Liquid crystal display panel and liquid crystal display device with backlight chromaticity balance

• US 9,024,923 B2
• Filed: 12/14/2012
• Issued: 05/05/2015
• Est. Priority Date: 12/14/2011
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Corporation of America (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation), Panasonic Liquid Crystal Display Company Limited (Panasonic Holdings Corporation)
• Inventors: Kobayashi, Takahiro, Umeda, Yoshio, Tanaka, Katuji
• Primary Examiner(s): Balaoing, Ariel
• Assistant Examiner(s): Ritchie, Darlene M
• Application Number:
  US13/715,960
• Publication Number:
  US 20130155040A1
• Time in Patent Office: 872 Days
• Field of Search: 345/102, 345/690, 345/204, 315/169.3, 315/169.4, 315/250, 315/77, 315/287, 348/801
• US Class Current: 345/204
• CPC Class Codes: G02B 6/0073 Light emitting diode [LED]
• CPC Class Codes: G02B 6/0083 Details of electrical connections of light sources to drivers, circuit boards, or the like
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• CPC Class Codes: G09G 2320/045 Compensation of drifts in the characteristics of light emitting or modulating elements
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
• CPC Class Codes: G09G 5/00 Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators image data processing or generation, in general G06T
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details

Abstract

The liquid crystal display panel includes a liquid crystal display unit, and a backlight unit illuminating the liquid crystal display unit. The backlight unit includes first and second white light-emitting diodes that respectively emit white light, and first and second drive units that respectively supply a current to the first and second white light-emitting diodes. The first and second drive units are respectively configured to be able to adjust supply current to the first and second white light-emitting diodes. Chromaticities of the first and second white light-emitting diodes are of a relationship of being positioned opposite each other across a blackbody locus on an xy chromaticity diagram. The first and second white light-emitting diodes change over time so that, on the xy chromaticity diagram, an intersection point of the blackbody locus and a line that passes through the chromaticities of the first and second white light-emitting diodes becomes constant.

Claims

1. A liquid crystal display panel, comprising:

a liquid crystal display unit that includes a display screen that displays an image; and

a backlight unit that illuminates the liquid crystal display unit from a rear face of the liquid crystal display unit, wherein;

the backlight unit includes;

a first white light-emitting diode and a second white light-emitting diode that respectively emit white light;

a first drive unit that supplies a current to the first white light-emitting diode; and

a second drive unit that supplies a current to the second white light-emitting diode,

the first drive unit is configured to be able to adjust a supply current to the first white light-emitting diode,

the second drive unit is configured to be able to adjust a supply current to the second white light-emitting diode,

a chromaticity point of the first white light-emitting diode and a chromaticity point of the second white light-emitting diode are of a relationship of being positioned opposite each other across a blackbody locus on an xy chromaticity diagram,

the first white light-emitting diode emits first white light corresponding to a first chromaticity point at a first point of time, and second white light corresponding to a second chromaticity point at a second point of time later than the first point of time,

the second white light-emitting diode emits third white light corresponding to a third chromaticity point at the first point of time, and fourth white light corresponding to a fourth chromaticity point at the second point of time,

a first line that passes through the first chromaticity point and the third chromaticity point intersects, on the xy chromaticity diagram, the blackbody locus at an intersection point,

a second line that passes through the second chromaticity point and the fourth chromaticity point intersects, on the xy chromaticity diagram, the blackbody locus at the intersection point, and

at least one of the first chromaticity point and the third chromaticity point is closer to the intersection point than the second chromaticity point and the fourth chromaticity point, respectively,

the first white light emitting diode includes;

a first light-emitting diode chip; and

a first phosphor and

the second white light-emitting diode includes;

a second light-emitting diode chip; and

a second phosphor.

2. The liquid crystal display panel according to claim 1, wherein the first drive unit adjusts a supply current to the first white light-emitting diode and the second drive unit adjusts a supply current to the second white light-emitting diode so that a chromaticity of the light emitted from the backlight unit becomes constant.

3. The liquid crystal display panel according to claim 1, further comprising a light guide plate that is disposed on a rear face side of the display screen of the liquid crystal display unit and guides incident light to the display screen, wherein:

plural first white light-emitting diodes and plural second white light-emitting diodes are provided, and

the plural first white light-emitting diodes and the plural second white light-emitting diodes are alternately disposed along at least one end part of the light guide plate, and emit the white light toward the end part.

4. The liquid crystal display panel according to claim 1, further comprising a light guide plate that is disposed on a rear face side of the display screen of the liquid crystal display unit and guides incident light to the display screen, wherein:

plural first white light-emitting diodes and plural second white light-emitting diodes are provided, and

the plural first white light-emitting diodes and the plural second white light emitting diodes are alternately disposed at a side of the light guide plate opposite to the display screen facing the light guide plate, and emit the white light toward the light guide plate.

5. A liquid crystal display device, comprising:

the liquid crystal display panel according to claim 1; and

a control circuit that controls the liquid crystal display unit of the liquid crystal display panel based on an input image signal.

