Backlight unit and liquid crystal display device

• US 20080049168A1
• Filed: 08/20/2007
• Published: 02/28/2008
• Est. Priority Date: 08/23/2006
• Status: Active Grant

• Current Assignee: Saturn Licensing LLC (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Kubota, Eigo
• Granted Patent: US 7,738,053 B2
• Time in Patent Office: Days
• US Class Current: 349/65
• 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 6/0055 Reflecting element, sheet or layer

Abstract

A backlight unit includes a light-source substrate having mounted thereon a plurality of light-emitting elements emitting illumination light; a light guide plate having a side surface with the light-source substrate attached thereto so as to receive the illumination light from the light-emitting elements, the light guide plate also having a first surface extending substantially perpendicular to the side surface, and a second surface; a reflective sheet attached to the first surface and reflecting the illumination light towards the second surface; and an optical sheet layer attached to the second surface and including a plurality of stacked optical sheets. The side surface has a reflective portion that reflects at least a part of the illumination light. The at least a part of the illumination light to be reflected at the reflective portion is incident on the reflective portion at an incidence angle equal to or above a critical angle.

Claims

1. A backlight unit comprising:

a light-source substrate having mounted thereon a plurality of light-emitting elements that emit illumination light;

a light guide plate having a side surface with the light-source substrate attached thereto so as to receive the illumination light from the light-emitting elements, the light guide plate also having a first surface extending substantially perpendicular to the side surface, and a second surface;

a reflective sheet attached to the first surface of the light guide plate so as to reflect the illumination light from the light-emitting elements towards the second surface of the light guide plate; and

an optical sheet layer attached to the second surface of the light guide plate and including a plurality of optical sheets in a stacked manner,

wherein the side surface of the light guide plate to which the light-source substrate is attached is provided with a reflective portion that reflects at least a part of the illumination light received by the light guide plate from the light-emitting elements, and

wherein the at least a part of the illumination light to be reflected at the reflective portion is incident on the reflective portion at an incidence angle that is equal to or above a critical angle.

2. The backlight unit according to claim 1, wherein the reflective portion of the light guide plate has a curved surface or a flat surface.

3. The backlight unit according to claim 1, wherein the light-source substrate is attached to the side surface of the light guide plate in a manner such that the light-emitting elements mounted on the light-source substrate are accommodated in the light guide plate.

4. The backlight unit according to claim 1, wherein the light guide plate contains a transparent resin material.

5. The backlight unit according to claim 1, wherein the reflective portion at the side surface of the light guide plate is provided with a reflective member having a specular reflection function.

6. The backlight unit according to claim 1, wherein the reflective portion at the side surface of the light guide plate has a stepped profile.

7. The backlight unit according to claim 1, wherein the light-emitting elements and the light guide plate have optically transparent resin filled therebetween.

8. A liquid crystal display device comprising:

a transmissive liquid crystal panel; and

a backlight unit that illuminates the transmissive liquid crystal panel from a rear side of the panel,

wherein the backlight unit includes

a light-source substrate having mounted thereon a plurality of light-emitting elements that emit illumination light,

a light guide plate having a side surface with the light-source substrate attached thereto so as to receive the illumination light from the light-emitting elements, the light guide plate also having a first surface extending substantially perpendicular to the side surface, and a second surface,

a reflective sheet attached to the first surface of the light guide plate so as to reflect the illumination light from the light-emitting elements towards the second surface of the light guide plate, and

an optical sheet layer attached to the second surface of the light guide plate and including a plurality of optical sheets in a stacked manner,

wherein the side surface of the light guide plate to which the light-source substrate is attached is provided with a reflective portion that reflects at least a part of the illumination light received by the light guide plate from the light-emitting elements, and

wherein the at least a part of the illumination light to be reflected at the reflective portion is incident on the reflective portion at an incidence angle that is equal to or above a critical angle.

9. The liquid crystal display device according to claim 8, wherein the reflective portion of the light guide plate has a curved surface or a flat surface.

10. The liquid crystal display device according to claim 8, wherein the light-source substrate is attached to the side surface of the light guide plate in a manner such that the light-emitting elements mounted on the light-source substrate are accommodated in the light guide plate.

11. The liquid crystal display device according to claim 8, wherein the light guide plate contains a transparent resin material.

12. The liquid crystal display device according to claim 8, wherein the reflective portion at the side surface of the light guide plate is provided with a reflective member having a specular reflection function.

13. The liquid crystal display device according to claim 8, wherein the reflective portion at the side surface of the light guide plate has a stepped profile.

14. The liquid crystal display device according to claim 8, wherein the light-emitting elements and the light guide plate have optically transparent resin filled therebetween.