Nanotechnology for ‘green’ inks

13 April 2010



Traditionally, most inks used in packaging have been petroleum based, releasing volatile organic compounds into the atmosphere. But nanotechnology has been a key driver in developing a new generation of inks. Mark Rowe reports.


Nanotechnology is proving more and more to be a tool in the production of efficient, ‘greener’ inks that are water-soluble, vegetable-based or synthetic, and which are highly versatile and can be used for a range of applications across the inks industry and recycled into new products at the end of their original working life.

However, Dr Peter Harrop, chairman of UK-based IDTechEx, the printed electronics analysts, cautions it would be wise to be wary of all such claims attributed to nanotechnology. “Nanotechnology is a much abused term,” he says. “There are some interesting things proving possible with nanotechnology, but much of it is happening at a level that is 10 times the size of what’s really meant by nano-sized. A lot of these things have been around for a long time, and people talk about nanotechnology slightly artificially because they hope investors will want to invest in it.”

Despite this caveat, Dr Harrop acknowledges the key role that nanotechnology can play in packaging, particularly for electrical inks, resistors and conductors in transistors with nano-silver based inks. NanoMarkets, a materials research company, based in Virginia, USA, has published a study paper on the relationship between nanotechnology and the ink industry: Opportunities in Materials for Printable Electronics. It singled out nanoparticulate silver inks because of their improved conductivity, lower temperature curing and the printing of finer lines. The development of nano inks sourced from copper, nickel and gold are less developed but should have similar properties, according to NanoMarkets.

In March this year, Innovalight, a California–based company, secured a patent for the manufacture of highly efficient crystalline wafer solar cells with silicon ink, which its manufacturers believe will have commercial packaging applications. Meanwhile, researchers at the USA’s Stanford University have developed a technique that can turn ordinary packaging paper into a battery by using enhanced, recycled inks made of carbon nanotubes and silver nanowires.

“Conventionally you used silver flakes for printing on packaging – it was rather expensive and you had to heat it quite a lot and use expensive paper,” said Dr Harrop. “Nano-silver ink has quite dramatic changes – when you create that amount of surface area the melting point drops to around 1000C, so you can end up with the electrical conductivity of bulk silver. At the moment they are rather expensive and not being adapted very quickly. But they have a real benefit of using less silver for printing.”

Copper-based inks used at a level approaching the nano scale offers similar properties. “Usually when copper is printed it oxidises and is not conductive,” said Dr Harrop. “But it is possible to print copper if it is used at a very small scale. These things ebb and flow. You can move from silver flakes to nano silver but that in turn is trumped by ‘nano-copper’ that is not technically at the nano level.”

Meanwhile, CSIRO, the Australian Commonwealth, Scientific and Industrial Research Organisation, has been investigating ‘reversible addition-fragmentation chain transfer’ (RAFT) technology, a form of controlled free radical polymerisation which enables the synthesis of tailored polymers, whose applications include novel pigment dispersants for inkjet printing on packaging. One of the attractions is that RAFT technology allows for complete control over the size and shape of molecules. In February this year, Belgium-based Agfa submitted a patent application for an inkjet printing method based on RAFT that is capable of handling a variety of different types of packaging. This uses an inkjet printer without compromising the consistency of image quality, physical properties, such as adhesion of the image to the substrate, and productivity. RAFT enables drying of the inks to be replaced by polymerisation, using ultraviolet radiation in the wavelength range of 100 to 400 nanometers.

Nanostructures at the scale of 10-20 nanometres are important for inkjet printing, according to Dr Harrop. These can be applied to packaging, and even enable companies to develop winking logos on the side of detergent bottles, he suggested. Crucially, research into the use of nanotechnology in the ink industry has not been slowed by the recession. “It’s quite the opposite,” said Dr Harrop. “The great recession made space for the new, and the same is happening again.”

Nanotechnology is also enhancing the ways in which inks can make packaging counterfeit- and tamper-proof. Hologram Industries, a Paris-based company, which has already developed technology to protect 50, 100, 200 and 500 euro banknotes, last year completed a two-year €2.6 million project into DID, an optical security element based on nano-ink structures and interferential layers. These offer high-resolution graphics and optical specifications of the image: DID enables the etching of optical microstructures on areas of micrometric dimension on thin films that are machine readable, and which reproduces a design made up of two distinct coloured elements made visible by direct reflection of light.

Sun Chemical invests in new plant for global food packaging market

Sun Chemical displayed its commitment to the food package printing market through the grand opening of its new state-of-the-art manufacturing plant in Frankfurt, Germany last month.

The plant was built using clean room and HACCP directives to ensure that the best possible standards are adopted in the manufacturing of Sun Chemical inks. Representing an investment of €4 million, the facility is dedicated to the highest level of cleanliness and uses the world’s most advanced technology to create high-quality sheetfed packaging inks.

There are two blending stations: one is specifically used for low migration inks; the other, which is housed in a separate building to avoid cross-contamination, is used for conventional inks.

All raw materials are hand-inspected to make sure they contain no contaminants and have low odour as required by strict European food regulations. Additionally, quality control officers are on-site to check product quality at all times.


Yellow and magenta coldset printing inks in 25g containers. (Photo: Julio - Wikimedia Commons) Inks Advanced ink plant for Sun Chemical Sun

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