Direct-lit liquid crystal displays with laminated diffuser plates

• US 7,446,827 B2
• Filed: 10/15/2004
• Issued: 11/04/2008
• Est. Priority Date: 10/15/2004
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Laumer, James W., Fabick, Ryan T., Park, Youngsoo, Gehlsen, Mark D., Epstein, Kenneth A., Rivard, Linda M., Emmons, Robert M., Lee, Ji-Hwa, Kim, Ji-Hyung, Kim, Chideuk, Ko, Byungsoo, Chen, Chingwen, Seo, Kang-il
• Primary Examiner(s): Dudek; James A
• Application Number:
  US10/966,610
• Publication Number:
  US 20060082698A1
• Time in Patent Office: 1,481 Days
• Field of Search: 349/64
• US Class Current: 349/64
• CPC Class Codes: G02F 1/133507 Films for enhancing the luminance
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• 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 1/13362 providing polarized light, e.g. by converting a polarisation component into another one
• CPC Class Codes: G02F 2201/086 UV absorbing

Abstract

In a directly-illuminated liquid crystal display (LCD), for example an LCD monitor or an LCD-TV, a number of light management films, including a diffuser layer, lie between the light source and the LCD panel to provide bright, uniform illumination. The diffuser layer is attached to a substrate which is separate from the light source and the LCD panel, or may be attached to either the LCD panel or, when using a two dimensional light source, to the light source. The other light management layers may also be attached to the separate substrate or to the LCD panel or two-dimensional light source. High levels of illumination uniformity at the LCD may be achieved with a uniform (non-patterned) diffuser, even with relatively low levels of diffusion, when the diffuser is used with a brightness enhancing layer.

Claims

1. A directly illuminated liquid crystal display (LCD) unit, comprising:

a light source;

an LCD panel; and

an arrangement of light management layers disposed between the light source and the LCD panel so that the light source illuminates the LCD panel through the arrangement of light management layers, the arrangement of light management layers comprising a diffuser plate, a brightness enhancing layer and a reflective polarizer, the diffuser plate being positioned closer to the one or more light sources than the brightness enhancing layer and the reflective polarizer, the diffuser plate comprising a substantially transparent substrate attached directly to edge portions of a first foam adhesive tape diffusing layer that diffuses light propagating from the light source towards the LCD panel, the edge portions defining a gap, and an intermediate layer in the gap, one of the reflective polarizer and brightness enhancement layer being attached to the side of the diffuser plate facing the LCD panel.

2. A unit as recited in claim 1, wherein the first diffusing layer comprises a matrix with a dispersed phase of diffusing particles.

3. A unit as recited in claim 1, wherein the light source comprises a plurality of light source.

4. A unit as recited in claim 1, wherein the arrangement of light management layers provides a spatially uniform diffusion characteristic.

5. A unit as recited in claim 1, wherein the substrate comprises a sheet of glass.

6. A unit as recited in claim 1, wherein the first diffusing layer is provided on a side of the substrate facing towards the array of light sources.

7. A unit as recited in claim 1, wherein the first diffusing layer is provided on a side of the substrate facing away from the array of light sources.

8. A unit as recited in claim 1, wherein the first diffusing layer is provided on a side of the substrate facing towards the array of light sources, and the diffuser plate further comprises a second diffusing layer provided on a side of the substrate facing away from the array of light sources.

9. A unit as recited in claim 1, wherein a first side of the brightness enhancing layer is attached to the diffuser plate.

10. A unit as recited in claim 9, wherein the reflective polarizer is attached to a second side of the brightness enhancing layer.

11. A unit as recited in claim 1, wherein a first side of the reflective polarizer is attached to the diffuser plate.

12. A unit as recited in claim 11, wherein the brightness enhancing layer is attached to a second side of the reflective polarizer.

13. A unit as recited in claim 1, wherein the reflective polarizer comprises a multilayer optical film reflective polarizer.

14. A unit as recited in claim 1, wherein the diffuser has a single pass optical transmission in the range of about 72% - 95%.

15. A unit as recited in claim 14, wherein the diffuser has a single pass optical transmission in the range of about 75% - 90%.

16. A unit as recited in claim 1, wherein a value of σ

/x is less than 1.5%, where x is the level of illumination light passing from the arrangement of light management layers to the LCD panel, averaged across the LCD panel, and σ

is the root mean square deviation in the level of illumination light across the arrangement of light management layers, and the diffuser plate has a single pass transmission of at least 72%.

17. A unit as recited in claim 16, wherein the value of σ

/x is less than 1.3%, and the diffuser plate has a single pass transmission of at least 75%.

18. A unit as recited in claim 1, further comprising a controller coupled to control an image displayed by the LCD panel.

19. A unit as recited in claim 18, wherein the controller comprises a computer.

20. A unit as recited in claim 18, wherein the controller comprises a television controller.

21. A unit as recited in claim 1 wherein the intermediate layer is a blank buffer layer or a reflective polarizer.

22. A unit as recited in claim 1 wherein the first foam adhesive tape diffusing layer contains hollow particles.