Fluorine-containing copolymer, optical resin composition, and optical resin formed body

A fluorine-containing copolymer comprising:

• a structural unit (A) represented by the following formula (1);
• and
• at least one selected from the group consisting of a structural unit (B) represented by the following formula (2), a structural unit (C) represented by the following formula (3), and a structural unit (D) represented by the following formula (4):
• in formula (1), Rff1 to Rff4 each independently represent a fluorine atom, a perfluoroalkyl group having 1 to 7 carbon atoms, or a perfluoroalkyl ether group having 1 to 7 carbon atoms, and Rff1 and Rff2 are optionally linked to form a ring;
• in formula (2), R1 to R3 each independently represent a fluorine atom or a perfluoroalkyl group having 1 to 7 carbon atoms, R4 represents a perfluoroalkyl group having 1 to 7 carbon atoms, the perfluoroalkyl group optionally has a ring structure, one or some of the fluorine atoms are optionally substituted by a halogen atom other than a fluorine atom, and one or some of fluorine atoms in the perfluoroalkyl group are optionally substituted by a halogen atom other than a fluorine atom;
• in the formula (3), R5 to R8 each independently represent a fluorine atom or a perfluoroalkyl group having 1 to 7 carbon atoms, the perfluoroalkyl group optionally has a ring structure, one or some of the fluorine atoms are optionally substituted by a halogen atom other than a fluorine atom, and one or some of fluorine atoms in the perfluoroalkyl group are optionally substituted by a halogen atom other than a fluorine atom;
• and
• in formula (4), Z represents an oxygen atom, a single bond, or —OC(R19R20)O—, R9 to R20 each independently represent a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a perfluoroalkoxy group having 1 to 5 carbon atoms, one or some of the fluorine atoms are optionally substituted by a halogen atom other than a fluorine atom, one or some of fluorine atoms in the perfluoroalkyl group are optionally substituted by a halogen atom other than a fluorine atom, one or some of fluorine atoms in the perfluoroalkoxy group are optionally substituted by a halogen atom other than a fluorine atom, s and t are each independently 0 to 5, and s+t represents an integer of 1 to 6 (when Z is —OC(R19R20)O—, s+t is optionally 0), wherein
• the fluorine-containing copolymer includes structural unit (D), and
• a content of structural unit (D) is 30 to 67 mol % relative to a total content of all structural units in the fluorine-containing copolymer.