Method of making a privacy film

Abstract

A method of making a privacy film includes generally the following steps: providing a polymeric material, depositing the polymeric material onto a microstructured mold comprising a plurality of substantially parallel, elongated channels with specific geometry; inducing the polymeric material to flow into the channels of the microstructured mold; solidifying the polymeric material inside the channels to yield a plurality of light directing elements that are connected with one another via a polymeric base sheet; and separating the privacy film from the microstructured mold.

1 . A method of making a privacy film comprising the steps of: 
 providing a polymeric material;    depositing the polymeric material onto a microstructured mold comprising a plurality of substantially parallel, elongated channels, wherein each channel is slanted and is separated from the next channel by a land region, wherein each channel has a base disposed adjacent to and a tip disposed distal to the land region, wherein each channel has a minor axis that runs from the base to the tip;    inducing the polymeric material to flow into the channels of the microstructured mold;    solidifying the polymeric material inside the channels to yield a plurality of light directing elements that are connected with one another via a polymeric base sheet having a first surface from which the light directing elements protrude and an opposing second substantially planar surface; and    separating the privacy film from the microstructured mold.    
   
   
       2 . The method of  claim 1 , wherein the channels of the microstructured mold are tapered at their tips.  
   
   
       3 . The method of  claim 1 , wherein the polymeric material is a thermoplastic polymer.  
   
   
       4 . The method of  claim 3 , wherein the thermoplastic polymer is selected from the group consisting of polypropylene, polyethylene, polystyrene, polycarbonate, polymethyl methacrylate, ethylene vinyl acetate copolymers, acrylate-modified ethylene vinyl acetate polymers, ethylene acrylic acid copolymers, nylon, polyvinylchloride, and combinations thereof.  
   
   
       5 . The method of  claim 1 , wherein the polymeric material comprises a light reflecting material.  
   
   
       6 . The method of  claim 5 , wherein the light reflecting material is selected from the group consisting of titanium dioxide, zinc oxide, zinc sulfide, zinc phosphate, calcium carbonate, alumina, silica, antimony oxide, barium sulfate, lithopene, calcined kaolin, lead carbonate, magnesium oxide, and combinations thereof.  
   
   
       7 . The method of  claim 6 , wherein privacy film comprises less than 20% by weight of the light reflecting material, based on the total weight of the film.  
   
   
       8 . The method of  claim 1 , wherein each channel has a height h, which is the distance from its base to its tip along its minor axis, and two adjacent channels have a center-to-center spacing P, and wherein the ratio of h to P is from about 0.5 to 5.  
   
   
       9 . The method of  claim 1 , wherein two adjacent channels are placed such that the tip of one channel, as viewed from an imaginary line normal to the land region, overlaps the base of the adjacent channel.  
   
   
       10 . The method of  claim 1 , wherein the polymeric material is molten resin.  
   
   
       11 . The method of  claim 10 , wherein the inducing step comprises heating the microstructured mold.  
   
   
       12 . The method of  claim 1 , wherein the polymeric material is a liquid resin or a thermoplastic film.  
   
   
       13 . The method of  claim 12 , wherein the inducing step comprises applying heat and pressure to the liquid resin.  
   
   
       14 . The method of  claim 1 , wherein the separating step results in substantially no distortion on the light directing elements of the privacy film.  
   
   
       15 . The method of  claim 1  further comprising laminating a light transmissive adhesive to the second surface of the polymeric base sheet.  
   
   
       16 . The method of  claim 1 , wherein the light transmissive adhesive is a repositionable pressure sensitive adhesive.  
   
   
       17 . The method of  claim 1 , wherein the channels of the microstructured mold are slanted at an angle greater than about 15° and less than about 90°, the angle being formed between the intersection of the minor axis of the channel and a line lying in the plane of the land region.  
   
   
       18 . The method of  claim 1 , wherein two adjacent channels are placed such that the tip of one channel, as viewed from an imaginary line normal to the land region, is coincident with the base of the adjacent channel.  
   
   
       19 . The method of  claim 1  further comprising applying a light absorbing coating to a top portion of the light directing elements.  
   
   
       20 . The method of  claim 1 , wherein the polymeric material comprises a light absorbing material.  
   
   
       21 . The method of  claim 1 , wherein the polymeric material comprises light absorbing and light reflecting materials.  
   
   
       22 . The method of  claim 1 , wherein the polymeric material comprises at least two layers, wherein a first layer is substantially free of light absorbing and light reflecting materials, and wherein a second layer comprises light absorbing material, light reflecting materials, or a combination thereof.