Method of manufacturing a diffusely-reflecting polarizer having a substantially amorphous nano-composite continuous phase

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 a substantially amorphous nano-composite material, and a second polymer, the first polymer being a major phase, and the second polymer being a dispersed minor phase, 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 2s , 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, stretch ratio for the process and Tg, and refractive index of the first and second polymers are selected to satisfy the equations: (1) R 1d is greater than R 1s ; and (2) T 2t / (1-0.5(R 1t +R 2t ))>1.35.

Description

technical field [0001] The present invention relates to a method of making a diffuse reflective polarizer comprising a film having a first polymer dispersed in the first polymer, the first polymer being substantially non- Crystalline nanocomposites are almost isotropic materials. technical background [0002] A reflective polarizing film transmits light of one polarization and reflects light of a polarization perpendicular to that polarization. They are used in LCDs to enhance light efficiency. A series of films have been disclosed to achieve the effect of reflective polarizing films, among them, diffuse reflective polarizers are the most attractive because their use eliminates the need for diffusers in LCDs, which reduces the LCD's performance. Complexity. U.S. Patent No. 5,783,120 teaches a diffusely reflective polarizing film comprising a film comprising an immiscible mixture having a first continuous phase (also referred to herein as the The proportion of the mixture...

AI Technical Summary

Problems solved by technology

But optical films made of polymers filled with inorganic dopants suffer from a series of problems

Typically poor adhesion between inorganic particles and polymer matrix

Consequently, the optical properties of the film degrade when stress or strain is applied to the matrix, both because the bond between the matrix and the dopant is compromised and because the rigid inorganic dopant may fragment

Additionally, inorganic dopant orientation requires processing steps and considerations that complicate production

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