Lighting unit and display provided with the same

• US 8,465,168 B2
• Filed: 02/23/2011
• Issued: 06/18/2013
• Est. Priority Date: 07/09/2010
• Status: Expired due to Fees

• Current Assignee: Hitachi Consumer Electronics Company Limited (Hitachi, Ltd.)
• Original Assignee: Hitachi Consumer Electronics Company Limited (Hitachi, Ltd.)
• Inventors: Adachi, Masaya, Tsumura, Makoto
• Primary Examiner(s): Mai, Anh
• Assistant Examiner(s): Breval, Elmito
• Application Number:
  US13/033,090
• Publication Number:
  US 20120008308A1
• Time in Patent Office: 846 Days
• Field of Search: 362/27, 362/29, 362/223, 362/218, 362/628, 362/624, 362/625, 362/601, 362606-607, 362612-613, 362/615, 349/62, 349/65
• US Class Current: 362/97.2
• CPC Class Codes: G02B 6/0021 for housing at least a part of the light source, e.g. by forming holes or recesses
• 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 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, 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

This lighting unit can control luminance in a plurality of block areas independently, and minimize luminance unevenness caused by discretely arrayed light sources, with a reduced number of parts. The lighting unit comprises: a light guide plate having a first and a second grooves formed therein; a first light source group accommodated in the first groove; and a second light source group accommodated in the second groove; the light guide plate having a first light mixing area, a first light emitting area and a second light mixing area; in the first light mixing area, the thickness of the light guide plate progressively increasing away from the first light source group; in the second light mixing area, the thickness of the light guide plate progressively increasing away from the second light source group; and in the first light emitting area, the light guide plate being flat-plate-like.

Claims

1. A lighting unit comprising:

a light guide plate having a first groove and a second groove formed therein;

a first light source group accommodated in the first groove; and

a second light source group accommodated in the second groove;

wherein the light guide plate has a first light mixing area, a first light emitting area and a second light mixing area in that order from the first groove toward the second groove;

wherein, in the first light mixing area, the thickness of the light guide plate progressively increases away from the first light source group;

wherein, in the second light mixing area, the thickness of the light guide plate progressively increases away from the second light source group;

wherein, in the first light emitting area, the light guide plate is flat-plate-like; and

wherein the first light mixing area satisfies a relation L01<

L02 where L01 is a quantity of light per block area of a front surface of the light guide plate, the light leaving the front side after being emitted from the first light source group and L02 is a quantity of light per block area of the front surface of the light guide plate, the light leaving the front side after being emitted from the second light source group.

2. A lighting unit according to claim 1, wherein a light reflector is provided at ends of the light guide plate;

wherein the light guide plate has a second light emitting area and a third light mixing area in that order from the ends of the light guide plate toward the first groove;

wherein, in the third light mixing area, the thickness of the light guide plate progressively increases away from the first light source group; and

wherein, in the second light emitting area, the light guide plate is flat-plate-like.

3. A lighting unit according to claim 1, wherein, in the first light mixing area, the light guide plate propagates light from the first light source group and causes light from the second light source group to leave the light guide plate from a front side thereof;

wherein, in the second light mixing area, the light guide plate propagates the light from the second light source group and causes the light from the first light source group to leave the light guide plate from the front side thereof; and

wherein, in the first light emitting area, the light guide plate causes the light from the first light source group and from the second light source group to leave the light guide plate from the front side thereof.

4. A lighting unit according to claim 1, wherein, in the first light mixing area and the second light mixing area, the cross section of the light guide plate is tapered;

wherein the cross section of the light guide plate in the first light mixing area and the cross section of the light guide plate in the second light mixing area are symmetrical with respect to a center line equidistant from the first groove and the second groove; and

wherein the cross sections of the light guide plate in the first light mixing area and in the second light mixing area are continuously connected to the cross section of the light guide plate in the first light emitting area.

5. A lighting unit according to claim 1, wherein, in the first light emitting area, a part of the light traveling from the first groove toward the second groove and a part of the light traveling from the second groove toward the first groove propagate and other parts of the light leaves the light guide plate from a front side thereof.

6. A lighting unit according to claim 1, wherein the first groove includes a first plane, a second plane, a third plane and a fourth plane;

wherein the first plane and the fourth plane of the first groove are normal to a flat-plate-like plane of the light guide plate; and

wherein the second plane and the third plane of the first groove are inclined to the flat-plate-like plane of the light guide plate.

7. A lighting unit according to claim 1, wherein the first groove is defined by a first plane, a second plane, a third plane and a fourth plane;

wherein a distance between the first plane and the fourth plane of the first groove progressively increases toward a front surface of the light guide plate; and

wherein a distance between the second plane and the third plane of the first groove progressively decreases toward the front surface of the light guide plate.

8. A lighting unit according to claim 1, wherein the first groove accommodates a third light source group and a heat sink;

and

wherein the first light source group is arranged on one side of the heat sink and the third light source group is arranged on the other side of the heat sink.

9. A lighting unit according to claim 1, wherein the light guide plate has a light path changing member on a front side thereof;

and

wherein the light path changing member changes directions of the light leaving the light guide plate from the front surface thereof.

