A photoreactive copolymer comprising: a copolymer of a cyclic olefin monomer represented by the following Chemical Formula 1 and a cyclic olefin monomer represented by the following Chemical Formula 2: wherein it includes a repeating unit of the following Chemical Formula 3a or 3b: in Chemical Formula 1, q is 0; at least one of R1, R2, R3, and R4 is a radical represented by the following Chemical Formula 1a, among R1 to R4, the remainders other than the radical of Chemical Formula 1a are hydrogen; in Chemical Formula 1a, A is a single bond, B is oxygen, R9 is selected from the group consisting of a single bond, and alkylene having 1 to 20 carbon atoms, C1 is C6-C40 arylene C2 and C3 are each independently the same or different C6-C40 arylene C5-C10 cycloalkylene; or C4-C40 heterocycloalkylene including a hetero element in Group 14, 15, or 16, D is a single bond, R10 is selected from the group consisting of hydrogen; and linear or branched alkyl having 1 to 20 carbon atoms; in Chemical Formula 2, q' is 0; at least one of R1', R2', R3', and R4' is a radical selected from the group consisting of compounds represented by the following Chemical Formula 2a among R1' to R4', the remainders other than the radical of Chemical Formula 2a are hydrogen; [Chemical Formula 2a] in Chemical Formulas 2a A' is a single bond, or oxygen B' is selected from the group consisting of a single bond, and ester, R9' is selected from the group consisting of a single bond, and alkylene having 1 to 20 carbon atoms, at least one of R10', R11', R12', R13', and R14' is halogen, in Chemical Formulas 3a and 3b, each independently, m, m', and k are integers from 50 to 5000, q and q' are 0, R1, R2, R3, and R4 are as defined in Chemical Formula 1, and R1', R2', R3', and R4' are as defined in Chemical Formula 2. wherein it includes a repeating unit of the following Chemical Formula 3a or 3b: in Chemical Formula 1, q is 0; at least one of R1, R2, R3, and R4 is a radical represented by the following Chemical Formula 1a, among R1 to R4, the remainders other than the radical of Chemical Formula 1a are hydrogen; in Chemical Formula 1a, A is a single bond, B is oxygen, R9 is selected from the group consisting of a single bond, and alkylene having 1 to 20 carbon atoms, C1 is C6-C40 arylene C2 and C3 are each independently the same or different C6-C40 arylene C5-C10 cycloalkylene; or C4-C40 heterocycloalkylene including a hetero element in Group 14, 15, or 16, D is a single bond, R10 is selected from the group consisting of hydrogen; and linear or branched alkyl having 1 to 20 carbon atoms; in Chemical Formula 2, q' is 0; at least one of R1', R2', R3', and R4' is a radical selected from the group consisting of compounds represented by the following Chemical Formula 2a among R1' to R4', the remainders other than the radical of Chemical Formula 2a are hydrogen; [Chemical Formula 2a] in Chemical Formulas 2a A' is a single bond, or oxygen B' is selected from the group consisting of a single bond, and ester, R9' is selected from the group consisting of a single bond, and alkylene having 1 to 20 carbon atoms, at least one of R10', R11', R12', R13', and R14' is halogen, in Chemical Formulas 3a and 3b, each independently, m, m', and k are integers from 50 to 5000, q and q' are 0, R1, R2, R3, and R4 are as defined in Chemical Formula 1, and R1', R2', R3', and R4' are as defined in Chemical Formula 2.