BACKLIGHT SUITABLE FOR DISPLAY DEVICES

• US 20080049419A1
• Filed: 08/25/2006
• Published: 02/28/2008
• Est. Priority Date: 08/25/2006
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Sanford, Quinn, Cheng, Ming, Ma, Jiaying
• Granted Patent: US 7,905,650 B2
• Time in Patent Office: Days
• US Class Current: 362/225
• CPC Class Codes: G02B 5/128 transparent spheres being embedded in matrix
• CPC Class Codes: G02B 6/0031 Reflecting element, sheet or layer
• 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: G02F 1/133604 with lamps
• CPC Class Codes: G02F 1/133605 including specially adapted reflectors
• CPC Class Codes: G02F 1/133606 including a specially adapted diffusing, scattering or light controlling members
• CPC Class Codes: G02F 1/133607 the light controlling member including light directing or refracting elements, e.g. prisms or lenses
• CPC Class Codes: G02F 1/133611 including means for improving the brightness uniformity

Abstract

A backlight suitable for use in a display device includes an illumination device having at least one light source and a back reflector stack including a reflective layer and a transparent layer having substantially uniform refractive index and having a plurality of light-directing protrusions disposed in a matrix array. The transparent layer is disposed between the reflective layer and the illumination device with the plurality of light-directing protrusions facing away from the reflective layer. The plurality of light-directing protrusions are configured and disposed in a configuration that is not registered to any light source of the illumination device.

Claims

1. A backlight suitable for use in a display device, comprising:

an illumination device comprising at least one light source; and

a back reflector stack comprising a reflective layer and a transparent layer having substantially uniform refractive index and comprising a plurality of light-directing protrusions disposed in a matrix array, the transparent layer being disposed between the reflective layer and the illumination device with the plurality of light-directing protrusions facing away from the reflective layer;

wherein the plurality of light-directing protrusions are configured and disposed in a configuration that is not registered to any light source of the illumination device.

2. The backlight as recited in claim 1, wherein the illumination device comprises a lightguide disposed in the optical path of light reflected by the back reflector stack and at least one light source optically connected to an edge of the lightguide.

3. The backlight as recited in claim 2, wherein the lightguide is wedge-shaped.

4. The backlight as recited in claim 1, wherein the illumination device comprises at least one light source disposed in the optical path of light reflected by the back reflector stack.

5. The backlight as recited in claim 1, wherein the reflective layer has a specular reflectivity component.

6. The backlight as recited in claim 1, wherein the reflective layer comprises a plurality of interleaved layers of at least two diverse polymeric materials.

7. The backlight as recited in claim 1, wherein the reflective layer has a diffuse reflectivity component.

8. The backlight as recited in claim 1, wherein the reflective layer has a reflectivity of at least 70%.

9. The backlight as recited in claim 1, wherein the back reflector stack further comprises a diffuser disposed between the transparent layer and the reflective layer.

10. The backlight as recited in claim 1, wherein the transparent layer is attached to the reflective layer.

11. A backlight suitable for use in a display device, comprising:

an illumination device comprising at least one light source; and

a back reflector stack comprising a reflective layer and a transparent layer comprising a plurality of beads disposed in a binder, the beads forming a plurality of light-directing protrusions and the binder having a refractive index that is close to a refractive index of the beads, the transparent layer being disposed between the reflective layer and the illumination device with the plurality of light-directing protrusions facing away from the reflective layer;

wherein the plurality of light-directing protrusions are configured and disposed in a configuration that is not registered to any light source of the illumination device.

12. The backlight as recited in claim 11, wherein the refractive index of the binder is within 0.1 of the refractive index of the beads.

13. The backlight as recited in claim 11, wherein the binder comprises an ionizing radiation curable material.

14. The backlight as recited in claim 11, wherein the illumination device comprises a lightguide disposed in the optical path of light reflected by the back reflector stack and at least one light source optically connected to an edge of the lightguide.

15. The backlight as recited in claim 14, wherein the lightguide is wedge-shaped.

16. The backlight as recited in claim 11, wherein the illumination device comprises at least one light source disposed in the optical path of light reflected by the back reflector stack.

17. The optical article of claim 11, wherein the light-directing protrusions formed by beads cover at least about 50% per unit area of a major surface of the transparent layer.

18. A backlight suitable for use in a display device, comprising:

an illumination device comprising at least one light source; and

a back reflector stack comprising a reflective layer and a transparent layer having substantially uniform refractive index and comprising a plurality of lenticular light-directing protrusions disposed in a matrix array, the transparent layer being disposed between the reflective layer and the illumination device with the plurality of light-directing protrusions facing away from the reflective layer;

wherein the plurality of light-directing protrusions are configured and disposed in a configuration that is not registered to any light source of the illumination device.

19. The display as recited in claim 18, wherein the lenticular light-directing protrusions are substantially hemispherically shaped.

20. The optical article of claim 18, wherein the lenticular light-directing protrusions cover at least about 50% per unit area of a major surface of the transparent layer.