White LED backlight device with color compensation and display device using the same

• US 8,531,382 B2
• Filed: 06/12/2007
• Issued: 09/10/2013
• Est. Priority Date: 11/29/2006
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Hamada, Tetsuya
• Primary Examiner(s): Yang, Kwang-Su
• Application Number:
  US12/514,708
• Publication Number:
  US 20100053064A1
• Time in Patent Office: 2,282 Days
• Field of Search: 345/102
• US Class Current: 345/102
• CPC Class Codes: F21K 9/00 Light sources using semiconductor devices as light-generating elements, e.g. using light-emitting diodes [LED] or lasers
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• 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 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources

Abstract

A backlight device (2) for emitting illumination light outward includes white light-emitting diodes (4w) for emitting white light, and red and blue light-emitting diodes (4r, 4b) for emitting red light and blue light, respectively. The backlight device (2) further includes a lighting drive circuit (lighting control portion) (11) for controlling the lighting/driving of each of the light-emitting diodes (4w, 4r, 4b).

Claims

1. A backlight device for emitting illumination light outward, comprising:

white light-emitting diodes for emitting white light, the white light-emitting diodes having chromaticity within a first chromaticity region of a color space;

two types of light-emitting diodes selected from three types of red, green, and blue light-emitting diodes for emitting red light, green light, and blue light, respectively; and

a lighting control portion for controlling lighting/driving of each of the white light-emitting diodes and the two types of light-emitting diodes to produce the illumination light of the backlight device of chromaticity in a second chromaticity region of the color space, the second chromaticity region defined as a line connecting a first chromaticity point and a second chromaticity point, wherein

the first chromaticity region of the color space is outside of the second chromaticity region and is bounded by

a partial arc of an ellipse,

a line passing through the first chromaticity point and a chromaticity point of the first type of the two types of light-emitting diodes, and

a line passing through the second chromaticity point and a chromaticity point of the second type of the two types of light-emitting diodes.

2. The backlight device according to claim 1, wherein the lighting control portion adjusts the chromaticity of the illumination light to a value within a predetermined range of a degree of whiteness by controlling an amount of light of said each of the white light-emitting diodes and the two types of light-emitting diodes.

3. The backlight device according to claim 2, wherein the light-emitting diodes that emit the white light that is within a tolerance of the degree of whiteness are selected as the white light-emitting diodes, and the tolerance of the degree of whiteness is determined using chromaticity of light from said each of the two types of light-emitting diodes and the predetermined range of the degree of whiteness.

4. The backlight device according to one of claims 2 and 3, wherein the two types of light-emitting diodes are the red light-emitting diodes and the blue light-emitting diodes.

5. The backlight device according to claim 1, wherein the light-emitting diodes having a dominant wavelength of 580 nm to 640 nm are used as the red light-emitting diodes.

6. The backlight device according to claim 1, further comprising a light guide plate with an incident surface through which light from the white light-emitting diodes and the two types of light-emitting diodes is introduced,

wherein the white light-emitting diodes and the two types of light-emitting diodes are alternately arranged to face the incident surface.

7. The backlight device according to claim 1, further comprising a light guide plate with an incident surface through which light from the white light-emitting diodes and the two types of light-emitting diodes is introduced,

wherein two opposing surfaces of four surfaces of the light guide plate serve as incident surfaces through which light from the white light-emitting diodes and one of the two types of light-emitting diodes is introduced, and the remaining two opposing surfaces serve as incident surfaces through which light from the white light-emitting diodes and the other of the two types of light-emitting diodes is introduced.

8. The backlight device according to claim 1, wherein light-emitting portions of the white light-emitting diodes and the two types of light-emitting diodes are located on a straight line with respect to an object to be irradiated.

9. The backlight device according to claim 1, wherein the lighting control portion comprises a driving circuit portion that lights and drives the white light-emitting diodes and the two types of light-emitting diodes by PWM dimming.

10. The backlight device according to claim 6, further comprising:

a color sensor for detecting the illumination light, wherein

the light guide plate includes a first surface facing toward a liquid crystal panel, and a second surface facing opposite of the first surface,

the color sensor has a position adjacent to the second surface, and

the lighting control portion controls the amount of light of said each of the white light-emitting diodes and the two types of light-emitting diodes using detection results of the color sensor.

11. A display device comprising a display portion,

wherein the display portion is irradiated with the illumination light from the backlight device according to claim 1.

12. The backlight device according to claim 6, wherein

a pattern of the white light-emitting diode, the first type of light-emitting diode, the white light-emitting diode, and the second type of light-emitting diode is repeated along the incident surface of the light guide plate.