocarbon group for R ^a21 , R ^a22 , R ^a23 and R ^a25 include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group and a tert-butyl group.
The halogen atom for R ^a18 , R ^a19 , R ^a20 and R ^a24 includes a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.
Examples of the alkyl group for R ^a18 , R ^a19 , R ^a20 , and R ^a24 include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, and a hexyl group, and are preferably alkyl groups having 1 to 4 carbon atoms, and more preferably a methyl group or an ethyl group.
Examples of the alkyl group having a halogen atom for R ^a18 , R ^a19 , R ^a20 , and R ^a24 include a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluoroisopropyl group, a perfluorobutyl group, a perfluorosec-butyl group, a perfluorotert-butyl group, a perfluoropentyl group, a perfluorohexyl group, a trichloromethyl group, a tribromomethyl group, and a triiodomethyl group.

Examples of the alkanediyl group in L ^a8 and L ^a9 include a methylene group, an ethylene group, a propane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group, and a 2-methylbutane-1,4-diyl group.

In formulae (a3-1) to (a3-3), L ^a4 to L ^a6 each independently represent preferably —O— or *-O-(CH ₂ ) _k3 —CO-O-, where k3 is an integer from 1 to 4, more preferably —O— and *-O-CH ₂ —CO-O-, and even more preferably an oxygen atom.
R ^a18 to R ^a21 are preferably methyl groups.
R ^a22 and R ^a23 each independently preferably represent a carboxy group, a cyano group, or a methyl group.
p1, q1 and r1 each independently represent preferably an integer of 0 to 2, and more preferably 0 or 1.

（式中、Ｒ^ａ２４、Ｌ^ａ７は、上記と同じ意味を表す。） In formula (a3-4), R ^a24 is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom, a methyl group or an ethyl group, and even more preferably a hydrogen atom or a methyl group.
R ^a25 is preferably a carboxy group, a cyano group or a methyl group.
L ^a7 is preferably —O— or *-OL ^a8 —CO—O—, and more preferably —O—, —O—CH ₂ —CO—O— or —O—C ₂ H ₄ —CO—O—.
w1 is preferably an integer of 0 to 2, and more preferably 0 or 1.
In particular, the formula (a3-4) is preferably the formula (a3-4)'.

(In the formula, R ^a24 and L ^a7 have the same meanings as above.)

Examples of the structural unit (a3) include structural units derived from monomers described in JP-A-2010-204646, JP-A-2000-122294, and JP-A-2012-41274. As the structural unit (a3), structural units represented by any one of formulas (a3-1-1), (a3-1-2), (a3-2-1), (a3-2-2), (a3-3-1), (a3-3-2), and (a3-4-1) to (a3-4-12), and structural units in which methyl groups corresponding to R ^a18 , R ^a19 , R ^a20 , and R ^a24 in formulas (a3-1) to (a3-4) are replaced with hydrogen atoms are preferred.

When the resin (A1) contains the structural unit (a3), the total content thereof is, based on all structural units of the resin (A1), 1 mol % or more, preferably 3 mol % or more, more preferably 5 mol % or more, and even more preferably 10 mol % or more. Also, 70 mol % or less, preferably 65 mol % or less, and more preferably 60 mol % or less. Specifically, 1 to 70 mol % is mentioned, preferably 3 to 65 mol %, and more preferably 5 to 60 mol %.
The content of the structural unit (a3-1), the structural unit (a3-2), the structural unit (a3-3) or the structural unit (a3-4) is preferably 1 mol% or more, more preferably 3 mol% or more, and even more preferably 5 mol% or more, based on the total structural units of the resin (A1). Also, it is preferably 60 mol% or less, more preferably 55 mol% or less, and even more preferably 50 mol% or less. Specifically, it is preferably 1 to 60 mol%, more preferably 3 to 55 mol%, and even more preferably 5 to 50 mol%.

［式（ａ４－１）中、
Ｒ^４１は、水素原子又はメチル基を表す。
Ｌ^４１は、単結合又は炭素数１～４のアルカンジイル基を表す。
Ｌ^４２ｆは、炭素数１～８のフッ素原子を有するアルカンジイル基又は炭素数３～１２のフッ素原子を有するシクロアルカンジイル基を表す。
Ｒ^４２ｆは、水素原子又はフッ素原子を表す。］ <Structural unit (a4-1)>
The structural unit (s) is different from the structural units represented by formulae (a4-2) and (a4-3) and also includes a structural unit having a halogen atom, such as a structural unit represented by the following formula (a4-1) (hereinafter, sometimes referred to as "structural unit (a4-1)").

[In formula (a4-1),
^R41 represents a hydrogen atom or a methyl group.
L ⁴¹ represents a single bond or an alkanediyl group having 1 to 4 carbon atoms.
L ^42f represents an alkanediyl group having 1 to 8 carbon atoms and containing a fluorine atom, or a cycloalkanediyl group having 3 to 12 carbon atoms and containing a fluorine atom.
R ^42f represents a hydrogen atom or a fluorine atom.

Examples of the alkanediyl group in L ⁴¹ include linear alkanediyl groups such as methylene, ethylene, propane-1,3-diyl, and butane-1,4-diyl, and branched alkanediyl groups such as ethane-1,1-diyl, propane-1,2-diyl, butane-1,3-diyl, 2-methylpropane-1,3-diyl, and 2-methylpropane-1,2-diyl. The terminal of the branched alkanediyl group may be a methyl group.
Examples of the alkanediyl group having a fluorine atom in L ^42f include linear alkanediyl groups having a fluorine atom, such as a methylene group having a fluorine atom, an ethylene group having a fluorine atom, a propane-1,3-diyl group having a fluorine atom, a butane-1,4-diyl group having a fluorine atom, a pentane-1,5-diyl group having a fluorine atom, a hexane-1,6-diyl group having a fluorine atom, a heptane-1,7-diyl group having a fluorine atom, and an octane-1,8-diyl group having a fluorine atom;
Examples of branched alkanediyl groups having fluorine atoms include an ethane-1,1-diyl group having a fluorine atom, a propane-1,1-diyl group having a fluorine atom, a propane-1,2-diyl group having a fluorine atom, a propane-2,2-diyl group having a fluorine atom, a pentane-2,4-diyl group having a fluorine atom, a 2-methylpropane-1,3-diyl group having a fluorine atom, a 2-methylpropane-1,2-diyl group having a fluorine atom, a pentane-1,4-diyl group having a fluorine atom, and a 2-methylbutane-1,4-diyl group having a fluorine atom. The end of the branched alkanediyl group may be a methyl group which may have a fluorine atom.
Examples of the cycloalkanediyl group having a fluorine atom in L ^42f include monocyclic cycloalkanediyl groups having a fluorine atom, such as a cyclobutane-1,3-diyl group having a fluorine atom, a cyclopentane-1,3-diyl group having a fluorine atom, a cyclohexane-1,4-diyl group having a fluorine atom, a cyclohexene-3,6-diyl group having a fluorine atom, a cycloheptane-1,4-diyl group having a fluorine atom, and a cyclooctane-1,5-diyl group having a fluorine atom;
Examples of the fluorine atom-containing polycyclic cycloalkanediyl group include a fluorine atom-containing norbornane-1,4-diyl group, a fluorine atom-containing norbornane-2,5-diyl group, a fluorine atom-containing 5-norbornene-2,3-diyl group, a fluorine atom-containing adamantane-1,5-diyl group, and a fluorine atom-containing adamantane-2,6-diyl group.
The number of fluorine atoms contained in the alkanediyl group and cycloalkanediyl group having a fluorine atom in L ^42f may be 1 or more, and is preferably 2 or more.
The alkanediyl group and cycloalkanediyl group having a fluorine atom in L ^42f are preferably a perfluoroalkanediyl group and a perfluorocycloalkanediyl group, respectively.

Examples of the perfluoroalkanediyl group in L ^42f include a difluoromethylene group, a perfluoroethylene group, a perfluoroethylfluoromethylene group, a perfluoropropane-1,3-diyl group, a perfluoropropane-1,2-diyl group, a perfluoropropane-2,2-diyl group, a perfluorobutane-1,4-diyl group, a perfluorobutane-2,2-diyl group, a perfluorobutane-1,2-diyl group, a perfluoropentane-1,5-diyl group, a perfluoropentane-2,2-diyl group, a perfluoropentane- Examples of the perfluorohexane-3,3-diyl group include perfluorohexane-1,6-diyl group, perfluorohexane-2,2-diyl group, perfluorohexane-3,3-diyl group, perfluoroheptane-1,7-diyl group, perfluoroheptane-2,2-diyl group, perfluoroheptane-3,4-diyl group, perfluoroheptane-4,4-diyl group, perfluorooctane-1,8-diyl group, perfluorooctane-2,2-diyl group, perfluorooctane-3,3-diyl group, and perfluorooctane-4,4-diyl group.
Examples of the perfluorocycloalkanediyl group for L ^42f include a perfluorocyclohexanediyl group, a perfluorocyclopentanediyl group, a perfluorocycloheptanediyl group, and a perfluoroadamantanediyl group.

L ⁴¹ is preferably a single bond or an alkanediyl group having 1 to 3 carbon atoms, more preferably a single bond, a methylene group or an ethylene group, and even more preferably a single bond or a methylene group.
L ^42f is preferably a perfluoroalkanediyl group having 1 to 8 carbon atoms or a perfluorocycloalkanediyl group having 3 to 12 carbon atoms, more preferably a perfluoroalkanediyl group having 1 to 6 carbon atoms, and even more preferably a perfluoroalkanediyl group having 1 to 3 carbon atoms.

樹脂（Ａ１）が、構造単位（ａ４－１）を含む場合、その含有率は、樹脂（Ａ１）の全構造単位に対して、１～１０モル％が好ましく、１～５モル％がより好ましく、３～５モル％がさらに好ましい。 Examples of the structural unit (a4-1) include the structural units shown below and structural units in which a methyl group corresponding to R ⁴¹ in the structural unit (a4-1) is replaced with a hydrogen atom.

When the resin (A1) contains the structural unit (a4-1), the content thereof is preferably from 1 to 10 mol %, more preferably from 1 to 5 mol %, and even more preferably from 3 to 5 mol %, based on all structural units in the resin (A1).

［式（ａ５－１）中、
Ｒ⁵¹は、水素原子又はメチル基を表す。
Ｒ⁵²は、炭素数３～１８の脂環式炭化水素基を表し、該脂環式炭化水素基に含まれる水素原子は炭素数１～８の脂肪族炭化水素基で置換されていてもよい。
Ｌ⁵⁵は、単結合又は炭素数１～１８の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよい。］ <Structural unit (a5)>
The non-leaving hydrocarbon group contained in the structural unit (a5) may be a group having a linear, branched or cyclic hydrocarbon group. Among these, the structural unit (a5) is preferably a group having an alicyclic hydrocarbon group.
An example of the structural unit (a5) is a structural unit represented by formula (a5-1).

[In formula (a5-1),
^R51 represents a hydrogen atom or a methyl group.
R ⁵² represents an alicyclic hydrocarbon group having 3 to 18 carbon atoms, and a hydrogen atom contained in the alicyclic hydrocarbon group may be substituted with an aliphatic hydrocarbon group having 1 to 8 carbon atoms.
L ⁵⁵ represents a single bond or a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and --CH ₂ -- contained in the saturated hydrocarbon group may be replaced with --O-- or --CO--.]

The alicyclic hydrocarbon group in ^R52 may be either monocyclic or polycyclic. Examples of the monocyclic alicyclic hydrocarbon group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. Examples of the polycyclic alicyclic hydrocarbon group include an adamantyl group, a norbornyl group, and the like.
Examples of the aliphatic hydrocarbon group having 1 to 8 carbon atoms include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, pentyl, hexyl, octyl, and 2-ethylhexyl.
An example of the alicyclic hydrocarbon group having a substituent is a 3-methyladamantyl group.
R ⁵² is preferably an unsubstituted alicyclic hydrocarbon group having 3 to 18 carbon atoms, and more preferably an adamantyl group, a norbornyl group or a cyclohexyl group.

The divalent saturated hydrocarbon group for L ⁵⁵ includes a divalent chain saturated hydrocarbon group and a divalent alicyclic saturated hydrocarbon group, and is preferably a divalent chain saturated hydrocarbon group.
Examples of the divalent chain saturated hydrocarbon group include a methylene group, an ethylene group, and an alkanediyl group such as a propanediyl group, a butanediyl group, and a pentanediyl group.
The divalent alicyclic saturated hydrocarbon group may be either monocyclic or polycyclic. Examples of the monocyclic alicyclic saturated hydrocarbon group include cycloalkanediyl groups such as cyclopentanediyl and cyclohexanediyl. Examples of the polycyclic divalent alicyclic saturated hydrocarbon group include adamantanediyl and norbornanediyl.

［式（Ｌ１－１）中、
Ｘ^x1は、＊－Ｏ－ＣＯ－又は＊－ＣＯ－Ｏ－を表す（＊はＬ^x1との結合部位を表す。）。
Ｌ^x1は、炭素数１～１６の２価の脂肪族飽和炭化水素基を表す。
Ｌ^x2は、単結合又は炭素数１～１５の２価の脂肪族飽和炭化水素基を表す。
ただし、Ｌ^x1及びＬ^x2の合計炭素数は、１６以下である。
式（Ｌ１－２）中、
Ｌ^x3は、炭素数１～１７の２価の脂肪族飽和炭化水素基を表す。
Ｌ^x4は、単結合又は炭素数１～１６の２価の脂肪族飽和炭化水素基を表す。
ただし、Ｌ^x3及びＬ^x4の合計炭素数は、１７以下である。
式（Ｌ１－３）中、
Ｌ^x5は、炭素数１～１５の２価の脂肪族飽和炭化水素基を表す。
Ｌ^x6及びＬ^x7は、それぞれ独立に、単結合又は炭素数１～１４の２価の脂肪族飽和炭化水素基を表す。
ただし、Ｌ^x5、Ｌ^x6及びＬ^x7の合計炭素数は、１５以下である。
式（Ｌ１－４）中、
Ｌ^x8及びＬ^x9は、単結合又は炭素数１～１２の２価の脂肪族飽和炭化水素基を表す。
Ｗ^x1は、炭素数３～１５の２価の脂環式飽和炭化水素基を表す。
ただし、Ｌ^x8、Ｌ^x9及びＷ^x1の合計炭素数は、１５以下である。］ Examples of the divalent saturated hydrocarbon group represented by L ⁵⁵ in which --CH ₂ -- is replaced by --O-- or --CO-- include groups represented by formulae (L1-1) to (L1-4). In the following formulae, * and ** each represent a bonding site, and * represents a bonding site with an oxygen atom.

[In formula (L1-1),
X ^x1 represents *--O--CO-- or *--CO--O-- (* represents the bonding site to L ^x1 ).
L ^x1 represents a divalent aliphatic saturated hydrocarbon group having 1 to 16 carbon atoms.
L ^x2 represents a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 15 carbon atoms.
However, the total number of carbon atoms of L ^x1 and L ^x2 is 16 or less.
In formula (L1-2),
L ^x3 represents a divalent aliphatic saturated hydrocarbon group having 1 to 17 carbon atoms.
L ^x4 represents a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 16 carbon atoms.
However, the total number of carbon atoms of L ^x3 and L ^x4 is 17 or less.
In formula (L1-3),
L ^x5 represents a divalent aliphatic saturated hydrocarbon group having 1 to 15 carbon atoms.
L ^x6 and L ^x7 each independently represent a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 14 carbon atoms.
However, the total number of carbon atoms of L ^x5 , L ^x6 and L ^x7 is 15 or less.
In formula (L1-4),
L ^x8 and L ^x9 each represent a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 12 carbon atoms.
W ^x1 represents a divalent alicyclic saturated hydrocarbon group having 3 to 15 carbon atoms.
However, the total number of carbon atoms of L ^x8 , L ^x9 and W ^x1 is 15 or less.

L ^x1 is preferably a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, more preferably a methylene group or an ethylene group.
L ^x2 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, more preferably a single bond.
L ^x3 is preferably a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^x4 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^x5 is preferably a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, more preferably a methylene group or an ethylene group.
L ^x6 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, more preferably a methylene group or an ethylene group.
L ^x7 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^x8 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, more preferably a single bond or a methylene group.
L ^x9 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, more preferably a single bond or a methylene group.
W ^x1 is preferably a divalent alicyclic saturated hydrocarbon group having 3 to 10 carbon atoms, more preferably a cyclohexanediyl group or an adamantanediyl group.

式（Ｌ１－２）で表される基としては、例えば、以下に示す２価の基が挙げられる。

式（Ｌ１－３）で表される基としては、例えば、以下に示す２価の基が挙げられる。

式（Ｌ１－４）で表される基としては、例えば、以下に示す２価の基が挙げられる。

Ｌ⁵⁵は、好ましくは、単結合又は式（Ｌ１－１）で表される基である。 Examples of the group represented by formula (L1-1) include the divalent groups shown below.

Examples of the group represented by formula (L1-2) include the divalent groups shown below.

Examples of the group represented by formula (L1-3) include the divalent groups shown below.

Examples of the group represented by formula (L1-4) include the divalent groups shown below.

L ⁵⁵ is preferably a single bond or a group represented by the formula (L1-1).

樹脂（Ａ１）が、構造単位（ａ５）を含む場合、その含有率は、樹脂（Ａ１）の全構造単位に対して、１～３０モル％が好ましく、２～２０モル％がより好ましく、３～１５モル％がさらに好ましい。 Examples of the structural unit (a5-1) include the structural units shown below and structural units in which the methyl group corresponding to R ⁵¹ in the structural unit (a5-1) shown below is replaced with a hydrogen atom.

When the resin (A1) contains the structural unit (a5), the content thereof is preferably from 1 to 30 mol %, more preferably from 2 to 20 mol %, and even more preferably from 3 to 15 mol %, based on all structural units in the resin (A1).

<Structural unit (a6)>
The structural unit (a6) is a structural unit having an —SO ₂ — group, and preferably has the —SO ₂ — group in a side chain.
The structural unit having an —SO ₂ — group may have a linear structure having an —SO ₂ — group, may have a branched structure having an —SO ₂ — group, or may have a cyclic structure (monocyclic or polycyclic structure) having an —SO ₂ — group. A structural unit having a cyclic structure having an —SO ₂ — group is preferred, and a structural unit having a cyclic structure containing —SO ₂ —O— (sultone ring) is more preferred.

Examples of the sultone ring include rings represented by the following formulae (T ¹ -1), (T ¹ -2), (T ¹ -3) and (T ¹ -4). The binding site can be any position. The sultone ring may be monocyclic, but is preferably polycyclic. The polycyclic sultone ring means a bridged ring containing -SO ₂ -O- as an atomic group constituting the ring, and examples of the polycyclic sultone ring include rings represented by formulae (T ¹ -1) and (T ¹ -2). The sultone ring may further contain a heteroatom as an atomic group constituting the ring in addition to -SO ₂ -O-, as in the ring represented by formula (T ¹ -2). Examples of the heteroatom include an oxygen atom, a sulfur atom or a nitrogen atom, and preferably an oxygen atom.

The sultone ring may have a substituent, and examples of the substituent include an alkyl group having 1 to 12 carbon atoms which may have a halogen atom or a hydroxyl group, a halogen atom, a hydroxyl group, a cyano group, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, a glycidyloxy group, an alkoxycarbonyl group having 2 to 12 carbon atoms, and an alkylcarbonyl group having 2 to 4 carbon atoms.

Examples of halogen atoms include fluorine, chlorine, bromine and iodine atoms.
Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, and a decyl group. Of these, an alkyl group having 1 to 6 carbon atoms is preferred, and a methyl group is more preferred.
Examples of the alkyl group having a halogen atom include a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluoroisopropyl group, a perfluorobutyl group, a perfluorosec-butyl group, a perfluorotert-butyl group, a perfluoropentyl group, a perfluorohexyl group, a trichloromethyl group, a tribromomethyl group, and a triiodomethyl group, and preferably a trifluoromethyl group.
Examples of the alkyl group having a hydroxy group include a hydroxymethyl group and a 2-hydroxyethyl group.
Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, an octyloxy group, a decyloxy group, and a dodecyloxy group.
Examples of the aryl group include a phenyl group, a naphthyl group, an anthryl group, a p-methylphenyl group, a p-tert-butylphenyl group, a p-adamantylphenyl group, a tolyl group, a xylyl group, a cumyl group, a mesityl group, a biphenyl group, a phenanthryl group, a 2,6-diethylphenyl group, and a 2-methyl-6-ethylphenyl group.
Aralkyl groups include benzyl, phenethyl, phenylpropyl, naphthylmethyl and naphthylethyl groups.
Examples of the alkoxycarbonyl group include groups in which an alkoxy group, such as a methoxycarbonyl group or an ethoxycarbonyl group, is bonded to a carbonyl group, and preferably, an alkoxycarbonyl group having 6 or less carbon atoms is used, and more preferably, a methoxycarbonyl group is used.
Alkylcarbonyl groups include acetyl, propionyl and butyryl groups.

［式（Ｔ１’）中、
Ｘ^１１は、酸素原子、硫黄原子又はメチレン基を表す。
Ｒ^４１は、ハロゲン原子もしくはヒドロキシ基を有していてもよい炭素数１～１２のアルキル基、ハロゲン原子、ヒドロキシ基、シアノ基、炭素数１～１２のアルコキシ基、炭素数６～１２のアリール基、炭素数７～１２のアラルキル基、グリシジルオキシ基、炭素数２～１２のアルコキシカルボニル基又は炭素数２～４のアルキルカルボニル基を表す。
ｍａは、０～９のいずれかの整数を表す。ｍａが２以上のとき、複数のＲ^４１は同一であっても異なってもよい。
結合部位は任意の位置である。］
Ｘ^１１は、好ましくは酸素原子又はメチレン基であり、より好ましくはメチレン基である。
Ｒ^４１としては、上述したスルトン環の置換基と同様のものが挙げられ、ハロゲン原子又はヒドロキシ基を有していてもよい炭素数１～１２のアルキル基が好ましい。
ｍａは、好ましくは０又は１であり、より好ましくは０である。 From the viewpoint of ease of production of the monomer from which the structural unit (a6) is derived, a sultone ring having no substituent is preferred.
The sultone ring is preferably a ring represented by the following formula (T1').

