Backlight for display device

• US 20060028842A1
• Filed: 08/05/2005
• Published: 02/09/2006
• Est. Priority Date: 08/05/2004
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Yoon, Ju-Young, Kim, Gi-Cherl, Lee, Sang-Yu, Song, Chun-Ho, Kang, Seock-Hwan
• Granted Patent: US 7,585,083 B2
• Time in Patent Office: Days
• US Class Current: 362/612
• CPC Class Codes: G02B 6/0018 Redirecting means on the surface of the light guide
• CPC Class Codes: G02B 6/003 Lens or lenticular sheet or layer
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0073 Light emitting diode [LED]

Abstract

A backlight for a display device includes a board, a plurality of light emitting diodes (LEDs) mounted on the board, and a light guiding plate that is provided on the LEDs and has light reflecting grooves formed directly on respective LEDs. The light reflecting grooves are formed at an upper surface of the light guiding plate, having a shape of a reversed cone. In this backlight, the light traveling directly upward from the LED is efficiently reflected by total internal reflection and then recycled, resulting in a uniform light distribution of the backlight.

Claims

1. A backlight for a display device comprising:

a board comprising a plurality of light emitting diodes provided thereon; and

a light guiding plate provided on the light emitting diodes and comprising a plurality of light reflecting grooves,

wherein the light reflecting grooves are provided at an upper surface of the light guiding plate, each of the light reflecting grooves having a reverse cone-like shape such that the backlight satisfies the following equation

$d\ge <br><br>\frac{6<br><br>l<br><br>\text{\hspace{1em}<br><br>}<br><br>\tan <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\theta <br><br>}}{2<br><br>\text{\hspace{1em}<br><br>}<br><br>\tan <br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\theta <br><br>}}_T-5<br><br>\text{\hspace{1em}<br><br>}<br><br>\tan <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\theta <br><br>}}$

where l is a distance between a light emitting chip of the light emitting devise and a bottom surface of the light guiding plate, θ

is the largest angle formed between the main axis of the light reflecting groove and the directly upward proceeding light to be intercepted, θ

_T is an angle formed between a cross-section of the light reflecting groove and the main axis thereof, and d is a thickness of the light guiding plate.

2. The device of claim 1, wherein the backlight satisfies the following equation:

${\mathrm{\theta <br><br>}}_T\le <br><br>90<br><br>\mathrm{°<br><br>}-{\sin }^{-1}<br><br>\frac{n_1}{n_2}$

where n₁ is a refraction index of air and n₂ is a refraction index of the light guiding plate.

3. The device of claim 1, further comprising:

a reflective plate including a plurality of holes for exposing the light emitting chips and reflects toward the light guiding plate.

4. The device of claim 1, further comprising:

a plurality of optical sheets provided on the light guiding plate.

5. The device of claim 1, wherein the LED produces white light.

6. The device of claim 1, wherein the plurality of light emitting diodes comprise a white LED producing white light and a red LED producing red light.

7. The device of claim 1, wherein of the plurality of light emitting diodes comprise a red light emitting diode producing red light, a green light emitting diode producing green light, and a blue light emitting diode producing blue light.

8. The device of claim 1, wherein each of the light emitting diodes comprise a body portion and a dispersion lens.

9. The device of claim 8, wherein the dispersion lens comprises:

a first portion having a rounded shape that includes a cone-like shaped groove extending upwardly to a point from a bottom surface of the first portion; and

a second portion having a shape that is similar to a partial portion of a reversed cone with the angular point portion removed, and includes a reversed cone-like shaped groove extending downward to a point from a top surface of the second portion,

wherein the main axis of the first portion and the second portion is the same.

10. A backlight for a display device comprising:

a board;

a plurality of light emitting diodes provided on the board; and

a light guiding plate provided on the light emitting diodes and comprising a plurality of light reflecting grooves,

wherein the light reflecting grooves are formed at an upper surface of the light guiding plate and have a reversed cone-like shape that extends downward to a point such that an angle formed between a main axis of the light reflecting groove and a line that is tangent to a point of the cross-section thereof increases as the point recedes from the main axis.

11. The device of claim 10, further comprising:

a reflective plate including a plurality of holes for exposing a plurality of light emitting chips of the light emitting diodes and reflects light toward the light guiding plate.

12. The device of claim 10, further comprising:

a plurality of optical sheets provided on the light guiding plate.

13. The device of claim 10, wherein the plurality of light emitting diodes comprise a white light emitting diode that produces a white light.

14. The device of claim 10, wherein the plurality of light emitting diodes comprise a white LED producing white light and a red LED producing red light.

15. The device of claim 10, wherein of the plurality of light emitting diodes comprise a red light emitting diode producing red light, a green light emitting diode producing green light, and a blue light emitting diode producing blue light.

16. The device of claim 10, wherein each of the plurality of light emitting diodes comprise a body portion and a dispersion lens.

17. The device of claim 16, wherein the dispersion lens comprises:

a first portion having a rounded shape and includes a cone-like shaped groove extending upward to a point from a bottom surface of the first portion; and

a second portion having a shape that is substantially similar to a partial portion of a reversed cone with the angular point portion removed, and is provided with a reversed cone-like shaped groove extending downward to a point from a top surface of the second portion,

wherein the main axis of the first portion and the second portion is the same.