DISPLAY DEVICE AND E-BOOK READER PROVIDED THEREWITH

• US 20110210949A1
• Filed: 02/17/2011
• Published: 09/01/2011
• Est. Priority Date: 02/26/2010
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: YAMAZAKI, Shunpei, KOYAMA, Jun
• Granted Patent: US 8,760,442 B2
• Time in Patent Office: Days
• US Class Current: 345/204
• CPC Class Codes: G09G 2340/0435 Change or adaptation of the frame rate of the video stream
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

An object is to provide a display device in which deterioration in display quality due to a change in voltage applied is reduced and a lower visible efficiency in changing display is prevented. The display device has a display controller configured to make the display portion perform display by switching a first still image display period including a writing period in which a first image signal is written and a holding period in which the first image signal is held, and a second still image display period including a writing period in which a second image signal is written and a holding period in which the second image signal is held. The display controller is configured to make a length of the writing period of the first still image display period and a length of the writing period of the second still image display period different from each other.

Claims

1. A display device comprising:

a display portion including a plurality of transistors; and

a display controller configured to make the display portion perform display by switching a first still image display period and a second still image display period,

wherein the first still image display period comprises a writing period in which a first image signal is written and a holding period in which the first image signal is

held,

wherein the second still image display period comprises a writing period in which a second image signal is written and a holding period in which the second image signal is held, and

wherein the display controller is configured to make a length of the writing period of the first still image display period and a length of the writing period of the second still image display period different from each other.

4. The display device according to claim 1, wherein the writing period of the first still image display period is 16.6 milliseconds or less and the writing period of the second still image display period is 1 second or more.

5. The display device according to claim 1, wherein at least one of the plurality of transistors includes an oxide semiconductor layer.

6. The display device according to claim 1, wherein a carrier concentration of at least one of the plurality of transistors is lower than 1×

10¹⁴/cm³.

7. The display device according to claim 1, wherein an off-state current of at least one of the plurality of transistors is less than or equal to 1×

10<sup>−

17</sup> A/μ

m.

8. An e-book reader comprising the display device according to claim 1.

2. A display device comprising:

a display portion including a plurality of transistors; and

a display controller configured to make the display portion perform display by switching a first still image display period and a second still image display period, wherein the first still image display period comprises a writing period in which a first image signal is written and a holding period in which the first image signal is held,

wherein the second still image display period comprises a writing period in which a second image signal is written and a holding period in which the second image signal is held,

wherein the display controller is configured to make a length of the writing period of the first still image display period and a length of the writing period of the second still image display period different from each other, wherein the display controller comprises a switching circuit and a display mode control circuit,

wherein the switching circuit is configured to switch a first clock signal and a second clock signal and output the first clock signal or the second clock signal, and wherein the display mode control circuit is configured to control the switching circuit.

3. A display device comprising:

a display portion including a plurality of transistors; and

a display controller configured to make the display portion perform display by switching a first still image display period and a second still image display period, wherein the first still image display period comprises a writing period in which a first image signal is written and a holding period in which the first image signal is held,

wherein the second still image display period comprises a writing period in which a second image signal is written and a holding period in which the second image signal is held,

wherein the display controller is configured to make a length of the writing period of the first still image display period and a length of the writing period of the second still image display period different from each other, wherein the display controller comprises a reference clock generation circuit, a dividing circuit, a switching circuit and a display mode control circuit, wherein the reference clock generation circuit is configured to output a first clock signal,

wherein the dividing circuit is configured to divide the first clock signal and output a second clock signal,

wherein the switching circuit is configured to switch the first clock signal and the second clock signal and output the first clock signal or the second clock signal, and wherein the display mode control circuit is configured to control the switching circuit.

9. A method for driving a display device comprising the steps of:

displaying a first still image during a first still image display period; and

switching from the first still image display period to a second still image display period, thereby displaying a second still image during the second still image display period,

wherein the first still image display period comprises a writing period in which a first image signal is written and a holding period in which the first image signal is held,

wherein the second still image display period comprises a writing period in which a second image signal is written and a holding period in which the second image signal is held, and

wherein a length of the writing period of the first still image display period is different from a length of the writing period of the second still image display period.

10. The method for driving a display device according to claim 9, wherein the first still image display period and the second still image display period are switched by using a display controller, wherein the display controller is configured to make the display portion perform display by switching the first still image display period and the second still image display period, and

wherein the display controller is configured to make the length of the writing period of the first still image display period and the length of the writing period of the second still image display period different from each other.

11. The method for driving a display device according to claim 9, wherein the first still image display period and the second still image display period are switched by using a display controller, wherein the display controller is configured to make the display portion perform display by switching the first still image display period and the second still image display period,

wherein the display controller is configured to make the length of the writing period of the first still image display period and the length of the writing period of the second still image display period different from each other, wherein the display controller comprises a switching circuit and a display mode control circuit,

wherein the switching circuit is configured to switch a first clock signal and a second clock signal and output the first clock signal or the second clock signal, and wherein the display mode control circuit is configured to control the switching circuit.

12. The method for driving a display device according to claim 9, wherein the first still image display period and the second still image display period are switched by using a display controller, wherein the display controller is configured to make the display portion perform display by switching the first still image display period and the second still image display period,

wherein the display controller is configured to make the length of the writing period of the first still image display period and the length of the writing period of the second still image display period different from each other, wherein the display controller comprises a reference clock generation circuit, a dividing circuit, a switching circuit and a display mode control circuit, wherein the reference clock generation circuit is configured to output a first clock signal,

wherein the dividing circuit is configured to divide the first clock signal and output a second clock signal,

wherein the switching circuit is configured to switch the first clock signal and the second clock signal and output the first clock signal or the second clock signal, and wherein the display mode control circuit is configured to control the switching circuit.

13. The method for driving a display device according to claim 9, wherein the writing period of the first still image display period is 16.6 milliseconds or less and the writing period of the second still image display period is 1 second or more.