1. Field of the Invention
The present invention relates to a luminescence device capable of converting electric energy into light to achieve light emission, in particular to an organic electroluminescence device (luminescence device or EL device).
2. Description of the Related Art
An organic electroluminescence (EL) device is being watched as a promising display device because light emission with high brightness is obtained at a low voltage. A consumed electric power is an important characteristic value of this organic electroluminescence device. The consumed electric power is expressed by a product of voltage and current. When not only a voltage value necessary for obtaining desired brightness is lower, but a current value is smaller, the consumed electric powder of the device can be made lower.
In recent years, high efficiency of the device is being advanced by using a phosphorescent material. Iridium complexes, platinum complexes and so on are known as the phosphorescent material (see, for example, JP-A-2001-247859 and JP-A-2007-19462). However, a device in which high efficiency and high durability are compatible with each other has not been developed yet.
Also, there have been reported organic EL devices using, as a material, a compound having a nitrogen-containing heterocyclic ring intending to provide a device with high efficiency and low voltage (see, for example, JP-A-2002-100476 and JP-A-2004-171808). However, higher efficiency and driving at a lower voltage are being demanded.
On the other hand, though Journal of Chemical Society, 1939, pages 1945 to 1956 describes a compound obtained by condensing a nitrogen-containing heterocyclic ring with an aromatic heterocyclic ring or an aromatic hydrocarbon ring, it does not describe any applications thereof.