SEMICONDUCTOR DEVICE AND METHOD FOR MANUFACTURING THE SEMICONDUCTOR DEVICE

• US 20110157252A1
• 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 9,448,433 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G02F 1/133302 Rigid substrates, e.g. inorganic substrates
• CPC Class Codes: G02F 1/133345 Insulating layers G02F1/1335, G02F1/1337, G02F1/135, G02F1/136 take precedence
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 1/133514 Colour filters
• CPC Class Codes: G02F 1/133555 Transflectors
• CPC Class Codes: G02F 1/1337 Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers
• CPC Class Codes: G02F 1/134309 characterised by their geometrical arrangement
• CPC Class Codes: G02F 1/136286 Wiring, e.g. gate line, drain line
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G02F 2201/121 common or background
• CPC Class Codes: G02F 2201/123 pixel
• CPC Class Codes: G02F 2203/01 transmissive
• CPC Class Codes: G02F 2203/04 wavelength independent
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2310/0237 Switching ON and OFF the backlight within one frame
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• 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 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• 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 2330/022 : in absence of operation, e.g. no data being entered during a predetermined time
• CPC Class Codes: G09G 3/2003 : Display of colours specific for liquid crystal displays G09G3/3607
• 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 3/3677 : suitable for active matrices only

Abstract

An object is to provide a liquid crystal display device which can recognize image display even when the liquid crystal display device is used in a dim environment. In one pixel, a pixel electrode including both of a region where incident light through a liquid crystal layer is reflected and a transmissive region is 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. When there is external light with insufficient brightness, that is, in a dim environment, the backlight emits weak light and an image is displayed in the reflective mode, whereby image display can be performed.

Claims

1. A display device comprising:

a display panel;

a backlight portion; and

an image processing circuit,

wherein the display panel comprises a plurality of pixels each including a pixel electrode provided with a transmissive region and a reflective region and configured to control an alignment state of liquid crystal and a transistor connected to the pixel electrode, and

wherein the image processing circuit comprises a memory circuit storing an image signal, a comparison circuit configured to compare the image signal stored in the memory circuit with image signals in a series of frame periods and to calculate a difference, a first driver circuit controlling the display panel, and a second driver circuit controlling light-emission of the backlight portion,

the display device comprising;

a moving-image display mode in which the comparison circuit determines that the series of frame periods in which a difference is detected is a moving image period, the image processing circuit outputs a first signal to the display panel, the display panel is driven by the driver circuit, the image processing circuit outputs a second signal to the backlight portion, and the backlight portion is driven by the second driver circuit; and

a still-image display mode in which the comparison circuit determines that the series of frame periods in which a difference is not detected is a still image period, the image processing circuit stops output of a signal to the display panel and the backlight portion.

2. The display device according to claim 1, wherein the pixel electrode includes a reflective electrode and a transparent electrode partly in contact and overlapping with the reflective electrode.

3. The display device according to claim 1, further comprising:

a structure between the backlight portion and the pixel electrode,

wherein the pixel electrode is provided over the structure, and

wherein the pixel electrode includes the reflective region provided over a side surface of the structure, and the transmissive region overlapping with a top surface of the structure.

4. The display device according to claim 1, further comprising a solar battery,

wherein the solar battery and the display panel are attached so as to be opened and closed freely, and

wherein power from the solar battery is supplied to the display panel, the backlight portion, or the image processing circuit.

5. A liquid crystal display device comprising:

a plurality of structures;

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

an insulating layer provided between adjacent side surfaces of the plurality of structures and covering the reflective layer;

a pixel electrode including;

a reflective region overlapping with the reflective layer with the insulating layer provided therebetween; and

a transmissive region overlapping with a top surface of the structure; and

a transistor electrically connected to the pixel electrode.

6. The liquid crystal display device according to claim 5, wherein the pixel electrode includes a reflective electrode and a transparent electrode partly in contact and overlapping with the reflective electrode.

7. The liquid crystal display device according to claim 5, further comprising:

two inclined planes facing each other at a cross section of the structures,

wherein an angle θ

T formed by an inclination of the inclined plane of the structure and an inclination of the inclined plane facing the inclined plane is greater than or equal to 20° and

less than or equal to 60°

.

8. The liquid crystal display device according to claim 5,

wherein the reflective region is a reflective electrode including a curving surface, and

wherein an angle θ

R at a point where the reflective electrode is most curved at the cross section of the reflective electrode, formed by two inclined planes facing each other is greater than or equal to 100° and

less than or equal to 120°

.