Liquid crystal display device

• US 7,034,789 B2
• Filed: 06/13/2003
• Issued: 04/25/2006
• Est. Priority Date: 06/17/2002
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Takeuchi, Masanori, Nagashima, Nobuyoshi, Kondo, Naofumi
• Primary Examiner(s): Osorio, Ricardo
• Assistant Examiner(s): Said, Mansour M.
• Application Number:
  US10/460,372
• Publication Number:
  US 20040001167A1
• Time in Patent Office: 1,047 Days
• Field of Search: 345 87- 88, 345/90, 345/92, 345 93- 95, 345/100, 345/204, 345205-206, 345210-211, 345/214
• US Class Current: 345/90
• CPC Class Codes: G02F 1/134345 Subdivided pixels, e.g. for grey scale or redundancy
• CPC Class Codes: G02F 1/136213 Storage capacitors associated with the pixel electrode
• CPC Class Codes: G09G 2300/0443 with several sub-pixels for the same colour in a pixel, not specifically used to display gradations G09G3/364 takes precedence
• CPC Class Codes: G09G 2300/0447 for multi-domain technique to improve the viewing angle in a liquid crystal display, such as multi-vertical alignment [MVA]
• CPC Class Codes: G09G 2300/0876 Supplementary capacities in pixels having special driving circuits and electrodes instead of being connected to common electrode or ground; Use of additional capacitively coupled compensation electrodes
• 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 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

In an active-matrix liquid crystal display device, each of multiple pixels includes a first sub-pixel and a second sub-pixel, through which different voltages are applicable to a portion of the liquid crystal layer. Each of the first and second sub-pixels includes a liquid crystal capacitor defined by a counter electrode and a sub-pixel electrode that faces the counter electrode by way of the liquid crystal layer, and a storage capacitor defined by a storage capacitor electrode, an insulating layer, and a storage capacitor counter electrode. The storage capacitor electrode is electrically connected to the sub-pixel electrode, and the storage capacitor counter electrode faces the storage capacitor electrode by way of the insulating layer. The counter electrode is shared by the first and second sub-pixels and the storage capacitor counter electrodes of the first and second sub-pixels are electrically independent of each other.

Claims

1. A liquid crystal display device comprising:

a plurality of pixels which are arranged in columns and rows and each of which includes an associated portion of a liquid crystal layer and at least two electrodes that are used to apply a voltage to the portion of the liquid crystal layer, each of said plurality of pixels including a first sub-pixel and a second sub-pixel, through which mutually different voltages are applicable to the associated portion of the liquid crystal layer, each of the first and second sub-pixels including;

a liquid crystal capacitor, which is defined by a counter electrode and a sub-pixel electrode that faces the counter electrode by way of the liquid crystal layer; and

a storage capacitor, which is defined by a storage capacitor electrode, an insulating layer, and a storage capacitor counter electrode, the storage capacitor electrode being electrically connected to the sub-pixel electrode, the storage capacitor counter electrode facing the storage capacitor electrode by way of the insulating layer; and

wherein the counter electrode is shared by the first and second sub-pixels and the storage capacitor counter electrodes of the first and second sub-pixels are electrically independent of each other.

2. The liquid crystal display device of claim 1, further comprising:

gate lines, which extend along the rows of pixels;

source lines, which extend along the columns of pixels; and

multiple pairs of switching elements, each of said pairs of switching elements being provided for the first and second sub-pixels of an associated one of the plurality of pixels and being connected to one of the gate lines and one of the source lines that are associated with the associated one of the plurality of pixels,

wherein ON/OFF states of each of said pairs of switching elements are controlled by a gate signal voltage to be supplied through the associated gate line, and

wherein when the pair of switching elements is ON, a source signal voltage is supplied through the associated source line to the sub-pixel electrodes and the storage capacitor electrodes of the first and second sub-pixels, and

wherein after the pair of switching elements has been turned OFF, voltages applied to the storage capacitor counter electrodes of the first and second sub-pixels vary, and

wherein the direction and magnitude of variation at the first sub-pixel are different from the direction and magnitude of variation at the second sub-pixel.

