Radiation curable inks

Abstract

A radiation curable ink is provided which is convertible to a conductive coating when cured on the surface of a substrate. A particulated electrically conductive .[.metal containing.]. material is used in combination with an organic resin binder. Low temperature cure of the ink can be achieved with either actinic or ionizing radiation.

What we claim as new and desire to secure by Letters Patent of the United States is: 
     
       1. A screen printable radiation curable ink convertible to an abrasion resistant conductive coating exhibiting a specific resistivity of less than 10 ohm-cm when cured on the surface of a substrate consisting essentially of by volume A. from about 10 to 60 percent of a radiation curable organic resin binder having a viscosity of from about 50 to 10,000 centipoises at 25° C., and   B. from about 90 to 40 percent of an electrically conductive filler consisting essentially of silver or copper containing particles with about 0 percent to about 15 percent by weight of silver or copper containing particles having an aspect ratio of diameter to thickness of a value greater than 20 based on the total weight of conductive filler.   
     
     
       2. A radiation curable ink in accordance with claim 1 where the electrically conductive filler is in the form of silver coated glass spheres. 
     
     
       3. A radiation curable ink in accordance with claim 1 where the electrically conductive filler is in the form of chemically reduced copper coated glass spheres. 
     
     
       4. A radiation curable ink in accordance with claim 1 where the electrically conductive filler is in the form of chemically reduced copper powder. 
     
     
       5. A radiation curable ink in accordance with claim 1, where the organic resin binder is in the form of a mixture of polyester prepolymer and styrene. 
     
     
       6. A radiation curable ink in accordance with claim 1, where the organic resin binder is in the form of a polyacrylate. 
     
     
       7. A radiation curable ink in accordance with claim 1, where the electrically conductive filler consists essentially of silver or copper containing spheres or spheroids having from about 0 percent to about 15 percent by weight of silver flake, based on the weight of conductive filler. 
     
     
       8. A radiation curable ink in accordance with claim 1, where the radiation curable resin is a polyester resin and the electrically conductive filler is in the form of .[.sliver.]. .Iadd.silver .Iaddend.coated copper beads. 
     
     
       9. A radiation curable ink convertible to an abrasion resistant conductive coating exhibiting a specific resistivity of less than 10 ohm-cm when cured on the surface of a substrate consisting essentially of by volume A. from about 10 to 60 percent of an epoxy resin containing an effective amount of an aromatic onium salt selected from the class consisting of an onium salt of a Group VIA element, an onium salt of a Group VA element, and an aromatic halonium salt, and   B. from about 90 to 40 percent of an electrically conductive filler consisting essentially of silver or copper containing particles having from about 0 percent to about 15 percent by weight of silver or copper containing particles having an aspect ratio of diameter to thickness of a value greater than 20 based on the total weight of conductive filler.   
     
     
       10. A radiation curable ink in accordance with claim 9, where the organic resin binder is in the form of a mixture of vinylcyclohexene dioxide, (3,4-epoxy cyclohexyl)-methyl-3,4-epoxy cyclohexane carboxylate and an effective amount of triphenylsulfonium hexafluoro arsenate. 
     
     
       11. A radiation curable ink in accordance with claim 9, where the electrically conductive filler consists essentially of .[.sliver.]. .Iadd.silver .Iaddend.or copper containing spheres or spheroids having from about 0 to 15 percent by weight of silver flakes, based on the weight of conductive filler. 
     
     
       12. A screen printable UV curable ink convertible to an abrasion resistant conductive coating exhibiting a specific resistivity of less than 10 ohm-cm when cured on the surface of a substrate consisting essentially of by volume A. from about 10 percent to 60 percent of a radiation curable organic resin binder having a viscosity of from about 50 to 10,000 centipoises at 25° C., .[.and.].   B. from about 90 percent to 40 percent of an electrically conductive filler consisting essentially of silver or copper containing particles with about 0 percent to about 15 percent by weight of silver or copper containing particles having an aspect ratio of diameter to thickness of a value greater than 20 based on the total weight of conductive filler, and   C. from 0.5 to 5 percent by weight of a UV sensitizer based on the weight of (A).   
     
     
       13. A radiation curable ink in accordance with claim 12, comprising A. a polyester reaction product of propylene glycol, fumaric acid and dicyclo pentadiene,   B. silver coated glass spheres having an average diameter of from about 10-50 microns.   
     
     
       14. A UV curable ink in accordance with claim 12, where the conductive filler consists essentially of silver or copper containing spheres or spheroids having from about 0 percent to about 15 percent by weight of silver flake based on the weight of conductive filler.  .[.15. A screen printable radiation curable ink in accordance with claim 12, convertible to an abrasion resistant conductive coating capable of withstanding exposure to 96 percent relative humidity for 14 days at 120° F. without a substantial change in its specific resistivity..]..Iadd. 16. A screen printable radiation curable ink convertible to an abrasion resistant conductive coating exhibiting a specific resistivity of less than 10 ohm-cm when cured into a non-tacky condition by ultraviolet radiation on a thermoplastic substrate, said ink consisting essentially of by weight A. from about 10 to 60 percent of a radiation curable organic resin binder having a viscosity of from about 50 to 10,000 centipoises at 25° C., and   B. from about 90 to 40 percent of an electrically conductive filler consisting essentially of a particulated electrically conductive material selected from the group consisting of a particulated electrically conductive metal and a particulated electrically conductive metal containing material, including mixtures thereof, with no more than about 15% by weight of said particulated electrically conductive material having an aspect ratio of diameter to thickness of a value greater than 20. .Iaddend..Iadd. 17. A radiation curable ink as in claim 16 in which at least 85 percent by weight of said particulated electrically conductive material is constituted by silver-coated glass spheres and in which up to about 15 percent by weight of said particulated electrically conductive material is constituted by silver flakes having an aspect ratio of diameter to thickness of a value greater than 20. .Iaddend..Iadd. 18. A radiation curable ink convertible to an abrasion resistant conductive coating exhibiting a specific resistivity of less than 10 ohm-cm when cured into a non-tacky condition by ultraviolet radiation on a thermoplastic substrate, said ink consisting essentially of a radiation curable organic resin binder and at least 40% and not more than about 90% by weight of said ink being formed by particles bound together by said resin binder and having electrically conductive outer surfaces which shield the transmission of ultraviolet radiation through the particles, and at least about 85 percent by weight of said particles being silver-coated glass spheres having a diameter of between 10 and 50 microns. .Iaddend.