Liquid crystal display device

• US 7,889,295 B2
• Filed: 12/01/2006
• Issued: 02/15/2011
• Est. Priority Date: 12/05/2005
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Kimura, Hajime, Uochi, Hideki
• Primary Examiner(s): Wong; Tina M
• Application Number:
  US11/565,989
• Publication Number:
  US 20070146591A1
• Time in Patent Office: 1,537 Days
• Field of Search: None
• US Class Current: 349/114
• CPC Class Codes: G02F 1/133345 Insulating layers G02F1/1335, G02F1/1337, G02F1/135, G02F1/136 take precedence
• CPC Class Codes: G02F 1/133371 Cells with varying thickness of the liquid crystal layer
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• CPC Class Codes: G02F 1/133555 Transflectors
• CPC Class Codes: G02F 1/134309 characterised by their geometrical arrangement
• CPC Class Codes: G02F 1/134363 for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]
• CPC Class Codes: G02F 1/134372 for fringe field switching [FFS] where the common electrode is not patterned
• CPC Class Codes: G02F 1/134381 Hybrid switching mode, i.e. for applying an electric field with components parallel and orthogonal to the substrates
• CPC Class Codes: G02F 1/136227 Through-hole connection of the pixel electrode to the active element through an insulation layer
• 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: H01L 27/12 the substrate being other than a semiconductor body, e.g. an insulating body

Abstract

It is an object of the present invention to provide a liquid crystal display device which has a wide viewing angle and less color-shift depending on an angle at which a display screen is seen and can display an image favorably recognized both outdoors in sunlight and dark indoors (or outdoors at night). The liquid crystal display device includes a first portion where display is performed by transmission of light and a second portion where display is performed by reflection of light. Further, a liquid crystal layer includes a liquid crystal molecule which rotates parallel to an electrode plane when a potential difference is generated between two electrodes of a liquid crystal element provided below the liquid crystal layer.

Claims

1. A liquid crystal display device including a transmission portion and a reflection portion, the device comprising:

a liquid crystal element including a pixel electrode in both of said portions and a first common electrode at least in the transmission portion, each having a light-transmitting property, a second common electrode having reflectiveness in the reflection portion, and a liquid crystal layer provided over the pixel electrode,

wherein the pixel electrode is provided over the second common electrode with an insulating layer interposed therebetween in the reflection portion; and

wherein the pixel electrode is provided over the first common electrode with the insulating layer interposed therebetween in the transmission portion; and

wherein a second insulating layer scarcely having refractive index anisotropy is provided in the reflection portion.

2. A liquid crystal display device according to claim 1, wherein the second common electrode is electrically connected to the first common electrode.

3. A liquid crystal display device according to claim 1, wherein the liquid crystal layer includes a liquid crystal molecule rotating parallel to a substrate plane.

4. A liquid crystal display device according to claim 1, wherein the pixel electrode is comb-shaped.

5. A liquid crystal display device according to claim 1, wherein the second insulating layer has a thickness such that a thickness of the liquid crystal layer in the reflective portion is greater than or equal to one-third and less than or equal to two-thirds of a thickness of the liquid crystal layer in the transmission portion.

6. A liquid crystal display device comprising:

a liquid crystal element between a first substrate and a second substrate, which includes

a pixel electrode having a light-transmitting property,

a first common electrode having a light-transmitting property,

a second common electrode having reflectiveness in a reflective portion of the liquid crystal element, and

a liquid crystal layer provided between the pixel electrode and the second substrate;

wherein the first common electrode and the second common electrode are provided over the first substrate;

wherein the pixel electrode is provided over the first common electrode and the second common electrode with an insulating layer interposed therebetween, and

wherein a second insulating layer scarcely having refractive index anisotropy is provided between the first substrate and the second substrate in the reflective portion.

7. A liquid crystal display device according to claim 6, wherein the liquid crystal layer includes a liquid crystal molecule rotating parallel to a substrate plane.

8. A liquid crystal display device according to claim 6, wherein the pixel electrode is comb-shaped.

9. A liquid crystal display device according to claim 6, wherein the second common electrode is electrically connected to the first common electrode.

10. A liquid crystal display device according to claim 6, wherein the second insulating layer has a thickness such that a thickness of the liquid crystal layer in the reflective portion is greater than or equal to one-third and less than or equal to two-thirds of a thickness of the liquid crystal layer in a portion other than the reflective portion.