Backlight unit and liquid-crystal display device using the same

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.

What is claimed is: 
     
       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 respective light sources of the light source unit at the light incident surface and guiding 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 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 said light, and emitting 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, and 
 wherein a base of said point-shaped light source unit is parallel to said light incident surface of the first light guide plate. 
 
     
     
       2. 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 respective light sources of the light source unit at the light incident surface and guiding 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 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 said light, and emitting 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, and 
 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. 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 respective light sources of the light source unit at the light incident surface and guiding 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 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 said light, and emitting 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, and 
 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 light source unit comprises a single Light Emitting Diode (LCD) unit. 
     
     
       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. 
 
     
     
       14. The backlight unit according to  claim 1 , wherein the backlight unit comprises an edge-light type unit. 
     
     
       15. The backlight unit according to  claim 1 , wherein the first optical filter and the second optical filter are selectively formed on one of the first light guide plate or said light incident surface of the second light guide plate. 
     
     
       16. The backlight unit according to  claim 1 , wherein said point-shaped light sources comprise a different light color at each side of the point-shaped light source unit. 
     
     
       17. The backlight unit according to  claim 13 , wherein the first optical filter and the second optical filter are located on the light exiting surface of the first light guide plate. 
     
     
       18. The backlight unit according to  claim 13 , wherein the first optical filter and the second optical filter are selectively formed on one of the first light guide plate or said light incident surface of the second light guide plate. 
     
     
       19. 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 respective light sources of the light source unit at the light incident surface and guiding 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 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 said light, and emitting 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 or said light incident surface of the second light guide plate. 
 
     
     
       20. The backlight unit according to  claim 19 , wherein the backlight unit comprises an edge-light type unit, and
 wherein a base of said point-shaped light source unit is parallel to said light incident surface of the first light guide plate. 
 
     
     
       21. A backlight unit comprising:
 a first light guide plate;   a second light guide plate;   a diffusing plate;   a first optical filter for controlling transmission of monochromatic light emitted from one of a set of point-shaped light sources disposed at one end of a point-shaped light source unit; and   a second optical filter for controlling transmission of monochromatic light emitted from another of the set of point-shaped light sources disposed at another end of the point-shaped 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, or the diffusing plate,   wherein a base of the point-shaped light source unit is substantially parallel to a light incident surface of the first light guide plate.   
     
     
       22. The backlight unit of claim 21, wherein the first optical filter and the second optical filter are respectively located on a light exiting surface of the second light guide plate. 
     
     
       23. The backlight unit of claim 22, 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. 
     
     
       24. The backlight unit of claim 23, wherein the first optical filter and the second optical filter respectively extend along the two ends of the light exiting surface of the second light guide plate. 
     
     
       25. The backlight unit of claim 21, wherein the first optical filter and the second optical filter are located on a surface of the diffusing plate. 
     
     
       26. The backlight unit of claim 25, 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. 
     
     
       27. The backlight unit of claim 26, wherein the first optical filter and the second optical filter extend respectively along the two ends of the surface of the diffusing plate. 
     
     
       28. The backlight unit of claim 21, wherein the point-shaped light source unit comprises a light emitting diode unit. 
     
     
       29. The backlight unit of claim 21, further comprising a liquid-crystal display panel configured to receive irradiated light from the set of point-shaped light sources. 
     
     
       30. The backlight unit of claim 21, wherein the backlight unit comprises an edge-type unit wherein the point-shaped light source unit is arranged along an edge of the first light guide plate. 
     
     
       31. The backlight unit of claim 21, wherein the first optical filter and the second optical filter are selectively formed on one of the first light guide plate or a light incident surface of the second light guide plate. 
     
     
       32. The backlight unit of claim 21, wherein the first optical filter and the second optical filter are located on a light exiting surface of the first light guide plate. 
     
     
       33. The backlight unit of claim 32, 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. 
     
     
       34. The backlight unit of claim 21, wherein the set of point-shaped light sources comprises a different light color at respective sides of the point-shaped light source unit. 
     
     
       35. A backlight unit comprising:
 a first light guide plate;   a first optical filter configured to limit or control transmission of monochromatic light emitted from one of a set of light sources disposed at one end of a light source unit; and   a second optical filter configured to limit or control transmission of monochromatic light emitted from another of the set of light sources disposed at another end of the light source unit,   wherein the first optical filter and the second optical filter are located on a light exiting surface of the first light guide plate.   
     
     
       36. The backlight unit of claim 35, 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. 
     
     
       37. The backlight unit of claim 35, wherein the light source unit comprises a light emitting diode unit. 
     
     
       38. The backlight unit of claim 35, further comprising a liquid-crystal display panel configured to receive light emitted from the set of point-shaped light sources. 
     
     
       39. The backlight unit of claim 35, wherein the backlight unit comprises an edge-type unit wherein the light source unit is arranged alone, an edge of the first light guide plate. 
     
     
       40. The backlight unit of claim 35, wherein the set of light sources comprising a set of point-shaped light sources. 
     
     
       41. A backlight unit comprising:
 a first light guide plate;   a second light guide plate;   a first optical filter configured to control transmission of monochromatic light emitted from one of a set of light sources disposed at one end of a light source unit; and   a second optical filter configured to control transmission of monochromatic light emitted from another of the set of light sources disposed at another end of the light source unit,   wherein the first optical filter and the second optical filter are located on a light incident surface of the second light guide plate.   
     
