At present, the research and development of various display elements using organic luminous materials (organic luminous elements) have been actively made, and particularly, organic EL (electroluminescence) elements have received attention as promising display elements because high-intensity luminescence can be obtained at low voltage. For example, EL elements have been known in which organic thin layers are formed by vapor deposition of organic compounds (Applied Physics Letters, 51, 913 (1987)). The organic EL elements described therein have the laminated structure of electron-transporting materials and hole-transporting materials, and the luminescence characteristics thereof are significantly improved, compared with conventional monolayer type elements.
With this report as a turning point, the research and development of organic EL elements have become active, and the development of electron-transporting materials and hole-transporting materials for improving the efficiency have been variously studied. However, in the development of electron-transporting materials, no compound having a performance exceeding that of Alq (tris(8-hydroxyquinolinato)aluminum) has been discovered yet, so that the improvement thereof has been desired. Further, Alq is unsuitable for electron-transporting materials for blue luminous elements because of its green fluorescence. In this respect, therefore, development has also been desired.
On the other hand, recently, applications of organic EL elements to full-color displays have been actively studied. For developing high performance full-color displays, it is necessary to heighten the luminous color purity of each of the blue, green and red colors. However, it is difficult to obtain luminescence of high color purity. For example, distyrylarylene compounds (DPVBi) described in Organic EL Elements and Forefront of Industrialization Thereof, page 38 (N. T. S. Co.) and benzo cyclocondensed nitrogen-containing heterocyclic compounds (Zn(OXZ).sub.2) described in Organic EL Elements and Forefront of Industrialization Thereof, page 40 (N. T. S. Co.) and JP-A-7-133483 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") are blue luminous materials widely studied. However, only blue luminescence of low color purity is obtained, so that the improvement thereof has been desired.