Color liquid crystal display device and gamma correction method for the same

• US 8,305,316 B2
• Filed: 05/31/2006
• Issued: 11/06/2012
• Est. Priority Date: 10/31/2005
• 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: Shimoshikiryoh, Fumikazu, Irie, Kentaro
• Primary Examiner(s): Wang, Quan-Zhen
• Assistant Examiner(s): LEE, DAVID J
• Application Number:
  US12/083,011
• Publication Number:
  US 20090153454A1
• Time in Patent Office: 2,351 Days
• Field of Search: 345/89
• US Class Current: 345/88
• CPC Class Codes: G02F 1/134345 Subdivided pixels, e.g. for grey scale or redundancy
• CPC Class Codes: G02F 1/134354 the sub-pixels being capacitively coupled
• CPC Class Codes: G09G 2300/0439 Pixel structures
• 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 2300/0452 Details of colour pixel setup, e.g. pixel composed of a red, a blue and two green components
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• 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 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/0673 for control of gamma adjustment, e.g. selecting another gamma curve
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

A color liquid crystal display device, configured to employ a pixel division method with two or more sub-pixels obtained by spatial or temporal division of one pixel in a division ratio, may include pixel formation portions configured to form a pixel with the sub-pixels; a drive circuit configured to provide each pixel formation portion with applied voltages based on a gradation value; a gamma correction part configured to correct a relationship between the gradation and luminance values of the pixel to be formed by that pixel formation portion; and a common electrode. The gamma correction part may suppress gradation dependence of chromaticity when the screen is viewed from a front and from an oblique direction. The gradation value may be determined by an area ratio of a first sub-pixel electrode to a second sub-pixel electrode and a difference in applied voltages between first and second auxiliary electrodes.

Claims

1. A color liquid crystal display device configured to employ a pixel division method in which each pixel of an image displayed in a screen is configured with two or more sub-pixels obtained by spatial or temporal division of one pixel in a division ratio, the device comprising:

a plurality of pixel formation portions corresponding to respective pixels of the image, each of the pixel formation portions configured to form a pixel of any of primary colors for color display with the two or more sub-pixels;

a drive circuit configured to provide each of the pixel formation portions with applied voltages corresponding to the two or more sub-pixels composing the pixel to be formed by that pixel formation portion, based on a gradation value indicated by an input signal provided from outside as a video signal representing the image;

a gamma correction part configured to correct a relationship between the gradation value indicated by the input signal and a luminance value of the pixel to be formed by that pixel formation portion according to the gradation value independently for each of the primary colors for color display; and

a common electrode provided commonly at the plurality of pixel formation portions;

each of the pixel formation portions including,

first and second sub-pixel electrodes facing the common electrode,

a liquid crystal layer between the first sub-pixel electrode and the common electrode, as well as between the second sub-pixel electrode and the common electrode,

a first auxiliary electrode disposed so as to form a first auxiliary capacitance between the first sub-pixel electrode and the first auxiliary electrode, and

a second auxiliary electrode disposed so as to form a second auxiliary capacitance between the second sub-pixel electrode and the second auxiliary electrode,

the drive circuit including,

a pixel electrode drive circuit configured to provide a voltage according to the input signal to the first and second sub-pixel electrodes with the common electrode as a reference, and

an auxiliary electrode drive circuit configured to apply voltages, which are different from each other and change in period and amplitude, to the first and second auxiliary electrodes,

wherein each of the pixel formation portions forms the respective pixel by displaying the two or more sub-pixels with luminance values different from one another based on the applied voltages,

wherein the gamma correction part is further configured to correct the relationship such that gradation dependence of chromaticity is suppressed when the screen is viewed from a front thereof, and also corrects the relationship in a vicinity of the gradation value, which is determined by the division ratio in the one pixel and differences in the applied voltages among the two or more sub-pixels, such that the gradation dependence of chromaticity is suppressed when the screen is viewed from an oblique direction, and

wherein the gradation value is determined by an area ratio of the first sub-pixel electrode to the second sub-pixel electrode and a difference in the applied voltages between the first auxiliary electrode and the second auxiliary electrode.

2. The color liquid crystal display device according to claim 1, wherein the gamma correction part is further configured to correct the chromaticity when viewed from the front to be shifted from a state maintaining a color balance toward blue in the vicinity of the gradation value such that the gradation dependence of chromaticity is suppressed when viewed from the oblique direction.

3. The color liquid crystal display device according claim 1, wherein the gamma correction part is further configured to correct the relationship such that a curve representing the gradation dependence of chromaticity when viewed from the front becomes approximately flat in a range except for the vicinity of the gradation value.

4. The color liquid crystal display device according claim 1, wherein the gamma correction part is further configured to correct the relationship such that a curve representing the gradation dependence of chromaticity when viewed from the front changes approximately monotonically with respect to the gradation value.

5. The color liquid crystal display device according claim 1, wherein the gamma correction part includes a correction table associating a gradation value before correction with a gradation value after correction for each of the primary colors for color display in order to correct the relationship, and outputs the gradation value after correction associated with the gradation value indicated by the input signal referring to the correction table, and

wherein the drive circuit is further configured to provide each of the pixel formation portions with the applied voltages based on the gradation value after correction.