Optical sheet, backlight unit and liquid crystal display device having the same

• US 8,704,973 B2
• Filed: 12/31/2007
• Issued: 04/22/2014
• Est. Priority Date: 02/22/2007
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Lee, Man Hoan, Park, Jae Hyun
• Primary Examiner(s): Glick, Edward
• Assistant Examiner(s): Kim, Dennis Y
• Application Number:
  US11/967,666
• Publication Number:
  US 20090073344A1
• Time in Patent Office: 2,304 Days
• Field of Search: 359/837, 362/339, 349/66, 349/62, 349/64
• US Class Current: 349/64
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02F 1/133606 including a specially adapted diffusing, scattering or light controlling members
• CPC Class Codes: G02F 1/133607 the light controlling member including light directing or refracting elements, e.g. prisms or lenses

Abstract

Provided are an optical sheet, a backlight unit and an LCD device having the same. The backlight unit includes a first layer, a second layer, and a refractive pattern. The first layer has a larger refractivity than an air layer, and the second layer has a larger refractivity than the first layer. The refractive pattern is disposed at a boundary surface between the first layer and the second layer and has ridges and furrows that change a traveling path of light. The optical sheet refracts light at least three times to condense the light in a direction perpendicular to a light-exiting surface.

Claims

1. An optical sheet disposed above a light guide plate, the optical sheet comprising:

a first layer having a larger refractivity than air;

a second layer having a larger refractivity than the first layer;

a refractive pattern disposed at a boundary surface between the first layer and the second layer, the refractive pattern having one or more ridges that change a traveling path of light;

a third layer having a lower refractivity than the first layer; and

a diffusion layer that diffuses light on the second layer,

wherein the third layer is disposed at the lower surface of the first layer and facing the light guide plate,

wherein the upper surface and the lower surface of the third layer is formed in a plate shape,

wherein the optical sheet is operable to refract light from the light guide at least three times in a direction of the upper area of the optical sheet to a light-exiting surface,

wherein the diffusion layer includes a plurality of beads,

wherein the optical sheet includes the first, second and third layers for condensing light and the diffusion layer for diffusing light,

wherein a boundary surface between the first layer and the third layer is not formed as a refractive pattern, and

wherein the lower surface of the third layer is not formed as a refractive pattern.

2. The optical sheet according to claim 1, wherein light entering the second layer is directed at a boundary surface between the first layer and the second layer in the direction of the upper area of the optical sheet perpendicular to the light-exiting surface.

3. The optical sheet according to claim 1, wherein both the first layer and the second layer include a medium with a refractivity of about 1.3 to about 2.0.

4. The optical sheet according to claim 1, wherein the one or more ridges of the refractivity pattern include a first inclined side and a second rounded side.

5. The optical sheet according to claim 1, wherein the one or more ridges of the refractivity pattern include a first side with two or more inclined surfaces and a second rounded side.

6. The optical sheet according to claim 1, wherein the one or more ridges of the refractivity pattern include a first side with two or more inclined surfaces and a second side with two or more inclined surfaces.

7. The optical sheet according to claim 1, wherein the first, second and third layers condense light by first refracting the light from the light guide at the lower surface of the third layer, by second refracting the first-refracted light at the interface between the upper surface of the third layer and the lower surface of the first layer, and by third refracting the second-refracted light at the refractive pattern at the boundary surface between the first layer and the second layer.

8. A backlight unit comprising:

a light source emitting light; and

an optical sheet disposed above a light guide plate, the optical sheet comprising;

a first layer having a larger refractivity than air;

a second layer having a larger refractivity than the first layer; and

a refractive pattern disposed at a boundary surface between the first layer and the second layer, the refractive pattern having one or more ridges that change a traveling path of light;

a third layer having a lower refractivity than the first layer; and

a diffusion layer that diffuses light on the second layer,

wherein the third layer is disposed at the lower surface of the first layer and facing the light guide plate,

wherein the upper surface and the lower surface of the third layer is formed in a plate shape,

wherein the optical sheet is operable to refract light from the light guide at least three times in a direction of the upper area of the optical sheet to a light-exiting surface,

wherein the diffusion layer includes a plurality of beads,

wherein the optical sheet includes the first, second and third layers for condensing light and the diffusion layer for diffusing light,

wherein a boundary surface between the first layer and the third layer is not formed as a refractive pattern, and

wherein the lower surface of the third layer is not formed as a refractive pattern.

9. The backlight unit according to claim 8, wherein the light entering the second layer is condensed at a boundary surface between the first layer and the second layer in the direction perpendicular to the light-exiting surface.

10. The backlight unit according to claim 8, wherein the one or more ridges of the refractivity pattern have a first inclined side and a second rounded side.

11. The backlight unit according to claim 8, wherein the one or more ridges of the refractivity pattern have a first side with two or more inclined surfaces and a second rounded side.

12. The backlight unit according to claim 8, wherein the one or more ridges of the refractivity pattern have a first side with two or more inclined surfaces and a second side with two or more inclined surfaces.

13. A liquid crystal display (LCD) device comprising:

a light source emitting light;

an optical sheet disposed above a light guide plate; and

a LCD panel displaying an image using light received from the optical sheet,

wherein the optical sheet comprises;

a first layer having a larger refractivity than air;

a second layer having a larger refractivity than the first layer; and

a refractive pattern disposed at a boundary surface between the first layer and the second layer, the refractive pattern having one or more ridges that change a traveling path of light;

a third layer having a lower refractivity than the first layer; and

a diffusion layer that diffuses light on the second layer,

wherein the third layer is disposed at the lower surface of the first layer and facing the light guide plate,

wherein the upper surface and the lower surface of the third layer is formed in a plate shape,

wherein the optical sheet is operable to refract light from the light guide at least three times in a direction of the upper area of the optical sheet to a light-exiting surface,

wherein the diffusion layer includes a plurality of beads,

wherein the optical sheet includes the first, second and third layers for condensing light and the diffusion layer for diffusing light,

wherein a boundary surface between the first layer and the third layer is not formed as a refractive pattern, and

wherein the lower surface of the third layer is not formed as a refractive pattern.

14. The LCD device according to claim 13, wherein the light entering the second layer is condensed at a boundary surface between the first layer and the second layer in the direction perpendicular to the light-exiting surface.

15. The LCD device according to claim 13, wherein the one or more include a first inclined side and a second rounded side.

16. The LCD device according to claim 13, wherein the one or more ridges include a first side with two or more inclined surfaces and a second rounded side.

17. The LCD device according to claim 13, wherein the one or more ridges include a first side with two or more inclined surfaces and a second side with two or more inclined surfaces.