A Tale of Two Inks
Ink has been around longer than writing. Some experts describe prehistoric art in Africa or France as paintings, but it’s basically ink on the wall. Sort of like what your kid does in his or her room. Just a tad more valuable.
A lot of ink these days comes in disposable pens, but most of it is in cartridges that are clicked into digital printers and rank among the most valuable fluids on Earth. The inks squirting out of print heads may seem identical, but the chemical stews that make up inks for digital devices are anything but generic. All adhere to tight specifications based on applications, substrates, print head designs and temperatures, drying times, and more. There are further big differences between dye-based and pigmented inks, notably in fluidity, meeting print head characteristics, durability and light fastness.
Inks Do the Heavy Lifting
Major equipment makers have invested seven- and eight-figure sums on R&D for inks, often more than they spend on developing a new print engine. Yet, when it comes to product roll-outs, the big focus is invariably on the device itself. The virtues of a new machine are extolled, especially its ability to lay down vibrant colors and even expand the color gamut. Print heads have a lot to do with this, but in very real ways, the inks are actually doing the heavy lifting. The printer itself is just a tool. Inks are what bring the visions of artists and designers to life.
Two of the commercial applications exemplifying this today are vehicle wraps and various types of large indoor and outdoor signage or display advertising. Two ink technologies””UV and latex””are at the forefront for these applications, and many print providers have different devices for addressing customer needs.
UV
UV (ultra-violet) inks have been used in offset printing for nearly 20 years, but cost slowed adoption in a time when today’s “need the job yesterday” mentality was rare rather than normal. Now, fuel for an inkjet printer, UV inks can be less expensive on a per-job basis because less ink is required to produce the same results. Moreover, almost any substrate is a ready surface for UV inks, making it a good choice for a wide range of applications. Especially compelling for busy shops, jobs using UV inks can be ready for use immediately.
This ready-to-go advantage is the result of some photochemical magic at the core of UV technology. On inkjet printers, which can be up to about ten feet wide, UV inks are sprayed onto a substrate where they tend to sit on the surface, rather than penetrate the top layers as do other inks. This helps control dot gain but leaves the ink in liquid form. The still wet inks are exposed to ultra-violet light (at 200 to 400 nanometer wavelengths for the geeks reading this) immediately after being printed, instantly “curing” the ink by transforming it from a liquid to a solid. This produces a print that is dry to the touch just seconds after printing. This is especially important on roll-fed devices that rewind substrates onto a take-up reel. Cured inks ensure minimal or no offsetting onto the backside of a newly printed roll. More of the magic is in the small amount of ink used in UV inkjet printing, which lowers the cost per job. Vibrant UV inks require only a very thin layer, and the RIP driving the printer determines the precise amount of ink required. Additionally, most UV inkjet printers can be configured with white ink, a hue needed for printing on various films used for signage and vehicle wraps.
This efficiency fosters productivity. Very often, more UV jobs can be turned out in less time compared to other technologies. After all, when a job is produced in less time but can be sold for the same price (or more) as when it took longer, it is a solid win for the print provider. Then, there’s customer satisfaction. Output is more consistent (so there are fewer rejects), the thin inks and almost zero absorption into substrates improve detail, while the more vivid CMYK inks improve color gamut and image quality. Some UV inks also have a glossier finish and better resistance to scratches, chemical, and solvents than solvent and eco-solvent inks. These traits help improve durability and weather- and fade-resistance, making them ideal for outdoor signage. Finally, an attractive advantage of UV inks is the total lack of volatile organic compounds (VOCs). This means UV printing, with almost zero carbon footprint, is more sustainable and presents less damage to the environment than solvent inks.
The old-school competition for UV is the wide-or large-format devices that use solvent or, more recently, eco-solvent inks. The former are still being used for some of the same applications as new UV printers but are burdened with the need to vent large areas of a print facility, require significantly more heat and energy for drying, and leave a larger environmental footprint. Several equipment vendors””some of which also offer UV machines””still sell solvent machines, especially large-format models, but these devices are destined to be replaced by UV or eco-solvent printers as their leases expire.
Some printers may recall the hot (mercury/quartz) UV lamps once used as part of the drying process for offset UV printing and even early UV inkjet systems. Now though, the frequency (or wavelength) of light used in modern LED-based UV lamps does the same job with almost no heat, much less energy, and a lamp life measured in thousands of hours. In fact, EFI-VUTEk refers to one of its UV printers as an LED printer, barely mentioning the term UV in its materials.