[In formula (T1′),
^X11 represents an oxygen atom, a sulfur atom or a methylene group.
R ⁴¹ represents an alkyl group having 1 to 12 carbon atoms which may have a halogen atom or a hydroxyl group, a halogen atom, a hydroxyl group, a cyano group, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, a glycidyloxy group, an alkoxycarbonyl group having 2 to 12 carbon atoms, or an alkylcarbonyl group having 2 to 4 carbon atoms.
ma represents an integer of 0 to 9. When ma is 2 or more, multiple R ⁴¹ may be the same or different.
The binding site is at any position.]
^X11 is preferably an oxygen atom or a methylene group, and more preferably a methylene group.
Examples of R ⁴¹ include the same substituents as those of the sultone ring described above, and an alkyl group having 1 to 12 carbon atoms which may have a halogen atom or a hydroxyl group is preferable.
ma is preferably 0 or 1, and more preferably 0.

Examples of the ring represented by formula (T1') include the following rings. The bonding site may be any position. Among them, the bonding site is preferably the 1st or 3rd position.

It is preferable that the structural unit having an —SO ₂ — group further has a group derived from a polymerizable group, such as a vinyl group, an acryloyl group, a methacryloyl group, an acryloyloxy group, a methacryloyloxy group, an acryloylamino group, a methacryloylamino group, an acryloylthio group, or a methacryloylthio group.
Among these, the monomer from which the structural unit (a6) is derived is preferably a monomer having an ethylenically unsaturated bond, and more preferably a (meth)acrylic monomer.

［式（ａ６－０）中、
Ｒ^ｘは、ハロゲン原子を有してもよい炭素数１～６のアルキル基、水素原子又はハロゲン原子を表す。
Ａ^ｘｘは、酸素原子、－Ｎ（Ｒ^ｃ）－又は硫黄原子を表す。
Ａ^ｘは、単結合又は炭素数１～１８の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－、－ＣＯ－又は－Ｎ（Ｒ^ｄ）－に置き換わっていてもよい。
Ｘ^１１、Ｒ^４１及びｍａは、上記と同じ意味を表す。
Ｒ^ｃ及びＲ^ｄは、互いに独立に、水素原子又は炭素数１～６のアルキル基を表す。］ The structural unit (a6) is preferably a structural unit represented by the formula (a6-0).

[In formula (a6-0),
R ^x represents an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, a hydrogen atom, or a halogen atom.
A ^xx represents an oxygen atom, —N(R ^c )— or a sulfur atom.
A ^x represents a single bond or a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and --CH ₂ -- contained in the saturated hydrocarbon group may be replaced by --O--, --CO-- or --N(R ^d )--.
X ¹¹ , R ⁴¹ and ma have the same meanings as above.
R ^c and R ^d each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

The halogen atom of R ^x includes a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.
Examples of the alkyl group of R ^x include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, and an n-hexyl group. An alkyl group having 1 to 4 carbon atoms is preferable, and a methyl group or an ethyl group is more preferable.
Examples of the alkyl group having a halogen atom for R ^x include a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluoroisopropyl group, a perfluorobutyl group, a perfluorosec-butyl group, a perfluorotert-butyl group, a perfluoropentyl group, a perfluorohexyl group, a trichloromethyl group, a tribromomethyl group, and a triiodomethyl group.
R ^x is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom, a methyl group or an ethyl group, and even more preferably a hydrogen atom or a methyl group.

Examples of the divalent saturated hydrocarbon group for A ^x include a linear alkanediyl group, a branched alkanediyl group, and a monocyclic or polycyclic divalent alicyclic saturated hydrocarbon group, and may be a combination of two or more of these groups.
Specifically, methylene group, ethylene group, propane-1,3-diyl group, propane-1,2-diyl group, butane-1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, decane-1,10-diyl group, undecane-1,11-diyl group, linear alkanediyl groups such as a dodecane-1,12-diyl group, a tridecane-1,13-diyl group, a tetradecane-1,14-diyl group, a pentadecane-1,15-diyl group, a hexadecane-1,16-diyl group, a heptadecane-1,17-diyl group, an ethane-1,1-diyl group, a propane-1,1-diyl group, and a propane-2,2-diyl group;
branched alkanediyl groups such as butane-1,3-diyl group, 2-methylpropane-1,3-diyl group, 2-methylpropane-1,2-diyl group, pentane-1,4-diyl group, and 2-methylbutane-1,4-diyl group;
monocyclic divalent alicyclic saturated hydrocarbon groups such as cycloalkanediyl groups, such as cyclobutane-1,3-diyl group, cyclopentane-1,3-diyl group, cyclohexane-1,4-diyl group, and cyclooctane-1,5-diyl group;
Examples of the polycyclic divalent alicyclic saturated hydrocarbon groups include norbornane-1,4-diyl group, norbornane-2,5-diyl group, adamantane-1,5-diyl group, and adamantane-2,6-diyl group.
The bonding position of ^Ax to the sultone ring may be any position, but is preferably the 1-position.

Examples of the structural unit (a6-0) include the following structural units.

Of these, structural units represented by formulae (a6-1), (a6-2), (a6-6), (a6-7), (a6-8) and (a6-12) are preferred, and structural units represented by formulae (a6-1), (a6-2), (a6-7) and (a6-8) are more preferred.
When the resin (A1) contains the structural unit (a6), the content thereof is preferably from 1 to 50 mol %, more preferably from 2 to 40 mol %, and even more preferably from 3 to 30 mol %, based on all structural units in the resin (A1).

［式（ａ７－Ａ）中、
Ｒ^ａ７は、水素原子、ハロゲン原子又はハロゲン原子を有していてもよい炭素数１～６のアルキル基を表す。
Ｘ^ａ７１は、単結合、＊－Ｏ－＊＊、＊－ＣＯ－Ｏ－＊＊、＊－Ｏ－ＣＯ－Ｏ－＊＊、＊－ＣＯ－ＮＲ^ａ７１－＊＊、＊－ＮＲ^ａ７１－ＣＯ－Ｏ－＊＊、＊－Ｏ－ＣＯ－ＮＲ^ａ７１－＊＊又は＊－Ａｘ－Ｐｈ－Ａｙ－＊＊を表す。
Ｒ^ａ７１は、水素原子又は炭素数１～６のアルキル基を表す。
Ｐｈは置換基を有してもよいフェニレン基を表す。
Ａｘ及びＡｙは、それぞれ独立に、単結合、エーテル結合、チオエーテル結合、エステル結合、アミド結合及び炭酸エステル結合から構成される群から選択される１種の結合種を表す。
＊及び＊＊は、結合部位を表し、＊はＲ^ａ７が結合した炭素原子との結合部位を表す。
Ｌ^ａ７１及びＬ^ａ７２は、それぞれ独立に、置換基を有してもよい炭素数１～２４の炭化水素基を表し、該炭化水素基に含まれる－ＣＨ₂－は、－Ｏ－、－Ｓ－、－ＣＯ－又は－ＳＯ₂－に置き換わっていてもよい。
Ｘ^ａ７２は、＊＊＊－ＣＯ－Ｏ－、＊＊＊－Ｏ－ＣＯ－、＊＊＊－Ｏ－ＣＯ－Ｏ－、＊＊＊－Ｏ－を表し、＊＊＊は、Ｌ^ａ７１との結合部位を表す。
ｎａ７は、０～２のいずれかの整数を表す。ｎａ７が２のとき、複数の括弧内の基は互いに同じでも異なっていてもよい。
ＲＡ^－は、スルホナートアニオン又はカルボキシルアニオンを表す。
ＺＡ^＋は、有機カチオンを表す。］ <Structural unit (a7)>
The resin may further contain a structural unit that decomposes upon exposure to generate an acid (hereinafter, may be referred to as "structural unit (a7)"). Specific examples of the structural unit (a7) include structural units described in JP-A-2016-79235, and are preferably structural units having a sulfonate group or carboxylate group and an organic cation in a side chain, or a structural unit having a sulfonio group and an organic anion in a side chain.
The structural unit having a sulfonate group or carboxylate group and an organic cation in a side chain is preferably a structural unit represented by formula (a7-A).

[In formula (a7-A),
R ^a7 represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
X ^a71 represents a single bond, *-O-**, *-CO-O-**, *-O-CO-O-**, *-CO-NR ^a71 -**, *-NR ^a71 -CO-O-**, *-O-CO-NR ^a71 -** or *-Ax-Ph-Ay-**.
R ^a71 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.
Ph represents a phenylene group which may have a substituent.
Ax and Ay each independently represent one type of bond selected from the group consisting of a single bond, an ether bond, a thioether bond, an ester bond, an amide bond, and a carbonate bond.
* and ** represent binding sites, and * represents the binding site to the carbon atom to which R ^a7 is bonded.
L ^a71 and L ^a72 each independently represent a hydrocarbon group having 1 to 24 carbon atoms which may have a substituent, and --CH ₂ -- contained in the hydrocarbon group may be replaced by --O--, --S--, --CO-- or --SO ₂ --.
^Xa72 represents ***-CO-O-, ***-O-CO-, ***-O-CO-O- or ***-O-, where *** represents a bonding site to ^La71 .
na7 represents an integer of 0 to 2. When na7 is 2, the groups in the parentheses may be the same or different.
RA ⁻ represents a sulfonate anion or a carboxyl anion.
ZA ⁺ represents an organic cation.

Examples of the alkyl group having 1 to 6 carbon atoms for R ^a7 and R ^a71 include a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, and a hexyl group.
Examples of the halogen atom in R ^a7 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Examples of the alkyl group having 1 to 6 carbon atoms and having a halogen atom for R ^a7 include a trifluoromethyl group, a difluoromethyl group, a perfluoroethyl group, a 2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, a perfluorobutyl group, a 1,1,2,2,3,3,4,4-octafluorobutyl group, a perfluoropentyl group, a 2,2,3,3,4,4,5,5,5-nonafluoropentyl group, a perfluorohexyl group, a trichloromethyl group, a dichloromethyl group, a triiodomethyl group, a diiodomethyl group, a tribromomethyl group, and a dibromomethyl group.
R ^a7 is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, still more preferably a hydrogen atom, a methyl group or an ethyl group, and even more preferably a hydrogen atom or a methyl group.

［式（Ｘ１０）中、
Ａｘは、Ｒ^ａ７が結合した炭素原子と結合する結合種を表し、単結合、エーテル結合、チオエーテル結合、エステル結合、炭酸エステル結合及びアミド結合から構成される群から選択される１種の結合種を表す。
Ａｙは、Ｌ^ａ７１と結合する結合種を表し、単結合、エーテル結合、チオエーテル結合、エステル結合、炭酸エステル結合及びアミド結合から構成される群から選択される１種の結合種を表す。
Ｒｘは、ハロゲン原子、ヒドロキシ基、炭素数１～６のフッ化アルキル基、炭素数１～１８のアルキル基又は炭素数１～６のアルコキシ基を表す。
ｍｘは、０～４のいずれかの整数を表し、ｍｘが２以上の整数の場合、複数のＲｘは互いに同じでも異なっていてもよい。］
Ａｘ及びＡｙのどちらかの一方が、単結合である場合、他方は、エーテル結合、チオエーテル結合、エステル結合、炭酸エステル結合及びアミド結合から構成される群から選択される１種であることが好ましい。
Ａｘ及びＡｙのいずれかがアミド結合の場合、－ＣＯ－ＮＲ^ａ７１－で表される結合であることが好ましい。
フェニレン基におけるＡｙの結合位置は、Ａｘの結合位置に対して、ｍ位又はｐ位であることが好ましく、ｐ位であることがより好ましい。
Ｒｘは、中でも、フッ素原子、ヨウ素原子、トリフルオロメチル基、メチル基又はエチル基が好ましい。
ｍｘは、０、１又は２が好ましい。
Ｘ^ａ７１としては、例えば、単結合、以下の式（Ｘ^１０－１）～式（Ｘ^１０－１０）で表される基が挙げられる。＊は－Ｒ^ａ７が結合する炭素原子との結合部位を表す。＊＊は、Ｌ^ａ７１との結合部位を表す。Ｘ^２０は、－Ｏ－又は－ＮＲ^ａ７１－を表す。

式（Ｘ^１０－１）～式（Ｘ^１０－１０）で表される基の具体例としては、以下の基が挙げられる。

なかでも、Ｘ^ａ７１は、単結合及び式（Ｘ^１０－１’）、式（Ｘ^１０－３’）～式（Ｘ^１０－９’）のいずれかで表される基であることが好ましく、単結合又は式（Ｘ^１０－１’）、式（Ｘ^１０－４’）、式（Ｘ^１０－５’）、式（Ｘ^１０－６’）及び式（Ｘ^１０－９’）のいずれかで表される基であることがより好ましく、単結合、式（Ｘ^１０－１’）で表される基、式（Ｘ^１０－５’）で表される基、式（Ｘ^１０－６’）又は式（Ｘ^１０－９’）で表される基であることがさらに好ましい。 When ^Xa71 is a group represented by *-Ax-Ph-Ay-**, it is preferably a linking group represented by the following formula (X10).

[In formula (X10),
Ax represents a bond bonded to the carbon atom to which R ^a7 is bonded, and represents one type of bond selected from the group consisting of a single bond, an ether bond, a thioether bond, an ester bond, a carbonate bond, and an amide bond.
Ay represents a bond that bonds to ^La71 , and represents one type of bond selected from the group consisting of a single bond, an ether bond, a thioether bond, an ester bond, a carbonate bond, and an amide bond.
Rx represents a halogen atom, a hydroxy group, a fluorinated alkyl group having 1 to 6 carbon atoms, an alkyl group having 1 to 18 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.
mx represents an integer of 0 to 4, and when mx is an integer of 2 or more, the multiple Rx's may be the same or different.
When either Ax or Ay is a single bond, the other is preferably one selected from the group consisting of an ether bond, a thioether bond, an ester bond, a carbonate ester bond, and an amide bond.
When either Ax or Ay is an amide bond, it is preferably a bond represented by --CO--NR ^a71 --.
The bonding position of Ay in the phenylene group is preferably the m-position or p-position relative to the bonding position of Ax, and more preferably the p-position.
Among these, Rx is preferably a fluorine atom, an iodine atom, a trifluoromethyl group, a methyl group or an ethyl group.
mx is preferably 0, 1 or 2.
Examples of X ^a71 include a single bond and groups represented by the following formulae (X ¹⁰ -1) to (X ¹⁰ -10). * represents a bonding site with the carbon atom to which -R ^a7 is bonded. ** represents a bonding site with L ^a71 . ^{X 20} represents -O- or -NR ^a71 -.

Specific examples of the groups represented by formulae (X ¹⁰ -1) to (X ¹⁰ -10) include the following groups.

Among these, X ^a71 is preferably a single bond or a group represented by any one of formulas (X ¹⁰ -1'), (X ¹⁰ -3') to (X ¹⁰ -9'), more preferably a single bond or a group represented by any one of formulas (X ¹⁰ -1'), (X ¹⁰ -4'), (X ¹⁰ -5'), (X ¹⁰ -6') and (X ¹⁰ -9'), and further preferably a single bond, a group represented by formula (X ¹⁰ -1'), a group represented by formula (X ¹⁰ -5'), a group represented by formula (X ¹⁰ -6') or a group represented by formula (X ¹⁰ -9').

脂環式炭化水素基が単環式のシクロアルキル基の場合、脂環式炭化水素基の炭素数は、３～１８であることが好ましく、３～１２であることがより好ましく、３～８であることがさらに好ましい。脂環式炭化水素基が多環式のシクロアルキル基の場合、脂環式炭化水素基の炭素数は、６～１８であることが好ましく、７～１２であることがより好ましい。
Ｌ^ａ７１及びＬ^ａ７２の芳香族炭化水素基としては、アリール基の１個の水素原子を取り除いた基が挙げられる。アリール基としては、フェニル基、ナフチル基、アントリル基、ビフェニル基、フルオレニル基等が挙げられる。芳香族炭化水素基の炭素数としては、５～１４であることが好ましく、６～１４であることがより好ましく、６～１０であることがさらに好ましい。
Ｌ^ａ７１及びＬ^ａ７２の炭化水素基に含まれる－ＣＨ₂－が、－Ｏ－、－ＣＯ－、－Ｓ－又は－ＳＯ₂－に置き換わっている場合、置き換わる前の炭素数を該炭化水素基の炭素数とする。
Ｌ^ａ７１及びＬ^ａ７２の炭化水素基のうち、鎖式炭化水素基に含まれる－ＣＨ₂－が、－Ｏ－、－ＣＯ－、－Ｓ－又は－ＳＯ₂－に置き換わった基としては、ヒドロキシ基（メチル基中に含まれる－ＣＨ₂－が、－Ｏ－に置き換わった基）、カルボキシ基（エチル基中に含まれる－ＣＨ₂－ＣＨ₂－が、－Ｏ－ＣＯ－に置き換わった基）、チオール基（メチル基中に含まれる－ＣＨ_２－が－Ｓ－に置き換わった基）、カルボニル基（メチレン基中に含まれる－ＣＨ₂－が、－ＣＯ－に置き換わった基）、オキシ基（メチレン基中に含まれる－ＣＨ₂－が、－Ｏ－に置き換わった基）、チオ基（メチレン基中に含まれる－ＣＨ₂－が、－Ｓ－に置き換わった基）、スルホニル基（メチレン基中に含まれる－ＣＨ₂－が、－ＳＯ_２－に置き換わった基）、アルコキシ基（アルキル基中に含まれる任意の位置の－ＣＨ₂－が、－Ｏ－に置き換わった基）、アルコキシカルボニル基（アルキル基中に含まれる任意の位置の－ＣＨ₂－ＣＨ₂－が、－Ｏ－ＣＯ－に置き換わった基）、アルキルカルボニル基（アルキル基中に含まれる任意の位置の－ＣＨ₂－が、－ＣＯ－に置き換わった基）、アルキルカルボニルオキシ基（アルキル基中に含まれる任意の位置の－ＣＨ₂－ＣＨ₂－が、－ＣＯ－Ｏ－に置き換わった基）、アルカンジイルオキシ基（アルカンジイル基中に含まれる任意の位置の－ＣＨ₂－が、－Ｏ－に置き換わった基）、アルカンジイルオキシカルボニル基（アルカンジイル基中に含まれる任意の位置の－ＣＨ₂－ＣＨ₂－が、－Ｏ－ＣＯ－に置き換わった基）、アルカンジイルカルボニル基（アルカンジイル基中に含まれる任意の位置の－ＣＨ₂－が、－ＣＯ－に置き換わった基）、アルカンジイルカルボニルオキシ基（アルカンジイル基中に含まれる任意の位置の－ＣＨ₂－ＣＨ₂－が、－ＣＯ－Ｏ－に置き換わった基）等が挙げられる。これらの置き換わった基は、炭素数の上限が許す範囲で、本明細書で例示した基と同様のものが挙げられる。
Ｌ^ａ７１及びＬ^ａ７２の炭化水素基のうち、脂環式炭化水素基に含まれる－ＣＨ₂－が、－Ｏ－、－ＣＯ－、－Ｓ－又は－ＳＯ₂－に置き換わった基としては、環状エーテル、環状ケトン、環状エステル（ラクトン）、環状チオエーテル、環状アセタール、環状スルホン酸エステル（スルトン）構造を含む基等が挙げられる。具体的には、以下の式で表される脂環式炭化水素基が挙げられる。以下の式で挙げた脂環式炭化水素基の結合位置は、任意の位置とすることができる。

Ｌ^ａ７１及びＬ^ａ７２の炭化水素基のうち、芳香族炭化水素基に含まれる－ＣＨ₂－は、－Ｏ－又は－Ｓ－に置き換わってもよく、－ＣＨ₂－が、－Ｏ－又は－Ｓ－に置き換わった基としては、それぞれフラン環又はチオフェン環に由来する基等が挙げられる。
Ｌ^ａ７１及びＬ^ａ７２の鎖式炭化水素基、脂環式炭化水素基及び芳香族炭化水素基の２種以上の基を組み合わせた基としては、上記の鎖式炭化水素基と上記の脂環式炭化水素基を組み合わせた基、上記の鎖式炭化水素基と上記の芳香族炭化水素基を組み合わせた基、上記の脂環式炭化水素基と上記の芳香族炭化水素基とを組み合わせた基、上記の鎖式炭化水素基と上記の脂環式炭化水素基と上記の芳香族炭化水素基を組み合わせた基が挙げられる。脂環式炭化水素基と芳香族炭化水素基を組み合わせた基としては、縮合環であってもよい。
Ｌ^ａ７１及びＬ^ａ７２の炭化水素基が有してもよい置換基としては、ハロゲン原子、シアノ基、ニトロ基が挙げられる。ハロゲン原子としては、フッ素原子、塩素原子、臭素原子、ヨウ素原子等が挙げられる。
Ｌ^ａ７１及びＬ^ａ７２が、脂環式炭化水素基又は芳香族炭化水素基と鎖式炭化水素基と組み合わせた基である場合、実質的に、該鎖式炭化水素基を脂環式炭化水素基又は芳香族炭化水素基が有する置換基とみなしてもよい。また、Ｌ^ａ７１及びＬ^ａ７２の炭化水素基に含まれる鎖式炭化水素基の－ＣＨ₂－が、－Ｏ－、－ＣＯ－、－Ｓ－又は－ＳＯ₂－に置き換わることで、Ｌ^ａ７１及びＬ^ａ７２の炭化水素基は、実質的に、ヒドロキシ基、カルボキシ基、アルコキシ基、アルキルカルボニル基、アルコキシカルボニル基、アルキルカルボニルオキシ基、チオール基、スルホニル基等の置換基を有することができる。
ｎａ７は、０又は１が好ましい。
式（ａ７－Ａ）中のＺＡ^＋は、式（Ｂ１）等で表される塩におけるカチオンと同様のものが挙げられる。 Examples of the hydrocarbon group for L ^a71 include a group obtained by removing one hydrogen atom from a chain hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, or a group combining two or more of these groups, and bonding X ^a71 to X ^a72 . Examples of the hydrocarbon group for L ^a72 include a group obtained by removing one hydrogen atom from a chain hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, or a group combining two or more of these groups, and bonding X ^a72 to ^RA- .
The chain hydrocarbon group of L ^a71 and L ^a72 includes an alkyl group or an alkenyl group with one hydrogen atom removed. The alkyl group may be linear or branched, and specific examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentanedecyl group, and a heptadecyl group. The alkenyl group includes an ethenyl group, a propenyl group, an isopropenyl group, a butenyl group, an isobutenyl group, a tert-butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an octenyl group, an isooctenyl group, and a nonenyl group.
The chain hydrocarbon group preferably has 1 to 20 carbon atoms, more preferably 1 to 18 carbon atoms, and even more preferably 1 to 10 carbon atoms.
The alicyclic hydrocarbon group of L ^a71 and L ^a72 includes a group in which one hydrogen atom has been removed from a monocyclic or polycyclic cycloalkyl group. Examples of the monocyclic cycloalkyl group include a cyclobutyl group, a cycloheptyl group, a cyclohexyl group, a cyclopentyl group, and a cyclooctyl group.
Examples of the polycyclic cycloalkyl groups of L ^a71 and L ^a72 include a cycloalkyl group having a bridged structure, a cycloalkyl group in which two or more rings are condensed, or a cycloalkyl group in which two rings are bonded by a spiro bond. Examples of the cycloalkyl group having a bridged structure include a norbornyl group and an adamantyl group. Examples of the cycloalkyl group in which two or more rings are condensed include a bicyclo[4,4,0]decane group and a steroid group (steroid skeleton). Examples of the cycloalkyl group in which two rings are bonded by a spiro bond include a spirocyclic cycloalkyl group in which one cycloalkyl group selected from the group consisting of a cyclopentyl group, a cyclohexyl group, a norbornyl group, and an adamantyl group is bonded by a spiro bond to a cycloalkyl group having 5 to 8 carbon atoms. A double bond may be formed between two carbon atoms contained in the alicyclic hydrocarbon group. More specifically, examples of the alicyclic hydrocarbon group represented by the following formula are given.

