US-12625312-B2 - Shaped optical film

Abstract

A curved optical film generally lying in a base plane and having a thickness of less than 500 microns, and an average optical absorption of less than 70% for unpolarized normally incident light in a predetermined wavelength range is described. A first cross-section of the optical film in a first plane perpendicular to the base plane has an actual first length AL 1 , a projected first length PL 1 , and a first stretch ratio S 1 of (AL 1 −PL 1 )/PL 1 . A second cross-section of the optical film in a second plane perpendicular to the first and base planes has an actual second length AL 2 , a projected second length PL 2 , and a second stretch ratio S 2 of (AL 2 −PL 2 )/P 2 . The optical film may have a maximum thickness variation of less than 20% along each of the first and second cross-sections, S 1 may be at least 0.1, and S 2 may be at least 0.01 and less than 0.8S 1.

Inventors

• Benjamin G. Sonnek
• Daniel J. RICHTER
• Gregg A. Ambur
• Chaodi Li
• Christopher S. DeGraw
• Jathan D. Edwards

Assignees

• 3M INNOVATIVE PROPERTIES COMPANY

Dates

Publication Date

20260512

Application Date

20190515

Claims (20)

1. 1 . A curved optical film generally lying in a base plane and having an average thickness of less than about 500 microns, and an average optical absorption of less than about 70% for substantially unpolarized substantially normally incident light in a predetermined wavelength range extending at least from 450 nm to 600 nm, a first cross-section of the optical film in a first plane perpendicular to the base plane having an actual first length AL 1 , a projected first length PL 1 on the base plane, and a first stretch ratio S 1 defined as (AL 1 −PL 1 )/PL 1 , S 1 ≥0.1, a second cross-section of the optical film in a second plane perpendicular to the first and base planes having an actual second length AL 2 , a projected second length PL 2 on the base plane, and a second stretch ratio S 2 defined as (AL 2 −PL 2 )/PL 2 , 0.01≤S 2 <0.8S 1 , the optical film having a maximum thickness variation of less than about 20% along each of the first and second cross-sections.
2. 2 . The optical film of claim 1 , wherein the maximum thickness variation is in a range from about 0.05S 1 to about 0.8S 1 along each of the first and second cross-sections.
3. 3 . The optical film of claim 1 , wherein the first cross-section of the optical film has a maximum slope M relative to the base plane and has a maximum deviation D 1 from a straight line connecting opposing ends of the first cross-section, 0.2*PL 1 *M≥D 1 ≥0.05*PL 1 .
4. 4 . The optical film of claim 1 , wherein the first cross-section of the optical film has a maximum slope M relative to the base plane of at least 1.
5. 5 . The optical film of claim 1 , wherein PL 1 ≥1.5PL 2 .
6. 6 . The optical film of claim 1 , wherein the optical film has opposite major surfaces having a substantially same shape, and wherein in the first cross-section of the optical film, the shape comprises one or more inflection points.
7. 7 . The optical film of claim 1 , wherein the optical film has opposite major surfaces having a substantially same shape, the shape comprising at least one saddle point.
8. 8 . The optical film of claim 1 , wherein for substantially normally incident light, each location on the optical film has a corresponding reflection band having a band edge wavelength, the band edge wavelength varying less than 15% along each of the first and second cross-sections.
9. 9 . A curved optical film generally lying in a base plane and having an average thickness of less than about 500 microns, and an average optical absorption of less than about 70% for substantially unpolarized substantially normally incident light in a predetermined wavelength range extending at least from 450 nm to 600 nm, a first cross-section of the optical film in a first plane perpendicular to the base plane having an actual first length AL 1 , a projected first length PL 1 on the base plane, and a first stretch ratio S 1 defined as (AL 1 −PL 1 )/PL 1 , a second cross-section of the optical film in a second plane perpendicular to the first and base planes having an actual second length AL 2 , a projected second length PL 2 on the base plane, and a second stretch ratio S 2 defined as (AL 2 −PL 2 )/PL 2 , 0.01<S 2 <0.7S 1 , the optical film having a maximum thickness variation in a range from about 0.05S 1 to about 0.8S 1 along each of the first and second cross-sections.
10. 10 . The optical film of claim 9 , wherein the maximum thickness variation is less than about 20% along each of the first and second cross-sections.
11. 11 . The optical film of claim 9 , wherein the second cross-section of the optical film has a maximum deviation D 2 from a straight line connecting opposing ends of the second cross-section, 0.1D 1 <D 2 <0.7D 1 .
12. 12 . The optical film of claim 9 , wherein the optical film has opposite major surfaces having a substantially same shape, and wherein in the first cross-section of the optical film, the shape comprises one or more inflection points.
13. 13 . The optical film of claim 9 , wherein the optical film has opposite major surfaces having a substantially same shape, the shape comprising at least one saddle point.
14. 14 . The optical film of claim 9 , wherein for substantially normally incident light, each location on the optical film has a corresponding reflection band having a band edge wavelength, the band edge wavelength varying less than 15% along each of the first and second cross-sections.
15. 15 . A stretched and shaped optical film stretched and shaped along at least mutually orthogonal directions and having an average optical absorption of less than about 70% for substantially unpolarized substantially normally incident light in a predetermined wavelength range extending at least from 450 nm to 600 nm, such that when the optical film is placed on a flat surface, a first cross-section of the optical film in a first plane perpendicular to the flat surface has a maximum deviation D 1 from a straight line connecting opposing ends of the first cross-section, the first plane chosen to maximize D 1 , a second cross-section of the optical film in a second plane perpendicular to the first plane and the flat surface has a maximum deviation D 2 from a straight line connecting opposing ends of the second cross-section, the second plane chosen to maximize D 2 , 0.1D 1 <D 2 <0.7D 1 , the optical film having a maximum thickness variation of less than about 15% along each of the first and second cross-sections.
16. 16 . The optical film of claim 15 , wherein in the first cross-section, the optical film has an actual first length AL 1 , a projected first length PL 1 on the flat surface, and a first stretch ratio S 1 defined as (AL 1 −PL 1 )/PL 1 , S 1 ≥0.1, and in the second cross-section, the optical film has an actual second length AL 2 , a projected second length PL 2 on the flat surface, and a second stretch ratio S 2 defined as (AL 2 −PL 2 )/PL 2 , 0.01≤S 2 <0.7S 1 .
17. 17 . The optical film of claim 16 , wherein the first cross-section of the optical film has a maximum slope M relative to the flat surface, 0.2*PL 1 *M≥D 1 ≥0.05*PL 1 .
18. 18 . The optical film of claim 15 , wherein the optical film has opposite major surfaces having a substantially same shape, and wherein in the first cross-section of the optical film, the shape comprises one or more inflection points.
19. 19 . The optical film of claim 15 , wherein the optical film has opposite major surfaces having a substantially same shape, the shape comprising at least one saddle point.
20. 20 . The optical film of claim 15 , wherein for substantially normally incident light, each location on the optical film has a corresponding reflection band having a band edge wavelength, the band edge wavelength varying less than 15% along each of the first and second cross-sections.

