Method and apparatus for forming microstructures on polymeric substrates

Abstract

Methods and apparatus for forming microstructures in the surface of polymeric web materials for use as optical memory substrates. The microstructures may be formed by laminating a hot stamper to a web of material with a selective time/temperature profile. The stamper may be heated to melt flow the surface of the web and stabilize before separation. The stamper may be carried by a support that is independent of the press. The web of polymeric material may be provided with a flow enhancer to improve image formation. Also described herein are methods and apparatus for making optical memory modules, such as disks, which include novel stampers, coating applicators, and finishing systems.

What is claimed is:  
     
         1 . A method of forming microstructures on the surface of polymeric material comprising the steps of: 
 providing a web of polymeric material; and    melt forming the surface of the web with a heated stamper.    
     
     
         2 . The method of  claim 1 , wherein the stamper is heated by induction heating.  
     
     
         3 . The method of  claim 1 , wherein the web of polymeric material includes a flow enhancer.  
     
     
         4 . The method of  claim 1 , wherein the web of polymeric material includes water in an amount sufficient to enhance surface flow during melt forming.  
     
     
         5 . The method of  claim 1 , wherein the temperature change of the heated stamper is 50° C. or less.  
     
     
         6 . The method of  claim 1 , wherein the stamper contact time with the material being formed is 300 milliseconds or less.  
     
     
         7 . The method of  claim 1 , wherein the stamper that has a lower coefficient of thermal expansion than nickel.  
     
     
         8 . The method of  claim 1 , wherein melt forming includes contacting the web with the stamper between a set of drums and the stamper is carried by a support that is detached from said drums.  
     
     
         9 . The method of  claim 1 , wherein the temperature of the heated stamper is above the melt flow temperature (Tf) of the polymeric material when contacting the web.  
     
     
         10 . The method of  claim 9 , further comprising the step of separating the stamper from the web when the surface of the web is at a temperature at or below the melt flow temperature (Tf) of the polymeric material.  
     
     
         11 . The method of  claim 9 , further comprising the step of separating the stamper from the web when the surface of the web is at a temperature below the melt flow temperature (Tf) but above the glass transition temperature (Tg) of the polymeric material.  
     
     
         12 . The method of  claim 1 , further including the step of heating the web on the side opposite of the stamper during forming.  
     
     
         13 . The method of  claim 1 , wherein forming includes contacting the web with a stamper between a set of drums, the drum on the web side is provided at a temperature sufficient to counter annealing from the stamper.  
     
     
         14 . The method of  claim 13 , wherein the drum on the web side is provided at a temperature below the peak process temperature.  
     
     
         15 . The method of  claim 1 , wherein forming includes contacting the web with a stamper between a set of drums, at least one of the drums having a compliant outer surface with a hardness of 80 shore D or less.  
     
     
         16 . A method of forming microstructures on the surface of polymeric material comprising the steps of: 
 providing a web of polymeric substrate; and    forming microstructures on a surface of the polymeric material with an inductively heated stamper.    
     
     
         17 . A method of forming microstructures on the surface of a web of polymeric material, comprising the steps of: 
 providing a web of polymeric material with a surface having a flow enhancer; and    forming microstructures on the surface with a heated stamper.    
     
     
         18 . The method of  claim 17 , wherein the surface flow enhancer comprises a fatty ester or fatty acid  
     
     
         19 . A method of forming microstructures on the surface of a web of polymeric material, comprising the steps of: 
 providing a web of polymeric material having a surface region with water; and    forming microstructures in the surface region with a heated stamper.    
     
     
         20 . The method of  claim 19 , wherein water is provided in an amount sufficient to lower Tf below that for dry material.  
     
     
         21 . The method of  claim 19 , wherein water is provided in an amount sufficient to enhance surface flow during forming, but less than an amount that produces substantial bubble formation.  
     
     
         22 . The method of  claim 19 , wherein water is 0.1% to 0.4% by weight of the polymeric material.  
     
     
         23 . The method of  claim 19 , wherein water is provided from the surface to the depth of 10 μm.  
     
