Liquid crystal display

• US 7,079,214 B2
• Filed: 05/17/2005
• Issued: 07/18/2006
• Est. Priority Date: 06/06/2002
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Shimoshikiryo, Fumikazu
• Primary Examiner(s): Parker, Kenneth
• Assistant Examiner(s): Chung, David Y.
• Application Number:
  US11/130,261
• Publication Number:
  US 20050213015A1
• Time in Patent Office: 427 Days
• Field of Search: 349/144, 349/143, 349/129
• US Class Current: 349/144
• CPC Class Codes: G02F 1/133707 Structures for producing distorted electric fields, e.g. bumps, protrusions, recesses, slits in pixel electrodes
• CPC Class Codes: G02F 1/134336 Matrix
• CPC Class Codes: G02F 1/134345 Subdivided pixels, e.g. for grey scale or redundancy
• CPC Class Codes: G02F 1/1362 Active matrix addressed cells G02F1/134336, G02F1/134363 take precedence
• CPC Class Codes: G02F 1/1393 the birefringence of the liquid crystal being electrically controlled, e.g. ECB-, DAP-, HAN-, PI-LC cells G02F1/1396, G02F1/141 take precedence
• 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 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• 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 3/3655 Details of drivers for counter electrodes, e.g. common electrodes for pixel capacitors or supplementary storage capacitors

Abstract

To reduce viewing angle dependence of γ characteristics in a normally black liquid crystal display.

Each pixel 10 has a first sub-pixel 10a and a second sub-pixel 10b which can apply mutually different voltages to their respective liquid crystal layers. Relationships ΔV12 (gk)>0 volts and ΔV12 (gk)≧ΔV12 (gk+1) are satisfied at least in a range 0<gk≦n−1 if it is assumed that ΔV12=V1−V2, where ΔV12 is the difference between root-mean-square voltage V1 applied to the liquid crystal layer of the first sub-pixel 10a and root-mean-square voltage V2 applied to the liquid crystal layer of the second sub-pixel 10b.

Claims

1. A liquid crystal display, comprising a plurality of pixels each of which has a liquid crystal layer and a plurality of electrodes for applying an electric field to the liquid crystal layer, wherein:

the plurality of pixels are arranged in a matrix (rp, cq) with a plurality of rows (1 to rp) and plurality of columns (1 to cq) and each pixel is expressed as P (p, q), where 1≦

p≦

rp and 1≦

q≦

cq;

each of the plurality of pixels has at least two sub-pixels SPa (p, q), SPb (p, q), etc. arranged in the column direction; and

the at least two sub-pixels differ from each other in brightness when displaying an intermediate grayscale, and the position of the brightest of the at least two sub-pixels arranged in the column direction changes periodically in the row direction in the case of a pixel in an arbitrary row, but it is constant in the case of a pixel in an arbitrary column.

2. The liquid crystal display according to claim 1, wherein in each of the plurality of pixels, correspondence between the order of brightness of the at least two sub-pixels and position of the at least two sub-pixels arranged in the column direction changes in the row direction periodically in the case of a pixel in an arbitrary row, but it is constant in the case of a pixel in an arbitrary column.

3. The liquid crystal display according to claim 1, wherein when displaying an intermediate grayscale, the at least two sub-pixels in each of the plurality of pixels are placed such that sub-pixels equal in the order of brightness will not adjoin each other.

4. The liquid crystal display according to claim 1, wherein the at least two sub-pixels are SPa (p, q) and SPb (p, q), and when displaying an intermediate grayscale:

the brightest sub-pixel in a pixel P (p, q) in an arbitrary row is SPa (p, q) in the case where q is an odd number and SPb (p, q) in the case where q is an even number, or SPb (p, q) in the case where q is an odd number and SPa (p, q) in the case where q is an even number; and

the brightest sub-pixel in a pixel P (p, q) in an arbitrary column is either SPa (p, q) or SPb (p, q) regardless of whether p is an odd number.

5. The liquid crystal display according to claim 4, wherein when displaying an intermediate grayscale, the at least two sub-pixels in each of the plurality of pixels are placed such that the brightest sub-pixels form a checkered pattern.

6. The liquid crystal display according to claim 1, wherein:

direction of the electric field applied to the liquid crystal layers in the plurality of pixels is reversed every vertical scanning period; and

when displaying an intermediate grayscale, the direction of the electric field is reversed periodically in the row direction in the case of pixels in an arbitrary row and it is reversed every pixel in the column direction in the case of pixels in an arbitrary column.