When the alicyclic hydrocarbon group is a monocyclic cycloalkyl group, the alicyclic hydrocarbon group preferably has 3 to 18 carbon atoms, more preferably 3 to 12, and even more preferably 3 to 8. When the alicyclic hydrocarbon group is a polycyclic cycloalkyl group, the alicyclic hydrocarbon group preferably has 6 to 18 carbon atoms, and more preferably 7 to 12.
The aromatic hydrocarbon group of L ^a71 and L ^a72 includes a group in which one hydrogen atom has been removed from an aryl group. Examples of the aryl group include a phenyl group, a naphthyl group, an anthryl group, a biphenyl group, and a fluorenyl group. The number of carbon atoms in the aromatic hydrocarbon group is preferably 5 to 14, more preferably 6 to 14, and even more preferably 6 to 10.
When --CH ₂ -- contained in the hydrocarbon group of L ^a71 and L ^a72 is replaced by --O--, --CO--, --S-- or --SO ₂ --, the number of carbon atoms before replacement is regarded as the number of carbon atoms of the hydrocarbon group.
Among the hydrocarbon groups of L ^a71 and L ^a72 , examples of the groups in which —CH ₂ — in a chain hydrocarbon group is replaced by —O—, —CO—, —S— or —SO ₂ — include a hydroxy group (a group in which —CH ₂ — in a methyl group is replaced by —O—), a carboxy group (a group in which —CH ₂ — in an ethyl group is replaced by —O—CO—), a thiol group (a group in which —CH ₂ — in a methyl group is replaced by _—S— ), a carbonyl group (a group in which —CH ₂ — in a methylene group is replaced by —CO—), an oxy group (a group in which —CH ₂ — in a methylene group is replaced by —O—), a thio group (a group in which —CH ₂ — in a methylene group is replaced by —S—), a sulfonyl group (a group in which —CH ₂ — in a methylene group is replaced by —SO ₂ -), alkoxy group (a group in which -CH ₂ - at any position contained in an alkyl group is replaced with -O-), alkoxycarbonyl group (a group in which -CH ₂ -CH ₂ - at any position contained in an alkyl group is replaced with -O-CO-), alkylcarbonyl group (a group in which -CH ₂ - at any position contained in an alkyl group is replaced with -CO-), alkylcarbonyloxy group (a group in which -CH ₂ -CH ₂ - at any position contained in an alkyl group is replaced with -CO-O-), alkanediyloxy group (a group in which -CH ₂ - at any position contained in an alkanediyl group is replaced with -O-), alkanediyloxycarbonyl group (a group in which -CH ₂ -CH ₂ - at any position contained in an alkanediyl group is replaced with -O-CO-), alkanediylcarbonyl group (a group in which -CH ₂ Examples of such substituted groups include an alkanediyl group (an alkanediyl group in which any --CH ₂ --CH ₂ -- at any position is replaced with --CO--), an alkanediylcarbonyloxy group (an alkanediyl group in which --CH 2 -- at any position is replaced with --CO--O--), etc. These substituted groups include the same groups as those exemplified in this specification, within the range permitted by the upper limit of the number of carbon atoms.
Among the hydrocarbon groups of L ^a71 and L ^a72 , examples of groups in which --CH ₂ -- contained in an alicyclic hydrocarbon group is replaced with --O--, --CO--, --S-- or --SO ₂ -- include groups containing a cyclic ether, cyclic ketone, cyclic ester (lactone), cyclic thioether, cyclic acetal, and cyclic sulfonate ester (sultone) structure. Specific examples include alicyclic hydrocarbon groups represented by the following formulas. The bonding position of the alicyclic hydrocarbon groups listed in the following formulas can be any position.

Of the hydrocarbon groups of L ^a71 and L ^a72 , the —CH ₂ — contained in the aromatic hydrocarbon group may be replaced by —O— or —S—, and examples of the group in which —CH ₂ — is replaced by —O— or —S— include groups derived from a furan ring or a thiophene ring, respectively.
Examples of the group obtained by combining two or more of the chain hydrocarbon group, alicyclic hydrocarbon group, and aromatic hydrocarbon group of L ^a71 and L ^a72 include a group obtained by combining the chain hydrocarbon group and the alicyclic hydrocarbon group, a group obtained by combining the chain hydrocarbon group and the aromatic hydrocarbon group, a group obtained by combining the alicyclic hydrocarbon group and the aromatic hydrocarbon group, and a group obtained by combining the chain hydrocarbon group, the alicyclic hydrocarbon group, and the aromatic hydrocarbon group. The group obtained by combining the alicyclic hydrocarbon group and the aromatic hydrocarbon group may be a condensed ring.
Examples of the substituent that the hydrocarbon group of L ^a71 and L ^a72 may have include a halogen atom, a cyano group, and a nitro group. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
When L ^a71 and L ^a72 are groups each comprising an alicyclic hydrocarbon group or an aromatic hydrocarbon group combined with a chain hydrocarbon group, the chain hydrocarbon group may be regarded as a substituent possessed by the alicyclic hydrocarbon group or the aromatic hydrocarbon group. In addition, the -CH ₂ - of the chain hydrocarbon group contained in the hydrocarbon group of L ^a71 and L ^a72 is replaced with -O-, -CO-, -S- or -SO ₂ -, so that the hydrocarbon group of L ^a71 and L ^a72 can substantially have a substituent such as a hydroxy group, a carboxy group, an alkoxy group, an alkylcarbonyl group, an alkoxycarbonyl group, an alkylcarbonyloxy group, a thiol group or a sulfonyl group.
na7 is preferably 0 or 1.
Examples of ZA ⁺ in formula (a7-A) include the same cations as those in the salt represented by formula (B1) and the like.

［式（ａ７－Ａ１）中、
Ｒ^ａ７、Ｘ^ａ７１、Ｌ^ａ７１、Ｘ^ａ７２、ｎａ７、ＲＡ^－及びＺＡ^＋は、上記と同じ意味を表す。
ｚ７は、０～６のいずれかの整数を表す。
Ｑ^ａ７、Ｑ^ｂ７、Ｒ^ｚ７１及びＲ^ｚ７２は、それぞれ独立に、水素原子、フッ素原子、炭素数１～６のペルフルオロアルキル基又は炭素数１～６のアルキル基を表し、ｚ７が２以上のとき、複数のＲ^ｚ７１及びＲ^ｚ７２は互いに同一であっても異なっていてもよい。］
Ｑ^ａ７、Ｑ^ｂ７、Ｒ^ｚ７１及びＲ^ｚ７２における炭素数１～６のペルフルオロアルキル基又は炭素数１～６のアルキル基としては、Ｒ^ａ７で例示した基と同様の基が挙げられる。 In formula (a7-A), when the hydrocarbon groups of L ^a71 and L ^a72 are saturated hydrocarbon groups, they may contain the same groups as the groups exemplified as the divalent linking group of A ^b7 in formula (a7-B) described later.
Examples of the structural unit represented by formula (a7-A) include a structural unit represented by formula (a7-A1).

[In formula (a7-A1),
R ^a7 , X ^a71 , L ^a71 , X ^a72 , na7, RA ^- and ZA ⁺ have the same meanings as above.
z7 represents an integer of 0 to 6.
Q ^a7 , Q ^b7 , R ^z71 and R ^z72 each independently represent a hydrogen atom, a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms, or an alkyl group having 1 to 6 carbon atoms, and when z7 is 2 or greater, a plurality of R ^z71 and R ^z72 may be the same or different.]
Examples of the perfluoroalkyl group having 1 to 6 carbon atoms or the alkyl group having 1 to 6 carbon atoms for Q ^a7 , Q ^b7 , R ^z71 and R ^z72 include the same groups as those exemplified for R ^a7 .

Examples of the structural unit represented by formula (a7-A) include the following structural units, structural units in which the group corresponding to the methyl group of R ^a7 is replaced with a hydrogen atom, a halogen atom (e.g., a fluorine atom) or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom (e.g., a trifluoromethyl group), and structural units described in WO 2012/050015: ZA ⁺ represents an organic cation.

［式（ａ７－Ｂ）中、
Ｒ^ａ７は、水素原子、ハロゲン原子又はハロゲン原子を有していてもよい炭素数１～６のアルキル基を表す。
Ａ^ｂ７は、単結合又は２価の連結基を表す。
Ｒ^ｂ７１は、置換基を有してもよい炭素数６～１８の２価の芳香族炭化水素基を表す。
Ｒ^ｂ７２及びＲ^ｂ７３は、それぞれ独立して、置換基を有してもよい炭素数１～１８の炭化水素基を表し、Ｒ^ｂ７２及びＲ^ｂ７３は互いに結合してそれらが結合する硫黄原子とともに環を形成していてもよい。
Ａ^－は、有機アニオンを表す。］
Ｒ^ａ７のハロゲン原子及びハロゲン原子を有してもよいアルキル基としては、式（ａ７－Ａ）と同様のハロゲン原子及びハロゲン原子を有してもよいアルキル基が挙げられる。
Ｒ^ｂ７１で表される炭素数６～１８の２価の芳香族炭化水素基としては、フェニレン基及びナフチレン基等が挙げられる。
Ｒ^ｂ７２及びＲ^ｂ７３で表される炭化水素基としては、アルキル基、脂環式炭化水素基、芳香族炭化水素基及びこれらを組み合わせることにより形成される基等が挙げられる。
アルキル基、脂環式炭化水素基、芳香族炭化水素基及びこれらを組み合わせることにより形成される基等は、上記と同様のものが挙げられる。
Ａ^ｂ７で表される２価の連結基としては、例えば、炭素数１～１８の２価の飽和炭化水素基が挙げられ、該２価の飽和炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－、－Ｓ－又は－ＣＯ－で置き換わっていてもよい。
２価の飽和炭化水素基としては、直鎖状又は分岐状アルカンジイル基等の２価の鎖式飽和炭化水素基、単環式又は多環式の２価の脂環式飽和炭化水素基が挙げられ、これらの組み合わせであってもよい。
具体的には、メチレン基、エチレン基、プロパン－１，３－ジイル基、プロパン－１，２－ジイル基、ブタン－１，４－ジイル基、ペンタン－１，５－ジイル基、ヘキサン－１，６－ジイル基、ヘプタン－１，７－ジイル基、オクタン－１，８－ジイル基、ノナン－１，９－ジイル基、デカン－１，１０－ジイル基、ウンデカン－１，１１－ジイル基、ドデカン－１，１２－ジイル基等の直鎖状アルカンジイル基；ブタン－１，３－ジイル基、２－メチルプロパン－１，３－ジイル基、２－メチルプロパン－１，２－ジイル基、ペンタン－１，４－ジイル基、２－メチルブタン－１，４－ジイル基等の分岐状アルカンジイル基；シクロブタン－１，３－ジイル基、シクロペンタン－１，３－ジイル基、シクロヘキサン－１，４－ジイル基、シクロオクタン－１，５－ジイル基等の単環式シクロアルカンジイル基である２価の単環式脂環式飽和炭化水素基；ノルボルナン－１，４－ジイル基、ノルボルナン－２，５－ジイル基、アダマンタン－１，５－ジイル基、アダマンタン－２，６－ジイル基等の多環式シクロアルカンジイル基である２価の多環式脂環式飽和炭化水素基等が挙げられる。
飽和炭化水素基に含まれる－ＣＨ_２－が、－Ｏ－、－Ｓ－又は－ＣＯ－で置き換わったものとしては、例えば以下の２価の基が挙げられる。ただし、飽和炭化水素基に含まれる－ＣＨ_２－が、－Ｏ－、－Ｓ－又は－ＣＯ－で置き換わる前の炭素数はそれぞれ１７以下である。下記式において、＊及び＊＊は結合部位を表し、＊はＲ^ｂ７１との結合部位を表す。

［式中、Ｘ^３は、２価の炭素数１～１６の飽和炭化水素基を表す。
Ｘ^４は、２価の炭素数１～１５の飽和炭化水素基を表す。
Ｘ^５は、２価の炭素数１～１３の飽和炭化水素基を表す。
Ｘ^６は、２価の炭素数１～１４の飽和炭化水素基を表す。
Ｘ^７は、３価の炭素数１～１４の飽和炭化水素基を表す。
Ｘ^８は、２価の炭素数１～１３の飽和炭化水素基を表す。］ The structural unit having a sulfonio group and an organic anion on the side chain is preferably a structural unit represented by formula (a7-B).

[In formula (a7-B),
R ^a7 represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
A ^b7 represents a single bond or a divalent linking group.
R ^b71 represents a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent.
R ^b72 and R ^b73 each independently represent a hydrocarbon group having 1 to 18 carbon atoms which may have a substituent, and R ^b72 and R ^b73 may be bonded to each other to form a ring together with the sulfur atom to which they are bonded.
A ⁻ represents an organic anion.
Examples of the halogen atom and the alkyl group which may have a halogen atom for R ^a7 include the same halogen atom and the alkyl group which may have a halogen atom as those of formula (a7-A).
Examples of the divalent aromatic hydrocarbon group having 6 to 18 carbon atoms represented by R ^b71 include a phenylene group and a naphthylene group.
Examples of the hydrocarbon group represented by R ^b72 and R ^b73 include an alkyl group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, and groups formed by combining these groups.
Examples of the alkyl group, alicyclic hydrocarbon group, aromatic hydrocarbon group, and groups formed by combining these groups include the same as those described above.
Examples of the divalent linking group represented by A ^b7 include divalent saturated hydrocarbon groups having 1 to 18 carbon atoms, and --CH ₂ -- contained in the divalent saturated hydrocarbon group may be replaced by --O--, --S-- or --CO--.
Examples of the divalent saturated hydrocarbon group include divalent chain saturated hydrocarbon groups such as linear or branched alkanediyl groups, and monocyclic or polycyclic divalent alicyclic saturated hydrocarbon groups, and combinations of these are also possible.
Specific examples of the alkyl group include linear alkanediyl groups such as methylene, ethylene, propane-1,3-diyl, propane-1,2-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, decane-1,10-diyl, undecane-1,11-diyl, and dodecane-1,12-diyl groups; and linear alkanediyl groups such as butane-1,3-diyl, 2-methylpropane-1,3-diyl, 2-methylpropane-1,2-diyl, pentane-1,4 divalent monocyclic alicyclic saturated hydrocarbon groups such as monocyclic cycloalkanediyl groups, such as cyclobutane-1,3-diyl group, cyclopentane-1,3-diyl group, cyclohexane-1,4-diyl group, and cyclooctane-1,5-diyl group; and divalent polycyclic alicyclic saturated hydrocarbon groups, such as polycyclic cycloalkanediyl groups, such as norbornane-1,4-diyl group, norbornane-2,5-diyl group, adamantane-1,5-diyl group, and adamantane-2,6-diyl group.
Examples of saturated hydrocarbon groups in which -CH ₂ - is replaced by -O-, -S- or -CO- include the following divalent groups, where the number of carbon atoms before -CH ₂ - in the saturated hydrocarbon group is replaced by -O-, -S- or -CO- is 17 or less. In the following formula, * and ** represent bonding sites, and * represents the bonding site with R ^b71 .

[In the formula, ^X3 represents a divalent saturated hydrocarbon group having 1 to 16 carbon atoms.
^X4 represents a divalent saturated hydrocarbon group having 1 to 15 carbon atoms.
^X5 represents a divalent saturated hydrocarbon group having 1 to 13 carbon atoms.
^X6 represents a divalent saturated hydrocarbon group having 1 to 14 carbon atoms.
^X7 represents a trivalent saturated hydrocarbon group having 1 to 14 carbon atoms.
^X8 represents a divalent saturated hydrocarbon group having 1 to 13 carbon atoms.

Examples of the structural unit containing a cation in formula (a7-B) include structural units represented by the following formulas and structural units in which a group corresponding to the methyl group in R ^a7 is replaced with a hydrogen atom, a halogen atom (e.g., a fluorine atom) or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom (e.g., a trifluoromethyl group, etc.).

Examples of the organic anion represented by ^A- include a sulfonate anion, a sulfonylimide anion, a sulfonylmethide anion, and a carboxylate anion. The organic anion represented by ^A- is preferably a sulfonate anion, and the sulfonate anion is more preferably the same as the anion exemplified for the acid generator (B). Examples of the sulfonylimide anion, sulfonylmethide anion, and carboxylate anion include the same anions exemplified for the acid generator (B).

樹脂（Ａ１）が、構造単位（ａ７）を含有する場合、構造単位（ａ７）は単独で含んでいてもよいし、２種以上を含んでいてもよい。その構造単位（ａ７）の合計含有率は、樹脂（Ａ１）の全構造単位に対して、好ましくは１～３０モル％であり、より好ましくは１～２５モル％であり、さらに好ましくは２～２０モル％であり、より一層好ましくはさらに好ましくは３～１５モル％であり、より一層好ましくは３～１０モル％である。 Examples of the structural unit represented by formula (a7-B) include structural units represented below.

When the resin (A1) contains the structural unit (a7), the structural unit (a7) may be contained alone or in combination of two or more kinds. The total content of the structural unit (a7) is preferably 1 to 30 mol%, more preferably 1 to 25 mol%, even more preferably 2 to 20 mol%, still more preferably 3 to 15 mol%, and even more preferably 3 to 10 mol%, based on the total structural units of the resin (A1).

The resin (A1) is preferably a resin composed of the structural unit (a4-2) and the structural unit (I6), a resin composed of the structural unit (a4-3) and the structural unit (I6), a resin composed of the structural unit (a4-2), the structural unit (a4-3) and the structural unit (I6), a resin composed of the structural unit (a4-2), the structural unit (I6) and the structural unit (a1), a resin composed of the structural unit (a4-3), the structural unit (I6) and the structural unit (a1), a resin composed of the structural unit (a4-2), ...) and the structural unit (I6). resins composed of structural units (a4-2), (a4-3), (I6), and (s); resins composed of structural units (a4-2), (a4-3), (I6), and (s); resins composed of structural units (a4-2), (I6), (a1), and (s); resins composed of structural units (a4-3), (I6), (a1), and (s); resins composed of structural units (a4-2), (a4-3), (I6), (a1), and (s); resins composed of structural units (a4-2), (a4-3), (I6), (a1), and (s);
The structural unit (a1) is preferably at least one selected from the group consisting of the structural unit (a1-0), the structural unit (a1-1), the structural unit (a1-2) (preferably a structural unit having a cyclohexyl group or a cyclopentyl group), and the structural unit (a1-5), more preferably at least two, and even more preferably at least two selected from the group consisting of the structural unit (a1-1) and the structural unit (a1-2).
The structural unit (s) is preferably at least one selected from the group consisting of the structural unit (a2) and the structural unit (a3). The structural unit (a2) is preferably the structural unit (a2-1) or the structural unit (a2-A). The structural unit (a3) is preferably at least one selected from the group consisting of the structural unit represented by formula (a3-1), the structural unit represented by formula (a3-2), and the structural unit represented by formula (a3-4).

