Composition containing fluorine-containing polymer, method for producing fluorine-containing polymer, and ultraviolet light-emitting element lens containing fluorine-containing polymer

Abstract

To provide, for example, a composition containing a fluorine-containing polymer which has high ultraviolet light transparency, a method for producing a fluorine-containing polymer which has high ultraviolet light transparency, and an ultraviolet light-emitting element lens containing a fluorine-containing polymer which has high ultraviolet light transparency.SOLUTION: A composition contains a fluorine-containing polymer (A) and at least one compound (BC) selected from the group consisting of polymerization initiators (B) and degradation products (C) of the polymerization initiators (B), where the compound (BC) is contained in an amount of 0.1-100 mass ppm based on the mass of the composition, and the fluorine-containing polymer (A) includes, as the main component thereof, a constituent unit represented by formula (A) in the figure, where R1 to R4 each independently represent a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a composition containing a fluoropolymer, a method for producing a fluoropolymer, and a lens for an ultraviolet light emitting device containing a fluoropolymer. [Background technology]

[0002] Fluorine-containing polymers containing oxolane rings are known to be highly transparent, and their applications in the optical field are being considered. On the other hand, the use of ultraviolet light-emitting devices has expanded in recent years, and polymers with high ultraviolet light transmittance are in demand.

[0003] Patent Documents 1 and 2 disclose that when the terminals of a fluoropolymer do not contain a carbonyl group, yellowing of the fluoropolymer is suppressed and the transmittance of ultraviolet light is improved. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2021-155736 A [Patent Document 2] International Publication No. 2014 / 156996 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the present inventors have noticed that even if a fluoropolymer containing an oxolane ring is a polymer that does not contain a carbonyl group at its terminal, the ultraviolet light transmittance may be low. The present disclosure aims to provide a composition containing a fluoropolymer having high ultraviolet light transmittance, a method for producing a fluoropolymer having high ultraviolet light transmittance, a lens for ultraviolet light emitting device containing a fluoropolymer having high ultraviolet light transmittance, and the like. [Means for solving the problem]

[0006] The present inventors have found that a polymerization initiator and / or decomposition products thereof used in the production of a fluoropolymer can absorb ultraviolet light and reduce the ultraviolet light transmittance of the fluoropolymer by being mixed into the produced fluoropolymer.

[0007] They have also found that in producing a fluoropolymer by precipitation polymerization, that is, in producing the fluoropolymer by polymerizing raw material monomers in a solvent and precipitating the resulting fluoropolymer in the solvent, if the solutes (monomers, polymerization initiator, and decomposition products of the polymerization initiator) and the solvent have a solubility index R within a specific range, a fluoropolymer can be produced in which the amount of polymerization initiator and / or decomposition products thereof mixed into the fluoropolymer is reduced.

[0008] The present disclosure typically encompasses the following aspects. Section 1. A composition comprising a fluoropolymer (A), and at least one compound (BC) selected from the group consisting of a polymerization initiator (B) and a decomposition product (C) of the polymerization initiator (B), The compound (BC) is contained in an amount of 0.1 to 100 ppm by mass relative to the mass of the composition, The fluoropolymer (A) is represented by the formula (A) [ka] [In the formula, R 1 ~R 4 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] Contains as a main component a structural unit represented by composition. Section 2. Item 2. The composition according to item 1, wherein the polymerization initiator (B) is a peroxide. Section 3. The polymerization initiator (B) is Formula (B1) [ka] [In the formula, R 11 , R12 , R 13 , and R 14 each independently represents a fluorine atom, a C1-C20 alkyl group, or a C1-C20 fluoroalkyl group; The alkyl group and the fluoroalkyl group each may have an etheric oxygen atom, and R 11 and R 12 may be linked together to form a 4-20-membered ring having 4 to 20 carbon atoms as ring-constituting atoms and at least one fluorine atom, or a 4-22-membered ring having 3 to 20 carbon atoms and one or two oxygen atoms or one sulfur atom as ring-constituting atoms and at least one fluorine atom, R 13 and R 14 may be linked together to form a 4-20-membered ring having 4 to 20 carbon atoms as ring constituent atoms and at least one fluorine atom, or a 4-22-membered ring having 3 to 20 carbon atoms and one or two oxygen atoms or one sulfur atom as ring constituent atoms and at least one fluorine atom.] A compound represented by the formula: Formula (B2) [ka] [In the formula, R 15 and R 16 each independently represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom.] A compound represented by the formula: Formula (B3) [ka] [In the formula, R 17 and R 18each independently represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom, and the alkyl group and the fluoroalkyl group each may have an etheric oxygen atom.] A compound represented by The composition according to item 1, wherein the compound is at least one compound selected from the group consisting of: Section 4. The decomposition product (C) is Formula (C1) [ka] [In the formula, R 41 and R 42 each independently represents a fluorine atom, a C1-C20 alkyl group, or a C1-C20 fluoroalkyl group; The alkyl group and the fluoroalkyl group each may have an etheric oxygen atom, and R 41 and R 42 may be linked together to form a 4-20-membered ring having 4 to 20 carbon atoms as ring-constituting atoms and at least one fluorine atom, or a 4-22-membered ring having 3 to 20 carbon atoms and one or two oxygen atoms or one sulfur atom as ring-constituting atoms and at least one fluorine atom, R 43 represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C2) [ka] [In the formula, R 45 represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group optionally having a fluorine atom; R 46 represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C3) [ka] [In the formula, R 47 represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom, wherein the alkyl group and the fluoroalkyl group each may have an etheric oxygen atom; R 49 represents a fluorine atom or a hydroxyl group. A compound represented by The composition according to any one of items 1 to 3, wherein the compound is at least one compound selected from the group consisting of: Section 5. Item 5. The composition according to any one of items 1 to 4, having an average transmittance of 85% or more at wavelengths of 240 nm to 340 nm. Section 6. The constitutional unit represented by the formula (A) is represented by the formula (A1) [ka] 6. The composition according to any one of items 1 to 5, wherein the structural unit is represented by the following formula: Section 7. The polymerization initiator (B) Formula (B1) [ka] [In the formula, R 11 and R 13 is a fluorine atom, R 12 and R 14 are each independently -(CF2) n1 CF3 (wherein n1 is an integer of 0 to 5), -(CF2) n2 CF2H (wherein n2 is an integer from 0 to 5), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 5), or -O-(CF2) n4 CF2H (wherein n4 is an integer of 0 to 5). A compound represented by the formula: Formula (B2) [ka] [In the formula, R 15 and R 16 each independently represents a C1-C7 linear or branched alkyl group, or a C1-C7 linear or branched fluoroalkyl group.] A compound represented by the formula: Formula (B3) [ka] [In the formula, R 17 is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R 18 represents tert-butyl, tert-hexyl, or trifluoromethyl. A compound represented by The composition according to any one of items 1 and 4 to 6, wherein the compound is at least one compound selected from the group consisting of: Section 8. The decomposition product (C) Formula (C1) [ka] [In the formula, R 41 represents a fluorine atom, R 42 teeth, -(CF2) n1 CF3 (wherein n1 is an integer of 0 to 5), -(CF2) n2 CF2H (wherein n2 is an integer from 0 to 5), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 5), or -O-(CF2) n4 CF2H (where n4 is an integer from 0 to 5.) indicates, R 43 represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C2) [ka] [In the formula, R 45 represents a C1-C7 linear or branched alkyl group or a C1-C7 linear or branched fluoroalkyl group; R 46 represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C3) [ka] [In the formula, R 47 is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R 49 represents a fluorine atom or a hydroxyl group. A compound represented by The composition according to any one of items 1 to 3 and items 5 to 7, wherein the compound is at least one compound selected from the group consisting of: Section 9. The constitutional unit represented by the formula (A) is represented by the formula (A1) [ka] It is a structural unit represented by The polymerization initiator (B) Formula (B1) [ka] [In the formula, R 11 and R 13 is a fluorine atom, R 12 and R 14 are each independently -(CF2) n1 CF3 (wherein n1 is an integer of 0 to 5), -(CF2) n2CF2H (wherein n2 is an integer from 0 to 5), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 5), or -O-(CF2) n4 CF2H (wherein n4 is an integer of 0 to 5). A compound represented by the formula: Formula (B2) [ka] [In the formula, R 15 and R 16 each independently represents a C1-C7 linear or branched alkyl group, or a C1-C7 linear or branched fluoroalkyl group.] A compound represented by the formula: Formula (B3) [ka] [In the formula, R 17 is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R 18 represents tert-butyl, tert-hexyl, or trifluoromethyl. A compound represented by At least one compound selected from the group consisting of The decomposition product (C) Formula (C1) [ka] [In the formula, R 41 represents a fluorine atom, R 42 teeth, -(CF2) n1 CF3 (wherein n1 is an integer of 0 to 5), -(CF2) n2 CF2H (wherein n2 is an integer from 0 to 5), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 5), or -O-(CF2) n4 CF2H (where n4 is an integer from 0 to 5.) indicates, R 43 represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C2) [ka] [In the formula, R 45 represents a C1-C7 linear or branched alkyl group or a C1-C7 linear or branched fluoroalkyl group; R 46 represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C3) [ka] [In the formula, R 47 is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R 49 represents a fluorine atom or a hydroxyl group. A compound represented by Item 6. The composition according to item 1 or 5, wherein the compound is at least one compound selected from the group consisting of: Section 10. A method for producing a fluoropolymer (A), comprising the steps of: Formula (M) [ka] [In the formula, R 1 ~R 4 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] The method includes a polymerization step of polymerizing the fluorine-containing monomer (M) represented by the following formula (1): The fluoropolymer (A) is represented by the formula (A): [ka] [In the formula, R 1 ~R 4 is the same as above.] The main component is a structural unit represented by The value of the solubility index R (R A )) is 4 or more, The value of the solubility index R (R B ) is 9 or less when the mass ratio of fluorine atoms in the polymerization initiator (B) is less than 50 mass%, and is 6 or less when the mass ratio is 50 mass% or more, The value of the solubility index R (R C ) is 9 or less when the mass ratio of fluorine atoms in the decomposition product (C) is less than 50 mass%, and is 6 or less when the mass ratio is 50 mass% or more; The solubility index R is expressed by the following formula: R = {4 × (δD1-δD2) 2 +(δP1-δP2) 2 +(δH1-δH2) 2} 0.5 [In the formula, δD1, δP1, and δH1 respectively represent the dispersion term, polar term, and hydrogen bond term in the Hansen solubility parameter of element 1, and δD2, δP2, and δH2 respectively represent the dispersion term, polar term, and hydrogen bond term in the Hansen solubility parameter of element 2.] It is calculated from Manufacturing method. Section 11. Item 11. The process for producing a fluoropolymer (A) according to Item 10, further comprising a filtration step of removing the precipitate produced in the polymerization step and the polymerization product liquid by filtering to obtain the fluoropolymer (A). Section 12. Item 12. The method for producing a fluorinated polymer (A) according to Item 10 or 11, wherein the polymerization initiator (B) is a peroxide. Section 13. The polymerization initiator (B) is Formula (B1) [ka] [In the formula, R 11 , R 12 , R 13 , and R 14 each independently represents a fluorine atom, a C1-C20 alkyl group, or a C1-C20 fluoroalkyl group; The alkyl group and the fluoroalkyl group each may have an etheric oxygen atom, and R 11 and R 12 are linked to each other to form a 4-20-membered ring having 4-20 carbon atoms as ring constituent atoms and at least one fluorine atom, or may form a 4- to 22-membered ring having two oxygen atoms or one sulfur atom as ring-constituting atoms and at least one fluorine atom, R 13 and R 14 may be linked together to form a 4-20-membered ring having 4 to 20 carbon atoms as ring constituent atoms and at least one fluorine atom, or a 4-22-membered ring having 3 to 20 carbon atoms and one or two oxygen atoms or one sulfur atom as ring constituent atoms and at least one fluorine atom.] A compound represented by the formula: Formula (B2) [ka] [In the formula, R 15 and R 16 each independently represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom.] A compound represented by the formula: Formula (B3) [ka] [In the formula, R 17 and R 18 each independently represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom, and the alkyl group and the fluoroalkyl group each may have an etheric oxygen atom.] A compound represented by Item 12. The method for producing a fluorinated polymer (A) according to item 10 or 11, wherein the compound (A) is at least one compound selected from the group consisting of: Section 14. The decomposition product (C) of the polymerization initiator (B) is Formula (C1) [ka] [In the formula, R 41 and R 42 each independently represents a fluorine atom, a C1-C20 alkyl group, or a C1-C20 fluoroalkyl group; The alkyl group and the fluoroalkyl group each may have an etheric oxygen atom, and R 41 and R 42 may be linked together to form a 4-20-membered ring having 4 to 20 carbon atoms as ring-constituting atoms and at least one fluorine atom, or a 4-22-membered ring having 3 to 20 carbon atoms and one or two oxygen atoms or one sulfur atom as ring-constituting atoms and at least one fluorine atom, R 43 represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C2) [ka] [In the formula, R 45represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group optionally having a fluorine atom; R 46 represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C3) [ka] [In the formula, R 47 represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom, wherein the alkyl group and the fluoroalkyl group each may have an etheric oxygen atom; R 49 represents a fluorine atom or a hydroxyl group. A compound represented by 14. The method for producing a fluorine-containing polymer (A) according to any one of items 10 to 13, wherein the fluorine-containing polymer (A) is at least one compound selected from the group consisting of: Section 15. The fluorine-containing monomer (M) is represented by the formula (M1): [ka] A compound represented by the formula: The constitutional unit represented by the formula (A) is represented by the formula (A1) [ka] 15. The method for producing the fluoropolymer (A) according to any one of items 10 to 14, wherein the structural unit is represented by the following formula: Section 16. the fluorine-containing monomer (M) contains a compound (N) in an amount of 0.0001 to 10% by mass based on the mass of the raw material monomer, The compound (N) is Formula (N) [ka] [In the formula, R 1 ~R 4 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group; R 71 and R 72 each independently represents a hydrogen atom or a fluorine atom; R 71 and R 72 When one of the groups is a hydrogen atom, the other group is a fluorine atom. 16. The method for producing the fluorine-containing polymer (A) according to any one of items 10 to 15, wherein the fluorine-containing polymer (A) is a compound represented by the following formula: Section 17. The compound (N) is Formula (N1) [ka] A compound represented by the formula: Formula (N2) [ka] Item 17. The method for producing a fluorinated polymer (A) according to item 16, wherein the fluorinated polymer (A) is at least one compound selected from the group consisting of compounds represented by the formula: Section 18. The polymerization initiator (B) Formula (B1) [ka] [In the formula, R 11 and R 13 is a fluorine atom, R 12 and R 14 are each independently -(CF2) n1 CF3 (wherein n1 is an integer of 0 to 5), -(CF2) n2 CF2H (wherein n2 is an integer from 0 to 5), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 5), or -O-(CF2) n4CF2H (wherein n4 is an integer of 0 to 5). A compound represented by the formula: Formula (B2) [ka] [In the formula, R 15 and R 16 each independently represents a C1-C7 linear or branched alkyl group, or a C1-C7 linear or branched fluoroalkyl group.] A compound represented by the formula: Formula (B3) [ka] [In the formula, R 17 is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R 18 represents tert-butyl, tert-hexyl, or trifluoromethyl. A compound represented by 18. The process for producing a fluorine-containing polymer (A) according to any one of items 10, 11 and 14 to 17, wherein the fluorine-containing polymer (A) is at least one compound selected from the group consisting of: Section 19. The decomposition product (C) Formula (C1) [ka] [In the formula, R 41 represents a fluorine atom, R 42 teeth, -(CF2) n1 CF3 (wherein n1 is an integer of 0 to 5), -(CF2) n2 CF2H (wherein n2 is an integer from 0 to 5), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 5), or -O-(CF2) n4 CF2H (where n4 is an integer from 0 to 5.) indicates, R 43 represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C2) [ka] [In the formula, R 45 represents a C1-C7 linear or branched alkyl group or a C1-C7 linear or branched fluoroalkyl group; R 46 represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C3) [ka] [In the formula, R 47 is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R 49 represents a fluorine atom or a hydroxyl group. A compound represented by 19. The method for producing a fluorinated polymer (A) according to any one of items 10 to 13 and items 15 to 18, wherein the compound (A) is at least one compound selected from the group consisting of: Section 20. 20. The method for producing a fluoropolymer (A) according to any one of items 10 to 19, wherein the solvent (D) is at least one selected from the group consisting of hydrofluoroethers and fluorinated alcohols. Section 21. The fluorine-containing monomer (M) is represented by the formula (M1) [ka] A compound represented by the formula: the fluorine-containing monomer (M) contains a compound (N) in an amount of 0.0001 to 10% by mass based on the mass of the raw material monomer, The compound (N) is Formula (N1) [ka] A compound represented by the formula: Formula (N2) [ka] At least one compound selected from the group consisting of compounds represented by The constitutional unit represented by the formula (A) is represented by the formula (A1) [ka] It is a structural unit represented by The polymerization initiator (B) Formula (B1) [ka] [In the formula, R 11 and R 13 is a fluorine atom, R 12 and R 14 are each independently -(CF2) n1 CF3 (wherein n1 is an integer of 0 to 5), -(CF2) n2 CF2H (wherein n2 is an integer from 0 to 5), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 5), or -O-(CF2) n4 CF2H (wherein n4 is an integer of 0 to 5). A compound represented by the formula: Formula (B2) [ka] [In the formula, R 15 and R 16 each independently represents a C1-C7 linear or branched alkyl group, or a C1-C7 linear or branched fluoroalkyl group.] A compound represented by the formula: Formula (B3) [ka] [In the formula, R 17 is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R 18 represents tert-butyl, tert-hexyl, or trifluoromethyl. A compound represented by At least one compound selected from the group consisting of The decomposition product (C) Formula (C1) [ka] [In the formula, R 41 represents a fluorine atom, R 42 teeth, -(CF2) n1 CF3 (wherein n1 is an integer of 0 to 5), -(CF2) n2 CF2H (wherein n2 is an integer from 0 to 5), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 5), or -O-(CF2) n4 CF2H (where n4 is an integer from 0 to 5.) indicates, R 43 represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C2) [ka] [In the formula, R 45 represents a C1-C7 linear or branched alkyl group or a C1-C7 linear or branched fluoroalkyl group; R 46 represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C3) [ka] [In the formula, R 47is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R 49 represents a fluorine atom or a hydroxyl group. A compound represented by At least one compound selected from the group consisting of The solvent (D) is at least one selected from the group consisting of hydrofluoroethers and fluorine-containing alcohols. Item 12. A method for producing a fluorine-containing polymer (A) according to item 10 or 11. Section 22. A lens for an ultraviolet light emitting device containing a fluorine-containing polymer (A), The fluoropolymer (A) is represented by the formula (A) [ka] [In the formula, R 1 ~R 4 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] The main component is a structural unit represented by The fluoropolymer (A) has an average transmittance of 85% or more at a wavelength of 240 nm to 340 nm. Lenses for ultraviolet light emitting devices. Section 23. The constitutional unit represented by the formula (A) is represented by the formula (A1) [ka] Item 23. The lens for an ultraviolet light emitting element according to item 22, wherein the structural unit is represented by the following formula: Section 24. Formula (M1) [ka] A composition comprising a fluoropolymer (A1) formed as a precipitate by polymerizing a fluoromonomer (M1) represented by the following formula (1): The fluoropolymer (A1) is represented by the formula (A1): [ka] The main component is a structural unit represented by The fluorine-containing monomer (M1) is Formula (N1) [ka] A compound represented by the formula: Formula (N2) [ka] The compound contains at least one compound selected from the group consisting of compounds represented by the formula: The value of the solubility index R (R A1 )) is 4 or more, and the value of the solubility index R (R B ) is 9 or less when the mass ratio of fluorine atoms in the polymerization initiator (B) is less than 50 mass%, and is 6 or less when the mass ratio is 50 mass% or more, The value of the solubility index R (R C ) is 9 or less when the mass ratio of fluorine atoms in the decomposition product (C) is less than 50 mass%, and is 6 or less when the mass ratio is 50 mass% or more; The solubility index R is expressed by the following formula: R = {4 × (δD1-δD2) 2 +(δP1-δP2) 2 +(δH1-δH2) 2} 0.5 [In the formula, δD1, δP1, and δH1 respectively represent the dispersion term, polar term, and hydrogen bond term in the Hansen solubility parameter of element 1, and δD2, δP2, and δH2 respectively represent the dispersion term, polar term, and hydrogen bond term in the Hansen solubility parameter of element 2.] It is calculated from composition. Section 25. Item 25. A composition containing a fluorine-containing polymer (A1) according to Item 24, wherein the polymerization initiator (B) is a peroxide. Section 26. The polymerization initiator (B) is Formula (B1) [ka] [In the formula, R 11 , R 12 , R 13 , and R 14 each independently represents a fluorine atom, a C1-C20 alkyl group, or a C1-C20 fluoroalkyl group; The alkyl group and the fluoroalkyl group each may have an etheric oxygen atom, and R 11 and R 12 may be linked together to form a 4-20-membered ring having 4 to 20 carbon atoms as ring-constituting atoms and at least one fluorine atom, or a 4-22-membered ring having 3 to 20 carbon atoms and one or two oxygen atoms or one sulfur atom as ring-constituting atoms and at least one fluorine atom, R 13 and R 14 may be linked together to form a 4-20-membered ring having 4 to 20 carbon atoms as ring constituent atoms and at least one fluorine atom, or a 4-22-membered ring having 3 to 20 carbon atoms and one or two oxygen atoms or one sulfur atom as ring constituent atoms and at least one fluorine atom.] A compound represented by the formula: Formula (B2) [ka] [In the formula, R 15 and R16 each independently represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom.] A compound represented by the formula: Formula (B3) [ka] [In the formula, R 17 and R 18 each independently represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom, and the alkyl group and the fluoroalkyl group each may have an etheric oxygen atom.] A compound represented by At least one compound selected from the group consisting of Item 25. A composition comprising the fluorine-containing polymer (A1) according to item 24. Section 27. The decomposition product (C) of the polymerization initiator (B) is Formula (C1) [ka] [In the formula, R 41 and R 42 each independently represents a fluorine atom, a C1-C20 alkyl group, or a C1-C20 fluoroalkyl group; The alkyl group and the fluoroalkyl group each may have an etheric oxygen atom, and R 41 and R 42 may be linked together to form a 4-20-membered ring having 4 to 20 carbon atoms as ring-constituting atoms and at least one fluorine atom, or a 4-22-membered ring having 3 to 20 carbon atoms and one or two oxygen atoms or one sulfur atom as ring-constituting atoms and at least one fluorine atom, R 43represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C2) [ka] [In the formula, R 45 is a C1-C20 linear or branched alkyl group, represents a branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom; R 46 represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C3) [ka] [In the formula, R 47 represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom, wherein the alkyl group and the fluoroalkyl group each may have an etheric oxygen atom; R 49 represents a fluorine atom or a hydroxyl group. A compound represented by At least one compound selected from the group consisting of Item 26. A composition comprising the fluorine-containing polymer (A1) according to item 24 or 25. Section 28. The polymerization initiator (B) Formula (B1) [ka] [In the formula, R 11 and R 13 is a fluorine atom, R 12 and R 14 are each independently -(CF2) n1 CF3 (wherein n1 is an integer of 0 to 5), -(CF2) n2 CF2H (wherein n2 is an integer from 0 to 5), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 5), or -O-(CF2) n4 CF2H (wherein n4 is an integer of 0 to 5). A compound represented by the formula: Formula (B2) [ka] [In the formula, R 15 and R 16 each independently represents a C1-C7 linear or branched alkyl group, or a C1-C7 linear or branched fluoroalkyl group.] A compound represented by the formula: Formula (B3) [ka] [In the formula, R 17 is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R 18 represents tert-butyl, tert-hexyl, or trifluoromethyl. A compound represented by Item 25. A composition comprising the fluorine-containing polymer (A1) according to item 24, which is at least one compound selected from the group consisting of: Section 29. The decomposition product (C) Formula (C1) [ka] [In the formula, R 41 represents a fluorine atom, R 42 teeth, -(CF2) n1 CF3 (wherein n1 is an integer of 0 to 5), -(CF2) n2CF2H (wherein n2 is an integer from 0 to 5), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 5), or -O-(CF2) n4 CF2H (where n4 is an integer from 0 to 5.) indicates, R 43 represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C2) [ka] [In the formula, R 45 represents a C1-C7 linear or branched alkyl group or a C1-C7 linear or branched fluoroalkyl group; R 46 represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C3) [ka] [In the formula, R 47 is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R 49 represents a fluorine atom or a hydroxyl group. A compound represented by 29. A composition comprising the fluorine-containing polymer (A1) according to any one of items 24 to 26 and 28, which is at least one compound selected from the group consisting of: Section 30. 30. A composition containing a fluorine-containing polymer (A1) according to any one of items 24 to 29, wherein the solvent (D) is at least one selected from the group consisting of hydrofluoroethers and fluorine-containing alcohols. Section 31. The polymerization initiator (B) Formula (B1) [ka] [In the formula, R11 and R 13 is a fluorine atom, R 12 and R 14 are each independently -(CF2) n1 CF3 (wherein n1 is an integer of 0 to 5), -(CF2) n2 CF2H (wherein n2 is an integer from 0 to 5), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 5), or -O-(CF2) n4 CF2H (wherein n4 is an integer of 0 to 5). A compound represented by the formula: Formula (B2) [ka] [In the formula, R 15 and R 16 each independently represents a C1-C7 linear or branched alkyl group, or a C1-C7 linear or branched fluoroalkyl group.] A compound represented by the formula: Formula (B3) [ka] [In the formula, R 17 is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R 18 represents tert-butyl, tert-hexyl, or trifluoromethyl. A compound represented by At least one compound selected from the group consisting of The decomposition product (C) Formula (C1) [ka] [In the formula, R 41 represents a fluorine atom, R 42 teeth, -(CF2) n1 CF3 (wherein n1 is an integer of 0 to 5), -(CF2) n2 CF2H (wherein n2 is an integer from 0 to 5), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 5), or -O-(CF2) n4 CF2H (where n4 is an integer from 0 to 5.) indicates, R 43 represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C2) [ka] [In the formula, R 45 represents a C1-C7 linear or branched alkyl group or a C1-C7 linear or branched fluoroalkyl group; R 46 represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C3) [ka] [In the formula, R 47 is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R 49 represents a fluorine atom or a hydroxyl group. A compound represented by At least one compound selected from the group consisting of The solvent (D) is at least one selected from the group consisting of hydrofluoroethers and fluorine-containing alcohols. Item 25. A composition comprising the fluorine-containing polymer (A1) according to item 24. Effect of the Invention

