Semiconductor Energy Laboratory Co., Ltd.

Aya Anazai

Mitsuaki Osame

Yu Yamazaki

Ryota Fukumoto

Masayuki Sakakura

Yoshifumi Tanada

Ritsuko Nagao

A display device with high-definition, in which display unevenness due to a voltage drop in a wiring or display unevenness due to a variation in characteristics of TFTs are suppressed. The display device of the invention comprises a first wiring for transmitting a video signal and a second wiring for supplying a current to a light emitting element. The first wiring and the second wiring extend parallel to each other, and are formed so as to overlap with each other at least partly with an insulating layer interposed therebetween.

Display device

The invention provides a light emitting device using transistors manufactured by the conventional process while reducing an area occupied by capacitors, whereby variations in luminance of light emitting elements caused by variations in gate voltage Vgs of the transistors are suppressed, and a luminance decay of the light emitting elements due to the degradation of light emitting materials and variations in luminance can also be suppressed. The light emitting device includes a first transistor for controlling a video signal input to a pixel, second and third transistors one of which is turned ON while the other is turned OFF according to a potential of the video signal, and a fourth transistor for supplying current to a light emitting element according to each drain potential of the second and third transistors, wherein the drains of the second and third transistors are connected to each other, the third and fourth transistors have the same conductivity, and the sources of the third and fourth transistors are connected to each other.

Light emitting device and element substrate

No need of lowering off-current of a switching transistor, fewer luminance variations of a light emitting element between pixels due to characteristic variations of a driving transistor, and less risk of steps due to increase in the number of wirings. A video signal for light emission or non-emission of a pixel is input to a gate of a current controlling transistor operated in a linear region, which is connected in series with the driving transistor, through a switching transistor. Since a voltage Vds between a source and a drain of the current controlling transistor is small, small changes in a voltage Vgs between a gate and a source thereof do not affect a current flowing in a load. The current flowing in the light emitting element is determined by the driving transistor operated in a saturation region, and a fixed potential is input to the gate thereof during light emission.

Growing community of inventors

Kanagawa, Japan

Aya Anazai