LIQUID CRYSTAL DISPLAY DEVICE AND ELECTRONIC DEVICE

• US 20110157216A1
• Filed: 12/27/2010
• Published: 06/30/2011
• Est. Priority Date: 12/28/2009
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Hirakata, Yoshiharu, Koyama, Jun, Yamazaki, Shunpei
• Granted Patent: US 9,298,035 B2
• Time in Patent Office: Days
• US Class Current: 345/596
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G09G 2300/0456 with a reflective area and a transmissive area combined in one pixel, such as in transflectance pixels
• CPC Class Codes: G09G 2310/063 Waveforms for resetting the whole screen at once
• CPC Class Codes: G09G 2320/10 Special adaptations of display systems for operation with variable images
• CPC Class Codes: G09G 3/36 using liquid crystals
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

To provide a liquid crystal display device which can perform image display in both modes: a reflective mode where external light is used as an illumination light source; and a transmissive mode where a backlight is used. In one pixel, a region where incident light through a liquid crystal layer is reflected to perform display (reflective region) and a region through which light from the backlight passes to perform display (transmissive region) are provided, and image display can be performed in both modes: the reflective mode where external light is used as an illumination light source; and the transmissive mode where the backlight is used as an illumination light source. In addition, two transistors connected to respective pixel electrode layers are provided in one pixel, and the two transistors are separately operated, whereby display of the reflective region and display of the transmissive region can be controlled independently.

Claims

1. A liquid crystal display device comprising:

a display panel comprising a plurality of pixels each including a first sub-pixel including a first pixel electrode having a light-transmitting property, a second sub-pixel including a second pixel electrode reflecting visible light, a first transistor electrically connected to the first pixel electrode, and a second transistor electrically connected to the second pixel electrode,

wherein the first pixel electrode is electrically connected to a first scan line and a first signal line, and configured to control an alignment state of liquid crystal, and

wherein the second pixel electrode is electrically connected to a second scan line and a second signal line, and configured to control the alignment state of liquid crystal;

a backlight portion comprising a plurality of light-emitting elements; and

an image processing circuit comprising;

a memory circuit configured to store image signals; and

a comparison circuit configured to compare the image signals stored in the memory circuit and to detect a difference among the image signals,

wherein the image processing circuit outputs a first signal including a moving image to the first signal line and a second signal in synchronization with the first signal to the backlight portion when the comparison circuit detects the difference in successive frame periods, and

wherein the image processing circuit converts a still image into a monochrome still image, outputs a first signal including the monochrome still image to the second signal line, and stops output of a signal to the backlight portion when the comparison circuit does not detect the difference in successive frame periods.

2. The liquid crystal display device according to claim 1,

wherein the first transistor and the second transistor each include an oxide semiconductor.

3. The liquid crystal display device according to claim 1,

wherein the plurality of light-emitting elements include first light-emitting elements emitting a first color, second light-emitting elements emitting a second color, and third light-emitting elements emitting a third color.

4. The liquid crystal display device according to claim 1, further comprising a field sequential signal generator circuit configured to compress an image signal from the comparison circuit and to supply a compressed image signal to the display panel.

5. The liquid crystal display device according to claim 1, further comprising a photometric circuit configured to detect a brightness and control the second signal for driving the plurality of light-emitting elements.

6. The liquid crystal display device according to claim 1, wherein a part of the first pixel electrode overlaps with a part of the second pixel electrode with an insulating film interposed therebetween.

7. An electronic device comprising:

the liquid crystal display device according to claim 1; and

a solar battery,

wherein the solar battery and the display panel are opened and closed freely, and electric power from the solar battery is supplied to the display panel, the backlight portion, and the image processing circuit.

