Patent ID: 9147720
Filing Date: 2015-09-29
Classification: G09G,H01L

Abstract:
1. A light emitting device comprising: a first transistor; a second transistor; a third transistor; a fourth transistor; a first line; a second line; a third line; a fourth line; a fifth line; a sixth line; a capacitor; and a light emitting element, wherein: a channel formation region of the second transistor and a channel formation region of the fourth transistor are formed of a same semiconductor island; a channel formation region of the first transistor and a channel formation region of the third transistor are formed of a same semiconductor island; a conductivity type of the first transistor and a conductivity of the third transistor is the same; one of a source and a drain of the first transistor is electrically connected to one of a source and a drain of the third transistor; a gate of the first transistor is electrically connected to one electrode of the capacitor; the gate of the first transistor is electrically connected to one of a source and a drain of the fourth transistor through a metal layer; the gate of the first transistor is electrically connected to one of a source and a drain of the second transistor through the metal layer; the metal layer comprises a region that overlaps with a part of the second line; a gate of the second transistor is electrically connected to the second line; the third line comprises a region that overlaps with a part of the channel formation region of the first transistor; the other of the source and the drain of the third transistor is electrically connected to the light emitting element; the other of the source and the drain of the fourth transistor is electrically connected to the fourth line; a gate of the fourth transistor is electrically connected to the first line; the other electrode of the capacitor is electrically connected to the third line; the other electrode of the capacitor is electrically connected to the sixth line; the third line is a power supply line; the sixth line is a power supply line; the light emitting element comprises: a luminescence from the organic light emitting compound is passed through the second electrode; and a ratio of a channel length to a channel width of the first transistor is different from a ratio of a channel length to a channel width of the third transistor.