Patent ID: 8212488
Filing Date: 2012-07-03
Classification: G09G,H01L

Abstract:
1. A light emitting device comprising: a first transistor; a second transistor; a third transistor; a fourth transistor; a capacitor; and a light emitting element, wherein: one of a source and a drain of the first transistor is electrically connected to the light emitting element, and the other of the source and drain of the first transistor is electrically connected to one of a source and a drain of a second transistor; the other of the source and the drain of the second transistor is electrically connected to one of a source and a drain of the fourth transistor, a gate of the second transistor is electrically connected to one of a source and a drain of the third transistor and the capacitor; the light emitting element is formed over the first transistor, the light emitting element comprises: a first electrode; a layer containing an organic light emitting compound over the first electrode; and a second electrode over the layer containing the organic light emitting compound; a luminescence from the organic light emitting compound is passed through the second electrode; and a channel length of the first transistor is longer than a channel length of the second transistor.