Transflective film and display

• US 20050134769A1
• Filed: 12/19/2003
• Published: 06/23/2005
• Est. Priority Date: 12/19/2003
• Status: Active Grant

• Current Assignee: SKC Hi-Tech & Marketing Co., Ltd.
• Original Assignee: Eastman Kodak Company
• Inventors: Mi, Xiang-Dong
• Granted Patent: US 6,972,827 B2
• Time in Patent Office: Days
• US Class Current: 349/114
• CPC Class Codes: G02B 27/285 comprising arrays of elements, e.g. microprisms
• CPC Class Codes: G02B 5/3016 involving passive liquid crystal elements optical properties of liquid crystals G02F1/0063; polarising elements associated with active liquid crystal devices G02F1/133528
• CPC Class Codes: G02B 5/3033 in the form of a thin sheet or foil, e.g. Polaroid
• CPC Class Codes: G02B 5/3083 Birefringent or phase retarding elements G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001
• CPC Class Codes: G02B 6/0056 for producing polarisation effects, e.g. by a surface with polarizing properties or by an additional polarizing elements
• CPC Class Codes: G02F 1/13362 providing polarized light, e.g. by converting a polarisation component into another one
• CPC Class Codes: G02F 2203/023 total internal reflection

Abstract

A transflective optical film reflects ambient light incident on the first surface and transmits light having a preferred polarization state incident on the opposite surface. The film has a substrate wherein a plurality of tapered cavities extends from a first surface of the substrate toward an opposite surface, the tapered cavities narrowing toward the opposite surface, and a filler material deposited within each the tapered cavity. A reflective layer is deposited on the filler material in each tapered cavity, along the first surface of the substrate. At least one of the substrate and the filler material is birefringent such that for a preferred polarization state, the refractive index of the filler is substantially lower than the refractive index of the substrate and that, for the polarization state orthogonal to the preferred polarization state, the refractive index of the filler is substantially the same as the refractive index of the substrate.

Claims

1. A transflective optical film for reflecting ambient light incident on a first surface and for transmitting light having a preferred polarization state incident on a second surface opposite the first surface, the optical film comprising:

(a) a substrate containing a plurality of tapered cavities extending from the first surface of said substrate toward the second surface opposite the first surface, said tapered cavities narrowing toward said second surface;

(b) a filler material deposited within each said tapered cavity; and

,

(c) a reflective material deposited on said filler material on the surface of the filler material adjacent the first surface of said substrate;

wherein at least one of said substrate and said filler material is birefringent such that;

(a) for said preferred polarization state, the refractive index of said filler is substantially lower than the refractive index of said substrate and,

(b) for the polarization state orthogonal to said preferred polarization state, the refractive index of said filler is substantially the same as the refractive index of said substrate.

2. A transflective optical film according to claim 1 wherein said filler material is birefringent.

3. A transflective optical film according to claim 1 wherein said substrate is birefringent.

4. A transflective optical film according to claim 1 wherein both substrate and filler material are birefringent.

5. A transflective optical film according to claim 1 wherein said tapered cavities are arranged as a series of elongated triangles extended in parallel along said first surface.

6. A transflective optical film according to claim 1 wherein said tapered cavities are arranged in a honeycomb pattern along said first surface.

7. A transflective optical film according to claim 1 wherein said tapered cavities are arranged in a random pattern along said first surface.

8. A transflective optical film according to claim 1 wherein said reflective layer comprises a material that is selected from the group consisting of aluminum, nickel, silver, gold, or combinations of two or more metals.

9. A transflective optical film according to claim 1 wherein said reflective layer comprises a plurality of dielectric layers.

31. A display apparatus utilizing both transmitted and ambient illumination, comprising:

(a) a backlight source for providing illumination;

(b) a liquid crystal spatial light modulator for modulating light of a preferred input polarization state to provide modulated light having an output polarization state; and

(c) the transflective optical film of claim 1.

32. A method for enhancing luminance of a liquid crystal display comprising:

(a) providing incident illumination from a two-dimensional surface;

(b) transmitting said illumination having a preferred polarization state to the liquid crystal display through a transflective optical film of claim 1.