[0009] The present disclosure can provide a composition containing a fluorine-containing polymer having high ultraviolet light transmittance, a method for producing a fluorine-containing polymer having high ultraviolet light transmittance, a lens for an ultraviolet light emitting device containing a fluorine-containing polymer having high ultraviolet light transmittance, and the like. The production method of the present disclosure can produce a fluorine-containing polymer with high ultraviolet light transmittance through a polymerization step and a filtration step, without requiring a step of removing the polymerization initiator and / or its decomposition products after polymerization. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The above summary of the present disclosure is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The remainder of the disclosure more particularly exemplifies example embodiments. In several places in this disclosure, guidance is provided through examples, which examples can be used in various combinations. In each instance, the exemplary group can serve as a non-exclusive and representative group. All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety.

[0011] term Unless otherwise specified, the symbols and abbreviations in this specification should be understood to have the meanings commonly used in the technical field to which this disclosure pertains, in accordance with the context of this specification.

[0012] As used herein, the phrase "comprising" is intended to encompass the phrases "consisting essentially of" and "consisting of."

[0013] Unless otherwise specified, the steps, treatments, or operations described herein are carried out at room temperature. It can be carried out. In this specification, room temperature can mean a temperature within the range of 10 to 40°C.

[0014] In this specification, the notation "Cn-Cm" (wherein n and m are each a number) indicates that the number of carbon atoms is n or more and m or less, as is commonly understood by those skilled in the art.

[0015] In this specification, unless otherwise specified, the "alkyl group" is a straight-chain, branched-chain or cyclic alkyl group. Examples of the alkyl group include methyl, ethyl, propyl (e.g., n-propyl, isopropyl), butyl (e.g., n-butyl, isobutyl, sec-butyl, tert-butyl), pentyl (e.g., n-pentyl, tert-pentyl, neopentyl, isopentyl, sec-pentyl, 3-pentyl), hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, Examples of such alkyl groups include linear or branched C1-C20 alkyl groups such as icosyl (e.g., C1-C10, preferably C1-C7, more preferably C1-C6, even more preferably C1-C4, and particularly preferably C1-C3 alkyl groups); and cyclic C3-C10 alkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and adamantyl (e.g., C3-C6, C4-C6, C3-C5, C5-C6, and C4-C8 alkyl groups).

[0016] In this specification, unless otherwise specified, the "alkoxy group" is a linear, branched or cyclic alkoxy group. The alkoxy group can be a group represented by RO- [wherein R is an alkyl group (e.g., a C1-C20 alkyl group, a C1-C10 alkyl group, a C1-C7 alkyl group, a C1-C6 alkyl group, a C1-C4 alkyl group, a C1-C3 alkyl group)].

[0017] Examples of alkoxy groups are methoxy, ethoxy, propoxy (e.g., n-propoxy, isopropoxy), butoxy (e.g., n-butoxy, isobutoxy, sec-butoxy, tert-butoxy), pentyloxy (e.g., n-pentyloxy, tert-pentyloxy, neopentyloxy, isopentyloxy, sec-pentyloxy, 3-pentyloxy), hexyloxy, heptyloxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy, tetradecyloxy, pentadecyloxy, hexadecyloxy, heptadecyloxyl. These include linear or branched alkoxy groups, for example, C1-C20 alkoxy groups (e.g., C1-C10, preferably C1-C7, more preferably C1-C6, even more preferably C1-C4, and particularly preferably C1-C3 alkoxy groups), such as cyclopropoxy, cyclobutoxy, cyclopentyloxy, cyclohexyloxy, cycloheptyloxy, cyclooctyloxy, and adamantyloxy; and cyclic C3-C10 alkoxy groups (e.g., C3-C6, C4-C6, C3-C5, C5-C6, and C4-C8 alkoxy groups).

[0018] In this specification, unless otherwise specified, a "fluoroalkyl group" refers to a linear, branched, or cyclic alkyl group in which at least one hydrogen atom is replaced with a fluorine atom. The fluoroalkyl group also includes a perfluoroalkyl group in which all hydrogen atoms of the alkyl group are replaced with fluorine atoms.

[0019] The fluoroalkyl group can have 1 to 20 carbon atoms, 1 to 10, 1 to 7, 1 to 6, 1 to 5, 1 to 4, 1 to 3, 1 to 2, or 1 carbon atom.

[0020] Examples of fluoroalkyl groups are methyl having 1 to 3 fluorine atoms, ethyl having 1 to 7 fluorine atoms (e.g., n-propyl, isopropyl), butyl having 1 to 9 fluorine atoms (e.g., n-butyl, isobutyl, sec-butyl, tert-butyl), pentyl having 1 to 11 fluorine atoms (e.g., n-pentyl, tert-pentyl, neopentyl, isopentyl, sec-pentyl, 3-pentyl), hexyl having 1 to 13 fluorine atoms, heptyl having 1 to 15 fluorine atoms, octyl having 1 to 17 fluorine atoms, nonyl having 1 to 19 fluorine atoms, decyl having 1 to 21 fluorine atoms, undecyl having 1 to 23 fluorine atoms, dodecyl having 1 to 25 fluorine atoms, tridecyl having 1 to 27 fluorine atoms, tetradecyl having 1 to 29 fluorine atoms, pentadecyl having 1 to 31 fluorine atoms, linear or branched C1-C20 fluoroalkyl groups (e.g., C1-C10, C1-C4, C1-C3, etc., preferably C1-C7, more preferably C1-C6 fluoroalkyl groups (preferably perfluoroalkyl groups) such as hexadecyl having 1 to 35 fluorine atoms, heptadecyl having 1 to 37 fluorine atoms, octadecyl having 1 to 39 fluorine atoms, and icosyl having 1 to 41 fluorine atoms; cyclic C3-C10 fluoroalkyl groups (e.g., C3-C6, C4-C6, C3-C5, C5-C6, C4-C8 fluoroalkyl groups) (preferably perfluoroalkyl groups) such as cyclofluoropropyl, cyclofluorobutyl, cyclofluoropentyl, cyclofluorohexyl, cyclofluoroheptyl, cyclofluorooctyl, and fluoroadamantyl.

[0021] The number of fluorine atoms contained in the fluoroalkyl group may be from 1 to the maximum number that can be substituted, for example, 1 to 41, 1 to 21, 1 to 19, 1 to 17, 1 to 15, 1 to 13, 1 to 11, 1 to 9, 1 to 7, 1 to 5, 1 to 3, etc. Specific examples of the "fluoroalkyl group" include monofluoromethyl, difluoromethyl, trifluoromethyl (CF3-), 2,2,2-trifluoroethyl, perfluoroethyl group (C2F5-), tetrafluoropropyl group (e.g., HCF2CF2CH2-), hexafluoropropyl (e.g., (CF3)2CH-), perfluoropropyl (e.g., CF3CF2CF2-, (CF3)2CF-), perfluorobutyl (e.g., CF3CF2CF2CF2-, (CF3)2CFCF2-, (CF3)3-), decafluorohexyl (e.g., HCF2CF2CF2CF2CF2-), octafluoropentyl (e.g., HCF2CF2CF2CF2CH2-), perfluoropentyl (e.g., CF3CF2CF2CF2CF2-, (CF3)2CFCF

[0023] Examples of fluoroalkyl groups include linear or branched fluoroalkyl groups such as perfluorohexyl (e.g., CF3CF2CF2CF2CF2CF2CF2-, (CF3)2CFCF2CF2CF2CF2-), perfluoroheptyl (e.g., CF3CF2CF2CF2CF2CF2CF2CF2-, (CF3)2CFCF2CF2CF2CF2-), and perfluorohexadecyl (e.g., CF3CF2CF2CF2CF2CF2CF2CF2CF2CF2CF2CF2CF2CF2CF2CF2CF2CF2-); and cyclic C3-C10 fluoroalkyl groups (preferably perfluoroalkyl groups) such as cyclofluoropropyl, cyclofluorobutyl, cyclofluoropentyl, cyclofluorohexyl, cyclofluoroheptyl, cyclofluorooctyl, and fluoroadamantyl.

[0022] In this specification, unless otherwise specified, a "fluoroalkoxy group" refers to a linear, branched, or cyclic alkoxy group in which at least one hydrogen atom is replaced with a fluorine atom. The fluoroalkoxy group also includes a perfluoroalkoxy group in which all hydrogen atoms of an alkoxy group are replaced with fluorine atoms.

[0023] The fluoroalkoxy group can have 1 to 20 carbon atoms, 1 to 10, 1 to 7, 1 to 6, 1 to 5, 1 to 4, 1 to 3, 1 to 2, or 1 carbon atom.

