Patent ID: 7745016

Claim:
An organic electroluminescence device emitting white light which comprises a pair of electrodes, at least two light emitting layers and an electron transporting layer comprising a heterocyclic derivative having a nitrogen atom, the light emitting layers and the electron transporting layer being between the pair of electrodes, wherein an energy gap of a host compound comprised in each light emitting layer Eg(Host-i) satisfies following relation (I): 2.9 eV≦Eg(Host- i ) (I) wherein Eg(Host-i) represents an energy gap of a host compound comprised in an i-th light emitting layer from the electron transporting layer, i representing an integer of 1 to n, an energy gap of the heterocyclic derivative having a nitrogen atom comprised in the electron transporting layer Eg(ETM) satisfies following relation (II): 2.9 eV<Eg(ETM) (II) and an ionization potential of a host compound comprised in a light emitting layer adjacent to the electron transporting layer (Ip(Host-1)) and an ionization potential of the heterocyclic derivative having a nitrogen atom comprised in the electron transporting layer (Ip(ETM)) satisfy following relation (III): Ip(ETM)≦Ip(Host-1)+0.3 eV (III); wherein the host compound is capable of emitting blue light and is selected from the group consisting of anthracene derivatives, styryl derivatives, aromatic amines, aluminum chelates having mixed ligands and carbazole derivatives; the energy gap is an excited singlet energy gap which is determined by obtaining an absorption spectrum of a 10 −5 mole/liter toluene solution of a sample using an ultraviolet visible absorption meter and converting a wavelength at an absorption end on the absorption spectrum into energy value; and the ionization potential is measured by obtaining a curve showing a change of discharged photoelectrons with a photon energy of irradiation using a photoelectron spectrometer, and determining by extrapolation a threshold value of the discharge of photoelectrons on the curve.