Milestones in inkjet
Wednesday, February 12, 2020
Of all the different print technologies currently in use, inkjet is probably the most interesting for its sheer versatility, working across documents and wide-format, labels and packaging and even 3D printing. The technology has evolved gradually over several decades and in this story we chart some of the major milestones.
The genesis of the inkjet concept is generally ascribed to the British scientist and Cambridge University academic Lord Rayleigh, who described a process whereby a liquid stream could be broken up into droplets way back in 1878. However, the first practical demonstration only appeared in the 1950s when Siemens developed an inkjet chart recorder called the Mingograph.
The first recognisable inkjet press came out of Dayton, Ohio, in what is now part of Kodak’s Enterprise Inkjet Solutions Division. The Dayton plant has been through several owners, starting out in 1963 as Mead Digital Systems with Kodak buying the company in 1983, selling it to Scitex in 1992 and then buying it back again in 2003.
Nonetheless, this operation was right at the start of high-volume inkjet printing, introducing the first continuous inkjet printer in 1967 with a binary array inkjet printhead boasting all of 100dpi resolution. The basis behind continuous inkjet is that a continuous stream of droplets is produced but only those that are actually needed are allowed to reach the substrate, with the rest diverted back into the ink system to be reused.
The first system was aimed at the billing market but by 1972 the company had progressed to adding variable graphic elements. The first VersaMark printer appeared in 1999 with an early 228mm page-wide printer offering mono and spot colour. This in turn ushered in a new print category of business colour by 2001. At Drupa 2004 Riso gave a taste of things to come when it showed a low-cost, high-speed inkjet printer that used Olympus printheads and Riso’s own inks.
More recently, Kodak has developed a new generation of continuous inkjet called Stream, which is the basis of its Prosper presses and imprinting modules. The company is currently further developing this with the UltraStream technology. Kodak has partnered with Uteco to develop a high-speed packaging press, the Sapphire Evo W, which should be shown at this year’s Drupa and will allow printing to flexible films.
Screen Truepress Jet 520HD+ for printing to offset litho stocks; Xaar 1003 printhead is widely used in industrial applications
Most printheads in use today follow the piezo-electric drop-on-demand principle. The first patents for these appeared in the early 1970s, with a design from Dr Edmund Kyser of Silonics, which was invented in 1970 and patented in 1976, generally recognised as the start of piezo printheads. Silonics was bought by Konishiroku Photo Industry (KPI), which later became Konica, with the initial plan being to use the technology for office printers. However, KPI struggled to perfect the technology and eventually sold the patents. By the mid 1990s Konica had regretted this decision enough to license Xaar’s printhead technology.
Xaar Itself was set up in 1990, having grown out of Cambridge Consultants. The original plan was to license its technology to other companies and by the year 2000 Xaar had 11 licensees including Sharp Corporation, Brother, Konica, Seiko Instruments and Toshiba Tec. Indeed, some of the printheads available are still largely based on this technology. This willingness to license its technology to other vendors is Xaar’s biggest contribution to the development of the inkjet market, as this kickstarted many of today’s printhead manufacturers.
The Cambridge connection
Xaar began manufacturing its own printheads in 1999 when it acquired the Swedish company MIT, and in 2006 it opened a state-of-the-art manufacturing facility in Huntingdon, UK. Xaar has produced a number of printheads that have played a leading part in opening up various markets. It’s no accident that almost all of the early ceramic printers used Xaar printheads, which proved robust enough to withstand the dusty conditions common to ceramic production. Xaar was the first company to recirculate fluids through the printhead, with the introduction of its TF technology on the 1001 head. Recirculation is now recognised as an essential design for many industrial applications such as textile printing and most printhead manufacturers offer a recirculating option in their portfolio.
In the late 1970s two separate teams working at HP and Canon both developed thermal inkjet, each only finding out about the other after the fact. The Canon team, led by Ichiro Endo, had been working on a piezo-electric design when they noticed that ink was ejected from a syringe when it was accidentally heated. They subsequently developed the BubbleJet system, which uses heat to create a water vapour bubble that forces ink from a nozzle.
