Display device comprising an oxide semiconductor layer
View Patent ↗The time taken to write a signal to a pixel is shortened in a display device. Further, a signal is written at high speed even when high voltage is applied. The display device includes a pixel including a transistor and a liquid crystal element electrically connected to a source or a drain of the transistor. The transistor includes an intrinsic or substantially intrinsic oxide semiconductor as a semiconductor material and has an off-state current of 1×10 −17 A/μm or less. The pixel does not include a capacitor. Since it is not necessary to provide a capacitor, the time taken to write a signal can be shortened.
1. A display device comprising:
a pixel, the pixel comprising:
a transistor; and
a liquid crystal element,
wherein the liquid crystal element is electrically connected to one of a source and a drain of the transistor,
wherein the transistor includes an intrinsic or substantially intrinsic oxide semiconductor layer which includes a channel formation region,
wherein an off-state current of the transistor is 1×10 −17 A/μm or less, and
wherein the pixel does not include a capacitor wiring.
2. The display device according to claim 1 , wherein a voltage higher than or equal to a voltage of a video signal is input to the liquid crystal element before the video signal is input.
3. A display device comprising:
a pixel, the pixel comprising:
a transistor; and
a liquid crystal element,
wherein the liquid crystal element is electrically connected to one of a source and a drain of the transistor,
wherein the transistor includes an intrinsic or substantially intrinsic oxide semiconductor layer which includes a channel formation region,
wherein an off-state current of the transistor is 1×10 −17 A/μm or less,
wherein the pixel does not include a capacitor wiring, and
wherein a parasitic capacitance in the pixel is less than or equal to 50 fF.
4. The display device according to claim 3 , wherein a voltage higher than or equal to a voltage of a video signal is input to the liquid crystal element before the video signal is input.
5. A display device comprising:
a pixel, the pixel comprising:
a first electrode;
a second electrode, the second electrode comprising a portion not overlapping with the first electrode;
an insulating film between the first electrode and the second electrode;
a transistor; and
a liquid crystal layer,
wherein the liquid crystal layer is over the first electrode and the second electrode,
wherein the second electrode is electrically connected to one of a source and a drain of the transistor,
wherein the transistor includes an intrinsic or substantially intrinsic oxide semiconductor layer which includes a channel formation region,
wherein an off-state current of the transistor is 1×10 ˜ 17 A/μm or less, and
wherein the pixel does not include a capacitor wiring.
6. The display device according to claim 5 , wherein a voltage higher than or equal to a voltage of a video signal is input to the first electrode before the video signal is input.
7. The display device according to claim 5 , wherein the second electrode is over the first electrode.
8. The display device according to claim 5 , wherein the first electrode and the second electrode do not overlap with each other.
9. A display device comprising:
a pixel, the pixel comprising:
a first electrode;
a second electrode, the second electrode comprising a portion not overlapping with the first electrode;
an insulating film between the first electrode and the second electrode;
a transistor; and
a liquid crystal layer,
wherein the liquid crystal layer is over the first electrode and the second electrode,
wherein the second electrode is electrically connected to one of a source and a drain of the transistor,
wherein the transistor includes an intrinsic or substantially intrinsic oxide semiconductor layer which includes a channel formation region,
wherein an off-state current of the transistor is 1×10 −17 A/μm or less,
wherein the pixel does not include a capacitor wiring, and
wherein a parasitic capacitance in the pixel is less than or equal to 50 fF.
10. The display device according to claim 9 , wherein a voltage higher than or equal to a voltage of a video signal is input to the first electrode before the video signal is input.
11. The display device according to claim 9 , wherein the second electrode is over the first electrode.
12. The display device according to claim 9 , wherein the first electrode and the second electrode do not overlap with each other.
13. A display device comprising:
a pixel, the pixel comprising:
a transistor; and
a liquid crystal element,
wherein the liquid crystal element is electrically connected to one of a source and a drain of the transistor,
wherein the transistor includes an oxide semiconductor layer including a channel formation region,
wherein the oxide semiconductor layer comprises a portion in which a concentration of hydrogen is 5×10 19 /cm 3 or lower,
wherein an off-state current of the transistor is 1×10 −17 A/μm or less, and
wherein the pixel does not include a capacitor wiring.
14. The display device according to claim 13 , wherein a voltage higher than or equal to a voltage of a video signal is input to the liquid crystal element before the video signal is input.
15. The display device according to claim 13 , wherein a parasitic capacitance in the pixel is less than or equal to 50 fF.
16. A display device comprising:
a pixel, the pixel comprising:
a transistor; and
a liquid crystal element,
wherein the liquid crystal element is electrically connected to one of a source and a drain of the transistor,
wherein the transistor includes an oxide semiconductor layer including a channel formation region,
wherein the oxide semiconductor layer comprises a portion in which a carrier concentration is 1×10 12 /cm 3 or lower,
wherein an off-state current of the transistor is 1×10 −17 A/μm or less, and
wherein the pixel does not include a capacitor wiring.
17. The display device according to claim 16 , wherein a voltage higher than or equal to a voltage of a video signal is input to the liquid crystal element before the video signal is input.
18. The display device according to claim 16 , wherein a parasitic capacitance in the pixel is less than or equal to 50 fF.