[0024] Examples of the fluoroalkoxy group are methoxy having 1 to 3 fluorine atoms, alkoxy having 1 to 5 fluorine atoms, ethoxy having a fluorine atom, propoxy having 1 to 7 fluorine atoms (e.g., n-propoxy, isopropoxy), butoxy having 1 to 9 fluorine atoms (e.g., n-butoxy, isobutoxy, sec-butoxy, tert-butoxy), pentyloxy having 1 to 11 fluorine atoms (e.g., n-pentyloxy, tert-pentyloxy, neopentyloxy, isopentyloxy, sec-pentyloxy, 3-pentyloxy), hexyloxy having 1 to 15 fluorine atoms, heptyloxy having 1 to 17 fluorine atoms, octyloxy having 1 to 19 fluorine atoms, decyloxy having 1 to 21 fluorine atoms, undecyloxy having 1 to 23 fluorine atoms, dodecyloxy having 1 to 25 fluorine atoms, tridecyloxy having 1 to 27 fluorine atoms, tetradecyloxy having 1 to 29 fluorine atoms, pentyoxy having 1 to 31 fluorine atoms, linear or branched C1-C20 fluoroalkoxy groups (e.g., C1-C10, preferably C1-C7, more preferably C1-C6, still more preferably C1-C4, particularly preferably C1-C3) fluoroalkoxy groups (preferably perfluoroalkoxy groups) such as tadecyloxy, hexadecyloxy having 1 to 33 fluorine atoms, heptadecyloxy having 1 to 35 fluorine atoms, octadecyloxy having 1 to 37 fluorine atoms, nonadecyloxy having 1 to 39 fluorine atoms, and icosyloxy having 1 to 41 fluorine atoms; and cyclic C3-C10 fluoroalkoxy groups (e.g., C3-C6, C4-C6, C3-C5, C5-C6, and C4-C8 fluoroalkoxy groups) such as cyclofluoropropoxy, cyclofluorobutoxy, cyclofluoropentyloxy, cyclofluorohexyloxy, cyclofluoroheptyloxy, cyclofluorooctyloxy, and fluoroadamantyloxy.

[0025] The number of fluorine atoms contained in the fluoroalkoxy group may be from 1 to the maximum number that can be substituted, for example, 1 to 41, 1 to 21, 1 to 19, 1 to 17, 1 to 15, 1 to 13, 1 to 11, 1 to 9, 1 to 7, 1 to 5, 1 to 3, etc.

[0026] Specific examples of the "fluoroalkoxy group" include monofluoromethoxy, difluoromethoxy, trifluoromethoxy (CF3O-), 2,2,2-trifluoroethoxy, perfluoroethoxy (C2F5O-), tetrafluoropropoxy (e.g., HCF2CF2CH2O-), hexafluoropropoxy group (e.g., (CF3)2CHO-), perfluoropropoxy (e.g., CF3CF2CF2O-, (CF3)2CFO-), perfluorobutoxy (e.g., CF3CF2CF2CF2O-, (CF3)2CFCF2O-, (CF3)3O-), decafluorohexyloxy (e.g., HCF2CF2CF2CF2CF2O-), octafluoropentyloxy (e.g., HCF2CF2CF2CF2CH2O-), perfluoropentyloxy (e.g., CF3CF2CF2CF2CF2O-, (CF3)2CFCF2C

[0023] Examples of fluoroalkoxy groups include linear or branched fluoroalkoxy groups such as F2O-), perfluorohexyloxy (e.g., CF3CF2CF2CF2CF2CF2CF2O-, (CF3)2CFCF2CF2CF2CF2O-), perfluoroheptyloxy (e.g., CF3CF2CF2CF2CF2CF2CF2CF2CF2O-, (CF3)2CFCF2CF2CF2CF2CF2O-), and perfluorohexadecyloxy (e.g., CF3CF2CF2CF2CF2CF2CF2CF2CF2CF2CF2CF2CF2CF2CF2CF2CF2CF2CF2CF2CF2O-); and cyclic C3-C10 fluoroalkoxy groups (preferably perfluoroalkoxy groups) such as cyclofluoropropoxy, cyclofluorobutoxy, cyclofluoropentyloxy, cyclofluorohexyloxy, cyclofluoroheptyloxy, cyclofluorooctyloxy, and fluoroadamantyloxy.

[0027] In this specification, unless otherwise specified, examples of the "4- to 20-membered ring having 4 to 20 carbon atoms as ring-constituting atoms" include a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a cycloheptane ring, a cyclooctane ring, a cyclononane ring, a cyclodecane ring, a cyclohexyl ... Examples of the aromatic ring include cycloalkane rings such as a lowendecane ring and a cyclododecane ring (preferably a cyclobutane ring, a cyclopentane ring, or a cyclohexane ring); non-aromatic unsaturated hydrocarbon rings such as a cyclobutadiene ring or a cyclooctatetraene ring; and aromatic rings such as a benzene ring, a naphthalene ring, an anthracene ring, or a phenanthrene ring.

[0028] In this specification, unless otherwise specified, examples of the "4- to 22-membered ring having 3 to 20 carbon atoms and 1 or 2 oxygen atoms or 1 sulfur atom as ring-constituting atoms" include oxygen-containing saturated heterocyclic rings having one oxygen atom as a ring-constituting atom, such as an oxetane ring, a tetrahydrofuran ring, a tetrahydropyran ring, an oxepane ring, an oxocane ring, and an oxonane ring; oxygen-containing unsaturated heterocyclic rings having one oxygen atom as a ring-constituting atom, such as an oxetane ring, a furan ring, a pyran ring, an oxepine ring, an oxocine ring, and an oxonine ring; a dioxetane ring, a dioxolane ring, a dioxane ring, a oxygen-containing saturated heterocycles having two oxygen atoms as ring-constituting atoms, such as a dioxepane ring or a dioxocane ring; oxygen-containing unsaturated heterocycles having two oxygen atoms as ring-constituting atoms, such as a dioxete ring, a dioxolene ring, a dihydrodioxine ring, a dihydrodioxepine ring or a tetrahydrodioxocine ring; sulfur-containing unsaturated heterocycles, such as a thiet ring, a thiophene ring, a thiopyran ring, a thiepin ring, a thiocine ring or a thionine ring; sulfur-containing saturated heterocycles, such as a thietane ring, a tetrahydrothiophene ring, a thiane ring, a thiepane ring, a thiocane ring or a thionane ring.

[0029] In this specification, unless otherwise specified, a "4- to 20-membered ring having 4 to 20 carbon atoms as ring constituent atoms and at least one fluorine atom" refers to a ring in which at least one hydrogen atom bonded to a ring constituent atom of a 4- to 20-membered ring having 4 to 20 carbon atoms as ring constituent atoms is substituted with a fluorine atom. The number of fluorine atoms may be 1 to the maximum number that can be substituted. Preferably, it is a ring in which all hydrogen atoms bonded to ring constituent atoms are substituted with fluorine atoms (so-called perfluoro ring).

[0030] In this specification, unless otherwise specified, a "4- to 22-membered ring having 3 to 20 carbon atoms and 1 or 2 oxygen atoms or 1 sulfur atom as ring constituent atoms and having at least one fluorine atom" refers to a ring in which at least one hydrogen atom bonded to a ring constituent atom of a 4- to 22-membered ring having 3 to 20 carbon atoms and 1 or 2 oxygen atoms or 1 sulfur atom as ring constituent atoms is substituted with a fluorine atom. The number of fluorine atoms may be 1 to the maximum number that can be substituted. Preferably, it is a ring in which all hydrogen atoms bonded to ring constituent atoms are substituted with fluorine atoms (so-called perfluoro ring).

[0031] In this specification, unless otherwise specified, the "aryl group" may be a monocyclic, bicyclic, or tricyclic aryl. The aryl group may be a C6-C14 aryl group, a C6-C10 aryl group, a C6-C9 aryl group, or a C6 aryl group. Examples of the aryl group include phenyl, 1-naphthyl, 2-naphthyl, indenyl, biphenylyl, anthryl, and phenanthryl. The aryl group may have methyl, ethyl, propyl, and the like, which may be the same or different when there are multiple groups. The number of groups that the aryl group has may be 6, 5, 4, 3, 2, 1, or 0.

[0032] In this specification, unless otherwise specified, an "aryl group having a fluorine atom" refers to an aryl group in which at least one hydrogen atom is substituted with a fluorine atom, and also includes a perfluoroaryl group in which all hydrogen atoms of an aryl group are substituted with fluorine atoms, with a perfluoroaryl group being preferred.

[0033] The number of fluorine atoms in the aryl group may be from 1 to the maximum substitutable number, for example, 1 to 16, 1 to 15, 1 to 14, 1 to 13, 1 to 12, 1 to 11, 1 to 10, 1 to 9, 1 to 5, 1 to 3, etc.

[0034] Examples of the aryl group having a fluorine atom include phenyl having a fluorine atom, 1-naphthyl having a fluorine atom, 2-naphthyl having a fluorine atom, indenyl having a fluorine atom, biphenylyl having a fluorine atom, anthryl having a fluorine atom, and phenanthryl having a fluorine atom.

[0035] In this specification, unless otherwise specified, examples of the "alkali metal" include lithium, sodium, potassium, rubidium, cesium, and francium, preferred examples include lithium, sodium, and potassium, and more preferred examples include sodium and potassium.

[0036] In this specification, unless otherwise specified, examples of the "alkaline earth metal" include beryllium, magnesium, calcium, strontium, barium, and radium, and preferred examples include magnesium and calcium.

[0037] Method for producing fluoropolymer (A) One embodiment of the present disclosure is a method for producing a fluoropolymer (A). The method for producing the present disclosure can produce a fluoropolymer having high ultraviolet light transmittance. The method for producing the present disclosure includes a polymerization step and a filtration step, but may or may not include a step for removing a polymerization initiator and / or its decomposition product, and is therefore a simple method for producing the present disclosure.

[0038] The method of the present disclosure comprises preparing a compound represented by formula (M) [ka] [In the formula, R 1 ~R 4 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] The method includes a polymerization step of polymerizing the fluorine-containing monomer (M) represented by the following formula (1): The fluoropolymer (A) is represented by the formula (A): [ka] [In the formula, R 1 ~R 4 is the same as above.] (sometimes referred to as structural unit (A) in this specification) as a main component.

[0039] The value of the solubility index R (R A )) can be 4 or more.

[0040] The value of the solubility index R (R B ) can be 9 or less when the mass proportion of fluorine atoms in the polymerization initiator (B) is less than 50 mass%, and can be 6 or less when the mass proportion is 50 mass% or more.

[0041] The value of the solubility index R (R C ) may be 9 or less when the mass proportion of fluorine atoms in the decomposition product (C) is less than 50 mass%, and may be 6 or less when the mass proportion is 50 mass% or more.

[0042] The solubility index R is expressed by the following formula: R = {4 × (δD1-δD2) 2 +(δP1-δP2) 2 +(δH1-δH2) 2} 0.5 [In the formula, δD1, δP1, and δH1 respectively represent the dispersion term, polar term, and hydrogen bond term in the Hansen solubility parameter of element 1, and δD2, δP2, and δH2 respectively represent the dispersion term, polar term, and hydrogen bond term in the Hansen solubility parameter of element 2.] It is calculated from:

[0043] Fluorine-containing polymer (A) The fluoropolymer (A) is represented by the formula (A) [ka] [In the formula, R 1 ~R 4 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] It contains a structural unit represented by the following formula as a main component.

[0044] "Containing a structural unit as a main component" means that the proportion of that structural unit in all structural units in the fluoropolymer (A) is 50 mol % or more.

[0045] The proportion of the structural unit (A) in the fluoropolymer (A) is preferably at least 80 mol %, more preferably at least 90 mol %, particularly preferably 100 mol %.

[0046] The structural unit (A) may be of one or more types, preferably 1 to 3 types, more preferably 1 or 2 types, and particularly preferably 1 type.

[0047] In the structural unit (A), R 1 ~R 4 may each independently be a fluorine atom, a C1-C5 linear or branched perfluoroalkyl group, or a C1-C5 linear or branched perfluoroalkoxy group.

[0048] In the structural unit (A), R 1 ~R 4may each independently be a fluorine atom, a C1-C4 linear or branched perfluoroalkyl group, or a C1-C4 linear or branched perfluoroalkoxy group.

[0049] In the structural unit (A), R 1 ~R 4 are each independently a fluorine atom, C1-C3 It can be a linear or branched perfluoroalkyl group, or a linear or branched C1-C3 perfluoroalkoxy group.

[0050] In the structural unit (A), R 1 ~R 4 are preferably each independently a fluorine atom, trifluoromethyl, perfluoroethyl, or trifluoromethoxy.

[0051] In the structural unit (A), R 1 ~R 4 are each more preferably a fluorine atom, trifluoromethyl, or trifluoromethoxy.

[0052] R 1 ~R 4 at least one group is a fluorine atom, and the remaining groups, when there are a plurality of such remaining groups, may independently be a C1-C2 perfluoroalkyl group or a C1-C2 perfluoroalkoxy group.

[0053] R 1 ~R 4 at least two groups are fluorine atoms, and the remaining groups, when there are a plurality of such remaining groups, may be independently a C1-C2 perfluoroalkyl group or a C1-C2 perfluoroalkoxy group.

[0054] R 1 ~R 4 At least three groups are fluorine atoms, and the remaining groups may be C1-C2 perfluoroalkyl groups or C1-C2 perfluoroalkoxy groups.

[0055] R 1 ~R 4 At least three groups are fluorine atoms, and the remaining groups may be C1-C2 perfluoroalkyl groups.

[0056] R 1 ~R 4 may all be fluorine atoms.

[0057] The structural unit (A) may be a structural unit represented by the following formula (A1) (sometimes referred to as structural unit (A1) in this specification). In this specification, the fluoropolymer (A) containing the structural unit (A1) as a main component may be referred to as the fluoropolymer (A1).

[0058] [ka]

[0059] R 1 ~R 4 In each of the above, the C1-C5 perfluoroalkyl group can be, for example, a linear or branched C1-C5 fluoroalkyl group, a linear or branched C1-C4 fluoroalkyl group, a linear or branched C1-C3 fluoroalkyl group, or a C1-C2 fluoroalkyl group. As the linear or branched C1-C5 fluoroalkyl group, a linear or branched C1-C5 perfluoroalkyl group is preferred. As the linear or branched C1-C4 fluoroalkyl group, a linear or branched C1-C4 perfluoroalkyl group is preferred. As the linear or branched C1-C3 fluoroalkyl group, a linear or branched C1-C3 perfluoroalkyl group is preferred. The C1-C2 fluoroalkyl group is preferably a C1-C2 perfluoroalkyl group.

[0060] The fluoropolymer (A) may contain, in addition to the structural unit (A) contained as the main component, a structural unit derived from a fluoroolefin (sometimes referred to as a fluoroolefin unit in this specification). The fluoroolefin unit may be one type alone or two or more types in combination. The proportion of the fluoroolefin unit in all the structural units in the fluoropolymer (A) may be 50 mol% or less, preferably 20 mol% or less, more preferably 10 mol% or less, and particularly preferably 0 mol%.

[0061] The fluoroolefin unit is a monomer unit formed after polymerization of a monomer containing a fluorine atom and a carbon-carbon double bond.

[0062] The atoms constituting the fluoroolefin unit may be limited to fluorine atoms, halogen atoms other than fluorine atoms, carbon atoms, hydrogen atoms, and oxygen atoms.

[0063] The atoms constituting the fluoroolefin unit may be only fluorine atoms, halogen atoms other than fluorine atoms, carbon atoms, and hydrogen atoms.

[0064] The atoms constituting the fluoroolefin unit may be only fluorine atoms, carbon atoms, and hydrogen atoms.

[0065] The atoms constituting the fluoroolefin unit may be only fluorine atoms and carbon atoms.

[0066] The fluoroolefin unit includes a fluorine-containing perhaloolefin unit, a vinylidene fluoride unit (-CH2-CF2-), a trifluoroethylene unit (-CFH-CF2-), a pentafluoropropylene unit (-CFH-CF(CF3)-, -CF2-CF(CHF2)-), and a 1,1,1,2-tetrafluoro-2-propylene unit (-CH2-CF(CF3)-).

[0067] The fluorine-containing perhaloolefin unit is a structural unit formed after polymerization of a monomer which contains a fluorine atom and a carbon-carbon double bond and may contain halogen atoms other than fluorine atoms.

[0068] The fluorine-containing perhaloolefin unit includes a chlorotrifluoroethylene unit (-CFCl-CF2-), a tetrafluoroethylene unit (-CF2-CF2-), a hexafluoropropylene unit (-CF2-CF(CF3)-), a perfluoro(methyl vinyl ether) unit (-CF2-CF(OCF3)-), a perfluoro(ethyl vinyl ether) unit (-CF2-CF(OC2F5)-), a perfluoro(propyl vinyl ether) unit (-CF2-CF(OCF2C2F5)-), a perfluoro(butyl vinyl ether) unit (-CF2-CF(O(CF2)2C2F5)-), and a perfluoro(2,2-dimethyl-1,3-dioxole) unit (-CF-CAF- (wherein A represents a perfluorodioxolane ring formed together with the adjacent carbon atoms shown in the formula, and two trifluoromethyls are bonded to the carbon atom at the 2-position of the dioxolane ring).

[0069] Fluoroolefin units include chlorotrifluoroethylene units, tetrafluoroethylene units, hexafluoropropylene units, perfluoro(methyl vinyl ether) units, and perfluoro(propyl vinyl ether) units.