10. A lighting unit according to claim 9, wherein the light path changing member is a transparent sheet;

wherein the light path changing member has a plurality of prism faces on a surface thereof; and

wherein ridges of the prism faces are parallel to a direction in which a plurality of light sources making up the first light source group are arrayed.

11. A lighting unit according to claim 1, wherein, in the first light mixing area and the second light mixing area of the light guide plate, a surface roughness Ra of a back surface of the light guide plate is greater than 0 nm and equal to or smaller than 38 nm.

12. A lighting unit according to claim 1, wherein a length Lm of the light guide plate in the first light mixing area satisfies an equation (1):

Lm≧

p/2 tan ζ

2≧

p/2 tan(sin−

1(n1/n2·

sin ζ

1)) 

 

(1)

where p is a pitch at which a plurality of light sources making up the first light source group are arrayed, ζ

1 is a half-value angle of an incident light emitted from the plurality of light sources into the light guide plate, and ζ

2 is an angle at which the incident light on the light guide plate travels through the light guide plate, n1 is a refractive index of a medium between the light guide plate and the plurality of light sources, and n2 is a refractive index of the light guide plate.

13. A lighting unit comprising:

a light guide plate having a first groove and a second groove formed therein;

a first light source group accommodated in the first groove; and

a second light source group accommodated in the second groove;

wherein the light guide plate has a first light mixing area, a first light emitting area and a second light mixing area in that order from the first groove toward the second groove;

wherein, in the first light mixing area, the thickness of the light guide plate progressively increases away from the first light source group;

wherein, in the second light mixing area, the thickness of the light guide plate progressively increases away from the second light source group;

wherein, in the first light emitting area, the light guide plate is flat-plate-like;

wherein the first groove accommodates a third light source group and a heat sink;

wherein the first light source group is arranged on one side of the heat sink and the third light source group is arranged on the other side of the heat sink; and

wherein a plurality of light sources making up the first light source group and a plurality of light sources making up the third light source group are staggered.

14. A lighting unit comprising:

a light guide plate having a first groove and a second groove formed therein;

a first light source group accommodated in the first groove; and

a second light source group accommodated in the second groove;

wherein the light guide plate has a first light mixing area, a first light emitting area and a second light mixing area in that order from the first groove toward the second groove;

wherein, in the first light mixing area, the thickness of the light guide plate progressively increases away from the first light source group;

wherein, in the second light mixing area, the thickness of the light guide plate progressively increases away from the second light source group;

wherein, in the first light emitting area, the light guide plate is flat-plate-like; and

wherein the quantity of light emitted from the first light source group is greatest in a direction parallel to a flat-plate-like plane of the light guide plate.

15. A lighting unit comprising:

a light guide plate having a first groove and a second groove formed therein;

a first light source group accommodated in the first groove; and

a second light source group accommodated in the second groove;

wherein the light guide plate has a first light mixing area, a first light emitting area and a second light mixing area in that order from the first groove toward the second groove;

wherein, in the first light mixing area, the thickness of the light guide plate progressively increases away from the first light source group;

wherein, in the second light mixing area, the thickness of the light guide plate progressively increases away from the second light source group;

wherein, in the first light emitting area, the light guide plate is flat-plate-like; and

wherein the quantity of light emitted from the first light source group is greatest in a direction inclined from a direction parallel to a flat-plate-like plane of the light guide plate toward a back side of the light guide plate.

16. A lighting unit comprising:

a light guide plate having a first groove and a second groove formed therein;

a first light source group accommodated in the first groove; and

a second light source group accommodated in the second groove;

wherein the light guide plate has a first light mixing area, a first light emitting area and a second light mixing area in that order from the first groove toward the second groove;

wherein, in the first light mixing area, the thickness of the light guide plate progressively increases away from the first light source group;

wherein, in the second light mixing area, the thickness of the light guide plate progressively increases away from the second light source group;

wherein, in the first light emitting area, the light guide plate is flat-plate-like;

wherein, after being emitted from the first light source group, the light leaving the first light emitting area of the light guide plate from a front side thereof is greater in quantity than the light leaving the first light mixing area of the light guide plate from the front side thereof; and

wherein, after being emitted from the second light source group, the light leaving the first light emitting area of the light guide plate from the front side thereof is greater in quantity than the light leaving the second light mixing area of the light guide plate from the front side thereof.

17. A lighting unit comprising:

a light guide plate having a first groove and a second groove formed therein;

a first light source group accommodated in the first groove;

a second light source group accommodated in the second groove;

a third light source group accommodated in the first groove; and

a heat sink accommodated in the first groove;

wherein the light guide plate has a first light mixing area, a first light emitting area and a second light mixing area in that order from the first groove toward the second groove;

wherein, in the first light mixing area, the thickness of the light guide plate progressively increases away from the first light source group;

wherein, in the second light mixing area, the thickness of the light guide plate progressively increases away from the second light source group;

wherein, in the first light emitting area, the light guide plate is flat-plate-like; and

wherein light sources constituting the first light source group and light sources constituting the third light source group are alternatively disposed in a single line on one side of the heat sink, and a direction of light emitted from the first light source group is opposite to a direction of light emitted from the third light source group.