Display device and electronic device

• US 9,047,836 B2
• Filed: 12/20/2010
• Issued: 06/02/2015
• Est. Priority Date: 12/24/2009
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Koyama, Jun
• Primary Examiner(s): Eisen, Alexander
• Assistant Examiner(s): Chatly, Amit
• Application Number:
  US12/972,737
• Publication Number:
  US 20110157128A1
• Time in Patent Office: 1,625 Days
• Field of Search: 345/76, 345/204, 345/211, 345/690
• US Class Current: 1/1
• CPC Class Codes: G09G 2320/0214 with crosstalk due to leakage current of pixel switch in active matrix panels
• CPC Class Codes: G09G 3/2025 the sub-frames having all the same time duration
• CPC Class Codes: G09G 3/2081 with combination of amplitude modulation and time modulation space and time error diffusion G09G3/2066
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

Multiple gray levels are expressed in a display device. The display device includes a pixel portion where pixels including transistors and display elements are arranged in matrix, a gate driver electrically connected to a gate of the transistor, a source driver electrically connected to a source or a drain of the transistor, and a data processing circuit which outputs a signal to the source driver. The transistor includes an oxide semiconductor. In the data processing circuit, n-bit digital data of input m-bit digital data (m and n are positive integers, where m>n) is used for voltage gradation and (m−n) bit digital data is used for time gradation.

Claims

1. A display device comprising:

a pixel portion comprising pixels arranged in matrix wherein each of the pixels includes a transistor and a display element;

a gate driver electrically connected to a gate of the transistor;

a source driver electrically connected to one of a source and a drain of the transistor; and

a data processing circuit configured to output signals to the source driver, wherein the transistor has a channel formation region including an oxide semiconductor, wherein the data processing circuit is configured to output the signals by using n-bit digital data of input m-bit digital data for voltage gradation and by using (m−

n) bit digital data for time gradation,

wherein m and n are positive integers, where m>

n, and

wherein an off-state current per unit channel width of the transistor is 10 aA/.mu.m or less.

2. The display device according to claim 1, wherein one frame period is divided into 2^m-n subframe periods for the time gradation.

3. The display device according to claim 1, wherein the source driver outputs (2ⁿ+1) or less voltage levels.

4. The display device according to claim 1, wherein the transistor has a mobility of 10 cm²/Vs or higher.

5. The display device according to claim 1,

wherein the transistor is formed over a substrate.

6. The display device according to claim 1, wherein the display element is a liquid crystal element.

7. An electronic device including the display device according to claim 1, wherein the electronic device is one selected from the group consisting of a portable game machine, a digital camera, a television receiver, a computer, an electronic paper, and a digital photo frame.

30. The display device according to claim 1, wherein the oxide semiconductor includes indium, gallium, zinc, and oxygen.

8. A display device comprising:

a pixel portion comprising pixels arranged in matrix wherein each of the pixels includes a transistor and a display element;

a gate driver electrically connected to a gate of the transistor;

a source driver electrically connected to one of a source and a drain of the transistor; and

a data processing circuit configured to output signals to the source driver, wherein the transistor has a channel formation region including an intrinsic or substantially intrinsic oxide semiconductor, wherein the data processing circuit is configured to output the signals by using n-bit digital data of input m-bit digital data for voltage gradation and by using (m−

n) bit digital data for time gradation,

wherein m and n are positive integers, where m>

n, and

wherein an off-state current per unit channel width of the transistor is 10 aA/.mu.m or less.

9. The display device according to claim 8, wherein carrier concentration of the intrinsic or the substantially intrinsic oxide semiconductor is lower than 1×

10¹⁴/cm³.

10. The display device according to claim 8, wherein one frame period is divided into 2^m-n subframe periods for the time gradation.

11. The display device according to claim 8, wherein the source driver outputs (2ⁿ+1) or less voltage levels.

12. The display device according to claim 8, wherein the transistor has a mobility of 10 cm²/Vs or higher.

13. The display device according to claim 8,

wherein the transistor is formed over a substrate.

14. The display device according to claim 8, wherein the display element is a liquid crystal element.

15. An electronic device including the display device according to claim 8, wherein the electronic device is one selected from the group consisting of a portable game machine, a digital camera, a television receiver, a computer, an electronic paper, and a digital photo frame.

31. The display device according to claim 8, wherein the intrinsic or substantially intrinsic oxide semiconductor includes indium, gallium, zinc, and oxygen.

16. A display device comprising:

a pixel portion comprising pixels arranged in matrix wherein each of the pixels includes a transistor and a display element;

a gate driver electrically connected to a gate of the transistor;

a source driver electrically connected to one of a source and a drain of the transistor; and

a data processing circuit configured to output signals to the source driver, wherein the transistor has a channel formation region including an oxide semiconductor and has an off-state current of 1 aA/.mu.m or less, wherein in the data processing circuit is configured to process n-bit digital data of input m-bit digital data as data related to voltage gradation and to process (m−

n) bit digital data as data related to time gradation,

wherein m and n are positive integers, where m>

n,

wherein the signals are output to the source driver through a switch in the data processing circuit, and

wherein an off-state current per unit channel width of the transistor is 10 aA/.mu.m or less.

17. The display device according to claim 16, wherein carrier concentration of the oxide semiconductor is lower than 1×

10¹⁴/cm³.

18. The display device according to claim 16, wherein one frame period is divided into 2^m-n subframe periods for the time gradation.

19. The display device according to claim 16, wherein the source driver outputs (2ⁿ+1) or less voltage levels.

20. The display device according to claim 16, wherein the transistor has a mobility of 10 cm²/Vs or higher.

21. The display device according to claim 16, wherein the display element is a liquid crystal element.

22. An electronic device including the display device according to claim 16, wherein the electronic device is one selected from the group consisting of a portable game machine, a digital camera, a television receiver, a computer, an electronic paper, and a digital photo frame.

32. The display device according to claim 16, wherein the oxide semiconductor includes indium, gallium, zinc, and oxygen.

23. A display device comprising:

a pixel portion comprising pixels arranged in matrix wherein each of the pixels includes a transistor and a display element;

a gate driver electrically connected to a gate of the transistor;

a source driver electrically connected to one of a source and a drain of the transistor; and

a data processing circuit, wherein the transistor has a channel formation region including an oxide semiconductor,

wherein the data processing circuit is configured to select two voltage levels, which is to be output from the source driver, among (n−

1) voltage levels based on n-bit digital data of input m-bit digital data, wherein the data processing circuit is configured to output 2.sup.m-n digital data for one pixel in one frame period to the source driver where each of the 2.sup.m-n digital data is selected from either of two digital data corresponding to the two voltage levels, and wherein m and n are positive integers, where m>

n, and

wherein an off-state current per unit channel width of the transistor is 10 aA/.mu.m or less.

24. The display device according to claim 23, wherein the one frame period is divided into 2^m-n subframe periods.

25. The display device according to claim 23, wherein the source driver outputs (2ⁿ+1) or less voltage levels.

26. The display device according to claim 23, wherein the transistor has a mobility of 10 cm²/Vs or higher.

27. The display device according to claim 23,

wherein the transistor is formed over a substrate.

28. The display device according to claim 23, wherein the display element is a liquid crystal element.

29. An electronic device including the display device according to claim 23, wherein the electronic device is one selected from the group consisting of a portable game machine, a digital camera, a television receiver, a computer, an electronic paper, and a digital photo frame.

33. The display device according to claim 23, wherein the oxide semiconductor includes indium, gallium, zinc, and oxygen.