wherein D1 and D2 each represents a condensed polycyclic aromatic heterocyclic moiety or an aromatic hetero ring-substituted amino group, which may contain an --SO3 M group, wherein M is a hydrogen atom, an alkali metal or an ammonium group; --A-- represents a divalent aromatic residue, which may contain an --SO3 M group, provided that the --A-- moiety should contain an --SO3 M group when no --SO3