Each structural unit constituting the resin (A1) may be used alone or in combination of two or more, and can be produced by a known polymerization method (e.g., radical polymerization method) using a monomer that derives these structural units. The content of each structural unit in the resin (A1) can be adjusted by the amount of the monomer used in the polymerization.
The weight average molecular weight of the resin (A1) is preferably 2,000 or more (more preferably 2,500 or more, even more preferably 3,000 or more) and 50,000 or less (more preferably 30,000 or less, even more preferably 15,000 or less), but may contain an oligomer having a weight average molecular weight smaller than these. In this specification, the weight average molecular weight is a value determined by gel permeation chromatography under the conditions described in the Examples.

<Resist Composition>
The resist composition of the present invention is a resist composition containing a resin (A1). In addition to the resin (A1), the resist composition of the present invention may also contain a resin (hereinafter sometimes referred to as "resin (A2)") that is different from the resin (A1) and contains a structural unit having an acid labile group, a resin other than the resin (A1) and the resin (A2), and an acid generator (hereinafter sometimes referred to as "acid generator (B)").
Furthermore, the resist composition of the present invention preferably further contains a quencher (hereinafter sometimes referred to as "quencher (C)") and/or a solvent (hereinafter sometimes referred to as "solvent (E)").
<Resin (A2)>
Resin (A2) has a structural unit having an acid labile group (hereinafter, may be referred to as "structural unit (a1)"). The structural unit (a1) is derived from a monomer having an acid labile group (hereinafter, may be referred to as "monomer (a1)"). It is preferable that resin (A2) further contains a structural unit other than the structural unit (a1). Examples of the structural unit other than the structural unit (a1) include the structural unit (s) described above.

When the resin (A2) contains the structural unit (a1-0) and/or the structural unit (a1-1) and/or the structural unit (a1-2), the total content of these is typically 10 to 95 mol %, preferably 15 to 90 mol %, and more preferably 20 to 85 mol %, based on all structural units in the resin (A2).
When the resin (A2) contains the structural unit (a1-3), the content thereof is preferably from 10 to 95 mol %, more preferably from 15 to 90 mol %, and even more preferably from 20 to 85 mol %, based on all structural units in the resin (A2).
When the resin (A2) has the structural unit (a1-4), its content is preferably from 10 to 95 mol %, more preferably from 15 to 90 mol %, and even more preferably from 20 to 85 mol %, based on all structural units in the resin (A2).
When the resin (A2) has the structural unit (a1-5), its content is preferably from 1 to 50 mol %, more preferably from 3 to 45 mol %, and even more preferably from 5 to 40 mol %, based on all structural units in the resin (A2).

As the structural unit (a1) having an acid labile group in the resin (A2), at least one selected from the group consisting of the structural unit (a1-0), the structural unit (a1-1), the structural unit (a1-2) and the structural unit (a1-5) is preferred, and at least two selected from the group consisting of the structural unit (a1-1) and the structural unit (a1-2), the structural unit (a1-1) and the structural unit (a1-5), the structural unit (a1-1) and the structural unit (a1-0), and the structural unit (a1-1) and the structural unit (a1-2) are more preferred. More preferred are combinations of structural unit (a1-2) and structural unit (a1-0), structural unit (a1-5) and structural unit (a1-0), structural unit (a1-0), structural unit (a1-1) and structural unit (a1-2), and structural unit (a1-0), structural unit (a1-1) and structural unit (a1-5), and particularly preferred are combinations of structural unit (a1-1) or structural unit (a1-2), and structural unit (a1-1) and structural unit (a1-2).

When the resin (A2) has the structural unit (a2-0), the content thereof is preferably from 5 to 95 mol %, more preferably from 10 to 80 mol %, and even more preferably from 15 to 80 mol %, based on all structural units in the resin (A2).
When the resin (A2) contains the structural unit (a2-1), the content thereof is, based on all structural units of the resin (A2), for example, 1 to 45 mol %, preferably 1 to 40 mol %, more preferably 1 to 35 mol %, and even more preferably 2 to 20 mol %.

When the resin (A2) contains the structural unit (a3), the total content thereof is 5 to 70 mol %, preferably 10 to 65 mol %, and more preferably 10 to 60 mol %, based on all structural units in the resin (A2).
Furthermore, the content of the structural unit (a3-1), the structural unit (a3-2), the structural unit (a3-3), and the structural unit (a3-4) is preferably from 5 to 60 mol%, more preferably from 5 to 50 mol%, and even more preferably from 10 to 50 mol%, based on the total structural units of the resin (A2).

When the resin (A2) has the structural unit (a4-1), its content is preferably from 1 to 20 mol %, more preferably from 2 to 15 mol %, and even more preferably from 3 to 10 mol %, based on all structural units of the resin (A2).
When the resin (A2) has the structural unit (a5), the content thereof is preferably from 1 to 30 mol %, more preferably from 2 to 20 mol %, and even more preferably from 3 to 15 mol %, based on all structural units in the resin (A2).
When the resin (A2) contains the structural unit (a6), the content thereof is preferably from 1 to 50 mol %, more preferably from 2 to 40 mol %, and even more preferably from 3 to 30 mol %, based on all structural units in the resin (A2).

The resin (A2) is preferably a resin composed of the structural unit (a1) and the structural unit (s), that is, a copolymer of the monomer (a1) and the monomer (s).
The structural unit (a1) is preferably at least one type selected from the group consisting of the structural unit (a1-0), the structural unit (a1-1), and the structural unit (a1-2) (preferably a structural unit having a cyclohexyl group or a cyclopentyl group), more preferably at least two types, and even more preferably at least two types selected from the group consisting of the structural unit (a1-1) and the structural unit (a1-2).
The structural unit (s) is preferably at least one selected from the group consisting of the structural unit (a2) and the structural unit (a3). The structural unit (a2) is preferably the structural unit (a2-1) or the structural unit (a2-A). The structural unit (a3) is preferably at least one selected from the group consisting of the structural unit represented by formula (a3-1), the structural unit represented by formula (a3-2), and the structural unit represented by formula (a3-4).

Each structural unit constituting the resin (A2) may be used alone or in combination of two or more, and can be produced by a known polymerization method (e.g., radical polymerization method) using a monomer that derives these structural units. The content of each structural unit in the resin (A2) can be adjusted by the amount of the monomer used in the polymerization.
The weight average molecular weight of the resin (A2) is preferably 2,000 or more (more preferably 2,500 or more, and even more preferably 3,000 or more) and 50,000 or less (more preferably 30,000 or less, and even more preferably 15,000 or less), but may contain an oligomer having a weight average molecular weight smaller than this.

The content of resin (A1) in the resist composition is preferably 1 to 60 parts by mass, more preferably 1 to 50 parts by mass, even more preferably 1 to 40 parts by mass, and particularly preferably 2 to 30 parts by mass, per 100 parts by mass of resin (A2).

<Resins other than resin (A1) and resin (A2)>
The resist composition of the present invention may contain a resin other than the resin (A1) and the resin (A2). Examples of the resin other than the resin (A1) and the resin (A2) include a resin consisting only of the structural unit (s), and a resin consisting of the structural unit (a2), the structural unit (a3) and/or a structural unit derived from other known monomers.

Other examples of the resin include a resin containing the structural unit (a4) or the structural unit (a5) (however, the structural unit (I6) and the structural unit (a1) are not contained; hereinafter, the resin may be referred to as "resin (X)").
As the resin (X), a resin containing the structural unit (a4) is particularly preferred.
When the resin (X) contains the structural unit (a4), the content of the structural unit (a4) in the resin (X) is 20 mol% or more, preferably 30 mol% or more, more preferably 40 mol% or more, and even more preferably 45 mol% or more, based on the total of all structural units in the resin (X). Also, 100 mol% or less is preferred, 80 mol% or less is preferred, 70 mol% or less is more preferred, 60 mol% or less is more preferred, and 55 mol% or less is even more preferred. Specifically, 20 to 100 mol% is preferred, 20 to 80 mol% is preferred, 30 to 70 mol% is more preferred, 40 to 60 mol% is even more preferred, and 45 to 55 mol% is even more preferred. When the resin (X) contains the structural unit (a5), the content of the structural unit (a5) is 20 mol% or more, preferably 30 mol% or more, more preferably 40 mol% or more, and even more preferably 45 mol% or more, based on the total of all structural units in the resin (X). Also, 100 mol% or less can be mentioned, 80 mol% or less is preferable, 70 mol% or less is more preferable, 60 mol% or less is even more preferable, and 55 mol% or less is even more preferable. Specifically, 20 to 100 mol% can be mentioned, 20 to 80 mol% is preferable, 30 to 70 mol% is more preferable, 40 to 60 mol% is even more preferable, and 45 to 55 mol% is even more preferable. Furthermore, when the resin (X) contains the structural unit (a4) and the structural unit (a5), the total content of the structural unit (a4) and the structural unit (a5) can be 40 mol% or more, preferably 60 mol% or more, more preferably 70 mol% or more, and even more preferably 80 mol% or more, based on the total of all structural units of the resin (X). Furthermore, 100 mol% or less can be mentioned. Specifically, 40 to 100 mol% can be mentioned, 60 to 100 mol% is preferable, 70 to 100 mol% is more preferable, and 80 to 100 mol% is even more preferable.
Examples of structural units that the resin (X) may further have include the structural unit (a2), the structural unit (a3), and structural units derived from other known monomers. Among these, the resin (X) is preferably a resin consisting only of the structural unit (a4) and/or the structural unit (a5).
Each structural unit constituting the resin (X) may be used alone or in combination of two or more, and can be produced by a known polymerization method (e.g., radical polymerization method) using a monomer that derives these structural units. The content of each structural unit in the resin (X) can be adjusted by the amount of the monomer used in the polymerization.
The weight average molecular weight of resin (X) is preferably 6,000 or more (more preferably 7,000 or more) and 80,000 or less (more preferably 60,000 or less), but may contain an oligomer having a lower weight average molecular weight than this. The method for measuring the weight average molecular weight of resin (X) is the same as that for resin (A2).

When the resist composition of the present invention contains resin (X), the content thereof is preferably 1 to 60 parts by mass, more preferably 1 to 50 parts by mass, even more preferably 1 to 40 parts by mass, even more preferably 1 to 30 parts by mass, and even more preferably 1 to 8 parts by mass, per 100 parts by mass of resin (A2).

The content of resin (A1) in the resist composition is preferably 1% by mass or more and 20% by mass or less, more preferably 3% by mass or more and 10% by mass or less, based on the solid content of the resist composition. The total content of resin (A1) and resin (A2) in the resist composition is preferably 20% by mass or more and 100% by mass or less, more preferably 50% by mass or more and 99% by mass or less, based on the solid content of the resist composition. In addition, when resins other than resin (A1) and resin (A2) are contained, the total content of resin (A1), resin (A2) and resins other than resin (A1) and resin (A2) is preferably 80% by mass or more and 99% by mass or less, more preferably 90% by mass or more and 99% by mass or less, based on the solid content of the resist composition. The solid content of the resist composition and the resin content therein can be measured by known analytical means such as liquid chromatography or gas chromatography.

<Acid Generator (B)>
The acid generator (B) may be either nonionic or ionic. Examples of nonionic acid generators include sulfonate esters (e.g., 2-nitrobenzyl ester, aromatic sulfonate, oxime sulfonate, N-sulfonyloxyimide, sulfonyloxyketone, diazonaphthoquinone 4-sulfonate), sulfones (e.g., disulfone, ketosulfone, sulfonyldiazomethane), and the like. Examples of ionic acid generators include onium salts containing onium cations (e.g., diazonium salts, phosphonium salts, sulfonium salts, iodonium salts). Examples of the anions of the onium salts include sulfonate anions, sulfonylimide anions, sulfonylmethide anions, and carboxylate anions.

As the acid generator (B), compounds that generate acid when exposed to radiation, such as those described in JP-A-63-26653, JP-A-55-164824, JP-A-62-69263, JP-A-63-146038, JP-A-63-163452, JP-A-62-153853, JP-A-63-146029, U.S. Pat. No. 3,779,778, U.S. Pat. No. 3,849,137, German Patent No. 3914407, and European Patent No. 126,712, can be used. Compounds produced by known methods may also be used. Two or more types of acid generators (B) may be used in combination.

［式（Ｂ１）中、全ての符号は、それぞれ前記と同じ意味を表す。］ The acid generator (B) is preferably a salt represented by formula (B1) (hereinafter may be referred to as “salt (B1)” or “acid generator (B1)”) and a salt represented by formula (B2) (hereinafter may be referred to as “salt (B2)” or “acid generator (B2)”).

[In formula (B1), all symbols have the same meanings as defined above.]

Examples of the cyclic hydrocarbon groups of Q ^b1 , Q ^b2 , L ^b1 and Y in formula (B1) include the same groups as the cyclic hydrocarbon groups of Q ^b1 , Q ^b2 , L ^b1 and Y ^b1 in formula (I6), and preferred examples are the same groups.

Examples of the substituent of the methyl group represented by Y include a halogen atom, a hydroxy group, an alicyclic hydrocarbon group having 3 to 16 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, a glycidyloxy group, a -(CH ₂ ) _ja -CO-O-R ^b1 group or a -(CH ₂ ) _ja -O-CO-R ^b1 group (wherein R ^b1 represents an alkyl group having 1 to 16 carbon atoms, an alicyclic hydrocarbon group having 3 to 16 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms or a combination thereof, -CH ₂ - contained in the alkyl group and the alicyclic hydrocarbon group may be replaced by -O-, -S-, -SO ₂ - or -CO-, and a hydrogen atom contained in the alkyl group, the alicyclic hydrocarbon group and the aromatic hydrocarbon group may be replaced by a hydroxy group or a fluorine atom; and ja represents an integer of 0 to 4).

Y is preferably an alicyclic hydrocarbon group having 3 to 24 carbon atoms which may have a substituent or an aromatic hydrocarbon group having 6 to 24 carbon atoms which may have a substituent, more preferably an alicyclic hydrocarbon group having 3 to 20 carbon atoms which may have a substituent or an aromatic hydrocarbon group having 6 to 20 carbon atoms which may have a substituent, even more preferably an alicyclic hydrocarbon group having 3 to 18 carbon atoms which may have a substituent or an aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent, and even more preferably a cycloalkyl group having 5 or 6 carbon atoms, a norbornyl group, an adamantyl group, a norbornane lactone group, an adamantane lactone group, an alicyclic hydrocarbon group in which a cycloalkyl group having 5 or 6 carbon atoms and a cycloalkyl group having 5 to 8 carbon atoms are bonded together in a spiro bond, an alicyclic hydrocarbon group in which a norbornyl group and a cycloalkyl group having 5 to 8 carbon atoms are bonded together in a spiro bond, an alicyclic hydrocarbon group in which an adamantyl group and a cycloalkyl group having 5 to 8 carbon atoms are bonded together in a spiro bond, or a phenyl group. Here, the alicyclic hydrocarbon group, the cycloalkyl group, the norbornyl group, the adamantyl group, the norbornane lactone group, the adamantane lactone group and the phenyl group each may have a substituent, and -CH2- contained in the alicyclic hydrocarbon group, the cycloalkyl group, the norbornyl group and the adamantyl group may each be replaced by -O-, -S-, -SO2- or -CO-.
Specific examples of Y include the following:

Among these, Y is preferably an adamantyl group, a hydroxyadamantyl group, an oxoadamantyl group, a norbornane lactone group, a phenyl group, a group containing these, or a group represented by formula (Y42), (Y100) to (Y114), or (Y134) to (Y139), and particularly preferably a hydroxyadamantyl group, an oxoadamantyl group, a group containing these, or a group represented by formula (Y42), (Y100) to (Y114), or (Y134) to (Y139).

The anion in the salt represented by formula (B1) is preferably an anion represented by formula (B1-A-1) to formula (B1-A-85) [hereinafter, may be referred to as "anion (B1-A-1)" depending on the formula number.], and more preferably an anion represented by any of formulas (B1-A-1) to (B1-A-4), (B1-A-9), (B1-A-10), (B1-A-24) to (B1-A-33), (B1-A-36) to (B1-A-40), and (B1-A-47) to (B1-A-85).

ここでＲⁱ²～Ｒⁱ⁷は、互いに独立に、例えば、炭素数１～４のアルキル基、好ましくはメチル基又はエチル基である。Ｒⁱ⁸は、例えば、炭素数１～１２の脂肪族炭化水素基、好ましくは炭素数１～４のアルキル基、炭素数５～１２の脂環式炭化水素基又はこれらを組合せることにより形成される基、より好ましくはメチル基、エチル基、シクロヘキシル基又はアダマンチル基である。Ｌ^A41は、単結合又は炭素数１～４のアルカンジイル基である。
Ｑ^b1及びＱ^b2は、上記と同じ意味を表す。
式（Ｂ１）で表される塩におけるアニオンとしては、具体的には、特開２０１０－２０４６４６号公報に記載されたアニオンが挙げられる。

Here, R ⁱ² to R ⁱ⁷ are each independently, for example, an alkyl group having 1 to 4 carbon atoms, preferably a methyl group or an ethyl group. ^{R i8} is, for example, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, preferably an alkyl group having 1 to 4 carbon atoms, an alicyclic hydrocarbon group having 5 to 12 carbon atoms, or a group formed by combining these, more preferably a methyl group, an ethyl group, a cyclohexyl group, or an adamantyl group. L ^A41 is a single bond or an alkanediyl group having 1 to 4 carbon atoms.
Q ^b1 and Q ^b2 have the same meanings as above.
Specific examples of the anion in the salt represented by formula (B1) include the anions described in JP-A-2010-204646.

Preferred anions in the salt represented by formula (B1) include anions represented by formulas (B1a-1) to (B1a-70), respectively. Among them, anions represented by any of formulas (B1a-1) to (B1a-4), (B1a-7) to (B1a-11), (B1a-14) to (B1a-30), and (B1a-35) to (B1a-70) are preferred.

［式（Ｂ２）中、全ての符号は、それぞれ前記と同じ意味を表す。］

[In formula (B2), all symbols have the same meanings as defined above.]

Examples of the hydrocarbon group containing a cyclic hydrocarbon group in R ²¹ include cyclic hydrocarbon groups such as monocyclic or polycyclic alicyclic hydrocarbon groups and aromatic hydrocarbon groups, or groups combining these, and groups in which cyclic hydrocarbon groups such as monocyclic or polycyclic alicyclic hydrocarbon groups and aromatic hydrocarbon groups are arbitrarily combined with chain hydrocarbon groups (alkyl groups, alkenyl groups, alkynyl groups, etc.). The number of carbon atoms in the cyclic hydrocarbon group in R ²¹ is, for example, 3 to 24, preferably 3 to 20, more preferably 3 to 18, even more preferably 3 to 16, and even more preferably 5 to 16. The total number of carbon atoms in the hydrocarbon group containing a cyclic hydrocarbon group in R ²¹ is, for example, 3 to 48, preferably 3 to 40, more preferably 3 to 36, even more preferably 3 to 30, even more preferably 3 to 24, even more preferably 3 to 18, and even more preferably 3 to 16.

脂環式炭化水素基の炭素数は、好ましくは３～２４であり、より好ましくは３～１８であり、さらに好ましくは３～１６であり、さらにより好ましくは５～１６である。
芳香族炭化水素基としては、フェニル基、ナフチル基、ビフェニル基、アントリル基、フェナントリル基、ビナフチル基等のアリール基等が挙げられる。芳香族炭化水素基の炭素数は、好ましくは６～２４であり、より好ましくは６～１８であり、さらに好ましくは６～１４であり、さらにより好ましくは６～１０である。 The alicyclic hydrocarbon group may be any of monocyclic, polycyclic and spirocyclic, and may be any of saturated and unsaturated. Examples of the alicyclic hydrocarbon group include monocyclic cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl and cyclododecyl, and polycyclic cycloalkyl groups such as decahydronaphthyl, norbornyl and adamantyl.
Specific examples of the alicyclic hydrocarbon group include the groups shown below. The bonding site can be any position.

The alicyclic hydrocarbon group preferably has 3 to 24 carbon atoms, more preferably 3 to 18 carbon atoms, even more preferably 3 to 16 carbon atoms, and even more preferably 5 to 16 carbon atoms.
Examples of the aromatic hydrocarbon group include aryl groups such as a phenyl group, a naphthyl group, a biphenyl group, an anthryl group, a phenanthryl group, a binaphthyl group, etc. The number of carbon atoms in the aromatic hydrocarbon group is preferably 6 to 24, more preferably 6 to 18, even more preferably 6 to 14, and even more preferably 6 to 10.

Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl groups.
Examples of the alkenyl group include ethenyl, propenyl, isopropenyl, butenyl, isobutenyl, tert-butenyl, pentenyl, hexenyl, heptenyl, octenyl, isooctenyl, and nonenyl groups.
Examples of the alkynyl group include an ethynyl group, a propynyl group, an isopropynyl group, a butynyl group, an isobutynyl group, a tert-butynyl group, a pentynyl group, a hexynyl group, an octynyl group, and a nonynyl group.
The number of carbon atoms in the chain hydrocarbon group is preferably 1 to 24, more preferably 1 to 18, even more preferably 1 to 12, still more preferably 1 to 8, even more preferably 1 to 6, still more preferably 1 to 4, and even more preferably 1 to 3.

The combined groups are:
Examples of such groups include a combination of an alicyclic hydrocarbon group and an aromatic hydrocarbon group, a combination of an alicyclic hydrocarbon group and an open chain hydrocarbon group, a combination of an aromatic hydrocarbon group and an open chain hydrocarbon group, a combination of an alicyclic hydrocarbon group, an aromatic hydrocarbon group and an open chain hydrocarbon group, etc. Here, -CH ₂ - contained in the combined group may be replaced by -O-, -S-, -CO- or -SO ₂ -.
In addition, in the combination, two or more of each of the alicyclic hydrocarbon group, aromatic hydrocarbon group, and chain hydrocarbon group may be combined. In addition, any group may be bonded to an oxygen atom. In addition, the above groups may contain groups with different valences (alkanediyl group, alkanetriyl group, cycloalkanediyl group, cycloalkanetriyl group, etc.).

