Signal conversion circuit and multi-primary color liquid crystal display device comprising same

• US 9,165,494 B2
• Filed: 12/22/2011
• Issued: 10/20/2015
• Est. Priority Date: 12/28/2010
• 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: Yoshida, Yuichi, Mori, Tomohiko, Tomizawa, Kazunari, Nakamura, Kohzoh, Ueki, Shun
• Primary Examiner(s): Eisen, Alexander
• Assistant Examiner(s): LAM, NELSON C
• Application Number:
  US13/976,150
• Publication Number:
  US 20130271356A1
• Time in Patent Office: 1,398 Days
• Field of Search: 345 87-104
• US Class Current: 1/1
• 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 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 2340/06 Colour space transformation
• CPC Class Codes: G09G 3/2003 Display of colours specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers
• CPC Class Codes: H04N 9/67 for matrixing camera processing pipelines for matrixing of colour signals H04N23/85

Abstract

A signal conversion circuit (20) is used for a multiple-primary color liquid crystal display device (100) which performs color display using four primary colors of red displayed by a red-sub pixel (R), green displayed by green-sub pixel (G), blue displayed by blue-sub pixel (B), and yellow displayed by yellow-sub pixel (Ye), and converts an input three-primary color video signal into a multiple-primary color video signal corresponding to four primary colors. The signal conversion circuit (20) performs signal conversion such that a gray scale level of the yellow-sub pixel (Ye) is higher than a gray scale level of the green-sub pixel (G) in at least some cases from among cases in which a red gray-scale level r, a green gray-scale level g, and a blue gray-scale level b which are displayed by the three-primary color video signal satisfy a relationship of r>g>b.

Claims

1. A signal conversion circuit which is used for a multiple-primary color liquid crystal display device that includes pixels each configured with a red-sub pixel, a green-sub pixel, a blue-sub pixel, and yellow-sub pixel, and that performs color display using four primary colors of red displayed by the red-sub pixel, green displayed by the green-sub pixel, blue displayed by the blue-sub pixel, and yellow displayed by the yellow-sub pixel, and which is configured to convert an input three-primary color video signal into a multiple-primary color video signal corresponding to the four primary colors, wherein

the signal conversion circuit performs signal conversion such that a gray scale level of the yellow-sub pixel is higher than a gray scale level of the green-sub pixel in at least some cases from among cases in which a red gray-scale level r, a green gray-scale level g, and a blue gray-scale level b which are displayed by the three-primary color video signal satisfy a relationship of r>

g>

b,

each of the red-sub pixel, the green-sub pixel, the blue-sub pixel, and the yellow-sub pixel can perform display 256 gray-scale levels from a gray scale level of 0 to a gray scale level of 255,

each of the red gray-scale level r, the green gray-scale level g, and the blue gray-scale level b, which are displayed by the three-primary color video signal, is equal to or greater than 0 and equal to or less than 255,

at least some cases include a case in which the red gray-scale level r is 255 and the green gray-scale level g is equal to or greater than 1 and equal to or less than 128, and

in a case in which the red gray-scale level r is 255 and the green gray-scale level g is equal to or greater than 1 and equal to or less than 128, The signal conversion is performed such that the gray scale level of the green-sub pixel becomes equal to or less than 80.

2. The signal conversion circuit according to claim 1,

wherein, in the case in which the red gray-scale level r is 255 and the green gray-scale level g is equal to or greater than 1 and equal to or less than 128, the signal conversion is performed such that the gray scale level of the green-sub pixel becomes 0.

3. The signal conversion circuit according to claim 1,

wherein, in at least some cases, the signal conversion circuit performs the signal conversion such that a color, obtained when the pixel is viewed from a front direction when display is performed based on the multiple-primary color video signal, is substantially equal to a color obtained when the pixel is viewed from a 60°

oblique direction.

4. A multiple-primary color liquid crystal display device comprising:

a signal conversion circuit according to claim 1; and

a liquid crystal display panel to which a multiple-primary color video signal generated by the signal conversion circuit is sent.

5. The multiple-primary color liquid crystal display device according to claim 4,

wherein the liquid crystal display panel includes a vertical alignment type liquid crystal layer, and includes the red-sub pixel, the green-sub pixel, the blue-sub pixel, and the yellow-sub pixel, and

wherein, in each of the red-sub pixel, the green-sub pixel, the blue-sub pixel, and the yellow-sub pixel, when a predetermined voltage is applied to the liquid crystal layer, liquid crystal molecules which are included in the liquid crystal layer incline to a plurality of orientations.