     
         24 . The method of  claim 19 , wherein water is provided from the surface to a depth of 3 μm.  
     
     
         25 . The method of  claim 19 , wherein the water is provided to a depth of at least 0.003 μm.  
     
     
         26 . A method of making a stamper for use in a continuous web forming process comprising the steps of: 
 providing a stamper with a transferable image;    curving the stamper; and    increasing the thickness of the stamper.    
     
     
         27 . A method of forming microstructures on the surface of polymeric material comprising the steps of: 
 providing a web of polymeric material; and    forming microstructures on the surface of the polymeric material with a hot stamper and a short contact time so that the temperature change in the hot stamper during forming is 50° C. or less.    
     
     
         28 . The method of  claim 27 , wherein the temperature change is 25° C. or less.  
     
     
         29 . The method of  claim 27 , wherein the temperature change is 10° C. or less.  
     
     
         30 . The method of  claim 27 , wherein the stamper/material contact time is 300 milliseconds or less.  
     
     
         31 . A method of forming microstructures on the surface of polymeric material with a hot stamper comprising the steps of: 
 providing a web of polymeric material; and    forming microstructures on a surface of the polymeric material with a stamper that has a lower coefficient of thermal expansion than nickel.    
     
     
         32 . An apparatus for forming microstructures on the surface of polymeric material for use in optical memory comprising: 
 a web feed;    a device for web forming, the device for web forming having a stamper and a set of rollers which form a nip zone in communication with the web feed, the stamper being carried by a support that is detached from the rollers.    
     
     
         33 . The apparatus of  claim 32 , wherein the support includes a carriage for independently carrying the stamper through the nip zone.  
     
     
         34 . The apparatus of  claim 33 , wherein one of the rollers is a backing roller for pressing the stamper into the web and the carriage includes a set of rigid hoops for supporting the stamper, the hoops having a diameter larger than that of the backing roller.  
     
     
         35 . The apparatus of  claim 34 , wherein the ratio of the diameter of each hoop to the diameter of backing roller is at least 5:4.  
     
     
         36 . The apparatus of  claim 34 , wherein the ratio of the diameter of each hoop to the diameter of backing roller is at least 13:8.  
     
     
         37 . An apparatus for use in making optical memory comprising: 
 a web feed;    a stamper for forming polymeric material, the stamper being carried on a loop and in communication with the web feed;    a web cutter for sectioning web material after forming; and    a collector for accumulating sections of web material after cutting.    
     
     
         38 . The apparatus of  claim 37 , wherein the collector includes a removable cassette for receiving sections of web material after cutting.  
     
     
         39 . A method of forming microstructures on the surface of polymeric material for use in optical memory comprising the steps of: 
 providing a roll of polymeric web material with a removable layer of softer material; and    forming the web with a heated stamper; and    re-rolling the formed polymeric material.    
     
     
         40 . An apparatus for use in making optical memory comprising: 
 a web feed;    a stamper for forming polymeric material, the stamper being carried on a loop and in communication with the web feed;    a web cutter for segmenting web material after forming;    an accumulator for receiving sections of web material after cutting;    an indexer for making registration holes in sections of web material;    a masking station for covering sections of web material after forming for coating; and    at least one coating applicator for applying a thin film to sections of web material after masking.    
     
     
         41 . A web sectioning station for use in making optical memory from a continuous web process comprising: 
 a platform for supporting sections of formed web material;    a plurality of optical positioning sensors for centering the image of formed web material on a die path; and    a die for cutting web supported on the platform.    
     
     
         42 . A method of forming microstructures on the surface of polymeric material for use in optical memory, the method comprising the steps of: 
 providing a web of polymeric material;    providing a heated stamper; and    pressing the heated stamper and the substrate between a set of nip rollers, wherein at least one of the nip rollers has a compliant outer surface with a hardness of 80 shore D or less.    
     
     
         43 . The method of claim  42 , wherein the compliant outer surface has a hardness of 90 shore A to 60 shore D and a thickness of 0.05 to 0.5 inches.