[0070] The fluoropolymer (A) may contain, in addition to the structural unit (A) and the fluoroolefin unit, one or more other structural units, but preferably does not contain any. Such other structural units include CH2=CHRf (Rf represents a C1-C10 fluoroalkyl group) units, alkyl vinyl ether units (e.g., cyclohexyl vinyl ether units, ethyl vinyl ether units, butyl vinyl ether units, methyl vinyl ether units), alkenyl vinyl ether units (e.g., polyoxyethylene allyl ether units, ethyl allyl ether units), organosilicon compound units having reactive α,β-unsaturated groups (e.g., vinyltrimethoxysilane units, vinyltriethoxysilane units, vinyltris(methoxyethoxy)silane units), acrylic ester units (e.g., methyl acrylate units, ethyl acrylate units), methacrylic ester units (e.g., methyl methacrylate units, ethyl methacrylate units), vinyl ester units (e.g., vinyl acetate units, vinyl benzoate units, "Veova" (vinyl ester manufactured by Shell) units), and the like.

[0071] The proportion of the other structural units can be, for example, 0 to 20 mol %, 0 to 10 mol %, etc., of all structural units.

[0072] The mass average molecular weight of the fluoropolymer (A) can be, for example, in the range of 5,000 to 1,000,000, 10,000 to 1,000,000, 10,000 to 500,000, or 90,000 to 350,000, preferably in the range of 10,000 to 750,000, more preferably in the range of 40,000 to 500,000, and particularly preferably in the range of 70,000 to 350,000.

[0073] The lower limit of the mass average molecular weight of the fluoropolymer (A) can be, for example, 5000 or more, preferably 10000 or more, more preferably 40000 or more, and particularly preferably 70000 or more. The upper limit of the mass average molecular weight of the fluoropolymer (A) can be, for example, 1000000 or less, preferably 750000 or less, more preferably 500000 or less, and particularly preferably 350000 or less. The lower limit and the upper limit may be appropriately combined.

[0074] The mass average molecular weight of the fluoropolymer (A) is a value determined by GPC (gel permeation chromatography) method (particularly the GPC method described in the examples).

[0075] Polymerization process In the polymerization step, the fluorine-containing monomer (M) is polymerized in the presence of the fluorine-containing monomer (M), a polymerization initiator (B) and a solvent (D). The fluorine-containing polymer (A) is formed as a precipitate in the product liquid.

[0076] Raw material monomer The raw material monomers used in the polymerization step contain at least a fluorine-containing monomer (M). The fluorine-containing monomer (M) is a monomer corresponding to the structural unit (A) contained as a main component in the fluorine-containing polymer (A). The fluorine-containing monomer (M) can be used alone or in combination of two or more kinds.

[0077] When the fluoropolymer (A) to be produced contains, in addition to the structural unit (A), a fluoroolefin unit and / or other structural unit, the raw material monomer may contain, in addition to the monomer (M), a fluoroolefin monomer corresponding to the fluoroolefin unit and / or a monomer corresponding to the other structural unit (sometimes referred to as other monomer in this specification).

[0078] Those skilled in the art can understand that a fluoropolymer (A) having a structural unit corresponding to a specific monomer can be obtained by polymerizing a specific monomer. Therefore, those skilled in the art can select an appropriate monomer to produce a desired fluoropolymer (A). Therefore, those skilled in the art can understand the monomer corresponding to the structural unit (A), the fluoroolefin monomer corresponding to the fluoroolefin unit, and the monomer corresponding to the other structural units.

[0079] For example, a monomer corresponding to the structural unit (A) is represented by the formula (M): [ka] [In the formula, R 1~R 4 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] The fluorine-containing monomer (M) is represented by the following formula:

[0080] For example, a monomer corresponding to the structural unit (A1) is represented by the formula (M1): [ka] (In this specification, this may be referred to as a fluorine-containing monomer (M1)).

[0081] The fluorine-containing monomer (M) may be contaminated with a compound (N). The amount of the compound (N) may be 0.0001 to 10 mass%, 0.0001 to 8 mass%, or 0.0001 to 6 mass% based on the mass of the raw material monomer. The compound (N) may be one type alone or two or more types in combination.

[0082] The compound (N) is Formula (N) [ka] [In the formula, R 1 ~R 4 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group; R 71 and R 72 each independently represents a hydrogen atom or a fluorine atom; R 71 and R 72 When one of the groups is a hydrogen atom, the other group is a fluorine atom. It is a compound represented by the formula:

[0083] R 1 ~R 4 The details are as described above. R 71 is a hydrogen atom and R 72 is a fluorine atom, and R 71 is a fluorine atom and R 72is preferably a hydrogen atom.

[0084] Further preferred compounds (N) are those of formula (N1) [ka] (hereinafter, may be referred to as compound (N1)) represented by the formula: Formula (N2) [ka] The compound is at least one compound selected from the group consisting of compounds represented by the following formula (hereinafter, may be referred to as compound (N2)).

[0085] The ratios (e.g., molar ratios) of the fluorine-containing monomer (M), fluoroolefin monomer and other monomers in the raw material monomers can be appropriately selected according to the ratios (e.g., molar ratios) of the respective structural units constituting the fluorine-containing polymer (A) to be produced. Therefore, those skilled in the art can understand the details of the fluorine-containing monomer (M), fluoroolefin monomer and other monomers from the above descriptions of the corresponding structural units (A), fluoroolefin units and other structural units.

[0086] As the fluoroolefin monomer, a monomer corresponding to the fluoroolefin unit can be used. The fluoroolefin may be, for example, at least one selected from the group consisting of fluorine-containing perhaloolefin, vinylidene fluoride, trifluoroethylene, pentafluoropropylene, and 1,1,1,2-tetrafluoro-2-propylene. The fluoroolefin monomer may be, preferably, at least one selected from the group consisting of chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(methyl vinyl ether), and perfluoro(propyl vinyl ether).

[0087] The fluorine-containing perhaloolefin may be at least one selected from the group consisting of chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), perfluoro(propyl vinyl ether), perfluoro(butyl vinyl ether), and perfluoro(2,2-dimethyl-1,3-dioxole).

[0088] Polymerization initiator (B) The polymerization initiator (B) can be any one that can polymerize the raw material monomer. The polymerization initiator (B) can be a peroxide, an azo, or the like, and is preferably a peroxide. The polymerization initiator (B) can be used alone or in combination of two or more.

[0089] The peroxides are represented by the formula (B1) [ka] [In the formula, R 11 , R 12 , R 13 , and R 14 each independently represents a fluorine atom, a C1-C20 alkyl group, or a C1-C20 fluoroalkyl group; The alkyl group and the fluoroalkyl group each may have an etheric oxygen atom, and R 11 and R 12 may be linked together to form a 4-20-membered ring having 4 to 20 carbon atoms as ring-constituting atoms and at least one fluorine atom, or a 4-22-membered ring having 3 to 20 carbon atoms and one or two oxygen atoms or one sulfur atom as ring-constituting atoms and at least one fluorine atom, R 13 and R 14 may be linked together to form a 4-20-membered ring having 4 to 20 carbon atoms as ring constituent atoms and at least one fluorine atom, or a 4-22-membered ring having 3 to 20 carbon atoms and one or two oxygen atoms or one sulfur atom as ring constituent atoms and at least one fluorine atom.] (hereinafter, sometimes referred to as compound (B1)). Formula (B2) [ka] [In the formula, R 15 and R 16 each independently represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom.] (hereinafter, may be referred to as compound (B2)) Formula (B3) [ka] [In the formula, R 17 and R 18 each independently represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom, and the alkyl group and the fluoroalkyl group each may have an etheric oxygen atom.] (In this specification, the compound represented by the formula (B3) may be referred to as compound (B3).) The compound (B) may be at least one compound selected from the group consisting of:

[0090] In formula (B1), R 11 and R 13 are the same, and R 12 and R 14 are the same, or R 11 and R 12 A ring structure formed by linking together R 13 and R 14 and the ring structure formed by linking them to each other are preferably the same.

[0091] In formula (B1), R 11 , R 12 , R 13 , and R 14 are each independently fluorine atom, -(CF2) n1 CF3 (wherein n1 is an integer of 0 to 5), -(CF2) n2 CF2H (wherein n2 is an integer from 0 to 5), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 5), or -O-(CF2) n4 CF2H (wherein n4 is an integer from 0 to 5), or R 11 and R 12 are linked to each other to form a 4- to 8-membered perfluorocycloalkane ring, a perfluorobenzene ring, a perfluoronaphthalene ring, a perfluorooxolane ring, or a perfluorodioxolane ring, and R 13 and R 14 are linked together to form a 4- to 8-membered perfluorocycloalkane ring, a perfluorobenzene ring, a perfluoronaphthalene ring, a perfluorooxolane ring, or a perfluorodioxolane ring, It could be.

[0092] In formula (B1), R 11 , R 12 , R 13 , and R 14 are each independently fluorine atom, -(CF2) n1 CF3 (wherein n1 is an integer of 0 to 5), -(CF2) n2 CF2H (wherein n2 is an integer from 0 to 5), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 5), or -O-(CF2) n4 CF2H (wherein n4 is an integer from 0 to 5), or R 11and R 12 are linked to each other to form a 4- to 6-membered perfluorocycloalkane ring, a perfluorobenzene ring, or a perfluoronaphthalene ring, and R 13 and R 14 are linked to each other to form a 4- to 6-membered perfluorocycloalkane ring, a perfluorobenzene ring, or a perfluoronaphthalene ring. It could be.

[0093] In formula (B1), R 11 , R 12 , R 13 , and R 14 are each independently -(CF2) n1 CF3 (wherein n1 is an integer of 0 to 5), -(CF2) n2 CF2H (wherein n2 is an integer from 0 to 5), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 5), or -O-(CF2) n4 CF2H (wherein n4 is an integer from 0 to 5), or R 11 and R 12 are linked to each other to form a 4- to 6-membered perfluorocycloalkane ring, a perfluorobenzene ring, or a perfluoronaphthalene ring, and R 13 and R 14 are linked to each other to form a 4- to 6-membered perfluorocycloalkane ring, a perfluorobenzene ring, or a perfluoronaphthalene ring. It could be.

[0094] In formula (B1), R 11 , R 12 , R 13 , and R 14 are each independently fluorine atom, -(CF2) n1 CF3 (wherein n1 is an integer of 0 to 2), -(CF2) n2CF2H (wherein n2 is an integer from 0 to 2), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 2), or -O-(CF2) n4 CF2H (wherein n4 is an integer from 0 to 2), or R 11 and R 12 are linked to each other to form a 4- to 6-membered perfluorocycloalkane ring, a perfluorobenzene ring, or a perfluoronaphthalene ring, and R 13 and R 14 are linked to each other to form a 4- to 6-membered perfluorocycloalkane ring, a perfluorobenzene ring, or a perfluoronaphthalene ring. It could be.

[0095] In formula (B1), R 11 , R 12 , R 13 , and R 14 are each independently -(CF2) n1 CF3 (wherein n1 is an integer of 0 to 2), -(CF2) n2 CF2H (wherein n2 is an integer from 0 to 2), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 2), or -O-(CF2) n4 CF2H (wherein n4 is an integer from 0 to 2), or R 11 and R 12 are linked to each other to form a 4- to 6-membered perfluorocycloalkane ring, a perfluorobenzene ring, or a perfluoronaphthalene ring, and R 13 and R 14 are linked to each other to form a 4- to 6-membered perfluorocycloalkane ring, a perfluorobenzene ring, or a perfluoronaphthalene ring. It could be.

[0096] In formula (B1), R 11 and R13 may be a fluorine atom, R 12 and R 14 are each independently -(CF2) n1 CF3 (wherein n1 is an integer of 0 to 5), -(CF2) n2 CF2H (wherein n2 is an integer from 0 to 5), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 5), or -O-(CF2) n4 CF2H (where n4 is an integer from 0 to 5.) It could be.

[0097] In formula (B2), R 15 and R 16 are preferably identical. In formula (B2), it is preferable that the alkyl group and the fluoroalkyl group do not have an etheric oxygen atom.

[0098] In formula (B2), the C4-C8 cyclic alkyl group can be cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl. In formula (B2), the C4-C8 cyclic fluoroalkyl group can be fluorocyclobutyl, fluorocyclopentyl, fluorocyclohexyl, fluorocycloheptyl, or fluorocyclooctyl. In formula (B2), the C4-C8 cyclic fluoroalkyl group can be a C4-C6 cyclic fluoroalkyl group. The C4-C6 cyclic fluoroalkyl group can be fluorocyclobutyl, fluorocyclopentyl, or fluorocyclohexyl.

[0099] In formula (B2), the C4-C14 aryl group which may have a fluorine atom may be a phenyl, naphthyl, anthryl or phenanthryl group which may have a fluorine atom. In formula (B2), the C4-C14 aryl group which may have a fluorine atom may be phenyl, naphthyl, anthryl or phenanthryl. In formula (B2), the C4-C14 aryl group which may have a fluorine atom may be phenyl or naphthyl.

[0100] In formula (B2), R 15 and R 16 may each independently be a C1-C7 linear or branched alkyl group, a C1-C7 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom. The alkyl group and the fluoroalkyl group may each have an etheric oxygen atom.

[0101] In formula (B2), R 15 and R 16 each independently represents a C1-C7 linear or branched alkyl group, a C1-C7 linear or branched fluoroalkyl group, cyclobutyl, It can be cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, fluorocyclobutyl, fluorocyclopentyl, fluorocyclohexyl, fluorocycloheptyl, fluorocyclooctyl, phenyl which may have a fluorine atom, naphthyl which may have a fluorine atom, anthryl which may have a fluorine atom, or phenanthryl which may have a fluorine atom.

[0102] In formula (B2), R 15 and R 16 may each independently be a C1-C7 linear or branched alkyl group, a C1-C7 linear or branched fluoroalkyl group, cyclobutyl, cyclopentyl, cyclohexyl, fluorocyclobutyl, fluorocyclopentyl, fluorocyclohexyl, phenyl, naphthyl, phenyl having a fluorine atom, or naphthyl having a fluorine atom.

[0103] In formula (B2), R 15 and R 16may each independently be a C1-C7 linear or branched alkyl group, or a C1-C7 linear or branched fluoroalkyl group.

[0104] In formula (B3), R 17 and R 18 are preferably not identical. In formula (B3), R 17 When is an alkyl group or a fluoroalkyl group, it preferably does not have an etheric oxygen atom.

[0105] In formula (B3), the C4-C8 cyclic alkyl group can be cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl. In formula (B3), the C4-C8 cyclic fluoroalkyl group can be fluorocyclobutyl, fluorocyclopentyl, fluorocyclohexyl, fluorocycloheptyl, or fluorocyclooctyl. In formula (B3), the C4-C8 cyclic fluoroalkyl group can be a C4-C6 cyclic fluoroalkyl group. The C4-C6 cyclic fluoroalkyl group can be fluorocyclobutyl, fluorocyclopentyl, or fluorocyclohexyl.

[0106] In formula (B3), the C4-C14 aryl group which may have a fluorine atom may be a phenyl, naphthyl, anthryl, or phenanthryl group which may have a fluorine atom. In formula (B3), the C4-C14 aryl group which may have a fluorine atom may be phenyl, naphthyl, anthryl or phenanthryl. In formula (B3), the C4-C14 aryl group which may have a fluorine atom may be a phenyl or naphthyl group which may have a fluorine atom. In formula (B3), the C4-C14 aryl group which may have a fluorine atom may be phenyl or naphthyl.

[0107] In formula (B3), R 17 and R 18may each independently be a C1-C9 linear or branched alkyl group, a C1-C9 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom. The alkyl group and the fluoroalkyl group may each have an etheric oxygen atom.

[0108] In formula (B3), R 17 and R 18 each independently represents a C1-C9 linear or branched alkyl group, a C1-C9 linear or branched fluoroalkyl group, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, fluorocyclobutyl, fluorocyclopentyl, fluorocyclohexyl, fluorocycloheptyl, fluorocyclooctyl, phenyl which may have a fluorine atom, naphthyl which may have a fluorine atom, anthryl which may have a fluorine atom, or phenyl which may have a fluorine atom. The alkyl group and the fluoroalkyl group may each have an ether oxygen atom.

[0109] In formula (B3), R 17 and R 18 may each independently be a C1-C9 linear or branched alkyl group, a C1-C9 linear or branched fluoroalkyl group, cyclobutyl, cyclopentyl, cyclohexyl, fluorocyclobutyl, fluorocyclopentyl, fluorocyclohexyl, phenyl, naphthyl, phenyl having a fluorine atom, or naphthyl having a fluorine atom. The alkyl group and the fluoroalkyl group may each have an etheric oxygen atom.

[0110] In formula (B3), R 17 can be a C1-C6 straight chain alkyl group, a C3-C9 branched chain alkyl group, a C1-C6 straight chain fluoroalkyl group, a C3-C6 branched chain fluoroalkyl group, or phenyl.

[0111] In formula (B3), R17 is methyl, tert-butyl, tert-nonyl, tri It may be fluoromethyl, perfluoroisopentyl, or phenyl.

[0112] In formula (B3), R 18 may be a C1-C6 linear alkyl group, a C3-C6 branched alkyl group, a C1-C6 linear fluoroalkyl group, or a C3-C6 branched fluoroalkyl group. The alkyl group and the fluoroalkyl group may each have an etheric oxygen atom.

[0113] In formula (B3), R 18 can be tert-butyl, tert-hexyl, or trifluoromethyl.

[0114] In formula (B3), R 17 is methyl, tert-butyl, tert-nonyl, tri fluoromethyl, perfluoroisopentyl, or phenyl; R 18 can be tert-butyl, tert-hexyl, or trifluoromethyl.

[0115] Examples of compound (B1) include compounds represented by the following structural formula: In the structural formula, m1 represents an integer of 0 to 6, m2 represents an integer of 0 to 6, m3 represents an integer of 0 to 2, and m4 represents an integer of 0 to 2, and m3 and m4 may be the same or different. [ka]

[0116] Preferred examples of the compound (B1) include bis(2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoro-1-oxoheptyl)peroxide (DHP) and bis(cyclohexylcarbonyl)peroxide.

