Optical films having at least one particle-containing layer

• US 6,268,961 B1
• Filed: 02/04/2000
• Issued: 07/31/2001
• Est. Priority Date: 09/20/1999
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Nevitt, Timothy J., Horn, Robert W., Kallman, Guy M., Hebrink, Timothy J., Stover, Carl A., Kausch, William L., Cross, Elisa M., Olson, James A., Kent, Susan L., OʼNeill, Mark B.
• Primary Examiner(s): Spyrou, Cassandra
• Assistant Examiner(s): Juba, Jr., John
• Application Number:
  US09/498,028
• Time in Patent Office: 543 Days
• Field of Search: 359/483, 359/485, 359/487, 359/488, 359/494, 359/495, 359/497, 359/498, 359/500, 359/599, 359/900, 349/84, 349/96, 264/1.31, 264/1.34
• US Class Current: 359/485.03
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: G02B 5/0226 having particles on the surface
• CPC Class Codes: G02B 5/0242 by means of dispersed particles
• CPC Class Codes: G02B 5/0278 used in transmission
• CPC Class Codes: G02B 5/0284 used in reflection
• CPC Class Codes: G02B 5/0289 used as a transflector
• CPC Class Codes: G02B 5/3008 comprising dielectric particles, e.g. birefringent crystals embedded in a matrix
• CPC Class Codes: G02B 5/305 including organic materials, e.g. polymeric layers
• CPC Class Codes: G02F 1/133504 Diffusing, scattering, diffracting elements associated to illuminating devices G02F1/133606
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/133545 Dielectric stack polarisers
• CPC Class Codes: G02F 1/13362 providing polarized light, e.g. by converting a polarisation component into another one
• CPC Class Codes: Y10S 359/90 Methods

Abstract

An optical film includes a reflective polarizing element and a particle-containing layer. The reflective polarizing element substantially reflects light having a first polarization state and substantially transmits a second polarization state. The particle-containing layer is disposed on the reflective polarizing element and in a same optical path as the reflective polarizing element. The particle-containing layer is configured and arranged to transmit light and includes a plurality of particles that roughen an exterior surface of the optical film. Preferably, using the optical film in an optical device does not substantially reduce the gain advantage of the optical device when compared with an optical device utilizing the same optical film without particles in the surface layer. Also described are optical devices using the optical film and methods of making and using the optical films.

Claims

1. An optical film comprising:

a reflective polarizing element substantially reflecting light having a first polarization state and substantially transmitting light having a second polarization state; and

a surface layer disposed on the reflective polarizing element and in a same optical path as the reflective polarizing element, the surface layer being configured and arranged to transmit light, the surface layer compr sing a plurality of particles that roughen an exterior surface of the surface layer;

wherein a gain advantage of an optical device utilizing the optical film is not reduced snore than about five percent when compared to a gain advantage of the optical device utilizing a salme optical film without the plurality of particles in the surface layer.

2. The optical film of claim 1, wherein at least some of the particles are partially embedded in the surface layer and partially projecting from the surface layer.

3. The optical film of claim 1, wherein substantially all of the plurality of particles are arranged in a monolayer at the exterior surface of the surface layer.

4. The optical film of claim 1, wherein substantially all of the plurality of particles are embedded in the surface layer.

5. The optical film of claim 1, wherein the particles and a remainder of the surface layer have indices of refraction that differ by no more than about 0.2.

6. The optical film of claim 1, wherein the particles are generally spherical.

7. The optical film of claim 1, wherein the reflective polarizing element and the surface layer are formed as a co-extruded film.

8. The optical film of claim 1, wherein the surface layer comprises a film coated on the reflective polarizing element.

9. The optical film of claim 1, wherein the reflective polarizing element comprises first and second materials, at least one of the first and second materials being birefringent, wherein a refractive index difference between the first and second materials for light having the first polarization is large enough to substantially reflect the light having the first polarization and a refractive index difference between the first and second materials for light having the second polarization is small enough to substantially transmit the light having the second polarization.

10. The optical film of claim 9, wherein the reflective polarizing element comprises a multilayer optical film having a plurality of birefringent first optical layers interleaved with a plurality of second optical layers.

11. The optical film of claim 9, wherein the first material is disposed in the second material.

12. The optical film of claim 1, wherein the reflective polarizing element comprises birefringent cholesteric material.

13. The optical film of claim 1, wherein the plurality of particles comprise at least one material selected from the group consisting of amorphous polymers, alumina, silica, alloys of alumina and silica, glass, talc, and combinations thereof.

14. The optical film of claim 1, wherein the optical film has a reduced tendency to form Newton'"'"'s Rings when placed proximate another surface, as compared to a same optical film without the particles in the surface layer.

