Backlight unit and liquid-crystal display device using the same

• US 20070201226A1
• Filed: 02/14/2007
• Published: 08/30/2007
• Est. Priority Date: 02/16/2006
• Status: Active Grant

• Current Assignee: Vista Peak Ventures LLC (Dominion Harbor Enterprises, LLC)
• Original Assignee: NEC LCD Technologies Limited (NEC Corporation)
• Inventors: Nishigaki, Eitaro
• Granted Patent: US 7,597,469 B2
• Time in Patent Office: Days
• US Class Current: 362/231
• CPC Class Codes: G02B 6/0026 Wavelength selective element, sheet or layer, e.g. filter or grating
• CPC Class Codes: G02B 6/0028 Light guide, e.g. taper
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources

Abstract

An edge-light type backlight unit reduces the color unevenness on the display screen caused by the arrangement of point-shaped light sources (e.g., LEDs) in a point-shaped light source unit comprising a set of point-shaped light sources aligned. The backlight unit includes at least one point-shaped light source unit having point-shaped light sources arranged in a single direction in a predetermined order, the light sources emitting monochromatic light of different colors. The unit further comprises a first optical filter for limiting or controlling transmission of the monochromatic light emitted from one of the light sources disposed at one end of the light source unit, and a second optical filter for limiting or controlling transmission of the monochromatic light emitted from another of the light sources disposed at the other end thereof. The first and second filters are selectively formed on a first or second light guide plate or a diffusing plate.

Claims

1. A backlight unit comprising:

at least one point-shaped light source unit having point-shaped light sources arranged in a single direction in a predetermined order, the light sources emitting monochromatic light of different colors;

a first light guide plate, which has a light incident surface and a light exiting surface, for receiving monochrome light emitted from the respective light sources of the light source unit at the light incident surface and guiding the said light to the light exiting surface;

a reflector for reflecting the light exiting from the light exiting surface of the first light guide plate;

a second light guide plate, which has a light incident surface and a light exiting surface, for receiving the light reflected by the reflector at the light incident surface of the second light guide plate and guiding the said light to the light exiting surface of the second light guide plate;

a diffusing plate for receiving the light exiting from the light exiting surface of the second light guide plate, diffusing the said light, and emitting the said light diffused;

a first optical filter for limiting or controlling transmission of the monochromatic light emitted from one of the light sources disposed at one end of the light source unit; and

a second optical filter for limiting or controlling transmission of the monochromatic light emitted from another of the light sources disposed at the other end of the light source unit;

wherein the first optical filter and the second optical filter are selectively formed on one of the first light guide plate, the second light guide plate, and the diffusing plate.

2. The backlight unit according to claim 1, wherein the first optical filter and the second optical filter are located on the light exiting surface of the first light guide plate.

3. The backlight unit according to claim 2, wherein the first optical filter and the second optical filter are respectively located at or near two ends of the light exiting surface of the first light guide plate, respectively.

4. The backlight unit according to claim 1, wherein the first optical filter and the second optical filter are located on the light incident surface of the second light guide plate.

5. The backlight unit according to claim 4, wherein the first optical filter and the second optical filter are respectively located at or near two ends of the light incident surface of the second light guide plate.

6. The backlight unit according to claim 1, wherein the first optical filter and the second optical filter are located on the light exiting surface of the second light guide plate.

7. The backlight unit according to claim 6, wherein the first optical filter and the second optical filter are respectively located at or near two ends of the light exiting surface of the second light guide plate.

8. The backlight unit according to claim 7, wherein the first optical filter and the second optical filter extend along the ends of the light exiting surface of the second light guide plate, respectively.

9. The backlight unit according to claim 1, wherein the first optical filter and the second optical filter are located on one surface of the diffusing plate.

10. The backlight unit according to claim 9, wherein the first optical filter and the second optical filter are respectively located at or near two ends of the surface of the diffusing plate.

11. The backlight unit according to claim 10, wherein the first optical filter and the second optical filter extend along the ends of the surface of the diffusing plate, respectively.

12. The backlight unit according to claim 1, wherein the count of the light source unit is unity.

13. A liquid-crystal display device comprising:

the backlight unit according to claim 1;

and

a liquid-crystal display panel to which the light emitted from the backlight unit is to be irradiated.