Optical film
First Claim
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1. A reflective mirror film, comprising:
- a first reflective polarizer having a first transmission axis and a first extinction axis, wherein the first reflective polarizer transmits light polarized parallel to the first transmission axis and reflects light polarized parallel to the first extinction axis; and
a second reflective polarizer having a second transmission axis aligned with respect to the first transmission axis and a second extinction axis aligned with respect to the first extinction axis, such that he second reflective polarizer reflects at least some of the light transmitted by the first reflective polarizer;
wherein the first and second reflective polarizers each comprise a plurality of layers, and further wherein at least two of the plurality of layers exhibit a refractive index difference between layers in a first in-plane direction that is greater than a refractive index difference between layers in a second in-plane direction.
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Abstract
Birefringent optical films have a Brewster angle (the angle at which reflectance of p-polarized light goes to zero) which is very large or is nonexistent. This allows for the construction of multilayer mirrors and polarizers whose reflectivity for p-polarized light decreases slowly with angle of incidence, are independent of angle of incidence, or increase with angle of incidence away from the normal. As a result, mirror films with high reflectivity in two different planes of polarization for any incident direction over a wide bandwidth can be achieved.
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Citations
15 Claims
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1. A reflective mirror film, comprising:
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a first reflective polarizer having a first transmission axis and a first extinction axis, wherein the first reflective polarizer transmits light polarized parallel to the first transmission axis and reflects light polarized parallel to the first extinction axis; and
a second reflective polarizer having a second transmission axis aligned with respect to the first transmission axis and a second extinction axis aligned with respect to the first extinction axis, such that he second reflective polarizer reflects at least some of the light transmitted by the first reflective polarizer;
wherein the first and second reflective polarizers each comprise a plurality of layers, and further wherein at least two of the plurality of layers exhibit a refractive index difference between layers in a first in-plane direction that is greater than a refractive index difference between layers in a second in-plane direction. - View Dependent Claims (2, 3)
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- 4. A mirror that substantially reflects light of two orthogonal polarizations, comprising a plurality of birefringent optical layers.
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