[0117] Examples of compound (B2) include di-sec-butyl peroxydicarbonate, di-n-propyl peroxydicarbonate (NPP), diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, ditrifluoromethyl peroxydicarbonate, dipentafluoroethyl peroxydicarbonate, diheptafluoro-n-propyl peroxydicarbonate, and diheptafluoroisopropyl peroxydicarbonate.

[0118] Preferred examples of the compound (B2) include diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate (NPP), and ditrifluoromethyl peroxydicarbonate.

[0119] Examples of compound (B3) include tert-butyl peroxyacetate (TBPOA), tert-butyl peroxypivalate, tert-hexyl peroxypivalate, tert-butyl peroxyneodecanoate, tert-butyl peroxybenzoate, trifluoromethyl-2,2,2-trifluoromethylethane peroxoate (CF3COOOCF3), and heptafluoroisopropyl-2,2,2-trifluoromethylethane peroxoate ((CF3)2CFCOOOCF3).

[0120] Preferred examples of compound (B3) include tert-butyl peroxyacetate (TBPOA), tert-butyl peroxybenzoate, trifluoromethyl-2,2,2-trifluoromethylethane peroxoate (CF3COOOCF3).

[0121] Decomposition product (C) of polymerization initiator (B) The decomposition product (C) of the polymerization initiator (B) is generated by decomposing the polymerization initiator (B) in the polymerization step. The decomposition product (C) is contained in the polymerization reaction liquid and the precipitate after the polymerization reaction. The decomposition product (C) in the polymerization reaction liquid is separated from the precipitate in the filtration step. The decomposition product (C) can be used alone or in combination of two or more kinds.

[0122] The decomposition product (C) is Formula (C1) [ka] [In the formula, R 41 and R 42 each independently represents a fluorine atom, a C1-C20 alkyl group, or a C1-C20 fluoroalkyl group; The alkyl group and the fluoroalkyl group each may have an etheric oxygen atom, and R 41 and R 42 may be linked together to form a 4-20-membered ring having 4 to 20 carbon atoms as ring-constituting atoms and at least one fluorine atom, or a 4-22-membered ring having 3 to 20 carbon atoms and one or two oxygen atoms or one sulfur atom as ring-constituting atoms and at least one fluorine atom, R 43 represents a fluorine atom or a hydroxyl group. (hereinafter, sometimes referred to as compound (C1)). Formula (C2) [ka] [In the formula, R 45 represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group optionally having a fluorine atom; R 46 represents a fluorine atom or a hydroxyl group. (hereinafter, may be referred to as compound (C2)) Formula (C3) [ka] [In the formula, R 47represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom, wherein the alkyl group and the fluoroalkyl group each may have an etheric oxygen atom; R 49 represents a fluorine atom or a hydroxyl group. (In this specification, this may be referred to as compound (C3)). At least one compound selected from the group consisting of (herein referred to as compound (C) There may be cases where.

[0123] In formula (C1), R 41 and R 42 are each independently fluorine atom, -(CF2) n1 CF3 (wherein n1 is an integer of 0 to 5), -(CF2) n2 CF2H (wherein n2 is an integer from 0 to 5), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 5), or -O-(CF2) n4 CF2H (wherein n4 is an integer from 0 to 5), or R 41 and R 42 are linked together to form a 4- to 8-membered perfluorocycloalkane ring, a perfluorobenzene ring, a perfluoronaphthalene ring, a perfluorooxolane ring, or a perfluorodioxolane ring; It may be R 43 can be a fluorine atom or a hydroxyl group.

[0124] In formula (C1), R 41 and R 42 are each independently fluorine atom, -(CF2) n1CF3 (wherein n1 is an integer of 0 to 5), -(CF2) n2 CF2H (wherein n2 is an integer from 0 to 5), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 5), or -O-(CF2) n4 CF2H (wherein n4 is an integer from 0 to 5), or R 41 and R 42 are linked to each other to form a 4- to 6-membered perfluorocycloalkane ring, a perfluorobenzene ring, or a perfluoronaphthalene ring. It may be R 43 can be a fluorine atom or a hydroxyl group.

[0125] In formula (C1), R 41 and R 42 are each independently -(CF2) n1 CF3 (wherein n1 is an integer of 0 to 5), -(CF2) n2 CF2H (wherein n2 is an integer from 0 to 5), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 5), or -O-(CF2) n4 CF2H (wherein n4 is an integer from 0 to 5), or R 41 and R 42 are linked to each other to form a 4- to 6-membered perfluorocycloalkane ring, a perfluorobenzene ring, or a perfluoronaphthalene ring. It may be R 43 can be a fluorine atom or a hydroxyl group.

[0126] In formula (C1), R 41 and R 42 are each independently fluorine atom, -(CF2) n1CF3 (wherein n1 is an integer of 0 to 2), -(CF2) n2 CF2H (wherein n2 is an integer from 0 to 2), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 2), or -O-(CF2) n4 CF2H (wherein n4 is an integer from 0 to 2), or R 41 and R 42 are linked to each other to form a 4- to 6-membered perfluorocycloalkane ring, a perfluorobenzene ring, or a perfluoronaphthalene ring. It may be R 43 can be a fluorine atom or a hydroxyl group.

[0127] In formula (C1), R 41 and R 42 are each independently -(CF2) n1 CF3 (wherein n1 is an integer of 0 to 2), -(CF2) n2 CF2H (wherein n2 is an integer from 0 to 2), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 2), or -O-(CF2) n4 CF2H (wherein n4 is an integer from 0 to 2), or R 41 and R 42 are linked to each other to form a 4- to 6-membered perfluorocycloalkane ring, a perfluorobenzene ring, or a perfluoronaphthalene ring. It may be R 43 can be a fluorine atom or a hydroxyl group.

[0128] In formula (C1), R 41 may be a fluorine atom, R 42 teeth, -(CF2) n1 CF3 (wherein n1 is an integer of 0 to 5), -(CF2) n2 CF2H (wherein n2 is an integer from 0 to 5), -O-(CF2) n3 CF3 (wherein n3 is an integer of 0 to 5), or -O-(CF2) n4 CF2H (where n4 is an integer from 0 to 5.) It may be R 43 can be a fluorine atom or a hydroxyl group.

[0129] In formula (C2), it is preferable that the alkyl group and the fluoroalkyl group do not have an etheric oxygen atom.

[0130] In formula (C2), the C4-C8 cyclic alkyl group can be cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl. In formula (C2), the C4-C8 cyclic fluoroalkyl group can be fluorocyclobutyl, fluorocyclopentyl, fluorocyclohexyl, fluorocycloheptyl, or fluorocyclooctyl. In formula (C2), the C4-C8 cyclic fluoroalkyl group can be a C4-C6 cyclic fluoroalkyl group. The C4-C6 cyclic fluoroalkyl group can be fluorocyclobutyl, fluorocyclopentyl, or fluorocyclohexyl.

[0131] In formula (C2), the C4-C14 aryl group which may have a fluorine atom may be a phenyl, naphthyl, anthryl or phenanthryl group which may have a fluorine atom. In formula (C2), the C4-C14 aryl group which may have a fluorine atom may be phenyl, naphthyl, anthryl or phenanthryl. In formula (C2), the C4-C14 aryl group which may have a fluorine atom may be phenyl or naphthyl.

[0132] In formula (C2), R 45may be a C1-C7 linear or branched alkyl group, a C1-C7 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group optionally having a fluorine atom, the alkyl group and the fluoroalkyl group each optionally having an ether oxygen atom; R 46 can be a fluorine atom or a hydroxyl group.

[0133] In formula (C2), R 45 is a C1-C7 linear or branched alkyl group, a C1-C7 linear or branched fluoroalkyl group, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, fluorocyclobutyl, fluorocyclopentyl, fluorocyclohexyl, fluorocycloheptyl, fluorocyclooctyl, phenyl which may have a fluorine atom, naphthyl which may have a fluorine atom, R may be an anthryl which may have a fluorine atom, or a phenanthryl which may have a fluorine atom; 46 can be a fluorine atom or a hydroxyl group.

[0134] In formula (C2), R 45 may be a C1-C7 linear or branched alkyl group, a C1-C7 linear or branched fluoroalkyl group, cyclobutyl, cyclopentyl, cyclohexyl, fluorocyclobutyl, fluorocyclopentyl, fluorocyclohexyl, phenyl, naphthyl, phenyl having a fluorine atom, or naphthyl having a fluorine atom; R 46 can be a fluorine atom or a hydroxyl group.

[0135] In formula (C2), R 45 may be a C1-C7 linear or branched alkyl group or a C1-C7 linear or branched fluoroalkyl group; R 46 can be a fluorine atom or a hydroxyl group.

[0136] In formula (C3), R 47When is an alkyl group or a fluoroalkyl group, it preferably does not have an etheric oxygen atom.

[0137] In formula (C3), the C4-C8 cyclic alkyl group can be cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl. In formula (C3), the C4-C8 cyclic fluoroalkyl group can be fluorocyclobutyl, fluorocyclopentyl, fluorocyclohexyl, fluorocycloheptyl, or fluorocyclooctyl. In formula (C3), the C4-C8 cyclic fluoroalkyl group can be a C4-C6 cyclic fluoroalkyl group. The C4-C6 cyclic fluoroalkyl group can be fluorocyclobutyl, fluorocyclopentyl, or fluorocyclohexyl.

[0138] In formula (C3), the C4-C14 aryl group which may have a fluorine atom may be a phenyl, naphthyl, anthryl or phenanthryl group which may have a fluorine atom. In formula (C3), the C4-C14 aryl group which may have a fluorine atom may be phenyl, naphthyl, anthryl or phenanthryl. In formula (C3), the C4-C14 aryl group which may have a fluorine atom may be phenyl or naphthyl. In formula (C3), the C4-C14 aryl group which may have a fluorine atom may be phenyl or naphthyl.

[0139] In formula (C3), R 47 may be a C1-C9 linear or branched alkyl group, a C1-C9 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group optionally having a fluorine atom, the alkyl group and the fluoroalkyl group each optionally having an ether oxygen atom; R 49 can be a fluorine atom or a hydroxyl group.

[0140] In formula (C3), R47 may be a C1-C9 linear or branched alkyl group, a C1-C9 linear or branched fluoroalkyl group, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, fluorocyclobutyl, fluorocyclopentyl, fluorocyclohexyl, fluorocycloheptyl, fluorocyclooctyl, or a phenyl group which may have a fluorine atom, a naphthyl group which may have a fluorine atom, an anthryl group which may have a fluorine atom, or a phenanthryl group which may have a fluorine atom, and the alkyl group and the fluoroalkyl group each may have an ether oxygen atom; R 49 can be a fluorine atom or a hydroxyl group.

[0141] In formula (C3), R 47 is a C1-C9 linear or branched alkyl group, C1-C 9, a straight-chain or branched-chain fluoroalkyl group, cyclobutyl, cyclopentyl, cyclohexyl, fluorocyclobutyl, fluorocyclopentyl, fluorocyclohexyl, phenyl, naphthyl, phenyl having a fluorine atom, or naphthyl having a fluorine atom, and the alkyl group and the fluoroalkyl group may each have an ether oxygen atom; R 49 can be a fluorine atom or a hydroxyl group.

[0142] In formula (C3), R 47 can be a C1-C6 linear alkyl group, a C3-C9 branched alkyl group, a C1-C6 linear fluoroalkyl group, a C3-C6 branched fluoroalkyl group, or phenyl; R 49 can be a fluorine atom or a hydroxyl group.

[0143] In formula (C3), R 47 is methyl, tert-butyl, tert-nonyl, tri fluoromethyl, perfluoroisopentyl, or phenyl; R 49 can be a fluorine atom or a hydroxyl group.

[0144] In formula (C3), R 49may be a C1-C6 linear alkyl group, a C3-C6 branched alkyl group, a C1-C6 linear fluoroalkyl group, or a C3-C6 branched fluoroalkyl group, each of which may have an etheric oxygen atom; R 49 can be a fluorine atom or a hydroxyl group.

[0145] In formula (C3), R 49 can be tert-butyl, tert-hexyl, or trifluoromethyl.

[0146] In formula (C3), R 47 is methyl, tert-butyl, tert-nonyl, tri fluoromethyl, perfluoroisopentyl, or phenyl; R 49 can be a fluorine atom or a hydroxyl group.

[0147] Examples of the compound (C1) include the compounds shown in the structural formula below. In the structural formula below, m1 represents an integer of 0 to 6, m2 represents an integer of 0 to 6, m3 represents an integer of 0 to 2, and m4 represents an integer of 0 to 2, where m3 and m4 may be the same or different, and R 43 represents a fluorine atom or a hydroxyl group. [ka]

[0148] Preferred examples of the compound (C1) include 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoro-1-oxoheptyl carboxylic acid, 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoro-1-oxoheptyl carbonyl fluoride, cyclohexyl carboxylic acid, and cyclohexyl carbonyl fluoride.

[0149] Examples of compound (C2) include n-propyloxycarboxylic acid, n-propyloxycarbonyl fluoride, sec-butyloxycarboxylic acid, sec-butyloxycarbonyl fluoride, isopropyloxycarboxylic acid, isopropyloxycarbonyl fluoride, 2-ethylhexyloxycarboxylic acid, 2-ethylhexyloxycarbonyl fluoride, trifluoromethyloxycarboxylic acid, trifluoromethyloxycarbonyl fluoride, pentafluoroethyloxycarboxylic acid, pentafluoroethyloxycarbonyl fluoride, heptafluoro-n-propyloxycarboxylic acid, heptafluoro-n-propyloxycarbonyl fluoride, heptafluoroisopropyloxycarboxylic acid, and heptafluoroisopropyloxycarbonyl fluoride.

[0150] Preferred examples of the compound (C2) include n-propyloxycarboxylic acid, n-propyloxycarbonyl fluoride, isopropyloxycarboxylic acid, isopropyloxycarbonyl fluoride, trifluoromethyloxycarboxylic acid, and trifluoromethyloxycarbonyl fluoride. Includes:

[0151] Examples of compound (C3) include acetic acid, methyl carbonyl fluoride, tert-butyl carboxylic acid, tert-butyl carbonyl fluoride, neononyl carboxylic acid, neononyl carbonyl fluoride, benzoic acid, phenyl carbonyl fluoride, heptafluoroisopentyl carboxylic acid, heptafluoroisopentyl carbonyl fluoride, trifluorocarboxylic acid, and trifluorocarbonyl fluoride.

[0152] Preferred examples of the compound (C3) include acetic acid, methylcarbonyl fluoride, benzoic acid, phenylcarbonyl fluoride, trifluorocarboxylic acid, and trifluorocarbonyl fluoride.

[0153] Solvent (D) The fluorine-containing monomer (M) is polymerized in the solvent (D). Any solvent can be used as long as it can dissolve the raw material monomer and precipitate the fluorine-containing polymer (A). Therefore, as the solvent (D), a known solvent used in producing the fluorine-containing polymer (A) by precipitation polymerization can be used. The solvent (D) can be used alone or in combination of two or more kinds.

[0154] The solvent (D) may be an aprotic solvent, such as a non-perfluorinated solvent. The non-perfluoro solvent is an aprotic solvent that contains at least a fluorine atom, a carbon atom, and a hydrogen atom. Examples of the non-perfluoro solvent include hydrofluorocarbons, hydrofluoroethers, fluorine-containing alcohols, and olefin compounds containing at least one chlorine atom. The non-perfluoro solvent can be used alone or in combination of two or more.

[0155] The hydrofluorocarbon may be, for example, a C3-C8 hydrofluorocarbon. Examples of hydrofluorocarbons include CF3CH2CF2H, CF3CH2CF2CH3, CF3CHFCHFC2F5, 1,1,2,2,3,3,4-heptafluorocyclopentane, CF3CF2CF2CF2CH2CH3, CF3CF2CF2CF2CF2CHF2, and CF3CF2CF2CF2CF2CF2CF2CH2CH3. Preferred examples of hydrofluorocarbons include 1,1,2,2,3,3,4-heptafluorocyclopentane.

[0156] Hydrofluoroethers are, for example, fluorine-containing ethers. The global warming potential (GWP) of the hydrofluoroether is preferably not more than 600, more preferably not more than 400, and particularly preferably not more than 300. The lower limit of the global warming potential (GWP) of the hydrofluoroether may be 1 or more, or 5 or more. An example of a hydrofluoroether is CF3CF2CF2CF2OCH 3、CF3CF2CF(CF3)OCH 3、 CF3CF(CF3)CF2OCH 3、 CF3CF2CF2CF2OC2H5, CF3CH2OCF2CHF2, (CF3)2CHOCH3, (CF3)2CFOCH3, CHF2CF2OCH2CF3, CHF2CF2CH2OCF2CHF2, CF3CHFCF2OCH3, CF3CHFCF2OCF3, trifluoromethyl 1,2,2,2-tetrafluoroethyl ether (HFE-227me), difluoromethyl 1,1,2,2,2-pentafluoroethyl ether (HFE-227m c), trifluoromethyl 1,1,2,2-tetrafluoroethyl ether (HFE-227pc), difluoromethyl 2,2,2-trifluoroethyl ether (HFE-245mf), 2,2-difluoroethyl trifluoromethyl ether (HFE-245pf), 1,1,2,3,3-hexafluoropropyl methyl ether (CF3CHFCF2OCH3), 1,1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (CHF2CF2OCH2CF3), and 1,1,1,3,3,3-hexafluoro-2-methoxypropane ((CF3)2CHOCH3). Preferred examples of hydrofluoroethers include CF3CH2OCF2CHF2, 1,1,2,3,3-hexafluoropropyl methyl ether (CF3CHFCF2OCH3; HFE-356mec), 1,1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (CHF2CF2OCH2CF3), and 1,1,1,3,3,3-hexafluoro-2-methoxypropane ((CF3)2CHOCH3).