Specific examples of the combined groups include:
Alicyclic hydrocarbon group-chain hydrocarbon group-*, such as adamantylmethyl group, adamantylethyl group, cyclohexylmethyl group, cyclohexylethyl group, etc. (-CH ₂ - contained in the chain hydrocarbon group and the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or -SO ₂ -).
Chain hydrocarbon group-alicyclic hydrocarbon group-*, such as a methyladamantyl group, a methylcyclohexyl group, a dimethylcyclohexyl group, etc. (-CH ₂ - contained in the chain hydrocarbon group and the alicyclic hydrocarbon group may be replaced with -O-, -S-, -CO- or -SO ₂ -).
a chain hydrocarbon group-aromatic hydrocarbon group-*, such as a tolyl group or a xylyl group ( _-CH2- contained in the chain hydrocarbon group may be replaced by -O-, -S-, -CO- or _-SO2- );
Chain hydrocarbon group-alicyclic hydrocarbon group-chain hydrocarbon group-*, such as methylcyclohexylmethyl group ( _-CH2- contained in the chain hydrocarbon group and the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or _-SO2- ),
Aromatic hydrocarbon group-chain hydrocarbon group-*, such as a benzyl group or a phenethyl group ( _-CH2- contained in the chain hydrocarbon group may be replaced by -O-, -S-, -CO- or _-SO2- ),
a chain hydrocarbon group such as a tolylmethyl group-aromatic hydrocarbon group-chain hydrocarbon group-* (-CH ₂ - contained in the chain hydrocarbon group may be replaced by -O-, -S-, -CO- or -SO ₂ -);
Aromatic hydrocarbon group-alicyclic hydrocarbon group-*, such as a phenyladamantyl group ( _-CH2- contained in the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or _-SO2- ),
Alicyclic hydrocarbon group-aromatic hydrocarbon group-*, such as a cyclohexylphenyl group or an adamantylphenyl group ( _-CH2- contained in the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or _-SO2- ),
A chain hydrocarbon group-alicyclic hydrocarbon group-aromatic hydrocarbon group-*, such as a methylcyclohexylphenyl group or a dimethylcyclohexylphenyl group ( _-CH2- contained in the chain hydrocarbon group and the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or _-SO2- ),
A chain hydrocarbon group-aromatic hydrocarbon group-alicyclic hydrocarbon group-*, such as a methylphenylcyclohexyl group or a dimethylphenylcyclohexyl group ( _-CH2- contained in the chain hydrocarbon group and the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or _-SO2- ),
Alicyclic hydrocarbon group-chain hydrocarbon group-aromatic hydrocarbon group-*, such as a cyclohexylmethylphenyl group or a cyclohexylethylphenyl group ( _-CH2- contained in the chain hydrocarbon group and the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or _-SO2- ),
Aromatic hydrocarbon group-chain hydrocarbon group-alicyclic hydrocarbon group-*, such as a phenylmethylcyclohexyl group or a phenylethylcyclohexyl group (-CH ₂ - contained in the chain hydrocarbon group and the alicyclic hydrocarbon group may be replaced with -O-, -S-, -CO- or -SO ₂ -);
Alicyclic hydrocarbon group-aromatic hydrocarbon group-chain hydrocarbon group-*, such as a cyclohexylphenylmethyl group or a cyclohexylphenylethyl group ( _-CH2- contained in the chain hydrocarbon group and the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or _-SO2- ),
Aromatic hydrocarbon group-alicyclic hydrocarbon group-chain hydrocarbon group-*, such as a phenylcyclohexylmethyl group or a phenylcyclohexylethyl group ( _-CH2- contained in the chain hydrocarbon group and the alicyclic hydrocarbon group may be replaced with -O-, -S-, -CO- or _-SO2- ),
Here, * represents the bonding site with an oxygen atom.

When —CH ₂ — contained in the hydrocarbon group represented by R ²¹ is replaced by —O—, —S—, —CO— or —SO ₂ —, the number of carbon atoms before the replacement is regarded as the total number of carbon atoms in the hydrocarbon group. In addition, the number may be 1 or 2 or more.
Examples of groups in which -CH ₂ - in a hydrocarbon group is replaced by -O-, -S-, -CO- or -SO ₂ - include a hydroxy group (a group in which -CH ₂ - in a methyl group is replaced by -O-), a thiol group (a group in which -CH ₂ - in a methyl group is replaced by -S-), a carboxy group (a group in which -CH ₂ -CH ₂ - in an ethyl group is replaced by -O-CO-), an alkoxy group (a group in which -CH ₂ - at any position in an alkyl group is replaced by -O-), an alkylthio group (a group in which -CH ₂ - at any position in an alkyl group is replaced by -S-), an alkoxycarbonyl group (a group in which -CH ₂ -CH ₂ - at any position in an alkyl group is replaced by -O-CO-), an alkylcarbonyl group (a group in which -CH ₂ - - is replaced with -CO-), an alkylsulfonyl group (a group in which -CH ₂ - at any position contained in an alkyl group is replaced with -SO ₂ -), an alkylcarbonyloxy group (a group in which -CH ₂ -CH ₂ - at any position contained in an alkyl group is replaced with -CO-O-), an oxy group (a group in which -CH ₂ - contained in a methylene group is replaced with -O-), a carbonyl group (a group in which -CH ₂ - contained in a methylene group is replaced with -CO-), a thio group (a group in which -CH ₂ - contained in a methylene group is replaced with -S-), a sulfonyl group (a group in which -CH ₂ - contained in a methylene group is replaced with -SO ₂ -), an alkanediyloxy group (a group in which -CH 2 - at any position contained in an alkanediyl group is replaced with -SO ₂ -), - is replaced by -O-), an alkanediyloxycarbonyl group (a group in which -CH ₂ -CH ₂ - at any position contained in an alkanediyl group is replaced by -O-CO-), an alkanediylcarbonyl group (a group in which -CH ₂ - at any position contained in an alkanediyl group is replaced by -CO-), an alkanediylcarbonyloxy group (a group in which -CH ₂ -CH ₂ - at any position contained in an alkanediyl group is replaced by -CO-O-), an alkanediylthio group (a group in which -CH ₂ - at any position contained in an alkanediyl group is replaced by -S-), an alkanediylsulfonyl group (a group in which -CH ₂ - at any position contained in an alkanediyl group is replaced by -SO ₂ -substituted), cycloalkoxy groups, cycloalkylalkoxy groups, alkoxycarbonyloxy groups, aromatic hydrocarbon group-carbonyloxy groups, aromatic hydrocarbon group-carbonyl groups, aromatic hydrocarbon group-oxy groups, and combinations of two or more of these groups.
Examples of the alkoxy group include alkoxy groups having 1 to 47 carbon atoms, such as a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, an octyloxy group, a 2-ethylhexyloxy group, a nonyloxy group, a decyloxy group, an undecyloxy group, etc. The number of carbon atoms in the alkoxy group may be 1 to 17, preferably 1 to 11, more preferably 1 to 6, even more preferably 1 to 4, and even more preferably 1 to 3.
The alkylthio group includes alkylthio groups having 1 to 47 carbon atoms, such as a methylthio group, an ethylthio group, a propylthio group, a butylthio group, a pentylthio group, a hexylthio group, an octylthio group, a 2-ethylhexylthio group, a nonylthio group, a decylthio group, an undecylthio group, etc. The number of carbon atoms in the alkylthio group may be 1 to 17, preferably 1 to 11, more preferably 1 to 6, even more preferably 1 to 4, and even more preferably 1 to 3.
Examples of the alkoxycarbonyl group include alkoxycarbonyl groups having 2 to 47 carbon atoms, such as methoxycarbonyl, ethoxycarbonyl, and butoxycarbonyl groups. Examples of the alkylcarbonyl group include alkylcarbonyl groups having 2 to 48 carbon atoms, such as acetyl, propionyl, and butyryl groups. Examples of the alkylcarbonyloxy group include alkylcarbonyloxy groups having 2 to 47 carbon atoms, such as acetyloxy, propionyloxy, and butyryloxy groups. The number of carbon atoms in the alkoxycarbonyl group may be 2 to 17, preferably 2 to 11, more preferably 2 to 6, even more preferably 2 to 4, and even more preferably 2 or 3. The number of carbon atoms in the alkylcarbonyl group may be 2 to 18, preferably 2 to 12, more preferably 2 to 6, even more preferably 2 to 4, and even more preferably 2 or 3. The alkylcarbonyloxy group may have 2 to 17 carbon atoms, preferably 2 to 11, more preferably 2 to 6, even more preferably 2 to 4, and even more preferably 2 or 3 carbon atoms.
Examples of the alkylsulfonyl group include alkylsulfonyl groups having 1 to 47 carbon atoms, such as a methylsulfonyl group, an ethylsulfonyl group, a propylsulfonyl group, a butylsulfonyl group, a pentylsulfonyl group, a hexylsulfonyl group, an octylsulfonyl group, a 2-ethylhexylsulfonyl group, a nonylsulfonyl group, a decylsulfonyl group, an undecylsulfonyl group, etc. The number of carbon atoms in the alkylsulfonyl group may be 1 to 17, preferably 1 to 11, more preferably 1 to 6, even more preferably 1 to 4, and even more preferably 1 to 3.
The alkanediyloxy group includes an alkanediyloxy group having 1 to 47 carbon atoms, such as a methyleneoxy group, an ethyleneoxy group, a propanediyloxy group, a butanediyloxy group, a pentanediyloxy group, etc. The number of carbon atoms in the alkanediyloxy group may be 1 to 17, preferably 1 to 11, more preferably 1 to 6, even more preferably 1 to 4, and even more preferably 1 to 3.
Examples of the alkanediyloxycarbonyl group include alkanediyloxycarbonyl groups having 2 to 47 carbon atoms, such as a methyleneoxycarbonyl group, an ethyleneoxycarbonyl group, a propanediyloxycarbonyl group, and a butanediyloxycarbonyl group. Examples of the alkanediylcarbonyl group include alkanediylcarbonyl groups having 2 to 48 carbon atoms, such as a methylenecarbonyl group, an ethylenecarbonyl group, a propanediylcarbonyl group, a butanediylcarbonyl group, and a pentanediylcarbonyl group. Examples of the alkanediylcarbonyloxy group include alkanediylcarbonyloxy groups having 2 to 47 carbon atoms, such as a methylenecarbonyloxy group, an ethylenecarbonyloxy group, a propanediylcarbonyloxy group, and a butanediylcarbonyloxy group. The number of carbon atoms in the alkanediyloxycarbonyl group may be 2 to 17, preferably 2 to 11, more preferably 2 to 6, even more preferably 2 to 4, and even more preferably 2 or 3. The number of carbon atoms in the alkanediylcarbonyl group may be 2 to 18, preferably 2 to 12, more preferably 2 to 6, even more preferably 2 to 4, and even more preferably 2 or 3. The number of carbon atoms in the alkanediylcarbonyloxy group may be 2 to 17, preferably 2 to 11, more preferably 2 to 6, even more preferably 2 to 4, and even more preferably 2 or 3.
The alkanediylthio group includes an alkanediylthio group having 1 to 47 carbon atoms, such as a methylenethio group, an ethylenethio group, a propylenethio group, etc. The number of carbon atoms in the alkanediylthio group may be 1 to 17, preferably 1 to 11, more preferably 1 to 6, even more preferably 1 to 4, and even more preferably 1 to 3.
The alkanediylsulfonyl group includes an alkanediylsulfonyl group having 1 to 47 carbon atoms, such as a methylenesulfonyl group, an ethylenesulfonyl group, a propylenesulfonyl group, etc. The number of carbon atoms in the alkanediylsulfonyl group may be 1 to 17, preferably 1 to 11, more preferably 1 to 6, even more preferably 1 to 4, and even more preferably 1 to 3.
Examples of the cycloalkoxy group include cycloalkoxy groups having 3 to 47 carbon atoms, such as a cyclohexyloxy group. Examples of the cycloalkylalkoxy group include cycloalkylalkoxy groups having 4 to 47 carbon atoms, such as a cyclohexylmethoxy group. Examples of the alkoxycarbonyloxy group include alkoxycarbonyloxy groups having 2 to 46 carbon atoms, such as a butoxycarbonyloxy group. Examples of the aromatic hydrocarbon group-carbonyloxy group include aromatic hydrocarbon group-carbonyloxy groups having 7 to 47 carbon atoms, such as a benzoyloxy group. Examples of the aromatic hydrocarbon group-carbonyl group include aromatic hydrocarbon group-carbonyl groups having 7 to 48 carbon atoms, such as a benzoyl group. Examples of the aromatic hydrocarbon group-oxy group include aromatic hydrocarbon group-oxy groups having 6 to 47 carbon atoms, such as a phenyloxy group.
Examples of groups in which --CH ₂ -- contained in an alicyclic hydrocarbon group is replaced by --O--, --S--, --CO-- or --SO ₂ -- include the groups shown below. --O-- or --CO-- in the groups shown below may be replaced by --S-- or --SO ₂ --. The bonding site may be at any position.

Examples of the substituent that the cyclic hydrocarbon group may have include a halogen atom, a cyano group, and an alkyl group having 1 to 12 carbon atoms ( _-CH2- contained in the alkyl group may be replaced with -O-, -S-, -CO- or _-SO2- ). When the cyclic hydrocarbon group has a substituent, the substituent is not included in the total number of carbon atoms of the hydrocarbon group including the cyclic hydrocarbon group in ^R21 .
Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Examples of the alkyl group having 1 to 12 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a hexyl group, an octyl group, a nonyl group, etc. The number of carbon atoms in the alkyl group is preferably 1 to 10, more preferably 1 to 9, still more preferably 1 to 8, even more preferably 1 to 6, still more preferably 1 to 4, and still more preferably 1 to 3.
When --CH ₂ -- contained in an alkyl group is replaced with --O--, --S--, --CO-- or --SO ₂ -- as a substituent, the number of carbon atoms before replacement is regarded as the total number of carbon atoms in the alkyl group. Examples of the substituted group include a hydroxy group (a group in which -CH ₂ - in a methyl group is replaced with -O-), a carboxy group (a group in which -CH ₂ -CH ₂ - in an ethyl group is replaced with -O-CO-), an alkoxy group (a group in which -CH ₂ - at any position in an alkyl group is replaced with -O-), an alkoxycarbonyl group (a group in which -CH ₂ -CH ₂ - at any position in an alkyl group is replaced with -O-CO-), an alkylcarbonyl group (a group in which -CH ₂ - at any position in an alkyl group is replaced with -CO-), an alkylcarbonyloxy group (a group in which -CH ₂ -CH ₂ - at any position in an alkyl group is replaced with -CO-O-), and a group in which two or more of these groups are combined. Examples of these substituted groups include the same groups as those exemplified in this specification, within the range permitted by the upper limit of the number of carbon atoms.
The alkoxy group preferably has 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and even more preferably 1 to 3 carbon atoms.
The number of carbon atoms in the alkoxycarbonyl group is preferably 2 to 6, more preferably 2 to 4, and even more preferably 2 or 3. The number of carbon atoms in the alkylcarbonyl group is preferably 2 to 6, more preferably 2 to 4, and even more preferably 2 or 3. The number of carbon atoms in the alkylcarbonyloxy group is preferably 2 to 6, more preferably 2 to 4, and even more preferably 2 or 3.
The cyclic hydrocarbon group may have one substituent or multiple substituents.
The substituent that the cyclic hydrocarbon group may have is preferably a halogen atom or an alkyl group having 1 to 6 carbon atoms (-CH ₂ - contained in the alkyl group may be replaced with -O-, -S-, -CO- or -SO ₂ -), more preferably a fluorine atom, an iodine atom or an alkyl group having 1 to 4 carbon atoms (-CH ₂ - contained in the alkyl group may be replaced with -O-, -S-, -CO- or -SO ₂ -), even more preferably a fluorine atom, an iodine atom, a hydroxy group, an alkoxy group having 1 to 3 carbon atoms or an alkyl group having 1 to 4 carbon atoms, and still more preferably a fluorine atom, an iodine atom, a hydroxy group or an alkyl group having 1 to 4 carbon atoms.

The cyclic hydrocarbon group (which may have a substituent, and the --CH ₂ -- contained in the cyclic hydrocarbon group may be replaced by --O--, --S--, --SO ₂ -- or --CO--) is
It is preferably an alicyclic hydrocarbon group having 3 to 18 carbon atoms (the alicyclic hydrocarbon group may have a substituent, and —CH ₂ — contained in the alicyclic hydrocarbon group may be replaced by —O—, —S—, —SO ₂ — or —CO—), or an aromatic hydrocarbon group having 6 to 18 carbon atoms (the aromatic hydrocarbon group may have a substituent),
More preferably, it is an alicyclic hydrocarbon group having 3 to 18 carbon atoms (the alicyclic hydrocarbon group may have one or more selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a hydroxy group, an iodine atom and a fluorine atom, and _-CH2- contained in the alicyclic hydrocarbon group may be replaced by -O-, -S-, _-SO2- or -CO-), or an aromatic hydrocarbon group having 6 to 18 carbon atoms (the aromatic hydrocarbon group may have one or more selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a hydroxy group, an iodine atom and a fluorine atom),
More preferably, it is an alicyclic hydrocarbon group having 5 to 16 carbon atoms (the alicyclic hydrocarbon group may have one or more groups selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a hydroxy group, an iodine atom and a fluorine atom, and _-CH2- contained in the alicyclic hydrocarbon group may be replaced by -O-, -S-, _-SO2- or -CO-).

上記式において、Ｒ^21’は、上述したＲ²¹と同じ定義であり、Ｒ²¹と同じであってもよいし異なっていてもよい。 Examples of the hydrocarbon group having 3 to 48 carbon atoms and containing a cyclic hydrocarbon group represented by R ²¹ (the cyclic hydrocarbon group may have a substituent, and the —CH ₂ — contained in the hydrocarbon group may be replaced by —O—, —S—, —SO ₂ — or —CO—) include:
Preferably, it is a hydrocarbon group having 3 to 48 carbon atoms including an alicyclic hydrocarbon group having 3 to 18 carbon atoms (the alicyclic hydrocarbon group may have a substituent, and the -CH ₂ - contained in the hydrocarbon group may be replaced by -O-, -S-, -SO ₂ - or -CO-), or a hydrocarbon group having 6 to 48 carbon atoms including an aromatic hydrocarbon group having 6 to 18 carbon atoms (the aromatic hydrocarbon group may have a substituent, and the -CH ₂ - contained in the hydrocarbon group may be replaced by -O-, -S-, -SO ₂ - or -CO-),
More preferably, it is a hydrocarbon group having 3 to 48 carbon atoms including an alicyclic hydrocarbon group having 3 to 18 carbon atoms (the alicyclic hydrocarbon group may have one or more selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a hydroxy group, an iodine atom and a fluorine atom, and the -CH ₂ - contained in the hydrocarbon group may be replaced with -O-, -S-, -SO ₂ - or -CO-), or a hydrocarbon group having 6 to 48 carbon atoms including an aromatic hydrocarbon group having 6 to 18 carbon atoms (the aromatic hydrocarbon group may have one or more selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a hydroxy group, an iodine atom and a fluorine atom, and the -CH ₂ - contained in the hydrocarbon group may be replaced with -O-, -S-, -SO ₂ - or -CO-),
More preferably, the alicyclic hydrocarbon group has 3 to 18 carbon atoms (the alicyclic hydrocarbon group may have one or more selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a hydroxy group, an iodine atom, and a fluorine atom, and the -CH ₂ - contained in the alicyclic hydrocarbon group may be replaced by -O-, -S-, -SO ₂ -, or -CO-), or a group formed by combining an alicyclic hydrocarbon group having 3 to 18 carbon atoms with a chain hydrocarbon group having 1 to 6 carbon atoms (the alicyclic hydrocarbon group may have one or more selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a hydroxy group, an iodine atom, and a fluorine atom, and the -CH ₂ - contained in the combined group may be replaced by -O-, -S-, -SO _{2 -} , or -CO-). - or -CO-), an aromatic hydrocarbon group having 6 to 18 carbon atoms (the aromatic hydrocarbon group may have one or more selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a hydroxy group, an iodine atom and a fluorine atom), or a group combining an aromatic hydrocarbon group having 6 to 18 carbon atoms with a chain hydrocarbon group having 1 to 6 carbon atoms (the aromatic hydrocarbon group may have one or more selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a hydroxy group, an iodine atom and a fluorine atom, and the -CH ₂ - contained in the combined group may be replaced by -O-, -S-, -SO ₂ - or -CO-),
Even more preferably, it is an alicyclic hydrocarbon group having 5 to 16 carbon atoms (the alicyclic hydrocarbon group may have one or more selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a hydroxy group, an iodine atom and a fluorine atom, and the -CH ₂ - contained in the alicyclic hydrocarbon group may be replaced with -O-, -S-, -SO ₂ - or -CO-), or a group combining an alicyclic hydrocarbon group having 5 to 16 carbon atoms with a chain hydrocarbon group having 1 to 4 carbon atoms (the alicyclic hydrocarbon group may have one or more selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a hydroxy group, an iodine atom and a fluorine atom, and the -CH ₂ - contained in the combined group may be replaced with -O-, -S-, -SO ₂ - or -CO-).
Examples of the hydrocarbon group having 3 to 48 carbon atoms and containing a cyclic hydrocarbon group represented by R ²¹ (the cyclic hydrocarbon group may have a substituent, and the —CH ₂ — contained in the hydrocarbon group may be replaced by —O—, —S—, —SO ₂ — or —CO—) include:
It is also preferable that W ²¹ -L ²¹ -* (W ²¹ represents a cyclic hydrocarbon group having 3 to 18 carbon atoms which may have a substituent, and -CH ₂ - contained in the cyclic hydrocarbon group may be replaced by -O-, -S-, -SO ₂ - or -CO-; L ²¹ represents a single bond or a chain hydrocarbon group having 1 to 6 carbon atoms, and -CH ₂ - contained in the chain hydrocarbon group may be replaced by -O-, -S-, -SO ₂ - or -CO-; * represents a bonding site with an oxygen atom).
Examples of the cyclic hydrocarbon group for W ²¹ , the substituent that W ²¹ may have, and the chain hydrocarbon group for L ²¹ include the same groups as those mentioned above.
W ²¹ is preferably an alicyclic hydrocarbon group having 3 to 18 carbon atoms (the alicyclic hydrocarbon group may have a substituent, and the -CH ₂ - contained in the alicyclic hydrocarbon group may be replaced by -O-, -S-, -SO ₂ - or -CO-), or an aromatic hydrocarbon group having 6 to 18 carbon atoms (the aromatic hydrocarbon group may have a substituent), and is preferably an alicyclic hydrocarbon group having 3 to 18 carbon atoms (the alicyclic hydrocarbon group may have one or more selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a hydroxy group, an iodine atom and a fluorine atom, and the -CH ₂ - contained in the alicyclic hydrocarbon group is replaced by -O-, -S-, -SO ₂ - or -CO-). - or -CO-), or an aromatic hydrocarbon group having 6 to 18 carbon atoms (the aromatic hydrocarbon group may have one or more selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a hydroxy group, an iodine atom and a fluorine atom), and even more preferably an alicyclic hydrocarbon group having 5 to 16 carbon atoms (the alicyclic hydrocarbon group may have one or more selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a hydroxy group, an iodine atom and a fluorine atom, and the -CH ₂ - contained in the alicyclic hydrocarbon group may be replaced by -O-, -S-, -SO ₂ - or -CO-).
L ²¹ is preferably a single bond or a chain hydrocarbon group having 1 to 6 carbon atoms (-CH ₂ - contained in the chain hydrocarbon group may be replaced by -O- or -CO-), more preferably a single bond or a chain hydrocarbon group having 1 to 4 carbon atoms (-CH ₂ - contained in the chain hydrocarbon group may be replaced by -O- or -CO-), and even more preferably a single bond or a chain hydrocarbon group having 1 to 3 carbon atoms.
m21 is an integer of 1 to 5, preferably an integer of 1 to 4, more preferably an integer of 1 to 3, still more preferably 1 or 2, and even more preferably 2. When m21 is 1 or 2, the following structure, which is m-substituted with respect to SO ₃ ^-, is preferable.

