LIQUID CRYSTAL DISPLAY DEVICE AND ELECTRONIC DEVICE

• US 20110157254A1
• Filed: 12/27/2010
• Published: 06/30/2011
• Est. Priority Date: 12/28/2009
• Status: Abandoned Application

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Hirakata, Yoshiharu, Koyama, Jun, Yamazaki, Shunpei
• Application Number:
  US12/978,798
• Publication Number:
  US 20110157254A1
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G02F 1/13624 having more than one switching element per pixel
• CPC Class Codes: G09G 2300/0443 with several sub-pixels for the same colour in a pixel, not specifically used to display gradations G09G3/364 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 2310/0281 Arrangement of scan or data electrode driver circuits at the periphery of a panel not inherent to a split matrix structure
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 2320/103 Detection of image changes, e.g. determination of an index representative of the image change
• CPC Class Codes: G09G 2340/0435 Change or adaptation of the frame rate of the video stream
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3659 the addressing of the pixel involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependant on signal of two data electrodes

Abstract

It is an object to provide a liquid crystal display device which can recognize image display even in the dim surrounding environment of the liquid crystal display device. It is another object to provide a liquid crystal display device which can perform image display in both modes: a reflective mode in which external light is used as an illumination light source; and a transmissive mode in which a backlight is used. A plurality pairs of a pixel in which incident light through a liquid crystal layer is reflected and a light-transmitting pixel are provided; therefore, display image can be performed in both modes: the reflective mode in which external light is used as an illumination light source; and the transmissive mode in which a backlight is used. Further, each reflective pixel and light-transmitting pixel may be connected to an independent signal driver circuit.

Claims

1. A liquid crystal display device comprising:

a display panel including a pixel, the pixel including;

a first sub-pixel including a first pixel electrode which transmits light and a first transistor electrically connected to the first pixel electrode; and

a second sub-pixel including a second pixel electrode which reflects visible light and a second transistor electrically connected to the second pixel electrode,

a backlight portion; and

an image processing circuit including;

a memory circuit configured to store image signals in successive frame periods;

a comparison circuit configured to compare the image signals in the successive frame periods and to detect a difference; and

a display control circuit configured to control the display panel and the backlight portion,

wherein the first transistor is electrically connected to a first signal line,

wherein the second transistor is electrically connected to a second signal line,

wherein the first pixel electrode and the second pixel electrode are each configured to control an orientation state of liquid crystal,

wherein the comparison circuit is configured to determine that the successive frame periods is a moving image period if the difference is detected, so that the display control circuit is configured to output a first signal including a moving image to the first signal line and a second signal to the backlight portion, and

wherein the comparison circuit is configured to determine that the successive frame periods is a still image period if the difference is not detected, so that the display control circuit is configured to output a third signal including a still image to the second signal line.

2. The liquid crystal display device according to claim 1, further comprising a photometric circuit configured to detect a brightness of external light, wherein the display control circuit is capable of outputting the first signal including the moving image to the first signal line in accordance with the brightness of external light even when the comparison circuit determines that the successive frame periods is a still image period.

3. The liquid crystal display device according to claim 1, further comprising a photometric circuit configured to detect a brightness of external light, wherein the display control circuit is capable of outputting the second signal including the still image to the second signal line in accordance with the brightness of external light even when the comparison circuit determines that the successive frame periods is a moving image period.

4. The liquid crystal display device according to claim 1, wherein each of the first transistor and the second transistor includes an oxide semiconductor layer.

5. An electronic device comprising the liquid crystal display device according to claim 1 and a solar battery,

wherein an electric power generated by the solar battery is supplied to at least one of the display panel, the backlight portion, and the image processing circuit.

6. The electronic device according to claim 5, wherein the electronic device is an electronic book reader.

7. The liquid crystal display device according to claim 1, wherein the display control circuit is configured to output a signal for controlling a backlight to the backlight portion if the comparison circuit determines that the successive frame periods is a still image period.

8. The liquid crystal display device according to claim 1, further comprising a mode-switching circuit configured to output a signal for switching between a moving-image mode and a still-image mode to the image processing circuit.

9. A liquid crystal display device comprising:

a plurality of structures over a substrate;

a reflective layer covering side surfaces of the plurality of structures;

an insulating layer covering the reflective layer;

a pixel electrode including;

a reflective electrode provided with a plurality of openings; and

a transparent electrode, portions of the transparent electrode being exposed at the plurality of openings;

a first transistor electrically connected to the transparent electrode; and

a second transistor electrically connected to the reflective electrode,

wherein the plurality of openings and top surfaces of the plurality of structures are overlapped with each other.

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

wherein each of the structures has two inclined surfaces facing each other at a cross section as side surfaces,

wherein an angle θ

T formed by the two inclined surfaces is less than 90°

.

11. The liquid crystal display device according to claim 10, wherein the angle θ

T is greater than or equal to 10° and

less than or equal to 60°

.

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

wherein a portion of the reflective electrode which overlaps with the reflective layer includes a curving surface, and

wherein an angle θ

R at a point where the portion of the reflective electrode is most curved at a cross section, formed by two inclined planes facing each other is greater than or equal to 90°

.

13. The liquid crystal display device according to claim 12, wherein the angle θ

R is greater than or equal to 100° and

less than or equal to 120°

.

14. A liquid crystal display device comprising:

a display panel comprising;

a first sub-pixel including a first transistor and a first pixel electrode which transmits light; and

a second sub-pixel including a second transistor and a second pixel electrode which reflects visible light; and

wherein the first pixel electrode and the second pixel electrode are capable of controlling an orientation state of liquid crystal,

wherein a coloring layer is provided to overlap with at least the first pixel electrode,

an image processing circuit configured to determine whether an image signal is a moving image or a still image,

wherein the image signal is output to the first sub-pixel if the image signal is determined to be the moving image, and the image signal is output to the second sub-pixel if the image signal is determined to be the still image.

15. The liquid crystal display device according to claim 14, further comprising a photometric circuit configured to detect a brightness of external light, wherein the image processing circuit is capable of outputting the image signal to the first sub-pixel in accordance with the brightness of external light even when the image processing circuit determines that the image signal is a still image.

16. The liquid crystal display device according to claim 14, further comprising a photometric circuit configured to detect a brightness of external light, wherein the image processing circuit is capable of outputting the image signal to the second sub-pixel in accordance with the brightness of external light even when the image processing circuit determines that the image signal is a moving image.

17. The liquid crystal display device according to claim 14, wherein each of the first transistor and the second transistor includes an oxide semiconductor layer.

18. An electronic device comprising the liquid crystal display device according to claim 14 and a solar battery,

wherein an electric power generated by the solar battery is supplied to at least one of the display panel and the image processing circuit.

19. The electronic device according to claim 18, wherein the electronic device is an electronic book reader.