Synthesis of Metallic Nanoparticle Dispersions

Abstract

Disclosed are compositions comprising metallic nanoparticles suitable for use in cohesive, highly conductive structures on substrates. Also disclosed are methods for synthesizing the compositions and methods for forming cohesive, highly conductive structures from the compositions.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of U.S. Provisional Pat. App. No. 60 / 752,143, “Low Temperature Curing Inks Utilizing Metallic Nanoparticles As A Sintering Aid”, filed Dec. 20, 2005, U.S. Provisional Pat. App. No. 60 / 752,144, “Low Temperature Curing Inks Containing Metallic Nanoparticle Dispersions”, filed Dec. 20, 2005, and U.S. Provisional Pat. App. No. 60 / 752,628, “Capacitance Coupled Interactive Electronics Using Printed Conductors”, filed Dec. 21, 2005. The entirety of each of these applications is incorporated by reference herein in their entirety.FIELD OF THE INVENTION [0002] The present invention pertains to the field of nanoparticles. The present invention also pertains to the fields of conductive inks and of printable conductive features. BACKGROUND OF THE INVENTION [0003] Various scientific and patent publications are referred to herein. Each is incorporated by reference in its entirety. [0004] Thin, conductive metal films...

AI Technical Summary

Problems solved by technology

Present methods of printing conductive compositions onto substrates have certain limitations.

These flake-based inks, however, generally cannot be processed at temperatures lower than 120° C. or at times less than 1 minute, regardless of temperature.

Furthermore, these materials are only capable of achieving conductivities of only 2 to 10% of bulk metal conductivity because of the continuous polymeric matrix and the manner with which the flakes pack together.

Conductivities as high as 20% of the bulk metal are possible when using such additives, but high temperatures are needed to decompose the metallo-organic into a conductive structure, and these high temperatures accordingly limit the range substrates suitable for use in conjunction with such ink systems.

Certain conductive ink compositions spread out on a substrate surface before curing, thus adversely impacting the ability to form structures of a certain, defined shape.

In addition, certain compositions incorporate organic solvents, which are difficult to dispose of.

Furthermore, systems comprising metallic nanoparticles dispersed in an organic solvent medium suffer from poor sintering characteristics once deposited onto a substrate, and may require comparatively long exposure to comparatively high temperatures in order to form conductive traces after deposition.

One potential hindrance to metallic nanoparticles' use in conductive inks is their limited ability to form relatively thick conductive traces.

While large metallic particles—typically characterized as having diameters of greater than about 500 nm—are limited in application because they do not sinter at low temperatures, large particles are nonetheless capable of forming thicker metal traces than metallic nanoparticles are capable of forming.

Hence, because of large metallic particles' inability to sinter and form conductive structures at low temperatures, manufacturers are limited in their ability to form thick conductive structures on substrates that are incapable of withstanding the temperatures necessary for large particles to cohere into conductive structures.

Furthermore, the difficulty in inducing large metallic particles to form conductive structures under moderate processing conditions also gives rise to a need for a method for forming thick conductive structures on substrates capable of tolerating only low temperatures.

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