[0157] A fluorine-containing alcohol is a compound in which at least one hydrogen atom of an alcohol is substituted with a fluorine atom. Examples of fluorine-containing alcohols include CF3CH2OH, CF3CF2CH2OH, CF3(CF2)2CH2OH, CF3(CF2)3(CH2)2OH, CF3(CF2)3(CH2)3OH, CF3(CF2)5(CH2)2OH, CF3(CF2)5(CH2)3OH, CF2HCF2CH2OH, CF2H(CF2)3CH2OH, CF2H(CF2)5CH2OH, (CF3)2CHOH, CF3CHFCF2CH2OH, HOCH2(CF2)4CH2OH, and HOCH2(CF2)6CH2OH. Preferred examples of the fluorine-containing alcohol preferably include CF3CF2CH2OH, CF2HCF2CH2OH, CF2H(CF2)3CH2OH, (CF3)2CHOH.

[0158] The olefin compound containing at least one chlorine atom is a C2-C4 (preferably C2-C3) olefin compound containing at least one chlorine atom in its structure. The olefin compound containing at least one chlorine atom is a compound in which at least one hydrogen atom bonded to a carbon atom in a hydrocarbon having 2 to 4 carbon atoms and having 1 or 2 (preferably 1) double bonds is substituted with a chlorine atom. The number of chlorine atoms is from 1 to the maximum number that can be substituted. The number of chlorine atoms can be, for example, 1, 2, 3, 4, 5, etc. The olefinic compound that contains at least one chlorine atom may also contain at least one (eg, 1, 2, 3, 4, 5, etc.) fluorine atom. Examples of olefinic compounds containing at least one chlorine atom include CH2=CHCl, CHCl=CHCl, CCl2=CHCl, CCl2=CCl2, CF3CH=CHCl, CHF2CF=CHCl, CFH2CF=CHCl, CF3CCl=CFCl, CF2HCl=CFCl, CFH2Cl=CFCl. Preferred examples of olefinic compounds containing at least one chlorine atom include CHCl=CHCl, CHF2CF=CHCl, CF3CH=CHCl, CF3CCl=CFCl.

[0159] As the solvent (D), hydrofluoroethers and fluorine-containing alcohols are preferred because they have a small environmental impact when used and can be easily distilled off from the polymer.

[0160] The global warming potential (GWP) of the solvent (D) can be 600 or less, 400 or less, etc., preferably 375 or less, more preferably 350 or less, and particularly preferably 0. The lower limit of the global warming potential (GWP) of the solvent (D) may be 1 or more, or 5 or more.

[0161] The amount of the fluorine-containing monomer (M) used in the polymerization step can be appropriately determined depending on the ratio of the structural unit (A) in the desired fluorine-containing polymer (A), etc. For example, the amount of the fluorine-containing monomer (M) is 50 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more, and particularly preferably 100 mol%, based on the total number of moles of the raw material monomers. When fluoroolefin monomers and / or other monomers are used in addition to the fluorine-containing monomer (M), the amounts of these monomers should be adjusted to the full extent of the desired fluorine-containing polymer (A). The amount of the fluoroolefin monomer can be appropriately determined depending on the ratio of the fluoroolefin units and other constituent units, etc. For example, the amount of the fluoroolefin monomer can be 50 mol % or less, preferably 20 mol % or less, more preferably 10 mol % or less, and particularly preferably 0 mol %, based on the total moles of the raw material monomers, and the amount of the other monomer can be 0 to 20 mol %, 0 to 10 mol %, etc., based on the total moles of the raw material monomers, preferably 20 mol % or less, and more preferably 10 mol % or less.

[0162] The amount of the polymerization initiator (B) used in the polymerization step may be, for example, within the range of 0.0001 g to 0.05 g, preferably within the range of 0.0001 g to 0.01 g, and more preferably within the range of 0.0005 g to 0.008 g, per 1 g of all raw material monomers.

[0163] The amount of the solvent (D) used in the polymerization step can be, for example, within a range of 20% by mass to 300% by mass, preferably within a range of 35% by mass to 250% by mass, and more preferably within a range of 50% by mass to 300% by mass, assuming that the amount of all raw material monomers is 100% by mass.

[0164] The temperature of the polymerization reaction may be, for example, within the range of -10°C to 160°C, preferably within the range of 0°C to 160°C, and more preferably within the range of 0°C to 100°C. The polymerization reaction may be carried out at a temperature not higher than 20°C higher than the boiling point of the lower of the fluorinated monomer (M) and the solvent (D) and not higher than 20°C higher than the 10-hour half-life temperature of the polymerization initiator. In this case, the lower limit of the temperature can be, for example, -10°C, and preferably 0°C.

[0165] The reaction time for the polymerization reaction is not particularly limited as long as the fluoropolymer (A) is produced, but may be preferably within the range of 0.5 to 72 hours, more preferably within the range of 1 to 48 hours, and even more preferably within the range of 3 to 30 hours.

[0166] The polymerization reaction may be carried out in the presence or absence of an inert gas (eg, nitrogen gas), and is preferably carried out in the presence of an inert gas.

[0167] The polymerization reaction may be carried out under reduced pressure, atmospheric pressure, or under elevated pressure.

[0168] In the polymerization step, the order of adding and mixing the raw material monomer, the polymerization initiator (B) and the solvent (D) is not particularly limited. For example, the polymerization step may be carried out by adding the raw material monomer to the solvent (D) containing the polymerization initiator (A), or by adding the polymerization initiator to the solvent (D) containing the raw material monomer.

[0169] The fluoropolymer (A) produced by the polymerization reaction can be isolated or purified, if desired, by a conventional method such as extraction, dissolution, concentration, filtration, precipitation, dehydration, adsorption, chromatography, etc., or a combination of these. Filtration is preferred from the viewpoint of simplicity.

[0170] Filtration process The production method of the present disclosure may include a filtration step. In the filtration step, the precipitate produced in the polymerization step and the polymerization product liquid are filtered to remove the polymerization product liquid, thereby obtaining a fluoropolymer (A). The filtered solid is a fluoropolymer (A) containing a very low amount of the polymerization initiator (B) and / or its decomposition product (C). To further reduce the amount of contamination, the filtered solid may be washed with a solvent (e.g., polymerization solvent (B)). Thus, in the production method of the present disclosure, after the polymerization step, a fluoropolymer (A) containing a very low amount of the polymerization initiator (B) and / or its decomposition product (C) can be obtained by only a simple step of the filtration step, or by a washing step in which the solid obtained by filtration is washed with a solvent (e.g., polymerization solvent (B)).

[0171] As the filter medium, resin products such as polyethylene, polypropylene, polyester, nylon, polytetrafluoroethylene, cotton fiber products such as cellulose, and metal products such as SUS can be used. The pore size of the filter medium can be 1 μm, 10 μm, 100 μm, 300 μm, 500 μm, 1000 μm, etc. The pore size can be a range obtained by appropriately combining two of these values. The pore size can be, for example, 1 to 1000 μm, 1 to 500 μm, 1 to 300 μm, 1 to 100 μm, 10 to 1000 μm, 100 to 1000 μm, or 300 to 1000 μm. The filtration process can be carried out under reduced pressure, atmospheric pressure, or pressurized conditions.

[0172] Hansen solubility parameters The Hildebrand solubility parameter (δ) is a physical property defined as the square root of the cohesive energy density, and is one of the indices that indicate the solubility behavior of a substance. It is expressed as "SP". This SP is expressed as the dispersion force term (δ D ), polarity term (δ P ), hydrogen bond term (δ HThe Hansen solubility parameter, which takes into account the polarity of the substance, is abbreviated as "HSP". The relationship between the two is "δ 2 = δ D 2 +δ P 2 +δ H 2 " is expressed as

[0173] In the production method of the present disclosure, the Hansen solubility parameters (sometimes simply referred to as "solubility parameters" or "HSP" in this specification) of the fluoropolymer (A), polymerization initiator (B), decomposition product (C), and solvent (D) may have a specific relationship. This makes it possible to reduce the amount of the polymerization initiator (B) and / or its decomposition product (C) mixed into the fluoropolymer (A) produced by polymerization.

[0174] The HSP of each of the fluoropolymer (A), the polymerization initiator (B), the decomposition product (C), and the solvent (D) may be either a value experimentally determined by a dissolution test (this includes literature values ​​and database values), or a value estimated from the chemical structure of the substance using software for determining HSP (e.g., HSPiP).

[0175] Dissolution index R The solubility index R is calculated from the following formula and corresponds to the distance between the HSP of element 1 and the HSP of element 2. If this distance is close, that is, if R is small, element 1 and element 2 are considered to have a soluble relationship. R = {4 × (δD1-δD2) 2 +(δP1-δP2) 2 +(δH1-δH2) 2} 0.5 [In the formula, δD1, δP1, and δH1 respectively represent the dispersion force term, polar term, and hydrogen bond term in the Hansen solubility parameter of element 1, and δD2, δP2, and δH2 respectively represent the dispersion force term, polar term, and hydrogen bond term in the Hansen solubility parameter of element 2.]

[0176] The value of the solubility index R calculated based on the HSP of the solvent (D) and the HSP of the fluoropolymer (A) (R A )) can be 4 or more.

[0177] When the mass ratio of fluorine atoms in the polymerization initiator (B) is less than 50 mass%, the value of the solubility index R calculated based on the HSP of the solvent (D) and the HSP of the polymerization initiator (B) (R B ) can be 9 or less, preferably 8 or less. When the mass ratio of fluorine atoms in the polymerization initiator (B) is 50 mass% or more, the value of the solubility index R calculated based on the HSP of the solvent (D) and the HSP of the polymerization initiator (B) (R B ) can be 6 or less, and is preferably 5 or less.

[0178] When the mass ratio of fluorine atoms in the decomposition product (C) is less than 50 mass%, the HSP of the solvent (D) and the value of the solubility index R calculated based on the HSP of the decomposition product (C) (R C ) can be 9 or less, preferably 8 or less. When the mass ratio of fluorine atoms in the decomposition product (C) is 50 mass% or more, the value of the solubility index R calculated based on the HSP of the solvent (D) and the HSP of the decomposition product (C) (R C ) can be 6 or less, and is preferably 5 or less.

[0179] The mass percentage (mass%) of fluorine atoms in a substance is the percentage of the mass of fluorine atoms (atomic weight: 19.00) in the molecular weight of the substance. For example, tetrafluoroethylene (molecular weight 100.02 The mass proportion of fluorine atoms in CF2 (CF2=CF2) is 75.98% (75.98 = ((19.00 × 4) / 100.02) × 100).

[0180] The production method of the present disclosure is suitable as a production method for compositions (1) and (2) described below.

[0181] Composition (1) One embodiment of the present disclosure is a composition (sometimes referred to as composition (1) in this specification) containing a fluoropolymer (A) and at least one compound (BC) selected from the group consisting of a polymerization initiator (B) and a decomposition product (C) of the polymerization initiator (B). Since the content of compound (BC) in composition (1) is small, composition (1) is useful as a source of a fluoropolymer (A) having high ultraviolet light transparency (for example, a source of a fluoropolymer (A) used in a product through which ultraviolet light passes (preferably a lens of an ultraviolet light emitting element)).

[0182] The fluoropolymer (A) is preferably produced by the production method of the fluoropolymer (A) of the present disclosure, since the content of the polymerization initiator and / or its decomposition products is low. The fluoropolymer (A) may be produced by a known production method and purified so that the content of the polymerization initiator and / or its decomposition products is low. The known production method can be, for example, synthesis by polymerizing a monomer corresponding to the structural unit of the fluoropolymer (A). As the polymerization method, radical polymerization, bulk polymerization, precipitation polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc. can be used. As the known production method, precipitation polymerization is preferred in terms of high permeability of the fluoropolymer (A).

[0183] In the composition (1), the content of the fluoropolymer (A) can be 95% by mass or more, preferably 97 to 100% by mass, more preferably 98 to 100% by mass, and particularly preferably 99 to 100% by mass, based on the mass of the composition (1).

[0184] In the composition (1), the content of the compound (BC) can be 0.1 to 100 ppm by mass, preferably 0.1 to 90 ppm by mass, more preferably 0.1 to 80 ppm by mass, and particularly preferably 0.1 to 70 ppm by mass, relative to the mass of the composition (1).

[0185] The composition (1) may contain other components in addition to the fluoropolymer (A) and the compound (BC), but preferably does not contain any other components. Examples of the other components include metals such as Fe and Ni, residual solvents, etc. In the composition (1), the content of the other components may be 0 to 0.1% by mass, or 0 to 0.01% by mass.

[0186] The composition (1) can be produced by the production method of the present disclosure. For example, the solid matter obtained in the filtration step, or the washed object obtained by washing the solid matter with a solvent, can be the composition (1). The composition (1) can also be produced by mixing the fluoropolymer (A) and the compound (BC).

[0187] The composition (1) may have an average transmittance at a wavelength of 240 nm to 340 nm of 85% or more, 86% or more, 87% or more, 85 to 95%, or 86 to 95%. The higher the average transmittance, the better. In this specification, the average transmittance is specified as follows. average transmittance The average transmittance of the sample at a specified wavelength (e.g., 240 nm to 340 nm) is measured using a Hitachi U-4100 spectrophotometer. The sample is a flat plate with an average thickness of 1 mm. An integrating sphere detector is used as the detector.

[0188] Lenses for ultraviolet light emitting devices One embodiment of the present disclosure is a compound of formula (A): [ka] [In the formula, R 1 ~R 4 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] The lens for an ultraviolet light emitting device contains a fluorine-containing polymer (A) which contains as a main component a structural unit represented by the following formula: and has an average transmittance of 85% or more in the wavelength range of 240 nm to 340 nm.

[0189] The fluoropolymer (A) has a high average transmittance of 85% or more at wavelengths of 240 nm to 340 nm. Such a fluoropolymer (A) is preferably produced by the production method of the present disclosure. According to the production method of the present disclosure, the produced fluoropolymer (A) has a very small content of the compound (BC). For this reason, it is presumed that the average transmittance of the fluoropolymer (A) at wavelengths of 240 nm to 340 nm is high.

[0190] The average transmittance of the fluoropolymer (A) at wavelengths of from 240 nm to 340 nm can be 85% or more, 86% or more, 87% or more, 85 to 95%, or 86 to 95%.

[0191] It is desired that the lens for ultraviolet light emitting element has high ultraviolet light transmittance, is resistant to scratches, and is resistant to cracking. The lens for ultraviolet light emitting element of the present disclosure is resistant to scratches because the raw material resin (fluoropolymer (A)) has high surface hardness. The lens for ultraviolet light emitting element of the present disclosure is resistant to cracking because the raw material resin has high toughness. Therefore, even if the raw material resin is molded into a lens having a fine structure, the fine structure is resistant to cracking and scratching. For example, the lens for ultraviolet light emitting element of the present disclosure is suitable as a lens having a fine structure such as a Fresnel lens.

[0192] Examples of lenses for ultraviolet light-emitting elements include Fresnel lenses, microlenses, curved lenses, ascurved lenses, biconvex lenses, plano-convex lenses, convex meniscus lenses, biconcave lenses, plano-concave lenses, concave meniscus lenses, cylindrical lenses, toroidal lenses, parabolic lenses, irregular lenses, diffractive lenses, and array lenses thereof, and are preferably Fresnel lenses, microlenses, biconvex lenses, plano-convex lenses, biconcave lenses, plano-concave lenses, irregular lenses, diffractive lenses, or array lenses thereof.

[0193] The lens for ultraviolet light emitting devices can be produced by molding the fluoropolymer (A) by a known lens molding method. The molding conditions can be appropriately adjusted from known conditions as necessary. For example, it is desirable to produce the lens for ultraviolet light emitting devices by molding the fluoropolymer (A) into a desired shape by an injection molding method in which the fluoropolymer (A) is melted and injected. The fluoropolymer (A) can also be molded by other methods, for example, by molding the fluoropolymer (A) into a plate shape in a heated mold. Alternatively, the lens for an ultraviolet light emitting device may be molded into a desired shape by a press molding method in which the lens is pressed against a surface of a substrate to be molded, for example.

[0194] The ultraviolet light emitting element to which the lens for ultraviolet light emitting element is applied is preferably an ultraviolet light emitting diode (LED). The ultraviolet light emitting element is an element that mainly emits ultraviolet light, for example, light with a wavelength of 100 to 400 nm (preferably 240 to 340 nm, more preferably 250 to 270 nm). The wavelengths include UV-A, UV-B, UV-C, etc., which are industrially valuable, and the lens for ultraviolet light emitting element can be applied to any type of ultraviolet light emitting element, but a lens applied to a UV-C light emitting element is preferred.

[0195] In this specification, the term "lens" does not include a so-called "encapsulant" for a light-emitting element.

[0196] Composition (2) One embodiment of the present disclosure is a compound represented by formula (M1): [ka] The composition (which may be referred to as composition (2) in this specification) contains a fluoropolymer (A1) formed as a precipitate by polymerizing a fluoromonomer (M1) represented by the following formula (I) in the presence of a polymerization initiator (B) and a solvent (D).

[0197] The fluoropolymer (A1) is represented by the formula (A1): [ka] It contains a structural unit represented by the following formula as a main component.

[0198] In the composition (2), the fluorine-containing monomer (M1) is Formula (N1) [ka] A compound represented by the formula: Formula (N2) [ka] The content of the compound (N1) is 0.0001 to 10% by mass, and may be 0.0001 to 8% by mass, or 0.0001 to 6% by mass, based on the mass of the raw material monomer. The compound (N1) and the compound (N2) may be one type alone or a combination of two or more types.

[0199] In the composition (2), the value of the solubility index R (R A1 )) can be 4 or more.

