Surface-emitting device and liquid crystal display device with enhanced utilization efficiency of light from light source

• US 20030165054A1
• Filed: 10/22/2002
• Published: 09/04/2003
• Est. Priority Date: 10/23/2001
• Status: Active Grant

• Current Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.)
• Original Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.)
• Inventors: Ohizumi, Mitsuo, Sugiura, Takuro
• Granted Patent: US 6,802,619 B2
• Time in Patent Office: Days
• US Class Current: 362/31
• CPC Class Codes: G02B 6/0018 Redirecting means on the surface of the light guide
• CPC Class Codes: G02B 6/0028 Light guide, e.g. taper
• CPC Class Codes: G02B 6/0031 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/0055 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources

Abstract

A front light includes a light guide panel, a light guide bar placed along an end face of the light guide panel, and light-emitting elements placed at both ends of the light guide bar. A cover member including a reflecting-surface covering portion for covering an end on the reflecting-surface side of the light guide panel, a light-guide covering portion for covering the light guide bar, and an emergent-surface covering portion for covering an end on the emergent-surface side of the light guide panel is mounted so as to cover at least the light guide bar and the ends of the light guide panel. The reflecting-surface covering portion protrudes longer in the light guide direction than the emergent-surface covering portion.

Claims

1. A surface-emitting device comprising:

a light guide panel having a reflecting surface containing irregularities that reflect light propagating therein and an emergent surface that emits light reflected by the reflecting surface;

a light guide placed along an end face of the light guide panel;

light sources placed at opposing ends of the light guide; and

a cover member including a reflecting-surface covering portion that covers an end of the light guide panel on the side of the reflecting surface, a light-guide covering portion said that covers the light guide, and an emergent-surface covering portion that covers an end of the light guide panel on the side of the emergent surface, and

wherein an end of the reflecting-surface covering portion is disposed more distal to the light guide than an end of the emergent-surface covering portion.

2. A surface-emitting device according to claim 1, wherein the end of the reflecting-surface covering portion is at least 0.5 mm more distal from the light guide than the end of the emergent-surface covering portion.

3. A surface-emitting device according to claim 2, wherein the end of the reflecting-surface covering portion is at least 0.8 mm more distal from than the end of the emergent-surface covering portion.

4. A surface-emitting device according to claim 1, wherein a reflective layer made of a metal thin film is formed on an inner surface of the cover member.

6. A surface-emitting device according to claim 1, wherein an antireflection layer is formed on one of the end face of the light guide panel and a side face of the light guide facing the end face.

7. A surface-emitting device according to claim 1, wherein a side face of the light guide facing the end face of the light guide panel is an emergent surface through which light from the light sources is supplied to the light guide panel, and a side face on an opposite side of the emergent surface is a reflecting surface on which concave grooves, each having a pair of inclined faces that reflect light propagating inside the light guide, are periodically formed at a predetermined pitch, and

wherein depths of the concave grooves closer to a center of the light guide are larger than depths of the concave grooves closer to the light sources, and an angle formed between the two inclined faces constituting each of the grooves is within a range of 105°

to 115°

.

8. A surface-emitting device according to claim 7, wherein the angle formed between the two inclined faces constituting each of the concave grooves is within a range of 108°

to 112°

.

9. A surface-emitting device according to claim 7, wherein the concave grooves are formed at a pitch within a range of 0.1 μ

m to 0.3 μ

m.

10. A surface-emitting device according to claim 1, wherein a distance between the emergent surface and the reflecting surface of the light guide is within a range of 3.2 mm to 5.0 mm.

11. A surface-emitting device according to claim 1, wherein centers of light-emitting portions of the light sources are aligned with almost a center in a thickness direction of the light guide.

12. A liquid crystal display device wherein a surface-emitting device according to claim 1 is provided in front of a liquid crystal display unit.

5. A surface-emitting device comprising:

a light guide panel;

a light guide placed along an end face of the light guide panel, the light guide containing a reflecting surface having irregularities that reflect light propagating therein and an opposing emergent surface that emits light reflected by the reflecting surface;

a reflective film that reflects light propagating inside the light guide and the light guide panel formed on the light guide and an end of the light guide panel; and

light sources placed at opposing ends of the light guide,

wherein a length of the reflective film from the end face of the light guide panel at which the light guide is placed is larger on a side of the reflecting surface of the light guide panel than on a side of the emergent surface of the light guide panel.