In the above formula, R ^21' has the same definition as R ²¹ described above, and may be the same as or different from R ²¹ .

Examples of the alkyl group having 1 to 6 carbon atoms for R ²² include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, and a hexyl group. The number of carbon atoms in the alkyl group is preferably 1 to 4, and more preferably 1 to 3. Examples of groups in which -CH ₂ - in the alkyl group is replaced by -O- or -CO- include the same groups as those exemplified in this specification, within the range permitted by the upper limit of the number of carbon atoms.
Examples of the halogen atom for R ²² include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Each R ²² is independently preferably a halogen atom or an alkyl group having 1 to 4 carbon atoms (wherein the --CH ₂ -- contained in the alkyl group may be replaced by --O-- or --CO--), more preferably a fluorine atom, an iodine atom or an alkyl group having 1 to 3 carbon atoms (wherein the --CH ₂ -- contained in the alkyl group may be replaced by --O-- or --CO--), and even more preferably a fluorine atom, an iodine atom, a hydroxy group, a methoxy group or a methyl group.
m22 is an integer of 0 to 4, preferably an integer of 0 to 3, and more preferably an integer of 0 to 2. In one embodiment, m22 is preferably 0. In another embodiment, m22 is preferably 1 or 2. When m22 is 1, R ²² is preferably a halogen atom, and more preferably R ²² is a fluorine atom or iodine atom. When m22 is 2, it is preferable that one of R ²² is a halogen atom and the other is a halogen atom or an alkyl group having 1 to 4 carbon atoms, and more preferably one of R ²² is a fluorine atom or iodine atom and the other is a fluorine atom, iodine atom, or an alkyl group having 1 to 3 carbon atoms.

Examples of the anion in the salt represented by formula (B2) include the following anions. Among them, the anions represented by formulas (B2a-1) to (B2a-20) are preferred, and the anions represented by formulas (B2a-1) to (B2a-11) and (B2a-16) to (B2a-20) are more preferred.

In addition, in another embodiment of the acid generator (B), a salt in which the anion in the salt represented by formula (B1) or the like is replaced with a sulfonylimide anion, a sulfonylmethide anion, a carboxylate anion, or the like, can also be suitably used as the acid generator (B).

スルホニルメチドアニオンとしては、以下のものが挙げられる。

カルボン酸アニオンとしては、以下のものが挙げられる。

Examples of the sulfonylimide anion include the following:

Examples of sulfonylmethide anions include the following:

Examples of carboxylate anions include the following:

［式（ｂ２－１）～式（ｂ２－４）中、
Ｒ^b4～Ｒ^b6は、それぞれ独立に、炭素数１～３０の鎖式炭化水素基、炭素数３～３６の脂環式炭化水素基又は炭素数６～３６の芳香族炭化水素基を表し、該鎖式炭化水素基に含まれる水素原子は、ヒドロキシ基、炭素数１～１２のアルコキシ基、炭素数３～１２の脂環式炭化水素基又は炭素数６～１８の芳香族炭化水素基で置換されていてもよく、該脂環式炭化水素基に含まれる水素原子は、ハロゲン原子、炭素数１～１８の脂肪族炭化水素基、炭素数２～４のアルキルカルボニル基又はグリシジルオキシ基で置換されていてもよく、該芳香族炭化水素基に含まれる水素原子は、ハロゲン原子、ヒドロキシ基、炭素数１～１８の脂肪族炭化水素基、炭素数１～１２のフッ化アルキル基又は炭素数１～１２のアルコキシ基で置換されていてもよい。
Ｒ^b4とＲ^b5とは、互いに結合してそれらが結合する硫黄原子と一緒になって環を形成してもよく、該環に含まれる－ＣＨ₂－は、－Ｏ－、－Ｓ－又は－ＣＯ－に置き換わってもよい。
Ｒ^b7及びＲ^b8は、それぞれ独立に、ハロゲン原子、ヒドロキシ基、炭素数１～１２の脂肪族炭化水素基、炭素数１～１２のフッ化アルキル基又は炭素数１～１２のアルコキシ基を表す。
ｍ２及びｎ２は、それぞれ独立に０～５のいずれかの整数を表す。
ｍ２が２以上のとき、複数のＲ^b7は同一でも異なってもよく、ｎ２が２以上のとき、複数のＲ^b8は同一でも異なってもよい。
Ｒ^b9及びＲ^b10は、それぞれ独立に、炭素数１～３６の鎖式炭化水素基又は炭素数３～３６の脂環式炭化水素基を表す。
Ｒ^b9とＲ^b10とは、互いに結合してそれらが結合する硫黄原子と一緒になって環を形成してもよく、該環に含まれる－ＣＨ₂－は、－Ｏ－、－Ｓ－又は－ＣＯ－に置き換わってもよい。
Ｒ^b11は、水素原子、炭素数１～３６の鎖式炭化水素基、炭素数３～３６の脂環式炭化水素基又は炭素数６～１８の芳香族炭化水素基を表す。
Ｒ^b12は、炭素数１～１２の鎖式炭化水素基、炭素数３～１８の脂環式炭化水素基又は炭素数６～１８の芳香族炭化水素基を表し、該鎖式炭化水素基に含まれる水素原子は、炭素数６～１８の芳香族炭化水素基で置換されていてもよく、該芳香族炭化水素基に含まれる水素原子は、炭素数１～１２のアルコキシ基又は炭素数１～１２のアルキルカルボニルオキシ基で置換されていてもよい。
Ｒ^b11とＲ^b12とは、互いに結合してそれらが結合する－ＣＨ－ＣＯ－を含めて環を形成していてもよく、該環に含まれる－ＣＨ₂－は、－Ｏ－、－Ｓ－又は－ＣＯ－に置き換わってもよい。
Ｒ^b13～Ｒ^b18は、それぞれ独立に、ハロゲン原子、ヒドロキシ基、炭素数１～１２の脂肪族炭化水素基、炭素数１～１２のフッ化アルキル基又は炭素数１～１２のアルコキシ基を表す。
Ｒ^b13とＲ^b14とは、互いに結合してそれらが結合するベンゼン環と一緒になって硫黄原子を含む環を形成してもよく、該環に含まれる－ＣＨ₂－は、－Ｏ－、－Ｓ－又は－ＣＯ－に置き換わってもよい。
Ｌ^b31は、硫黄原子又は酸素原子を表す。
ｏ２、ｐ２、ｓ２、及びｔ２は、それぞれ独立に、０～５のいずれかの整数を表す。
ｑ２及びｒ２は、それぞれ独立に、０～４のいずれかの整数を表す。
ｕ２は０又は１を表す。
ｏ２が２以上のとき、複数のＲ^b13は同一又は相異なり、ｐ２が２以上のとき、複数のＲ^b14は同一又は相異なり、ｑ２が２以上のとき、複数のＲ^b15は同一又は相異なり、ｒ２が２以上のとき、複数のＲ^b16は同一又は相異なり、ｓ２が２以上のとき、複数のＲ^b17は同一又は相異なり、ｔ２が２以上のとき、複数のＲ^b18は同一又は相異なる。］
ｕ２が０のとき、ｏ２、ｐ２、ｑ２及びｒ２のうちいずれか１つは１以上であり、Ｒ^b13～Ｒ^b1６のうち少なくとも１つはハロゲン原子であることが好ましく、ｕ２が１のとき、ｏ２、ｐ２、ｓ２、ｔ２、ｑ２及びｒ２のうちいずれか１つは１以上であり、Ｒ^b13～Ｒ^b18のうち少なくとも１つはハロゲン原子であることが好ましい。
さらに、ｕ２が０のとき、ｒ２は１以上であることが好ましく、１であることがさらに好ましい。また、ｕ２が０、かつ、ｒ２が１以上のとき、Ｒ^ｂ１６がハロゲン原子であることが好ましい。 Examples of the organic cation of Z ⁺ include an organic onium cation, an organic sulfonium cation, an organic iodonium cation, an organic ammonium cation, a benzothiazolium cation, and an organic phosphonium cation. Among these, an organic sulfonium cation and an organic iodonium cation are preferred, and an arylsulfonium cation is more preferred. Specific examples include cations represented by any one of formulas (b2-1) to (b2-4) (hereinafter, these may be referred to as "cation (b2-1)" depending on the formula number).

[In formulas (b2-1) to (b2-4),
R ^b4 to R ^b6 each independently represent a chain hydrocarbon group having 1 to 30 carbon atoms, an alicyclic hydrocarbon group having 3 to 36 carbon atoms, or an aromatic hydrocarbon group having 6 to 36 carbon atoms, a hydrogen atom contained in the chain hydrocarbon group may be substituted with a hydroxy group, an alkoxy group having 1 to 12 carbon atoms, an alicyclic hydrocarbon group having 3 to 12 carbon atoms, or an aromatic hydrocarbon group having 6 to 18 carbon atoms, a hydrogen atom contained in the alicyclic hydrocarbon group may be substituted with a halogen atom, an aliphatic hydrocarbon group having 1 to 18 carbon atoms, an alkylcarbonyl group having 2 to 4 carbon atoms, or a glycidyloxy group, and a hydrogen atom contained in the aromatic hydrocarbon group may be substituted with a halogen atom, a hydroxy group, an aliphatic hydrocarbon group having 1 to 18 carbon atoms, a fluorinated alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms.
R ^b4 and R ^b5 may be bonded to each other to form a ring together with the sulfur atom to which they are bonded, and --CH ₂ -- contained in the ring may be replaced by --O--, --S-- or --CO--.
R ^b7 and R ^b8 each independently represent a halogen atom, a hydroxyl group, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, a fluorinated alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms.
m2 and n2 each independently represent an integer of 0 to 5.
When m2 is 2 or more, multiple R ^b7s may be the same or different, and when n2 is 2 or more, multiple R ^b8s may be the same or different.
R ^b9 and R ^b10 each independently represent a chain hydrocarbon group having 1 to 36 carbon atoms or an alicyclic hydrocarbon group having 3 to 36 carbon atoms.
R ^b9 and R ^b10 may be bonded to each other to form a ring together with the sulfur atom to which they are bonded, and --CH ₂ -- contained in the ring may be replaced by --O--, --S-- or --CO--.
R ^b11 represents a hydrogen atom, a chain hydrocarbon group having 1 to 36 carbon atoms, an alicyclic hydrocarbon group having 3 to 36 carbon atoms, or an aromatic hydrocarbon group having 6 to 18 carbon atoms.
R ^b12 represents an open chain hydrocarbon group having 1 to 12 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, or an aromatic hydrocarbon group having 6 to 18 carbon atoms, a hydrogen atom contained in the open chain hydrocarbon group may be substituted with an aromatic hydrocarbon group having 6 to 18 carbon atoms, and a hydrogen atom contained in the aromatic hydrocarbon group may be substituted with an alkoxy group having 1 to 12 carbon atoms or an alkylcarbonyloxy group having 1 to 12 carbon atoms.
R ^b11 and R ^b12 may be bonded to each other to form a ring including the --CH--CO-- to which they are bonded, and --CH ₂ -- contained in the ring may be replaced by --O--, --S-- or --CO--.
R ^b13 to R ^b18 each independently represent a halogen atom, a hydroxyl group, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, a fluorinated alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms.
R ^b13 and R ^b14 may be bonded to each other to form a ring containing a sulfur atom together with the benzene ring to which they are bonded, and --CH ₂ -- contained in the ring may be replaced by --O--, --S-- or --CO--.
L ^b31 represents a sulfur atom or an oxygen atom.
o2, p2, s2, and t2 each independently represent an integer of 0 to 5.
q2 and r2 each independently represent an integer of 0 to 4.
u2 represents 0 or 1.
When o2 is 2 or more, multiple R ^b13 are the same or different, when p2 is 2 or more, multiple R ^b14 are the same or different, when q2 is 2 or more, multiple R ^b15 are the same or different, when r2 is 2 or more, multiple R ^b16 are the same or different, when s2 is 2 or more, multiple R ^b17 are the same or different, and when t2 is 2 or more, multiple R ^b18 are the same or different.
When u2 is 0, it is preferable that any one of o2, p2, q2, and r2 is 1 or more, and at least one of R ^b13 to R ^b16 is a halogen atom; and when u2 is 1, it is preferable that any one of o2, p2, s2, t2, q2, and r2 is 1 or more, and at least one of R ^b13 to R ^b18 is a halogen atom.
Furthermore, when u2 is 0, r2 is preferably 1 or more, and more preferably 1. Furthermore, when u2 is 0 and r2 is 1 or more, R ^b16 is preferably a halogen atom.

特に、Ｒ^b9～Ｒ^b12の脂環式炭化水素基は、好ましくは炭素数３～１８、より好ましくは炭素数４～１２である。 The aliphatic hydrocarbon group refers to a chain hydrocarbon group and an alicyclic hydrocarbon group.
Examples of the chain hydrocarbon group include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, pentyl, hexyl, octyl and 2-ethylhexyl groups.
In particular, the chain hydrocarbon groups of R ^b9 to R ^b12 preferably have 1 to 12 carbon atoms.
The alicyclic hydrocarbon group may be either monocyclic or polycyclic, and examples of the monocyclic alicyclic hydrocarbon group include cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and cyclodecyl groups. Examples of the polycyclic alicyclic hydrocarbon group include decahydronaphthyl, adamantyl, and norbornyl groups, as well as the following groups:

In particular, the alicyclic hydrocarbon groups of R ^b9 to R ^b12 preferably have 3 to 18 carbon atoms, and more preferably have 4 to 12 carbon atoms.

Examples of the alicyclic hydrocarbon group in which a hydrogen atom is substituted with an aliphatic hydrocarbon group include a methylcyclohexyl group, a dimethylcyclohexyl group, a 2-methyladamantan-2-yl group, a 2-ethyladamantan-2-yl group, a 2-isopropyladamantan-2-yl group, a methylnorbornyl group, an isobornyl group, etc. In the alicyclic hydrocarbon group in which a hydrogen atom is substituted with an aliphatic hydrocarbon group, the total number of carbon atoms in the alicyclic hydrocarbon group and the aliphatic hydrocarbon group is preferably 20 or less.
The fluorinated alkyl group refers to an alkyl group having 1 to 12 carbon atoms and a fluorine atom, and examples of such groups include a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a perfluorobutyl group, etc. The number of carbon atoms in the fluorinated alkyl group is preferably 1 to 9, more preferably 1 to 6, and even more preferably 1 to 4.

Examples of the aromatic hydrocarbon group include aryl groups such as a phenyl group, a biphenyl group, a naphthyl group, a phenanthryl group, etc. The aromatic hydrocarbon group may have a chain hydrocarbon group or an alicyclic hydrocarbon group, and examples thereof include aromatic hydrocarbon groups having a chain hydrocarbon group (such as a tolyl group, a xylyl group, a cumenyl group, a mesityl group, a p-ethylphenyl group, a p-tert-butylphenyl group, a 2,6-diethylphenyl group, a 2-methyl-6-ethylphenyl group, etc.) and aromatic hydrocarbon groups having an alicyclic hydrocarbon group (such as a p-cyclohexylphenyl group, a p-adamantylphenyl group, etc.).
When the aromatic hydrocarbon group has a chain hydrocarbon group or an alicyclic hydrocarbon group, a chain hydrocarbon group having 1 to 18 carbon atoms and an alicyclic hydrocarbon group having 3 to 18 carbon atoms are preferred.
An example of the aromatic hydrocarbon group in which a hydrogen atom is substituted with an alkoxy group is a p-methoxyphenyl group.
Examples of the chain hydrocarbon group in which a hydrogen atom has been substituted with an aromatic hydrocarbon group include aralkyl groups such as a benzyl group, a phenethyl group, a phenylpropyl group, a trityl group, a naphthylmethyl group, and a naphthylethyl group.

Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, an octyloxy group, a decyloxy group, and a dodecyloxy group.
Examples of the alkylcarbonyl group include an acetyl group, a propionyl group, and a butyryl group.
Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Examples of the alkylcarbonyloxy group include a methylcarbonyloxy group, an ethylcarbonyloxy group, a propylcarbonyloxy group, an isopropylcarbonyloxy group, a butylcarbonyloxy group, a sec-butylcarbonyloxy group, a tert-butylcarbonyloxy group, a pentylcarbonyloxy group, a hexylcarbonyloxy group, an octylcarbonyloxy group, and a 2-ethylhexylcarbonyloxy group.

The ring formed by R ^b4 and R ^b5 bonding to each other together with the sulfur atom to which they are bonded may be any of monocyclic, polycyclic, aromatic, non-aromatic, saturated and unsaturated rings. Examples of this ring include rings having 3 to 18 carbon atoms, and preferably rings having 4 to 18 carbon atoms. Examples of the ring containing a sulfur atom include 3- to 12-membered rings, and preferably 3- to 7-membered rings, and examples of such rings include the following rings. * represents a bonding site.

The ring formed by R ^b9 and R ^b10 together may be any of monocyclic, polycyclic, aromatic, non-aromatic, saturated and unsaturated rings. This ring may be a 3- to 12-membered ring, preferably a 3- to 7-membered ring. Examples of the ring include a thiolane-1-ium ring (tetrahydrothiophenium ring), a thian-1-ium ring, and a 1,4-oxathiane-4-ium ring.
The ring formed by R ^b11 and R ^b12 together may be any of monocyclic, polycyclic, aromatic, non-aromatic, saturated and unsaturated rings. This ring may be a 3- to 12-membered ring, preferably a 3- to 7-membered ring. Examples of the ring include an oxocycloheptane ring, an oxocyclohexane ring, an oxonorbornane ring, and an oxoadamantane ring.

カチオン（ｂ２－２）としては、以下のカチオンが挙げられる。

カチオン（ｂ２－３）としては、以下のカチオンが挙げられる。

カチオン（ｂ２－４）としては、以下のカチオンが挙げられる。

Among the cations (b2-1) to (b2-4), the cation (b2-1) is preferred.
Examples of the cation (b2-1) include the following cations.

Examples of the cation (b2-2) include the following cations.

Examples of the cation (b2-3) include the following cations.

Examples of the cation (b2-4) include the following cations.

The acid generator (B) is a combination of the above-mentioned anion and the above-mentioned organic cation, which can be combined in any desired manner. The acid generator (B) is preferably a combination of an anion represented by any of formulas (B1a-1) to (B1a-4), (B1a-7) to (B1a-11), (B1a-14) to (B1a-30), (B1a-35) to (B1a-70), and (B2a-1) to (B2a-20), and a cation (b2-1), a cation (b2-2), a cation (b2-3), or a cation (b2-4).

The acid generator (B) is preferably any of those represented by formulae (B1-1) to (B1-105) and (B2-1) to (B2-20). Among them, those containing an arylsulfonium cation are preferred, and those represented by formulae (B1-1) to (B1-3), (B1-5) to (B1-7), (B1-11) to (B1-14), (B1-20) to (B1-26), (B1-29), (B1-31) to (B1-105), and (B2-1) to (B2-20) are particularly preferred.

