US 12,332,466 B2
Optical film
Ryan T. Fabick, Shoreview, MN (US); Matthew E. Sousa, Rosemount, MN (US); William B. Black, Eagan, MN (US); and Edward J. Kivel, Stillwater, MN (US)
Assigned to 3M INNOVATIVE PROPERTIES COMPANY, St. Paul, MN (US)
Appl. No. 17/274,309
Filed by 3M INNOVATIVE PROPERTIES COMPANY, St. Paul, MN (US)
PCT Filed Sep. 13, 2019, PCT No. PCT/IB2019/057744
§ 371(c)(1), (2) Date Mar. 8, 2021,
PCT Pub. No. WO2020/053832, PCT Pub. Date Mar. 19, 2020.
Claims priority of provisional application 62/731,325, filed on Sep. 14, 2018.
Prior Publication US 2021/0333455 A1, Oct. 28, 2021
Int. Cl. G02B 5/28 (2006.01)
CPC G02B 5/287 (2013.01) [G02B 5/282 (2013.01)] 10 Claims
OG exemplary drawing
 
1. An optical film comprising a plurality of alternating polymeric first and second layers disposed on a skin layer, each of the first and second layers having an average thickness less than about 250 nm, the skin layer having an average thickness greater than about 2 microns, an optical transmittance of the optical film for substantially normally incident light comprising a band edge separating first and second wavelength ranges, the first wavelength range extending at least from about 400 nm to about 700 nm, the second wavelength range extending at least from about 950 nm to about 1300 nm, such that for substantially normally incident light in air:
an optical reflectance of the optical film is greater than about 95% for each wavelength in the first wavelength range;
an average optical transmittance of the optical film is greater than about 80% in the second wavelength range; and
a difference between maximum and minimum values of the optical transmittance of the optical film in the second wavelength range is less than about 25%; and
a best linear fit to the band edge correlating the optical transmittance to wavelength at least across a wavelength range where the optical transmittance increases from about 10% to about 70% has a slope that is greater than about 2%/nm, wherein the first and second layers and the skin layer are formed integrally with one another,
wherein in planes of the first and second layers, the first and second layers having respective indices of refraction: n1x and n2x along a first polarization state, n1y and n2y along a second polarization state orthogonal to the first polarization state, and n1z and n2z along a z-axis orthogonal to the first and second polarization states, such that for at least one wavelength in at least one of the first and second wavelength ranges:
each of n1x and n1y is greater than n1z by at least 0.2;
a difference between n1x and n1y is less than about 0.04;
a maximum difference between n2x, n2y and n2z is less than about 0.01; and
a difference between n1x and n2x is greater than about 0.2.