Color Liquid Crystal Display Device and Gamma Correction Method for the Same

• US 20090153454A1
• Filed: 05/31/2006
• Published: 06/18/2009
• 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
• Granted Patent: US 8,305,316 B2
• Time in Patent Office: Days
• US Class Current: 345/89
• 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

In one embodiment of the present application, a color liquid crystal display device is disclosed which can realize display having a high color reproducibility when a screen is viewed from an oblique direction as well as from a front direction, while improving a viewing angle dependence of γ-characteristics by employing a pixel division method. Gamma correction is carried out as follows independently for each R, G, and B with reference to R, G, and B correction tables so as to obtain a good color tracking. That is, the gamma correction is carried out such that chromaticity in the front view is shifted toward blue in an oblique hue correction range, which is determined by a pixel division ratio and the like, so as to reduce a shift of the chromaticity in the oblique view toward yellow in the oblique hue correction range, while maintaining a color balance in the other range (a gradation value range of 32 to 255 except for the oblique hue correction range). The present invention is suitable for a color liquid crystal display device employing the pixel division method.

Claims

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

a plurality of pixel formation portions provided correspondingly to respective pixels of the image, each of the portions forming a pixel of any of primary colors for color display with the predetermined number of sub-pixels;

a drive circuit for providing each of the pixel formation portion with applied voltages respectively corresponding to the 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; and

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

wherein each of the pixel formation portions forms the pixel by displaying the predetermined number of sub-pixels with luminance values different from one another based on the applied voltages, and

wherein the gamma correction part corrects 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 the vicinity of a predetermined gradation value, which is determined by the division ratio in the one pixel and differences in the applied voltage among the predetermined number of sub-pixels, such that the gradation dependence of the chromaticity is suppressed when the screen is viewed from a predetermined oblique direction.

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

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

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

5. The color liquid crystal display device according to 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 provides each of the pixel formation portions with the applied voltages based on the gradation value after correction.

6. The color liquid crystal display device according to claim 1, further comprising

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

each of the pixel formation portions including:

a first and a second sub-pixel electrodes disposed facing the common electrode so as to sandwich a liquid crystal layer inbetween;

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

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

the drive circuit including;

a pixel electrode drive circuit for providing 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 for applying voltages which are different from each other and changes in a predetermined period and a predetermined amplitude, to the first and second auxiliary electrodes,

wherein the predetermined 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 voltage between the first auxiliary electrode and the second auxiliary electrode.

7. A gamma correction method for correcting a relationship between a gradation value indicated by an input signal provided from outside as a video signal representing an image and a luminance value of a pixel formed according to the gradation value, in a color liquid crystal display device employing a pixel division method in which each pixel of the image displayed on a predetermined screen is composed of a predetermined number of two or more sub-pixels obtained by spatial or temporal division of one pixel in a predetermined division ratio, the method comprising

a correction step of correcting the relationship independently for each of primary colors for color display,

wherein in the correction step, the relationship is corrected such that gradation dependence of chromaticity is suppressed when the screen is viewed from a front thereof, and the relationship in the vicinity of a predetermined gradation value is also corrected such that the gradation dependence of the chromaticity is suppressed when the screen is viewed from a predetermined oblique direction, the predetermined gradation value being determined by the division ratio in the one pixel and differences in a voltage applied to liquid crystal among the predetermined number of sub-pixels.

8. The gamma correction method according to claim 7, wherein in the correction step, the chromaticity when viewed from the front is corrected to shift from a state maintaining a color balance toward blue in the vicinity of the predetermined gradation value such that the gradation dependence of the chromaticity is suppressed when viewed from the oblique direction.

9. The gamma correction method according to claim 7, wherein in the correction step, the relationship is corrected such that a curve representing the gradation dependence of the chromaticity when viewed from the front becomes approximately flat in a range except for the vicinity of the predetermined gradation value.

10. The gamma correction method according to claim 7, wherein in the correction step, the relationship is corrected such that a curve representing the gradation dependence of the chromaticity when viewed from the front changes approximately monotonically with respect to the gradation value.