Provided are polyimide and a thin film thereof which have a three-dimensional
structure and therefore are excellent in a mechanical strength and a heat resistance
as compared with those of conventional linear polyimide. The polyimide is obtained
from a salt of multifunctional amine represented by Formula (1):
##STR1##
(wherein A represents a tetravalent organic group, and n represents an integer
of 0 to 3) and tetracarboxylic diester represented by Formula (2):
##STR2##
(wherein B represents a tetravalent organic group having 1 to 20 carbon
atoms, and R1 and R2 each represent independently an alkyl
group having 1 to 5 carbon atoms).