Canon, one of the leaders in UV for wide- and large-format, rolled out a unique UVgel ink technology in its roll-to-roll Colorado 1640 model. UVgel is a thicker, gel-like ink that yields a broad color gamut. Other Canon UV devices are flatbed machines bearing the company’s Arizona brand but do not share the gel inks of the Colorado. Canon’s offerings compete with models from EFI-VUTEk, HP-Scitex, Mimaki, and Roland, among others. No matter the maker, UV machines are typically more expensive to acquire than competing technologies, but the total cost of consumables is less expensive and throughput is greater, so a busy shop can make up the higher entry fee with lower operating costs.
Latex
You may think of latex as a substance for painting your house or a room, but it is also one of the top options for many wide- and large-format print providers. In its natural form, latex is a kind of rubber produced by a variety of flowering trees. But whether used on your house or in a digital printer, latex is what chemists call a synthetic aqueous polymer. That just means it is a cluster of molecules (monomers) that can be bonded together to form, you guessed it, a polymer. But enough of the science. Today, several companies do the chemical magic to make latex inks for various printer manufacturers. And no, the inks are neither the same nor interchangeable, because each company’s flavor of ink is matched to the print heads and machine on which it is used.
Latex printing competes for market- and mind-share with eco-solvent printing, especially for vehicle wraps, wall murals, and both indoor and outdoor signage. Each offers advantages that may affect workflow in some printshops. For example, latex printers use more energy and can be slower than eco-solvent devices because the substrate must be warmed before printing and the inks must be dried immediately after printing. The water-based inks mean drying is not instantaneous and requires a fair bit of heat. On the other hand, eco-solvent quickly dries to the touch with less heat but still requires 24 hours or more to fully “out-gas” the ether-based solvent used in the inks. Although the right choice for any business varies mostly by the applications being run, neither process has a truly significant edge in the time required for printing””which brings us to the next step.
Lamination Required
Lamination is generally necessary for both eco-solvent and latex. Eco-solvent inks are pigmented and harder than their latex counterparts but are prone to scratching. Latex inks, on the other hand, can be more resilient but need protection from the elements to avoid fading and streaking. This makes lamination part of the production process and requires prints that are dry and fully-out-gassed””or the laminate won’t adhere correctly and the job will need to be run again.
Such mechanical processes aside, a major benefit of latex is that its water-based inks completely eliminate volatile organic compounds (VOCs), the bane of solvent-ink printers. Eco-solvents do well in this regard, and both latex and eco-solvent machines deliver quality prints quickly and profitably.
First rolled out by HP, latex printers initially seemed to be just another wide”“format device. But timing was everything. Vehicle wraps were just beginning to become a popular way of showcasing a company’s products and services and the flexibility of latex made it easier to do. This is not to say wrapping a vehicle is easy. To the contrary, it is quite demanding, especially on some of today’s curvaceous autos. But the flexibility of new substrates and certain characteristics of latex inks are an ideal match for wrapping everything from aircraft to trucks to racecars. Substrates and inks alike can conform to complex curves and shapes, especially when heat is used. With the caress of a heat gun or even a torch, substrates for latex printing can mold to a compound curve or even regain their original shape. In many cases, either print technology can be used, but there are applications, such as the complex aerodynamics of some racecars where latex ink and a flexible substrate are the best option for conforming and adhering to tight curves while ensuring sponsors’ logos always look exactly right.
As with UV devices, most of the major equipment makers have latex printers in their product mix. As the originator of latex on wide machines, HP leads the way, but competing machines are available from Canon, Epson, and Mimaki, among others. All are worth considering.
What’s Best for Your Customer?
The main thing to understand is that when it comes to wide- and large-format printing, it is not a matter of one technology being better than the other, but which is best for your customer mix and the applications customers need to run. Having a latex machine available can get you jobs where a UV machine can’t play, and vice versa.
Depending on how you crunch the numbers, UV machines are often more expensive to buy, but can be more productive and cost less to operate. What is most telling though, is that other than businesses like vehicle wrap firms that specialize in one kind of work, many shops have multiple wide- or large-format machines using different printing technologies. This allows them to offer different products, often at different price points, to meet customer needs.
Wide- and large-format printing is well down the road to being mainstream. It pays to take the time to learn about the nuances and find out how it may fit with your customers. These machines all command attractive values, offer a compelling ROI, and run very reliably, while using large amounts of consumables. And many first-time buyers come back for more. And you can take that to the bank.
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