Aculon Inc. were granted a patent on 15 October for “Electroconductive Inks made with Metallic Nanoparticles”. Aculon are well known for their surface coatings using nanoparticle technology, featuring improved adhesion to a wide range of surfaces and adding functionality for numerous applications including printed electronics. It is therefore no surprise that conductive inks are described with advantageous adhesion to a variety of substrates including silicon, glass and plastic.
The granted patent is US8558117 and the claims are quite broad but require the inks to have an omega substituted organophosphoric acid, this is the added ingredient which helps to improve the adhesion.
The first 10 claims are shown below:
What is claimed is: 1. An electroconductive ink comprising: (a) a dispersion of metal nanoparticles with a dispersant on the surface of the metal nanoparticles and as a separate component, (b) an omega substituted organophosphorus acid; the metal nanoparticles being present in amounts of 5 to 80 percent by weight and the omega substituted organophosphorus acid being present in amounts of 0.0005 to 5 percent by weight; the percentages by weight being based on total weight of the electroconductive ink.
2. The composition of claim 1 in which the metal is selected from copper, silver, palladium, gold or any combination thereof.
3. The composition of claim 2 in which the metal is silver.
4. The composition of claim 3 in which the dispersant is an organic carboxylic acid.
5. The composition of claim 4 in which the organocarboxylic acid contains from 4 to 36 carbon atoms.
6. The composition of claim 1 in which the metal nanoparticles have a particle size of 1 to 500 nanometers.
7. The composition of claim 1 in which the dispersion contains an organic diluent.
8. The composition of claim 7 in which the organic diluent is selected from hydrocarbons, alcohols, esters and ketones.
9. The composition of claim 1 in which the organo groups of the organophosphorus acid have omega substituted functional groups.
10. The composition of claim 1 in which the omega substituted functional groups are selected from phosphonic acid, carboxylic acid, hydroxyl, thiol and amine including various combinations thereof.
I have reported on a number of conductive ink patents over the past year or two and a common theme running through them is the need for good adhesion along with their conductivity. The patents generally differ in the description of the adhesion promoting substances used in the nanoparticle inks and on other improved properties that enhance their application for printed electronics. Successful conductive ink formulations are essential for printed electronics to become a mainstream technology for building new devices and specialist inks with patented formulations will continue to dominate the scene for a number of years before generic formulations will be cheaply available as we see for conventional inkjet printing.