BACK LIGHT UNIT

• US 20090213571A1
• Filed: 12/17/2008
• Published: 08/27/2009
• Est. Priority Date: 02/22/2008
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Jin, Min Ji, Park, Hee Jeong
• Granted Patent: US 7,950,815 B2
• Time in Patent Office: Days
• US Class Current: 362/97.100
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/133607 the light controlling member including light directing or refracting elements, e.g. prisms or lenses
• CPC Class Codes: G02F 1/133608 including particular frames or supporting means
• CPC Class Codes: G02F 1/133611 including means for improving the brightness uniformity
• CPC Class Codes: G02F 2201/46 Fixing elements

Abstract

A back light unit includes a bottom cover, a plurality of light source modules mounted on the bottom cover, and an optical sheet unit over the light source modules, wherein each of the light source module includes a PCB having the plurality of light source modules mounted thereon, a diffusing plate spaced a distance from the LED light sources and surrounding the PCB fully for diffusing a light incident thereon from the LED light sources throughout a surface thereof uniformly, and a diffusing plate supporter for securing the diffusing plate to the PCB, and the diffusing plate includes a flat plate portion, a side wall portion extended from opposite edges of the plate portion to the diffusing plate supporter, and a plurality of light diffusing units each projected from a surface facing the LED light source on the plate portion at a position matched to the LED light source, thereby enabling to make effective response to fabrication of thinner liquid crystal display device and improve a light uniformity, and improve light utilization efficiency to improve a luminance, and enhance mechanical reliability.

Claims

1. A back light unit comprising:

a bottom cover;

a plurality of light source modules mounted on the bottom cover; and

an optical sheet unit provided above the light source modules;

wherein each of the light source module includes;

a PCB (Printed Circuit Board) having a plurality of LED (Light Emitting Diode) light sources mounted thereon,

a diffusing plate spaced a distance from the LED light sources and surrounding the PCB, wherein the diffusing plate diffuses a light incident thereon from the LED light sources throughout a surface thereof uniformly, and

a diffusing plate supporter that secures the diffusing plate to the PCB,

wherein the diffusing plate includes;

a flat plate portion,

a side wall portion extended from opposite edges of the plate portion to the diffusing plate supporter, and

a plurality of light diffusing units each projected from a surface facing the LED light source on the plate portion at a position matched to the LED light source.

2. The back light unit as claimed in claim 1, wherein the light source module further includes a reflective plate mounted to the side wall portion of the diffusing plate.

3. The back light unit as claimed in claim 2, wherein the reflective plate has a height shorter than a height of the side wall portion of the diffusing plate.

4. The back light unit as claimed in claim 3, wherein the reflective plate has a height which is ⅔

of a height of the side wall portion of the diffusing plate.

5. The back light unit as claimed in claim 2, wherein the reflective plate is formed in a recess of the side wall portion of the diffusing plate.

6. The back light unit as claimed in claim 1, wherein the light diffusing unit is formed of a material different from a material of the plate portion.

7. The back light unit as claimed in claim 1, wherein the light diffusing unit is formed as one unit with the plate portion.

8. The back light unit as claimed in claim 6, wherein the light diffusing unit is formed of a material having a refractive index lower than a refractive index of the plate portion.

9. The back light unit as claimed in claim 1, wherein the light diffusing unit has one of shapes selected from the group consisting of a circular cone, a pyramid, a circular truncated cone, a truncated pyramid and an elliptical truncated cone.

10. The back light unit as claimed in claim 1, wherein the plate portion includes an optical pattern formed on a surface opposite to a surface having the light diffusing unit formed thereon at position matched to the light diffusing unit.

11. The back light unit as claimed in claim 1, wherein the light diffusing unit includes an optical pattern formed at a portion of the light diffusing unit opposite to the LED light source.

12. The back light unit as claimed in claim 11, wherein the light pattern has a wedge shape.

13. The back light unit as claimed in claim 2, wherein the diffusing plate supporter includes;

a recess for placing the side wall portion of the diffusing plate therein, and

a reflective layer formed on an inside surface of the diffusing plate supporter adjacent to the LED light source.

14. The back light unit as claimed in claim 1, wherein the light source module includes a reflective layer formed on a surface of the PCB opposite to the diffusing plate.