6. The liquid crystal display panel according to claim 1, wherein, on the xy chromaticity diagram, the second chromaticity point and the fourth chromaticity point are not positioned on the first line.

7. The liquid crystal display panel according to claim 1, wherein a plurality of white light-emitting diodes included in the backlight unit consist of a plurality of first white light-emitting diodes and a plurality of second white light-emitting diodes.

8. The liquid crystal display panel according to claim 1, wherein, on the xy chromaticity diagram, the second chromaticity point and the fourth chromaticity point are positioned on the first line.

9. The liquid crystal display panel according to claim 8, wherein:

a composition of a material forming the first light-emitting diode chip and a composition of a material forming the second light-emitting diode chip are the same, and

a composition of a material forming the first phosphor and a composition of a material of a second phosphor are the same.

10. The liquid crystal display panel according to claim 8, wherein, on the xy chromaticity diagram, the second chromaticity point is closer to the intersection point than the first chromaticity point and the third chromaticity point is closer to the intersection point than the fourth chromaticity point.

11. The liquid crystal display panel according to claim 8, wherein, on the xy chromaticity diagram, the first chromaticity point is closer to the intersection point than the second chromaticity point, and the third chromaticity point is closer to the intersection point than the fourth chromaticity point.

12. A liquid crystal display panel, comprising:

a liquid crystal display unit that includes a display screen that displays an image; and

a backlight unit that illuminates the liquid crystal display unit from a rear face of the liquid crystal display unit, wherein;

the backlight unit includes;

a first white light-emitting diode and a second white light-emitting diode that respectively emit white light;

a first drive unit that supplies a current to the first white light-emitting diode; and

a second drive unit that supplies a current to the second white light-emitting diode,

the first drive unit is configured to be able to adjust a supply current to the first white light-emitting diode,

the second drive unit is configured to be able to adjust a supply current to the second white light-emitting diode,

a chromaticity point of the first white light-emitting diode and a chromaticity point of the second white light-emitting diode are of a relationship of being positioned opposite each other across a blackbody locus on an xy chromaticity diagram,

the first white light-emitting diode emits first white light corresponding to a first chromaticity point at a first point of time, and second white light corresponding to a second chromaticity point at a second point of time later than the first point of time,

the second white light-emitting diode emits third white light corresponding to a third chromaticity point at the first point of time, and fourth white light corresponding to a fourth chromaticity point at the second point of time,

a first line that passes through the first chromaticity point and the third chromaticity point intersects, on the xy chromaticity diagram, the blackbody locus at an intersection point,

a second line that passes through the second chromaticity point and the fourth chromaticity point intersects, on the xy chromaticity diagram, the blackbody locus at the intersection point, and

at least one of the second chromaticity point and the fourth chromaticity point is closer to the intersection point than the first chromaticity point and the third chromaticity point, respectively,

the first white light emitting diode includes;

a first light-emitting diode chip; and

a first phosphor and

the second white light-emitting diode includes;

a second light-emitting diode chip; and

a second phosphor.

13. The liquid crystal display panel according to claim 12, wherein the first drive unit adjusts a supply current to the first white light-emitting diode and the second drive unit adjusts a supply current to the second white light-emitting diode so that a chromaticity of the light emitted from the backlight unit becomes constant.

14. The liquid crystal display panel according to claim 12, further comprising a light guide plate that is disposed on a rear face side of the display screen of the liquid crystal display unit and guides incident light to the display screen, wherein:

plural first white light-emitting diodes and plural second white light-emitting diodes are provided, and

the plural first white light-emitting diodes and the plural second white light-emitting diodes are alternately disposed along at least one end part of the light guide plate, and emit the white light toward the end part.

15. The liquid crystal display panel according to claim 12, further comprising a light guide plate that is disposed on a rear face side of the display screen of the liquid crystal display unit and guides incident light to the display screen, wherein:

plural first white light-emitting diodes and plural second white light-emitting diodes are provided, and

the plural first white light-emitting diodes and the plural second white light-emitting diodes are alternately disposed at a side of the light guide plate opposite to the display screen facing the light guide plate, and emit the white light toward the light guide plate.

16. A liquid crystal display device, comprising:

the liquid crystal display panel according to claim 12; and

a control circuit that controls the liquid crystal display unit of the liquid crystal display panel based on an input image signal.

17. The liquid crystal display panel according to claim 12, wherein a plurality of white light-emitting diodes included in the backlight unit consist of a plurality of first white light-emitting diodes and a plurality of second white light-emitting diodes.

18. The liquid crystal display panel according to claim 12, wherein on the xy chromaticity diagram, the second chromaticity point and the fourth chromaticity point are positioned on the first line.

19. The liquid crystal display panel according to claim 18, wherein:

a composition of a material forming the first light-emitting diode chip and a composition of a material forming the second light-emitting diode chip are the same, and

a composition of a material forming the first phosphor and a composition of a material of a second phosphor are the same.