Method of manufacturing a reflective polarizer

Abstract

The present invention provides a method for manufacturing a diffusely reflecting polarizer, comprising: extruding and stretching a 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, Tg, and refractive index and the stretch temperature and stretch ratio of the first and second polymers are selected to satisfy the equations: (1) R 1d is greater than R 1s ; and (2) T 2 t / ( 1 - 0.5 ( R 1 t + R 2 t) )> 1.35.

Description

technical field [0001] The present invention relates to a method of making a diffusely reflective polarizer comprising a film having a first polymer, and a second polymer dispersed in the first polymer, the first polymer being substantially amorphous Nanocomposite and almost isotropic materials. Background technique [0002] Reflective polarizing films transmit light of one polarization state and reflect light of the orthogonal polarization state. They can be used in LCDs to improve light efficiency. A number of films have been disclosed that perform the function of reflective polarizing films, among which diffuse reflective polarizers are more attractive because they eliminate the need for a diffuser in the LCD, thereby reducing the complexity of the LCD. U.S. Patent No. 5,783,120 describes a diffuse reflector diaphragm comprising a film containing an immiscible mixture having a first continuous phase (also referred to in this 50% by weight of the mixture) and a second d...

AI Technical Summary

Problems solved by technology

However, according to the '440 patent, only a very limited number of materials can be effectively used to make diffuse reflective polarizers

As such, the optical performance of diffuse reflective polarizers can be compromised due to the limited possibility to tune the optical properties, especially the refractive index and birefringence

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