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Abstract

The present invention provides a method for manufacturing a diffusely reflecting polarizer, comprising the steps of: coextruding first and second polymers through a chaotic mixer and a sheeting die to produce a cast sheet with a desired blend morphology and stretching said cast sheet to produce a composite film containing a first polymer having a birefringence of less than 0.02, with said first polymer being an amorphous material and a continuous phase, and a second polymer which forms a dispersed phase, and having an index of refraction that differs from said continuous phase by greater than about 0.05 along a first axis and by less than about 0.05 along a second axis orthogonal to said first axis, wherein said first and second polymers taken together along a first axis for one polarization state of electromagnetic radiation exhibit a diffuse reflectivity R_1d, a specular reflectivity R_1s, a total reflectivity R_1t, a diffuse transmittance T_1d, a specular transmittance T_1s, and a total transmittance T_1t, and along a second axis for another polarization state of electromagnetic radiation exhibit a diffuse reflectivity R_2d, a specular reflectivity R_2t, a total reflectivity R_2t, a diffuse transmittance T_2d, a specular transmittance T_2s, and a total transmittance T_2t, the said first and second axes being orthogonal, wherein the parameters of composition, chaotic mixing, stretch temperature and stretch ratio for the process and Tg, and refractive index of the first and second polymers are selected to satisfy the equations:

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First Claim