Post-forming continuous/disperse phase optical bodies

• US 6,256,146 B1
• Filed: 07/31/1998
• Issued: 07/03/2001
• Est. Priority Date: 07/31/1998
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Condo, Peter D., Benson, Olester Jr., Merrill, William W., Allen, Richard C.
• Primary Examiner(s): Shafer, Ricky D.
• Application Number:
  US09/127,314
• Time in Patent Office: 1,068 Days
• Field of Search: 359/487, 359/488, 359/490, 359/492, 359/494, 359/495, 359/500, 359/599, 359/900, 252/585, 264/1.31, 264/1.34, 264/1.7, 264/1.9, 264/2.7, 264/288.4, 264/290.2, 427/163.1
• US Class Current: 359/487.02
• 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: Y10S 359/90 Methods

Abstract

Diffusely reflective articles manufactured from optical bodies including continuous and disperse phases are disclosed along with methods of manufacturing such articles. Also disclosed are underdrawn continuous/disperse phase optical bodies that are particularly well-suited to post-forming operations. The articles, methods and optical bodies of the present invention preferably allow for post-forming of the optical bodies while retaining desired levels of diffuse reflectivity in the articles formed from the optical bodies.

Claims

1. A method of manufacturing a diffusely reflective article, said method comprising:

providing an optical body having a generally sheet-like configuration, said optical body comprising;

a first phase having a birefringence of at least about 0.05; and

a second phase, disposed within said first phase, whose index of refraction differs from said first phase by greater than about 0.05 along a first axis and by less than

about 0.05 along a second axis orthogonal to said first axis;

wherein diffuse reflectivity of said first and second phases taken together along at least one axis for at least one polarization of electromagnetic radiation is at least about 30%;

post-forming said optical body into a diffusely reflective article, wherein a selected area of said optical body undergoes permanent deformation, and further wherein said selected area of said optical body comprises only a portion of said optical body.

2. A method according to claim 1, wherein said selected area of said optical body exhibits diffuse reflectivity of said first and second phases taken together along at least one axis for at least one polarization of electromagnetic radiation of at least about 30%.

3. A method according to claim 1, wherein said first and second phases taken together exhibit diffuse reflectivity along said at least one axis of at least about 50% for both polarizations of electromagnetic radiation in said selected area before and after post-forming.

4. A method according to claim 1, wherein said optical body exhibits a total reflectivity of greater than about 50% for a first polarization of electromagnetic radiation and a total transmission of greater than about 50% for a second polarization of electromagnetic radiation orthogonal to said first polarization in said selected area before and after post-forming.

5. A method according to claim 4, wherein said optical body exhibits a total reflectivity of greater than about 60% for said first polarization of electromagnetic radiation in said selected area after post-forming.

6. A method according to claim 4, wherein said optical body exhibits a total reflectivity of greater than about 70% for said first polarization of electromagnetic radiation in said selected area after post-forming.

7. A method according to claim 4, wherein said optical body exhibits a total transmission of greater than about 60% for said second polarization of electromagnetic radiation in said selected area after post-forming.

8. A method according to claim 1, wherein said post-forming further comprises thinning said selected area of said optical body along a third axis that is mutually orthogonal to said first and second axes.

9. A method according to claim 8, wherein said thinning is non-uniform.

10. A method according to claim 8, wherein said optical body has a generally uniform thickness t_o as provided and said thinning comprises reducing the thickness of at least a portion of said selected area of said optical body from the thickness t_o to a thickness t_f, and further wherein the ratio t_o:

t_f is at least about 1.1;

1 or greater.

11. A method according to claim 10, wherein said ratio is at least about 1.5:

1 or greater.

12. A method according to claim 1, wherein said post-forming comprises stretching said optical body along at least one in-plane axis, and further wherein the permanent deformation is strain-induced.

13. A method according to claim 1, wherein said post-forming comprises stretching said optical body along at least one in-plane axis to a draw ratio of at least about 2.

14. A method according to claim 1, wherein said post-forming comprises stretching said optical body along at least one in-plane axis to a draw ratio of at least about 4.

15. A method according to claim 1, further comprising heating said optical body to a forming temperature.

16. A method according to claim 1, wherein the index of refraction of said second phase differs from the index of refraction of said first phase by less than about 0.03 along said second axis before post-forming and less than about 0.05 after post-forming.

17. A method according to claim 1, wherein said second phase is discontinuous along at least two of any three mutually perpendicular axes.

18. A method according to claim 1, wherein said optical body is a film, and wherein the index of refraction of said first phase differs from the index of refraction of said second phase by less than about 0.05 along an axis perpendicular to a surface of said film.