8. A liquid crystal display device comprising:

a display panel comprising a plurality of pixels each including a first sub-pixel including a first pixel electrode having a light-transmitting property and a second sub-pixel including a second pixel electrode having a light-reflecting property,

wherein the first pixel electrode is electrically connected to a first transistor electrically connected to a first scan line driver circuit, and

wherein the second pixel electrode is electrically connected to a second transistor electrically connected to a second scan line driver circuit;

a backlight portion comprising a plurality of light-emitting elements having a plurality of different emitting colors; and

an image processing circuit comprising;

a memory circuit configured to store image signals of respective frame periods;

a comparison circuit configured to detect a difference between image signals of successive frame periods among the image signals of the respective frame periods stored in the memory circuit;

a selection circuit configured to select whether or not to output an image signal in accordance with the difference detected by the comparison circuit; and

a display control circuit configured to supply a first signal including the image signal to the display panel and a second signal including a control signal to the backlight portion when the comparison circuit detects the difference, and to stop supplying the first signal and the second signal when the comparison circuit does not detect the difference,

wherein the display control circuit supplies the first signal to the first sub-pixel when the comparison circuit detects the difference in successive frame periods, and

wherein the display control circuit supplies the first signal to the second sub-pixel when the comparison circuit does not detect the difference in successive frame periods.

9. The liquid crystal display device according to claim 8,

wherein the first transistor and the second transistor each include an oxide semiconductor.

10. The liquid crystal display device according to claim 8,

wherein the plurality of light-emitting elements include first light-emitting elements emitting a first color, second light-emitting elements emitting a second color, and third light-emitting elements emitting a third color.

11. The liquid crystal display device according to claim 8, further comprising a field sequential signal generator circuit configured to compress the image signal from the display control circuit and to supply a compressed image signal to the display panel.

12. The liquid crystal display device according to claim 8, further comprising a photometric circuit configured to detect a brightness and control the second signal for driving the plurality of light-emitting elements.

13. The liquid crystal display device according to claim 8, wherein a part of the first pixel electrode overlaps with a part of the second pixel electrode with an insulating film interposed therebetween.

14. An electronic device comprising:

the liquid crystal display device according to claim 8; and

a solar battery,

wherein the solar battery and the display panel are opened and closed freely, and electric power from the solar battery is supplied to the display panel, the backlight portion, and the image processing circuit.

15. A liquid crystal display device comprising:

a display panel comprising;

a first driver circuit;

a second driver circuit; and

a pixel portion comprising a plurality of pixels each including a first transistor, a second transistor, a first pixel electrode having a light-transmitting property, and a second pixel electrode having a light-reflecting property,

wherein the first pixel electrode is electrically connected to the first transistor,

wherein the second pixel electrode is electrically connected to the second transistor,

wherein the first driver circuit is electrically connected to a first gate electrode of the first transistor, and

wherein the second driver circuit is electrically connected a second gate electrode of the second transistor;

a backlight portion comprising a backlight including a plurality of light-emitting elements having a plurality of different emitting colors; and

an image processing circuit comprising a display control circuit configured to selectively supply an image signal to one of the first transistor and the second transistor in accordance with a difference between image signals of successive frame periods.

16. The liquid crystal display device according to claim 15,

wherein the plurality of light-emitting elements include first light-emitting elements emitting a first color, second light-emitting elements emitting a second color, and third light-emitting elements emitting a third color.

17. The liquid crystal display device according to claim 15,

wherein the first transistor and the second transistor each include an oxide semiconductor.

18. The liquid crystal display device according to claim 15, further comprising a field sequential signal generator circuit configured to compress the image signals from the display control circuit.

19. The liquid crystal display device according to claim 15, further comprising a photometric circuit configured to detect a brightness and control a signal for driving the plurality of light-emitting elements.

20. The liquid crystal display device according to claim 15, further comprising a switching circuit configured to selectively supply an image signal to one of the first transistor and the second transistor by hand.

21. The liquid crystal display device according to claim 15,

wherein a part of the first pixel electrode overlaps with a part of the second pixel electrode with an insulating film interposed therebetween.

22. An electronic device comprising:

the liquid crystal display device according to claim 15; and

a solar battery,

wherein the solar battery and the display panel are opened and closed freely, and electric power from the solar battery is supplied to the display panel, the backlight portion, and the image processing circuit.