Diffuse reflectors

• US 6,018,419 A
• Filed: 03/17/1998
• Issued: 01/25/2000
• Est. Priority Date: 06/26/1995
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Cobb, Sanford Jr., Weber, Michael F., Ouderkirk, Andrew J., Wortman, David L., Cull, Brian D.
• Primary Examiner(s): Spyrou, Cassandra
• Assistant Examiner(s): Schuberg, Darren E.
• Application Number:
  US09/040,039
• Time in Patent Office: 679 Days
• Field of Search: 359/485, 359/487, 359/488, 359/495, 359/498, 359/500, 359/599, 156/99
• US Class Current: 359/485.04
• CPC Class Codes: G02B 5/0841 comprising organic materials, e.g. polymers
• CPC Class Codes: G02B 5/3033 in the form of a thin sheet or foil, e.g. Polaroid
• CPC Class Codes: G02B 5/305 including organic materials, e.g. polymeric layers
• CPC Class Codes: G02B 5/3066 involving the reflection of light at a particular angle of incidence, e.g. Brewster's angle
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/133545 Dielectric stack polarisers

Abstract

Highly efficient diffusely reflecting multilayer mirrors diffusely reflect light incident upon them. Highly efficient diffusely reflecting multilayer polarizers diffusely reflect light of one polarization while diffusely transmitting the other polarization. The diffusely reflecting mirror includes a light diffusing element and a multilayer mirror element. The diffusely reflecting polarizer includes a light diffusing element and a multilayer reflective polarizing element.

Claims

1. A diffuse reflector, comprising:

a reflecting element; and

a diffusing adhesive adhered to the surface of the reflecting element, the diffusing adhesive altering the directionality of light as it transmits through the diffusing adhesive while preserving an initial polarization state of the light.

2. A diffuse reflector as recited in claim 1, wherein the reflecting element comprises a reflective polarizer, the reflective polarizer reflecting light of a first polarization state and transmitting light of a second polarization state.

3. A diffuse reflector as recited in claim 2, wherein the reflective polarizer comprises at least two materials where at least one of the two materials is birefringent such that there exists a refractive index difference between the two materials for light of the first polarization state.

4. A diffuse reflector as recited in claim 3, wherein the two materials form multiple layers.

5. A diffuse reflector as recited in claim 1, wherein the diffusing adhesive preserves at least 70% of the initial polarization state.

6. A diffuse reflector as recited in claim 1, wherein the diffusing adhesive preserves at least 85% of the initial polarization state.

7. A diffuse reflector as recited in claim 1, wherein the diffusing adhesive preserves at least 90% of the initial polarization state.

8. A diffuse reflector as recited in claim 1 wherein the diffusing adhesive has a reflectivity of less than 20%.

9. A diffuse reflector as recited in claim 1 wherein the diffusing adhesive has a reflectivity of less than 8%.

10. A diffuse reflector as recited in claim 1 wherein the diffusing adhesive has a reflectivity of less than 4%.

11. A diffuse reflector as recited in claim 1 wherein the diffusing adhesive comprises beads dispersed in a pressure sensitive adhesive.

12. A diffuse reflector as recited in claim 1 wherein the diffusing adhesive comprises styrene beads dispersed in a water-based emulsion adhesive.

13. A diffuse reflector as recited in claim 1, wherein the reflecting element is a mirror.

14. A diffuse reflector as recited in claim 13, wherein the mirror comprises a multilayer stack of at least two materials having different refractive indices.

15. A diffusely reflecting polarizer, comprising:

a reflective polarizer, the reflective polarizer reflecting light of a first polarization state and transmitting light of a second polarization state; and

a diffusing adhesive adhered to a surface of the reflective polarizer, the diffusing adhesive being adapted to diffuse light transmitted through the diffusing adhesive while substantially maintaining the polarization of the light.

16. A diffuse reflector, comprising:

a reflecting element having spectral variations in at least one of reflected and transmitted light; and

a polarization preserving diffuser disposed to improve the spectral uniformity of the at least one of reflected and transmitted light.

17. A diffuse reflector as recited in claim 16, wherein the polarization preserving diffuser comprises a diffusing adhesive.

18. A diffuse reflector as recited in claim 17, wherein the diffuse reflector is laminated to another component via the diffusing adhesive.

19. A diffuse polarizing reflector system, comprising:

a reflective polarizer that reflects light of a first polarization and transmits light of a second polarization, the reflective polarizer having changes in at least one of spectral reflectivity and transmission; and

a polarization preserving diffuser disposed to improve the spectral uniformity of light that is at least one of reflected and transmitted by the reflective polarizer.

20. A diffuse polarizing reflector system as recited in claim 19, wherein the polarization preserving diffuser comprises a diffusing adhesive.

21. A diffuse polarizing reflector system as recited in claim 20, wherein the diffusing adhesive is used to laminate the reflective polarizer to another system component.

22. An liquid crystal display incorporating the diffuse polarizing reflector of claim 19.