Faster, cooler, bright white: New Latex R Series ups the graphics printing game

The engineers behind the new, versatile printers explain the miracle of white ink (with a side of salad dressing).

By Sarah Murry — May 15, 2018

The release of HP’s rigid latex printing technology, the Latex R Series, this week at FESPA Global Print Expo in Berlin will undoubtedly have those in the graphics world swooning. Not only does it offer extreme flexibility — with the ability to print on both rigid and flexible surfaces such as plastic, wood and metal — but it also serves up the holy grail of latex-based printing: gorgeous white ink. But each lusciously laid pixel of pigment represents major breakthroughs for the engineers at HP’s printing lab facilities in Barcelona, Spain and San Diego, Calif.

“HP’s combined expertise in physics, chemistry and engineering training comes in, which is how we think of new approaches to industry-wide problems,” explains Thom Brown, HP’s chief inkologist. “All of the scientists and engineers at HP look around at other things in their lives and see if they could apply it to printing.” 

Development of HP’s first white latex ink presents a technical challenge on its own. If you want it to look good on almost any surface and be easy for printer operators to manage, it’s an engineering puzzle that required HP’s scientists to draw upon multiple disciplines to crack the code. For the Latex R Series to come to market, three big engineering feats had to happen.

First, HP engineers had to redesign the ink to melt at a lower temperature while keeping the same high level of durability that latex is known for. Second, they had to figure out how to keep the inkjet nozzles from getting clogged. Third, they had to change up the print path for applying ink to the printing substrate — since materials that aren’t flexible can’t zip through the interior of a large-format printer — while making sure flexible materials still could.

Courtesy of HP

Reducing the melting temperature of ink

Among the first questions they asked themselves, according to Brown, was, “How do we make ink less wet?” The end goal, he says, is to lower the drying temperature of HP latex-based ink, so that you can print on common, heat-sensitive materials that might melt at high temperatures, such as plastic.

The trick is to make the process of laying down ink modular, by separating out components that were combined in previous HP Latex systems so that they can dry at lower temperatures.

“We also increased the pigment load in the ink,” he says. “This, combined with the modular approach of laying down less liquid at one time allows for less aggressive drying temperatures because less water needs to be evaporated.” 

“It’s typically a tradeoff: good opacity, or good printhead reliability. But why not have both?”

Thom Brown, Chief Inkologist, HP Inc.

Latex R Series technologies enables printing on hard surfaces, such as wood.

Courtesy of HP

Latex R Series technologies enables printing on hard surfaces, such as wood.

HP’s first Latex White Ink

The result of these innovations are printers that improve upon the typical white ink experience, with less waste and hands-on time for machinists to maintain the intricate workings inside the printers. The result is HP White Latex Ink that prints on flexible, textured or hard surfaces in a bright white and opaque image that won’t yellow over time.

“It all goes back to the pigment size,” Brown says. “If you want to make white, it takes more. To get really good opacity, you need larger pigment sizes, and a lot of them.” To help non-engineers understand, Brown says to think of Italian salad dressing with herbs, right after you’ve given the bottle a shake. “The problem is that the dressing wants to settle way faster than usual, because of the weight and density of pigments which fall to the bottom and don’t want to mix evenly again. Imagine it’s like a thick mud.”

This so-called hard sediment mucks up the works in the tiny, fast-moving inkjet nozzles, making it difficult or impossible for ink to squirt out at a velocity of up to 31 miles per hour.

“It’s typically a tradeoff: good opacity, or good printhead reliability,” Brown says, “But why not have both? We developed special chemistry and mechanics to prevent a hard sediment from forming.”

Developing clog-free inkjet nozzles

Another conundrum: How to keep the rock-like pigment particles from settling in the ink (remember the salad dressing?) so they don’t block the roughly 80,000 microscopic inkjet nozzles in the printer.

The solution was to charge the pigment molecules so they would not clump together, ensuring they stay mixed in solution. The ink is kept constantly moving by tiny “microcirculation pumps” in each printhead, “so every nozzle always has fresh ink,” Brown explains.

Courtesy of HP

White ink pops on rigid surfaces, shown here in a mock-up of a yoga studio and boutique.

Being flexible about non-flexible surfaces

In a traditional printer, a flexible piece of something — paper, a roll of vinyl or other bendable substance — is fed through the machine, the printheads rapidly move back and forth over it.  You can’t do that with a piece of wood. So, HP engineers designed a special table that moves under printheads, enabling novel materials that could never before be printed on, such as foam board, ceramic, wood, metal and even glass, says Roman Barba, large-format printing and applications manager at HP.

“The R Series inks are high-adhesion, flexible and resist chipping, so you can use one set of inks for a limitless set of applications,” he says.

Picture lettering on outdoor signage, product advertisements on corrugated boxes, or tableaus on mural-sized decals. The R-Series is designed to print smoothly on tricky, rigid surfaces such as cardboard, glass, acrylic, aluminum sheeting and PVC.

The proof, says HP’s Brown, is in the “alive and glossy” end products produced by these inks and printers.

“Seeing is believing in this case,” he says. “The output is stunning. The color is extremely vibrant, and it’s glossy, and you are going to get that pop.”

Learn more about the Latex R Series and HP Latex White Ink innovation.