6. A signal conversion circuit which is used for a multiple-primary color liquid crystal display device that includes pixels each configured with a red-sub pixel, a green-sub pixel, a blue-sub pixel, and yellow-sub pixel, and that performs color display using four primary colors of red displayed by the red-sub pixel, green displayed by the green-sub pixel, blue displayed by the blue-sub pixel, and yellow displayed by the yellow-sub pixel, and which is configured to convert an input three-primary color video signal into a multiple-primary color video signal corresponding to the four primary colors, wherein

the signal conversion circuit performs signal conversion such that a gray scale level of the yellow-sub pixel is higher than a gray scale level of the green-sub pixel in at least some cases from among cases in which a red gray-scale level r, a green gray-scale level g, and a blue gray-scale level b which are displayed by the three-primary color video signal satisfy a relationship of r>

g>

b,

each of the red-sub pixel, the green-sub pixel, the blue-sub pixel, and the yellow-sub pixel can perform display 256 gray scale levels from the gray scale level of 0 to the gray scale level of 255,

each of the red gray-scale level r, the green gray-scale level g, and the blue gray-scale level b, which are displayed by the three-primary color video signal, is equal to or greater than 0 and equal to or less than 255,

at least some cases include a case in which the red gray-scale level r is 80 and the green gray-scale level g is equal to or greater than 1 and equal to or less than 40, and

in a case in which the red gray-scale level r is 80 and the green gray-scale level g is equal to or greater than 1 and equal to or less than 40, the signal conversion is performed such that the gray scale level of the green-sub pixel becomes equal to or less than 25.

7. The signal conversion circuit according to claim 6,

wherein, in the case in which the red gray-scale level r is 80 and the green gray-scale level g is equal to or greater than 1 and equal to or less than 40, the signal conversion is performed such that the gray scale level of the green-sub pixel becomes 0.

8. The signal conversion circuit according to claim 6,

wherein, in at least some cases, the signal conversion circuit performs the signal conversion such that a color, obtained when the pixel is viewed from a front direction when display is performed based on the multiple-primary color video signal, is substantially equal to a color obtained when the pixel is viewed from a 60°

oblique direction.

9. A multiple-primary color liquid crystal display device comprising:

a signal conversion circuit according to claim 6; and

a liquid crystal display panel to which a multiple-primary color video signal generated by the signal conversion circuit is sent.

10. The multiple-primary color liquid crystal display device according to claim 9, wherein

the liquid crystal display panel includes a vertical alignment type liquid crystal layer, and includes the red-sub pixel, the green-sub pixel, the blue-sub pixel, and the yellow-sub pixel, and

in each of the red-sub pixel, the green-sub pixel, the blue-sub pixel, and the yellow-sub pixel, when a predetermined voltage is applied to the liquid crystal layer, liquid crystal molecules which are included in the liquid crystal layer incline to a plurality of orientations.

11. A signal conversion circuit which is used for a multiple-primary color liquid crystal display device that includes pixels each configured with a red-sub pixel, a green-sub pixel, a blue-sub pixel, and yellow-sub pixel, and that performs color display using four primary colors of red displayed by the red-sub pixel, green displayed by the green-sub pixel, blue displayed by the blue-sub pixel, and yellow displayed by the yellow-sub pixel, and which is configured to convert an input three-primary color video signal into a multiple-primary color video signal corresponding to the four primary colors, wherein

the signal conversion circuit performs signal conversion such that a gray scale level of the yellow-sub pixel is higher than a gray scale level of the green-sub pixel in at least some cases from among cases in which a red gray-scale level r, a green gray-scale level g, and a blue gray-scale level b which are displayed by the three-primary color video signal satisfy a relationship of r>

g>

b,

the signal conversion circuit comprising;

a multiple-primary color conversion unit that generates the multiple-primary color video signal based on the input three-primary color video signal; and

a correction unit that corrects a red gray-scale level r₁, green gray-scale level g₁, signal obtained by the multiple-primary color conversion unit,

the multiple-primary color conversion unit includes a color component extraction unit which extracts a red component, a green component, a blue component, a yellow component, a magenta component, a cyan component, and a white component from the input three-primary color video signal, and

at least some cases in which the signal conversion is performed such that the gray scale level of the yellow-sub pixel is higher than the gray scale level of the green-sub pixel include a case in which the gray scale level y₀ of the yellow component extracted by the color component extraction unit is equal to or greater than 1 and equal to or less than 200.

12. The signal conversion circuit according to claim 11, further comprising:

a look-up table that includes a correction value corresponding to a gray scale level y₀ of the yellow component which is extracted by the color component extraction unit,

wherein the correction unit corrects the red gray-scale level r₁, the green gray-scale level g₁, and the yellow gray-scale level y₁ with reference to the look-up table.

13. The signal conversion circuit according to claim 11,

wherein, in at least some cases, the signal conversion circuit performs the signal conversion such that a color, obtained when the pixel is viewed from a front direction when display is performed based on the multiple-primary color video signal, is substantially equal to a color obtained when the pixel is viewed from a 60°

oblique direction.

14. A multiple-primary color liquid crystal display device comprising:

a signal conversion circuit according to claim 11; and

a liquid crystal display panel to which a multiple-primary color video signal generated by the signal conversion circuit is sent.

15. The multiple-primary color liquid crystal display device according to claim 14, wherein

the liquid crystal display panel includes a vertical alignment type liquid crystal layer, and includes the red-sub pixel, the green-sub pixel, the blue-sub pixel, and the yellow-sub pixel, and

in each of the red-sub pixel, the green-sub pixel, the blue-sub pixel, and the yellow-sub pixel, when a predetermined voltage is applied to the liquid crystal layer, liquid crystal molecules which are included in the liquid crystal layer incline to a plurality of orientations.