The content of the acid generator (B1) is preferably 30% by mass or more and 100% by mass or less, and more preferably 50% by mass or more and 100% by mass or less, based on the total amount of the acid generator (B), and further preferably the acid generator (B1) is essentially the only component.

The content of the acid generator (B) in the resist composition is preferably from 1 mass % to 45 mass %, more preferably from 1 mass % to 40 mass %, and even more preferably from 3 mass % to 40 mass %, based on the solid content of the resist composition.
The content of the acid generator (B) is preferably 1 part by mass or more (more preferably 3 parts by mass or more) and preferably 45 parts by mass or less (more preferably 35 parts by mass or less) per 100 parts by mass of the resin (A2).
The resist composition of the present invention may contain one type of acid generator (B) alone, or may contain multiple types.

<Solvent (E)>
The content of the solvent (E) in the resist composition is usually from 90% by mass to 99.9% by mass, preferably from 92% by mass to 99% by mass, and more preferably from 94% by mass to 99% by mass. The content of the solvent (E) can be measured by a known analytical method such as liquid chromatography or gas chromatography.

Examples of the solvent (E) include glycol ether esters such as ethyl cellosolve acetate, methyl cellosolve acetate, and propylene glycol monomethyl ether acetate; glycol ethers such as propylene glycol monomethyl ether; esters such as ethyl lactate, butyl acetate, amyl acetate, and ethyl pyruvate; ketones such as acetone, methyl isobutyl ketone, 2-heptanone, and cyclohexanone; cyclic esters such as γ-butyrolactone; and the like. One type of solvent (E) may be used alone, or two or more types may be used.

<Quencher (C)>
Examples of the quencher (C) include a salt that generates an acid having a weaker acidity than the acid generated from the acid generator (acid generator (B)), and a basic nitrogen-containing organic compound. The content of the quencher (C) is preferably about 0.01 to 15 mass %, more preferably about 0.01 to 10 mass %, even more preferably about 0.1 to 8 mass %, and even more preferably about 0.1 to 7 mass %, based on the solid content of the resist composition.

<Salt generating an acid weaker in acidity than the acid generated from the acid generator>
The acidity of a salt that generates an acid weaker than the acid generated from an acid generator is indicated by the acid dissociation constant (pKa). A salt that generates an acid weaker than the acid generated from an acid generator is a salt whose acid dissociation constant of the acid generated from the salt is usually -3<pKa, preferably -1<pKa<7, and more preferably 0<pKa<5.
Examples of the salt that generates an acid having a weaker acidity than the acid generated from the acid generator include a salt represented by the following formula, a salt represented by formula (D) described in JP-A-2015-147926 (hereinafter, sometimes referred to as "weak acid inner salt (D)"), and salts described in JP-A-2012-229206, JP-A-2012-6908, JP-A-2012-72109, JP-A-2011-39502, and JP-A-2011-191745. The salt that generates an acid having a weaker acidity than the acid generated from the acid generator is preferably a salt (salt having a carboxylate anion) that generates a carboxylic acid having a weaker acidity than the acid generated from the acid generator, more preferably a weak acid inner salt (D), and even more preferably, among the weak acid inner salts (D), a diphenyliodonium salt containing a phenyl group substituted with a carboxylate anion.

［式（Ｄ）中、
Ｒ^D1及びＲ^D2は、それぞれ独立に、炭素数１～１２の炭化水素基、炭素数１～６のアルコキシ基、炭素数２～７のアシル基、炭素数２～７のアシルオキシ基、炭素数２～７のアルコキシカルボニル基、ニトロ基又はハロゲン原子を表す。
ｍ’及びｎ’は、それぞれ独立に、０～４のいずれかの整数を表し、ｍ’が２以上の場合、複数のＲ^D1は同一であっても異なってもよく、ｎ’が２以上の場合、複数のＲ^D2は同一であっても異なってもよい。］
Ｒ^D1及びＲ^D2の炭化水素基としては、鎖式炭化水素基、脂環式炭化水素基、芳香族炭化水素基及びこれらを組み合わせることにより形成される基等が挙げられる。
鎖式炭化水素基としては、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基、イソブチル基、ｔｅｒｔ－ブチル基、ペンチル基、ヘキシル基、ノニル基等のアルキル基が挙げられる。
脂環式炭化水素基としては、単環式及び多環式のいずれでもよく、飽和及び不飽和のいずれでもよい。シクロプロピル基、シクロブチル基、シクロペンチル基、シクロへキシル基、シクロノニル基、シクロドデシル基等のシクロアルキル基、ノルボニル基、アダマンチル基等が挙げられる。
芳香族炭化水素基としては、フェニル基、１－ナフチル基、２－ナフチル基、２－メチルフェニル基、３－メチルフェニル基、４－メチルフェニル基、４－エチルフェニル基、４－プロピルフェニル基、４－イソプロピルフェニル基、４－ブチルフェニル基、４－ｔ－ブチルフェニル基、４－ヘキシルフェニル基、４－シクロヘキシルフェニル基、アントリル基、ｐ－アダマンチルフェニル基、トリル基、キシリル基、クメニル基、メシチル基、ビフェニル基、フェナントリル基、２，６－ジエチルフェニル基、２－メチル－６－エチルフェニル基等のアリール基等が挙げられる。
これらを組み合わせることにより形成される基としては、アルキル－シクロアルキル基、シクロアルキル－アルキル基、アラルキル基（例えば、フェニルメチル基、１－フェニルエチル基、２－フェニルエチル基、１－フェニル－１－プロピル基、１－フェニル－２－プロピル基、２－フェニル－２－プロピル基、３－フェニル－１－プロピル基、４－フェニル－１－ブチル基、５－フェニル－１－ペンチル基、６－フェニル－１－ヘキシル基等）等が挙げられる。
アルコキシ基としては、メトキシ基、エトキシ基等が挙げられる。
アシル基としては、アセチル基、プロパノイル基、ベンゾイル基、シクロヘキサンカルボニル基等が挙げられる。
アシルオキシ基としては、上記アシル基にオキシ基（－Ｏ－）が結合した基等が挙げられる。
アルコキシカルボニル基としては、上記アルコキシ基にカルボニル基（－ＣＯ－）が結合した基等が挙げられる。
ハロゲン原子としては、フッ素原子、塩素原子、臭素原子等が挙げられる。
Ｒ^D1及びＲ^D2は、それぞれ独立に、炭素数１～８のアルキル基、炭素数３～１０のシクロアルキル基、炭素数１～６のアルコキシ基、炭素数２～４のアシル基、炭素数２～４のアシルオキシ基、炭素数２～４のアルコキシカルボニル基、ニトロ基又はハロゲン原子が好ましい。
ｍ’及びｎ’は、それぞれ独立に、０～２のいずれかの整数であることが好ましく、０であることがより好ましい。ｍ’が２以上の場合、複数のＲ^D1は同一であっても異なってもよく、ｎ’が２以上の場合、複数のＲ^D2は同一であっても異なってもよい。
より具体的には、以下の塩が挙げられる。

The weak acid inner salt (D) is preferably a diphenyliodonium salt having an iodonium cation to which two phenyl groups are bonded and a carboxylate anion substituted for at least one of the two phenyl groups bonded to the iodonium cation, and examples of such salts include those represented by the following formula:

[In the formula (D),
R ^D1 and R ^D2 each independently represent a hydrocarbon group having 1 to 12 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an acyl group having 2 to 7 carbon atoms, an acyloxy group having 2 to 7 carbon atoms, an alkoxycarbonyl group having 2 to 7 carbon atoms, a nitro group, or a halogen atom.
m' and n' each independently represent an integer of 0 to 4, and when m' is 2 or greater, multiple R ^D1s may be the same or different, and when n' is 2 or greater, multiple R ^D2s may be the same or different.
Examples of the hydrocarbon group for R ^D1 and R ^D2 include chain hydrocarbon groups, alicyclic hydrocarbon groups, aromatic hydrocarbon groups, and groups formed by combining these groups.
Examples of the chain hydrocarbon group include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, and nonyl groups.
The alicyclic hydrocarbon group may be either monocyclic or polycyclic, and may be either saturated or unsaturated. Examples of the alicyclic hydrocarbon group include cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclononyl, and cyclododecyl, norbornyl, and adamantyl groups.
Examples of the aromatic hydrocarbon group include aryl groups such as a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a 2-methylphenyl group, a 3-methylphenyl group, a 4-methylphenyl group, a 4-ethylphenyl group, a 4-propylphenyl group, a 4-isopropylphenyl group, a 4-butylphenyl group, a 4-t-butylphenyl group, a 4-hexylphenyl group, a 4-cyclohexylphenyl group, an anthryl group, a p-adamantylphenyl group, a tolyl group, a xylyl group, a cumenyl group, a mesityl group, a biphenyl group, a phenanthryl group, a 2,6-diethylphenyl group, and a 2-methyl-6-ethylphenyl group.
Groups formed by combining these groups include alkyl-cycloalkyl groups, cycloalkyl-alkyl groups, and aralkyl groups (e.g., phenylmethyl group, 1-phenylethyl group, 2-phenylethyl group, 1-phenyl-1-propyl group, 1-phenyl-2-propyl group, 2-phenyl-2-propyl group, 3-phenyl-1-propyl group, 4-phenyl-1-butyl group, 5-phenyl-1-pentyl group, and 6-phenyl-1-hexyl group).
Examples of the alkoxy group include a methoxy group and an ethoxy group.
Examples of the acyl group include an acetyl group, a propanoyl group, a benzoyl group, and a cyclohexanecarbonyl group.
Examples of the acyloxy group include the above acyl groups to which an oxy group (—O—) is bonded.
Examples of the alkoxycarbonyl group include the above alkoxy groups bonded to a carbonyl group (--CO--).
Examples of the halogen atom include a fluorine atom, a chlorine atom, and a bromine atom.
^R and ^R are each preferably an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an acyl group having 2 to 4 carbon atoms, an acyloxy group having 2 to 4 carbon atoms, an alkoxycarbonyl group having 2 to 4 carbon atoms, a nitro group, or a halogen atom.
Each of m' and n' is preferably an integer of 0 to 2, and more preferably 0. When m' is 2 or more, multiple R ^D1s may be the same or different, and when n' is 2 or more, multiple R ^D2s may be the same or different.
More specifically, the following salts are included:

The basic nitrogen-containing organic compound includes amines and ammonium salts. The amines include aliphatic amines and aromatic amines. The aliphatic amines include primary amines, secondary amines, and tertiary amines.
Examples of amines include 1-naphthylamine, 2-naphthylamine, aniline, diisopropylaniline, 2-, 3- or 4-methylaniline, 4-nitroaniline, N-methylaniline, N,N-dimethylaniline, diphenylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine, triethylamine, trimethylamine, tripropylamine, tributylamine, Amines, tripentylamine, trihexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, methyldibutylamine, methyldipentylamine, methyldihexylamine, methyldicyclohexylamine, methyldiheptylamine, methyldioctylamine, methyldinonylamine, methyldidecylamine, ethyldibutylamine, ethyldipentylamine, ethyldihexylamine, ethyldiheptylamine, ethyldioctylamine, ethyldinonylamine, ethyldidecylamine amine, dicyclohexylmethylamine, tris[2-(2-methoxyethoxy)ethyl]amine, triisopropanolamine, ethylenediamine, tetramethylenediamine, hexamethylenediamine, 4,4'-diamino-1,2-diphenylethane, 4,4'-diamino-3,3'-dimethyldiphenylmethane, 4,4'-diamino-3,3'-diethyldiphenylmethane, 2,2'-methylenebisaniline, imidazole, 4-methylimidazole, pyridine, 4-methylpyridine, 1,2-di(2-pyridyl)ethane Examples of the amines include 1,2-di(4-pyridyl)ethane, 1,2-di(2-pyridyl)ethene, 1,2-di(4-pyridyl)ethene, 1,3-di(4-pyridyl)propane, 1,2-di(4-pyridyloxy)ethane, di(2-pyridyl)ketone, 4,4'-dipyridyl sulfide, 4,4'-dipyridyl disulfide, 2,2'-dipyridylamine, 2,2'-dipicolylamine, and bipyridine. Preferred are aromatic amines such as diisopropylaniline, and more preferred are 2,6-diisopropylaniline.
Examples of the ammonium salt include tetramethylammonium hydroxide, tetraisopropylammonium hydroxide, tetrabutylammonium hydroxide, tetrahexylammonium hydroxide, tetraoctylammonium hydroxide, phenyltrimethylammonium hydroxide, 3-(trifluoromethyl)phenyltrimethylammonium hydroxide, tetra-n-butylammonium salicylate, and choline.

The resist composition of the present invention may also contain salt (I6-s) as an acid generator. The content of salt (I6-s) is preferably 1 part by mass or less, and more preferably 0.1 parts by mass or less, per 100 parts by mass of resin (A2).

<Other Ingredients>
The resist composition of the present invention may contain components other than the above-mentioned components (hereinafter, sometimes referred to as "other components (F)") as necessary. There are no particular limitations on the other components (F), and additives known in the resist field, such as sensitizers, dissolution inhibitors, surfactants, stabilizers, dyes, etc., can be used.

Preparation of Resist Composition
The resist composition of the present invention can be prepared by mixing resin (A1), optionally acid generator (B), resin (A2), resins other than resin (A1) and resin (A2), solvent (E), quencher (C), and other components (F). The order of mixing is arbitrary and is not particularly limited. The temperature during mixing can be selected from 10 to 40° C. depending on the type of resin, the solubility of the resin in the solvent (E), and the like. The mixing time can be selected from 0.5 to 24 hours depending on the mixing temperature. The mixing means is not particularly limited, and stirring and mixing can be used.
After mixing the components, it is preferable to filter the mixture using a filter having a pore size of about 0.003 to 0.2 μm.

<Method for Producing Resist Pattern>
The method for producing a resist pattern of the present invention comprises the steps of:
(1) applying the resist composition of the present invention onto a substrate;
(2) A step of drying the applied composition to form a composition layer;
(3) exposing the composition layer to light;
(4) a step of heating the composition layer after exposure, and (5) a step of developing the composition layer after heating.
The resist composition can be applied onto a substrate using a commonly used device such as a spin coater. Examples of the substrate include inorganic substrates such as silicon wafers and organic substrates having a resist film or the like formed on the surface. Before applying the resist composition, the substrate may be cleaned, and an anti-reflective film or the like may be formed on the substrate.
The composition after coating is dried to remove the solvent and form a composition layer. Drying is carried out, for example, by evaporating the solvent using a heating device such as a hot plate (so-called pre-baking), or by using a vacuum device. The heating temperature is preferably 50 to 200° C., and the heating time is preferably 10 to 180 seconds. The pressure during drying under reduced pressure is preferably about 1 to 1.0×10 ⁵ Pa.
The obtained composition layer is usually exposed using an exposure machine. The exposure machine may be an immersion exposure machine. As the exposure light source, various types can be used, such as those that emit ultraviolet laser light such as KrF excimer laser (wavelength 248 nm), ArF excimer laser (wavelength 193 nm), and _F2 excimer laser (wavelength 157 nm), those that convert the wavelength of laser light from a solid laser light source (YAG or semiconductor laser, etc.) to emit harmonic laser light in the far ultraviolet or vacuum ultraviolet range, and those that irradiate electron beams or extreme ultraviolet light (EUV). In this specification, irradiation with these radiations may be collectively referred to as "exposure". During exposure, exposure is usually performed through a mask corresponding to the desired pattern. When the exposure light source is an electron beam, exposure may be performed by direct drawing without using a mask.
The composition layer after exposure is subjected to a heat treatment (so-called post-exposure bake) in order to promote a deprotection reaction in the acid labile groups. The heating temperature is usually about 50 to 200° C., preferably about 70 to 150° C. A chemical treatment (silylation) may be performed to adjust the hydrophilicity or hydrophobicity of the resin on the surface side of the composition after heating. In addition, before development, the steps of applying a resist composition, drying, exposing, and heating may be repeatedly performed on the composition layer after exposure.
The heated composition layer is usually developed using a developing device and a developer. Examples of the developing method include a dip method, a paddle method, a spray method, and a dynamic dispense method. The developing temperature is preferably, for example, 5 to 60° C., and the developing time is preferably, for example, 5 to 300 seconds. By selecting the type of developer as follows, a positive resist pattern or a negative resist pattern can be produced.
When a positive resist pattern is produced from the resist composition of the present invention, an alkaline developer is used as the developer. The alkaline developer may be any of various alkaline aqueous solutions used in this field. Examples include aqueous solutions of tetramethylammonium hydroxide and (2-hydroxyethyl)trimethylammonium hydroxide (commonly known as choline). The alkaline developer may contain a surfactant.
After development, the resist pattern is preferably washed with ultrapure water, and then water remaining on the substrate and the pattern is removed.
When producing a negative resist pattern from the resist composition of the present invention, a developer containing an organic solvent (hereinafter sometimes referred to as an "organic developer") is used as the developer.
Examples of the organic solvent contained in the organic developer include ketone solvents such as 2-hexanone and 2-heptanone; glycol ether ester solvents such as propylene glycol monomethyl ether acetate; ester solvents such as butyl acetate; glycol ether solvents such as propylene glycol monomethyl ether; amide solvents such as N,N-dimethylacetamide; and aromatic hydrocarbon solvents such as anisole.
The content of the organic solvent in the organic developer is preferably from 90% by mass to 100% by mass, more preferably from 95% by mass to 100% by mass, and further preferably consists essentially of the organic solvent.
Among them, the organic developer is preferably a developer containing butyl acetate and/or 2-heptanone. The total content of butyl acetate and 2-heptanone in the organic developer is preferably 50% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably substantially only butyl acetate and/or 2-heptanone.
The organic developer may contain a surfactant and may contain a small amount of water.
During development, the development may be stopped by replacing the organic developer with a different type of solvent.
The resist pattern after development is preferably washed with a rinse solution. There are no particular limitations on the rinse solution as long as it does not dissolve the resist pattern, and a solution containing a general organic solvent can be used, preferably an alcohol solvent or an ester solvent.
After cleaning, it is preferable to remove any rinsing liquid remaining on the substrate and the pattern.

<Application>
The resist composition of the present invention is suitable as a resist composition for KrF excimer laser exposure, a resist composition for ArF excimer laser exposure, a resist composition for electron beam (EB) exposure, or a resist composition for EUV exposure, and is particularly suitable as a resist composition for ArF excimer laser exposure, and is useful for semiconductor microfabrication.

The present invention will be described in more detail with reference to examples. In the examples, "%" and "parts" expressing the content or amount used are based on mass unless otherwise specified.
The weight average molecular weight is a value determined by gel permeation chromatography under the following analytical conditions:
Column: TSKgel Multipore HXL-M x 3+guardcolumn (Tosoh Corporation)
Eluent: Tetrahydrofuran Flow rate: 1.0 mL/min
Detector: RI detector Column temperature: 40℃
Injection volume: 100 μl
Molecular weight standard: Standard polystyrene (Tosoh Corporation)
The structure of the compound was confirmed by measuring the molecular ion peak using mass spectrometry (LC: Agilent 1100 model, MASS: Agilent LC/MSD model). In the following examples, the value of this molecular ion peak is indicated by "MASS".

Synthesis of Resin The compounds (monomers) used in the synthesis of Resin (A) are shown below. Hereinafter, these compounds will be referred to as "monomer (a1-1-3)" etc. according to their formula numbers.

Synthesis Example 1: Synthesis of Resin A2-1 Monomers were used, and the molar ratio [monomer (a1-1-3):monomer (a1-2-5):monomer (a2-1-3):monomer (a3-4-2)] was mixed to 45:14:2.5:38.5, and propylene glycol monomethyl ether acetate was added in an amount 1.5 times the total monomer amount to obtain a solution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to this solution in amounts of 1 mol% and 3 mol%, respectively, relative to the total monomer amount, and these were heated at 73 ° C. for about 5 hours. The resulting reaction mixture was poured into a large amount of a methanol/water mixed solvent to precipitate the resin, and the resin was filtered. The obtained resin was dissolved again in propylene glycol monomethyl ether acetate, and the resulting solution was poured into a methanol/water mixed solvent to precipitate the resin, which was then filtered. This reprecipitation procedure was repeated twice to obtain Resin A2-1 having a weight average molecular weight of 7.6 x ¹⁰³ in a yield of 68%. This Resin A2-1 has the following structural units.

Synthesis Example 2: Synthesis of Resin A2-2 Monomers (a1-1-3), (a1-5-1), (a2-1-3) and (a3-4-2) were used as monomers, and the molar ratio [monomer (a1-1-3): monomer (a1-5-1): monomer (a2-1-3): monomer (a3-4-2)] was mixed to be 45: 14: 2.5: 38.5, and propylene glycol monomethyl ether acetate was added in an amount of 1.5 times the total monomer amount to obtain a solution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to this solution in an amount of 1 mol% and 3 mol% relative to the total monomer amount, respectively, and these were heated at 73 ° C. for about 5 hours. The resulting reaction mixture was poured into a large amount of methanol / water mixed solvent to precipitate the resin, and the resin was filtered. The obtained resin was dissolved again in propylene glycol monomethyl ether acetate, and the resulting solution was poured into a methanol/water mixed solvent to precipitate the resin, which was then filtered. This reprecipitation procedure was repeated twice to obtain Resin A2-2 having a weight average molecular weight of 7.8×10 ³ in a yield of 63%. Resin A2-2 has the following structural units.

Synthesis Example 3: Synthesis of Resin X1 Monomer (a4-2A-4) was used as a monomer, and 1.5 times the mass of the total monomer amount of methyl isobutyl ketone was added to prepare a solution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to this solution in amounts of 0.7 mol% and 2.1 mol% relative to the total monomer amount, respectively, and the mixture was heated at 75°C for about 5 hours. The resulting reaction mixture was poured into a large amount of a methanol/water mixed solvent to precipitate the resin, which was then filtered to obtain Resin X1 having a weight average molecular weight of 1.7 x 10 ⁴ in a yield of 77%. This Resin X1 has the following structural units.