15. The optical film of claim 1, wherein the multilayer optical film has a reduced tendency to wet-out when placed proximate another surface, as compared to a same multilayer optical film without the particles in the surface layer.

16. The optical film of claim 1, wherein a gain advantage of an optical device utilizing the optical film is reduced by no more than 3% when compared to a gain advantage of the optical device utilizing a same optical film without the plurality of particles in the surface layer.

17. The optical film of claim 16, wherein the optical film is capable of transmitting visible light through the reflective polarizing element and then the surface layer with substantially more uniform intensity over a range of 400 to 650 nm than a same optical film without the plurality of particles.

18. An optical device comprising;

light source; and

the optical film of claim 1.

19. The optical device of claim 18, wherein the surface layer is disposed on a surface of the reflective polarizing element opposite a surface receiving light from the light source.

20. The optical device of claim 18, wherein the surface layer comprises a skin layer of the reflective polarizing element.

21. The optical device of claim 18, wherein the surface layer comprises a coating disposed on a surface of the reflective polarizing element.

22. The optical device of claim 18, wherein at least a portion of the plurality of particles project from the surface layer.

23. The optical device of claim 18, wherein the reflective polarizing element and the surface layer transmit visible light with substantially more uniform intensity over a range of 400 to 650 nm than a same reflective polarizing element and surface layer without the plurality of particles.

24. The optical device of claim 18, wherein the light source comprises a backlight.

25. The optical device of claim 18, further comprising a display medium.

26. The optical device of claim 25, wherein the display medium comprises a liquid crystal display medium.

27. The optical device of claim 25, wherein the reflective polarizing element and surface layer are disposed between the light source and the display medium.

28. The optical device of claim 27, wherein the surface layer is disposed between the reflective polarizing element and the display medium.

29. A method of making an optical film, comprising:

forming a reflective polarizing element that substantially reflects light having a first polarization state and substantially transmits light having a second polarization state; and

forming a surface layer on a first major surface of the reflective polarizing element, the surface layer comprising a plurality of particles that roughen an exterior surface of the surface layer, wherein a gain advantage of an optical device utilizing the optical film is not reduced by more than about five percent when compared to a gain advantage of the optical device utilizing a same optical film without the plurality of particles in the surface layer.

30. The method of claim 29, wherein forming a reflective polarizing element and forming a surface layer comprise coextruding the reflective polarizing element and the surface layer.

31. The method of claim 29, further comprising disposing at least one surface layer without particles on a second major surface of the reflective polarizing element.

32. The method of claim 29, wherein forming a surface layer comprises

mixing a plurality of particles with monomers used to form a surface layer polymer;

polymerizing the monomers to form the surface layer polymer in the presence of the plurality of particles; and

forming the surface layer using at least a portion of the surface layer polymer and plurality of particles.

33. The method of claim 29, wherein forming the surface layer comprises depositing a surface layer polymer containing a plurality of particles on the reflective polarizing element.

34. The method of claim 29, wherein forming the surface layer comprises

disposing a surface layer polymer on the reflective polarizing element;

and

disposing a plurality of particles in the surface layer polymer on the reflective polarizing element.

35. An optical film comprising:

a reflective polarizing element substantially reflecting light having a first polarization state and substantially transmitting light having a second polarization state; and

a particle-containing layer disposed on the reflective polarizing element and in a same optical path as the reflective polarizing element, the particle-containing layer being configured and arranged to transmit light, the particle-containing layer comprising a plurality of particles that roughen an exterior surface of the optical film;

wherein a gain advantage of an optical device utilizing the optical film is not reduced by more than about five percent when compared to a gain advantage of the optical device utilizing a same optical film without the plurality of particles in the particle-containing layer.

36. The optical film of claim 35, further comprising a cover layer disposed over the particle-containing layer, wherein the plurality of particles in the particle-containing layer roughen an exterior surface of the cover layer.

37. The optical film of claim 35, wherein the reflective polarizing element comprises first and second materials, at least one of the first and second materials being birefringent, wherein a refractive index difference between the first and second materials for light having the first polarization is large enough to substantially reflect the light having the first polarization and a refractive index difference between the first and second materials for light having the second polarization is small enough to substantially transmit the light having the second polarization.

38. The optical film of claim 37, wherein the reflective polarizing element comprises a multilayer optical film having a plurality of birefringent first optical layers interleaved with a plurality of second optical layers.

39. The optical film of claim 37, wherein the first material is disposed in the second material.

40. The optical film of claim 35, wherein the reflective polarizing element comprises birefringent cholesteric material.