Plasma surface treatment of silicone hydrogel contact lenses

Abstract

The present invention provides a method for treating a contact lens to provide an optically clear, hydrophilic coating upon the surface of a silicone hydrogel lens by subjecting the surface of the lens to a process comprising plasma treatment, hydration, and heat sterilization that is controlled to result in a silicate-containing film having a mosaic pattern of projecting plates surrounded by fissures when viewing a 50×50 micron square AFM image, wherein the peak-to-valley distances of the fissures are on average between about 100 and 500 angströms and the plate coverage is on average between about 40% to 99%.

1 . A method for treating the surface of a silicone hydrogel contact lens by a controlled manufacture comprising the following steps: 
 (a) plasma treating the lens with an oxygen-containing atmosphere for more than 4 minutes per side, at a wattage of 100 to 1000 watts and a pressure of 0.1 to 1.0 torr, to produce a silicate-containing coating,    (b) hydrating the lens by immersing the lens in an aqueous solution, whereby the amount of water absorbed by the lens is at least five percent by weight of the lens material,    (c) subjecting the hydrated lens to heat sterilization, 
 whereby the heat sterilized lens has a silicate-containing coating characterized by a mosaic pattern of projecting plates surrounded by receding fissures when viewing a 50×50 square micron AFM image, wherein the depth of the fissures is on average between about 100 and 500 angströms and the plate coverage is on average between about 40 to 99 percent.  
   
     
     
         2 . The method of  claim 1 , wherein the plasma treatment in step (a) is 300 to 500 watts for a period of 6 to 60 minutes per side.  
     
     
         3 . The method of  claim 1 , wherein the plasma treatment in step (a) is for a period of 8 to 30 minutes per side.  
     
     
         4 . The method of  claim 1 , wherein step (b) swells the lens 5 to 25 percent.  
     
     
         5 . The method of  claim 1 , where in the autoclaving is 100° C. to 200° C. for a period of 10 to 120 minutes.  
     
     
         6 . The method of  claim 1 , wherein the fissure depth is on average between about 150 and 200 angstroms.  
     
     
         7 . The method of  claim 1 , wherein the plate coverage is on average between about 60 to 80 percent.  
     
     
         8 . The method of  claim 1 , wherein at least 80 percent of the lens in a commercially manufactured lot are within the said ranges for the depth of the fissures and plate coverage.  
     
     
         9 . The method of  claim 8 , wherein at least 90 percent of the lenses are within said ranges.  
     
     
         10 . The method of  claim 1 , wherein the silicone hydrogel comprises in bulk formula 5 to 50 percent by weight of one or more silicone macromonomers, 5 to 75 percent by weight of one or more polysiloxanylalkyl (meth)acrylic monomers, and 10 to 50 percent by weight of a hydrophilic monomer  
     
     
         11 . The method of  claim 10 , wherein the silane macromonomer is a poly(organosiloxane) capped with an unsaturated group at two or more ends.  
     
     
         12 . The method of  claim 10  wherein the silane macromonomer is a silicon-containing vinyl carbonate or vinyl carbamate or a polyurethane-polysiloxane having one or more hard-soft-hard blocks and end-capped with a hydrophilic monomer.  
     
     
         13 . The method of  claim 1 , wherein the polysiloxanylalkyl (meth)acrylic monomers is methacryloxypropyl tris(trimethyl-siloxy)silane.  
     
     
         14 . The method of  claim 1 , wherein the hydrophilic monomer is selected from the group consisting of unsaturated carboxylic acids, acrylic substituted alcohols, vinyl lactams, acrylamides, vinyl carbonate or vinyl carbamate, oxazolone monomers, and mixtures thereof.  
     
     
         15 . The method of  claim 14 , wherein the hydrophilic monomer is selected from the group consisting of methacrylic and acrylic acids, 2-hydroxyethylmethacrylate and 2-hydroxyethylacrylate, N-vinyl pyrrolidone, methacrylamide, N,N-dimethylacrylamide, and mixtures thereof.