Optical properties of oriented polymer/dye polarizers

Abstract

A theoretical framework is presented to describe the optical properties of polarizers produced by tensile deformation of semicrystalline polymers containing dichroic dyes. In the model it is assumed that orientation of both the host polymer and guest molecule occurs in the f f i e mode. The development of optical anisotropy with Orientation is described using an aggregate model. The theory is employed to evaluate the optical Characteristics of the polarizers, i.e., dichroic ratio, order parameter, polarizing efficiency, and single-piece transmittance. Good agreement is observed between theoretical predictions and experimental data produced in this work on oriented linear polyethylendSudan Red polarizing films. It is shown that the model is useful to estimate the limiting polarizing efficiency and single-piece transmittance of the polarizing films at hand. IntroductionSeveral processes exist for the production of polymeric sheet polarizers, chiefly for use in the visible wavelength range.i-9 These polarizers are widely employed in, for instance, liquid-crystalline display applications. In most of the aforementioned processes, semicrystalline polymers, such as poly(viny1 alcohol) and polyolefins, are oriented by tensile drawing at temperatures close to, but below, the melting temperature of the p~l y m e r ; l -~ dichroic chromophores are introduced in the oriented films either by chemical modification of the polymer or by incorporation of dichroic dyes in the films prior to or

Stretched Polyethylene Films Probed by Single Molecules

“…Aligned dopant molecules in stretched PE have mostly been studied in order to determine the directions of transitiondipole moments of various electronic transitions. [12][13][14][15][16] The process of orienting solute molecules in PE by stretching has been described as an interplay between macroscopic (film deformation) and microscopic (partial alignment along certain defined axes) perturbations. [11] Generally speaking, models explaining the orienting process are based upon (1) molecular shapes/ cross-sections, (2) polarizability, or (3) epitaxial deposition/crystallization.…”

Effect of the dispersion of the chromophore on the optical performances of polarizers from polyethylene and 5”-thio- (3-butyl)nonyl-2,2’:5’,2”-terthiophene

“…The optical polarizing properties and performances were then evaluated by calculating the dichroic ratio (R), the order parameter (S), the polarization efficiency (PE) and the single piece transmittance [15].…”

Optical anisotropy and photostability of polarizing films dyed with Brilliant Yellow

“…The transmission coefficient (T 0 ), which is related to the optical density (D 0 ) by the expression D 0 = -log T 0 , was measured first for one sample and then for both samples with the orientation axes of the film parallel (D par , T par ) and crossed (D cr , T cr ). The spectral properties of an anisotropic film are characterized by the optical density (D , D ) and the transmission coefficient (T , T ), which are described by the expressions [5]:…”

“…The characteristics of the optical properties of the polarizer are the transmission of a single film (T 0 ), the polarizing power (PP), the dichroic ratio (DR) which is a measure of the optical anisotropy of the polarizing film, and an orientational parameter (S) which characterizes the degree of ordering of the dye molecules in the polymer [5,6]. The first two parameters are calculated from the equations:…”