Light source and liquid crystal display device using this light source

• US 6,824,285 B2
• Filed: 10/23/2002
• Issued: 11/30/2004
• Est. Priority Date: 11/29/2001
• Status: Active Grant

• Current Assignee: Vista Peak Ventures LLC (Dominion Harbor Enterprises, LLC)
• Original Assignee: NEC Corporation
• Inventors: Saitoh, Goroh, Sumiyoshi, Ken, Mimura, Koji, Yagi, Yoshie
• Primary Examiner(s): CARIASO, ALAN B
• Application Number:
  US10/277,930
• Publication Number:
  US 20030099118A1
• Time in Patent Office: 769 Days
• Field of Search: 362/31, 362/326, 362/327, 362/330, 362/331, 362/551, 362/559-561, 359/837, 349/65, 385/36, 385/88, 385/89, 385/131, 385/133, 385/146, 385/147
• US Class Current: 362/629
• CPC Class Codes: G02B 6/0016 Grooves, prisms, gratings, scattering particles or rough surfaces
• CPC Class Codes: G02B 6/0028 Light guide, e.g. taper
• CPC Class Codes: G02B 6/003 Lens or lenticular sheet or layer
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide

Abstract

A small light source unit of simple structure that emits light forward with high efficiency is well-suited as a backlight in a liquid crystal display device. The light director in this unit has reflective internal faces adjacent opposite peripheral regions of the entrance face and two refractive index interfaces in it. The reflective internal faces and the refractive index interfaces are oriented on inclined planes. The refractive index of a middle region between the two interfaces is the smallest among those of the three regions making up the light director.

Claims

1. The light source unit comprising:

a primary light source; and

a light director, comprising plural adjacent regions,

wherein said light director takes in light from said primary light source through an entrance face and outputs the light as emergent light from an exit face,

wherein said light director has

i) reflective internal surfaces adjacent opposite peripheral regions of the entrance face,

ii) a first refractive index interface and a second refractive index interface disposed along a light path from the entrance face to said exit face, each of said first and second refractive index interfaces delineating the adjacent regions within said light director having different refractive indices, and

iii) a refractive index of a region between said first refractive index interface and said second refractive index interface and said second refractive interface has a smallest value among those of said light director,

wherein at least one of said first and said second refractive index interfaces describes inclined planes that refract said light from said primary light source causing refracted light to pass through said first and second refractive index interfaces in a direction of the emergent light from said exit face.

5. The light source unit of claim 1, wherein said primary light source is an LED (light emitting diode).

6. The light source unit of claim 1, wherein the primary light source contacts said entrance face.

7. The light source unit of claim 1, wherein all internal surfaces of said light director other than said exit face are reflective.

8. The light source unit of claim 1, further comprising:

a linear light guide which is provided in the direction of emergent light from the exit face of said light director.

9. The light source unit of claim 8, wherein a reflection face is provided on a face opposite to an exit face of said linear light guide.

10. The light source unit of claim 8, wherein a face opposite to an exit face of said linear light guide is inclined.

11. The light source unit of claim 8, wherein said light director contacts an entrance face of said linear light guide.

12. The light source unit of claim 8, wherein said light director and said linear light guide are formed into one body.

13. The light source unit of claim 8, further comprising a planar light guide which is provided in the direction of emergent light from an exit face of said linear light guide.

14. The light source unit of claim 13, wherein projections or grooves are provided on a face opposite to an exit face of said planar light guide.

15. The light source unit of claim 14, wherein the refractive index of said projections or grooves is larger than that of said planar light guide.

16. The light source unit of claim 13, wherein the exit face of said linear light guide and an entrance face of said planar light guide contact each other.

17. The light source unit of claim 13, wherein said linear light guide and said planar light guide are formed into one body.

18. A liquid crystal display device comprising:

the light source unit of claim 1; and

a liquid crystal display panel operatively positioned in relation to the light source unit.

19. The liquid crystal display device of claim 18, further comprising:

a planar light guide serving as a substrate of said liquid crystal display panel, and

a transparent layer having a smaller refractive index than said planar light guide provided at a liquid crystal layer side of said planar light guide.

20. The light source unit of claim 1,

wherein at least one of said first and said second refractive index interfaces is a folded line.

21. The light source unit of claim 1, wherein

said first refractive index interface and said second refractive index interface are each in a v-shape, and

said v-shape of said first refractive index interface and said second refractive index interface are different shapes.

22. The light source unit of claim 1, wherein the inclined planes of the at least one index interface are v-shaped.

2. A light source unit comprising:

a primary light source; and

a light director,

wherein said light director takes in light from said primary light source through an entrance face and outputs the light from an exit face,

wherein said light director has

i) reflective internal surfaces adjacent opposite peripheral regions of the entrance face, and

ii) a first refractive index interface and a second refractive index interface disposed along a light path from the entrance face to said exit face, each of said first and second refractive index interfaces delineating adjacent regions within said light director having different refractive indices,

wherein at least one of said first and second refractive index interfaces describes inclined planes, and said inclined planes satisfying the following equation;

3. A light source unit comprising:

a primary light source; and

a light director,

wherein said light director takes in light from said primary light source through an entrance face and outputs the light from an exit face,

wherein said light director has

i) reflective internal surfaces adjacent opposite peripheral regions of the entrance face, and

ii) a first refractive index interface and a second refractive index interface disposed along a light path from the entrance face to said exit face, each of said first and second refractive index interfaces delineating adjacent regions within said light director having different refractive indices,

wherein at least one of said first and second refractive index interfaces describes inclined planes, and said inclined planes satisfying the following equation;

4. A light source unit comprising:

a primary light source; and

a light director,

wherein said light director takes in light from said primary light source through an entrance face and outputs the light from an exit face,

wherein said light director has

i) reflective internal surfaces adjacent opposite peripheral regions of the entrance face, and

ii) a first refractive index interface and a second refractive index interface disposed along a light path from the entrance face to said exit face, each of said first and second refractive index interfaces delineating adjacent regions within said light director having different refractive indices,

wherein at least one of said first and second refractive index interfaces describes inclined planes, and said inclined planes satisfying the following equation;