Meanwhile, a separate group at HP, led by John Vaught, found while testing thin-film silicon that heat could cause fluid droplets underneath the film to be expelled. Both Canon and HP originally developed this technology for desktop printing, as an alternative to dot matrix printers that could be cheaper and deliver better image quality. But HP in particular has pushed thermal inkjet into many new applications, using the same basic thermal printhead design for its wide-format Latex and dye-sublimation textile printers, as well as the T-series PageWide inkjet presses. HP even uses the same inkjet head technology for its 3D printers.
Mike Willis, managing director of Pivotal Resources, suggest that the most significant single development was the black pigment ink that DuPont developed for HP in the early 1990s and then launched in the HP DeskJet 850C around 1995. He says: “This was as far as I know the first commercial use of a pigment ink. Up until then many people thought pigments would just block the nozzles, inkjet was unreliable enough anyway. It gave better print quality on paper – higher optical density and neutral colour – and was relatively waterfast. The ink needed a polymer included in the formulation to both disperse the pigment and glue it to the substrate. Once DuPont and HP had shown pigments could be used, that opened up people’s minds to commercial and industrial applications. It took a few years, but then we began the expansion of inkjet beyond the office with much improved colorants.”
The first part of the print industry to really embrace inkjet was wide-format printing though this really starts with the Iris 2044, which was developed in 1985 by Iris Graphics, based in Massachusetts, US. This essentially used a variation on continuous inkjet, largely based on patents licensed from Professor Helmuth Hertz of Lund University in Sweden. It was ground-breaking technology at the time and was widely used in photographic labs. The quality was so good that it led directly to the inkjet giclée concept for reproducing fine art prints. Iris Graphics was acquired by Scitex in 1990, and the Iris printers eventually ended up with Kodak when it took over CreoScitex in 2005.
The introduction of solvent inks lead to wide-format printing being adopted by the signmaking sector. But the technology took a big step forward with the move to UV-curable inks. Initially the UV inks were only suitable for rigid materials, with the first UV printers being flatbeds. One of the pioneers was Inca Digital, based in Cambridge, and another company to be spun out from Cambridge Consultants. Inca’s Eagle, which was launched in 2000, was the first flatbed, quickly followed by the even larger Columbia Turbo. Inca has generally taken an uncompromising approach, producing some of the largest and fastest printers available with its stated aim being to challenge offset as well as other wide-format printers.
In 2005, the company was acquired by Screen, which has put Inca’s engineers to work on a variety of industrial applications, such as developing an inkjet module that can be added to the BHS range of corrugated printers.
Screen was one of the first companies to develop a viable high-speed, single-pass printer able to go beyond the transactional market back in 2005. It is true that the original TruePress Jet 520 series, fitted with Epson printheads, work best with inkjet coated materials but these printers helped develop the transpromo concept of mixing variable data with reasonably good graphics. Screen has built a portfolio that now includes a number of TPJ 520 variations but the basic concept remains the same today.
Screen was also one of the first vendors to develop an inkset capable of printing to litho coated stocks without the need to first lay down a primer. The SC inks, which were introduced in 2017, are available for the TPJ 520HD series presses that use Ricoh Gen5 printheads. This is likely to be one of the main trends at Drupa – the ability to print direct to a wide range of media without having to use expensive inkjet coated substrates.
Meanwhile, in the emerging B1 sheetfed inkjet press market, both Heidelberg and Landa are using Fujifilm Dimatix Samba heads. Fujifilm acquired Dimatix in 2006 and the high-res heads are also used in its own Jet Press B2 inkjet press.
Indeed, inkjet technology has been the major focus of the last couple of Drupa shows. There’s still plenty of room for further development, particularly around the inks in use. The printheads are still limited to mostly using low viscosity inks, which limits the range of applications, and there’s a notable trend towards water-based inks, partly for reasons of cost, but mainly for their perceived sustainability, which is opening a new chapter in the inkjet story.