Patent ID: 11927783
Assignee: 3M INNOVATIVE PROPERTIES COMPANY
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 9:
10. An optical film comprising a plurality of alternating first and second polymeric layers numbering between 200 and 500,
each first and second polymeric layer having an average thickness less than about 500 nm, for each pair of adjacent first and second polymeric layers:
the first layer has an index n1x along a first axis in a plane of the optical film, an index of refraction my along an orthogonal second axis in the plane of the optical film, and an index n1z along a z-axis orthogonal to the first and second axes; and
the second layer has an index n2x along the first axis, an index of refraction n2y along the second axis, and an index n2z along the z-axis, such that for at least one wavelength in a predetermined wavelength range extending at least from about 450 nm to about 600 nm:
a maximum difference between n1x, my and n1z is less than about 0.002; and
a difference between n2x and n1x is greater than about 0.2;

such that for a substantially normally incident light having the at least one wavelength in the predetermined wavelength range, the plurality of alternating first and second polymeric layers has an average optical reflectance Rs for a first polarization state along the first axis, and an average optical transmittance Tp and an average optical reflectance Rp for a second polarization state along the second axis, Tp≥80%, Rp≤0.25%, and 80%≤Rs≤95%.