Multilayer optical film with antistatic additive

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 . An article, comprising: 
 a multilayer optical film composed of alternating coextruded polymer layers, at least one of the polymer layers being birefringent; and    an antistatic additive incorporated into the multilayer optical film.    
   
   
       2 . The article of  claim 1 , wherein one of the coextruded polymer layers is a skin layer, and the antistatic additive is disposed in the skin layer.  
   
   
       3 . (canceled)  
   
   
       4 . The article of  claim 1 , wherein the antistatic additive comprises salts of sulfonic acid polymers.  
   
   
       5 . The article of  claim 1 , wherein the multilayer optical film is a polarizing film.  
   
   
       6 . The article of  claim 1 , wherein the multilayer optical film is a mirror film.  
   
   
       7 . An article, comprising: 
 a multilayer optical film composed of alternating coextruded polymer layers, at least one of the polymer layers being birefringent; and    an antistatic additive coated onto the multilayer optical film.    
   
   
       8 . The article of  claim 7 , wherein the article includes a coating applied to the multilayer optical film, and the antistatic additive is disposed in the coating.  
   
   
       9 . (canceled)  
   
   
       10 . The article of  claim 7 , wherein the antistatic additive comprises salts of sulfonic acid polymers.  
   
   
       11 . The article of  claim 7 , wherein the multilayer optical film is a polarizing film.  
   
   
       12 . The article of  claim 7 , wherein the multilayer optical film is a mirror film.  
   
   
       13 . A method for making an article, comprising: 
 (a) making a multilayer optical film having alternating polymeric layers formed by coextrusion; and    (b) incorporating an antistatic additive into the multilayer optical film.    
   
   
       14 . The method of  claim 13 , wherein the step of making the multilayer optical film includes providing the multilayer optical film with at least one skin layer, and wherein the incorporating step includes incorporating the antistatic additive into the at least one skin layer.  
   
   
       15 . The method of  claim 13 , wherein the step of making the multilayer optical film includes forming a cast multilayer web having the alternating polymeric layers, and stretching the cast multilayer web along at least one axis to orient at least some of the alternating polymeric layers.  
   
   
       16 . The method of  claim 15 , wherein the stretching step stretches the multilayer web substantially uniaxially to form a reflective polarizing film.  
   
   
       17 . The method of  claim 15 , wherein the stretching step stretches the multilayer web substantially biaxially to form a mirror film.  
   
   
       18 . The method of  claim 13 , wherein the step of making a multilayer optical film includes at least: 
 (1) providing at least a first and a second stream of resin;    (2) providing a feeder tube plate having a first plurality of conduits, and having a second plurality of conduits interleaved with the first plurality of conduits;    (3) feeding the first stream into the first plurality of conduits and the second stream into the second plurality of conduits;    (4) 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;    (5) 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    (6) heating the first and second streams of resin with at least one axial rod heater.    
   
   
       19 . The method of  claim 18 , further comprising: 
 (7) positioning the at least one axial rod heater proximate the first and second plurality of conduits.    
   
   
       20 . The method of  claim 18 , further comprising: 
 (7) positioning the at least one axial rod heater between the first and second plurality of conduits.    
   
   
       21 . The method of  claim 18 , further comprising: 
 (7) varying temperature of the at least one axial rod heater in zones along a length of the axial rod heater.    
   
   
       22 . The method of  claim 18 , wherein the heating step comprises heating with a plurality of axial rod heaters.  
   
   
       23 . The method of  claim 22 , wherein the heating step 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.  
   
   
       24 . The method of  claim 18 , further comprising after step (4): 
 (7) passing the composite stream into a multiplier where the composite stream is divided into a plurality of substreams, the multiplier expanding at least one of the substreams in a direction transverse to its direction of flow; and    (8) recombining the substreams to increase the number of layers in the composite stream.    
   
   
       25 . The method of  claim 18 , further comprising: 
 (7) casting the multilayer web onto a casting roll to form a cast multilayer film.    
   
   
       26 . The method of  claim 25 , further comprising: 
 (8) quenching said multilayer web during the casting step.    
   
   
       27 . The method of  claim 25 , wherein the casting step includes micro-embossing a surface of the multilayer web.