Process and apparatus for fabricating precise microstructures and polymeric molds for making same

Abstract

There is disclosed a method and apparatus for producing a polymeric film that accurately replicates a complex mold surface at least a portion of which surface has microstructured or nano-structured dimensions. A polymeric powder is electrodeposited on an underlying mold surface. Then the powder is cured to create a polymeric film. Finally the film is removed from the mold surface.

1 . A method of producing a polymeric film that accurately replicates a complex mold surface at least a portion of which surface has microstructured or nano-structured dimensions, comprising the steps of: 
 (a) electrodepositing a polymeric powder on an underlying mold surface;    (b) curing the powder to create a polymeric film; and    (c) removing the polymer film.    
     
     
         2 . The method of  claim 1 , wherein the polymeric powder comprises either a thermosetting resin or a thermoplastic resin.  
     
     
         3 . The method of  claim 2 , wherein the thermoplastic resin comprises one or more of: acrylic, polycarbonate, polyester, urethane, nylon, polypropylene, polyethylene, polyvinylchloride or silicones.  
     
     
         4 . The method of  claim 2 , wherein the thermosetting resin is one of the following: functional epoxy, epoxy-polyester, silicone and UV curable polymer.  
     
     
         5 . The method of  claim 1 , wherein the polymeric powder comprises essentially a commercially pure material.  
     
     
         6 . The method of  claim 1 , wherein the polymeric powder consists essentially of a commercial pure material without any additives.  
     
     
         7 . The method of  claim 1 , wherein the polymeric powder includes a further phase or filler material.  
     
     
         8 . The method of  claim 1 , wherein said film is formed continuously by electrodepositing the powder onto a moving mold surface.  
     
     
         9 . The method of  claim 1 , wherein the underlying mold is itself formed of a polymeric material made by electrodepositing a powder against an underlying substrate having the desired complex pattern formed therein.  
     
     
         10 . The method of  claim 9 , wherein the polymeric powder used to form said mold has a higher melting point than the polymeric material used to form said film.  
     
     
         11 . The method of  claim 1 , and comprising the further step of adhering said film to a further film of polymeric material.  
     
     
         12 . The method of  claim 11 , wherein said further film has a different composition and different properties than said first-mentioned film.  
     
     
         13 . The method of  claim 11 , wherein said further film is adhered in a continuous fashion to said first-mentioned film.  
     
     
         14 . The method of  claim 11 , wherein said further film is made of a material harder than said first-mentioned film.  
     
     
         15 . The method of  claim 11 , wherein said further film is adhered by electrodepositing a polymeric powder material to said first-mentioned film and then curing said further film.  
     
     
         16 . The method of  claim 15 , wherein the thickness of said first-mentioned film is between 0.001 inch (25 microns) and 0.020 inch (500 microns) and the thickness of said further film is between 0.001 inch (25 microns and 0.020 inch (500 microns).  
     
     
         17 . The method of  claim 11 , wherein said first-mentioned film is a UV curable coating, hard thermoplastic such as nylon or polysufone, and the further film is made of polycarbonate, acrylic or polyurethane.  
     
     
         18 . The method of  claim 11 , wherein said further film is applied by either using a charged mold and powder coating or a coating knife or by coating rollers.  
     
     
         19 . The method of  claim 1 , wherein the particle size of said powder is sufficiently small so that the film is formed by filling the patterned recesses in said mold surface from the bottom up so as substantially to avoid any air entrapment.  
     
     
         20 . The method of  claim 19 , wherein said particle size is no greater than about 50 microns in maximum dimension.  
     
     
         21 . The method of  claim 19 , wherein said particle size is in the range of about 5-20 microns.  
     
     
         22 . The method of  claim 1 , wherein the mold surface is configured to provide throughholes or vias in the removed film.  
     
     
         23 . The method of  claim 22 , wherein said vias are formed by only partially filling the depth of the mold with the polymeric powder followed by the step of pressing a resilient layer of material to the surface of the deposited powder to press the powder layer to some uniform level, and then curing the powdered material to form said film.  
     
     
         24 . The method of  claim 1 , wherein the curing step is accomplished by either UV or radiation.  
     
