Transflective liquid crystal display device

• US 7,876,406 B2
• Filed: 04/01/2008
• Issued: 01/25/2011
• Est. Priority Date: 04/02/2007
• Status: Expired due to Fees

• Current Assignee: NLT Technologies, Ltd. (Tianma Microelectronics Company Limited)
• Original Assignee: NEC LCD Technologies Limited (Tianma Microelectronics Company Limited)
• Inventors: Naka, Kenichirou, Mori, Kenichi, Nagai, Hiroshi, Sakamoto, Michiaki
• Primary Examiner(s): QI, ZHI QIANG
• Application Number:
  US12/060,708
• Publication Number:
  US 20080239178A1
• Time in Patent Office: 1,029 Days
• Field of Search: 349/114, 349/141, 349/117, 349/124, 349/33, 349/96
• US Class Current: 349/114
• CPC Class Codes: G02F 1/133555 Transflectors
• CPC Class Codes: G02F 1/133757 with different alignment orientations
• 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

Abstract

A transflective LCD includes a LC layer sandwiched between a pair of substrates, and a pair of polarizing films. The LCD device includes a reflection area and a transmission area in each pixel, the transmission area having a reflection film. A retardation film has a first portion in the refection area between the reflection film and the LC layer, and a second portion in the transmission area between the LC layer and the rear polarizing film. The retardation film has a slow axis perpendicular to an initial orientation direction of the LC molecules upon absence of an applied voltage and perpendicular or parallel to the optical axis of the front polarizing film. The orientation of the LC molecules upon display of a dark state has a direction different between the reflection area and the transmission area.

Claims

1. A transflective liquid crystal display (LCD) device comprising:

a liquid crystal (LC) cell comprising a LC layer including therein LC molecules homogeneously oriented and a pair of transparent substrates sandwiching therebetween the LC layer to define an array of pixels, each of said pixels including a transmission area and a reflection area juxtaposed each other;

first and second polarizing films sandwiching therebetween said LC cell, said first polarizing film being disposed at a front side of said LC cell and having an optical axis perpendicular to an optical axis of said second polarizing film disposed at a rear side of said LC cell;

a reflection film disposed in said reflection area at a rear side of said LC layer; and

a retardation film including a first portion disposed in said reflection area between said reflection film and said LC layer, and a second portion disposed in said transmission area between said LC layer and said second polarizing film, said retardation film having a slow axis perpendicular to an initial orientation direction of said LC molecules upon absence of an applied voltage, said slow axis being perpendicular or parallel to said optical axis of said first polarizing film,

wherein an orientation of said LC molecules upon display of a dark state has a direction which is different between said reflection area and said transmission area.

2. The transflective LCD device according to claim 1, wherein said first polarizing film extends to cover both said reflection area and said transmission area.

3. The transflective LCD device according to claim 1, wherein said second polarizing film extends to cover both said reflection area and said transmission area.

4. The transflective LCD device according to claim 1, wherein said first portion is in contact with said second portion.

5. The transflective LCD device according to claim 4, wherein said first portion and said second portion are integrally formed and have the same retardation.

6. The transflective LCD device according to claim 1, wherein the orientation of said LC molecules in said transmission area upon display of a dark state has a direction substantially equal to a direction of said initial orientation, and the direction of said LC molecules in said reflection area has a direction substantially deviated from said initial orientation by 20 to 25 degrees.

7. The transflective LCD device according to claim 6, wherein a potential difference applied between a pixel electrode and a common electrode for applying an electric field to said LC layer upon display of a dark state in said transmission area is lower than in said reflection area.

8. The transflective LCD device according to claim 1, wherein a drive voltage of said LC layer in said reflection area is an inversion of a drive voltage of said LC layer in said transmission area, for display of an image in said reflection area and said transmission area.

9. The transflective LCD device according to claim 1, wherein said reflection area and said transmission area operate in a normally white mode and a normally black mode, respectively.

10. The transflective LCD device according to claim 1, said retardation film has a retardation of λ

/4.

11. The transflective LCD device according to claim 1, wherein said LC layer is driven in an in-plane-switching mode.

12. The transflective LCD device according to claim 1, wherein a pixel electrode and a common electrode are disposed on said retardation film.

13. The transflective LCD device according to claim 1, wherein said second polarizing film includes a polarizing layer and a protective layer disposed between said polarizing layer and said LC layer, and said protective layer has an optical isotropy and an optical transmission axis perpendicular to a slow axis of said retardation film.

14. The transflective LCD device according to claim 1, wherein said first polarizing film includes a polarizing layer and a protective layer disposed between said polarizing layer and said LC layer, and said protective layer has an optical isotropy.

15. The transflective LCD device according to claim 1, wherein said first polarizing film includes a first polarizing layer and a first protective layer disposed between said first polarizing layer and said LC layer, said first protective layer has an optical isotropy, said second polarizing film includes a second polarizing layer and a second protective layer disposed between said second polarizing layer and said LC layer, and said second protective layer has a positive mono-axis anisotropy.

16. The transflective LCD device according to claim 15, wherein said second protective film has a retardation of 180 nm or smaller in a thickness direction thereof.

17. The transflective LCD device according to claim 15, wherein said second polarizing film has an optical transmission axis substantially parallel to said initial orientation of said LC layer.

18. The transflective LCD device according to claim 1, further comprising another retardation film between said retardation film and said polarizing film, wherein said first polarizing film includes a first polarizing layer and a first protective layer disposed between said first polarizing layer and said another retardation film.

19. The transflective LCD device according to claim 18, wherein said second polarizing film has an optical transistors axis substantially parallel to said initial orientation of said LC layer.