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Small developments make a big impact
Nanotubes and Buckyballs are two examples of nanotechnology structures being applied to the development of new generations of screen printing inks and substrates
Just when many observers thought screen ink development was being forced to a halt by digital technology, in steps nanotechnology to revolutionise the industry and breathe new life into the screen process
by Peter Kiddell
From the ink maker’s perspective screen printing is an ink friendly process. Screen printing mesh meters ink onto the substrate and, provided the pigment particulate size is less than one third the mesh opening, it will pass through the mesh without blocking. That is not the only characteristic an ink formulation must have. The fluid or binder that carries the pigment has to ensure it remains in suspension with an even dispersion. There are additives and solvents (diluents in the case of UV inks) that help them flow and others that assist in wetting the substrate. A complex mix of chemicals combine to produce a controlled ink film with the characteristics that printers demand. This is pretty fancy chemistry and the emergence of nanotechnology is going to turn conventional ink thinking on its head.
A nanometre is one billionth of a metre: 1/1,000,000,000. Screen printing normally works in microns or one thousandth of a millimetre. Thus, one nanometre is one thousandth of a micron. Nanotechnology involves structures sized between one to 100nm. These are made up of atoms and can come in different forms. Two typical structures are nanotubes and Buckyballs.
Molecular level
Using structures like these it is possible to create materials at an atomic level that can be attached to other materials to alter their characteristics or create completely new materials at a molecular level. So a pigment that is not conductive to electricity could be turned into a conductor or have its electrical characteristics greatly improved. There are also nano-pigments that are produced by encapsulating organic dyes into clay particles to form a nano-dye/clay composite pigment. Nanotechnology can improve pigment dispersion and act as a barrier to UV radiation.
The new composite pigments appear to exhibit significantly improved light and thermal stability characteristics (weathering) when compared with organic dyes. The improved weathering makes the new composites particularly useful as colorants for materials destined for outdoor applications. Nanotechnology is also being applied to substrates, with paper being re-engineered to offer completely different properties regarding reflectivity, water absorbency, mechanical strength and the like.
Imagine textiles that can relax you by altering your mood, woven materials that filter pollutants, stain resistant clothing and materials that kill bacteria. A students dream: boxer shorts and knickers that don’t need washing and make them happy. This is not fantasy. They exist in laboratories and some of these materials are in large-scale production. (Come on Peter, back to inks. Ed)
It is considered that nanotechnology will be the for the 21st century, what information technology was for the 20th century.
This adds up to an increasing armoury of inks that printers can use to generate business opportunities. With the frenzy about digital printing it is easy to think that screen printing ink development would have stalled. However, major manufacturers and specialists are still developing them. Visit their Fespa stands and see the innovative approaches.
A key aim is to improve the business case for screen printing, particularly reducing ink inventory by developing a multi-substrate UV curing ink for multi-colour lines. Fujifilm Sericol and Sun Chemical Screen have recognised the need, with the Sun’s UV U range and Sericol’s Display Master XX. Great minds thinking alike.
Masters of screen printing
Its is also noticeable how the masters of screen printing ink technology are addressing other prickly issues. Sericol recognises the need for the viscosity of UV ink to remain stable throughout the print run. This variation has been a constant problem, particularly when adding new ink to a screen during a long run. One solution is to warm inks prior to printing and before addition. New ink formulations are much less affected by temperature variations.
Also, to get inks to stick to substrates it has been necessary to include reactive chemistries. These attack the squeegee, causing it to swell. The aim is to use squeegees for long periods before they need to rest and be redressed. New formulations are less aggressive and ensure squeegees can be used throughout a shift.
The message from the ‘big boys’ is that screen printing inks form the largest part of their product offering and they are still investing heavily in the process. Undoubtedly there is a move towards the industrial sector with inks for difficult substrates and inks for electronic applications.
As a notable member of the ink production fraternity eloquently phrased it: ‘The notion that screen printing is a dead process is a pile of *****. Even though the perception is that ink jet technology has taken over, screen printing ink is still our most important product’.
It is easy to forget the amount of development and chemistry that goes into manufacturing the inks that we use. The ‘inkies’ of this world enable sophisticated formulations which answer the problems of overstressed printers. Ink technologists must account for the variables that users impose on their carefully researched compounds. It would be fair to say that 80 per cent of users do not read the technical data sheet. This is a mine of information that can help printer to avoid problems that ignorance create.
An area where chemical developments have had significant impact is printing onto uncoated glass. Traditionally, this was achieved with glass frit inks fired onto the glass at temperatures approaching the glass’ melting temperature. Two component inks worked reasonably well but came off almost immediately in the dishwasher. Marabu has developed its GL two component ink that can withstand dishwashing up to 300 cycles and is now used extensively on glass bottles. To achieve this resistance it must be dried at 140°C for 30mins. This shows enormous energy savings over fired ink systems. This ink also works on a wide range of metal and plated surfaces. There are currently no digital ink systems that get anywhere near this level of resistance.
Ink guru
The ink guru behind many of the formulations used in Fespa’s Sensations special effects portfolio is Dak Patel of Small Products. He sees tremendous growth in special effects printing where there is a synergy between digital and screen printing. The ability to print special effects with screen provides significant added value and offers a unique selling point compared with digital alone.
There are hundreds of UK companies making a good living printing onto a vast range of substrates with many different inks. It is easy to be blinded by the downturn in large format PoS screen printing. Big PoS printers can only dream about the profit margins of small specialist printers. Specialists have learnt that difficult jobs are the ones that set them apart from the ‘squeegee bashers’ of old.
My advice is see what inks are available. Use their characteristics as selling tools. Surprise your customer with your innovative approach to their needs. Please, always read the Technical Data Sheets.
Speaking of screen printing inks, the following list is all the manufacturers I am aware of with UK representation. These are not necessarily all the manufacturers, representatives or agents just the ones I know.
www.davisonchemographicsltd.com
www2.dupont.com/MCM/en_US
www.coates.com/screen/scrnuk/home.html
