A copolymer containing a repeating unit of formula (1) and a repeating unit of formula (2-1) or (2-2): ##STR00001## wherein R.sup.1 and R.sup.2 represent alkyl or aryl, R.sup.3 represents alkyl, aryl, alkoxy or amino, R.sup.5 and R.sup.6 represent hydrogen, alkyl or aryl. The copolymer exhibits excellent mechanical properties, and capable of forming a coating film having low reflectivity.