Patent ID: 7456425

Claim:
A light emitting device comprising: an anode; a cathode; and an organic compound film containing a hole transporting material and an electron transporting material, the organic compound film comprising: a hole transporting region comprising the hole transporting material adjacent to the anode; an electron transporting region comprising the electron transporting material adjacent to the cathode; a mixture region disposed between the hole transporting region and the electron transporting region and comprising the hole transporting material and the electron transporting material at a constant proportion in a direction along the anode and the cathode, wherein the mixture region is doped with a light emitting material at least partly; a first concentration changing region disposed between the hole transporting region and the mixture region wherein the proportion of the electron transporting material relative to the hole transporting material monotonically increases in the first concentration changing region in a direction from the hole transporting region to the mixture region; and a second concentration changing region disposed between the mixture region and the electron transporting region wherein the proportion of the electron transporting material relative to the hole transporting material monotonically increases in the second concentration changing region in a direction from the mixture region to the electron transporting region.