Printed Electronics Patents Granted in 2011 – Conductive Ink

This is the second in the series covering patents granted during 2011 in the printed electronics field.

US7968011: Conductive Ink

Inventor(s): Gerardus Cornelis Overbeek, Michael Arnoldus Jacobus Schellekens, Alfred Jean Paul Bückmann

Assignee(s): DSM IP Assets B.V.

Filed: 6 Mar 2007; Issued: 28 Jun 2011

Abstract: A conductive ink comprising 10 to 75 wt % of at least one solvent comprising ≦20 wt % water; 0 to 50 wt % of at least one radiation curable material having a Mn in the range of from 50 to 10,000 g/mol; 5 to 70 wt % of at least one polyurethane having a Mw in the range of from 4,000 to 70,000 g/mol, 0 to 5 wt % of isocyanate-reactive component(s) bearing ionic or potentially ionic water-dispersing groups and a free isocyanate group content <0.5 wt % and 20 to 85 wt % of a conductive material.

The claims provide more details around the various components but rather than copying the claims I’ll explain in simple English.

The problem being solved by this invention is the lack of a common binder that can be used across a range of different conductive ink materials.  The inventors have provided a polyurethane based binder which they have found can be used to create inks suitable for flexography, gravure and ink-jet printing.  The method does not require high temperature curing and leads to good conductivity. Claim 1 requires that a UV radiation curing material is also included with the binder and this gives additional improvements in film properties and faster printing speeds.

The conductive materials are described as any form of conductive particle and the scope is very broad, including nanoparticles of silver or copper.  The particles can be flakes, fibres, nanotubes or mixtures, the particles can be silver coated.

The system requires a solvent which can be alcohol based (e.g. ethanol, iso-propanol, etc.) or any from a broad range of esters, ethers, ketones, etc. and preferably contains less than 10% water.

Any reader interested in the full formulation should refer to the patent for details of the preferred formulations.

Printed Electronics Patents granted in 2011

I recently reviewed the patents that are granted in the field of printed electronics and a recent search indicated that during 2011 there have already been nearly 100 granted patents in this technology sector.  It is not possible to provide a comprehensive overview in this format but over my next few posts I will provide brief details of a few of the patents that caught my eye.  (If anyone is interested in a more thorough analysis or any particular technology field then please leave a comment or get in touch with me and I can provide details of how to obtain the data.)

US7879688 – Methods For Making Electronic Devices With A Solution Deposited Gate Dielectric

Issued: 1st Feb 2011

Inventors: James C. Novack, Dennis E. Vogel, Brian K. Nelson

Assignee: 3M Innovative Properties Company

Abstract:  A method of making an electronic device comprises solution depositing a dielectric composition onto a substrate and polymerizing the dielectric composition to form a gate dielectric. The dielectric composition comprises a polymerizable resin and zirconium oxide nanoparticles.

Granted claim 1:

1. A method of making an electronic device comprising: (a) solution depositing a dielectric composition onto a substrate, the dielectric composition comprising an ultraviolet radiation polymerizable resin comprising tris-(2-hydroxy ethyl) isocyanurate triacrylate, an ultraviolet photoinitiator, and zirconium oxide nanoparticles; and (b) polymerizing the dielectric composition via at least ultraviolet radiation to form a gate dielectric.

The additional claims generally expand on the ZrO2 nanoparticles and dielectric composition which is preferably ink-jet printed.  Further claims elaborate on a method for making the thin-film transistor.

The claims are fairly self explanatory and the method is said to allow a higher charge carrier mobility for a solution deposited semiconductor.  Obviously, the patent can be circumvented by using other types of metal oxide but for those exploring its potential as a dielectric this is a key patent.