[0200] In the composition (2), when the mass ratio of fluorine atoms in the polymerization initiator (B) is less than 50 mass%, the value of the solubility index R calculated based on the HSP of the solvent (D) and the HSP of the polymerization initiator (B) (R B ) can be 9 or less, preferably 8 or less. In the composition (2), when the mass ratio of fluorine atoms in the polymerization initiator (B) is 50 mass% or more, the value of the solubility index R calculated based on the HSP of the solvent (D) and the HSP of the polymerization initiator (B) (R B ) can be 6 or less, and is preferably 5 or less.

[0201] In the composition (2), when the mass ratio of fluorine atoms in the decomposition product (C) is less than 50 mass%, the value of the solubility index R calculated based on the HSP of the solvent (D) and the HSP of the decomposition product (C) (R C) can be 9 or less, preferably 8 or less. In the composition (2), when the mass ratio of fluorine atoms in the decomposition product (C) is 50 mass% or more, the value of the solubility index R calculated based on the HSP of the solvent (D) and the HSP of the decomposition product (C) (R C ) can be 6 or less, and is preferably 5 or less.

[0202] Since the content of compound (BC) in composition (2) is small, composition (2) is useful as a source of fluorine-containing polymer (A1) having high ultraviolet light transparency (for example, a source of fluorine-containing polymer (A) used in products through which ultraviolet light passes (preferably lenses of ultraviolet light-emitting devices)).

[0203] The fluoropolymer (A1) is preferably produced by the production method of the fluoropolymer (A) of the present disclosure, since the content of the polymerization initiator and / or decomposition products thereof is low. The fluoropolymer (A1) may be produced by a known production method and purified so that the content of the polymerization initiator and / or decomposition products thereof is low. The known production method can be, for example, synthesis by polymerizing monomers corresponding to the structural units of the fluoropolymer (A1). As the polymerization method, radical polymerization, bulk polymerization, precipitation polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc. can be used. As the known production method, precipitation polymerization is preferred in terms of high permeability of the fluoropolymer (A1).

[0204] In the composition (2), the content of the fluoropolymer (A1) can be 95% by mass or more, preferably 97 to 100% by mass, more preferably 98 to 100% by mass, and particularly preferably 99 to 100% by mass, based on the mass of the composition (2).

[0205] Regarding the composition (2), the details of the polymerization can be the same as those described in the polymerization step.

[0206] The composition (2) may contain other components in addition to the fluoropolymer (A), but preferably does not contain any other components. Examples of the other components include metals such as Fe and Ni, residual solvents, etc. In the composition (2), the content of the other components may be 0 to 0.1% by mass, or 0 to 0.01% by mass.

[0207] Composition (2) can be produced by the production method of the present disclosure. For example, the solid matter obtained in the filtration step or the washed matter obtained by washing the solid matter with a solvent can be composition (2).

[0208] Although the embodiments have been described above, it will be understood that various changes in form and details are possible without departing from the spirit and scope of the claims. EXAMPLES

[0209] Hereinafter, one embodiment of the present disclosure will be described in more detail with reference to an example, but the present disclosure is not limited thereto.

[0210] The symbols and abbreviations in the examples are used with the following meanings. PFMMD: Fluorine-containing monomer (M1) HF adduct: Compound (N1) NPP: Di-n-propyl peroxydicarbonate 50% methanol solution (NOF Corporation) DHP: Bis(2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoro- 1-Oxoheptyl) peroxide 8% fluorine-based solvent dilution solution (NOF Corporation) TBPOA: tert-butyl peroxyacetate, 50% diluted with hydrocarbon solvent (NOF Corporation) HFE-356mec: 1,1,2,3,3,3-hexafluoropropyl methyl ether n=2 Alcohol: 2,2,3,3,4,4,5,5-octafluoro-1-pentanol (manufactured by Daikin Industries, Ltd.) FC-3283: Perfluoro-n-tripropylamine (3M)

[0211] The polymerization initiators and their decomposition products are as follows: In this example, the decomposition product of NPP was the -COOH form, the decomposition products of DHP were the -COOH form and the -COF form, and the decomposition product of TBPOA was the -COOH form. [ka]

[0212] The Hansen solubility parameters are as follows: [Table 1]

[0213] average transmittance The average transmittance of the sample at a specified wavelength (e.g., 240 nm to 340 nm) was measured using a Hitachi U-4100 spectrophotometer. The sample was a flat plate with an average thickness of 1 mm. An integrating sphere detector was used as the detector.

[0214] Example 1 In a SUS autoclave with a capacity of 300 mL, fluorine-containing monomer (M1) (100 g) containing 3.6% of compound (N1), HFE-356mec (400 g; solvent), and then DHP (0.1 g; polymerization initiator) were placed. After cooling the autoclave to -78°C, the atmosphere in the system was replaced with nitrogen gas, and nitrogen gas was filled so that the internal pressure was 0.1 MPaG. The mixture was subjected to a polymerization reaction at 15°C for 24 hours, and a polymer-solvent mixture was obtained in which the produced fluorine-containing polymer (A1) precipitated in the solvent. This mixture was filtered and dried at 120°C to obtain a solid polymer. This polymer corresponded to composition (1) and also to composition (2). 1 g of the polymer was dissolved in 10 g of hexafluorobenzene, and the compound (BC) in the polymer was quantitatively determined by gas chromatography, and found to be 20 ppm. The polymer was melt-molded to produce a plate with an average thickness of 1 mm, and the average transmittance (240 nm to 340 nm) of this plate was 90%. A Fresnel lens was fabricated by cutting a flat plate with an average thickness of 1 mm formed in the same manner. When the uneven structure of the Fresnel lens surface was observed using a laser microscope VKX-1000 manufactured by KEYENCE Corporation, the surface roughness Sa was 74 nm and Sq was 118 nm.

[0215] Example 2 The procedure was the same as in Example 1, except that NPP was used instead of DHP and the polymerization temperature was changed to 40° C. The compound (BC) content in the obtained polymer was 43 ppm, and the average transmittance (240 nm to 340 nm) of the flat plate was 87%.

[0216] Example 3 Except for using n=2 Alcohol instead of HFE-356mec, the same procedure was followed as in Example 1. The compound (BC) in the obtained polymer was 17 ppm, and the average transmittance (240 nm to 340 nm) of the flat plate was 92%.

[0217] Example 4 The procedure was the same as in Example 1, except that n=2 Alcohol was used instead of HFE-356mec, TBPOA was used instead of DHP, and the polymerization temperature was changed to 100° C. The compound (BC) in the obtained polymer was 23 ppm, and the average transmittance of the plate (240 nm to 340 nm) was 90%.

[0218] Comparative Example 1 Except for using CF3CH2OH instead of HFE-356mec, the procedure was the same as in Example 1. The compound (BC) in the obtained polymer was 163 ppm, and the average transmittance (240 nm to 340 nm) of the flat plate was 81%.

[0219] Comparative Example 2 The procedure was the same as in Example 1, except that CF3CH2OH was used instead of HFE-356mec, NPP was used instead of DHP, and the polymerization temperature was changed to 40° C. The compound (BC) in the obtained polymer was 155 ppm, and the average transmittance of the plate (240 nm to 340 nm) was 83%.

[0220] Comparative Example 3 Except for using CHCl3 instead of HFE-356mec, the procedure was the same as in Example 1. The compound (BC) in the obtained polymer was 124 ppm, and the average transmittance (240 nm to 340 nm) of the flat plate was 80%.

[0221] Comparative Example 4 The procedure was the same as in Example 1, except that the fluorine-containing monomer (M1) containing 17% of compound (N1) was used instead of the fluorine-containing monomer (M1) containing 3.6% of compound (N1), n=2 Alcohol was used instead of HFE-356mec, TBPOA was used instead of DHP, and the polymerization temperature was changed to 100° C. The compound (BC) in the obtained polymer was 118 ppm, and the average transmittance (240 nm to 340 nm) of the flat plate was 83%.

[0222] Comparative Example 5 Same as Example 1, except that FC-3283 was used instead of HFE-356mec. The mixture after polymerization was a solution in which the produced polymer (A1) was dissolved in the solvent.

[0223] The conditions, solubility indices, measurement results, etc. of the examples and comparative examples are summarized in Table 2 below.

[0224] [Table 2]

Claims

1. A composition comprising a fluoropolymer (A), and at least one compound (BC) selected from the group consisting of a polymerization initiator (B) and a decomposition product (C) of the polymerization initiator (B), The compound (BC) is contained in an amount of 0.1 to 100 ppm by mass relative to the mass of the composition, The fluoropolymer (A) is represented by the formula (A): 【Chemistry 1】 [In the formula, R １ ~R ４ each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] Contains as a main component a structural unit represented by composition.

2. The composition according to claim 1 , wherein the polymerization initiator (B) is a peroxide.

3. The polymerization initiator (B) is Formula (B1) 【Chemistry 2】 [In the formula, R １１ , R １２ , R １３ , and R １４ each independently represents a fluorine atom, a C1-C20 alkyl group, or a C1-C20 fluoroalkyl group, The alkyl group and the fluoroalkyl group may each have an etheric oxygen atom, and R １１ and R １２ may be linked together to form a 4- to 20-membered ring having 4 to 20 carbon atoms as ring constituent atoms and at least one fluorine atom, or a 4- to 22-membered ring having 3 to 20 carbon atoms and 1 or 2 oxygen atoms or 1 sulfur atom as ring constituent atoms and at least one fluorine atom, R １３ and R １４ may be linked together to form a 4- to 20-membered ring having 4 to 20 carbon atoms as ring constituent atoms and at least one fluorine atom, or a 4- to 22-membered ring having 3 to 20 carbon atoms and one or two oxygen atoms or one sulfur atom as ring constituent atoms and at least one fluorine atom.] A compound represented by the formula: Formula (B2) 【Chemistry 3】 [In the formula, R １５ and R １６ each independently represents a C1-C20 linear or branched alkyl group; a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom.] A compound represented by the formula: Formula (B3) 【Chemistry 4】 [In the formula, R １７ and R １８ each independently represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom, and the alkyl group and the fluoroalkyl group each may have an etheric oxygen atom.] A compound represented by 2. The composition of claim 1, wherein the compound is at least one compound selected from the group consisting of:

4. The decomposition product (C) is Formula (C1) 【Chemistry 5】 [In the formula, R ４１ and R ４２ each independently represents a fluorine atom, a C1-C20 alkyl group, or a C1-C20 fluoroalkyl group, The alkyl group and the fluoroalkyl group may each have an etheric oxygen atom, and R ４１ and R ４２ may be linked together to form a 4- to 20-membered ring having 4 to 20 carbon atoms as ring constituent atoms and at least one fluorine atom, or a 4- to 22-membered ring having 3 to 20 carbon atoms and 1 or 2 oxygen atoms or 1 sulfur atom as ring constituent atoms and at least one fluorine atom, R ４３ represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C2) 【Chemistry 6】 [In the formula, R ４５ represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom; R ４６ represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C3) 【Chemistry 7】 [In the formula, R ４７ represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom, wherein the alkyl group and the fluoroalkyl group each may have an etheric oxygen atom; R ４９ represents a fluorine atom or a hydroxyl group. A compound represented by The composition according to any one of claims 1 to 3, wherein the compound is at least one selected from the group consisting of:

5. The composition according to any one of claims 1 to 4, having an average transmittance of 85% or more in the wavelength range of 240 nm to 340 nm.

6. The structural unit represented by the formula (A) is represented by the formula (A1): 【Chemistry 8】 The composition according to any one of claims 1 to 5, wherein the structural unit is represented by the following formula:

7. The polymerization initiator (B) Formula (B1) 【Chemistry 9】 [In the formula, R １１ and R １３ is a fluorine atom, R １２ and R １４ are each independently -(CF ２ ) ｎ１ CF ３ (where n1 represents an integer from 0 to 5). -(CF ２ ) ｎ２ CF ２ H (wherein n2 is an integer from 0 to 5); -O-(CF ２ ) ｎ３ CF ３ (wherein n3 represents an integer from 0 to 5), or -O-(CF ２ ) ｎ４ CF ２ H (wherein n4 represents an integer of 0 to 5). A compound represented by the formula: Formula (B2) 【Chemistry 10】 [In the formula, R １５ and R １６ each independently represents a C1-C7 linear or branched alkyl group, or a C1-C7 linear or branched fluoroalkyl group. A compound represented by the formula: Formula (B3) 【Chemistry 11】 [In the formula, R １７ is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R １８ represents tert-butyl, tert-hexyl, or trifluoromethyl. A compound represented by The composition according to any one of claims 1, 4 to 6, wherein the compound is at least one selected from the group consisting of:

8. The decomposition product (C) is Formula (C1) 【Chemistry 12】 [In the formula, R ４１ represents a fluorine atom, R ４２ teeth, -(CF ２ ) ｎ１ CF ３ (where n1 represents an integer from 0 to 5). -(CF ２ ) ｎ２ CF ２ H (wherein n2 is an integer from 0 to 5); -O-(CF ２ ) ｎ３ CF ３ (wherein n3 represents an integer from 0 to 5), or -O-(CF ２ ) ｎ４ CF ２ H (wherein n4 is an integer from 0 to 5). indicates, R ４３ represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C2) 【Chemistry 13】 [In the formula, R ４５ represents a C1-C7 linear or branched alkyl group or a C1-C7 linear or branched fluoroalkyl group; R ４６ represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C3) 【Chemistry 14】 [In the formula, R ４７ is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R ４９ represents a fluorine atom or a hydroxyl group. A compound represented by The composition according to any one of claims 1 to 3 and 5 to 7, wherein the compound is at least one selected from the group consisting of:

9. The structural unit represented by the formula (A) is represented by the formula (A1): 【Chemistry 15】 It is a structural unit represented by The polymerization initiator (B) Formula (B1) 【Chemistry 16】 [In the formula, R １１ and R １３ is a fluorine atom, R １２ and R １４ are each independently -(CF ２ ) ｎ１ CF ３ (where n1 represents an integer from 0 to 5). -(CF ２ ) ｎ２ CF ２ H (wherein n2 is an integer from 0 to 5); -O-(CF ２ ) ｎ３ CF ３ (wherein n3 represents an integer from 0 to 5), or -O-(CF ２ ) ｎ４ CF ２ H (wherein n4 represents an integer of 0 to 5). A compound represented by the formula: Formula (B2) 【Chemistry 17】 [In the formula, R １５ and R １６ each independently represents a C1-C7 linear or branched alkyl group, or a C1-C7 linear or branched fluoroalkyl group. A compound represented by the formula: Formula (B3) 【Chemistry 18】 [In the formula, R １７ is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R １８ represents tert-butyl, tert-hexyl, or trifluoromethyl. A compound represented by At least one compound selected from the group consisting of The decomposition product (C) is Formula (C1) 【Chemistry 19】 [In the formula, R ４１ represents a fluorine atom, R ４２ teeth, -(CF ２ ) ｎ１ CF ３ (where n1 represents an integer from 0 to 5). -(CF ２ ) ｎ２ CF ２ H (wherein n2 is an integer from 0 to 5); -O-(CF ２ ) ｎ３ CF ３ (wherein n3 represents an integer from 0 to 5), or -O-(CF ２ ) ｎ４ CF ２ H (wherein n4 is an integer from 0 to 5). indicates, R ４３ represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C2) 【Chemistry 20】 [In the formula, R ４５ represents a C1-C7 linear or branched alkyl group or a C1-C7 linear or branched fluoroalkyl group; R ４６ represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C3) 【Chemistry 21】 [In the formula, R ４７ is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R ４９ represents a fluorine atom or a hydroxyl group. A compound represented by The composition of claim 1 or 5, wherein the compound is at least one compound selected from the group consisting of:

10. A method for producing a fluoropolymer (A), comprising the steps of: Formula (M) 【Chemical Formula 22】 [In the formula, R １ ~R ４ each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] The method includes a polymerization step of polymerizing the fluorine-containing monomer (M) represented by the following formula (1): The fluoropolymer (A) is represented by the formula (A): 【Chemistry 23】 [In the formula, R １ ~R ４ is the same as above.] The main component is a structural unit represented by The value of the solubility index R (R Ａ ) is 4 or more, The value of the solubility index R (R Ｂ ) is 9 or less when the mass ratio of fluorine atoms in the polymerization initiator (B) is less than 50 mass%, and is 6 or less when the mass ratio is 50 mass% or more, The value of the solubility index R (R Ｃ ) is 9 or less when the mass ratio of fluorine atoms in the decomposition product (C) is less than 50 mass%, and is 6 or less when the mass ratio is 50 mass% or more; The solubility index R is expressed by the following formula: R={4×(δD １ -δD ２ ) ２ +(δP １ -δP ２ ) ２ +(δH １ -δH ２ ) ２ } ０．５ [In the formula, δD １ , δP １ , and δH １ respectively indicate the dispersion term, polar term, and hydrogen bond term in the Hansen solubility parameter of element 1, and δD ２ , δP ２ , δH ２ represent the dispersion term, polar term, and hydrogen bonding term in the Hansen solubility parameters of element 2, respectively. It is calculated from Manufacturing method.

11. The method for producing a fluoropolymer (A) according to claim 10, further comprising a filtration step of removing the precipitate produced in the polymerization step and the polymerization product liquid by filtering the polymerization product liquid to obtain the fluoropolymer (A).

12. The process for producing a fluoropolymer (A) according to claim 10 or 11, wherein the polymerization initiator (B) is a peroxide.