Synthesis Example 4: Synthesis of Resin AX1-1 Monomer (a4-x-1) and monomer (I6-287) were used as monomers, and the molar ratio [monomer (a4-x-1):monomer (I6-287)] was mixed to a ratio of 95:5, and further, 1.5 times the mass of methyl isobutyl ketone was mixed with this monomer mixture relative to the total mass of all monomers. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to this solution at 0.7 mol% and 2.1 mol%, respectively, relative to the total monomer amount, and these were heated at 75 ° C. for about 5 hours. Thereafter, the polymerization reaction liquid was poured into a large amount of n-heptane to precipitate the resin, and the resin was filtered and collected to obtain resin AX1-1 having a weight average molecular weight of about 1.8 × 10 ⁴ in a yield of 87%. This resin AX1-1 has the following structural units.

Synthesis Example 5: Synthesis of Resin A1-1 Monomer (a4-2A-4) and monomer (I6-1) were used as monomers, and the molar ratio [monomer (a4-2A-4):monomer (I6-1)] was mixed to a ratio of 95:5. Furthermore, 1.5 times the mass of methyl isobutyl ketone was mixed with this monomer mixture relative to the total mass of all monomers. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to this solution at 0.7 mol% and 2.1 mol% relative to the total monomer amount, respectively, and these were heated at 75 ° C. for about 5 hours. Thereafter, the polymerization reaction liquid was poured into a large amount of n-heptane to precipitate the resin, which was then filtered and collected to obtain resin A1-1 having a weight average molecular weight of about 1.7 × 10 ⁴ in a yield of 84%. This resin A1-1 has the following structural units.

Synthesis Example 6: Synthesis of Resin A1-2 Monomer (a4-2A-4) and monomer (I6-2) were used as monomers, and the molar ratio [monomer (a4-2A-4):monomer (I6-2)] was mixed to a ratio of 95:5. Furthermore, 1.5 times the mass of methyl isobutyl ketone was mixed with this monomer mixture relative to the total mass of all monomers. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to this solution at 0.7 mol% and 2.1 mol% relative to the total monomer amount, respectively, and these were heated at 75 ° C. for about 5 hours. Thereafter, the polymerization reaction liquid was poured into a large amount of n-heptane to precipitate the resin, which was then filtered and collected to obtain resin A1-2 having a weight average molecular weight of about 1.8 × 10 ⁴ in a yield of 87%. This resin A1-2 has the following structural units.

Synthesis Example 7: Synthesis of Resin A1-3 Monomer (a4-2A-4) and monomer (I6-16) were used as monomers, and the molar ratio [monomer (a4-2A-4):monomer (I6-16)] was mixed to a ratio of 95:5. Furthermore, 1.5 times the mass of methyl isobutyl ketone was mixed with this monomer mixture relative to the total mass of all monomers. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to this solution in amounts of 0.7 mol% and 2.1 mol%, respectively, relative to the total monomer amount, and these were heated at 75°C for about 5 hours. Thereafter, the polymerization reaction liquid was poured into a large amount of n-heptane to precipitate the resin, which was then filtered and collected to obtain Resin A1-3 having a weight average molecular weight of about 1.7 x 10 ⁴ in a yield of 88%. This Resin A1-3 has the following structural units.

Synthesis Example 8: Synthesis of Resin A1-4 Monomer (a4-2A-4) and monomer (I6-287) were used as monomers, and the molar ratio [monomer (a4-2A-4):monomer (I6-287)] was mixed to a ratio of 95:5. Furthermore, 1.5 times the mass of methyl isobutyl ketone was mixed with this monomer mixture relative to the total mass of all monomers. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to this solution in amounts of 0.7 mol% and 2.1 mol%, respectively, relative to the total monomer amount, and these were heated at 75°C for about 5 hours. Thereafter, the polymerization reaction liquid was poured into a large amount of n-heptane to precipitate the resin, which was then filtered and collected to obtain resin A1-4 having a weight average molecular weight of about 1.9 x 10 ⁴ in a yield of 92%. This resin A1-4 has the following structural units.

Synthesis Example 9: Synthesis of Resin A1-5 Monomer (a4-2A-4) and monomer (I6-348) were used as monomers, and the molar ratio [monomer (a4-2A-4):monomer (I6-348)] was mixed to a ratio of 95:5. Furthermore, 1.5 times the mass of methyl isobutyl ketone was mixed with this monomer mixture relative to the total mass of all monomers. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to this solution at 0.7 mol% and 2.1 mol% relative to the total monomer amount, respectively, and these were heated at 75 ° C. for about 5 hours. Thereafter, the polymerization reaction liquid was poured into a large amount of n-heptane to precipitate the resin, which was then filtered and collected to obtain Resin A1-5 having a weight average molecular weight of about 1.8 × 10 ⁴ in a yield of 86%. This Resin A1-5 has the following structural units.

Synthesis Example 10: Synthesis of Resin A1-6 Monomer (a4-2A-4) and monomer (I6-323) were used as monomers, and the molar ratio [monomer (a4-2A-4):monomer (I6-323)] was mixed to a ratio of 95:5. Furthermore, 1.5 times the mass of methyl isobutyl ketone was mixed with this monomer mixture relative to the total mass of all monomers. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to this solution in amounts of 0.7 mol% and 2.1 mol%, respectively, relative to the total monomer amount, and these were heated at 75°C for about 5 hours. Thereafter, the polymerization reaction liquid was poured into a large amount of n-heptane to precipitate the resin, which was then filtered and collected to obtain Resin A1-6 having a weight average molecular weight of about 1.5 x 10 ⁴ in a yield of 76%. This Resin A1-6 has the following structural units.

Synthesis Example 11: Synthesis of Resin A1-7 Monomer (a4-2A-4) and monomer (I6-435) were used as monomers, and the molar ratio [monomer (a4-2A-4):monomer (I6-435)] was mixed to a ratio of 95:5. Furthermore, 1.5 times the mass of methyl isobutyl ketone was mixed with this monomer mixture relative to the total mass of all monomers. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to this solution at 0.7 mol% and 2.1 mol%, respectively, relative to the total monomer amount, and these were heated at 75 ° C. for about 5 hours. Thereafter, the polymerization reaction liquid was poured into a large amount of n-heptane to precipitate the resin, which was then filtered and collected to obtain Resin A1-7 having a weight average molecular weight of about 1.7 × 10 ⁴ in a yield of 69%. This Resin A1-7 has the following structural units.

Synthesis Example 12: Synthesis of Resin A1-8 Monomer (a4-3-2) and monomer (I6-16) were used as monomers, and the molar ratio [monomer (a4-3-2):monomer (I6-16)] was mixed to a ratio of 95:5. Furthermore, 1.5 times the mass of methyl isobutyl ketone was mixed with this monomer mixture relative to the total mass of all monomers. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to this solution at 0.7 mol% and 2.1 mol% relative to the total monomer amount, respectively, and these were heated at 75 ° C. for about 5 hours. Thereafter, the polymerization reaction liquid was poured into a large amount of n-heptane to precipitate the resin, which was then filtered and collected to obtain Resin A1-8 having a weight average molecular weight of about 1.9 × 10 ⁴ in a yield of 71%. This Resin A1-8 has the following structural units.

<Preparation of Resist Composition>
Resist compositions were prepared by dissolving each of the components shown below in a solvent in the parts by mass shown in Table 2, and then filtering through a fluororesin filter having a pore size of 0.2 μm. The prepared resist compositions were stored at 30° C. for 3 weeks, and then the resist properties were evaluated.

＜弱酸分子内塩（Ｄ）＞
Ｄ１：式（Ｄ１）で表される塩（東京化成工業（株）製）

＜溶剤＞
プロピレングリコールモノメチルエーテルアセテート ２６５部
プロピレングリコールモノメチルエーテル ２０部
２－ヘプタノン ２０部
γ－ブチロラクトン ３．５部 <Resin>
A1-1 to A1-8: Resin A1-1 to Resin A1-8
A2-1, A2-2, AX1-1, X1: Resin A2-1, Resin A2-2, Resin AX1-1, Resin X1
<Acid Generator (B)>
B1-21: A salt represented by the formula (B1-21) B1-22: A salt represented by the formula (B1-22)

<Weak Acid Inner Salt (D)>
D1: Salt represented by formula (D1) (manufactured by Tokyo Chemical Industry Co., Ltd.)

<Solvent>
Propylene glycol monomethyl ether acetate 265 parts Propylene glycol monomethyl ether 20 parts 2-heptanone 20 parts γ-butyrolactone 3.5 parts

<Production of Resist Pattern and Its Evaluation>
A composition for organic antireflective coating (ARC-29; manufactured by Nissan Chemical Industries, Ltd.) was applied to a silicon wafer and baked at 205° C. for 60 seconds to form an organic antireflective coating having a thickness of 780 Å. Next, the resist composition was spin-coated onto the organic antireflective coating so that the film thickness after drying (pre-baking) would be 85 nm. The silicon wafer coated with the resist composition was pre-baked on a direct hot plate at the temperature shown in the “PB” column of Table 2 for 60 seconds to form a resist film (composition layer). The silicon wafer on which the resist film was formed was exposed to light using an immersion exposure ArF excimer laser stepper (XT: 1900 Gi; manufactured by ASML, NA=1.35, 3/4 Annular XY polarization) with a mask for forming a contact hole pattern (hole pitch 150 nm/hole diameter 75 nm) while changing the exposure dose stepwise. Note that ultrapure water was used as the immersion medium.
After exposure, the silicon wafer was post-exposure baked on a hot plate for 60 seconds at the temperature shown in the "PEB" column of Table 2. Then, the silicon wafer was paddle-developed for 60 seconds with a 2.38% aqueous tetramethylammonium hydroxide solution to obtain a resist pattern.

When forming a resist pattern from each resist composition, the effective sensitivity was determined as the exposure dose at which the hole diameter of the pattern formed using a mask with a hole diameter of 75 nm became 55 nm.

<CD Uniformity (CDU) Evaluation>
In the effective sensitivity, the hole diameter of a pattern formed with a mask having a hole diameter of 75 nm was measured 24 times for each hole, and the average value was taken as the average hole diameter of one hole. The standard deviation was calculated as a population of 400 average hole diameters of a pattern formed with a mask having a hole diameter of 75 nm on the same wafer.
The results are shown in Table 3. The values in parentheses indicate standard deviation (nm).

Compared with Comparative Compositions 1 and 2, Compositions 1 to 9 had smaller standard deviations and better CD uniformity (CDU) ratings.

The resist composition of the present invention is suitable for semiconductor microfabrication because it can produce resist patterns with good CD uniformity (CDU), making it extremely useful industrially.

Claims (15)

At least one structural unit selected from the group consisting of structural units represented by formula (a4-2) and structural units represented by formula (a4-3),
A resin comprising a structural unit represented by formula (I6):

[In formula (a4-2) and formula (a4-3),
^R41 represents a hydrogen atom or a methyl group.
L ^43h and L ^44h each independently represent a saturated hydrocarbon group having 1 to 20 carbon atoms which may have a halogen atom, and --CH ₂ -- contained in the saturated hydrocarbon group may be replaced by --O-- or --CO--.
R ^43h and R ^44h each independently represent a saturated hydrocarbon group having 1 to 20 carbon atoms which may have a halogen atom, and --CH ₂ -- contained in the saturated hydrocarbon group may be replaced by --O-- or --CO--.
However, at least one of L ^43h and R ^43h has a halogen atom, at least one of L ^44h and R ^44h has a halogen atom, and the upper limit of the total number of carbon atoms of L ^43h and R ^43h and the upper limit of the total number of carbon atoms of L ^44h and R ^44h are each 21.]

[In formula (I6),
Q ^b1 and Q ^b2 each independently represent a hydrogen atom, a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms, or an alkyl group having 1 to 6 carbon atoms.
L ^b1 represents a saturated hydrocarbon group having 1 to 24 carbon atoms, in which -CH ₂ - may be replaced by -O- or -CO-, and in which a hydrogen atom may be replaced by a fluorine atom or a hydroxyl group.
Y ^b1 represents a single bond or a cyclic hydrocarbon group having 3 to 24 carbon atoms which may have a substituent, and --CH ₂ -- contained in the cyclic hydrocarbon group may be replaced by --O--, --CO--, --S-- or --SO ₂ --.
mm1 represents 0 or 1.
R ¹⁰ represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
^X10 represents a single bond, *-O-**, *-CO-O-**, *-O-CO-O-** or *-Ax-Ph-Ay-**.
Ph represents a phenylene group which may have a substituent.
Ax and Ay each independently represent one type of bond selected from the group consisting of a single bond, an ether bond, a thioether bond, an ester bond, an amide bond, and a carbonate bond.
* and ** represent bonding sites, and * represents the bonding site with the carbon atom to which R ¹⁰ is bonded.
L ¹⁰ represents a single bond or a hydrocarbon group having 1 to 36 carbon atoms which may have a substituent, and --CH ₂ -- contained in the hydrocarbon group may be replaced by --O--, --S--, --SO ₂ -- or --CO--.
R ³ , R ⁴ , R ⁵ , and R ⁶ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, -CH ₂ - contained in the hydrocarbon group may be replaced by -O-, -S-, -NR ⁷ -, -SO ₂ - or -CO-, R ³ and R ⁴ , and R ³ , R ⁴ and R ⁵ may each be bonded to form a cyclic hydrocarbon group, which may have one or more double bonds between two adjacent carbon atoms, -CH ₂ - contained in the cyclic hydrocarbon group may be replaced by -O-, -CO- or -NR ⁷ -, and -CH= contained in the cyclic hydrocarbon group may be replaced by -N=.
^R7 represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, and _--CH2-- contained in the hydrocarbon group may be replaced by --O--, --S--, _--SO2-- or --CO--.] The resin according to claim 1, which contains a structural unit represented by formula (a4-2). Contains a structural unit represented by formula (a4-2):
The resin according to claim 1, wherein the structural unit represented by formula (a4-2) is a structural unit represented by formula (a4-2A) or a structural unit represented by formula (a4-2B).

[In formula (a4-2A) and formula (a4-2B),
R ⁴¹ has the same meaning as in formula (a4-2).
L ^43f represents a saturated hydrocarbon group having 1 to 20 carbon atoms which may have a fluorine atom, and --CH ₂ -- contained in the saturated hydrocarbon group may be replaced by --O-- or --CO--.
R ^43fA represents a saturated hydrocarbon group having 1 to 20 carbon atoms and containing a fluorine atom.
A ^43f represents a divalent saturated hydrocarbon group having 1 to 17 carbon atoms which may have a fluorine atom, and --CH ₂ -- contained in the saturated hydrocarbon group may be replaced by --O-- or --CO--.
X ⁴³ represents **-O-CO- or **-CO-O-, and ** represents a bonding site with A ^43f .
R ^43fB represents a saturated hydrocarbon group having 1 to 17 carbon atoms which may have a fluorine atom.
provided that in formula (a4-2A), the total number of carbon atoms of L ^43f and R ^43fA is 21 or less, and in formula (a4-2B), the total number of carbon atoms of L ^43f , A ^43f , X ⁴³ and R ^43fB is 21 or less, and at least one of A ^43f and R ^43fB has at least one fluorine atom.] The resin according to claim 1, wherein Y ^b1 is a single bond or an alicyclic hydrocarbon group having 3 to 18 carbon atoms which may have a substituent (-CH ₂ - contained in the alicyclic hydrocarbon group may be replaced by -O-, -CO-, -S- or -SO ₂ -). Y ^b1 is an alicyclic hydrocarbon group having 3 to 18 carbon atoms which may have a substituent,
The resin according to claim 1, wherein the alicyclic hydrocarbon group is a cycloalkanediyl group, norbornanediyl group, adamantanediyl group, adamantanelactonediyl group or norbornanelactonediyl group having 5 or 6 carbon atoms, -CH ₂ - contained in the cycloalkanediyl group, norbornanediyl group or adamantanediyl group may be replaced by -O- or -CO-, and the cycloalkanediyl group, norbornanediyl group, adamantanediyl group, adamantanelactonediyl group or norbornanelactonediyl group may have a substituent. 2. The resin according to claim 1, wherein X ¹⁰ is a single bond or a group represented by any one of formulae (X ¹⁰ -1) to (X ¹⁰ -10).

[Formula (X ¹⁰ -1) to (X ¹⁰ -10),
* and ** are bonding sites, and * represents the bonding site with the carbon atom to which R ¹⁰ is bonded.
Rx represents a halogen atom, a hydroxy group, a fluorinated alkyl group having 1 to 6 carbon atoms, an alkyl group having 1 to 18 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.
mx represents an integer of 0 to 4.
X ²⁰ represents —O— or —NR ³ —.
^R3 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. 2. The resin according to claim 1, wherein X ¹⁰ is a single bond or a group represented by any one of formulae (X ¹⁰ -1'), (X10-3') to (X ¹⁰ -8') and (X ¹⁰ -10').

[Formula (X ¹⁰ -1'), Formula (X ¹⁰ -3') to (X ¹⁰ -8') and Formula (X ¹⁰ -10'),
* and ** are bonding sites, and * represents the bonding site with the carbon atom to which R ¹⁰ is bonded.] 8. The resin according to claim 7, wherein X ¹⁰ is a single bond or a group represented by any one of formulas (X ¹⁰ -1'), (X ¹⁰ -5'), (X ¹⁰ -6') and (X ¹⁰ -10'). L ¹⁰ is a single bond, an alkanediyl group having 1 to 6 carbon atoms, a cyclic hydrocarbon group having 3 to 18 carbon atoms, or a group formed by combining an alkanediyl group having 1 to 6 carbon atoms and a cyclic hydrocarbon group having 3 to 18 carbon atoms,
-CH ₂ - contained in the alkanediyl group and the cyclic hydrocarbon group may be replaced by -O-, -S-, -SO ₂ - or -CO-;
The resin according to claim 1 , wherein the cyclic hydrocarbon group optionally has a substituent. A resist composition comprising the resin according to any one of claims 1 to 9. The resist composition according to claim 10 further comprises a resin that contains a structural unit having an acid labile group, unlike the resin according to any one of claims 1 to 9. The resist composition according to claim 11, wherein the structural unit having an acid labile group comprises at least one selected from the group consisting of a structural unit represented by formula (a1-0), a structural unit represented by formula (a1-1), a structural unit represented by formula (a1-2), and a structural unit represented by formula (a1-5).

[In formula (a1-0), formula (a1-1) and formula (a1-2),
L ^a01 , L ^a1 and L ^a2 each independently represent --O-- or *-O--(CH ₂ ) _k1 --CO--O--, where k1 represents an integer of 1 to 7, and * represents a bonding site with --CO--.
R ^a01 , R ^a4 and R ^a5 each independently represent a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
R ^a02 , R ^a03 , and R ^a04 each independently represent an alkyl group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a combination thereof, and the alkyl group, alicyclic hydrocarbon group, and aromatic hydrocarbon group may have a halogen atom.
R ^a6 and R ^a7 each independently represent an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group formed by combining these.
m1 represents an integer of 0 to 14.
n1 represents an integer of 0 to 10.
n1′ represents an integer of 0 to 3.

[In formula (a1-5),
R ^a8 represents an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, a hydrogen atom or a halogen atom.
Z ^a1 represents a single bond or *-(CH ₂ ) _h3 -CO-L ⁵⁴ -, h3 represents an integer of 1 to 4, and * represents the bonding site to L ⁵¹ .
L ⁵¹ , L ⁵² , L ⁵³ and L ⁵⁴ each independently represent --O-- or --S--.
s1 represents an integer of 1 to 3.
s1′ represents an integer of 0 to 3. Further, the composition contains an acid generator,
The resist composition according to claim 10, wherein the acid generator comprises a salt represented by formula (B1) or a salt represented by formula (B2).

[In formula (B1),
Q ^b1 and Q ^b2 each independently represent a hydrogen atom, a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms, or an alkyl group having 1 to 6 carbon atoms.
L ^b1 represents a saturated hydrocarbon group having 1 to 24 carbon atoms, in which -CH ₂ - may be replaced by -O- or -CO-, and in which a hydrogen atom may be replaced by a fluorine atom or a hydroxyl group.
Y represents a methyl group which may have a substituent or a cyclic hydrocarbon group having 3 to 24 carbon atoms which may have a substituent, and -CH ₂ - contained in the cyclic hydrocarbon group may be replaced by -O-, -S-, -SO ₂ - or -CO-.
Z ⁺ represents an organic cation.

[In formula (B2),
m21 represents an integer of 1 to 5, and when m21 is 2 or greater, the groups in the parentheses may be the same or different.
R ²¹ represents a hydrocarbon group having 3 to 48 carbon atoms, including a cyclic hydrocarbon group having 3 to 18 carbon atoms, the cyclic hydrocarbon group may have a substituent, and -CH ₂ - contained in the hydrocarbon group may be replaced by -O-, -S-, -SO ₂ - or -CO-.
R ²² represents a halogen atom or an alkyl group having 1 to 6 carbon atoms, and --CH ₂ -- contained in the alkyl group may be replaced by --O-- or --CO--.
m22 represents an integer of 0 to 4, and when m22 is 2 or greater, multiple R ²² may be the same or different.
Z ⁺ represents an organic cation. The resist composition according to claim 13, further comprising a salt that generates an acid with a lower acidity than the acid generated from the acid generator. (1) A step of applying the resist composition according to claim 10 onto a substrate;
(2) A step of drying the applied composition to form a composition layer;
(3) exposing the composition layer to light;
(4) a step of heating the composition layer after exposure; and (5) a step of developing the composition layer after heating.
A method for producing a resist pattern comprising the steps of: