Method for making pen/pmma multilayer optical films

Abstract

Methods and apparatuses are provided for the manufacture of coextruded polymeric multilayer optical films. The multilayer optical films have an ordered arrangement of layers of two or more materials having particular layer thicknesses and a prescribed layer thickness gradient throughout the multilayer optical stack. The methods and apparatuses described allow improved control over individual layer thicknesses, layer thickness gradients, indices of refraction, interlayer adhesion, and surface characteristics of the optical films. The methods and apparatuses described are useful for making interference polarizers, mirrors, and colored films that are optically effective over diverse portions of the ultraviolet, visible, and infrared spectra.

1 . A method for making an article, comprising:
 making a multilayer optical film having alternating polymeric layers formed by coextrusion; and   incorporating an antistatic additive into the multilayer optical film;   wherein making the multilayer optical film comprises:
 providing at least a first stream of resin and a second stream of resin; 
 providing a feeder tube plate having a first plurality of conduits, and a second plurality of conduits interleaved with the first plurality of conduits; 
 feeding the first stream into the first plurality of conduits and the second stream into the second plurality of conduits; 
 providing a slot die for each of the first and second plurality of conduits such that the first and second streams are divided into a plurality of interleaved layers to yield a composite stream; 
 passing the composite stream through an extrusion die to form a multilayer web in which each layer is generally parallel to the major surface of adjacent layers; and 
 heating the first and second streams of resin with at least one axial rod heater. 
   
   
   
       2 . The method of  claim 1 , wherein making the multilayer optical film further comprises providing the multilayer optical film with at least one skin layer, wherein the antistatic additive is incorporated into the at least one skin layer. 
   
   
       3 . The method of  claim 1 , further comprising positioning the at least one axial rod heater proximate the first and second plurality of conduits. 
   
   
       4 . The method of  claim 1 , further comprising positioning the at least one axial rod heater between the first and second plurality of conduits. 
   
   
       5 . The method of  claim 1 , further comprising varying temperature of the at least one axial rod heater in zones along a length of the axial rod heater. 
   
   
       6 . The method of  claim 1 , wherein heating the first and second streams of resin comprises heating with a plurality of axial rod heaters. 
   
   
       7 . The method of  claim 6 , wherein heating the first and second streams of resin comprises heating with a first axial rod heater disposed proximate the first plurality of conduits and heating with a second axial rod heater disposed proximate the second plurality of conduits. 
   
   
       8 . The method of  claim 1 , further comprising casting the multilayer web onto a casting roll to form a cast multilayer film. 
   
   
       9 . The method of  claim 8 , further comprising quenching the multilayer web while casting the multilayer web onto the casting roll. 
   
   
       10 . The method of  claim 8 , wherein casting the multilayer web further comprises micro-embossing a surface of the multilayer web. 
   
   
       11 . The method of  claim 8 , further comprising stretching the cast multilayer web along at least one axis to orient at least some of the alternating polymeric layers. 
   
   
       12 . The method of  claim 11 , wherein stretching the cast multilayer web comprises substantially uniaxially stretching the cast multilayer web to form a reflective polarizing film. 
   
   
       13 . The method of  claim 11 , wherein stretching the cast multilayer web comprises substantially biaxially stretching the cast multilayer web to form a mirror film.