10. A transflective optical film for reflecting ambient light incident on a first surface and for transmitting light having a preferred polarization state incident on a second surface opposite the first surface, comprising:

(a) a substrate having a first index of refraction n₁, wherein said substrate comprises a plurality of tapered cavities extending from a first surface and narrowing toward the second surface;

(b) a birefringent filler material deposited within each said tapered cavity, said filler material having a second index of refraction n₂ for light having said preferred polarization state and a third index of refraction n₃ for light having an orthogonal polarization state to said preferred polarization state; and

,

(c) a reflective layer deposited on the end of said filler material in each said tapered cavity adjacent said first surface;

wherein n₃ is substantially equal to n₁ and n₂ is substantially less than n₁.

11. A transflective optical film according to claim 10 wherein n₁ differs from n₂ by more than about 0.01.

12. A transflective optical film according to claim 10 wherein n₁ differs from n₃ by less than about 0.01.

13. A transflective optical film according to claim 10 wherein said substrate is birefringent.

14. A transflective optical film according to claim 10 wherein said tapered cavities are arranged as a series of elongated triangles extended in parallel along said first surface.

15. A transflective optical film according to claim 10 wherein said tapered cavities are arranged in a honeycomb pattern along said first surface.

16. A transflective optical film according to claim 10 wherein said tapered cavities are arranged in a random pattern along said first surface.

17. A transflective optical film according to claim 10 wherein said reflective layer comprises a material that is selected from the group consisting of aluminum, nickel, silver, gold, or combinations of two or more metals.

18. A transflective optical film according to claim 10 wherein said reflective layer comprises a plurality of dielectric layers.

19. A transflective optical film for reflecting ambient light incident on a first surface and for transmitting light incident on the opposite second surface having a preferred polarization state, the optical film comprising:

(a) a birefringent substrate having a first index of refraction n₁ for light having the preferred polarization state and a second index of refraction n₂ for light having the orthogonal polarization state, wherein said substrate comprises a plurality of tapered cavities extending from the first surface and narrowing toward the opposite second surface;

(b) a filler material deposited within each said tapered cavity, said filler material having a third index of refraction n₃; and

,

(c) a reflective layer deposited on said filler material in each said tapered cavity adjacent said first surface;

wherein n₃ is substantially equal to n₁ and n₃ is substantially less than n₂.

20. A transflective optical film according to claim 19 wherein n₂ differs from n₃ by more than about 0.01.

21. A transflective optical film according to claim 19 wherein n₁ differs from n₃ by less than about 0.01.

22. A transflective optical film according to claim 19 wherein said filler material is birefringent.

23. A transflective optical film according to claim 19 wherein said tapered cavities are arranged as a series of elongated triangles extended in parallel along said first surface.

24. A transflective optical film according to claim 19 wherein said tapered cavities are arranged in a honeycomb pattern along said first surface.

25. A transflective optical film according to claim 19 wherein said tapered cavities are arranged in a random pattern along said first surface.

26. A transflective optical film according to claim 19 wherein said reflective layer is selected from the group consisting of aluminum, nickel, silver, gold, or combinations of two or more metals.

27. A transflective optical film according to claim 19 wherein said reflective layer comprises a plurality of dielectric layers.

28. An optical film for receiving, on an input first surface, incident illumination from a light source, for transmitting said illumination having a first polarization state and reflecting said illumination having a second polarization state back toward the light source, the optical film comprising:

(a) a reflector for reflecting light incident on the opposite surface;

(b) means for transmitting light incident thereon from a first surface of the film;

such that the sum of the following exceeds about 140 percent of illumination;

(i) light incident on said second surface being reflected relative to the total amount of the light incident on said second surface;

plus,

(ii) light of the first polarization transmitted from said first surface relative to the amount of light of the first polarization incident on said first surface.

29. An optical film according to claim 28 wherein the transmissivity of the optical film along said first direction for light of said first polarization is greater than about 70% relative to the amount of incident light of said first polarization.

30. An optical film according to claim 28 wherein the reflectivity of the optical film along said second direction for light of said second polarization is greater than about 70% relative to the amount of incident light of said second polarization.

33. A method for forming a transflective optical film for reflecting ambient light incident on a first surface and for transmitting light incident on the opposite surface having a preferred polarization state, the method comprising:

(a) forming a plurality of tapered cavities into the first surface of a film substrate, said film substrate having a first index of refraction n₁;

(b) depositing a birefringent filler material within each said tapered cavity, said filler material having a second index of refraction n₂ in a first direction and a third index of refraction n₃ in a second direction orthogonal to said first direction; and

,

(c) depositing a reflective layer onto said filler material along said first surface in each said tapered cavity.

34. A method for forming a transflective optical film according to claim 33 wherein the step of forming a plurality of tapered cavities comprises the step of forming a series of parallel grooves.