     
       42. The backlight unit of claim 41, 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. 
     
     
       43. The backlight unit of claim 41, wherein the light source unit comprises a light emitting diode unit. 
     
     
       44. The backlight unit of claim 41, further comprising a liquid-crystal display panel to which light emitted from the set of point-shaped light sources is to be irradiated. 
     
     
       45. The backlight unit of claim 41, wherein the backlight unit comprises an edge-type unit wherein the light source unit is arranged along an edge of the first light guide plate. 
     
     
       46. The backlight unit of claim 41, wherein the set of light sources comprises a set of point-shaped light sources. 
     
     
       47. A backlight unit comprising:
 a first light guide plate;   a second light guide plate;   a first optical filter configured to limit transmission of monochromatic light emitted from one of a set of light sources disposed at one end of a light source unit; and   a second optical filter configured to limit transmission of monochromatic light emitted from another of the set of light sources disposed at another 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 or a light incident surface of the second light guide plate.   
     
     
       48. The backlight unit of claim 47, wherein the backlight unit comprises an edge-type unit, and
 wherein a base of the light source unit is substantially parallel to a light incident surface of the first light guide plate.   
     
     
       49. The backlight unit of claim 47, wherein the light source unit comprises a single light emitting diode unit. 
     
     
       50. The backlight unit of claim 47, further comprising a liquid-crystal display panel to which light emitted from the set of light sources is to be irradiated. 
     
     
       51. The backlight unit of claim 47, wherein the backlight unit comprises an edge-type unit wherein the light source unit is arranged along an edge of the first light guide plate. 
     
     
       52. The backlight unit of claim 47, wherein the first optical filter and the second optical filter are located on a light exiting surface of the first light guide plate. 
     
     
       53. The backlight unit of claim 52, 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. 
     
     
       54. The backlight unit of claim 47, wherein the set of light sources comprises a different light color at respective sides of the light source unit. 
     
     
       55. A method comprising:
 receiving, at a light incident surface of a first light guide plate, first light emitted from a first light source disposed on a first end of a light source unit having a base that is substantially parallel to the light incident surface of the first light guide plate;   receiving, at the light incident surface of the first light guide plate, second light emitted from a second light source disposed on a second end of the light source unit;   guiding, by a second light guide plate, the first light and the second light to a diffusing plate;   controlling transmission of the first light by a first optical filter formed on one of the first light guide plate, the second light guide plate, or the diffusing plate; and   controlling transmission of the second light by a second optical filter formed on one of the first light guide plate, the second light guide plate, or the diffusing plate.   
     
     
       56. The method of claim 55, wherein:
 the controlling transmission of the first light includes controlling transmission of the first light by the first optical filter located on a light exiting surface of the second light guide plate; and   the controlling transmission of the second light includes controlling transmission of the second light by the second optical filter located on the light exiting surface of the second light guide plate.   
     
     
       57. The method of claim 55, wherein:
 the controlling transmission of the first light includes controlling transmission of the first light by the first optical filter located on a first end of a surface of the diffusing plate; and   the controlling transmission of the second light includes controlling transmission of the second light by the second optical filter located on a second end of the surface of the diffusing plate.   
     
     
       58. The method of claim 55, wherein the receiving the first light and the receiving the second light includes receiving the first light and the second light from a light emitting diode unit. 
     
     
       59. The method of claim 55, wherein:
 the controlling transmission of the first light includes controlling transmission of the first light by the first optical filter located on a first end of a light exiting surface of the first light guide plate; and   the controlling transmission of the second light includes controlling transmission of the second light by the second optical filter located on a second end of the light exiting surface of the first light guide plate.   
     
     
       60. The method of claim 55, wherein:
 the controlling transmission of the first light includes controlling transmission of the first light by the first optical filter located on a light incident surface of the second light guide plate; and   the controlling transmission of the second light includes controlling transmission of the second light by the second optical filter located on the light incident surface of the second light guide plate.   
     
     
       61. The method of claim 55, further comprising guiding the first light and the second light to a light exiting surface of the first light guide plate. 
     
     
       62. The method of claim 61, further comprising reflecting the first light and the second light from the light exiting surface of the first light guide plate to a light incident surface of the second light guide plate. 
     
     
       63. The method of claim 59, wherein the receiving first light and the receiving the second light includes receiving the first light and the second light emitted from a first point-shaped light source and a second point-shaped light source, respectively. 
     
     
       64. A system comprising:
 means for receiving first light and second light from a first end and a second end, respectively, of a light source unit having a base that is substantially parallel to a light incident surface of the means for receiving the first light and the second light;   means for guiding the first light and the second light to a diffusing plate;   means for limiting or controlling transmission of the first light; and   means for limiting or controlling transmission of the second light,   wherein the means for limiting or controlling transmission of the first light and the means for limiting or controlling transmission of the second light are formed on one of the means for receiving the first light and the second light, the means for guiding, or the diffusing plate.