7. The liquid crystal display according to claim 6, wherein the direction of the electric field is reversed every pixel in the row direction in the case of pixels in an arbitrary row.

8. The liquid crystal display according to claim 6, wherein the direction of the electric field is reversed every two pixels in the row direction in the case of pixels in an arbitrary row.

9. The liquid crystal display according to claim 1, wherein:

the liquid crystal display operates in normally black mode;

the at least two sub-pixels include two sub-pixels SPa (p, q) and SPb (p, q); and

when each of the plurality of pixels displays a grayscale gk which satisfies 0≦

gk≦

n, where gk and n are integers not less than zero and a larger value of gk corresponds to higher brightness, relationships Δ

V12 (gk)>

0 volts and Δ

V12 (gk)≧

Δ

V12 (gk+1) are satisfied at least in a range 0<

gk≦

n−

1 if it is assumed that Δ

V12 (gk)=V1 (gk)−

V2 (gk), where V1 (gk) and V2 (gk) are root-mean-square voltages applied to the liquid crystal layers of the first sub-pixel and the second sub-pixel, respectively.

10. The liquid crystal display according to claim 9, wherein a relationship Δ

V12 (gk)≧

Δ

V12 (gk+1) is satisfied at least in a range 0<

gk≦

n−

1.

11. The liquid crystal display according to claim 9, wherein:

SPa (p, q) and SPb (p, q) each comprise;

a liquid crystal capacitor formed by a counter electrode and a sub-pixel electrode opposing the counter electrode via the liquid crystal layer, and

a storage capacitor formed by a storage capacitor electrode connected electrically to the sub-pixel electrode, an insulating layer, and a storage capacitor counter electrode opposing the storage capacitor electrode via the insulating layer; and

the counter electrode is a single electrode shared by SPa (p, q) and SPb (p, q), and the storage capacitor counter electrodes of SPa (p, q) and SPb (p, q) are electrically independent of each other.

12. The liquid crystal display according to claim 11, comprising two switching elements provided for SPa (p, q) and SPb (p, q), respectively,

wherein the two switching elements are turned on and off by scan line signal voltages supplied to a common scan line;

display signal voltages are applied to the respective sub-pixel electrodes and storage capacitor electrodes of SPa (p, q) and SPb (p, q) from a common signal line when the two switching elements are on;

voltages of the respective storage capacitor counter electrodes of SPa (p, q) and SPb (p, q) change after the two switching elements are turned off; and

the amounts of change defined by the direction and magnitude of the change differ between SPa (p, q) and SPb (p, q).

13. The liquid crystal display according to claim 12, wherein the changes in the voltages of the storage capacitor counter electrodes of SPa (p, q) and SPb (p, q) are equal in amount and opposite in direction.

14. The liquid crystal display according to claim 12, wherein the voltages of the storage capacitor counter electrodes of SPa (p, q) and SPb (p, q) are oscillating voltages 180 degrees out of phase with each other.

15. The liquid crystal display according to claim 14, wherein the oscillating voltages of the storage capacitor counter electrodes of SPa (p, q) and SPb (p, q) each have a period approximately equal to one horizontal scanning period.

16. The liquid crystal display according to claim 14, wherein the oscillating voltages of the storage capacitor counter electrodes of SPa (p, q) and SPb (p, q) each have a period shorter than one horizontal scanning period.

17. The liquid crystal display according to claim 14, wherein the oscillating voltages of the storage capacitor counter electrodes of SPa (p, q) and SPb (p, q) are approximately equal within any horizontal scanning period if averaged over the period.

18. The liquid crystal display according to claim 16, wherein the period of the oscillation is one-half of one horizontal scanning period.

19. The liquid crystal display according to claim 14, wherein the oscillating voltages are rectangular waves with a duty ratio of 1:

1.

20. The liquid crystal display according to claim 1, wherein SPa (p, q) and SPb (p, q) have different areas, of which the smaller area belongs to SPa (p, q) or SPb (p, q) whichever has a larger root-mean-square voltage applied to its liquid crystal layer.

21. The liquid crystal display according to claim 1, wherein the area of SPa (p, q) and area of SPb (p, q) are practically equal.