3. The liquid crystal display device of claim 2, wherein the switching elements comprise one of TFTs and MIMs.

4. The liquid crystal display device of claim 1, wherein voltages applied to the storage capacitor counter electrodes invert polarities thereof at regular intervals.

5. The liquid crystal display device of claim 4, wherein voltages applied to the storage capacitor counter electrodes of the first and second sub-pixels are out of phase with each other by 180 degrees.

6. The liquid crystal display device of claim 5, wherein voltages applied to the storage capacitor counter electrodes of the first and second sub-pixels have the same amplitude.

7. The liquid crystal display device of claim 4, wherein the source signal voltage to be supplied through each of said source lines inverts its polarity every time a predetermined number of gate lines have been selected.

8. The liquid crystal display device of claim 2, wherein the source signal voltages to be supplied through each pair of adjacent source lines have mutually opposite polarities.

9. The liquid crystal display device of claim 8, wherein the source signal voltage to be supplied through each of said source lines inverts its polarity every time two of the gate lines have been selected, and

wherein voltages applied to the storage capacitor counter electrodes and the source signal voltage invert their polarities at the same interval but are out of phase with each other by one half period.

10. The liquid crystal display device of claim 8, wherein the source signal voltage to be supplied through each of said source lines inverts its polarities every time two of the gate lines have been selected, and

wherein voltages applied to the storage capacitor counter electrodes invert their polarities at one half of the interval at which the source signal voltage inverts its polarities, but are in phase with the source signal voltage.

11. The liquid crystal display device of claim 8, wherein the source signal voltage to be supplied through each of said source lines inverts its polarities every time one of the gate lines is selected, and

wherein voltages applied to the storage capacitor counter electrodes invert their polarities at the same interval as the source signal voltage and are in phase with the source signal voltage.

12. The liquid crystal display device of claim 2, wherein each of said gate lines is provided between the first and second sub-pixels of its associated pixels.

13. The liquid crystal display device of claim 2, further comprising storage capacitor lines, each of which is connected to the storage capacitor counter electrodes of the first and second sub-pixels of its associated pixels and is provided between its associated adjacent pixels substantially parallel to the gate lines.

14. The liquid crystal display device of claim 1, wherein when each of said plurality of pixels conducts a display operation at a grayscale gk falling within a range of 0≦

gk≦

n (where gk and n are both integers and the greater the grayscale gk the higher the brightness of the grayscale), a difference Δ

Vlc (gk) between root-mean-square voltages to be applied to the portions of the liquid crystal layer that are associated with the first and second sub-pixels is greater than 0 volts, Δ

Vlc (gk)≧

Δ

Vlc (gk+1) is satisfied, and the display operation is conducted in a normally black mode.

15. The liquid crystal display device of claim 1, wherein the liquid crystal layer is a vertical aligned liquid crystal layer and includes a nematic liquid crystal material having negative dielectric anisotropy.

16. The liquid crystal display device of claim 15, wherein the portions of the liquid crystal layer that are associated with the first and second sub-pixels include four domains in which liquid crystal molecules are tilted in four different directions when a voltage is applied thereto, the four different directions being defined by four azimuth angles that are different from each other by 90 degrees.

17. The liquid crystal display device of claim 1, wherein the liquid crystal layer is a parallel aligned liquid crystal layer and includes a nematic liquid crystal material having positive dielectric anisotropy, and

wherein the counter electrode and the sub-pixel electrodes generate an electric field substantially parallel to the surface of the liquid crystal layer.

18. The liquid crystal display device of claim 1, wherein the liquid crystal display device is one of an MVA mode liquid crystal display device, an ASM liquid crystal display device and an IPS mode liquid crystal display device.

19. The liquid crystal display device of claim 1, wherein the liquid crystal display device is a dot inversion and frame inversion liquid crystal display device.

20. The liquid crystal display device of claim 1, further comprising a TFT on-gate structure.