     
         25 . The method of  claim 1 , wherein the thickness of said film is between 0.001 inch (25 microns) and 0.020 inch (500 microns).  
     
     
         26 . The method of  claim 1 , wherein said mold is formed of a polymeric material of a high glass transition temperature than the polymeric product to be formed against said mold.  
     
     
         27 . The method of  claim 1 , further comprising the step of laminating said film to a thicker flexible backing material, said laminated flexible material being usable as a mold to form complex microstructural surfaces.  
     
     
         28 . The method of  claim 1 , wherein said mold moves at a speed of between 50 and 100 ft./min.  
     
     
         29 . The method of  claim 1 , wherein the polymeric powder is obtained directly from a polymerizing process and without the need to grind a larger material to provide the powder.  
     
     
         30 . A method of making a polymer film having at least one area of complex pattern of recesses and raised areas above and below the plane of the film, with the pattern shapes including at least some of small macrostructure dimensions, comprising the steps of 
 (a) electrodepositing a polymeric powder into the facing areas of opposed mold faces defining the pattern shapes to be formed;    (b) transporting the opposing faces through a cure station where the powder is melted and then coated; and    (c) stripping the cured film from the opposing mold faces.    
     
     
         31 . The method of  claim 30 , wherein the electrodeposited powder is applied to a first mold face, the powder is heated to a flowable condition and a second mold face is applied to said molten powder from the opposite side thereof, thereby to provide the complex pattern on opposite sides of said film, and then curing and stripping said film from both mold faces.  
     
     
         32 . An article comprising a polymeric film having a portion which is a surface area of a complex array of microstructure of optically precise dimensions and wherein said article is formed by curing a powder which has been electrodeposited against a mold surface defining the shape of at least a portion of the article.  
     
     
         33 . The article of  claim 32 , wherein at least a portion of said array includes vias therethrough.  
     
     
         34 . The article of  claim 32 , wherein said article has at least a further layer of polymeric material adhered to said first-mentioned layer.  
     
     
         35 . The article of  claim 34 , wherein said further layer comprises a polymeric material of a different composition than said first polymeric layer.  
     
     
         36 . The article of  claim 34  wherein said further layer of polymer material is relatively rigid thereby to provide structural integrity to said article.  
     
     
         37 . The article of  claim 32 , wherein said article comprises a mold for the formation of additional articles.  
     
     
         38 . The article of  claim 32 , wherein said polymer material is comprised of a roll of continuous film having repeating sections of said complex array.  
     
     
         39 . The article of  claim 32 , wherein said mold is formed by assembling a plurality of said articles to provide a continuous flexible belt having a repeating pattern therein of said complex array.  
     
     
         40 . The article of  claim 32 , wherein said film has a flexible backing layer therein thicker than said first-mentioned layer to provide strength to said film.  
     
     
         41 . Apparatus for continuously producing a web of film having a complex microstructured or nano-structured pattern in at least a portion thereof, comprising: 
 (a) a mold having the microstructured or nano-structured pattern in a surface thereon;    (b) means for electrodepositing a polymeric powder onto said surface;    (c) means for effecting a cure of said powder to form a film having the desired microstructured or nano-structured pattern thereon; and    (d) means for facilitating removal of said film from said mold.    
     
     
         42 . The apparatus of  claim 41 , wherein said mold is of a polymeric material having a higher melt point than the film to be formed thereon.  
     
     
         43 . The apparatus of  claim 41 , wherein said mold is in the form of a continuous surface that passes the means for depositing said powder, thereby to produce said film on a continuous basis.  
     
     
         44 . The apparatus of  claim 43 , further including means for electrodepositing a further layer of powder to said first-mentioned layer and means for curing said further layer.  
     
     
         45 . The apparatus of  claim 43 , and further including means for laminating a further relatively stronger and rigid polymer layer of material to said first-mentioned layer to provide a relatively rigid polymeric article having the complex microstructure or nano-structure surface thereon.  
     
     
         46 . The apparatus of  claim 41  and further including a further mold having a pattern complementary to said first-mentioned mold pattern; means for engaging said further mold with said electrodeposited powder prior to curing same, whereby to produce a film having a pattern on both sides of the film.