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Issue: Graphic Repro On-line features 2009
Chapter: 02 Technology-related 2014

Both controversial and interesting: ‘Miracle-Plate’ technology offers the possibility of imaging uncoated litho ‘blanks’. By Tony King

Miracle-Plate technology

Industry CTP veteran Tony King has been taking a closer look at the technology and people behind the latest industry headlines, the so called ‘Miracle-Plate’ technology which offers the possibility of imaging uncoated litho ‘blanks’.

Sometime ago I took a call from a former colleague, Dr. Rod Potts, who was R&D Director at Agfa. Potts explained that he had made a breakthrough with a new CTP technology. He was working with Kodak’s former R&D Director, Dr. Peter Bennett who just happened to live nearby. Along with former DuPont Plate Manufacturing manager John Adamson, they formed the science company JPI and applied for a Government grant to fund university research. Government funds were granted and some very clever research led to the patent applications being filed and the Miracle-Plate technology was born.

Much has been said about the Miracle-Plate technology in the last few weeks. The technology is as controversial as it is interesting. In simple terms JPI have found a way to switch the ink-receptivity (or ‘hydrophobicity’) of uncoated aluminium using pulses from a new type of laser called an ultra fast pulsing laser. These lasers pulse tens of trillions of times per second, numbers that are difficult to comprehend. But compared to normal ‘constant output’ lasers they open up a whole new field of science.

Figure 1,below, shows how the action of laser exposure varies dramatically according to the time and power with which the laser interacts with the surface. The new area of ultrafast laser exposure is largely uncharted territory with more questions than answers.

Figure 1. Graph showing varying effect of power and time on laser exposure, courtesy of Strategies Unlimited.

The reason for the high levels of interest in the Miracle-Plate technology is the potential savings that can be made to the aluminium demand from the industry. The printing industry uses about 600 million square metres of aluminium plates each year. If a plate could be re-imaged and re-printed just once, then 300 million sq/m can be saved each year. In the lab, the Miracle-Plate team have re-imaged and re-printed a plate five times. The aluminium usage is one of the biggest environmental problems for the print industry, and one of the reasons for that is the highly energy-intensive process that is needed to extract aluminium from the earth. Recycled aluminium isn’t used for litho plates, so it is the high-energy footprint of virgin aluminium (non-recycled) that we have to consider. Remember also the large economic savings and environmental benefits that can be made if plates could be re-used. Less transportation is required, no chemical developers need transporting, and less energy is required throughout the entire process.

Initially the new ultra fast pulsed lasers were examined to see how they changed the plate coatings on digital and analogue plates. The lasers pump large amounts of energy into the surface of the ‘host’ material but the laser moves on quickly before any heat has chance to be generated in the surface material. Normally it only takes a nano second for a laser to start transferring large amounts of heat energy into the host material. However the new ‘femto’ second pulsed lasers image the material for just one millionth of a nanosecond, numbers that are hard to grasp for most of us. These new femtosecond lasers pulse up to 10 to the power of 15 times per second and are opening up new fields of scientific research in micro-machining, surface treatment and medical applications. Concepts such as ‘cold ablation’ and other unusual possibilities are attracting cutting-edge scientific research from material scientists.

The Miracle-Plate team tried two initial experiments using these new lasers. In one experiment the laser was used to image the substrate from a digital plate, in another they exposed the substrate of an analogue plate. The expectation was that (hopefully) one of the experiments would show some kind of surface change that would point them in the right direction for future research. To everyone’s surprise both experiments showed a dramatic switch in the aluminium ink receptivity. R&D rarely works as quickly as that, and the term ‘miracle-plate’ was first coined as the researchers came to terms with what they had found. Research was then done using different metal oxide surfaces such as Titania (Titanium oxide) and this also worked extremely well. The technology appears to offer a broad working latitude in which it works – this always bodes well for technologies that hope to become products.

The image below (Figure 2) shows a highly magnified piece of grained and anodised aluminium. The area on the left of the picture has been exposed by a laser and has been rendered water receptive. The darker coloured area has not been exposed by the laser and is hydrophobic. Aluminium, if left un-gummed quickly and permanently becomes hydrophobic within hours of manufacture. Exposure to the femto-second laser modifies the surface and makes it hydrophilic again.

Figure 2, above. Highly magnified view of grained and anodised aluminium surface. The left hand portion has been exposed by the pulsed laser making it water receptive or ‘hydrophilic’. The area on the right is slightly darker and is ink receptive (or ‘oleophilic’).

Once a blank sheet of grained and anodised aluminium has been imaged, the image remains in place for one to two days before gradually disappearing. The exact lifetime the image has can be ‘steered’ by various factors including e.g. the type of material being imaged. This gives JPI the confidence to believe that further optimisation is possible, for example to increase the ‘lifetime’ of the image. To erase the image, the plate is simply left for a couple of days or heated for a few minutes.

JPI has demonstrated that several thousand copies can be printed but believe the actual ‘run length’ of the image could be tens or hundreds of thousands. The image does not rely on a polymer ‘dot’ on the plate, rather it relies on the hydrophobicity / hydrophilicity balance of the aluminium substrate, so the team are confident of long run lengths though they are keen to point out that a lot of work still remains necessary as this is very much a technology rather than a product.

The practical challenge is to remove the ink, and able to re-image the plate, and then re-clamp it on the press. The obstacles ought not to be insurmountable, given the attractions and benefits of a re-usable plate. An alternative to a ‘plate’ concept is a ‘cylinder concept’ where the printing surface is a cylinder. The cylinder is imaged (on-line or in a stand-alone platesetter) and then is slid onto the press where it is printed and the ink removed later. The plate can then be re-imaged and re-printed so long as the grained and anodised surface is in good condition, and that could be one to two million copies. Perhaps enough for a week’s worth of printing for the shorter to medium run printer. Savings to a printer could be quite significant, but it is the savings to the environment that are attracting the most enthusiastic comment.

Even if the re-image / re-print concept isn’t used, the elimination of plate coating and all the energy / solvents / chemicals / processors that go with it is a significant saving. However, the attraction in the Miracle-Plate technology is not just about elimination of coatings, it is the re-usability that is attracting the interest and media attention.

Today the team behind Miracle-Plate are keen to push the technology closer to the point where it can be made into a product. Much work remains to be done, especially further characterisation of press performance and here JPI will work with one of the UK’s top print colleges to get an impartial assessment of press performance. But the initial results have exceeded anyone’s expectations and the team have a high level of confidence that the technology they have discovered will make a very real impact on our industry and the environmental demands it places on aluminium usage.

To download the White Paper PDF, which is illustrated, please use the Adbobe link below.

© Graphic Repro On-line, 6 August 2009.

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