Transflective liquid-crystal-display device with pair switching device

• US 7,864,274 B2
• Filed: 03/06/2007
• Issued: 01/04/2011
• Est. Priority Date: 03/07/2006
• Status: Expired due to Fees

• Current Assignee: NLT Technologies, Ltd.
• Original Assignee: NEC LCD Technologies Limited (NEC Corporation)
• Inventors: Ikeno, Hidenori, Naka, Kenichirou, Nagai, Hiroshi, Sakamoto, Michiaki, Mori, Kenichi
• Primary Examiner(s): Nguyen; Hoan C
• Application Number:
  US11/682,646
• Publication Number:
  US 20070211198A1
• Time in Patent Office: 1,400 Days
• Field of Search: 349/141, 349/117
• US Class Current: 349/114
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G02F 1/133555 Transflectors
• CPC Class Codes: G02F 1/133565 inside the LC elements, i.e. between the cell substrates
• CPC Class Codes: G02F 1/13363 Birefringent elements, e.g. for optical compensation
• CPC Class Codes: G02F 1/133631 with a spatial distribution of the retardation value
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n
• 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 2413/03 Number of plates being 3
• CPC Class Codes: G09G 3/3607 for displaying colours or for displaying grey scales with a specific pixel layout, e.g. using sub-pixels display of colours in flat matrix panels other than liquid crystal displays G09G3/2003; grey scales specific for television H04N3/127

Abstract

A LCD device has a LC layer sandwiched between a TFT substrate and a counter substrate, first and second polarizing films, a first λ/2 film between the first polarizing film and the counter substrate, and a second λ/2 film between the second polarizing film and the TFT substrate. Angle θ1 between the direction of the optical axis of the LC layer and the polarized direction of the light entering the LC layer satisfies the relationship: 0 degree<θ1<45 degrees. The resultant LCD device has lower leakage light and coloring.

Claims

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

a liquid crystal (LC) layer defining a plurality of pixels each having a transmissive area and a reflective area, at least said transmissive area operating in a lateral-electric-field mode;

first and second polarizing films sandwiching therebetween said LC layer, said first polarizing film being effective common to said transmissive area and said reflective area, said second polarizing film being effective only to said transmissive area; and

a retardation film sandwiched between said first polarizing film and said LC layer,

wherein each of said pixels includes a pixel electrode driven by a pixel data signal supplied in common to said transmissive area and said reflective area, a first common electrode driven by a first common signal supplied in common to said reflective areas of said plurality of pixels, and a second common electrode driven by a second common signal supplied in common to said transmissive areas of said plurality of pixels,

wherein said first and second common signals are inverted in synchrony with a synchronizing signal, and said first common signal is substantially an inverted signal of said second common signal.

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

a liquid crystal (LC) layer defining a plurality of pixels each having a transmissive area and a reflective area, at least said transmissive area operating in a lateral-electric-field mode;

first and second polarizing films sandwiching therebetween said LC layer, said first polarizing film being effective common to said transmissive area and said reflective area, said second polarizing film being effective only to said transmissive area; and

a retardation film sandwiched between said first polarizing film and said LC layer,

wherein each of said pixels includes a pixel electrode driven by a pixel data signal supplied in common to said transmissive area and said reflective area, a first common electrode driven by a first common signal supplied in common to said reflective areas of said plurality of pixels, and a second common electrode driven by a second common signal supplied in common to said transmissive areas of said plurality of pixels,

wherein each of said pixels includes a first pixel electrode in said transmissive area, a second pixel electrode in said reflective area, a first switch for supplying a data signal to said first pixel electrode, and a second switch for supplying said data signal to said second pixel electrode.

3. The transflective LCD device according to claim 2, wherein said reflective area includes a reflection film maintained at an intermediate potential between a potential of said pixel electrode and a potential of said first common electrode.

4. The transflective LCD device according to claim 2, wherein said intermediate potential of said reflective film is supplied by a capacitive coupling from said pixel electrode and said first common electrode.

5. The transflective LCD device according to claim 2, wherein said intermediate potential of said reflective film is provided by an intermediate-potential generator.

6. The transflective LCD device according to claim 2, wherein said reflective film has an opening underlying said pixel electrode and said first common electrode.

7. The transflective LCD device according to claim 2, wherein said reflective film has a flat surface in a region underlying said pixel electrode and said first common electrode, and a rough surface in the other region.

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

a liquid crystal (LC) layer defining a plurality of pixels each having a transmissive area and a reflective area, at least said transmissive area operating in a lateral-electric-field mode;

first and second polarizing films sandwiching therebetween said LC layer, said first polarizing film being effective common to said transmissive area and said reflective area, said second polarizing film being effective only to said transmissive area; and

a retardation film sandwiched between said first polarizing film and said LC layer,

wherein each of said pixels includes a pixel electrode driven by a pixel data signal supplied in common to said transmissive area and said reflective area, a first common electrode driven by a first common signal supplied in common to said reflective areas of said plurality of pixels, and a second common electrode driven by a second common signal supplied in common to said transmissive areas of said plurality of pixels,

wherein each of said pixels includes a first pixel electrode in said transmissive area, a second pixel electrode in said reflective area, a first switching device for supplying a data signal to said first pixel electrode, and a second switch for supplying said data signal to said second pixel electrode.

9. The transflective LCD device according to claim 8, further comprising a first common electrode including a plurality of common electrodes connected in common and disposed in said reflective areas of a plurality of said pixels, and a second common electrode including a plurality of common electrodes connected in common and disposed in said transmissive areas of a plurality of said pixels.

10. The transflective LCD device according to claim 9, wherein one of said first common electrode and said second common electrode receives a common signal obtained by inversion of a common signal applied to the other of said first common electrode and said second common electrode.

11. The transflective LCD device according to claim 8, wherein said first and second switching devices are connected to a common data line, and driven by separate control lines.

12. The transflective LCD device according to claim 8, wherein said first and second switching devices are connected to a first data line and a second data line, respectively.

13. The transflective LCD device according to claim 11, wherein one of said first and second common electrodes is applied with a first data signal output from a voltage converter for converting a second data signal applied to the other of said first and second common electrodes.

14. The transflective LCD device according to claim 13, wherein said voltage converter includes a data memory for storing said second data signal, and a gray-scale level converter for converting a gray-scale level of said second data signal to output said first data signal.

15. The transflective LCD device according to claim 14, wherein said voltage converter includes a look-up table for converting said gray-scale level.

16. The transflective LCD device according to claim 15, wherein said look-up table tabulates a maximum of said gray-scale level and a minimum of said gray-scale level in association.

17. The transflective LCD device according to claim 16, wherein said look-up table is configured by logic gates.

18. The transflective LCD device according to claim 11, further comprising a first common electrode including a plurality of common electrodes connected in common and disposed in said reflective areas of a plurality of said pixels, and a second common electrode including a plurality of common electrodes connected in common and disposed in said transmissive areas of a plurality of said pixels.

19. The transflective LCD according to claim 8, wherein a potential to be written in said first and second common electrodes is inverted at a timing of switching for writing data through said first switching device or said second switching device.