Process for Making Angstrom Scale and High Aspect Functional Platelets

Abstract

A process for making functional or decorative flakes or platelets economically and at high production rates comprises applying a multi-layer sandwich of vapor deposited metal and release coats in alternating layers to a rotating chilled drum or suitable carrier medium contained in a vapor deposition chamber. The alternating metallized layers are applied by vapor deposition and the intervening release layers are preferably solvent soluble thermoplastic polymeric materials applied by vapor deposition sources contained in the vapor deposition chamber. The multi-layer sandwich built up in the vacuum chamber is removed from the drum or carrier and treated with a suitable organic solvent to dissolve the release coating from the metal in a stripping process that leaves the metal flakes essentially release coat free. The solvent and dissolved release material are then removed by centrifuging to produce a cake of concentrated flakes which can be air milled and let down in a preferred vehicle and further sized and homogenized for final use in inks, paints or coatings. In one embodiment the finished flakes comprise single-layer thin metal or metal alloy flakes or flakes of inorganic materials, and in another embodiment flakes are coated on both sides with protective polymeric coatings that were applied from suitable vacuum deposition sources or the like contained in the vapor deposition chamber.

1 . Apparatus for making nanoscale flakes comprising:
 a vacuum deposition chamber containing a deposition surface;   a release coat source and a flake deposition source in the vacuum deposition chamber each directed toward the deposition surface;   in which the release coat source and the flake deposition source are controllable and adapted for depositing on the deposition surface under vacuum in alternating layers a vaporized dissolvable polymeric release coat layer from the release coat source and vapor deposited discrete islands of flake material from the flake deposition source to build up in sequence a multi-layer vapor deposit of flake material layers comprising discrete islands of the flake material separated by and deposited on corresponding intervening dissolvable release coat layers;   the release coat layers comprising a polymeric material for being vaporized under vacuum to form a smooth continuous solvent soluble and dissolvable barrier layer and support surface on which each of the layers of flake material is formed;   the multi-layer vapor deposit comprising discrete islands of flake material on dissolvable polymeric release coat layers for being removable from the vacuum deposition chamber and adapted for separating the vapor deposit into nanoscale flake particles by treatment with a solvent which dissolves the release coat layers and yields nanoscale flakes with smooth, flat surfaces which are essentially free of the release coat material.   
     
     
         2 . Apparatus according to  claim 1  in which the flake layer comprises a vapor-deposited material selected from the group consisting of metal in elemental form, an inorganic material, and a non-metal; and in which the non-metal comprises silicon monoxide, silicon dioxide, or a polymeric material; in which the inorganic material is selected from the group consisting of magnesium fluoride, silicon monoxide, silicon dioxide, aluminum oxide, aluminum fluoride, indium tin oxide, titanium dioxide and zinc sulfide; and in which the metal is selected from the group consisting of aluminum, copper, silver, chromium, indium, nichrome, tin and zinc. 
     
     
         3 . Apparatus according to  claim 1  in which the flake deposition source deposits the flake material layers to a flake (discrete island) thickness of less than about 100 nanometers. 
     
     
         4 . Apparatus according to  claim 1  in which the release coat layer comprises a thermoplastic polymeric material. 
     
     
         5 . Apparatus according to  claim 1  in which:
 a high energy radiation source is positioned in the vacuum deposition chamber and directed toward the deposition surface; 
 the release coat layers comprise a polymeric material of low crosslink density adapted for being vapor deposited on the deposition surface and cured and crosslinked by exposure to the radiation source, forming a release coat layer which is dissolvable in a solvent and which, when vaporized under vacuum and cured, forms the barrier layer and support surface on which each of the flake material layers is formed; and 
 the multi-layer vapor deposit is removable from the vacuum chamber for being separated it into flakes by treatment with the solvent which dissolves the release coat layers and yields single layer flakes which are essentially free of the release coat material. 
 
     
     
         6 . Apparatus according to  claim 1  in which the polymeric release coat material is melted outside the vacuum chamber and delivered to the chamber where the release coat source comprises a heating device which vaporizes the release coat material, and in which the vaporized release coat material is conveyed to the deposition surface and deposited thereon to form said release coat layer; and in which the flake deposition source comprises a thermal source in the vacuum chamber for evaporating the flake material. 
     
     
         7 . Apparatus according to  claim 6  including a differential pressure area produced adjacent the heating device and the deposition surface to prevent the escape of vapor toward the thermal source. 
     
     
         8 . Apparatus according to  claim 1  in which the flake deposition source deposits the flake material layers to a film thickness from about 5 to about 500 angstroms. 
     
     
         9 . Apparatus according to  claim 1  in which the release coat source comprises a wire feed mechanism in which the polymeric release coat material is coated onto a wire fed to the vacuum chamber and evaporated under heat therein to be deposited as said release coat layer. 
     
     
         10 . Apparatus according to  claim 9  in which the wire feed mechanism delivers the coated release coat material to a heater block positioned adjacent the deposition surface for evaporating the release coat material. 
     
     
         11 . Apparatus according to  claim 1  in which the release coat source comprises a heater block positioned adjacent the deposition surface and a carrier for delivering the release coat material to the heater block; and in which the flake deposition source comprises a thermal source for evaporating the flake material and directing it toward the deposition surface.