Diamine, polymer, liquid crystal aligning agent, liquid crystal alignment film, and liquid crystal display element

A diamine characterized by being represented by formula (1) (wherein X 1 represents a single bond or an alkylene group having 1 to 6 carbon atoms (wherein non-adjacent -CH 2 - groups in the alkylene group may be independently substituted by an ether bond, an ester bond or an amide bond); X 2 represents -OCO-CH=CH- or -CH=CH-COO-; X 3 represents a single bond, an alkylene group having 1 to 10 carbon atoms or a bivalent benzene ring; X 4 represents a single bond, -OCO-CH=CH- or -CH=CH-COO-; and X 5 represents a single bond or an alkylene group having 1 to 6 carbon atoms (wherein non-adjacent -CH 2 - groups in the alkylene group may be independently substituted by an ether bond, an ester bond or an amide bond); wherein at least one cinnamoyl group is contained in formula (1)).