TRANSFLECTIVE LIQUID CRYSTAL DISPLAY DEVICE

• US 20070002226A1
• Filed: 06/29/2006
• Published: 01/04/2007
• Est. Priority Date: 06/30/2005
• Status: Active Grant

• Current Assignee: NLT Technologies, Ltd.
• Original Assignee: NEC LCD Technologies Limited (NEC Corporation)
• Inventors: Ikeno, Hidenori, Sumiyoshi, Ken, Mori, Kenichi, Nagai, Hiroshi, Sakamoto, Michiaki, Matsushima, Jin, Kudo, Yasuki
• Granted Patent: US 7,705,937 B2
• Time in Patent Office: Days
• US Class Current: 349/114
• CPC Class Codes: G02F 1/133555 Transflectors
• CPC Class Codes: G02F 1/134363 for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]
• CPC Class Codes: G09G 2300/0408 Integration of the drivers onto the display substrate
• 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 2320/028 by changing the viewing angle properties, e.g. widening the viewing angle, adapting the viewing angle to the view direction
• CPC Class Codes: G09G 3/3655 Details of drivers for counter electrodes, e.g. common electrodes for pixel capacitors or supplementary storage capacitors
• CPC Class Codes: G09G 3/3659 the addressing of the pixel involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependant on signal of two data electrodes

Abstract

An IPS-mode transflective LCD device includes an array of pixels each including a reflective region and a transmissive region juxtaposed. The reflective region operates in a normally-white mode, and the transmissive region operates in a normally-black mode. A common data signal is supplied to the reflective region and transmissive region, whereas the common electrode signal in the transmissive region is an inverted signal of the common electrode signal in the reflective region, to thereby obtain similar gray-scale levels.

Claims

1. A transflective liquid crystal display (LCD) device comprising first and second polarizing films having polarizing axes perpendicular to one another, a liquid crystal (LC) layer interposed between said first polarizing film and said second polarizing film, said LC layer defining an array of pixels each including a reflective region and a transmissive region juxtaposed, wherein:

LC molecules of said LC layer have a longer axis extending parallel to or normal to the polarization direction of the light incident onto said LC layer in said reflective region; and

each of said pixels includes a pixel electrode receiving a pixel signal which is common between said reflective region and said transmissive region, a first common electrode receiving a first common signal which is common among said reflective regions of a plurality of said pixels, and a second common electrode receiving a second common signal which is common among said transmissive regions of said plurality of said pixels.

2. The LCD device according to claim 1, wherein said first common signal is substantially an inverted signal of said second common signal.

3. The LCD device according to claim 1, wherein said pixel electrode includes a first pixel electrode in said reflective region and a second pixel electrode in said transmissive region, and each of said pixels is associated with a first switching device for coupling a data line to said first pixel electrode, and a second switching device for coupling said data line to said second pixel electrode.

4. The LCD device according to claim 3, wherein said reflective region includes therein a reflection film having a potential substantially equal to a median between a potential of said first pixel electrode and a potential of said first common electrode.

5. The LCD device according to claim 4, wherein said potential of said reflection film is determined by a capacitive coupling between the same and said first pixel electrode and a capacitive coupling between the same and said first common electrode.

6. The LCD device according to claim 4, wherein said potential of said reflection film is determined by a potential setting circuit.

7. The LCD device according to claim 4, wherein a portion of said reflection film is omitted in an area directly behind said first pixel electrode and said first common electrode.

8. The LCD device according to claim 4, wherein a portion of said reflection film in an area directly behind said first pixel electrode and said first common electrode has a flat surface, and the other portion of said reflection film has an uneven surface.

9. A transflective liquid crystal display (LCD) device comprising a liquid crystal (LC) layer defining an array of pixels arranged in a matrix, each of said pixels including therein a reflective region and a transmissive region juxtaposed, wherein:

each of said pixels includes a first pixel electrode in said reflective region, and a second pixel electrode in said transmissive region; and

each of said pixels is associated with a first switching device for coupling said first electrode to a data line supplying a data signal, and a second switching device for coupling said second electrode and said data line.

10. The LCD device according to claim 9, further comprising a first common electrode including a plurality of common electrodes connected in common and disposed in said reflective regions 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 regions of a plurality of said pixels.

