LIQUID CRYSTAL DISPLAY DEVICE AND ELECTRONIC DEVICE

• US 20110157253A1
• 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 8,866,725 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G02F 1/133555 Transflectors
• 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 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• 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 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2340/0435 Change or adaptation of the frame rate of the video stream
• CPC Class Codes: G09G 2340/06 Colour space transformation
• 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 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

An object is to provide a liquid crystal display device in which image display can be recognized even in an environment where light is dim around the liquid crystal display device. Another object is to provide a liquid crystal display device capable of image display in both modes of a reflective mode in which external light is used as a light source and a transmissive mode in which a backlight is used. One pixel is provided with a pixel electrode having both of a region where light incident through a liquid crystal layer is reflected and a region having a light-transmitting property, so that image display can be performed in both modes of a reflective mode in which external light is used as a light source and a transmissive mode in which a backlight is used.

Claims

1. A liquid crystal display device comprising:

a display panel, the display panel comprising;

a plurality of pixels each including a transparent electrode, a reflective electrode, a transistor electrically connected to the transparent electrode and the reflective electrode; and

a first driver circuit configured to drive the plurality of pixels;

an image processing circuit, the image processing circuit comprising;

a memory circuit capable of storing image signals in successive frame periods;

a comparison circuit configured to compare the image signals in the successive frame period and calculate a difference; and

a display control circuit; and

a backlight portion, the backlight portion comprising;

a plurality of light emitting elements; and

a second driver circuit configured to drive the plurality of light emitting elements,

wherein the transparent electrode and the reflective electrode are each configured to control an orientation state of liquid crystal,

wherein the display panel is configured to be driven in a moving-image display mode or a still-image display mode,

wherein in the moving-image display mode, the comparison circuit judges successive frame periods during which the difference is detected as a moving-image display period, the image processing circuit outputs a first signal to the display panel, the first driver circuit drives the display panel, the image processing circuit outputs a second signal to the backlight portion, and the second driver circuit drives the backlight portion; and

wherein, in the still-image display mode, the comparison circuit judges successive frame periods during which the difference is not detected as a still-image display period and the image processing circuit stops the output of the second signal to the backlight portion.

2. 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.

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

4. The liquid crystal display device according to claim 1, further comprising a field sequential signal generation circuit configured to compress a image signal from the display control circuit with respect to time axis.

5. The liquid crystal display device according to claim 1, wherein the transistor includes an oxide semiconductor.

6. The liquid crystal display device according to claim 1, wherein the transparent electrode is partly in contact with and overlapped with the reflective electrode.

7. An electronic device comprising the liquid crystal display device according to claim 1 and a solar battery, wherein the solar battery is attached to the display panel so as to be opened and closed, 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, the display panel comprising;

a plurality of pixels, each including a transparent electrode, a reflective electrode, a transistor electrically connected to the transparent electrode and the reflective electrode; and

a first driver circuit configured to drive the plurality of pixels;

a backlight portion, the backlight portion comprising;

a plurality of light-emitting elements including 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, and

a second driver circuit configured to drive the plurality of light-emitting elements; and

an image processing circuit, the image processing circuit comprising;

a memory circuit configured to store image signals;

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

a selection circuit configured to select and output the image signals of the successive frame periods in accordance with the difference detected in the comparison circuit; and

a display control circuit configured to control supplying of first signal to the first driver circuit and a second signal to the second driver circuit in accordance with an output signal from the selection circuit,

wherein the display control circuit is configured to stop supplying the second signal in case the comparison circuit does not detect the difference, and

wherein the first light-emitting elements, the second light-emitting elements and the third light-emitting elements are controlled by the second driver circuit to emit light sequentially.

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

10. The liquid crystal display device according to claim 8, further comprising a field sequential signal generation circuit configured to compress a image signal from the display control circuit with respect to time axis.

11. The liquid crystal display device according to claim 8, wherein the transistor includes an oxide semiconductor.

12. The liquid crystal display device according to claim 8, wherein the transparent electrode is partly in contact with and overlapped with the reflective electrode.

13. An electronic device comprising the liquid crystal display device according to claim 8 and a solar battery, wherein the solar battery is attached to the display panel so as to be opened and closed, and electric power from the solar battery is supplied to the display panel, the backlight portion, and the image processing circuit.

14. A liquid crystal display device comprising:

a display panel, the display panel comprising;

a plurality of pixels, each including a transistor and a pixel electrode; and

a first driver circuit operationally connected to the transistor,

wherein the pixel electrode comprises a transparent electrode and a reflective electrode,

a backlight portion, the backlight portion comprising;

a plurality of light-emitting elements each having different emission colors; and

a second driver circuit; and

an image processing circuit,

wherein the image processing circuit comprises a memory circuit including a plurality of memories, a comparison circuit, a selection circuit and a display control circuit,

wherein the memory circuit is electrically connected to the comparison circuit and the selection circuit,

wherein the comparison circuit is electrically connected to the selection circuit and the display control circuit,

wherein the selection circuit is electrically connected to the display control circuit, and

wherein the display control circuit is electrically connected to the first driver circuit and the second driver circuit.

15. The liquid crystal display device according to claim 14, further comprising a photometric circuit, configured to detect a brightness and supply a signal to the second driver circuit for driving the plurality of light-emitting elements.

16. The liquid crystal display device according to claim 14, 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 and the second driver circuit controls the first, second and third light emitting elements to emit light sequentially.

17. The liquid crystal display device according to claim 14, wherein the transparent electrode is partly in contact with and overlapped with the reflective electrode.

18. The liquid crystal display device according to claim 14, further comprising a field sequential signal generation circuit configured to compress a image signal from the display control circuit with respect to time axis.

19. The liquid crystal display device according to claim 14, wherein the transistor includes an oxide semiconductor.

20. An electronic device comprising the liquid crystal display device according to claim 14 and a solar battery, wherein the solar battery is attached to the display panel so as to be opened and closed, and electric power from the solar battery is supplied to the display panel, the backlight portion, and the image processing circuit.