19. A method of manufacturing a diffusely reflective article, said method comprising:

providing an optical body having a generally sheet-like configuration, said optical body comprising;

a first phase having a birefringence of at least about 0.05; and

a second phase, disposed within said first phase, whose index of refraction differs from said first phase by greater than about 0.05 along a first axis;

wherein diffuse reflectivity of said first and second phases taken together along at least one axis for at least one polarization of electromagnetic radiation is at least about 30%;

post-forming said optical body into a diffusely reflective article, wherein a selected area of said optical body undergoes permanent deformation, and further wherein the index of refraction of said second phase differs from the index of refraction of said first phase by less than about 0.05 along a second axis orthogonal to said first axis in said selected area of said optical body after post-forming, and further wherein said selected area of said optical body comprises only a portion of said optical body.

20. A method according to claim 19, wherein, before post-forming, the index of refraction of said second phase differs from the index of refraction of said first phase by more than about 0.01 along said second axis in said selected area of said optical body.

21. A method according to claim 19, wherein, after post-forming, the index of refraction of said second phase differs from the index of refraction of said first phase by less than about 0.03 along said second axis in said selected area.

22. A method according to claim 19, wherein, before post-forming, the index of refraction of said second phase differs from the index of refraction of said first phase by more than about 0.07 along said first axis.

23. A method according to claim 19, wherein the diffuse reflectivity of said first and second phases taken together along at least one axis for at least one polarization of electromagnetic radiation is at least about 50% in said selected area of said optical body.

24. A method according to claim 19, wherein said diffusely reflective article comprises a self-supporting three dimensional shape.

25. A method of manufacturing a diffusely reflective article, said method comprising:

providing an optical body having a generally sheet-like configuration, said optical body comprising;

a first phase having a birefringence of at least about 0.05; and

a second phase, disposed within said first phase, whose index of refraction differs from said first phase by greater than about 0.05 along a first axis;

wherein diffuse reflectivity of said first and second phases taken together along at least one axis for at least one polarization of electromagnetic radiation is at least about 10%;

post-forming said optical body into a diffusely reflective article, wherein a selected area of said optical body undergoes permanent deformation, and further wherein said selected area of said optical body comprises only a portion of said optical body; and

annealing the optical body after post-forming, wherein the index of refraction of said second phase differs from the index of refraction of said first phase by less than about 0.05 along a second axis orthogonal to said first axis in said selected area of said optical body after annealing.

26. A method of manufacturing a diffusely reflective article, said method comprising:

providing an optical body having a generally sheet-like configuration, said optical body comprising;

a first phase having a birefringence of at least about 0.05;

a second phase, disposed within said first phase, whose index of refraction differs from said first phase by greater than about 0.05 along a first axis; and

a dichroic dye;

wherein diffuse reflectivity of said first and second phases taken together along at least one axis for at least one polarization of electromagnetic radiation is at least about 10%;

post-forming said optical body into a diffusely reflective article, wherein a selected area of said optical body undergoes permanent deformation, and further wherein said selected area of said optical body comprises only a portion of said optical body.

27. A method according to claim 26, wherein said second phase has an index of refraction that differs from the index of refraction of said first phase by less than about 0.05 along a second axis orthogonal to said first axis.

28. A method according to claim 26, wherein said dichroic dye is located within said second phase.

29. A diffusely reflective article comprising an optical body including a first phase having a birefringence of at least about 0.05 and a second phase, disposed within said first phase, whose index of refraction differs from said first phase by greater than about 0.05 along a first axis and by less than about 0.05 along a second axis orthogonal to said first axis, wherein diffuse reflectivity of said first and second phases taken together along at least one axis for at least one polarization of electromagnetic radiation is at least about 30%;

wherein at least one surface of said optical body comprises a self-supporting three-dimensional shape.

30. An article according to claim 29, wherein said optical body comprises a self-supporting three-dimensional shape.

31. An article according to claim 29, wherein said first and second phases taken together exhibit diffuse reflectivity along said at least one axis of at least about 50% for both polarizations of electromagnetic radiation.

32. An article according to claim 29, wherein said optical body exhibits a total reflectivity of greater than about 50% for a first polarization of electromagnetic radiation and a total transmission of greater than about 50% for a second polarization of electromagnetic radiation orthogonal to said first polarization.

33. A diffusely reflective article comprising an optical body including a first phase having a birefringence of at least about 0.05 and a second phase, disposed within said first phase, whose index of refraction differs from said first phase by greater than about 0.05 along a first axis and by less than about 0.05 along a second axis orthogonal to said first axis, wherein diffuse reflectivity of said first and second phases taken together along at least one axis for at least one polarization of electromagnetic radiation is at least about 30%;

wherein the thickness of said optical body as measured along a third axis orthogonal to said first and second axes varies over said optical body.

34. An article according to claim 33, wherein the thickness variations are non-uniform over said optical body.

35. An article according to claim 33, wherein said optical body has maximum thickness t_o and a minimum thickness t_f, and further wherein the ratio t_o:

t_f is at least about 1.1;

1 or greater.

36. An article according to claim 35, wherein said ratio is at least about 1.5:

1 or greater.