Conformal coatings comprising carbon nanotubes

Abstract

The invention is directed to conformal coatings that provide excellent shielding against electromagnetic interference (EMI). A conformal coating comprises an insulating layer and a conducting layer containing electrically conductive material. The insulating layer comprises materials for protecting a coated object. The conducting layer comprises materials that provide EMI shielding such as carbon black, carbon buckeyballs, carbon nanotubes, chemically-modified carbon nanotubes and combinations thereof. The insulating layer and the conductive layer may be the same or different, and may be applied to an object simultaneously or sequentially. Accordingly, the invention is also directed to objects that are partially or completely coated with a conformal coating that provides EMI shielding.

1 - 32 . (canceled)  
     
     
         33 . A method for imparting EMI shielding to a substrate, comprising coating said substrate with a conformal coating wherein said conformal coating comprises: 
 an insulating layer, and    a nanotube-containing layer disposed on said insulating layer, wherein said nanotube-containing layer comprises a plurality of carbon nanotubes.    
     
     
         34 . The method of  claim 33 , wherein the substrate is part of a device component selected from the group consisting of keypads, catheters, integrated circuits, printed circuit boards, printed wire boards, hybrids, transducers, sensors, cores, accelerometers, catheters, coils, fiber optic components, heat exchangers, pacemakers, implants, flow meters, magnets, photoelectric cells, electrosurgical instruments, and plastic encapsulated microcircuits.  
     
     
         35 . The method of  claim 33 , wherein the insulating layer comprises a material selected from the group consisting of polyurethanes, parylene, acrylics, expoxy and silicone.  
     
     
         36 . The method of  claim 33 , wherein the carbon nanotubes are selected from the group consisting of single-walled nanotubes, double-walled nanotubes, multi-walled nanotubes, and mixtures thereof.  
     
     
         37 . The method of  claim 33 , wherein the carbon nanotubes are substantially single-walled nanotubes.  
     
     
         38 . The method of  claim 33 , wherein the nanotube-containing layer further comprises a polymeric material, wherein the polymeric material comprises a material selected from the group consisting of thermoplastics, thermosetting polymers, elastomers, conducting polymers and combinations thereof.  
     
     
         39 . The method of  claim 33 , wherein the carbon nanotube-containing layer further comprises a polymeric material, wherein the polymeric material comprises a material selected from the group consisting of polyethylene, polypropylene, polyvinyl chloride, styrenic, polyurethane, polyimide, polycarbonate, polyethylene terephthalate, cellulose, gelatin, chitin, polypeptides, polysaccharides, polynucleotides and mixtures thereof.  
     
     
         40 . The method of  claim 33 , wherein the carbon nanotube-containing layer further comprises a polymeric material, wherein the polymeric material comprises a material selected from the group consisting of ceramic hybrid polymers, phosphine oxides and chalcogenides.  
     
     
         41 . The method of  claim 33 , wherein the carbon nanotube-containing layer further comprises a conformal coating material selected from the group consisting of polyurethanes, parylene, acrylics, epoxies and silicone.  
     
     
         42 . The method of  claim 33 , wherein the carbon nanotube-containing layer further comprises an additive selected from the group consisting of a dispersing agent, a binder, a cross-linking agent, a stabilizer agent, a coloring agent, a UV absorbent agent, and a charge adjusting agent.  
     
     
         43 . The method of  claim 33 , wherein the carbon nanotube-containing layer has a total transmittance of at least about 60%.  
     
     
         44 . The method of  claim 33 , wherein the carbon nanotubes are oriented.  
     
     
         45 . The method of  claim 33 , wherein the coating further comprises an over-coat comprising a conformal coating material selected from the group consisting of polyurethanes, parylene, acrylics, epoxies and silicone.  
     
     
         46 . The method of  claim 33 , wherein the carbon nanotube-containing layer provides EMI shielding properties in the 10-70 dB attenuation range.  
     
     
         47 . The method of  claim 33 , wherein the carbon nanotubes are chemically modified.  
     
     
         48 . A conformal coating that provides EMI shielding, wherein said coating comprises a plurality of carbon nanotubes and a polymer selected from the group consisting of acrylics, epoxies, silicone, polyurethane, and parylene.  
     
     
         49 . The conformal coating of  claim 48 , wherein the carbon nanotubes are selected from the group consisting of single-walled nanotubes, double-walled nanotubes, multi-walled nanotubes, and mixtures thereof.  
     
     
         50 . The conformal coating of  claim 48 , wherein the carbon nanotubes are substantially single-walled nanotubes.  
     
     
         51 . The conformal coating of  claim 48 , wherein the coating has a surface resistance in the range of less than about 10 4  ohms/square.  
     
     
         52 . The conformal coating of  claim 48 , wherein the film has a surface resistance in the range of less than about 10 3  ohms/square.  
     
     
         53 . The conformal coating of  claim 48 , wherein the film has a surface resistance in the range of about 10 −2 -10 0  ohms/square.  
     
     
         54 . The conformal coating of  claim 48 , wherein the coating provides EMI shielding properties in the 10-70 dB attenuation range.  
     
     
         55 . The conformal coating of  claim 48 , wherein the carbon nanotubes are chemically modified.  
     
     
         56 . The conformal coating of  claim 48 , wherein the carbon nanotubes are present on a surface of said conformal coating.  
     
     
         57 . A dispersion comprising a plurality of carbon nanotubes and a conformal coating material selected from the group consisting of polyurethanes, parylene, acrylics, epoxies and silicone.  
     
     
         58 . The dispersion of  claim 57 , wherein the carbon nanotubes are selected from the group consisting of single-walled nanotubes, double-walled nanotubes, multi-walled nanotubes, and mixtures thereof.  
     
     
         59 . The dispersion of  claim 57 , wherein the carbon nanotubes are substantially single-walled nanotubes.  
     
     
         60 . The dispersion of  claim 57 , further comprising a polymeric material, wherein the polymeric material comprises a material selected from the group consisting of thermoplastics, thermosetting polymers, elastomers, conducting polymers and combinations thereof.  
     
     
         61 . The dispersion of  claim 57 , further comprising a plasticizer, softening agent, filler, reinforcing agent, processing aid, stabilizer, antioxidant, dispersing agent, binder, a cross-linking agent, a coloring agent, a UV absorbent agent, or a charge adjusting agent.  
     
     
         62 . The dispersion of  claim 57 , further comprising conductive organic particles, inorganic particles or combinations or mixtures thereof.  
     
     
         63 . The dispersion of  claim 62 , wherein the conductive organic particles are selected from the group consisting of buckeyballs, carbon black, fullerenes, and combinations and mixtures thereof.  
     
     
         64 . The dispersion of  claim 62 , wherein the conductive inorganic particles are selected from the group consisting of nickel, silver and copper.  
     
     
         65 . The dispersion of  claim 62 , wherein the dispersion can form a coating, wherein the coating provides EMI shielding properties in the 10-70 dB attenuation range.  
     
     
         66 . The conformal coating of  claim 48 , wherein the carbon nanotubes are single-wall carbon nanotubes and the EMI shielding is from 10-70 dB attenuation range.