13. A surface-emitting device according to claim 5, wherein the light guide panel has a reflecting surface containing irregularities that reflect light propagating therein and an emergent surface that emits light reflected by the reflecting surface.

14. A surface-emitting device according to claim 5, further comprising an antireflection layer formed on one of the end face of the light guide panel and a side face of the light guide facing the end face of the light guide panel.

15. A surface-emitting device according to claim 13, wherein the irregularities on the reflecting surface of the light guide panel are concave grooves periodically formed at a predetermined pitch, each concave groove having a pair of inclined faces that reflect light propagating inside the light guide, depths of the concave grooves closer to a center of the light guide are larger than depths of the concave grooves closer to the light sources, and an angle formed between the two inclined faces constituting each of the grooves is within a range of 105°

to 115°

.

16. A surface-emitting device according to claim 15, wherein the concave grooves are formed at a pitch within a range of 0.1 μ

m to 0.3 μ

m.

17. A surface-emitting device according to claim 15, wherein a distance between the emergent surface and the reflecting surface of the light guide is within a range of 3.2 mm to 5.0 mm.

18. A surface-emitting device according to claim 5, wherein centers of light-emitting portions of the light sources are aligned with almost a center in a thickness direction of the light guide.

19. A liquid crystal display device wherein a surface-emitting device according to claim 5 is provided in front of a liquid crystal display unit.

20. A method of increasing luminescence of a surface-emitting device, the method comprising:

placing a light guide along an end face of a light guide panel having a reflecting side including a reflecting surface containing irregularities that reflect light propagating therein and an emergent surface that emits light reflected by the reflecting surface;

placing light sources at opposing ends of the light guide; and

introducing a light reflector to the light guide panel, the light reflector reflecting light from the light sources and impinging on the reflecting side toward the emergent surface, the light reflector covering a first section of the reflecting side adjacent to the reflecting surface and a second section of the emergent surface opposing a portion of the first section, the first section larger than the second section.

21. The method of claim 20 further comprising introducing the light reflector such that the light reflector extends continuously along the reflecting side.

22. The method of claim 20, further comprising introducing the light reflector such that the light reflector covers at least a portion of the light guide.

23. The method of claim 22, further comprising introducing the light reflector such that the light reflector covers the light sources.

24. The method of claim 20, further comprising forming irregularities on a reflecting surface of the light guide, the irregularities reflecting light propagating therein towards the light guide panel.

25. The method of claim 20, further comprising coating one of an end face of the light guide panel and a side face of the light guide facing the end face of the light guide panel with an antireflection layer.

26. The method of claim 20, further comprising limiting an angle formed between inclined faces constituting periodic concave grooves that form the irregularities to be within a range of 105°

to 115° and

limiting depths of the grooves closer to a center of the light guide to be larger than depths of the concave grooves closer to the light sources.

27. The method of claim 20, further comprising limiting a pitch of the concave grooves to be within a range of 0.1 μ

m to 0.3 μ

m.

28. The method of claim 20, further comprising limiting a distance between the emergent surface and the reflecting surface of the light guide to be within a range of 3.2 mm to 5.0 mm.

29. The method of claim 20, further comprising aligning centers of light-emitting portions of the light sources with almost a center in a thickness direction of the light guide.

30. The method of claim 20, further comprising providing the surface-emitting device of claim 20 in front of a liquid crystal display unit.

31. A surface-emitting device comprising:

a light guide panel having a reflecting surface containing irregularities that reflect light propagating therein and an emergent surface that emits light reflected by the reflecting surface; and

a light guide placed along an end face of the light guide panel having a reflecting surface containing irregularities that reflect light propagating therein and an emergent surface that emits light reflected by the reflecting surface towards the light guide panel.

32. The surface-emitting device of claim 31, further comprising light sources placed at opposing ends of the light guide.

33. The surface-emitting device of claim 31, further comprising an antireflection layer on one of the emergent surface of the light guide and the end face of the light guide panel opposing the emergent surface of the light guide.

34. The surface-emitting device of claim 31, further comprising a light reflector that permits substantially no light to be emitted from a first section of the light guide panel adjacent to irregularities of the light guide panel.

35. The surface-emitting device of claim 33, wherein the light reflector has an upper surface that is disposed on the first section and a lower surface that is disposed on a second section of the light guide panel opposing the first section, the light that is not emitted from the first section is reflected by the second section.

36. The surface-emitting device of claim 35, wherein the first section extends further from the light guide than the second section.