11. The LCD device according to claim 10, wherein said first and second switching devices are connected to a common data line.

12. The LCD device according to claim 10, wherein said first and second common electrodes are applied with voltages each obtained by inverting the other of said voltages.

13. The LCD device according to claim 9, further comprising a first gate line for controlling said first switching devices and a second gate line for controlling said second switching devices, wherein said first and second switching devices are connected to said data line in common.

14. The LCD device according to claim 9, wherein said data line for each column includes a first data line connected to said first switching devices, and a second data line connected to said second switching devices.

15. The LCD device according to claim 13, further comprising a data converter for converting a first gray-scale level of a data signal received from outside of said LCD device into a second gray-scale level to be supplied to one of said first pixel electrode and said second pixel electrode.

16. The LCD device according to claim 15, wherein said data converter includes a memory for storing therein said data signal received from outside, and a gray-scale level converter for converting said first gray-scale level of said data signal into said second gray-scale level, and writes said second and first gray-scale levels into said one and the other, respectively, of said first pixel electrode and said second pixel electrode.

17. The LCD device according to claim 16, wherein said gray-scale level converter converts said first gray-scale level into said second gray-scale level by using a look-up table.

18. The LCD device according to claim 17, wherein said look-up table tabulates said first gray-scale level and corresponding second gray-scale level in association so that said first gray scale level assumes a maximum when said corresponding second gray-scale level assumes a minimum.

19. The LCD device according to claim 13, wherein said gray-scale level converter is configured by a logic circuit.

20. The LCD device according to claim 13, further comprising a single common electrode including a plurality of common electrodes disposed in said reflective regions and said transmissive regions of a plurality of said pixels.

21. The LCD device according to claim 20, wherein a potential to be written in said single common electrode is inverted at a timing of switching for writing data through said first switching device or said second switching device.

22. A method for driving a transflective liquid crystal display device (LCD) including a reflective region and a transmissive region in each of pixels arranged in an array, said method comprising the steps of:

generating a first data signal and a second data signal having therebetween a specific potential relationship; and

applying said first data signal and said second data signal to said reflective region and said transmissive region, respectively.

23. The method according to claim 22, wherein said relationship between said first data signal and said second data signal is such that said first data signal assumes a maximum gray-scale-level potential when corresponding said second data signal assumes a minimum gray-scale-level potential.

24. The method according to claim 22, further comprising the step of applying a first common electrode signal to a first common electrode disposed in said reflective regions of a plurality of said pixels and a second common electrode signal to a second common electrode disposed in said transmissive regions of a plurality of said pixels, said first common electrode signal having a potential different from a potential of said second common electrode signal.

25. The method according to claim 22, wherein said LCD device includes a first switching device for coupling a data line to said first pixel electrode and a second switching device for coupling said data line to said second pixel electrode, a first gate line for controlling said first switching device, a second gate line for controlling said second switching device, said method further comprising the steps of:

turning ON said first and second switching devices in a time-division scheme, to apply a common data signal to said first and second pixel electrodes;

applying a first common electrode signal to a common electrode during applying said common data signal to said first pixel electrode; and

applying a second common electrode signal to said common electrode during applying said common data signal to said second pixel electrode, said first common electrode signal having a potential different from a potential of said second common electrode signal.

26. The method according to claim 22, wherein said LCD device includes a first switching device for coupling a first data line to said first pixel electrode, a second switching device for coupling a second data line to said second pixel electrode, said method further comprising the step of:

applying said first and second data signals to said first and second data lines, respectively.

27. The method according to claim 26, wherein one of said first and second data signal is supplied from outside of said LCD device, and the other of said first and second data signals has a gray-scale level converted from a grays-scale level of said one of said first and second data signals by using a look-up table.

28. The method according to claim 27, wherein said look-up table is such that similar γ

-characteristics are obtained for both said reflective and transmissive regions.

29. The method according to claim 22, wherein said LCD device includes a single common electrode for both said reflective region and said transmissive region of a plurality of said pixels, said method further comprising the steps of:

applying said single common electrode with a first common electrode signal at the timing of writing said first data signal; and

applying said single common electrode signal with a second common electrode signal at the timing of writing said second data signal.