The power of ink

While new printers always get the glory, ink is the unsung hero of inkjet development. Printheads and mechanisms help push resolutions higher and speeds faster, but without the work that goes into new ink formulations these improvements might never happen. New inks have allowed inkjet printers to move from simple three-colour graphics to high-resolution photo printing, and radically enhanced colour fastness and fade resistance. Developing them takes time and money. HP spends hundreds of thousands of dollars every year on ink research, and a new ink might be the result of hundreds of man-years of combined experience from chemists, engineers and other specialists.

The power of ink

You see, developing printer inks is no trivial task. First, you’re looking at a liquid that will be propelled from a nozzle at speeds in excess of 31mph over 36,000 times every second, each time with incredible accuracy. Put into a human context, it’s like dropping a grape into a bucket from thirty floors up. Secondly, inkjet inks are water-based. This makes them less expensive, lower maintenance and less potentially hazardous than oil-based or solvent-based inks, but also more challenging to work with. When a water-based ink lands on uncoated paper, it’s in its nature to spread along the paper fibres and into the paper. This helps to dry the ink, but has a negative effect on colour quality and resolution. Coated papers will help, controlling the spread and penetration, but that can only go so far – and many of us expect great prints on ordinary paper.

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That’s why HP spends so much on formulating inks, and why each new one goes through over 70 tests to check its purity, viscosity, surface tension, smear-fastness and compatibility with different media. It’s also why every ink contains a range of ingredients beyond the colorant (the pigment or dye that makes the colour) and the carrier (the liquid the colorant is suspended in). These include the surfactant – active agents that lower the surface tension of the ink ready for deployment and control the way the colorant disperses – anti-curl agents to restrain the ink from causing paper curl and anti-cogation agents to stop ink drying in the printhead. And that’s without mentioning the preservatives and other agents that fine-tune the behaviour of the ink at every stage. There’s a lot more to an ink than what you see on the printed page.

Developments in Ink Technology

Just as HP has played a leading role in the development of thermal inkjet technology, so it has also pushed forward ink technology. HP’s work began with the development of ink for the original ThinkJet, launched in 1984. Initially the development team adopted a commercially available non-toxic water/glycol mix commonly used in fountain pens. This ran smoothly through the nozzles and dried quickly, but wasn’t light-fast or resistant to water. More seriously, it was prone to cogation, where a crusty residue would bake onto the thermal elements in the printhead. HP Labs developed its own formulation which solved or mitigated against many of these issues.

In 1988 HP introduced the first Deskjet, using new dye-based inks optimised for 300dpi, near-laser-quality printing. Then, in 1991 it launched the Deskjet 500C, which took technology from the 1987 Paintjet to build the first mainstream 300dpi colour printer. This produced primary colours and an extensive range of additional tones using halftoning. For the time this was a revolutionary printer, but the colour came at a cost. With no black in place during colour printing, blacks were created from a composite cyan, magenta, yellow mix, resulting in a greenish near-black rather than a proper black.

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HP fixed this in 1992 with the launch of the Deskjet 550C, which carried two cartridges, one tri-colour, one black. Yet black ink remained a problem; prints were still far from water-resistant, and not as crisp as on a laser print, particularly on plain paper. Text would still smear, for example, if you used a highlighter pen. In 1993, therefore, HP introduced its first pigment-based black ink. Pigment inks are more stable, the tiny solid particles of colorant staying nearer the surface of the paper rather than sinking deeper in. They are also more light-fast, and less affected by air and moisture. The introduction of pigment-based black inks to the Deskjet line enabled printers to print text with sharper edges and blacker blacks that lasted longer.

Brighter Colours and Lifelike Photos

HP’s R&D team realised, however, that pigment inks weren’t the answer to everything. Dye-based inks might be more liquid, but they can be layered to create a smoother image with more subtle colour tones, allowing inkjet printers to reproduce a wider range of colours by accurately layering dots not just in halftone patterns, but directly on top of each other. In 1996 HP took this one stage further, with an optional photo cartridge containing light dye-load inks of light cyan and light magenta, along with a dye-based black ink. This dramatically increased the range of available colours, and allowed HP’s Deskjet 690C printer and its successors to print images of near-photographic quality.

In 2004 HP launched a new range of dye-based inks, HP Vivera, designed to produce brilliant, lifelike colours and strong blacks. The product of 12,000 hours of science and engineering over three years, Vivera inks were designed to resist fading for up to 115 years when used in conjunction with HP papers, and produce higher-quality photo prints than ever before. HP also moved to eight-ink photo printing, combining three specialist cartridges to produce dark grey, light grey and photo black as well as the existing cyan, magenta, yellow, light cyan and light magenta inks.

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In 2006, HP introduced its first Vivera Pigment inks. Formulated with durability and water-resistance in mind, these produced an even more extensive palette of vibrant colours, deep blacks and subtle greys for photo printing, enabling printers like the PhotoSmart Pro B9180 and DesignJet Z3100 to create true fine-art quality photo prints. These inks use something called Electrostatic Encapsulation Technology to optimise the pigment chemistry and particle size so that the particles of pigment separate and don’t clump, creating a freer-flowing, less viscous ink that runs smoothly through the nozzles and settles more evenly on the paper.

Sharper Lines and Crisper Blacks

Vivera also crossed over into the office, with Vivera Office Inks that help Officejet and Officejet Pro printers produce consistently strong graphics and sharp black text, on pages that dry fast and resist smearing from handling and moisture. The formulation was designed to allow the ink components to quickly penetrate the paper, while colorants stated close to the service. The ink was also designed to resist bleeding, so that colours and black inks wouldn’t mix together when in close proximity.

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Today’s Officejet Pro and Officejet Pro X printers now use pigment-based inks, which effortlessly produce laser-quality black text and high-quality graphics and photos that are as water and smear-resistant as anything you’ll get from an office laser printer. These inks dry fast, which makes them perfect for a fast-paced office environment, and will also resist fading for decades. The inks used in the HP Officejet Pro X range are designed specifically to cope with the demands of the new high-speed, PageWide print head, resisting mixing and cross-contamination during the print process, and providing well-saturated, high-density blacks and colours in a single pass.

As the Officejet Pro X range proves, inkjet technology is only moving forwards, and the same is true of the ink that runs through it. Whether the future lies with pigment inks, dyes, water-based inks or other formulations yet to come, you can expect to find HP sitting right at the forefront.

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