Description

BACKGROUND An optical film can be thermoformed into a shaped optical film having a thickness that varies as a result of the thermoforming process. SUMMARY In some aspects of the present description, a curved optical film generally lying in a base plane and having an average thickness of less than about 500 microns, and an average optical absorption of less than about 70% for substantially unpolarized substantially normally incident light in a predetermined wavelength range extending at least from 450 nm to 600 nm is provided. A first cross-section of the optical film in a first plane perpendicular to the base plane has an actual first length AL1, a projected first length PL1 on the base plane, and a first stretch ratio S1 defined as (AL1−PL1)/PL1, where S1≥0.1. A second cross-section of the optical film in a second plane perpendicular to the first and base planes has an actual second length AL2, a projected second length PL2 on the base plane, and a second stretch ratio S2 defined as (AL2−PL2)/PL2, where 0.01≤S2<0.8S1. The optical film has a maximum thickness variation of less than about 20% along each of the first and second cross-sections. In some embodiments, 0.02≤S2<0.8S1. In some embodiments, the optical film has a maximum thickness variation of less than about 15% along each of the first and second cross-sections. In some embodiments, the optical film has a maximum thickness variation in a range from about 0.2S1 to about 0.8S1 along each of the first and second cross-sections. In some aspects of the present description, a curved optical film generally lying in a base plane and having an average thickness of less than about 500 microns, and an average optical absorption of less than about 70% for substantially unpolarized substantially normally incident light in a predetermined wavelength range extending at least from 450 nm to 600 nm is provided. A first cross-section of the optical film in a first plane perpendicular to the base plane has an actual first length AL1, a projected first length PL1 on the base plane, and a first stretch ratio S1 defined as (AL1−PL1)/PL1. A second cross-section of the optical film in a second plane perpendicular to the first and base planes has an actual second length AL2, a projected second length PL2 on the base plane, and a second stretch ratio S2 defined as (AL2−PL2)/PL2, where 0.01<S2<0.7S1. The optical film has a maximum thickness variation in a range from about 0.05S1 to about 0.8S1 along each of the first and second cross-sections. In some embodiments, the optical film has a maximum thickness variation in a range from about 0.2S1 to about 0.8S1 along each of the first and second cross-sections. In some aspects of the present description, a stretched and shaped optical film stretched and shaped along at least mutually orthogonal directions and having an average optical absorption of less than about 70% for substantially unpolarized substantially normally incident light in a predetermined wavelength range extending at least from 450 nm to 600 nm is provided. When the optical film is placed on a flat surface, a first cross-section of the optical film in a first plane perpendicular to the flat surface has a maximum deviation D1 from a straight line connecting opposing ends of the first cross-section, where the first plane is chosen to maximize D1; and a second cross-section of the optical film in a second plane perpendicular to the first plane and the flat surface has a maximum deviation D2 from a straight line connecting opposing ends of the second cross-section, where the second plane chosen to maximize D2, and where 0.1D1<D2<0.7D1. The optical film has a maximum thickness variation of less than about 15% along each of the first and second cross-sections. In some aspects of the present description, a stretched and shaped optical film stretched and shaped along orthogonal first and second directions and comprising a plurality of polymeric layers, each layer less than about 500 nm thick is provided. When the optical film is laid on a flat surface, a first cross-section of the optical film in a first plane parallel to the first direction and perpendicular to the flat surface has an actual first length AL1, a projected first length PL1 on the flat surface, and a first stretch ratio S1 defined as (AL1−PL1)/PL1, where S1≥0.15; and a second cross-section of the optical film in a second plane parallel to the second direction and perpendicular to the flat surface has an actual second length AL2, a projected second length PL2 on the flat surface, and a second stretch ratio S2 defined as (AL2−PL2)/PL2, where 0.01≤S2<S1. For substantially normally incident light, each location on the optical film has a corresponding reflection band having a band edge wavelength, the band edge wavelength varying less than 15% along each of the first and second cross-sections. In some aspects of the present description, a method of forming a stretched and shaped optical film is provided. The meth