13. The polymerization initiator (B) is Formula (B1) 【Chemistry 24】 [In the formula, R １１ , R １２ , R １３ , and R １４ each independently represents a fluorine atom, a C1-C20 alkyl group, or a C1-C20 fluoroalkyl group, The alkyl group and the fluoroalkyl group may each have an etheric oxygen atom, and R １１ and R １２ are linked together to form a 4- to 20-membered ring having 4 to 20 carbon atoms as ring constituent atoms and at least one fluorine atom, or a 4- to 20-membered ring having 3 to 20 carbon atoms and 1 or may form a 4- to 22-membered ring having two oxygen atoms or one sulfur atom as ring-constituting atoms and at least one fluorine atom, R １３ and R １４ may be linked together to form a 4- to 20-membered ring having 4 to 20 carbon atoms as ring constituent atoms and at least one fluorine atom, or a 4- to 22-membered ring having 3 to 20 carbon atoms and one or two oxygen atoms or one sulfur atom as ring constituent atoms and at least one fluorine atom.] A compound represented by the formula: Formula (B2) 【Chemistry 25】 [In the formula, R １５ and R １６ each independently represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom.] A compound represented by the formula: Formula (B3) 【Chemistry 26】 [In the formula, R １７ and R １８ each independently represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom, and the alkyl group and the fluoroalkyl group each may have an etheric oxygen atom.] A compound represented by The process for producing a fluoropolymer (A) according to claim 10 or 11, wherein the compound (A) is at least one compound selected from the group consisting of:

14. The decomposition product (C) of the polymerization initiator (B) is Formula (C1) 【Chemical 27】 [In the formula, R ４１ and R ４２ each independently represents a fluorine atom, a C1-C20 alkyl group, or a C1-C20 fluoroalkyl group, The alkyl group and the fluoroalkyl group may each have an etheric oxygen atom, and R ４１ and R ４２ may be linked together to form a 4- to 20-membered ring having 4 to 20 carbon atoms as ring constituent atoms and at least one fluorine atom, or a 4- to 22-membered ring having 3 to 20 carbon atoms and 1 or 2 oxygen atoms or 1 sulfur atom as ring constituent atoms and at least one fluorine atom, R ４３ represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C2) 【Chemistry 28】 [In the formula, R ４５ represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom; R ４６ represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C3) 【Chemical 29】 [In the formula, R ４７ represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom, wherein the alkyl group and the fluoroalkyl group each may have an etheric oxygen atom; R ４９ represents a fluorine atom or a hydroxyl group. A compound represented by The method for producing a fluoropolymer (A) according to any one of claims 10 to 13, wherein the compound (A) is at least one compound selected from the group consisting of:

15. The fluorine-containing monomer (M) is represented by the formula (M1): 【Chemistry 30】 A compound represented by the formula: The structural unit represented by the formula (A) is represented by the formula (A1): 【Chemistry 31】 The method for producing a fluoropolymer (A) according to any one of claims 10 to 14, wherein the structural unit is represented by the following formula:

16. The fluorine-containing monomer (M) contains a compound (N) in an amount of 0.0001 to 10% by mass based on the mass of the raw material monomer, The compound (N) is Formula (N) 【Chemistry 32】 [In the formula, R １ ~R ４ each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group; R ７１ and R ７２ each independently represents a hydrogen atom or a fluorine atom; R ７１ and R ７２ When one of the groups is a hydrogen atom, the other group is a fluorine atom. The method for producing the fluoropolymer (A) according to any one of claims 10 to 15, wherein the compound is represented by the formula:

17. The compound (N) is Formula (N1) 【Chemical 33】 A compound represented by the formula: Formula (N2) 【Chemical 34】 The process for producing a fluoropolymer (A) according to claim 16, wherein the compound (A) is at least one compound selected from the group consisting of compounds represented by the following formula (1):

18. The polymerization initiator (B) Formula (B1) 【Chemistry 35】 [In the formula, R １１ and R １３ is a fluorine atom, R １２ and R １４ are each independently -(CF ２ ) ｎ１ CF ３ (where n1 represents an integer from 0 to 5). -(CF ２ ) ｎ２ CF ２ H (wherein n2 is an integer from 0 to 5); -O-(CF ２ ) ｎ３ CF ３ (wherein n3 represents an integer from 0 to 5), or -O-(CF ２ ) ｎ４ CF ２ H (wherein n4 represents an integer of 0 to 5). A compound represented by the formula: Formula (B2) 【Chemical 36】 [In the formula, R １５ and R １６ each independently represents a C1-C7 linear or branched alkyl group, or a C1-C7 linear or branched fluoroalkyl group. A compound represented by the formula: Formula (B3) 【Chemical 37】 [In the formula, R １７ is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R １８ represents tert-butyl, tert-hexyl, or trifluoromethyl. A compound represented by The method for producing a fluoropolymer (A) according to any one of claims 10, 11, and 14 to 17, wherein the compound (A) is at least one compound selected from the group consisting of:

19. The decomposition product (C) is Formula (C1) 【Chemical Formula 38】 [In the formula, R ４１ represents a fluorine atom, R ４２ teeth, -(CF ２ ) ｎ１ CF ３ (where n1 represents an integer from 0 to 5). -(CF ２ ) ｎ２ CF ２ H (wherein n2 is an integer from 0 to 5); -O-(CF ２ ) ｎ３ CF ３ (wherein n3 represents an integer from 0 to 5), or -O-(CF ２ ) ｎ４ CF ２ H (wherein n4 is an integer from 0 to 5). indicates, R ４３ represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C2) 【Chemical Formula 39】 [In the formula, R ４５ represents a C1-C7 linear or branched alkyl group or a C1-C7 linear or branched fluoroalkyl group; R ４６ represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C3) 【Chemistry 40】 [In the formula, R ４７ is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R ４９ represents a fluorine atom or a hydroxyl group. A compound represented by The method for producing a fluoropolymer (A) according to any one of claims 10 to 13 and 15 to 18, wherein the compound (A) is at least one compound selected from the group consisting of:

20. The method for producing a fluoropolymer (A) according to any one of claims 10 to 19, wherein the solvent (D) is at least one selected from the group consisting of hydrofluoroethers and fluorine-containing alcohols.

21. The fluorine-containing monomer (M) is represented by the formula (M1): 【Chemistry 41】 A compound represented by the formula: The fluorine-containing monomer (M) contains a compound (N) in an amount of 0.0001 to 10% by mass based on the mass of the raw material monomer, The compound (N) is Formula (N1) 【Chemistry 42】 A compound represented by the formula: Formula (N2) 【Chemistry 43】 At least one compound selected from the group consisting of compounds represented by The structural unit represented by the formula (A) is represented by the formula (A1): 【Chemistry 44】 It is a structural unit represented by The polymerization initiator (B) Formula (B1) 【Chemistry 45】 [In the formula, R １１ and R １３ is a fluorine atom, R １２ and R １４ are each independently -(CF ２ ) ｎ１ CF ３ (where n1 represents an integer from 0 to 5). -(CF ２ ) ｎ２ CF ２ H (wherein n2 is an integer from 0 to 5); -O-(CF ２ ) ｎ３ CF ３ (wherein n3 represents an integer from 0 to 5), or -O-(CF ２ ) ｎ４ CF ２ H (wherein n4 represents an integer of 0 to 5). A compound represented by the formula: Formula (B2) 【Chemistry 46】 [In the formula, R １５ and R １６ each independently represents a C1-C7 linear or branched alkyl group, or a C1-C7 linear or branched fluoroalkyl group. A compound represented by the formula: Formula (B3) 【Chemistry 47】 [In the formula, R １７ is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R １８ represents tert-butyl, tert-hexyl, or trifluoromethyl. A compound represented by At least one compound selected from the group consisting of The decomposition product (C) is Formula (C1) 【Chemistry 48】 [In the formula, R ４１ represents a fluorine atom, R ４２ teeth, -(CF ２ ) ｎ１ CF ３ (where n1 represents an integer from 0 to 5). -(CF ２ ) ｎ２ CF ２ H (wherein n2 is an integer from 0 to 5); -O-(CF ２ ) ｎ３ CF ３ (wherein n3 represents an integer from 0 to 5), or -O-(CF ２ ) ｎ４ CF ２ H (wherein n4 is an integer from 0 to 5). indicates, R ４３ represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C2) 【Chemistry 49】 [In the formula, R ４５ represents a C1-C7 linear or branched alkyl group or a C1-C7 linear or branched fluoroalkyl group; R ４６ represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C3) 【Chemistry 50】 [In the formula, R ４７ is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R ４９ represents a fluorine atom or a hydroxyl group. A compound represented by At least one compound selected from the group consisting of The solvent (D) is at least one selected from the group consisting of hydrofluoroethers and fluorine-containing alcohols. A process for producing the fluoropolymer (A) according to claim 10 or 11.

22. A lens for an ultraviolet light emitting device containing a fluorine-containing polymer (A), The fluoropolymer (A) is represented by the formula (A): 【Chemistry 51】 [In the formula, R １ ~R ４ each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] The main component is a structural unit represented by The fluoropolymer (A) has an average transmittance of 85% or more at a wavelength of 240 nm to 340 nm. Lenses for ultraviolet light emitting devices.

23. The structural unit represented by the formula (A) is represented by the formula (A1): 【Chemistry 52】 The lens for an ultraviolet light emitting element according to claim 22, wherein the structural unit is represented by the following formula:

24. Formula (M1) 【Chemistry 53】 A composition comprising a fluoropolymer (A1) produced as a precipitate by polymerizing a fluoromonomer (M1) represented by the following formula (1): The fluoropolymer (A1) is represented by the formula (A1): 【Chemical 54】 The main component is a structural unit represented by The fluorine-containing monomer (M1) is Formula (N1) 【Chemistry 55】 A compound represented by the formula: Formula (N2) 【Chemistry 56】 The compound contains at least one compound selected from the group consisting of compounds represented by the formula: The value of the solubility index R (R Ａ１ )) is 4 or more, and the value of the solubility index R (R Ｂ ) is 9 or less when the mass ratio of fluorine atoms in the polymerization initiator (B) is less than 50 mass%, and is 6 or less when the mass ratio is 50 mass% or more, The value of the solubility index R (R Ｃ ) is 9 or less when the mass ratio of fluorine atoms in the decomposition product (C) is less than 50 mass%, and is 6 or less when the mass ratio is 50 mass% or more; The solubility index R is expressed by the following formula: R={4×(δD １ -δD ２ ) ２ +(δP １ -δP ２ ) ２ +(δH １ -δH ２ ) ２ } ０．５ [In the formula, δD １ , δP １ , and δH １ respectively indicate the dispersion term, polar term, and hydrogen bond term in the Hansen solubility parameter of element 1, and δD ２ , δP ２ , δH ２ represent the dispersion term, polar term, and hydrogen bonding term in the Hansen solubility parameters of element 2, respectively. It is calculated from composition.

25. The composition containing the fluorine-containing polymer (A1) according to claim 24, wherein the polymerization initiator (B) is a peroxide.

26. The polymerization initiator (B) is Formula (B1) 【Chemistry 57】 [In the formula, R １１ , R １２ , R １３ , and R １４ each independently represents a fluorine atom, a C1-C20 alkyl group, or a C1-C20 fluoroalkyl group, The alkyl group and the fluoroalkyl group may each have an etheric oxygen atom, and R １１ and R １２ may be linked together to form a 4- to 20-membered ring having 4 to 20 carbon atoms as ring constituent atoms and at least one fluorine atom, or a 4- to 22-membered ring having 3 to 20 carbon atoms and 1 or 2 oxygen atoms or 1 sulfur atom as ring constituent atoms and at least one fluorine atom, R １３ and R １４ may be linked together to form a 4- to 20-membered ring having 4 to 20 carbon atoms as ring constituent atoms and at least one fluorine atom, or a 4- to 22-membered ring having 3 to 20 carbon atoms and one or two oxygen atoms or one sulfur atom as ring constituent atoms and at least one fluorine atom.] A compound represented by the formula: Formula (B2) 【Chemistry 58】 [In the formula, R １５ and R １６ each independently represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom.] A compound represented by the formula: Formula (B3) 【Chemistry 59】 [In the formula, R １７ and R １８ each independently represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom, and the alkyl group and the fluoroalkyl group each may have an etheric oxygen atom.] A compound represented by At least one compound selected from the group consisting of A composition comprising the fluoropolymer (A1) according to claim 24.

27. The decomposition product (C) of the polymerization initiator (B) is Formula (C1) 【Chemistry 60】 [In the formula, R ４１ and R ４２ each independently represents a fluorine atom, a C1-C20 alkyl group, or a C1-C20 fluoroalkyl group, The alkyl group and the fluoroalkyl group may each have an etheric oxygen atom, and R ４１ and R ４２ may be linked together to form a 4- to 20-membered ring having 4 to 20 carbon atoms as ring constituent atoms and at least one fluorine atom, or a 4- to 22-membered ring having 3 to 20 carbon atoms and 1 or 2 oxygen atoms or 1 sulfur atom as ring constituent atoms and at least one fluorine atom, R ４３ represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C2) 【Chemistry 61】 [In the formula, R ４５ is a C1-C20 linear or branched alkyl group, represents a branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom; R ４６ represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C3) 【Chemistry 62】 [In the formula, R ４７ represents a C1-C20 linear or branched alkyl group, a C1-C20 linear or branched fluoroalkyl group, a C4-C8 cyclic alkyl group, a C4-C8 cyclic fluoroalkyl group, or a C4-C14 aryl group which may have a fluorine atom, wherein the alkyl group and the fluoroalkyl group each may have an etheric oxygen atom; R ４９ represents a fluorine atom or a hydroxyl group. A compound represented by At least one compound selected from the group consisting of A composition comprising the fluorine-containing polymer (A1) according to claim 24 or 25.

28. The polymerization initiator (B) Formula (B1) 【Chemistry 63】 [In the formula, R １１ and R １３ is a fluorine atom, R １２ and R １４ are each independently -(CF ２ ) ｎ１ CF ３ (where n1 represents an integer from 0 to 5). -(CF ２ ) ｎ２ CF ２ H (wherein n2 is an integer from 0 to 5); -O-(CF ２ ) ｎ３ CF ３ (wherein n3 represents an integer from 0 to 5), or -O-(CF ２ ) ｎ４ CF ２ H (wherein n4 represents an integer of 0 to 5). A compound represented by the formula: Formula (B2) 【Chemistry 64】 [In the formula, R １５ and R １６ each independently represents a C1-C7 linear or branched alkyl group, or a C1-C7 linear or branched fluoroalkyl group. A compound represented by the formula: Formula (B3) 【Chemistry 65】 [In the formula, R １７ is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R １８ represents tert-butyl, tert-hexyl, or trifluoromethyl. A compound represented by A composition comprising the fluoropolymer (A1) according to claim 24, which is at least one compound selected from the group consisting of:

29. The decomposition product (C) is Formula (C1) 【Chemistry 66】 [In the formula, R ４１ represents a fluorine atom, R ４２ teeth, -(CF ２ ) ｎ１ CF ３ (where n1 represents an integer from 0 to 5). -(CF ２ ) ｎ２ CF ２ H (wherein n2 is an integer from 0 to 5); -O-(CF ２ ) ｎ３ CF ３ (wherein n3 represents an integer from 0 to 5), or -O-(CF ２ ) ｎ４ CF ２ H (wherein n4 is an integer from 0 to 5). indicates, R ４３ represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C2) 【Chemistry 67】 [In the formula, R ４５ represents a C1-C7 linear or branched alkyl group or a C1-C7 linear or branched fluoroalkyl group; R ４６ represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C3) 【Chemistry 68】 [In the formula, R ４７ is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R ４９ represents a fluorine atom or a hydroxyl group. A compound represented by A composition containing the fluoropolymer (A1) according to any one of claims 24 to 26 and 28, which is at least one compound selected from the group consisting of:

30. A composition containing a fluoropolymer (A1) according to any one of claims 24 to 29, wherein the solvent (D) is at least one selected from the group consisting of hydrofluoroethers and fluorine-containing alcohols.

31. The polymerization initiator (B) Formula (B1) 【Chemistry 69】 [In the formula, R １１ and R １３ is a fluorine atom, R １２ and R １４ are each independently -(CF ２ ) ｎ１ CF ３ (where n1 represents an integer from 0 to 5). -(CF ２ ) ｎ２ CF ２ H (wherein n2 is an integer from 0 to 5); -O-(CF ２ ) ｎ３ CF ３ (wherein n3 represents an integer from 0 to 5), or -O-(CF ２ ) ｎ４ CF ２ H (wherein n4 represents an integer of 0 to 5). A compound represented by the formula: Formula (B2) 【Chemistry 70】 [In the formula, R １５ and R １６ each independently represents a C1-C7 linear or branched alkyl group, or a C1-C7 linear or branched fluoroalkyl group. A compound represented by the formula: Formula (B3) 【Chemistry 71】 [In the formula, R １７ is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R １８ represents tert-butyl, tert-hexyl, or trifluoromethyl. A compound represented by At least one compound selected from the group consisting of The decomposition product (C) is Formula (C1) 【Chemical 72】 [In the formula, R ４１ represents a fluorine atom, R ４２ teeth, -(CF ２ ) ｎ１ CF ３ (where n1 represents an integer from 0 to 5). -(CF ２ ) ｎ２ CF ２ H (wherein n2 is an integer from 0 to 5); -O-(CF ２ ) ｎ３ CF ３ (wherein n3 represents an integer from 0 to 5), or -O-(CF ２ ) ｎ４ CF ２ H (wherein n4 is an integer from 0 to 5). indicates, R ４３ represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C2) 【Chemical Formula 73】 [In the formula, R ４５ represents a C1-C7 linear or branched alkyl group or a C1-C7 linear or branched fluoroalkyl group; R ４６ represents a fluorine atom or a hydroxyl group. A compound represented by the formula: Formula (C3) 【Chemical Formula 74】 [In the formula, R ４７ is methyl, tert-butyl, tert-nonyl, trifluoromethyl , perfluoroisopentyl, or phenyl; R ４９ represents a fluorine atom or a hydroxyl group. A compound represented by At least one compound selected from the group consisting of The solvent (D) is at least one selected from the group consisting of hydrofluoroethers and fluorine-containing alcohols. A composition comprising the fluoropolymer (A1) according to claim 24.

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